Good vs Bad Welds - In-Depth Examples and Images
This article explains how you can identify weld quality and what are the signs of good and bad welds. Additionally, it will describe weld inspection methods and procedures. In the end of the article it will point out how to turn bad welds into good welds.
Welding is a skill that's much in demand today. And with so many segments of our economy relying on it, there is no reason to believe that will change anytime soon. Buildings, vessels, and automobiles are some of the items where welding is the key to their construction, but they represent a small percentage since so many other things are built using metal that requires some welding.
Bad welds can cause anything from a minor annoyance to a complete catastrophe, so they must be recognized and repaired or prevented in the first place. However, determining whether a weld is good or bad can be complicated. Still, it is essential to be able to do so since welding in industries such as constructions building means lives depend on practical and durable welds.
Learn more about Welding Defects To Look Out For!
Bad welds can cause anything from a minor annoyance to a complete catastrophe, so they must be recognized and repaired or prevented in the first place. However, determining whether a weld is good or bad can be complicated. Still, it is essential to be able to do so since welding in industries such as constructions building means lives depend on practical and durable welds.
Learn more about Welding Defects To Look Out For!
Usual Criteria to Help You Identify
Weld Quality
Weld Quality
- Appearance: Welds should have a smooth and uniform appearance.
- Profile: Depending on the application, welds must be flat, concave, or convex.
- Coloration: An acceptable weld will have a color-free appearance, indicating no oxidation.
- Defects: Two of these are porosity caused by contamination of the weld and craters from a rapid reduction in the current.
- Too much or too little penetration: If the weld penetrates too little, the joint will be weak, and if it over-penetrates, the backside of the joint could have a poor finish.
- Undercutting: If the parent metal thins at the edges of the weld, it typically indicates filler metal relative to the current.
What are the Signs of Good and Bad Welds in
Different Techniques?
Different Techniques?
Metal Inert Gas Welding (MIG)
Metal inert gas welding (MIG) is one of the most frequently-chosen welding methods.
Metal inert gas welding (MIG) is one of the most frequently-chosen welding methods.
Let's look at the signs of a good MIG weld:
- No cracks, slags, or holes on the bead
- A smooth, consistent weld without patterns or discoloration
- Some coloration on the base metal
- A flat bead profile, which is neither concave nor convex
- Straight and uniform appearance
- No craters or dips in the bead
- No uniformity and straightness of the bead
- Cracks along the bead
- No discoloring of the base metal
- Thin bead
- Visible spatter
- Joined structure lacks strength
Tungsten Inert Gas Welding (TIG)
TIG is considerably more challenging to achieve and requires a higher skill level before producing quality welds. It is a technique used on various metals, including stainless steel, aluminum, magnesium, and copper alloys, and quite frequently in the aerospace industry.
TIG is considerably more challenging to achieve and requires a higher skill level before producing quality welds. It is a technique used on various metals, including stainless steel, aluminum, magnesium, and copper alloys, and quite frequently in the aerospace industry.
A good TIG weld has the following characteristics:
- No signs of tungsten metal particles in the weld
- A distinct pattern of consistent beads
- No pores on the surface of the weld
- No slag or burn-through
- Consistent thickness, width, and height
- Visually appealing
- Burn-through on the underside of the joint
- Black heat marks that are difficult to remove
- Flat and wide bead with no distinct pattern
- Not enough filler
- Inclusion of tungsten in the weld
- Weld defects
Shielded Metal Arc Welding (Stick Welding)
Stick Welding is relatively easy to learn and works with several materials, including carbon steel, stainless steel, cast iron, copper, and aluminum.
Stick Welding is relatively easy to learn and works with several materials, including carbon steel, stainless steel, cast iron, copper, and aluminum.
The following are signs of good stick welds:
- Consistent thickness
- No spatter
- Straight and uniform bead
- No holes or cracks in the bead
- Inconsistent bead width and height
- Slag on the weld surface
- Weld defects, such as cracking, undercutting, or breaks in the bead
- Spatter
Professional Welds Inspection Tools
The following are commonplace weld inspection methods and procedures:
For example visual inspection can be done by welding inspector,
who is checking the weld with welding gauge.
Picture credit: https://www.smartveritas.com
who is checking the weld with welding gauge.
Picture credit: https://www.smartveritas.com
Visual Inspection
Visual inspections are the most common and cost-effective way of testing welds. Weld inspectors must have significant experience and knowledge from years of hands-on welding to visually inspect a weld and understand the difference between acceptable appearance and welding defects.
