Laval University

From the SelectedWorks of Fathi Habashi

April, 2019

MetallurgyFathi Habashi

Available at: https://works.bepress.com/fathi_habashi/390/

Fathi Habashi

METALLURGY

1. Introduction

Metals and metalloids (Fig. 1) are obtained from the Earth’s crust, and metallurgyis the art and science of obtaining these materials from ores and their fabricationinto useful products. It can be divided into two principal fields: mineral processingand metal processing.

2. Mineral Processing

This field involves the treatment of ores to get metals (Fig. 2). It involves twodistinct operations: the first is physical called mineral beneficiation or mineraldressing, and the second is chemical called extractive metallurgy. Both operationsare overlapping since, in some cases, a physical method of separating the compo-nents of the material processed is inserted in the scheme of metal extraction. Infew cases, the mineral raw material is directly subjected to chemical treatmentwithout being beneficiated.

2.1. Mineral Beneficiation. Mineral beneficiation is concerned with theenrichment of ores and separation of unwanted gangue minerals so that the sub-sequent treatment to get the metals by the extractive metallurgist is moreefficient. The beneficiation engineer uses only mechanical, physical, and physic-ochemical methods for conducting his operations, which are all done at normaltemperature and pressure. These operations can be divided into two distinctsteps:

Liberation. In this operation, the rock is broken down by mechanical meansso that the individual mineral components become independent of each other, thatis, each is detached or liberated.

Separation. In this operation, the valuable minerals are separated fromthe rest by means of physical and physicochemical methods, making use of differ-ences in specific gravity, magnetic properties, and so on.

There is a group of some 300 minerals that are used as such or as a rawmaterial for the chemical or other industries, that is, they are not used for theproduction of metals. These are known as “industrial minerals.” They may ormay not be beneficiated. For example, clays, sands, and limestone are used in theconstruction industry. Sulfur, phosphate rock, and fluorite are used in the chem-ical industry. Diamonds and other precious and semiprecious stones are used injewelry.

2.2. Extractive Metallurgy. While the beneficiation engineer uses onlymechanical, physical, and physicochemical methods, the extractive metallurgistuses chemical methods. Another important difference is that while all benefi-ciation operations are conducted at normal temperature and pressure, extrac-tive metallurgical processes are seldom conducted at ambient conditions—usually

1

Kirk-Othmer Encyclopedia of Chemical Technology. Copyright © 2019 John Wiley & Sons, Inc. All rights reserved.DOI: 10.1002/0471238961.1921182208091910.a01.pub2

2 METALLURGY

Li

Na

Be3

11

Mg12

Al13

K19

Ca20

Sc21

Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

B C N O F Ne5 6 7 8 9 10

H He1 2

Si P S Cl Ar14 15 16 17 18

Rb37

Sr38

Y39

Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

Cs55

Ba56

*La57

Fr87

Ra88

**Ac89

Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn72 73 74 75 76 77 78 79 80 81 82 83 84

Ce58

Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu59 60 61 62 63 64 65 66 67 68 69 70 71

Th90

Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lw91 92 93 94 95 96 97 98 99 100 101 102 103

85 86

4

Typical metals

Transition metals

Horizontal similarity

Vertical similarity

*Lanthanides

**Actinides

Vertical and horizontalsimilarity

Less typical metals

Metals

Inner transition metals

Metalloids

Monatomic

Nonmetals

Covalent

Fig. 1. Metals and metalloids.

Mineralbeneficiation

(physical)

Extractivemetallurgy(chemical)

MetalOre

Industrial minerals

Fig. 2. Mineral processing: metals from ores.

at high temperature, and sometimes also at high pressure. An extractive metal-lurgist must have a good knowledge of:

• Chemistry. Physical, electro, organic, and analytical• Mineralogy. Crystallography and the properties of minerals• Engineering. Mathematics, physics, economics, and computer applications.

The border area between chemistry and mineralogy is mineral chemistry,that is, inorganic chemistry (known in French as chimie minérale), and thatbetween chemistry and engineering is chemical engineering. Extractive metal-lurgy is thus related to all of these disciplines. It is also closely related to chemicalindustry, for example, fertilizers and industrial gases. Extractive metallurgy,therefore, is concerned with the chemical methods for treating ores to recovertheir metal values in a pure form. It is one of the oldest branches of chemistry.

