The history of the production of steel , like the majority of the stories of discovered and technological advances, is not linear. One finds Acier S at various places of planet during the history. One can quote for example Indian steels called Wootz used for the manufacture of weapons whose development probably started about the year 300. At the end of the 19th century, whereas considerable progresses were made, Grüner describes in its metallurgy treaty, published in 1878, the use of Low-furnace X to extract iron from the ore in the forging mills from the the French and Spanish Pyrenees. This metallurgist showed thus that it is not of good process of production that as much as it remains effective. This technical pragmatism is a constant of the history of the metallurgy and history of the techniques in general.

Iron, cast iron, Steel a definition changing during time

Antiquity

The Greeks use two words:

  • for iron (and generally seem metals): sideros (ιδερος),
  • for steel: khalybs (καλιϐ).

It is probable besides that the significance that we give to these two words is deformed by our current knowledge. It is known that they practiced the cementing of iron to harden it and thus manufacture steel.

Latin will preserve the term of chalyb and will call iron ferrum . Word which will be preserved in the Latin languages ( ferro in Italian, Portuguese and Catalan, hierro in Spanish).

The Middle Ages

During the Middle Ages, the term of iron recuts any kind of alloy. The cast iron is called “iron cast”. This name will perdurera and will be still used by Gaspard Monge at the end of the 18th century.

Réaumur, Monge, Berthollet, Vandermonde

From the 18th century, the definition of the terms iron , steel and cast iron is based on the carbon rate contained in alloy.

Rene-Antoine Ferchault de Réaumur studies by observing scientific and even industrial rules (calculation of cost price) between 1716 and 1726 the methods of manufacture of “iron”. He affirms against the common spirit of the time: “steel is an iron less refined where the iron molecules are separated by masses from sulfur and salts which give him its hardness. ” .

During the French revolution, like much of scientists, Gaspard Monge, Claude Louis Berthollet and Alexandre-Theophilus Vandermonde put themselves at the service of the French Republic. France is in war against the rest of Europe, it needs steel to manufacture weapons. However, it is dependant on its neighbors (Germany, England) for the supply steel. To stimulate national industry they publish a work giving a progress report on the steel industry of the time: “Opinion with the French iron workmen on the manufacture of steel”. The work begins thus by:

“While our brothers lavish their blood against the enemies of freedom…, it is necessary that our energy draws from our ground all the resources which we need, and which we learn in Europe that France finds in its center all that is necessary to its courage.

steel we miss

, steel must be used to manufacture the weapons whose each citizen must be used for himself to finally finish the fight of freedom against slavery. ”

In spite of some errors (the role of oxygen), they establish the distinction between the three types of alloys while being based on the carbon rate. Monge defines in its work “description of art to manufacture guns”, steel as being “… refined iron which absorbed coal, and it is mainly by the quantity whose coal is distributed in the mass that steels differ between them. ”.

Current definition

The distinction between these three families of ferrous alloys, is based on the chemical element Fer. It is the rate of Carbone contained in the Alliage and more exactly the limit of solubility of carbon in the matrix iron which allows classification:
  • industrial iron and ingot-iron: <  carbon 0,050%
  • steel: between 0,050% and 2,1% of carbon (the totality of carbon is in solid solution in the solid phases)
  • cast iron: between 2,1% and 6,67% of carbon (part of the carbon dissolved in a solid state precipitates in the form of Graphite or of carbide).

The precise and scientific definition of steel is recent and was definitively established and allowed at the end of the 19th century.

The definition by the carbon rate is rather theoretical, it is established for an alloy purely binary iron-carbon without another alloy element. It is an exceptional situation which takes account neither of the impurities nor of possible alloy elements added voluntarily.

15th century

In Europe, starting from the Middle Ages, the production of steel took several forms:

  • the natural steel , speciality of the German technical space, obtained by decarburization of a cast iron specific “cast iron to steel” (Rohstahleisen and especially Spiegeleisen). This process claimed a certain type of ore (manganiferous) a control of fire, a know-how composition speed of descent of the load different from those necessary for the production from common cast iron (grey iron);
  • the crucible steel , obtained by the pure iron carburation. This process, which required excellent qualities (Swedish, Catalan), speciality of British technical space, was developed in the current of the 17th century.

The production of natural steel thus belonged to the die known as “of indirect production”: production of cast iron to the Blast furnace then steel refining; while steel by cementing concerned the die known as “of direct production” (Low-furnace). Steel was used mainly for the clothes industry of knives and tools of quality. The English practice, which gave a steel of less quality, widens its use with hardware, cutlery and other bimbeloteries, and made the fortune of the town of Sheffield.

Natural steel

The refining of the cast iron is carried out by empirical methods which make it possible to remove the carbon of the Gueuse S of cast iron coming from the blast furnaces. The various methods are in the beginning regional and correspond probably partly to qualities of the iron ores used. The most widespread method is the method known as “Walloon”. This method was used in a great part of Europe until the 17th century. There are alternatives like the Champagne method or the method comtoise in which the pig mould is placed in the middle of the hearth and not above.

