Linde - Shielding Gasses

8/10/2019 Linde - Shielding Gasses

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Shielding GasesDevelopment . Consulting . Applications


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Cost-Effective Industrial Gases from Linde...................................................................... 3

The Right Shielding Gas - for Every Welding Process ..................................................... 4

Compositions of Linde Shielding Gases .......................................................................... 5

Properties of Shielding Gas Constituents ........................................................................ 6

Arc Types: Their Actions and Applications....................................................................... 8

Shielding Gases for MAG Welding of Structural Steels.................................................... 10

Shielding Gases forLINFAST ......................................................................................... 12

Shielding Gases for MAG Welding of High-Alloy Steels and Ni Base Alloys ................... 14

Shielding Gases for MIG Welding of Non-Ferrous Metals................................................ 16

Shielding Gases for TIG Welding...................................................................................... 18

Oxidation Prevention Using Forming Gases .................................................................... 20

Shielding Gases for Plasma-Arc Welding......................................................................... 22

Shielding Gases for Arc Stud Welding ............................................................................. 23

Shielding Gases for Laser Beam Welding ........................................................................ 24

Linde Publications, Application Notes and Training Materials ......................................... 26

Photo on title page:

The use of the well-proven shielding gases from Linde

together with LINFASTleads to quality improvement and cost savings

Contents Page


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Quality improvement and ratio-nalisation are crucial for any com-pany that wishes to maintain and im-prove its competitive position in the

welding industry. Linde shieldinggases provide a variety of options forachieving these aims.

As one of the leading suppliers ofindustrial gases, Linde has decadesof experience in the development,production and application of shield-ing gases. Linde expertise encom-passes all modern welding applica-tions and is continuously updated byinnovative solutions.

The most up-to-date productionplants, regular quality controls and anational sales network ensure thebest possible reliability of supply.

Our supply channels are not onlymanifold, they are above all eco-nomical: Linde offers tailor-madeand cost-optimised supply conceptsto each customer, from the 10 litrecylinder to the 75,000 litre tank. Ourdense network of sales agents anddepots, the numerous Linde produc-

tion facilities and a comprehensiverange of products ensure high avail-ability, reliability of supply and shortdistances for customers who wantto collect their own supplies.

The Linde Technology Centreuses the most advanced weldingequipment to solve customer prob-lems on a case-by-case basis. Ap-plications engineers provide on-siteassistance to customers to ensureoptimal use of Linde shielding gases.

Storage tanks

Contents

600 75,000 litres

Cost-Effective Industrial Gasesfrom Linde

Steel cylinders

Water capacity Contents*

litres m3

10 2.1 2.4

20 4.0 4.7

52 9.1 11.8

* Gaseous contents; the contents is

dependent on the type of gas

Cylinder bundles

Contents*

m3

106.8 141.6

* Gaseous contents; the contents isdependent on the type of gas


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The Right Shielding Gas for Every Welding Process

Process DIN 1910 Shielding Gases Material

MAGGMAW with active gas

MIGGMAW with inert gas

TIGTungsten inert gas

PAWTungsten plasma-arc

Rootprotection

Laserbeam

CORGON 1 CORGON S8CORGON 2 CORGON He 30CORGON 18 CORGON He 25 CCORGON 10-40 CORGON He 25 SCarbon dioxide T.I.M.E. + T.I.M.E. II

CRONIGON S1 CRONIGON He 20CRONIGON S3 CRONIGON He 30SCRONIGON 2 CRONIGON He 50SCRONIGON He 50 CRONIWIG N series

Argon Aluminium, copper, nickelVARIGON He and other alloysVARIGON SVARIGON He S

Argon All weldable metals such asHelium VARIGON S unalloyed and alloy steels,VARIGON He VARIGON He S aluminium, copper,

VARIGON H Nickel and Ni alloysCRONIWIG N-series CrNi steels

Argon 4.8 Reactive and refractory materials(Special applications) such as titanium, tantalum, zirconium

Plasma gas/Shielding gas: All weldable metals

Argon see TIG

VARIGON H

VARIGON He

Forming gas: Nitrogen-hydrogen For all materials where oxidation

N2 H2 at the root must be avoided.

