GALVANNEALED STEEL SHEET WHICH DOES NOT ADVERSELY AFFECT CHEMICAL CONVERSION TREATMENT BY CONTAINING Fe IONS IN TREATMENT SOLUTION AND IS EXCELLENT IN ADHESIVE COMPATIBILITY DUE TO EXCELLENT ADHESION OF COATING LAYER-OXIDE LAYER AND METHOD FOR MANUFACTURING THE SAME

摘要

PURPOSE: To provide a galvannealed steel sheet having excellent sliding performance during press forming as well as excellent chemical conversion treatment and adhesive compatibility, and a method for stably manufacturing the galvannealed steel sheet. CONSTITUTION: The method for manufacturing galvannealed steel sheet comprises: a process(a) of hot dip galvanizing a steel sheet; a process(b) of alloying the hot dip galvanized steel sheet by heat treating the hot dip galvanized steel sheet; a process(c) of skin pass rolling the galvannealed steel sheet; a process(d) of maintaining the skin pass rolled galvanized steel sheet for 1 to 30 seconds after contacting the skin pass rolled galvanized steel sheet with an acid solution having pH-buffering action and containing Fe ions to form an oxide film on the surface of the galvanized steel sheet; and a process(e) of washing the skin pass rolled steel sheet, on which the oxide film is formed, with water. The galvannealed steel sheet comprises an oxide layer having thickness of 10 mm or more formed on a flat part of the surface of a hot dip galvanized steel sheet manufactured by the method comprising: a process(a) of hot dip galvanizing a steel sheet; a process(b) of alloying the hot dip galvanized steel sheet by heat treating the hot dip galvanized steel sheet; a process(c) of skin pass rolling the galvannealed steel sheet; a process(d) of maintaining the skin pass rolled galvanized steel sheet for 1 to 30 seconds after contacting the skin pass rolled galvanized steel sheet with an acid solution having pH-buffering action and containing Fe ions to form an oxide film on the surface of the galvanized steel sheet; and a process(e) of washing the skin pass rolled steel sheet, on which the oxide film is formed, with water.