Effective November 30, 2023, Joe A. Powell has sold his remaining shares in Akron Steel Treating Company, his family’s commercial heat treating business for over 80 years in Akron, Ohio, USA, to a fourth generation of new “family” ownership.
The team at AST will continue to deliver ISO and Nadcap aerospace heat treating and related metallurgical services to part making customers.
Joe A. Powell, AST’s Chairman of the Board, will remain active in the heat treating and metallurgical services community as president ofIntegrated Heat Treating Solutions, LLC. (IHTS). IHTS is a “heat transfer” consulting company for product development teams to enable more sustainable heat treating equipment and practices to be integrated into their new product designs. IHTS and its team of part making consultants enable their part making clients to deliver more “total added value” from heat treating and forging per BTU expended in making their products for their end users; including the design of the associated heating and quench cooling equipment for "leaner + greener, more sustainable, manufacturing" and for greater recyclability of metal alloys.
Pictured in the image above: AST’s new shareholder team, and Joe A. Powell, Chairman of the Board, are pictured from left to right: Matt Moldvay, President; Steve Powell, Vice President of Quality, Christina Powell Somogye, Vice President of Administration; Joe A. Powell, Chairman; and Joe N. Powell, Vice President of Sales. (Source: AST)
(Click the name above or the image to the right to view and download the report.)
The following report was featured in a Heat Treat Radio episode with Joe Powell, president of Integrated Heat Treating Solutions. In the episode, Heat Treat Radio: Rethinking Heat Treating (Part 4 of 4) — Direct from the Forge, Joe shared the time- and resource-saving potential by intensively quenching parts straight from the forge. This interview was the fourth in a series of episodes in which Joe explained how heat treaters could bring their processes into the 21st century.
An excerpt from the episode: “We can save up to 66% of the energy that’s needed to heat treat that part[…] I’m not going to make a lot of friends in the areas that do this, but if we’re going to compete in the world and make great parts, be lean, save energy, and also have safe carbon emissions, we’ve got to stop heating parts that don’t need to be reheated if you can avoid it[…] there’s a lot of parts that could be made a lot more efficiently if we would quench them right at the trim die.”
“This report presents results of the application of the Direct from Forge Intensive Quenching (DFIQTM) process to steel forgings obtained in the project’s Investigation, Development, Testing and Implementation stages. For proving and quantifying of the DFIQ process benefits, a portable 600-gallon IQ water tank was designed and built. Forgings of different configurations, ranging in weight from 4 to 80lb and made of plain carbon, alloy and high-alloy steels were subjected to the DFIQ process. DFIQ trials were conducted at three forging shops: Bula Forge & Machine of Cleveland, Ohio, Welland Forge of Welland, Ontario and Clifford-Jacobs Forgings of Champaign, Illinois (both of the IMT Forge Group). The following material mechanical properties were evaluated: tensile strength, yield strength, elongation, reduction in area and impact strength. Data obtained on the mechanical properties of DFIQ forgings were compared to that of forgings after applying a conventional post-forging heat-treating process. Values of heat transfer coefficients in the DFIQ tank were determined experimentally using a special probe. This data was needed for calculating an optimal dwell time when quenching forgings in the DFIQ tank. It was shown that the application of the DFIQ process allows elimination of the normalizing process and, in some cases, quench and tempering processes. The use of the DFIQ process significantly reduces energy consumption and work-in-process handling costs, as well as a production lead-time since a post-forging heat-treating process will be eliminated for many forgings.”
Source: Joe Powell, Integrated Heat Treating Solutions
In this episode, Heat TreatRadio host Doug Glenn talks with Joe Powell of Integrated Heat Treating Solutions in this fourth and final episode about bringing heat treating into the 21st century. This episode covers Direct from Forge Intensive Quenching – forge shops, listen up!
You are about to listen to the 4th and final episode in a series on rethinking heat treatment, with Joe Powell, of Integrated Heat Treating Solutions. You can find the previous episodes at www.heattreattoday.com/radio.
Below, you can either listen to the podcast by clicking on the audio play button, or you can read an edited version of the transcript.
The following transcript has been edited for your reading enjoyment.
DG: Joe, if you don't mind, take us on a 30,000 foot overview of what you've been doing at Integrated Heat Treating Solutions.
JP: What we've been doing for the past 23 years at Integrated Heat Treating Solutions and the last 75 years at Akron Steel Treating is applying heat treatments to parts made by others. We had over 1200 customers on our customer list at Akron Steel Treating and they use various materials. We kind of grew up in the shadow of the Cleveland market, which is the largest market for heat treaters, and there is the largest number of commercial heat treaters in the Cleveland market. This was possibly outnumbered by Detroit at one time, but I still think that we're probably the number one market for heat treating in this part of the country.
What has happened over the last century, in the 20th century, is that heat treating has become very, very good. New equipment has been developed like controls, thermocouples, oxygen probes, vacuum furnaces, vacuum quenching, high pressure vacuum quenching, oil skimmers, new quenchants made with reverse solubility polymers - all of these things have come together and made heat treating very, very good. However, as part of that, there has been a commoditization of heat treatment. That means that heat treating became so good that parts rarely crack or distort unacceptably, and companies have devised methods for correcting the distortion through hard turning, grinding, straightening, flattening, you name it. And the part makers and the heat treaters got along, in a kind of peaceful coalition, to get the parts out the door to the end user.
However, in the 21st century, that is just not good enough. In lean manufacturing, you have to offer an integrated solution for what you're doing. The entire value chain for making a product has to be on the same page; they have to be in alignment. The processes have to be in the proper order. What we're trying to do with Integrated Heat Treating Solutions is bring the last dimension of part design, what we call the Z dimension, to the part makers, their designers, and their material suppliers, so that we present a solution that delivers the optimal amount of value and eliminates the waste from heat treatment, or forging, as we'll talk about today.
[1] Defense Logistics Agency, "About," https://www.dla.mil/AboutDLA/ [2] DFIQ FIA Technical Committee Presentation, "Evaluation of Intensive Quenching Hardening Process Immediately After Completion of Hot Forging Operations," 2018. [3] Forging Process Improvement Using Intensive Quench, 2019.DG: Right. In these four episodes we've been talking to people about bringing heat treating into the 21st century. On your website, integratedheattreatingsolutions.com, there is a good illustration table that shows what heat treating was like in the 20th century and what it is like in the 21st century. That's basically what we're talking about. Just a quick recap of the previous three podcasts we've done: It all revolves around a customized heating, but more importantly, a customized quenching of materials so that the distortion of those parts is predictable, and that the part design can be altered so that there is essentially no post heat treatment processing. In other words, you can pretty much eliminate grinding or any type of machining, straightening, and that type of thing. Once heat treated and quenched with the technologies that you're talking about, the part is essentially pack and go.
We've talked about several examples, but the two we talked about in the recent podcasts were an 18” bevel gear, which was quite interesting. Then we talked about a fracking pump valve seat, which was also quenched in this way. So today, you and I want to talk about, as you alluded to, the forging industry. We're going to talk about something called (direct from the) forge intensive quenching (DFIQ). If you don't mind, tell us what that is. For those people in the forging industry, what is direct from forge intensive quenching?
