Miller Electric Millermatic 155 And M-15 Gun Owner's Manual page 23

Possible Causes
Inadequate shielding gas coverage.
Wrong gas.
Dirty welding wire.
Workpiece dirty.
Welding wire extends too far out of
nozzle.
Possible Causes
Workpiece dirty.
Insufficient heat input.
Improper welding technique.
Excessive Penetration
Possible Causes
Excessive heat input.
OM-1314 Page 8
Table 6-2. Porosity
Porosity − small cavities or holes resulting from gas pockets in weld metal.
Check for proper gas flow rate.
Remove spatter from gun nozzle.
Check gas hoses for leaks.
Eliminate drafts near welding arc.
Place nozzle 1/4 to 1/2 in (6-13 mm) from workpiece.
Hold gun near bead at end of weld until molten metal solidifies.
Use welding grade shielding gas; change to different gas.
Use clean, dry welding wire.
Eliminate oil or lubricant on welding wire.
Remove oil, moisture, rust, and paint, etc. from work surface before welding.
Use a more highly deoxidizing welding wire (contact supplier).
Be sure welding wire does not extend more than 1/2 in (13 mm) beyond nozzle.
Table 6-3. Incomplete Fusion
Incomplete Fusion − failure of weld metal to fuse completely with base metal or
a preceeding weld bead.
Remove oil, moisture, rust, and paint, etc. from work surface before welding.
Select higher voltage range and/or adjust wire feed speed.
Place stringer bead in proper location(s) at joint during welding.
Adjust the work angle or widen groove to access bottom during welding.
Momentarily hold arc on groove side walls when using weaving technique.
Keep arc on leading edge of weld puddle.
Use correct gun angle of 0 to 15 degrees.
Table 6-4. Excessive Penetration
Good Penetration
Select lower voltage range and reduce wire feed speed.
Increase and/or maintain steady travel speed.
Corrective Actions
Corrective Actions
Excessive Penetration − weld metal melt-
ing through base metal and hanging un-
derneath weld.
Corrective Actions
S-0635
S-0637