Shielding Gases
Innovation . Consultation . Application
Industrial gases from Linde:
practical development
for better quality and productivity
Good ideas are often just “in the air”.
One example is the invention of air liquefaction in 1895 and of air separation in
1902 by Carl von Linde. That was the
birth of “industrial gases” and right from
the beginning their range of applications
was so varied that the inventor himself
took on the marketing of these innovations.
Back in 1903 the first air separation
plant started operation in Höllriegelskreuth near Munich. That was the foundation for a company that is still expanding successfully today.
Linde Gas now has a worldwide network of production sites and sales offices and is market leader in Europe and
a leading gas supplier worldwide. Linde
Gas cares for 1.5 million customers.
However, size is indeed not everything. Therefore, “Think global -act local”
is our motto, which means that we are
flexible at every location and take care of
the individual requirements of our customers.
Continuous development –
following the inventor’s
spirit
Carl von Linde’s innovative spirit is
still present everywhere in the company.
For example, it can be seen in the successful sales strategy and, in particular,
in the constant further development of
our products and the development of
new applications. And behind this there
is the one clear aim of making applica-
tions with gas even more efficient and
more economical.
Besides high motivation and self-initiative, this demand for quality requires
extensive specialist knowledge. This
special know-how is continually kept updated in our company through training
courses, seminars and qualification programmes. And this bears fruit for our engineers apply for around 100 patents
every year. This range of services is supplemented by joint research projects
with institutes and by co-operation with
innovative manufacturers of equipment
and materials.
Our technical facilities are an important building block for further development. The modern Linde Technology
Centre in Unterschleissheim near Munich
Welding laboratory in Linde’s Technology Centre
Cover photo: CORGON® He 30 improves process stability and results during MAG tandem welding
2
That is why our shielding gases and
welding solutions are always tailored
specifically for the customer’s requirements and tested with regard to quality
and performance in our Technology
Centre, the aim always being to produce
excellent results while increasing the
travel speed and/or the deposition rate.
The advantages for our customers are
reduced manufacturing time and consequently lower wage costs per component with manual welding and especially
with robot welding, a field with dynamic
growth.
Metallurgical impact of shielding gases:
control of the ferrite/austenite ratio in the weld metal
of a duplex steel
offers our specialists ideal conditions for
them to evaluate results from all over the
world and to try out and optimise new
technologies and manufacturing
processes.
They always work with practical applications in mind, i.e. using specific
problems which we regularly receive for
example from our customers. In this way
customised solutions are developed that
fulfil all the customer’s requirements.
The right connections
for good results
Industrial gases from Linde are used
as “invisible helpers” in virtually all fields
of industry and trade and in science, research, medicine and aerospace technology. For example, they fulfil important
tasks in metal processing , e.g. in welding and cutting, which are tasks that require not only first-class quality but also
increasingly need to be solved very efficiently.
Nowadays, the value of a certain
product or technique is not however
measured entirely using values that can
be counted and calculated exactly. With
the increasing significance of environmental regulations and the elevated demands for compatibility of process and
human the selection of the gas should
also take into account the criterion of
pollution at the workplace. And even on
these issues you can always depend on
us for expert advice and support.
Shielding gas from Linde:
more than a commodity
The developments in our technical
and financial environment require new
ways of thinking in the classification of
our product and your relationship to
us as a gas partner. The potential of a
welding process can only be fully
utilised if the shielding gas succeeds
in changing from a “commodity” to
become an “optimising tool”. Our
knowledge about how this tool works
is what we offer to you as our active
contribution to the value adding in
your production chain.
3
The right shielding gas
for every welding process
Process
Shielding gases
ISO 857
EN 439
ISO 14175
CORGON® 1 and 2
CORGON® S5 and S8
CORGON® 10 and 18 CORGON® He series
®
Carbon dioxide
GMAW with active gas MISON 8®and 18
CORGON 6 to 40
MAG
CRONIGON® 2
MISON® 2
CRONIGON® He 20
CRONIGON® He 50
MIG
CRONIGON® S1 and S3
CRONIGON® He 30S
CRONIGON® He 50S
CRONIGON® HT
Structural steel, steel for shipbuilding,
boilers and pipes, fine-grain steels, casehardened and heat-treated steels, galvanised and aluminised coated steel sheets
Stainless steels,
Nickel alloys, duplex steel
Aluminium, copper, nickel
and their alloys
GMAW with inert gas
Argon
VARIGON® He
MISON® Ar
VARIGON® S
MISON® He
VARIGON® He S
TIG
Argon
MISON® Ar
Helium
VARIGON® He
MISON® He
VARIGON® S series
Tungsten inert gas
Materials
All weldable metals such as
unalloyed and alloy steels
aluminium, copper
VARIGON® H
Stainless steel and Ni alloys
VARIGON® N
Ni alloys, duplex, austenitic steels
Argon 4.8 and 5.0
Reactive materials such as titanium,
tantalum, zirconium
Plasmagas:
Argon
VARIGON® H
VARIGON® He
Shielding gas:
Argon
VARIGON® H
VARIGON® He
All weldable metals
See TIG
Root
protection
Argon
Nitrogen
Forming gas with 5 – 20 % H2
and balance N2
VARIGON® H
VARIGON® N
For all materials where oxidation
at the root must be avoided.
