Amazing Vacuum Furnaces – Great way to make money – fast
Today, the Shakespearian question is „where you can make money fast and how do you make a lot of it”? It is most likely that thermal chemical diffusion processes and vacuum assisted coating will become the most profitable branch in the metal improvement business. I was told recently by the owner of European vacuum assisted vacuum coating company that the average net profit from his shops around the world is between 30% to 50%.
Why are coating and thermo diffusions in such high demand, and why is that business so profitable? First, there is limited knowledge on vacuum assisted coating and thermo diffusion processes. Second, there are a limited number of companies that perform those processes and competition among these companies is much less compared to other heat treatment services. Third, the equipment for these processes are costly and relatively difficult to open these operations. Lastly, in many cases these techniques are patented or are kept confidential.
Plasma-assisted vacuum coating technologies include:
• PVD (Physical Vapor Deposition)
• Arc-Evaporation and
• PECVD (Plasma Enhanced Chemical Vapor Deposition)
PVD stands for Physical Vapor Deposition. It is a process carried out under high vacuum and at temperatures between 150 and 500 °C. In the PVD process, the solid coating material (metals such as titanium, chromium, and aluminum) are either evaporated by heat or by bombardment with ions (sputtering). At the same time, a reactive gas (e.g. nitrogen or a gas containing carbon) is added to the process and forms a compound with the metal vapor which is deposited on the tools or components as a thin, highly adherent coating. A uniform coating thickness is obtained by rotating the parts at a constant speed about several axes. (Source: www.oerlikon.com)
Popular examples of thermal chemical diffusion are processes such as Boycote’s Specialty Stainless Steel Processes (S3P) featuring Kolsterising®, Expanite®, AS Denmarks and Ipsen’s SolNit®, which offers unique surface hardening solutions for austenitic stainless steel, nickel-based alloys and cobalt-chromium alloys that produce increased mechanical and wear properties without adversely affecting corrosion resistance.
The SolNit® low-temperature process can overcome extremely shallow diffusion layer, and to create hardened layers on stainless steels with thicknesses of up to 1 and even 2 mm without any loss of corrosion resistance. The SolNit® process uses the capability of stainless steels to dissolve nitrogen at temperatures above 1832°F (1000°C) to a large extent without formation of chromium nitrides. The industrialization of the solution nitriding technology SolNit® was done in a joint co-operation between Professor Berns, Ipsen International and Härterei Gerster AG, Switzerland.
Amazing Vacuum Furnaces – Cost of Heat Treatment around the World (2016)
The first price table with heat treatment costs around the world was published in 2014 and generated several comments. There is no good approach to accurately estimate the price charged by commercial heat treating shops. The only way is to find the average the prices and convert it into $ per kg. We have added two new countries to the survey, Sweden and the U.K. Pricing from the table may vary substantially from the actual amount charged because the pricing is dependent on commercial heat treating shops’ discretion. Actual pricing will depend on each shop’s service level, fix and variables cost the volume, additional services provided such as pick-up and delivery, furnace availability, market competitiveness, certification requirements, etc.
*No change from 2014. Prices are converted from local currencies to dollars per kilogram.
Most prices overlap regardless of the country-specific labor rates, utility costs and environmental regulations. One exception is the pricing in countries that are less integrated into world economy for political (Russia), economical (Brazil) or geographical (Australia) reasons. Select works for the Aerospace, Additive Manufacturing, and Motorsport industries, are more costly to run. Heat treatment services for Additive Manufacturing require higher prices due to their sophisticated processes, higher cost of equipment and smaller volumes. Compliance to NADCAP, CQI-9, NADCA and other specifications increases the quality assurance and the overall operational cost and consequently pricing.
Pricing varies substantially based on the volume. List prices are for clients that only run one load, three a week. One method to determine these rates is to get a certain price-per-hour for each piece of high-temperature equipment. Each job would be quoted based on the weight of the load (per kg) and cycle time (per hour). Different parts yield different prices (200 kg of small springs can be a maximized load in a furnace that might also hold 800 kg of winch shafts). If a commercial heat treater has a customer that has a lot of work (in other words, enough to fill one furnace or more), then the price will lower substantially. Heat Treaters have a spectacular ability to determine their exact variable operating cost (gas, electricity, water, labor, oil drag out, etc.) and will price volume work at pennies on the dollar for variable costs to fill equipment. Successful commercial heat treating shops can beat the market and make a profit while doing so when they know their costs and operate their equipment more efficiently than anyone else in the industry.
The Internet of Things (IoT) is coming to heat treating shops by new software and apps applications, and this new approach is forcing changes how the heat treatment shops are operating. The IoT system is improving maintenance operations, customer satisfaction, quality assurance and operational cost. The Internet oThings is built on a consistent collection of data, analytic of data and matching patterns of past failure to predict future breakdowns. Using data gathered by sensors is not new in vacuum operations. What is new today, is the volume, accuracy and the ability of the software to analyze information and transform data into useful information that saves money.
Amazing Vacuum Furnaces –
Heat Treatment Operations for Parts Made by Additive Manufacturing (AM) Methods
Additive manufacturing (AM) is one of the most significant developments in modern industrial technology. AM is the process of adding, melting and joining layers of metal on top of each other as opposed to a subtractive method such as machining. The heat treatment process is used to ensure AM parts achieve proper metallurgical and dimensional properties. With this need for heat treatment, the AM process necessitates the use of more precise heat-treating systems that are capable of meeting specific criteria such as heating uniformity, temperature range, and purity of atmosphere or vacuum level. Batch furnaces with either vacuum or a protective atmosphere are preferable for AM heat treatment. The AM parts require the use of vacuum furnaces for a variety of heat treatment processes, such as stress relieving, annealing, solution, aging, nitriding, carburizing, and sintering. Vacuum furnaces equipped with high-pressure gas quenching can also be used for hardening, carburizing and other surface modification processes. However, if AM is ever to make the leap into large-scale production, it needs to be able to 3 D print in metal faster, more economically, from less costly powder alloys, and bigger parts. As such, the current challenge facing the heat treatment industry is integrating heat treatment into one continuous Additive Manufacturing process.
Leading the charge in the next generation of metal component fabrication is additive manufacturing (AM). After all, “No other technology has the potential to change the design process and the appearance of new products so fundamentally” . The AM heat treatment process aim is the same as that of traditional subtractive manufacturing, and it is performed to ensure AM parts possess the right physical properties.
When it comes to heat treatment, the AM process necessitates the use of single chamber furnaces with fine or high vacuum level capability. AM also requires the use of vacuum furnaces that are capable of a variety of heat treatment processes (e.g., stress relieving, annealing, Nitriding, carburizing, and sintering). When hardening, carburizing and other surface modification processes are needed, a vacuum furnace with high-pressure gas quenching is then required.
Currently, the penetration of parts produced using AM methods represents around one percent of total shipment values for the Automotive, Aerospace, Military and Tooling industries and reach 5.165B Euro in 2015 and grew last year by 25.9% . However, this number is rapidly changing with the fast-growing adaptation of AM technologies. The largest AM technology penetration is in the Medical and Dental industries with, in some estimation, over 50 percent of dental implants being made by AM processes.
Additive manufacturing is complementing other powder metallurgy (PM) technologies. Hot Isostatic Pressing (HIP), MIM, and Sintering offer the possibility to produce net shape parts. Each PM technology is covering a different segment of the market and production requirement. . Net shape AM manufactured parts could save up to 90% material versus the same part made by machining.
Below Figure 1, describes the market segments for each net shape technologies.
Fig.1. Net shape technologies versus production market segment size (source: Introduction to AM technology, www.epma.com)
Fig. 2. Timeline of 3-D printing adoption curves (source Christopher Barnatt http://www.explainingthefuture.com/)
An example of an early adopter within the Automotive industry is Ford Motor; the company has been using this technology to develop prototype parts for test vehicles since the 1980s. With AM technology, Ford engineers have produced prototypes of cylinder heads, brake rotors, and rear axles in less time than the traditional manufacturing process would require .
In addition to Ford Motor, BMW uses additive processes to produce more than 100,000 parts a year for its vehicles. Turbomeca also uses metal AM for its serial production of helicopter engine components, as well as Selective Laser Melting (SLM) to manufacture fuel injector nozzles and combustion swirls for its engines. These engines are Turbomeca’s latest models and are claimed to be amongst the most advanced turboshafts ever designed .
Most popular powder metals use in AM are stainless steel, Inconel, magnesium, cobalt, titanium, copper, tool steels, and aluminum. Powder particle size has a direct influence on final part density, dimensional accuracy, and surface roughness. The smaller particle, the better final part quality. Non-weldable powder alloys cannot be processed by AM and challenging–to-weld alloys such as aluminum will require individual approach . During additive process, layers of powder metal are added, melted and joined on top of each other until the final part shape and size is achieved. Recommended minimum wall thickness is usually 2 mm with a maximum length to high ratio shall not exceed 8:1 and minimum strut is 0.15 mm.. For example, the SLM additive manufacturing process used by Turbomeca builds the components from a nickel-based superalloy powder in layers between 20 to 100 micron thick.
The ASTM International Committee on Additive Manufacturing Technologies has developed standard terminologies for AM. Below are the categories from the ASTM F2792 standard; four among them are suitable for metal AM (Table1).
ASTM F2792 categories of 3-D printing
Even though AM offers the opportunity to reproduce most parts currently manufactured by conventional technologies such as milling or casting, only in some cases are the results better or cheaper than the original part. Parts densities of 99.9% are achievable, but still, there can be some residual internal porosities, cracks, high surface roughness, and impurities. Mechanical properties are usually superior to cast parts, but inferior to wrought parts . Parts that need extensive machining after AM rarely will be competitive with traditional technology. Experience has shown that AM technology efficiency improves with smaller and more complex components. Fig. 4.4 highlights the break-even point for manufacturing, according to a study conducted by Atzeni and Salmi .
Heat Treatment for the Additive Manufacturing Process
During the AM process, defects, stresses, and anisotropic mechanical properties are induced due to columnar grain structures on the parts. These imperfections negatively influence the mechanical properties of the material, especially the fatigue behavior . To achieve the necessary metallurgical specifications – such as surface quality, geometrical accuracy, and mechanical properties – AM parts are post-process by machining, EDM, grinding, polishing, heat treatment, and hot isostatic pressing, . One of the processes that help improve the properties of AM parts is Hot Isostatic Press (HIP). HIP is a proven heat treatment technology that consolidates powder and removable porosities from the material. Also, the use of HIP high-pressure quenching avoids thermal stresses, deformation or cracking as compared to quenching with oil or water.
According to a metal powder manufacturer, vacuum furnaces must possess certain features to meet the requirements of AM processes, as summarized below :
In addition to the above criteria, part size and production volume also affect and influence the effective vacuum furnace size.
Overall, the vacuum heat treatment process for AM manufactured parts is the same process as that of traditional subtractive manufacturing, and its purpose is to ensure AM parts have the necessary physical and metallurgical properties for specific applications. Heat treatment is essential for homogenizing the anisotropic AM parts’ structure and making it uniform. It is important that the heat-treated AM parts do not have surface or internal oxidation, decarburization or a discolored surface from water vapor, oxygen or alloy evaporation.