METALLURGY 3

In its modern form it is broadly divided into three areas: pyro-, hydro-, andelectrometallurgy.

Pyrometallurgy. This is the oldest sector of extractive metallurgyand involves dry methods usually conducted at high temperature, such as oxi-dation, reduction, chlorination, melting, and slagging, and often involvingthe melting of the minerals and the separation of the valuable components in theliquid state. Typical ores treated by this technology are those of iron, copper,and lead.

Hydrometallurgy. This is a relatively new sector of extractive metallurgyand involves the wet methods, usually conducted at room temperature or nearthe boiling point of water. It includes the leaching of ores or the precipitation of ametal or its compounds from aqueous solutions, as well as methods of isolationand purification such as ion exchange and solvent extraction. Typical ores treatedby this technology are those of gold, uranium, and aluminum.

Electrometallurgy. This is the newest domain of extractive metallurgyand involves all processes based on the use of electric current for metal recoveryor refining either in aqueous solution or in a fused salt. Typical metals producedby this technology are aluminum, copper, and zinc.

These areas, however, cannot be considered isolated one from the other,because a combination of these processes is generally used in the productionof a single metal. Thus, bauxite, the most important aluminum ore, is alwaystreated by a hydrometallurgical method, but the final metal production step isachieved by electrometallurgical technique. On the other hand, uranium oresare also treated by hydrometallurgical technique, while the metal productionis achieved by pyrometallurgical methods. Also, there are different routes forextracting the same metal. Thus, nearly 80% of the zinc produced annually isby the hydrometallurgy–electrometallurgy route, while the remaining 20% isproduced by pyrometallurgical technique. In the case of magnesium, the amountsare nearly equal.

This classification of pyro-, hydro-, and electrometallurgy is, nevertheless,convenient because each field has its own types of equipment, techniques, andtheoretical basis. Thus, the hydrometallurgist is concerned, for example, with thedesign of leaching tanks, pressure reactors, decantation and filtration systems,and pumps for transportation of aqueous solutions. He/she would also be con-cerned with reaction kinetics and the chemistry of ions in aqueous solutions. Thepyrometallurgist, on the other hand, is mainly concerned with fuels, furnaces,refractories, and molten materials such as matte, slag, or metals. He would alsobe interested in thermodynamics, and reactions between solids and gases at hightemperature, handling of hot gases laden with dust, and so on. The electrometal-lurgist must have a strong knowledge of electrochemistry and electrode reactions.He/she would be concerned with the design of electrolytic cells, electrodes, purifi-cation of solutions and recycling, fused salts, and so on.

All extractive metallurgists, whether in the hydro-, pyro-, or electrometal-lurgy area, are interested in the design of new processes as well as the analysisand improvement of those already existing to increase yields and to lower pro-duction costs. Sometimes, the term process metallurgy is introduced to cover themathematical modeling of the different areas of metal extraction, for example,flow of fluids (gases, aqueous solutions, suspensions, molten materials, etc) and

4 METALLURGY

Ore

Liberation

Separation Undesired minerals(gangue)

Valuable minerals

Hydrometallurgy Pyrometallurgy

Electrometallurgy

Metal

Metal Metal

Mineral beneficiation(physical)

Extractivemetallurgy

Fig. 3. An approximate scheme for the extraction of metals from ores.

heat transfer. It is basically the application of chemical engineering principles tometallurgical processes.

Extractive metallurgy is based on three elements:

• Chemical reactions of the processes taking place• Equipment where reactions take place• Flow sheet, that is, movement of material from one reactor to the other.

An approximate scheme for the extraction of metals from ores is shown inFig. 3.

3. Metal Processing

Once a metal is obtained by the extractive metallurgist, it is taken over by othermetallurgists for processing into finished products for the different industries.This field involves the fabrication of marketable products from metals. Metallur-gists working in this field have a strong background in physics and the mechanicalproperties of matter. The major divisions in this field are physical metallurgy,engineering metallurgy, mechanical metallurgy, and powder metallurgy (Fig. 4).

3.1. Physical Metallurgy. This field includes vast areas of studies. Forexample:

• Metals. Their physical and mechanical properties• Heat treatment. Heating metals to a certain temperature followed by rapid

cooling (quenching) to improve the mechanical properties

METALLURGY 5

Powdermetallurgy

Mechanicalmetallurgy

Metallic productsto market

Engineeringmetallurgy

Physicalmetallurgy

Metal

Fig. 4. Metal processing.

