4

4

m

4

m

4

m

4

m

4mm

6

m

6mm

2

2

Translations are restricted to only certain values to get symmetry (periodicity)

Each block is represented by a point

This array of points is a LATTICE

a

a

vector S = an integer x basis translation t

a

a

S

t t

vector S = an integer x basis translation t

t cos a = S/2 = mt/2

m cos a a axis

2 1 0 2 π 1

1 1/2 π/3 5π/3 6

0 0 π/2 3π/2 4

-1 -1/2 2π/3 4π/3 3

-2 -1 - π π 2

a

a

S

t t

m cos a a axis

2 1 0 π 1

1 1/2 π/3 5π/3 6

0 0 π/2 3π/2 4

-1 -1/2 2π/3 4π/3 3

-2 -1 - π - π 2

Only rotation axes consistent with lattice periodicity in 2-D or 3-D

We abstracted points from the shape:

We abstracted points from the shape:

Now we abstract further:

Now we abstract further:

This is a UNIT CELL

Now we abstract further:

This is a UNIT CELL

Represented by two lengths and an angle …….or, alternatively, by two vectors

T = t a + t b a b

a and b are the basis vectors for the lattice

a

b

T

a

b

a, b, and c are the basis vectors for the lattice

c

T = t a + t b + t c a b

a

b

T

a, b, and c are the basis vectors for the lattice

c

c

a

b

c

g

b

a

Lattice parameters:

The many thousands of lattices classified into

crystal systems

System Interaxial Axes Angles Triclinic a ≠ b ≠ g ≠ 90° a ≠ b ≠ c Monoclinic a = g = 90° ≠ b a ≠ b ≠ c Orthorhombic a = b = g = 90° a ≠ b ≠ c Tetragonal a = b = g = 90° a = b ≠ c Cubic a = b = g = 90° a = b = c Hexagonal a = b = 90°, g = 120° a = b ≠ c Trigonal a = b = 90°, g = 120° a = b ≠ c

The many thousands of lattices classified into

crystal systems

System Minimum symmetry Triclinic 1 or 1 Monoclinic 2 or 2 Orthorhombic three 2s or 2s Tetragonal 4 or 4 Cubic four 3s or 3s Hexagonal 6 or 6 Trigonal 3 or 3

Within each crystal system, different types of centering consistent with symmetry

System Allowed centering Triclinic P (primitive) Monoclinic P, I (innerzentiert) Orthorhombic P, I, F (flächenzentiert), A (end centered) Tetragonal P, I Cubic P, I, F Hexagonal P Trigonal P, R (rhombohedral centered) The 14 Bravais lattices

For given lattice, infinite number of unit cells possible:

When choosing unit cell, pick: Simplest, smallest Right angles, if possible Cell shape consistent with symmetry

© Boardworks Ltd 2006 54 of 49

How many different uses of metal can you spot?

Metals are a highly valuable group of materials, used for hundreds of products and produced in huge quantities.

35,500,000 tons of aluminium were produced in 2005.

The production of copper increased by more than

20 times in the 20th century.

Gold is worth more than £10,000 per kilogram.

Metals have played a vital role in human development. Periods of civilization are even classified by the metals that were used during those times, such as the Iron Age.

It is easy to find products made from metals, but there are other uses of metals that are less obvious.

Compounds containing metals have many uses. For example, metal compounds are used to colour materials including stained glass and even make-up!

Metals are used as catalysts to speed up reactions. Nickel is used as a catalyst to make margarine. Platinum is used in catalytic converters in car exhausts to clean up fumes and reduce pollution.

Can you find any other uses of metals?

It is not only the properties of a metal that determines its use.

What other factors might determine how metals are used?

For example, aluminium only became a commonly used metal in the late 19th century as better extraction methods made it cheaper.

For example, silver is a better conductor than copper but it is too expensive to be used for electric wires.

