X&XI Cast Iron

7/21/2019 X&XI Cast Iron

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METALLURGY II(RM-1421)

Dosen:

Wahyu Wijanaro

Me!hani!a" En#ineerin#

IT$- $ura%aya

Introduction

Classifications of Cast Iron

Chemical Composition of Cast Iron

Cooling Rate of Cast Iron

Phase Diagram of Cast Iron

Schematic of Types of Cast Iron

Alloying Elements

Jadwal kuliah :

Tiap hari Selasa pukul 19.40 21.20 Ruang c-119

MINGGU X&XIMINGGU X&XI


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METALLURGY II Wahyu Wijanaro

|Jurusan Teknik Mesin ITS|

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Inrou!ionInrou!ion

Family of ferrous alloys

Cast into desired shape 2!" C # $%" Si

Properties affected &y'( chemical composition

( solidification process

( solidification rate

( heat treatments

)ide range of strengths and hardness

In most cases are easy to machine *ood hardness+ ,ear resistance and corrosion

resistance effect of alloying elements

-o, cost and .ersatile engineering properties


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+"assi,i!aions o, +as Iron+"assi,i!aions o, +as Iron

()hite cast iron

(/allea&le cast iron

(*ray cast iron

(0odular1Ductile cast iron

(igh alloys cast iron

$3 4lasifi5asi tergantung

dari &entu5 grafit 6Cyang &er5umpul7+ atau5ar&ida yang ter&entu5+dan stru5tur mi5rodominan3

23 Tergantung 8uga oleh '4omposisi 5imia+ -a8upendinginan+ danPerla5uan panas3


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+hei!a" +o.osiion o, +as Iron+hei!a" +o.osiion o, +as Iron

Faktor yang

berpengaruh terhadappembentukan jenis besituang :

% C

% Si

Temperatur (Cooling

rate)


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0hase Dia#ra o, +as Iron0hase Dia#ra o, +as Iron

G


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0hase Dia#ra o, +as Iron0hase Dia#ra o, +as Iron

9ila ter8adi pendinginan &esi tuang melalui garis

:Eutectic; dari


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$!heai! o, Ty.es o, +as Iron$!heai! o, Ty.es o, +as Iron

METALLURGY II


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Irre#u"arsha.enou"e

5rosee

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Whie +as IronWhie +as Iron

Chemical composition'

( Car&on $3%3B "( Silicon 3$3 "

( /anganese 323 "

( Sulfur 3B32 "

( Phosphorus 3B3$ "

Solidification rate fast enough

Car&on com&ined ,ith iron cementite 6hard+

&rittle7 /icrostructure pearlite in a ,hite interdendritic

net,or5 of cementite

Sho,s a


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igh compressi.e strength and ecellent ,ear resistance

&ut etremely &rittle and difficult to machine Gsed ,here'

( resistance to ,ear is most important

( The ser.ice does not re@uire ductility

)hite cast iron /allea&le cast iron 6mallea&iliHation7

/echanical properties'( ardness &rinell % ( B 90

( Tensile strength 23 ( 3 psi

( Compressi.e strength 23 ( 23 psi

( /odulus of elasticity 2! ( 2 milionpsi

METALLURGY II


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Pada % '

rea5si eutectic

li@uid ? Fe%C 6lede&urite7

Pada !'

rea5si eutectoid

? Fe%C 6pearlite7

Fasa li@uid primer

4omposisi !3%" C 6titi5 E7 2" C 6titi5 C7

Jumlahrelatif 22" "

Pada $ ' fasa li@uid

5omposisi 5imia 23"C

8umlah relatif $"

Pada 2 ' mulai ter&entu5 primer

Fasa Fe%C ? primer

4omposisi B3B" C 6titi5 D7 2" C 6titi5 C7

Jumlahrelatif $$" "

Fasa Fe%C ? primer

4omposisi B3B" C 6titi5 47 3" C 6titi5 J7

Jumlahrelatif 2" $"

Fasa Fe%C

4omposisi B3B" C 32" C

Jumlahrelatif %" B%"

METALLURGY II


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METALLURGY II W h Wij


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Ma""ea%"e +as IronMa""ea%"e +as Iron


( Car&on 2323B "( Silicon $3$$3B "

( /anganese 32$3 "

( Sulfur 3!3$ "

