pengetahuan bahan teknik - universitas...

PENGETAHUAN BAHAN TEKNIK YUSRON SUGIARTO

• Bahan Teknik adalah semua unsur atau zat yang berbentuk padat, cair, atau gas yang banyak di gunakan untuk kebutuhan keperluan dunia teknikatau industri• Padat : Logam, keramik, plastik, kaca, karet,kayu• Cair : Pelumas, air, bensin, solar, bahan kimia lain• Gas : Oksigen, Asitelen, hidrogen, CO2 dan lainnya

PENGETAHUAN BAHAN TEKNIKyusronsugiarto.lecture.ub.ac.id

Flow chart Pemilihan Proses dan Material


• Seorang ahli teknik dituntut untuk merancang suatuproduk.

• Seorang ahli teknik dituntut untuk membuat suatuproduk

• Seorang ahli teknik mesin harus memilih bahan dalampembuatan atau perbaikan.

• Tuntutan ekonomik (optimasi antara fungsi danharga)


PEMILIHAN BAHAN

Sifat teknis bahan yang perlu diperhatikan dalam pemilihan bahan

PENGELOMPOKAN BAHAN

BAHAN TEKNIK

LOGAM

NON-LOGAM

FERRO

NON-FERRO

yaitu merupakan logam yang mengandung unsur besi (Fe) dalamsusunan unsur dasarnya;logam yang tidak mengandung unsurbesi (Fe) dalam susunan unsurdasarnya. Logam non-ferrodiantaranya adalah Alumunium (Al), Magnesium (Mg), Tembaga (Cu), Seng(Zn), Nickel (Ni), dan Logam Mulia.

ORGANIK

AN-ORGANIK

kayu, kertas, plastik, karet, kulit, kapas

batu, pasir, semen, keramik, gelas, grafit

PENGELOMPOKAN BAHAN

LOGAM FERRO

Bahan logam ferro mengandung karbon antara 0 sampai4,5%, dan dibagi atas tiga golongan yaitu:

Besi dengan kadar karbon; 0 sampai 0,008%

Baja dengan kadar karbon; 0,008% sampai 2,0%

Besi cor dengan kadar karbon; 2,0 sampai 4,5%

Iron

• Pure iron rarely exists outside of the laboratory. Iron is produced by reducing iron ore to pig iron through the use of a blast furnace. From pig iron many other types of iron and steel are produced by the addition or deletion of carbon and alloys. The following paragraphs discuss the different types of iron and steel that can be made from iron ore.

PIG IRON.-• Pig iron is composed of about

93% iron, from 3% to 5% carbon, and various amounts of other elements. Pig iron is comparatively weak and brittle; therefore, it has a limited use and approximately ninety percent produced is refined to produce steel. Cast-iron pipe and some fittings and valves are manufactured from pig iron.

WROUGHT IRON.-• Wrought iron is made from pig

iron with some slag mixed in during manufacture. Almost pure iron, the presence of slag enables wrought iron to resist corrosion and oxidation.

• The chemical analyses of wrought iron and mild steel are just about the same. The difference comes from the properties controlled during the manufacturing process.

• Wrought iron can be gas and arc welded, machined, plated, and easily formed; however, it has a low hardness and a low-fatigue strength.

CAST IRON.-• Cast iron is any iron containing

greater than 2% carbon alloy.

• Cast iron has a high-compressive strength and good wear resistance; however, itlacks ductility, malleability, and impact strength. Alloying it with nickel, chromium, molybdenum, silicon, or vanadium improves toughness, tensile strength, and hardness. A malleable cast iron is produced through a prolonged annealing process

INGOT IRON.-• Ingot iron is a commercially pure

iron (99.85% iron) that is easily formed and possesses good ductility and corrosion resistance. The chemical analysis 'and properties of this iron and the lowest carbon steel are practically the same. The lowest carbon steel, known as dead-soft, has about 0.06% more carbon than ingot iron. In iron the carbon content is considered an impurity and in steel it is considered an alloying element. The primary use for ingot iron is for galvanized and enameled sheet.

