Continuous Casting Production Research Articles

Influence of operating parameters on metal flow and thermal characteristics in an EMBr-single-ruler controlled CSP funnel-shaped mould

Electro-magnetic brake (EMBr), as a necessary technique to adjust the metal flow within the mould, has been extensively applied in the continuous casting (CC) production. The EMBr technique, if appropriately applied, can take the benefit of braking effect to weaken jet impingement effect, suppress fluid disturbance and stabilize surface fluctuation. As a result, to obtain a reasonable flow pattern within the CC mould, the braking performance of EMBr technique needs to be flexibly adjusted according to the variation of operational parameters. In this article, to obtain a braking performance of a commonly used EMBr-single-ruler technique within an optimal range, the effect of operating parameters on the metal liquid flow and thermal characteristics in a compact strip production (CSP) thin slab mould is described through a 3-D mathematical modeling of multi-physical field coupling. The results illustrate that the braking performance of the EMBr-single-ruler device is weakened with the increase of the casting speed or the mould width. For the effect of the casting speed and mould width on the metal flow with the application of an EMBr device, an optimum braking performance of the EMBr-single-ruler device can be obtained under the matching parameters of a magnetic induction intensity of 0.30 T and a casting speed of 4.5 m ∙ min‒1 together with a mould width of 1500 mm. Relative to the absence of the EMBr-single-ruler device, the maximum surface fluctuation height is controlled at 6.2 mm, and the mean surface temperature is raised to 1803.6 K. Based on these findings, we conclude that the proper utilization of the EMBr-single-ruler device can avoid the entrainment of flux powder and improve the melting performance of flux powder.

Physical and Numerical Simulation Study on Structure Optimization of the Inner Wall of Submerged Entry Nozzle for Continuous Casting of Molten Steel

The submerged entry nozzle (SEN) plays an important role in the continuous casting production process. It is a cast refractory pipe fitting installed in the lower part of the tundish and inserted below the molten steel level of the mold. It not only affects the speed of molten steel flow, but is also prone to nodules and affects production. In the present work, the flow behavior of molten steel in a traditional nozzle and that in a new type of nozzle whose inner wall was distributed with arrays of hemispherical crowns were studied by means of both physical simulation (using a water model) and numerical simulation (using ANSYS CFX) based on the prototype of a production continuous casting slab mold. Both experimental and numerical simulation results show that, compared with the traditional nozzle, the impact depth generated by the new-type nozzle in the mold is reduced by 21.06–26.03 cm, the impact angle is reduced by 14–17 degrees, and swirl flow was generated inside the new-type nozzle, which not only improves the flow characteristics inside the submerged entry nozzle and changes the dead zone size in the submerged entry nozzle, but also improves the velocity distribution at the outlet of the nozzle and minimizes the possibility of nodulation. In addition, in contrast to the traditional nozzle that generates flat body-shaped jets of molten steel flow, the new-type nozzle produces baseball glove-shaped jets that penetrate shallower into the molten steel bath in the mold, which significantly reduces the outlet velocity and is conducive to the floating of inclusions.

Analysis of Flow and Fluctuation Characteristics in Coated Slag Using a 2D Model in the Meniscus Region of Mold

Steel is mainly produced through continuous casting; molten steel flows into the mold from the tundish, where it cools and then enters the secondary cooling zone, ultimately solidifying into a billet. During the continuous casting production process, the quality of the casting billet is mainly related to the lubrication state of the coated slag. In the upper part of the mold, the consumption of liquid protective slag directly affects the friction state of the initial solidified billet shell. Therefore, the flow and fluctuation characteristics of coated slag in the meniscus area are very important. There is limited research on the flow and fluctuation characteristics of coated slag in the meniscus area, and little consideration has been given to the shape of the meniscus. In this work, a two-dimensional numerical model for the flow and fluctuation of coated slag in the meniscus region was established, and the transient flow velocity of protective slag and molten steel at each moment of the vibration cycle was obtained, as well as the fluctuation of the slag/steel interface in the meniscus region. The results show that when the surface mold vibrated upwards, the protective slag in the meniscus area flowed clockwise. When the mold moved downwards, the protective slag in the slag pool generated a counterclockwise flow vortex. When the mold was in a positive slip state, the negative pressure formed by the upward flow of the protective slag on the meniscus and the inertia force of steel liquid pushed the meniscus toward the inner wall of the mold. During negative slip, the flow of coated slag generated positive pressure on the slag/steel interface, pushing the meniscus toward the steel liquid, and at the initial moment of negative slip, the steel liquid overflowed into the slag channel. This model could provide a theoretical basis for the flow control of protective slag.

