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GMAW Fundamentals

GMAW Fundamentals. Gas Metal Arc Welding Metal Inert Gas By: Wanda Sue Benton ESAB University & Florence-Darlington Technical College. Introduction. GMAW is defined as arc welding using a continuously fed consumable electrode and a shielding gas.

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GMAW Fundamentals

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  1. GMAW Fundamentals Gas Metal Arc Welding Metal Inert Gas By: Wanda Sue Benton ESAB University & Florence-Darlington Technical College

  2. Introduction • GMAW is defined as arc welding using a continuously fed consumable electrode and a shielding gas. • GMAW is also known as MIG (Metal Inert Gas). • Produces high-quality welds • Yields high productivity

  3. Advantages • Large gaps filled or bridged easily • Welding can be done in all positions • No slag removal required • High welding speeds • High weld quality • Less distortion of work piece

  4. Types of Metal Transfer The basic GMAW process includes three distinctive process techniques: • Short Circuit (Short Arc) • Globular Transfer • Spray Arc Transfer

  5. Short Circuit (Short Arc) • Operates at low voltages and welding current • Small fast-freezing weld puddle obtained • Useful in joining thin materials in any position, as well as thick materials in vertical and overhead positions • Metal transfer occurs when an electrical short circuit is established

  6. Globular Transfer • Welding current and wire speed are increased above maximum for short arc • Droplets of metal have a greater diameter than the wire being used • Spatter present • Welding is most effectively done in the flat position when using globular transfer

  7. Spray Arc Transfer • Occurs when the current and voltage settings are increased higher than that used for Globular Transfer • Used on thick sections of base material, best suited for flat position due to large weld puddle • Spatter is minimal to none

  8. Manual GMAW Equipment • Three major elements are : 1.) Welding torch and accessories 2.) Welding control & Wire feed motor 3.) Power Source • GMAW equipment can be used either manually or automatically

  9. WIRE CONTROL & WIRE FEED MOTOR POWER SOURCE

  10. Welding Torch & Accessories • The welding torch guides the wire and shielding gas to the weld zone. • Brings welding power to the wire also • Major components/parts of the torch are the contact tip, shielding gas nozzle, gas diffuser, and the wire conduit

  11. GAS DIFFUSER NOZZLE TRIGGER CONTACT TIP INSTALLED COMPONENTS

  12. Welding Control & Wire Feed Motor • Welding control & Wire feed motor are combined into one unit • Main function is to pull the wire from the spool and feed it to the arc • Controls wire feed speed and regulates the starting and stopping of wire feed • Wire feed speed controls Amperage

  13. WIRE FEEDER

  14. Power Source • Almost all GMAW is done with reverse polarity also known as DCEP • Positive (+) lead is connected to the torch • Negative (-) lead is connected to the work piece • Provides a relatively consistent voltage to the arc • Arc Voltage is the voltage between the end of the wire and the work piece

  15. POWER SOURCE POSITIVE TERMINAL NEGATIVE TERMINAL

  16. Shielding Gases • Purpose of shielding gas is the protect the weld area from the contaminants in the atmosphere • Gas can be Inert, Reactive, or Mixtures of both • Gas flow rate is between 25-35 CFH • Argon, Helium, and Carbon Dioxide are the main three gases used in GMAW

  17. FLOW METER CFH PRESSURE ADJUSTMENT KNOB CYLCINDER PRESSURE GAUGE

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