What process holds a soft spot in your heart? Tempering or annealing? For Valentine's Day, turn up the heat -- errr heat treatments -- with this look at the differences in tempering and annealing! Heat TreatToday has resources for you to spark some thought and learning on these processes.
Sentiments and strong feelings can certainly be heightened this Valentine's Day. While tempering and annealing may not lend themselves easily to the holiday, we hope you enjoy a bit of a nod to the day in our headings below. Make use of the Reader Feedback button, too, and keep us in the loop with questions and comments on what heat treatment you love.
Problem with Annealing? Get to the Heart of the Issue
An automotive parts manufacturer was running into problems with cracking parts. The variable valve timing plates were returning from heat treatment with this problem. To determine why those parts were cracking after the annealing process, an investigation was launched by metallurgists at Paulo.
The presence of nitrogen combining with the aluminum already present in the particular steel being used was forming aluminum nitrides. What could be done? Read more in the case study article below to find out a workable solution that allowed the annealing to create a crack-free product.
Induction, Rapid Air, Oven and Furnace Tempering: Which One do You Love?
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This article gives some perspectives, from experts in the field, on what kinds of tempering are available and for what the processes are used.
Hear from Bill Stuehr of Induction Tooling, Mike Zaharof of Inductoheat, and Mike Grande of Wisconsin Oven with some basics and background information on tempering. Those reasons alone make this resource helpful with information like this: "tempering at higher temperatures results in lower hardness and increased ductility," says Mike Grande, vice president of sales at Wisconsin Oven. "Tempering at lower temperatures provides a harder steel that is less ductile."
More specific in-depth study is presented as well. The Larson-Miller equation is considered, and the importance of temperature uniformity is emphasized. Read more of the perspectives: "Tempering: 4 Perspectives — Which makes sense for you?"
Cast or Wrought Radiant Tubes in Annealing Furnaces - is Cheaper Really What to Fall For?
Marc Glasser, director of Metallurgical Services at Rolled Alloys, takes a look at radiant tubes. He particularly discusses the cast tubes and wrought tubes. For use in continuous annealing furnaces, there are several factors contributing to choice of radiant tube type.
Marc says, "Justification for the higher cost wrought alloy needs to take into consideration initial fabricated tube cost, actual tube life, AND the lost production of each anticipated downtime cycle as these downtime costs are often much more than material costs." He probes into areas that may not be considered when thinking of all the costs involved. Read more of his article "Radiant Tubes: Exploring Your Options."
Tempering Furnaces: Improvements are Thrilling
The expert behind this piece shows the importance of tempering, particularly in automotive fastener production. Tim Donofrio, vice president of sales at CAN-ENG Furnaces International Limited examines what's working in the tempering furnaces. The products are meeting and exceeding expectations.
To wrap up this Technical Tuesday post on tempering and annealing, head over to this additional resource to round out the scope of each process. "What is the Difference: Tempering VS. Annealing" gives a summary perspective on the heat treatments discussed above.
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Tempering. A vitally important step in the hardening process and a process that is used extensively throughout the heat treatment industry. There are three main schools of thought on how to achieve a properly tempered part. Here we have asked three experts to share their knowledge on the specific approach they feel works best for tempering: Bill Stuehr of Induction Tooling, Mike Zaharof of Inductoheat, and Mike Grande of Wisconsin Oven. Learn how each approaches tempering and why they feel it works well for them.
Please note that mechanical properties and microstructure, in addition to hardness, need to be carefully considered when choosing any tempering process so as to help ensure the part is fit for its intended purpose.
This Technical Tuesday article first appeared inHeat Treat Today’sMay 2022 Induction Heating print edition.
Induction Tempering: Captive Heat Treating
By William I. Stuehr, President/CEO, Induction Tooling, Inc.
William I. Stuehr President/CEO Induction Tooling, Inc.
I can only speak to this subject through a lens of 46 years and thousands of induction hardening applications. That said, I have had many tempering inductor requests within the domain of captive heat treating. The commercial induction heat treaters that I service most always use oven tempering because it is accurate, economical, and easy.
