A welder is running GMAW outdoors in a steady breeze and the beads are full of surface pinholes. What is the most likely cause?
- The travel speed is too slow for the wire feed speed
- The wire has too much silicon and manganese in it
- The shielding gas is being blown away from the arc
- The work lead is clamped too close to the weld
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C. The shielding gas is being blown away from the arc
Wind strips the shielding gas from the puddle so air reaches the molten metal and gas is trapped as porosity. Wind screens, or a process that does not rely on external gas, are the cure. Deoxidizers in the wire reduce porosity; they do not cause it.
Reference: Weld discontinuities: causes of porosity
Which steel can normally be welded with the fewest special precautions?
- Low-carbon (mild) steel
- Medium-carbon steel
- High-carbon tool steel
- Gray cast iron
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A. Low-carbon (mild) steel
Low-carbon steel does not harden much when it cools quickly, so in ordinary thicknesses it welds readily without preheat. Medium- and high-carbon steels and cast iron form hard, brittle structures next to the weld unless preheat and controlled cooling are used.
Reference: Welding metallurgy: weldability of carbon steels
Which type of welding power source output is used for SMAW?
- Constant current
- Constant voltage
- Constant wattage
- Constant wire speed
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A. Constant current
SMAW uses a constant-current (drooping) machine so that the amperage stays close to the set value as the welder's arc length changes by hand. Constant-voltage machines are used for wire-fed processes such as GMAW and FCAW, where the arc self-adjusts.
Reference: Welding power sources: constant current vs constant voltage