Common Welding Defects and Their Remedial Measures !!

Abstract: 

There are several types of weld defects which may fall under different classifications depending on their location, size and shape in a particular consideration. We can break down weld defects into the following main categories:

• Inclusions
• Lack of fusion
• Porosity
• Undercut
• Under-fill
• Cracks
• Excess reinforcement and excess penetration
• Over-roll/Overlap
• Mechanical damage
• Spatter

Keywords

Welding Defects, Inclusions

 Fusion ,  Porosity, Undercut

Under-fill, Cracks, Excess Reinforcement,   Excess Penetration, Over-roll / Overlap

Learning Outcomes

After undergoing this article you will be able to understand about the following

• Inclusions
• Lack of fusion
• Porosity
• Undercut
• Under-fill
• Cracks
• Excess reinforcement and excess penetration
• Over-roll/Overlap
• Mechanical damage
• Spatter

Some common welding defects are explained briefly include: 

Porosity

Gas bubbles trapped in the weld metal, which can weaken the weld and make it more likely to crack or corrode. 

Causes of Porosity 

This can be caused by improper shielding gas, contaminated filler metal, or poor welding technique. 

Here are some common causes of porosity: 

Gas shielding

Poor shielding, leaks in the gas line, or excessive gas flow rate can cause the weld pool to absorb nitrogen and oxygen. 

Turbulence

Excessive turbulence in the weld pool can also cause porosity. 

Surface treatments

Coatings like primer paint or zinc, as well as rust, oil, grease, or water on steel surfaces, can also cause porosity. 

Other issues

Windy conditions, damaged O-ring seals, cut or burnt hoses, or a defective gas solenoid can also contribute to porosity. 

Remedial Measures 

Porosity in welding is a defect that occurs when gas gets trapped in a weld. 

Here are some things you can do to prevent porosity: 

Clean the base material

Before welding, remove all dirt, rust, grease, oil, paint, and other contaminants from the base metal along the entire joint you plan to weld. You can use a wire brush or an angle grinder to clean the metal. 

Use the correct welding parameters

Make sure the gas flow rate is correct, and that the shielding gas coverage is adequate. If the gas flow rate is too low, the weld pool may be exposed to air, which can cause porosity. 

Use the correct filler material

You can use filler metals that have added de-oxidizers to prevent contaminated welds. 

Avoid weld pool turbulence

Using high pressures can cause turbulence, which can lead to porosity. 

Avoid moisture

Keep your working environment clean and avoid moisture, which can evaporate and cause porosity. 

Prepare the joint

If you're using plasma cutting to prepare the joint, use oxygen to reduce the risk of porosity. You can also use a grinding method. 

Undercut

A groove or depression that forms along the edge of the weld bead, where the base metal has melted but the filler metal hasn't filled it properly. This weakens the joint and makes it more likely to crack, corrode, or fail. It can be caused by too much welding current, incorrect technique, or not enough filler material. 

Undercut is a welding defect that occurs when a groove is melted into the base metal next to the weld root or toe, but is not filled with weld metal. The main cause of undercut is improper welding technique, which can include: Incorrect torch angle or position, Excessive welding speed, Unstable arc, Incorrect welding machine settings, and External factors like wind or drafts. 

Other causes of undercut include: 

Using too high voltage or too fast weld speed, which causes melting at the top edge 

Using the wrong filler metal 

Incorrect selection of shielding gas 

Arc blow 

Faulty electrode manipulation 

To avoid undercut, you can try these tips: 

Select the appropriate voltage value 

Keep the arc height high 

Reduce the arc distance 

Approach weld pieces at angles between 30° and 45° 

Select consumables with lower diameters 

Slightly increase the welding speed 

Incomplete fusion

A gap in the joint that's not filled with molten metal, which can occur when there's not enough fusion between the base metal and the weld metal. It can also happen between adjoining weld beads. 

Incomplete fusion in welding, also known as lack of fusion, is a common defect that occurs when the weld metal doesn't fully fuse with the base metal or previous weld layer. This can lead to a weak joint that's prone to failure under stress or load. 

