GTU MSMT UNIT 2 STUDY MATERIAL

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QUESTION AND ANSWER BANK FOR GTU EXAMINATION,
MATERIALSCIENCE AND METALLURGY(3321902)
PREPARED BY:ANKITKUMAR A BRAHMBHATT
ASST PROFF PIET DS 1(MECHANICAL).

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UNIT 2 PHASE DIAGRAM
2 MARKS
1.a).Grain b).Grain Boundary
Answer: GRAIN: The metal structure formed by the crystal is known as grain.
GRAIN BOUNDRY:Each grain starts from the nucleus so the crystallisation obtained is
dependent on the number of nucleus the orientation of the atoms arise from grain to grain.
The two hereby grain meet in a surface these surface is known as grain boundary.
2.What is Equilibrium Diagram?
Answer: The temperature composition diagram shows the changes of the structure taking
place during the heating and cooling is called as Equilibrium diagram.
On X AXIS: Metal Composition, Y AXIS :Temperature. It is also known as Phase Diagram
When any Alloy after heating cooled down then changes taking place in it is shown by a
curve known as Equilibrium Diagram or Phase Diagram or Constitutional Diagram.
3.Define Solid Solution and give examples.
Answer: In liquid stage metal form homogeneous liquid solution, The solid Solution is
formed. If Solvent &Solute atoms are of similar size and electron structure, solid solution
forms very readily if elements A in B forms solid solution in B by its 10%.
E.g Brass: Copper & Zinc,Steel:Iron & Carbon,Monel:Nickel&Copper,Au-Ag:Gold & Silver,
Sterling Silver: Silver & Copper.
4.What Is Cooling Curve and Draw Cooling Curve Of Metal Compound
Answer: By measuring the temperature at definate interval of time when the liquid metal or
alloy is cooling the time temperature curve is plotted this curve of metal and alloy is called
cooling curve.
Fig:1 Cooling Curves

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5.Properties Of Solid Solution
Answer: Properties
• Thermal &Electrical properties are reduced due to formation of solid solution.
• The strength and hardness of all the alloy metals increases due to solid solution
• Solid solution reduces the ductility &malleability of the alloys.
• The density, specific heat &heat distribution get changed according to the proportions
of alloying elements.
• By changing the proportion of the alloying element, there is no possibility to change
the stiffness any more.
• Solid solution alloys exhibit differential freezing.
• Solid solution are conductors but not as the pure metals on which they are based.
• The Constituents of the solid solution cannot be detected by the microscope.
• It is simply a solution in the solid state consisting of atoms combimned in one type of
space lattice.
6.State Lever Rule
Answer: On basis of phase Diagram No Of phase, and Composition Of phase can be
calculated .
Fig 2:Phase Diagram
lever rule is very important in two phase system to calculate the percentage of phase present
two lines are drawn and point is obtained which is between liquidus and solidus line G E H
Solid Phase Percentage=GE/GH*100 Liquid Phase Percentage=EH/GH*100
7.Why Heat Treatment Should be carried Out?
Answer:(ANY FOUR)
 To improve combination of different properties.

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 To remove internal residual stresses from the component after basic manufacturing
processes such as casting,forging,Rolling.
 To improve grain size of the material.
 To increase the hardness of the material.
 To improve the toughness of the compomnent.
 To improve machinability of the material.
 To make the material soft so that the process like wire drawing,Cold Rolling,Can be
performed on the same.
 To improve heat,wear,and corrosion resistance of the materials.
 To improve magnetic and electrical properties of the material.
 To impart harder surface and softer core to the component.
 To make the structure of the component homogenous.
 To improve ductility and toughness of the material.
 To stabilize size of the component.
 To facilitate diffusion process in the steel.
 To obtain desired structure in the material as per specific application requirement.
8.Differentiate between Process Metallurgy and Physical Metallurgy
Answer: Process Metallurgy: It deals with the extraction of metal from its ore.
Physical Metallurgy: Study of physical &Mechanical properties of metals of alloys as well as
the governing laws by which these attribute varry owing to external influences such as
thermal, mechanical, chemical, electromagnetic and radioactive effect.
9.Give Name Of Alloying Element used in Alloy Steel
Answer: C,Si,Mn,Cr,Mo,Ni,W,S,P,Nb,Ti,Ta,Etc
10.Types Of Solid Solutions
Answer:
Fig 3: Types Of Solid Solution

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11.Why Alloying is done?
Answer:(Any Four)
• increase hardenability.
• improve strength at ordinary temperature.
• improve mechanical properties at either high or low temperature.
• improve toughness at any minimum hardness or strength.
• increase wear resistance.
• increase corrosion resistance.
• improve magnetic properties.
12.Use OF iron carbon Diagram
Answer:
• To predict no type and composition of the phases.
• To predict amount of the phases .
• Guide heat treater.
• Predict microstructure of an alloy.
13.Limitation Of Iron Carbon Diagram.
Answer:
• It does not give information about ferrite or cementite formed ejected from austenite
on cooling.
• It does not give information about size of micro constituents present.
• It does not give information of Physical and Mechanical Properties of the material.
14.Classification Of Heat Treatment Process
Answer:.
Fig 4:Classification of Heat Treatment Process

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15.Why Annealing is carried out?
Answer: Purpose Of Annealing:(Any Four)
• To produce the desired microstructure having mechanical.physical,and other
properties as per the requirement.
• To reduce hardness and soften the steel
• To relieve the internal stress.
• To restore the ductility and thereby facilitate further cold working
• To improve Mach inability.
• To refine and make homogeneous structure by reducing structural in homogeneities
• To create complete stable structure.
• Increase or restore toughness.
16.Types Of Annealing?
Answer:
Fig 5:Types Of Anneling Process
17.Application OF Annealing
Answer:
• To make the parts soft.
• To improve the structure of the parts.
• To bring the properties required for cold working.
• To remove irregularities
• To prevent Cracking of the parts during process.
• To relieve internal stress.
• To improve machinability.
• To get Good structure for hardening.
• To increase formability.

