Shielding Gases
Development . Consulting . Applications
Photo on title page:
The use of the well-proven shielding gases from Linde
together with LINFAST® leads to quality improvement and cost savings
Contents
Page
Cost-Effective Industrial Gases from Linde...................................................................... 3
The Right Shielding Gas - for Every Welding Process ..................................................... 4
Compositions of Linde Shielding Gases .......................................................................... 5
Properties of Shielding Gas Constituents ........................................................................ 6
Arc Types: Their Actions and Applications ....................................................................... 8
Shielding Gases for MAG Welding of Structural Steels.................................................... 10
Shielding Gases for LINFAST® ......................................................................................... 12
Shielding Gases for MAG Welding of High-Alloy Steels and Ni Base Alloys ................... 14
Shielding Gases for MIG Welding of Non-Ferrous Metals................................................ 16
Shielding Gases for TIG Welding...................................................................................... 18
Oxidation Prevention Using Forming Gases .................................................................... 20
Shielding Gases for Plasma-Arc Welding......................................................................... 22
Shielding Gases for Arc Stud Welding ............................................................................. 23
Shielding Gases for Laser Beam Welding ........................................................................ 24
Linde Publications, Application Notes and Training Materials ......................................... 26
2
Cost-Effective Industrial Gases
from Linde
Q
uality improvement and rationalisation are crucial for any company that wishes to maintain and improve its competitive position in the
welding industry. Linde shielding
gases provide a variety of options for
achieving these aims.
As one of the leading suppliers of
industrial gases, Linde has decades
of experience in the development,
production and application of shielding gases. Linde expertise encompasses all modern welding applications and is continuously updated by
innovative solutions.
The most up-to-date production
plants, regular quality controls and a
national sales network ensure the
best possible reliability of supply.
Our supply channels are not only
manifold, they are above all economical: Linde offers tailor-made
and cost-optimised supply concepts
to each customer, from the 10 litre
cylinder to the 75,000 litre tank. Our
dense network of sales agents and
depots, the numerous Linde production facilities and a comprehensive
range of products ensure high availability, reliability of supply and short
distances for customers who want
to collect their own supplies.
The Linde Technology Centre
uses the most advanced welding
equipment to solve customer problems on a case-by-case basis. Applications engineers provide on-site
assistance to customers to ensure
optimal use of Linde shielding gases.
Steel cylinders
Water capacity
litres
Contents*
m3
10
2.1 – 2.4
20
4.0 – 4.7
52
9.1 – 11.8
* Gaseous contents; the contents is
dependent on the type of gas
Cylinder bundles
Contents*
m3
106.8 – 141.6
* Gaseous contents; the contents is
dependent on the type of gas
Storage tanks
Contents
600 – 75,000 litres
3
The Right Shielding Gas –
for Every Welding Process
Process
Shielding Gases
DIN 1910
CORGON® 1
CORGON® 2
®
GMAW with active gas CORGON® 18
CORGON 10-40
Carbon dioxide
MAG
CRONIGON® S1
CRONIGON® S3
CRONIGON® 2
CRONIGON® He 50
MIG
GMAW with inert gas
TIG
Tungsten inert gas
CORGON® S8
CORGON® He 30
CORGON® He 25 C
CORGON® He 25 S
T.I.M.E. + T.I.M.E. II
Steels for pipe, boilers, shipbuilding;
structural and fine-grain steels,
case-hardening and heat-treatable
steels
CRONIGON® He 20
CrNi, Cr and other alloy steels,
CRONIGON® He 30 S Ni base alloys,
CRONIGON® He 50 S
CRONIWIG® N series Duplex and super duplex steels
Argon
VARIGON® He
VARIGON® S
VARIGON® He S
Argon
Helium
VARIGON® He
Material
Aluminium, copper, nickel
and other alloys
VARIGON® S
VARIGON® He S
All weldable metals such as
unalloyed and alloy steels,
aluminium, copper,
VARIGON® H
CRONIWIG® N-series
Nickel and Ni alloys
CrNi steels
Argon 4.8
(Special applications)
Reactive and refractory materials
such as titanium, tantalum, zirconium
Plasma gas/Shielding gas:
Argon
VARIGON® H
VARIGON® He
All weldable metals
see TIG
Root
protection
Forming gas: Nitrogen-hydrogen
H2
N2
100 %
–
95 %
5%
90 %
10 %
85 %
15 %
80 %
20 %
For all materials where oxidation
at the root must be avoided.
Burn off hydrogen at levels
overs 10 %
Laser
beam
LASPUR ® quality:
Argon
Helium
Gas mixtures
All weldable metals
Arc stud
welding
CORGON® 18
Structural steel, high-alloy steels
VARIGON® He 30
Aluminium
and Al alloys
PAW
Tungsten plasma-arc
Without Forming gas
With Forming gas
4
EN 439
Materials supposed to be difficult
to weld
Compositions of Linde Shielding Gases
Shielding gas
EN 439
Argon
% by vol.
