What is the definition of "overlap"?
The protrusion of unfused weld metal beyond the weld toe or weld root. Overlap is almost always unacceptable in a welded part.

Learn more about overlap in the class Visual Inspection of Welds 280 below.


Welding Training


Class Information
Welding Training Tooling U-SME classes are offered at the beginner, intermediate, and advanced levels. The typical class consists of 12 to 25 lessons and will take approximately one hour to complete.
Class Name:Visual Inspection of Welds 280
Description:This class will teach you about the visual inspection of welds, the equipment used during a visual inspection, proper inspection procedure, and common discontinuities in the surface of a weld.
Prerequisites: 650110  650130 
Difficulty:Intermediate
Number of Lessons:15
Language:English, Spanish
 
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Class Outline
  • Objectives
  • Weld Quality
  • Visually Inspecting a Weld
  • Visual Inspection Procedure
  • Visual Inspection Equipment
  • Procedure Before Welding
  • Procedure During Welding
  • Procedure After Welding
  • Weld Discontinuities
  • Distortion: Internal Stress, Porosity, and Slag Inclusion
  • Distortion: Weld Spatter, Incomplete Fusion, and Melt-Through
  • Weld Size
  • Weld Profile
  • Cracking
  • Summary
  
Class Objectives
  • Describe weld quality.
  • Describe visually inspecting a weld.
  • Describe the procedure used to visually inspect a weld.
  • List the equipment used to visually inspect a weld.
  • Describe operator procedure before welding.
  • Describe operator procedure during welding.
  • Describe operator procedure after welding.
  • Describe weld discontinuities.
  • Identify internal stress, porosity, and slag inclusion.
  • Identify weld spatter, incomplete fusion, and melt-through.
  • Identify weld size discontinuities.
  • Identify weld profile discontinuities.
  • Identify weld cracks.

