Steel Casting Process Research Articles

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.

Effect of depressions on the three-dimensional propagation of longitudinal surface crack in continuous casting strands of hypo-peritectic steel

Surface depressions are common defects in the continuous casting process of hypo-peritectic steel, categorised into transverse and longitudinal depressions. While the formation processes of these depressions are well understood, their influence on the propagation of longitudinal surface cracks remains unclear. This study developed a new method for large-area surface depth measurement of the strand based on optical focusing. Utilising this method, we investigated the impact of surface depressions on the three-dimensional propagation of longitudinal surface crack in terms of width, depth and casting direction through macrostructure characteristics and finite element static analysis. The results indicated that transverse and longitudinal depressions affect crack propagation differently. Specifically, the depth of longitudinal depressions increases crack width, while transverse depressions can inhibit it to some extent. Macrostructure analysis of the cross-section revealed a continuous segregation line at the bottom of the depression, closely related to heat transfer, thermal stress, and the flow of solute-enriched liquid steel. Statistical analysis indicated that the depth of longitudinal depressions significantly affects the length of the segregation line, which in turn influences crack depth. However, no surface cracks were found at the bottom of transverse depressions adjacent to longitudinal depressions. This may be due to the banded grains at the bottom of transverse depressions resisting tensile thermal stress parallel to the strand's width direction. Along the casting direction, crack propagation primarily occurs along the bottom of longitudinal depressions due to continuous thermal disturbances at the meniscus. Meanwhile, the transverse depression can restrict the propagation of the existing crack while promoting the formation of the new crack at the other site. Finally, the study proposed mechanisms by which depressions influence the propagation of the longitudinal surface crack. This research further elucidates the impact patterns of surface depressions on macrostructure and stress distribution and how these factors subsequently influence crack propagation in three dimensions. It underscores the importance of controlling surface depressions to mitigate the longitudinal surface crack.

Worldwide Research Trend on Steel Casting: A Visualization and Future Research Directions

Aims: In this study, we conducted a bibliometric study about steel casting between the year 2000-2023. We carried out a bibliometric analysis of sand casting, investment casting, die casting, and squeeze casting in which optimization and simulation models are available and have been thoroughly developed to enhance the quality of the casting product, according to the keyword co-occurrence network and word cloud generated by the bibliometric analysis and text mining of the publications. Methods: By delving further into the optimisation and simulation models, this study finds multiple casting procedures with various process parameters that have a major effect on the process results. Defects of the mechanical kind are the most prevalent, and factors taken into consideration are emissions, yield, dimensional tolerances, and qualities. Results: The necessity for data-driven modelling in new casting environments has been identified in this study, which will allow for a dynamic casting process and fine-tuning and aid in attaining desirable results in today's competitive markets. In order to illustrate the future prospects of this sector, this research focuses on potential technical interventions in steel casting processes that could enhance the efficiency of the process and the quality of the products produced by steel casting. Conclusion: This study examines the body of literature on various researchers' contributions to the production of excellent casting components and performs a bibliometric examination of the publications. However, the literature study examines research publications from high-quality essential sources to determine the essential criteria influencing steel casting quality.

DESIGN AND ANALYSIS OF THE GATING AND RISERING SYSTEM FOR STEEL SAND CASTING

Steel sand casting involves complex processes that significantly impact the quality and integrity of the final product. Among these processes, the design of the gating and risering systems plays a crucial role in ensuring defect-free castings. This research focuses on optimizing the gating and risering system design for steel sand casting with the aim of improving casting quality and minimizing defects. Through a detailed case study, the study seeks to develop a robust gating and risering system specifically tailored for steel casting applications. Computational applications using CATIA software for 3D modelling and Altair Inspire Cast for process simulation and analysis was employed to rigorously evaluate and validate the effectiveness of the proposed design. The study aims to meet performance criteria and enhance casting integrity. The ultimate goal is to propose an optimal gating and risering system configuration that not only addresses the challenges identified in the case study but also serves as a practical guideline for improving the overall efficiency and quality of steel casting processes. Key findings from the study highlight velocity, solid fraction, and porosity as significant parameters during the filling and solidification process, providing benchmarks for improving the casting process. Ultimately, an improved model with a yield improvement of 17.65% and an enhanced casting process was achieved. The findings underscore the importance of an optimized gating and risering system in enhancing the casting process, reducing defects, and producing high-quality steel products through detailed filling and solidification analysis, ultimately improving casting yield.

Investigation of Mold Flux Entrapment in Deep Oscillation Mark of Interstitial-Free Steel Shell Using Mold Simulator.

