Rack and pinion steering apparatus and method of manufacturing rack shaft
A rack and pinion steering apparatus which does not need quenching of the rack shaft after gear cutting of the rack shaft in manufacturing processes is provided. The rack and pinion steering apparatus comprises a pinion shaft and a rack shaft meshing with the pinion shaft. The rack shaft is formed to have a substantially uniform hardness.
1. A method of manufacturing a rack shaft of a rack and pinion steering apparatus, comprising steps of:
quenching a rod-shaped material formed of CrMo steel to generate a martensitic structure;
tempering the rod-shaped material at a temperature of 400 to 650° C. to generate a fine mixed structure of cementite and ferrite and to refine the rod-shaped material to have a Brinell hardness of approximately 300 to 360;
drawing the rod-shaped material so as to be a round bar having a substantially uniform outer diameter;
forming end portions of the rod-shaped material into a predetermined shape; and
gear-cutting the rod-shaped material to finish the rack shaft.