Inexperienced welders who repair steel structures and components on their own often discover welding defects that reduce the strength of the welds. They crack, leak water, and collapse under load.
This article explains what a welding defect is, how a defect appears when a welding defect occurs, and what the causes and remedies for the defect could be.
What is Welding Defect?
Welding defects often occur during welding operations for the following reasons: improper welding technique; inexperienced or untrained craftsmen; defects in the structure of the welding process.
The earlier these defects are identified, the easier it is to eliminate them and the lower the risk of leaks or cracks.
As for changes in the size and shape structure of the weld metal during welding, this can occur due to improper welding process or improperly performed arc welding in a protective metal sheath.
It is important to understand that a quality weld has adequate weld penetration and good penetration between the filler metal and the prepared edge. Structural defects can occur in different types of welding, such as shielded gas welding, laser welding, resistance welding, and plasma welding.
Types of Welding Defects
Types of common welding defects are listed below:
- Undercut
- Weld crack
- Excess reinforcement
- Overlap
- Incomplete or lack of fusion
- Lamella tear
- Slag inclusion
- Incomplete penetration
- Spatter
- Whiskers
- Pores and voids
- Distortion
- Hot Tear
- Damage to mechanical type
- Skew
- Burn Through
The cause of welding defects occur is the incorrect welding process and improper welding techniques.
#1 Internal welding defects — porosity and blowhole
Porosity is a set of small bubbles, and voids are relatively large, inconspicuous pores, and openings. They are formed mainly as a result of gas ingress. The presence of porosity is the result of contamination of the weld metal.
Causes and methods of elimination of porosity
| 1 | Use of insufficient amount of electrode antioxidants | Selection of suitable electrodes and welding materials. |
| 2 | Excessive gas flow. | Check the gas flow meter and make sure that it is installed correctly and that the pressure and flow settings are correct |
| 3 | Use of larger sheet size. | Check that elbow spacing is correct. |
| 4 | Presence of moisture during the process | Cleaning of metal before starting the welding processes. |
| 5 | Insufficient gas shielding | Reduce the welding speed to allow the gas to escape. |
| 6 | Dirty work surfaces such as scale, rust, oil, grease, etc. | Clean separately and keep dirt out of the welding area. |
#2 Undercut
Undercutting of the weld defect, i.e. the formation of grooves in the weld that reduces the cross-sectional thickness of the parent metal. As a result, the weld and the workpiece become weaker.
The causes of and ways to eliminate undercuts
| 1 | Low heat input. Incorrect application of the angle, during which more heat is transferred to the free edges | Apply an appropriate electrode angle, during which more heat is transferred to the thickened parts. |
| 2 | The welding process is too fast | It is necessary to reduce the electrode travel speed, but not too slow. |
| 3 | Poor welding technique. | Use of a multi-pass welding technique. |
| 4 | Use of incorrect shielding gas and filler metal. | Choose the proper gas shielding for the material being welded. |
| 5 | The welding current is too high. | Use proper current when approaching thin sections and loose edges |
| 6 | Use larger diameter electrodes. | Reduce the arc length. |
#3 Metal weld crack
The most dangerous and extremely strong are these types of welding defects. Most standard standards exclude them from production. At high temperatures, they can occur on the weld surface or in a single high-temperature area.
During weld cracks occur in different types depending on the temperature.
Hot cracks
Can occur during the shielded metal arc welding process of an unwelded component, as well as during crystallization. Temperatures can reach as high as 10,000 degrees Celsius.
Cold cracks occur
After a weld is welded and the temperature of the metal drops, cracks form. Sometimes they can appear hours or even days after the welding steel. When a steel structure is deformed, weld cracks occur most often.
Cracks that appear at the end of the work process, before the specialist has finished welding, are found in hot crater welding. Most often they are found at the end of the process.
When the weld pool cools and hardens, the weld acquires volume to compensate for metal shrinkage. Otherwise, cracks form in the form of a crater.
Primary causes and methods for removing welding cracks
| 1 | Application of hydrogen technology for welding ferrous metals. | Proper types of substances must be used. |
| 2 | Too fast weld speed and low current. | Use appropriate welding speed and current. |
| 3 | Incorrect welding patterns. | Use appropriate design patterns. |
| 4 | Lack of preparation before welding. | Preheat the metal. |
| 5 | Contaminated metal. | Clean metal surface immediately before commencing work. |
| 6 | Residual curing due to shrinkage. | Cool down the weld area. |
| 7 | A high amount of sulfur and carbon in the metal. | Apply the correct amount of sulfur and carbon in the metal. |
| 8 | The crater was not filled correctly. | Make sure the crater is filled correctly to prevent a defect. |
#4 Incomplete fusion
It is a type of welding defects present when there is not enough quality penetration between the metal part and the weld. In addition, the defect can be detected in the joint area between the weld bead.
This results in the formation of a gap within the weld that is not filled with molten weld metal.
