welding gases 303

8/10/2019 welding gases 303

1/28

Peak performance throughinnovation and expertise.The Linde welding gases.


2/28

Contents.

Advanced technology secures competitiveness. Innovations from Linde Gas 3

The two product lines Competence Line and Performance Line 4

The Linde welding gases at a glance 6Complex properties for specific uses 8

CORGON: MAG welding of structural steel 10

CRONIGON: MAG welding of stainless steels 12

VARIGON: MIG welding of aluminum alloys 14

Shielding gases for arc brazing 16

VARIGON: TIG welding 18

VARIGON: plasma welding 20

Process gases for laser and laser-hybrid welding 21

Gases for root protection 22

Welding gases for special materials 24

Linde Gas supply solutions: efficient and economic 26

Information and services 27

CORGON, CRONIGON, LASGON, LINDATA, LINFAST, LIPROTECT, LISYtec and VARIGON are registered trademarks of

the Linde Group.

Nicrofer is a registered trademark of ThyssenKrupp VDM.

2 Contents


3/28

Advanced technology secures competitiveness.Innovations from Linde Gas.

the essence. Explosive growth in the variety of

modern welding materials, rapid developments

in the field of electronics and an informed

awareness of occupational health and safety

also make new demands on shielding gases for

welding. Within this context, productive GMA

welding of nickel alloys as well as arc stabiliza-

tion through active doping in the shielding gas

for aluminum welding are just two examples of

our successful development work.

As a leading supplier of technology, we have

a special responsibility to our customers. We

continue to uphold the traditions of our found-

er, Carl von Linde, for whom ongoing develop-

ment and progress were a way of life.

We owe our great potential to decades of ex-

pertise, which continues to be translated into

specific product innovations developed in close

collaboration with our customers. Let our ex-

pertise help you to invest in new markets, prod-

ucts and people. Innovations are what we dobest. Day after day.

Linde Gas is part of the Linde Group, a world-

wide operation with two business divisions,

Gas & Engineering and Material Handling,

each of which occupies a leading market

position. As such, we are fully committed to

the Groups claim to leadership. Our companys

guiding principle to be the best in class

in every respect provides us with the nec-

essary orientation in much the same way as

a compass needle indicates the way ahead.

This claim is expressed, on the one hand, by

innovations at the product level and, on the

other, by the commitment of our employees

working in all areas, ranging from production

to service. It is this commitment that enables us

to earn the confidence of more than 1.5 million

customers worldwide. The successful combina-

tion of outstanding engineering services and

market-oriented entrepreneurship afford us the

strength to consolidate our leading position on

a competitive global market.

Today, change is one of the few constants that

shape the economy, markets and commercial

activities. Nothing stands still and speed is of

3Introduction


4/28

A versatile tool in the value-added process.The two product lines Competence Line and

Performance Line.

Competence Line

Proven gases and gas mixtures offering the

very highest quality and supported by out-

standing Linde service. This line contains our

all-rounders, such as CORGON 18,

CRONIGON 2 and argon, products that are

indispensable to everyday welding technolo-

gy and that are ranked amongst some of the

best-selling gas products in the world. How-

ever, this line also contains some more recent

developments, such as VARIGON N2; this is a

TIG process gas that has a metallurgical effectfor duplex-steel applications. Or oxygen-

doped VARIGON S, a gas that was specially

developed for aluminum.

Reliability

Quality

Versatility

User-friendliness

4 The two product lines Competence Line and Performance Line


5/28

Performance Line

Highly productive specialists with admixtures

of helium or hydrogen. These two compo-

nents improve arc efficiency and enhance

heat transfer from the arc to the joint, re-

sulting in higher welding speeds. If improve-

ments in quality alone are required, helium

or hydrogen can be used without increasing

the welding speed. For example, helium can

be used as an additive in many robot appli-

cations to better compensate for component

tolerances. The wider acting arc improvesedge wetting and reduces lack of fusion

problems.

Greater output

Improved quality

Specialization

Customer-specific

Our customers continue to demand specialized

solutions to keep pace with the growing re-

quirements in the field of welding. Advances

made in equipment and materials science, new

measuring technologies and simulation tech-

niques require state-of-the-art, innovative gas

products. Expensive specialized materials re-

quire customized solutions sometimes even at

a molecular level. Gases require the same di-

versification as materials and joining processes.

To improve product transparency and to make

selecting a product easier, we will be offering

two product lines in the future. Both lines con-

tain shielding gases for every conceivable ma-

terial and process combination.

In order to achieve both technically and

economically high-quality weld seams,

everything involved in the process material,

equipment, process gas and welding tech-

nology has to do its part. This requires a

new attitude towards our products. Shielding

gases are much more than welding con-

sumable commodity, they also:

Influence the arc both electrically and

thermally

Determine viscosity and surface tension

both of the drop and of the pool

Control wetting properties

Control penetration, seam geometry and

seam surface

React metallurgically with filler metal and

pool

Influence radiation, heat transfer and arc

efficiency

Determine metal transfer and energy

distribution in the arc

Influence certain pollutant emissions

These properties have to be optimally utilized in

order to reap the full potential of gases in the

welding process. Through our understanding ofhow this tool functions, we are able to make an

active contribution towards the added value in

our customers production processes.

5The two product lines Competence Line and Performance Line


6/28

Process Material group Competence Line Performance Line

MAG Unalloyed steels CORGON 18 CORGON 10He30

Metal active gas Fine-grained structural CORGON 10 CORGON 25He25

steels, pressure-vessel and CORGON S5 CORGON S3He25

pipe steels, hot or cold- CORGON S8

rolled steels, etc. CORGON 5S4

CORGON 13S4

Carbon dioxideStainless steels CRONIGON 2 CRONIGON 2He20

Corrosion-resistant, heat- CRONIGON S1 CRONIGON 2He50

resistant, creep-resistant, CRONIGON S3

duplex steels, etc.

