Simulation Of Casting Process Research Articles

Integrated numerical simulation of the industrial continuous casting process

The production of a continuously cast strand involves a large number of coupled phenomena involving flow, heat transfer, solidification and thermo-mechanics. In this paper, different approaches are described for the numerical modelling of industrial continuous casting processes at different levels of detail, dependent on the questions to be investigated. In the simplest case to obtain a rough estimate of the process conditions, the solidification of the strand is considered with a prescribed convective flux profile in the strand body based on the withdrawal speed. In the most complicated case, the process phase of filling of the empty mould is first calculated, followed by the phase of the withdrawal of the strand including consideration of the flow in both strand and tundish.

Numerical simulation and optimization of casting process of copper alloy water-meter shell

The water-meter shell has a complex-structured thin-walled cavity, and it can cause casting defects such as shrinkage and misrun. On the basis of structural analysis of a water-meter shell, a three-dimensional model and a finite element model of the water-meter shell were constructed using the SOLIDWORKS and ProCAST software as a modeling tool and a casting numerical simulation tool, respectively. Three processes associated with the bottom gating system without a riser, a step gating system with a preliminary riser, and a step gating system with an optimum riser were successively numerically simulated. The mold-filling sequence, temperature distribution, liquid-phase distribution during solidification, and shrinkage distribution of these three processes are discussed here. The numerical simulation results indicated that optimization of the casting process and the rational assembling of the riser led to the shrinkage volumes at the inlet position, regulating sleeve, and sealing ring of the water-meter shell decreasing from 0.68 to 0 cm3, 1.39 to 0.22 cm3, and 1.32 to 0.23 cm3, respectively. A comparison between model predictions and experimental measurements indicated that the castings produced by the optimized process had good surface quality and beautiful appearance, without casting defects, demonstrating that numerical simulation can be used as an effective tool for improving casting quality.

Constitutive modeling of injection‐molded short‐fiber composites: Characterization and model application

AbstractA previously developed constitutive model for short‐fiber reinforced thermoplastics is applied to an injection‐molded component with a complex geometry and microstructure. This macro‐scale continuum‐based model is able to capture the anisotropic viscoelastic‐viscoplastic response of the material. In injection‐molded short‐fiber composites, the anisotropic mechanical properties depend strongly on the fiber orientation distribution, which generally displays a marked variation throughout the product. This makes the material characterization and model application challenging. In this article, two characterization and model application strategies are proposed. These techniques, together with the developed constitutive model provide a strong tool for reliable prediction of the mechanical response of an injection molded product, where inputs to the finite element analysis are obtained directly from a numerical simulation of the injection molding process. In this article, from the output provided by an injection molding process simulation software such as Moldflow, the distribution of anisotropic elastic and plastic properties throughout the component is found and the data is imported to the finite element mesh. Mechanical tests are performed on a validation product and results are compared with model predictions from finite element simulations. Through this comparison, the performance of the constitutive model and also proposed procedures for characterization and model application are investigated.

Simulation of Shrinkage Porosity Formation During Alloy Solidification

Porosity due to solidification shrinkage is a troublesome defect in metal casting. It results in low yields and increased costs in production and limits the performance of cast components in service. By reliably predicting porosity in casting process simulation, porosity can be minimized or eliminated. Here, a new model for simulating the formation of shrinkage porosity during solidification is presented. The model is based on the recent discovery that shrinkage porosity nucleates and grows in regions of a casting where the solid fraction is the lowest. It calculates the feeding flows and pressure distribution in the liquid while accounting for the density variation during cooling and solidification. It predicts the location, extent and amount of all types of shrinkage porosity in a casting, including riser pipes and large internal holes, surface sinks, and distributed micro-shrinkage. Porosity predictions are presented for simple casting geometries and for a more complex Mn-steel experimental casting. The comparisons to the observations made in the experimental casting demonstrate the capability of the model to accurately predict the various types of shrinkage porosity. Numerical studies are performed to investigate the sensitivity of the predictions to various model parameters.

