Welding Defect Types

Welding Defect Types are some sort of imperfections or irregularities that occur during welding. They can compromise the integrity and performance of a welded joint. Nothing is complete in this world, including welding work. Welding activities employ various parameters and are potentially subjected to defects. These defects may arise from various factors such as welding process parameters, material properties, and skill levels. So, understanding different welding defect types becomes crucial for ensuring the reliability of welded structures. Therefore, here we aim to explore the common welding defect types. By knowing these defect types, we can gain insights into preventive measures as well. Let us dive into the details of various types of welding defects, their prevention, and related aspects.

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Post Highlights:

• What is a Welding Defect?
• Welding Defect Types
• Mig Weld Defects
• Tig Weld Defects
• Stick Welding Defects
• AWS Welding Defects Chart
• Weld Defects Chart
• Welding Defects Causes
• Welding Defects Prevention

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What is a Welding Defect?

A welding defect means any deviation or imperfection in a welded joint. It may/can compromise its mechanical properties, structural integrity, or overall functionality. These defects potentially can occur during the welding process due to many factors such as welding parameters, environmental conditions, material characteristics, and the skill of the welder. Welding defect types can be in different forms, ranging from surface irregularities to internal flaws. The presence of defects in welded material can weaken it and lead to a higher likelihood of failure under applied loads.

Welding Defect Types

Some common types of welding defects include-

• Distortion
• Excess Reinforcement
• Hot Tear
• Incomplete Fusion
• Incomplete Penetration
• Lamellar Tearing
• Mechanical Damage
• Misalignment
• Overlap
• Porosity/Blowholes
• Slag Inclusion
• Spatter
• Undercut
• Weld Crack
• Whiskers
• Burn Through

1. Distortion

This is the difference in location and size between the positions of the two metal plates. It happens before and after welding due to the temperature grade present at several points along the weld joints.

Distortion Causes-

• Employ incorrect welding orders
• High residual stresses in the plate to be welded
• Not using any measuring instrument for dimension purposes
• Slow speed of arc travel
• Use a large number of passes with small diameter electrodes
• Use too much time for the welding process

Distortion Remedies-

• Decrease the time of the welding process
• Employ the appropriate number of weld passes
• Ensure to use the correct welding order
• Maintaining arc travel speed
• Use a measuring instrument for dimensional accuracy
• Use an appropriate amount of welded metal

2. Excess Reinforcement

This occurs when there is too much filler material in the welding joint and the excess reinforcement is uneven and ragged. It is a common type of welding defect but happens occasionally.

Excess Reinforcement Causes-

• Leaving a big gap between the welding pieces
• Over flux or fast/uneven travel speed on the feed wire
• The presence of more current and heat
• Varying voltage (mostly low)

Excess Reinforcement Remedies-

• Adjust the voltage (ensure it is not too low)
• Align the pieces properly (no too big gap)
• Maintain the proper running speed of the torch
• Set the current correctly and avoid overheating

3. Hot Tear

When the deposited metal starts to develop cracks from the nearby edge, it will solidify the crack increase.

Hot Tear Causes-

• Incorrect choice of proper materials
• Not employing suitable welding current
• Wrong thickness of the electrode

Hot Tear Remedies-

• Use the right thickness of the electrode (as per base metal)
• Use suitable welding current (as needed)
• Use a suitable type of material for the electrode

4. Incomplete Fusion

This occurs due to a shortage of suitable fusion between the metal and weld. It may also be visible between adjacent weld beads. Actually, it produces a gap inside the joint not filled with molten metal.

Incorrect Fusion Causes-

• Contamination of metal surface
• Employ too fast travel speed
• Incorrect angle of electrode
• Using low heat input
• The Weld pool is very large and moving ahead of the arc
• The wrong diameter of the electrode for the material thickness

Incorrect Fusion Remedies-

• Clean metal surface before welding
• Decrease arc travel speed
• Ensure proper weld pool according to the movement of the arc
• Use a suitable electrode angle for welding
• Use the correct diameter of the electrode as per material thickness
• Utilize proper heat input for welding

5. Incomplete Penetration

In this case, the penetration is the distance from the uppermost surface of the base plate to the maximum extent of the weld nugget. This happens when the metal groove is not entirely filled. This means the weld metal does not fully spread through the joint thickness.

