36 | DECEMBER 2019
Skills
Read online at www.proinstaller.co.uk
WELDING
TECHNIQUES
EXPLAINED
FOR STEEL
WINDOWS
Welding is essential in the manu-
facture of buildings, bridges, cars, aero-
planes, pipelines, power stations and a
host of other structures and objects. There
are four main welding techniques used in
the modern manufacturing and construc-
tion industries.
Welding is a process that is rarely seen,
oft-forgotten, and largely invisible – out of
sight, out of mind. Disregarding it, how-
ever, could also leave you severely out of
pocket. That’s why it pays to take welding
and fabrication seriously in the steel win-
dow industry.
But this begs a fundamental question
– given that there are so many different
welding techniques, which is the right one
for a specific application? There are essen-
tially four main types of welding.
Gas metal arc welding (GMAW) and flux
core arc welding (FCAW) use the same
core process – consumable electrode wire
is automatically fed into the welding arc so
that users do not need to replace the elec-
trode as often as they do in, say, shielded
metal arc welding (SMAW).
A wire feeder synchronises with the pow-
er supply to deliver wire from a spool at the
appropriate speed. Most electrode wires also
require a shield gas which feeds through
the same cable as the wire. However, with
self-shielded flux-core wire, the wire produc-
es its own shield gas and protective slag.
The tip conducts electricity through the
electrode wire. A gas diffuser releases the
gas into the nozzle, which then blows out
around the weld puddle to repel contam-
inants. When gas, wire and electric power
are united properly, the wire melts steadily
into the workpiece.
The amperage, voltage and wire speed
used in GMAW/FCAW will vary depending
on the metal being welded and the type of
wire being used.
GMAW and FCAW have many different
options for nozzles, tips and diffusers. Pro-
truding tips and tapered nozzles can aid
welding in narrow spaces while recessed
tips enable higher burn-off rates.
Self-shielded FCAW does not normally
require a nozzle as there is no external
shield gas. However, FCAW with a shield
gas is extremely resistant to atmospheric
interference like wind.
GMAW and FCAW welding tips
1. Be sure to follow safety and setup pro-
cedures in the owner’s manual.
2. Varying the wire feed speed/amperage
must be done manually. The thicker the
electrode wire, the higher the wire feed
speed and the more amperage that is
required to burn off the electrode wire.
3. Increasing wire feed speed and volt-
age or increasing wire thickness will
increase the rate that filler metal is
deposited to the workpiece.
4. Most automatic wire systems maintain
a voltage. However, voltage can be
varied on a machine manually to alter
the distance between the tip and the
point where wire burns out (the ‘stick-
out distance’).
5. How a user welds can greatly affect
weld properties. The angle of the tip
and the travel speed while welding
can alter the weld depth.
there are four main
‘ welding
techniques
used in modern
manufacturing and
construction industries
’
Shielded metal arc welding (SMAW) –
commonly known as ‘stick welding’ – is
one of the most widely used welding pro-
cesses for joining metal. For stick welding,
each electrode has a metal core that can
contain different types of metal and an
outer covering of flux.
The flux coating shields the arc from con-
taminants in the air, making the finished weld
stronger. Flux also helps eliminate tiny holes
that can form in the weld (metal porosity), as
well as cracking, undercutting, and spatter.
If an electrode has absorbed moisture,
using an electrode oven to dry it out can
restore its ability to deposit quality welds.
Mastering the following
five elements should ensure
successful stick welding:
• Current: using the appropriate current
(AC or DC) is imperative.
• Length of arc: the distance between
the electrode and workpiece should
be the length of the diameter of the
electrode’s core wire.
• Angle of electrode: the angle of the
electrode affects weld penetration. Too
much penetration can make the weld
brittle and lead to stress cracking and
create holes in the metal; too little pen-
etration can result in a weak weld.
• Manipulation of weld pool: as stick
welding is performed, gas pockets
can form which can compromise weld
integrity. These can be eliminated
with a slight side-to-side motion when
welding.
• Speed of travel: A weld speed that is
too slow leads to a weld bead that is
too large while a fast weld can lead to
a weld bead that is too narrow.
SMAW welding tips
1. Take care when handling stick weld-
ing electrodes. Rough handling can
cause the flux coating to break loose
from the core wire, rendering the elec-
trode unusable.
2. Don’t use an electrode if the core wire
is exposed because the missing flux