Figure 1. Wheel bearing hub and spindle sectioned and etched to show the selective hardened surfaces. Source: Induction Tooling, Inc.
For the captive heat treat departments processing high volume components, the interest in induction tempering as an in-line process sparked in the mid-1970s with the production “cell” concept. This was most evident in the manufacturing of modular wheel bearing assemblies – raw forgings were fed into the cell and completed units exited. Modular wheel bearings are composed of a hub and a spindle. Within the production cell both needed selective induction hardening and tempering. The specification for the wheel spindle required a casehardened profile to provide wear and strength and for the wheel hub, the bearing races were hardened. Equipment manufacturers designed and built specialized high-volume parts handlers, integrated with the proper induction power supplies to operate efficiently within the cell. The inductors, both hardening and tempering, were designed, built, and characterized to produce a specification hardened part (Figure 1).
Figure 2. Thermal image of a wheel spindle Source: Induction Tooling, Inc.Figure 3. Truck axle and truck axle temper inductor Induction Tooling, Inc.
Induction hardening for the hub and spindle is quick – usually five seconds or less; induction tempering is a much longer heating process. Both parts required a low power soak until the optimum temperature was achieved. For the two wheel bearing components, tempering had to be accomplished either in a long channel-type inductor or several multi-turn inductors to keep pace with hardening. The long channel inductor was designed to hover over a conveyor belt. The belt would move the hardened hub or spindle at a slow, even pace allowing the precisely controlled induction energy to migrate throughout. Care was taken in the design and length of the channel inductor to assure temperature uniformity. Multi-turn inductors are circular solenoid designs that required the hub or spindle to lift and slowly rotate at three or four locations in order to complete the temper. As in hardening, the temper installation required its own induction power supply. Thermal imaging confirmed the results (Figure 2).
Truck axle shafts are another high production component that is induction hardened and tempered. Often the axle shafts are robotically loaded in a vertical or horizontal inductor. The shaft is rotated, heated, and then shuttled to a quench position. The loading robot then moves the hardened axle shaft to another inductor, usually within the same unit, specifically designed for the tempering process. A separate induction power supply controls the input energy. The temper time can be equal to the induction hardening time added to the quenching time. This will allow for the proper input of uniform induction temper energy (Figure 3).
Today, high production automotive driveline components are routinely induction tempered. Among the examples explained are CV joints, gears, and camshafts. Monitoring of the induction energy is different compared with furnace tempering. When heating parts with complex geometries, it is necessary to focus upon where the induction energy is concentrated. Heat conduction can be carefully monitored to confirm that an overheat condition does not occur at the target temper areas. Power input, soak time, and inductor characterization control these
fundamentals.
Induction tempering is sometimes attempted using the hardening inductor. For some very low volume parts, depending upon the part geometry and induction power supply frequency, the results may be acceptable. Careful power control and timing along with thermal imaging is needed to confirm the results. Again, since tempering takes longer, output will be much slower. Experience has demonstrated that a part specific tempering inductor coupled with a dedicated induction power supply works best.
About the Author: Bill Stuehr is the founder and president of Induction Tooling, Inc, a premier heat treat inductor design and build facility. The holder and partner of many induction application patents, Bill shares his expertise and generously donates his time and facility resources to mentor young students entering the heat treat industry.
By Michael J. Zaharof, Customer Information & Marketing Manager, Inductoheat
Michael J. Zaharof Customer Information & Marketing Manager Inductoheat
Induction tempering is the process of heating a previously hardened workpiece to reduce stress, increase toughness, improve ductility, and decrease brittleness. A medium-to-high carbon steel (i.e., 1045, 1050, 4140, 5160) heated above the upper critical temperature causes a high-stress shear-like transformation into very hard and brittle martensite. This untempered martensite is generally undesirable and too brittle for postprocessing operations such as machining and can pose a concern for poor performance in high fatigue applications. Therefore, tempering is needed to reduce internal stresses, increase durability, and reduce the possibility of cracking.