Cost. A metal may have the best properties for a job but it might be too expensive.

Extraction method. This can greatly affect the price and availability of a metal.

What are the properties of different metals?

What are the general properties of most metals?

solid at room temperature

Why do metals have these particular properties?

high melting point

good conductors of electricity and heat

malleable: they can be shaped

ductile: they can be drawn into wires

strong

dense

sea of electrons

metal ions

The atoms in a pure metal are in tightly-packed layers, which form a regular lattice structure.

The outer electrons of the metal atoms separate from the atoms and create a ‘sea of electrons’.

These electrons are delocalized and so are free to move through the whole structure.

The metal atoms become positively charged ions and are attracted to the sea of electrons. This attraction is called metallic bonding.

How does the sea of electrons affect the properties of metals?

Metals often have high melting points and boiling points. Gold, for example, has a melting point of 1064 °C and a boiling point of 2807 °C.

The properties of metals are related to their structure.

In metal extraction and other industrial processes, furnaces often run continuously to maintain the high temperatures needed to work with molten metals.

This property is due to the strong attraction between the positively-charged metal ions and the sea of electrons.

Delocalized electrons in metallic bonding allow metals to conduct heat and electricity.

This makes heat transfer in metals very efficient.

Delocalized electrons also conduct electricity through metals in a similar way.

For example, when a metal is heated, the delocalized electrons gain kinetic energy.

These electrons then move faster and so transfer the gained energy throughout the metal.

heat

Metals are usually strong, not brittle. When a metal is hit, the layers of metal ions are able to slide over each other, and so the structure does not shatter.

The metallic bonds do not break because the delocalized electrons are free to move throughout the structure.

metal after it is hit

force force

This also explains why metals are malleable (easy to shape) and ductile (can be drawn into wires).

metal before it is hit

Corrosion is the gradual destruction of a metal due to reactions with other chemicals in its environment.

Over time, corrosion changes the appearance of the metal as it breaks down and it becomes weaker.

Coating the surface of a metal with paint and certain chemicals can protect it from corrosion.

What happens if the protective coating becomes damaged?

Corrosion can seriously damage metallic objects and structures.

Metals behave differently when exposed to the environment.

Items made from gold can survive for thousands of years and have even been found in good condition underwater.

In many cultures, gold is considered a precious metal and is used to make sacred and decorative objects.

Gold is an unreactive metal and does not corrode easily.

In general, objects made from metals that corrode easily do not survive for as long.

coating of oxygen atoms

The outer aluminium atoms react with oxygen in the atmosphere. This forms a thin layer of aluminium oxide on the metal’s surface, which protects the metal from corrosion.

Aluminium is a very reactive metal. However, it does not corrode in the presence of oxygen. Why is this?

oxygen in the atmosphere

aluminium atoms

Salt can increase the rate of rusting. This iron bolt is on a seaside structure and is nearly completely corroded.

Rusting is the specific name given to the corrosion of iron. It is a chemical reaction between iron, oxygen and water.

What is the word equation for the formation of rust?

What is rusting?

The chemical name for rust is hydrated iron oxide. Rust can form on cars and buildings, making them unsafe. It is an expensive problem.

hydrated iron oxide water + + iron oxygen

Are some metals easier to find than others?

Most metals are actually found combined with other elements, as compounds in ores. These metals must be extracted from their ores before they can be made useful.

Metals can be found in the Earth’s crust combined with other elements or uncombined as pure substances.

Metals that are found in a pure form are said to occur ‘native’.

Highly reactive metals, such as titanium, require complicated

extraction. This can increase the cost of the pure metal.

Some unreactive metals, like gold, silver and copper, can be found uncombined as elements.

potassium

sodium

calcium

magnesium

aluminium

zinc

iron

copper

gold

incr

easi

ng

react

ivit

y

Metals above carbon in the reactivity series must be extracted using electrolysis. Electrolysis can also be used to purify copper.

