Most common welding defects
Defects are common in any form of production, including welding. During the process, defects can occur in the shape and size of the metal structure. This can be caused by using the wrong welding process or welding technique. Below are the most common welding defects, their causes and solutions.
Incomplete penetration occurs when the groove of the metal is not completely filled, meaning that the weld metal does not fully protrude through the thickness of the weld seam.
- Misalignment
- Improper joint
- Large electrode diameter
- There was too much space between the metal you are welding together
- You move the welding bead too fast, so not enough metal enters the weld
- You use a too low amperage setting, so the current is not strong enough to melt the metal properly
- Use proper joint geometry
- Check for proper alignment
- Select the correct welding current
- Use an appropriately sized electrode
- Reduce the movement speed of the arc
This type of weld defect occurs when there is no proper fusion between the base metal and the weld metal. It can also occur between adjacent weld beads. This creates a gap in the weld that is not filled with molten metal.
- Low heat supply
- Surface contamination
- The advance speed is too high
- The electrode angle is incorrect
- The weld pool is too large and it runs ahead of the arc
- The electrode diameter is incorrect for the material thickness you are welding
- Reduce the deposition rate
- Clean the metal before you start welding
- Prevent the weld pool from flooding the arc
- Use the correct electrode diameter and angle
- Use a sufficiently high welding current with the correct arc voltage
The most serious form of weld failure is a weld crack and is almost unaccepted by all standards in the industry. It can appear on the surface, in the weld metal or in the area affected by intense heat. There are different types of cracks, depending on the temperature at which they appear.
These can occur during the welding process or during the crystallization process of the welded joint. The temperature at this point can exceed 10,000°C.
These cracks occur after the weld has been completed and the temperature of the metal has dropped. They can form hours or even days after welding. This usually occurs when welding steel. The cause of this defect is usually deformations in the structure of the steel.
These form at the end of the welding process before the operator has finished welding the weld. They usually occur at the end of the weld. When the weld pool cools and solidifies, it must have sufficient volume to overcome the shrinkage of the weld metal. Otherwise, it will form a crater crack.
- Poor joint design
- No preheating before welding
- Contamination of the base metal
- High welding speed but low current
- Use of hydrogen when welding ferrous metals
- High sulfur and carbon content in the metal
- Residual stress caused by solidification shrinkage
- Remove impurities
- Use suitable metal
- Use good weld design
- Preheat the metal as required
- Use proper welding speed and amperage
- Ensure proper cooling of the welding area
- Ensure adequate cross-sectional area is welded
- Avoid crater cracks by properly filling the crater
Porosity results from contamination of the weld metal. The trapped gases create a bubble-filled weld that becomes weak and may fail over time.
- Improper gas mask
- Use of a longer arc
- Contaminated surface
- The presence of moisture
- Use of excessive gas flow
- Improper surface treatment
- Presence of rust, paint, grease or oil
- Insufficient deoxidation of the electrode
- Use proper electrodes
- Use proper welding technique
- Use the correct arc distance
- Use dry electrodes and materials
- Clean materials before starting welding
- Reduce arc movement speed to allow gases to escape
- Check the gas flow meter and make sure it is optimized as required with proper settings for pressure and current
This weld imperfection is the groove formation at the weld, which reduces the cross-sectional thickness of the base metal. The result is a weakened weld and workpiece.
- Wrong filler material
- Poor welding technique
- Welding current too high
- The electrode is too large
- Improper use of gas shielding
- Welding speed that is too high
- Using the wrong angle, leading more heat to the free edges
- Reduce the arc length
- Use proper electrode angle
- Using the multipass technique
- Reduce the electrode travel speed, but it should not be too slow either
- Use the proper electrode angle, with more heat focused on thicker parts
- Choosing a proper welding technique that does not involve excessive weaving
- Choose shielding gas with the correct composition for the material to be welded
- Use proper current, reducing current when approaching thinner areas and free edges
Slag inclusion is one of the welding defects that are usually easily visible in the weld. Slag is a glassy material produced as a subproduct of stick welding, arc welding with flux and arc welding under powder cover. It can form when flux, the solid protective material used in welding, melts in the weld or on the surface of the weld zone.
- Wrong weld angle
- Improper cleaning
- Welding speed too high
- Welding current too low
- The weld pool cools down too quickly
- The weld is not cleaned before starting a new weld
- Reduce rapid cooling
- Increase current density
- Adjust the welding speed
- Adjust the electrode angle
- Remove slag from previous weld bead
In welding, the goal is to make welds that meet requirements, not to make perfect welds. Some interruptions are allowed in compliant welds, but too many interruptions will result in a defective weld. Be sure to pay attention to all variables to reduce inconsistencies and the risk of a defective weld.
Reference.. welding.org.au