100 % Burn off hydrogen at levels

95 % 5 % overs 10 %

90 % 10 %

85 % 15 %80 % 20 %

LASPUR quality: All weldable metals

Argon

Helium Materials supposed to be difficult

Gas mixtures to weld

Without Forming gas

With Forming gas

EN 439

Arc stud

welding

CORGON 18 Structural steel, high-alloy steels

VARIGON He 30 Aluminiumand Al alloys

Steels for pipe, boilers, shipbuilding;

structural and fine-grain steels,

case-hardening and heat-treatable

steels

CrNi, Cr and other alloy steels,

Ni base alloys,

Duplex and super duplex steels


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Compositions of Linde Shielding Gases

Shielding gas EN 439 Argon Carbon Oxygen Helium Nitrogen Hydrogendioxide

% by vol. % by vol. % by vol. % by vol. % by vol. % by vol.

Argon (Ar) I 1 100

Helium (He) I 2 100

Carbon dioxide (CO2) C 1 100

CORGON 1 M 23 Balance 5 4

CORGON 2 M 24 Balance 13 4

CORGON 10 25 M 21 Balance 10 25

CORGON S 5 M 22 Balance 5

CORGON S 8 M 22 Balance 8

T.I.M.E. M 24 (1) Balance 8 0.5 26.5

T.I.M.E. II M 24 (1) Balance 25 2 26.5

CORGON He 30 M 21 (1) Balance 10 30

CORGON He 25 C M 21 (1) Balance 25 25

CORGON He 25 S M 22 (1) Balance 3.1 25

CRONIGON 2 M 12 Balance 2.5

CRONIGON He 50 M 12 (2) Balance 2 50

CRONIGON He 20 M 12 (1) Balance 2 20

CRONIGON He 30 S M 11 (1) Balance 0.05 30 2

CRONIGON He 50 S M 12 (2) Balance 0.05 50

CRONIGON S 1 M 13 Balance 1

CRONIGON S 3 M 13 Balance 3

CRONIWIG N 2/3 SAr+N2 Balance 2/3

CRONIWIG N H SR1+2N2 Balance 2 1

CRONIWIG N He SI3+2N2 Balance 20 2

VARIGON S M 13 Balance 0.03

VARIGON He 30 I 3 Balance 30




VARIGON He 30 S M 13 (1) Balance 0.03 30

VARIGON H 2 15 R 1 Balance 2 15

VARIGON H 20 R 2 Balance 20

Nitrogen (N2) F 1 100

Forming gas 95/5 80/20 F 2 Balance 5 20

Note: In addition to the above-mentioned shielding gases other mixtures for special applications are available.


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Proper Use of ShieldingGases Leads to Optimum

Welding Results

Shielding gases allow many parame-ters of the welding process to be con-trolled and optimised for specific appli-cations.

The gas or gas mixture is selectedaccording to the required effects.

The possibilities for optimisationcover virtually every factor in the weldingprocess:

Physical properties of the gas affectmetal transfer, wetting behaviour, depthand shape of penetration, travel speed,

and arc starting. Gases with low ionisa-tion energy, such as argon, facilitate arcstarting and stabilisation better thanthose with high ionisation energy, suchas helium.

On the other hand, helium is a betterchoice for laser beam welding, where ithelps to control the plasma and thus thepenetration depth.

The dissociation energy of polyatomiccomponents in gas mixtures enhancesheat input to the base material due tothe energy released by recombination.

CORGONgas mixtures for safety-relevant components in car manufacture

Plasma-arc welding of pipes

Properties

of Shielding Gas Constituents

Gas Dissociation First ionisationenergy energy

eV/molecule eV/molecule(first

ionisation stage)

H2 4.5 13.6

O2 5.1 13.6

CO2 4.3 14.4

N2 9.8 14.5

He 24.6

Ar 15.8

Kr 14.0

Physical properties of gases


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Thermal Conductivity of Gas Components The thermal conductivity influencesweld geometry, weld-pool temperatureand degassing, and travel speed. Forexample, travel speed and penetrationcan be markedly increased by the addi-

tion of helium in MIG and TIG welding ofaluminium materials, or by the additionof hydrogen in TIG welding stainlesssteels.

Chemical properties influence boththe metallurgical behaviour and the weldsurface quality. Oxygen, for example, re-sults in alloying elements and leads tomore fluid weld pools, while carbon diox-ide results in carbon pickup in alloyedmaterials. Argon and helium have a me-tallurgically neutral behaviour, and hydro-gen acts as a reducing agent. Nitrogenis added to the shielding gas to control

the ratio of austenite to ferrite.

MIG welding of aluminium heat exchangers using an Ar/He mixture

10,0008,0006,0004,0002,000

0.16

0.12

0.08

0.04

0

CO2

H2

O2

He

Ar

Linde provides optimum shieldinggases for all welding applications.Special gases can be developed forindividual requirements

Slag formation with different

CO2additions to the shielding gas

Temperature [ C ]

Thermalconductivity[W/cmC]


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A variety of arc types are employed ingas metal arc welding (GMAW) with con-sumable wire electrodes. Crucial factorsin the selection of the arc type are theshielding gas, the plate thickness and

the welding position.

