Published on 13-Dec-2022

What Is Lack Of Fusion In Welds? Here's What You Need To Know

What Is Lack Of Fusion In Welds? Here's What You Need To Know

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All the welders utilize numerous techniques to ensure that the welds they generate are powerful and strong, also free of any kind of defects. One of the most general defects that the welders observe is — lack of fusion, which can occur due to a number of factors like — incorrect parameters of welding, contaminated surface, etc. This article provides all the relevant information related to the lack of fusion, its cause, how to check the lack of fusion, and much more. Let's start the article by understanding the meaning of lack of fusion!



What Is The Lack Of Fusion?

When it comes to welders, they are often equipped with the task of combining two different pieces of metal together. This is accomplished by heating up metal to bring it to the molten stage and then utilizing a welding rod to combine both pieces. The weld will become strong if only the two pieces of metal are fused appropriately.

Nonetheless, if there is a lack of fusion, the weld might fall weak and be a total failure. Plus, many factors can lead to a lack of fusion, including rusted or dirty metal, improper welding settings, as mentioned earlier, and poor welding methods. If you observe a lack of fusion in the welds, then you must take some steps to solve the problem before moving forward with that particular weld.

There are different regions where a lack of fusion can occur in welding, such as:

a) Lack of root fusion.

b) Lack of interpass fusion.

c) Lack of sidewall fusion.

d) Lack of capping bead fusion which is also referred to as overlap in welding.


Causes Of Lack Of Fusion


There are a lot of factors that can cause a lack of fusion, some of them are explained below:

1) Improper preparation of weld bevel; yes, this is an important factor that needs to be considered. An uneven preparation of the weld surface of the weld joint or an insufficient weld bevel angle can be the reason for the lack of fusion.

2) Wrong welding parameters, i.e., if the input of heat is extremely low, the weld will not be able to fuse correctly.

3) Inadequate fit-up between the two elements of the metal can result in a lack of fusion. A Huge gap in the weld joint will not deliver a direct arc to the base metal weld surface & can lead to a lack of fusion.

4) The mode of metal transfer that provides low heat input can be the reason for the lack of fusion.

5) If the base metal is filled with rust or any kind of dirt, then it can prevent the proper fusion between the weld metal and the base metal. This will result in a lack of fusion.

6) Wrong welding method, for example — if the welder does not have a grasp of the electrode steadily and is in the right place, it can eventually lead to a lack of fusion.


Lack of weld fusion can bring in a number of problems, comprising reduced strength and declined corrosion resistance. The lack of fusion present in the weld will be the reason for the reduced notch strength & power of the weld metal.


How can the Lack Of Fusion Be Fixed?


One of the biggest problems that every welder comes across is the problem of lack of fusion. The problem can be caused by many different factors, as already mentioned above — incorrect welding parameters, wrong welding technique, poor preparation of the weld joint, and much more. In a few cases, a lack of fusion can be solved by adjusting the welding parameters.

Before you start with the process of welding, you will have to check whether the weld is properly cleaned or free of contaminants. It is extremely important to clean the weld before welding. And if the weld puddle is too large, it may be necessary to curtail the welding current. On the other hand, if the weld bead is extremely small, it might become essential to increase the welding current.

In different situations, lack of fusion is difficult or impossible to fix by adjusting the parameters of welding. In these circumstances, it is essential for you to make use of a different welding procedure or to utilize a different kind of filler metal.


How To Know If There Is A Lack Of Fusion?


When it comes to welding, it is a significant procedure in various industries, but the thing is, if the welds are not conducted properly, they can result in a lot of difficult problems. And one such difficulty is none other than — lack of fusion! This can happen when the weld metal does not combine with the base metal properly. And substantially, this can cause the weld to become weak & delicate and exposed to failure.

Lack of fusion is the linear indication with the same traits, similar to welding cracks, and very destructive. They tend to drastically decrease the welding joint's strength, specifically for cyclic or dynamic loading applications. There Are a lot of ways to keep a check on the lack of fusion in welds. The two most common non-destructive testing methods — ultrasonic testing and radiographic testing- can be utilized to determine this type of defect.

Ultrasonic testing utilizes sound waves to develop images out of the weld, while radiographic testing uses X-rays or other radiation to develop images out of the welds. These pictures ultimately help in finding any regions where the weld metal has yet to be fused appropriately with the base metal. If a lack of fusion is discovered, then it must be corrected as soon as possible.


Summing It Up

This was all about the lack of fusion, its causes, etc. But if you want to read more about such topics, you can visit our website for more informative articles. Also, if you have any questions regarding the topic or any other relevant subject, you can contact us immediately! We are right here to help you in every possible way. 

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