In most cases, induction tempering occurs in-line and directly after the induction heating, quenching, and cool-down operations. Traditionally, workpieces are moved to a tempering spindle or separate machine after hardening. Once moved, the part is then inductively heated and often force cooled to ambient temperature. The induction tempering process itself generates temperatures on the workpiece (typically) well below the curie point (248°F-1112°F/120°C-600°C – solid blue line in Figure 1). This phenomenon is referred to as “skin effect,” where the current density is highest at the surface of the material. Therefore, a lower inverter frequency is most desirable in order to increase the electrical reference depth.
However, while most cases reflect a secondary/separate station for induction tempering, this is not always the case. Recent advancements in power supply technology permit “real-time” frequency and power adjustments. These next-generation induction power supplies have brought tremendous flexibility into the market and have allowed induction hardening and tempering to occur at the same station, on the same induction coil. Using such a novel approach with induction heating often speeds up production while reducing the number of part movements. Induction tempering is a preferred method for many manufacturers as it offers several notable advantages. In production applications, it is viewed as a fast-tempering method, as the parts are heated quickly, cooled, then moved on to the next operation, reducing potential bottlenecks.
There is no need to collect the parts, place them into batches, and wait for long subsequent processes to finish before moving them down the production line.
Figure 1. The induction tempering process itself generates temperatures on the workpiece (typically) well below the curie point. Source: Inductoheat
Induction is a clean process and does not rely on combustible gases or chemicals that may be harmful to the environment. Additionally, it is also a very efficient process as induction power supplies are only powered on when needed compared to batch processing (like those requiring an oven). Ovens must be preheated prior to use and can often stand idle for long periods between batches, as the pre-heat/cooldown cycles can be lengthy. Induction heating equipment is also physically smaller in most cases and occupies much less real estate on the manufacturing floor.
Individual part traceability and data collection are possible when utilizing induction tempering. If paired with a quality monitoring system (QAS), data can be evaluated in real-time and compared to a known good “signature” for the part during the induction tempering process. This allows precise control of the process and the ability to reject parts that deviate outside of established metrics. It is also an effective tool for detecting process issues early when a variation occurs minimizing potential scrap and helping to prevent delivery of “bad” parts to the end customer.
Induction tempering offers many advantages over other methods of tempering and is an effective choice in many applications. Due to the benefits of speed, efficiency, repeatability, and environmental cleanliness, induction technology is widely accepted and is being used throughout many industries today.
References:
[1] “In-Line Tempering on Induction Heat Treating Equipment Relieves Stresses Advantageously,” by K. Weiss: Industrial Heating, Vol. 62, No. 12, December 1995, p. 37-39.
[2] “Induction Heat Treatment: Basic Principles, Computation, Coil Construction, and Design Considerations,” by V.I. Rudnev, R.L. Cook, D.L. Loveless, and M.R. Black: Steel Heat Treatment Handbook, G.E. Totten and M.A.H. Howes (Eds.), Marcel Dekker Inc., Monticello, N.Y., 1997, p. 765-871.
About the Author: Michael Zaharof is a customer information & marketing manager at Inductoheat in Madison Heights, Michigan. He has been with the company since 2011 and has worked in the sales application, digital media, outside sales, and engineering departments. Michael has a bachelor’s degree in computer science in information system security.
By Mike Grande, Vice President of Sales, Wisconsin Oven
Mike Grande Vice President of Sales Wisconsin Oven
Tempering (also known as “drawing”) is a process whereby a metal is heated to a specific temperature, then cooled slowly to improve its properties. It is commonly performed on ferrous alloys such as steel or cast iron after quench hardening. Quenching rapidly cools the metal, but leaves it brittle and lacking toughness, which is a desirable characteristic that represents a balance of hardness and ductility. After quenching, the material is tempered to reduce the hardness to the required level and to relieve internal stresses caused by the quenching process. The resulting hardness is dependent on the metallurgy of the steel and the time and temperature of the tempering process. Tempering is performed at a temperature between approximately 255°F (125°C) and 1292°F (700°C). In general, tempering at higher temperatures results in lower hardness and increased ductility. Tempering at lower temperatures provides a harder steel that is less ductile.