Nickel-base metals Argon (MIG process) CRONIGON Ni series

MIG Aluminum, copper, Argon VARIGON He series

Metal inert gas nickel and their alloys VARIGON S VARIGON HeS series

GMA brazing Coated and uncoated sheet Argon VARIGON He series

Gas metal arc brazing steels, stainless ferritic CRONIGON S1 VARIGON HeS series

steels CRONIGON 2

TIG All fusion-weldable metals, Argon VARIGON He15

Tungsten inert gas all unalloyed and alloyed VARIGON He30

steels, non-ferrous metals VARIGON He50

VARIGON He70

VARIGON He90

Helium

Aluminum and its alloys Argon VARIGON He series

VARIGON S VARIGON HeS series

Austenitic stainless steels, Argon VARIGON H2

nickel alloys VARIGON H6

VARIGON He15

Duplex and super-duplex Argon VARIGON N2He20steels VARIGON N series

Fully austenitic steels Argon VARIGON N2H1

VARIGON N series

PAW All fusion-weldable metals Argon VARIGON He series

Plasma arc welding VARIGON H series

Root protection All materials for which Argon Forming gas: 520% H2 in N2oxidation on the root side Nitrogen VARIGON H series

has to be avoided VARIGON N series Observe the safety informa-

tion in the specialist literature!

Laser All fusion-weldable metals Argon LASGON series

Joining technologies Specialty mixturesHelium

Arc stud welding Steel CORGON 18 CORGON 10He30

Aluminum Argon VARIGON He30S

The optimum solution for every application.The Linde welding gases at a glance.

MAG

MIG

GMA brazing

TIG

PAW

Root protection

Laser

Arc stud welding

6 The Linde welding gases at a glance


7/28

Competence Line Performance Line EN 439 Carbon Oxygen Nitrogen Helium Hydrogen Argon

dioxide

Vol.-% Vol.- % Vol.- % Vol.- % Vol.-% Vol.- %

Argon (Ar) I1 100

Helium (He) I2 100

Carbon dioxide (CO2) C1 100

CORGON 10 M21 10 balance

CORGON 10He30 M21 (1) 10 30 balanceCORGON 18 M21 18 balance

CORGON 25He25 M21 (1) 25 25 balance

CORGON S5 M22 5 balance

CORGON S8 M22 8 balance

CORGON S3He25 M22 (1) 3,1 25 balance

CORGON 5S4 M23 5 4 balance

CORGON 13S4 M24 13 4 balance

CRONIGON 2 M12 2,5 balance

CRONIGON 2He20 M12 (1) 2 20 balance

CRONIGON 2He50 M12 (2) 2 50 balance

CRONIGON S1 M13 1 balance

CRONIGON S3 M13 3 balance

CRONIGON Ni10 M11 (1) 0,05 30 2 balance

CRONIGON Ni20 M12 (2) 0,05 50 balance

CRONIGON Ni30 S M12 (1) + 5N2 0,05 5 5 10 balance

VARIGON N2 S I1 + 2N2 2 balance

VARIGON N3 S I1 + 3N2 3 balance

VARIGON N2H1 S R1 + 2N2 2 1 balance

VARIGON N2He20 S I 3 + 2 N2 2 20 balance

VARIGON He15 I3 15 balance





VARIGON S M13 0,03 balanceVARIGON He30S M13 (1) 0,03 30 balance

VARIGON H2 R1 2 balance

VARIGON H5 bis H15 R1 5 15 balance

Forming gas 95/5 70/30 F2 balance 5 30

Nitrogen (N2) F1 100

Note: In addition to the above-mentioned shielding gases, other industrial gas mixtures can also be supplied to meet customer

requirements.

Subject to change due to continuing development and in the service of our customers.

7The Linde welding gases at a glance


8/28

An in-depth understanding of the internalproperties of gas components and their

interaction in specialized mixtures is essen-

tial for successful use of process gases in

specific welding applications. The welding

arc itself, a highly efficient but complex tool,

consists largely of different amounts of ion-

ized gas and metal vapor. This means the

physical properties of the gas have a direct

and immediate impact on the arc. In addi-

tion, the process gases also contact the hot

metal, a highly reactive area, in which the

chemical and metallurgical effects of the

gases also play an important role. The fol-lowing criteria serve as examples only and

do not claim to be complete.

Dissociation and ionization energyIonization occurs directly in the case of the

monatomic inert gases, Ar and He. Diatomic or

polyatomic gases, such as H2 or CO2, have to be

initially dissociated in the arc, a process which

requires additional energy. The less energy

required for these processes, the easier it is to

ignite the arc. If components that are compara-

tively difficult to ionize, such as He or CO2, are

present, the welding voltage has to be increased

accordingly. However, this additional electrical

energy is released again in the form of recom-

bination energy, which can both improve heat

input and increase welding speed.

Thermal conductivity

Some of the arcs heat is transferred to the

workpiece via the plasma or gas flow. Especially

at high temperatures, the two components He

and H2 can significantly improve process effi-

ciency. Good thermal conductivity has a positive

effect on seam geometry, wetting, degassing of

the molten pool and on welding speed.

Chemical reactivity and metallurgical impactCO2 and O2 are both active, oxidizing gases.

Especially at high temperatures, they react

quickly with the materials present to form

oxides. In appropriate quantities, metal oxides

can improve arc stability; this phenomenon is

put to good use, for example, in the VARIGON

HeS and CRONIGON Ni series specialty gases.

If larger percentages of active gases are present,

for example, when MAG welding structural

steel, the resulting increase in oxidation gener-

ates additional heat. The product of oxidation,

otherwise known as slag or silicate, is often

found on the surface of the seam. O2 as a shield-ing gas component has a greater oxidizing ef-

fect than the same quantity of CO2. If quality

demands require lower levels of these deposits,

the active gas component in the CORGON/

CRONIGON series can be reduced. However,

this should only be done if requirements re-

garding fusion, penetration and the number of

pores are taken into consideration. In the case

of a higher CO2 content, carbon pickup may

occur, depending on the metal being used.

Our gases' capabilities grow with your requirements.Complex properties for specific uses.

Oxygen doping in the VARIGON HeS series facilitates

electron emission at the cathode for MIG-AC welding;

the picture shows the wire electrode in the phase of

negative polarity.

8 Complex properties for specific uses


9/28

N2

is considered a low-activity gas, i.e.

whether or not reactions take place depends on

the metal and the process conditions. An exam-

ple of positive reactivity is the austenitizing

effect of VARIGON N gases when TIG welding

fully austenitic materials or duplex steels. In

contrast, the pore-forming or embrittling effect

of N2 with MAG welding steel is detrimental.

