About 420|A higher-carbon version of
410 (0.30-0.40% C vs 0.15% max for 410). Heat treats to HRC 50-55, making it the standard for plastic injection mold cavities, surgical instruments, and cutlery. In the annealed condition it machines well for a stainless, significantly better than
304. After hardening, plan on grinding or EDM for final dimensions. Corrosion resistance is fair when hardened and polished but degrades if the surface is rough or the part isn't passivated. Compare to 410 (lower hardness, better corrosion resistance) and
440C (even higher hardness, more carbon, slightly better corrosion resistance).
