MIG (metal inert gas) welding and MAG (metal active gas) welding are two sub types of welding method classified as GMAS (gas metal arc welding). In both there processes a continuous metal wire surrounded by a shielding gas are fed through a welding gun. Of the two processes the first one to be developed was MIG process. This process was costly because of high cost of inert gas and therefor was not used that widely. It was mostly used for welding of non-ferrous metals. Subsequently the MIG process was developed which used semi active gas such as carbon dioxide (CO2). This allowed the process to be used for much wider applications.