1. School of Metallurgy and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China; 2. State Key Lab of Metastable Materials Science and Technology, Yanshan University,Qinhuangdao 066004, Hebei, China; 3. Tangshan Stainless Steel Co., Ltd., Tangshan 063100, Hebei, China
Abstract:The nozzle clogging of an ultra-low carbon Al-killed steel was analyzed using scanning electron microscopy-energy dispersive spectrometer to study the formation and evolution of FeOx containing clogs. Clogs were divided into the frozen steel layer and the main layer. Due to the difference in morphology and composition of oxides, the main layer of clogs presented obvious stratification phenomenon and varied from the matrix of the nozzle to the molten steel as follow: a network formed by elongated strips of Al2O3,single particles of Al2O3 distributed in a dotted pattern, continuous sheets of FeOx-Al2O3 and dot-like particles of Al2O3. There was a thin layer of FeOx-Al2O3 at the edge of frozen steels with the main components of FeOx,Al2O3 and FeO·Al2O3. In the FeOx-Al2O3 layer,the part near the frozen steel had a higher content of Al2O3,while the part relatively far from the frozen steel had a higher content of FeOx. Thermodynamic calculation results show that when the content of [O] in the molten steel at 1 536 ℃ is greater than 0.041 0%,FeO and FeO·Al2O3 can be generated in the molten steel. When oxidation occurs,composite oxides of FeOx-Al2O3 form first. Then FeOx will react with [Al] in the steel drop and Al2O3 will be formed,while the external Al2O3 will adhere to the composite oxide of FeOx-Al2O3. FeOx acted as a binder in the nozzle clogging.
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