Patent ID: 6635128
Filing Date: 2003-10-21
Classification: B21K,B23P,C21D,C22C,F01L,Y10T

Abstract:
A stainless steel work-hardened poppet exhaust valve having the composition comprising 14-18% by weight chromium, 9-14% by weight nickel, 1-3% by weight manganese, 2-4% by weight copper, 0.09-0.4% by weight interstitial elements, wherein carbon comprises 0.05-0.2% by weight of the composition and nitrogen 0.04-0.2% by weight of the composition, and 3-5% by weight molybdenum, the balance of the composition being essentially iron; said poppet exhaust valve having been work-hardened by extruding a coil or bar stock having said composition to a poppet exhaust valve preform configuration at a temperature in a range of room temperature to 1,000Â° F. under conditions effective to work harden said coil or bar stock; said work-hardened poppet exhaust valve having a stem hardness more than Rc=31, the amount of molybdenum being sufficient to precipitate Fe2Mo intragranularly when said exhaust valve is placed in services of an internal combustion engine.