A Range of Solutions for a Variety of Semi-solid Casting Methods

Semi-solid casting is a process where metal is partly solidified at the time of injection. The main benefit of this process is the ability to produce pressure tight, heat treatable parts with very low porosity^† in a very fast cycle time^†. It is theorized that the semi-solid starting point promotes a more globular grain size that gives greater strength.

Various methods of making the semi-solid slurry have been developed. Some of these are:

• Thixocasting
• Thixomolding
• Rheocasting

In all cases, the viscosity of the shot^† decreases when pressure is applied, allowing the metal to enter and fill the die cavity^†.

Porosity is one of the biggest problems in die casting^†. The die casting process is very often used to make lightweight components out of light metals to replace steel or iron parts. Since the intrinsic strength of these lighter metals is less than that of steel, anything that can adversely affect the strength of the component is undesirable. The presence of small pores within the cross section of the casting can have a big impact on the tensile strength. In semi-solid casting^†, care is taken to prevent both kinds of porosity by the design of the process. Chem-Trend’s die lubricants are specially designed to preserve the integrity of the casting by not contributing to gas formation within the die.

Due to the lower temperatures of the melt, injection velocities in semi-solid casting may be higher than in conventional high-pressure die casting^†. In order to prevent premature solidification of the semi-molten metal, the lubricant must provide some thermal insulation. It is also conjectured that the presence of solids in the mix may contribute to erosion of the lubricant film. To protect against these conditions, Chem-Trend formulations are designed to form adherent films that deliver exceptional performance under these conditions.

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