MANUFACTURING HEAT TREAT

In this episode, Heat Treat Radio 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 4^th 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.

 

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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 20^th 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 21^st 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.

DG:  Right. In these four episodes we've been talking to people about bringing heat treating into the 21^st century.  On your website, integratedheattreatingsolutions.com, there is a good illustration table that shows what heat treating was like in the 20^th century and what it is like in the 21^st 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.

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.

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 19^th 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 21^st 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 21^st 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 20^th century fully into the 21^st century.

 

 

 

 

 

Resources:

[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.

 

 

 

 

 

 

 

 

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To find other Heat Treat Radio episodes, go to www.heattreattoday.com/radio and look in the list of Heat Treat Radio episodes listed.