CWI Welding Process Principles 2 — Questions and Answers
Question 1: In SMAW, what is the primary purpose of the flux coating on the electrode?
- Increase electrical conductivity
- Provide shielding gas and slag protection (Correct answer)
- Increase deposition rate
- Preheat the base metal
Correct answer: Provide shielding gas and slag protection
The flux coating decomposes during welding to produce shielding gases and form a slag layer that protects the molten weld pool from atmospheric contamination.
Question 2: Which welding process uses a non-consumable tungsten electrode?
- SMAW
- GMAW
- GTAW (Correct answer)
- SAW
Correct answer: GTAW
Gas Tungsten Arc Welding (GTAW/TIG) uses a non-consumable tungsten electrode, with filler metal added separately if needed.
Question 3: What does the term 'polarity' refer to in arc welding?
- The angle of the electrode
- The direction of current flow in the welding circuit (Correct answer)
- The type of shielding gas used
- The travel speed of the electrode
Correct answer: The direction of current flow in the welding circuit
Polarity describes whether current flows from electrode to workpiece (DCEP) or from workpiece to electrode (DCEN), which affects heat distribution.
Question 4: In GMAW short-circuit transfer, metal transfer occurs when:
- The arc voltage is very high
- The wire tip contacts the weld pool and the arc extinguishes momentarily (Correct answer)
- Shielding gas pressure drops
- The wire feed speed decreases
Correct answer: The wire tip contacts the weld pool and the arc extinguishes momentarily
In short-circuit transfer, the wire periodically touches the weld pool, causing a short circuit that extinguishes the arc until electromagnetic pinch forces separate the droplet.
Question 5: Which of the following best describes the 'keyhole' technique used in plasma arc welding?
- A narrow groove preparation in the base metal
- A small hole formed through the full thickness of the joint by the plasma arc (Correct answer)
- A fixture used to align pipe joints
- A post-weld inspection method
Correct answer: A small hole formed through the full thickness of the joint by the plasma arc
In keyhole PAW, the concentrated plasma jet penetrates completely through the base metal, forming a small hole that is filled as the arc travels along the joint.
Question 6: What is the main advantage of using DCEP (direct current electrode positive) in SMAW?
- Reduced spatter and deeper penetration (Correct answer)
- Better arc stability on thin materials
- Suitable for welding aluminum with AC
- Lower heat input to the electrode
Correct answer: Reduced spatter and deeper penetration
DCEP concentrates approximately two-thirds of the arc heat at the electrode/weld pool side, producing deeper penetration and a stable arc suitable for most SMAW applications.
Question 7: In submerged arc welding (SAW), the arc is shielded by:
- A mixture of argon and CO2 gas
- A layer of granular flux that covers the arc (Correct answer)
- Slag from a coated electrode
- Pure helium gas
Correct answer: A layer of granular flux that covers the arc
In SAW, a blanket of granular flux completely submerges the arc, providing shielding and producing a slag layer that refines the weld metal.
CWI Welding Process Principles 2
In SMAW, what is the primary purpose of the flux coating on the electrode?