Comparison of porosity alleviation with the multi-roll and single-roll reduction modes during continuous casting

Industrial experiments were conducted to investigate the differences in the porosity alleviation between the multi-roll and single-roll reduction modes during continuous casting and develop a simulation model of the porosity closure. The experimental results revealed that heavy reduction and a high solid fraction were beneficial to the porosity alleviation in billets. The simulation results showed that the large plastic strain along the thickness direction (PE22) at the center region caused by the heavy reduction contributed to the porosity closure. The PE22 at the center region of the billet between the single-roll and the multi-roll reduction mode was little different for the same reduction amounts and reduction positions. The reduction efficiency was high at the position of the low solid fraction, which contributed to porosity closure. Since most areas of porosities were formed at the center region of the billet at a high solid fraction, the reduction prior to the formation of the porosities had little effect on the porosity alleviation. The single-roll reduction mode had a better effect on the porosity alleviation than the multi-roll reduction mode because the solid fraction was higher for the single-roll reduction mode. The experimental results are mostly in agreement with the simulation results.