| 摘要 |
PROBLEM TO BE SOLVED: To provide a 440 MPa class high strength molten galvanized steel sheet excellent in secondary processing brittleness resistance.SOLUTION: A 440 MPa class high strength molten galvanized steel sheet excellent in secondary processing brittleness resistance, having a molten galvanized steel layer satisfying C:less than 0.0040%, Si:0.7% or less, Mn:1.0 to 2.5%, P:0.05 to 0.13%, S:0.025% or less, Al:0.005 to 0.20%, N:0.010% or less, Ti:0.005 to 0.035%, Nb:less than 0.005%, B:0.0005 to 0.0030%, 25×P+4×Si≤3.2, [B-(11/14)[N-(14/48)×Ti]≥0.0005, [C-(12/93)×Nb-(12/48)[Ti-(48/14)×N]≥0.0002, 110×Si+48×Mn+550×P≥150, containing the balance Fe with inevitable impurities and Fe of 7 to 15 mass%, with average r value ≥1.5 and -0.5≤&Dgr;r value ≤0.5. |
