I heat treated eight AEB-L kitchen knife blanks yesterday and out of the eight, only one came out straight and the rest were warped to varying degrees. Four of them did not just warp side-to-side, but picked up a curve along the spine, like sori on a katana. I cannot think of anything I did differently compared to my last batch, where all the blades came out perfectly straight.
My process is as follows: 1,950°F for 15 minutes, aluminum quench plates for about 90 seconds, then dry ice/alcohol slurry. Prior to that, I used
@DevinT's
prequench followed by a subcritical anneal. These last two steps were done on separate days for four of the blanks each time. I tempered the blades at 325°F for a couple hours last night and left it at that.
Does anybody have any ideas what I might be doing wrong that would create the sori? I have another batch of knives I want to heat treat next week and would really like to avoid this problem.
The knives are all hidden tang and I can take a lot of the curvature out of the tang and nobody will ever know, so I am not too worried about that. But I have to figure out how to get rid of the side-to-side warp first. There has been some discussion recently about chisels and hammers with carbide inserts for straightening in this
thread about straightening high-speed steels. How well do these tools work on AEB-L and how much of a warp can one expect to correct with them? Some of the blades I did yesterday have pretty minor warps, but a couple of the 0.06" thick blades have about a 1mm gap when I put them on the surface plate and they are only short little petty knives. Can a warp that bad be corrected with a carbide tipped hammer or a chisel? I've straightened minor warps with a sandblaster in the past, but I am pretty certain it will not work to correct some of the blades I did yesterday.
Are there any other methods for straightening AEB-L? I have tried straightening during tempering by overcorrecting the curvature in a jig a couple of times without success, so I don't think I'm going to bother trying that again. This method seems to only work on carbon steel knives for me. Any suggestions would be greatly appreciated.