| 摘要 |
PURPOSE:To produce a Zn hot dipped steel plate of superior drawability by heating a cold rolled low carbon steel strip to above its recrystallization temperature, and soaking the same at this temperature then quickly cooling the same at the specific cooling rates and Zn hot dipping the strip before or after the over-aging treatment. CONSTITUTION:A cold rolled steel strip of low carbon steel is annealed by being heated to above its recrystallization temperature and is soaked at this temprature, after which it is quenched down to 300-500 deg.C temperatures at cooling rates of >=70 deg.C/sec. with water-cooled type rotators. The solid solubilized carbon amount before over aging treatment is increased by this quick cooling. It is then subjected to over aging treatment by being held for more than 10sec within a 300-500 deg.C temperature range to accelerate the deposition of solid solubilized carbon and obtain over aging treatment effect within a short time. Zinc hot dipping is performed before or after the over aging treatment. In the case of galvanizing before the over aging treatment, the over aging treatment temperature is made 300-400 deg.C, and in the case of performing the galvanizing after the over aging treatment, the over aging treatment temperature is made 460-500 deg.C. |
