MIG Welding



WHAT IS MIG WELDING?



MIG or Metal Arc Welding, is an arc welding process which produces the coalescence of metals by heating them with an arc between a continuously fed filler metal electrode and the work.



This method uses a wire welding electrode on a spool that is fed automatically at a constant pre-selected speed. The arc, created by an electrical current between the base metal and the wire, melts the wire and joins it with the base, producing a high-strength weld with great appearance and little need for cleaning.



The process uses shielding from an externally supplied gas to protect the molten weld pool. The application of GMAW generally requires DC+ (reverse) polarity to the electrode.



BENEFITS OF MIG WELDING



• The ability to join a wide range of material types and thicknesses.



• MIG has higher electrode efficiencies, usually between 93% and 98%, when compared to other welding processes.


• Higher welder efficiencies and operator factor, when compared to other open arc welding processes.



• All-position welding capability.



• A minimum of weld spatter and slag makes weld clean up fast and easy.



• Less welding fumes when compared to Stick Welding and Flux-Cored Arc Welding processes.



CHALLENGES/CONSIDERATIONS OF MIG WELDING



• Requires a shielding gas to function



• Can be sensitive to surface contamination such as rust, paint, mill scale.



• Possibility of weld fusion issues where the material has not been joined together correctly.



MIG Welding

WHICH GAS TO USE?



In simple terms, various metals react differently when melted and are impacted by oxygen and other elements in the air.



Subsequently, a ‘shielding gas’ is required to protect a job from contamination when the material melts and also to maintain the quality of the weld.



There are a number of gas options with MIG welding with the most common being Argon, Helium, Carbon Dioxide and Oxygen.



Argon – The most commonly used inert gas and because of its lower ionization energy, assists with arc starting. Nickel, copper, aluminum, titanium, and magnesium alloyed base materials use 100% argon shielding.



Helium - Commonly added to the gas mix for stainless and aluminum applications. Provides an inert shield and helps prevent contamination in welds. Helium is often used for thicker materials in combination with Argon as it produces deeper penetration and a ‘hotter’ arc.



Carbon Dioxide (CO2) – Widely used in MIG Welding as it is the only ‘reactive’ gas which can be used on its own without adding an ‘inert’ gas such as argon or helium. Pure CO2 provides deep weld penetration which can be beneficial on thick materials but it also produces more spatter.



CO2 if often mixed with Argon to provide a more stable arc, leading to higher quality welds with less spatter.



Oxygen – A reactive gas which is used in small penetrations in combination with Argon to provide good arc stability and excellent weld bead appearance. Used on carbon, stainless steel and low alloy. It should not be used with aluminium, copper or magnesium.



WHAT CAN MIG WELDING BE USED FOR?



MIG Welding is often considered the easiest process to learn and can be used on thin or thicker plate metals.



Generally, MIG Welding is fast, clean and it produces less fumes than other methods of welding.



The process also enjoys widespread use because of its ability to provide high quality welds, for a wide range of ferrous and non-ferrous alloys, at a low price.



Commonly used in automotive repairs, plumbing, construction and general fabrication. Usually the best method for ‘DIY’ and hobbyist-type welding.



WHAT DO YOU NEED TO GET STARTED?



• MIG Welding Machine with MIG Gun, Work Leads, Earth Clamp & Regulator.  



• MIG Wire – available in various sizes for use on different size materials.



• Shielding Gas – Argon or a ‘mixed gas’ where Helium, CO2 or Oxygen is combined with Argon – depending on the materials being welded.



• Safety Equipment – Helmet, Gloves and Jacket.