Home / Welding / Welding Defects Causes and Remedies

Welding Defects Causes and Remedies

Welding is a permanent fastener and uses in many manufacturing processes. During welding, a welder faces many welding defects. These welding defects weaken the strength of the weld and also affect the beauty of joints. In addition to residual stresses and distortion in the final assembly, some of the other welding defects can occur in welding joints. Following is a brief description of each welding defects.

Welding Defects Types
Welding Defects

Cracks:

Cracks are fracture-type interruptions. It can be present either in the weld itself or in the base metal adjacent to the weld or inside of the weld material. This is the most serious and unwanted welding defect because it significantly reduces weld strength. Welding cracks are caused by embrittlement or low ductility of the weld and/or base metal combined with high restraint during contraction. Generally, this defect must be repaired.

Causes of cracks:

  • Too small welds
  • Rigid Joints
  • Base metal Poor ductility
  • Improper Penetration
  • When during welding of ferrous metals, Using of hydrogen as a shielding gas
  • Residual stress caused by the solidification shrinkage
  • Base metal contamination
  • Low current with High welding speed
  • No, preheat before starting welding
  • Improper/ Fast cooling of weld metals
  • Poor joint design
  • sulfur and carbon contents high in the metal

Remedies of cracks:

  • Preheat the metal as required
  • Provide proper cooling of the weld area.
  • Use design that has not rigid joints, Use proper joint design
  • Remove Contamination and impurities
  • Use appropriate metal
  • Ensure good fusion
  • Make sure to weld a sufficient sectional area (Large weld between heavy plates)
  • Avoid stringer beads for heavy welds
  • Use proper welding speed and amperage current
  • To prevent crater cracks make sure that the crater is properly filled.

Porosity/ Cavities:

These include various porosity and shrinkage vacuum/ cavities. Porosity consists of small cavities or holes in the weld metal formed by gases entrapped during solidification. The shapes of the cavities vary between spherical (blowholes) to elongated (wormholes). Porosity usually results from the inclusion of atmospheric gases, sulfur in the weld metal, or contaminants on the surfaces. Shrinkage voids are cavities formed by shrinkage during solidification. Both of these cavity-type defects are similar to defects found in castings and emphasize the close kinship between casting and welding. In short trapped gas or small bubbles in the welding zone creates a cavity in welds which weakens the joint.

Causes of Porosity:

  • Arc traveling speed faster
  • Usage of a long arc
  • Moisture presence (moisture in electrode coating)
  • Improper electrode
  • Excessive/ Insufficient current (Too high and too low current)
  • During solidification of the weld joint, entrapment of gases
  • Dirty or unclean weld surface that includes rusting, paint, grease, oil, and presence of other scale impurities

Remedies of Porosity:

  • Sufficient selection of filler materials and electrodes
  • Use dry electrodes and filler materials
  • Improves welding techniques (preheating the weld area or rate of heat input increases)
  • Use proper welding speed to allow gases to escape
  • Cleaning the weld surface and ensure prevention of contaminations from entering the welding zone

Slag or Solid inclusions:

These are nonmetallic solid materials trapped inside the weld metal. Flux is the most common form of slag inclusions generated during arc-welding processes. Instead of floating to the top of the weld pool, bubbles of slag become encased during solidification of the metal. Another form of inclusion is metallic oxides that form during the welding of metals such as aluminum, which normally has a surface coating of Al2O3.

Causes of Slag Inclusion:

  • Too low or too high arc current
  • Large electrode diameter
  • Long arc
  • Insufficient chipping and cleaning in multi-pass welding
  • The too-small angle of joint

Remedies Slag Inclusion:

  • Use medium arc length
  • Clean the weld surface with the help of wire brush before the next layer deposition
  • Use sufficient shielding gases
  • Provide sufficient space for manipulation of the puddle of molten weld metals
  • Use recommended current with moderate weld speed

Incomplete fusion:

Incomplete fusion is also known as a lack of fusion. It is simply a weld bead in which fusion has not occurred throughout the entire cross-section of the joint. In other words, it is a lack of fusion between the base metal and weld metal. A related defect is a lack of penetration which means that fusion has not penetrated deeply enough into the root of the joint.

