MANUFACTURE OF DOUBLE TAPERED WIRE AND DEVICE THEREOF

PROBLEM TO BE SOLVED: To obtain a wire having the optimum high durability for manufacturing a coil compressive spring by manufacturing a tapered wire section with hot-forming in the case of manufacturing the wire alternately provided with a cylindrical wire section and the tapered wire section. SOLUTION: The hot-forming is executed at 400-950 deg.C and the heating to the forming temp. is executed by using an induction heating method. Thereafter, the heating unit 1 is constituted as the induction type heating unit. The blank is sometimes heated to the hot-forming temp. or higher and cooling to the hot-forming temp. with the air or the water. A cooling unit 3 is provided between the heating unit 1 and a forming unit 2. The formation of the tapered wire section is executed with a rolling. The forming unit 2 is provided with roll pair arranged while mutually shifted at 90 deg.. The forming unit 2 can be constituted as three roll type or inclining roller rolling mechanism and the rolls can be adjusted to approach each other during working and the rolling gap can be changed.