So you think it's as simple as grabbing the
gun and pulling the trigger, eh?
me this then - what types of welding are there?
Not completely sure? read on...
welding is a process utilizing the concentrated
heat of an electric arc to join metal by fusion
of the parent metal and the addition of metal
to joint usually provided by a consumable electrode.
Either direct or alternating current may be used
for the arc, depending upon the material to be
welded and the electrode used.
Welding (ESW) deposits the weld metal into the
weld cavity between the two plates to be joined.
This space is enclosed by water cooled copper
dams or shoes to prevent molten slag from running
off. The weld metal is produced from a filler
wire that forms an initial arc with the workpiece
until a sufficient pool of liquid metal is formed
to use the electrical resistance of the molten
process requires special equipment used primarily
for horizontal welds of very large plates up
to 36 inches or more by welding them in one
pass as in large machinery and nuclear reactor
are also variations of ESW where shielding is
provided by an appropriate gas and a continuous
arc is used to provide weld metal. These are
termed Electrogas Welding or EGW machines.
to view larger JPEG. Fluxed-Core Arc-Welding
(FCAW) uses a tubular electrode filled with
flux that is much less brittle than the coatings
on SMAW electrodes while preserving most of
its potential alloying benefits.
emissive fluxes used shield the weld arc from
surrounding air, or shielding gases are used
and nonemissive fluxes are employed. The higher
weld-metal deposition rate of FCAW over GMAW
(Gas Metal Arc Welding) has led to its popularity
in joining relatively heavy sections of 1"
major advantage of FCAW is the ease with which
specific weld-metal alloy chemistries can be
developed. The process is also easily automated,
especially with the new robotic systems.
Gas Metal-Arc Welding
to view larger JPEG. Gas Metal-Arc Welding (GMAW),
also called Metal Inert Gas (MIG) welding, shields
the weld zone with an external gas such as argon,
helium, carbon dioxide, or gas mixtures. Deoxidizers
present in the electrode can completely prevent
oxidation in the weld puddle, making multiple
weld layers possible at the joint.
is a relatively simple, versatile, and economical
welding apparatus to use. This is due to the
factor of 2 welding productivity over SMAW processes.
In addition, the temperatures involved in GMAW
are relatively low and are therefore suitable
for thin sheet and sections less than ¼
may be easily automated, and lends itself readily
to robotic methods. It has virtually replaced
SMAW in present-day welding operations in manufacturing
Gas Tungsten-Arc Welding
to view larger JPEG. Gas Tungsten-Arc Welding
(GTAW), also known as Tungsten Inert Gas or
TIG welding, uses tungsten electrodes as one
pole of the arc to generate the heat required.
The gas is usually argon, helium, or a mixture
of the two. A filler wire provides the molten
material if necessary.
GTAW process is especially suited to thin materials
producing welds of excellent quality and surface
finish. Filler wire is usually selected to be
similar in composition to the materials being
Hydrogen Welding (AHW) is similar and uses an
arc between two tungsten or carbon electrodes
in a shielding atmosphere of hydrogen. Therefore,
the work piece is not part of the electrical
Plasma Arc Welding
to view larger JPEG. Plasma Arc Welding (PAW)
uses electrodes and ionized gases to generate
an extremely hot plasma jet aimed at the weld
area. The higher energy concentration is useful
for deeper and narrower welds and increased
Shielded-Metal Arc Welding
to view larger JPEG. Shielded-Metal Arc Welding
(SMAW) is one of the oldest, simplest, and most
versatile arc welding processes. The arc is
generated by touching the tip of a coated electrode
to the workpiece and withdrawing it quickly
to an appropriate distance to maintain the arc.