Technical literature recommends
burning off excess gas if H2 percentage
is above 10%.
Laser
beam
LASGON®
Helium
Argon
Gas mixtures
All weldable metals
Arc stud
welding
CORGON® 18
Structural steel, high-alloy steels
VARIGON® He 30
Aluminium and aluminium alloys
PAW
Plasma Arc Welding
without gas backing
With gas backing
4
®
CORGON, CRONIGON, MISON, VARIGON, LASGON are all registered trademarks of the Linde Group
Composition of Linde shielding gases
Linde gas
Name according
to EN 439
Carbon
dioxide
% by vol.
Argon (Ar)
Helium (He)
Kohlendioxid (CO2)
I1
I2
C1
CORGON® 1
CORGON® 2
CORGON® 6 – 25
MISON® 8
MISON® 18
CORGON® S 5
CORGON® S 8
CORGON® He 30
CORGON® He 25 S
CORGON® He 25 C
T.I.M.E.
M 23
M 24
M 21
S M21+0,03 NO*
S M21+0,03 NO*
M 22
M 22
M 21 (1)
M 22 (1)
M 21 (1)
M 24 (1)
5
13
6 – 25
8
18
CRONIGON® 2
MISON® 2
CRONIGON® S 1
CRONIGON® S 3
CRONIGON® He 20
CRONIGON® He 50
CRONIGON® He 30 S
CRONIGON® He 50 S
CRONIGON® HT
M 12
S M12+0,03 NO*
M 13
M 13
M 12 (1)
M 12 (2)
M 11 (1)
M 12 (2)
S M12(1) + 5 N2
2,5
2
VARIGON® N 2
VARIGON® N H
VARIGON® N He
VARIGON® He 30
VARIGON® He 50
VARIGON® He 70
VARIGON® He 90
MISON® Ar
VARIGON® S
MISON® He 30
VARIGON® He 30 S
VARIGON® H 2 – 15
Forming gas 95/5 – 70/30
Nitrogen (N2)
Oxygen
% by vol.
R1
F2
F1
Nitrogen Helium Hydrogen Argon
monoxide
% by vol. % by vol. % by vol. % by vol. % by vol.
100
100
100
4
4
30
25
25
26,5
Balance
Balance
Balance
Balance
Balance
Balance
Balance
Balance
Balance
Balance
Balance
20
50
30
50
5 – 10
Balance
Balance
Balance
Balance
Balance
Balance
Balance
Balance
Balance
0,03
0,03
5
8
10
3,1
25
8
0,5
0,03
1
3
2
2
0,05
0,05
0,05
5
S I 1+2 N2
S R 1+2 N2
S I 3+2 N2
I3
I3
I3
I3
S I 1+0,03 NO
M 13
S I 3+0,03 NO
M 13 (1)
Nitrogen
2
2
2
2
1
20
30
50
70
90
Balance
Balance
Balance
Balance
Balance
Balance
Balance
Balance
0,03
0,03
0,03
0,03
Balance
100
Balance
Balance
Balance
30
30
2 – 15
5 – 30
Balance
* These mixtures have the same welding properties as Ar/CO2 mixtures with corresponding carbon dioxide content.
Note:
In addition to the shielding gases listed above other gas mixtures are available for special applications.
Subject to change in the course of technical progress and upon customer request.
5
Properties of shielding gas
components
Aimed choosing of the
shielding gas with the right
properties
The welding process can be influenced in numerous ways with the aid of
shielding gases and can thus be optimised for specific applications.
This means that the gas or gas mixture must be selected according to the
required effects on the welding process.
The opportunities for optimisation
cover virtually every factor that is relevant
for the welding process:
Physical gas properties affect metal
transfer, wetting behaviour, depth of
penetration, shape of penetration, travel
speed and arc starting. Compared with
gases with high ionisation energy (e.g.
helium), gases with low ionisation energy
(e.g. argon) facilitate arc starting and arc
stabilization.
Plasma welding of pipes
Proper doping of inert gases with vpm
amounts of active components such as
CO2, NO or O2 results in arc stabilisation
which can improve the weld result. The
dissociation energy of polyatomic components in gas mixtures enhances the
heat input to the base material due to
the energy released by recombination.
Gas
Dissociation
energy
[eV/molecule]
Ionization
energy
[eV/molecule]
(first
ionization 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 automotive industry
6
Thermal conductivity [ W/cm°C ]
Thermal conductivity of gas components
The thermal conductivity of the
shielding gas 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 of stainless steels.
