You Don't Know Anything About Steel

I would like to describe a field in which little has been done, but in which an enormous amount can be done. This field is not quite the same as the others, and that it will tell us little of fundamental physics. But it will tell us much about the strange phenomena that occurred just below our perception. In contrast to the natural philosophers of the past, the scientists of this field delve into the recesses of nature and show how she works in her hiding places. Her quest is to understand and create the imperceptible. After all, there is plenty of room at the bottom. Hello and welcome to the materialism podcast, an exploration of the past, present, and future of material science engineering. My name is Taylor Sparks. I'm a professor of material science engineering at the University of Utah, and I'm joined by Andrew Falkowski. And today, you know, we talk about the past, present, and future, and what better material than steel to embody that. Look, we've already done an episode on the history of steel. It's rad. Look it out. It's number one for us. We should rerecord it because we've gotten better since then. But steel is also our future. It's not going away, and it's not a simple topic. If there's anything I learned by getting ready for this one, is that I thought I understood it, and I did not. It's a burly area, and we're going to try and demystify it, including all the different ways you can alloy it with lots of different elements. And if you're going to be buying elements, can we recommend American elements? This episode is, in fact, brought to you by American elements. It is the world's manufacture of advanced materials, AmericanElements.com now in vent. And to help us explore this, because we started looking into it and realized that it was above our pay grade. We reached out to the Steel Founders Society of America, and asked them to lend their expertise to help us uncover the complexities and the breadth of what steel can do. So without further ado, we are delighted to introduce our guest today, which is Kaelin Kennedy of the Steel Founders Society of America, Kaelin. How are you, man? I'm doing great. Thank you for having me. Dude, we are so happy to have you on this episode. Andrew and I in our hubris thought that maybe we could record this episode. And that's right around the time that we realized that we needed to rename this to, you don't know anything about steel, and that they're doing, right? So we're pumped that you're here to help us understand a lot more about steel than probably your average listener thinks about. It's a lot more complicated than people tend to realize. It's not just some commodity that you go by steel as a single item. There's a lot to it. Yeah. I mean, I knew that there was different grades. I don't think I realized how much even the grades vary based off of form factor or many other things, right? And so we're excited to have you here today to tell us all about it. Maybe to kick it off. Tell us what is steel. I know. We've done an episode on it. We know it's iron and carbon. Tell us a little more about it. What's it made up of? So it is iron and carbon. Unfortunately, there's not a great definition anywhere for steel because there are so many different types. The easiest, biggest definition is iron with a little bit of carbon. When you start to get into the technicalities, we tend to say it's below 2.1% carbon because above that point, you start to get into cast iron. OK. So at its fundamental, it's that that said, even though there's only two elements present, you can have lots of different phases that can evolve here, and that's going to give us a lot of the variety as a first starting point on different types of steel. What are these phases? So when you look at the basics of steel, when you're just looking at iron and carbon, carbon is essential to everything steel. That's why steel is so important, so strong, so tough because of the carbon. So we tend to define our phases and steel on where the carbon is. At room temperature, it's what we call fair right, a body centered cubic structure. When we get to higher temperatures, it transforms to face centered cubic, an austenite is what we call that, and that can hold a lot more carbon in it. And that's the beauty of steel because there are two phases at different temperatures that can contain a different amount of carbon, we can really control where that carbon goes. So depending on fast, we cool it from the high temperature. We might start to form pearlite, which is going to be stronger than fair right, and that's layers of carbide and ferrite. If you cool fast and have the right composition, you could form bay night, which is going to be even harder, even stronger, depending on the type of bay night that might have better toughness than the pearlite, but really what we aim for and what's made steel so important throughout history is forming martensite, cooling it really fast, getting a distorted ferritic microstructure, and the finest version of carbides throughout it. So tell us about that distorted structure in my intro to MSc class. We talk about this, right? So FCC is face centered cubic, and technically if you cool it quickly enough, that structure won't transform to BCC, instead it slightly elongates on one axis there, it's like a slight expansion, and it switches face group, it goes from face centered cubic to body centered tetragonal, and in that structure you've got carbon where really you don't, has no business being there. It's super saturated, the amount of carbon in that body centered tetragonal structure. That is the as quenched martensite structure, right? Yes, and it doesn't take a lot of carbon to form that body centered tetragonal because ferritic can hold almost no carbon in it, so if you cool it fast enough, you might have one carbon out of every 300 BCC unit cells, 500 unit cells depending on your carbon content. It's really not that many carbon atoms compared to the number of iron atoms, but because the carbon out of is so much bigger than the hole it's trying to fit in, it just causes a massive amount of distortion, and none of the atoms are happy, they're all strained, and that causes really high strength. Yeah, from a mechanics standpoint, that means like dislocations aren't traveling through the lattice, right? That is a strengthening mechanism, but you don't ever use it as quenched typically, right? We modify it. Tell us about that. So you temper it