Prediction of Zinc Deposition on Mold Surfaces in Zinc Alloy Die Casting Using a New Simulation-Based Evaluation Method

Sakuragi T, Fuwa D, Nakayama I and Tomioka Y

Published on: 2024-10-31

Abstract

In the die casting process, the adhesion of the zinc alloy to the mold surface, which occurs over an extended period, hinders continuous production. The adhesion of the metal alloy to the mold surface is believed to occur not only due to the soldering reaction between the zinc alloy and the mold surface but also due to lamination caused by rapid solidification.

In this study, our goal is to predict the areas of zinc alloy adhesion on the mold surface that result from lamination after prolonged die casting. We derived the cooling rate at which lamination occurs. Additionally, it has been confirmed from actual die casting experimental data that this lamination causes zinc alloy adhesion on the movable mold surface [3].

We propose a new evaluation method based on the cooling rate predicted from mold filling simulation and heat transfer analysis inside the mold to predict the areas where lamination will occur on the mold surface. The predicted results using the proposed method showed a very good agreement with the areas where zinc deposition was observed in the experiments.

Keywords

Soldering reactions; Adhesion of metal alloy; Casting Defect; Prediction of lamination; Cooling rate; Zinc die casting

Introduction

In the manufacturing process of die casting, lamination is a major issue because it causes blisters after plating on the surface of castings, as shown in previous papers [1-3]. In die casting, the tip of the molten metal runs ahead, causing the cavity near the mold surface to be filled with molten metal before the entire cavity in the mold is fully filled. Immediately after that, the molten metal attaching to the mold surface solidifies rapidly due to cooling from the mold. Subsequently, the solidified metal on the mold surface deforms rapidly due to initial solidification deformation [4-6]; this deformation causes the rapidly solidified tip to detach from the mold surface, creating a gap.

The cooling rates of the casting can be predicted from DAS? (Dendrite Arm Spacing?) data measured from the microstructures of actual castings [3]. Therefore, it is possible to predict the areas of the chill layer near the surface of the casting based on the cooling rate predicted by the analysis of the mold filling and solidification processes; this means we can predict the lamination areas by predicting the area of the chill layer. Furthermore, lamination causes the adhesion of zinc alloy to the mold surface when castings are ejected from the mold. Consequently, we can also predict the areas on the mold surface where the adhesion of zinc alloy occurs by predicting the area of the chill layer.

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