Metals below carbon can be extracted from their ores by reduction using carbon, coke or charcoal.

Platinum, gold, silver and copper can occur native and do not need to be extracted.

lead

silver

The reactivity of a metal determines how it is extracted.

(carbon)

(hydrogen)

platinum

Metals that are less reactive than carbon can be extracted from their ores by burning with carbon.

Iron is extracted by this method in a blast furnace. The iron ore is heated with carbon-rich coke at very high temperatures.

The iron collected from a blast furnace is only 96% pure.

How is carbon used to extract metals?

molten iron

hot air

molten slag

raw materials

Usually, this product will be treated further because the impurities make iron brittle.

Metals that are more reactive than carbon are extracted using electrolysis.

This process uses an electrical current to extract the metal.

Electrolysis is more expensive than using a blast furnace, and this increases the price of the metal.

Electrolysis is also used to further purify metals, such as copper, after extraction with carbon.

Aluminium is extracted from its ore, bauxite, using this method.

Metals are easy to recycle and do not change their properties.

What are the benefits of recycling metals?

Saves energy Recycling aluminium uses 95% less energy than extracting it from its ores.

Uses fewer resources

Reduces waste

Less damage to environment

Profitable

Recycling reduces the need to mine sensitive areas for new ores.

Recycling one car saves over 1,000 kg of iron ore and over 600 kg of coal.

14 million fewer dustbins would be filled per year by recycling aluminium in the UK.

Recycled copper can be resold for up to 90% of what it was worth when new.

Recycled copper is too impure for electric wires. However, scrap copper can be used in products that do not need pure metal, such as coins and ornaments.

Metallic materials are often mixtures of different metals. Pure metals can be obtained by purifying recycled materials but this can be expensive and may use more electricity than extracting metals from ores.

Sorting mixed metals for recycling can be difficult. Iron and steel (a mixture of iron and other elements) are exceptions. These materials can be separated from waste

using a magnet.

An alloy is a mixture of a metal with at least one other element.

The final alloy may have very different properties to the original metal.

By changing the amount of each element in an alloy, material scientists can custom-make alloys to fit a given job.

Steel is a common example of an alloy. It contains iron mixed with carbon and other elements. Adding other elements to a metal changes its structure and so changes its properties.

Alloys have been used for thousands of years. Bronze, an alloy of copper and tin, was commonly used by civilizations before iron extraction methods were developed.

brass: an alloy of copper and zinc. It does not tarnish and is used for door knobs, buttons

and musical instruments.

solder: an alloy of zinc and lead. It is used in electronics to attach components to circuit boards.

amalgam: an alloy of mercury and silver or tin. It is used for dental fillings because it can be shaped when warm

and resists corrosion.

Other well-known alloys include:

Although pure gold is sometimes used in electronics, gold jewellery is always a mixture of gold and other metals.

Pure gold is actually quite soft. Adding small amounts of other metals makes the gold hard enough to use in jewellery. Alloying gold with different metals also affects its colour.

The familiar yellow gold is an alloy of gold with copper and silver. Adding more copper than silver gives redder shades.

White gold is an alloy of gold with nickel, platinum or palladium. Around 12% of people may be allergic to the nickel in white gold.

When it is a copper-coated alloy!

Since 1992, UK copper coins have been made from copper-plated steel and are magnetic. A magnet can be used to separate copper coins by age.

Copper coins used to be made from pure copper but most ‘copper’ coins used around the world are now made from copper alloys.

Previously, as the value of copper increased, the metal used to make the coin became worth more than the actual coins. A melted-down, pure copper coin could have been sold for more than the face value of the coin!

Steel is an alloy of iron and other elements, including carbon, nickel and chromium.

Steel is stronger than pure iron and can be used for everything from sauce pans… …to suspension bridges!

The atoms of other elements are different sizes. When other elements are added to iron, their atoms distort the regular structure of the iron atoms.

