Transcript Document 7128436

1
Metals-Ferrous and Non Ferrous
By
Engr. Prof. Dr. Attaullah Shah
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Ferrous
Metals.
Ferrous is an adjective used to indicate the presence of iron.
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The word is derived from the Latin word ferrum "iron").
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Ferrous metals include steel and pig iron (with a carbon content
of a few percent) and alloys of iron with other metals (such as
stainless steel).
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The term non-ferrous is used to indicate metals other than iron
and alloys that do not contain an appreciable amount of iron
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All forms of iron and steel / manufactured to meet wide variety of
specification
Chemical composition & internal structure is highly controlled
during manufacturing.
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Good strength and hard. Fabricated in shops to desired size &
shape
Good quality control during manufacturing
Brief History:
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Iron age (12th century BC) (mostly wrought iron) – weapons made
with inefficient smelting methods. The best weapons? When iron
combined with carbon!
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Became more common after more efficient production methods
were devised in the 17th century.
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With invention of the Bessemer process in the mid-19th century,
steel became a relatively inexpensive mass-produced good
IRON
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Basic constituent of steel.
Most abundant metallic in the earth’s crust after aluminum
Found in the form of ores as oxides, carbonates, silicates
& sulfides
Produced in blast furnaces.
It can be produced into 3 commercial
forms that is:
a) wrought iron
b) steel
c) cast iron
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Increase in the amount of carbon decreases
the melting point of the metal.
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Carbon exerts the most significant effects
on the microstructure and properties of iron
products.
Iron Ores
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Iron ores are rocks and minerals from which
metallic iron can be economically extracted.
The ores are usually rich in iron oxides and
vary in color from dark grey, bright yellow, deep
purple, to rusty red.
The iron itself is usually found in the form of
magnetite (Fe3O4), hematite (Fe2O3), goethite
(FeO(OH)), limonite (FeO(OH).n(H2O)) or
siderite (FeCO3).
Hematite is also known as "natural ore", a
name which refers to the early years of mining,
when certain hematite ores containing up to
66% iron could be fed directly into iron-making
blast furnaces.
Iron ore is the raw material used to make pig
iron, which is one of the main raw materials to
make steel.
98% of the mined iron ore is used to make
steel. Indeed, it has been argued that iron ore
is "more integral to the global economy than
any other commodity, except perhaps oil.
Pig Iron
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Pig iron is the intermediate product of smelting iron ore with a
high-carbon fuel such as coke, usually with limestone as a
flux. Charcoal and anthracite have also been used as fuel.
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Pig iron has a very high carbon content, typically 3.5–4.5%,
which makes it very brittle and not useful directly as a material
except for limited applications.
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The Chinese were making pig iron by the later Zhou Dynasty
(1122–256 BC).
An ingot is a material, usually metal,
that is cast into a shape suitable for further
processing.
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WROUGHT IRON
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Manufactured by melting & refining iron to a high degree
of purity.
Then, molten metal is poured into a ladle and
mixed with hot slag.
The fluxing action of the slag causes a spongy mass to
form which is processed by rolling & pressing.
It is only iron-bearing material containing slag.
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It’s a low carbon steel (less than 0.1% carbon by
weight) containing a small amount of slag,
usually less than 3%.
It contains small amount of manganese (less than 0.1%) and
silicon (0.2%).
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It’s ductility is lower than steel.
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It’s tensile strength is lower.
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It can be molded easily and has good resistance to corrosion.
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It is used to make pipes, corrugated sheets, grills,
bars, chains and other products.
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It can be cold worked, forged and welded like steel.
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Forging is working a metal to predetermined shape by one
or more processes such as hammering, pressing and
rolling at a temperature above the re-crystallization
temperature.
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Cold working is the process of working at a temperature
that doesn’t alter the structural changes caused by the
work or that is below the re-crystallization temperature.
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Wrought iron is used extensively where corrosion
resistance is needed.
Wrought Iron Gate & Wrought Iron Fence
Wrought Iron Rack
CAST IRON
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Manufactured by reheating pig iron (in a cupola) and
blending it with other material of known composition.
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Alternate layers of pig iron (with or without scrap steel) and
coke are charged into furnace.
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Limestone is added to flux the ash from the coke.
