Innovative Stainless Steel Applications in transport ... - Euro Inox

• Tungsten inert gas welding (TIG)
• Plasma arc welding (PAW)
Shielded metal arc welding (SMAW, “stick welding”)
Shielded metal arc (SMAW), also called manual metal arc welding (MMAW), is an arc
welding process that uses a consumable shielded electrode, up to approximately
400 mm in length, as the filler material. The arc is formed between the electrode and the
workpiece. The core wire of the electrode melts and molten metal transfers into the
weld pool through the arc in droplets, which are shielded from oxidation by the gases
and slag formed from the electrode coating. Eventually, the slag solidifies on top of the
weld bead, where it continues to protect the solidified weld metal. It is removed after
welding. The main disadvantages of SMAW are the use of a non-continuous electrode
and the formation of slag that has to be removed. As a consequence of the former, the
technique is non-automated and requires skilled welders. Today, SMAW has been
mostly superseded in production by more productive methods, such as MIG/MAG, but
it still plays an important role in on-site installation and repair work.
Metal inert or active gas welding (MIG/MAG) and variants
In MIG/MAG or gas metal arc welding (GMAW), the arc is formed between a
continuous, consumable filler-metal wire and the workpiece. A wire feed unit delivers
thin (typically ø 0.8 to 1.2 mm) filler metal wire through the welding torch into the arc.
The molten metal is transferred either by dipping into the weld pool or through a spray
of coarse or fine droplets. The shielding gas may be either inert (pure argon) or active
(an argon and carbon dioxide mixture). Carbon steel welding is almost always MAG
(using active gas). MIG (using inert gas) is usually used for non-ferrous metals.“MIG
welding”, however, is often employed as a general term covering both variants. A multipurpose
welding hose supplies the wire, welding current, shielding gas, control power
and (in some cases) cooling water – in their own conductors, cables and hoses – to the
torch.
With the introduction of increasingly high-strength C-Mn and stainless steel grades,
new developments in MIG/MAG-based welding techniques have emerged. The high
material strength achieved, at least partially, by complex thermo-mechanical treatments,
is easily diminished by the heat input of arc welding processes. The consequent need to
control and decrease heat input has led to more sophisticated power-source
technologies, such as digital welding current control and even wire-feed pulsing
techniques. Another approach is to use lower-melting filler metals (usually various
copper-based alloys, such as silicon or aluminium bronzes), in which case not fusion
welding but brazing or braze-welding is performed, using MIG/MAG equipment.
83