Relationships between the surface quality of a single crystal copper ingot and the process parameters of a heated mould continuous casting method

The relationships between the surface quality of a single crystal copper ingot and the process parameters of heated mould continuous casting method were studied experimentally using our own design of horizontal heated mould continuous casting apparatus, and the mechanism by which process parameters affect the surface quality of a single crystal copper ingot is analyzed in the present paper. The results show that the process parameters affect the surface quality of a pure copper ingot by affecting the position of the liquid-solid interface in the mould. The position of the liquid-solid interface in the mould must be controlled carefully within an appropriate range, which is determined through a series of experiments, in order to gain a single crystal copper ingot with good surface quality.

Analysis of inhomogeneity of solidified microstructure of continuous casting copper tubular billet based on factor analysis

The horizontal continuous casting process,the initial step in TP2 copper tubular processing,directly determines the microstructure and properties of copper tubular.However,the process parameters of the continuous casting characterize time variation,multiple disturbances and strong coupling.As a consequence,their influence on a casting billet is difficult to be determined.Due to the above issues,the common factor and special factor analysis of the factor analysis model were used in this study,and the casting experiment and billet metallographic experiment were carried out to diagnose and analyze the reason of the microstructure inhomogeneity.The multiple process parameters were studied and classified using common factor analysis,2 the cast billets with abnormal microstructures were identified by GT^(2) statistics,and the most important factors affecting the microstructural homogeneity were found by special factor analysis.The calculated and experimental results show that the principal parameters influencing the inhomogeneity of solidified microstructure are the primary inlet water pressure and the primary outlet water temperature.According to the consequence of the above investigation,the inhomogeneity of the copper billet microstructure can be effectively improved when the process parameters are controlled and adjusted.

Theoretical and experimental analysis of continuous casting with soft-contacted mould

Coupling the quasi 3D numerical simulation of electromagnetic field and the experiments with some metals such as tin, aluminum, copper and steel, the electromagnetic characteristics of continuous casting with soft contacted mould, especially the influences of power frequency, the mould structure, and the inductor position, size and current on the electromagnetic force and pressure on the billet, were analyzed. The result shows that, in continuous casting with soft contacted mould, the electromagnetic pressure on the surface of billet increases with the rising of the power frequency as a logarithmically parabolic function and, with that of inductor current as a parabolic function. The design principle of the soft contacted mould is that 1) the mould structure should be ‘more segments and thin slits’; 2) the topside of inductor should be at the same location with the meniscus of molten metal; 3) the inductor should cover the initial solidifying shell of billet.

THE COMPUTATION AND EXPERIMENT ANALYSIS OF ELECTROMAGNETIC CONTINUOUS CASTING WITH SOFT-CONTACTED MOULD

In this paper, coupling the quasi-3D numerical simulation of electromagnetic field and the experiments of continuous casting with soft-contacted mould with some metals such as tin, aluminum, copper and steel, the electromagnetic characteristics of continuous casting with soft-contacted mould is analyzed. It is shown that the electromagnetic pressure on the surface of billet is increasing with the rising of power frequency as a logarithmically parabolic function, with that of electric conductivity of billet as a power junction, and with that of the current in inductor as a parabolic junction.

Modeling of unsteadiness of fluid flows and level fluctuations in thin slab continuous casting moulds

Unsteady fluid flows and level fluctuations in a thin slab continuous casting mould have significant influence on product quality. In this study, the phenomena concerning transient flow features and free surface motions were analyzed by means of the large eddy simulation （LES） software with the smagorinsky SGS model--VisualCast （VCast） II, where the Simpler algorithm on a body-fitted mesh was used to resolve governing equations. A series of water analog experiments on the fluid flow and the surface wave in the moulds of thin slab continuous casting were also performed. The results of fluid regions, middle of vortex and level fluctuation from digital simulations were identical with the results of the water analog experiments.