0.16
H2
Chemical properties influence both
the metallurgical behaviour and the weld
surface quality. Oxygen and carbon
dioxide, for example, cause alloying elements to be burnt off and more fluid
weld pools to be formed. Both gases act
as oxidising agents. Hydrogen is a reducing gas. Argon and Helium do not react with metals: they are inert.
0.12
0.08
He
0.04
O2
CO2
0
2,000
4,000
Ar
6,000
8,000
10,000
Temperature [ °C ]
The nitrogen contained in the
VARIGON® N shielding gases is dissolved by unstabilised high-alloy weld
metal and thus enables the control of
austenite/ferrite formation.
Argon + 6 % CO2
CORGON® 18
Slag formation with different amounts of
CO2 in the shielding gas
Linde provides optimized shielding
gases for all welding applications.
Special gases can be developed to
suit individual requirements.
MIG welding of aluminium heat exchangers using VARIGON® He
7
Arc types in GMA welding
– their impact and range of
applications
● Transition arc for medium-performance MAG welding of moderate plate
thicknesses under argon gas mixtures.
Metal transfer is globular with partial
short-circuiting, but spatter formation is
higher than with short arc welding.
ting
Pulsed
rc
Short a
arc
rc
Spray a
ort arc
Arc instability
Rota
Transition arc
● Short arc for thin sheets, out-of-position welding, and root-pass welding at
Iow performance levels. The metal transfer takes place with short-circuiting and
little spatter.
GMAW arc ranges with Ar/CO2 mixtures (schematic)
Arc voltage [ V ]
A variety of different arcs are employed in gas-shielded metal arc welding
(GMAW) with consumable wire electrodes. The type of arc is selected taking
into consideration the material and its
thickness, the welding position and the
weld requirements. A crucial factor for
good work with a certain arc is the
shielding gas. In the tandem process
(MIGT/MAGT) using two electrodes a
combination of two arc types is possible,
mainly pulse-pulse or spray-pulse.
HP-sh
Wire feed rate [ m/min ]
HP
= High-performance
● Long arc for higher-performance
MAGC welding of thicker sections under
carbon dioxide. Metal transfer is globular
and there is considerable spatter.
Short arc
8
Transition arc/long arc
rc
ray a
HP-sp
arc
● Pulsed arc generally for all performance levels. Preferably used in MIG
and MAG welding with argon-rich mixtures (instead of transition arc). Metal
transfer without short-circuiting with welldefined droplet formation and transfer
per pulse. Less spatter than with other
arc types. The pulsed arc cannot be
used with shielding gases containing
more than 20-25 % CO2.
Pulsed arc
● Spray arc for high deposition rates
and travel speeds on thicker sections
under argon gas mixtures. Metal transfer
in fine droplets, without short-circuiting,
and virtually spatterless.
Spray arc
● High-performance arcs for high
deposition rates and travel speeds,
preferably under special argon gas mixtures containing helium. The composition
of the shielding gas influences metal
transfer and arc stability. This enables
defects caused by certain types of arc
and instability to be avoided.
Rotating arc
9
Shielding gases
for MAG welding of structural steel
The shielding gases for MAG welding
of structural steels are:
CORGON® 1
CORGON® 2
CORGON® 10
CORGON® 18
CORGON® other mixtures with
Besides quality criteria such as penetration or spatter, the composition also
affects the mechanical and technological
properties of the deposited weld metal.
Recommendations on permissible
wire/gas combinations should also be
taken into account for demanding applications.
Filler metals in the form of solid wire
are standardised in EN 440 and in the
form of cored wire in EN 758. Leaflet
DVS-0916 gives filler metal recommendations for high-strength fine-grain structural steels.
6 – 40 % CO2
MISON® 8
MISON® 18
CORGON® S 5
CORGON® S 8
Carbon dioxide/CO2
These shielding gases are also suitable for pipe steels, fine-grain structural
steels, case-hardened steels and heattreatable steels. The composition of the
shielding gas affects the welding
process and the results.
Using CORGON®
for MAG robot welding
Effect of shielding gas on
mechanical and technological 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 energyJ
mean of 4 specimens
+ 20 °C ± 0 °C – 20 °C – 30 °C – 40 °C
O2 content
in weld metal
– 50 °C % by weight
47 J boundary
Shielding gas
* Rm: Tensile strenght Re: Yield strength A5: Elongation at break
Effects of shielding gases on MAG process and the weld results
Ar/CO2
Ar/O2
CO2
Good
More reliable with
increasing CO2 content
Good
Can become critical if fluid
weld pool leads arc (risk of
incomplete fusion)
Good
Very reliable
Thermal load on torch
Lower with higher
quantities of CO2
High.
Excessive torch temperature
can limit performance
Lower
Degree of oxidation
Increases with higher
quantities of CO2
High,
e.g. at 8% O2
High
Porosity
Decreases with higher
quantities of CO2
Most sensitive
Very low
Gap bridging
Improves with lower
quantities of CO2
Good
Worse than
with gas mixtures
Spatter formation
Increases with higher
quantities of CO2
Low
Highest spatter, increases
with higher performance
Heat input
Increases with higher
quantities of CO2
Lowest
High
Slower cooling rate.
