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Defects exist even at the atomic level. Errors are a reality in the world of fabrication and the welding process is no exception. Given the nature of welding imperfections and mistakes are unavoidable. The real challenge lies in identifying and correcting them. In this blog, we will look into the common welding mistakes and the practical solutions to correct them. 

Identifying and Correcting Welding Mistakes

Welding mistakes can be categorized into two based on their visibility: 

External defects that can often be seen on the surface of the metal such as undercutting, porosity, and many more; Internal defects, those which are not visible through naked eyes, such as incomplete fusions and penetrations. 

Common Welding Mistakes

1.Porosity

Wormholes weld, also known as porosity, is a defect that happens when air bubbles of the gas get stuck in the weld. It is a common defect that occurs in welding processes that rely on shielding gases such as TIG and Stick welding. 

- Cause

Porosity can be caused by various reasons such as:

• Using the wrong electrode
• Absence or excessive presence of shielding gas
• Moisture 
• Unclean welding surface 
• Fast welding speed

- Solution

• Use appropriate electrodes such as medium carbon steel and alloy. 
• Clean the welding surface
• Ensure proper gas flow ( neither too high nor too low)
• Preheat the metals before welding. 
• Adjust the weld speed and angle. 

2.Undercut

Undercut is caused by two major reasons- the first being the use of excessive current that leads to the melting of joint ends and the second, the lack of enough filler metal. This can lead to reduced cross-section, forming notches along the weld. They will in turn be stress concentrators, making the workpiece prone to long-term damage. 

- Cause

• Overheating of the base metal due to the use of excessive current. 
• Use of wrong electrode 
• Incorrect electrode angle. 
• Excessive travel speed of the welding torch
• Solution

• Adjust the speed of the welding torch
• Use the apt amount of current throughout the process
• Maintain the electrode angle in a range between 30 to 45 degrees. 
• Choose the appropriate electrode. 

3.Slag Inclusion

Slag inclusion happens when certain non-metallic particles get trapped inside the weld. They may harden and form an external layer, which can weaken the structural integrity of the metal. 

- Cause

• Low welding current intensity and the consequent insufficient heating of the metal.
• Incorrect welding angle 
• High travel speed of the welding torch. 
• Inadequate cleaning of the weld edge
•  Solution

• Increase the welding current density
• Maintain the correct welding angle and optimum speed of the welding torch. 
• Clean the weld edge consistently and prevent slag buildup. 

4.Cracks

Cracks are one of the worst welding defects. It can grow bigger across the entire length of the metal surface, weakening the structural integrity of the workpiece. Cracks are of two types based on the temperature: 

Hot crack occurs at high temperatures, during welding solidification, when the partially solid metal is weak and cannot stretch. Instead it shrinks during cooling, which forces it to tear. 

Cold crack on the other hand, is formed after the weld metal is cooled. It happens when three conditions come together: presence of hydrogen atoms, the workpiece metal is hard and brittle and the residual stress caused by uneven heating and cooling during welding.  When these conditions come together, crack occurs. 

- Causes

• Use of hydrogen shielding gas during welding ferrous metals.
•  Poor joint design that prevents expansion/ contraction
• Presence of high sulphur and phosphorus content in the base metal. 

- Solution

• Preheat the base metal to reduce thermal stress and slow cooling. 
• Ensure the metal surface is clean and free from dust and contaminants. 
• Maintain the right weld joint gaps. 

5.Spatter

Spatter occurs when small metallic particles are scattered out from the welding arc and spread all over the base metal. It then solidifies and gets stuck on the metal surface. 

- Cause

• High welding current
• High arc length 
• Poor shielding of the heat-affected zone
• Wrong polarity

- Solution

• Chose a better shielding gas and shielding technique
• Maintain the right weld polarity. 
• Maintain optimal welding current and arc length. 

6. Incomplete Fusion

Incomplete fusion happens when the weld metal is not properly fused with the parent metal or base metal. This leaves gaps in the weld zone. 

- Cause

• Low heat input causes the metal not to melt properly.
• Incorrect bead position and joint and torch angle. 

- Solution

• Maintain right positions such as torch and joint angle and bead position. 
• Higher welding current and slow torch movement to ensure proper welding 
• Clean the metal surface.

Conclusion

To conclude, these are some of the most common welding mistakes and their corresponding solutions. Welding is an important process that requires accuracy and precision. No process is free from mistakes or defects and welding is no exception. If welding defects are not properly addressed it can lead to structural issues, safety risks and financial setbacks as well. Therefore,  understanding common welding defects and their solutions will help to ensure durable and quality welds are formed.