Mms Manual.2008

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MAHATMA GANDHI INSTITUTE OF TECHNOLOGY

Chaitanya Bharathi (P.O.), Gandipet, Hyderabad - 75

Department of

Metallurgy & Materials Technology

LAB MANUAL

Metallurgy & Materials Science

Dr. J. Viplava Kumar P.K. Subramanian

Lab Incharge Head of the Department

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MAHATMA GANDHI INSTITUTE OF TECHNOLOGY

Metallurgy & Materials Technology

II/IV B.Tech. II Semester

Metallurgy & Materials Science

CONTENT

[

S.No Name of the Experiment Page. No

1 Preparation and study of the microstructure of pure metals like Iron, Cu, Al. 2-6

2Preparation and study of the microstructure of Mild steels, low Carbon steels,

high carbon steels.7-8

3 Study of microstructures of Cast irons.

9-10

4 Study of microstructures of Nonferrous alloys.

11-12

5 Study of microstructures of Heat treated steels.

13-15

6 Hardenability of steels by Jominy end Quench Test.

16-20

7 To find out the hardness of various treated and heat treated steels.21-22

Experiment 1

Preparation and study of the Microstructure of pure metals

Aim:

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To prepare a metallographic specimen.

Procedure:

The successive microscopic study depends largely upon the care taken in the preparation of the

specimen. The ultimate objective is, to prepare a metallographic specimen. The steps followed during

the preparation of metallurgical specimen are:

1. Sampling

2. Rough grinding

3. Mounting

4. Ruler mediate polishing

5. Fine polishing

6. Etching

Sampling:

The choice of a sample for a microscopic study is very important. If the material is soft, such as

non-ferrous metal and non-heated steels, the section may be obtained by hack Sawing. If the

material is hard, the section is obtained by use of an abrasive cut off wheel. This wheel is a thin

disk of suitable cutting abrasive, rotating at high speed. The specimen should be kept cool during

the cutting operation.

Rough grinding:

The specimen should be of a size that is convenient to handle. A soft sample is made flat by

smooth filing. The soft or hard specimen may be rough ground on a belt sander, with the specimen

kept cool by frequent dropping in water during the grinding operation. In all grinding and polishing

operations the specimen should be moved perpendicular to existing scratches. This will facilitate

recognition of the stage when shallower ones have replaced deeper scratches, is the characteristic

of the finer abrasive. The rough grinding is continued until the surface is flat and free of nicks,

burrs etc., and all scratches due to the hacksaw or cut-off wheel are no longer visible.

Mounting:

Specimens that are small should be mounted to facilitate intermediate and fine polishing. Wires,

small rods, sheet metal specimens and thick sections must be appropriately mounted with a suitable

material or rigidly clamped in a mechanical mount. The most common thermosetting used for

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mounting is Bakelite. Lucite is the most common thermoplastic resin for mounting. Synthetic

plastic materials applied in special mounting press will yield mount of uniform convenient size for

handling in subsequently polishing operations. Mounts made are resistant to attack by etching

reagent and thermosetting rising for mounting is Bakelite. It is available in variety of substances,

which specifies identification of mount specimens. Specimen, Bakelite powder is placed in

cylinder of mounting press and temperature is raised to 180C and pressure to 4000 psi. Bakelite isset and used when temperature is reached. The specimen mount may be ejected from mount when

it is hot.

Intermediate polishing:

After mounting, the specimen is polished with a series of emery papers containing successively

finer abrasives. The first paper is usually numbered 1/0 followed by 2/0, 3/0, and 4/0. The

intermediate polishing process is usually done dry. In certain cases such as preparation of such

materials, silicon carbide abrasive may be used. As compared to emery paper, silicon carbide has a

greater removal rate, and is resin bonded, can be used with a lubricant. Using a lubricant prevents

overheating of sample, minimizes smearing of soft metals, and also provides a rinsing action to

flush away surface removal products so that paper will not become clogged.

