ALUMINUM PLATED STEEL SHEET FOR RAPID HEATING HOT-STAMPING, PRODUCTION METHOD OF THE SAME AND RAPID HEATING HOT-STAMPING METHOD BY USING THIS STEEL SHEET

摘要

An aluminum-plated steel sheet for hot pressing is provided which is free from the conventional problem that an aluminum-plated steel sheet, when applied to hot pressing, suffers aluminum melting during preheating for the hot pressing.  The steel sheet is further free from the problem concerning delayed fracture caused by residual hydrogen.  Also provided are: a process for producing the aluminum-plated steel sheet; and a method of hot pressing with rapid heating in which the aluminum-plated steel sheet is used. The aluminum-plated steel sheet for hot pressing is produced by annealing an aluminum-plated steel sheet in a coiled state in an annealing box furnace under holding-time and temperature conditions which are within the range shown in Fig. 5, whereby the aluminum deposit is alloyed with the steel sheet. The method of hot pressing with rapid heating is characterized in that a blank cut out of the aluminum-plated steel sheet for hot pressing is preheated at a heating rate of 40 ºC/sec or higher on the average so that the time period over which the blank is exposed to an environment of 700ºC or higher is 20 seconds or shorter, and the preheated blank is hot-pressed.