Certified Welder Welding Processes and Equipment 3 — Questions and Answers
Question 1: What is the primary advantage of using DCEN (straight polarity) in SMAW?
- Deeper penetration on thick plate
- Greater heat at the electrode, less at the base metal (Correct answer)
- Better arc stability with all electrode types
- Reduced spatter compared to DCEP
Correct answer: Greater heat at the electrode, less at the base metal
DCEN directs more heat to the electrode end rather than the base metal, which can be useful for specific electrodes and thin materials.
Question 2: Which GMAW transfer mode produces the least spatter and is characterized by very small droplets transferred across the arc?
- Globular transfer
- Short-circuit transfer
- Spray transfer (Correct answer)
- Pulsed spray transfer
Correct answer: Spray transfer
Spray transfer uses high voltage and amperage to project tiny droplets axially across the arc with minimal spatter.
Question 3: What is the function of the contact tip in a GMAW welding gun?
- It directs shielding gas around the weld pool
- It transfers welding current to the wire electrode (Correct answer)
- It holds the nozzle in place
- It regulates wire feed speed
Correct answer: It transfers welding current to the wire electrode
The contact tip conducts welding current to the continuously fed wire electrode as it passes through the tip.
Question 4: In resistance spot welding, what creates the heat needed to fuse the metal?
- An open arc between two electrodes
- Friction between the workpieces
- Electrical resistance at the interface when current flows through the parts (Correct answer)
- A gas flame directed at the joint
Correct answer: Electrical resistance at the interface when current flows through the parts
Resistance spot welding generates heat through the electrical resistance at the contact point between workpieces when high current is applied.
Question 5: Which shielding gas mixture is most commonly used for GMAW of carbon steel with spray transfer?
- 100% CO2
- 75% Argon / 25% CO2 (Correct answer)
- 100% Argon
- 50% Argon / 50% Helium
Correct answer: 75% Argon / 25% CO2
A 75% Ar / 25% CO2 mixture (C25) is the most common blend for GMAW of carbon steel, providing good arc stability and penetration.
Question 6: What does OCV (Open Circuit Voltage) refer to in a welding power source?
- The voltage at maximum amperage output
- The voltage present at the output terminals when no arc is established (Correct answer)
- The voltage required to strike an arc
- The secondary voltage inside the transformer
Correct answer: The voltage present at the output terminals when no arc is established
OCV is the voltage measured at the output terminals of the power source when it is energized but not welding (no arc).
Question 7: For which base metal is it most critical to use a dry, low-hydrogen SMAW electrode to prevent weld cracking?
- Low-carbon steel under 1/4 inch thick
- High-strength, high-carbon, or alloy steel (Correct answer)
- Pure copper
- 1100-series aluminum
Correct answer: High-strength, high-carbon, or alloy steel
High-strength and high-carbon steels are susceptible to hydrogen-induced (cold) cracking, making low-hydrogen electrodes essential.
Certified Welder Welding Processes and Equipment 3
What is the primary advantage of using DCEN (straight polarity) in SMAW?