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The transient evolution of inclusions during Al and Ti additions in a Fe-20 mass pct Cr alloy was investigated using polished cross sections and electrolytic extraction. After Al addition, the evolution of Al2O3-based inclusions based upon the area and particle size passed through the following three main stages with time: Particle agglomeration, inclusion floating, and a slow decrease of the remaining Al2O3-based inclusions. Titanium wire was fed into the steel at the end of the floating stage after Al addition when the Ostwald ripening process was finished. Immediately after Ti addition, the transient phase of Ti oxide was readily generated on the existing Al2O3-based inclusion and disappeared due to Al reduction as time progressed. The formation of the transient TiOx phase was affected by the low disregistry between Al2O3 and TiOx and the local Ti supersaturation, which cannot be predicted by the equilibrium relations of Ti–O–N or Ti–Al–O in the high-Cr-containing melt. Because of the local supersaturation of dissolved [%Ti] and [%N] shortly after Ti addition, TiN associated with existing inclusions and three types of individual TiN including single cubes, twinned inclusions, and clusters were identified. In order to minimize the Ti loss caused by the formation of Ti-rich zones during the transient stages, the removal of large Al2O3-based particles including aggregates, clusters, and flower-shaped inclusions should be promoted by stirring before Ti addition. After Ti addition, Brownian and turbulent were the major factors affecting the collision of particles smaller than the threshold of 2.7 μm. The agglomeration of inclusions larger than this threshold was mainly dominated by turbulent and Stokes’ collisions.

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The grain growth kinetics, texture and misorientation distribution function (MDF) evolutions of a non-ferromagnetic metal sheet with isotropic and anisotropic grain boundary under magnetic field are studied using a modified two-dimensions (2D) Potts model, in which the grain boundary migration is driven by the grain boundary energy and the difference in magnetic free energy between grains and their neighbors. Monte Carlo simulation results show that the texture and MDF evolutions of materials intensively depend on the magnetic field and grain boundary anisotropy, whereas the grain boundary growth kinetics is insensitive to the magnetic field.

This study aims to investigate the effect of tundish level control on the change in element content and inclusion amount in molten steel during the low tundish-level steel grade transition. Based on multiphase flow, mass transfer, and discrete phase, a three-dimensional transient numerical simulation of the tundish was established in Ansys Fluent. The model uses moving mesh refinement technology to obtain clear steel and slag interface with a small number of meshes. The numerical simulation results were verified through industrial experiments and physical simulations. The results indicate that when the tundish is at a low level, strand 3 becomes a short-circuit flow, and the number of inclusions in strand 3 is approximately four times that in strand 1. If the old grade density is higher than that of the new grade, the unqualified length of the element content in the transition billet is 10.2 m shorter than that in the opposite order. When the filling speed of the tundish is three times the normal flow rate, the length of the transition billet with an unqualified number of inclusions is 7.1 m less than that when the filling speed is 2 times the normal flow rate. In addition, at the initial stage of the low tundish level steel grade transition, the minimum amount of inclusions in the transition billet can be reduced to 40% of the average amount of inclusions in the old grade; however, the maximum number of inclusions in the transition billet increase by a factor of 2.5 times the average number of inclusions in the new grade at the end stage of the low tundish-level steel grade transition. It can be observed that the inclusions in the initial stage of the low tundish-level steel grade transition have less effect on the quality of the old grades; however, they have a greater effect on the new grades in the final stage of the low tundish-level steel grade transition.