This document provides information on gas metal arc welding (GMAW), including: - GMAW uses an arc between a continuous filler metal electrode and the weld pool to fuse metals. An inert shielding gas is supplied externally. - It allows welding of various metals in all positions with quality welds and little slag or spatter formation. However, it requires more equipment and is not portable or suitable for windy conditions. - Proper safety equipment like a welding helmet, gloves, and clothing are needed to protect from burns, sparks, radiation, and flying debris.

2.  An arc welding process that uses an arc between a
continuous filler metal electrode and the weld pool to
produce a fusion (melting) together of the base metal
 The process is used with a shielding gas supplied from
an external source without pressure.

3.  Wire Feed
 MIG = Metal Inert Gas
 Inert Gas= Inactive gas that does not combine chemically with base
or filler metal
 MAG= Metal Active Gas
 Active Gas= Gas will combine chemically with base or filler metal

4. Advantages
 Variety of Metals
 All Position Welding
 Quality Welds
 No Slag
 Low Spatter
Disadvantages
 Cost
 Not portable
 Easy to lack of fusion
 Not suitable for
windy conditions
 Only for clean Base
Material

5.  Cover all skin to prevent Radiation burns
 Cover hair to prevent sparks setting hair on fire
 Wear ear plugs to protect from noise and burning
ear drums with sparks
 Use a 14 shade welding helmet to protect eyes
 Wear safety glasses at all times
 Make sure pants pockets are empty

6.  Power Supply
 Direct Current Electrode Positive (DCEP)
 (Electrons flow from – to +)
 Wire Feeder
 Electrical mechanical device that feed required amount
of filler material at a constant rate of speed

7.  Welding filler electrode
 Small diameter consumable electrode that is supplied to
the welding gun by the roller drive system
 Shielding Gas
 Gas used to protect the molten metal from atmospheric
contamination :
 75%Argon (inert gas) & 25% Carbon Dioxide most
common gas used for GMAW

9. A. Hand wheel
B. Flow meter
C. Wire spool
D. Wire
E. Feed roll tension
F. Voltage meter
G. Wire speed meter
H. Wire speed adjustment
I. Voltage adjustment
J. Power switch
K. Gun cable
L. Gun
M. Ground clamp
N. Ground cable
O. Feed rolls
P. Wire guide
Q. Wire overrun
R. Safety nut

11.  Plug ground wire into (Neg) Terminal
 Plug Wire Feeder into (Pos) Terminal
 Select CV-Wire mode
 Hot start is not used
 Set Arc Control to “-5”
 -10= soft arc (for use with inert gases)
 +10= crisp arc (for use with CO2)
(See Next Slide)

12. Min. Arc Control
• Soft Arc
• Thicker Materials
• Deeper Penetration
• More Fluid Weld Pool
• Flatter / Smoother Weld
• Reduce Spatter
• Stainless Steels
Max Arc Control
• Crisp Arc
• Thin Materials
• Arc Stability On Open Gaps
• Convex Weld Bead
• Increased Spatter
• Colder Arc
• Improved Weld Pool Control

13.  Set Volts
 See Chart for proper setting
 Set Wire Speed
 See Chart for proper setting
 Increase wire speed = Increase amps
 Decrease wire speed = Decrease amps
 Set gas flow
 See Chart for proper setting
 Pull trigger to get gas flowing then adjust regulator

14.  Hold tip 1/16” to 1/8” from work piece
 Angle of tip should be 10-15°
 Can push or pull bead
 Pull (preferred)
 More stable arc
 Less Spatter
 Deeper penetration
 Push
 More spatter
 Less penetration
 Good cleaning action

16. Possible Causes Corrective Actions
* Drive Rolls in Poor Condition *Tighten, Clean, or Replace
Drive Rolls
* Excessive Welding Voltage * Reduce Voltage
* Insufficient Electrical Stickout* Increase Contact Tip to Work
Piece Distance
* Contact Tip in Poor Condition * Clean or Replace Contact tip
* Spatter on Contact Tip * Remove Spatter

17. Possible Causes Corrective Actions
* Excessive Amperage *Reduce Amperage
* Improper Travel Angle *Use a Push Angle
*Travel Speed Too Low *Increase Travel Speed
* Insufficient Electrical Stickout *Increase Contact
Tip to Work Distance

18. Possible Causes Corrective Actions
* Insufficient Amperage *Increase Amperage
* Improper Travel Angle * Use Less of a Drag angle
* Excessive Electrical Stickout * Decrease Contact Tip to
Work Piece Distance
* Weld Joint Too Narrow * Increase the Opening of
the Weld Joint

19. GMAW Process Parameters
Steel Material .035” wire Short-Arc Mode
Thickness Gas
75%AR-
25%CO2
Amps Wire
Speed
Volts
1/8” 18-19 140-150 280-300 23-24
3/16” 18-19 160-170 320-340 24-25
1/4” 21-22 180-190 360-380 24-25
5/16” 21-22 200-210 400-420 25-26
3/8” 23-24 220-250 420-520 26-27