Tig Welding Booklet

WELDWELL NEW ZEALANDPrivate Bag 6025NAPIERTelephone (06) 834-1600Fax (06) 835-4568

INTRODUCTIONOur business is welding and we offer this handbook to both the handyman and industry in general, in an earnest endeavour to assist all those engaged in TIG welding.

We have not covered all phases of welding, but present briefly, the basic facts of the TIG welding process and techniques.

LIST OF CONTENTS Page NoHistory of TIG 2 TIG Overview 3Power Sources 4Types of Welding Current used for TIG 5Characteristics of Current Types for Gas Tungsten Arc Welding 7TIG Handpiece (TIG Torch) 9Selecting the Correct Torch Nozzle 10Gas Lens Benefits 10

Regulators 11Connection Diagrams 12Tungsten Selection and Preparation 13Tungsten Colour Code and Proper Torch Use 14TIG Wires 15Shielding Gas 16Shield Gas Selection and Use 17Typical Manual GTA (TIG Welding Parameters) 18Guide for Shield Gas Flows, Current Settings and Cup Selection 20Correct Torch and Rod Positioning 20Pulsed TIG 21Personal Protection 22Recognising Your Tungsten 23Operator Inspection for Weld Quality 24TIG Troubleshooting Guide 25

Branches and Outlets throughout New ZealandCheck your Yellow pages

or www.weldwell.co.nz1

HISTORY OF GTAW (TIG WELDING)TIG welding was, like MIG/MAG developed during 1940 at the start of the Second World War.

TIGs development came about to help in the welding of difficult types of material, eg aluminium and magnesium. The use of TIG today has spread to a variety of metals like stainless mild and high tensile steels.

GTAW is most commonly called TIG (Tungsten Inert Gas).

The development of TIG welding has added a lot in the ability to make products, that before the 1940s were only thought of.

Like other forms of welding, TIG power sources have, over the years, gone from basic transformer types to the highly electronic power source of the world today.

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OVERVIEWTIG welding is a welding process that uses a power source, a shielding gas and a TIG handpiece. The power is fed out of the power source, down the TIG handpiece and is delivered to a tungsten electrode which is fitted into the handpiece. An electric arc is then created between the tungsten electrode and the workpiece. The tungsten and the welding zone is protected from the surrounding air by a gas shield (inert gas). The electric arc can produce temperatures of up to 19,400oC and this heat can be very focused local heat.

The weldpool can be used to join the base metal with or without filler material.

The TIG process has the advantages of - 1) Narrow concentrated arc 2) Able to weld ferrous and non-ferrous metals 3) Does not use flux or leave a slag 4) Uses a shielding gas to protect the weldpool and tungsten 5) A TIG weld should have no spatter 6) TIG produces no fumes but can produce ozone

The TIG process is a highly controllable process that leaves a clean weld which usually needs little or no finishing. TIG welding can be used for both manual and automatic operations.

The TIG welding process is so good that it is wisely used in the so-called high-tech industry applications such as 1) Nuclear industry 2) Aircraft 3) Food industry 4) Maintenance and repair work 5) Some manufacturing areas

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POWER SOURCESTIG welding power sources have come a long way from the basic transformer types of power sources which were used with add-on units to enable the power source to be used as a TIG unit, eg high frequency unit and/or DC rectifying units,

The basics of TIG welding has almost remained the same, but the advent of technology TIG welding power sources have made the TIG processes more controllable and more portable in some cases.

The TIG power source uses main power connected to a suitable power for the TIG process being used. This can be either AC or DC.

The one thing that all TIGs have in common is that they are CC (Constant Current) type power sources. This means only output adjustment will control the power source amps. The voltage will be up or down depending on the resistance of the welding arc.

A TIG power source can be of the AC or DC type. The principle of electric circuits will apply to only DC power sources. This means 70% of the heat is always on the positive side. So when a DC power source is used whatever is connected to the positive side will have 70% of the energy output (heat). When using an AC power source, which has an output of a wave form, the average on both terminals will be the same. This is because for one half of the wave form (cycle) the positive terminal will have 70% of the energy, but as the wave form moves to the other half of the cycle it will move to the negative terminal, which will then have the 70% of the energy.

Other things to check on TIG power sources are - 1) Amperage to do the job. Will it be sufficient? 2) Does the amperage go low enough for light material and high enough

for thick material? 3) Power Supply - 400 Volt, 230 Volt - single or three phase. Is there

enough main power to do the job? 4) Is weight a problem? If so, is the inverter type power source more

suitable. 5) Will an engine driven power source be better to do the job? (Must

have CC range). Might need suitable extra add-ons to do the eg, HF unit.

