4. 1. METALS & ALLOYS
4
• Metals are extremely good conductors of electricity and
heat and are not transparent to visible light
• Two or more pure metals are melted together to form a new
metal of different properties called an alloy
• Steel is an alloy of iron, carbon and other alloying elements
• Brass is an alloy of copper and zinc
• Bronze is an alloy of copper and tin
5. A) FERROUS METALS
5
• Iron is the principal constituent
• Ferrous alloys contain significant amount of non-ferrous
metals
Steel- % of carbon content in iron is up to 2.14%
Cast Iron- % of carbon content in iron is above 2.14%
( brittle in nature)
Cast iron is used for
• Automobile motor casing, car parts-cylinder heads-gear
box cases, rail road, marine, bridges, lathe bed…etc
6. Two kind of steel
6
a) Plain carbon steel- major alloying element is carbon
• Plain carbon steel is again divided into 3
• Mild steel- 0.15% to 0.25% carbon, used for gears, valves,
boiler plates…etc
• Medium carbon steel- 0.3% to 0.6% carbon content, used
in turbines, nut, bolt..etc
• High carbon steel- 0.65% to 1.5% carbon content, hard and
tough material, used in cutting tools, dies,drills…etc
7. b) Alloy steels- steel in which one or more elements other
than carbon have been added. Common elements added
are molybdenum, manganese, nickel, silicon, boron,
chromium and vanadium
Stainless steel: 11%chromium, high corrosion resistance,
used for making surgical instruments, ball bearing…etc
B) NON-FERROUS METALS
• Substances are composed of metals other than iron
• Brass is an alloy of copper and zinc
• Bronze is an alloy of copper and tin
• Used in medical, automobile, electrical, electronics,
construction, aerospace industries…etc
7
10. 2. CERAMICS
10
• Non-metallic solids made of oxides, nitrides, borides and
carbides
• The wide range of materials that falls within this
classification includes ceramics that are composed of clay
minerals, cement, and glass. These materials are typically
insulative to the passage of electricity and heat, and are
more resistant to high temperatures and harsh
environments than metals and polymers.
• Ceramics are hard but very brittle
11. APPLICATIONS
11
• Electrical insulators
• Abrasives
• Thermal insulation and coatings
• Windows, television screens, optical fibers(glass)
• Corrosion resistant applications
• Electrical devices: capacitors, transducers, etc.
• Highways and roads (concrete)
• Biocompatible coatings (fusion to bone)
• Self-lubricating bearings
• Magnetic materials (audio/video tapes, hard disks,etc.)
• Optical wave guides
• Night-vision
13. 3. POLYMERS
13
include the familiar plastic and rubber
• Polymers
materials
• These materials typically have low densities and may be
extremely flexible
• Thermoplastic- soft at high temperatures and become
hard on cooling
• Thermosetting plastic- formed into shape under heat and
pressure which results in a permanently hard product
14. APPLICATIONS
14
Adhesives and glues
Containers
Moldable products (computer casings, telephone handsets,
disposable razors)
Clothing and upholstery material (vinyls, polyesters,nylon)
Water-resistant coatings (latex)
Biodegradable products (corn-starch packing“peanuts”)
Biomaterials (organic/inorganic interfaces)
Liquid crystals
Low-friction materials (Teflon)
Synthetic oils and greases
Gaskets and O-rings (rubber)
Soaps and surfactants
16. 4. COMPOSITES
16
• A combination of two or more materials to achieve better
properties than that of the original materials
• A composite is designed to display a combination of
the best characteristics of each of the component
materials.
• Fiberglass is a familiar example, in which glass fibers
are embedded within a polymeric material.
• Fiberglass acquires strength from the glass and
flexibility from the polymer
17. APPLICATIONS
• Sports equipment (golf club shafts, tennis rackets,
bicycle frames)
• Aerospace materials
• "Smart" materials (sensing and responding)
• Brake materials
• Space shuttle heat shields (interwoven ceramic fibers)
• Paints (ceramic particles in latex)
• Tank armor (ceramic particles in metal)
17
19. 5. SEMI-CONDUCTORS
19
• Semiconductors have electrical properties that are
intermediate between the electrical conductors and
insulators.
