Engineering Alloys(Ferrous)
-
Upload
sukhwinder-singh-gill -
Category
Documents
-
view
234 -
download
4
Transcript of Engineering Alloys(Ferrous)
-
8/10/2019 Engineering Alloys(Ferrous)
1/103
Engineering Alloys
Ferrous systems
-
8/10/2019 Engineering Alloys(Ferrous)
2/103
Ferrous Alloys
Allotropy of Fe and its Alloys
Fe-Fe 3C Phase Diagram
Reactions in Fe-Fe 3C Diagram
-
8/10/2019 Engineering Alloys(Ferrous)
3/103
Ferrous Alloys
Classification of Fe-Fe 3C Diagram
Definition of Structures
Types of Ferrous alloys
-
8/10/2019 Engineering Alloys(Ferrous)
4/103
Allotropy of Fe and its Alloys
AllotropyMultiple crystal structure of the samechemical composition is calledpolymorphism or allotropy.Example: Iron, Graphite, etc.
The different crystal structures existsat different temperatures andpressure.
-
8/10/2019 Engineering Alloys(Ferrous)
5/103
Allotropy of Fe and its Alloys
910
1400
1535
T C
Time
Cooling curve of Fe
Liquid
iron(BCC)
iron(FCC)
iron(BCC)
L
-
8/10/2019 Engineering Alloys(Ferrous)
6/103
The temperature at which theallotropic changes takes place in ironis influenced by alloying elements.
The most important alloying element
is carbon.
A portion of the Iron-Carbon system
is called Fe - Fe 3C diagram.
Allotropy of Fe and its Alloys
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
7/103
Fe-Fe 3C Phase Diagram
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
8/103
There are three horizontal lines whichcorresponds to three isothermalreactions.
The first reaction occurs at 1493 C iscalled Peritectic reaction:
Reactions in Fe-Fe 3C Diagram
Liquid + iron Austenite ( )Cool ing
Heating
-
8/10/2019 Engineering Alloys(Ferrous)
9/103
The second reaction occurs at 1150 C and 4.3%C is called Eutectic reaction:
The eutectic mixture formed is called
ledeburite .
The mixture is not stable at roomtemperature.
Reactions in Fe-Fe 3C Diagram
Liquid Austenite + Cementite( ) (Fe 3C)
Cool ing
Heating
-
8/10/2019 Engineering Alloys(Ferrous)
10/103
The third reaction occurs at 725 C and 0.8%C is called Eutectoid reaction:
The eutectoid mixture formed iscalled pearlite .
Austenite( )
Ferrite + Cementite( ) (Fe 3C)
Cool ing
Heating
Reactions in Fe-Fe 3C Diagram
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
11/103
Classification of Fe-Fe 3C Diagram
Alloys containing less than 2%C areknown as steels .
Steels containing less than 0.8%C iscalled hypo eutectoid steels andgreater than 0.8%C is called hyper
eutectoid steels .
Alloys containing more than 2%C are
called Cast irons . NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
12/103
1. FerriteFerrite is an interstitial solidsolution of carbon in BCC Iron.
It is stable over -273 C to 910 C inpure iron.
The maximum solubility at roomtemperature is 0.008wt% and0.025wt% at 725 C
Definition of Structures
-
8/10/2019 Engineering Alloys(Ferrous)
13/103
The solubility is limited due to the
size difference between carbon atom(0.19A ) and the void size (0.17A ).
It is the softest phase present in Fe-Fe 3C diagram.
Definition of Structures
-
8/10/2019 Engineering Alloys(Ferrous)
14/103
2. Austenite( )It is an interstitial solid solution ofcarbon in FCC Iron.
It is stable over 910 C to 1410 C inpure iron.
Maximum solubility of carbon is 2wt%at 1150 C. This is due to the void size
(0.52A
).
Definition of Structures
-
8/10/2019 Engineering Alloys(Ferrous)
15/103
3. CementiteIt is nothing but Fe 3C phase. The
crystal structure is orthorhombic .
The carbon content is 6.67wt%
It is the hardest phase in the Fe- Fe 3CDiagram.
