WELDWELL NEW ZEALAND
Private Bag 6025
NAPIER
Telephone (06) 834-1600
Fax (06) 835-4568
INTRODUCTION
Our 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 No
History of TIG
2
TIG Overview
3
Power Sources
4
Types of Welding Current used for TIG
5
Characteristics of Current Types for Gas Tungsten Arc Welding
7
TIG Handpiece (TIG Torch)
9
Selecting the Correct Torch Nozzle
10
Gas Lens Benefits
10
Regulators
11
Connection Diagrams
12
Tungsten Selection and Preparation
13
Tungsten Colour Code and Proper Torch Use
14
TIG Wires
15
Shielding Gas
16
Shield Gas Selection and Use
17
Typical Manual GTA (TIG Welding Parameters)
18
Guide for Shield Gas Flows, Current Settings and Cup Selection
20
Correct Torch and Rod Positioning
20
Pulsed TIG
21
Personal Protection
22
Recognising Your Tungsten
23
Operator Inspection for Weld Quality
24
TIG Troubleshooting Guide
25
Branches and Outlets throughout New Zealand
Check your Yellow pages
or www.weldwell.co.nz
1
HISTORY OF GTAW (TIG WELDING)
TIG welding was, like MIG/MAG developed during 1940 at the start of the
Second World War.
TIG’s 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 1940’s 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.
2
OVERVIEW
TIG 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
3
POWER SOURCES
TIG 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.
4
TYPES OF WELDING CURRENT USED FOR TIG
1)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 wasn’t 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.
5
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.
6
CHARACTERISTICS OF CURRENT TYPES FOR
GAS TUNGSTEN ARC WELDING
When 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 end
30% at electrode end
Penetration Profile
Deep, narrow
Electrode Capacity
Excellent
DC TIG
POWER
SUPPLY
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.
DC TIG
POWER
SUPPLY
CURRENT TYPE
DCRP
Electrode Polarity
Electrode Positive
Oxide Cleaning Action
Yes
Heat Balance in the Arc
30% at work end
70% at electrode end
Penetration Profile
Shallow, wide
Electrode Capacity
Poor
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.
7
AC TIG
POWER
SUPPLY
8
CURRENT TYPE
ACHF
Electrode Polarity
Alternating
Oxide Cleaning Action
Yes (once every half cycle)
Heat Balance in the Arc
50% at work end
50% at electrode end
Penetration Profile
Medium
Electrode Capacity
Good
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 nozzle’s 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.
9
SELECTING THE CORRECT TORCH NOZZLE
Design diameter
to fit
GTAW torch
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.
Exit
diameter
measured
in 1.6 mm
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.)
10
REGULATORS
The 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.
Fig. 3
Fig. 1
Fig. 2
11
CONNECTION DIAGRAMS
2 piece Cable Assembly
FOR GAS COOLED
TORCHES
Power
Source
Shield
gas
supply
FOR WATER COOLED
TORCHES
RegulatorFlowmeter
TIG
Torch
Power Source
Water
out
Power cable
adaptor
required
Coolant
Recirculator
WATER IN
Shield
gas
supply
ARGON IN
Note: 1 litre per minute flow rate. Water in through water line. Water out
through power cable.
