Low-pressure Casting Research Articles

Research on a quantitative model of rheological distance by pressurizing

In the pressurized rheoforming, such as squeeze casting, die casting and low-pressure casting, the filling and feeding processes are essentially related to the limit rheological distance of alloy melt under certain conditions. If the maximum rheological distance can be quantitatively predicted, it will be of great significance for the process design and quality control. Based on rheological model of non-Newtonian fluid and attenuation characteristics of temperature and pressure along the path, a quantitative model of rheological distance by pressurizing was established for heterogeneous complex structures of alloy melt including pure liquid, pure solid and semisolid with the solid-liquid coexistence during the process of pressurized rheoforming. It includes process parameters of pressurized rheoforming, material property parameters and mold structure parameters in this theoretical model, which can be used to predict the maximum rheological distance. The validity of the theoretical model was verified by comparisons between theoretical calculation values and length of the Archimedes spiral samples obtained by indirect squeeze casting using 6066 aluminium alloy. The results showed that the rheological distances calculated by this theoretical model coincided better with the experimental results and the maximum relative deviation was only 8.2%.

Research on design and technology of aluminium alloy conductor low pressure casting die

Basic principles of aluminium alloy conductor low pressure casting are introduced in the paper. Casting die design and casting system are respectively introduced aiming at the low-pressure casting process of aluminium alloy conductor, the influence of cylindrical riser tube and cone riser tube on liquid rising pressure and liquid rising stability in liquid rising process are analysed in details. It is concluded that the liquid rising pressure for liquid rising process is relatively low during selection of cone liquid rising, and liquid rising process of cone riser tube is more stable. Therefore, cone riser tube is more suitable for liquid rising process of aluminium alloy conductor low pressure casting than cylindrical riser tube. Low pressure casting technological parameters of aluminium alloy conductors are summarized through analysis on low pressure casting technology, thereby providing reference for low pressure casting technique of aluminium alloy conductors.

The Research of the Effect of High Fe Content on AlSi9NiCuMg0.5 Alloy

The aim of the research on the newly developed eutectic silumin type AlSi9NiCuMg0.5, developed and patented by a team of staff of the Faculty of Mechanical Engineering, was to determine the cause of the cracking of castings under operating conditions. When the technology was put into practice, the casting was cast and then used to break the entire casting section and create a crack that crosses the whole cross section. Castings were cast by low-pressure die casting technology, where the mold is fed into the mold cavity via a cast iron tube. The essence of the research was to perform a fractographic analysis of the fracture area, to identify the structure of the casting, to identify the structural components on the surface of the fracture surface by EDS analysis on an electron scanning microscope and to determine the chemical composition of the material in the area of refraction compared to the declared alloy. From these results we can clearly identify the cause of premature cracking of castings from the newly developed eutectic silumin. Additionally, material analyzes have been carried out to see if the material has been contaminated with iron, for example by dissolving a cast-iron filler tube or a batch material. From all the analyzes and fractographic investigations carried out, it can be stated that the initiator of crack insertion and the subsequent cracking of the casting under load is the high content of rough fragments of the fractured intermetallic phases of the Al5FeSi type on the fracture surface (over 20%), which are subject to fission. The high iron content was due to the dissolution of the cast iron ascension tube by low-pressure casting.

Gas production ability of coatings used in low-pressure casting of car wheels

Gas production ability of coatings used in low-pressure casting of car wheels

Effect of vibration on seepage feeding during low-pressure casting of ZL205A alloy

Appropriate vibration can promote the feeding capacity of gravity casting, but the effect of vibration on the feeding of low-pressure casting is not clear. The effect of vibration on the seepage feeding of ZL205A alloy was investigated by vibration casting experiment and physical simulation. The aqueous solution of sodium carboxymethyl cellulose (CMC) with the same rheological characteristic of metal melt was used. The results show that vibration can improve the feeding capacity and reduce shrinkage defects of ZL205A alloy in lowpressure casting. The orthogonal physical simulation experiments indicate that vibration with low frequency and great exerted force can significantly improve the seepage velocity of non-Newtonian fluid with solid particles in porous medium. The seepage phenomenon in CMC solution shows that vibration can change the structure of accumulated particles at the seepage entrance, and thus open the blocked feeding channel. The numerical simulation of one-dimensional semisolid fluid seepage reveals that vibration can form a wave field in the porous medium, which can reduce the adhesion force between fluid and capillary wall and destroy the boundary layer of fluid, and thus promote the seepage velocity.

