| 摘要 |
PROBLEM TO BE SOLVED: To prevent a crack of a gear end part at the time of gear molding and to improve service life of a gear molding tool by using steel containing specific amounts of C, Si, Mn, P and S as steel for a gear. SOLUTION: Steel containing 0.32 to 0.38% C, 0.1% or less Si, 0.60 to 0.90% Mn, 0.03% or less, P and 0.035% or less, S is used as steel for a gear optimum for molding a teeth by rolling. For example, a drive plate gear is formed by such steel for gear, and the gear is formed into a circular ring in an outer peripheral part of an arm 1 and is provided with a rim 2 having a predetermined thickness in the axial direction and a plurality of teeth 3 rolled on an outer peripheral face of the rim 2. This gear is formed by rolling the teeth 3 from an outer peripheral face side by a molding tool 5 using a molding support die 6 provided with an inner peripheral support face 61a which supports an inner peripheral face of the rim 2 and has a resistance means giving resistance to a flow of rim 2 at the time of rolling. |
