Abstract
The reaction between [Al] in molten steel and (SiO2) in the liquid slag layer was one of the restrictive factors in the quality control for high Al-TRIP steel continuous casting. In this work, the composition and property variations of two slags during a slag-steel reaction were analyzed. Accordingly, the crystalline morphologies of slag were discussed and the solid layer lubrication performance was evaluated by Jackson α factors. In addition, a simple kinetics equilibrium model was established to analyze the factors which affected SiO2 consumption. The results reflected that slag-steel reacted rapidly in the first 20 minutes, resulting in the variation of viscosity and the melting temperature of slags. The slag-steel reaction also affected the crystal morphology significantly. Slag was precipitated as crystals with a higher melting temperature, a higher Jackson α factor, and a rougher boundary with the consumption of SiO2 and the generation of Al2O3. In other words, although generated Al2O3 acted as a network modifier to decrease the viscosity of the liquid slag layer adjacent slab shell, the consumption of SiO2 led to the deterioration of the lubrication performance in the solid slag layer adjacent copper, which was detrimental to the quality control for high Al-TRIP steel. Finally, a kinetics equilibrium model indicated that it is possible to reduce a slag-steel reaction by adjusting factors, such as the diffusion coefficient k, cSiO2, ρf and Lf, during the actual continuous casting process.
Highlights
While the “environmentally friendly, safety, long-life and low-cost” have become an international consensus of the automobile industry, attention for developing advanced automobile strength steel have been paid to high Al-TRIP (Transformation Induced Plasticity), which had a good combination of high strength and high toughness [1,2,3,4]
The chemical composition of high Al-TRIP steel is listed in Table 1, samples were cut with a weight of 300 g from an industrial slab
Generated Al2 O3 acted as network modifier direction. This was favorable for the formation of crystals with regular geometrical shapes, and to decrease the viscosity of liquid slag layer adjacent slab shell, the consumption of SiO2 led to the the anisotropy of crystals was increased, which resulted in the decrease of lubrication performance deterioration of lubrication performance in solid slag layer adjacent copper, which was detrimental to in solid slag layer adjacent to the copper
Summary
While the “environmentally friendly, safety, long-life and low-cost” have become an international consensus of the automobile industry, attention for developing advanced automobile strength steel have been paid to high Al-TRIP (Transformation Induced Plasticity), which had a good combination of high strength and high toughness [1,2,3,4]. Park et al [13] studied the addition of CaF2 that was beneficial to the reduction of the viscosity of high Al steel slag, but because of the high basicity of Na2 O, when the content of CaF2 exceeds 8%, the viscosity-reducing effect was weakened significantly It was the drastic slag-steel reaction during the continuous casting process that led to slag performance deterioration. Cho et al [18] designed the CaO-Al2 O3 based slag for continuous casting of 1.45% Al steel and found that the reactivity of Equation (1) was reduced significantly, resulting in a certain improvement of the slab quality. Al-TRIP steel continuous casting process, a kind of low-reactive slag based on CaO-SiO2 -Al2 O3 system was adopted in this work. A kinetics equilibrium model of (SiO2 ) in liquid slag was established to analyze the factors that affected SiO2 consumption
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