Arc welding processes use a welding power supply to create an electric arc
between an electrode and the base material to melt metals at the welding point.
They can use either direct (DC) or alternating (AC) current, and consumable or
non-consumable electrodes. The welding region is sometimes protected by some
type of inert or semi-inert gas, and filler material is sometimes used as well.
Shielded metal arc welding (SMAW), also known as manual metal arc welding (MMA)
or stick welding, uses electric current to strike an arc between the consumable
electrode rod and the base material. The electrode is made of steel and is
covered with a flux that protects the weld area from oxidation and contamination
by producing CO2 gas during the welding process. The electrode core itself acts
as filler material, making a separate filler unnecessary. The process is very
versatile, requiring little operator training and inexpensive equipment.
However, weld times are rather slow, since the consumable electrodes must be
frequently replaced and because slag, the residue from the flux, must be chipped
away after welding. Furthermore, the process is generally limited to welding
ferrous materials, though specialty electrodes have made possible the welding of
cast iron, nickel, aluminum, cooper, and other metals. It is one of the most
common welding techniques, and is used extensively in construction.
Gas metal arc welding (GMAW), also known as metal inert gas welding (MIG),
is a manual or automatic welding process that uses an automatic wire feed as an
electrode and an inert or semi-inert gas mixture to protect the weld from
contamination. Since the electrode is continuous, welding speeds are greater for
GMAW than for SMAW. However, because of the additional equipment, the process is
less portable and versatile, but still useful for industrial applications. The
process can be applied to a wide variety of metals, both ferrous and
Similar to GMAW, flux-cored arc welding (FCAW) uses the same equipment but
use wire that consists of a steel electrode surrounding a powder fill material.
This cored wire is more expensive than the standard solid wire and can generate
fumes and/or slag, but it permits higher welding speed and greater metal
Gas tungsten arc welding (GTAW), or tungsten inert gas (TIG) welding, is a
manual welding process that uses a non-consumable electrode made of tungsten, an
inert or semi-inert gas mixture, and a separate filler material. Especially
useful for welding thin materials, this method is characterized by a stable arc
and high quality welds, but it requires significant operator skill and can only
be accomplished at relatively low speeds. It can be used on nearly all weldable
materials, though it is most often applied to stainless steel and light metals.
It is often used when quality welds are extremely important, such as in aircraft
and naval applications.
Plasma arc welding uses a plasma gas that flows around the electrode
(usually made of tungsten), while a shielding gas protects the welding region
from contamination. The arc is more concentrated that the GTAW arc, making
transverse control more critical and thus generally restricting the technique to
a mechanized process. Because of its stable current, the method can be used on a
wider range of material thicknesses than can the GTAW process, and furthermore,
it is much faster. It can be applied to all of the same materials as GTAW except
magnesium, and automated welding of stainless steel is one important application
of the process. A variation of the process is plasma cutting, an efficient steel
Submerged arc welding (SAW) is a high-productivity welding method in which
the arc is struck beneath a covering layer of flux. This increases arc quality,
since contaminants in the atmosphere are blocked by the flux. The slag that
forms on the weld generally comes off by itself, and combined with the use of a
continuous wire feed, the weld deposition rate is high. Working conditions are
much improved over other arc welding processes, since the flux hides the arc and
no smoke is produced. The process is commonly used in industry, especially for