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CERAMIC
Ceramic items are made of clay. The composition and type of fire on the clay, determines what type of
ceramic you have. There are three types, pottery, stoneware or porcelain. Here is a list of characteristics
of each.
1. Pottery
Pottery, also known as earthenware is a porous, lightweight material. While larger piece can get very
heavy, lightweight refers to the strength of the material. Pottery is easily scratched and has a grainy
texture. This is why it is used mainly for plants, bowls or vases. While plates can be made of pottery,
these should be mainly for show. If you have to cut any food on your pottery plate, the plate will be
scratched by the knife. Because of pottery's composition, it is easy to manipulate. This is why many
people spin pottery as a hobby, making all sorts of items.
2. Ironstone
Ironstone, or stoneware, is a heavier material. It is nonporous, which gives it a fine-grain. If these pieces
are left unfired, they can be very casual or rugged, and used for big pots or jugs. When ironstone is fired
it is very smooth. You can use it for large cooking dishes or delicate plates and candy jars. It is very
difficult to scratch with a knife.
3. Porcelain
Porcelain is widely used as plate. Its nonporous and glassy structure makes it impossible to scratch with
a knife. Depending on the style and fire on a porcelain plate, it is probably called china. We used to call
plates china only if they originated from China. But, now, it is a common term, like Kleenex, to describe a
type of dish ware. Porcelain is a moderate weight. This give it an advantage as well for dishes, so that
everyone can pick them up and move them from place to place.
figure
Ceramic Properties
What is a Ceramic ?
The properties of ceramic materials, like all materials, are dictated by the types of atoms present,
the types of bonding between the atoms, and the way the atoms are packed together. This is
known as the atomic scale structure. Most ceramics are made up of two or more elements. This is
called a compound. For example, alumina (Al2O3), is a compound made up of aluminum atoms
and oxygen atoms.
The atoms in ceramic materials are held together by a chemical bond. The two most common
chemical bonds for ceramic materials are covalent and ionic. For metals, the chemical bond is
called the metallic bond. The bonding of atoms together is much stronger in covalent and ionic
bonding than in metallic. That is why, generally speaking, metals are ductile and ceramics are
brittle. Due to ceramic materials wide range of properties, they are used for a multitude of
applications. In general, most ceramics are:
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hard,
wear-resistant,
brittle,
refractory,
thermal insulators,
electrical insulators,
nonmagnetic,
oxidation resistant,
prone to thermal shock, and
chemically stable.
What to do after BE in metallurgy?
A metallurgist can pursue his education further to M.Tech/M.E. and even can take up a Phd. in a
particular subject. Besides that jobs in industries, research institutes and laboratories can also be...
What is iron metallurgy?
The science of metal iron and its alloys is called iron metallurgy.
What is metallurgy?
Metallurgy is the art of working metals, comprehending the whole process of separating them from
other matters in the ore, smelting, refining, and parting them; sometimes, in a narrower sense, only...
What is primary metallurgy?
Primary Metallurgy is the science of extraction of metals from ores & minerals. If there are more than
one ways of extracting a metal from its ore or mineral, then the process which gives a more...
VANDER WAALS BOND
Van der Waals force
From Wikipedia, the free encyclopedia
In physical chemistry, the van der Waals force (or van der Waals interaction), named after
Dutch scientist Johannes Diderik van der Waals, is the attractive or repulsive forces between
molecules (or between parts of the same molecule) other than those due to covalent bonds or to
the electrostatic interaction of ions with one another or with neutral molecules.[1] The term
includes:
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force between two permanent dipoles (Van der Waals-Keesom force)
force between a permanent dipole and a corresponding induced dipole (Van der WaalsDebye force)
force between two instantaneously induced dipoles (London dispersion force or Van der
Waals-London force)
It is also sometimes used loosely as a synonym for the totality of intermolecular forces. Van der
Waals forces are relatively weak compared to normal chemical bonds, but play a fundamental
role in fields as diverse as supramolecular chemistry, structural biology, polymer science,
nanotechnology, surface science, and condensed matter physics. Van der Waals forces define the
chemical character of many organic compounds. They also define the solubility of organic
substances in polar and non-polar media. In low molecular weight alcohols, the properties of the
polar hydroxyl group dominate the weak intermolecular forces of van der Waals. In higher
molecular weight alcohols, the properties of the nonpolar hydrocarbon chain(s) dominate and
define the solubility. Van der Waals-London forces grow with the length of the nonpolar part of
the substance.
Contents
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1 Definition
2 Calculation
3 London dispersion force
4 Use by animals
5 Footnotes
6 References
7 External links
Definition
Van der Waals forces include attractions between atoms, molecules, and surfaces. They differ
from covalent and ionic bonding in that they are caused by correlations in the fluctuating
polarizations of nearby particles (a consequence of quantum dynamics).
Intermolecular forces have four major contributions. In general an intermolecular potential has a
repulsive component (which prevents the collapse of molecules because of the Pauli exclusion
principle). It also has an attractive component, which, in turn, consists of three distinct
contributions:
1. The electrostatic interactions between charges (in the case of molecular ions), dipoles (in
the case of molecules without inversion center), quadrupoles (all molecules with
symmetry lower than cubic), and in general between permanent multipoles. The
electrostatic interaction is sometimes called the Keesom interaction or Keesom force after
Willem Hendrik Keesom.
2. The second source of attraction is induction (also known as polarization), which is the
interaction between a permanent multipole on one molecule with an induced multipole on
another. This interaction is sometimes measured in debyes after Peter J.W. Debye.
3. The third attraction is usually named after Fritz London who himself called it dispersion.
This is the only attraction experienced by non-polar atoms, but it is operative between
any pair of molecules, irrespective of their symmetry.
Returning to nomenclature, different texts refer to different things using the term "van der Waals
force". Some texts mean by the van der Waals force the totality of forces (including repulsion);
others mean all the attractive forces (and then sometimes distinguish van der Waals-Keesom, van
der Waals-Debye, and van der Waals-London); finally, some use the term "van der Waals force"
solely as a synonym for the London/dispersion force.[clarification needed] A common trend is that
biochemistry and biology books, more frequently than chemistry books, use "van der Waals
forces" as a synonym for London forces only.
