GTU Examination Solved Paper

1. 1
GUJARAT TECHNOLOGICAL UNIVERSITY
MSMT NOVEMBER 2013
SOLVED QUESTION PAPER
ANKITKUMAR BRAHMBHATT
11/30/2013
PARUL INSTITUTE OF ENGINEERING AND TECHNOLOGY DS FIRST
SHIFT(MECHANICAL)

2. 2
Q.1 Answer any seven out of ten. 14
1. Explain the construction properties of Ionic or Electrovalent bond.
ANSWER: IONIC:
1) They are rigid,Unidirectional,Crystalline in nature.
2) Ionic Solids are bad conductors of electricity in their solid state.
3) Ionic solids are good conductors of electricity in their moltern state.
4) Ionic Solid have high melting and boiling temperatures.
5) Ionic Solids are freely soluble in water but they are slightly soluble in organic
solvants.
ELECTROVALENT:
1) They are bad conductors of electricity.
2) This Covalent solids are directional in nature.
3) Crystal of covalent bonding are strong,hard,and have high melting points.
4) Covalent solids are insoluble in water. There are soluble in organic solvents like
benzene,toluene,etc.
2. Explain secondary bond and state its characteristics.
ANSWER: It is also known as waander waals bonds secondary bonds. They are formed in the
elements or compounds whose electron configuration is such that very little electron transfer is taking
place between the atoms. Due to Dipole attraction Types:Dispersion,Dipole,Hydrogen.
Characteristics:
1) Molecular Compounds are generally transparent to lights.
2) Molecular Compounds are generally good insulator, with the oxception of water .
3) Molecular Compounds have low strength as they are held by weak forces of attraction.
4) Molecular compounds have low melting points.
3. Define: (1) Space lattice (2) Unit cell.
ANSWER: Space Lattice: During Solidification of metals, their atoms are take up fixed
positions in a regular pattern, referred as space lattice.
Unit cell: The minimum value of the crystal which gives an idea of the atomic structure of a
metal through its volume is called is called Unit cell.
4. Define: (1) Density (2) Melting point.
ANSWER: Density: The density of the material is the weight of it per unit volume.
Melting Point: The Temperature at which solid metals get transformed into liquid state is called
Melting Point.

3. 3
5. Write short note on a super conductivity.
ANSWER: Super Conductivity::It is the Phenomenon of abrupt drop of resistivity of some
materials, at a temperature called super conducting transition temperature before absolute
zero is reached .It is due to the condition by the drift of electrons in the direction of the
applied electric field being opposed by irregularities within the lattice.
6. Explain thermal expansion and thermal diffusivity.
ANSWER: Thermal Expansion: It is increase in dimension of a material on application of
heat. It depends upon the interatomic and intermolecular forcesae well as on structural
arrangement.
Thermal Diffusivity: it is the ratio of thermal conductivity of a material to its heat capacity
per unit volume.
h=Kt/C where, Kt=Thermal Conductivity ,C=Specific Heat Capacity.
Thermal Diffusivity is the rate at ehich a disturbance in temperature of one part of a body
travels to another part.It is also a measure of how little the distribution is attempted as it
travels from point to point.
7. Write definition of Equilibrium diagram.
ANSWER:
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
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.

4. 4
Fig: Phase Diagram
8. Write definition of solid solution.
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%.
Fig: Types of Solid Solution
9. Define an alloy and binary and ternary alloy.
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: Pure metal are considered as single phase, likewise the solid
solution is also a single phase.
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 .

