Weld defects, their Causes & Remedies

Two Major Aspects of Fusion Welding

Effects of weldingDefects of welding
Effects of welding are those which will always happen when we weldDefects are those which can be theoretically eliminated, such as
Residual stresses
Cracks, Lack of Fusion, slag inclusions, porosity and undercuts
DistortionOnly when we understand the nature of these defects and why they occur, can we eliminate them
Formation of HAZ with metallurgical changes

Discontinuities & Defects

Discontinuity
An interruption of the typical structure of a material, such as a lack of homogeneity in its mechanical, metallurgical, or physical characteristics.
A discontinuity is not necessarily a defect but all defects are discontinuities.
Defect
A defect is a rejectable discontinuity, which occurs in an amount great enough to render a particular object or structure unsuitable for its intended service based on criteria in the applicable code.

Classification of Defects

Planar defects / Two dimensional defectsGeometric defectsGeometric defects
cracks, lack of fusion, lack of penetration, are critical in nature and are not tolerated to any extentslag inclusion, cavities, porosity, etc are tolerated to a certain extent depending on the product class and applicable code.excess reinforcement, under fill, root suck back, distortion are also permitted to a certain extent.

Types of Defects

External defectsInternal defectsDimensional defects
Cracks
Blowhole and porosity
Slag Inclusions
Lack of fusion
Lack of Root penetration
Tungsten inclusion
Lamination
Cracks
Blowhole and porosity
Slag Inclusions
Lack of fusion
Lack of Root penetration
Tungsten inclusion
Lamination
Distortion
Incorrect Joint Penetration
Incorrect Weld Size
Incorrect Weld Profile
Misalignment
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