• Alloys. Their production, their physical, and their mechanical properties• Crystallography. Studying the crystal structure of metals and alloys using

X-rays• Metallography. Studying the crystal structure of metals and alloys using

the optical microscope• Corrosion. Studying the influence of the environment on metals and alloys• Wear. The abrasion resistance of metals• Fracture. The grain size and defects in metals on breaking.

3.2. Engineering Metallurgy. This branch of metallurgy involvesthe processing and handling of metals in the molten state such as castingand welding.

Casting. Metals refined in the molten state are usually cast into ingots,that is, poured into suitable molds and allowed to solidify. To achieve this,the metal must be sufficiently superheated above its melting point so that itwill not solidify before it is poured into the mold. If this operation is not carriedout properly, ingots with undesirable defects will result. The following typesof defects may take place.

• Cavities. When metal is poured into a mold, the outer skin freezes rapidlyas it comes in contact with the cold mold wall, forming a shell of solidi-fied metal with a molten interior. If the top also freezes, the remainingmolten metal will be confined in a closed rigid box. On cooling and solid-ification, all metals (except bismuth) contract, that is, the solid will occupyless volume than the molten metal. This leaves a void in the finished ingot.This void is usually filled with gases which had been dissolved in the moltenmetal and released on cooling. The upper portion of the ingot must be cutaway and scrapped.

• Dendrite crystals. Metal crystals in the form of dendrites tend to grow atright angles to the walls of the mold and form planes of weakness at their

6 METALLURGY

junction. Such a product is objectionable because it tends to tear apart whenrolled.

• Segregation. On slow cooling, the first crystals of metal that separate usu-ally contain any remaining impurities in the melt. If these impurities arelighter than the metals, they tend to float to the surface, and in doing sothey are segregated as individual micro phases.

To avoid the defects outlined above, the metal is usually allowed to freezeas it is poured so that there would be no more than a small pool of liquid metalpresent. Such a procedure would almost completely eliminate cavity formation.Also, freezing the metal rapidly to form small crystals prevents the growth oflarge dendrites. Some metals, for example, steel, pig iron, copper, lead, zinc, nickel,gold, silver, tin, and antimony, can be freely exposed to air when molten. Others,for example, magnesium and uranium, will oxidize rapidly with ignition if themolten metal is exposed to air. These metals must be cast under a protective layerof molten flux or in an inert atmosphere. High melting point metals, for example,tungsten, are very difficult to melt and cast; they are usually compacted by powdermetallurgical methods.

One important modern development of casting has been the invention of thecontinuous casting machine (Figs. 5 and 6). In this technique, the molten metal

Molten steel

Water-cooledmold

Water sprays

Starting bar

Supporting rolls

Straightening rolls

Slab sizingCutter

Fig. 5. Continuous casting system.

METALLURGY 7

Fig. 6. A roll of red-hot steel produced by continuous casting.

is continuously fed from a reservoir and is allowed to solidify rapidly in a moldso that at any time there is only a small pool of molten metal present at the topof the ingot. As the solidified ingot emerges, it is grasped by a set of rolls thatregulate its downward progress. The contraction of the freezing metal causes it topull away from the mold walls. Beneath the pinch rolls is an oxyacetylene flame,which cuts the emerging ingot into convenient lengths. The process is well adaptedto large-scale production. It produces much less scrap than in batch casting, thereare no cavities because the metal is frozen as soon as it is cast, and is a small grainsize solidified product because of rapid cooling. It is also more economical becausethe molten metal is directly shaped, whereas in ingot casting, the solidified ingotmust be reheated before shaping.

Die casting is a casting method in which molten metal is forced by a pumpunder considerable pressure into the cavity of a metal mold. This is usuallyapplied for low-melting metals such as zinc, aluminum, and magnesium. It isa very fast and much more economical method for casting a large number ofarticles in a short time.

