welding defect

Welding Defects – Types, Causes and Remedies

What is Welding Defects – Types, Causes and Remedies?

Welding Defect is the result of ineligible welding that has been written in standard (ASME IX, AWS, API, ASTM). All conditions are not in accordance with standards or code, we call it defect. the welding defects san be caused by several thing, e.g. incorrect welding procedures, poor preparation, equipment and consumables that are not compliant to WPS.

Based on defect location, welding defect can be divided into 2 types, namely internal welding defects (inside the weld results) and surface welding defects (can be seen with the eyes). If we want to know the defect of internal welding, we need a test equipment such as Ultrasonic Test and Radiography Test (Non destructive test), or bending test and microstructure check (destructive test). For surface defect, we can use Penetrant Test, Magnetic Test or magnifying glass.

undercut welding defect
undercut

1.Undercut

Undercut is a welding defect located on the surface or root, this defect form is like an overdraft that occurs in base metal or parent metal. This type of welding defect can occur in all welding joints, be it fillets, butts, rags, corner and edge joints.

Causes of Undercut:

  • The welding current used is too large
  • Travel speed is too high
  • The length of the welding arc is too high
  • Electrode position is not right
  • The swing of the hand is less even, the swing time at the side is too fast.

How to prevent Undercut:

  • Adjusting the welding current. You can see the recommended ampere in the electrode wrap or WPS (Welding Procedure Specification).
  • reduce welding speed
  • The length of the bow is shortened or as high as 1.5 x the diameter of the electrode.
  • Tilt angle 70-80 degrees (adjust position).
  • Practice swinging more often to suit your abilities.
porosity welding defect
porosity

2. Porosity

Porosity is a welding defect in the form of a small hole in the weld metal, can be on the surface or inside. This porosity has several types namely Cluster Porosity, Blow Hole and Gas Pore.

Causes of Porosity :

  • The electrodes used are still moist or exposed to water
  • The weld bow is too long.
  • The welding current is too low.
  • Travel Speed is too high.
  • The presence of dirty substances in the work object (rust, oil, water etc.)
  • Hydrogen gas is created due to welding heat.

How to Overcome Porosity:

  • Make sure the electrodes used are well prepared (baked if required), do not let the electrode be exposed to water or damp.
  • Set the arc height approximately 1.5 x the diameter of the electrode.
  • Ampere is adapted to the procedures or recommendations of the electrode manufacturer.
  • Correct welding preparation, ensuring there are no dirt in the workspace.
  • For certain materials, the heat should not be too high, so it is necessary to treat the heat.
slag inclusion welding defect
slag inclusion

3. Slag Inclusion.

Slag Inclusion is a defect that occurs in the area in the weld results. This defect is in the form of slag (melting flux) in the weld, which often occurs in the stop and run area (the beginning and stop of the welding process). To see this defect, we need to do radiography or bending testing.

Causes of Slag Inclusion :

  • The process of cleaning Slag is lacking, so it is stacked by welds.
  • Ampere is too low.
  • The weld bow is too far away.
  • Wrong welding angle.
  • The corner is too small.

How to Prevent Slag Inclusion :

  • Make sure the weld is properly cleaned before welding again.
  • Ampere is adapted to the procedure.
  • Adjustable welding arc.
  • The welding angle should be appropriate.

4. Tungsten Inclusion.

Tungsten Inclusion welding defect is a welding defect caused by the melting of tungsten during the welding process that melts into weld metal. This defect is almost the same as slag inclusion but when  we conduct a radiography test, tungsten inclusion will has very bright color (because the weight of the type is greater than the welding metal). This defect only occur in the GTAW welding process or TIG welding.

Causes of Tungsten Inclusion:

  • Tungsten is already blunt during the welding process.
  • The tungsten distance is too close.
  • Ampere is too high.

How to Overcome Tungsten Inclusion:

  • Tungsten should be tapered before use for welding.
  • The distance must be adjusted.
  • Follows the range of ampere in the WPS.
incomplete penetration welding defect
incomplete penetration

5. Incomplete Penetration.

Incomplete Penetration (IP) is a welding defect that occurs in the root area or the root of the weld. A welding is said to be IP if the welding on the root area is not translucent or reinforcement on the root of the weld is concave.

Causes of Incomplete Penetration :

  • Travel speed is too high.
  • The gap or root opening distance is too wide.
  • The distance of the electrode or welding arc is too high.
  • Wrong electrode angle.
  • Ampere is too small.

