8 Welding Defects To Look Out For! (Detailed Images)
This article explains the types of welding defects that can happen and how to avoid them. It will also point out different external and internal defects.
Welding defects are flaws that can form at any stage of the welding process, and when they do, they can compromise the intended use of a weldment. They are deviations in size and shape from the technical and design requirements. Although some defects are allowed since they do not compromise set standards and quality, others are unacceptable.
Flaws that do not compromise the weld are called weld discontinuities. However, if too many of these discontinuities exist, they are classified as defects and are subject to rejection.
While it is virtually impossible to create a defect-free weld, welders must reduce the occurrence of defects to prevent material loss and maintain the intended quality. And since every welder's goal is to avoid having their welds rejected, everyone should learn the types of defects that can happen and how to avoid them.
Flaws that do not compromise the weld are called weld discontinuities. However, if too many of these discontinuities exist, they are classified as defects and are subject to rejection.
While it is virtually impossible to create a defect-free weld, welders must reduce the occurrence of defects to prevent material loss and maintain the intended quality. And since every welder's goal is to avoid having their welds rejected, everyone should learn the types of defects that can happen and how to avoid them.
Why is it Essential to Avoid Welding Defects?
The primary reason to identify and prevent weld defects is the potential danger a poor-quality weld can pose since they are more likely to fail. The consequences of a weld failing might be merely the inconvenience of a pipe bursting in the bathroom. However, if the weld on a gas pipe should fail, the results could be catastrophic, including loss of life. The same is true of a structural weld in which a bad weld could injure or kill motorists crossing a bridge or workers in a high-rise office.
Image credit: https://blog.thepipingmart.com
High-quality welds help improve the safety of structures and the innocent people who depend on them for their well-being. Most professional welders already understand that welding defects are about much more than aesthetics, and many of them are passing that message on to those new to the trade who have yet to realize the potential dangers of welding defects.
Two Broad Categories of Welding Defects
Defects in welding joints can be classified into two categories: defects you can see (external) and those that are hidden (internal).
- External welding defects, sometimes called surface defects, manifest on the weld's surface. Some examples include cracks, overlaps, undercuts, porosity and spatter.
- Internal welding defects occurring in the depth of the weld might not be visible but are as troublesome as external ones. Included among these are fusion, slag inclusion and incomplete penetration.
Let's look at these five external defects first:
1. Cracks
Cracks are among the most common and severe defects since they weaken the weld and can occur anywhere on its surface. There are two types of cracks:
1. Cracks
Cracks are among the most common and severe defects since they weaken the weld and can occur anywhere on its surface. There are two types of cracks:
- Hot cracks occur during welding when temperatures reach 10,000 degrees Celsius.
View of a hot cracks. These cracks are barely visible to the naked eye.
Image credit: https://weldinganswers.com
Image credit: https://weldinganswers.com
- Cold Cracks appear after welding and during the solidification process and show up several hours or days after the welding is completed.
Prevention measures for cracks include:
- Avoid rapid cooling of the weld area
- Preheat the joint to the required level
- Avoid low currents coupled with high travel speeds
- Use the correct joint design
- Use proper amperage settings.
- Use the correct alloy filler material
2. Undercuts
Undercuts look like narrow gutters or notches at the edge of the weld. They occur when the base metal melts away from the weld area, reducing the thickness of the base metal and weakening the workpiece.
Prevent undercuts by doing the following:
Undercuts look like narrow gutters or notches at the edge of the weld. They occur when the base metal melts away from the weld area, reducing the thickness of the base metal and weakening the workpiece.
Prevent undercuts by doing the following:
- Decrease the travel speed
- Use the correct electrode size
- Reduce the length of the arc and lower the voltage
- Use the proper welding techniques
- Do multiple passes
- Keep the torch at the correct angle
Example of overlap on a weld.
Example of Image credit: https://weldgears.com
Example of Image credit: https://weldgears.com
3. Overlaps
Overlap results when the weld pool overflows on the surface, covering the base metal without bonding.
Prevention measures for overlap include:
Overlap results when the weld pool overflows on the surface, covering the base metal without bonding.
Prevention measures for overlap include:
- Use the recommended welding technique to avoid the wrong arc length
- Position the torch at the appropriate angle
- Use the correct deposition
- Use low welding current.
- Avoid letting your travel speed get too slow
- Do not use oversized electrodes
- Set the correct amperage; avoid a high setting
Round holes in the weld bead are a sign of a defect called porosity.
Image credit: https://www.boconline.co.uk
Image credit: https://www.boconline.co.uk
4. Porosity
Porosity occurs when gas bubbles accumulate and get trapped inside a weld. Porous welds typically happen because of contamination of the weld metal. During welding, gases, including steam, hydrogen, and carbon dioxide are generated and can become trapped, weakening the joint and ruining the work.