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• To improve the electrical &Magnetic properties.
18.Purpose of Normalizing.
Answer: Purpose Of Normalizing(Any Four)
• To obtain desired microstructure and mechanical properties.
• To improve the Machinability of low carbon steels.
• To eliminate coarse grained structure resulted from working operation such as rolling,
Forging etc.
• To modify and improve cast dendritic structure and reduce segregation by
homogenizing the micro structure.
• To improve tensile strength of casting and forging component.
• To improve weld structure after welding process.
19.Application OF Normalizing.
Answer: Application of the normalizing Process(Any Four)
• To obtain uniform structure.
• To refine the grain size.
• To obtain desired strength of too soft & ductile steel.
• To reduce internal stress.
• To improve weld structure.
• To remove the carbide network from the grain boundaries hypo eutectoid steel.
• To improve engineering properties of steel.
20. Advantages Of Hardening Process.
Answer: Any Four
• It increases the hardness of steel.
• Makes tools & machines parts useful for heavy duty.
• It increases the wear resistance of steel.
• Makes steel hard so as to cut the other materials.
• Increases the strength, toughness & ductility of steel.
• A good combination of strength & ductility is obtained.

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21.Dis advantages Of Hardening Process.
Answer: Any Four
• Cracks are developing in the part due to hardening.
• Required hardness can not be obtained.
• It increases the brittleness of the parts.
• Soft Parts develops in the part due to non uniform hardness.
• The dimension & size of the part change.
• Due to warpsage ,the shape of the part gets altered.
• Surface of the part becomes rough.
• Scaling of the surface results when high speed steel having thickness more than 12
mm is hardened.
22.Advantages Of Case Hardening.
Answer: Advantages Of Surface Hardening
• Only 1 to 5 second time is required for heating ,therefore huge work can be done with
benefits.
• There is no scaling &cracking of the parts.
• Less possibility of change of shape like heat treatments.
• This is an automatic process imparts wear resistance property to the material.
• Increase fatigue limit.
• This process does not create any harm to surface finish.
• It increases impact strength.
• Cheaper material can be employed to manufacture the parts.
• Hard surface prevents wear & tough core resists he fracture
• The cost of equipment is less.
• The process is simple.
• The process can be done on lengthy parts. This process is proved most suitable for
producing medium sized components by using mass production.

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23.What is Eutectic ,Eutectoid .
Answer:
Eutectic: in eutectic system certain metal melts at minimum constant temperature this
temperature is known as eutectic temperature and the point at which the eutectic composition
is formed is known as eutectic point E.g. 1130°C,the liquid metal containing 4.3%C is
transformed into eutectic.
Eutectoid: As per eutectic system the transformation of liquid into solid state is known as
eutectoid ,The point at which transformation occurs is known as eutectoid point, E.g 0.85%C
if contained in an austenite it transforms at 723°Cin ferrite & cementite.
24.What is Critical Points, Delta Solid Solution.
Answer:
Critical Point: When liquid metal is allowed to cool at certain temperature heat evolution
takes place and structural changes occurs in the metal. The temperature at which the
structural changes are taking place are known as critical points E.g. 768°C,910°C,and
1400°C.
Delta Solid Solution: Iron is the major element of the steel. It is available in its three
allotropic forms .Therefore the iron has three types of crystal transformation with respect to
temperature. in all these three forms of carbon is soluble and forms the solid solution .The
three allotropic forms are APLPHA,GAMMA,DELTA iron.
25.What Is Ferrite and Cementite.
Answer:
Ferrite: The iron not containing more than 0.025%C in solid solution is the Alpha iron having
BCC structure. It is the major constituent in wrought iron &low Carbon Steel It is having
hardness between 50-100BHN and UTS 3400Kg f/Cm2.Its elongation is about 40% and can
be worked very easily.
Cementite: The iron Carbide Fe3C containing 6.67%C is known as Cementite. Its hardness is
650BHN and UTS 450Kgf/Cm2.It is brittle and white in colour. It is brittle and white in
colour it is occurring due to slow cooling in steel below the temperature of 205°C it can be
magnetised .It is present as a component of another constituent Pearlite in steel if %C is more
than 0.8%,it exists as a grain boundary film.
3 MARKS
1.What is Phase Diagram? Write About Important terms Associated With it?
Answer: The Solidification of Metal Alloy is Clearly understood by means of equilibrium
diagrams.

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• These are graphical representation of the changes in state due to variation in
temperature and concentration.
• This indicate the nature and constitution of the alloys and the amount and the
composition of the phases in a given system.it is also called constitutional diagram or
Phase diagram.
• Equilibrium refers to the changes taking place in a system as a result of process
Occurring in one direction are fully compensated by the changes due to reversal of
the process in the system. Equilibrium diagram indicates the temperatures at which
the solid alloy will start melting and finish melting & possible place changes which
will occur as the result of the altering the composition or temperatures.
• Properties of the materials depends on the Type,Number,Amounts and Form Of the
phases present, the properties can be changed by altering these quantities.
The Equilibrium Diagram
• The temperature composition diagram shows the changes of structure taking place
during heating& cooling. This diagram is known as an Equilibrium Diagram. On
X axis: Metal Composition Y axis: Temperature Scales are plotted. The full name of this
diagram is “Thermal Equilibrium Diagram" known as Phase Diagram or Constitutional
Diagram.
• It represent the equilibrium condition. Which is not possible to have in
reality.eventhough provide basic information for the heat treatment & to study the
properties of alloy.
• If two elements it is known as Binary alloy, If three elements it is known as Ternary
alloy.
Fig 6:Types Of Phase Diagram
• System: Part of the substance which is completely separated from the surrounding.

