Guidelines for the Manufacture of Advanced High-Strength Steel Vehicle Applications. Dr. Chris Lahaije, Sascha Sikora Aachen,

Transcription

1 Guidelines for the Manufacture of Advanced High-Strength Steel Vehicle Applications Dr. Chris Lahaije, Sascha Sikora Aachen,

2 WorldAutoSteel A t Automotive ti Group G off the th World W ld Steel St l Association A i ti MEMBER COMPANIES: Ansteel ArcelorMittal Baosteel China Steel JFE JSW Steel y Steel Hyundai Kobe Nippon Steel & Sumitomo Nucor POSCO Severstal SSAB T t Steel Tata St l ThyssenKrupp USIMINAS U. S. Steel voestalpine

3 Lightweighting with AHSS: Application Guidelines Application Guidelines Key Challenges with AHSS - Forming Key Challenges with AHSS - Joining Case study; CP800 for high energy absorption Case study; HF1900 for hot forming

4 Lightweighting with AHSS: Application Guidelines 5.0 Key Enablers: Development of new grades of AHSS that meet today s functional performance and lightweighting needs Information that allows our stakeholders to successfully apply these highly sophisticated materials Our Technical Editors AHSS METALLURGY, FORMING Dr. Stu Keeler, Keeler Technologies AHSS JOINING DMS 1150/1400 MS 950/1200 D DP 700/1000 D Professor M. Kimchi, Ohio State University

5 Lightweighting with AHSS Can Steel Continue to Provide Competitive Materials Solutions for the Automotive Industry? FutureSteelVehicle (FSV) A2mac1 benchmarking Cadillac ATS, VW Golf

6 Lightweighting with AHSS: Application Guidelines 5.0 Key Elements of Version New Materials Building on FSV, our materials portfolio now includes 50 steel grades, compared with 28 in Version 4.0. And still growing... Exposed surface quality success achieved with DP steels up to 600 Mpa Greater ductility in DP, CP and HSLA (based on nano precipitation) grades for lighter gage forming Available at

7 Lightweighting with AHSS: Application Guidelines 5.0 DP 210/440 IF 260/410 BH 280/400 IF 300/420 DP 300/500 FB 330/450 DP 350/600 TRIP 350/600 TRIP 400/700 HSLA 420/500 FB 450/600 TRIP 450/800 TWIP 480/900 HSLA 490/600 DP 500/800 CP 500/800 HSLA 550/650 CP 600/900 TWIP 600/900 DP 600/980 TRIP 600/980 CP 680/780 HSLA 700/780 DP 700/1000 CP 750/900 DP 750/980 Materials Portfolio TRIP 750/980 TWIP 750/1000 CP 800/1000 DP 800/1180 CP 850/1180 MS 950/1200 TWIP 950/1200 CP 1000/1200 MS 1050/1470 CP 1050/1470 HF 1050/1500 DP 1150/1270 HF 1200/1900 ULSAB AVC Grades FutureSteelVehicle V5.0 New Grades Available at

8 Lightweighting with AHSS: Application Guidelines 5.0 Key Elements of Version Updated Fabrication Technologies Servo presses for programmable forming Press-hardened steels (hot forming) Tool & die maintenance practices Laser welded blanks, roll forming, hydroforming, etc. Available at

9 Lightweighting with AHSS: Application Guidelines 5.0 Key Elements of Version Significant Joining Revision From 30 pages to 110 pages Partnership with automotive OEMs, technical organizations New joining processes with unique qualities applicable to AHSS grades laser welding, hybrid welding, mechanical joining and adhesive bonding Available at

10 Key Challenges with AHSS Materials Understanding of material behavior Development of qualification procedures Develop materials specifications Forming Predictable make-ability, e.g.springback, edge cracking Process robustness Joining Process and parameters development Design for AHSS Static and dynamic weld performance Development of accurate FEA tools Development of accurate FEA tools Successful plant implementation

11 Key Challenges with AHSS - Forming Spring-back in AHSS Open-ended Section Comparison

12 Key Challenges with AHSS Forming Draw die clearance in AHSS Low r-value might prompt larger die clearance, to avoid jamming. But too large a clearance will cause materials to reverse bend over a large area increasing severity of side wall curl

13 Key Challenges with AHSS Forming Bendability Conventional HSS can be folded without issues. This is not the case with AHSS Two ways of characterising the performance of the material Minimum bend radius Bend angle in VDA-238 test

14 Key Challenges with AHSS Forming Edge ductility The forming of sheared edges is more challenging g than in mild steel or HSS E.g. stretch flanging Because the process is more critical the sensitivity to tool wear also becomes a concern

15 Key Challenges with AHSS Forming Formability = Stretchability & Bendability AHSS present a compromise Improving both aspects a bit or one aspect a lot. Stretch- ability DP800 DH DP1000 DH Formability DP600 DP800 DP1000 CP1000 Bendability CP800 Increasing Rm

