CWB WELDING INSPECTOR LEVEL 3 EXAM NEWEST ACTUAL EXAM QUESTIONS
AND CORRECT DETAILED ANSWERS/NEWEST UPDATE!!!!
Question 1
Which of the following Aluminum-Copper alloys would you expect to give the highest risk of
hot cracking during solidification?
A) Al-0.1%Cu
B) Al-3%Cu
C) Al-8%Cu
D) Al-12%Cu
E) Pure Aluminum
Correct Answer: B) Al-3%Cu
Rationale: Hot cracking risk is highest in alloys with a specific range of alloying elements
that create a wide "mushy zone" or freezing range. At approximately 3% Copper, there is
sufficient solute to create low-melting-point liquid films between grains, but not enough
eutectic liquid to "heal" the cracks as they form, leading to peak crack sensitivity.
Question 2
If centerline solidification cracking is occurring while welding a structural steel, which of the
following is the most likely procedural cause?
A) Electrical extension (stick-out) is too long
B) Arc voltage is too low for the current
C) Welding current and travel speed are too high
D) The weld bead is too large and wide
E) Excessive use of preheat
Correct Answer: C) welding current and speed too high
Rationale: High current and high travel speeds create a "teardrop-shaped" weld pool.
During solidification, the grains grow inward and meet at a sharp centerline, trapping low-
melting-point impurities (like sulfur and phosphorus) at the center. The resulting shrinkage
stresses act on this weak zone, causing a longitudinal crack.
Question 3
What is the primary and most likely cause of porosity in aluminum welds?
A) Nitrogen absorption from the air
B) Hydrogen gas
C) Argon entrapment from the shielding gas
D) Oxygen reacting with aluminum to form alumina
E) Carbon monoxide from surface oils
Correct Answer: B) hydrogen
Rationale: Aluminum has a very high solubility for hydrogen in its liquid state and a very
low solubility in its solid state. As the weld metal freezes, the rejected hydrogen is trapped
as bubbles, causing porosity. Common sources include moisture in the air, hydrated oxides
on the filler wire, or contaminated base metal.
, 2
Question 4
How can porosity caused by nitrogen be specifically controlled when welding nickel and nickel-
based alloys?
A) By increasing the flow rate of pure Argon
B) By using a filler metal containing titanium
C) By decreasing the arc length
D) By using a basic flux-cored wire
E) By increasing the travel speed to reduce exposure
Correct Answer: B) By using filler metal containing titanium
Rationale: Titanium acts as a "denitrifier" in nickel welding. It reacts with nitrogen to form
stable titanium nitrides, which prevents the nitrogen from forming gas bubbles (porosity)
during the solidification of the weld pool.
Question 5
What is the most likely chemical cause of porosity in carbon steel welds when deoxidizers are
insufficient?
A) Hydrogen gas trapped in the lattice
B) Nitrogen absorption from the atmosphere
C) Carbon monoxide formed by the reaction of oxygen with carbon
D) Argon gas trapped during shielding
E) Water vapor trapped in the slag
Correct Answer: C) carbon monoxide from reaction of oxygen with carbon
Rationale: In "rimmed" or under-deoxidized steels, oxygen reacts with the carbon in the
steel to form Carbon Monoxide (CO) gas. If this gas is not removed or suppressed by
deoxidizers like Silicon or Manganese, it becomes trapped as porosity.
Question 6
Which elements are typically included in electrodes or fluxes specifically to act as deoxidizers
and control porosity in steel welds?
A) Silicon, aluminum, and manganese
B) Copper, nickel, and molybdenum
C) Sulphur, phosphorus, and selenium
D) Silica, alumina, and magnesia
E) Chromium, vanadium, and carbon
Correct Answer: A) silicon, aluminum, manganese
Rationale: These elements have a higher affinity for oxygen than carbon does. They react
with dissolved oxygen to form solid oxides that float into the slag, thereby preventing the
formation of carbon monoxide gas bubbles.
Question 7
The mathematical value of thermal conductivity divided by the product of specific heat and
, 3
specific gravity is known as:
A) Thermal Gradient
B) Heat Input
C) Thermal Diffusivity
D) Melting Efficiency
E) Isothermal Coefficient
Correct Answer: C) Thermal diffusivity
Rationale: Thermal diffusivity measures the rate at which heat moves through a material. It
determines how quickly a metal will "wick" heat away from the weld zone, which directly
influences the cooling rate and the size of the Heat Affected Zone (HAZ).
Question 8
True or False: A metal with a low thermal conductivity is more likely to reach the maximum
melting efficiency when welded.
