Papers by Keyword: Low Pressure Die Casting

Abstract: To achieve a required product quality during Low Pressure Die Casting (LPDC) process, it is necessary to identify and also control the main input parameters affecting the casting defects to arrive at the desired output quality. In industrial scale LPDC, where the issues of part quality, cost, and cast speed are the main driving forces for the industries, the cast process optimization to have minimum defects is quite essential. The LPDC process of light weight metals is defined as a casting process where the die is filled relatively slowly at low pressure. The melt flow regime has low turbulence, and filling process can be defined as relatively smooth filling. In recent years, in order to limit the component defects, the through process simulation has widely been used. In an interactive simulation environment, a full multi-phase casting process simulation (thermal-fluid simulation using multi-physical domain) along with its material and mechanical simulations are carried out in a single environment. One of the main contributions of this paper is to show the advantages of using full through process simulation of LPDC to limit the defect in the component. An experimental program along with a comprehensive process simulation has been setup to optimize the casting process and the results were presented for real world case studies.

Abstract: Aluminium AC4B alloy is widely used in automotive industries for various components. However, when this alloy is used to produce motorcycle cylinder head by Low Pressure Die Casting (LPDC) process, high reject rate was often found due to shrinkage, porosity and misrun. Addition of grain refiner and modifier is an alternative for this problem, through the control of solidification process that results in grain refining and microstructure modification. This study was aimed to investigate the effect of combination of 0.02 wt. % Sr modifier with variation of Ti grain refiner on the characteristics of AC4B alloy and the reject rate of cylinder head components. The Ti grain refiner was varied 0.063, 0.083 and 0.108 wt. % Ti and added at the holding furnace prior to LPDC process. A series of test was conducted including hardness test from the thin and thick regions of the part, tensile test, fluidity test, vacuum test as well as observation of microstructure by using optical microscope and Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-Ray Analysis (EDAX). The results showed that the higher the Ti content, the higher the hardness for both thin and thick areas, the lower the fluidity of the molten metal. At the maximum level of Ti of 0.108 wt. % and 0.02 wt. % Sr, the reject rate was significantly reduced from 3.59 % to 1.38 %.

Abstract: The Liquid Surface Pressure Control is the key factor for the guarantee of Low Pressure Die Casting Quality. Regarding to the disadvantages of conventional PID Control such as pressure fluctuation, poor repeatability of the pressure curve, and so on, we propose Liquid Surface Pressure Control System (LSPCS) based on Fuzzy Adaptive PID. Design method of Fuzzy PID Controller has been discussed, and the realization methods of the hardware and software in this system are developed. This proposed system has a good performance in practice.

Abstract: The Quality Index is a useful tool allowing to assess the metallurgical quality of aluminium AlSiMg foundry alloys (AlSi7Mg03/AlSi7Mg06, or A356/357 in North America). Its value, calculated from the ultimate tensile strength and elongation, increases with the metallurgical quality of the casting, i.e. with finer dendrites, lower microporosity, lower iron content and cleaner metal. This Quality Index does not depend on the degree of temper applied during the heat treatment (aging time and temperature). This paper will briefly explain how solidification modeling can provide the local value of the Quality Index, via the secondary dendrite arm spacing and level of microporisity calculated from the predicted values of the local solidification time and solidus velocity. The validity of the predictions has been assessed against the properties of tensile specimens excised from parts of different geometries produced by a variety of casting processes, as reported in the literature. The case study of a race car bell housing poured by two processes, namely gravity sand casting (GSC) and low pressure die casting (LPDC, or LPPM for Low Pressure Permanent Mold in North America), will be the focus of the present paper. The Quality Index has been measured and predicted at 3 locations in the castings after a T6 temper was applied which resulted in a minimum elongation of 5% for both the GDC and LPDC bell housings. Metallographic examination and image analysis allowed to quantify the superior metallurgical quality of the LPDC housings when compared to their GDC competitors.

Abstract: 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.

Abstract: A modified Cellular Automaton model was presented to simulate the evolution of dendritic microstructure in low pressure die casting of Al-Si Alloy, which accounted for the heterogeneous nucleation, the solute redistribution both in liquid and solid, the interface curvature and the growth anisotropy during solidification. The free growth of single equiaxed dendrite and the evolution of multi dendrites with various crystallographic orientations were predicted. The variation of the dendrite tip velocity and local solute concentration at the solid/liquid interface were analyzed. The grain morphology of aircraft turbine wheel casting at different specimen points were predicted and compared with experimental results.

Abstract: Canadian researchers are actively engaged in the development of novel cast, wrought and composite materials that are based on Mg. An overview is provided of Canadian research projects for new applications of Mg alloys that are targeted to the growing needs of the automotive sector. The research work described is funded primarily through two federal programs: the Canadian Lightweight Materials Research Initiative, and the Materials and Manufacturing Theme of the AUTO21 Network of Centres of Excellence. It includes work on mechanical and corrosion performance of high-pressure die castings, gravity and low pressure castings using permanent and sand molds, sheet Mg development and magnesium matrix composites. The metallurgical research facilities at the CANMET Materials Technology Laboratory are featured.