Steel • Of all the different metals and

materials that we use in our trade, steel is by far the most important. When steel was developed, it revolutionized the American iron industry. With it came skyscrapers, stronger and longer bridges, and railroad tracks that did not collapse. Steel is manufactured from pig iron by decreasing the amount of carbon and other impurities and adding specific amounts of alloying elements.

Carbon Steel • Carbon steel is a term applied to a broad range of steel

that falls between the commercially pure ingot iron and the cast irons. This range of carbon steel may be classified into four groups:

• Low-Carbon Steel 0.05% to 0.30% carbon

• Medium-Carbon Steel 0.30% to 0.45% carbon

• High-Carbon Steel 0.45% to 0.75% carbon

• Very High-Carbon Steel 0.75% to 1.70% carbon

LOW-CARBON STEEL

• Steel in this classifi-cation is tough and ductile, easily machined, formed, and welded. It does not respond to any form of heat treating, except case hardening.

MEDIUM-CARBON STEEL

• These steels are strong and hard but cannot be welded or worked as

• easily as the low-carbon steels. They are used for crane

• hooks, axles, shafts, setscrews, and so on.

HIGH-CARBON STEEL• Steel in these classes

respond well to heat treatment and can be welded. When welding, special electrodes must be used along with preheating and stress-relieving procedures to prevent cracks in the weld areas. These steels are used for dies, cutting tools, mill tools, railroad car wheels, chisels, knives, and so on.

STAINLESS STEEL

• This type of steel is classified by the American Iron and Steel Institute (AISI) into two general series named the 200-300 series and 400 series. Each series includes several types of steel with different characteristics.

• The 200-300 series of stainless steel is known as AUSTENITIC. This type of steel is very tough and ductile in the as"welded condition; therefore, it is ideal for welding and requires no annealing under normal atmospheric conditions. The most well-known types of steel in this series are the 302 and 304. They are commonly called 18-8 because they are composed of 18% chromium and 8% nickel. The chromium nickel steels are the most widely used and are normally nonmagnetic.

Alloy Steel

• Other elements (besides carbon) can be added to iron to improve mechanical property, manufacturing, or environmental property.

• Example: sulfur, phosphorous, or lead can be added to improve machine ability.• Generally want to use for screw machine parts or parts

with high production rates!• Examples: 11xx, 12xx and 12Lxx

Alloy Steel

• Again, elements added to steel can dissolve in iron (solid solution strengthening):• Increase strength, hardenability, toughness, creep, high

temp resistance.

• Alloy steels grouped into low, med and high-alloy steels.• High-alloy steels would be the stainless steel groups.• Most alloy steels you’ll use fall under the category of low

alloy.

Alloy Steel• > 1.65%Mn, > 0.60% Si, or >0.60% Cu• Most common alloy elements:

• Chromium, nickel, molybdenum, vanadium, tungsten, cobalt, boron, and copper.

• Low alloy: Added in small percents (<5%)• increase strength and hardenability

• High alloy: Added in large percents (>20%)• i.e. > 10.5% Cr = stainless steel where Cr improves

corrosion resistance and stability at high or low temps

Alloying Elements used in Steel

Manganese (Mn)• combines with sulfur to prevent brittleness• >1%

• increases hardenability• 11% to 14%

• increases hardness• good ductility• high strain hardening capacity• excellent wear resistance

• Ideal for impact resisting tools


Sulfur (S)• Imparts brittleness• Improves machineability• Okay if combined with Mn• Some free-machining steels contain

0.08% to 0.15% S• Examples of S alloys:

• 11xx – sulfurized (free-cutting)


Nickel (Ni)• Provides strength, stability and toughness,

Examples of Ni alloys:• 30xx – Nickel (0.70%), chromium (0.70%)• 31xx – Nickel (1.25%), chromium (0.60%)• 32xx – Nickel (1.75%), chromium (1.00%)• 33XX – Nickel (3.50%), chromium (1.50%)

Alloying Elements used in SteelChromium (Cr)

• Usually < 2%• increase hardenability and strength• Offers corrosion resistance by forming stable oxide surface• typically used in combination with Ni and Mo

