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A History of Cast Iron

Authors:
A History of Cast Iron
Doru M. Stefanescu, The Ohio State University and The University of Alabama
THE STORY OF CAST IRON is an intricate
part of the saga of metal casting, a glamorous,
fascinating story whose beginnings are traced
to the dawn of human civilization. It is interwo-
ven with legends of fantastic weapons and
exquisite artworks, and, as such, it was and is
involved in the two main activities of humans
since they began walking the planet Earth: pro-
ducing and stealing/defending wealth. Casting
of iron has emerged from the darkness of antiq-
uity, first as magic, later to evolve into an art,
then into a technology, and finally as the com-
plex, interdisciplinary science that it is today
(2016). Civilization as we know it would not
have been possible without metal casting in gen-
eral and without iron casting in particular. This
article takes the reader through a short time-
travel of the evolution of cast iron from witch-
craft to virtual cast iron, a road paralleled by
the gigantic stride from a low-quality, “corrupt
metal” to the high-tech material that it is today.
The Beginnings of Metal Casting
and of the Iron Age
A history incursion in any subject matter
starts with the “who was the first to...
?” query.
Thus, we should wonder who poured the first
casting and how did this casting look? It
appears that the birthplace of metals can be
traced with some accuracy to the area north of
the Black Sea in the Carpathian Mountains in
today’s Romania, as shown by the arrow in
Fig. 1 (Ref 1). Other sources place the begin-
ning in southeastern and central Anatolia,
where shaped copper objects dating from circa
8200 B.C. were found (Ref 2). Our ancestors
started the long road in the mastery of metal
fabrication and use with wrought native copper.
It was not until approximately 5000 B.C. that
metal casting was invented, as humans learned
to melt and cast copper.
A partial chronological list of the progress
achieved by human civilization in the use of
metals and, in particular, of cast iron before the
Modern Era is provided in Table 1 (Ref 2–4).
For a more complete list of metal casting devel-
opments, the reader is referred to Ref 5.
The beginning of the iron civilization (Iron
Age) is still subject to controversy. The use of
iron was delayed compared to copper, because
of its lack of availability as a native metal.
Some archeological findings place it at approx-
imately 6000 B.C. in Mesopotamia, while
surveys in Anatolia dated it with confidence to
3000 B.C. (Ref 6). Primitive people appear to
have worked with meteoric iron long before
learning to extract iron from iron ore. The
ASM Handbook, Volume 1A, Cast Iron Science and Technology
D.M. Stefanescu, editor
Copyright #2017 ASM International
W
All rights reserved
www.asminternational.org
Fig. 1 Birthplace of metals. Source: Ref 1
Table 1 Chronological list of developments and use of cast iron during prehistory,
antiquity, and the medieval ages
Date
Development
LocationPrehistory and antiquity (B.C.)
9000 B.C. Earliest metal objects of wrought native copper Near East,
Anatolia
5000–3000 B.C. Chalcolithic period: melting of copper Near East
3000–1500 B.C. Bronze Age: arsenical copper and tin bronze alloys cast in stone molds Near East
3200 B.C. The oldest casting in existence, a copper frog Mesopotamia
3000 B.C. Iron Age: wrought iron Near East
2000 B.C. Two-part axe head bronze mold in Macon France
600 B.C. First iron casting, a 70 kg (154 lb) tripod China
280 B.C. Colossus of Rhodes built with an iron framework plated with brass to create the skin and
outer structure of Helios. At 30 m (98.4 ft) high, it was one of the tallest statues of the
ancient world.
Greece
233 B.C. Iron plowshares are cast. China
Medieval Ages (5 to 15th century A.D.)
~1122 Theophilus’s On Divers Arts, the first monograph on metalworking Germany
1313 Castings produced from furnace pig iron Germany
~1500 The Basilicas, first famous cast iron gun England
1540 Vannoccio Biringuccio’s De la pirotechnia, published posthumously; the first printed
account of proper foundry practice
Italy
Sumerian word “AN.BAR,” the oldest word
designating iron, is made up of the pictograms
“sky” and “fire.” Similar terminology is found
in Egypt, “metal from heaven,” and with the
Hittites, “black iron from sky” (Ref 7). Genesis
4:22 records that Tubal-cain (ancestry line:
Adam, Cain, Enoch, Irad, Mehujael, Methusael,
Lamech, Tubal-cain) was the “forger of all
instruments of bronze and iron” or an “instruc-
tor of every artificer in brass and iron” and thus
a metalsmith. It is further suggested (Ref 8) that
he “discovered the possibilities of cold forging
native copper and meteoric iron.” In most
ancient cultures, this sky connection led to the
belief that the metallurgist had a direct link to
the divine, if not of divine origin himself. It ele-
vated the social status of the early metallurgist
in the tribal hierarchy to that of a chief or sha-
man. Metalworkers sometimes rose to the level
of royalty. Genghis Khan was a simple smith
before acceding to power. Even in later history,
the metal worker ranked highly in the social
hierarchy. In Ireland, foundrymen ranked with
the nobility from early times.
While the meteorite iron/sky/divine connec-
tion is undoubtedly flattering to the metallur-
gist, another theory of the initial advent of
iron mastery in human accomplishments was
promulgated. Some iron examples uncovered
in Anatolia suggest that iron was a by-product
obtained during smelting of iron-containing
copper ores (Ref 6). However, the beginning
of iron metallurgy on an industrial scale was
not possible until the secret of smelting magne-
tite or hematite was discovered, followed by the
art of hardening the metal through quenching
(approximately 1200 to 1000 B.C.) in the
mountains of Armenia (Ref 7).