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• Component: Basic chemical substance, whose mass is constant and which can be
used to form a chemical mixture.
• Phase: The part of material system uniformly mixed physically.
• Constituent:The part of multiphase mixture which can be identified seperately.
• Liquidus:The locus of temperature at which solidification is complete. below solidus
only solids are stable.
• Solidus:The locus of temperature of a transformation at which solidification starts.
• Solvent: The major element of a sold solution.
• Solute: The minor element of a solid solution.
2.What is Solid Solution? Types Of Solid Solution?
• Answer: Solid Solution
• In liquid stage metal form homogeneous liquid solution,The solid Solution is
formed.If Solvent &Solute atoms are of similar size and electron structure,solid
solution forms very readily if elements A in B forms solid solution in B by its 10%.
• Hume Rodhery Rule :if metal A is in lesser proportion than B,therefore A is known as
solute and metal B is known as solvent.There is homogenouus distribution of two or
more constituents in the solid state so as to form a single phase known as solid
solution.A is solid solution is the result of metals dissolving in each other’s crystal
Lattice.In solid solution in both the liquid and the solid state.While in solid solution of
Cu and Zinc both having sub valence electrons,forms substitutional solid solution.
• Solid Solution
• Substitutional Solid Solution
• The substitutional solid solution is formed when the atoms of solute metal occupy the
position of the atoms of solute metal.due to the size differencde in atoms of the two
metals,there is the possibilities lattice distortion.e.g Cu-Ni and Bi-sb alloys.
• As per the arrangement of the solvent &solute atoms in the substitutional solid
solution there are two types as stated below:
• Random or Disordred substitutional solid solution,Ordered substituitonal solid
solution.
• Disordered Substitutional Solid Solution
• While forminmg the solid solution soluter atoms instead of occupying specific
position get distributed random in the lattice structure of the solvent.This alloy is in

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the disordered condition.in this type of condition the concentration of solute atoms
can vary considerably in the lattice structure.
• Ordered Solid Solution
• If an alloy of disordered condition,cooled slowly because of diffusion .its atoms get
rearranged .The diffusion products uniform distribution of solvent & solute atoms and
solute atoms move into definite orderly positions in the lattice .The structure is then
known as super lattice or ordred substitutionasl solid solution.The prolonged anneling
of the alloy can produce still more uniform &ordred solid solution.
• Interstitial Solid Solution
• When the solute atoms are smaller in size than solvent atoms this type of solid
solution is formed. The solute atoms in this case occupies the vacant spaces between
the solvent atoms. Due to mixing of small atomic radii elements like
Carbon,Nitrogen,&hydrogen in the metal interstitial solid solution is formed. In this
type of solid solution the constituent elements are in flexible proportions. They have
very strong bonding forces between them. The alloy Fe3C and Fe4N are solid solution
of this type. This solid solution is shown in figure.
• Properties
space lattice.
3.Factor Of Hume Rodhery Rule
Answer:
• Hume Rodhery Rules

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• Size Factor: The difference of atomic diameter of solvent & solute metals is not more
than 15%the possibilities of forming solution is 100 %.if this difference is more than
15% the possibilities of forming solid solution is limited .The monel metal is an alloy
of Cu and Ni formed by substitution solid solution has
Atomic Diameter Of Cu=da 2.551A
Atomic diameter of Ni=da 2.487A
The difference is 2.508%
• Chemical affinity factor: The greater chemical affinity of two metals tends to form
an intermediate phase instead of solid solution. Due to their greater affinity the metals
are further apart elements in the periodic table.
• Crystal Structure Factor: The crystal lattice structure of the metals should be same
means both must posses BCC or FCC or HCP structure .The similar structure gives
complete solubilities .Dissimilar structure of metals does not allow then to merge into
each other .For complete solubility the size should also be complied
• The binary alloy of similar space lattice & two types of atoms in solid state is known
as Isomorphism alloy. The alloy metal solidifies at a fixed temperature while the
isomorphism alloy has arrange of temperature for solidification.
• E.g Brass: Copper & Zinc,Steel:Iron & Carbon,Monel:Nickel&Copper,Au-Ag:Gold
& Silver, Sterling Silver: Silver & Copper.
• Relative Valency Factors:The metal of high valancy electron can dissolve in small
amount in alowerr vacnacy metal.While the lower valency metals have good
solubility in the higher valency metal.Al-Ni alloy,Ni has lower valency then Al hence
Ni can dissolve only n0.04%of Al and Al can dissolve 5 of Ni in therir solid states
4.What is Alloy? Types Of Alloys
Answer:
An Alloy is an intimate mixture with metallic properties and is composed of two or more
elements of which at least one is metal.
While the other is constituents or elements are known as alloying element, The cast
iron,brass,Wrought iron,Steel,Bronze,White metal,Gun Metal, Duralumin and Mangalium are
all alloys.
Binary and Ternary Alloy:Pur metal are considered as single phase,like wise the solid
solution is also a single phase.

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If pure metal and chemical compounds are in existance together in an alloy then in existance
together in an alloy than in that alloy there exists two phases which are different from each
other .in this way solid solution & pure metal together will give two phase .
This phase formed by physical &Chemical mixture occupies different positions with respect
to one another.
P=C+E-F
P=No of Phase, C-No Of Composition, E=No of Environment Factor, F=Degree OF Freedom
Single phase Alloy, Two Phase Alloy based on the Metallurgical Structure.
Aluminium Alloy ,Copper alloys etc based on principal metals
Cast Alloys wrought alloys, based on method of fabrication.
Solder Alloys, bearings alloys, based on application.
Binary Ternary etc based on no of element.
5.Write Effect Of Any Three alloying Element
Answer: Effect of Alloying Element on Mechanical Property of The Material
Carbon
• The basic metal, iron, is alloyed with carbon to make steel and has the effect of
increasing the hardness and strength by heat treatment but the addition of carbon
enables a wide range of hardness and strength.
Manganese
• Manganese is added to steel to improve hot working properties and increase strength,
toughness and hardenability. Manganese, like nickel, is an austenite forming element
and has been used as a substitute for nickel in the A.I.S.I 200 Series of Austenitic
stainless steels (e.g. A.I.S.I 202 as a substitute for A.I.S.I 304)
Chromium
• Chromium is added to the steel to increase resistance to oxidation. This resistance
increases as more chromium is added. 'Stainless Steel' has approximately 11%
chromium and a very marked degree of general corrosion resistance when compared
with steels with a lower percentage of chromium. When added to low alloy steels,
chromium can increase the response to heat treatment, thus improving hardenability
and strength.