( Phosphorus 3$ " ma )hite cast iron /allea&le cast iron 6mallea&iliHation7

Car&on in the form of irregularly shaped nodules ofgraphite

Cementite irregularly shaped nodules graphite

/allea&iliHation'( First stages of the anneal

( Second stages of the anneal



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First stages

(Reheated to $B and $oF(Austenite of the metasta&le

system can dissol.e more

car&on than can austenite of the

sta&le system

(Dri.ing force for the car&on toprecipitate out of the austenite

as free graphite 6temper car&on7

(Structure at completion of first

stages graphitiHation consist of

temper car&on nodulesdistri&uted throughout the

matri of saturated austenite

(Cooled as rapidly as practical

to a&out $!oF



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Second stages

(Slo,ly cooled at a rate of to

$oF1h

(The car&on dissol.ed in the

austenite is con.erted to graphite on

the eisting temper car&on particles+

and the remaining austenitetransforms into ferrite

(The structure consist of temper

car&on nodules in a ferrite matri

6ferritic mallea&le iron7

(Temper car&on nodules does not

&rea5 up the continuity of the tough

ferritic matri3 This result in a

higher strength and ductility than

ehi&ited &y gray cast iron



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Second stages

( Fast enough cooled to retainedcom&ined car&on throughoutthe matri

( If the air @uenched produces afast enough cooling ratethrough the eutectoid range+

the matri ,ill &e completelypearlitic

( The strength and hardness ofthe castings ,ill &e increasedo.er those of ferritic mallea&leiron

Type Tensile

Strength

$ Psi

Kield

Strength

$ Psi

Elongation

" in 2 in

90

Ferritic B %2% 2$ $$$!

Pearlitic B$2 !$ $B2 $B%2B



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Second stages(If the cooling rate through the

critical range is not @uite fastenough to retain all thecom&ined car&on+ the areassurrounding the temper car&onnodules ,ill &e completelygraphitiHed+ ,hile those atgreater distance from thenodules ,ill &e pearlitic3

(9ecause of its generalappearance+ this is referred to

as a bulls-eyestructure



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Pearlitic mallea&le irons

tempered at relati.ely hightemperatures spheroidiHethe pearlite

Impro.e machina&ility and

toughness+ and lo,er thehardness



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Gray +as IronGray +as Iron


( Car&on 23!3 "

( Silicon $3%3 "

( /anganese 32$3 "

( Sulfur 3232 "

( Phosphorus 3$3 "

Car&on in the iron separates or graphitiHes during

solidification to form separate graphite fla5es

The most fluid of the ferrous alloys a.e ecellent machina&ility

Fracture surface appearance has a gray color



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The graphitiHation process is

aided &y high car&on content+high temperature+ and theproper amount of graphitiHingelements+ nota&ly silicon

)ith proper control of the

a&o.e factors+ the alloy ,illfollo, the sta&le irongraphitee@uili&rium diagram

These alloys solidify &y firstforming primary austenite

Forming austenite and graphiteat the eutectic temperature of2oF



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The graphite appears as

many irregular+ generally

elongated and cur.ed

plates3 The fla5e are three

dimensional particles



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The strength the matri

This matri the condition of the

eutectoid cementite

The eutectoid cementite alsographitiHes+ then the matri ,ill &eentirely ferritic

*raphitiHation of the eutectoid

cementite is pre.ented+ the matri,ill &e entirely pearlitic

The matri'

6pearlite7(6pearlite#ferrite7(6ferrite7

*raphiteferrite softest and

,ea5est

Com&ined car&on increased

strength and hardness increased

*raphitepearlite strongest and

hardest



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A""oyin# E"eens in Gray +as IronA""oyin# E"eens in Gray +as Iron

Silicon

(Increased fluidity(*raphitiHer car&on is precipitated as primary graphite in the

form of fla5es during solidification



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Sulfur

(Restrict graphitiHation(Sulfur L com&ined car&on L hard+ &rittle ,hite iron

(Reduce fluidity

(Responsi&le for the presence of &lo,holes in casting

(Com&ined ,ith iron FeS

Manganese()ea5ly retard primary graphitiHation

(Strong car&ide sta&iliHer on eutectoid graphitiHation

(Promote pearlite formation

(Com&ined ,ith sulfur /nS

(/anganese content t,o or three times the sulfur content



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Phosphorus

(Com&ined ,ith iron Fe%P 6iron phosphide

called steadite7

(Steadite is hard and

&rittle(Increased steadite increased its hardness+

&rittleness+ ,earresistance and decreased

machina&ility(Increased fluidity



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7ea Treaen o, Gray +as Iron7ea Treaen o, Gray +as Iron

