WELDING TYPES EXPLAINED
Welding joins metals together with heat. Both brazing and soldering are also used to join metal materials, but they do not apply high enough temperatures to provide both fusion and a structurally-strong joint, which is why those methods are unsuitable for effective structural mild-steel repairs. Methods that fuse the metals together (including MIG/MAG, TIG and MMA, or ‘stick’ welding) are more structurallysound, but most types require a joining filler material.
Manual Metal Arc (MMA) or ‘stick’ welding is more suited to heavy-duty repairs and, as such, tends to be too aggressive for the thin steel sheets that form a typical monocoque car body, although the method can be considered for separate chassis repairs, where the metal is much thicker. The user feeds the metal-cored stick into the work area manually, which requires both patience and experience to achieve a result that is strong and neat.
While Tungsten Inert Gas (TIG) welding is more common when working with metal alloys, it can be used for steel repairs. It consists of a negativelycharged (although the polarity can be reversed) tungsten-tipped torch, which helps to create the metal arc. As the tungsten electrode is not consumed, the user needs to feed a jointing material rod with the other hand, while pure Argon gas is used to shield the weld and surrounding area. TIG welding is a slow process but can produce very neat results.
Due to it being more cost effective and notably easier to use, Metal Inert Gas (MIG), or Metal Active Gas (MAG), welding tends to be the preferred method for the DIY car repairer. A MIG welder’s biggest enemy is the atmosphere, which can oxidise the hot metals and create a very weak joint. To remedy this, an inert-based shielding gas is blown over the weld and repair area to keep natural air away from the molten metal. As with TIG, MIG welding requires argon gas, but a small percentage of carbon dioxide is added (the British Oxygen Company’s trade name for this is Argoshield), which allows for superior fusion, while the argon provides a calm atmosphere and less spatter. It may still be possible to obtain pure carbon dioxide gas, used by publicans to pressurise their bar drinks dispensers (hence the term ‘pub gas’), but using CO2 alone produces a fierce arc and a greater chance of metal particles, or spatter, exiting the work area.