All intermolecular/van der Waals forces are anisotropic (except those between two noble gas
atoms), which means that they depend on the relative orientation of the molecules. The induction
and dispersion interactions are always attractive, irrespective of orientation, but the electrostatic
interaction changes sign upon rotation of the molecules. That is, the electrostatic force can be
attractive or repulsive, depending on the mutual orientation of the molecules. When molecules
are in thermal motion, as they are in the gas and liquid phase, the electrostatic force is averaged
out to a large extent, because the molecules thermally rotate and thus probe both repulsive and
attractive parts of the electrostatic force. Sometimes this effect is expressed by the statement that
"random thermal motion around room temperature can usually overcome or disrupt them"
(which refers to the electrostatic component of the van der Waals force). Clearly, the thermal
averaging effect is much less pronounced for the attractive induction and dispersion forces.
The Lennard-Jones potential is often used as an approximate model for the isotropic part of a
total (repulsion plus attraction) van der Waals force as a function of distance.
Van der Waals forces are responsible for certain cases of pressure broadening (van der Waals
broadening) of spectral lines and the formation of van der Waals molecules. The London-van der
Waals forces are related to the Casimir effect for dielectric media, the former being the
microscopic description of the latter bulk property. The first detailed calculations of this were
done in 1955 by E. M. Lifshitz.[2][3]
Calculation
London dispersion force
Main article: London dispersion force
London dispersion forces, named after the German-American physicist Fritz London, are weak
intermolecular forces that arise from the interactive forces between instantaneous multipoles in
molecules without permanent multipole moments. London dispersion forces are also known as
dispersion forces, London forces, or induced dipole–dipole forces.
[edit] Use by animals
Gecko climbing glass using its natural setae
The ability of geckos - which can hang on a glass surface using only one toe - to climb on sheer
surfaces has been attributed to van der Waals force,[4][5] although a more recent study suggests
that water molecules of roughly monolayer thickness (present on virtually all natural surfaces)
also play a role.[6] Efforts continue to create a dry glue that exploits this knowledge.
[edit] Footnotes
1. ^ International Union of Pure and Applied Chemistry (1994). "Van der Waals forces".
Compendium of Chemical Terminology Internet edition.
2. ^ IE Dzyaloshinskii, EM Lifshitz, LP Pitaevskii: GENERAL THEORY OF VAN DER
WAALS' FORCES
3. ^ For further investigation, one may consult the University of St. Andrews' levitation
work in a popular article: Science Journal: New way to levitate objects discovered, and in
a more scholarly version: New Journal of Physics: Quantum levitation by left-handed
metamaterials, which relate the Casimir effect to the gecko and how the reversal of the
Casimir effect can result in physical levitation of tiny objects.
4. ^ http://www.clemson.edu/newsroom/articles/2009/august/geckos.php5
5. ^ Kellar Autumn; Metin Sitti ; Yiching A. Liang; Anne M. Peattie; Wendy R. Hansen;
Simon Sponberg; Thomas W. Kenny; Ronald Fearing; Jacob N. Israelachvili; Robert J.
Full. Evidence for van der Waals adhesion in gecko setae. Proceedings of the National
Academy of Sciences of the USA 2002, 99, 12252–12256. doi:10.1073/pnas.192252799
6. ^ G. Huber, H. Mantz, R. Spolenak, K. Mecke, K. Jacobs, S. N. Gorb, and E. Arzt.
Evidence for capillarity contributions to gecko adhesion from single spatula
nanomechanical measurements. Proceedings of the National Academy of Sciences of the
USA 2005, 102, 16293–16296. doi:10.1073/pnas.0506328102
[edit] References
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Iver Brevik, V. N. Marachevsky, Kimball A. Milton, Identity of the Van der Waals Force
and the Casimir Effect and the Irrelevance of these Phenomena to Sonoluminescence,
hep-th/9901011
I. D. Dzyaloshinskii, E. M. Lifshitz, and L. P. Pitaevskii, Usp. Fiz. Nauk 73, 381 (1961)
o English translation: Soviet Phys. Usp. 4, 153 (1961)
L. D. Landau and E. M. Lifshitz, Electrodynamics of Continuous Media, Pergamon,
Oxford, 1960, pp. 368–376.
Mark Lefers, "Van der Waals dispersion force". Holmgren Lab.
E. M. Lifshitz, Zh. Eksp. Teor. Fiz. 29, 894 (1955)
o English translation: Soviet Phys. JETP 2, 73 (1956)
Western Oregon University's "London force". Intermolecular Forces. (animation)
J. Lyklema, Fundamentals of Interface and Colloid Science, page 4.43
[edit] External links

Senese, Fred (1999). "What are van der Waals forces?". Frostburg State University.
