Ok the blade is 1075 the edge that has a surface hardness that is about 60-62 HRC the spine is 40-42HRC...i am sure everyone can see the crack and the teeth marks from my post vise...i bent this 90 without it snapping...i am reasonably sure a through-hardened knife would have snapped...I find it impressive...and i dont think anyone has tried to bend a cracked blade 90...because it's a cracked blade, why would you bend it... Because I had a cracked blade, I wanted to see if it would snap with A clay-hardened differential heat treatment like a through-hardened blade would. So is this impressive?
I am fairly sure i overheated the tip a little, and that caused the crack.
As this is an old post, what did you figure out on this issue? Did you try snapping the blade off at the fracture point and perhaps further down towards the tang to compare the grain structure?
I am going to be honest: I just bent the thing... That is a good idea; fortunately, I actually have another blade made from the same grade of steel, 1075, with a crack, and I am going to go do that. (I cracked a few after I was sick with COVID and could not forge for a while. I forgot some things with heat treating and overheated sections a little due to letting it sit in my forge instead of moving it). That is the interesting thing: grains are actually fairly fine uniform grain. top piece is were the crack was, larger bottom piece is farther down the steel. The left side is a pearlite grain structure due to the differential heat treatment, and the right side is a finer martensite grain. You literally have to clamp it at the crack for it to break with this heat treatment. it will bend to about a 70ish degree angle before breaking but you have to bend it farther still to break the pearlite. i had to cut a notch in the steel to b i think its becasue pearlite is more ductle even though it takes the same amount of force to break steel regardless of the phase its in it but i am not 100% on this.