Argon (Ar)
I1
Helium (He)
I2
Carbon dioxide (CO2)
C1
Carbon
dioxide
% by vol.
Oxygen
Helium
Nitrogen
Hydrogen
% by vol.
% by vol.
% by vol.
% by vol.
100
100
100
CORGON® 1
M 23
Balance
5
4
CORGON® 2
M 24
Balance
13
4
CORGON® 10 – 25
M 21
Balance
10 – 25
CORGON® S 5
M 22
Balance
5
CORGON S 8
M 22
Balance
8
T.I.M.E.
M 24 (1)
Balance
8
T.I.M.E. II
M 24 (1)
Balance
25
CORGON® He 30
M 21 (1)
Balance
10
30
CORGON® He 25 C
M 21 (1)
Balance
25
25
CORGON He 25 S
M 22 (1)
Balance
M 12
Balance
2.5
CRONIGON® He 50
M 12 (2)
Balance
2
50
CRONIGON® He 20
M 12 (1)
Balance
2
20
CRONIGON He 30 S
M 11 (1)
Balance
0.05
30
CRONIGON® He 50 S
M 12 (2)
Balance
0.05
50
CRONIGON® S 1
M 13
Balance
1
CRONIGON S 3
M 13
Balance
3
®
®
CRONIGON® 2
®
®
CRONIWIG® N 2/3
0.5
26.5
2
26.5
3.1
25
2
SAr+N2
Balance
2/3
CRONIWIG® N H
SR1+2N2
Balance
2
CRONIWIG N He
SI3+2N2
Balance
®
VARIGON® S
20
M 13
Balance
VARIGON® He 30
I3
Balance
30
VARIGON He 50
I3
Balance
50
VARIGON® He 70
I3
Balance
70
VARIGON He 90
I3
Balance
90
VARIGON He 30 S
M 13 (1)
Balance
VARIGON® H 2 – 15
R1
Balance
VARIGON H 20
R2
Balance
®
®
®
®
2
0.03
0.03
30
2 – 15
20
Nitrogen (N2)
F1
100
Forming gas 95/5 – 80/20
F2
Balance
Note:
1
5 – 20
In addition to the above-mentioned shielding gases other mixtures for special applications are available.
5
Properties
of Shielding Gas Constituents
Proper Use of Shielding
Gases Leads to Optimum
Welding Results
Shielding gases allow many parameters of the welding process to be controlled and optimised for specific applications.
The gas or gas mixture is selected
according to the required effects.
The possibilities for optimisation
cover virtually every factor in the welding
process:
Physical properties of the gas affect
metal transfer, wetting behaviour, depth
and shape of penetration, travel speed,
and arc starting. Gases with low ionisation energy, such as argon, facilitate arc
starting and stabilisation better than
those with high ionisation energy, such
as helium.
On the other hand, helium is a better
choice for laser beam welding, where it
helps to control the plasma and thus the
penetration depth.
Plasma-arc welding of pipes
The dissociation energy of polyatomic
components in gas mixtures enhances
heat input to the base material due to
the energy released by recombination.
Gas
Dissociation
energy
eV/molecule
First ionisation
energy
eV/molecule
(first
ionisation stage)
H2
O2
CO2
N2
He
Ar
Kr
4.5
5.1
4.3
9.8
13.6
13.6
14.4
14.5
24.6
15.8
14.0
Physical properties of gases
CORGON® gas mixtures for safety-relevant components in car manufacture
6
Thermal conductivity [ W/cm°C ]
Thermal Conductivity of Gas Components
The thermal conductivity influences
weld geometry, weld-pool temperature
and degassing, and travel speed. For
example, travel speed and penetration
can be markedly increased by the addition of helium in MIG and TIG welding of
aluminium materials, or by the addition
of hydrogen in TIG welding stainless
steels.
0.16
H2
0.12
0.08
He
0.04
O2
CO2
0
2,000
4,000
Ar
Chemical properties influence both
the metallurgical behaviour and the weld
surface quality. Oxygen, for example, results in alloying elements and leads to
more fluid weld pools, while carbon dioxide results in carbon pickup in alloyed
materials. Argon and helium have a metallurgically neutral behaviour, and hydrogen acts as a reducing agent. Nitrogen
is added to the shielding gas to control
the ratio of austenite to ferrite.
6,000
8,000
10,000
Temperature [ °C ]
Slag formation with different
CO2 additions to the shielding gas
Linde provides optimum shielding
gases for all welding applications.
