Slab Continuous Casting Machine Research Articles

Fluid Flow, Solidification and Solute Transport in Slab Continuous Casting with Different S-EMS Installation Positions

During continuous slab casting, strand electromagnetic stirring (S-EMS) has a significant effect on improving the slab quality. In the current work, a numerical model based on the practical slab continuous casting machine and coupled electromagnetic field, flow field, solidification, and solute transport was established to investigate and evaluate the effect of the S-EMS installation position with various current intensities on metallurgical behavior. The model was verified by magnetic field measurement, infrared camera, and nail shooting experiments. The results show that moving the S-EMS installation position to the solidification end reduces the stirring effect due to the skin effect and the increasing thickness of the slab shell. A higher installation position is beneficial for improving the equiaxed grain rate, while a lower one is beneficial for reducing carbon segregation. The maximum segregation index and range decrease from 1.26 to 1.2 and from 0.42 to 0.36 with the installation position being decreased from −3 m to −12.8 m, respectively. The industrial trials show that S-EMS installed at 3 m has a significant effect on expanding the equiaxed grain zone and a deteriorating effect on reducing carbon segregation.

Study and modeling of rational design of tundish for slab continuous-casting machine

The results of mathematical modeling of the melt movement in the working volume of tundish of continuous-casting machine a capacity of 50 tons are presented when changing the type of flow modifiers used and methods of argon injection, which have a decisive effect on the hydrodynamics of the bath and the formation of dead zone that determine the quality parameters of the cast blanks produced.

Flow and Heat Transfer on the Surface of Molten Steel Slag Layer in Continuous Casting Mold

Protective slag is coated on the surface of molten steel during continuous casting, the flow and heat transfer state of the protective slag is a decisive factor affecting the inflow and consumption of liquid slag and is also an important prerequisite for stabilizing and improving the quality of continuous casting billets. Based on the Navier Stokes fluid momentum conservation equation and energy equation, a two-dimensional longitudinal numerical model describing the flow/heat transfer of liquid protective slag on the surface of steel is established. The data comes from the equipment parameters and casting process of an arc shaped slab continuous casting machine in a domestic steel plant. The flow field and temperature field distribution of protective slag are calculated and analyzed, and the effects of factors such as slag layer thickness and shear speed on the flow and heat transfer status of the liquid slag layer are discussed. When the bottom shear velocity increases from 0.005 m/s to 0.2 m/s, the maximum flow velocity of liquid slag from the nozzle to the narrow surface in the center area of the model increases from 0.0012 m/s to 0.0617 m/s, and the average longitudinal flow velocity of liquid slag near the nozzle increases from 0.0012 m/s to 0.0627 m/s. The research results provide reference for investigating the complex metallurgical behavior of protective slag.

Numerical Simulation and Application of Tundish Cover Argon Blowing for a Two-Strand Slab Continuous Casting Machine

During continuous casting, argon blowing from tundish cover (ABTC) can greatly prevent the flow of the remaining air and decrease the reoxidation of molten steel in tundish. In the current study, a numerical model based on a tundish of a two-strand slab continuous casting machine was established to investigate the feasibility and evaluate the protective casting effect of the ABTC process. The influence of operation parameters, including sealing schemes of tundish cover holes and the argon flow rate of the remaining oxygen content, were studied in tundish. Then, industrial trials based on the operation parameters from the numerical model were carried out to evaluate the protective effect of ABTC. The results indicate that the ABTC process has a great protective effect in avoiding increasing levels of nitrogen and losing titanium and aluminum. With the ABTC process applied, the average increment of nitrogen (△w[N]) in steel from the end of RH to tundish decreases by 90% from 10 × 10−6 to 1 × 10−6, the average loss of titanium (△w[Ti]) by 12.7% from 63 × 10−6 to 55 × 10−6, and the amount of aluminum (△w[Al]) decreases by 7.1% from 70 × 10−6 to 55 × 10−6. The injecting hole and baking holes should be sealed during the period of empty tundish to efficiently discharge the air. In order to ensure that the oxygen volume fraction in tundish is less than 1%, the argon flow rate should be ≥220 Nm3/h during the period of empty tundish and ≥80 Nm3/h during the period of normal casting.