H2 is unique as a particularly effective reducing

component for arc welding. It can be used, for

example, in TIG/PAW welding and forming of

austenitic stainless steels with VARIGON H

gases, in other words, in cases in which it isimportant to prevent oxidation of very expen-

sive and sensitive metals. Owing to their supe-

rior thermal conductivity and additional recom-

bination energy, VARIGON H gases permit

much higher TIG/PAW welding speeds than

argon. Unfortunately, these extremely benefi-

cial properties cannot be used for welding all

metals. For example, H2 leads to pore formation

in aluminum and to cracks in ferritic steels.

Thus, H2s compatibility with a given material

always has to be tested.

Ar and He are the inert gases used in welding.

Since they do not react with any metal, they

can be used with all metals that can be fusion

welded.

Other relevant properties

Relative density: influences the position-

dependent effectiveness of the shielding gas

Heat transfer coefficient: He can transfer heat

to a metal surface much more effectively

than Ar

Purity levels and mixing accuracies

Shielding gases are standardized in EN 439 andISO 14175. These standards specify, amongst

other things, the minimum quality requirements

of the components and mixtures. However,

depending on the material, process, method

and quality requirements, higher qualities may

be necessary. In this case, please contact the

specialists at Linde.

302520151050

Argon (Ar)

Helium (He)

Hydrogen (H2)

Nitrogen (N2)

Carbon dioxide (CO2)

Oxygen (O2)

15.8

24.6

4.5

9.8

4.3

5.1

13.6

14.5

14.4

13.6

Dissociation and ionization energy of the gas components

Parameters for ignition properties, welding voltage and arc energy

Ionization energy, 1st stage Dissociation energy

2,000 4,000 6,000 8,000 10,000

0.16

0.12

0.08

0.04

0

H2

He

Ar

O2

CO2

Thermal conductivity of the gasesHeat transfer from the arc to the base metal depends on the thermal conductivity of

the different gases. Helium and hydrogen offer particularly high thermal conductivity

values.

Thermalcondu

ctivity

[W/cmK]

Temperature [C][eV]

Metallurgy via process gases: control of austenite-

ferrite ratio when TIG welding duplex steels with

VARIGON N

9Complex properties for specific uses

Use of scientific research methods to investigate plas-

ma-physical processes in the arc: section of a spectral

analysis of the MIGp welding process of aluminum with

VARIGON He30S


10/28

Proven under toughest conditions.CORGON: MAG welding of structural steel.

The collective term structural steel refersto unalloyed and low-alloyed steels, fine-

grained structural steels that are suitable for

welding, including tubular and mild steels,

unalloyed high-grade steels, as well as other

alloyed steels that are not classified as stain-

less steels. The choice of the most suitable

shielding gas depends mainly on the type of

filler metal, the material thickness and sur-

face condition of the base metals, the de-

gree of mechanization, working position, arc

type and the requirements of the welded

joint.

MAG welding with solid-wire electrodes and gas

mixtures, consisting of Argon and CO2, such as

CORGON 18, is by far the most common method

for joining structural steels. Owing to their

unbeatable advantages in terms of quality and

economy, gas mixtures are now much more

widely used than pure CO2. Thus, the general

rule of thumb applies to how much active gas,

CO2 or O2, should be used: as little as possible

and as much as necessary. Due to the increasing

degree of mechanization and the greater use of

pulse techniques, mixed gases with a reducedCO2 or O2 content are becoming increasingly

popular.

However, a lower level of active gases results in

lower heat input, which can jeopardize fusion

penetration and welding performance. In this

respect, helium admixtures have proven effec-

tive in many applications.

A He content of 2040 % can improve heat

transfer from the arc to the component, how-

ever, without the known disadvantages of the

oxidizing components. The increased efficiency

of CORGON He gases can be used either for

achieving higher welding speeds or for improv-

ing quality, such as better gap-bridging or for

reducing the risk of lack of fusion.

MAG high-performance welding is defined in

DVS leaflet 0909-1 as a process with a deposition

rate of greater than 8 kg/h; this corresponds to

wire feed rates of more than 15 m/min with

a 1.2-mm solid-wire electrode. The LINFAST

concept offers application-specific, sometimes

patented solutions in this highly productive

field. The optimal process, arc type, and shield-

ing gas type and supply for the task at hand

should be selected based on the specific re-

quirements.

Whether single-wire, double-wire, strip elec-

trode or tandem, the targeted use of CORGON

He mixtures can produce outstanding results

with very little effort.

The shielding gas for metal-cored wires is se-

lected according to the same criteria as those

for solid-wire electrodes. These cored wires are

flexible with regard to special alloying compo-

nents and are characterized by a generally soft

arc. Thanks to the powder filling, the power

required for melting is lower than at comparable

melt-down rate with solid-wire electrodes; this

can also lead to a lower heat input.

Slag-forming flux-cored wires offer advantages

for certain tasks. For example, when welding out

of position, a quickly solidifying slag can act as a

backing. By carefully defining the filling compo-

sition, the chemical and metallurgical reactions

in the weld pool can be affected. As a rule,

CORGON 18 or CO2 is used; lower levels of CO2are not recommended since penetration can

become critical.

