| 摘要 |
PROBLEM TO BE SOLVED: To produce a high tensile strength electric resistance welded tube excellent in corrosion resistance and withstanding use in a bare state even in a severe corrosive environment as an automobile structural member. SOLUTION: A hot rolled steel sheet contg., by weight, <=0.1% C, 0.1 to 2.0% Mn, 0.03 to 0.20% P, <=0.020% S, 0.05 to 1.0% Cu, 0.01 to 0.10% acid soluble Al and <=0.008 N and furthermore contg. one or >= two kinds among Ti: (48/32)×%S to [(48/32)×%S+(48/14)×%N]×2wt.%, 0.05 to 1.0% Si, 0.05 to 2.0% Ni, 0.05 to 5% Cr and 0.01 to 0.05% N is formed into an electric resistance welded tube, and after that, the weld zone is annealed in the temp. range of 520 to 800 deg.C.
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