Download - phase degine
-
8/14/2019 phase degine
1/22
Chapter 9 - 1
ISSUES TO ADDRESS... When we combine iron and carbon what kinds of steels do we get?
In particular, if we specify the composition, what kinds ofmicrostructures are created & how do they control the properties
Steel is the most important structural material created by humans
so what is the terminology of the Fe-Fe3C diagram & microstructures
Chapter 9: Phase Diagrams III:
The Fe Fe3C Phase Diagram
Class 14 Chapter 9: Phase Diagrams Fe-Fe3C- Topic #5.3
What are these microstructures, how are they created, what are
their properties, and what applications are they used for?
-
8/14/2019 phase degine
2/22
Chapter 9 -
Fe Fe3C Phase Diagram
Concept Map
-
8/14/2019 phase degine
3/22
Chapter 9 -
Fe Fe3C Phase Diagram Cast Irons & Steels
-
8/14/2019 phase degine
4/22
Chapter 9 -
The Fe Fe3C Phase Diagram - Steels
Year 1781
Lower Tm;
higher %C
Year 1891
Higher Tm;
lower %C
Cast Irons
Steels
-
8/14/2019 phase degine
5/22
Chapter 9 -
The Worlds First First Cast Iron Bridge, 1-1-1781
Ironbridge, Shropshire, England
-
8/14/2019 phase degine
6/22
Chapter 9 -
Monadnock Building, 1891-1893 Chicago
The First Steel Skyscraper, AT Least of It Was
-
8/14/2019 phase degine
7/22
Chapter 9 -
Where is Pearlite & Where Does It Come From?
-
8/14/2019 phase degine
8/22
Chapter 9 -
Steel Microstructures The Big Picture
-
8/14/2019 phase degine
9/22
Chapter 9 - 9
Iron-Carbon (Fe-C) Phase Diagram and Steel Microstructures
2 importantpoints
- Eutectoid (B):
+Fe3C
- Eutectic (A):
L +Fe3C
Adapted from Fig. 9.24,
Callister & Rethwisch 8e.
Fe3
C
(cem
entite)
1600
1400
1200
1000
800
600
4000 1 2 3 4 5 6 6.7
L
(austenite)
+L
+Fe3C
+Fe3C
+
(Fe) C, wt% C
1148C
T(C)
727C = Teutectoid
4.30
Result: Pearlite =alternating layers of
and Fe3C phases
120 m
(Adapted from Fig. 9.27,
Callister & Rethwisch 8e.)
0.76
B
AL+Fe3C
Fe3C (cementite-hard)
(ferrite-soft)
-
8/14/2019 phase degine
10/22
Chapter 9 -
General Properties:
Ferrite - BCC Fe 0.2wt% C max. Fairly Soft.Austenite - FCC Fe can have more C. Ductile.Cementite Fe3C - Hard ceramic.
Terminology: YY XXX steel
First two or three numbers give steel alloy type
10xx is plain carbon steel (no alloy elements)
43xx is low alloy steel (.5-1% Ni, Cr, Mo)
Second 2 or 3 numbers give %C content x 100
YY80 has 0.80 wt% C
YY100 has 1.0 wt.% C
Steel Terminology & Phase Properties
727 C
-
8/14/2019 phase degine
11/22
Chapter 9 -
Eutectoid Steel Microstructure
-
8/14/2019 phase degine
12/22
Chapter 9 -
Hypoetutectoid Steel Microstructure Proeutectoid Ferrite + Pearlite
-
8/14/2019 phase degine
13/22
Chapter 9 -
Hyperetutectoid Steel Microstructure Proeutectoid Carbide + Pearlite
-
8/14/2019 phase degine
14/22
Chapter 9 -
.
..
Effect of C on Microstructure & Properties
-
8/14/2019 phase degine
15/22
Chapter 9 -
1060 (0.60wt% C) Hypoeutectoid Steel Microstructure: Te +1oC
proeutectoid ferritepearlite
100 mHypoeutectoid
steel
-
8/14/2019 phase degine
16/22
Chapter 9 -
1060 (0.60wt% C) Hypoeutectoid Steel Microstructure: Te -1oC
proeutectoid ferritepearlite
100 mHypoeutectoid
steel
-
8/14/2019 phase degine
17/22
Chapter 9 - 17
Hypereutectoid Steel
Fe3
C
(cementite)
1600
1400
1200
1000
800
600
4000 1 2 3 4 5 6 6.7
L
(austenite)
+L
+Fe3C
+Fe3C
L+Fe3C
(Fe) C, wt%C
1148C
T(C)
Adapted from Figs. 9.24
and 9.32,Callister &
Rethwisch 8e. (Fig. 9.24
adapted from Binary AlloyPhase Diagrams, 2nd
ed., Vol. 1, T.B.
