Abstract
The performance of gas blown in side walls of a single strand tundish is numerically simulated. Three cases are studied, i.e. tundish without gas blown, tundish with gas blown from the right ...side wall, and from the front wall. The vortex circulating flow is the main flow structure in tundish without gas blown. The gas blown from the right side wall of tundish will significantly change the flow field. The short-circuit flow that the tracer flow along the bottom of tundish to the outlet is becoming the main flow pattern. The RTD curve shows a rapid increase tendency. An anticlockwise flow near the top surface is formed. The mixing of tracer in the tundish is delayed and the dead volume fraction is increased when compared with the tundish without gas blown case. In contrast, the gas blown from the front wall of tundish will divide the tundish into two parts. The strong circulation flow in two parts is formed. Besides, the mixing of tracer is faster and the dead volume fraction is lower than that of the case without gas blown. This case may be an optimized gas blown technology in tundish.
The multiphase flows involving steel—slag—air phases in a two‐strand tundish during ladle change are investigated using mathematical modeling. Experimental results from water modeling are used to ...validate the simulated results. Tundish cover powder (TCP) and steel samples are taken from eight heats in one sequence to evaluate the effect of the multiphase flows during ladle change on the composition of the TCPs and steel cleanliness. Furthermore, the effect of the refilling time on the air entrainment and slag aperture during ladle change is analyzed and discussed. It is found that the strong turbulent flows in the tundish impact zone during ladle change promote the mix of the two‐layer cover powder, which consists of a basic TCP layer at the bottom and a top layer of rice hull balls. It results in a significant change in the composition of the TCPs and gradually deteriorates the steel cleanliness by the slag—steel reaction. Increasing the refilling time can effectively decrease the amount of entrained air and area of slag layer aperture in the tundish bath during ladle change. To reduce the steel reoxidation during ladle change, the refilling time should be larger than 184 s. Moreover, a new TCP is developed instead of the top layer of rice hull balls in industrial production. The use of the new TCP significantly improves the steel cleanliness in the tundish.
The multiphase flow behavior in the tundish during ladle change not only easily causes the air entrainment and slag aperture, but also promotes the mix of the two‐layer cover powder. It has much influence on the steel cleanliness. Increasing the refilling time and controlling the composition of tundish cover powder can significantly improve the steel cleanliness in the tundish.
In this paper, the radial electromagnetic force in the horizontal circular channel of an induction-heating tundish is derived. A dimensionless trajectory model of the inclusion is developed and ...numerically solved to acquire the trajectory of the moving inclusion. When the inclusion is in the lower half of the horizontal circular channel, the direction of the vertical component of the radial electromagnetic pinch force which acts on the inclusion is opposite to the buoyancy. Provided their magnitudes are the same, there is a balanced-position for the inclusions in a circular channel. Therefore, a dead-zone exists near the balanced-position, where the removal time of the inclusion with an AC magnetic-field is longer than without it. Then, the effect of the AC magnetic-field parameters on the range of the dead-zone is identified, which makes it possible to improve the removal efficiency of inclusions. The range of the dead-zone decreases with increasing magnetic-field intensity. When the dimensionless magnetic-field intensity is 56.3, the shielding parameter of 10–15.9 are optimal to decrease the range of the dead-zone.
Continuous casting is an industrial process whereby molten metal is solidified into a semi-finished billet, bloom, or slab for subsequent rolling in finishing mills; it is the most frequently used ...process to cast not only steel, but also aluminium and copper alloys. Since its widespread introduction for steel in the 1950s, it has evolved to achieve improved yield, quality, productivity and cost efficiency. It allows lower-cost production of metal sections with better quality, due to the inherently lower costs of continuous, standardized production of a product, as well as providing increased control over the process through automation. Nevertheless, challenges remain and new ones appear, as ways are sought to minimize casting defects and to cast alloys that could originally only be cast via other means. This Special Issue of the journal "Metals" consists of 14 research articles that cover many aspects of experimental work and theoretical modelling related to the ongoing development of continuous casting processes.
