Moog

Heat Treat Radio #111: Heat Treat NextGen Brynna Keelin Kelly-McGrath

If curiosity were a person, Brynna Keelin Kelly-McGrath would be her name. Having risen at Moog, Inc. to the position of materials and process engineer, Brynna shares her early STEM interests and how she stays up-to-date on industry trends and ideas. In this highly engaging NextGen profile on Heat Treat Radio — with host and Heat Treat Today’s publisher, Doug Glenn — get to know this talented metallurgist.  

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.

Meet Brynna Keelin Kelly-McGrath (01:00)

Doug Glenn: Let’s jump into today’s Heat Treat Radio episode with Brynna Keelin Kelly-McGrath from Moog, Inc. It’s a great pleasure to be here today with Brynna, who is one of our 40 Under 40 Class of 2023 award recipients. First off, congratulations on that award, and welcome to Heat Treat Radio.

Brynna Keelin Kelly-McGrath: Thank you so much. That was an honor.

Doug Glenn: Brynna lives just south of Buffalo, New York. As you know, this interview is to get to know you a little bit more — how you got into metallurgy, heat treating, and all that good stuff. Let’s start way back. Give us a little bit about yourself as a younger person, maybe high school age and moving on up through, and then how you got involved with heat treating and metallurgy.

Check out Brynna’s 40 Under 40 profile. Click the logo.

Brynna Keelin Kelly-McGrath: Sure. I grew up in a little town called West Falls, south of Buffalo, New York, and about 20 minutes from Moog. While I was in high school, I took AP chemistry and physics and fell in love with those topics. I knew from a younger age that I was going to wind up being an engineer eventually; I just didn’t know what kind. But I was pretty sure I wanted to be a chemical engineer, so I toured a couple of colleges.

At one of them, I met with a materials science professor to talk about the differences between chemical and materials science engineering. I was sold. I was all set and ready to go be a polymers engineer. I picked Purdue University, started going there, and was absolutely loving it.

The summer after my freshman year, I got an internship with Moog, which was right around the corner from my hometown. The internship was primarily metallurgical, due to the nature of Moog’s products, and I absolutely loved it. I was not expecting to like it, and it was just so great. So, I transitioned all of my coursework over to metallurgy, and I kept coming back to Moog for internships, and that was fantastic.

Learning from Industry Experts (03:32)

When I started off at Moog, it was right around the time when two of our subject matter experts in heat treatment were transitioning to retirement. I started learning as much as I could as fast as I could about heat treatment. There was obviously a lot to learn there, but it was a great time.

After working at Moog for a couple of years, I decided I wanted to go back and pursue my other passion, which was manufacturing engineering. So, right now I’m working on a master’s degree after work to combine metallurgy and manufacturing.

“When I started off at Moog, it was right around the time when two of our subject matter experts in heat treatment were transitioning to retirement. I started learning as much as I could as fast as I could about heat treatment.”

Brynna Keelin Kelly-McGrath, Moog

Doug Glenn: Wow. You’re a classic overachiever. That’s pretty good. And you said Purdue, correct?

Brynna Keelin Kelly-McGrath: Yeah.

Doug Glenn: Okay. And you did your undergrad there. Did you actually end up graduating with a materials engineering degree or a metallurgy degree?

Brynna Keelin Kelly-McGrath: Materials science and engineering.

Brynna shares how she got started in the industry.
Source: Heat Treat Today

Doug Glenn: All right. Good. You spent the summers back at Moog and enjoyed that. You know, we see a lot of the older generation retiring, so you’re filling the brain drain, as we say, which is great. Are there are many other young people at Moog?

Brynna Keelin Kelly-McGrath: Yeah, their internship co-op program has been fantastic in bringing in a lot of students right out of college and getting them hooked on our product line and the sort of manufacturing we do. And we’re definitely getting more recent college graduates. But, you know, with people retiring, those are some awfully big shoes to fill.

Doug Glenn: For sure. What exactly does Moog make at your facility? They’re a large corporation; I know they usually make a lot of automotive, maybe aerospace, components but are you able to say specifically what Moog does there?

