Permanent Mold Casting Process Research Articles

Deep learning–based inline monitoring approach of mold coating thickness for Al-Si alloy permanent mold casting

AbstractIn the permanent mold casting process, the distribution of mold coating thickness is a significant variable with respect to the coating’s thermal resistance, as it strongly influences the mechanical properties of cast parts and the thermal erosion of expensive molds. However, efficient online coating thickness measurement is challenging due to the high working temperatures of the molds. To address this, we propose an indirect monitoring concept based on the analysis of the as-cast surface corresponding to the coated area. Our previous research proves linear correlations between the as-cast surface roughness parameter known as arithmetical mean height (Sa) and the coating thickness for various coating materials. Based on these correlations, we can derive the coating thickness from the analysis of the corresponding as-cast surface. In this work, we introduce a method to quickly evaluate the as-cast surface roughness by analyzing optical images with a deep-learning model. We tested six different models due to their high accuracies on ImageNet: Vision Transformer (ViT), Multi-Axis Vision Transformer (MaxViT), EfficientNetV2-S/M, MobileNetV3, Densely Connected Convolutional Networks (DenseNet), and Wide Residual Networks (Wide ResNet). The results show that the Wide ResNet50-2 model achieves the lowest mean absolute error (MAE) value of 1.060 µm and the highest R-squared (R2) value of 0.918, and EfficientNetV2-M reaches the highest prediction accuracy of 98.39% on the test set. The absolute error of the surface roughness prediction remains well within an acceptable tolerance of ca. 2 µm for the top three models. The findings presented in this paper hold significant importance for the development of an affordable and efficient online method to evaluate mold coating thickness. In future work, we plan to enrich the sample dataset to further enhance the stability of prediction accuracy.

Development of manufacturing technology for a hybrid induction rotor

General Motors is developing designs and manufacturing processes for new generations of electric motors intended for use in electric vehicles. There is interest in replacing the aluminum traditionally used in induction motor rotors with copper to improve motor capability. This work explored the use of casting aluminum end-rings to copper conducting bars (spokes) in the fabrication of copper rotors. Gravity casting trials were carried out in experimental foundry. Pure aluminum end-rings were overcast and interlocked over C101 copper conductor bars encapsulating a laminate stack of highly magnetic steel. Steel permanent mold was designed and constructed specifically for the project. The mold was capable of casting one end-ring of the rotor at a time and allowed for the assembly to be reoriented for casting of the opposite end-ring. The objective of this work is to investigate the effects of intermetallic compound (IMC) formation at the interfaces of cast-bonded Cu-Al bars on the rotor mechanical integrity and electrical resistance. The Cu-Al bonding strength was measured by tension tests, and the influence of IMC layer variation on the tension load and electrical resistance were analysed. This research phase showed that sufficient bonding and interlocking were achieved among the aluminum and copper by using a special feature and/or flux at the bar ends in the permanent mold casting process. The paper reviews the data collected for evaluation of the quality of hybrid rotor cage.

금형 주조 대형 펜듈럼 밸브 바디의 최적 공정 조건 결정을 위한 열변형 거동 분석

The aim of this study is to investigate the process factors that affect the thermal deformation of a product during permanent mold casting using the commercial analysis program, Abaqus. The permanent mold casting process was implemented in the analysis program to configure the optimal process conditions. In addition, the deformation pattern generated by heat was analyzed during the manufacturing process of a product with a thin hollow wall. Because the product had a thin top and bottom and was deformed through the expansions of the core and chill, which combined inside during casting, the removal time of the core had the most significant effect on the deformation. The accuracy was reviewed by comparing the simulation deformation results under the optimal process conditions with the actual measurement results of the prototype.

