Shielded Metal Arc Welding (SMAW) or Manual Metal Arc Welding (MMA or MMAW) is one of the most versatile forms of welding, and definitely the most widespread. Commonly referred to as Stick welding, the process involves using a flux-covered electrode that is consumed as the weld is laid. It is the only form of welding that produces consistent results outdoors, where the wind and other conditions make TIG and MIG almost impossible.
The arc required for the welding can be produced with both AC and DC. Further, the DC output may be positive or negative, essentially referring to the electrode polarity. DC is more common but AC is the norm for entry-level welders or when welding with thicker electrodes. Working with larger electrodes can cause a phenomenon called ‘arc blow,’ especially at higher currents. Using AC can solve this problem. The type of flux coating also determines the use of AC or DC. For instance, a carbon steel electrode with a low-hydrogen sodium coating needs positive DC, but with a high-titania sodium coating, it needs AC or negative DC.
The arc in SMAW is the result of the current from the MMA welder ‘jumping’ from the consumable electrode to the metal. This generates a temperature that exceeds 3,500C, melting the electrode and forming the weld. The flux coating shields the weld and prevents the oxygen in the air from reacting with the hot metals.
An MMA welder has various settings that determine how strong the weld is. Among other things, it also determines penetration, or how deep the weld is. It is a widely held misconception that deep penetration is better. However, higher penetration without adequate weld width will cause the weld to crack under pressure. As a rule of thumb, higher penetration is best for dirtier metals, while mild penetration is sufficient if the metal is clean. The setting can also be determined by looking at the rod number of the electrode.
MMA welders are not ideal for welding nonferrous metals. With some skill and patience, they can be used to weld metals and alloys of nickel, copper or aluminium, but other processes serve them better. However, MMA excels in construction, maintenance and repair. Its low cost makes it popular among small businesses and amateurs, or even professionals when they start out. MMA welders and supplies can be easily obtained at any welding supply store, whether physical or online. If you plan to upgrade your skills or try something new later, you can also opt for a more expensive, but versatile MMA/TIG or even an MMA/TIG/MIG welder.