Draw batch ovens: the high-powered workhorses of the tempering process Wisconsin Oven
Tempering is performed in a convection oven using a high volume of air circulating through and around the load of steel being tempered. The air is heated in a plenum separated from the load, then delivered to the load at high velocity through distribution ductwork using a recirculation blower. Since the air is the medium used to carry the heat from the source (a gas burner or heating elements) to the load, it is important that the blower recirculates a high volume of air through the heating chamber. Further, since air becomes significantly less dense at higher temperatures, the recirculated air volume must be higher for ovens operating at higher temperatures in order to provide sufficient mass (pounds or kilograms) of air to transfer the heat from the source to the load.
For example, a typical batch tempering oven designed to process a 2,000 lb. load with dimensions of 4′ x 4′ x 4′ might have a recirculation rate of 10,000 cubic feet per minute (CFM). At this airflow volume, the oven recirculating system operates at 156 air changes per minute, which means all the air passes from the recirculating blower through the heating chamber 2.6 times per second. At a temperature of 1000°F (538°C), for example, the weight of the air being recirculated is 290 lbs. (132 kg) per minute, or 17,400 lbs. (7,909 kg) per hour. It is this high volume of air that provides good heat distribution to the load being processed and ensures tight temperature uniformity within the load during tempering.
The higher the mass of air being recirculated, the tighter the temperature uniformity will be. The temperature uniformity (±10°F or 6°C, for example) defines how much the temperature is allowed to vary within the load being tempered. If the oven operates too far outside of this tolerance, the parts may not be tempered uniformly, and the hardness might vary among different parts in the same load. It is important that the temperature uniformity of a tempering oven be verified (“certified” or “qualified”) by testing, and that this is repeated periodically, as well as after any changes or repairs are made that could affect the uniformity.
About the Author: Mike Grande is the vice president of Sales at Wisconsin Oven with a bachelor’s degree in mechanical engineering and over 30 years of experience in the heat processing industry. Over that time, he has been involved with convection and infrared technologies, and several industrial oven energy efficiency design advancements.
The next type of tempering we’d like to address is rapid air tempering. This process involves “any tempering technology taking advantage of rapid heating methods combined with shortened soak times at temperature based on those predicted by use of the Larsen-Miller calculator.”1 Here “rapid heating” is defined as “any heating method that accelerates conventional furnace heating.”2
Table 1.3 Thermal profile of conventional tempering and vertical rapid air furnaces
Rapid air tempering takes advantage of the use of a higher initial heating temperature (i.e., the use of a so-called heat head) to drive heat into the part more quickly. Additionally, rapid air tempering shortens soak time at temperature (from the more conventional furnace tempering times).
The Larson-Miller calculator is used in rapid air tempering to provide a comparison of hold times at various tempering temperatures and the results of tempering time change is assumed be the same (see example below); however, the interpretation of the data and results are left to the end user.
Larson-Miller Calculator
There are various reports describing the use of the Larson-Miller equation for assessing stress-relieving and tempering process conditions.4 “The relationship between time and temperature can be described as a logarithmic function in the form of the Larson-Miller equation, which shows that the thermal effect (TE) is dependent on the temperature and the logarithm of time:
“This thermal effect is also interpreted as the tempering parameter. For example, a material that is required to be tempered at a temperature of 740°F for one hour has the same TE as a material treated at 800°F for 6 minutes (Fig. 1).”5
Figure 1.5 The “TE” is a logarithmic function of time
References:
[1] Roger Gingras, Mario Grenier, and G.E. Totten, “Rapid Stress Relief and Tempering,” Gear Solutions, May 2005, pg. 27-31.
[2] N. Fricker, K.F. Pomfret, and J.D. Waddington, Commun. 1072, Institution of Gas Engineering, 44th Annual Meeting, London, November 1978.
[3] Thomas Neumann and Kenneth Pickett, “Rapid Tempering of Automotive Axle Shafts,” Heat Treating Progress, March/April 2006, pg. 44.
