annealing cast steel?

[waksupi]

I have a John Bivins trigger plate, that is hard as the hubs of hell. I don't have any cobalt bits on hand. Anyone remember the proper annealing process for cast steel, right off hand?

[dnepr]

heat to red hot and cool slowly . that is the unscientific method someone else can probably add some more info.

[waksupi]

That is what I had recalled doing in the past, but haven't did any blacksmithing for some years. Right now, I have it in a bed of charcoal, and will test it in the morning. I had tried taking it to bright polish, and bring it up to blue several times to draw the hardness, but that didn't seem to be working. If all else fails, I'll take a run out to work tomorrow for a cobalt. Seldom fails!

[leftiye]

You might not want to cool that in carbon (charcoal) as when it is hot it will absorb carbon and get even harder (case harden). If you've got some Brownell's keep brite, then just heat it red hot, and bury it in lime to cool. If it doesn't get soft, then it's made of a hard alloy. If you think it's just case hardened, sometimes you can file through the case.

[grumpy one]

To get it soft you have to heat it above 723*C for a while. That's yellow-orange, not red. If you can't get it that hot you're only tempering it, not annealing it. Depending on the alloy, it might be sensitive to how slowly you cool it afterward. Overnight is good, which means it has to be buried in a good refractory material that starts off just as hot as the steel. Put it in a bed of the right stuff (crushed bricks or whatever), heat the whole bed area that's close to the part, and heap hot stuff over the top of the part, keeping the heat on while you do it. Then heap more on it so its buried inches deep.

[shooter575]

I keep a covered 5 gallon bucket of lime next to the forge just for that reason. As a side note I had a lockplate for a M/L that I was annealing.It was clean and brite.I was using a hot plate for heat.Anyway I burryed it in the lime and pulled it out the next day.Dang thing had the most purddy case colors I have ever seen.But it was dead soft??? That aint suppose to happen.As I wanted this one brite I pollished it back.

[waksupi]

Well, the charcoal soak worked. I am able to cut it with a file this morning, so am good to go.Thanks!

[uscra112]

Color from lime? Interesting. The color case process uses bone, which has a lot of calcium in it. Wonder if adding, say, crushed limestone to charcoal (rather than bone) would give colors when case hardening? Any chemists in there?

[32 20 Mike]

I have a John Bivins trigger plate, that is hard as the hubs of hell. I don't have any cobalt bits on hand. Anyone remember the proper annealing process for cast steel, right off hand?

Do not add lime to the parts unless you want to remove the carbon in the steel, as it will draw it out to soften. If you heat the part to cherry red and then allow to cool slowly, the temper should be removed without removing the carbon. As this is needed to reharden.

When case hardening is wanted, the parts are reheated to cherry red and then the hardening powder is piled onto it and returned to temp. Quench the heated part in cold water after the hardening powder " pops". You should now have a surface that is hard as glass ( a file will not cut it) and the core still soft.
Case hardening powder is carried by Brownell's.

Case hardening was done with a mixture of bone meal and charcoal packed around the part in a metal container that is placed into a furnace for a given time. The part is then removed ,red hot, and dropped into cold water that has high pressure air forced into it. The bubbles cause the range of colors to form. Or you send the parts to Turnbul, for his great color process.
I have played with parts ( things that can be replaced) to be softened by placing them in my wife's oven, when she is not home, at 500 degrees F. for about 2 hrs then allowing to cool slowly. This will remove the temper from old files prior to making knives. The only danger is that you might burn out the heat sencer in the oven. Or place it in a self cleaning oven and running it. Good luck, Mike