GUIDE TO TIG
WELDING
This is a free basic guide
on how to do TIG welding using a TIG welder (Tungsten Inert Gas)
You can download this TIG Welding Guide by clicking the link below:
TIG welding is a skill
that needs to be developed over time, with a piece of metal in front of you and
with a welding torch in your hands. TIG welding requires patience and
practice.
The R-Tech
Tig201 AC/DC TIG Welder used in this guide
1. WHAT IS TIG
WELDING?
-
TIG Welding can
be used to weld aluminium, copper, titanium etc… and even two
dissimilar metals. This process is ideally suited to handling tricky
welds such as S-Shapes, curves, corners or where the weld is going to
be visible and where accuracy and finish is important. TIG welding
allows a greater variety of metals to be welded than other forms of
welding
-
With superior arc
and weld puddle control, TIG welding allows you to create clean welds when
appearances count. Because the heat input is often controlled by pressing
on a foot pedal, similar to driving a car, TIG welding allows you to heat
up or cool down the weld puddle giving you precise weld bead control. This
makes TIG welding ideal for cosmetic welds like sculptures, architectural
and automotive welds
-
The TIG welder
generates heat via an arc of electricity jumping from a tungsten
metal electrode to the metal surface that you intend to weld – which
is usually aluminium or steel
-
TIG stands for
Tungsten Inert Gas – named from the tungsten electrode and the shield
of inert gas (Argon or argon mixture) surrounding
it.
-
A TIG welder
needs a filler rod to provide the welding bead when joining two
pieces of metal together
-
TIG welding
produces no sparks or spatter because only the necessary amount of
filler metal is added to the welding pool.
-
TIG welding
produces no smoke and fumes unless the base metal contains
contaminants or has a dirty surface
-
TIG welding
doesn’t produce slag and requires no flux because the argon gas
protects the weld pool from contamination
2. CHOOSING AND PREPARING THE TUNGSTEN
ELECTRODE
A tungsten electrode is
required when TIG welding and this is inserted into the welding torch. This
electrode carries the welding current to the work. For welding aluminium the
most popular choice is a Zirconiated TIG tungsten eletrode (White
tipped), for steel the most popular is a Thoriated TIG tungsten
electrode (Red Tip)
A
number of tungsten alloys are also available (including Thoriated
Tungsten)
There are different sizes of tungsten’s available which relate to the
welding power you are using for a particular job. It is important to use the
correct size of electrode for the welding power you are going to use. See
below:
|
ELECTRODE
|
RATINGS
|
|
Electrode
Diameter (mm)
|
2%
Thoriated on DC
(amps)
|
Pure
Tungsten on DC (amps)
|
Zirconiated
Tungsten on AC (amps)
|
1.0
|
80
|
30
|
60
|
1.6
|
150
|
80
|
120
|
2.4
|
250
|
130
|
180
|
3.2
|
400
|
180
|
250
|
4.0
|
500
|
240
|
320
|
4.8
|
750
|
300
|
390
|
6.4
|
1000
|
400
|
525
|
Preparation of the tungsten electrode is
important. The end needs to be ground to a point (see images below). Brand new
electrodes will always need to be prepared in this way. When welding on
aluminium the tungsten will begin to form a ball, this is perfectly normal. When
welding steel the electrode will always stay pointed.
Below you can see me holding a new tungsten electrode ready to start the
grinding process. I prefer to use the side of a clean wheel as I have more
control. Position the tip where you feel comfortable. Remember to ensure all
health and safety requirements are taken when using a grinding
wheel.
The
picture on the right hand side of this page shows the tungsten in the end of the
tig torch, you can see the ball formed on end of
the tungsten as this has been used for aluminium welding
With the
introduction of new power source technologies, the use of pure tungsten is
decreasing.
Pure
tungstenmelts at a lower temperature causing it
to easily form a rounded ball at the tip. When the ball grows too large, it
interferes with your ability to see the weld puddle and causes the arc to
become unstable.
Ceriated
tungstencan withstand higher temperatures and
works very well with the new squarewave and inverter machines for the
following reasons:
-
Holds a
point longer and starts well at low amperages.
