This doc. will provide complete info about cast iron.

1. Introduction to Cast Iron
Muhammad Umair Akram, Muhammad Shariq Masood, Syed Haseeb Ahmed, Javeria Haseeb
Industrial Manufacturing Engineering Department, NED University of Engineering and Technology University Road, Karachi 75270, Pakistan
umair.an@ymail.com
shariquemasood@yahoo.com
haseebahmed60@gmail.com
scorpio2470@hotmail.com
Abstract— this document contains information about Cast Iron which is an engineering material. It also contain information about: 1) the types of cast iron 2) its different composition 3) structure it posses at different conditions and environments 4) the mechanical properties of Cast Iron This document also gives information regarding the applications of cast iron including its advantages and disadvantages and a market survey that provides information regarding the price and availability of Cast Iron.
Keywords— Structures, Matrix, Austenite, Pearlite, Ferrite, Cementite, Graphatization, Eutectic, Corrosion, Susceptible.
I. INTRODUCTION
In the family of metals there are two types of alloys. Ferrous and Nonferrous. The cast iron belongs to family of ferrous alloys i.e. alloy of carbon, iron, silicon, and other impurities.
According iron-iron carbon equilibrium diagram cast iron contains 2 to 6.67% carbon due to which it attains the brittle property. Commercially the cast iron which is used contains 2.5 to 4 % of carbon and 1.0 to 3.5% of silicon 0.4 to 1.0 % of manganese. Cast iron is the most popular and common engineering materials characterized with the wide range of mechanical properties such as strength, hardness, machineability, corrosion resistance and also have good foundry properties.
The ductility of cast iron is very low and cannot be work at room temperature however they melt readily and can be casted into complicated shapes. So the suitable process for manufacture the things from cast iron is casting.
As they are inexpensive and have good fluidity and low liquid temperature so that, they occupy important place in engineering applications.
II. COMPOSITION
The commercially the cast iron contains a significant amount of silicon. A cast iron contains 2.0 % to 4.0 % carbon, 0.5 to 3 % silicon, less than 1.0 % manganese and less than 0.2 % sulfur. Due to the significant amount of silicon in cast iron the wt% of carbon in equilibrium phase diagram is replaced by the carbon equivalent i.e. calculated as
Carbon equivalent = (wt% carbon) +1/3 (wt% silicon)
High addition of silicon increases the oxidation of silicon increase the oxidation and corrosion resistance property.
TABLE. 1
Composition Of Cast Iron
Iron Type
Percentage %
Carbon
Silicon
Manganese
Sulfur
Phosphorous
Gray
2.5-4.0
1.0-3.0
0.2-1.0
0.02-0.25
0.02-1.0
Ductile
3.0-4.0
1.8-2.8
0.2-1.0
0.01-0.03
0.01-0.1
Malleable (Cast Iron)
2.0-2.9
0.9-1.9
0.15-1.2
0.02-0.2
0.02-0.2
White
1.8-3.6
0.5-1.9
0.25-0.8
0.06-0.2
0.06-0.2
Primarily cast iron is the alloy of iron-carbon and silicon which also contains manganese, phosphorous, sulfur, Ni, Cr, Mo and V.
III. TYPES OF CAST IRON:
The best method for the classification of cast iron is according to the metallographic structure. There are four ways to differentiate the type of cast iron. By carbon contact, Alloy of Impurity content, the cooling rate during and after freezing, and heat treatment after casting. These variables control the physical form and carbon condition. So, now the types of cast iron are as follows:

2. A. White cast iron:
In which all carbons is in combined form as cementite.
B. Malleable cast iron:
In which most or all of the carbon is in uncombined form or irregular round practice known as temper carbon, this is obtained by the heat treatment of white cast iron.
C. Gray Cast Iron:
In which most of the carbon is in uncombined form i.e. (in the form of graphite flake)
D. Nodular/Ductile Cast Iron:
In which by special alloy additions the carbon in largely uncombined in form of spheroids (graphite in form of spheres).
