Optimization of Thermal Soft Reduction on Continuous-Casting Billet

Abstract

Thermal soft reduction (TSR) is an effective technique to improve the inner quality of continuous-casting billet, but it may lead to undesired internal and surface cracks. In this work, the technologic parameters of TSR were optimized to ensure its effect and control the cracks of 82A tire cord steel billet. A heat transfer model with comprehensive thermo-physical parameters was established to simulate the thermal behavior of continuous-casting billet. The model was verified by comparing the measured surface temperatures and the calculated ones. According to the mechanism of TSR on billet, both the location and water flow rate were comparatively optimized. TSR was determined to locate at 6.96 m–8.46 m from meniscus, where the temperature of billet center dropped rapidly to liquid impenetrable temperature. The water flow rate of TSR was set to 2.2 m³/h, which allowed the reheating rate and surface temperature in a reasonable range and prevented the formation of the cracks. Plant trials were conducted to verify the effect of the optimized TSR. The results showed that the central porosity, V segregation and central segregation of the billet were obviously improved by applying TSR. Meanwhile, the internal and surface cracks were well controlled in the billet.