Discoveries and Inventions of the Nineteenth Century

by Robert Routledge

The headpiece to our chapter on Fire-Arms gives but a very inadequate idea of the magnitude of the Essen Works about 1870. A better notion will be obtained from a few figures which we select from a list giving some of the contents of the Essen Works in 1876. There were 1,109 furnaces of various kinds, of which 250 were for smelting; 77 steam hammers, 294 steam engines, 18 rolling mills, 365 turning lathes, and 700 other machine tools; 24 miles of ordinary gauge railway for traffic within the works; together with 10 miles of narrow gauge railway; 38 miles of telegraph lines, with 45 Morse apparatus, etc. (J. S. Jeans’ Steel: its History, etc., 1880). These figures belong, be it observed, to the state of things in 1876; but we learn from a later authority that in 1894 these works employed 15,000 men, and we must suppose that the plant has been proportionately increased since the earlier period, when 10,000 men were employed.

In the year 1854 a regular system of records began to be kept of the amounts of coal and ores raised in Great Britain, and also of the quantities of the various metals produced. These show that in 1894 very nearly three times as much coal was raised as in 1854, and that in the same period the quantity of British pig iron smelted annually had increased four-fold; these increases look small when compared with the expansion of the steel production in Britain within the same period of forty years, for this had enlarged thirty-fold. This extraordinary development is attributable to the introduction of two processes by either of which various steels of excellent quality, and adapted to a great range of applications, can be produced cheaply and with certainty. These processes are respectively known as the Bessemer and the Open Hearth, and the reader should observe that with the main principles involved in these he has already been made acquainted.

Henry Bessemer, who first saw the light in England in 1813, may be said to have been born an inventor, for his father was one before him—a Frenchman employed in the royal mint at Paris, afterwards appointed by the Revolutionary authorities to superintend a public bakery; on an accusation of giving short weight, thrown into prison, from which, and probably from the guillotine, he escaped, and found employment in the English mint. Subsequently he devised some notable improvements in the art of producing letterpress type, and for many years carried on a prosperous business as a typefounder. The son developed inventive faculties at a very early age: in lathe engraving, dies, dating stamps, etc. His name became familiar to everyone by his production of the metallic powder long known as “Bessemer’s Gold Paint.” It became known to Bessemer that the raw material of this substance, which was then sold at £5, 10s. per lb., really cost only about one shilling per lb., and he set himself to discover its composition and mode of manufacture. He succeeded in this so well that he could produce the article at the insignificant cost of four shillings a pound, and his first order for a supply of it was at the rate of £4 per lb., and the business was continued, realising profits of something like 1,000 per cent. at first. For this article no patent was taken out, but Bessemer himself, assisted by two trustworthy workmen, carried on the manufacture in secret, and he some time afterwards rewarded the fidelity of his men by handing over the business to them as a free gift. Then he took out patents for improvements in the manufacture of oils, varnishes, sugar, plate glass, etc. Several of his machines for these purposes were shown at the London Exhibition of 1851. Bessemer is said to have obtained altogether some 150 patents, including those granted for inventions connected with our subject. He may be regarded as the type of the very fortunate inventor, since on the patents of the one process we are going to describe he ultimately obtained royalties to the value of more than £1,057,000, and this irrespective of profits derived from commercially working it himself.

At the time of the Crimean War, Bessemer had some experiments made at Vincennes with cylindrical projectiles he had devised for firing from smooth-bore guns, yet so as to impart to the projectile at the same time rotation about its axis. The experiments were successful, but it was pointed out that the guns of cast iron then in use would not bear heavy projectiles, and he was induced, at the suggestion of the Emperor Napoleon III., to undertake some researches with the view of finding metal more suitable for artillery. Bessemer, having then little knowledge of the metallurgy of iron, applied himself on his return to England to the study of the best books on the subject, visited the principal iron-working districts, and began a series of experiments at a small experimental installation he set up in London. There, after repeated failures, he did at length succeed in producing a metal much tougher than the cast iron then used, and a small model gun was submitted to the Emperor, who encouraged Bessemer to persevere with his experiments; which he did, though the expense was a great tax on his capital, continued as the experiments were for two years and a half. But by this time he had acquired a knowledge of many important facts, and these gradually led him to the experimental realization of the idea he had conceived, but only after many trials in which several thousand pounds were expended. At length the agenda of the British Association for the Cheltenham meeting of 1856 announced that a paper would be read by H. Bessemer, entitled “The Manufacture of Iron and Steel without Fuel.” It will be easily understood that a title in such terms would give rise to much derisive incredulity; and we may imagine the iron-masters on that occasion crowding into Section G, while asking each other in the spirit of certain philosophers of old, “What will this babbler say?” Some of what he did say may here be quoted, as at once explanatory and historically memorable.

“I set out with the assumption that crude iron contains about 5 per cent. of carbon; that carbon cannot exist at a white heat in the presence of oxygen without uniting therewith and producing combustion; that such combustion would proceed with a rapidity dependent on the amount of surface of carbon exposed; and lastly, that the temperature which the metal would acquire would be also dependent on the rapidity with which the oxygen and carbon were made to combine; and consequently, that it was only necessary to bring the oxygen and carbon together in such a manner that a vast surface should be exposed to their mutual action, in order to produce a temperature hitherto unattainable in our largest furnaces.

Fig. 23.—Experiments at Baxter House.

