Herein, laboratory experiments and thermodynamic calculations are conducted to study the influence of Mg treatment on the inclusion behavior of M50 aerospace bearing steels under different S/O mass ratios (mass ratios of S content to O content). The type, morphology, and distribution of inclusions in ingots with and without Mg treatment are characterized by the scanning electron microscope, energy‐dispersive X‐Ray spectroscopy, and ASPEX automated inclusions analysis system. In addition, the phase distributions of inclusions in M50 steels are simulated using FactSage software to clarify the mechanism of inclusion evolution during the smelting and solidification processes. For both high and low S/O mass ratio steels, the primary spinel and Al2O3 inclusions can be completely modified into MgO inclusions and MnS can be partially transformed into MgS inclusions by Mg treatment. After Mg treatment, the size and number density of inclusions show a noticeable increase in high S/O mass ratio steel resulted from a mass of MgS formation but a slight decrease in low S/O mass ratio steel due to the MgO removal by floatation. Based on the present study, an optimal S/O mass ratio for tight control of detrimental inclusions in Mg‐treated M50 steels is obtained.
Herein, laboratory experiments and thermodynamic calculations are conducted to study the influence of Mg treatment on the inclusion behavior of M50 aerospace bearing steels under different S/O mass ratios (mass ratios of S content to O content). The type, morphology, and distribution of inclusions in ingots with and without Mg treatment are characterized by the scanning electron microscope, energy‐dispersive X‐Ray spectroscopy, and ASPEX automated inclusions analysis system. In addition, the phase distributions of inclusions in M50 steels are simulated using FactSage software to clarify the mechanism of inclusion evolution during the smelting and solidification processes. For both high and low S/O mass ratio steels, the primary spinel and Al2O3 inclusions can be completely modified into MgO inclusions and MnS can be partially transformed into MgS inclusions by Mg treatment. After Mg treatment, the size and number density of inclusions show a noticeable increase in high S/O mass ratio steel resulted from a mass of MgS formation but a slight decrease in low S/O mass ratio steel due to the MgO removal by floatation. Based on the present study, an optimal S/O mass ratio for tight control of detrimental inclusions in Mg‐treated M50 steels is obtained.
The dynamic behavior of nonmetallic inclusions at the bubble–steel interface is a key factor contributing to the formation of large‐sized inclusions or clustered particles and is particularly important for the production of high‐quality‐oriented silicon steel. In this study, high‐temperature confocal laser scanning microscopy is employed for in situ observation of the agglomeration behavior of Al2O3 inclusions of varying sizes. The critical distance of attraction decreases with the decrease in inclusion size. The effects of particle size, distance, surface tension, density, and different types of inclusions on the capillary force are explored in detail using the Kralchevsky–Paunov model. In the model results, it is highlighted that the degree of influence among the factors affecting the capillary force decreases in the following order: contact angle > size > distance > density > surface tension. Furthermore, the observed results are compared with the model calculation results. The trends of the model calculations and the experimental results show good agreement, but most of the experimental values are higher than the theoretical values. The errors primarily stem from inclusion shape, interference from other inclusion forces, and interactions between the crucible wall and inclusions.
The precipitation process of inclusions in the high sulfur steel with the cerium addition is observed using the high‐temperature confocal scanning laser microscope (CSLM). Rare earth (Re) inclusions formed in the molten steel, and MnS inclusions precipitate along grain boundaries or on oxide cores at the end of solidification. With the addition of cerium, the average aspect ratio of inclusions in the steel decreases from 6.5 to 5.0, and the addition of cerium effectively modifies the elongated MnS. Thermodynamic calculations show the inclusion transformation during solidification, yet it lacked the formation of Ce2O2S and Re sulfides. According to the first‐principles calculation, the priority of the inclusion formation was Ce2O3 > CeAlO3, Ce2O2S > CeS > Ce3S4 > MnS. The stability of MnS inclusions is much lower than that of cerium‐containing inclusions. It is in situ observed that the addition of cerium promotes the formation of cerium‐containing inclusions and reduces the precipitation of MnS in the high sulfur steel.
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