Thin-walled Castings Research Articles

Numerical Simulation of Lost-Foam Casting for Key Components of A356 Aluminum Alloy in New Energy Vehicles.

The intricate geometry and thin walls of the motor housing in new energy vehicles render it susceptible to casting defects during conventional casting processes. However, the lost-foam casting process holds a unique advantage in eliminating casting defects and ensuring the strength and air-tightness of thin-walled castings. In this paper, the lost-foam casting process of thin-walled A356 alloy motor housing was simulated using ProCAST software (2016.0). The results indicate that the filling process is stable and exhibits characteristics of diffusive filling. Solidification occurs gradually from thin to thick. Defect positions are accurately predicted. Through analysis of the defect volume range, the optimal process parameter combination is determined to be a pouring temperature of 700 °C, an interfacial heat transfer coefficient of 50, and a sand thermal conductivity coefficient of 0.5. Microscopic analysis of the motor housing fabricated using the process optimized through numerical simulations reveals the absence of defects such as shrinkage at critical locations.

A Method for Straightening Distorted Giga-Cast Large Thin-Walled Components.

Giga-casting, a revolutionary approach for manufacturing large, single-piece car body components from aluminium, has emerged as a potential game-changer in the automotive industry. However, these large, thin-walled castings are prone to distortions during solidification and heat treatment processes. Straightening these distortions is crucial to ensure structural integrity, facilitate downstream assembly, and maintain aesthetic qualities. This paper proposes a novel method for straightening giga-cast components using a multi-pin straightening machine. The machine's versatility stems from its ability to adapt to various geometries through multiple strategically controlled straightening pins. This paper introduces the concept of a "straightening stroke decision algorithm" to achieve precise straightening and overcome the challenges of complex shapes. This algorithm determines the stroke length for each pin, combining a polynomial model representing the global stiffness of the component with a machine learning model that captures the stiffness changes arising from the current geometry. The effectiveness of the proposed approach is evaluated through comprehensive numerical experiments using finite element analyses. The straightening performance is assessed for the straightening algorithm with different machine learning models (deep neural network and XGBoost) and compared to a traditional optimisation method. The proposed surrogate models decided the straightening strokes so that the maximum remaining distortion became 0.02% of the largest dimension of each target geometry. The results of the numerical experiment showed that the proposed straightening method is suitable for straightening distortion in large thin-walled components.

Effect of secondary orientation on the microstructures in thin-walled castings of nickel-based single-crystal superalloys

With the increasing turbine inlet temperature of aero-engine, the requirement of temperature capacity of turbine blades is more stringent. A variety of complex cooling structures have been designed, among which the micro cooling represented by lamilloy is the latest development. At present, the thickness of lamilloy turbine blade is 0.5 mm or less. The reason for performance degradation caused by thin-walled is still controversial and the understanding of dendrite growth behaviour under space constraints is insufficient. In this study, 0.75 mm wall thickness nickel-based superalloy DD403 samples were cast by high-rate directional solidification. The growth and evolution of dendrites in plank-shaped specimens with different secondary deviation angles were investigated. The variation of dendrite spacing and the arrangement of dendrites under different secondary deviation angles were studied. It is found that the primary dendrite arm spacing in the thin-walled region decreased with the increase of the secondary deviation angle, but there was no significant change in the average size of γ′ phases and elements segregation.

ANALISA CACAT PENYUSUTAN MATERIAL FCD450 DAN ALUMINIUM A356 PADA PROSES PENGECORAN STANG PISTON DINDING TIPIS MENGGUNAKAN SIMULASI

