Process optimization and causes analysis on"sand hole"defect of automobile sheet with ultra-deep drawing
With the rapid development of the automobile industry,the surface quality of the automobile sheet is be-coming more and more severe in the main machine factories at home and abroad,especially the"sand hole"phenome-non of the substrate surface in the stamping process of the ultra-deep drawing and large reduction complex forming automobile sheet,becomes the restriction factor which limits the automobile board high quality development.In view of the"sand hole"defect in the stamping of automobile sheet with ultra-deep drawing and large reduction,by means of scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS),it was clear that the re-moval of Al2O3 inclusions enriched by submerged nozzle was the fundamental cause of"sand hole"defect in sheet metal stamping.Through the analysis of the correspondence between the key steelmaking process and the"sand hole"defect,it was shown that the main causes of the"sand hole"defect were the end-point oxygen of the convert-er,the top slag TFe of the RH outlet,the fluctuation of the mold level,and the continuous casting of transition blank were the main causes of"sand hole"on the substrate surface.The cleanliness of molten steel can be improved by reducing oxygen content in molten steel,optimizing TFe content in RH slag,reducing oxygen transfer at slag/gold interface,protecting casting to prevent secondary oxidation of molten steel,optimizing flow field of mold to re-duce fluctuation of liquid level and steady state control of liquid level in tundish.The"sand hole"defect of the ultra-deep drawing and large thinning volume automobile sheet is effectively improved,and the defect incidence is reduced from 0.086％to 0.026％.The research results provide technical support for high cleanliness smelting of ultra-low carbon steel,and provide reference for improving the surface quality of ultra-deep drawing and large reduction auto-mobile sheet.
"sand hole"defectAl2O3 inclusioncleanliness of molten steelrelevanceoptimization measure
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