FEATURED NEWS

rectangular promo of HTR, smiling bearded man, blue background, HTR banner

Heat Treat Radio #110: Isolated Heat, the Future of Vacuum Furnaces

Heat Treat Radio host, Doug Glenn, and guest Bryan Stern from Gasbarre Thermal Processing Systems discuss the shift from single chamber batch furnaces to isolated heat vacuum furnaces. They explore the benefits and challenges of isolated heat systems, including temperature control, cycle times, and cost effectiveness for handling various parts. 

Below, you can watch the video, listen to the podcast by clicking on the audio play button, or read an edited transcript.




The following transcript has been edited for your reading enjoyment.

Introduction to Isolated Heat Vacuum Furnaces (00:01:30)

Doug Glenn: We want to talk about something that Gasbarre is calling isolated heat furnaces. In this case, these are vacuum furnaces. What’s an isolated heat vacuum furnace? And why is it called “isolated heat?”

Contact us with your Reader Feedback!

Bryan Stern: To start off, this isn’t something that’s Gasbarre specific. This is a generic distinction and concept with furnaces. It’s been around for a while, but the primary difference with an isolated heat furnace is that the heat chamber in that furnace stays at temperature, in between processing and throughout the process, and it’s held under vacuum during that time as well.

Doug Glenn: Gotcha. We’re going to talk primarily about vacuum furnaces — though, I know that’s also possible in an atmosphere — and the typical vacuum furnace today is the single-chamber vacuum furnace. Maybe it’s obvious already, but can you explain the differences between the isolated heat and a typical single chamber?

Bryan Stern: The single-chamber, batch processing furnace is by far and away the most prevalent technology that’s used. And the difference is that everything in that process is going to happen in a sequential order — everything from loading, evacuating the chamber, ramping everything (the chamber and the work) up to temperature, holding it, doing whatever process you have, cooling it back down, backfilling it, and then unloading it. It’s all a sequential operation. You close the door, the work sits in the same place, and you run through the entire process.

gray vacuum oil quench furnace from Gasbarre
Gasbarre’s Vacuum Oil Quench Furnace, with isolated graphite heating chamber, includes 2 BAR gas quench capabilities.
Source: Gasbarre Thermal Processing Systems

Whereas, with the isolated heat, it remains at temperature. That requires three primary additional components in addition to your single-chamber batch. It requires an extra chamber, for evacuating because you’re going to need an antechamber or a way to load that work in after having pumped it down. So, by default you need a second chamber. You need some kind of dynamic sealing door between the two chambers that you can open once your evacuation chamber is pumped down; and you need some means of moving the work between those two chambers.

These are the fundamental differences. But where it gets interesting is the impact it has on the rest of operations and efficiency.

Doug Glenn: The single chamber has dominated the market for a long time. How have those single-chamber furnaces really affected the design of vacuum furnaces? And are there some significant design differences in these isolated heat furnaces?

Bryan Stern: Yeah. It’s kind of funny, but anyone who’s familiar with single-chamber batch furnaces recognizes there are a lot of challenges to doing vacuum processing that way.A simple way to look at it is if you were trying to cook pizzas in an oven: But if you had to start with the oven cold, open the door, put the pizza in, and then you can’t touch it until the whole thing goes through its process; you heat up the oven and then wait till it cools down at the end and pull it out. It wouldn’t be an ideal approach.

A simple way to look at it is if you were trying to cook pizzas in an oven: But if you had to start with the oven cold, open the door, put the pizza in, and then you can’t touch it until the whole thing goes through its process; you heat up the oven and then wait till it cools down at the end and pull it out. It wouldn’t be an ideal approach.

Bryan Stern, Gasbarre

That’s the distinction with the vacuum portion of it specifically. For a lot of single-chamber batch equipment, you have to pump it down and wait to preheat the oven. That adds a lot of time. So, the then it makes vacuum processing more expensive, and it’s harder to scale. People know there is inconvenience around vacuum processing in general. And the answer to that has typically been to increase workload sizes because if you’re going to have dead time at the front, you’d rather distribute that cost over a thousand parts instead of a hundred parts.

You want to increase the throughput so you’re not waiting for a bunch of little batches and paying for all that dead time with a few parts.

Equipment Challenges with Single Chamber (00:06:32)

Bryan Stern: There’s been a general trend to just increase load sizes, and I am generalizing. It’s not necessary for everything. But you get into some massive single-chamber batch furnaces that are often larger than necessary for the parts. And, unfortunately, those load sizes are kind of detrimental to a lot of the objectives of heat treating.

You have a much more difficult time maintaining uniformity for both process temperature and gas for the parts while you’re heating up and cooling down. And you’re going to have a much higher deviation between the temperature at the center of the load and the surface of the load, as well as process gas concentrations.

That trend toward larger load sizes than necessary (because of the inherent challenges of the single-chamber batch method) leads to other challenges that you then have to overcome. It takes longer to soak out, and quite often (something that I’m sure a lot of people will be familiar with) you end up leaving gaps in the work zone anyway — spaces between parts to allow gas circulation to achieve quench rates enabling you to cool faster because you’re not getting enough gas to the center of the load. Since you have these massive loads, you’ve moved in a direction that’s not really helping anything that you’re trying to do. And that’s a bus that we’ve all been on.

Doug Glenn: So, you’ve got uniformity issues inside the load. And that’s an interesting perspective. The process takes so long inside that one chamber, it tends to increase the size of the load so that you’re doing more at once.

How about the efficiency of the process? If you’ve got a chamber that is designed just for isolated heat, and you’re just heating in that chamber, I would assume that chamber can be designed differently than a chamber in which you’re going to do preheat convective.

Bryan Stern: Absolutely. There are of trying to do everything in one space. I think the equipment challenges come from exactly what you’re talking about — trying to heat and cool in the same space. Anyone who’s been remotely involved in the production of single-chamber batch equipment knows that you’re doing a bunch of things that are in tension with one another. To start, if you’re trying to cool in the same space, very often you’re putting nozzle penetrations all through your insulation pack.

Right away you’ve shot your thermal efficiency in the foot because you have direct radiation out of those nozzles. And people have tried with marginal success to come up with ways of sealing off those nozzles during the heating section and opening them during cooling. Some tried more static approaches, some active changes to the furnace.

But the other issue is that you’re hurting the cooling, too, because you’re restricting your gas flow. You’re heating up the gas that you’re trying to cool with by flowing it through this hot insulation pack. Your parts are sitting inside that heat cage. They’re radiating to a hot surface. Another thing worth pointing out is that often with a single-chamber batch, because you have such a limited time to pump down and you’re trying to decrease your cycle time as much as possible, the installation’s reduced just to help with vacuum levels.

Again, if you’re holding that under vacuum and you can allow it to outgas and decay, now you can have a much thicker insulation pack. You’re not putting penetrations through it. So, it’s helping your thermal efficiency in multiple ways. For example, it’s helping your cooling. When you’re struggling to get those cooling rates, you’re going to do things like bump up gas pressure. Since you’re consuming more processed gas, you’ll put a bigger motor in it — which not only costs more upfront, but it also costs more to run.

That’s a fun fact about especially high horsepower, single-chamber batch equipment: Very often the current rating for the entire system can be driven by the gas blower alone. It’s more than all the rest of the power supply, so they’re not cheap to run.

I’m not saying that you get away with half the size motor, but intuitively you know you’re requiring more than you would need if you placed that load in a dedicated cooling space, no response to gas flow radiating to a water cool jacket. So, it’s a pretty intuitive observation about the way we’re currently approaching this.

