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16 Most Common Types of Welding Defects: Causes & Remedies

Welding, as we know, is a method that employs different techniques to join two partially or completely broken metal pieces. This is a common practice the world over. However, in some cases, the procedure can leave the metal with certain imperfections. If that happens, there is no need to discard the material. These issues can be addressed or avoided to maintain the integrity of the metal. 

This article will discuss the most commonly sighted welding defects. We will highlight the main causes and also how to prevent them. 

What are Welding Defects?

Welding defects are defined as irregularities or inconsistencies in the welded pieces. Sometimes, these imperfections can be serious and result in the product’s failure. A wrong welding method or human error may cause the issue. 

Weld defects can take various shapes and sizes. Also, the extent of the defect may vary depending on the welding process and the stress applied while carrying out the procedure. 

On the basis of the location of the defect, these are classified as external or internal. 

External welding defects: These are visible irregularities on the outer surface of the base metal. These can be tiny or big in size. 

Internal welding defects: As the name suggests, these occur inside or within the depths of the parent metal. While they are invisible to the naked eye, one cannot undermine their existence or importance in ruining a product’s functionality. 

Types of Welding Defects


Types of Welding Defects, Cracks

Cracks in welding are by far the most undesirable defects. These are visible in the form of a rupture on the surface, in the weld metal, or in the area subject to the maximum impact. To elaborate, extreme heat or cold creates stress at the crack’s tip and, hence, the fracture. 

Welding cracks can be seen in various forms, such as:

  • Branching
  • Crater
  • Radiating
  • Longitudinal
  • Transverse

The type of crack incurred depends on the temperature applied during welding. These are of two types:

Hot Cracks

Also known as solidification cracking, it happens when the liquid weld metal is not in enough quantity to fill in the gaps. This leads to the formation of a shrinkage as the weld metal solidifies after the procedure. At times, the crack becomes apparent right after the procedure, while in other instances, it is visible as the welds are in operation.

These can be further categorized into:

  1. Solidification cracks (SC): Cracks forming in the welded metal 
  2. Liquation cracks (LC): Cracks forming in heat-affected zones. 

Factors responsible for hot cracking are:

  • High force on the weld pool
  • Presence of impurities
  • Blockage in the supply of weld liquid
  • High thermal impact (temperatures higher than 1200 degrees Celsius)

Remedies to combat hot cracks are:

  • Reduce heat
  • Lower the strain on the metal
  • Select the right material
  • Select the right welding procedure. Also, check the parameters beforehand.

Cold Cracks

A crack that happens at or below 200 degrees Celsius is a cold crack. It is visible after a few hours or some days of welding. Hence, it is also called delayed cracking. All ferritic and martensitic steels are prone to cold cracks. These may include carbon steel, low alloy steel, and high alloy steel. 

Cold cracks can be of many types:

  • Toe cracks: They start at the edge of the weld where there is a change in size, and this is where stress gathers.
  • Root cracks: Cracks at the root happen because stress gathers at the sharp corner of a fillet joint.

Factors responsible for cold cracks

  • Low ductility of the weld
  • Diffusible hydrogen in the weld
  • Residual stress

Remedies to combat cold cracks include

  • Always heat the base metal before beginning the procedure. This lowers the cooling rate of the weld and keeps the weld from becoming brittle. It also gets rid of hydrogen in the weld.
  • Stop any interruptions in the weld to prevent stress buildup.
  • Choose welding materials that have low hydrogen to lessen the amount of movable hydrogen in the weld.


Types of Welding Defects, Porosity

Porosity occurs when holes are formed in the weld pool due to the inability of the air bubbles to move out. These are most certainly experienced when shielding gas is used, for instance, in TIG and stick welding. Using too much, too little, or no shielding gas can result in metal contamination, eventually making the metal weak. 

Concurrently, when large amounts of gas bubbles are trapped, then extreme forms of porosity can manifest in the form of blow holes or pits. The mixing of tiny gas molecules with welded metal will make the compound impure. 

