| 摘要 |
PURPOSE:To obtain a metal gasket which does not cause creep at its sealing edge nor cause damages to a valve seat even if it is used for a long time under a high temperature in the state that a valve is closed. CONSTITUTION:A metal gasket of this invention is manufactured as follows. At first, a nickel plating 3'' having a thickness of several mum is appied over the surface of a base 3' of stainless steel by immersing the base 3' in a bath of nickel chloride, and then a copper plating 3''' having a thickness of several mm. and a hardness of 180-220Hv is applied over the nickel plating 3'' by immersing the same in a bath of copper pyrophosphate added with a sulfuric compound containing additive. After appplying the copper plating 3''', heat treatment is applied at 250 deg.C for 20min-3hr so as to increase the hardness of the copper plating 3''' to 100-180Hv. In case that a metal gasket manufactured as above is used for a long time at a high temperature in the state that a valve is sealed by a load acted thereto, its sealing edge portion has a high resistance against creep, so that the stainless steel 3' does not come into direct contact with the valve seat. Thus, it is enabled to improve durability of the seal. |