Metal castings are generally used to manufacture machine parts with complex shapes, including the manufacture of thin wall components. Thin wall casting (TWC) is a casting method for producing lightweight component objects by thinning the component walls such as plates or parts of the cast object that can be thinned. Thin wall ductile iron (TWDI) is nodular cast iron, casted through TWC. TWDI makes nodular cast iron possible to compete with aluminum when compared to the weight between these two materials. The application of aluminium to TWC aluminum will lead to lighter components production. The main reason aluminum is replacing cast iron in the automotive field is the inability or lack of interest on the part of cast iron manufacturers to produce lightweight iron components, which is TWDI. The use of simulation in the casting process helps to show the whole process in casting. This research was conducted to determine the effect of using the TWC design made for nodular cast iron on aluminum and the defects formed by using this design through software simulation. The casting design used uses Sulamet-Ariobimo et al. casting design [10] which has succeeded in producing connecting rod components using TWDI on an industrial scale. The simulation software used is the Altair Inspire Cast simulation (serial number: 680344) owned by PT. Wisma Teknik Lestari. Simulations were carried out for both FCD450 and A356 materials. Based on the results of the shrinkage simulation, there are shrinkage defects in the TWDI material and there are no shrinkage defects in Aluminum A356. This is due to the solidification characteristics and cooling rate of the two materials, where the cooling rate for TWDI is 3.84E+4 J, and 8.85E+4 J for Aluminum A356. In addition, based on the solid fraction simulation results, there are hotspots on cast components for TWDI materials which result in shrinkage defects in the components

Unveiling the failure mechanism on creep response of a casting Ni-based superalloy in thin-wall thickness

With the improvement of thermal efficiency and the lightweight tendency of engine blades, Ni-based superalloy is widely used owing to its excellent performance in high-temperature atmospheres. This work studied the effects of surface oxidation, internal environmental attack, and matrix damage on the failure mechanism in a thin-walled casting Ni-based superalloy at 980 °C/160 Mpa. At the edge of the fracture, the sample suffered a severe environmental attack, resulting in the oxidation-affected zone forms. However, the loss of effective bear area induced by surface damage could not be the main reason for the sample's failure. At the interior of the matrix, voids were preferably initiated at the interface of MC carbides. As the increase of creep deformation, dynamic recrystallization (DRX) occurred at the tip of the voids, which increased the transverse grain boundaries and promoted crack propagation. Moreover, the DRX provided a short penetration path for the nitrogen, causing internal nitridation with AlN and Ti(Ta)N to precipitate. EBSD analysis confirmed that nitrides induced significant dislocations to accumulate at the boundaries of nitrides/γ, accelerating the failure of the sample.

A multimodal data-driven design of low pressure die casting gating system for aluminum alloy cabin

The design of gating systems for large and complex thin-wall castings requires the application of empirical equations and a substantial number of iterative experiments. In this study, a novel machine learning-based design strategy is proposed for the gating system of large and complex thin-walled castings. The gating system of castings was estimated using a multi-input multi-output neural network model, which incorporated visual, textual, and numerical multimodal features. The R2 value of the model accuracy reached 0.981, and the predicted parameters for the gating system were a slot runner width of 27 mm, a slot runner length of 48 mm, a riser runner diameter of 60 mm, and the number of riser runners of 8. The EasyCast and Procast simulation software were utilized for comparison and verification, resulting in a smooth filling and the achievement of sequential solidification. Finally, the mechanism of casting defects is discussed using the solidification phase-field model of EasyPhase system, elucidating how the alloy system can serve as a distinguishing feature in machine learning models that impact gating system parameters. This strategy is anticipated to enhance the efficiency of low pressure die casting process design, thereby serving as a valuable reference for intelligent process design in low pressure die casting.

Production of thin-walled cast iron castings of frame-cellular and ordered honeycomb structures

Production of thin-walled cast iron castings of frame-cellular and ordered honeycomb structures

Effect of barbotage refining time and recycled scrap content on the microstructure of EN AC 44200 alloy

The article presents the results of research on the effect of the barbotage refining time and recycled scrap content on selected properties, the microstructure and the degree of gasification of the EN AC 44200 alloy (EN AC-AlSi12). The input material consisted of various proportions of pure ingots and scrap; the scrap contents were 80%, 70% and 60%, respectively. Each batch of material was subjected to different refining times, which were 0, 7, 9 and 15 min, respectively. Microstructure studies were conducted with the techniques of light and scanning electron microscopy. Additionally, the distribution of pores in the volume of the material and their proportion were determined by means of the X-ray computed tomography method. In addition, the hardness and degree of gasification depending on the refining time were performed. It was proved that the refining process fosters homogenization of the microstructure and reduces porosity. Moreover, extending the refining time has a positive effect on reducing the porosity of thin-walled castings and reducing the level of outgassing of the alloy.

