Gas Metal Arc Welding (GMAW)

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

Proper Attire

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

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

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

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

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

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

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

Electrode WIRE ER70S-6 ER = ELETRODE ROD 70,000 TENSILE STRENGTH S = SOLID WIRE 6 = CHEMICAL COMPOSITION Wire Diameter Range (.025” - .125”) Copper coated vs. non-coated wire

Starting the Arc

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

Bead Initiation

Bead Manipulation

Travel Angle

Bead Termination

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

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

Globular Arc Initiated Large Droplet Forms Projected into weld pool 17

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

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

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

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” 160-170 320-340 24-25 1/4” 21-22 180-190 360-380 5/16” 200-210 400-420 25-26 3/8” 220-250 420-520 26-27

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

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

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

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

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

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)