Doug Glenn: I don’t think people have thought about it because that has not been the typical way of doing it. It’s almost all single chamber.

Bryan Stern: We’re locked in there.

Doug Glenn: But when you do start thinking about it, it makes a lot of sense that your efficiencies would improve — design and operational efficiencies. All those things would improve because you’ve got dedicated chambers.

Bryan Stern: Another thing with regard to efficiency is your size and your power supply to overcome all those losses, the decreased insulation. When you move to dedicated positions, you know in your position that ramping your power supply can be sized for it. And people have worked to overcome that with typical power supply sizing by doing things like adding multiple taps on the secondary side of the transformer to try to get a better power factor. But if you’re dedicating stations within your equipment, then you can right-size your power supply.

Two men (Doug Glenn, Bryan Stern) talking, HTR banner on top
Bryan Stern: “When you move to dedicated positions, you know in your position that ramping your power supply can be sized for it. And people have worked to overcome that with typical power supply sizing by doing things like adding multiple taps on the secondary side of the transformer to try to get a better power factor. But if you’re dedicating stations within your equipment, then you can right-size your power supply.”

Recent Developments (00:13:21)

Doug Glenn: That brings me to a question about the single-chamber vacuum furnaces that have typically been used. To my knowledge, there are not a lot of isolated heat furnaces or dedicated chamber vacuum furnaces out there, although, I know that one of the companies you guys acquired years ago made their name there. But have there been any developments in recent years that have led to more popularity for, or the possibility of doing, isolated heat vacuum furnaces?

Bryan Stern: Yeah, it’s a great question. It’s something that I’ve done a lot of thinking about because we tend to have a mentality with technology that if it was such a great idea, people would be doing it. So, why aren’t more people doing this?

We can learn a lot from looking at another industry. Specifically, the prevalence and immersion of some of the emissions regulations that are coming along is newer to our industry. I think we’ve been able to get away with doing things in a way that might be really inefficient for a while. But it’s not new in some other industries.

There is a great example that I love because it has so many analogies for what we’re looking at in vacuum heat treating specifically: If you look at the history of the adoption of fuel injection in the automobile industry — I’ve always assumed that fuel injection was adopted as soon as it came along because it was a better technology, and it had been around since the 1920s and 30s.

It was developed and used in some military applications, and right away it was hailed as a better technology. It was more efficient, it was cleaner, but people just didn’t want to change. That wasn’t the direction that everyone was moving in. There were some manufacturers that tried. There were some mass-produced vehicles that had fuel injection in the early 1950s, but it still wasn’t taking off.

And then in 1970 the pushed manufacturers specifically to start adapting it more. But it wasn’t welcome. Some supporting technologies needed to be developed better, especially with computers controlling those systems. As reliability increased for those throughout the ‘80s, there were some amendments to the Clean Air Act from 1970. Then it really started to hit the market and be adopted. And what finally sent it is that consumers started to experience the benefits.

Now we don’t even think twice about it. It’s the de facto standard. You’re not going to go find a car dealership in your area that has their specialty line of carbureted vehicles. There are still places they’re used, but the advantages of fuel injection are so great because you’ve got dramatically improved fuel efficiency and much longer engine life. People say cars last way longer than they used to. And it’s because this new technology that had been around for almost a century, by the early 2000s, had been sitting around, and people hadn’t experienced the advantages of it.

One of the things that I love about that analogy is that it also demonstrates this isn’t a complete switch. It’s a gradual change, and there’s still a place for the old technology. It doesn’t mean that isolated are going to completely replace single-chamber batch vacuums. But if you look at the places carbureted engines are still used, you’ll find them on a racetrack or in lawn equipment.

So, in these places where the upfront cost is really important and you’re not getting enough operating time on it, the improved efficiency is not going to pay off if you were to pay up-front since you’re not using it enough. That carries over well to some of the single-chamber batch vacuums because they will always be around, and they’re going to be more preferred for intermittent use applications where the runtime is not as long.

Doug Glenn: That’s an interesting perspective. Have any of the technologies developed recently — like transfer mechanisms, control systems, or anything of that sort? Is there anything substantially new that had to take place before you could get isolated heat furnaces, or have most of those technologies, similar to the fuel injection, been around for a long time?

Bryan Stern: I think they’ve been around like that analogous technology adoption. There’s certainly going to be a refinement of some technologies to be robust for it to work.

screenshot of smiling bearded man with 40U40 profile
Click on the link to read more about Bryan Stern in his Heat Treat Today 40Under40 profile.

There are some good solutions out there. There are some bad solutions out there. And I think the higher possibility of getting into a bad solution with a less mature product is one of those obstacles people are facing. Things don’t change when forces are in equilibrium. So, the fact that we’re not changing as an industry to adopt some of this stuff just means that the forces motivating that change have not overcome the obstacles. There are definitely some obstacles to it.

And I’m sure we’ll get into talking about those some, but we have that nudge from regulation that’s happening. We’ll see, and continue to see, this type of product mature and those dynamic sealing mechanisms and transfer systems. And I think what’s really going to send it is that there are a lot of benefits that address a lot of problems that we’re all familiar with. It’s just not the de facto standard.

There are ways that the industry is organized around the methods that we use currently. A great example of that is the pizza example where you look at the back of the box of pizza, and you’ve got a recipe that says to preheat the oven and then pop it in for 15 minutes. If you can’t do that anymore, and you have to put the pizza in while the oven is cold and let it ramp up, now you have to change the recipe. And that’s the way we’re organized right now. We’re organized with processes for material that’s starting cold. It’s actually a harder way to do things, because the way that different equipment ramps up is harder to control. So, it’s not necessarily a better recipe, but it’s what we have.

The vacuum level specifications are another big impact. In single-chamber batch equipment, you’re exposing it to atmosphere every cycle, and you’ve got to pump it down quickly. So even when you pump it to very low vacuum levels, what’s left is still often oxidizing constituents.

If you can hold it at vacuum (even though it’s not getting to the same ultra-low pressures), and if it’s allowed to absorb from the surfaces and outgassing from materials (even at a higher pressure), you can have a pure environment. And that’s really counterintuitive. It’s not built into equipment specs because people associate the vacuum level with purity, and it’s really more about dew point and the constituents of what’s in the gas. You can have just as pure an environment with much higher pressure. And again, we’re just not organized around that right now.

Continuous and Non-Continuous Systems (00:21:56)

Doug Glenn: Let me restate something you said earlier and tell me if I’m accurate on it. You were saying that because of the single-chamber vacuum furnaces, we tend to increase the load sizes. So, I’m assuming the load size of the isolated heat furnaces could be significantly smaller and, therefore, have better uniformity within the load, both in the heat up and the quench. Is that an inherent advantage of the isolated heat?

Bryan Stern: It’s not specific to all isolated heat equipment. We’d have to get into discussing the fact that you can’t have continuous and non-continuous isolated heat systems. And it’s an important distinction. The distinction being that you have your heat chamber, you’re keeping it at temperature in a multi-chamber batch system, which is still a form of isolated heat equipment. You’re going to be moving your work in and out the same direction.

So, you’ll get a lot of the advantages that we’ve talked about. You’re able to have dedicated design for heating and cooling. You’ll have your thermal efficiency. There are a couple things you’re not going to get. You’re not going to be able to increase the throughput. Whereas, if you move to a continuous furnace where you’re moving that work in, and then you’re moving it to the other side . . . We can keep working with the pizza analogy: If you need more pizzas, and it takes 15 minutes for a pizza, you can move it through three stations for five minutes per station. Now, you’re getting a pizza every five minutes instead of every 15 minutes, right? If you’re able to do that and produce loads faster, then you can decrease the load size. And then you’re going to see all the benefits of decreasing that load size — improved uniformity, faster times, and better cooling.

red lettering and green lettering to the right of a red flame with green arrows circling it
Click on the image to read “Vacuum Heat Treating in a Carbon-Conscious Market” by Bryan Stern, in Heat Treat Today’s November 2023 Sustainability issue.