Retrieved March 2010. An introductory description of the van der Waals force (as a sum
of attractive components only)
[hide]
v•d•e
Chemical bonds
Intramolecular Covalent bonds
Sigma bond · Pi bond · Delta
("strong")
bond
Double bond · Triple bond ·
Quadruple bond · Quintuple
bond · Sextuple bond
3c-2e · 3c-4e · 4c-2e
Agostic bond · Bent bond ·
Dipolar bond · Pi backbond
Conjugation ·
Hyperconjugation ·
Aromaticity · Hapticity ·
Antibonding
Ionic bonds
Cation-pi bond · Salt bond
Metallic bonds
Metal aromaticity
Hydrogen bond
Dihydrogen bond ·
Dihydrogen complex ·
Low-barrier hydrogen
bond · Symmetric
hydrogen bond
Other noncovalent
van der Waals force ·
London dispersion force ·
Mechanical bond ·
Halogen bond ·
Aurophilicity ·
Intercalation · Stacking ·
Entropic force · Chemical
polarity
Intermolecular
("weak")
Updated 06/24/10
DIS Meetings - 2010 Fall Meeting, October 27-29, 2010
Ductile Iron Data for Design Engineers
Download Ductile Iron Data
TABLE OF CONTENTS
PREFACE
I. FORWARD
II. INTRODUCTION
III. ENGINEERING DATA
A. Introduction (p. 1)
B. Tensile Properties (p.1&2)
C. Other Mechanical (p.2)
D. Physical Properties (p.2)
E. References (p.2)
IV AUSTEMPERED DUCTILE
IRON
V. ALLOY DUCTILE IRONS
A. Introduction
B. Silicon-Molybdenum Ductile
Irons
C. Austenitic Ductile Irons
D. References
VI. MACHINABILITY
VII HEAT TREATMENT
VIII WELDING, BRAZING AND
BONDING
A. Welding
B. Brazing
C. References
IX SURFACE TREATMENTS
X DESIGNING WITH DUCTILE
IRON
XI ORDERING CASTINGS
XII SPECIFICATIONS
XIII SEARCH (Index)
Search (Index)
SECTION 2. INTRODUCTION
The Casting Advantage
Design Flexibility
Reduced Costs
Materials Advantages
Cast Iron: The Natural Composite
Types of Cast Irons
History of Ductile Iron
The Ductile iron Advantage
The Ductile Iron Family
A Matter of Confidence
References
The Casting Advantage
The casting process has been used for over 5000 years to produce both
objects of art and utilitarian items essential for the varied activities of
civilization. Why have castings played such a significant role in man's diverse
activities? For the artist, the casting process has provided a medium of
expression which not only imposed no restrictions on shape, but also
faithfully replicated every detail of his work, no matter how intricate.
Designers use the same freedom of form and replication of detail to meet the
basic goal of industrial design - the matching of form to function to optimize
component performance. In addition to design flexibility, the casting process
offers significant advantages in cost and materials selection and
performance.
Back to Top
Design Flexibility
The design flexibility offered by the casting process far exceeds that of any
other process used for the production of engineering components. This
flexibility enables the design engineer to match the design of the component
to its function. Metal can be placed where it is required to optimize the load
carrying capacity of the part, and can be removed from unstressed areas to
reduce weight. Changes in cross-section can be streamlined to reduce stress
concentrations. The result? Both initial and life-cycle costs are reduced
through material and energy conservation and increased component
performance.
Designer engineers can now optimize casting shape and performance with
increased speed and confidence. Recent developments in CAD/CAM, solid
modelling and finite element analysis (FEA) techniques permit highly
accurate analyses of stress distributions and component deflections under
simulated operating conditions. In addition to enhancing functional design,
the analytical capabilities of CAD/CAM have enabled foundry engineers to
maximum casting integrity and reduce production costs through the
optimization of solidification behaviour.
Back to Top
Reduced Costs
Castings offer cost advantages over fabrications and forgings over a wide
range of production rates, component size and design complexity. The
mechanization and automation of casting processes have substantially
reduced the cost of high volume castings, while new and innovative
techniques such as the use of styrofoam patterns and CAD/CAM pattern
production have dramatically reduced both development times and costs for
prototype and short-run castings. As confidence in FEA techniques
increases, the importance of prototypes, often in the form of fabrications
which "compromise" the final design, will decrease and more and more new
components will go directly from the design stage to the production casting.
As shown in Figure 2. 1, as component size and complexity increase, the
cost per unit of weight of fabricated components can rise rapidly, while those
of castings can actually decrease due to the improved castability and higher
yield of larger castings. Near net shape casting processes and casting
surface finishes in the range 50-500 microinches minimize component
production costs by reducing or eliminating machining operations.
Replacement of a multi-part, welded and/or fastened assembly by a casting
offers significant savings in production costs. Inventory costs are reduced,
close-tolerance machining required to fit parts together is eliminated,
assembly errors cannot occur, and engineering, inspection and administrative
costs related to multi-part assemblies are reduced significantly. A recent
study by the National Center for Manufacturing Sciences (NCMS) has shown
that in certain machine tool applications, the replacement of fabricated
structures by Ductile Iron castings could result in cost savings of 39-50%.
Commenting on the NCMS study, Mr. Gary Lunger, President of Erie Press
Inc., stated:
"We make huge presses and we have relatively clear specifications for what
goes into each press. We have been able to use Ductile Iron as a substitute
material primarily for cylinders and other parts at a significant cost saving
over cast or fabricated steel."
Back to Top
Materials Advantages
Castings offer advantages over forgings in isotropy of properties and over
fabrications in both isotropy and homogeneity. The deformation processes
used to produce forgings and plate for fabrications produce laminations which
can result in a significant reduction in properties in a direction transverse to
the lamination. In fabricated components, design complexity is usually
achieved by the welding of plate or other wrought shapes. This method of
construction can reduce component performance in two ways. First, material
shape limitations often produce sharp corners which increase stress
concentrations, and second, the point of shape change and stress
concentration is often a weld, with related possibilities for material weakness
and stress-raising defects. Figure 2.2 shows the results of stress analysis of
an acrylic joint model in which the stress concentration factor for the weld is
substantially higher than for a casting profiled to minimize stress
concentration.
Back to Top
Cast Iron: The Natural Composite
Iron castings, as objects of art, weapons of war, or in more utilitarian forms,
have been produced for more than 2000 years. As a commercial process, the
production of iron castings probably has no equal for longevity, success or
impact on our society. In a sense, the iron foundry industry produces an
invisible yet vital product, since most iron castings are further processed,
assembled, and then incorporated as components of other machinery,
equipment, and consumer items.
The term "cast iron" refers not to a single material, but to a family of materials
whose major constituent is iron, with important amounts of carbon and
silicon, as shown in Figure 2.3. Cast irons are natural composite materials
whose properties are determined by their microstructures - the stable and
metastable phases formed during solidification or subsequent heat treatment.
The major microstructural constituents of cast irons are: the chemical and
morphological forms taken by carbon, and the continuous metal matrix in
which the carbon and/or carbide are dispersed. The following important
microstructural components are found in cast irons.
Graphite
This is the stable form of pure carbon in cast iron. Its important physical
properties are low density, low hardness and high thermal conductivity and
lubricity. Graphite shape, which can range from flake to spherical, plays a
significant role in determining the mechanical properties of cast irons. Figures
2.4 and 2.5 show that graphite flakes act like cracks in the iron matrix, while
graphite spheroids act like "crackarresters", giving the respective irons
dramatically different mechanical properties.