The quality of steel and continuously cast semi-finished products largely depend on the degree and control of the interaction between slag, gas, and refractories, with the steel melt. In this work, ...through the analysis of some samples from a used refractory lining of a tundish, with the help of optical microscopy, the wear of the refractory layer was highlighted, due to the erosion and infiltration of steel microparticles into the pores of the lining. The examination of the samples was carried out in the interface area, metal-shotcrete, shotcrete-concrete, and the area with refractory concrete.
In response to the frequent problem of inconsistent quality of billet castings and their rolled products from each strand by a five-strand tundish, the flow field in tundish is optimized by ...presenting new flow control devices and conducting isothermal physical modelling along with numerical simulation. The results show that the dead volume fraction of the optimized case A6 is reduced from 27.74% to 19%, the stagnation time is prolonged from 12 s to 35 s, and the flow dynamic consistency for each strand is improved as well. In the subsequent industry production tests, the temperature difference of molten steel at the outlet of each strand is reduced to 1~5 °C. The maximum difference of the as-cast equiaxed crystal rate among five strands is reduced from 5.67% to 2.7%, and the consistency of carbon segregation index is also improved with a basically identical appearance through the billet cross section. The maximum differences in oxygen and nitrogen contents for the rolled products of all strands are 2.7 ppm and 5.7 ppm respectively, which are lower than 5.0 ppm and 13.8 ppm before tundish optimization. The yield strength of rolled products is stabilized with much less divergence as compared to the products with the original tundish. Thus, it is believed that the reasonable flow field optimization to a multi-strand tundish not only will have a well-known positive impact on its tranditional metallurgical effect, but also may bring out an approaching identical steel quality from the same caster as we expected.
Three-dimensional computational fluid dynamics simulations were carried out to investigate the multiphase flow and heat transfer in a round mold, when using swirling flow generator (SFG) designs in a ...tundish. The results show that an impinging flow in the mold is significantly suppressed by using a SFG design, compared to when using a conventional tundish. This is due to the rotational flow momentum, which forces the steel to move toward the mold wall. When using SFG designs, the whole flow field shows periodic characteristics in transient simulations. At a given casting speed, the velocity fluctuation period and fluctuation range in the submerged entry nozzle depend on the SFG inlet area as well as the inlet velocity. As the inlet velocity increases from 0.185 to 0.37 m/s (inlet area decreases from 0.0048 to 0.0024 m
2
), the velocity fluctuation period decreases from 3 to 2 seconds and the fluctuation range increases from ± 10.5 to ± 18.2 pct. However, a symmetrical distribution of the flow field is obtained in the time-averaged results of 9 and 6 seconds intervals for SFG inlet velocities of 0.185 and 0.37 m/s, respectively. In addition, within one velocity fluctuation period, the time-averaged temperature field generally has a uniform distribution. As the SFG inlet velocity increases from 0.185 to 0.37 m/s, the steel super-heat further decreases in the mold and the temperature is increased by around 2 K near the meniscus. Finally, in the current mold with a diameter of only 150 mm, the removal ratio of inclusions to the mold top surface is low by using both SFG designs. The removal ratio of 10
μ
m spherical inclusions is 10 pct lower compared to when using a conventional tundish.
A fluid–solid‐coupled numerical model is established on the motion and removal of inclusions in the continuous casting tundish with a multichannel filter. The flow field, heat transfer, and motion of ...inclusions in continuous casting tundish are simulated. The erosion of the lower part of the weir and filter is the most serious; at the casting speed of 2.2 m min−1, the maximum displacements in the upstream and downstream directions are 4.25 and −3.81 mm, respectively. The casting speed effect on the flow pattern and removal of inclusions is investigated. The weir and filter erosion increases with increased casting speed, the total removal efficiency is raised, and the dead zone fraction is reduced. After the casting speed exceeds 2.2 m min−1, the total removal efficiency of inclusions starts to decline. When the casting speed is raised from 1.4 to 3.0 m min−1, the share of inclusions removed by the filter drops from 8.2 to 2.5%, which is nearly 70%.
