Investigation on Cooling Efficiency of Plasma Arc Welding Torch and Narrow Gap Welding by Thin-type Torch

Abstract

Cooling efficiency of the plasma arc welding torch was investigated using visualization of water flow inside the nozzle cap. Cooling water in the heated nozzle is partially boiled and bubbles generate and extinguish repeatedly. Then water pressure vibration occurs by this phenomenon and it became clear that amplitude and frequency of this vibration correspond to changes in heat load and temperature of the nozzle.
The thin-type torch was made as a trial and this torch can be inserted in the narrow gap (10 to 12 mm) joint. We used this torch for root pass welding in keyhole method in narrow gap joints and obtained satisfactory results.