Fine polishing:

The time consumed and successes of fine polishing depend largely upon the care that was

exercised during the previous polishing steps. Finally a flat, scratch free surface is obtained by use

of a wet rotating wheel covered with a special cloth that is charged with carefully sized abrasive

particles. A wide range of abrasives is available for final polishing. alumina oxide is the abrasive

for ferrous and copper based materials and Cerium oxide is the abrasive for aluminum, magnesium

and their alloys. Other final polishing abrasives often used are diamond paste, Chromium oxide and

magnesium oxide.

Etching:

The purpose of etching is to make visible many structural characteristic of metal or alloy. The

process must be such that, the various parts of microstructure may be clearly differentiated. This is

accomplished by use of an appropriate reagent, which subjects the polished surface to chemical

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action. As alloys composed of two or more phases, the components are revealed during etching by

a preferential attack of one or more of the constituents by the reagent, because of difference in

chemical composition of the phases. In uniform single-phase alloys or pure metals, contrast is

obtained in between grains and grain boundaries made visible because of differences in the rate at

which various grains are attacked by reagent. As grain boundaries are having more free energy than

that of grains, they react more than the grains. So light is not reflected back to Objective from thevalleys of grain boundaries, hence they appear darker and make the structure visible. The selection

of appropriate etching reagents is determined by metal alloy and specific structure desired for

viewing. Some of the most common etching reagents are given in the table [1].

Metallographic polishing abrasives

The abrasive must produce a polished surface, by uniformly removing or cutting away surface

metal with almost no metal flow. For polishing abrasive material must be very hard and abrasive

particles should have sharp edge and cutting corners. Soft abrasives are not used in metallographic

polishing as they loose their cutting edges. Round particles shape is not desirable as they roll in

between the surface and specimen.

Alumina :

Alumina is available in the form of dry powder or paste, white in color and available in three grades A,

B, C. A-grade alumina has coarse particles and c-grade alumina has fine particles. Generally A-grade

suitable for polishing of ferrous materials, B-grade is suitable for non-ferrous and C-grade for photo

microscopy.

Chromium Oxide:

Used for polishing of ferrous materials and is green in color. The powder is mixed with distilled water

and suspension is used.

Diamond Paste:

This is suitable for polishing very hard materials such as sintered carbides and cutting tools. Also

diamond paste mixed with some suitable lubricant and used for some polishing work. While using

diamond paste the surface becomes oily and hence it is necessary to clean the surface by suitable

cleaning solution as trichloro ethylene or ethyl/methyl alcohol, before etching.

Magnesium Oxide :

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Generally used in the final polishing stage of soft metals. Always MgO mixed with distilled water and

never with ordinary water.

Etchants for Microscopic Examination

Material Etchant & Composition Characteristics revealed

Iron and steels Nital:

Con. Nitric acid 2 5 ml

Ethanol 100 ml

It produces maximum contrast between

ferrite and pearlite or cementite and pearlite.

Copper & alloys Ferric Chloride:

Ferric chloride 10g

Hydrochloric acid 30 ml

Water or 50:50 water-

ethanol mixture

It darkens beta in brass. Etching can be

continued to get proper contrast.

Table: 1

Result: Thus the microstructure was obtained

Questions

1. Define Metallography.

2. What do you mean by Sampling?

3. Match the following:

a. If the material hard, sectioning done with

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b. If the material soft, sectioning done with

(1) Hack sawing (2) Abrasive cutting wheel.

4. At what angle, the specimen should be moved, to the existing scratches while polishing?

5. When you go for mounting? Or why mounting is done to a sample?

6. Following are the series of emery papers containing successively finer abrasives. Say whether

(a) or (b) is correct

a. 1/0, 2/0, 3/0, 4/0

b. 4/0, 3/0, 2/0, 1/0

7. What is the material used for Intermediate polishing?

8. How fine polishing is done?

9. What is the purpose of Etching?

10. Give principle of Metallurgical microscope.

Experiment 2

Preparation and study of Microstructure of Mild Steels, low carbon steels,

high carbon steels

Aim:

To prepare and study of the microstructure of Mild Steels, low carbon steels, high carbon steels.