Carbide
Carbide, or cementite, is an extremely hard, brittle compound of carbon with
either iron or strong carbide forming elements, such as chromium, vanadium
or molybdenum. Massive carbides increase the wear resistance of cast iron,
but make it brittle and very difficult to machine. Dispersed carbides in either
lamellar or spherical forms play in important role in providing strength and
wear resistance in as-cast pearlitic and heat-treated irons.
Ferrite
This is the purest iron phase in a cast iron. In conventional Ductile Iron ferrite
produces lower strength and hardness, but high ductility and toughness. In
Austempered Ductile Iron (ADI), extremely fine-grained accicular ferrite
provides an exceptional combination of high strength with good ductility and
toughness.
Pearlite
Pearlite, produced by a eutectoid reaction, is an intimate mixture of lamellar
cementite in a matrix of ferrite. A common constituent of cast irons, pearlite
provides a combination of higher strength and with a corresponding reduction
in ductility which meets the requirements of many engineering applications.
Martensite
Martensite is a supersaturated solid solution of carbon in iron produced by
rapid cooling. In the untempered condition it is very hard and brittle.
Martensite is normally "tempered" - heat treated to reduce its carbon content
by the precipitation of carbides - to provide a controlled combination of high
strength and wear resistance.
Austenite
Normally a high temperature phase consisting of carbon dissolved in iron, it
can exist at room temperature in austenitic and austempered cast irons. In
austenitic irons, austenite is stabilized by nickel in the range 18-36%. In
austempered irons, austenite is produced by a combination of rapid cooling
which suppresses the formation of pearlite and the supersaturation of carbon
during austempering, which depresses the start of the austenite-to-martensite
transformation far below room temperature. In austenitic irons, the austenite
matrix provides ductility and toughness at all temperatures, corrosion
resistance and good high temperature proper-ties, especially under thermal
cycling conditions. In austempered Ductile Iron stabilized austenite, in volume
fractions up to 40% in lower strength grades, improves toughness and
ductility and response to surface treatments such as fillet rolling.
Bainite
Bainite is a mixture of ferrite and carbide, which is produced by alloying or
heat treatment.
Back to Top
Types of Cast Irons
The presence of trace elements, the addition of alloying elements, the
modification of solidification behaviour, and heat treatment after solidification
are used to change the microstructure of cast iron to produce the desired
mechanical properties in the following common types of cast iron.
White Iron
White Iron is fully carbidic in its final form. The presence of different carbides,
produced by alloying, makes White Iron extremely hard and abrasion
resistant but very brittle.
Gray Iron
Gray Iron is by far the oldest and most common form of cast iron. As a result,
it is assumed by many to be the only form of cast iron and the terms "cast
iron" and "gray iron" are used interchangeably. Gray Iron, named because its
fracture has a gray appearance, consists of carbon in the form of flake
graphite in a matrix consisting of ferrite, pearlite or a mixture of the two. The
fluidity of liquid gray iron, and its expansion during solidification due to the
formation of graphite, have made this metal ideal for the economical
production of shrinkage-free, intricate castings such as motor blocks.
The flake-like shape of graphite in Gray Iron, see Figure 2.4, exerts a
dominant influence on its mechanical properties. The graphite flakes can act
as stress raisers which may prematurely cause localized plastic flow at low
stresses, and initiate fracture in the matrix at higher stresses. As a result,
Gray Iron exhibits no elastic behaviour and fails in tension without significant
plastic deformation. The presence of graphite flakes also gives Gray Iron
excellent machinability, damping characteristics and self-lubricating
properties.
Malleable Iron
Unlike Gray and Ductile Iron, Malleable Iron is cast as a carbidic or white iron
and an annealing or "malleablizing" heat treatment is required to convert the
carbide into graphite. The microstructure of Malleable Iron consists of
irregularly shaped nodules of graphite called "temper carbon" in a matrix of
ferrite and/or pearlite. The presence of graphite in a more compact or spherelike form gives Malleable Iron ductility and strength almost equal to cast, lowcarbon steel. The formation of carbide during solidification results in the
conventional shrinkage behaviour of Malleable Iron and the need for larger
feed metal reservoirs, causing reduced casting yield and increased
production costs.
Back to Top
History of Ductile Iron Development
In spite of the progress achieved during the first half of this century in the
development of Gray and Malleable Irons, foundrymen continued to search
for the ideal cast iron - an as-cast "gray iron" with mechanical properties
equal or superior to Malleable Iron. J.W. Bolton, speaking at the 1943
Convention of the American Foundrymen's Society (AFS), made the following
statements.
"Your indulgence is requested to permit the posing of one question. Will real
control of graphite shape be realized in gray iron? Visualize a material,
possessing (as-cast) graphite flakes or groupings resembling those of
malleable iron instead of elongated flakes."
A few weeks later, in the International Nickel Company Research Laboratory,
Keith Dwight Millis made a ladle addition of magnesium (as a coppermagnesium alloy) to cast iron and justified Bolton's optimism - the solidified
castings contained not flakes, but nearly perfect spheres of graphite. Ductile
Iron was born!
Five years later, at the 1948 AFS Convention, Henton Morrogh of the British
Cast Iron Research Association announced the successful production of
spherical graphite in hypereutectic gray iron by the addition of small amounts
of cerium.
At the time of Morrogh's presentation, the International Nickel Company
revealed their development, starting with Millis' discovery in 1943, of
magnesium as a graphite spherodizer. On October 25, 1949, patent
2,486,760 was granted to the International Nickel Company, assigned to
Keith D. Millis, Albert P. Gegnebin and Norman B. Pilling. This was the official
birth of Ductile Iron, and, as shown in Figure 2.6, the beginning of 40 years of
continual growth worldwide, in spite of recessions and changes in materials
technology and usage. What are the reasons for this growth rate, which is
especially phenomenal, compared to other ferrous castings?
