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MIG Welding

MIG Welding. Wire speed (Top Knob) Voltage (Middle Knob) Trigger, Over Temperature, and On/Off Switch Wire speed (amperage) controls weld penetration Voltage controls height and width of weld bead Low voltage: wire stubs into work High voltage: arc is unstable (spatters)

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MIG Welding

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  1. MIG Welding

  2. Wire speed (Top Knob) Voltage (Middle Knob) Trigger, Over Temperature, and On/Off Switch Wire speed (amperage) controls weld penetration Voltage controls height and width of weld bead Low voltage: wire stubs into work High voltage: arc is unstable (spatters) **BACON & EGGS FRYING!**

  3. Uses unishield gas (argon and 25% carbon dioxide) Select voltage and wire speed based on thickness of metal being welded Chart inside of machines for reference Examples Thickness of steel Voltage Wire Speed ¼” 8 80 3/16” 5 75 1/8” 4 70 16 ga. 2.5 55

  4. ***Wire should always stick out of gun about ¼”.*** Weld bead shape depends on gun angle, direction of travel, electrode extension (stickout), travel speed, thickness of base metal, wire feed speed, and voltage Good Weld BeadPoor Weld Bead Fine Spatter Large spatter deposits Uniform bead Rough, uneven bead Good penetration into base material Slight crater during weld Moderate crater during weld Bad overlap Poor penetration

  5. Excessive spatter: scattering of molten metal particles that cool to solid form near weld bead Causes: voltage too high, wire speed too high, stickout too long Porosity: small cavities or holes resulting from gas pockets in weld metal Causes: stickout too long, workpiece is dirty Excessive penetration: weld metal melting through base metal and hanging underneath weld Causes: excessive heat input Lack of penetration: shallow fusion between weld metal and base metal Causes: insufficient heat input Incomplete fusion: failure of weld metal to fuse completely with base metal or preceding bead Causes: dirty workpiece, insufficient heat input Burn-through: weld metal melting completely through base metal resulting in holes where no metal remains Causes: excessive heat

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