But you only get that if you go to continuous. With that specific type of isolated heat equipment, versus just any isolated heat equipment, you’ll get much better thermal efficiencies because in the multi-chamber batch setup you’re not heating and cooling the furnace every time and throwing that energy away. But because you’re loading and unloading on the same size, you’re still going to leave that heat chamber unoccupied, sitting and holding its temperature, consuming energy in between loads. With continuous furnaces, you’re not going to do that. You’re never going to throw all that energy away. There’s minimal holding power required. So, there is a distinction between the continuous and non-continuous isolated.

Doug Glenn: How would it work with a non-continuous isolated heat furnace? If the process required you to preheat, heat, and quench, what is it you’re going to use? Transfer cars? How does that work?

Bryan Stern: If you have multiple heating levels, you can still control the heat. But often you’d introduce it at an intermediate temperature and then ramp it up the rest of the way. So again, all the advantages that you get as far as quenching, typically with a two-chamber piece of equipment like that, your quench chamber is going to serve double duty as your evacuation chamber. You’re putting it into the quench chamber first, evacuating it again, and bringing it back and quenching it.

Challenges with Isolated Heat Systems (00:26:39)

Doug Glenn: These systems sound good, but I’m sure there are some challenges. Are there some drawbacks? I can hear some people saying, these sound like great pieces of equipment — especially the continuous version. I can understand the efficiencies, but what about the complexity? Is the design complexity of these units an issue?

Bryan Stern: It’s definitely one that I face a lot on the application side. It’s a much more complicated process — especially because the process itself is going to impact each of those positions. And you would care if I sold you an oven for your kitchen, and the only thing I cared about was that it can go to this temperature, and it can operate at this pressure, but I didn’t care what you did with it, I didn’t care how much work you get through it. I just had these maximum parameters.

As soon as you move to talking about continuous, you’re right away much more involved in throughput — going to drive and often the number of positions to get the index rate you need for the load size. Now you care how long each step of the process takes, and you’re trying to balance that among positions so that you’re not letting anything sit longer than it needs to because you’re over this particular soak time.

Trying to get continuous equipment sized for an application is more of a process than some people are expecting. And again, we’re just not wired that way. So, you can throw out a spec for a single-chamber batch furnace and say you need this operating temperature, this ultimate vacuum level, and this uniformity . . . and more! But when you come and want to get into a piece of equipment like this, we’re going to have a couple conversations — we’re going to talk about some things no one else is asking. And that’s what can be a hurdle up front, though we’re able to overcome it.

Two men (Doug Glenn, Bryan Stern) talking in split screen, no hands seen
Bryan Stern, Gasbarre, discusses furnace cost effectiveness and flexibility. “It’s just going to be a lot more expensive if you’re doing a process that doesn’t require the way that that furnace was built. So, it’s not that you locked yourself in. It’s just that if you’re constantly changing processes or you have much shorter processes or the throughput isn’t a benefit, then that’s where a single-chamber batch might be a better solution.”

Doug Glenn: But it also may limit flexibility, I assume, of the different processes you could run in that equipment, too. In a batch system, you can put the load in there and do whatever you want, it’s going to potentially take longer to get it done. But maybe in an isolated heat system, where the heat chamer is only designed to do X, maybe you can’t do X times two. Does that make sense?

Bryan Stern: Yeah. It’s not as much true for a two-chamber or multi-chamber isolated heat batch style furnace because you have the same flexibility of dedicated design. On a continuous furnace, but if you’re going to be doing that a lot, is it worth paying for something that can be optimized one way if you’re going to be using it in a flexible way. They have a lot of flexibility — I would argue just as much as batch. It’s just going to be a lot more expensive if you’re doing a process that doesn’t require the way that that furnace was built. So, it’s not that you locked yourself in. It’s just that if you’re constantly changing processes or you have much shorter processes or the throughput isn’t a benefit, then that’s where a single-chamber batch might be a better solution.

Cost Effectiveness (00:30:23)

Doug Glenn: And then the other objection that jumps to my mind is capital equipment outlay. Can we address that, compared to single chamber?

Bryan Stern: This is this is another one that’s near and dear to my heart because I think there’s a lot of misconception here since it’s very application specific and hard to answer generally. But like we talked about, you’re going to have another chamber.

So, if you’re looking at a smaller system, it may not immediately be more cost effective. If you’re looking at a continuous system that’s replacing several furnaces, now you’re not paying for that oversized power supply on each piece of equipment; you’re not paying for a pumping system for each piece of equipment; you’re just buying it for the one evacuation chamber. Or maybe you have a backup, but now you’re starting to distribute and be much more selective about your material cost, and there’s definitely a break-even point in there.

It’s really a question of whether or not the process improvements are enough of a benefit on the smaller size. But very quickly the upfront cost starts to lean in favor of the continuous, especially if you’re looking at multiple pieces of equipment.

But the bigger thing here, the thing that I feel more passionate about, is that we tend to get really hung up on the upfront cost. And I think that’s something that can be very detrimental to missing out on value. It’s very easy to say: I’m going to have this amount of revenue, I’m going to pay this for equipment, and I’m not going to dive into maintenance and operating costs — and that’s a difficult question to answer but is a huge piece of the puzzle. Yet we often don’t put in the legwork because the information is not readily available. And it takes a more sophisticated accounting approach to look at project value over the life of the equipment.

Intuitively, we know that you could pay more for something that would improve efficiency or throughput or performance because in the long run that would pay off. And going back to the car analogy, when is the last time you bought a car and didn’t pay any attention to the fuel economy on it? It’s hard to do that without a little bit more accounting elegance.

Intuitively, we know that you could pay more for something that would improve efficiency or throughput or performance because in the long run that would pay off. And going back to the car analogy, when is the last time you bought a car and didn’t pay any attention to the fuel economy on it? It’s hard to do that without a little bit more accounting elegance.

Bryan Stern, Gasbarre

So, you have to look at the cash flow problem, do something like a net present value approach. And when you start looking at the operating cost savings, the efficiency improvements, and then a huge one that people miss is in the single-chamber batch furnaces we’re heating it up and down. That’s aggressive thermal shock and cycling. A lot of design goes into trying to get components to last because there’s thermal ratcheting and things wear out super quickly. For these continuous systems that are just sitting at temperature, that goes away for the most part.

They’re still consumable products, but the maintenance costs are dramatically improved, and you can talk to people who are using the systems. But again, that’s not something a lot of people have experienced, and it’s hard to quantify. So, if you just look at the upfront costs then it’s easy to miss out. You’re looking for an aggressive payback because you’re just hoping it’s going to cover the operating and maintenance expenses versus actually factoring those in and saying that those overall for the project life are going to increase value.

Limitations and Benefits of Isolated Heat (00:34:09)

Doug Glenn: That makes sense. Two final questions for you here: Are there any types of companies out there where it doesn’t make sense to use an isolated heat type system, whether it be a double chamber or continuous or whatever? And are you seeing, from the activity of , any industries that really should be looking at them?

Bryan Stern: Answering your first question with regards to the limitations, there are a couple situations where you’re not going to want to be looking at isolated heat.

