METALLURGY I(RM-1420)

Dosen:

Wahyu Wijanarko

Mechanical Engineering

ITS- Surabaya

Crystal Structures of Iron

Fe – Fe3C Phase Diagram

Steels

Cast Iron

MINGGU XMINGGU X

Jadwal kuliah :

Tiap hari Senin pukul 07.00 – 08.40 Ruang C-117

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Crystal Structures of ironCrystal Structures of iron

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Crystal Structures of ironCrystal Structures of iron

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Reactions (Summary)Reactions (Summary)

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Fe - FeFe - Fe33C Phase DiagramC Phase Diagram

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Fe - FeFe - Fe33C Phase DiagramC Phase Diagram

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Four Solid Phases Four Solid Phases

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Four Solid PhasesFour Solid Phases

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Three Invariant ReactionsThree Invariant Reactions

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Critical TemperaturesCritical Temperatures

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Plain Carbon SteelsPlain Carbon Steels

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Plain Carbon SteelsPlain Carbon SteelsPlain Carbon Steels

1. They are very satisfactory where strength and other requirement are not too severe

2. They are used successfully at ordinary temperatures and in atmospheres that are not highly corrosive

3. Plain-carbon steels can be produced in a great range of strengths at a relatively low costPlain Carbon Steels Limitation

1. They cannot be strengthened beyond about 100.000 psi without significant loss in toughness (impact resistance) and ductility

2. Large section cannot be made with a martensitic structure throughout, and thus are not deep-hardenable

3. Rapid quench rates are necessary for full hardening in medium-carbon plain carbon steels to produce a martensitic structure. This rapid quenching leads to shape distortion and cracking of heat-treated steel

4. Plain-carbon steels show a marked softening with increasing tempering temperature

5. Plain-carbon steels have poor impact resistance at low temperatures

6. Plain-carbon steels have poor corrosion resistance for many engineering environments

7. Plain-carbon steels oxidize readily at elevated temperatures

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Effect of Other Elements in Plain Carbon SteelsEffect of Other Elements in Plain Carbon SteelsPlain carbon steels contain the following other elements:

–Sulfur up to 0.05 percent

• Sulfur in commercial steels is generally kept below 0.05 percent

• Sulfur combines with iron to form iron sulfide (FeS), which usually occurs as a grain boundary precipitation

• FeS is hard and has a low melting point, it can cause cracking during hot working of steel (hot-short)

–Manganese up to 1.0 percent

• Manganese is present in all comercial plain carbon steels, in range of 0.03 to 1.00 percent

• The fuction of manganese in counteracting the ill effects of sulfur

• Manganese combines with the sulfur persent in the steels to produce manganese sulfide (MnS)

–Phosphorus up to 0.04 percent

• The phosphorus content is generally kept below 0.04 percent

• This small quantity tends to dissolve in ferrite, increasing the strength and hardness slightly

• In large quantities, phosphorus reduces ductility, thereby increasing the tendency of the steel to crack when cold worked (cold-short)

–Silicon up to 0.30 percent

• Most comercial steels contain between 0.05 and 0.3 percent silicon

• Silicon dissolves in ferrite, increasing the strength of the steel without greatly decreasing the ductility

• Silicon is used as a deoxidizer, and forms SiO2 or silicate inclusions

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Alloying SteelsAlloying Steels

Plain Carbon SteelsPlain-carbon steels properties are

not always adequate for all engineering applications of steel

Alloy Steels1. Alloy steels have been developed which,

although they cost more, are more economical for many uses

2. In some applications, alloy steels are the only materials that are able to meet engineering requirements

3. The principal element that are added to make alloy steels are nickel, chromium, molybdenum, manganese, silicon, and vanadium

4. Other elements sometimes added are cobalt, cooper, and lead

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Eutectoid SteelEutectoid Steel

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Eutectoid SteelEutectoid Steel

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Eutectoid SteelEutectoid Steel

Fe3C-Fe

Fe3C

-Fe

Fe3C

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Eutectoid SteelEutectoid Steel

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Hypoeutectoid SteelHypoeutectoid Steel

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Hypoeutectoid SteelHypoeutectoid Steel

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Hypoeutectoid SteelHypoeutectoid Steel

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Hypereutectoid SteelHypereutectoid Steel

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Hypereutectoid SteelHypereutectoid Steel

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Hypereutectoid SteelHypereutectoid Steel

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SummarySummary

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Hardness and StrengthHardness and Strength

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Toughness and DuctilityToughness and Ductility

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PropertiesProperties

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Cast IronCast Iron

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White Cast IronWhite 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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White Cast IronWhite Cast Iron

• High compressive strength and excellent wear resistance but extremely brittle and difficult to machine

• Used where:– resistance to wear is most important– The service does not require ductility

• White cast iron Malleable cast iron (malleabilization)• Mechanical properties:

– Hardness brinell 375 – 600 BHN– Tensile strength 20.000 – 70.000 psi– Compressive strength 200.000 – 250.000 psi– Modulus of elasticity 24 – 28 milion psi

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White Cast IronWhite Cast IronPada x3 :

reaksi eutectic

liquid + Fe3C (ledeburite)

Pada x4 :

reaksi eutectoid

+ Fe3C (pearlite)

Fasa liquid primer

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

Jumlah relatif 22% 78%

Pada x1 : -fasa liquid

-komposisi kimia 2.5%C

-jumlah relatif 100%

Pada x2 : -mulai terbentuk primer

Fasa Fe3C + primer

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

Jumlah relatif 11% 89%

Fasa Fe3C + primer

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

Jumlah relatif 29% 71%

Fasa Fe3C

Komposisi 6.67% C 0.025% C

Jumlah relatif 37% 63%

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White Cast IronWhite Cast Iron

METALLURGY I(RM-1420)

Dosen:

Wahyu Wijanarko

Mechanical Engineering

ITS- Surabaya

MINGGU XI-XIIIMINGGU XI-XIII

Jadwal kuliah :

Tiap hari Senin pukul 07.00 – 08.40 Ruang C-117

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