CHANGES IN MANUFACTURING MATERIALS BRING NEW CHALLENGES FOR THE AUTO INDUSTRY
It may not seem readily apparent but there’s been a decades-long battle going on in the auto industry over the choice of materials for virtually every part and component that goes into
a car or truck.
That battle was thrust into the public spotlight earlier this year with Ford’s announcement that the body structure of its next-generation 2015 F-150 pickup will be made from aluminum. Suddenly, people began thinking about what their vehicles are constructed from. Aluminum bodywork is nothing new. It was the material of choice for some early auto bodies as well as several sports cars. On a larger scale, various Land Rovers have employed aluminum bodywork, while Audi’s A8 and Jaguar’s XF and XJ models extensively use it in their body and chassis structure.
But, for most consumers, it’s a safe assumption that they think their cars and trucks are made
primarily of iron and steel. In most cases they would be right, but the degree of dominance those materials once held has been under siege since as far back as the 1970s. The amounts of aluminum, plastic and other materials in vehicles has been gradually increasing since then, at the expense
of traditional ferrous metals.
Fuel economy push
The driving force behind the switch to other materials is the continuous tightening of fuel consumption standards, which are now on track toward a fleet-average rating of 4.32 L/100 km (54.5 mpg U.S.) by 2025. In theory, reducing weight leads directly to reduced fuel consumption and aluminum is lighter than steel, for a given volume.
There is still potential for further fuel economy improvements from powertrain efficiency gains, as well as from other areas such as aerodynamics, reduced drivetrain losses and tires with reduced rolling resistance. But the consensus is broad that such measures alone won’t achieve the established target. Most engines and transmissions are now built primarily of aluminum and most of the non-structural parts that can offer significant weight savings have already been given the lightening treatment. The low-hanging fruit has all been picked.
To achieve the mandated efficiency, those measures will have to be accompanied by further reductions in mass of as much as 30 per cent from current levels, according to one industry executive. That’s in the range of 400 to 600 kg (900 to 1300 lb) for a typical car or light truck.
Lighter structures
The biggest component remaining with the potential to yield weight savings of that magnitude is the vehicle structure itself. Which is why Ford took the big decision to build the F-150 body of aluminum. And why it won’t be the last to do so.
Ford says its aluminum-bodied F-150 is about 330 kg (730 lb) lighter than if it were made of steel. There’s more to consider than just weight, however — a point both the steel industry and other manufacturers are quick to make.
While aluminum has only about one-third the density of steel, the two have different strength and fatigue properties, so they aren’t exact replacements for each other and not all the theoretical weight savings can in reality be necessarily achieved. Each component and system has to be designed with those properties in mind to satisfy the long-term requirements of the application.
So while making vehicles lighter, engineers also face the challenge of keeping costs under control. In that respect, aluminum is less competitive with steel — some say it’s about three times as expensive. That cost premium is just one of the reasons why the majority of today’s cars and trucks are still made primarily of steel.
Proven methodology
There’s also well more than a century of experience working with steel in the auto industry, at every level, from component design to end-use body repair. Experience that is both hard and costly to replace — not just at the manufacturing level but at the dealer level.
The steel industry is fighting back with new alloys, collectively known as high-strength (HSS) or advanced high-strength (AHSS) steels, designed and controlled right down to their microscopic structure to enable increased structural strength with reduced weight.
They’ve been widely adopted throughout the industry, with impressive results. General Motors claims that high-strength steels comprise 71 per cent of the body of its new Chevrolet Colorado mid-size pickup, which also uses aluminum for its hood and various chassis components.
There’s also the possibility, perhaps probability, that carbon composite materials will seriously
challenge all the metals for use in structural components. About the only thing that’s certain is that the materials mix in tomorrow’s vehicles will be different than it is today — and that adapting to those changes will add yet another challenge for auto dealers.
