Light Metals And Their Alloys

Prepared By: 07301,07302,07303,

07304,07305,07307,07309,07117

LIGHT METALS AND THEIR ALLOYS

SCOPE Light alloys have become of great importance in engineering for construction of transportation equipment. Many of these light weight alloys have sufficiently high strength to warrant their use for structural purposes , and as a result of their use , the total weight of transportation equipment has been considerably decreased . Probably the greatest application of light metals is in the construction of aircraft.At present , the metals that serves as the base of the principal light alloys are aluminum and magnesium .Titanium and its alloys are included in this group since they have density much lower than that of steel.

ZINC

Centuries before zinc was discovered in the metallic form, its ores were used for making brass and zinc compounds were used for healing wounds and sore eyes. Brass was produced by the Romans in the time of Augustus (20 B.C. - 14 A.D.).

75ppm (.oo7%) of earth’s crust. 24th most abundant element on Earth. 4th most common metal in use with annual production of around 10 million

tons. Found in association with base metals. Large deposits in Australia, Canada and the United States. At the current rate of consumption, these reserves are estimated to be

depleted sometime between 2027 and 2055. Naturally occurring zinc is composed of 5 stable isotopes, Zn-64, Zn-66, Zn-

67, Zn-68 and Zn-70 with Zn-64 being the most abundant (48.63% natural abundance).

ZINC(Zn) General Properties

Name, Symbol, At. Number zinc, Zn, 30

Element Category Transition ElementGroup, Period, Block 12, 4, dStandard Atomic Wt. 65.38 gm/molMagnetic Ordering DiamagneticYoung’s, Shear, Bulk Modulus 108, 43, 70 GPa

Poission’s Ratio 0.25Brinell Hardness 412 MPaCrystal St. HexagonalMelting, Boiling Point 693, 1180 kAppearance

Colour Bluish-White

Processing

o 95% of the zinc is mined from Zinc Blende ore(ZnS) deposits mixed with sulfides of the Copper, Iron and Lead.

o Zinc metal is produced using extractive metallurgy. 1. Froth flotation(zinc of about 50% is reached by this process).

Main impurities after froth flotation are sulphur (32%), iron (13%), and SiO2 (5%).

2. Roasting converts the zinc sulphide concentrate produced during processing to zinc oxide:

2 ZnS + 3 O2 → 2 ZnO + 2 SO2

3. After that zinc oxide Is treated with carbon or carbon monoxide at 950 °C (1,740 °F) into the metal, which is distilled as zinc vapor. The zinc

vapor is collected in a condenser.2 ZnO + C → 2 Zn + CO2

2 ZnO + 2 CO → 2 Zn + 2 CO2

4. Zinc oxide is converted into Zinc sulphate by treating it with Sulphuric acid. ZnO + H2SO4 → ZnSO4 + H2O

5. After this process electrolysis is done with Lead as anode and Aluminium as cathode. Zn is collected on Aluminium .

Alloys• Nickel Silvers : Alloys of Cu(50-70), Zn(5-40), Ni(5-30).

Good corrosion resistance, ductile, high Young’s modulus, good luster etc. Used for screws, rivets, costume jewelry, surgical equipments etc.

• Al-Zn Alloys : Good corrosion resistance, good machineability, high strength etc. Used for aircraft str. Parts, turret housings, radio equipments, die casting.

• Brasses : Two types of brasses:- α-Brass(5-36%Zn)

1. Yellow α Brass(20-36%): Good strength, corrosion resistance, high ductility

Used for drastic cold working operations.2. Red Brasses(5-20% Zn): High corrosion resistance, Not used for

cold working. Gilding metal(5%Zn) : Used for coins, tokens, medals etc.

β-Brass(48-52%) : β phase is harder & more brittle than α.Difficult for cold

working.

α+β Brass(36-48%Zn) : Middle phase of both types.Naval Brass(60cu,39.75Zn,.75Sn): Used for propeller shafts,

piston rods etc. Forging Brass(60cu,38Zn,2Pb): Used for hot forging, plumbing parts etc.

Applications

The most important application of zinc and the largest use of the metal is as an anti-corrosion agent.

Zinc used as material for the negative terminus or anode in batteries.