There exist however methods presenting of the important differences like the Nevers-native method .

Walloon method

The cast iron pig mould is pushed on the flames of a hearth ventilated by bellows. Under the effect of heat, the carbon contained in the cast iron oxidizes while burning. The iron drops fall into the box containing the hearth. This last being cooled by the lower part in order to allow the solidification of the iron magnifying glass.

This process presented several disadvantages: the magnifying glass took care of slag in the hearth and the temperature was not sufficient to oxidize the Phosphore (*) so that it was possible to use only pig iron and cast iron white because low in phosphorus.

A workman helped the process while pricking using an old-fashioned to prick the soft end of the pig mould.

As for the iron magnifying glasses obtained with the low hearth slags are eliminated by shingling . This operation of forging mill is carried out using a trip hammer by vigorously striking with sharp and repeated blows the magnifying glass.

Nevers-native method

The cast iron is molten (or it seems strongly softened) in a furnace called finery with charcoal and slags. This cast iron is then run on a refractory brick lining refoidi by water. Refining is carried out while making pass from the air on the unit.

In 1786, the baron DE DIETRICH described this method thus:

“the work of the finery is mainly in force in Nivernois, & it is a clerk of this province which put it of use at the forging mill of Uza. It is too little known elsewhere. I on the occasion to see this work in rather great detail in the royal forging mills of Nivernois, which puts to carry to give an idea of it.

It consists of three distinct processes: 1°. in the recasting complette of the pig mould, to convert it into cakes: 2°. in the netting of these cakes: 3°. in their refining.

In some places one refines the pig mould, & one refines the cakes in same fire; in others there is a fire intended for fusion, & another with refining.

the fire of fusion bears the name of finery .

Its dimensions are from sixteen to eighteen inches of depth; its with dimensions has of them sixteen to eighteen in any direction, of the ground on their board: the bottom of the crucible is tilted towards the tap-hole which is with the short-nap cloth of the ground.

the conduit enters the surface, by levelling the edges of fire, & one more or less gives him jump, according to the quality of the cast iron: if it is soft one raises it; if it is hard & bitter, it more is inclined; while raising it, it relates more immediately on the pig mould, & less to the molten matter.

the pig mould is placed at the wind-brace by its end. It is surrounded & recovers it of slag of heavy forgings, & one charges it into same tems with the caps with fordes or with old-fashioned: this operation requires work very little; one obtains in few tems a small part which bears the name of maffiot, weight of forty & some books. ” .

This method will persist. It is thus described by Grüner and Lan in 1862:

“… it will be enough to quickly point out the principles and the results… of refining.

This handling is always carried out, in England, in the low coke hearths, known under the name of English finery. Work, each one knows it: it is the fusion of the cast iron, only or added with hammer-scale or slag of forging mills, under the influence of a draft. The position of the cast iron compared to the conduits, the slope of the wind, its pressure, the depth of the hearth, etc, etc, are as much which vary the intensity the action of the air on metal. ”

Crucible steel: cementing

Irons obtained can undergo operations of cementings. Operation which consists in increasing the carbon rate of alloy in order to obtain higher mechanical characteristics.

Rene-Antoine Ferchault de Réaumur designs a made furnace of mobile refractory plates. On these plates, it places forged iron bars drowned in various mixtures made containing crushed wood, of ashes and soot. The unit is heated to cause a migration of carbon by diffusion in the bars.

18th century

The metallurgy becomes scientist

The scientific knowledge of steel is indissociable work of the scientists of the 18th century: Réaumur, Gabriel Jars, Grignon, Guillot-Duhamel, Lavoisier, Hassenfratz, to quote the principal ones, which invented the " term; sidérurgie" to express the need for rationalization of the production of ferrous metals.

Gaspard Monge, Claude Louis Berthollet and Alexandre-Theophilus Vandermonde categorize in three categories “steels” while being based on their method of development:

  • natural steel (or steel of Germany): manufactured by decarburization of cast iron layer.

“These layers are intended to be converted into iron or out of steel… is steel that one for making? A narrower furnace of finery is used and deeper, one lutes it with coal cinders which one moistens… then one lays out the layers to with it, and one recovers them slags and of coal… ”.

  • carburizing steel : manufactured starting from solid iron in which one increases the carbon rate by diffusion.

“One makes in the body floor a bed of duff…: one puts on this bed a row of iron band, which one places so that each band can be surrounded of coal dust; then one completely recovers this first rank with a bed of a half inch thickness of duff: one continues thus successively until the crucible is full: the last row is covered with duff, over which one puts a sand bed, to entirely cover its surface, and to prevent that it is destroyed by combustion… In Newcastle where one cements in two cases, contained in a furnace, from 25 to 30 thousands of steel, the operation lasts 5 days and 5 nights. ”.