Smaller risk of cracking
as a result of hardening
Fast cooling rate.
Greater risk of cracking
as a result of hardening
Slow cooling rate.
Little danger of cracking
as a result of hardening
Short arc
Transition arc
Spray arc
Pulsed arc (max. 20-25% 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
Criteria
Penetration
● Flat position
● Out-of-position
Arc type
Knowledge of the properties listed above is necessary for successful welding. Cost-effectiveness is improved by the selection of
the right gas. Thanks to their diversity and universality, CORGON® shielding gases are the predominant gases used. The addition
of helium extends the range of performance .
11
High-performance MAG welding with
the LINFAST ® concept
The preferred shielding gases for
high-performance MAG welding are:
CORGON® He 30
CORGON® He 25 S
CORGON® He 25 C
T.l.M.E. Gas
High-performance MAG welding is
defined in DVS leaflet No. 0909-1. The
term high-performance MAG welding is
valid for processes with deposition rates
above 8 kg/h, which is equivalent to wire
feed rates above 15 m/min for a 1.2 mm
solid wire. The LlNFAST ® concept offers
specific solutions for applications in this
highly productive field. The right process,
arc type, shielding gas and supply
method are selected taking the individual
requirements into account.
High-performance MAG welding
with single wire
Travel speeds of 150 cm/min with MAG tandem welding under CORGON® He 30
in shipbuilding
The spray arc (MAGs) or pulsed arc
(MAGp), e.g. under CORGON® He 30, is
used for wire feed rates up to approx. 18
m/min.
For faster rates CORGON® He 25 C
stabilizes the spray arc (MAGs). Above
approx. 20 m/min CORGON® He 25 S
stabilizes the rotating arc (MAGr). The
composition of the shielding gas is thus
decisive for the type of arc* and for the
prevention of weld defects.
High-performance MAG welding
with two wires
Fully mechanised welding with two
electrodes allows a further increase in
travel speeds and/or deposition rates.
Separate control of each arc in the
Tandem method (MAGT) offers the
advantage of flexible application. The
balanced proportions of CO2 and He in
the CORGON® He 30 improves the
process and the welding results.
*Linde patents: EP-0857533/ 0857534
12
CORGON® He gas mixtures used
for manual high-performance MAG
welding on machinery
Robot welding of machine beds with
deposition rates of up to 13 kg/h with
a rotating arc under CORGON® He 25 S
Processes
Penetration profiles
Performance
In the single wire process seam
preparation, weld requirements and the
equipment available determine the
choice of the arc type. The selection of
the shielding gas depends on the arc
and individual quality criteria:
CORGON® He 25 S
for spray, pulsed and rotating arcs
Advantages: Good seam surface particularly on thin sheets, highest possible deposition rate for the single-wire
process with a rotating arc on thick
sheets
CORGON® He 30
for pulsed and spray arcs
Advantages: Good wetting behaviour
over the entire sheet thickness, minimum formation of spatter and oxidation
CORGON® He 25 C for spray arc and to a limited extent for pulsed arc
Advantages: Low-porosity weld for
demanding tasks, reliable penetration
Of course, every gas can also be
used for conventional MAG welding.
Here too, the helium content offers
advantages:
Improved wetting behaviour
Increased travel speed
Avoidance of lack of side wall fusion
Examples of performance possible with MAG single wire:
Shielding gas:
Process:
Wire feed rate:
Welding speed:
CORGON® He 30
MAGs / MAGp
17 m/min
80 cm/min
Whereas single-wire welding can be
used for semi-mechanised (manual) applications, welding with two wire electrodes (two electrode welding) is only
used for fully mechanised applications.
With the MAG Tandem process seam
preparation, seam requirements and the
CORGON® He 25 C
MAGs
22 m/min
100 cm/min
equipment available determine the
choice of the arc combination and the
different control of the separate wires.
The advantage compared with singlewire welding is the possible increase in
the travel speed.
CORGON® He 25 S
MAGr
24 m/min
80 cm/min
CORGON® He 30 enables optimum
results for a wide range of sheet thicknesses. Other mixtures can be used for
special requirements.
Examples of performance possible with MAG Tandem:
Shielding gas:
Task:
Welding speed:
CORGON® He 30
Overlap joint PB on 2.5 mm sheet
2.8 m/min
CORGON® He 30
Fillet weld PB on 10 mm steel
2 m/min
13
Shielding gases for MAG welding
of high-alloyed materials
Shielding gases for the MAG welding
of high-alloyed materials are:
CRONIGON® 2
MISON® 2
CRONIGON® S 1
CRONIGON® S 3
CRONIGON® He 20
CRONIGON® He 50
CRONIGON® He 30 S
CRONIGON® He 50 S
CRONIGON® HT
These shielding gases are suitable for:
● stainless steels according
to EN 100088
● high-temperature rolled and forged
steels according to SEW 4670
● special stainless steels
● nickel-based alloys
The filler metals for the shielding gas
welding of stainless and high-temperature steels are standardized in
EN 12072.
