WELD DEFECTS, CAUSES AND CURE

I. SMAW PROCESS

1. Weld Spatter
   

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   Causes:
   

   1. Current too high.
      
   2. Wrong Polarity.
      
   3. Arc length too long.
      
   4. Presence of arc blow.
      
   5. Wet electrodes
      

   
    

       Cure:
   

   1. Try lowering the current. Be sure the current is within the range for the type and diameter of the electrode.
      
   2. Be sure the polarity is correct for the electrode type.
      
   3. Try a shorter arc length.
      
   4. If the molten metal is running in front of the arc, change the electrode angle.
      
   5. Look for arc blow conditions, and control it as follows;
      
      1. Change to AC welding.
         
      2. Use lower current and smaller electrodes.
         
      3. Try reducing the arc length.
         
      4. Weld in the direction of the blow.
         

 

 

 

1. Change the electrical path to work by:
   
   1. Shifting the work connection to the other end of the work or making connections in several locations.
      
   2. Welding toward heavy tacks, finished welds, or back-stepping on long welds.
      
   3. Using run-out tabs, adding steel blocks to change work current path, or tacking small plates across the seam at weld ends.
      

1. Be sure the electrode is not wet.
   

   
    

   
    

   
    

   
    

 

1. Underfill
   

   Sketch:
   

   
    

   
    

   
    

   Cause:
   

   1. Improper welding technique.
      

   
    

   Cure:
   

   1. Ensure that the fill passes are enough prior to the deposition of cap pass.
      

   
    

2. Overlap
   

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   Cause:
   

   1. Current too low.
      
   2. Improper preparation of the joint.
      

   
    

   Cure:
   

   1. Use higher current.
      

 

 

1. Undercut
   

   Sketch:
   

   
    

   
    

   
    

   Causes:
   

   1. Current too high.
      
   2. Improper welding technique.
      

   
    

   Cure:
   

   1. Reduce current, travel speed, or electrode diameter until you have a puddle size you can handle.
      
   2. Change electrode angle so the arc force holds the metal in the corners. Use a uniform travel speed and avoid excessive weaving.
      
2. Porosity
   

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1. Cluster Porosity
   

 

Causes:

1. Unstable or poor shielding.
   
2. Improper initiation or termination of weld.
   

 

Cure:

1. Keep the arc length as close as possible.
   
2. For the initiation of the arc, use the backstepping method to re-melt the cold start area and float the gas out of the bead. Whenever possible, use tab plates on each end of the joint.
   

 

1. Piping/Wormhole Porosity
   

 

Causes:

1. Presence of foreign materials contaminating the weld metal i.e. moisture, rust, paint,oil, etc.
   
2. Poor or unstable shielding i.e. poor moisture and wind protection, too long arc length, unstable electrode manipulation.
   
3. Electrode
   

Cure:

Cure:

1. Remove scale, rust, paint, moisture or dirt from the joint.
   
2. For the initiation of the arc, use the back-stepping method to re-melt the cold start area and float the gas out of the bead. Whenever possible, use tab plates on each end of the joint.
   
3. Keep the puddle molten for a longer time. This allows the gases to boil out before it freezes.
   
4. The steel may have a low carbon or manganese content or a high sulfur (free machining steel) or phosphorous content. Weld these steels with a low hydrogen electrode. Minimize admixture of base metal into weld metal by using low currents and fast travel speeds for less penetration.
   
5. Try using a shorter arc length. A light drag technique is recommended for low hydrogen electrodes.
   

 

 

1. Slag Inclusion
   

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   Causes:
   

   1. Poor interpass cleaning.
      
   2. Current too low.
      
   3. Unstable electrode manipulation
      
   4. Groove angle too narrow.
      
   5. Weld bead too convex.
      

 

Cure:

1. Observe proper interpass cleaning.
   
2. Increase the current.
   
3. Correct the too convex bead by grinding.
   

 

1. Incomplete Fusion
   

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   Causes:
   

   1. Welding speed too high.
      
   2. Groove angle too narrow.
      
   3. Too irregular beads.
      

   
    

   Cure:
   

   1. Increase the current and decrease the welding speed.
      
   2. Observe proper joint preparation.
      
   3. Correct the irregular bead by grinding.
      

   
    

   
    

2. Burn-Through
   

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   Causes:
   

   1. Too wide root gap, and too short root face.
      

   
    

   Cure:
   

