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Laser welding and its industrial applications
Heidi Piili on behalf of Antti Salminen
Lappeenranta University of TechnologyFaculty of TechnologyLaser processing research group
June 16th 2014
LAPPEENRANTA UNIVERSITY OF TECHNOLOGY (LUT)
LAPPEENRANTA CAMPUS
Lappeenranta Laser Processing Centre, LPCLUT Laser, Lappeenranta University of Technology
VTT Laser processing team
Lappeenranta University of Technology (LUT)LondonLondon
BerlinBerlin
MoscowMoscow
TallinnTallinn
LappeenrantaLappeenranta
OsloOsloStockholmStockholm
HelsinkiHelsinki
FINLANDFINLAND
LondonBerlin
Moscow
Tallinn
Lappeenranta
OsloStockholm
Helsinki
FINLANDSt. Peters-burg
LUT Laser
LASER TECHNOLOGY RESEARCH AT LUT
LUT LaserActivities since 1985− New building 1999 (Factory of Future)− LPC the Lappeenranta Laser Processing Centre,
joint research environment with VTT 2005− Turku Unit 2008− Head of laboratory: Prof. Antti Salminen− Research staff: 20 persons− Offer laser solutions to the manufacturing
challenges− High quality educational role for M.Sc. Students,
Ph.D. students and industry
Tampere 24.10.2012Tampere 24.10.2012Ohutlevypäivät, Hämeenlinna, 22.3.2013Outotec, Lappeenranta, 24.4.2013Lappeenranta, 30.4.2013Imatra, 17.5.2013Messukeskus, Helsinki 3.9.2013Messukeskus, Helsinki 4.9.2013Lappeenranta, 17.10.2013Tampere, 24.10.201326.11.201428.11.2013, LaitilaEuromold, 4.12.201316.6.2014 Appolo
LUT Laser - Activities− Welding of metals− Welding of polymers− Surface treatments− Cutting− Micro/milli laser processing− Laser additive manufacturing
Ohutlevypäivät, Hämeenlinna, 22.3.2013Outotec, Lappeenranta, 24.4.2013Lappeenranta, 30.4.2013Imatra, 17.5.2013Messukeskus, Helsinki 3.9.2013Messukeskus, Helsinki 4.9.2013Lappeenranta, 17.10.2013Tampere, 24.10.201326.11.201428.11.2013, LaitilaEuromold, 4.12.201316.6.2014 Appolo
Machinery− 5 kW multi mode fiber laser− 10 kW multi mode fiber laser− 2.7 kW CO2-laser− 200 W single mode fiber laser (water cooled)− 200 W single mode fiber laser (air cooled)− 200 W diode laser with scanner− 2 kW single mode fiber laser − 20 W pulsed fiber laser − Workstations:
• Laser additive manufacturing work station• 11x4 m gantry workstation• 125 kg robot• small xy-workstation for welding and cutting• small xy-workstation for milli/micro processing• fast xy-workstation and rotational stations for
ultra hight speed cutting testing
Euromold, 4.12.201316.6.2014 Appolo
International co-operation
Euromold, 4.12.201316.6.2014 Appolo
LASER WELDING
Keyhole
Salminen & Fellman, 2006
asa 17.09.2012 1616.6.2014 Appolo
Introduction
− Laser welding is a is rapid, high quality method of joining a wide range of metals and alloys, as well as polymers
− Principle: create a sufficiently high power density at the surface of a material for vaporisation to occur, which will lead to the formation of a deeply-penetrating vapour cavity surrounded by molten material.
− Practice select appropriate materials determine in-service requirements select appropriate processing parameters
− Process modelling: laser welding diagrams− Process selection− Industrial application
Major industrial sectors of application
asa 17.09.2012 1716.6.2014 Appolo
Effect of power density (steel)
asa 17.09.2012 18
Intensity = Power density, W/mm2
I = PL/AB
16.6.2014 Appolo
Keyhole vs. conduction limited
− Conduction limited welding brings the heat on the workpiece surface melting as a point heat source to the surface and the heat is conducted deeper into the material.
− Keyhole welding brings the heat directly into the material trough considerable thickness and heat is conducting from this vertical line energy source to material.
asa 17.09.2012 1916.6.2014 Appolo
Keyhole welding
− There is quite a lot conduction limited applications with Plasma welding.
− EB-welding is typically using keyhole welding− For laser welding In any thicker section is usually welded with
keyhole. Modern lasers enable keyhole welding also for thin sections.
− Typically conduction limited is done up to 1.5 mm, e.g. with diode laser.
asa 17.09.2012 2016.6.2014 Appolo
Heat sources
− There is three heat sources capable to perform keyhole i.e. deep penetration welding process Laser Electron beam Plasma welding
− Each of these can also be used for conventional welding i.e. heating via heat conduction
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Laser processing chart
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Melting
Cutting
Metals andalloys
Ion, 2005
16.6.2014 Appolo
Keyhole welding
− Beam welding typically enables high enough power density for keyhole formation.