Brynna Keelin Kelly-McGrath: We specialize in high precision motion actuation systems. From a metallurgical side, we’re working with a ton of really cool materials. So it’s not just steels or aluminum, it is a lot of aerospace applications, defense. The materials and process engineering group is physically orchestrated on our headquarters campus as well as the space and defense building, so we do get to see quite a bit of that. From the metallurgical perspective, there is a lot to see and work on.

Doug Glenn: You mentioned you were thinking about being a chemical engineer, but then you saw the materials. Do you remember what it was about that and metallurgy that attracted you? Anything specific?

Brynna Keelin Kelly-McGrath: I remember sitting through that talk with a materials professor at Purdue, and he was talking about what the day to day of a chemical engineer versus materials engineer looks like. I will not pretend that he wasn’t biased, because he was a materials professor. But the work he described for materials engineering was so diverse, and there were options for different settings and what you could end up working on — from being in a steel mill to working in a lab like I do. There are a lot of options, a lot of cool things. The slogan at Purdue was something along the lines of: you can’t make it without materials.

Brynna’s Family Background (07:30)

Doug Glenn: That’s really neat. So, I haven’t asked you about your family at all. What did they think when you told them, hey, I’m thinking about being a materials engineer or a metallurgist?

Brynna Keelin Kelly-McGrath: My father is an industrial engineer, and my mother is a pharmacometrician, so they’re both in the stem field already. I think it was no surprise that I was going to pursue engineering and then, metallurgical engineering specifically. I think they were happy to encourage me to pursue any of my passions. And my father knew a couple of materials engineers and thought that it would work out for me. They were excited.

Undergraduate Research (08:16)

Doug Glenn: They were very supportive. That’s great. When you did your undergrad at Purdue, did you have to work on a final paper or any specific projects that were of interest to you?

Brynna Keelin Kelly-McGrath: I did some undergraduate research in the metallurgy realm. But my senior project for graduation was along the lines of characterizing shot for shot peening and the degradation of shot and the residual stress that it imparts. It was like a cool mix of FEA modeling with actually characterizing the material. It was a neat project.

Doug Glenn: Have you had to do any of that at Moog?

Brynna Keelin Kelly-McGrath: There’s a fair deal of materials characterization. We have shot peening, but I’m not super involved with it.

Current Work at Moog (09:35)

Doug Glenn: Gotcha. That’s interesting. Can you describe what your typical day at Moog looks like now and what you’re working on?

Brynna Keelin Kelly-McGrath: Sure. My typical day is a good deal of talking with all types of engineers, explaining metallurgical concepts. Because we work on a lot of different materials, there’s a lot to understand there. A good portion of my role is talking with other engineers about how a heat treatment procedure works or what’s metallurgically happening, how to modify a manufacturing sequence, how to design so that the product’s going to work.

But then I also specifically work in a failure analysis lab. This could be anything from something’s coming off the manufacturing line a little bit wrong or something failed in the field. We’ve got a beautiful characterization lab full of all the toys that you could think of, including two SEMs and a chemical lab. There’s a good deal of analysis there, too.

Doug Glenn: You seem like a person who enjoys your work. Is there any specific story or instance of something happening, either in school or at work, that really made you happy that you were in metallurgy and heat treat?

Brynna Keelin Kelly-McGrath: Oh, goodness. That’s a good question.

I would have to say I’ve had a couple projects at work, without getting into too many specifics, where we discovered something new metallurgically that we didn’t know was happening before. And then working through that, how did we not know it before? What do we know about it now? And what are we going to do to utilize this new thing that we discovered and take advantage of it? From a heat treat perspective, sometimes that means modifying our procedures, modifying our fixturing, creating something new.

It’s neat to see the modifications happen and come up with the new parts on the other end. It’s been very exciting to work on interdisciplinary teams like that.

“My typical day is a good deal of talking with all types of engineers, explaining metallurgical concepts. Because we work on a lot of different materials, there’s a lot to understand there. A good portion of my role is talking with other engineers about how a heat treatment procedure works or what’s metallurgically happening, how to modify a manufacturing sequence, how to design so that the product’s going to work.”
Source: Heat Treat Today

Doug Glenn: Yeah. I’m curious about this. You’ve been out in the work world for how many years?

