Overlap in Welding – What Is It? And How to Prevent It

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Many welding techniques came about to prevent defects. In fact, much of welding is about avoiding defects, and the more careful you are, the better the weld. 

This emphasizes the importance of understanding various welding defects and their remedies. 

This article focuses on welding overlap, a common defect that can be easily prevented. The discussion below includes its definition, causes, and solutions. So, please stick with us to learn more about welding overlap.

What is Welding Overlap?

Ideally, the base metals and filler metal melt and fuse into each other to create a weld joint. 

Sometimes, however, the extra filler metal is added into the weld pool, and it does not mix properly with the base metal, allowing it to flow outside the weldment. This is known as welding overlap.

An overflowing swimming pool is a good analogy since we are already talking about a pool. When surplus water exceeds a pool’s capacity, it flows out of the pool and onto surfaces where it should not be. 

Welding overlap is extra filler material that spreads out around the bead. Technically speaking, welding overlap is extra filler material that protrudes beyond the weld toe or root.

4 Main Causes of Overlap & How to Prevent it

Radiography example of a overlap on a weld

Welding overlap is classified as a weld defect. But it is low on the list of defects. Unlike other flaws, it does not affect the performance of the weld very much. 

Instead, weld overlap negatively affects costs and aesthetics. No welder wants a sloppy weld or to waste money, so avoiding it must be a welder’s priority. 

The four major causes and remedies are summarized below.

1. Amperage

Amperage, or current, is a significant factor in overlaps. A large amount of filler material gets deposited in the weld pool if it is set too high. If this amount is more than required, it naturally flows out and solidifies elsewhere. 

To avoid this, consult a chart or an experienced welder about amperage settings for your material, fillet dimensions, and joint type. Once you have a good starting amperage level, do a few tests and fine-tune the settings before ruining the workpiece.  

Test it out first. If you see overlap, keep lowering the value until you get satisfactory results. 

2. Travel Speed

Low travel speed also causes overlap. The filler deposition rate is constant during the weld, so if you go too slow, filler will accumulate in the weld pool and cause overlapping.  

The solution is obvious. Go a bit faster when you detect overlap. It is pretty likely that you will see improved results. Yet, also keep in mind that going too fast is also problematic. Finding the right balance should be the goal.

3. Electrode Selection & Usage

Incorrect electrode selection and poor technique cause many welding defects, including overlap. 

Electrode Angle

The electrode angle impacts weld penetration and how much filler is deposited on either side of the weld bead. So, if the angle is incorrect, it causes more filler to enter on one side. 

In this case, overlapping is unavoidable. To keep it from happening, optimize the electrode angle to ensure even deposition of filler material. 

Electrode Size

From the discussion above, it is clear that the amount of filler metal decides whether or not overlapping occurs. 

The electrode is the filler, and if you use a large electrode, there is more filler. So, if you see an overlap, it might be due to a large electrode. Make sure to select the correct electrode size. You can study the guides/charts or ask an experienced welder. 

4. Welding Technique

Edge preparation, base metal arrangement, and cleanliness also contribute to overlapping. If there are bumps or craters on the base metal’s edges, or you do not align the joint properly, defects will occur. 

Take as much care as possible during pre-weld preparations to avoid mishaps like overlaps.

How to Fix Welding Overlap

No matter how attentive you are, weld defects will occur now and then. In the event you do have some overlap, fear not. You can fix it with a bit of elbow grease. 

First, identify the boundaries of your weldment or the weld toe, and mark it. Then grind off the overlap up to the line. Take care not to harm the joint in the process. 

When finished, you will see that the weld looks more pleasing and professional. 

Conclusion

Welding overlap is a common defect caused by several factors.

But with a bit of care and practice, you can produce defect-free welds. Take care when selecting your electrode and setting the amperage. And as always, be sure to understand the welding techniques/procedures for the weld at hand.

If overlap does occur, you can always remove it by grinding carefully to avoid damaging the joint. 

If you think we missed something or want to chime in on welding overlap – leave a comment below! Thanks for reading.

About Jeff Grill

Jeff Grill hails from Long Island, a 118 mile stretch of land that starts just off the coast of Manhattan and stretches deep into the Atlantic ocean. He has always been interested in welding from an early age and has the cuts and bruises to prove it as he set out to work with a variety of metals.

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