Numerical and Experimental Study on Carbon Segregation in Square Billet Continuous Casting with M-EMS.

Electromagnetic stirring (M-EMS) has been extensively applied in continuous casting production to reduce the quality defects of casting billets. To investigate the effect of continuous casting electromagnetic stirring on billet segregation, a 3D multi-physics coupling model was established to simulate the internal heat, momentum, and solute transfer behavior, to identify the effect of M-EMS on the carbon segregation of a continuous casting square billet of 200 mm × 200 mm. The results show that M-EMS can move the high-temperature zone upward, which is favorable for the rapid solidification of the billet, and can promote the rotational flow of the molten steel in the horizontal direction. When the electromagnetic stirring current is varied in the range of 0-500 A, the degree of carbon segregation first decreases and then increases, with the best control of segregation at 300 A. In the frequency range of 3-5 Hz, the degree of carbon segregation degree increases with frequency. Meanwhile, the simulation and experimental results show that 3 Hz + 300 A is the best electromagnetic stirring parameter for improving the carbon segregation of casting billets with a size of 200 mm × 200 mm. So, a reasonable choice of the M-EMS parameters is crucial for the quality of the billet.

Automatic Casting Control Method of Continuous Casting Based on Improved Soft Actor–Critic Algorithm

Continuous casting production is an important stage in smelting high-quality steel, and automatic casting control based on artificial intelligence is a key technology to improve the continuous casting process and the product quality. By controlling the opening degree of the stopper rod reasonably, the mold can be filled with liquid steel stably in the specified time window, and automatic casting can be realized. In this paper, an automatic casting control method of continuous casting based on an improved Soft Actor–Critic (SAC) algorithm is proposed. Firstly, a relational model of the stopper rod opening degree and the liquid steel outflow velocity is established according to historical casting data. Then the Markov Decision Process (MDP) model of the automatic casting problem and the reinforcement learning framework based on the SAC algorithm are established. Finally, a Heterogeneous Experience Pool (HEP) is introduced to improve the SAC algorithm. According to the simulation results, the proposed algorithm can predict the stopper rod opening degree sequence under the constraint of the target liquid level curve. Under different billet specifications and interference conditions, an accuracy of 80% of liquid level in the mold and a stopper rod opening degree stability rate of 75% can be achieved, which is 4.29% and 3.17% higher than those for the baseline algorithms, respectively.

Inverse coefficient super-linear problem for a time fractional parabolic equation under integral overdetermination conditions

In this paper, we investigate the inverse problem of the determining the right-hand side of a nonlinear fractional parabolic equation with integral overdetermination condition. For the solvability of the direct problem we use the energy inequality method also known as the methode of functional analysis or the method of a priori estimates, this method has a higher character in that the existence theorem can be derived from the solution of the problem posed, begining with the uniqueness theorem. The most difficult aspect of this method is selecting the functional spaces E and F and for the unique solvability of the iverse problem is estblished under suitable conditions. The fixed point theoremis used to establish the existence and uniqueness of the solution to the inverse problem based on the data, this inverse problem appears frequently in engineering and physics modeling of various phenomena. Sismology, medicine, continuous casting, fusion welding, oil and gas production during drilling and well operation.

Investigation of the Erosion Mechanism of the Mold Flux Containing Rare Earth Oxide on the Submerged Entry Nozzle Affected by an External Electric Field

Considering the change and unpredictability of the mold flux containing rare earth oxides, the impact of controlling the erosion behavior of the mold flux containing rare earth oxide on the submerged entry nozzle is thoroughly investigated herein by applying an electric field. The extracted results show that the rare earth is reduced, and Ce3+ ions and compounds are formed. Under the control of electrochemical reaction in the negative enforced electric field, a stable and dense protective film with a multilayer structure is formed on the surface of the electrode. The existence of this film can effectively prevent the erosion of the submerged entry nozzle. In addition, the phase composition of the mold flux is not affected by the externally applied electric field. The implementation of the external electric field is anticipated to be used as a new method for the high‐quality and high‐efficiency continuous casting production of rare earth steel.

