Never change the Alloy, right?

There are several reasons to keep the existing alloy. One key argument is the complexity of the foundry’s handling of multiple alloys. Separate melting furnaces and crucibles are needed to transport the alloys, and internal scrap streams must be kept separate.

Example: Climate Compressor Housing

However, to achieve something new, several things must be changed. One current example is climate compressor housing. Several thousand die-casting machines are currently producing these parts, but the end of that production is near.

I can predict the end of production for a large portion of these machines without being a conspiracy theorist because there is legislation. The EU implemented the F-Gas Ban, which prevents the use of current climate gases. So, OEMs need to follow this law to sell cars in Europe after 2026.

On the technical side, the F-Gas Ban prohibits the current climate gas R-134a and similar products. The solution is to use CO2 gas. Because of its small molecule size, CO2 requires a few changes. The major change is the operating pressure. R-134a compressors operate at 12 to 15 bars of pressure. For the CO2 compressors, you need to 10x that pressure.

Currently, the R-134a compressor housings are made of high-silicon alloys like ADC-12 and AlSi10Mg. Because of the high eutectic fraction, the solidification is quite quick. So, the shrinkage porosity is distributed over the whole casting. With impregnation, the parts can be made leak-tight for the R-134a at a maximum of 15 bars.

No HPDC casting can hold 130-160 bars of operating pressure for a tiny molecule like CO2. Microporosity, which cannot be detected by X-rays or CT scans, causes leakages. Even impregnation does not help much.

What are the alternatives?

Forgings offer the porosity levels needed to sustain the high pressures. However, there are insufficient forging shops in Europe to supply the demand. And even if the forging capacity is built up, the matching capacity is the next bottleneck.

Also, the investment already made will be wasted, as new products for small DCM are rare and in a price war.

Rheocasting is the solution!

Rheocasting is just a melt preparation method that can be attached to an existing DCM. However, changing the alloy requires changing it, as these high-silicon alloys cannot be used.

As we already know the high eutectic fraction of the alloy causes porosity during solidification. When you take out even more alpha-phase aluminium by creating the slurry, the silicon content increases even more, causing a swamp-like microstructure. Lowering the silicon content can prevent that and produce highly pressure-tight castings that sustain the 160 bars of helium testing. On a side note, the carbon footprint is also better!

The disruption of the climate compressor market is an excellent opportunity to acquire new businesses for your small DCMs. And that is just one application where a new alloy brings new life and an unfair advantage to the market. Book a Rheocasting Workshop at your foundry to find out which application is the best for your product portfolio to acquire new castings. Schedule a free consultation for more information down below.