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

H13 (AISI H13, 1.2344, JIS SKD61) and H11 (AISI H11, 1.2343, JIS SKD6) are both 5% chromium hot-work tool steels in the Cr-Mo-V family. Both run nominally 0.40% C, 5% Cr, 1.3% Mo, and the rest of the matrix is essentially identical. The one composition difference that drives the application split is vanadium. H13 carries about 1.0% V. H11 carries about 0.4% V.

Vanadium forms hard MC carbides that pin grain boundaries during austenitizing and resist solution during service. Those carbides give H13 better temper resistance and meaningfully better abrasive wear resistance than H11 at the same hardness. They also nucleate cracks under impact loading, which is why H11 with fewer of them tolerates shock better. Both grades temper to the same 44-52 HRC range used in forging, so the choice is alloy chemistry, not hardness spec.

The practical split: pick H13 for hot-die forging with sliding contact and scale (hot-trim dies, brass and aluminum hot forging cavities, extrusion dies), and pick H11 for shock-loaded impact-dominant work where toughness beats wear (heavy drop-hammer dies, large open-die work, press dies with peak loads but cooler surfaces). North American shops default to H13 because it is the AISI house grade. On a heavy hammer die, that reflex costs the toughness the application needed.