Residence Time Distribution (RTD) Applications in Continuous Casting Tundish: A Review and New Perspectives

The continuous casting tundish is a very important metallurgical reactor in continuous casting production. The flow characteristics of tundishes are usually evaluated by residence time distribution (RTD) curves. At present, the analysis model of RTD curves still has limitations. In this study, we reviewed RTD curve analysis models of the single flow and multi-flow tundish. We compared the mixing model and modified combination model for RTD curves of single flow tundish. At the same time, multi-strand tundish flow characteristics analysis models for RTD curves were analyzed. Based on the RTD curves obtained from a tundish water experiment, the applicability of various models is discussed, providing a reference for the selection of RTD analysis models. Finally, we proposed a flow characteristics analysis of multi-strand tundish based on a cumulative time distribution curve (F-curve). The F-curve and intensity curve can be used to analyze and compare the flow characteristics of multi-strand tundishes. The modified dead zone calculation method is also more reasonable. This method provides a new perspective for the study of multi-strand tundishes or other reactor flow characteristics analysis models.

A Distributionally Robust Scheduling Approach for Uncertain Steelmaking and Continuous Casting Processes

This article presents a new model to handle the cast break problem caused by small daily disruptions in the processing time of the steelmaking and continuous casting (SCC) production process. In this model, the exact distribution of the uncertain parameters is unknown, and support set, mean, and covariance information is used to describe the uncertain processing time. The problem aims to determine the assignments, sequences, and time points of the charges to be processed on corresponding machines. The main goal is to minimize the expected value of the production objective while reducing the number of cast break occurrences. The problem is solved in two steps. First, a subproblem is developed by fixing the sequences and the assignments of the charges. This subproblem is formulated as a distributionally robust chance-constrained (DRCC) model, in which the constraints are established with certain probabilities even when the uncertain processing times are in their worst cases. A dual approximation method is proposed to convert the model into a semidefinite programming problem so that it can be solved by standard solvers. Additionally, a linear programming approximation method is used to accelerate the solving procedure. A Tabu search algorithm incorporated with a speed-up strategy is also designed to determine the assignments and sequences of the charges. Both simulated data generated from different distributions and actual production data are used to test the efficacy of our model. Results of the numerical experiments show that the schedule obtained from the DRCC model is more robust, i.e., it causes fewer cast breaks than the nominal schedule obtained from a deterministic model.

Effects of Sulfur on the Surface Crack in Medium Carbon Bloom

The surface cracking problem in medium carbon sulfur‐containing steel is gradually emerging in continuous casting production. Therefore, this article investigates the effect of sulfur content on the surface cracks of medium carbon steel. In addition to macroscopic cracks, network cracks are visible on the surface of medium carbon sulfur‐containing bloom. 3D confocal laser scanning microscopy and industrial computed tomography are used to characterize the 3D realistic morphology of the network and macroscopic cracks. Thermodynamic calculations and hot ductility tests’ results exhibit the higher precipitation of MnS in the sulfur‐containing steel, resulting in the second brittle zone of steel. The microstructure near the cracks revealed a high correlation between cracks and a high proportion of proeutectoid ferrite near the surface of the medium carbon sulfur‐containing bloom. In addition, the sulfur‐containing steel has 0.05% more linear shrinkage than the low‐sulfur steel during the transformation from austenite to ferrite, which increases its crack sensitivity. As a result, this article clarifies the effect of sulfur on the surface crack of medium carbon bloom.

Hot ductility behavior of medium carbon sulfur-containing alloy steel

Sulfur-containing free-cutting steels are widely used because of their excellent processability. However, the crack problem of sulfur-containing steel during continuous casting production is still not solved. Therefore, this paper investigates the effect of sulfur content on the crack susceptibility or hot ductility of medium carbon alloy steel in detail. This research designed and produced four kinds of medium carbon alloy steel with different sulfur content. It also investigated the hot ductility of steel through a hot tensile test. This study focuses on the effect of sulfur content on the flow stress–strain curve, hot ductility curve, fracture morphology, and inclusions of the steel. The results show that the sulfur-containing steel has better hot ductility at low temperatures (750–900 °C) and worse hot ductility at medium temperatures (1000–1250 °C) compared to the sulfur-free steel. The difference is mainly related to the precipitation behavior of the MnS inclusions in the steel. The hot ductility behavior of medium-carbon sulfur-containing alloy steel grade is primarily related to DRX and the precipitation behavior of MnS inclusions.

