CWB level 3 Module 21 practice Questions with
100% Correct Answers
The maximum solubility of carbon in a iron is:
(a) 2%.
(b) 0.002%.
(c) 0.02%.
(d) There is no solubility. Correct Answer: (c) 0.02%.
True or false?
When a steel is heated into the austenite region, all
carbon and most other compounds dissolve
to form a single phase. Correct Answer: True
True or false?
Pearlite is a single phase. Correct Answer: False
What is the resulting structure of a 0.6% carbon steel
slowly cooled from 900°C to room
,temperature? Correct Answer: About 25% proeutectoid
ferrite and 75% pearlite
Most fine grain steels retain their fine grains: (
(a) up to the melting temperature.
(b) up to the grain coarsening temperature, but above
that behave as coarse grain steel. C
(c) only up to the transformation temperature. Correct
Answer: (b)
Why is martensite produced rather than pearlite when a
steel is rapidly quenched from, 900°C? Correct Answer:
Insufficient time for carbon to diffuse to form carbides
The hardness of martensite depends mainly on the:
(a) alloy content.
(b) rate of cooling.
(c) carbon content.
(d) size of the part. Correct Answer: (c)
, Can bainite normally be produced in continuous
cooling of a plain carbon steel? Correct Answer: No
Increasing the carbon content:
(a) lowers the martensite start temperature M.
(b) raises the M.
(c) has no effect on M. Correct Answer: (a) lowers the
martensite start temperature M.
Calculate the ideal critical diameter (hardenability) for
a steel with 0.2%C, 0.25%Si, 1
.0%Mn,
0.5%Cr, 0.5%Mo, 1.0%Ni (assume an initial grain size of
ASTM 8). Use section 2.5.3 and 2.5.4
as a reference. Correct Answer: 5.0
Using Figure 2.34, estimate the fastest rate a weld could
cool without the HAZ becoming
harder than 350 HV for a
100% Correct Answers
The maximum solubility of carbon in a iron is:
(a) 2%.
(b) 0.002%.
(c) 0.02%.
(d) There is no solubility. Correct Answer: (c) 0.02%.
True or false?
When a steel is heated into the austenite region, all
carbon and most other compounds dissolve
to form a single phase. Correct Answer: True
True or false?
Pearlite is a single phase. Correct Answer: False
What is the resulting structure of a 0.6% carbon steel
slowly cooled from 900°C to room
,temperature? Correct Answer: About 25% proeutectoid
ferrite and 75% pearlite
Most fine grain steels retain their fine grains: (
(a) up to the melting temperature.
(b) up to the grain coarsening temperature, but above
that behave as coarse grain steel. C
(c) only up to the transformation temperature. Correct
Answer: (b)
Why is martensite produced rather than pearlite when a
steel is rapidly quenched from, 900°C? Correct Answer:
Insufficient time for carbon to diffuse to form carbides
The hardness of martensite depends mainly on the:
(a) alloy content.
(b) rate of cooling.
(c) carbon content.
(d) size of the part. Correct Answer: (c)
, Can bainite normally be produced in continuous
cooling of a plain carbon steel? Correct Answer: No
Increasing the carbon content:
(a) lowers the martensite start temperature M.
(b) raises the M.
(c) has no effect on M. Correct Answer: (a) lowers the
martensite start temperature M.
Calculate the ideal critical diameter (hardenability) for
a steel with 0.2%C, 0.25%Si, 1
.0%Mn,
0.5%Cr, 0.5%Mo, 1.0%Ni (assume an initial grain size of
ASTM 8). Use section 2.5.3 and 2.5.4
as a reference. Correct Answer: 5.0
Using Figure 2.34, estimate the fastest rate a weld could
cool without the HAZ becoming
harder than 350 HV for a