Other sources (Ref 6) place the beginning of
large-scale production of iron with the Renn
kilns in eastern Anatolia, at approximately
2000 to 1000 B.C. While iron was still a precious
metal, as attested by the iron artifacts found in the
royal tombs of Alacahoyuk, Anatolia, and by cune-
iform tablets in Assyrian which state that iron was
more valuable than gold, it was increasingly used
to make weapons and tools in addition to luxury
and art objects. The principle of the Renn kiln
involves reduction of the iron ore with charcoal to
obtain sponge iron (loupe or luppe), which is a
mixture of slag, charcoal, pure iron, and unreduced
iron ore. The sponge iron is then forged and
cleaned of residuals to produce a malleable iron.
Early Cast Iron in Mesopotamia and
China
The earliest successful iron founding is gen-
erally credited to the ancient Mesopotamian
civilizations (Babylonians, Assyrians, and Chal-
deans) many centuries before Christ (Ref 9).
Although the Greeks and Romans understood
the art of casting iron, their early applications
did not compare with the extensive development
of cast iron in China. There is ample evidence
that the Chinese capitalized on the early
evolutionary work, probably passed along to
them by migrating Mesopotamian craftsmen.
The Chinese became the first people to produce
iron castings successfully and regularly as early
as 800 to 700 B.C., with the earliest sand mold
being traced to 645 B.C. (Ref 1). One ancient
document (513 B.C.) refers to a requisition for
272 kg (600 lb) of iron for casting a tripod on
which the criminal code was to be inscribed.
Cast iron plowshares were recorded in 233 B.C.
Theoldestcastironobjectsfoundtodate
were cast during the Han dynasty (206 B.C.
to 220 A.D.) and include a stove (Fig. 2), an
ink pallet, a vase, a pan, and various fittings.
Cast iron became so popular in China that it
was used not only for home implements but
also for art (Fig. 3), worship objects such as
incense burners and statues, pagoda roof tiles,
and even true cast iron pagodas, such as the
iron pagoda of Yuquan Temple (Fig. 4).
One of the major surviving masterpieces is
the iron lion of Cangzhou, cast in a single mold
(Fig. 5). The technique, also used in ancient
Chinese bronze casting, starts with a clay model
of the sculpture, which is covered with a new
layer of clay after drying. This outer layer of
clay is then cut into pieces and removed before
it dries completely. In the next step, material is
taken off the surface of the inner clay model to
provide room for pouring the iron between the
outer and inner mold. Because casting pro-
ceeded in several stages, fault lines were intro-
duced into the cast at regular intervals, which
mark the filling height of the mold at successive
casting stages. These fault lines were bridged
with wrought iron rods that were plunged into
the solidifying surface of the iron from the pre-
vious pour and then covered in the next pour.
The amazing progress in cast iron technology
that occurred in China is attributed to the devel-
opment of melting equipment capable of pro-
ducing greater air draft (the box-bellows
furnace) and to the abundant supply of the nec-
essary raw materials. Evidence suggests that
blast furnaces that convert raw iron ore into
pig iron, which can be remelted in a cupola
Fig. 2 Oldest known cast iron stove, from the Han
dynasty
Fig. 3 Recumbent cast iron lion, 502 A.D.
Fig. 4 Iron pagoda in front of Yuquan Temple in
Dangyang. Built in 1061, it incorporates
38,300 kg (84,400 lb) of cast iron and stands 17.9 m
(58.7) tall.
Fig. 5 The iron lion of Cangzhou, cast in 953 A.D., is
the largest (40 to 50 tons) known old surviving
iron cast artwork in China.
4 / Introduction
furnace to produce cast iron, were operational
in China by 722 to 481 B.C. (Ref 10).
A second reason for the shift from bronze to
iron in China seems to be the understanding of
a process consisting of holding an iron ore/car-
bon mixture at low temperature to produce a soft
mass of pure iron (melting point 1530 C, or
2785 F), followed by holding this iron at high
temperature in the presence of carbon, to pro-
duce a carbon-rich iron with a melting point of
1170 C(2140F). In addition, because the iron
ore was rich in phosphorus, and high-phosphorus
coal was added during melting, the resulting iron
contained 6 to 7% P, which allowed pouring of
this iron at 980 C(1795F)—100 C(180F)
below the melting point of copper.
Cast Iron in Europe in the
Medieval Ages
While metal casting was known to both the
ancient Greeks and Romans, little evidence of
cast iron was found from that period in Europe.
After the Roman legions departed the island,
iron was smelted in Britain by Anglo-Saxon
monks, as attested by a small cast statuette
dated 170 A.D. found in Sussex. In continental
Europe, as Europe descended into the Dark
Ages, the metal-casting art was preserved dur-
ing the Merovingian dynasty by the Gauls,
famous for their metalworking talent during
the Roman period (Ref 1). Knowledge was kept
secret and transferred almost solely by word of
mouth. It was not until 1122 A.D. that the monk
Theophilus, in his manuscript On Divers Arts,
included some description of foundry practice.
The cast iron of those days was an inferior
material termed “corrupt metal” even as late
as the 15th century, because it was believed that
the melting of iron ruined its properties. Not
surprising, because the iron had very high car-
bon content (since charcoal was used as fuel)
and little silicon and thus was very brittle.
