| 摘要 |
PURPOSE: A method of manufacturing hot-dip galvannealed steel sheets with good stone chipping resistance is provided, which is characterized in that crater formed inside galvannealed layer plays roles both as crack arrest and as locking that improves binding force between galvannealed layer and matrix. CONSTITUTION: The method is characterized in that the temperature of steel sheet to be fed into galvanizing bath with aluminum concentration of 0.13 to 0.14 wt.% is kept between 460 and 480 deg.C; alloying degree of galvanized layer is controlled within 10.5 to 12.5 wt%Fe; crater portion in galvannealed layer is regulated in the range of 11 to 20 %.
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