| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength screw and steel for a high strength screw provided with high tensile stress and shearing stress and also excellent in tapping properties and moreover to impart interchangeability with a machine screw to a female screw formed by a tapping screw so that the machine screw can be screwed onto the female screw after the tapping screw is once disengaged from a corresponding member. SOLUTION: A screw stock with a prescribed size obtained by subjecting steel containing, by weight, 0.05 to 0.20% C, <=0.20% Si, 0.5 to 1.8% Mn, <=0.015% P, <=0.015% S, 0.02 to 0.08% Al and <=0.0060% N, and the balance iron with inevitable impurities to hot rolling is cold-forged to form into a screw shape, and, after carburizing treatment as surface hardening treatment, tempering is performed to impart surface hardness Hv of 550 to 700, core part hardness Hv of 200 to 320, hardened layer depth of 0.05 to 0.7 mm, and tensile strength of 800 to 1,200 N/mm2 to the steel.
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