[4] Lauralice C.F. Canale, Xin Yao, Jianfeng Gu, and George E. Totten, “A Historical Overview of Steel Tempering Parameters,” Int. J. Microstructure and Materials Properties, Vol. 3, Nos. 4/5, 2008, pg. 496.
[5] Roger Gingras and Mario Grenier, “Tempering Calculator,” in ASM Heat Treating Society, Heat Treating: Proceedings of the 23rd ASM Heat Treating Society Conference September 25-28, 2005, David L. Lawrence Convention Center, Pittsburgh, Pennsylvania, USA, Daniel Herring and Robert Hill, eds., Materials Park, Ohio: ASM International, 2006. pg. 147-152.
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Heat TreatToday was honored with the opportunity to visit the University of Akron and meet several senior engineering students in a Senior Capstone Program focused on a collaboration with heat treat industry leaders.
Applying their academic knowledge and background experience of heat treat and engineering, the students collaborated with and were mentored by Bill Stuehr of Induction Tooling, Inc. and Joe Powell of Akron Steel Treating Co. and Integrated Heat Treating Solutions. The result was an innovative new approach to push the bounds of heat treat. Read about how these students were a part of developing an induction and intensive quench heat treat solution.
By Bethany Leone, Editor,Heat Treat Daily
“You'll never be bored of learning from others. And then, people learn to work as a team and come up with crazy ideas and make that dream a reality! That's [why] this is God's own country. Again, invention country.”
– Dr. Gopal Nadkarni Ph. D., University of Akron
Introduction
At the University of Akron, innovation and invention are being pushed to their limits. Senior engineering students under the guidance of Dr. Gopal Nadkarni have, for the second consecutive year, taken on heat treat theory and practice to test accepted norms in heat treat. But this isn’t just for an academic grade. Their collaboration with professional heat treaters in Ohio makes them engineers on the frontlines of advancing heat treat methodologies and part design.
Left to Right: (Top Row) Dennis Kopacz, Jared McLean, Shadoe Beatty, Tom Benenati, Matthew Yokosuk; (Bottom Row) Dr. Gopal Nadkarni, Bill Stuehr, Joe Powell
Dennis Kopacz, University of Akron ‘21: Age 23. “I’ve always been a problem-solver when I was in class and anything. I loved it . . . As a mechanical engineer, I feel we have a very, very broad spectrum of different avenues we can take.”
Jared McLean, University of Akron ‘21: Age 28. Prior to college, he worked four years in industry and would troubleshoot operations at his former manufacturing employer and was a big part of transitioning them to automation. Jared will return to his former employer and hopes to get his foot back into automation and learn more about design.
Shadoe Beatty, University of Akron ‘21: Age 23. Shadoe shared, “I do enjoy manufacturing. . . but I would like to be a design engineer as well.”[/tab][tab title ="Thomas (Tom) Benenati"]
Thomas Benenati, University of Akron ‘21: Age 22. “Understanding different material properties and how you can get those properties in different ways was really interesting. The induction and quenching project, just put a whole new perspective on that. . . As of right now, I just really like learning I really like. . . Every single engineering process, I’ve just been really interested in.”
Matthew Yokosuk, University of Akron ‘21: Age 23. “I’ve always been a hands-on learner, I’ve always loved to build things. . .So it just felt kind cool that I could go into something engineering where I could just build more.” Matthew is focused on looking for jobs in manufacturing.
Dr. Gopal Nadkarni Ph. D.: Academic professor who initiated the Capstone Senior Project between University of Akron students and Bill Stuehr and Joe Powell.
Bill Stuehr: Bill started his company in his parents’ garage. Now, Induction Tooling, Inc. is helping clients — and students — out of Ohio. Bill’s contributions in both a financial and mentorship capacity were thanked by students from both phases of the project.
Joe Powell: Joe Powell is a leading expert in quenching technology who leads Akron Steel Treating Company and Integrated Heat Treating Solutions in various, innovative heat treat applications. His knowledge on intensive water quenching, molten salt quenching, and gas quenching brought him into the fold, particularly in the second year of this project’s development of the patent pending modified Jominy + HPIQ™ end-quench tester that was developed with co-inventor, Bill Stuehr.
