Sir Henry Bessemer's process for making steel, which is now so largely practised in England, on the continent of Europe, and in
America, was patented in 1856. It was first applied to the making of malleable iron, but this has never been successfully made by
the Bessemer method.[Pg 22] For the manufacture of a cheap but highly serviceable steel, however, its success has been so splendid that no other metallurgical process has given its inventor so great a renown. Although the apparatus actually used is somewhat costly and elaborate, yet the principle of the operation is very simple. A large converting vessel, with openings called tuyeres in its bottom, is partially filled up with from 5 to 10 tons of molten pig-iron, and a blast of air, at a pressure of from 18 to 20 lb. per square inch,
is forced through this metal by a blowing engine. Pig-iron contains from 3 to 5 per cent. of carbon, and, if it has been smelted with charcoal from a pure ore, as is the case with Swedish iron, the blast is continued till only from .25 to 1 per cent. of the carbon is left in the metal, that is to say, steel is produced. Sometimes, however, the minimum quantity of carbon is even less than .25 per cent.
In England, where a less pure but still expensive cast-iron--viz. haematite pig--is used for the production of steel in the ordinary Bessemer converter, the process differs slightly. In this case the whole of the carbon is oxidised by the blast of air, and the requisite quantity of this element is afterwards restored to the metal by pouring into the converter a small quantity of a peculiar kind of cast-iron, called spiegeleisen, which contains a known quantity of carbon. But small quantities of manganese and silicon are also present in Bessemer steel. The 'blow' lasts from 20 to 30 minutes. Steel made from whatever kind of pig-iron, either by this or by the 'basic' process, is not sufficiently dense, at least for most purposes, and it is accordingly manipulated under the steam-hammer and rolled into a variety of forms. Bessemer steel is employed, as we have said, for heavy objects, as rails, tires, rollers, boiler-plates, ship-plates, and for many other purposes for which malleable iron was formerly used.[Pg 23]
Basic steel is now largely made from inferior pig-iron, such as the Cleveland, by the Thomas-Gilchrist process patented in 1878.
It is, however, only a modification of the Bessemer process to the extent of substituting for the siliceous or 'acid' lining generally used, a lime or 'basic' lining for the converter. Limestone, preferably a magnesian limestone in some form, is commonly employed for the lining. By the use of a basic lining, phosphorus is eliminated towards the end of the 'blow.' Phosphorus is a very deleterious substance in steel, and is present, sometimes to the extent of 2 per cent., in pig-iron smelted from impure ore.
The four inventions of this century which have given the greatest impetus to the manufacture of iron and steel were--the introduc-
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tion of the hot blast into the blast-furnace for the production of crude iron, made by J. B. Neilson, of the Glasgow Gas-works, in
1827; the application of the cold blast in the Bessemer converter which we have just described; the production of steel direct from the ore, by Siemens, in the open hearth; and the discovery of a basic lining by which phosphorus is eliminated and all kinds of iron converted into steel. This last was the discovery of G. J. Snelus, of London, and it was made a practical success by the Thomas & Gilchrist process just described. In 1883, Mr Snelus was awarded the Bessemer gold medal of the Iron and Steel Institute 'as the first man who made pure steel from impure iron in a Bessemer converter lined with basic materials.'
SIR HENRY BESSEMER.
Sir Henry Bessemer, the inventor of the modern process of making steel from iron, which has just been described, was the son of
Anthony Bessemer,[Pg 24] who escaped from France in 1792, and found employment in the English Mint. He was born in 1813, at Charlton, Herts, where his father had an estate, was to a great extent self-taught, and his favourite amusement was in modelling buildings and other objects in clay. He came up to London 'knowing no one, and no one knowing me--a mere cipher in this vast sea of enterprise.' He first earned his living by engraving a large number of elegant and original designs on steel with a diamond point, for patent medicine labels. He found work also as designer and modeller. He has been a prolific inventor, as the volumes issued by
the Patent Office show. It has been said that he has paid in patent stamp duties alone as much as PS10,000. At twenty he invented a mode of taking copies from antique and modern basso-relievos in such a way that they might be stamped on card-board, thousands being produced at a small cost.
His inventive faculty also devised a ready method whereby those who were defrauding the government by detaching old stamps from leases, money-bills, and agreements, and by using them over again, could be defeated in their purpose.
His first pecuniary success was obtained by his invention of machinery for the manufacture of Bessemer gold and bronze powders, which was not patented, but the nature of which was long kept secret. Another successful invention was a machine for making Utre-cht velvet. He also interested himself in the manufacture of paints, oils, and varnishes, sugar, railway carriages, ordnance, projectiles, and the ventilation of mines. In the Exhibition of 1851 he exhibited an ingenious machine for grinding and polishing plate-glass.
Like Lord Armstrong, Bessemer turned his attention to the subject of the improvement of projectiles when there was a prospect of a European war in 1853. He[Pg 25] invented a mode of firing elongated projectiles from smooth-bore guns, but received no counte-nance from the officials at Woolwich.
Commander Minie, who had charge of the experiments which Bessemer was making on behalf of the Emperor of the French, said:
'Yes, the shots rotate properly; but if we cannot get something stronger for our guns, these heavy projectiles will be of little use.' This started Bessemer thinking and experimenting further, and led up, as we will see, to the great industrial revolution with which his name stands identified. He informed the Emperor that he intended to study the whole subject of metals suitable for artillery purposes. He built experimental works at St Pancras, but made many failures, furnace after furnace being pulled down and rebuilt. His prolonged and expensive experiments in getting a suitable ordnance metal were meanwhile using up his capital; but he was on the eve of a great discovery, and began to see that the refinement of iron might go on until pure malleable iron or steel could be obtained. His wife aided and encouraged him at this time as only a true wife can. After a year and a half, in which he patented many
improvements in the existing systems of manufacture, it occurred to him to introduce a blast of atmospheric air into the fluid metal, whereby the cast-iron might be made malleable. He found that by blowing air through crude iron in a fluid state, it could thus be rendered malleable. He next tried the method of having the air blown from below by means of an air-engine. Molten iron being poured into the vessel, and air being forced in from below, resulted in a surprising combustion, and the iron in the vessel was transformed into steel. The introduction of oxygen through the fluid iron, induced a higher heat, and burned up the impurities. Feeling that he
had succeeded in his experiment, he acquainted Mr George Rennie with the result. The[Pg 26] latter said to him: 'This must not be hid under a bushel. The British Association meets next week at Cheltenham; if you have patented your invention, draw up an account of it in a paper, and have it read in Section G.' Accordingly Bessemer wrote an account of his process, and in August 1856, he read his paper before the British Association 'On the Manufacture of Malleable Iron and Steel without Fuel,' which startled the iron trade of the country.
On the morning of the day on which his paper was to be read, Bessemer was sitting at breakfast in his hotel, when an iron-master to whom he was unknown, laughingly said to a friend: 'Do you know that there is somebody come down from London to read us a paper on making steel from cast-iron without fuel? Did you ever hear of such nonsense?'
Amongst those who spoke generously and enthusiastically of Bessemer's new process was James Nasmyth, to whom the inventor offered one-third share of the value of the patent, which would have been another fortune