Definition of Structures
-
8/10/2019 Engineering Alloys(Ferrous)
16/103
4. PearliteIt is a very fine plate like or lamellarmixture of ferrite and Cementite.
It is the eutectoid mixture containing0.8wt%C and is formed at 725 C onvery slow cooling.
The mixture has good strength andtoughness than soft ferrite and hardCementite.
Definition of Structures
-
8/10/2019 Engineering Alloys(Ferrous)
17/103
Definition of Structures
Ferrite
Fe3C
Microstructure of Pearlite
-
8/10/2019 Engineering Alloys(Ferrous)
18/103
5. MartensiteThis is a metastable structure occursdue to rapid cooling of austenite.
The crystal structure is BCT (Bodycentered tetragonal)
It is formed through displacivetransformation while cooling fromFCC austenite.
Definition of Structures
-
8/10/2019 Engineering Alloys(Ferrous)
19/103
The microstructure of martensite willlook like needles.
It is the hardest phase and itshardness depends on the carboncontent (i.e for higher hardness
higher the carbon content and viceversa).
Definition of Structures
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
20/103
Types of Ferrous alloys
STEELS
CAST IRONS
WROUGHT IRON
-
8/10/2019 Engineering Alloys(Ferrous)
21/103
1. Plain carbon (PC) steels
2. Effect of impurities on PC steels
2. Alloy steels
STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
22/103
Classification of PC steels
1. Low carbon steels ( 0 - 0.1%C)
2. Mild steels (0.15 - 0.25%C)
3. Medium carbon steels (0.3 - 0.7%C)
4. High carbon steels ( 0.7 - 1.4%C)
Classification of Steels
-
8/10/2019 Engineering Alloys(Ferrous)
23/103
It has carbon content up to 0.1%
They are soft, ductile, tough,machinable, weldable and nothardenable by heat treatment.
It is used in the form of cold rolledsheets.
Low carbon Steels
-
8/10/2019 Engineering Alloys(Ferrous)
24/103
Its microstructure consists of smallamount of pearlite.
Has Strength between 300 370 MPa and %elongation of 28 40.
Used in automobile and refrigeratorbodies, tin cans, corrugated sheets,
nails, welding rods, fan blades, etc.
Low carbon Steels
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
25/103
This steel has carbon contentbetween 0.15 0.25%.
It is used in as rolled and air cooledconditions.
Microstructure consists of 25% offine pearlite and remaining ferrite.
Mild Steels
-
8/10/2019 Engineering Alloys(Ferrous)
26/103
Strength between 400 - 450 MPa.
% elongation between 26
30.
Used as structural steels, building
bars, grills, ship hulls, boilers, oilpipelines, beams, angles, etc.
Mild Steels
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
27/103
They contains carbon contentbetween 0.3 0.7%.
They are medium hard, not soductile and malleable, mediumtough, slightly difficult to machineweld and harden.
They are also calledmachinery steels.
Medium carbon Steels
-
8/10/2019 Engineering Alloys(Ferrous)
28/103
They are used as:
1. Agricultural implements
2. Rail structures
3. Spring steels
Medium carbon Steels
-
8/10/2019 Engineering Alloys(Ferrous)
29/103
Agricultural implementsIt has carbon content between 0.3 0.5%.
The agricultural implements areused in hot forged and air cooledforms.
Microstructure consists of fineferrite pearlite mixture.
Medium carbon Steels
-
8/10/2019 Engineering Alloys(Ferrous)
30/103
-
8/10/2019 Engineering Alloys(Ferrous)
31/103
Spring steelsCarbon content is between 0.5 0.65%.
They are quenched and tempered to havea high yield strength so that resilience( y /2E) of the steel is increased, because
the elastic modulus cannot be increased.
Tempering can increase the yield
strength about 1500 MPa.
Medium carbon Steels
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
32/103
Carbon content between (0.7 1.4%C)
They are hard, wear resistant,brittle, difficult to machine, difficultto weld and can be hardened by
heat treatment.
These steel cannot be cold worked
and are hot worked.
High carbon Steels
-
8/10/2019 Engineering Alloys(Ferrous)
33/103
They are also called tool steels.
They are used for applications likeforging dies, punches, hammers,files, drill bits, razor blades, knives,
ball bearings, etc.
High carbon Steels
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
34/103
1. Sulphur
In commercial steels it is kept below0.05%.
