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MAG Welding - Principles and Characteristics
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Principles and Characteristics |
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MAG welding is a gas metal arc welding (GMAW) method where an electric arc forms between the consumable welding wire and the work piece, which heats and melts the wire and work piece, welding them together. The welding wire is automatically fed at a constant sped, based on the welder settings.
During welding, shielding gas is supplied from a gas cylinder protect the welding area from atmospheric gases such as nitrogen and oxygen. These gases can cause fusion defects, porosity, and weld metal embrittlement if they come in contact with the electrode, the arc, or the welding metal.
In carbon-dioxide gas-arc welding, a unique, melt-drop-transfer process know as the ‘‘short circuit method’’ is used.
When welding thin panels, problems such as distortion and burn through tend to occur. To prevent such problems, it is necessary to reduce the heat input. The short-circuit method illustrated below keeps the depth of penetration lower for optimum welding of thin panels.
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Transfer of molten droplets in short-circuit welding:
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The end of the welding wire melts due to heat from the arc. This makes a molten droplet that contacts the work piece, creating a short circuit, which briefly extinguishes the arc. As the short circuit occurs, high current passes until surface tension of the weld pool pulls the molten metal bead off electrode tip. The Arc then restarts again and the process repeats itself about 100 times per second.
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Characteristics of MAG Welding:
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The risk of distortion and burn through is reduced, allowing thin plates to be welded. | |
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Simple to learn. Weld quality is not dependent upon the welder’s skill level. | |
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Low molten metal temperature, little fluidity, all position welding is possible with high workability. | |
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Very little formation of welding slag, so there is no need to remove it. | |
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Because shielding gas must remain around welding area, it is unsuitable for welding outdoors or where a strong breeze exists.
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Metal Active Gas welding where the shielding gas used is pure carbon dioxide (CO2), or contains a mixture carbon dioxide (CO2) and other gases. It is considered active because the CO2 undergoes a limited reaction with the molten weld pool. MAG welding reaches a temperature of approximately 2732 °F (1500 °C). | |
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Metal Inert Gas welding where an inert shielding gas such as 100% argon (Ar) is used. Because argon is inert, it does not react with the molten weld pool. | |
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A metal jointing method that bonds the work pieces together using a filler material at a much lower temperature than MAG welding, approximately 1742 °F (950 °C). The base metal remains below a temperature that would weaken UHSS such as 1,500 MPa steel. A pulsed MIG welder, Silicon bronze wire (CuSi-A or CuSi3), and inert 100% Argon (Ar) shielding gas must be used. | | | | |
