In this method, the heat is generated by an electric current passing between the consumable electrode (filler metal) and the work piece through a molten slag covering the weld surface.
The gap between the two work pieces is filled with a welding flux. It is initiated by an arc between the electrode and the work piece.
Heat generated by the arc melts the fluxing powder and forms molten slag.
The slag having low electric conductivity is maintained in liquid state due to heat produced by the electric current.
The slag reaches a temperature of about 3500°F. This temperature is adequate for melting the consumable electrode and work piece edges.
The weld pool is contained within this space and due to contact with the copper blocks it cools, solidifies, and is shaped.
Metal droplets fall to the weld pool and join the work pieces.
Circumferential seams will be welded by the electro-slag process. By using special devices to overcome the difficulty of joining the start and finish of a weld.
The bead on the reverse side will be moulded by a water-cooled copper chill ring, a permanent steel ring, or a travelling shoe. Pieces of variable cross sections can be electro slag welded using consumable electrode guides.
An A.C. or D.C. power source in the range 300-800 amps is appropriate as used for automatic and MMA processes.
This welding is capable of welding plates with thicknesses ranging from 50 mm to more than 900 mm and welding is done in one pass.
The current required is about 600 A at 40 to 50 Volts although higher currents are used for thick plates.
The travel speed of the weld is in the range from 12 to 36 mm/min.
ADVANTAGES :
High deposition rate
Low slag consumption
Low distortion
Unlimited thickness of work piece.
DISADVANTAGES :
Coarse grain structure of the weld
Low toughness of the weld
Only vertical position is possible.
APPLICATIONS :
Used for heavy machinery, bridges, ships and nuclear reactor vessels.
Comments