to relieve some of that strain, as you said, the carbon has no right being there. When you temper it, you get a findous version of carbides, and the form of carbide can depend on a lot of metallurgical factors, but that's ideally what you're going for. You're relieving some of that stress and precipitating out carbides throughout the matrix. What I'm hearing here is that there's actually a lot of play, not only in the composition, but also in the heat treatment process, meaning that alloys can take on a lot of different microstructures, and also thus result in a lot of different properties as well. Yes, and we use that to our advantage, regardless of product form, a common thing to do is if I'm going to do a lot of machining on a component, do I want to do that? Well, it's hard or well, it's really soft. Yeah. Well, the machinists will say, please give me the soft thing, so I don't have to replace my tool bit every hour. You will modify the properties through heat treatments throughout the process to give us the best performance at the most reasonable cost every step of the way. I mentioned for really high tolerance stuff because there are, you know, thermal expansion and volume expansions as you go from one phase to another. Let's say you did your heat treatment in a soft phase, but then you've got your machining done then. And for the final phase, you have to go through a phase transformation or something. Is it hard to keep it to spec for these things like, I'm thinking like dyes, for example, I have, I have tools to deal dyes made all the time. And they've got to be exactly bang on because if there's gaps, they don't do their job anymore. Is that a challenge? Or do you just end up machining it once it's hard and pay the price in terms of the tooling cost to keep the specs, right? There are a lot of different ways to try to tackle that problem. I'll say a common one might be to machine it while it's soft in a roughing machine. Do your final heat treat and then do a finish pass. So you have that dimensional precision, but you didn't have to spend as much money to get there. That's, of course, to kind of depend on the size of it and how much time you're going to take away heat treating a lot of other factors, but it's not non-common route. And I also imagine that the nature of the processing is going to change quite a bit depending on the final application, right? Steel can take a lot of different forms. It could be an IBM or it could be a sheet. I have to imagine that you're going to process that quite differently if you're targeting a different application. Yes. So with steel, there are quite a few different product forms in the United States when we think of steel making. We tend to think of the large mills that are making sheet, bar, eye beams, rails, plate, any number of form factors like that. There are also smaller portions of the steel industry like the forging business that then takes usually a bar or an ingot and forges that new a shape. Foundries will cast the metal straight into near net or the final shape. Additive is another option that's come onto the scene more recently, whether you're talking about laser powder bed fusion or should I forget the welding one, filament deposition, FD, I think. There's also been, since I'd say probably the 1930s fabrication has been a major way to make steel components, buying plate, sheet, or bar and welding it into the shape you want. And all of those products are going to have different requirements, different ways you get the performance out of the steel. and ultimately everything's driven by cost. No one wants to spend more money than they have to. So what's the cheapest way to get performance for this given application? - Gotcha. So we could do a whole episode just on iron and a little bit of carbon and there's so much more to get into. We've talked a little bit about it in our previous episode, but today we really wanted to, given that foundation, pivot now to talk about alloying, right? We make lots and lots of different compositions other than just pure iron, little bit of carbon. So maybe you want to talk broadly speaking, why do we go beyond it? What's wrong with those two, right? Why do we bother adding other things, especially when they're going to be typically more, we're adding cost in terms of the composition. What are the deficiencies that we see in base steel? - I wouldn't necessarily say deficiencies 'cause plain carbon steel is quite large. (laughing) It's the most produced in terms of tonnage. We use it for anything and everything because it's incredibly strong and incredibly tough. And if you need something cheap that's strong and tough, it's hard to go wrong with steel. That being said, even in the plain carbon steels, we always, they're almost always talk about additions of manganese and silicon. And that gets to the first reason why we alloy steel. We need other elements in the steel to help with its processing. So by that, I mean, manganese is almost always added to steel because if you don't have manganese, there's a little bit of sulfur in your steel and that usually comes from the ore or the coal that was used to smelt it. That sulfur without manganese there will react with the iron and form iron sulfides, which is really bad for the toughness of the steel. But if you add manganese, the manganese prefers the sulfur over the iron, and so you'll form manganese sulfides, which do not have anywhere near as bad an effect. - So they're bad, but not nearly as bad? - They are, for the most part irrelevant in terms of properties that you can intentionally add sulfur to form a lot of manganese sulfides to improve the machine ability. That's common in some automotive steels. But for the most part, they're harmless. You typically don't want that many inclusions in your steel 'cause that has better repeatability, better overall performance of your steel, but the manganese sulfides are a real soft phase that aren't gonna, they don't tend to be all that deleterious for performance. And you can't get rid of them in most commercial processing. It's the least detrimental phase to have. - So that's manganese. What about silicon? - Silicon, so from a casting's perspective, the founder world, we have to add silicon 'cause that helps the steel flow. It increases the fluidity, so we can fill all the cavities in our molds. Aside from that, silicon is a mild deoxidizer, so it helps reduce the oxygen content up until a couple hundred degrees shy of the