ANALYSIS OF LARGE NONMETALLIC INCLUSIONS IN HIGH STRENGTH AUTOMOBILE GIRDER STEEL CASTING SLAB
To investigate the content,size,morphology and types of large non-metallic inclusions in high-strength automotive beam steel casting slabs,large-scale electrolysis combined with scanning electron microscopy and energy dispersive spectroscopy was used to analyze the large inclusions in 700L steel.The results indicate that the content of inclusions at 1/4 of the wide surface of the test slab is higher than that at 1/2 of the wide surface;the content of inclusions on the inner arc side is higher than that on the outer arc.Adopting a dual process can better remove large inclusions in the steel.The inclusions mainly consist of irregular block shaped aluminosilicate systems larger than 80 μm and spherical aluminum calcium systems smaller than 80 μm.Aluminum silicate inclusions are mainly composed of deoxidation products,ladle refractory materials and protective slag rolled in crystallizer,aluminum-calcium inclusions are mainly formed by refining slag.After the process improvement,the O content in the final molten steel of the converter decreased,and the fluctuation control of the crystallizer liquid level was stable.The number of inclusions at 1/4 of the inner arc was significantly reduced under the single link process,reaching the control level of inclusions in the double link process.
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