Air Hammer Dies
I bought some "H13" Blocks that I had cut at a local (now defunct) tool and die manufacturing place. i just recently installed them on my hammer after hardening and tempering in my digital kiln. I wrapped in stainless foil, slowly raised temp to 1800°, held for 3 hours, air cooled, then tempered at 1100° for 2 hours. Very quickly after installing I noticed that they weren't hard. I forged a few things with a pinball as a top swage, and the pinball made deep divots in the die and did not distort the pinball. For reference I included pics of my 15 year old mild steel dies. I used a ball swage hundreds of times on them with no divots, and the balls would get distorted after a few uses.
I assume the die manufacturer just sold me some random bar stock, because even annealed I thought H13 was tougher than mild steel.
Any opinions / advice? Die faces are 2.5" x 4" x 2"H. I have 2 more chunks of this "H13". I guess I can weld em to new plates and try again.