2. 2
Introduction
• A material is that, out of which anything is made. It relates itself
to matter.
• The knowledge of materials and their properties is of great
significance for a design engineer.
• The machine elements should be made from such a material
which has properties suitable for the operating conditions.
• Property of a material is a factor that influences qualitatively or
quantitatively the response of a given material under the action
of forces, temperature, pressure etc.
• Property indicates that, whether a material is suitable or
unsuitable for a particular use in industry.
4. 4
FerrousMetals
• The ferrous metals are those which have the iron as their main
element or constituent.
• Ferrous materials are the most important metals in the metallurgical
and mechanical industries because of their extensive use.
• The commonly used ferrous metals are as follows:
1. Cast iron
2. Alloy cast iron
3. Steel (Plain carbon steel)
4. Alloy steel
5. 5
FerrousMetals
1. CastIron
• Cast iron are the alloy of iron and carbon.
• Generally, commercial cast iron are complex in composition and
their carbon content is in the range of 2.3 to 3.7 % with other
elements like sulphur, manganese, phosphorus and silicon.
• Cast iron are formed by melting a metal and casting with or without
machining to the desired final shape and size, hence called cast iron.
6. 6
FerrousMetals
1. CastIron
Characteristicsofcast iron
• While manufacturing of cast iron, raw materials like pig iron, scrap
limestone, coke etc.
• The melting point of cast iron is low i.e. 1140 to 1240°C.
• Due to high fluidity of melt, cast iron has excellent castability.
• By altering the chemical composition, cast iron can provide a wide
range of metallicproperties.
7. 7
FerrousMetals
1. CastIron
Advantagesofcast iron
• It is low cost material.
• It can provide good damping capacity and high compressive
strength.
• Cast iron has high resistance to wear and abrasion.
• It has highhardness.
• Corrosion resistance of cast iron is fairly good.
• It has excellentmachinability.
8. 8
FerrousMetals
1. CastIron
Limitationsofcast iron
• It is brittle in nature.
• Its mechanical properties like toughness, stiffness, resilience etc. are
poor.
• Due to brittleness, it is poor against fatigue and impact loading.
9. 9
FerrousMetals
1. CastIron
Applicationsofcast iron
• Machine beds, columns, hammers, road-rollers.
• Pipe fittings, valves, farm equipment's, automotive parts.
• Camshafts, crank shafts, gears, ordnance parts.
• Motor covers, pump bodies, furnace parts.
• Engine frames, piston and cylinder, cylinder blocks and bearing
blocks etc.
11. 11
FerrousMetals
2.AlloyCast Iron
• Generally, cast iron has low impact resistance, corrosion resistance
and temperature resistance. Hence, to increase these properties
certain alloying elements are added in suitable amount.
• Usually, nickel, chromium, copper, silicon, vanadium, molybdenum
etc. are used for this purpose.
12. 12
FerrousMetals
2.AlloyCast Iron
PropertiesofAlloyCast Iron
• It has highstrength.
• It has high oxidation resistance.
• It has high wear resistance and corrosion resistance.
ApplicationsofAlloyCast Iron
• Gear, automobile parts like pistons, piston rings, camshaft, crank
shaft, cylinders.
• Brake drum, pulleys, grinding machinery parts, etc.
13. 13
FerrousMetals
3.PlainCarbon Steel
• Steel is an alloy of iron and carbon with carbon content up to 1.6 %
approximately.
• Carbon content increases the strength and hardness of steel.
• Plain carbon steel or carbon steel is defined as a steel which has its
properties mainly due to its carbon content and does not contain
more than 0.5% of silicon and 1.5% of manganese.
14. 14
FerrousMetals
3.PlainCarbon Steel
PropertiesofPlainCarbon Steel
• They are ductile in nature.
• They have high fatigue and impact strength.
• Their mechanical properties like toughness, stiffness, resilience, etc.
are high.
AdvantagesofPlainCarbon Steel
• They have high tensile strength.
• They have high resilience and toughness.
• They can sustain fatigue and impact load
15. 15
FerrousMetals
3.PlainCarbon Steel
LimitationsofPlainCarbon Steel
• The vibration damping property of steel is poor.
