Chapter # 4                                                                                       PROCESSES

4.2.4   Methods

          The welding method adopted in the manufacture of Busbar Systems is product-specific.  The industry has matured and there is near unanimity on the method to be adopted for a specific metal, based on its application and desired performance.

4.2.4.1   Shielded Metal Arc Welding (SMAW) Or Manual Metal Arc (MMA)

          This is the most common method of welding.  It is economical and the process is simple.  A flux-coated electrode is connected to a phase winding of the welding transformer and the plates/sections to be welded together with the ground terminal of the welding transformer are connected to an earth electrode.  When in contact, an arc is created in the gap, generating a high temperature that melts the electrode and the metal, resulting in a weld.  This process does not require a shielding gas.

4.2.4.2   Gas Metal Arc Welding (GMAW)

          This type of welding was perfected in the 1960s. Metal inert gas welding uses a gun that is continuously fed with a consumable electrode. The process uses an external gas to shield the welded metal from environmental factors like Oxygen, making it continuous and quick. This method produces less welding fumes, has high electrode efficiency, and requires less heat input. However, the equipment is costly and requires an external shielding gas.  Tungsten inert gas welding uses a Tungsten electrode and an external filler rod which is a consumable. 

4.2.4.3   Flux Cored Arc Welding (FCAW)

          This was developed as an alternative to shield welding as it does not require an external shield.  The process comprises a tubular electrode containing the flux, that is continuously fed on the earthed object.  The flux has ingredients that generate gaseous and liquid slag for weld protection.  If required, external shielding gas may be introduced for additional protection.  It is ideally suited for site-welding, due to its speed.

4.2.4.4   Electric Resistance Welding (ERW)

The resistance welding method is a thermos-electric process where heat is generated at the interface of the parts to be joined by passing an electrical current through them for a precisely controlled time and pressure.  Spot welding and seam welding are carried out by this process.  This process is effective for thin sheets.  Steel is a good metal for ERW on a readily available conventional spot and seam welding equipment.  However, because of higher electrical conductivity, Copper and Aluminium will require a much greater power source to produce acceptable spot and seam weld.

Continued..........