Richard B. Conway Founder/Director/CTO DELTA H® Technologies, LLC Source: DELTA H
Multiple military facilities now operate more than 50 heat treat systems from a North American furnace and oven supplier. These facilities include Air National Guard bases, USAF bases stateside, Guam, Alaska, and Hawaii, Air Bases in Japan, Germany, United Kingdom – Royal Air Force, Middle East, the U.S. Navy, U.S. Coast Guard, and U.S. Army facilities.
The systems from DELTA H included either single, dual or triple chamber designs of both the heavy duty commercial aviation standard models DCAHT® / SCAHT® Series, the supplier’s Defender Series – developed for the armed forces, and aircraft composite walk-in ovens.
All systems are in full compliance to NAVAIR Tech Order 1-1A-9, and meet AMS2750 accountability standards for accuracy, temperature uniformity, calibration, and secure batch records.
Ellen Conway Merrill with USAF Metal Technology personnel Source: DELTA H TECHNOLOGIES, LLC
Richard Conway, director & CTO of DELTA H®, shares: “It is a deep honor and humbling for the DELTA H team to support our armed forces. We take the utmost care to ensure the best of our craftsmanship and abilities are utilized to deliver the finest heat treating equipment for aircraft maintenance to our Warfighters.”
Military personnel are provided full operator and heat treating and maintenance training, as well as on-site qualifying assistance to meet and maintain the stringent pyrometry standards. Successful trainees receive Certificates of Training as qualified to use their DELTA H® furnace for heat treatment of aircraft parts.
This press release is available available upon request.
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Readers are checking out Heat Treat Today's magazine from February 2023. The annual Air & Atmosphere Furnace Systems edition has a piece that sparked a comment from a reader. The letter from the publisher Doug Glenn entitled ± 0.1°F – The Debate discusses revision to AMS2750 regarding compliance temperature.
Would you like to weigh in on the topic? Submit your question, comments, thoughts, or queries here or email Bethany Leone at editor@heattreattoday.com.
Here is an excerpt from the article:
“Both Revision D and E of AMS2750 required compliance temperatures to be ±2°F or ±1.1°C (“or ±0.2%” was added in Revision E). That pesky “.1” in ±1.1°C appears to be the source of this most current “situation.” The folks using °C were recording temperatures down to 1/10th of a degree, while the folks using °F — which was not a small number of people — were not. So, the standards committee needed to make a decision on what to do about this discrepancy. The options were to round up or down or to the nearest integer for both °F and °C people OR require EVERYONE to record their temperatures down to 1/10th of a degree. After surveying end-users, the committee decided that end-users wanted to be required to record the 1/10th of a degree rather than round it up or down to the nearest integer. Thus, the new AMS2750 standard requires accuracy to 1/10th of a degree.”
The article prompted this feedback from reader Aaron Crum:
“I could not agree with you more. This is like measuring a piece of lumber with a tape measure, but being required to record the number in microns. Making requirements more stringent just for the sake of it costs companies real money with no improvement to the process or the product. I hope this gets removed in the next revision.
Thanks for the good write-up Doug!”
We welcome your inquiries to and feedback on Heat Treat Today articles. Submit your questions/comments to editor@heattreattoday.com.
A new, fully automated quenching system is nearing completion and will be installed at C/A Design’s heat treat facility in Exeter, NH, which serves the aerospace and defense industry. It has been custom designed and developed specifically to service aluminum brazing applications, expanding capabilities and services.
The system, from Wakefield Thermal, adheres to the guidelines set by both AMS2750 and AMS2770, ensuring proper heat treatment for aluminum brazements and adherence to critical specifications. The custom solution for C/A Design includes temperature and quenching control technology.
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What is the connection between AMS2750 specifications and furnace classifications? With tight specifications, what does the heat treater need to know to be compliant? Follow along as we take a brief look into this often-overlooked topic.
This Technical Tuesday article, written by Douglas Shuler, owner and lead auditor, Pyro Consulting LLC, was first published in Heat Treat Today's March 2023 Aerospace Heat Treating print edition.
Doug Shuler Lead Auditor Pyro Consulting
AMS2750 is the specification that covers pyrometric requirements for equipment used for the thermal processing of metallic materials. AMEC (Aerospace Metals Engineering Committee) is one of the committees which oversees the changes and revisions of AMS2750. There are five main sections in the technical requirements of the specification: sensors, instrument calibrations, thermal processing classification, SAT (system accuracy testing), and TUS (temperature uniformity surveys). Additionally, there are quality provisions that detail what happens if a calibration or test is either past due or fails.1
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Revisions to the original requirements have occurred over the years, with the newest being Revision G. The structure of Revision G has carried over from Revision F and has remained the current structure of the AMS2750 specification. This structure includes furnace classes, which are based on the minimum requirements for temperature uniformity.
