Continuous Casting Of Steel Research Articles

Insights into clogging behavior of Al2O3-C and ZrO2-C submerged entry nozzle during continuous casting of ultra-low carbon steel

Insights into clogging behavior of Al2O3-C and ZrO2-C submerged entry nozzle during continuous casting of ultra-low carbon steel

Effect of Al2O3/SiO2 Ratio on Structure and Properties of Mold Flux for High-Al Steel Continuous Casting

The conventional CaO–SiO2-based mold fluxes are not suitable for high-Al steel casting because of the strong reaction between silica in the flux and aluminum in the steel strand. In the process of casting of high-Al steel, flux composition changes, with the decrease of the silica concentration and increase of alumina. Knowledge and understanding of the effect of the Al2O3/SiO2 ratio on flux structure and properties are useful for flux design for the high-Al steel continuous casting. This paper investigated the effect of the Al2O3/SiO2 ratio in the range from 0.7 to 10.8 on structure, viscosity, and heat transfer of CaO–Al2O3–SiO2–B2O3–Na2O–Li2O–MgO–F fluxes. It was found that flux melting temperature increased with the increase in Al2O3/SiO2 ratio. Viscosity of the flux melts increased significantly with the increase of the Al2O3/SiO2 ratio from 0.7 to 1.2, reaching the maximum value, and then decreased with further increase of the Al2O3/SiO2 ratio. Raman spectroscopy analysis revealed that the change of the Al2O3/SiO2 ratio led to the change of aluminate and silicate structural units. The turning point for viscosity was attributed to the change in the degree of flux polymerization which was governed by the amphoteric nature of Al2O3. X-ray diffraction (XRD) analysis showed that increasing Al2O3/SiO2 ratio increased crystallization tendency of the fluxes. Heat transfer measurement by infrared emitter technique (IET) revealed that increasing Al2O3/SiO2 ratio led to the decrease in heat flux which is correlated well with the increased crystallinity of the flux. The results suggested that the fluxes with Al2O3/SiO2 ratio 2.1–4.3 are the best candidates among the studied CaO–Al2O3-based mold fluxes for casting of high-Al steel.Graphical

Effect of Nickel Content and Cooling Rate on the Microstructure of as Cast 316 Stainless Steels

To meet the requirement of low magnetic permeability, which, in turn, lowers the ferrite content of castings, of special interest is 316 stainless steel, whose low ferrite content renders it suitable also for nuclear power applications. Therefore, the effects of the composition and cooling rate of 316 stainless steel castings on the ferrite content are investigated. Three 316 stainless steel continuous casting samples with different compositions (primarily differing in the Ni content) are studied, i.e., low-alloy type (L-316), medium-alloy type (M-316), and high-alloy type (H-316). The austenite-forming element nickel of three different industrial samples is 10%, 12%, and 14%, respectively. The effect of the cooling rate on the ferrite content and precipitation phases of the high Ni content of the 316 stainless steel casting (H-316) is studied by remelting experiments and different methods of quenching of liquid steel. In both cases, the ferrite content and the precipitate phases in the microstructure are analyzed using SEM and EBSD. The results indicate that compositional changes within the 316 stainless steel range lead to changes in the solidification mode. In the L-316 casting, solidified by the FA mode (ferrite–austenite mode), ferrite precipitates first from the liquid phase, followed by the formation of austenite, and the ferrite content is 11.2%. In contrast, the ferrite content in the M-316 and H-316 castings, solidified by the AF mode (austenite–ferrite mode), is 2.88% and 2.45%, respectively. The effect of the solidification mode on the ferrite content is more obvious than that of the composition. The microstructure of the L-316 casting is mainly composed of the austenitic phase and the ferritic phase. The microstructure of the M-316 casting is composed of austenite, ferrite, and a small amount of sigma phase, with a small amount of ferrite transformed into the sigma phase. The microstructure of the H-316 casting is basically composed of austenite and the sigma phase, with the ferrite has been completely transformed into sigma phase. Changes in composition have a greater influence on the precipitate phases, while the solidification mode has a lesser impact. In the remelting experiments, the ferrite content in the H-316 ingot obtained through furnace cooling and air cooling is 1.49% and 1.94%, respectively, and the cooling rates are 0.1 °C/s and 3.5 °C/s, respectively. Under oil- and water-cooling conditions, with cooling rates of 11.5 °C/s and 25.1 °C/s, respectively, the ferrite content in the ingot is controlled to below 1%. The effect of the cooling rate on the precipitation phase of the H-316L ingot is that the amount of precipitated phase in the ingot decreases with an increase in cooling rate, but, when the cooling rate exceeds a certain value (air cooling 3.5 °C/s), the change in cooling rate has little effect on the amount of the precipitated phase.