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6.What Is Cooling Curve? Draw Cooling Curve for Alloy
Answer: By measuring the temperature at various locus of temperature when the metal or
alloy is cooled the Time Temperature Curve is plotted that curve is called as Cooling Curve
Fig 7:Cooling Curves
One Method of plotting this curve is at which temperature the phase change occurs in a
system consists of following the temperature as a function of time as different alloys in the
system are very slowly cooled.
7.Draw TTT Diagram
Answer:
Fig 8:TTT Diagram

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8.Explain Allotropic forms Of Iron, What Is Curie Temperature?
Answer:
• Iron, as shown in figure, exists in three crystal (atomic) allotropes, namely: alpha (a)
iron, delta (d) iron, and gamma (g) iron.
• The a-iron form exists below 1625oF (885oC) while d-iron is stable above 2540oF (
1395oC). Gamma iron exists at the temperatures between these two ranges. It is the
allotropy of iron that allows for these crystal structures to change with temperature. At
room temperature, the a-iron crystal structure has its atoms arranged in a geometric
pattern known as body-centered cubic or bcc .
Fig 9:Allotropic Forms Of Iron
• This atomic arrangement of iron atoms is magnetic up to 1420oF (770oC), called the
curie temperature. This temperature was of practical importance to the early
blacksmiths who used an iron horseshoe magnet with a steel bar across the two ends
for temperature measurement.
• When the steel bar fell from the magnet, the blacksmith knew the approximate
temperature of the hearth and was able to adjust the heat treat schedule accordingly.
Above the curie temperature is still bcc but is no longer magnetic.
• Slow heating of a-iron to 1625oF (885oC) produces an allotropic change to gamma
(g) iron, a face-centered cubic (fcc) crystal structure which is non-magnetic. A change
from one crystal structure to another is called a transformation and the temperature at
which it occurs is called the transformation temperature.
• When fcc g- iron is slowly heated above 2540oF (1395oC) it transform back to bcc
iron. To distinguish the elevated temperature bcc iron from its lower temperature
counterpart, it is given its own name, delta (d) iron. This d-iron is non-magnetic and
exists until the temperature is raised to 2800oF (1540oC) which causes melting of the
solid d-iron to liquid iron. Since atoms in the liquid iron have no distinct

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arrangement (each atom moving freely within the liquid) there no longer exists a
crystal structure above the melting temperature.
• For the allotropic transformations described, there is another driving force equally
important to the transformation temperature, namely, time. For allotropic
transformations to occur at the temperatures suggested in figure 1, sufficient time is
required for the atoms to reorganize themselves in the new crystal structure. At the
lower end of the temperature ranges for each allotrope of iron, lower energy levels
exist, so more time is required for crystal structure transformation to occur. The
interaction of time and temperature to achieve the allotropic transformations shown in
figure is called equilibrium.
9.Define Heat Treatment Process? Objectives Of Heat Treatment?
Answer:
• It is sequential process of heating and cooling the steel component to get desired
combination of properties in the component.
• Heating Component at higher temperature called austenitizing temperature, during
which the previous structure of steel is converted in to Austenite phase.
• Holding the steel at austenitizing temperature for some time period so that formation
of homogenous austenite can occur throughout the entire cross section of the part.
• Cooling back the part which is having homogenous austenitic structure to the room
temperature at a particular cooling rate depending upon the properties required.
• Reheating of component to a higher temperature but lower than lower critical
temperature and cooling again this is an optional process and performed if required.
Objective Of Heat Treatment
 To improve the toughness of the component.
 To improve machinability of the material.Etc

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10.What is Carburising? Types Of Carburising Process ?Explain any one.
Answer:
• Carburizing: It is the process of increasing the carbon content in the surface or case
of the part. Due to this parts becomes hard. Hardness of the parts is obtained only on
its surface. While its interior known as core is remains soft and tough.
1.Pack Carburizing
2.Liquid Carburizing
3.Gas Carburizing
• The Addition of carbon in low carbon steel parts surfaces to make them hard is known
as carburising.This process is known as carburizing it is also called as cementation.
• In pack Or Solid Carburizing The parts along with the carburizing mixture are packed
in steel box after machining.
• The carburizing mixture contains 50-70% charcoal .5-10%barium Carbonate,2-
15%calcium and 3-13%sodium carbonate.
• First of all 25 mm thick layer of this mixture is provided at the bottom of the steel
box.
• The parts are kept in the box such that they should not touch one another and to the
box.
• Then cover is place on the box and packed with the fire clay to prevent gases to flow
in or Out.
• The surface of the parts which is not to be hardened are passed through a process like
electroplating to make it non absorbent of carbon.
• The box is placed in the furnace and heated to 900-980°c for a period of the time 6 to
8 hours.
•
Fig 10:Carburizing Process