Short arc for sheet metal, out-of-po-sition welding, and root-pass welding atlow performance levels. The metal trans-fer takes place with short-circuiting andlittle spatter.

Transition arc for medium-perform-ance MAG welding of moderate platethicknesses using argon-based gas mix-tures. Metal transfer is globular with par-tial short-circuiting, but spatter is lessthan with long-arc welding using CO2.

Long arc for high-performance MAGwelding of thicker sections using CO2.Metal transfer is globular, with consider-able spatter.

Arc Types:

Their Actions and Applications

Short arc Transition arc/long arc

GMAW Arc Ranges with ArCO2 mixtures (schematic)

Weldingvoltage[V]

Wire feed rate [ m/min ]

KLB

RLB

HL-SLB

HL-KLB

LB

unstable

arc

SLB

ILB

KLB = Short arc

ILB = Pulsed arc

LB = Transition arcSLB = Spray arc

RLB = Rotating arc

HL-KLB = High-performance short arc

HL-SLB = High-performance spray arc


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Spray arc for high deposition ratesand travel speeds on thicker sectionsusing argon-based gas mixtures. Metaltransfer is by droplets, without short-cir-cuiting, and nearly spatterfree.

High-performance arc for higherdeposition rates and travel speeds using

special argon gas mixtures containinghelium. The composition of the shieldinggas influences the arc type and metaltransfer, e.g.high-performance short arc,high-performance spray arc, rotating arc.

Pulsed arc for all performance levels;used in MIG and MAG welding with ar-gon-rich mixtures, chiefly at moderateperformance levels (replacing transitionarc). Metal transfer without short-circuit-ing with one well-defined droplet formedper pulse. Less spatter than with other

arc types. The pulsed arc cannot beused with shielding gases with morethan 20 25 % CO2.

Rotating arc

Spray arc

Pulsed arc


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Linde shielding gases for MAGwelding of structural steels are

CORGON 1

CORGON

2CORGON with 10 40 % CO2CORGON S 5 / S 8CO2

These shielding gases are suitable forpipe steels, structural and fine-grainstructural steels, case-hardening steelsand heat-treatable steels of all qualities.

Filler metals in the form of solid wireare standardised in EN 440 and in theform of cored wire in EN 758. TheGerman Welding Society bulletin DVS-Merkblatt 0916gives filler metal recom-

mendations for higher-strength fine-grainstructural steels.

The properties of gas mixtures varywith composition. The composition alsoinfluences the mechanical and engineer-ing qualities of the weld metal and theweld geometry.

Shielding Gases

for MAG Welding of Structural Steels

Use of CORGON 18 for robot welding of lifting masts

Effect of Shielding Gason Mechanical and Engineering Properties * Rm: ensile strength Re: yield strength A5: elongation at fracture

Shielding gas Weld metal Impact energy J O2 content

Rm Re A5 * analysis % (mean of 4 specimens) of weld metal

N/mm2 N/mm2 % C Mn Si + 20 C 0 C 20 C 30 C 40 C 50 C % by weight

CORGON 1

91 % Ar, 5 % CO2 610 472 28.1 0.08 1.32 0.67 138 124 87 83 58 48 0.031

4 % O2

CORGON 10640 544 25.7 0.09 1.43 0.72 130 88 64 55 60 41 0.029

90 % Ar, 10 % CO2

CORGON 18620 522 26.8 0.09 1.37 0.70 144 120 86 62 50 40 0.0305

82 % Ar, 18 % CO2

CORGON 25601 505 29.3 0.09 1.30 0.65 124 97 76 61 51 41 0.034

75 % Ar, 25 % CO2

CORGON S 12591 510 27.5 0.06 1.20 0.60 138 126 87 67 46 40 0.0355

88 % Ar, 12 % O2

100 % CO2 594 437 27.8 0.10 1.21 0.62 84 54 48 35 28 22 0.062

Wire electrode to0.115 1.53 0.98

EN 440 G3Si1

47-

J-

limit


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Properties

Penetration Flat position

Out-of-position

Thermal load

on torch

Degree of oxidation

Porosity

Gap bridging

Spatter

Heat input

Arc type

Ar/CO2

Good

More reliable

with increasing CO2 level

Lower


Higher


Lower


Better

with decreasing CO2 level

Increasing


Increasing


Cooling rate lower,less danger of cracking

Short arc

Transition arc

Spray arc

Pulsed arc/up to 20 % CO2High-performance short arc

High-performance spray arc

Ar/O2

Good

Can become critical

if fluid weld pool leads arc

High;

