Shielded Metal Arc Welding (SMAW)
It is ‘the Arc Welding Process’ known to even a layman and can be considered a ‘roadside welding process’ in india. When invented in 1880’s it used bare electrodes, however the subsequent developments led to the use of coated electrodes. This process is also known as stick electrode welding or coated electrode welding or manual metal arc welding. It uses coated electrodes of 2.5 to 6.35 mm diameter and 300-450 mm length held in an electrode holder. The power source used is of the constant current type and both ac and dc supplies can be employed with equal ease and effectiveness in most of the cases.
In arc welding machine when an arc is struck between an electrode and the work piece, the electrode core wire and its coating melt, the latter provides a gas shield to protect the molten weld pool and the tip of the electrode from the ill effects of the atmospheric gases. The temperature in the core of the arc ranges between 6000-70000C. The radiations originating from the welding arc can damage the eyes thus necessitating the use of a protective shield.
In all types of welding machines, arc welding machine process is very versatile and is used for welding in all positions and all metals for which electrodes have been developed. The coated electrodes are presently available for welding low carbon steels, low alloy steels, quenched and tempered (Q&T) steels, high alloy steels, corrosion resistance steels and stainless steel as well as for cast iron and malleable iron. It is also used for welding nickel and nickel alloys and to a lesser extent for welding copper and copper alloys. It finds a limited use in welding aluminium alloys. Typical applications of the process include its extensive use by the industry for fabrication of ships, bridges, pressure vessels and structurals. However, as the process can be used in its manual mode only. It is slowly getting replaced by other welding processes for heavy fabrication where large quantity of metal need be deposited.