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• After heating box along with parts is allowed to cool in the furnace it self. Austenite
absorb the carbon at high temperature. So %C of surface gets increased. During the
process of carburizing ,due to heating the grain near to core becomes becomes
coarser. To refine these coarse grains parts are heated to 880°C temperature and then
cooled by quenching in oil or allowed to cool in air.
• Grain refinement part are heated to 760-780°c and quenched in water to make its
surface hard.
• By obtaining required hardness parts also becomes brittle, so part are tempered
around 180-280°c.The hardness depth of 1-1.5 mm is obtained in low carbon steel
containing 1.1-1.2%C.
11.Explain Induction Hardening
Answer:
Induction Hardening
• Parts are heated by induction heating.
• High frequency induction current is used.
• Required current is produced by using motor generator set with spark gas oscillator or
tube oscillator.
• Frequency of 1000-1000C/s.
Fig 11:Induction Hardening Process
• The gap oscillator can generate the current having frequency of 100000 to 400000
C/s.
• When Current of required frequency is passed through induction coil, magnetic lines
will pass through the part surface, due to that AC current will induce in the surface
which cause hysteresis loss in it and as a result of that parts get heated.
• The induced current travels along the surface of the part. For Quenching ,water is
sprinkled on the parts through the voids of inductor block & coil.

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• This contain 0.35-0.55%c can be done. The induction hardening process is used for
the parts like camshafts,Gears,Cranckshaft,axles,and other automobile parts and
tractor parts.
12Explain Flame Hardening and Cyaniding.
Answer: Flame Hardening:
• This process is used for hardening stell,dye,gears,tappet screw,rocker arms and
valves. This is the process of obtaining wear resistant layer on the tough core by
heating the parts using gas torch.
• This process is utilized for the parts containing 0.4 % to 0.6% C.The surface is heated
by the oxy acetylene flame. By heating for sufficient time the temperature of the part
is raised above AC3 temperature and thereafter fast quenching is done. The surfaces
of large size parts can be hardened is an advantage of this process.
Fig 12:Flame Hardening
• Heating cycle is less,which cause scaling. A fixed temperature can not be maintained
is the disadvantage of this process.
• The parts are also damaged due to overheating or cracks are formed in it.
Cyniding:
In liquid Carburizing Salt is used which is solid in normal temperature but it becomes
liquid at carburizing temperature.
Basically Cynogen radical are there in the Salt.They are basically Sodium and
potasium cynide salt it is called as cyniding process.
Heated parts what are to be made are immersed in the salt bath,Salt bath is having
30%Sodium Cynide part to be immeressed at 870° for 1 hour .Cynide gives Co and N
which react with iron .
N increses the hardness of the case .The case thickness is 0.25 mm thin but time
required is very slow.
Sonow liquid cyniding in which floating Calcium Cynide is used From that case depth
is incresed in which amt of N is less and carbon is more,Cynidi is very poisunous.

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4 MARKS
1.Explain Quenching Mediums.
Answer: From Red hot Condition of work piece to relieve the heat in which medium it is
immersed in called as Quenching Medium.Quechnching medium should be able of so that no
Pearlite is transformed from Austenite.
1.5-10% Caustic Soda,2.5-10%Nacl,3.Cold Water,4.Hot Water,5.Mineral Oil,6.Anemal Oil
7.Vegetable Oil ,8.Air Quenching
Factor Affecting for liquid coolant:
Temperature of Quenching Medium, Amount Of Heat To form Vapour, Specific heat of
liquid, Thermal Conductivity Of liquid, Viscosity Of Liquid, Motion Of Liquid.
Factor Affecting for Solid Work piece:
Dimension Of WorkPiece,Temperature Of WorkPiece,Specific Heat Of Work Piece, Surface
Condition OF Work Piece.
Different Quenching Mediums: According to severity of Quench
Brine(5-20% Nacl in Water),Cold Water, Warm Water,Oil,Salt Bath, Air
2.Draw Equilibrium Diagram ,Write the Terms Related To it.
Answer: Concept Of Equilibrium Diagram
• The Solidification of Metal Alloy is Clearly understood by means of equilibrium
diagrams.
• These are graphical representation of the changes in state due to variation in
temperature and concentration.
• This indicate the nature and constitution of the alloys and the amount and the
composition of the phases in a given system.it is also called constitutional diagram or
Phase diagram.
• Equilibrium refers to the changes taking place in a system as a result of process
Occurring in one direction are fully compensated by the changes due to reversal of
the process in the system. Equilibrium diagram indicates the temperatures at which
the solid alloy will start melting and finish melting & possible place changes which
will occur as the result of the altering the composition or temperatures.

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Properties of the materials depends on the Type,Number,Amounts and Form Of the phases
present, the properties can be changed by altering these quantities.
• The information regarding phase changes in many alloy systems are recovered as data
in the form of Phase, Equilibrium Consolidated Diagrams.
• In order tom specify completely the state of a system in
equilibrium,temperatures,purposes and the composition are the three variables which
are extremely controlled be specified.
• If the pressure is assumed to be constant of atm,The equilibrium diagram indicates the
structural changes due to temperatures and composition by equilibrium it is meant that
under equilibrium condition, there will be no change with time .These condition are
approached by extremely slow heating and cooling.
Equilibrium Diagram
• The temperature composition diagram shows the changes of structure taking place
during heating& cooling. This diagram is known as an Equilibrium Diagram. On
X axis: Metal Composition Y axis: Temperature Scales are plotted. The full name of this
diagram is “Thermal Equilibrium Diagram" known as Phase Diagram or Constitutional
Diagram.
Fig 13:Phase Diagram
• It represent the equilibrium condition. Which is not possible to have in
reality.eventhough provide basic information for the heat treatment & to study the
properties of alloy.
• If two elements it is known as Binary alloy, If three elements it is known as Ternary
alloy.
• System: Part of the substance which is completely separated from the surrounding.

