GRADE GUIDE · D2
D2 (1.2379) is the classic cold-work tool steel: about 1.5% carbon and 12% chromium loaded into a matrix that hardens to 58–62 HRC with outstanding wear resistance. Blanking dies, punches, shear blades, forming rolls and trim tools are its daily work.
Also listed as: 1.2379 · X153CrMoV12 · SKD11 (JIS) · AISI D2
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When a tool must cut or form other steel thousands of times without losing its edge, D2 is the historical answer — the massive chromium carbide population resists abrasion the way plain hardened steel cannot, and its air-hardening habit keeps distortion low through heat treatment. It even carries mild corrosion resistance from all that chromium, though not enough to call it stainless.
The trade-offs are known and managed: toughness is modest (sharp shocks chip it — for impact tooling look elsewhere), welding is a specialist repair job, and in the hardened state it machines only by grinding or EDM. Supply is annealed flat bar and die blocks that toolrooms machine and then harden. Die-block drops and bar ends from the region's toolmaking shops are exactly the off-cuts a die repair or a short-run tool needs.
No — most of its 12% chromium is locked up in carbides rather than protecting the surface, so it stains and rusts slowly in humid air. Oil hardened tools and store them dry.
In the annealed delivery state (~255 HB) it machines conventionally, if stubbornly. After hardening, only grinding and EDM touch it — finish all milling and drilling before heat treatment.
Whenever heat or impact dominates: H13 trades D2's abrasion resistance for hot strength and far better toughness. Cold blanking favours D2; die-casting, extrusion and hot forging favour H13.