Incomplete Penetration Causes-

• Move the bead too fast (not allow sufficient metal to accumulate in the joint)
• Too much space between the metal that you are welding with
• Use a very low ampere setting (currently unable to melt the metal properly)
• Use improper joints
• Use larger diameter electrode
• The wrong position of the electrode

Incomplete Penetration Remedies-

• Assure the surface is jointly fine
• Decrease arc travel speed
• Employ proper diameter electrodes suitable for welding
• Ensure electrode position is very accurate
• Improve the joint design
• Select a decent welding current

6. Lamellar Tearing

This occurs at the bottom of the weld. This occurs within the parent plate, often outside the heat-affected zone. Also, it usually occurs parallel to the weld fusion boundary. This is mainly found in rolled steel plate fabrication.

Lamellar Tearing Causes-

• Depositing weld metal on the metal surface where optimum cohesion occurs
• Improper welding orientation and material selection

Lamellar Tearing Remedies-

• Conduct welding rest at the end
• Select the best quality materials
• Use proper welding orientation

7. Mechanical Damage

This occurs by employing incorrect use of welding tools such as grinders, hammers, and other welding tools. This is an indentation in the surface of the parent metal or weld.

Mechanical Damage Causes-

• Apply additional force during chipping
• Incorrect handling of the electrode holder
• Inefficient use of a grinder
• Not engaging the arc to the metal parts

Mechanical Damage Remedies-

• Employ moderate hammering when used
• Engage an arc before welding
• Ensure other parts do not fall on the welded metal
• Operate welding tools properly

8. Misalignment

This happens when the decomposition of filler metals occurs in the welded joint. It can be wavy or curvy forms on the surface.

Misalignment Causes-

• Employ unskilled Welder
• Improper checking while welding
• Using a rapid welding process
• Welding wire is not inline properly

Misalignment Remedies-

• Apply a slow or steady welding process
• Check wire location properly
• Conduct proper checks before welding
• Employ skilled welders
• Maintain welding wire inline

9. Overlap

This occurs when the filler material at the toe of the weld covers the base metal without bonding. Simply, it is an excessive flow of weld metal.

Overlap Causes-

• Applying improper welding technology
• Using large-size electrodes in welding
• Varying torch angle

Overlap Remedies-

• Achieve improvements in welding techniques
• Ensure not to use large-size electrodes
• Maintain the correct torch angle

10. Porosity/Blowholes

This occurs when trapped gases create relatively large hidden holes or pores due to weld metal contamination. Basically, they are a group of small bubbles and blowholes.

Porosity Causes-

• Apply too large a gas flow
• Dirty job surface (metal)
• Moisture presence in the process
• Unsuitable gas shield
• Use a larger arc
• Use insufficient electrode deoxidant

Porosity Remedies-

• Check the gas flow meter (appropriate pressure/flow settings)
• Choose suitable electrode and filler materials
• Clean the metal surface before welding
• Decrease welding speed (allowing gas to escape)
• Ensure arc distance is correct
• Prevent pollution from entering the weld zone

11. Slag Inclusion

This occurs when the flux (solid shielding material) is applied in welding and melts in the weld or on the surface of the weld region. Slag inclusion weakens the strength of the joint.

Slag Inclusion Causes-

• Employing too low welding current
• Fast welding speed
• Improper cleaning of metal
• Incorrect angle of the electrode
• Insufficient space for molten weld metal puddle
• May be cooling is very fast
• Poor cleaning of previous passes in multipass welding

Slag Inclusion Remedies-

• Adjusting the angle of the electrode
• Clean metal properly before welding
• Clean the weld bed surface before the next layer deposition
• Decrease the rapid cooling of weld
• Increase the current density
• Redesign the joint allowing sufficient space for the use of molten weld metal puddle
• Reduce welding speed

12. Spatter

This occurs when tiny metal particles that are ejected from the arc during welding accumulate on the base metal throughout the weld bead along its length. It commonly happens in gas-metal arc welding.