Different Types of porosity

  • Surface porosity
    A type of porosity welding defect that appears like Swiss cheese. The pores are visible on the top surface of the bead. They are either distributed uniformly or scattered all across the bead.
  • Subsurface Porosity

This kind of porosity may lie under the surface of the bead and is difficult to learn about. In some rare cases, it may manifest in the form of a small bubble. The only way to learn about them is an X-ray or a grinder.

  • Wormhole

These are elongated pores that look like a worm, hence the name. You can only know about the presence of wormhole porosity after removing the slag from a bead. 

  • Cratering

It is a small depression at the end of a bead. In other words, cratering is a combined effect of gravity and the contraction of molten metal as it solidifies.

Causes of Porosity

  • Wrong electrode selection
  • Unclean welding surface, e.g., scales, rust, oil, grease, etc, on the surface
  • Damaged shielding gas cylinder
  • Little or no shielding gas
  • Extreme low or too high welding current
  • Quick travel speed


  • Always keep the weld surface clean
  • Set the gas flow rate to ensure adequate shielding.
  • Warm up the metals before starting the welding process.
  • Inspect the shielding gas cylinder for moisture contamination.
  • Fine-tune welding current and travel speed settings.


Types of Welding Defects, Undercut

An undercut can manifest due to many reasons. The first one involves the use of extreme current, making the edges of the joint melt and flow into the weld. The other reason for this kind of imperfection is the insufficient deposition of filler metal into the weld. 

This leads to a decreased cross-section, creating notches or grooves along the weld. One can witness the undercut near the toe of the weld. In the multi-run welds, it may be seen in the fusion face. Not only this, the groove is susceptible to trapping water and dirt, thus enhancing the corrosion in the already compromised area.

Causes of undercut

  • The wrong use of angle leads to excessive heat exposure at the free edges.
  • High weld speed
  • Base metal and filler material have different thermal properties. 
  • Incorrect electrode size
  • Wrong shielding gas


  • Maintain the stability of the arc throughout the welding
  • Decrease the current if you notice inconsistency in the welding
  • Use compatible base metal and filler material
  • Employ an electrode that delivers energy in equal measure, as this will deposit material evenly
  • Select the correct gas mixture to achieve optimal weld quality and performance.


Types of Welding Defects, Overlap

As the name suggests, the defect is a result of filler material overlapping the metal without joining it. The extra metal can be seen peeping out around the joint and will form a less-than-acute angle. Often, this happens when the wrong welding technique is used.  

Causes of overlap

  • Excess of current use
  • Low deposition speed, which leads to accumulation. 
  • Wrong angle and create a crown-like structure. 
  • A large electrode.
  • Improper alignment of the edge
  • Contamination of the base metal 


  • Use an appropriate amount of current. A shiny metal means the current is too high.
  • Make sure the speed is sufficient enough to move the weld material and not too high or too low.
  • Use smaller electrodes
  • Pre-prepare your metal. Make sure the base metal is properly aligned 
  • Always clean the metal before welding  

Incomplete Penetration

Penetration can be stated as the depth to which the molten metal (filler metal and base metal) blends, creating a strong and unified joint. An incomplete penetration occurs when the root gap is too narrow and fills incompletely. This creates a space that the weld material has not filled. Hence, we call it incomplete penetration.

Causes of penetration defect

  • Excess of space between the metal for welding.
  • A high weld bead speed stops enough metal from gathering in the joint.
  • A low current setting is insufficient to achieve enough melt depth
  • Incorrect joint
  • The electrode was positioned in an incorrect place.
  • Using thicker electrode 


  • Ensure proper joint alignment 
  • Keep the arc travel speed sufficient enough to move the welded metal.
  • Choose a moderate weld speed
  • Use the right joint design
  • Maintain the right electrode position
  • Pick the electrode diameter as needed for welding.


