There is a technique to straighten a blade bent after heat treatment – you repeatedly strike the inside of the bent curve with a very hard object, thus spreading the material on that side only and straightening the bend. For that you usually have a hammer made with a very hard carbide tip, either in the form of a chisel or more commonly a ball. I made one myself and it worked very well on the first try, even though the straightening marks are fairly deep and need to be ground away after the fact. I was worried that the grinding would also grind away the layer that straightened the blade in the first place, thus cancelling the effect, but it was not so. Highly recommended.
English