What is a lift-arc start in GTAW and how does it differ from a scratch start?

• A. Lift-arc starts arc by lifting the electrode from the work via the power source.
• B. Scratch start begins by lifting electrode.
• C. Lift-arc start requires touching the tungsten to the work.
• D. Scratch start is done by moving the torch quickly.

Answer: (A)

In GTAW, lifting-arc start is a method where you briefly bring the tungsten into contact with the work to establish a small short circuit, then you lift the electrode away from the surface while the current remains on. As you lift, the arc forms between the tungsten tip and the work, and you can then move into welding. This approach uses the power source to initiate and sustain the arc and avoids the need for high-frequency start circuitry, while also generally reducing tungsten contamination and spatter.

Scratch start, by contrast, initiates the arc by dragging or scratching the tungsten across the work surface to ionize the gas and start the arc, typically without the brief deliberate contact-and-lift that lift-arc uses. This can be less controllable and more prone to contaminating the tungsten or creating an inconsistent arc.

So, the lift-arc method is about starting the arc by lifting the electrode off the work after brief contact, using the power source to drive the arc, whereas scratch start starts the arc through dragging/contact across the surface.