Ultra-strong steel to aid fuel goal

Advanced high-strength steels could play a key role in helping car makers achieve safety and fuel economy targets from 2004, according to an international consortium of 33 steelmakers.

At the Geneva Motor Show this week the Ultra Light Steel Auto Body consortium revealed two concept cars to demonstrate how these goals could be achieved, as the culmination of the ULSAB Advanced Vehicle Concepts project. The advanced steels could be produced at several of Anglo-Dutch steelmaker Corus’s UK plants if required.

The concept cars, a three-door hatchback typical of the European market, and a medium US-style four-door saloon, were designed and computer analysed by consultant Porsche Engineering Services. The consortium says they could be built for no more than the cost of a typical car of today, using essentially the same forming technology.

Frank Walker, chairman of the ULSAB AVC technical committee, said that whereas previous ULSAB projects had used technology that could be implemented immediately, the AVC study looked into the future. ‘These are options we think will enable designers to use steel to achieve their primary objectives in 2004 and beyond,’ he said.

Plus, the project looked at the whole car, not just the body.

Kerb weights range from 933kg for the petrol hatchback to 1,031kg for the diesel saloon, which is relatively light compared to mass-produced cars. Projected fuel consumption is 64.2mpg (4.4 litre/100km) in the European driving cycle for the hatchback and 88.2mpg (3.2l/ 100km) for the diesel. Manufacturing costs are estimated at $9,200-$10,200 (£6,500-£7,000).

Key to the project is the availability of advanced low-carbon steels with a dual-phase microstructure. Dual-phase steels have a low initial yield stress, so they can be formed fairly easily into complex shapes, combined with a large capacity for work-hardening, which gives good crash performance. ‘Developments in the past 10 years or so mean the international steel industry is confident of producing consistent, high-quality advanced high-strength steels,’ said Walker.

Such steels can be made in a hot rolling mill, by controlling the cooling cycle, on a continuous annealing line, again by controlling the maximum annealing temperature and cooling rate, and on hot dip galvanising lines. Corus has a range of all these facilities in the UK including, at Port Talbot, one of Europe’s most efficient annealing lines.

The high-strength steel makes 80 per cent of the concept vehicle. The consortium will now try to persuade manufacturers to adopt the concept cars’ techniques.

The ULSAB project was started to fight back against a perceived threat by aluminium and composites as car makers sought to reduce the weight of cars.