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