Whether they're used in steel
wagons or station wagons, high-strength steels (HSS) are
gaining more and more acceptance from customers. Well, OK, not
many station wagons are among North American automobile
lines-people prefer minivans or smaller, more environmentally
friendly cars that weigh less and have les overall impact on
But other customers are responding. A
Swedish manufacturer of steel wagons for the transport of iron
ore, for example, has seen great success with the use of
high-strength steels manufactured by Svenskt Stal AB (SSAB),
The new steel wagons are in service between
Lulea, Sweden, and Narvik, Norway, where the highest
permissible axle load is 30 tonnes, which means that every
wagon could weigh a maximum of 120 tonnes when fully laden.
Sweden's LKAB, which manufactures the
wagons, has raised its delivery capacity substantially in
recent years, and the trend will continue in the immediate
future, according to a case study on SSAB's Web site. In order
to succeed, transport must take place without disturbances and
at high efficiency. The designers have outfitted the wagons for
rapid loading and unloading, which takes place while the train
"We had to put to use everything possible
within the framework set by the authorities for railway
wagons," said Jonas Finn, LKAB's project leader for the
development of the new wagon bodies. "In the design work, we
also had to take into consideration that the wagons must be
more efficient and simpler to maintain." The lighter wagons
have led to more profitable transport, since the payload
capacity of the wagons has been increased by 20 percent in
terms of weight and around 25 percent in terms of volume.
General Motors Corp., Detroit, has got into
the act in a more traditional way, working with steel producers
through the American Iron and Steel Institute's Steel Market
Development Initiative to increase the use of high-strength
steels in the vehicles it manufactures.
Curt Horvath, GM's technical fellow of
materials and corrosion engineering, global technology
engineering, body structure and closure materials, advanced
vehicles and global programs, said the automaker sees numerous
advantages in the use of high-strength steels and is having
good success using the products in many vehicles and
"Depending on the type and strength of the
steel, we can engineer vehicle components to absorb energy from
crash events and significantly reduce the amount of energy
transfer to the occupants and, where necessary, we can select
the steel grade to resist deformation and prevent intrusion
into the passenger compartment, such as in side impacts and
rollover events," Horvath said. "There is a lot of engineering
and materials science involved in vehicle design. We routinely
use a wide range of high-strength steels, and the newer
advanced high-strength and ultra high-strength steels."
It isn't uncommon to have a body structure
mass with 60 to 70 percent high-strength steel content, he
said. "The real key is to use the steels where they provide the
most benefit, and then select the proper material for the
application. Almost every major structural member uses some
form of HSS. I guess it would be easier to identify
non-high-strength steel parts floor and compartment pans and
dash panels are generally low-carbon steel."
But Detroit has to do a better job of
informing the car-buying public of the use and benefits of
high-strength steels, Horvath said. "Consumers benefit from
high-strength steels in the safety and improved fuel economy of
the vehicles they purchase. However, for the most part, I don't
think consumers recognize how much high-strength steels are
used in the vehicles they purchase. In fact, I am not even sure
that they really care. Today's consumers are largely driven by
reported safety ratings from federal government crash tests. As
a group, I don't think consumers understand how much material
technology is commonplace in the vehicles they are purchasing.
As long as a vehicle meets their expectations for safety and
other needs, such as fuel economy, they are happy.
"I don't think that the auto industry as a
whole has really educated the consumer about the advantages of
high-strength steel usage," Horvath said.
Based on the performance requirements for
each part, Chrysler LC uses a material application plan, which
is a detailed strategy of which materials make best sense for
every part in the body structure, to determine the best
material for each application, David Reed, lightweight body
supervisor at Chrysler, said, noting that increased costs of
materials can be minimized.
"High-strength steels are typically more
expensive per pound than traditional steel, so they do incur a
cost penalty," he said. "In some applications, the increased
strength of the steel will allow a thickness down-gauge of the
material, resulting in a weight reduction. If enough weight is
reduced, the cost increase is minimized. It is often not
efficient to add numerous reinforcements when higher-strength
materials are increasingly available."
Chrysler was the first North American
automaker to use high-strength, low-alloy steel on its vehicles
in 1974 and the first to use "interstitial-free rephosphate"
steel in 1990, Reed said. The Chrysler Sebring today rides with
more than 40 percent high-strength steel grades on board, and
the current Chrysler 300 uses almost 50 percent HSS. Future
models will contain even more high-strength steels.
The environmental benefits of increased
use of high-strength steels are significant, he said.
"Improvements in fuel economy directly correlate to reductions
in CO2 emissions. A 10-percent reduction in mass can result in
a 6- to 8-percent reduction in fuel consumption, with
commensurate reduction in emitted pollutants." SCOTT