Miller Bobcat 250 Owner's Manual page 77

13-14. Troubleshooting – Distortion
Possible Causes
Excessive heat input.
13-15. Common MIG Shielding Gases
This is a general chart for common gases and where they are used. Many different combinations (mixtures) of shielding gases have been devel-
oped over the years. The most commonly used shielding gases are listed in the following table.
Short Cir-
Gas
Spray Arc
Steel
Argon
Argon + 1% Flat & Hori-
O zontal Fillet
2
Argon + 2% Flat & Hori-
O zontal Fillet
2
Argon + 5% Flat & Hori-
CO zontal Fillet
2
Argon + Flat & Hori-
10% CO zontal Fillet
2
Argon +
25% CO
2
Argon +
50% CO
2
CO
2
Helium
Argon +
Helium
90% HE +
7-1/2% AR
+ 2-1/2%
CO
2
65% AR +
33% HE +
2% CO
2
* Heavy Thicknesses
Distortion - contraction of weld metal during welding that forces base metal to move.
Illustration: Base metal moves in the direction of the weld bead.
Use restraint (clamp) to hold base metal in position.
Make tack welds along joint before starting welding operation.
Select lower voltage range and/or reduce wire feed speed.
Increase travel speed.
Weld in small segments and allow cooling between welds.
Spray Arc
GMAW-P
cuiting Stainless
Steel
Steel Steel
All
Positions
All Flat & Hori-
Positions zontal Fillet
All Flat & Hori-
Positions zontal Fillet
All
Positions
All All
Positions Positions
All
Positions
All
Positions
All
Positions
Corrective Actions
Application
Short Cir-
GMAW-P
cuiting Spray Arc
Stainless
Stainless Aluminum
Steel
Steel
Positions
Positions*
Positions*
All
Positions
All
Positions
Short Cir-
GMAW-P
cuiting
Aluminum
Aluminum
All All All
Positions Positions
All
All
OM-249336 Page 73