55钢小方坯连铸轻压下试验研究

针对55钢150 mm×150 mm连铸小方坯中心疏松、缩孔和中心偏析等常见质量缺陷，进行轻压下试验。通过比较不同压下总量以及拉速下铸坯的低倍组织和中心偏析，提出了合适的连铸工艺方案。试验结果和理论分析表明，在现有设备与工艺条件下轻压下工艺可有效改善55钢小方坯内部质量。其中，中心缩孔和疏松可以降至0.5级和1级以下，凝固中心偏析指数可降至1.1，并仍具有优化提升空间。

Experimental study on soft reduction for 55 steel billet casting

In order to improve the center porosity， shrinkage and center segregation and other common quality defects of the 55 steel 150 mm×150 mm billets， the adoption of soft reduction was carried out. Based on the observation of the macrostructure and center segregation under different reduction amounts and casting speeds， suitable process are put forward for the internal quality improvement. Through theoretical analysis along with the experimental results， it is concluded that under the existing process， the 55 steel billets can be produced with accepted internal quality through soft reduction operation， in which the center shrinkage and porosity intensity can be controlled to grade 1 to 0.5 or below， and the center segregation index can be decreased to 1.1. Further quality improvement for the billet castings can be expected at the present caster.