Experimental Analysis of a Slab Continuous-Casting SEN with an Inner Flow Divider

In slab continuous-casting machines, the quality of the finished product mainly depends on the hydrodynamic behavior of the molten steel in the cavity of the continuous-casting mold, where the submerged entry nozzle is the central element. Recently, a nontraditional nozzle design was reported, where a solid barrier attached to the inner bottom wall of the nozzle divides its internal volume, particularly around the outlet ports. The solid barrier was named a flow divider. In this work, the effect of the flow divider is analyzed by comparing the performance of traditional nozzles with the performance of nozzles altered with the flow divider. The performance of the nozzles was evaluated experimentally, employing a scaled model of the mold section, using cold water as the working fluid. The shape of the nozzle outlet jets and the fluid flow pattern in the mold cavity were used to determine the performance of the nozzles. In addition, several factors affecting the process stability and the quality of the product were analyzed: the casting speed, the tilt of the nozzle outlet ports, and the injection of gas in the liquid stream entering the nozzle. The analysis showed that for the nozzles with the flow divider, (i) the outlet jets are narrow and symmetric, (ii) the symmetrical double-roll flow pattern in the mold cavity is obtained, (iii) the liquid-free surface is stable and has low distortions, and (iv) the flow divider neither increases the bubble breakage nor the coalescence between them.

Impingement Density Analysis on Heat Transfer and the Appearance of Edge Cracks in Conventional Slab Using Hydraulic Nozzles

In this work, the fluid dynamics and heat transfer of two hydraulic nozzles used in the secondary cooling of the conventional slab continuous casting machine were analyzed. Impingement density maps, the jet opening angle and heat flux associated with different operating conditions (impingement distance, pressure) were experimentally determined. The opening angle and impingement density footprint were found to vary considerably in shape and magnitude with varying operating pressure and distances. Finally, it was found that when short operating distances are used, a greater heat extraction gradient occurs in the major axis of the impingement footprint, which promotes edge-cracks in the slab in plant.

Analysis of a New SEN Design with an Inner Flow Divider

To minimize the product imperfections due to slag entrapment and surface defects, the fluid flow pattern inside the mold must be symmetric, commonly named double-roll flow. Thus, the liquid steel must enter into the mold evenly distributed. The submerged entry nozzle (SEN) is crucial in product quality in vertical steel slab continuous casting machines because it distributes the molten steel from the tundish into the mold. This work evaluates the performance of a novel bifurcated nozzle design named “SEN with flow divider”. The symmetry at the outlet ports is obtained by imposing symmetry inside the SEN. The flow divider is a solid barrier attached at the SEN bottom inner wall, the height of which slightly surpasses the upper edges of the outlet ports. The performance analysis is done first using numerical simulations, where the Computational Fluid Dynamics (CFD) technique and the Smoothed Particle Hydrodynamics (SPH) approach are used. Then, experimental tests on a scaled model are also used to evaluate the SEN performance. Numerical and physical simulations showed that the flow divider considerably reduces the SEN outlet jets’ broadness and misalignment, producing compact, aligned, and symmetric jets. Therefore, the SEN design analyzed in this work is a promising alternative to improve process profitability.

Study of the Principles for Ensuring the Accuracy of CCM Design Parameters

It is established that the defining factor of accuracy of the designing parameters of S-type billet continuous casting machine (CCM) is relative difference of curvature of the adjacent arc-like sections, which form process axis of strand. An analysis of the local radius change of CCM ingot path curvature is carried out. In the process of CCM equipment alignment, it is necessary to ensure alignment of its curvature centers under condition of curvature value equality for minimization of its relative difference. Developed technology of position control and CCM equipment alignment allows meeting this requirement. The developed technology is based on the use of “Vizir 3D” a high-precision measurement system built on the base of electronic total station. Practical experience of alignment showed the efficiency of geodesic and combined method of equipment alignment on both billet and slab CCM.

