welding

Seven Types of Welding Defects

Imperfections such as welding defects are common in all types of manufacturing processes. The defects can affect the quality and shape of the product. Defects can occur at any stage of the manufacturing process and are usually caused by the use of incorrect welding techniques.


Aggressive Tube Bending has been providing personalized tube, pipe and structural steel services for over 30 years. Let’s take a look at the common welding defects and their causes.

1. Weld cracks
These are one of the most critical welding defects and can appear on the weld metal’s surface or the area affected by intense heat.
Causes of weld cracks are:
• Use of hydrogen to weld ferrous metals
• Base metal contamination
• Residual stress due to solidification shrinkage
• Low current but high welding speed
• Poor joint design
• High carbon and sulphur content in the metal

2. Undercuts
These are narrow gutters formed in the parent metal and the sides of the weld bead. Undercuts reduce the strength of the weld and the thickness of the plate.
Causes of undercuts are:
• Use of an incorrect angle while welding, which results in free edges being heated more than what is needed
• Electrode is larger than what is needed
• Incorrect use of gas shielding
• Incorrect filler metals
• Substandard welding techniques

3. Porosity
Porosity is a form of weld metal contamination. It is caused when shielding gas is trapped inside the metal and released during solidification, leading to the formation of pores. Causes of porosity are:
• Inadequate electrode de-oxidant
• Use of a longer arc
• Improper gas shield
• high gas flow
• Contaminated surfaces
• Rust, grease or oil

4. Incomplete joint penetration
This defect occurs when the depth of the welded joint isn’t sufficient. Here, the metal groove won’t be filled completely resulting in the weld not extending through the entire joint.
Causes of incomplete penetration are:
• More space than what is needed between the weld metals during welding
• The bead was moved too fast, not allowing enough metal to be deposited
• To large of an electrode diameter for the joint requirements
• Misalignment
• Improper joint

5. Incomplete fusion
This occurs when the base metal and the weld metal are not accurately welded because of improper melting. Incomplete fusion can also occur between layers within the weld beads. It creates gaps in the joints that aren’t filled with molten metal.
Causes of incomplete fusion are:
• Low heat input
• Surface contamination
• Electrode diameter being incorrect
• Travel speed is too fast

6. Slag inclusion
Slags are vitreous materials produced as by-products after flux-cored arc welding, submerged arc welding and stick welding. They affect metal weldability and toughness, resulting in decrease of structural performance of the weld material.
Causes of slag inclusion can are:
• Improper cleaning
• Fast weld speed
• Not cleaning the weld pass
• Incorrect welding angle
• Weld pool cooling too fast
• Low welding current

7. Spatter
It occurs when small metal particles from the weld remain attached to the surrounding surface. It’s very common in gas metal arc welding and most of the time, it is very hard to remove these metal particles.
Causes of spatter are:
• High running amperage
• Low voltage
• Too steep electrode angle
• Surface contamination
• Arc is too long
• Incorrect polarity
• Erratic wire feeding

 Let Us Help
Aggressive Tube Bending has been working with businesses from all industries for over three decades. Our technicians and welders are certified to CWB (Canadian Welding Bureau), AWS (American Welding Society) and ASME (American Society of Mechanical Engineers) and experienced to complete any job with perfection. To learn why you can count on us, go through our blog post- Keys to Select the Right Metal Fabrication Company.


Call us for our welding services. You can also count on us for our other customized steel services.

 

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