Immediately after welding, operators perform the first visual inspection, looking for obvious defects, uneven weld beads, undercut edges, and other inconsistencies. However, remember that a weld that doesn't look good isn't necessarily a bad weld. Other tests, such as those listed below, can find hidden flaws (or the absence of them) more reliably than a visual inspection.
Visual inspections are the most common and cost-effective way of testing welds. Weld inspectors must have significant experience and knowledge from years of hands-on welding to visually inspect a weld and understand the difference between acceptable appearance and welding defects.
Immediately after welding, operators perform the first visual inspection, looking for obvious defects, uneven weld beads, undercut edges, and other inconsistencies. However, remember that a weld that doesn't look good isn't necessarily a bad weld. Other tests, such as those listed below, can find hidden flaws (or the absence of them) more reliably than a visual inspection.
X-ray inspection is a required test to comply the demanding international quality standards.
Picture credit: https://www.orangecoasttesting.com
Picture credit: https://www.orangecoasttesting.com
X-Ray Inspection
Also called radiographic inspection, x-rays are an accurate and efficient inspection method. The process uses gamma rays to pass through the weld and the surrounding base metal. Experienced inspectors look at the x-rays and can determine if a weld meets strength requirements or contains deformities or defects.
Also called radiographic inspection, x-rays are an accurate and efficient inspection method. The process uses gamma rays to pass through the weld and the surrounding base metal. Experienced inspectors look at the x-rays and can determine if a weld meets strength requirements or contains deformities or defects.
Liquid penetrant inspection is widely used to detect surface breaking flaws.
Image credit: https://yenaengineering.nl
Image credit: https://yenaengineering.nl
Liquid Penetration
This inspection method involves spraying a brightly colored liquid dye over the weld and left to soak in after it has cooled. After a short period, an inspector can see any irregularities or defects in the weld since the liquid's color will change, usually becoming darker in the area of a crack or hole.
This inspection method involves spraying a brightly colored liquid dye over the weld and left to soak in after it has cooled. After a short period, an inspector can see any irregularities or defects in the weld since the liquid's color will change, usually becoming darker in the area of a crack or hole.
Magnetic particle inspection is used for detecting defects in ferromagnetic materials.
Image credit: https://www.flyability.com
Image credit: https://www.flyability.com
Magnetic Particle Inspection
Probes are placed on either side of the inspection area, allowing amperage to pass through the material. Whenever the amperage encounters a discontinuity, the probes are diverted, and amperage leaks to the surface, creating magnetic poles and allowing the inspector to determine the location of the irregularity.
Probes are placed on either side of the inspection area, allowing amperage to pass through the material. Whenever the amperage encounters a discontinuity, the probes are diverted, and amperage leaks to the surface, creating magnetic poles and allowing the inspector to determine the location of the irregularity.
A technician tests a pipeline weld for defects using an ultrasonic instrument.
Picture credit: https://www.wermac.org/others
Picture credit: https://www.wermac.org/others
Ultrasonic Weld Inspection
With ultrasonic testing, a high-powered mechanical frequency beams into the weld, and if it strikes a discontinuity, it is reflected to a transducer (receiver). The signal is measured to help determine the size, shape, and type of weld failure. This method is effective at finding internal discontinuities but requires exceptional operator knowledge and expensive equipment.
With ultrasonic testing, a high-powered mechanical frequency beams into the weld, and if it strikes a discontinuity, it is reflected to a transducer (receiver). The signal is measured to help determine the size, shape, and type of weld failure. This method is effective at finding internal discontinuities but requires exceptional operator knowledge and expensive equipment.
Turning Bad Welds into Good Welds
Welding techniques and settings are typically the primary sources of bad welds, which can be countered by improving a welding operator's techniques, set-ups, and knowledge base. Bad welds contain porosity, pinholes, undercut edges, excessive penetration, spatter, slag on the weld surface, lack of fusion, heat marks, overlap, and more.
These defects and inconsistencies can be controlled by following the examples of professional welding operators with greater field experience than you do. The accumulated knowledge of veteran welders significantly outweighs studying other resources or technical books. Understanding welding theory is essential, but the guidance of a professional is the best way to ensure most of your current work consists of good welds, and bad welds have become a thing of the past!
These defects and inconsistencies can be controlled by following the examples of professional welding operators with greater field experience than you do. The accumulated knowledge of veteran welders significantly outweighs studying other resources or technical books. Understanding welding theory is essential, but the guidance of a professional is the best way to ensure most of your current work consists of good welds, and bad welds have become a thing of the past!
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