One of those is really large parts. If an individual part is going to take up your whole work zone, then you’re not going to be able to decrease the load size and go to continuous and match the throughput. So, very large batch applications are going to be an obstacle; large parts are one area that it’s not going to shine. We’re seeing the 36” x 36” x 48” work zone is the practical cutoff. Another is the ability to use work TCs to monitor internal temperatures of the parts. That’s possible with continuous equipment. You can do a data pack and record temperatures, but it’s certainly not as convenient. So, when it comes to R&D, validating internal temperatures, and processes that require that, that’s another hurdle and limitation of this type of system.

The footprint is another one due to a second chamber for a batch style process is probably going to be larger in the space that it occupies because you’re not getting smaller in the work zone. So, it’s a question of whether you have the floor space, and do the other benefits of that system make up for the space it’s going to take up?

gasbarre logo

Doug Glenn: Those are good caveats. How about industries that you’re seeing who really should be adopting these things that either are or ought to be?

Bryan Stern: I don’t think it’s super industry specific, but there are some processes that benefit. And just a couple would be anything with a really short cycle time, because the dead time is going to consume more of the process.

If you can eliminate that and you only need to be at temperature for a little piece of time, then getting the rest of that dead time to be in parallel with the process to increase your throughput makes you a great candidate. But on the other hand, long processes are also a good candidate. If you’re holding it at temperature for a long period of time, boosting that efficiency while you’re in temperature, and better matching a power supply to what you’re doing.

So, good candidates could have short or long cycle times, involve any processes that require tight control, or benefit from isolating them from the space. Censoring can be a good candidate for rising carbon trading, where you can now actually have a dedicated space that maybe even operates at a higher vacuum level for whatever you’re trying to do, or you’re not worried about contaminating the parts with whatever process we’re running, or you need a tight time control. So, gas processes like that.

Oil quenching is an obvious candidate because you already have two chambers most of the time and isolating it, maintaining it at temperature, and keeping it clean from any oil vapors makes it a great example.

For anything with expensive parts, you can minimize the risk by decreasing the load size instead of having a many thousand-pound load where if something goes wrong, you’ve lost it. And especially for applications where that can be a really expensive thing if something goes wrong, you’d rather have it go wrong with much less material at risk.

Doug Glenn: I would think traceability is also probably easier in one sense. With this isolated heat system; you don’t have a huge batch in there. You’re processing potentially smaller batches, and you’re able to isolate which batches are at what temperature or what kind of quench they go through. Those may be some advantages.

Bryan Stern: You had a very specific application for a client who was concerned with a lot of small parts and traceability down to each part, and we’re looking at that system. Anytime you have a high volume of work, if you’re looking at multiple batch, single-chamber batch furnaces to meet throughput, that’s one of the biggest indicators you really should probably be looking, or at least considering, these other systems. And any time you have a lot of small parts in baskets, a large single-chamber batch furnace with stacked baskets of tiny parts, you’ll probably have a lot of benefit.

Doug Glenn: I assume that if somebody is looking at purchasing multiple single-chamber furnaces, you guys would have some sort of a calculator to help them assess if it makes sense financially and process-wise to go with six batch furnaces or one continuous. Is that a safe assumption?

HTR logo, gasbarre 110, image of smiling man with slight beard, text about isolated heat

 

Bryan Stern: Yeah, that’s one of my favorite parts of the process is to take a specific application, go through and break it down, and put together that full project ROI where you’re actually starting to assemble what are we looking at for maintenance costs? What is it going to cost to operate? And now you’re starting to see at a project level, not just the upfront cost, which option is going to be best. And it is so application specific. It’s kind of neat to walk through that with a client and see what comes out the other end. Because at the end of the day, you want what the best solution is. It could be this or that. But when you can actually put that picture together for a process and assist someone with picking the best equipment for what they need for their process, that’s fun.

Doug Glenn: And just for the listener’s benefit, because we haven’t done a lot of talking about your company Gasbarre Thermal Processing Systems. You guys can provide either the isolated heat systems or, if you do the calculations on your handy dandy spreadsheet and it turns out they’re better doing the standard single chamber, you guys can do those, too. So, it’s not like you’re going to push one over the other but whatever makes sense. Right?

Bryan Stern: I see that as a huge advantage. You’re not going to get a bias of us at Gasbarre trying to push you into this because it is what we’re selling. We are able to wade through that decision with the client and help pick the equipment that’s best for them.

Doug Glenn: Helping them make a better choice, super, Bryan. Thank you.

About the Expert

Bryan Stern is the product development manager at Gasbarre Thermal Processing Systems. He has been involved in the development of vacuum furnace systems for the past 8 years and is passionate about technical education and bringing value to the end-user. Bryan holds a B.S. in Mechanical Engineering from Georgia Institute of Technology and a B.A. in Natural Science from Covenant College. In addition to being a member of ASM, ASME, and a former committee member for NFPA, Bryan is a graduate of the MTI YES program and recognized in Heat Treat Today’s 40 Under 40 Class of 2020.

Contact Bryan at bstern@gasbarre.com or go to gasbarre.com.


Search Heat Treat Equipment And Service Providers On Heat Treat Buyers Guide.Com

Heat Treat Radio #110: Isolated Heat, the Future of Vacuum Furnaces Read More »

Gray drop bottom furnace bg with headshot male, dark hair, white shirt

Aerospace Heat Treating Upgrades Capacity with Drop Bottom Furnace

An electrically heated drop bottom furnace with a traveling quench tank and a maintenance platform has been shipped to an aerospace company for the solution heat treatment
Mike Grande
Vice President of Sales
Wisconsin Oven Corporation
Source: Wisconsin Oven Corporation
of aluminum parts.
 
Wisconsin Oven designed the drop bottom furnace with sufficient capacity to heat 600 pounds of aluminum per load and provide a quench delay that does not exceed 5 seconds. The system also includes a slow drop speed program to be used for heating applications that do not require a quench.
 
“This drop bottom furnace was designed with a 5 second quench delay, and a temperature uniformity of +/- 5°F at the set points 850°F and 1,100°F. In addition, the system was tested to be in compliance with AMS2750F, Class 1 furnaces and instrumentation Type C prior to shipment from our manufacturing facility,” said Mike Grande, vice president of sales at Wisconsin Oven.
 
 
The press release is available in its original form here.

Find Heat Treating Products And Services When You Search On Heat Treat Buyers Guide.Com

Aerospace Heat Treating Upgrades Capacity with Drop Bottom Furnace Read More »

Green-toned electric socket photo bg w/professional headshot in fg

US DOE Strategy: Ramifications for Heat Treaters

As heat treaters strive for a sustainable future, pressure mounts to make the right choices while running commercially viable operations. In this Technical Tuesday installment of a continuing series, guest columnist Michael Mouilleseaux, general manager at Erie Steel, Ltd., explores the potential ramifications of the DOE effort for industrial decarbonization in the heat treating industry. The first installment, “US DOE Strategy Affects Heat Treaters”, appeared on April 10, 2024, in Heat Treat Today, as well as in Heat Treat Today’s March 2024 Aerospace print edition.

This informative piece was first released in Heat Treat Today’s May 2024 Sustainability Heat Treat print edition.


As regulatory agencies set industrial decarbonization goals aimed at achieving net zero greenhouse gas emissions (GHGE) by 2050, heat treaters should prepare for action. But where do heat treatment technologies stand today, and what is the path going forward?  