6) Would a multi-process type power source be better to do the job? Must have CC range.

7) Does the TIG welding need an AC power source or DC power source, as different material will need a different power type.

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TYPES OF WELDING CURRENT USED FOR TIG1) DCSP - Direct Current Straight Polarity - (the tungsten electrode is

connected to the negative terminal). This type of connection is the most widely used in the DC type welding current connections. With the tungsten being connected to the negative terminal it will only receive 30% of the welding energy (heat). This means the tungsten will run a lot cooler than DCRP. The resulting weld will have good penetration and a narrow profile.

2) DCRP - Direct Current Reverse Polarity - (the tungsten electrode is connected to the positive terminal). This type of connection is used very rarely because most heat is on the tungsten, thus the tungsten can easily overheat and burn away. DCRP produces a shallow, wide profile and is mainly used on very light material at low amps.

3) AC - Alternating Current is the preferred welding current for most white metals, eg aluminium and magnesium. The heat input to the tungsten is averaged out as the AC wave passes from one side of the wave to the other.

On the half cycle, where the tungsten is positive electron welding current will flow from base material to the tungsten. This will result in the lifting of any oxide skin on the base material. This side of the wave form is called the cleaning half. As the wave moves to the point where the tungsten becomes negative the electrons (welding current) will flow from the welding tungsten to the base material. This side of the cycle is called the penetration half of the AC wave form.

Because the AC cycle passes through a zero point the arc goes out. This can be seen with fast film photography. At this point the arc would stay out if it wasnt for the introduction of HF (high frequency). High frequency has very little to do with the welding process; its job is the re-ignition of the welding current as it passes through zero. (How good the HF is will often have a bearing on how well the re-ignition of the arc is.) HF is also often used for starting the welding arc initially without the tungsten touching the workpiece. This helps on materials that are sensitive to impurities. HF start can also be used on DC welding current to initially start the welding current without the tungsten touching the workpiece.

It is a common misunderstanding that the HF does the cleaning action. This is not the case, it only serves to re-ignite the welding arc.

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4) AC - Alternating Current - Square Wave

+

-

With the advent of modern electricity AC welding machines can now be produced with a wave form called Square Wave. The square wave has the benefit of a lot more control and each side of the wave can be, in some cases, controlled to give a more cleaning half of the welding cycle, or more penetration.

Once the welding current gets above a certain amperage (often depends on the machine) the HF can be turned off, allowing the welding to be carried on with the HF interfering with anything in the surrounding area.

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CHARACTERISTICS OF CURRENT TYPES FOR GAS TUNGSTEN ARC WELDINGWhen TIG welding, there are three choices of welding current. They are: Direct Current Straight Polarity, Direct Current Reverse Polarity, and Alternating Current with High Frequency stabilisation. Each of these has its applications, advantages, and disadvantages. A look at each type and its uses will help the operator select the best current type for the job. The type of current used will have a great effect on the penetration pattern as well as the bead configuration. The diagrams below, show arc characteristics of each current polarity type.

CURRENT TYPE DCSP

Electrode Polarity Electrode Negative

Oxide Cleaning Action No

Heat Balance in the Arc 70% at work end30% at electrode end

Penetration Profile Deep, narrow

Electrode Capacity Excellent

CURRENT TYPE DCRPElectrode Polarity Electrode Positive

Oxide Cleaning Action Yes


Penetration Profile Shallow, wide

Electrode Capacity Poor

TIG welding with DCSP (direct current straight polarity) produces deep penetration because it concentrates the heat in the joint area. No cleaning action occurs with this polarity.

TIG welding with DCRP (direct current reverse polarity) produces good cleaning action as the argon ions flowing towards the work strike with sufficient force to break up oxides on the surface.

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DC TIGPOWER SUPPLY

DC TIGPOWER SUPPLY

CURRENT TYPE ACHFElectrode Polarity Alternating

Oxide Cleaning Action Yes (once every half cycle)


Penetration Profile Medium

Electrode Capacity Good

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AC TIGPOWER SUPPLY

TIG HANDPIECE (TIG TORCH)The function of the TIG handpiece is to 1) hold the electrode tungsten 2 deliver welding current to the tungsten via a welding power cable 3) deliver shielding gas to the TIG torch nozzle. The nozzle then directs

the shielding gas to cover the weldpool protecting it from contamination from the surrounding air.

4) often will be the way of getting the welder control circuit to the operation, eg on/off and/or amperage control.

5) the TIG handpiece can be watercooled. Hoses in the TIG lead will supply cooling water to the TIG torch head assembly.

6) the TIG torch length will allow a distance from the TIG power source and workpiece.