excessive torch temperature

can limit performance

High;

e.g. at 8% O2

Most sensitive

Good

Low

Lowest

Cooling rate high,greater danger of cracking

Short arc

Transition arc

Spray arc

Pulsed arc

High-performance short arc

Rotating arc

CO2

Good

Reliable

Low

because of good

thermal conductivity

High

Reliable

Worse

than with gas mixtures

Highest spatter,

increasing with increasing

performance

High

Cooling rate low,little danger of cracking

Short arc

Long arc

Properties of Shielding Gases

The above properties of the various shielding gases govern their use in welding.

The versatility of Ar-CO2and Ar-CO2-oxygen mixtures (the Linde CORGONshielding gases) has led to their high popularity.

The addition of helium extends the range of applications.


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Linde shielding gases for high-per-formance MAG welding are:

CORGON He 25 C

CORGON

He 25 SCORGON He 30T.I.M.E. GasT.I.M.E. II Gas

These shielding gases were speciallydeveloped for high-performance MAGwelding (T.I.M.E. process), a methodwith increased wire feed rates for higherdeposition rates and travel speeds.

Variation of the shielding gas compo-sition influences the arc characteristics,metal transfer, penetration, weld surface

and porosity.

TheLINFAST concept is based onthe relationship between the weldingparameters (wire feed rate, contact tube-to-work distance and welding voltage)and the shielding gas composition tostabilise the arc types at high perform-ance levels. Unstable arcs at a wire feedrate of 22 30 m/min are reliably avoid-ed by theLINFAST concept in order toachieve optimum welding results.

Shielding Gases for LINFAST

the MAG High-Performance Welding

Concept from Linde

LINFASTMAG high-performance welding of dredging shovels using CORGONHe 30:

cost savings and quality improvement

Weldingvoltage[V]

Wire feed rate [ m/min ]

15 18 20 22 27 30 35

ConventionelMAG-M Welding

MAG High-PerformanceWelding

CORGONHe 25 S

T.I.M.E. IICORGONHe 25 C

RLB

RLB

RLB

HL-SLB

HL-SLB

unstable

arc

HL-KLB

HL-KLB

HL-KLB

SLB

SLB

SLB

LB

LB

KLB

KLB

KLB LB

HL-SLB

T.I.M.E.CORGONHe 30

KLB = Short arc

LB = Transition arcSLB = Spray arc

RLB = Rotating arc

HL-KLB = High-performance short arc

HL-SLB = High-performance spray arc

Effect of LINFAST Gases on the Stabilityof Different Arc Types


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The MAG High-Performance Arc Types

- Penetration Profiles

and Avoiding Defects

Spray arcat a wire feed rate of >15 m/min, sprayarc results in a typical v-shaped penetra-tion profile.

High-performance short arcThis type of arc is particularly suitable forlow wall thicknesses and higher travelspeeds.

High-performance spray arcWeld defects are caused by arc insta-bility. Unstable arcs are reliably avoidedby theLINFAST concept.

Rotating arcTheLINFAST concept stabilises arcrotation and guarantees wide and deepweld penetration in the root region in ad-dition to excellent side wall fusion.

Stable spray arc due to the use

of CORGONHe 25 C at a wire

feed rate of 23 m/min, position

PB, semi-mechanised

Extremely high travel speeds

of more than 2 m/min are

achievable with a high-per-

formance short arc and a

T.I.M.E. shielding gas (in the

photo: wire feed rate

= 17 m/min)

Weld defects due to arc in-

stability between rotating arc

and high-performance spray

arc at wire feed rates between

22 and 30 m/min (in the photo:

wire feed rate = 26 m/min, fully

mechanised).

CORGONHe 25 S guarantees

stable rotation at wire feed

rates above 20 m/min

(in the photo: wire feed rate

= 26 m/min, position PB, fully

mechanised).

RLB

HL-SLB

RLB

HL-SLB

cross section

longitudinal section


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Linde shielding gases for the MAGwelding of high-alloy steels are

CRONIGON S 1

CRONIGON

S 3CRONIGON 2CRONIGON He 20CRONIGON He 50CRONIGON He 30 S

CRONIGON He 50 SCRONIWIG N series

These shielding gases are suitable for:

stainless steels to DIN 17440(BS 970 part 4)

high-temperature rolled

and forged steels to SEW 4670 special stainless steels Ni base alloys

Filler metals for the welding of stain-less and high-temperature steels arestandardised in DIN 8556(BS 2901 part 2).