Zinc is used as a major alloying element. Brass is used for utensils. Brass is used for sculptures. Zinc alloys are used in die casting. Zinc is used for sheet metal. Cadmium zinc telluride (CZT) is a semi conductive alloy that

can be divided into an array of small sensing devices. Zinc oxide is widely used as a white pigment in paints, and as

a catalyst in the manufacture of rubber.

MAGNESIUMCommercially pure magnesium has a specific gravity of 1.74 and is 99.8 percent pure.In the annealed condition the wrought metal has a tensile strength of about 27000 lb/in.2 and elongation of 15% in 2 in. It can be cold-rolled to a strength of about 37000 lb/in.2 but is cold-formed with difficulty.The pure metal is used largely in Magnesium base alloys as a de-oxidiser and alloying agent in non-ferrous metals, in vacuum-tube and dry-rectifier manufacture, and in pyrotechnics.The desirable low specific gravity of Magnesium is offset by two disadvantages: namely, lack of stiffness and ease of oxidation.The modulus elasticity of Magnesium is only 6.5×106 lb/in2 compared with 10.3×106 and 29.5×106 lb/in2 for Aluminium and steel respectively.

COATING OF Mg ALLOYS Magnesium and its alloys has poor resistance to corrosion, particularly in

salt water and salt atmosphere thus requiring a protective surface coating. A protective coating may be applied to Magnesium and its alloys by

dipping the material into a dichromate bath of by electrolytic anodizing.

Electrolytic anodizing treatment has the advantage of abrasion resistance and improved resistance to salts spray and provide an excellent base for paint.

The coating is applied in an aqueous acidic electrolyte containing phosphate, fluoride and chromate ions.

ALLOYING ELEMENTS IN Mg The alloying elements commonly added to Mg are Al, Zn,Mn and for special

purposes Sn,Zr,Ce,Th and Be. Cu, Fe and Ni are considered impurities and must be kept at a minimum to

provide the best corrosion resistance in the alloy. Al in amounts ranging from 3-10% is the principle alloying element in most

Mg alloys. It increases the strength, hardness and cast-ability of Mg.In excess of about 10%, the alloy becomes brittle.

. Zn is used together with Al in Mg based alloys in amounts upto about 3% to increase salt water corrosion resistance and to offset the harmful effects of Fe and Cu impurities. It also improves casting properties. An excessive amount of Zn produces porosity and brittleness because of the formation of the compound MgZn2

Manganese has a very limited solubility in magnesium , particularly in the presence of Al. It is used In magnesium-aluminum and magnesium –aluminum-zinc alloys in quantities less than about 0.5percent to improve corrosion resistance and weld ability without effecting the strength properties.

Silicon is not soluble in magnesium ,but it forms the compound Mg 2Si. Which increases the hardness of the alloy. It is usually held below 0.30% to avoid extreme brittleness.

Sn is soluble in Mg up to about 15% at 1200F(649 C), decreasing rapidly insolubility to room temperature with the precipitation of the beta phase(Mg2Sn). A Mg-Al-Mn alloy containing 5% Sn has improved hammer-forging properties.

CLASSIFICATION OF Mg ALLOYS

ON THE BASIS OF THE RECOMMENDATIONS OF THE AMERICAN SOCIETY FOR TESTING MATERIALS (ASTM DESIGNATION B275-59), THE Mg ALLOYS ARE BROADLY CLASSIFIED AS:

CASTING Mg ALLOYS

WROUGHT Mg ALLOYS

DESIGNATIONSFirst part Second part Third part

Indicates the two principal alloying elements Indicates the amounts of the two principal alloying elements

Distinguishes between different alloys with the same percentages of the two principal alloying elements

Indicates condition (temper)

Consists of two code letters representing the two main alloying elements arranged in order of decreasing percentage (or alphabetically if percentages are equal)

Consists of two numbers corresponding to rounded-off percentages of the two main alloying elements and arranged in same order as alloy designations in first part

Consists of a letter of the alphabet assigned in order as compositions become standard

Consists of a letter followed by a number (separated from the third part of the designation by a hyphen)

A-aluminumB-bismuthC-copperD-cadmiumE-rare earthF-ironG-magnesiumH-thoriumK-zirconiumL-lithiumM-manganeseN-nickelP-leadQ-silverR-chromiumS-siliconT-tinW-yttriumY-antimonyZ-zinc

Whole numbers Letters of alphabet except I and O

F-as fabricatedO-as annealedH10 and H11- slightly strain hardenedH23,H24 and H26- strain hardened and partially annealedT4-solution heat treatedT5-artificially aged onlyT6-solution heat treated and artificially agedT8-solution heat treated, cold worked and artificially aged

For example:

As an example of this designation system, consider magnesium alloy AZ81A-T4.

