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Common Joining Methods Used in Aluminum Structures
D.J. SpinellaAlcoa Technical Center
November 21, 2013
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Common Joining Methods Used for Aluminum Structures Agenda
IntroductionTrends in Automotive Structures
Design
Manufacturing Approaches
Automotive Joining Technology
Baseline Joining Technologies
Fusion-Based
Solid State
Mechanical
Conclusions
Questions
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MPG
Requirem
ents
Multi-Material
High Volume Auto Body Evolution
Steel & Aluminum Hybrid(High scrap utilization, Steel to aluminum joining)
Tailoring Products
Aluminum Intensive Vehicle(Strength & ductility for safety, Robust joining)
Aluminum Closures(Increased formability for design/styling)
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2013 Jaguar XJAluminum since 2003
2013 Jaguar XKAluminum since 2006
2013 Jaguar F Type
2013 Range Rover
Jaguar Land Rover Aluminum Vehicles
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www.jaguarusa.com
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2014 Mercedes-Benz S-Class
2014 S-Class BIW Weight (kg) 362
Front Doors (2) (Kg) 21.8
Rear Doors (2) (Kg) 21.2
Hood (Kg) 12.7
Liftgate/Decklid (Kg) 6.7
Front Fenders (Kg) 3.3
Front Bumper/Other (kg) 7
Total (kg) 434.7
Aluminum roof, doors, hood, decklid, rear packageshelf, frontend, front subframe
Saved 50 kg using aluminum over the steel body
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Ref: 2013 Euro Car Body Conference
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Automotive JoiningNorth American Industry Trends
Closures: RSW, Laser, SPR, Cl inch, Frict ion Sp ot
Structures: MIG, Adhesives, SPR, EJOT
Steel
Assembly Line
(Single / Multi)
Aluminum
Assembly Line
(Single Platform)
St / AlAssembly Line
St / Al / Hybrid
Assembly
Line
Today
Future State
All Steel
Vehicle
All Alum
Vehicle
Steel or Al
Vehicle
Steel, Al or
St/Al Hybrid
Vehicle
.
Moving to aluminum intensive vehicles
requires separate pieces of capital inaddition to assets in place for steelvehicles
Several aluminum joining technologiesnot considered as flexible to productchanges as those employed for steel
Can you proc ess mult ip le mater ials dow n the same f lowpath?
Closures: RSW, LaserStructures: RSW, Adhesives, MIG
Multiple Al
Platforms
Aluminum
Assembly Line
(Multi Platform)
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Automotive Joining TodaySteel Sheet RSW
3k to 5k resistance spot welds pervehicle in galvanized sheet steels
Gauge Ranges
0.6 to 1.0mm (closures)
1.2 to 2.5mm (structural)
Cycle Time: 1.52.0 sec/weld to weld
Costs
Capital
Electrodes (~$0.0003/weld)
Labor, Electricity, Water Cooling
Robotic RSW is well entrenched
Extensive integrator & supply chain
AWS, ISO, JIS weld specifications Decades of data & experience
QA & NDE procedures established
Weld through lubricants & adhesives
Very flexible to product changes http://www.romaneng.com/engineering.html
http://www.romaneng.com/engineering.html
Steel RSW Section
Respot RSW Cell
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Automotive RSW LinesFlexibility is King
Multiple automotive models flow down single respot lines. Each
gun dynamically changes its weld schedule to accommodate
the multiple stackups for each individual assembly
www.abb.com/cawp/seitp202/522132200f15d417c12577ee005a784c.aspx
Auto 1
Auto 2
Gun A
ExampleTwo different auto assemblies run down the same respot line
Stackup Range:
2.3 to 4.6mm
Force Range:
3.1 to 6.5kN
Current Range:
8 to 13kN
Gun A welds each assembly in seven locations byelectronically changing weld schedules rather than tooling
RSW process flexibility enables OEMs tomake gauge or product changes without the
downtime and capital costs to retool
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Temperature
Pressure
Time Explosion
Ultrasonic
MagneticPulse
Cold
Friction,Upset
Al MeltingPoint
Fusion
Resistance
Soldering
Comparison of Various Joining Processes
Brazing
FSW
620 C450 C
Many welding processes dont reach the melting point of the material
Alloy of parent, heat & pressure profile, and filler metal determines Mechanical Properties (tensile, yield, elongation, fatigue)
Physical Properties (corrosion, electrical resistivity, color match
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Competing Technologies vs. Robotic Steel RSW
Mechanical
Performance
Consumable
Cost
Flexibilityto
GaugeChang
es
GunAccessib
ility
Aluminum
to
Stee
Joining
HighStrength
Materials
Surface
Pretreatmen
ts
Adhesive
Compatible
ProcessSpee
d
Precision
Alignment
Aluminum RSW Lower Low Yes 2 Sided No Special
Practices No Yes Fast Low
