SLAG INCLUSIONS/LACK OF FUSION

SLAG INCLUSIONS
CAUSES
• when two adjacent beads are deposited without proper over lap
• multi-pass welding with excessive undercuts in weld toe
• uneven profile of the preceding weld runs
• poor welding technique and type of flux (properties)
• access restrictions in doing a weld and cleaning the flux
• poor convex weld bead profile
PREVENTION
• clean the slag between runs by using circular wire brush (cup brush not allowed)
• use correct welding techniques to produce a smooth bead
• plan your sequence of the deposits with proper over lap
• Use the correct current and travel speed to avoid undercutting.


LACK OF FUSION
CAUSES
• narrow joint preparation
• incorrect welding parameter setting
• poor welding technique
• magnetic arc blow
• insufficient cleaning of oily or scaled surface
• LOF mainly appears in the vertical position
PREVENTION
• ensure the joint preparation is wide enough as per joint geometry
• ensure the correct welding parameters(high current, high speed, short arc length is used
• ensure the correct electrode/torch angle is used for manipulation of the arc in the joint
• Use the correct weaving limits

Seam weld orientation
• -check before make any fit up that the seam weld of the pipe at least 45 degree from the bottom of the pipe specially for field run avoiding the seam to intersect with any support will be install later.
• -check the distance between to seam welds is 2 times the thickness of the thicker member at least