| 摘要 |
<p>A method for manufacturing a high strength galvanized steel sheet having a tensile strength TS of 540 MPa or more and having excellent stability of mechanical properties, formability, and coating appearance is provided. A first heating step, in which heating to 400°C to 750°C is performed in an atmosphere containing O 2 : 0.1 to 20 percent by volume and H 2 O: 1 to 50 percent by volume and heating to 600°C to 850°C is performed in an atmosphere containing O 2 : 0.01 to less than 0.1 percent by volume and H 2 O: 1 to 20 percent by volume, is applied to a steel sheet containing C: 0.04% or more and 0.13% or less, Si: 0.7% or more and 2.3% or less, Mn: 0.8% or more and 2.0% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.1% or less, and N: 0.008% or less, on a percent by mass basis, a second heating step, in which holding of the steel sheet is performed in an atmosphere containing H 2 : 1 to 50 percent by volume and having a dew point of 0°C or lower at 750°C to 900°C for 15 to 600 s, cooling to a temperature range of 450°C to 550°C is performed, and holding is performed at that temperature for 10 to 200 s, is applied, and a galvanization treatment is applied.</p> |
