Innovative Weld Solutions Ltd. Patent Pending 1 Strong-Al Welding Improved Joint Efficiencies in...

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Innovative Weld Solutions Ltd. Patent Pending

Strong-Al WeldingImproved Joint Efficiencies in Aluminum Alloys

Presented By V. (Anthony) Ananthanarayanan, Ph.D.

Distinguished Alumnus, The Ohio State University

President, Innovative Weld Solutions Ltd

&

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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

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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

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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

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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

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Conventional and Strong-Al Resistance Welds:6061 T6 Aluminum alloy sheets(1.5 inches * 0.060 inch)

Strong-Al WeldsConventional RSW

• 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

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

6061 T-6 sheets 0.060" thickTypical RSW spot weld tensile-shear strengths

0

500

1000

1500

2000

2500

3000

1 2 3 4 5

Sample Number

Wel

d B

reak

Lo

ad

(po

un

ds)

Series1

6061 T-6 sheets 0.060" thickTypical Strong-Al weld tensile-shear strengths

0

500

1000

1500

2000

2500

3000

1 2 3 4 5

Sample NumberW

eld

Bre

ak L

oad

(p

ou

nd

s)

Series1

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Resistance welds in a 5000 series alloyConventional RSW Strong-Al Welding (FCRW)

Better HAZ microstructures and properties as seen from peel tested Strong-Al weld

Typical defect-like Indications along grain boundaries in the

HAZ

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

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Conventional and Strong-Al Welds: A Comparison of Hardness Values

Microhardness Traverses Across Strong-Al and Conventional Spot Welds

0

20

40

60

80

100

120

0 1 2 3 4 5 6

Distance from within weld pool (mm)

Vic

kers

Har

dn

ess

(VP

N @

100

gra

m l

oad

)

Conventional spot welds

Strong-Al FCRW welds

Weld Pool

Fusion Boundary

Heat Affected Zone (HAZ)

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

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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

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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

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Strong-Al Welding: Work on hand

1” long and 0.25” to 0.4” wide welds in 0.25” thick 6061-T6 sheets

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Strong-Al Welding: Other geometries possible

• This geometry can be used to resistance weld

• Aluminum-Aluminum• Copper-Copper• Copper-Aluminum• Aluminum-Magnesium• Lead-Lead

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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

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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

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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.

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Strong-Al Welding: Contact Information

V. (Anthony) Ananthanarayanan

+1 937 545 7695

[email protected]

Dan Thomas+1 519 668 4142

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Questions?

Date post:	26-Mar-2015
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Innovative Weld Solutions Ltd. Patent Pending 1 Strong-Al Welding Improved Joint Efficiencies in...

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