• The electrical characteristics of these materials are extremely
sensitive to the presence of small concentrations of impurity
atoms
22. 6. BIO MATERIALS
22
• Biomaterials are employed in components implanted into
the human body for replacement of diseased or damaged
body parts.
• These materials must not produce toxic substances and
must be compatible with body tissues (i.e., must not cause
adverse biological reactions).
• All of the above materials—metals, ceramics, polymers,
composites, and semiconductors—may be used as
biomaterials
25. 7. ADVANCED MATERIALS
25
• Materials that are utilized in high-technology (or high-tech)
applications are sometimes termed advanced materials
• Examples include electronic equipment (VCRs, CD players,
etc.), computers, fiberoptic systems, spacecraft, aircraft, and
military rocketry
• Materials that are used for lasers, integrated circuits,
magnetic information storage, liquid crystal displays (LCDs),
fiber optics, and the thermal protection system for the Space
Shuttle Orbiter
26. a) Nano materials: molecules have dimensions in the range
of 1nm to 100nm.
26
b) Smart materials: materials are able to sense changes in
their environment and then respond to thesechanges
32. CASTING
32
• It is a manufacturing process in which molten metal is
poured in a mould or cavity and allowed tosolidify
• Molten metal on solidification gets the shape of themould
• Mould has the shape of the product to bemade
34. SAND CASTING
34
• Molten metal: metal in the form of a liquid
• Mould: negative print of the product to be cast (cavity
whose geometry determines the shape of the cast part),
open and closed mould
• Moulding: process of making mould of desired shape using
sand, pattern and core
Mould consists of two halves
a) Cope: upper half of the mould
b) Drag: bottom half of the mould
38. • Pouring basin: top of the mould for pouring the molten
metal at the required rate into the mouldcavity
• Sprue: vertical passage made through the cope for
connecting pouring basin with the gate
• Runner: for connecting the sprue and gate
• Gates: passage for connecting the base of the runner with
the mould cavity
• Riser: passage made in the cope to permit molten metal to
rise up after filling the mould cavity
38
40. • Pattern: model or replica of the component to be made
by casting( mould formingtool)
Types of patterns are
• One piece pattern
• Split pattern
• Loose piece pattern
• Match plate pattern
• Cope and Drag pattern
40
48. • Core: solid mass prepared using dry sand, in order to
introduce into the mould cavity, to form a hole
• Core produces a hollow casting
Types of core
• Horizontal core
• Vertical core
• Hanging core
48
61. MOULDING SAND PROPERTIES
61
• FLOWABILITY: behave like a fluid, sand to get compacted to
uniform density
• GREEN STRENGTH: strength of the sand in moistcondition
• DRY STRENGTH: strength of the sand in dry condition
• POROSITY/ PERMEABILITY: ability to allow the passage of
mould gases
• REFRACTORINESS: ability of the sand to withstand high
temperature
62. • ADHESIVENESS: ability of the sand to stick on to the mould
walls
• CHEMICAL STABILITY: resist chemical reaction
• COLLAPSIBILITY: ability of the sand to collapse after the
casting solidifies
• FINENESS: ability of the sand to produce smooth surfaced
castings
• COEFFICIENT OF EXPANSION: less coefficient of expansion
• DURABILITY: ability of the sand to be used again and again
62
63. Advantages
• Production process is simple
• Cost of casting is low
• Sand can be reused
Disadvantages
• More chances of defects
• Does not impart good surfacefinish
63
64. METAL MOULD CASTING
64
• Process in which molten metal is poured/forced into metal
mould cavities
• It requires less floor space
65. 1. Permanent Mould Casting
65
• The moulds(dies) are made in two halves, hinged together to
facilitate quick opening and closing and removal ofcasting
• Filling the mould is achieved due togravity
• One half is movable called movable die
• Other half is stationary called stationary die
• Ejector pins are used for ejecting out the casting from the
die
• Clamps are used for clamping the two halves of the die
together
70. 2. DIE CASTING
70
• Molten metal is forced into mould cavity under pressure
•Pressure is obtained by compressed air orhydraulically
Two types
a) Hot chamber process
b) Cold chamber process
• Ejector pins are used for ejecting out the casting from the
die
• Clamps are used for clamping the two halves of the die
together
71. a. Hot Chamber Die Casting
71
• Plunger is activated by compressed air or by hydraulic
pressure
• Intake Port allows the molten metal to enter thecylinder
