The weldelectrode which is used in electric arc welding as a conductor carry the
current to the work and produce the heat for the welding process.
This is worked as a filler metal not only conductor in the electric arc welding.
The metal of the electrode used basically same properties or chemically composition
of parent. During welding the nitrogen and oxygen is reacted with metal produce some
impurity. These impurities causes weaken the welding joint. Due to this reason the
electrode used in electric arc welding often coated around with a type of substance.
The coating materials are contain of flux, inert gas and slag producing substances.
substance prevents the oxides, nitrides formation when electrodes are melts in welding
process. The oxides and nitrides which already formed in the weld that also removed.
This is helping for anti-oxidation formation in welding cooling period by the slag
deposition on the joint.
Reason for coating
By the following reasons the electrodes are coated-
To produce a flux to prevent oxidation and to dissolve oxides if already formed.
To protect the molten metal from the action of oxygen and nitrogen presence in the
air by the produce of inert gas, which is surrounded in the weld portion. (The inert
gas is purely chemically non effected).
To make the arc stabilize.
By the producing of slag deposition the oxide can not formed during cooling period.
This control the rate of melting and amount of penetration.
Paper pulp, cotton etc. used for gas producing agent.
Silicates, manganese etc. used for slag production.
Fluxing materials or de-oxides materials like Silicon, Aluminium and manganese.
Types of current used in different core dia electrode:
Some electrodes work well on either AC or DC. If DC is needed then it indicated that
polarity change. Here are current ranges for the different size electrodes for different
positions and various thickness of materials.