16 Key Challenges with AHSS - Joining Process and parameter development Possible solutions to Improve Peel behavior on AHSS Spot Welds Passive methods Long weld time Pre/post pulsing Short hold time Increased minimum i weld size Active methods Weld and temper Dilution (AHSS to Mild Steel, HSLA) Weld Down Slope Dilution Electrode Force Quench Temper Hold Weld

17 Key Challenges with AHSS - Joining Process and parameter development Effect of Temper and dilution on fracture mode % Area Inter rfacial Fra acture Frac cture App pearance 0% 10% 20% 50% 100% No Temp, No Diln Temp Only Diln Only Temp & Diln Tensile Stat X Dyn X Chisel Shear Tensile Tensile

18 Key Challenges with AHSS - Joining Selection of joining technique Body-in-White joining processes Resistance spot Projection welding GMAW MIG brazing Laser welding (TWB) Mechanical fastening Magnetic pulse welding Deformation resistance welding

19 Key Challenges with AHSS - Joining Selection of joining technique Comparison between spot welds and 20 mm laser welds Laser weld performance varies with width / sheet thickness ratio Max. Tensile Load DP-Wide DP-Remote DP-Narrow DP-Spot TP-Wide TP-Remote TP-Narrow TP-Spot MS-Wide MS-Remote MS-Narrow MS-Spot All Guided d Laser m/min (wide) Laser - Remote 4.8 m/min MS-Spot MS-Narrow MS-Remote MS-Wide TP-Spot TP-Narrow TP-Remote TP-Wide DP-Spot DP-Narrow DP-Remote DP-Wide Laser - 10 m/min (narrow)

20 Key Challenges with AHSS - Joining Process control and quality monitoring i Process monitoring Strain Gauge Pressure Transducers Nondestructive evaluation LVDTs Current Toroid Voltage Leads

21 Key Challenges with AHSS - Joining Weld quality monitoring i Planar Metallographic Imaging Destructive testing fracture mode Criteria Peel and Chisel Criteria - Failure Modes Button pulled without evidence of interfacial fracture Partial thickness fracture with button pull Partial thickness fracture with no button pull Interfacial fracture with button pull and partial thickness fracture Interfacial fracture with button pull Interfacial fracture with partial thickness fracture Full interfacial Fracture No fusion

22 Study of fracture behaviour Closed-Top-Hat 22 In crushing of Closed-Top-Hat, bending is very apparent fracture occurs next to the original corners few cracks seen in zones with only bending cracks in relatively flat areas Cl t d f f t l ti d f t Closer study of fracture location and fracture appearance indicated that shear fracture is very important

23 Bending and shear properties 23 Failure strain in 3 point bend test Failure strain in shear test Bending failure strain s Shear failure str rain DP800HpF CP800 CP800HE 0.00 DP800HpF CP800 CP800HE CP grades better bending performance compared to DP CP800HE significant better shear performance Combination of high bending and high shear failure strain for CP800HE Combination of high bending and high shear failure strain for CP800HE results in good crash behaviour

24 The value of crash-ability: CP800 High Energy absorption CP800 HE High strength level with good crashability 24 CP800 HE is within specifications of CP800 grade but with improved crash properties: CP800HE CP800 DP800HpF The improved crash-ability of CP800HE create value in terms of weight The improved crash-ability of CP800HE create value in terms of weight saving compared to DP800 for crash structures

25 Hot Formed Steels Material behaviour at the manufacturing process Exemplary benefits of Hot Forming: - Springback issues eliminated, which is remarkable considering the extremely high final part strength. 2 - Very high strength resists stamping deformation - Hot-forming has the highest potential for weight reduction of crash components. - Controlling the 1 temperature in various locations of the forming die can create zones with different strength levels in the final stamping

26 Structural Elements of Passenger Compartment Lightweight solutions by using hot formed components Used for safety critical parts, especially for maintaining a passenger survival space in crash elements 1 A-pillar upper 2 B-pillar 3 C-pillar Side impact beam Tunnel Crossmember rear seat 80 7 Crossmember 60 firewall 40 8 Long member 20 9 A-pillar lower 0 10 Sill 11 Bumper 12 Long member rear 13 Crossmember roof +15% to +25% REF -5% to -10% -10% to -15% -20% to -30% -25% to -35% 26

27 HF 1200/1900: increased strength for lightweight potential Improvement of crash performance After following tempering process to increase ductility High deformation resistance Potential processes Cataphoretic painting process / paint shop Separated tempering process Typical temperatures and process times 160 C to 190 C / 20 to 30 minutes 200 C to 250 C / 15 to 30 minutes Quasistatic bending test HF 1050/1500 HF 1200/1900 HF 1200/1900 HF 1200/