Furnace classes are defined in Figure A of Revision D Figure 1.
Figure 1. AMS2750G furnace class uniformity tolerances Source: Doug Shuler
Originally, furnace classes were based on temperature uniformity, but also subzero transformation, refrigerated storage of aluminum alloys, and embrittlement relief, Figure 2.
Figure 2. Original AMS2750 instrument accuracy requirements, no class structure Source: Doug Shuler
AMS2750 Revision C was released in May 1990 and started to implement the class and instrumentation type structure and differentiated between furnaces for heat treating parts versus furnaces for heat treating raw materials. Furnaces for heat treating parts were classified based on uniformity, but also on a readability requirement. Furnaces for heat treating raw materials were classified based on a readability requirement alone.
AMS2750 Revision D was released in September 2005 and continued to define equipment class (Figure A)* and instrumentation type (Section 3.3.1.1)*. It also clarified chart recorder resolution (Table 4)*, print and chart speed (Table 5)*, and testing frequencies for SAT (Tables 6, 7)* and TUS (Tables 8, 9)* for the processing of parts versus raw materials.
AMS2750 Revision E was released in July 2012 and continued to build on the clarity presented in Revision D by adding an instrumentation type table (Figure 3)* instead of a simple text description in the body of the specification.
Figure 3. AMS2750 Revision C: distinguishment between furnaces for heat treating parts versus raw materials Source: Doug Shuler
Moving to AMS2750 Revision F, the specification saw a major rewrite and restructuring where the tables were moved from the end of the document to the first area text that called out the specific table. Revision F also put into place a sunset date for analog instruments.
That brings us to the current revision of AMS2750, Revision G, which has carried forward the structure of Revision F and only sought to further clarify the intent of the requirements.
Over the years, the technology of sensor, instrument, and furnace manufacture and capability has continued to produce better and tighter controls for the process of heat treating. The evolution of AMS2750 has recognized these advancements and has kept pace with them in technology. The understanding of the origins of AMS2750 and how it has evolved is vital in understanding its application to today’s heat treat special processes.
*Specified figure, table, or section is associated with the AMS2750 revision being discussed.
About the Author: In 2009, Douglas (Doug) Shuler became the owner of Pyro Consulting LLC and also began working with Performance Review Institute (PRI), first as an instructor and course developer and later as an auditor for the Nadcap program. As a lead auditor for Nadcap, he has conducted over 380 Nadcap special process and aerospace quality management system audits on behalf of the Aerospace Primes over the past 10+ years. Doug continues to focus on instruction, training, and education for the heat treat industry, developing courses, authoring exams, and employing the PIE method: “Procedures that Include all requirements, and Evidence to show compliance.”
Derek Dennis President Solar Atmospheres California
Solar Atmospheres of California (SCA) installed a new 14 foot long car bottom air furnace. With a maximum operating temperature of 1450°F, this furnace tempers large tool steel components, age hardens 15-5 PH, 17-4 PH, 13-8PH and nickel-based alloys, and anneals titanium forgings.
SCA is typically known around the world as a “vacuum only” heat treater. However, there is a great need for heat treating non finished parts and materials in accordance with the same specifications (AMS, MIL, Boeing, and Airbus) within different atmospheres where surface oxidation is permissible. This furnace allows for a “raw material” option.
“Solar Atmospheres of California is excited to be adding this new furnace and the added capability/capacity," stated Derek Dennis, president of SCA. The furnace has a working zone that is 60" square by 168" long with a total load capacity of up to 30,000 pounds.
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Heat Treat Today publishes eight print magazines a year and included in each is a letter from the publisher, Doug Glenn. This letter first appeared in Heat Treat Today's February 2023 Air & Atmosphere Furnace Systems print edition.
Doug Glenn Publisher and Founder Heat TreatToday
When dealing with temperatures in excess of 1000°F, one would think that a ±0.1°F variation would not be a big deal. Apparently, not!
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As of the most recent AMS2750 standard, 1/10th of a degree Fahrenheit matters — and if your process recorders are not recording temperatures down to 1/10th of a degree, you are out of compliance.
This is a big deal and a real hardship for many in the Heat Treat Today audience.
At the most recent Nadcap meeting held in Pittsburgh this last October, I had the chance to discuss this most recent stringent requirement with some of the people who were responsible for putting it in the standard. Even after talking to them, I’m not sure I fully understand why it is we went in this direction, and I’m not alone.