JP: It's the principle that the forging processes use a lot of BTUs of heat to heat up a billet, and then bang it into a shape and get the grain flow going in the direction that will be great for the part mechanical properties. Once that forged shape is attained and the grain flow is attained, the part is usually allowed to cool at the end of the forging trim die line, and those cooling forgings will all cool at different rates. Because they cool at different rates, you have some fast cooling on the surface, the corners and the thin sections; but you have some very slow cooling in the core. At the end of the day, the part needs to be heated a second time in a normalization process, which heats the part to a high temperature and then does a controlled cooling of the part to align the grains of the part and the size of the grains to remove the kind of mishmash of structure that is present in an as-forged part. Then, if the part is going to be hardened at some point, and usually there is a lot of rough machining that goes on to remove the scale from the forging process, machining is necessary to remove the scale from the steel mill that has basically been hammered into the surface of the forging. All of that rough machining is done to basically present a rough machine part that can then be heat treated. So, companies like Akron Steel Treating or the captive heat treats at the forging plants will then heat the part a third time to the austenitizing temperature. If the part is made out of a martensitic steel, they'll quench it, usually in oil or polymer, and then possibly temper it to stabilize the part, and present it to the part maker for final machining, grinding and whatever final processing needs to be done to turn that forging into a useful part with the desired mechanical properties.
Akron Steel Treating doesn't do a lot of forged heat treat. We do some aerospace parts for braking systems for airplanes, called torque tubes, which is basically the hub of the braking system. Those torque tubes are generally made out of forgings which we see after forging, and then see again after 50% of the material is removed. Then the part is heat treated. In those instances, direct from the forge intensive quenching is not going to work.
Direct from the Forge Intensive Quenching
This direct from the forge intensive quench (DFIQ) project came out of a desire by the Forging Industry Association (FIA), which incidentally Akron Steel Treating has been a member since 2012. We've always felt that we could create more streamlined processing as well as a better part with leaner material if we worked together with the forgers and integrated the heat treat process with the forging process. Companies like the TimkenSteel Company have come out with low alloy materials that are forged all the time, and then they do a controlled cooling where they'll actually air cool the forging. With the alloying elements that are in there, they are able to come up with mechanical properties directly from the forge after a controlled air cool. No normalization is needed and no further austenization, or third heating, is needed. Basically, the part is air quenched and tempered right there in a controlled manner from the hot forge.
Some folks in India and Japan have tried several times to do direct from the forge liquid quenching using oils directly from the forge. What they found is that the oil quench catches on fire, and if they can keep it from catching on fire by enclosing the quench under an inert atmosphere, they're still going to have the problem of the very high heat, like 2000°-2200° F, creating a steam blanket of hot oil, or in the case of polymer water, a steam blanket of polymer water mix around the outside of the part. This then produces an inability to uniformly quench the part because the thin sections will very quickly quench out, the thick sections will sit there under a blanket of gas and essentially those two mixes of nucleat boiling - very fast evaporative cooling in the thin sections and a full-blown gas blanket on the thick sections - create a nonuniform shell around the outside of the forging. As that part cools under that nonuniform shell, it is also going to thermally shrink in a nonuniform way. Also, when it cools to the martensite start temperature, it's going to start transformation and face change in a nonuniform way in that shell.
The successes of direct from the forge quenching didn't happen until this project we started in 2015 with the Defense Logistics Agency (DLA), which “manages the global supply chain – from raw materials to end user to disposition – for the Army, Marine Corps, Navy, Air Force, Space Force, Coast Guard, 11 combatant commands, other federal agencies, and partner and allied nations,”and the FIA tech committee members who sat down and asked: “Do you think we can do this in water?” If we can do it in water, we obviously eliminate the fire hazard, but how do we eliminate the boiling hazard, or the boiling issue in the nonuniformity? And that's where we had, at that time, 15 years of experience in applying the intensive quenching process or intensive quench process.
Luckily, John Tirpak, who was then working with the DLA and the FIA as a technical advisor, saw the benefit in giving it a try. We had done lots of parts that people had said, over the years both at Akron Steel Treating and Euclid Heat Treating, couldn’t be done. And we did it. We applied it in the case of the valve seat to ductile iron to replace an 8620 carburized seat. So, we have this great flexibility, we have this great new tool, we just need to use it, or at least try it, at the forge. And that's what the DLA funded. They basically gave us a budget for the building of a prototype unit which was built and is pictured in the final report It shows the test parts that were actually quenched directly from the forge at Bula Forge in Cleveland, and then we moved the prototype unit next to Welland Forge in Canada and finally to Clifford-Jacobs Forge in Illinois.
The upshot of all of this was that once we figured out that if we could remove the film boiling from the outside of the hot forging, we could basically set the shell, and once the shell is set, we get, on most parts and most geometries, a martensite shell that is formed. That martensite shell continues to form down into the layers of the onion below the surface as the martensite temperature is reached and that martensite transformation continues by conduction, very uniformly through the mass of the part. What you end up with is a part that comes out of the quench pretty much like it went through a normalization process and then a third reheating and an oil quench and a temper. We get some self-tempering as well because we interrupt the intensive water quench before the part is fully cooled. Nonetheless, we found in the first phase of testing that parts should be tempered in a tempering furnace to develop the full effects of the tempering process, so that process is still done after the parts come out of the quench. But you eliminate the normalization process and the third reheating for an oil quench and temper that would normally be required.
Examples of DFIQ equipment (Photo source: Joe Powell)
DG: Can you tell us what parts were actually run?
JP: Yes, there were a variety of parts, and they're all pictured in that report. They ranged from a link that weighed, I believe, close to 50 pounds all the way down to a tine that was on a tiller machine (ground engaging tool) that went into a piece of farming equipment. One of the parts in between was a pintle adapter that was basically a mounting post for a machine gun for the Army. This part went through several operations. It's documented in the report, but we basically saved $13 per part to the Army by eliminating the multiple steps that took place after forging and just incorporated it into an integrated heat treating solution right there at the trim die.
DG: How did that look? Let's take the tine, for example. It's stamped out on a forge press. You've got a hot piece of metal put on a forge press stamped out. Then, one at a time, these parts are taken off of the forge press and immediately put in a quench?
JP: After they come out of the trim die, they're still pretty hot - they're still austenitic, and range in temperature from like 1900°F all the way up to 2200°F - and then they go directly into the quench. 15-45 seconds later another one comes out of the trim die and goes down into the shoot and up the conveyor and into a box to await tempering. We time the conveyor so that the dwell time in the intensive water quench is properly timed so that the core still has enough heat to self-temper, but not too hot that it over tempers the part.
DG: I'm curious about the part. After the part comes off the trim die, is it manipulated? Is there a manipulating hand that comes in and grabs it, takes it off, puts in the quench tank?
JP: In the case of the prototype, the manipulating hand was the forger. He came with tongs and provided a very 19th century placement of that part. But, obviously, all of this stuff can be automated and integrated, and with the proper equipment can be done in a way that is seamless from the time the billet is heated all the way through.
