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Improved Joint Efficiencies in Aluminum Alloys

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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?

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