Upload
maher-shehab
View
217
Download
0
Embed Size (px)
Citation preview
8/10/2019 10355 r of in Fine Welding With Laser
1/52
Fine Welding with Lasers
Michael Mller
8/10/2019 10355 r of in Fine Welding With Laser
2/52
Lasers and Systems
Welding principle
Weld types and tolerances
Material selection
Influencing factors / Advanced process approaches
ISO Standards
!a"le of contents
2
8/10/2019 10355 r of in Fine Welding With Laser
3/52
Notation according EN ISO 1145 : 1994
Laser source
Laser
Supply cabinet(power,cooling)
Work piece
Handling system(positioning, movement,clamping, gas supply)
Beam formingBeam guiding system
Process gas supply
Laser Working Station
3
8/10/2019 10355 r of in Fine Welding With Laser
4/52
8/10/2019 10355 r of in Fine Welding With Laser
5/52
8/10/2019 10355 r of in Fine Welding With Laser
6/52
Fi( Optics
6
8/10/2019 10355 r of in Fine Welding With Laser
7/52
Advantages
fast positioning
fle(i"le in terms of part
geometry
easy to use software
Suita"le for fi"er and direct
"eam delivery
)ision system through the lense
'alvo head
7
8/10/2019 10355 r of in Fine Welding With Laser
8/52
8/10/2019 10355 r of in Fine Welding With Laser
9/52
*
Laser material interaction
AbsorptionIn a thin surface layer +optical penetration depth depends on
material , -. nm0
Generation o heat1y transition of the energy of the light +photons0 to the
electrons of the material within the optical penetration depth
Heat transport1y heat conduction from the optical penetration depth into
"ul2 material +temperature gradient0
t
t.
Laser "eam
Laser "eam
!aterials reactionSolid state3, li4uid state3, vapour phase processes
+e5 g5 recristallisation, anealing, hardening, melting,5550
depending on power density and interaction time
*
Laser As a !hermal !ool
Laser beam
Laser beam
Isotherme
8/10/2019 10355 r of in Fine Welding With Laser
10/52
The absorbtivity of materials at room temperature and perpendicular incidence angle
of low intensity laser radiation is strongly depending on the wave length
St
Fe
Mo
Cu
Au
AgAl
30
25
20
15
10
5
Absorption
Abso
rptionin%
Wave length in m
0.1 0.2 0.4 0.8 1 2 4 6 8 10 20
Nd:YAG1,06 m
CO2
10,6 m
Laser 1eam A"sorption
10
8/10/2019 10355 r of in Fine Welding With Laser
11/52
Heat cond"ction weldingThe material is heated above meltingtemperature but there is no vaporization.
aspect ratio appro(5 .
ma(5 penetration appro(5 56 mm )ery smooth surface
#rocess types conduction welding
.0 Molten material70 Weld depth
.0
80
11
Applications#
Welding of thin wor2pieces, cosmetic welding
of enclosures
8/10/2019 10355 r of in Fine Welding With Laser
12/52
$eep % &eyhole weldingHeating of the material above vaporization
temperature and formation of a keyhole
aspect ratio appro(5 99 .