12
TUNGSTEN SELECTION AND PREPARATION
Base Metal
Type
Thickness
Range
All
Desired
Results
General
Purpose
Welding
Electrode Type Shield Gas
Current
AC/HF
Aluminium
Alloys and
Magnesium Only thin
Alloys
sections
Control
penetration
Only
thick
sections
Increase
penetration
or travel
speed
Copper
Alloys,
DCRP
DCSP
and Nickel
Alloys
Titanium
Alloys
2% Thoriated
(EW-Th2)
75 Argon
25 Helium
2% Ceriated
(EW-Ce2)
Argon
Helium
2% Thoriated
(EW-Th2)
75 Argon
25 Helium
2% Ceriated
(EW-Ce2)
Helium
2% Thoriated
(EW-Th2)
75 Argon
25 Helium
2% Ceriated
(EW-Ce2)
75 Argon
25 Helium
Only thin
sections
Control
penetration
ACHF
Zirconiated
(EW-Zr)
Argon
Only
thick
sections
Increase
penetration
or travel
speed
DCSP
2% Ceriated
(EW-Ce2)
75 Argon
25 Helium
2% Thoriated
(EW-Th2)
75 Argon
25 Helium
2% Ceriated
(EW-Ce2)
75 Argon
25 Helium
2% Lanthanated
(EWG-La2)
75 Argon
25 Helium
Zirconiated
(EW-Zr)
Argon
2% Ceriated
(EW-Ce2)
75 Argon
25 Helium
2% Lanthanated
(EWG-La2)
Helium
All
General
Purpose
DCSP
Steels,
Steels and
Argon
DCSP
Carbon
Alloy
Zirconiated
(EW-Zr)
General
Purpose
Mild
Steels,
Argon
All
Cu-Ni
Alloys
Pure (EW-P)
Only thin
sections
Control
penetration
Only
thick
sections
Increase
penetration
or travel
speed
ACHF
DCSP
Tungsten Performance
Characteristics
Balls easily, low cost, tends to spit at
higher currents, used for non-critical
welds only.
Balls well, takes higher current, with
less spitting and with better arc starts
and arc stability than pure tungsten.
Higher current range and stability,
better arc starts, with lower tendency
to spit, medium erosion.
Lowest erosion rate, widest current
range, AC or DC, no spitting, best arc
starts and stability.
Best stability at medium currents,
good arc starts, medium tendency to
spit, medium erosion rate.
Low erosion rate, wide current range,
AC or DC, no spitting, consistent arc
starts, good stability.
Best stability at medium currents,
good arc starts, medium tendency to
spit, medium erosion rate.
Low erosion rate, wide current range,
AC or DC, no spitting, consistent arc
starts, good stability.
Use on lower currents only, spitting
on starts, rapid erosion rates at higher
currents.
Low erosion rate, wide current range,
AC or DC, no spitting, consistent arc
starts, good stability.
Best stability at medium currents,
good arc starts, medium tendency to
spit, medium erosion rate.
Low erosion rate, wide current range,
AC or DC, no spitting, consistent arc
starts, good stability.
Lowest erosion rate, wide current
range on DC, no spitting, best DC arc
starts and stability.
Use on lower currents only, spitting
on starts, rapid erosion rates at higher
currents.
Low erosion rate, wide current range,
no spitting, consistent arc starts, good
stability.
Lowest erosion rate, highest current
range, no spitting, best DC arc starts
and stability.
13
TUNGSTEN COLOUR CODE AND PROPER TORCH
USE
COLOUR CODE AND ALLOYING ELEMENTS FOR VARIOUS TUNGSTEN
ELECTRODE ALLOYS
AWS
Classifications
Alloying
Element
Colour*
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 TIP
PREPARATION
DCSP (EN) or DCRP (EP)
Flat: 1/4 to
1/2 x dia
2-3 dia
Taper Length
TUNGSTEN EXTENSION
Standard Parts
General
Purpose
3 x dia.
ACHF
General Purpose
Max.
ball
1 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 GRINDING
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.
14
TIG WIRES
The 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
15
SHIELDING GAS
Like 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)
2)
3)
4)
Helium
1)
2)
3)
Better arc starting
Good cleaning action
Lower arc voltage
Low gas flows needed
Faster travel
Better penetration
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
16
SHIELD GAS SELECTION AND USE
Base Metal
Type
Thickness
Range
Weld
Type
Shield
Gas Type
Thin
Manual
Pure Argon
Best arc starts, control of penetration,
cleaning and appearance on thin
gauges.
Thick
Manual
75 Ar - 25 He
Increase heat input with good arc
starts of argon, but with faster welding
speeds.