The Guinea Pigs
A senior project collaboration between the University of Akron and Induction Tooling, Inc. (ITI) began in the Fall of 2019. Can a heat treater conduct a Jominy end-quench test* by integrating induction heating above the quenching system versus using a furnace and having to carry the sample across the laboratory floor? This was the question that this first group of students and their professor, Dr. Nadkarni, had for Bill Stuehr, president of ITI.
“I remember us telling Bill exactly what [we] wanted to do,” one senior engineer student recalled, “and his response was ‘So what is your budget?’ My answer was simply, ‘Well kind of [. . .] zero.’ I still look back and laugh, because I know that's not what he was expecting to hear. But that didn't stop Bill from wanting to help, and I know most companies would have laughed at us and walked us out.”
With Bill from ITI and Joe Powell from Integrated Heat Treating Solutions, the University of Akron students did design an induction to quench process with new machinery to perform a Jominy end-quench test in one space.
Bill Stuehr with Senior Project 2020: Induction Quench Tub.
“It's a green energy process,” described Stuehr, “so, we can put in an induction unit, heat the rod to a proper temperature using IR [infrared] to control that temperature to the feedback [going] to the induction unit, and then transfer it, drop it right into the Jominy quench, and do your testing. That way, it eliminates heating up a furnace and the energy it takes to [use it] and the dissipated energy that's wasted. And the transfer is almost immediate, because we're going to be heating in the same position [that] we're going to be quenching [the heated sample] with the Jominy tester.”
The students, having learned about traditional and innovative heat treat practices in this hands-on process, walked away with a deeper knowledge of heat treat and a deeper understanding of the equipment that goes into the development of new processes. A graduating student from this first group in 2020 succinctly stated: “Working with Induction Tooling Inc. really made me want to understand more and more about induction heating. This technology, to me, used to be black magic, but now, getting to understand what is happening, it just keeps getting more and more fascinating.”
Taking the Induction Jominy End-Quench Test to the Next Level
Seeing the success of the first projects, the 2021 seniors and their professional heat treating partners decided to redesign the set-up based on the previous class’s work on integrating these two processes in order to intensively quench the part. Instead of a “drinking fountain,” the team set the goal on 400 PSI “instant-impact” quench on the end of the rod.
Going from a standard Jominy end-quench to an intensive quench with a blast of 400 PSI, said Jared, 2021 senior engineering student, was unthinkable. “At first,” Jared McLean, 2021 senior engineering student reflected, "I thought there's no way. But with the help of Bill and Joe in the design process, [we were] able to capture all that water . . ., and we got great results.” Further, Jared noted, the results mimicked the traditional Jominy end-quench test and “help prove intensive water quenching" can enhance the inherent hardenability for a given alloy.
The team went through a variety of designs, eventually deciding on the use of a different shaped sample rod, versus the traditional flat ended rod, for the test; the high pressure necessitated the use of a lid with one hole to contain the 400 PSI water coming from a “pepper shaker head” and redirect the excess water into the holding tank. In the words of the students, they used an inverted stainless steel “salad bowl” with a hole in the center that went on top of this structure to contain the high pressure quench media. An induction heated Jominy end-quench test rod (of a patent pending design) was lowered into the “salad bowl” hole to be quenched in situ.
Stuehr narrated how Jared, Dennis, and other students developed this construction:
“We [Jared, Dennis, and Bill] tested the [multi-hole] saltshaker [. . .] out in a parking lot on a cold day like today getting wet [. . .]. It didn't work.
“So, we decided, Okay, now what? Let's go down to one hole, so we have a [single-hole] pepper shaker. Now the pepper shaker [. . .] it's got a hole in it, right? And the water comes in through from the pump into the pepper shaker and shoots up and hits the end of this rounded rod. So, we tested it again in the parking lot, just shooting it out there, and [some of the] students did measurements in the tank to measure the flow to see if we could reach the four gallons per minute, at least 400 PSI, because we felt that's about what maximum we're going to be able to get out of this pump.