:eyhole diameter appro(5 spot
diameter
;w% ma(5 penetration depending on
laser power
#w% ma( penetration appro(5 < mm
.0 #lasma cloud
70 Molten material
8/10/2019 10355 r of in Fine Welding With Laser
13/52
=(ample%
Spot diameter 58 mm, #ower 7 W 39 I > .5? ( .@ W/cm
Spot diameter 57 mm, #ower 7 W 39 I > ?5< ( .6 W/cm
#ower density BW/cmC
DepthBmmC
;onduction
mode
:eyhole
mode
;riticalintensity
power
.6 .? .@ .E
#lasma
shielding
#O;=SS !=S
8/10/2019 10355 r of in Fine Welding With Laser
14/52
=
! > ./
#A)
##:
##uls
Power P
'ime t
.5 #ea2 power ##:75 #ulse power ##uls ##ulsG
#A) > = G =nergy too high
=nergy too low
##ulse
process threshold
Spot welding
Laser #arameters 3 pulsed
14
8/10/2019 10355 r of in Fine Welding With Laser
15/52
1) Increase of peak power (W)
2) Increase of pulse duration (ms)
3) Increase of spot size (mm)
1000 W-2 ms-Focus 0,4 mm 2000 W-2 ms-Fokus 0,4 mm 3000 W-2 ms-Fokus 0,4 mm
1000 W-2ms-Fokus 0,4 mm 1000 W-10ms-Fokus 0,4 mm 1000 W-50 ms-Fokus 0,4 mm
1000 W-2 ms-Fokus 0,4 mm 1000 W-2 ms-Fokus 0,8 mm 1000 W-2 ms-Fokus 1,2 mm
=ffect of #arameter ;hanges #ulsed Laser
15
8/10/2019 10355 r of in Fine Welding With Laser
16/52
(1))* overlap+)*
!he overlap indicates which
percentage of a pulse is covered "y
the following pulse5
From overlap, spot diameter and
velocity the necessary fre4uency can
"e calculated5
!he overlap in pulsed laserwelding is usually in the range of 6 to * H5
!o achieve good strentgh a little more than 6 H are sufficient5 If hermetic
sealing is re4uiered the overlap needs to "e @6 H or more5
;ross section
70 % 50 %
#ulsed Welding 3 Overlap
16
8/10/2019 10355 r of in Fine Welding With Laser
17/52
Laser parameters 3 cw
=
#A) > ##:
'ime t
process threshold
Power P
cw - Laser
#ea2 power > average power in cw mode, pea2 power of a
modulated puls is as ma(imum the ma(5 average power
#ulse width% 58 ms 3 . ms or cw mode
Fre4uency% cw +up to .@ 2J in modulated mode0
#ower density +#/+K/8D00 has to "e a"ove process threshold
17
8/10/2019 10355 r of in Fine Welding With Laser
18/52
=ffects of !emperature ;ycle
18
Laser welding has the following characteristics%
,ery high gradients and heating3 +9. :/s0 and cooling rates +. 55 Some
. :/s05 es"lt# high state o stress5
Material areas close to the molten Jone are heated up close to the solidus
temperature5
!he formation of "alanced microstructures is nearly impossi"le5 !ypically we
find coarse grained, hard and "rittle microstructures in the A5
8/10/2019 10355 r of in Fine Welding With Laser
19/52
1utt
weld
Lap Noint
Fillet
weld
!hin material should "e on top
Incidence angle of the laser"eam
as much in Noint direction as possi"le
Weld Noint types
19
8/10/2019 10355 r of in Fine Welding With Laser
20/52
.oint types / 0"tt Weld
20
0"tt weld
Advantages%
optimum distri"ution of forces
optimum solution for light weight structures
no pro"lems at welding coated material
Disadvantages%
high re4uirements on tolerances high re4uirements on clamping and positioning
8/10/2019 10355 r of in Fine Welding With Laser
21/52
.oint types / Lap .oint
21
Lap oint
Advantages%
low re4uirements in tolerances and positioning accuracy
low distortion indistri"ution of forces
more than 7 layers possi"le
Disadvantages%
risc of crevice corrosion
difficult degassification
#lease note% !hin material should "e on top5
8/10/2019 10355 r of in Fine Welding With Laser
22/52
.oint types / 2illet Weld
22
2illet weld
Advantages%
easy to clamp
good distri"ution of forces
Disadvantages%
high re4uirements on clamping and positioning
#lease note% Angle of weld follows incidence angle of laser"eam
.6 3
8/10/2019 10355 r of in Fine Welding With Laser
23/52
Butt weld
Lap joint
< 0,15 d
< 0,1 d
d
< 0,1 d d = 0.75 mm
d
'olerances
23
8/10/2019 10355 r of in Fine Welding With Laser
24/52
Spot si3es
24
600 m 30 m
8/10/2019 10355 r of in Fine Welding With Laser
25/52
8/10/2019 10355 r of in Fine Welding With Laser
26/52
Without gas $itrogen Argon
Goal#
#revent o(idation
Improve seam 4uality
Sol"tion# 4se protection gas
$itrogen cheap
Argon "etter seam 4uality
elium difficult to handle
5mportant#
Laminar flow At ? mm noJJle diameter
. l/min are reasona"le
#rotection 'as
26
8/10/2019 10355 r of in Fine Welding With Laser
27/52
Welda"ility of a material is given, if in production due to the chemical,metallurgical and physical properties a weld according to the re6"irements can
"e done5
from% DI$ E67E !eil .