Machine learning techniques for the comprehensive analysis of the continuous casting processes: Slab defects

Continuous casting route is the most widely produced process in the world every year, accounting for around 95% of global steel production. Due to the various inevitable defects, including cracks, segregations, inclusions and breakout involved in the production process, tranditional control and monitoring approaches are pushed to their limits. Over the past decade, the increasing global competition has combined metals engineering with digital technology and artificial intelligence skills, to help the manufacturing industries to reap the benefits of “big data.” By targeting critical machine learning (ML) techniques, the casting industry leaders rapidly take advantage of the latest discoveries in manufacturing processes through digital twinning to enable defect-free casting. This study offers an analytical overview of ML methods applied to the examination of the continuous casting procedure. This paper examines the current research on ML in steel continuous casting, organizing the findings into categories, which aids in identification of typical application cases and approaches. This comprehensive analysis concludes with the elaboration of challenges, potential solutions, and a future outlook for further cutting-edge research and development to unleash the potential of future ML techniques and maintain casting industry's reputation.

Slag rim structure and phase formation mechanism in molds during the continuous casting of high-Mn high-Al steel

Slag rim structure and phase formation mechanism in molds during the continuous casting of high-Mn high-Al steel

Research on Constitutive Modeling of DH460 Continuous Casting Steel with the Solidification End Reduction Process.

The constitutive model was commonly used to describe the flow stress of materials under specific strain, strain rate, and temperature conditions. In order to study the thermal-mechanical behavior of DH460 continuous casting steel during the solidification end heavy reduction (HR) process accurately. The high-temperature compression experiment was carried out, and phenomenological constitutive models were established based on the experimental results. A new strain-strengthening factor (D(ε)) was proposed in order to improve the prediction accuracy of the current constitutive models. Then, the further-modified models were established. It was found that the new strain-strengthening factor significantly reduced the error of models. The average relative error (AARE) of the further-modified Johnson-Cook model and the further-modified Zerilli-Armstrong model were 6.27% and 5.54%, respectively. The results showed that the further-modified models were more suitable for describing the constitutive behavior of DH460 continuous casting steel during the solidification end reduction.

Numerical and Physical Modeling of Steel Flow Behavior in the Two Strand Tundish During Nonconventional Pouring Conditions

permeable barrier or advanced ladle shroud equipped, its shape of the internal working volume and the number of outlets visible in the formation of individual hydrodynamic structures. During numerical and physical simulations, the process of continuous steel casting of two slabs with dimensions of 1.15 m × 0.225 m at a speed of 1 m/min was simulated. Two-strand tundish with and without subflux flow controller (SFC) was tested. Off-centered location of subflux flow controller and ladle shroud misalignment in the tundish pouring zone were investigated. Basis on the obtained results the non-standard interaction of the feed stream with the SFC working space revealed the occurrence of a favorable hydrodynamic structure in the tundish working space in the context of limiting the stagnation flow. This is show by the formed hydrodynamic structure consists of vertically circulating streams of liquid steel, effectively eliminating and limiting the impact of reverse streams.

X-ray computed tomography (XCT) study on the porosity structure of slag film in the steel continuous casting

X-ray computed tomography (XCT) has been utilised to investigate the porosity structure of slag films in the steel continuous casting. This study explores the efficacy of the XCT technique in characterising and identifying porosity within slag films, including comparisons between vertical XCT slices and images from traditional 2D methods. The results of 3D visualisation reveal that higher porosity on the mould side is not consistent across all slag films, thereby challenging existing beliefs. It has also been observed that the distributions of pore locations vary across different slag films, correlating with their porosity levels. In slag films with low porosity, pores predominantly appear on the sides, whereas, in those with higher porosity, they are distributed throughout. Analysis of pore sizes across various slag films indicates that, although smaller pores are numerous, larger pores significantly contribute to the overall porosity. This research in-depth explored the internal pore structure in slag film via XCT technique, offering insights for optimising slag film design and improving steel casting processes.

Dominant factors of thermal conduction in alkali silicate glasses and melts: A molecular dynamics study

AbstractAs representative compositions of the mold flux used in the continuous casting of steel, the temperature and composition dependence of the thermal conductivity of alkali silicate glasses and melts was investigated in the range of 300–1700 K using molecular dynamics (MD) simulations. MD simulations can exclude disturbances such as radiation, convection, and impurities, and extract only the effect of phonons on the thermal conduction. Thermal conductivity determined by the laser flash (LF) method was reported to be three times higher than that obtained by the unsteady hot wire (HW) method in the high‐temperature range of 1250–1550 K for 33.3Na2O–66.7SiO2 (mol%). This study shows that (1) the thermal conductivity estimated by MD simulations was closer to the experimental value of the LF method than those of the HW method above 1200 K, which suggests that the LF method is reliable and that the effect of radiation on the thermal conductivity is not significant. (2) The decrease in the thermal conductivity measured by the LF method in the range of 1250–1550 K was attributed to the decrease in the bulk modulus of the 33.3Na2O–66.7SiO2 melt. (3) In a series of Na2O–SiO2 melts, the sound velocity calculated by MD decreased with increasing Na2O content, which is consistent with Shiraishi's ultrasonic wave measurements.

