Introduction Wrought iron is a mechanical mixture of very pure iron and a silicate slag Wrought iron is a ferrous material aggregated from a solidifying mass of pasty particles of highly refined metallic iron with which a minutely and uniformly distributed quantity of slag is incorporated witho ID: 460586
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Slide1
Wrought Iron Slide2
Introduction
Wrought iron is a mechanical mixture of very pure iron and a silicate slag.
Wrought iron is a ferrous material, aggregated from a solidifying mass of pasty particles of highly refined metallic iron with which a minutely and uniformly distributed quantity of slag is incorporated without subsequent fusion. Slide3
Chemical composition
C
– 0.02% - 0.03%
P
– 0.05% - 0.25%
Si
– 0.02% - 0.10%
S
– 0.008-0.02%
Mn
– Nil-0.02%
Slag
– 0.05%-1.50%
Iron
- BalanceSlide4
Properties
W.I is never cast.
Shaping is accomplished by hammering pressing and forging.
High ductility
Can be forged and Welded.
Ultimate tensile strength of W.I. can be increased considerably by cold working followed by a period of aging.
W.I. possesses a high resistance towards the corrosion.
W.I. possesses the property of recovering rapidly from overstrain, which enables it to accommodate sudden and excessive shocks without permanent injury.Slide5
High resistance towards fatigue.
Property
Value
Ultimate tensile strength [psi (MPa)]
34,000–54,000 (234–372)
Ultimate compression strength [psi (
MPa
)]
34,000–54,000 (234–372)
Ultimate shear strength [psi (MPa)]
28,000-45,000 (193-210)
Yeild point [psi (MPa)]
23,000–32,000 (159–221)
Elongation, % in 200 mm
18-25
Modulus of elasticity (in tension) [psi (MPa)]
28,000,000 (193,100)
Melting point [°F (°C)]
2,800 (1,540) Slide6
Uses and Application
Building Construction:
Underground services lines and electrical conduit. Soil, waste, vent and downspout piping.
Public Works:
Bridge railings, blast plates, drainage lines, and troughs, sewer outfall lines, weir plates, sludge tanks and lines.
Industrial:
Condenser tubes, unfired heat exchanges, acid and alkali process lines, skimmer bars.
Rail road and marine:
Diesel exhaust and air brake piping, ballast and brine protection plates, hull and deck planting, tanker heating coils etc.
Others :
Gas collection hoods, coal handling equipment, cooling tower and spray pond piping. Slide7
Cast IronSlide8
ORE
Blast Furnace
PIG IRON
CUPOLA FURNACE
CAST IRONSlide9
CAST IRONS
Grey CI
Ductile CI
White CI
Malleable CI
Alloy CI
Good castability
C > 2.4%
Malleabilize
Stress concentration
at flake tips avoidedSlide10
Gray Cast Iron
Gray cast iron
is characterized by its graphitic microstructure, which causes fractures of the material to have a gray appearance.
It is the most commonly used cast iron and the most widely use cast material base on weight.
Most cast irons have a chemical composition of 2.5 to 4.0% carbon, 1 to 3% silicon, and the remainder is iron.
Gray cast iron has less
tensile strength
and
shock resistance
than steel.
Its
compressive strength
is comparable to low and medium carbon steel. Slide11
Gray Cast Iron
A low cost material that can be used for many purposesSlide12
Characteristics:
Gray Iron basically is an alloy of carbon and silicon with iron.
It is readily cast into a desired shape in a sand mould.
It contains 2.5-3.8% C, 1.1-2.8%Si, 0.4-1%Mn, 0.15% P and 0.10% S.
It is marked by the presence of flakes of graphite in a matrix of ferrite, pearlite and austenite.
Graphite flakes occupy about 10% of the metal volume
Length of flakes may vary from 0.05 mm to 0.1 mm
When fractured, a bar of Gray Cast Iron gives gray appearanceSlide13
Gray iron possesses lowest melting point of the ferrous alloys.
G.C.I. possesses high fluidity and hence it can be cast into complex shapes and thin sections.
It possesses machinability better than steel.
It has higher resistance to wear
It possesses high vibration damping capacity
Gray iron has low ductility and low impact strength as compared with steel.
G.C.I. has a solidification range of 2400 – 2000°F
It associates low cost combined with hardness and rigidity.Slide14
G.C.I. possesses high compressive strength
G.C.I. possesses excellent casting qualities for producing simple and complex shapes.Slide15
Application
Machine tools and structures (bed, frame and details)
Gas or water pipes for underground purpose
Manhole covers
Cylinder blocks and heads for I.C. engines
Tunnel segments
Frames for electric motors
Ingot moulds
Sanitary Wares
Piston Rings Slide16
Malleable Cast Iron
Malleable iron: dark graphite rosettes (temper carbon) in an –ferrite matrixSlide17
Malleable Cast Iron
Malleable iron
starts as a white iron casting, that is then
heat treated
at about 900 °C (1,650 °F).