Possible re6"irements#
P static strength
P dynamic strength
P heremtical sealing
P electrical conductivity
P reproduca"ility
P process sta"ility
Welda"ility is no
material specific value5
Due to this most often
tests need to "e done5
Welda"ility of Materials
27
8/10/2019 10355 r of in Fine Welding With Laser
28/52
Material Selection
!aterial Comment
Carbon steel Welds well5 If car"on content 9 57 H "rittle welds5
Stainless steel
8/10/2019 10355 r of in Fine Welding With Laser
29/52
8/10/2019 10355 r of in Fine Welding With Laser
30/52
#lating Issues
30
9inc coating 1oiling issues have to "e considered
'in May cause "rittle intermetallic phases with ;u
;ickel =lectroless 39 leads to crac2ing due to # in plating process
=lectrolytic 39 to "e preferred Gold
Often with $i underplating , avoid electroless $i plating ShinyT Au more difficult than dullT Au
Silver
!ends to spatter
8/10/2019 10355 r of in Fine Welding With Laser
31/52
!he welda"ilty of steel depends strongly on the following material
characteristics%
chemical composition metallurgical processes at melting and solidification
physical properties
Material composition limits% ;3 content - ,7 H
S3 and #3content as small as posi"le + usually 5
8/10/2019 10355 r of in Fine Welding With Laser
32/52
non- and low alloyed steel General str"ct"ral steel#
hardening in A possi"le5
'o"gh at s"b3ero steel and heat resisting str"ct"ral steel# Welda"ilty good "esides martensitic heat resisting structural steel 5
Case hardening-: nitriding heat treatable steel%
good welda"ility for ;= > ;QMn/7QMo/.6Q$i/8Q;r/.Q)/.Q;u/7QSi/76 - ,
8/10/2019 10355 r of in Fine Welding With Laser
33/52
Stainless steel 2erritic chrome steel 71< * = Cr = 1+*: C = ):1 *8#
welda"ility has to "e proved5
!artensitic chrome steel 71) * = Cr = 1>*: ):1 * = C = 1:< *8# Danger of cold crac2ing, increase of hardness and "rittleness5 welda"ility has to "e proved5 welda"ility for martensitic chrome nic2el steel with . H - $i - ?H and ; - ,6 H is
"etter5
A"stenitic chrome / nickel 7-molybden"m8-steel# mainly good welda"ilty5
A"stenitic erritic steel 7d"ple? steel8# ;ool down time not sufficient for complete change of microstructure5
Steel Welda"ility Stainless steel
33
8/10/2019 10355 r of in Fine Welding With Laser
34/52
8/10/2019 10355 r of in Fine Welding With Laser
35/52
Welda"ility of aluminium depends
strongly on the composition of the
alloy5
#ure aluminium is for e(ample well
welda"le5
When using Al alloys containing Si, Mg
and ;u care should "e ta2en to avoidthe pea2 of hot crac2 sensitivity5
Aluminium Welding 3 1asics
35
Sol"tion#
Filler wire, increase fle(i"ilty inmaterial selection "ut difficult
handling
;hoose the material of one of the
parts to weld in a way that the
resulting microstructure in the weldseam is not critical5 +e5 g5% 667 and
88@0
8/10/2019 10355 r of in Fine Welding With Laser
36/52
1 2 3 4 5 6 7
Felative;rac2
Sensitivity
#ercentage Alloying =lement BWeight HC
Al-Li
Al-Cu
Al-Mg2-Si
Al-Mg
Al-Si
Aluminium Welding ot ;rac2ing
36
8/10/2019 10355 r of in Fine Welding With Laser
37/52
Series
;on-heat-treatable alloys.(((
8/10/2019 10355 r of in Fine Welding With Laser
38/52
Weld Depth #ulsed Laser
38
,6
.
.,6
7
7,6