Steel selection by application — hot-work, warm-work, and the special cases

A supplier recommends premium ESR H13 for a hot-trim cavity that has been scrapping at 40K cycles for the last three campaigns. The failure mode is edge wear and slight rounding at the cutting profile. The supplier's pitch is that the certificate documents a tighter ASTM E45 inclusion rating, NADCA #207 Grade A carbide segregation, and a 50% improvement in fracture toughness over standard H13. None of that addresses why the die is failing. The cleanliness gains in remelted H13 buy a longer life against thermal fatigue and inclusion-initiated cracking. They do not buy a longer life against abrasive wear. The recommendation is a real product applied to the wrong failure mode, and the right answer is a different grade family entirely.

Steel selection for forge dies is a failure-mode-first decision, not a hardness or cleanliness-tier decision. The four base axes are toughness, hot hardness, wear resistance, and machinability, and the substrate sits on a fixed trade surface. Push one axis up and another comes down. Pick the wrong axis for the failure mode and the surface treatment downstream cannot rescue the die.