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Shielded Metal Arc Welding: An Introduction. Shielded Metal Arc Welding Defined:.
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Shielded Metal Arc Welding Defined: • The Shielded Metal Arc Welding process is a consumable welding process where an arc is generated between the grounded work-piece and the electrode. Heat from the arc melts the electrode and the metal being welded allowing them to be joined into a solid piece. The molten weld puddle is protected from the atmosphere by a “gaseous envelope” that is created when the electrode coating is vaporized by the heat of the arc.
SMAW Equipment Requirements: • Constant current power source (AC, DC or AC/DC). • Welding cables with electrode holder and ground clamp. • Electrodes
Advantages of the SMAW Process: • Cheapest common arc welding equipment to purchase. • Used to weld ferrous and non-ferrous metal. • All position welding. • Ideally suited for outdoor work. • Highly portable. • Consumables and equipment readily available.
Disadvantages of the SMAW Process • Low productivity, especially when compared to the GMAW process. • High amount of electrode loss. • Dirtiest of the common arc welding processes. • Requires much post weld clean-up. • Can be difficult to master.
SMAW Variables: In order to create consistent, quality welds using the SMAW process, the operator must know and control the following welding variables: • Welder polarity setting. (based on electrode type and material thickness). • Initial amperage setting (based on electrode size and type).
SMAW Variables: • Electrode angle: 10 to 20 degrees in the trailing or drag direction. • Arc length: One electrode diameter • Travel speed: Finished beads should be three electrode diameter in width. • Electrode manipulation (if needed)
Troubleshooting Quality Issues in SMAW Welds: • Excessive weld bead width; reduce amperage setting and/or increase travel speed. • Excessive weld bead convexity (convex-too much curve); increase amperage setting. • Lack of weld puddle control; reduce amperage setting and/or reduce arc length. • Lack of bead width: increase amperage setting and/or reduce travel speed.