Research on the control technology of Ds inclusion and Oxygen content in GCr15 bearing steel

This paper presents a method for controlling Ds inclusions and oxygen content in bearing steel produced by EAT-LF-VD-CCM process, including EAF initial refining process, LF external refining process, VD vacuum treatment process and continuous casting production process. By reasonably reducing the basicity of slag, adjusting the amount and sequence of alloy addition, the carbon content of EAF steel is appropriately increased and the temperature of steel extraction is reasonably selected. Optimize the amount of deoxidizer added in off~furnace refining, improve the basicity of refining slag, control the vacuum time, aluminum loss and stirring volume; In the continuous casting process, middle alkaline coating agent, constant drawing speed and protective pouring process are used to control and remove Ds inclusions in bearing steel. The bearing steel produced by this process can remove big sized Ds inclusions in the steel, while the total oxygen content is controlled below 7ppm.

Ladle intelligent re-scheduling method in steelmaking–refining–continuous casting production process based on BP neural network working condition estimation

Frequent delays will be experienced in the start-up of molten steel on the converter equipment during the steelmaking–continuous casting (SCC) production process due to the untimely supply of molten iron or scrap, which may cause conflicts between adjacent heat on the same equipment or in the same casting. The casting machine is cut off, resulting in the failure of the static scheduling plan. SCC production ladle re-scheduling is based on the premise that the production process path remains unchanged, the operation of adjacent heat on the converter and refining furnace does not conflict, and the casting of adjacent heat within the same casting is continuous. The ladle re-scheduling of steelmaking and continuous casting production aims at continuously casting many charges with the same cast and avoiding conflicts of adjacent charges on the same machine. This mechanism proposes a method of ladle re-scheduling in the production process of steelmaking–refining–continuous casting, which is divided into two parts: plan re-scheduling and ladle optimisation scheduling. Firstly, a re-scheduling optimisation model of the steelmaking and continuous casting production is built. This model aims at minimising the waiting time of all charges. The re-scheduling strategy of steelmaking and continuous casting production is proposed by interval processing time of charges and scheduling expert experience. This strategy is composed of two parts: re-scheduling charge decision and charge processing machine decision. Then, the first-order rule learning is used to select the optimisation target to establish the ladle optimal scheduling model. The ladle matching rules are extracted on the basis of the rule reasoning of the minimum general generalisation. The ladle optimisation scheduling method that consists of the optimal selection of the ladle and the preparation of the optimal path of the ladle is proposed. Ladle selection is based on the production process and adopts rule-based reasoning to select decarburised ladle after choosing dephosphorised ladle. Ladle path preparation, which is a multi-priority heuristic method, is designed to decide the path of the ladle from the converter to the refining furnace to the continuous casting machine. Finally, this mechanism was actually verified based on the large-scale data of a steel company in Shanghai, China. Results showed that the production efficiency of steelmaking-refining-continuous casting was improved.

Solvability of the Nonlocal Inverse Parabolic Problem and Numerical Results

In this paper, we consider the unique solvability of the inverse problem of determining the right-hand side of a parabolic equation whose leading coefficient depends on time variable under nonlocal integral overdetermination condition. We obtain sufficient conditions for the unique solvability of the inverse problem. The existence and uniqueness of the solution of the inverse parabolic problem upon the data are established using the fixed point theorem. This inverse problem appears extensively in the modelling of various phenomena in engineering and physics. For example, seismology, medicine, fusion welding, continuous casting, metallurgy, aircraft, oil and gas production during drilling and operation of wells. In addition, the numerical solution of the inverse problem is studied by using the Crank-Nicolson finite difference method together with the Tikhonov regularization to find a stable and accurate approximate solution of finite differences. The resulting nonlinear system of parabolic equation is solved computationally using the MATLAB subroutine lsqnonlin. Both analytical and numerically simulated noisy input data are inverted. The root mean square error values for various noise levels for both continuous and discontinuous time-dependent heat source term are compared. Numerical results presented for two examples show the efficiency of the computational method and the accuracy and stability of the numerical solution even in the presence of noise in the input data. Furthermore, the choice of the regularization parameter is also discussed based on the trial and error technique.

