| 摘要 |
PURPOSE: A hardening method of a valve face part in an poppet valve is provided to obtain high hardness and stable quality. CONSTITUTION: An expansion part(3) is formed on an umbrella part(1a) as a valve face part(2b) in a heat-proof steel or heat-proof alloy made poppet valve intermediate product(1) before work, so that a work ratio L1 of the vertical direction of a part corresponding to a nearly center part of a diameter direction in the valve face part(2b) of the poppet valve(2) after work is maximized, and a work ratio is gradually reduced toward inner and outer peripheral ends of the valve face part(2b) from its part. The expansion part(3) is plastically deformed by push-pressing, and thereby, the valve face part(2b) is work hardened. |