Back to Top
The Ductile Iron Advantage
The advantages of Ductile Iron which have led to its success are numerous,
but they can be summarized easily - versatility, and higher performance at
lower cost. As illustrated in Figure 2.7, other members of the ferrous casting
family may have individual properties which might make them the material of
choice in some applications, but none have the versatility of Ductile Iron,
which often provides the designer with the best combination of overall
properties. This versatility is especially evident in the area of mechanical
properties where Ductile Iron offers the designer the option of choosing high
ductility, with grades guaranteeing more than 18% elongation, or high
strength, with tensile strengths exceeding 120 ksi (825 MPa). Austempered
Ductile Iron (ADI), offers even greater mechanical properties and wear
resistance, providing tensile strengths exceeding 230 ksi (1600 MPa).
In addition to the cost advantages offered by all castings, Ductile Iron, when
compared to steel and Malleable Iron castings, also offers further cost
savings. Like most commercial cast metals, steel and Malleable Iron
decrease in volume during solidification, and as a result, require attached
reservoirs (feeders or risers) of liquid metal to offset the shrinkage and
prevent the formation of internal or external shrinkage defects. The formation
of graphite during solidification causes an internal expansion of Ductile Iron
as it solidifies and as a result, it may be cast free of significant shrinkage
defects either with feeders that are much smaller than those used for
Malleable Iron and steel or, in the case of large castings produced in rigid
molds, without the use of feeders. The reduction or elimination of feeders can
only be obtained in correctly design castings. This reduced requirement for
feed metal increases the productivity of Ductile Iron and reduces its material
and energy requirements, resulting in substantial cost savings. The use of the
most common grades of Ductile Iron "as-cast" eliminates heat treatment
costs, offering a further advantage.
Back to Top
The Ductile Iron Family
Ductile Iron is not a single material, but a family of materials offering a wide
range of properties obtained through microstructure control. The common
feature that all Ductile Irons share is the roughly spherical shape of the
graphite nodules. As shown in Figure 2.5, these nodules act as "crackarresters and make Ductile Iron "ductile". This feature is essential to the
quality and consistency of Ductile Iron, and is measured and controlled with a
high degree of assurance by competent Ductile Iron foundries. With a high
percentage of graphite nodules present in the structure, mechanical
properties are determined by the Ductile Iron matrix. Figure 2.8 shows the
relationship between microstructure and tensile strength over a wide range of
properties. The importance of matrix in controlling mechanical properties is
emphasized by the use of matrix names to designate the following types of
Ductile Iron.
Ferritic Ductile Iron
Graphite spheroids in a matrix of ferrite provides an iron with good ductility
and impact resistance and with a tensile and yield strength equivalent to a
low carbon steel. Ferritic Ductile Iron can be produced "as-cast" but may be
given an annealing heat treatment to assure maximum ductility and low
temperature toughness.
Ferritic Pearlitic Ductile Iron
These are the most common grade of Ductile Iron and are normally
produced in the "as cast" condition. The graphite spheroids are in a matrix
containing both ferrite and pearlite. Properties are intermediate between
ferritic and pearlitic grades, with good machinability and low production costs.
Pearlitic Ductile Iron
Graphite spheroids in a matrix of pearlite result in an iron with high strength,
good wear resistance, and moderate ductility and impact resistance.
Machinability is also superior to steels of comparable physical properties.
The preceding three types of Ductile Iron are the most common and are
usually used in the as-cast condition, but Ductile Iron can be also be alloyed
and/or heat treated to provide the following grades for a wide variety of
additional applications.
Martensitic Ductile Iron
Using sufficient alloy additions to prevent pearlite formation, and a quenchand-temper heat treatment produces this type of Ductile Iron. The resultant
tempered martensite matrix develops very high strength and wear resistance
but with lower levels of ductility and toughness.
Bainitic Ductile Iron
This grade can be obtained through alloying and/or by heat treatment to
produce a hard, wear resistant material.
Austenitic Ductile Iron
Alloyed to produce an austenitic matrix, this Ductile Iron offers good corrosion
and oxidation resistance, good magnetic properties, and good strength and
dimensional stability at elevated temperatures. The unique properties of
Austenitic Ductile Irons are treated in detail in Section V.
Austempered Ductile Iron (ADI)
ADI, the most recent addition to the Ductile Iron family, is a sub-group of
Ductile Irons produced by giving conventional Ductile Iron a special
austempering heat treatment. Nearly twice as strong as pearlitic Ductile Iron,
ADI still retains high elongation and toughness. This combination provides a
material with superior wear resistance and fatigue strength. (See Section IV).
Back to Top
A Matter of Confidence
The automotive industry has expressed its confidence in Ductile Iron through
the extensive use of this material in safety related components such as
steering knuckles and brake calipers. These and other automotive
applications, many of which are used "as-cast", are shown in Figure 2.9. One
of the most critical materials applications in the world is in containers for the
storage and transportation of nuclear wastes. The Ductile Iron nuclear waste
container shown in Figure 2.10 is another example of the ability of Ductile
Iron to meet and surpass even the most critical qualification tests for
materials performance. These figures show the wide variety of parts
produced in Ductile Iron. The weight range of possible castings can be from
less than one ounce (28 grams) to more than 200 tons. Section size can be
as small as 2 mm to more than 20 inches (1/2 meter) in thickness.
Back to Top
References
S. Jeffreys, "Finite Element Analysis - Doing Away with Prototypes", Industrial
Computing, September, 1988, pp 34-36.
"NCMS Study Reveals DI Castings May Mean Cost Savings." Modem
Casting, May, 1990, p 12.
Jay Janowak, "The Grid Method of Cast Iron Selection". Casting Design and
Application, Winter 1990, pp 55-59.
D. P. Kanicki, "Marketing of Ductile Iron," Modern Casting, April, 1988.
A Design Engineer's Digest of Ductil2 Iron, 5th Edition, 1983, QIT-Fer et
Titane Inc., Montreal, Quebec, Canada.
S. I. Karsay, Ductile Iron II, Quebec Iron and Titanium Corporation, 1972.
B. L. Simpson, History of the Metalcasting Industry, American Foundrymen's
Society.
Des Plaines, IL, 1969.
