Effect of vibrational strip feeding on solidification structure evolution under visualization condition
The technology of feeding steel strip to mold in continuous casting process is an effective method to control the temperature field distribution of molten steel and restrain or reduce the internal defects such as central segrega-tion and central porosity.However,the continuous casting process is invisible at high temperature,so it is impossi-ble to observe and measure the evolution of solidification structure in the mold online.A visual solidification experi-ment system was set up to investigate the effects of no cold strip,fixed cold strip and vibrational strip feeding on the microstructure evolution of NH4Cl-70％H2O solution during solidification.The results show that:firstly,feeding cold strip can significantly reduce the superheat in the center of mold,fuse dendrites,effectively increase the number of free grains,and then increase the volume ratio of equiaxed grains in solidification structure.Secondly,the super-heat in the mold center decreases more rapidly after the cold strip is vibrated,and the nuclei formed by fusing are more and finer,and the proportion of equiaxed crystal volume increases further.The proportion of equiaxed crystal volume under three conditions of no cold strip,fixed cold strip and vibrational feeding strip is 26％,31％and 36％,respectively.
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