The beginning of the progress of blast fur-
naces in Europe has been traced to the char-
coal-fueled Catalan forge developed by the
Moors in the 8th century A.D. The product
was sponge iron (loupe), which was further pro-
cessed by forging. This furnace was followed
by improved models in Switzerland, Germany,
and Sweden. The Swedish model used manu-
ally operated leather bellows. In 1325, the
water-driven bellows was introduced, marking
the beginning of modern iron-foundry practice.
The temperature in the furnace was high
enough to allow removal of the slag and
tapping the molten iron into a large basin and
then into smaller and smaller molds, resembling
a sow with suckling pigs, which is probably the
origin of the term pig iron (Ref 1).
Large-scale introduction of cast iron in Europe
did not occur until approximately 1200 to 1450
A.D. For more than 400 years, foundry processes
and materials often relied on the methods
described by Biringuccio (Fig. 6), an Italian met-
allurgist and author of De la pirotechnia,a
manual on metalworking that was published
posthumously in 1540. This book is credited
with starting the tradition of scientific and
technical literature. It preceded by 14 years the
printing of De re metallica by Georgius Agri-
cola. Biringuccio, who is considered the father
of the foundry industry, recommended using
the dregs of beer vats and human urine as bin-
ders for molding sand, both of which were in
use well into the 20th century. Development by
Biringuccio of a standard bell scale is one of
the earliest instances on record of the metal
caster and the engineer combining their skills
for the production of perfect castings.
An important cast iron success was the intro-
duction of cast iron water pipes in the 15th cen-
tury. Apparently, the first one was installed at
the Dillenburg Castle in Germany in 1455,
although earlier installations are mentioned.
Early Modern Period (16th
to Mid-18th Century)
A partial chronological list of the advance-
ment in cast iron technology and science
achieved after 1500 A.D. is presented in
Table 2.
By the early 17th century, cast iron reached
America. The Virginia Company of London
established Falling Creek Ironworks in 1619,
the first iron production facility in North Amer-
ica, which was short-lived due to an attack by
Native Americans three years later. However,
cast iron developments continued, as attested
by the Saugus pot shown in Fig. 7, the first
Fig. 6 Vannoccio Biringuccio, as depicted in the
Specola Museum in Florence
Table 2 Chronological list of developments and use of cast iron during the modern period
Date
Development
LocationEarly modern period (16th to mid-18th century)
1619 North America’s first iron furnace is built at Falling Creek, VA, on a branch of the
James River, 100 km (62 miles) from the Jamestown colony.
United States
1642 The first American casting: iron pot made at the Saugus Iron Works in Massachusetts,
America’s first iron metal-casting facility (and second industrial plant)
United States
1664 Flanged cast iron pipes laid at Versailles France
1709 Cast iron produced with coke as fuel, Coalbrookdale England
1715 Boring mill of cannon developed Switzerland
1722 de Reaumur develops whiteheart malleable iron France
Late modern period
1776 Metalcasters Charles Carroll, James Smith, George Taylor, James Wilson, George Ross,
Philip Livingston, and Stephen Hopkins sign the American Declaration of
Independence.
United States
1779 Cast iron used as architectural material: Iron Bridge over the Severn River England
1794 John Wilkinson invents the first metalclad cupola furnace, using a steam engine to provide
the air blast.
England
1809 Centrifugal casting is developed by Eckhardt. England
1825 Aluminum, the most abundant metal in the Earth’s crust, is isolated from aluminum
chloride by Hans Oerstad.
Denmark
1863 Henry Sorby develops metallography after the invention of the microscope in1860. England
1886 Electrolytic refining of aluminum (the Hall-He
´roult process) is invented independently
by Charles Hall and Paul He
´roult.
United States, France
1908 First attempts at liquid treatment of cast iron with FeSi, Ca, and V by Geilenkirchen Germany
1928 First specification (DIN 1691) for cast iron; classes 140–280 MPa (20–41 ksi) Germany
1931 Augustus Meehan obtains a U.S. patent for the addition of calcium silicide. United States
1935 First scanning electron microscope image by Max Knoll England
1940 Chvorinov develops the relationship between solidification time and casting geometry. Germany
1942 Piwowarsky in Aachen publishes Hochwertiges Gusseisen, the first cast iron “bible.” Germany
1943 Keith Millis discovers that magnesium addition to molten iron produces a spheroidal
graphite structure.
United States
1938–
1949
Patent rights for the production of cast iron with spheroidal graphite granted to Adey
(1938) to Millis, Gagnebin, and Pilling (1949), and to Morrogh (1949)
Germany, United
States, England
1948 Industry’s first ductile iron pipe is cast at Lynchburg Foundry, Lynchburg, VA. United States
1951 Ford Motor Co. in Dearborn converts 100% of its crankshaft production to ductile iron. United States
1956 Formulation of the constitutional undercooling criterion by Chalmers opens the road for
applications of solidification science to metal casting.
Sweden
1965 First scanning electron microscope marketed by the Cambridge Scientific Instrument Co. England
1966 Mathematical theory of eutectic solidification by Jackson and Hunt England
1966 First computer model for the solidification of alloys (cast iron) by W. Oldfield England
1969 Patent rights for the production of cast iron with at least 50% vermicular graphite granted
to Schelleng
United States
1972 Commercialization of austempered ductile iron: a 0.5 kg (1 lb) crankshaft for a refrigerator
compressor produced at Wagner
United States
1976 Foote Mineral Co. and the British Cast Iron Research Association develop compacted
graphite iron.