Material Characterization for Reliable Resin Transfer Molding Process Simulation

Resin transfer molding (RTM) technologies are widely used in automotive, marine, and aerospace applications. The need to evaluate the impact of design and production critical choices, also in terms of final costs, leads to the wider use of numerical simulation in the preliminary phase of component development. The main issue for accurate RTM analysis is the reliable characterization of the involved materials. The aim of this paper is to present a validated methodology for material characterization to be implemented and introduce data elaboration in the ESI PAM-RTM software. Experimental campaigns for reinforcement permeabilities and resin viscosity measurement are presented and discussed. Finally, the obtained data are implemented in the software and then compared to experimental results in order to validate the described methodology.

Uncertainty analysis of the influence of delivery system nozzle structure on fluid-thermal coupling in casting molten Pool

The quality of thin strip products is determined by the flow and heat transfer in a molten pool of twin-roll casting, thus it is of great significance to study the structure parameters of the delivery system, including the angle and height of end face nozzle, the angle and height of side nozzle as well as the taper angle of side nozzle. A methodology for simulation of twin-roll thin strips continuous casting process under uncertainty is presented by a three-dimensional numerical model of the flow field and solidification of liquid steel in the molten pool. A sampling-based stochastic model is developed to elucidate the effects of uncertainty in several nozzle structure parameters on the variability of maximum outlet temperature difference and maximum liquid surface turbulence kinetic energy. The results show that taper angle of side nozzle significantly affects the variability in maximum outlet temperature difference, and the uncertainty in angle and height of end face nozzle as well as the height of the side nozzle affects the variability in maximum liquid surface turbulence difference evidently.

Influence of the edge effect on mirror shape in spin casting and the cause analysis

This paper attempts to study the abnormal bulge generated near the contact position between the mould and the surface of the mirror blank produced in spin casting. The generation of this phenomenon, which is named the edge effect, will significantly affect the shape accuracy of the mirror blank. Therefore, it is necessary to explore the causes of the edge effect and the method of its elimination. Through setting different contact angles, a simulation of the spin casting process was conducted to determine the relationship between the generation of the edge effect and the wettability between the glass melt and the mould. And then, the proportion of the raw materials of the ceramic fibre that is used to make the mould in spin casting has been changed in the experiment, so that the contact angle between the glass melt and the material of ceramic fibre was reduced from 140.489° to 75.642°. After using the mould that has been modified wettability for processing mirror blank, no edge effect happened, and the shape accuracy of the mirror bank was also improved.

Optimization of Semi-solid High-Pressure Die Casting Process by Computer Simulation, Taguchi Method and Grey Relational Analysis

The main aim of this research was to simulate high-pressure die casting of A356 semi-solid aluminum alloy using casting process simulation tool. Taking into account the viscosity of the semi-solid slurry and the mold-filling characteristics in high-pressure die casting, the mold for semi-solid aluminum alloy had been designed. Also, the influence of the three input parameters (liquid fraction of slurry, plunger velocity at 2nd phase and mold geometry) on the casting time, shrinkage and bubble formation during semi-solid high-pressure die casting processes were investigated. The Taguchi-based ‘grey relational analysis’ approach was used to identify the optimal process parameters. A method used in this study for finding out the importance of the controllable parameter on the performance characteristic is called the analysis of variance. It was observed that the optimal parameters are the liquid fraction of 50%, the plunger velocity at 2nd phase of 1 m/s and the angle between the vertical plane and the cavity of 60°.

Titanium alloy design and casting process development using an Integrated Computational Materials Engineering (ICME) approach

