Laser Joining of Aluminum with Filler Wire
Steffen Mueller Craig Bratt, Christian Gebhardt, Thomas Kretzschmar Fraunhofer USA Center for Coatings and Laser Applications Plymouth, Michigan.
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Outline Purpose of Using Filler Wire Aluminum Alloys and Types of Filler Wire Weld Setup and Equipment
Laser Welding Processes Application Examples Conclusions
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Need For Mass Reduction in Cars Federal economy regulations require significant improvement in fuel efficiency, in order to: • • •
Save fuel costs for car owner Save oil/energy Reduce carbon dioxide pollution
2025 54.5 MPG
Sept.2012 29.3 MPG
2017 36.6 MPG (fleet wide average)
(fleet wide average)
One solution: Reduce vehicle weight as much as possible! “Around 400lb weight loss for an Average car is required to achieve 54.5 mpg”
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Germany
USA
(fleet wide average)
Benefits of Using Aluminum for Automotive Applications Aluminum and it’s Alloys •
Light – 2.7g/cm3 1/3 mass of Steel
•
High strength-to-weight ratio – depending on alloy and heat treatment, up to 300 MPa
•
Corrosion resistant
•
Easy to fabricate
•
In some cases difficult to weld
Typical Aluminum Alloy Series for Automotive Applications •
5000er series – Al-Mg alloy (e.g. Al5083, Al5754)
•
6000er series – Al-Mg-Si alloy (e.g. Al6061, Al6083)
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Purpose of Using Filler Wire Metallurgical Requirements Dimensional Requirements Post-Weld Requirements
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Purpose of Using Filler Wire Metallurgical Requirements •
Susceptibility to solidification cracks
Relative Crack Sensitivity
Solidification Cracking Curve
Percentage of Alloying Addition Source: Maxal [3]
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Purpose of Using Filler Wire Metallurgical Requirements •
Loss of alloying elements
Source: M.Pastor et al.[1]
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Source: J.Weston, et al. [2]
Purpose of Using Filler Wire Dimensional Requirements •
Different weld specification, depending on application
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Purpose of Using Filler Wire Dimensional Requirements •
Increase of cross-sectional area with Filler wire
Increase of cross-sectional area
Avoid of undercut/notches
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Purpose of Using Filler Wire Post Weld Requirements • •
Tensile Strength and Elongation requirements close to parent material Forming of welded sheets
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Aluminum Alloys and Types of Filler Wire 2xxx Aluminum Alloys •
Suitable filler wire for weldable alloys: Al2319, Al4145 filler wire
5xxx Aluminum Alloys • • •
Alloys with low Mg content: Al5183, Al5356, Al4047 filler wire Alloys with high Mg content: Al5183, Al5356, Al5556 filler wire For increased ductility and toughness: Al5356 and Al5554 filler wire
6xxx Aluminum Alloys • •
Best filler wire for reducing crack sensitivity: Al 4047 and Al4043 filler wire For increased strength and ductility: Al 5183 and Al5356 filler wire
Welding of dissimilar Al-alloys requires different filler wire! © Fraunhofer USA
Weld Setup and Equipment Laser for Welding of Aluminum •
Absorption of Laser beam depending on wavelength - CO2 Laser - Diode Laser - Nd:YAG/Disk/Fiber Laser Diode Laser 900-1030 nm
•
High beam quality
•
Back reflection protection
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Disk/Fiber/ Nd:YAG Laser
CO2 Laser 10.6 μm
Weld Setup and Equipment CNC-machines and Robots • •
Flexibility Accuracy
Multi-Axis CNC-machine for large structural aircraft components
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Industrial Robot for sheet metal welding
Weld Setup and Equipment Welding Optics for Aluminum Welding and Filler Wire Feeding • •
Laser beam spot size Single Spot and Twin Spot Optics
Filler Wire Feeding Equipment • • •
Push-pull system Wire Feed Torch Roller groove
