Clearview National December 2019 - Issue 217 | Page 34

PROUD SPONSOR OF DOORS & WINDOWS
DOORS&WINDOWS
Welding techniques
explained for
steel windows
Welding is essential in the manufacture of buildings,
bridges, cars, aeroplanes, pipelines, power stations
and a host of other structures and objects. There are
four main welding techniques used in the modern
manufacturing and construction industries.
» WELDING IS A PROCESS THAT IS
rarely seen, oft-forgotten, and largely invisible
– out of sight, out of mind. Disregarding it,
however, could also leave you severely out of
pocket. That’s why it pays to take welding
and fabrication seriously in the steel window
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 essentially 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 electrode as
often as they do in, say, shielded metal arc
welding (SMAW).
A wire feeder synchronises with the power
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 produces 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 contaminants.
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.
34 » DEC 2019 » CL EARVI E W- UK . C O M
GMAW and FCAW have many different
options for nozzles, tips and diffusers.
Protruding 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.
‘How a user welds can
greatly affect weld properties’
GMAW AND FCAW WELDING TIPS
1. Be sure to follow safety and setup
procedures 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 voltage 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.
Shielded metal arc welding (SMAW) –
commonly known as ‘stick welding’ – is one
of the most widely used welding processes
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
contaminants 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.