Spatter Causes-

• Contamination of metal surface
• Much rigid working angle of the electrode
• Use a wet electrode and a larger arc
• Utilize too-high ampere current and too-low voltage settings

Spatter Remedies-

• Clean metal surfaces before welding
• Decrease arc length
• Increase electrode angle
• Use proper arc and electrode as per the welding
• Use proper polarity with adjusting the weld current

13. Undercut

This happens when there is the formation of grooves in the weld toe. It decreases the cross-sectional thickness of the base metal and weakens welds.

Undercut Causes-

• Apply too-fast weld speed
• Incorrect gas shielding and filler metal
• Incorrect use of angle (delivering more heat to free edges)
• Use larger diameter electrodes
• Use poor welding methods
• Using too high weld current

Undercut Remedies-

• Apply the multipass technique
• Decrease the arc length
• Decrease the travel speed of the electrode (but not too slowly)
• Select the right shielding gas as per the material structure
• Use appropriate stream when approaching thin areas/free edges
• Use of suitable electrode angle (delivering more heat towards thicker components)

14. Weld Cracks

This occurs when there is a strong heat during welding and appears on the surface or in the weld metal. These are the most risky welding defect types. Depending on the temperature, the different types of cracks include.

(i) Hot Cracks – This happens when the temperature exceeds 10,000°C during the welding process or the crystallization process of the weld joint.

(ii) Cold Cracks – This happens mostly in steel structures after the weld is created and the metal temperature has passed down. They can come even after hours or days of welding steel.

(iii) Crater Cracks – This occurs at the end of the welding process before the operator completes the weld joint. There must be sufficient weld in volume to overcome the metal shrinkage.

Weld Crack Causes-

• Apply low current with high welding speed
• Contamination of base metal
• A high mixture of sulfur and carbon in the metal
• Improper filling of the crater in welding
• Lack of preheating before starting welding
• Poor design concept
• Residual stress solidification due to shrinkage
• Use hydrogen while welding ferrous metals

Weld Crack Remedies-

• Clean the metal surface before welding
• Ensure the crater is properly filled to prevent crater cracks
• Keep decent cooling of the weld area
• Preheat the metal before starting to welding
• Use a correct mixture of sulfur and carbon in the metal
• Use proper design concepts
• Using suitable metals
• Utilize appropriate welding speed/current

15. Whiskers

This occurs when the short lengths of electrode wire are glued through the weld on the root side of the joint. This is because of the electrode wire protruding from the leading edge of the weld pool.

Whiskers Causes-

• Apply an increase in the electrode wire feed speed
• Excessive travel speed

Whiskers Remedies-

• Keep travel speed optimal (avoid going too fast)
• Reduce the electrode wire feed speed

16. Burn Through

This happens when a lot of heat is applied during the welding, the metal can blow a hole through the center. This commonly occurs while welding thin parts less than 1/4 inch thick.

Burn Through Causes-

• Happens with thick stock if welder settings are too high
• Improper use of metal hold-down and clamping
• Significantly large gap between the pieces
• Very slow moment of the torch

Burn Through Remedies-

• Avoid excessive gaps between plates
• Employ normal travel speed (not too slow or too fast)
• Keep current control (not increasing too much)
• Propper use of metal hold-down and clamping

Mig Weld Defects

Metal Inert Gas welding is a popular welding process. It uses a consumable electrode and a shielding gas to create a weld. Similar to other welding processes, Mig welding also experiences various welding defect types.

