Subsurface macro-inclusions and solidified hook character in aluminum-killed deep-drawing steel slabs

To the authors' best knowledge, unsteady period casting is detrimental for the sound casting and good quality. On the basis of mathematical model and experimental observation, some typical unsteady phenomena including breakout shell, unsteady solidification, level hunching, and steel cleanliness are discussed presently. The results show that solidification factor in the mold is within 22–28 mm min−1/2 and the superheat carried by the impinging flow, about 300 mm below the meniscus, is enough to remelt the thin solidified shell of narrow face. After the analysis of unsteady crater end transition mechanism, mathematical model verified by pin shooting is established and the expression for predicting the actual unsteady length is derived. There is also a typical mold level hunching occurring during the ladle change period of high‐speed casting, which cannot be elucidated by unsteady bulging due to the aperiodic profile. Therefore, the clog–unclog mechanism is proposed. With respect to the cleanliness, powder entrapment occurs during the first two slabs of casting start, ladle change, SEN change, casting end period and the reoxidation is dominant in the casting start. Finally, the quality of cold‐rolled coils is improved by the optimization of speed transition route in the casting start.

“…The details about the analysis method are described in refs . And the cleanliness is represented by the total oxygen and number density of inclusions in the current study.…”

Section: Steel Cleanliness Evaluationmentioning

confidence: 99%

Discussion on Some Typical Phenomena during Unsteady Casting Process

Wang

Deng

et al. 2016

“…It leads to slag entrapment in casting products [4,5] and sliver defects in rolled products. [6,7] Many factors can affect the wetting behavior (interfacial properties) of slag on steel. The surface-active solutes, such as oxygen and sulfur; the alloying elements like Cr, Ni, etc.…”

Section: Introductionmentioning

confidence: 99%

“…It leads to slag entrapment in casting products [ 4,5 ] and sliver defects in rolled products. [ 6,7 ]…”

Section: Introductionmentioning

confidence: 99%

Influence of Fluorine and CaO/Al₂O₃ Ratio on the Wetting Behavior Between CaO–Al₂O₃‐Based Mold Flux and Steel Substrate

Yang

Wang

Zhou

et al. 2022

The wetting behavior of flux melt on the initial solidified shell greatly determines the slag entrapment in the casting product and the sliver defect in the rolled product. Herein, the wetting behavior of CaO–Al2O3‐based mold flux with various fluorine (F) contents and CaO/Al2O3 (C/A) ratio on steel substrate is studied using the sessile drop method. Results show that the contact angle decreases from 71.35° to 59.86° and from 65.96° to 22.73°, meanwhile, the interfacial tension decreases from 1743.02 to 1669.69 mN m−1 and from 1705.40 to 1448.53 mN m−1, with the addition of F and the increase of C/A ratio, respectively. X‐ray photoelectron spectroscopy analysis indicates that the addition of F and increase of C/A ratio lead to positive adsorption () of non‐bridging oxygen (O−) and free oxygen (O2−) at the interface, which is the main reason why the interfacial tension between the mold flux and steel is reduced and the wettability of flux droplet on the steel is enhanced.

“…For clean steel production, it is highly important to investigate the distribution of the inclusions and argon bubbles in the slabs. The particle distributions of the slabs have been studied by both experimental measurements [3][4][5][17][18][19][20] and numerical simulations. [16,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Due to the limitations for scope and accuracy of the instruments used for the detection of particles in the slabs, the measurements of particle distributions in the slab are usually not comprehensive.…”

Section: Introductionmentioning

confidence: 99%

Large Eddy Simulation of Transient Flow, Particle Transport, and Entrapment in Slab Mold with Double‐Ruler Electromagnetic Braking

Yin

Zhang

et al. 2021

To study the transient transport and capture of inclusions and argon bubbles simultaneously in slab mold with double-ruler electromagnetic braking (EMBr), a transient large eddy simulation model coupling molten steel flow, solidification, electromagnetic field, and particle motion is constructed. In this model, momentum transfer between argon bubbles and molten steel is implemented by two-way coupling. The results indicate that the EMBr changes the molten steel transient flow pattern in the liquid pool. Due to the braking effect, the asymmetry and instability of the molten steel transient flow are weakened. Moreover, EMBr changes the transient particle (inclusion and argon bubble) transports inside the liquid pool. The particle motions inside the liquid pool are constrained, and the dispersion of the particles inside the liquid pool is weakened by EMBr. In addition, the contents of particles within the slab surface layer are decreased under the application of EMBr. Nevertheless, in the slab interior, the contents of the particles under the application of EMBr are higher than those in the absence of EMBr.