-
Can be used
on both AC and DC polarities. When welding aluminum, it has become very
acceptable to grind a point on ceriated tungsten (especially when welding
on thinner materials).
-
Allows
welding amperages to be increased by 25-30% compared to Pure tungsten of
the same diameter.
3. SAFTEY GEAR
TIG welding can be a pretty
safe thing to do so long as you follow a few important safety precautions. TIG
welding produces lots of heat and lots of harmful light, you need to take a few
steps to protect yourself.
·The light that is generated
by any form of arc welding is extremely bright. It will burn your eyes and your
skin just like the sun will if you don't protect yourself. The first thing you
will need to weld is a welding helmet I am wearing an auto-darkening
welding helmet below. They are really helpful if you are going to do a lot
of welding and make a great investment if you think you will be working with
metal often. Manual masks require you to jerk your head dropping the mask into
position or require to use a free hand to pull the mask down. This allows you to
use both your hands to weld, and not worry about the mask. Always ensure to
protect others from the light as well and use a welding screen to make a border
around yourself. The light has a tendency to draw on lookers who might need to
shielded from being burned too.
·Wear gloves and leathers to
protect yourself from molten metal splattering off of your work piece. Some
people like thin tig welding gloves for welding so you can have a lot
of control. In TIG welding this is especially true. The leathers will not only
protect your skin from the heat produced by welding but they will also protect
your skin from the UV light produced by welding. If you are going to be doing
any amount of welding more than just a minute or two you will want to cover up
because UV burns happen fast!
·If you are not going to wear
leathers at least make sure that you are wearing clothing made from cotton.
Plastic fibers like polyester and rayon will melt when they come into contact
with molten metal and will burn you. Cotton will get a hole in it, but at least
it won't burn and make hot metal goop.
·Do not wear open toed shoes
or synthetic shoes that have mesh over the top of your toes. Hot metal often
falls straight down and I have burned many holes through the tops of my shoes.
Molten metal + hot plastic goo from shoes = no fun. Wear leather shoes or boots
if you have them or cover your shoes in something non-flammable to stop
this.
·Weld in a well ventilated
area. Welding produces hazardous fumes which you shouldn't breathe in if you can
avoid it. Wear either a mask, or a respirator if you are going to be welding for
a prolonged amount of time.
Fire hazards Molten metal can spit
several feet from a weld. Grinding sparks are even worse. Any sawdust, paper or
plastic bags in the area can smolder and catch fire, so keep a tidy area for
welding. Your attention will be focused on welding and it can be hard to see
what's going on around you if something catches fire. Reduce the chance of that
happening by clearing away all flammable objects from your weld area.
Keep a fire extinguisher beside the exit door from your workshop. CO2 is the best
type for welding. Water extinguishers are not a good idea in a welding shop since
you are standing next to a whole lot of electricity.
Important Safety Warning DO NOT WELD GALVANIZED STEEL.
Galvanized steel contains a zinc coating that produces carcinogenic and poisonous
gas when it is burned. Exposure to the stuff can result in heavy metal poisoning
(welding shivers) - flu like symptoms that can persist for a few days, but that can
also cause permanent damage.
Gloves, auto-darkening helmet and a suitable cotton based jacket are
essential to keep safe
4. PREPARING FOR THE WELD
Before you start welding
make sure things are properly setup at both the welder and on the piece you are
about to weld.
The Welder Getting the correct settings for type of
weld you are doing requires some trial and error, especially if you are new to
using TIG welders. Some basic parameters are consistent to all TIG welding
whereas many other functions may only be available on higher specification
machines. For welding today we will be using an R-Tech Tig201 Tig Welder which
is a fully featured Tig Welder and in the picture below you can see the front
panel with a description of the controls and what they actually
do.
Fig 4
1.Base current
control
This adjusts the main welding current and is shown in L.E.D (Fig
4.11)
2.Pulse peak current
adjustment
This sets pulse amperage and must be set above the base (main) current amperage. If
set to zero pulse welding is disabled.
