STEEL MATERIAL FOR SEAT BELT TORSION BAR, MANUFACTURING METHOD OF STEEL MATERIAL FOR SEAT BELT TORSION BAR, AND SEAT BELT TORSION BAR COMPONENT

摘要

To provide a steel material for seat belt torsion bar capable of exhibiting high twisting characteristic and high initial torque even with general steel components.SOLUTION: There is provided a steel material for seat belt torsion bar containing C:0.03 to 0.25 mass%, Si:over 0 to 0.35 mass%, Mn:over 0 to 0.6 mass%, P:over 0 to 0.05 mass%, S:over 0 to 0.05 mass%, Al:0.005 to 0.2 mass% and the balance Fe with inevitable impurities, and having a metal structure containing ferrite and the balance having at least one of pearlite and spheroidal carbide, crystal grain size number of the ferrite of 8.5 or more, half width of X ray diffraction peak on a (211) surface of the ferrite of 0.90° or less.SELECTED DRAWING: None