IV. MICRO STRUCTURE
A. White Cast Iron:
Microstructure of cast iron consisting of dendrites of transformed austenite (pearlite). Higher magnification of the same sample is tell that the structure is pearlite.
Fig. 1 Microstructure of White Cast Iron
B. Malleable Cast Iron:
The decomposition of cementite i.e. white iron at high temperature causes to produce the malleable iron ( )
And forming graphite which exist in form of clusters or rosettes surrounded by the ferrite or pearlite material, depending on the cooling rate.
Malleable cast iron has range of composition is shown in TABLE 2.
TABLE. 2
Composition of Malleable Cast Iron
Carbon
2.00-2.65%
Silicon
0.90-1.40%
Manganese
0.25-0.55%
Phosphorous
less than 0.18%
Sulfur
0.05%
Fig. 2 Microstructure of Malleable Cast Iron
C. Gray Cast Iron:
In Gray Cast Iron graphite exists in form of flakes normally surrounded by ferrite or pearlite matrix. Due to graphite flakes fracture surface takes place is gray. By the adjustment of composition and using of suitable treatment such as if the composition and cooling also graphitizes then the matrix will be entirely ferritic and if the graphitization of eutectoid cementite is presented the matrix will be entirely pearlitic.
Fig. 3 Microstructure of Gray Cast Iron
D. Ductile/Nodular Cast Iron:
Nodular cast iron also known as ductile iron, spheroidal graphite iron and sulpherulitic iron, is cast iron in which the

3. graphite is present as tiny balls of spheroids. It has small amount of magnesium and cerium to the gray iron.
At typical micro structure matrix phase surrounding their particles is either pearlite or ferrite depending on the heat treatment. Structure of pearlite can be produced as cast or by normalizing i.e. cooling from temperature 1600◦F to 1650◦F i.e. 871◦C to 898◦C. They are stronger but less than ductile ferrite iron. Nodular iron with a matrix having maximum of 10% pearlite are known as Ferritic irons have maximum ductility, toughness and machine ability. Martensitic structure is obtained by quenching in water or oil from 1600◦-1700◦F
Fig. 4 Microstructure of Ductile Cast Iron
E. Alloy Cast Iron:
Alloy Cast Iron which contains the special elements. Elements normally obtain form raw material such as Silicon, manganese, sulfur and phosphorus are not considered as alloy addition.
Most alloy elements in cast iron will accelerate their properties with the addition of common alloying elements as chromium, copper molybdenum, nickel and vanadium.
V. PROPERTIES OF CAST IRON
Cast Iron is a material that is the alloy of iron and carbon. It has the great contribution in engineering applications. There are the number of properties which vary with respect to their composition and structure.
In general the ductility of cast iron is very low it can’t be rolled, drawn or worked at room temperature. They melt readily and can be cast into complicated shapes. Since casting is only suitable process applied for these alloys, they are known as cast irons. Usually cast irons are brittle, have low strength than steel but can be cast rapidly than steel. The properties of different types of cast iron varies over the wide range
A. White Cast Iron:
We know that cementite is a hard, brittle, interstitial compounds. It makes cast iron hard wear resistant an also brittle in nature. White cast iron are limited in engineering application due to lack of machineability.
The mechanical property for unalloyed white iron is as follows:
TABLE. 3
Mechanical properties of White Cast Iron
Hardness
375 to 600 BNN
Tensile strength
20000 to 70000 Psi
Compressive Strength
200000 to 250000 Psi
Modulus of elasticity
24 to 28 million Psi
B. Malleable Iron:
The mechanical properties of malleable cast iron are
TABLE. 4
Mechanical Properties of Malleable Iron
Tensile strength
58000-65000 Psi
Yield point
40000 - 45000 Psi
Elongation % in 2 in
15 – 20
BHN
135 – 155
C. Gray Cast Iron:
 Gray irons are comparatively weak and brittle in tension.