3.Pulse frequency
adjustment
This sets how often pulse will occur 0.5 – 25hz
4.Up
slope
Adjustment 0-10 seconds. The main welding current raises from minimum amperage to
main current selected in time selected when weld started
5.Pulse
width
Pulse width adjustment – This sets length of pulse 0.1 – 0.9
seconds
6.Down
slope
Down-Slope adjustment 0-10 seconds. The main welding current decreases from main
amperage to minimum amperage in time selected when weld finished – Sometimes known
as crater fill.
7.AC – DC Selector
switch
This switch selects either DC for welding steels or AC for welding alloys
DO NOT SWITCH WHEN WELDING AS DAMAGE TO MACHINE CAN OCCUR.
8.2/4 Way selector
switch
2/4 Step trigger mode switch – TIG welding can either be done in 2 or 4 step
mode.
When the trigger mode is in the 2 step position the following sequence will
occur
Press and hold the TIG torch switch to start sequence.
The machine will open gas valve to start flow of shield gas, after a 0.5 seconds
pre-flow time to purge air from torch hose the welding output of machine will be
turned on and the arc will be started. After the arc is started the output current
will increase from the start (min) current to base (main) current in time selected
by slope-up. Main power will be achieved instantly if no slope up is in the ‘0’
minimum position.
Release the TIG torch switch to end sequence.
The machine will now decrease output to finish (min) current in time set by
slope-down, once at finish (min) current the machine will stop output and the gas
valve will continue to operate for the selected time (post flow)
Possible variations of this standard sequence are shown in diagram below. It is
possible to press and hold tig torch switch a second time during downslope time to
restart. After the switch is pressed the output current will raise to base (main)
current
When the trigger mode is in the 4 step position the following sequence will
occur
Press and hold the TIG
torch switch to start sequence.
The machine will open gas valve to start flow of shield gas, after a 0.5 seconds
pre-flow time to purge air from torch hose the welding output of machine will be
turned on and the arc will be started. After the arc is started the output current
will be at start (min) current
This condition can be maintained as long as required.
Release the TIG torch switch to go to step 2
The machine will now increase output to base (main) current in time set by
slope-up.
Press and hold the TIG torch switch when main weld is complete
The machine will now decrease the welding output current to finish (min) in
down-slope time set. Once at finish (min) output you can release the TIG torch
switch to end weld the gas post-flow will continue to run for set
time.
9.MMA – TIG mode
switch
MMA-TIG mode switch. Switches between TIG (GTAW) & MMA STICK (SMAW)
welding
10.AC squarewave
frequency adjuster
AC Squarewave frequency adjustment 20-250Hz.
Traditional TIG welders have a fixed frequency of 60Hz, the TIG201 advanced
technology allows AC frequency adjustment from 20-250hz, as you turn up the
frequency the width of arc from tungsten decreases allowing more control of weld
pool and an increase travel speed
The pitch noise of weld will increase when AC frequency is turned up, this is
normal.
100 - 120Hz is the ‘sweet spot’ for most AC welding.
11.LED
Display
3 digit LED meter is used to display the pre-set (before welding) amperage and
actual amperage (when welding).
12.Gas post flow
adjustment
Gas post flow adjustment 1 – 25 seconds. The gas keeps flowing after weld has
finished, this cools & stops tungsten from getting contaminated.
Note: Gas pre-flow time is fixed at 0.5 seconds in TIG mode but no pre-flow time
will occur if the arc is restarted during post flow time as gas is already
flowing.
13.AC squarewave
balance (SP%)
SP% AC Squarewave balance control 30% – 70%
Set at 50% this provides balanced control suitable for most AC Welding. 30% is max
cleaning and 70% is max penetration.
When welding dirty/contaminated material more cleaning may need to be selected.
Tip. If you are welding close to the tungsten limits,
I.E 200amps on a 2.4mm tungsten and the end of tungsten is wobbling and falling
off, turning down the SP% will give better tungsten stability
-
Arc force
(Stick – SMAW only)
This provides better arc starting when in MMA stick mode, useful when you
are welding dirty/rusty material or cold/damp welding
electrodes
The
Metal An earthing clamp should be
present and attached to your workpiece or, as in the picture below, the bench.