• They cannot be cast into complicated shapes.
• They have low wear resistance.
• Its cost is more than cast iron.
ApplicationsofPlainCarbon Steel
• Stampings, fan blades, rivets, nuts, bolts, wires, structural steel, grill,
shafts.
• Gears, valves, crank shaft, camshaft, axles, screws, springs.
• Cutting tools, milling cutters, blades, drill bits, musical instruments,
agricultural applications, etc.
16. 16
FerrousMetals
4.Alloy Steel
• To obtain the specific properties various alloying elements areadded
in steel.
• The specific properties define the applications of steel.
• The various alloying elements are as follows:
Carbon, Sulphur, Phosphorus, Silicon, Manganese, Nickel, Chromium,
Titanium, Tungsten, Molybdenum, Vanadium, Cobalt etc.
17. 17
FerrousMetals
4.Alloy Steel
PropertiesofAlloy Steel
• They are ductile in nature.
• They have high corrosion resistance.
• They have highstrength.
• They are soft and having high toughness.
AdvantagesofAlloy Steel
• They have high tensile and fatigue strength.
• They have high wear resistance, corrosion resistance and creep
resistance.
• They have high toughness and resilience.
18. 18
FerrousMetals
4.Alloy Steel
LimitationsofAlloy Steel
• Alloy steel cannot be cast into complicated shapes.
• Their vibration damping properties is poor.
• They are costlier than steel and cast iron.
ApplicationsofAlloy Steel
• Aircraft engine parts, heat exchangers, wrist watches, sanitary
fittings.
• Combustion chamber, furnace parts, gas burners, screws.
• Valves, pumps, surgical instruments, razor blades, turbine blades,
missiles, structural components,etc.
19. 19
Non-FerrousMetals
• Non-ferrous metals are those which contain a metal other than iron
as their main element or constituent.
• Non-ferrous metals find wide applications in various industrial
sectors because of following advantages:
1. Low density, hence light in weight.
2. High electrical conductivity.
3. Easy to fabricate.
4. High corrosion resistance.
• The commonly used non-ferrous alloys are as follows:
1. Copper and itsalloys
a) Brasses b) Bronzes
2. Aluminium and itsalloys
20. 20
Non-FerrousMetals
1. Copperandits Alloys
• Copper is one of the most widely used non-ferrous metal.
• Various alloying elements are added to copper to improve and add
some properties.
• Major alloying elements are zinc, silicon, aluminium, lead,
manganese, nickel, phosphorous, tin, magnesium, etc.
21. 21
Non-FerrousMetals
1. Copperandits Alloys
Propertiesof Copper
• It has high ductility and malleability.
• It has high electrical and thermal conductivity.
• It is non-magnetic in nature.
• It can be easily alloyed with other metals.
• Its corrosion resistance is also high.
Applicationsof Copper
• Electrical parts
• Heat exchangers
• Household utensils etc.
23. 23
Non-FerrousMetals
1.Brasses(Alloyofcopperand zinc):
• Brasses are alloys of copper and zinc with small amount of other
alloying elements.
• According to the percentage of copper and zinc, there are various
types of brasses. For example α-brasses.
• The properties of brasses can be changed by adding small amount of
other alloyingelements.
24. 24
Non-FerrousMetals
1.Brasses(Alloyofcopperand zinc):
• Advantagesof Brasses
• It has high corrosion resistance.
• It has high ductility and malleability.
• Due to addition of zinc, it has high strength.
• It has highmachinability.
• Limitationsof Brasses
• It has low thermal and electrical conductivity.
• Its cost is also high.
28. 28
Non-FerrousMetals
2.Bronzes(Alloyofcopperandtin):
Limitationsof Bronzes
• The cost of bronzes is higher than the brasses.
• The strength of bronzes is lower than the ferrous metals.
Applicationsof Bronzes
• Springs, gears, bearings, electrical appliances.
• Bolts, rivets, pressure vessels, bells, marine containers.
• Valve bodies, ordnance parts, gun barrels, pipe fittings etc.
29. 29
Non-FerrousMetals
AluminiumanditsAlloys
• Aluminium is another widely used non-ferrous metal.
