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 COâ‚‚ 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.