CO Welding Contractor Exam Questions
and Correct Answers (Verified Answers)
Plus Rationale 2027 Q&A| Instant
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1. Which welding process uses a continuously fed consumable wire
electrode and a shielding gas to protect the weld pool?
A. Shielded metal arc welding (SMAW)
B. Gas tungsten arc welding (GTAW)
C. Gas metal arc welding (GMAW)
D. Oxyfuel welding
Rationale: GMAW, commonly called MIG welding, uses a continuously
fed wire electrode. Shielding gas is supplied externally to protect the
molten weld metal from atmospheric contamination. SMAW uses stick
electrodes, GTAW uses a nonconsumable tungsten electrode, and
oxyfuel welding uses a fuel-gas flame.
2. What is the primary purpose of shielding gas during arc welding?
,A. Increase the hardness of the base metal
B. Prevent atmospheric gases from contaminating the molten weld
pool
C. Cool the electrode
D. Increase the electrical resistance of the arc
Rationale: Oxygen, nitrogen, and moisture from the atmosphere can
cause porosity, embrittlement, oxidation, and other weld defects.
Shielding gas creates a protective environment around the arc and
molten pool, reducing these problems.
3. In shielded metal arc welding (SMAW), what provides the filler
metal?
A. Separate copper wire
B. Tungsten electrode
C. Shielding gas
D. The consumable coated electrode
Rationale: SMAW uses a consumable electrode covered with flux. As
the electrode melts, it supplies filler metal while the flux produces
shielding gases and slag that protect the weld.
4. Which electrode characteristic is most directly associated with the
AWS classification E7018?
,A. It is a nonconsumable tungsten electrode
B. It is designed only for aluminum
C. It is a low-hydrogen electrode with a nominal tensile strength
classification of 70 ksi
D. It must be used only with alternating current
Rationale: In E7018, “70” indicates approximately 70 ksi minimum
tensile strength, while the final “8” identifies the electrode
coating/current characteristics. E7018 is commonly used as a low-
hydrogen electrode when properly stored and handled.
5. What is the purpose of preheating steel before welding?
A. Eliminate the need for shielding
B. Reduce the cooling rate and help minimize cracking
C. Increase arc voltage automatically
D. Remove all surface scale
Rationale: Preheating raises the temperature of the base metal before
welding. It slows cooling, reduces thermal gradients, assists hydrogen
control, and can reduce the risk of cracking in susceptible steels.
6. Which welding position is designated as the flat position?
A. 2G
B. 3G
, C. 4G
D. 1G
Rationale: In the common pipe and plate position designations, “1G”
represents a groove weld in the flat position. The second number or
letter identifies the orientation and type of weld.
7. What does the term “root opening” refer to?
A. The width of the weld cap
B. The depth of the weld crater
C. The separation between the members at the root of a joint
D. The thickness of the electrode coating
Rationale: Root opening is the gap between the joint members at the
root before welding. Proper root opening is important because it
affects penetration, fusion, and the amount of filler metal required.
8. What is incomplete fusion?
A. Excessive weld reinforcement
B. Failure of the weld metal to properly fuse with the base metal or an
adjacent weld layer
C. Excessive penetration through the joint
D. Removal of slag after welding
and Correct Answers (Verified Answers)
Plus Rationale 2027 Q&A| Instant
Download Pdf
1. Which welding process uses a continuously fed consumable wire
electrode and a shielding gas to protect the weld pool?
A. Shielded metal arc welding (SMAW)
B. Gas tungsten arc welding (GTAW)
C. Gas metal arc welding (GMAW)
D. Oxyfuel welding
Rationale: GMAW, commonly called MIG welding, uses a continuously
fed wire electrode. Shielding gas is supplied externally to protect the
molten weld metal from atmospheric contamination. SMAW uses stick
electrodes, GTAW uses a nonconsumable tungsten electrode, and
oxyfuel welding uses a fuel-gas flame.
2. What is the primary purpose of shielding gas during arc welding?
,A. Increase the hardness of the base metal
B. Prevent atmospheric gases from contaminating the molten weld
pool
C. Cool the electrode
D. Increase the electrical resistance of the arc
Rationale: Oxygen, nitrogen, and moisture from the atmosphere can
cause porosity, embrittlement, oxidation, and other weld defects.
Shielding gas creates a protective environment around the arc and
molten pool, reducing these problems.
3. In shielded metal arc welding (SMAW), what provides the filler
metal?
A. Separate copper wire
B. Tungsten electrode
C. Shielding gas
D. The consumable coated electrode
Rationale: SMAW uses a consumable electrode covered with flux. As
the electrode melts, it supplies filler metal while the flux produces
shielding gases and slag that protect the weld.
4. Which electrode characteristic is most directly associated with the
AWS classification E7018?
,A. It is a nonconsumable tungsten electrode
B. It is designed only for aluminum
C. It is a low-hydrogen electrode with a nominal tensile strength
classification of 70 ksi
D. It must be used only with alternating current
Rationale: In E7018, “70” indicates approximately 70 ksi minimum
tensile strength, while the final “8” identifies the electrode
coating/current characteristics. E7018 is commonly used as a low-
hydrogen electrode when properly stored and handled.
5. What is the purpose of preheating steel before welding?
A. Eliminate the need for shielding
B. Reduce the cooling rate and help minimize cracking
C. Increase arc voltage automatically
D. Remove all surface scale
Rationale: Preheating raises the temperature of the base metal before
welding. It slows cooling, reduces thermal gradients, assists hydrogen
control, and can reduce the risk of cracking in susceptible steels.
6. Which welding position is designated as the flat position?
A. 2G
B. 3G
, C. 4G
D. 1G
Rationale: In the common pipe and plate position designations, “1G”
represents a groove weld in the flat position. The second number or
letter identifies the orientation and type of weld.
7. What does the term “root opening” refer to?
A. The width of the weld cap
B. The depth of the weld crater
C. The separation between the members at the root of a joint
D. The thickness of the electrode coating
Rationale: Root opening is the gap between the joint members at the
root before welding. Proper root opening is important because it
affects penetration, fusion, and the amount of filler metal required.
8. What is incomplete fusion?
A. Excessive weld reinforcement
B. Failure of the weld metal to properly fuse with the base metal or an
adjacent weld layer
C. Excessive penetration through the joint
D. Removal of slag after welding