Some common Mig welding defects include-

1. Porosity – They are small gas pockets or voids within the weld metal.

Causes-

• Contaminated shielding gas
• Dirty or rusted base material
• Improper gas flow rates

Prevention-

• Ensure clean base materials
• Maintain appropriate gas flow rates
• Use proper gas shielding

2. Incomplete Fusion – when the weld metal does not fully fuse with the base material.

Causes-

• Improper welding technique
• Insufficient heat input
• Too fast welding speed

Prevention-

• Adjust welding parameters for proper heat input
• Ensure good joint preparation
• Maintain a consistent travel speed

3. Burn-Through – This is the complete penetration of the weld, resulting in a hole.

Causes-

• Excessive heat input
• Too high welding current
• Welding on thin materials

Prevention-

• Adjust welding parameters
• Use appropriate filler metal
• Weld carefully on thin materials

4. Spatter – This is the expulsion of molten metal droplets that can deposit on the surrounding surfaces.

Causes-

• Excessive welding current
• Incorrect shielding gas
• Using an improper electrode

Prevention-

• Ensure proper gas shielding
• Optimize welding parameters
• Use the correct electrode type

5. Lack of Penetration – When the weld metal does not fully penetrate the joint.

Causes-

• Improper joint preparation
• Incorrect welding technique
• Insufficient heat input

Prevention-

• Adjust welding parameters for sufficient heat
• Ensure adequate joint preparation
• Maintain proper technique

6. Undercutting – This is a groove or depression along the weld toe or adjacent base metal.

Causes-

• Excessive heat input,
• Improper welding technique
• Incorrect electrode angles

Prevention-

• Control heat input
• Maintain correct electrode angles
• Use proper welding techniques

7. Irregular Weld Bead – This is an irregular or uneven appearance in the shape of the weld bead.

Causes-

• Improper electrode manipulation
• Inconsistent travel speed
• Variations in joint geometry

Prevention-

• Ensure uniform joint geometry
• Maintain a consistent travel speed
• Use proper technique

8. Wire Feed Issues – This is an erratic or uneven deposition of weld metal.

Causes-

• Improper tension
• Issues with the wire feeder
• Tangled or kinked welding wire

Prevention-

• Address any issues with the wire feeder
• Ensure proper wire feeding
• Maintain appropriate tension

Tig Weld Defects

Tungsten Inert Gas welding is a precise welding process. It is commonly used for welding thin sections of aluminum, stainless steel, and other non-ferrous metals. Despite producing high-quality welds, it is not immune to welding defect types.

Some common Tig welding defects include-

1. Lack of Fusion – When there is incomplete bonding between the weld metal and the base material.

Causes-

• Improper welding technique
• Inadequate cleaning of the joint surfaces
• Insufficient heat input,

Prevention-

• Adjust welding parameters for proper heat input
• Ensure thorough joint preparation
• Use correct techniques

2. Tungsten Inclusion – This happens when tungsten particles from the electrode become trapped in the weld metal.

Causes-

• Excessive electrode extension
• Improper electrode grinding
• Incorrect welding current

Prevention-

• Adjust welding parameters accordingly
• Maintain the correct electrode extension
• Use proper grinding techniques

3. Porosity – They are small gas pockets or voids within the weld metal.

Causes-

• Contaminated shielding gas
• Dirty base material
• Improper gas flow rates

Prevention-

• Ensure the use of clean shielding gas
• Maintain proper gas flow rates
• Prepare base materials thoroughly

4. Undercutting – This is a groove or depression along the weld toe or adjacent base metal.

Causes-

• Excessive heat input
• Improper electrode angles
• Incorrect welding technique

Prevention-

• Control heat input
• Maintain correct electrode angles
• Use proper welding techniques

5. Crater Cracks – This occurs when the weld pool solidifies and contracts, at the end of a weld.

Causes-

• Inadequate filler metal in the crater
• Rapid termination of the welding arc

Prevention-

• Ensure proper crater filling with filler metal
• Reduce the welding current gradually before terminating the arc

6. Incomplete Penetration – This happens when the weld metal does not fully penetrate the joint.

Causes-

• Improper joint preparation
• Incorrect welding technique
• Insufficient heat input

Prevention-

• Adjust welding parameters for sufficient heat
• Ensure proper joint preparation
• Use correct techniques

7. Overlap – This occurs when the weld metal fails to fuse properly with the base metal.

Causes-

• Excessive welding speed
• Inadequate joint preparation
• Incorrect welding parameters

Prevention-

• Adjust welding parameters
• Ensure proper joint preparation
• Maintain appropriate welding speed

8. Arc Strikes – This is an unintentional contact between the tungsten electrode and the base metal outside the weld area.