Manual
Pure Argon
Magnesium
General
Purpose
Alloys
Thin
Mechanised
50 Ar - 50 He
Higher weld speed under 20mm thick,
with good arc stability and starting.
Thick
Mechanised
Pure Helium
Highest weld speeds, deeper
penetration with DCSP, demanding
arc starting and fixturing requirements,
high flow rates needed.
Thin
Manual
Pure Argon
Good control of weld puddle, bead
contour, and penetration on thin
gauges.
Thick
Manual
75 Ar - 25 He
Increase heat input with good arc
starts of argon, but with faster welding
speeds.
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 Helium
Highest weld speeds, deeper
penetration with DCSP, demanding
arc starting and fixturing requirements,
high flow rates needed.
Thin
Manual
Pure Argon
Best arc starts, control of penetration,
cleaning and appearance on thin
gauges.
Thick
Manual
75 Ar - 25 He
Increase 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
Pure Argon
Best overall for good arc starts,
control of penetration, cleaning and
appearance.
Thick
Mechanised
75 Ar 25 He
Increase heat input with good arc
starts of argon, but with faster welding
speeds.
Aluminium
Alloys and
Copper
Alloys
Cu-Ni Alloys
Nickel
Alloys
Low Carbon
Alloys and
Low Alloy
Steels
Characteristics
Best overall for good arc starts,
control of penetration, cleaning and
appearance.
17
TYPICAL MANUAL GTA (TIG) WELDING PARAMETERS
ALUMINIUM (ACHF)
Metal
Gauge
1.6 mm
3.2 mm
4.8 mm
6.4 mm
Joint
Type
Butt
Fillet
Butt
Fillet
Butt
Fillet
Butt
Fillet
Shield Gas Flow
Tungsten
size
Filler
Rod
Size
Cup
Size
Type
CFH
(L/Min)
PSI
1.6 mm
1.6 mm
4, 5, 6
Argon
15 (7)
20
2.4 mm
2.4 mm
3.2 mm
6, 7
Argon
17 (8)
20
3.2 mm
3.2 mm
7, 8
Argon/
Helium
21 (10)
20
4.8 mm
3.2 mm
8, 10
Argon/
Helium
25 (12)
20
Welding
Amperes
Travel
Speed
60-80
70-90
125-145
140-160
190-220
210-240
260-300
280-320
307 mm
256 mm
307 mm
256 mm
258 mm
230 mm
256 mm
205 mm
WELDING ALUMINIUM
The 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.
MAGNESIUM (ACHF)
Metal
Gauge
1.6 mm
3.2 mm
6.4 mm
12.8 mm
Joint
Type
Butt
Fillet
Butt
Fillet
Butt
Butt(2)
Butt(2)
Shield Gas Flow
Tungsten
size
Filler
Rod
Size
Cup
Size
Type
CFH
(L/Min)
PSI
1.6 mm
2.4 mm
3.2 mm
5, 6
Argon
13 (5)
15
2.4 mm
3.2 mm
4.0 mm
7, 8
Argon
19 (9)
15
4.8mm
4.0 mm
8
Argon
25 (12)
15
6.4 mm
4.8 mm
10
Argon
35 (17)
15
Welding
Amperes
60
60
115
115
100-130
110-135
260
Travel
Speed
512 mm
435 mm
563 mm
512 mm
256 mm
WELDING MAGNESIUM
Magnesium alloys are in three groups, they are (1) aluminium-zinc-magnesium, (2) aluminiummagnesium, 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.