Special gases can be developed for
individual requirements
MIG welding of aluminium heat exchangers using an Ar/He mixture
7
Arc Types:
Their Actions and Applications
● Long arc for high-performance MAG
welding of thicker sections using CO2.
Metal transfer is globular, with considerable spatter.
Short arc
8
ILB
SLB
unstable arc
● Transition arc for medium-performance MAG welding of moderate plate
thicknesses using argon-based gas mixtures. Metal transfer is globular with partial short-circuiting, but spatter is less
than with long-arc welding using CO2.
RLB
ÜLB
● Short arc for sheet metal, out-of-position welding, and root-pass welding at
low performance levels. The metal transfer takes place with short-circuiting and
little spatter.
GMAW Arc Ranges with ArCO2 mixtures (schematic)
Welding voltage [ V ]
A variety of arc types are employed in
gas metal arc welding (GMAW) with consumable wire electrodes. Crucial factors
in the selection of the arc type are the
shielding gas, the plate thickness and
the welding position.
HL-SL
B
B
HL-KL
KLB
Wire feed rate [ m/min ]
KLB
ILB
ÜLB
SLB
RLB
=
=
=
=
=
Short arc
Pulsed arc
Transition arc
Spray arc
Rotating arc
HL-KLB = High-performance short arc
HL-SLB = High-performance spray arc
Transition arc/long arc
● Spray arc for high deposition rates
and travel speeds on thicker sections
using argon-based gas mixtures. Metal
transfer is by droplets, without short-circuiting, and nearly spatterfree.
Spray arc
● High-performance arc for higher
deposition rates and travel speeds using
special argon gas mixtures containing
helium. The composition of the shielding
gas influences the arc type and metal
transfer, e.g.high-performance short arc,
high-performance spray arc, rotating arc.
Rotating arc
● Pulsed arc for all performance levels;
used in MIG and MAG welding with argon-rich mixtures, chiefly at moderate
performance levels (replacing transition
arc). Metal transfer without short-circuiting with one well-defined droplet formed
per pulse. Less spatter than with other
arc types. The pulsed arc cannot be
used with shielding gases with more
than 20 – 25 % CO2.
Pulsed arc
9
Shielding Gases
for MAG Welding of Structural Steels
Linde shielding gases for MAG
welding of structural steels are
CORGON® 1
CORGON® 2
CORGON® with 10 – 40 % CO2
CORGON® S 5 / S 8
CO2
These shielding gases are suitable for
pipe steels, structural and fine-grain
structural steels, case-hardening steels
and heat-treatable steels of all qualities.
Filler metals in the form of solid wire
are standardised in EN 440 and in the
form of cored wire in EN 758. The
German Welding Society bulletin “DVSMerkblatt 0916” gives filler metal recommendations for higher-strength fine-grain
structural steels.
The properties of gas mixtures vary
with composition. The composition also
influences the mechanical and engineering qualities of the weld metal and the
weld geometry.
Use of CORGON® 18 for robot welding of lifting masts
Effect of Shielding Gas
on Mechanical and Engineering Properties
Rm
Re
A5 *
N/mm2 N/mm2 %
Weld metal
analysis %
C
Mn
Si
CORGON® 1
91 % Ar, 5 % CO2
4 % O2
610
472
28.1
0.08
1.32
0.67
138
124
87
83
58
48
0.031
CORGON® 10
90 % Ar, 10 % CO2
640
544
25.7
0.09
1.43
0.72
130
88
64
55
60
41
0.029
CORGON® 18
82 % Ar, 18 % CO2
620
522
26.8
0.09
1.37
0.70
144
120
86
62
50
40
0.0305
CORGON® 25
75 % Ar, 25 % CO2
601
505
29.3
0.09
1.30
0.65
124
97
76
61
51
41
0.034
CORGON® S 12
88 % Ar, 12 % O2
591
510
27.5
0.06
1.20
0.60
138
126
87
67
46
40
0.0355
100 % CO2
594
437
27.8
0.10
1.21
0.62
84
54
48
35
28
22
0.062
0.115 1.53
0.98
Wire electrode to
EN 440 – G3Si1
10
Impact energy J
(mean of 4 specimens)
+ 20 °C ± 0 °C – 20 °C – 30 °C – 40 °C
O2 content
of weld metal
– 50 °C
47-J-limit
Shielding gas
* Rm: ensile strength Re: yield strength A5: elongation at fracture
% by weight
Properties of Shielding Gases
Properties
Ar/CO2
Ar/O2
CO2
Good
More reliable
with increasing CO2 level
Good
Can become critical
if fluid weld pool leads arc
Good
Reliable
Thermal load
on torch
Lower
with increasing CO2 level
High;
excessive torch temperature
can limit performance
Low
because of good
thermal conductivity
Degree of oxidation
Higher
with increasing CO2 level
High;
e.g. at 8% O2
High
Porosity
Lower
with increasing CO2 level
Most sensitive
Reliable
Gap bridging
Better
with decreasing CO2 level
Good
Worse
than with gas mixtures
Spatter
Increasing
with increasing CO2 level
Low
Highest spatter,
increasing with increasing
performance
Heat input
Increasing
with increasing CO2 level
Lowest
High
Cooling rate lower,
less danger of cracking
Cooling rate high,
greater danger of cracking
Cooling rate low,
little danger of cracking
Short arc
Transition arc
Spray arc
Pulsed arc/up to 20 % CO2
High-performance short arc
High-performance spray arc
Short arc
Transition arc
Spray arc
Pulsed arc
High-performance short arc
Rotating arc
Short arc
Long arc
Penetration
● Flat position
● Out-of-position
Arc type
The above properties of the various shielding gases govern their use in welding.
