Use of ULSAB Technologies by Automakers Growing Rapidly

Applications of High-Strength Steel, Tailor Welded Blanks, Hydroforming and Laser Welding All Are Up

DETROIT, MI, February 16, 2000 — In the nearly two years since the global steel industry unveiled its UltraLight Steel Auto Body (ULSAB), the world’s automakers steadily have been increasing their uses of the advanced steel technologies that ULSAB demonstrated so effectively.

The primary ULSAB technologies that have been showing up in new vehicles include high and ultra high-strength steel, tailor welded blanks, hydroforming and laser welding.

"Car companies don’t want to tip their hands so it has been difficult for us to learn in advance exactly how our customers are applying ULSAB technologies," said Darryl C. Martin, senior director, Automotive Applications, American Iron and Steel Institute (AISI). "But, we know they are. We see abundant examples of these technologies in the vehicles they have put on the road since we unveiled ULSAB in March 1998. The feedback we have received — both formal and informal — has been very encouraging," said Martin.

ULSAB demonstrated that through the use of advanced steels, the latest in process technologies and holistic engineering, it is possible to substantially reduce the mass of body structures using steel. Doing so helps vehicle makers gain all the numerous benefits of steel including safety, low cost and environmental friendliness, while reducing emissions and increasing fuel economy.

High-Strength Steel — Fastest Growing Automotive Light Weighting Material

ULSAB used more than 90 percent high-strength and ultra high-strength steels, which played a significant role in reducing body weight while providing excellent crash performance. Examples of current vehicles using high amounts of high-strength steel include:

  • The 1999 BMW 3-series has a body structure weighing 230 kg with a high-strength steel content of 50 percent. The previous model contained less than 5 percent.
  • Ford's new Focus uses high-strength steel for both the body structure and exterior body panels.
  • The new Mercedes Benz S-Class uses 38 percent high-strength steel, which contributes to lower body weight, an increase in torsional stiffness of 70 percent and improved crash performance.
  • Toyota’s latest sub-compact car, Vitz, uses high-strength steel in 48 percent of the mass of its 253-kg body-in-white, which weighs 17 kg less than its predecessor, the Starlet.
  • Ford's Windstar utilizes almost 60 percent high-strength steel.

Tailor Welded Blanks Save Weight, Cost

ULSAB pushed the envelope by using 14 tailor welded blanks, representing 45 percent of the body structure mass.

  • The new GM "G" platform (Cadillac DeVille, Buick LeSabre, Pontiac Bonneville and Oldsmobile Aurora) uses a tailor welded blank for the body side inner panel, similar to a body side outer panel used in ULSAB. Use of a tailor welded blank for the body side outer in ULSAB added an extra challenge to the project because the rear quarter panel is a visual part.

  • The GM "G" platform also employs North America’s first non-linear tailor welded blank applications in the floor pan.
    The Volkswagen Golf, the car with the highest number of tailored blanks, employs 14 to 21 tailored blank parts, depending on the specific version.

  • GM’s 2000 full size SUVs incorporate finished blanks that measure 103 in. by nearly 71 in., the largest tailored units that the company has ever used.

  • Nearly all Chrysler platforms now use tailor welded blanks. The Jeep Grand Cherokee uses nine, four of which are in the body structure.

  • The most common use for tailored blanks is the door inner panel: the new BMW 3-series (with a diagonal running weld line), Mercedes S-Class, 2001 Ford Explorer, Dodge Durango, Chrysler LH platform, Jeep Grand Cherokee, Honda Accord, Dodge/Plymouth Neon, PT Cruiser, Cadillac Seville and VW Golf.

Hydroforming Use Grows

ULSAB demonstrated an innovative, hydroformed side roof rail that runs from the A-pillar along the B- and C-pillars into the rear floor panel. It is a key element in the structure and provides an excellent load path for structural stiffness and performance in crash. Instead of using a standard tube with a relatively low diameter to thickness ratio (D/t), the ULSAB hydroformed roof rail is constructed from a tube with a diameter of 96 mm and a thickness of 1 mm, resulting in a D/t ratio of 96.

  • GM has been using hydroforming for a similar roof rail application as ULSAB in the body structure of such vehicles as the Buick Park Avenue and Cadillac Seville. Size and location of the roof rail are different than in ULSAB in that the tubes GM is using are much thicker gauge.

  • GM also is using this technology for the front part of the main frame members for the Sierra/Silverado trucks.

Currently, the main application for hydroforming is in engine cradles, suspension, radiator supports and IP beams, but carmakers are using more hydroforming in the body-in-white. At the 1999 International Body Engineering Conference (IBEC), Rover presented a paper on a hydroformed space frame concept for the Land Rover Freelander. Rover initiated the project after assessing ULSAB and plans to demonstrate additional innovative hydroforming for main body structure members.

Laser Welding

The ULSAB body structure features 18 m of laser welding, approximately 60 percent of which is required to join the hydroformed side roof rails to the roof. This approach accommodates one-sided access and enhances the stiffness of the body-in-white.

  • Volvo began using laser welding for the roof in the 850 (the predecessor of the V70), followed by other European automakers including BMW, Volkswagen and Mercedes.

ULSAB extended the use of laser welding to the upper and lower front rails to enhance crash performance, over an alternative design using standard spot welding. Instead of using thicker, heavier material, Porsche Engineering Services elected the innovative approach of employing laser welding, resulting in a stronger, continuous joint.

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.

This release and other steel-related information are available for viewing and downloading at American Iron and Steel Institute/Automotive Applications Committee’s website at http://www.autosteel.org.

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