The Background
"the new AMS2750 standard requires accuracy to 1/10th of degree." Source: Heat TreatToday
Here’s a very short explanation of how we got here. Both Revision D and E of AMS2750 required compliance temperatures to be ±2°F or ±1.1°C (“or ±0.2%” was added in Revision E). That pesky “.1” in ±1.1°C appears to be the source of this most current “situation.” The folks using °C were recording temperatures down to 1/10th of a degree, while the folks using °F — which was not a small number of people — were
not. So, the standards committee needed to make a decision on what to do about this discrepancy. The options were to round up or down or to the nearest integer for both °F and °C people OR require EVERYONE to record their temperatures down to 1/10th of a degree. After surveying end-users, the committee decided that end-users wanted to be required to record the 1/10th of a degree rather than round it up or down to the nearest integer. Thus, the new AMS2750 standard requires accuracy to 1/10th of a degree.
Thoughts
Even as I type it, it doesn’t make sense. Why would end-users want to record temperatures down to 1/10th of a degree? If you’re at 1750°F, a full 1°F amounts to only 0.05% of your total temperature. It is inconceivable that 1% makes that much of a difference in nearly 100% of all standard heat treat processes. In those very few processes where temperature tolerances ARE required to be that tight, SAE’s AMEC committee could have come up with a separate standard.
Most temperature recorders and reporting devices don’t currently allow for the display of anything to the right of the decimal, especially above temperatures at or above 1000°F. That’s because no instrumentation company in the history of heat treating ever anticipated that end-users would want to know, much less be required to record, anything to the right of the decimal.
Even if recorders and other instruments were capable of displaying 1/10th of a degree readings, most temperature sensing devices are nowhere near that accurate. Special case T/Cs can do it in certain situations, but by and large, thermocouples are calibrated to ±2°F or higher. How much sense does it make to worry about recording 1/10th of a degree accuracy from a thermocouple (and wire) that is rated at ±2°F or ±5°F.
Let’s pretend for a minute that our thermocouples could accurately and consistently record temperatures down to 1/10th of a degree. The question that really needs to be asked is: Just because we CAN do it, does that mean we SHOULD do it? As stated earlier, for that vast majority of heat treatment processes a full degree of temperature variance won’t typically make a difference.
As some of the people I’ve talked to about this situation have readily admitted, well-intended quality committees such SAE’s AMEC committee, who have inadvertently started this little kerfuffle, are not perfect. This would be a case in point. The men and women who make up the heat treat industry’s quality systems are excellent people: highly detailed and well-motivated. But, as all of us are, they are prone to over-do the things they’re good at. In this case, that’s deciding to take it down to 1/10th of a degree when rounding to the next closest integer probably would have done the trick.
Postscript: I’m open to your responses to this column, positive or negative. And, assuming there is no foul language or threats of physical violence (!), we would be glad to publish your comments. Please let us know what you think: htt@heattreattoday.com
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Where did the ±0.1°F AMS2750 requirement come from and how should heat treaters approach this specification, an important change that entails major buy-in? Andrew Bassett, president and owner of Aerospace Testing and Pyrometry, was at the AMS2750F meeting. He shares the inside scoop on this topic with Heat Treat Today and what he expects for the future of this standard.
Heat Treat Radio podcast host and Heat Treat Today publisher, Doug Glenn, has written a column on the topic, which you can find here; read it to understand some of the background, questions, and concerns that cloud this issue.
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.
Doug Glenn: Andrew Bassett, president and owner of Aerospace Testing and Pyrometry, Inc., somewhere in eastern Pennsylvania. We don’t know because you’re on the move! What is your new address, now, by the way?
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Andrew Bassett: We are in Easton, Pennsylvania at 2020 Dayton Drive.
Doug Glenn: Andrew, we want to talk a bit about this ±0.1°F debate that is going on. It was actually precipitated by the column that I wrote that is in the February issue.
I just wanted to talk about that debate, and I know that you’ve been somewhat involved with it. So, if you don’t mind, could you give our listeners a quick background on what we are talking about, this ±0.1°F debate.
Andrew Bassett: To be honest with you, being part of the AMS2750 sub team, one of the questions came up for us during the Rev F rewrite was this 0.1°F readability — wanting to kind of fix this flaw that’s been in the standard ever since the day that AMS2750 came out. With instrumentation, for instance, you have ±2°F (the equivalent would be 1.1°C). At 1.1°C, the question became, If your instrumentation does not show this 0.1 of a degree readability, how can you show compliance to the standards?