DG: Tell me this, that tine again, when the guy took it off the trim die, did he just throw it in an intensive quench tank or was it fixtured?
JP: Picture an elevator platform. It was placed on an elevator and then the elevator went down between two panels that presented water at very high flow to the part and knocked off the film boiling. I should add, the tine was the thinnest part and the enthusiasm at Clifford-Jacobs was very, very high because once they figured out that this worked, the guys on the floor said, “Let's try this part, let's try that part, let's try this part.” And of course, in the first test at Bula Forge, we actually tested at least four different alloy materials and so all of those variables would have to be integrated into the design. I call it the Z dimension of the design. You pick the right material, you have the right forging temperature of the billet, and you don't overheat it. One of the lessons learned in the four-year study is that if you overheat the forging to “help with die life” - that overheating of the forging to 2400°F (almost to the melting point) - the grains blow up. No amount of intensive quenching is going to bring them back. So, you've got to keep the temperature around 2150°F; that's about the maximum in Fahrenheit.
All I can say is that if you maintain a forging temperature uniformly around 2150°F in the billet, we can devise a quenching system that will blow the film boiling off and set that shell in the part in all but the thinnest parts in the prototype. We did about 150 tines in a row with the protype, and then the water heated up because we only had so much chilling capacity in the water tank. But as the water heated up, the quench wasn't as effective, and the tines actually exhibited some cracks when we ran another 150 - that's because there was film boiling in the mounting holes. The lesson learned was you have to have a flow, but you also have to have some pressure in order to instantly impact that part. That instant impact is key in the proprietary processes that Integrated Heat Treating Solutions is developing to bring the next version of the DFIQ unit to make it able to do the thinner parts without cracking.
DG: DFIQ, of course, standing for direct from forge intensive quench.
You've referred to a study multiple times and that study is a 2019 study called,Forging Process Improvement Using Intensive Quench. It looks like that was, as you mentioned, funded by the DLA in either 2014 or 2015. We will make that report available and people can take a look at it. Anyone that is a forger in a forge shop, or a captive forge would certainly want to take a look at that. Would forge press companies be interested in this? Could they build quenches into the actual press itself so that this process could be, more or less, in line?
JP: Yes, absolutely. Again, it is a different paradigm for them. Just like I mentioned before, all the heat treating equipment makers call themselves furnace companies and all the forging equipment makers call themselves press makers or forging die makers. The reality is the process continues and the mechanical properties in the setting of those grain flows happen in the heat treating process; the refinement of those grains happens in the heat treating process which happens in the quenching process. So, again, we need to integrate that quench into the forming equipment. Again, I have no intention, as Integrated Heat Treating Solutions or Akron Steel Treating, of getting into the business of building systems- that's not my thing. My thing is to develop a robust process that can be applied and implemented using automation and new equipment with the proper pumps and material handling that is all integrated into a seamless process.
DG: Let's talk very briefly about the benefits. We've already alluded to quite a few of them, but let's try to enumerate them here. What are the benefits to a captive forge shop in considering a DFIQ type system- why do it? What's the commercial value?
JP: We can save up to 66% of the energy that's needed to heat treat that part. The part comes off the trim die and is cooled in a box or set aside somewhere. Next, it needs to be reheated and normalized. Then, it has to be reheated a third time and austenitized before quench and temper, and that's a lot of energy. And it's also not usually done at the forge plant. It's usually done either at a captive heat treat that is integrated with the forging company or it goes to a commercial heat treat where they use huge continuous furnaces to reheat the parts and quench and temper them. I'm not going to make a lot of friends in the areas that do this, but if we're going to compete in the world and make great parts, be lean, save energy, and also have safe carbon emissions, we've got to stop heating parts that don't need to be reheated if you can avoid it. I'm not going to claim that it works on each and every part and that it should be used for each and every part. I'm just saying that there's a lot of parts that could be made a lot more efficiently if we would quench them right at the trim die.
DG: So, one of the benefits you just mentioned is potentially saving 66%, basically two-thirds, because you don't have to do a second and third heat. What else do we have?
JP: What you can have is better uniformity of mechanical properties. You can also elicit more hardenability out of a particular alloy by having this higher ability to harden with a very, very fast quench. That intensity of quench locks in mechanical properties that are unattainable in a typical oil quench or polymer water quench. One example of that is a forging that we do for a company, in fact it was one of the companies in the study. It's a 44” gear rack- it's 44 inches long, about 5 inches wide and about 4 inches thick. This gear rack is used as a piece of mining equipment and actually 10 of them are used on each side of a tower. This gear rack allows the spinning, drilling rig to go up and down and spin as it is drilling holes in the earth. This part was traditionally made from 4330 material but the end use customer, the people using this piece of mining equipment, said they’d really like to be able to replace and repair these gear racks when they get worn or a tooth gets broken.
If we could do this in the field, that would be great; but with 4330 material, we can't because we have to pre- and post-heat the weld when we replace or repair a tooth in the field. That’s just not practical in some cases, especially if this piece of equipment is on the side of a mountain and it's pretty cold outside. So, is there a way to get field repairability? That's a topic the DLA is very interested in because equipment used by the Army is often times used in very cold environments, so is there a way to repair that piece of equipment without taking it offline or bringing back for repairs?
For this particular gear rack, after they forged it to a rough shape with the gear teeth in on one side and it looked pretty much like a gear rack that was ready for rough machining, they wanted to be able to still get the same mechanical properties from a leaner hardenability steel like 4130 to replace the 4330, so that they could weld it in the field without pre- and post-heating to avoid cracking the part for the weld. They came to us at Akron Steel Treating and they asked if we could this with our 6,000-gallon batch system. We didn’t know. I took a look at the jominy curve for 4330 and the jominy curve for 4130 and said it's going to be close. The thing is 4” inches thick by 5” wide, and I just didn’t know. But I was willing to try. That has always been my favorite answer, “Let's try it.” If it blows up or it doesn't work, I'm going to learn something. You might not be happy because I blew up your part, but I learned a lot and I'm happy and we're going to move on.
So, they gave us five actual parts made out of 4130 and we heat treated them in our 6,000- gallon system. Next, we sectioned them and found that they turned out very, very uniform. They had the right surface hardness all over the part and also had the right core hardness throughout the 44” length. Then they did some field trials, and everybody was happy.
DG: So, in that case, the benefit is potentially being able to replace higher alloy parts with lesser alloy parts, field repairability, lower cost to manufacture the part, and easier to machine. You also talked about the fact that you can do significant energy savings which also potentially shortens the lead time because you're not having to go through two or three processes, but only one. The one thing we haven't mentioned, which I think probably should be mentioned explicitly, although we've alluded to it, is the elimination of some environmentally unfriendly quench media.
JP: It's a water quench. You use just a little of restorentative salt and that's it. It's water.
DG: And obviously you've got better mechanical properties which you've also mentioned.
