BASIC GTAW
•
Metal preparations
•
Steps in manual welding in all positions
•
Stringer Beads, Flat Position, on Mild Steel
Metal preparations
Both the base metal and the filler metal used in
the GTAW process must be thoroughly cleaned before
welding. Contamination left on the metal will be
deposited in the weld because there is no flux to
remove it. Oxides, oils, and dirt are the most common
types of contaminants. They can be removed
mechanically or chemically. Mechanical metal cleaning
may be done by grinding, wire brushing, scraping,
machining, sand blasting, or filing. Chemical cleaning
may be done by using acids, alkalies, solvents, or
detergents.
Here is a list of
things you can TIG
weld:
• Shiny, clean metal
Here is a list of things you can’t TIG
weld:
•
•
•
•
•
•
Rust
Aluminum oxide
Mill scale
Paint
Grease
Dirt
Why You Need to Clean
Before we go into the details of different cleaning
methods, you need to understand why TIG welding
requires so much cleaning. When you TIG weld, you
are melting the edge of each piece of metal along
with the filler rod. The melted metals flow together
and are permanently fused. If you weld metal that is
dirty or rusted, the filler doesn’t stick to the joint – it
sticks to the rust. When the bead or joint is stressed,
the rust pulls off and the weld breaks.
Why You Need to Clean
Other welding processes include flux with the filler
rod. The flux reacts with surface contaminants to
remove them from the weld. TIG welding doesn’t
include any kind of flux, so you have to remove the
contaminants before you crack an arc. There are two
steps to removing the contaminants, mechanical
cleaning, and chemical cleaning. You need to do both
before TIG welding.
Why You Need to Clean
Other welding processes include flux with the filler
rod. The flux reacts with surface contaminants to
remove them from the weld. TIG welding doesn’t
include any kind of flux, so you have to remove the
contaminants before you crack an arc. There are two
steps to removing the contaminants, mechanical
cleaning, and chemical cleaning. You need to do both
before TIG welding.
Mechanical Cleaning
The first step to prepare metal for TIG welding is
mechanical cleaning. You need to remove the surface
contaminants from the surface physically. Tools you
can use for mechanical cleaning include wire
brushes, angle grinders, sanders, and bench grinders.
Each has its place, depending on the surface
condition and the size and shape of the stock. Let’s
take a look a look at each one.
Chemical Cleaning
Once you have removed the rust and dirt, you need
to remove any grease, oil, paint, or other chemicals
that are left along the joint. These are all chemicals
that can be ground into pores in the metal. You need
a chemical to remove these chemicals. You also need
to remove any traces of the cleaning solution.
Using Chemical Cleaners
The actual cleaning process is simple. Once you
have ground down the joint, just dip the rag into the
solvent and wipe down the weld joint. That is all you
need to do. The trick is to be safe while you are doing
it.
Using Chemical Cleaners
If you are using any flammable chemical, make
sure you have good ventilation. The volatile organic
compounds given off by acetone and paint thinner
will make you sick if you breathe them. The best way
to use acetone is under a fume hood that sucks away
all the fumes before you have a chance to breathe
them in.
Joint Preparation
Once the metal is clean, you can start with joint
preparation. If you are welding material that is 3/16
inch or less, you don’t have to do much prep. If you
are welding thicker metal, the edges of the joint
should be beveled. Beveling means grinding back one
corner of the edge so that the pieces meet in a Vshape rather than in two parallel lines.
Joint Preparation
Beveling is important because it allows the heat of
the weld to penetrate deeper into the metal. If you
just weld along the edge of a thick joint, the bead will
be “tall,” and the heat won’t penetrate the joint. If
the heat doesn’t penetrate, the pieces won’t fuse, and
the weld will be weak.
Joint Preparation
If you are welding very thick metal, it may take
more than one pass to fill the bevel with filler. This is
known as “root and cap” welding. The first bead is
the root pass, while the bead (or beads) that go over
the top are cap beads. Using a root and cap technique
lets the joint fuse fully and gives the strongest weld.
Weld It Up
Once you have cleaned the metal, beveled the
joint, and laid everything out, you are finally ready to
TIG weld. It may seem like more work is spent on
preparation than welding, but that’s what it takes to
prepare a good weld. If you skip steps, the weld will
be contaminated and won’t be as strong. It’s also
subject to defects like porosity, slag inclusion, or even
breaking.
Weld It Up
The whole point of using TIG welding instead of
arc or MIG welding is to get that attractive “stack-ofdimes” look for the weld bead. Trying to weld dirty or
corroded metal will make a mess of your weld and
guarantee an ugly, spotty bead. Skipping on joint
preparation and layout will produce a weak weld
that’s likely to break sooner or later.
Weld It Up
If you have spent the time and money to set up a
TIG welding shop, it’s because you want to lay down
pretty beads. If you fail to grind, degrease, bevel, and
lay out your joints properly, you can’t do that. To get
the most from your TIG setup, take the time to
prepare your joints before you weld.
Steps in manual welding in
all positions
Step 1: Choose the Electrode
Your TIG is likely to have the right electrode in it
already.
For aluminum, the best choice is a pure tungsten rod.
You can alternately choose from any number of tungsten
alloys (including thoriated tungsten - which is
radioactive!) which are uniquely suited to welding
particular alloys of metal.
Step 2: Grind the Electrode
Grind the tungsten rod to a point.
Do this, especially if the rod is a brand-new cylinder and
doesn't have a pointed or rounded tip yet.
The tip will become rounded due to heat as you weld.
It is best to use a balled tip for AC welding, and a pointed tip
for DC welding.
