| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of manufacturing a low-yield ratio and high-strength electric resistance welded tube having YS (yield strength) of 379-552 MPa and TS (tensile strength) of≥655 MPa. SOLUTION: To a steel material having a composition composed of, by mass%, 0.38-0.45% C, 0.15-0.25% Si, 1.0-1.8% Mn,≤0.03% P,≤0.007% S, 0.01-0.07% sol.Al,≤0.005% N, 0.001-0.003% Ca and the balance Fe with inevitable impurities, finish-rolling in which finish-rolling end temperature lies in the range of 820-920°C is applied to produce a hot-rolled steel strip, and the hot-rolled steel strip is wound in a coil-state with winding temperature of 600-800°C. The hot-rolled steel strip wound in the coil-state is subjected to a tube-making process composed of a delivery, forming and electric resistance welding at room-temperature without heating to manufacture the electric resistance welded tube. By the method, occurrence of cracking in tube making can be prevented. COPYRIGHT: (C)2011,JPO&INPIT |