Background

President Biden’s 2021 executive order calling for a “clean energy economy” led the U.S. Department of Energy (DOE) and the Environmental Protection Agency (EPA) to develop “The Industrial Decarbonization Roadmap,” a strategic plan for reducing industrial emissions. The plan identified five sectors — chemical, petroleum, iron and steel, cement, and food and beverage production — as targets for mitigation efforts. According to “The Roadmap,” process heating operations within these five industries represent the greatest opportunity to apply what were established as four pillar technologies:

  • Energy efficiency
  • Low carbon fuels, feedstocks, and energy sources (LCFFES)
  • Carbon capture, utilization, and storage (CCUS)
  • Industrial electrification using green electricity

In May 2023, heat treating was specifically named as a target process for reducing GHGE during the DOE’s Office of Energy Efficiency & Renewable Energy’s Low Carbon Process Heating Forum.  

A Closer Look at the Technology Pillars

To determine the path forward, it’s important to understand where heat treatment technology stands today regarding the four pillars.

Energy Efficiency: Among energy efficiency opportunities are furnace insulation, controls, and burner design. According to furnace and controls manufacturers that I have spoken with, advancements in insulation and heating system controls offer less than a 20% opportunity in efficiency improvement over

LCFFES: In the U.S., the primary hydrocarbon fuel for heat treating is natural gas, which has an average (commodity) cost of $2.57/MMBTU. Hydrogen has been endorsed as the preferred replacement. Hydrogen manufacturing and distribution issues aside, hydrogen has a 2023 (commodity) cost ranging from $14.00 to $40.00 per MMBTU, and a carbon footprint of 30–130% that of natural gas. “Green hydrogen” is “under development.”

CCUS: Carbon capture, utilization, and storage is currently relegated to natural gas production operations where the captured CO2 is injected into existing wells to “enhance” production. Although the DOE suggests development of advanced CO2 capture technologies are still underway, a 2023 Congressional Budget Office report states there are “fifteen CCS facilities . . . operating in the United States . . . [with] an additional 121 . . . in development.” It is fair to state there are no CCS (carbon capture and storage) facilities currently operating on the scale of a heat treating operation.

Electrification: For electrification to be impactful, electricity must be generated via green sources. Currently, 40% of the electricity generated in the U.S. comes from natural gas, 20% from coal, 19% from nuclear, 10% from wind, and 3% from solar. It is my opinion that, regardless of the incentives federal and state governments offer wind and solar energy operations, they will not reach the scale — and most certainly not the reliability — necessary to achieve the stated 2035 GHGE goals.

Cost also must be considered. The average U.S. cost for electricity was $0.086/KWH in 2023. In California, however, the cost for electricity generated with 40% renewables was $0.1819/KWH. In Germany, it was $0.289/KWH with 55% renewables. To put this into perspective, today the differential in (industrial) electricity (commodity) costs demonstrably increase as the percentage of that electricity is generated by “green” sources. To think that this trend is going to be reversed by federal mandate is paradoxical.  

A Realistic Look at the “Road Map”

While industrial decarbonization targets called for an 85% reduction in GHGE by 2023 and net zero by 2050, the goals seem unreachable using currently available technology. Replacing natural gas with hydrogen will result in significant cost increases as the commodity is 5–15 times more expensive, the equipment will require retrofitting to accommodate hydrogen, and the national infrastructure will need to be modified for hydrogen.

Electrification of existing gas-fired processes will result in a cost increase of four times, according to DOE estimates; however, based on today’s cost trends, 7–9 times higher is more likely. Additionally, the cost of converting equipment to electric operation must be considered. Mitigation efforts suggested by the DOE include improvements in efficiency that rely on yet-to-be-developed technologies and cost reductions in electricity facilitated by the wholesale use of renewable energy.

Overall, decarbonization efforts are noble. The timeframe and methodology, however, are unrealistic as they are based on the use of still-conceptual technologies.  

What Can Heat Treaters Do?

Following the lead of the automotive industry may be key. This sector reacted to the government mandates for GHGE reductions by going all in for electrification — with projections of 50% electric vehicles by 2030. A funny thing happened; these vehicles were not wholly accepted by the American public. The auto industry, led by the dealers, with the support of the UAW, and the car manufacturers petitioned their U.S. Representatives to “pause” these requirements. This political pressure caused the EPA to roll-back the implementation schedule.

Heat treaters must act now with a similar effort, but it must be aimed at preventing the promulgation of regulations that rely on still-conceptual technologies within an unachievable timeframe. Contact your local government leaders; let them know what we do means jobs and tax revenues. Contact your U.S. Representatives and Senators to let them know heat treaters are critical to our national security, the transportation system, and, in fact, the infrastructure of this country. What we do should not be outsourced, and we need to be given all the considerations of a critical industry.

The next column in this series will address the role of process heating in GHGE, analyze DOE assessments of GHGE for industry and process heating operations, and propose a fact sheet intended for use in our effort to set a realistic timeline for decarbonization goals In the next column, we’ll address potential ramifications of the DOE effort for industrial decarbonization in the heat treating industry to help you be better informed and prepared.    

About the Author:

Michael Mouilleseaux General Manager at Erie Steel, Ltd.

Michael Mouilleseaux is general manager at Erie Steel, Ltd. He has been at Erie Steel in Toledo, OH since 2006 with previous metallurgical experience at New Process Gear in Syracuse, NY, and as the director of Technology in Marketing at FPM Heat Treating LLC in Elk Grove, IL. Michael attended the stakeholder meetings at the May 2023 symposium hosted by the U.S. DOE’s Office of Energy Efficiency & Renewable Energy.

For more information: Contact Michael at mmouilleseaux@erie.com.  

Attend the SUMMIT to find out more about the DOE’s actions for the heat treat industry.

Find Heat Treating Products and Services When You Search on Heat Treat Buyers Guide.com

  1.  

US DOE Strategy: Ramifications for Heat Treaters Read More »

Allied Mineral Products Jobs

Refractory Manufacturer’s $23.5M Expansion To Create Jobs in Alabama

Thirteen new manufacturing jobs will open up with the $23.5 million expansion of an Alabama heat containment refractory production facility. The Ohio-based company supplies products used in a variety of industrial applications, including heat treating operations.

headshot Paul Jamieson
Paul Jamieson
President & CEO
Allied Mineral Products

Allied Mineral Products, an Ohio-based producer of monolithic refractory ceramics, recently broke ground on the major expansion at its Pell City, Alabama, location.  The growth project will add a 200,000-square-foot production facility on the company’s current site and expand the workforce with thirteen new manufacturing jobs added to the company’s current workforce of 81 full-time employees. The project is expected to be completed in late 2025, increasing the facility’s production capacity and improve efficiency. State and local officials joined executives and employees of Allied Mineral Products, LLC (Allied) at the groundbreaking ceremonies marking the investment.

“Our partnership with Alabama is strengthened yet again with the expansion of this plant which we originally built in 2019,” said Paul Jamieson, president and CEO of Allied Mineral Products. “Locating our facility in Alabama was part of a long-term strategy to expand our manufacturing presence in the south to be closer to our customers. Because of the quality of this workforce and the local support here, our growth in Alabama has been faster than we planned. We are excited to be expanding our facility so soon and are confident this will help us to continue that growth.”  

 

The press release is available in its original form here.


Find Heat Treating Products And Services When You Search On Heat Treat Buyers Guide.Com

 

Refractory Manufacturer’s $23.5M Expansion To Create Jobs in Alabama Read More »

NASA Aids AM’s Adoption

NASA has selected Elementum 3D (a developer and supplier of metal additive manufacturing (AM) advanced materials, print parameters, and services) to be one of four companies that will produce and distribute GRX-810 material under a commercial co-exclusive license. This is a material that has undergone significant post-processing heat treat research.

The 3D printable high-temperature metal superalloy material has been noted as “breakthrough technology” and will be offered to original equipment manufacturers of airplanes and rockets as well as the entire supply chain.