5. 5
10. Define heat treatment and its objectives.
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 combination of different properties.
 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 component.
 To improve machinability of the material.Etc

6. 6
Q.2 (a) Explain time temperature transformation (TTT) curve. 03
ANSWER:
OR
(a) Explain pit furnace with neat figure. 03
ANSWER: Small size parts to be heat treated can be charged in a pit furnace.
fig: Pit furnace

7. 7
(b) Describe normalizing process. 03
ANSWER:
Normalizing
• It is defined as heating the steel to austenite phase and cooling it in the air. When steel is cold
worked the crystal structure and the metal may be brittle and unreliable.
• The internal structure of the hot worked forged part may also be discoed owing to being
worked at a very low temperature.
• It can also be seen that a variable finishing temperature will result in a variable structure for
forging of the same carbon content.
• Likewise if a casting is poured at a somewhat indefinite temperature and cools at different
rates in different parts, it may be unreliable. Normalizing is therefore, used particularly for the
following purpose
1. To eliminate coarse grained structure.
2. To remove the internal stresses that may have been caused by working..
3. To improve the mechanical properties of the steel.
Purpose Of Normalizing
• 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.
Process
• In normalizing ,steel is uniformly heated to a temperature which causes complete
transformation to austenite .Different normalizing temperature and resulting hardness with
respect to different carbon content is shown in the table .
• The steel is held at the Austenizing temperature for sufficient amount of the time for the
formation of homogeneous austenite structure through the cross section. The soaking time is
one hour per25 mm thickness of the component.Cooliing is done in still air in a uniform
manner, which is faster than furnace cooling.
• Application of the normalizing Process

8. 8
• 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.
OR
(b) Explain optical principal of microscope with neat figure. 03
ANSWER:
Principal: It works on the principle of reflection of the light rays.
Fig: Ray Diagram Of Metallurgical Microscope.

9. 9
(c) State the sequential steps of preparing a micro-specimen. 04
ANSWER:
1) To examine the internal details % structure of the metal specimen of 1cm,size should
be prepared.
2) The surface of the specimen should be prepared by filing & grinding for grinding the
specimen use emery paper of grades 1 and 0.after grinding on one emery paper. This
will clear the scratches from the surface by grinding.
3) After Completing the rough grinding using grade 1 emery paper, fine grinding should
be done by using 0,00,000,0000 emery papers. If zero grade fine emery papers are not
available then used equivalent emery papers of 200grit,320 grit,400 grit and ,600 grit
for the purpose of polishing.
4) The disc covered with shifon velvet containing diamond dust or dimontine should be
rotated. On this rotating disc the final polishing of the surface of specimen should be
done.
5) After final polishing of specimen obtain its surface like mirror and free from
scratches.
6) he specimen surface should be immersed in etching reagent to make the grain
boundaries visible. Without etching usually specimen can not be seen under the
microscope. Etching imparts unlike appearances to the metal constituents and thus
makes metal structure apparent under the microscope. Before etching the specimen
should be thoroughly washed in running water.Innerse the polished surface in the
etching reagent or by rubbing the polished surface gently with a cotton swab wetted
with the etching reagent.
7) After etching again wash the specimen thoroughly and allow it to dry.
8) Now the specimen can be said ready to be studied under microscope.
OR
(c) Classify cast iron .give difference between white cast iron and grey cast iron. 04
ANSWER:
WHITE CAST IRON GREY CAST IRON
It is white in colour It is having Grey Colour
It is brittle It is soft material
It is very hard It absorbs Vibrations
Low Compressive Strength It is having less ductility
Poor Mechanical Properties Melting Point is 1150 to 1200°C
Manufacture Anvil, Wheel of railway coach Pipe and Pipe fittings, Agricultural
Equipments.

10. 10
(d) State the effect of phosphorus, sulphur,silicon,manganese as impurities on C.I. 04
ANSWER:
Effects
Phosphorus:
• It is an impurity in the cast iron makes it fusible and increases the fluidity.
• It makes the cast iron brittle hence its content is limited mostly to 1%.
• The cast iron containing P can be used to cast intricate shapes of the castings.
• P lower the melting point and reduces shrinkage.
• Strength of cast iron is slightly improved by P i.e up to 0.3%
Sulphur:
• It is harmful to have sulphur present as an impurity in cast iron.
• It decreases the viscosity of the CI and makes it hard and brittle.
• It tend to react with iron and forms the FeS which is low melting point compound and
it increases the possibilities of cracking at elevated temperatures known as HOT
SHORTNESS.
Silicon:
• The silicon in the CI is 2.5%.
• It promotes the formation of free graphite in cast iron.so it makes it soft so that its
machining can be done easily.
• Blowhole does not appear in the casting if this impurity is present in the casting.
• It gives freedom from oxides and blow holes by remaining oxygen as Sio2 and
promotes Fluidity.
Manganese:
• Impurity promotes the formation of carbide and makes the cast iron white and tough.
• The cast iron is protected by Mn against harmful effects of So Amt of Mn is set
according to the S content.
• MnS increases the Tensile strength and hardness, Mn improves the soundness of
casting.

