1. Improved Joint Efficiencies in Aluminum Alloys
Strong-Al Welding
Improved Joint Efficiencies in Aluminum Alloys
Presented By
V. (Anthony) Ananthanarayanan, Ph.D.
President, Innovative Weld Solutions Ltd
&
Distinguished Alumnus, The Ohio State University

2. Contents Why are aluminum alloys difficult to weld?
How is Strong-Al welding done?
How does Strong-Al welding counteract the problems?
Comparison of the properties of conventional and Strong-Al Focused Current Resistance Welds (FCRW)
Tensile-shear strengths, microstructures and microhardness traverse details
Summary of Strong-Al weld features
Advantages and limitations
Contact Information

3. Why are aluminum alloys difficult to weld?
Their conductivity
Increases heat input needed for welding
Results in considerable heating and softening of the heat-affected zone (HAZ) surrounding the weld
Much loss of strength in the HAZ
Solidification defects
Cracks and porosity in weld nugget and HAZ
In general, higher strength alloys are more difficult to weld
Oxide absorbs moisture from atmosphere
Porous welds
Variable surface resistance

4. How does Strong-Al welding (FCRW) solve these issues?
Their conductivity
A water-cooled copper alloy electrode cools the near-HAZ during and after welding
The weld current is focused, generating an order-of-magnitude higher current density at the weld than at the electrode-metal interfaces
Low indentation and sensitization on the outer surfaces of parts welded
Strong-Al weld HAZ is harder and stronger by 50% w.r.t. HAZ from conventional welding such as arc welding or friction-stir welding
Solidification defects
Forging during solidification in FCRW eliminates cracks and porosity
Higher strength aluminum alloys are weldable
Oxide absorbs moisture from atmosphere
Very high current density at the weld
Faying surface resistance is no longer a large variable
Porosity is prevented by the forging action during solidification

5. Focused Current Resistance (Strong-Al) Welds
Made in commonly used resistance weld machines with improved controller software
Can weld dissimilar conductive materials such as copper-aluminum for battery applications
Can weld magnesium alloys and magnesium-aluminum alloy dissimilar material combinations
Many different weld shapes are possible, including long welds, ring welds and seam welds

6. Conventional and Strong-Al Resistance Welds: 6061 T6 Aluminum alloy sheets(1.5 inches * 0.060 inch)
Conventional RSW
Strong-Al Welds
Very sensitive to surface cleaning prior to welding
Weld strength pounds in a tensile-shear test
Nugget size limited by expulsion, electrode indentation, electrode sticking and weld defects
Little or no part stretching prior to failure in the tensile-shear test
Weld quality and strength not sensitive to cleaning prior to welding
Weld strength >2300 pounds and can be increased by increasing spot size
Failure through HAZ of relatively high hardness due to large weld size
Nugget size independent of sheet thickness
Considerable stretching prior to failure

7. A comparison of typical tensile-shear strengths: RSW and Strong-Al (FCRW)welds

8. Resistance welds in a 5000 series alloy
Conventional RSW
Strong-Al Welding (FCRW)
The Strong-Al weld is free from porosity and cracks; It also does not have sharp stress-risers at the edge of the weld nugget
Typical defect-like Indications along grain boundaries in the HAZ
Better HAZ microstructures and properties as seen from peel tested Strong-Al weld

9. Conventional and Strong-Al Welds: A Comparison of Hardness Values
Strong-Al Welds are nearly 50% harder in the near-heat affected zone than conventional spot/arc or friction-stir welds due to the focusing of weld current, while being free of defects such as cracks and porosity
Fusion Boundary
Heat Affected Zone (HAZ)
Weld Pool

10. Strong-Al (FCRW) weld appearance and geometry: Sheets of thickness 0
Strong-Al (FCRW) weld appearance and geometry: Sheets of thickness inch and width 1.5 inches
Welded parts possible (as-welded)
Both sides smooth
Both sides with outward projections to increase thickness and strength
one side smooth-one side with outward projections
Failure in the parent metal in a peel test
Microstructure shows
No defects/cracks in the weld nugget
Steep temperature gradient from the surface to the nugget as a result of the focused current

11. Issues in a Manufacturing Operation
High weld current needs
Robot designs to support heavier trans-guns
Higher welding forces
Methods of locating filler between parts welded

12. Strong-Al Welding: Work on hand
1” long and 0.25” to 0.4” wide welds in 0.25” thick 6061-T6 sheets

13. Strong-Al Welding: Other geometries possible
This geometry can be used to resistance weld
Aluminum-Aluminum
Copper-Copper
Copper-Aluminum
Aluminum-Magnesium
Lead-Lead

14. Strong-Al Welding: Other geometries
FCRSEW Seam welds of thick-thin and equal thickness combinations without outer surfaces being melted or indented are being planned
Temperature gradients from the outer surfaces to the weld nuggets will be steep
Weld nugget width will be large enough to force HAZ failure in tensile-shear test
Looking for partners to work with

15. Strong-Al Welding: Advantages
Better quality welds than by any other method
50% higher tensile-shear strength of the welded structure
Significantly less heating of outer surfaces and the heat-affected-zone (HAZ)
Better cosmetic welding
Improved corrosion resistance
Solidification under pressure/HAZ cooled by the electrode
Weld/HAZ microstructure with no cracks or porosity
Much larger electrode area than nugget size
Stable electrode surface condition for consistent manufacture

16. Strong-Al Welding: Advantages
Less distortion of welded part
Eliminates the need for adhesive sealant?
Can weld with sealant if necessary
Consistent positive positioning and placement of the weld
Reduces the need for auxiliary fastening techniques
Adhesive bonding, drilling, riveting, tacking, etc.

17. V. (Anthony) Ananthanarayanan
Strong-Al Welding: Contact Information
V. (Anthony) Ananthanarayanan
Dan Thomas

18. Questions?