NASA’s goal of the licensing agreement is to accelerate the adoption of GRX-810 to benefit U.S. technologies, industry, and space exploration. The 3D printer supplier notes that engineers are eager to print with a material capable of creating lighter and thinner engine parts, reducing fuel burn, lowering operating costs, increasing durability, and lowering the tolerance for failure for critical applications.

GRX-810 is an oxide dispersion strengthened (ODS) alloy that can endure higher temperatures and stress. Its strength is derived from the dispersion of tiny particles containing oxygen atoms. The breakthrough superalloy was specifically developed for the extreme temperatures and harsh conditions of aerospace applications, including liquid rocket engine injectors, combustors, turbines, and hot-section components, capable of enduring temperatures up to 1,100°C. Compared to other alloys, GRX-810 can endure higher temperatures and stress up to 2,500 times longer. It’s also 3.5 times better at flexing before breaking and twice as resistant to oxidation damage.

Jeremy Iten Chief Technology Officer Elementum 3D Source: LinkedIn

Over the past nine years, Elementum 3D has gained extensive knowledge and experience in developing, commercializing, and distributing “impossible-to-print” dispersion-strengthened materials similar to GRX-810.

“We are excited to be working with Tim Smith and NASA to bring this exceptional new alloy to the commercial market,” said Jeremy Iten, chief technology officer at Elementum 3D.

NASA’s investment in developing GRX-810 demonstrates its dedication to advancing additive manufacturing. Elementum 3D and the other co-exclusive licensees now assume the responsibility of investing the time and resources to supply the industry with a stronger, more durable superalloy.

The original press release is available here.


Find Heat Treating Products And Services When You Search On Heat Treat Buyers Guide.Com

NASA Aids AM’s Adoption Read More »

Anatomy of Induction Coils

Contact us with your Reader Feedback!

Consider the numerous systems in your heat treat operations. What makes up the anatomy of each furnace or system? In this “Anatomy of a . . .” series, industry experts indicate the main features of a specific heat treat system. In this feature, the full-page spread identifies main features of induction coils.

The mark-ups for these reference images are provided by John Gadus, design and sales specialist, Induction Tooling, Inc.

View the full graphics by clicking the image below.

This Technical Tuesday article is drawn from Heat Treat Today’s April/May 2024 Sustainable Heat Treat Technologies print edition, that had a special focus on green heat treat technologies.

Search www.heattreatbuyersguide.com for a list of induction equipment providers to the North American market. If you are an induction equipment supplier and are not listed here, please let us know at editor@heattreattoday.com.

This series will continue in subsequent editions of Heat Treat Today’s print publications. Stay tuned!


Find Heat Treating Products And Services When You Search On Heat Treat Buyers Guide.Com

Anatomy of Induction Coils Read More »

Fringe Friday: Additive Manufacturing Brings Metal Processing to New Heights

We’re celebrating getting to the “fringe” of the weekend with a Heat Treat Fringe Friday a press release detailing how additive manufacturing continues to move into the metals manufacturing industry.

While not exactly heat treat, “Fringe Friday” deals with interesting developments in one of our key markets: aerospace, automotive, medical, energy, or general manufacturing.


Desktop Metal, a global company at the forefront of additive manufacturing 2.0 technologies for mass production, announced that it has installed four Figur G15 Pro systems featuring digital sheet forming (DSF) technology to three manufacturers, including Evology Manufacturing in Waukesha, Wisconsin.

With 30+ years as a contract manufacturer, Evology has a full suite of both traditional and additive technologies to service companies in a wide range of industries, including aerospace, defense, automotive, agricultural, marine, mining, medical, electronics, and consumer goods. Evology serves companies ranging from small startups to Fortune 50 companies with prototyping and low-volume production, typically under 10,000 pieces.

Evology is now offering digital sheet form parts off its Figur G15 for cold rolled steel up to 2 mm thick and 6061 aluminum up to 3.175 mm thick, with more materials in development.

“We are delighted to offer our customers this cutting-edge rapid sheet metal forming technology from Desktop Metal,” said Sean Momsen, VP of Business Development and Marketing at Evology. “In addition to our ability to fabricate sheet metal parts rapidly, we also have a full suite of traditional finishing equipment to deliver finished final products to customers.”

Justin Nardone, CEO of Figur, a Desktop Metal brand, said, “We are encouraged by the continued demand we see for our rapid sheet metal forming technology, which truly saves manufacturers time and money when it comes to sheet metal production. The G15 eliminates a lot of the work required when forming metal, such as the design and manufacturing of tools and dies. Our system produces designs quickly, accurately, and repeatedly, so manufacturers are able to focus on the craftsmanship of design while getting their products to market faster and more efficiently.”

Introduced in 2022, the Figur G15 is the first commercial platform of its kind to shape sheet metal on demand directly from a digital file. A software-driven proprietary tooling system on an XY gantry forms the sheet with up to 2,000 lbs of force in a highly engineered and proprietary build zone.

With a maximum sheet size of 1,600 x 1,200 mm (63.0 x 47.2 in), the Figur G15 delivers parts with a draw depth up to 400 mm (16 in) in Z without custom forming tools, molds, dies, or presses. The G15 supports forming a range of metals and sheet thicknesses – including steel up to 2.0 mm and aluminum up to 2.5 mm – and delivers a high quality surface finish

Pro configurations of the Figur G15 include an automatic tool changer and measurement, through tool part lubrication, and automated work holding capabilities.

This press release is available in its original form here.


Find heat treating products and services when you search on Heat Treat Buyers Guide.Com


Fringe Friday: Additive Manufacturing Brings Metal Processing to New Heights Read More »

The Role of Heat Treatment in Space Exploration

Precise heat treating is essential to enable components to withstand space exploration. In this Technical Tuesday, Mike Grande, vice president of Sales at Wisconsin Oven Corporation, discusses the role of aluminum solution treatment and aluminum aging in heat treating space exploration components.

This column was first released in Heat Treat Today March 2024 Aerospace Heat Treat print edition.


Contact us with your Reader Feedback!

In space exploration, the various parts, electronic components, and materials used to make the rockets, crew capsules, rovers, and other equipment, are subjected to brutal extremes of temperature, vacuum, and radiation. In order to withstand these extreme environments without failure, the parts must be manufactured to very tight tolerances and precisely heat treated. Therefore, convection heat treatment emerges as a critical process in the manufacturing of space exploration components and materials, offering tight control over temperature profiles and the microstructure of materials.

Heat treatment involves heating a material to a specific temperature, holding it at that temperature for a certain duration, and then cooling it down at a controlled rate, which can be rapid or gradual, depending on the objective. The purpose of heat treatment is to improve the material’s mechanical properties, such as strength, ductility, and toughness. Probably the most common metal used in space exploration is aluminum. It is an excellent choice for spacecraft components because it is lightweight, durable, and has excellent thermal conductivity, which is necessary for components that need to dissipate heat.

The first stage of the Falcon 9, for example, utilizes four legs used during landing. They are manufactured from an extremely light, rigid, aluminum honeycomb material that also contains carbon fiber and has a very high strength to weight ratio. Another aluminum component common in space exploration is gas transfer tubes, used to transfer gases, such as methane, between chambers in the interior of rocket propulsion systems. Additionally, there are composite overwrapped pressure vessels (COPVs), which carry compressed fuels such as hydrogen and oxygen, among other gases. These are made of an aluminum tank covered with filament-wound, resin-impregnated composite material, which forms an extremely robust structure capable of withstanding the high pressures created by compressed gases and the rigors of high-speed propulsion. For aluminum to be useful in space applications, it must be heat treated to give it the strength and durability required.