Brynna Keelin Kelly-McGrath: Three and a half.

Doug Glenn: Okay. So, you’ve been out of school and working four years, and the amount you know about metallurgy and heat treating now is four years’ worth. Does it kind of amaze you the amount of stuff we don’t know?

Brynna Keelin Kelly-McGrath: Absolutely. Metallurgy is an old science, but you know we’re still [developing] the tools and technology and it’s great to find out new things.

Doug Glenn: Right. A lot of people get involved and say, “Well, I don’t want to go into metallurgy and heat treat because it’s a mature industry,” but I was curious if you felt the same way.

It’s really quite fascinating because there is a lot that happens. Like you were saying at Moog when you discovered things, a lot of stuff that’s happening and we really don’t know why. The more we can discover about it, the better.

Brynna Keelin Kelly-McGrath: Absolutely.

Top Industry Resources (12:58)

Doug Glenn: Let me ask you this. You obviously come from a smart family; you’ve got parents who are well educated, and you are as well. What are some of the metallurgical/heat treat resources that you use to stay current?

Brynna Keelin Kelly-McGrath: I think the best resource that’s out there is people. The network that I’ve been growing comes from a variety of different sources. I’m part of a few industrial committees, and it’s just a great way to meet people from all ends of the spectrum of metallurgy — from those producing the material to those making something out of it to the people who are going to use it all the way down the line.

Finding other metallurgists in those realms, and also through venues like ASM and our local Buffalo chapter — meeting people who have more experience than I do and have seen it before. If I’m seeing something for the first time, there’s definitely someone who spent their whole career on that. It’s really great to tap into those resources. That’s my number one.

And then my second choice would be the ASM handbooks. I’ve always got at least two open on my desk.

“I think the best resource that’s out there is people.”

Brynna Keelin Kelly-McGrath, Moog

Doug Glenn: Those are great resources. ASM over the years has pumped out some very, very good stuff. Is there anything else about your work or your schooling that is of interest or excited you that you’d like to share?

Brynna Keelin Kelly-McGrath: I really liked working at Moog because it’s a cool application where I can use my metallurgical knowledge along with this new manufacturing knowledge that I’m building up. That was my favorite intersection with my undergrad degree. And now I get to actually try that out in a working sense. That’s been great.

Doug Glenn: And you’re doing a master’s in industrial engineering?

Brynna Keelin Kelly-McGrath: Manufacturing engineering.

Doug Glenn: Where are you doing that?

Brynna Keelin Kelly-McGrath: The University of Michigan.

Doug Glenn: Remotely, I’m assuming?

Brynna Keelin Kelly-McGrath: Yes.

Doug Glenn: Very nice. And how far along are you, and how much longer do you have to go there?

Brynna Keelin Kelly-McGrath: I’m hoping to graduate in December, so I’m coming closer to the finish line.

Doug Glenn: Congratulations. That’s really good.

Rapid-Fire Round (15:44)

Doug Glenn: I want to move off of metallurgy and heat treat just to learn a little bit more about Brynna. All right, so these quick questions are what I call the rapid-fire round. Brace yourself. Are you a Mac or a PC person?

Digital vs. print?: “I prefer digital. I like to have all of my work life very organized by topic, and it’s way easier for me to organize everything if I have a digital copy of it.”

Brynna Keelin Kelly-McGrath: I am a Mac person through and through. I love my Mac.

Doug Glenn: Do you use a Mac at work?

Brynna Keelin Kelly-McGrath: I wish, but no.

Doug Glenn: We have an ongoing debate here. We had a couple people that came into the organization with Macs, and I’ve always been a PC guy. So, anytime there’s a computer problem, we tease each other, “Well, that’s because you’re working on a Mac/you’re working on a PC.” Well, that’s good to know. And for your phone: Are you an Apple phone person?

Brynna Keelin Kelly-McGrath: Yeah, I’ve got an iPad. And I just got a new MacBook Air the other day.

