| 摘要 |
PROBLEM TO BE SOLVED: To attain excellent workability, excellent corrosion resistance at a worked area, and excellent roll formability in a surface-treated steel sheet comprising, as an underlying steel sheet, an Al-Zn dip-plated steel sheet whose plated film contains 20 to 95 mass% Al. SOLUTION: The surface-treated steel sheet has a chemical conversion film comprising a chromate film with a specified Cr deposition amount on a plated steel sheet and a thermosetting organic resin film formed thereon and is desirably such a steel sheet that the plated film experiences at least the following heat histories (a) and (b): (a) a heat history wherein the average cooling rate in the 10-second period just after leaving the plating bath is lower than 11°C/second, and (b) a heat history wherein the average cooling rate during the period in which the sheet is heated to a temperature T (°C) in the range of 130 to 300°C after the coagulation of the plated metal and is then cooled from the temperature T (°C) to 100°C satisfies C (°C/hr) or smaller (wherein C=(T-100)/2 ) and/or a heat history wherein the average cooling rate during cooling from the temperature T (°C) in the range of 130 to 300°C after the coagulation of the plated metal to 100°C satisfies the above C (°C/hr) or smaller. COPYRIGHT: (C)2006,JPO&NCIPI
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