Microstructure and Phase Formation of Novel Al80Mg5Sn5Zn5X5 Light-Weight Complex Concentrated Aluminum Alloys

In this work, three novel complex concentrated aluminum alloys were developed. To investigate the unexplored region of the multicomponent phase diagrams, thermo-physical parameters and the CALPHAD method were used to understand the phase formation of the Al80Mg5Sn5Zn5Ni5, Al80Mg5Sn5Zn5Mn5, and Al80Mg5Sn5Zn5Ti5 alloys. The ingots of the alloys were manufactured by a gravity permanent mold casting process, avoiding the use of expensive, dangerous, or scarce alloying elements. The microstructural evolution as a function of the variable element (Ni, Mn, or Ti) was studied by means of different microstructural characterization techniques. The hardness and compressive strength of the as-cast alloys at room temperature were studied and correlated with the previously characterized microstructures. All the alloys showed multiphase microstructures with major α-Al dendritic matrix reinforced with secondary phases. In terms of mechanical properties, the developed alloys exhibited a high compression yield strength up to 420 MPa, high compression fracture strength up to 563 MPa, and elongation greater than 12%.

Evaluating the Application of Heating Conductor Surfaces Inside Plasma Sprayed Coatings in Permanent Mold Metal Casting Processes for Local, Near-Surface Heat Release

With casting being a complex process which involves several physical effects and interactions, a wide array of means for influencing such processes exist. Here, the liquid–solid phase change is of utmost importance, as it is a deciding factor for a part’s final properties. Especially with today’s high critical material property requirements, control of the solidification process is indispensable. For the most part, the cooling of a casting defines its solidification. What determines the cooling process is the heat balance of the system. The foundry industry has been using different approaches for influencing the heat balance for a long time. The application of different kinds of coatings with either insulating or heat transfer promoting properties as well as temperature control via cooling channels inside the mold is widely used. Progress in the field of plasma spraying of coatings and the application of heating conductor surfaces have rendered a new concept possible: The integration of heating conductors inside a coating allows for the release of heat in closest vicinity of the melt–mold interface. This paper depicts the use of numerical simulations to investigate the local application of heating conductor layers inside the mold surface coating for a permanent mold casting process and discusses concepts for influencing the heat balance that would not be possible with state-of-the-art cooling channel approaches.

Modeling of cooling and heat conduction in permanent mold casting process

Motivated by the need to understand the heat transfer process in permanent mold casting, the heat conduction problem in the casting and the mold is modeled as transient one-dimensional heat flow in a double-layer cylinder with radial interfacial heat flux to emulate the cooling process of the casting. The cylinder is cooled down by dissipating heat to surrounding by convection. Green's function method, which obtained by separation of variables technique, is used to obtain a closed form solution of temperature distribution. The results of the derived analytical expressions are verified with numerical results of finite-element analysisand the published experimental results. The simulations are performed for different casting/mold materials with diversified thermo-physical properties to figure out the relationship between those properties and heat transfer process. The analytical results are justified by their good agreement with both of numerical and experimental results and its time efficiency in computation which offers advantages in potential real-time application to casting process monitoring. The mean absolute percentage error between the obtained temperatures using the developed analytical model and the measured ones was 14.5% and 2.4% for the casting and mold, respectively.

Interfacial Heat Transfer Coefficient in Unidirectional Permanent Mold Casting: Modeling and Inverse Estimation

The thermal control of the permanent mold casting process is highly dependent on the Interfacial Heat Transfer Coefficient (IHTC). Based on that, many works proposed several models in order to estimate its behavior. This work intends to study three IHTC models present in the literature, as well as to propose and analyse two new models. The proposed models are based on two distinct methodologies: thermal resistance method and analytical comparison to the thermal gradient formulation at the metal/mold interface. All these models will be analysed in terms of their ability to reduce the error between the simulated and experimental thermal profiles by using an inverse method and verifying their respective parameter sensitivity based on the relative sensitivity coefficient. It is observed that the exponential formulation model, proposed in this paper, is able to reduce the numerical/experimental error more efficiently than the others methods in all three hypoeutectic alloys of the Al-Si system considered.

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.