Andrew Bassett President Aerospace Testing and Pyrometry Source: DELTA H
Then, it morphed into other issues that we’ve had in the previous revisions where we talk about precise temperature requirements, like for system accuracy testing: You’re allowed a hard number ±3° per Class 2 furnace or 0.3% of reading, whichever is greater. Now, we have this percentage. With anything over 1000°F, you're going to be able to use the percentage of reading to help bring your test into tolerance. In that example, 1100°F, you’re about 3.3 degrees. If your instrumentation doesn’t show this readability, how are you going to prove compliance?
That’s what it all morphed into. Originally, the first draft that we proposed in AMS2750F was that all instrumentation had to have 0.1°F readability. We got some feedback (I don’t know if I want to say “feedback” or "pitchforks and hammers") that this would be cost-prohibitive; most instrumentation doesn't have that readability, and it would be really costly to go out and try to do this. We understood that. But, at the end of the day, we said: The recording device is your permanent record, and so that’s what we’re going to lean on. But we still had a lot of pushback.
We ended up putting a poll out to AMEC and the heat treating industry to see what their opinions were. We said that with the 0.1 readability (when it came to a percentage reading), recording devices would read hard tolerances. So, for instance, an SAT read at 3° would be just that, not "or .3% of reading."
There was a third option that we had put out to the community at large, and it came back as the 0.1° readability for digital recorders, so that’s where we ran with the 0.1° readability.
When it was that big of an issue, we didn’t make the decisions ourselves; we wanted to put it out to the rest of the community. My guess is not everyone really thought the whole thing through yet. Now people are like, ok, well now I need to get this 0.1° readability.
Again, during the meetings, we heard the issues. Is 0.1° going to really make a difference to metal? If you have a load thermocouple that goes in your furnace and it reads 0.1° over the tolerance, does it fail the load? Well, no, metallurgically, we all know that’s not going to happen, but there’s got to be a line in the sand somewhere, so it was drawn at that.
"...that hard line in the sand had to be drawn somewhere..." Source: Unsplash.com/Willian Justen de Vasconcellos
That’s a little bit of the background of the 0.1° readability.
Doug Glenn: So, basically, we’re in a situation, now, where people are, in fact (and correct me if I’m wrong here), potentially going to fail SATs or tests on their system because of a 0.1° reading, correct? I mean, it is possible, correct?
Andrew Bassett: Yes. So, when the 0.1° readability came out in Rev F, we gave it a two-year moratorium that with that requirement, you still had two more years. Then, when Rev G came out, exactly two years to the date, we still had a lot of customers coming to us, or a lot of suppliers coming back to us, and saying, “Hey, look, there’s a supply shortage on these types of recorders. We need to buy some time on this.” It ranged from another year to 10 years, and we’re like — whoa, whoa, whoa! You told us, coming down the pike before, maybe you pushed it down the road, whatever, probably Covid put a damper on a lot of people, so we added another year.
So, as of June 30th of 2023, that requirement is going to come into full play now. Like it or not, that’s where the standard sits.
Doug Glenn: So, you’re saying June 30th, 2023?
Andrew Bassett: Yes.
Doug Glenn Alright, that’s good background.
I guess there were several issues that I raised. First off, you’ve already hit on one. I understand the ability to be precise, but in most heat treatment applications, one degree is not going to make a difference, right? So, why do we push for a 0.1° when 1° isn’t even going to make a difference?
Andrew Bassett: We know that, and it’s been discussed that way. But, again, that hard line in the sand had to be drawn somewhere, and that was the direction the community wanted to go with, so we went with that. Yes, we understand that in some metals, 10 degrees is not going to make a difference, but we need to have some sort of line in the sand and that's what was drawn.
Doug Glenn: So, a Class 1. I was thinking the lower number was a tighter furnace. So, a Class 1 (±5), and you’re saying, that’s all the furnace is classified for, right, ±5? So, if you get a reading of 1000°, it could be 1005° or it could be 995°. Then, you’re putting on top of that the whole idea that your temperature reading has got to be down to 0.1°. There just seems to be some disconnect there.
So, that was the first one. You also mentioned the instrumentation. It’s been pointed out to me, by some of the instrumentation people, that their instruments are actually only reading four digits. So up to 99.9 you actually have a point, but if it goes to 1000°, you’re out of digits; you can’t even read that. I mean, they can’t even read that down to a point.
"So, if you get a reading of 1000°, it could be 1005° or it could be 995°." Source: Unsplash.com/Getty Images
Andrew Bassett: Correct. On the recording side of things, we went away from analog instrumentation. The old chart papers, that’s all gone, and we required the digital recorders with that 0.1° readability, as of June 30th of this year.