“We tested in the parking lot, and we're shooting it up to the roof. It looked pretty good. We were measuring the outflow, and we were matching the 4 gpm at about 400 PSI. So, then we took that, and then with the students help, we built a container.
“[We began testing.] First test worked perfectly. Worked perfectly, it just quenched out. You had to hold the handle down because we were afraid of ejecting the Jominy rod from the high pressure, but it contained the quench and did everything it was supposed to do[. . .] hitting the end of the rod and dissipating the quench around this end into this salad bowl, and then delivering the water back into the 55-gallon drum…”
The project was a success, and Dr. Nadkarni accepted the work between the students, Joe Powell, and Bill Stuehr. The students walked away with a better understanding of both traditional Jominy hardenability test standards and had actually developed a new heat treating tool to test the “maximum” hardenability of a given alloy of martensitic steel – all from this “crazy idea.”
2021 Student Reflections on Phase 2
Several of the senior students from the 2021 graduating class noted that their experience was a smooth transition from academics to hands-on heat treat equipment. Jared and another 2021 senior, Dennis Kopacz, said that they were constantly learning on the job; and with the knowledge of Joe Powell and Bill Stuehr, the work transition was smooth, since they had so much to do in such a short time.
Left to Right: Jared McLean, Bill Stuehr, Tom Benenati, Dennis Kopacz, and Shadoe Beatty.
Jared added that they learned a lot using the CNC computer numerical control router controls for the induction heater used to moderate the induction heating temperature and heating rate as well as the quenching process; everything was so precise, and it was incredible to see those types of processes.
“When I first got into the Senior Capstone Project,” Jared reflected, “I had very little knowledge of material science and getting into hands-on and really involved projects; I had to do a bunch of research on what was going on, and I learned a great deal, specifically about how heat treating works.”
These senior engineering students were also surprised at the success of the high pressure intensive water quenching method that Joe Powell and Bill Stuehr introduced to them. “We were in shock,” Dennis admitted, “because we didn't expect it to [work]." The expectation, Dennis continued, was that something would go wrong, like the lid would not be able to clamp down, or the container would leak. But when he and his classmate, Shadoe Beatty, 2021 senior engineering student, witnessed the successful increase in hardness, “it blew our expectation out of the water.”
Not only that, but the passion of this new method struck a chord with several students: “I think the most surprising thing for me was just even with the whole gravity of this project,” Matthew stated. “I think I speak for all of us: we didn't really know that much about material properties coming into this, but quickly, I realized that this project was . . . something almost groundbreaking, even.” He later added, “The opportunity to work with Bill especially has been eye opening to what is possible. Bill and his team at Induction Tooling were so eager to help, and our team is very appreciative of their willingness to support this project. Their knowledge on this subject is invaluable for us graduating engineers.”
The Future
According to Dr. Gopal Nadkarni, each year, the process develops further: “Successive generation of student who [come] in get fired up, red hot; they learn the material properties. They learn the value in manufacturing.” He expressed his hope for changing heat treatment practice, saying that as each new round of students come through, they will raise the bar of heat treatment by working through this one project and developing new standards.”
Rising seniors, Josh Ramirez and James MacKita, are both looking forward to getting into the in-depth co-op as they finish their academics in 2021-2022.
Bill Stuehr said that as one sees the enthusiasm of the students on this project, “one can see underlying aspects of their personalities and how they contribute to the overall process of manufacturing in the United States in the future. This is their future, and this is what we're trying to encourage.”
*Editor’s note: Our friends over at Thermal Processing published an insightful article by D. Scott MacKenzie, PhD., FASM on this test. Find it here.
What process holds a soft spot in your heart? Tempering or annealing? For Valentine's Day, turn up the heat -- errr heat treatments -- with this look at the differences in tempering and annealing! Heat Treat Today has resources for you to spark some thought and learning on these processes.
Find heat treating products and services when you search on Heat Treat Buyers Guide.com
Rapid Air Tempering