Apparatus:

Belt polishers, Emery papers, Disc polisher, Microscope, Specimen.

Chemicals used:

Alumina solution and Nital.

Procedure:

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After sampling and rough grinding, the specimen is subjected to intermediate polishing. It is

done on 1/0,2/0,3/0 and 4/0 emery papers in a perpendicular direction to that of scratches, to align

scratches in one direction. After intermediate polishing, the specimen is subjected to fine polishing on

a disc polisher. During this, A-grade Alumina solution is used as abrasive, to remove scratches further.

After getting a mirror finish surface, it is cleaned with water and the sample is subjected to etching

with a 2% Nitaletchant. The etching time is 30-40 seconds. After etching, the sample is washed and

dried with hot or cold air. Then the dried sample is observed under a microscope, where the

magnification of the objective lies from (45 x) to (10x) and that of the eyepiece is (10 x). Thus the

microstructure is observed.


Precautions:

1. The Etched specimen must be seen immediately after drying, under a metallurgical

microscope.

2. Specimen should not be moved while observing the microstructure. This would produce a

blurred image.

Questions

1. Give examples for ferrite stabilizers.

2. Give examples for Austenite stabilizer

3. Define Ferrite, Cementite, and Pearlite?

4. Define Ledeburite?

5. What is the PyroEutectoid phase in Hypo eutectoid steels?

6. What is the proeutectoid phase in Hyper eutectoid steels?

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7. Give the Eutectic reaction, Eutectic temperature and Eutectic composition in Fe-C system.

8. Give the Peritectic reaction, Peritectic temperature, Peritectic composition

9. Define Hyper Eutectoid steels?

10. What is the Etchant for Hyper Eutectoidsteels?

Experiment 3

Study of the Microstructure of Cast Iron

Aim:

To study the microstructure of Cast Iron

Apparatus:

Belt polishers, Emery papers, Disc polisher, Microscope, Specimen.

Chemicals used:

Alumina solution and Nital (Nitric Acid + Ethyl/methyl Alcohol).

Procedure:


done on 1/0, 2/0, 3/0 and 4/0 emery papers in a perpendicular direction to that of scratches, to align


a disc polisher. During this, A-grade alumina solution is used as abrasive, to remove scratches further.


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with a Nitaletchant. The etching time is 30-40 seconds. After etching, the sample is washed and dried

with hot or cold air. Then the dried sample is observed under a microscope, where the magnification of

the objective lies from (45 x) to (10x) and that of the eyepiece is (10 x). Thus the microstructure is

observed.


Precautions:


Microscope.


blurred image.

Questions

1. What are cast irons?

2. Mention the different types of cast irons.

3. What are the applications of grey cast iron?

4. Draw the microstructure of grey cast iron.

5. What is malleable cast iron?

6. What is grey cast iron?

7. What is the difference between nodular and malleable cast iron?

8. Mention the etchant for cast irons.

9. What is graphitization?

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Experiment 4

Study of the Microstructure of Nonferrous alloys

Aim:

To observe the microstructure of nonferrous alloys.

Apparatus:

Belt Polishers, Emery papers, Disc polisher, Microscope and Specimen.

Chemicals used:

Alumina powder and FeCl2,

Procedure:


done on 1/0,2/0,3/0 and 4/0 emery papers in a perpendicular direction to that of scratches, to align


a disc polisher. During this, B-grade alumina solution is used as abrasive, to remove scratches further.


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with a Fecl etchant. The etching time is 30-40 seconds. After etching, the sample is washed and dried

with hot or cold air. Then the dried sample is observed under a microscope, where the magnification of

the objective lies from (45 x) to (10x) and that of the eyepiece is (10 x). Thus the microstructure is

observed.

Result:Thus the microstructure was obtained

A two-phase microstructure is observed under the metallurgical microscope. It consists of mixture of

and phases where phase appears brighter surrounded by darker grains . During etching, the and

phases are revealed by a preferential attack of phase by the etchant, is due to the difference in

chemical composition of the phases.

Precautions:


microscope.


blurred image.

