Abstract
Kambara Reactor (KR) desulfurization slag used as slag-making material for converter smelting can promote early slag melting in the initial stage and improve the efficiency of dephosphorization. However, its direct utilization as a slagging material can increase the sulfur content in molten steel since KR desulfurization slag contains 1~2.5% sulfur. Therefore, this research focuses on the effect of basicity on the precipitation behavior and occurrence state of sulfur in KR desulfurization slag in order to provide an academic reference for the subsequent removal of sulfur from slag through an oxidizing atmosphere. The solidification process of slag was simulated by the Factsage8.0. The slag samples were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM), and the amount of CaS grains was analyzed using Image-ProPlus6.0 software. The thermodynamic calculation showed that the crystallization temperature of CaS in the molten slag gradually decreased with the increase in basicity, and the CaS crystals in the molten slag mainly existed in the matrix phase and at the silicate grain boundaries. A large number of CaS grains were precipitated along the silicate grain boundary in low-basicity (R = 2.5 and 3.0) slags and fewer CaS grains were precipitated along the silicate grain boundary, while the CaS grain density in the matrix phase was higher in the high-basicity (R = 3.5, 4.0, 4.5) slag. With the increase in basicity, the number of CaS grains gradually decreased, and the CaS grain sizes in slag sample increased gradually. The sulfur in the synthetic slag was in the form of CaS crystals and the amorphous phase, and the content of amorphous sulfur gradually increased with increasing basicity.
Highlights
Sulfur is a detrimental impurity in molten steel that can form long strips or flake-shaped sulfide inclusions, causing a decrease in the transverse compressive strength and plasticity of steel [1]
In the injection desulfurization process, inert gas and desulfurizer are injected into the molten iron at the same time by a spray gun, and the inert gas plays the main role of carrying the desulfurizer and stirring the molten iron [7,8]
Two phases coex0isted in the molten slag at 1600 °C, and the particle concentration of the MeO#1 phase increased2w.5 ith the i3ncrease oB3f.5abciassitiycity.4During t4h.5e equilibrium solidification process, the sulfur in the slag completely precipitated in the form of a CaS phase, and the crystallizatFiiognurteem3. pReerlaattiuorneshoifpCbaetSwienenthteheslmagolgternadsluagalplyhadseecaarnneddasttehhdee bbwaasistiichciitttyyhaeatti11n66c00r00e◦a°Cse.. in basicity
Summary
Sulfur is a detrimental impurity in molten steel that can form long strips or flake-shaped sulfide inclusions, causing a decrease in the transverse compressive strength and plasticity of steel [1]. Relevant researchers [17,18,19] have reported that C2S can form a stable solid solution C2S-C3P (2CaO·SiO2-3CaO·P2O5) with C3P (3CaO·P2O5) to improve the stability of phosphorus in the molten slag To this end, the reuse of KR desulfurization slag in converter smelting process has been studied. It can be seen that reusing KR desulfurization slag for converter smelting directly increases the sulfur content and reduces the quality of molten steel. Minerals 2021, 11, 977 of KR desulfurization slag in the form of synthetic slag to provide a theoretical basis for the subsequent removal of sulfur in KR desulfurization slag through an oxidizing atmosphere and realize the comprehensive utilization of KR desulfurization slag in the converter smelting process
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