Short, transition, spray and pulsedarc types can be used.

The carbon content is important formaintaining the corrosion resistance. Forlow-carbon ELC steel qualities, the maxi-

mum level in the weld metal should be0.03 % if annealing is necessary.

Measurements of carbon burn offand pick up clearly show that no corro-sion problems should occur when usingCRONIGON shielding gases.

Although the carbon content whenusing CORGON 1 stays below the ELClimit, this shielding gas should not beused for components that will be used incorrosive environments.

Shielding Gases

for MAG Welding of High-Alloy Steels

and Ni Base Alloys

Carbon Burnoff and Pickupwith Various Shielding Gases

0.002

0.07

0.06

0.04

0.02

CORGONS8

0.05

0.03

0.016

0.01

0

0.0060.01

0.023

0.049

CO2CORGON18CORGON1CRONIGON2CRONIGONS1

ELC limit

Wireelectrode

% C

Alloy type (ELC)

MAG welding of an exhaust gas diffuser using CRONIGONHe 50 S


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ImportantApplication Notes

Austenitic CrNi steels and ferritic Crsteels can be welded quite well with the

spray arc, which begins at currentssome 20 % below those struck on un-alloyed materials.

The use of the pulsed arc ensuresstable metal transfer with little spatterover the full range of melting rates. Hea-vier wires, which can be fed more re-liably and offer better current transfer,can thus be used. What is more, pulsed-arc welding is an excellent technique forvertical-down welds. Nickel-based mate-rials and most special steels should pre-ferably be welded with the pulsed arc.

Interpass welding temperaturesdepend on the type of base metal:

150 200 Cfor austenitic CrNi steels

50 100 C for Ni-based materials

Research at the Linde TechnologyCentre has revealed some interestingfeatures:

The weld geometry, surface finish,wetting behaviour, and arc stabilityare affected in different ways by thebase and filler metals.

The torch position should be approx.10 forehand for all materials.

The weld metal should be applied instringer beads (less thermal stress).The arc must always lead the weldpool. Heavy spatter results if the weldpool leads the arc even slightly,especially with Ni-based materials.

Shielding gas Properties Materials

CRONIGON S 1 Low oxidation Ferritic Cr steels Moderate wetting

CRONIGON S 3 Greater oxidation Corrosion-resistant, austenitic Adequate wetting CrNi steels

CRONIGON 2 Low oxidation High-temperature Good wetting austenitic steels Higher travel speed Minimal spatter Special steels. e.g. duplex

CRONIGON He 20 Excellent wetting Special steels, e.g. duplexCRONIGON He 50 even at great section thickness and super duplex

Very good interpass fusion Corrosion-resistant Stable arc and high-temperature Minimal spatter CrNi steels High travel speeds, Ni base materials

especially suited with low corrosion stressfor fully mechanised welding

CRONIGON He 30 S Excellent wetting All Ni-based materials,Cronigon He 50 S Excellent arc stability especially

compared to other inert gases highly corrosion-resistant Extremely low surface oxidation Ni base alloys

due to considerably reducedactive gas content

Very good interpass fusion High corrosion resistance

which is comparableto TIG and MMA/SMA welding

Next to no spatter

CRONIWIG N Reduction of ferrite content Full austenites

Control of the Duplex and super duplex steelsaustenite/ferrite ratio

Survey of Applications

MAG welding of a plated beam

with CRONIGON2


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Shielding gases for the MIG weldingof non-ferrous metals are inert gasessuch as:

ArgonVARIGON HeVARIGON SVARIGON He S mixtures

Short, spray and pulsed arc typescan be used with these gases.

The pulsed arc offers significant ad-vantages, especially for softer Al fillermetals, because it allows the use of larg-er-diameter wire electrodes with their im-proved feeding reliability.

Filler metals for non-ferrous basemetals are standardised as follows:

Al materials in DIN 1732 Part 1(BS 2901 part 4)

Copper and copper alloysin DIN 1733 (BS 2901 part 3)

Nickel and nickel alloysin DIN 1736 (BS 2901 part 5)

The hotter arc in VARIGON He andVARIGONHe S mixtures has provenespecially suitable for aluminium andcopper materials with their high thermalconductivity.

