08_Other Significant Alloys

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Suranaree University of Technology May-Aug 2007

Other significant alloysOther significant alloys

Subjects of interest

Objectives / Introduction

Lead and its alloys

Tin and its alloys

Chromium and its alloys

Cadmium and its alloys

Antimony and its alloys

Bismuth and its alloys

Lecture 8

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ObjectivesObjectives

This chapter provides basic information of other

significant non-ferrous alloys such as alloys of lead,

tin, chromium, cadmium, antimony, bismuth.

This includes its source, nature, properties which

are related to its applications.


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IntroductionIntroduction

Apart from alloys ofAl, Mg, Cu, Zn, Ti,

Ni, there are a variety of other alloys,

which have been used for other

applications with however in a smallerextent but still important.

There are for example: Pb, Sn, Bi, Sb, Cd

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Lead and its alloysLead and its alloys --Applications

Lead sheet

Lead sheets are used in x-ray and gamma-ray

protection, building construction of roofing and

flashing, shower pan, flooring, vibration dampingand soundproofing.

Lead pipe

Lead pipes are made from pure leadmetal (99.97% min.) or lead alloys

- Readily fabricated by extrusion.

- Excellent corrosion resistance

applications in chemical industry.

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LeadLead-- Resources

Lead (Pb) is found in many countries but mainly produced from

USA, Australia, Mexico, Canada and Germany.

In Thailand, found in Kanchanaburi (cerussite).

Normally found in the forms below (or the combination of both)

1) Lead sulphide (PbS) or called Galena orGalenite.

2) Lead carbonate (PbCO3) called Cerussite.

Also found in the form ofanglesite (PbSO4) andpyromorphite

(2Pb3P2O5.PbCl2) but not commercially significant.

Normally containAg, Zn, Ni, Co as impurities.

Galenite Cerussite

webmineral.com

Anglesite Pyromorphite

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LeadLead Extraction of lead

Concentrated Pb ore is produced

through flotation process and it is then

roasted at T ~450-700oC with air blow

to reduce sulphur.

2422

72 SOPbSOPbOOPbS +++

Other reactions also occur due to the

existence ofZn.

222

3

2422

72

SOFeOOFeS

SOZnSOZnOOZnS

++

+++

The obtained Pb ore (with decreased amount of

sulphur) is then reduced in the blast furnace or

reverberatoryby mixing with coke oriron.

Ore (PbS)

Concentration

Flotation

RoastingAt T ~ 450-700oC

with air blowing

Blast furnace or

reverberatory

Lead

Mixed with coke

T ~ 900oC

Reduce

sulphur

Pyrometallurgical process

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LeadLead Reduction of lead in blast furnace

FeSPbFePbS

COPbCOPbO

COPbCPbO

++

++

++

2

Reduction of leadis carried out in

a blast furnace at T~ 900oC.

The obtained ore is mixed with flux

(limestone) and coke (~10%) whichwill reduce PbOorPbSinto lead.

Lead blast furnace

During reduction, matte or speiss

(mixtures of sulphide ofFe and Cu)

form on top of the molten lead.

The molten leadforms at the bottom

of the furnace is then drained out.

Charge hopper

Exhaust off-take toafterburne

Charge

Cool water

Charge hole

Average level

of charge

Shalf

www.osha.gov

Hot water

Cold water

Hot water

Slag layer

Water jacket

Working height ofcharge 2.4-3.0 m

Lead spoutDam

Drain tapLoad layer

Slag spout

Crucible

Tuyere

Diameter at Tuyeres

68 120 cm

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LeadLead Refining of lead

As, Bi, Sb, Sn, Cuare typical impurities in lead high

hardness but low toughness.

Removal ofSn, Sb, As is called softeningby heating at

500oC. They will form oxides (Dross) which float on the top oflead due to their lower densities. easily remove.

Cuis removed by mixing molten lead with PbSto give Cu2S

and Pb.

PbSCuCuPbS ++ 22

Biis removed via electrolysis process using PbSiF6and H2SiF6acid as

electrolyte, givingpure leadat cathode and the remained Biat anode.

Desilveringis carried out using two methods : Pattinson and Parkes.

Pattinson: High purity lead is extracted at the eutectic temperature (304oC).

Parkes: Stirring Zn rodin molten lead to dissolveAgon its surface. Let it

cool down to form crust and then remove.

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LeadLead - Physical properties and

application

PbLead

CCP

207.2

Crystal structure Cubic closed packed

Atomic number 82

Atomic weight 63.546Density (g.cm-3) 11.34

Melting point (oC) 327.35

Boiling point (oC) 1740.0

82

High density. Good corrosion resistance

Low strength but high ductility.

Lubricating properties.

Lead ingots of 99-98 % purity can be

produced with Sb, Sn, As, Fe, Bi, Cu

as impurities.

Used in batteries, chemicalapplications.

www.gravitaindia.com

Lead screws


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Lead alloysLead alloys - Classification

Lead alloys can be classified as follows:

1) Calcium-lead alloys

2) Antimony-selenium lead alloys

3) Antimony-lead alloys

4) Copper lead alloys

5) Tin-lead alloys

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Classification -Antimony lead alloys

AntimonySb is partially soluble in lead and give a eutecticreaction at 250oC at 11.2% Sb.

+L

Hypo-eutectic structure

(11.2%Sb) consists ofand eutectic

phases.

Sb addition gives highereutectic

structure more strength / hardness.

Used in batteries and cable wire coating.Sb-Pb phase diagram

6.5% Sb (Hypo) 12.25% Sb (Hyper)11.5% Sb (eutectic)Tapany Udomphol


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Classification - Tin-lead alloys

Tin Sn can form solid solution ( phase upto 19.2% Sn) withlead and give a eutectic reaction at 183oC at 61.9% Sn.