Effects of continuous casting mould fluxes on reducing longitudinal and star cracks on a slab surface

In the continuous casting production of medium carbon steel (whose mass fraction of carbon is 0.09 % to 0.16 %) and high strength low alloy steel (whose mass fraction of Mn is 0.90 % to 1.40 %), flecks occurring the most often are usually longitudinal and star cracks. In additional to the employment of a galvanized plate mould, two kinds of fluxes with special properties were studied and used to harmonize the conflicts between the function of heat transfer and lubrication. An industrial application revealed that the crystallizing temperature (Tc) and crystal ratio (R) of fluxes have a crucible effect on impeding the occurrence of above defects on a slab surface. In the case of slab section (180 to 240) mm(1000 to 1400) mm and casting speed Vc of (0.7 to 1.2) m/min, the optimized parameters of fluxes are Tc of (1170 to 1190) ℃, R of 80 % to 95 % for medium carbon steel, and Tc of (1100 to 1150) ℃, plus R of 40 % to 60 % for high strength low alloy steel.

Theoretical and experimental analyses of continuous casting with soft-contacted mould (Ⅱ)—EMF calculation and experimental analyses

Coupling the quasi 3D numerical simulation of the electromagnetic field and the experiments with some metals, a series of phenomena in the processes of continuous casting with soft contacted mould was analyzed. Some theoretical and experimental models were presented, from which following results were obtained. 1) The electromagnetic force is related with electric conductivity of billet as a power function to 0.4. 2) The heat transfer between billet and mould is related with the contacting pressure, and it is a linear function for tin billet approximately. 3) The distance between initial solidification point and meniscus in billet is related with the surface magnetic flux density as a fourth root function. 4) The temperature gradient in the initial solidifying shell is reduced, which can decrease the tendency of hot tearing on the surface of billet, and increase the equiaxed crystal zone in billet. 5) The stronger the magnetic flux density is, the more shallow and the thinner the oscillation mark on the surface of billet is. 6) The depth of oscillation mark on the billet cast by the soft contacted mould can be reduced to about 10% in comparison with that on the billets cast by traditional mould. 7) In non dimensional condition, the average depth of the oscillation marks on the billets cast by the soft contacted mould decreases with increasing magnetic flux density on there as a complementary error function. [

MATHEMATICAL AND PHYSICAL MODELING OF INTERFACIALPHENOMENA IN CONTINOUS CASTING MOULD WITH ARGONINJECTION THROUGH SUBMERGED ENTRV NOZZLE

The study on the fluid flow, meniscus oscillation, slag entrapment in continuous casting mould was conducted mathematically and experimentally. The results show that the injection of argon into submerged nozzle enhances the meniscus oscillation, thus increases the probability of slag entrapment, and the critical argon blowing flow rate, which will give rise to slag entrapment, is around 10l/min. The trajectory of bubble is affected by the bubble diameter and the molten steel flow, and the bubble diameter is dominant. The bubble with diameter 1.4mm floats fastest with 0.47m/s terminal velocity.

Rheologic behaviors of A356 aluminum alloy billet produced by semisolid continuous casting process

The experiments for rheologic behaviors of semisolid continuous casting billets of A356 alloy in semisolid state had been carried out with a multifunctional rheometer. The results show that the deformation rate increases with loading time, the maximum strain reaches to 120％ （which is one time larger than that of traditional mold casting billet） and the strain can be rapidly eliminated to 10％ after unloading. Moreover, there is a critic stress for billet deformation even in semisolid state, which is named as critic shear stress. This stress increases with the decreasing of heating time. The theologic behaviors can be expressed by five elements mechanical model （H2- [N1|H2]-[N2|S]） and can be modified with the increasing of heating time.

Development and investigation of electroslag continuous casting

The principle and technological design of electroslag continuous casting （ESCC）, including bifilar mode, T-shaped mould, and metal level detecting system, are detailed. Remelting was carded out for 1Crl8Ni9Ti stainless steel with ESCC. The surface finish, chemical composition, macroand microstructures, and inclusions of the remelted billets were characterized. ESCC reduces the cost and increases the productivity in comparison to traditional ESR, while achieves comparably excellent products.

