(1. Research Institute of Technology, Shougang Group Co., Ltd., Beijing 100043, China 2. Beijing Key Laboratory of Green Recyclable Process for Iron and Steel Production, Beijing 100043, China 3. Qian’an Iron and Steel Company, Shougang Stock Company, Qian’an 064404, Hebei, China)
Abstract:The demand of inclusion control for ultra low carbon steel has become increasingly urged,and Al-Ti complex inclusions have a major impact on nozzle clogging and quality of products. So the characteristics,formation and evolution process,formation mechanism and control factors of Al-Ti inclusions are analyzed in detail. Many samples were carried out in refining process and tundish. The number,size,morphology and chemical composition of inclusions were analyzed automatically by using Aspex scanning electron microscope. The result shows that a high concentration area of titanium is formed in molten steel after addition of titanium alloy,then Al2O3 inclusions change into Al-Ti inclusions in this area. In order to suppress the transformation reaction,the aluminum and titanium interval time should be controlled in 4 min. The reoxidation of molten steel in the continuous casting process will affect the formation of Al-Ti inclusions,the more serious of reoxidation in molten steel,the more inclusions in tundish. This is caused by two reasons-the increase of [w([O])]in molten steel inhibits the reaction of Al-Ti inclusions transformed to Al2O3 inclusions;Al,Ti,O react directly to form Al-Ti inclusions in molten steel area with high[w([O]).]
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