| 摘要 |
PURPOSE:To manufacture galvanized cold rolled steel plate having excellent deep drawability and excellent zinc-adhesiveness by the procedure in which steel plate is continuously annealed, cooled gradually, hardened with water, coated with a flux for plating, galvanized with molten zinc, and then subjected to an overaging treatment. CONSTITUTION:A steel, containing 0.06% C, 0.30% Mn, 0.015% P, 0.012% S, and 0.0018% N, is cold rolled and then annealed at 600 to 900 deg.C continuously for recrystallization. Then, the steel is gradually quenched from the temperature to 500 to 650 deg.C to form a ferrite-carbide structure, and then rapidly quenched in water for hardening so as to keep the C solid solution formed at high temperatures at ordinary temperature. Then a flux aqueous solution for galvaniztion, containing zinc chloride as the main component and being kept at a temperature between room temperature and 90 deg.C, is coated on the steel, dried with hot air, and then galvanized in a molten zinc plating bath. Lastly, it is held at 250 to 450 deg.C for 10 to 300 sec. for overaging treatment to obtain galvanized cold rolled steel plate which is excellent in deep drawability. |
