May 30, 2014
Q: What are the reasons to oscillate a weld process?
A: Oscillation helps a steelworker using electroslag to fabricate components for San Francisco’s Bank of America building; it helped to minimize the arm fatigue of a pipefitter as he built Louisiana’s River Bend nuclear power plant; and it will assist the ironworker building the One World Trade Center to achieve better weld toe fusion, allowing his welds to transfer stress smoothly between support beams.
Oscillation is the side-to-side manipulation of a weld in progress. It is measured in amplitude (how far), frequency (how often), and dwell time (for how long). There are a number of ways and reasons a weld process would be oscillated.
If you spend any time around robotic gas metal arc welding (GMAW), you;ll notice that the welding torch performs a constant side-to-side motion. Typically referred to as a weave, this form of oscillation helps the robot find its way along the joint by monitoring changes in the arc.
Another good example of oscillation is the “walking the cup” technique during gas tungsten arc welding (GTAW). A welder, typically a pipefitter, will do this to minimize body fatigue, increase bead width, and improve tie-in at the weld’s toe. A real craftsman will rock that GTAW cup along the joint and make a beautiful finish weld with a consistent fact completely around the pipe joint. The end result can be a real work of art (or a real cobbled mess, for that matter).
Another type of oscillation is manipulating the molten weld pool with a magnetic force. Common with (but not limited to) mechanized GMAW and GTAW processes, this magnetic force moves the molten puddle, not the torch, from side to side. I’ve used this technique to increase bead width for cosmetic appeal, but it also can be used to improve sidewall fusion or tie-in at the weld toe. Some wire-fed processes, such as submerged arc welding (SAW) and electroslag welding (ESW), actually twist the electrode as it is fed as a form of oscillation
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