Shielded Metal-arc Welding (SMAW)

Shielded Metal-arc Welding (SMAW) is the simplest and is used for many joining processes. More than 50% of industrial and maintenance welding is currently performed by this process. In this welding operation, an electric arc is generated by touching the tip of a coated electrode against the workpiece and withdrawing it quickly to a distance sufficient to maintain the arc, as shown in the picture below.

Schematic illustration of the shielded metal-arc welding process

The electrodes are in the shape of thin, long rods held manually. The heat generated melts some electrode tips, coating, and base metal in the immediate arc area. The molten metal consists of a mixture of the base metal, the electrode metal, and substances from the coating on the electrode; this mixture forms the weld when it solidifies. The electrode coating de-oxidizes the weld area and provides a shielding gas to protect it from oxygen in the surroundings. A bare section at the end of the electrode is clamped to one power source terminal, while the other terminal is connected to the workpiece being welded. The current may be either DC or AC, usually 50 to 300 A.

DC is suitable for sheet-metal welding because of the steady arc it produces. The power requirement is generally less than 10 kW.

weld shield metal arc beads

The shield Metal-arc welding process has the advantages of being relatively simple and requiring fewer electrodes. The equipment includes a power supply, cables, and an electrode holder. The shield metal-arc welding process is commonly used in general construction, shipbuilding, pipelines, and other maintenance work. It is used primarily for work in remote areas where a portable fuel-powered generator can be used as the power supply. Shield metal-arc welding is best suited for workpieces with thicknesses of 3 to 19 mm, although skilled operators can extend this range using multiple-pass techniques, as shown in the picture. The multiple-pass approach requires that the slag is removed after each weld bead. Unless removed entirely, the solidified slag can cause severe corrosion of the weld area and lead to failure of the weld, but it also prevents the fusion of welded layers. Before applying another weld, the slag should be obliterated using wire brushing or weld chipping.