On the Liquid Portion Composition Deviation in the RheoMetal Process

Semisolid processing can provide an avenue to reduced rejection rates during casting and increased capability of thin-walled castings leading to improved resource efficiency and reduced climate impact. In the RheoMetalTM process, the slurry is formed far from equilibrium. A consequence to the deviation from equilibrium is that conventional guidelines for process stability may not give the correct appreciation of the process window, nor on the correct solid fractions generated. The solid fraction provides the slurry properties and its dependence on temperature should in theory provide the stable process window. This is discussed using data from literature and an alternative approach to identify the process stability window is given.

Experimental Investigation and Modeling of Force-Induced Surface Errors for the Robot-Assisted Milling Process

A series of experiments were performed aiming at controlling milling force-induced surface errors in the robot-assisted milling process, for the sub-area of the multi-stiffener reinforced inner wall of complex cylindrical thin-walled casting parts, to investigate the relationship between surface errors, milling forces, and robot-assisted milling parameters. Firstly, based on the design of experiments (DoE) method, milling forces and surface errors were investigated based on a series of experiments with different groups of milling parameters. Secondly, the modeling of milling forces, surface errors, and milling parameters was realized by means of response surface methodology (RSM), then the parametric expression was obtained of the robot-assisted milling process. Finally, the parameters of the milling process toward the surface error were obtained based on an evolutionary algorithm. The results show that the surface errors are different for the different milling styles of down milling and up milling. In up milling processes, the surface errors are positive, and the actual material removal amounts are generally higher than the nominal ones, while negative in down milling processes. The surface errors induced by milling forces can be effectively controlled and reduced using process optimization in the robot-assisted milling process, while maintaining relatively high milling forces and high machining efficiency. This provides theoretical support for industry applications.

Phase-field modeling of austenitic steels used in turbines

The performance in hydro-electric turbine casting and repair requires understanding of how process parameters and chemistry selection affect solidification microstructures. The aim of this study is to provide a quantitative phase-field formulation for process-microstructure relationships that seeks to model stainless steels. We have developed a phase-field model to simulate austenitic stainless steel solidification under experimental thermal histories. To this end we look at a pseudo-binary approximations for numerical efficiency. The pseudo-binary formulation is underpinned by the alloying element equivalent value, a metallurgical tool used to analyze the microstructural impact of “minor” alloying elements in stainless steels. For model validation we develop thin wall casting experiments to measure the thermal history and chemistry controlled microstructure. The models incorporate a thermodynamic parameterization and are linked to a thermal-phase transformation model which represents the experimentally measured thermal history. The results display a good agreement with the primary branch spacing and cellular to dendritic transition of the casting experiments. These models and software provide the basis for future expansion to include more complex microstructures.

Numerical Simulation and Optimization of Investment Casting for Complex Thin-walled Castings

Numerical Simulation and Optimization of Investment Casting for Complex Thin-walled Castings

Structural stability of thin-walled austempered ductile iron castings

The structural stability of ausferrite in thin-walled Austempered Ductile Iron (ADI) castings with 5 mm wall thickness is compared to a reference casting with 25 mm wall thickness. The thin-walled and reference castings were first austenitized between 850 and 925 °C, and then austempered between 250 and 380 °C. X-ray diffraction (XRD) investigations with changing temperature were performed between − 260 up to + 450 °C to investigate the change of phase fraction, lattice parameters and strain in ausferrite. The role of the austenitization temperature on structural stability and homogeneity of the investigated ADI castings has been provided. In addition, the problem of the occurrence of “blocky” high-carbon austenite that was not completely involved during austempering, has been taken into account. Finally, it has been shown that the thin-walled castings provided higher structural homogeneity and stability if compared to the reference castings.