Graphite separates out much more slowly in this case, so that
surface tension
has time to form it into spheroidal particles rather than flakes.
In general, the properties of malleable cast iron are more like mild steel Slide18
Characteristics:
M.C.I. is one which can be hammered and rolled to obtain different shapes.
M.C.I. is obtained from the hard and brittle white iron through a controlled heat conversion process.
(i) A ferritic M.C.I. has Ferrite matrix
(ii) A pearlitic M.C.I. has pearlite matrix
(iii) An alloy M.C.I. contains chromium and nickel and possess high strength and corrosion resistance.
4) M.C.I. possess high yield strength.
5) High young’s modulus and low coefficient of Thermal expansion. Slide19
Malleable Iron
Ferritic Matrix
Pearlitic Matrix
Fully Malleabilized Iron
Complete Ferritizing Anneal
10
m
Partially Malleabilized Iron
Incomplete Ferritizing Anneal
Pearlite
(grey)
Graphite
(black)
Ferrite
(White)
Ferrite
(White)
Graphite
(black)Slide20
6) Good wear resistance and vibration damping capacity.
7) Can be used from – 60 to 1200°F
8) Solidification range of 2550-2065°F
9) Low moderate cost.
10)M.C.I. contains 2-3% C, 0.6 -1.3% Si, 0.2 -0.6% Mn, 0.15% P and 0.10% S. Slide21
Application
Automotive Industry
Rail Road
Agricultural implements
Electrical line Hardware
Conveyor chain links
Gear case
Universal joint yoke
Rear axle banjo housing
Automotive crankshaft.Slide22
Spheroidal Cast Iron
Nodular (ductile) iron: the dark graphite nodules are surrounded by an -ferrite matrix.Slide23
Spheroidal Cast Iron
Nodular
or
ductile cast iron
. Tiny amounts of
magnesium
or
cerium
added to these alloys slow down the growth of graphite precipitates by bonding to the edges of the graphite planes.
Along with careful control of other elements and timing, this allows the carbon to separate as spheroidal particles as the material solidifies.
The properties are similar to malleable iron, but parts can be cast with larger sections. Slide24
Characteristics:
Unlike long flakes as in G.S.I., graphite appears as rounded particles, or nodules or spheroids in N.C.I.
Ductile cast iron possesses very good machinablity.
Soft annealed grades of S.C.I. can be turned at very high feeds and speeds.
The properties of S.C.I. depend upon the metal composition and the cooling rate.
Spheroidal or Nodular or Ductile C.I. contains 3.2%-4.2% C, 1.1%-3.5% Si, 0.3% - 0.8% Mn, 0.08% P and 0.2% S.
It possesses excellent damping capacity, casteblity and wear resistance.Slide25
Mechanical Properties of SG IronSlide26
Application
Paper industries machinery
I. C. engines
Power transmissions equipment
Farm implements and tractors
Earth moving machinery
Valves and fittings
Steel mills rolls and mill equipment
Pipes
Pumps and compressors Slide27
White Cast iron
White iron: the light cementite regions are surrounded by pearlite, which has the ferrite–cementite layered structure.Slide28
White cast iron
With a lower silicon content and faster cooling, the carbon in
white cast iron
precipitates out of the melt as the
metastable
phase
cementite
, Fe3C, rather than graphite.
The cementite which precipitates from the melt forms as relatively large particles, usually in a eutectic mixture, where the other phase is
austenite
(which on cooling might transform to
martensite
).
It is difficult to cool thick castings fast enough to solidify the melt as white cast iron all the way through.
However, rapid cooling can be used to solidify a shell of white cast iron, after which the remainder cools more slowly to form a core of grey cast iron. Slide29
Characteristics:
W.C.I. derives its name from the fact that its freshly broken surface shows a bright white fracture.
Unlike gray iron, W.C.I. has almost all its carbon chemically bonded with the iron- as iron carbide, Fe
3
C which is very hard and brittle constituent.
W.C.I. possesses excellent abrasive wear resistance.
W.C.I. under normal circumstances is brittle and not machinable.
By using a fairly low silicon content, cast iron may be made to solidify as white iron.
W.C.I. casting can be made in sand moulds.
W.C.I. can also be made on the surface of a gray iron casting provided the material is of special composition.Slide30
If iron of proper composition is cooled rapidly, the free carbon will go in the combined form and give rise to white iron casting.
W.C.I. contains 1.8-3.6% C, 0.5 – 2.0% Si, 0.2- 0.8% Mn, 0.18% P and 0.10% S.
The solidification range of W.C.I. is 2550-2065°F Slide31
Application
For producing malleable iron casting
For manufacturing those component parts which require a hard and abrasion resistant material.Slide32
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