High-strength aluminum alloys hollow billet prepared by two-phase zone continuous casting

The two-phase zone continuous casting(TZCC)technique was used to continuously cast high-strength aluminum alloy hollow billets,and a verified 3D model of TZCC was used to simulate the flow and temperature fields at casting speeds of 2-6 mm·min^(-1).Hollow billets under the same conditions were prepared,and their macro/microstructures were analyzed by an optical microscope and a scanning electron microscope.During the TZCC process,a circular fluid flow appears in front of the mushy zone,and the induction heated stepped mold and convective heat transfer result in a curved solidification front with depressed region near the inner wall and a vertical temperature gradient.The deflection of the solidification front decreases and the average cooling rate in the mushy zone increases with increasing casting speed.Experimental results for a 2D12 alloy show that hot tearing periodically appears in the hollow billet accompanied by macrosegregation near the inner wall at casting speeds of 2 and 4 mm·min^(-1),while macroscopic defects of hot tearing and macrosegregation weaken and the average size of columnar crystals in the hollow billets decreases with further increasing casting speed.2D12 aluminum alloy hollow billets with no macroscopic defects,the finest columnar crystals,and excellent mechanical properties were prepared by TZCC at a casting speed of 6 mm·min^(-1),which is beneficial for the further plastic forming process.

Secondary cooling technology for high-efficiency continuous billet-casting

The mathematical model of high-efficiency continuous billet casting was developed, incorporating the effective spraying water coefficient and the effective specific spraying water flowrate of secondary cooling. To realize uniform cooling in secondary cooling zones, the spraying cooling structure and the arrangement of nozzles were redesigned and optimized, and an additional spraying cooling zone was used. A new secondary cooling model of spraying water was built. It was found that the required spraying water flowrate of a cooling zone was related with the casting speed, the casting temperature, the compositions of liquid steel and the cooling water temperature of secondary cooling. The operation of the reformed caster proved that the spraying cooling structure and the new secondary cooling model were suitable, and the casting speed was greatly enhanced. The highest casting speed was (3.8 to 4.0) m/min for billet with a section of 150×150 mm2. The quality and the output of the billet were improved, and the economical benefit was heightened.

Optimization of flow control devices in a tenstrand billet caster tundish

The physical model of a ten-strand billet caster tundish was established to study the effects of various flow control devices on the melt flow. Before and after the optimization of the melt flow, the inclusion removal in the tundish was evaluated by plant trials. The physical modeling results show that when combined with a baffle, the turbulence inhibitor, instead of the impact pad, can significantly improve the melt flow. A turbulence inhibitor with a longer length of inner cavity and without an extending lip at the top of the sidewall seems to be efficient in the improvement of the melt flow. Various types and designs of baffles all influence the flow characteristics significantly. The "V" type baffles are better than the straight baffles for flow control. The "V" type baffle with four inclined holes at the sidewall away from the stopper rods is better in melt flow control than the one with one inclined hole at each sidewall. The combination of a well-designed turbulence inhibitor and an appropriate baffle shows high efficiency on improving the melt flow and an optimal proposal was presented. Plant trials indicate that, compared with the original tundish configuration in prototype, the inclusions reduce by 42% and the inclusion distribution of individual strands is more similar with the optimal one. The optimal tundish configuration effectively improves the melt flow in the ten-strand billet caster tundish.

Extensive Analysis of Multi Strand Billet Caster Tundish Using Numerical Technique

Continuous casting of steel involving different grades in the same casting sequence remains a challenge to billet caster operators. The intermixed composition obtained during the grade change does not meet the specification of either grade and must be downgraded. Incorrect identification of this intermixed region may result in non-conforming products reaching the customer. In this study, a numerical model based on CFD (computational fluid dynamics approach) has been developed which predicts the start and end of the intermixed composition and the tonnage to be downgraded under different casting conditions. This model was validated and the results were in good agreement with the actual plant data for a 6-strand billet caster at LD-1 of TATA Steel, India. This model is used to calculate transition tonnage for different scenarios, e.g. when one of the outermost strands is not functional or some combinations are not functional and varying casting speed during operation. Furthermore, impact of different design of baffles on performance of Tundish has been evaluated to find a way to reduce transition or intermixed composition.