Welding. Welding is the connection of two pieces of metal by fusion. Theprocess of electric welding consists of transmitting electrical energy from one pointto another, which is converted into heat. This heat is used for the fusion togetherof metallic materials. A metal electrode is melted in this way, and the two metallicparts are connected together. To protect the molten metal from oxidation, easilyfusible inert mineral material called flux is usually added to the electrode so thatwhen the electrode is hot, the flux immediately melts and floats on the surface ofthe molten metal. Welding electrodes can be coated on the outside with the fluxesfor batch operation, or filled inside long hollow electrodes for continuous welding.Sometimes the flux is not enough to protect the molten metal from oxidation, anda nitrogen atmosphere is necessary for conducting the welding. For some metalsnitrogen is not a suitable protective atmosphere since nitrides may be formed, for

8 METALLURGY

example, welding of titanium. In such cases, argon should be used. The weldedjoint is usually the weakest part in a structure, and therefore great care is devotedto welding technology.

3.3. Mechanical Metallurgy. This branch of metallurgy involves the pro-cessing of metals in the solid state. Metals are usually cast in the form of ingots.They cool quickly on the surface and slowly through the center. For this reason,they must be placed in furnaces called soaking pits where they are heated andbrought to uniform temperature throughout. Hot metal is fairly soft and can besqueezed into various shapes under strong pressure. The operations commonlyused are forging, rolling, extrusion, piercing, and drawing.

Forging. In this method, the metal is hammered or pressed into requiredshapes. The pressure may be applied by means of a hydraulic press (30,000 tons)or drop hammer having moving parts as heavy as 30 tons (Fig. 7).

Rolling. The hot ingots are passed between powerful steel rolls where theyare rolled on separate mills into slabs, blooms, and billets (Figs. 8 and 9). Thesethree semifinished shapes then go to finishing mills. There, they are rolled asfollows:

• Slabs. These flat metal shapes are called plates when reduced to about6 mm. Thinner forms are strips or sheets, and when rolled much thinnerthey are called foils. These are used mainly for fabricating equipment fortransportation or for home needs. Sheets and plates are also used to makewelded pipe and tubing.

• Blooms. These are square-shaped bars of varying sizes that can be shapedinto beams and other forms for structural purposes.

• Billets. These are produced from blooms to make bars and rods in round,square, or other shapes in varying sizes from which tools, bolts, rivets,cables, wires, and so on are made.

Fig. 7. Processing metals in the solid stage: a 1500-ton forging press.

METALLURGY 9

Slab Bloom Billet

Fig. 8. Rolling mills (principle).

Fig. 9. Rolling plant.

In the earlier stages, rolling is often done while hot, and in the later stageswhen cold. Cold rolling hardens the metal and after some reduction it becomestoo hard to economically roll any thinner. At this stage it is annealed (heated) tosoften it for further rolling, and these alternate operations are continued until thespecified gauge is reached.

Extrusion and Piercing. Extrusion and piercing are the principal methodsof fabricating structural shapes, tubes, and so on from solid billets. In extrusion(Fig. 10), a heated billet is placed in a powerful hydraulic press, and a steel man-drel is pushed through it, and the remaining metal is then forced through a dieand around the mandrel. In piercing (Figs. 11 and 12), the heated billet is rotatedand fed forward over a pointed plug. The tube shells are then drawn down to therequired size through a succession of dies.

Drawing. In the process of drawing, the cross section of a metallic rod isreduced by drawing through a die and depends for its success on the propertyof ductility, which permits the metal to undergo considerable elongation. It ismainly used for wire manufacture, the raw material being rod about 6 mm diam-eter, which is being rolled down from billets or extruded. It is then drawn succes-sively through smaller holes in steel plates (dies), each hole through which thewire is drawn reducing its diameter. The dies are subjected to much wear and,accordingly, the orifices are usually composed of tough material such as tungstencarbide. For the production of very fine wire, industrial diamonds are employed.

10 METALLURGY

(a) (b)

(c) (d)

A B

C

Fig. 10. Extrusion: (a) Heated billet A placed in hydraulic press; (b) Outer ram B presseson the billet and holds it firmly in place; (c) The inner ram C pierces the billet and projectsthrough the die, at the same time ejecting part of the metal displaced; (d) The pressureof the outer ram on the billet is increased, forcing the metal through the annular openingbetween the inner ram and the die.

Fig. 11. Piercing: Heated billets are passed between two convex-tapered work rolls whoseaxes are not quite parallel. This imparts a helical rotary motion to the billet as it is piercedby a pointed mandrel.

In order to reduce friction, a lubricant is used. Drawing tends to make wire hardand somewhat brittle; this effect is relieved by annealing.

