PRODUCTION OF HOT DIP ZN-AL SERIES ALLOY PLATED STEEL SHEET EXCELLENT IN CORROSION RESISTANCE AND WORKABILITY

摘要

PROBLEM TO BE SOLVED: To obtain a hot dip Zn-Al series alloy plated steel sheet improved in corrosion resistance and workability, after the regulation of the coating weight of plating, by starting the atomization of water or aq. soln. to a plating layer at a specified plating layer temp., continuing the atomization to the specified plating layer temp. and regulating the grain size in the plating layer to specified value or below. ;SOLUTION: When the temp. of the plating layer reaches the one equivalent to liq. phases in a Zn-Al series alloy phase diagram, atomization by water or the like is started to the plating layer, and the atomization is continued till the temp. of the plating layer reaches less than the one in which the liq. phases changes mixed phases of liq. phases-solid phases. The crystal nuclei generated by the adhesion of liq. drops in the liq. phases grow into crystal grains. In the case the grain size in the plating layer is regulated to ≤1 mm, the grain boundaries per unit area increase and the stress to be applied to each grain boundary is also made small, by which, even in the case cracking is generated on the grain boundaries, the stress to be applied to the steel sheet directly below the same is made small, and cracking and breaking are not generated. Furthermore, since the Zn-concentrated grains and Al-concentrated grains in the plating layer are refined and uniformly dispersed, the corrosion resistance of the plating layer improves.;COPYRIGHT: (C)1998,JPO