August 19, 2015
by Bob Keith, AAM Senior Director - Operations Training for CARSTAR
Aluminum! Aluminum! Aluminum!
Now that I have your attention, this article is not about aluminum. It is about steel, the material of choice for automotive manufacturers for more than 100 years. But it certainly isn’t the same steel that we repaired just a few short years ago. Today we have UHSS, AHSS, Boron, Martensitic, Bake Hardened, Dual Phase, Nano Steels and or some cocktail of alloys that no one has even named!
The recent “Great Designs in Steel” (GDIS) seminar in Livonia, Mich., in May made it clear that the core material of choice for the manufacturers is still steel. But not just mild steel — advanced steels are the core of most new vehicle designs. Advanced steel content is increasing with each new design to as much as 60 percent to 70 percent.
Why these trends? We all know that a big driver is CO2 emission reductions mandating that the C.A.F.E. standard of 54.5 mpg be achieved by 2025. During GDIS, Abey Abraham of Ducker Worldwide said, “A curb weight reduction of 460 lbs. per vehicle is needed to meet the 2025 CO2 compliance levels. AHSS continues its growth trajectory with approximately 254 pounds per vehicle in 2014, surpassing our estimates in 2010 for 2014 by over 20 lbs. per vehicle (prior 2014 estimate was 232 lbs.).”
Lighter bodies also allow for smaller more efficient engines with similar performance characteristics and higher fuel economy. Improved fuel economy is just one piece of the puzzle. The other incentive is safety — the new roof crush, side impact and offset crash test standards have also accelerated the use of advanced steels. These steels are capable of handling extreme collision energy, but it is thinner and lighter. Also, new crash energy designs Like Honda’s “ACE” allow for crash energy to be directed around the passenger compartment. There is also increasing use of steels in the 1000+ Mega Pascal (Mpg) range in tensile strength (a measure of crushability).
American Honda announced a breakthrough rear rail that is 1500 Mpg, yet has “softened areas” (780 Mpg) at the end, allowing the rail to crush in a “Z” shape to absorb energy.
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