GAS METAL ARC WELDING (GMAW)

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GAS METAL ARC WELDING (GMAW)
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What is GMAW

• 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.

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Also Known AS

• 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

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• Advantages
• Variety of Metals
• All Position Welding
• Quality Welds
• Little to No Slag
• Low Spatter

• Disadvantages
• Cost
• Portability
• Outdoor Welding
• Clean Base Material

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GMAW Safety

• 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

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GMAW Equipment

• 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

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GMAW Equipment (Cont)

• 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
• 75Argon (inert gas) 25 Carbon Dioxide most
  common gas used for GMAW

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Principles of the GMAW Process
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GMAW Set UP

• 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)

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• 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

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GMAW Set Up (Cont)

• 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

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Running a Bead

• 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

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Bead Formation
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Wire Burnback

• 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

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Burnthrough

• 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

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Incomplete Penetration

• 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

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