| 摘要 |
PROBLEM TO BE SOLVED: To provide a hot dip galvanized steel sheet having excellent strain age hardening properties, and suitable for an automobile structural member, and to provide its production method. SOLUTION: A steel stock having a composition comprising 0.04 to 0.12% C,≤0.4% Si, 1.0 to 3.0% Mn,≤0.05% P, 0.001 to 0.1% Al and 0.005 to 0.02% N, and further comprising one or more kinds of metals selected from≤0.1% Ti,≤0.1% Nb and≤0.1% V is hot-rolled, or is further cold-rolled so as to be a steel sheet. The steel sheet is thereafter subjected to treatment so as to be heated to a temperature region of the temperature T(°C) defined by T=860-250C-150N+45Si-30Mn+700P+400Al-15Ni-10Cr+30Mo+400Ti+80Nb or higher, and subsequently, be cooled to 550°C at an average cooling rate of 5 to 50°C/s, and is then subjected to hot dip galvanizing treatment. In this way, excellent strain age hardening properties satisfyingΔTS:≥80MPa can be obtained. Further, pretreatment of heating to the T°C or higher and pickling treatment of removing a component-concentrated layer on the surface can be performed in order before the heating treatment. COPYRIGHT: (C)2005,JPO&NCIPI
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