Vacuum furnaces with a non-contaminating heat treatment environment are required for thin wall parts. Stress relieving is commonly performed before parts are cut off from the platform. In some cases when a bidder is involved, the purpose of the heat treatment process is to debind and eliminate parts’ dimensional imperfections. Most vacuum furnaces use up to 800 ºC to relieve stress and then a higher temperature of up to 1,600 ºC for other processes. Using vacuum furnaces with high vacuum levels and the smaller hot zone is preferred for AM parts. Stress relieving, solution treatment and aging of parts made from alloys prone to oxidation require all metal hot zones.
AM parts made from titanium, cobalt and aluminum require vacuum levels of up to 10-6 mbar with 99.9995 argon purity with a dew point of 60C or better. Argon is the preferred gas because of its inert nature, as well as the fact that it has no adverse reaction with the alloy components. Creating an Alfa layer on titanium parts is not desirable and should be avoided.
Fig. 3. Ipsen furnaces at GE AM Pittsburgh facility (Source: Metal AM Magazine Spring 2016)
However, in spite of these recent advances in AM technology, the next challenge facing the heat treatment industry is determining how to integrate heat treatment into AM equipment so as to create one continuous process.
Another innovative way to print metallic parts is to use metal oxides, such as iron oxides (e.g., rust). Rust powder is lighter, cheaper and more stable to handle than pure iron metal. Northwestern University researchers discovered that they could first 3-D print structures with rust powder and then use hydrogen to turn green bodies into the metal before sintering it in the vacuum furnace .
Heat Treatment Diligence
The majority of parts manufactured by AM method will require debinding, sintering, annealing, stress relieving, aging, or surface modification process. Heat treatment’s challenge is to maintain the straightness, roundness, tolerances and material metallurgical properties of these parts. Minimizing the cost of the heat treatment is an important aspect of manufacturing, particularly during the additive manufacturing process. Below are several suggestions on how to enhance AM technics to optimize heat treatment cost:
As the heat treatment industry focuses on the integration of heat treatment and additive manufacturing into one continuous AM process, it is essential to remember the characteristics that make a vacuum furnace most suitable for AM processes. This include:
All too soon, industries can expect to see one-piece-flow heat treatment systems opening a new, efficient and controllable way to incorporate 3-D printing and heat treatment into the continuous manufacturing process.
1. Composite Manufacturing Magazine , Article on website magazine October 15, 2014 http://compositesmanufacturingmagazine.com/
2. Metal AM Magazine 2016 Summer Edition, Inovar Commumication, Ltd, Vol2, No2, 6
3. Introduction to Additive Manufacturing Technology, A Guide for Designers and Engineers, European Powder Metallurgy Association 2015, 1st edition, 4.
4. Ford, Sharon. “Additive Manufacturing Technology: Potential Implications for U.S. Manufacturing Competitiveness.” Journal of International Commerce and Economics. Published electronically September 2014. http://www.usitc.gov/journals
5. Boulton, “Barbie, Auto Parts Hot of the Press,” June 6, 2013, B5
6. Introduction to Additive Manufacturing Technology, A Guide for Designers and Engineers, European Powder Metallurgy Association 2015, 1st edition, 6.
7. Introduction to Additive Manufacturing Technology, A Guide for Designers and Engineers, European Powder Metallurgy Association 2015, 1st edition, 29.
8. Introduction to Additive Manufacturing Technology, A Guide for Designers and Engineers, European Powder Metallurgy Association 2015, 1st edition, 24.
9. Atzeni, Eleonora, Luca Iuliano, and Allessandro Salmi. 2011. “On the Competitiveness of Additive Manufacturing for the Production of Metal Parts” 9th International Conference on Advanced Manufacturing Systems and Technology
10. J.Hjane, M.Ahlfors, Hot Isostatic Pressing for AM parts. www.Quintus.com white paper
11. Introduction to Additive Manufacturing Technology, A Guide for Designers and Engineers, European Powder Metallurgy Association 2015, 1st edition, 17.
13. Private discussion with metal powder manufacturer VVT.
14. Northwest team develop innovative method for metal Additive Manufacturing, Article from Metal AM, Vol2 No.1 Spring 2016;34
Amazing Vacuum Furnaces – Price Trends
Considering the way vacuum furnaces are made today, the process is incredibly complicated and time consuming. Tons of machines and formed metal, graphite, composite and electrical parts are used to making the vacuum furnace. All these parts are connected, welded, glued, bolted or press-fitted to create one perfectly working vacuum furnace. The control system utilizes PLCs with sophisticated software and easy to follow graphic displays. Considering the above mentioned design complexity and added engineering and manufacturing know-how, it is very expensive to manufacture a vacuum furnace, and there is a steep learning curve for newcomers. The Asian companies are getting there slowly but only by replicating what more established companies are doing.
Today’s vacuum furnace design is the result of years of incremental change that has added to the complexity, robustness, and the furnace’s operational safety. The current price for the standard vacuum furnace is lower that it was couple years ago. It seems like the majority of vacuum furnace manufacturers were able to increase performance and lower capital costs at the same time. To understand why the price for a vacuum furnace is lower today, one needs to consider only two factors: the new disruptive business model and increased competition.
The new disruptive business model is being introduced in some part thanks to better material supply chains. The supply chain has become much more global, with sub-suppliers located in different places in the world. Communication and transportation costs are significantly lower compared to few years ago. We cannot overlook the ease of communication across continents between buyers and suppliers. This easy communication was not possible just few years ago. Tariffs, shipment restrictions, duties and customs clearances are much simpler or have been altogether eliminated. To compete in any market – European, Asian or American – a perfectly synchronize global supply chain is necessary to succeed.
Second, the business model of vacuum furnace manufacturers is shifting from selling manufacture to order furnaces, to the sale of standard or modular vacuum furnace. Various vacuum furnace manufacturers are including process softwares such as the carburizing or nitriding process technology in the standard future.
Competition is intense amongst furnace companies in each sub-segment of the vacuum heat treatment market. As the vacuum heat treatment industry matures, vacuum furnace costs and process softwares will emerge as primary differentiators. Closer collaboration with customers will be crucial since it otherwise would be difficult to develop solutions targeted to their particular needs. As an added benefit, collaboration with end users could give furnace manufacturers more insight into the decision-making process and technological process needs. Strategic partnerships with clients could also be important for individual furnace players, especially with R&D costs rising. For instance, furnace makers could shift to a business model in which their customers provide sales guarantees to develop a new vacuum furnace similar to airplane industry practice.
To be more competitive in a new business model and more customer-centric oriented, vacuum furnace companies are adopting a system in which more revenue comes from maintaining the installed furnace base and optimizing its performance rather than from selling new equipment. The percentage of revenue generated from aftermarket activities are growing for most vacuum furnace companies. This new trend is transforming the vacuum furnace making company into a more service-oriented one. Janusz Kowalewski
Amazing Vacuum Furnaces – Repeatability and Capability Tests
The difficult task in heat treatment operation is to control and eliminate heat treatment variables – temperature uniformity, heating rate, vacuum level, etc. In the quest for the highest quality results in material science current heat treatment standards are not tough or precision enough to satisfy the new quality expectations. Recently, I was attending heat treatment conference in Munich, Germany when Klaus Herbold from BMW Group gave a brutal assessment of the metallurgical variation happening in different furnace systems. The presentation was so much different from the usual presentations that we are so used to listen during heat treatment conferences (I need to admit that this criticism includes my own numerous presentations given at different heat treatment conferences). It was very refreshing to hearing and watching data after data of how badly furnaces performed and listen to his opinion that we are not doing enough as a heat treatment community to improve current heat treatment quality.
Luckily for us the new digital technology has the potential to unlock new ways of managing heat treatment process variables and enhance productivity in vacuum heat treatment operations. The new IT technology implemented into vacuum furnace control system combine with new standards for testing furnace performances may reasonably be an answer to Mr. Herbold needs.
For example, gear grinding operation is very costly to achieve a final dimensional tolerance requirement. The new requirement driven by NVH specification [noise, vibration, harshness] requires gears to be grinding instead of rolling to achieve high dimensional precision.
To eliminate heat treatment variation, new dynamic standards should be developed and used along traditional testing procedures such as temperature uniformity (ASM2750E), vacuum leaks (ASM2769), process parameters ASM2759 (1 to 10).
The purpose of new testing procedures is to assure a vacuum furnace ability to perform constantly within the same expected outcome range within specific time period. Example of two new tests to evaluate vacuum furnaces are repeatability and capability tests. Repeatability test aim is to verify that the furnace is able to reproduce process parameters such as vacuum level, quenching speed, heating rate constantly. Capability test aim is to verify furnace consistency in terms of distortion and microstructure during heat treatment or surface modification processes such as Nitriding or Carburizing.
Understanding and addressing customer needs more effectively is a key reason for a vacuum furnace company to achieve success in today’s more customer-centric heat treating marketplace. Janusz Kowalewski
Amazing Vacuum Furnaces – LPC Technology within Gear Industry
The growth potential
Vacuum – Low Pressure Carburizing (LPC) was introduced in the 1990s to carburize high-end transmissions components. New LPC technology provided numerous advantages that sparked interest amongst many car and OEM gear manufacturers. By 2015, more than 1500 LPC chambers have been installed around the world. Volkswagen, GM, BMW, Ford, CFA, Renault, Porsche, Honda, Hyundai, and Indian car manufacturers (although with some limits) such as Mahindra and Tata have vacuum Low Pressure Carburizing systems for heat treatment its car gearboxes. The majority of gear manufacturers like EATON, ZF, GETRAG (MAGNA), Hoerbiger, JATCO, AISIN SEIKI, AICHI KIKAI, SAGW, GREAT WALL, GKN, LINAMAR, and DANA use LPC processes for heat treatment gears. The new generation of transmissions such as the dual clutch (DCT) and six-eight-nine speed automated transmissions are all carburized with LPC technology.
Still, the LPC has much room to grow in the near future. According to industry estimations, currently between 25% -30% of gears are vacuum carburizing with LPC technology. Graph 1 shows the LPC status in 2014 and the estimation for 2019. Graph 2 illustrates the adoption life cycle for a new technology. Assuming that in 2015 vacuum carburizing market penetration reaches 25% to 30%, we are very close to a period of exponentially increasing demand for vacuum furnace systems with LPC technology.
Low Pressure Vacuum Carburizing for Gears Heat Treatment
The vacuum carburizing technology (LPC) combine with new generation multi-chamber furnaces has several distinct operational advantages in manufacturing gears:
In vacuum carburizing, it has been proven that acetylene offers better carbon efficiency compared to propane, because of its instability and higher carbon content per mole of gas. By using acetylene, densely packed loads, especially parts with complicated shapes, can be carburized at a highly reproducible quality. Process parameters like temperature and gas flow are selected according to part-effective case departments, carbon surface concentration requirements and the total carburized surface of the parts. To achieve a specified carbon profile, the carburizing is done in alternating steps for carburizing boost and diffusion, followed by a final diffusion step (See below Graph 3). The root-to pitch case depth ratio in gears obtained in vacuum carburizing is much better 90 to 95% compare to conventional carburizing methods, which is under 70%.
According to Dr. Herwig Altena and Frank Schrank’s article published in Gear Technology (March-April 2004), higher carburizing temperatures will not have adverse results on grain coarsening if the carburizing is performed within a specific time frame. “… By implementing vacuum technology, the increase of carburizing temperature can be applied without any limitations caused by the furnace… However, an increase in carburization temperature may not be possible depending on steel quality and other metallurgical factors. Detailed tests performed by V. Schüler … on standard fine-grain stabilizing rods have shown that if the aluminum and nitrogen levels of the steel are sufficiently high, a carburization temperature of 980°C at a holding time of 4–8 hours will not lead to grain coarsening. The maximum admissible share of grain coarsening is limited to 10% (see Fig. 4). This gives the possibility of achieving effective hardening depths of 1.4–2 mm by direct hardening without intermediate isothermal annealing….”
