Why is Rheocasting not in Series Production everywhere?

Prof. Flemings invented Rheocasting in the 1970s, around 50 years ago. That is a long time to have not taken over a significant part of the world’s casting production. But why is that?

1. Temperature Control
   Over the decades, various attempts have been made to try out the technology for small-volume parts. There are 87 different ways to make the slurry, which never really worked. The main reason here is that 86 of these ways are temperature-controlled. So, consistent production is impossible as the production-based variations in liquidus temperature are larger than the temperature difference between the solid fractions. Comptech released their enthalpy-controlled Rheometal process first in 2020. So, it is brand new, perfectly production-stable and has to fight the negative experiences of the past.
   
   

2. Property Requirements
   When we go back in time, ductile and weldable high-pressure die-casting was first introduced in 1994. And until a few years ago, the sizes were not too big, so HPDC had no issues producing good structural parts. However, since the introduction of Gigacastings, the long flow length and extended tool lifetimes of these expensive dies have become a totally different animal. A similar principle applies to thermal conductivity. Even 4G antennas couldn’t saturate the thermal conductivity of HPDC alloys. Starting from 5G, thermal conductivity becomes the bottleneck. Rheocasting is the solution for that as well. Also, the latest iteration of the compressor housings for F-Gas-Ban systems using CO2 as a medium requires 160 bar of Helium-tight castings. That is far outside the scope of HPDC.
   
   

3. High Silicon Alloys
   The most common HPDC alloys are AlSi10MnMg, AlSi9CuMg, and AlSi12. These alloys are selected because they are near the aluminium-silicon-eutectic point, which allows for good castability and quick solidification. Quick solidification is what holds Rheocasting back from implementing its potential. However, an alloy change used to be nearly impossible for most applications. The good thing is that this is currently changing to accommodate more sustainable alloys without heat treatment and lower silicon contents. They are way more challenging to cast in HPDC but perfect for Rheocasting, as the silicon content does not define the castability in Rheocasting.
   
   

4. Tool Design Adjustments

   In HPDC, you try to get the liquid metal as quickly as possible in the cavity, which causes turbulent filling of the mould. To improve the filling capabilities and allow for easy trimming, the ingates are thinner than the part. However, in Rheocasting, you try to get a laminar filling of the cavity. Therefore, you need thicker gates that do not accelerate the metal. If you’re not accommodating these changes, which happens in many trial castings, the results in Rheocasting are not at the expectation. This is not because of the process; it is because the surroundings limit the process.

If you sum these points up, it is pretty clear that without cooperation through the supply chain, a switch to Rheocasting for better properties, better sustainability, and longer tool lifetime is needed. However, it still requires more business development than classical HPDC castings.

But the cool thing is that the market is wide open for you to take it. If you don’t know the best starting point for your foundry, learn more about the Rheocasting Business Development Package. You can also directly schedule a Free Consultation Call to inquire more information about your foundry’s current situation.