18
STAINLESS STEEL (DCSP)
Metal
Gauge
1.6 mm
3.2 mm
4.8 mm
6.4 mm
Joint
Type
Butt
Fillet
Butt
Fillet
Butt
Fillet
Butt
Fillet
Shield Gas Flow
Tungsten
size
Filler
Rod
Size
Cup
Size
Type
CFH
(L/Min)
PSI
1.6 mm
1.6 mm
4, 5, 6
Argon
11 (5.5)
20
1.6 mm
2.4 mm
4, 5, 6
Argon
11 (5.5)
20
2.4 mm
2.4 mm
3.2 mm
3.2 mm
5, 6, 7
Argon
13 (6)
20
3.2 mm
4.8 mm
8, 10
Argon
13 (6)
20
Welding
Amperes
Travel
Speed
80-100
90-100
120-140
130-150
200-250
307mm
256 mm
307 mm
256 mm
307 mm
225-275
256 mm
275-350
300-375
256 mm
205 mm
WELDING STAINLESS STEEL
In 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.
LOW ALLOY STEEL (DCSP)
Metal
Gauge
1.6 mm
3.2 mm
4.8 mm
6.4 mm
Joint
Type
Butt
Fillet
Butt
Fillet
Butt
Fillet
Butt
Fillet (2)
Shield Gas Flow
Tungsten
size
Filler
Rod
Size
Cup
Size
Type
CFH
(L/Min)
PSI
1.6 mm
1.6 mm
4, 5, 6
Argon
15 (7)
20
1.6 mm
2.4 mm
2.4 mm
4, 5, 6
Argon
15 (7)
20
2.4 mm
3.2 mm
7, 8
Argon
16 (6.5)
20
3.2 mm
4.0 mm
8, 10
Argon
18 (8.5)
20
Welding
Amperes
Travel
Speed
95-135
95-135
145-205
145-205
210-260
210-260
240-300
240-300
384 mm
384 mm
282 mm
282 mm
256 mm
256 mm
256 mm
256 mm
WELDING LOW ALLOY STEEL
Mild 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.
19
GUIDE FOR SHIELD GAS FLOWS, CURRENT
SETTINGS AND CUP SELECTION
Welding Current
(Amps)
- Tungsten Type
Electrode
Diameter
(mm)
Cup
Size
0.50
3, 4 or 5
AC
Zirconiated
DCSP
Thoriated
5 - 20
5 - 20
Argon Flow
- Ferrous Metals
Standard
Body
Gas Lens
Body
Argon Flow
- Aluminium
Standard
Body
Gas Lens
Body
CFH (L/min)
CFH (L/min)
CFH (L/min)
CFH (L/min)
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
Vertical
Tungsten Electrode
Welding Rod
60o - 75o
Shield Gas
Nozzle
15o - 30o
Direction of Travel
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.
20
PULSED TIG
Pulsed 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 materials
The down side is - more set-up cost and more operator training.
Pulsed TIG consists of
Peak 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.
21
PERSONAL PROTECTION
Skull Cap
Helmet
Mask
Jacket
Welding
helmet lens
Gloves
TIG WELDING HAZARDS
22
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.
RECOGNISING YOUR TUNGSTEN
“A”
“B”
“C”
“D”
“E”
“F”
“G”
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.
23
OPERATOR INSPECTION FOR WELD QUALITY
PROBLEM:
CAUSE:
PROBLEM:
CAUSE:
PROBLEM:
CAUSE:
PROBLEM:
CAUSE:
PROBLEM:
CAUSE:
PROBLEM:
CAUSE:
PROBLEM:
CAUSE:
PROBLEM:
CAUSE:
• Excessive build up
• Poor penetration
• Poor fusion at edges
Welding current too low
• Bead too wide and flat Welding current too high
• Poor penetration
• Excessive burn through
• Bead too small
Travel speed too fast
• Insufficient penetration
• Ripples widely spaced
• Bead too wide
Travel speed too slow
• Excessive build up
• Excessive penetration
• Undercut
Welding current too high
• Insufficient weld deposit and/or wrong placement of
• Uneven penetration
filler rod
• Poor penetration
• Poor fusion
•
•
•
•
Proper build-up
Good appearance
good penetration
Bead edges fused in
Faulty joint preparation and
too low welding current
Correct technique and
current setting
• No undercut
Correct technique and
• Legs of fillet weld equal current setting
to metal thickness
• Slightly convex bead face
24
TIG TROUBLESHOOTING GUIDE
Problem
Cause
Solution
Excessive
Electrode
Consumption
1. Inadequate gas flow
2. Improper size electrode for current required
3. Operating of reverse polarity
4. Electrode contamination
5. Excessive heating inside torch
6. Electrode oxidising during cooling
7. Shield gas incorrect
1. Increase gas flow
2. Use larger electrode
3. Use larger electrode or change polarity
4. Remove contaminated portion, then prepare again
