MANUFACTURE OF HOT DIP GALVANIZING STEEL SHEET HAVING GOOD IMAGE CLARITY AND PRESS FORMABILITY

摘要

PURPOSE:To obtain a hot dip galvanizing steel sheet having good image clarity and press formability by transferring and forming surface patterns of a skin pass roll onto an alloyed hot dip galvanizing surface by use of the skin pass roll whose surface has regularly arranged patterns of craters formed by laser dull working. CONSTITUTION:Flanges 2 having nearly uniform heights on the surface of a skin pass roll 3 are pressed onto a plated layer surface of an alloyed hot dip galvanizing steel sheet 7 by strong pressure. Hence in the plated layer flows into the inside of craters 1 on the roll 3 to form peak parts by generation of local plastic flow of the material near to the plated layer surface being softer than a material of the roll 3. In that time, a top face 8 of a frustum shape peak parts embossed into the inside of the craters 1 maintains a flat face of an initial plated layer surface. Intermediate flat parts 9 pressed by flat faces 6 outside from the flanges 2 between adjacent craters 1 of the roll 3 maintain flat faces as they are. The top faces 8 are somewhat higher than the faces 9 or are at the same level.