Carbon pick-up and burn-off
for different shielding gases
0.07
0.06
%C
0.05
0.023
0.04
0.03
ELC limit
0.01
0.006
0.02
Wire
electrode 0.016
0.01
0.002
0
CORGON® S8 CRONIGON® S1 CRONIGON® 2
The carbon content is decisive for
maintaining the intercrystalline corrosion
resistance. For low-carbon CrNi steels
(ELC steels) the amount of carbon in the
weld metal should not exceed 0.03 %.
The diagram with carbon pick-up and
burn-off clearly shows that corrosion
problems cannot occur when
CRONIGON® shielding gases are used.
Although the carbon content measured in the weld metal lies below the
ELC limit with CORGON® 1, this gas
should not be used for parts made of the
above-mentioned alloys if they are to be
used in corrosive environments.
Stainless steel cladded beam using CRONIGON® 2
14
0.049
Type of alloy (ELC)
CORGON® 1
CORGON® 18
CO2
Important
application notes
Selecting the shielding gas
Duplex and Superduplex
Pulsed arcs have advantages for the
welding of high-alloy steels. They ensure
stable metal transfer with little spatter
over the full range of melting rates. It is
also possible to use thicker wires, which
are easier to feed. Nickel steels and
most special stainless steels should
preferably be welded with a pulsed arc.
CRONIGON® HT is a new shielding
gas for the MAG welding of certain hightemperature and heat-resistant nickel alloys. The nitrogen content minimizes the
risk of hot cracking, which is characteristic for these materials. With CRONIGON®
HT the economic advantages of MAG
welding can also be made available for
these demanding materials.
CRONIGON® 2
MISON® 2
CRONIGON® He20
CRONIGON® He50
CRONIGON® He30S
CRONIGON® He50S
CRONIGON® HT
Properties
CRONIGON® S3
Ni and Ni alloys
Because of their improved wetting
characteristics, gas mixtures containing
helium are especially advantageous for
use with relatively viscous Mo-alloy
steels.
The CRONIGON® He S series shielding gases have been developed for the
MAG welding of nickel alloys*. Their low
CO2 content of only 0.055% ensures a
very stable arc, retaining the corrosion
properties of the material at the same
time. Helium and hydrogen are added to
ensure excellent wetting properties and
suitability for out-of-position welding.
Corrosion-resistant
austenitic stainless steels
Heat-resistant
austenitic stainless steels
CRONIGON® S1
Austenitic and ferritic Cr(Ni) steels
can be welded excellently in short and
spray arcs. Compared with unalloyed
steels the spray arc begins at approx.
20 % lower wire speeds.
Material
Ferritic Cr steels
Oxidation
+
o
+
+
+
+
++
++
++
Wetting properties
o
+
+
+
++
++
++
++
++
Travel speed
o
o
+
+
++
++
++
++
++
Interpass fusion
+
o
+
+
++
++
++
++
++
Spatter
+
++
+
+
+
+
++
++
++
Arc stability
+
++
+
+
+
+
++
++
++
Out-of-position suitability
o
o
+
+
+
+
+
o
o
o conditional
+ good
++ very good
*Linde patents:
*EP-05 44 187, EP-06 39 423,
*EP-06 39 427
MAG welding of an exhaust gas diffuser
made of a nickel alloy.
CRONIGON® He 50 S is the shielding gas.
15
Shielding gases for MIG welding
of aluminium and
other non-ferrous metals
The shielding gases for MIG welding
of non-ferrous metals are:
Argon
VARIGON® He
MISON® Ar
MISON® He
VARIGON® S
VARIGON® He S
Short-, spray- and pulsed arcs can
be used. Besides less spatter, pulsed
arcs have the advantage of allowing the
use of the next largest diameter of wire
electrode. The thicker the wire is, the
more constant the feed rate is.
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 filler metals for non-ferrous materials can be found in the following standards:
● aluminium in EN ISO 18273
● copper in DIN 1733
The comparatively hotter arc produced by helium gas mixtures has
proven to be especially suitable for materials with good thermal conductivity
such as aluminium and copper. Magnesium and its alloys can be welded better
using shielding gases without helium.
Doping of inert gases (275 vpm NO in
MISON® Ar or MISON® He and 300 vpm
O2 in the VARIGON® S series) results in
improved arc stabilization for gas-shielded welding of aluminium.
Advantages:
• Considerably less spatter in MIG
welding
• Improved weld appearance due to
finer bead ripples
Helium in the shielding gas alters the weld geometry and affects welding voltage
16
Information on MIG welding using shielding gases
containing helium
Arc voltage
For a given arc length, a higher arc
voltage is required as the helium content
increases.
Weld geometry
A higher level of helium produces a
wider and flatter weld. Penetration is no
longer “finger-shaped” as when argon is
used but is rounder and deeper.