 Strength and ductility are much higher under compressive loads.
 They are very effective in damping vibrational energy.
 Gray cast iron exhibit high resistant to wear.
 In molten state it has high fluidity property.
 The casting shrinkage property is less.
 Gray cast iron is among the least expensive of metallic materials.
 Gray Iron also has the property of readily machineability.
 The electrical resistance of Gray Iron is sufficienly high therefore, they are used for resistance grids.
The mechanical properties of Gray casting vary widely with respect to grades.
TABLE. 5
Mechanical Property of Standard Gray-iron
ASTM Class
Tensile Strength PSI
Compressive Strength PSI
TORSIONAL SHEAR STRENGTH PSI
BHN
20
22000
83000
26000
156
25
26000
97000
32000
174
30
31000
109000
40000
201
35
36500
124000
48500
212
40
42500
140000
57000
235
50
52500
164000
73000
262
60
62500
187500
88500
302
ASTM(American Society of testing Materials)
D. Nodular Cast Iron:
As it is also called ductile iron so, it is ductile. It has higher strength and toughness compared with similar structure of

4. gray iron. The properties of Nodular Iron vary with microstructure.
 Nodular Iron with matrix 10% pearlite known as ferritic iron has high ductility, toughness and machineability.
 Nodular Iron with largely pearlity are more stronger but less, ductility than ferritic iron.
 A martensitic matrix obtained by quenching are usually tempered after hardening, to the desired strength and hardness levels.
 Austenitic ductile irons relatively have high corrosion resistance and good creep property at elevated temperature.
TABLE. 6
Mechanical Properties of Basic Types of Nodular Iron
TYPE
ALLOY CONTANT
Tensile Strength PSI
YIELD Strength PSI
ELONGATION % IN 2 inch
BHN
Ferritic
Low
55000
35000
25
130
High
90000
70000
12
210
Pearlitic
Low
80000
60000
10
200
Low
130000
90000
7
275
High
130000
110000
2
275
Quenched
100000
80000
10
215
150000
130000
2
320
Austenitic
60000
30000
40
130
60000
40000
10
160
E. Alloy Cast Iron:
Different elements are added in to cast irons to variates their properties such as:
1) Chromium: Small amount of chromium increases the strength, hardness, depth of chill and resistance to wear but decreases the machine ability
2) Copper: Copper tends to break up massive cementite and strengthen the matrix.
3) Molybdenum: It improves the fatigue strength, tensile strength, hardness of cast iron, transverse strength, heat resistance.
4) Vanadium: It is powerful carbide former, stabilizes cementite, increase the tensile strength, transverse strength and hardness.
5) Nickel: The addition of nickel in the different types of cast iron effects on their micro structure. The addition in gray cast iron results in increasing heat resistance, high corrosion resistance and low expansivity and due to nickel the structure will be austenitic.
VI. BENEFITS OF CAST IRON
Ref. [5] shows ―Some Benefits and Advantages of Cast Irons in Engineering Applications
 Available in a wide range of mechanical/physical properties, i.e. tensile strength from 20 Ksi to over 200 Ksi, hardness from 120 to about 300 Brinell in standard grades and up to about 600 Brinell in special abrasion resistant grades.
 Good strength to weight ratio.
 Typically lower cost than competing materials and relatively low cost per unit of strength than other materials.
 Lower density and higher thermal conductivity than steels at comparable tensile strength levels.
 Excellent machinability, allowing for high speeds and feeds and reduced (minimal) energy due to the presence of free graphite.
 Many iron castings can be used without heat treatment (as-cast) but, when needed, can be heat treated to enhance overall properties or localized properties such as surface hardness.
 Excellent damping capacity, especially in Gray Irons.
 Chemical analysis can be modified to provide improved special properties such as corrosion resistance, oxidation resistance, wear or abrasion resistance, etc.
 Rapid transition from design to finished product.
 Capability of producing highly complex geometries and section sizes in a wide range of sizes, from ounces to over 100 tons.