TIG torches come in different styles depending on the brand being selected. But they all have things in common - 1) aircooled or watercooled 2) current rating. The operator must select the correct amperage rating

TIG torch.Using a TIG torch that is not sufficiently rated for the machine may result in the TIG torch overheating. A TIG torch wiith an excessive rating may be larger and heavier than a lower amperage TIG torch.

The TIG torch is made up of

1) Leads - The lead will be set up for either aircooled or watercooled. It will be at a length suitable to do the job, eg 4 metre, 8 metre, etc. The lead will be made up of a power cable, gas hose and water leads in and out if the TIG torch is watercooled. The lead may also include a control lead.

2) Tungsten Holders - Holders may vary with different brands of TIG torches.

3) Nozzles - The nozzles job is to direct the correct gas flow over the weldpool. (Please see Selecting the Correct Torch Nozzle, page 10.)

4) Back Caps - The back cap is the storage area for excess tungsten. They can come in different lengths depending on the space the torch may have to get into (eg. long, medium and short caps).

Please make sure when ordering a TIG torch to tell the supplier the amperage rating, whether water- or air-cooled, and the fitting that is to go on the end of the TIG torch lead suitable to fit the TIG power source it will be used from. This may include power cable fit up, gas fittings and control plug fittings.

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SELECTING THE CORRECT TORCH NOZZLE

Design diameterto fit

GTAW torch

Exit diameter

measuredin 1.6 mm

The exit diameter (diameter closest to the arc) is manufactured in a variety of sizes. GTAW nozzles are also made in various lengths from short nozzles to extra-long nozzles.

Alumina nozzles, are the most commonly used nozzles in GTAW. Alumina nozzles are moulded from alumina oxide and the density of the alumina oxide determines the quality of the nozzle in relationship to impact resistance and thermal sock. Alumina nozzles are more impact resistant than lava nozzles. The impact resistance of the alumina nozzles makes them more durable and are used for general applications.

The exit diameter for any nozzle is specified with a number that represents the diameter in 1.6 mm increments. A number 5 nozzle is therefore 8 mm diameter. A number 6 nozzle is 9.6 mm and so on.

The diameter for any nozzle must be large enough to allow the entire weld area to be covered by the shielding gas. The exist diameter can be neither too large nor too small, or poor shield gas coverage will result. (Refer to page ? for correct cup size.)

GAS LENS BENEFITS

A collet body with a gas lens can be very useful to a welder. The purpose of a gas lens is to make the shielding gas exist the nozzle as a column instead of as a turbulent stream of gas that begins to spread out after exiting. The column of gas allows the electrode to stick out farther for visibility, allowing for better access to the weld area, and a reduction in gas flow (CFH/L/Min.)

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REGULATORSThe function of the gas regulator is to reduce bottle pressure gas down to a lower pressure and deliver it at a constant flow. This constant flow of gas flows down through the TIG torch lead to the TIG torch nozzle and around the weldpool.

There are three main styles of regulator used for TIG

One made up with a single flow tube assembly (Fig. 1).

Another made up with a twin-flow tubes assembly (Fig. 3) (this set-up is excellent for when purging is necessary).

The third style does not have a flow tube and the flow is set by turning a handwheel (Fig. 2). The amount of gas flow needed to do the job will depend on the welding job being done and the type of material being welded. But a common setting to start with is 5 L/min.

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Fig. 1Fig. 3

Fig. 2

CONNECTION DIAGRAMS

FOR GAS COOLED TORCHES

FOR WATER COOLED TORCHES

2 piece Cable Assembly

PowerSource

Shieldgas

supply

TIGTorch

Waterout

Power Source

Power cable adaptor required

CoolantRecirculator

WATER INARGON IN

Regulator-Flowmeter

Shieldgas

supply

Note: 1 litre per minute flow rate. Water in through water line. Water out through power cable.

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Base Metal Type

Thickness Range

DesiredResults

Welding Current Electrode Type Shield Gas

Tungsten Performance Characteristics

Aluminium

Alloys and

Magnesium

Alloys

All General Purpose AC/HF

Pure (EW-P) ArgonBalls easily, low cost, tends to spit at higher currents, used for non-critical welds only.

Zirconiated(EW-Zr) Argon

Balls well, takes higher current, with less spitting and with better arc starts and arc stability than pure tungsten.

2% Thoriated(EW-Th2)

75 Argon25 Helium

Higher current range and stability, better arc starts, with lower tendency to spit, medium erosion.

Only thin sections

Control penetration DCRP

2% Ceriated(EW-Ce2)

ArgonHelium

Lowest erosion rate, widest current range, AC or DC, no spitting, best arc starts and stability.