3.4. Powder Metallurgy. The powder metallurgist is specialized in pro-duction and handling metal powders and making solid industrial products outof them (Fig. 13). Powdered metals are produced by a number of processes:electrolysis, hydrogen reduction from solutions, reduction of oxides, atomization,milling, and grinding. They are available in various forms: spherical, dendritic,

METALLURGY 11

Fig. 12. Production of a pipe by piercing a red hot billet.

Fig. 13. Powder metallurgy: fabrication of metallic articles from metal powder.

spongy, irregular, and as flakes. There are also a number of alloy powders thathave gained technical importance.

In powder metallurgy, powders are compacted into special shapes, whichare then heated and sintered. An increasing number of small parts, for instance,gears, bearings, bushings, nuts, padlocks, and ordnance parts, are made thisway. In most cases, this way is more economical than by machining the partsfrom wrought or cast metal. Porous, oil impregnated bearings and porousfilters, the pore size being controlled by the size of spherical powder particles,are made by powder metallurgical technique. In recent years, processes havesuccessfully been perfected to roll metal powder into sheet and strip and toextrude tubing direct from powder. Metal powders, for example, copper and goldbronze powders, are being used as pigments in the surface coating industry andin graphic arts.

12 METALLURGY

4. Metallurgy and the Chemical Industry

Extractive metallurgy is closely related to the chemical industry:

• During exploration for petroleum, it is common that mineral depositsare discovered. As a result, an extensive portion of extractive metallur-gical research is conducted within the research activities of petroleumindustry, and many petroleum companies now operate metallurgicalplants.

• Products of the chemical industry may be raw materials for the metallur-gical industry, and vice versa.

Quite often, inventions made in the chemical plants were adopted laterin the metallurgical industry. For example, when the Austrian chemist KarlJosef Bayer (1847–1904) invented the process known by his name to producealuminum hydroxide from bauxite about a 100 years ago, the work was done ina Russian chemical plant engaged in supplying chemicals for the textile indus-try. Now, the process is a major step in the production of metallic aluminum.Further, the nickel carbonyl process used today on a large scale for refiningnickel was discovered in an alkali manufacture plant in England. Thanks tothe keen observation of Ludwig Mond (1839–1909), who noticed that a valvemade of nickel in a carbon monoxide pipe was corroding. When the matter wasinvestigated in detail, it was found that a gaseous nickel compound, Ni(CO)4,was formed at low temperature and decomposed at high temperature, hencethe process of refining nickel—a process that is used today on an industrialscale.

4.1. Sulfuric Acid Industry. For many years, sulfuric acid was producedby the thermal oxidation of pyrite. The iron oxide residue known as pyritecinder formed after oxidation was usually shipped to metallurgical plants forisolating traces of metal values such as copper, cobalt, and zinc before usingthe iron oxide to make iron. Recently, however, the process became economicallyunfavorable as compared to the process using elemental sulfur for makingH2SO4.

4.2. Iron and Steel Industry. Coke is an essential material for themanufacture of iron in the blast furnace where it is used both as a fuel and areducing agent. It is manufactured by heating coal in a special furnace in theabsence of air. Coke-manufacturing plants are usually located in iron works;gases and volatile liquids produced from this operation are collected becausethey are a valuable raw material for the chemical industry. The gases containappreciable amounts of hydrogen, which can also be used for making ammo-nia, while the volatile liquids are a source of benzene, toluene, naphthalene,anthracene, and numerous other organic compounds. In Linz, Austria, forexample, the steel works VÖEST is on the opposite side of the Danube wherethe chemical complex Linz Chemie is situated, which uses coke oven gas for NH3synthesis.

4.3. Petrochemical Industry. A plastics manufacturer may also be aproducer of metallic magnesium: the plastics industry uses chlorine for trans-forming hydrocarbons into chlorinated hydrocarbons producing at the same time

METALLURGY 13

waste hydrochloric acid. This in turn is used in the production of magnesiumby the fused salt electrolysis of MgCl2. The circuit is closed because duringthis electrolytic step, chlorine is generated and is returned to the plasticsplant.