The pointed tip will give a smaller, more directed arc. The arc
will tend to dance around, when from a rounded tip.
Step 3: Insert the Electrode Into Its
Collet
Unscrew the back of the electrode holder, insert the
rod, replace back.
The tip of the electrode should be about 1/4" away
from the protective sheath, but not much more.
Step 4: Choose the Settings
The typical TIG rig will have three main electricity options AC, DCEP, and DCEN.
AC is for aluminum - choose "AC".
Set the "Cleaning/Penetrating" setting to the more
"Penetrating" side - around 7 on a scale from 1 to 10.
Set the "Air on" to about 5 seconds, if you have the option to do
so.
This is the amount of time the gas stays on after the arc stops,
to keep your weld from oxidizing/rusting.
Set the "Max Amps" pretty high - perhaps around 250.
Step 4: Choose the Settings
For the curious:
Cleaning/Penetrating is a modification to the positive/negative ratio of
the AC that changes the depth of your weld (cleaning is more
shallow).
DCEP means "DC, Electrode Positive". This setting is used for balling
the tungsten tip, or stick welding.
DCEN means "DC, Electrode Negative", and is for welding steel.
The difference between the two DC settings is the direction the
electricity flows - to the metal from the electrode, or to the electrode
from the metal. This makes a big difference in the amount of heat the
metal absorbs, and the width and depth of the weld.
Step 5: Turn on the Gas
For aluminum, use pure argon.
For steel, you would use an argon/carbon
dioxide mixture.
The gas is important to keep the weld from
becoming corroded, as metal will rust (or in the
case of aluminum, oxidize) ridiculously quickly
at the high temperatures the metal reaches.
Step 6: Prepare Metal and Welding Table
Some kind of large metallic area is necessary to let electricity flow
through your metal. We're using a welding table, purchased for the
purpose. Otherwise, a large piece of sheet metal will do perfectly
well (just make sure it's flat).
Beauty Tip: Use a wire brush to scrub the surfaces of the metal.
It's good practice to keep a dedicated aluminum brush (separate
from what you use to clean steel). If you want really nice-looking
welds, you can also wipe down the welding rods with acetone.
If you don't care about the way the welds look when finished, don't
bother and you'll be fine. However, your welds will be a little
weaker and not as pretty.
Clamp your metals so they'll stay where you want them when you
weld.
Step 7: PPE
TIG will give you sunburns. TIG will make you see stars (or go
blind). TIG will burn your hands.
Use thick leather welding gloves, and a welding helmet, and closedtoe shoes.
To avoid sunburn, wear a long-sleeved shirt or jacket, or a welding
coat.
Clean your helmet - the better you can see what you're doing, the
better you can weld.
Step 7: PPE
Some people like auto-darkening welding helmets. Others don’t
like relying on the device's reaction time - you have to invest a lot,
to get a good-quality, fast one.
We're using always-dark helmets.
You might use a bright flashlight, if you want to see what you are
doing without lifting your helmet.
Step 8: Check control of tig gun
Hold the electrode in your dominant hand.
Make sure it can move freely (untangled,
unhampered cord).
Stringer Beads, Flat Position,
on Mild Steel
Stringer Beads, Flat Position,
on Mild Steel
Using a properly set-up and adjusted GTA
welding machine on DCEN, proper safety
protection, and one or more pieces of mild steel
6 in. (152 mm) long, 16 gauge, and 1/8 in.
(3 mm) thick, you will push a weld pool in a
straight line down the plate. Maintain uniform
weld pool size and penetration.
Stringer Beads, Flat Position,
on Mild Steel
● Starting at one end of the piece of metal that is 1/8 in. (3
mm) thick, hold the torch as close as possible to a 908 angle.
● Lower your hood, strike an arc, and establish a weld pool.
● Move the torch in a stepping or circular oscillation pattern
down the plate toward the other end.
● If the size of the weld pool changes, speed up or slow down
the travel rate to keep the weld pool the same size for the
entire length of the plate.
Stringer Beads, Flat Position,
on Mild Steel
● Starting at one end of the piece of metal that is 1/8 in. (3
mm) thick, hold the torch as close as possible to a 908 angle.
● Lower your hood, strike an arc, and establish a weld pool.
● Move the torch in a stepping or circular oscillation pattern
down the plate toward the other end.
● If the size of the weld pool changes, speed up or slow down
the travel rate to keep the weld pool the same size for the
entire length of the plate.
Stringer Beads, Flat Position,
on Mild Steel
The ability to maintain uniformity in width and keep a
straight line increases as you are able to see more than just
the weld pool. As your skill improves, you will relax and
your field of vision will increase.
Stringer Beads, Flat Position,
on Mild Steel
Repeat the process using both thicknesses of metal
until you can consistently make the weld bead visually
defect-free. Turn off the welding machine, shielding gas,
and cooling water, and clean your work area when you are
finished welding.
LEARNING ASSESSMENT
ESSAY
Direction: Answer the following
question in 3-5 sentences. 5pts each,
15 mins to answer.
LEARNING
EXPERIENCE
INSTRUCTIONAL
VIDEO
Direction: Create a 3-5
minute instructional
video about wearing a
proper Personal
Protective Equipment
use in welding.
20pts – all basic welding PPE are
present, all PPE are explained of
its function, video is clear from
start to finish.
15pts – all basic welding PPE are
present, only 4 PPE are explained
of its uses, video is clear from star
to finish.
10pts – only 4 basic welding PPE
are present, only 4 PPE are
explained of its uses, video is clear
from the start only
5pts - only 2 basic welding PPE
are present, only 2 PPE are
explained of its uses, video is not
clear