Only thick

sections

Increase penetration

or travel speed

DCSP


75 Argon25 Helium

Best stability at medium currents, good arc starts, medium tendency to spit, medium erosion rate.

2% Ceriated(EW-Ce2) Helium

Low erosion rate, wide current range, AC or DC, no spitting, consistent arc starts, good stability.

Copper

Alloys,

Cu-Ni

Alloys

and Nickel

Alloys

All General Purpose DCSP


75 Argon25 Helium


2% Ceriated(EW-Ce2)

75 Argon25 Helium


Only thin sections

Control penetration ACHF


Use on lower currents only, spitting on starts, rapid erosion rates at higher currents.

Only thick

sections


or travel speed

DCSP 2% Ceriated(EW-Ce2)75 Argon25 Helium


Mild

Steels,

Carbon

Steels,

Alloy

Steels and

Titanium

Alloys

All General Purpose DCSP


75 Argon25 Helium


2% Ceriated(EW-Ce2)

75 Argon25 Helium


2% Lanthanated(EWG-La2)

75 Argon25 Helium

Lowest erosion rate, wide current range on DC, no spitting, best DC arc starts and stability.

Only thin sections

Control penetration ACHF


Use on lower currents only, spitting on starts, rapid erosion rates at higher currents.

Only thick

sections


or travel speed

DCSP

2% Ceriated(EW-Ce2)

75 Argon25 Helium

Low erosion rate, wide current range, no spitting, consistent arc starts, good stability.

2% Lanthanated(EWG-La2) Helium

Lowest erosion rate, highest current range, no spitting, best DC arc starts and stability.

TUNGSTEN SELECTION AND PREPARATION

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COLOUR CODE AND ALLOYING ELEMENTS FOR VARIOUS TUNGSTEN ELECTRODE ALLOYS

AWSClassifications Colour*

AlloyingElement

Alloying Oxide

Nominal Weight of Alloying Oxide Percent

EWP Green - - -

EWCe-2 Orange Cerium CeO2 2

EWLa-1 Black Lanthanum La2O3 1

EWTh-1 Yellow Thorium ThO2 1

EWTh-2 Red Thorium ThO2 2

EWZr-1 Brown Zirconium ZrO2 .25

EWG Grey Not Specified** - -

* Colour may be applied in the form of bands, dots, etc, at any point on the surface of the electrode.** Manufacturers must identify the type and nominal content of the rare earth oxide additions.

TUNGSTEN COLOUR CODE AND PROPER TORCH USE

TUNGSTEN TIP PREPARATIONDCSP (EN) or DCRP (EP)

Flat: 1/4 to 1/2 x dia2-3 diaTaper Length

ACHFGeneral Purpose

Max.ball1 x dia

Ball tip by arcing on clean metal at low current DCRP (EP) then slowly increase current to form the desired ball diameter. Return setting to AC.

TUNGSTEN EXTENSIONStandard Parts

GeneralPurpose3 x dia.

Shape by grinding longitudinally (never radially). Remove the sharp point to leave a truncated point with a flat spot. Diameter of flat spot determines amperage capacity. (See below.)

The included angle determines weld bead shape and size. Generally, as the included angle increases, penetration increases and bead width decreases.

Use a medium (60 grit or finer) aluminium oxide wheel.

TUNGSTEN GRINDING

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TIG WIRESThe selection of the TIG wire to be used in the TIG process is a decision that will depend on

1) The composition of the material being welded

2) Mechanical properties of the weld material and those that are a match for the base material

3) Corrosion resistance should match

4) Joint design

5) Thickness of the base material

6) Cost

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SHIELDING GASLike other welding processes the job of the shielding gas is to protect the weld pool from contamination from air, which can cause porosity and defects in the weld. The shielding gas is a pathway for the welding arc and will help in the starting and running of the welding arc.In New Zealand the most common gas being used for TIG welding is Argon gas.

Overseas Helium is also being used and in days gone by in some countries the weld process was called Heliarc welding.

Each of these two gases has advantages.

Argon 1) Better arc starting 2) Good cleaning action 3) Lower arc voltage 4) Low gas flows needed

Helium 1) Faster travel 2) Better penetration 3) Higher arc voltages

Because of the cost of Helium we are now seeing mixtures of Argon and Helium. This is to gain the best part of each gas. Please see your local gas

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SHIELD GAS SELECTION AND USE

Base Metal Type

ThicknessRange

Weld Type

Shield Gas Type

Characteristics

Aluminium

Alloys and

Magnesium

Alloys

Thin Manual Pure ArgonBest arc starts, control of penetration, cleaning and appearance on thin gauges.