Process Parameters of Manufacturing Single Crystal Copper by Heated Mold Continuous Casting

The effect of process parameters on the surface quality of single crystal copper ingot was studied through experiment with a self-designed horizontal heated mould continuous casting apparatus,and the mechanism was analyzed.The results show that the process parameters affect the surface quality of pure copper ingot by affecting the position of the liquid-solid interface in the mould.The position of the liquid-solid interface in the mould must be controlled carefully in an appropriate range determined through experiments in order to gain a single crystal copper ingot with a high surface quality.

Simulation of inside-grooved mould improving heat transfer of original shell of casting slab

The dipping experiment was carried out by putting the water-cooled copper plate into the stannum-lead alloy to simulate the process of initial solidification of steel, and the result that the heat transfer of original shell improved by grooving on the surface of the water-cooled copper plate was investigated. A mathematical model of heat transfer was set up and the temperature field of casting slab 1000 mm×200 mm was calculated. The experimentation and simulation results indicate that the inside-grooved mould could improve the heat transfer of original shell, decrease the non-uniformity of original shell thickness and reduce the longitudinal surface cracks of casting slab.

Numerical Simulation and Prediction for Sticking Type Breakout Behavior in Slab Contiuous Casting

A two-dimensional heat transfer model was developed to calculate the mould wall temperature field under normal operations condition and to determine its changing behavior when breakout occured. On the numerical simulation of sticking type breakout process and the breakout related wall temperature evolution, parameters of prediction were suggested.

Influence of mechanical reduction amount on internal quality of continuous casting billets by thermal and numerical simulation

With establishment of thermal and numerical simulation models,the influence of reduction amount on solidification structure,segregation and shrinkage porosity of continuous casting(CC)billets was investigated.The thermal–mechanical coupled simulation results indicated that with an increase in reduction amount,the temperature in the central area decreases,and the reduction efficiency firstly increases and then decreases,reaching the maximum value at reduction amount of 6 mm.Metallographic analysis showed that increasing the reduction amount is beneficial for the refinement of central solidification structure.Moreover,the internal cracks are more likely to appear at higher reduction efficiency.The X-ray computerized tomography results revealed that a higher reduction amount can significantly reduce the volume fraction and equivalent diameter of the central shrinkage porosities of CC billets and increase the sphericity of them.Simultaneously,the macrosegregation of carbon along the central line is improved as the reduction amount increases;while the reduction amount exceeds 8 mm,the segregation degree will not change any more.

Solidification microstructure of M2 high speed steel by different casting technologies

The present work investigated the solidification microstructure of AISI M2 high speed steel manufactured by different casting technologies, namely iron mould casting and continuous casting. The results revealed that the as-cast structure of the steel was composed of the iron matrix and the M2C eutectic carbide networks, which were greatly refined in the ingot made by continuous casting process, compared with that by the iron mould casting process. M2C eutectic carbides presented variation in their morphologies and growth characteristics in the ingots by both casting methods. In the ingot by iron mould casting, they have a plate-like morphology and grow anisotropically. However, in the ingot made by continuous casting, the carbides evolved into the fiber-like shape that exhibited little characteristics of anisotropic growth. It was noticed that the fiber-like M2C was much easier to decompose and spheroidize after heated, as a result, the carbides refined remarkably, compared with the case of plate-like carbides in the iron mould casting ingot.

Lab experiments on the innovative rapid thick strip casting process

Rapid thick strip casting （RTSC） by Anton Hulek, Inventmetall, is an innovative concept for the production of hot strips with a final as-cast thickness of about 25 mm before rolling. The innovation of the mechanism consists in a vertical mould performing a caterpillar motion. This moving mould has an unconventional parallelogram-shaped cross-section. The conventional rectangular shape is formed in the shaping machine, which is placed straight below the mould. Further elements of the technology are state-of-the-art. For the investigation of this new casting system theoretical calculations were complemented with practical experiments. The investigation focused mainly on two key aspects： the characteristics of the mould and the shaping process. For the practical analysis a static mould with three pairs of elements in laboratory scale was developed and commissioned by the Dept. of Ferrous Metallurgy @ RWTH Aachen University. The shaping experiments were carried out in model scale with two different materials and in variable boundary conditions. The results of these experiments delivered important mechanical as well as thermal informations about the casting system.