| 摘要 |
PROBLEM TO BE SOLVED: To improve the reliability of a weld zone by suppressing the occurrence of a weld defect such as a SR crack in the fillet welding of an inspection plug made of a ferritic high strength heat resistant steel. SOLUTION: In the welding structure for performing the fillet welding of the plug after screwing the screw-in type inspection plug made of the ferritic high strength heat resistant steel containing Nb, V, etc., to a set portion on the outside surface of piping, the seat of the plug is provided, with which a part of an outer peripheral part on the plug side, comes into close contact with the outer edge part of an opening part on the piping side and fits (or comes into contact) with it. The plug is screwed into the seat to make its contact part in close contact with the piping, thus the forming of the route gap of a weld zone is suppressed, and the welding structure applying the fillet welding of the plug to the piping is obtained. The fillet welding structure uses the ferritic heat resistant steel containing no elements such as Nb, V and having tensile strength lower than that of a piping material as a plug material or the ferritic heat resistant steel having tensile strength lower than that of the piping material or the plug material as a welding material.
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