▎ 摘　　要

NOVELTY - Manufacture of coil spring involves supplying a circularly wound steel wire in a straight line, transferring the steel wire, pushing the steel wire in several directions to form a coil spring shape by a forming unit, cutting the molded spring, heating the cut spring, and coating a protective film on the surface of the heat-treated spring. The protective film comprises a surface layer comprising 100 pts. wt. binder, 12 pts. wt. titanium tetrachloride, 0.3 pts. wt. platinum ions, 10 pts. wt. calcium magnesium acetate and 5 pts. wt. loess powder, an intermediate layer comprising 3 pts. wt. hygroscopic resin containing styrene-ethylene glycol acrylate, 3 pts. wt. bactericide containing a dermatan sulfate copolymer, and 1 pt. wt. weakly acidic material provided under the surface layer, and a lower layer comprising 3 pts. wt. graphene mesh, 2 pts. wt. adhesive composition, and 2 pts. wt. monodecyl ether surrounding the adhesive composition provided under the intermediate layer. USE - Manufacture of coil spring. ADVANTAGE - The method enables manufacturing a center part of the coil spring to have a larger diameter than left and right sides, so that manufacturing time can be shortened. DETAILED DESCRIPTION - Manufacture of coil spring involves supplying a circularly wound steel wire in a straight line, transferring the steel wire, pushing the steel wire in several directions to form a coil spring shape by a forming unit, cutting the molded spring, heating the cut spring, and coating a protective film on the surface of the heat-treated spring. In the transferring step, the steel wire is transferred by transfer rollers. The protective film comprises a surface layer comprising 100 pts. wt. binder, 12 pts. wt. titanium tetrachloride, 0.3 pts. wt. platinum ions, 10 pts. wt. calcium magnesium acetate and 5 pts. wt. loess powder, an intermediate layer comprising 3 pts. wt. hygroscopic resin containing styrene-ethylene glycol acrylate, 3 pts. wt. bactericide containing a dermatan sulfate copolymer, and 1 pt. wt. weakly acidic material provided under the surface layer, and a lower layer comprising 3 pts. wt. graphene mesh, 2 pts. wt. adhesive composition, and 2 pts. wt. monodecyl ether surrounding the adhesive composition provided under the intermediate layer.