Doug Glenn: You’re hardcore. Very good.

So, we’re a publishing company here at Heat Treat Today. And I like to ask this question: When you consume media, do you prefer hard copy or digital?

Brynna Keelin Kelly-McGrath: I prefer digital. I like to have all of my work life very organized by topic, and it’s way easier for me to organize everything if I have a digital copy of it. So even if it’s a print copy, I’ve been known to scan and file it the way that I file everything else.

Doug Glenn: Okay. Now what do you value more in work — a flexible work schedule or high pay?

Brynna Keelin Kelly-McGrath: I’m going to go with flexible work schedule. I’ve had some people close to me who have the high pay but no flexibility. And they’re the ones more jealous, so I’m going to go with that. I’ll take the flexibility.

Doug Glenn: That’s a great answer. Here’s one: Would you rather work remotely or in an office?

Brynna Keelin Kelly-McGrath: In an office 100%, I am definitely of the variety that likes to be around people. I would rather have people to talk to face to face than doing it over Teams.

Doug Glenn: I kind of assumed you were like that. How did you handle all the isolation that came with the recent pandemic?

Brynna Keelin Kelly-McGrath: I was still in college at that time for most of Covid. Purdue was only remote for half of one semester. It was a reasonably short time. And then the rest of the time we had limited capacity in classrooms and things. But when I was coming back for my internships, our department was classified as essential. We were coming into the office every day, and that was good, I enjoyed that.

Doug Glenn: So, you didn’t necessarily really have a lot of the isolation or as much as you might have had.

Brynna Keelin Kelly-McGrath: Yep.

Doug Glenn: That’s good. Okay, I won’t keep going down that road. I think that whole time period has been very impactful on our society. And I’m curious how people feel it has affected them.

I know you love working at Moog, but if you had a dream job, what would it be?

Brynna Keelin Kelly-McGrath: I don’t know. I think someday down the line, it would be cool to have my own manufacturing business. I don’t have a product in mind at the moment, but in my thoughts it has to do with metallic components and heat treatment, because that’s my passion. That would be great.

Doug Glenn: Very interesting, owning your own company and manufacturing something metal. You know what? That’s where it starts. You’re three and a half years out, and you’ve got time to develop more specificity over time. But that’s good to even know that you’re moving in that direction.

I assume you don’t work all the time. What do you do? What do you do in your free time? What do you like? What are your passions outside of work?

Brynna Keelin Kelly-McGrath: The number one time consumer at the moment is that master’s degree. But then, you know, on a pure fun basis, my husband and I are avid golfers. And all of the very short Buffalo summer we’re trying to be out there on the golf course.

“But then, you know, on a pure fun basis, my husband and I are avid golfers. And all of the very short Buffalo summer we’re trying to be out there on the golf course.”
Source: Richard-7 / Getty Images Signature

Brynna Keelin Kelly-McGrath: I’m also a bluegrass fiddler. I play in a couple bands. And that’s pretty fun, too. It’s almost Saint Patrick’s Day.

Doug Glenn: You’re a musician? You know, I’ve heard that there are some engineering schools who don’t ask you if you play an instrument, they ask you what instrument you play because there is a correlation somehow or other between music and engineering. Maybe it’s the methodical-ness, the orderliness, and all that stuff.

Brynna Keelin Kelly-McGrath: Neat, I didn’t know that.

Doug Glenn: If you’re playing bluegrass fiddle, I assume you play some by ear. I mean, I assume you’ve got some sort of natural talent there. Is that safe to say?

Brynna Keelin Kelly-McGrath: Yeah, I started that at a decently young age. And now my husband and I are learning piano as well, so it’s been fun.

Doug Glenn: What does your husband do by chance?

Brynna Keelin Kelly-McGrath: He’s a software engineer.

Doug Glenn: Two engineers in one house. That’s got to be interesting dinner time talk. That’s wonderful.

Okay. Last question for you. I give people an option here. You can answer any one of these three. What would be your favorite app, movie, or magazine?

