高真空壓鑄件開發

傳統的壓鑄製程在金屬液充填模穴的過程中會捲入大量的氣體，容易在壓鑄件內形成氣孔，導致機械性質不穩定，因此不會用在需要承受負荷的結構件上。也不能銲接或熱處理，因為壓鑄件加熱後，捲入的氣體會膨脹形成氣泡。但近年來已發展出「高真空壓鑄」技術，藉由將壓鑄模穴內的空氣抽走，使壓鑄件的含氣量低於5 cc/100 g Al，不僅使壓鑄件的機械性質穩定，並且可以銲接與熱處理。本文以雪地摩托車零件為例，介紹高真空壓鑄件的開發過程。包括高真空壓鑄方案設計、澆流道設計與模流分析、壓鑄機設定與試模結果。

In conventional die casting process, a large amount of gas will be trapped in the melt when the melt fills the die cavity. The trapped gas may form porosities and cause large variance of mechanical properties. So conventional die castings are not used in structural parts that need to bear large load. Conventional die castings cannot be welded or heat-treated because the trapped gas will be bubbling when heated. Recently, the technology of “high vacuum die casting” has been developed, which reduces the air content of castings below 5 cc/100 g Al by evacuating the die cavity so that the mechanical properties of die castings are stable and die castings can be welded and heat-treated. This article uses a snow mobile part as example to introduce the development of a high vacuum die casting. The development includes die casting design, gating system design and filling simulation, die casting machine configuration and the result of die trial.