• The first part of the designation, AZ, signifies that aluminium and zinc are the two principal alloying elements.

• The second part of the designation, 81, gives the rounded-off percentages of aluminium and zinc (8 and 1, respectively).

• The third part, A, indicates that it is the fifth alloy standardized with 8% Al and 1% Zn as the principal alloying additions.

• The fourth part, T4, denotes that the alloy is solution heat-treated.

Mg CASTING ALLOYS

THE FIRST GROUP OF ALLOYS CONTAINS Al AND Zn AS THE ALLOYING ELEMENTS.POSSESS GOOD CASTING CHARACTERISTICS.DEVELOP HIGH STRENGTH.HAVE STABLE PROPERTIES AT TEMPERATURES AS HIGH AS ABOUT 200° F (95 C)

Mg-CAST ALLOY

DESCRIPTION

AZ63A HIGH YEILD STRENGTH, MAXIMUM TOUGHNESS

AZ81A HIGH DUCTILITY, YEILD STRENGTH SIMILAR TO AZ63A-T4

AZ91C POSSESS PRESSURE TIGHTNESS, GOOD WELDABILITY OF CASTING

EK30A EK41AEZ33A

CONTAIN RARE EARTH AND ZIRCONIUM, HAVE RELATIVELY LITTLE DIFFERENCE IN MECHANICAL PROPERTIES. PRODUCE EXCELLENT PRESSURE-TIGHT CASTINGS AND POSSESSGOOD CREEP STRENGTH

HK31AHZ32A

CONTAIN THORIUM, USEFUL AT TEMPERATURES AS HIGH AS 345 -370C , BEST UNDER SHORT TIME ELEVATED TEMPERATURE CONDITIONS.

ZH62AZK51A

PRIMARILY Mg, Zn, Zirconium. CREEP AND FATIGUE PROPERTIES SIMILAR TO ZK 51A

AZ91AAZ91B

USED FOR DIE-CASTING, DIFFER IN AMOUNT OF COPPER

Mg WROUGHT ALLOYS

MAY BE ROLLED AS SHEET AND PLATE, EXTRUDED AS BARS, SHAPES, OR TUBINGS , AND FORGED BY PRESS OR HAMMER FORGING.READILY HOT WORKED AND FORMED AT TEMPERATURES OF 400-700F.ENDURANCE CURVES SIMILAR TO THAT OF Al ALLOYS.

Mg-WROUGHT ALLOYS DESCRIPTION

AZ31BWIDELY USED FOR EXTRUSIONS, POSSESS GOOD FORMING CHARACTERISTICS, MODERATE GOOD STRENGTH, GOOD DUCTILITY.

AZ31CSIMILAR TO AZ31C BUT POSSESS HIGHER

LIMITS OF IMPURITIES.

AZ61A

•HIGH STRENGTH•DUCTILITY SAME AS THAT OF AZ31 ALLOYS•HIGHEST STRENGTH OBTAINED IN THE ARTIFICIALLY AGED CONDITION(-T5)

NICKEL

• Nickel is the one of the most important metals used in the engineering. Pure nickel finds considerable application where resistance to corrosion is required under certain conditions. It finds extensive use in the chemical industry and in the production of caustic soda.

• It serves as an excellent coatings for the electroplating of chromium. Nickel clad steel is used for the construction of heavy tanks and kettles.

• “A” nickel is commercially pure nickel which is obtainable in the wrought form and contains 99.4 % nickel with the remainder particularly cobalt.

• “D” nickel> An alloy of the nickel containing 4.5% manganese and is used where improved resistance to the attack by sulfur compounds at temperature below about 1000F(540°C) is desired.

