WELDING-Wire
M.I.G.(Metal Inert Gas) – Points to Remember
1. Mig (GMAW) welding is often referred to
by the manufacturer’s trade name as Micro-wire,
Aircomatic, Sigma, and Millermatic Welding.
2. Mig welding is faster than stick electrode
welding and is much easier to learn.
3. Spray transfer type of welding is particu-
larly adapted for welding heavy gage metals.
4. Short circuiting transfer welding is best
for welding light gage metals.
5. For optimum efficiency, DCRP current is
required for Mig welding.
6. For Mig welding, a constant potentiaI
power supply with a nearly flat volt-ampere char-
acteristic produces the best results.
7. As a general rule, an air-cooled gun is
satisfactory when welding with amperage
around 200 and a water-cooled gun for welding
heavy metals requiring higher amperages.
8. The use of CO2 as a shielding gas is most
effective and less expensive when welding steel.
9. Argon or a mixture of argon and oxygen
will produce the most effective results in welding
aluminum and stainless steel.
10. The rate of gas flow for welding most
metals is approximately 35 cu ft/hr. However,
this rate may have to be varied somewhat, de-
pending on the type, electrode size, and thick-
ness of metal.
11. The effectiveness of the shielding gas is
often governed by the distance of the gun from
the workpiece. Generally the gas nozzle should
not be spaced more than 2″ from the workpiece.
12. The use of correct diameter wire electrode
is necessary for good welds. Check recommen-
dations for correct electrode diameters.
13. The correct current for welding must often
be determined by trial. Check recommendations
for starting current.
14. Be sure the wire feed is set for the amper-
age which is to be used for welding.
15. For most Mig welding applications, the
wire stick-out should be about 3/8″ to 3/4″.
16. Keep the gun properly positioned to insure
uniform weld with proper penetration.
17. Cold laps will occur if the arc does not
melt the base metal sufficiently.
18. Check the weld for surface porosity. Sur-
face porosity is usually caused by improper gas
shielding.
19. Do not remove the gun from the weld area
until the puddle has solidified, otherwise cracks
may develop.
20. Remember, insufficient or excessive pene-
tration is the result of failure to control heat
input.