• Plunger moves downward, closes the intake port and
applies pressure on the moltenmetal
• Molten metal is forced into the die cavity
• After solidification, plunger moves upward, uncovers intake
port and hot molten metal enters thecylinder
74. b. Cold Chamber Die Casting
74
• Metal is melted separately and transferred to the cylinder
using a hand ladle
• Molten metal is forced into the die cavity by applying
pressure on the plunger
• After solidification, die is opened and the casting is ejected
77. CASTING DEFECTS
77
• Blowholes: holes below the surface of casting, not visible
from outside
• Inclusions: foreign material in the casting
• Swell: localized enlargement of the casting
• Scab: erosion or breaking down a portion of the mould
• Honey combing: small cavities present on the castingsurface
• Misrun: molten metal fails to reach all the sections of the
mould
• Fin: thin projection of metal, which is not a part of thecasting
• Shift: mismatching of casting sections
85. Metal Forming By Deformation
85
• Process in which shape of the metals are changed to desire
shapes by subjecting them to stresses greater than yield
stress of the metal
• It is a deformation process
Types are
• Forging
• Rolling
• Extrusion
88. • Process of
88
plastically deforming metal by passing it
between rolls
• Cylindrical rolls are used to reduce the cross sectional
area of a bar or plate with a corresponding increase in the
length
• Process of rolling basically consists of passing metal
between two rolls rotating in opposite direction at the
same speed
Two types
• Hot rolling
• Cold rolling
96. • Two rolls
• Lower roll will be fixed
• Upper roll can be moved to adjust the space between the
rolls
• Both the rolls rotate at the same speed but in opposite
directions
96
99. • Three rolls positioned one over another
• Upper and lower rolls rotate in the same direction
• Middle roll rotates in the oppositedirection
• Middle roll is fixed
• Upper and lower rolls are moved to adjust the rollgap
99
104. • Used for rolling very thin sheet or foils
• It consists of a Pair of working rolls of very small diameter,
supported by a number of back up rolls on eitherside
104
107. • Series of rolling mills are placed one after another
• Different reduction takes place at each stand, the strip
will be moving at different velocities
107
108. 2. FORGING
108
• Process of changing the shape of metals when it is in the
plastic state, by applying compressive force
• Hot forging – forging at high temperature
• Cold forging- forging at room temperature
• Forged product has better mechanical properties than a cast
one
109. Components produced by forging
• Nails
• Bolts
• Spanners
• Crane hooks
• Axles
• Crankshafts
• Connecting rods
110
110. Dies used for forging
a) Open die forging
b) Closed / Impression die forging
111. a) Open Die Forging
• Work piece is upset, compressed or forged between two
flat dies
• Used for simple shapes and low productionvolumes
112.
113.
114. b) Closed/Impression Die Forging
• Work piece takes the shape of the die cavity while being
forged between two shaped dies
• Used for forging complicated shapes
• Process is usually carried out at elevated temperatures
119. A. HAND FORGING
120
• Traditional forging operation carried out by blacksmith in a
section of workshop called smithy
• Hand tools are used for forging(eg. Hammer, chisel…etc)
• Not suitable for mass production
120.
121. Hand forging operations
a) Upsetting
b) Drawing down(necking down)
c) Setting down
d) Bending
e) Welding
f) Cutting
g) Swaging
h) Drifting
i) Fullering
j) Edging
122. a. Upsetting
• Process of increasing the cross sectional area of a bar at
any desired portion at the expense of length of the bar
• Portion to be upset is heated and then hammeredaxially
135. e. Welding
• Joining two metallic surfaces
• Surfaces to be joined are heated to a temperatureof
about 1000⁰C
• Metal surfaces are joined by applying pressure at the
mating surfaces
136.
137.
138. f. Cutting
Process of removing pieces of metal from the work pieceby
means of a chisel
142. g. Swaging
• Operation by which the required cross sectional shape is
obtained
• Two swage blocks, top swage and bottom swage are used
for swaging operation
• Work piece is held between the top and bottom swages
and is hammered
145. h. Drifting
• Process of increasing the diameter of a punched hole
• Drift which has tapered end is made to pass through the
punched hole to produce a finished hole
151. j. Edging
• Process of concentrating material using a concave
shaped open die
• Used to shape the ends of bars
152.
