| 摘要 |
Cold finished seamless steel tubes according to the present invention are made such that the residual stress F to be generated at the stage of the correction process after cold working is controlled to be 30 MPa or more and the scattering thereof is 30 MPa or less, when measured by Crampton method. Further, when in need, by adjusting the average grain size of spheroidized carbides, the dimensional change which emerges in lathe turning of the outside and inside diameter of relevant steel tubes due to the residual strain can be suppressed to be small, and the strict roundness as well as the excellent machinability can be secured at the final processing stage of the work pieces for bearing parts. Consequently, the present invention can contribute to cost reduction for bearing parts and can provide relevant steel tubes with high dimensional accuracy and less dimensional change at the final steps such as lathe turning, heat treatment and the like, to be used for bearing parts. |