Grain growth vs. carburizing temperature and duration (after V. Schüler,)
Amazing Vacuum Furnaces – Industrial Revolution 4.0 – A new eco-system for the agile gear heat treatment operation
According to a statement made by the American economist Wassily Leontief – “The industrial Revolution wasn’t very good if you were a horse” since the need for horses in the economy was eradicated when other forms of transportation and power were introduced. – So who will benefit from and who will be eradicated by Industry Revolution 4.0? Human labor – maybe? What is certain is that heat treatment operations will survive and prosper, but in a very different way compared to its current practice. To start off, lets concentrate on the multi chamber – Low Pressure Carburizing vacuum furnaces for gear industries.
Most automotive and gear companies are now able to digitally simulate their plant layouts and production processes in an effort to improve efficiency. The digital manufacturing processes could be an opportunity for furnace companies to compete with sophisticated software that controls and creates an entire Eco-System for gear manufacturers. The digitalization of the manufacturing process compels furnace companies to develop better software that expands beyond the traditional PLC/SCADA furnace controls functions. The operations of the multi-chamber Low Pressure Carburizing (LPC) vacuum system is highly computerized and cannot be efficiently operated manually. The new generation of multi chamber LPC vacuum furnaces for gear heat treatment requires highly sophisticated software to integrate furnace operations with the entire manufacturing process. This advanced furnace’s operational software allows for more synchronous monitoring processes and reduces human interference during operation.
New Predictive Maintenance software and sensors system installed in furnaces aim to reduce unscheduled downtime time to nearly none. This sort of predictive maintenance is particularly valuable in mass heat treatment operation, where any furnace breakdown causes damage to a valuable load, stops further downstream production, and disrupts upstream production’s schedule. It is far better for operators to be able to predict when a part will fail and replace it before it breaks down completely, or before the scheduled maintenance replacement.
The current multi-chamber LPC vacuum furnaces have numerous sensors across the entire heat treatment equipment that allows furnace integration into the entire manufacturing chain. In turn, this new software’s capability helps gear manufacturers enhance production speed and process quality. To adopt Internet of Things (IoT) into the factory setting, some furnace control systems will need to be upgraded or replaced to accommodate IoT sensors, gauges and actuators. Improvements in factory settings to accommodate connectivity and interoperability (for both machine-to-machine communications and for relaying large streams of data from the production floor) will also be required to adapt to IoT. This can be done by remote tracking, monitoring, and adjusting, based on the furnace operation’s sensor data from different furnaces performing heat processes across the entire gear production cycle.
Amazing Vacuum Furnaces – How the Internet of Things Has Optimized the Future of Vacuum Heat Treatment Operations
The heat treatment industry is at a turning point, in which digital technology has the potential to unlock new ways of managing process variables and enhance productivity in vacuum heat treatment operations. Significant untapped potential for improving productivity lies in the adaptation of Internet of Things (IoT). The Internet of Things refers to the use of embedded sensors, actuators, and other devices that can collect or transmit information about the vacuum furnace operations. The greatest value-creating potential of the IoT is optimizing vacuum furnace operations through the data collection, data computation and maximizing production schedule. This mode of operation requires using sensors, rather than human judgment (and human error), to adjust the furnace’s operational parameters. In addition to optimizing operations, the next most valuable application of IoT in heat treatment is predictive maintenance adaptation and spare parts inventory. Predictive maintenance involves continuously using sensors to monitor furnace components’ performance to avoid breakdowns and to determine when maintenance will be required, rather than relying on regularly scheduled maintenance routines.
For example one of the main tenants of gear manufacturing’s lean manufacturing movement is to increase productivity by reducing the work in progress inventory. A type of system that fits these criteria is the new generation multi-chamber vacuum system. However, as the supply chain becomes leaner, it also becomes more vulnerable to production interruptions caused by equipment breakdown. In this situation, implementing predictable maintenance system is an important and necessary element to assuring seamless gear manufacturing. The tracking of furnace performance is essential in enabling sensors to real time sensing and tracking the heat treatment process parameters (such as vacuum level and temperature fluctuation, carburizing gas flow, time of each segments…etc.) and furnace conditions (such as vacuum pumps oil temperature, motors temperature, heating element amperage…etc.).
For IoT applications to be adopted in heat treatment settings, furnace control systems need to be upgraded or replaced to accommodate IoT sensors, actuators and software that can analyze the stream of data from sensors. It is also required to improve connectivity and interoperability between furnace control systems and plant ERP systems. The success and speed of adapting this new technology will depends on lowering the cost of the basic technology such as sensors, micro-electromechanical systems (MEMs), and cloud data storage and computing. IoT can improve furnace spare part inventory management as well by automatically ordering spare parts based on usage frequency.
Finally, capturing the value from digital innovations represents a fundamental shift in vision, strategy, operating model, and capabilities in the heat treatment industry. The path to improving heat treatment productivity will come through reducing technology costs and, where possible, eliminating the variability in heat treatment operations. For the full benefit of IoT in heat treatment industry to be realized, security needs to be addressed. Furnace operators need data to know how furnaces are operating and at the same time managers need to trust that the system is maintaining strict data security.
Amazing Vacuum Furnaces – LPC Technology for Powder Metal Gears and Parts
Carburizing is one of the leading surface-hardening processes applied to the sintered, low-alloyed steel gears in the automotive industry. While diffusion of carbon in wrought steel is well documented, this is not the case for PM steel subject to carburizing in vacuum furnaces. In the article “Vacuum Carburizing Technology for Powder Metal Gears and Parts” presented in 2006 at the AGMA conference, Karol Kucharski and I presented results that show that the density of the powder metal is the main factor for the final carbon content and distribution. Also important for carbon case formation is the state of the surface of the part; either sintered with open porosity or machined with closed porosity.
Chemical composition 8620 P.M. and 8620 steel*.
*A standard TRS bars compacted at the pressure from 480 MPa to 1080 MPa, from the blend equivalent to 8620 steel to green densities 7.0, 7.1, 7.2, 7.3, 7.4 and 7.5 g/ccm where used for carburizing test.
During Low Pressure Carburizing (LPC) process is not possible to set the carbon potential and control case composition due to absence of thermodynamic equilibrium. Vacuum LPC the boost-diffusion empirical / computer simulated process is applied to control the surface carbon contend and carbon distribution in the case. During the first carbon boost the flow of the carburizing gas (C2H2) has to be sufficient but well below saturation point for 8620 steel is reach and before carbide formation begins to form. The first pulse with shorten time will avoid soot deposition and formation of the massive carbides. To accomplish this goal, the calculation of the proper gas flow rate and time according specific carburizing temperature have to be made. In the case of P.M. parts, the amount of carbon absorbed by the part’s surface can be few times higher due to additional internal surface created by pores present in the carburized case [1,2]. This amount will depend on the density of the 8620 P.M. part and the stage of the surface – “as machined” or “as sintered”. It is believed that enhanced gas diffusion after initial evacuation of the P.M. parts leads to faster carburization from within the pores, especially when pores are open – surface “as sintered” and interconnected – low density. Vacuum carburizing of PM materials is much faster than of solid steel. The most important factors are porosity and type of surface. In experiments conducted by Karol Kucharski, P.M. samples with lowest density and open porosity showed the dramatic increase of the surface carbon content up to 2.5% C and 3 times deeper case compare to 8620 steel parts. Massive carbides formation and increase of retained austenite in the 8620 P.M.sample was also observed.
 R. G. Weber: Vacuum Carburizing and Carbonitriding of Powder Metallurgy Ferrous Alloys (Powder Metall. Int. 15 (1983)  94).
 Y. T. Chen, R. W. Kiefer, Jr. Pitney Bowes, Inc. Stamford, Connecticut, USA;:
Carburizing Of P/M Materials (Carburizing Processing And Performance, Proceedings on an International Conference, p. 199, July 12-14, 1989, Lakewood, Colorado, USA).
This post is dedicated to my friend Karol Kucharski PhD, Ontario, Canada. I hope you will fully recover very soon. Cheers Karol!
Amazing Vacuum Furnaces – Hardening O1 Steel
Could vacuum furnaces with 10/12 Bar pressure quench successfully harden tool and die steel such as O1? The answer is yes, but the heat treatment should be carefully settled for this particular type of steel, including at the initial pump down to the high vacuum level of 10-3 mbar or better range to avoid surface decarburization. Heating should be performed at partial pressure of 0.15 mbar (Torr) Also, the cross section of the tool and die should be no more than 3-4” (75-100 mm) depending on furnace cooling capability. Normally, oil hardened steels such as O1 (C 0.90; Mn 1.20; V 0.20; W 0.50; Cr 0.50) need oil hardening and single or sometimes double tempering. However, today a single chamber high pressure quench furnaces are preferred for O1 steel especially for small tools and dies.
Hardening of O1 steel requires a change in structure from the body-centered cubic structure found at room temperature to the face-centered cubic structure found in the Austenitic region. The steel is heated to the Austenitic region of 790-815°C (1450-1500°F) and holds 30 min per 25 mm (1”). Martensite is formed when the steel is suddenly quenched at 10 Bar or higher with Nitrogen. This is a very quick and brittle structure. The cooling should stop at (100-125°F) and parts should be immediately tempered. Hardness Rockwell „C” as-quenched should reach 64/65.
You can soak at the proper heat for 2 hours per inch (25 mm) of thickness for each temper. Air cool to room temperature between tempers. The normal tempering range for this grade is 175-260°C (300 to 450° F) 63/58 HRC.
Hardenability, which is a measure of the depth of full hardness achieved, depends on the type and amount of alloying elements. Different alloys that have the same amount of Carbon content will achieve the same amount of maximum hardness; however, the depth of full hardness will vary between them. The reason for alloying steels is not to increase their strength, but to increase their hardenability – the ease at which full hardness can be achieved throughout the material. http://www.efunda.com/processes/heat_treat/hardening/direct.cfm
Creating a Customer for Life – Just a Dream or Possible Reality?
The goal of any furnace company is to interact with its customers in a way that creates a Customer for Life. Visiting many captive and commercial heat treaters, and seeing so many different furnaces from different manufacturers in the same area, it is obvious that only a few furnace companies had created total customer satisfaction. In other words, only few furnace companies were able to deliver a great furnace and create a Customer for Life. Here are three simple suggestions that may help create a Customer for Life:
1. Design Furnace with Connectivity
Furnace connectivity is key to improving a furnace company’s interaction with its customers and helping the customers operate the furnaces easily. Furnace connectivity boosts the number of self-service options that help resolve a furnace problem quickly, assure communications to be more relevant, and deliver consistent customer satisfaction. The furnace with control system connectivity can drive furnace operation costs down, and is also necessary so that furnace companies can have more flexibility in responding to furnace problems and anticipating customer needs.
2. Assure Technical and Process Support through out Useful Life of the Furnace
To provide meaningful technical and process support, furnace companies should first understand how a consumer is interacting with a furnace and modify those interactions to improve the customer’s experience. For example, if a customer needs a new process, then the furnace company should have the ability to provide guidelines on how to best utilize the furnace for that particular process. The more a customer interacts with a furnace company, the more the furnace company understands what their customers want. The rapid rise of wearable technology and the Internet of Things represents the latest wave of touch points that will enable furnace companies to have positive and meaningful cooperation with the customer.
