F-Gas Ban - Replace forgings with Rheocasting

Let me tell you in this article why it is necessary to replace forgings with Rheocasting and how you can do it.

The F-Gas Regulation is a crucial piece of EU legislation designed to address fluorinated greenhouse gases (F-gases), commonly used in climate compressors, air conditioning systems, refrigeration equipment, and heat pumps. The regulation focuses on mitigating the environmental impact of these F-gases, as they significantly affect global warming and ozone depletion.

The regulation promotes the transition to refrigerants with lower GWP (Global Warming Potential) values. This shift toward low-GWP alternatives, such as natural refrigerants (e.g., carbon dioxide, propane, and ammonia) and hydrofluoroolefins (HFOs), helps minimise climate compressors’ environmental impact. These alternatives have significantly lower GWP values and are more environmentally friendly.

Climate compressors are standard HPDC parts that run on several hundred DCMs worldwide. With some usage of an impregnating agent, they are used for today’s climate compressors. That production method is no longer usable when the climate gas changes to smaller molecules like CO2. They will creep through the casting and the impregnating agent—no chance of keeping them leak-tight. The leakage allowance is often measured with helium, which is even more mobile at high pressures.

Forging is the first production method that comes to mind for these tightness requirements. The excessive force closes all pathways and makes the part leak-tight. The downside is that forgings cost 5 to 10 times more than castings.

Rheocasting is the solution. Many leaking issues come from feeding and shrinkage problems in conventional HPDC. The solidification shrinkage in aluminium from the liquid to the solid state is 6.6%. In HPDC, you need to compensate for the whole 6.6%. In Rheocasting, there are already solid globulites in the slurry. So, the shrinkage is lower, so there are fewer shrinkage issues to feed.

In HPDC, a dendritic microstructure is typical. These dendrites introduce microporosity into the microstructure and physically block the shrinkage’s feeding. This blockage leads to porosity pathways through the part, which results in high leakage rates.

In Rheocasting, dendrites are broken up during the slurry-making process, forming spherical globulites. The mixture of solid and liquid phases, with their thixotropic properties, has excellent flow behaviour. It also helps to prevent these porosity pathways. Therefore, a leak-tight battery casting can be cast with Rheocasting.

When Rheocasting is implemented correctly, you can keep using the hundreds of DCMs and gain an unfair advantage over every forging shop. A production lot using the Comptech RheoMetal process achieved a 100% tightness rating at 160 bar of helium pressure.

When you want the be on the receiving end of millions of compressor housings each year, the Rheocasting Expert on Demand is the right service for you. In that remote consulting program, our Experts guide you into series production of Rheocasting CO2 compressor housings.