Multi-pass welding technique
Multi-pass welding technique is a method for filling large groove cross-sections by successively depositing multiple weld passes. Each new pass hides and improves the underlying, partially remelted zone.
Physico-Chemical Mechanism of Action
In multi-pass welding, a joint is filled in several steps. Each new weld pass tempers the underlying, partially remelted zone and bonds it with the material above. This creates a stronger connection and improves the toughness of the joint.
Metallurgical Relevance & Welding Risks
Multi-pass welding technique reduces the risk of porosity and increases joint strength. However, inaccurate layering can lead to irregularities or distortion, which can affect overall alignment. Missing tempering of the lower layers can also cause pitting or cracks.
Workshop Practice & Action Instructions
For multi-pass welding, precise alignment and uniform layering are crucial. Welding times and temperatures must be exactly observed. A typical procedure: start with a thin weld pass, let it cool, then add a second pass, and repeat until the joint is fully filled. The total thickness of the layers should match the original material.