Advanced Welding Processes: Technologies and Process Control

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Advanced welding processes
qualification is both time consuming and costly and, once a procedure has
been established, the additional cost involved in adopting a new process may
be prohibitive unless the cost of re-qualification can be recovered from the
potential savings.
The success of this control technique also depends on ensuring that the
predetermined procedure is actually followed in production; this in turn
means monitoring the performance of the equipment used and ensuring that
the operator adheres to the original technique. Unfortunately this is not
always the case and additional costs are often incurred in post-weld inspection
and weld repair. The development of techniques which enable the welding
process to be controlled more effectively should have a significant impact on
costs. The use of more tolerant consumables, more repeatable equipment and
processes, automation, on-line monitoring and real-time control systems all
contribute to improved overall process control. In addition, there is renewed
interest in the use of modelling and parameter prediction techniques to enable
the optimum welding parameters to be established for a given welding situation.
Joint design
Over-specifying the joint requirements has a marked effect on the cost of
welding; in the case of a simple fillet weld, a 1 mm increase in the specified
leg length can increase the cost by 45% as shown in Fig. 2.3.
The choice of a specific joint design can automatically preclude the use of
the most cost-effective process; for example, limited access or complex joint
profiles may limit the process choice and it is important for the designer to
understand the limitations of the joining process to avoid these restrictions.
Conversely, the selection of an appropriate process may reduce both joint
preparation costs and joint completion time. In general, the joint completion
time is related to the required weld metal volume and it can be seen from
Cross sectional area mm 2
180
160
140
120
100
80
60
40
20
0
3 5 8 12
Fillet leg length (mm)
2.3 Effect of joint design (fillet leg length) on weld metal
requirements.