Because sulphur combines withiron to form iron sulfide ( FeS ).
Effect of impurities in Steels
-
8/10/2019 Engineering Alloys(Ferrous)
35/103
Iron sulfide forms a lowtemperature eutectic with ironwhich tends to concentrate on grain
boundaries.
When steel is hot worked at
elevated temperatures the steelbecomes brittle due to the meltingof the iron sulfide eutectic.This iscalled hot shortness.
Effect of impurities in Steels
-
8/10/2019 Engineering Alloys(Ferrous)
36/103
2. Manganese
It is kept between 0.03 to 1% in allcommercial P.C steels.
In the presence of manganese sulfertends to form manganese sulfide (MnS) rather than FeS.
Effect of impurities in Steels
-
8/10/2019 Engineering Alloys(Ferrous)
37/103
The MnS may pass out in the slag orremain as well distributed inclusionthroughout the structure.
When there is more manganesepresent than the amount required toform MnS , the excess combineswith the carbon to form Mn 3C whichis found associated with Fe 3C.
Effect of impurities in Steels
-
8/10/2019 Engineering Alloys(Ferrous)
38/103
3. Phosphorous
It is generally kept below 0.04%.
Small quantities dissolves in ferrite
an increasing the strength andhardness slightly.
Effect of impurities in Steels
-
8/10/2019 Engineering Alloys(Ferrous)
39/103
In large quantities, phosphorousreduces ductility, there byincreasing the tendency of the steelto crack when cold worked. This iscalled cold shortness.
Effect of impurities in Steels
-
8/10/2019 Engineering Alloys(Ferrous)
40/103
4. SiliconMost commercial alloys containbetween 0.05 to 0.3%.
Silicon dissolves in ferrite,increasing the strength of the steelwithout greatly decreasing ductility.
It promotes the de-oxidation ofmolten steel through the formationof SiO 2 .
Effect of impurities in Steels
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
41/103
-
8/10/2019 Engineering Alloys(Ferrous)
42/103
DEFINITIONAlloy steels are the steels containingother elements like Ni, Mn, Cr, W, Mo,
etc which are added to plain carbonsteels for enhancement of their one ormore properties.
They are classified into low alloysteels ( 10%).
ALLOY STEELS
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
43/103
REASON FOR ALLOYING
To increase hardanability.
To improve mechanical properties
either at low or high temperatures.
ALLOY STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
44/103
Increase wear resistance.
Improve corrosion resistance.
Improve magnetic properties, etc.
ALLOY STEELS
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
45/103
EFFECT OF ALLOYING ELEMENTS
1. Solid solution strengthening.
2. Formation of carbides.
3. Formation of intermediatecompounds.
ALLOY STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
46/103
ALLOY STEELS
4. Formation of inclusion.
5. Influence on critical temperaturesand eutectoid composition.
-
8/10/2019 Engineering Alloys(Ferrous)
47/103
Solid solution strengtheningMost of the alloying elements aresoluble in ferrite to some extendand form solid solutions.
The strengthening effect of P, Si,Mn, Ni, Mo, V, Cr, etc are indecreasing order.
ALLOY STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
48/103
ALLOY STEELS
Alloying element(wt%)
H a r d n e s s
P SiMn Ni
Mo
VCr
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
49/103
Formation of carbidesSome of the alloying elementscombine with carbon in steel and
form respective carbides.
They increase wear resistance.
In the absence of carbonconsiderable amount dissolve inferrite.
ALLOY STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
50/103
Mn, Cr, W, Mo and V are examplesof carbide forming elements.
Chromium and vanadium areoutstanding in hardness and wearresistance.
ALLOY STEELS
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
51/103
Formation of intermediate compounds
Some of the elements formintermediate compounds with ironlike Fe 3W2, FeS, etc.
These phases increases thebrittleness of steel.
ALLOY STEELS
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
52/103
Formation of inclusions
Some elements may combine withoxygen and forms oxides whenadded to steel
Example: Si, Al, Mn, Cr, etc.
ALLOY STEELS
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
53/103
INFLUENCE ON CRITICAL TEMPERATUREAND EUTECTOID CARBON
Some elements like Ti, Mo, Si, W, Cr, etc increases the critical temperature.
