Low Pressure Die Casting Research Articles

LPDC Process Optimization of Copper-Alloy Taps Based on CAE Technique

Low pressure die casting (LPDC) process of a copper-alloy tap was simulated by the finite element software ProCAST. The casting defect and its reason were analyzed. The optimized design was discussed and the simulation was validated against the low pressure die casting experiment. Results showed that the main defect is misrun and its reason is that the melt solidifies too fast. It’s well solved by increasing the wall thickness of the relational pipe properly. The result agrees with the experiment.

Correlation between Mechanical Properties and Porosity Distribution of A356 in Gravity Die Casting and Low Pressure Die Casting

Gravity die casting (GDC) and low pressure die casting (LPDC) methods were used to compare the mechanical properties and porosity distribution in a 5-step mould design. Commercially available A356 alloy was used for the experiments. Ar and Ar+H2 mixture were used to achieve two different hydrogen levels, i.e. 0,1 and 0,2 ml/100g Al, respectively. Although the porosity level was lower in LPDC, the tensile properties were lower than GDC due to the fact that LPDC melt had 50 mm bifilm index, whereas GDC melt had 20 mm. This investigation has shown that the metal quality has a larger effect over the mechanical properties than the porosity content.

Correlation between Mechanical Properties and Porosity Distribution of A356 in Gravity Die Casting and Low Pressure Die Casting

Gravity die casting (GDC) and low pressure die casting (LPDC) methods were used to compare the mechanical properties and porosity distribution in a 5-step mould design. Commercially available A356 alloy was used for the experiments. Ar and Ar+H2 mixture were used to achieve two different hydrogen levels, i.e. 0,1 and 0,2 ml/100g Al, respectively. Although the porosity level was lower in LPDC, the tensile properties were lower than GDC due to the fact that LPDC melt had 50 mm bifilm index, whereas GDC melt had 20 mm. This investigation has shown that the metal quality has a larger effect over the mechanical properties than the porosity content.

A356 합금의 고주기 피로특성에 미치는 미소기공율의 영향

The present study was aimed to investigate the dependence of fatigue property on microporosity variation of low-pressure die-cast (LPDC) A356 alloy. The fatigue property of A356 alloy was evaluated through high cycle fatigue test, and the microporosity-terms used were the fractographic porosity measured from SEM observation on fractured surface and the volumetric porosity obtained through the density measurement using Archimedes's principle. The number of cycles to failure of A356 alloys depends obviously upon the variation of fractographic porosity, and can describe in terms of the defect susceptibility which depends on the microporosity variation at a given value of stress amplitude. The modified Basquin's equation was suggested through the combination of microporosity variation and static maximum tensile stress to fatigue strength coefficient. Using modified Basquin's equation, it could suggest that the maximum values of fatigue strength coefficient and exponent achievable in defect-free condition of A356 alloy are 265 MPa, -0.07, respectively.

Optimization of LPDC Process Parameters Using the Combination of Artificial Neural Network and Genetic Algorithm Method

In this article, the low-pressure die-cast (LPDC) process parameters of aluminum alloy thin-walled component with permanent mold are optimized using a combining artificial neural network and genetic algorithm (ANN/GA) method. In this method, an ANN model combining learning vector quantization (LVQ) and back-propagation (BP) algorithm is proposed to map the complex relationship between process conditions and quality indexes of LPDC. The genetic algorithm is employed to optimize the process parameters with the fitness function based on the trained ANN model. Then, by applying the optimized parameters, a thin-walled component with 300 mm in length, 100 mm in width, and 1.5 mm in thickness is successfully prepared and no obvious defects such as shrinkage, gas porosity, distortion, and crack were found in the component. The results indicate that the combining ANN/GA method is an effective tool for the process optimization of LPDC, and they also provide valuable reference on choosing the right process parameters for LPDC thin-walled aluminum alloy casting.