Brynna Keelin Kelly-McGrath: The first thing that came to my mind when you asked that question was Audible. At the moment, I’m hooked on reading, or listening, to a lot of books. I consider it reading in the little bits of downtime here and there grocery shopping and driving in the car and things like that. It’s nice to spend that time a little bit more productively.

Doug Glenn: I’m with you. I think that’s great. I assume maybe you can even do some of your school reading on Audible?

Brynna Keelin Kelly-McGrath: I haven’t tried that yet. Honestly.

Doug Glenn: Sometimes people learn better by actually reading. But other people learn better by listening, so that’s fine.

If you were to encourage young people to really look into metallurgy materials, what would you tell them? What would be your encouragement to them?

Brynna Keelin Kelly-McGrath: I think the most impactful thing for me at that age was actually getting to see what they do. At Moog, I act as a tour guide for a lot of high school students. I try to show them as closely as possible what we do and what a day looks like. Because it’s great to think about the theory, but at the end of the day when you graduate with that degree, you’ve got to go work. I encourage high school students to get out there and see as many jobs as possible. Shadow people — I guess that would be my advice.

Doug Glenn: That’s good. Well, Brynna, thanks so much. Congratulations again on being awarded 40 Under 40 this last year. And thanks for taking some time to chat with us.

Brynna Keelin Kelly-McGrath: Thank you so much.

About The Guest

Brynna Keelin Kelly-McGrath
Materials and Process Engineer
Moog, Inc.
Source: Brynna Keelin Kelly-McGrath

Brynna Keelin Kelly-McGrath received her bachelor’s degree in Materials Science and Engineering from the Purdue University Honors College. She is currently working on a master’s degree in Manufacturing Engineering from the University of Michigan Ann Arbor. Brynna conducts metallurgical support for day-to-day heat tree issues and non-conformances across several divisions within Moog, Inc. She was recognized in Heat Treat Today’s 40 Under 40 Class of 2023.

Contact Brynna by visiting Moog, Inc.’s website: www.moog.com.


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Demonstrating Oil Quenching Effectiveness

In this article by Lee Gearhart, Principal Engineer, Materials and Processes, Moog, Inc., and Chair, Aerospace Metals Engineering Committee, read about a “real time” heat treat inquiry regarding the interpretation of changed oil quenching effectiveness testing in AMS 2759, and Lee’s desire to ensure that the heat treater’s system maintains its effectiveness.

This article article first appeared in the latest edition (June 2020) of Heat Treat Today’s Automotive Heat Treat magazine.

* Please see the bottom of the article to view the AMS2759 sections to which Lee refers.


The Query:

Lee Gearhart, Principal Engineer, Materials and Processes, Moog, Inc., Chair, Aerospace Metals Engineering Committee

A gentleman, to whom I’ll refer as Mr. XXXX, sent the following query to SAE, the publisher of Aerospace Materials Specifications. The subject line was as follows: “Clarification of AMS 2759G for Committee ‘E’.”

The letter read:

I would like to get some clarification about AMS 2759, Revision G, paragraphs 3.10.3 through 3.10.3.1.5.5. My issue, as an independent testing lab, is the terminology used in 3.10.3.1.5.1 and 3.10.3.1.5.3., and how

I am to determine the acceptance criteria for the hardness in the center diameter of the quench effectiveness samples supplied to us by heat treating companies. Let me walk through the steps that lead up to the determination of minimum hardness at the center of the diameter of the coupon prepared.

Paragraph 3.10.3.1.2 states specific size test bars to use for the quench effectiveness testing, based on the alloy, in sub-paragraphs a., b., c., and d. For 4130 (a.), use 1.5” long, 0.50” diameter bar and for 4330V (c.), use 7.5” long, 2.5” diameter bar. Then, we cut the test coupon from this specimen todetermine hardness at the center diameter, per 10.3.1.4.

Next, we have to determine whether this hardness result, taken at the center diameter, conforms to the spec, and here is where my issue is. Paragraphs 10.3.1.5.1 and 10.3.1.5.3 both state, “…shall not be less than the hardness on the end-quench hardenability curve corresponding to the diameter of the specimen…” So, if I am to use the diameter of the specimen as my guide from paragraph 3.10.3.1.2, a.and c., then the end-quench result on the mill cert corresponding to 8/16 would represent the 0.50”diameter, and 40/16 would represent the 2.5” diameter. ASTM A255 has you stop taking readings on the Jominy bar at 32/16 (2.0”), so there would not be a result on the Mill Cert for the 40/16 requirement.

