GTAW WLD 150 Welding And Joining Practice Test

In a multi-pass GTAW butt weld, what is the primary purpose of the root pass?

To finish the surface and shape To fill the weld to full height To establish fusion and penetration To apply final surface texture

Correct Answer:

To establish fusion and penetration

Explanation:

In a multi-pass GTAW butt weld, the root pass establishes fusion and penetration at the joint root. It is the first layer that fuses the two base metals together at the bottom of the joint, creating a continuous weld through the joint depth. This solid foundation lets subsequent passes fill and cap the weld reliably. If the root doesn’t properly fuse and penetrate, you can end up with weak root fusion or lack of fusion at the base of the weld, even if later passes are added. Finishing the surface, filling to full height, or applying final texture are tasks for later passes and finishing steps, not the root itself.

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