Jerrod Miller

I love this thread. Please keep at it Ibor!

Also, they may be better to trade with other people for other tools you need, or old files for blades.

They are not likely to be good blade material, but they should be good for misc. other tools. Or it you really want them in a blade, just make sure they aren't on the edge.

Hah, I read right over that, too. Which is why it is probably a good idea to never tell anyone they are full of anti-scale powder.

That is a new one, and I would never say that to or about you. I would like to start by noting (as I have at other times) that I do not think that these steels are worth the effort. Only at the upper echelon of users will there be anyone that could appreciate the difference. The ABS Journeyman test is more abuse than I would ever expect a knife to see, and 5160 works just fine (as do many other simple alloys). The only caveat to this is where saltwater and other such corrosive environments may favor a more corrosion resistant material. That being said... I would love to see the TTT for this steel. Something to really consider is not just martensite start temperatures, but also martensite finish (hence cryo-treatments). It would be especially nice to see the TTT for this alloy with 2 or 3 distinct autenitizing temps, because that changes things (as noted in the link Dan and Alan posted earlier). An interesting thing about retained austenite (in addition to the stability and transformation things Alan mentioned) is that it is worse at impact toughness, while better and deforming. This is a major concern for my day-job with high chrome white irons. These alloys have very high volume fraction of carbides (25-30% or more). The goal is to have those carbides in a completely martensitic matrix, because any retained austenite will cause premature failure in impact situations. The only time that retained austenite is a good thing (as far as I am aware, but I could certainly be wrong) is when dealing with high temperature applications. You don't want your part to go through phase changes in service, so if it is always austenite, you're a step ahead. This is done via chemistry. Check out the Schaeffler Diagram, and importantly the equations for Cr equivalency and Ni equivalency, for a little more insight into controlling phase stability through chemistry. Things get a little weird with carbide formation versus what is actually in the matrix, too. Speaking of carbides, that is why the 300 series limits C to low amounts: to prevent Cr Carbides, not to have austenite, that is just a non-critical side-effect. The presence of carbides can really throw off a file skate hardness test. That is all the time I have at the moment. Hopefully I covered things fairly well. Please let me know if there is anything else you want touched on a bit more and I'll see what I can do.

I would think FeCl (ferric chloride) would be much preferred. You can buy that from many places, or make your own from HCl (Hydrochloric/muriatic acid). Nital generally leaves surfaces a bit cloudy to the naked eye. Great from microstructural analysis, but not as good for macro. Also, I have bought concentrated nitric acid and diluted down to 3-10% for etching. Never have had an issue with ordering, but it was to a work address. Fisher Scientific is often a go-to for etchants.

Their source for that was a paper from 1942. [6] Gordon, Paul, and Morris Cohen. “The transformation of retained austenite in high speed steel at subatmospheric temperatures.” Transactions of American Society for Metals 30 (1942): 569-591. That isn't to say it is wrong, just that there is likely more information out there. It is also for a single alloy. I would bet that chart would be a bit like a TTT diagram, in that different chemistries will produce varying levels of austenite stabilization. In other words: your mileage may vary. Side note: During WWII there were nerds in a lab playing with liquid nitrogen... and helping the war effort. If that doesn't make you feel better about humanity, I can't help you.

If you really want to try liquid nitrogen, you can probably get some pretty easily. Just bring an insulated container (e.g. a styrofoam cup) to a welding gas supplier. They should be able to fill it for you. Not saying you should do this, but that you probably can. Probably best to call ahead first.

I completely agree Dan, that is why I posted the second section. If his needs do not meet those requirements, he shouldn't go for a casting.

The big difference between green sand for low temp (Al and Cu base) and higher temp (Fe base) applications is the type of bentonite used. Southern bentonite undergoes oolitization at a lower temp, so when you have higher pour temperatures it is best to use western bentonite. The trade-off is that western bentonite tends to leave sand sticking to the casting more, causing more work in final processing. For the record, there are 2 main reasons for casting over wrought product/fabrication: 1) If you can't get the shape you need otherwise. Whether this is due to impossible geometry otherwise, or simply because it is cheaper to get the shape with casting. Some materials are not machinable or weldable (we cast parts that go up to 700+ Brinell). I dare say getting the desired shape cheaper is the number 1 reason castings are used for geometry concerns, as most shapes can be achieved otherwise. 2) If you can't get the material any other way. This can be a custom chemistry for a needed application, or getting a casting for a part that could otherwise be a wrought product, but is going to be used with a different part that must be cast, therefore you get both parts cast for matching properties. Again, our 700+ Brinell material cannot be made any other way besides casting.

I didn't see this until today. I've been a metallurgist in foundries making steel and iron castings (and a little brass and nickel base) for over a decade. There are a lot of things that need to be thought out. Pouring temperatures are highly alloy AND geometry dependent, and are going to be very important to getting a quality casting. Shrink rate is going to be pretty important, and most steels are going to be around 1/4" per foot. But this also has geometry considerations. You also have to plan for centerline shrink and solidification paths in general. More information on what your goal is would be helpful, as then we could better steer you to the right process. It sounds like you are going to want to heat the metal up to at least 3000 F, but possibly more depending on your set-up. It is going to take a lot of work to get a set-up that will melt that well. Stainless also likes to create a slag that is a bit like molasses (granted, I have a lot more experience with slag than molasses). For small scale casting, I would probably wear the same PPE as I would for forging (probably with heavier welding gloves), and wouldn't be all that concerned as far as extra safety precautions go. But I know what I am doing. It is hard to say what is not obvious to others which seems obvious to me.

I'd suggest trying a sub-critical anneal (AKA extreme temper). Normalize it then heat again to just before the phase change and hold for a few minutes, slow cool. Don't get it too hot on the second heating, you're just tempering the structure that is there, no phase changes.

And the phrase of the day award goes to Alan!

Follow the links at the end of this thread: Specifically this one.

The Cast In Steel project is great. They asked me to help judge the axes last year, but I was scheduled for other meetings at the same time. I'll definitely see you there then! I'll also be on a cast irons panel regarding mold media (silica replacements).