Abstract
In high-pressure die casting, attention has been paid to the J factor, which is defined by the speed of the metal injected at the gate and the shape of the gate. In casting experiments using a piston die, the porosity of the product can be reduced by increasing the J factor such that the metal flow passing through the gate forms an atomized flow. To clarify the underlying mechanisms, we developed a system for simulating a two-phase flow of air and aluminum by large-scale calculations of turbulent flow. During the development of the system, we injected metal into an open space and performed imaging to confirm the state of the atomized flow. The system was then verified by reproducing the atomized flow. The analysis results visualized the many small turbulent vortices generated in the thick part far from the gate. We demonstrated that the change from small to longitudinal vortices promoted entrainment of air into the aluminum and increased the efficiency of air expulsion outside the die through an increase in the J factor.
Highlights
High-pressure die casting (HPDC) is a method of casting at high speed and high pressure that offers the advantages of rapid cooling and production of fine microstructures
A relationship was demonstrated between increased J factor and quantitatively enhanced casting quality, the J factor is an empirical formula that defines the flow of metal as it passes through the gate, whereas the internal quality that we aim to enhance in this experiment is in the thick parts, which are far from the gate
We developed a system for performing turbulence calculations of this two-phase flow and investigated the mechanisms underlying the reduction in porosity by increasing the J factor
Summary
High-pressure die casting (HPDC) is a method of casting at high speed and high pressure that offers the advantages of rapid cooling and production of fine microstructures. One issue with HPDC is that the strength of manufactured pieces is degraded by porosity arising from gases such as air that are entrained into the metal when it is injected into the die at high speed Approaches for solving this issue have generally involved use of a strong vacuum or substitution of oxygen in the cavity [1,2]. In computational fluid dynamics (CFD), large-scale turbulence simulations using high-speed computational processing (e.g., parallel processing) are being applied to understand an increasingly wide variety of phenomena Against this background, research has been conducted into basic simulations to reproduce the injection condition of the metal at the gate in order to visualize the flow during HPDC [7].
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