The versatility of Ar-CO2 and Ar-CO2-oxygen mixtures (the Linde CORGON® shielding gases) has led to their high popularity.
The addition of helium extends the range of applications.
11
Shielding Gases for LINFAST ®
– the MAG High-Performance Welding
Concept from Linde
Effect of LINFAST ® Gases on the Stability
of Different Arc Types
CORGON® He 25 C
CORGON® He 25 S
CORGON® He 30
T.I.M.E. Gas
T.I.M.E. II Gas
The LINFAST ® concept is based on
the relationship between the welding
parameters (wire feed rate, contact tubeto-work distance and welding voltage)
and the shielding gas composition to
stabilise the arc types at high performance levels. Unstable arcs at a wire feed
rate of 22 – 30 m/min are reliably avoided by the LINFAST ® concept in order to
achieve optimum welding results.
T.I.M.E. II
CORGON® He 25 C
LB
HL-S
SLB
B
unstable arc
ÜLB
KLB
SLB
KLB
HL-KLB
SLB
KLB
RLB
HL-KL
ÜLB
Variation of the shielding gas composition influences the arc characteristics,
metal transfer, penetration, weld surface
and porosity.
MAG High-Performance
Welding
RLB
Welding voltage [ V ]
These shielding gases were specially
developed for high-performance MAG
welding (T.I.M.E. process), a method
with increased wire feed rates for higher
deposition rates and travel speeds.
Conventionel
MAG-M Welding
ÜLB
Linde shielding gases for high-performance MAG welding are:
HL-SLB
T.I.M.E.
CORGON® He 30
RLB
CORGON® He 25 S
HL-SLB
B
HL-KL
15
18 20 22
27
30
35
Wire feed rate [ m/min ]
KLB
ÜLB
SLB
RLB
=
=
=
=
Short arc
Transition arc
Spray arc
Rotating arc
HL-KLB = High-performance short arc
HL-SLB = High-performance spray arc
LINFAST® MAG high-performance welding of dredging shovels using CORGON® He 30:
cost savings and quality improvement
12
The MAG High-Performance Arc Types
- Penetration Profiles
and Avoiding Defects
● Spray arc
at a wire feed rate of >15 m/min, spray
arc results in a typical v-shaped penetration profile.
Stable spray arc due to the use
of CORGON ® He 25 C at a wire
feed rate of 23 m/min, position
PB, semi-mechanised
● High-performance short arc
This type of arc is particularly suitable for
low wall thicknesses and higher travel
speeds.
Extremely high travel speeds
of more than 2 m/min are
achievable with a high-performance short arc and a
T.I.M.E. shielding gas (in the
photo: wire feed rate
= 17 m/min)
cross section
● High-performance spray arc
Weld defects are caused by arc instability. Unstable arcs are reliably avoided
by the LINFAST® concept.
Weld defects due to arc instability between rotating arc
and high-performance spray
arc at wire feed rates between
22 and 30 m/min (in the photo:
wire feed rate = 26 m/min, fully
mechanised).
longitudinal section
HL-SLB
RLB
● Rotating arc
The LINFAST® concept stabilises arc
rotation and guarantees wide and deep
weld penetration in the root region in addition to excellent side wall fusion.
HL-SLB
RLB
CORGON ® He 25 S guarantees
stable rotation at wire feed
rates above 20 m/min
(in the photo: wire feed rate
= 26 m/min, position PB, fully
mechanised).