4.4. Nonferrous Plants. Producers of copper, lead, and zinc usually oper-ate sulfuric acid plants because sulfur dioxide is produced during the processingof ores of these metals. They usually ship it to a nearby phosphatic fertilizer man-ufacturer. Some nickel and cobalt producers have their own ammonia synthesisplants since ammonia is used to extract these metals from their ores. At the sametime they produce ammonium sulfate fertilizer as a by-product, for example, atSherritt-Gordon plant in Fort Saskatchewan. Aluminum producers usually oper-ate their own sodium hydroxide plants to produce the sodium hydroxide neces-sary for treating the bauxite and their own hydrofluoric acid plants to produceHF necessary for the production of aluminum fluoride needed for the electrolyticcells.

4.5. Other Industries. Steelmakers and some nonferrous industries havetheir own air liquefaction plants to make oxygen for use in their processes, andsome produce nitrogen for the ammonia synthesis industry. Some metallurgicalplants electrolyze water to use the oxygen produced for the oxidation of sulfideconcentrates and the hydrogen for the ammonia synthesis. Some hydrometallurgi-cal plants treating sulfide concentrates produce elemental sulfur for the chemicalindustry, for example, the pressure leaching of zinc sulfide concentrates by Com-inco in Trail, British Columbia.

Many pigments are produced by the metal industry. Lead oxide (red lead)and zinc oxide are produced in lead–zinc refineries. Iron oxide pigment, Fe2O3,is produced in steel industry in the pickle solution regeneration plant. Ilmenitereduction in electric furnaces, for example, at Sorel in Quebec, produces a titaniumslag, the raw material for producing TiO2 white pigment.

The metal industry usually produces metallic salts needed by other indus-tries. For example:

• Aluminum sulfate. Produced by aluminum companies by dissolvingAl(OH)3, an intermediate product of aluminum production, in H2SO4followed by crystallization. It is used in water-treatment plants.

• Copper sulfate. A by-product of electrolytic copper refining; used in agricul-ture as herbicide.

• Nickel sulfate. A by-product of electrolytic copper refining; used by the elec-troplating industry.

The metal industry may also be the supplier of catalysts needed by the chem-ical industry, for example, Al2O3, V2O5, and platinum. The copper industry is themain supplier of arsenic oxide, which is used in making wood preservatives. Theoxide is volatilized during smelting of copper concentrates, which usually contain0.5–2% As. Arsenic oxide collected in the gas filtration system is then mixed withCuSO4 and sodium dichromate to form chromated copper arsenate preservative.Table 1 gives a summary of the different fields of metallurgy.

14 METALLURGY

Table 1. Summary: Fields of Metallurgy

Field Description Example of topics

mineralprocessing

mineral bene-ficiation

theory and practice ofliberation of mineralsfrom ores and theirseparation by physicalmethods at ambientconditions

crushing and grinding,magnetic and electricalmethods, flotation, etc

extractivemetallurgy

Chemical methodssometimes at hightemperature andpressure for treatingores to recover theirmetal values in a pureform

leaching, precipitation,electrolysis, oxidation,reduction, etc

metalprocessing

physicalmetallurgy

study of physicalproperties of metalsand alloys, preparationof alloys

crystal structure, effect ofimpurities,metallography, heattreatment, etc

engineeringmetallurgy

processing of metals inthe molten state

casting, welding, etc

mechanicalmetallurgy

processing of metals inthe solid state

forging, rolling, extrusion,and piercing

powdermetallurgy

processing of metalpowders into finishedproducts

preparation of metals inpowder form, hotpressing, etc

BIBLIOGRAPHY

“Metallurgy, Survey” in ECT 4th ed., Vol. 16, pp. 313–320, by Brent Hiskey, Universityof Arizona; Published Online: 4 December 2000; “Metallurgy” in ECT 5th ed., Vol. 16,pp. 125–132, by Brent Hiskey, University of Arizona.

CITED PUBLICATIONS

F. Habashi, Metals from Ores. An Introduction to Extractive Metallurgy, MétallurgieExtractive Québec, Québec City, Canada, 2003. Distributed by Laval UniversityBookstore “Zone”. www.zone.ul.ca.

GENERAL REFERENCES

F. Habashi, ed., Handbook of Extractive Metallurgy, 4 Volumes, Wiley-VCH, Weinheim,Germany, 1997.

F. Habashi, Extractive Metallurgy Today. Progress and Problems, Métallurgie ExtractiveQuébec, Québec City, Canada, 2000. Distributed by Laval University Bookstore “Zone”.www.zone.ul.ca

FATHI HABASHI

Laval University, Quebec City, Canada