Steel Past Future

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La Revue de Mtallurgie-CIT Novembre 2004 937

The Steel Industry today is a large and capital-

intensive industry, which has reached a high level

of sophistication, complexity and efficiency.

This benefits the consumer, as the price of steel has

been steadily decreasing, which helps bring downthe price of consumer goods. Steelmaking has

therefore become focused on a small number of

process routes, which connect together standard,

mainstream and high performance technologies.

It seems therefore that the industry is very mature

and that little leeway is available for change,

as past progress has already brought it close to

physical limits.

This is a view of the Steel Industry, which is

contemporary and central to the strategy of this

business. A Steel Mill that does not operate withinthe paradigms of the mainstream state-of-the art

technologies will be doomed by economic troubles

and eventual bankruptcy.

However, Steel or Iron have remained at the core of

civilization for roughly 3,000 years and the model of

the Steel Industry discussed above is only roughly

30 years old. There have been many more different

models in the past, from Prehistory to History, and

it is likely that even more will emerge in the Future.

Indeed, it is reasonable to assume that Iron and

Steel will continue to be used for a very long time.

The present paper discusses Steel from the

standpoint of an Enduring Material and the Steel

Industry from that of a Cumulative Technology and

explores how these two important concepts have led

to industry changes in the Past and will most likely

contribute to more changes in the Future.

From an historical standpoint, iron was initially

produced from meteorites, but very quickly moved

on to the reduction of ores.

The reduction technology went from a solid-state

route to a molten state one and, because carbon

was used as the reducing agent, pig iron was

invented in addition to the pure iron which was

commonplace before. Steel was the next concept,also made initially in the solid state and then

in the liquid state. The modern world brought

recycling into the picture, because of the sheer size

of recycled streams.

From an economical standpoint, the drivers for

changes were mainly the demand of the economy :

From weapons, pots and pans to machines and

ubiquitous consumer goods. Looking at a shorter

timescale, i.e. the end of the 20th century, other

drivers were instrumental in bringing change, such

as meeting the steady drop in the market price ofsteel, improving quality and helping steel be better

integrated and used in products (steel solutions or

customer engineering). The progress thus generated

made it possibly to become and remain

environmentally friendly.

In the future, what will be the drivers for change ?

Mass production at an even larger scale, to meet

the growth of the world population and the

equalization of the standard of living, in spite of a

dematerialization of the economy, will be a major

driver. On the other hand, Global EnvironmentalIssues, the first of which will certainly be Global

Warming, will reshuffle priorities and call for

breakthrough solutions meeting demands different

from today's.

From a technological standpoint, if one projects far

enough in the future, many new possibilities open

up, in terms of energy, processes, raw materials and

of course, also of new materials competing with

steel.

Alternative ways of making steel :Retrospective and prospective

J.-P. Birat (Arcelor)

La Revue de Mtallurgie 2004.


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938 La Revue de Mtallurgie-CIT Novembre 2004

s INTRODUCTION

Like the statue of Hercules used by Aristotle to explain histheory of causes (1) the role that iron plays in our society andour civilization has many causes. Some are contemporary,modern and even post-modern, while others are fundamental,basic, archetypical and as old as the world or as the history ofmankind.

The value of Iron and of Steel, not just to the shareholder ofthe Steel Companies or to their customers but to mankind, isrelated to the complex and ambivalent relationships that ironentertains with the physical world and the living world, withhistory and modern society. There is a tension between itsenduring and its innovative features, i.e. between the cosmo-logical, geological and historical past on the one hand and thepresent and the future on the other hand. Between eons and

time-to-market or time-to-volume! Between culture or heri-tage and change and breakthroughs

This is what we are planning to review in this article for thisjubilee issue of the Revue de Mtallurgie.

s IRON AND LIFE

Iron has been incorporated early into the fabric of life and itsrole is essential in all living things, from microorganisms tothe complex systems that mammals and men have become. Itis a trace element, as there are approximately 4 g of Fe in thehuman body, with a concentration of 415 ppm in the blood,3-380 ppm in bones and 180 ppm in tissue (2, 3). Biochemistsestablish a clear relationship between this essential role ofiron and its abundance in the Universe (cf. next section).

Iron is present in the blood of vertebrates, as the heme of thehemoglobin of the red blood cells (C34H32FeN4O4), whichtransports oxygen and CO2 between the lungs and the cells.

Iron is also present in various enzymes, called non-hemeenzymes, which also act in the exchange of oxygen within thecell by helping free one O atom from an O2 molecule and

introduce it into an amino-acid or to other molecules, thanksto a specific Fe-O interaction (4). Iron is active in the synthe-sis of DNA, in the scavenging of free radicals, in the metabo-

lic mechanism that releases energy in the cell by usingglucose (2). The prevalent biological redox states of iron areFe2+ (ferrous), Fe3+ (ferric) and Fe4+ (ferryl). The easy cyclingbetween Fe2+ and Fe3+ makes iron-bearing proteins a biologi-cal tool for manipulating individual electrons. Surplus iron isstored in the liver in proteins such as ferritin (several thou-sands of Fe atoms) or hemosiderin. Bone marrow, wherehemoglobin is synthesized, is also rich in iron. A protein cal-led transferrin transfers iron between cells (5) (fig. 1).

Iron is also important in the functioning of the brain, of theear, of the pancreas, etc. There is a competition for iron in thebody between the host and bacteria during an infection andthe production of transferrin is then accelerated, thus provi-

ding a kind of antibiotic effect.Deficiency in iron leads to anemia and a daily intake is neces-sary, at the level of 7 g for a man and 11 g for a woman (2)with a yield of roughly 25 % compared to the food content.The diet in developed countries easily provides the needsof the body, but anemia is prevalent among several millionpeople elsewhere.

Iron is therefore central to life on Earth and probably to life inthe Universe, if this is indeed an option.

Life is also part of ecosystems and iron plays an importantrole in controlling their equilibrium. For example, recentexperiments have shown that the iron (and manganese)

content of the sea in its surface layers is directly related to theteeming of life there, through the trophic chain that connectsplankton and fish. Indeed, iron is an essential nutrient ofplankton, which itself can feed large fish populations. Theissue has been seen as a possible solution path, both forincreasing the fish resource and for controlling CO2 emissionsfrom the ocean, as plankton interacts with this gas throughphotosynthesis (6 - 9). The matter of controlling GlobalWarming by using this lever, what is called "climate enginee-ring", is far from settled, however.

Fig. 1 Ferritin and transferrin molecules, the basic proteins that store and transfer Fe atoms in the human body.


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s ONCE UPON A TIME INTHE UNIVERSE

Iron, as a chemical element, was forged by nucleosynthesis inthe nuclear furnaces of the stars. Stars are nuclear fusion reac-tors, where nuclei are formed because the density of matter islarge enough for nuclear reactions to take place by nucleonaddition or fusion of nuclei. The theory of nucleosynthesis istoo complex to be explained here, but the trend is for heavierelements to be formed as the star ages (it heats up due to gra-vitational densification and reaches a temperature, expressedin millions of K, that depends on its mass). Stars will gothrough a sequence, which comprises the generation ofhelium (the present state of the Sun), then of carbon, of sili-con and possibly of iron, through the reaction :

[(Si28 + He4) + He4) + He4] Fe56+

Small stars will stop their evolution on the way, depending ontheir mass. It takes many times the mass of the Sun to enterthe club of iron-producing stars and an eventual temperaturelarger than 3 x 109 K ! (10).

Iron Fe56 is actually the heavier element that can be generatedin this manner, because this peculiar combination of 26protons and 30 neutrons happens to be very stable, whichmeans that no more energy can be released either by fission

or fusion. A massive star will thus have an onionstructure with an iron core and layers of Si, O, C,He and H. It is interesting to note that astronomersmeasure the age of stars by the ratio Fe/H (11).

From the standpoint of elements, i.e. of ordinarymatter thus excluding black matter and quintes-sence (12), the one that are most abundant in theUniverse range from hydrogen to iron in the perio-dic table (13) (fig. 2). Heavier elements, which aresynthesized by less likely nuclear reactions, aremuch fewer. The over-abundance of hydrogen andhelium is due to the fact that they were produced inthe primordial nucleosynthesis of the big bang.

