2003 年 2003 巻 48 号 p. 7-14
Weight reduction and high capacity of corrosion fatigue strength have been demanded for suspension springs from hot-formed coiling process. We suggested SUP190 for the hot-formed coil springs for this purpose. On the other hand, shift from the hot-formed coil springs to cold-formed coil springs has been proceeding recently, because the cold-formed coil springs have advantage of high formability and high shape freedom. The cold-formed coil spring materials are generally obtained by the quick heat treatment. The quick heat treatment have the advantage of fine structure, fine austenitic grain and minimum decarburization. We focused on the advantage of the cold-formed coil springs made of material processed by the quick heat treatment. In the meanwhile, we have further developed a means of applying the quick heat treatment to the hot-formed coil spring materials of SUP190. However since SUP190 is alloy steel, it is necessary to consider the change of transformation temperature and solid solution of carbides. Therefore, we concentrated on the basic evaluation for heat treatment by using the hot-working simulator. In addition, the evaluation of the heat treatment in production furnace and the examination of spring characteristic were conducted.