Here are some common causes of incomplete fusion: 

Welding technique: Incorrect angle or positioning of the welding gun, incorrect weaving technique, or lack of access to all faces of the joint 

Travel speed: Travel speed that's too slow or too fast 

Settings: Inaccurate settings, such as amperage that's too low 

Cleaning: Insufficient cleaning of the base metal, which can include rust, oil, or other contaminants 

Joint preparation: Inadequate joint preparation or wrong joint designs 

Electrode: Using an electrode that's too large for the joint, or using the wrong electrode type 

Incomplete fusion can be detected by visual inspection during welding, or by using ultrasonic testing, liquid penetrant, or magnetic particle testing methods. 

Here are some tips to prevent incomplete fusion in weldin

Here are some tips to prevent incomplete fusion in welding: 

Clean the metal: Before welding, clean the metal surface and welding area thoroughly. 

Use the right electrode: Select the correct electrode diameter for the thickness of the material being welded. 

Adjust the travel speed: Lower the travel speed and weave in between the edges. 

Use the correct heat input: Ensure you're using proper heat input. 

Use an adequate weld pool: Make sure the weld pool is adequate and doesn't flood the arc. 

Preheat the metals: Preheat the metals before welding. 

Set the gas flow rate: Set the gas flow rate to achieve the right amount of shielding. 

Check for moisture contamination: Regularly check for moisture contamination in the shielding gas cylinder. 

Incomplete fusion can occur when the metal components aren't properly bonded together. This can happen due to inadequate joint preparation, insufficient heat input, or poor welding technique. You can visually inspect the weld during welding to detect pure lack of fusion. Other types of lack of fusion can be detected using ultrasonic testing, liquid penetrant testing, or magnetic particle testing. 

Incomplete fusion can occur when the metal components aren't properly bonded together. This can happen due to inadequate joint preparation, 

Under-fill

Under-fill is a longitudinal continuous or intermittent area in the surface of a weld that is below the adjacent surface of the parent metal due to insufficient deposition of weld metal. This is external and can easily be detected by visual inspection. High welding travel speeds and high heat inputs can cause under-fill.

Incomplete penetration

When the root of the weld bead doesn't reach the root of the joint to weld the other side of the part. This can happen if the metal groove is too narrow and doesn't get filled, which reduces the strength of the weld joint and can cause it to fail. 

Cracks

The most common welding defect, and welds with cracks almost always fail to meet standards. There are two types of welding cracks: hot cracks and cold cracks. 

Welding cracks are fractures or separations that can appear in materials that are joined by welding. They can be a serious defect that can weaken the welded connection. Cracks can be seen with the naked eye or may require more sophisticated methods to detect them. 

Cracks can be caused by a number of factors, including: 

Hydrogen diffusion: Also known as "underbead cracking", "toe cracking", "cold cracking", or "delayed cracking" 

Crater cracks: Form at the end of the bead, where the arc ends 

Excess hydrogen 

Moisture: In the air, on the surface of the base material, or in the welding electrode 

Oil or other contaminants: On the base material 

Internal stresses: When these stresses exceed the strength of the weld metal or the base metal 

Loads: Tensile and fatigue loads, bending, twisting, or flexing, and hot and cold expansion and contraction 

Cracks can be classified by how they form in the weld bead: 

Longitudinal cracks: Form parallel to the weld bead 

Transverse cracks: Form across the width 

To prevent cracks, you can try: 

Preheating the metal 

Cooling the weld area properly 

Using a proper joint design 

Removing impurities 

Using the appropriate metal 

Welding a sufficient sectional area 

Using proper welding speed and amperage current 

Filling the crater properly to prevent crater cracks 

Slag inclusions

An inclusion is a solid foreign matter that is entrapped during welding. It can be a metallic inclusion such as tungsten, copper or other metal or a slag inclusion which may be linear, isolated or grouped. It can also be a non-metallic inclusion such as sulphide and oxide which are a product of chemical reactions, physical effects and contamination which occurs during welding. Inclusion defects are usually internal and volumetric in nature. They are most commonly caused by incorrect welding parameters, incorrect manipulation of the electrode by the operator, incorrect inter-run cleaning or poor storage of consumables.

