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1 Great Designs in Steel is Sponsored by: AK Steel Corporation, ArcelorMittal Dofasco, ArcelorMittal USA, Nucor Corporation, Severstal North America and United States Steel Corporation

2 LIGHTWEIGHTING AUTOMOTIVE BODY ENABLERS AND MANUFACTURING CHALLENGES Daniel J. Grieshaber General Motors

3 Outline Drivers Enablers Manufacturing Challenges Summary 3

4 Drivers for Lightweighting Consumer Requirements Cost Quality Performance + Features Fuel Economy Balance Government Regulations CAFE/CO 2 Crash Performance Emissions Competitive Pressures Manufacturability Cost, Quality, Performance Fuel Economy 4

5 U.S. CAFE Standards Ref. US Dept of Transportation, NHTSA, April 1,

6 Enablers Product Design Optimization 6

7 Integration of Efficient Load Paths Based on Front ODB, NCAP, side impact and side pole requirements from SID IIS and IIHS, tunnel and rail shapes are straightened. 7

8 Efficient Size and Shape Based on strain maps, unloaded metal at the lower portion of the bracket was removed in final design. Removed metal was beyond original weld pattern. Tighter and fewer welds needed. 8

9 Design Iteration of Geometry From Bending to Shear Joint 9

10 Local Reinforcement Strategy (including Laser Welded Blanks and inserts) 1 0

11 Lightening Holes and Scalloping 1 1

12 Thinnest Possible Part Gauges Best practice gauge and grade templates are used to drive designs. 1 2

13 Material & Design Impact on Lightweighting Increased Usage of AHSS Improved Design through Efficient: Load Path Joint Design Part Size/Geometry Material Gauge

14 Enablers Light weight Materials 1 4

15 North American Body Material Trends Body and Closure Metallic Material Content by Type Advanced HSS Conventional HSS Aluminum & Magnesium Advanced HSS Aluminum & Magnesium Mild Steel Bake Hardenable & Medium HSS Mild Steel Conventional HSS Bake Hardenable & Medium HSS 850 Pounds 800 Pounds with an Equal Footprint to 2007 Source: Ducker Worldwide 1 5

16 Dual Phase Steel Part Applications Vehicle Components Front Structure Passenger Compartment & Side Structure Upper Structure Rear Structure DP Mild DP HSLA Underbody Applications DP M 1 6

17 Manufacturing Challenges 1 7

18 Springback Management Why: Still re-cutting dies getting better, but not there yet Dimensional requirements getting tighter Topics: Springback reduction and management through part and process design Springback prediction 1 8

19 Effect of Beads on Springback Beads can significantly reduce sidewall springback Wall Opening Angle (degrees) With Beads Without Beads 340LA DP600 DP750 TRIP800 DP980-5 Material 1 9

20 Effect of 4-break Lock Flange on Sidewall Curl Springback and sidewall curl can be reduced through wall stretching enabled by 4- break lock flange 2 0

21 Effect of 4-break Lock Flange on Springback Wall Opening Angle (Degrees) Break Lock Flange Short Blank 340LA 590R DP600 DP750 TRIP800 DP980 Material 2 1

22 Rocker Example Material Change Material Change: CR900T/700Y-MS to CR980T/700Y-MP-LCE Advantages Disadvantages Greatly Improved Shape Control Significantly Improved Part Dimensional Tolerances Improved Global Availability Higher Cost Compared to CR Martensite

23 Rocker Example Material Change

24 Dimensional Control Design / Geometry: Panel thickness Radii Depth of draw Product features Material Properties: Yield Strength Tensile Strength Accurate Models Variability Requirement = +/- 0.5mm Other: Shear Fracture 2 4

25 High loads require stronger materials - Cast steel displacing cast iron A/SP Tribology Project - Increased use of tool steel inserts and details - Advanced coatings displacing chrome plating 1.2 mm DP980 on Caldie Trim Insert Plasma nitride CVD, PVD, TD VC Guidelines under development Form, flange, trim, and pierce 2 5

26 Die Materials & Surface Treatments Under Evaluation Substrates S7, D2 Vanadis 4E Carmo Caldie M2 M4 Carmo with PVD CrN, 65,000 hits Surface Treatments CVD TiC PVD CrN, TiCN, TiAlN Ion Nitride with CrN Chrome Plating D2 Insert, 100,000 hits 2 6

27 Impact of Manufacturing Challenges Manufacturing Challenges: Springback / Dimensional Control Press Tonnage Die Wear, Galling, Burrs, etc. Joining Known Manufacturing Processes (current infrastructure) 2 7

28 Summary Enablers Efficient Designs Effective Use of Advanced High Strength Steel Increased Usage of AHSS Improved Design through Efficient: Load Path Joint Design Part Size/Geometry Material Gauge Manufacturing Challenges Springback Prediction & Management Tool Design & Maintenance Manufacturing Challenges: Springback / Dimensional Control Press Tonnage Die Wear, Galling, Burrs, etc. Joining Known Manufacturing Processes (current infrastructure) 2 8

29 Challenges for Suppliers Availability of Advanced High Strength Steels grades, coatings, gauges, and coil widths Accurate Springback Prediction Tools Improved Die Materials & Surface Treatments

30 Great Designs in Steel is Sponsored by: AK Steel Corporation, ArcelorMittal Dofasco, ArcelorMittal USA, Nucor Corporation, Severstal North America and United States Steel Corporation