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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
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Fahmi Mubarok
xi 3Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
Hypoeutectoid steel ->Lever Rule
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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
xi 4Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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.
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Fahmi Mubarok
xi 5Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
xi 6Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
Phase Diagram of Cast Iron
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Fahmi Mubarok
xi 7Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
xi 8Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
Type of Cast Iron
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Fahmi Mubarok
xi 9Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
Gray vs nodular cast iron (250x)
Fahmi Mubarok
xi 10Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
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Fahmi Mubarok
xi 11Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
xi 12Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
Effect of Alloying Elements in Cast Iron
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Fahmi Mubarok
xi 13Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
xi 14Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
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Fahmi Mubarok
xi 15Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
Struktur mikro white cast iron
Fahmi Mubarok
xi 16Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
71%29%Jumlah relatif
0.8% C (titik J)6.67% C (titik K)Komposisi
γ + γ primerFe3CFasa
63%37%Jumlah relatif
0.025% C6.67% CKomposisi
αFe3CFasa
Pada x2 : -mulai terbentuk γ primer
Pada x4 :
reaksi eutectoid: γ α + Fe3C (pearlite)
a
b
a
b
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Fahmi Mubarok
xi 17Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
xi 18Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
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Fahmi Mubarok
xi 19Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
xi 20Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
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Fahmi Mubarok
xi 21Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
xi 22Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
Keunggulan gray cast iron
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Fahmi Mubarok
xi 23Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
xi 24Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
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Fahmi Mubarok
xi 25Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
xi 26Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
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Fahmi Mubarok
xi 27Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
xi 28Metallurgy Lab. Mech. Eng. Dept. ITS Surabaya
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
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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