Effects Of Casting Parameters Research Articles

Experimental Investigation and Numerical Simulation of the Fluidity of A356 Aluminum Alloy

The fluidity of A356 aluminum alloy was experimentally determined at the melt temperatures and vacuum degrees by a series of suction fluidity tests. In order to achieve different cooling rates during the test, quartz tubes, as well as stainless steel tubes, were employed as the fluidity channels. As the melt temperature increased from 650 to 730 °C, fluidity lengths either linearly increased from 26 to 36 cm or parabolically increased from 13 to 29 cm when quartz tubes or stainless steel tubes were employed, respectively. As the vacuum degree of the fluidity test increased from 0.005 to 0.03 MPa, fluidity increased from 25 to 43 cm in quartz tubes while the smaller increase in fluidity from 20 to 31 cm was observed in stainless steel tubes. Shorter fluidity lengths in stainless steel tubes than those in quartz tubes under the same fluidity measurement condition were due to faster solidification speed confirmed by microstructural analysis. In order to predict the fluidity of the A356 alloy obtained from the suction fluidity tests, a mathematical model was developed based on heat and mass transfer equations coupled with thermodynamic calculations by ChemApp software. The simulation results show good agreement with the fluidity length obtained in the present study. From a series of model calculations, the effects of casting parameters on the fluidity of the A356 melt were discussed.

Three-Dimensional CFD Simulation Coupled with Thermal Contraction in Direct-Chill Casting of A390 Aluminum Alloy Hollow Billet

A three-dimensional CFD model coupled with melt flow, heat transfer, and thermal contraction was developed to simulate the direct-chill (DC) casting process of A390 alloy hollow billet with a cross-section size of Φ164 mm/Φ60 mm. This study considered the effects of contact height and air gap width between the core and the hollow billet, which dominated the heat transfer at the inner wall of the hollow billet. The effects of core taper angle, relative vertical position of core in the mold, and casting speed on the steady-state temperature distribution and formability of hollow billet were investigated. According to the criterion used in this study, the optimal core taper angle is 3 deg for DC casting of A390 alloy hollow billet. With the optimal core taper angle, the A390 alloy hollow billet can be cast successfully regardless of the variation of the relative vertical position of core in the mold and casting speed. The coupled model developed in this study can be applied to optimize the core taper angle and study the effects of casting parameters in various dimensions of hollow billet.

Development of a mathematical model and its application to the stress evolution of a multi-crystalline silicon billet during continuous casting

Abstract A mathematical model of the continuous casting process for multi-crystalline silicon billet has been developed to predict the stress evolution in the billet using the commercial finite element package, ProCAST. The calculated temperature was validated by the measured data, and the good agreement shows the reliability of the present model. The effects of casting parameters on the stress of a billet were investigated and the simulation results were validated by the analytical calculation data. The results indicated that the stress slightly decreased with the increasing of the pouring temperature. With increasing the cooling intensity in the secondary cooling zone and decreasing the casting speed, the billet stress increased. In the present work, it was found that at a pouring temperature of 1560°C, with air cooling in the secondary cooling zone and a casting speed of 1 mm s–1, a billet with low stress could be continuously cast.

Numerical Simulation of Solidification Processes of Copper Alloys by Vacuum Continuous Casting

A numerical simulation method is used to analyse the microstructure evolution of 8-mm-diameter brass (70wt%Cu30wt%Zn) rods during the vacuum continuous casting (VCC) process. The macro-and micro-scale coupling method is adopted to develop a temperature field model and a microstructure prediction model. The effects of casting parameters, including casting speed and pouring temperature, on the shape of the solid-liquid (S/L) interface and solidified microstructure are considered. Simulation results show that the casting speed has a large effect on the shape of the S/L interface and grain morphology.

Influence of casting parameters on microstructure and mechanical properties of AC2A thixocasting

Thixocasting is a semisolid metal (SSM) casting technology that combines the benefits of spheroidal non-dendritic microstructure of SSM and near net shape casting of conventional die casting, leading to extremely high integrity and exceptional mechanical properties of cast components. In this paper, the effects of casting parameters and T6 heat treatment on the microstructure and mechanical properties of fork-like thixocast components of AC2A aluminium alloy were investigated. The microstructures of specimens of both as cast and T6 cast components were observed. Uniform distribution of fine solid particles of globular primary phase was found for all casting conditions. However, low solid fraction of the primary phase was noticed at the edge of each casting, where enriched solutes were also detected. Significant increase in porosity was found in the biscuit and runner part of the castings. The effects of casting parameters on phase separation, porosity distribution and mechanical properties of the castings are discussed.