Heat necessary for the smelting is supplied by the
combustion of coke and air supplied by the blast.
Cupola function to purify iron and produce a more
uniform product.
When sufficient metal is accumulated at the bottom of the
furnace, it is tapped.
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Composed primarily of iron, carbon and silicon
Shaped by being cast in a mold
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It has the greatest amount of carbon
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Basically, the amount and form of carbon could affect the
strength, hardness, brittleness and stiffness of cast iron.
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Adding carbon to iron increases its hardness and strength
but lowers the ductility.
Cast iron has high compressive strength but its tensile
strength is low.
There are 2 types of cast iron that is:
a) Gray Cast Iron b) White Cast Iron
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Cast Iron
Teapot
Cast Iron Pots
Cast Iron Bench
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GRAY CAST IRON
“Gray Cast Iron” also known as ordinary ast iron owing to
the color of fracture.
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It contains free carbon (graphite flakes) that makes the
metal weak and soft.
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Contains high carbon content and large numbers of
graphite flakes.
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The flakes gives a gray appearance to a fractured surface
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most widely used cast iron
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Have poor ductility
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Advantages of cast iron are as follows:
a) Cheap
b) Low melting point
c) Fluid – easy to cast, especially advantageous
into large complex shapes.
d) Excellent bearing properties
e) Excellent damping properties (ability to absorb noise
and vibration)
g) Can be heat threatened
h) Can be alloyed
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White Cast Iron
“White Cast Iron” is called in such name due to the fracture
surface that has a silvery white metallic color.
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Carbon is combined chemically with iron in the form of
cementite that makes this metal strong, hard and brittle.
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harder and more resistant to wear from abrasion compared
to gray iron.
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Excellent wear resistance
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High compressive stress
White Cast Iron Daybed
Steel Products
– alloy consisting mostly of iron with a little
carbon (0.2% - 2.04% by weight)
 Cast iron = carbon content between 2.1% - 4.0%
 Iron = iron-carbon alloy with less than 0.005% carbon.
 Wrought iron – contains 1 – 3% by weight of slag in
the form of particles elongated in one direction – more
rust resistant than steel and welds better
 Steel
Steel
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Steel is an alloy that consists mostly of iron and has a carbon
content between 0.2% and 2.1% by weight, depending on the
grade. Carbon is the most common alloying material for iron, but
various other alloying elements are used, such as manganese,
chromium, vanadium, and tungsten.
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Steel with increased carbon content can be made harder and
stronger than iron, but such steel is also less ductile than iron.
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Steel is an alloy of iron and carbon. Pure iron’s strength
remarkably increases when alloyed with carbon. The tensile
strength increases with increasing carbon content but the ductility
reduces. Steel having its properties because of the presence of
carbon alone is called “Plain carbon steel”
Types of Plain Carbon steel
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Low carbon steel or mild steel:
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Medium-carbon steel :
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The carbon content does not increases 0.25%
Soft and ductile
mostly used for construction purpose
Uses ► Sheets, rods, wires, pipes, hammers, chains, shafts et
The carbon content is 0.25 to 0.5 %
Stronger than the mild steel slightly less ductile
Uses ► Shafts, connecting rods and rails etc
High- carbon steel :
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Carbon content is above 0.5%
Harder and stronger than mild steel and medium carbon steel
Uses ► Keys, knifes, drills etc
The “abc’s” of Steel Making:
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Raw Material:
 Carbon
in the form of coke
 Iron ore (Fe2O3)
 Limestone (CaCO3)
 Air (lots of it!!)
The “abc’s” of Steel Making:
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Coke
 Solid
residue product from the destructive
distillation of coal.
 About 80 to 95% C.
 Made by heating black coal in small ovens at
300 C for 24 hours in a coke plant.
The “abc’s” of Steel Making:
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The iron ore
 Consists
of oxides in nature of iron and
oxygen
Primarily magnetite (Fe3O4) or hematite (Fe2O3)
 The blast furnace basically separates the iron from
the oxygen in a reduction process
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 Mined
primarily in Australia, Brazil and
Canada.
The “abc’s” of Steel Making:
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The limestone
as a flux – converts impurities in the ore
into a fuse able slag
 Acts
The “abc’s” of Steel Making:
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Air
 Preheated
by fuel gas from the coke ovens to
about 1000 C.
