What holds the molten ball of tungsten in place at the tip during DCEP welding?

• A. Magnetic attraction between the electrode and work.
• B. The liquid tungsten surface tension with the larger mass above the molten ball holds it in place like a drop of water on your fingertip.
• C. Electrical attraction from the welding power supply.
• D. Gravity only.

Answer: (B)

During DCEP welding, the tip of the tungsten electrode heats intensely and forms a small molten ball. The force that actually holds that molten ball in place on the tip is surface tension of the liquid tungsten. The cohesive forces at the molten surface pull the metal into a spherical shape and keep it attached to the end of the electrode, behaving like a drop of liquid clinging to a fingertip. Gravity plays a role, but it’s the surface tension that is the dominant factor. Magnetic or electrical attraction to the work isn’t what keeps the ball attached.