• Aluminium can be easily alloyed with elements like silicon, copper,
nickel, zinc, manganese, titanium, magnesium etc.
AdvantagesofAluminium Alloys
• It has high thermal and electrical conductivity.
• It has high corrosion resistance.
• It has hightoughness.
• They are malleable and ductile.
• It can be easily cast and rolled.
31. 31
Non-Metals
• Now-a-days use of non-metals is increasing in the industries because
of following properties:
1. They are having low density.
2. They are light in weight.
3. Use of non-metals provides flexibility in the design.
4. They have high resistance to heat and electricity.
5. They have lowcost.
• The commonly used non-metals are as follows:
1. Plastics
2. Ceramics
3. Composites
32. 32
Non-Metals
1. Plastics
• A large group of engineering materials which have increasing
importance in industrial applications are composed of natural
synthetic organic polymers(Plastics).
• Now-a-days in some of the applications, metal and wood parts are
replaced by plastics, which have satisfactory properties and may be
produced atlower cost.
• Plastics are moulded into any required shape by the applications of
pressure and heat, for example toys, chairs, refrigerator equipment's
and radiator fans etc.
• The plastics can be cast, rolled, laminated and machined easily.
• The word ‘mer’ means a unit, monomer stands for a single unit and
polymer means many units joined together by a chemical reactions.
33. 33
Non-Metals
1. Plastics
Characteristicsof Plastics/Polymers
• Low density and weight.
• High corrosion resistance.
• Low thermal, mechanical and electrical properties.
• Low coefficient offriction.
• Excellent surface finish can be obtained.
• It can be produced in different colours.
• It can be produced with close dimensional tolerances.
• It has goodmouldability.
• It is more economical than the metals.
35. 35
Non-Metals
1. Plastics
Types of Plastics/Polymers
1.Thermoplastic or Thermoplasts (Soften when heated and harden
when cooled).
2.Thermosetting or Thermosets (Soften when heated and permanently
harden when cooled).
36. 36
Non-Metals
1. Thermoplastics (Thermoplasts)
• Thermoplastic polymers soften when heated and harden when
cooled.
• These types of polymers are soft and ductile.
• They have low melting temperatures and can be repeatedly moulded
and remoulded to the desired shapes.
• These polymers are usually fabricated by the simultaneous
applications of heat and pressure.
37. 37
Non-Metals
1. Thermoplastics(Thermoplasts)
Applications
• These types of plastics are used in electrical insulations, toys,
machine guards, musical instruments, fuel container coatings, hoses,
photographic films, bottles, gaskets, packings, refrigerator parts, floor
tiles, plastic lensesetc.
• Some of the commonly used thermoplastics are: Polyamide, Poly-
Tetra-Fluaro-Ethylene (PTFE), Poly-Vinyl-Chloride (PVC), Poly-
Propylene (PP), Poly-Ethylene (PE)etc.
38. 38
Non-Metals
2.Thermosetting (Thermosets)
• Thermosetting polymers become soft during first heating and
become permanently hard when cooled. Hence, these type of
polymers cannot be remoulded or reshaped by subsequent heatings.
• These type of plastics are generally more stronger, harder, brittle and
resistant to heat and solvents than the thermoplast.
• It they are heated to high temperature, decompositions and
degradation of the polymer takes place.
39. 39
Non-Metals
2.Thermosetting (Thermosets)
Applications
• These type of plastics are used in telephone receivers, electric plugs,
radio and T.V. cabinets, camera parts, automobile parts, switch panels
etc.
• Some of the commonly used thermosets are: Phenolic, Epoxies,
Aminos (Urea formaldehyde and melamine formaldehyde),
Unsaturated polyesters etc.
40. 40
Non-Metals
Ceramics
• Ceramics is a compound formed by combination of inorganic and
non-metallic materials.
• Ceramics are hard and brittle materials used for high temperature
applications.
• They are mainly oxides, carbides, sulphides and nitrides of metals.
41. 41
Non-Metals
Ceramics
Propertiesof Ceramics
• Ceramics have high hardness and stiffness.
• It consists of high strength at high temperatures.
