Hand Tools Archive

Subject:
Re: I just learned the term warm forging..

Rum
My limited experience is that the low end of the "safe" (no cracking) temperature varies quite a bit depending on the steel. Given the number of variables there and my relatively limited set of experiences I'm hesitant to try to quantify it much more than "it depends" hah. I've had a few pieces I remember that seemed to want to crack some even when hot forged around mid orange. My recollection is that the higher the carbon the more of a problem it is. The extreme example of this being cast iron which is 2.5-5% and works like crumbly brittle crap until you heat/beat some of the carbon out, vs say super low carbon wire that's hard to get to even work harden quickly. There is also some technique around how you move the metal that lessens the problem as well, I can't adequately describe that very well.

I should probably put in the disclaimer here that I'm mostly dredging up experiences 25+ years old here... so.. memory is a fallible thing, add an appropriately sized grain of salt.

I do believe that post forging annealing prior to hardening can be super important for stress relief. Forging (or really any deformational shaping) can add a lot of weird stress points into the steel and that doesn't come out with just a tempering heat.

The way steel behaves in response to heat is still very weird to me, I really haven't internalized it at all. The fact that heating it 30 degrees harder changes the composition so much is .. expected .. but still fascinating and odd. Really makes you want to break/cut a bunch pieces apart and put them under a scope (I"m unsure I'd learn anything useful but it would still be fun lol).

The more I read your experiences the more I'm thinking that running a coal or bark fired forge was doing a lot to keep me from getting in trouble being that I was able to maintain very reducing fire. The fact you're not getting scale is encouraging, but the bolster experience is mildly troubling. I'm wondering if you can adjust the gas/oxy mix to get even more of a reducing atmosphere, I don't have a lot of propane forge experiences (heated a couple of horseshoes in one, but shortly after left for a more sendentary occupation with arguably less back pain). Granted it doesn't matter to much for the bolster itself, but as a test piece it's still an interesting data point.

It's pretty cool that it worked as well as it did though, I honestly don't think 4 hours is all that bad for trying out something entirely new like that.. I'd bet I'd have managed to stretch it out to a whole day somehow :D

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