Again, the first draft was all instrumentation. That would be your controllers, your overtemps, and we know that limitation. But everyone does have to be aware of it. We still allow for this calibration of ±2 or 0.2%. If you’re doing a calibration, let’s say, on a temperature control on a calibration point at 1600° and the instrument only reads whole numbers, you can use the percentage, but you would have to round it inward. Let’s use 1800°, that would be an easier way to do it. So, I’m allowed ±2 or 3.6° if I’m using the percentage of reading, but if the instrument does not read in decimal points for a controller or overtemp, you would have to round that down to ±3°.
Doug Glenn: ±3, right; the 0.6° is out the window.
Andrew Bassett: Correct. I shouldn’t say we like to bury things in footnotes, but this was an afterthought. In one of the footnotes, in one of the tables, it talks about instrumentation calibration that people need to be aware of.
Doug Glenn: Let’s just do this because I think we’ve got a good sense of what the situation is, currently. Would you care to prognosticate about the future? Do you think this is going to stand? Do you think it will be changed? What do you think? I realize you’re speaking for yourself, here.
Andrew Bassett: I’m conflicted on both sides. I want to help the supply base with this issue but I’m also on the standards committee that writes the standard. I think because we’re so far down the road, right now — this requirement has been out there since June 2022 — I don’t see anything being rolled back on it, at this point. I think if we did roll it back, we have to look at it both ways.
If we did roll this back and say alright, let’s just do away with this 0.1° readability issue, we still have to worry about the people processing in Celsius. Remember, we’re pretty much the only country in the world that processes in Fahrenheit. The rest of the world has been, probably, following these lines all along. If we rolled this back, just think about all the people that made that investment and moved forward on the 0.1° readability and they come back and say, “Wait a minute. We just spent a $100,000 on upgrading our systems and now you’re rolling it back, that’s not fair to us.”
At this point, with the ball already rolling, it would be very interesting to see when Nadcap starts publishing out the audit findings when it comes to the pyrometry and this 0.1° readability to see how many suppliers are being hit on this requirement and that would give us a good indication. If there are a lot of yeses on it then, obviously, a lot of suppliers haven’t gone down this road. My guess is, for the most part, anybody that’s Nadcap accredited in heat treating — and this goes across chemical processing, coatings, and a few other commodities — I think has caught up to this.
Personally, I don’t think this is going to go away; it’s not going to disappear. It’s going to keep going down this road. Maybe, if people are still struggling with getting the types of devices that can have that 0.1° readability, then maybe another year extension on it, but I don’t know where that is right now. I haven’t gotten enough feedback from aerospace customers that say, "Hey, I can’t get the recorder." I mean,
Doug Glenn: I just don’t understand, Andrew, how it’s even physically possible that companies can record something as accurately as 0.1° if the assembly or thermocouple wire is rated at ±2°? How is that even possible that you can want somebody to be accurate down to ±0.1° when the thing is only accurate up to ±2°?
Andrew Bassett: Right, I get that. We can even go a lot further with that and start talking about budgets of uncertainty. If you look at any reputable thermocouple manufacturer or instrument calibration reports that are ISO 17025, they have to list out their measurements of uncertainty, and that gives you only the 98% competence you’re going to be within that accuracy statement.
Yes, I get the whole issue of this .1° readability. There were good intentions were to fix a flaw, and it spiraled. We’ve seen where PLCs and some of these high logic controllers now can show the .1° readability, but they automatically round up at .5°. Are you now violating the other requirements of rounding to E29? Now, I think we’ve closed out the poll in the standard, but you’re right. We were trying to do the right thing. Personally, I don’t think we gave it all that much further thought on that except hey, let’s just make recorders this way and this should be okay.
Doug Glenn: Right. No, that’s good. Let me be clear, and I think most everybody that was involved with the standards are excellent people and they’re trying to do the right thing. There is no dissing on anybody that was doing it. I’m not a furnace guy, right, I’m a publisher — but when I look at it, I’m going: okay, you’re asking somebody to be as accurate as 0.1° on equipment that can only do ±2°. That’s a 4° swing and you’re asking them to be within 0.1°, basically.
Andrew, this has been helpful. It’s been good hearing from you because you’re on the frontline here. You’ve got one foot firmly planted in both camps.
Andrew Bassett: I’m doing my best to stay neutral with it all.
Doug Glenn: Anyhow, I appreciate it, Andrew. You’re a gentleman. Thanks for taking some time with us.
Andrew Bassett: Thanks, Doug. Appreciate it.
