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Using sand cores, the weld-able, hollow die-cast parts have been developed. For casting, the transition flow filling method is applied to reduce gas containment and to minimize damages to the core. In designing the products, the newly developed core stress prediction system by melt pressure distribution and the newly developed in-product gas containment prediction system have been applied. The hollow die-cast frame made by the new method attains a 30% increase in rigidity and 1kg reduction of weight.

In general, welding of high-pressure die casting (DC) parts has been difficult due to gases trapped in the castings. This is a result of the high-speed turbulent flow condition of the DC process. These gases are liberated during welding and produce porosity in the weld joint. The Author had found the range where an enough welding quality was obtained without great drop in castability to the middle of the laminar flow and turbulent flow. This range has been defined as the transition zone. Moreover high strength Al-Mg-Ni alloy was developed by non-heat-treatment. The Transition Flow Filling Method(TFFM) has been developed, that can not only reduce the amount of trapped gases but also is applicable to standard high pressure die casting equipment. With this method, high quality DC parts can be produced that are weldable, strong and have high toughness.

The atomization of molten aluminum when injected during high-pressure die casting is analyzed to determine its effect in enhancing the strength of the product being cast. In the previously reported first step of this study, molten aluminum was injected into open space and its atomization was observed photographically. Now in the second step of the study, a simulation is conducted to determine how the molten aluminum becomes atomized at the injection nozzle (gate) and how this atomized material flows and fills the cavity. A new simulation method is developed based on large-eddy simulation coupled with the volume-of-fluid method. The simulation system is verified by comparing its output with photographs taken in the first step of the study. Simulations are then conducted using an approximation of a real cavity to visualize how it is filled by the atomized molten aluminum.

In recent years, studies have been conducted on the relationship between the J factor, which indicates flow of molten aluminum at the time of injection, and the quality of HPDC products. The flow of molten metal at a high J factor is referred to as “Atomized Flow.” The authors and others conducted studies on the relationship between the J factor and the strength of HPDC products. An area exceeding 300MPa was found in the product produced at a high J factor corresponding to the “Atomized Flow.” The defect was less in the above-mentioned position because the gas porosity was finely dispersed. Considering that the fine dispersion of gas porosity is related to the “Atomized Flow”, pictures were taken to analyze “Atomized Flow.” The molten aluminum was ejected into an open space at a high speed and the splashed conditions were photographed. From the images taken by the pulse laser permeation, the conditions of microscopic atomized flow were observed precisely.

When using aluminum for vehicle body parts to reduce weight, the high pressure die casting (HPDC) is widely applied due to its adaptability to thin-wall products, near-net-shape castability, and short casting cycle time. Since a hollow construction is advantageous to increase stiffness of body parts, there has been a need of development of techniques for casting of hollow parts by HPDC. So far, hollow casting by HPDC has been realized for small parts using sand cores. When applying that method to large parts, however, it is necessary to increase filling speed. When the filling speed is increased, the core tends to break. In this project, we have developed a method to estimate changes of pressure distribution when filling molten metal by the casting simulation in order to analyze damages to the core. Through the analysis, we discovered occurrence of impulsive pressure waves.