I don’t believe this is the correct depth. I believe the end-quench result corresponding to one-half the diameter would be the appropriate depth to use as a minimum requirement, since we are taking the hardness reading at one-half the diameter; in the center of the diameter. So, the end-quench result on the mill cert corresponding to 4/16 would represent the 0.50” diameter and 20/16 would represent the 2.5” diameter bar. These requirements are more stringent and would better represent the effectiveness of the quench media to properly quench the specimens and correlate this back to the certified values of the material based on the mill cert reading for the corresponding J values.

Please review this and consult with the Committee to see if this would better represent the intent of these paragraphs for acceptance of quench effectiveness.

The Response:

Because of my position as chairperson of the Aerospace Metals Engineering Committee, the question eventually made its way to my desk. Here is my response:

When reading your question, it suddenly struck me – you’re missing the secret decoder ring! In other words, you cannot directly compare an oil quenched sample to a water quenched (Jominy) test coupon.

Allow me to give you a long-winded explanation that I wrote for Committee E on Steel for the Aerospace Materials Division, the committee that has jurisdiction of AMS2759 on Heat Treating of Steel. The committee had been asked for an explanation of what the 3.10.3 Quench System Monitoring is supposed to do; after the text in italics, I’ll directly answer you.

Let me start by noting the whole purpose of 3.10.3.1, which was to provide a means for a heat treater to demonstrate that their oil quenching system continues to work well. If they do the steps outlined in 3.10.3.1, they do not need to seek approval from their customers for this method. If they choose a different method for monitoring the quench system, they need approval by the cognizant engineering organization (CEO). Since a heat treat firm will probably have many customers with different CEO’s, it makes sense to have one test procedure on which all can agree.

The method starts with the heat treat quality function choosing one of the suggested alloys and bar size configurations noted in 3.10.3.1.2. The constraints of the choice are that the hardenability of the sample has to be enough that they will get full hardening in the center, but not so much that a bar 1.25 times the diameter chosen would get full hardening. (That prevents me from using an air hardening steel, which will not show any difference when my quench system degrades.) If the three choices in 3.10.3.1.2 (a-c) will not work, then (d) offers an out, using other materials and dimensions, established in pre-production testing.

Prior to initial production, and quarterly afterward, the heat treater runs one of the test bars in a typical or simulated production load. They then section out a half-inch slice from the middle of the length of the bar and test the hardness. If in the quarterly testing it remains above the acceptance criterion established by the pre-production testing, their quench system passes.

Figure 1. Cert 4130

Accept/reject criteria is that the hardness in the center meets the hardness of the end-quench hardenability curve done by the original mill, or someone else, per ASTM A255, on the material used for the test. AMEC wanted this because using the generic curves in ASTM A304 is too general, and the curves are routinely done by the steel mills. I’ve attached an example cert (Figure 1) for some 4130 we bought not long ago, and at the bottom of the page are the Jominy numbers! They range from 51 to 24; so, which should I use?

To find the correct accept/reject hardness, I go to a curve that shows what Jominy distance in sixteenths of an inch reflects the cooling at the center of the size of test bar I use. If I’m using 4130 steel from my certified lot of material, the specimen is half inch in diameter, and the attached Timken curves say that the center of a half inch bar cooled with an H of 5 (good agitation) corresponds to a Jominy distance of 3/16, so the hardness required is 49 HRC. If I use a different curve, like the other one attached from an old Copperweld brochure (Figure 2), I get a Jominy distance of 31⁄2, so my acceptance number is somewhere between 49 and 46, so I’ll use 48 HRC. This difference is small, and unimportant, since I’m only using it to show if there is degradation in the oil quench performance.

