| 摘要 |
PURPOSE:To remove segregated structure and to improve quality of ppt. hardened stainless steel casting, by applying subzero treatment to the casting after completion of casting, successively applying soln. heat treatment. CONSTITUTION:The titled casting after completion of high temp. heating treatment for soaking after casting completion or succeeded to casting is subjected to subzero treatment. In this way, the part converted to austenite structure at normal temp. due to segregation is transformed to martensite, say, partially. Successively this is soln. heat treated to rapidly precipitate chromium carbide in crystal grain to convert the structure to uniform martensite structure. In case the segregation is excessive, the subzero treatment to soln. heat treatment is repeatedly applied. In this way, segregation is uniformly dispersed, unevenness in mechanical property is removed and deterioration of corrosion resistance or increase, etc., of stress corrosion cracking susceptibility are prevented. |
