Sheet Metal Trade And SMWIA 2nd Year Practice Test

Under DCEN, a thoriated 1/16 inch tungsten should be operated in which amperage range?

5 to 15 Amps 20 to 60 Amps 70 to 150 Amps 150 to 250 Amps

Correct Answer:

70 to 150 Amps

Explanation:

In GTAW with DCEN, the tungsten is negative and the arc heat is directed into the workpiece, so the electrode must carry enough current without overheating. A 1/16 inch thoriated tungsten has the right balance of size and emission for mid-to-high currents, making 70 to 150 amps the practical range. Running in this window gives a stable arc and good penetration for typical welds on many steels and thicknesses. If you drop well below 70 A, the arc can become unstable and the tungsten may not perform well; pushing above 150 A risks overheating the tip, causing instability or tungsten contamination of the weld. For thinner work or different setups, you’d adjust by using a smaller tungsten or different current.

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