Questions

1. Give color & crystal structure of pure Cu?

2. Draw microstructure of Cu at 100X and 400X magnification?

3. What is the Etchant for Cu?

4. Define Resolving Power?

5. Is Copper magnetic (or) non-magnetic?

6. What is Brass?

7. What is the purpose of alloying Zn to Cu?

8. Give two applications of Brass

9. What is the Etchant for brass?

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10. Mention the applications of copper.

Experiment 5

STUDY OF THE MICROSTRUCTURES OF HEAT TREATED STEELS

Aim:

To study the microstructure of annealed, normalized, & hardened steels.

Apparatus:

1) Steel sample (0.4%C / 0.8%C / 1.2%C)

2) Silicon carbide furnace / Muffle furnace

3) Tongs

4) Hand gloves

5) Rockwell hardness tester

6) Rough polishing grinder

7) Disc polisher

8) Etching agents

9) Metallurgical Microscope

Description:

In general, annealing involves heating to a predetermined temperature holding at thistemperature for sufficient time (to get homogeneous temperature), and finally cooling at a very slow

rate. The temperature to which steel is heated, the holding time and cooling rate are determined by

various factors such as chemical composition, size and shape of the component and final properties

desired.

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The purposes of annealing are

1) To relieve internal stresses developed during solidification, machining, forging rolling,

welding, etc.

2) To improve or restore ductility and toughness

3) To enhance machinability

4) Refine grain size.

Normalizing:

Normalizing is a process of heating steels to about 40C-50C above the upper critical

temperature, holding for sufficient time, and then cooling in still air or slightly agitated air to room

temperature. The resultant microstructure should be fine pearlitic since the temperature and cooling

rate involved in this process are more than that for annealing, the homogeneity of austenite increases

and it results in better distribution of ferrite and cementite in the final structure. This results in

enhanced mechanical properties. By normalizing chemical inhomogenity is eliminated, an optimum

combination of strength and ductility is achieved which results in satisfactory level of machinability in

steels. Normalizing treatment is frequently applied to steels in order to achieve any one or more of the

objectives, namely Grain Refinement, improvement in machinability and enhanced mechanical

properties such as hardness, ductility, strength and toughness

Hardening:

Hardening treatment consists of heating to predetermined temperature, holding at that

temperature for sufficient time to get homogenous austenite, followed by quenching in water, oil or

salt baths. The high hardness developed by this process is due to phase transformation accompanying

rapid cooling. Rapid cooling results in the transformation of austenite at considerably low temperature

into non-equilibrium products. The product of low temperature transformation of austenite is

martensite, which is a hard micro constituent of steel. Martensite is supersaturated solid solution of

carbon in gamma iron. The term hardening by quenching is used for this process in order to

differentiate it from other hardening process.

Procedure:

After sampling and rough grinding, the specimen is subjected to intermediate polishing. It is done on

1/0, 2/0, 3/0 and 4/0 emery papers in a perpendicular direction to that of scratches, to align scratches in

one direction. After intermediate polishing, the specimen is subjected to fine polishing on a disc

polisher. During this, A-grade alumina solution is used as abrasive, to remove scratches further. After

getting a mirror finish surface, it is cleaned with water and the sample is subjected to etching with a

Nitaletchant. The etching time is 30-40 seconds. After etching, the sample is washed and dried with

hot or cold air. Then the dried sample is observed under a microscope, where the magnification of the

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objective lies from (45 x) to (10x) and that of the eyepiece is (10 x). Thus the microstructure is

observed.


Precautions:


microscope.


blurred image.

Questions

1. Why hyper eutectoid steels are not heated above Acm?

2. What isannealing?

3. What is the purpose of annealing?

4. What is tempering?

5. What is normalizing?

6. What is the hardness of martensite?

7. What is martensite?

8. What is the purpose of normalizing?

9. What is hardening?

10.what is the significance of TTT diagrams?

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Experiment 6

JOMINY END QUENCH TEST

Aim:

To determine the hardenability of a given steel specimen by Jominy End Quench test.

