Steel Industry Unveils Auto Door that is up to 42 Percent Lighter than Benchmarks

DETROIT, MI, May 24, 2000 -- The UltraLight Steel Auto Closures (ULSAC) Consortium today unveiled results of its Validation Phase, in which it fabricated a frameless door that is 22 to 42 percent lighter in weight than a range of benchmarked doors. The door meets or exceeds a range of performance requirements and would cost no more to build than doors in the benchmark group.

The validated door weighs 23.15 pounds (10.5 kg) and would cost $66.50 to manufacture in typical high-volume production (greater than 225,000 units per year). The door meets or exceeds performance and structural requirements for dent resistance, oil canning, upper and lower lateral stiffness, quasi-static intrusion, and longitudinal door crush.

With use of high- and ultra high-strength steels and technologies such as tailor welded blanks, stamping and hydroforming, the ULSAC door achieved 33 percent mass savings over the average benchmark from a wide range of door structures. It is 42 percent lighter than the benchmarked average of frameless doors only, and 22 percent lighter than the lightest benchmarked unit, a framed door structure. The door achieved these results without compromise to safety or structural performance.

The ULSAC study is an initiative of the global steel industry to demonstrate the effective use of steel in producing lightweight, structurally sound steel automotive closures that are manufacturable and affordable. American Iron and Steel Institute (AISI) showed results and demonstration hardware at a briefing for journalists today.

"This ULSAC door is evidence that our car company customers can use steel to achieve necessary mass reductions in closures, while improving their performance and reducing their cost," said Darryl C. Martin, senior director, Automotive Applications, AISI. "This is the third major auto structural design study we have completed during the past two years and, separately and in combination, these initiatives have demonstrated significant mass reduction at no increase in cost. We continue to increase the potential for steel to remain our customers’ material of choice when safety, affordability, manufacturability and recyclability are key."

Based on a design from the Concept Phase of the ULSAC program, the frameless ULSAC door is made from just nine major parts, which employ tailor welded blanks, hydroformed tubular and stamped parts. The door features an innovative structure that eliminates the need for a structural full inner panel that is typical in current designs.

The structure comprises high-strength steel tube hydroformed latch and hinge parts and two straight ultra high-strength steel tubes. These separate components allow for selection of precise diameter, material grade and thickness combination for each part -- independently of one another and based entirely on functional requirements.

In an excellent example of functional consolidation, the two horizontal tubes provide stiffness and work together as side impact intrusion beams, simultaneously meeting both structural and crash energy management responsibilities. In side collisions, they provide strength and absorption capabilities to effectively manage impact energy forces. In a frontal collision, these two parts provide excellent load carrying capabilities between the A- and B-pillars.

ULSAC’s door outer panel uses relatively thin and higher yield strength 0.7 mm, Bake Hardenable (BH) 260 MPa high-strength steel, usage that pushes the envelope for this type of application. Car companies have been using BH grades but not this thin and not at this yield strength.

"As we have seen in our previous UltraLight projects, a key to success is the use of high- and ultra high-strength steels," Martin said. "As in the other projects, we did not have to sacrifice structural performance to reduce weight. Rather, we looked at innovative ways to get smarter about how we use steel. And, the results of the cost analysis show that the ULSAC door would actually save a few dollars in the process."

Detailed results of the ULSAC Validation Phase appear in the Consortium’s "April 2000 Engineering Report," which is available by calling 1-877-STEELINDUSTRY (1-877-783-3546). An overview of the Validation Phase will be available this summer on AISI’s website www.autosteel.org and the Consortium website, http://www.ulsac.org.

The ULSAC study is a companion to the UltraLight Steel Auto Body (ULSAB) study released in 1998, the UltraLight Steel Auto Suspension (ULSAS) study released in May 2000, and ULSAB-AVC (Advanced Vehicle Concepts) study, which will be complete in 2001.

The Automotive Applications Committee (AAC) is a subcommittee of the Market Development Committee of AISI and focuses on advancing the use of steel in the highly competitive automotive market. With offices and staff located in Detroit, cooperation between the automobile and steel industries has been significant to its success. This industry cooperation resulted in the formation of the Auto/Steel Partnership, a consortium of DaimlerChrysler, Ford and General Motors and the member companies of the AAC.

American Iron and Steel Institute/
Automotive Applications Committee:
AK Steel Corporation
Bethlehem Steel Corporation
Dofasco Inc.
Ispat Inland Inc.
National Steel Corporation
Rouge Steel Company
Stelco Inc.
United States Steel Corporation
WCI Steel, Inc.
Weirton Steel Corporation