23
• Component: Basic chemical substance, whose mass is constant and which can be
used to form a chemical mixture.
• Phase: The part of material system uniformly mixed physically.
• Constituent:The part of multiphase mixture which can be identified seperately.
• Liquidus:The locus of temperature at which solidification is complete. below solidus
only solids are stable.
• Solidus:The locus of temperature of a transformation at which solidification starts.
• Solvent: The major element of a sold solution.
• Solute: The minor element of a solid solution.
• When an alloy after heating ,cooled down then the changes taking place in it is shown
by a curve known as “Equilibrium Diagram” known as Phase Diagram.It is graphical
description of the alloy system.
• The system shows the Melting points and Freezing points of all its alloy.
• Temperature, Pressure of Element& Proportion of the constituent are the major
factors in this equilibrium diagram with the help of variation the equilibrium diagram
is constructed.
3. What Is Solid Solution? Types Of Solid Solution
Answer: Solid Solution
• In liquid stage metal form homogeneous liquid solution, The solid Solution is
formed.If Solvent &Solute atoms are of similar size and electron structure,solid
solution forms very readily if elements A in B forms solid solution in B by its 10%.
Solid Solution
• Substitutional Solid Solution
• Random or Disordred substitutional solid solution,Ordered substituitonal solid
solution.

24
Fig 14:Types Of Solid Solution
• Disordered Substitutional Solid Solution
While forminmg the solid solution soluter atoms instead of occupying specific
position get distributed random in the lattice structure of the solvent.This alloy is in
the disordered condition.in this type of condition the concentration of solute atoms
can vary considerably in the lattice structure.
• Ordered Solid Solution
If an alloy of disordered condition,cooled slowly because of diffusion .its atoms get
known as super lattice or ordred substitutionasl solid solution.The prolonged anneling
of the alloy can produce still more uniform &ordred solid solution.
• Interstitial Solid Solution
When the solute atoms are smaller in size than solvent atoms this type of solid
Carbon,Nitrogen,&hydrogen in the metal interstitial solid solution is formed. In this
type of solid solution the constituent elements are in flexible proportions. They have
very strong bonding forces between them. The alloy Fe3C and Fe4N are solid solution
of this type. This solid solution is shown in figure.
Properties

25
space lattice.
4.Draw Diagram Of Heat Treating Temperature For Carbon Steel.
Answer:
Fig 15:Heat Treating Temperature Diagram
5.Draw TTT Diagram
Answer:
Draw As Shown on Page No
6.What Is Tempering ?Explain it
Answer: Tempering
• It is Process of heating previously hardened steel to temperature below the lower
critical temperature (A1) and cooling back to room temperature.
PROCESS
• Tempering Temperature for a hardened steel can very from 100 to 680 °C depending
upon the requirements. Low alloy constituents steels are tempered above 400°C to get
good combination of strength and ductility. Spring steels are tempered between 300 to
400°C.Folowing guideline are generally adopted for deciding tempering temperature.

26
1.Low temperature is used for carbon and alloy cutting tools and measuring tools, They are
also carburized and surfaced hardened.
2.Medium Temperature is used to increase elongation and ductility by reducing hardness and
strength.
3.High temperature is used to maintain the ration of strength and ductility of structural steel
Table 1:Tempering Temperature
Effects Of Tempering
• Relief Of Internal Stress.
• Formation Of Stable Phases.
• Increase In Toughness.
• Decrease in Hardness
• Provide Right structural Condition Combined with toughness and Shock Resistance.
• Surface Hardening Process
• All load bearing Component requires this treatment for better properties at the outer
region than the inner region.
7 MARKS
1.What Is Solid Solution? Types Of Solid Solution, Properties Of Solid Solution?
Answer: Solid Solution:
Type of tempering Temperature of
tempering
Properties obtained Application
1st
stage / low
temp. Tempering
LESS THAN 250C. Improve strength Useful for high
carbon and low
alloy steels used for
cutting and
measuring tools.
2nd
stage / Medium
temp. Tempering
350-500c Steel develops
maximum elastic
properties.
Useful for coil and
laminated spring.
3rd
stage/ high
temp. Tempering.
500-680c Improves yield,
tensile, and impact
strength makes
steel free from
internal stresses.
Useful for
connecting rods
shaft and gear.

27
• In liquid stage metal form homogeneous liquid solution, The solid Solution is formed.
If Solvent &Solute atoms are of similar size and electron structure, solid solution
forms very readily if elements A in B forms solid solution in B by its 10%.
• Hume Rodhery Rule :if metal A is in lesser proportion than B,therefore A is known as
solute and metal B is known as solvent. There is homogenous distribution of two or
more constituents in the solid state so as to form a single phase known as solid
solution. A is solid solution is the result of metals dissolving in each other’s crystal
Lattice. In solid solution in both the liquid and the solid state. While in solid solution
of Cu and Zinc both having sub valence electrons, forms substitutional solid solution.
Hume Rodhery Rules
• Size Factor: The difference of atomic diameter of solvent & solute metals is not more
than 15%the possibilities of forming solution is 100 %.if this difference is more than
15% the possibilities of forming solid solution is limited .The Monel metal is an alloy
of Cu and Ni formed by substitution solid solution has
Atomic Diameter Of Cu=da 2.551AAtomic diameter of Ni=da 2.487A
The difference is 2.508%
• Chemical Affinity Factor: The greater chemical affinity of two metals tends to form
an intermediate phase instead of solid solution. Due to their greater affinity the metals
are further apart elements in the periodic table.
• Crystal Structure Factor: The crystal lattice structure of the metals should be same
means both must posses BCC or FCC or HCP structure .The similar structure gives
complete solubilities .Dissimilar structure of metals does not allow then to merge into
each other .For complete solubility the size should also be complied
• The binary alloy of similar space lattice & two types of atoms in solid state is known
as Isomorphism alloy. The alloy metal solidifies at a fixed temperature while the
isomorphism alloy has arrange of temperature for solidification.
• E.g Brass: Copper & Zinc,Steel:Iron & Carbon,Monel:Nickel&Copper,Au-Ag:Gold
& Silver, Sterling Silver: Silver & Copper.
• Relative Valency Factors:The metal of high valancy electron can dissolve in small
amount in alowerr vacnacy metal.While the lower valency metals have good
solubility in the higher valency metal.Al-Ni alloy,Ni has lower valency then Al hence
Ni can dissolve only n0.04%of Al and Al can dissolve 5 of Ni in therir solid states
Fig 16 :Types Of Solid Solution

