17-4PH Stainless Steel is a Precipitation Hardening martensitic stainless steel, hardened by a single age H900°-H1150°F temperature range. Corrosion resistant, excellent mechanical properties at high strength for aircraft structural components. UNS S17400 TYPE 630. Electric Arc Furnace AOD Refined. VAR (CEVM) Consumable Electrode Vacuum Melted.