melting point. And then we'll add other elements to finish the job. But it just helps keep the oxygen out. - And how much are we talking about are these like 1% to 2% of these per million? Like how much are we adding? - So in the rock world, the mills, you might be talking about 0.25% silicon up to about half a percent. They of course can go much higher than that. I've seen steels with three or four percent silicon. In the founder world, our silicon's tend to be a bit higher than that, half a percent to one percent. For manganese, it gets into another challenge when we look at howling. We might add an element for more than one reason. So the manganese might be in there 0.3%, 1%, 2%, typically you tend to see around that half a percent to 1% manganese for most commercial steels. But manganese is also beneficial for increasing the performance of your steel. - Yeah, that makes sense. I think there's a number of other interest as well in changing the magnetic permeability of the steel for certain applications that require that as well. - You can. That tends to be a high performance specialty reason while you might add manganese. Manganese is also really good for improving the hardenability, which is a measure of how well you can heat treat the steel and manganese does wonders for that. - That makes sense. When I look through a list of just some common steel grids and workets added, I also see a lot of nickel, chromium, aluminum, vanadium, can you talk a little bit why some of these others are being added? I assume these are probably more for performance reasons. - Yes, so when you start looking at other elements from silicon and manganese, most common you'll see chrome nickel and molly. Those three elements are, I joke, the most common ones you'll ever see, any grade you see in AISI or SE is probably just a combination of chrome nickel and molly. So if you know that you're already most of the way there, you just have to figure out what amounts of each. It's not just for performance, so they help with the heat treatability being able to form martensite, what we're really trying to get and a lot of low alloy steels. Chrome and nickel are useful for corrosion resistance. You'll see those commonly applied to make a stainless steel. Molly will also come into the equation when you need even better corrosion performance out of stainless steels. There are a lot of other new onsteries and so like molybdenum atoms are really big. So they help slow down tempering processes and give you more time to work with when you add molybdenum to a steel. - I was just gonna ask that. So we cover time, temperature, transformation by these TTT diagrams in the intro course. And there's this whole idea of like the nose in the curve. Like you have to quench it fast if they don't touch the nose, right? So you're saying the adding molybdenum essentially moves that to the right. It gives you longer time frames to quench, which I imagine becomes really important as you move towards bigger pieces, right? Where the volume of getting that heat out of a volume now it depends on the thermal transport of that material which you've lost control of to some degree. So for big components that must be a more important consideration than really thin wires and films or something. - Absolutely, and it's not just moly chrome does that too. Nickel has a less severe effect on the time temperature transformation. It is beneficial, but chrome moly and actually manganese are some of the best ones for modifying that nose. But yes, we're absolutely trying to avoid the nose on that diagram so we can achieve a martensitic structure and a lot of traditional quench temperate steels. But to your other point, in heavy sections, we run into that all the time of a customer saying, I want this part that, let's say it's eight inches thick, but I want to use the most commercial commodity steel that's out there that physically can't get the properties in the middle of that heavy section. - You're going to just dip with perlite and bay night, you're saying you just can't hit the martensite in some of that. - You're not even going to wind up with bay night. You're going to wind up with some coarse perlite and ferrite and it's going to be good properties compared to most other materials, but not the quench tempered properties that you're hoping to achieve because it physically can't get there. - Yeah, that makes a lot of sense. So a downside of this customizability of these alloys is that it also means that there's more degrees of freedom in terms of all the different directions and the ways that things can end up. - Yes, absolutely. And you might get advice on one component that was great advice for that component, but suddenly when you look at making another component out of steel and you're a different process, a different size, different limitations, different operating environments that advice might no longer be applicable. - So with these additives, something that comes to mind in the titanium world, we're doing another episode on that sort of concurrently with this. There are these phases where there are elements that stabilize the high temperature phase or the low temperature phase preferentially. I'm curious, does that also happen? Can you end up with alloying things that will stabilize, say, austenitic steels where you're going to try and preserve that austenic structure as opposed to the ferritic structure or is that not the case? - Oh, absolutely. One of the earliest designations I've seen of alloying elements and steel was characterizing whether or not they stabilize the austenite phase or the ferrit phase. I think that was done by weaver back in the, and I'm probably mispronouncing that name, back in the early 1900s. So a lot of steel alloying is relatively recent. We didn't come up with stainless steel until the 1900s, like 1905-ish. And a lot of this is due to the fact that steel was a luxury premium good up until about 1850. - It's crazy to think about. 