Shielding gas quantity
Helium is lighter than air. This property must be taken into account both in
measuring the flow rate and in setting
the minimum quantity of shielding gas.
See Linde brochure No. 158 for correction factors.
Advantages of added helium:
1. Better penetration
• Avoidance of lacks of fusion
• Higher travel speed
2. Hotter arc
• Reduced porosity
• Savings in filler metal
3. Wider, flatter seam
• Lower notch effect
• More favourable lines of force
Using Linde Argon in MIG welding of safety relevant chassis components
in the automotive industry
These positive properties make
helium mixtures more cost-effective than
argon for many applications.
Portchester Microtools (U.K.) Specialist Aluminium Container Manufacture & Design
MIG welding of aluminium containers with VARIGON® He 50: considerable savings in
costs due to doubling of the travel speed and reduction of the arc time by 50 % compared with argon.
17
Shielding gases for TIG welding
In contrast to MIG/MAG welding, the
arc in TIG welding is generated between
a non-consumable tungsten electrode
and the base material. Inert gases such
as argon or helium or gas mixtures with
non-oxidizing components are necessary to protect the tungsten electrode
and the weld pool.
TIG welding can be used with all fusion-weldable metals. The choice of current, polarity and shielding gas depends
on the parent material.
Shielding gas
Argon
Material
All weldable metals
for reactive materials, purity 4.8
● Increased arc stability
VARIGON® He 30
VARIGON® He 50
VARIGON® He 70
VARIGON® He 90
● Additional helium for hotter arc
Al and Al alloys
Cu and Cu alloys
18
➜ better penetration
➜ increased travel speed
with old power sources
➜ arc starting under argon
VARIGON® H 2
VARIGON® H 5
VARIGON® H 6
VARIGON® H 10
VARIGON® N2/N3
VARIGON® NH
VARIGON® NHe
● Additional Hydrogen for hotter arc
High-alloy CrNi steels
➜ better penetration
➜ increased travel speed
Ni and Ni alloy
● To avoid porosity
Fully austenitic steels
Duplex
Superduplex steels
● Control of the austenite/ferrite ratio
● Higher performance through
additions of H2 or He
Shielding gases and materials
Materials
Small additions of active components
such as NO or O2 to the inert gases provides additional arc stabilisation. The results obtained especially in welding aluminium with alternating current can be
improved through the use of these gases.
Very pure argon or argon-helium mixtures are recommended as shielding
gases for the welding of metals such as
titanium, tantalum or zirconium that react
with gases. Therefore, gases with a minimum purity of 4.8 (equivalent to 99.998
%) are used for these materials whereas
other materials can be welded using 4.6
(equivalent to 99.996 %).
and arc starting reliability
in AC welding
● Arc starting difficulties may occur
Helium
Hydrogen can also be used to improve the energy balance of the TIG arc
although it should only be used with
high-alloy CrNi or Ni and Ni alloys. Up to
10 % hydrogen in the argon improves
penetration and travel speed. Gases
containing hydrogen should never be
used to weld aluminium alloys (increased
porosity) and steels that react with hydrogen.
● Most common application
● Root protection necessary
MISON® Ar
Al and Al alloys
VARIGON® S
MISON® He 30
VARIGON® He 30 S
Application notes
Argon-helium mixtures promote the
development of heat in the arc. Increased amounts of helium allow higher
travel speeds.
Comments
Unalloyed and alloy steels
Copper and Cu alloys
Nickel and Ni alloys
Titanium and Ti alloys
Zirconium, tantalum, tungsten
Aluminium
and Al alloys
Magnesium
and Mg alloys
Current type
Polarity
= (–)
~
and
= (–)
VARIGON® He 90 or helium is used for
direct current TIG welding of Al and Mg
alloys.
TIG welded container connections
TIG Argon arc
TIG Helium arc
TIG VARIGON® H5 arc
Three shielding gases used in TIG welding and their effects on the arc. Current I = 240 A. Base material = 1.4301
Travel speed:
Argon
VARIGON® He 50
10 l/min
15 l/min
10 cm/min
20 cm/min
Effects of shielding gases on the travel speed. A higher level of helium results in a higher travel speed.
The photographs show welds in a 3 mm thick AlZn 4.5 Mg 1 alloy.
Travel speed:
Argon
VARIGON® H 6
7 cm/min
11 cm/min
TIG arcs with and without addition of H2.
Penetration and travel speed can be considerably increased by adding H2 to the shielding gas.
19
Root protection and forming gases
for improved corrosion resistance
In many cases protection of the weld
root is needed in order to ensure optimal
corrosion resistance of the part. Oxidation and tarnish are prevented by displacing atmospheric oxygen.
Relative densities of shielding gases for root protection
1.4
● Displacement of air by inert gases
such as argon or by virtually inert
gases such as nitrogen
● Displacement of air plus utilization of
the reducing action of hydrogen
Reducing root shielding gases consist
of:
Heavier than air
Two methods can be used:
● Nitrogen with hydrogen additions
These mixtures are generally
called “forming gases”.