“With a view of testing practically this theory, I constructed a cylindrical vessel of 3 ft. in diameter and 5 ft. in height, somewhat like an ordinary cupola furnace (see Fig. [23]). The interior is lined with firebricks, and at about 2 in. from the bottom of it I inserted five tuyère pipes, the nozzles of which are formed of well-burned fire-clay, the orifice of each tuyère being about three-eighths of an inch in diameter; they are so put into the brick lining (from the outer side) as to admit of their removal and renewal in a few minutes, when they are worn out. At one side of the vessel, about half-way up from the bottom, there is a hole made for running-in the crude metal, and on the opposite side there is a tap-hole, stopped with loam, by means of which the iron is run out at the end of the process. In practice this converting vessel may be made of any convenient size, but I prefer that it should not hold less than one nor more than five tons of fluid iron at each charge; the vessel should be placed so near to the discharge hole of the blast furnace as to allow the iron to flow along a gutter into it. A small blast cylinder is required capable of compressing air to about 8 lbs. or 10 lbs. to the square inch. A communication having been made between it and the tuyères before named, the converting vessel will be in a condition to commence work; it will however on the occasion of its first being used after re-lining with firebricks be necessary to make a fire in the interior with a few baskets of coke, so as to dry the brickwork and heat up the vessel for the first operation, after which the fire is to be all carefully raked out at the tapping-hole, which is again to be made good with loam: the vessel will then be in readiness to commence work, and may be so continued without any use of fuel until the brick lining, in the course of time, becomes worn away, and a new lining is required. I have before mentioned that the tuyères are situated nearly close to the bottom of the vessel, the fluid metal will therefore rise some 18 in. or 2 ft. above them; it is therefore necessary, in order to prevent the metal from entering the tuyère holes, to turn on the blast before allowing the fluid crude iron to run into the vessel from the blast furnace. This having been done, and the metal run in, a rapid boiling up of the metal will be heard going on within the vessel, the metal being tossed violently about and dashed from side to side, shaking the vessel by the force with which it moves; from the throat of the converting vessel flame will immediately issue, accompanied by a few bright sparks such as are always seen rising from the metal when running into the pig-beds. This state of things will continue for about fifteen minutes, during which time the oxygen in the atmospheric air combines with the carbon contained in the iron, producing carbonic oxide, or carbonic acid gas, and at the same time evolving a powerful heat. Now, as this heat is generated in the interior of, and is diffused in innumerable fiery bubbles through, the whole fluid mass, the metal absorbs the greater part of it, and its temperature becomes immensely increased, and by the expiration of the fifteen minutes before named that part of the carbon which appears mechanically mixed and diffused throughout the crude iron has been entirely consumed: the temperature however is so high that the chemically combined carbon now begins to separate from the metal, as is at once indicated by an immense increase in the volume of flame rushing out of the throat of the vessel. The metal in the vessel now rises several inches above its natural level, and a light frothy slag makes its appearance and is thrown out in large foam-like masses. This violent eruption of cinder generally lasts about five or six minutes, when all further appearance of it ceases, a steady and powerful flame replacing the shower of sparks and cinder which always accompanies the boil. The rapid union of carbon and oxygen which thus takes place adds still further to the temperature of the metal, while the diminished quantity of carbon present allows a part of the oxygen to combine with the iron, which undergoes combustion and is converted into an oxide. At the excessive temperature that the metal has now acquired, the oxide as soon as formed undergoes fusion, and forms a powerful solvent of those earthy bases that are associated with the iron; the violent ebullition which is going on mixes most intimately the scoria and metal, every part of which is thus brought in contact with the fluid oxide, which will thus wash and cleanse the metal most thoroughly from the silicon and other earthy bases which are combined with the crude iron, while the sulphur and other volatile matters which cling so tenaciously to iron at ordinary temperatures are driven off, the sulphur combining with the oxygen and forming sulphurous acid gas.

“The loss in weight of crude iron during its conversion into an ingot of malleable iron was found, on a mean of four experiments, to be 12½ per cent., to which will have to be added the loss of metal in the finishing rolls. This will make the entire loss probably not less than 18 per cent. instead of about 28 per cent., which is the loss on the present system. A large portion of this metal is however recoverable by heating with carbonaceous gases the rich oxides thrown out of the furnace during the boil. These slags are found to contain innumerable small grains of metallic iron, which are mechanically held in suspension in the slags and may be easily recovered.

“I have before mentioned that after the boil has taken place a steady and powerful flame succeeds, which continues without any change for about ten or twelve minutes, when it rapidly falls off. As soon as this diminution of flame is apparent the workman will know that the process is completed, and that the crude iron has been converted into pure malleable iron, which he will form into ingots of any suitable size and shape by simply opening the tap-hole of the converting vessel and allowing the fluid malleable iron to flow into the iron ingot moulds placed there to receive it. The masses of iron thus formed will be free from any admixture of cinder, oxide, or other extraneous matters, and will be far more pure and in a forwarder state of manufacture than a pile formed of ordinary puddle bars. And thus it will be seen that by a single process, requiring no manipulation or particular skill, and with only one workman, from three to five tons of crude iron pass into the condition of several piles of malleable iron in from thirty to thirty-five minutes, with the expenditure of about a third part the blast now used in a finery furnace, with an equal charge of iron, and with the consumption of no other fuel than is contained in the crude iron.