Steel for induction hardening with excellent cold workability, rolling member made of the same, and motion guide device using rolling member

Abstract

This steel for induction hardening contains, by percent by mass, C: 0.7 to 0.9%, Si: 0.4 to 1.0%, Mn: 0.5 to 1.25%, P: 0.030% or less, S: 0.030% or less, Cr: 0.4% or less, Al: 0.05% or less, Ti: 0.003% or less, and O: 0.0020% or less, wherein [Mn]≦0.5+0.35/[Si] is met, the steel further contains Fe and unavoidable impurity and the steel has annealing hardness of 93 HRB or less, and wherein an induction hardening layer after induction hardening has residual austenite of 20 to 40% and hardness of 61 HRC or more. This makes it possible to provide steel for induction hardening in which lowering of a fatigue life hardly occurs even though foreign objects incorporates into lubricating oil of a motion guide device and concentration of stress on its dent causes flaking due to lubrication failure to be generated on a steel surface of a device, or even though rolling/sliding contact occurs.

1 . Steel for induction hardening containing: by percent by mass, C: 0.7 to 0.9%;
 Si: 0.4 to 1.0%;   Mn: 0.5 to 1.25%;   P: 0.030% or less;   S: 0.030% or less;   Cr: 0.4% or less;   Al: 0.05% or less;   Ti: 0.003% or less; and   O: 0.0020% or less,   wherein [Mn]≦0.5+0.35/[Si] is met, the steel further contains Fe and unavoidable impurity and the steel has annealing hardness of 93 HRB or less, and   wherein an induction hardening layer after induction hardening has residual austenite of 20 to 40% and hardness of 61 HRC or more.   
     
     
         2 . A rolling member wherein an induction hardening layer having residual austenite of 20 to 40% and hardness of 61 HRC or more is formed by subjecting the steel for induction hardening as claimed in  claim 1  to cold working to form a shape of the rolling member and then subjecting the shape of the rolling member to induction hardening and tempering. 
     
     
         3 . A motion guide device formed by using the rolling member as claimed in  claim 2  as a part of members of the motion guide device.