Lack of union between the weld metal and the parent
metal or between the successive layers of weld metal
LACK
OF SIDEWALL FUSION
Lack of union between the weld and parent metal at
one or both sides of the weld
Causes
Low heat input to weld
Molten metal flooding ahead of arc
Oxide or scale on weld preparation
Excessive inductances in MAG dip transfer welding
Prevention
Increase arc voltage and/or welding current;
decrease travel speed
Improve electrode angle and work position; increase
travel speed
Improve edge preparation procedure
Reduce inductance, even if this increases spatter
Comments
During welding sufficient heat must be available at
the edge of the weld pool to produce fusion with the parent metal.
LACK
OF INTER RUN FUSION
A lack of union along the fusion line, between the
weld beads
Causes
Low arc current resulting in low fluidity of weld
pool
Too high a travel speed
Inaccurate bead placement
Prevention
Increase current
Reduce travel speed
Retrain welder
Comments
Lack of inter-run fusion produces crevices between
the weld beads and causes local entrapment of slag.
LACK
OF ROOT FUSION
Lack of fusion between the weld and parent metal at
the root of a weld
Causes
Low heat input Excessive inductance in MAG dip
transfer welding,
MMA electrode too large (low current density)
Use of vertical down welding
Large root face
Small root gap
Incorrect angle or incorrect electrode manipulation
Excessive misalignment at root
Prevention
Increase welding current and/or arc voltage;
decrease travel speed
Use correct induction setting for the parent metal
thickness
Reduce electrode size
Switch to vertical up procedure
Reduce root face
Ensure correct root opening
Use correct electrode angle. Ensure welder is fully
qualified and competent
Ensure correct alignment
LACK
OF PENETRATION
Incomplete
Penetration
The difference between actual and nominal
penetration
Causes
Excessively thick root face, insufficient root gap
or failure to cut back to sound metal in a ‘back gouging’ operation
Low heat input
Excessive inductance in MAG dip transfer welding,
pool flooding ahead of arc
MMA electrode too large (low current density)
Use of vertical down welding
Prevention
Improve back gouging technique and ensure the edge
preparation is as per approved WPS
Increase welding current and/or arc voltage;
decrease travel speed
Improve electrical settings and possibly switch to
spray arc transfer
Reduce electrode size
Switch to vertical up procedure
Comments
If the weld joint is not of a critical nature, i.e.
the required strength is low and the area is not prone to fatigue cracking, it
is possible to produce a partial penetration weld. In this case incomplete root
penetration is considered part of this structure and is not an imperfection
(this would normally be determined by the design or code requirement).
Incomplete
Root Penetration
One or both fusion faces of the root are not melted.
When examined from the root side, you can clearly see one or both of the root
edges unmelted.
Causes
and prevention
Same as for lack of root fusion
Comments
Post a Comment