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Welder’s Handbook
Incomplete Fusion & Incomplete Penetration
Incomplete fusion (lack of fusion) and incomplete joint penetration (lack of penetration) are similar discontinuities. They result from incomplete melting at the interface between weld passes or in the root of the joint.
Incomplete fusion happens more often in some welding methods than in others. It causes unwanted stresses, and most fabrication standards and codes have strict limits on allowing incomplete fusion. Incomplete Fusion Inclusions
Incomplete penetration in a groove weld happens when the weld metal doesn't go all the way through the joint's thickness. During arc welding, the arc starts between the electrode and the nearest part of the base metal. The rest of the base metal gets heated mostly through conduction. If the part of the base metal closest to the electrode is far from the joint root, the heat might not spread enough to reach the necessary temperature for proper fusion at the root. Incomplete Penetration
INCOMPLETE FUSION)
Single Bevel Groove
INCOMPLETE FUSION)
Incomplete Penetration
INCOMPLETE FUSION)
Double Bevel Groove
INCOMPLETE FUSION)
Incomplete Fusion
Fillet Groove
INCOMPLETE FUSION)
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