CO Welding Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which type of welding uses a non-consumable tungsten electrode?
A. Shielded Metal Arc Welding (SMAW)
B. Gas Metal Arc Welding (GMAW)
C. Gas Tungsten Arc Welding (GTAW)
D. Flux-Cored Arc Welding (FCAW)
Rationale: GTAW, also known as TIG welding, uses a tungsten electrode
that does not melt.
2. The primary function of a welding electrode coating is to:
A. Increase arc length
B. Stabilize the arc and protect the weld
C. Reduce electricity consumption
D. Cool the weld faster
Rationale: Electrode coatings shield the molten weld from atmospheric
contamination and stabilize the arc.
3. Which gas is commonly used as a shielding gas in MIG welding of
carbon steel?
A. Oxygen
B. Helium
C. Carbon Dioxide
D. Nitrogen
Rationale: CO₂ is widely used for MIG welding carbon steel because it
provides good penetration and arc stability.
, 4. In SMAW, a 6013 electrode indicates:
A. Maximum voltage rating
B. Tensile strength, position, and coating type
C. Electrode diameter
D. Arc length
Rationale: “60” indicates tensile strength in ksi, “1” indicates all-position
use, and “3” indicates the type of flux coating.
5. Preheating before welding is important because it:
A. Speeds up electrode consumption
B. Reduces weld size
C. Reduces the risk of cracking
D. Eliminates slag
Rationale: Preheating slows cooling, reducing thermal stresses that can
cause cracking.
6. Which of the following welding processes is considered most suitable
for thin stainless steel?
A. SMAW
B. FCAW
C. GTAW
D. Oxyacetylene welding
Rationale: GTAW provides precise heat control, which is critical for thin
stainless steel.
7. Heat-affected zone (HAZ) refers to:
A. The electrode tip
B. The base metal affected by heat but not melted
C. The slag coating
D. The weld filler only
Rationale: HAZ is the portion of base metal whose microstructure has
changed due to welding heat.
8. Which welding defect is characterized by a localized depression along
the weld?
, A. Porosity
B. Undercut
C. Crater crack
D. Overlap
Rationale: Undercut is a groove at the toe of the weld caused by excessive
heat or improper technique.
9. In MIG welding, wire feed speed primarily controls:
A. Arc length
B. Gas flow rate
C. Deposition rate and weld bead size
D. Electrode melting temperature
Rationale: Higher wire feed speeds increase deposition rate and bead size.
10. Backhand welding technique is generally used to:
A. Increase weld penetration
B. Control weld pool and reduce spatter
C. Weld vertical down
D. Increase electrode consumption
Rationale: Backhand technique pushes the arc away, improving control
over the weld pool.
11. Which of the following metals requires a special electrode for
SMAW?
A. Mild steel
B. Aluminum
C. Low-carbon steel
D. Cast iron
Rationale: Aluminum cannot be welded with standard steel electrodes; it
requires specific electrodes for proper fusion.
12. What is the main hazard of welding galvanized steel?
A. Arc instability
B. Toxic fumes (zinc oxide)
Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which type of welding uses a non-consumable tungsten electrode?
A. Shielded Metal Arc Welding (SMAW)
B. Gas Metal Arc Welding (GMAW)
C. Gas Tungsten Arc Welding (GTAW)
D. Flux-Cored Arc Welding (FCAW)
Rationale: GTAW, also known as TIG welding, uses a tungsten electrode
that does not melt.
2. The primary function of a welding electrode coating is to:
A. Increase arc length
B. Stabilize the arc and protect the weld
C. Reduce electricity consumption
D. Cool the weld faster
Rationale: Electrode coatings shield the molten weld from atmospheric
contamination and stabilize the arc.
3. Which gas is commonly used as a shielding gas in MIG welding of
carbon steel?
A. Oxygen
B. Helium
C. Carbon Dioxide
D. Nitrogen
Rationale: CO₂ is widely used for MIG welding carbon steel because it
provides good penetration and arc stability.
, 4. In SMAW, a 6013 electrode indicates:
A. Maximum voltage rating
B. Tensile strength, position, and coating type
C. Electrode diameter
D. Arc length
Rationale: “60” indicates tensile strength in ksi, “1” indicates all-position
use, and “3” indicates the type of flux coating.
5. Preheating before welding is important because it:
A. Speeds up electrode consumption
B. Reduces weld size
C. Reduces the risk of cracking
D. Eliminates slag
Rationale: Preheating slows cooling, reducing thermal stresses that can
cause cracking.
6. Which of the following welding processes is considered most suitable
for thin stainless steel?
A. SMAW
B. FCAW
C. GTAW
D. Oxyacetylene welding
Rationale: GTAW provides precise heat control, which is critical for thin
stainless steel.
7. Heat-affected zone (HAZ) refers to:
A. The electrode tip
B. The base metal affected by heat but not melted
C. The slag coating
D. The weld filler only
Rationale: HAZ is the portion of base metal whose microstructure has
changed due to welding heat.
8. Which welding defect is characterized by a localized depression along
the weld?
, A. Porosity
B. Undercut
C. Crater crack
D. Overlap
Rationale: Undercut is a groove at the toe of the weld caused by excessive
heat or improper technique.
9. In MIG welding, wire feed speed primarily controls:
A. Arc length
B. Gas flow rate
C. Deposition rate and weld bead size
D. Electrode melting temperature
Rationale: Higher wire feed speeds increase deposition rate and bead size.
10. Backhand welding technique is generally used to:
A. Increase weld penetration
B. Control weld pool and reduce spatter
C. Weld vertical down
D. Increase electrode consumption
Rationale: Backhand technique pushes the arc away, improving control
over the weld pool.
11. Which of the following metals requires a special electrode for
SMAW?
A. Mild steel
B. Aluminum
C. Low-carbon steel
D. Cast iron
Rationale: Aluminum cannot be welded with standard steel electrodes; it
requires specific electrodes for proper fusion.
12. What is the main hazard of welding galvanized steel?
A. Arc instability
B. Toxic fumes (zinc oxide)