Numerical simulation of the solidification processes of copper during vacuum continuous casting

A numerical simulation method is used to analyze the microstructure evolution of 8-mm-diameter copper rods during the vacuum continuous casting (VCC) process. The macro–microscopic coupling method is adopted to develop a temperature field model and a microstructure prediction model. The effects of casting parameters, including casting speed, pouring temperature, cooling rate, and casting dimension on the location and shape of the solid–liquid (S/L) interface and solidified microstructure are considered. Simulation results show that the casting speed has a large effect on the position and shape of the S/L interface and grain morphology. With an increase of casting speed, the shape of the S/L interface changes from a planar shape into an elliptical shape or a narrow, pear shape, and the grain morphology indicates a change from axial growth to axial–radial growth or completely radial growth. The simulation predictions agree well with the microstructure observations of cast specimens. Further analysis of the effects of other casting parameters on the position and shape of the S/L interface reveals that the casting dimension has more influence on the position and shape of the S/L interface and grain morphology than do pouring temperature and cooling rate. The simulation results can be summarized to obtain a discriminant of shape factor (η), which defines the shape of the S/L interface and grain morphology.

Liquid steel flow in continuous casting machine: modelling and measurement

Single phase (liquid steel) and two-phase (liquid steel and argon bubbles) three-dimensional computational fluid dynamic and heat transfer models were developed for the continuous casting machines of ArcelorMittal. The computational domains include tundishes, slide gates, submerged entry nozzles and moulds. The effects of buoyancy, tundish design, tundish practices, nozzle design and caster practices on flow structure were investigated. Mathematical modelling is discussed in detail. In addition, submeniscus velocity measurements in the slab caster mould are performed with the method of torque measurement. A consumable probe is inserted into the liquid steel meniscus from the top of the mould through mould powder and slag layer. The liquid steel flow applies a drag force to the probe, which then generates a torque. This torque value is measured and then converted back to velocity. The concept and challenges of the technique are discussed, and the effects of casting parameters on mould flow structure are investigated. Product quality in relation to real time meniscus velocity measurements is also discussed.

Numerical simulation of thermal stress in cast billets made of AZ31 magnesium alloy during direct-chill casting

A comprehensive two-dimensional (2D) mathematical model based on the ANSYS software has been developed for the computation of the thermomechanical state of the solidifying strand during direct-chill (DC) casting of abnormity ingots and during subsequent cooling. Stress and the strain formation mechanism had been studied. The boundary and initial conditions used for primary and secondary cooling were based on the heat transfer during the solidification of the billet. The effects of casting parameters on the distribution of temperature and stress were researched, which helped to optimize the casting parameters (casting speed, pouring temperature, length of crystallizer, and so on). The simulation results of thermal stress and strain field gave a better understanding of the formation mechanism of some casting defects, which was very useful for optimizing casting parameters and obtaining high-quality billets.

Evaluation of heat transfer coefficients along the secondary cooling zones in the continuous casting of steel billets

In the present work, heat transfer coefficients (h) along different cooling zones of a continuous caster billet machine were determined during casting of low and medium carbon steels. The effects of casting parameters, such as machine characteristics, the ingot dimension, mold, sprays zones, radiant cooling, melt composition, and casting temperature were investigated and correlated with heat transfer coefficients. By using industrial measured billet surface temperatures, linked with a numerical solution of the solidification problem, ingot/cooling zones heat transfer coefficients were quantified based on the solution of the inverse heat conduction problem (IHCP). The experimental temperatures were compared with simulations furnished by an explicit finite difference numerical model, and an automatic search has selected the best theoretical–experimental fit from a range of values of h. The computer software algorithm has been developed to simulate temperature profiles, solid shell growth, phase transformations, and the point of complete solidification in continuous casting of steel billets and blooms. Industrial experiments were monitored with an optical infrared pyrometer to analyze the evolution of surface temperatures during solidification along the machine. The results permitted the establishment of expressions of h as a function of position along the caster, for different steel compositions, casting parameters and melt superheats.

The cast structure of a 7075 alloy produced by a water-cooling centrifugal casting method

A water-cooling centrifugal casting method was applied to cast the 7075 Al alloy to generate a much finer cast structure than that produced by conventional ingot casting methods. The effects of casting parameters, i.e., rotation speed, pouring temperature, water flow, and grain refiner, on casting structure were systematically studied so that the optimum casting condition and the solidification mechanism could be established. The typical cast structure along the thickness direction of a cast ring could be divided into four equiaxed zones, including the chill zone which is in contact with the mold wall. All zones have their characteristic grain size, morphology, and relative thickness, which are all dependent on the casting condition. The optimum casting condition yielding the finest structure available was found to be 3000 rpm, 650 °C, and sufficient water cooling. A uniform portion occupying 90 pct of the whole thickness and having a grain size of 17 μm could be achieved under such a casting condition. When a grain refiner was added, the whole ring became further concentrated with grains of fine structure. A mechanism concerning the overall effects of rapid solidification, turbulent flow, and centrifugal force has been proposed for the present casting method and might explain the zone-structure formation and the effects of the casting parameters on microstructural features.