Self Pierce Rivet Good Yes Limited 2 Sided Yes Special
Practices No Yes Fast Low
EJOT, Flowdrill Good Yes Yes 1 Sided Yes - w/
pilot Yes No Yes Mod Mod
Mechanical Clinch Lower Yes Limited 2 Sided Yes Special
Practices No Yes Fast Low
Adhesives Good Yes Yes 1 Sided Yes Yes Yes Yes Fast Mod
Blind Fastener Good Yes Yes 1 Sided Yes Yes No Yes Slow Mod
Ultrasonic Lower Low Limited 2 Sided Limited Yes No Limited Mod Mod
Friction Stir Spot Lower Low Limited 2 Sided Yes Yes No Limited Mod High
LimitedImprovement Base line Lower
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Joining Technology Example
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2014 GM Corvette Stingray
Resistance Spot Welding EJOTS (Flow Drill Screws) Laser Beam Welding
media.gm.com
www.technologytell.com
http://www.technologytell.com/in-car-tech/files/2013/10/BGCorvetteAssembly043.jpg7/26/2019 Donald Spinella-Joining Methods Nov21
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Automotive Joining TodayAluminum Sheet RSW
Aluminum sheet is spot welded in several high
volume closure applicationsStructural applications have been limited toonly a few niche vehicles
Issues versus steel RSW1. Process consistency (its all about surface)
2. Requires higher capacity welding transformers(2.5X weld current)
3. Questions on process robustness toproduction conditions (electrode angularity,gaps, etc.)
4. QA and NDE procedures are not as mature
5.Lubricant and adhesive impact on weld qualityAdvantages
Equipment designed to weld aluminum caneasily process steel
Leverages steel RSW infrastructure & logistics
Al Closure Panel Line
Aluminum Weld Section
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Ref: AA Welding Aluminum, Table 13.1
Aluminum RSW Size, Spacing, Edge Distance & Overlap
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Ref: AA T10, Table 7
Parameter Guidelines for RSW Aluminum Sheet
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TSS Performance of AL Resistance Spot Welds
0.0
2.0
4.0
6.0
8.0
10.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
MINIMUMS
HEAR
TENSION
STRENGTH
(kN
)
THICKNESS (mm)
386 MPa and above240 MPa to 385.9 Mpa
135 MPa to 239.9 Mpa
Below 135 Mpa
Typical
AutoAlloys
AWS D17.2:2007 Aluminum Tensile Shear Strength
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wire feed rolls
shielding gas
consumable
electrode wire
arc plasma
weld metal
base metal
Gas Metal Arc Welding - GMAW
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www.lincolnelectric.com
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Advantages
Can be used manually and automatically Suitable for welding most joint types Applicable to joining various thicknesses
(1.5 mm) and thickness combinations Lends itself to automation with mechanized
straight-tracks and robots Good travel speeds - 0.5 to1.5 m/minDisadvantages
Sensitive to variations in joint gaps andlateral positioning of the joint edges,relative to the welding torch
More prone to formation of weld porositythan GTAW
Can be used in the flat downward,horizontal, vertical, overhead andintermediate welding positions
Not as fine to control as GTAW May require parts to be cleaned of
lubricants and contaminants
GMAWAdvantages and Disadvantages
www.lincolnelectric.com
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Vs
Laser Beam Welding - LBW
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Laser Beam WeldingAdvantages and Disadvantages
Advantages
Higher welding speeds of travel on thin
sections
High penetration/width ratio of welds
Strong welds with UTS joint efficiency >90% insome alloys
Precise heat input which leads to narrowerweld beads, heat-affected zones and distortion
Welds Lap-Penetration and Square-Butt joints
Can maximize system utilization by switchingbetween continuous and stitch welding modes
Can be readily automated using robot or gantrysystems
Ready beam-sharing between different stationsand/or use with Hybrid welding processes(e.g., GMA/Laser) of 6xxx
Disadvantages
Certain alloys will require a filler alloy
Joint fitup and precision
Capital costs
Laser Stir Fillet Weld
Laser Beam Fillet Weld
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Solid-State WeldingKey Characteristics
Surface oxides must be removed / displaced / dispersed so that
parent metals come into direct contact
Combinations of heat, pressure & time
Deformation may be present
Plasticized materials displace oxides, pressure allows
intimate contact resulting in metallurgical bonding
Temperatures below materials melting point
Allows dissimilar material combinations (AL to ST, AL to CU)
since intermetallics are not generated
If temperatures above melting, molten metals and
intermetallics must be expelled for good properties.