28
Substitutional Solid Solution
Fig 17:Substitutional Solid Solution
• Random or Disordred substitutional solid solution, Ordered substitutional solid
solution.
Disordered Substitutional Solid Solution
• While forming the solid solution solute atoms instead of occupying specific position
get distributed random in the lattice structure of the solvent.
• This alloy is in the disordered condition. in this type of condition the concentration of
solute atoms can vary considerably in the lattice structure.
Fig 18:Ordered and Disordered Solid Solution
Ordered Solid Solution
• If an alloy of disordered condition, cooled slowly because of diffusion .its atoms get
known as super lattice or ordred substitutional solid solution. The prolonged
annealing of the alloy can produce still more uniform &ordred solid solution.

29
Interstitial Solid Solution
• When the solute atoms are smaller in size than solvent atoms this type of solid
Carbon,Nitrogen,&hydrogen in the metal interstitial solid solution is formed.
Fig 19:Intertstitial Solid Solution
• In this type of solid solution the constituent elements are in flexible proportions. They
have very strong bonding forces between them. The alloy Fe3C and Fe4N are solid
solution of this type. This solid solution is shown in figure.
Properties
• It is simply a solution in the solid state consisting of atoms combined in one type of
space lattice.

30
2.Draw TTT Diagram ,and Explain Need & Application Of TTT Diagram.
Answer:
Fig 20:TTT Diagram
• The IC Diagram shows the Change of Phase of Iron as per the change of carbon
content in percentage .This is happening due to slow Heating & Cooling known as
Equilibrium Diagram.
• The Iron Carbon Equilibrium Diagram does not show the change due to Different
Cooling Rates as the time is not takes as a variable on any axis in this Diagram.

31
• The steel is passed through the process with different rate of cooling in the industries
for which any kind of information is not available from the IC Eqm Diagram.
• From TTT the Information related to formation of pearlite ,bainite,martensite by the
different cooling rates of the austenite are obtained. Hence TTT diagram shows the
austenite transformation by relating it with the Time & Temperature and Gives
information related to the structure formed.
• The principal source of information on the actual process of austenite decompose
under non equilibrium condition the TTT Diagram which relates the transformation of
austenite to the time & Temperature.
• X Scale: Time on logarithmic Scale,Y Scale:Tempearature.
3.Draw Neat and Clean Labelled Iron Carbon Diagram, Also Define
Ferrite,Cementite,Austenite,Pearlite
Answer:
Ferrite: The Iron not Containing more than 0.025% C in solid solution is the Alpha iron
having BCC structure .It is the major Constituent in Wrought Iron &low Carbon Steel Its
Hardness is in between 50-100BHN and ultimate Strength is about 3400Kgf/cm2.Its
Elongation is about 40% and can be worked very easily.
Fig 21:Iron Carbon Diagram

32
Fig: Iron Carbon Diagram in °F and°C.
Cementite: The iron Carbide Fe3C containing 6.67%C is known as Cementite. Its Hardness is
650BHN and Ultimate Tensile Strength 450Kgf/cm2,It is brittle and White in Colour It is
occurring due to slow cooling in steel below temperature of 205°C.It can be magnetised it is
present as a component of another constituent "pearlite "in steel containing less than 0.8%C
in steels if % elongation is more than 0.8% it exists as again boundary film.
Austenite: Austenite is a solid solution of carbon in gamma iron. It has face centered cubic
structure(FCC).It contains 0.2%C at 1130°C.It is non magnetic and tough above critic
temperature it exists in plain carbon steel elements like Mn ,Cr in steel present all or some of
Austenite down to 0°C.The austenite consists of polyhedral grains showing twins.
Pearlite: In the microstructure of pearlite there is alternate layers of ferrite and cementite it is
contained about 0.8%C in iron it is the strongest constituent of steel having hardness of about
180BHN ,UTS 9400Kgf/Cm2,%Elongation of about 5% after polishing of Viewer with
oblique lighting under microscope it appears like Mother of Pearl hence it is known as
Pearlite.
4.What Is Heat Treatment? Objective Of Heat Treatment, Classification Of Heat Treatment
0f Process.
Answer:The Entire heat treatment process depends upon following three important principle
a. Phase transformation during heating
b. Structural changes during cooling due to different cooling rates.
c. Effect of carbon content and other alloying elements.
Definition of Heat treatment Process
• It is sequential process of heating and cooling the steel component to get desired
combination of properties in the component.
Fig 22:Basic Of Heat Treatment
• Heating Component at higher temperature called austenitizing temperature, during
which the previous structure of steel is converted in to Austenite phase.
• Holding the steel at austenitizing temperature for some time period so that formation
of homogenous austenite can occur throughout the entire cross section of the part.
TEMP
TIME
ROOM TEMP

33
• Cooling back the part which is having homogenous austenitic structure to the room
temperature at a particular cooling rate depending upon the properties required.
• Reheating of component to a higher temperature but lower than lower critical
temperature and cooling again this is an optional process and performed if required.
Objective Of Heat Treatment
 To improve the toughness of the compomnent.
 To improve machinability of the material.
 To make the material soft so that the process like wire drawing,Cold Rolling, Can be
performed on the same.
 To improve heat,wear,and corrosion resistance of the materials.
 To improve magnetic and electrical properties of the material.
 To impart harder surface and softer core to the component.
 To make the structure of the component homogenous.
 To improve ductility and toughness of the material.
 To stabilize size of the component.
 To facilitate diffusion process in the steel.
 To obtain desired structure in the material as per specific application requirement.
Fig 23 :Classification Of heat Treatment