• “E ” nickel > It is similar to the D nickel and contain 2% manganese and is used for the similar purposes.

• “L” nickel > It contain low carbon content and is used for the applications where the large plastic deformations involved in the forming. This material is not as the work harden as the others.

• “Z” nickel> alloy of the nickel contain 4.5 % aluminum. This material is subjected to precipitation hardening and have good combination of the high strength and resistance to corrosion. It is used for springs, pumps ,rods and shaft etc.

NICKEL BASE ALLOYS

• The alloys that contains a substantial portion of the nickel are of the great commercial importance.

• There are low expansion alloys contain 36% nickel ,the glass sealing alloys with 30-50% nickel ,the alloys with low temperature coefficient of modulus of elasticity, and the magnetic alloys containing up to about 65% nickel.

• The alloys containing up to 50% nickel are classified as nickel based alloys.

MONEL

• MONEL containing 67% Nickel 30% copper and containing small amount of iron and manganese. The Monels are particularly used in the applications that required resistance to acids alkalis, brines water and food products. The Monel family of alloys consist of five composition : Monel , R-Monel , K- Monel , H-Monel , S-Monel .

R-Monel > It possesses same general characteristics as Monel , but it is a free machining alloy intended for processing in the automatic screw machine. The improved machining qualities are derived from the addition of 0.025 to 0.060 % sulfur.

K-Monel > It is a precipitation hardenable Monel which contains 3% aluminum. Its strength approaches to that of heat treated alloy steel and having similar corrosion resistance.

• S-Monel > It is used primarily in casting and containing about 4% silicon. This alloy is responsive to precipitation hardening. A hardness of about 350 Brinell make it suitable for use when resistance to galling and erosion is important as in valve seats and where sliding contact is involved under corrosive conditions.

• H-Monel> It is similar to the s Monel but contain 2.75- 3.25% silicon. This alloy cannot be treated to as high a strength and hardness as the s-Monel , but for many application it is adequate.

• Inconel > It consist of 80% nickel,14% chromium and remainder is iron. Its specific gravity is 8.55 and melting point is 1395°C . It can be cast, rolled and cold drawn. It is used for making springs which have to withstand very high temperature and are exposed to corrosive action.

• Nichrome > It consist of 65% nickel,15% chromium and 20% iron. It is used for making electric resistance wires for electric furnaces and heating elements.

• Nimonic > It consist of 80% nickel and 20% chromium. It is widely used in the gas turbine engine.

COPPER -NICKEL ALLOYS

• The addition of nickel to the copper has marked effect on the color of the alloy .The alloy become whiter in appearance until it 2% nickel it is practically white.

• An alloy contain 45% nickel with remainder copper has very high resistivity and an extremely low temperature coefficient of resistivity which make its use in certain types of resistors. Used extensively in the thermocouples . this alloy is commonly called “constantan”.

CUPRONICKEL

• It is a term which is not necessarily applied to any specific alloy, although it has used principally in connection with the alloy containing 15,20,30% nickel with remainder copper.

• Others have been employed containing 2.5,5,10& 25% nickel. 30% cupronickel alloy has been used with considerable success for condenser tubes and tubing in conducting salt water and other corroding substances.

• The alloy containing lower nickel content such as 20% cupronickel alloy are used for turbine blades and for parts requiring resistance to corrosion and erosion. These alloys are formed by hot forging and cold working operations.

NICKEL SILVER • The alloys referred to as nickel silver, their importance principally to their

color and corrosion-resistance characteristics. The composition of nickel silver varies widely, but it is usually customary to maintain the copper content between 60 to 65 percent .These alloys can be obtained in cast, rolled, and extruded forms. Nickel silver is used principally as the base for silver-plated ware, the advantage being that in the event of wear of the silver plate, the color of the base substance does not differ greatly from that of the silver plate.

HIGH TEMPRATURE ALLOYS

• Those alloys which can withstand temperature in excess of 2012F are called high temperature alloy. They are used in components of nuclear plants, jet and rocket engines.

• Incoloy > It is a nickel base alloy. It consist of 42% nickel, 13% chromium,6% molybdenum 2.4% titanium 0.4% carbon and remaining is iron.