Grain refinement of AA333 aluminium cast alloy by Al–Ti granulated flux

Addition of grain refiner is an option to obtain higher mechanical properties of aluminium cast alloy. Grain refiner will react with molten aluminium and will form nucleant particles that initiate solidification. Therefore, the grain refiner will also be useful to control the solidification processes to reduce shrinkage formation. This study evaluated grain refinement in AA333 aluminium alloys by using Al–Ti granulated flux. Experiments were conducted by adding 0.056 and 0.078 wt.% Ti granulated flux to the molten aluminium during rotary gas bubble floatation and it was subsequently transferred into the Low Pressure Die Casting (LPDC) holding furnace. The pressure in the LPDC holding furnace was initially 256 kPa and no stirring was applied. The melt was injected to cylinder head moulds with cycle time of 180 s. Samples were cut at the thin and thick sections of the cylinder head to analyze the effects of cooling rate on grain refinement. Fading of grain refiner was studied for the period of 4 h. Hardness testing and microstructural observation were conducted. The results showed that addition of Al–Ti granulated flux for 0.056 and 0.078 wt.% Ti, increased the hardness and lowered the dendrite arm spacing (DAS). The refinement is more significant in thin samples, because of the assistance by higher cooling rate. The mechanism of grain refinement of Al–Ti granulated flux in AA333 alloy is a combination of high growth restriction factor by the large amount of solute and nucleation by Al 3Ti particles. Fading of grain refiner was detected by the increase in DAS, the lowering of Ti concentration in the melt and the reduction in hardness and strength. The pressure utilized in LPDC was not adequate to give stirring effect to prevent fading.

Thermal Stress Analysis for Ceramics Stalk in the Low Pressure Die Casting Machine

Low pressure die casting (LPDC) is defined as a net shape casting technology in which the molten metal is injected at high speeds and pressure into a metallic die. The LPDC process is playing an increasingly important role in the foundry industry as a low-cost and high-efficiency precision forming technique. The LPDC process is that the permanent die and filling systems are placed over the furnace containing the molten alloy. The filling of the cavity is obtained by forcing the molten metal by means of a pressurized gas in order to rise into a ceramic tube, which connects the die to the furnace. The ceramics tube called stalk has high temperature resistance and high corrosion resistance. However, attention should be paid to the thermal stress when the stalk is dipped into the molten aluminum. It is important to develop the design of the stalk to reduce the risk of fracture because of low fracture toughness of ceramics. In this paper, therefore, the finite element method is applied to calculate the thermal stresses when the stalk is dipped into the crucible by varying the dipping speeds and dipping directions. It is found that the thermal stress can be reduced by dipping slowly if the stalk is dipped into the crucible vertically, while the thermal stress can be reduced by dipping fast if it is dipped horizontally.

An investigation of predictive control for aluminum wheel casting via a virtual process model

An advanced control solution, specifically Model-based predictive control (MPC), has been developed for a low-pressure die casting (LPDC) process used to manufacture aluminum alloy wheels. The control solution was developed offline using a high-fidelity 3D finite element model as a virtual process on which open and closed loop trials were performed. Open loop trials were used to assess the influence of process variables and to facilitate the development of a reduced-order state-space model to predict the approximate input–output behaviour of the casting process. An MPC controller employing this state-space model was used to regulate die temperatures in the virtual process during disturbance scenarios. Two disturbances typically found in the industrial process were simulated, that is, the temperature behaviour of the molten metal in the industrial process and the length of time the die remains open after the cast wheel is ejected from the dies. These disturbances cause the die temperatures to deviate from their optimal values, which can result in defective wheels. The developed control solution improved the process performance by rejecting the simulated disturbances and maintaining the die temperatures near their optimal values.

Numerical Simulation for Low Pressure Die Casting of Al-Alloy Motor Enclosure and Technology Improvement

The FDM numerical simulation software, View-Cast system, was employed to simulate the mould-filling and solidification process in low pressure die casting (LPDC) of Al-alloy motor enclosure. The distribution of liquid fraction, temperature field and the solidification pattern of casting were revealed and the formation mechanism as well as distribution rule of the potential defects, namely gas pores and shrinkage pores, were predicted. Furthermore the solutions to eliminate them were presented. By reducing the pouring rate, the turbulent flow at the corner of casting had eased, so the gas pores could be eliminated. Then the force-cooling system was installed on the top of mould, which could reduce the volume of liquid islands efficiently so that the shrinkage defects can be decreased to its limit.