Figure 2. Jominy Cooling Rates (Copperweld Steel Brochure)

This “compare it with the Jominy curve done by the mill” is only for the 4130 and 4330V specimens noted in 3.10.3.1.5.1 and 3.10.3.1.5.3. For specimens made of 4140, we call out HRC 44 in the center and HRC 50 in the 3⁄4 radius position of the 11⁄2 inch diameter specimen.

So, the 8/16 position on the Jominy curve doesn’t mean it’s appropriate for a half inch diameter specimen – it’s just pointing to the spot on the Jominy bar that’s 8/16 inch from the end that gets sprayed with water. The “secret decoder ring” I mentioned are the “Jominy cooling rates” or the “Pages from Timkin” attachment (Figures 3). These translate the speed of quenching at any sixteenth- inch position of a Jominy bar to the equivalent rate of quenching of surface, mid-radius, and center of bars of different size quenched in various coolants. I tend to use the “Jominy cooling rates” attachment, which I got from an old Copperweld Steel brochure, but since the Timkin Practical Data Handbook for Metallurgists is on the web for free, it’s probably a more universal reference.

Hence for 0.50” diameter 4130 bar, the center hardness should be that corresponding to between 3 and 4 sixteenths of an inch. For the 2.5” diameter bar, quenched in mildly agitated oil, the cooling rate at the center would be represented by the 14/16” position on the Jominy bar. Maybe 15/16” – it’s kind of hard to read. Hence you read the data from the mill cert FOR THE STEEL FROM WHICH THE PIECES WERE MADE and use those numbers as accept/reject. HTT

About the author: Lee Gearhart, P.E., has worked for Moog, Inc. since 1982 and is currently Principal Engineer, Materials and Process Engineering.  In addition to being a worldwide resource for the company, Lee is the current chair of the Aerospace Metals Engineering Committee, where much of the discussion on heat treating specifications occurs. 

 For more information, contact Lee at lgearhart@moog.com or 716-687-4475 


*Section 3.10.3 from AMS2759 Heat Treatment of Steel Parts (This section is one of the big changes to AMS2759 revision F, April 2018, which was then tweaked to revision G in August 2019) 

 The sections to which the article discusses is 3.10.3.1, 3.10.3.1.2 (a-d)3.10.3.1.5.1 and 3.10.3.1.5.3 

 3.10.3 Quench System Monitoring 

The quench system includes the quench volume, type of fluid, recirculation velocity and uniformity, and heat exchange capacity. The consistency of the quench system shall be monitored quarterly, by processing test parts, as outlined below, which are capable of detecting changes in the cooling characteristics of the system. Testing of water quench systems is not required. Quench system monitoring test procedures other than those described in 3.10.3.1 shall be approved by the cognizant engineering authority. When destructive mechanical property testing is required for part acceptance, quench system monitoring is not required.  

3.10.3.1 Test Specimen Requirements  

3.10.3.1.1 Test Specimen Alloy/Configuration  

3.10.3.1.1.1 Round specimens of carbon or low alloy steel, of appropriate hardenability and dimensions shall be used. Selection of the specimen dimensions/hardenability combination shall be aimed at achieving full hardening (e.g., 95% martensite) at the center of the specimen. The specific combination of alloy/dimensions chosen shall be such that the specimen would not be capable of achieving full hardening at 1.25 times the diameter chosen for the test specimen. The length of the test specimen shall be at least three times the diameter.  

3.10.3.1.1.2 The test specimens used for the initial and subsequent evaluation of a particular quenchant shall be from the same alloy and preferably the same chemistry heat of material to eliminate material chemistry and hardenability differences from the alloy selection. Hardenability results shall not be lower than that represented by requirements in 3.10.3.1.5.  

3.10.3.1.2 Test specimen alloy/dimensions shall be one of the following:  

  1. 4130 round bar, minimum 1.50 inches (3.81 cm) long, 0.50 inch (1.27 cm) nominal diameter
  2. 4140 round bar, minimum 4.50 inches (11.43 cm) long, 1.50 inches (381 cm) nominal diameter. 
  3. 4330V round bar, minimum 7.50 inches (19.05 cm) long, 2.5 inches (6.35 cm) nominal diameter. 
  4. Other material and dimensional requirements established in pre-production testing or as specified by the cognizant engineering organization. See 8.5 for shape equivalent guidelines. 