The atoms in pure iron are arranged in densely-packed layers. These layers can slide over each other. This makes pure iron a very soft material.

It is more difficult for the layers of iron atoms in steel to slide over each other and so this alloy is stronger than pure iron.

Steel can contain up to 2% carbon.

low carbon steel contains less than 0.25% carbon

high carbon steel contains more than 0.5% carbon.

Two other important types of steel are:

stainless steel – an alloy of iron that contains at least 11% chromium and smaller amounts of nickel and carbon

titanium steel – an alloy of iron and titanium.

Varying the amount of carbon gives steel different properties. For example, a higher carbon content makes a hard steel.

Different types of steel are classified by how much carbon they contain.

We have noted that how TTT and CCT diagrams can help us design heat treatments to

design the microstructure of steels and hence engineer the properties. In some cases a

gradation in properties may be desired (usually from the surface to the interior- a hard

surface with a ductile/tough interior/bulk).

In general three kinds of treatments are: (i) Thermal (heat treatment), (ii) Mechanical

(working), (iii) Chemical (alteration of composition). A combination of these treatments are

also possible (e.g. thermo-mechanical treatments, thermo-chemical treatments).

The treatment may affect the whole sample or only the surface.

A typical industrial treatment cycle may be complicated with many steps (i.e. a combination

of the simple steps which are outlined in the chapter).

Heat Treatment of Steels

Thermal (heat treatment)

Chemical

Treatments Mechanical Or a combination

(Thermo-mechanical,

thermo-chemical)

Bulk

Surface

Click here to revise the basics required for this topic: Phase_Transformations

E.g. heat and quench

E.g. shot peening

E.g. case carburizing

HEAT TREATMENT

BULK SURFACE

ANNEALING

Full Annealing

Recrystallization Annealing

Stress Relief Annealing

Spheroidization Annealing

AUSTEMPERING

THERMAL THERMO-

CHEMICAL

Flame

Induction

LASER

Electron Beam

Carburizing

Nitriding

Carbo-nitriding

NORMALIZING HARDENING

&

TEMPERING

MARTEMPERING

An overview of important heat treatments

A broad classification of heat treatments possible are given below. Many more specialized

treatments or combinations of these are possible.

A1

A3

Acm

T

Wt% C

0.8 %

723C

910C

Spheroidization

Recrystallization Annealing

Stress Relief Annealing

Full Annealing

Ranges of temperature where Annealing, Normalizing and Spheroidization treatment are

carried out for hypo- and hyper-eutectoid steels.

Details are in the coming slides.

Full Annealing

The purpose of this heat treatment is to obtain a material with high ductility. A microstructure

with coarse pearlite (i.e. pearlite having high interlamellar spacing) is endowed with such

properties.

The range of temperatures used is given in the figure below.

The steel is heated above A3 (for hypo-eutectoid steels) & A1 (for hyper-eutectoid steels) → (hold) → then the

steel is furnace cooled to obtain Coarse Pearlite.

Coarse Pearlite has low (↓) Hardness but high (↑) Ductility.

For hyper-eutectoid steels the heating is not done above Acm to avoid a continuous network of

proeutectoid cementite along prior Austenite grain boundaries (presence of cementite along grain boundaries

provides easy path for crack propagation).

A1

A3

Acm

T

Wt% C

0.8 %

723C

910C

Full Annealing

Full Annealing

Recrystallization Annealing

Heat below A1 → Sufficient time → Recrystallization

A1

A3

Acm

T

Wt% C

0.8 %

723C

910C

Recrystallization Annealing

During any cold working operation (say cold rolling), the material becomes harder (due to

work hardening), but loses its ductility. This implies that to continue deformation the material

needs to be recrystallized (wherein strain free grains replace the ‘cold worked grains’).

Hence, recrystallization annealing is used as an intermediate step in (cold) deformation

processing.

