PURPOSE: To reduce residual stress after welding into compression stress to prevent stress corrosion and cracking of a metallic material, by using a grinding stone which is formed by making abrasive particles adhere to an elastic fiber core material, to grind the surface of a welded section of the metallic material.
CONSTITUTION: An elastic fiber core material has an unwoven fabric as a core material which is formed by mixing filaments made of chemical fibers such as, for example, urethan, polyester, etc. in addition to natural fibers, such as, for example, cotton yarn, sheep wool yarn in order to obtain a plate-like fabric. Abrasive particles may be of alumina group, silundum group, or the like. An inorganic or organic adhesive agent is coated on the surfaces of the abrasive particles which are then made adhere to the fiber core material so that the thus obtained material is used as a grinding stone. Soft grinding may satisfies the grinding condition, but the grinding should be made until beads and recess, which causes the start points of stress corrosion and clacking, on and in the surface of a welded section are completely removed. By grinding the outer surface of even a part where no defects exsist upto a section in the vicinity of a thermal affected position, residual stress under tension due to welding may be reduced in a large part into compression stress.
YOSHIKAWA SHIYUNSUKE
TOKURA IWAO
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