METHOD OF MANUFACTURING TORSION BAR FOR VEHICLE STEERING DEVICE AND TORSION BAR

摘要

A method of manufacturing a torsion bar, comprising a first shaping step for setting the hardness of a round steel bar material in an area ranging from an inner part to a surface layer part to 320 to 450 in Vickers hardness (HV) by reducing the diameter of the round steel bar material by cold drawing and a second shaping step for providing a spring part by cutting the longitudinal intermediate area of the round steel bar material.