Mastering of the Filling Stage in Low Pressure Sand Casting Process

In Low Pressure Casting (LPC), the counter gravity filling at low velocity and the protective gas atmosphere above the metal can potentially reduce gas and oxides entrapment in the metal. However, the relationship between the imposed gas pressure evolution and the melt filling dynamics cannot be analytically determined as it is geometry-dependent. This issue is the missing link to master and automate the filling step in LPC process. In this work, the filling dynamics is numerically investigated for different mold geometries and pressure ramps. The simulation, carried out using ANSYS Fluent® simulation software, is combined with an analytical model. As the results are quantitatively predictive of the filling flow, it permits to develop a numerical study, considering different sudden or progressive section changes and pressure ramps. The impact of the different process parameters on the flow dynamics is analyzed, particularly the transition smoothing impact.

A novel Zn-Cu-P master alloy and its modification performance on primary Si of A390 alloy

The requirement of modification on primary Si particles at low temperature has restricted the development of inoculants in low pressure casting industries. In this paper, by dissolving Cu-14P master alloy into Zn melt and utilizing the diffusion of Zn atoms into Cu3P phase, a novel Zn-8.6Cu-1.4P master alloy has been synthesized. Except for η-Zn matrix, ε-CuZn5 and α-Zn3P2 are the main intermetallics. After introducing into A390 melt at a relatively low temperature (≤720 °C), the α-Zn3P2 phase evolves to AlP, and the in-situ formed AlP nucleus exhibits attractive modification performance on primary Si. The Zn-Cu-P master alloy may be a promising candidate for application in low pressure casting industries.

ANALISIS KEKUATAN VELG ALUMUNIUM MODEL D30D PADA PERUSAHAAN “A”

Wheels are one of the main components in a vehicle. Without wheels of vehicles will not be to function. The damage that occurs in aluminium alloy wheels for the outbreak spoke mostly occur due to a force and tension that occurs exceeds the maximum allowable voltage. With these considerations it is necessary to redesign using 3D software and simulated using finite element method. After simulated, part produce with low pressure casting and machining. Sample part test with several testing as single part such as : life test, drum test, 13° impact test. After that sample part test as running test such as : curb stone evaluation and rectangle evaluation. The results of sample testing parts such as life test, the drum test, 13 ° impact test and running test in the form of curb stone rectangle evaluation and evaluation did not reveal any cracks on the sample part. Nut torque results of sample testing parts such as curb stone evaluation have smaller in 70 N.m, with allowed limit 61,6 N.m until 88 N.m. And nut torque results of sample testing parts such as rectangle evaluation have smaller in 76 N.m, with allowed limit 61,6 N.m until 88 N.m

Defect Detection of Aluminum Alloy Wheels in Radiography Images Using Adaptive Threshold and Morphological Reconstruction

In low-pressure casting, aluminum alloy wheels are prone to internal defects such as gas holes and shrinkage cavities, which call for X-ray inspection to ensure quality. Automatic defect segmentation of X-ray images is an important task in X-ray inspection of wheels. For this, a solution is proposed here that combines adaptive threshold segmentation algorithm and mathematical morphology reconstruction. First, the X-ray image of the wheel is smoothed, and then the smoothed image is subtracted from the original image, and the resulting difference image is binarized; the binary image resulting from the low threshold is taken as the marker image, and that from the high threshold is taken as mask image, and mathematical morphology reconstruction is performed on the two images, with the resulting image being the preliminary result of the wheel defect segmentation. Finally, with area and diameter parameters as the conditions, the preliminary segmentation result is analyzed, and the defect regions satisfying the conditions are taken as the ultimate result of the whole solution. Experiments proved the feasibility of the above solution, which is found capable of extracting different types of wheel defects satisfactorily.

Effect of casting methods on microstructure and mechanical properties of ZM5 space flight magnesium alloy

The counter-gravity casting methods have been developed to remove the casting defects of Mg based alloys. However, the effects of different counter-gravity casting methods on the microstructure and mechanical properties have not been studied in detail. ZM5 alloys were prepared by gravity casting, low-pressure casting and counter-pressure casting, respectively. The mechanical properties, microstructure and fracture morphologies were examined and compared by means of optical microscopy, scanning electron microscopy methods and tensile testing. Results show that casting defects such as gas pore, shrinkage porosity and cavity can be eliminated by counter-pressure casting. The grain size of α-Mg is decreased significantly by counterpressure casting. Moreover, the precipitated particles are more uniform and finer in the counter-pressure casting sample. As a result, the mechanical properties of the alloys are greatly improved. The tensile strength and elongation of the samples by counter-pressure casting are 285 MPa and 13.9%, respectively, which are much higher than those of the low pressure casting and gravity casting.