Causes of incomplete fusion:

  • Welding Current too low, Low heat input, Improper weaving
  • Surface contamination
  • Electrode angle is incorrect
  • Incorrect electrode size, The electrode diameter is incorrect for the material thickness you’re welding
  • Too fast Travel speed
  • The weld pool is too large and it runs ahead of the arc

Remedies incomplete fusion:

  • Use a sufficiently high welding current with the appropriate arc voltage (Increase current with weld plate thickness)
  • Before welding, clean the metal
  • Avoid molten pool from flooding the arc
  • Use correct electrode diameter and angle
  • Reduce deposition rate
  • Weave sufficient to melt sides

Undercut/ Imperfect shape:

The weld should have a certain desired profile for maximum strength. This welding imperfection is the groove formation at the weld toe, reducing the cross-sectional thickness of the base metal. The result is a weakened weld and workpiece. The weld profile maximizes the strength of the welded joint and avoids incomplete fusion and lack of penetration.

Causes of undercut:

  • Too high weld current
  • Too fast weld speed
  • The use of an incorrect angle, which will direct more heat to free edges
  • The electrode is too large
  • Incorrect usage of gas shielding
  • Incorrect filler metal
  • Poor weld technique

Remedies of undercut:

  • Reduce the arc length
  • Avoid the excessive heating of base metal
  • Reduce the electrode’s travel speed, but it also shouldn’t be too slow
  • Choose shielding gas with the correct composition for the material type
  • Use of proper electrode angle, with more heat directed towards thicker components
  • Use of correct welding current, reducing  the current when approaching thinner areas and free edges
  • Choose a correct welding technique that doesn’t involve excessive weaving
  • Use the multi-pass technique
  • Ensure proper arc length

Spatter:

During different welding processes, we observed some metal drops found around the welded joints surface. These metal drops around the weld are called spatter. This category includes arc strikes, in which the welder accidentally allows the electrode to touch the base metal next to the joint, leaving a scar on the surface; and excessive spatter, in which drops of molten weld metal splash onto the surface of the base parts. Mostly spatter occurs in gas metal arc welding. Some of the main causes and remedies of spatter listed below.

Causes of spatter:

  • High welding current (running ampere too high)
  • Longer arc, more chances of spatter
  • Contaminated surface
  • Electrode angle too steep
  • Incorrect polarity
  • Improper gas shielding

Remedies of spatter:

  • Reduce the arc length
  • Adjust or reduce the welding current
  • Use proper polarity according to the welding conditions
  • Suitable gas shielding
  • Electrode angle increased

Overlapping:

This welding defect occurs in welding face toe. Weld metal put over the surface of base metal because weld metal does not melt with base metal sufficiently. In this condition the weld metal rolls and forms an angle less than 90 degrees.

Causes of overlapping:

  • Welding current high
  • Improper size of the electrode
  • Poor welding technique

Remedies of overlapping:

  • Use the correct or proper welding current
  • Select the proper electrodes
  • Correct manipulation speed and proper welding technique also minimizes the overlapping

Incomplete penetration:

Incomplete penetration is another important welding defect. It occurs in the grooves where grooves not filled with metal. Incomplete penetration weakens the weld joint and decreases the life of weld.

Causes incomplete penetration:

  • Too much space between the welded metals
  • Quickly moving of bead also the main reason for incomplete penetration (Poor welding technique)
  • Misalignment of welded plates
  • Poor/ improper joint design
  • Electrode size not suitable (improper size of the electrode)

Remedies incomplete penetration:

  • Reduce or use proper arc travel speed
  • Proper use of welding techniques
  • Ensure alignment of welded parts
  • Usage of the proper size of the electrode
  • Joint design geometry properly design

Welding defects mostly occurs due to inexperienced or unskilled welder. Skilled welder with proper use of welding techniques reduces the different welding defects.

About ahmed

Check Also

Weldability of metals

What is Weldability|Factor Affecting Weldability

Weldability also is known as joinability. Weldability is the capacity of metal or combination of …

Leave a Reply

Your email address will not be published. Required fields are marked *