  • crucible cast steel : it with is not properly spoken another manufacturing method but a method making it possible to improve the grade of the steel produced by one of the two preceding methods. Steel is molten to homogenize its composition.

“One puts steel in the crucible with a flow, which one makes a secrecy; and one places the crucible on a round brick, one poses on the grid. One has pit coal reduced in coak which one puts around the crucible, and one fills the furnace; one puts fire at it, and one entirely closes the higher opening of the furnace, with a made brick door, surrounded by an iron circle.

the crucible is five hour with the furnace, before steel is perfectly molten. ”

1784 puddling

Description

The method is invented almost simultaneously by Peter Onions (patent on May 7th 1783) and Henry Cort (patent February 13rd 1784). It is revolving in the industrial history. The quantities of produced steel will increase quickly. Its use will start to spread.

The word Puddlage comes from the English verb to puddles which means to brew.

The method consists in placing cast iron of piece with iron oxide slags on a coke fire. This mixture is then placed in a Four with reverberator with slags in order to cause a fusion (metal east seems it worked in a pasty state). It is vigorously brewed by a workman using old-fashioned with hook. Carbon oxidizes and slags involve the impurities. The iron mass with slags is then nut. The invention of puddling involves a strong increase in the production.

According to Grüner, there exist two alternatives: fatty, hot or ebullient puddling (known as in English boilling process ) and dry ordinary puddling or older cold. This classification is based on the manner of carrying out puddling. This classification is taken again by Jacques Corbion in his dictionary:

  • dry Puddling or cold ( dry puddling in English) carried out on plate out of sand (which corresponds thus to the primitive method)
  • fatty or ebullient Puddlage or in filth: carried out on cast iron plate.

The work of puddling

The result is based on the working work puddling it which worked under difficult conditions. Thus Grüner written in connection with dry puddling:

“… Whatever the fluidity of the mass, the work of the workman consists in for this second period plowing the cast iron and slags using an old-fashioned fort, bent with right angle at its end; it is the tool called hook . One thus mixes the metal particles with the oxidized elements and exposes them both to the influence of the air. To operate mixing, one does not open the door of work itself. The workman would test a too sharp heat, and the furnace itself would be cooled. One is satisfied to introduce the tools by a simple opening of 0m, 10 with 0m, 15 of dimensioned, practiced in the bottom of the door mobile, and easy to close using a simple plate apart from the moments when the workman works the load…

As iron is purified, it becomes less fusible (*); it is thus necessary, to continue mixing, gradually to record the temperature, by reopening little by little the valve stack.

In the place of the hook, the workman rather often makes use of old-fashioned with bevel, called pallet, or plane, which makes it possible to detach from the plate the cooled parts, or become firm, which tends to adhere to it.

It is the end of the mixing itself, which lasts on average from twenty to thirty minutes during dry puddling. ”

(*) Carbon the rate of the decreasing mixture, the constant temperature remaining in the furnace, the melting point being of the Eutectic type, the melting point of the mixture increases (see the diagram of phase iron-carbon in the article Acier) causing an increase in viscosity.

Jules Verne in the Five Hundred Million the Begum will also make a more literary description of it but nevertheless specifies (one will note in the passing her very good definition of steel based on the presence of carbon):

“the operation of the " puddling " is to carry out this metamorphosis. Teams of half-naked cyclops, armed with a long iron hook, devoted themselves to it with activity.

the cast iron ingots, thrown in a doubled furnace of a slag coating, were initially brought there up to an high temperature. To obtain iron, one would have started to brew this cast iron at once that it would have become pasty. To obtain steel, this iron carbide, so close and yet so distinct by its properties from its congeneric, one waited until the cast iron was fluid and one had care to maintain in the furnaces a stronger heat. The puddler then, of the end of his hook, kneaded and rolled in all directions the metal mass; he turned it and turned over in the middle of the flame; then, at the exact moment when it reached, by its mixture with slags, a certain degree of resistance, he divided it into four balls.”

evolutions of the process

The puddling furnace will undergo many improvements:

  • 1818 : Baldwin Rogers invents a cast iron plate air cooled by the lower part.

  • 1825 : this cast iron plate is covered with a basic refractory which eliminates the Silicium and makes it possible to avoid the first refining. It is possible to pass directly from the blast furnace to the puddling furnace.

“the use of the cast iron plates appears to be proposed by Baldwin Rogers dice 1818, but they were really adopted only ten to fifteen years afterwards. In the metallurgical voyages Misters Dufrénoy, Coste and Perdonnet, one sees (1st edition) that in 1823 the use of the sand plates was still general. About 1820 one starts to substitute slags crushed for sand. In 1829 one starts, one notes that and there plates out of cast iron, but the authors add that while puddling directly on the cast iron (without layer of scraps or slags), the results were defective. Lastly, in 1837 (2nd edition), the cast iron plates are of a general use. ”

Industrial steel

But the industrial takeoff of the production of steel, started at the beginning of the 19th century (Jackson, Terrenoire in Saint-Etienne), was carried out truly in the end of the year 1860, with the invention of Bessemer processes, Thomas-Gillchrist and Martin-Siemens. At the origin of the invention of these three processes, there is the crucial need for the European railroad companies to find for their rails a metal which resists the wear caused by the passage of the trains  ; there is also, and by-effect, the need in which was the sector, advantageously to recycle the mountains of worn cast iron rails which accumulated monthly. The arms race, as from the years 1880, made the remainder, in incentive with the invention of the alloy steels, whose large initiators were Boussingault with Unieux (Saint-Etienne) and Fayol. Thus was born metallography (Châtelier, Osmond in Creusot, Leon Guillet with the CNAM).

