Casting Solidification Process Research Articles

Design and Development of LM24 plate Casting using Solid Cast Simulation Technique

Abstract: This research deals with the elimination of defects in aluminium alloy castings and enhancement in the casting yield and quality. The main intention of the work is to improve the quality of a cast component using Computer Aided Casting Simulation Software. SOLID Cast simulation software is used for simulating the solidification process of casting and visualizing outputs showing possible problematic areas or defects which may occur in the cast product. Plate Castings of aluminium alloy - LM 24 are produced with different designs of gating systems and tested for defects like porosity using Archimedes immersion Technique and also Radiographic testing is used to check the quality of the castings. The produced castings are observed to be sound, and the results obtained are in agreement with the simulation results. Hence it is verified that solidification simulation helps in improving the quality of castings without any shop-floor trails. Casting yield and percentage porosity values are determined for 12 castings produced with different gating systems. The best results are observed to be produced by the castings having a 1-Ingate system in horizontal or lateral positions.

Analysis of Cooling a Printed 3D Mold Using a Casting and Solidification Simulation of a CuSn20 Bronze Bell Casting

The work done in this study is a preliminary investigation into the possibility of modelling the filling and solidification process of castings in molds made with the additive method. The work originated from an experiment to produce a bronze casting with a high tin content in an additive mold. The mold filling and solidification simulation was carried out in the MAGMASO FT program, and the lambda thermal conductivity coefficient used in the program’s material database was corrected based on the actual temperature values of the printed form. The results were compared with the modeling results for the physical properties of furan molds based on the program database. The microstructure of the castings obtained in the compared forms was assessed.

Optimization Analysis of a Deep Learning-Based Model for Predicting Temperature Fields in the Solidification Process of Castings

Optimization Analysis of a Deep Learning-Based Model for Predicting Temperature Fields in the Solidification Process of Castings

A variational inequality approach for the numerical simulation of steel solidification of two-phase continuous casting process

In this paper, we study a nonlinear parabolic type model with an inequality constraint on the solution describing the phase liquid-solid heat transfer during the solidification process in continuous casting. We consider a semi-discretization with respect to time (implicit Euler method in time) of the studied thermal problem. We have a sequence of stationary constrained problems. Reformulating the problem into a variational inequality problem and thanks to the approximation (linearization) of the nonlinear boundary condition (radiation condition) and appropriate assumptions, we establish a result of existence and uniqueness of the solution of the stationary problem. We also consider a multivalued formulation of the same problem allowing the analysis of the behavior of the iterative relaxation algorithm used for the numerical solution of the discretized problem. Finally, numerical simulations are displayed.

Analysis of the solidification process of castings depending on their configuration and material of the mold

Analysis of the solidification process of castings depending on their configuration and material of the mold

Effectively mitigated macro-segregation and improved tensile properties of twin-roll cast Al–Mg–Si (6022) alloy strips via Zr addition

It is a great challenge to avoid the central macro-segregation during the solidification process of twin-roll casting (TRC), which seriously limits the mechanical properties of 6xxx series Al alloys. In this study, we find that the trace addition of 0.08 wt% Zr to Al-1.0Mg-1.2Si (6022) alloy can effectively promote the columnar-to-equiaxed transition and refine the solidification microstructure (particularly α-Al dendrites and π-AlFeMgSi phase). More importantly, the macro-segregation of the as-cast TRC strip is well mitigated with Zr addition. The refinement of α-Al dendrites and π-AlFeMgSi phase may be attributed to the formation of (Al, Si)3Zr phases when introducing Zr element, which can act as heterogeneous nucleation sites for both of them. The secondary dendrite arm spacing (SDAS) in the central region of strips is sharply decreased from ∼33 to ∼16 μm, which facilitates the incorporation of more solute elements into the Al matrix, thus increasing the partition coefficients of Mg (kMg) and Si (kSi) elements. As a result, there are fewer solute atoms in the residual liquid phase during the final stage of solidification, leading to the alleviation of central macrosegregation. The tensile properties of the as-cast, solid solution treated (T4) and paint baking treated (T6) alloys are synchronously optimized with Zr addition. In particular, the fracture elongation of the T4 alloy is increased from ∼30.9% to ∼33.4%, indicating excellent formability. The yield strength of the T6 alloys is increased from ∼227 MPa to ∼239 MPa, satisfying the more demanding service requirements. This work can provide a strategy for the effective control of macro-segregation and produce alloy strips with high performance by the TRC process.

