What Is Full Penetration Weld

What Is Full Penetration Weld? Complete Detail & Types

As you know welding is a process of joining two metals without leaving any gap because defects in the welding process can influence the welding quality of the material. Welding is also a process of creating a permanent bond between two metals by melting and fusing them together.

The welding process uses heat from an electric arc between a consumable metal electrode and the workpiece. In other words, welding is a method of joining two metal parts together. In this article, we will let you know about full penetration techniques, their importance, and different ways to achieve full penetration.

What is Full Penetration Weld?

When welding metals, it’s important to use the correct welding technique to ensure that the final product is as strong as possible. Full penetration welds are a type of welding in which the entire piece of metal is melted and fused together.

In this type of weld, the filler material infuses the joint’s roots. This approach is usually applied to metal products with high-strain resistance. If you want a thick weld, this welding approach is best.

However, there are two types of penetration weld name as:

  1. Complete Joint Penetration (CJP)
  2. Partial Joint Penetration (PJP)
types of penetration weld

Complete Joint Penetration (CJP):

A full penetration weld is also known as complete joint penetration (CJP), it involves a special kind of track in which a circumferential bead (or fillet) of weld metal is poured to fulfill the joint gap entirely. CJP weld joints provide superior fatigue strength to conventional butt welds from top to bottom.

Partial Joint Penetration (“PJP”):

In contrast, a Partial Joint Penetration (PJP) is a second type of weld is a type of welding in which the entire piece of metal is melted and fused together, but the metal doesn’t completely meld. Instead, a crack or crevice, known as a weld neck, remains between the joined pieces of metal. These types of welds aren’t as durable as some of the other welding techniques, but they can be practical in situations.

To achieve full penetration, the metals edges are beveled to reach the entirely. When it is properly done it increase the strength and durability of the weld. CJP welding has a higher penetration rate, meaning that it penetrates more metal with each weld. It produces less spatter, meaning more weld metal is getting into the workpiece. CJP welds can be visually inspected. CJP welding requires less effort for starting and stopping than stick welding, and it does not require an auxiliary power source.

Importance of Full penetration weld:

There are number of reasons and desirable properties of full penetration weld, as this increases the strength and life of the joint’s quality. 

1. High strength:

The process requires a lot of power and energy because it requires melting of metals during the welding process. To ensure the process is carried out properly, welders use electric arc welding equipment. Welding requires great precision and control. This explains why a welder must possess high level of physical strength and stamina. In CJP deep penetration allow better strength and fusion in joints.

Importance of Full penetration weld

2. Corrosion resistance

The corrosion resistance of weld is an important parameter which decides the service life of a weld joint. The corrosion rate of a weld joint can be decreased by increasing the corrosion resistance of the base metal. CJP welds are also more corrosion-resistant than PJP welds as it leaves no gaps between the joints and avoids trap moisture and other dirty particles which cause corrosion.

How to Achieve a Durable Full Penetration Weld:

Full penetration requires some techniques, skills, setting and a stable hand control. As a welder you should be aware of all welding necessities so you can wled according to specifications and diagnosed problems.

1. High current

A higher current is usually required to achieve full penetration weld (FPW) than when welding. This is usually due to higher heat input per unit. The current required depends on joint thickness and the joint configuration. The current and power density are important factor and also have direct relationship with CJP. In some cases, you can also use automatic wire feed techniques (like MIG) for welding.

2. Voltage

Voltage is the another important factor in CJP. As welder it is important to know about voltage’s importance during welding process. A high voltage increases the power density and blend the welding incredibly but it doesn’t reach deeply into the material. You may get surprised to know that high voltage led to low penetration. If you are experiencing it consider lowering the voltage at stable position.

How to Achieve a Durable Full Penetration weld

3. Electrode Selection

The choice of electrode and selection of welding process will determine whether a weld will be successful or not. Electrode selection plays a major role in weld penetration, weld metal appearance and the weldability of materials. Some electrodes are designed to penetrate. In small electrode, the charge flow through small cross section area, this means that higher current density produces penetrating welds.

Side Effects of Full Penetration

Despite of having so much advantages of full penetration there are also some side effects outweigh the pros.

A main side effect is excessive admixture in full penetration welding. It means that extra-base metal melt into the weld pool because of high energy. It disrupts the mechanical properties of the metal and deformed the material as result the base metal in the joint will not be ideal. Keep this important side effect of high energy in full penetration welding.


Welding is a process where two pieces of metal are joined together to form a permanent bond. And for full penetration weld a lot of knowledge, skill, experience, and proper welder settings is required. Your techniques and a stable hand control also impact the weld penetration. Plus, U, J, and V-grooves and beveled edges produce thicker stock. So, we recommend you to practice it daily to get better results and also seek out advice from experienced welders.

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