1856, acid Bessemer steel

The discovery

Henry Bessemer is an engineer and inventive English fertile. In the beginnings of the year 1850, he works with the improvement of the reverberatory furnace used for the fusion of the cast iron. He causes a draft on the surface of the liquid molten iron bath to poke the combustion of gases. He observes whereas on the surface of the liquid cast iron is formed fine solid decarbonized iron plates (**). He draws from it the conclusion which it is possible to decarbonize the cast iron by the action of the air without puddling.

(**) The melting point of pure iron (1535°C) is higher than that of the cast iron. In spite of the strong temperature in the furnace of H. Bessemer, the temperature is sufficient to dissolve the cast iron but insufficient for that of the iron which is solidified. Quickly, he seeks to check his assumption. Initially, it builds a crucible of laboratory with a cane making it possible to make splash air in cast iron in fusion. The crucible is heated by outside. This assembly, enables him to check its assumption. He will discover quickly that the reactions are sufficiently exothermic and that it is not necessary to maintain a heating around the crucible. He builds an experimental converter of four feet top, comprising one walked on in the center of the lid and the base six conduits horizontal. The reaction is rather violent. Bessemer will realize its importance by seeing a cast iron plate placed at the mantelpiece to melt it.

In 1895, Ledebur thus describes the reaction in an industrial converter: “When one treats in an acid converter a very silicieuse cast iron and that the temperature of the apparatus, or that of the cast iron is not very high, the gases which escape first of all are not very lighting; they have a reddish color which had with the metal pieces which they involve, carbon does not burn yet or, at least its combustion is unimportant, oxidation goes about only on the Silicium and the Manganèse; many sparks are projected out of the apparatus, and one hears inside a noise of clapotement coming from the passage of the air through the metal mass…

Soon after, the combustion of carbon starts, the flame appears with a color of a blue blanchâtre and in the shape of a lengthened cone; then it more highly becomes lighting, while the number and the size of the sparks fall…

As from the moment when carbon started to burn, the release of gases increases, the flame becomes of a bright white, it reaches until 6m length; clapotement of the beginning transforms itself into resounding explosion caused by the production of great quantity of carbon monoxide in a restricted place. It is made projections of slags and metal shot pulled by the fast movement of gases…''

As of the moment or the flame becomes sharper, one distinguishes with his point a brown smoke which increases intensity as decarburization advances; it is composed of manganese iron oxide and of oxide carried by the gas current… ”' '

Cependant the carburation of metal decreases more and more, oxygen less easily reached carbon more diluted, its combustion is done more slowly; the flame becomes weaker, more unequal, more transparent; brown smoke increases and wraps all the point of the flame, the explosions inside the retort are calmed…

H. Bessemer will test the various shapes of fixed converters. Those presented many defects which limited the use of the method.

It solved the problem by creating a fixed and rotary converter: “I was to solve the difficulties related to the fixed character of a fixed converter. For these converters the majority of heat dissipates itself by the breath which appears during the transformation of metal and the continuation of the breath when metal converts and during the time of unloading, which represents one variable duration. There is also the problem of the stop of the operation if something occurs badly with the blower or the conduit. I actively sought a solution for these serious defects without success, until the moment when I had the idea to thus mount the converter on axes I could maintain the conduits above metal until the moment when the totality of the cast iron in fusion was in the converter. That allows the realization of the blowing of the totality of the load at the same time and also allows the stopping of the blower during unloading. This movement of the converter allows a stop of the operation constantly to repair a damaged conduit and facilitates work enormously. ”

Advertisement of Cheltenham

The method invented by Henry Bessemer raises much skepticism. Thus, he tells this exchange with his foreman who summarizes the general opinion:

“Where do you want to put metal, Mister? ”

I answered him: “I want that you put it using a gutter in this small furnace”, by indicating the converter to him, `'

“That of which you stopped all the heating and in which I must blow of the cold air to heat it”. The man looked me of an air where the surprise and pity for my ignorance were curiously frays.

It says then: “it will quickly be taken masses” of it

With the invitation of George Disavows president of the mechanical section of the British Association, it goes on August 13rd, 1856 to Cheltenham to explain his process in front of the congress of this prestigious association. Its speech will have a great repercussion and will be reproduced the following day in the Times.

