Patent ID: 9340859
Filing Date: 2016-05-17
CPC Classification: B32B,C21D,C22C,C23C

Claim Text:
1. A method of manufacturing a high strength galvanized steel sheet having excellent stability of mechanical properties, formability, and coating appearance, comprising: applying a first heating step 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, N: 0.008% or less, and the remainder composed of Fe and incidental impurities, on a percent by mass basis, in which, in a former part, heating is performed in an atmosphere containing O applying a second heating step to the resultant steel sheet, in which holding is performed in an atmosphere containing H applying a galvanization treatment, wherein the galvanized steel sheet includes 75% or more of ferrite phase, 1.0% or more of bainitic ferrite phase, and 1.0% or more and 10.0% or less of pearlite phase, on an area ratio basis, the area ratio of martensite phase is 1.0% or more and less than 5.0%, and the area ratio of the martensite phase/(area ratio of bainitic ferrite phase+area ratio of pearlite phase)<0.6 is satisfied.