Semi-solid metal casting for lower cost production of metal components

The CSIR’s patented rheocasting technology allows for lower cost production of metal components. It is flexible and capable of processing just about any alloy or metal with a melting temperature below 1000°C.

Technical Field/Operating Unit or Centre:

CSIR Material Science and Manufacturing

Business Opportunity:

The aim is now to find a commercial partner for which a component can be produced using the R-HPDC technology.  Discussions of this nature are currently underway with bicycle  manufacturers.

Technology Description: 

Following research conducted at the University of KwaZulu-Natal in the mid 1990s, the CSIR, in collaboration with its research partners, secured an Innovation Fund project to develop a rheocasting system in 2000.
This resulted in the patented CSIR rheocasting system for the preparation of semi-solid slurries.

This process stems from a recent trend in the automotive industry to produce fuel-efficient vehicles through the use of aluminium and magnesium alloys. The bulk of the automotive industry’s needs in this
regard are satisfied through the use of liquid metal, high-pressure die casting (HPDC). The growing demand for improved quality and weight reduction is driving the development of new processing technologies. The problems inherently associated with liquid metal HPDC led to increased interest in semi-solid metal casting processes, which in turn led to the development of rheocasting.

There are two technologies that can produce metal slurries at a temperature at which semi-solid casting can take place, namely, thixocasting and rheocasting. Thixocasting is a two-step process, the main disadvantages being the higher cost of the process compared to conventional casting processes. Special feedstock material is purchased at a much higher cost and reheated to a semi-solid state – which is highly capital and energy-intensive – before being formed into a final
component. The scrap material from the manufacturing process cannot be recycled on site and is sold as conventional scrap. With rheocasting, in contrast, the molten metal is cooled and cast into a solid shape in one step. The biggest advantage of this process is that the slurry can be made on demand and ‘in-house’. The chemical composition of the cast metal can also be modified and tailored to meet the quality and property specifications of the components, and scrap and other used metal can be directly re-melted for subsequent rheocasting, which contributes to the lower production costs,
and hence growing interest by industry.

The rheo-high pressure die casting (R-HPDC) technology developed by the CSIR, which incorporates its rheocasting system, is both flexible and capable of processing just about any alloy or metal with a melting temperature below 1000°C.

The current focus is on the commercialisation of the R-HPDC technology. In order to achieve this, an advanced research
and testing laboratory has been established at the CSIR, comprising two HPDC machines: a research scale facility (130 tons) and an industrial scale facility (630 tons). Both machines have real-time shot control and monitoring capabilities, and will ensure that component research and testing can be done effectively before being tested on an industrial scale. It will also enable the research team to simulate industry conditions to cast components on an industrial scale.

Similar systems have been developed in other countries, using semi-solid metal and high-pressure die casting  techniques, but by taking these devices to market before being thoroughly tested,  high failure rates were experienced.
According to Dr Sagren Govender, leader of the CSIR’s advanced  casting technologies group, it is essential that the manufacture of components using this process should be proven to be consistent and reliable, and should not produce more than 5-10% scrap metal, preferably less than 5%. Only then can it be taken to market.

Before commercialising the R-HPDC technology, it is essential to ensure that the process can provide high-quality components at a competitive price. Because the automotive industry is cost driven and highly regulated, the focus of the research group is on demonstrating the technology on a product that is less regulated, and which can enter the market
much sooner than would be the case with automotive components. Once its feasibility is proven in a less regulated  market, e.g. the recreational market, it would be possible to expand the application of the technology to other market
sectors.

“We are currently in the final stages of development and are entering the commercialisation phase,” says Ulyate Curle, a senior metallurgical engineer and member of the research group. With the establishment of the industrial scale facility at the CSIR, the patented rheocasting device can be tested on a commercial scale to optimise the process.

Target Market:

The research group has already identified several potential products on which to demonstrate the technology, which would enable them to cast components and put them onto a platform to prove that it works. The technology can be used to develop components for a number of end-users, from the aerospace industry to prosthetics.

Govender believes that the ideal route would be to incubate the technology within the CSIR and, once it is found to be financially sustainable, to develop it into an independent company or transfer the technology to a local casting company that is willing to adopt this technology. By setting up a central manufacturing facility, it would be possible to create jobs and produce components that can be marketed locally and internationally.

Team / Inventor:

Dr Sagren Govender:  sgovender@csir.co.za

 

Contact:  Delon Mudaly

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