Massalski (Ed.-in-Chief),
ASM International,
Materials Park, OH,
1990.)
(Fe-C
System)
0.76 C0
Fe3C
Adapted from Fig. 9.33, Callister & Rethwisch 8e.
proeutectoid Fe3C
60mHypereutectoidsteel
pearlite
pearlite
-
8/14/2019 phase degine
18/22
Chapter 9 -
Activity Identify and Describe Microstructural Components in
Steels that are Hypoeutectoid, Eutectoid, & Hypereutectoid
For each micrograph
identify each microstructural
component by:
1) Labeling each one,
2) Describing each one, &
3) Stating how each got there
Describe components & how they got there
Print labels and draw arrows
Describe components & how they got there Describe components & how they got there
Print labels and draw arrowsPrint labels and draw arrows
-
8/14/2019 phase degine
19/22
Chapter 9 -
Activity Drawing Steel Microstructures
Teutectoid + 1 C
Teutectoid - 1 C
727C
0.76
Describe how the microstructure developed
Teutectoid + 1 C Teutectoid + 1 C
Teutectoid - 1 C
Teutectoid - 1 C
Describe how the microstructure developed
Describe how the microstructure developedDescribe how the microstructure developed
Describe how the microstructure developed
Describe how the microstructure developed
1020 steel
727C
1076 steel 10120 steel
-
8/14/2019 phase degine
20/22
Chapter 9 - 20
The phase diagram of steel helps explain microstructure & properties:
-- number and types of phases present,
-- composition of each phase,
-- weight fraction of each phase
Given the temperature and composition of the system.
The microstructures and associated properties of steel depend on
-- its composition, and
-- the manner in which it was cooled.
For steel the most important phase transformation is the eutectoid
Summary
Steels with %C less thatn, equal to, and greater than the euectoidcomposition are call hypoeutectoid, eutectoid, & hypereutectoid
The microstructure of hypoeutectid steels contain proeutecoid ferrite &
the microstructure of hypereuteoid steels contain proeutectoid carbide &
the microstructure of eutectoid steel contains pearlite
-
8/14/2019 phase degine
21/22
Chapter 9 -
Homework #14 Fe Fe3C Phase Diagram Phases and Microstructures
1. For a 0.30 wt% C steel (1030) at 728C and then at 726C, identify the phases present, the chemical composition of each
phase, the fraction of each phase, and draw the microstructure and label the components of the microstructure.
2. For a 1.20 wt% C steel (10120) at 728C and then at 726C, identify the phases present, the chemical composition of each
phase, the fraction of each phase, and draw the microstructure and identify the components of the microstructure
3. The microstructure of the reinforcing rod of Frank Lloyds Fallingwater house in Pennsylvania was studied and is shown
at the right. Specify the microstructural components present and the wt% C in the steel.
4. The properties of steels are controlled by the carbon content, the alloy content, and the thermal treatment. When a steel
is cooled faster from the gamma (austenite region) below the eutectoid temperature,the lamellar, alternating platelets of
ferrite and carbide in pearlite get thinner and are more closely spaced. Why do you think that this is so? What do youthink will happen to the strength and ductility of the steel which has been cooled faster and why do you think that is so?
-
8/14/2019 phase degine
22/22
Chapter 9 -
Points of Reflection on Todays Class
Please briefly describe your insights on the following points from todays class.
Point of Interest: Describe what you found most interesting in todays class.How Interesting? (circle) Little Bit 1 2 3 4 5 Very Much
Muddiest Point: Describe what was confusing or needed more detail.How Muddy? (circle) Little Bit 1 2 3 4 5 Very Much
Learning Point: Describe what you learned about how you learn?
Letter + 4 digit number ______________ F M
Class Topic: _______________________Date: ________________
22