Thick Manual 75 Ar - 25 HeIncrease heat input with good arc starts of argon, but with faster welding speeds.

General Purpose Manual Pure Argon

Best overall for good arc starts, control of penetration, cleaning and appearance.

Thin Mechanised 50 Ar - 50 He Higher weld speed under 20mm thick, with good arc stability and starting.

Thick Mechanised Pure HeliumHighest weld speeds, deeper penetration with DCSP, demanding arc starting and fixturing requirements, high flow rates needed.

Copper

Alloys

Cu-Ni Alloys

Nickel

Alloys

Thin Manual Pure ArgonGood control of weld puddle, bead contour, and penetration on thin gauges.


General Purpose Manual 75 Ar - 25 He

Increase heat input with good arc starts of argon, but with faster welding speeds.

Thin Mechanised 25 Ar - 75 He Higher weld speed under 20mm thick, with good arc stability and starting.

Thick Mechanised Pure HeliumHighest weld speeds, deeper penetration with DCSP, demanding arc starting and fixturing requirements, high flow rates needed.

Low Carbon

Alloys and

Low Alloy

Steels

Thin Manual Pure ArgonBest arc starts, control of penetration, cleaning and appearance on thin gauges.


General Purpose Manual Pure Argon

Best overall for good arc starts, control of penetration, cleaning and appearance.

Thin Mechanised Pure ArgonBest overall for good arc starts, control of penetration, cleaning and appearance.

Thick Mechanised 75 Ar 25 HeIncrease heat input with good arc starts of argon, but with faster welding speeds.

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TYPICAL MANUAL GTA (TIG) WELDING PARAMETERS

Metal Gauge

Joint Type

Tungsten size

Filler Rod Size

Cup Size

Shield Gas FlowWelding Amperes

Travel SpeedType CFH(L/Min) PSI

1.6 mmButt

1.6 mm 1.6 mm 4, 5, 6 Argon 15 (7) 2060-80 307 mm

Fillet 70-90 256 mm

3.2 mmButt

2.4 mm2.4 mm

6, 7 Argon 17 (8) 20125-145 307 mm

Fillet 3.2 mm 140-160 256 mm

4.8 mmButt

3.2 mm 3.2 mm 7, 8 Argon/Helium 21 (10) 20190-220 258 mm

Fillet 210-240 230 mm

6.4 mmButt

4.8 mm 3.2 mm 8, 10 Argon/Helium 25 (12) 20260-300 256 mm

Fillet 280-320 205 mm

WELDING ALUMINIUMThe use of TIG welding for aluminium has many advantages for both manual and automatic processes. Filler metal can be either wire or rod and should be compatible with the base alloy. Filler metal must be dry, free of oxides, grease, or other foreign matter. If filler metal becomes damp, heat for 2 hours at 120oC before using. Although ACHF is recommended, DCRP has been successful up to 2.4mm, DCSP with helium shield gas is successful in mechanised applications.

ALUMINIUM (ACHF)

Metal Gauge

Joint Type

Tungsten size

Filler Rod Size

Cup Size



1.6 mmButt

1.6 mm 2.4 mm3.2 mm 5, 6 Argon 13 (5) 1560

512 mmFillet 60

3.2 mmButt

2.4 mm 3.2 mm4.0 mm 7, 8 Argon 19 (9) 15115

435 mmFillet 115

6.4 mmButt

4.8mm 4.0 mm 8 Argon 25 (12) 15100-130 563 mm

Butt(2) 110-135 512 mm

12.8 mm Butt(2) 6.4 mm 4.8 mm 10 Argon 35 (17) 15 260 256 mm

WELDING MAGNESIUMMagnesium alloys are in three groups, they are (1) aluminium-zinc-magnesium, (2) aluminium-magnesium, and (3) maganese-magnesium. Since magnesium absorbs a number of harmful ingredients and oxidize rapidly when subjected to welding heat, TIG welding in an inert gas atmosphere is distinctly advantageous, the welding of magnesium is similar, in many respects, to the welding of aluminium. Magnesium was one of the first metals to be welded commercially by TIG. Magnesium requires a positive pressure of argon as a backup on the root side of the weld.