 Flexibility in design and ability to optimize appearance for sales appeal.
 Possibility of casting intricate shapes as well as very thin to very thick section sizes.
 Capability of redesigning and combining two or more components from other materials into a single casting, thus reducing assembly cost and time.
 Capability of casting with inserts of other materials.
 Variety of casting processes for low, medium or high production.
 Reduced tendency toward residual stresses and warpage than some competitive materials.
 A family of materials capable of meeting a wide variety of engineering and manufacturing requirements (the family includes Gray Iron, Ductile Iron, Compacted Graphite Iron, Malleable Iron, and White Iron).‖

5. VII. PROBLEMS AND DETERIORATION:
Ref. [6] shows ―Cast iron is extremely strong and durable when used appropriately and protected from adverse exposure. It is much stronger in compression than in tension, therefore it is commonly found in columns, but not in structural beams. It is, however, highly susceptible to corrosion (rusting) when exposed to moisture and, has several typical problems which usually can be identified by visual inspection. The following sections will identify and discuss the most common problems encountered with cast iron. For general guidance on inspecting for cast iron failures.
A. Natural Or Inherent Problems:
The typical deterioration or corrosion process for cast iron is a one-step straight line process of oxidation (or rusting) which begins on exposure to air and moisture and will continue (unless interrupted) until the metal is gone. This process is described in the following section.
1) Rusting: Rusting, or oxidation, is the most frequent and easily recognizable form of cast iron deterioration. Cast iron is highly susceptible to rusting when the humidity is higher than 65%.
2) Graphitization: Due to graphitization the cast iron piece retains its shape and appearance but becomes weaker mechanically because of the loss of iron.
B. COATINGS FAILURE:
Barrier coatings are the most commonly used protective mechanisms for cast iron. Some type of coating (such as a wax, paint or metallic coating) should probably be considered an integral feature of cast iron in service. The absence of such a coating, or a failure in an existing coating should be corrected
C. MECHANICAL FAILURE:
Mechanical failures of cast iron are typically of two types and are relatively common problems.
1) Structural Failure: Cast iron may contain various imperfections due to the manufacturing process. These may occur due to air holes, interrupted pouring, uneven cooling (cold sheets), cracks and cinders. Where such imperfections occur, the piece may be weakened mechanically, sometimes severely.
2) Mechanical Failure of Connections: Larger cast iron pieces are generally systems composed of smaller castings, mechanically connected. This can even be the case for a simple baluster or historical marker. One of the most common failures which occurs with such systems is the failure of the connectors or joints. Loose, missing or broken screws, clamps or bolts may result in loose, failed or missing components.‖
VIII. CONCLUSION
Cast Iron is a very essential element in our daily lives and we cannot imagine our life without using it. Its different properties and wide range of features allow us to use it in our homes, automobiles and in industries as well. it has advantages and disadvantages as well but the huge list of advantages surely do exceed the list of disadvantages which makes it a very good and non-compete-able engineering material.
REFERENCES
[1] Sidney H Avner, 2nd Ed, Introduction to Physical Metullargy.
[2] J. Breckling, Ed., The Analysis of Directional Time Series: Applications to Wind Speed and Direction, ser. Lecture Notes in Statistics. Berlin, Germany: Springer, 1989, vol. 61.
[3] S. Zhang, C. Zhu, J. K. O. Sin, and P. K. T. Mok, ―A novel ultrathin elevated channel low-temperature poly-Si TFT,‖ IEEE Electron Device Lett., vol. 20, pp. 569–571, Nov. 1999.
[4] M. Wegmuller, J. P. von der Weid, P. Oberson, and N. Gisin, ―High resolution fiber distributed measurements with coherent OFDR,‖ in Proc. ECOC’00, 2000, paper 11.3.4, p. 109.
[5] http://www.ironcasting.org/benefits.html/
[6] http://www.gsa.gov/portal/content/111738/