| 摘要 |
PROBLEM TO BE SOLVED: To restrain stress corrosion cracking in a valve body surface. SOLUTION: A groove part 310b is arranged in a vicinal part of a welding part 310a in a valve body 310 so that an outside diametral dimension of the valve body 310 is reduced in the vicinity of the welding part 310a. Thus, when the welding part 310a of the valve body 310 is expansively contractively deformed by welding heat, restriction to expansive contractive deformation of the welding part 310a is relieved by the groove part 310b, the welding part 310a can be easily expansively contractively deformed, and the expansive contractive deformation of the welding part 310a can be absorbed by the groove part 310b. Thus, residual stress can be reduced in a part on the opposite side of the welding part 310a to the groove part 310b in the surface of the valve body 310 more than a conventional structure having no groove part 310b so that the stress corrosion cracking can be restrained.
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