By providing customers technical and process support, furnace companies learn what the customer needs and wants. For example, a furnace company can help its existing customers branch into new businesses and services. This service extends the furnace company’s relationship with the customer, ideally to the benefit of both parties. In return, these services provide a path to a more interactive, more informative, and more valuable furnace company-customer relationship.
3. Improve Customer Competitiveness
“Money talks” and heat treatment is no exception to this rule (in a positive way, though). Helping the customer improve its technical and economic competiveness in the market place creates a lasting bond between the furnace company and its customer. If a furnace company provides a reliable and economic furnace that requires less maintenance, then the customer’s profits rise. The furnace company’s goal should thus not only be to sell the furnace but to help the customer with their heat treatment daily operations. A furnace company has the responsibility to help their customer succeed in the market place. And in the business world, success creates success.
By helping a customer become more successful, a furnace company creates a Customer for Life.
Five Financial Ratios I Use to Runs my Company more Efficiently
A company could not be operated well based on account receivables – that’s a basic fact. With cash bills are paid. This is very true in every country and especially in developing countries where the rules of law, contracts validity and financial responsibilities are not very well defined. There are several ratios and financial tools that help track, understand and improve the furnace company operation. According to Bankrate.com, there are more than 150 financial ratios available for managers to monitor their companies. Here are my five financial ratios that may help you to better understand your company operation.
Gross Profit Margin ratio:
Gross margin ratio is a profitability ratio that compares the gross margin of a business to the net sales. This ratio measures how profitable a company sells its furnaces, pare parts and services. This is the profit from the sale of furnace that can go to paying operating expenses. Higher ratios mean the company is selling their furnaces at a higher profit percentage. High ratios can typically be achieved by two ways. One-way is to lower your cost of material, engineering and labor. The second way a furnace company can achieve a high ratio is by marking their furnaces up higher profit margin.
A company with a higher gross margin ratios mean that the company will have more money to pay operating expenses like salaries, utilities, rent and capital improvements and new development. Since this ratio measures the profits from selling furnaces, it also measures the percentage of sales that can be used to help fund other parts of the business.
The current ratio is a liquidity ratio that measures a company’s ability to pay off its short-term liabilities with its current assets. The current ratio is an important measure of liquidity because short-term liabilities are due within the next year.
This ratio is extremely important for a small and newly establishes companies where the long-term investment does not exist and ability to borrowing money against collectable are very limited.
Account Receivable Ratio:
Account Receivable ratio is also called activity ratios measure how well companies utilize their assets to generate income. Activity ratios often look at the time it takes companies to collect cash from customer or the time it takes companies to convert furnace into cash—in other words, make sales. I use this ratio to monitor and to help improve the company manufacturing process by shortening the delivery time. Efficiency ratios go hand in hand with profitability ratios. Most often when companies are efficient with their resources, they become more profitable.
Return on Capital Employed Ratio:
Return on capital employed or ROCE is a profitability ratio that measures how efficiently a company can generate profits from its capital employed by comparing net operating profit to capital employed. The return on capital employed ratio shows how much profit each dollar of employed capital generates.
This ratio is based on two important calculations: operating profit and capital employed. Net operating profit is often called EBIT or earnings before interest and taxes. EBIT is often reported on the income statement because it shows the company profits generated from operations. The return on capital employed ratio shows how much profit each dollar of employed capital generates. Obviously, a higher ratio would be more favorable because it means that more dollars of profits are generated by each dollar of capital employed.
Book to Invoice Ratio:
Book to invoice is the ratio of orders received for furnaces to shipped and billed for a specified period, generally a quarter or six month. This ratio is my favorable because it is an indication of the performance and outlook for my company. A ratio of above 1 implies that more orders were received than filled, indicating strong demand, while a ratio below1 implies weaker demand. Also indicates the company the ability to efficiency build furnaces. Ratio well above 1, may indicates inability to build furnaces effciently or some of the furnaces are stuck during testing for unforsseble problems. Janusz Kowalewski
Amazing Vacuum Furnaces: Global Vacuum Furnace Market
Around 500 to 525 single chamber vacuum furnaces are manufactured annually worldwide. Approximately 15 multi-chamber systems are sold annually with ±90 chambers, plus 35 custom-made vacuum chambers, such as double chambers and special purpose furnaces. Most, if not all, vacuum furnaces are manufactured in these 12 countries: China, U.S., Germany, France, Japan, Poland, India, Italy, the U.K. Turkey, Taiwan and Canada. Some of the largest vacuum furnace builders are ALD Group-Germany, Ipsen-Germany/USA, IHI-Japan, Chugai Ro-Japan, ECM-France, Seco/Warwick-Poland, GM-USA, Tenova Group –Italy/France/Germany, Fendong-China, SIMUWU-China, Beijing Hua, – China, Solar Mfg.-USA, Centorr-US, and Vac Aero-Canada. For the full list, please go to Furnace Manufacturers page on this Global Heat Treatment Network website.
The table below describes the 30 biggest manufacturing countries with the most attractive markets for vacuum furnaces.
Source: Data from World Bank 2014 and Janusz Kowalewski
Some of the most innovative ideas introduced to vacuum furnaces in the last few months are: a dynamic gas flow, 150 mm curved heating elements, round one piece hot zone insulation with CFC hot face, gas heating, and 3 D control system. Each furnace design differs drastically in cooling speed therefore it is difficult and impractical to classify vacuum furnaces according to cooling pressure. Different vacuum furnaces will cool with different characteristics, even if they share the same cooling pressure. NADCA’s cooling specifications for block 400x400x400 mm (16”x16”x16”) is good for dies but for typical heat treatment loads, a new cooling specification/test should be developed by third and independent organizations such as the Center Heat Treatment Excellence in Wooster MA. One suggestion is that the cooling test should consists of 9 loading thermocouples that are already used for the temperature uniformity, and inserted into 9 inside rods with dimensions of 1” or 2” diameter by 12” long or even bigger, and located in the hot zone in the same pattern as the temperature uniformity thermocouples.
Amazing Vacuum Furnaces: Some Important Details for You to Know
The long delivery items for vacuum furnaces are vessels, flanges, pumping systems, and cooling motors. The number of engineering hours required to design a non-standard single chamber vacuum furnace is between 500 to 3000 of Mechanical, Electrical Engineering and Project Management Hours. Depending on the labor classification and the percentage of fabrication outsourced, the amount of time it takes to fabricate and assemble a single chamber vacuum furnace can takes from 1000 to 3000 working hours. Most vacuum furnaces have standardized designs with similar dimensions. The standard dimension for vacuum furnaces manufactured by the majority of furnace companies in the US and Europe are:
Most heat treatment vacuum furnaces with convection heating are operating from 150°C to 1320°C with good temperature uniformity (AMS 2750 E ±5°C) and vacuum levels in the range of 10-2 mbar (Torr) or with a 10-5 mbar (Torr) with diffusion pump. Special vacuum furnace temperatures may go as high as 3000°C and reach a vacuum level in the 10-8 mbar (Torr) range.
The table below describes the dimensions for a non-standardized vacuum furnace:
Amazing Vacuum Furnaces: Disappointing Market Position of New & Better Technologies
The biggest heat treatment trade show of this year’s Thermoprocess, The Bright Future of Metals, occurred in Düsseldorf and had great press coverage. The next crown master will be the ASM trade show in Detroit in October and the Heat Treatment trade show in Beijing during September.
Companies that started off small couple years ago have grown larger and companies that dominated in 1990 are starting to take the back seats at these shows. The disappointing part of the show in Germany this year was how few new and exciting technologies were displayed. We have all read about the Internet of Things, we all use smart phones, and we’ve all heard of or own our own wearable technology, but heat treatment is slow in adopting these new technologies to make furnaces more efficient and predictable. These new technologies were all missing from the displays at the trade show. The most exciting displays were a one-piece-flow furnace, a concept pioneered by ALD, and a melting furnace door that automatically opened and closed.
When considering the number of vacuum furnaces with Low Pressure Carburizing compared to the number with traditional Sealed Quench furnaces and pusher furnaces, why has the adaptation of Low Pressure Carburizing in heat treatment industry been such a relatively slow process?
From this graph, it is obvious that the two major obstacles for accepting new vacuum technologies are the initial investment cost and the knowledge about the process. Capital costs are declining and interests are low, so the biggest obstacle is the lack of knowledge of the process since the Internet of Things has not penetrated the heat treatment market. This is because of two reasons. First, there aren’t enough real time carburizing sensors that allow heat treat treaters to monitor carbon case creation and the LPC is a computer empirically design process. Second, the people responsible for selecting new vacuum technologies are not familiar enough with vacuum technology and so they are reluctant to select something that is difficult for them to evaluate at the vendor and at their workplace. Some OEMs are more likely to choose well-known and proven technologies than to invest in novel technology.
Amazing Vacuum Furnaces: Vacuum Air and Water Leaks in to Vacuum Chamber.
Until now, I have presented how important the vacuum furnaces are to the heat treatment industry. Today, we will discuss one of common event that is influencing negatively a vacuum furnace performance: air and water leaks into a vacuum chamber.
Air and water leaks to vacuum furnace.
Q1- Leak rate , V – vessel volume, dp/dt pressure rise over time.
Leaks to vacuum chambers (air / water leaks) cost thousands of dollars, creates countless technical problems for the furnace operators. There are two leaks that coexists in any vacuum system: the real and virtual leak. Real Leak is any path through the wall of a vacuum chamber that allows the air/gas to pass through. The Virtual leak is a source of gas in vacuum system that acts like a leak in that gas is trapped in a tight crevice, blind holes, porous welds and leaks out over a long period of time. (Source: AMS2769B) The root cause of these leaks is usually a manufacturing defect within the material or a lack of complying with good vacuum practice.
The below graph is presenting a both leaks. On the Internet there are thousands of articles regarding leak rates measure technique and suggestion how to find a vacuum leaks. Ones of the most difficult to find leaks are:
The furnace insulation, heating element and almost all other components within the furnace will be negatively influence by excessive leak rate. The most effective method to find leak is the Helium Mass Spectrometer. Leak test should be only performed after burn out cycle is performed and furnace is cold, clean, degassed, and empty. To learn more read AMS 2769 B. Paragraph 18.104.22.168 leak checking procedure.
Below is a graph presenting water leak into vacuum chamber through thermocouple port weld in the vessel chamber.
Amazing Vacuum Furnaces: Vacuum History
Vacuum word come from the Latin adjective vacuus for vacant and describes an empty physical space. The 2,500 years ago the Greek philosopher Demokrit thought the first time about and empty space (vacuum), but the famous Aristoteles denied such an idea and he thought about a special matter, what he called Ether. In the middle of the 17th century Torricelli made the first vacuum with mercury filled bended glass tube. Later Pascale prove of the possibility of vacuum with his famous test “vide dans le vide”, what means empty in the empty.
Otto von Guerike made a test with two hemispheres with a diameter of 42cm. The sealing was made of leather soaked with turpentine and wax. The evacuation was done by an air pump, developed by Otto von Guericke. The air pressure within the ball was ~ 100 mbar (75 Torr). In total 16 horses try to pull the both hemisphere, but they could not succeed, as they could not overcome the 13,850 N.