   1. Correct the joint preparation.
      
   2. Decrease the current, and increase the welding speed.
      

   
    

3. Internal Concavity
   

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   Cause:
   

   1. Higher current.
      
   2. Arc length too long.
      
   3. Root gap too wide, groove angle too narrow.
      

   
    

   Cure:
   

   1. Decrease the current.
      
   2. Put the electrode deeper to the groove.
      
   3. Correct the joint preparation.
      

   
    

   
    

4. Incomplete Root Penetration
   

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   Causes:
   

   1. Current too low.
      
   2. Arc length too long.
      
   3. Improper joint preparation i.e. root face too long, root gap too narrow, groove angle too narrow.
      

   
    

   Cure:
   

   1. Increase the current.
      
   2. Put the electrode deeper to the groove.
      
   3. Correct the joint preparation.
      

 

 

 

1. Cracking
   

   Sketch:
   

 

 

 

1. Cold Cracks (Toe/Underbead Cracks)
   

   
    

   Causes:
   

   1. Rapid cooling from the welding temperature of a relatively high carbon or alloy content steel.
      
   2. Hydrogen pick-up during welding.
      
   3. The joint is so restrained.
      

   
    

   Cure:
   

   1. Use low hydrogen welding electrodes.
      
      1. Observe proper handling of electrodes, and cleanliness of the joint for welding.
         
   2. Preheat the joint to reduce the cooling rate. Use high preheats for heavier plate and rigid joints.
      
   3. Reduce penetration by using low currents, small electrodes. This reduces the amount of alloy added to the weld from melted base metal.
      

   
    

2. Hot Cracks (Crater/Throat/Root Cracks)
   

   
    

   Causes:
   

   1. Wrong welding technique.
      

   
    

   Cure:
   

   1. To control crater cracking, fill each crater before breaking the arc.
      
   2. On multiple pass or fillet welds, be sure the first bead is of sufficient size and of flat or convex shape to resist cracking until the later beads can be added for support. To increase bead size, use slower travel speed, a short arc, or weld
      5^O uphill. Always continue welding while the plate is hot.
      
   3. For rigid joints, whenever possible, weld towards the unrestrained end. Leave at least 1/32" gap between plates for free shrinkage as the weld cools.
      

 

 

II. GTAW PROCESS

1. Incomplete Fusion
   

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   Cause:
   

   1. Insufficient application of heat to all faces of the joint.
      

   
    

   Cure:
   

   1. Use higher current and decrease the travel speed.
      

      
       

      
       

2. Tungsten Inclusion
   

   Sketch:
   

   
   

   
    

   
    

   
    

   
    

   
    

   
    

   
    

   Cause:
   

   1. Accidental touching of the tungsten electrode to the weld puddle.
      

 

Cure:

1. Avoid contact of the tungsten electrode with the molten weld puddle.
   

 

1. Porosity
   

   Sketch:
   

   
   

   
    

   
    

   
    

   
    

   
    

   
    

   
    

   
    

   Cause:
   

   1. Impurities on the surface or within the base metal.
      
   2. Inadequate shielding gas.
      

   
    

   Cure:
   

   1. Cleaning of the joint prior to welding.
      
   2. Increase the shielding gas flow rate as required.
      
   3. Check the shielding gas hose and connections for possible leaks.
      

   
    

2. Cracks
   

   Sketch:
   

   1. Hot Cracks (Longitudinal/Crater Cracks)
      

      Cause:
      

      1. High travel speed.
         
      2. Improper control of the welding current.
         

      
       

      Cure:
      

      1. Observe proper travel speed.
         
      2. Trail the bead up to the bevel of the groove to leave no crater.
         

      
       

   2. Cold Cracks
      

           Cause:
   

   1. Water leaks into the shielding gas.
      

   
    

           Cure:
   

   1. Check the gas hose and connections for leaks
      
   2. Verify the purity of the shielding gas and change with the higher grade when necessary.
      

 

 

 

 

 

 

ACCEPTABLE GROOVE WELD PROFILES IN BUTT JOINTS

 

 

 

 

 

 

(a) Butt Joint - Equal Thickness

 

 

 

 

(b) Butt Joint (Transition) – Unequal Thickness

 

Note: Reinforcement R shall not exceed 1/8" (3mm)

 

UNACCEPTABLE GROOVE WELD PROFILES IN BUTT JOINTS

 

 

 

 

 

 

 

 

 

 

 

DESIRABLE FILLET WELD PROFILES