GMAW / Mig Welding GMAW / Mig Welding

Basic equipment setup and Basic equipment setup and welding procedures welding procedures

Gas Metal Arc Welding Gas Metal Arc Welding

Is a process where a continuously Is a process where a continuously fed metal electrode ( Wire ) fed metal electrode ( Wire ) contacts the base metal and contacts the base metal and produces heat . The arc is shielded produces heat . The arc is shielded by an inert gas by an inert gas

GMAW Components GMAW Components

DC or Direct Current power supply DC or Direct Current power supply Electrode or wire feed controller Electrode or wire feed controller Wire drive roller assembly Wire drive roller assembly Shielding gas source (cylinder) & Shielding gas source (cylinder) &

regulatorregulator Manually held Gun & ground clamps Manually held Gun & ground clamps Wire reel Wire reel

GMAW component GMAW component diagram diagram

Gas Metal Arc Welding Gas Metal Arc Welding Principles Principles

Gas metal arc welding is generally Gas metal arc welding is generally used due to the high efficiency of filler used due to the high efficiency of filler metal that can be deposited per hour. metal that can be deposited per hour.

GMAW is approximately 92% - 98% GMAW is approximately 92% - 98% efficientefficient

GMAW requires a shielding gas GMAW requires a shielding gas

Gas Metal Arc Welding Gas Metal Arc Welding Principles Principles

The GMAW process is performed The GMAW process is performed using DCEP using DCEP ( Direct Current Electrode Positive)( Direct Current Electrode Positive)

Alternating current is never used Alternating current is never used for GMAWfor GMAW

DCEN is used only for a specialized DCEN is used only for a specialized process using emissive electrodes process using emissive electrodes

GMAW AdvantagesGMAW Advantages

• Welding can be done in all positions Welding can be done in all positions • No slag removal requiredNo slag removal required• High efficiencyHigh efficiency• Less work piece distortion Less work piece distortion • Large gaps bridged easily , Good Large gaps bridged easily , Good

for poor fitupfor poor fitup• High Weld Quality High Weld Quality

Typical Setup for voltage Typical Setup for voltage

• The GMAW machine is a “Constant The GMAW machine is a “Constant Voltage” power supply. This is set using Voltage” power supply. This is set using the voltage dial the voltage dial

• This setting can be monitored by the “Volt” This setting can be monitored by the “Volt” meter on the front panel of the weldermeter on the front panel of the welder

• Ideal voltage settings can be found in the Ideal voltage settings can be found in the wire manufactures data book wire manufactures data book

Typical Setup for Wire Typical Setup for Wire speed speed

• The wire feed rate or speed is set using the dial The wire feed rate or speed is set using the dial on the wire controller This setting increases or on the wire controller This setting increases or decreases current or “Heat”. This setting is decreases current or “Heat”. This setting is measured in AMPS or IPM (inches per minute )measured in AMPS or IPM (inches per minute )

• Ideal settings can be monitored by the “Amp” Ideal settings can be monitored by the “Amp” meter on the front panel of the welder. Note : meter on the front panel of the welder. Note : Some machines display “Current” (Same as Some machines display “Current” (Same as AMPS) or IMP AMPS) or IMP

• Ideal settings can be found in the wire Ideal settings can be found in the wire manufactures data book for both IPM and Current manufactures data book for both IPM and Current

Shielding Gas Shielding Gas

• Air in the welding zone is displaced by inert Air in the welding zone is displaced by inert gas to “Shield” the molten weld pool and gas to “Shield” the molten weld pool and prevent it from contamination from prevent it from contamination from Oxygen, Nitrogen and Water present in the Oxygen, Nitrogen and Water present in the atmosphere. atmosphere.

• Insufficient gas flow will not displace the Insufficient gas flow will not displace the atmosphere resulting in “porosity” or voids atmosphere resulting in “porosity” or voids in the deposited weld.in the deposited weld.

• Flow is measured in CFH (Cubic Feet per Flow is measured in CFH (Cubic Feet per Hour).Hour).

Insufficient Shielding Gas Insufficient Shielding Gas coverage coverage

• Gas not turned on Gas not turned on • Flow rate not properly adjustedFlow rate not properly adjusted• Leaks in the hose supplying the Leaks in the hose supplying the

shielding gas to the machineshielding gas to the machine• GMAW / MIG Gun loose at wire GMAW / MIG Gun loose at wire

drive connection drive connection • Spatter buildup on gas cupSpatter buildup on gas cup• Windy environment Windy environment

Excessive Gas coverage Excessive Gas coverage

• Will cause porosity.Will cause porosity.• The turbulence caused by the rapid The turbulence caused by the rapid

flow of shielding gas exiting from the flow of shielding gas exiting from the gas cup will draw the surrounding gas cup will draw the surrounding atmosphere into the stream of gas.atmosphere into the stream of gas.

• It will reduce weld pool temperatures It will reduce weld pool temperatures causing decreased penetration . causing decreased penetration .

Check the Manufactures data Check the Manufactures data for settings for settings