Stress relieving

(The most fre@uently heattreatment

(*ray iron in the ascast residual stresses differentof cooling rates

(Residual stresses reduce

strength+ distortion+ andcrac5ing

(The temperature &elo,eutectoid temperature

(olding time $ h #

temperature of $$oF stress relief o.er percent



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|Jurusan Teknik Mesin ITS|&'&I - *1


Annealing

(eating

high enough to soften and impro.e machina&ility(Annealing temperature $% ( $!oF 6recommended7

(eld at temperature long enough to allo, the graphitiHing process to go tocompletion

Normalizing(Treated to a temperature a&o.e the transformation range

(eld at this temperature for a period of a&out $ h1in3 of maimum sectionthic5ness

(Cooled in still air to room temperature

(0ormaliHing temperature $B2 $oF(Gsed to enhance mechanical properties+ such as hardness and tensile

strength

(To restore ascast properties that ha.e &een modified &y another heattreatment process



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METALLURGY II



Hardening(Furnacehardened from a temperature of $$BoF

(Muenched from a suita&le ele.ated temperature

(Muenching medium' air+ salt &ath+ oil or ,ater

(Nil throughhardening

()ater too drastic and may cause crac5ing and distortion unless thecastings are massi.e and uniform in cross section

()ater often used for @uenching ,ith flame and induction hardening

(As@uenched &rittle

(Tempered from %$2oF to increase toughness and relie.e stresses

(Tempered impro.es strength and toughness &ut decreases hardness

(Muenched and tempered not ordinarily used to increased strength strength can &e increased at less cost &y reducing silicon and total car&oncontent or &y adding alloying elements

(Muenched and tempered increase the resistance to ,ear and a&rasion &yincreasing the hardness

(A structure consisting of graphite em&edded in a hard martensitic matri



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Gra.hie 8"ae o, Gray +as IronGra.hie 8"ae o, Gray +as Iron

*raphite fla5es L interrupt the continuity of the pearlitic matri

O the strength and ductility *raphite fla5es O less damaging generally preferred

ypoeutectic iron slo, cooling graphitiHation # crystals ofprimary austenite L restricts the eutectic miture or graphite tothe grain &oundary graphite fla5es fe, in num&er and coarse

Car&on content L the amount of eutectic # graphite formed L ,ea5en more than a smaller fla5e siHe can strengthen it

Silicon content 6strong graphitiHing7 L the amount of eutecticformed L reducing fla5e siHe the matri ,ill ferritic ,ea5

casting Reducing the siHe and impro.ing the distri&ution of the graphite

fla5e addition of a small amount of material 6inoculant7

Inoculating agents metallic calcium+ aluminum+ titanium+Hirconium+ silicon car&ide+ calcium silicide+ or com&inations of these



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METALLURGY II



The procedure for preparation and measurement of fla5e siHe is

gi.en in AST/ Designation A2!B+ $$ 9oo5 of AST/Standards+ Part %$

The measurement is made of the lengths of the largest graphitefla5es in a unetched section at $



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*raphite fla5es are arranged in the microstructure prepared &y

the AFS and the AST/



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METALLURGY II



Type D and E

(From the graphitiHation of a normal eutectic structure(Appear in irons of .ery high purity or in commercial irons that ha.e &eencooled rather rapidly during solidification

(Although the graphitic fla5e siHe is small+ the interdendritic pattern andhigh graphite content ,ea5en the material

(Type D and E undesira&le in gray irons

()hen cooling rate is slo,er sho, complete di.orcement of the eutectictype D and E fla5e patterns do not occur

Type A

(The most desira&le fla5e pattern(This results from a completely di.orced eutectic structure

(The siHe of the indi.idual graphite fla5es is determined &y the siHe of theaustenite crystals around ,hich they form



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METALLURGY II



Type 9

(Common only in the intermediate region of a chilled cast iron 6mottled7(Consist of a miture of gray and ,hite cast iron

(The cooling rate is maimum that ,ould permit graphitiHation

Type C

(The fe, large+ straight graphite fla5es present in type C al,ays indicate thatthe iron is hypereutectic in car&on content