To achieve this the sample is heated below A1 and held there for sufficient time for

recrystallization to be completed.

Stress Relief Annealing

Annihilation of dislocations, polygonization

Welding

Differential cooling

Machining and cold working

Martensite formation

Residual stresses → Heat below A1 → Recovery

A1

T

Wt% C

0.8 %

723C

910C

Stress Relief Annealing

Due to various processes like quenching (differential cooling of surface and interior),

machining, phase transformations (like martensitic transformation), welding, etc. the residual

stresses develop in the sample. Residual stress can lead to undesirable effects like warpage of

the component.

The annealing is carried out just below A1 , wherein ‘recovery*’ processes are active

(Annihilation of dislocations, polygonization).

* It is to be noted that ‘recovery’ is a technical term.

Spheroidization Annealing

A1

A3

Acm

T

Wt% C

0.8 %

723C

910C

Spheroidization

This is a very specific heat treatment given to high carbon steel requiring extensive

machining prior to final hardening & tempering. The main purpose of the treatment is to

increase the ductility of the sample.

Like stress relief annealing the treatment is done just below A1.

Long time heating leads cementite plates to form cementite spheroids. The driving force for

this (microstructural) transformation is the reduction in interfacial energy.

NORMALIZING

Refine grain structure prior to hardening

To harden the steel slightly

To reduce segregation in casting or forgings

Purposes

The sample is heat above A3 | Acm to complete Austenization. The sample is then air cooled to

obtain Fine pearlite. Fine pearlite has a reasonably good hardness and ductility.

In hypo-eutectoid steels normalizing is done 50C above the annealing temperature.

In hyper-eutectoid steels normalizing done above Acm → due to faster cooling cementite does

not form a continuous film along GB.

The list of uses of normalizing are listed below.

A1

A3

Acm

T

Wt% C

0.8 %

723C

910C

Normali

zatio

n

Normalization

HARDENING

Heat above A3 | Acm → Austenization → Quench (higher than critical cooling rate)

The sample is heated above A3 | Acm to cause Austenization. The sample is then quenched at a

cooling rate higher than the critical cooling rate (i.e. to avoid the nose of the CCT diagram).

The quenching process produces residual strains (thermal, phase transformation).

The transformation to Martensite is usually not complete and the sample will have some

retained Austenite.

The Martensite produced is hard and brittle and tempering operation usually follows

hardening. This gives a good combination of strength and toughness.

A1

A3

Acm

T

Wt% C

0.8 %

723C

910C

Full Annealing

Harden

ingHardening

Severity of quench values of some typical quenching conditions

Process Variable H

Air No agitation 0.02

Oil quench No agitation 0.2

" Slight agitation 0.35

" Good agitation 0.5

" Vigorous agitation 0.7

Water quench No agitation 1.0

" Vigorous agitation 1.5

Brine quench

(saturated Salt water) No agitation 2.0

" Vigorous agitation 5.0

Ideal quench

Note that apart from the nature of the

quenching medium, the vigorousness of the

shake determines the severity of the quench.

When a hot solid is put into a liquid

medium, gas bubbles form on the surface of

the solid (interface with medium). As gas

has a poor conductivity the quenching rate is

reduced. Providing agitation (shaking the

solid in the liquid) helps in bringing the

liquid medium in direct contact with the

solid; thus improving the heat transfer (and

the cooling rate). The H value/index

compares the relative ability of various

media (gases and liquids) to cool a hot solid.

Ideal quench is a conceptual idea with a heat

transfer factor of ( H = ).

1[ ]f

H mK

Severity of Quench as indicated by the heat transfer equivalent H

f → heat transfer factor

K → Thermal conductivity

Before we proceed further we note that we have a variety of quenching media at our

disposal, with varying degrees of cooling effect. The severity of quench is indicated by the

‘H’ factor (defined below), with an ideal quench having a H-value of .