Study of Solidification Process of Ni-Based Superalloy Castings Manufactured in Industrial Conditions with the Use of Novel Thermal Insulating Module Technique

The solidification process of IN713C Ni-based superalloy rod castings made by the investment casting method without and with the use of novel insulating module applied on the ceramic mold was studied in this article. The design of the cone-shaped insulating module was developed based on numerical simulations of the distribution of local solidification parameters, ensuring the lowest centerline shrinkage porosity along the castings. The effectiveness of the design of the insulating module was tested in industrial casting trials. It was found that the use of a novel insulation module increases temperature gradient G and decreases cooling rate v, thus leading to a favorable increase of the Niyama criterion value (Ny = G/√v) and also ensuring directional solidification of the casting rod compared to the process where thermal insulation was not used. In this way, the centerline shrinkage porosity was removed, maintaining the equiaxed grain structure of the castings. The presented results show that it is possible to use the same insulating module multiple times, in the subsequent manufacturing processes, to control the solidification of Ni-based superalloy precision castings in industrial conditions.

Effect of double-layer-shell sand mold on the residual stress of casting and itself crack tendency

Controlling the solidification of metals is the most essential to prevent defects and realize required quality and mechanical properties of castings. However, the conventional sand mold structure is generally dense and thick, which makes it difficult to accurately control the solidification process of castings. The hollow sand molds prepared by 3D printing technology provide the possibility to adopt measures to control the cooling of castings, but the crack on the mold itself is a new problem. Here, a kind of double-layer-shell structure of hollow sand mold is designed. It is proved that it can effectively reduce the crack tendency of the hollow sand mold, the residual stress of the casting decreases as well. Both experiment and numerical simulation results unveil the mechanism.

Gradient-controlled freeze casting of preceramic polymers

Solidification is the foundation upon which freeze casting is built, and this work seeks to understand the solidification process in freeze casting, especially with respect to the growth of dendrites. To this end, two solidification parameters, freezing front velocity and temperature gradient, were independently controlled using a gradient-controlled freeze casting setup to investigate the effects of each parameter. Changes in dendritic pore size and morphology with solidification parameters were investigated by scanning electron microscopy and mercury intrusion porosimetry. The results agree with dendrite growth theory. The theory of constitutional supercooling is used to describe the morphological changes of dendritic pores to cellular pores by the control of freezing front velocity, temperature gradient, and preceramic polymer concentrations.

Ellipsoidal equiaxial grain of 7055 aluminium alloy in vacuum centrifugal casting

The 7055 aluminium alloy cast tube was prepared by vacuum centrifugal casting technology. The radial and axial microstructure of the alloy was observed by optical microscope and electron probe. The results showed that the as-cast microstructure is uniform and fine equiaxed, and intermetallic compounds are distributed at grain boundaries. In addition, the circumferential grain size and the number of intermetallic compounds were larger than that in the axial direction. The grains are ellipsoidal and equiaxed. This is the result of directional heat conduction, solid solubility migration and redistribution of solute during the solidification process of centrifugal casting. After homogenisation, the grains tend to be spherical equiaxed crystals, which is the result of different degrees of recrystallisation in the circumferential and axial directions.

Casting Process at Roll Bite in Strip Cast Using Vertical-Type High-Speed Twin-Roll Caster

The solidification process in strip casting using a vertical-type high-speed twin-roll caster was clarified by inserting a 0.1 mm diameter K-type thermocouple into a strip during casting. The roll speeds of the copper rolls were 10 m/min and 30 m/min, and the roll loads were 5 kN and 20 kN. Al-Si alloys with a Si content of 2%, 6%, and 12% were used to investigate the influence of latent heat and viscosity in the semisolid state. The strip temperature increased after exiting the rolls. This indicated that the inside of the strip had not completely solidified at the roll bite, and secondary cooling was necessary to rapidly solidify the inside of the strip. The distance from the roll bite to the solidification starting position ranged from 30 mm to 63 mm. The cooling rate and degree of supercooling increased as the Si content decreased. The cooling rate ranged from 400 °C/s to 4000 °C/s. The cooling rate and degree of supercooling decreased as the viscosity of the semisolid increased.