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Butt Lap (Spot or Seam)
Cold UpsetResistance
FrictionFriction
StirMagnetic
PulseUltrasonic Explosion
Area
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Ultrasonic Welding Process
Anvil
Sonotrode TipVibrates @High Freq
Force
Force
Wedge-ReedLateral Drive
Sonotrode
Transducer
Transducer
WedgeReed
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Hetrick et al., Ultrasonic Spot Welding, A New Tool for
Aluminum Joining, AWS Welding Journal, Vol 84, Feb 2005.
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Advantages
Low # Process Inputs
Low heat distortion
Low heat-affected zone
Weld through lubricants
Surface preparation not criticalExcellent electrical joint properties
Low energy joining process
No arcs & fume emissions (clean)
2 to 3 second cycle timesBimetallic combinations
No water cooling or filler materials
Disadvantages
Thickness limited to approx. < 3mm
Difficult for deep parts (throat depth)
Requires good workpiece alignment
Applications
Electrical Wiring
Light gauge sheet joining
Sheet to wire joints
Bimetallic, multi-material joining
Products in consumer, industrial,
auto, defense, and aero
Ultrasonic WeldingAdvantages and Disadvantages
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Ultrasonic Process Variables and Mechanical Performance
Major Process Variables
Vibration Amplitude (Microns), Force (Pressure), Time,Tool Geometry
Weld Energy = Power * Time = (Amplitude * Force ) * Time
Increased Power or Time necessary with partcontamination or tool wear
Hetrick et al., Ultrasonic Spot Welding, A New Tool for Aluminum Joining, AWS Welding Journal, Vol 84, Feb 2005.
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Advantages
Good mechanical properties Minimal weld induced distortion
Full or partial penetration from one side
Square butt & lap-penetration type joints
High quality welds involving fewer repairs
and rejects No filler alloy addition & shielding gas
Very simple to operate and maintain
Welds aluminum alloys normally considerednon-fusion weldable (e.g., 7050, 7075)
Disadvantages
Requires good fitup and clamping systems
Friction Stir Welding Process
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Lap-Fillet
Lap-
Penetration
Square-Butt
Square-
Butt
Lap-
PenetrationLap-Fillet
Part A
Part B
Ideal for FSW Challenging Highly specialized
FSW Joint Types
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Advancing SideRetreating Side
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4540
35
30
2520
15
10
5
0
Tensile Strength Yield Strength % Elongation
Mechanical Property
S
trength(ksi)orelongation(%)
Base Metal
Friction Stir Weld
GMA Weld
FSW versus GMAW Property Comparison: 6061-T6
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Friction Stir Spot Welding
Advantages
Replaces RSW and mechanicalfastening joints
Minimal weld induced distortion
Stitch and refill variants
Low consumable & infrastructure
costs (low electricity, no chillingwater)
Welds aluminum alloys normallyconsidered non-fusion weldable(e.g., 7050, 7075)
Disadvantages
Cycle time for thick stackups
Switching between different stackupsand material combinations
www.kawasakirobotics.com
Arul et. al., Effects of Surface Treatment (Lubricant)on Spot Friction Welded Joints Made of 6111-T4Aluminum Sheets, SAE Paper 2007-01-1706
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Friction Spot Welding Fatigue Performance0.94mm 6111-T4
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Lin et.al., Failure modes and fatigue life estimations of spot friction welds in lap -shear specimens of aluminum6111-T4. Part 2: Welds made by a flat tool, International Journal of Fatigue, Vol. 30 (2008) 90 -105
Alcoa RSW FatigueData on 1mm Al
Auto Alloys
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Friction Welding Process - Direct Drive
Position, Clamp, &rotate parts
Advance non-rotary part,
start pressure
Heating
Forge / Upset
Force pushingparts, increasingfrictional heat
Flash-off
High forgingforce applied
Rotation and forceapplied for aspecific period
Single part rotatesto desired speed
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Advantages
Low Number Process Inputs
Low heat distortion
Good joint properties (low heat-affectedzone)
Weld through lubricants
Surface preparation not critical
Excellent joint properties
Low energy joining process
Clean process - no arcs and fume
emissionsFast second cycle times
Bimetallic combinations
No water cooling or filler materialsrequired
Disadvantages
Equipment may be capitallyintensive
Requires good workpiece alignment