A) True
B) False
Correct Answer: A) True
Rationale: Melting efficiency is the fraction of heat input used to actually melt the metal. In
metals with low thermal conductivity (like stainless steel), heat stays localized at the arc
point rather than dissipating into the surrounding plate, allowing more of the arc energy to
contribute to melting.
Question 9
Would a joint geometry designed for thick stainless steel (e.g., a 60-degree V-groove) be
perfectly acceptable for welding thick aluminum?
A) Yes, joint design is independent of material type.
B) No, aluminum requires a narrower angle to focus heat.
C) No, aluminum requires a wider angle to ensure proper penetration and gas shielding.
D) Yes, but only if using the GTAW process.
E) No, aluminum must always use a U-groove regardless of thickness.
Correct Answer: C) No. Grooves for thick aluminum would have a wider angle than for
stainless steel.
Rationale: Aluminum’s high thermal conductivity and diffusivity mean heat is rapidly lost
to the side walls. A wider groove angle is necessary to allow the welder to manipulate the
arc and ensure the heavy side walls reach the melting temperature for proper fusion.
Question 10
When welding on a thick plate (where 3D heat flow occurs), the cooling rate is proportional to:
A) The heat input.
B) The inverse of the heat input (
, 4
1/𝐻
).
C) The inverse of the square of the heat input (
1/𝐻 2
).
D) The square root of the heat input.
E) The plate thickness cubed.
Correct Answer: B) inverse of the heat input.
Rationale: For thick plates, the cooling rate (
𝑅
) is expressed as being inversely proportional to the heat input (
𝐻
). Therefore, if you double the heat input, you essentially halve the cooling rate, which is a
critical calculation for managing hardness in the HAZ.
Question 11
Using standard cooling rate charts (Module 20), what is the estimated cooling rate for a
submerged arc bead on a 19 mm plate (no preheat) with an energy input of 1.77 kJ/mm (45
kJ/in)?
A) 5°C/s at 540°C
B) 16°C/s at 540°C
C) 45°C/s at 540°C
D) 100°C/s at 540°C
E) 12°C/s at 800°C
Correct Answer: B) 16°C/s at 540°C
Rationale: Based on the 3D heat flow equations and charts for thick plates, a heat input of
1.77 kJ/mm results in a cooling rate of approximately 16°C per second as the weld passes
through the critical 540°C temperature range.
Question 12
Which of the following metals is likely to need the greatest degree of shielding from the
atmosphere (including trailing shields) during welding?
A) Copper
B) Lead
C) Titanium
D) Carbon Steel
E) Gold
AND CORRECT DETAILED ANSWERS/NEWEST UPDATE!!!!
Question 1
Which of the following Aluminum-Copper alloys would you expect to give the highest risk of
hot cracking during solidification?
A) Al-0.1%Cu
B) Al-3%Cu
C) Al-8%Cu
D) Al-12%Cu
E) Pure Aluminum
Correct Answer: B) Al-3%Cu
Rationale: Hot cracking risk is highest in alloys with a specific range of alloying elements
that create a wide "mushy zone" or freezing range. At approximately 3% Copper, there is
sufficient solute to create low-melting-point liquid films between grains, but not enough
eutectic liquid to "heal" the cracks as they form, leading to peak crack sensitivity.
Question 2
If centerline solidification cracking is occurring while welding a structural steel, which of the
following is the most likely procedural cause?
A) Electrical extension (stick-out) is too long
B) Arc voltage is too low for the current
C) Welding current and travel speed are too high
D) The weld bead is too large and wide
E) Excessive use of preheat
Correct Answer: C) welding current and speed too high
Rationale: High current and high travel speeds create a "teardrop-shaped" weld pool.
During solidification, the grains grow inward and meet at a sharp centerline, trapping low-
melting-point impurities (like sulfur and phosphorus) at the center. The resulting shrinkage
stresses act on this weak zone, causing a longitudinal crack.
Question 3
What is the primary and most likely cause of porosity in aluminum welds?
A) Nitrogen absorption from the air
B) Hydrogen gas
C) Argon entrapment from the shielding gas
D) Oxygen reacting with aluminum to form alumina
E) Carbon monoxide from surface oils
Correct Answer: B) hydrogen
Rationale: Aluminum has a very high solubility for hydrogen in its liquid state and a very
low solubility in its solid state. As the weld metal freezes, the rejected hydrogen is trapped
as bubbles, causing porosity. Common sources include moisture in the air, hydrated oxides
on the filler wire, or contaminated base metal.
, 2
Question 4
How can porosity caused by nitrogen be specifically controlled when welding nickel and nickel-
based alloys?
