Welding Discontinuities

Some examples of welding discontinuities are shown below.  Evaluation of the discontinuity will determine if the discontinuity is a defect or an acceptable condition

Incomplete Fusion - A weld discontinuity in which fusion did not occur between weld metal and fusion faces or adjoining weld beads.
		Undercut - A groove melted into the base metal adjacent to the weld toe or weld root and left unfilled by weld metal. Overlap - The protrusion of weld metal beyond the weld toe or weld root.
		Underfill - A condition in which the weld face or root surface extends below the adjacent surface of the base metal. Incomplete Joint Penetration - A joint root condition in a groove weld in which weld metal does not extend through the joint thickness
Partial joint penetration groove welds are commonly specified in lowly loaded structures.  However, incomplete joint penetration when a full penetration joint is required, as depicted above, would be cause for rejection.  A fix for an incomplete penetration joint would be to back gouge and weld from the other side.   Another acceptable partial penetration joint is shown below.
	Partial penetration joint on the left without discontinuities is an acceptable condition where appropriate.  Appropriate engineering decisions need to be applied to determine what type of joint should be specified for a given application.

Engineering should be contacted to determine whether partial penetration of full penetration joints are appropriate for a particular situation.

Above are several different representations of weld cracking.
Below is a representation of a convex fillet weld without discontinuities.

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About Mukhamad Aziz

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