The other end should be attached to your welding machine. Some kind of large
metallic area is necessary to let electricity flow through your metal. If you
don’t have a welding bench then a large sheet of metal will do the job. Be sure
to securely clamp down the metals you are working on
1. Earth clamp secured to the workpiece or bench
5. GETTING STARTED ON THE WELD
Holding the
torch
Hold the torch as shown in the photograph below. The tungsten should
be raised from the surface of the work by about 3-6mm. Do not let the tungsten
touch the work or it will contaminate your material and you will have to re-grind
the tungsten. aim for a working angle of about 45° to the work surface.
Grab a filler
rod Take a filler
rod in your left hand and position horizontally so that it rests at a
15° angle to the
work, when you insert the filler rod into weld pool, do so by adding it to the
edge of the pool keeping it away from the tungsten to avoid tungsten
contamination. The filler rod will melt and flow into the weld
pool.
Foot Pedal Control Controlling the weld current is best done
by using a remote foot pedal (pictured on
the left). Check to see if your machine can run one of these. This kind of
control will help you keep the weld pool steady and help make sure that the pool
doesn’t grow, shrink, spread or narrow during the weld. It’s a good idea to
practice controlling the welding amperage with a foot pedal on some scrap before
you start welding for real. The picture on the right shows a good, controlled
weld.
6. LETS DO SOME TIG WELDING!
Establishing
the arc with torch switch operation Set the amperage desired on
the main amperage control on machine and press the torch switch and the arc will
be started.
Establishing
the arc with foot pedal operation Getting the arc started
requires at least a half press of the foot pedal especially if welding at very
low amperages. NOTE: A foot pedal in operation will only allow the maximum
amperage that you have set on the machine to travel to the torch head. If you
experience difficulty starting the arc this is very commonly down to an
insufficient amperage setting on the welder and not related to the operation of
the foot pedal.
Tacking
Tack welding two pieces together will hold your work in place and
prevent the work from moving as you progress along the weld. Metals like aluminium
spread heat very quickly so work that is not tacked may have a tendency to warp or
distort by the time you reach the end of a section of the weld. Tacking to stop
distortion is very important.
Creating a weld
pool The arc will rapidly build
heat into the metal and form a ‘pool’ of fluid metal. At this point the filler
rod needs to be presented to the edge of the pool. The filler rod will become
fluid and form into the weld pool. If you heat the metal in one place for too
long the metal will warp and deform. (If practicing, try backing off the
pressure on the foot pedal and lowering the amperage to the weld pool to see
what happens). Do not put the filler rod to close to the tungsten electrode as
it will contaminate the tungsten and you will have to grind it down and restart,
a contaminated tungsten will produce a dirty weld and can be very hard to start
the arc too.
Creating a
bead Once a pool is established
and the filler rod presented you must move along with the torch – pushing the
pool along the joint and repeating the process of adding in the filler rod as
you go. This is called ‘leading’ the electrode
If the metal starts
to burn or melt away then too much current is being fed to the pool and you should
lift off the foot pedal
If the metal gets a
flaky but not liquid look to it, put in more power by increasing the pressure on
the foot pedal
7. TYPES OF WELD
The real secret of producing
quality TIG welds is mostly in getting the weld pool to form, at the same time, on
both pieces of metal. The easiest type of weld is the ‘fillet’, two metals joined
at right angles. See below:
To make
a sound weld you must learn to combine all the mechanical techniques into one
fluid motion. A good weld should look like a stack of fish scales lying on top
of each other. Practice so that welding on all joints in all positions becomes
second nature.
Visually and structurally
test your welds on pieces of scrap before starting a real piece of
work.
TIG welding aluminum progresses at a faster travel rate than steel. Due to
aluminum's high thermal conductivity and low melting point, the travel speed will
increase as the welding progresses. If the travel speed is not increased, there is
a chance of excessive melt-through on thin aluminum parts
Advanced features found on R-Tech TIG Welders and their benefits
·Slope Up (only used with
torch trigger operation)
This enables you to set a time that when you start welding the machine will start
at minimum amps and slope up to the main amperage you have set on control panel in
the time you have set on slope up control.
