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Advanced High Strength Steel Considerations

“Everyone wants to treat these materials just like other materials,” Dr.

“Everyone wants to treat these materials just like other materials,” Dr. Jay Baron, president and CEO for the Center for Automotive Research (www.cargroup.org; Ann Arbor), says, referring to advanced high-strength steels (AHSS), those materials with tensile strengths of 500 MPa or greater. “Nothing is changing for these advanced materials; they’re just using the same processes.” Which, Baron explains, doesn’t work. Not only are these materials stronger than conventional high-strength steels, but they have different requirements when it comes to forming and welding. The parameters are different. “They design parts the same, they use the same GD&T. The buyoff standards and the tooling standards are the same. That’s what will get them in trouble.” The same thinking, that is.

It’s not exactly everyone who treats these advanced materials as though they are the status quo. Baron says that the European vehicle manufacturers are “clearly leaders” when it comes to AHSS. He cites Volvo and BMW as two companies that are deploying the AHSS materials in vehicles (e.g., boron steel is used for the roof and B-pillars on the Volvo XC90), and says that they’re developing in-house knowledge of the characteristics of the materials. In the U.S., apparently the knowledge base is external, with a dependence on tooling suppliers to understand what needs to be done. One of the problems, however, is that these companies have to learn about the materials, as well, and must have the opportunity to run more tests so that they’re able to build dies that, for example, eliminate the springback that is characteristic of forming AHSS materials. But there are a couple of issues related to this, Baron notes. For one thing, purchasing people don’t necessarily like to make a commitment to a specific material early on in the vehicle development process, which reduces the available time for the tooling suppliers to learn about the material that is to be used. Second, he says that the tendency is to supply the tooling manufacturers with steel coupons, and that the coupons don’t always exhibit the same kind of behaviors of larger pieces.

One company that’s familiar with advanced high-strength steels is Volvo, which uses boron steel to construct the passenger safety cage for the XC90.
One of Baron’s areas of particular concern and interest is with the tooling suppliers, which are under pressure from foreign sources, especially as the U.S.-based vehicle manufacturers look to cut costs. He thinks that while it is likely for tooling or parts to continue to be sourced from places like China and India, when it comes to more complex or demanding dies, like those for the AHSS materials, these are likely to stay local because of the need to engineer and adjust them during development. He consequently says that it is vitally important for the domestic tooling suppliers to gain the know-how required to handle the advanced steels. The easy stuff will be going—or gone.—GSV