Apparatus:

1) Steel sample (0.4%C / 0.8%C / 1.2%C)

2) Silicon carbide furnace / Muffle furnace

3) Tongs

4) Hand gloves

5) Rockwell hardness tester

6) Rough polishing grinder

7) Disc polisher

8) Etching agents.

9) Metallurgical Microscope

Procedure:

In this test, a steel bar of 1-inch diameter and 4 inches long is heated to proper austenitising

temperature. After being soaked for sufficient time, the specimen is quickly placed in Jominy fixture,

as shown in the figure. Water comes out at a constant pressure through an orifice of inch diameter.

The distance between orifice and the bottom end of the steel bar is kept at inch. The free jet height

is 2.5 inches, and the temperature of water is kept around 24 0C. A stream of water strikes the lower

end of the specimen. The end quenching is continued for about 20 minutes to cool the bar nearly to

ambient temperature. The cooling rate is very rapid at the lower end and decreases gradually with

increase in distance from the lower end. After quenching, two flat surfaces of 0.02 inch deep are

ground 1800 apart on the test bar. The hardness is determined at intervals of 1/16 inch along one end

of the flat surface of the bar. Near the quenched end, this interval is reduced to 1/32 inch as hardness

impressions are smaller and hardness value may vary rapidly. Curve is then plotted showing hardness16

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against distance from the quenched end. With 50% martensite and 50% pearlite, hardness value of Rc

54 is obtained. This distance is measured from the quenched end in units 1/16 inch. This distance is

called the Jominy distance.

The master plot between ideal critical diameter, Di , and the distance from the quenched end

under specific conditions is plotted. When the distance from the quenched end is 5/16 inch at Rc50 it

is shown by J50 = 5. Then corresponding value for hardenability or ideal critical diameter will get from

the master plot.

Result:

Draw the plot between hardness Vs distance from quenched end.

Conclusions:

1.

2.

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Questions

1. What is Hardenability?

2. What is the difference between Hardness and Hardenability?

3. What are the conditions to be followed to develop max hardness in the steel?

4. What is ideal quenching medium?

5. What do you mean by severity of quench?

6. Explain the process of heat removal during quenching.

7. What is the effect of quenching media on Hardenability?

8. What is the effect of temperature on Hardenability?

9. Mention the methods used for the determination of Hardenability.

10. What is critical diameter method?

Experiment-7

HARDNESS OF VARIOUS TREATED AND UNTREATED STEELS

AIM:

To determine the hardness values of annealed, normalized, hardened & untreated steels.

APPARATUS:

Rockwell Hardness Tester, disc polisher, grinding belts, sand papers, emery papers

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THEORY:

Rockwell Hardness test is a direct reading instrument based on the principle of differential

depth measurement. The higher the hardness, the smaller will be the depth of penetration. No

calculation is required. There are two types of scales B scale 1/16 ball indenter and 100kg load C

scale 1200 diamond indenter and 150Kg load both obtained with normal tester where the minor load

is 10 Kg.

PROCEDURE:

1. Raise the specimen against the hardened steel ball indenter 1/16 until a fixed minor load of 10

Kg. on the normal tester has been applied.

2. It is indicated on the dial guage.

3. Then, a major load of 100 kg is applied through a loaded lever system.

4. After the dial pointer comes to rest, the major load still acting, the Rockwell hardness number

is read on the dial guage.

5. Since the order of the numbers is reversed on a dial guage, a shallow impression on a hard

material will result in a high number while a deep impression on soft material will result in a

low number.

PRECAUTIONS:

1. Care must be taken to seat the anvil and indenter firmly.

2. The performance of the machine should be checked frequently with standard test blocks

supplied by the manufacturer.

RESULT: Thus the Hardness was obtained

Questions

1. What is hardness?

2. Mention the different hardness testing methods.

3. Mention the units for Rockwell hardness test.

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4. What are the indenters used for Rockwell test?

5. Mention the scale used for determining the hardness for soft materials.

6. Given annealed, normalized and hardened steel which will show high hardness.

7. What is Ferrite?

8. What is Pearlite?

9. What Austenite?

10. What is Cementite? And proeutectoid Cementite?

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