Vacuum Levels at:
Deep Space ≈ 10-17 Torr § Mars ≈ 5 Torr § Lunar Surface ≈ 10-11 Torr § Geosynchronous Satellites ≈ 10-11 Torr § Space Station (ISS) ≈ 10-9 Torr § >264,000 Feet (80.5 km) = U.S. definition of space flight ≈ 10-3 Torr § > 105,000 Feet (32 km) turbojets no longer function ≈ 8 Torr § < 40,000 Feet (12.1 km) cargo & passenger airline flights ≈ 141 Torr Source: Orbitec.com
Fig. 1. Vacuum pumps and the vacuum level.
Fig. 2. Vacuum Gages for the Different Vacuum Requirements.
Fig. 3. Influence of vacuum level (Oxygen level) on metal parts discoloration.
For more information regarding vacuum level requirements for steel and alloys check AMS 2769B Specification, Table 1.
Amazing Vacuum Furnaces: Low Pressure Carburizing
Demand for a higher quality and dissatisfaction with the existing vacuum carburizing processes were the main reasons for development of a new carburizing technology called – Low Pressure Carburizing. The advancement was due to the following achievements:
In the early stage of development in late 1960’s, vacuum carburizing furnaces were using Methane (CH4) as a carburizing gas. Carburizing technology base on Methane requires higher temperature and pressure up to 13 mbar (10 Torr). The process has not provided case uniformity or repeatability needed for parts specifications. Propane popularity in 1970 as carburizing gas was due to ease of transportation and worldwide availability. The major drawbacks of propane are tendency to create soot and tar because of thermal dissociation difficulty, poor holes penetration and problem with carburizing case uniformity in dense pack loads. The process with propane was run at 200–400 mbar (150–300 Torr). The environmental awareness, and a high furnace maintenance requirement was inspiration to develop a new process without the above problems. Russian scientists Krilow, Yumatow and Kubatow developed in 1979 a carburizing process using acetylene in vacuum furnace. The scientists patented process when acetylene is used for carburizing between 9 mbar (7 Torr) to 931 mbar (698 Torr) pressure. The Japanese company IHI (JH) patented in 1999 the low presure carburizing under vacuum with below < 3-mbar pressure. The latest achievements in vacuum carburizing are technologies using Acetylene (C2H2) for carburizing fewer than 20 mbar (15 Torr) pressures. The thermal dissociation of Acetylene last several seconds, enough to react with the hot load surface but not enough to create soot or tar on the furnace elements. The new low pressure vacuum carburizing is applied to a wide range of components from tiny precision parts to automotive gears and transmission components for aerospace, construction and machine industries.
To avoid tar/sooth formation, a vacuum carburizing process must be precisely established and maintain during the cycle. The main parameters influencing carburizing process are mass flow of carbon (gas flow rate), carburizing temperature, vacuum pressure, carburizing and diffusion durations stages. The parts in single chamber furnaces are usually heated by convection heating – up 750°C (1400°F) at 1.5 Bar Nitrogen pressure, follow by further heating in vacuum by radiation up to carburizing temperature. Time of heating and holding depends on particular cross-section, weight and density of load. The vacuum carburizing temperature depends on the alloy steel being treated and is typically between 930° C (1706°F) to 1050°°C (1922°F). When carburizing temperature is reached the carburizing gas is admitted into heating zone from numbers of jets located evenly throughout the entire hot zone. The number and location of carburizing nozzles ensures proper carburizing gas inflows and uniform charge penetration.
The carburizing process is automatically control by PLC/SCADA system.
Acetylene starts to decompose rapidly above 500ºC (932ºF). As the temperature increases decomposition of C2H2 accelerates to form atomic carbon. Hydrogen is a by-product of this decomposition resulting in the reduction of the metal oxides on the surface of components. Reduction of oxides on the surface leads to better penetration of carbon into the surface. The carburizing process can be continues (single pulse) or repeatable carburizing (boost) and diffusion steps (multi pulses). At the first stage the inflow of carburizing gas provide a very high concentration of carbon that can be absorbed by austenite. At the diffusion stage the inflow of carburizing gas is cut-off and replace by Nitrogen to keep constant partial pressure to prevent alloys sublimation. The free carbon atoms are allowed to diffuse into the part.
Diffusion reduces the carbon concentration on the surface and allowing for further carburization. The carburizing and diffusion stages are time controlled. The rapid and continue flow of carbon (gas flow) and higher process temperature shorten the carburizing process. As of today there is no sensor that could effectively control and measure carburizing case formation. Entire process is design by empirical knowledge.
– Acetylene supply pressure: 1,5 bar pe (Europe, Asia); max.
0,9 bar pe (North America)
– Stainless steel pipe connection to furnace min. 1” (DN25) up to 50m length
– Customer has to follow local law for combustible gases if applicable
– For best result use of DMF dissolved Acetylene or Acetylene with 99.5% purity is recommended.
– Acetylene consumption for typical load for single chamber furnace:
|Effective case depth
|300 – 500||0,6||12||400|
|300 – 500||0,8||12||500|
|300 – 500||1,0||12||700|
Amazing Vacuum Furnaces: 10 Best Improvements Made to Vacuum Furnaces Throughout the Years
Amazing Vacuum Furnaces with Broad Process Flexibilities
Vacuum furnaces are designed to process parts that have complicated shapes with high dimensional accuracy. Today, is common to have brazing, austenitizing, quenching capabilities with martempering simulation and double tempering in the same vacuum furnace. Standard modern vacuum furnaces can cover an entire temperature range from 150°C to 1360°C. In the lower temperature range of 150°C to 700°C, the heat can be transferred by convection heating. In the temperature range from 600°C to 1360°C, the heat transfer takes place by means of radiation.
Vacuum furnaces with Nitrogen/Helium pressures reach up to 25 bar, a quenching intensity similar to that of the thermal hardening oils. So a broad range of widely varying material such as superalloys, high– speed steel, cold working steel, High Strength Low Alloy steel (HSLA) and medium-alloy tool steels can be heat treated in the vacuum furnaces. When there is a martempering simulation in quenching the distortion, cracking and the bulging a parts surfaces are minimized.
Brazing is a common process performed in vacuum furnaces. For example, parts that are designed for high thermodynamics, mechanical loading, and resistance to corrosion are commonly made from the material 1.4120 from two or more components. A low distortion, high temperature brazing process followed by a hardening and tempering process, is necessary because machining up later is no longer possible. The parts are first manufactured to 1 mm over production dimensions, mill and drill. Next, parts are annealed in the vacuum furnace and then reworked to within a 3/10 mm accuracy. The level surface must have a plane parallelism of 2 to 3/100 mm and perfect evenness. Surface roughness of 32 to 125 RMS adds surface area to the joint, which provides an extra capillary path for braze filler material to follow and straighten the braze joints. Next, the entire brazing and heat treatment process is carried automatically by PLC/SCADA control system in the vacuum furnace.
The cycle consists of heating, brazing, austenizing, quenching with martempering simulation and double tempering. End user records show that the braze part life increases on average from 300,000 pressing operations to 617,000 after switching brazing processes to run in the vacuum furnace. High temperatures in vacuum brazing and subsequent heat treatment reduces the distortion of the part as well.
For a guide on furnace brazing’s minimum equipment regulations and the process’ procedural requirements, follow the American Welding Society AWS C3.6M/C3.6 2008 specifications.
How To Manage a Furnace Company in the Age of Connectivity
In the new age, where an economy of “sharing resources” plays an important role, new management styles are needed. The sharing economy is when renting, outsourcing and borrowing everything become on demand. In order to adapt to the sharing economy, companies need to create a better working organization to achieve total and absolute customer satisfaction. The traditional management styles in many global markets are not enough to sustain success and create new social capital.
The traditional management styles today are based on principles from the Babylonian, Mahabharata or Benedictine age. What has changed since this time is the speed that decisions are made, the speed of furnace delivery and the importance of total customer satisfaction. Because there is such high competition and the sharing economy allows customers to consider a wider range of companies, companies must focus on customer satisfaction. A company cannot succeed without it. This means that a company needs to not only respond to the customer’s needs, but also anticipate the customer’s wants. Success stories of this include Henry Ford and Apple. Henry Ford successfully created an entire automobile industry without asking customers what they needed, but managed to achieve total customer satisfaction with the Model T. Apple created a product that anticipated customer wants and increased the customer’s own self-satisfaction.
This principle should be converted and applied to the furnace business. Companies should shift their goal to achieving total customer satisfaction. Building a good furnace is not enough to succeed. There are many companies worldwide that manufacture good furnaces, but only a few provide total customer satisfaction. Good furnace performance, sound technological support and available after-sales support do not create an outstanding furnace company. The ability to create something of unexpected value that adds future or extra performance capability is what distinguishes an outstanding furnace company. The goal of the truly amazing furnace company is to provide equipment to the customer that will help the customer successfully compete in their market, lower their heat treatment cost, and improve the end product’s quality.
Outstanding furnace companies striving to be the world’s most connected furnace company with whole supply chain and customer base, and to create extra value futures that don’t just meet customer’s needs but amaze and delight their customers. Janusz Kowalewski
Efficient and Agile Heat Treatment Operations for Competitiveness and Growth
“Inexpensive goods can be produced even when workers are paid high wages”1
“The Principle of Scientific Management” by Frederick W. Taylor, 1911
Improvements in heat treatment technology and complementary changes in organizational structures are necessary to stay competitive in today’s worldwide market. Advancement in heat treatment technology is successful only if it is applied continuously to the entire heat treat process, equipment and organization structure. In order for the manufacturing organization to accept and practice continuous improvement, new organizational structures and new management concepts are needed. An agile organizational structure combined with the advanced digitalization of the manufacturing processes and new equipment based on PLC /IC (Programmable Logic Control / Industrial Computer) allows simplified operation and facilitate automatic diagnostics (routine and preventive maintenance) on the factory floor.
Importance of Equipment Layout, Sequence of Operation and Equipment Utilization in the Lean / Agile Manufacturing System.
The heat treatment process is ingrained in any manufacturing process, regardless of whether the heat treatment is performed in a commercial heat-treating shop or in an in-house heat-treating department. In many cases, efficiency in heat treatment has an important impact on the total efficiency of the manufacturing process and the scheduling and orderliness of the production flow. The following are general guidelines for designing an efficient heat treatment facility:
The challenges facing today’s heat-treating shops are numerous and could be divided into four groups: (1) equipment condition, maintainability and efficiency; (2) process suitability; (3) heat treatment shop layout and cleanness and (4) workforce experience. The equipment disconnection with process requirements is a major problem in achieving production efficiency. Optimizing the heat-treating shop layout requires careful consideration, time, and motion and material movement study. The payback from correctly operation layouts comes in form of reduction of operation cost and safety improvement. Heat treatment equipment layout involves locating the furnaces so that each task follows a pre-arranged route through a series of processes. The parts should flow along a line of processes that is clear, predictable and easy to control. The heat treatment equipment can be laid out according to process, cell production or product type.
Table 1: Layout Assessment
|Process||High mix, low volume and product flexibility
Robust against disruptions
Easy to supervise equipment
|Low utilization of machines
Can have high work-in-progress
Complex flow can be difficult to control,
|Cell||Good compromise between cost and flexibility for high-variety operations
Fast throughput and traceability
|More machines needed
Can give lower equipment utilization
|Product||Low unit costs for high volume
Equipment can be specialized, improving efficiency
Materials movement optimized
Not very robust to disruptions
Source: FACTORY LAYOUT PRINCIPLES, Mark Allington, December 2006 3
An example of a layout according to process and cell production type is presented in the graph below, Graph 1. One-piece flow is gaining popularity in aerospace companies, where traceability is an important factor in production and quality system 4.
