|
| Problem |
Possible Cause |
Corrective Measures |
| Poor arc ignition |
Gas not turned on
Gas depleted
Wrong polarity
Poor connection
Control circuit |
Check gas cylinder valve.
Replace cylinder.
Check polarity for DCEP
(Electrode must be +, the work -).
Check ground.
Readjust control circuit.
Replace defective part if necessary. |
| Burn-backs and arc-length fluctuations |
Improper drive rolls
Insufficient drive roll pressure
Excessive drive roll pressure
Wire feed too slow
Contact tube plugged
Arcing in contact tube
Power circuit fluctuations
Wrong polarity
Gun overheating
Conduit liner dirty or worn |
Check for correct size and type.
Increase pressure.
Decrease pressure.
Increase wire feed speed.
Clean, replace contact tube.
Clean, replace contact tube.
Check line voltage.
Check polarity for DCEP (Electrode must be +, the work -).
Replace with higher amp gun (all guns having current ratings above 200 amps should be
water cooled).
Check for water leaks causing gun to overheat. Check for filter on the water inlet
line to prevent clogging and overheating of the gun.
Replace liner. |
| Porosity |
Gas entrapped due to turbulence in weld pool
Gas entrapped due to excessive current
Oil or other contaminants on filler wire
Oily drive rolls
Oily, dirty liner
Wet shielding gas
Water leaks in gun
Oily base metal
Spatter particles ahead of weld pool
Cooling rate of weld too rapid
Drive roll slip
Excessive bending of guide liner |
Adjust parameters.
Reduce current and/or travel speed.
Prevent by storing wire, covered, in clean, dry area.
Do not open wire package until ready for use.
Keep spool on welder covered.
Do not use wire that has been open for any length of time.
If a new spool seems oxidized or dirty, remove two or three outer layers and use remainder
only if it is clean.
Change to clean high quality wire.
Clean rolls with solvent.
Replace with new liner.
Check dewpoint of gas. Reject cylinders above -40°F dewpoint.
Repair guns overheated due to water failure.
Clean plate with solvent and clean with stainless steel wire brush.
Adjust parameters to minimize spatter.
Use higher current and/or slower travel. Consider preheat if seems necessary.
Increase pressure on rolls. Change size and type of rolls if necessary.
Change position of MIG unit to minimize bending of cable. |
| Dirty welds |
Inadequate gas shielding
Dirty filler wire
Dirty base metal |
Hold gas cup closer to work.
Increase gas flow.
Adjust gun angle.
Check gun and cables for air or water leaks.
Shield arc from drafts.
Center contact tube in gas cup.
Replace gas cup if damaged.
(See "Porosity").
(See "Porosity"). |
| Hot short cracking |
Improper filler wire
Faulty joint design
Faulty fixturing
Travel speed too slow
Improper technique |
Check filler metal for compatibility with base
metal.
Check root opening, root face dimensions, included angle.
Reduce the stress level by changing the restraining fixtures for the design of the part
where possible.
Use a higher welding speed.
Change angle of gun to improve deposition. |
| Crater cracks |
Leaving crater open at end of weld |
Quickly reverse direction fo travel and
"seal" the crater, or
Speed rate of travel approaching end of weld, reducing size of weld pool as arc is broken,
or
Use runoff tabs at the end of weld. |
| Incomplete penetration |
Faulty joint design
Welding speed too rapid
Welding current too low
Arc length too long
Improper welding angle |
Check root opening, root face dimensions,
included angle.
Slow travel speed.
Increase welding current.
Shorten arc length.
Change gun angle. |
| Incomplete fusion |
Faulty joint preperation
Arc length too long
Dirty joint |
Check root opening, root face dimensions,
included angle.
Shorten arc length.
Clean chemically and/or mechanically with clean stainless steel wire brush. |
| Welding cables overheating |
Cables too small
Cable connections loose
Cables too long
Inadequate cooling of the in-out water cables |
Check current requirements.
Replace.
Check, tighten.
Check current carrying capacity.
Check water flow rate.
Check for possible leaks. |