鎂合金於薄壁鑄件之模流分析

Abstract

壓鑄法是利用高壓力將熔融金屬液注入金屬模具的模穴內，以便形成所需形狀尺寸之鑄件的一種加工方法。高生產性及良好的金屬熔液流動性以致可以使形狀複雜的鑄件也容易成形是壓鑄的優點，但加工中高速充填的之熔融金屬，常容易捲入氣體造成鑄件孔洞缺陷。 本研究的目的在瞭解鎂合金金屬熔液在模穴中的流動行為，並以電腦軟體模擬充填過程中流體的充填模式以及熱傳冷卻的現象，以預測鑄件充填過程中可能產生的缺陷。本研究中，針對傳統的扇形澆口應用於大面積薄鑄件可能會產生的缺點及限制深入探討，然後討論扇形澆口寬度及長度的比值對充填模式的影響，以及討論並瞭解厚度漸縮型澆口的充填模式，以解決傳統扇形澆口應用上的限制問題。

Die casting is a process which melted metal is filled into the die cavity by high pressure. High productivity and good castability by virtue of fluidity of melted metal under pressure are advantages of die casting. However, melted metal fluid filled into die cavity in high speed often rolls up the air remained in the cavity which in turn results in porous defects of the casted parts. The purpose of this research is to study the flow behavior of the metal fluid of Mg alloy in the cavity. Commercially available computer software package (namely Flow-3D) is adopted for simulation of the filling process. Temperature distribution of the casted metal in die cavity is also investigated. Effects of fan gate geometry on the flow pattern of the melted metal are also studies. Finally various fan gate geometry are proposed for improving the castability of Mg alloy in die casting.