The slag entrapment defect has become a big issue for the IF steel casting process. In this study, the mechanism of mold flux entrapment in deep oscillation mark of an IF steel shell was studied by a high-temperature mold simulator. Results show that both temperature and heat flux in a copper mold become lower when mold flux B with lower melting and viscosity is used, compared with these when mold flux A with higher melting and viscosity is used. The average thickness of the slag film for mold fluxes A and B is 1.31 mm and 1.63 mm, and the consumption of them is 0.33 kg/m2 and 0.35 kg/m2, respectively. The shell for mold flux A exhibits sharper oscillation marks, while the shell for mold flux B has shallower oscillation marks. These deeper oscillation marks capture the mold flux by overflow of molten steel at the meniscus, which finally produces the slag entrapment defect in the shell.

Numerical Simulation of Mold Slag Entrapment Behavior in Nonoriented Silicon Steel Production Process

This paper is based on the surface defects of casting billets in the production process of nonoriented silicon steel plates at a steel plant in North China. Taking the parameters of a slab mold in the nonoriented silicon steel production process as a prototype, the flow field characteristics of the mold under the same section, different drawing speed and immersion depth were systematically studied by using a LES (large eddy simulation) and VOF (volume of fluid) coupling algorithm. The results show that under the current conditions, when the critical slag entrapment speed increases from 1.0 m/min to 1.2 m/min, the nozzle insertion depth increases linearly with the critical slag entrapment speed, while when the nozzle insertion depth exceeds 130 mm, the increasing effect of further increasing the nozzle insertion depth on the critical slag entrapment speed begins to decrease. When the drawing speed of continuous casting is kept constant at 1.4 m/min, the abnormal fluctuation height of the steel slag interface is significantly improved when the angle of the water nozzle is increased from 15° to 20°, and the proportion of slag entrapment is also reduced from 0.376% to 0.015%. When the nozzle angle is 25°, the slag entrapment ratio is reduced to 0%, and the steel slag interface also ensures a certain activity. The numerical simulation results were applied to the industrial site, and the slag inclusion rate and crack rate of the billet in the continuous casting process of nonoriented silicon steel were obviously improved after the optimization process.

A Research on Metal and Metallurgical Properties of Chisel Plough Shanks

Reduced tillage forms a subgroup of conservation tillage. In this system, chisel or disc tools are generally used for primary soil tillage, and milling machines, disc tools or cultivators are used for secondary soil tillage and seedbed preparation. The entire area is tillaged so that the plant residues are on the soil surface and prone to the surface. It provides significant fuel and energy savings compared to conventional tillage due to less machine traffic. In order to ensure sustainability, conservation tillage (using a chisel instead of the mouldboard plough that works by turning the soil) as an alternative to conventional tillage and the development of agricultural tools and machines used for this purpose have gained great importance. Chisel is a soil cultivation tool widely used in stubble destruction and conservation tillage system. It is known that the chisel provides significant savings in terms of fuel consumption compared to the mouldboard plough. For a chisel construction that can operate at an optimal level, the basic requirement is to have optimal material quality, optimal weight and optimal cost. In this research, the physical and chemical processes of chisel shanks produced as cast steel were examined. It is of primary importance that it provides minimum fuel consumption with its optimal chemical content, easy mounting to the chassis, unbreakable model structure and angles. A casting and agricultural machinery company that helped with the study was visited and the GS-52 steel casting process, which is widely used for chisel shank in our country, was examined and tensile, yield and rupture tests were performed. As a result, it has been observed that a better construction can be created by changing the chemical content of GS-52 steel. Different trials to be carried out as the continuation of the research will help determine the optimal structure of the chisel shank.

Simulation of a new process of mixing liquid metal in CCM mold with rotating cooling jacket with vertical ribs

The article proposes a new technology of filling the CCM mold with liquid metal and mixing it. The original patented device consists of a closed bottom nozzle and a rotating jacket. Experimental studies of liquid metal flow in a mold are long, complex and time-consuming, therefore, in the work was used mathematical modeling by numerical method. The objects of research are the hydrodynamic and thermal flows of liquid metal during the new process of steel casting into a CCM mold of rectangular cross-section, and the result is a spatial mathematical model that describes the flows and temperatures of liquid metal in the mold. To simulate the processes occurring during the metal flow in the mold, the authors used a specially crea­ted software package. The theoretical calculations are based on the fundamental equations of hydrodynamics, the equations of mathematical physics (equation of thermal conductivity taking into account mass transfer) and a proven numerical method. The area under study is divided into elements of finite dimensions, for each element a formulated system of equations is written in a difference form. The result is the velocity and temperature fields of the metal flow in the mold volume. According to the developed numerical schemes and algorithms, a calculation program was compiled. The paper considers an example of calculating the steel casting into a mold of rectangular cross-section and flow diagrams of liquid metal over various mold sections. Vector flows of liquid metal in various mold sections are clearly presented for different rotary speed of the rotating jacket. The authors identified the areas of intense turbulence and presented the results of the problem numerical solution in graphical form by diagrams of the velocity fields of liquid metal flows and their temperature over various mold sections.

