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

Combined with modern pulsing techniques, considerable heat-input reduction has been
achieved with these arc brazing methods.
MAG welding with tubular cored filler wire – i.e. flux cored arc welding (FCAW) or
metal cored (MCAW) arc welding – is a MIG/MAG variant in which solid filler metal
wire is replaced by hollow filler wire. Flux cored wire is filled with gas and slag
formers similar to those used in SMA electrode coating – hence the expression “insideout
stick electrode”. Alternatively, the wire electrode can be filled with metal powder,
for increased filler-metal deposition rate and productivity. Advantages over MIG/MAG
are improved productivity (deposition rate kg/h), improved penetration and protection
against certain weld defects, such as porosity. The productivity of MIG/MAG processes
with solid or tubular wire can be further improved by using two or more wires instead of
one. The most common versions are twin arc, where one source powers two wires, and
tandem, where two wires are powered by two separate sources.
Submerged arc welding (SAW)
Even higher deposition rates can be reached with submerged arc welding (SAW), which
is not a gas arc method but a technique of its own. As with MIG/MAG, the arc is
formed between a continuous consumable wire electrode and the workpiece, but instead
of a shielding gas, the molten filler metal and weld pool are protected by a layer of flux
powder. This flux consists of metal powders and elements also found in SMA electrode
coating and MAG flux cored electrode wires, that form both shielding gases and
protective slag. Productivity can be further increased by using multiple wires and power
sources – up to six have been reported – or by feeding metal powder into the weld pool.
A typical use for all these high-productivity methods is thick-section welding of mild
and stainless steel. The process cannot be performed manually and the welding position
is limited to flat, horizontal or horizontal-vertical. Overhead welding is not feasible.
SAWs tend to have a higher heat input and thus a slower cooling rate than the other
processes described here.
Tungsten inert gas welding (TIG)
Tungsten inert gas welding (TIG) or gas tungsten arc welding (GTAW) is also a gas arc
process, where an electric arc is formed between a non-consumable tungsten electrode
and the workpiece. The weld pool and possible filler metal are protected by an inert
shielding gas. Tungsten –possibly with small alloying additions – is used for the
electrode, because of its high melting point of around 3400 °C. The weld zone and
electrode are protected by an inert shielding gas. TIG welding can be carried out either
autogenously (i.e. without filler wire addition) or with filler wire. In manual TIG
welding, the filler wire rod, typically ø 1.6 to 3.2 mm and 1 m long, is fed into the weld
pool with one hand while the torch is held in the other. In mechanised TIG welding, a
continuous wire filler metal is automatically fed into the weld zone. The productivity of
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