• Hastelloy > It consist of 45% nickel, 22% chromium ,9% molybdenum, 1.5% cobalt, 0.5% tungsten 0.15% carbon and remaining is iron.

• Vitallium> it consist of 62% cobalt,28% chromium,5.5% molybdenum, 2.5% nickel, 1.7%iron and 0.28% carbon.

NOMINAL COMPOSITION OF NICKEL BASED ALLOYS

Ni Cu Fe Mn Si C S Other elements

Nickel grade A 99.4 0.1 0.15 0.2 0.05 0.1 0.005

“D”Nickel 95.2 0.05 0.15 4.5 0.05 0.1 0.005

“E”Nickel 97.7 0.05 0.10 2.0 0.05 0.1 _

“L”Nickel 99.4 0.1 0.15 0.2 0.05 0.02 0.005

“Z”Nickel 94.0 0.05 0.25 0.25 0.40 0.16 0.005 0.33 Ti

Monal 67.0 30.0 1.4 1.0 0.1 0.15 0.01

R-Monel 67.0 30.0 1.7 1.1 0.05 0.1 0.035

K-Monel 66.0 29.0 0.9 0.75 0.5 0.15 0.005 2.75 Al

H-Monel 65.0 29.5 1.5 0.9 3.0 0.1 0.015

S-Monel 63.0 30.0 2.0 0.9 4.0 0.1 0.015

OBTAINING ALUMINA(BAUXITE)

Mine Bauxite from Earth

Crush and spray with water.

Kiln-dry

Mix with soda ash and crushed lime.

Process in digester

Reduce under pressure Settling tank where additional impurities are removed.

Precipitator

Thickener

Heat in calcinating kiln to get alumina

ALUMINIUM HISTORY

Most Abundant Metal in Earth’s Crust

1825 discovered

1852 $545 per pound

1888 Economical Processing

PROPERTIES OF ALUMINIUM

Commercially pure aluminum with a specific gravity of 2.71 is 99% pure ,the remainder consisting principally of iron and silicon .

In the annealed state , it has a tensile strength of 13,000 lb/in^2 .with an elongation of about 40% in 2 in.

Its resistance to action of atmosphere and to several chemicals gives it further advantages , although commercially pure aluminum is not usually resistant to strong alkalies or to some weak alkaline solutions.

Its corrosion resistance under oxidizing conditions depends upon the natural development of an aluminum oxide surface.

On weight basis ,the electrical conductivity of aluminum is about 200% that of copper; on a volume basis ,it is about 61% that of copper.

The aluminum alloys are used most extensively for structural purposes

ALLOYING ELEMENTS IN ALUMINIUM

The alloying elements commonly used in commercial aluminium alloys include copper, silicon, magnesium ,mangnese ,and occasionally zinc, nickel, and chromium.

The overall efect of these alloys additions is to raise the tensile strength,yeild strength, and hardness with corresponding reduction of percentage elongation.

Alloying elements are added extensively to aluminum casting to improve casting qualities as well as mechanical properties..

Copper has been the principal alloying element in aluminum for many years. It is employed in amounts up to 4% in wrought alloys and up to about 8% in casting.Its effect is to decrease shrinkage and to provide a basis for age hardening in many aluminium alloys.

Silicon is probably second to copper in its importance as an alloying element ,principally in casting alloys.It is used in amounts ranging from about 1% to 14%.Silicon improves casting qualities, such as fluidity ,in addition to providing corrosion resistance,low thermal expansion,and high thermal conductivity.

Magnesium is alloyed with aluminium in amounts ranging from 1% to 10%.Such alloys are lighter than aluminium, posses good mechanical properties,and are easily machined.

Zinc is added in amounts up to 10%, to improve mechanical properties.

Manganese and chromium are added in small amounts to increase both strength and corrosion resistance of aluminium alloys.

CLASSIFICATION OF ALUMINIUM ALLOYS The aluminium alloys are broadly classified as: (1)casting alloys (2)wrought alloys

CAST ALLOY DESIGNATION SYSTEM

No classification system for cast aluminium alloys has international acceptance. That of the Aluminium Association of the United States (AAUS) is the most widely used.