'Cause it's just like a dirt cheap material now that we use for everything. It's hard to imagine a time when like, boy, if you had steel, that was something. - And if you had the money to do it, you'd make it out of steel. That's why when people counted their lives on it, they'd make their armor out of steel if they could afford it. They'd make their sword out of steel so it wouldn't snap off at the handle. It was, if you had to put your money into something to save your life, that's what you did. Or luxury goods, like it was used in watch springs early on. But that was a very tiny amount of material, so you could offset the costs. Yeah, that makes sense. Another common application in alloying that I see is trying to create precipitates in the material, specifically carbides, and I've noticed that they usually had vanadium, niobium, or titanium to try to form these carbides as well. Is that the case? And are there other reasons for adding this beyond that? And how does that scale to larger bulk parts? So, is that practice generally referred to as micro alloying? I think that was developed in the 1980s or so using vanadium, niobium, titanium, and you could sometimes count aluminum as being a micro alloy. And there's probably other elements. There's always a caveat of people have probably tried to throw a different metal into steel. I saw like an iron gold phased diagram just the other day, and that's not for general structural applications. So the idea with the precipitates is it's going to depend on your process, but you're trying to form usually carbides, sometimes carbon nitrides, to help either precipitation strengthen or refine the grain structure. So you get then finer grain structures tend to improve your performance. They all happen at different temperature ranges though. So we have all these different additives, you've already thrown out like many different components you're adding together. I imagine that this is where we sort of saw the rise of nomenclatures. There's just so many different types of alloys. Obviously, some are going to send a cluster together by performance, maybe, or by process ability. Can you talk us a little bit through some of the conventions of high versus low carbon alloys? I can try. That's a mouthful, I'm sure. So one of the big challenges that I've worked in a couple of different portions of the steel industry. And I talked to people all over the steel industry. What does high carbon mean? Well, it depends on who you're talking to. For a cast iron version, that's going to be different, right? Well, if you're making cast iron, high carbon is four and a half percent. When steel guys can't handle any carbon. So as I said earlier, the general definition for steel is 2.1%. If I was more semantic, I'd probably say 2.11% and show off that I know an extra decimal point on the standard iron carbon phase diagram. But technically, when we make steel, we're rarely over half a percent carbon. Because when you get above half a percent, it becomes a lot more difficult to handle that steel without cracking it or breaking it in some manner. Now, if I'm in the bearing market, I still might get high carbon steels that are 1.2% carbon. But that's because I need that from the performance of my application. If I'm in sheet steel, high carbon might mean 0.1% carbon. That's interesting. The form factor, I had never given any thought to, that that would totally change how you think about the compositions. And that also must affect discussions with producers or even trying to do your own research as well, right? You mentioned that one person's alloy isn't necessarily going to be the same as another depending on the scale of the part. Well, all of a sudden, if one person's high carbon isn't the same as another's, you might be relying on some traditional spec that mentions high carbon steel. That might not translate well to a different application. Well, that's why we always push back if someone says high carbon, what do you mean by that? If someone says high temperature, what do you mean by high temperature? Give me an actual number rather than just saying a general class because we're all well to aware that the nomenclature isn't well defined. We don't even have a good definition for steel that applies to everything. Really write down quantitatively what we mean when we're talking about grades to the best of our ability. And that's really just tied to good open communication. So if we talk some broad categories, then when people look up steel grades, that's introduced a couple naming conventions for the broad ones like the ones that are rich in chromium or so the ones that are rich in malignant or other categories. Could you talk us through that a little bit? So if I look very high level, we tend to talk about plain carbon steels or carbon steels that's going to be the same nomenclature low alloy steels. Oh, I suppose I should define what they are as I go through. Yeah, plain carbon, we usually just talk about iron carbon, silicon, manganese, and then we always measure sulfur and phosphorus when we look at steels. Those come from the ore from the coal, we can't get rid of them, but we like to keep them as low as possible. So they're usually not intentionally added, but they're always in a requirement. Okay. When you look at low alloy steels, that's when we're adding a lot of the other components to increase the performance, the chrome nickel molley, of the nadium, niobium, titanium, off and see aluminum called out, but that's typically for a deoxidation practice. It's still not a good definition for low alloy steels. The one that I see that I most often use is five percent or so alloy or less. But if I see a steel, it's five and a half percent and it doesn't have anything strange in it. I'm still probably going to call it a low alloy. And then you start to get into the high alloy space and we tend to bucket those into stainless steels or tool steels. Stainless steels are usually where you go when you need corrosion resistance and oftentimes high temperature performance with some corrosion resistance. And then tool steels are really specialty steel steels. There's a whole bunch of different buckets of what that really means and what the target application is. The tool steels are where you go when you can't find any other steel that will work for your application. You can also get into stuff like micro alloyed steels, which would be a subclass of low alloy steels. Or you could even say like a big topic in the news lately is electrical steels because those are critical for EVs and the power grid. But that starts to get down to the weeds of different steel groups, okay, perfect. So it seems like there's a lot of different categories being used here. In some sense, you can have the low versus high carbon, low versus high alloy, but that breaks down. You can also define it by the application area. It seems based on what's going to be found there. But then if you go and you look up maybe like the SAE grades, it's