Numerical Simulation of the 65Mn-Cr Steel Slab Solidification Process and Analysis of the Formation Mechanism of Internal Cracks

There are still internal defects such as triangular zone cracks, centerline cracks, and intermediate cracks in 65Mn-Cr steel during the production process, which mostly occur in the initial solidification. In order to explore the evolution of intermediate cracks during the initial solidification process of 230 mm × 1255 mm slab 65Mn-Cr steel, this study was based on a combination of numerical simulation and experiment, using COMSOL numerical simulation software to establish a flow and heat transfer coupling model and stress model, and carried out simulation research. The results show that the solidification speed of slab 65Mn-Cr steel is different at different positions from the meniscus. At the position where the reheating occurs, the heat transfer speed from the solidification front to the surface of the slab slows down, but the solidification speed varies in different areas of the section. At the same time, the flow field, temperature field, and cross-sectional stress and strain field are all non-uniformly distributed, and the maximum plastic strain value exceeds the critical strain 0.004. The experimental results show that internal cracks occur within the range of 9-35 mm below the surface. This shows that the intermediate crack defects of 65Mn-Cr steel are easily caused by stress and strain. Adjusting the spray distribution and cooling intensity of the spray water in the secondary cooling section can be a feasible solution to reduce the occurrence of internal cracks.