AWS Certified Welding Inspector — FundamentalsWelding ProcessesMedium
A CWI is evaluating a Weld Procedure Specification (WPS) for Gas Tungsten Arc Welding (GTAW) of thin-walled stainless steel tubing. The WPS specifies a 2% Thoriated Tungsten electrode (EWTh-2) with Direct Current Electrode Negative (DCEN). Which of the following is a primary characteristic and advantage of using EWTh-2 electrodes with DCEN for this application?
- AIt provides excellent arc starting and stability with a balled tip, ideal for AC welding of aluminum.
- BIt forms a stable, hemispherical tip, which is essential for deep penetration in thick materials.
- CIt prevents tungsten contamination by forming a non-consumable electrode tip that requires no grinding.
- DIt offers high electron emission, allowing for higher current carrying capacity and good arc stability with a pointed tip.
Show answer & explanationAnswer & explanation
Correct answer: D. It offers high electron emission, allowing for higher current carrying capacity and good arc stability with a pointed tip.
Thoriated tungsten electrodes (EWTh-2) have excellent electron emission characteristics, allowing them to carry higher current loads and maintain a stable arc, especially when ground to a pointed tip for DCEN applications, which is common for stainless steel.
Why the other options are wrong
- A. Balled tips are characteristic of pure tungsten or zirconiated tungsten on AC; EWTh-2 on DCEN uses a pointed tip.
- B. A hemispherical tip is not characteristic of EWTh-2 with DCEN; a pointed tip is used for penetration. Also, GTAW is often for thinner, precise work, not primarily deep penetration in very thick materials.
- C. All tungsten electrodes require proper preparation (grinding) for optimal performance and can cause contamination if mishandled or overloaded.
EWTh-2 (Thoriated) Tungsten with DCEN
Thoriated tungsten electrodes (EWTh-2) used with DCEN provide high electron emission, superior current carrying capacity, and excellent arc stability, typically with a pointed tip, making them suitable for welding steels and stainless steels.
- High electron emission.
- Higher current carrying capacity than pure tungsten.
- Excellent arc stability.
- Typically ground to a pointed tip for DCEN.
- Used for carbon steel, stainless steel, nickel alloys, copper.
Memory trick: GTAW electrodes are like specific tools, each with a unique power and purpose.