Design and application of a multichannel “cross” hot tearing tendency device: A study on hot tearing tendency of Al alloys

Hot tearing is one of the most serious defects during the casting solidification process. In this study, a new type of multichannel “cross” hot tearing device was designed. The hot cracks initiation and propagation were predicted by the relationship between temperature, shrinkage force and solidification time during the casting solidification process. The reliability and practicability of the multichannel “cross” hot tearing device were verified by casting experiments and numerical simulations. The theoretical calculation based on Clyne-Davies model and numerical simulation results show that the hot tearing tendency decreases in the order: 2024 Al alloy>Al-Cu alloy>Al-Si alloy at a pouring temperature of 670 °C and a mold temperature of 25 °C. Feeding of liquid films at the end of solidification plays an important role in the propagation process of hot tearing. The decrease of hot tearing tendency is attributed to the feeding of liquid film and intergranular bridging.

Research methods and influencing factors of interfacial heat transfer during sub-rapid solidification process of strip casting

Research methods and influencing factors of interfacial heat transfer during sub-rapid solidification process of strip casting

A spectrum-domain instance segmentation model for casting defects

Accurate segmentation of casting defects plays a positive role in the quality control of casting products, and is of great significance for accurate extraction of the mechanical properties of defects in the casting solidification process. However, as the shape of casting defects is complex and irregular, it is challenging to segment casting defects by existing segmentation methods. To address this, a spectrum domain instance segmentation model (SISN) is proposed for segmenting five types of casting defects with complex shapes accurately. The five defects are inclusion, shrinkage, hot tearing, cold tearing and micro pore. The proposed model consists of three sub-models: the spectrum domain region proposal model (SRPN), spectrum domain region of interest alignment model (SRoIAlign) and spectrum domain instance generation model (SIGN). SRPN uses a multi-scale anchoring mechanism to detect defects of various sizes, where the SSReLU and SCPool functions are used to solve the spectrum domain gradient explosion problem and the spectrum domain over-fitting problem. SRoIAlign uses the floating-point quantization operation and the tri-linear interpolation method to quantize the 3D proposals to the feature values in an accurate manner. SIGN is a full-spectrum domain neural network applied to 3D proposals, generating a segmentation instance of defects in a point-wise manner. In the experiments, we test the effectiveness of the proposed model from three aspects: segmentation accuracy, time performance and mechanical property extraction accuracy.

Effect of pouring temperature on hot tearing susceptibility of Al-Cu cast Alloy: Casting simulation

Al-Cu alloy more prone to hot tear in the foundry metals in casting process. It is widely using in structural, aerospace, marine and automotive industry. Defect-free casting is being challenge in the foundry. In the present investigation, the hot tearing of the molten Al-Cu cast alloy is reported by varying the pouring temperature at 700 °C, 750 °C and 780 °C by means of casting simulation. It has a direct impact on production cycle time, casting internal quality, material utilization, and gating design optimization. Simulation was performed by AutoCAST-X software; it enables directional solidification and feed metal paths. In the simulation set up have been considered green sand mould system with the wooden pattern, and the steel metallic cores are facilitated in the cavity to contrast the temperature while solidification process; as a result pouring temperature is subject to crack susceptibility. The results revealed that the dependence on pouring temperature is a key factor for the prediction of hot tearing susceptibility. The microscopic cracks were observed in casted part by simulation. The Casting simulation forecast the hot spot zone in casting solidification process to facilitate the riser for compensation of shrinkage allowance of molten metal. Simulation enhances the material utilization, quality of casting, productivity and optimization of gating design. The relation of pouring temperature was developed with solidification time.

Numerical Simulation of Latent Heat of Solidification for Low Pressure Casting of Aluminum Alloy Wheels

In this paper, aiming at focusses on many problems existing in the mathematical model of temperature change in the low-pressure casting solidification process of aluminum alloy wheel hub, there is a big gap between the simulation and the actual temperature change, which affects the research on the solidification defects of the wheel hub. In order to study the solidification behavior of aluminum alloy hub in low-pressure casting process, the mathematical model describing the temperature change in the process of casting solidification is established by using different solidification latent heat methods. through finite element simulation and experiment, the temperature change in the process of aluminum alloy (A356) solidification is obtained to compare the difference between the temperature change described by different mathematical models, simulation and experiment. The results show that the temperature numerical model of "the temperature compensation heat capacity method" proposed in this paper is most consistent with the simulation temperature change during the solidification process of the aluminum alloy wheel in the simulation mold, which lays a good theoretical foundation for the study of the low-pressure casting process of the aluminum alloy wheel hub.