JP: There's one more chapter to this and it ties back to podcast #2. First of all, we do these parts 15 at a time on racks in our controlled atmosphere furnace and then transfer all of them to the handling cart and quench them in our 6,000-gallon system. We noticed that when they went into the quench, they were straight, but when they came out of the quench, they were all uniformly bowed about 1 inch at the middle of the 44” length. We mentioned to the customer, that when it's time to redo these forging dies, they should bow the forging so that it comes out of the trim die with a 1” bow in the opposite direction. Once it quenches, it will quench to fit and be relatively straight and will avoid the cold straightening operation that is done after heat treat and temper to get the part straight enough so it can be rough machined.
Again, time savings as well as monetary savings and we're not imparting cold strains into the part that has been hardened after heat treat, which is a no-no, because those cold strains can find a discontinuity in the material or an inclusion, and the two combined can, once in a great while, literally blow up as it is being straightened and fly across the room into two pieces. Cold straightening is something you want to avoid if at all possible.
DG: So, again, the benefit there is that you can go back to the part designer and the heat treater.
Let's back out again to 30,000 feet. We're not talking about the gear racks anymore, just talking generally. In your concluding thoughts, what is the main message we're trying to communicate here?
JP: The integration of lean and heat treating and forging. I think bringing all that together, all of that lean thinking and applying it to the part design at the front end, and the material selection at the front end, so that we deliver the most added value with the least amount of waste in the process to the end user.
DG: I would like to wrap up by saying this too, there are a large number of people who are in the Heat Treat Today audience that I think ought to be interested in this. Basically, anybody who is a captive heat treater, manufacturer with their own in-house heat treat who is doing oil quenching, or anything of that sort, and currently doing it in batch, ought to be thinking about contacting Joe to see if they can eliminate that batch process and put the heat treat directly in line. Those are manufacturers.
Also, as we just talked today- the forging shops ought also to be interested in this. Taking forge parts of the finish/trim forge and putting them directly into a quench. But there is one other group that also ought to be interested in this and ought to be talking to you Joe, and that is the heat treat equipment manufacturers who have a stake here. They have a stake here because their current batch processes, if we continue to move down this path into the 21st century, they could be on the cutting edge of providing the type of equipment that can be potentially more inline and more quench type equipment. For what it's worth, I think that's worth mentioning.
JP: Yes. The 21st century of heat treating is moving towards induction heating and individual part by part quenches. That is really the only way to control distortion consistently, and also to effectively get the most that an alloy hardenability has to offer for the end user, in terms of strength and ductility.
DG: If these people want to get in touch with you, Joe, what's the best way for them to do that?
JP: Through the website integratedheattreatingsolutions.com or ihtsakron.com. The other person who is working with me very closely in the FIA technical committee is Rick Brown. Rick Brown is a former executive at TimkenSteel here in Canton, OH. He helped develop a supply chain for making parts out of seamless tubing that Timken made and still makes, and that supply chain included not only cutting up tubing into rings and making parts out of those rings, but also heat treatment, and in some cases, forging. Rick has a wealth of experience. He's a great guy and is one of our Integrated Heat Treating Solutions consultants who helps people at the part makers, part designers and end users get the most value out of the heat treating and forging processes. We're all working towards that goal of moving heat treatment from the 20th century fully into the 21st century.
Heat Treat Radio host, Doug Glenn, discusses how one company saved over $700.00 in hard grinding costs PER GEAR on an 18-inch bevel gear. Joe Powell of Integrated Heat Treating Solutions tells how they did it. Listen to find out how Joe helped this company upgrade their heat treating and bring it into the 21st century.
Below, you can either listen to the podcast by clicking on the audio play button, or you can read an edited version of the transcript.
The following transcript has been edited for your reading enjoyment.
Doug Glenn (DG): This episode is the second in four conversations with Joe Powell on “quench to fit” technologies. Joe is from Akron Steel Treating and Integrated Heat Treating Solutions. We wanted to review a bit of what we talked about last time in our first podcast. Probably the best way to summarize it to say that we’re trying to get heat treaters to think about heat treating differently: not heat treating in the 20th century or even the 19th century, but in the 21st century. What do you say to that?
Joe Powell (JP): Yes, we’re trying to integrate heat treating solutions into the part making process and take advantage of all of the sensor technologies, all of the manufacturing technologies, all of the other advantages that happened in metallurgy in the last half of the 20th century in terms of atmosphere control, temperature control, vacuum furnaces, and integrate them with the part design.
Professor Jack Wallace (Source: Southern Illinois State University website)
DG: You and I were talking about a statement that was said by one of our mutual friends, and the statement was this: “Every metallurgist knows the faster the quench cooling rate, the higher the probability of cracking a hot part.” What do you say to that?
JP: It was professor Jack Wallace who was the head of the metallurgy department in 1997. When he heard about intensive water quenching, he said it would absolutely not work. He was so sure of it, he basically blurted it out, “It will never work! The parts will blow up in the quench!” If anybody knows Jack, they know that’s exactly how he would say it! The other people in the conference room, just kind of looked at each other: Wayne Samuelson from Shore Metal Treating, myself representing Akron Steel Treating, and John Vanas representing Euclid Heat Treating.
The other two heat treaters in the room heard Jack say this and thought, “Well, you’ve got to be right, majority rules,” but I said to myself, “Well I don’t know who Jack Wallace is, (because I didn’t at the time), but I do know Michael Aernoff and he’s introducing this water quenching technology that was discovered by Dr. Nikolai Kobasko back in the former Soviet Union, and I’m willing to give it a try. All he wanted me to do is heat up some parts (made by Timken Bearing) and quench them in a water bath. They were made out of 52/100. I knew 52/100 blows up when you look at it sideways and when you quench it because it’s a deep hardening steel. But if Michael says you can do it, the worst that can happen is it’s going to blow up, in which case everybody will be wearing a face-shield when it goes in the water. The best thing that could happen is that it doesn’t blow up, and we’ll learn something.
About six months later, this prototype tank shows up at Akron Steel Treating with some tapered bearing rings about 10 inches in diameter. We basically said to ourselves, “Let’s heat them up and see what happens.” They came out of the water about 20 seconds after going in; they flash dried as the core heat had just tempered the martensite that we had just formed on the shell; and they didn’t crack. Then, we did a whole bunch more of them. Jack Wallace was present for that demonstration and he just looked at it and said, “We gotta figure out how this works.” That was in 1998, I believe.
Dr. Nikolai Kobasko (Source: wseas.org)
DG: For the reader’s benefit, let’s give them the birds-eye view of what happened.
Last time, you had said that if you can quench a part fast enough in all areas so that you get below the martensite start temperature, then that actually forms what you could imagine in your mind to be a dye shell. It just holds the part in place.
JP: Yes, it’s a hardened shell over the still hot and plastic core of the part. So, whatever the geometry is, that is what you have locked it in.
DG: And that is, in fact, the key, right? Just reviewing what we talked about last time: The key is you lock the geometry of the part in, regardless of what the shapes are, regardless of whether you have hidden holes, whether you have grooves and everything; you lock it in and then all you have to do is keep that shell at below the martensitic start temperature until the core “cools,” which can be calculated. Then, you’re done.