·Slope Down (only used
with torch trigger operation)
This enables you to set a time that that when you stop welding the machine will
slope down to minimum amps you have set on control panel in the time you have set
on slope down control. This is also known as crater fill and allows you to have a
better finish off weld and no crater
·Gas post flow
adjustment
This allows you to set the time the gas will keep
flowing once the weld is finished, this cools the torch on air cooled torch systems
and stops the tungsten from getting contaminated. If the tungsten turns blue on
gets pitted after welding, turn the post flow up. The rule of thumb is to set the
gas post flow time to 4 x size of tungsten being used, I.E 2.4mm tungsten set post
flow to 9-10 seconds. The amperage you are welding at will also affect this, higher
amperages need longer post flow time
·AC Balance control
(SP%)
This controls the cleaning / penetration of the arc.
On the above tig welder 50% is balanced and will perform best for most welding
requirements.
If the work material is very dirty, you can turn the balance control down towards
30% and the machine will spend more time cleaning (lifting the oxidization of the
work) and less time penetrating the work.
If you are welding at amperages close to the tungsten limit and are experiencing
the end of tungsten wobbling too much and falling of, turning the balance to more
cleaning can stop this happening and also can lengthen electrode life
Turning the balance control up towards 70% makes the machine spend more time
penetrating the work and less time cleaning (lifting the oxidization of the work),
this can speed up the process of welding and give better penetration at the cost of
the finished look of the weld. Also when turning up penetration it will cause more
heat on the tungsten and hence quicker wear of tungsten and if set to high it can
cause the end of tungsten to wobble and fall off into work. It is quite normal
never to turn the balance control past 50% balanced
·AC Squarewave frequency
control
This is only found on the very advanced TIG welders
and has many benefits
On most TIG welders this is fixed at 60Hz – On the Tig201 Tig welder we used above
you control the AC frequency from 20 – 250Hz
When turning up the AC frequency you have more weld cycles per second so this gives
you first of all:-
A faster travel speed helping you to keep ahead of the heat transfer.
The width of the arc from tungsten gets smaller the higher the frequency is set so
you get pinpoint accuracy and the weld width is much easier to control.
When you turn up the AC frequency the pitch of the weld will increase this is
completely normal.
Beginners will find welding with a tig welder that has AC frequency control is a
lot easier than using one without this feature.
Do not confuse AC frequency control with pulse frequency which I will cover next,
this is for pulse welding.
·Pulse Welding (used only
on torch trigger operation)
Pulse welding is not as complicated and some people
think, instead of welding at one amperage for the entire weld you can set two
amperage for the machine to use I.E Base / Main amperage 40amps, Pulse amperage
100amps
What will happen is the welder will switch between the two amperages and this
allows you to limit the amount of heat going into work, especially good for welding
stainless steel, it can give a very small width of weld or limit heat
deformation.
You can also set the following:
Pulse width – This is how long the pulse will last and on the Tig201 we used above
can be set between 0.1 to 0.9 seconds
Pulse frequency adjustment - This sets how often pulse will occur and on the Tig201
can be adjusted between 0.5 – 25hz
So turning up the pulse width will make the pulse last longer than the base/main
current set and turning up the frequency will mean the pulse amperage will happen
more often.
Setting up pulse welding is down to the individual user and its best to get some
scrap and play about with the settings, pulse welding when mastered can really help
with the appearance of finished weld and on this machine be used on both DC and AC
settings.
·Remote foot pedal
This allows you to control the amperage when actually
welding which can be very beneficial especially when welding aluminium. You simply
unplug the torch switch plug from machine and plug in the foot pedal.
You set the main control amperage on machine to the maximum you wish the foot pedal
to go to on a maximum depression. So if you set the main amperage control to
100amps the foot pedal when fully depressed with give 100amps.
Once a weld pool is formed and you are moving along the weld as the heat has
transferred along the work you may require less amperage as you move along
otherwise the weld pool width / penetration will get too big, reducing the welding
current will stop this happening. Over a 300mm long weld, you may need 100amps at
the beginning and only 80 amps at the end of weld.
Most experienced tig welders prefer to use a foot pedal, unless the welding in not
being done at a workbench i.e. in the back off a lorry trailer
etc.
For further support information see our
welding support page
|