Rheocasting vs Thixocasting and High-Pressure Die Casting

Rheocasting, Thixocasting, and High pressure die casting (HPDC), all these manufacturing processes are done by applying external pressure. But there are some differences between all these processes.

In this article, we will discuss each of the processes in detail.

The Rheocasting Process

Rheocasting is a semi-solid die casting process, where the metal is kept in a state when it is neither fully solid nor liquid. This state is called slurry. We have described the steps involved in a typical rheocasting process:

  • Firstly, melt the metal.
  • Then, pass the metal through a chamber to form the slurry.
  • After that, inject the slurry inside the die cavity.
  • Wait until the casting has solidified.
  • Finally, retrieve the casting from the mold.

Flow Diagram of the Rheocasting Process

Production with rheocasting is cheaper than thixocasting. The solidification shrinkage of the parts is less compared to the thixocasting and HPDC process. However, it is difficult to maintain the cleanliness of the metal in rheocasting.

The Thixocasting Process

In the thixocasting process, the slurry is not made by cooling the molten metal. Instead, it utilizes pre-cast billets that are cast similarly to a traditional HPDC process. A typical rheocasting process may consist of the following steps shown in the diagram.

Flow Diagram of the Thixocasting Process

The components made by this process have excellent functional and mechanical properties because of the microstructure. However, this process is costlier than rheocasting.

High Pressure Die Casting

In this process, you have to inject the molten metal directly into the mold and then use pressure to fill the cavity. So, there is no need to make a slurry in this case. Therefore, it is simpler than the previous processes.

High Pressure Die Casting

HPDC is cheaper than thixocasting, and it is used for the mass production of aluminum die casting for various industries. It is a cost-effective and efficient process for casting a large volume of metal parts.

 

Is Rheocasting more Expensive than Other Processes?

Rheocasting and thixocasting are both semi-solid die casting processes. However, rheocasting is comparatively cheaper than thixocasting. In the thixocasting method, you have to make billets first and then use this to make the slurry for casting. But in rheocasting, you can form slurry out of the molten metal directly.

High-pressure die casting is cheaper than rheocasting in terms of production quantity. But for small-scale production, rheocasting is cheaper than HPDC. Because the machines and tools used in rheocasting are inexpensive, thus cost less.

What Are the Differences between Rheocasting and High Pressure Die Casting?

Though both rheocasting and high-pressure die casting use external pressure for the casting process, there are some differences between them. We have shown these differences in the table below:

Key Point Rheocasting High Pressure Die Casting
State of the Metal The metal used in rheocasting has to be in a semi-solid state before forcing into the mold. This state is also known as slurry. In high-pressure die casting, the metal has to be in a liquid state (molten metal) before forcing into the mold.
Cost of Production Rheocasting will cost less than HPDC if it is not used in mass production. For mass production, the cost will be higher than HPDC. If HPDC is used for mass production, the overall cost will be less than rheocasting.
Quality Rheocasting gives a more consistent microstructure than HPDC. Thus the quality of the parts is better than HPDC. Parts made with the HPDC process have good quality but not better than rheocasting.
Shrinkage of Parts After solidification, parts made with rheocasting will shrink less than parts made with HPDC. After solidification, parts made with HPDC will shrink more than parts made with rheocasting.

 

What Are the Differences between Rheocasting and Thixocasting?

Although thixocasting and rheocasting, both processes are part of the semi-solid die casting process, there are some differences between them. We have listed them down on the table below.

Key Point Rheocasting Thixocasting
Number of steps Rheocasting is a one-step process. Here, you will take the molten metal, make the slurry, and then pour it into the mold. After that, you’re done. Thixocasting is a two-steps process. In step one, you have to make billets using the HPDC process. In the second step, you will melt the metal to make a slurry and then continue.
State of the Metal In rheocasting, you will make a slurry by solidifying the molten metal. Hence it’s easier. In thixocasting, you will make a slurry by melting the billets. That is why it’s complicated.
Cost of Production It is cheaper than thixocasting. It is costlier than rheocasting.
Quality of the Parts The parts made by rheocasting are less consistent than the parts made by thixocasting. Parts made by thixocasting are more consistent.

You can also check out this Researchgate discussion to learn more.

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