Incr

easi

ng s

ever

ity o

f q

uen

ch

Through hardening of the sample

Schematic showing variation in cooling rate from surface

to interior leading to different microstructures

The surface of is affected by the quenching medium and experiences the best possible

cooling rate. The interior of the sample is cooled by conduction through the (hot) sample and

hence experiences a lower cooling rate. This implies that different parts of the same sample

follow different cooling curves on a CCT diagram and give rise to different microstructures.

This gives to a varying hardness from centre to circumference. Critical diameter (dc) is that

diameter, which can be through hardened (i.e. we obtain 50% Martensite and 50% pearlite at

the centre of the sample).

Typical hardness test survey made along a

diameter of a quenched cylinder

Jominy hardenability test Variation of hardness along a Jominy bar

(schematic for eutectoid steel)

Schematic of Jominy End Quench Test

Q & A How to increase hardenability?

Hardenability should not be confused with the ability to obtain high hardness. A material

with low hardenability may have a higher surface hardness compared to another sample

with higher hardenability.

A material with a high hardenability can be cooled relatively slowly to produce 50%

martensite (& 50% pearlite). A material with a high hardenability has the ‘nose’ of the CCT

curve ‘far’ to the right (i.e. at higher times). Such a material can be through hardened easily.

TTT diagram of low alloy steel (0.42%

C, 0.78% Mn, 1.79% Ni, 0.80% Cr,

0.33% Mo)

U.S.S. Carilloy Steels, United States

Steel Corporation, Pittsburgh, 1948)

Hardenability of plain carbon steel can increased by

alloying with most elements (it is to be noted that this is

an added advantage as alloying is usually done to

improve other properties).

However, alloying gives two separate ‘C-curves’ for

Pearlitic and Bainitic transformations (e.g. figure to the

right).

This implies that the ‘nose’ of the Bainitic

transformation has to be avoided to get complete

Martensite on quenching.

Tempering

A sample with martensitic microstructure is hard but brittle. Hence after quenching the

sample (or component) is tempered. Maternsite being a metastable phase decomposes to

ferrite and cementite on heating (providing thermal activation).

Tempering is carried out just below the eutectoid temperature (heat → wait→ slow cool).

In reality the microstructural changes which take place during tempering are very complex.

The time temperature cycle for tempering is chosen so as to optimize strength and

toughness. E.g. tool steel has a as quenched hardness of Rc65, which is tempered to get a

hardness of Rc45-55.

Cementite

ORF

Ferrite

BCC

Martensite

BCTTemper

)( Ce)( )( ' 3

aa

Austenite

Pearlite

Pearlite + Bainite

Bainite

Martensite 100

200

300

400

600

500

800

723

0.1 1 10 102 103 104 105

Eutectoid temperature

Ms

Mf

t (s) →

T

→

a + Fe3C

MARTEMPERING & AUSTEMPERING

These processes have been developed to avoid residual stresses generated during quenching.

In both these processes Austenized steel is quenched above Ms (say to a temperature T1) for

homogenization of temperature across the sample.

In Martempering the steel is then quenched and the entire sample transforms simultaneously

to martensite. This is followed by tempering.

In Austempering instead of quenching the sample, it is held at T1 for it to transform to

bainite.

Martempering

Austempering

T1

Plastic are easily formed materials.

The advantage to the manufacturer is that plastic products can be mass-produced and require less skilled staff.

Plastics require little or no finishing, painting, polishing etc. Plastic is referred to as a self-finishing material. Particular finishes can be achieved at relatively low cost.

Plastics can be easily printed, decorated or painted.

Plastics are corrosion resistant, and generally waterproof although certain types of plastics such as UPVC can become brittle and it is possible for the sun’s rays to cause the colour of the plastic to fade. It becomes bleached.

Plastics are lighter than metals, giving deeper sections for a given weight, and hence stronger sections.

The main source of synthetic plastics is crude oil.

