Optimization of heat treatment mode for HiCr steel rolls

The paper examines the possibility of conducting a qualitative assessment of the stressstrain state that occurs in a HiCr steel roll. For this purpose, a quantitative assessment of the distribution of temperature gradients over the cross section of the casting body was used. It is noted that defects in cast workpieces often occur during heat treatment in the form of a violation of the continuity of the casting body. This fully applies to cast rolling rolls, which have a compact surface and, as a result, are susceptible to defects due to the formation of cold cracks. A mathematical apparatus was adapted based on the numerical solution of the thermal conductivity problem to assess the thermal state of the rolling roll during heat treatment. Based on the obtained algorithms, a software product has been developed that predicts the thermal state of a rolling roll and the temperature gradients that arise in it over time. The stress state of a range of HiCr rolls has been analyzed. Critical temperature gradients were identified, the magnitude of which made it possible to adjust the existing heat treatment regime for rolling rolls. It is noted that the largest gradients occur during thermal shock due to sudden cooling of the body of the cast billet during the hardening process. However, this deformation effect is mitigated by the high ductility of the metal in the area of thermal shock. There maining extremes of temperature gradients are significantly lower.Considering their effect in temperature regions with low ductility of the material, they can lead to disruption of the continuity of the casting body. Based on the results of the research, a “softened” heat treatment regime for HiCr steel rolls was developed while simultaneously reducing its duration by 6.25 %. The work was carried out within the framework of the implementation of technological projects of the REC “Development of a new chemical composition of an alloy for the production of two-layer rolling rolls for hot rolling mills with a barrel diameter of more than 1000 mm to replace imported ones.”