● Argon with hydrogen additions
VARIGON® H series
Proper use of forming gases requires
that their relative densities are taken into
account, e.g. in the purging of containers from below (high-density gases) or
above (Iow-density gases).
Ar mixtures
1.2
1.1
Air
1.0
Lighter than air
Pure argon is only used rarely, for example for steels that react with hydrogen
or nitrogen or for highly reactive materials
such as titanium. Gases in the MISON®
series are unsuitable for root protection
because they contain NO as an active
component.
1.3
0.9
0.8
N2 mixtures
0.7
0.6
4
8
12
16
20
24
% by vol. H2
Safety information:
For safety reasons DVS leaflet No. 0937 recommends the burning off of hydrogen in the case of mixtures containing
10 % by vol. hydrogen and more. Shielding gases for root protection with more than 4 % by vol. hydrogen can form explosive mixtures with air or oxygen. The user must take precautions to prevent the formation of such gas mixtures,
e.g. prevention of air pockets, prevention of uncontrolled air penetration, etc.
During forming processes involving large closed parts, it should be ensured that there is no risk of suffocation before any
worker enters the part. The possible lack of oxygen must also be taken into account during work in confined spaces.
20
Application notes
Gases for root protection are standardized in EN 439 as follows:
– Group R (Ar/H2 mixtures)
– Group I (Ar + Ar/He mixtures) and
– Group F (N2+ N2/H2 mixtures).
To prevent the formation of any tarnish, forming gas must be continually
supplied until the part has cooled to
approx. 220 °C.
To prevent any oxidation during
welding, certain pre-purging times must
be observed to displace air. The times
required depend on the relevant purge
gas flow rate and the geometry of the
part.
As a guideline, the required volume of
shielding gas is 2.5-3.0 times the geometric volume of the pipe measured from
the injection point to the weld. The flow
rate should be approx. 5 to 12 l/min.
depending on the diameter of the workpiece.
In titanium-stabilized CrNi steels.
forming gases containing N2 cause a yellow discoloration of the weld root. For
base materials containing N2. e.g. super
duplex steels, forming gases containing
high percentages of N2 (up to 100 %)
are beneficial, e.g. to improve corrosion
resistance.
Welding under forming gas
Forming gas
Base material
Argon
All materials
Ar/H2 mixtures
Austenitic steels.
Ni and Ni alloys
N2/H2 mixtures
Steels, excepted high-strength
fine-grain structural steel,
austenitic steel
(not Ti-stabilized)
N2
Ar/N2 mixtures
Austenitic CrNi steels,
duplex- and
super duplex teels
Root protection gases
for various materials
Typical yellow discoloration: titanium-stabilized CrNi steel with nitrogen forming
No discoloration: titanium-stabilized CrNi
steel with argon/hydrogen forming
21
Shielding gases
for plasma-arc welding
As in TIG welding, the arc in plasma
welding is generated between a nonconsumable tungsten electrode and the
base material. However, in contrast to
TIG welding, the plasma-arc is concentrated 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 sheets
– at least approx. 0.1 mm with minimum currents of approx. 0.3 A
● Melt-in welding for sheet thicknesses
of 1 -3 mm
● Keyhole plasma-arc welding for thick
sections up to approx. 8 mm in one
run, or thicker sections in multiple
runs
Plasma-arc welding always requires two
gases:
Plasma-arc welding of spiral aluminium pipes
● Plasma gas (centre gas), chiefly argon, sometimes with hydrogen or helium additions
● Shielding gas (outside gas), which
may have other constituents added
to argon, e.g. hydrogen for stainless
steel and Ni alloys, or helium for
welding aluminium, AI alloys, titanium
and copper alloys.
Other plasma techniques include:
● Plasma powder arc welding
for joining and cladding
● Plasma hot-wire cladding
● Plasma-MIG welding
for high-performance joining.
Plasma-arc welding of galvanized structural steel
22
Shielding gases for arc stud welding
Recent investigations have shown
that the quality of drawn arc stud welding using the methods BH 10 and BH
100 can be improved significantly
through the use of proper shielding gases.
Tried and tested combinations of
shielding gases and materials are shown
in the table on the right.
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
Through the avoidance of ceramic
rings, shielding gases are particularly advantageous for fully mechanised welding, including robot welding.
Steel and aluminium studs welded using
shielding gas
23
Shielding gases for laser welding
In comparison with conventional
welding processes (MAG, TIG, etc.) laser
beam welding allows heat to be applied
more accurately with less distortion and
higher travel speeds. The majority of
laser welds can be made without filler
metal. However, filler metal may be necessary for gap bridging or metallurgical
reasons. Laser welding is suitable for example on steel, light metal and thermoplastics.