The cast alloy designation system is based on a 3 digit-plus decimal designation xxx.x (i.e. 356.0). The first digit (Xxx.x) indicates the principal alloying element, which has been added to the aluminum alloy

The second and third digits are significant in 1xx.x series, in which they provide the minimum aluminium percentage above 99% .For other series second and third digits (xXX.x) are arbitrary numbers given to identify a specific alloy in the series. The number following the decimal point indicates whether the alloy is a casting (.0) or an ingot (.1 or .2). A capital letter prefix indicates a modification to a specific alloy.Example: Alloy - A356.0 the capital A (Axxx.x) indicates a modification of alloy 356.0. The number 3 (A3xx.x) indicates that it is of the silicon plus copper and/or magnesium series. The 56 (Ax56.0) identifies the alloy within the 3xx.x series, and the .0 (Axxx.0) indicates that it is a final shape casting and not an ingot.

DESIGNATION MAJOR ALLOYING ELEMENT

1XX.X >99% ALUMINIUM

2XX.X COPPER

3XX.X SILICON, COPPER &/ORMAGNESIUM

4XX.X SILICON

5XX.X MAGNESIUM

6XX.X UNUSED

7XX.X ZINC

8XX.X TIN

ALUMINIUM WROUGHT ALLOYS

The AAA (Aluminium Association of America) classification for wrought aluminium alloys has been adopted by the IADS (International Alloy Development System).The classification is based on a four –digit system.

We shall first consider the 4-digit wrought aluminum alloy identification system.

The first digit (Xxxx) indicates the principal alloying element, which has been added to the aluminum alloy and is often used to describe the aluminum alloy series, i.e., 1000 series, 2000 series, 3000 series, up to 8000 series.

The second single digit (xXxx), if different from 0, indicates a modification of the specific alloy, and). The third and fourth digits are significant in the 1xxx series but not in the others. In the 1xxx series the last two digits provides the minimum aluminium percentage above 99% ; thus 1145 has a minimum purity of 99.45%; 1200 has a minimum purity of 99.00%. In all other series, the third and fourth digits are simply serial numbers; thus 5082 and 5083 are two distinct aluminium-magnesium alloys. The second digit has a curious function: it indicates a close relationship: thus 5352 is closely related to 5052 and 5252; and 7075 and 7475 differ only slightly in composition.

DESIGNATION MAJOR ALLOYING ELEMENT

1XXX >99%ALUMINIUM

2XXX COPPER3XXX MANGANESE

4XXX SILICON

5XXX MAGNESIUM

6XXX MAGNESIUM AND SILICON

7XXX ZINC

8XXX OTHER ELEMENT

9XXX UNUSED SERIES

In addition to four digits, specific letters are added to denote the thermal/mechanical treatment given.

O annealed

H strain hardened H1 strain hardened only H2 strain hardened and recovery annealed H3 strain hardened and stabilized H4 strain hardened and painted HX2 quarter-hard HX4 half hard HX8 full

T age hardened T1 naturally aged after hot working T4 solution treated,quenched and naturally aged T6 solution treated,quenched and artificially aged T8 same as T6, except cold working before ageing

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ALUMINUM CAST ALLOYSThe nominal compositions and typical mechanical properties of common aluminium sand casting alloys are given in table.Aluminium alloys are not only cast in sand moulds ,but certain compositions are ideally suited to permanent moulds and die casting process.

NOMINAL COMPOSITION OF SOME ALUMINIUM SAND-CASTING ALLOYS.

ALLOY Cu% Fe% Si% Mg% Zn% Ni%

43 0.1 0.8 5.0 0.05 0.2

113 7.0 1.5 1.0 0.07 2.2 0.3

122 10.0 1.5 1.0 0.2 0.5 0.3

142 4.0 0.8 0.6 1.5 0.1 2.0

355 1.3 0.6 5.0 0.5 0.2

356 0.2 0.5 7.0 0.3 0.2

750 1.0 0.7 0.7 1.0

A750 1.0 0.7 2.5 0.5

B750 2.0 0.7 0.4 0.75 1.2

PROPERTIES OF CAST ALLOYS

Aluminium-magnesium alloy such as 214 and 220 are corrosion resistant even in marine atmosphere.

Aluminium-silicon alloy such as 43 and 356 are noted for excellent casting characteristics.

