HIGH-STRENGTH WELDED STEEL PIPE FOR REINFORCING AUTOMOBILE EXCELLENT IN RESISTANT ROPERTY TO DELAYED-FRACTURE

摘要

PROBLEM TO BE SOLVED: To make a welded steel pipe excellent in resistant property to delayed fracture whose heat treatment after making a pipe is unnecessary and moreover without adding special elements. SOLUTION: This welded steel pipe for reinforcing automobiles is manufactured by forming a steel plate having tensile strength TS of >=1180N/mm<2> into a pipe shape and welding its open edge parts and the residual stressσR on the surface of the pipe after welding satisfies the relationship ofσR(N /mm<2> )<=-7.5×TS+12000 (where,σR>=0).