United States, England
A History of Cast Iron / 5
surviving cast iron artifact produced in Amer-
ica. In France, cast iron pipes were installed at
the palace of Versailles by order of King Louis
XIV (Fig. 8); some of these pipes are still being
used today (2016).
An important development occurred in 1709,
when Abraham Darby from Coalbrookdale,
England, initiated the use of coke as a furnace
fuel for iron production. In 1715, Johann Mar-
itz, Master Founder at Burgdorf, Switzerland,
developed the procedure of casting cannon
solid and then machining the bore, a technology
further developed by the French. Another sig-
nificant French contribution to cast iron during
this period was the development of whiteheart
malleable iron by de Reaumur, which dispelled
the notion that cast iron is an inherently brittle
material and opened the way to the many dis-
coveries that the understanding of metallurgy
bestowed on cast iron.
Late Modern Period
The late modern period in human civilization
begins at approximately 1760, when the
Industrial Revolution started in England. It ush-
ered the change from muscle power (hand
production methods) to water power and then
steam power (steam engine). New chemical
manufacturing and iron-production processes,
the development of machine tools, and the rise
of the factory system were also the hallmarks
of this first Industrial Revolution. Cast iron
tram-road rails produced in Coalbrookdale in
1756 replaced wooden rails, and the famous
Iron Bridge was built in 1779 (Fig. 9).
Before the invention of the microscope, only
two types of iron were known, and they were
classified based on the appearance of their frac-
ture: white and gray. The strength was limited
to 80 to 100 MPa (12 to 15 ksi). In 1863, Sorby
used a microscope to study polished samples,
enabling metalcasters to microscopically exam-
ine metal surfaces and understand the constitu-
ents of alloys. Still, cast iron was slow to
develop to the modern, high-properties, widely
used material that we know today (2016). The
limited knowledge of the subject is summarized
in the first paper on cast iron to be published in
the newly created Journal of the American
Foundrymen’s Association in 1896 (Ref 11),
which stated, “The physical properties of cast
iron are shrinkage, strength, deflection, set,
chill, grain and hardness. Tensile test should
not be used for cast iron, but should be confined
to steel and other ductile materials. Compres-
sion test should be made, but is generally
neglected, from the common erroneous impres-
sion that the resistance of a small cube or cylin-
der, which is enormous, is always in excess of
loads which can be applied.”
Fig. 7 The Saugus pot (1642), the first casting made in
the Americas
Fig. 8 Sewer pipes in Versailles (1664). The initials
“LF” stand for Louis of France. Source: Ref 1 Fig. 9 The cast Iron Bridge over the Severn River near Coalbrookdale, England (1779). (a) General view. (b) Detailed
view showing surface defects of the castings poured in open molds. Photos taken by the author in 2012
6 / Introduction
The march of cast iron toward higher
mechanical properties achieved a turning point
during the late 1920s and early 1930s, when
the Ross Meehan foundry in Chattanooga, Ten-
nessee, discovered the advantages of inoculat-
ing iron with controlled additions of calcium
silicide. The initial patent on the process was
issued to Augustus Meehan in 1931. The pro-
cess allowed the production of gray iron with
tensile strength up to 500 MPa (72 ksi).
Significant progress was also achieved in
Germany, where, beginning in 1930, Piwo-
warsky performed systematic studies of the
use of sodium, calcium, lithium, magnesium,
cerium, strontium, and barium for inoculation
of gray iron. By 1936, Adey was preoccupied
in obtaining spheroidal graphite. Quoting from
the famous book by Piwowarsky (Ref 12),
whose first edition was published in 1942, Adey
obtained a patent in 1938 for a “process for pro-
duction of cast iron of higher strength, charac-
terized by a eutectic or hypereutectic cast iron
free of slag inclusions with a minimum content
of 1% Si in which, after fast solidification, the
graphite is whole or in part of spheroidal form
in the metallic matrix.” As can be inferred from
Fig. 10, it appears that the material was malleable
iron with spheroidal graphite obtained through
heat treatment (“thermische vergu
¨tung”).
Yet, the quest for an ideal as-cast iron with
properties equal or superior to malleable iron
continued. At the 1943 Convention of the
American Foundrymen’s Society, one of the
speakers, J.W. Bolton, addressed the following
question to the audience: “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 resem-
bling those of malleable iron instead of
elongated flakes.” A few weeks later, in the
International Nickel Company Research Labo-
ratory, Keith D. Millis made a ladle addition
of magnesium (as a copper-magnesium alloy)
to cast iron and produced spheroidal graphite,
discovering ductile iron, whose expansion in
industry in the following years was explosive
(Ref 5). At the American Foundryman’s Society
annual meeting on May 7, 1948, in Philadelphia,
Millis announced this achievement during a
brief discussion period after a technical presen-
tation by H. Morrogh, who independently con-
ducted work in England on spheroidizing the
graphite through additions of cerium. This led
to patents by Millis (U.S. Patent 2,485,760 in
1949) and Morrogh (U.S. Patent 2,488,511 in
1949). The major discoveries related to graphite
shape control ended in 1969 with the recogni-
tion of compacted graphite iron as a grade in
its own merit through a patent for “cast iron
with at least 50% of the graphite in vermicular
form” granted to R.D. Schelleng. Finally, with
the commercialization of austempered ductile
iron, the strength of cast iron rivaled that of
many steels, as shown in Fig. 11, which sum-
marizes the increase in strength of cast iron
over the years.