Immediately, some ironmasters buy the right to manufacture acid Bessemer steel. It grants this right in exchange of the transfer of a royaltie of ten Shilling per produced iron or steel ton.

“Fatal Phosphorus, this enemy”

“fatal British pig-iron abonded with this enemy, phosphorus'”'' (the British cast iron contains in an abundant way this mortal enemy, the phosphore") thus Bessemer in its autobiography is expressed.

The Phosphore is a chemical element which makes lose with steel or iron its Ductilité making them fragile. They lose any interest while becoming extremely breakable. However, it covered the interior of its converter with acid refractory bricks. Its process is unable to withdraw the phosphorus of the cast iron if this one contains some.

“The apparatus imagined by Bessemer… is covered with silicieuse matter, the iron oxides… are used to furnish the furnaces in which one practices the refining of the cast iron were unable to resist the high temperatures that the production of the crucible cast steel requires and one did not know at that time, of sufficiently refractory basic matter… The iron oxides meet very facilitated to saturate themselves with silica and to form an acid slag in the presence of which phosphorus cannot be eliminated.

Later, the phenomenon will be explained in a more precise way:

“the combustion of phosphorus is made by forming phosphoric acid (P2O5) which cannot remain that if it is fixed by a basic slag”. “The phosphoric anhydride P2O5 is not stable in the presence of liquid iron…''

P2O5 + 5 Fe = 2P + 5 FeO''

In addition, the anhydride forms with iron oxide a phosphate P2O5, 3FeO. The complete reaction can be written: ''

8FeO + 2P = P2O5, 3FeO + 5 Fe”

It is an hard blow for Bessemer. Its advertisement with Cheltenham was a little premature. It had not carried out this phenomenon yet. Unfortunately, the majority of the British pig iron and cast iron contain phosphorus. The process will quickly be given up by those which had tested it. It will spend two years before finding the explanation of the phenomenon and to regain the confidence of the ironmasters. He will seek in England and Sweden of the pig iron and cast iron without phosphorus able to be refined in good steel by his process. In 1858, it creates with Sheffield “Henry Bessemer and Company”, factory in which it will industrialize his process in order to market it. It is in the towns of Sheffield and Edsken in Sweden that the process will take its industrial rise.

May 24th 1859, colonel Eardley Wilmot superintendent in “Royal Gun Factory” makes a speech and present samples acid Bessemer steel in front of the association of the civil engineers ( Institution off Civil Engineers ) in London. He indicated that the process is used successfully to manufacture steel intended for the manufacture of gun.

The co-operation between Bessemer and Wilmot was obviously determining. H. Bessemer, devotes to him a whole chapter in its autobiography (chapter XIII: Bessemer steel and colonel Eardley Wilmot ).

The way is opened, the industrialization of steel is on the way.

“it is quite obvious for us that puddled steel, as well as steely puddled iron (iron with grains), made their time. It will yield the step to acid Bessemer steel, as they replaced themselves the old forging steel and the more or less wrought cement steel. ”''

1877 Thomas and Gilchrist dephosphorizes the cast iron

How to convert the pig iron and cast iron phosphorous

If the process of Henry Bessemer is a major change, its limit poses problem with many countries. In fact, England is practically the only country with really benefitting from its discovery. British iron and steel industry profits from two Innovation S: Bessemer conversion but in fact also the first country for lack of sufficient resource in forest massively converted its blast furnaces with the Charcoal into blast furnaces with coke. She then experiences a development much faster of her iron and steel industry than that of the other countries. Thus appear the first steps of new a technical system founded on the generalized use of metal, the Steam engine and the coal.

Many countries have only phosphorous ores. It is the case of France with famous the Lorraine Minette, but it is also the case of Germany, Belgium, Luxembourg and even of Wales. Not only, of many industrialists cannot use the process but because of the strong demand, the price of the English ore becomes extremely expensive. Many engineers and researchers concentrate themselves on the problem.

In 1872, certain Snelus proposes to use the lime in the converter. Unfortunately, the basic character of this product makes that it is unusable in the converters of the time.

The French metallurgist Grüner foresees the solution: “lime and the magnesia, as infusible as alumina, can also act refractory as agent. It is known that Mr. H. Deville bottom the Platine in small furnaces with lime wall; and one prepares pure magnesia crucibles. These strong bases are linked with silica and form with clay, of double or multiple silicates easy to melt. Under these conditions, they would be bad refractory brick linings…

the strong affinity of the two bases for the acids, vermin when it is about a siliceous element, can be useful to other points of view. Here is a exemple : when a phosphorous pig iron is subjected to refining, it occurs an iron phosphate which, under the combined influence of silica, iron or coal, is easy to bring back to the state phosphide, while in presence of lime or magnesia, it tends to be formed more stable phosphates. It is thus necessary to make use of these two bases in the operations where one proposes to refine rough metals.