DURA-BAR 65-45-12X

Abstract Dura-Bar 65-45-12X is a ductile iron that is used for the production of continuous cast products. Its microstructure consists of nodular graphite and a matrix comprising ferrite and 10–50% pearlite. The predominantly ferritic matrix of Dura-Bar 65-45-12X allows it to be easily machined as opposed to steels and pearlitic irons. Dura-Bar 65-45-12X is a suitable alternative to low and medium carbon non-alloy steels. It is appropriate for applications necessitating fatigue strength and ductility. This datasheet provides information on composition, physical properties, microstructure, hardness, elasticity, and tensile properties. It also includes information on heat treating and machining. Filing Code: CI-88. Producer or source: Charter Dura-Bar, Inc.

DURA-BAR 60-40-18

Abstract Dura-Bar 60-40-18 is a ductile iron that is used for the production of continuous cast products. Its microstructure consists of nodular graphite in a fully ferritic matrix. Dura-Bar 60-40-18 is typically used for applications requiring excellent ductility and impact strength. This datasheet provides information on composition, physical properties, microstructure, hardness, elasticity, and tensile properties. It also includes information on heat treating and machining. Filing Code: CI-86. Producer or source: Charter Dura-Bar, Inc.

Research of the Process of Production of Steel Square Continuous Billets for Rolling Balls of Large Diameter

The paper investigates the technology of production of steel billets continuously cast billets for rolling balls of large diameter. In Kazakhstan, in connection with the development of new copper deposits such as Aktogay and Bozshakol, the need for large diameter steel grinding balls for primary ore processing has increased. The main problem in the operation of large diameter grinding balls is the tendency of the grinding media to break during operation. The authors of the work investigated the process of production of steel billets continuously cast billets with a cross section of 150 × 150 mm for rolling balls of large diameter (d 125 mm) in the PB LLP "KSP Steel", which showed that the breaking of grinding balls is initiated mainly by the presence of internal discontinuities (gas axial looseness) in continuously cast billets. Studies have shown that the technological scheme for the production of grinding balls with a diameter of 125 mm from continuously cast billets with a section of 150 × 150 mm, including steel smelting in an arc furnace with steel finishing on a ladle-furnace unit, deoxidation with aluminum and degassing in a ladle vacuum apparatus, casting steel in a closed jet on a continuous casting and further production of rolled stock on a rough rolling mill ensures the absence of internal discontinuities (gas bubbles, axial looseness) in the workpieces and ensures the production of high quality balls.

Measurement model of molten steel flow velocity in the continuous casting mould based on the Seebeck principle

ABSTRACT To measure the velocity of molten steel in continuous casting mould conveniently, a new method is proposed in this paper. The relationship model between thermoelectric force and velocity is established by using the Seebeck effect and the relationship between convective heat transfer and velocity. This model and method can be applied in more continuous casting production to realize the real-time measurement of molten steel velocity in mould.

DURA-BAR GX

Abstract Dura-Bar GX is a heat-treatable, pearlitic gray cast iron that is used for the production of continuous cast products. It is ideal for applications that require a combination of moderate strength, good wear resistance, and good vibration damping capacity. This datasheet provides information on composition, physical properties, microstructure, hardness, and tensile properties. It also includes information on heat treating and machining. Filing Code: CI-83. Producer or source: Charter Dura-Bar, Inc.

Hybrid optimization for charge planning problem in twin strands continuous casting production

Charge planning is one of batching problems for steelmaking and continuous casting production, and its optimization will be conducive to subsequent cast planning. Charge planning problem in the twin strands continuous casting production was studied, where casting width of the odd strand might be different from that of the even strand. Considering the different widths in the twin strands, the resulting counterweights and the constraints of steelmaking and continuous casting, a multi-objective optimization model was established to minimize the number of charges, the number of scale pairs, the surplus and the upgrading costs of steel grades. Furthermore, a hybrid optimization algorithm combined with heuristic and mutation-based estimation of distribution algorithm was proposed to solve the model. Experiments were conducted on several groups of test data collected from practical production orders of Baosteel. The computational results demonstrate that the proposed algorithm can generate better solutions than the manual method. The proposed model and algorithm proved to be effective and practical.