| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a hot rolled steel sheet for hydroforming which has strength of≥500 MPa and has excellent hydroformability without cracking in bulging by hydroforming. SOLUTION: The hot rolled steel sheet for hydroforming having tensile strength of≥500 (MPa) and tensile strength (MPa)×uniaxial tensile elongation (%) of≥13,500 (MPa×%) is manufactured by heating a billet or continuous casting slab having a steel composition containing >0.01 to≤0.1% C,≥0.01 to≤0.5% Si,≥0.1 to≤2.0% Mn,≤0.04% P,≤0.03% S,≥0.01 to≤0.1% Al, >0.03 to≤0.2% Ti,≥0.002 to≤0.05% Nb≤0.01% N, further satisfying -0.15<4(C+N)-(Ti+V+Nb/2+Mo/2)<0.2 and consisting of the balance Fe and inevitable impurities at≥1,150°C and subjecting the billet or slab to roughing, confining the time up to the coiling to 3 to 60 seconds and coiling the sheet at≥300 to≤700°C. COPYRIGHT: (C)2006,JPO&NCIPI
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