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Strong-Al Welding

Strong-Al Welding. Presented By V. (Anthony) Ananthanarayanan, Ph.D. Improved Joint Efficiencies in Aluminum Alloys . President, Innovative Weld Solutions Ltd. &. Distinguished Alumnus, The Ohio State University. Contents. Why are aluminum alloys difficult to weld?

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Strong-Al Welding

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  1. Strong-Al Welding Presented By V. (Anthony) Ananthanarayanan, Ph.D. Improved Joint Efficiencies in Aluminum Alloys 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 700-1300 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. Conventional RSW Strong-Al Welding (FCRW) Resistance welds in a 5000 series alloy 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 0.060 inch and width 1.5 inches • 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 • 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

  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. Strong-Al Welding: Contact Information V. (Anthony) Ananthanarayanan +1 937 545 7695 anthony@innovativeweldsolutions.com Dan Thomas +1 519 668 4142

  18. Questions?

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