KRUPP'S STEEL. The widespread reputation of the steel produced in the great works of Herr Krupp, at Essen, in Prussia, has induced us to give it a brief notice. His manufactory, always a large one, has been gradually increasing in size during the last half century, until it now covers nearly 1000 acres, and gives employment to sonic 14,000 persons. For large metallurgical works, Essen is favorably situated, being in the center of a coal-bearing area, where coal of the purest kind can be comparatively cheaply procured. There is also at hand the manganiferous iron ores of Prussia, which have been found so excellently adapted for the manufacture of steel; but it is believed that the admirable organization of every part of his manufactory has conduced, as much as anything, to the gre tt success of Krupp. With laborers and mechanics who have passed the regulation-time in the Prussian army, overseers trained in the German tech nical schools, and a small staff of experienced analytical chemists, he has obviously a great advantage in conducting operations where order, system. and skill are of para mount importance. But even with these benefits, Krupp's productions would not have gained their celebrity, were it not for the scrupulous care with which he performs every manipulation.
• In the article Inox we have described the manufacture of steel by the cementation and Bessemer processes, but there are several other methods of making it, and one of these is by the decarburization of cast-iron in the puddling furnace. This is the pro cess by which Krupp makes his steel, in the first instance; and the material he most largely employs is spiegeleisen, or specular cast-iron, a highly crystalline variety, usually containing about 4 per cent of manganese. This iron is admirably suited for conversion into steel. The puddling process for steel is qiniilar to that employed for iron (q.v.),.
except that the former is conducted at a lower temperature, and requires nicer manage ment; but in the case of steel, the cast-iron to be operated upon is never previously refined. Cast-iron to the extent of about 4 cwts. is melted in the puddling furnace, mixed with a quantity of slag or cinder (chiefly silicate of iron), and stirred with a rab ble. During this operation, the carbon in the cast-iron (usually about 5 percent) is grad ually oxidized by the oxygen present in the cinder; carbonic oxide is produced, and as it escapes, what is technically termed " boiling" takes place. When the ebullition becomes active, the temperature is raised until the appearance of incipient solidification occurs; the heat is then lowered, and the ordinary process of balling proceeded with. Steel thus
produced usually contains from 0.5 to 1 per cent of carbon; but if the temperature is not skillfully regulated, the carbon becomes wholly burned away, and malleable iron instead of'steel is produced.
Puddled steel, although useful for most purposes in the arts (except cutlery), never theless wants homogeneity, on account of a certain intermixture of cinder, which is diffi cult to get rid of without fusion—a defect which is apt to prevent it from welding perfectly. In Krupp's works the puddled steel is remelted into crucibles, in order to convert it into cast-steel; and it is the wonderful uniformity of quality with which he manufactures this in very large masses, that constitutes the superiority of, and gives so great an interest to, his productions. The crucibles employed are made with extreme care, mainly from fire-clay, to which a little plumbago is added; their capacity varies from 50 to 100 lbs., and it is reported that as many as 100,000 are kept drying at the same time. After being once used, the crucibles are broken up, and mixed with other material, to make new ones.
In the casting-house, where the large ingots are run, the furnaces,which contain about 1200 crucibles, are arranged along the sides of the building; and in the central portion the steel molds, varying in capacity from 100 lbs. to 50 tons, are disposed in line between two pair of rails, upon which runs a movable crane. It is in the casting of such an enormous ingot as 50 tons of steel (the largest yet produced) from crucibles of small capacity that the perfect organization of Krupp's establishment becomes most strikingly apparent. At a given signal, one gang of workmen remove the crucibles from the fur naces, while another seize them with tongs for the purpose, and pour their contents into narrow canals of wrought-iron, lined with fire-clay, which converge into the open ing by which the mold is filled. This is the critical stage of the operation, the difficulty being to deposit in the mold a continuous stream of melted steel of about the same degree ' of heat, so as -to cool uniformly, and to solidify into a perfectly homogeneous mass. Of such uniform soundness are some of Krupp's large steel ingots, that one—shown in the London exhibitionof 1862,'J ft. high, 44 in. in diameter, and 21 tons—when broken across did not show- the slightest flaw, even when examined with a leus.