There are several different options when it comes to choosing a process for the fusion of metals. Arc welding is one of these options where an electrode is manually or mechanically guided along the joint.
- Arc welding is one of several fusion processes for joining metals.
- By applying intense heat, metal at the joint between two parts is melted and caused to intermix - directly, or more commonly, with an intermediate molten filler metal.
- Since the joining is an intermixture of metals, the final weldment potentially has the same strength properties as the metal of the parts.
- Basic Welding Circuit: An arc is created across the gap when the energized circuit and the electrode tip touches the workpiece and is withdrawn, yet still with in close contact. The arc produces a temperature of about 6500ºF at the tip.
- Arc Shielding: Metals at high temperatures tend to react chemically with elements in the air - oxygen and nitrogen. When metal in the molten pool comes into contact with air, oxides and nitrides form which destroy the strength and toughness of the weld joint.
- Therefore, many arc-welding processes provide some means of covering the arc and the molten pool with a protective shield of gas, vapor, or slag. This is called arc shielding. T
- Nature of the Arc: An arc is an electric current flowing between two electrodes through an ionized column of gas. A negatively charged cathode and a positively charged anode create the intense heat of the welding arc.
- The choice of current and polarity depends on the process, the type of electrode, the arc atmosphere, and the metal being welded.
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Arc welding may be done with direct current (DC) with the electrode either positive or negative or alternating current (AC). The choice of current and polarity depends on the process, the type of electrode, the arc atmosphere, and the metal being welded.
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