ABSTRACT
The use of arc welding depended naturally upon the development of electricity, and dynamos or generators were not developed until 1880. Manual metal arc welding (MMAW or MMA) is used extensively in modern practice. It is based on the principle whereby intense heat is obtained from an electric current which creates an arc between a metal electrode and the plates which are to be welded. The AC welding machine employs a transformer instead of a generator to provide the required welding current. Most modern electrodes are coated or covered and consist of a metal core wire surrounded by a thick coating applied by extrusion or other processes. Vertical welding is done by depositing a weld in an upward or downward direction. The technique of welding stainless steel does not differ greatly from that of welding mild steel, but as the material being handled is very expensive, extra precautions and attention to detail at all stages of welding are desirable.