The "onion" star may not be the end of the stellaradventure though, if the mass is big enough, as theincrease of the core iron mass will lead to an elec-

tron-proton fusion (-reaction), which transformsprotons into neutrons : the star collapses on itselfand turns into a supernova, the ashes of which

become a neutron star on the one hand and a stream of inter-stellar matter projected into space on the other hand Furtherdown this path may even lie a black hole!

New stars will be born from that projected material as well astheir pageant of planets. Our own solar system originated inthis way and this is the reason why iron constitutes the majorpart of the heavy telluric planets, to which our Earth belongs.Figuratively speaking, one may say that the first steelmakersoperated billions of years ago (more than 4.6 billions, the ageof the Solar System) in the core of the stars and produced all

the stock of iron atoms from which we are sampling a minutefraction for our own needs today. The Steel "industry" wasthen quite different from today's !

Metallic iron is the most abundant constituent of planet Earth(3) followed by oxygen, silicon, magnesium, nickel, sulphur,etc. (fig. 3). This stems directly from the features of nucleo-synthesis. This iron is in a liquid state mainly, alloyed withnickel in the so-called Ni-Fe core (80 % Fe, 5 % Ni, + Si, O,

Fig. 2 Distribution of chemical elements in the Universe.

Fig. 3 Proportion of elements in the Earth. Fig. 4 Internal structure of the Earth.


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S, 135-330 GPa, 3,300-5,800 K, 2,900-5,000 km from thesurface), but it is believed that at the core itself, under theconditions of temperature and pressure that prevail there

(330-365 GPa, 5,500-5,800 K, d = 10-12), it turns into a solidof a peculiar hexagonal structure, more compact than any ofthe Face-Centered Cubic and Body-Centered Cubic phasesthat metallurgists are more familiar with (3) (fig. 4).

The outer layer of the planet, however, concentrates otherlighter elements, including oxygen and sulphur, which com-bine easily with iron and other metals. The Earth crust there-fore is made of a soup of most of the chemical elements,heavier and lighters ones combined according to the laws ofchemistry and thermodynamics and spatially organized by thehappenings of geology in their grandest sense.

Iron is only the fourth most common element in the Earth

crust, at a concentration of 4.6 %, behind oxygen, silicon, alu-minum and calcium (fig. 5). Because various processes havebeen at work over geological times to transport and concen-trate some of these elements, metallogenesis has collectedmetals in specific locations known as ore deposits, whichhave been later mined by man, if they have been discovered.The most common and useful iron ores are oxides, most noti-ceably hematite (Fe2O3) and magnetite (Fe3O4) (fig. 6). In theocean, the concentration of Fe is 2.5 ppb, a very low figure[1].

Before treading into the history of mankind, one must first tellof the cosmic cataclysms where Earth-like planets haveexploded and scattered their core in the vacuum of space.These metal meteors, with a quenched structure and a com-

position in iron and nickel similar to that of the Earth core, arelost forever in space, except for the few that cross a planetary

orbit and make it to the surface. These are the siderites (fig. 7),the iron meteorites, which have provided man with his firstcontact with metallic iron, probably since the dawns of timeand, as a material for making various artifacts, in theNeolithic (3500 BC).

The role that iron plays as a core material of past and presentcivilization is directly related to these cosmological and geo-

logical storylines, which explain its abundance and, in parti-cular, the large reserves that are still available today ascompared to other resources such as oil, for example.

s ONCE UPON A TIME INPREHISTORY

Anthropology defines mankind as the species that inventedboth tools and abstract metaphysical concepts of the worldand of its own place in that world. Tools offered pragmaticsolutions for experimenting with and shaping abstractthought, so that both are closely interrelated.

Tools are made of materials and materials are extracted fromthe environment. They are actually abstracted from it in a waythat is not completely different from that of shaping philoso-phical or religious thought. The first materials industry of ourPaleolithic ancestors was thus at the same time metaphysicsand pragmatic ecology, in their first intrusive interaction withthe environment, and economy, offering solutions to meet theneeds of the group, i.e. of society. Man the hunter and thegatherer needs tools and weapons to kill his preys, butcher themeat, prepare food, make his cloths and adorn himself.Materials are bones, antlers, teeth, tusks, wood (biomaterials)but also stones, lithic material collected from the ground.Biomaterials are collected from preys, at the same time asmeat, but sometimes the priorities may have been turnedaround : a mammoth might have become more attractive forits tusks than for the organoleptic quality of its flesh.

Fig. 5 Proportion of elements in the Earth's crust.

Fig. 6 Hematite and magnetite iron ores.

Fig. 7 An iron meteorite (siderite).


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Small groups traveling to find their subsistence had limitedneeds, which they could accommodate without disruptingtheir nomadic style of living. The raw materials were thus

transformed directly into the final artifact and into the mate-rial at the same time. The technology remained simple andbased mainly on mechanical crafts, i.e. on cutting, breaking,shaving and polishing.

Some tools were used to make the tools of daily use and theyused different materials, with different properties chosen tomake them perform well in their special tool-for-making-toolcapacity.

Specialized industries developed as early as 200,000 years BCto prepare flints from rich deposits operated, mutatis mutandis,in a similar way as a modern mine. The technique known asLevallois (from an archeological site in Levallois-Perret, near

Paris) of splitting the nuclei into various blades was very effi-cient in terms of material utilization (high yield) and comple-tely mature within the episteme of the crafts of the time(fig. 8). These are the prehistory equivalent of the modernmaterials industry, especially in the way that specialized orga-nizations have dedicated themselves to providing materialsthat would be turned into various tools. The distance betweenthe material and the object that is shaped from it increases withtime. Conceptually first, then diachronically as the object isborn of the material, and finally in terms of production tech-nology in the Levallois technology the mining of nuclei andthe preparation of splinters, that could be given various mis-sions, are carried out upstream and fairly independently of theworkshops where knifes or hatchets are made.

Biomass and lithic materials could meet the needs of mankindfor tens of thousands of years. There was a clear social equi-librium between the technology of the times and the needs ofa small population of nomadic scattered groups of hunters-gatherers. Exposure to other materials, which were to becomemore modern, must have happened often,but without creatingthe driver towards something different during the longPaleolithic era, the Mesolithic and even much of the Neolithic.

Technology, though, was brewing with the use of fire to cookfood first, to conserve it by drying or roasting and to dry things,change matter and give it new desirable properties. The "art offire" was used to harden wood, which is probably the first step

towards the production of modern materials from earths.

Pottery and ceramics (10th millennia BC in Mureybet), cal-ling for more heat and higher temperatures, as well as the pro-duction of lime cement from the roasting of chalk (Serbia, 7th

millennia BC) (14) were thus the first ventures of mankindinto making complex materials.

In addition to breaking and cutting hard and brittle materials,shaving and polishing hard but also softer materials, techno-logy now has added the art of fire to its "process toolbox" andthat of shaping things, using soft and malleable materials,which result from mixtures, mainly with water and from someexposure to heat.

Both concepts have survived in the slitting process, carriedout on steel, hot or cold, with corrugated rolls, but also in theold French word offenderie, which designated a plant wherea bloom or ingot was cut or shaven into pieces or sheets.

Wood is commonly shaved in thin layers today, from whichplywood is produced. The idea of shaving round steel bars forproducing foils has also been contemplated (15), but withoutmuch practical success.

Metals, which are easy to shape and tough, i.e. do not breakeasily, came about in steps. Those metals which exist in anative metallic state, because they have a low affinity for oxy-gen and sulphur, like copper, gold and to a lesser extend sil-ver, of course came first (fig. 9). For this same reason but alsobecause of their rarity in the ground (Cu : 50 ppm,Au : 1 ppb,Ag : 70 ppb), they seem to have appeared historically in thatorder. The recycling of metals in our modern society is arediscovery of this early use of metals, as scrap is similar to

native metals ; it is also easier to use and leaner in energyneeds and CO2 emissions. Technology, not only materials, isthus also recycled!

Metallurgy does not simply consist in using native metals, butalso in making metals from earths (ores) and in producingnew metals by mixing (alloying). Extractive metallurgy(smelting) and physical metallurgy (forging), which are 20thcentury concepts, were empirically discovered in their craftversion during the Neolithic. Native alloys of gold and silver(electrum) were known in Egypt in the 2nd millennia. Copperextractive metallurgy came first, followed by the alloyingwith other elements: copper was too soft to use as a blade andthe addition of small amounts of arsenic and then of tin (5 to

10 % initially, 30 % ideally and eventually) was sufficient toproduce bronze, a hard material which sustained for severalthousands years as a basic military material (16).

