Originally posted by Ed Fowler
Decarb: "Rex shot a chemistry on a 5 1/2" round bar, Doc forged it to a 3" bar, Rex sent it to me.
I forged the 3" to four billets and blades from them, send some of the blades to Rex, multiple quenched and hardened, surface had scale from heat treat left on. A chemistry on the surface showed one point down on carbon. Rex polished the scale off and and shot another chemistry. The result, "no measurable loss of carbon from the chemistry of the origonal bar".
Warp: Warp comes from uneven forging, When blades are forged evenly they do not warp. Warp can also be the result of uneven grinding and sometimes from uneven heating when hardening.
Unfortunately, this is exactly what I meant by not wanting to shake up the status quo, I am now in the position of taking on Ed Fowler himself or compromising on what I see as correct. I should have stayed away because my principles require that I stand by whatI hold as correct.
I must first say that Ed has my utmost respect for the position he holds in the knifemaking community and I would in no way wish to tell him how to make knives. Nobody can argue that he has found success with the way he does things. So I will still not delve into the original triple quench debate if, I can avoid it.
In my statement, I said that the multiple quenched blade would be
more likely to have decarb, I didnt say that it was an absolute that it would. Decarb is the result of high temperatures in environments or atmosphere conducive to carbon loss. It is just undeniable logic that a blade subjected to these conditions more times would have a higher probability of it occurring. No bladesmithing or metallurgy, just simple odds.
Although distortion can be caused by an infinite amount of things I must strongly and respectfully disagree with the reasons given. It does not jive with basic metallurgical precepts or with any of my experience. I wish that there was a simple universal rule that stated blades cannot warp if forged evenly but the universe that I have to deal with will not honor that bargain. I would go with this one if all blades were heat treated immediately following the last hammer blow.
Distortion results from uneven stress in the blade, this can come from uneven heating, uneven cooling, inconsistant microstructures, residual strain from machining operations, unnoticed decarb, looking cross-eyed at the steel etc
You list forging as most likely and uneven heating as sometimes. I would definitely invert this. Uneven heating and cooling offers a much greater threat of distortion than forging if the proper follow up heat treatments have been applied. Normalizing and annealing will simply wipe the slate clean of that time you hit the blade three times on the left side instead of two. If this were not the case nobody could get away with making straight blades out of leaf springs. Of course this could fall on deaf ears to anyone who firmly embraces the concept of steel having a memory.
Now lets talk about internal stresses, there is nothing better for the highest stress than untempered (body centered tetragonal) martensite. Left un-tempered, steel in this state can warp or crack all on its own, not even forging with your feet, on one side only, could give you this affect. Reheating and quenching from such a state is certainly increasing the odds of distortion. I have had blades that I have thrown away because they moved on the first quench and I tried to simply reheat them, straighten them and re-quench (yes, with another proper austenitizing heat). The problem was simply increased on every step by all the new variables until I decided it would be more efficient to go with a new blade.
And once again if distortion manifests itself in the heating and quenching operation, then it is just pure logical odds that the blade subjected to this more times will be more prone to it.
Mete was doing so well, I really should have kept my mouth shut.
