Process for making exhaust valves.

摘要

A method of making work-hardened poppet exhaust valves for internal combustion engines comprises the steps of: providing a solutioned work-hardenable austenitic stainless steel coil or bar stock in which chromium is present in the range of 13%-25% by weight, nickel is present in the range of 4%-16% by weight, manganese is present in the range of 0.25%-8% by weight, copper is present in the range of 0.5%-7% by weight, the interstitial elements carbon plus nitrogen are present in a total amount less than 0.45% by weight, and at least one refractory metal selected from the group consisting of molybdenum, niobium, vanadium, tungsten and tantalum is present in the range of 1%-5% by weight; extruding said coil stock to a poppet valve preform configuration at a speed in the range of 60 to 100 strokes per minute and a a temperature in the range of room temperature to 1,000 DEG F; and heading said preform at the same speed while maintaining the head of said preform at a temperature in the range of room temperature to 2,200 DEG ; the parameters of extrusion providing said work-hardened poppet valve with a stem hardness more than Rc = 25.