an entirely different nomenclature that might not cooperate with some of those other categorical approaches. Can you talk a little bit about that and is the SAE grade really what's being used still? So in the United States, when we're generally talking about steel grades, we're using that SAE AISI system. I think in the 1930s, they realized that all these steel companies and SAE for the automotive business were buying steel. And there wasn't one standard way to look at or call out what steel you wanted to buy. So SAE and AISI about the same time tried to come up with a system and they wound up being pretty similar systems and eventually in the 90s, they collapsed into one system managed by SAE. So when we're talking about grades, trying to get a general understanding of what steel we're talking about, we tend to use the SAE system in the US. And it's nowhere near as simple as you might hope. So when we talk about most steels that an engineer is going to look at, you're looking at a four digit number. The first two digits are the family of the steel. So since plain carbon steels are the most common that's usually going to start off with 10, maybe 13, 15 or 17, those are all plain carbon or carbon with manganese. Outside of that, everything above 10, so starting with the 2000 series, 3000 up to 9,000 are all typically chrome nickel ally. Some combination thereof, at least for the most common grades. The second two digits are the carbon content and weight percent points. So 10, 10 is a plain carbon steel with 0.1 carbon in it, the relatively common sheet grade. Pass that is if you're an engineer and you're trying to figure out what steel you want to use and you have no idea to start because you thought steel was just one material. You probably start with a 10, 10, 20, maybe 10, 30, those are all going to be cheap, common, depends on your product form, what would make the most sense. And if that's not going to be good enough, that's when you start looking at the low alloy steels and the three most common low alloy steels that you're going to look at. You've got no idea what you're doing are going to be 8630 or 4140 and then if you need better performance 4340. Now there's a lot more nuance to that you can always get slightly better performance by changing the grade and maybe. you want to look at a 93 series or a 33. But those grades are the most common for a reason. They have really good combinations of strengths, toughness, whatever other properties you may be looking for in a general steel application, and they're usually a good starting. Gotcha, that makes sense. And if I'm not mistaken, the stainless steel, which are also very common, actually just using an entirely different numbering system, right? So it's still SAE, and that's where it gets confusing. As I said, for most applications, you're going to use that four-digit numbering system. When I start looking at stainless steel, it's still SAE, but it changes to a three-digit numbering system. And the first digit roughly means what kind of stainless steel, but not always. So we usually break stainless steels up into whether they're ferritic at room temperature, austenitic. So we've put enough elements like manganese and Michelin there so that we have austenite stable to room temperature. Duplex stainless steels where we've got a mixture of both ferrite and austenite. And sometimes martensitic is broken out into its own category, but martensitic and ferritic stainless steels are usually lumped together, whether it's ferrite or martensite. The second two numbers in the stainless system though, as far as I don't mean nothing, it's it's not current content, it's not yeah. The most common, if you go to stainless, start with 304, that's going to be by and large. The most common stainless steel, it's an austenitic. If you need something cheaper, that's when you look at the martensitic stainless steel. So in the cast world, there'd be a C-A-6 and M or if you're in the rock world, 410 stainless, the reason they're cheaper is because they don't have all that nickel in it. It's just enough chrome to make it corrosion resistant. If you need something a little higher performance, that's when I said you need to throw some mullion and you go from 304 to 316. Again, the second two digits don't really mean anything, just how it wound up. And then to make the SA more confusing, what do you think it means if there's a five digit number? Three digit was stainless, four digit was carbon and low alloy. I couldn't tell you, man. Probably the higher one was right. No, it's still carbon and low alloy. So if I'm making one of those steels that's 1% carbon or greater, I just add an extra digit on. So 5,200 is a carbon bearing grade and that 100 would mean it's 1% carbon. Yeah, so that's a really helpful at all. And even from like a material science standpoint, just these numbers don't tell me exactly what's in them. It might put things into broad families, but if you really start looking into them, you see that the rules get broken more often that they're followed, it seems. And so, from my understanding, a more common way to do this is to actually go the ASTM route and specify a performance and then have a foundry or supplier match and appropriate steel grade to that performance. Makes a lot more sense because I wouldn't even know what names to begin with, but I can dictate what my product has to do in terms of strength, in terms of stiffness. That makes a lot more sense. So that's where you start to run into a challenge that I've been thinking through recently of when I talk about grades, I'm usually talking just about the composition, but as a customer, I typically don't care about the composition. I just want something that performs and that's where the specs come into play. So the specs not only have the composition typically, there are some that don't have limits on composition, but they also have product requirements, or typically it's mechanical property requirements that you test at a heat level, since you can't guarantee every component inside a steel piece that I give you without fully destructively testing that piece that I give you, and suddenly you have a pile of scraps. So we do general heat requirements on top of the composition, and that's a whole other world of how do you get into the specs and understand what steel spec is relevant for my application. Other than the grade, which is just compositions, suddenly we're starting to put processing and mechanical