Simulation and Experimental Study of Fluid Flow and Solidification Behavior in Thin Slabs Continuous Casting Process under Secondary Electromagnetic Stirring

During the thin slab continuous casting process of silicon steel, electromagnetic stirring (EMS) can control the flow, heat transfer, and solidification of molten steel through electromagnetic force. Herein, a 3D mathematical model coupling the fluid flow, heat transfer, solidification, and the electromagnetic field is built. The effects of varied current intensities on the flow, heat transfer, and solidification of molten steel in the thin slab under secondary EMS are explored based on applying the electromagnetic brake in the mold region. In the findings, it is demonstrated that increasing the current intensity increases the flow rate and vorticity of the molten steel in the second cooling zone, eliminating the superheating phenomenon and improving the uniformity of the molten steel's temperature distribution. Meanwhile, based on the nucleation and growth parameters determined from thermal simulation experiments, the cellular automation finite‐element model is used to simulate the microstructure evolution during the solidification of thin slab. In the results, it is shown that the stirring energy increases when the current intensity increases, potentially promoting equiaxed crystal growth and grain refinement. Compared to the production sample, a reasonable qualitative agreement is achieved for the grain morphology, equiaxed crystal ratio, and columnar to equiaxed transition.

Numerical and Experimental Study on Carbon Segregation in Shaped Billet of Medium Carbon Steel with Combined Electromagnetic Stirring

Carbon segregation is the major and classical internal defect in the continuous casting process of carbon steel. Based on the combined electromagnetic stirring equipment for new billet in a steel plant, China, the influence of combined electromagnetic stirring (M-EMS + F-EMS) on the carbon segregation of 300 mm × 340 mm special-shaped billet was studied via numerical simulation and on-site industrialization tests. The Lorentz force and carbon solute distribution were simulated under different EMS parameters. The formation mechanism of the carbon segregation of medium carbon steel with different combined electromagnetic stirring processes was analyzed. The results show that: (1) with the combined action of “solute flushing” effect and gravity, the carbon concentration in the loose side of the medium carbon steel casting billet is gradually lower than the fixed side, while the carbon concentration on the fixed side gradually accumulates more; and (2) under the action of combined electromagnetic stirring, the segregation index of casting billet could be controlled to remain between 0.96–1.05 and shows an increasing change in solidification from the skin to the center. When the current and frequency of M-EMS are 250 A and 2.0 Hz and the F-EMS are 180 A and 8.0 Hz, the carbon segregation defects in the special-shaped (300 mm × 340 mm) casting billet can be significantly improved.

Modelling Microstructure in Casting of Steel via CALPHAD-Based ICME Approach

Integrated computational materials engineering (ICME) is emerging as an increasingly powerful approach to integrate computational materials science tools into a holistic system and address the multiscale modeling challenges in the processing of advanced steels. This work aims at incorporating macroscopic model (finite element-based thermal model) and microscopic model (CALPHAD-based microstructure model), building an industry-oriented computational tool (MICAST) for casting of steels. Two case studies were performed for solidification simulations of tool steel and stainless steel by using the CALPHAD approach (Thermo-Calc package and CALPHAD database). The predicted microsegregation results agree with the measured ones. In addition, two case studies were performed for continuous casting and ingot casting with selected steel grades, mold geometries and process conditions. The temperature distributions and histories in continuous casting and ingot casting process of steels were calculated using in-house finite-element code which is integrated in MICAST. The predicted temperature history from the casting process simulation was exported as input data for the DICTRA simulation of solidification. The resulting microsegregation by the DICTRA simulation can reflect the microstructure evolution in the real casting process. Current computational practice demonstrates that CALPHAD-based material models can be directly linked with casting process models to predict location-specific microstructures for smart material processing.

Research on Solid Shell Growth during Continuous Steel Casting.

