High-strength steel adds new wrinkle to repairs

Advances in high-strength steel have helped automotive manufacturers improve their vehicle designs by increasing safety and reducing weight, but these new materials complicate the repair process.

Dave Anderson, director, long products, at the American Iron and Steel Institute (AISI), provided an overview of these new materials and how they impact reparability during his technical presentation, “Application and Reparability of Advanced High-Strength Steels,” during the I-CAR International Annual Meeting Saturday.

Advanced high-strength steels (AHSS) already are being used in several new models, including Honda’s Ridgeline, the Chevy Malibu, Ford Mustang, three Mercedes-Benz models and other vehicles.

“There are a lot of concerns about working with all of the new and improved steels,” Anderson says. “The work that’s been done by AISI shows that these steels can be repaired within certain guidelines. These guidelines have to be implemented and expanded into the industry by the individual OEMs.”

Adoption of these lightweight, high-strength materials has been driven by crash safety and fuel efficiency standards and regulations. OEMs are increasing the use of AHSS to meet crash targets without adding mass.

“As the new fuel economy requirements are introduced, there will be an increased push toward lighter weight vehicles, and more application of these advanced high-strength steels, as well as alternative materials,” Anderson says.

One factor complicating the repair of AHSS materials is that they are strengthened by a combination of soft and hard phases. Applying heat can alter the steel.

“If you add more heat to the product, you change its properties,” Anderson says. “These steels cannot absorb as much heat as traditional products, so that’s a real concern.”

AISI and General Motors performed a study of the response of AHSS to conventional collision repair processes, such as welding and flame straightening. Those tests showed that repair procedures for those components could vary depending on the location of the damage. As a result, AISI recommends that OEM collision repair experts be contacted for procedures specifically designed for individual AHSS parts.

“Don’t flame straighten any longer, and if you weld, make sure you cut at a non-critical strain or stress area,” he says.

Anderson displayed a slide showing how General Motors is developing a color-coded chart to help technicians identify where these high-strength steels are utilized in their vehicles, and what the approved repair techniques are.

In separate I-CAR technical sessions, Chrysler and Mercedes-Benz outlined their new programs for helping repairers identify the different types of steel in its vehicles as well.

For more information, visit AISI’s Web site at www.autosteel.org