Shielded Metal Arc Welding Process
- Shielded Metal Arc Welding Process is also called Flux shielded metal arc welding.
- It is an arc welding process where coalescence is produced by heating the work piece with an electric arc set up between the flux coated electrode and the work piece.
- Due to arc heat, the flux covering decomposes and performs functions of arc stability, weld metal protection, etc.
- The electrode itself melts and supplies the necessary filler metal.
Principle of Shielded Metal Arc Welding Process:
- Required heat for welding is obtained from the arc struck between the coated electrode and the work piece.
- By employing higher or lower currents, the arc temperatures and thus arc heat can be increased or decreased.
- Generally, the arc temperature is about 2400 “C to 2600 ‘C.
- A high current with a smaller arc length produces very intense heat.
- The arc melts the electrode and the work piece.
- Material droplets are transferred from the electrode to work piece through the arc and are deposited along the welded joint.
- The coaling of flux melts and produces a gaseous shield and slag to prevent atmospheric contamination of the molten weld metal.
- Figure shows the working of flux shielded metal arc welding.
Advantages of Shielded Metal Arc Welding Process
- It is the simplest of all arc welding processes.
- The equipment is portable and less expensive.
- Various metals and their alloys can be welded.
- Welding can be done in any position with high weld quality.
Limitations of Shielded Metal Arc Welding Process
- Due to limited length of electrode and brittle flux coating on it, mechanisation is difficult.
- It is a slow process.
- Because of flux coated electrodes, the chances of slag entrapment and other related defects are more.
- Welding control in this process is difficult.
Applications of Shielded Metal Arc Welding Process
- Used for all commonly used metals and their alloys.
- It is used as a fabrication process and for maintenance and repairs.
- Also used in,
Air receiver, boiler and pressure vessel fabrications
Automotive and aircraft industry
Ship building and bridge construction.