GALVANNEALED STEEL SHEET HAVING EXCELLENT PRESSING, CHEMICAL CONVERSION TREATING AND ELECTRODEPOSITION COATING PROPERTIES

摘要

PURPOSE: To suppress the generation of craters and to improve pressing, chemi cal conversion treating and welding properties by adjusting the number of the recessed parts on the surfaces of the plating layer of a galvannealed steel sheet and forming an inorg. oxide on the surfaces. ;CONSTITUTION: The number of the recessed parts which is of d/h≥1 in the length (h) of the depth (d) of the recessed parts 2 of the plating layer 1 of the galvannealed steel sheet and the length (h) in the apertures of the recessed parts 2 is confined to ≤100 points per 10mm, more preferably to ≤60. The galvannealed steel sheet constituting the recessed parts is produced by cleaning the surfaces of the steel sheet, then coating the surfaces with the inorg. zinc oxide, subjecting the steel sheet to annealing, introducing the steel sheet into a hot-dip galvanizing bath to applying plating thereon, then heating the steel sheet to alloy the steel sheet, thereby forming the inorg. oxide to 1 to 500mg/m² on the surfaces. As a result, the galvannealed steel sheet having the excellent electrodeposition coating property is obtained.;COPYRIGHT: (C)1996,JPO