153. B. DROP FORGING
• Force for shaping the component is applied in a series of
blow by using drop hammers
• Open die or closed dies are used for this purpose
154.
155.
156. C. PRESS FORGING
• Process is similar to drop forging but for the methodof
application of force
• In this case the force is applied by a continuoussqueezing
operation by means of a hydraulic press
• Mass production technique
157.
158.
159. 3. EXTRUSION PROCESS
160
• Process of forcing a metal enclosed in a container toflow
through the opening of a die
• Metal is subjected to plasticdeformation
• Metal undergoes reduction and elongation during extrusion
• Used for manufacture rods, tubes, circular, rectangular,
hexagonal and other shapes both in hollow and solidform
160. Types of Extrusion
a) Direct Extrusion
b) Indirect Extrusion
c) Cold Extrusion/ ImpactExtrusion
161. a. Direct Extrusion
• Also called forward extrusion
• Flow of metal through the die is in the same directionas
the movement of ram
• Hot billet(work piece) is used
162.
163.
164. b. Indirect Extrusion
• Also called backward extrusion
• Flow of metal through the die is in the opposite directionas
the movement of ram
• Hot billet(work piece) is used
• Ram used is hollow
• Billet remains stationary while die is pushed into the billetby
the hollow ram
• Less force is required as compared to directextrusion
165.
166.
167.
168.
169. c. Cold/Impact Extrusion
170
• Carried out at higher velocity
• Unheated metal is placed in the die cavity
• Punch is forced into the die cavity causing the metal toflow
upwards through the gap between punch anddie
• Tooth pastes tubes are made by thisprocess
170.
171.
172. SHEET METAL FORMING
Process in which force is applied to a piece of sheet metalto
modify its geometry rather than remove any metal
174. 1. BENDING
Process in which a force is applied to a piece of sheetmetal,
causing it to bend at an angle and form the desired shape
175.
176.
177. 2. ROLL FORMING
• Process in which sheet metal is progressively shaped
through a series of bending operations
• Sheet metal is fed through a series of roll stations
• Each station has a roller, positioned on both sides of the sheet
182. 3. SPINNING
• Process used to form cylindrical parts by rotating a piece of
sheet metal while forces are applied to one side
• A sheet metal disc is rotated at high speeds while rollerspress
the sheet against a tool, called mandrel, to form the shape of
the desired part
183.
184.
185.
186. 4. DEEP DRAWING
• Process in which sheet metal is stretched into the desired
part shape
• A tool pushes downward on the sheet metal, forcingit
into a die cavity in the shape of the desiredpart
190. 5. STRETCH FORMING
• Process in which a piece of sheet metal is stretched and
bent simultaneously over a die
• Stretch forming is performed on a stretch press, in which a
piece of sheet metal is securely gripped along its edges by
gripping jaws. The gripping jaws are each attached to a
carriage that is pulled by pneumatic or hydraulic force to
stretch the sheet. The tooling used in this process is a stretch
form block, called a form die, which is a solid contouredpiece
against which the sheet metal will be pressed
191.
192. SHEET METAL CUTTING
• Sheet metal cutting is done using shearing
technique
• Shearing is a cutting operation used to removea
blank of required dimensions from a largesheet
• Here the die is stationary and the punch that
shears off the metal of the sheet
197. 1. BLANKING
• Operation of cutting a shape from a metalstrip
• Piece detached from the strip is called blank, remaining
metal strip is called scrap
• Setup consists of a punch and a blankingdie
• Clearance is provided on punch
198.
199.
200. 2. PUNCHING
• Process of producing a hole in a metal piece using a punch
and die
• Metal with hole is the required product and partremoved
is the scrap(slug)
• Clearance is provided on die
201.
202.
203.
204.
