laser and hybrid processes

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Welding &Materials for the Fast Track

Evolution of Laser and Hybrid Processes for Light-Metal automotive structural Components

Viwek Vaidya, P. Eng

October 22nd, 2002

9H30 to 10H15

Fraunhofer USA

Center for Surfaceand Laser Processing

Future trend for process choices with high strength steel and Aluminum alloys

Laser Beam Welding - Laser

- CO2 Gas excited

- Wavelength 10.6 µm

- Efficiency approx. 10%

- Very high power density 5E+7 W/cm2

- Keyhole welding

- Nd:YAG laser

- Wavelength 1.06 µm

- Efficiency approx. 2 - 10%

- High power density 1E+6 W/cm2

- Keyhole welding

- Semi Conductor laser

- Wavelength 680 - 940 nm

- Efficiency 30%

- Low power density 1.5E+5 W/cm2

- Heat conduction welding

Diode Laser – Efficiency and ease of use

•Direct diode laser – 6 KW max power

•4 KW laser head weighs 14 pounds and is only 8 inches wide, making robotic mounting easy!

•1.5 KW diode laser used for edge welding

laser spot motion6 axes (linear, circular path)orientation variable laser spot motion

3 (4) axes (linear, circular path) orientation not variable laser spot motion

9 axes (linear, circular path)orientation variable

ConventionalCoupled Axes System

(CAS)

Remote Welding System (RWS)

Laser Beam Welding - Systems

Laser Beam Welding – Remote Welding

Laser Beam Welding – Remote Welding

Application potential of Remote welding

• overlap weldingSubstitution of resistance spot weldingSmall welding seams on different positionsof the workpiece

• butt welding welding of geometries with small radii

Minimization of positioning timeMinimization of positioning time

Increase of mean welding speedIncrease of mean welding speed

Laser Beam Welding

Nd:YAG laser vs. CO2 laser

Process Start Phase• Higher power density of the CO2

compared to higher absorption of Nd:YAG

Welding Phase

• Comparable energy absorption in keyhole

BUT

• No direct interaction between plasma

plume and Nd:YAG laser radiation

Important Differences Between Nd:YAG and CO2 Laser Welding of Aluminum

root

laser beam

melt pool

solidified material(weld)

metal vapor

part

direction of motion

plasma

keyhole

Spot size : CO2 laser : 0.005” min ( 0.125mm)

Kerf width: 0.007”

Evolution in the Laser industry in the last 15 years : 400% Growth

• Linear drive motors : 6000 + inch/min travel speeds

• Higher power lasers now available

• High speed controllers with better position accuracy

• Laser blanking and cutting of hydro-formed components

• 22,500 Laser welding systems in the world

Laser Marking41%

Lithography & rapid

prototyping22%

Laser Cutting21%

Laser Welding 16%

Laser Marking

Lithography & rapidprototyping

Laser Cutting

Laser Welding

150,000 Laser system population ( 2002)

Laser Beam Welding of Aluminum

Surface Quality

Heat conduction welde.g. diode laser

Keyhole welde.g. Nd:YAG laser

Hybrid welde.g. CO2 laser + TIG


low low low

Heat Input per Unit Length

DistortionTolerable Gap

high high high

Nd:YAG -Laser Hybrid: Nd:YAG-Laser + TIG + Filler

vS = 1.9 m/ minPL = 2.9 kWE = 0.9 kJ/ cm

TIG + Filler

1 mm

vS = 2.1 m/ minvw = 3.0 m/ minPL = 2.9 kWI = 75 A E = 1.2 kJ/ cm

vS = 0.3 m/ minvw = 2.5 m/ minI = 160 AE = 5.2 kJ/ cm

Comparison of Welding Technologies - Cross Sections 3 mm Butt Joint 5754 (AlMg3)


high high low low

Welding Speed

Edge PreparationHeat Input per Unit Length Distortion

low low high high 1 mm

CO2-LaservS = 10 m/ minPL = 2.4 kWE = 0.14 kJ/ cm

Plasma + Filler WirevS = 1 m/ minvW = 2.0 m/ minI = 55 AE = 0.65 kJ/ cm

TIG + Filler WirevS = 0.3 m/ minvW = 0.8 m/ minI = 60 AE = 2.30 kJ/ cm

Hybrid: CO2-Laser+Plasma

vS = 10 m/ minPL = 2.4 kW I = 50 A

E = 0.20 kJ/ cm

Comparison of Welding Technologies - Cross Sections 1 mm Butt Joint 6111 (AlMgSi1)

Common Automotive Alloys – Aluminium• 5XXX : Magnesium solid solution effects

• 6XXX : Magnesium + Silicon precipitates of Mg2Si for strengthening

• Sheet : 6111, 6022, 6016, 5182, 5754, 5454

•Extrusions : 6061, 6063, 6008, 6060, 6014

• Castings : A356.0, 319.0, A380.0

• Filler metals : 5356, 4043, 5183

• 5XXX alloys may experience grain growth with heat

• 6XXX alloys need filler metal to compensate for crack sensitivity


Possible Weld DefectsHydrogen Pores

• Due to a sudden reduction in

hydrogen solubility at solidification.

• Hydrogen from base alloy, oxide layer,

surfaces and surrounding atmosphere.

Minimization through shielding gas,

“0”- gap, surface cleanliness and

parameter optimization.