11. 11
OR
(d) Draw neat sketch of Iron-carbon equilibrium diagram. 04
ANSWERFigfigfifigfi
Fig: Iron Carbon Diagram

12. 12
Q.3 (a) Write the properties of copper and give four use of copper, with reasons for its
selection. 03
ANSWER:
Properties of Copper:
1) It is having Shining Yellowish red colour.
2) It is anti corrosive metal.
3) Density is 8.9 gm/cm3.
4) It is Good Conductor of Heat and Electricity.
5) Melting point is 1083°C.
6) It is having FCC Crystal Structure.
7) Machinability is very good.
8) It can be easily welded.
9) It is easy to cast.
10) It can be hot and cold worked.
11) Tensile strength 180-200 N/mm2
12) Hardness is 30-40 B.H.N
If annealed we can get elongation up to 50-60%.
Use Of Copper & Reason for its Selection
1) Electrolytic copper is good conductor of electricity &hence the electrical conductors
& wires are produced by using electrolytic copper.
2) Copper is forming solid solution with zinc, therefore it is used for producing brass.
By changing its percentage content its strength can be increased. Its properties can be
imported by cold working .Therefore to produce different variety of brass, the copper
is used.
3) Copper used to form its alloy known as Gunmetal. The gun metal is tough and have
good strength. It is corrosion resistant. Therefore gun metal is used to produce pump
parts, bolt & nut, Bushing etc.for ships building.
4) Copper alloy aluminium bronze has good strength &toughness. It is resistant to
corrosion due to the effect of atmosphere, acid and salt. Therefore it is in gears, valves
stem, pump parts,bushings,propeller nut etc.
5) Copper is heat conductive materials, hence used in radiators pipes& fins.
6) Copper has high heat conductivity so used in locomotive fire box, water heating
equipments etc.

13. 13
7) Due to its shining it is used in medals, buckles and name plates.
OR
(a) Compare high carbon steel and tool steel. 03
ANSWER:
TOOL STEEL: Tool and Die steels may be defined as special steels which have been developed to
form ,cut or otherwise change the shape of a material into a finished or semi finished product.
Properties of tool steel
1) Slight change of form during hardening.
2) Little risk of cracking during hardening.
3) Good Toughness.
4) Good Wear Resistance.
5) Very Good Machinability.
6) A good Degree of Thorough hardening.
7) Resistance to decarburization.
HIGH CARBON STEEL:
C:0.6-0.8 %,Having Ferrite+Pearlite Micro structure,Hardness:350-600 B.H.N, Tensile
strength:765-1420°C,Yield Strength:645-1170.
Die,Saw,Screw-Driver,Band Saw, Anvil Face,Hammer,Winch,Laminated Spring, Cable
Wire, Big Dies of Cold Press,Chisels,Shearing blades, Punch & Drill, Spanners etc,are made
from high carbon steel.
(b) Explain cooling method of alloy steel as per BIS. 03
ANSWER:
OR
(b) Give appropriate material for following. (1)Cycle frame (2) car body (3) piston ring
(4) hacksaw blade (5) anvil. 03
ANSWER:
Cycle Frame: 50 Carbon(Vehicle Spring Steel),Carbody:C-Mn lighter ,
Piston Ring: Alloy Cast Iron ,Hacksaw Blade: Carbon Mn Steel or Hardened Steel ,
Anvil: White Cast Iron(WCI).