MHD-physical modification effect on microstructure control of the 7xxx high-strength Alalloys

In this study, the possibilities of the microstructure refinements effect of processing by electromagnetic and magneto-hydrodynamic means on high-strength casting aluminium alloys Al-Zn-Mg-Cu/Ni (0.2%Zr) system has been studied. In the case of direct manufacturing of high-strength casting Al-alloy by the MHD-physical affecting, the unidirectional 120Hz pulse electromagnetic force(70∼143.5N, 2.5∼3.5m/s) created in working area(WA) of the magneto-dynamic installation electromagnetic pump has provide a fine emulsion distribution of intermetallic particles in liquid melt during intensive MHD-processing for melt capacity of 150∼500kg. Microstructure of permanent chill-mold specimens (1” rod and 3” billet) has shown the unique non-dendrite microstructure with compact grains in range of 50∼100μm, and distributed homogeneity by all cross-section, instead an over 250μm dendrites for the non-treated state at sampling from conventional melting furnace.As well, applying MHD-processed alloy for low pressure casting method at manufacturing 3” billet for 550mm lengths into graphite tube have an mainly compact globular microstructure, characterized as non-dendrite state with 80∼120μm grain size and 50∼80μm in the central part of billet. Achieved effect can be explained by an artificial heat-force effect of the pulse unidirected electromagnetic force, created in the MDI working area which affecting the solidification structure. In addition just 10 minutes for 150kg alloy by artificial pumping mode MHD melt processing was found to increase cast-ability of the Al-Zn-Mg-Cu casting high-strength alloy at pouring temperature of 680∼720°C, wherein hot-cracks disappear, and hot-cracks effect is not occurs for the different conditions of the pouring speed.Tensile stress test of the developed high-strength casting Al-Zn-Mg-Cu alloys has been shown 547∼566MPa, 516∼547 yield stress and 2.9-3.4°% elongation for the case of chill mold gravity casting.

Effect of pressurizing speed on filling behavior of gradual expansion structure in low pressure casting of ZL205A alloy

The mold filling behavior of gradual expansion structure in low pressure casting was studied by two phase flow model using the Volume of Fluid method, and was verified by water simulation with a Plexiglas mold. To get smooth mold filling process and provide a guide for the pressurizing speed design in the producing practice, the mathematical model with the pressurizing speed, expansion angle and height of the gradual expansion structure was established. For validation experiments, ZL205A alloy castings were produced under two different pressurizing speeds. Weibull probability plots were used to assess the fracture mechanisms under different pressurizing speeds. Mechanical properties of ZL205A alloy were applied to assess the entrainment of oxide film. The results show that the filling process of a gradual expansion structure in a low pressure casting can be divided into the spreading stage and filling stage by gate velocity. The gate velocity continues to increase in the gradual expansion structure, and increases with the increase of pressurizing speed or expansion angle. Under the effect of the falling fluid raised by the jet flow along the sidewall, the fluid velocity decreases in the jet zone from ingate to free surface. As such, oxide film entrainment does not occur when the gate velocity is greater than the critical velocity, andthe gate velocity no longer reflects the real state of the free surface. The scatter of the mechanical properties is strongly affected by the entrainment of oxide films.

Similitude analysis on flow characteristics of water, A356 and AM50 alloys during LPC process

The present work endeavours to map mold filling characteristics of water to real melts of A356 aluminium alloy and AM50 magnesium alloy during low pressure casting process (LPC). The analogy of dynamic similitude has been applied on a benchmarked computational fluid dynamics (CFD) based simulation model developed for tracking fluid free surfaces. Scaling factors for A356 and AM50 melts with respect to water are calculated by equating the non-dimensional numbers deduced from forces acting on the fluids. Buckingham's Pi theorem is used to verify the derived scaling equations. The mold filling time for water in the benchmarked simulation model and for real alloy melts in the scaled computational models is compared for different inlet pressure regimes. The proposed analogy is verified using variations occurring in velocity scaling factors for the melts during mold filling.

