Excessive Root Penetration
Macroscopic root sag is an excess at the weld root, caused by too much heat input or poor root backing. It affects flow in pipes and can create a notch effect.
Physicochemical Mechanism of Action
Macroscopic root sag forms when the heat input during welding is too high or the root backing is inadequate. The metal gap then is not fully bridged and a visible sag appears.
Metallurgical Relevance & Welding Risks
Macroscopic root sag can cause various problems. It hurts the flow mechanics in pipelines, which leads to pressure losses and efficiency losses. It can also create a notch effect that makes the material prone to cracking.
Workshop Practice & Instructions
To avoid macroscopic root sag, take these measures:
• Reduce the heat input through optimal machine settings.
• Use adequate root backing, e.g. a stable holder or extra fixing on the workpiece.
• Check the welding parameters regularly and adjust them to the specific conditions.