Coal and natural gas are also used.

Petrol, paraffin, lubricating oils and high petroleum gases are bi-products, produced during the refining of crude oil.

These gases are broken down into monomers. Monomers are chemical substances consisting of a single molecule.

A process called Polymerisation occurs when thousands of monomers are linked together. The compounds formed as called polymers.

Combining the element carbon with one or more other elements such as oxygen, hydrogen, chlorine, fluorine and nitrogen makes most polymers.

Natural ‘plastic products’ occur in such things as animals’ horns, animals’ milk, insects, plants and trees.

Animals horns - Casein (glue)

Animals milk - Formaldehyde (glue)

Insects - Shellac (French polishing)

Plants - Cellulose (table tennis balls), Cellulose acetate (cloth, photographic film, handles), Cellophane (wrapping), Bitumen (roads, flat roofs)

Trees - Latex (rubber)

There are a wide range of thermoplastics, some that are rigid and some that are extremely flexible.

The molecules of thermoplastics are in lines or long chains with very few entanglements. When heat is applied the molecules move apart, which increases the distance between them, causing them to become untangled. This allows them to become soft when heated so that they can be bent into all sorts of shapes.

When they are left to cool the chains of molecules cool, take their former position and the plastic becomes stiff and hard again. The process of heating, shaping, reheating and reforming can be repeated many times.

Long chain molecules

Each time a thermoplastic is reheated it will try and return to its original shape, unless it has been damaged due to overheating or overstretching. This property is called plastic memory. This is why a shape formed in thermoplastic becomes flat when reheated.

The molecules of thermosetting plastics are heavily cross-linked. They form a rigid molecular structure.

The molecules in thermoplastics

sit end-to-end and side-by-side. Although they soften when

heated the first time, which allows them to be shaped they become permanently stiff and solid and cannot be reshaped.

Thermoplastics remain rigid

and non-flexible even at high temperatures. Polyester resin and urea formaldehyde are examples of thermosetting plastics.

Cross-linked molecules

This is used for disposable food packaging, disposable cups, heat insulation and protective packaging for electrical equipment.

Image: Protective

packaging

It was first used to make aircraft canopies. It is ten times more impact resistant than glass.

Image: Perspex top of a container

Polystyrene is used to make plates, cutlery and model kits.

It is stiff hard and comes in a wide range of colours.

Image: cup and saucer

Nylon is hard, tough, self-lubricating, has a high melting point and has very good resistance to wear and tear.

It has been used to make clothing, bearings and propellers.

Image: A nylon castor (wheel).

The rigid type is used to make pipes, guttering and roofing. It is very lightweight and is resistant to acids and alkalis.

The plasticised type is used for suitcases, hosepipes, electrical wiring and floor coverings.

Image: plumbing U-bend

High-density polythene has been used to manufacture milk crates, bottles, buckets, bowl and gear wheels.

It is stiff, hard, can be sterilised and is dense.

INTRODUCTION Advancements made in engineering materials technology have resulted in a situation where metallic materials are no longer the only choice available for various applications. Over the last 30 years, plastics have been rapidly developed to the point where they have already started replacing many traditional materials in Automobile industry. Engineering Plastics and PP becomes a choice by virtue of its superior versatility and cost economics. Polymer scientists/ Chemists are building giant molecules in a dazzling array of plastics as substitutes for metals. Though only a few years ago selection of so called “ Engineering Plastics” was a simple and crude choice, today there is an almost inexhaustible list of different thermoplastics available and Polypropylene is leading the way by virtue of its versatility in different applications.