Aluminium-copper-silicon alloy,108,319 combine certain properties of aluminium copper and aluminium-silicon alloys to produce good casting characterstics ,weldibility,moderate strength and pressure tightness.

Aluminium wrought alloys

The nominal composition and typical mechanical properties of some standard wrought aluminium alloys are given in table:

ALLOY Cu% Si% Fe% Mn% Mg% Zn% Cr% Ni% Other

1050 0.05 0.25 0.4 0.05 0.05 0.05

1060 0.05 0.25 0.35 0.03 0.03 0.05

2014 4.4 0.9 1.0 0.8 0.5 0.25 0.10 Ti 0.15

2017 4.0 0.8 1.0 0.7 0.5 0.25 0.10

3003 0.2 0.6 0.7 1.2 0.10

3004 0.25 0.3 0.7 1.2 1.0 0.25

6063 0.1 0.4 0.35 0.10 0.67 0.10 0.10 Ti 0.10

PROPERTIES OF SOME IMPORTANT WROUGHT ALUMINIUM ALLOYS

Alloys such as 1100,3003,3004,4043,5052,5056,7072 are relatively low in cost,corrosion resistant and are welded easily.

Alloys 2014,2018,2025,4032,and 6151 are forging alloys,2014 is particularly used in aircraft-propeller forging.

Alloys 6053,6063 are extrusion alloys. The ability of 6063 to extrude compliclated shapes makes it useful for architecture work

The Properties of the Element Lead

Name of Element : Lead Symbol of Element : PbAtomic Number of Lead : 82 Atomic Mass: 207.2 amu Melting Point: 327.5 °C - 600.65 °KBoiling Point: 1740.0 °C - 2013.15 °KNumber of Protons/Electrons in Lead : 82 Number of Neutrons in Lead : 125 Crystal Structure: Cubic (Face Centered)Density @ 293 K: 11.34 g/cm3Color of Lead : bluish-grey(freshly cut)

What are the origins of the word Lead ?The name originates from the Greek word protos meaning 'first' and the Symbol Origin 'Pb' from the Latin word plumbum meaning 'lead'. Plumbism is the medical term for lead poisoning

LEAD

Lead is usually found in ore with zinc, silver and (most abundantly) copper, and is extracted together with these metals. The main lead mineral is galena (PbS), which contains 86.6% lead. Other common varieties are cerussite (PbCO3) and anglesite (PbSO4).

The chief ore of lead is galena. In order to extract lead from galena, the ore is first concentrated by froth floatation process.

The concentrated ore is roasted in air to convert it into lead oxide (PbO) and lead sulphate (PbSO4). Some galena is also left unchanged. If the air supply is now reduced; the unreacted PbS reacts with PbO and PbSO4 to produce lead metal (self-reduction method).

In another method, the mixed sulphides (PbS and ZnS) are roasted to obtain oxides. The mixed oxides are reduced to their respective metals with coke by heating in blast furnace.

The properties of lead that make it useful in a wide variety of applications are density, malleability, lubricity, flexibility, electrical conductivity, and coefficient of thermal expansion, all of which are quite high; and elastic modulus, elastic limit, strength, hardness, and melting point, all of which are quite low.

Lead also has good resistance to corrosion under a wide variety of conditions. Lead is easily alloyed with many other metals and casts with little difficulty.

The high density of lead (11.35 g/cm3, at room temperature) makes it very effective in shielding against x-rays and gamma radiation. The combination of high density, high limpness (low stiffness), and high damping capacity makes lead an excellent material for deadening sound and for isolating equipment and structures from mechanical vibrations.

The low tensile strength and low creep strength of lead must always be considered when designing lead components. The principal limitation on the use of lead as a structural material is not its low tensile strength but its susceptibility to creep. Lead continuously deforms at low stresses and this deformation ultimately results in failure at stresses far below the ultimate tensile strength. The low strength of lead does not necessarily preclude its use.

Alloying with other metals, notably calcium or antimony, is a common method of strengthening lead for many applications. In general, consideration should always be given to supporting lead structures by lead-covered steel straps. When lead is used as a lining in a structure made of a stronger material, the lining can be supported by bonding it to the structure.