MAGNESIUM (ACHF)

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Metal Gauge

Joint Type

Tungsten size

Filler Rod Size

Cup Size



1.6 mmButt

1.6 mm 1.6 mm 4, 5, 6 Argon 11 (5.5) 2080-100 307mm

Fillet 90-100 256 mm

3.2 mmButt

1.6 mm 2.4 mm 4, 5, 6 Argon 11 (5.5) 20120-140 307 mm

Fillet 130-150 256 mm

4.8 mmButt 2.4 mm

3.2 mm 5, 6, 7 Argon 13 (6) 20200-250 307 mm

Fillet 2.4 mm3.2 mm 225-275 256 mm

6.4 mmButt

3.2 mm 4.8 mm 8, 10 Argon 13 (6) 20275-350 256 mm

Fillet 300-375 205 mm

WELDING STAINLESS STEELIn TIG welding of stainless steel, welding rods having the AWS-ASTM prefixes of E or ER can be used as filler rods. However, only bare uncoated rods should be used. Stainless steel can be welded using ACHF, however, recommendations for DCSP must be increased 25%. Light gauge metals less than 1.6 mm thick should always be welded with DCSP using argon gas. Follow the normal precautions for welding stainless such as: Clean surfaces; dry electrodes; use only stainless steel tools and brushes, carefully remove soap from welds after pressure testing; keep stainless from coming in contact with other metals.

STAINLESS STEEL (DCSP)

Metal Gauge

Joint Type

Tungsten size

Filler Rod Size

Cup Size



1.6 mmButt

1.6 mm 1.6 mm 4, 5, 6 Argon 15 (7) 2095-135 384 mm

Fillet 95-135 384 mm

3.2 mmButt 1.6 mm

2.4 mm 2.4 mm 4, 5, 6 Argon 15 (7) 20145-205 282 mm

Fillet 145-205 282 mm

4.8 mmButt

2.4 mm 3.2 mm 7, 8 Argon 16 (6.5) 20210-260 256 mm

Fillet 210-260 256 mm

6.4 mmButt

3.2 mm 4.0 mm 8, 10 Argon 18 (8.5) 20240-300 256 mm

Fillet (2) 240-300 256 mm

WELDING LOW ALLOY STEELMild and low carbon steels with less than 0.30% carbon and less than 25 mm thick, generally do not require preheat. An exception to this allowance is welding on highly restrained joints. These joints should be preheated 10 to 38oC to minimise shrinkage cracks in the base metal. Low alloy steels such as the chromium-molybdenum steels will have hard heat affected zones after welding, if the preheat temperature is too low. This is caused by rapid cooling of the base material and the formation of martensitic grain structures. A 90 to 200oC preheat temperature will slow the cooling rate and prevent the martensitic structure.

LOW ALLOY STEEL (DCSP)

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GUIDE FOR SHIELD GAS FLOWS, CURRENT SETTINGS AND CUP SELECTION

ElectrodeDiameter

(mm)Cup Size

Welding Current (Amps)

- Tungsten Type

Argon Flow- Ferrous Metals

Argon Flow- Aluminium

ACZirconiated

DCSPThoriated

StandardBody

CFH (L/min)

Gas LensBody

CFH (L/min)

StandardBody

CFH (L/min)

Gas LensBody

CFH (L/min)

0.50 3, 4 or 5 5 - 20 5 - 20 5-8 (3-4) 5-8 (3-4) 5-8 (3-4) 5-8 (3-4)

1.00 4 or 5 15 - 80 20 - 80 5-10 (3-5) 5-8 (3-4) 5-12 (3-6) 5-10 (3-5)

1.60 4, 5 or 6 70 - 150 50 - 150 7-12 (4-6) 5-10 (3-5) 8-15 (4-7) 7-12 (4-6)

2.40 6, 7 or 8 140 - 235 135 - 235 10-15 (5-7) 8-10 (4-5) 10-20 (5-10) 10-15 (5-7)

3.20 7, 8 or 10 220 - 325 240 - 350 10-18 (5-9) 8-12 (4-6) 12-25 (6-12) 10-20 (5-10)

4.00 8 or 10 300 - 425 350 - 500 15-27 (7-12) 10-15 (5-7) 15-30 (7-14) 12-25 (6-12)

4.80 8 or 10 400 - 525 475 - 800 20-35 (10-17) 12-25 (6-12) 25-40 (12-19) 15-30 (7-14)

6.40 10 500 - 700 700 - 1100 25-50 (12-24) 20-35 (10-17) 30-55 (14-26) 25-45 (12-21)

CORRECT TORCH AND ROD POSITIONING

The suggested electrode and welding rod angles for welding a bead on plate. The same angles are used when making a butt weld. The torch is held 60o - 75o from the metal surface. This is the same as holding the torch 15o - 30o from the vertical.Take special note that the rod is in the shielding gas during the welding process.

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Vertical

Tungsten Electrode

Welding Rod

15o - 30o

60o - 75oShield Gas

Direction of Travel

Nozzle

PULSED TIGPulsed TIG has the advantages of 1) better penetration with less heat 2) less distortion 3) better control when welding out of position 4) Easy to use on thin materialsThe down side is - more set-up cost and more operator training.