In approximately 1950, the second Industrial
Revolution started with the advent of transis-
tors, computers, and microchips, which helped
to replace and enhance mental effort, made pos-
sible the invention of robots to perform danger-
ous or boring jobs, triggered major productivity
increases, and decreased demand on natural
resources. The second Industrial Revolution
helped propel cast iron in the body of advanced
materials following the birth and growth of
solidification science and computational model-
ing. The formulation of the mathematical corre-
lation between casting volume/surface ratio and
solidification time by Chvorinov (Ref 13)
in 1940 had a major impact. Then, Chalmers
(Ref 14) transformed solidification science
from a purely physics discipline into an engi-
neering science with his formulation of the con-
stitutional undercooling criterion, which opened
the road to the understanding of the effects
of cooling rate on the microstructure of cast
alloys. Two of the most significant advances
in the mathematics of solidification, with major
effect on the engineering science of cast iron,
occurred in 1966 with the publication of two
papers. The first one is the classic paper on
eutectic alloys by Jackson and Hunt (Ref 15),
a rigorous analytical analysis of regular lamel-
lar eutectic growth that established the correla-
tion between the processing parameters and
microstructure for eutectic alloys, including
cast iron.
The age of virtual cast iron (computational
modeling of microstructure, properties, and
soundness of cast iron) was started by the bril-
liancy of scientist W. Oldfield (Ref 16), who
developed a computer model that could calcu-
late the cooling curves of gray iron. His seminal
paper was the first attempt to predict solidifica-
tion microstructure through computational
modeling and the first attempt to validate such
a model against cooling curves. Nobody ever
remembers the first one to be second in any
human endeavor. Yet, the author of this article
will have to take credit for this position, since
in 1973 he was the first one to continue Old-
field’s work (Ref 17). By 1985, solidification
modeling of cast iron became an area of inten-
sive research (Ref 18). Simulation of cast iron
microstructure and properties has made gigantic
strides. Today (2016), computer software com-
panies offer complete packages that include
integrated simulation of the entire process
(mold filling, solidification, and cooling) using
a micromodeling approach to investigate final
structures and properties of iron casting. Some
models predict graphite morphology (lamellar,
nodular), carbide formation, and microstructure
length scale (eutectic grain size, type and aver-
age size of lamellae, or number of nodules).
Fig. 10 Page from the laboratory notebook of C. Adey from 1936, showing malleable iron with spheroidal graphite
Fig. 11 Temporal evolution of the tensile strength of
cast iron. ADI, austempered ductile iron; DI,
ductile iron; CGI, compacted (vermicular) graphite iron;
LG, lamellar graphite
A History of Cast Iron / 7
They can calculate the eutectoid transformation
and thus the final structure and predict proper-
ties such as hardness, yield and tensile strength,
and fracture elongation.
Cast Iron—A High-Tech,
Economical, Modern Material
A recent commercial produced by Cleveland
Golf that introduced a new line of golf wedges
stated, “The CG10 wedge is made from a pro-
prietary material called carbon-metal matrix.
This material, while not a composite, is infused
with 17 times more carbon than traditional car-
bon steels. The carbon is infused into micro-
scopic spheres suspended within the molecular
structure, creating a matrix that is 10% less
dense and 15% softer than steel. The density-
relieving spheres damp vibrations...
”. The
reader may have guessed, and the published
microstructure confirms, that the material is
nothing else but spheroidal graphite iron, which
is indeed a graphite-iron composite, the first
man-made composite. This is further confirma-
tion that cast iron has achieved the status of a
high-tech material. There are more compelling
examples of high-performance cast iron parts,
such as large ductile iron castings for the wind-
mill industry (e.g., the hub in Fig. 12, frame,
and gearboxes) or ductile iron bodies for naval
engines (Fig. 13).
The application of cast iron in works of art is
as old as cast iron itself. More modern art appli-
cations are in architecture. Cast iron architec-
ture became a prominent style in the Industrial
Revolution era, when cast iron was relatively
cheap and modern steel had not yet been devel-
oped. Ditherington Flax Mill in England, built
in 1796, is the oldest iron-framed building in
the world. As such, it is seen as the world’s first
skyscraper and is described as “the grandfather
of skyscrapers.” A famous example is the
Bulgarian Iron Church in Istanbul. The richly
ornamented church is a three-domed, cross-
shaped basilica with a 40 m (131 ft) high bell
tower (Fig. 14). It was completed in 1898.
The main skeleton of the church was made of
steel and covered by prefabricated cast iron
boards weighing 500 tons that were produced
in Vienna.
Many other examples of cast iron architec-
ture survived in London, New York, Boston
(Fig. 15), and many other cities.
Another exciting application of cast iron is in
the art of cooking. Cast iron distributes heat
evenly, favoring the development of the Mail-
lard reaction (Ref 19) during cooking, which
is a chemical reaction between amino acids
and reducing sugars that gives browned food
its desirable flavor. Thus, it is one of the best
media for cooking now advertised by such tele-
vision celebrities as Alton Brown. The author
of this article is himself a big fan of cast iron
cookware (Fig. 16).
The markets for iron castings include con-
struction, motor vehicles, farm equipment,
mining machinery, engines, valves, pumps,
home appliances, ware, and oil and natural gas
pumping and processing equipment. The reader
is referred to the paper by Prucha et al. (Ref 5)
for a more complete list. These examples
should be convincing, but a more rigorous anal-
ysis may be used to fully establish cast iron
credentials.
