Advanced Welding Processes: Technologies and Process Control

Filler materials for arc welding 57
inert dust, some of the consumables and flux constituents give rise to substances
that are thought to be toxic; hexavalent chromium from chromium-bearing
consumables and barium compounds found in the fume of some self-shielded
wires are the main areas of concern.
The level of both the particulate fume and, in particular, potentially toxic
substances must be controlled to comply with health and safety requirements
and this is normally achieved by means of simple local fume extraction.
Consistency of the consumable
The manufacture of flux-cored consumables is more complex than the
manufacture of solid wires, but similar to that involved in the production of
MMAW electrodes. It is important that the flux core is chemically homogeneous
and evenly distributed throughout the consumable. It is also important that
the surface of the wire is clean and free from excess drawing lubricant.
Although these requirements presented a problem in early consumables the
introduction of improved manufacturing techniques and on-line quality
monitoring [54] now ensures that consistent consumable properties are
maintained.
4.5 Summary
There have been steady improvements in consumables for MMAW, SAW
and GMAW welding. The introduction of high-toughness, moisture-resistant
low-alloy steel and enhanced-performance rutile-coated stainless steel MMA
electrodes, iron powder addition and Ti–Bo microalloyed wires for SAW and
the use of low-residual wires for GMAW are useful examples of this
evolutionary process. The introduction and exploitation of FCAW is perhaps
more remarkable as indicated by the application trends that have been discussed
in Chapter 2.