The heat generated melts a portion of the electrode
tip, its coating, and the base metal in the
immediate area. The weld forms out of the alloy
of these materials as they solidify in the weld
area. Slag formed to protect the weld against
forming oxides, nitrides, and inclusions must
be removed after each pass to ensure a good
SMAW process has the advantage of being relatively
simple, only requiring a power supply, power
cables, and electrode holder. It is commonly
used in construction, shipbuilding, and pipeline
work, especially in remote locations.
Submerged Arc Welding
to view larger JPEG. Submerged Arc Welding (SAW)
shields the weld arc using a granular flux fed
into the weld zone forming a thick layer that
completely covers the molten zone and prevents
spatter and sparks. It also acts as a thermal
insulator, permitting deeper heat penetration.
process is obviously limited to welding in a
horizontal position and is widely used for relatively
high speed sheet or plate steel welding in either
automatic or semiautomatic configurations. The
flux can be recovered, treated, and reused.
Arc Welding provides very high welding productivity....4-10
times as much as the Shielded Metal Arc Welding
(Metal Inert Gas) or as it even is called GMAW
(Gas Metal Arc Welding) uses an aluminium alloy
wire as a combined electrode and filler material.
The filler metal is added continuously and welding
without filler-material is therefore not possible.
Since all welding parameters are controlled by
the welding machine, the process is also called
MIG-process uses a direct current power source,
with the electrode positive (DC, EP). By using
a positive electrode, the oxide layer is efficiently
removed from the aluminium surface, which is
essential for avoiding lack of fusion and oxide
inclusions. The metal is transferred from the
filler wire to the weld bead by magnetic forces
as small droplets spray transfer. This gives
a deep penetration capability to the process
and makes it possible to weld in all positions.
It is important for the quality of the weld
that the spray transfer is obtained.
are two different MIG-welding processes, conventional
MIG and pulsed MIG:
MIG uses a constant voltage DC power
source. Since the spray transfer is limited
to a certain range of arc current, the conventional
MIG process has a lower limit of arc current
(or heat input). This also limits the application
of conventional MIG to weld material thicknesses
above 4 mm. Below 6 mm it is recommended that
backing is used to control the weld bead.
MIG uses a DC power source with superimposed
periodic pulses of high current. During the
low current level the arc is maintained without
metal transfer. During the high current pulses
the metal is transferred in the spray mode.
In this way pulsed MIG is possible to operate
with lower average current and heat input compared
to conventional MIG. This makes it possible
to weld thinner sections and weld much more
easily in difficult welding positions.
(Tungsten Inert Gas) or GTAW-welding (Gas Tungsten
Arc Welding) uses a permanent non-melting electrode
made of tungsten. Filler metal is added separately,
which makes the process very flexible. It is also
possible to weld without filler material.
most used power source for TIG-welding generates
alternating current (AC). Direct current can
be used, but due to high heat generation on
the tungsten electrode when DC-EP (electrode
positive) welding, that particular polarity
is not feasible. In some cases DC-EN (electrode
negative) is used, however, this requires special
attention before welding, due to the arc's poor
oxide cleaning action.
TIG-welding usually uses argon as a shielding
gas. The process is a multi purpose process,
which offers the user great flexibility. By
changing the diameter of the tungsten electrode,
welding may be performed with a wide range of
heat input at different thicknesses. AC TIG-welding
is possible with thicknesses down to about 0,5
mm. For larger thicknesses, > 5 mm, AC TIG-welding
is less economical compared to MIG-welding due
to lower welding speed.
TIG-welding with electrode negative is used
for welding thicknesses above 4 mm. The negative
electrode gives a poor oxide cleaning compared
to AC-TIG and MIG, and special cleaning of joint
surfaces is necessary. The process usually uses
helium shielding gas. This gives a better penetration
in thicker sections. DC TIG-welding is applicable
for welding thicknesses in the range 0,3 - 12
mm. More and more popular is also pulsed DC
TIG-welding, which makes it possible to weld
uniform welds with deeper penetration at the
same heat input. Pulse frequency is usually
in the range 1 - 10 Hz.