Malheureusement their employment offers certain difficulties. The lime carbonate is broken up by heat; the quicklime absorbs moisture and fall out of powder… The day when one puts except fires, lime is fused and fall out of powder. The magnesia would be appropriate better, because it is not surbedded with the air  ; unfortunately the magnesia carbonate is a mineralogical scarcity. Perhaps could one have recourse to dolomite, the double carbonate of lime and magnésie ? Dolomite, cooked at high temperature, especially if it contained enough clay to sinter itself a little, would resist better than pure lime the action of the humid air.

The invention of Thomas

The intuition of Grüner is the good one. But they are two young English who will make the discovery and will develop the method.

Sidney Gilchrist Thomas is twenty-five years old when he thinks of finding the solution. It was appropriate his cousin Percy Carlyle Gilchrist chemist in an iron-foundry of the Wales, to help it. They develop a refractory brick lining of basic type containing dolomite. Thanks to this coating, it is possible to put lime in the converter before charging the cast iron.

The laboratory tests are done in 1877 with the steel-works of Blaenavon. Sidney Thomas then deposits a patent to protect its invention. An industrial test is carried out on April 4th, 1879 in the factory of Eston pertaining to Bolkow-Vaughan de Middlesborough. Sidney Thomas and its cousin are unaware of it but it is revolving in the industrial development of Europe.

Like Bessemer with Chelteham, the two inventors make a communication with L ` Iron and Steel Institute at the time of a meeting in Paris in 1878. Like Bessemer, and taking into account unhappy experiments, Thomas and Gilchrist have evil to be made hear. But the period of doubt will be of short duration and the process will be diffused quickly.

The Thomas-Gilchrist method

The refractory brick lining
The Dolomie is a magnesium and calcium carbonate. It is a rock close to the Calcaire. Part of the atoms of Calcium are replaced by atoms of Magnésium. Its formula is CaCO3, MgCO3. To obtain a stable refractory it is mixed with tar:

At the end of the 19th century the manufactoring process is described by Ledebur:

“the refractory matter which one is generally used for oneself to manufacture these kinds of materials is dolomite. It is made up from approximately 45% from carbon dioxide, lime 30%, magnesia 20%, 1 to silica 2%, 2% of alumina and some other foreign matters. It could not be employed if it closed again more than oxide 3% iron or much more than 2% of silica…

the preparation of dolomite consists of a cooking pushed until the agglomeration. Cooking is essential to decrease the tendency of the matter to absorb again in contact with the air, of the water and the carbon dioxide which would make them impossible to use. In German one says that dolomite is killed by cooking (in France, one says sintered). It is the same for magnesia and lime carbonates…

sintered dolomite contains approximately 35% lime, 35 of magnesia, 5 of silica, the remainder is composed of one of alumina iron oxide, of the traces of manganese and some other bodies…

dolomite is crushed under edge runners or by any other means, is filtered if it necessary and is mixed with small proportion of varying tar from 2 to 8% which makes it possible to agglomerate it. The proportion of tar varies with its nature and also with the employment for which one intends the mixture. This operation is done either with the shovel, or with the mixer driven mechanically, or even the grinding stones which were used for the crushing to which one adds scrapers to obtain a good mixture of the matters.

the matter thus prepared is employed either to make a cob for the coating of a furnace, or with being moulded in the form of bricks which are used for construction of the walls of a furnace.

Before inserting them in a construction industry, however, these bricks must undergo a new cooking which removes them from the volatile parts of the tar; the carbon of this last remainder and is used as binder with the dolomite grains. At the beginning of cooking, the matter softens under the influence of heat, then the hardness of the stone acquires some.

As for cob and bricks employed believed, one cooks them on the spot. It is necessary to heat during 12 hours at the temperature of 300° of bricks of the weight of 25kg. ”

The process

Separately the coating, the process is very close to the' acid' process `' Bessemer. Contrary to this last, one pours beforehand in retort 12 to cold quicklime 15%, then the cast iron is charged.

An article published in the metallurgy review in 1959 described the process in four distinct phases:

  • First phase: the cast iron is charged in the converter, at a temperature of approximately 1150°C (the average temperature of solidification is of 1110°C). Blowing starts. The temperature believes rather quickly (40°C per minute for a load of 30 tons with an air flow of 600 m ³ per minute.). During this phase, the totality of the Silicium is eliminated as well as a great part from the Manganèse. Phosphorus and carbon start to be eliminated to a lesser extent. At the end of this phase, the temperature is between 1250 and 1350°C.

  • Second phase: the carbon rate strongly decreases, phosphorus slightly also decreases. The speed of increase in the temperature is lower than that of the first phase. At the end of this phase, the temperature is included/understood between 1330 and 1460 °C.

  • Third phase: The phosphorus rate remains constant, carbon continues with S `to eliminate. The temperature lies between 1470°C and 1500°C at the end of this phase. The speed of increase in the temperature with increased again.

  • Fourth phase: the beginning of this phase corresponds at the end of decarburization. Carbon was eliminated. During the first part for one short duration (including between 10 seconds and a minute), the temperature is practically stable and increases very little. It passes by a point which the authors name the temperature S then increases very quickly to reach a temperature ranging between 1600 and 1650°C. During this phase, phosphorus is eliminated completely. Strong rise in the temperature being explained by the Exothermic aspect very of the oxidation of this element.

