Shrinkage porosity and its alleviation by heavy reduction in continuously cast strand

Heavy reduction process was proposed as a novel strategy to alleviate the porosity during strand continuous casting, and a few studies were performed to investigate the formation of shrinkage porosity and the effect of heavy reduction on the porosity. A simplified model was applied to quantitatively predict shrinkage porosity, about 2.7 mm in diameter in the experimental conditions was obtained. A series of plant trials, including single-roll heavy reduction and multi-roll heavy reduction, were performed to study the effect of the application on porosity. The heavy reduction process effectively alleviated the porosity in the billets, and large reduction and a high central solid fraction showed a large contribution to the alleviation. Traditional soft reduction was also conducted for comparison, and heavy reduction was found to be more effective than the soft reduction in the improvement on porosity. The morphology of porosity during reduction process was analyzed with numerical simulation. Both the closure index and hydrostatic stress proved the effective role of heavy reduction in the alleviation of porosity.