13
Shielding Gases
for MAG Welding of High-Alloy Steels
and Ni Base Alloys
Linde shielding gases for the MAG
welding of high-alloy steels are
CRONIGON® S 1
CRONIGON® S 3
CRONIGON® 2
CRONIGON® He 20
CRONIGON® He 50
CRONIGON® He 30 S
CRONIGON® He 50 S
CRONIWIG® N series
Carbon Burnoff and Pickup
with Various Shielding Gases
0.07
0.049
Alloy type (ELC)
0.06
%C
0.05
0.023
0.04
These shielding gases are suitable for:
● stainless steels to DIN 17440
(BS 970 part 4)
● high-temperature rolled
and forged steels to SEW 4670
● special stainless steels
● Ni base alloys
ELC limit
0.03
0.01
0.006
Wire
electrode
0.02
0.016
0.01
0.002
0
CORGON® S8
CRONIGON® S1
CRONIGON® 2
CORGON® 1
CORGON® 18
Filler metals for the welding of stainless and high-temperature steels are
standardised in DIN 8556
(BS 2901 part 2).
Short, transition, spray and pulsed
arc types can be used.
The carbon content is important for
maintaining the corrosion resistance. For
low-carbon ELC steel qualities, the maximum level in the weld metal should be
0.03 % if annealing is necessary.
Measurements of carbon burn off
and pick up clearly show that no corrosion problems should occur when using
CRONIGON® shielding gases.
Although the carbon content when
using CORGON® 1 stays below the ELC
limit, this shielding gas should not be
used for components that will be used in
corrosive environments.
MAG welding of an exhaust gas diffuser using CRONIGON ® He 50 S
14
CO2
Important
Application Notes
Austenitic CrNi steels and ferritic Cr
steels can be welded quite well with the
spray arc, which begins at currents
some 20 % below those struck on unalloyed materials.
The use of the pulsed arc ensures
stable metal transfer with little spatter
over the full range of melting rates. Heavier wires, which can be fed more reliably and offer better current transfer,
can thus be used. What is more, pulsedarc welding is an excellent technique for
vertical-down welds. Nickel-based materials and most special steels should preferably be welded with the pulsed arc.
Survey of Applications
Shielding gas
Properties
Materials
CRONIGON ® S 1
● Low oxidation
● Moderate wetting
● Ferritic Cr steels
CRONIGON ® S 3
● Greater oxidation
● Adequate wetting
● Corrosion-resistant, austenitic
CrNi steels
CRONIGON ® 2
●
●
●
●
● High-temperature
austenitic steels
● Excellent wetting
even at great section thickness
● Very good interpass fusion
● Stable arc
● Minimal spatter
● High travel speeds,
especially suited
for fully mechanised welding
● Special steels, e.g. duplex
and super duplex
● Corrosion-resistant
and high-temperature
CrNi steels
● Ni base materials
with low corrosion stress
CRONIGON ® He 30 S
Cronigon ® He 50 S
● Excellent wetting
● Excellent arc stability
compared to other inert gases
● Extremely low surface oxidation
due to considerably reduced
active gas content
● Very good interpass fusion
● High corrosion resistance
which is comparable
to TIG and MMA/SMA welding
● Next to no spatter
● All Ni-based materials,
especially
highly corrosion-resistant
Ni base alloys
CRONIWIG ® N
● Reduction of ferrite content
● Control of the
austenite/ferrite ratio
● Full austenites
● Duplex and super duplex steels
Research at the Linde Technology
Centre has revealed some interesting
features:
● The weld geometry, surface finish,
wetting behaviour, and arc stability
are affected in different ways by the
base and filler metals.
● The torch position should be approx.
10° forehand for all materials.
● Special steels. e.g. duplex
CRONIGON ® He 20
CRONIGON ® He 50
Interpass welding temperatures
depend on the type of base metal:
● 150 – 200 °C
for austenitic CrNi steels
● 50 – 100 °C for Ni-based materials
Low oxidation
Good wetting
Higher travel speed
Minimal spatter
● The weld metal should be applied in
stringer beads (less thermal stress).
The arc must always lead the weld
pool. Heavy spatter results if the weld
pool leads the arc even slightly,
especially with Ni-based materials.
MAG welding of a plated beam
with CRONIGON ® 2
15
Shielding Gases
for MIG Welding of Non-Ferrous Metals
Shielding gases for the MIG welding
of non-ferrous metals are inert gases
such as:
Argon
VARIGON® He
VARIGON® S
VARIGON® He S mixtures
Short, spray and pulsed arc types
can be used with these gases.
Argon: 20 l/min
280 A / 25 V
VARIGON® He 30: 20 l/min
282 A / 27 V
VARIGON® He 50: 28 l/min
285 A / 30 V
VARIGON® He 70: 38 l/min
285 A / 34 V
The pulsed arc offers significant advantages, especially for softer Al filler
metals, because it allows the use of larger-diameter wire electrodes with their improved feeding reliability.
Filler metals for non-ferrous base
metals are standardised as follows:
● Al materials in DIN 1732 Part 1
(BS 2901 part 4)
● Copper and copper alloys
in DIN 1733 (BS 2901 part 3)
● Nickel and nickel alloys
in DIN 1736 (BS 2901 part 5)
The hotter arc in VARIGON® He and
VARIGON®He S mixtures has proven
especially suitable for aluminium and
copper materials with their high thermal
conductivity.