JP: That’s part of the science behind it, yes. At the end of the day, the trick is to have the equipment to be able to do that. The equipment in 1998 was available to do batch quenching. In fact, in 1999, Akron Steel Treating spent a good deal of money to build a 6,000 gallon quench tank that essentially we are still using today at Akron Steel Treating to do intensive water quenching.
DG: Just to be clear, also from our last episode, it isn’t always that it has to be an intensive quench. It doesn’t have to be instantaneous.
JP: Right, so it also works at the other end of the continuum. If you can build a uniformly hardened shell on a part that is made of high alloy air hardening steels, you can actually develop in a gas quench a very uniform, very predictable size change in that shell. That allows you to predict how the part is going to move so that you can machine it before heat treatment so that it literally morphs into the hardened shape that you want.
For instance, take a very thin, complex bearing ring that has a very thin wall that’s made out of a Pyrowear 53 material, which would basically harden up in air — this is part of the DANTE Solutions patent that we discussed last time. [See original DANTE Solutions HTR] The gas quenching process first creates a shell at the thin section, then stalls out the temperature to keep the temperature hot in the gases, which are flowing across the part during the quench, thus allowing the thick sections to catch up. When the thick sections catch up, and once the thin and thick sections have thermally shrunk a certain amount, then you go to the next plateau in temperature cooling. Here, the gases are introduced to the part surface to bring the thin section down first, and then the thick section. You would continue to do that until you get to the martensite start temperature.
[blocktext align=”left”]“If you go too fast, it will crack the part and it will blow the shell off, and that’s what gives water quenching such a bad name; because the core swells up and blows the corner off the part.” – Joe Powell[/blocktext]At the martensite start temperature, you then do the same thing: let the part stabilize at that temperature in the thin and thick sections, and now you have a shell that’s locked in the part. As the part is cooling down into the core, the thin and thick sections of that core are now going to start the transformation to martensite at about the same time. That means that you have a very predictable size change from the thermal shrinkage, and then the following phase change expansion as the austenite kicks over to martensite. That phase change expansion is the thing that you really don’t think about, but that’s what has to be controlled in order not to blow the shell off. If you go too fast, it will crack the part and it will blow the shell off, and that’s what gives water quenching such a bad name because the core swells up and blows the corner off the part.
DG: You said that there is a need for equipment that is able to do what you’re talking about. In the last episode, you said that there are a lot of really good furnace companies out there and that they are “furnace companies” but what they really ought to be doing is focusing on becoming “quenching companies.” Can you expound on that just a bit?
JP: They obviously need to focus on the heating part and that needs to be uniform, but they’ve given absolutely no focus to the quenching part and how uniform it is over time, and between part to part in a load, and how it affects the compressive stresses. The quenching process is more important, in my mind, than the heating process. And yet, there are no specifications on quench zone uniformity. We have to run surveys at Akron Steel Treating all the time on our heating zones. But when you open the door on an integral quench furnace and go into a quench tank, how uniform is that quench? We don’t know. We hope it’s uniform.
DG: We need a “TQS,” a temperature quench survey.
JP: Yes, exactly! Well, it’s really a uniformity survey for the quench cooling rate.
DG: A “QUS,” a quench uniformity survey, how about that?
JP: Doug, we don’t need another acronym– People will go crazy!
DG: I’d like to ask you a few questions about this one example of an 18-inch bevel gear that Integrated Heat Treat Solutions worked on with a company that may remain nameless, unless you would like to name them.
JP: They will remain nameless, but I can tell you that it’s an Ohio company that makes rolls for steel mills. For years, they refurbished and made rolls and “shavs” for steel mills and bought all their gears from outside. They got gears from various sources, and some of the gears that they got over the years were these large roll drives for steel mills in which some of the teeth would fall off. It was very unpredictable. They had the right hardness on the surface, they appeared to be made out of a high quality 8620 carburizing steel, but when cut apart, a very fine gear metallurgist indicated that the teeth, which were a pretty good size, had carburization of 60,000th effective case steps on the tip, but at the root of the teeth, they only had 15,000th effective case steps. This indicated to us that there was an ineffective oil quench after the carburization process. The carbon is there, but it just didn’t quench out to give you the 50 Rockwell effective case steps at the root of the teeth. When we thought about it, we asked, “How do you run bevel gears?” You stack them on top of each other in the furnace, you heat them up, you carburize them, and you quench them. Well, when they’re stacked on top of each other, the oil cannot circulate and quench the teeth either effectively or uniformly, especially at the root where the heat from the hub is constantly coming out. Additionally, you have a long period of basically gas quenching as the oil boils in all of those big teeth at the root.
Image of Quality Inspection from Akron Steel Treating website
So the first thing we said was, “Well, if we do them, we’re not going to stack them up like that.” The second thing we said was, “Why don’t you let us try our water quenching process in our 6,000 gallon tank?” They said they had nothing to lose, and they gave us some gears. Believe it or not, with no gear cutting equipment, they were making the gears on a 5-axis CNC machine. Then they cut the gears out. These gears are not high quantity gears; these are for steel mills and you use hundreds per year, not thousands or millions. And each gear is a pretty good buck, so they can afford to make it on a 5-axis CNC machine. What they did was they cut the gear out by measuring a gear that had a broken tooth, using the metrology that this company also had, (and they have some really cool laser based metrology for measuring parts), and they created a cloud map.
That cloud map was then used to program their CNC machine. They then sent us these rough-cut gears, and we heat treated them. We carburized them for like 20 hours and I think we left around 60,000th of grind stock on them. When they got the gears back, they said, “These are pretty doggone uniform. Do you think we could tighten up and not leave so much grind stock so we could save some money on our grinding?” And I said, “Yes! Let’s try it.” So, on the next part, we left less grind stock. By the sixth sample gear, we had it down to the point where the gear literally was cut in the 5-axis CNC machine in such a way that the gear teeth came out, but they didn’t need any grinding. They were as straight across the top and they quenched to fit.
I asked, “How much does that save you per gear?” They estimated about $750/gear in grinding costs that they were avoiding. “Well that sounds pretty good,” I said, and they said, “Yes, we think so too.” So, we’ve been doing them ever since. We do them in lots of 12 at a time on racks in our radiant tube batch furnace, (it’s an atmosphere furnace), across the aisle from our 6,000-gallon batch quench tank.
[Image.furnace grate] The other thing that we learned from this experience was that the distortion was very, very predictable as long as we didn’t set the hub on the furnace grate. The furnace grate has two areas where the rollers in the integral quench furnace ride on the furnace grate, and those 4-inch-wide tracks essentially block the quenching water from hitting the bottom of the hub. In those areas, their cloud map showed that there was a distinctly different kind of an ovality to the hub on the ones that were quenched on the grate. Now that could be ground out; it wasn’t that big of an ovality. But, it was a non-uniformity that could be avoided simply by raising up the part on the grid allowing the water to reconnect when it rose from the bottom in the batch quench tank to flow around the hub of the part.