14. 14
(c) Differentiate brass and bronze. 04
ANSWER:
BRASS BRONZE
Brass contains alloying elements like
lead,Zinc,Silicon,Tin
Bronze contains alloying elements like
Zinc,Tin,Lead,Iron,Aluminium,and Nickel.
It is Corrosion resistant & possesses good
strength.
It is resistant to heat and corrosion high
temperature strength is good. It resists
oxidation.
Pipes,Tubes,&Fittings,Plumbing Goods,
Hardware, Small gears, Pump Impeller,
Valve & Its Fittings, Ornamental Castings,
High cast part, Structural Parts, Bearing
Steam Pipe Fittings, Marine
Castings,Hydrallic Valves etc,are made from
brass.
Pressure Castings,Bushings,Bearings,Steam
pressure castings,Gears,Pumps,Heavy Duty
parts, Marine Equipments, Valve Sheet,
Valve Guide, Valve Stem, Acid Resistant
pump, Dairy Equipments etc are made from
bronze.
By increasing the Zinc Content in brass it is
becoming Cheaper.
In Comparison to brass this metal is costlier.
OR
(c) State merits and demerits of adhesive materials. 04
ANSWER:
MERITS(any four)
1) Time for joint making is less.
2) They are moisture resistant materials.
3) They are free from the attacks of insects.
4) They can be used to join very thin parts.
5) It acts as an insulator between the two parts to be joined.
6) Different types of materials can be joined together.
7) High temperature is not required to make the joint.
8) Less skill is required to make the joint.
9) Good finished joints are obtained.
10) Simple design is sufficient to make the joint.

15. 15
DEMERITS(any four)
1) If surface cleaning is improper then poor joints results.
2) Intricate equipments required to provide heat & pressure for joint making.
3) Joint has lesser strength.
4) The joints damages due to more heat & moisture.
5) This joint is less stable in comparison to metal joints.
6) Testing methods for testing these joints are not developed.
(d) What are the ceramic materials? Give the classification of ceramic materials. 04
ANSWER:
• Ceramic are the materials produce from inorganic substance and are non metallic.
They possess good thermal & electrical insulation properties.
• Ceramic word is derived from a Greek word keramos which means potter man's clay,
but modern ceramic are the mixture of metallic & non metallic elements.
• Ceramic products are tiles,bathtub,sanitry wares, surgical instruments, auto parts&
tools.
• Today the production of ceramic tiles in the world is getting momentum. In India
Spartech ceramic of India limited is the leading manufacturer.
• The other manufacturer are Hindustan sanitary wares,EID,Parry & Naysor are also
producing sanitary wares.
• Application base classification of ceramic are
Fig: Classification of Ceramic Material
CERAMIC
CEMENTS ABRASSIVE GLASSES CLAY PRODUCTS REFRACTORIES ADVANCE CERAMIC
STRUCTURAL CERAMIC
CLAY PRODUCT
WHITE WAVES FIRE CLAY SILICA
BASIC SPECIAL

16. 16
OR
(d) Write the difference between thermoplastic and thermosetting plastics. 04
ANSWER:
THERMOPLASTIC THERMOSETTING PLASTIC
It is produced by addition polymerisation. It is produced by condensation
polymerisation.
Its Structure is linear and Chain Type Its Structure is cross linked
Its Strength is less. Its Strength is more
Its Structure is granular It has polymeric type of structure.
This plastic cannot be used for higher
temperatures.
This can be used at higher temperatures.
P.V.C,Acrylic,Polyethylene polystyrene are
the examples of thermo plastic.
Phenolics,Epoxy,Melamine,are the examples
of thermo setting plastics.
It is used to produce toys,Toiletwares,and fan
blades,etc
It is used to produce Radio TV cabinets,
Body of Phones, Automobile parts.
Q.4 (a) Explain uniform corrosion and pitting corrosion. 03
ANSWER:
Uniform: This type of corrosion initially occur on some portion of the surface and then
spread on the whole surface. Continuous reduction in metal volume is caused by this
corrosion. As this type of corrosion occurs equally on whole surface hence it is called
"Uniform Corrosion".
If the parts are not produced from the corrosion resistant material, then strength of them are
reduces due to this corrosion. The ways of preventing it are change of material and coating
the surface with corrosion resisting material. This type of corrosion results into grater loss
hence parts are to be produced using corrosion resistant material.
Pitting: This type of corrosion occurs due to metal loss by the electro chemical process from
the surface of positive polarity parts. Its effect is seen on limited surface area but it is serious.
The corrosion occurs very fast and can not be noticed till the part fails. Usually the type of
corrosion is seen in aluminium parts but in humid environment SS parts are also corroded by
it. The formation of crack by due to breakage of protective layer anodic region forms on the
part surface.
The surface surrounding to this anode behave as cathode giving rise to galvanic cell. Small
holes are developed on the parts surface by this type of corrosion. Repairing is costly. The
dimension of the part are reducing based on the depth of pits, which reduces the area resisting
the stress and part is failing.

