What is MMA welding? (also called stick welding)
Arc Welding without Shielding Gas
The arc and the weld pool are protected by means of certain minerals that create gases and slag during welding. The most important process is metal arc welding with coated electrodes. The following metal arc welding processes without shielding gas should be mentioned:
- Arc welding with coated electrodes (SMAW)
- Gravity arc welding with coated electrodes
- Arc welding with fluxcored filler wire (FCAW)
- Submerged arc welding (SAW)
Arc welding with coated electrodes
Arc welding with coated electrodes requires an electrode that is made of a core wire of steel and a coating. The arc burns between the end of the coated electrode and the work piece. The steel core melts into the weld pool and provides the necessary filler material. The coating produces shielding gases and slag during the welding which protect the arc and the weld pool, thus making it possible to produce welds unaffected by the harmful atmospheric air. Welding produces welding fumes and fierce light.
Arc welding with a coated electrode is a typical manual arc welding process. The electrode has a limited length that means that the welding process is frequently interrupted and the working time is badly utilised.
The many stops typically mean that the arc is only ignited 25-60% of the working time. Many initiatives have been taken to improve the productivity of MMA welding.
Using wire electrodes that are fed continuously can increase the productivity, but this has caused problems with the coating. However, this problem has been solved by the use of fluxcored wire and by submerged arc welding where the coating is either inside the wire or placed loose on the surface of the weld.
The arc burns between the melting electrode and the workpiece. When the coating is burning/melting it produces shielding gases and slag which protect the weld pool. The slag should be removed after welding of each run. It is often self-releasing.
Arc welding with coated electrodes (SMAW) is primarily used for welding in nonalloyed, low-alloyed and high-alloyed steels in thickness ranges from about 2 mm, for instance welding of steel constructions, vessels under pressure, construction of ships and all other similar construction in one unit production or small serial production. When working on larger serial production it is advantageous to use welding processes that are easier to mechanise.