 Delivered to the blast furnace at 6,000 m3/min
 Passes through furnace and burns the coke to
produce heat required and also generates the
carbon monoxide.
The “abc’s” of Steel Making:
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Typical blast furnace:
 1.6
tons of iron ore
 0.18 tons of limestone
 0.6 tons of coke
 2 -3 tons of preheated air
The “abc’s” of Steel Making:
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Step 1 – The Blast Furnace:
 Stands
300 feet tall
 Designed to run continuously for 4 -5 years
before being relined.
 Heat generated by burning coke in the
preheated air.
 Coke acts as reducing agent and changes to
carbon monoxide (the reducing agent) which
removes the oxygen from the iron oxide.
The “abc’s” of Steel Making:
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Step 1 – The Blast Furnace:
primary zones – the bottom zone (zone
4) reaches temperature of 1800 C – this is
where iron is tapped off.
 The top zone (zone 1) – where coke is burned
and moisture driven off.
 Zone 2 – slag coagulates and is removed.
 Four
The “abc’s” of Steel Making:
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Step 1 – The Blast Furnace:
 Two
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important chemical reactions:
Oxidation of the carbon from coke:
2C  O2  2CO
• Reduction of iron ore:
Fe3O3  3CO  2 Fe  3CO2
The “abc’s” of Steel Making:
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Step 1 – The Blast Furnace:
 Products
from the blast furnace:
Iron stored in steel shelled ladles
 Pig iron (brittle w/ 4% carbon)
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Step 2: Manufacturing of Steel
from Iron
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Two common methods:
 Bessemer
Furnace = Ingots = molten steel
poured into molds to create ingots which then
go through forging press and roughing mill to
create billet, bloom or slab, OR:
 Continuous cast – continuous process to
again create a billet, bloom, slab or “as cast
semis”
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Step 2 – The Bessemer converter:
 Used
for REFINEMENT:
Takes pig iron with high C content and removes C.
 Removes impurities such as Si and Mn (via
oxides)
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 Much
smaller furnace (vs. Blast furnace)
 Lowered cost of steel making
 Poured into molds to form ingots
Replaced by basic oxygen process
and electric arc furnace.
Steel Ingots
Heat treatment of Steel:
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To develop steel of particular structure or conditions best
suited for particular work.
Basis of heat treatment:
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At certain temperature called critical temperature, all alloys
undergo reversible constituent change or inversions.
At heating the critical point differs from that in the cooling.
Holding of material at elevated temperature may help it to
establish equilibrium of constituents.
Slow cooling from an elevated temperature above critical point
permits natural constitutional change.
Rapid cooling or quenching completely inhibits the natural
change and so tends to retain the particular structure.
Heat Treatment process of steel.
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Hardening process:
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The degree of hardness of steel depends on proportions of these three forms:
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Quenching:
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At comparatively higher temperature and below critical temp, the steel is
drawn and cooled softens steel.
Annealing:
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When a piece of steel is hardened by heating above the critical range and then
quenched, it is too hard for practical purpose.
Drawing:
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Rapid Cooling:
Tampering:
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For steel containing less than 0.85% carbon, the hardening temperature must
be above 885C0 to ensure that ferrite is dissolved.
In case of steel having more than 0.85% of Carbon, comentite itself is very
hard and needs temperature slightly above 730C0
For steel with very low carbon, to harden the steel.
Heating above the critical Temp, and then very slowly cooling it making it
more ductile and tough.
Normalizing:
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Steel is heated above the critical Temp but cooled rapidly, which refines the
grains of the steel.
Steel Products:
• Steel is marketed in a wide variety of sizes and shapes, such
as rods, pipes, railroad rails, tees, channels, and I-beams.
• These shapes are produced at steel mills by rolling and
otherwise forming heated ingots to the required shape. The
working of steel also improves the quality of the steel by
refining its crystalline structure and making the metal tougher.
• The basic process of working steel is known as hot rolling. In
hot rolling the cast ingot is first heated to bright-red heat in a
furnace called a soaking pit and is then passed between a
series of pairs of metal rollers that squeeze it to the desired
size and shape. The distance between the rollers diminishes
for each successive pair as the steel is elongated and reduced
in thickness.