Evaluation of Mechanical Properties of Locally Recycled Aluminium Alloy Scrap

Recycling of aluminium alloy scraps reduce the amount of waste directed into landfills. It is a vital part of the aluminium smelting industries. However, some local aluminium smelting craftsmen/artisans in Nigeria cast their aluminium scraps without considering the mechanical properties of the casting obtained from aluminium scraps. This study investigated some of the mechanical properties of cast aluminium alloy namely; tensile strength, impact, and hardness, and the microstructure of the locally recycled aluminium alloy in Nigeria. A permanent mould casting process was adopted in the smelting of the scraped aluminium and their properties were examined. The metallographic specimen of the sample was grinded and polished in a Dia-Pro suspension solution (3μm) on an MD-DAC and DP-DAC 300mm polishing cloth while the surface was exposed to a Keller enchant of 15mil of hydrochloric acid, 10mil of water and 10mil of hydrofluoric acid before viewing under the microscope. From the result, the ultimate tensile strength, impact, and Brinell hardness were 54.87MN/m2, 6.1J and 64.33BHN, respectively. The metallographic result from the smelted sample revealed a coarse and rough surface microstructure.

Effect of Zn Concentration on the Microstructure and Mechanical Properties of Al-Mg-Si-Zn Alloys Processed by Gravity Die Casting

The microstructure and mechanical properties of Al-8.1Mg-2.6Si-(0.08 to 4.62)Zn alloys (in wt pct) have been investigated by the permanent mold casting process. X-ray diffraction analysis shows that the τ-Mg32(Al, Zn)49 phase forms when the Zn content is 1.01 wt pct. With higher Zn contents of 2.37 and 3.59 wt pct, the η-MgZn2 and τ-Mg32(Al, Zn)49 phases precipitate in the microstructure, and the η-MgZn2 phase forms when the Zn content is 4.62 wt pct. Metallurgical analysis shows that the η-MgZn2 and τ-Mg32(Al, Zn)49 phases strengthen the Al-8.1Mg-2.6Si-(0.08 to 4.62)Zn alloys. After solutionizing at 510 °C for 180 minutes and aging at 180 °C for 90 minutes, the η′-MgZn2 phase precipitates in the α-Al matrix, which significantly enhances the mechanical properties. Addition of 3.59 wt pct Zn to the Al-8.1Mg-2.6Si alloy with heat treatment increases the yield strength from 96 to 280 MPa, increases the ultimate tensile strength from 267 to 310 MPa, and decreases the elongation from 9.97 to 1.74 pct.

Multivariate statistical inference in a radial basis function neural network

Regression models and analysis of variance are widely used methods for analyzing manufacturing processes in the industry. Its objective is to analyze the effect of process input variables on a final quality characteristic. However, some processes have complex data that cannot be described by linear regression or have several product quality characteristics to be controlled, having several correlated responses makes it difficult to analyze and optimize the process, thus, it is common to ignore the correlation between responses and make several independent models for each response, causing problems for decision-making based on these models. This paper shows the application of multivariate statistical analysis in a Radial Basis Function neural network, considering the statistical significance between independent and dependent variables and the correlation and verifying if the assumptions for this analysis are fulfilled. The results evidence that the multivariate statistical analysis in the Radial Basis Function is a good method to analyze the process based on correlated variables: it satisfies the assumptions required for this analysis, it determines the process variation, and it also determines the most important variable that had influence in the process used to evaluate the permanent mold casting process.

Comparison Between Cemented Carbide and PCD Tools on Machinability of a High Silicon Aluminum Alloy

The high content of silicon of aluminum casting alloys challenges the tool life of conventional cemented carbide inserts, and polycrystalline diamond (PCD) tools appear as an interesting material to machine these alloys because they improve substantially the durability of cutting tools and consequently the productivity of machining. However, the surface roughness, cutting forces and chip morphology are equally important factors in machining evaluation. Therefore, an experimental study is performed aiming at comparing the performance of cemented carbide and PCD tools taking into account cutting forces, surface roughness and chip morphology, under dry longitudinal turning, performed for the AlSi9Cu3 alloy produced by permanent mold casting process. Different chip breaker geometries were also considered, and their influence on the referred parameters was also investigated. Analysis of variance was employed to study the different contributions of inserts, cutting speed, feed rate, depth of cut and their interactions in machinability performance. The results show low cutting forces and better results for surface roughness for uncoated cemented carbide tools, with simpler chip breakers and flat rake face PCD tool, but an efficient chip control was obtained for inserts with small grooves with high cutting forces and power consumption. Nevertheless, the feed rate and depth of cut have the highest influence on the machinability performance of the alloy under investigation.