Macro-physical field of large diameter magnesium alloy billet electromagnetic direct-chill casting: A comparative study

Abstract A comprehensive two-dimensional axisymmetric mathematical model that couples transient electromagnetic force with fluid flow, heat transfer, and solidification was established to describe the interaction of multiphysics field during DC casting. The melt flow, heat transfer, and solidification characteristics under differential phase pulse magnetic field and differential phase low-frequency electromagnetic field (DP-PMF and DP-LFEF) were numerically investigated by means of numerical simulation during electromagnetic direct-chill (DC) casting of AZ31 alloy at the same casting conditions. The effects of differential phase electromagnetic fields on Lorentz forces distributions, melt flow, heat transfer, and liquid sump shape were discussed systematically. Based on measured current waveform, the results were compared with those obtained without magnetic field (MF) and under conventional pulse magnetic field (PMF) and low-frequency electromagnetic field (LFEF) under the same conditions. The results show that the application of magnetic fields can significantly change the solidification process of DC casting. Differential phase magnetic fields (DP-LFEF and DP-PMF) can effectively reduce the temperature of the melt in the liquid sump, and the shallower liquid sump depth can be obtained under the differential phase magnetic fields. A large velocity vibration amplitude and a lower temperature are available simultaneously under DP-PMF, resulting in more uniform temperature distribution.

Effects of metallurgical factors on reticular crack formations in Nb-bearing pipeline steel

AbstractMicroscopic morphologies of reticular cracks in Nb-bearing pipeline surfaces are shown in this work. A decarburization layer, oxidized round spots, and the distributions of residual elements are each detected to better understand the mechanisms of reticular crack formations. The results show that reticular cracks are discontinuously distributed and filled with iron oxide. The oxidized round spots near the crack sides are larger and more intensive than steel matrix, with primary chemical compositions of Fe, Mn, and Si oxides. There is no obvious enrichment of Cu, Cr, or Sn near the crack zones. The formation of reticular cracks occurs prior to both decarburization and the formation of oxidized round spots. The ferrite potential (FP) of the examined pipeline steel is 1.05, which leads to a higher relative crack susceptibility. It is concluded that reticular cracks are generated during the continuous casting solidification process due to the extension of intergranular microcracks along grain boundaries under the abnormal conditions of the continuous casting process.

In situ steel solidification imaging in continuous casting using magnetic induction tomography

The solidification process in continuous casting is a critical part of steel production. The speed and quality of the solidification process determines the quality of the final product. Computational fluid dynamics (CFD) simulations are often used to describe the process and to design its control system but, so far, there has been no tool that provides an online measurement of the solidification front of hot steel during the continuous casting process. This paper presents a novel magnetic induction tomography (MIT) solution, developed in the EU-funded SHELL-THICK project, to work in a real casting setting and to provide a real-time and reliable measurement of the shell thickness in a cross section of the strand. The new MIT system was installed at the end of the secondary cooling chamber of a casting unit and tested over several days in a real production process. MIT is able to create an internal map of the electrical conductivity of hot steel deep inside the billet. The image of electrical conductivity is then converted to a temperature profile that allows the measurement of the solid, mushy and liquid layers. In this study, such a conversion is done by synchronizing in one time step the MIT measurement and the thermal map generated with the actual process parameters available at that time. The MIT results were then compared with the results obtained with the CFD and thermal modelling of the industrial process. This is the first time in situ monitoring of the interior structure has been carried out during a real continuous casting.

Temperature field model and control strategy in gravity casting process.

Temperature control is one of the most important processes during aluminum (Al) alloy engine cylinder head product casting. An improper temperature control may result in no uniformity and microstructure defects in casting parts and give rise to high defect ratio. In this paper, a mathematical model with high nonlinearity, strong coupling, and less uncertainty is developed for the solidification process in Al alloy casting. The interfacial heat transfer coefficient is combined with the mold structure comprehensively to build the temperature-structure model, and the characteristics of the uncertainty conversion are also used in order to achieve optimal temperature control during the solidification process. The cloud model integrated with Proportion-Integral-Differential (PID) temperature control system enables evaluation of the uncertainty conversion quantitatively. By inputting the temperature error and the temperature error rate, the PID inference is output through the cloud inference engine to achieve the optimal temperature curve. The superiority of the control algorithm was verified on a customized experimental platform with the temperature control system. Compared with manual operation and traditional PID control, the result shows that the error of the cloud model control is lower than the manual operation and traditional PID control. The experimental results also suggest that the performance of our cloud model is better than that of the manual operation model and the traditional PID control model regarding to stability and controllability.