Function of Electrode Coating in Arc Welding
Shielding of molten metal - Electrode coating produces shield gas such as carbon dioxide under heat, which can shield molten metal from atmospheric oxygen, nitrogen and hydrogen. This shielding is necessary to ensure no gas pockets in welding and then avoids contamination of the weld joint.
Stabilization of arc - Some element that can stabilize the arc also added in electrode coating. It helps to arc igniting and give a smooth arc.
Formation of slag and slag control - Slag shields metal from atmospheric air and reduces cooling rate. Slag influence metal droplets made them high viscous. Viscous slag is useful in welding in a vertical position.
Provide deoxidizer - Coating help to reduce oxide impurities by providing deoxidizer like Si, Mn.
Metal Alloying - Special alloying elements such as nickel, vanadium, molybdenum, etc. can be added to weld joint by introducing them through the electrode coating to improve the properties of weld metal.
Concentrating the arc and reduce heat loss - The electrode coating is consumed slower than filler metal, i.e. coating is extended beyond the filler metal. It helps to focus arc and direct the filler metal. It also reduces the thermal loss at the electrode tip; it improves the metal deposition rate.
TIG welding advantages and disadvantages