Reduction of Residual Stress in Bimetallic Work Roll by Tempering

Abstract

Bimetallic rolls are used in steel rolling industries because of their excellent hardness and wear resistance. To reduce the center residual stress, quenching heating treatment is performed immediately after heating the roll nonuniformly instead of uniformly. In this study, we found that by using a nonuniform heating quenching method the maximum tensile stress that appears near the shell-core boundary was decreased by about 26%. It may be concluded that nonuniform heating quenching is useful in reducing the risk of roll failure by decreasing the center tensile stress without decreasing the surface compressive stress. Analysis including a tempering process was also conducted. It was found that for uniform heating quenching, the maximum stress at the center of the roll decreases by 33% from 396 MPa to 264 MPa after the first tempering and the maximum stress decreases by about 54% after a second tempering. On the other hand, with nonuniform heating quenching, the maximum stress decreases by 25% from 286 MPa to 214 MPa after the first tempering and by about 46% after the second tempering. This tempering effect is mainly caused bycreep, whereas the transformation factors only slightly affect the result. Therefore, it is important to consider creep in the analysis.