Fig. 8 Levallois technology for preparing flints fromlithic nuclei - the first material technology

in the history of mankind.Fig. 9 Early metal artifacts made of copper,

bronze and iron.


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This intrusion of metallurgy in civilization accompanies aradical complexification of the economy, with specializedactivities in mining, material production, and artifact manu-

facturing, bound together by trade : The tin needed by thebronze producers of Greece was thus brought from Turkey,Spain, Brittany and Cornwall. This also goes along with thepopulation growth that has started with the settling down of theNeolithic through the discovery of agriculture, urbanizationand the organization of larger political areas, which called fortools and weapons on a large scale. One can probably arguethat only metals were in position to answers such needs andthat metallurgy became therefore a necessity, which led to itsinvention.

The concept of material has by then been fully constructed. Itgoes along with the specialized work of different trades, car-ried out at a scale that was more that of various crafts than of

an industry but which served the same purposes.The stage was set for more change in terms of materials, as ananswer to more needs in terms of volume, properties and cost.Iron was thus the next player to enter the play of history. Itwas stronger, tougher, potentially more versatile and muchmore abundant than any other materials used until then. Itsupplemented and competed with wood and ceramics, a situa-tion that is still true today, when cement, steel and wood arethe three most common basic materials produced at the levelof about 1 billion tons per year each. Iron slowly displacedcopper and bronze, over several hundred years ; in NorthernEurope though, copper has remained a construction materialfor roofs, which can be found as far south as the French city

of Metz on the railway station[2]

.

s HISTORICAL METALLURGY -PREREDUCED IRON ANDCEMENTED STEEL

Iron was produced by the reduction[3] of ores (mainly oxides,Fe2O3 hematite or Fe3O4 magnetite, but also (Fe2O3, n H2O)goethite, siderose FeCO3, pyrite FeS2, etc.), found almostanywhere, where man had settled (in lakes and bogs andeventually in the ground (17)). Indeed, until the end of the19th century, iron was produced in Europe in workshops scat-tered all over the map. The reducing agent was carbon, artifi-cially produced by converting wood into charcoal. The largeforests that had sprung up in Europe in the post-Pleistoceneperiod[4] (18) could thus sustain the needs of man for severalmillennia until the 18th century.

The production of charcoal as well as the reduction of ironinvolved the building and operation of chemical/metallurgicalreactors, where raw materials, carefully prepared, mixed andarranged, were subjected to heat and made to interact.

Charcoal kilns, as they are still built in some parts of the worldtoday, have probably not changed much over centuries : woodis piled up and enclosed inside an ad hoc chamber, made ofearth and later of bricks, to avoid contact with the atmosphereand provide heat insulation. Some limited air ingress is orga-nized through a small hole where the pile is lit up and thecombustion of a small fraction of wood and of the freed vola-

tiles provides the heat that increases the temperature andallows the pyrolysis to proceed and transform wood into car-bon. A chimney vents the fumes to the outside.

The reduction itself takes place in a simple hole dug in theground (1 m deep and 25 cm in diameter) and eventually in ashaft furnace, which is the ancestor of the modern blast furnaceinto which it evolved[5], as the horse carriage is the ancestor ofthe automobile. Ore, charcoal and additives such as lime, clayor sand are piled up in a small furnace, not very different fromthe charcoal kiln, except for the provision of a chimney, thatprovides a draft for the air that was injected laterally through apipe (19, 20) (fig. 10 - 13). Natural ventilation was the norminitially - sometimes an orogenic wind on the slope of a hill,but bellows and water pumps were added in the Middle Agesto supplement natural convection. The air combusted the char-coal into CO, an exothermic reaction that brought the tempe-rature up to maybe 1,100C, a major feat that must have taken

hard work in empirically process design to achieve. CO wouldthen take care of reducing the oxide to iron (indirect reduction),

Fig. 10 Steelmaking in Egypt.

Fig. 11 Schematic diagram of a bloomery, in the stageof development of the early Middle Ages.


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through the intermediary step of wustite (FeO), while somedirect contact of charcoal with the ore performed part of the job(direct reduction). The non-iron compounds of the charge, the"gangue", remained mainly unchanged. The temperature washigh enough for the gangue to melt into a slag that could flowout of the furnace near its bottom. The reduced iron, however,would be produced in the solid state and accumulate at the bot-tom of the furnace as a lump of metal that the English even-tually called a bloom[6] ; the furnace itself was a bloomery (21)and a bas-foyer ou bas-fourneau in France (22). Because itaccumulated in a furnace region devoid of carbon, it was madeof rather pure iron, neither steel nor pig iron, mixed with gan-gue and full of holes. The process was a batch operation. Ofcourse, no "theoretical" chemistry was available to understandwhat was actually accomplished in this process : these scienti-

fic concepts would not be evolved until the 19th century, aftera false start related to the phlogiston theory. Everything wasderived by trial and error.

The first process to make steel was thus a direct reductionprocess that produced unalloyed but dirty[7] iron, or rathermild steel. Direct reduction was later all but forgotten whenthe blast furnace came of age and became the mainstreamtechnology, from the Middle Ages onwards, but it was "redis-covered" in the 20th century when natural gas started to beused as a replacement for carbon.

The Hittites of Anatolia in the 2nd millennium BC and possi-bly before (23rd century ?) have the reputation of havingalready mastered the art of producing iron : they have given

some metal as a present to the pharaohs of the 18th Dynasty(1380-1340 BC). This is much earlier than the Ages of Iron inWestern Europe known as the Hallstatt (800 BC) and the La

Tne (400 BC) cultures. The knowledge traveled also to theEast and bloomeries have been known in early China andKorea, and in Japan during the Kofun period (23). Iron and

steel were not known in the Americas, which maintained abronze-based technology until the arrival of the European : thecontrol of iron technology by the Spanish invaders has beenone of the factors of their easy conquest of that continent.

The bloom was still a rather useless material, which wouldhardly compete with bronze in terms of hardness. It wasnecessary to clean it up by removing the gangue and to com-pact it. This was carried out by forging the hot bloom with ahammer, in the hands of the blacksmith and latter with aforge-hammer moved by hydraulic energy (un martinet, inFrench). The gangue was beaten out of the bloom by theimpacts and the pores were welded shut. In Roman times, abloom would weigh no more than a few hundred grams. Theworkshop was eventually called the Finery, Martinet ;

Martinette orMoulin (moulines) Ferin France (fig. 14).

The bloom was not fully homogeneous and parts of it some-times exhibited contamination by the carbon of the charcoal,which turned the iron into a harder carbon steel (natural steel).The control of this cementation (i.e. the diffusion of carboninto iron) was carried out in a further process, where thebloom was heated up for long periods of time inside a char-coal bed. This "steeling" of iron, actually a case-hardening,was carried out as soon as Roman times and its first occur-rence may be as old as 400 BC (19). But other evidence seemsto indicate that sometimes only the sharp edge of a bladewould be carbon-hardened, while, in Eastern Europe (Styria),

Fig. 12 Early versions of the bloomery.

Fig. 13 Bloomery and forging.

Fig. 14 The finery.


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it may have been possible to produce steel (0.4 to 0.9 % C)directly in the bloomery, due to the use of ores rich in man-ganese, which produced a slag that did not wash the carbonfully out of the bloom (19).

The entry of steel on the scene was rapidly followed by thepragmatic mastering of quenching and tempering, which

made available a range of hard materials that clearly outclas-sed bronze.

Another breakthrough occurred when the smiths discoveredforge welding, thus making it possible to produce larger sam-ples with the sheer strength of their arms. Moreover, it waspossible to assemble iron and steel together and thus to pro-duce a kind ofpte feuillete (puff pastry dough) by repeatingthe process over and over again and doing it with twists, bothproperly and figuratively speaking. This was the art ofDamascus steel, mastered as early as the La Tne period, butwhich retains the name of Damascus, a city in Syria where itwas produced for the late Roman Empire. The result is notonly a composite material, which is both tough and hard and

therefore particularly appreciated in swords, but a delicatelycrafted piece of steel jewelry, where the pattern of mild andhard steel shows at the surface with various regular geometri-cal shapes, after polishing and etching. Damascus steels havebeen produced all over the world, not least in the classicalArab world and in Japan (Katana). The modern equivalent ofproducing Damascus steel is the production of compositematerials but also mechanical alloying.

