| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To obtain a galvanized steel sheet having high strength and excellent workability by adjusting a pre-Fe plating layer formed on the surface of a plating original plate in a relation with a Zn plating coating weight and alloying the Fe plating layer at a low temperature between the Fe layer not containing Si and Mn and the Zn layer in manufacturing the galvanized steel sheet using a steel sheet containing a large amount of the Si and the Mn as the original plate. <P>SOLUTION: After the steel sheet containing 0.05 to 0.25mass% C, 0.6 to 2.0mass% Si, and 0.8 to 3.0mass% is subjected to Fe plating, the steel sheet is annealed at 700 to 900°C and thereafter the steel sheet is cooled down to 350 to 500°C at an average cooling rate of 2 to 200°C/sec and is then subjected to holding for 0 to 20 minutes or to hot dip galvanizing at the coating weight satisfying the formula (1), 0.08[Fe coating weight]/([Fe coating weight]+[Fe coating weight])≤0.15 without the holding and is immediately cooled down to≤250°C at a cooling rate of≥5°C/sec after holding for 2 seconds to 2 minutes in a temperature region of 460 to 530°C, thereby forming the plating layer of aδ1 single phase. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