Low-pressure die casting of magnesium alloy AM50: Response to process parameters

Low-pressure die casting (LPDC) process has been successfully used to produce sound magnesium alloy AM50 castings. The influence of process parameters: filling time, pressure holding time, die temperature, holding pressure and casting temperature, on the mechanical properties, microstructure and density of LPDC castings were studied. The optimal process parameters for LPDC casting have been experimentally determined as follows: filling time 15–22 s, pressure holding time 8–12 s, die temperature 390–410 °C, casting temperature 705–710 °C and holding pressure 0.08 MPa. The mechanical properties of the experimental part under the optimal process conditions are: yield strength (YS) 57.5 MPa, ultimate tensile strength (UTS) 193.8 Mpa and elongation 9.1%.

Microstructure and Mechanical Properties of Low Pressure Die Cast AM50 Magnesium Alloy

Compact AM50 alloy components were cast by Low Pressure Die Casting (LPDC) process. The microstructure and mechanical properties of cast components were investigated under as-cast and heat treated states. It was found that the microstructure of LPDC AM50 is composed of α-Mg and second phases - Mg17Al12 and Al8Mn5. Compared with Gravity die casting, LPDC AM50 alloy had much coarser grains and higher density, with smaller sizes and less content of second phases. The density of AM50 alloy by LPDC process was ρ=1.7836g/cm3, with increase of 0.45% based on Gravity die casting and much more increase compared with high pressure die casting. The as-cast mechanical properties by LPDC process were: σ0.2=57.8Mpa, σb=192.3Mpa, δ=8.7%. These of Gravity die casting were: σ0.2=53Mpa, σb=173.4Mpa, δ=8.1%. UTS in LPDC increased about 20MPa, with better YTS and Elongation. Compared with that of high pressure die cast AM50, the YTS of LPDC was much lower, with comparable UTS and Elongation. The mechanical properties of the heat treated AM50 alloy were still in the same level of as-cast state. AM50 alloy by LPDC process is not necessary subjected to tempering treatment.

Development of a 3-D thermal model of the low-pressure die-cast (LPDC) process of A356 aluminum alloy wheels

A mathematical model of the low-pressure die casting process for the production of A356 aluminum alloy wheels has been developed to predict the evolution of temperature within the wheel and die under the auspices of a collaborative research agreement between researchers at the University of British Columbia and a North American wheel casting facility. The heat transfer model represents a three-dimensional, 30° slice of the wheel and die, and was developed within the commercial finite-element package, ABAQUS. Extensive temperature measurements in the die and in the wheel taken over several cycles in the casting process were used to develop key process boundary conditions and validate the model. The predicted and measured temperatures agree very well, with the maximum difference less than 20 °C at the majority of locations examined. A heat flux analysis conducted with the model has identified the complex path that the heat follows within the die and wheel during the solidification process. A solidification path analysis conducted with the model showed the presence of a hot spot in the rim/spoke junction area, which was confirmed by the observation of macro-porosity in a sectioned wheel.

Microstructure and second-phase particles in low- and high-pressure die-cast magnesium alloy AM50

The microstructure and phase composition of low-pressure die-cast (LPDC) and high-pressure diecast (HPDC) magnesium alloy AM50 were examined by transmission electron microscopy (TEM) techniques in combination with optical microscopy, scanning electron microscopy (SEM), and electron-probe microanalysis (EPMA). It has been established that the dimensions and morphology of the constituent phases (α-Mg solid solution, Mg17Al12, and Al8Mn5) depend on the processing parameters. The results obtained suggest that there is a ternary eutectic with the aforementioned three phases in the Mg-Al-Mn system. Phase transformations leading to the observed microstructures are discussed.

Low pressure diecasting gives better yields and a finer finish

Low pressure diecasting gives better yields and a finer finish