Abstract
Al2O3, Al2O3·TiN, Al2O3·MgO, and CaO·2Al2O3 are four different types of inclusions in high Al steels. To improve the steel cleanness level, the effective removal of such inclusions during secondary refining is very important, so these inclusions should be removed effectively via inclusion dissolution in the slag. The dissolution behavior of Al2O3, Al2O3·TiN, Al2O3·MgO, and CaO·2Al2O3 in CaO-SiO2-Al2O3-MgO slags, as well as the steel-slag reaction, was investigated using laser scanning confocal microscopy (LSCM) and high-temperature furnace experiments, and thermodynamic calculations for the inclusion in steel were carried out by FactSage 7.1. The results showed that Al2O3·TiN was observed to be completely different from the other oxides. The composite oxides dissolved quickly in the slags, and the dissolution time of the inclusions increased as their melting point increased. SiO2 and B2O3 in the slag were almost completely reacted with [Al] in steel, so the slags without SiO2 showed a positive effect for avoiding the formation of Al2O3 system inclusions and promoting inclusions dissolution as compared with SiO2-rich slags. The steel-slag reaction was also found to influence the inclusion types in steel significantly. Because of the rapid absorption of different inclusions in the slag, it was found that the dissolution time of inclusions mainly depends on the diffusion in the molten slag.
Highlights
High-Al steel usually refers to steel grades with more than 0.7% aluminum in molten steel
∆ = 2 cos / ( − )δ where w is the width of plates; g is the gravity acceleration; γ is the liquid surface tension; θ is the contact angle between the liquid and solid plate; δ is the spacing between two parallel plates; and ρL and ρG are the densities of the liquid and gas phasesn, rEeDspSe. cItnivaedlyd.itOiobnv, itohuestlyyp, eΔhofisinpclruospioorntsiocnaanl btoe dδe−1t,ewrmhiincheddbeyterremfeinrreisngthteo stthreenmgtohrpohf othloegaicttarladctiifofenr.ences of different inclusions in the references [15,16,17,18]
We focused on the behavior of Al2O3, Al2O3·TiN, Al2O3·MgO, and CaO·2Al2O3 inclusions in high Al steel in contact with three different slag compositions in this study
Summary
High-Al steel usually refers to steel grades with more than 0.7% aluminum in molten steel. Monaghan reported that spinel inclusion dissolution can be affected by changing the slag composition, where the rate controlling mechanism for Al2O3 microparticle dissolution in the liquid oxide compositions was found to be controlled by mass transfer in the liquid oxide [9] On this basis, further research on the separation of inclusions from molten steel, and the adsorption and dissolution behavior in the slag become a scientific frontier issue. There are few in-situ studies on fine composite inclusions such as calcium aluminate, spinel, and alumina-titanium nitride It has not been studied for the absorption and dissolution process of fine inclusions in refining slag used for high Al steel in particular. The dissolution process of the composite inclusions in refining slag and the modification of inclusions in high Al steel after the interaction with top slag were analyzed, the absorption and reaction process of the inclusions was studied
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