Compositions and Grades

Bellow is listed the Unified Numbering System (UNS) designations for various pure lead grades and lead-base alloys.

Pure leads L50000 - L50099 Lead - silver alloys L50100 - L50199 Lead - arsenic alloys L50300 - L50399 Lead - barium alloys L50500 - L50599 Lead - calcium alloys L50700 - L50899 Lead - cadmium alloys L50900 - L50999 Lead - copper alloys L51100 - L51199 Lead - indium alloys L51500 - L51599 Lead - lithium alloys L51700 - L51799 Lead - antimony alloys L52500 - L53799 Lead - tin alloys L54000 - L55099 Lead - strontium alloys L55200 - L55299

Grades are 1)pure lead (also called corroding lead) 2)common lead (both containing 99.94% min lead), 3)chemical lead and acid-copper lead (both containing 99.90% min lead) 4)Lead of higher specified purity (99.99%) is also available in commercial quantities. Specifications other than ASTM B 29 for grades of pig lead include federal specification QQ-L-171, German standard DIN 1719, British specification BS 334, Canadian Standard CSA-HP2, and Australian Standard 1812.

Corroding Lead. Most lead produced is pure (or corroding) lead (99.94% min Pb). Corroding lead which exhibits the outstanding corrosion resistance typical of lead and its alloys. Corroding lead is used in making pigments, lead oxides, and a wide variety of other lead chemicals.

Chemical Lead. Refined lead with a residual copper content of 0.04 to 0.08% and a residual silver content of 0.002 to 0.02% is particularly desirable in the chemical industries and thus is called chemical lead.

Copper-bearing lead provides corrosion protection comparable to that of chemical lead in most applications that require high corrosion resistance. Common lead, which contains higher amounts of silver and bismuth than does corroding lead, is used for battery oxide and general alloying.

Lead-Base Alloys

Because lead is very soft and ductile, it is normally used Commercially as lead alloys. Antimony, tin, arsenic, and calcium are the most common alloying elements.

Antimony generally is used to give greater hardness and strength, as in storage battery grids, sheet, pipe, and castings. Antimony contents of lead-antimony alloys can range from 0.5 to 25%, but they are usually 2 to 5%.

Lead-calcium alloys have replaced lead-antimony alloys in a number of applications, in particular, storage battery grids and casting applications. These alloys contain 0.03 to 0.15% Ca. More recently, aluminum has been added to calcium-lead and calcium-tin-lead alloys as a stabilizer for calcium.

Adding tin to lead or lead alloys increases hardness and strength, but lead-tin alloys are more commonly used for their good melting, casting, and wetting properties, as in type metals and solders. Tin gives the alloy the ability to wet and bond with metals such as steel and copper; unalloyed lead has poor wetting characteristics.

Tin combined with lead and bismuth or cadmium forms the principal ingredient of many low-melting alloys.

Arsenical lead (UNS L50310) is used for cable sheathing. Arsenic is often used to harden lead-antimony alloys and is essential to the production of round dropped shot.

A solder is a fusible metal alloy with a melting point or melting range of 90 to 450 °C (200 to 840 °F), used in a process called soldering where it is melted to join metallic surfaces. It is especially useful in electronics and plumbing. Alloys that melt between 180 and 190 °C are the most commonly used.

Tin/lead solders, also called soft solders, are commercially available with tin concentrations between 5% and 70% by weight. The greater the tin concentration, the greater the solder’s tensile and shear strengths. At the retail level, the two most common alloys are 60/40 Sn/Pb which melts at 370 °F or 188 °C and 63/37 Sn/Pb used principally in electrical work.

It has the lowest melting point (183 °C or 361.4 °F) of all the tin/lead alloys; andThe melting point is truly a point — not a range

In plumbing, a higher proportion of lead was used, commonly 50/50. This had the advantage of making the alloy solidify more slowly, so that it could be wiped over the joint to ensure watertightness.

Terne is an alloy coating of lead and tin used to cover steel, in the ratio of 20% tin and 80% lead. Terne is used to coat sheet steel to inhibit corrosion. It is the one of the cheapest alloys suitable for this, and the tin content is kept at a minimum while still adhering to a hot-dipped iron sheet, to minimize the cost.

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