The advantages of MIG welding are:
• Increased deposition rate (Weight of weld deposited per hour).
• Increased operating factor (The time that the welder actually is welding).
Basic principles of MIG Welding
The process can roughly be divided into two distinctive methods depending on the wire being fed. GMAW – Gas metal arc welding and FCAW – Flux cored arc welding.
GMAW – Gas metal arc welding
Gas metal arc welding uses a solid wire. Depending on shielding gas the process can further be divided
In MIG welding we use inert gases like Argon. Pure inert gas shielding is essential for welding alloys of aluminium, magnesium, copper, titanium, stainless steel, nickel alloys and highly alloyed steel. Gas mixtures of inert gases and reactive gases (Argon + CO2) are regarded as MIG welding. Metal transfer with the GMAW process is by one of two methods:
Spray Arc or Short Circuiting Arc
The spray-Arc is recognized by a relatively intense arc between the welding wire and the
To obtain a spray-arc it is necessary to have welding current above a
certain minimum value, the transition current. This current level depends on the shielding gas, (consisting of minimum 80% Argon or Helium), the alloy and the size of the welding wire. As a guideline a 0.8 mm solid steel wire will provide a spray arc if the welding current is above approximately 150 Ampere. At currents below this level the steady
Short Arc is also called short circuit transfer. No metal is transferred through the arc with this
This sequence repeats itself continuously approximately 100 times per second, providing a concentrated arc with low heat input to the