Design and Analysis of Hot Core Box Mold for New Energy Vehicle Motor Shell

To achieve rapid batch production with high-quality stability for the integral molding process of sand cores in low-pressure casting for the water-cooled aluminum alloy shell of new energy vehicle motors many process parameters were measured. The forming process and die structure of a circumferential sand core were analyzed. In addition, the electric heating power of each core box mold was accurately calculated using thermodynamic calculations. These details, combined with the three-dimensional shape of the core mold, the layout of the electric heating rod and the hole position for temperature measuring as well as the entire cylindrical waterway of a hot core box mold and the core way were designed to realize accurate control of the box temperature by adjusting the curing temperature and time parameters. Thus, improving the sand core curing quality and production efficiency, which will meet the casting specifications for mass production of the water-cooled motor shell.

Quality Management and Control of Low Pressure Cast Aluminum Alloy

This paper briefly reviews the history of low pressure casting and summarizes the major production processes of low pressure casting. It briefly introduces the quality management and control of low pressure cast aluminum alloy. The main processes include are: preparation of raw materials, Melting, refining, physical and chemical analysis, K-mode inspection, sand core, mold, heat treatment and so on.

Experimental and numerical study of section restriction effects on filling behavior in low-pressure aluminum casting

The molten metal flow under low-pressure filling was investigated both experimentally and numerically inside sand molds with different cross sections and different pressure ramps. The proposed fluid dynamics simulation predicts quantitatively the observed filling oscillations. An analytical model is developed to link the over-height with the geometrical restriction and the pressure ramp. The calculated over-height is proportional to the ramp and non-linearly impacted by the section change as confirmed by the experimental results.

Formation Mechanism of Surface Crack in Low Pressure Casting of A360 Alloy

A surface crack defect is normally found in low pressure castings of Al alloy with a sudden contraction structure. To further understand the formation mechanism of the defect, the mold filling process is simulated by a two-phase flow model. The experimental results indicate that the main reason for the defect deformation is the mismatching between the height of liquid surface in the mold and pressure in the crucible. In the case of filling, a sudden contraction structure with an area ratio smaller than 0.5 is obtained, and the velocity of the liquid front increases dramatically with the influence of inertia. Meanwhile, the pressurizing speed in the crucible remains unchanged, resulting in the pressure not being able to support the height of the liquid level. Then the liquid metal flows back to the crucible and forms a relatively thin layer solidification shell on the mold wall. With the increasing pressure in the crucible, the liquid level rises again, engulfing the shell and leading to a surface crack. As the filling velocity is characterized by the damping oscillations, surface cracks will form at different heights. The results shed light on designing a suitable pressurizing speed for the low pressure casting process.

Investigation of the response surface describing the mathematical model of the effects of the Al/Mg rate and temperature on the Al-Mg alloy castability

Ridge analysis is used to investigate the response surface describing the mathematical model of the influence of the Al / Mg ratio and temperature on the Al-Mg alloy castability during the low-pressure casting. It is shown that the suboptimal values of the technological regimes ensuring the maximum castability values of the Al-Mg alloy can be determined taking into account the limitations imposed on the technological process on the basis of a mathematical model constructed by implementing a second order central orthogonal composite design (COCD)

Investigating surface roughness of ZE41 magnesium alloy cast by low-pressure sand casting process

The sand mold 3D printing technologies enable the manufacturing of molds with great dimensional accuracy. However, the roughness of as-cast components is higher when cast in a 3D printed mold rather than in a traditional sand mold. Coating the inner cavity is an efficient solution but can be costly and, in the narrowest cavities, not achievable. Finding a procedure to reduce the as-cast roughness without coating would ease the casting procedures. In the present work, surface analysis of ZE41 magnesium alloy is presented after being cast in 3D printed furan sand molds without coating using the low-pressure casting process. The molten metal temperature was measured during casting at different positions along the cast cavity. The as-cast surface roughness was correlated to the molten metal temperature and solid fraction at the time of contact against the sand mold surface.

Numerical simulation and experimental validation of free surface flows during low pressure casting process

The present work analyzes the free surface flow characteristics during mold filling in a low pressure casting process (LPC) through water model experiments and numerical simulations. The flow patterns visualized through the water analog experiments using different input pressure sequences have been verified with numerical simulation results for the entire LPC process. The benchmarked numerical model has been further used to study the impact of different in-gate shapes on fluid free surface behavior inside the mold cavity. The mold filling and solidification simulation is then carried out using magnesium alloy as liquid for the same geometry and the same input pressure profile to highlight the effect of thermo physical properties of actual melts on the free surface flow behavior.