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Secondary dendrite arm spacing (SDAS), which is an important parameter for solidification structure, has a significant effect on the level of segregation and the time for dispelling micro-segregation. The solidification structure of billets, poured under different drawing speeds for high-carbon chromium continuous casting and etched by saturated water solution of picric acid, was investigated by OLYMPUS BX51 optical microscope; and the indexes of carbon and sulfur segregation were also determined. It is concluded that the solidification structure consists of fine grain region, columnar region, cross dendrite region and central equiaxed grain region. In the columnar grain region, the SDAS at outer arc of billet is about 30 μm bigger than that of inner arc; the SDAS increases with the increasing drawing speed and the indexed of carbon and sulfur segregation change from positive segregation to the negative with the increasing SDAS. The SDAS can be used as an important parameter not only to establish reasonable secondary cooling system and drawing speed but also to judge the level of segregation in the unidirectional solidification region.
Secondary dendrite arm spacing (SDAS), which is an important parameter for solidification structure, has a significant effect on the level of segregation and the time for dispelling micro-segregation. The solidification structure of billets, poured under different drawing speeds for high-carbon chromium continuous casting and etched by saturated water solution of picric acid, was investigated by OLYMPUS BX51 optical microscope; and the indexes of carbon and sulfur segregation were also determined. It is concluded that the solidification structure consists of fine grain region, columnar region, cross In the columnar grain region, the SDAS at outer arc of billet is about 30 μm bigger than that of inner arc; the SDAS increases with the increasing drawing speed and the indexed of carbon and sulfur segregation change from positive segregation to the negative with the increasing SDAS. The SDAS can be used as an important parameter not only to establish reasonable secondary cooling system and drawing speed but also to judge the level of segregation in the unidirectional solidification region.