34
5.What is Annealing Process? Types Of Annealing and Purpose of Annealing Process,
Explain Any One In Detail.
Answer:Annealing
• Heating the steel to austenite phase and then cooling slowly through the
transformation range. Slow cooling is generally achieved in a closed furnace by
switching off the supply to the furnace.
Fig 24:Types Of Anneling
Purpose Of Annealing:
• To produce the desired microstructure having mechanical.physical,and other
properties as per the requirement.
• To reduce hardness and soften the steel
• To relieve the internal stress.
• To restore the ductility and thereby facilitate further cold working
• To improve Machinability.
• To refine and make homogeneous structure by reducing structural in homogeneities
• To create complete stable structure.
• Increase or restore toughness.
6.Difference Of Annealing & Normalising Process.
Answer Table 2:Comparsiom Annelinf And Normalizing
Sr
No
Annealing Process Normalizing Process

35
7.What is Hardening? Types Of Hardening Process, Explain Any One Case Hardening
Process.
Answer: Hardening
• It is defined as heating the steel to form uniform austenite phase and cooling the same
rapidly by quenching it in a suitable medium such as water,oil,brine etc.as per the
requirements.
Surface Hardening Process
surface hardening Case hardening
1.Induction Hardening 1.Carburizing
2.Flame Hardening 2.Nitriding
3.Cyniding
Case Hardening
Flame Hardening:
1 Components are heated to form
uniform austenite and then cooled
slowly by keeping the same in the
switched off furnace.
Components are heated to form uniform
austenite and then cooled faster than annealing
process in the steady air.
2 Amount of pearlite is less in annealed
structure.
Amount of pearlite is more in normalized
structure.
3 Hardness Of annealed Steel Varies
from 110BHN to 230BHN
Hardness Of normalized steel varies from 120
BHN to 300 BHN
4 Annealed steels can have less
strength and more elongation.
Normalized steels can have more strength and
less elongation.
5 Impact strength of annealed parts
less.
Impact strength of normalized parts is more.
6 Annealing process is slow and more
costly.
Normalizing process is faster then annealing
process.

36
• This process is used for hardening stell,dye,gears,tappet screw,rocker arms and
valves. This is the process of obtaining wear resistant layer on the tough core by
heating the parts using gas torch.
• This process is utilized for the parts containing 0.4 % to 0.6% C.The surface is heated
by the oxy acetylene flame. By heating for sufficient time the temperature of the part
is raised above AC3 temperature and thereafter fast quenching is done. The surfaces
of large size parts can be hardened is an advantage of this process.
• Heating cycle is less,which cause scaling. A fixed temperature can not be maintained
is the disadvantage of this process.
• The parts are also damaged due to overheating or cracks are formed in it.
• Case Hardening Process: Hardness of the steel increase in carbon content. Nitrogen
Content can also increase the hardness by forming hard nitrides.
• Low carbon steel are heat treated to increase carbon and nitrogen contents at the
surface of the component to increse the hardness at the surface.
• Carburizing: It is the process of increasing the carbon content in the surface or case
of the part. Due to this parts becomes hard. Hardness of the parts is obtained only on
its surface. While its interior known as core is remains soft and tough.
1.Pack Carburizing
2.Liquid Carburizing
3.Gas Carburizing
• The Addition of carbon in low carbon steel parts surfaces to make them hard is known
as carburising.This process is known as carburizing it is also called as cementation.
• In pack Or Solid Carburizing The parts along with the carburizing mixture are packed
in steel box after machining.
• The carburizing mixture contains 50-70% charcoal .5-10%barium Carbonate,2-
15%calcium and 3-13%sodium carbonate.
• First of all 25 mm thick layer of this mixture is provided at the bottom of the steel
box.
• The parts are kept in the box such that they should not touch one another and to the
box.

37
Fig 34 :Flame Hardening
Then cover is place on the box and packed with the fire clay to prevent gases to flow
in or Out.
• The surface of the parts which is not to be hardened are passed through a process like
electroplating to make it non absorbent of carbon.
• The box is placed in the furnace and heated to 900-980°c for a period of the time 6 to
8 hours.
• After heating box along with parts is allowed to cool in the furnace it self. Austenite
absorb the carbon at high temperature. So %C of surface gets increased. During the
process of carburizing ,due to heating the grain near to core becomes becomes
coarser. To refine these coarse grains parts are heated to 880°C temperature and then
cooled by quenching in oil or allowed to cool in air.
• Grain refinement part are heated to 760-780°c and quenched in water to make its
surface hard.
• By obtaining required hardness parts also becomes brittle, so part are tempered
around 180-280°c.The hardness depth of 1-1.5 mm is obtained in low carbon steel
containing 1.1-1.2%C.
8.Types Of Furnaces ,Classify it ,Draw Any One Heat Treatment Furnace?
Answer:
A.According to Use
1.Anneling Furnace
2.Tempering Furnace
3.Carburizing Furnace
B.According to Source Of Heat
1.Oil Fired Furnace
2.Gas Fired Furnace
3.Electric Furnace

38
C.According to type of Work
1.Batch Furnace
2.Contiunous Furnace
3.Semi Countinuous Furnace
D.According to Working Environment
1.Air Furnace
2.Protective Atmosphere Furnace
3.Special Environment Furnace
4.liquid bath furnace a.Slat bath,b.Lead bath,c.Oil bath
5.Universal furnace:
6.Batch Furnaces
a.Vertical Pit Furnace
b.Horizontal Box
c.Stationary Hearth 1.Direct Fuel Fired 2.Indirect Fuel Fired.
d.Movable Hearth 1.Carbottom Furnace 2.Rotary Type Furnace
Fig 35:Heat treatment Furnace (Countonous)
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