Study on Mineralogical Constituents of Slag Film of Casting Powder for Continuous Casting of Plates

The mineral compositions,crystallization rates,thicknesses,layered structures of slag film of casting powder for continuous casting of Q235B steel plates were analyzed by optical microscope and Xray diffractometer.The result shows that the mineral compositions of slag film consist of akermanite,cuspidine,wollastonite and glass phase.When longitudinal cracks are found on strand surface during casting,the crystalline phases of the slag film are mainly melilite and cuspidine with a crystallization rate of 50%~55%,and the film exists in a glassy layer-crystallizing layer-glassy layer structure.When sticking-type breakouts are found on strand,the slag film is dominated by crystallizing layer consisting of cuspidine and wollastonite.The crystalline phases of slag film under normal circumstances consists of melilite with crystallization rate of 90%.In order to avoid longitudinal cracks on medium carbon steel's strand surface and sticking-type breakout of strand,it it suggested that the crystallization rate be improved and the content of wollastonite be reduced.