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| CSIRO | SOLVE | Issue 5 Nov 05 | |
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ARTICLE
METALS MANUFACTURING: Sheets Ahead of the Rest
By David Adams
A new sheet-rolling process for magnesium can help manufacturers meet growing demand for the metal. Used in everything from mobile phones to laptop computers, magnesium has become the very fabric of the telecommunications revolution. But making the sheet material from which these items are produced involves a time-consuming and costly process in which huge slabs of the metal are reduced to the wafer-thin thicknesses used in the manufacture of portable electronic products.
Brad Cowley, CMIT’s business development manager, says magnesium sheet has traditionally been made by producing a large ingot or slab of magnesium (which can measure as much as 25 centimetres thick, a metre wide and five or six metres long) in a process known as ‘direct chill casting’. It is then trimmed by a process called ‘scarfing’ before being repeatedly hot-rolled to reduce it to the required thickness. The new process developed at CSIRO’s laboratories in Clayton, Victoria, is faster and more efficient because it eliminates much of the repeated rolling. Instead, TRC produces a product that finishes at three millimetres thick, direct from the molten metal casting. “We are producing a hot-rolled product very close to finished size, invoking further cost reductions due to the thinner starting size for finish rolling,” Mr Cowley says. “It then only needs moderate rolling – six, seven, 10 passes, whatever it might be – to get the product down to the sort of dimensions that are wanted, typically around 1 mm thick (for the manufacture of portable electronic devices).” Mr Cowley says industry is expecting the processing costs to drop by about 40 per cent, with an associated lift in productivity. “We have an expectation of achieving total manufacturing cost reductions in the order of 60 per cent of current costs. This will be achieved by producing a cast material at 3 mm thick.” This is a significant reduction on the current DC casting process. Illustrating potential demand for the process, Mr Cowley says the manufacture of lithographic plate has traditionally accounted for most of the magnesium sheet produced around the world – about 600 to 800 tonnes a year. However, the use of magnesium sheet in the manufacture of portable electronic communications devices, including music players, mobile phones, cameras and PDAs as well as laptops, accounts for only 200 tonnes a year, but is expected to reach similar levels in the next three or four years. “It’s a growth area,” he says. “There’s not much material used in each particular item – a PDA or similar doesn’t consume much weight – but the volumes are significant.” The project to develop the TRC process was launched four years ago. A core team of four people has since established an industrial-scale pilot plant to produce the magnesium sheet. In June this year, CMIT announced it had signed an exclusive agreement with Magnesium International Limited’s subsidiary Magnesium International (No 1) Pty Ltd for its magnesium sheet technology production process. Under the terms of the agreement, Magnesium International staff are working with CSIRO to commercialise the technology. Following a series of successful tests, production trial runs of high-end 3 mm magnesium alloy sheet have now begun. Patrick Elliott, deputy chairman of Magnesium International Limited, says that while there is a great deal of research around the world seeking better ways of producing magnesium sheet, the company feels CSIRO’s TRC application is “well ahead of the pack”. He estimates the technology should result in savings of up to 60 per cent on the current processes. “It’s a dramatic reduction in costs that will enable magnesium sheet applications to be developed and also be cost-competitive in the automotive sector,” he says. “This could see the magnesium sheet market grow to several hundred thousand tonnes per annum over a 10–15-year timeframe.” APPLICATION Through twin roll casting, magnesium sheet is produced at 3 mm, creating a more efficient starting size for finish rolling
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As with all manufacturing, reducing time and cost is an ongoing objective. In this case it is being achieved through a new ‘twin roll casting’ (TRC) process for magnesium sheet developed by CSIRO Manufacturing and Infrastructure Technology (CMIT).
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