ULSAB: Tailor-Welded Blanks Expected to Soar Through 2000

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Tailor-Welded Blanks Expected to Soar Through 2000

With few exceptions, just about every business segment in the automotive industries is expected to skyrocket in the next ten years. Most ink goes to the hot items -- vehicle stability control, cabin communications and other technical widgets for cars and trucks. As a result, few people outside of the automotive body business recognize that the tailor-welded blank industry is poised for its own run up the chart.

Demand is expected to jump from 20 million tailor-welded blanks in 1999 to more than 90 million in 2005, according to Stanley L. Ream, senior project manager, research and development for Worthington Industries. "We compared these numbers with our major competitors and we are quite confident that these are the right numbers reflecting actual vehicles that are going to use tailor-welded blanks, " says Ream. There are 13 tailor-welded blank companies in North America with about 90 welding stations ready to fill orders.

But Tom Fant, president of TWB LLC, a partnership between Worthington Industries and Thyssen Inc., a wholly owned subsidiary of Thyssen Krupp AG, says the anticipated growth is going to drastically change the picture. "The welding stations you have in the market today would probably support 30 to 32 million parts. So we need to look at 270 welding stations in order to meet the anticipated demand in 2005." Engineers seek advanced technology Pressure for tailor-welded blanks comes largely from the demands for lighter, stronger, more complicated vehicle designs planned for future years. Engineers need technology that will push their designs forward. Currently, most blanks are still single-weld pieces. But by 2002, the number of multiple-weld blanks will run around 25 million units.

"We have just scratched the surface on applications," says Fant. "The applications that are being done now are pretty much the straightforward configurations driven primarily by weight and cost reduction. We've got a whole new generation of ideas to go through -- engineered applications where tailor-welded blank technology is integrated up front and in the early engineering phase of new vehicle development programs."

This early involvement lets engineers take a holistic design approach, allowing them to build for noise vibration and harshness and crashworthiness early in the planning stage. The value of holistic engineering was effectively demonstrated during the UltraLight Steel Auto Body (ULSAB) project completed in 1998.

"As the design committees get more and more comfortable with the technology, we are going to be willing to apply the technology to a broader range of product or part applications. That's why we're looking at the growth potential in the industry," says Fant. Right material for the right application Steel continues to be the material of choice for tailor-welded blanks. The ability to mix and match different strengths within a single component gives auto engineers a whole battery of new options that weren't previously available. General Motors Corporation currently uses a tailor-welded blank to stamp its side frame for the Cadillac deVille sedan composed of five different steels with variations in both yield strength and coating width.

Despite the relative simplicity steel provides tailor-welded blank producers, the industry will be challenged to continue improving its product. "This particular technology requires a lot more refinement in the incoming material," says Fant. "The steel we weld has to be flatter for laser welding than it does for just conventional deep welding or forming. Flatness of our coil stock, edge quality -- not just the straightness of the edge, but the edge in cross section --all of these issues will challenge the steel industry."

Most major automakers are increasing the use of tailor-welded blanks in their designs. Many already incorporate them to some small degree. GM has one of the largest tailor-welded blank volume applications anywhere -- the GMT 800 light-truck platform that uses these specialty blanks for the side frames. " It's just another indication that the OEMs are comfortable in applying this technology on their high volume vehicles," says Mark Eisenmenger, operations planning manager at TWB.

Future applications Straight-line welds (linear-welded blanks where two pieces of steel with roughly the same dimensions and different gauge are brought together) compose most of the applications currently found on production lines. More complex 2D welds - parts that require welds across two axes -allow production of intricate designs, which are becoming more popular. Their benefits versus linear welded blanks include:

  • Reduced Weight in Vehicle
  • Higher Body-In-White Resonant Frequency
  • Improved Die Condition in Forming
  • Improved Assembly (Hemming)
  • Enhanced Energy Management

Of course, 2D blank welding is far more complicated than straight-line welds, demanding higher accuracy in the blank cuts and flatness and gap closing. But the benefits can be remarkable. Ream demonstrates weight savings of ten percent when an inner-door assembly design moves from a straight-line weld to a 2D configuration. The header sealing on the 2D design is improved, too. With the proper configuration, engineers can even reduce the scrap on certain high-cost materials.

2D blanks are still evolving, but that hasn't tempered the pace of technical development in the industry. Already, GM has drawn the line between its successful hydroforming applications and tailor-welded blanks, filing a patent for tailor-welded tubes.

"It's a whole new ballgame because the way the tube is manufactured is different than the way steel sheet is manufactured," says Fant. "It really gets back to the issue of the quality of the edge, the straightness of the edges that are going to be joined together, and whether the overlap or the step occurs on the inside or the outside of the tube. These are all discussions going on with the design committee trying to decide which is the best way to go with this technology."