The application of titanium components is generally limited by their high raw material and manufacturing costs. In this paper, a lower cost cast titanium alloy based on the Ti-Al-Fe system has been designed using an ICME approach. The new alloy Ti-6Al-5Fe-0.05B-0.05C (all wt.%) significantly reduces raw material cost and demonstrates improved castability compared with the baseline Ti-6Al-4V alloy. The fine primary and secondary α phase microstructure in the new alloy, due to Fe partitioning, provides exceptionally high strength (1023 MPa yield strength and 1136 MPa ultimate tensile strength) and reasonable ductility (3.7% elongation) for structural applications. On the manufacturing front, the high cost multi-step investment casting process currently used can now be replaced with a low-cost permanent mold casting process using steel molds and a novel ceramic coating. An experimental casting setup, including an induction skull melting (ISM) system, a gravity tilt-pour system and a ceramic-coated H13 steel mold, has been used to produce near-net-shape permanent metallic mold castings with the new titanium alloy developed. Using this setup, and aided by casting process simulation, a prototype automotive connecting rod was cast successfully. The ZrO2 ceramic coating applied to the H13 steel mold was proven effective in minimizing the metal-mold reactions.

Numerical simulation and optimization of shell mould casting process for leaf spring bracket

Although the shell mould casting process has a wide range of application in many fields, the prediction of casting defects is still a problem. In the present work, a typical leaf spring bracket casting of ZG310-570 was fabricated by shell mold casting. The finite element model and ProCAST software were utilized for simulating the filling and solidification processes of the casting; and the formation mechanism of the gas pore, and shrinkage porosity defects were analyzed. The results indicate that the gas pore and shrinkage porosity defects are formed due to air entrapment, insufficient feeding and non-sequential solidification. Subsequently, through changing the position of risers, adding a connecting channel between the risers, and setting blind risers at the U-shaped brackets, an optimized gating and feeding system was established to improve the quality of the casting. After optimization, the gas pore and shrinkage porosity defects of the leaf spring bracket casting are effectively eliminated. The experiment results with the optimized casting process are in good agreement with the numerical simulation, which verifies the validity of the finite element model in the shell mould casting.

CFD simulation of direct chill casting process of magnesium alloy billets

This work demonstrates and simulates the industry scale direct chill casting of magnesium alloy (AZ31) billets processed under various conditions. The solidification mechanisms involved the conventional and melt-conditioned direct chill casting processes are simulated using the computational fluid dynamics. The heat flow and the solid-liquid interface are clearly identified for various casting speeds, depth of the rotor-stator device and the device geometry. The results also indicate that the shape and depth of the solid-liquid interface sump is sensitive to the casting parameters.

Computational Evolving Technique for Casting Process of Alloys

The challenging task of bringing together the advanced computational models (with high accuracy) with reasonable computational time for the practical simulation of industrial process applications has promoted the introduction of innovative numerical methods in recent decades. The time and efforts associated with the accurate numerical simulations of manufacturing processes and the sophisticated multiphysical and multiscale nature of these processes have historically been challenging for mainstream industrial numerical tools. In particular, the numerical simulations of industrial continuous and semicontinuous casting processes for light metal alloys have broadly been reinvigorated to investigate the optimization of casting processes. The development of advanced numerical techniques (e.g., multiscale/physical, finite zoning, and evolving domain techniques) for industrial process simulations including the transient melt flow, heat transfer, and evolution of stress/strain and damage during continuous casting processes have endeavored many new opportunities. However, smarter and broader improvements are needed to capture the underlying physical/chemical phenomena including multiscale/physical transient fluid-thermal-mechanical coupling and dynamic heat-transfer changes during these processes. Within this framework, the cooling system including its fluid flow and its characteristic heat transfer has to be modelled. In the research work herein, numerical studies of a novel transient evolving technique including the thermal-mechanical phenomena and Heat Transfer Coefficient (HTC) estimation using empirical and reverse analyses are presented. The phase change modeling during casting process including liquid/solid interface and also the implementation of dynamic HTC curves are also considered. One of the main contributions of this paper is to show the applicability and reliability of the newly developed evolving numerical simulation approach for in-depth investigations of continuous casting processes.