Causes-

• Improper grounding
• Incorrect electrode handling
• Poor welding technique

Prevention-

• Use proper welding techniques
• Handle the electrode carefully
• Ensure adequate grounding

Stick Welding Defects

Some common Stick welding defect types include-

1. Porosity – This is caused by the presence of gas pockets or voids within the weld metal.

Causes-

• Contaminated base material
• Excessive moisture in the flux coating
• Improper storage of electrodes

2. Incomplete Fusion – This occurs when there is a failure to achieve complete bonding between the weld metal and the base material.

Causes-

• Incorrect welding technique
• Insufficient heat input
• Poor joint preparation

3. Incomplete Penetration – This is when the weld metal does not fully penetrate the joint.

Causes-

• Improper welding technique
• Inadequate joint preparation
• Insufficient heat input

4. Cracking – They can develop on the surface or within the weld and adjacent base material.

Causes-

• High residual stresses
• Improper material selection
• Rapid cooling

5. Undercutting – This is the formation of a groove or depression along the weld toe or the base metal adjacent to the weld.

Causes-

• Excessive heat input
• Incorrect welding technique
• Improper electrode angles

6. Overlap – This occurs when the weld metal fails to fuse properly with the base metal.

Causes-

• Excessive welding speed
• Inadequate joint preparation
• Incorrect welding parameters

7. Spatter – This is the expulsion of molten metal droplets during welding, on the weld surface and surrounding areas.

Causes-

• Excessive welding current
• Improper arc length
• Incorrect electrode type

8. Arc Strikes – They are an unintentional contact between the welding electrode and the base metal outside the weld area.

Causes-

• Improper electrode handling
• Inadequate grounding
• Poor welding technique

9. Slag Inclusions – This occurs when non-metallic solid material from the flux becomes trapped in the weld metal.

Causes-

• Improper welding technique
• Inadequate removal of slag between weld passes
• Insufficient cleaning

10. Irregular Weld Bead – This is when the weld bead may appear uneven or irregular in shape.

Causes-

• Improper electrode manipulation
• Inconsistent travel speed
• Variations in joint geometry

AWS Welding Defects Chart

The American Welding Society (AWS) is an apex body in the field of welding. AWS provides comprehensive guidelines and standards for welding processes, including information on welding defects. Apparently, AWS may not provide a specific “defect chart“. Yet the AWS does offer various publications and resources that cover welding defect types and inspection criteria.

The AWS’s key documents for welding defects are AWS D1.1/D1.1M: Structural Welding Code – Steel. This AWS code provides requirements for welding various types of structural steel. Further, it includes information on testing, inspection, and acceptance criteria for welded joints. AWS D1.1 outlines the acceptance criteria for various welding defects such as cracks, undercutting, porosity, incomplete penetration, and more.

Weld Defects Chart-

Generally, there is not a single universal “Weld Defects Chart” applicable across all welding processes and materials. Different educational and industry resources provide diagrams, charts, and visual representations of common welding defect types. Normally, these charts are used for training and reference purposes. Typically, these charts illustrate different types of defects, their causes, and corrective actions. The general outline of common welding defects is burn-through, cracks, incomplete fusion, incomplete penetration, overlap, porosity, spatter, and undercutting.

The causes of welding defects can vary depending on the welding process (Mig, Tig, Stick, etc.) and the materials being welded.