How to prevent incomplete penetration defects:

  • Travel speed is adapted to WPS.
  • Standard gap or root opening 2-4 mm.
  • Standard electrode distance is 1.5 x electrode diameter.
  • Adjust the ampere according to Welding Procedure Specification.

6. Incomplete Fusion (Lack Of Fusion).

Causes of Incomplete Fusion Defects:

  • Angle position of welding electrode is wrong.
  • Ampere is too low.
  • The corner is too small.
  • There is dirt in welding surface.
  • Travel Speed is too high.

How to Overcome Incomplete Fusion Defects:

  • Correcting The Position of Electrode Angles.
  • Raise the Ampere according to WPS
  • The angle of the welding surface corresponds to that in WPS.
  • Carry out the correct welding preparations, clean up all the dirt
  • Set up the appropriate Travel Speed.

7. Over Spatter.

Spatter is a splash of welding. in fact if the spatter can be cleaned then it does not include defects. However, if the number is excessive and cannot be cleaned then it is categorized in visual defects.

Causes of Spatter or excess welding splashes:

  • Ampere is too high.
  • The electrode distance with the metal base is too far.
  • Moist electrodes.

How to prevent the occurrence of welding defects Over Spatter:

  • The current is lowered according to the recommendations
  • Arc length ( 1.5 x electrode diameter).
  • The electrodes are well prepared ( baked ) according to the handbook (especially the low hydrogen electrode).

8. Hot Crack.

Hot Crack is a crack in welding where the crack occurs after the welding process is complete or during the welding metal compaction process.

Causes of Hot Crack:

  • Wrong electrode selection.
  • No heat treatment.

How to Prevent Hot Crack:

  • Using electrodes that correspond to WPS or Low Hydrogen type that have high strain properties.
  • Performing heat treatment (PWHT and Preheat)

9. Cold Cracking

Cold Cracking is a crack that occurs in the weld area after the welding process is complete (takes some time, it can be 1 hour, or 1 day) . Usually to check the crack, welding inspector use penetrant test or Magnetic Test.

Causes of Cold Cracking or Cold Cracking:

  • Cold Cracking in Welding Materials.
  • Cooling Rate is too fast.
  • The welding current is too low.
  • Travel speed is too high.
  • No preheat

How to prevent the occurrence of Cold Cracking:

  • Slow down cooling after welding process.
  • Heat received is adjusted to WPS.
  • Use recommended flows.
  • Travel speed welding is not too fast (see existing WPS).
  • Preheat

10. Distortion.

The definition of distortion in welding is a change in the shape of the material caused by excessive heat during the welding process. This distortion occurs during the cooling process, due to the presence of excessive heat, the material can undergo shrinkage or development so that it will pull and make the material curved.

Causes of distortion:

  • Excessive heat.
  • Ampere is too high.
  • Take weld is less powerful.
  • Incorrect welding preparation.

How to prevent weld distortion:

  • Adjust the current (ampere) according to WPS
  • Tack weld or give a stopper (amplifier on the parent metal).
  • Doing the correct welding preparation.

11. Arc Strike.

Arc Strike is a welding defect caused by the sticking of the tip of welding electrode to the area of welding metal or base metal briefly. usually this is not intentional by the welder. Arc Strike welding defects are very dangerous for the strength of the metal, because it can reduce the value of toughness and strength of the welding metal.

12. Underfill.

Defects that occur on the surface. the filling weld is still less so that the surface of the base metal is higher than the area of weld. To overcome, repeat welding process again in the area or flattened all welding areas.

13. Lack Of Inter Run Fusion.

Welding that does not fusion between layers or weld metal passes. this defect occurs can be due to too low current, incorrect electrode angle and too fast welding.

14. Misalignment (hi-lo) or Linear Misalignment

The height between the plates is different or uneven. This is due to incorrect welding preparations. To overcome it the material is cut and re-prepared correctly, if not allowed then the weld area is grinded until exhausted and the plate is reset.

15. Excessive Root Penetration.

Welding results in the root area of welding is too high, the maximum height of the welding root is 2 mm and the minimum is flat or 0. The cause can be because the gap is too wide, the welding current is too high and the root face is too thin.

16. Overlap.

Overlap can occur on the surface and roots of the weld. The cause of overlap is due to incorrect welding movement that is too wide.

for your reference, you can download weld inspection check list :

AWS Weld_Inspection_Checklist

source: https://app.aws.org/files/199/622219/Weld_Inspection_Checklist.pdf

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