Competence LineCORGON 10 CORGON 18

CORGON S5 CORGON S8

CORGON 5S4 CORGON 13S4

Carbon dioxide (CO2)

Performance LineCORGON 10He30 CORGON 25He25

CORGON S3He25

10 CORGON: MAG-welding of structural steel


11/28

Effect of shielding gas composition on the MAG process and result

Gas components Ar + CO2 Ar + CO2 + He Ar + O2 CO2Performance Line

Criteria

Penetration in flat Good Good Adequate; good with Good

position welding thin sheets

Penetration in out-of- Safer with more CO2 Safer with more CO2 Can be critical due to Very safe

position welding very liquid weld pool

Avoidance of lack-of- Good Improved by He Adequate, risk with Adequate

fusion content weld pool flowing ahead

Degree of oxidation Decreases with decreasing Decreases with decreasing Higher than comparable High

(slag formation) CO2 content CO2 content gases containing CO2

Pore formation Becomes lower with Becomes lower with Most sensitive Very lowin the weld seam increasing CO2 content increasing CO2 content

Gap bridging Becomes better with Improved by Good Poor

decreasing CO2 content He content

Spatter ejection Decreases with Decreases with Low spatter Heaviest

decreasing CO2 content decreasing CO2 content

Notch effect at weld toe Low Lowest Increases with High

sheet thickness

Heat transfer, heat input Increases with Increases with rising Lowest High

rising CO2 content CO2 or He content

Arc types that are Short arc, Spray arc, Short arc, Spray arc Spray arc Short arc

particularly recommended Pulsed arc (max. 25 % CO2) (also high-performance) Pulsed arc

Pulsed arc (also high-performance)

CORGON 10 CORGON 18 CORGON S5 CORGON 10He30

Influence of gas components on penetration and seam surface: as an example, a fillet weld on a T-joint, sheet thickness 10 mm

Fully mechanized MAGprobot weldments with constant travel- and wire feed speed

11CORGON: MAG-welding of structural steel


12/28

Special material properties require special gases.CRONIGON: MAG welding of stainless steels.

Application instructionsAustenitic and ferritic stainless steels are highly

suitable for welding in the short and spray arc.

The spray arc range starts at wire feed speeds

about 20 % lower than in welding of unalloyed

steels. The pulse technique offers certain ad-

vantages for welding high-alloyed materials,

particularly with solid wire. It guarantees stable,

almost spatter-free metal transfer throughout

the performance range.

Due to their helium content, Lindes Perfor-

mance Line process gases offer improved heat

input and a higher arc temperature. Conse-quently, it is possible to further increase the

productivity of the MAG process. However, even

if the welding speed is not increased, highly

viscous materials, such as high-alloy CrNiMo

steels and nickel-based alloys, also benefit

from a higher energy input; fluidity and thus

also wetting are improved considerably.

The carbon content of the weld metal is a key

factor in ensuring resistance to intergranular

corrosion. In stainless steels with particularly

low carbon contents, referred to as ELC steels,

the carbon content also of the weld metal

should not exceed 0.03 %. To prevent unac-

ceptably high carbon pickup from the shielding

gas, the CO2 content of the above-mentioned

products should be limited to a maximum of

2.5 %. If welding is performed correctly, this

prevents sensitization to intergranular corro-

sion. The graph on the right illustrates the ten-

dency of various shielding gases to cause the

carburization or decarburization of the weldmetal.

These guidelines apply if a solid wire or a metal-

cored wire is used as filler metal. However, if a

slag-forming flux-cored wire is used, the shield-

ing gas recommended by the manufacturer

should be used. An EN439-M21 shielding gas is

usually recommended for these wires, e.g.

CORGON 18, since the slag that forms prevents

oxidation or carbon pickup.

The shielding gases used for stainless steels

differ from those used in MAG welding of unal-

loyed steels since they contain much less active

gases, such as oxygen and carbon dioxide. This

is necessary to prevent excessive oxidation of

the passive layer responsible for the corrosion

resistant properties of these metals. It is impor-

tant to remember that the oxidation properties

of oxygen are much greater than those of CO2.

However, welding in an inert atmosphere, for

example, with argon, is not recommended

either since the pure argon arc is instable and

penetration is significantly decreased.

Competence LineCRONIGON 2 CRONIGON S1

CRONIGON S3

Performance LineCRONIGON 2He20 CRONIGON 2He50

CRONIGON 2He50 for MAG welding of professional

kitchen systems (source: Convotherm)

12 CRONIGON: MAG welding of stainless steels


13/28

0.07

0.06

0.05

0.04

0.03

0.02

0.016

% C

0.01

Shielding gases at a glance

CRONIGON 2 CRONIGON S1 CRONIGON S3 CRONIGON CRONIGON

2He20 2He50

Degree of oxidation Good Good Limited Very good Very good

Wetting properties Good Good Good Very good Very good

Welding speed Good Limited Good Very good Very goodInterpass weldability Good Good Limited Good Very good

Spatter Good Good Very good Good Good

Arc stability Good Good Very good Good Good

Penetration Good Limited Good Very good Very good

Carbon pickup and loss with different shielding gasesCarbon content of the wire electrode: 0.016 %

CORGON S8

0.014

CRONIGON S1

ELC-limit

CRONIGON 2

0.022

CORGON 5S4

0.026

CORGON 18

0.039

CO2

0.065

For austenitic-ferritic stainless steels, referred

to as duplex steels, the same gases are recom-

mended as for austenites. If duplex steel is

used in a particularly corrosive environment,

argon-oxygen mixtures are not suitable. Due

to their higher oxidation properties, these gas

mixtures would unnecessarily reduce the poten-

tial for corrosion resistance.

CRONIGON S1 CRONIGON 2 CRONIGON 2He50

Impact of gases on surface oxidation

MAGp fillet welds on stainless steel 1.4301/304, sheet thickness 8 mm, mechanized welding

13CRONIGON: MAG welding of stainless steels

0.016


14/28

Quality, visible not only in the arc behavior.VARIGON: MIG welding of aluminum alloys.

MIG welding of aluminum can be performedin the short, spray or pulsed arc. The advan-

tages of the pulsed technique are that spat-

ter formation is reduced and a wire elec-

trode with the next largest diameter can be

used. The thicker wire is easier to feed and,

at identical melt-down rate, has a smaller

surface area. Consequently, fewer impurities

and less moisture are introduced into the

weld seam via the wire.

The pulsed arc method can be further sub-

divided into direct current pulse and alternating

current pulse since power equipment designed

for both types of processes are now available.

Welding with pulsed AC enables targeted distri-

bution of the arc energy between the work-

piece and the wire electrode. This technology

expands the range of application of classical

MIG welding of aluminum to include thinner

components. It is also much easier to bridge

gaps and to use thicker wire electrodes.

Argon is by far the most frequently used shield-

ing gas for MIG welding of aluminum. It has

impressive all-round properties and can be

used for all types of arcs and in all positions.

