Advanced Welding Processes: Technologies and Process Control

20
Labour cost ($)
1200
1000
800
600
400
200
0
Advanced welding processes
20%
50%
80%
0 2 4 6 8 10 12
Arc time (h)
2.5 Effect of operating factor on costs (for a labour rate of $50 per
hour).
Post-weld operations
The welding process may generate problems which need to be rectified after
welding. The most common problems of this type are distortion and residual
stresses, although metallurgical problems such as grain growth and hydrogeninduced
cold cracking and cosmetic problems such as damage to surface
coatings and spatter deposits must also be considered. The need to carry out
additional mechanical or thermal operations after welding will obviously
increase the cost of fabrication and process developments that reduce this
requirement are desirable.
The risk of defects often generates a requirement for costly post-weld
inspection and non-destructive examination and, although recent codes of
practice allow the significance of defects to be related to the service conditions,
if rectification is required, this involves increasing the value of work in
progress, causes delays in production and is often labour intensive. Early
identification of potential quality problems is therefore both desirable and
cost effective.