When most people think of car and truck
frames they think of steel stampings, but they might want to
consider a more rounded perspective, according to some
producers of tubular auto parts, who argue that the role of
steel tubes in automobile frames could grow.
That's especially true in the wake of new
emissions rules and more-stringent rollover standards in the
United States as well as stricter crash survival standards in
Europe, they say, because tubular structures are lighter, safer
and more efficient to produce than traditional stampings for
Increased U.S. fuel economy standards are
scheduled to take effect in 2020, which means automakers will
begin concept work by 2015 at the latest, according to Paul
Schurter, principal engineer of advanced engineering at
ArcelorMittal SA's automotive product applications unit. "But
they will not wait until then. It's not the type of thing that
can be accomplished in a normal product-design cycle," he
Hydroformed tubes are made by placing a steel
tube in a die and then injecting liquid under high pressure,
forming the tube into the desired shape and also to pierce or
otherwise modify it.
Steel tubes traditionally have been used in a
variety of automotive applications, including powertrains,
exhaust systems, axles and trailer hitches. Several sources say
the tubular content for those products isn't likely to grow
much. But in auto bodies, the story might be different.
General Motors Corp.'s Pontiac Solstice and
Saturn Sky feature hydroformed, advanced high-strength steel
(AHSS) body tubes, running from the front end to the rear
bumper on both sides of the vehicles to form the backbone of
the body structure. They might also provide a glimpse of what
the future holds, Rick Owens, general manager of sales at
ArcelorMittal's Dofasco tubular products unit, said.
But while there is "tremendous opportunity"
for AHSS tubes, especially in smaller diameters, there is also
fierce competition from other technologies, Owens cautioned,
noting that steel tubes are actually losing ground to stamped
parts in door beams. Vehicle assembly lines generally are
geared toward stampings, which historically have required a
different type of welding than tubes. Tube makers have made
efforts to integrate their products into traditional assembly
line welding techniques. Still, tubes generally cost more than
stampings and take more time to produce.
ArcelorMittal bills itself as one of the
largest suppliers of steel tubing for automotive components. It
also makes subassemblies and finished parts that eventually end
up in automobiles. In addition, the company ships tubes
directly to original equipment manufacturers and other
companies that bend, pierce or hydroform them into auto
One such company is Vari-Form Inc., Troy,
Mich., which specializes in hydroformed tubular components.
Hydroformed tubes were "all the rage" in the
early 1990s and the market matured in the mid- to late-1990s,
according to Terry Nardone,Vari-Form's commercial manager, who
adds that the industry has grown more modestly since then.
"It's still a solid growth industry," he said. "Applications
continue to be developed."
Vari-Form also has developed prototypes for
hydroformed tubes made from aluminum and magnesium but none has
gone into production, largely due to cost concerns on the part
"Between stamping, roll-forming and even
plastics, it's very competitive," he said. "No one can sit back
and wait for something to happen."