Optimization of a Permanent Step Mold Design for Mg Alloy Castings

Abstract

The design of a permanent Step mold for the evaluation of the mechanical properties of light alloys has been reviewed. An optimized Step die with a different runner and gating systems is proposed to minimize the amount of casting defects. Numerical simulations have been performed to study the filling and solidification behavior of an AM60B alloy to predict the turbulence of the melt and the microshrinkage formation. The results reveal how a correct design of the trap in the runners prevents the backwave of molten metal, which could eventually reverse out and enter the die cavity. The tapered runner in the optimized die configuration gently leads the molten metal to the ingate, avoiding turbulence and producing a balanced die cavity filling. The connection between the runner system and the die cavity by means of a fan ingate produces a laminar filling in contrast with a finger-type ingate. Solidification defects such as shrinkage induced microporosity, numerically predicted through a dimensionless version of the Niyama criterion, are considerably reduced in the optimized permanent Step mold

Evaluating the Tensile Properties of Aluminum Foundry Alloys through Reference Castings—A Review

“…The comparison between reference dies #3 and #4 indicates that the die configuration is an important parameter in assessing the tensile potential of an alloy as much as the melt quality and the pouring conditions. Timelli et al [ 23 ] noted that by modifying the runner and gating systems in reference die #3, the amount of casting defects could be minimized. This was shown in both experimental and numerical simulation studies.…”

“…Variations of the step design have been recently studied to improve the quality of test specimens obtained. It is worth noticing the optimization of the step mold design proposed by Timelli et al for Mg alloys, which could be probably used for other foundry alloys [ 23 ].…”

“… ( a ) step casting produced with reference die #3; ( b ) defects observed under X-ray scan; ( c ) distribution of micro-porosity due to shrinkage predicted by magma-simulation; ( d ) modified step casting; ( e ) improved quality of casting as observed under X-ray scan; ( f ) distribution of micro-porosity percentage (%) as indicated by the color code [ 23 ]. …”

Investigation of rheo-diecasting mold filling of semi-solid A380 aluminum alloy slurry

“…Using the orthogonal experiment range method, Zhong et al [13] deduced the rank of the process parameters affecting the mold filling capacity. A step mold has been developed by the Aluminum Association [14]; this mold can reduce the influence of the process parameters on mold filling [15] and reduce their effects during the process of rheo-diecasting mold filling in the absence of turbulent flow [16]. The short-shot process, in conjunction with the formula L N = L f / W (L N is the length of the normalized flow interface, L f is length of the flow front interface, and W is the width of the flow channel), has been used by Janudom et al [17] to investigate the flow pattern of the semi-solid slurry.…”

Repeatability of tensile properties in high pressure die-castings of an Al-Mg-Si-Mn alloy

“…This results in a high probability of forming defects, in particular porosities in individual die-casting. More importantly, the defect distribution in the die-castings is random and irregular, resulting in a large uncertainty in the mechanical properties and a poor repeatability between different types of die-castings and even in the same location of a casting made in different manufacturing cycles [8,9]. In reality, a relatively large design margin is usually given in order to compensate for the detrimental effect caused by the internal defects in die-castings.…”