As with metal inert gas techniques,
more and more uses are being found for
gas mixtures for laser welding. As the
process becomes more widespread,
further advances are being made in the
development of shielding gases. One example is LASGON® C1 that is used for
the laser welding of unalloyed, alloyed
and galvanised steels.
Two different types of laser are commonly used for laser welding: the CO2
laser and the Nd:YAG laser. Both types
of laser require shielding gases to make
high-quality welds.
Welding a gear with a CO2 laser
CO2 lasers are the most commonly
used lasers for welding in the automotive
and related industries. The choice of the
right shielding gas is of major importance
in order to produce high-quality welding
seams. High-quality shielding gases
such as LASGON® C1, diverse gas mixtures, helium or argon assist the user.
But it is not simply the type of gas that is
of importance for the quality of the resulting weld: the way the shielding gas is
supplied also plays a significant role. A
large nozzle allowing a slow, laminar flow
as near as possible to the welding site
prevents turbulences of the shielding gas
and the surrounding air, the result being
an optimum weld.
Cam welded with a CO2 laser
Source: Trumpf
24
CO2 lasers
Argon
Helium
Plasma development and penetration behaviour using a CO2 laser with different shielding gases
Nd:YAG lasers
The main welding applications for
Nd:YAG lasers are in precision engineering and in electrical and electronic engineering. However, more and more applications are also arising in metal machining. Laser powers of up to 4 kW are
commonly used. Since the wavelength
of a 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 mainly used, although Helium, Nitrogen or gas mixtures
are also suitable.
Heart pacemaker casing welded with a Nd:YAG laser
Source: Lumonics
25
Linde Publications and
Applications Notes for Practical Use
Special Releases
Data Sheets (on request)
Tips for practitioners
(on request)
92
146
Effect of Welding Conditions on
Airborne Contaminants Generated in Gas-Shielded Arc Welding
and Effect of the Workplace
Conditions
MAGM Welding (GMAW) of
Corrosion Resistant Duplex Steel
- 22 Cr 5 (9) Ni 3 Mo - Effect of
Shielding Gases and Process
Variations
● Safety Data Sheets (on request)
● Safety Instructions (on request)
–––––––––––––––––––
Brochures
● Centralised Gas Supply Systems
● LASPUR® Gases for Laser
Technology
156
Application Technology Criteria
for Orbital TIG (GTA) Welding of
Electropolished High-Alloy Steel
Tubes
● LASPUR® Guide for Laser Users:
Gases and Gas Supply Systems
● Tank Installations for the Supply
158
Shielding gas for Welding and
Backup Purging - Factors to be
taken into account
of Liquefied Gases
● Technology Centre - Research,
Development, Consulting
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
Alloy
36/97 High-performance MAG Welding
with the LINFAST® Concept
38/97 TIG Welding of Aluminium Alloys
04/99 A Choice of Shielding Gases for
Welding the Variety of Steel
Grades
11/99 Hydrogen in the Shielding gas
42/01 Shielding gases for Welding and
Root shielding of Chrome Nickel
Steels
26
Economical gas supply
Modern production plants, regular
quality control and a international supply
network lead to our extremely reliable
supply service.
Not only are our supply methods very
diverse, they are also economical. Linde
offers tailored and economical supply
methods for every customer: from 10
litre cylinders to 75,000 litre tanks. Our
dense network of supply sites, the many
production sites and a complete product
range are a guarantee for high product
availability, excellent supply reliability and
short distances for personal callers.
In addition, Linde offers safe and reliable, economic and functional gas supply systems. We design and manufacture these systems to suit your special
requirements.
Steel cylinders
Capacity
Litres
Contents*
m3
10
2.1 – 2.4
20
4.0 – 4.7
52
9.1 – 11.8
* Gaseous contents. The amount in the
cylinder depends on the type of gas.
Cylinder bundles
Contents*
m3
106.8 – 141.6
Caution:
New colour markings
To comply with the new EN 1089
Part 3, the colour markings must
now be on the cylinder shoulder.
As the standard foresees a transition period up to 2006, there may
still be cylinders with the old
colour markings in circulation up
to this date.
* Gaseous contents. The amount in the
bundle depends on the type of gas.
Storage tanks
Contents
600 – 75,000 l
Further information on the transition to the new colour markings is
available from every Linde sales
centre.
27
Linde Gas is in the business of making
a difference in everything we do. For the
benefit of our customers. Through innovative solutions within manufacturing industry, metallurgy, chemistry,
food processing, medicine, specialty
gases, alternative fuel technologies
and the environment. This difference
is reflected in our position as a leading
company in Europe and as a major driving force world-wide.
Created through forward thinking, a
close customer relationship and a sound
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of gas products and support services,
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and on-site supply systems generates
new and profitable opportunities.
Linde Gas technology daily drives
entrepreneurship the world over with our
employees all working concertedly to
keep making that difference.
Gas technology that works for you
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Linde Gas –
Making the difference
Linde AG
Linde Gas Division
Phone: +49 89 7446-0
Fax: +49 89 7446-1230
www.linde-gas.com