ApplicationsAutomotive driveshafts
Suspension rods, axles
Bimetallic joining
Products in Auto, Defense, Aero
Friction WeldingAdvantages & Disadvantages
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Mechanical Fastening: SPRSelf-Piercing Rivet
Factors for SPR Joint Design
Total Stack-Up Thickness
Determines rivet length
Flange or Overlap Width
Edge Distance
Tool Clearance
Materials being Joined
Aluminum
Steel
Multi-Materials (Hybrids)
Stack-up / Orientation
Softer (top) to Harder (bottom)
Thick to thin, thin should be no less than1/3t of the thicker
Rivet Diameter
3 mm or 5 mm
Joint strength Robustness of joint
Access
Rivet Length
3 mm rivet, 1.5 - 3.0 mm > than stack
5 mm rivet, 2.0 - 4.0 mm > than stack
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Mechanical Fastening: SPRSelf-Piercing Rivet
6000
5000
4000
3000
2000
1000
03 mm 5 mm 3 mm 5 mm
1 mm to 1.5 mm
Material
1.5 mm to 1.5 mm
Material
6111-T4 Alloy
Rivet Diameter
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LapShearTensileS
trength,
N,
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Mechanical Fastening: EJOT Flow Drill Screws
Weber Screw Driving Systems
1. FLOW DRILLING SCREW (FDS) is applied to surface with medium thrust andspindle rotation.
2. As friction and heat increases, the surface plasticizes and begins to flow.3. Material begins to form the extended threading are behind the application.4. As the flow phase ends the thread rolling phase begins with lower RPM on the
spindle.5. The screw now begins to act like a normal fastener and is driven to a torque.6. The fastener is seated as it would be in any normal toque strategy. As the
materials cool it also contacts around the threads for added joint integrity.
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Mechanical Fastening: TOX Mechanical Clinch
TOX Clinching Process
Material Stack-up / OrientationPreferable to have thicker or harder material on punch sideMinimum single sheet thickness of 0.3 mm (depend on TOX diameter)Maximum combine thickness is 8 mm (depend on TOX diameter)
Total stack-up of 2 to 4 layers possible
TOX diametersAvailable in 3, 4, 5, 6, 8, 10, and 12 mm button diameters
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Mechanical Fastening: TOX Mechanical Clinch
0
50
100
150
200
250
300
350
400
450
500
lbs
Force
6 mm 8 mm
Button Diameter
Effect of Button Diameter
1mm : 1mm 6111-T4 Joints
Pull Strength
Shear Strength
0
50
100
150
200
250
300
350
400
450
500
lbs.
force
1mm:1mm 6111-T4 1mm: 2mm 5754-0
Alloy / Gauge Combination
Effect of Alloy
with 8 mm TOX
Pull Strength
Shear Strength
TOX Joint Strength
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Aluminum Automotive Joining Applications
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Aluminum Now, Aluminum Association, January/February 2003 6061 Extrusions
Friction Stir Welded Suspension Link for Lincoln Town Car
39
www.aluminum.org
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Aluminum Now, Aluminum Association,
November/December 2002
Pretreated aluminum sheet 40% lighter, 60% stiffer than previous
steel-body XJ
Stamped sheet panels assembledwith adhesive bonding incombination with self-pierce
riveting
Jaguar XJ
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Aluminum Now, Aluminum Association,
November/December 2001
30 meters of laser welds
http://www.autoaluminum.org/
Aluminum Associations Aluminum Welding Seminar, 2003
Audi A2
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A i Cl P l RSW A li i
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General Motors YukonAL liftgate
DaimlerChrysler Pacifica
AL hood
http://www.autoaluminum.org/
www.chrysler.com
http://www.autoaluminum.org/
Automotive Closure Panel RSW Applications
Nissan Altima
AL hood and decklid
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Ford Explorer
AL hood and fenders
Acura MDX
AL hoodwww.acura.com
www.ford.com
www.nissanusa.com
www.gm.com
A t ti Cl P l M h i l F t
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Chrysler Concord
AL hood (SPR, TOX)
GM U-Van (Venture)AL hood (TOX)
Plymouth ProwlerSPR body and panels
Automotive Closure Panel Mechanical Fastener
43
www.gm.com
www.chrysler.com
www.chrysler.com
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A k l d t
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Acknowledgements
The presenter would like to thank the following individuals for supplyinginformation and slides for this presentation: Dan Bergstrom, Russ Long,Israel Stol, and Kyle Williams.
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