Twin-spot weld head with filler wire torch for robotic applications © Fraunhofer USA
Push-pull wire feed system with enclosed wire spool cabinet
Weld head with filler wire torch and integrated clamp tool
Laser Welding Processes with Filler Wire Aluminum Sheet Laser welding with filler wire Thick Section Aluminum Laser welding with filler wire Laser Hybrid welding
Laser Remote Welding
Aluminum Sheet Welding
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GMAW-Laser Hybrid Welding
Laser Remote Welding
Laser Welding Processes with Filler Wire Aluminum Sheet Laser welding with filler wire •
Al5083 sheet in overlap configuration, Al5183 filler wire
•
Al6061 sheet in butt joint configuration, Al4047 filler wire
•
Al5754 sheet in step joint configuration, Al5554 filler wire
Al5083 sheet and Al 5183 wire
Al6013 sheet and Al4047 wire
Al5754 sheet and Al5554 wire
Laser Power: 5 kW Travel Speed 4.5 m/min Wire Feed Rate: 4.5 m/min
Laser Power: 6 kW Travel Speed 2.0 m/min Wire Feed Rate: 6.8 m/min
Laser Power: 5 kW Travel Speed 6.0 m/min Wire Feed Rate: 6.0 m/min
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Laser Welding Processes with Filler Wire Thick Section Aluminum Laser welding with filler wire •
High power, single pass weld – insufficient distribution of filler material
•
Low power, multi pass welds – consistent distribution of filler material Si-content 8,5 %
Si-content
top
approx. 1,7 %
7,9 % middle
3,9 % bottom
Inconsistent filler material distribution for plates above 5 mm 30 KW laser power and insufficient filler wire in lower part of weld
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22 mm
middle
Narrow gap, multi pass welds with more even filler wire distribution
Laser Welding Processes with Filler Wire Thick Section Aluminum Laser welding with filler wire •
Narrow gap, multi pass welds - 25 mm thick Al 6061 plates, Al4047 filler wire
Comparison between conventional weld (top) and narrow gap, multi pass weld (bottom)
Narrow gap, multi pass welds Laser Power: 2.5 kW Travel Speed: 1.0 m/min Wire Feed Rate: 1.0 m/min
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Laser Welding Processes with Filler Wire Laser Hybrid welding •
GMAW-Laser Hybrid welding - Al 6061 sheets in lap fillet configuration, Al4047 filler wire - Less dependent on work piece tolerances
Al6061 sheet and Al4047 wire
Laser- GMAW Hybrid Welding process
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Laser Power: 3 kW Travel Speed 3.0 m/min Wire Feed Rate: 8.0 m/min
Application Examples Aluminum Hood Welding • • •
Overlap joints Al6111 to Al6111 and Al6111 to Al5754 material combinations Stitch welds
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Application Examples Aluminum Airframe Components •
Fully welded metallic integral structure - Loading tolerant stringer-skin- joints - Load adapted clip-skin-joints - Damage tolerant skin-skin joints Clip-Skin Joint
Skin-Skin Joint
Stringer-Skin Joint
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Conclusions Increased use of Aluminum continuing for both automotive and aerospace applications. In addition to advanced high strength steels, Aluminum will enable future vehicle mass reduction and enable fuel efficiency improvements. Laser Welding is fast, flexible and automated and provides minimal heat input and distortion compared to conventional welding technology. Laser Welding with filler material can reduce crack susceptibility and loss of alloying elements, and can generate welds with strength properties close to the parent material Laser welding process applications development for Aluminum is ongoing at Fraunhofer as the Automotive and Aerospace industries continue to move towards lighter more fuel efficient vehicles.
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Thank you for your attention! For additional information please contact: Steffen Mueller Fraunhofer USA – Center for Coatings and Laser Applications Plymouth Michigan USA. Email:
[email protected] Website: www.ccl-laser.fraunhofer.org Telephone: 734 738 0551
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