This is a question that I have had for some time and I suspect that there won't be a simple answer, but I'm going to ask it any way. In looking at a differentially heat treated blade with a distinct quench line, if the blade is cross sectioned like the dotted line in the drawing below, what is happening with the hard/softer steel internally. Should it be like the drawing in the second picture with the softer steel dipping toward the edge in illustration A, resulting in a hard edge that is relatively thin? Or straight across to the quench line on the other side like in B. Or does it peak toward the spine as in C?
I have seen the results, illustrated by A, when I sectioned a blade made of 1084 after testing it. Clay was used to coat the back of the blade during the heat treatment. While I have no way to test the hardness of the ends of the cut blade, when it was etched the result looked like that illustrated by drawing A.
I have heard it suggested that results illustrated by C is what is obtained when a maker uses a torch to heat the edge prior to quenching, but have a problem understanding how harder steel can extend under softer when it seems the center would cool off slower than the outside of the steel. I guess I am assuming that during the quench, the steel cools off from the outside in, rather than the inside out.
There are several different ways to get a hard edge and softer spine. I suppose that the different methods might generate different results, but have never seen it addressed. Anyone want to take a shot at this?
I have seen the results, illustrated by A, when I sectioned a blade made of 1084 after testing it. Clay was used to coat the back of the blade during the heat treatment. While I have no way to test the hardness of the ends of the cut blade, when it was etched the result looked like that illustrated by drawing A.
I have heard it suggested that results illustrated by C is what is obtained when a maker uses a torch to heat the edge prior to quenching, but have a problem understanding how harder steel can extend under softer when it seems the center would cool off slower than the outside of the steel. I guess I am assuming that during the quench, the steel cools off from the outside in, rather than the inside out.
There are several different ways to get a hard edge and softer spine. I suppose that the different methods might generate different results, but have never seen it addressed. Anyone want to take a shot at this?