17. 17
OR
(a) Explain galvanic and crevice corrosion. 03
ANSWER:
Galvanic: When a cell is made by using less active metal cathode with active metal anode,
then destruction of cathode occurs very fast in comparison to its normal rate. Less active
metal destruct very fast under electro chemical action. This is called as Galvanic Corrosion, It
is proportional to the difference of electric potential and surface area. It is caused when two
dissimilar metals comes in contact.E.g joint of Copper, Copper earth connection with steel
pipe which gives rise to galvanic cell.Galvenic Corrosion is dependent on
1.High potential difference between anode & cathode
2.More Acidic Electrolyte
3.More Oxygen Concentration in electrolyte nearer to cathode.
Crevice: It is localised electrochemical corrosion Occurring at crevice and udnershiled
surface where stagnant solution can exist. It is Occurring and gasket,rivets,bolts,between
valve seats, valve disk etc.
It is caused to SS,Titanium,Copper,and Aluminium Alloy, The crevice formed at joint allow
liquid to enter into them and they are narrow enough to keep the entered liquid stagnant.
Fibrous gasket acts as wicks, absorbs an electrolyte solution and keep it min contact with the
metal surface. This developes location for crevice corrosion. The mechanism of this corrosion
is similar to that of pitting.It initiates anodic Cathodic reaction on surface to cause crevice
corrosion.
(b) Write differences of erosion and pitting corrosion. 04
ANSWER: (Write any four point)
EROSION PITTING
It is caused due to separation of surface
coating under effect of velocity.
It occurs due to metal loss by the electro
chemical process from the surface of positive
polarity parts.
The rate of Corrosion is more. Its effect is seen on limited surface area but it
is serious.
The pump impeller, pipelines and pipe
fittings becomes victim of this corrosion if
solid matters are following with liquid flow.
The corrosion occurs very fast and cannot be
noticed till the part fails.
Reduction of velocity, change in atmosphere
and change in energy of solution can reduce
the amount corrosion occurring.
It is observed in Al parts but in humid
environment SS parts are also corroded by it.
Pipe surface carrying liquid and gas gets
eroded due to this corrosion.
The formation of crack due to breakage of
protective layer anodic region forms on the
parts of surface. The surface surrounding to

18. 18
this anode behave as cathode giving rise to
galvanic cell.
When metal layer breaks in pipe by
reosion,than it cannot be repaired. Due to
striking of liquid in condenser
pipes,tubes,agitator and vessels their surfaces
are more eroded.
Small holes are developed on the part surface
by this type of corrosion. Repairing of the
surface having such pits is costly as many
many number of pits are produced in surface
having such small pits is costly as many
many numbers of pits are produced in surface
by this corrosion.
The Dimension of the parts are reduced based
on depth of pits, which reduces the area
resisting the stress and part is failing.
OR
(b) State industrial application of electrolysis. 04
ANSWER:
Application Of Electrolysis.
1) To obtain galvanized products by developing layer of Zinc on Steel.
2) The parts are used in marine application are plated with cadmium layer to protect ferrous
metal parts from corrosion.
3) Nickel plating is done to protect parts surfaces against corrosion and to provide them
attractive &Decorative appearance.
4) Chromium platting is used to obtain wear resistant property and attractive appearance.
5) The kitchen utensils ,Equipments, tin cases, food containers are electroplated to keep them
free from acidic effect.
6) The electroplating is also used to increase soldering possibility.
7) Gold Plating is used for electric contacts and surfaces of reflectors.
8) Solver plating is used to decorate jwellery,cutlery,musical,surgical and electronics
instruments.
(c) Define powder metallurgy and explain basic concept and application of powder
metallurgy 07
ANSWER:
Powder Metallurgy is the process of manufacturing the component using the powder of the metal and
alloy.Non metallic element are also added in the powder based on the property requirement of the
product.

