Question

what is an undesirable method to start the arc?

scratch start
low frequency
lift arc
high frequency

Explanation:

Identify arc starting methods

Using the TIG Arc Starting Methods knowledge point

In Gas Tungsten Arc Welding (GTAW/TIG), there are several methods used to initiate the welding arc:

• High frequency (HF) start: A non-contact method that uses high-frequency current to jump the gap.
• Lift arc start: A contact method where the tungsten touches the work briefly and is lifted to draw the arc.
• Scratch start: An older contact method where the electrode is scraped across the metal like a match.

Evaluate the scratch start method

Using the TIG Arc Starting Methods and Lift Arc Start knowledge points

The scratch start method is generally considered undesirable in high-quality TIG welding because scraping the tungsten electrode directly against the base metal often causes tungsten contamination in the weld pool and damages the electrode tip. Modern techniques like high frequency and lift arc are preferred to prevent this contamination. "Low frequency" is not a standard arc starting method. Therefore, scratch start is the undesirable method.

Answer:

• (A) Scratch start (Correct answer)
• (B) Low frequency
• (C) Lift arc
• (D) High frequency