LIGHTBLANK Reducing the Weight of Al BIW by using Friction Stir Tailor Welded Blanks Pressed by HFQ

Transcription

1 LIGHTBLANK Reducing the Weight of Al BIW by using Friction Stir Tailor Welded Blanks Pressed by HFQ Joao Gandra 1

2 Overview Transport sector demands How can FSW be combined with HFQ for BIW LightBlank project findings Automotive technology demonstrators B-pillar Cross member 2

3 Context: Transport sector demands More efficient and lower consumption vehicles Progressively stricter CO2 emission regulations EU committing vehicle manufacturers to cut emissions from new cars to 95g/km by 2020 Weight saving is most immediate solution Cold stamping of steel dominated BIW since 1920s Courtesy of The Society of Motor Manufacturers and Traders Introduction of hot stamped B-steel enabled down-gauging Al, Mg and Ti alloys progressively replacing steel parts Al alloys are the often the most commercially viable choice 3

4 Context: Transport sector demands Tailor welded blanks (TWB) Weight reduction without compromising performance Tailoring part topology according to loading requirements Thickness variation Dissimilar alloys within a single pressed panel (2xxx, 6xxx or 7xxx) MERKLEIN, Marion, et al. A review on tailored blanks - Production, applications and evaluation. Journal of Materials Processing Technology, 2014, 214.2:

5 Friction Stir Welding Friction Stir Welding (FSW) is becoming the technique of choice for joining Al (2xxx, 6xxx and 7xxx) A rotating tool is used to plasticise the material and producing a solid state joint Aluminium alloy 6mm thick plate 5

6 FSW in automotive (1) (2) (3) (4) (5) (1) FSW of TWB using dissimilar thickness Al sheets (2) Fundo Wheels FSW of cast Al hub to wrought Al rim section (3) Mazda RX-8 FSSW used for manufacture of rear doors and bonnet (4) Ford GT FSW of tunnel to Al frame to form housing of transmission system and fuel tank (5) Toyota Prius FSSW of rear hatch 6

7 Why is FSW revolutionary? No cracking or porosity when joining 2xxx, 6xxx and 7xxx Reduced distortion compared to fusion welding processes Less susceptible to Al stock variations Reduced CO 2 emissions, no fumes or spatter Suitable for all positions (2D and 3D trajectories) No special pre-weld edge profiling or cleaning No filler materials or gas shielding required Weld region features a ultrafine grain microstructure 7

8 What is HFQ? Enabling technology for stamping complex-shaped components from high strength aluminium alloys (2xxx, 6xxx and 7xxx) Enables mass reduction and provides increased design freedom Cost reduction mainly by - Simplifying assemblies - Elimination of reinforcements - Lowering cost of complex stamping HFQ is a registered trade mark of Impression Technologies Ltd and the HFQ stamping process is a patented technology Inner door panel pressed by HFQ Technology courtesy of ITL and Lotus Engineering for Innovate UK project UlCab 8

9 How does HFQ work? Heat Treatment Forming and cold-die Quenching system Integrates SHT, hot forming, quenching and artificial ageing HT moved from rolling mill to the Tier 1 (no additional stages) Does not require pre-tempered material Courtesy of Impression Technologies Ltd 9

10 Metallurgical principles of HFQ Courtesy of Imperial College of London 10

11 HFQ design freedoms Exchange steel parts for aluminium without the need to simplify or split the geometry Consolidate aluminium assemblies due to improved formability while maintaining acceptable mechanical performance Use high-strength grades to down-gauge (reduce weight, reduce material usage) Minimised spring-back compensation in tool and part design Remove reinforcement extrusions or panels with fully strenghtened Al pressings Courtesy of Impression Technologies Ltd 11

12 FSW-HFQ approach Welding results in a local reduction of mechanical properties at joint and HAZ (FSW lessens this effect compared to fusion welding) The HFQ technology allows restoring any losses of the strength due to the weld heat input (incorporates solution heat treatment and artificial ageing) FSW joints exhibit the ductility required to form the most ambitious geometries More attractive TWB aluminium combinations are only feasible by FSW (2xxx, 6xxx and 7xxx) Combining the FSW and HFQ expands the capability of both technologies 12

13 LightBlank Project Objective Develop and fully implement a UK-based supply chain to manufacture aluminium alloy friction stir tailor welded blanks formed by HFQ User benefits TWB production costs reduction with improved product quality Welding and complex forming of 2xxx, 6xxx and 7xxx Al alloys Optimised use of alloys/thicknesses for maximised specific performance Consortium 13

14 LightBlank Project Economical assessment UK supply chain Review potential applications for each end-user Full size technology demonstrators (inc. forming and stress FEA) Preliminary FSW and HFQ R&D (coupon size) 14

15 Material combinations developed AA6082-T mm AA7075-T mm AA6082-T6 TWB 1.5-2mm AA6082-T6 TWB 2-2.5mm AA6082-T6 TWB 2-3mm AA6082-T6 TWB 3-5mm AA6082-T6 TWB2-2.5 AA6082-T6 TWB1.5-2 AA7075-T6 FSW1.5 AA6082-T6 TWB5-3 15

16 Microstructural analysis EBSD mapping was used to analyse the grain microstructure and orientation of the crystalline structure TWB3-5 W14 mapping regions 16

17 Hardness distribution (before and after HFQ ) FSW AA6082-T6 panels combining a thickness of mm Courtesy of Imperial College of London 17

18 Tensile properties (before and after HFQ ) FSW AA6082-T6 and AA7075-T6 with a thickness of mm Courtesy of Imperial College of London 18

19 Technology demonstrators FSW B-pilar TWB combining AA6082-T6 sheets of and 5-3mm 19

20 Technology demonstrators MORGAN AERO Front X-Member The current design is made of 11 parts Bolted, riveted and adhesively bonded It is a low investment but assembly intensive (high piece cost solution) It suffers from reduced stiffness over joints Current total weight of kg Courtesy of Morgan Motor Company 20

21 Technology demonstrators MORGAN AERO Front X-Member The main panel is a FSW mm TWB formed by HFQ Total weight of 5.021kg 32% saving New solution is made of 8 parts FSW 3mm 2mm 3mm Courtesy of Morgan Motor Company 21

22 Conclusions HFQ and FSW allow fabricating complex AA6xxx TWB pressings in a fully hardened state For the automotive case studies considered so far, it was possible to reduce part weight and part count while meeting all performance targets Clear economic advantages 22

23 Useful links LightBlank project TWI s role in the project HFQ technology FSW and other friction-based processes FSW - creating a 'stir' in the welding industry 23