(Silicon and se.eral other alloying elements reduce the car&on content of theeutectic+ and if they are present in sufficient amounts the eutecticcomposition may &e reduced to &elo, %3 percent car&on



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METALLURGY II


Me!hani!a" 0ro.eries ' A.."i!aion o, Gray +as IronMe!hani!a" 0ro.eries ' A.."i!aion o, Gray +as Iron

The gray cast iron are classed in se.en classes 60os3 2+ 2+ %+

%+ !+ + B7 ,hich gi.e the minimum tensile strength of test&ars in thousand of pounds per s@uare inch3(Class 2 minimum tensile strength of 2 psi



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Tensile strength(

Tensile strength is important for part thatare su&8ected to static load in indirecttension or &ending3 Such parts include

pressure .essels+ housing+ .al.es+ fittingsand le.ers

(Iron a&o.e ! psi in tensile strength are

usually considered high-strength ironsandare more epensi.e to produce and moredifficult to machine

(*ray irons do not ehi&it a ,elldefined yield point as do most mild steels

(The stressstrain cur.e does not sho, a straight line portionQ thus a definitemodulus of elasticity cannot &e determined

(Gsual method are to determined the


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Compressi.e strength(

Compressi.e strength is important ,hen the gray iron is used for machineryfoundations or supports

(-i5e all &rittle material+ the compressi.e strength of gray iron is muchgreater than its tensile strength and is largely a function of the shearingstrength

(Failure in compression usually occurs along an o&li@ue plane unless the

specimen is long enough to allo, failure &y &uc5ling

Torsional shear strength(/any grades of gray iron ha.e higher torsional shear strength than some

grades of steel(This characteristic+ along ,ith lo, notch sensiti.ity+ ma5es gray iron asuita&le material for types of shafting



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Compressi.e strength(

Compressi.e strength is important ,hen the gray iron is used for machineryfoundations or supports

(-i5e all &rittle material+ the compressi.e strength of gray iron is muchgreater than its tensile strength and is largely a function of the shearingstrength

(Failure in compression usually occurs along an o&li@ue plane unless the

specimen is long enough to allo, failure &y &uc5ling

Torsional shear strength(/any grades of gray iron ha.e higher torsional shear strength than some

grades of steel(This characteristic+ along ,ith lo, notch sensiti.ity+ ma5es gray iron asuita&le material for types of shafting



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METALLURGY II

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ardness(

The hardness is an a.erage result of the soft graphite in the iron andmetallic matri

(ariation in graphite siHe and distri&ution ,ill cause ,ide .ariations inhardness 6particularly Roc5,ell hardness7

(The &rinel tester+ co.ering a larger area+ tend to gi.e a more accuratehardness .alue than Roc5,ell test

(Compressi.e strength steadily increases ,ith increasing hardness

(The microstructure is the primary factor in determining the hardness of grayiron



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METALLURGY II





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U G

|Jurusan Teknik Mesin ITS|&'&I - 4/

+hi""e +as Iron+hi""e +as Iron

Chillediron casting are made &y casting the moltenmetal against a metal chiller+ resulting in a surface of

,hite cast iron Case hard+ a&rasionresistant ,hite iron

Core softer gray iron

This casecore structure is o&tained &y careful controlof the o.erall alloy composition and ad8ustment of the

cooling rate 0ormal cooling rate at the surface is 8ust fast enough to

produce ,hite iron ,hile the slo,er cooling rate &elo,the surface ,ill produce mottled or gray iron

If only selected area to &e ,hite iron+ it is common

practice to use a composition ,hich ,ould normallysolidify as gray iron and employ metal liners 6chills7 toaccelerate the cooling rate of the selected areas

The depth of the ,hiteiron layer is controlled &y usingthin plates ,hene.er a thin ,hiteiron layer is desiredand hea.ier metal plates ,here the deeper chill is

necessary



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Car&on(decreases the depth of chill and increases the hardness of the chilled Hone

Silicon 6graphitiHer7(decreases the depth of chill

/anganese(decreased the depth of chill until the sulfur has &een neutraliHed &y formation

of manganese sulfide(A&o.e this amount+ manganese increases chill depth and hardness

Phosphorus(decreases the depth of chill

0ic5el(reduces the chill depth+ and its influence is a&out onefourth that of silicon(*radual increase in hardness until the nic5el content reaches a&out percent

(Refines the car&ide structure of the chill and the grayiron structure &elo, thechill



