Page 21 - MetalForming Magazine April 2023

...continue to allow advanced high-strength grades to push high- strength low-alloy steels to the sidelines, giving body-in-white designers more design freedom
and allowing for improved lightweighting and safety.
BY BRAD F. KUVIN, EDITORIAL DIRECTOR
Follow the developments in the automotive-steel industry and it’s clear that steelmakers con- tinue to invest mightily to improve pro- cessing techniques and refine compo- sitions, resulting in the continuous introduction of new advanced high- strength steel (AHSS) grades and the continued push of conventional high- strength low-alloy (HSLA) grades out of the picture. And, automakers are eager to adopt these new grades, as
REFINED STEEL
Recipes & Annealing Curves
This time-lapse photograph illustrates a Nucor DC electric-arc furnace in operation at the steelmaker’s facility in Hickman, AR. That facility also boasts a Flex galvanizing line that can support the production of 3rd Gen AHSS grades, coated and uncoated, and has an over-aging section capable of producing Q&P grades.
18 MetalForming/April 2023
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evidenced by presentations made annually at the Great Designs in Steel conference.
For example, at GDIS 2022 we learned of the material mix in the 2021 Nissan Rogue, whose body in white (BIW ) comprises 13 percent of 980- MPa steel and another 4.5 percent of 780-MPa steel. And, at GDIS 2021 we learned that the 2021 Ford Mach E BIW includes a mere 19 percent of mild steel and 25 percent of HLSA, and a whopping 29.5 percent of boron steel, 9.5 percent of ultra-high-strength steel (UHSS) and another 14.3 percent of AHSS. (Good news—the GDIS 2023 agenda is available for viewing and registration is open; see the accompa- nying sidebar.)
And in yet another example, directly comparing the 2021 GM Escalade to its previous generation, HSLA and mild-steel use decreased from 85 per- cent to 64 percent, while AHSS use tripled and UHSS use shot up from just 2 percent in the previous genera- tion to 12 percent in the 2021 Escalade.
New Extra-Formable Tata Grades
Steelmakers are all too prepared for this evolution. Case in point: Tata Steel, which recently launched a new extra- formable dual-phase (DP) 600-MPa steel as an addition to its HyperForm product range. So notes Basjan Berk- hout, the steelmaker’s head of market- ing, automotive. “And, we are about to start a development program to extend our range of AHSS with extra forma- bility to 1000 MPa and above,” Berk- hout adds, also noting the steelmaker’s plans to launch a new version of its hot-rolled CP800, with improved edge ductility, “which should be especially suited for the U.S. market as it is used a lot in the frames of pickup trucks.”
Editor’s note: Per WorldAutoSteel, while HSLA grades have a typical ratio of yield to tensile strength of 0.8, DP steels (such as the new Tata grade ref- erenced above) have a ratio closer to 0.6. This improved formability has led to automakers replacing HSLA with DP for safety-cage components—DP 600- 980 for B-pillars, floor-panel tunnels,