The continuous steel casting process must simultaneously meet the requirements for production performance, quality and safety against breakouts. Knowing the thickness of the solidified shell, particularly at the exit of the mould, is useful for the casting process control and breakout prevention. Shell thickness is difficult to measure during casting; in practice, it is predicted by indirect methods and models. But after undesired rupture of the shell and leakage of the liquid steel, it is possible to measure the shell thickness directly. This article is focused on the problem of the growth and measurement of the solid shell obtained after the breakout of a round block with a diameter of 410 mm. An original methodology was developed in which a surface mesh of points was created from the individual scanned parts of the block using a 3D laser scanner. Research has shown differences of up to 6 mm between the maximum and minimum shell thickness at the mould exit. A regression function of the average shell thickness on time was found. The results of the real shell growth were further used for the verification of the original numerical model of cooling and solidification of the round block.

Flame-sprayed alumina molten metal filters for dead-mould casting application

Ceramic foam filters are applied to remove non-metallic inclusions during steel melt filtration. The flame-spray technology can contribute to improving such filters by increasing the deposition capability of inclusions and decreasing the impairment of the filter substrate by the steel melt. This makes them suitable for application to the continuous steel casting process and foundry casting. The ball-on-three-balls test was utilized at elevated temperatures to determine the high-temperature behaviour of thermally sprayed alumina. Additionally, the flame-spray technology was used to produce carbon-free filters composed of flame-sprayed alumina by coating and burning out the Al2O3–C filter substrate during a sintering step. The B3B revealed a ductile behaviour with increasing temperature and a bending strength of 23.28 MPa at 1400 °C. After sintering at 1400 °C, the filters showed a sufficient CCS of 0.16 MPa, which allows the performance of casting tests (immersion and pouring) with molten steel at 1580 °C.

Evolution mechanism of inclusions during refining and continuous casting process of 321H stainless steel

ABSTRACT The evolution of inclusions during the refining and casting process was investigated on an industrial scale to clarify the quantity and distribution of non-metallic inclusions for 321H stainless steel. The analyses showed that Al2O3-SiO2-MnO-CaO and Al2O3 as the main types of inclusions at the late of AOD and VOD, respectively. Pure titanium nitride and titanium nitride with oxide as the nuclei dominated the inclusions at the late of LF. The types of inclusions in mold and slab were similar to those obtained at the late of LF, while titanium nitride inclusions in slab were higher in numbers and larger in size. The titanium nitride inclusions precipitating with MgO-Al2O3-CaO-(TiO2) nuclei showed a higher number density and area fraction than other oxide inclusions. The calcium treatment of molten steel was optimized by FactSage software and it was necessary to accurately control the calcium content in molten steel before titanium addition.

Failure analysis of Al2O3–C–SiO2 slide gate plates during continuous casting based on numerical simulation

The thermo-mechanical and failure behavior of the burning-free Al2O3 –C–SiO2 slide gate plate materials during the steel casting process are investigated. Firstly, the instantaneous coefficient of thermal expansion and the Young's modulus of the slide gate plate materials with different component contents at high temperature are measured. Secondly, a material constitutive model and a concrete damage plasticity mode are established based on the experiments, and adopted to simulate the failure behavior of the burning-free Al2O3–C–SiO2 slide gate plate during casting based on Finite Element Method (FEM) analysis. Results show that temperature gradient in the slide gate plate near the casting hole increased significantly and had a significant influence on cracking. The area near the casting hole of the slide gate plate is under tensile stress conditions, and then changes towards compressive stress conditions. Under those severe thermal stress conditions, crack formation is evaluated and an optimized composite structure of the slide gate plate combining advantages of reducing the risk of cracking and extending the service life is proposed. Moreover, the thermal shock test further verified that the microcrack extension was significantly alleviated due to the SiC distributed in whisker form and formed an interlocking structure in material. This work provides a reliable theoretical and experimental basis for the design and optimization of high performance Al2O3–C–SiO2 slide gate plates.

Effect of CaO/Al2O3 Ratio on Physical Properties of Lime-Alumina-Based Mould Powders

