As a versatile and simple process, MMA welding has become established in many steel processing sectors. Due to its minimal equipment requirements, the process speaks for itself thanks to the fact that it is highly portable, especially on building sites. That wind-sensitive shielding gas is not required, is a further point in its favour. Despite its low-cost applicability, high-quality results can be achieved. Innovations in power source technology mean a stable arc, even in unfavourable conditions or when the mains cable is long.
Basic system principle
As with MIG/MAG welding, so too in MMA welding the electrode fulfils a dual function of arc carrier and consumable filler material. In MMA welding, the electrode is referred to as filler rod or rod electrode. The heat from the arc melts the core wire of the filler rod and the base metal. At the same time, the filler rod casing acts as bell jar and layer of slag to protect the heated workpiece surface from chemical reactions with the surrounding air. This maintains the strength and durability of the weld metal. The filler rod is connected to one pole on the power source via the welding cable and electrode holder. The earth connection runs via the workpiece terminal and earthing cable to the other pole on the power source. The pole that represents the welding potential depends on the type of rod electrode being used. Rutile electrodes are mostly welded at the power source?s negative pole, whereas basic electrodes are mainly used at the positive pole. Under certain conditions, rutile electrodes are also suitable for alternate current welding with simple welding transformers and no current rectifier. Other characteristics of basic electrodes include easy weldability, even weld seam and spray transfer. In addition to large drop transfer, basic electrodes on the other appear to incorporate moisture, thereby causing pores in the weld metal in its undried state. Advantages include weldability in several positions and good mechanical properties of the weld. A further type of electrode is the cellulose electrode. In addition to spray transfer, cellulose electrodes have a very deep fusion penetration, good mechanical strength, and are suited to all welding positions, including vertical down seam. Disadvantages include difficult weldability and the generation of a substantial amount of smoke. Furthermore, these electrodes are not suitable for all types of power source.