The bloomery, a technology born 2000 years BC in Anatolia,remained conceptually the same until the Middle Ages inEurope. For more than 3000 years therefore, iron was smel-ted from ore in a bloomery and further "steeled" by cementa-

tion and casehardening. Sophisticated blades were producedby forge welding. Steel technology was thus sustainablybased on solid-state transformations. This was slow in termsof kinetics, because diffusion controlled everything. The pro-ductivity was small and the cost correspondingly high: Steelwas therefore devoted only to strategic applications, the fore-most of which was weapon production.

This is no longer the mainstream technology for making steeltoday, but it has not been fully dismissed: Besides prereduc-tion and mechanical alloying, one ought to mention powdermetallurgy, which is a contemporary large-scale technologyfor producing steels in the solid state. Tentative solid statereduction in preformed material has been tempted in the1980's at the University of Swansea by Professor Singer (24)and the concept also survives for the production of powder byhydrogen prereduction of pure hematite fines (25). On theother hand, the solid state reactions discovered so long ago arestill very much alive in the modern technology of thermo-mechanical processing, which covers everything done on hotmetals, and constitutes the core of physical metallurgy, mate-rials science and of much of nanotechnology.

s HISTORICAL METALLURGY -PIG IRON AND BLAST FURNACES

The steel technology, that the Roman Empire inherited, waspassed on to the new order of the Goths. The bloomery did notchange much in most of Europe, busy as it was at looking forthe new geopolitical equilibria that would emerge from theexhausted and collapsed Empire. Only in Spain did steel tech-nology strive and progress, under the Visigoths first and then

Fig. 15 Aspect and metallographic structure Damascus steel blades from Japan.

Fig. 16 Early and "improved" Catalan Forge.

Stack

The charge

Bloom

Tuyere


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under the Moors. In Catalonia, the antique bloomery built in ahole in the ground and with the heap of raw materials simplycovered with clay was slowly transformed into the CatalanForge, a fitter precursor to the Blast Furnace by its shape (26).

The Catalan Forge was a construction built on a hillside, witha hearth stone 30'' square and three stonewalls 3' high (fig. 16).A hole near the bottom let in the nozzle of the leather bellows(27) for introducing the air. The typical output in the 8th cen-tury was 350 lbs for a 5-hour heat, to be compared with the50 lbs that the old technology was only able to yield.

The Catalan forge was disseminated all over Europe as theBest Available Technology of the times, but as soon as theeconomy called for more production, inventors were at workto improve its productivity. The furnace height grew to 8' andthen to 16' and the production of each batch jumped to 400and 600 lbs. This high bloomery was called Stckofen orWolf Furnace along the Rhine and in Austria, where it origi-nated: The bloom was called a Stck or a Wolf, which gaverise to the French word ofLoup. The Stckofen could pro-duce 100 to 150 tons of iron per year surpassing the produc-tion capability of a Catalan forge.

The increase in the furnace height soon placed the tuyere too

high for manual labour to activate the bellows. Hydraulicpower, already known since the 12th century (28) was soonput to use to power the bellows as well as the hammer of theblacksmiths (to become the tilt hammer). The idea originatedin the silver mines of South Tyrol in the early 13th centuryand then the ironmaking community got hold of the techno-logy, especially the Cistercian Monks, who spread it withtheir monasteries all over Christian Europe. The SteelIndustry moved from the hillsides and the middle of foreststhat could provide a steady stream of wood for charcoal, tothe riversides of springy streams and rivers (fig. 17).

The bellows grew in size faster than the height of the furnace,so that the temperature inside the shaft increased also. Liquid

iron started to trickle down the charge to the bottom of thehearth. This did not necessarily please the ironmaker, as thenew iron was indeed pig iron, carburized and melted because

the furnace had locally become hot enough to reach its liqui-dus temperature, but too brittle to utilize like the wrought ironthat he was used to: The drippings were therefore charged

back at the top of the furnace to become honest iron again. Ittook time and ingenuity to find applications for this pig iron :It started to eat at the niches that the bronze industry had kept,i.e. bells and soon cannons and cannon balls.

Thus the industry became ready for the next breakthrough,the Blast Furnace, which appeared initially as a result ofincremental innovation. The Blast Furnace was thus a bloo-mery that produced liquid metal, in a carburized state that dis-tinguished it strongly from the wrought iron and even the steelthat has been part of civilization for the last few thousands ofyears. It was initially called Fluofen in Germany to indicatethat the metal was indeed flowing out of it. But it becamerapidly the Hochofen and the Haut-Fourneau, while, in

England, the bellows were seen as more important, hence theword ofBlast Furnace replaced that ofHigh Furnace. Thefirst Blast Furnaces have seemingly been built in the 13th cen-tury[8] in Sweden at Lapphyttan (17) and at Jubachstal inGermany, but probably also in Wallonia and in France(fig. 18, 19). An intermediary process capable of switchingback and forth between the production of solid iron and liquid

Fig. 17 A bloomery with details of the water-wheeldriven bellows (29).

Fig. 18 A blast furnace in Europe during the Middle Ages.

Fig. 19 A blast furnace ca the 18th century.


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pig iron, by changing the fuel rate and the size of the tuyeres,called the Blauofen, coexisted for a while with the old and thenew processes.

"In the 16th century these furnaces were 6.7 m (22 ft) highand could produce 4,000 lbs of iron per day with a fuel rate of250 lbs of charcoal per 100 lbs of iron produced. These fur-naces had a low life expectancy of approximately 45 days"(26).

The displacement of the bloomery process by the blast fur-nace was the result of the strong economic driver due to theincreasing demand for steel and also of the invention of newways to make iron (wrought) and steel from liquid pig iron,i.e. of the evolution of steelmaking, in the modern acceptanceof the word, to accommodate the jump in productivity of theironmaking processes. This game of pursuit between ironma-king and steelmaking will keep going on until the present and

constitute a strong driver for progress.

Indeed, it had become simpler to make steel now that pig ironwas available in solid and liquid forms. Steelmaking thusevolved over a period extending from the High Middle Agesand the end of the 20th century (19), with a variety of alter-native technological solutions :

The first concept consisted in heating up layers (sheets) ofwrought and cast iron together without contact with air to justbelow the melting point of cast iron. This is the so-calledChinese process[9]which was invented in China as early as theearly 2nd century. Diffusion produced steel, more or lesshomogeneous, depending on the skill of the operator.

One could also introduce bars of wrought iron into liquidcast iron. The bar would absorb carbon by diffusion and thencould be forged. The process, developed in Northern Italy,gave rise to Brescian Steel[10].

Heating up layers of wrought iron with powdered charcoalin large sealed chests produced blister steel by the cementa-tion process. It could then be broken into shorter pieces, madeinto faggots and forge-welded together to make shear steel.Cementation was the major process for making steel inEngland during the modern period (1700-1850).

Blowing air over pig iron melted in a bed of charcoal toremove carbon, a process called "fining" the iron and carried

out in the finery furnace (l'affinerie), is the ancestor of themodern steelmaking processes. The product of the finery wasa bloom, as complete melting of the steel after its transforma-tion from the cast iron was impossible due to the low tempe-rature (1,400C). It precipitated into small pieces that floatedout of the melt and a worker called the Rabbler brought themtogether with a long steel pole (un ringuard) and much work.The melt was decarburized to less than 0.50 % carbon. Avariant appeared in Austria, whereby the process could bestopped at a higher carbon content, thus directly producing aharder, quenchable steel known as Styrian Steel[11]. The pro-cess was difficult to handle, labour intensive and full of know-how[12] as the trick of the technology was to eliminate carbonas CO2 at the top and to avoid excessive recarburization by thecarbon hearth. With this technology, the word finery hadtaken a new meaning as compared to the forging workshopthat it used to designate downstream of the bloomery : indeed

this former finery has now been split up in two differentshops, the new finery, where some liquid metallurgy was car-ried out and a further shop called the chafery, where the

bloom would be heated up and hammered (cingl). The technology of furnaces came to the rescue of the fineryin the shape of the reverbatory furnace, a clever devise, wherecharcoal was gasified in a chamber where the hot flames werereverberated by the roof and transported the heat towards thecharge spread out in a second chamber, thus avoiding recar-burization to a large extend. The furnace changed into apuddle furnace[13] and the bloom it produced was puddlediron (fig. 20). The material was likely to be heterogeneous incarbon content and in hardness within one "heat" and betweenheats : low-carbon (fer doux) and high-carbon (fer fort)steels had to be sorted out by hand from the true steel. On theother hand the heterogeneous material was convenient formaking blades, as it mimicked the Damascus steel, morepainful to make. The final evolution of this technology wasthe Siemens-Martin furnace, which produced liquid steeldirectly.

