METHOD FOR MANUFACTURING WHEEL DISK

Japanese Patent JP3770865

B

PROBLEM TO BE SOLVED: To increase the strength of a wheel disk without increasing the man-hour. SOLUTION: An aluminum stock is preliminarily drawn in the shape of a curved section by using a second die 36 having one set of a first punch 38a and a second punch 38b with tips thereof formed in a substantially spherical shape corresponding to the diameter, the shape or the like of a bolt hole 16 so as to be protruded in a space 42, and compression and permanent drawing are simultaneously performed on a primary shaped article of the thickness slightly larger than the thickness t of the aluminum stock. The strength of an outer circumferential edge 16a of the bolt hole 16 is increased by the work-hardening effect by the compression, and at the same time, a shoulder part 10b and an edge part 10c are formed in the shape of further curved section by the permanent drawing, and formed in the thickness t2 as large as or slightly larger than the thickness t of the aluminum stock, resulting in the increased strength.