Gas Metal Arc Welding

GMAW

5 Essentials of Arc Welding

• Arc Length• Travel Speed• Electrode Angle• Electrode• Machine Setting

GMAW Machine Settings

• Machine setting depends on thickness of metal.• Voltage (see chart on machine)• Wire speed (see chart on machine)• Shielding gas (100% Carbon Dioxide = 25cfh)– Protects weld area from contamination.– Non-Inert = CO2– Inert = Argon– Gas Drift: Windy conditions move the shielding gas

away from the weld area resulting in a poor weld.

Electrode (wire)

• Type of wire depends on base metal.– Mild steel base metal = mild steel wire.– Various sizes (.023”, .030”, .035”, .045”)– All machines in our shop are set up with .030”

mild steel wire.

Electrode Angle

• Work angle (front to back)– Flat welds = 90– T – Joint = 45

• Travel angle (right to left)– Always 90

Travel Speed

• Resulting weld should be 3/16” – ¼” wide.

Arc Length

• Stickout: Length of wire sticking out from the welding tip. Should be around ¼”.

• Listen carefully to your weld, should have a constant sizzle, no cracking or popping.

Welding Gun

• When you pull the trigger on the welding gun 3 things happen simultaneously:– Shielding gas starts– Wire-feed starts– Arc starts

• Parts: – Nozzle: Directs shielding gas to weld area/– Tip: Directs the wire to weld area.– Distributor: Disperses shielding gas.– Trigger: Starts and stops welding operation.

GMAW Related Terms

• Cold lap: Non-penetrating weld; weld sits on top of or overlaps base metal.– Causes: Improper machine setting, low heat,

improper arc length(stickout).

GMAW Safety Equipment/Tools

• Welding helmet• Safety glasses• Gloves• Long sleeves• Hair tied back• Needle-nose pliers• Wire-brush