Publication history Created:. Cite Icon Cite. Abstract This article provides an overview of the types of weld discontinuities that are characteristic of specialized welding processes.
You do not currently have access to this chapter. Sign in. You could not be signed in. Reset Password. Safe Practices Welding, Brazing, and Soldering. Type of discontinuities Incomplete Joint penetration Results when the weld metal fails to extend completely through the joint thickness.
Depends upon the accessibility of the heat source and filler rod to the face area, can also result from improper joint designs. Type of discontinuities Inclusions Results when solid materials are trapped in solidifying. Because inclusions interrupt the continuity of the weld, the presence of inclusions will result some loss of structural integrity. Types of Discontinuities Porosity Proper welding technique avoids gas formation and entrapment.
Type of discontinuities Undercut Is a surface discontinuity that results from melting of the base metal at either the weld toe or weld root. It takes the form of a mechanical notch at these locations. Type of discontinuities Underfill Is a depression on the face or root surface of the weld below the surface plane of the adjacent base metal.
Is fail of welder or welding. On pipe. Type of discontinuities Overlap Is the protrusion of weld metal beyond the toe or weld root of the weld joint without fusion. Type of discontinuities Convexity This particular weld discontinuity applies only to fillet welds. Is the maximum distance from the face of a convex fillet weld perpendicular to a line joining the weld toes. Occurs to welding travel speed are to slow and too little heat or incorrect manipulation of the electrode.
Type of discontinuities Weld Reinforcement Describes a condition which can only be present in a groove weld. As well as have two other terms: Face reinforcement and root reinforcement.
Type of discontinuities Arc Strike Represent unintentional melting or heating outside the intended weld deposit area. Type of discontinuities Spatter Metal particles expelled during fusion welding that do not form a part of the weld. Type of discontinuities Lamination and delamination Are flat, generally elongated, planar base metal discontinuities found near the center of the products rolled. Seam and laps Differ from the lamination in that they always appear on the rolled surfaces. Type of discontinuities Lamellar Tearing Is a fracture separation in heavy weldments, found within or just beneath the HAZ of thick plates that were not adequately refined by steel mill.
Massive welds that are poorly located, transmit weld shrinkage stresses into the plate in its weakest direction. This create tears parallel to the surface, which then are linked together by shear fractures to form steps connected by risers perpendicular to surface. The phenomenon is called lamellar tearing. Type of discontinuities Discontinuities in Laser and Electron Beam Welding These discontinuities are due to the narrow and deep weld profiles produced by these process as well as the high travel speeds used.
Miki Jaksic. Basic Metallurgy for Welding and Fabricating Professionals. Puneet sharma. NDT may also need to be further applied after any additional postweld heat treatment has been carried out. Casting repair, a work of patience. Cast Iron have different types and only some have limited weldability while other are not weldable at all such as white cast iron. Using a correct approach, Three of the most commonly recognized forms of regulatory documents are codes, standards, and specifications.
Codes and other standards contain minimum engineering and regulating information pertinent Skip to content. Hello friends.. Weld size is affected by travel speed and welding procedures, specifically wire feed speed. It can be easily measured by the use of weld gages. Slag Inclusions — This consists of slag trapped between passes. This is impossible to detect via weld inspection after welding is complete and very hard to detect while welding. Causes are inadequate cleaning of weld surface between passes.
It can also occur in single pass welds when slag gets trapped in the root and toes of the weld. Slag inclusions prevent proper fusion and can have sharp ends which creates a crack-like behavior. Excessive Reinforcement — This is a weld that is too big or has too much convexity too much build up. Usually caused by low travel speeds or incorrect procedures. Excessive reinforcement creates high levels of stress concentrations at the toes of the weld. Melt-through from a tack weld on thin gauge material.
This is not just a heat mark, there is metal that is protruding from the surface of the base metal. Cracks — Cracks are the most detrimental discontinuity for the integrity of a welded connection. Cracks, in any amount, will constitute a defect with very few exceptions.
Cracks due to stress relieving of hardfacing welds is one of these exceptions. Cracks have sharp ends which allows them to grow, in some cases very quickly. For further explanation you can read Understanding Why Welds Crack. Cracks can lead to catastrophic failure in a relative short amount of time. It will be welding codes, standards and specifications that determine the amount allowed, if any, of the above described discontinuities.
Codes are concerned with the structural integrity of welds, no so much with aesthetics. So some fabricators will have internal quality standards that do not allow any amount of spatter or which will reduce the allowable amounts of other discontinuities.
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