Lack of Fusion
Lack of fusion is when the weld metal is not fused to the base metal.
This can occur between the weld metal and the base metal or between
passes in a multiple pass weld. Causes of this defect can be:
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excessive travel speed
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electrode size too large
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welding current too low
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poor joint preparation
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letting the weld metal get ahead of the arc.
Lack of fusion can usually be prevented by:
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reducing the travel speed
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using a smaller diameter electrode
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increasing the welding current
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better joint preparation
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using a proper electrode angle.
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BOC Smootharc Advance II MIG 400R Operating manual