A fluid–solid‐coupled numerical model is established on the motion and removal of inclusions in the tundish with a multichannel filter. The casting speed effect on the flow pattern and removal of inclusions is investigated. When the casting speed is raised from 1.4 to 3.0 m min−1, the share of inclusions removed by the filter drops from 8.2 to 2.5%.
In this study, the effect of involvement of CaO–Al2O3–SiO2–MgO tundish flux into CaO–SiO2–Al2O3–Na2O–CaF2 mold flux on viscosity and structure of mold flux was investigated through employing the ...rotating viscometer and associated structure analysis including high resolution Raman spectroscopy and solid-state 27Al magic angle spinning nuclear magnetic resonance (27Al MAS-NMR). The results showed that the viscosity continuously increases with increasing involvement of tundish flux. The apparent activation energy obtained from the temperature dependence of the viscosity presents an increase from 128.5 kJ/mol to 149.1 kJ/mol with increase of involvement ratio from 0 to 0.75. Semi-quantitative analysis using the deconvoluted Raman spectra and 27Al MAS-NMR spectra revealed an increase in amounts of AlO4 and Si–O–Al units, but in the meanwhile a decrease in amounts of AlOnF4-n and AlO5 units, this indicates the structure transformation from prevalent silicate structure to complex alumino-silicate structure with increasing involvement ratio. A self-developed structurally-based viscosity model can predict the viscosity of mold flux with varying involvement ratio and presents a smallest deviation of 15.8% compared to those prevalent viscosity models despite of the great transformation of the melt from silicate system to alumino-silicate system.
This study presents a groundbreaking exploration into the potential use of refractory tundish deskulling waste (TUN), a magnesium oxide-based by-product from continuous steel casting, as a ...stabilizing agent for remediating metal and metalloids contaminated soils. Up-flow column horizontal percolation tests were conducted to measure the concentrations of metals and metalloids, pH, and electrical conductivity (EC) in the leachates of two different combinations of contaminated soil and stabilizer (95–5 wt% and 90–10 wt%). The effectiveness of TUN as a soil-stabilizing agent for contaminated soils with metals and metalloids was evaluated by comparing its leachates with those obtained from a sample of a well-established low-grade magnesium oxide (LG-MgO) by-product, which underwent the same testing procedure.
The findings revealed a significant correlation between the mobility of the examined metals and metalloids, and the water-soluble or acid phase of the contaminated soil, primarily governed by precipitation-solution reactions. While the stabilizing impact on non-pH-dependent metals, particularly redox-sensitive oxyanions, was less pronounced, both MgO-based stabilizers exhibited a favourable influence on soil pH-dependent metals and metalloids. They achieved this by establishing an optimal pH range of approximately 9.0–10.5, wherein the solubility of metal (hydr)oxides is minimized. Notably, metals like Zn and Cu, which have high leaching potential, experienced a remarkable reduction in leaching - Zn by over 99% and Cu by around 97% - regardless of the stabilizer content.
In a broader context, this research champions the principles of the circular economy by offering a technical remedy for treating soils contaminated with pH-dependent metals and metalloids. The proposed solution harnesses industrial waste - currently relegated to landfills - as a resource, aligning with sustainable practices and environmental responsibility.
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•Tundish improves heavy metals retention conditions during leaching processes.•Magnesium oxides makes tundish viable for stabilization of heavy metals in soils.•Tundish and common stabilizer had similar effect on heavy metal retention in soil.•Tundish offers environmental and economic advantages compared to current options.•Use of tundish promotes the circular economy through industrial waste valorization.
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