The Eiffel Tower is a brilliant example of the achievement ofthis mid-19th century steel technology (fig. 21).

The next breakthrough in steelmaking consisted in obtainingsteel in the liquid state, systematically and reliably. This nee-ded a stronger heat source, which was provided by the switchover from charcoal to earth coal - that made available a den-ser form of energy, and by the improvement in furnace tech-nology.

The first man to achieve the breakthrough in Europe wasBenjamin Hunstman, a clockmaker who was unhappy withthe steel available on the market because of its lack of consis-tency in composition and properties (30). He had the intuitionthat if he somehow managed to get the steel in the liquidphase he would obtain a uniform composition that would becarried over to the solidified product. His practical conceptwas to heat up blister steel in a clay crucible placed in a cokebed properly activated by bellows and he did succeed inachieving melting without direct contact with the hot cokeand therefore without recarburization. This was the beginningin 1742 of the crucible process, which was to be used formaking special steels well into the 20th century.

The induction furnace is actually a modern avatar of this pro-cess concept modified to use electricity as a source of heatand ordinary scrap as a substitute for blister steel.

Fig. 20 Schematics of a puddling furnace.


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The ingots that Hunstman produced were indeed uniformenough for his needs. He also produced the first castings ofsteel, thus inventing steel foundry, and sorted out the basicissues of deoxidation.

But another breakthrough had happened earlier, when anotherclever Englishman thought of using coal rather charcoal in theblast furnace and, moreover, to use a pyrolyzed product fromcoal, coke. In 1708, Abraham Darby leased a small charcoal

blast furnace in Coalbrookdale, Shropshire and by 1709 hewas producing coke. Over the next ten years, coke was mixedwith charcoal in ever increasing proportions until 1718 wheniron was produced from 100 % coke as a fuel. Darby did nottry to keep the use of the new fuel a secret, but he didnt publi-cize it either. Up until 1750, the only ironworks using coke ona regular basis were two furnaces at Coalbrookdale and one atWhilley, all operated by the Darby family. Finally, during theperiod from 1750 to 1771, the use of coke spread with a totalof 27 coke furnaces in production. The coke Blast Furnacewill replace the charcoal furnace on a steady state basis and atthe same time grow in size. The European forest are no lon-ger able to provide a sustainable stream of wood for makingpig iron and it was time to find a substitute fuel or to faceextinction. This has been done and the risk of extinction hasbeen replaced by the potential of unlimited growth at the his-torical horizontal of the 18th century at least[14].

The Steel Industry has now discovered some of the majortools for modernizing its operations and for making Steel theflag bearer of the industrial revolution. It will help ushering in

the deep transformation of mankind's lifestyle of the 19th adthe 20th centuries, i.e. a massive increase in life-expectancyand standard of living and, as a consequence, lead to thepopulation explosion.

Coal was the major instrumental cause of this profound revo-lution : it allowed the production of larger amounts of castiron and also that of steel by the crucible process. Processmetallurgy is now based on the manipulation of liquid phasesat every stage, thus not only deeply changing the old para-digms, but also opening up the way for exponential growth ofthe production that was to continue well into the 21st century.

Until now, we have told a story focusing on Europeanhistory.

Steelmaking technology elsewhere took different routes : inChina, the bloomery, which may have come from the MiddleEast, was rapidly improved in terms of heat efficiency so thatthe production of pig iron became possible several centuriesBC (23). Tradition puts the origin of the charcoal blast fur-nace in the 3rd century BC, but claims of earlier manufacturehave surfaced recently (Zhou Dynasty, ca 550 BC) : plow-shares may thus have been cast by and for farmers as early asthe 6th century, while the nobility understood its usefulnessfor warfare only in the 3rd century BC. China knew aboutcoal long before Europe did and the first coke blast furnace

appeared there several hundred years before the Darby fur-nace. The technology was not exported outside of Chinahowever and it eventually stopped evolving so that themodern western blast furnace, which had become moreadvanced, was imported from Europe in the 19th century.

In Japan, where iron was only present in sands in very dilutecontents (2 % and up to 8 % after beneficiation), a differentkind of bloomery called a Tatara ( ), was invented in the 7thcentury AD (31) and used continuously thereafter, mainly tomake swords. The process, shown infigure 22 is a version ofthe bloomery specially designed to handle low-grade ore : thehearth is wide and low, so that charcoal and sand can be added

continuously for the 70 hours of operation, during which thetemperature rises high enough to let the slag melt and flow outin large quantities, while the iron is reduced into a variety ofproducts, from pig iron to iron and steel, depending on thephysical proximity to carbon. The various irons were separa-ted and recombined to make swords. Only when rich iron orewas discovered in Kamaishi, was it possible to switch back tothe western style blast furnace (1857) with a 100 to 1 reduc-tion in operating cost[15].

The evolution of steelmaking technologies in Europe and inAsia, which shows large discrepancies in the timeline ofintroduction of new processes, is a clear example of how tech-nology development responds to local conditions, both geo-graphic and economic. Change does not follow a linear andunivocal path but explores a complex and non-deterministicarborescence.

Fig. 21 The Eiffel Tower.


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The number of available technological concepts, however, isfinite and the various timelines rearrange this basic alphabetin different combinations springing up at different times.Charcoal and then coal and coke have been providing energyand reducing agents to the steelmakers everywhere on Earth.The pyrolysis of wood or of coal was also eventually used byeveryone to deliver a more carbon-like material than wasavailable in nature. The bloomery, low or high, slim or squat,has also been present everywhere in several avatars.

s HISTORICAL METALLURGY - MODERNSTEELMAKING, BESSEMER,THOMAS,MARTIN AND HROULT

Coming back to the European timeline, there was still a mis-sing link in the production of steel, as the available productionroute still required too many steps, including that of the pudd-ling furnace, which would feed material to the chafing plantand then to the crucible plant : metal was not yet liquid allthroughout the route, which slowed things down, was verylabour intensive and kept costs high. What was direly neededwas a true steelmaking plant that would convert cast iron intosteel directly, liquid to liquid.

Once again, the light came from England, which was advan-cing fast on the tracks of the Industrial Revolution. Indeed, SirHenry Bessemer invented the converter, a reactor in which airis blown through the liquid cast iron through tuyeres placed atthe bottom of the vessel (32-34) (fig. 23). He was thus the firstman to completely achieve a liquid phase production of steeland thus to invent what is commonly known today as steel-making in a one-step process. It proved capable of convertingpig iron (which could soon be used as taped from the blastfurnace and henceforth could be called hot metal) in quanti-ties that could eventually range to several hundred tons, to doit fast (the hour was the norm, but modern steelmakers havegone below 30 minutes) and to produce the whole range ofvery pure steels that is the core of today's steel production.

Bessemer's breakthrough was soon followed by that of theMartin brothers in France, who managed to produce liquidsteel in a reverberatory furnace modified by Sir William

Siemens (fig. 24). The process was more time-consuming andmore in continuity with the concept of the puddled furnace. Italso made a kind of steel, which was easier to control in termsof properties as the interaction with the oxygen of the air wasless violent than in the converter process. The Siemens-Martin Process, which was also known as the Open HearthProcess (OH), rapidly overcame the Bessemer process in pro-duction volume and shouldered most of the growth of theSteel Industry until the middle of the 20th century.

From then on, the steel industry had been dealt all the cards thatwere needed to play the steelmaking game in the modern, tem-porary and mainstream styles that we are familiar with today.

One elementary technology was still missing though, becauseelectricity had not yet been invented. As soon as it was available,particularly in the mountains such as the Alps or the CentralMountains in France, an explosion of concepts appeared to useit as an energy source for melting iron, or scrap, as this materialwas becoming available as a consequence of the growth in steelproduction. Paul Hroult, who invented the electrolysis cell onwhich aluminum production is based, also proposed to have anelectric arc kindle between electrodes, which led him to inventthe Electric Arc Furnace in 1899 (fig. 25).

Fig. 22 Schematic drawing and old painting of a Tatara furnace.

Fig. 23 The Bessemer process as installedin Sir Henry's own steelshop.