Argon: 20 l/min 280 A / 25 V

VARIGON He 30: 20 l/min 282 A / 27 V



Shielding Gases

for MIG Welding of Non-Ferrous Metals

Helium alters the weld contour, shape of penetration and welding voltage


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Application Noteson Helium

Arc voltageFor a given arc length, a higher arc

voltage is required as the helium contentincreases.

Form of penetrationA rise in helium content leads to a

wider and therefore flatter weld. The pe-netration is no longer finger-shapedaswhen argon is used, but becomes morerounded and deeper.

The better penetration behaviour faci-litates good root fusion and permitshigher travel speeds.

Helium is significantly lighter than air.

This fact must be considered whenmeasuring the flow rate (correctionfactor) and also when specifying the mi-nimum flow rate. Helium improves thedegassing conditions of the weld pooland reduces porosity. Higher gas pricescan often be offset by reduced costs forpost-weld machining.

MIG welding of Al materials with Argon or Ar-He mixtures

Shielding gas Correction factor Minimum

multiply flow meter flow rate

reading by

VARIGON He 30

VARIGON He 30 S1.14 18 l/min

VARIGON He 50 1.35 28 l/min

VARIGON He 70 1.75 35 l/min

100 % He 3.16 40 l/min

Correction Factors and Minimum Gas Flow Rates


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In contrast to MIG and MAG, whichare gas metal-arc processes, in TIGwelding the arc burns between a non-consumable tungsten electrode and thework. Inert gases, such as argon or he-

lium, or mixtures of these with non-oxidising components are used to pro-tect the tungsten electrode and the weldpool.

TIG welding can be used with allfusion-weldable metals. The section ofcurrent type, polarity and shielding gasdepends on the base material.

Application Notes

Higher helium levels in argon-heliummixtures promote heat evolution in thearc and permit higher travel speeds.

Hydrogen can also be used to im-prove the energy balance of the TIG arc,but only with high-alloy CrNi steels,nickel and nickel base alloys. Up to 10 %hydrogen in argon improves penetrationand travel speed. Gases containing hy-drogen must never be used for weldingaluminium materials (increased porosity)or reactive steels.

Shielding gases of higher purity arerecommended for the welding of reactivematerials such as titanium or tantalum.

The 4.8 quality is therefore used for

these metals (versus 4.6 for other ma-terials) with a purity of 99.998.

Shielding Gases

for TIG Welding

Shielding gas Materials Remarks

Argon All weldable metals Used most frequently

Root protection required

for reactive materials

VARIGON S Al and Al alloys Increased arc stability

VARIGON He 30 S and arc starting reliability

in AC welding

VARIGON He 30 Hotter arc results in

VARIGON He 50Al and Al alloys

better penetration

VARIGON He 70Cu and Cu alloys

higher travel speed

VARIGON He 90

Helium Arc starting difficulties

with old power sources possible

use argon for ignition

VARIGON H 2 Hotter arc results in

VARIGON H 5 High-alloy CrNi steels better penetration

VARIGON H 6 higher travel speed

VARIGON H 10Ni and Ni base alloys To avoid porosity

CRONIWIG N Full austenites Control of the

Duplex and austenite/ferrite ratio

Super duplex steels

Materials Current typeand polarity

Unalloyed and alloyed steels

Copper und Cu alloysNickel and Ni alloys dc ( )

Titanium and Ti alloys

Zirkonium, tantalum, Tungsten

Aluminium ac

and Al alloys dc ( )

Magnesium with helium

and Mg alloys and VARIGON He 90

Magnesium acand Mg alloys

Shielding gases and materials

TIG-welded container connections Materials, current type and polarity


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Argon VARIGON He 5010 l/min 15 l/min

Travel speed: 10 cm/min 20 cm/min

A higher level of helium leads to higher travel speeds.This photograph shows welds in a 3 mm thick AlZn 4.5 Mg 1 alloy

Argon VARIGON H 6

Travel speed: 7 cm/min 11 cm/min

Fillet weld in material 1.4301

Penetration and travel speed improve considerably with increased hydrogen


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Protection of the weld root is oftenneeded in order to ensure optimal corro-sion resistance of the part. Oxidationand tints are prevented by excluding at-mospheric oxygen.

Two methods can be used:

Displacement of air by inert gasessuch as argon or by quasi-inert gasessuch as nitrogen

Displacement of air plus utilisation ofthe reducing action of hydrogen

For this reason, most forming gasesconsist of

Nitrogen with hydrogen additions Argon with hydrogen additions

Pure argon, on the other hand, isonly used rarely, for example with steelsreacting with hydrogen.

Proper use of forming gases requiresthat their relative densities are taken intoaccount, e.g. when purging containersfrom below (use high-density gases) orabove (use low-density gases).