Helium alters the weld contour, shape of penetration and welding voltage
16
Application Notes
on Helium
Arc voltage
For a given arc length, a higher arc
voltage is required as the helium content
increases.
Form of penetration
A rise in helium content leads to a
wider and therefore flatter weld. The penetration is no longer “finger-shaped” as
when argon is used, but becomes more
rounded and deeper.
The better penetration behaviour facilitates good root fusion and permits
higher travel speeds.
Helium is significantly lighter than air.
This fact must be considered when
measuring the flow rate (correction
factor) and also when specifying the minimum flow rate. Helium improves the
degassing conditions of the weld pool
and reduces porosity. Higher gas prices
can often be offset by reduced costs for
post-weld machining.
MIG welding of Al materials with Argon or Ar-He mixtures
Correction Factors and Minimum Gas Flow Rates
Shielding gas
Correction factor –
multiply flow meter
reading by
Minimum
flow rate
VARIGON® He 30
VARIGON® He 30 S
1.14
18 l/min
VARIGON® He 50
1.35
28 l/min
VARIGON He 70
1.75
35 l/min
100 % He
3.16
40 l/min
®
17
Shielding Gases
for TIG Welding
In contrast to MIG and MAG, which
are gas metal-arc processes, in TIG
welding the arc burns between a nonconsumable tungsten electrode and the
work. Inert gases, such as argon or helium, or mixtures of these with nonoxidising components are used to protect the tungsten electrode and the weld
pool.
TIG welding can be used with all
fusion-weldable metals. The section of
current type, polarity and shielding gas
depends on the base material.
Shielding gas
Materials
Remarks
Argon
All weldable metals
● Used most frequently
● Root protection required
for reactive materials
VARIGON® S
VARIGON® He 30 S
Al and Al alloys
● Increased arc stability
and arc starting reliability
in AC welding
VARIGON® He 30
VARIGON® He 50
VARIGON® He 70
VARIGON® He 90
Al and Al alloys
Cu and Cu alloys
● Arc starting difficulties
with old power sources possible
➜ use argon for ignition
Helium
Application Notes
Higher helium levels in argon-helium
mixtures promote heat evolution in the
arc and permit higher travel speeds.
Hydrogen can also be used to improve the energy balance of the TIG arc,
but only with high-alloy CrNi steels,
nickel and nickel base alloys. Up to 10 %
hydrogen in argon improves penetration
and travel speed. Gases containing hydrogen must never be used for welding
aluminium materials (increased porosity)
or reactive steels.
VARIGON® H 2
VARIGON® H 5
VARIGON® H 6
VARIGON® H 10
CRONIWIG® N
● Hotter arc results in
➜ better penetration
➜ higher travel speed
High-alloy CrNi steels
● Hotter arc results in
➜ better penetration
➜ higher travel speed
Ni and Ni base alloys
● To avoid porosity
Full austenites
Duplex and
Super duplex steels
● Control of the
austenite/ferrite ratio
Shielding gases and materials
Materials
Shielding gases of higher purity are
recommended for the welding of reactive
materials such as titanium or tantalum.
The 4.8 quality is therefore used for
these metals (versus 4.6 for other materials) with a purity of 99.998.
Unalloyed and alloyed steels
Copper und Cu alloys
Nickel and Ni alloys
Titanium and Ti alloys
Zirkonium, tantalum, Tungsten
TIG-welded container connections
18
Current type
and polarity
dc (–)
Aluminium
and Al alloys
Magnesium
and Mg alloys
ac
dc (–)
with helium
and VARIGON® He 90
Magnesium
and Mg alloys
ac
Materials, current type and polarity
Travel speed:
Argon
VARIGON® He 50
10 l/min
15 l/min
10 cm/min
20 cm/min
A higher level of helium leads to higher travel speeds.
This photograph shows welds in a 3 mm thick AlZn 4.5 Mg 1 alloy
Travel speed:
Argon
VARIGON® H 6
7 cm/min
11 cm/min
Fillet weld in material 1.4301
Penetration and travel speed improve considerably with increased hydrogen
19
Oxidation Prevention
Using Forming Gases
Protection of the weld root is often
needed in order to ensure optimal corrosion resistance of the part. Oxidation
and tints are prevented by excluding atmospheric oxygen.
Relative Densities of Forming Gases
1.4
● Displacement of air by inert gases
such as argon or by quasi-inert gases
such as nitrogen
● Displacement of air plus utilisation of
the reducing action of hydrogen
For this reason, most forming gases
consist of
Heavier than air
Two methods can be used:
● Nitrogen with hydrogen additions
● Argon with hydrogen additions
Pure argon, on the other hand, is
only used rarely, for example with steels
reacting with hydrogen.