The second thing that we learned was that the parts have higher residual compressive surface stresses on the teeth. Our new gears were wearing down case carburized and oil quenched gears that were on the motors driving the steel mill rolls, yet those case carburized gears are the exact same hardness. The difference was that they don’t have as high of compressive residual surface stresses in the case as we developed in our carburizing and intensive water quenching process.
The third thing we learned—and we knew this a long time ago—is that we could cut the carburizing cycle time by about 36%, versus using oil quenching, and still get the same effective case step because we don’t need to drive in as much carbon into the gradient to develop the 50 Rockwell minimum hardness for the effective case step.
[blockquote author=”Joe Powell” style=”1″]“It’s a win-win-win. The customer is happy, we’re happy and it works. This demonstrates that you can indeed quench very, very intensively. We’re talking about 400-600 degrees Centigrade/second of quenching.”[/blockquote]It’s a win-win-win. The customer is happy, we’re happy and it works. This demonstrates that you can indeed quench very, very intensively. We’re talking about 400-600 degrees Centigrade/second of quenching. You can set the shell and once that shell is set, the part predictably changes to a martensitic case-hardened structure on the outside and a relatively ductile core from the 8620 material, and you get a good gear that is very, very consistent that doesn’t need to be ground after heat treat.
DG: The material that they initially came in with was 8620, and you didn’t change the material; you just changed the processing cycle, which was shortened by about 10 hours (36%), and you were able to get the same hardness. But you were also able to get higher compressive residual surface stresses which actually made that bevel gear all the more effective and more robust. And you saved $750/per gear in grinding costs.
JP: Right, and this is from a company that never made a gear before. They had a 5-axis CNC machine and a bunch of smart guys and this new metrology that they have, (which gives them millions of points of measurement on that gear). And at the end of the day, all I can say is it is pretty amazing, because now they can adjust the green size by comparing the post-heat treat cloud map to the pre-heat treat cloud map and constantly whittle away at the amount of grinding stock that they need with each load until they get it to the point where it doesn’t need to be ground.
DG: So all they do is quench it and fit it, thus your statement, “quench to fit.”
JP: Yes, quench to fit. We obviously temper after quenching, but that’s it. They do clean up the hub, and they do clean up the ID of the hub just to make sure everything is square, so that the gear runs true. But the teeth are not ground in this application.
DG: You mentioned earlier that the initial gears that came in had 60,000th effective case step at the top and 15,000 at the root. Did you do tests on yours, and how did it turn out?
JP: They are super consistent. They have the 60,000th required case all the way around.
DG: This is one excellent example of what you’re talking about with “quench to fit.” I know that you’ve had other applications where you’ve done the same thing, so what part do you want to talk about next time?
JP: We’ll talk about fracking pump valve seats that can be made for about $150, which competes against the typical $800 sintered carbide valve seat.
DG: Stay tuned for that. We’ll get that one on our next podcast.
In this 4-part series, Heat Treat Radio host, Doug Glenn, talks with Joe Powell of Integrated Heat Treating Solutions about bringing heat treating into the 21st century.
According to Joe, the real focus should be on the quenching portion of the process where distortion often happens. In many instances, distortion is able to be eliminated. Find out how in this episode.
Below, you can either listen to the podcast by clicking on the audio play button, or you can read an edited version of the transcript.
The following transcript has been edited for your reading enjoyment.
Doug Glenn (DG): On today’s episode, I sit down with Joe Powell, president of Akron Steel Treating Company to hear what he and his team are doing to combat heat treat distortion. Joe Powell is a veteran in the industry and carries a wealth of knowledge with him. Joe, your company has 75 years of experience working with different part makers, and after a very brief conversation with you, pretty much anyone would conclude that you’re a man on a mission to bring heat treating into the 21st century. Before we turn you loose on that topic, first tell us a little bit about Akron Steel Treating and how it got started.
Joe Powell (JP): It was founded by my father in our garage in 1943 at the behest of the Department of the Army who wanted him to heat treat some parts, and it grew along with all the tool and dye makers in Akron, OH by making machinery for making various rubber products like tires, belts and hoses . . . you name it.
DG: You’ve also spearheaded another company: Integrated Heat Treating Solutions. What are you doing with that company?
[blocktext align=”right”]”It should be ‘quench treating’ not ‘heat treating.’ That’s the way I look at it.” -Joe Powell[/blocktext]JP: Integrated Heat Treating Solutions is the culmination of 75 years of commercial heat treating experience with literally over a 1000 different part makers. What we’ve learned that if we can integrate our heat treating solutions with the part-making design and the optimal material selection, we can produce better parts. And what I mean by “better parts” is they could be lighter, they could have longer fatigue life, and they could have less distortion after heat treating. All of these benefits are brought to the table to part makers so that heat treating becomes a fully integrated part of lean manufacturing.
Once heat treating becomes a lean, integrated part of manufacturing, everybody wins. It enables the use of leaner alloy materials; it eliminates oil quenching; it eliminates long carburizing cycles and batch carburizing cycles; and we now are able to literally do the heat treating in the manufacturing cell where the parts are made.
DG: What do those two companies look like now?
JP: We have about 50,000 square feet and are currently in the process of acquiring another building to our east. We have 48 employees and there are three shifts; and again, we do salt heat treatment, vacuum heat treatment and controlled atmosphere heat treatment. Also, we are currently getting into induction heat treating with our friends at Induction Tooling.
For the last 23 years, we have been concentrating on finding the best way to quench parts and to drive the distortion out of the part-making process. The heat treat distortion has been a problem for centuries. Parts crack, they distort, they come out of the heat treat process unpredictably with size change that is absolutely necessary to get the mechanical properties, but also, if it’s nonuniform, that size change can cause major problems down the line that have to be corrected by hard turning, grinding, flattening, straightening, you name it.
Dynamics of uniform and Uniform Intensive Quenching model (Source: integratedheattreatingsolutions.com)
We’ve also delved into the science of computer modeling, finite element modeling as well as computation of fluid dynamic modeling with our friends at DANTE Solutions. What has happened from that modeling is seeing this concept: the surface of the part contains a bunch of grains, and those finite elements – if they are not quenched uniformly – will transform nonuniform, leading to nonuniform thermal shrinkage upon beginning quenched. Then they will also transform to martensite nonuniformly, which means that the thin and thick sections of a part will have different amounts of distortion and size change. In order to control that, we’ve developed what we call “quench to fit” technologies where we literally build a shell on the outside of the part, using a gas quench or a uniform salt quench or uniform water quench. Once you’ve built that shell in the first few seconds of the quench on the outside of the part, that martensite shell acts like a custom-made quench dye, and that custom-made quench dye allows the part core to cool by conduction through that shell. So, if that cooling by conduction happens by very uniform conduction through the geometry and the mass of a given part, you will have a predictable size change after heat treat. And, you will enable the part designer to go back to the initial part design and adjust it accordingly so that it quenches to fit during the quench process.
