Combined Effects of EMBr and SEMS on Melt Flow and Solidification in a Thin Slab Continuous Caster

Electromagnetic fields have emerged as powerful tools for addressing current problems in thin slab continuous casting processes in the iron and steel industry. Substantial studies have been undertaken on the fundamental effects of electromagnetic brakes (EMBr) and strand electromagnetic stirring (SEMS). However, little attention has been focused on melt flow and solidification in a thin slab continuous caster with the simultaneous application of an EMBr and SEMS. The present study aimed to predict transient fields in the caster using a large eddy simulation and an enthalpy-porosity method. The electric potential method was applied in the braking process, and the conductivity change with solidification was considered. The suppressive effect on the intensity of the nozzle jet, the balance effect on the mold flow, and a dispersion effect could be observed. The dispersion effect was a novel finding and was beneficial to a flatter nozzle jet. In contrast, SEMS caused a highly turbulent flow in the strand. A large vortex could be observed in the casting direction. The solidified shell became more uniform, and the solidification rate became obviously slower. These findings supported the view that a high-quality thin slab can be produced by the application of an EMBr and SEMS.

Physical simulation of liquid steel motion in a thin-slab continuous caster mold

Industrial experience of steel casting at the thin-slab continuous caster (CC) revealed processes, having negative effect on the quality of internal structure and surface of CC thin slab. The main problems are as follows: flat streams of liquid steel, flowing through submerged snorkel into restricted dead volume, form circulating flows of extremely high velocity in both liquid core and on the slab surface. This circumstance makes specific requirements to the design and parameters of the submerged snorkel to supply the metal into the thin-slab CC mold. Despite the more than 25 years’ experience of the snorkel form and geometric parameters development, there is no single opinion on its optimal design. Results of physical simulation of the liquid motion processes in a thinslab Caster mold presented (for slab maximum width 1800 mm, thickness – 90 mm) of JSC “Vyksa Steel-works” casting and rolling complex. Description of the physical model facility quoted, as well as description of the experiment methodology and its results. The speed was measured and structure of liquid steel flows revealed in depth and sub-surface layers, as well as in slag-forming mixture at the mold surface. The comparison of two principally different variants of liquid steel feeding into the mold made. The two variants were as follows: by a flat down-directed stream with a narrow central divider (direct-flow submerged snorkel) and by four streams , two of them directed down under an angle relating the vertical axe, and the other (about 20% of total liquid consumption) – directed upward to the bath mirror (the snorkel of “hammer” type). It was determined, that steel casting with technological speed through the direct-flow snorkel was most effective into the slab of 1400 mm width and less, since in this case the sub-surface flows speed did not resulted in the intensive waves formation, constant whirls formation and slag particles dragging into deep layers of the slab. For steel casting into slab of width more than 1400 mm, it is reasonable to use a snorkel of the “hammer” type, which enables to create a favorable stable structure of circulation and decrease the tendency of slag particles dragging in the deep layers of the slab.

Formation Mechanism and Influence Factors of the Sticker between Solidified Shell and Mold in Continuous Casting of Steel

Based on the stress characteristics of primary solidified shell in the mold, formation model of the shell’s sticker is established according to the theory of mechanical strength, and the mechanism and internal factors of the shell tearing are analyzed by the model. Furthermore, based on the measured data of many stickers in a slab-continuous caster, the influence of casting process factors on the sticker is analyzed statistically. The possible causes for the stickers in the studied caster are discussed. The results provide a reference for optimizing the continuous casting production process and effectively preventing the occurrence of the sticker from the source.

Application of the Dynamic Soft-Reduction Technology on the No.4 Slab Continuous Caster of Bayi Steel

The revamping & upgrading work has been done smoothly for the old soft-reduction system of the No.4 slab continuous caster in Bayi steel, as a result, all the segments (include both arc segments and level segments ) now have the dynamic soft-reduction function, which have been put into the industrial application successfully. Through the production practice, we can see that, after the revamping project, the dynamic soft-reduction function could be applied normally both in the arc segments and in the level segments for the No.4 slab caster, the whole soft-reduction process has been conducted steady and smoothly, the precision of roll gap control is good, the L2 model always makes an exact trace for the casting process and has the advanced algorithm, the L1 program has the reasonable control function and the reliable execution. When the soft-reduction action was executed in the unbending segment (Seg.7), there was no internal crack taking place for all the slabs, and the internal quality of slab such as center segregation was improved obviously, which had shown the metallurgical effect of the dynamic soft-reduction technology fully.

Measurement and Research of Oscillating State of Hydraulic Oscillation in Slab Continuous Casting

The stability of mold oscillation can directly influence on slab surface quality and operational safety in continuous casting. In recent years, the hydraulic oscillation is developed and applied as the driven equipment of mold oscillation. In the present work, based on the slab continuous caster of hydraulic oscillations, the displacement and other parameters of hydraulic oscillator are measured and the evaluation method of oscillation is studied. The displacement difference and phase difference of oscillation with sinusoidal waveform and non-sinusoidal waveform are analyzed. Especially, the dynamic characteristics of the driving force of left and right cylinders are evaluated. The results indicated that the hydraulic oscillator is quite a good device in terms of precision. The method proposed may be useful for evaluating oscillators.