METALS
Composition and Microstructure
Ferrous Metals and Alloys
Non-Ferrous Metals and Alloys
Specifications and Proof Testing
Corrosion
Composition and
Microstructure
Metal: element that readily loses
electrons to form positive ions,
characterized by high electrical
conductivity and malleable
Alloy: combinations of metals in a
crystalline structure
Structure of Metals
Microstructural
properties determine
all of the material
properties of metals
and alloys.
Different from
Covalent and Ionic
Bonds
Alloying Structure
3-D lattice in metalic bonds provides


opportunity for other element to occupy
some of the positions.
or for small element to enter the lattice
Interstitial Alloy
Between atomic
lattice location
< 60% of the size
of the lattice atoms
only a small % can
fit interstitially
For Transition metals
only a few fit
H, B, C, N
Substitutional Alloy
Replacing elements in
the lattice
+ 15% radius of lattice
atoms
large percentage is
possible
 Alloys may contain both
interstitial and
substitutional elements
Forming a Crystalline
Structure
Liquid: large degree of disorder
Freezing Point: order begins to form
Grain Initiation: initiation energy
Solidification: ordered lattice structures form
Grain Boundary: separate lattices collide
FCC:BCC or FCC:FCC with different angle
Forming a Crystalline
Structure
Grain Structure:
each grain has its
own lattice structure
(FCC, BCC, HCP).
Introduction to Steel
Production
Commercial Forms
Applications
Microstructure
Strengthening Mechanisms
Corrosion
Metal Processing
Crushing and Calcining, or Separation
Extraction

Smelting
 Ore is melted and separated in solution

Electrolytic processing
 electric furnace or process is used to separate
metal

Leaching (liquid processing)
 metal is recovered from leachate
Ferrous Metals
principle element is iron, cast iron,
steel, wrought iron.
Metals come from ore, "minerals" ore
consists of metal and gangue (valueless
extra)
Mining


open pit
underground
Refining the Metal
Refining the Metal




oxidizing impurities
distillation
chemical agents
electrolysis
Iron Production
Blast Furnace


Reduces iron ore
to metal
Separates metal
from impurities
Molten Iron
Slag
Processing of Virgin Steel
1) first step in reducing iron ore,
2) separates impurities
3) absorbs carbon (leaves 2.5 - 4.5 %
carbon)
End product is cast in bars, "pigs".
Ferrous Metals
Pig Iron

Iron ore is combined with coke, and
limestone (fluxing agent). Blasts of
hot air are forced through the
material to ignite the coke and melt
the iron ore. The impurities in the
iron are absorbed by the limestone
and forms blast furnace slag.
Forms of Ferrous Alloys
Cast Iron

cast iron is pig iron is any other shape.
Remelted and cast into desired shape.
Malleable Cast Iron

annealed (heating then slow cooling to
encourage refined grains and soften
mechanical properties, removes internal
stresses, removes gases) cast iron that has
been made more ductile and formable.
Forms of Ferrous Alloys
Wrought Iron

a form of iron that contains slag, and
virtually no carbon. making it workable
when it is hot but hardens very rapidly
when cooled rapidly.
Ingot Iron

low carbon steel or iron cast from a molten
state.
Forms of Ferrous Alloys
Steel


Iron - Carbon alloy which is cast from a
molten mass in a form which is malleable.
Carbon steel is steel with less than 1.5%
carbon. Alloy steel is steel which has
properties controlled by elements other
than carbon.
Steel has the best structural properties of
these materials
Carbon Steels
Carbon steels have between .008 and 1.7
percent C (most are between 0.1 and 0.8%)
Carbon may be substitutional or interstitial
depending upon the amount present
Alloys with greater than 1.7 percent carbon
become very brittle and hard, i.e. cast iron
properties.
Phase Diagrams
Phase Diagrams relate the


composition & temperature
to the
crystalline structure (“phase”)
Inverse Lever Law