property requirements. Okay, so killing so far we've talked a lot about some different distinctions. We have some broad categories that I'm starting to feel kind of a handle for, right? But you've already been using a bunch of words. You've said raw, you said cast, right? So there's different ways to make these things. Do those also influence? Do they become their own categories? Do they influence the category naming system? How do that? What are they and how do they come into play? They absolutely can influence the naming system processing you name it. So if I look at a high level, I'm typically going to break it up into rot and cast. So what I mean by rot is at some point, I've still cast the steel. It's been liquid. I poured it, I let it solidify, but then I'm going to do some sort of work into it. Typically we work it hot, hit it with a hammer, send it through a set of rolls, because that's easier. It's austenite at that point, and it's a lot less force on my hammer. You can do working cold. You tend to get better. You can get better dimensional tolerances that way. And by doing cold working, you can get some surface effects that may be beneficial for your process, but it's a lot more expensive, a lot more difficult to do it that way. So most working that's done hot. And that applies to both the mills and the forges. They are kind of grouped together in rot products. Cast products, we don't have the benefit of hammering the steel. And the reason that's so important is any steel that solidifies is going to wind up with porosity, whether it's tiny triple point porosity between grains as they grow together, or larger solidification porosity that happens as it is steel strength and the last spot to solidify, there's just a hole. Because almost all materials shrink as they cool. In a rot product, do you get a hammer all those holes shut and kind of fusion weld them? And a cast product, we can't do any of that working after the fact. So we're stuck with all of those holes. Now we do engineering to get those holes out of the component as best we can. We add additional reservoirs and get it out of there. But that has an effect on the performance you get out of the steel and ways you can post process the steel to get the best performance out of it. So when you buy like a junky tool set, you know, they'll say like we're, you know, cast versus rot. And I've done I've used like a ratchet where you go to put a force on it and you to share that thing and it's just gone. Typically higher strength better products are going to be rot uniformly, is that the case? Not necessarily. So you can get incredibly high performance out of a casting. Okay. There are plenty of ways to do that. They're not necessarily always the most convenient. But at the end of the day, it's steel. So one of the problems that we have in the foundry and casting business is people think that all castings are brittle. As you said, it says cast, I put some force on it and it just I just assume that's going to be crappy. Should I not though? Like you're saying you can do it right. So in the case of a ratchet, you can get really high performance out of a rot product. And part of that is using engineering judgment to get the best benefit out of the process. So when I work a material like in rot products, I tend to elongate the grains in the direction I'm working in, which gives me really good performance in that direction, but tan gentle to that, I tend to get not so good performance. If I can engineer my component or my application, I only see loads in the direction where I get the best performance out of a rot product that can be really beneficial. But I can't always do that or I may have loads that are coming from multiple directions. So a casting without being worked tends to have a more uniform grain structure. Now that grain structure is going to provide us with isotropic properties and all directions and that can be beneficial for other applications. So there's an engineering judgment involved of how can I best utilize the process to get the performance I need. At the end of the day, I'm still talking about steel castings. Steel is incredibly strong and incredibly tough. We use it for demanding applications every day. And it's successful at that. So I've got a question for you. When I teach my intro class, we do these TTT diagrams, for example, and technically right, you can come up with any crazy question. We're like, okay, you're going to quench it. So you miss the the nose and now you've got a martensitic, but then you're going to heat it up and you're allowed, you know, 50% become bay night or whatever. How often do they do that sort of stuff? Or they typically just do relatively simple processes, or do they really do daisy chain complicated processes together? We do both. Everything ties back to cost and how much performance you need out of that component. - What you get out of the processing. - So by and large, since steel is steel, it's strong and tough. If you have a general application and you're not doing quenched and tempered, you're just buying a normalized and tempered steel, a prolitic matrix where it's hard to mess up that processing too much. You normalize it, you let it cool the air temperature, you temper it a little bit, and you get good performance out of that. By tonnage, especially in the founder role, that's the largest application we have. When you get into low alloys, it's most common to do a relatively simple normalized quenched and tempered. That's pretty well ubiquitous across industry. You might skip the normalized depending on your pre-processing, but most people will still do that. But we absolutely can and do every day make those complex heat treatments where I do a double quenched followed by a lamellarize and temper and then stress relief at the end and followed by a carburize or who knows what else after that. And we're even looking at developing that further. Are there other approaches I can do that are non-equilibrium? I mean, martensite's already non-equilibrium, but we've done these fairly standardized processes for the past 100 years. Are there other things we can look at? Do I just partially quench into the martensite phase and not fully form martensite and let carbon diffuse? What happens then? What happens if I heat it back up from there? What if I only partially transformed to aros tonight and do an intercritical step? Typically, we wouldn't do anything like that. But we have better modeling capability, better