Pulsed TIG consists ofPeak Current - This is set up higher than for non-pulsed TIG.Background Current - This is set lower than peak current and is the bottom current the pulse will drop to, but must be enough to keep the arc alive.Pulses Per Second - This is the number of times per second that weld current reaches peak current.% on Time - This is the pulse peak duration as a percentage of the total time, which controls how long the peak current is on for before dropping to the background current.

Down Slope - This is the way and the time taken for the welding current to wind down at the end of the TIG weld. Down slope will help prevent the uneven cooling of the final weld pool and will help stop pinholes forming at the completion of a TIG weld.Post Flow - Post flow is the time taken for the shielding gas to stay on after the welding current has stopped. This time will 1) protect the end of the weld 2) protect the cooling down of the tungsten (the oxidation of the

tungsten).Pre-Flow - Preflow is used at the start of the welding process to help protect the start of the weld from contamination and to make sure the shielding gas is flowing before the welding current starts up.

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PERSONAL PROTECTION

Gloves

Skull Cap HelmetMask

JacketWelding helmet lens

TIG WELDING HAZARDS

1) Gases - Ozone is formed under the extreme temperature of the arc.

2) Heat

3) Ultra Violet Light - TIG produces one of the highest ratio of ultra violet light per amperage of any welding process.

4) Fumes - coming from the heating of the base material and the burning of any contaminates that might be present.

5) Magnetic fields may interfere with medical devices.

6) HF Radiation - can cause interference with other equipment, eg computers and communication equipment.

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Electrode A has the ball end. This pure tungsten was used with alternating current on aluminium. Notice the end is uniform in shape and possesses a shiny bright appearance.Electrode B is a 2% thoriated tungsten ground to a taper and was used with direct current straight polarity.Electrode C is a 2% thoriated tungsten which was used with alternating current on aluminium. Note that this electrode has several small ball shaped projections rather than a round complete ball end like the pure tungsten.Electrode D is a pure tungsten used with alternating current on aluminium. This electrode was subjected to a current above the rated capacity. Notice the ball started to droop to one side. It becomes very molten during operation and continuing to operate would have caused the molten end to drop into the weld puddle.Electrode E is a pure tungsten that was tapered to a point and used on direct current straight polarity. Notice the ball tip characteristic of the pure tungsten. Pointing of pure tungsten is not recommended as the extreme point will always melt when the arc is established. The electrode in this illustration melted back, however, often times the point may melt and drop into the weld puddle.Electrode F was severely contaminated by touching the filler rod to the tungsten. In this case the contaminated area must be broken off and the electrode reshaped as desired.Electrode G did not have sufficient gas post-flow. Notice the black surface which is oxidized because the atmosphere contacted the electrode before it cooled sufficiently. If this electrode were used the oxidized surface will flake off and drop into the weld puddle. Post-flow time should be increased so the appearance is like electrode A after welding.

A FB EDC G

RECOGNISING YOUR TUNGSTEN

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OPERATOR INSPECTION FOR WELD QUALITY

PROBLEM: Excessive build up Poor penetration Poor fusion at edges

CAUSE:Welding current too low

PROBLEM: Bead too wide and flat Poor penetration Excessive burn through

CAUSE:Welding current too high

PROBLEM: Bead too small Insufficient penetration Ripples widely spaced

CAUSE:Travel speed too fast

PROBLEM: Bead too wide Excessive build up Excessive penetration

CAUSE:Travel speed too slow

PROBLEM: Undercut Insufficient weld deposit Uneven penetration

CAUSE:Welding current too high and/or wrong placement of filler rod

PROBLEM: Poor penetration Poor fusion

CAUSE:Faulty joint preparation and too low welding current

PROBLEM: Proper build-up Good appearance good penetration Bead edges fused in

CAUSE:Correct technique and current setting

PROBLEM: No undercut Legs of fillet weld equal

to metal thickness Slightly convex bead face

CAUSE:Correct technique and current setting

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TIG TROUBLESHOOTING GUIDEProblem Cause Solution

ExcessiveElectrodeConsumption

1. Inadequate gas flow2. Improper size electrode for current required3. Operating of reverse polarity4. Electrode contamination5. Excessive heating inside torch6. Electrode oxidising during cooling7. Shield gas incorrect

1. Increase gas flow2. Use larger electrode3. Use larger electrode or change polarity4. Remove contaminated portion, then prepare again5. Replace collet, try wedge collet or reverse collet6. Increase gas post flow time to 1 sec. per 10 amps7. Change to proper gas (no oxygen or CO2)