determines the percentage of each
crystalline phase
Two Component (Binary) Phase Diagram for
Temperature, °C
completely soluble elements or compounds
Melting
Temperature of A
Liquid
Components
Liquid +
Solida
Solid a
Melting Temperature of B
Percent A by weight 0
10
20
30
40
50
60
70
80
90
100
Percent B by weight 100
90
80
70
60
50
40
30
20
10
0
Two Component (Binary) Phase
Diagram: Ni - Cu
1700
Nickel - Copper Alloy
Temperature, °C
1600
Liquid
1500
Liquidus Line
1455°C
1400
1300
Liquid +
Solida
1200
Solid a
Solidus Line
1100
1084°C
1000
Percent Ni by weight 0
10
20
30
40
50
60
70
80
90
100
Percent Cu by weight 100
90
80
70
60
50
40
30
20
10
0
Binary Phase Diagram for
Temperature. °C
insoluble elements or compounds
Liquid A + B
Liquid + A
Liquid + B
Solid A + B
Composition of A
Actual atomic form will depend
on the composition of formation
(will discuss later for steel)
Composition of B
Definitions
Eutectic Reaction –
Eutectic Point –
Eutectic Solid –
Water - NaCl Phase Diagram
15
10
Temperature. °C
5
Liquid – Brine (Water + Dissolved NaCl)
0
-5
Eutectic Point
-10
Salt +
Brine
Ice + Brine
-15
-20
-25
Ice + Salt
-30
0
-21 oC (-5.8°F)
5
10
15
Weight Percent NaCl
20
25
23.3%
30
Binary Phase Diagram for
partially soluble elements or compounds
Temperature. °C
Liquid
Eutectic Point
a + Liquid
b + Liquid
b
a
Solid a + b
Composition of A
Composition of B
Lead-Tin Phase Diagram
350
327°C
Liquid
250
a
232°C
Liquid + a
b
200
19.2%
150
97.5%
61.9%
183°C
100
a+b
50
Percent Tin
100
90
80
70
60
50
40
30
20
10
0
0
Temperature, °C
300
Definitions
Eutectoid Reaction –
Eutectoid Point –
Eutectoid –
Steps to Analyzing a Phase Diagram
1. Determine the phase/phases present at the point
(composition vs. temperature)
2. The mass percentage composition of each phase at the
point can be determined by the drawing a horizontal
through the point for the length of the entire region.
3. The intersection of the horizontal line and a line on the
phase diagram defines the composition of the solution.
A Point with 2 Phases
4. If the point is located in a region with
more 2 phases, the mass percentage of
each phase within the region can be
determined by the inverse lever law.
Inverse Lever Law
Inverse Lever Law
(Derivation on pgs 56 + 57 of text)
The mass percentage of a phase present in a two phase
region is the length along the “tie line” portion from the
state point to the other phase region divided by the total
“tie line” length. Compositions are used as a measure of
length.
State Point
y
Phase I + Phase II Region
(e.g. Solid + Liquid)
Phase II Region
(e.g. Liquid)
Mass percentage of Phase II
In the two-phase region:
x/(x+y)
x
Phase I Region
(e.g. Solid)
Mass percentage of Phase I
in the two-phase region:
y/(x+y)
Example: Ni-Cu
For a 1000 kg block of Ni-Cu metal at a defined
state point of 53% Nickel and 47% Copper at
1300 oC, determine the following:
Compositions (%) of both the liquid and solid
phases
Mass percentages of the liquid and solid phases
The mass of Nickel in the Liquid Phase
Example: Ni - Cu
1700
Nickel - Copper Alloy
Temperature, °C
1600
1500
Liquid
Liquid +
Solida
State Point 53% Ni, 47 % Cu
1400
1300
1200
Solid a
1100
1000
Percent Ni by weight 0
10
20
30
40
50
60
70
80
90
100
Percent Cu by weight 100
90
80
70
60
50
40
30
20
10
0
Phase diagram for Fe-C
Cementite:



above 4.35 to 6.67
very hard and brittle alloy forms
6.67% Carbon 93.33% Iron "iron carbide"
Ferrite:

iron which contains very little carbon. this
is soft ductile material
Phase diagram for Fe-C
Pearlite:


combination of ferrite and cementite
structures
intermediate property structure
Austinite:

solid state gamma phase iron-carbon
combination.
Phase Diagram for C-Fe
Microstructure
Phases of Steel




