1. Gas Metal Arc Welding (GMAW)

2. GMAW Gas Metal Arc Welding MIG ( Metal Inert Gas )
MAG (Metal Active Gas)
Wire Welding

3. Proper Attire

4. What is GMAW? Gas Metal Arc Welding MIG - MAG Welding
MIG = Metal Inert Gas
MAG= Metal Active Gas
Solid Wire with External Shielding Gas
DCEP (DC+) Polarity 2

5. LIMITATIONS: ADVANTAGES: All Position Welding Quality Welds
Little to No Slag
Low Spatter
Variety of Metals
Various Material Thickness
High Efficiency
High Radiated Heat
LIMITATIONS:
Cost
Portability
Outdoor Welding
Clean Base Material
Potential for Cold Lap
Potential for Undercut
High Radiated Heat

6. Identify Major Components
Power Source, Wire Feeder, Shielding Gas, Electrode Wire, Gun

7. Power Source
Converts Primary ( Outside ) Power To Secondary ( Useable ) Power
DCEP Direct Current Electrode Positive / Reverse Polarity
DCEP = Lower spatter levels, Deeper Penetration levels

8. Wire Feeder Delivers Wire To The Weld Pool At A Very Constant Speed
Wire Feeder starts gas flow, current, wire feed
Wire Speed Is Measured In Inches Per Minute

9. Shielding Gas
To Shields The Weld Pool Form Contaminants That are In The Atmosphere
Stabilize The Arc
Helps Regulate Penetration
Argon 75% - CO2 25% (C-25)
75-25 is used in the Lab
Show Flow meter over the ELMO

10. Mig GUN Trigger Liner Contact Tip Diffuser Nozzle
Show parts over the ELMO

11. Electrode WIRE ER70S-6 ER = ELETRODE ROD 70,000 TENSILE STRENGTH
S = SOLID WIRE
6 = CHEMICAL COMPOSITION
Wire Diameter Range (.025” ”)
Copper coated vs. non-coated wire

12. Starting the Arc

13. Electrode Stick Out - ESO
Sheet ESO = 3/8 - 1/2 inch
Plate ESO = ¾ - 1 inch

14. Bead Initiation

15. Bead Manipulation

16. Travel Angle

17. Bead Termination

18. Modes of Metal Transfer
1. Short Circuiting (Short Arc)
2. Globular
3. Spray
The welding machine automatically selects mode of transfer dependent upon settings & variables.
Type/mix of shielding gas
Electrode diameter
Voltage
ESO 5

19. Short Circuiting Droplet Forms Droplet Shorted Metal Transfers
Fuse Forms
Arc Re-established
Low Cost
Deep Penetration
Less Spatter
More Fluid Weld Pool 9

20. Globular
Arc Initiated
Large Droplet Forms
Projected into weld pool 17

21. Globular Advantages Deep Penetration High Deposition Low Cost Gas
Limitations
Excessive Spatter
Flat / Horizontal Position Only 16

22. Spray Arc Initiated Point Forms on End of Electrode Wire
Numerous tiny Drops Form the Weld Pool
100% Argon 21

23. Spray Advantages Limitations Smooth Weld Bead Potential Undercut
Deep Penetration
High Deposition
Little to No Spatter
Limitations
Potential Undercut
Higher Shielding Gas Cost
Flat / Horizontal Position Only
High Radiated Heat 20

24. GMAW Process Parameters
Steel Material ” wire Short-Arc Mode
Thickness
Gas 75%AR-25%CO2
Amps
Wire
Speed
Volts
1/8”
18-19
23-24
3/16”
24-25
1/4”
21-22
5/16”
25-26
3/8”
26-27

25. Determining IPM without readout
Cut shielding gas
Pull trigger & count to 6
Measure length of wire
Multiply x 10

26. Wire Burnback Wire welds itself to the tip
Possible Causes Corrective Actions
* Drive Rolls in Poor Condition *Tighten, Clean, or Replace 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

27. Burnthrough Hole burns through base metal
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 Distance

28. Repairing Burn through
Turn voltage slightly down
Extend ESO to ¾”
Small tack welds in a “star pattern”
Allow metals to cool sufficiently

29. Incomplete Penetration
Toes should tie into metal
1/8 bead height max
Possible Causes Corrective Actions
* Insufficient Amperage *Increase Amperage
* Improper Travel Angle * Use Less of a Drag angle
* Excessive Electrical Stickout * Decrease Distance
* Weld Joint Too Narrow * Increase joint opening

30. Lincoln V350 Setup - GMAW Plug ground wire into (-) Terminal
Plug Wire Feeder into (+) 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)