Other elements like Ni, Mn reduces thecritical temperature are called austenitestabilizers.
ALLOY STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
54/103
ALLOY STEELS
Alloying element(wt%) C r i
t i c a l t e m p e r a
t u r e
Ti MoSi W
Cr
Ni Mn725 C
-
8/10/2019 Engineering Alloys(Ferrous)
55/103
Some elements like Mo, Cr, Si tendto reduce the austenite region asthe amount increases are calledferrite stabilizers.
All the alloying elements shift theeutectoid carbon content to lowervalues ( i.e, < 0.8%)
ALLOY STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
56/103
-
8/10/2019 Engineering Alloys(Ferrous)
57/103
They have high corrosion resistancein most of the usual environmentconditions, hence the name stainlesssteel.
High corrosion resistance is due tothe presence of Chromium which
forms a passive and self healingChromium oxide thin film on thesurface when exposed to oxidationenvironments.
STAINLESS STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
58/103
The minimum amount of Cr in solidsolution should be >13% forsufficient corrosion resistance in
most general environmentconditions.
When Cr is added to steel itcombines with carbon (17 times theamount of Carbon) and formscomplex chromium carbides.
STAINLESS STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
59/103
The remaining chromium goes inthe solid solution.
Therefore the Cr present in thesolid solution form is
= Total Cr (17 * %C)
STAINLESS STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
60/103
Types of Stainless steels
Martensitic stainless steel
Ferritic stainless steel
Austenitic stainless steel
STAINLESS STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
61/103
Martensitic stainless steelThey have Cr content in solidsolution form < 13%
( i.e, %Cr (17* %C) < 13% )
These steels show austenitic phase
at high temperatures and hence canbe hardened by martensitictransformation, hence the name martensitic stainless steel.
STAINLESS STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
62/103
Therefore, these steels contains 12 -18 %Cr and 0.15 - 1.2 %C.
They are hard, wear resistant andmagnetic in character.
Used for springs, ball bearings,valves, razor blades, surgicalinstruments, etc.
STAINLESS STEELS
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
63/103
Ferritic stainless steelThey have Cr content in solidsolution form > 13%
( i.e, %Cr (17* %C) > 13% )
Since Cr is a ferrite stabilizer as the
Cr content increases the ferritephase becomes stable over theentire temperature range and hencecalled ferritic stainless steel.
STAINLESS STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
64/103
They cannot be hardened bymartensitic transformation.
Cold working can be done toincrease the strength and hardness.
These steels contains 13 - 27 %Cr and < 0.2 %C.
STAINLESS STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
65/103
They have higher oxidation andcorrosion resistance compare tomartensitic stainless steel.
They are soft, ductile and magneticin character.
Used for vessels in chemical andfood industries, pans, pipes insugar industries, etc.
STAINLESS STEELS
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
66/103
Austenitic stainless steelThis group contains at least a totalof 24% Cr, Ni & Mn and the amountof Cr alone is at least 18% with thecarbon content between 0.03 to0.25%.
The presence of austeniticstabilizers makes the austenitephase stable at room temperatureand hence called austenitic stainless steel.
STAINLESS STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
67/103
The equilibrium phases in this steelis + + carbide at roomtemperature and homogeneous
austenite above 900
C , however,due to fast cooling only austenitephase is present at roomtemperature.
They are soft, ductile and non-magnetic in character.
STAINLESS STEELS
-
8/10/2019 Engineering Alloys(Ferrous)
68/103
Their corrosion resistance issuperior to other stainless steels.
They have low thermal conductivityand high coefficient of expansion.
Used for food and chemical plants,utensils, sanitary fittings, etc.
STAINLESS STEELS
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
69/103
CAST IRON Definition
White cast iron
Malleable cast iron
Gray cast iron
Nodular cast iron
-
8/10/2019 Engineering Alloys(Ferrous)
70/103
Definition
Cast irons are the alloys of Ironand carbon with 2 to 6.67% C in it.
Most commercial alloys containcarbon only between 2.5 to 4%.
CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
71/103
It cannot be forged, rolled, drawn orpressed into the desired shape.
They are formed by melting andcasting and hence the name cast iron.