Possible Weld DefectsProcess pores

• Related to instability of the keyhole

during welding

Elimination through reduction in

travel speed and/or widening of the

keyhole


Possible Weld DefectsHot Cracking

• Due to differences in the solidification temperature of the alloy phases in

respect of the alloying content (6xxx alloys)

Suppressing through the use of filler

wire to adjust the alloying content in

the weld0 1 2 3 4 5 6

Alloying Content in %

Cra

ck F

orm

atio

n P

roba

bilit

y

Magnesium

Silicon


Possible Weld DefectsBlowholes

• Due to keyhole instabilities

Avoidance through parameter

optimization and/or widening of

keyhole


Possible Weld DefectsUndercut

• Appears usually in full-penetration

welds due to low viscosity of melt

Use of filler wire, tighter fit-up

tolerances, root shielding


Possible Weld DefectsWeakening of weld through loss of alloying elements

• Magnesium and silicon loss may cause

a degradation of the mechanical properties

Minimization through the use of filler wire

Laser Beam Welding of Windshield Wiper Linkage

juch: 99_30_14_003e_bre.ppt, erstellt: 26.2.99

Example of an Industrial Aluminum Laser Welding Station

Specification

– 2,500 W CO2-laser DC 025

– 2 stations with beam shuttle

– filler wire feeding

– cooled clamping devices

– cycle time: 18 s

– start of production: 4/98

Laser Welding of Windscreen Linkages


Laser Welding of Fuselage Shells- Skin/Stringer Connection- Frames to Skin

- Reduce Cost and Weight

- Online-Quality Assurance


Welding of aluminum profiles

Laser : DC 025

Material : Al Mg Si 1 + Al Si 12- wire

Power : 2500 W f : 150 mm

Weld depth : 2.5 mm V : 5 m/min

System : x-y CNC machine + microplasma

advantages :- minimum pores - high welding speed - low running costs - high reliability - high process stability

Hybrid Laser Welding Process

LASER + GMAW Hybrid torch – Air Liquide

LASER + GTAW Hybrid torch – Air Liquide

LASER + Plasma Hybrid torch – Air Liquide

LASER + Plasma Hybrid movie – Air Liquide

What is a tailor Welded Blank?

A tailored welded blank is often composed of several flat sheets of steel, each having different strengths, thicknesses and/or finishes. The blank welding process welds these individual sheets together before they are stamped into a single auto-body panel.

TBW systems in the world automotive industry

• 180 systems produced about 100 million parts in 2001

• By 2004 world population to grow to 300 systems

• 47% TBW are doors

• 13% TBW are rails

• 11% are body sides

Ultra-light Steel Auto-body Side Panel: Tailor welded blank and part


Tailored Blanks

AimWelding Technology for Tailored Blanks

Thickness 1 mm / 2 mmAlloy 5754 (AlMg3)

Demands- Low Edge Preparation- Plain Weld Surface for Improved Formability- High Welding Speed

SolutionWider Weld Width with Hybrid Technology

Laser WeldingCO2-Laser DC035 (ROFIN SINAR)vS = 6 m/ minPL = 3.0 kWBeam Position Tolerance ±0.1 mm

Hybrid Welding: Laser + PlasmaCO2-Laser DC035 (ROFIN SINAR)vS = 6 m/ minPL = 3.0 kWI = 35 ABeam Position Tolerance ±0.2 mm

2 m

m

Aluminium Lap-fillet welding : 3 mm 6061 Aluminium alloy : Travel speed: 4M/min

3 KW Nd-YAG + CDT 450 Pulsed MIG

Dashboard Support

AimWelding Technology for Structure Car Component

Thickness 2.5 mm / 2.5

mmAlloy 5754 (AlMg3)

Demands- Rounded Edges to Protection of electric Cables- Minimum Heat Input- High Welding Speed- High Load Bearing Capacity

Sheet 1

Sheet 2

Weld 1

Weld 2



Application Dashboard Support

AimWelding Technology for

Structure Car Component

Thickness 2.5 mm / 2.5

mmAlloy 5754 (AlMg3)

SolutionMultifunktional Geometry

of Edge Weld with Hybrid Technology

Laser WeldingCO2-Laser DC035 (ROFIN SINAR)vS = 4.0 m/ minPL = 3.4 kWWeld Depth = 3.5 mm

Hybrid Welding: Laser + TIGCO2-Laser DC035 (ROFIN SINAR)vS = 4.5 m/ minPL = 3.4 kWI = 150 AWeld Depth = 3.5 mm


ApplicationsChassis Component

AimWelding Technology for Chassis ComponentAlloy 5754 (AlMg3)

Demands- Leakproof Joint - Smooth Weld Surface- High Welding Speed- Low Porosity

Component 1

Component 2

Weld


Applications Chassis Component

AimWelding Technology for Chassis ComponentAlloy 5754 (AlMg3)

SolutionRobust Process with Hybrid Technology

Laser WeldingCO2-Laser DC025 (ROFIN SINAR)vS = 3.0 m/ minPL = 2.4 kWBeam Position Tolerance ±0.15 mm

Hybrid Welding: Laser + TIGCO2-Laser DC025 (ROFIN SINAR)vS = 4.5 m/ minPL = 2.4 kWI = 100 ABeam Position Tolerance ±0.25 mm

1 mm

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laser and hybrid processes

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