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Full Penetration Welding & How To Achieve ?

Welding is full of challenges, and it’s pretty complex. You can make various complexities and solutions while performing it.

Full penetration of welding is the same as others in welding. You must know where to apply this welding technique, how to make it work perfectly, and make the weld achieve the goal.

This article will let you know the basics and complexities of full penetration welding. So let’s dive deep into it to have insight.

What Is a Full Penetration Weld?

The most important thing you must know before doing a full penetration weld is if you’re going to make it a complete or partial fill. These are the two basics that you must keep on your list.

Complete joint penetration, or CJP, is done by filling the groove or gap between the two metal plates. The metal plates must be fused without leaving a little space to cross the air. The metal plates, in this case, are primarily beveled, making U, V, or J shapes. But if the metal plates are flat, there’s no need to make these shapes appear. Complete joint penetration strengthens the joint by filling it thoroughly from toe to root. Welders mainly recommend it.

In contrast to CJP, there’s Partial Joint penetration or PJP. It leaves a gap between the filling of two metal plates and makes it more vulnerable than CJP. The filler metal is filled so that it doesn’t reach the root of the metal plates when seen cross-sectionally.

What Is The Difference Between The Full Penetration Weld And The Fillet Weld?

Mostly the welders took fillet weld and the full penetration weld as one, but it’s not true. Let’s clear this confusion between these two welds.

Fillet weld is done between two metal plates held at some angle or perpendicular. This doesn’t involve any penetration; instead, it stays up on the surface of the metal. There’s no toe found in their geometry.

While in the case of the Full penetration weld, the filler metal flows down from toe to root without leaving any groove or space.

Why Is Full Penetration In Welding Necessary?

Full penetration welding contains a hefty amount of benefits. Due to this, they are primarily used in welding. Let’s discuss the most inevitable in them:

High Strength: How Strong Is a Full Penetration Weld?

The most important feature that is taken care of while welding is strength. This is easily achieved through Full penetration welding. As described above, the CJP method fuses both metal plates without leaving a groove.

It makes the metal plates unified as one. It makes the weld strong with a high mechanical or physical bear. It allows them to perform heavy duties and doesn’t let them break when the workload is increased. It makes the use of CJP more in the welding industry.

Corrosion Resistant

Corrosion happens when there’s room for air or moisture, as in the case of PJP. It leaves gaps or grooves that trap water, air, or humidity and causes corrosion that affects the quality of the weld directly.

But in the case of CJP, there’s no room left for decay as it fills the cavity between the metal plates, making it stronger. A full penetration weld is mainly preferred due to its ability to make the joint or weld corrosion accessible.

How To Achieve Full Weld Penetration?

Full weld penetration can be achieved by making specific settings in your weld machine and changing some variables. These are described below:

1. High Current

High current results in increased heat, simultaneously leading to a high penetration rate. They have a direct relationship with each other. Heat enhancement makes penetration easy and more profound.

This current can easily be increased by enhancing the power supply of your weld machine. It can also be done by improving your amperages.

2. Voltage: Not Too High or Too low

The voltage setting sometimes needs to be clarified. Voltages are the direct pursuers of power density. If you increase the voltage to a high limit, you might encounter a spread in the arc that will lead to low penetration.

But if you decrease the voltage to a low limit, you might meet poor penetration. So it would help if you had to find a boundary between low and high to maintain penetration.
You can do this by observing the pattern changes or consulting a chart or an experienced welder.

3. Low Travel Angle

Travel angle matters a lot in the penetration. The grade set for the filler rod or the torch must be lower than 20 degrees or close to perpendicular. It will assist you in the regular formation of the joint.

In contrast, when the angle is not set accordingly, you will encounter the appearance of shallow beads on your weld. So it’s advisable to make the angle nearly perpendicular when doing the full penetration weld.

4. Balanced Travel Speed

The electrode or the filler metal speed acts as a contributing factor in welding. If the rate of the electrode is kept too high, the electrode or the weld pool will not produce enough, and it’ll restrain it from deep penetration. It is simultaneously resulting in poor welding.

In contrast to high speed, if you do it at a meager pace, it can cause you trouble. At low rates, the weld pool increases and then creates an overflow. It’ll also lead to poor penetration.

That’s why it’s advisable to keep the speed of the electrode at a balanced pace. Neither too high nor too low.

5. Polarity

Polarity is a minor factor in penetration but still has a lot to do with it. Polarity leads the heat in the right direction. In case of deep penetration, the workpiece must be kept negative while the electrode positive.

It is because of the flow of electrons as they move from negative to positive. If the electrons flow towards the electrode, it’ll cause more weld pool and poor penetration. But if the flow is towards the workpiece, it’ll lead to more penetration.
Keeping the electrode positive and the workpiece negative is advisable to create a better weld pool and penetration.

6. Electrode Selection

ELectrode nature and size play a key role in penetration. Electrode nature includes its thermal properties, fluidity or viscosity, and affinity. Some electrodes are made to be more penetrating than others. So you must check the heart of the electrode before making a weld.
When it comes to the diameter, small diameters perform fantastically in deep penetration due to their passage from smaller cross-section areas.

Downsides Of Full Penetration Welding

Full penetration welding is an excellent technique to opt for but still has some downsides. These can be minor to ignore but a welder must know before deciding.

Full penetration welding requires a high amount of heat that results in more melting of base metal than the filler making more dissipation of the base penetration.

This results in more heat-affected zone areas and creates performance issues sometimes.

Due to the enhanced limit of heat, sometimes welding the thinner metal plates can cause the formation of a hole in the base metal, which is different from what any welder will want.

Always remember these downsides while going for the Full penetration weld.


Full penetration welding requires skills, practice, and welding settings. This proves beneficial in most welding cases, but there are better options when dealing with thinner metal plates.

You can get a hand on it by practicing it and consulting it with an experienced welder. We’ve clarified the pros and cons of welding settings for full penetration. If you still got some queries, you can ask us in the comments below.

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