• They have high resistance to abrasion and wear.
• Chemical stability of ceramics is good.
Advantagesof Ceramics
• Ceramics can have excellent compressive strength.
• They have low thermal conductivity.
• They have low coefficient of thermal expansion.
• Also, they possess good electrical insulation properties.
42. 42
Non-Metals
Ceramics
Limitationsof Ceramics
• Due to their hardness machinability of ceramics is very low.
• They are brittle in nature.
Applicationsof Ceramics
• Spark-plug insulators, vacuum tubes, metal cutting tool tips, grinding
wheels, nuclear equipments.
• Rotor blades in turbines, die materials, engine components, artificial
hip joints, refractory tubes and containers.
• Nozzles, bearings, pump parts, electronic parts, components of paper
industry etc.
43. 43
Non-Metals
Composites
• Composite material is defined as a material formed by the
combination of two or more chemically dissimilar materials with
different boundaries betweenthem.
• Composite material exhibit properties that are vastly different from
those of the individual constituents and better suited for a particular
applications.
• Many composite materials are composed of just two phases; one is
called as matrix (soft phase) which is continuous and surrounds the
other phase i.e. called as dispersed phase (hard phase).
45. 45
Non-Metals
Composites
1. Fiberreinforced composites
• The hard phase consists of fibres of high strength material. These
fibres are dispersed in the soft and ductile matrix.
• The combined material has better stiffness, strength and toughness.
• The function of fibres is to withstand the load, while matrix ensures
uniform distribution of applied load.
46. 46
Non-Metals
Composites
1. Fiberreinforcedcomposites
Applications
• These type of composites are used in piston, connecting rods,
aerospace applications, aircraft wing applications, propeller for ships,
cutting tool inserts for machining hard metals, springs containers,
pressure vessels, gasketsetc.
47. 47
Non-Metals
Composites
2.Particlereinforced composites
• In this type of composites, the strengthening is produced by particles
of hard material.
• The function of particles is to impart strength and stiffness to the
composite mix.
• Matrix ensures uniform distribution of applied load on the
composite. It also provides protective covering to the particles.
49. 49
Non-Metals
Composites
3.Structural Composites
• Structural composites are made up of two or more homogeneous
materials.
• The properties of these composites depend on the constituent
materials and their geometrical design.
• Structural composites can be of laminate type or sandwich panel
type.
• In case of laminated composites, two or more layers or sheets
arranged in a stacking order. These sheets are cemented by using a
bonding agent.
• The load on the composites is shared by all the layers. It is used as a
skin material foraircraft.
50. 50
Non-Metals
Composites
3.Structural Composites
• In case of sandwich panel composites, two strong outer sheets are
separated by a layer of less-dense material.
• It is used in roofs, floors and walls of buildings, aircraft wings etc.
51. 51
Metallography
• Metallography is a study of the structural characteristics or constitution
of a metal or alloy, in relation to its physical and mechanical properties.
• There are two examination methods in metallography:
1. Microscopy
2. Macroscopy
52. 52
Microscopy
• In microscopy, the examination is done with the prepared metal
specimens, employing magnifications with the optical metallurgical
microscope, from 100X to high as 2000X of magnification.
• Microstructural examination can provide quantitative information about
the following parameters:
1. The grain size of specimen
2. The amount of interfacial area per unit volume.
3. The dimensions of constituent phases.
4. The amount and distribution of phases.
53. 53
Macroscopy
• In case of macroscopic examination the nature of in homogenities and
flow lines in a metal by unaided dye or with the help of low power
magnifying glass.
• The general distribution and variation in size of non-metallic inclusions,
the uniformity of structure, the location and extent of segregation, flow
lines etc. can be examine by macroscopy and these cannot be examined
by microscopy.
1. Crystalline heterogeneity i.e. manner of solidification and the crystalline
growth of the metal or alloy.
2. Chemical heterogeneity i.e. impurities in a metal or alloy.
3. Mechanical heterogeneity i.e. due to cold working or heterogeneity
occurs in metals or alloy due cold rolling or forging etc.