Fig. 12 Ductile iron hub for large windmill
Fig. 13 Ductile iron cylinder head for a naval engine weighing 83 tons
Fig. 14 Bulgarian St. Stephen Iron Church in Istanbul. Photo taken by the author in 2004
8 / Introduction
Over recent years, aluminum has been the
material of choice for a large number of auto-
motive components because of its low density
and lower energy requirements during use and
postuse, compared with ferrous materials.
Automotive aluminum use has grown steadily
for 40 years. A survey of North American auto-
makers found that automakers will increase
their use of aluminum from 148 kg (327 lb) in
2009 to 250 kg (550 lb) in 2025, doubling the
aluminum percent of vehicle curb weight from
8 to 16%. Yet, when conducting optimization
analysis on the two competing materials, alumi-
num and cast iron, an interesting picture emerges
(Ref 20). The objective of optimization when
selecting a material for a particular application
is to optimize a number of performance metrics
(P) in a particular product. Typical metrics for
the problem of interest are cost, mass, fatigue
resistance, strength, stiffness, and so on. A first
approach to optimization is to directly compare
selected properties of the competing materials
or, when the weight is important, as in the case
of automotive parts, the specific property of the
material (property/density ratio).
For example, fatigue strength can be used as
an optimization parameter. The ability of a
material to withstand long-term cyclic stress is
typically described by the stress (S)/number of
cycles (N) curve. As shown in Fig. 17(a),
Fig. 15 Cast iron fac¸ade on a building in Boston. Photo taken by the author in 2002
Fig. 16 Cast iron cookware, produced by Lodge Manufacturing, in the author’s kitchen
Fig. 17 Optimization through direct comparison of
properties. (a) Typical applied stress (S)/
cycles to failure (N) curves for cast aluminum alloys and
ductile iron (DI). (b) Typical specific stress/cycles to
failure curves for cast aluminum alloys and DI. r,
density. Source: Ref 20
A History of Cast Iron / 9
aluminum alloys exhibit a lower S-N curve than
ductile iron (DI). In addition, cast iron exhibits
a fatigue limit (stress under which failure does
not occur, regardless of the number of cycles),
while aluminum does not. More importantly,
the specific stress of DI is superior to that of
aluminum alloys when the number of cycles
exceeds 10
7
(Fig. 17b).
The more detailed analysis presented in
Fig. 18 shows that die cast alloys have similar
fatigue resistance to ferritic ductile irons, but
even the premium A357 die cast alloy cannot
compete with pearlitic iron. The fatigue
strength of tempered and austempered DI
exceeds several times that of solution-treated
as-cast aluminum alloys.
Another property of particular interest for
automotive parts is the strength at elevated tem-
peratures. As shown in Fig. 19, at temperatures
above 200 C (390 F), the specific strength of
ductile iron rapidly overtakes that of aluminum
Fig. 18 Specific fatigue strength of selected solution-
treated cast aluminum alloys and ductile
iron. r, density; SC, sand cast; DC, die cast; DI, ductile
iron; F, ferritic; FP, ferritic-pearlitic; P, pearlitic; T,
tempered; AUST, austempered. 355 = Al7Si; 356 =
Al7Si0.4Cu; 357 = Al7Si0.8Cu. Source: Ref 20
Fig. 19 Influence of temperature on the specific tensile
strength of aluminum alloys and ductile iron
(DI). UTS,ultimate tensile strength; r, density. Sou rce: Ref 20
D
AUS CG
Gray
AI DI
0.3
0.1
0
00.2
0.2
0.4
0.4
Cost × ρ/E
ρ/E
D
D
D
DD
D
1
1
0.5
0.5
0
01.5
1.5
Cost × ρ/σ
y
1/2
ρ/σ
y
1/2
2.50.50
01.5
2
3.5
4
Cost ×
ρ/
E1/3
ρ
/E1/3
D
D
1234
D
DD
D
0.2 0.4 0.6
0.4
0
00.8
0.8
Cost × ρ/σ
y
2/3
ρ
/
σ
y
2/3
(a)
(c) (d)
(b)
Fig. 20 Comparison between cast iron (AUS, austempered; DI, ductile iron; CG, compacted graphite iron) and
aluminum alloys for multiobjective optimization using mass-cast as performance metrics. (a) Tie, stiffness
prescribed. (b) Panel, stiffness prescribed. (c) Panel, strength prescribed. (d) Beam, strength prescribed. The cost is in
$/kg; density (r) is in Mg/m
3
; Young’s modulus (E) is in GPa; and yield strength (s
y
) is in MPa. Source: Ref 20
Table 3 Materials indices for different
applications
Function Example Objective Constrain Index(a)
Tie Cable support Minimum
weight
Stiffness r/E
Beam Aircraft wing Minimum
weight
Stiffness r/E
1/2
Panel Automobile
door
Minimum
weight
Stiffness r/E
1/3
Beam Auto
suspension
arm
Minimum
weight
Strength r/s
y2/3
Panel Table top Minimum
weight
Strength r/s
y1/2
(a) r, density; E, Young’s modulus; s
y
, yield strength. Source: Ref 21
1.20×108
8.00×107
6.00×107
4.00×107
Production, metric tons
2.00×107
1.00×108
0
2006 2008 2010 2012 2014 2016
Magnesium,
0.2%
Aluminum,
15.5% Other nonferrous, 2.8%
Cast iron,
70.9%
Steel,
10.8%
Total
Cast iron
Steel
Aluminium
Year(a) (b)
Fig. 21 Worldwide cast iron production. (a) Evolution of tonnage of various casting alloys between 2007 and 2014. (b) Share of total production of various casting alloys in 2014
10 / Introduction
alloys. Thus, for high-temperature applications
(e.g., engine parts), ductile iron is a better
choice than aluminum.