Types of Welding Defects, Spatter

This unsightly imperfection happens when the liquid filler material splashes or scatters during the welding procedure. These are visible around the weld bead as small, tiny droplets. These are most commonly found to occur in ARC welding, GAS welding, or tack welding. In rare cases, it may happen in mig welding. 

It becomes worrisome when these tiny globules gather in the nozzle. If they detach from here, they can 

damage the weld bead. Even the welders can face injuries if the process creates sharp spatter projections. They may incur burns or serious injuries to the handlers.

Causes of spatter

  • The metal surface is contaminated
  • Electrode working angle is rigid
  • High amperage and low voltage settings
  • Using a wet electrode
  • Using a larger arc


  • Include cleanup of metal as part of pre-preparation for welding
  • Decrease arc length and increase electrode angle
  • Adjust the weld AC and DC with proper alignment
  • Do not use a wet electrode


Types of Welding Defects, Distortion

It takes place as the base metal; the weld expands and contracts while the heating and cooling take place. What this essentially means is that the welded part is not able to maintain its geometry, which leads to bucking, shrinkage, and angular movement.  

The major reason for distortion is excessive heat. The temperature plays a key role during and after the welding process as it alters the size and location of the plate. Remember, these are most commonly seen in thinner weld plates.

Causes of distortion

  • Applying for incorrect welding orders
  • Using too many weld passes with electrodes that have a smaller diameter
  • High residual stress in the to-be welded metal 
  • Low arc travel speed
  • Not using a measuring device
  • Taking too long for the welding process


  • Employ correct welding orders
  • Optimize your design for the right number of passes 
  • Use only the right amount of weld metal. This will reduce contraction after the welding process
  • Use an optimum arc travel speed. 
  • Take a measuring device for accurate dimensions
  • Complete the welding process in less time to prevent metal expansion

Note: A 10 to 20 inches per minute of arc travel speed is considered perfect for workpieces that are rotated. However, orbital welding equipment requires a welding speed between 4 to 10 inches per minute.

Burn Through

Types of Welding Defects, Burn Through

An unwanted hole appears as a result of the melting of the base metal. This takes place when the weld reaches the weld root, which is perhaps why it is also called a melt-through defect. Usually, this weld defect is visible near the weld seam or on it. Thinner materials and workpieces are also prone to burn-through welding defects. 

Burn-through can lower joint strength, making it weak and more prone to cracking and deformation. The aesthetics are also in disorder, and due to this, it may face rejection. 

Causes of burn-through

  • High welder settings in case of thick metal stocks
  • Huge gap between the metal pieces
  • Excessively slow movement of the torch
  • Use the wrong metal sizes
  • Avoiding sufficient metal clamping and and-down


  • Do not use high current for welding 
  • Do not have any gaps between the metals
  • Use travel speed just enough to carry out the weld procedure. Avoid high melt speed.
  • Employ correct wire sizes
  • Make sure you have enough metal hold-down and clamping

Note: Change the weld speed as you change the weld technique. 14 to 19 inches per minute is perfect for MIG welding, and 4 to 10 IPM is ideal for orbital welding equipment. 

Lamellar Tearing

Types of Welding Defects, Lamellar Tearing

It is a type of crack that arises deep inside a welded metal piece, just where the layers meet. These can be differentiated from the rest of the defects as they have a terraced appearance. They are mostly a result of thermal contraction in the steel plate. You can also find them just around the areas affected by the heat. 

Both the low ductility of the plate and high thermal stress lead to this kind of defect during welding. 

Causes of lamellar tearing

  • Weld metal accumulates at the place where the highest joining takes place
  • Incorrect material selection and metal orientation


  • Conduct welding toward the end of metal fabrication
  • Pick the correct material and welding orientation

Slag Inclusion

Types of Welding Defects, Slage Inclusion

When non-metallic substances are trapped in the weld metal or the weld surface, a defect arises. This is slag inclusion. The word slag denotes foreign particles. Depending on the welding technique, they are waste materials you get from stick welding, flux-core arc welding, shielded metal, submerged arc welding, and more. 