− Usually the advantages of laser welding are fully utilized only with keyhole welding process
asa 17.09.2012 2316.6.2014 Appolo
Keyhole
− Due to features of keyhole the efficiency of keyhole welding is high, in range of 70-98 %
− Pressure of the metal vapor keeps the keyhole open− There is balance between vapor pressure, gravitation, flow of molten
material and surface tension
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Principle of keyhole welding
asa 17.09.2012 25
John Ion
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Keyhole
− Due to keyhole and the line heat input the weld is narrow− If there is no keyhole, the weld is narrow and deep− With incorrect parameters there is no keyhole (e.g. the focal point
position compared to workpiece surface)
asa 17.09.2012 2616.6.2014 Appolo
Keyhole welding process
Metal vapor
Melt poolWeld metal
Key hole
Laser beam
Welding direction
Weld cross section
5 kW, 2,3 m/min3+3 mm lap joint
1.4301asa 17.09.2012 2716.6.2014 Appolo
Power, continuous wave
− The range of parameters of high quality is restricted with lack of penetration (too low a heat input) and sagging weld (too high a heat input)
− Maximum speed is increased with the power− Other parameters like beam mode, beam quality, plasma formation,
have intermixed effect on performance
asa 17.09.2012 2816.6.2014 Appolo
Power, continuous wave
− In practice high power laser has larger parameter window, since required performance can be reached with several parameter combinations
− The penetration depth is increased with decrease in speed (constant beam quality and dimensions and laser power)
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Power, pulsed wave
− Pulsing adds few new parameters: Frequency (Hz) Pulse on-time (ms) Pulse off-time (ms) Overlap (%) Shape of the pulse
− Welding speed = spot diameter X frequency X overla− Pulse maximum power dictates penetration− Quality is depending on several factors
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Focal point diameter
− Dimensions of focal point Joining efficiency, joint cross section divided with welding speed,
depends strongly of the focal point dimensions Mode, optics (focal length of focusing and collimation, optical fiber,
beam diameter at focusing optics) define the dimension of focal point− Beam mode is typically not an issue if optical fiber is used for beam
transfer. It can be seen if diameter of optical fiber is more than 300 µm
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Focal point
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Beam characteristics
Radius 84 µmDiameter 168 µmBPP 4.4 mm*mradM2 13.1
Salminen & Fellman, 2007
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Effect of beam quality
asa 17.09.2012 34Katayama et al., 2011
Pen
etra
tion
dept
h, m
m
Welding speed, m/min
16.6.2014 Appolo
Focal point diameter and penetration
16.6.2014 Appolo 35
Katayama, 2010
Laser power 10 kW
Weldability window
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Welding speed, m/min
Laser b
eam pow
er, kW
0 1 2 3 4 5 6 7
2
0
4
6
10
8
12
14
16
No penetrationTransition borderFull penetration
S355 steel, Thickness 8 mm, Bead on plate
Quality window for welding
16.6.2014 Appolo 37
Welding speed, m/min
Laser p
ower, kW
S355, EN 10025‐2 Thickness 20 mmButt joint 30 kW fiber laser
Fiber core 200 µmCollimation length 140 mmFocal length 300 mm
Acceptable weldCut throughImperfectionsIncomplete pentration
Typical weld flaws
16.6.2014 Appolo 38
S355, 20 mm
Laser power 16kWWelding speed 2 m/minFiber core 200µmFocal length 300 mmFocal point 420 µmFocal point -7,5 mmAWJ cut edges
16.6.2014 Appolo 39
S355, 25 mm
16.6.2014 Appolo 40
Thickness 25mmLaser power 20kWWelding speed 2 m/minFiber core 200µmFocal length 300 mmFocal point 420 µmFocal point -10 mmAWJ cut edges
Productivity of welding
16.6.2014 Appolo
Process mmmm/minGas 3,2 90MMA 5 200TIG 2,3 500MIG 10 600SAW 38 200CO2 laser 2 2000
6 125012 132035 1000
Fiber laser 2 70004,5 1000025 2000
EB 38 100050 1000
0 1 2 3 4 5
Joining efficiency = Thickness X welding speed
41
2 kW5 kW
12 kW40 kW4 kW
10 kW30 kW45 kW75 kW
Kutsuna, 2008
Laser welding of airbus 300
16.6.2014 Appolo 42
T-joint, case airbus
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The advantages of laser welding, airbus
− Lower cost due to higher automation − Joint save material− Fewer work phases− Savings in weight by lower density of materials − Fewer sealings− Better corrosion resistance by new joint type− Riveting speed about 0.1 m/min, laser up to 10 m/min
16.6.2014 Appolo 44
Tailored blanks
Laser : 860HF x-flow CO2 laserMaterial: QStE 110 Zn/QStE 700Laser power: 6 kWFocal Length 150 mmThicknesses: 2.0 and 2.1 mmWelding speed: 8 m/minWeld widht: 0.9 mmSystem: X/Y CNC system
16.6.2014 Appolo
Tailored blanks
Advantages:• Higher stiffness and strength• More efficient use of materials• Lower body weight • Lower cost of forming• No installation tools• Lower installation costs• Higher productivity• Lower design costs• Better accuracy• Lower mass of coatings and
coated materials
Rofin
16.6.2014 Appolo
Tailored blanks
− Tailored base plate
16.6.2014 Appolo
Roof welding at volvo car
850 855 C70S70 V70classicS60 V70S80 V70XC
XC90
S40 V50, ….
> 5.000 km laser weld in car roof since 1991
Johnny K Larsson Volvo car
16.6.2014 Appolo
Hybrid Welding: Offshore
6/16/2014 49IPG Photonics Confidential Information
Offshore Application
P=10kW
v=1,5m/min
Flange thickness: 15mm
16.6.2014 Appolo
Hybrid Welding: Ship Yard
6/16/2014 50
IPG Photonics
Que
lle: B
IAS
Laser-HybridX70t = 12 mmPL = 10.5 kWvS = 2.2 m/min
Welding with Singlemode-Fiber Lasers
6/16/2014 51IPG Photonics Confidential
Information
Stainless steel200W 80m/min
CopperAluminium
Fe-Cu-Joint
Quelle: BIAS