Further improvement can be achieved by using

VARIGON S, in which the inert argon is doped

with small quantities of active components to

stabilize the arc. The benefits are improved

seam appearance, more uniform weld rippling

and lower spatter ejection.

Competence LineArgon VARIGON S

Performance Line

VARIGON He VARIGON HeS

Maximum productivity: MIGp and MIG tandem welding of

safety relevant chassis components with VARIGON

He15S (source: BMW AG)

14 VARIGON: MIG welding of aluminum alloys


15/28


16/28

The somewhat colder joint.Shielding gases for arc brazing.

Gas metal arc brazing (GMA brazing) is analternative method for joining primarily thin

(t < 3.0 mm) sheets that have been coated

for corrosion protection. This method offers

considerable advantages over MAG welding

since an alloy metal with a lower melting

point than the base metal is used as filler

metal.

Lower heat input

Less burn-off of the coating

Corrosion-resistant, copper-based filler metal

Much less spatter formation

Almost no seam corrosionReduced distortion

Good gap bridging

The right choice of shielding gas can further

boost these positive properties. In addition to

the shielding gas, other key factors influencing

the quality of the join are the base metal, the

type and thickness of the coating, and the al loy

used for the filler metal.

Both short and pulsed arc GMA brazing are

possible. Pulsed arc brazing can be further

classified as DC pulsed and AC pulsed brazing

since power sources enabling brazing with an

alternating current have now been available

for some time. AC pulsed brazing enables an

accurate distribution of energy between theworkpiece and the wire electrode. This is even

gentler on the coating and results in even

better gap bridging.

The shielding gas has a varying effect on the

final brazing result, depending on the type of

solder used and the base metal or its surface

condition. Argon is the universal shielding gas

for GMA brazing since it can be used with all

solders, for all types of arcs and in all positions.

It offers impressive all-round properties and a

low heat input. The disadvantages of argon are

a somewhat unstable arc and a tendency to-

wards porosity. Although the very small gas

pockets do not have a negative effect on the

strength of the join, they appear when the

seam is being polished. This results in extensive

finishing work, particularly in visible areas.

When brazing coated sheets with SG-CuSi3, the

result can be improved by adding active com-

ponents. CRONIGON S1, in particular, but also

CRONIGON 2, stabilize the arc and reduce

porosity. The slightly increased heat input in

comparison with argon translates into higher

process speeds and improved wetting.

Competence LineArgon

CRONIGON S1 CRONIGON 2

Performance LineVARIGON He VARIGON HeS

GMA brazing of hydraulic components with CuAl8Ni2

and VARIGON He50 (source: HAWE Hydraulik)

16 Shielding gases for arc brazing


17/28

When brazing with CuAl alloys, the amount of

active component content in the shielding gas

has to be restricted. However, here too, adding

specific quantities of inert helium can also im-

prove the final results. Products in the VARIGON

He and VARIGON HeS series improve seam

appearance, offer outstanding flow and wetting

properties and, owing to a much higher brazing

speed, also result in a lower heat input.

Performance Line shielding gases are also the

gases of choice for soldering stainless steel.

Since no zinc vapors are produced that disturb

the arc, the above-mentioned advantages areeven more pronounced.

Tungsten inert gas (TIG) or plasma arc (PA braz-

ing) brazing are also possible. Since the tung-

sten electrode cannot be used with gases with

a high active-component content, only inert

argon or gases in the VARIGON He /VARIGON

HeS series can be used.

1,600

1,400

[C]

1,200

1,000

800

600

400

200

Stainless steel Aluminum Zinc

ca. 1,450 C G3Si1

Melting point

of wire electrodes

ca. 1,035 C CuAI8

ca. 960 C CuSi3

Structural steel

907

Low melting point of the copper solder enables lower heat input and thus lowerZn vaporization with coated sheets

Melting point Boiling point

660

420

1,4601,450

Argon CRONIGON S1

Improvement in process stability, seam appearance, and wetting

with robotic GMAp brazing of coated sheets with SG-CuSi3 using CRONIGON S1

17Shielding gases for arc brazing


18/28

Application adviceThe addition of hydrogen or helium is especially

beneficial to heat distribution and heat transfer

in the arc, particularly with TIG welding. The

Performance Line offers a broad range of special-

ty gases that, owing to their hydrogen or helium

content, enable a distinct increase in productivity.

The products in the VARIGON H series are

primarily recommended for TIG welding of

austenitic stainless steels and some nickel-

based alloys. The hydrogen content in the gas

permits more energy to be exchanged in the

arc. This, in turn, results in deeper penetrationand/or greater welding speeds. The hydrogen

content may be as much as 15%, although the

realistic upper limit for manual welding is 6.5%.

As a rule, gases with a higher hydrogen content

are only recommended for mechanized weld-

ing, since it is more difficult to control the heat

and the pool is very fluid. Gases containing

hydrogen must not be used to weld aluminum

alloys or steels sensitive to hydrogen since this

can lead to greatly increased porosity or embrit-

tlement.

Since helium, like argon, is an inert gas, the gas

mixtures in the VARIGON He series can also be

used for aluminum alloys, all types of steel, and

for gas-sensitive metals.

In TIG welding, the arc burns between theworkpiece and a non-consumable tungsten

electrode. To protect the electrode and molten

pool from oxidation, both are purged with

an inert shielding gas, generally argon. This

welding process is suitable for all fusion-weld-

able metals. The type of current, polarity and

shielding gas used depends on the base

metal. TIG welding can be carried out both

with and without filler metal.

The doped gases VARIGON He30S and

VARIGON S contain argon or helium, as well as

a very small amount of oxygen for additional

arc stabilization. These gases can greatly im-

prove welding results, particularly when using

an alternating current for TIG welding aluminum.

The gases in the VARIGON N series were

developed especially for TIG welding duplex

steels or fully austenitic materials. The addition

of nitrogen causes the austenization of the

weld metal, which is particularly beneficial

when TIG welding duplex steel without filler

metal. These gases have also proven valuablefor low-ferrite welding of high-alloy metals in

the chemical industry. It should be noted that,

due to its hydrogen content, VARIGON N2H1 is

not suitable for duplex steels.

For top quality requirements.VARIGON: TIG welding.