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s THE STEEL INDUSTRY IN THE SECONDHALF OF THE 20TH CENTURY

We have now travelled to the present, or rather to the post-second World War Period that gave birth to the present SteelIndustry (35).

Five drivers for growth have driven innovation further in theSteel Industry during the second half of the 20th century(fig. 26) :

initially, it was necessary to catch up with the explo-ding demand due to the need for reconstructing theeconomies destroyed by war and, in parallel, to caterto the beginning of the consumer era, foremost ofwhich is the birth of a consumer car industry ;

once the 30 Glorious Years had gone by, it was neces-sary to ensure higher and more consistent steel qua-lity ;

to increase productivity in order to match the 2.5 %steady yearly decrease in steel prices ;

to focus the production more narrowly on customerneeds by providing them with tailored-made pro-

ducts, incorporating customer-specific value-addedtechnology that are usually called "steel solutions" or"solutions in steel"[16] ;

more recently, environmental issues taken in a broad context,i.e. eco-efficiency and sustainable development,have come tothe forefront as the leading driver for change and the ClimateChange issue will certainly accelerate this trend (36).

Technologies were centered on shorter process routes andcontinuous processes, but also on technological break-throughs such as oxygen steelmaking, top, bottom and mixedblowing, continuous casting, continuous rolling such as whatthe hot strip mill performs, continuous annealing, etc.

Fig. 24 The Open Hearth Process.Fig. 25 One of the first Electric Arc Furnace builtby Hroult and an industrial one in Dommeldange

(Luxembourg).

Fig. 26 - Evolution of steel production in the 20th century showingthe drivers behind the deep changes that took place after

the 2nd World War.


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In parallel, prereduction, based on the use of natural gas grewto occupy a niche of roughly 10 % of the iron ore processingroutes[17] and, because of the accumulation of steel and its lea-

kage back into the economy as scrap, the EAF has grasped ashare of steel production as high 43 % (37).

The OH process waned slowly only, as it still accounted for3.6 % of world steel production in 2003, with 30.1 % of thetotal production of the former USSR countries and somemore furnaces left in India (5.7 %). On the other side of his-torical development, new processes have appeared, whileeven more have been studied but did not yet pass the glassboundary that separates R&D from commercial implementa-tion : smelting reduction and near-net-shape casting havebeen the major families of endeavour at this point in history.

Figure 27, conceptually borrowed from (38), shows the histo-rical evolution of the steelmaking processes in two coupled

Fe-O and Fe-C binary diagrams. Native metals and solid-state reduction have provided a direct route to making steel(bloomery) in the early days of history and well into theEuropean Middle Ages. The use of carbon, from charcoal andfrom earth coal, has made it possible to explore the liquidmetal paradigm and its strong advantages in terms of highoutput and high purity : initially, liquid steel was out of reach,but the mastery of heat transfer made it possible to produce it,with a variety of concepts that culminated in the converter andespecially the oxygen converter (BF & Blister steel, BF &Crucible or Bessemer Steel, BF and modern BOF). Naturalgas has revived the prereduction direct steel concept and theavailability of electricity has made it possible to obtain liquid

steel without going through the pig iron stage. This is thepoint in history where we stand now.

s THE STEEL INDUSTRY TOMORROW

The 21st century has started with a strong acceleration ofSteel production due to the steady demand of the fastest gro-wing Asian economies, China and India, but also of SouthAmerica and Eastern Europe. These enormous increases incapacity are obtained by introducing the newest and best tech-nology available on shelf from plant builders but also byimproving the productivity of existing facilities beyond thestate-of-the-art as defined in Japan or Europe. On the business

side of things, mergers have brought to the market playerswith a capacity in excess of 40 Mt/annum, such as Arcelorand LMN. Moreover, the industry seems to have switchedover from a supply to a demand-driven sector and thereforethe price of steel has stopped declining, at least in the shortterm.

Does this foretell of incoming change of steelmaking techno-logies or, on the contrary, will this mean the end of change inthis area ?

This is by no means a rhetorical question, as the technologylegated by the 20th century has reached a scale and a proxi-mity to thermodynamic limits that makes it difficult to conti-nue changing at the same pace as it did in the past centuries.For example,10 to 15% improvement in energy needs per tonof steel is the most that can be forecast. The Steel Industry hasmatured and reached an asymptotic level of technology and

the future growth of capacity might be based on this mainst-ream technology with a strong emphasis on products and steelsolutions rather than on new steelmaking technologies.

This certainly looks like what is happening in China today,but is by no means certain in the longer term. Indeed, the sus-tainability driver is becoming stronger than ever before, espe-cially in its environmental component, and the GlobalWarming issue is probably the most pressing one. It willremain pressing for a long time.

In such a context, the Steel Industry would need technologiesthat have the potential of reducing GHG emissions by the"factor 4" that European governments are setting as targets for2050 and this will make it necessary to re-examine this effi-cient mainstream steelmaking technologies of today and refo-cus them on lowering GHG gas emissions while maintainingthe same energy efficiency level.

There are currently three ways of addressing this question.

One consists in staying close to the carbon-based BlastFurnace technology and to ensure that the ensuing CO2 is cap-tured and sequestrated; this would lead to deep changes inprocess in order to make CO

2

capture easier to achieve, suchas recycling the BF top gas after decarbonatation and thusoperating the furnace under nitrogen-free conditions.

Another solution would consist in replacing carbon by otherreducing agents and fuels, such as natural gas, hydrogen orelectricity. This might open the way to using electrolysis forproducing steel, a proposal that was never seriously examinedin the past because of the high cost of electricity. On the otherhand, electricity or hydrogen would have to be produced bydedicated generation plants based on CO2-free fuels, i.e. rene-wables, fossil fuels with CO2 capture and sequestration ornuclear.

A third solution would be based on the use of biomass, which

contains "short-cycle" carbon and would not contribute toGHG emissions because a steady-state production of biomassby agriculture or forestry would be included in the carbon loop.

Fig. 27 Historical evolution of steelmaking processes.


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Various programs are being started around the world to add-ress these issues and come up with a commercial solutionwithin the next 10 years. One of them is the Europe-wide

ULCOS[18]

project (39) but others are under way elsewherecoordinated from IISI in a "CO2 breakthrough program"(40). Any solution that comes out of this program would be adeep paradigm shift in steelmaking technologies as comparedto the present routes. The new ones, which would at thebeginning probably be more expensive to operate than themainstream technology, would compensate this extra-cost byadded environmental value, translatable into cash throughCO2 trading markets or CO2 taxes. Whatever direction iseventually chosen, it will prove a major breakthrough, on apar with those that took place in the long historical past thatwe have reviewed here.

In the longer term, the world will face other societal and geo-

political changes.

Eventually population growth will stop and, when this hap-pens, the reliance on virgin iron will not be as strong as it wasin the past: Recycling will be in a position to provide all themore of the iron units as the recycling rate will be high. Asmuch as 70 or 80 % of the iron units could thus be providedby scrap.

The economy will also dematerialize, because materials willbe re-used, recycled and used in consumer goods with longerlives and because the intensity of artifact use in the economymay also decrease. Design for Recycling (DfR) and Designfor Durability (DfD) will pull in this direction. This will also

help decrease GHG emissions[19].Another important change is that the technology trend, whichhas been pointing towards larger output, more complexity andupscaling, will branch off to another direction : simpler,more frugal and rustic solutions will be preferred in parts ofthe world which are presently emerging into development."Less is beautiful" will become a new slogan. In terms ofsteelmaking technologies this may mean that smaller plants,in equilibrium with local conditions, will appear as a counter-model to the large mainstream integrated mill of today, a paththat the mini-mills have been treading since the 1960's. Thereis for example no reason to believe that the 5 Mt/annum millthat is the baseline "best" solution today would remain the

best solution for an electrolysis-based steel mill. Otherconcepts based on the use of local raw materials are likely tobe developed, provided that the new technology remains rus-tic and cheap to develop: A small blast furnace, either fed withcharcoal or non-coking coal, in combination with a simple

prereduction process (e.g. rotary kiln, carbon-based) couldbecome very successful in countries like India.

