Transcript INDUSTRIAL MATERIALS

INDUSTRIAL MATERIALS
Instructed by:
Dr. Sajid Zaidi
PhD in Advanced Mechanics, UTC, France
MS in Advanced Mechanics, UTC, France
B.Sc. in Mechanical Engineering, UET, Lahore
B.TECH Mechanical Technology
IQRA COLLEGE OF TECHNOLOGY (ICT)
INTERNATIONAL ISLAMIC UNIVERSITY, ISLAMABAD
Classification of Ferrous Alloys
INDUSTRIAL MATERIALS
Ferrous Alloys
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Plain Carbon Steel
◦ Plain Carbon steel contains up to 2.14% of Carbon
◦ These steels may also contain other elements, such as Si
(maximum 0.6%), copper (up to 0.6%), and Mn (up to 1.65%).
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Alloy Steel
◦ Alloy steels are compositions that contain more significant levels
of alloying elements.
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Cast Iron
◦ Cast Iron contains 2.14 % to 6.70 % of Carbon.
INDUSTRIAL MATERIALS
Ferrous Alloys
Classification of Ferrous Alloys
Steel
Cast Iron
Plain Carbon Steel
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Ferrous Alloys
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Decarburized steels contain less than 0.005% C.
Ultra-low carbon steels contain a maximum of 0.03%
carbon. They also contain very low levels of other
elements such as Si and Mn.
Low-carbon steels contain 0.04 to 0.15% carbon. These
are used for making car bodies and hundreds of other
applications.
Mild steel contains 0.15 to 0.3% carbon. This steel is
used in buildings, bridges, piping, etc.
Medium-carbon steels contain 0.3 to 0.6% carbon. These
are used in making machinery, tractors, mining
equipment, etc.
High-carbon steels contain above 0.6% carbon. These
are used in making springs, railroad car wheels, etc.
Plain Carbon Steel
Steel can be defined as an Iron alloy which transforms to
Austenite on heating.
 A plain-carbon steels has no other major alloying
element beside carbon.
 When a plain-carbon steel is slowly cooled from the
Austenitic range it undergoes the eutectoid
transformation.
INDUSTRIAL MATERIALS
Ferrous Alloys
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Alloy Steel
Alloy steels are compositions that contain more significant
levels of alloying elements.
 Alloying elements are added to steels
◦ To provide solid-solution strengthening of ferrite,
◦ To cause the precipitation of alloy carbides rather than that
of Fe3C,
◦ To improve corrosion resistance and other special
characteristics of the steel, and
◦ To improve hardenability.
 The AISI defines alloy steels as steels that exceed in one or
more of these elements: ≥ 1.65% Mn, 0.6% Si, 0.6% Cu.
 The total carbon content is up to 1% and the total alloying
elements content is below 5%.
INDUSTRIAL MATERIALS
Ferrous Alloys
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Alloy Steel
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Ferrous Alloys
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A material is also an alloy steel if a definite concentration of
alloying elements, such as Ni, Cr, Mo, Ti, etc., is specified.
These steels are used for making tools (hammers, chisels,
etc.) and also in making parts such as axles, shafts, and gears.
These are used in making springs, railroad car wheels, etc.
Silicon, chromium, molybdenum, and vanadium are ferrite
stabilizing elements whereas manganese and nickel are
austenite stabilizers.
Certain specialty steels may consist of higher levels of sulfur
(>0.1%) or lead (0.15–0.35%) to provide machinability.
These, however, can not be welded easily.
Recently, researchers have developed ‘‘green steel’’ in which
lead, an environmental toxin, was replaced with tin (Sn)
and/or antimony (Sb).
Alloy Steel - Stainless Steel
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INDUSTRIAL MATERIALS
Ferrous Alloys
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Stainless steels are selected for their excellent resistance to
corrosion.
All true stainless steels contain a minimum of about 11% Cr,
which permits a thin, protective surface layer of chromium
oxide to form when the steel is exposed to oxygen.
The chromium is what makes stainless steels stainless.
Chromium is also a ferrite stabilizing element. It causes the
austenite region to shrink, while the ferrite region increases in
size.
For high-chromium, low-carbon compositions, ferrite is
present as a single phase up to the solidus temperature.
There are several categories of stainless steels based on
crystal structure and strengthening mechanism.
Cast Iron
Cast irons are iron-carbon-silicon alloys, typically containing
2.14 to 4% C and 0.5–3% Si.
 They pass through the eutectic reaction during solidification.
 In cast irons, silicon is the catalyzing agent that allows free
carbon (graphite) to appear in the microstructure by breaking
down the cementide to iron and carbon.
 Silicon, therefore, is a graphite stabilizing element.
Gray cast iron
 It contains small, interconnected graphite flakes that cause
low strength and ductility. This is the most widely used cast
iron and is named for the dull gray color of the fractured
surface.
 Higher strengths are obtained by reducing the carbon
equivalent, by alloying, or by heat treatment.
INDUSTRIAL MATERIALS
Ferrous Alloys
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Cast Iron
Gray iron has a number of attractive properties, including
high compressive strength, good machinability, good
resistance to sliding wear, good resistance to thermal fatigue,
good thermal conductivity, and good vibration damping.
White cast iron
 It is a hard, brittle alloy containing massive amounts of Fe3C.
 A fractured surface of this material appears white.
 A group of highly alloyed white irons are used for their
hardness and resistance to abrasive wear.
 Elements such as chromium, nickel, and molybdenum are
added.