Effect of mould temperature, grain refinement and modification on hot tearing test in Al-7Si-3Cu alloy

Abstract In the past decades, a great deal of work had been done on improving the mechanical properties and castability of Al-Si-Cu alloy in foundry industries through grain refinement and modification techniques. Among these alloys, Al-7Si-3Cu alloys are popularly used in automotive applications to produce lighter and more fuel efficient vehicles. In spite of these advantages, when this alloy is cast via permanent mould casting process, it shows a high susceptibility to hot tearing. Inoculation and hot tearing are important factors affecting the quality of the final casting products. Effect of mould temperatures on hot tear formation has been studied at room temperature, 90 °C, 160 °C, 230 °C and 300 °C. Higher mould temperature helps in reducing hot tear susceptibility of the alloy by refilling the material in later stage of solidification. For hot tear test, a permanent mould having test bar of size 260 mm long and 20 mm in height with constraint at the end has been used. Al-5Ti-1B grain refiner has been added in order to Ti content in order to from 0.040 wt% Ti to 0.050 wt% Ti to minimize the hot tear susceptibility of the alloy through alterations in grain size and morphology. The Al-7Si-3Cu alloy has a columnar grain structure with a large grain size, while with the addition of grain refiner it shows a finer equiaxed structure. The effect of processing of Al-5Ti-1B grain refiner and hot rolled or cast in combination with Al-10Sr modifier have also been studied to observe their effect on minimizing hot tear formation. The fracture surfaces of the specimen have been investigated by SEM. The closed packed plans and presence of intermetallic particle on the fracture surface is identified using TEM.

Microstructural Origins of Variability in the Tensile Ductility of Tilt-Pour Permanent Mold Cast Al Alloy at a Warm Temperature

Abstract Light-alloy castings often exhibit variability in the fracture sensitive properties such as ductility that does not necessarily correlate to the global average microstructural parameters such as dendrite cell size and porosity volume fraction in the three-dimensional microstructure. Nonetheless, in numerous such cases, the variability in the fracture sensitive properties does correlate to the variability in the local distributions of microstructural features and processing defects because the fracture path preferentially goes through the regions containing large concentrations of the defects and/or microstructural extrema. This paper presents the results of a detailed quantitative metallography and quantitative fractography based investigation of the relationships between microstructure and variability in uniaxial tensile ductility of the tensile test specimens drawn from very large size Al alloy automotive component castings fabricated using tilt-pour permanent-mold casting process. The percent tensile ductility e shows strong quantitative correlation with the area fraction of the porosity f in the corresponding fracture surfaces, which can be represented by the following power-law relationship, where e0 and n are empirical constants.

Numerical Simulation of Mold Filling and Solidification Behavior in Permanente Casting Process

Melt flow and casting solidification are essential parts of the permanent mold casting process and affect significantly the quality of castings．For this reason, accurate prediction of mold filling pattern and temperature field in permanent mold castings plays on an important role in producing sound castings. In this paper, the model filling and solidification of a box casting produced from an aluminum alloy is studied. Different casting processes are employed, simulated and optimized to obtain sound castings. Simulation results reveal that with appropriate gating system, pouring rate, cooling line, a smooth mold filling, reduced shrinkages and other defects are available and desired sound castings can be produced.

Wear behaviour of eutectic and hypoeutectic Al‐Si‐Mg‐Ce alloys

PurposeThe purpose of this paper is to study the wear behaviour of eutectic and hypoeutectic Al‐Si‐Mg‐Ce alloys.Design/methodology/approachThe eutectic and hypoeutectic alloys were prepared using permanent mould casting process by varied cerium (Ce) addition in the alloy from 1 to 3 wt%. Dry sliding wear tests were performed against a hardened carbon steel (Fe‐2.3%Cr‐0.9%C) using a pin‐on‐disc configuration with fixed sliding speed of 1 m/s and load 50 N at room temperature of ∼25 degree. Morphologies of both worn surfaces and collected debris were characterised by a scanning electron microscope (SEM) equipped with an energy dispersive X‐ray spectrometer (EDS).FindingsIt was revealed that following the addition of cerium, intermetallic Al4Ce needle‐like structure was present in eutectic alloys whereas CeMg2Si2 blocky phase was present in the hypoeutectic alloys. The increasing of Ce addition up to 3.0 wt% in hypoeutectic alloy led to formation of AlCe3 intermetallic phase. The increase in cerium content up to 2 wt% led to higher wear resistance behaviour for both as‐cast alloys. Formation of craters and localised plastic deformation were observed on the worn surface of both as‐cast alloys, resulting fine particulate and sheet‐like wear debris. The wear resistance was found to be higher for hypoeutectic alloy compared to the eutectic alloy containing Ce.Originality/valueAn attempt has been made to study the influence of intermetallic compound containing Ce in the Al‐Si‐Mg alloys on wear behaviour of both as‐cast alloys.