Lack Of Fusion And Incomplete Penetration

Lack of fusion is another serious weld defect which can occur as a result of;

• A lack of fusion between the weld metal and the parent metal at the root of the weld when complete penetration is required
• A lack of sidewall fusion which occurs between weld metal and parent metal at a side weld outside of the root of the weld
• A lack of inter-run fusion which occurs between adjacent layers of weld metal on a multi-run welds

These are normally detected in welds where improper welding variables have been used and where there are improper manipulations of the electrode from the welding operator. Incorrect joint design and fit-up can also lead to lack of fusion issues.

Mechanical Damage

Mechanical damage is an indentation in the surface of the parent metal or weld caused by damage during preparation, welding, dressing or handling. These could be caused by the incorrect use of grinders, hammers, chipping hammers etc.

Spatter 

Welding spatter is a welding defect that occurs when molten metal droplets are ejected from the welding arc and land on nearby surfaces. The droplets solidify and stick to the surface once they cool, creating unsightly globules of material.

Causes 

Spatter can be a safety hazard if it comes into contact with skin or eyes, and it can also damage nearby surfaces. 

Spatter can be caused by a number of factors, including: 

Poor quality welding wire 

Incorrect gas mixtures 

Poor welding surface conditions 

Improper torch angle 

Wire stick-out length 

Grounding location 

Wind or loss of shielding gas 

Moisture in the atmosphere 

Inconsistent feedback from the welding power supply 

Arc explosion or arc repulsion force 

Remedial Measures 

To reduce spatter, you can try these techniques: 

Prepare surfaces

Make sure your working area is free of rust, paint, scale, grease, or other contaminants. 

Use spray transfer

Spray transfer is more effective than short arc or globular transfer for keeping spatter to a minimum, especially on thicker materials. 

Ensure a smooth wire feed

Check for dirt and make sure you're using the correct wire liner, contact tip, and wire. Also, adjust your spool tension or brake correctly and check for loops in your torch cables. 

Use anti-spatter spray or gel

These products contain silicone or a similar ingredient that prevents spatter from sticking to your welding table. 

Overlap. 

Overlap welding is a common welding defect that occurs when molten metal flows over the base material and cools without fusing with it. This is weld metal at the toe of the weld that covers the parent metal surface but has not fused to it. Generally caused by slow travel speed and wrong torch angle.

This creates an extra layer of material that doesn't properly fuse with the base metal. Overlap can affect the appearance, cost, and quality of the weld, and should be avoided whenever possible. 

Some causes of overlap welding include: 

Too much weld metal: This can be caused by a low welding speed. 

Gravity: In fillet welds, gravity can cause excessive molten metal to droop, which can lead to overlap. 

FAQs

Q. How to fix the common welding defects ?

Ans. : 

Common welding defects and how to fix them: 

Undercut

This can happen when the arc voltage is too high, the weld speed is too fast, or the wrong angle is used. It can also be caused by poor welding technique, gas shielding, or more heat on the edges. 

Burn-through

This happens when the weld pool goes through the base metal, creating a hole or cavity. It can weaken the weld and its structural integrity. 

Porosity

This can happen when there's too much arc time, which allows oxygen to enter the molten pool and create gas pockets. To reduce this, you can keep weld beads small and break up long beads with short pauses. 

Incomplete fusion

This happens when there's not enough fusion between the base metal and the weld metal. You can try using the multipass technique to fix this. 

Here are some other tips for avoiding welding defects: 

Use a proper weld technique 

Use proper joint design, including proper joint geometry and electrode size 

Reduce arc travel speed 

Use dry electrodes and materials 

Check the gas flow meter and make sure it's optimized with the correct pressure and flow settings 

Adjust the voltage and amperage settings based on the welding process, joint configuration, and material thickness 

References

ResearchGate

https://www.researchgate.net

(PDF) Welding defects, Causes and their Remedies: A Review

between the welding turns. ... 

Tuffaloy

https://www.tuffaloy.com

5 Common Welding Defects, and How To Prevent Them - Tuffaloy

Fractory

https://fractory.com

Welding Defects - Types, Causes, Prevention 

Technoweld

https://technoweld.com.au

The Most Common Welding Defects: Causes and Remedies

Arccaptain

https://www.arccaptain.com

9 Common Weld Defects: Causes, Types, and Prevention