METHOD FOR PRODUCTION OF FLAT WIRE FOR RING GEAR

PROBLEM TO BE SOLVED: To provide a method for producing, by using a round steel rod material, a flat wire for a ring gear which satisfies the requirements of both surface hardness and dimensional accuracy thereof and has reduced hardness variation without requiring a heat treatment for absorbing the hardness elevation of a flat wire surface. SOLUTION: When producing the flat wire for the ring gear by a cold working process using the round steel rod material having a carbon content of 0.30-0.60%, at least one two-way or four-way rolling reduction is performed after at least one cold rolling or cold roller drawing process. In the final step of such cold working process, drawing is performed by using a drawing die to process the whole peripheral surface of the flat wire so as to achieve the maximum area reduction rate of a total sectional area of ≤65%. Thereby, excellent dimensional accuracy and reduced variation in both width and thickness directions are achieved, and thus a required hardness can be obtained while suppressing the occurrence of crack at the side face of the flat wire without requiring intermediate heat treatment. COPYRIGHT: (C)2008,JPO&INPIT