Such a deconstruction of the steelmill model will probably be

matched by a deconstruction of the steel market. Theconcept of "steel solutions" is the first step in this directionand has proved a major driver for generating economic valueand for steering the creativity of the steel industry downst-ream of its present core-business. Among the longer-termtrends, we might expect a departure from the comodificationof steel that would be driven by aesthetic values under theinfluence of architects, artists and designers. Modern auto-mobiles are beautiful because of the rounded shapes thatdeep-drawing steels allow. Weathering steels change aspectand surface texture with their ability to accommodate oxida-tion, a smart material behaviour.

s THE STEEL INDUSTRY INTHE FAR FUTURE

The implicit statement that we have taken for granted in theprevious section is that steel will continue to be needed andused by mankind long into any foreseeable future. Indeed, nomaterial yet in history has proved as sustainable as iron andsteel and there is no sign of any emerging material that cancompete with it at a global scale. We have agreed that thisstems from the abundance of iron as an element, which is dueto the cosmological production of iron in the star furnaces.This is likely to be very enduring. A consequence is that ashortage of iron will probably never happen unlike what is

probable for fossil energy.

The iron at the core of the earth is probably forever out ofreach. Maybe mankind should plan to recover it when the Sunexpands into a red giant rather than let it seed the Galaxy forthe benefit of future planets and civilizations. This howeverwould constitute very-long term planning!

Meteoritic iron on the other hand would probably be withinreach of our present technology, if we so chose to allocate ourresources. It is interesting to imagine what would be a space-based technology (41) : it could use nickel-bearing metalliciron as iron sources, the Sun as the energy source, surfacetension as the container for liquid steel and 3-D Urchin

Continuous Casting to directly cast net-shape long and flatproducts at the same time. Using the material in orbit wouldprobably be more cost effective, but steel could also be floa-ted down planetside on giant gliders or ferried down in thespace elevator (42).

Fig. 28 A panoramic view of Mars from the Sagan Memorial Station where Pathfinder landed in 1997(the red rock is mostly hematite) (43).


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In interplanetary space, iron would be the material of choice,because of its availability. On other planets, if mankind eversettles on them, this might still be the case. For example, iron

ore is everywhere on Mars (fig. 28). NASA is consideringvarious systems for producing hydrogen and the electrolysisof iron oxide is one of the explored routes, which would alsoproduce iron as a by-product (44).

A more immediate issue is energy shortage. The peakoil ispredicted soon, 15 to 30 years from now. This will drive theprice of energy to such heights that energy demand will peakin the 2040's or slightly earlier, depending on whether there isa carbon constraint (45) and assuming that renewable ener-gies are developed at the a brisk pace[20] that coal is used morethan it is today and that any energy still needed is provided bynuclear power[21].

Cosmologists like to talk about the arrow of time to designatean irreversible and deterministic course of events ; there ishowever no such irreversibility in historical trends and inexercises in foresight or technological forecasting. Short ofdeterminism, some invariants are however likely to be obser-ved: The needs of the economy and of society will continueto drive the offer and the choice of technologies. Moreover,new technologies will be born from the accumulated wealthof know-how and knowledge accumulated over historicaltimes, a fact that is recognized when it is said that the SteelIndustry is based on Cumulative Technologies. One stronginvariant is that steelmaking will continue to be based on pro-cesses involving a liquid steel phase, everything else remai-

ning subject to change.

s CONCLUSIONS

Iron is a very common element in the universe and on planetEarth, which is mainly made of metallic iron. This fact is dueto the particularly stable nature of the iron nucleus that directsstellar nucleosynthesis towards producing iron as the final by-product of nuclear fission. The reserves of iron in theUniverse are enormous and growing, as the stellar furnacesare still operative. They amount to 1045 t (1018 Suns). TheEarth itself contains about 1020 t of iron or enough raw mate-rial to ensure the present production of steel (109 t/annum) foras long as 7 times the age of the Universe! In the crust, theamount is estimated at 1017 t, while the world mining reser-ves are estimated at 230 billions of tons (46). Cosmology,geology and mining projections agree on the fact that ironwill remain widely available for any foreseeable future

Not only does the nucleus of the iron atom exhibit special pro-perties that explain the previous conclusions, but its electroniccloud also has special features which have turned it into anecessary trace element in living organisms and into a materialthat exhibits a rare combination of strength, ductility and tough-ness and an ability to combine with other elements in alloys thatconstitute the largest family of inorganic compounds known toChemistry, Materials Science and Metallurgy.

This combination of ready availability and of outstandingproperties explains the enduring presence of iron and steel inthe history of mankind and guarantees that it will continue toaccompany it in the future for a very long time indeed.

Man has learned to domesticate iron in ways related to mining

and metallurgy. The development of steelmaking technology

Fig. 29 A timeline of materials and steelmaking technologies over the last 200,000 years.


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has been driven by the demand for volume production, whichhas followed the increase in population and the materialintensification brought by "civilization". Processes have beenscaled up at the pace required by history and the scale-up hasbeen accompanied by a reduction of costs : the materialbecame cheaper as it became more widely available. Anotherstrong enabler of this rise in volume has been the switch fromsolid to liquid metallurgy with the use of high temperatures.This in turn allowed access to better-defined materials, withconsistent compositions and properties. Besides this hard"economic" explanation, a softer socio-historical approachshould emphasize the point that the needs of society are alsoa search for more refined concepts for describing the physicalworld and that this intellectual need cannot be distinguishedfrom the economical need (47).

If we look closer at the technology timeline (fig. 29), we finda tree-like structure : change or progress follows one branchuntil a particular technology exhausts its promises and thebranch stops. Breakthroughs are like new twigs, branching offin different directions originating from new concepts.

We have currently been exploring a solid, strong and longbranch of steelmaking technology, but it looks like we arenearing its limits : mainstream technology has reached a kind

of frozen perfection. The driving force for this momentouschange and also for this evolutionary cul-de-sac has been theimmersion of the Steel Industry in the free market consumereconomics of the end of the 20th century and the globaliza-tion it brought along.

Is this the end of the story or the prelude to the birth of a newtechnology branch?

If the past gives any clue to the future, picking up the first ans-wer would be foolhardy : the end of history (48, 49) has beenpredicted many times without much empirical confirmation

The steelmaking branch that the present Steel Industry hasbeen built on will remain strong and might even grow thicker,but it will probably not grow longer. On the other hand, newbranches are likely to sprout, driven by two outside drivers,which will act as paradigm shifts :

global environmental issues such as Climate Change willprobably pull technology and steel-making in new directions;

and the end of population growth, expected some timestowards the end of this century, will channel human creati-vity towards post-modern societies, where the creation ofvalue will not be based on material production nor on ser-vice, but on subtler deliverables related to pleasure and aes-thetics.

The toolbox of robust technologies (41) that is available as the

result of the cumulative nature of steelmaking will probablybe put to use ever more eagerly, in the same way that modernphysics has learned to weave robust enduring concepts likequantum mechanics and general relativity into new yarns likeSuperstring or M theories. The keys to the future can there-fore be read in the past with appropriate insight.

A somewhat more explicit projection of what the future steelproduction may look like is shown infigure 30 showing thelikely steelmaking processes in 2050 (41, 50).

The invariants, as compared to today's technologies, are thefollowing :

Iron units stem from ore and scrap. Liquid steel is processed either in an Oxygen Converter or

an Electric Arc Furnace.

Solidification is carried out continuously on a series ofcontinuous casting processes that produce a range of thick-ness from slab to thin strips.

Coated and composite materials are produced downstreamin specialized plants.

Changes are likely to occur in the following areas :

The reduction of iron ore will be based on a mixture ofreducing agents, from coal to electrons, with natural gas and

hydrogen as new players. The Blast Furnace will change toaccommodate capture and sequestration of CO2.

The iron ore/scrap ratio will be tipped to the scrap side.

Fig. 30 Production routes for steel in 2050. In light-blue rectangles are shown technologies,which will need to be fully developed until then.


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New and revived concepts like direct steelmaking, electro-lysis and continuous steelmaking will lead to commerciallyimportant technologies.

Near-net-shape casting ought to catch a larger market share,when older production capacity needs to be replaced, and itwill move towards net-shape casting (thin strip casting, wirecasting).

There is another context, though, where the liquid phasemetallurgy paradigm could be broken. It is related to trans-

materialization and to nanotechnology (fig. 31). Indeed,liquid phase metallurgy has the objective of easily achievingthe spatial mixture of atoms that equilibrium allows.Nanotech on the other hand proposes to directly arrangeatoms at the atomic scale, one at a time. Today, this is under-stood as a technology in the making that opens up new fron-tiers at very small scales to make tiny objects that could besmall enough to apply the mechanical paradigm to the realmof life sciences. More forward looking thinkers dreamers? talk about self-replicating machines, which would take careof the difficulty of mass producing these machines.