Ar mixtures
1.2
1.1
Air
1.0
Lighter than air
Proper use of forming gases requires
that their relative densities are taken into
account, e.g. when purging containers
from below (use high-density gases) or
above (use low-density gases).
1.3
0.9
0.8
N2 mixtures
0.7
0.6
4
8
12
16
20
24
% by vol. H2
Safety Notes:
Gases containing more than ca. 10 % hydrogen can form explosive mixtures with air.
Safety measures should be taken to avoid explosions.
For safety reasons, the DVS safety sheet 0937 recommends burning off hydrogen at H2 levels
higher than 10 vol.%.
20
Application Notes
Gases should comply with the
following EN 439 groups:
– Group R (Ar/H2 mixtures)
– Group I (Ar + Ar/He mixtures) and
– Group F (N2 + N2/H2 mixtures)
In order to positively prevent oxidation tints, the forming gas feed must
continue until the part has cooled to
approx. 220 °C.
Preventing oxidation in the welding of
pipe requires pre-purging for a time that
depends on the purge gas flow rate and
the geometry of the part.
To prevent oxidation when welding
pipes, air must be eliminated by purging
before starting to weld. A guideline for
the required volume of shielding gas is
2.5 – 3.0 times the geometric volume of
the pipe from the injection point to the
weld. The flow rate should be approx.
5 to 12 l/min, depending on the diameter
of the pipe.
In titanium-stabilised CrNi steels,
forming gases containing N2 cause a
yellow coloration of the weld root. For
base materials containing N2, e.g. super
duplex steels, forming gases containing
high N2-percentages (up to 100 %), e.g.
to improve corrosion resistance arc of
benefit.
Welding with forming gas
Forming gas
Base material
Argon
All materials
Ar/H2 mixtures
Austenitic steels,
Ni and Ni base materials
N2/H2 mixtures
Steels with the exception
of high-strength fine-grain
structural steel, austenitic
steel (not Ti-stabilised)
N2
Ar/N2 mixtures
Austenitic CrNi steels,
duplex- and
super duplex steels
Root protection gases
for various materials
Typical yellow coloration: titanium-stabilised CrNi steel with nitrogen forming
No coloration: titanium-stabilised CrNi
steel with argon/hydrogen forming
21
Shielding Gases
for Plasma-Arc Welding
As in TIG welding, the arc in plasma
welding is formed between a non-consumable tungsten electrode and the work
piece. However, in contrast to TIG welding, the plasma arc is constricted by
the torch design (water-cooled copper
tip), resulting in a significantly higher power density.
There are three variants of the
plasma-arc welding process:
● Microplasma welding for thin and
very thin sheet (minimum thickness
approx. 0.1 mm at minimum current
approx. 0.3 A)
● Melt-in welding for thicknesses
of 1 - 3 mm
● Keyhole plasma-arc welding for
thicker sections, up to approx. 8 mm
in one run or thicker work in multiple
runs
Plasma-arc welding always involves
two gases:
Plasma-arc welding of spiral aluminium pipes
● Plasma gases, chiefly argon,
sometimes with hydrogen
or helium additions
● Shielding gases which may have
other constituents added to the
argon, for example hydrogen for
welding CrNi steel and Ni alloys,
or helium for welding aluminium,
Al alloys, titanium and copper base
alloys.
Other plasma techniques include
plasma-arc powder (PTA) surfacing for
the application of refractory alloy coatings, plasma hot-wire surfacing, and
plasma/MIG welding for high-performance joining.
Plasma-arc welding of galvanised structural steel
22
Shielding Gases
for Arc Stud Welding
Recent investigations have shown
that the quality of arc stud welding using
the methods BH 10 and BH 100 can be
improved significantly with the appropriate choice of shielding gases.
The combinations of shielding gases
and materials shown in the table on the
right have proven well in workshop tests
and in the field.
Combinations of Shielding Gases and Materials
Base material
Stud material
Shielding gas
Structural steel
Structural steel
CORGON® 18
High-alloy steel
High-alloy steel
CORGON® 18
AlMg 3
Al 99.5 or AlMg 3
VARIGON® He 30
By avoiding the use of ceramic rings,
shielding gases are particularly advantageous for fully mechanised welding, including welding with industrial robots.
Steel and aluminium studs welded using
shielding gas
23
Shielding Gases
for Laser Beam Welding
Two different laser types are commonly used for laser beam welding: The
CO2 laser and the Nd:YAG laser. Both
laser types require the use of shielding
gases to obtain high-quality welds.