The carburizing process was incorporated into cell type production mode. By eliminating storage space, there was more space available and as a result, an improved product flow and traceability was achieved. In One Piece Flow (Cell Layout) gear, components are not heat-treated in conventional big batches with multiple layers, but they are processed in small batches. The One Piece Flow heat treatment provides
All the variations from layer to layer are eliminated, which leads to reductions in variations within the load. In addition, this new technology allows higher cost–savings for logistics. The manufacturing–line can be completely automated since the parts are first taken one by one from the soft machining unit, then heat treated in time with the cycle–time of soft machining (“Synchronized heat treatment”). Then, finally, the parts are passed down one by one to the hard machining unit5.
Fig. 1 Source: Enhance Distortion Control through One Piece Flow, Heuer… AGMA publication 20066
Table 2. Layout furnace and product compatibility
|Layout||Furnace Type||Sample Product Type|
|Process||Batch type furnaces: Sealed Quench, Bell, Box, Single or Double Chamber Vacuum furnaces||Middle size production lot such as mandrels,cutting tools, dies and molds, fuel injection nozzles, high end bearings, electric interrupters, pinions, aluminum coils, forging bars, airplane parts|
|Cell||Batch type/semi-continues: Sealed Quench, Box, Single Chamber Vacuum furnaces.||Small production lots. Semi finish parts, precision gears, shafts, saw blades, complex sub-assembly parts for machinery.|
|Product||Continues furnaces: Roller hearth, pushers, mesh belts, cast links, walking beams, Multi-chamber vacuum furnaces||Mass production parts such as fasteners, automotive gears, bearings, heat exchangers, PM parts, aluminum slabs and sheets|
Source: Janusz Kowalewski
Importance of New Ideas, Quality and the Human Factor in Agile and Growth Oriented Heat Treatment Operation
The future success of any manufacturer in the global market will depend on their ability to correctly implement organizational structure that effectively utilize employees, equipment and natural resources. This means that the success of a company depends on its ability to manage, control and direct resources to maximize manufacturing output. Additionally, quality should be built into every stage of heat treatment activities.
Even the largest and best heat-treating companies cannot succeed in the market without tapping into outside knowledge. The great success of Apple and other technology companies is their ability to draw technical knowledge from experts outside of their own organization. Employees are not the only sources of knowledge for the company. End users, universities and related businesses can provide necessary knowledge to compete successfully. Several years ago, research was conducted on the effectiveness of the engineering staff at the ATT Bell Lab organization. The most productive engineers did not differ from the least effective engineers by education or experience. The single source of difference was that the most effective engineers used the knowledge of several other engineers and established a large support group. Global Heat Treatment Network, Research Association of Industrial furnace manufacturers (FOGI) and ASM (American Society of Metals), play an important role in facilitating and improving interconnectivity between heat treaters worldwide and the newest process and equipment developments.
Management Systems That Increase Effectiveness of Heat Treating Operation
According to the John Boyd studies, a majority of companies will increase their productivity by changing the way they organize production and create “an organizational climate for operation success”7. Optimizing heat treatment equipment up-time, improving employee access to technical assistance and implementing an e-Kanban inventory reduction system will improve a heat treatment operation significantly.
Different management tools are used to increase effectiveness of heat treatment and problem identification such as Six Sigma, Quality Circles, Game Theory, etc. According to research conducted by Clayton M. Christensen and Michael Overdorf “…three factors effect what organization can and cannot do: its resources, its organization and its value.”8
Operation transparency and visualization of a heat treatment operation have the potential to significantly improve the company’s performance. Utilizing one of several computer software programs that are available for visualization of the furnace performance allows gradual cost improvement. Visual representation of the factory floor helps eliminate redundancy and provides Internet connectivity between the equipment and manufacturing processes. Visualization and flat organizational structure allow an efficient allocation of resources and by doing so will increase both the productivity and the competitiveness of the organization.
Continuously monitoring furnaces, washers, loading/unloading, cryogenic freezers, water, gas systems, and loading station allows timely problem recognition. Visualizing the furnace problem on an HMI display allows a faster respond time and more accurate problem definition. Intuitive skill and knowledge of the operation group will allow for more efficient allocation of resources and will increase productivity of the organization.
Lean / Agile Manufacturing Concept Applied to Heat Treatment Equipment
The ability to lower the cost of heat treatment could have significant cost advantages for manufacturers. Heat treatment can be an important competitive edge for any manufacturer that master heat treatment efficiency. According to study, part distortion for gear manufacturers runs in millions dollars per year for the additional cost of machining, scrap and extra material requirements to account for excessive distortion.
In order to increase the efficiency of the heat treatment process, furnaces should be integrated into the production flow of the manufacturing process. Integration is only possible if the control system of the furnace has communication capability with the facility ERP (Enterprise Resource Planning) and CMMS (Computer Maintenance Management System). The furnace integration with the company ERP and CMMS systems assures visualization of the heat treatment process. The goal is to simplify furnace operation and at the same time increase the reliability and efficiency of the furnace. The control system should have the following capabilities:
Furnace operations have changed drastically in the last 5 years. The next task is to design furnaces capable of automatic reasoning during the heat treatment cycle and provide solutions to furnace performance problems. Current development in the control system with PLC/Computer allows instantaneous communication with company production software. PLC/Computer base controls are designed to analyze furnace performance by monitoring all critical components such as vacuum pumps, valves, SCR, contactors, actuators, safety switches, heating elements, water flows, etc. Sensors monitor such parameters as motor vibration, motor temperature, motor’s electric power characteristic, water flow and temperature and heating element resistance. Data indicating parameters outside of the acceptable norm triggers an email or phone massage notification. The new e-manufacturing and lean manufacturing requirements do not make the furnace’s basic design in terms of heat treatment transfer, efficiency of insulation, and sturdy design less important. The “old fashioned” methods are still important, if not more important, for successful furnace operation.
The following are examples which principles should be considered in the equipment design stage:
The three main problems with furnaces on the factory floor are: (1) design, (2) workmanship and (3) operational faults. To eliminate the design and workmanship faults, strict testing is required. To eliminate the operator’s faults, training and “foolproof” control system are required. Each individual component and its subsystem should be tested to confirm their suitability for the task and how they will perform during operation. Testing processes should start from the individual component before it’s assembled into the sub-system. After the components are assembled into an operational sub-system, the sub-system should be tested. After all sub-systems are assembled into operating machines, the entire furnace should be tested. The final testing should be done by the equipment’s manufacturer in an environment as closed as possible to simulate the operational conditions of the end user’s factory floor.
In addition to technical furnace ability the following factors are also important:
The furnaces should be designed with minimum interface between the sub-system and components. A good indication of interface simplicity is the number of interconnecting cables between sub-systems. Another indication of simplicity is what a failed sub-system would do to the operation of the furnace. Will it disrupt the furnace operation completely or allow the furnace operation to continue?
New Vacuum Furnace Design for Agile Manufacturing
Advancements in Vacuum furnaces could be classified in several ways: First, improvement in furnace design, such as insulation improvement (lowering heat input per part or weight of the product) or improvements in heat transfer between the heat source and the load by utilizing combination of convection, conduction and radiation heat transfers. For example, in vacuum furnaces, the convection heating from ambient to 750°C (1400º F.) By combining radiation and convection heating, the heating cycle is shorted by 10% to 45%, depending on load configuration. Recent developments in Vacuum furnaces with gas heating system instate of electric resistance heating elements may lower the cost of operation for vacuum furnaces in the near future. Recent developments in gas burner controls allow them to overcome common problems with gas heating un-uniformly in the vacuum furnaces. The second advancement could be described in terms of operation improvement, such as the flexibility of the furnace, multipurpose furnace usage, self-diagnostic operational and maintenance simplicity. The ability to combine several surface modification processes, such as Carburizing /Nitriding, with traditional hardening or even PM Sintering significantly improve furnace operation and process cost. The third way is to improve the heat treatment process by changing technology; for example, changing a gasto the vacuum low pressure carburizing. Today’s vacuum furnaces are widely used for heat treatment such as annealing, de-gassing, de-stressing, aging (ageing), diffusion welding, sintering, brazing, sputtering, hardening, tempering, carburizing, nitriding and many other specialized processes. This list of applications is certainly not complete and, what more, some of the traditional technologies of heat treatment will change entirely to vacuum in the future. The best example from recent history is increasing the usage of Low Pressure Carburizing (LPC) technology for heat treatment of automobile gears.
Heat treatment equipment and control systems will change significantly over the next few years due to advancements in the Internet of Things, e-manufacturing and Agile Manufacturing requirements. These changes require careful planning, increased time, and a systematic approach to retooling the entire manufacturing operation. The new agile manufacturing principles allow fast and constant transformation of manufacturing processes to satisfy global customers’ wants and needs. The new worldwide market and redesigned factory floor requires employees to be capable of analyzing problems, formulating solutions and utilizing Computerized Artificial Intelligence to it’s maximum potential. Janusz Kowalewski
1 Taylor, Frederick W., The Principle of Scientific Management (1911), W. W. Norton & Company, Inc., 500 Fifth Avenue, New York, NY, 1967
2 Richardson, Chet, Certain To Win: The Strategy Of John Boyd, Applied To Business, Xlibris, 2004, p. 51-57
3 Allington M. Factory Layout Principles, December, 2006
4 Pete Komrowski and Chris Marinucci, Improving Production Safely with Integrated Heat Treat and Quenching Cell Heat Processing for Gear Solution, Fall-Winter, 2013, p. 50
5, 6 Dr. Volker Heuer, Dr. Klaus Löser, and Dr. Thorsten Leist, ALD, and David Bolton, ALD TT Enhancing Control of Distortion Through ‘One Piece Flow – Heat Treatment’
7 Chester W. Richardson, A Swift, Elusive Sword: What if Sun Tzu and John Boyd Did a National Defense Review? Center for Defense Information, 2003, p. 64
8 Clayton M. Christensen and Michael Overdorf, Harvard Business Review on Innovation, Meeting the Challenge of Disruptive Change, 2001.p. 105
Industrial Revolution Version 4.0
Is your heat treatment equipment and organization ready for the 4th Industrial Revolution? This new industrial revolution – Industry 4.0 – is expected to bring major changes in heat treatment, production and how organizations are operated. It is believed there will be a shift from mass heat treatment operations to batch and one – piece flow production models. This is due to the increasing demand for customized products, the need for heat treatment process traceability, and a desire for lower prices.
The advancements in additive technology (3 D Printing) significantly speed up the customization process and how parts are heat-treat and integrated into the manufacturing process. In addition to accommodating the digitalization process (Industrial Internet), additive manufacturing offers several game changes in the field of: geometrical freedom, by allowing one to design new parts without traditional manufacturing constrains; create parts with precise designs customized for individual need; and reducing the amount of waste during the manufacturing process to almost nothing. For example, 20% of the additive manufacturing market arises from medical tools and parts. The new Industrial Revolution started in Europe.
According to a recent PWC study, German companies spend 50% of their capital investment on the digitalization of vertical and horizontal operations. This investment represents an amount of 40 billion Euros every year over the next 5 years. The PWC study shows a dramatic increase in spending on equipment connectivity and the digitalization of the organization process. To fully benefit from the world of the Industrial Internet and achieve a noticeable improvement in productivity by standardizing communication codes, there needs an assurance of communication data security. The digitalization of furnaces, process and service support is essential in sustainable organizational success and profitability.
