Patent ID: 7622009
Filing Date: 2009-11-24
Classification: C23C

Abstract:
1. A steel material comprising a hardened layer on a surface of the steel material, the hardened layer containing B ranging from 7 to 30 ppm by weight and N ranging from 10 to 70 ppm by weight, Vickers hardness of the hardened layer being in excess of 720 and the hardened layer having a depth in excess of 0.3 mm, wherein B and N are contained as an Fe (B, N) solid solution or an Fe (C, B, N) solid solution or an Fe—C—B—N boronitride, Fe and C are constituent elements of the steel material, and concentration of the Fe (B, N) solid solution or concentration of the Fe (C, B, N) solid solution or concentration of the Fe—C—B—N boronitride decreases from the surface to the inner structure of the hardened layer, and the Vickers hardness in the hardened layer decreases from the surface to the inner structure of the hardened layer wherein said steel material is made by covering or surrounding a raw steel with a boron compound comprising hexagonal BN or B