What are defects or faults of welding ?

• Generally located parallel to the junction of weld metal & base metal at the toe or root of the weld
• Reduces the cross-sectional thickness of the base metal
• Acts as stress raiser in fatigue loading

Cause and prevention of undercut:

Cause – 

• High welding current & arc voltage
• Too large electrode dia
• Incorrect electrode angle
• Longer arc length

 Prevention:

• Use prescribed welding current for electrode size.
• Adjust electrode angle to fill undercut area.
• Correct travel speed, arc length, etc.
  

  Lack of penetration –

“Improper penetration of weld metal through the thickness of joint or weld metal not extending to the required depth into the joint root”