About the expert: Andrew Bassett has more than 25 years of experience in the field of calibrations, temperature uniformity surveys, system accuracy testing, as well an expertise in pressure, humidity, and vacuum measurement calibration. Prior to founding Aerospace Testing & Pyrometry, Andrew previously held positions as Vice President of Pyrometry Services and Director of Pyrometry Services for a large commercial heat treater and Vice President and Quality Control Manager for a small family owned business.
Heat treating solutions are important for more than keeping an airplane flying in the sky or a bridge suspended above the water. These two examples are high profile, but what about the heat treating solutions that do not zoom through the air or mark the skyline above rivers? In the medical industry, heat treating solutions are often unseen unless something goes wrong.
When it comes to medical implant and device heat treating, what options are available to manufacturers that will benefit patients? What should we know about the heat treating processes that make metal parts functional as knees, hips, and elbows? Find out in this expert analysis from Quintus Technologies and ECM USA, Inc.
This Technical Tuesday article was first published in Heat Treat Today's December 2022 Medical and Energy print edition.
Introduction
Dan McCurdy, former president at Bodycote, Automotive and General Industrial Heat Treatment for North America and Asia, knows full well just how much time, energy, and pain the right medical heat treating practice and alloy composition can save a patient. Dan’s wife suffered from complications due to a nickel allergy in a traditionally thermally-processed ASTM F75 knee implant. She dealt with constant inflammation, swelling, and pain. Physical therapy and a second procedure did nothing to ease the discomfort. The best medicine for Dan’s wife? A specially heat treated medical implant (more of Dan's story can be found at the end of this article).
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To understand the stories behind final medical products, Heat Treat Today asked Quintus Technologies and ECM USA, Inc. to share two different approaches on medical implant and device heat treatment. These two companies at the forefront of the medical heat treating industry shared about hot isostatic pressing (HIP) with additive manufacturing, and vacuum heat treating. Read their answers to our questions and learn how, when it comes to implantable medical devices, heat treating can be the best medicine.
How do you ensure your equipment maintains the precise specifications required in the medical industry? What specifically is necessary to maintain compliance when it comes to medical implants?
Quintus Technologies
Chad Beamer Applications Engineer Quintus Technologies
Quintus Technologies has observed a trend in bringing Nadcap to the medical industry. Historically the medical industry has focused on the standards and regulations for the quality management system of their approved supplier, but a consistent transition to technical aspects of critical processes (including HIPing) is becoming the norm. Quintus Technologies’ background is one of delivering HIP equipment in line with Nadcap and AMS2750 specifications. The medical industry requires best-in-class temperature uniformity and accuracy; systems designed with production driven flexibility (such as thermocouple quick-connectors for T/C sensor installation
to minimize downtime); HIP furnaces equipped with uniform rapid cooling (URC®) for optimized cycle productivity; active involvement in standards committees; and working directly with the industry.
Requirements are increasing in terms of productivity and the introduction of more complex surface requirements. It is crucial to work closely with the industry to reduce oxidation of orthopedic implants during the HIP and heat treatment processes.
Steering of the HIP cycle is key, along with in-HIP heat treatments to achieve the desired microstructure for the application, which is a standard offering for High Pressure Heat Treatment™ (HPHT™) equipment.
ECM USA, Inc.
Dennis Beauchesne General Manager ECM USA, Inc.
Some of the features that are most important are leak rate at deep vacuum along with a chamber and furnace design that does not contribute to any contamination. In our systems, these features, along with others, are of the utmost importance when supplying equipment for the medical implant market.
What are the top 3–5 key requirements or compliance/quality issues needed to heat treat medical implants?
Quintus Technologies
There are several industry standards that have been released to establish key requirements for the HIP process that are often leveraged for medical applications demanding performance and reliability. For example, Nadcap has released AC 7102/6 which details the audit criteria for HIP. This document was developed with significant input from the industry and the government to define operational requirements for quality assurance. It offers a checklist for the HIP processing of metal products and includes requirements for:
managing the equipment per pyrometry standard AMS2750
qualifying technical instructions and personnel training
handling product during the loading and unloading operations
complying with gas purity requirements of the pressure medium
controlling temperature, including uniformity and accuracy evaluations and management
These aspects are critical to ensure product quality meeting medical customer requirements and expectations. Recent additions beyond conventional requirements highlighted above include high speed cooling in the HIP process (>200 K/min) for some materials which is important for metallurgical results.
ECM USA, Inc.