•The first pair of rollers through which the ingot passes is
commonly called the blooming mill, and the square billets of
steel that the ingot produces are known as blooms. From the
blooming mill, the steel is passed on to roughing mills and
finally to finishing mills that reduce it to the correct cross
section. The rollers of mills used to produce railroad rails and
such structural shapes as I-beams, H-beams, and angles are
grooved to give the required shape.
•Modern manufacturing requires a large amount of thin sheet
steel. Continuous mills roll steel strips and sheets in widths of
up to 2.4 m (8 ft). Such mills process thin sheet steel so
rapidly, before it cools and becomes unworkable. A slab of
hot steel over 11 cm (about 4.5 in) thick is fed through a
series of rollers which reduce it progressively in thickness to
0.127 cm (0.05 inc) and increase its length from 4 m (13 ft) to
370 m (1210 ft).
Continuous mills are equipped with a number of accessory
devices including edging rollers, de-scaling devices, and
devices for coiling the sheet automatically when it reaches
the end of the mill.
The edging rollers are sets of vertical rolls set opposite each
other at either side of the sheet to ensure that the width of
the sheet is maintained. De-scaling apparatus removes the
scale that forms on the surface of the sheet by knocking it
off mechanically, loosening it by means of an air blast, or
bending the sheet sharply at some point in its travel. The
completed coils of sheet are dropped on a conveyor and
carried away to be annealed and cut into individual sheets.
A more efficient way to produce thin sheet steel is to feed
thinner slabs through the rollers. Using conventional
casting methods, ingots must still be passed through a
blooming mill in order to produce slabs thin enough to
enter a continuous mill.
By devising a continuous casting system that produces an
endless steel slab less than 5 cm (2 in) thick, German
engineers have eliminated any need for blooming and
roughing mills. In 1989, a steel mill in Indiana became the
first outside Europe to adopt this new system.
Pipe
Cheaper grades of pipe are shaped by bending a flat strip, or
skelp, of hot steel into cylindrical form and welding the edges
to complete the pipe. For the smaller sizes of pipe, the edges
of the skelp are usually overlapped and passed between a
pair of rollers curved to correspond with the outside diameter
of the pipe. The pressure on the rollers is great enough to
weld the edges together. Seamless pipe or tubing is made
from solid rods by passing them between a pair of inclined
rollers that have a pointed metal bar, or mandrel, set between
them in such a way that it pierces the rods and forms the
inside diameter of the pipe at the same time that the rollers
are forming the outside diameter.
Tin Plate
By far the most important coated product of the steel
mill is tin plate for the manufacture of containers. The
“tin” can is actually more than 99 percent steel. In some
mills steel sheets that have been hot-rolled and then
cold-rolled are coated by passing them through a bath
of molten tin. The most common method of coating is by
the electrolytic process. Sheet steel is slowly unrolled
from its coil and passed through a chemical solution.
Meanwhile, a current of electricity is passing through a
piece of pure tin into the same solution, causing the tin
to dissolve slowly and to be deposited on the steel. In
electrolytic processing, less than half a kilogram of tin
will coat more than 18.6 sq m (more than 200 sq ft) of
steel.
For the product known as thin tin, sheet and strip
are given a second cold rolling before being coated
with tin, a treatment that makes the steel plate extra
tough as well as extra thin. Cans made of thin tin
are about as strong as ordinary tin cans, yet they
contain less steel, with a resultant saving in weight
and cost. Lightweight packaging containers are also
being made of tin-plated steel foil that has been
laminated to paper or cardboard.
Other processes of steel fabrication include forging,
founding, and drawing the steel through dies.
Figure 9-12: processing of refined steel into products.
F 9-13 – The whole spectrum of steel products!
Classifications of Steel
Steels are grouped into five main classifications.
Carbon Steels
More than 90 percent of all steels are carbon
steels. They contain varying amounts of carbon
and not more than 1.65 percent manganese, 0.60
percent silicon, and 0.60 percent copper.
Machines, automobile bodies, most structural steel
for buildings, ship hulls, bedsprings, and bobby
pins are among the products made of carbon
steels.
Classifications of Steel
Steels are grouped into five main classifications.