CO2 Laser
5
The CO2 laser is the most common
type of laser used for welding by the car
manufacturing industry and its component suppliers. The correct choice of
shielding gas is very important to ensure
high quality welds. Due to its interaction
with the laser beam, the shielding gas
has a major influence on the heat input
to the work piece. If a particular laser
beam intensity is exceeded on the surface of the work, this causes a thermallyinduced plasma which affects the penetration depth in combination with other
factors. Due to its high ionisation energy,
especially helium in LASPUR ® quality
gives excellent results. However, other
shielding gases can also be used, such
as argon, nitrogen and various gas mixtures such as VARIGON® He 50.
Laser performance:
P = 2 kW
He
Penetration depth d [mm]
Compared to conventional welding
techniques (MAG, TIG etc.), laser beam
welding is characterised by more concentrated heat input, lower distortion
and higher processing speeds. For many
applications, laser beam welding does
not require filler materials, although this
may be necessary for gap bridging or for
metallurgical reasons. Laser beam welding can be used e.g. for steel, light metals and thermoplastic materials.
Focus radius:
4
rF = 100 µm
3
N2
Ar
2
1
Material: St 52-3
Shielding gas flow: 20 l m-1
0
10
20
30
40
50
60
-1
Travel speed v [mm s ]
Influence of shielding gas on penetration
depth and travel speed.
Laser beam welding and cutting machine
at the Linde Technology Centre
24
Cam welded with a CO2 laser
Argon
Helium
Plasma development and penetration behaviour of a CO2 laser with different shielding gases.
Nd:YAG laser
The main welding application for the
Nd:YAG laser is in precision engineering
for the electrical/electronics industry. A
few applications can also be found in the
car manufacturing industry. Laser powers
generally do not exceed 2 kW. Since the
wavelength of the Nd:YAG laser exhibits
little or no interaction with shielding gases, their choice only needs to take
account of metallurgical factors.
Accordingly, argon in LASPUR ®quality is
commonly used, although helium, nitrogen and gas mixtures are also suitable.
Case of a heart pacemaker
welded with a Nd:YAG laser
Photo: Lumonics
25
Linde Publications,
Application Notes and Training Materials
Special Publications
92 Effect of Welding Conditions on
Airborne Contaminants Generated
in Gas-Shielded Arc Welding, and
Effect of the Workplace Conditions
Data Sheets
Brochures
● Safety Data Sheets (on request)
● Centralised Gas Supply Systems
● Safety instructions (on request)
● LASPUR ® Gases for Laser Technology
● LASPUR ® Guide for Laser Users
Gases and Supply System
101 MAGM Welding Stainless Steel Effect of Type of Shielding Gas
● Acetylen … there is no better fuel gas
for oxy-fuel gas processes
105 Demands on Welding Systems
and Manipulating Equipment
Design in Fully Mechanised and
Automated MAG Welding
● Heat Treatment
with Linde Supplied Gases
● Storage Tanks
145 Shielding Gases and Process
Technology in Welding with HighAlloy Cored Wire
146 MAGM Welding (GMAW) of
Corrosion-Resistant Duplex Steel
- 22 Cr 5 (9) Ni 3 Mo
Effect of Shielding Gases
and Process Variations
156 Application Technology Criteria for
Orbital TIG (GTA) Welding of
Electropolished High-Alloy Steel
Tubes
158 Shielding Gas for Welding and
Backup purging - Factors to Be
Taken into Account
03/90 Control of the Arc Welding
Process in Manufacturing
22/93 Gas-Shielded Arc Welding of
Aluminium
34/97 Pulsed MAGM Welding of Nickel
Alloys
36/97 High-performance MAG Welding
with the LINFAST ® Concept
38/97 TIG Welding of Aluminium Alloys
26
27
Competence Where You
Need It – With Linde Gases
Advice
Service
Production
Know-how
Competent, thorough
advice
Service on the spot
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and supply
equipment
Air separation plant
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Supply
ECOVAR®
Glass
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8767/0
0598 . 0998 - 2.2 ma
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Pipeline
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Linde industrial gases are used for welding,
freezing or driving purposes, and where
heating, industrial cleaning, artificial respiration
or testing is required. They improve the quality
of life, helping you to produce more economically and thus safeguarding your future.
We offer advice, know-how, customer-specific
hardware, and carry out tests for our customers
and do all the gas-related handling.
It goes without saying that we tailor-make an
economic supply-concept according to customer specifications: Gas cylinders and cylinder bundles, tank supply of cryogenic liquid
gases, the ECOVAR® supply concept and
pipeline supply.
Your sales and distribution centre:
Linde AG
Industrial Gases Division
Seitnerstraße 70
82049 Höllriegelskreuth
Telefon (0 89) 74 46 - 0
Telefax (0 89) 74 46 -12 30
http://www.Linde.de/Linde-Gas