轻压下调整对模具钢宽厚板坯中心质量的优化

 为解决塑料模具钢1.231 1（450 mm×2 180 mm）宽厚板连铸坯出现的中心偏析和疏松等质量问题，首先通过射钉试验对板坯坯壳厚度进行准确测量，结合ProCAST数值模拟软件直观呈现连铸坯凝固传热过程。根据软件导出的数值模拟结果获得与弯月面不同距离处铸坯的中心固相率，为该钢种宽厚板坯轻压下位置的确定提供可靠信息。参照连铸坯的中心固相率分别就连铸机压下区间、压下量以及压下率对铸坯中心质量的影响进行了一系列研究。最终试验结果表明，压下位置由铸坯中心固相率fs＝0.30～0.70]后移至fs＝0.50～0.85]所对应区间、压下率由0.8升高至1.4 mm/m，铸坯中心疏松问题消失，中心偏析宽度明显减小。

Optimization for internal quality in wide and heavy die billets by soft reduction

To eliminate the central segregation and porosities in wide and heavy billets of plastic die steel 1.231 1 （450 mm× 2 180 mm），the pin-shooting experiments combined with mathematical simulation by the software of ProCAST have been carried out to measure slab shells’ thickness as well as intuitively display the process of slab solidification and heat transmission. The position of soft reduction facilities were determined according to the center solid fraction of slab in different positions which were directly exported by ProCAST. Then the study of soft reduction was arranged and the industrial experiments were carried out systematically on position，amounts and ratio of soft reduction. The results showed that the position and rate of reduction is significant to macroscopic quality. The internal porosities were effectively eliminated after the position of soft reduction was moved fromfs＝0.30～0.70]tofs＝0.50～0.85.]The degree of segregation especially the width was reduced remarkably after the reduction rate was raised from 0.8 to 1.4 mm/m .