Key requirements include thermal performance (both uniformity and ramp control); real-time vacuum and gas management; traceability and production lot follow up through human machine interface (HMI); quality procedures for all sensor calibrations; and remote access for control and troubleshooting.
Can you share an example of how your equipment could be used to heat treat a medical implant/device from start to finish?
Quintus Technologies
Many medical implants — whether fabricated using conventional processing techniques such as casting, or more novel approaches such as additive manufacturing — require HIP to eliminate process related material defects. Defects include shrinkage porosity for castings and lack-of-fusion and keyhole defects for fusion based additive manufacturing techniques. These defects can have a negative impact on product quality, impacting performance and reliability. Once HIP has been applied to a material, post processing is often not complete, with additional thermal treatments required to achieve the optimum microstructure leading to the desired material properties and performance. Such thermal treatments are material and process dependent, but could include a stress relief, solution anneal, rapid cooling or quenching, and aging and are often applied in separate heat treat equipment.
Hot Isostatic Press QIH 60 offering our most advanced Uniform Rapid Cooling (URC®) furnace technology with industry leading temperature control and accuracy
Quintus Technologies has introduced HIP systems providing capabilities beyond conventional densification. Decades’ worth of work in equipment design, system functionality, and control now offers an opportunity to perform HIP and heat treatment in a combined cycle, referred to as HPHT. Combined HIP and heat treatment for castings and AM implants can mitigate the risk of thermally induced porosity, as well as grain growth, which can offer advantages for mechanical and chemical properties in implants. This methodology provides a more sustainable processing route with improved productivity and energy efficiency. A joint HIP and heat treatment offers significant advantages with lead time, and this improvement in lead time couples well with the demands placed on the personalized medical implants. It also offers opportunities to further optimize microstructures for improvement in material properties coupled with ease of manufacturability. HPHT and modern HIP equipment may allow for a higher performing material system, which produces an implant with improved reliability and life.
Within the medical industry, fine grain AM microstructure, repeatability, and low porosity are key concerns. There are many reported benefits by applying the combined HPHT route such as reduced number of process steps, reduced cycle time and lead time, and improved process and quality control. Other advantages include spending less time at elevated temperatures helping to preserve the fine grain AM microstructure by minimizing grain growth. Tight control and steering of the cooling rates during the different steps of the HPHT cycle ensures repeatability of the properties. Manufacturability can be improved through HPHT as this approach reduces the cooling or quench severity during cooling segments which can often lead to part distortion or cracking. Improved functionality and
control go hand-in-hand with the high quality and reliability demanded in the medical industry.
ECM USA, Inc.
We have several customers making titanium alloy prothesis for various applications: shoulders, hips. Our furnaces are used for post printing processes, such as stress relieving and solution annealing.
Given concerns of metal poisoning, do you know of any changes in alloy composition of medical devices over the last decade?
Quintus Technologies
There are some metals that are becoming more common for implants, including tantalum, magnesium, CP Titanium, etc., and there have been major steps in improving ceramic materials to compete with metals for many applications.
ECM USA, Inc.
As a vacuum furnace equipment supplier, we are not deeply involved in the entire process of material selection. In the early stages of 3D printing joint replacements, from 2013 to 2014, we saw cobalt being part of some alloys. Lately it seems, indeed, that there is a trend in removing that element from the finished parts.
A Happy Ending
Dan McCurdy Former president, Bodycote, Automotive and General Industrial Heat Treatment for North America and Asia
(The rest of Dan's story from the beginning of the article....) The effects of metal poisoning and metal allergies post-surgery can be devastating. In the narrative below, Dan McCurdy shares the story of his wife’s struggle with an allergic reaction to a knee implant, and the heat treating solution that proved to be the best medicine for her.
My wife, an avid runner up and down the hills of Cincinnati, was diagnosed with osteoarthritis in both knees at the age of 53. Her orthopedist suggested a knee replacement for the most degraded one. The replacement was a well-known brand, made from investment-cast ASTM F75 (nominally a Co-Cr-Mo alloy) with full FDA-approval. After a successful surgery and diligent physical therapy, her recovery plateaued, and she experienced chronic inflammation, swelling, and pain.
A blood test, designed to detect allergies to materials used in orthopedic implants, showed a reaction to nickel that was nearly off the charts. We were surprised, as she had previously tested negative for nickel allergies through skin patch testing. The ASTM F75 specification allows for up to 0.5% bulk nickel as a tramp element in implantable devices; however, depending on foundry practices, the concentration of tramp alloys at any point on the surface of a casting can vary significantly. Titanium implants may be the solution to this, but FDA-approved titanium alloys can still contain up to 0.1% Ni.
