Patent ID: 6558484
Filing Date: 2003-05-06
Classification: C21D,C22C

Abstract:
A high-strength screw made of the steel comprising (by % mass):C: 0.05 to 0.20, Si: 0.20 or less (not including 0), Mn: 0.5 to 2.0, P: 0.015 or less, S: 0.015 or less, sol. Al: 0.020 to 0.080, N: 0.0060 or less, Cr: more than 0.80 to 2.0, with the balance of the mass being iron and unavoidable impurities wherein said steel has been hardened by cementation and tempering to form a surface hardness Hv of 550 to 700, an internal hardness Hv after cementation of 200 to 320, and the effective depth of the hardened layer is 0.05 to 1.00 mm, and the strength of 800 N/mm2 or more.