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:

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

2024\2025

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Contents
Introduction to Metallurgical Engineering..........................................................3
PURPOSE:................................................................................................................. 4
APPARATUS:............................................................................................................. 4
THEORY:.................................................................................................................... 5
Experiment samples :................................................................................................... 7
White cast iron : .......................................................................................................... 7
Experimental Procedure:....................................................................................... 8
DISCUSSIONS:.......................................................................................................... 9
Reference :............................................................................................................. 10

Introduction to Metallurgical Engineering

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processing techniques, and applications. It combines materials science
with engineering concepts to understand the structure and behavior of
metals and alloys. Professionals in this field focus on extracting metals
from their ores and refining them into functional forms using methods such
as smelting and electrolysis.

Introduction to metals
Additional Points on the Structure and Properties of Metals
1. Thermal Properties Metals possess high thermal conductivity,
allowing efficient heat transfer. Coefficients of thermal expansion
vary, impacting their behavior under temperature changes.
Heat treatment processes like annealing, quenching, and
tempering alter properties such as hardness and ductility
2. Electrical Properties Metals like copper, silver, and aluminum
are excellent electrical conductors due to the free movement
of electrons. Conductivity decreases with impurities and
increases with lowering temperatures (in pure metals).Alloy
soften have lower conductivity than pure metals.
3. Density and Specific Strength Metals have high densities
compared to other materials, affecting their weight in
applications Specific strength (strength-to-weight ratio) is
crucial for applications in aerospace and automotive
industries Lightweight metals like aluminum and titanium
are preferred for such uses.
4. Magnetic Properties Ferromagnetic metals (e.g., iron, cobalt,
nickel) exhibit strong magnetic behavior. Magnetic
properties depend on electron configurations and are
influenced by alloying and
5. Alloying and Microstructure Alloying metals improve
properties such as strength, hardness, and corrosion
resistance. Microstructure, determined by grain size and
phase distribution, directly impacts mechanical and thermal
behavior.

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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%

(Fig.1)Grinding and polishing machine

(Fig.2)Cutting Machine

(Fig.4)Itching
(Fig.3)Microstructure

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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

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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 (Al
, the size ranges from 0.5 to 0.03 μm). This is done due to
fact
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.

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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.5 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.6 medium carbon st

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

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DISCUSSIONS:
Microstructural analysis of low carbon steel and gray cast
iron is crucial for understanding their properties and
applications.
Low Carbon Steel: With a carbon content below 0.3%, low
carbon steel primarily consists of ferrite and pearlite. The
arrangement of these phases impacts its mechanical
properties, offering high ductility and toughness suitable
for automotive and structural applications. Heat
treatments can refine the microstructure, allowing
engineers to optimize properties for specific uses.
Gray Cast Iron: Gray cast iron, characterized by higher
carbon content in the form of graphite flakes, offers
unique mechanical properties, including strength and
wear resistance. The size and shape of these flakes are
influenced by the cooling rate and alloy composition.
Understanding these microstructural features helps
manufacturers achieve desired performance
characteristics.
Both materials highlight the significant impact of
microstructure on performance. Advancements in
microscopy enhance our understanding and enable better
material design, driving innovation in various industries.
In essence, analyzing microstructure is key to predicting
performance outcomes and advancing material science.

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Reference :
1. https://m.indiamart.com/proddetail/iron-cutting-machine-13954466630.html
2. https://www.tgindt.com/product/Metallographic-Sample-Grinding-and-
Polishing-Machine-TIME-2DE-150.html
3. https://www.solmedialtd.com/a-step-by-step-guide-to-sample-preparation/

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