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1 (a) The weld is covered with heavy oxide films.

2 (b) No, the oxide films on the weld pool surface kept the filler metal droplets from entering the pool properly.

3 (c) DC electrode negative was used.

4 (d) Use AC of DC electrode positive to keep the weld pool surface clean.

Example 1.2 In the hot wire GTAW process shown in Figure E1.2, the tip of the filler metal wire is dipped in the weld pool and the wire itself is resistance heated by means of a second power source between the contact tube of the wire and the workpiece. In the case of steels, the deposition rate can be more than doubled this way. (a) Is an AC or DC power source preferred for heating the wire, and if so, why? (b) Can this process be expected to be as effective for aluminum and copper alloys? (c) Why is this process better than conventional GTAW for depositing a corrosion‐ or wear‐resistant overlay on steel?

Figure E1.2 Hot wire GTAW process.