Welding, like any other metal work process, is subject to a variety of defects. Not only does welding involve the application of fire on metal surfaces, but there are many technical aspects involved as well. Due to the complex nature of the processes, it’s possible to experience a few bumps along the way.

A common defect that may occur during the welding process is known as overlap welding, which can be identified as the bulge of weld metal beyond the root. The overlap is a protrusion that occurs beyond the weld toe and resembles a circle that extends into unnecessary places. . When an overlap occurs, it means that the metal is not completely fused. Although overlap is more of a weld discontinuity, it’s still classified as a defect and typically occurs in butt and fillet welds.

 What Causes Overlap Welding?

Various factors may cause the occurrence of an overlap. Generally, overlap welding occurs after the overflow of the weld pool on the weld metal surface. When the molten metal does not fuse with the base of the metal, it results in an overlap. This overlap might extend to form an angle less than 90 degrees.

Other factors that may cause overlap welding include: 

Excess Current: Using too much electric current often causes an overlap. Too much current leads to over-melting the weld material and a consequential overflow above the metal.

Excess Weld Metal: An excess supply of weld metal is another cause of overlap. Excess weld metal occurs due to a low weld speed. The gravity on the molten material causes overlapping in fillet welds.

Wrong Electrode Angle: Electrodes are highly porous, and using an electrode at the wrong angle contributes to overlap welding. Larger electrodes create a greater opportunity for too much weld material to be applied to the surface. Because of this, using an electrode larger than the metal size can lead to an overlap.

How to Prevent Overlap Welding

A proper welding technique is the ultimate solution to prevent overlaps in welding. Using smaller electrodes, the right amount of current and correct welding techniques are all effective ways to prevent overlap defects.  

Use Small Electrodes: Small electrodes reduce gaps that are created when not enough weld is applied. Small electrodes also lessen the chance of excess materials and overlaps left on the surface. 

Apply the Right Amount of Current: Currents should be regulated depending on the material you’re working with. The levels of alternating or direct current should reflect the nature of the job at hand. When an electrode glows or appears over-brightened, too much current is being applied. A general rule of thumb is that the ratio of an inch of electrode diameter to amperage should be 1:1000. This means that a quarter-inch diameter will take about 250 amps.

Strengthen Welding Techniques: Welding is a technique that should be mastered. Slow welding often results in the overlap of the weld material. Correcting your welding speed is one way to avoid an overlap. Additionally, how you align your materials is important. Depending on the specific welding technique, proper preparation and a good choice of materials is critical. 

Correcting Overlap in Welding

Overlap welding is often considered more of an excess disposition than a defect. Unlike other welding defects, it’s possible to fix a visible overlap by grinding the excess weld metal. Surface grinding smoothly at the base of the metal removes overlaps.

It is essential to exercise as much precision as possible when welding. By following the fight welding procedure, you can easily avoid welding overlaps all together.