CAST IRON
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
72/103
1. White cast ironThey are hypoeutectic alloyspresent in the Fe-Fe 3C diagram.
The fracture surface of the whitecast iron looks white in colourhence the name white cast iron.
Carbon is present in the combinedform (Fe 3C).
WHITE CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
73/103
The microstructure consisting ofdendritic network of Cementite(Fe 3C).
Due to the presence of large amountof Cementite, it is hard and wearresistant but extremely brittle anddifficult to machine.
WHITE CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
74/103
WHITE CAST IRON
Microstructural Changes during cooling of a
hypoeutectic white cast iron
Liquid
Primary-Dendrites
Fe3CPearlite Eutectic
(a)
(d)
(b)
(c)
-
8/10/2019 Engineering Alloys(Ferrous)
75/103
At eutectic temperature, the liquidundergoes a eutectic reaction toform ledeburite ( i.e, Austenite +
Fe 3C).
At the eutectoid temperature, all theaustenite, primary ( pro-eutectic ) aswell as eutectic, transforms topearlite ( i.e, ferrite+ Fe 3C).
WHITE CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
76/103
Therefore, the final microstructureconsists of dendritic areas oftransformed austenite ( i.e, pearlite) in a matrix of transformedledeburite (Fe 3C + pearlite).
WHITE CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
77/103
Properties & applicationsIt is hard, wear resistant, extremelybrittle and difficult to machine.
Used in high wear resistanceapplications such as liners forcement mixtures, ball mills, etc.
Used for making malleable castiron.
WHITE CAST IRON
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
78/103
2. Malleable cast ironThey are produced from white castiron by a malleablizing heattreatment.
The silicon present (1%Si) is lowenough to prevent the formation ofgraphite flakes during casting, butadequate to keep the subsequentannealing time within reasonablelimit.
MALLEABLE CAST IRON
MALLEABLE CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
79/103
Heat treatment consists of heatingwhite cast iron to 900- 950 C andholding at this temperature for along time (24 hrs to several days) followed by cooling to room
temperature.
MALLEABLE CAST IRON
MALLEABLE CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
80/103
MALLEABLE CAST IRON
Cooling900 C
Time
T e m p e r a
t u r e
Malleablizing Heat treatment Cycle
MALLEABLE CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
81/103
At 900 C the structure consists ofaustenite and Cementite.
Cementite being a metastable phasedecomposes to austenite andgraphite with a long holding time.
The free carbon precipitates in theform of spheroidal particles calledtemper-carbon.
MALLEABLE CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
82/103
MALLEABLE CAST IRON
Microstructure Malleable Cast Iron
Temper -carbonPearlite
MALLEABLE CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
83/103
Therefore, the microstructure atroom temperature consists oftemper-carbon in the matrix of
pearlite.
However, the cooling rate is veryslow (or Si in white cast iron ismore ), the Cementite from pearlitemay also decomposes to give amatrix of temper-carbon in ferrite
matrix .
MALLEABLE CAST IRON
MALLEABLE CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
84/103
Properties & applicationsThe temper carbon doesn t break upthe continuity of the tough ferrite (orpearlite) matrix, this results in higher
strength (700MPa) and ductility (10-15%) than gray cast iron.
More expensive than gray cast iron.
Used in automobile crankshafts, pipefittings, etc.
MALLEABLE CAST IRON
NEXT
GRAY CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
85/103
3. Gray cast ironCast irons containing graphite in theform of flakes are called gray cast irons, because the fracture surface looks black(gray) in colour.
Due to the presence of high siliconcontent (2-3%Si), the alloy will formaustenite and graphite (in the form ofirregular elongated and curved flakes) at
the eutectic temperature.
GRAY CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
86/103
GRAY CAST IRON
Graphite Flakes Pearliteor
Ferrite
Microstructure Gray Cast Iron
GRAY CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
87/103
The microstructure consists of graphite
embedded in a matrix of ferrite or pearlite.
Gray cast iron is brittle ( % elongation )
due to the presence of graphite flakeswhich has sharp tips and act like internalcracks or stress raisers.
The properties of gray cast iron dependson the morphology and size of graphite
flakes and matrix
GRAY CAST IRON
GRAY CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
88/103
Properties & applicationsExcellent machinability due to thepresence of graphite flakes.