H. Bornstein, "Progress in Iron Castings", The Charles Edgar Hoyt Lecture,
Transactions of the American Foundrymen's Society, 1957, vol 65, p 7.
G.J. Marston "Better cast than fabricated", The Foundryman, March 1990,
108-113.
Back to Top
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Metal
From Wikipedia, the free encyclopedia
This article is about metallic materials. For other uses, see Metal (disambiguation).
Metals
Alkali metals
Lithium, Sodium, Potassium
Rubidium, Caesium, Francium
Alkaline earth metals
Beryllium, Magnesium, Calcium
Strontium, Barium, Radium
Transition metals
Zinc, Molybdenum, Cadmium
Scandium, Titanium, Vanadium
Chromium, Manganese, Iron
Cobalt, Nickel, Copper
Yttrium, Zirconium, Niobium
Technetium, Ruthenium, Rhodium
Palladium, Silver, Hafnium
Tantalum, Tungsten, Rhenium
Osmium, Iridium, Platinum
Gold, Mercury, Rutherfordium,
Dubnium, Seaborgium, Bohrium,
Hassium, Meitnerium,
Darmstadtium, Roentgenium, Copernicium
Post-transition metals
Aluminium, Gallium, Indium
Tin, Thallium, Lead, Bismuth
Ununtrium, Ununquadium
Ununpentium, Ununhexium
Lanthanoids
Lanthanum, Cerium, Praseodymium
Neodymium, Promethium, Samarium
Europium, Gadolinium, Terbium
Dysprosium, Holmium, Erbium
Thulium, Ytterbium, Lutetium
Actinoids
Actinium, Thorium, Protactinium
Uranium, Neptunium, Plutonium
Americium, Curium, Berkelium
Californium, Einsteinium, Fermium
Mendelevium, Nobelium, Lawrencium
v•d•e
A metal is a chemical element that is a good conductor of both electricity and heat and forms
cations and ionic bonds with non-metals. In chemistry, a metal (from Greek "μέταλλον" métallon, "mine"[1]) is an element, compound, or alloy characterized by high electrical
conductivity. In a metal, atoms readily lose electrons to form positive ions (cations). Those ions
are surrounded by delocalized electrons, which are responsible for the conductivity. The solid
thus produced is held by electrostatic interactions between the ions and the electron cloud, which
are called metallic bonds.[2]
Usage in astronomy is quite different.
Contents
[hide]
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1 Definition
o 1.1 Astronomy
2 Properties
o 2.1 Chemical
o 2.2 Physical
o 2.3 Electrical
o 2.4 Mechanical
3 Alloys
4 Categories
o 4.1 Base metal
o 4.2 Ferrous metal
o 4.3 Noble metal
o 4.4 Precious metal
5 Extraction
6 Metallurgy
7 Applications
8 Trade
9 See also
10 References
11 External links
[edit] Definition
This section does not cite any references or sources.
Please help improve this article by adding citations to reliable sources. Unsourced material may be
challenged and removed. (July 2010)
Metals are sometimes described as an arrangement of positive ions surrounded by a cloud of
delocalized electrons. They are one of the three groups of elements as distinguished by their
ionization and bonding properties, along with the metalloids and non-metals.
Metals occupy the bulk of the periodic table, while non-metallic elements can only be found on
the right-hand-side of the Periodic Table of the Elements. A diagonal line drawn from boron (B)
to polonium (Po) separates the metals from the nonmetals. Most elements on this line are
metalloids, sometimes called semiconductors. This is due to the fact that these elements exhibit
electrical properties common to both conductors and insulators. Elements to the lower left of this
division line are called metals, while elements to the upper right of the division line are called
non-metals.
An alternative definition of metal refers to the band theory. If one fills the energy bands of a
material with available electrons and ends up with a top band partly filled then the material is a
metal. This definition opens up the category for metallic polymers and other organic metals,
which have been made by researchers and employed in high-tech devices. These synthetic
materials often have the characteristic silvery gray reflectiveness (luster) of elemental metals.
[edit] Astronomy
Main article: Metallicity
In the specialized usage of astronomy and astrophysics, the term "metal" is often used to refer
collectively to all elements other than hydrogen or helium, including substances as chemically
non-metallic as neon, fluorine, and oxygen. Nearly all the hydrogen and helium in the Universe
was created in Big Bang nucleosynthesis, whereas all the "metals" were produced by
nucleosynthesis in stars or supernovae. The Sun and the Milky Way Galaxy are composed of
roughly 74% hydrogen, 24% helium, and 2% "metals" (the rest of the elements; atomic numbers
3-118) by mass.[3]
The concept of a metal in the usual chemical sense is irrelevant in stars, as the chemical bonds
that give elements their properties cannot exist at stellar temperatures.
[edit] Properties
[edit] Chemical
Metals are usually inclined to form cations through electron loss,[2] reacting with oxygen in the
air to form oxides over changing timescales (iron rusts over years, while potassium burns in
seconds). Examples:
4 Na + O2 → 2 Na2O (sodium oxide)
2 Ca + O2 → 2 CaO (calcium oxide)
4 Al + 3 O2 → 2 Al2O3 (aluminium oxide)
The transition metals (such as iron, copper, zinc, and nickel) take much longer to oxidize. Others,
like palladium, platinum and gold, do not react with the atmosphere at all. Some metals form a
barrier layer of oxide on their surface which cannot be penetrated by further oxygen molecules
and thus retain their shiny appearance and good conductivity for many decades (like aluminium,
some steels, and titanium). The oxides of metals are generally basic, as opposed to those of
nonmetals, which are acidic.
Painting, anodizing or plating metals are good ways to prevent their corrosion. However, a more
reactive metal in the electrochemical series must be chosen for coating, especially when chipping
of the coating is expected. Water and the two metals form an electrochemical cell, and if the
coating is less reactive than the coatee, the coating actually promotes corrosion.