Consider the following to prevent porous welds:
Porosity occurs when gas bubbles accumulate and get trapped inside a weld. Porous welds typically happen because of contamination of the weld metal. During welding, gases, including steam, hydrogen, and carbon dioxide are generated and can become trapped, weakening the joint and ruining the work.
Consider the following to prevent porous welds:
- Clean the weld surface before you begin welding
- Allow gases to escape by slowing the welding process
- Confirm the settings of the gas flow meter
- Properly clean and prepare the base metal
- Make sure the joint is dry
- Set the shielding gas flow correctly
- Prevent the amperage from getting too high
- Use the correct electrode alloy for the job
Molten metal is spat all over called spatter.
Image credit: https://www.twi-global.com
Image credit: https://www.twi-global.com
5. Spatter
Spatter frequently occurs with MIG welders, and it happens when metal particles from the weld become attached to the surface next to the weld area. Although it's usually not a threat to structural integrity, spatter is a defect because the aesthetics of a weld are often as critical as the weld's strength.
Reduce spatter with the following suggestions:
Spatter frequently occurs with MIG welders, and it happens when metal particles from the weld become attached to the surface next to the weld area. Although it's usually not a threat to structural integrity, spatter is a defect because the aesthetics of a weld are often as critical as the weld's strength.
Reduce spatter with the following suggestions:
- Make sure the base metal is clean
- Use proper gas shielding
- Use the correct amperage
- Keep a short arc
- Increase the electrode angle
- Check the feed wire to ensure it is unimpeded.
And here are three examples of internal welding defects:
Example of poor penetration in welding.
Image credit: https://weldinganswers.com
Image credit: https://weldinganswers.com
1. Poor Penetration
Poor or incomplete penetration results when the bead does not fill a butt joint to the bottom, compromising the integrity of the joint.
Prevent incomplete penetration with these welding tips:
Poor or incomplete penetration results when the bead does not fill a butt joint to the bottom, compromising the integrity of the joint.
Prevent incomplete penetration with these welding tips:
- Ensure there is enough weld deposition
- Be sure to use the correct joint geometry and proper alignment
- Use the optimum welding amperage
- Reduce the travel speed
- Use a correctly sized electrode
- Prepare V-grooves for butt joints with 60 to 70-degree sloped sides
Example of weld slag inclusion.
Picture credit: https://primeweld.com
Picture credit: https://primeweld.com
2. Inclusion
Slag inclusions are impurities trapped in the weld or on the surface of the weld zone. These contaminants are byproducts of stick welding and arc welding and can significantly weaken the joint.
Prevent inclusions with the following steps:
Slag inclusions are impurities trapped in the weld or on the surface of the weld zone. These contaminants are byproducts of stick welding and arc welding and can significantly weaken the joint.
Prevent inclusions with the following steps:
- Prepare and clean the base metal thoroughly
- Avoid low amperage
- Ensure the weld cools moderately
- Maintain the proper torch angle
- Increase the welding speed so that weld and slag don't mix
When there's a lack of proper fusion between the base metal and the weld metal it is called lack of fusion (incomplete fusion).
Picture credit: https://www.boconline.co.uk
Picture credit: https://www.boconline.co.uk
3. Incomplete Fusion
Lack of fusion (a.k.a. incomplete fusion), occurs when the weld metal and the base metal are not bonded. Incomplete fusion can also occur between layers within the weld itself if the filler material is not well connected to the base metal on both sides and to welds underneath during multiple passes.
Here are a few tips for preventing incomplete fusion:
Lack of fusion (a.k.a. incomplete fusion), occurs when the weld metal and the base metal are not bonded. Incomplete fusion can also occur between layers within the weld itself if the filler material is not well connected to the base metal on both sides and to welds underneath during multiple passes.
Here are a few tips for preventing incomplete fusion:
- Clean the base metal to remove all impurities
- Use the correct size electrode
- Ensure the correct electrode alloy is being used
- Don't move the torch too fast
- Keep the arc from getting too short
- Keep the amperage high enough
The Darkside of Welding Defects
Welding defects are not merely unsightly but can create serious issues if they are not addressed. In addition to being costly and time-consuming, they could eventually result in injuries or even loss of life if left unchecked.
By learning and using correct welding techniques, professional welders are doing their part to keep themselves and end-users safe in the future. Focusing on improving welding machinery and technical skills helps to limit welding defects and enables manufacturers to produce higher-quality products.
By learning and using correct welding techniques, professional welders are doing their part to keep themselves and end-users safe in the future. Focusing on improving welding machinery and technical skills helps to limit welding defects and enables manufacturers to produce higher-quality products.
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