54. 54
SpecimenPreparation
• Specimen preparation is necessary to study it’s microstructure as
metallurgical microscope makes use of the principle of reflection of light
to obtain image of the metal structure.
• A satisfactory image of the microstructure can be obtained only when the
specimen has been carefully prepared.
• Even the most expensive microscope will not reveal the metal structure,
if the specimen has been poorly prepared.
• The procedure to be followed in the preparation of a specimen is simple
but the technique gets develop only after practice.
55. 55
SpecimenPreparation
• The final objective is to produce a flat, scratch free and a mirror like
finish surface.
• The procedure for preparing the specimen for both microscopy and
macroscopy examination is the same except that in the case of
microscopy the final surface finish is more important.
• The steps required to prepare a metallographic specimen are as under:
2. Cutting of specimen
4. Mounting of specimen
6. Polishing
1. Selection of specimen
3. Rough grinding
5. Fine grinding
7. Etching
56. 56
SpecimenPreparation
1. Selection of specimen
• Specimen should be selected from, that area of a metal, which can be
taken as representative of the metal that is being studied.
• In case of study of failures, specimen should be taken as close as possible
to the fracture or to the initiation of the failure.
• Generally in many cases, specimens are required to be taken from a
sound area for a comparison of structure and properties.
• After deciding the location of the specimen, the type of section to be
examined must be decided. The location of surface examined should
always be given in reporting results.
57. 57
SpecimenPreparation
1. Selection of specimen
• Size of specimen be proper for handling during all sample preparation
techniques.
• If the specimen sample is too small, then it should be mounted on the
mounting press, along with thermosetting resign or cold mounting
process.
58. SpecimenPreparation
2. Cutting of Specimen
• After selecting a particular area, the specimen may be removed from the
metallic piece by sawing or cutting using abrasive wheel which is carried
out on abrasive wheel cutting machine.
58
59. SpecimenPreparation
3. Rough Grinding
• After cutting, a soft specimen may be made flat by slowly moving it up
and back across the surface of a smooth file, and hard specimens may be
rough ground on a belt grinder.
59
60. 60
SpecimenPreparation
4. Specimen Mounting
• It is carried out for convenience in handling it during the subsequent
steps of metallographic preparation and examination. For this the
specimen is mounted.
• Compression mounting involves molding around the specimen by a
material like Bakelite, acrylic resins, by application of heat and pressure.
This is known as hot mounting process.
• Epoxy or polyester resins are used for cold molding, and this is known as
cold mounting process.
62. 62
SpecimenPreparation
4. Specimen Mounting
• Specimen mounting is necessary because very thin, irregular shape
specimens are difficult to handle during sample preparation techniques,
due to which those specimen are mounted by two methods.
1. Hot mounting
2. Cold mounting
63. 63
SpecimenPreparation
4. Specimen Mounting
1. Hot mounting
• In this process a small hydraulically operated press is used and which is
consists of a small furnace / heater to heat the resin material.
• A temperature up to 200°C and a pressure up to 50 kN are applied during
the embedding of the specimen.
• A thermoplastic resin material is used.
• A small metallic mould is used to embedding the specimen, in the resin
material.
64. 64
SpecimenPreparation
4. Specimen Mounting
2. Cold mounting
• As this process is carried out room temperature it is known as cold
mounting.
• A resign material in the powder form is mixed with hardener to provide
the mounting compound.
• This slurry or mixture is then poured around the specimen, surrounded to
metallic mould.
• Cold mounting is preferred for specimens that are sensitive to head or
pressure, as in case of hot mounting used.
65. SpecimenPreparation
5. Fine Grinding
• After rough grinding the specimen is finely ground using fine abrasive
paper (grit sizes from 180 mesh to 600 mesh).
• Fine grinding is generally carried out on many papers, of grades from 01
to 04 i.e. 01 is coarse grained and it’s fineness goes on increasing towards
04.
65
66. SpecimenPreparation
6. Polishing
• The fine scratches caused by final grinding operation are removed by
polishing. Polishing is carried out on single disc or double disc polisher.
66
68. 68
SpecimenPreparation
7. Etching
• Etching is defined as, a intentionally made chemical attack on the
prepared metallic specimen surface, to reveal microstructure or micro
constituents.