Carbon Steels
More than 90 percent of all steels are carbon
steels. They contain varying amounts of carbon
and not more than 1.65 percent manganese, 0.60
percent silicon, and 0.60 percent copper.
Machines, automobile bodies, most structural steel
for buildings, ship hulls, bedsprings, and bobby
pins are among the products made of carbon
steels.
Alloy Steels
These steels have a specified composition, containing
certain percentages of vanadium, molybdenum, or
other elements, as well as larger amounts of
manganese, silicon, and copper than do the regular
carbon steels. Automobile gears and axles, roller
skates, and carving knives are some of the many things
that are made of alloy steels.
High-Strength Low-Alloy Steels
Called HSLA steels, they are the newest of the five chief
families of steels. They cost less than the regular alloy steels
because they contain only small amounts of the expensive
alloying elements. They have been specially processed,
however, to have much more strength than carbon steels of
the same weight. For example, freight cars made of HSLA
steels can carry larger loads because their walls are thinner
than would be necessary with carbon steel of equal strength;
also, because an HSLA freight car is lighter in weight than the
ordinary car, it is less of a load for the locomotive to pull.
Numerous buildings are now being constructed with
frameworks of HSLA steels. Girders can be made thinner
without sacrificing their strength, and additional space is left
for offices and apartments.
Stainless Steels
Stainless steels contain chromium, nickel, and other alloying
elements that keep them bright and rust resistant in spite of
moisture or the action of corrosive acids and gases. Some
stainless steels are very hard; some have unusual strength and
will retain that strength for long periods at extremely high and
low temperatures. Because of their shining surfaces architects
often use them for decorative purposes. Stainless steels are
used for the pipes and tanks of petroleum refineries and
chemical plants, for jet planes, and for space capsules. Surgical
instruments and equipment are made from these steels, and
they are also used to patch or replace broken bones because
the steels can withstand the action of body fluids. In kitchens
and in plants where food is prepared, handling equipment is
often made of stainless steel because it does not taint the food
and can be easily cleaned.
Tool Steels
These steels are fabricated into many types of tools or into
the cutting and shaping parts of power-driven machinery for
various manufacturing operations. They contain tungsten,
molybdenum, and other alloying elements that give them
extra strength, hardness, and resistance to wear.
Alloys of Steel:
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Most of the steel used in the buildings
Engineering is purposefully alloyed with one or
more elements to modify its properties.
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By the terms alloying, it is understood that
some other element other than carbon is
added to iron. The ordinary steel containing
carbon is termed as alloy of Carbon and Iron.
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Usually metals like nickel, chromium,
manganese, vanadium, are added to steel for
making alloys.

Nickel steel:
 The amount of nickel varies from 1 to 4.5 % and Carbons
varies from 0.1% to 0.4%.

Nickel improves the tensile strength and reduces brittleness
and imparts hardness and ductility to steel.

Rust formation is resisted with higher content of nickel.
Nickel steel having 3 to 4.5% nickel is frequently used for
long span bridge construction, shafting, rifle barrels,
bearings, castings.
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Steel alloys having 36% nickel and 0.5% carbon is called
Invar which is used for measuring tapes and pendulum of
clocks, where change in dimensions is minimum.

Steel alloy with 46% nickel and very little carbon is known
as Platinite, which has same thermal coefficient as glass.
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Chrome Steel:
 0.5% to 2% Chromium, 0.2% to 1.5% carbon
are used for parts where great hardness, high
strength and fair degree of toughness is
required.
 Steel with 0.5% chromium and 0.6% to 0.9%
carbon are generally used for manufacturing of
chisels, drills, razors and saw blades.
Tungsten Steel:
 Oldest of steel alloys, used for permanent
magnets.
 With 3% Tungsten, it becomes suitable for lath
tools.
 With about 1% carbon, it produces good steel
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Molybdenum steel:
 MB used in small quantity 0.3% in combination with
Chromium and Manganese, makes high tensile steel
suitable for automobile parts.
Silicon steel:
 Used for Transformer cores and dynamos.
High Speed Steel:
 It may run at red heat without losing its hardness
 15-20%Tungsten, 3-5% Cr, 0.5-2% Vanadium,0.60.8% Carbon with silicon, sulphur, and phosphorous.
 Used in parts which withstands high heat and wear
as required for exhaust valves.