Research On Composition And Phase Change Of Slag Skin And Slag Pool In ESR

The slag properties have great influence on the product qualit y, relavant technical and economic index in electro-slag remelting process(ESR), and the slag properties are compactly related with the composition of the slags. It shows that the slag composition is in changing in electro-slag remelting process. The mechnism and the influence to the remelting process of this change is not sufficiently studied up to now. The relavant research will be of theoretical and practical significance. In this paper, the factors related to slag pool composition was analyzed and the composition and phase change of slag skin was researched to obtain the slag pool composition change pattern.Based on the relevant references, the factors that affect the slag pool, such as weight loss by volatile, metal/slag reaction, and slag skin forming, were studied. Representative slag systems of binary, three-element and quaternionic slag system were chosen and slag samples were collected from industrial. Polarizing microscope, X-ray diffraction analysis, scanning electron microscope analysis and electron probe microanalysis were used to measure the slag phase and composition. Finally, material balance calculation of slag in remelting process were set up to analyze the influence quantitatively of different factors.The main results can be obtained as following:(1) The dust collected in ESR is mainly composed of CaF2, AlF3 and some oxides in small quantity.(2) Slag skin is deposited in layers in thickness direction. The component with higher melting point is trend to solidify first. To the slag skin with two layers, the Al2O3 and aluminate content decreased and CaO increased gradually from mould side to the inner. To the slag skin with three layers, the Al2O3 and aluminate content increased and then decreased from mould side to the inner.(3) The composition change of slag pool in ESR process can be reflected in slag skin quenching layer of near mould. In the quenching layer, CaF2, Al2O3 content decrease and CaO content increase gradually from down to up side the ingot bottom.(4) To the slag quantity and composition in slag pool, the evaporation of fluorides as well as dust escaping and oxidation of element in metal(with deoxidants added) are of the biggest impact. Absorption of inclusion from metal is of less effect.