19. 19
• Chart shows the basic process steps to be followed to manufacture a product by powder
metallurgy process.
• Pre sintering is an optional operation. It is performed to impart machinability to the competed
powder metallurgy parts. Once the parts are sintered ,it becomes very difficult to machine the
same.So,if machining is required in producing a part,pre sintering is done prior to machining
and after doing required machining on the part final sintering is performed.
• Secondary operation are mainly done to finish the parts. Depending upon dimensional and
functional requirement of the product, secondary operations can be machining,rolling,heat
treatment, surface coating,impregnation,etc.
Application
• To produce refractory parts of tungsten,Tantalum,Molybdenum which are used in the
electrical bulb, radio valves ray tube filaments,cathod,anode and control grids e.g. WC.
• To produce refractory carbide, which are difficult to machine e.g. WC
• Automobile applications, electrical contracts,Cranckshaft drive, camshaft sprockets, piston
rings, brake lining by PM root.
• To produce self lubricating bearings and filters.
• To produce intricate gears which needs more machining if produced by conventional method.
• Components of two metals and non metals like non porous bearings, electric motor brush are
produced by powder metallurgy.
• Aerospace application:rocket,missile,satellite,space vehicle parts,e.g Be,Al,Zr powders are
used in Solid fuel rocket.

20. 20
• Atomic Energy application are Be as fuel canning material, powder control rod,Rediation
reflector,Zr and alloy as cladding material.
• Grinding Wheels containing steel & diamond powders are produced by powder metallurgy.
• Various parts of watches, type writter.calculator,Clutch&brake by P/M root.
Q.5 (a) State the properties of solid solution. 04
ANSWER:
Properties Of Solid Solution
• 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 combined in one type of space
lattice.
(b) Describe hardening and tempering process. 04
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 vary from 100 to 680 °C depending upon the
requirements. Low alloy constituents steels are tempered above 400°Cto 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.
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.

21. 21
3.High temperature is used to maintain the ration of strength and ductility of structural steel.
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.
Hardening:
• It is a process for hardening a ferrous materials in such a manner that the surface layer is
substantially harder than the remaining material.
• This is achieved by having different chemical composition and structure at the surface and at
the core. For that following two methods are in use.
1) Hardening is the surface by changing phases and micro constituents of the material without
changing the chemical composition at the surface. This is called surface hardening.
2) Hardening the surface by changing the chemical composition at the surface .This is called
case hardening.
TYPES OF SURFACE
HARDENING
SURFACE
HARDENING
CASE HARDENING
INDUCTION HARDENING FLAME HARDENING CARBURIZING NITRIDING
CYNIDING

22. 22
(c) State properties and application of following material. (1) Muntz metal (2)
gun metal. 03
ANSWER:
MUNTZ METAL GUN METAL
This alloy is known as Muntz Metal,Cu 60%,Zn
40%.
This alloy contains 2 to 5%Zn ,5 to 10%Sn and
remaining Cu.
Possesses good properties to work with hot
working properties.
It is resistant to corrosion & have good strength.
It is used for sheet castings and stamping
production.
It is used for producing bearing,stamping,marine
components, hydraulic valve & gears.
(d) State compotation and application of following material. (1) Bell metal (2) Babbitt
metal. 03
ANSWER:
BELL METAL BABBITT METAL
It is having 20%Sn and remaining Cu. It is having less than 10% Sn.
This alloy is hard therefore wear resistant. Lead alloys with Tin and Aluminium makes
bearing metals like babbits.
The bell of bell metals are used in
church,schools,and hospitals.
It is used to produce shots of ammunitions.
Lead alloyed with antimony ,tin, copper makes
this type of metal.
BEST OF LUCK