Phosphorus is eliminated only at the end from the operation. Thus with the difference in the acid process Bessemer, the end of conversion can take place only when carbon is completely eliminated. This period is called the overblowing . For this period releases itself from characteristic brown smoke. If one wants to increase the carbon rate of steel, in a controlled way fused metal should be recarburized.

For the tapping into the laddles, it is necessary to clean the cast iron i.e. to eliminate phosphorous slags.

This slag very rich in phosphorus is used like manure. Sidney Thomas which in addition to his qualities of metallurgist was also engaged in the improvement of the social conditions of its time had promoted this quality.

Its composition is the following one:

The phosphoric acid is there in the form of phosphate, will tétra calcic (P2O5, 4 CAD) of which the major part is assimilable by the vegetation. The quantity of slag is approximately 200 to 250 kg of slag per ton of steel.

1924 will have to be waited until to see appearing the first important improvements of the treatment of Thomas conversion with oxygen air enriched in Germany. This technique starts to be used industrially in 1932. It corresponds to a search for reduction in the duration of treatment and also of increase in quality by the fall of the rate in Azote in particular.

Effects on the economy

The new process will allow the intensive use of the phosphorous ores and in particular the use of the Lorraine ore , called the iron ore . This ore is rich in phosphorus (approximately 2% of the content of iron of the ore) and is unusable with the acid process.

In 1880, England produces 1310 thousands of tons of molten steel, the group Germany, Belgium, France, Luxembourg produces 1220 thousands of ton. The day before the First World War in 1913, the group of the four continental countries produces 27400 kt (molten steel Thomas and Open-hearth steel) against 7780 kt for England. The increase in production was much more considerable in continental Europe than in England. The American production is comparable with the production of Europe continentale : 3380  kt in 1880 and 33500  kt in 1913. It should be noted that for the figures of continental the Europe group, the proportion of basic Bessemer steel is close to zero in 1880 and accounts for 62% of the tonnage of molten steel in 1913.

The new process thus completely modified the industrial weight of the nations, in particular in Europe. Taking into account also the level of the investments, it is also the starting of the reign of the large companies which are capable of vertical integration and/or specialization.

Inside the countries, the metallurgical production will concentrate around certain areas. In France, many small rural metallurgical centers which had survived on arrival and the improvements of the blast furnaces at the beginning of the 19th century will disappear with the profit in particular from Lorraine. The factories of Meurthe-et-Moselle provide out of basic Bessemer steel 75% of the national production since 1890. This evolution is also accentuated by the very strong improvement of the means of transport which allow the delivery of the manufactured goods even far from the production centres.

1864: Pierre-Emile Martin dissolves steel

The reverberatory furnaces of first half of the 19th century do not provide a sufficient temperature to dissolve steel. In 1864, the French Pierre-Emile Martin succeeds in with Sireuil in the factory of his/her father Emile Martin developing a Four with reverberator making it possible to dissolve a mixture of cast iron and scraps (waste of production of iron or unusable steel in the state) or scrap recycled. The use of Siemens Martin process presents a great economic interest thanks to the use of the steel and iron scrap which because of the development of the production started to represent significant amounts. The duration of the operation of refining takes a longer time in comparison with the process with the converter. This point if it is a disadvantage for the productivity present the great advantage of allowing a better control of the process and thus to obtain steels of better quality. Quickly, the “Open-hearth steels” will be selected for the armament (rifle Chassepot, naval guns French) or bindings of the wheels of railroad.

The Siemens furnace

In fact Pierre Martin its manufactoring process by using a technology of furnace astutely developed in 1856 by Carl Wilhelm Siemens succeeds in developing. The technology of these furnaces rests on the pre-heating of combustion gases in four rooms filled with refractory bricks piled up out of baffle or domino to have a large surface of contact.

The installation consists of a hearth and four regenerators of heat. The latter are covered refractory material rooms in which one piles up bricks. These bricks will be used as heat accumulators. The combustion gases are recovered with an higher temperature with 1500°C on the outlet side of furnace and are directed towards two of the rooms. The bricks recover the heat of these gases. When they reach a sufficient temperature one reverses gas flow using a valve. The carburizing gas as well as the combustive air is then directed towards these two rooms in order to warm up before being directed towards the furnace. They arrive at the level of the burner (called the carmeau) in the furnace at an important temperature what causes significantly to increase the temperature inside the furnace.