Competence LineArgon VARIGON N

VARIGON S

Performance LineVARIGON H VARIGON N2H1

VARIGON He VARIGON N2He20

VARIGON HeS

TIG the arc method for top quality results, also in the

aerospace industry

18 VARIGON: TIG welding


19/28

Competence Line Performance Line Material Comments

Argon All fusion-weldable metals Suitable for universal use, minimum purity requirement

with highly reactive materials 4.8

VARIGON S VARIGON He30S Al and Al alloys Improved arc stability and ignition safety with alternating-

current welding

VARIGON He15 Al and Al alloys Higher heat input due to addition of He

VARIGON He30 Cu and Cu alloys Better penetration

VARIGON He50 Higher welding speed

VARIGON He70

VARIGON He90 Al and Al alloys TIG direct-current welding with electrode

Helium with negative polarity

VARIGON H2 Austenitic stainless steels Addition of H2 results in hotter arc

VARIGON H6 Ni-base metals Better penetration

VARIGON H10 Higher welding speedVARIGON H15 Cleaner seams due to reducing action

VARIGON N2 VARIGON N2He20 Duplex and super duplex steels Control of the austenite-ferrite ratio in the weld metal

VARIGON N3 Increase in performance due to addition of He

VARIGON N2 VARIGON N2H1 Fully austenitic steels Suppresses ferrite phase for special requirements

VARIGON N3 Increase in performance due to addition of H2

TIG DC, argon, vs = 13 cm/min TIG DC, VARIGON H6, vs = 18 cm/min TIG AC, argon TIG AC, VARIGON

S

VARIGON H6 improves speed of welding and penetration

Manual welding of stainless steel 1.4301, sheet thickness 4 mm

VARIGON S for arc stabilization with aluminum

Mechanized melt run on oxide-free surface

19VARIGON: TIG welding


20/28

Two gas flows are required for PA welding:

inner plasma gas and shielding gas. Argon is

generally used as the plasma gas. In rare cases,

argon with a H2 content of up to 2% is also

used, but it must be compatible with the metal.

The shielding gas is selected according to the

same criteria as for TIG welding. Argon is a very

good all-round gas that can be used with all

materials. The use of VARIGON S when weld-

ing aluminum stabilizes the arc.

Performance Line shielding gases are gen-

erally used to increase welding performance.

VARIGON He gases are suitable for all materi-als. VARIGON H gases have been optimized for

high-alloy stainless steels and VARIGON HeS

gases for aluminum.

Depending on the type of method and perfor-

mance range, PA welding can be further classi-

fied into micro-plasma welding (0.150 A,

t = 0.05 2.5 mm), plasma thick-sheet welding

(50350 A, t = 2.510 [12] mm) and plasma

keyhole welding (from 60 A, t > 2 mm).

Plasma arc welding (PA welding) differs fromTIG welding in that the arc is constricted by

means of an additional, water-cooled nozzle.

At the same time the electrode is moved

backwards to the inside of the burner. This

constricted arc has a much greater power

density than a TIG arc.

Metals suitable for plasma weldingUnalloyed/low-alloy steels

High-alloyed steels: CrNi and CrNiMo (good

for keyhole methods due to high viscosity of

the melt)

Ni, nickel-based alloys

Titanium and its alloys

CuNi alloys, Cu

Aluminum and its alloys

Applications of this welding method include

Chemical equipment manufacture

Aerospace industry

Vessel constructionFood industry

Automotive industry

Greater power density thanks to constricted arc.VARIGON: plasma welding.

Competence LineArgon

Performance Line

VARIGON H VARIGON He

Plasma-spirally-welded aluminum pipes

(Source: Linde Engineering)

20 VARIGON: plasma welding


21/28

Where precision and speed meet.Process gases for laser and laser-hybrid welding.

Laser welding (Source: TRUMPF GmbH + Co. KG)At high welding speeds, laser welding offerstargeted heat input and low distortion.

Mostly laser welding is performed without

any additional material. However, in some

cases this may be necessary due to metallur-

gical reasons or to bridge gaps. Steels, light-

weight metals and thermoplastics are suit-

able for laser welding.

Different types of lasers are used for laser

welding: CO2 lasers or solid-state lasers

(Nd:YAG, diode, fiber or disc lasers). Shielding

gases are essential for high-quality welds,

whatever the laser type. Whereas material

considerations determine the choice of shield-

ing gas when using solid-state lasers, when

using CO2 lasers, the interaction between the

shielding gas and the laser beam also has to

be taken into account.

Therefore, helium and gas mixtures containing

helium are used when welding with CO2 lasers.

For example, LASGON C1 is used for laserwelding low-alloy or galvanized steels. Argon

and mixed gases of LASGON quality are used

with solid-state lasers.

Laser-hybrid welding is a combination of laser

welding with an arc process, such as GMA, TIG

or plasma. Both processes act simultaneously

in one molten pool. The choice of shielding gas

essentially depends on the arc process and on

the material to be welded. Thus, for low-alloy

steel, CORGON S3He25 is a good choice to

attain a high-quality weld seam for example.

21Process gases for laser and laser-hybrid welding


22/28

For top-quality workmanship.Gases for root protection.

Differentiating between two differentpurging methods

In the case of gas displacement, the backing

gas pushes forward the air to be removed,

with only little mixing occurring. This principle

is conceivable, for example, for large vessels.

With this method it is very important to take

the relative density of the backing gas into

account. In a purely theoretical ideal-case

scenario, with this type of purging, only as

much backing gas is used as that of the volume

to be purged.

In the case of dilution purging, the backing gasis distributed uniformly throughout the area and

mixes with the air to be removed. The purging

continues until the amount of residual oxygen

has fallen below a certain threshold. The amount

of shielding gas required is thus several times

that of the purging volume.

When subjected to high temperatures andatmospheric oxygen, many metals tend to

intense oxidation. The oxides generally ap-

pear as temper color, for example, with

stainless steel or titanium materials. Temper

colors will greatly impair the corrosion resis-

tance of such metals. Furthermore, severe

oxidation will impair the formation of weld

roots. Thus, in many cases, the root side has

to be protected against oxygen in order to

ensure optimum corrosion resistance. The

careful exclusion of atmospheric oxygen can

prevent oxidation and temper colors.