Malleable cast iron
 It is formed by the heat treatment of white cast iron, produces
rounded clumps of graphite.
INDUSTRIAL MATERIALS
Ferrous Alloys
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Cast Iron
It exhibits better ductility than gray or white cast irons. It is
 also very machinable.
 It is produced by heat treating unalloyed 3% carbon
equivalent (2.5% C, 1.5% Si) white iron.
Ductile (or nodular) cast iron
 Ductile iron is produced by treating liquid iron with a carbon
equivalent of near 4.3% with magnesium.
 Compared with gray iron, ductile cast iron has excellent
strength and ductility.
 Due to the higher silicon content (typically around 2.4%) in
ductile irons compared with 1.5% Si in malleable irons, the
ductile irons are stronger but not as tough as malleable
 irons.
INDUSTRIAL MATERIALS
Ferrous Alloys
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Non-Ferrous Alloys
Nonferrous alloys (i.e., alloys of elements other than iron)
include, but are not limited to, alloys based on aluminum,
copper, nickel, cobalt, zinc, precious metals (such as Pt, Au,
Ag, Pd), and other metals (e.g., Nb, Ta, W).
INDUSTRIAL MATERIALS
Non-Ferrous Alloys
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Comparison of Steel and some non-ferrous metals
INDUSTRIAL MATERIALS
Non-Ferrous Alloys
Aluminum Alloys
General Properties and Uses of Aluminium
 Aluminum has a density of 2.70 g/cm3, or one-third the
density of steel, and a modulus of elasticity of 69 103 MPa.
 Aluminum alloys have lower tensile properties compared
with those of steel, their specific strength (or strength-toweight ratio) is excellent.
 Aluminum can be formed easily, it has high thermal and
electrical conductivity, and does not show a ductile-to-brittle
transition at low temperatures.
 It is nontoxic and can be recycled easily.
 Aluminum’s beneficial physical properties include
nonmagnetic behavior and its resistance to oxidation and
corrosion.
 Aluminum does not display a true endurance limit, so failure
by fatigue eventually may occur, even at low stresses.
INDUSTRIAL MATERIALS
Non-Ferrous Alloys
Aluminum Alloys
General Properties and Uses of Aluminium
 Because of its low-melting temperature, aluminum does not
perform well at elevated temperatures.
 Finally, aluminum alloys have low hardness, leading to poor
wear resistance.
 Aluminum responds readily to strengthening mechanisms.
INDUSTRIAL MATERIALS
Non-Ferrous Alloys
Aluminum Alloys
General Properties and Uses of Aluminium
 About 25% of the aluminum produced today is used in the
transportation industry, another 25% is used for the
manufacture of beverage cans and other packaging, about
15% is used in construction, 15% in electrical applications,
and 20% in other applications.
 About 200 pounds of aluminum was used in an average car
made in the United States in 1996.
 Aluminum reacts with oxygen, even at room temperature, to
produce an extremely thin aluminum-oxide layer that protects
the underlying metal from many corrosive environments.
Aluminum Alloys
Aluminum alloys can be divided into two major groups:
wrought and casting alloys, depending on their method of
fabrication.
 Wrought alloys, which are shaped by plastic deformation,
have compositions and microstructures significantly different
from casting alloys.
 Within each major group we can divide the alloys into two
subgroups: heat treatable and non-heat treatable alloys.
 Casting Alloys contain enough silicon to cause the eutectic
reaction, giving the alloys low melting points, good fluidity,
and good castability. Fluidity is the ability of the liquid metal
to flow through a mold without prematurely solidifying, and
castability refers to the ease with which a good casting can be
made from the alloy.
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Non-Ferrous Alloys
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Non-Ferrous Alloys
Aluminum Alloys
Copper Alloys
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Non-Ferrous Alloys
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Copper occurs in nature as sulfides and also as elemental
copper.
Copper was extracted successfully from rock long before
iron, since the relatively lower temperatures required for
copper extraction could be achieved more easily.
Copper is typically produced by a pyro-metallurgical (hightemperature) process.
The copper ore containing high-sulfur contents is
concentrated, then converted into a molten immiscible liquid
containing copper sulfide-iron sulfide and is known as a
copper matte. This is done in a flash smelter.
In a separate reactor, known as a copper converter, oxygen
introduced to the matte converts the iron sulfide to iron oxide
and the copper sulfide to an impure copper called blister
copper, which is then purified electrolytically.
Copper Alloys
INDUSTRIAL MATERIALS
Non-Ferrous Alloys
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Copper-based alloys have higher densities than that for steels.
Although the yield strength of some alloys is high, their
specific strength is typically less than that of aluminum or
magnesium alloys.
These alloys have better resistance to fatigue, creep, and wear
than the lightweight aluminum and magnesium alloys.
Many of these alloys have excellent ductility, corrosion
resistance, electrical and thermal conductivity, and most can
easily be joined or fabricated into useful shapes.
Applications for copper-based alloys include electrical
components (such as wire), pumps, valves, and plumbing
parts, where these properties are used to advantage.
Copper alloys are also unusual in that they may be selected to
produce an appropriate decorative color. Pure copper is red;
zinc additions produce a yellow color, and nickel produces a
silver color.
Copper Alloys
INDUSTRIAL MATERIALS
Non-Ferrous Alloys
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Copper containing less than 0.1% impurities is used for
electrical and microelectronics applications. Small amounts
of cadmium, silver, and Al2O3 improve their hardness without
significantly impairing conductivity.