Multi-flow integration process safety management at steelmaking production site through wireless sensor network and AI-enabled data prediction

Industrial production process includes complex and high-risk operational procedures. Maintaining process safety and stability is essential to prevent casualties, equipment damage, and asset loss. Traditional process safety management (PSM) on production site heavily relies on manual inspections and video surveillance which inevitably overlook some hidden risks. Therefore, this paper proposes a novel multi-flow integration PSM framework to overcome the trouble. Firstly, risk factors of the material flow (MF) and energy flow (EF) are systematically analyzed and organized based on the 4M1E method. The wireless sensor network (WSN) is established by deploying multiple sensors which facilitate the data flow (DF), including data perception, collection, transmission and aggregation of different risk variables. Additionally, the analysis model to extract the information flow (IF) is obtained by comparing prediction performance of different deep learning (DL) models. Finally, response strategies against potential dangers are formulated and the control flow (CF) across production layers are achieved relying on the circulation of safety directives, the execution of control measures and the feedback. The effectiveness of this framework is verified in a steel continuous casting scenario through the acquisition of DF, the extraction of IF and the loop of CF. Results indicates that the Bi-LSTM model can achieve the most outstanding prediction performance with relative root mean square error of 4.2428%, root mean square error of 0.0551 and R-square of 0.9816. This study can aid in advancing the digitization and intelligence of the PSM and providing a practical research perspective and application mode.

Design and Analysis of Fluorine-Free Mold Fluxes for Continuous Casting of Peritectic Steels.

Fluorine-based mold fluxes are critical for continuous casting of peritectic steels, controlling heat transfer and preventing cracks. However, environmental and health concerns associated with fluorine have spurred the search for alternative flux compositions. This study applied a factorial design to explore the effects of Na2O, TiO2, B2O3, and fluorine on key properties such as viscosity, crystallization temperature, and melting behavior. Analytical methods, including viscosity measurements, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM-EDS), combined with thermodynamic modeling, were used to evaluate performance. Four formulations were selected based on factorial design results. Sample A, with high Na2O, exhibited intense crystallization of merwinite (Ca3MgSi2O8) and perovskite (CaTiO3). Sample B, incorporating B2O3, had reduced crystallization and suitable viscosity (2.97 Pa·s). Sample C, with a slightly higher fluorine content than Sample B and without B2O3, presented balanced low viscosity (1.75 Pa·s) with a moderate crystallization tendency. Sample D, free of fluorine and B2O3, showed high viscosity (4.58 Pa·s) and significant crystallization. These results demonstrate that fluorine-free fluxes with properties comparable to fluorine-based compositions can be developed, offering a sustainable alternative for steelmaking. Industrial trials are necessary to validate their performance under operational conditions.

A systematic study of carbon-free oxide-based lining for preventing submerged entry nozzle clogging in continuous casting of rare earth steel

AbstractThe reaction of carbon-free oxide-based (corundum, spinel, zirconia, and mullite) submerged entry nozzle (SEN) lining with rare earth inclusions and its anti-clogging effects under near working conditions were systematically studied. A variety of lining composite test methods were innovatively used to ensure the consistency of test conditions. The experimental results showed that the mullite (acidic oxide) has strong reactivity with rare earth inclusions, and the spinel (basic oxide) has stable chemical properties and weak reactivity with rare earth inclusions. Because alumina is one of the main reactants of clogging formation, corundum is not suitable for SEN lining. There are less clogs on the surface of zirconia, but it will be exsoluted and unstable. Therefore, solving the problem of zirconia exsolution will greatly strengthen its application in SEN lining.

Kinetic Study of NaF Gas Formation During Mold Flux Melting Based on Different Fluorides by Experimental and Computational Methods

Low‐basicity fluorine‐containing mold flux, which forms a porous slag film with NaF pores, is expected to solve the contradiction between heat transfer and lubrication in the continuous casting of peritectic steel. Herein, the kinetic mechanism and the influence of NaF gas formation based on the different fluorine raw materials (NaF, CaF2, and Na3AlF6) at 0.9 basicity and 6 wt% fluorine are investigated by the combination of experiments and calculations. The results show that CaF2 is the first to generate NaF gas at 1189 K, followed by Na3AlF6 (1238 K) and NaF (1328 K). NaF raw material produces the most NaF gas with the lowest activation energy in the three raw materials, due to high Na ion kinetic energy, the simple degree of polymerization, and Na‐F1 bonds. Correspondingly, NaF bubbles in the molten slag are the largest based on their aggregation. Na3AlF6 and CaF2 raw materials rank second and third, with F atoms primarily bonded as Al‐Fx and Ca‐Fx and the higher proportion of and structure. Notably, at 0.9 basicity and 6 wt% fluorine, Na3AlF6 as raw material generates a suitable amount of gas, making diffuse and fine NaF bubbles in the molten slag.