Thermophysical Properties of a Hot-Work Tool-Steel with High Thermal Conductivity

In the highly productive permanent mold-casting process, the released enthalpy of the solidifying metal has to be transported through the surrounding hot-work tool-steel to the cooling system. For that reason, the thermal conductivity is a key property of the employed tool-steel. Recently, a new type of steel (Rovalma HTCS 130) has been developed and superior thermal properties have been claimed. In this study, measurements of the thermal diffusivity, heat capacity, and thermal expansion as a function of temperature are described for this steel and results of the computed thermal conductivity are reported. There is quite a discrepancy between the specification of the steel supplier and the results of this study; however, an improvement of the thermal conductivity for this type of steel can be confirmed.

Maximizing average efficiency of process time for pressure die casting in real foundries

Scheduling of casting processes is the problem of determining the number of products that will be manufactured in each casting shift so as to optimize a predetermined objective function. In this paper, we propose a linear programming (LP) model that maximizes the average efficiency of process time for casting in real foundries. The considered casting process is pressure die casting, the most prevalent permanent mold casting process, equipped with an automated die exchange device. In permanent mold casting, the use of a mold or die installed on a casting machine requires a significant process time for casting. The objective function of the proposed LP model is defined as the average ratio of the actual process time to the pre-assigned operating time in a shift. A solution that minimizes the objective function will provide the maximum surplus time, hence optimizing the efficiency of casting operations in terms of process time. Numerical examples are presented to illustrate the applicability and reliability of the proposed model. The results demonstrate that this model is an effective and conveniently implemented tool for solving real casting sequences in a simple and practical framework.

Formation of Fold Defects in Permanent Mold Cast AE42 Magnesium Alloy

Application of magnesium alloys potentially plays a key role in weight reduction of automotive and aerospace components. Majority of magnesium components are manufactured via the high-pressure die-casting (HPDC) or permanent-mold casting (PMC) processes. In general, castability of magnesium alloys is comparable to aluminum alloys. However, unique defects related to the high susceptibility of magnesium to rapidly solidify, dissolve hydrogen or form oxides potentially contribute to material failure. In this research, AE42 magnesium alloy castings were manufactured via the PMC process. Formation of fold defects in regions of high melt turbulence was observed on the macro-scale as visible surface flow-lines. Microstructural analysis revealed that folds in the AE42 alloy we related to the rapid solidification and short alloy freezing range. Further, segregation of Al2RE intermetallics at the metal front hindered proper fusion of merging metal fronts.

Characterization of fold defects in AZ91D and AE42 magnesium alloy permanent mold castings

Casting premium-quality magnesium alloy components for aerospace and automotive applications poses unique challenges. Magnesium alloys are known to freeze rapidly prior to filling a casting cavity, resulting in misruns and cold shuts. In addition, melt oxidation, solute segregation and turbulent metal flow during casting contribute to the formation of fold defects. In this research, formation of fold defects in AZ91D and AE42 magnesium alloys cast via the permanent mold casting process was investigated. Computer simulations of the casting process predicted the development of a turbulent metal flow in a critical casting region with abrupt geometrical transitions. SEM and light optical microscopy examinations revealed the presence of folds in this region for both alloys. However, each alloy exhibited a unique mechanism responsible for fold formation. In the AZ91D alloy, melt oxidation and velocity gradients in the critical casting region prevented fusion of merging metal front streams. In the AE42 alloy, limited solubility of rare-earth intermetallic compounds in the α-Mg phase resulted in segregation of Al 2RE particles at the leading edge of a metal front and created microstructural inhomogeneity across the fold.