Analysis And Research On Soft Reduction In Continuous Casting Of Heavy Rail Bloom

Center segregation and porosity are easily found in continuous casting of heavy rail steel for its high carbon content. Soft reduction is one of the important methods to solve the problem. Soft reduction technology will be applied for the new-built heavy rail bloom caster of a steel corporation. In the paper heat transfer, shell shrinkage and soft reduction models are established to provide technique guides for the cooling scheme and the soft reduction application of the heavy rail bloom caster on the basis of its equipment and process parameters.The heat transfer model is testified correctly by the practical data of the old bloom caster. On this basis, the temperature field and shell growth of the new-built bloom caster are simulated at different processs conditions. The results of the heat transfer model provide temperature data for the shell shrinkage and soft reduction models.According to the theoretical analysis on solidification shrinkage and soft reduction of heavy rail bloom, stress-strain rules of solidification shrinkage and soft reduction are concluded, the stablishment basis of reduction process parameters is summarized, crack criterion on the basis of critical strain is established.The shell shrinkage model provides thermal stress-strain data for the soft reduction model and the premise for the thermal-mechanical analysis of soft reduction.The results of soft reduction simulation indicate: narrow side bulging is found in soft reduction process, the corner of the bloom will bear huge pressure making reduction difficult, even generating crack for oversize reduction. Therefore the two aspects would be considered when the process parameters of soft reduction are established.While the ferrostatic pressure has a less effect on soft reduction that can be neglected in the simulation. According to the results on standard process parameters, the reduction location is the distance from meniscus as in a range from 14m to 19.1m, the corresponding fraction of solid is 0.60-0.80,the reduction amount rage is 3mm-4mm, the reduction rate is about 0.59 mm/m-0.78 mm/m and the reduction speed rate is about 0.41mm/min-0.55 mm/min. With these reduction parameters center segregation and porosity are reduced and cracks will not occur. The soft reduction model provides the basis for establishment of soft reduction process parameters and crack prediction in soft reduction process.