ErraticArc

1. Incorrect voltage (arc too long)2. Current too low for electrode size3. Electrode contaminated4. Joint too narrow5. Contaminated shield gas, dark stains

on the electrode or weld bead indicate contamination

6. Base metal is oxidised, dirty or oily

1. Maintain short arc length2. Use smaller electrode or increase current3. Remove contaminated portion, then prepare again4. Open joint groove5. The most common cause is moisture or aspirated air

in gas stream. Use welding grade gas only. Find the source of the contamination and eliminate it promptly

6. Use appropriate chemical cleaners, wire brush, or abrasives prior to welding

Inclusion of Tungsten or Oxides in Weld

1. Poor scratch starting technique

2. Excessive current for tungsten size used3. Accidental contact of electrode with puddle4. Accidental contact of electrode to filler rod5. Using excessive electrode extension

6. Inadequate shielding or excessive draughts

7. Wrong gas

8. Heavy surface oxides not being removed

1. Many codes do not allow scratch starts. Use copper strike plate. Use high frequency arc starter

2. Reduce the current or use larger electrode3. Maintain proper arc length4. Maintain a distance between electrode and filler

metal5. Reduce the electrode extension to recommended

limits6. Increase gas flow, shield arc from wind, or use gas

lens7. Do not use ArO2 or ArCO2 GMA (MIG) gases for TIG

welding8. Use ACHF, adjust balance control for maximum

cleaning, or wire brush and clean the weld joint prior to welding.

Porosity in Weld Deposit

1. Entrapped impurities, hydrogen, air, nitrogen, water vapour

2. Defective gas hose or loose connection3. Filler material is damp (particularly

aluminium)4. Filler material is oily or dusty5. Alloy impurities in the base metal such as

sulphur, phosphorous, lead and zinc6. Excessive travel speed with rapid freezing

of weld trapping gases before they escape7. Contaminated shield gas

1. Do not weld on wet material. Remove condensation from line with adequate gas pre-flow time

2. Check hoses and connections for leaks3. Dry filler metal in oven prior to welding4. Replace filler metal5. Change to a different alloy composition which is

weldable. These impurities can cause a tendency to crack when hot

6. Lower the travel speed

7. Replace the shielding gas

Cracking in Welds

1. Hot cracking in heavy section or with metals which are hot shorts

2. Crater cracks due to improperly breaking the arc or terminating the weld at the joint edge

3. Post weld cold cracking, due to excessive joint restraint, rapid cooling, or hydrogen embrittlement

4. Centreline cracks in single pass welds

5. Underbead cracking from brittle microstructure

1. Preheat, increase weld bead cross-section size, change weld bead contour. Use metal with fewer alloy impurities

2. Reverse direction and weld back into previous weld at edge. Use Amptrak or foot control to manually down slope current

3. Preheat prior to welding, use pure or non-contaminated gas. Increase the bead size. Prevent craters or notches. Change the weld joint design

4. Increase bead size. Decrease root opening, use preheat, prevent craters

5. Eliminate sources of hydrogen, joint restraint, and use preheat 25

TIG TROUBLESHOOTING GUIDE (continued)Problem Cause Solution

InadequateShielding

1. Gas flow blockage or leak in hoses or torch2. Excessive travel speed exposes molten

weld to atmospheric contamination

3. Wind or draughts4. Excessive electrode stickout5. Excessive turbulence in gas stream

1. Locate and eliminate the blockage or leak2. Use slower travel speed or carefully increase the

flow rate to a safe level below creating excessive turbulence. Use a trailing shield cup

3. Set up screens around the weld area4. Reduce electrode stickout. Use a larger size cup5. Change to gas saver parts or gas lens parts

Arc Blow

1. Induced magnetic field from DC weld current

2. Arc is unstable due to magnetic influences

1. Change to ACHF current. Rearrange the split ground connection

2. Reduce weld current and use arc length as short as possible

Short Parts Life

1. Short water cooled leads life

2. Cup shattering or cracking in use

3. Short collet life

4. Short torch head life

5. Gas hoses ballooning, bursting, or blowing off while hot

1. Verify coolant flow direction, return flow must be on the power cable lead

2. Change cup size or type, change tungsten position, refer to chart

3. Ordinary style is split and twists or jams, change to wedge style

4. Do not operate beyond rated capacity, use water cooled model, do not bend rigid torches

5. I ncorrect flowmeter, TIG flowmeters operate at 35 psi with low flows. MIG flowmeters operate with high flows at 65 psi or more.

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Tig Welding Booklet

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Transcript of Tig Welding Booklet