When a commercial heat treater receives the part, 99 times out of 100, that part is using a material that was selected many, many years ago, because that is what they’ve always used. Additionally, it’s going to be heat treated in legacy equipment that has always been used. For instance, case carburized 8620 steel valve seats have been used for decades now, and they last about 40-70 hours in the fracking pump, but a ductile iron valve seat can be made to last many times longer; it’s cheaper to buy the material and our heat treating equipment can heat treat it in 5 minutes instead of a 20 hour case carburizing cycle in batches. That single part flow of that new induction heat treating equipment and quenching equipment that is built into it can be built in right at the end of the CNC machines.
I am a commercial heat treater who believes that part design should be integrated for heat treating by the part-maker. It’s a nuance, but what it really boils down to is that sometimes commercial heat treaters do it best, but sometimes the part-maker can do it better. [Side bar quote: I am a commercial heat treater who believes that part design should be integrated for heat treating by the part-maker. It’s a nuance, but what it really boils down to is that sometimes commercial heat treaters do it best, but sometimes the part-maker can do it better.]
[blockquote author=”Joe Powell” style=”2″]I am a commercial heat treater who believes that part design should be integrated for heat treating by the part-maker. It’s a nuance, but what it really boils down to is that sometimes commercial heat treaters do it best, but sometimes the part-maker can do it better.[/blockquote]DG: So, the importance in the part design process of including the heat treater is that you can more consistently predict what the distortion will be, because if I understand it correctly, you can actually predict distortion in the part and therefore design the part with the distortion that will come consistently every time you design that part, yes?
JP: Yes. And it doesn’t matter if it’s an air quench or a hot salt quench or a uniform water quench, it just has to be very, very uniform from the initiation of the quench. In other words, you can’t take it out of the furnace and air cool it for 45 seconds and then begin a water quench, it doesn’t work that way. That shell is starting to form instantaneously when the heat is turned off. An air quench is very slow compared to an intensive water quench and so you have to introduce that quench all over the part surface shell as instantaneously, and with as much uniform impact, as possible. That’s what we do in terms of designing equipment to do the quench process.
DG: Right now, there are a lot of companies, a contractor or commercial heat treater, that send you parts to heat treat. Is it not possible that if the part designer and the heat treater talk in advance as they design the part, that some of these parts could be, in fact, heat treated in-house and not be sent out to a commercial heat treater? Is that possible?
JP: They could actually be heat treated not only in-house, but directly after the CNC machine, right in the manufacturing cell, right after the forge. It takes the proper selection of the optimal hardened ability material. In other words, part of that part design with the heat treater has to be considerations like, “Is it going to get too hard in the core? Is it going to swell up too much in the core? Is it going to be unable to build that shell on the surface without blowing it off, because the core starts to harden up?” So again, the optimal material selection and the design of the mass and the geometry of the part need to be considerations that the heat treater gets a chance to look at.
A “textbook” example of the bell curve. (Source: integratedheattreatingsolutions.com)
DG: So, if the part designer and the heat treater get together and talk about the part design before the part is finalized, or if they’ve got a legacy part, they can sit down and talk with a heat treater that understands what you’re doing over at Akron Steel and Integrated Heat Treating Solutions. If they can understand that, and if they can talk with you about how that part might be redesigned, it’s very possible that you could use lower cost materials to get the same thing, minimize the amount of time to actually heat treat, and you may be able to put that part in a single piece or at least possibly a small batch flow so that there’s not a bottleneck at heat treat, yes?
JP: Yes.
Sponsorship for this episode is Furnaces North America the Virtual Show.
DG: Joe, let’s talk about the quenching bell curve as it relates to distortion.
JP: There are many, many metallurgists and many metallurgical textbooks that indicate that the faster the quench cooling rate, the higher the probability of distortion. There is a curve that is generated that basically says that if you quench very slowly in gas, or if you increase that quench rate and go to a hot salt or a martemper bath or an austemper bath or you increase it even further with warm oil or highly agitated oil, or you go to a brine quench where you do a polymer or a polymer water quench where you increase the rate of quench cooling, there is a point at which most of the parts are going to crack and you’re going to have major distortion. It is not because of the quench speed being faster, it is because the uniformity tends to be less the faster your quenchant. In other words, you need to keep the water from film-boiling and creating a situation where the initial quench is actually done under a steam blanket, or gas, very slowly. Once the thin sections of the part quench-out under gas, then you have the thick sections that are still under that gas blanket, and you have very rapid cooling and very rapid martensite transformations that cause a shift in the size of the part where the shell now cannot contain the core swelling that’s happening underneath the surface.
Whereas 21st century heat treating practice is, what I call, a “uniform quench renewal rate” and an instant impact. In other words, you instantly impact the shell, create that shell, and once it’s created with uniform cooling, then the rest of the cooling happens by conduction through that shell. Whatever the geometry and the mass of the part is will determine that uniform conduction cooling which ends up being very predictable. Once it’s predictable, then you can morph the green size of the part before heat treating so that it predictably quenches to fit during the quench process.
(source: integratedheattreatingsolutions.com)
DANTE Solutions has a method where they use their model to model the finite elements in the part so that the thin and thick sections of the part quench uniformly. IQ Technologies Inc. and my company, Integrated Heat Treating Solutions, have gone on the other side and shown that it is really a bell-shaped curve, and that the probability of distortion goes back down if you can create that shell on the outside of the part instantaneously, and then provide a uniform quench renewal rate to the part surface so that the core can cool by uniform conduction through that shell.
DG: Let’s just put in our listener’s minds the standard bell curve. Most of the quenching and most of the textbooks that we see these days is done on the left hand side of that bell curve, and as you approach the peak of that bell curve, the probability of distortion and/or cracking occurs. People are saying – don’t quench too fast because you’ll get cracking. You’re kind of switching the whole paradigm to say that it’s not the speed at which you quench, but more so: Can you create, almost instantaneously, a hard shell because of exceptionally rapid cooling on the whole part so that that shell basically holds the part in place? If you can get that, then you can cool the rest of the part, however slow or fast, in a sense, you want, because it’s not going to distort because it’s already locked in.
JP: Right, and this is cooling by conduction which is the physics of the material. How fast will it give up the heat through its mass? It’s the difference between 100 degrees or 50 degrees or 10 degrees per second of cooling and 400 to 600 degrees centigrade cooling per second, so it’s very, very intensive. The middle of the bell curve, where most parts are cracking, is because there is not a uniform quench renewal rate. You start off with a gas quench, then you end up with a very intensive evaporative cooling quench with nucleate boiling. You then end up with water quenching without boiling, and so you have three different phases of cooling happening on different parts of the part. This is exacerbated by different parts in different sections of the batch which will have different cooling rates.
It’s almost impossible to get the full benefits of very, very intensive quenching or even very, very uniform gas quenching in a vacuum furnace unless you have staged the cooling in such a way that you create that uniform shell at the beginning of the quench, and you hit that martensite start temperature and cool to that martensite start temperature all over the shell of the part uniformly. That’s the key.
DG: There are several things that jump into my mind like questions that might arise from people. You’ve already hit on the differences in part thickness – you may have thick sections, you may have thin sections. It’s very possible to maybe get down to the martensite start temperature on the thin section right away, but the thick section may not be, and therefore you’re going to distort because you haven’t created that “frozen shell” uniformly around the entire part. Let’s talk about, not just part thickness, but part geometry in the sense of the awkward curves and turns or lips and things of that sort on parts. How would we deal with that?
