Warping during annealing

S

sirwilliamjr

Joined
Feb 2, 2004
Messages
44
I've got a laminated knife (two pieces of mild steel surrounding a higher carbon center, san mai maybe?) that I'm trying to anneal before quenching, and it keeps warping on me. I put it in my forge and watched the tip bend to the side as it heated up. I have the edge facing up, so it's not bending under its own weight or anything. I then tryed pulling it out and straightening it, but then it warps again as it cools. Any ideas as to what's going on? This is only knife 3 or 4 for me, but my other knifes never had any trouble like this. I did finish this one thinner than the others, and I know that could have something to do with it, but I didn't think it was THAT thin.

-Will
 
Generally, when steel warps during heating, it is "running away" from the heat. You might try rotating it as it is heating, so that all areas come up to temp. at the same time, or close to it. I would anneal before grinding and normalize, at least once (depending on the steel), before quenching. Normalizing will set up the grain structure for the quench. If the blade is warping during cooling, I would normalize, normalize, normalize, and then normalize a few more times(depending on the steel, of course). Maybe Mete or Kevin will chime in with better suggestions or explanations.

Todd

Is it normallize or normalize? I forget. :rolleyes:
 
Is your blade warping while it comes up to temperature or while it is cooling? If it is warping while it comes up to temperature, it is either because the heat is more concentrated in one area or because the outer layer of steel in the san mai construction is thicker on one side than the other. Does it warp in the same direction every time? If it is warping while cooling, I would straighten it, and normallize it again. I'm sure Mete, Kevin, or Fitzo will chime in and give better answers than I have.

Todd
 
Are you straightening it hot or cold ? Try straightening while still hot.Normalizing relieves stresses. If you keep normalizing [three times is usually enough] and it keeps warping you have uneven heat .
 
Is it acting like a bi-metal strip. i.e. one of the metals has a lower specific heat capacity and it is expanding faster than the other, ergo the warp/bend?
 
I've finished working on it for the night, and after trying to normalize and straighten it a bunch, I think that the problem is with the welds or thickness of the sides (bi-metal strip kinda deal). I flipped the blade over in the forge, and every time it curved in the same direction. Anyway, I finally got it pretty straight, heated it, and quenched it, and it warped like crazy. So I did everything again and quenched it, twice, and finally got it pretty straight on the third quench (after which I was planning on giving up). I started grinding of the scale, and realized that, although the blade was pretty straight, it was cupped in the other direction. So now I have a knife that has a convex grind on one side and a concave grind on the other. Not to mention a little curve down the spine and edge. I guess this was a learning experiance, and at least I wasn't planning on this being a real working knife. Although, I might be on to something with the two different grinds. I'm sure it doesn't really do any good, but you could market it as "the best of both worlds" :).

-Will
 
You must log in or register to reply here.
Back
Top