In light of the shift to digitalization (Industrial Internet), how is this practically implemented in heat treatment process management and the equipment control itself? The key difference today compared to several years ago is the amount of sensors and software necessary to control the furnace in real time and the furnace’s communication with rest of the organization and even with the original furnace manufacturer. In a typical control system, the setting of the vacuum furnace operation is controlled by the PLC (Programmable Logic Controller) with a SCADA display. The furnace performance is supervised by process control software provided by the original furnace manufacturer. This system is connected through interfaces with the company enterprise resource ERP (Enterprise Resource Planning). The furnace control is also connected with furnace manufacturer and the operators via Smart Phones by utilizing a special design app. The special design software controls the furnace production schedule and sequence of the processes in order to fully utilize furnace time. When there is an alarm, an operator, or, in some instances, the furnace manufacturer receive a notification sent by the furnace control system. The use of software tools with text, video and audio ability has lead to significant furnace utilization improvements and time reductions in correctly diagnosing the problem’s root cause. The benefit of correctly applied Industrial Internet is magnified when all equipment in the shop floor are connected into one controlling and analyzing system. Advances in furnace control software and analytic techniques provide means to understand furnace performance conditions and optimize furnace efficiency. Connectivity among heat treatment equipment will enable enhanced asset reliability by optimizing preventive maintenance and repair processes. Are you ready for even bigger game changer – quantum computers? Janusz Kowalewski
Ten New Trends in Heat Treatment: A Global Perspective
Trend # 1:
Demand for heat treatment services and equipment is expanding at a higher global rate (5 to 6%) compare to rest of economic activities (0.5 to 1,5%). The high growth rate leads to an increasing number of furnace manufacturers expecially in Asia and creates intensive competition amongst furnace manufacturers.
Trend # 2:
An increasing usage of vacuum heat treatment technology. An increasing number of double and multichamber chamber vacuum furnaces with lights-out operation capabilities.
Trend # 3:
Increasing digitalization of the heat treatment operations. The growing trend of heat treatment integration into the manufacturing process (One Piece Flow Process). Increasing level of furnace controlability and mantainability by applying “Internet of Things” concept and systems integration.
Trend # 4:
Globalization of heat treatment standards, procedures, processes and furnace designs. Global equalization of heat treatment quality and furnace designs. Increasing importance of furnace safety operation with Zero Accident Furnace Design Philosophy.
Trend # 5:
Replacement of furnaces and technologies that generate high CO2 polution. Increasing importance of brazing, PM sintering and processes with shorten heat treatment cycle in heat treatment.
Trend # 6:
Increasing the importance of Nano and Thermo/Chemical Surface Modification processes. Replacement and modification of quenching mediums – Nanoquenchants, oil mist and vegetable oil.
Trend # 7:
Gradual dismay of mass heat treatment. Growing influence of 3 D Printing – Additive Manufacturing Method on heat treatment.
Trend # 8:
New Sources of Heat – Rotational Magnetic, Active Screen Plasma, Microwave, Laser and Infrared Heating.
Trend # 9:
Increasing sizes of sealed quench furnaces and we may see it decreasing usage of ceramic fiber insulation.
Trend # 10:
Markets with high growth potential for heat treatment – Mexico, India, Indonesia. New markets for future growth – Vietnam, Egypt, Ehtiopia, Ghana and Kenia.
The Two Furnaces That Have Changed the Heat Treatment World Forever
The two furnaces that have changed the heat treatment forever are the Integral Quench and the Vacuum Furnaces.
Integral Quench Furnace:
In late 1940s, Herald Ipsen developed one of the first Integral Quench furnaces in the US. This new furnace revolutionized heat treatment technology by processing parts under a protective atmosphere and quench in oil. Decarburizing, scaling, and discoloration were minimized while metallurgical results reach new level…. Today, Integral quench furnaces are the most popular furnaces worldwide and are used in every corner of the world.
The second furnace that revolutionized heat treatment technology was the vacuum furnace. In early 1910’s, two German companies – Leybold and Heraeus – independently developed the first industrial vacuum furnace with molecular and diffusion pumps. In 1916, Heraeus developed the first metallurgical furnace for melting chromium nickel alloys. Leybold started manufacturing industrial furnaces on a much larger scale in the 1930’s, and Degussa from the 1950’s. In the US a Rhode Island company C.I. Hayes built in 1940’s a first commercial vacuum furnace for RCA for degassing vacuum tube components. National Research Corp, NRC, a startup out of MIT started to build small Industrial vacuum furnace for very high temperature applications starting in the 1950’s. From there spun off Vacuum Industries and Brew and Abar in about 1960. In late 1960’s, a growing need for a vacuum nickel brazing for aircraft jet engine parts created a great demand for vacuum furnaces….
(It will continue…)
This was how it all began. Janusz Kowalewski
Future of the Heat Treatment:
Growing Technologies and Control System in Heat Treatment
The driving force behind developing new heat treatment equipment is reducing the environmental footprint, shortening production cycles, and lowering the cost of operation through more efficient utilization of utilities. The low temperature surface modification processes, with their low distortion attractiveness, will gain higher market shares. Nano Carburizing, Nitriding, Sulfonitriding, Low Temperature Vacuum Carburizing, and LPC are good candidates for a high growth potential within the next decade. Thermo-Chemical surface hardening processes such as CVD/PVD, Boronizing / Boriding will gain more acceptance. Processes with low NOx emission will be replacing the higher and more polluted processes. Vacuum technologies will gain market shares in the heat treatment. The major obstacle for more rapid growth of vacuum heat treatment is the high cost of equipment. As vacuum technologies mature, we can predict that the cost of manufacturing vacuum equipment will decrease. At the same time, the environmental concerns will justify higher costs of vacuum equipment compared to traditional furnaces with protective atmospheres. New sources of heat such as infrared heating and microwave assist technology will be more prevalent on the commercial scale.
Furnace control systems changed drastically in the last 10 years and the progress will continue. In order to increase the efficiency of the heat treatment process, furnaces will be integrated into the manufacturing production flow. Current development in the control system with PLC/HMI allows instantaneous communication with company production software. The goal is to simplify furnace operation, and at the same time increase the reliability and efficiency of the furnace.
The next task for a furnace control development is to design control systems capable of automatic reasoning during the heat treatment cycle and provide solutions to furnace performance problems. Janusz Kowalewski
Sticking problems during heat treatment in vacuum furnaces
A forum discussion, that took place some time back in which I participated, brought me to the idea to write an article about a phenomenon in vacuum heat treatment, called Sticking. Obviously an issue not always understood or not taken care of to avoid this by heat treating operators working on vacuum furnaces. Physical processes like sublimation, evaporation and solid-state diffusion contribute or are causing sticking problems, in fact parts contacting other parts or fixtures may stick together during vacuum operations. Another aspect not always considered during operating a vacuum furnace is the fact that friction coefficients in vacuum and at high temperature are higher than in air and ambient temperature, which may contribute to deformation. The first subject was raised by a heat treater who had problems with sticking problems when hardening high speed steel M4.
It concerned running rolls, up to 15 kg stacked on top of each other. The hardening temperature was 1190 ⁰ C in a vacuum furnace at a partial pressure of 1.2mbar. The question was whether anybody experienced this issue or has any advice on how to prevent the sticking. 45 years after introduction of vacuum furnaces in our heat treatment branch, I considered it remarkable that this issue in vacuum heat-treating operations might still be a problem. As a matter of fact it is a basic physical issue of solid state diffusion that occurs at elevated temperature when contacting clean parts are under a certain load and low vacuum pressure, atoms of one part diffuse into the surface of a contacting part, as such creating a bonding between both parts. When burrs or other irregularities are present on the contacting surfaces, like metal dust or small metal particles are slept in, having a high vapour pressure, this may cause sticking as well. According to table 1 at a hardening temperature of around 1200⁰C, if the partial pressure in the furnace is less than 1.3 x 10¯²mbar chromium will vaporize. Although the pressure chosen of 1.2mbar is not wrong, however obviously too low in the range to avoid sticking. It is often better to select a much higher pressure to reduce evaporation and sticking, also taking into account the tolerance thermocouples and pressure gauges may have. A partial pressure in the range of 5- 7 mbar or even higher, taking into account the weight of the rolls of 15 kg stacked on each other, it would be more reliable to avoid sticking. In the mentioned forum discussion, about 20 comments on this issue were brought in. To avoid metal/metal contact the majority of the forum members suggested to use magnesium oxide, brazing stop-off, alumina paint, boron nitride spray, Fiberfrax, binder free ceramic-and regular paper, mesh made of Kanthal and so on. Some of them work well others require cleaning after vacuum heat treatment or disintegrate. Instead of the risk of contaminating the pump oil or condensation of vaporized metal elements e.g. chromium on cold places in the vacuum furnace, I preferred to suggest to raise the partial pressure, at the same time to put small ceramic bars between the rolls. The intention was not only solving the sticking problem but also to improve more uniform cooling. By putting ceramic bars or plates between the rolls and between the bottom roll and the grid or basket as such creating separation of the metallic surfaces as well as creating space between the rolls improving more uniform and faster quenching the outside as well inside diameter.
An additional advantage of separating component surfaces by ceramic is lowering the friction coefficient, which in vacuum and at high temperature can be 2-3 times higher than in air and ambient temperature. An important issue because the general opinion is that vacuum hardening renders the least deformation, which is not always true. Why? Next time we will discuss this. Hans Veltrop
Table 1. Temperature (⁰C) at which specific vapor pressure (mbar) exists.
More than once I was asked what I was doing for a living and when I answered “heat treatment”, the person thought I was working on central heating systems in homes and buildings.
No one hit on the idea of e.g. steel and other metals and alloys to make them more durable as a tool or a construction part in machinery by heat treatment.
When asked how they thought about making products by tools or car components like gears in gear- boxes to withstand a 100.000 miles and more without making these wear resistant it was understood that without heat treatment we might still live in the early Middle Ages.
This introduction shows how many men and women in the street are aware of what heat treatment brought to them on comfort and allowing them to live a comfortable life.
Although according to archeologists evidence of steel hardening started 3000 years ago it lasted till the Middle Ages that alchemists described processes by which carburizing and nitriding have taken place obviously. Carried out by blacksmiths who annealed hot forgings in bird faeces and quenching knives and swords in boys urine, not knowing why, probably realized the first nitriding effect.
It lasted till the early 1900s when Machlet and Fry introduced the gasnitriding and use of ammonia and Flow published the two-stage process reducing the compound zone.
In 1932 Berghaus and Wehnheldt developed the plasma-or ion nitriding process
Saltbath processes were developed by ICI and later acquired by Degussa introducing Tenifer or Tufftride nitrocarburizing in the 50s.
These three base processes led to a large number of derivative processes developed later on during which over the last decennia the controle of nitriding processes have been optimized.
The large variety of processes and trade names created by commercial heat treaters and furnace builders however may create confusion and misunderstanding.
World trading and global sourcing of parts and products can create purchase specification problems.
In the past consultation between components- or service supplier and buyer, when near-by, national or international opposite to intercontinental was more extensive.
This gearing to one another often was not documented and more an unaware client service. This advising may be lacking in many occasions nowadays in particular when trading globally.