understanding, and we're exploring a lot of these advanced high-strength steels now. Another thing that's interesting, we typically only talk about the thermodynamics. What would you expect to happen? We touch on the kinetics, but kinetics gets complicated. So we only briefly mention that if you go fast enough, you can form martensite. What if I use something like induction where I go insanely fast? And suddenly diffusion doesn't have time to happen. Can I get better performance out of that process? When suddenly thermodynamics has just been thrown out the window and I only care about the kinetics of things? Maybe. - That's interesting. - Yeah. So there's been a lot of developments over the past. I'll say 30 years or so on, how do I get even better performance out of steels using the tools we have today? And they get complex fast. - I'm kind of curious. I remember, was it five, six years ago, when the Cybertruck was announced, he talked about they're gonna use their own new proprietary stainless steel. I think they called it ultra-hard, 30X cold rolled. How much stock do you take in companies, Tesla, SpaceX, or otherwise, that are developing their own grades of steel? How much of this is marketing versus genuinely changing the steel to do uniquely new things and what we've been able to do in the past? - It is sometimes difficult to tell. So everyone will claim that they have their own proprietary mixes steel, which may be true. There are thousands of grades out there. And as we've already talked about, there are so many different things we put in the steel. - And you can change it. - It'll do something, right? - So absolutely, there's a lot of proprietary steels out there. With Tesla coming out with a new stainless steel, there are always new ways to combine and process the steel to get better performance. - I hope so, man. Hi, our students, we want them to have a job going in the future. I'd like to imagine that clever minds could come up with innovative new materials to do what we want them to do. - The big thing to do when you look at proprietary materials is try to get some material data to better understand how much of an improvement and is that important for your given application. - So maybe that's a good segue to a final component of what we want to cover today. I certainly realize that this is a much bigger, more complex, kind of a hairy naming system. There are so many grades out there. I don't know if it's reasonable. I'm thinking about me as a teacher. Like, should I be trying to teach my students like to know the difference between 2016 and 2004? Or what's the right way for me to help engineers select the right grade? 'Cause what I'm afraid is that they're all just using the same greatest steel. Not knowing how to tackle the complexity. There's like, I'm just gonna use the one I've heard of before. 316 sounds great to me, let's use it. But I know that there's better steels out there for different applications. So how do we equip our engineers to pick the right grade for the right application? - So unfortunately, I don't know of any system or any book to go by that'll help answer that question. There's probably some that exist. I'm not aware of any and I can't comment on how good they are of a tool to help guide engineer and steel selection. There are a couple of different ways you could probably look at it. So, I mean, the first thing what you're doing with this podcast and it sounds like you're already trying to do with your classes, making sure they understand it's a complex system. There's a lot that goes on. There's always gonna be more ways you can improve your steel. If I know nothing about steel and I don't wanna know anything about steel, you could do the simple system that I said earlier of start with a 1020. If I need higher strength and toughness, switch to a low alloy of 4140, something like that. If I realize, oh crap, my part is rusting all the time. Think about a stainless steel and then if nothing is really working, that's when you start to look at tool steels, which are gonna increase in cost, reduce the number of places you can go, but those are really the specialty places. The other approach I'd suggest, if say you've made steel components for a little while and you're trying to order something similar to something you've made in the past or something similar has been made in the past and you can look up what it was made out of. Start there, talk with the company supplying your steel 'cause they will likely have people that are in this every day, understand their material, performance and what works for given applications and just open communication with the companies that are providing your steel. They don't want you to buy a steel that doesn't work for your application either. - Right, they wanna return customer. They want you to be happy. So if I'm an engineer and I call them and say, here's what I need it to be, here's the stiffness, here's the strength, here's the use environment, so you got an idea about corrosion. They can help me pick the one that's gonna be the most economical or available or whatever else that will meet those specs typically. - So yes, and I'm glad you mentioned it economical because if I'm an engineer buying something, I'm gonna say that the strength is the most important or toughness or fatigue, but my purchasing department is gonna say something quite to the contrary. And there are a lot of different ways to get the strength you need. - Right. - Typically you're looking for the lowest cost solution to get you all the performance you need. And that can be challenging to get through across to customers of, you can use a lower strength steel and you're gonna have to buy more of it for the same equivalent strength. Sometimes it makes more sense to buy that more expensive but stronger steel, if I then goes through the design work to reduce the weight, reduce the overall tonnage that I need, it may be a lower cost solution overall to buy the more premium higher strength steels. I saw something that if the Golden Gate Bridge were built today, they could do it with about half the amount of steel that they used to build it. - Yeah, I'll bet. - Just with other vans and higher strengths and, I don't believe it. Well, Kaelin, this episode's been awesome. I hope that we haven't, like look, part of my goal for our audience here today is to realize how big and gnarly the system is so that they're not naive about it and that they don't come into it with