Advanced Welding Processes: Technologies and Process Control

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Advanced welding processes
based flux coatings. These coatings give improved arc stability and excellent
weld bead surface finish. Electrodes have also been developed for the fabrication
of the new corrosion-resistant alloys and, in particular, duplex and high
molybdenum stainless steels. [41]
4.3 Submerged arc welding consumables
The submerged arc process is well established and a standard range of wires
and fluxes has been devised for the most common applications. Two important
advances in the process have been realized by:
∑ the development of high-toughness consumables;
∑ the use of iron powder additions.
4.3.1 High-toughness consumables
Higher-toughness consumables have been developed in response to the
requirement for reasonable impact properties down to –40 ∞C for offshore
structures. This has been achieved by the use of wires which are microalloyed
with titanium and boron and a semi-basic flux. [42] Typical Charpy-
V notch curves showing the improvement in toughness compared with a
conventional SD3 molybdenum wire are shown in Fig. 4.2. [43]
4.3.2 Addition of iron powder
The addition of iron powder to the submerged arc weld increases the deposition
rate of the process by more than 60% [44–46] as well as offering improvements
in weld metal quality. The technique takes advantage of the fact that excess
arc energy is normally available in submerged arc welding; this usually
results in increased melting of the parent plate and high levels of dilution. If
a metal powder is added to the weld pool, some of the arc energy is dissipated
in melting this powder and the additional metal which results improves the
C v energy absorbed (J)
200
150
100
50
C-Mn Wire
Tl-B Wire
0
–120 –100 –80 –60 –40 –20 0
Test temperature (∞C)
4.2 High-toughness SAW consumables: lower bound Charpy-V
impact transition curves for different SAW wires. [43]