CWB WELDING INSPECTOR LEVEL III
STUDY GUIDE 100% ACCURATE
Which of the following metals has the highest thermal conductivity?
(a) carbon steel
(b) stainless steel
(c) aluminum - ANSWER(c)
The Ellingham diagram
(a) is a plot of thermal conductivity against temperature,
(b) shows the free energy of oxide formation against temperature.
(c) shows the rate of oxidation of metals against temperature. - ANSWER(b)
True or False?
A metal with a high negative free energy of oxide formation will generally require greater
shielding from the atmosphere during welding. - ANSWERTrue
Electricity can be conducted by:
(a) atoms and electrons.
(b) electrons and ions.
(c) only ions. - ANSWER(b)
Which of the following elements is often present in submerged arc fluxes to improve arc
stability?
(a) copper
(b) potassium
(c) nickel
(d) tungsten - ANSWER(b)
Thoria is added to tunsten electrodes for what purpose? - ANSWERTo increase
thermionic emission by lowering the work function.
True or False?
All pure metals have the same crystal structure. - ANSWERFalse. Metals generally
have one of three basic structures.
Which crystal structure(s) is (are) composed of close-packed planes? - ANSWERFCC
and HCP
The real strength of metals is lower than the theoretical value because:
(a) real crystals always fracture along specific crystal planes.
(b) grain boundary sliding occurs.
(c) the presence of dislocations facilitates slip. - ANSWER(c)
, Multiplication and subsequent congestion of moving dislocations causes:
(a) elastic extension.
(b) work or strain hardening.
(c) a drop in the yield stress. - ANSWER(b)
Which of the following elements are most likely to form interstitial solid solutions?
(a) copper
(b) nickel
(c) carbon - ANSWER(c)
If FCC iron has a denser structure than BCC iron, why does it have a higher solubility
for carbon? - ANSWERThe preferred site for carbon in BCC iron is smaller than that in
FCC iron.
If two metals have complete mutual solid solubility how many phases are formed in the
solid- one or two? - ANSWEROne
How many phases are there in a eutectic- one or two? - ANSWERTwo
Without referring to the text, draw the phase diagram for a eutectic system with limited
mutual solid solubility of the two components. - ANSWERRefer to Figure 6.6(Module
20-2014, page 18)
Using the portion of the iron-carbon phase diagram in Figure 6.10(Module 20-2014,
page 21), use the lever rule to determine the precentage of ferrite and eutectoid pearlite
present in a slowly cooled 0.2% carbon steel. - ANSWERAbout 25% pearlite and 75%
ferrite. Here the tie line begins at 0.0%C (α ferrite) and ends at 0.08%C (pearlite).
The fulcrum for the lever rule is at 0.2%C
% pearlite = (0.2%C - 0.0%C)/).8%C - 0.0%C) x 100%
% pearlite = (0.2/0.8) x 100%
% pearlite = 25%
Which of the following alloys would you expect to give the highest risk of hot cracking?
(a) Al-0.1%Cu
(b) Al-3%Cu
(c) Al-8%Cu - ANSWER(b)
If centerline solidification cracking is occuring in welding a structural steel what is a
likely cause?
(a) electrical extension too long
(b) arc voltage too high
(c) welding current and speed too high
(d) weld too large - ANSWER(c)
What is the most likely cause of porosity in aluminum welds?
(a) hydrogen
STUDY GUIDE 100% ACCURATE
Which of the following metals has the highest thermal conductivity?
(a) carbon steel
(b) stainless steel
(c) aluminum - ANSWER(c)
The Ellingham diagram
(a) is a plot of thermal conductivity against temperature,
(b) shows the free energy of oxide formation against temperature.
(c) shows the rate of oxidation of metals against temperature. - ANSWER(b)
True or False?
A metal with a high negative free energy of oxide formation will generally require greater
shielding from the atmosphere during welding. - ANSWERTrue
Electricity can be conducted by:
(a) atoms and electrons.
(b) electrons and ions.
(c) only ions. - ANSWER(b)
Which of the following elements is often present in submerged arc fluxes to improve arc
stability?
(a) copper
(b) potassium
(c) nickel
(d) tungsten - ANSWER(b)
Thoria is added to tunsten electrodes for what purpose? - ANSWERTo increase
thermionic emission by lowering the work function.
True or False?
All pure metals have the same crystal structure. - ANSWERFalse. Metals generally
have one of three basic structures.
Which crystal structure(s) is (are) composed of close-packed planes? - ANSWERFCC
and HCP
The real strength of metals is lower than the theoretical value because:
(a) real crystals always fracture along specific crystal planes.
(b) grain boundary sliding occurs.
(c) the presence of dislocations facilitates slip. - ANSWER(c)
, Multiplication and subsequent congestion of moving dislocations causes:
(a) elastic extension.
(b) work or strain hardening.
(c) a drop in the yield stress. - ANSWER(b)
Which of the following elements are most likely to form interstitial solid solutions?
(a) copper
(b) nickel
(c) carbon - ANSWER(c)
If FCC iron has a denser structure than BCC iron, why does it have a higher solubility
for carbon? - ANSWERThe preferred site for carbon in BCC iron is smaller than that in
FCC iron.
If two metals have complete mutual solid solubility how many phases are formed in the
solid- one or two? - ANSWEROne
How many phases are there in a eutectic- one or two? - ANSWERTwo
Without referring to the text, draw the phase diagram for a eutectic system with limited
mutual solid solubility of the two components. - ANSWERRefer to Figure 6.6(Module
20-2014, page 18)
Using the portion of the iron-carbon phase diagram in Figure 6.10(Module 20-2014,
page 21), use the lever rule to determine the precentage of ferrite and eutectoid pearlite
present in a slowly cooled 0.2% carbon steel. - ANSWERAbout 25% pearlite and 75%
ferrite. Here the tie line begins at 0.0%C (α ferrite) and ends at 0.08%C (pearlite).
The fulcrum for the lever rule is at 0.2%C
% pearlite = (0.2%C - 0.0%C)/).8%C - 0.0%C) x 100%
% pearlite = (0.2/0.8) x 100%
% pearlite = 25%
Which of the following alloys would you expect to give the highest risk of hot cracking?
(a) Al-0.1%Cu
(b) Al-3%Cu
(c) Al-8%Cu - ANSWER(b)
If centerline solidification cracking is occuring in welding a structural steel what is a
likely cause?
(a) electrical extension too long
(b) arc voltage too high
(c) welding current and speed too high
(d) weld too large - ANSWER(c)
What is the most likely cause of porosity in aluminum welds?
(a) hydrogen