• The purpose of etching is to make visible structural characteristics of the
metal or alloy. This is achieved by a use of an appropriate etching reagent
which carry out chemical action on a polished surface.
• Etching is done by immersing the polished surface in the reagent or by
rubbing the polished surface gently with cotton swab, wetted with the
etching reagent.
77. 77
Electron Microscope
• Electron microscopes are quite different from optical microscopes.
• In these microscopes, a high velocity electron beam is used instead of
ordinary light.
• The resolving power of electron microscope is very high as the
wavelength of electron beam is small i.e. 0.05 to 0.07A°.
• The magnification obtained is very high in the range of 1 to 5 lakhs.
• Built on the principal of transmission and hence sample required to be
very thin .
80. 80
ScanningProbeMicroscope (SPM)
• SPM that forms images of surfaces using a physical probe that
scans the specimen.
• An image of the surface is obtained by mechanically moving
the probe in a raster scan of the specimen, line by line, and
recording the probe-surface interaction as a function of position.
• SPM techniques have been applied over a wide range of
materials.
81. GrainSize
• It is important to study the grain size of polycrystalline metals.
• The grain size is specified in terms of average grain volume, dimeter or
area.
• The grain size has an influence on the mechanical properties of the metal
viz. ductility, strength, toughness etc.
• Usually, fine grained structures have better mechanical properties as
compared to coarse grained structures.
• Hence, many time, special treatments such as heat treatment are carried out
to refine the grain structure. 82
82. GrainSize
Sr.No. Property CoarseGrained
Structure
FineGrained
Structure
1 Yield Strength Less More
2 Tensile Strength Less More
3 Toughness Less More
4 Resilience Less More
5 Hardness Less More
6 Fatigue Resistance Less More
7 Creep Resistance More Less
8 Corrosion Resistance More Less
9 Ductility Less More
10 Hardenability More Less 83
83. 83
GrainSize
• Grain size measurement can be carried by several methods, such as:
1. Comparison method
2. Heyn’s Intercept method
3. Jefferies Planimetric method.
84. 84
GrainSize Determination
1. Comparison method
• Comparison method is mainly used for equiaxed grains and this method is
device by ‘ASTM’.(American Society for testing and management)
• ASTM has prepared number of standard comparison charts, all having
different average grain sizes.
• Each average grain size is characterized by ASTM grain sizenumber.
N = 2n-1
Where, N= Number of grains per square inch at 100X magnification
n= ASTM grain size number.
85. GrainSize Determination
Sr.No. ASTM grain
sizenumber
(n)
Average number ofgrains
per square inch of 100X
magnification (N)
Actual average diameter of
equivalent spherical grain in
microns (1 micron= 10-3 mm)
1 1 1 287.0
2 2 2 203.0
3 3 4 144.0
4 4 8 101.0
5 5 16 71.8
6 6 32 50.7
7 7 64 35.9
8 8 128 25.4
9 9 256 18.0
10 10 512 12.7 86
86. GrainSize Determination
2. Heyn’s Intercept Method
• Intercept method is mainly used for non-equiaxed grains or elongated
grains.
• In this method, straight lines of same length are drawn on the
photomicrograph of the specimen that shows the grain structure.
• Hence, grains intersected by each line are counted.
• 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑔𝑟𝑎𝑖 𝑛 𝑠𝑖𝑧𝑒 𝑎𝑡100𝑋 =
𝑇𝑜𝑡𝑎𝑙 𝑙 𝑒 𝑛𝑔𝑡ℎ 𝑜𝑓 𝑙𝑖 𝑛𝑒𝑎𝑡100𝑋
86
𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑔𝑟𝑎𝑖𝑛𝑠 𝑖 𝑛𝑡𝑒𝑟𝑐𝑒𝑝𝑡𝑒𝑑 𝑏𝑦 𝑡ℎ𝑒 𝑙𝑖 𝑛𝑒
• The result of the above equation is divided by the linear magnification
photo micrograph i.e. by 100 to get the actual grain diameter.
87. 87
GrainSize Determination
3. Jefferies Plainmetric Methods
• It is similar to the Heyn's intercept method, with the difference that it is
based on area intercept rather the line intercept.