Oxidation Prevention

Using Forming Gases

24

1.4

20161284

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

Relative Densities of Forming Gases

% by vol. H2

Heavierthanair

Lighterthanair

Air

Ar mixtures

N2 mixtures

Safety Notes:

Gases containing more than ca. 10 % hydrogen can form explosive mixtures with air.

Safety measures should be taken to avoid explosions.

For safety reasons, the DVS safety sheet 0937 recommends burning off hydrogen at H2 levels

higher than 10 vol.%.


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Application Notes

Gases should comply with thefollowing EN 439 groups: Group R (Ar/H2 mixtures)

Group I (Ar + Ar/He mixtures) and Group F (N2 + N2/H2 mixtures)

In order to positively prevent oxida-tion tints, the forming gas feed mustcontinue until the part has cooled toapprox. 220 C.

Preventing oxidation in the welding ofpipe requires pre-purging for a time thatdepends on the purge gas flow rate andthe geometry of the part.

To prevent oxidation when weldingpipes, air must be eliminated by purging

before starting to weld. A guideline forthe required volume of shielding gas is2.5 3.0 times the geometric volume ofthe pipe from the injection point to theweld. The flow rate should be approx.5 to 12 l/min, depending on the diameterof the pipe.

In titanium-stabilised CrNi steels,forming gases containing N2 cause ayellow coloration of the weld root. Forbase materials containing N2, e.g. superduplex steels, forming gases containinghigh N2-percentages (up to 100 %), e.g.to improve corrosion resistance arc of

benefit.

No coloration: titanium-stabilised CrNi

steel with argon/hydrogen forming

Typical yellow coloration: titanium-sta-

bilised CrNi steel with nitrogen forming

Forming gas Base material

Argon All materials

Ar/H2 mixtures Austenitic steels,

Ni and Ni base materials

N2/H2 mixtures Steels with the exception

of high-strength fine-grain

structural steel, austenitic

steel (not Ti-stabilised)

N2 Austenitic CrNi steels,

Ar/N2 mixtures duplex- and

super duplex steels

Root protection gases

for various materials

Welding with forming gas


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As in TIG welding, the arc in plasmawelding is formed between a non-consu-mable tungsten electrode and the workpiece. However, in contrast to TIG wel-ding, the plasma arc is constricted by

the torch design (water-cooled coppertip), resulting in a significantly higher po-wer density.

There are three variants of theplasma-arc welding process:

Microplasma welding for thin andvery thin sheet (minimum thicknessapprox. 0.1 mm at minimum currentapprox. 0.3 A)

Melt-in welding for thicknessesof 1 - 3 mm

Keyhole plasma-arc welding forthicker sections, up to approx. 8 mmin one run or thicker work in multipleruns

Plasma-arc welding always involvestwo gases:

Plasma gases, chiefly argon,sometimes with hydrogenor helium additions

Shielding gases which may haveother constituents added to theargon, for example hydrogen for

welding CrNi steel and Ni alloys,or helium for welding aluminium,

Al alloys, titanium and copper basealloys.

Other plasma techniques includeplasma-arc powder (PTA) surfacing forthe application of refractory alloy coat-ings, plasma hot-wire surfacing, andplasma/MIG welding for high-per-formance joining.

Shielding Gases

for Plasma-Arc Welding

Plasma-arc welding of spiral aluminium pipes

Plasma-arc welding of galvanised structural steel


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Recent investigations have shownthat the quality of arc stud welding usingthe methods BH 10 and BH 100 can beimproved significantly with the appro-priate choice of shielding gases.

The combinations of shielding gasesand materials shown in the table on theright have proven well in workshop testsand in the field.

By avoiding the use of ceramic rings,shielding gases are particularly advan-tageous for fully mechanised welding, in-cluding welding with industrial robots.

Base material Stud material Shielding gas

Structural steel Structural steel CORGON

18High-alloy steel High-alloy steel CORGON 18

AlMg 3 Al 99.5 or AlMg 3 VARIGON He 30

Shielding Gases

for Arc Stud Welding

Combinations of Shielding Gases and Materials

Steel and aluminium studs welded using

shielding gas


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Compared to conventional weldingtechniques (MAG, TIG etc.), laser beamwelding is characterised by more con-centrated heat input, lower distortionand higher processing speeds. For many

applications, laser beam welding doesnot require filler materials, although thismay be necessary for gap bridging or formetallurgical reasons. Laser beam weld-ing can be used e.g. for steel, light me-tals and thermoplastic materials.

