University of Zakho

College of engineering
Mechanical department
2ndstage 3th semester

Experiment No(2)
Preparation the specimen & observation of
microstructure of steel ( white cast iron , medium carbon
steel)

Prepared By: Supervised by:

Yasser sardar Mr.Shivan

Date of Exprement:11\14\2024
Date of submitting:11\17\2024

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Contents
Introduction to Metallurgical Engineering .................................................... 3
Introduction to metals :................................................................................ 3
PURPOSE: ................................................................................................. 5
APPARATUS: ............................................................................................. 5
THEORY:.................................................................................................... 7
Experiment samples : ................................................................................. 9
Experimental Procedure: .......................................................................... 10
DISCUSSIONS: ........................................................................................ 10
Reference : ............................................................................................... 10

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Introduction to Metallurgical Engineering
Metallurgical engineering is a crucial field of engineering that focuses on the
study of metals, their characteristics, processes, and practical uses. It
integrates materials science with engineering principles to explore the
structure and behavior of metals and alloys. Metallurgical engineers
specialize in extracting metals from ores and refining them into usable forms
through processes like smelting and electrolysis.
After extraction, they utilize manufacturing techniques such as casting,
welding, and forging to shape metals into final products. Ensuring the quality
and dependability of these materials is essential, and metallurgical engineers
use various testing methods to evaluate properties like strength, ductility,
and resistance to corrosion.

Introduction to metals :
Here are some additional points on the structure and properties of metals:
1. Mechanical Properties and Testing
Metals exhibit properties such as tensile strength, hardness, ductility,
toughness, and elasticity. These are influenced by their crystal structure,
grain size, and phase composition.
Standard testing methods like tensile tests, hardness tests (e.g., Brinell,
Rockwell), and impact tests (e.g., Charpy test) are used to evaluate these
properties.
2. Corrosion Resistance
The ability of a metal to resist degradation due to environmental factors, such
as moisture or chemicals, depends on its composition.
Alloying elements like chromium and nickel improve corrosion resistance,
making materials like stainless steel highly durable.

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3. Work Hardening
Deforming a metal through processes like rolling or hammering introduces
dislocations, increasing its strength through work hardening (strain
hardening). This process enhances metal performance but can reduce
ductility.
4. Anisotropy in Metals
Metals may exhibit anisotropy, meaning their properties vary based on
direction due to crystal orientation or manufacturing processes.
For example, rolled steel often has higher strength along the rolling direction
compared to other directions.
5. Thermal Conductivity
Metals are excellent conductors of heat due to free electron movement in
their crystalline structures.
This property is critical in applications like heat exchangers, cooking utensils,
and electronics
6. Electrical Conductivity
Metals also conduct electricity well, with materials like copper and aluminum
widely used in electrical applications. The crystal structure and impurities in
the metal influence its conductivity.
7. Density and Weight Considerations
The density of metals varies based on atomic weight and packing structure.
For instance, aluminum is lightweight and suitable for aerospace
applications, while steel provides higher strength but is heavier.

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PURPOSE:
To Preparation the specimen &, observe the composition, structure and
properties of metals and their a lloys by means of an optical microscope.

APPARATUS:
Cutting machine, grinding and polishing machine, itching (2-3%
nitric acid in ethanol), microstructure

Fig.1 Grinding and polishing machine

Fig. 2 Cutting machine Fig. 3 Itching

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 Fig. 4 microscope

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THEORY:
Before examining the steel specimen, there are some before in hand
procedures to follow for a better observation. Initially the specimen should
be prepared for the examination;
Mounting: Is done for the ease of holding the specimen during the grinding
and polishing process. Here, in one process, cold mounting is conducted
where
using two components resins which are liquid to start with but which set solid
shortly after mixing. Cold mounting requires very simple equipment
consisting of a cylindrical ring which serves as a mold and a flat piece which
serves as the base of the mold. The sample is placed on the flat piece within
the mold and the mixture poured in and allowed to set. Cold mounting takes
few hours to complete. Another method is hot-mounting which uses a heating
method.
Grinding: Is done using rotating discs covered with silicon carbide paper and
water. There are a number of grades of paper, with 180, 240, 400, 1200,
grains
of silicon carbide per square inch. 180 grade therefore represents the
coarsest
particles and this is the grade to begin the grinding operation. We should
always use light pressure applied at the center of the sample. Continuation
of
this grinding should be carried out until the blemishes are removed.
Polishing: Is done to get a mirror like surface to clearly observe the structure
here it is being polished by polishers which has rotating discs covered with
soft cloth impregnated with a pre-prepared slurry of hard powdery alumina
particles (Al2O3, the size ranges from 0.5 to 0.03 μm). This is done due to
fact

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that the surface unevenness will be removed.
The specimen should be put in acid in which the acid will attack the grain
boundaries taken into a reaction.
Etching: Is done due to Grinding and polishing operations produce a highly
deformed, thin layer on the surface which is removed chemically during
etching. Secondly, the etchant attacks the surface with preference for those
sites with the highest energy, leading to surface relief which allows different
crystal orientations, grain boundaries, precipitates, phases and defects to be
distinguished in reflected light microscopy as demonstrated in Figure bellow.

Fig .5 surface reflections

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Experiment samples :
1.Sample No .12

White cast iron : A hypoeutectic type white cast iron structure is observed.
Dendrites of original Austenite transfomed to Pearlite are observed. White
bright phase Cementite is observed in the interdendritic region.
• Mechanical treatment : As Cast
• Heat treatment : Nil
Average Composition :
A. 2.8% Carbon
B. 1% Silicon
Magnification :200 X
Etchant : Nital Fig.6 white cast iron
2.Sample No .3
Medium carbon steel : Description: A typical two phase structure is
observed. Ferrite is Bright phase whereas Pearlite is dark phase. Fernte
occupies about 50% volume and pearlite is the balance Grains of ferrite
phase are polygonal and equiaxed. Pearlite is unresolved.
• Mechanical treatment : Hot
Rolled
• Heat treatment : Annealing
Average composition :
A. 0.40% Carbon
B. 0.50% Manganese
Magnification :200X
Etchant : Nital Fig.7 medium carbon steel

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Experimental Procedure:

Step 1: preparation the steel materials.

Step 2: Cutting the materials to specific size .
Step 3: Grinding and polishing the specimen.
Step 4: itching specimen.
Step 5: observation of microstructure by using microscope for knowing the
ferritic pearlitic structural steels & grain boundary

DISCUSSIONS:
First the teacher informed us about the subject and how to use this test. I will
say that at the beginning we will do the grinding and polishing machine.
When we finish this, we will do the cutting machine When we put it on the
microscope, we will put it under the microscope as a piece of paper and the
composition of the iron will be visible. We only took two materials in this
experiment: low carbon steel and gray cast iron.

Reference :
1- https://www.atri.edu.in/images/pdf/departments/METALLURGY%20&
%20MATERIAL%20SCIENCE%20Lab%20manual.pdf
2- https://www.researchgate.net/publication/223430466_Mechanical_an
d_microstructural_properties_of_low-carbon_steel-plate-
reinforced_gray_cast_iron
3- https://www.struers.com/en/Knowledge/Materials/Cast-Iron

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