The solution for my wife, as it turned out, was a different material, originally developed for the nuclear industry, along with an innovative heat treatment process. Created with an alloy of zirconium and niobium (with a maximum nickel content of 0.0035%), her new knee was heat treated at a high temperature in an oxidizing environment, which converts the soft zirconium surface into hard ceramic zirconia, increasing hardness and wear resistance. With this specially heat treated implant in place, my wife is back to nearly 10K steps a day.
References
[1] Magnus Ahlfors and Chad Beamer. “Hot Isostatic Pressing for Orthopedic Implants.” quintustechnologies.com/knowledge-center/hot-isostatic-pressing-for-orthopedic-implants. Quintus Technologies. 2020.
[2] Chad Beamer and Derek Denlinger. “Hot Isostatic Pressing: A Seasoned Player with New Technologies in Heat Treatment — Expert Analysis.” www.heattreattoday.com/processes/hot-isostatic-pressing/hot-isostatic-pressing-technical-content/hot-isostatic-pressing-a-seasoned-player-with-new-technologies-in-heat-treatment-expert-analysis/. Heat Treat Today. 2020.
ThermTech, heat treat service provider in Waukesha, WI, has increased their capabilities to provide services for the medical, aerospace, mining and oil, nuclear, and agricultural industries.
Jason Kupkovits, vice president of Sales & Strategic Direction at the company, commented on that ThermTech will be continuing their 40 years of quality assurance, turnaround time, on-site engineering, and customer service standards.
Ben Gasbarre Executive Vice President of Sales Gasbarre Thermal Processing Systems
Partnering with Gasbarre Thermal Processing Systems, ThermTech significantly increased their normalizing, annealing, stress relieving, tempering, and neutral hardening capacity through the acquisition of three new furnaces. These three furnaces --- now fully operational --- include: a dual zone, direct-fired box austenitizing furnace; a large batch tempering furnace; and an additional tempering furnace. These furnaces are compliant with AMS2750 at different class certifications.
ThermTech has also added two additional vacuum furnaces from Ipsen, USA. The furnaces have dimensions of 36” wide x 36” tall x 48” long with capabilities of quenching up to 6 bars of pressure utilizing nitrogen or argon gas as the quench medium. These large vacuum furnaces are AMS class 3 (+/-15°F) certified capable of AMS2750.
ThermTech added a solution annealing furnace from Williams Industrial Service to give their operational aluminum line additional heat treat capabilities. This line is capable of a sub-15 second transfer to air blast quench, a water quench range of 55°F up to boiling, a sub-7 second transfer to water quench which exceeds AMS 2770/AMS2771 specifications, as well as load thermocouple monitoring during the solution treatment, quenching, and aging.
Daniel Hill, PE Sales Engineer AFC-Holcroft Source: AFC-Holcroft
Another recent acquisition includes a new austempering/marquenching furnace from Michigan based AFC-Holcroft. This furnace can handle a single part racked in the vertical orientation up to 56" long. The working dimension of the furnace is 36" W x 72" L x 56" H and is capable of operating with salt temperatures ranging from 350°F -- 750°F. "The UBQA system is an environmentally friendly ‘green technology,’" commented Dan Hill, sales engineer at AFC-Holcroft, "which can be used to impart resistance to distorting, cracking or warping of heat-treated components.” Applicable processes include marquenching, austempering, and carburizing with additional washing and tempering capacity accompanying the new marquenching/austempering furnace. Installation is expected in early 2023.
The heat treat service provider's long-term strategy is to increase growth in the Midwest and on a national scale. This includes adding more workers and integrating the use of a robotics handling systems, which is expected to be installed in late 2022.
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A firearms manufacturer based in the U.S. has ordered a vacuum heat treating furnace from a Pennsylvania manufacturer.
Solar Manufacturing Inc. announced the receipt of the heat treat furnace, a model HFL-5748-2IQ, which has a hot zone of 36” x 36” x 48” deep with a weight capacity of 5,000 lbs. Its maximum operating temperature is 2400°F and it heats to 2500°F for hot zone bake out. The furnace design also has a temperature uniformity of ±10°F and is AMS2750 compliant with vacuum levels in the low micron range.
For rapid turnaround for work cooling, a 100 HP gas blower is provided for operating at 15 PSIG (2-bar) in nitrogen gas. The furnace is complete with a SolarVac® Polaris fully automated and programmable industrial controls package, and a Eurotherm digital chart recorder.
What is the connection between AMS2750 specifications and furnace classifications? With tight specifications, what does the heat treater need to know to be compliant? Follow along as we take a brief look into this often-overlooked topic.