A) By increasing the flow rate of pure Argon
B) By using a filler metal containing titanium
C) By decreasing the arc length
D) By using a basic flux-cored wire
E) By increasing the travel speed to reduce exposure
Correct Answer: B) By using filler metal containing titanium
Rationale: Titanium acts as a "denitrifier" in nickel welding. It reacts with nitrogen to form
stable titanium nitrides, which prevents the nitrogen from forming gas bubbles (porosity)
during the solidification of the weld pool.
Question 5
What is the most likely chemical cause of porosity in carbon steel welds when deoxidizers are
insufficient?
A) Hydrogen gas trapped in the lattice
B) Nitrogen absorption from the atmosphere
C) Carbon monoxide formed by the reaction of oxygen with carbon
D) Argon gas trapped during shielding
E) Water vapor trapped in the slag
Correct Answer: C) carbon monoxide from reaction of oxygen with carbon
Rationale: In "rimmed" or under-deoxidized steels, oxygen reacts with the carbon in the
steel to form Carbon Monoxide (CO) gas. If this gas is not removed or suppressed by
deoxidizers like Silicon or Manganese, it becomes trapped as porosity.
Question 6
Which elements are typically included in electrodes or fluxes specifically to act as deoxidizers
and control porosity in steel welds?
A) Silicon, aluminum, and manganese
B) Copper, nickel, and molybdenum
C) Sulphur, phosphorus, and selenium
D) Silica, alumina, and magnesia
E) Chromium, vanadium, and carbon
Correct Answer: A) silicon, aluminum, manganese
Rationale: These elements have a higher affinity for oxygen than carbon does. They react
with dissolved oxygen to form solid oxides that float into the slag, thereby preventing the
formation of carbon monoxide gas bubbles.
Question 7
The mathematical value of thermal conductivity divided by the product of specific heat and
, 3
specific gravity is known as:
A) Thermal Gradient
B) Heat Input
C) Thermal Diffusivity
D) Melting Efficiency
E) Isothermal Coefficient
Correct Answer: C) Thermal diffusivity
Rationale: Thermal diffusivity measures the rate at which heat moves through a material. It
determines how quickly a metal will "wick" heat away from the weld zone, which directly
influences the cooling rate and the size of the Heat Affected Zone (HAZ).
Question 8
True or False: A metal with a low thermal conductivity is more likely to reach the maximum
melting efficiency when welded.
A) True
B) False
Correct Answer: A) True
Rationale: Melting efficiency is the fraction of heat input used to actually melt the metal. In
metals with low thermal conductivity (like stainless steel), heat stays localized at the arc
point rather than dissipating into the surrounding plate, allowing more of the arc energy to
contribute to melting.
Question 9
Would a joint geometry designed for thick stainless steel (e.g., a 60-degree V-groove) be
perfectly acceptable for welding thick aluminum?
A) Yes, joint design is independent of material type.
B) No, aluminum requires a narrower angle to focus heat.
C) No, aluminum requires a wider angle to ensure proper penetration and gas shielding.
D) Yes, but only if using the GTAW process.
E) No, aluminum must always use a U-groove regardless of thickness.
Correct Answer: C) No. Grooves for thick aluminum would have a wider angle than for
stainless steel.
Rationale: Aluminum’s high thermal conductivity and diffusivity mean heat is rapidly lost
to the side walls. A wider groove angle is necessary to allow the welder to manipulate the
arc and ensure the heavy side walls reach the melting temperature for proper fusion.
Question 10
When welding on a thick plate (where 3D heat flow occurs), the cooling rate is proportional to:
A) The heat input.
B) The inverse of the heat input (
, 4
1/𝐻
).
C) The inverse of the square of the heat input (
1/𝐻 2
).
D) The square root of the heat input.
E) The plate thickness cubed.
Correct Answer: B) inverse of the heat input.
Rationale: For thick plates, the cooling rate (
𝑅
) is expressed as being inversely proportional to the heat input (
𝐻
). Therefore, if you double the heat input, you essentially halve the cooling rate, which is a
critical calculation for managing hardness in the HAZ.
Question 11
Using standard cooling rate charts (Module 20), what is the estimated cooling rate for a
submerged arc bead on a 19 mm plate (no preheat) with an energy input of 1.77 kJ/mm (45
kJ/in)?
A) 5°C/s at 540°C
B) 16°C/s at 540°C
C) 45°C/s at 540°C
D) 100°C/s at 540°C
E) 12°C/s at 800°C
Correct Answer: B) 16°C/s at 540°C
Rationale: Based on the 3D heat flow equations and charts for thick plates, a heat input of
1.77 kJ/mm results in a cooling rate of approximately 16°C per second as the weld passes
through the critical 540°C temperature range.
Question 12
Which of the following metals is likely to need the greatest degree of shielding from the
atmosphere (including trailing shields) during welding?
A) Copper
B) Lead
C) Titanium
D) Carbon Steel
E) Gold