Welding Defects Causes

Some common welding defect types and their potential causes-

1. Porosity – The main causes include improper shielding gas, incorrect welding parameters, contaminated base material, and inadequate cleanliness of the welding area.

2. Cracks – The main causes are improper material selection, high residual stresses, rapid cooling, and excessive hydrogen content in the weld.

3. Incomplete Fusion – The causes include poor joint preparation, incorrect welding technique, insufficient heat input, and improper electrode angle.

4. Incomplete Penetration – The causes are inadequate joint preparation, improper welding technique, insufficient heat input, and incorrect welding parameters.

5. Overlap – The causes include excessive welding speed, inadequate joint preparation, incorrect welding parameters, and improper electrode manipulation.

6. Crater Cracks – The causes include inadequate filler metal in the crater, rapid termination of the welding arc, and insufficient heat input during crater filling.

7. Undercutting – This is due to incorrect welding technique, improper electrode angles, excessive heat input, and incorrect travel speed.

8. Spatter – The main causes are improper electrode type, incorrect shielding gas, excessive welding current, and poor electrode cleanliness.

9. Burn-Through – This is caused due to too high a welding current, thin base material, excessive heat, and incorrect welding technique.

10. Tungsten Inclusion – This is caused by improper electrode grinding, excessive electrode extension, and incorrect welding current.

11. Arc Strikes – The causes include incorrect electrode handling, poor welding technique, and improper grounding.

12. Lack of Fusion – The causes are improper welding technique, insufficient heat input, and inadequate cleaning of joint surfaces.

13. Slag Inclusions – The main causes are improper welding technique, incomplete removal of slag between weld passes, and inadequate shielding.

14. Wire Feed Issues – This occurs due to improper tension, tangled or kinked welding wire, and issues with the wire feeder.

15. Irregular Weld Bead – The main causes are improper electrode manipulation, inconsistent travel speed, and variations in joint geometry.

Persons performing welding must understand the causes of welding defects to implement preventive measures and corrective actions.

Welding Defects Prevention Tips

Follow some of the tips to prevent welding defect types-

1. Cool Weld Slowly – Do not quench the weld in water or cool it with compressed air. This can cause the weld to crack. So, allow the weld to cool slowly.

2. Clean Base Metal Properly – Remove grease, dirt, and rust. They can cause defects in the weld. Clean the base metal before welding. For this, use a wire brush or grinder to clean the base metal before welding.

3. Inspect Weld after Cooling – Look for any defects such as porosity, cracks, or undercut. If there are any defects, repair them before using the weld.

4. Use Correct Filler Metal – The filler metal must be compatible with the base metal for creating defect-free welds. The filler metal is the metal that is melted and added to the weld joint.

5. Use Correct Welding Parameters – The parameters include the welding machine settings that control the heat and current of the weld. Also, the welding parameters vary depending on the thickness of the material, the material being welded, and the type of weld being made.

6. Use Correct Welding Procedure – Different materials require different welding procedures to achieve a strong weld. For example, high-carbon steels require preheating before welding to prevent cracking.

7. Use Correct Welding Technique – Different welding techniques work on different metals with different properties. For example, Tig welding is a suitable or good choice for welding thin materials. And, Mig welding is a good choice for welding thicker materials.

So, these are some of the tips to follow before or while welding to remedy potential welding defects and create durable welds.

Conclusion

Welding Defect Types are various irregularities that occur during welding. They need to be addressed to ensure the integrity and reliability of welded joints. Whatever use, either Mig, Tig, Stick, or other welding processes, the defects such as cracks, porosity, incomplete fusion, and spatter can compromise the structural integrity of the weld. However using preventive measures such as suitable welding parameters, proper welding techniques, and adequate joint preparation can minimize defects. Besides this, regular inspection and adherence to industry standards (such as those provided by the AWS) are essential for correcting defects promptly. Furthermore, the continuous training and education for welders also contribute to enhancing skills in producing high-quality welds. Ultimately, all these measures ensure the safety and longevity of welded structures and components in the welding industry.