Class Vocabulary

Vocabulary TermDefinition
American Welding Society AWS. A professional organization that supports the welding industry and promotes welding and related processes.
arc blow A condition resulting from the interaction of an electric current and the magnetic field the current induces. Arc blow can cause excessive spatter, incomplete fusion, and porosity.
AWS American Welding Society. A professional organization that supports the welding industry and promotes welding and related processes.
centerline crack A gap or break in the surface of a weld parallel to the weld axis that may be along the centerline of the weld or near the weld toes. A centerline crack is also called a longitudinal crack.
concave Curving inward like the inside of a bowl.
consumable An electrode that conducts electricity to the arc but also melts into the weld as a filler metal.
convex Curving outward like the exterior of a circle or sphere.
crack A discontinuity characterized by a break or gap in the surface of a weld. Cracks can be classified as longitudinal, transverse, crater, and heat affected zone.
crater crack A gap or break in the surface of a weld that occurs at the crater of a weld because welding was improperly terminated. Crater cracks are also called star cracks.
defect An irregularity in the specified and expected composition of a weld that exceeds the part design's tolerances. A defect is a rejectable discontinuity.
discontinuity An irregularity in the specified and expected composition of a weld. A discontinuity is not always a defect.
distortion A disfigurement that signals that a weld joint was not prepared properly.
excess concavity The distance from the weld face perpendicular to a line joining the weld toes that arcs in and toward the weld joint.
excess convexity The distance from the weld face perpendicular to a line joining the weld toes that arcs out and away from the weld joint. Excess convexity has a greater potential for weld failure, causing longitudinal cracking and crater cracking.
excess penetration A discontinuity characterized by an excess of weld metal on the back side of the joint. Excessive heat, slow movement, and poor joint alignment can cause excessive penetration.
excessive reinforcement The use of more weld metal than is required to fill a groove weld joint. Excessive reinforcement creates high concentrations of stress at the weld toes.
fillet gage A device that determines whether or not a fillet weld is within specified tolerances. A fillet gage is a specific kind of weld gage.
fillet weld A type of weld that is triangular in shape and joins two surfaces at right angles to each other in a lap joint, T-joint, or corner joint. Fillet welds are the most common types of welds.
heat affected zone crack A cold gap or break in the surface of a weld that forms in the heat-affected zone of a base metal. Heat affected zone cracks are also called underbead cracks.
hold point A predetermined stopping point in the fabrication process at which the weld must be inspected. Hold points are used between passes of multi-layer welds to assure a weld is properly cleaned between passes.
incomplete fusion The lack of complete integration between the weld metal and adjoining weld beads. Incomplete fusion is caused by faulty operator technique, improper preparation of the base metal, insufficient welding heat, lack of access to the adjoining beads, and improper joint design.
incomplete penetration A discontinuity characterized by an unpenetrated and unfused area in a joint that occurs when weld metal does not extend through the thickness of the joint. Incomplete penetration can result from insufficient welding heat, improper joint design, and improper lateral control of the welding arc.
internal stress A force from within the material of an object that attempts to deform that object. In a weldment, internal stress is caused by thermal expansion and contraction as the weld metal cools and solidifies.
interpass temperature A specific temperature range of the base material. The interpass temperature should not fall below the preheat temperature.
longitudinal crack A gap or break in the surface of a weld parallel to the weld axis that may be along the centerline of the weld or near the weld toes. A longitudinal crack is also called a centerline crack.
melt-through The visible reinforcement of a weld root that happens when a joint is welded from only one side.
non-destructive examination The evaluation of a weld, or material to be welded, that does not affect the servicability of the weld or material. Non-destructive examination costs less because the part is not destroyed.
overlap The protrusion of unfused weld metal beyond the weld toe or weld root. Overlap is almost always unacceptable in a welded part.
part drawing A document that includes the specifications for a part's production.
porosity A discontinuity characterized by the appearance of tiny voids or bubbles on a weld bead, resulting from trapped gases in a material. Excessive porosity can weaken a weld.
preheat temperature A specific temperature to which the base material is heated prior to welding.
root opening The point at which fusion should occur between the weld metal and adjoining weld beads. The root opening provides access to the root of a weld.
root pass The first layer of a multi-layer weld. The root pass is the most critical layer of a weld because it is susceptible to slag inclusion and cracking.
slag inclusion A discontinuity resulting from the mutual dissolution of flux and nonmetallic impurities in some welding processes. Slag inclusion can affect the strength and integrity of a weld in its final application.
specifications The design parameters that set the limits of acceptable deviation for a part's intended application. Specifications are also called specs.
specs The design parameters that set the limits of acceptable deviation for a part's intended application. Specs are also called specifications.
star cracks A gap or break in the surface of a weld that occurs at the crater of a weld because welding was improperly terminated. Star cracks are also called crater cracks.
transverse crack A gap or break in the surface of a weld perpendicular to the weld axis that may be completely within the weld metal or may extend from the weld metal into the base metal. Excess hydrogen, an excessively strong weld metal, and high levels of residual stress result in transverse cracks.
underbead crack A cold gap or break in the surface of a weld that forms in the heat-affected zone of a base metal. Underbead cracks are also called heat affected zone cracks.
undercut A groove melted into the base metal at the weld toe or weld root that is left unfilled by weld metal. The groove concentrates stress on the weld, and could be a defect if outside the part's tolerances.
underfill The extension of a weld face or root surface of a groove weld below the adjacent surface of the base metal. Underfill results from the failure of a welder to completely fill the weld joint.
weld face The exposed surface of a weld on the side from which the welding was done.
weld gage A device that determines whether or not a weld is within specified tolerances. Some weld gages are designed for specific weld types like the fillet weld gage.
weld root The point at which the back of a weld intersects the surfaces of the base metal.
weld spatter Small particles of nonmetallic material that are expelled during the fusion of the weld and base metals. Weld spatter is considered a serious discontinuity if it interferes with the servicability of the part or with an additional operation, like painting.
weld toe The point at which the weld face and the base metal meet. Weld toes can experience cracking and undercut.
weldment A welded joint.