Effect of Pressure on Microstructure and Cooling Curves of A356 Aluminum Alloy During Solidification

During solidification process of metals and alloys in die casting, the cooling rate of molten material and also freezing time are affected by the heat transfer coefficient of metal/mold interface which is not constant at whole casting time. Therefore, determination of the cooling curves and the heat transfer coefficient is a crucial step in optimization of casting process by simulation because the resultant microstructure of cast components is affected by cooling rate. In the present study, the effect of applied pressure on cooling curves and microstructures of A356 aluminum alloy was investigated using a specially designed apparatus. Results showed that the cooling curves obtained from the central axis of cylindrical sample clearly represent the solidus and liquidus temperatures which can be used for determination of freezing time. It was observed that the solidification time decreases with increasing applied pressure. Also, the side thermocouples showed a temperature drop at the moment of applying pressure in which its magnitude increases with the increase in applied pressure. Moreover, the metallographic examinations showed that the microstructure of as-cast samples is refined with the increase in pressure. Also, the heat transfer coefficient obtained from experiments was used in the simulation of casting process and the simulated cooling curves were matched carefully with the experimental curves.

Predicting grain structure in high pressure die casting of aluminum alloys: A coupled cellular automaton and process model

Grain structure is one of the most important factors that affect the mechanical properties of metallic alloys. Accurate prediction of as-cast grain structure is critical in the design and manufacturing of metal castings using an integrated computational materials engineering (ICME) approach. In this paper, a three-dimensional (3-D) model based on cellular automaton (CA) and process simulation was developed for predicting grain size of components produced by high pressure die casting (HPDC) of aluminum alloys. The concurrent nucleation and growth of grains were considered in the model. A test specimen casting, consisting of different wall thicknesses, was simulated using a finite element based casting process simulation software ProCAST®. The thermal history of the simulated casting was extracted and used in subsequent mesoscale CA modeling. Different thermal conditions were used to simulate grain nucleation and growth during HPDC. The grain morphology, grain density and grain size were obtained by CA modeling. Electron backscatter diffraction (EBSD) analysis was performed on aluminum castings of different wall thicknesses under various cooling rates to validate the simulation results. The 3-D grain structure model is in excellent agreement with the experimental results, and can be used in ICME design and development of aluminum castings.

Numerical simulation of investment casting process of nickel-based alloy.

In this paper, we elaborated the nickel-based alloy type Hastelloy G30 and we analyzed it by techniques of characterization in order to interpret the results obtained through a computer simulation. The calculation of the thermo-physical properties of the alloy and the simulation of filling and solidification of the casting was performed by the software ProCAST. The validation of the numerical results was done by the following experimental techniques: optical microscopy and hardness test. In the center of the elaborate piece, the experimental results showed the appearance of porosity and leading to embrittlement of the alloy. According to the numerical simulation, this is caused by a fraction of the liquid that remains trapped in this area.

Numerical Simulation of Hot Tears Initiation and Growth in Castings

Hot tearing is a common defect encountered with casting process. Current experimental means can only analyze the final hot tearing morphology of castings, and the initiation and growth of hot tears are difficult to observe. In order to predict the initiation and propagation of hot tears, the thermo-mechanical simulation of casting process was conducted by using a thermal elastoplastic finite element model. A new prediction method of hot tearing based on isothermal strain on high temperature was proposed, and the tearing initiation location of the casting was determined. Based on the results of thermal stress field of the casting, the growth of the hot tearing was simulated by the extended finite element method (XFEM) combined with the adaptively refined meshing and sub-model technology. The simulation results show that hot tears tend to occur at the isolated liquid boundary of the casting, and propagate along the solid-liquid interface. The predicted tearing is consistent with the hot tearing observed in the actual casting, both in terms of location and morphology, which proves the reliability of the numerical simulation of hot tears initiation and propagation.

Atomistic simulation of the formation and fracture of oxide bifilms in cast aluminum