Ferrite (BCC)
Austenite (FCC)
Cementite (Orthorhombic)
Delta Iron (BCC)
Grain Size
Time-Temperature-Transition Curves
Critical Temp.
Fine
Pearlite
Coarse
Pearlite
Bainite
Martinsite
Heat Treatments
Annealing



heated above critical temperature and
cooled slowly
softens structure
Quenching



heated above critical temperature and
cooled rapidly in water or oil
improves hardness and strength
Heat Treatments
Tempering





heated below critical temperature,
held and
quenched
improves ductility and toughness
while retaining hardness
Mild Steel Grades
A992 “Low Alloy” Carbon Steel



<0.23% Carbon
Common Structural Sections
Replaced A36 steel
A 572 “High-Strength Low-Alloy
Columbium-Vanadium Steel”


Grades 42, 50, 60, 65
Structural sections and bolts.....
Mild Steel Grades
A 615 Billet Reinforcing Steel


low alloy, high ductility steel
reinforcing bars
A588 Weathering Steel


should not be used in Cl water
environments
Free from moisture 40% of the time;
avoid extreme humid environments
Corrosion
Oxidation of metal requires




oxygen,
water,
two different metals connected electrically
electrolyte
Corrosion
Major problem with steel
Control Methods




Protective Coatings
Galvanic Protection
Cathodic Protection
Corrosion-resistant Steels
S-N Curve
1
0.9
0.8
0.7
0.6
%Fy 0.5
0.4
0.3
0.2
0.1
0
10
1000
100000
Number of Cycles to Failure
Strengthening Mechanisms
Alloying
Heat Treating
Cold Working
Alloying
Forming Solid Solution with Iron

Carbon, Chromium, Manganese, Nickel,
Copper, and Silicon
Formation of Carbide

Titanium, Vanadium, and Molybdenum
Formation of an Undissolved, second
phase

Lead, Sulfur, and Phosphorus
Heat Treatments
Full Annealing
Process Annealing
Normalizing
Quenching
Cold Working
Plastic deformation
Done below recrystallization
temperature
Other Properties of Steel
Impact

resistance to dynamic loadings (toughness)
Creep

time dependent deformation due to
sustained loads
Ductility


mild steels may yield at  = 0.002 and
fracture at  > 0.200
Forms of Steel
Structural Shapes




Wide flange sections,
Channels,
Tubing,
Plate
Reinforcing Steel
Cold Rolled forms, pans, sheet
Pipe
Structural Grades
ASTM



A36 & A 572 (being phased out)
A992 Structural Shapes
A325 Bolts
AISI - SAE

10XX
 XX defines Carbon content

13XX
 13 defines a manganese alloy steel
Applications
Structural Members
Bolts, Connectors
Reinforcement
Tools
Machines
Steel Grades
ASTM
Grade
A36
36
A 500
50
A 572
42
50
60
65
A 588
50
A 615
60
A 616
60
Physical Reqmnts
Chemical Reqmnts
Comments
Low Carbon Structural Steel
<.26C <.40Si Mn, P, S, Cu
General purpose
8”=20% Fu=58-80
Cold Form Tubing w/ maximum perifery of 1.6 m; t <16mm
<.30C (Mn, P, S, Cu)
General Purpose
2”=21% Fu>60
High-Strength Low-Alloy Columbium (Nb)-Vanadium (V )Steel
<.21C <1.35Mn Si,P,S,V,Nb Rivet, Bolt, Weld
8”=20% Fu=60
Building&Bridge
<.23C <1.35Mn,Si
Rivet, Bolt, Weld
8”=18% Fu=65
Building&Bridge
<.26C <1.35Mn,Si
Rivet, Bolt Bridge;
8”=16% Fu=75
Weld Building
<.26C <1.35Mn,Si
Rivet, Bolt Bridge;
8”=15% Fu=80
Weld Building;
High-Strength Low-Alloy Structural Steel (Weathering Steel)
Billet Reinforcing Steel
Fu=90
8”=8%
Rail Reinforceing Steel
Fu=90
<.C
8”=4.5
%