Aluminum Solution Treatment

Since aluminum has such widespread use in space exploration, aluminum heat treatment plays a central role in this industry, with solution treatment and aging being the most common heat treatments utilized. All aluminum materials that require high strength are solution heat treated, then subsequently aged, in two separate heat treat processes. The purpose of solution heat treatment is to evenly dissolve the alloys contained in the aluminum, such as manganese, magnesium, copper, zinc, and silicon, and then rapidly quench it to retain the grain structure. The aluminum alloy is heated and held at a temperature of 800°F to 1000°F (420°C to 540°C), which is just below its melting point. The aluminum is then quenched in water or a water/glycol mixture quickly (within 7 to 15 seconds) to essentially “freeze” the microstructure before the alloying elements can redistribute themselves.

Aluminum Aging

After quenching, aluminum is precipitation hardened. Also known as artificial aging, this process involves heating the aluminum at a lower temperature, typically in the range of 200°F to 400°F (93°C to 204°C) for several hours. This final process dramatically increases the hardness, yield strength, and ultimate strength of the aluminum, making it suitable for use in space applications.

A solution treatment system for processing aluminum

The above is just a sample of the many types of heat treatments for materials used in space exploration. Other examples are annealing, tempering, normalizing, and hydrogen embrittlement relief, to name a few. In conclusion, heat treatment plays a critical role in the manufacturing of parts used in space exploration and is essential to the reliability and safety of space missions.

About the Author

Mike Grande, Vice President of Sales, Wisconsin Oven Corporation

Mike Grande has a 30+ year background in the heat processing industry, including ovens, furnaces, and infrared equipment. He has a BS in mechanical engineering from University of Wisconsin-Milwaukee and received his certification as an Energy Manager (CEM) from the Association of Energy Engineers in 2009. Mike is the vice president of Sales at Wisconsin Oven Corporation.

For more information: Contact sales@wisoven.com.

Find Heat Treating Products And Services When You Search On Heat Treat Buyers Guide.Com

The Role of Heat Treatment in Space Exploration Read More »

All About the Quench and Keeping Cool: Thru-process Temp Monitoring and Gas Carburizing

The future of heat treating requires new manufacturing solutions like robotics that can work with modular design. Yet so also does temperature monitoring need to be seamless to know how effectively your components are being heat treated — especially through being quenched. In this Technical Tuesday, learn more about temperature monitoring through the quench process.

Gas Carburization

Contact us with your Reader Feedback!

Carburizing has rapidly become one of the most critical heat treatment processes employed in the manufacture of automotive components. Also referred to as case hardening, it provides necessary surface resistance to wear, while maintaining toughness and core strength essential for hardworking automotive parts.

Figure 1. Typical carburizing heat treat temperature profile showing the critical temperature/time steps: (i) carburization, (ii) quench, and (iii) temper. (Source: PhoenixTM)

The carburizing process is achieved by heat treating the product in a carbon rich environment (Figure 1), typically at a temperature of 1562°F–1922°F (850°C–1050°C). The temperature and process time significantly influence the depth of carbon diffusion and other related surface characteristics. Critical to the process is a rapid quenching of the product following the diffusion in which the temperature is rapidly decreased to generate the microstructure, giving the enhanced surface hardness while maintaining a soft and tough product core.

The outer surface becomes hard via the transformation from austenite to martensite while the core remains soft and tough as a ferritic and/or pearlitic microstructure. Normally, carburized microstructures following quench are further tempered at temperatures of about 356°F (180°C) to transform some of the brittle martensite into tempered martensite to enhance ductility and grindability.

Critical Process Temperature Control

As discussed, the success of carburization is dependent on accurate, repeatable control of the product temperature and time at that temperature through the complete heat treatment process. Important to the whole operation is the quench, in which the rate of cooling (product temperature change) is critical to achieve the desired changes in microstructure, creating the surface hardness. It is interesting that the success of the whole heat treat process can rest on a process step which is so short (minutes), in terms of the complete heat teat process (hours). Getting the quench correct is not only essential to achieve the desired metal microstructure, but also to ensure that the physical dimensions and shape of the product are maintained (no distortion/warping) and issues such as quench cracking are eliminated.

Obviously, as the quench is so critical to the whole heat treat process, the correct quench selection needs to be made to achieve the optimum properties with acceptable levels of dimensional change. Many different quenchants can be applied with differing quenching performances. The rate of heat transfer (quench rate) of quench media in general follows this order from slowest to quickest: air, salt, polymer, oil, caustic, and water.

Technology Challenges for Temperature Monitoring

When considering carburization from an industry standpoint, furnace heat treat technology generally falls into one of two camps, embracing either air quench (low pressure carburization) or oil quench (sealed gas carburization/LPC with integral or vacuum oil quench). Although each achieves the same end goal, the heat treat mechanisms and technologies employed are very different, as are the temperature monitoring challenges.

To achieve the desired carburized product, it is necessary to control and hence monitor the product temperature through the three phases of the heat treat process. Conventionally, product temperature monitoring would be attempted using the traditional trailing thermocouple method. For many modern heat treat processes including carburization, the trailing thermocouple method is difficult and often practically impossible.1 The movement of the product or product basket from stage to stage, often from one independent sealed chamber to another (lateral or vertical movement), makes the monitoring of the complete process a significant challenge.

With the industry driving toward fully automated manufacturing, furnace manufacturers are now offering the complete package with full robotic product loading that includes shuttle transfer systems and modular heat treat phases to process both complete product baskets and single piece operations. Although trailing thermocouples may allow individual stages in the process to be measured, they cannot provide monitoring of the complete heat treat journey. Testing is therefore not under true normal production conditions, and therefore is not an accurate record of what happens in normal day to day operation.

Figure 2 shows schematic diagrams of two typical carburizing furnace configurations that would not be possible to monitor using trailing thermocouples. The first shows a modular batch furnace system where the product basket is transferred between each static heat treat operation (preheat, carburizing furnace, cooling station, quench, quench wash, temper furnace) via a charge transfer cart. The second shows the same heat treat operation but performed in a continuous indexed pusher furnace configuration where the product basket moves sequentially through each heat treat operation in a semi-continuous flow.

Figure 2.1. Modular batch furnace system (Source: PhoenixTM)
Figure 2.2. Continuous pusher furnace schematic (Source: PhoenixTM)

Thru-process temperature monitoring as a technique overcomes such technical restrictions. The data logger is protected by a specially designed thermal barrier, therefore, can travel with the product through each stage of the process measuring the product/process temperature with short, localized thermocouples that will not hinder travel. The careful design and construction of the monitoring system is important to address the specific challenges that different heat treat technology brings including modular batch and continuous pusher furnace designs (Figure 2).2

The following section will focus specifically on monitoring challenges of the sealed gas carburizing process with integral oil quench. Technical challenges of the alternative low pressure carburizing technology with high pressure gas quench have previously been discussed in an earlier publication.3

Monitoring Challenges of Sealed Gas Carburization — Oil Quench

Figure 3. “Thru-process” temperature monitoring system for use in a sealed carburizing furnace with integral oil quench — (3.1) Monitoring system entering furnace with thermocouple fixed to automotive gears, product test pieces (3.2) System exiting oil quench tank (3.3) System inserted into wash tank with product basket (Source: PhoenixTM)

Presently, the most common traditional method of gas carburizing for automotive steels is often referred to as sealed gas carburizing. In this method, the parts are surrounded by an endothermic gas atmosphere. Carbon is generated by the Boudouard reaction during the carburization process, typically at 1562°F–1832°F (850°C –1000°C). Despite the dramatic appearance of a sealed gas carburizing furnace, with its characteristic belching flames (Figure 3), from a monitoring perspective, the most challenging aspect of the process is not the heating, but the oil quench cooling. For such furnace technology, the historic limitation of “thru-process” temperature profiling has been the need to bypass the oil quench and wash stations, missing a critical process step from the monitoring operation. Obviously, passing a conventional hot barrier through an oil quench creates potential risk of both system damage from oil ingress and barrier distortion, as well as general process safety. However, the need to bypass the quench in certain furnace configurations by removing the hot system from the confined furnace space could create significant operational challenges, from an access and safety perspective.