under appreciation of the incredible material that is steel and all of its flavors. But also I want them to come away feeling a little bit empowered to understand the basic fundamentals of what goes into it, how they might get it, how they might go about making the right choices and you've just been really instrumental in that. So thank you so much for joining us today. - Absolutely, I really appreciate you having me once again and if anyone has questions, I hope I've communicated it well and I'm still out this podcast that everyone in the steel industry wants to help you find the right grade. And if you're not running it into that, for foundry applications, I'm always happy to help if everyone in steel founders is happy to try to connect you with either a foundry or help guide your grade selection. I know in the mill world, it's the same thing in the forging industry, we just want people to be using the right steel for the job. - And then lastly, I wasn't really familiar with steel founder, Society of America before we started interacting getting ready for this episode but you guys are awesome, you do some really great stuff and one of the things that we've learned about that you have a student competition, which is red, right? if people, I think our listeners are broad. familiar with the TMS bladesmithing competition we've talked with that before. But you guys have some similar competitions where students can learn by doing, which is really the right way to do it. You want to talk about that at all? Absolutely. We have a couple of competitions. We have one for college students called Caston Steel. It's open to any college that wants to participate. We make a different item every year. So this year we're making a Revolutionary War sword in the style of something George Washington would like. So cool. We try to keep the competition wide open in terms of requirements. So the students get to make what they want. We just ask it not be over a certain weight or over a certain length. Part of that was the first year we made a Viking axe and some team showed up with a birdie pound monster of an axe and other team showed up with a little three and a half pound axe. And it's a little difficult to come up with tests that will work across that spectrum. But it's just a wonderful time. We got inspiration from the TV show Forged in Fire. Oh yeah, we love it. And so the first year when we got a lot higher participation than we thought we would. We had I think 19 teams sign up that first year and we thought we might get four or five. We reached out to the judges on Forged in Fire. So Ben Abbott has been a judge of our competition since the very first year, two years ago Dave Baker joined us as another judge. We've got two of the judges from Forged in Fire that the students get to meet. We get to swing around swords and axes. And last year was a halogen bar, a forced entry tool. And we just get to test what items work the best and how the teams did. And the teams just make beautiful art out of it. It's been a wonderful competition to support. The other one we do just started last year casting dreams. We're trying to get more high schoolers interested in manufacturing specifically steel because I'm a little partial to it. But we just ask high schoolers to make whatever they want as a casting and send it in any material, anything you want, a one page right up of why it's important to you. And we showcase those at a national casting convention. Is that where both of these are sort of happening? Is that some sort of national casting event or? Yes, we co-locate with American Founders Society. They're big casting convention every year, which this year it will be in Atlanta, Georgia in April 2025. So as these things go at September, it's probably time to be looking at that and applying. It might be too late even, but take a look at it by time the episode comes out. So the early deadline is December, but if you want to compete, send us a note. We just want students to be excited about manufacturing. So you might take some penalties on your reports if they get in late, something like that. But we'll still let you compete. We want students to have fun and be excited about making things with their hands. Very cool. Well, if any of our listeners are interested in that, they should definitely apply even if they think it's too late. But thanks again for walking us through this. This was a fantastic episode. And I think our listeners will get a lot of valuable information out of it. And hopefully a greater appreciation for how much complexity there is in steel. I think a lot of people and students they see like, okay, steel, whatever I know what that is. And then they move on to some of the fancier more novel allies that are coming out. But if this episode has showed us anything, there's still room to push steel even further than it's been. No doubt about it. Today's episode is brought to you by American elements, the world's manufacturer of advanced materials. American elements now invent this episode. Obviously, it's also brought to you by Kalono. We love this company. There's somebody that we've worked with for many episodes at this point. We think they're great. And when it comes to making materials processing, you heard how important it was to do processing in different ways in today's episode. When I think of processing, I'm thinking of Kalono. They, you heard us talk at length about their cryo milling, about their spark plasma centering. They have some great resources. We hope that you'll check them out because we just think they're good people and they're helping serial scientists do even cooler things. This episode was sponsored by the Steel Founders Society of America. If you're a student and you're interested in metallurgy, consider applying to their upcoming competitions. For undergraduates, they have their cast and steel competition. Or details on that can be found on their website at sfsa.org. And if you, or if you know someone who's interested in metallurgy in the eight to 18-age range, consider checking out their casting dreams competition at casting dreams.org. We also want to point out materials today. They have been an amazing sponsor for a very long time. Thanks to materials today. We can keep producing this show. We hope that you'll check out materials today.com to stay update with the latest happenings. Material science field. Read some of their great articles. 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