754 Fahmi Metalurgi II Lecture12 Cast Iron(2)

1

METALLURGY II(RM-1421)

Dosen:Fahmi Mubarok, ST., MSc.Metallurgy LaboratoryMechanical EngineeringITS- Surabaya2008

Review Fe – Fe3C Phase DiagramIntroduction

Classifications of Cast IronChemical Composition of Cast Iron

Cooling Rate of Cast IronPhase Diagram of Cast Iron

Schematic of Types of Cast IronAlloying Elements

http://www.its.ac.id/personal/material.php?id=fahmi

LECTURE XILECTURE XI

Fahmi Mubarok

xi 2Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya

Fe Fe -- FeFe33C C Phase Phase DiagramDiagram

2

Fahmi Mubarok


Hypoeutectoid steel ->Lever Rule

3

αt(total ferrite)

Fe C (Cementite)

6.70 0.386.70 0.022

= 0.95%1 0.95 0.05%

W

W

−=

−

= − =

(proeutectoid ferrite)

γ(that will form pearlite)

0.76 0.38(0.76 0.022)

0.52%1 0.52 0.48%

W

W

α−

=−

== − =

1

2

3

4Example: Calculating composition of steel with 0.38 wt%CT = 730oC T=725oC4.3.

The fraction of eutectoid ferritethus are:

αe ααt 0.95 0.52

0.43%

W W W= −

= −=

Fahmi Mubarok


Classification of Cast Iron

• Tipe besi tuang– White cast iron– Malleable cast iron– Gray cast iron– Nodular/ductile cast iron– Chilled cast iron

• Aplikasi dan keuntunganpemakaian besi tuang

• Faktor yang berpengaruh padagrafitisasi

• Proses perlakuan panas untukmengontrol struktur mikronya

1. Tipe tergantung daribentuk grafik (C yang berkumpul) ,atau karbidayang terbentuk, danstruktur mikro dominan.

2. Tergantung juga oleh : Komposisi kimia, Lajupendinginan, danperlakuan panas.

3

Fahmi Mubarok


Type of Cast Iron

Faktor yang berpengaruh terhadap pembentukan jenis besi tuang :% C (2-4% C)% Si (1-3% Si)Temperatur (Cooling rate)

Fahmi Mubarok


Phase Diagram of Cast Iron

4

Fahmi Mubarok


Phase Diagram of Cast Iron

Bila terjadi pendinginan besi tuang melalui garis ‘Eutectic’ dari“A” atau dari “B” apakah grafit akan terbentuk?• γ + eutectic liquid pada “A”

– Pendinginan cepat ⇒ γ + Fe3C (White cast iron)– Pendinginan lambat ⇒ γ + Graphite (Gray cast iron)

• γ + graphite (gray cast iron) pada titik “B”– α + Fe3C ⇒ pearlitic gray cast iron– α + graphite ⇒ ferritic gray cast iron

Fahmi Mubarok


Type of Cast Iron

5

Fahmi Mubarok


Gray vs nodular cast iron (250x)

Fahmi Mubarok


Chemical composition of cast iron

Cast iron Carbon Equivalen (C.E.)C.E. = % C + 1/3 % SiGray and nodular cast iron akan makin mudah terbentuk jika % C dan % Si makin tinggi

6

Fahmi Mubarok


Effect of Alloying Elements in Cast Iron

Silicon 1. Silicon is added to cast irons in the range of 1% to 4% in order to increase

the amount of under-cooling required for the formation of cementite and promote the formation of graphite during solidification.

2. Influence fluidity3. Graphitizer agent4. Cooling rate control to decomposed carbide eutectic5. Silicon promotes the precipitation of secondary graphite on the primary

graphite during the eutectoid transformation, which results in large areas of ferrite (commonly called “free ferrite”) around the graphite particles.

Sulfur – High sulfur tend to reduce fluidity and some ime responsible for blow

hole Manganese

– Manganese is carbide stabilizer

Fahmi Mubarok


Effect of Alloying Elements in Cast Iron

7

Fahmi Mubarok


Terbentuk eutectic carbide pada saat pendinginanMikrostruktur terbentuk karenapendinginan yang cepat danfaktor unsur paduanSusah dimachiningSifat :

Keuletan rendah (brittle)Kekerasan tinggi (hard)Baik ketahanan aus (wear resistance)High compressive stress

☺ Fe3C + pearlit☺ Menunjukkan warna putih pada

permukaan patahan

White cast iron

AplikasiExcellent compression stressBanyak digunakan untuk bed mesin

Fahmi Mubarok


White Cast Iron

• Chemical composition:– Carbon 1.8-3.6 %– Silicon 0.5-1.9 %– Manganese 0.25-0.80 %– Sulfur 0.06-0.20 %– Phosphorus 0.06-0.18 %

• Solidification rate fast enough• Carbon combined with iron cementite (hard, brittle)• Microstructure pearlite in a white interdendritic network of

cementite• Shows a “white” crystalline fractured surface

8

Fahmi Mubarok


Struktur mikro white cast iron

Fahmi Mubarok


White Cast Iron

Pada x3 :

reaksi eutectic: liquid γ + Fe3C (ledeburite)78%22%Jumlah relatif

2% C (titik C)4.3% C (titik E)Komposisi

γ primerliquidFasa

Pada x1 : -fasa liquid-komposisi kimia 2.5%C-jumlah relatif 100% liquid

89%11%Jumlah relatif

2% C (titik C)6.67% C (titik D)Komposisi

γ + γ primerFe3CFasa


0.8% C (titik J)6.67% C (titik K)Komposisi

γ + γ primerFe3CFasa


0.025% C6.67% CKomposisi

αFe3CFasa

Pada x2 : -mulai terbentuk γ primer

Pada x4 :

reaksi eutectoid: γ α + Fe3C (pearlite)

a

b

a

b

9

Fahmi Mubarok


Malleable cast iron

Malleable cast irons are formed by annealing white irons to transform the eutectic cementite to graphite.Malleable irons have good ductility and good strength.Matrix microstructure is dependent upon the cooling rate from the graphitization annealing.Before the discovery of nodular irons, malleable irons were the only ductile class of cast irons.