[edit] Physical
Gallium crystals
Metals in general have high electrical conductivity, thermal conductivity, luster and density, and
the ability to be deformed under stress without cleaving.[2] While there are several metals that
have low density, hardness, and melting points, these (the alkali and alkaline earth metals) are
extremely reactive, and are rarely encountered in their elemental, metallic form. Optically
speaking, metals are opaque, shiny and lustrous. This is due to the fact that visible lightwaves are
not readily transmitted through the bulk of their microstructure. The large number of free
electrons in any typical metallic solid (element or alloy) is responsible for the fact that they can
never be categorized as transparent materials.
The majority of metals have higher densities than the majority of nonmetals.[2] Nonetheless,
there is wide variation in the densities of metals; lithium is the least dense solid element and
osmium is the densest. The metals of groups I A and II A are referred to as the light metals
because they are exceptions to this generalization[2]. The high density of most metals is due to
the tightly packed crystal lattice of the metallic structure. The strength of metallic bonds for
different metals reaches a maximum around the center of the transition series, as those elements
have large amounts of delocalized electrons in a metallic bond. However, other factors (such as
atomic radius, nuclear charge, number of bonding orbitals, overlap of orbital energies, and
crystal form) are involved as well.[2]
[edit] Electrical
The electrical and thermal conductivity of metals originate from the fact that in the metallic
bond, the outer electrons of the metal atoms form a gas of nearly free electrons, moving as an
electron gas in a background of positive charge formed by the ion cores. Good mathematical
predictions for electrical conductivity, as well as the electrons' contribution to the heat capacity
and heat conductivity of metals can be calculated from the free electron model, which does not
take the detailed structure of the ion lattice into account.
When considering the exact band structure and binding energy of a metal, it is necessary to take
into account the positive potential caused by the specific arrangement of the ion cores - which is
periodic in crystals. The most important consequence of the periodic potential is the formation of
a small band gap at the boundary of the Brillouin zone. Mathematically, the potential of the ion
cores can be treated by various models, the simplest being the nearly free electron model.
[edit] Mechanical
Mechanical properties of metals include ductility, which is largely due to their inherent capacity
for plastic deformation. Reversible elasticity in metals can be described by Hooke's Law for
restoring forces, where the stress is linearly proportional to the strain. Forces larger than the
elastic limit, or heat, may cause a permanent (irreversible) deformation of the object, known as
plastic deformation or plasticity. This irreversible change in atomic arrangement may occur as a
result of:

The action of an applied force (or work). An applied force may be tensile (pulling) force,
compressive (pushing) force, shear, bending or torsion (twisting) forces.

A change in temperature (or heat). A temperature change may affect the mobility of the
structural defects such as grain boundaries, point vacancies, line and screw dislocations,
stacking faults and twins in both crystalline and non-crystalline solids. The movement or
displacement of such mobile defects is thermally activated, and thus limited by the rate of
atomic diffusion.
Hot metal work from a blacksmith.
Viscous flow near grain boundaries, for example, can give rise to internal slip, creep and fatigue
in metals. It can also contribute to significant changes in the microstructure like grain growth and
localized densification due to the elimination of intergranular porosity. Screw dislocations may
slip in the direction of any lattice plane containing the dislocation, while the principal driving
force for "dislocation climb" is the movement or diffusion of vacancies through a crystal lattice.
In addition, the nondirectional nature of metallic bonding is also thought to contribute
significantly to the ductility of most metallic solids. When the planes of an ionic bond slide past
one another, the resultant change in location shifts ions of the same charge into close proximity,
resulting in the cleavage of the crystal; such shift is not observed in covalently bonded crystals
where fracture and crystal fragmentation occurs.[4]
[edit] Alloys
Main article: Alloy
An alloy is a mixture of two or more elements in solid solution in which the major component is
a metal. Most pure metals are either too soft, brittle or chemically reactive for practical use.
Combining different ratios of metals as alloys modifies the properties of pure metals to produce
desirable characteristics. The aim of making alloys is generally to make them less brittle, harder,
resistant to corrosion, or have a more desirable color and luster. Of all the metallic alloys in use
today, the alloys of iron (steel, stainless steel, cast iron, tool steel, alloy steel) make up the largest
proportion both by quantity and commercial value. Iron alloyed with various proportions of
carbon gives low, mid and high carbon steels, with increasing carbon levels reducing ductility
and toughness. The addition of silicon will produce cast irons, while the addition of chromium,
nickel and molybdenum to carbon steels (more than 10%) results in stainless steels.
Other significant metallic alloys are those of aluminium, titanium, copper and magnesium.
Copper alloys have been known since prehistory—bronze gave the Bronze Age its name—and
have many applications today, most importantly in electrical wiring. The alloys of the other three
metals have been developed relatively recently; due to their chemical reactivity they require
electrolytic extraction processes. The alloys of aluminium, titanium and magnesium are valued
for their high strength-to-weight ratios; magnesium can also provide electromagnetic
shielding[citation needed]. These materials are ideal for situations where high strength-to-weight ratio
is more important than material cost, such as in aerospace and some automotive applications.
Alloys specially designed for highly demanding applications, such as jet engines, may contain
more than ten elements.
[edit] Categories
[edit] Base metal
Main article: Base metal
In chemistry, the term base metal is used informally to refer to a metal that oxidizes or corrodes
relatively easily, and reacts variably with dilute hydrochloric acid (HCl) to form hydrogen.
Examples include iron, nickel, lead and zinc. Copper is considered a base metal as it oxidizes
relatively easily, although it does not react with HCl. It is commonly used in opposition to noble
metal.
In alchemy, a base metal was a common and inexpensive metal, as opposed to precious metals,
mainly gold and silver. A longtime goal of the alchemists was the transmutation of base metals
into precious metals.
In numismatics, coins used to derive their value primarily from the precious metal content. Most
modern currencies are fiat currency, allowing the coins to be made of base metal.
[edit] Ferrous metal
Main article: Ferrous and non-ferrous metals
The term "ferrous" is derived from the Latin word meaning "containing iron". This can include
pure iron, such as wrought iron, or an alloy such as steel. Ferrous metals are often magnetic, but
not exclusively.
[edit] Noble metal
Main article: Noble metal
Noble metals are metals that are resistant to corrosion or oxidation, unlike most base metals.