A more detailed optimization analysis must
include the particular function of the product.
Then, the metrics depend on the geometry of
the product and the constraints imposed on it.
More complicated equations that define a mate-
rial index are developed (Ref 21), as exempli-
fied in Table 3. The values of the performance
metric for competing materials scale with the
material index. By using this concept, selection
of a material becomes a simple case of choos-
ing materials with the smallest index character-
izing the performance metrics. For example,
examining the data in Fig. 18, the best material
is austempered DI having a density/fatigue
strength of 0.14 to 0.18, while sand cast alumi-
num alloys are in the range of 0.41 to 0.5.
When there are two or more optimization
objectives, solutions rarely exist that optimize
all at once. One way of optimizing several objec-
tives is to compare the materials in a P
1
-P
2
graph, where P
1
and P
2
are the metrics of the
two objectives. An example is provided in
Fig. 20 for mass-cost optimization for four dif-
ferent applications. The slopes of the parallel
lines on the graphs are drawn such that a unit
increase in P
1
corresponds to a unit increase in
P
2
. For all applications in this example, cast iron
is either clearly superior or slightly superior to
aluminum alloys, because the values for cast iron
are closer to the origin of the graph show lower
cost for higher indexes.
This analysis demonstrates that in applica-
tions where mass and cost are the objective of
optimization, cast iron should be selected over
aluminum alloys. The main reason why alumi-
num is replacing cast iron in automotive appli-
cations seems to be the inability or lack of
interest of iron foundries to produce lightweight
iron castings, that is, iron castings with thin
walls, despite the significant advances made in
this direction (see the articles “Thin-Wall Gray
Iron Castings” and “Thin-Wall Ductile Iron
Castings” in this Volume).
To conclude this section, it is useful to pro-
vide an analysis of current trends in the world-
wide casting production. As shown in Fig. 21
(a), the tonnage of all casting alloys has
increased by almost 11% between 2007 and
2014. While the percentage of cast iron from
the total tonnage has slightly decreased in
2014 compared with 2007, it is still at more
than 70%, by far the highest in the competition
of casting alloys (Fig. 21b).The share of alumi-
num over the same time period has increased
from 13.4 to 15.5%, while that of magnesium
has decreased from 0.3 to 0.2%.
Today (2016), cast iron remains the most
important casting material. The main reasons
for cast iron longevity are the wide range of
mechanical and physical properties associated
with its competitive price. If all ferrous alloys
are considered, their share of the world casting
production is above 81%. Thus, as far as
this author is concerned, we are still in the
Iron Age.
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A History of Cast Iron / 11
... Cast iron, an alloy of iron-carbon-silicon, dates back to at least 500 BC [1]. However, it still constitutes the majority (≈70%) of today's metal castings. ...
... However, it still constitutes the majority (≈70%) of today's metal castings. Applications of such castings may range from mundane (water pipes to cooking pots) to challenging (auto component to gas turbines and even aerospace) [1][2][3]. One of the key factors for challenging applications of cast iron, demanding better mechanical behavior [4], is the morphology of the graphite phase. ...
... Free graphite exists in the metallic matrix as flake (in grey cast iron), intermediate (in compacted or vermicular cast iron), or spheroidal (in nodular or ductile cast iron) [1,[5][6][7][8][9][10]. ...
Article
Full-text available
Applications of cast irons, from mundane to more challenging, are decided by the morphology of free graphite in the metallic matrix. The morphology changes from flake to spheroidal, as controlled by magnesium (Mg) addition during metal castings. Though this technology dates back several decades, the exact mechanism remains debatable. This study used a combination of industrial casting trials, analytical microscopy, and molecular dynamics (MD) simulations to address this question. It was experimentally established that the shape change was accompanied by a change in the growth direction, from prism to basal in the graphite, and atomic segregation of Mg at the interface. MD simulations indicated a combination of migration of oxygen (O) atoms and Mg-O interactions, respectively in the prism and basal oriented graphite, resulted in cross-over in interfacial free energy with Mg concentration. The anisotropic growth by high energy interface, controlled by interface chemistry, thus defined the mechanistic origin for the graphite morphology in cast iron.
... Cast iron represents a family of alloys composed by graphite wrapped in a metallic matrix 1 . It is considered the 1 st composite material produced by man and one of the most manufactured alloys in the world 2,3 . Due to the various possibilities for modifying the microstructure, cast irons have numerous applications, being a more viable competitor even for some steels. ...
Article
Full-text available
Nodular cast iron is a fundamental material used in engineering. It has unique properties and is one of the most produced materials in the world nowadays. The production of nodular cast iron involves melting of raw materials such as steel scrap, pig iron, machining returns and alloy irons. With the development of in-creasingly technological steels through the addition of chemical elements to meet a specific application, there is an increasing difficulty in acquiring steel scrap content low alloy for the production of nodular cast iron. The chemical elements present in the steel scrap favor the appearance of unwanted phases and particles. The present study evaluated the effect of the addition of the elements copper, chromium, molybdenum and nickel in levels between 0.50% w and 1.0% w in the formation of nodular cast iron microstructure. While nickel and copper were evenly distributed in the matrix, chromium and molybdenum formed carbides. In addition, chromium strongly favored the formation of perlite in nodular cast iron and molybdenum, the martensite.
