Patent ID: 6386810
Filing Date: 2002-05-14
Classification: F16B,Y10S

Abstract:
A high strength screw formed from a screw material that comprises a high tensile steel, in which a surface hardening processing is performed on, at the least, the thread part to form a surface hardened layer,wherein when a nominal diameter of the screw is not more than 6 mm, said screw material contains carbon in an amount in the range 0.09 to 0.13%, manganese in an amount in the range 1.00 to 1.30%, aluminum in an amount in the range 0.02 to 0.05%, and the residual, apart from a plurality of metal elements contained in minute amounts, is iron, and the depth of said surface hardened layer is set within the range 0.05 to 0.3 mm by a quenching gas carburization process performed at a constant temperature; and when a nominal diameter of the screw is 8 to 12 mm, said screw material contains carbon in an amount in the range 0.15 to 0.18%, manganese in an amount in the range 1.00 to 1.50%, aluminum in an amount in the range 0.02 to 0.05%, and the residual, apart from a plurality of metal elements contained in minute amounts, is iron, and the depth of said surface hardened layer is set within the range 0.3 to 0.7 mm by a quenching gas carburization process performed at a constant temperature, and the surface hardness of the thread part is a Vickers hardness of 550 to 700 Hv, the hardness of the core part is a Vickers hardness of 200 to 320 Hv, and the tensile strength is 800 to 1200 N/mm.