• 30XX – Nickel (0.70%), chromium (0.70%)• 5xxx – chromium alloys• 6xxx – chromium-vanadium alloys• 41xxx – chromium-molybdenum alloys

Molybdenum (Mo)• Usually < 0.3%• increase hardenability and strength• Mo-carbides help increase creep resistance at elevated temps

• typical application is hot working tools


Vanadium (V)• Usually 0.03% to 0.25%• increase strength

• without loss of ductility

Tungsten (W)• helps to form stable carbides• increases hot hardness

• used in tool steels


Copper (Cu)• 0.10% to 0.50%• increase corrosion resistance• Reduced surface quality and hot-working ability• used in low carbon sheet steel and structural steels

Silicon (Si)• About 2%• increase strength without loss of ductility• enhances magnetic properties


Boron (B)• for low carbon steels, can drastically

increase hardenability• improves machinablity and cold

forming capacityAluminum (Al)

• deoxidizer• 0.95% to 1.30%• produce Al-nitrides during nitriding

PENGELOMPOKAN BAHAN

LOGAM FERROKlasifikasi Baja Karbon

PENGELOMPOKAN BAHAN

LOGAM FERRO

KlasifikasiBesi Cor

PENGELOMPOKAN BAHAN

LOGAM NON- FERRO

Ada beberapa ciri-ciri sifat bukan logam (non-ferro), diantaranya adalah

Tahan terhadap korosi (pengkaratan)

Mempunyai daya hantar listrik yang baik

Mudah dibentuk

PENGELOMPOKAN BAHAN

LOGAM NON- FERRO

TEMBAGA

Tembaga adalah suatu unsurkimiadalam tabel periodic memilikilambang Cu (Cuprum) dan nomoratom29.

unsur ini memiliki korosi yang lambat sekali.

PENGELOMPOKAN BAHAN

LOGAM NON- FERRO

TEMBAGA

Tembaga murni dibagi dalam tiga jenis yang didasarkankepada cara pemurniannya.

tembaga tangguh yang dibuat denganmencairkan kembali tembaga hasil elektrolisa.

tembaga bebas oksigen yang dibuat denganmendeoksidasi tembaga hasil elektrolisa

tembaga bebas oksigen hantaran tinggi yang dibuat dengan mencairkan tembaga elektrolisadalam atmosfir hidrogen.

PENGELOMPOKAN BAHAN

LOGAM NON- FERRO

TEMBAGA

Sebagai unsur paduan pada tembaga umumnyadigunakan adalah Zn, Si, Sn, Al, Ni dan lain-lainya.

Paduan antara Cu-Zn disebut brass atau kuningan

paduan antara Cu-Sn disebut brons atau perunggu.

paduan yang mengandung fosfor disebut brons fosfor,

Cu-Si disebut brons silikon

CU-Al disebut perunggu aluminium

PENGELOMPOKAN BAHAN

LOGAM NON- FERRO

ALUMUNIUM Aluminium adalah unsur kimia yang mempunyai simbolAl dan nomor atom 13.

Paduan aluminium

berdasarkan pembuatan dengan klasifikasipaduan cor dan paduan tempa

berdasarkan perlakuan panas denganklasifikasi dapat atau tidak dapat diberlakupanaskan

berdasarkan unsur-unsur paduan

PENGELOMPOKAN BAHAN

LOGAM NON- FERRO

TIMBAL (Pb)Timbal adalah suatu unsur kimiadalam tabel periodic yang memiliki lambang Pb (Plumbum) dan nomor atom 82.

Timbal mempunyai warna biru kelabu.

Sifatnya dapat ditempa

Sangat liat

Tahan korosi, air, asam.

PENGELOMPOKAN BAHAN

LOGAM NON- FERRO

TIMAH (Sn)Timah adalah sebuah unsur kimia dalam tabel periodic yang memiliki simbol Sn (bahasa Latin: stannum) dan nomor atom 50.

Warna aluminium bening keperak-perakan, sifatnya dapat ditempa, liat dan tahankorosi.

Timah digunakan sebagai pelapis lembaranbaja lunak (pelat timah) dan untukpembuatan peralatan di industri pengawetandan pelapis/ bungkus makanan

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