Investigating Dynamic Thermal Behavior of Continuous Casting of Steel with CONOFFLINE

A new model, CONOFFLINE, has been developed to simulate transient thermal behavior of a longitudinal section down a continuous steel slab-casting machine. The model was first verified by comparing its predictions of shrinkage through the strand thickness with transient measurements of roll forces in a thick-slab caster during a series of speed changes. The model was then applied to investigate the evolution of temperature and shell thickness in a typical caster after sudden changes in casting speed. Simple equations are proposed to estimate the settling time of metallurgical length and surface temperature during sudden speed changes for both thin- and thick-slab casters. Finally, the influence of different spray cooling control methods on these behaviors during casting speed changes is investigated.

Influence of the Design of Metal Receivers of Slab Continuous-Casting Machines on the Motion of Flow in the Tundish in the Case of Deviations of the Metal Stream from the Required Position. Part III. Results of Investigations

Influence of the Design of Metal Receivers of Slab Continuous-Casting Machines on the Motion of Flow in the Tundish in the Case of Deviations of the Metal Stream from the Required Position. Part III. Results of Investigations

Continuous casting control via drive monitoring

The paper describes the investigation’s results of functional capabilities of the equipment testing systems as applied to the withdrawal roll drives provided with individual power supply using the frequency converter-asynchronous motor system. All the experimental investigations were carried out at the “Magnitogorsk Iron and Steel Works” (MISW). The statistical analysis of time diagrams and frequency-response curve of changes in instantaneous values of withdrawal roll drives load torques were used. The diagnostic signs of the withdrawal roll bending, occasional slippage along the slab, wear of ring seals, and teeth of the mounted gearbox on the basis of the analysis of the component range of spectrum density of changes in load torques were computed. It was found that variance inhomogeneity of scattering of load torque change for adjacent time intervals can be used as a diagnostic sign of the withdrawal roll occasional slippage along the slab. We considered the developed diagnostic methods for withdrawal roll drive equipment at continuous casting machines (CCMs) which provide the increase productivity due to decreasing of the CCM repair work downtime. A functional diagram and a generalized algorithm of the diagnostic system for equipment of the withdrawal roll were developed taking into account the characteristics of continuous casting of steel at a slab CCM. An experimental estimate was carried out to assess the efficiency of the developed diagnostic system.

Influence of the Design of Metal Receivers of Slab Continuous-Casting Machines on the Motion of Flow in the Tundish in the Case of Deviations of the Metal Stream from the Required Position. Part I. Statement of the Problem

We study the problem of evaluation of the influence of design of the metal receiver of a large-capacity tundish of slab continuous-casting machine on the decrease in the turbulence of flows in the case of deviation of the metal stream from the required position in the process of casting. We present the results of computer simulations of various types of deviations from the target point of input for the metal stream flowing from the steel-teeming ladle into the tundish. We perform the comparison of the distributions of metal flows in tundishes with metal receivers of different designs. We also give recommendations concerning the possibilities of weakening of the turbulence of flows in the analyzed cases.

Prediction of Conditions for Occurrence of Thermal Fatigue Cracks on the Surface of Continuous Rollers of Slab CCMS

The authors propose a technique for predicting the conditions for the appearance of thermal fatigue cracks on the surface of rotating continuous rollers of slab continuous-casting machines (CCMs) based on the asymptotic analysis of the problem of thermoelasticity on planar deformation. The technique enables to estimate tension, displacements, and deformations in the surface layer of rollers considering the magnitude and nature of the thermal load, and the angular velocity of rotation. It can serve as the basis for choosing the material for the production of rollers, the conditions for their cooling, and the rhythm of casting. The effectiveness and justification of the proposed method are confirmed by an experiment.

Influence of the Design of Metal Receivers of Slab Continuous-Casting Machines on the Motion of Flow in the Tundish in the Case of Deviations of the Metal Stream from the Required Position. Part II. Procedure of Simulation1

Influence of the Design of Metal Receivers of Slab Continuous-Casting Machines on the Motion of Flow in the Tundish in the Case of Deviations of the Metal Stream from the Required Position. Part II. Procedure of Simulation1

The effect of the design of the metal receiver slab continuous casting machine on the movement of metal in the intermediate ladle when the metal stream deviates from the desired position. Part I. Formulation of the problem

The article is devoted to assessing the effect of the design of the metal receiver in the intermediate ladle of the large capacity slab continuous casting machine on reducing the turbulence of flows when the metal stream deviates from the required position during casting. The results of computer simulation of industrial variants of displacement of a stream of metal from a steel pouring ladle to an intermediate ladle from the target input point are presented. The distribution of metal flows in the tundish is compared with different designs of metal receivers. Recommendations are given for reducing flow turbulence for the cases considered. Ill. 6. Ref. 5.