It has excellent fluidity and takes themould impression quite well.
The wear resistance of gray castiron is very good, as the graphiteflakes acts as lubricant.
GRAY CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
89/103
NODULAR CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
90/103
4. Nodular cast iron
Spheroidal graphite iron ductile iron ornodular
iron is the cast iron which has thegraphite present in the form of tinyballs or spheroids.
The fairly high silicon content(2.5%Si) promotes graphitizationduring solidification.
NODULAR CAST IRON
NODULAR CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
91/103
The modifier (i.e, magnesium andcerium) makes the growth rate of
graphite to be approximately same inall directions.
The graphite nodules in this iron ismore spherical than that of tempercarbon.
NODULAR CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
92/103
NODULAR CAST IRON
GraphiteSpheroids Pearlite
Microstructure Nodular Cast Iron
NODULAR CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
93/103
Properties & applications
It has tensile strength of (400-700MPa) and %elongation between 10-18.
It is the major engineering material asit combines the engineering advantageof steel with the processingeconomics of cast iron.
NODULAR CAST IRON
NODULAR CAST IRON
-
8/10/2019 Engineering Alloys(Ferrous)
94/103
Used in agricultural implements,automotive crankshaft, pistons,gears, chuck bodies, elevatorbuckets in mining, etc.
NODULAR CAST IRON
NEXT
-
8/10/2019 Engineering Alloys(Ferrous)
95/103
WROUGHT IRON
Definition
Manufacturing process
Properties & applications
WROUGHT IRON
-
8/10/2019 Engineering Alloys(Ferrous)
96/103
DEFINITION
Wrought iron is essentially a two-component metal consisting ofhigh-purity iron and slag ( slag iscomposed mainly of iron silicate).
WROUGHT IRON
NEXT
WROUGHT IRON
-
8/10/2019 Engineering Alloys(Ferrous)
97/103
Manufacturing processi. To melt and refine the base metal.
ii. To produce and keep molten aproper slag.
iii. To disintegrate the base metal andmechanically incorporate the slag ofdesired amount into the base metal.
WROUGHT IRON
WROUGHT IRON
-
8/10/2019 Engineering Alloys(Ferrous)
98/103
In the Byer
s process of manufacturingconsists of the following steps:
The raw materials such as pig iron,scrap, etc. are melted in cupolas.
The pig iron is purified to a highlyrefined state in a Bessemer converterand then transferred to the ladle of theprocessing machine.
WROUGHT IRON
WROUGHT IRON
-
8/10/2019 Engineering Alloys(Ferrous)
99/103
Iron silicate slag made by meltingtogether iron oxide and certainsiliceous materials in an open-hearthfurnace is poured into a ladle andmoved directly below the processingmachine.
The base metal kept at 1535 C ispoured at a predetermined rate into theladle containing the molten slag whichis at about 1260 C.
WROUGHT IRON
WROUGHT IRON
-
8/10/2019 Engineering Alloys(Ferrous)
100/103
Since the slag is maintained at lowertemperature than the base metal themetal solidifies rapidly.
Due to this rapid solidification thedissolved gases in the liquid isliberated in the form of smallexplosion and this explosion shattersthe metal into small fragments whichsettle at the bottom of the slag ladle.
WROUGHT IRON
WROUGHT IRON
-
8/10/2019 Engineering Alloys(Ferrous)
101/103
Since the iron is in the weldingtemperature the fragments sticktogether to form a sponge like ball
of iron globules coated with silicateslag.
This globules are passed throughgrooved rollers as a result they getconverted into puddle bars.
WROUGHT IRON
NEXT
WROUGHT IRON
-
8/10/2019 Engineering Alloys(Ferrous)
102/103
Properties & applications
The carbon content is between 0.02 -0.03% and slag content between 1-3%.
It possess high resistance tocorrosion.
It is never cast, and all shaping is doneby hammering, pressing, forging, etc.
WROUGHT IRON
WROUGHT IRON
-
8/10/2019 Engineering Alloys(Ferrous)
103/103
Strength can be increased by coldworking and aging.
Owing to the nature of slagdistribution the tensile strength andductility is greater along the rollingdirection.
It is used in oil industries, shipbuilding under ground service
WROUGHT IRON