WHY PLASTICS ? Plastics are not simply replacement materials, whereas it is based on technical merits, cost and other benefits makes plastics suitable due to the following: ECONOMY WEIGHT REDUCTION STYING – ASTHETICS FUNCTIONAL DESIGN PROPERTIES REDUCED MAINTENANCE CORROSION AND CHEMICAL RESISTANCE

11.5 Mil. MT 9%

124 Mil. MT 91%

Demand of Thermoplastics

High Performance Plastics <0, 1%

Engineering Plastics

Standard Products

Market 2002 Mil. MT LCP, PEEK, PEI, PES, PSU < 0.1

ABS, ASA, SAN 5.8 PA 2 PC 2 POM 0.7 PBT/PET 0.7 PPO 0.3

PE 55.5 PP 30.6 PVC 27.6 PS 10.7

PLASTICS CONSUMPTION IN A CAR - ABOUT 162 Kg

11.6% of Total Weight of the car

TYPE OF PLASTICS Kg

Polypropylene (PP) 29

Polyurathane (PUR) 34

Polyvinyl Chloride (PVC) 5

Acrylonitrile – butadiene-

styrene (ABS)

6

PP+ EPDM 18

Polyamides (PA, Nylon) 22

Polyethelene 12

TYPE OF PLASTICS Kg

Polycarbonate (PC) 10

ABS + PC 10

Polyformaldehyde (POM, acetal) 2

Polymethyl methacrylate

(PMMA)

2

Thermoplastics Polyesters (PET

and PBT)

2

Others 10

TOTAL 162

Engineering Plastics

FR System

Thermal Properties

Processing

Various e.g. Pigmentability

Price

Toxicology/ Safety in Use

Electrical Properties

Mechanical Properties

Factors for Material Choice

PLASTICS IN AUTOMOBILES

INTERIOR SYSTEMS

Cockpit Systems

Door Systems

Interiors Hard Trims

Overhead Systems

PLASTICS IN AUTOMOBILES

EXTERIOR SYSTEMS

Bumper Systems (Lately integrated into Front-end systems)

Body side claddings and cowl grills

Spoilers, capping and exterior trims

Body panels (Moving from sheet metal to plastics)

PLASTICS IN AUTOMOBILES UNDER THE BONNET SYSTEMS Fuel Systems – Fuel Delivery, Fuel Tanks Air/ Water induction System – engine cooling and climate

control systems OTHER SYSTEMS Safety related parts – impact zones Electrical & Electronics Lighting Systems Power train & chasis systems – steering, pedal & braking system Soft Trim Systems – Headliners, acoustics & carpets

ADVANTAGES

More complex assemblies can be easily produced as one unit

Improved performance by reduction of vibration and noise

Improved Impact Resistance

Improved power to weight ratio

Improved aesthetics

Reduced Maintenance

No corrosion

Speedo meter Housing PP Talc Filled

Door Trim PP Talc Filled

Reflector Housing

PP Talc Filled

Hyundai Car Bumper

PP Talc Filled

Seat Components

PP Unfilled

Wheel Chair Base

PP Unfilled

Mixie Body

PP Unfilled

Switch Frame ABS

Instrument Holder Ford

ABS

Engine Manifold – Nylon 6 GF 30

Toyota Tray – Nylon 6 GF 25

Honda Tray – Nylon 6 GF 45

Radiator Fan Nylon 6 GF 30

Fuel Sub Tank Nylon 66 GF 30

Timing Chain Cover & Engine Oil Filter

Nylon 66 GF 30

Glove Rail Nylon 66 GF 45

Seat Belt Anchor Nylon 6

Lever Combination Switch

Nylon 6 GF 30

Relay Box Nylon 6 Alloy

Wire Harness Connector

PBT

ECU Case PBT GF 30

Switch Base PBT GF 40%

Actuator Case PBT GF 30%

Air Conditioner Fin

PBT GF 45% Mirror Housing

PBT GF 30 Alloy

Alternator Parts PPS GF/ MD 30

Power Module PPS GF/ MD 50

Neutral Start Switch PPS GF 40 Alloy

Engine Mounting parts

PPS GF 40

Lamp Reflector PPS GF/ MD 60

Lamp Socket PPS 40