The effect of the design of the metal receiver slab continuous casting machine on the movement of metal in the intermediate ladle when the metal stream deviates from the desired position. Part III. Research results

The article is devoted to assessing the influence of the design of a metal receiver in an intermediate ladle of large capacity slab continuous casting machines on reducing turbulence in flows when the metal stream deviates from the required position during casting. The results of computer simulation of industrial variants of displacing a stream of metal from a steel pouring ladle to an intermediate ladle from the target input point are presented. The distribution of metal flows in the tundish is compared with different designs of metal receivers. Recommendations are given for reducing flow turbulence for the cases considered. Ill. 5. Ref. 3.

The effect of the design of the metal receiver slab CCM on the movement of metal in the intermediate carpet with a deviation of the metal stream from the desired position. Part II Modeling technique

The article is devoted to assessing the influence of the design of a metal receiver in an intermediate ladle of large capacity slab continuous casting machines on reducing turbulence in flows when the metal stream deviates from the required position during casting. The results of computer simulation of industrial variants of displacing a stream of metal from a steel pouring ladle to an intermediate ladle from the target input point are presented. The distribution of metal flows in the tundish is compared with different designs of metal receivers. Recommendations are given for reducing flow turbulence for the cases considered. Ill. 4. Ref. 2.

Improvement in the Reliability of Mechanical Flux Feed Systems for Continuous Slab-Casting Machine Molds

Improvement in the Reliability of Mechanical Flux Feed Systems for Continuous Slab-Casting Machine Molds

Optimization of Pulse-Step Method for Liquid Steel Alloying in One Strand Slab Tundish

Introduction to the Fe-C-X system: Si, Mn, Al and Nb, Ti, V, B allow the ultimate tensile strength and ductility of steel to be increased at the same time. Therefore, multiphase steels of the TRIP, DP, MART and CP are the steels of the future. The scientific aim of the researches were to obtain new basic information on alloying process of liquid steel in a tundish with the use of the pulse–step method. The facility under investigation was a single outlet tundish being a component of a slab continuous casting machine. Computer simulations of the liquid steel flow and alloy behaviour in turbulent motion conditions were done using the Ansys-Fluent computer program. For generating the computational grids, Gambit program was used. For pulse–step method optimisation two aspects were considered. At first numerical simulations were performed for the selection of the time interval between the pulse feed of the first alloy batch and the continuous feed of subsequent alloy batches in order to maintain the required homogenisation level. Next simulations were done for determination of the mass of the pulse charge that ensures not only the attainment of the 95% homogenisation level, but also the limitation of alloy concentration peaks occurring in the liquid steel and going beyond the 95% homogenisation zone. On the basis of numerical investigations the mixing curves and time mixing for different variants of pulse-step method optimization were obtained.

High-temperature creep constitutional model of Q460E steel and effect of creep on bulging deformation of continuous casting slab

Mechanical properties and creep behavior of Q460E continuous casting slab were studied by means of uniaxial tensile tests on a Gleeble-3800 thermomechanical simulator from 1000 to 1100 °C. The high-temperature creep constitutional equation was derived based on experimental data. The parameters in the equation were calculated by using the regression analysis inverse-estimation method. The experimental curves in the primary and secondary creep stages are fitted well. A three-dimensional elastic–plastic and creep finite element model was proposed in order to investigate the bulging deformation of slab and the bulging deformation at the beginning position of bending segment on the slab continuous casting machine was computed accurately. The results indicate that the maximum bulging deformation appears at the geometric center of the slab. The maximum value of the bulging deformation obtained by the elastic–plastic analysis is 1.301 mm. Considering the creep effect, the deformation increases to 1.827 mm which is about 1.4 times the value obtained by the elastic–plastic analysis. The calculation of bulging deformation using the elastic–plastic creep model is more reliable and accurate.