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Chromium(9ecause of the formation of chromium car&ides+ chromium is used in amount

of $ to ! percent in chilled irons to increase hardness and impro.e a&rasionresistance

(Sta&iliHes car&ide and suppresses the formation of graphite in hea.y section

()hen added in amount of $2 to % percent+ chromium ,ill impart resistanceto corrosion and oidation at ele.ated temperature

Cooper(In additions of less than ! percent+ decreases the depth of chill

(In ecess of this amount the chill depth and hardness increase

(Reduces ration oh the mottled portion to the ,hiteiron portion

/oly&denum(A&out onethird as effecti.e as chromium in increasing the chill depth

(Impro.es the resistance of the chilled face to spalling+ pitting+ chipping andheat chec5ing



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A constant chill depth may &e o&tained &y using a com&ination ofalloying elements that ha.e opposite effect

Since nic5el reduces chill depth+ it common practice to addchromium+ ,hich increases chill depth+ to neutraliHe the nic5el andresult in a constant chill depth

Chillediron casting is used for rail,aycar ,heels+ crushing rolls+

stamp shoes and dies+ sproc5ets+ plo,shares and many other hea.yduty machinery parts



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9ou"ar +as Iron9ou"ar +as Iron


( Car&on %3!3 "( Silicon $323 "

( /anganese 3$$3 "

( Sulfur 3%" ma

( Phosphorus 3$" ma

4no,n as ductile iron, spheroidal graphite ironand

spherulitic iron

*raphite is present as tiny &alls or spheroids The compact spheroids interrupt the continuity of the

matri much less than graphite fla5es higher strength

and toughness compared ,ith gray iron



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0odular cast iron differs from mallea&le iron in that is

usually o&tained as a result of solidification and doesnot re@uire heat treatment

0odular spheroids car&on

/allea&le irregular temper car&on

Spheroidal graphite particles form during solidification

&ecause of the presence of a small amount of certain

alloying elements+ usually magnesium or cerium

Since these elements ha.e a strong affinity for sulfur+the &ase iron alloy sulfur content must &e &elo, 3$

percent desulfuriHed



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The amount of ferritein the ascast matri

depends oncomposition and rateof cooling

0odular irons ,ith amatri ha.ing a

maimum of $percent pearlite are5no,n asferritic irons

This structure gi.esmaimum ductility+toughness and

machina&ility



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Pearlite can &e produced as cast or &y normaliHing

0ormaliHing is carried out &y air cooling from temperature of$B to $BoF

Peralitic ductile irons are stronger &ut less ductile than ferrite

irons

A martensitic matri may &e o&tained &y @uenching in oil or,ater from $B to $oF3 The @uenched structures are usually

tempered+ after hardening+ to the desired strength and hardness

le.els

Austenitic ductile irons are highly alloyed types ,hich retainaustenitic structure do,n to at least oF3 These irons are of

interest &ecause of their relati.ely high corrosion resistance and

good creep properties at ele.ated temperatures



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Application

Agricultural' tractor and implement parts

Automoti.e and diesel' cran5shafts+ pistons and cylinder headsQ

electrical fittings+ s,itch &oes+ motor frames+ and circuit &rea5er

parts

/ining' hoist drums+ dri.e pulley+ fly,heels and ele.ator &uc5ets

Steel mill' ,or5 rolls+ furnace doors+ ta&le rolls and &earings

Tool and die' ,renches+ le.ers+ handles+ clamp frames+ chuc5 &odies

and miscellaneous dies for shaping steel+ aluminum+ &rass+

&ronHe+ and titanium



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A""oy +as IronA""oy +as Iron

Added elements in sufficient amount to produce

modification in the physical or mechanical properties( Resistance to corrosion+ heat and ,ear

( To impro.e mechanical properties

Nne of the important reasons for alloying is accelerate

or retard graphitiHation

Elements o&tained from ra, material+ such as silicon+

manganese+ sulfur+ and phosphorus+ are not considered

alloy additions The most common alloying elements are chromium+

copper+ moly&denum+ nic5el and .anadium



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METALLURGY II(RM-1421)

Dosen:

Wahyu WijanaroMe!hani!a" En#ineerin#

IT$- $ura%aya

!""!SI!N!""!SI!N

MINGGU XIIMINGGU XII

Jadwal kuliah :

Ti h i S l k l R

Documents

X&XI Cast Iron