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What is a Shielded Metal Arc Welding?
Shielded Metal Arc Welding (SMAW in short) is a welding process in which the welding heat is produced by an electric arc formed between the work surface and a solid, consumable, covered electrode. During the welding process, the decomposition of the electrode covering forms a shield of gas and slag around the molten metal on the work surface. The electrode also provides filler metal to the weld pool. See picture above.
Shielded Metal Arc Welding Welding applications.
Shielded Metal Arc Welding enjoys widespread use on farms and ranches, in auto repair facilities and home and equipments workshops and in other areas where maintenance and repair work is required. It is still a widely used process in pipelining and structural steel construction.
SMAW can be used to weld carbon steel, low alloy steel, high strength steel, cast iron, malleable iron, bronze, nickel, stainless steel and aluminium in all thickness. The SMAW process is also used for hardsurfacing.
SMAW Advantages
- Equipment is self contained, portable and relatively inexpensive.
- Electrode provides its own flux.
- Most metals and alloys can be welded with SMAW.
- Useful process for welding in confined spaces.
- Performs better on unclean surfaces than other welding processes.
- Most metal thickness can be welded with SMAW.
- All welding positions are possible with SMAW.
- Can be used under almost all weather conditions.
- Arc is continuously visible to the welder.
- Welder controls the arc.
SMAW Disadvantages
- Not recommended for welding metals less than 1/16″ thick.
- Excessive spatter.
- Slag cleanup is required.
- Produces weld beads with rough surfaces.
- Welds are subjected to porosity.
- Arc blow must be controlled.
- Frequent stop and starts are required to replace electrodes, resulting in a lower electrode deposition rate than the GMAW (MIG) and FCAW wire-feed welding processes.
- Greater possibility of weld defects as a result of frequent stops and starts.
- Some electrode waste (about 10% from discarded stub loss).
- Potential electric shock from open circuit voltage.
- Ventilation must be provided when welding in confined spaces. The SMAW process produces large amounts of fumes and smoke.
Shielded Metal Arc Welding Equipments.
A typical metal arc welding system is shown figure below. Its principal components are (1) the welding machine (Power source) (2) The covered electrode (3) The electrode holder (4) the welding circuit cables. Additional equipments may include shielding walls and light shields; jig, fixtures and positioners for securing the work; and a ventilation system when working indoors.
SMAW
SMAW Electrodes are critical in the selection process during welding. Please refer to other post on the selection of electrodes.