3.10.3.1.3 Test Specimen Processing  

Quarterly quench system monitoring tests shall be run with a typical or simulated production load. Heat treat loads shall be processed in accordance with the appropriate AMS2759 slash specification requirements.  

3.10.3.1.4 Specimen Testing Requirements  

After quenching the test specimen, a 0.5-inch-thick specimen shall be cut from the center of the test specimen length and prepared for hardness testing in the untempered condition. Specimen shall be prepared to ensure it is free from overheating. The minimum hardness at the center of the diameter shall meet the hardness requirements of the approved procedure in 3.10.3.  

3.10.3.1.5 Test Specimen Hardenability  

3.10.3.1.5.1 Round Bar Specimen 4130  

After quenching, the center of the diameter shall not be less than the hardness on the end-quench hardenability curve corresponding to the diameter of the specimen when tested in accordance with ASTM E18. The end-quench hardenability curve shall be the actual hardenability curve determined in accordance with ASTM A255 on the material used for the test specimen.  

3.10.3.1.5.2 Round Bar Specimen 4140  

The hardness in the center of the diameter shall not be less than HRC 44 and the 3/4 radius shall not be less than HRC 50 when tested in accordance with ASTM E18.  

3.10.3.1.5.3 Round Bar Specimen 4330V  

The hardness in the center of the diameter shall not be less than the hardness on the end-quench hardenability curve corresponding to the diameter of the specimen when tested in accordance with ASTM E18. The end-quench hardenability curve shall be the actual hardenability curve determined in accordance with ASTM A255 on the material used for the test specimen.  

3.10.3.1.5.4 If other combinations are established, the accept/reject criteria shall be as specified in the ordering information.  

3.10.3.1.5.5 It is the responsibility of the heat treater to provide the material and hardenability data specified above.  

3.10.3.2 Any failures shall be documented by the heat treater’s corrective action system.  

3.10.3.2.1 As a minimum, if the test specified in 3.10.3 fails, the quench medium shall be analyzed as specified in 3.10.3.3.  

3.10.3.3 Quench Media Control  

3.10.3.3.1 Each new shipment of quenchant from a vendor shall meet the requirements for the particular quenchant listed in 3.10.3.3.1.1 through 3.10.3.3.1.3 as applicable. The vendor shall furnish a certificate of conformance stating that the quenchant meets the requirements including, in addition to the vendor designation, the cooling curve, the cooling rate curve, the maximum cooling rate, and:  

3.10.3.3.1.1 For mineral oil based quenchants, the certificate shall also include the viscosity, flash point, temperature at the maximum cooling rate.  

3.10.3.3.1.2 For vegetable or ester-based oil quenchants, the certificate shall also include the viscosity, flash point, temperature at the maximum cooling rate.  

3.10.3.3.1.3 For polymer quenchants, the certificate shall also include the undiluted pH and viscosity. The pH, viscosity, maximum cooling rate and the temperature at the maximum cooling rate shall be provided at 20% concentration by weight.  

3.10.3.3.2 Cooling curve tests shall be performed semi-annually, or when required by corrective action (3.10.3.2), in accordance with ASTM D6200, ISO 9950 or JIS K 2242, ASTM D6482, or ASTM D6549, as applicable to the specific quench medium. If no alternative limits have been established by pre-production tests or specified by the cognizant engineering authority, exceeding the following limits compared to the initial shipment of quenchant shall be cause for corrective action:  

  • For mineral oils: Temperature of the Maximum Cooling Rate: (±68 °F) (37.8 °C) Maximum Cooling Rate: (±25 °F/s) (13.9 °C/s) 
  • For vegetable or ester-based oils: Maximum Cooling Rate: (±25 °F/s) (13.9 °C/s) Temperature of the Maximum Cooling Rate: (±68 °F) (37.8 °C) 
  • For polymer quenchants: Maximum Cooling Rate: ±15% Temperature of the Maximum Cooling Rate: ±15% 

(Photo source: global.ihs.com)

 

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