• A photomicrograph of the grain structure of the sample is obtained with a
suitable magnification.
• The magnification should be such that at least 50 grains should be seen in
the above photomicrograph.
• A circle or a rectangle of known area is drawn on the photomicrograph.
• The actual area covered by the circle or rectangle should be at least 5000
mm2.
• The total number of grains covered by the circle or rectangle is counted.
88. GrainSize Determination
3. Jefferies Plainmetric Methods
• 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑔𝑟𝑎𝑖 𝑛𝑠𝑝𝑒𝑟𝑠𝑞𝑢𝑎𝑟𝑒 𝑚𝑖𝑙𝑖 𝑚𝑒𝑡𝑒𝑟 = 𝑇𝑜𝑡 𝑎𝑙𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑔𝑟𝑎𝑖 𝑛𝑠𝑐𝑜𝑣𝑒𝑟𝑒𝑑 ×𝐽𝑒𝑓𝑓𝑒𝑟𝑖𝑒𝑠𝑀𝑢𝑙𝑡𝑖𝑝𝑙𝑖𝑒𝑟 𝑓
• Jefferies Multiplier (f) is a function of the magnification used as given in the following
table.
88
Magnification used f Magnification used f
1 0.002 200 8.00
10 0.02 250 12.50
25 0.125 300 18.00
50 0.50 500 50.00
75 1.125 750 112.50
100 2.00 1000 200.00
150 4.50 1500 450.00
2000 800.00
89. Macroscopy
• The results obtained by metallurgical microscopy are not representative of
entire component because of the heterogeneous nature of these materials.
• Macroscopic examination is the process of examining the metals with or
without proper etchant and by unaided eyes or by a magnifying glass.
• Macroscopy is mainly used for investigation of defects and structures.
• As compared to microscopy, a large surface observation is possible in
macroscopy. Also preparation of specimen is easy in macroscopy.
1. Uniformity of structure
2. Distribution of non-metallic inclusions
3. Extent of segregation
4. Presence of defects
5. Examination of fractures
6. Flowlines in extruded, forged and drawn parts. 90
90. SulphurPrinting
• Sulphur printing is used to detect sulphur in ferrous metals and alloys.
• It is also produces a permanent record of sulphur distribution in steel.
• To reduce the harmful effect of sulphur, manganese is added.
• Sulphur printing is used to determine distribution of sulphur impurity in
the steel sample. Sulphur impurity has the effect of including brittleness in
the steel or the distribution of such impurities in the steel is very important.
91
91. SulphurPrinting
• The surface of the specimen is initially polished on 0 or 00 number emery
paper and then washed under running water.
• A matt finish photographic bromide paper is soaked in 2% aqueous
solution of sulphuric acid for 3 to 4 minutes.
• The paper is taken out from the solution and excess drops of solution are
removed.
• The emulsion side of the paper is then kept in contact with polished
surface of the specimen for 2 to 3 minutes with moderate pressure.
• The photographic paper is then removed from the surface of specimen,
washed in running water and then it is immersed in photographic fixer
solution for about 15 minutes.
• Finally, the paper is taken out from the solution, washed in running water
for about 60 minutes and dried. 92
92. 92
FlowLines Observations
• Flow lines indicate the direction in which the steel was mechanically
worked.
• We know that, forged components have better properties than the cast,
rolled and machined components.
• Also the properties of forged components are governed by the metal flow
pattern.
• Hence, it is necessary to know whether the component is manufactured by
forging, casting, rolling or machining.
93. FlowLines Observations
• It is achieved by macro-etching the polished surface of component in a
50% aqueous solution of hydrochloric acid (HCl) at 60 to 70°C for 5 to 10
minutes.
93
94. 94
SparkTest
• Spark test is a simple test used for identification of Metals and their alloys
before a detailed chemical analysis.
• This test is performed by holding a piece of metal or alloy against a
revolving grinding wheel.
• The grinding wheel tears off the small particles from the metal. These
heated, glowing particles of metal produce a visible beam of sparks.
• The characteristics of spark produced are observed to identify the metal or
alloy
