PURPOSE: To produce a galvannealed steel sheet excellent in die sliding characteristics and powdering resistance at the time of press forming by subjecting a hot-dip galvanized steel sheet to heating under specific conditions and controlling iron content in a plated layer.
CONSTITUTION: A steel sheet is galvanized by immersion in molten zinc and the resulting galvanized steel sheet is heated, by which a galvannealed steel sheet is produced. At this time, the above galvanized steel sheet is heated up to 470-530°C at ≥30°C/sec temp.-rise rate. Subsequently, this steel sheet is held at a temp. in the above temp. region, by which iron content in the plated layer is controlled so that zinc coating weight W(g/m2) and the above Fe content CFe(wt.%) in the plated layer satisfy the condition of 18-(W/10)≥CFe≥9. By this method, the galvannealed steel sheet excellent in die sliding characteristics and powdering resistance at the time of press working even under the condition of high zinc coating weight, improving productivity at the time of press working, and capable of producing a high quality press worked part can be obtained.
KYONO KAZUAKI
YAMATO KOJI
| JPH0257670A | 1990-02-27 | |||
| JPH01279738A | 1989-11-10 |