The formation and entrainment of double layer oxides (bifilms) in aluminum casting is inevitable due to the high oxidation rate of liquid aluminum and particularly turbulence during the mold filling process. The final mechanical properties of the aluminum castings suffer from these inclusions but neither the formation process nor fracture mechanism is fully understood due to the difficulty of in-situ observation on nano-scale aluminum oxide thin film. To understand the impact of bifilms on the fracture mechanism at different bifilm formation stages and the aging processes, atomic level bifilm slab models were built according to their formation history. ReaxFF reactive forcefield-based molecular dynamics (MD) method was used to simulate the formation and deformation of different types of bifilms. The MD simulations showed that an incomplete “healing” process happened at the oxide/oxide interface during bifilm formation and the fracture occurred at the Al/oxide interface instead of the oxide/oxide interface. When the oxide transformed from amorphous to α-Al2O3 due to aging, the fracture energy increased from 0.43 J/m2 to 0.53 J/m2. With 30% coverage of hydroxyl group surface contamination, the –OH terminated oxide bifilm fractured at the oxide/oxide interface and the corresponding fracture energy dropped to 0.30 J/m2. This is most likely due to the H2 bubbles being trapped in the aluminum oxide bifilm interface. To facilitate multiscale modeling, such as casting process simulation and component durability analysis, the MD predicted oxide bifilms fracture energy and fracture strength were converted to cohesive zone parameters, via a simple size bridging relationship.

Virtual Casting: State of the Art in Metal Casting Simulation Tools

The demands on the productivity and robustness of metal casting processes for high quality components are continuously increasing. Moreover, the financial considerations necessitate meticulous and reliable planning of the entire casting process before it is actually put into practice. A holistic approach to perform cradle to grave analysis of cast products is simulation-based metal casting. This method allows engineers to model, verify, and validate the process followed by its optimization and performance prediction in virtual reality. This paper provides insights on state of the art in simulation-based metal casting with reference to some case studies. Casting simulations software, mathematical models and solution methods, and casting process simulation together with the results obtained are clearly explained. The current practices revealed extensive utilization of simulation packages for defect minimization, yield maximization, and improved quality. The ongoing research on integration of casting simulations with mechanical performance simulations makes it possible to analyze the serviceability of cast parts. The reliability of cast part in service with dynamic loading of varying thermal and mechanical load cycles can be predicted through this integration. However, more rigorous work is needed in this area, particularly by developing the reliability prediction modules embedded in advanced simulation tools.

Virtual Casting: State of the Art in Metal Casting Simulation Tools

The demands on the productivity and robustness of metal casting processes for high quality components are continuously increasing. Moreover, the financial considerations necessitate meticulous and reliable planning of the entire casting process before it is actually put into practice. A holistic approach to perform cradle to grave analysis of cast products is simulation-based metal casting. This method allows engineers to model, verify, and validate the process followed by its optimization and performance prediction in virtual reality. This paper provides insights on state of the art in simulation-based metal casting with reference to some case studies. Casting simulations software, mathematical models and solution methods, and casting process simulation together with the results obtained are clearly explained. The current practices revealed extensive utilization of simulation packages for defect minimization, yield maximization, and improved quality. The ongoing research on integration of casting simulations with mechanical performance simulations makes it possible to analyze the serviceability of cast parts. The reliability of cast part in service with dynamic loading of varying thermal and mechanical load cycles can be predicted through this integration. However, more rigorous work is needed in this area, particularly by developing the reliability prediction modules embedded in advanced simulation tools.

Simulation of casting process: case study on the gating and feeding design for outlet diaphragms of iron ore ball mill

In this paper, the sand casting process was evaluated using ProCAST simulating software and practical experience for manufacturing of the high chromium stainless steel outlet diaphragms used in iron ore ball mill. In the simulation practice, the effects of feeding and gating designs on the liquid flow, heat transfer and solidification phenomenon were evaluated to minimize the liquid surface turbulence during filling of the mold cavity and the shrinkage porosity formation during the liquid solidification in the mold. The effects of different gating ratios and number of feeders were numerically studied using different indicators in the software such as linear velocity, niyama criteria, fraction solid and shrinkage porosity. Further, the optimal design obtained by simulating process was empirically examined. The simulation results showed that the 1:3:4 gating ratio is the proper gating system that it obtains an unpressurized fluid flow without any surface turbulent of the liquid steel in the filling step. In addition, the simulation of solidification phenomenon was indicated that four feeders are required to eliminate of the shrinkage porosities. The empirical casting examination shown the optimal design by the simulation is proper for manufacturing of the steel part without critical defects.