Faced with increasingly tough federal collision standards, automakers are turning to boron steel -- which is six times stronger than conventional steel -- to reinforce the body-in-white without adding pounds.
Boron steel is increasingly used for door pillars, door beams, body sills, roof rails and bumpers -- components that must protect the passenger cabin during a collision.
But as demand grows, suppliers are short of presses that can heat the steel to the proper temperature for stamping.
In the 2015 model year, a typical vehicle will have about 24 pounds of boron steel, according to an estimate by Ducker International, a consulting firm based in suburban Detroit. That's up from 15 pounds in 2012.
Magna International Inc., Germany's Benteler Automotive and Gestamp Automocion of Spain are leading producers of boron steel parts.
Boron steel got some attention last month when Magna and steel-maker ArcelorMittal won an Automotive News PACE Award for producing the boron steel door rings used in the Acura MDX.
While the use of boron steel is growing, there's a catch. The blanks used for boron steel components must be heated to 1,688 degrees Fahrenheit before they are stamped.
The heat treatment, along with the subsequent quenching process, allows manganese, boron and carbon additives to transform the steel into the particularly hard and strong boron steel.
Steel-makers such as ArcelorMittal, Severstal and AK Steel can produce enough boron steel to meet demand, according to the American Iron and Steel Institute.
But the industry's bottleneck is downstream in the stamping plants. Suppliers must use special lines to produce hot-stamped components.
In North America, there are about 40 stamping presses that can handle boron steel, up from 22 in 2012, according to Ducker. To keep up with rising demand, Ducker estimates that suppliers will need as many as 60 presses by 2020.
"You have to have special equipment," said Dick Schultz, Ducker's managing director. "To get the weight out, they make these parts" very thin.
There are other problems, too. Hot-stamped components require more time to produce, thus raising costs. Boron steel also is hard to form into complex shapes. Bumpers, for example, must be straight or only slightly curved, Schultz says.
And since boron steel components are so strong, manufacturers must use lasers -- not punch presses -- to create bolt holes.
Automakers put up with these headaches because boron steel is still cheaper than lightweight aluminum. A pound of raw aluminum ranges from 90 cents to $1, while boron steel costs roughly 70 to 80 cents.
Although conventional steel typically costs just 50 cents per pound, boron steel's great strength allows automakers to save weight.
By switching from conventional steel to boron steel, for example, Honda was able to eliminate 3 kilograms, or 6.6 pounds, of weight from the Acura MDX -- with better crash performance, too.
And there was yet another benefit: Honda was able to eliminate five reinforcing parts, thus simplifying assembly.
Magna's stamping subsidiary, Cosma International, makes those door rings at a hot-stamping press in Eagle Bend, Tenn.
Cosma operates 22 hot-stamping presses worldwide, but that may not be enough to meet growing demand, said Del Matharoo, Cosma's vice president of engineering.
To boost productivity, Cosma and other suppliers are trying to reduce the time required to hot-stamp a component.
"All of our competitors are facing the same challenges," Matharoo noted. "As we look from 2014 to 2020, the biggest problem the industry will confront is capacity."
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