These are more prevalent in flux-based welding methods such as flux-cored arc welding and stick welding. They can be distinguished due to their glass-like appearance with pinholes or thin lines, which are at times visible to the naked eye, while on other occasions, an ultrasound or X-ray is needed to locate them. 

Causes of slag inclusion

  • Wrong material used
  • Using low welding amperes
  • Not enough space for molten weld metals
  • Rapid cooling 
  • The base metal was not cleaned before the welding started
  • Fast welding speed


  • Use compatible materials
  • Increase the current density to prevent early slag solidification
  • Redesign the joint to ensure ample space for the molten weld metals
  • Reduce quick cooling
  • With a wire brush, clean the surface prior to applying the next weld layer
  • Maintain weld speed

Incomplete Fusion

Types of Welding Defects, Incomplete Fusion

It is a flaw in the welding wherein the filler material did not blend perfectly with the base metal. This can happen when:

  • Incomplete fusion at the weld’s root prevents the weld metal from bonding completely with the parent metal.
  • Weld metal does not fully merge with the base metal on the sidewalls.
  • Inter-run fusion issues arise in multi-run welding between the adjacent weld metal layers.

Causes of incomplete fusion

  • Using low heat for melting
  • The electrode diameter is incorrect for the material thickness
  • Wrong electrode angle
  • Using high travel speed
  • The weld pool is too big for the movement of the arc
  • Unclean metal surface


  • Adjusting the heat to optimum levels for welding
  • Selecting an electrode as per the thickness of the material
  • Make sure the angle is suitable for particular metal welding
  • Reduce the speed of the arc 
  • Use an appropriate weld pool as per the arc movement

Mechanical Damage

Depressions form on the surface of the parent metal due to some damage during dressing, handling, preparation, and welding. These are mechanical damages.

Causes of mechanical damage

  • Excessive force applied while chipping the metal
  • Improper handling of the electrode
  • Grinder use is inefficient
  • Inability to engage the arc to the base metal


  • Use the welding apparatus correctly
  • Post-welding, do not let the other component fall back on the newly welded metal.
  • Apply hammering at a moderate rate
  • Engage the arc before beginning welding

Note: Handling the workpieces and the welding equipment correctly is sufficient to avert mechanical damage.  

Excess Reinforcement

Excess reinforcement

Reinforcement of a weld is an extra material often used to strengthen the weld joint. When one uses more material than needed, it results in excess reinforcement defects. Due to this, the surface appears uneven and worn out. 

Causes of excess reinforcement

  • Overusing flux or moving the feed wire too quickly or unevenly
  • More heat and current than needed
  • Inconsistent voltage that is mostly low
  • Leaving space between the welding metal pieces


  • Make sure the torch runs at an optimum speed
  • Preset the temperature correctly. Make sure you do not overheat the metal
  • Make adjustments to voltage so that it stays at a set level and is not too low
  • Leave as little space as possible when aligning the pieces 


These refer to the small segments of electrode wires that protrude through the weld. You can see them on the side where the joint is originating. They occur when the electrode wire is pushed beyond the forefront of the weld pool.

While they are responsible for compromising the aesthetic value of the metal, they also affect the mechanical properties of the metal. 

Causes of whiskers

  • Applying high feed speed
  • Excessive travel speed


  • Lower the electrode wire feed speed
  • Maintain optimum travel speed and do not go too quickly

Hot Tear

It is an imperfection that emerges when cracks begin to form in the deposited metal. It originates from an adjacent edge and leads to the expansion of the crack as the solidification progresses.

Another name for this is solidification cracking, as the tearing takes place before the metal freezes. 

