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 by creep, whereas the transformation factors only slightly affect the result. Therefore, it is important to consider creep in the analysis.

Bimetallic rolls are widely used in steel rolling industries because of the excellent hardness, wear resistance, and high-temperature properties. The control of the residual stress distribution is necessary since the compressive residual stress at the surface may improve fatigue life although the central tensile residual stress may cause fracture originating at the center. Recently, to reduce the tensile stress appearing at the roll center, quenching heat treatment is performed just after heating the roll nonuniformly instead of uniformly with sufficient time. In this paper, the quenching processes after uniform and nonuniform heating are compared on the basis of FEM simulation. It should be noted that a large amount of experimental data of the core and shell materials is utilized for the wide range of temperature including the quenching process. The results show that the tensile stresses at the roll center for nonuniform heating are less than that for uniform heating by 89MPa (26%) at the maximum stress point, although the same compressive stresses appear at the surface. The inner layer tensile residual stress increased by 14% with increasing diameter from 600mm to 800mm in uniform heating, but tensile residual stress was almost unchanged in nonuniform heating.

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