ALUMINUM ALLOY SHEET HAVING EXCELLENT RESISTANCE SPOT WELDING CHARACTERISTIC AND ITS ADJUSTING METHOD

摘要

PURPOSE: To improve a resistance spot welding characteristic by forming a front layer film which is of a specific value in the inter-electrode initial resistance value at a peak current value at the time of resistance spot welding on the front surface of an aluminum alloy sheet. CONSTITUTION: The kind and thickness of the front layer film is so adjusted that the inter-electrode initial resistance value attains 35 to 65μΩ. The surface layer film may be any among an oxidized film, resin film, metal plating, etc., insofar as these films are used foe the surface treatment of the aluminum alloy sheet. The resistance heat generation between the electrodes and the sheet is suppressed but the resistance heat generation for forming a fused part between the sheet and the sheet is insufficient and the resistance spot welding characteristic is deteriorated if the inter-electrode initial resistance value is smaller than 35μΩ. The resistance heat generation between the electrodes and the sheet increases and induces the deposition of the electrodes and the sheet or electrode loss and the degradation in the strength of the joint is resulted by the excessive resistance heat generation even between the sheet and the sheet when the resistance value is larger than 65μΩ.