| 摘要 |
PROBLEM TO BE SOLVED: To form a Zn-Fe alloy plating layer of specific iron content and to produce a plated steel sheet excellent in plating adhesion by cooling an annealed steel sheet at specific cooling velocity, applying hot dip galvanizing to the steel sheet, regulating coating weight, and subjecting the plated steel sheet to temp. raise and to holding to and at a specific alloying temp. SOLUTION: After a degreased and pickled steel sheet is annealed, rapid cooling is performed at a rate of >=10 deg.C/sec to apply stress. After the temp. of this steel sheet is regulated to the prescribed temp., hot dip galvanizing is applied, and successively, coating weight is regulated. Subsequently, the hot dip galvanized steel sheet is subjected to temp. raise at a high rate of >=30 deg.C/sec up to an alloying temp. of 475-510 deg.C and held at this temp. until alloying treatment is completed. By this procedure, a Zn-Fe alloy plating layer of 8-11 wt.% iron content is obtained without developingΓ-phase. Further, it is preferable to cool this steel sheet, after the completion of alloying treatment, down to 420 deg.C at a high rate of >=30 deg.C/sec to prevent the formation ofΖ-phase.
|
