To make the diameter of a mounting flange large so as to obtain an enough margin for joining, also prevent the mounting flange from cracking and restrain the thickness of the mounting flange from thinning, in the case of forming the mounting flange on an end of the shaft as a one-piece member by electromagnetically spreading an end of a tube of extruded aluminum alloy in the direction of the outer diameter.
Notches 33 are formed at a plurality of places on the circumference of an end of a tubular stock 27. The tubular stock 27 is surrounded by a mold 28 and its end is made to project from an end face 29 of the mold. The length of the projection from the end face 29 is large at the places where the notches 33 are not formed, and is small between those places. The tubular stock 27 is spread in the direction of the outer diameter by impressing an electromagnetic forming coil 32 with an instantaneous heavy-current. The circumferential wall at an end of the tubular stock 27 is spread open and struck against the end face 29 so that the flange 22 is formed on the end of the shaft. The overhang width of the flange 22 from the shaft 24 differs in the circumferential direction of the flange 22, and an enough margin for joining can be obtained at the places where the overhang width is large.
COPYRIGHT: (C)2005,JPO&NCIPI
Seiichi Hashimoto
Hiroyuki Yamashita
Mihisa Imamura
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