| 摘要 |
PURPOSE: To provide a method for producing a work-hardened poppet exhaust valve for an internal combustion engine. CONSTITUTION: A work-hardenable stainless coil or bar stock is prepd. This coil or bar stock contains by weight, 13 to 25% chromium, 4 to 16% nickel, 0.25 to 8% manganese, 0.5 to 7% copper, <0.45% interstitial elements and 1 to 5% cemented carbide selected from the group consisting of molybdenum, niobium, vanadium, tungsten and tantalum. The coil or bar stock is extruded to a poppet valve perform at a temp. in the range of room temp. to about 538 deg.C and also at the true distortion of about >0.8 and is work-hardened. While maintaining the head of the preform at a temp. in the range of room temp. to about 1204 deg.C, the preform is subjected to heading at the true distortion of 1.4 to 2 so as to form into a finally machined shape. The work-hardened poppet valve has a stem hardness (Rc) of about >25. |
