This is a group of processes in which heat required for fusion is generated by the electric arc formed between a metallic electrode & the base metal. The electrode is consumed in the arc & provides the filler metal for the joint. The electric arc is an ideal source of welding heat. The extremely high arc temperature of over 50000C permits it to supply a large amount heat to a small area. Hence the melting in the base metal is restricted to a narrow zone. Among the arc processes, manual metal arc is the most common, versatile and inexpensive one and account for 60% of the total welding in advanced countries and over 90% of the total welding in India. It is a manual process, and hence depends on the skill and experience of the welder. It makes use of a flux –coated electrode having a core of solid wire (diameter 6.3-1.6mm, length 450-250mm). It needs a power source, either a transformer supplying AC or generator/ rectifier supplying DC.
AR: Consumable: Gas Metal Arc Welding.
Metal Inert Gas Welding Uses a Consumable bare metal wire as electrode with shielding by Flooding arc with a gas.
1. Wire is fed continuously and automatically from a spool through the welding gun.
2. Shielding gases include argon and helium for aluminum welding, and CO₂ for steel welding.
3. Bare electrode wire (no flux) plus shielding gases eliminate slag on weld bead. No need for manual grinding and cleaning of slag.