Welding Defects: Common Types and How to Avoid Them

Marcus Colson Last updated on September 4, 2023
Reading Time: 5 Minute

Welding defects are conditions where the welding is not in accordance with established standards. 

So, what defects often appear in welds, and how can they prevent them?

Let’s find out below.

Various Kinds of Defects in Welding

Knowing the equipment needed to check for welding flaws, such as multipurpose welding gauges, rulers, flashlights, and magnifying glasses, is essential before examining many welding defects. 

Defect types are split into three categories according to where they occur, including faults at the weld face, defects at the root, and defects on the parent metal.

Read Also : Welding Joints: 5 Types and Tips for Top-Quality Results

Weld Defects at Root

There are 5 types of defects in the root. Below are the five types of defects. 

  1. Incomplete Root Penetration or Lack of Root Penetration

Due to the welding position performed by the metal not penetrating the roots, this fault results in the root’s partial penetration, resulting in gaps between the parent metals. 

To prevent this, adjust the electrode size, set the angular position, and widen the space at the root by 2-4 mm to prevent.

Also, use the WPS to change the travel speed.

  1. Incomplete Root Fusion Welding Defects 

This is a defect where the edges of the weld at the root have a straight or intact shape.

To avoid this, modify the amperage value in accordance with the WPS and the gap width at the root by 2-4 mm. 

Afterward, adjust the electrode angle position and tighten the process before welding to prevent linear misalignment.

Read Also : Lack of Fusion in Welding: Definition and How to Avoid

  1. Weld Defects Excessive Root Penetration 

This is a flaw where the weld’s root penetration is more than the required level.

This flaw appears as a result of improper welding technique, excessive root gap, and excessive amperage applied during the welding process.

The usage of too-large electrodes and frigid ambient temperatures can also cause defects.

Follow the steps in the previous defect to avoid this.

Be mindful of the electrode, surrounding temperature, and welding process, and adjust it to the WPS.

Read Also : Excess Reinforcement in Welding: Causes and How to Avoid

  1. Root Concavity

This is a situation when the weld metal does not fill the joint entirely, leaving visible weld metal at the root in the shape of depressions.

This is due to both an excessive amount of grinding and an enormous gap between the roots.

Simply modify the gap’s width at the root by 2-4 mm to prevent this.

  1. Undercut Roots 

With a flashlight, it is possible to check for this flaw plainly.

When a light source is shone from the root edge, this fault will cause a shadow to be visible. Set the root face’s size appropriately to avoid this.

Moreover, you may use WPS to change the speed of travel and the quantity of current used.

Defects on The Weld Face

Divided into 6 kinds of defects, as follows. 

  1. Cap Undercut 

The only difference between this flaw and the root undercut is where the undercut cap is located on the toe weld face.

Choose a current that complies with the norm to avoid this, and pay attention to the electrode’s size as well. The magnitude and speed of the current must meet the WPS.

Read Also : What is Undercut in Welding, Causes and How to Avoid Them

  1. Lack of Inter-Run Fusion 

Welding has two gaps in between each pair of run welds. Inadequate welding methods result in a defect.

Hence, conform the welding procedure to the norm.

  1. Incomplete Filled Grooves

The weld face is lower than the parent metal, which results in this fault.

This type of defect’s root cause is the same as the root of flaws in inter-run fusion.

  1. Gas Pores or Porosity 

Little holes are what make up this kind of flaw.

If there is one, they are referred to as gas pores or porosity; if there are several or more than two, they are called cluster porosity.

The electrode is damp, the welding arc is too long, the electrode flux is damaged, and there is a loss of protective gas, among other factors contributing to this problem.

To avoid this, use a current that matches the WPS and modify the welding arc’s length.

Before welding, make sure to examine the electrode’s condition as well. Correct procedures must also be followed before welding.

  1. Slag Inclusion 

This kind of imperfection also resembles holes, much like porosity does.

The distinction is that this kind of flaw is found on the weld face and will appear black as a result of impurity particles trapped there.

The reason is that the welding arc is too far, the welding angle is wrong, and the amperage is low. 

Use a welding arc, welding angle, and amperage that are compliant with the regulations to avoid this flaw.

Read Also : Slag Inclusion in Welding: Definition, Causes & How to Avoid

  1. Burn Through 

The inappropriate use of amperage, as well as the motion’s angle, speed, and poor welding techniques, are the causes of this flaw, which manifests as a pretty sizable hole with molten metal surrounding it.

Read Also : Burn Through Welding Causes and Tips to Avoid Them

Defects in the Parent Metal

There are 6 types of this defect. Check below. 

  1. Spatter 

This flaw is characterized by several bumps or tiny spots caused by the dripping of metallic or non-metallic material during welding.

Little hot bits of material that fly onto the parent metal or the weld face when welding is the cause.

Arc length and too much electricity flowing across the arc are additional factors.

Read Also : What is Welding Spatter: Causes and Tips to Avoid It

  1. Arc Strikes 

There appears to be more than one amount of an elongated or round metal melt.

Due to the electrode’s exposure to the parent metal, an electro-grip with inadequate insulation, and improper grounding on the welding tool, this fault develops.

  1. Mechanical Damage 

This flaw can be caused by a number of factors, including chisel marks, which are cuts in the parent metal, and pitting corrosion, which refers to holes brought on by corrosion.

And depressions brought on by the use of grinders.

  1. Linear Misalignment 

This flaw occurs when there is an uneven height difference between the plates or parent metal being joined.

This flaw was brought on by improper welding preparation.

  1. Angular Distortion 

The parent metal is the same height, but one of the parent metals or plates is tilted by a specific amount, which is a fault.

The fusion zone area’s contraction is the root of the problem.

  1. Crack 

This welding flaw may appear on the base metal, weld face, or root face.

There are two types of crack: hot crack and cool crack.

The cold crack appears after welding is finished, while the hot crack happens when the temperature is above 400 degrees Fahrenheit.

Hot cracks are a result of improper processes and materials being employed.

Moreover, the employed metal filler does not adhere to WPS standards. paired with an unsuitable welding technique.

Meanwhile, the lack of preheating causes cold cracks because the welding current is too low and the cooling rate is too high.

Read Also : Welding Crack: Causes & Effective Prevention Methods


You can prevent numerous types of welding defects by identifying these problems.

Inadequate, incorrect, or even non-use of welding methods can result in the appearance of welding faults or defects.

Thus, welding methods must be used before, during, and after welding.

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Marcus Colson
Marcus Colson

Welding is more than a hobby for me - it's a passion. The art of fusing metal together to create something new and functional never gets old. From intricate sculptures to sturdy structures, I love the endless possibilities that welding offers.

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