90MnCrV8 (O2)

Böhler Uddeholm carbon knife steel, equivalent K720.

AISI equivalent O2 carbon steel

Forging
Heat the 90MnCrV8 steel slowly and uniformly to 1000°C. Forge within a temperature range of 1050-850°C reheating if required. Cool slowly, in a furnace to avoid setting up stresses.

Annealing
Heat the steel uniformly to 720°C, equalise, then furnace cool. (Hardness about 229 Brinell). Fully machined tools in grade 90MnCrV8 should be packed during annealing.

Hardening
Heat uniformly to 790-820°C until heated through. (If possible pre-heat the component at 300-500°C). Allow 30 minutes per 25 millimetre of section and quench immediately in oil.

Tempering
Heat the component uniformly and thoroughly at the selected tempering temperatures and hold for at least one hour per 25mm of thickness.