Influences of Material Selection, Infill Ratio, and Layer Height in the 3D Printing Cavity Process on the Surface Roughness of Printed Patterns and Casted Products in Investment Casting

As 3D-printed (3DP) patterns are solid and durable, they can be used to create thin wall castings, which is complicated with wax patterns because of the wax's fragility and high shrinkage ratio. According to this study's experiment results, polylactic acid (PLA), polyvinyl butyral (PVB), and castable wax (CW) are suitable materials for preparing investment casting (IC) cavities. The results indicate that the casting product with the highest-quality surface is obtained using a cavity prepared using a CW-printed pattern. PLA- and PVB-printed patterns provide a good surface finish for casted products. In addition, the roughness of both the printed and casted surfaces increases as the printing layer height increases. The roughness of the casted surface varies from 2.25 μm to 29.17 μm. This investigation also considers the correlation between the infill ratio and mechanical properties of PLA-printed patterns. An increase in the infill ratios from 0% to 100% leads to a significant increase in the tensile properties of the PLA-printed pattern. The obtained results can be practically used.

An overview on Thin Wall Cast Iron Castings and its Applications in Automotive Industry

An overview on Thin Wall Cast Iron Castings and its Applications in Automotive Industry

The effects of I-Beam thickness to microstructure and compression load of thin wall ductile iron connecting rod

Lighter automotive components are needed to reduce energy consumption. The manufacturing processes of the components should also consume less energy and be environmentally friendly. Aluminum is a lightweight material, but the manufacturing processes consume a lot of energy. Ductile iron has outstanding design flexibility and applying a thin wall casting technique to the ductile iron components will reduce the weight and make it possible for ductile iron to compete with lightweight materials. The achievement of making a 3 mm I-beam thickness connecting rod which fulfills the design requirement in previous research has encouraged a further reduction in the I-beam thickness. This action is taken to enhance the weight reduction gained from the connecting rod. The aims of this work are to ensure the repeatability resulting from the design of 3 mm I-beam thickness and the ability of the casting design to produce the 2 mm I-beam thickness. Solidification rates in thin wall casting are critical due to the differences in thicknesses in the product. It is also to analyze the effect of I-beam thickness on the compression load. Two types of I-beams, which differ in their thickness, 3 mm and 2 mm, were produced in the foundry scale. All the I-beams were characterized by their microstructure and compression load. The compression load was measured using the tensile method. The results of microstructure observations revealed that the microstructure in I-beam is different from the one in the end rod except for one casting position, while the result of compression load shows a similar value for average compression load between the 3 mm and 2 mm which fulfill the compression load requirement of connecting rod. The casting designs built in this research can produce thin wall ductile iron (TWDI) connecting rods that could stand similar load with the original one.

On the Prediction of Material Fracture for Thin-Walled Cast Alloys Using GISSMO

Thin-walled cast alloys are one of the most significant enhancements for automotive applications. This paper aims to evaluate the applicability of the “Generalized Incremental Stress-State dependent damage MOdel” (GISSMO) in modern thin-walled cast alloys. Comprehensive experimental tests are carried out to assess the instability and fracture strains on three thin-walled structure alloys that are commonly used. Numerical studies are conducted on the two most common modeling methods, shell-based and tetrahedral models. The parameters in GISSMO are calibrated using theoretical fitting and the inverse analysis approach. Comparisons of the shell-based and tetrahedral-based models with the test results and shell elements are carried out. The characteristics of the two modeling methods are discussed, including element formulas, extrapolating the hardening curves, and mesh-size dependency. It is evaluated that both modeling methods could be applied to thin-walled cast alloys in satisfying agreement.

Use of experimental casting equipment for research of castings crystallized through individual cooling procedures