Two groups of gases are used for rootprotection

Inert or low-activity gases, such as argon or

nitrogen (4.6 or higher)Inert or low-activity gases with added

hydrogen

Thanks to the reducing action of hydrogen,

root-shielding gases containing hydrogen offer

greater protection against the formation of

temper colors. However, they are not suitable

for all metals. The type of gas used for root

protection primarily depends on the type of

metal of the component to be purged. Steelsthat are sensitive to hydrogen or highly reactive

metals, such as titanium, are generally purged

with argon. Austenitic stainless steels can be

protected with root shielding gases containing

hydrogen, for example, with gases from the

Forming gas or the VARIGON H series.


Nitrogen

Performance LineForming gas 95/5 70/30

VARIGON H

Welding with additional forming gas

22 Gases for root protection


23/28

To prevent the formation of temper colors,

after welding, purging should continue until the

component has cooled to a temperature of

below approx. 220 C. If the root of the weld is

not accessible after welding for reworking, a

root shielding gas should be used when tacking

the component since temper colors will not be

dissolved by welding over the tack point.

In the case of Ti-stabilized stainless steels, gases

containing N2 cause a clearly visible yellowing

of the root of the weld as a result of the forma-

tion of titanium nitride. With duplex and super-

duplex steels, using root-shielding gases thatcontain nitrogen or pure nitrogen improves

corrosion resistance.

Application adviceThe gases for root protection are standardized

in EN439.

Group R (Ar-H2 mixtures)

Group I (Ar or Ar-He mixtures)

Group F (N2 or N2-H2 mixtures)

Minimum purging times have to be observed to

prevent the formation of temper colors. The re-

quired purging time depends on the geometry of

the component and on the volumetric flow rate

of the gas. The recommended value for required

backing gas volume for pipelines, for example, is

2.53 times the geometric volume of the compo-nent, calculated from the supply point to the

welding point. Depending on pipe diameter, a

gas flow rate of 512 l/min is recommended. The

use of a measuring device to measure the resid-

ual oxygen content is recommended.

Root shielding gases for various materials

Shielding gas Material

Argon All fusion-weldable metals

VARIGON H series Ar-H2 mixtures Austenitic stainless steels

Forming gas N2-H2 mixtures Austenitic stainless steels (not Ti-stabilized)Unalloyed steels (not high-strength fine-grained steels!)

VARIGON N Ar-N2 mixtures Austenitic stainless steels (not Ti-stabilized)

series N2 Duplex and super duplex steels

Heavierthanair

Lighterthanair

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

N2 mixtures

Ar mixtures

Air

4 8 12 16 20

% o f H2 by volume

24

Safety informationRoot shielding gases with a hydrogen content

of more than 4% can form explosive mixtures

if they come into contact with air or oxygen.

Users must take certain precautionary mea-

sures to prevent the formation of such gas

mixtures. For safety reasons, DVS leaflet 0937

recommends burning-off if the hydrogen con-

tent in the root shielding gas is 10% or higher.

When forming large, closed components,

adequate ventilation must be available before

inspection to prevent the risk of suffocation.

When working in small rooms, oxygen deple-tion should be taken into account.

TIG seam, root side , no root protection

TIG seam, root side, with root protection

Relative density of root shielding gases

23Gases for root protection


24/28

Practical solutions for extraordinary materials.Welding gases for special materials.

Nickel metalsIn the case of nickel alloys, the choice of a

suitable shielding gas greatly depends on the

type of alloy to be welded. A variety of nickel

alloys are available on the market, which, de-

pending on their area of application, vary great-

ly in terms of their metallurgical properties and

suitability for welding. As a result, there are

also a number of different recommended gases.

Users should contact Linde Gas or the material

manufacturer if there is any doubt as to which

gas to use.

TIG weldingMany nickel alloys can be easily welded using

argon-hydrogen mixtures, e.g. VARIGON H2.

Other materials, for example, those that are

particularly susceptible to hot cracks, are better

processed with pure argon. However, for metal-

lurgical reasons, some high-temperature nickel-

based alloys require the addition of nitrogen to

the shielding gas, e.g. VARIGON N2.

Reactive materials: Ti, Ta, ZrTitanium, tantalum and zirconium are termed

reactive materials since they react readily with

O2, N2 and H2. These processes are promoted by

the heat generated during welding. Picking up

even tiny quantities of atmospheric gases can

lead to the total embrittlement of the weld

seam. This embrittlement cannot be reversed

by heat treatment. Under the influence of heat,

oxygen also causes greater surface oxidation,

which severely affects the corrosion resistance

of these materials. The use of appropriate gas

protection during welding is the most important

factor in protecting such valuable materialsfrom these negative influences.

TIG welding, generally with pure argon as

shielding gas, is the most common welding

process used for such materials. Purity should

be at least 4.8 (99.998 %). Inert He mixtures,

such as VARIGON He30, can also be used for

thicker walls and for improved penetration.

The group of so-called special metals is notclearly defined. In general, special materials

are defined as materials that are not consid-

ered standard materials, such as aluminum,

structural steel or stainless steel. These spe-

cial metals include nickel-based metals, cop-

per or magnesium, as well as reactive metals

such as titanium, tantalum and zirconium.


Performance Line

VARIGON He VARIGON HeSCRONIGON Ni10 CRONIGON Ni20

CRONIGON Ni30

MAGp arc under CRONIGON Ni30

24 Welding gases for special materials


25/28

MAG welding

The gases in the CRONIGON Ni series were

specially developed for MAG welding of nickel-

based materials. These patented gas mixtures

are all doped with CO2. This minute amount of

CO2 stabilizes the arc perceptibly without imper-

missibly altering the carbon content of the weld

metal.

CRONIGON Ni10 and CRONIGON Ni20 also

contain hydrogen or helium, which improves

flow properties and seam appearance and at

the same time, maintains the materials corro-

sion resistance.

CRONIGON Ni30 was developed especially for

MAG welding of the high-temperature alloy

602CA. In addition to CO2 doping, this gas con-

tains helium and nitrogen. The latter clearly

reduces the risk of hot cracking during welding.