High-aluminium steels contain a significant amount of aluminium. The reaction between Al in the liquid steel and SiO2 in lime-silica-based mould powders during the continuous casting process of high Al steel causes chemical compositional changes in the mould powders, subsequently affecting the surface quality of slabs. In order to solve the aforementioned problem, lime-alumina-based mould powders have been developed, which can lead to an increase in the surface quality of cast slabs by inhibiting steel/slag interaction. However, the mould slag tends to crystallise easily, which leads to a deterioration of the mould lubrication. In view of this aspect, it is important to develop and optimize lime-alumina-based mould powders to meet the requirements of continuous casting of high-aluminium steels. In this study, the changes in crystallinity, viscosity and melting temperature of lime-alumina-based mould powders with the effects of increasing the CaO/Al2O3 ratio have been observed through STA (Simultaneous Thermal Analysis), HSM (Hot Stage Microscopy), XRD (X-ray Diffraction), IPT (Inclined Plate Test) and rotational viscometer. The crystallisation behaviour of these mould powders was evaluated by generating CCT (continuous cooling transformation) diagrams. Additionally, the changes in steel chemistry have also been analysed using XRF (X-ray fluorescence) and ICP (Inductively Coupled Plasma Mass Spectrometer). The results of these analyses demonstrated that crystallinity of lime-alumina-based mould powder is increased while the initial crystallisation temperature and viscosity are decreased by CaO/Al2O3 additions. However, the degree of steel/slag interaction decreases with an increase in Al2O3 content.

Numerical modelling of hyperbolic phase change problems: Application to continuous casting

Heat diffusion processes are generally modeled based on Fourier’s law to estimate how the temperature propagates inside a body. This type of modeling leads to a parabolic partial differential equation, which predicts an infinite thermal wave speed of propagation. However, experimental evidence shows that diffusive processes occur with a finite velocity of thermal propagation in many applications. In this paper, we develop a mathematical formulation to predict the finite speed of heat propagation in multidimensional phase change problems. The model generalizes the enthalpy formulation by adding a hyperbolic term. The governing equations are simulated by the finite element method. The proposed model is first verified by comparing numerical and experimental results illustrating the difference between the infinite and finite propagation velocity for heat inside biological tissues. Then, the results of the two and three-dimensional numerical solution of the continuous steel casting process are presented. We will illustrate that the effects of the initial conditions vanish faster when using the parabolic equation, while they persist in the hyperbolic modeling approach. The results demonstrate significant differences in the initial thermal dynamics and at the solid-liquid interface position when adding the hyperbolic term. The changes are more noticeable in the regions of the steel beam where rapid heat loss and, consequently, faster phase change occur.

Evolution Mechanism of MgO–Al2O3–SiO2–CaO Inclusions During Continuous Casting of Si‐Killed Spring Steel

In article number 2200475, Qing Liu and co-workers show the inclusion evolution during the continuous casting process of the 55SiCrA spring steel. The primary inclusions are CaO-Al2O3-SiO2-MgO inclusions. The [Si], [Al], and [Mg] reacted with [O] because of the secondary oxidation and the temperature decline, increasing the amount of SiO2, Al2O3, and MgO in oxide inclusions. The melting point of inclusions increased.

Identifying Oxide and CaS Non-Metallic Inclusions in Steel with Raman Spectroscopy

Identification and characterization play an essential role in the study of non-metallic inclusions (NMIs) in monitoring the steel casting process and product quality. This study uses Raman spectroscopy, a versatile, relatively fast, and non-destructive technique for characterizing oxide and sulfide-based inclusion phases in steel samples. The relative Raman peak intensities and positions were used to qualitatively estimate the inclusion phases of Al2O3, CA, C12A7, C3A, MgO·Al2O3, and CaS. For a quantitative estimation, FESEM-EDS (field emission scanning electron microscope with energy dispersive X-ray spectroscopy) was used to evaluate the inclusion phases in the samples. This study demonstrates that Raman spectroscopy can be used to rapidly estimate the content of Al2O3, magnesium aluminate spinel (MgO·Al2O3), and the calcium aluminate phases of CA, C3A, and C12A7 in steel samples to complement established characterization techniques for NMIs analysis such as FESEM-EDS.

Manufacturing information-based energy usage simulation for energy-intensive steel casting process

Energy efficiency improvement in the industrial sector is critical in achieving carbon neutrality by 2050. A discrete-event-based dynamic energy simulation method is suggested to enhance the efficiency of energy-intensive manufacturing processes. The statistical characteristics of an actual manufacturing site were reflected in the simulation using data from the factory energy management system (FEMS) and manufacturing execution system (MES). The proposed method integrates discrete event simulation (DES) and transient thermal analysis. The dynamic behavior resulting from the interaction between sub-processes is simulated in DES. The energy conversion and detailed heat loss occurring at the facilities were modeled in the transient thermal analysis. The concept of process loss was suggested for the analysis to account for the energy that could have been not wasted at the factory level. The simulation results provided three key performance indicators (KPIs) representing the energy usage, production, and product quality of a manufacturing site. Investigation of these KPIs under various operating conditions found that the specific energy consumption could be reduced by 12.6% with a better operating strategy. We expect that the integrated simulation method can provide a practical solution for improving the energy efficiency of manufacturing sites equipped with a FEMS.