Monitoring of the quench is important as ageing of the oil results in decomposition (thermal cracking), oxidation, and contamination (e.g. water) of the oil, all of which degrade the viscosity, heat transfer characteristics, and quench efficiency. Control of physical oil temperature and agitation rates is also key to oil quench performance. Quench monitoring allows economic oil replacement schedules to be set, without risk to process performance and product quality.

Figure 4. “Thru-process” temperature monitoring system oil quench compatible thermal barrier design: (1) Robust outer structural frame keeping insulation and inner barrier secure; (2) Internal thermal barrier — completely sealed with integral microporous insulation protecting data logger; (3) Mineral insulated thermocouples sealed in internal thermal barrier with oil tight compression fitting; (4) Multi-channel high temperature data logger; and (5) Sacrificial insulation blocks replaced after each run. (Source: PhoenixTM)

To address the process challenges, a unique thermal barrier design has been developed that both protects the data logger in the furnace (typically three hours at 1697°F/925°C) and also protects during transfer through the oil quench (typically 15 mins) and final wash station (Figure 3). The key to the barrier design is the encasement of a sealed inner barrier with its own thermal protection with blocks of high-grade sacrificial insulation contained in a robust outer structural frame (Figure 4).

Quench Cooling Phases

Monitoring the oil quench in carburization gives the operator a unique insight into the product’s specific cooling characteristics, which can be critical to allow optimal product loading and process understanding and optimization. From a scientific perspective, the quench temperature profile trace, although only a couple of minutes in duration, is complex and unique. From a zoomed in quench trace (Figure 5) taken from a complete carburizing profile run, the three unique heat transfer phases making up the oil quench cool curve can be clearly identified:

Figure 5. Oil quench temperature profile for different locations on an automotive gear test piece shows the three distinct heat transfer phases: (1) film boiling “vapor blanket”, (2) nucleate boiling, and (3) convective heat transfer. (Source: PhoenixTM)
  1. Film boiling “vapor Blanket”: The oil quenchant creates a layer of vapor (Leidenfrost phenomenon) covering the metal surface. Cooling in this stage is a function of conduction through the vapor envelope. Slow cool rate since the vapor blanket acts as an insulator.
  2. Nucleate boiling: As the part cools, the vapor blanket collapses and nucleate boiling results. Heat transfer is fastest during this phase, typically two orders of magnitude higher than in film boiling.
  3. Convective heat transfer: When the part temperature drops below the oil boiling point. the cooling rate slows significantly. The cooling rate is exponentially dependent on the oil’s viscosity.

From a heat treat perspective, the quench step relative to the whole process (hours) is quick (seconds), but it is probably the most critical to the performance of the metallurgical phase transitions and achieving the desired core microstructure of the product without risk of distortion. By being able to monitor the quench step, the process can be validated for different products with differing size, form, and thermal mass. As shown in Figure 6, the quench curve profile over the three heat transfer phases is very different for two different automotive gear sizes.

Figure 6. Oil quench temperature profile for different automotive gear sizes (20MnCr5 case hardening steel) with different thermal masses: Passenger Car Gear (2.2 lbs) and Commercial Vehicle Gear (17.6 lbs) (Source: PhoenixTM)

Summary

As discussed in this article, one of the key process performance factors associated with gas carburization is the control and monitoring of the product quench step. Employing an oil quench, the measurement of such operation is now very feasible as part of heat treat monitoring. Innovations in thru-process temperature profiling technology offer specific system designs to meet the respective application challenges.

References

[1] Dr. Steve Offley, “The light at the end of the tunnel – Monitoring Mesh Belt Furnaces,” Heat Treat Today, February 2022, https://www.heattreattoday.com/processes/brazing/brazing-technical-content/the-light-at-the-end-of-the-tunnel-monitoring-mesh-belt-furnaces/.

[2] Michael Mouilleseaux, “Heat Treat Radio #102: Lunch & Learn, Batch IQ Vs. Continuous Pusher, Part 1,” interviewed by Doug Glenn, Heat Treat Radio, October 26, 2023, audio, https://www.heattreattoday.com/media-category/heat-treat-radio/heat-treat-radio-102-102-lunch-learn-batch-iq-vs-continuous-pusher-part-1/.

[3] Dr. Steve Offley, “Discover the DNA of Automotive Heat Treat: Thru-process Temperature Monitoring,” Heat Treat Today, August 2023, https://www.heattreattoday.com/discover-the-dna-of-automotive-heat-treat-thru-process-temperature-monitoring/.

About the Author

Dr Steve Offley (“Dr O”), Product Marketing Manager, PhoenixTM

Dr. Steve Offley, “Dr. O,” has been the product marketing manager at PhoenixTM for the last five years after a career of over 25 years in temperature monitoring focusing on the heat treatment, paint, and general manufacturing industries. A key aspect of his role is the product management of the innovative PhoenixTM range of thru-process temperature and optical profiling and TUS monitoring system solutions.

For more information: Contact Steve at Steve.Offley@phoenixtm.com.

Find Heat Treating Products And Services When You Search On Heat Treat Buyers Guide.Com

All About the Quench and Keeping Cool: Thru-process Temp Monitoring and Gas Carburizing Read More »

Automotive Manufacturer Orders Second Endo Generator

An automotive manufacturer in South America has recently placed a follow-up order for a second Endothermic generator from a manufacturer of industrial process control, automation, and digitalization solutions with North American locations.

UPC-Marathon, a Nitrex company, installed a 200 m³/h EndoFlex unit last year. The new generator, with a similar capacity, aims to enhance stability, to ensure consistent composition and gas flows, and to prioritize quality of automotive gear boxes while achieving efficiencies in heat treatment operations.

UPC-Marathon EndoFlex unit (Source: Nitrex)

Prior to adopting the EndoFlex solution, the manufacturer relied on four generator units, each with a capacity of 70 m³/h and consuming 80 kW of power. With the same 80 kW of power consumption, the EndoFlex generator delivers a 200 m³/h capacity.

This transition to the new unit represents a 75% reduction in power consumption and a contribution to operational efficiency and sustainability efforts. The new generator streamlines maintenance procedures, adheres to stringent quality standards, and reduces CO2 emissions. Control over gas quality and production for the neutral hardening furnace enhances product quality, reduces operating costs, and optimizes energy consumption. By automatically adjusting gas production to match real-time furnace demand, the generator eliminates overproduction and waste.

Marcio Boragini
Sales Director for Brazil at UPC-Marathon

“We’re proud to continue our partnership with this automotive customer,” remarked Marcio Boragini, UPC-Marathon’s Sales Director for Brazil. “Moreover, EndoFlex . . . empower[s] the manufacturer to achieve their business objectives fast, while reinforcing our commitment to [drive] success together.”

This press release is available in its original form upon request.


Find Heat Treating Products And Services When You Search On Heat Treat Buyers Guide.Com

Automotive Manufacturer Orders Second Endo Generator Read More »