Causes of hot tear

  • Incorrect thickness of the electrode
  • The welding current used is not appropriate
  • Wrong selection of welding materials


  • Pick the right electrode that suits the base metal
  • Employ correct welding current
  • Pick the correct material for welding


Just before the completion of the weld and after the welding process, cracks appear in weld joints. These occur due to inadequate filling of the crater prior to breaking the arc. This results in faster cooling of the outer edges. 

The weld does not have the necessary volume to prevent shrinkage, and therefore, a crater 

a crack appears.  

Causes of crater

  • Incorrect filling of the carter
  • Wrong welding method
  • Wrong torch angle


  • Fill the crater properly
  • Select the appropriate welding technique
  • Use a torch angle that helps lower metal stress
  • Employ a small electrode

How to Identify the Different Welding Defects?

There are many ways you can evaluate the weld defects, including: 

Visual inspection: The first method involves the visible imperfections. With this method, you can watch the cracks, undercuts, overlaps, and surface-breaking porosity.

Non-destructive evaluation: This is carried out through a procedure, Liquid or dye penetrant testing (PT). In this method,  a liquid penetrant is applied to the test metal. The latter uses capillary forces to learn about the cracks or the pores so that you can see them with your naked eye. 

Defects such as porosity, cracks, undercut, and surface lack of fusion are detected with this method. 

Destructive testing and analysis: with this method, the weld is tested using the following methods:

  • Macro Etch Testing: A sample is taken from the welded area, and then it is etched using a mild acid.
  • Fillet Weld Break Test: It examines the one-sided fillet welded joints. Thai type of mechanical testing is great at penetrating the root cause. The best part about this test is that it can assess the flaws all through the base metal rather than just the sample.
  • Transverse Tension Test: the specimen for this test is extracted in the transverse section. It can also be taken across the test metal such as pipe or plate. With this test, the technician can test the tensile strength, proof stress, yield strength, elongation, and solidification of the metal. 
  • Longitudinal Tension Test: as you might have guessed, the specimen in this is removed in the longitudinal axis of the base metal. Sometimes, both weld metal and base metal are extracted for the purpose of testing. 

How do you make good welding in mold making?

Whether to repair or restore parts, molds require welding. While it removes the need to fabricate new parts, it also helps in bringing down the cost of mold making. One of the ways to do good welding in molds is to use the micro welding method. It uses electric current to produce heat at the arc gap. A molten pool builds up wherein the filler rod is added. The entire process is handled by a technician who looks after the equipment to the wire. 

Another good method that can be employed is laser welding. With this method, the welders can access places that are hard to reach otherwise. A beam of light falls on the weld zone, heating it. This melts the filler rod in addition to the neighboring points that need joining. This method is also found to be more effective as it does not modify molds and is quick and exact. 

Parting Thoughts

Welding is a critical process for various industries. Whether it is the automotive industry, aviation, or others, welding helps them a great deal. It helps in constructing both robust and lightweight materials and keeps these sectors functioning flawlessly.

To make it work for everyone, make sure the right weld tools, techniques, and parameters are applied. This will result in fewer errors and a quick, hassle-free, and effective procedure. Also, you may think of partnering with HiTop Industrial mold designing and CNC professionals. They can help you build precise parts with clean and aesthetically pleasing parts.


What is a tensile test in welding, and what is its main purpose?

The tensile test is a method to check the strength and ductility of the metallic material. The test helps to measure the amount of force that is needed to break the metal.

How does amperage cause overlapping in welding?  

An excess of current leads to the pooling of filler material in the weld area. It occurs due to the over-melting of the material, which flows out and solidifies incorrectly.

What is the right angle for the electrode in welding?

When you’re welding in the horizontal position, your electrode angle should be 5- to 10-degree. However, if the welding is in a vertical position, again keep it at a 5- to 10-degree angle.

What is the importance of angle in welding?

With the help of the right angle and degrees, you can ensure a well-informed weld bead. This assessment also helps while preparing tubing or piping. 

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