Effect of Bubbles on Crystallization Behavior of CaO–SiO2 Based Slags

Abstract

Surface longitudinal cracks are a serious problem and particularly prevalent in the casting of peritectic steel (carbon content between 0.10%C and 0.18%C, non-alloyed). It is usually alleviated by controlling the horizontal heat transfer from the steel shell to the mold through increasing the crystallization performance of slags. In the actual continuous casting process, a large number of bubbles are formed in the molten slags, and the crystallization properties of the mold fluxes are affected by bubbles. Therefore, an investigation of the influence of bubbles on the crystallization performance of mold fluxes was carried out by applying the hot thermocouple technique and it is hoped that surface longitudinal cracks can be solved in this way in the peritectic steel casting process. The continuous cooling transformation (CCT) diagrams and time–temperature transformation (TTT) diagrams were constructed for an analysis of the crystallization kinetics. The results showed that the crystallization ability of mold fluxes was enhanced by adding bubbles through shortening the incubation time of crystallization, increasing the critical cooling rate, and decreasing the activation energy of crystallization. As a result, the crystalline fraction, slag film thickness, and surface roughness of the slag films were improved, but the crystalline phase was not affected by bubbles. With an increase of the bubble content remaining in the molten slag, the growth mechanism of the cuspidine crystal phase changed from a low dimension to a high dimension, and the content of the molten slag’s structure unit (Q1) needed for cuspidine in the molten slag was markedly increased.

Effect of B2O3 on the Crystallization Behavior of CaF2-Based Slag for Electroslag Remelting 9CrMoCoB Steel

“…The activation energies of crystallization were determined by the Freeman-Carroll method [20][21][22][23]. The Freeman-Carroll method is one of the most commonly methods to analyze the crystallization kinetics based on DSC/DTA experiments.…”

Exploring the Crystallinity of Mold Fluxes by Pulsed Electric Current

“…Li et al observed that by stirring the molten mold flux, the crystallization temperature could be increased, and the crystallization fraction of the stirred mold flux at the initial stage of crystallization was significantly higher than that of the static one. In addition, the addition of carbonate materials, such as CaCO 3 , Na 2 CO 3 , and Li 2 CO 3 , into mold fluxes can produce bubbles, and the bubble formation also influences the crystallization behavior of the mold fluxes . The effects of different methods and factors on the crystallization of mold fluxes have been explored, but it is difficult to achieve real‐time regulation of the crystallinity of mold fluxes.…”