The main causes and remedies for the lack of fusion
| 1 | Surface contamination. | Before the welding operation, the joint area must be cleaned of all contaminants left on the metal surface. |
| 2 | Application of an excessively high travel speed. | Reduce the travel speed of the arc. |
| 3 | The weld pool is very large and it goes ahead of the arc. | Check that the weld pool is properly sized to match the movement of the arc. |
#5 Slag inclusions in the flux core arc welding
Slag inclusions are welding defects that are most visible in welds. A dangerous substance is slag, which is formed during crucible welding, stick welding, TIG welding, resistance welding.
This problem can occur when the flux, which is the solid shielding material used when welding, begins to melt in the weld or on the surface of the welding area.
The strength of the joint is impaired by the slag inclusion, making it more brittle.
The main causes and solutions to the slag inclusion
| 1 | Improper brushing and grinding of previous welds. | Clean the surface of the welding layer with a wire brush before surfacing the next layer. |
| 2 | Incorrect electrode angle. | You must select a proper electrode angle. |
| 3 | A low welding current was applied. | Increase current value. |
| 4 | Not enough space for molten metal. | Change desired weld bead shape to allow enough space for proper use of molten weld metal. |
| 5 | Rapid cooling. | Reduce the intensity of rapid cooling. |
| 6 | Insufficient degree of metal cleaning. | Metal must be cleaned properly before welding. |
By solving these causes, you will be able to solve the problem of slag inclusion.
#6 Incomplete penetration
In such welding defects, penetration is defined as the distance from the top of the base metal surface to the largest value in the weld joint.
In the case of incomplete penetration occurs when the metal groove has not been filled. As a consequence, the weld metal is not fully distributed throughout the thickness of the weld. There may be a change in the metal structure.
Cases of incomplete penetration and how to eliminate them
| 1 | The gap between the metal being worked is too large | The weld must be checked for cleanliness. |
| 2 | Arc moving too fast causes insufficient penetration of the weld metal. | Arc speed should be reduced. |
| 3 | Ultra-low current is being used, making it impossible to melt the metal workpiece properly. | The correct welding current must be selected. |
| 4 | Unsuitable welds are being used. | Improve weld design to solve the weld defects. |
| 5 | An electrode is not positioned correctly. | Check if the electrode is installed correctly. |
| 6 | The electrode diameter is too large. | Use the correct electrode diameter. |
So, we have looked at incomplete penetration. It must be eliminated mechanically.
#7 Spatter of the weld metal
Spatter is small metal particles that are ejected from the arc during operation and accumulate right next to the weld bevel on the base metal. This is especially common with shielding gas.
Examples of spatter and how to eliminate it
| 1 | Weld metal contamination | Metal surfaces should be cleaned before welding. |
| 2 | The working angle of the electrode is insufficient. | The arc length should be shorter and the angle of the electrode should be increased. |
| 3 | Current too high and voltage too low. | Polarity and current must be adjusted correctly. Use a larger arc and electrode to suit the weld. |
#8 Distortion
A distortion or deformation is a discrepancy in the size and position of two plates of metal before and after welding due to temperature differences existing at several points along the course of the welds.
In other words, if we talk about distortion, we can say that it is caused by uneven expansion and contraction of the weld metal, and all types of distortion increase as the degree of metal settlement increases.
Examples of mistakes and ways to eliminate distortions
| 1 | Use of incorrect welding procedure. | Ensure the correct welding procedure. |
| 2 | A large number of passes when using small electrodes. | Make the required number of passes. |
| 3 | High residual stress in the plate to be welded. | Make a sufficient amount of weld metal for welding to meet the requirements of the joint. This will assist in relaxing the compressive forces. |
| 4 | Insufficient arc travel speed. | Maintain proper arc travel speed. |
| 5 | A dimensional gauge has not been used. | Use a dimensional gauge if necessary to ensure high accuracy. |
| 6 | Too much time is devoted to welding. | Try to shorten the work time so that there is no volume expansion directly around the metal. |
#9 Hot Tearing
In these types of welding defects, hot cracks appear in the weld metal from the adjacent edge, causing it to solidify as the crack increases.
Cracking occurs along the boundaries of the weld zone until it solidifies, and the metal remains in a ductile state. Because of this, it is also referred to as a solidification weld crack.
Cases and Methods of Fixing a Hot Tear
| 1 | The thickness of the electrode may not be correct. | Select the appropriate electrode thickness depending on the base metal to be welded. |
| 2 | Proper welding current is not being applied. | Check that the correct welding current is being used. |
| 3 | The wrong material was selected. | Select the proper electrode weld material. |
#10 A welded tub has damage of a mechanical nature
Mechanical damage is defined as a depression in the coating of the base metal or weld, which was formed due to a breach of integrity during welding operations. Damage is caused by improper use of welding implements, such as grinding hammers, grinders, and other tools involved in the process.
