There is a saying that adding silicon to hardware can increase the fluidity of the alloy. This argument is not comprehensive, but biased and misleading. The main role of Xiasi in metal die casting is introduced below!

1. Adding silicon can increase liquidity. This function is mainly used for bottom filling under extreme low pressure, such as gravity casting. In fact, when the filling pressure exceeds 1 MPa, there is not much difference between the filled alloy and the alloy without silicon. The filling pressure can exceed 100MPa, and the alloy with poor fluidity will lead to insufficient filling.

2. It can reduce the volume shrinkage of "liquid-solid" phase transition. According to many experiments, hardware with silicon content of about 20% can achieve almost the same phase change volume. Therefore, if the aluminum piston is used for high temperature applications, it is usually an alloy with high silicon content. Due to the essential characteristics of the die casting process, it is a unidirectional high-pressure high strength mold filling casting, without reverse feeding function. It is completely different from the low-pressure casting and gravity casting in reverse feeding and mold filling process characteristics. For this reason, the industry has specially formulated a relatively low phase transformation shrinkage and the highest possible silicon content, especially for the hardware grades that cannot be reverse fed during the die casting process.

3. Adding silicon to the alloy also has disadvantages. In this way, the strength of the alloy is greatly reduced, the alloy is more brittle, and the elongation is also greatly reduced.