Inducing columnar-to-equiaxed transition by gradient impediment-flow optimization mechanism: The inheritance chain of solidification

Inducing columnar-to-equiaxed transition by gradient impediment-flow optimization mechanism: The inheritance chain of solidification

Development of the High‐Temperature Knudsen Effusion Mass Spectrometry in the Nordic Countries

In this article, a brief review of the development of the Knudsen effusion mass spectrometric (KEMS) approach in the Theoretical Metallurgy Department of the KTH Royal Institute of Technology and in the in the Laboratory of Metallurgy of the Helsinki University of Technology and modifications of quadrupole model QMG420 mass spectrometers, is presented. The thermodynamic data obtained from vaporization of standards, such as NaCl, CsCl, B2O3, and Ag, and of the B2O3–Al2O3 and ZnO–P2O5 systems is compared with the data obtained using a magnetic MS1301 mass spectrometer. For the first time, composition of the vapor phase over the Dy2O3–DyF3, CaO–CaCl2, and Cu–Mg systems and the partial pressures of components at high temperatures are investigated. The experimental data obtained for the investigated systems are used for prediction of the vaporization processes and modeling of thermodynamic properties and high‐temperature phase equilibria in the multicomponent systems used in metallurgy. An account is given of the detailed studies of the vaporization processes and thermodynamic properties of some multicomponent systems composed of oxides, fluorides, and carbonates forming mold powders for continuous casting of steel. Some new directions of the ongoing studies by the KEMS method are summarized.

The Role of Powder Used in the Continuous Molding of Alloys

Abstract The aim of the work was to obtain advanced oxide materials, obtained through technologies compatible with sustainable development materials. These materials are used in special operating conditions, such as in the case of continuous steel casting, where there is a temperature difference of over 10000C between the mold wall and the steel crust. These are the lubricating powders for the crystallizer.

Quality of high-carbon wire rod from steel obtained by various smelting methods

This article considers modern methods of steel production and their impact on the quality of wire rod made from grade 80 steel and applied for hardware products manufacturing. From research data on the chemical composition of wire rod produced by the oxygen-converter method and in an arc steelmakingfurnace, it can be noted that, in general, the chemical composition of the wire rod meets the requirements, while the steel produced in the converter contains less phosphorus, sulfur and non-ferrous metal impurities and nitrogen. This fact should have a beneficial effect on the ductility of the wire during further cold drawing. The analysis of the quality indicators of the finished wire rod produced from billets obtained according to various technological schemes showed that the integral quality indicator is at the same level when using optimal modes of out-of-furnace processing and continuous casting of steel.

Evolution of microstructure and mechanical properties of electroplated nanocrystalline Ni–Co coating during heating

Evolution of microstructure and mechanical properties of electroplated nanocrystalline Ni–Co coating during heating

Serpentinised olivine used in tundish refractory working layer: A source of blowhole defect in steel billets

In this research, the effect of different types of commercial tundish refractory working layers (gunning mix, prefabricated board (PB), and dry mix) on the formation of blowhole defect in continuous casting steel billets was investigated. To protect the tundish body, three refractory layers are applied on its metallic shell including a safety layer, a permanent layer, and a working layer. Due to the direct contact of molten metal and slag with the tundish working layer, this layer plays an important role in guaranteeing the quality of steel. In the current research, the amount of molten metal hydrogen pick-up due to contact with the abovementioned tundish working layers was measured by a Hydris device. The hydrogen content of all the melts increased after transferring from ladle to tundish, but the rising rate strongly depended on the type of tundish working layer with PB having a minimum amount of hydrogen pick-up. To characterise the working layers, their chemical and mineralogical composition as well as their thermal behaviour up to 1400 °C were evaluated using X-ray fluorescence, X-ray diffraction, and thermogravimetry-differential scanning calorimetry techniques. The results showed that olivine is a main constituent of all the working layers. Also, the amount and quality of olivine (especially the amount of its serpentinization) have a great effect on the formation of blowhole defects in the steel billets.

Characteristic analysis of mold level fluctuation during continuous casting of Ti-bearing IF steel

Characteristic analysis of mold level fluctuation during continuous casting of Ti-bearing IF steel