1. Gas Metal Arc Welding

2. DEFINITION
Intense heat of an electric arc is used to melt filler material and base metal while a wire electrode is continuously fed into the arc. A shielding gas protects the weld from contamination.

3. Equipment
Direct Current
Constant Voltage Power Source
Wire Feeder w/control system
Electrode wire
Welding gun
Electrical Cable
Shielding Gas

4. Types of Metal Transfer
Short Circuit- molten metal is deposited in repeated short circuits
Globular- molten metal is transferred across arc in large droplets
Spray- molten metal is propelled axially across the arc in small droplets

5. Advantages High Deposition Rates High Utilization of Filler Material
Elimination of Flux/Slag Removal
Reduction of Smoke & Fumes
Can be Automated
Less Skill Required

6. Disadvantages
1. Cost 2. Metal preparation time 3. Unsuitable for outdoor welding 4. Fast cooling rates 5. Unsuitable for thick metals 6. Shielding gas required

8. Internal Diagram of Wire Feed System

9. Tip Distance Diagram

11. Welding Terminology

12. Arc Welding
Type of welding when weld is produced by heating metal with an arc with or without the use of filler material or pressure

13. Electrode
A component of the welding circuit through which current is conducted to the arc, molten, slag or base metal

14. Flux
Material used to prevent, dissolve or remove oxides and other undesirable materials from a weld

15. The metal to be welded, soldered or cut
Base Metal
The metal to be welded, soldered or cut

16. Cavity formed by gas entrapment during solidification
Porosity
Cavity formed by gas entrapment during solidification

17. Splatter
Metal particles expelled during welding that does not form as part of the weld

18. Tack Weld
Weld made to hold part of the weldment in proper alignment until the final welds are made

19. Inert Gas
A gas that goes not normally combine chemically with the base metal or filler metal. Creates a protective atmosphere.

20. Undercut
A groove melted into the base metal adjacent to the toe or root of a weld and left unfilled by weld metal

21. A localized joining of metal produced by heat
Weld
A localized joining of metal produced by heat

22. Filler Metal
The metal to be added in making a welded joint.

23. ER-70S-6 E=Electrode R=Filler Metal Rod 70= Tensile Strength
Reading Electrodes
ER-70S-6
E=Electrode
R=Filler Metal Rod
70= Tensile Strength

24. ER-70S-6
S= Solid Wire
6=Chemical Composition of the Wire

25. Practice Reading Electrodes

26. Weld Anatomy