White cast iron + annealing treatment

Eutectic cementit ⇒ graphite

Fahmi Mubarok


Malleable Cast Iron

• Chemical composition:– Carbon 2.00-2.60 %– Silicon 1.10-1.60 %– Manganese 0.20-1.00 %– Sulfur 0.04-0.18 %– Phosphorus 0.18 % max

• White cast iron Malleable cast iron (malleabilization)• Carbon in the form of irregularly shaped nodules of graphite• Cementite irregularly shaped nodules graphite• Malleabilization:

– First stages of anneal: reheat to 1650 – 1750o F– Second stages of anneal :

• Slowly cooled at a rate of 5 to 15oF/h ferritic malleable cast iron• Fast cooled to retained combined carbon throughout the matrix -> pearlitic mellable

cast iron

10

Fahmi Mubarok


Gray cast iron

Gray cast irons form graphite flakes during solidification.The gray iron microstructure is due to slow solidification rates and silicon alloying that promotes graphite formation.Gray irons typically have low ductility and moderate strength, but they have high thermal conductivity and excellent vibration damping properties

Fahmi Mubarok


Gray Cast IronGray Cast Iron

• Chemical composition:– Carbon 2.5-4.0 %– Silicon 1.0-3.0 %– Manganese 0.25-1.00 %– Sulfur 0.02-0.25 %– Phosphorus 0.05-1.0 %

• Carbon in the iron separates or graphitizes during solidification to form separate graphite flakes

• The most fluid of the ferrous alloys• Have excellent machinability• Fracture surface appearance has a gray color

11

Fahmi Mubarok


Keunggulan gray cast iron

• Excellent machineability• Excellent bearing

properties• Excellent damping

properties• Excellent wear resistance

(jika mengandung % C tinggi)

• Dapat di heat treatment (mis : surface hardening)

• Mudah dipadukan denganunsur lain

• Murah• Titik leleh cukup rendah• Fluid – mudah mengalir saat

pengecoran, sehinggamenguntungkan untuk pengecoranbentuk yang kompleks

Fahmi Mubarok


Keunggulan gray cast iron

12

Fahmi Mubarok


Application of Gray Cast Iron

Typical gray cast iron castings used in automobiles, includingtransmission valve body (left) and hub rotor with disk-brake cylinder (front).

A cast transmission housing.

Fahmi Mubarok


Nodular/Ductile Cast Iron

Bentuk grafit nodular Pendinginan yang lambatdengan penambahanmagnesium dan seriumPenambahan Mg dan Ce akanmembantu terbentuknyaspherodize graphite

Sedikit mengandung unsur S dan P

13

Fahmi Mubarok


Mechanical Properties

• Ferritic – softest• Pearlitic - strongest• Memiliki variasi

modulus elastis• Untuk memperoleh

ukuran butir seragamdilakukan dengan:– Meningkatkan

panaspelelehenansebelum dicor

– Innokulasidenganferrosilicon ataucalcium silicon

Tensile properties

Fahmi Mubarok


Aplikasi ductile cast iron

• Gray iron composition for C and Si• Impurity level control important as it will affect nodule formation• Have nodule instead of flake if we add in 0.05% Mg and/or Ce• As cast structure : graphite forms as nodules instead of flakes

14

Fahmi Mubarok


Nodular Cast Iron

ApplicationAgricultural: tractor and implement partsAutomotive and diesel: crankshafts, pistons and cylinder heads; electrical

fittings, switch boxes, motor frames, and circuit breaker partsMining: hoist drums, drive pulley, flywheels and elevator bucketsSteel mill: work rolls, furnace doors, table rolls and bearingsTool and die: wrenches, levers, handles, clamp frames, chuck bodies and

miscellaneous dies for shaping steel, aluminum, brass, bronze, and titanium

Fahmi Mubarok


Alloy Cast Iron

• Added elements in sufficient amount to produce modification in the physical or mechanical properties– Resistance to corrosion, heat and wear– To improve mechanical properties

• One of the important reasons for alloying is accelerate or retard graphitization

• Elements obtained from raw material, such as silicon, manganese, sulfur, and phosphorus, are not considered alloy additions

• The most common alloying elements are chromium, copper, molybdenum, nickel and vanadium

15

METALLURGY II(RM-1421)

Dosen:Fahmi Mubarok, ST., MSc.Metallurgy LaboratoryMechanical EngineeringITS- Surabaya2008

CORROSIONCORROSION

MINGGU XIIMINGGU XII

Jadwal kuliah :

Tiap hari Senin pukul 15.00 – 16.40 Ruang c-121

Documents

754 Fahmi Metalurgi II Lecture12 Cast Iron(2)