1. GMAW

2. GMAW
Gas
Metal
Arc
Welding

4. Definitions Gas Metal Arc Welding Also called MIG welding
an arc welding process in which a consumable electrode is fed into a weld joint at a controlled rate while a blanket of inert gas shields the weld zone from contamination by the atmosphere.
Also called MIG welding

5. FCAW flux cored arc welding
a form of GMAW with a cored consumable electrode filled with flux

6. Short circuit transfer (short arc)
a welding application of the GMAW process where low currents, low voltages, and small diameter wires are used to weld on thin to heavy metal in all positions.

7. Spray transfer (spray arc)
a welding process performed in GMAW usually done on thicker metal using larger diameter wires and a shielding gas mixture of Argon with 1-5% oxygen done in the flat and horizontal positions only.

8. Welding current (amperage)
will usually be direct current reverse polarity (DCRP) with the welding wire positive (+) and the work negative. (-)

9. Welding voltage (arc length)
the heat generated by the flow of current through the gap between the end of the wire and the work piece.

10. Slope
the slant of the voltage versus amps curve, generally referred to as voltage change per 100 amps.

11. Slope control
a control of power supply that regulates the amount of pinch of force available on welding wire, thereby controlling spatter or the pinch effect.

12. Inductance
controls the rate of rise of current without controlling the final amount of current available.
In short arc welding, the inductance control will increase or decrease the number or short circuit metal transfers per second, from times per second with an average of 100 times per second, increasing or decreasing the arc on time, thereby making the weld puddle more or less fluid.

13. Stick out
the distance from the contact tip of the gun to the end of the wire electrode.

14. Whiskers
short lengths of welding wire that feed through the root gap of a groove joint and extend out from the root of the weld in all directions.

15. Open circuit voltage
voltage indicated by a voltmeter on GMAW power supply when machine is running but not welding.

16. Arc voltage
voltage indicated on by a voltage meter on GMAW power supply when the machine is welding.

17. Ferrous
any metal containing iron such as mild steel or stainless steel.

18. Non-ferrous
any metal that contains no iron such as aluminum or magnesium.

19. Shielding gases
gases, inert or otherwise, used to displace the air around the arc to prevent contamination by oxygen, nitrogen, or hydrogen from the atmosphere.

20. Advantages of GMAW Arc always visible to the welder
No slag and a minimum spatter
High deposition rate with 90% of the welding wire being deposited in the joint
Weld metal deposit of low hydrogen quality
Wide range of metal thickness can be welded without changing wire

21. excellent for bridging gaps or misaligned joints without burn through
greatly reduced distortion in gage metal
adaptable to weld most any metal by selecting the correct filler wire and shielding gas
adaptive to either automatic or semi-automatic

22. Disadvantages shielding gas susceptible to drafts
high initial equipment cost
limited portability
difficult to use in hard to reach places
operator resistance to radiated heat and arc intensity
lack of fusion with short circuit transfer (cold lapping)
welding equipment is more complex

23. Major Parts Of GMAW Equipment

24. Applications of GMAW process
Short circuiting (short arc)
employs low currents, low voltage and small diameter wires.
most popular of the GMAW processes
Spray arc
uses high current, high voltage and larger diameter wires on thicker metals.
Flux cored wire
designed primarily for welding steel
some self-shielded flux cored and solid wire applications utilize DCSP rather than DCRP.