They tend to be precious metals, often due to perceived rarity. Examples include tantalum, gold,
platinum, silver and rhodium.
[edit] Precious metal
A gold nugget
Main article: Precious metal
A precious metal is a rare metallic chemical element of high economic value.
Chemically, the precious metals are less reactive than most elements, have high luster and high
electrical conductivity. Historically, precious metals were important as currency, but are now
regarded mainly as investment and industrial commodities. Gold, silver, platinum and palladium
each have an ISO 4217 currency code. The best-known precious metals are gold and silver.
While both have industrial uses, they are better known for their uses in art, jewelry, and coinage.
Other precious metals include the platinum group metals: ruthenium, rhodium, palladium,
osmium, iridium, and platinum, of which platinum is the most widely traded. Plutonium and
uranium could also be considered precious metals.
The demand for precious metals is driven not only by their practical use, but also by their role as
investments and a store of value. Palladium was, as of summer 2006, valued at a little under half
the price of gold, and platinum at around twice that of gold. Silver is substantially less expensive
than these metals, but is often traditionally considered a precious metal for its role in coinage and
jewelry.
[edit] Extraction
Main articles: Ore, Mining, and Extractive metallurgy
Metals are often extracted from the Earth by means of mining, resulting in ores that are relatively
rich sources of the requisite elements. Ore is located by prospecting techniques, followed by the
exploration and examination of deposits. Mineral sources are generally divided into surface
mines, which are mined by excavation using heavy equipment, and subsurface mines.
Once the ore is mined, the metals must be extracted, usually by chemical or electrolytic
reduction. Pyrometallurgy uses high temperatures to convert ore into raw metals, while
hydrometallurgy employs aqueous chemistry for the same purpose. The methods used depend on
the metal and their contaminants.
When a metal ore is an ionic compound of that metal and a non-metal, the ore must usually be
smelted — heated with a reducing agent — to extract the pure metal. Many common metals,
such as iron, are smelted using carbon as a reducing agent. Some metals, such as aluminium and
sodium, have no commercially practical reducing agent, and are extracted using electrolysis
instead.[5]
Sulfide ores are not reduced directly to the metal but are roasted in air to convert them to oxides.
[edit] Metallurgy
Main article: Metallurgy
Metallurgy is a domain of materials science that studies the physical and chemical behavior of
metallic elements, their intermetallic compounds, and their mixtures, which are called alloys.
[edit] Applications
Some metals and metal alloys possess high structural strength per unit mass, making them useful
materials for carrying large loads or resisting impact damage. Metal alloys can be engineered to
have high resistance to shear, torque and deformation. However the same metal can also be
vulnerable to fatigue damage through repeated use or from sudden stress failure when a load
capacity is exceeded. The strength and resilience of metals has led to their frequent use in highrise building and bridge construction, as well as most vehicles, many appliances, tools, pipes,
non-illuminated signs and railroad tracks.
The two most commonly used structural metals, iron and aluminium, are also the most abundant
metals in the Earth's crust.[6]
Metals are good conductors, making them valuable in electrical appliances and for carrying an
electric current over a distance with little energy lost. Electrical power grids rely on metal cables
to distribute electricity. Home electrical systems, for the most part, are wired with copper wire
for its good conducting properties.
The thermal conductivity of metal is useful for containers to heat materials over a flame. Metal is
also used for heat sinks to protect sensitive equipment from overheating.
The high reflectivity of some metals is important in the construction of mirrors, including
precision astronomical instruments. This last property can also make metallic jewelry
aesthetically appealing.
Some metals have specialized uses; radioactive metals such as uranium and plutonium are used
in nuclear power plants to produce energy via nuclear fission. Mercury is a liquid at room
temperature and is used in switches to complete a circuit when it flows over the switch contacts.
Shape memory alloy is used for applications such as pipes, fasteners and vascular stents.
[edit] Trade
Metal and ore imports in 2005
The World Bank reports that China was the top importer of ores and metals in 2005 followed by
the U.S.A. and Japan.[7]
[edit] See also



Amorphous metal
ASM International (society)
Ductility









Electric field screening
Metal theft
Metalworking
Periodic table (metals and non-metals)
Properties and uses of metals
Solid
Steel
Structural steel
Transition metal
[edit] References
1. ^ μέταλλον, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus Digital
Library
2. ^ a b c d e f Mortimer, Charles E. (1975). Chemistry: A Conceptual Approach (3rd ed.). New York::
D. Van Nostrad Company.
3. ^ Sparke, Linda S.; Gallagher, John S. (2000). Galaxies in the Universe (1 ed.). Cambridge
University Press. p. 8. ISBN 0521592410.
4. ^ Ductility - strength of materials
5. ^ "Los Alamos National Laboratory – Sodium". Retrieved 2007-06-08.
6. ^ Frank Kreith and Yogi Goswami, eds. (2004). The CRC Handbook of Mechanical Engineering,
2nd edition. Boca Raton. p. 12-2.
7. ^ Structure of merchandise imports
[edit] External links
Look up metal in Wiktionary, the free dictionary.
Wikimedia Commons has media related to: Metals
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Martindale's 'The Reference Desk' - International Art, Business, Science & Technology
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Periodic tables
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Periodic table
H
He
Li
B
e
B C
N
O
F
Na
M
g
Al Si
P
S
Cl Ar
K
C
a
Ne
S
M F C
C Z
Ti V Cr
Ni
Ga Ge As Se Br Kr
c
n e o
u n
Rb Sr
Y
Z N M
R R P A C
Tc
In Sn Sb Te I
r b o
u h d g d
Xe
Cs
B L C P N P S
G T D H
T Y L H
O
A H
Eu
Er
Ta W Re
Ir Pt
Tl Pb Bi Po At Rn
a a e r d m m
d b y o
m b u f
s
u g
Fr
R A T P
N
A C B
F M N
R D
H M D R C Uu Uu Uu Uu Uu Uu
U
Pu
Cf Es
Lr
Sg Bh
a c h a
p
m m k
m d o
f b
s t s g n t q p h s o
Alkali
metals
Alkaline
earth
metals
Lanthanides Actinides
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metals
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