205. 3. PIERCING
• Piercing is a process by which a hole is cut or torn in ametal
• The metal is pushed back to form a jagged flange onthe
back side of the hole
• No metal removal will take place
213. 1. SOLDERING
• Method of joining two or more metal pieces by means ofa
fusible alloy or metal called solder(filler alloy), applied in
molten state
• The melting temperature of filler metal is lower than 450°C
and also lower than the melting point of the components to
be joined
214. • No direct melting of the metals beingjoined
• During the process, the filler alloy(solder) flows between
the two closely adjacent surfaces of the work pieces by
capillary action
• Solder is melted by using a soldering iron, which isheated
by electrical resistance
• Soldering iron tips are made of copper core platedwith
iron. The copper is used for heat transfer and the iron
plating is used for durability
215.
216.
217.
218. 2. BRAZING
• Metal pieces are joined by heating the closely placedparts
and then filler alloy called spelter applied in the molten
state which upon solidification produces the desiredjoint
• Melting temperature of filler metal is more than 450°C but
lower than the melting temperature of the components to
be joined
219. • No direct melting of the metals beingjoined
• Brazing gives a much stronger joint compared to soldering
• During the process, the filler alloy(spelter) flows between
the two closely adjacent surfaces of the work pieces by
capillary action
• Torch brazing is the most versatile method
(Oxygen-Acetylene)
220
224. 3. WELDING
• Process of joining similar or dissimilar metals by the
application of heat, with or without the application of
pressure and with or without the addition of fillermaterial
Two types
• Plastic welding
• Fusion welding
225. • Plastic welding: metals to be joined are to be heated tothe
plastic state and then forced together by external pressure
without the addition of filler material. Eg. forgewelding,
resistance welding…etc
• Fusion welding: no pressure is involved but a very high
temperature is produced in or near the joint. The metal at
the joint is heated to the molten state and allowed to
solidify. A filler material may be used during the welding
process. Eg. Oxy-acetylene welding, carbon arc welding…etc
227. 1. GAS WELDING
• Welding process that uses a fuel gas combined with oxygen
to produce a flame
• Fusion welding process
• It joins metals using the heat of combustion ofoxygen/air
and fuel gas(acetylene, hydrogen, propane or butane)
230. • It joins the metals using the heat of combustion of oxygen
and fuel gas(acetylene)
• Acetylene gas is mixed with oxygen in correct proportions in
the welding torch and ignited, the flame resulting at the tip
of the torch is sufficiently hot(3200⁰C) to melt and join the
metal
• Volume of gas passing through the torch is controlled bytwo
control valves provided in the torch
231. • The gases are mixed in the mixer part of the torch, before
delivering to the torch tip
• Filler metals are additional metal added to theweld
• Flux is added to remove impurities and oxides(fluxreacts
with oxides and a slag is formed) formed during welding
operation
239. 2. ARC WELDING
240
• Method of fusion welding in which the metals at the joint
is heated to molten state by an electric arc
• Arc column is generated between an anode(electrode) and
the cathode(metal to be joined)
• Temperature of the arc is about 6000⁰C to 7000⁰C
240. ELECTRODES
• Non- consumable electrodes: carbon, graphiteor
tungsten(they are not consumed during weldingoperation)
• Consumable electrodes: steel(consumed during welding
operation), electrode may be bare(uncoated) or fluxcoated
241. Arc
Welding
Metal Arc
Welding
Carbon Arc
Welding
Metal Inert
Gas Arc
Welding
Tungsten
Inert Gas
Welding
Plasma Arc
Welding
Submerged
Arc
Welding
Shielded
Metal Arc
Welding
Electro Slag
Welding
Flux Cored
Arc
Welding
243. • The heat is generated by an electric arc between base
metal and a consumable electrode.
• In this process electrode movement is manuallycontrolled
hence it is termed as manual metal arcwelding
• In shielded metal arc welding, the protection to the weld
pool is provided by covering of a) slag formed over the
surface of weld pool/metal and b) inactive gases generated
through thermal decomposition of flux/coating materials on
the electrode
244. • This process can use both AC and DC. The constantcurrent
DC power source is invariably used with all types of
electrode irrespective of base metal (ferrous and non-
ferrous)
• AC can be unsuitable for certain types of electrodes and base
materials
• SHIELDED METAL ARC WELDING welding normally uses
constant current type of power source with weldingcurrent
50-600A and voltage 20-80V
• Welding current (A) is generally selected in range of 40-60
times of electrode diameter (mm)
245.
246.
