GMAW GAS METAL ARC WELDING GMAW A welding

GMAW GAS METAL ARC WELDING

GMAW • A welding process in which metals are joined by heating them with a welding arc between the base metal and a continuous consumable electrode. • Shielding gas or gas mixture is used to prevent the atmosphere from contaminating the weld.

TECHNICAL TERMS • GMAW • FCAW • MIG

GMAW Wire as electrode DC always used DCEP, DCRP is used DCEN, DCSP seldom used • CV is used, current varies • •

FCAW • Similar to GMAW • Only difference is shielding gas is obtained from flux inside the electrode.

Advantages • • • Longer Faster No slag Deeper penetration Less training/ skill

Disadvantages • Costs • Some joints hard to reach • Rapid air movement

Short circuiting transfer • Contacts base metal • Some molten metal is transferred

Globular transfer • Does not touch base metal • Drops of molten metal • Large globs

Spray transfer • Does not touch base metal • Smaller globs • Drops of molten metal on base metal

Pulsed spray transfer • Wire doesn’t neck down • Droplets form at a constant rate

Wire Feeder/ Welding Gun • Used to feed electrode wire to the welding gun • Feed is set on the wire feeder by welder • Make electrical contact with the electrode • Direct the shielding gas to the work piece • Remove heat from gun • Switch to start and stop welding

Finish Review Questions on Page 124 first! • Then turn to page 177 and do the review questions 1 -20