Development of Innovative Steel Grades and Their Applications in Automotive Structures

Transcription

1 Development of Innovative Steel Grades and Their Applications in Automotive Structures Jonathan Powers AK Steel Corporation GDIS2017

2 AK Steel s Commitment to Innovation 2

3 Next Generation NEXMET TM 440EX, 1000 & EX NEXMET TM Grade Families reproduced from World Auto Steel Advanced High- Strength Steels Applications Guide Version 5.0 May

4 Next Generation AHSS Capital Improvements Upgrade Completed Fall 2016 Additional control of thermal profile Additional control of furnace atmosphere Option to bypass zinc pot (bare) 4

5 NEXMET 1000 and 1200 Properties Mill produced material NEXMET 1000 NEXMET 1200 Yield Strength, MPa Tensile Strength, MPa Total Elongation, % Hole Expansion Ratio, % n-value (4-6%) n-value (6-12%) n-value (10- UTS%) NEXMET NEXMET Production Data: Tensile data by ASTM E8, 50 mm gage. HER by conical punch, 12% die clearance.

6 NEXMET 1000 and 1200 Microstructures NEXMET 1000 NEXMET

7 NEXMET 1000 and 1200 Strain Hardening Mill Behavior produced material NEXMET 1200 NEXMET 1000 NEXMET 1000 NEXMET

8 NEXMET 1000 and 1200 Potential Applications Bare (CR) or Galvanized (GI) 1-2 mm thick <1320 mm wide Nonexposed applications NEXMET 1000 NEXMET

9 NEXMET 1000 and 1200 Welding Resistance spot weld properties for bare NEXMET Acceptable curent range, >2 ka Properties consistent with expectations for given base metal strengths 9

10 NEXMET 1000 and 1200 Other Characterization High strain rate In Progress Corrosion No issues Fatigue In testing queue 10

11 Stamping Validation with T-Shaped Panel NEXMET Tensile Strength (MPa) vs Draw Depth (mm) Dual Phase NEXMET 1000 NEXMET NEXMET 1000

12 Stamping Validation with Hole Expansion Tensile Strength (MPa) vs HER (%) NEXMET Dual Phase NEXMET 1000 NEXMET NEXMET 1000

13 NEXMET 1000 NEXMET 1200 vs. DP980 13

14 NEXMET 1000 and 1200 Springback Prediction NEXTMET 1000 NEXTMET 1200 Formability Formability Springback Springback 14

15 NEXMET 1000 and 1200 OEM Collaboration Internal Material Characterization Oct Mar Plant Trials Mar Mar Internal Qualification Testing Oct Oct Customer Qualifications & Characterization Apr Apr Customer Trials Apr Apr

16 Application 1: Optimize Body Side Structure TARGETS Reduce mass Maintain roof crush performance Maintain side impact performance 16 * Public domain models courtesy of George Washington University * Fully validated and correlated crash models

17 Application 1: Baseline Design Mass: kg Roof Rail: 2.3 mm A-pillar Upper: 1.4 mm B-pillar Upper: 2.1 mm B-pillar Reinforcement: 2.6 mm A-pillar Lower: 1.4 mm B-pillar Inner: 1.0 mm Rocker: 1.4 mm B-pillar Lower: 1.2 mm 17

18 Application 1: Optimized Results Material and gage optimization was conducted to minimize mass. Utilizing LS-Dyna & VisualDOC design optimization software Side impact survival space of the baseline model is Acceptable > 50 mm, which correlates well with the IIHS physical test result. Roof crush strength-to-weight ratio of of the baseline model correlates well with the IIHS physical test result of Iterations Side Impact Driver Side Survival Space % Improvement from Baseline Roof Crush Strength-to- Weight Ratio % Improvement from Baseline Mass (kg) % Mass Reduction from Baseline Baseline Optimized

19 Application 1: Optimized Design Mass: kg (28.1%) Roof Rail: mm A-pillar Upper: mm A-pillar Lower: mm B-pillar Reinf: mm B-pillar Upper: mm NEXMET 1000 B-pillar Lower: mm B-pillar Inner: mm 19 Rocker: mm NEXMET 1200

20 Application 2: Improved Deflector Assembly Baseline AK Steel Part Grade Thick mm Mass Kg Grade Thick mm Mass Kg Mass Saving Deflector Assembly DP NEXMET % 20

21 Application 3: Light-Weight Front Lower Control Arm Front Lower Control Arm (FLCA) component gage was reduced to minimize mass while keeping the permanent sets and the buckling load capacities of the baseline material. Permanent sets (Dx and Dy) were measured at ball joint after loading (Fx = Fy = 30 kn) and then unloading. Buckling load capacities (LCx and LCy) were also measured at ball joint with loading (Fx = Fy = 40 kn). Both loading cases have the same constraints at two bushings. Abaqus FEA solver was used. 21

22 Application 3: Front Lower Control Arm Results Iterations Permanent set after BJ, Dx (mm) Permanent set after BJ, Dy (mm) Buckling Load BJ LCx (kn) Buckling Load BJ LCy (kn) Mass (kg) (One side) % Mass Reduction from Baseline Baseline NEXMET > > NEXMET >

23 NEXMET 1000, 1200 Product Highlights Applications of NEXMET 1000 and 1200 Grades Energy absorbing parts Parts needing additional formability High strength parts Potential part consolidation Mass reduction 23

24 NEXMET 440 EX Exposed Surface Quality Improved Dent Resistance Material Commercially Available Grade YS, MPa UTS, MPa TE, % BHI MPa NEXMET 440 EX

25 NEXMET 440 Applications NEXMET440EX Replacement of BH240 Similar performance for Dent/Ding. Current Applications: 2011 Suzuki MR Wagon (Front Door Outer) 2014 Suzuki Hustler (Rear Door Outer) 2011 Suzuki D-Max (Hood Outer) (Thailand) 25

26 NEXMET 440EX Stamping Feasibility Full Sized Truck Fender Down gauge with NEXMET 440EX at 0.6 mm Performs better than BH 250 with 0.77 mm NEXMET 440EX at 0.6 mm YS = 290 MPa TS = MPa BH mm YS = 254 MPa TS = 370 MPa Formability Issue 100% Holding force Formability Issue 100% Holding force 26

27 Advanced High-Strength Steel (AHSS) Strategy 27

28 Advanced High-Strength Steel (AHSS) Strategy 28

29 Advanced High-Strength Steel (AHSS) Strategy 29

30 Advanced High-Strength Steel (AHSS) Strategy 30

31 Advanced High-Strength Steel (AHSS) Strategy 31

32 Advanced High-Strength Steel (AHSS) Strategy Mill Trials 32

33 Advanced High-Strength Steel (AHSS) Strategy Lab Development 33

34 For More Information Jonathan Powers AK Steel Corporation NEXMET 34