5. Replace collet, try wedge collet or reverse collet
6. Increase gas post flow time to 1 sec. per 10 amps
7. Change to proper gas (no oxygen or CO2)
1. Incorrect voltage (arc too long)
2. Current too low for electrode size
3. Electrode contaminated
4. Joint too narrow
5.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 length
2. Use smaller electrode or increase current
3. Remove contaminated portion, then prepare again
4. Open joint groove
5.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
Erratic
Arc
1. Poor scratch starting technique
Inclusion of
Tungsten or
Oxides in
Weld
1.Many codes do not allow scratch starts. Use copper
strike plate. Use high frequency arc starter
2. Excessive current for tungsten size used
2. Reduce the current or use larger electrode
3. Accidental contact of electrode with puddle 3. Maintain proper arc length
4. Accidental contact of electrode to filler rod 4.Maintain a distance between electrode and filler
5. Using excessive electrode extension
metal
5.Reduce the electrode extension to recommended
6. Inadequate shielding or excessive draughts
limits
6.Increase gas flow, shield arc from wind, or use gas
7. Wrong gas
lens
7.Do not use ArO2 or ArCO2 GMA (MIG) gases for TIG
8. Heavy surface oxides not being removed
welding
8.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 connection
3.Filler material is damp (particularly
aluminium)
4. Filler material is oily or dusty
5.Alloy impurities in the base metal such as
sulphur, phosphorous, lead and zinc
6.Excessive travel speed with rapid freezing
of weld trapping gases before they escape
7. Contaminated shield gas
Cracking in
Welds
1.Do not weld on wet material. Remove condensation
from line with adequate gas pre-flow time
2. Check hoses and connections for leaks
3. Dry filler metal in oven prior to welding
4. Replace filler metal
5.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
1.Hot cracking in heavy section or with metals 1.Preheat, increase weld bead cross-section size,
which are hot shorts
change weld bead contour. Use metal with fewer
alloy impurities
2.Crater cracks due to improperly breaking
2.Reverse direction and weld back into previous weld
the arc or terminating the weld at the joint
at edge. Use Amptrak or foot control to manually
edge
down slope current
3.Post weld cold cracking, due to excessive
3.Preheat prior to welding, use pure or nonjoint restraint, rapid cooling, or hydrogen
contaminated gas. Increase the bead size. Prevent
embrittlement
craters or notches. Change the weld joint design
4. Centreline cracks in single pass welds
4.Increase bead size. Decrease root opening, use
preheat, prevent craters
5.Underbead cracking from brittle
5.Eliminate sources of hydrogen, joint restraint, and
microstructure
use preheat
25
TIG TROUBLESHOOTING GUIDE (continued)
Problem
Inadequate
Shielding
Arc
Blow
Cause
Solution
1. Gas flow blockage or leak in hoses or torch
2.Excessive travel speed exposes molten
weld to atmospheric contamination
1. Locate and eliminate the blockage or leak
2.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 area
4. Reduce electrode stickout. Use a larger size cup
5. Change to gas saver parts or gas lens parts
3. Wind or draughts
4. Excessive electrode stickout
5. Excessive turbulence in gas stream
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
1. Short water cooled leads life
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. Incorrect flowmeter, TIG flowmeters operate at 35 psi
with low flows. MIG flowmeters operate with high
flows at 65 psi or more.
2. Cup shattering or cracking in use
Short Parts
Life
3. Short collet life
4. Short torch head life
5.Gas hoses ballooning, bursting, or blowing
off while hot
26