247.
248.
249. 3. RESISTANCE WELDING
250
• Parts to be joined are heated to a plastic state over a limited
area by their resistance to flow of electric current(resistance
heating) and then by mechanically pressingtogether
• Pressure is applied continuously till the weld coolsdown
• It is generally used for joining thin plates and structures
253. • Pieces are assembled and placed between electrodes and
pressure is applied
• When current passes, the pieces are heated at the contact
area, and due to the pressure, the contact spot getswelded
257. • Similar to spot welding except that the electrodes aredisc
shaped rollers
• Electrodes roll over the sheet and a continuous weldis
obtained
• Process is also called continuous spot weld process
• Timed pulses of current pass through the metal to form the
overlapping welds. Welding current is usually higher thanthe
conventional spot welding
265. • Heat obtained from the resistance to electric currentthrough
the area of contact of two surfaces
• Pressure is applied before heating is started and ismaintained
throughout the heatingperiod
• Heavy current is passed from one metal piece to other.The
resistance to electric current flow heats the faces to fusion
temperature
• Both pressure and current are applied throughout theweld
cycle
266. • When the faces of the pieces become plastic, they are
pressed together more firmly, upsetting the metal pieceto
form a dense joint
• Force is released as the welded joint has cooled to the desired
temperature
• Here one Clamp is stationary and other one ismovable
270. • Flash welding process was developed from resistance butt
welding process
• One clamp is movable and other one is stationary,clamps
hold the work pieces
• Movable work piece is moved closer to the fixed one untilthe
two come in light contact
• Welding current(high voltage) is turned ON, flashing between
the two faces are established
271. • Flashing produces higher temperature in the two facesuntil
they attain the welding temperature
• At this stage, the pressure of the moving clamp is increasedto
forge the parts together and expel the moltenmetal
• Finally welding current is cut off and the work piecesare
unclamped
272. 4. THERMO CHEMICAL WELDING PROCESS
It involves exothermic reactions
Two types: Thermit Welding and Atomic hydrogen welding
273. THERMIT WELDING
• Fusion welding process in which the required heatis
obtained by an exothermal chemical reaction
• Mixture of powdered aluminium and iron oxide is placed
inside the crusible. This mixture is ignited. The resultant
products obtained are highly purified iron and aluminium
oxide slag, which floats on top of the crusible
• Bottom plug of the cruisible is removed and the molten ironis
made to flow into the mould
274. Chemical equation for exothermic reaction is given by
8Al + 3Fe3O4 = 9Fe + 4Al2O3 +heat
275.
276.
277. POWDER METALLURGY
Powder metallurgy is the art and science of producing fine
metal powders and then making objects from individual,
mixed or alloyed metal powders
278.
279. Powder Metallurgy Process
280
1)Producing metal powders
Various methods for manufacturing powdersare
a) Atomization
b) Reduction
c) Crushing
d) Milling
e) Shotting
f) Electrolysis
281. 6)Finishing and sizing the finalproduct
• Sizing
• Coining
• Impregnation
• Infiltration
• Heat treating
• Machining
282. 1)Producing metal powders: metals are transformed into
powder form using different methods. Widely usedmetal
powders are aluminium, chromium, copper,lead…etc
2)Mixing/Blending: homogeneous mixture of metal powders
or alloy powders is prepared
Blending : Mixing powder of the same chemicalcomposition
but different sizes
Mixing : Combining powders of different chemistries
283. 3)Pressing/compacting: Pressing the powders into desired part
shape as closely as possible to final dimensions. Powders are
compacted using high pressure(100MPa to1000MPa)
4) Pre-sintering: Presintering is done before actualsintering
operation. Compact is heated for a short timeat
a temperature below sintering temperature. Presintering
removes lubricants and binders added to powders during
blending operation. After pre-sintering, the part acquires
sufficient strength to be handled and machined without
difficulty
284. 5) Sintering: Sintering is the heat treatment process, to bond
the metallic particles, thereby increasing strength and
hardness. Sintering consists of heating pressed metal
compacts in batch or continuous furnaces to atemperature
below the melting point of material. Most metals are
sintered at 70 % to 80 % of meltingtemperature
6)Finishing and sizing the final product: Used to improvethe
quality of the final part