The research is devoted to development of experimental foundry pattern equipment, allowing to obtain two or more castings in a sand-loam mould; these casting are crystallized via individual cooling procedures within structurally sensitive intervals (dendrite, eutectic crystallization and recrystallization). Influence of scale factor is excluded in this case and it makes possible to obtain control and pilot castings, which have equal sizes; influence of chemical composition is excluded as well, because all castings located in a mould have common gating and feeding system. It provides the same temperature and casting speed for two or more castings in one mould with different compositions and technological properties of moulding mixtures for each of the comparing castings. Thereby, variable cooling rate, which is individual for each casting obtained in the experimental mould, remains the main factor having influence on forming of structure, mechanical and operating properties of cast metal. Possibility of investigation of rise of mechanical and operating properties of castings owing to only adjusting of cooling rate without use of alloying and modification appears in this case. Increase of the cooling rate in local temperature-time crystallization intervals is provided by blowing with cooling gases which are fed in the mould via the stand (receiver). Retarding of cooling rate occurs as a result of mould heating during thermal oxidizing destruction of exothermal carbon-containing additives which are specially introduced in the facing layer of moulding mixture. It is necessary to mention that variation of cooling rate can be conducted via the procedures which are individual for each casting located in the experimental mould. Developed and fabricated experimental foundry equipment was used for testing of the concrete cooling procedures of thin-walled castings made of grey cast iron. Pressure of cooling compressed air, which was fed during the process, and amount of exothermal carbon-containing additive, which was introduced in composition of the facing layer of moulding mixture for pilot castings were varied. As a result, the efficient cooling procedure was selected; it allowed to rise tensile strength for the pilot casting by 13 %, to improve cast iron quality (quality index) by 23 % and to increase structure dispersity of primary austenite by 21 % without introduction of alloying elements and modifiers in cast iron composition.

ПЕРЕДУМОВИ ВИРОБНИЦТВА ВУЗЛІВ-КОНЕКТОРІВ БУДІВЕЛЬНИХ МЕТАЛОКОНСТРУКЦІЙ ЛИВАРНИМ СПОСОБОМ ЗА РАЗОВИМИ МОДЕЛЯМИ

The article reviews the common elements of prefabricated modular building metal structures with a list of their advantages and assessment of the prospects for the manufacture of their important components of the Lost Foam Casting (LFC) process. Such construction with the use of metal structures must have all the prerequisites to become an impetus and an effective solution in the construction industry, which will contribute to the reconstruction of the country. The fabrication of connector assemblies and bolt brackets for connecting beams and connectors with flexible steel plates for seismically unstable conditions is considered. A number of frame-cell thin-walled cast structures have been patented by the PTIMA Institute of the National Academy of Sciences of Ukraine since 2011 on the basis of patterns made of expanded polystyrene, which are assembled mainly from repeating elements, and which is similar to the modern method of mounting prefabricated building metal structures. We have also gained experience in casting with LFC parts with cast threads, which simplifies the serial production of ball joints and conical tips for tubular elements. When constructing hangars and warehouses with shell vaults, reducing the weight of metal shells with the obligatory preservation of their required strength is an important requirement for the design of such structures. For this purpose, in particular, the method of inversion of flexible hanging nets formed from a flat state by gravity is used for building structures. The article uses the fact that the inverted chain line serves as an ideal outline for arches and domes, as homogeneous arches in the form of such a line undergo only compression deformation, but not bending. The method of physical modeling of the support surface of the momentless vault shell of a complex curved surface by the method of inversion of the sagging heated thermoplastic synthetic film was developed, which turned out to be simpler than the method of inversion of hanging nets.

Improving the technology of late inoculation in the production of thin-walled castings from ductile iron

The article presents the results of evaluating the impact of late inoculation on formation the microstructure of thin-wall castings from ductile iron. Existing hypotheses about the mechanism of formation and growth of graphite inclusions in the iron are analyzed. The analysis of the existing theories makes it possible to predict the high efficiency of inoculation treatment as close as possible to melt crystallization. It is noted that idea of late treatment is in introducing of inoculants into the iron melt in the pre-crystallization period, what make it is possible to provide high inoculation impact on the molten metal by creating additional crystallizing nuclei of graphite. Presented type of inoculation treatment makes it possible to obtain the required shape and diameter of nodular graphite, its uniform distribution, increase the area of graphite inclusions, reduce risk of shrinkage defects, and prevent the formation of cementite. In the presented research work the late inoculation was carried out by integrating of solid inserts of the INOCSIL® series produced by NPP Technology Company in the gating feeding system of the mould on the existing foundry factory. It is given the results of metallographical tests of samples from the castings obtained both by the current inoculation treatment of iron and by late inoculation treatment technology. The analysis of results of metallographical research showed the high efficiency of late inoculation compare with the existing technology of ladle treatment on the foundry. The use of late inoculation treatment technology made it possible to improve the microstructure of metal and increase the elongation by more than two times.