Hypo-eutectic structure

(61.9%Sn) consists ofand eutectic

phases.

Sn addition also gives strength andhardness and lowerTm , fluidity .

Used as soldering materials.Sn-Pb phase diagram

70% Sn 50% SnEutectic 60% SnTapany Udomphol


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Tin alloysTin alloys - Introduction

Tin is found in the form of oxide (SnO2) as vein tin or

stream tin. Its colour is in white and grey.

Found in Malaysia, Indonesia, (Thailand), Myanmar, China,Australia. Note: Most resources are almost used up.

Easily extractedbecause it is already in its oxide form.

Used for applications such as in soldering metals.

Tin oxide

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Tin alloysTin alloys - Extraction

Ore(SnO2)

Concentration

Mixing with

coke and flux

T ~ 1350oCBlast furnace or

reverberatory

Tin

22

22

2

22

22

2

COSnCSnO

COSnCOSnO

COCCO

COOC

++

++

+

+

The ore is first concentrated and then mix with

coke and flux (CaCO3) in the blast furnace

(reverberatory) at T~1350oC.

CaCO3 will decompose at 1350oC to give CaO,

which will catch high melting point oxides (SiO2,

FeO) to form slag (low Tm). Molten tin at the bottom of the furnace is

drained out forfurther refiningwhile slag on its

top surface is skimmed out Sn will be

separated again.Tapany Udomphol


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Tin alloysTin alloys - Refining

Fire refining

Electrolytic refining

For tin with Fe


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TinTin - Physical properties

SnTin

118.7

Crystal structure FC Tetragonal (white tin)

Cubic (grey tin)

Atomic number 50

Atomic weight 118.7

Density (g.cm-3) 7.298 (white tin)

5.765 (grey tin)

Melting point (oC) 231.9oC

50

High corrosion resistance. Low strength but high ductility not suitable for

structural materials.

Lubricating properties.

Transformation from white to

grey tin occurs at T = 13.2oC,

giving a change in densityfrom

7.3 to 5.76 g/cm-3. tin pest.

Tin pest

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TinTin - Applications

Tin is used as coatingfor structural steels for corrosion protection. Used as an alloying element.

Soldering materials and in electrical applications.

Tin or tin foil for food containers and wrapping.

Tin alloys are also used as vases, candle stands, jewellery.

Electrical

applicationsSoldering

Tin foils for capacitors

www.winter-wolff.com

Steel can coated with tin.

Tin as jewellery

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Tin alloysTin alloys Classification

Tin alloys are used as soldering materials.

- 30-50% Pb Sn alloy- 5% Sb Sn alloy

- 5%Ag Sn alloy

Tin alloys (pewter) are used as vases, candle stands, etc.

- 7% Sb 2% Cualloys (40% ductility, 9.5 HBN).

Tin alloys are used as bearingcalled Babbit

- 10-15% Sb 3-4% Cu 60-90% Sn alloys.

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CadmiumCadmium

Cadmium has a bluish white colour and appears

in a form ofCdS.

Normally obtained from zinc extraction process. Hardness Sn


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AntimonyAntimony Physical properties and

applications

Antimonyhas a silvery white colour and found as stibnite Sb2S3. Hard and brittle and cannot be deformed at RT.

React with oxygen at high temperature, giving Sb2O3 (white powder).

Used as alloying element in Sn and Pb alloys, providing better

fluidity and hardness.

Applications: storage battery plates, soldering materials, shrapnel

bullets and bearing or babbit.

SbAntimony121.76

Crystal structure Trigonal

Atomic number 51

Atomic weight 121.76

Density (g.cm-3) 6.62

Melting point (oC) 630oC

Boiling point (oC) 1140oC

51

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AntimonyAntimony - Extraction

Ore(Sb2S3)

Liquation

Roasting

Blast furnace

Sb

T ~ 500-600oC

Antimony ore is concentrated by

liquation process (heating at 500-600oC)

to give low Tm antimony (85-90%)separating from the ore.

Roasting at 500oC to convert to oxide

Sb2O4, which is then reduced to Sb metal

by using charcoalwith flux(Na2CO3) inthe blast furnace.

S, Pb and Fe appear as impurities in the

obtained Sn metal. good enough for

alloying. Higher purity is achieved by electrolytic

process.

T ~ 500oC

Charcoal

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BismuthBismuth Physical properties and

applications

Bismuth is found as native Bismuth in nature orBismuth ocherorBismite (Bi2O3).

Low melting point used as alloying elements to

lowerTm, soldering materials and thermoelectric

applications -fuses. Provide thermal expansion during solidification.

Hard and brittle similar to Sb.

BiBismuth209

Crystal structure Monoclinic

Atomic number 83

Atomic weight 209

Density (g.cm-3) 9.80

Melting point (oC) 271oC

Boiling point (oC) 1436oC

83

Fuseswww.tableauperiodique.be

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BismuthBismuth - Extraction

Bismuth ore (Bi2O3) is reduced using

charcoal and CaCO3 with fluoride and

Na2CO3 as flux.

Roastingshould be applied if the ore is a

sulphur type.

Higher purity Biis produced by liquation

to give molten Biat the bottom of the

furnace.

For higher purity, bismuth is dissolved in

nitric acidto give Bi(NO3)

3and then

precipitate as Bi(OH)2NO3. washed and

heated to givepure Bi oxide. reduced to

give Bi metal.

Ore(Bi2O3)

Reduction

Liquation

Bi

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ReferencesReferences

,F, 2536,, ISBN

974-582-155-1.

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08_Other Significant Alloys

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