Copper metalsCopper and most copper alloys are character-

ized by very high thermal conductivity. To com-

pensate for the rapid dissipation of welding

heat, gases containing helium are recommend-

ed for use with these metals. VARIGON He30

or VARIGON He50 are the gases of choice for

both TIG and for MIG welding, particularly if

pre-heating can be reduced as a result of their

use. To prevent the risk of hydrogen brittleness

when welding copper, shielding gases contain-

ing H2 should not be used.

Magnesium metalsInert gas mixtures, namely argon, helium and

their compounds, are used for gas-shielded arc

welding of magnesium alloys. Argon can be

used for all welding methods, apart from TIG

direct current. However, VARIGON He mixtures

are generally recommended as shielding gas as

they can reduce pore formation.

Only shielding gases with very high helium

content, such as VARIGON He90 or pure helium,

can be used for TIG DC welding of magnesium

with the electrode at negative polarity. Other-

wise, there will be not enough heat for welding.

In the case of MIG welding, due to the high

electrical resistance of magnesium and the

associated heating of the free end of wire, the

amount of energy that can be transferred in the

wire is limited. This can be somewhat compen-

sated for by using a welding gas that contains

helium. In addition to the classical pulsed and

short arc processes, MIG welding has recentlyalso been carried out in the form of special

pulsed or controlled short arc welding.

VARIGON He mixtures can also be used with

these methods to reduce pore formation.

Production of a furnace roll made of Nicrofer 6025HT/

alloy 602CA with CRONIGON Ni30.

(Source: H. BUTTING GmbH & Co. KG)

25Shielding gases for special materials


26/28

Linde Gas supply solutions:efficient and economic.

State-of-the-art production facilities, regularquality checks and a national supply net-

work offer maximum supply reliability.

Caution: new color-codingIn accordance with the new standard EN 1089

part 3, cylinders are color-coded on the shoul-

der. As the standard has a changeover period

until 2006, cylinders with the old color-coding

may be still in circulation until this time. For

further information on the changeover to the

new color-coding system, please contact the

Linde Distribution Center.

Total Gas Management

Would you prefer to sit back and turn over all

your gas business to a safe and reliable part-

ner? When it comes to supplying gas, servicing,maintenance or safety, our Total Gas Manage-

ment team takes care of it all.

Our supply channels are both diverse and eco-

nomical. Linde offers the right quantity at the

right price for every customer: from small 10-

liter cylinders to 75,000-liter liquid tanks. The

companys dense supply network, its many

production sites and comprehensive product

lines guarantee high product availability, trans-

port safety, short delivery channels for self

serving customers.

In addition, Linde also offers safe, economical

and functional central gas supplies. We plan

and manufacture these to your own individual

requirements.

Steel cylinders

Capacity Filling*

Liter m3

10 2.12.4

20 4.04.7

50 9.111.8

* Content gaseous, filling quantity of the cylin-

der depends on the type of gas.

Upright tanks

Content

60075,000 l

Cylinder bundle

Content* m3 106.8141.6

* Content gaseous, filling quantity of the bundle

depends on the type of gas.

26 Linde Gas supply solutions


27/28

Information and services.

LISY

tecLISYtec is a system for supplying oxygen,

acetylene and welding gases in cylinders that

combines a high level of safety with great ease

of use. The ergonomic valve protection device

allows for easy handling of the cylinder and

protects the fittings from damage. The built-in,

two-stage pressure regulator enables almost

constant working pressures. LISYtec saves you

the expense of having to buy and install your

own pressure regulator.

LIPROTECT a comprehensive safety program

for handling gasesLegal requirements regarding the safe handling

of gases are becoming increasingly strict. The

German Workplace Safety Ordinance 2002 and

the Pressure Equipment Ordinance 2002 have

increased safety requirements for operators of

gas equipment. More than ever before, safety is

being viewed as the responsibility of the opera-

tor. LIPROTECT offers you a complete safety

program for handling gases.

Safety training

Safety servicesSafety products

BrochuresPerformance Line. Next-level gas-shielded

arc welding

Centralized Gas Supply Systems

LASERLINE. The perfect solution for a

perfect gas supply

Tank Installations for the Supply of

Liquefied Gases

People creating solutions for people.

International Research and Development by

Linde Gas

Tools

Slide rule: MAG welding with CORGON

gas mixtures

LINDATA slide rule: weld seam with

CORGON mixed-gas welding

LINDATA slide rule: CRONIGON

for CrNi steels

Tips for practitioners

(on request)

Special editionsApplication Technology Criteria for Orbital TIG

Welding of Electropolished High-Alloy Steel

Tubes (156)

Shielding gas for Welding and Purging-

Factors to be taken into account (158)

Control of the Arc Welding Process in

Manufacturing (03/90)

Gas-Shielded Arc Welding of Aluminum

(22/93)

Pulsed MAGM Welding of Nickel Alloy

(34/97)

TIG Welding of Aluminum Alloys (38/97)

A Choice of Shielding Gases for Welding theVariety of Steel Grades (04/99)

Hydrogen in the Shielding Gas (11/99)

Shielding Gases for Welding and Root Shield-

ing of Chrome Nickel Steels (42/01)

Duplex Steels: A special Set of Rules

Current Process Variants of High-Performance

MAG Welding

Influence of shielding gases on corrosion

properties of nickel alloy weldments

Data sheets

Safety data sheets (on request)Safety instructions (on request)

Also available from www.linde-gas.de

27Information and services


28/28

Getting ahead through innovation.

With its innovative concepts, Linde Gas is playing a pioneering role in the global market. As a technology leader, it is our task

to constantly raise the bar. Traditionally driven by entrepreneurship, we are working steadily on new high-quality products

and innovative processes.

Linde Gas offers more. We create added value, clearly discernible competitive advantages, and greater profitability. Each

concept is tailored specifically to meet our customers requirements offering standardized as well as customized solutions.

This applies to all industries and all companies regardless of their size.

If you want to keep pace with tomorrows competition, you need a partner by your side for whom top quality, process

optimization, and enhanced productivity are part of daily business. However, we define partnership not merely as being

there for you but being with you. After all, joint activities form the core of commercial success.

Linde Gas ideas become solutions.

43487670

02061.2

Au

Subjecttocha

nge.

welding gases 303

Documents