Two different laser types are com-monly used for laser beam welding: TheCO2 laser and the Nd:YAG laser. Bothlaser types require the use of shieldinggases to obtain high-quality welds.

Shielding Gases

for Laser Beam Welding

CO2 Laser

The CO2 laser is the most commontype of laser used for welding by the carmanufacturing industry and its compo-

nent suppliers. The correct choice ofshielding gas is very important to ensurehigh quality welds. Due to its interactionwith the laser beam, the shielding gashas a major influence on the heat inputto the work piece. If a particular laserbeam intensity is exceeded on the sur-face of the work, this causes a thermally-induced plasma which affects the pene-tration depth in combination with otherfactors. Due to its high ionisation energy,especially helium in LASPUR qualitygives excellent results. However, othershielding gases can also be used, suchas argon, nitrogen and various gas mix-

tures such as VARIGON He 50.

N2

He

Ar

5

605040302010

4

3

2

1

0

Laser performance:

P = 2 kW

Focus radius:

rF = 100 m

Material: St 52-3

Shielding gas flow: 20 l m-1

Travel speed v [mm s-1]

Penetration

depth

d[m

m]

Influence of shielding gas on penetration

depth and travel speed.

Laser beam welding and cutting machine

at the Linde Technology Centre Cam welded with a CO2laser


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Argon Helium

Nd:YAG laserThe main welding application for the

Nd:YAG laser is in precision engineeringfor the electrical/electronics industry. Afew applications can also be found in thecar manufacturing industry. Laser powersgenerally do not exceed 2 kW. Since thewavelength of the Nd:YAG laser exhibitslittle or no interaction with shielding gas-es, their choice only needs to takeaccount of metallurgical factors.Accordingly, argon in LASPURquality iscommonly used, although helium, nitro-gen and gas mixtures are also suitable.

Plasma development and penetration behaviour of a CO2laser with different shielding gases.

Case of a heart pacemaker Photo: Lumonics

welded with a Nd:YAG laser


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Special Publications

92 Effect of Welding Conditions onAirborne Contaminants Generatedin Gas-Shielded Arc Welding, and

Effect of the Workplace Con-ditions

101 MAGM Welding Stainless Steel -Effect of Type of Shielding Gas

105 Demands on Welding Systemsand Manipulating EquipmentDesign in Fully Mechanised andAutomated MAG Welding

145 Shielding Gases and ProcessTechnology in Welding with High-Alloy Cored Wire

146 MAGM Welding (GMAW) ofCorrosion-Resistant Duplex Steel- 22 Cr 5 (9) Ni 3 MoEffect of Shielding Gasesand Process Variations

156 Application Technology Criteria forOrbital TIG (GTA) Welding ofElectropolished High-Alloy SteelTubes

158 Shielding Gas for Welding andBackup purging - Factors to BeTaken into Account

03/90 Control of the Arc WeldingProcess in Manufacturing

22/93 Gas-Shielded Arc Welding ofAluminium

34/97 Pulsed MAGM Welding of NickelAlloys

36/97 High-performance MAG Weldingwith the LINFAST Concept

38/97 TIG Welding of Aluminium Alloys

Brochures

Centralised Gas Supply Systems

LASPUR Gases for Laser Technology

LASPUR Guide for Laser UsersGases and Supply System

Acetylen there is no better fuel gasfor oxy-fuel gas processes

Heat Treatmentwith Linde Supplied Gases

Storage Tanks

Data Sheets

Safety Data Sheets (on request)

Safety instructions (on request)

Linde Publications,

Application Notes and Training Materials

26


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Competence Where You

Need It With Linde Gases

Linde AG

Industrial Gases Division

Seitnerstrae 70

82049 Hllriegelskreuth

Telefon (0 89) 74 46 -0

Telefax (0 89) 74 46 -12 30

http://www.Linde.de/Linde-Gas

8767/00

598.0998-2.2ma

Printedonchlorine-freebleeche

dpaper

Linde industrial gases are used for welding,

freezing or driving purposes, and where

heating, industrial cleaning, artificial respiration

or testing is required. They improve the quality

of life, helping you to produce more econom-

ically and thus safeguarding your future.

We offer advice, know-how, customer-specific

hardware, and carry out tests for our customers

and do all the gas-related handling.

It goes without saying that we tailor-make an

economic supply-concept according to cus-

tomer specifications: Gas cylinders and cylin-

der bundles, tank supply of cryogenic liquid

gases, the ECOVAR supply concept and

pipeline supply.

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and supply

equipment

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advice

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Linde - Shielding Gasses

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