The consequence is that false expectations of norms arise as the requirements of the user may not be described in norms, e.g. steel parts to be surface hardened
The purchase order often contains only the name of a heat treatment e.g. nitriding or nitro- carburizing and a reference to a norm and price & delivery conditions. The required profile of the properties for supplying is often not clear and established. Manufacturing, processing, delivery according to a certain norm guarantees normally a standard quality.
The requirements regarding the properties of the heat treatment are sometimes more comprehensive than the standard quality.
There are standard norm systems globally, covering all kind of details on the processing of nitriding and nitrocarburizing however many individual suppliers prefer to keep their processing confidential.
Therefore besides referring to a norm it is essential to specify certain or better specific requirements on max. temperature, required structure, surface hardness, effective nitriding depth and so on.
Since some decades tremendous developments on diffusion processes like nitriding, nitro- carburizing and surface engineering (Coatings) have seen daylight and implemented into the heat
treatment world. Almost all furnace suppliers and commercial heat treatment shops with or without own input, trademarked their processes. The consequence is that people, not involved in heat treatment, are not aware what is behind the fancy proprierty names.
Global sourcing has increased the confusion buyers and design engineers experience.
It is not sufficient to refer only to existing norms, as they may not reflect what is needed.
Culture and language differences may increase mutual misunderstanding.
Temperature ranges of Nitriding / Nitrocarburizing (2)
Low Temperature Nitriding / Nitrocarburizing for stainless steels Max N 450 ⁰C, C 550⁰ C
Nitriding: Class 1/ Class 2 (Floe process) 500-565⁰ C
Oxynitriding, Sulfonitriding, Oxysulfonitriding 510- 580⁰ C
Ferritic nitrocarburizing 550- 585⁰ C
Austenitic nitrocarburizing 595-720⁰ C
High temperature nitriding 700- 800⁰ C
Solution nitriding of stainless steels 1050-1150⁰ C
If the core hardness is important, tempering of pre heat treatment should be about 30⁰ C higher than the nitriding/nitrocarburizing temperature
For Classic nitriding single and two-stage the norms are clear also for no experts.
SAE AMS 2759/6 specifies the nitriding of low- and higher alloy steels by the use of ammonia and dissociated ammonia.
Single-stage (class 2) nitriding requires a nitriding at 500-525⁰ C and a dissociation rate of 15 to 35%
Two-stage (class 1) nitriding (Floe process) requires a first stage at 500-525⁰ C and a dissociation rate of 15 to 35% and second stage at550 to 575⁰ C and a dissociation rate of 65 to 85%
SAE AMS 2759/10A specifies the nitriding potential to be used instead of the dissociation rate. The specification limits the compound layer thickness in AMS 2759/6 in the same way but adds class 0, where no compound layer is permitted.
Nitriding is carried out in following media:
Gas Nitriding at atmospheric,-low or high pressure in just ammonia with or without addition of nitrogen and or hydrogen. In ammonia with or without nitrogen, oxygen (oxynitriding), sulpher- compound (sulfonitriding)
Plasma as Ion nitriding, DC plasma, Pulsed plasma and Active screen with nitrogen as processing gas with or without hydrogen or argon
Nitrocarburizing processes are carried out in:
Aerated salt baths diffusing nitrogen and carbon into the steel, quenching in oxidation baths and polishing operations in between and subsequently oxidized in an oxidizing bath.
Sulpher containing salt baths.
At atmospheric pressure in ammonia and hydrocarbon or endothermic mixtures, post oxidation, with or without quenching and polishing operations.
Plasma nitrocarburizing adding nitrogen and carbon into the surface.
Nitrotec, Nitemper, Deganit, Soft Nitriding, Triniding, Nitroc, Vacuum Nitrocarburizing, Controlled Nitrocarburizing, Nitro Wear, Corr-i-dur, Oxycad NT
And many more!
Nitreg Potential-Controlled Gas Nitriding
Nitreg –C Potential-Controlled Gas Nitrocarburizing (FNC process)
ONC In-process Post-Nitriding/Nitrocarburizing Oxidation
Nitreg -S Potential-Controlles Nitriding of Stainless Steel
Nano-S Potential-Controlled Nitriding of Stainless Steel with better corrosion resistance
New Nitreg -Ti Nitriding of Titanium Alloys
Black-Tride Post-Nitriding/Nitrocarburizing Oxidation
Plasma (Ion) Nitriding
Sulfinuz, Sursulf, Tufftride, QPQ, KQ-500, SBN, Nitride, Nutride, , Melonite, Meli 1, Isonite, Palsonite
And many more!
Oxinit, Fernit, Plasox, Plastek, Planit, Ultra Glow NC, Nivox LH
And many more!
NITROTEC, KOLENE QPQ, IE.NU-TRIDE, LINDURE,NQ40, NITEMPER, ALLNIT, OXYCAD, TRINIDING,
NITROC, MALCOMIZING, NITRAL, NITREG,CORRIDUR, NITROCARBURIZING, FNC, ANC, NIVOX 2,
NIVOX 4, EXPANITE L, EXPANITE H, SUPEREXPANITE, LOW PRESSURE GASNITRIDING,LINDURE, NAKAL CATALYTIC NITRIDING, OXYNITRIDING, SULFONITRIDING, OXYSILFONITRIDING, PULSED PLASMA NITRIDING, ACTIVE SCREENNITRIDING, NITRAFI, NITROLOX, SOLNIT, IONIT-OX,MALONITE, TUFFTRIDE, ARCOR, NUTRIDE, N-QUENCH, DEGANIT, SOFT NITRIDE, NITRO WEAR, OXINIT, FERNIT, PLASOX, PLASTEK,PLANIT, ULTRA GLOW NC, NIVOX LH, SULFINUZ, SURSULF, KQ-500, SBN, MELI 1, ISONITE, PALSONITE,VACUUM NITROCARBURIZING, CONTROLLED NITROCARBURIZING
What’s in a name!
To get what you want and need you should specify, functional properties such as wear-, fatigue- and corrosion resistance.Important properties of the compound layer are: structure, chemistry, hardness and hardness depth.On the diffusion zone: hardness and depth.Steel properties as supplied: alloy composition, heat treatment condition and core hardness before nitriding / nitrocarburizing.
Based on the above the process parameters are to be defined: such as temperature, time, nitriding potential and gas composition.Quality control at the end should verify to what extend the results meet the specification and the required functional properties.Based on the foregoing it would be an advantage when suppliers of heat treatment processes give some more background info to make selection for buyers and design engineers easier. Hans Veltrop
1). Excerpt of a presentation given earlier at the Nitriding Summit, Wroclaw 8.10.2014
2). Courtesy of Karl-Michael Winter; Process-Electronic GmbH
This morning I read in my daily paper that it is expected that at this fall a number of casualties will be lost due to CO poisoning in their homes starting up their heating system now again as it becomes colder. Lack of professional maintenance is often the main cause that the heating system is dirty or out of balance with the consequence that incomplete burning of the hydrocarbon gas is taking place producing Carbon monoxide.
In chemistry class on high school we learnt that carbon and oxygen are essential elements that rule our being. We never realized that a difference of just one atom in composition of a chemical compound may be a healthy or a deadly issue.
CO is: colourless, poisonous, very inflammable, some lighter than air, odourless and tasteless, large diffusion power and in air mixture explosive. All IQ’s, chamber- and pit furnaces in which CO containing process gases are used, leak CO into and raise CO content in the working area when not adequately ventilated, caused by:
International regulation is diverse concerning what is allowed in working areas.
Mac-values which might be slightly adjusted meanwhile are:
In case of the following CO values, actions to be done and consequences are:
In case of peak values to stay in an environment is limited:
The above values mean in fact that workers on the shop floor when in case of higher CO values are exposed to working conditions that are unhealthy and that their functioning may be less alert and might lead to wrong decisions. As such it is not only a health & safety issue but an economical and quality issue as well.
Fact is that circumstances which cannot be tolerated and in practise occur have been shown by an international investigation on working conditions in western state of the art heat treatment shops of which 40 % showed high and far too high CO contamination in the working zone.
The reason that these circumstances occur is the sneaky properties of CO and in many cases is not recognized by the management of heat treatment shops. To get insight in this phenomenon is simple by installing cheap analysing equipment in the vicinity of heat treatment equipment, measuring and monitor the CO ppm in the air by which corrective actions can be taken.
I remembered the results of this investigation when I read a column on the site of the “Monty” in June in which the question was raised on the future of heat treatment and to what extent the Japanese model should be followed, in fact the discussion on furnace emissions.
Because of the importance of the issue, I copy the article in full with permission of “The Monty”:
The Future of Heat Treating (will we be following the Japanese model)? Over the years we have asked a number of very experienced heat treaters what they expect the industry to look like in the future. While we have heard a number of ideas none of them (with all due respect) were very definite or “earth shattering” for the obvious fact that none has a crystal ball to the best of our knowledge. A fellow the other day though did have a very definite opinion, an opinion which we didn’t particularly like but one which we feel is quite possible furnace emissions. The current almost cult like, fanaticism about greenhouse gas emissions causing global warming (or global changeor whatever it seems to change daily) shows no sign of abating in the near future and the recent decision by the US to work towards closing down coal fired power plants is a perfect example of this (we do agree that reducing pollution is a very worthwhile cause but greenhouse gases are another story in our humble opinion). A recent visit to Japan showed that heat treaters there are constantly trying to reduce all forms of furnace emissions and energy usage with the result that most of the atmosphere furnaces we saw have vacuum purge chambers on both the load and unload stations specifically to trap all emissions. While Japan has taken the largest steps towards this no issue parts of Europe appear to be going this direction also leaving North and South America as the outsiders. All of this takes us to this point; will North Americans be forced within the next few years to be equally as concerned with reducing green- house gas emissions? Far fetched as it might sound our understanding is that one of the largest captive heat treaters in North America has already mandated that all atmosphere furnaces will be shut down within 5 years to be replaced by vacuum carburizing units. We at “The Monty” believe that the only way emissions can be reduced are by switching to vacuum furnaces, expensive modifications toatmosphere furnaces or by converting all gas fired furnaces to electric which of course only pushes the issue down the road to the electrical suppliers. Perhaps it might be far fetched but it is also possible that within a few short years this will become a major issue and we in North and South America will all be looking towards Japan and Europe for suggestions. While we would find this an incredible waste of time and money stranger things have certainly happened. The future? Perhaps. June 26/2014″ End of the Monty article
Although I fully endorse the opinion of ‘The Monty”, I am the opinion that a difference should be made between emissions due to energy usage and atmospheric related emissions.
The solution on energy emissions are still a long way to go whereas emissions due to process atmospheres can be easily accomplished by evacuating before loading and de-loading as described above, but I expect after many attempts in the past, developments recently revealed by S.Bischoff of ROHDE Schutzgasöfen GmbH in Germany in cooperation with IWT Stiftung Institut für Werkstofftechnik,Bremen-Germany but also a promising project of Air products and Chemicals Ltd and inventer Zbigniew Zurecki et al, are quite promising to reduce CO₂ and CO emissions from furnace atmospheres by absence of oxygen in mixtures of just nitrogen and hydrocarbons at the same time reducing IGO.
After all it is remarkable that a difference of one atom of oxygen in a molecule CO which by lack of one oxygen atom causes that our blood is incapable to transport the oxygen to our vital organs and may cause dead, whereas an additional oxygen atom in the molecule CO₂ is needed to bring us so much joy drinking beer with a nice foam on it or making champagne sparkling and to finish this blog on a technical manner CO₂ is used to stop a fire; very remarkable but we have to live with it. Hans Veltrop