JP: That’s where new 21st century heat treating equipment needs to be designed. Every furnace company that is selling furnaces to either captive heat treaters or commercial heat treaters calls itself a furnace company. The reality is, yes, heating is important and it is the precursor to getting the mechanical properties, but the heat treatment is actually done, and the mechanical properties are actually obtained, in the quenching process. It should be “quench treating” not “heat treating.” That’s the way I look at it.
Image from Smarter Everyday YoutTube video on Prince Rupert’s Drop (source: https://www.youtube.com/watch?v=xe-f4gokRBs&ab_channel=SmarterEveryDay)
For the last 23 years that’s what has been more apparent to me. My dad taught me how to quench stamps that were used for marking the inside of tire molds, and these steel stamps would uniformly blow up if you just quenched them. But if you were able to uniformly quench the marking end, you could get it hard as hell and it would last a long, long time, but you had to kind of bifurcate the quench. You had to make sure that you created that shell in the marking area of the stamp and let the rest of the stamp kind of cool much more slowly. In other words, create the shell in the face of the stamp where the lettering is, and set those letters. Then the rest of the stamp can basically cool much slower because you don’t need the hardness there; it’s not the working part of the part.
Also, the designers of the stamps had to integrate the right radius in the face of the stamp. If they had sharp corners, those sharp corners would blow off during the heat treat. So, over time, we said, “If you don’t want us to crack this stamp, you’re going to have to put a radius over here and change the design slightly.” It didn’t take much change, but it did take a recognition of the fact that this was not going to work. There’s no way to eliminate the nonuniform cooling in the shell if you’ve got a corner. Steam collects in that corner and it doesn’t quench, so you can’t create the hardened shell.
DG: Let’s take a little deviation and talk about something non-metal. Let’s talk about the Prince Rupert’s drop to illustrate residual compressive stresses.
JP: The mystery of the Prince Rupert’s drop of glass is that glass makers noticed that if they dropped a drop of molten glass into a bucket of cold water it would form a drop that has a head and then a tail – it almost looks like a tadpole. If you hit the head of that glass drop with a hammer or try to break it with a pair of pliers, you can’t do it. It is literally unbreakable at the head. However, if you snap the tail off, it instantaneously explodes. This is because there are counterbalancing tensile stresses that are below the surface in the tail that once you break the compressive stresses off, it’s like taking the hoop off a barrel and the barrel staves explode; the elements on the surface just explode. The reason they don’t explode on the drop of glass at the other end is because there are sufficiently high compressive stresses on that surface that hold the drop of glass and keep it from fracturing.
DG: This is a fascinating video where you take a Prince Rupert’s drop, actually hang this Prince Rupert’s drop and shoot it with a .38 or a .45 or a 9 mm, hitting the head of that tadpole, if you will, and it shatters the bullet while the glass remains untouched. However, if a guy just simply takes his finger, or whatever, and snaps the tail, not just the tail shatters, but the whole tadpole blows up.
JP: What we’ve been able to do with all of the research that we’ve done is to harness those compressive stresses and make them available to the part-marker for making their parts more robust, making them lighter, and making them basically carbide hard and hammer tough. They don’t chip when hit with a hammer.
DG: Let’s jump back to some of the projects you’ve done at Integrated Heat Treating Solutions. Do you have any current projects that you’re working on where this integrated solution – where you were involved with part design or improvement of part design – worked well?
JP: Yes. There are several case studies. The first case study was a punch that lasts 2 – 9 times longer than an oil quench punch.
DG: A punch for what?
JP: Punching holes in metal plates. And the other thing that has happened is that since we’ve begun working with Induction Tooling, we’re able to then bring this down to the level of thinner parts and more complex geometry parts. We’re able to get more hardenability out of lean hardenability alloy such as ductile iron. Plain ductile irons are now acting as carbides. Even the people that make the material said it couldn’t be done, but we’re doing it.
DG: Can you give an example of that?
Watch more resources at Integrated Solutions website. Click the image above to access these resources.
JP: Yes, that would be a fracking pump valve seat made out of ductile iron and heat treated with our special heating and quenching technologies.
DG: What was the performance prior to the treatment and afterwards?
JP: 40 to 60 hours and our initial testing we got 166 hours, so 2 ½ times longer.
DG: So 2 ½ times better performance on this fracking valve seat, and you were using the same material?
JP: No. Rather, we replaced an 8620 carburized steel that needed to be carburized for 20 hours in the furnace, and we did it with a 5 minute induction heating process.
DG: Of what type of material?
JP: Ductile iron.
DG: So we’ve got a punch, a valve seat in the fracking industry. What else?
JP: We have bevel gears that we do. We have worked with the part manufacturer and they’ve adjusted their CNC program so that it actually quenches to fit and doesn’t require a final grind.
DG: Expensive hard machining or hard grinding after heat treat.
JP: Right. And it saves them about $750 per gear in final grind costs. And, the gear lasts longer because it has high residual compressive surface stresses versus a standard carburization process and quenching in oil that does not have as high of a residual compressive surface stress. Especially after you grind it all off to get the final dimensions you want.
DG: Right. So you put all these nice hard stresses in, then you grind them off.
JP: Exactly.
DG: Any other examples?
JP: We have a company that wanted to have a weldable gear rack that could be welded on in the field on mining equipment that’s out on the side of a mountain. Because it might be cold up there, and they didn’t want to have to pre- and post-heat in order to weld on the gear rack, or repair a tooth on the gear rack, they wanted to have a material that had less hardenability but still wanted to have all of the mechanical properties. We were able to get the mechanical properties of 4330 from a 4130 material that doesn’t need to be pre- and post-heated to prevent it from cracking when welding it onto the machinery. They call that “field repairability.” So, we were able to enable field repairability and still maintain the mechanical properties’ requirements.
DG: In future episodes, we’ll go into some depth on some of those applications you just described, but before we wrap up things for this episode, is there a last impression you’d like to leave with us?
JP: Professor Jack Wallace* did not believe that there was a right half of the bell-curve, he did not believe that intensive quenching would work, but, again, he became a believer. It is all key to understanding the dynamics and uniformity of quenching over time. If you get the uniformity, you’re in good shape and eliminate a lot of heat treating problems.
DG: Thanks, Joe. Looking forward to you joining us for future episodes.
JP: Thanks so much.
*Professor Jack Wallace was the “Dean of the College of Metallurgical Engineering at Case Western Reserve University in Cleveland Ohio – who said in 1997, ‘Intensive water quenching would not work! – The parts will blow up in the quench!’ He became a convert once he figured out how compressive surface stresses worked during uniform quenching.” Information provided by Joe Powell.
Doug Glenn, Heat Treat Today publisher and Heat Treat Radio host.
To find other Heat Treat Radio episodes, go to www.heattreattoday.com/radio and look in the list of Heat Treat Radio episodes listed.
