| 摘要 |
PROBLEM TO BE SOLVED: To provide an induction hardening tapping screw which is composed of low carbon steel wire for cold forging but has high surface hardness and toughness and can be used for self-tapping to a fastened member having high hardness.SOLUTION: An induction hardening tapping screw 1 is composed of low carbon steel wire of which carbon content is 0.06% or more and 0.22% or less. Carbon is diffused from a screw surface to form a carburization layer of which carbon content is 0.7% or more and 1.0% or less, and the carburization layer is hardened. Furthermore, induction hardening is performed to the tip part of a shaft part 4 to harden surface hardness to HV650 or more while the hardness of a center part is maintained to HV200 or more and HV400 or less. The induction hardening tapping screw 1 has an excellent surface hardness in the shaft part 4 and an excellent toughness in a neck lower round part 6, and can be self-tapped to a fastened member having high hardness. Furthermore, because the wire material is low carbon steel for cold forging, the induction hardening tapping screw 1 is superior in processability and cost. |