... In the world of metallurgy, spheroidal graphite irons is a relatively new foundry material dating back to the patent by Millis et al. in 1949 [4], though various previous historical records have been reported [5]. The negative effect of trace elements on graphite nodularity was already mentioned in the patent but it was very soon realized that adding rare earths (RE) would offset the problem in most cases [6]. ...
Article
Since the discovery that magnesium and cerium (and more generally rare earths) added at low level to cast iron melts lead to spherodized graphite, it is known that some other elements are detrimental even when present as traces. In all practicality, it has soon been recognized that adding rare earths to the melt helps counteracting the effect of these detrimental elements. Accordingly, only few works have been devoted to studying the effect of trace elements in melts without any rare earths. This is the first aim of the present work to review those studies as they contain the material to understand the mechanism for spheroidal graphite degeneracy. From this review, three types of degeneracy have been defined which show up when the critical level of any particular element is exceeded. These results are then discussed to show that all degeneracies certainly proceed in the same way. To substantiate this discussion, the growth of compacted graphite as obtained by low level treatment of cast iron melt with magnesium is also presented. Finally, a mechanism is suggested for describing the action of trace elements on spheroidal graphite degeneracy. This mechanism is partly substantiated by first-principles calculations which showed that all elements can strongly adsorb on the prismatic planes which are the planes on which carbon atoms add on during graphite growth.
... The main skeleton of the church was made of steel and covered by prefabricated cast-iron boards weighing 500 tons that were produced in Vienna. Many other examples of cast-iron architecture survived in London, New York, Boston(Figure 16), and other cities.29 ...
Article
Full-text available
Unlike in a democracy where selection criteria serve the concept of political equality between the members of the category, meritocracy means equality of opportunity rather than outcome. The US economy was built on meritocratic principles. The world of sports is meritocratic, as building a winning culture is crucial, and so is the world of materials. Cast iron, a material with impressive longevity going back to at least the 5th century BC, survived in the materials competition based on merit. A review of these merits is one of the objectives of this lecture. However, as developing the material properties that kept cast iron competitive is rooted in knowledge, a short escapade in the history of knowledge pertinent to cast iron will also be attempted. The US iron casting production has continuously decreased since 1990. A discussion of the effect of generation and transfer of knowledge and of ill-advised and debatable environmental constrains is provided.
Article
The research aims to provide an alternative to austempering treatment of ductile cast iron with a simple and cost-effective heat-treatment process. This goal was accomplished by applying a simple one-step spheroidization heat treatment to the as-cast ductile iron, which would normally possess a coarse pearlitic microstructure to a significant extent. Spheroidization experiments involving isothermal holding below the lower critical temperature (A1) were conducted followed by standard mechanical testing and microstructural characterization for an experimental ductile iron. After improving the spheroidization holding time at a given temperature, the work shows that the ductility and toughness of an as-cast ductile iron can be improved by 90% and 40%, respectively, at the cost of reducing the tensile strength by 8%. Controlled discretization of the continuous cementite network in pearlitic matrix of the ductile iron is deemed responsible for the improved properties. The work also shows that prolonged holding time during spheroidization heat treatment leads to degradation of mechanical properties due to the in-homogenous microstructure formation caused by heterogeneous decomposition and cementite clustering in the material. The main outcome of this work is the demonstration of ductile cast iron's necking behavior due to spheroidization heat treatment.
Article
The development or selection of a material to meet given design requirements generally requires that a compromise be struck between several, usually conflicting, objectives. The ways in which multi-objective optimization methods can be adapted to address this problem are explored. It is found that trade-off surfaces give a way of visualizing the alternative compromises, and that value functions (or “utility” functions) identify the part of the surface on which optimal solutions lie. The method is illustrated with examples.
Timeline of Casting Technology
Timeline of Casting Technology, Mod. Cast., Cast Expo Issue, May 2005
  • T E Prucha
  • D Twarog
  • R W Monroe
T.E. Prucha, D. Twarog, and R.W. Monroe, History and Trends of Metal Casting, Casting, Vol 15, ASM Handbook, ASM International, 2008, p 3-154
Iron Technology in Antiquity, Anatolia, Cradle of Castings
  • U Yalçin
U. Yalçin, Iron Technology in Antiquity, Anatolia, Cradle of Castings, Ö. Bilgi, Ed., Graphis Matbba, Istanbul, 2004, p 221-224
The Gray Iron Castings Handbook, Gray Iron Founders Society
  • C F Walton
C.F. Walton, The Gray Iron Castings Handbook, Gray Iron Founders Society, Cleveland, OH, 1958
The State and the Iron Industry in Han China
  • D B Wagner
D.B. Wagner, The State and the Iron Industry in Han China, Copenhagen: Nordic Institute of Asian Studies Publishing, ISBN 87-87062-83-6, 2001
  • B Chalmers
B. Chalmers, Trans. AIME, Vol 200, 1956, p 519
  • K A Jackson
  • J D Hunt
K.A. Jackson and J.D. Hunt, Trans. Metall. Soc., Vol 236, 1966, p 1129
  • W Oldfield
W. Oldfield, ASM Trans., Vol 59, 1966, p 945