Question

Temperatura (°C) 2.- The following figure shows the ITT and CTT diagrams corresponding to an eutectoid steel: 900 y 800 A 700 14 600 P ? P 38 P+ 500 40 400 B 42 B Bf 300 52 Mi 200 57 Mf M+Yu 100 (d) (c) (b) (a) 66 M M 0 0.1 1 10 102 103 104 105 106 Tiempo (s) a) (2.5 points) A steel wire is cooled from 800 °C down to room temperature with the cooling rates described by curves (a), (b), (c) and (d) of the diagram. Describe the resulting microstructures. What differences in microstructural and mechanical properties are there if they are cooled by treatment (a) and (b)? b) (2.5 points) Indicates the critical cooling rate of the steel c) (2.5 points) If 9% Mn is added, how is the diagram modified? And if 12% Cr is added instead of Mn? d) (2.5 points) Describe the simplest heat treatment to carry out the following transformations and indicate the name of the treatment: i. Pearlite ? Bainite ii. Martensite ? Pearlite iii. Martensite ? Ferrite + Spheroidal Cementite (Spheroidite) iv. Bainite ? Martensite (100%) (without stress) Dureza Rockwell C

          Temperatura (°C)
2.- The following figure shows the ITT and CTT diagrams corresponding to an eutectoid
steel:
900
y
800
A
700
14
600
P
?
P
38
P+
500
40
400
B
42
B
Bf
300
52
Mi
200
57
Mf
M+Yu
100
(d)
(c)
(b)
(a)
66
M
M
0
0.1
1
10
102
103
104
105
106
Tiempo (s)
a) (2.5 points) A steel wire is cooled from 800 °C down to room temperature with the
cooling rates described by curves (a), (b), (c) and (d) of the diagram. Describe the
resulting microstructures. What differences in microstructural and mechanical
properties are there if they are cooled by treatment (a) and (b)?
b) (2.5 points) Indicates the critical cooling rate of the steel
c) (2.5 points) If 9% Mn is added, how is the diagram modified? And if 12% Cr is added
instead of Mn?
d) (2.5 points) Describe the simplest heat treatment to carry out the following
transformations and indicate the name of the treatment:
i. Pearlite ? Bainite
ii. Martensite ? Pearlite
iii. Martensite ? Ferrite + Spheroidal Cementite (Spheroidite)
iv. Bainite ? Martensite (100%) (without stress)
Dureza Rockwell C

Temperatura (°C)
2.- The following figure shows the ITT and CTT diagrams corresponding to an eutectoid
steel:
900
y
800
A
700
14
600
P
?
P
38
P+
500
40
400
B
42
B
Bf
300
52
Mi
200
57
Mf
M+Yu
100
(d)
(c)
(b)
(a)
66
M
M
0
0.1
1
10
102
103
104
105
106
Tiempo (s)
a) (2.5 points) A steel wire is cooled from 800 °C down to room temperature with the
cooling rates described by curves (a), (b), (c) and (d) of the diagram. Describe the
resulting microstructures. What differences in microstructural and mechanical
properties are there if they are cooled by treatment (a) and (b)?
b) (2.5 points) Indicates the critical cooling rate of the steel
c) (2.5 points) If 9% Mn is added, how is the diagram modified? And if 12% Cr is added
instead of Mn?
d) (2.5 points) Describe the simplest heat treatment to carry out the following
transformations and indicate the name of the treatment:
i. Pearlite ? Bainite
ii. Martensite ? Pearlite
iii. Martensite ? Ferrite + Spheroidal Cementite (Spheroidite)
iv. Bainite ? Martensite (100%) (without stress)
Dureza Rockwell C

Added by Jessica S.

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