Steel Attacks Closure Panels Doors, hoods, decklids can be made 10% to 30%lighter

Exactly how much weight can you take out of a steel car without substituting lighter alternative materials? That's the question an international consortium of 35 sheet steel producers -at considerable expense - continues to research.

The efforts started in the mid-1990s with the so-called body-in-white: a car or truck's raw steel body without the doors, hood or decklid attached. The result, $22 million later, is 12 physical prototypes of the UltraLight Steel Auto Body (ULSAB), which are at least 25% lighter than conventional steel car bodies. Now steelmakers are focusing attention - and some big bucks - on closure panels and suspension parts with the UltraLight Steel Auto Closure (ULSAC) and UltraLight Steel Auto Suspension (USLAS) studies. The results of the ULSAC research were released in late September. Results of the suspension research are expected next year.

The aim of all these projects, of course, is to convince automakers they should use new steel alloys and processing techniques to reduce weight rather than resorting to lighter-weight alternative materials such as aluminum.

Steel usually is the material of choice for body panels because of its strength, dimensional stability and low cost. But lighter-weight materials such as aluminum, thermoplastic and sheet molding composite (SMC) have been making inroads in specific cases where special styling touches are needed on niche vehicles, or when a car or truck is having weight problems. In fact, slapping aluminum hoods on chronically overweight cars to save a few precious pounds has become a tradition in Detroit. It isn'tcheap, but it is fast and effective. And, of course, this is one tradition the steel industry doesn't like.

All of these steel engineering exercises would be hopelessly self-serving if it weren't for one fact: steel almost always is the lowest-cost automotive material, and the one that engineers and assembly plants are most familiar with. Also, as with the ULSAB, the highly respected Porsche Engineering Services Inc., the engineering arm of the famed carmaker, is performing the closure panel study. So it is worthwhile for automakers to pay attention.

The results of this latest ULSAC study show it is possible to make steel hoods, door panels, deck lids and hatchbacks that weigh 10% to 30% less than what's out there today. Furthermore, the research shows that lightweight steel panels also can be produced at the same cost or only a few dollars more than traditional closures.

How is this accomplished? Just like they did with the ULSAB, Porsche engineers threw out the old, established ways of designing doors, hoods, and hatchbacks and started with a clean sheet of paper. Tailor-welded blanks, high-strength steel and sheet-metal hydroforming techniques all were used to create a new breed of much lighter, more structurally efficient closure panels.

In some cases, new steel "sandwich" materials that use a thin sheet of polypropylene plastic pressed between outer layers of steel sheet were used, but nothing outlandish. Theoretically, a car with four doors, a hood and decklid made using these lightweight steel designs could be made well over 100 lbs. (45 kg) lighter.

If these results are proven out with physical prototypes (initial results are only computer-engineering studies), lightweight material producers should take note. Today hoods made of aluminum and SMC also weigh about 30% less than comparable steel components.