The production of bulk materials by nanotechnology seemsmainly out of reach today, because of time limitations (kine-

tics), energy need and cost unless these self-replicating sys-tems bring about a solution.

One might even say that classical technologies are nothingless than large-scale nanotech : the Steel Industry thus opera-tes at the scale of 1038 atoms per year

s REFERENCES(1) ARISTOTLE Seconds analytiques, II,11.

(2) EMSLEY (J.) Nature's building blocks, an A-Z guide to theelements, Oxford University Press (2001).

(3) FOX (B.-G.) Cofactors and Coenzymes,

www.biochem.wisc.edu/biochem625/index.html(4) FOX (B.-G.) Iron cofactors: non-haem, Encyclopedia of

Life Sciences,A668, Macmillan Reference Ltd (2001).

(5) www.rcs.org , Protein data bank.

(6) COALE (K.-H.) et al Southern Ocean Iron EnrichmentExperimen t: Carbon Cycling in High- and Low-S, Science

304: 408-414 (2004).(7) BISHOP (K.-B.) et al Robotic Observations of Enhanced

Carbon Biomass and Export at 55 degrees S D, Science 304:417-420 (2004).

(8) BUESSELER (K.-O.) et al. The Effects of Iron Fertili-zation on Carbon Sequestration in the Southern Oc..., Science304: 414-417 (2004).

(9) BLAIN (S.) La Recherche, n 376, 12-13 (June 2004).

(10) SEGUIN (M.), VILLENEUVE (B.) Astronomie, Astro-physique, Masson (1995).

(11) REEVES (H.) Dernires nouvelles du Cosmos, vers la pre-mire seconde, Seuil (1994).

(12) GREENE (B.) The fabric of the cosmos, Alfred A. Knof(2004).

(13) TROMPETTE (R.) La Terre, Belin Pour la Science (2003).

(14) MOHEN (J.-P.), TABORIN (Y.) Les socits de laPrhistoire, Hachette Suprieur (1998).

(15) Shorter routes to thin sheets and strip, the Metals Society(1982).

(16) MARGURON (J.-C.), PFIRSCH (L.) Le Proche-Orient etlgypte antiques, Hachette Suprieur (2001), p. 95-98.

(17) Iron & Steel, today, yesterday and tomorrow, a conference tocelebrate the 250th anniversary of Jernkontoret, vol. 3 (June

11-14, 1997).(18) RILEY (C.-L.) The origin of civilization, Southern Illinois

University Press (1969).

(19) BARRACLOUGH (K.-C.) Blister Steel, the birth of anindustry, The Metals Society (1984).

(20) BURTEAUX (M.), CORBION (J.) Le savoir fer, Glos-saire du Haut-Fourneau, Association Le Savoir Fer, 57-Florange, Presses du Tilleul, 4e dition (2003).

(21) SACHSE (M.) Damascus Steel, Stahl und Eisen (1994).

(22) http://www.sollacmediterranee.com/decouverte/histoire/his-toire.htm

(23) WAGNER (D.-B.) The earliest use of iron in China,

in Metals in antiquity, ed. by Suzanne M. M. Young,A.M. Pollard, P. Budd and R.-A. Ixer (BAR internationalseries,792), Oxford : Archaeopress (1999), p. 1-9.

(24) AHNIER (S.-N.), SINGER (A.-R.-E.) Ironmaking andSteelmaking n 3 (1983), p. 135-141.

(25) wwwepma.com/rv@pm/PM%20Process

(26) WAKELIN (D.-H.), RICKETTS (J.-A.) The Nature ofIronmaking, in The Making, Shaping and Treating of Steel,11th Edition, Iron-making Volume.

(27) FISHER (D.-A.) The Epic of Steel, Haper & Row, NY(1963).

(28) http://lamop.univ-paris1.fr/W3/lamop1.html

(29) http://moulinafer.free.fr/[email protected](30) BARRACLOUGH (K.-C.) Crucible Steel, the birth of a

technology, The Metals Society (1984).

Fig. 31 Artist's view of a nano-machine operatingat the micro-scale.


19/19

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(31) TATSUO INOUE - Science of Tatara and Japanese Sword,Traditional Technology viewed from Modern Science,ICBTT 2002, The 1st International Conference on Business& Technology Transfer, Kyoto, Japan (October 20-21, 2002).

(32) BIRAT (J.-P.) The relevance of Sir Bessemers ideas to theSteel Industry in the 21st century, First Bessemer Lecture,London, Ironmaking & Steelmaking, 2004, vol. 31, No. 3,(September 2003), p. 1-7..

(33) BESSEMER (F.-F.) The Technology and the Times, SteelWorld, vol. 3, No. 1, 11-18.

(34) BESSEMER (H.) Sir Henry Bessemer, FRS, an auto-biography, London, The Institute of Metals, reprint (1989).

(35) BIRAT (J.-P.) Sustainable steelmakingparadigms forgrowth and development in the early 21st Century,La Revuede Mtallurgie-CIT, 98, n 1 (2001), p. 19-40.

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Brussels (12 March 2004), ftp://ftp.cordis.lu/pub/coal-steel-rtd/docs/steel_stp@[email protected]

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s AUTHORS NOTES

[1] Na is for example at the concentration of 1.05 %.[2] and Louis XIV had copper plates bought from Sweden to cover

the roofs of the Palace of Versailles.

[3] a "chemical" word, that states that the weight of the ore isreduced in the process of turning it into a metal.

[4] and (anecdotically?) terminated the large herds of wooly mam-

moths and European rhinoceros.[5] a 12th century blast furnace in Sweden produced 100 kg of pig

iron per day, as compared to 10,000 t/day in a large modern onetoday, a 105 increase over 700 years.

[6] in French, loupe, massot, masseau, saumon, mazelle, renard andloup; the word bloom has a different etymological origin fromthe homonym that means flower : the bloom, therefore, is not theflower of the furnace.

[7] in the sense of non-metallic inclusion cleanliness, although thelevel of contamination was several orders of magnitudes largerthan for a modern steel.

[8] the first blast furnace built in North America was at FallingCreek, Virginia in 1622.

[9] also called co-fusion, although no melting was taking place.[10] 1% C and 0.8 % oxides.[11] or German Steel, or Cullen Steel (for Cologne, the City through

which it was exported), or even, confusingly, natural steel.[12] the Styrian, for example, used a manganese rich iron ore, which

produce pig iron with 5-10 % manganese, known as spiegeleisen(because it showed when broken flat grains similar to mirrors).The spiegeleisen was easier to reduce because of the interme-diary manganese oxides that formed early in the process.

[13] invented by Henry Cort (1784).[14] direct quote from reference (19).

[15] the Tatara process, which is closely related to the technology ofmaking swords in the traditional Japanese way, a technology pre-served as a "living" museum, has been recently revived and a fur-nace has been build by the Nippon Bijutsu Token Hozon Kyokai,in Torigami, Shimane Prefecture, in cooperation with HitachiMetals in 1977. It provides 3-4 tons of steel every year (3).

[16] Laser-welded blanks, hydroforming, steel construction, mainte-nancefree steels for shipbuilding, etc.

[17] what distinguishes the modern prereduction processes from theold bloomery process is the use of liquid steel metallurgy toseparate steel and gangue : there is no need for brute mechanicalforce anymore to maneuver hammers or tilt hammers. Moreover,natural gas is used as the preferred reducing agent in a shaft con-

tinuous furnace ; which does evoque the bloomery, which is itshistorical ancestor. Coal-based prereduction has not dis-appeared, but is carried out in rotary-kilns.

[18] Ultra-Low CO2 Steelmaking.

[19] Ehrlich & Holdren's equation : ,where CO2 is the anthropogenic CO2, Tsteel is the steel produc-tion, GDP is the Gross Domestic Product and POP is the popu-lation size.

[20] including, possibly, solar towers.

[21] on the other hand, it does not take into account longer-term solu-tions, such as Nuclear Fission or Space-Based Solar Energy,beamed back by microwave to the Earth surface. The projectionsare for them to become available beyond the middle of this cen-tury at the earliest, which is a very far forecasting horizon. Suchenergy would probably be limitless but also quite expensive interms of capital expenditure.

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