Causes and remedies for mechanical damage
| 1 | The problems are because at the time of formation of chips, additional force is applied. | This defect can be easily prevented by proper operation of the welding tools. |
| 2 | The problem is caused by improper handling of the electrode holder. | After the welding is complete, make sure that no other piece of metal gets on the welded metal |
| 3 | Improper use of the grinder. | Moderation and care must be exercised when using a grinder. |
| 4 | The problem also arises because the metal parts have not been arc fed. | The arc must be brought up before welding begins. |
#11 Incorrect positioning in the welding process
In some cases, the filler metal in the weld joint is subject to decomposition, which is the result of improper positioning. This can be detected by a bent or wavy surface.
Problems of misalignment and methods for solving them
| 1 | The occurrence of misalignment is related to the rapid progress of the work. | To avoid this, use a slow or steady method of work execution. |
| 2 | The reason is an unskilled welder or inadequate control during the work. | Involve qualified professionals and perform proper control checks before welding. |
| 3 | Welding wire mismatch or improper wire positioning. | Welding wire must be in functional condition; check wire location. |
#12 Excessive Reinforcement
Another one of the most typical common welding defects occurs periodically. These defects, compared to insufficient reinforcement, occur if too much solder is present in the weld. In addition to this, overflows are characterized by irregular and hump-shaped shapes.
The main factors for the occurrence of reinforcement, ways to eliminate them
| 1 | Overflows can be caused by excessive current or excessive or erratic wire feed speeds. | Adjust the current value and avoid overheating. |
| 2 | Voltage fluctuations, which are most of the time insignificant. | Adjust the voltage to prevent it from dropping too much. |
| 3 | The excessive gap between components. | Try to align the parts so that the gap does not exceed the permissible value. |
#13 Overlapping of the weld pool
Overlap is a type of welding defect in which the filler material in the upper zone of the weld overlaps the base metal without joining. In other words, it is an excessive waste to weld metal, most often caused by the wrong welding technique.
Overlaps in welding are formed when the molten metal from the liquid metal bath flows over the cold base metal, and the surface area of the joint protrudes over the weld toe.
Causes and solutions to Overlap problems
| 1 | Improper welding technique is the main cause of this defect. | A better welding technique is needed to correct this defect. |
| 2 | Incorrect angle of the torch. | The right angle should be chosen. |
| 3 | Larger electrodes were used. | Large electrodes should not be used to solve the problem of overlap when submerged arc welding. |
#14 Tearing of the lamellar layer
This is a crack-shaped defect that occurs at the bottom of the weld and occurs mainly in the manufacturing process of rolled sheets. The crack usually occurs within the base plate, often outside the heat-affected zone, and most often runs parallel to the weld boundary.
Causes and remedies for plate fractures
| 1 | The metal of the weld is deposited on the surface of the metal where the strongest adhesion occurs. | This can be prevented by welding residue in the final stage. |
| 2 | Incorrect weld metal orientation and wrong choice of material. | Use the proper weld orientation and select high-quality materials. |
#15 Whiskers in the flux cored arc welding
If MIG welding causes a small portion of the electrode wire to stick through the weld on the root side of the weld, this is called a “whisker”. This is caused by the edge of the electrode wire sticking out of the leading edge of the weld pool.
Causes and Remedies of Whiskers
| 1 | Increasing the wire feed rate for the electrodes. | Reducing the electrode wire feed rate can help prevent this problem. |
| 2 | The travel speed is too high. | Maintain a stable operating travel speed and do not exceed it. |
#16 Burn Through
When a lot of heat is applied during a weld, the metal can blow a hole through the center. This defect is called burn-through. This is a common welding defect when welding thin parts less than 1/4 inch thick. Improper welding technique is partly responsible for this problem.
The main types of causes and methods of elimination of burns
These external welding defects can happen when working on thick parts if the welding machine parameters are chosen too high. Make sure that the amperage is not increased too much. The too high gas flow.
Other causes and solutions:
| 1 | Pay attention to the gap between the parts as it can be very large. | Do not allow large gaps between the sheets. |
| 2 | Do not use the proper degree of metal clamping and clamping. | Use proper metal fasteners and clamping devices. |
| 3 | Very slow rotation of the torch. | Make sure that the speed of rotation is optimal: neither too slow nor too high gas metal arc welding flow. It is also possible that the gas consumption is too high gas a flow. |
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FAQ
1. What causes weld cracks?
Most defects are caused by the following reasons: Improper choice of materials; Improperly placed welds; Crystallization of metal; Abrupt cooling of the welding spot. The following defects occur as a result of the above causes: slag inclusions (a byproduct of flux cored due to high welding speed), seam cracking, undercuts, spatter, porosity, overlap, and craters.
2. What is IP in welding?
For example, the IP rating – short for Ingress Protection – indicates how well the device is protected against dust, moisture, etc. In short, the degree of protection is indicated by letters and numbers.
3. What is the crack defect?
These are all deviations from the specified parameters of weld joints resulting from violations of the requirements for welding materials, preparation, assembly, and welding of the joined elements, heat and mechanical treatment of it, and the overall structure. Defects can also start in case of improper welding technology.