The use of this type of furnace was limited because of the brittleness of refractories used for the manufacture of the plate. It will be used initially only for puddling or in the glassmakings. Pierre Martin succeeds in developing a siliceous refractory plate (thus acid) which resisted the temperature:

“In the majority of the furnaces, this cob is composed of quartz as pure as possible crushed in the form of sand coarse of the size of a pea as one mixes with a quantity of fireclay which varies from 2 to 5%, and which ensures the agglomeration. Sometimes one establishes the plate in only once on all his thickness, then one lets dry slowly, after which one carries out cooking by raising the temperature gradually, sometimes one builds it by layer successive of 20 millimetres which one cooks one after the other. ”

In 1879, engineers Varlands and Alexandre Pourcel with Terrenoire (beside Saint-Etienne) and with the Creusot by using work of Thomas, develop basic plates manufactured starting from magnesia and out of dolomite. This type of plate will allow exactly same manner as for the basic Bessemer converters to treat raw materials which contain phosphorus.

It will be noted that the translators of the work of Ledebur also mention the “neutral” existence of chrome iron plate known as made up. Contrary to the two other types of plates, in this case, the plate does not play any part in the metallurgical reactions with fused metal.

Raw materials

The great interest of Siemens Martin process is the possibility of using iron or steel is in the form of scraps or on the shape of recovered scrap: “the principal raw material forming the load of a open hearth furnace is the soft iron in the form of remains, scraps of all leave, end of bar rolled, scrap, etc; all in all, there hardly exists of piece of iron some qualities which is, which one cannot benefit with the open hearth furnace. ” .

The other large raw material is the cast iron. During the transformation, the cast iron will be refined by losing its carbon and its silicon. More the proportion of cast iron is important (what increases the proportion of carbon in the mixture) more refining will have to be energetic.

The proportion enters the quantity of ferrous waste and the cast iron and extremely variable going to the extreme until loads containing only cast iron. According to Dovecote, the minimum quantity of cast iron being of 20% for the acid process.

In the basic hearths have can directly use iron ore for the process called “to the ore”. In order to dephosphorize the load, in this type of furnace one also uses lime or limestone.

“… it presents certain circumstances where one is brought to prefer a matter proportioning comprising more cast iron and less iron… Often, it is while being based on the relative price of the cast iron and scrap that one establishes the composition of the bed of fusion, and nothing is opposed so that the proportion of cast iron is higher, if one increases the oxidizing reactions during fusion. The simplest means that one can employ to achieve this goal, consists in the addition of iron ore, whose oxygen intervenes to burn carbon; part of the iron of this ore is reduced and comes to be added to that of the bath. ” .

The process

The furnace is manually or mechanically charged. The order and the provision of loading depend on many factors. Ledebur notes for example into 1895 that in the small furnaces the founder charges initially the cast iron in only one operation. It waits until it is molten before adding by successive operations iron and steel. Whereas in the large furnaces and in particular those with basic plate one charges at the same time the metal cast iron and the other matters (. Dovecote indicates in the 1957 that for the acid hearth one charges the load in only one operation, initially cast iron on the plate then ribblons them with the top of the load.

At the 19th century, the control of the operation rests mainly on the knowledge to make and the glance of the founder who leads the furnace:

“the oxidation of carbon appears by the boiling which produces the carbon monoxide bubbles which are released from fused metal… When the boiling ceased, or calmed down, the first test specimen is made; for this purpose one plunges in the bath a small iron pocket heated beforehand, and one withdraws them a little metal which one pours in a cast iron mould; a test-tube is obtained; sparks which is released from metal while it is run, the bloating which occurs in the mould, or retassement are already of the indices of the nature of metal, one carries it under the hammer, one forges it quickly and one tries to cold fold it… for an exerted eye, the simple examination of the break is enough to show the decarburization of metal. ” .

It will be necessary to wait many years to see appearing measuring devices in particular of the temperature. Dovecote notes in 1957 in its work: `' “one could not insist too much on the importance which there is to introduce the most possible measurements into the steelmaking whose control was left so a long time with the sense of smell acquired by an long experience. ” `'.

When the operator judges that decarburization is sufficient, one adds various elements (ferro-manganese, aluminum) to deoxidize and degas (to calm) the load: '' “wants one to obtain soft iron intended for rolling, the addition will be composed of ferro-manganese containing from 50 to manganese 80%, and its weight will be from 0,5 to 1% of metal charged. To obtain less soft iron or steel, one will add 1 to ferro-manganese 3%. ” `'.

Once the whole of the operations carried out one runs the metal obtained in a pocket or an ingot mould.

Refining is not carried out by the passage of the air through the cast iron load as in the converters but by the contact between fused metal and the Laitier. The total duration of the operation is thus much longer and strongly varies according to the proportion of cast iron, of the nature of the plate, the temperature of the furnace and the time employed with the loading (because of the time of loading but also of the cooling of the furnace if the doors remain longer open) and of the weight of the load. Ledebur gives a varying time from four to twelve hour with more classically a varying time from 5 to 8 a.m. What made it possible to make three to four cast in the course of the day. The duration is a disadvantage in term of productivity but is an advantage in term of control of the quality of the product obtained. Longer time and the possibilities of adjustment or addition in the load made it possible to obtain steels of better quality compared to those obtained with Bessemer processes and Thomas.

See also

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