To secure welding strength and to prevent generation of weld crack at the time of rim forming by reducing the thickness of a surface oxide layer in a part containing the sides that form the end face of an alloy plate to be welded.
The thickness of an oxide layer 15 is adjusted to be 100 or less, desirably 10 or above and 100 or below, for the forming-required area 16a, 16b of an aluminum alloy plate 10 for wheel rims, the area including the end face 12a, 12b of the plate and having an width of at least about twice the thickness t of the plate from its side 13a, 13b. As a result, in the DC butt welding of the end face 12a, 12b, the oxide is reduced that flows into the weld zone, thereby preventing a weld crack caused by the oxide at the time of subsequent rim forming. The thickness of the oxide layer 15 is adjusted by acid cleaning of the base material in two steps using for example a sulfuric acid solution and a nitric acid solution. Incidentally the acid cleaning area is the entire surface, which is advantageous costwise in view of a means like masking, rather than the limited area of 16a, 16b for which forming is required.
SANO KEIJI
SUZUKI YUKIMITSU
SUMITOMO LIGHT METAL IND
CHUO MOTOR WHEEL CO LTD
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