Hello all, I created an account here just for the sole purpose of picking your brains on some san mai I've made into a puukko style blade. Let me start out by introducing myself. I'm Keith from Indiana, I've been blacksmithing as a hobby for around 14ish years. I'm comfortable forge welding and I'd like to think decent with a hammer. I know there's always more to learn, but I just wanted everyone to know where I was coming from.
My san mai construction is hardware store weldable mild on either side (the bar of stock that I got doesn't specify 1018 or A36), with a file for the core. Im using a coal fire pot btw with a hand crank blower, but burning charcoal. Kind of a pain to get that neutral fire with charcoal in a shallow pot. My steps were as follows, Welded a billet taking about 5 welding heats. It all seemed to have welded up just fine, flattened out into a billet, normalized starting from welding heat and my 3rd normalizing heat was only brought up to critical and slow cooled in ashes. The next day I cut out two puukko blanks and ground a blade out of one of them. Sanded to 320 then quenched in water. After about 3 seconds in the water, I started to hear all sorts of ticking noises, and assumed the core was tearing itself apart. When I pulled it from the water I saw no obvious cracks so I tempered immediately and the cracks showed when I went to polish after tempering. It was the mild steel core that cracked!!! The blade did warp away from the side that cracked, and there is a touch more mild cladding on the side that didn't crack. I figured that side having more mild made the blade pull that way in the quench, but why on earth did the mild on the far side crack like it did? The only thing I can think is that it was A36 and with all the forge welding heats I took on it, some extra carbon migrated into it making some alloy of medium-ish carbon steel that couldn't handle the stress of the warp? Thoughts? The cracks run perpendicular to the cutting edge. Also, do I have the grind right for a puukko? A diamond cross section that follows the curve of the bevel along the belly? I have one more blank from this billet, thinking of grinding the 2nd blade and trying oil. But from what I've read, don't you want a faster quench medium to keep the san mai core from tearing itself apart. Especially with a combo like this that doesn't have similar heat treating properties?