| 摘要 |
PURPOSE:To provide stress corrosion cracking resistance to the surface of a stainless steel product by successively melting the surface of the stainless steel product by a local heating means then gradully cooling the steel product so that a specific ratio of delta ferrite is deposited and formed on the surface thereof. CONSTITUTION:An inert gas 3 such as gaseous Ar is ejected from a gas nozzle 4 to form a gas seal 5; at the same time, voltage is impressed via a conductor 6 to a tungsten electrode 7 to generate an arc 8, by which the surface 9 to be treated of the stainless steel product 2 is locally melted. While a TIG torch 1 is moved, the surface 9 is once melted and is then slowly cooled by air cooling to form a melt-treated layer 10 over the entire surface 9. Some delta ferrite phase is thus formed in the crystal grains and grain boundaries of the austenite structure. The delta ferrite phase is deposited and formed at 8-15% of the melt thickness by adjusting the quantity of the heat input to the torch 1. The propagation and growth of cracks are thereby suppressed and the substantial stress corrosion cracking resistance is provided to the surface 9 of the stainless steel product. |
