Idiomas disponibles
Idiomas disponibles
Welding technique
4.1 MIG (GMAW/FCAW) basic welding technique
Two different welding processes are covered in this sec- tion (GMAW and FCAW), with the
intention of providing the very basic concepts in using the MIG mode of welding, where a
MIG Gun is hand held, and the electrode (welding wire) is fed into a weld puddle, and the
arc is shielded by an inert welding grade shielding gas or inert welding grade shielding gas
mixture.
GAS METAL ARC WELDING (GMAW): This process, also known as MIG welding, Co welding,
Micro Wire Welding, short arc welding, dip transfer welding, wire welding etc., is an electric
arc welding process which fuses together the parts to be welded by heating them with an arc
between a solid continuous, consumable electrode and the work.
Shielding is obtained from an externally supplied welding grade shielding gas or welding
grade shielding gas mix- ture. The process is normally applied semi automatically; however
the process may be operated automatically and can be machine operated. The process can
be used to weld thin and fairly thick steels, and some non-ferrous metals in all positions.
FLUX CORED ARC WELDING (FCAW): This is an electric arc welding process which fuses
together the parts to be welded by heating them with an arc between a continu- ous flux filled
electrode wire and the work. Shielding is obtained through decomposition of the flux within
the tubular wire. Additional shielding may or may not be ob- tained from an externally supplied
gas or gas mixture. The process is normally applied semi automatically; however the process
may be applied automatically or by machine. It is commonly used to weld large diameter
electrodes in the flat and horizontal position and small electrode diameters in all positions.
The process is used to a lesser degree for welding stainless steel and for overlay work.
Position of MIG Gun
The angle of MIG Gun to the weld has an effect on the width of the weld.
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MIG SERIES EQUIPMENT
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MIG SERIES EQUIPMENT
The MIG Gun should be held at an angle to the weld joint. (See Secondary Adjustment
Variables below)
Hold the MIG Gun so that the welding seam is viewed at all times. Always wear the welding
helmet with proper filter lenses and use the proper safety equipment.
WARNING
Do NOT pull the MIG Gun back when the arc is established. This will create excessive wire
ex- tension (stick-out) and make a very poor weld.
The electrode wire is not energized until the MIG Gun trigger switch is depressed. The wire
may therefore be placed on the seam or joint prior to lowering the helmet.
Distance from the MIG Gun Nozzle to the Work Piece
The electrode wire stick out from the MIG Gun nozzle should be between 10 - 20 mm (3/8" - 3/4").
This distance may vary depending on the type of joint that is being welded.
Travel Speed
The speed at which the molten pool travels influences the width of the weld and penetration
of the welding run.
Establishing the Arc and Making Weld Beads
Before attempting to weld on a finished piece of work, it is recommended that practice welds
be made on a sample metal of the same material as that of the finished piece.
The easiest welding procedure for the beginner to experiment with MIG welding is the flat
position. The equipment is capable of flat, vertical and overhead positions.
For practicing MIG welding, secure some pieces of 1.6 mm or 5.0 mm (1/16" or 3/16") mild
steel plate 150 mm x 150 mm (6" x 6"). Use 0.9 mm (.035") flux cored gasless wire or a solid
wire with shielding gas.
Distance from the MIG Gun Nozzle to the Work Piece
The electrode wire stick out from the MIG Gun nozzle should be between 10 - 20 mm (3/8" - 3/4").
This distance may vary depending on the type of joint that is being welded.
Travel Speed
The speed at which the molten pool travels influences the width of the weld and penetration
of the welding run.
Welding technique
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