Imagens das páginas
PDF
ePub

All the pig made from this mixture of ores the exhibitors state will give a steel without the use of spiegeleisen, which is not at all red short. The analysis of gray iron from the same works, used for the Bessemer process, is given as follows:

[blocks in formation]

The cinder, produced at the same time as the gray iron, shows on analysis a composition of

[blocks in formation]

The analysis of mottled pig, (la fonte truité,) consisting of two-thirds gray and one-third white, is

[blocks in formation]

Of each of these it is stated that the steel produced without the employment of spiegeleisen is not at all red short, (cassant à chaud.) The most noticeable feature in the composition of these irons is the large percentage of manganese which they contain, together with the extremely minute proportion of sulphur. The latter quality is due to the exclusive employment of charcoal in the blast furnaces, together with the adoption of a very high temperature in the roasting kiln. These latter are constructed on Westman's patent, and are made very high and heated by the waste gas drawn from the blast furnaces. The heat is carried as high as is possible without agglomerating the materials, and by this treatment the ore is changed from a hard and compact substance to a very porous one, while at the same time it is stated that any percentage of sulphur less than four per cent. is driven off. The blast furnaces are very small, being generally but eight feet in diameter at the boshes and about three feet at the hearth, with a height of forty feet. With these ores prepared in this manner, such a furnace will yield from seventy to eighty tons per

week. It is thought by the best informed engineers in Sweden that these furnaces should be made larger, and in future they probably will be so; but these dimensions represent the furnaces that now exist, and with which the iron in use has been produced.

In the process of conversion, from motives of economy, a fixed form of vessel is employed, instead of one mounted on trunnions, as in England and elsewhere. The tuyeres, about nineteen in number, are placed horizontally just above the bottom of the vessel, and are inclined a little from a radial direction so as to give a rotary motion to the mass of molten metal. An air passage surrounds the vessel at the back of the tuyeres, with a movable plate opposite each to allow access to them. The upper portion of the vessel, from the line of the top of the blast passage, is made removable, for lining, &c.; the bottom of the vessel is slightly inclined towards the taphole, so that the whole of the metal and slag may run off. The metal is run in at a spout in the upper portion of the vessel, and from the fixed position of the vessel it is of course necessary to have the blast on all the time that the metal is being run in and drawn off, to prevent its flowing into the tuyeres. This fact must make it more difficult to regulate the exact amount of decarbonization of the metal, and tend to render the last portion drawn off overdone. The removal of the cinder remaining in the vessel after a blow is not so easily accomplished in the fixed vessels as in the revolving one, as ordinarily used.

Accompanying the analysis of ores and irons, given above, the Fagersta works exhibit an analysis of the slag from the converter, taken at the close of the process, and it shows the composition to be as follows: Silica...

Alumina..

Lime..

Magnesia.

Protoxide of manganese .

Protoxide of iron..

44.30

10.85

0.65

0.45

24.55

19.45

100.25

The case of specimens exhibited by these works is the most interesting by far in the Exposition. It contains a most extensive collection of pieces of various forms, with which a very elaborate set of experiments has just been made at Mr. D. Kirkaldy's testing works at London, the result of which will be found in Appendix D. The samples are classified according to the percentage of carbon which they contain, and have been tested to show their action under strains of tension, compression, torsion, bending, and, in the case of plates, bulging.

The amount of carbon contained in the steel varies from 0.1 to 1.50 per cent., though most of the experiments were made between the limits of 0.3 and 1.20 per cent. In addition to the large collection of test pieces, they exhibit some railway carriage axles containing 0.3 per cent. of carbon, one being bent double with a radius of curvature at the bend of about 5

inches; a locomotive axle containing 0.4 per cent., and a tire having 0.5 per cent. of carbon. There is, also, as already mentioned, a fine display of cutlery, razors, some beautiful hand mirrors containing 1.0 per cent., a small drill containing 1.50 per cent., with a plate beside it containing 1.00 per cent., through which it had drilled several holes; a number of long turnings taken off in a lathe, showing remarkably the absolute continuity of the grain-one of 0.3 per cent. of carbon measures 36 feet in length, and is closely coiled with a diameter of about inch; another of 0.9 per cent. is 27 feet long and slightly less in diameter. There are also a large number of files, and, as previously mentioned, coils of wire of all sizes, and apparently any required length. A very interesting table of results was obtained from a series of eleven small square bars containing varying percentages of carbon, as follows:

Strength of steel containing different amounts of carbon.

[blocks in formation]

The cost of steel for the more delicate uses, such as razors, &c., is very much less by the Bessemer process than by the old method of remelting in the crucible. The materials in ordinary use are sufficiently pure to give such a steel, and the only special precaution which has to be observed in producing these qualities is to add a sufficient amount of recarbonizing pig to give the required per cent. of carbon, and then in the process of tilting the bars to carefully reject any piece which may show sign of flaw, as would of course be necessary under any circumstances. The total production of Bessemer steel in Sweden in 1864 was 3,178 tons; that of crucible steel exceeded 4,500 tons.

AUSTRIA.

The conditions under which Bessemer metal is produced in Austria are in many respects similar to those existing in Sweden. The iron employed is smelted with charcoal, is nearly free from sulphur and phosphorus, and contains a large percentage of manganese. There are differences in the manner of conducting the process, but these important conditions

IRON.

insure the production of a metal of similar excellence to the Swedish, and, like this, much superior to the ordinary metal produced in England.

The principal works in Austria are at Neuberg, in the province of Styria, and are carried on by the government. The iron is obtained from spathic ores smelted in two furnaces 43 feet high, and yielding from 100 to 150 tons per week. The iron produced is found by analysis to contain 3.46 per cent. of manganese, and, as in Sweden, it is used for recarbonizing in the place of the usual spiegeleisen. Originally a fixed vessel was erected at these works similar to those used in Sweden, but this has been superseded by a pair of three-ton vessels of the ordinary construction. Fixed or Swedish vessels are, however, still in use at other Austrian works. The metal is run directly from the blast furnaces into the converters. Very interesting tables are exhibited by these works, giving analyses of the iron and slag at five periods in its conversion from its condition as tapped from the furnace to its final state as Bessemer metal. These are extremely interesting from the light which they throw upon the relative rapidity with which the components of the pig iron are attacked by the blast, and the permanency of some ingredients, such as phosphorus and copper, during the entire process. The results are as follows:

Analyses of iron and slag during conversion to steel.

[blocks in formation]
[blocks in formation]
[blocks in formation]

From each charge blown at these works a small test ingot is cast, and this is immediately reheated and subjected to a number of tests to ascertain the quality of the steel; and according to the results of these trials, all the metal produced is divided into seven grades of varying hardness, No. 1 being a blue steel, containing from 1.12 to 1.58 per cent. of carbon; and No. 7 a soft iron, with from 0.05 to 0.15 per cent.

The test employed consists in hammering the little ingot into a bar, and subjecting it to severe working on the anvil, in a way which would tend to crack it if of a red, short nature, or of inferior quality. It is then heated and plunged into water, and the amount of hardening produced proved by striking it with a hammer, and observing the amount of flexure produced. It is then heated again and bent over upon itself and welded into an eye, the welded portion being drawn out to a small section and broken off. These tests take but a short time, and the expense of making them is insignificant in comparison with the accurate knowledge thereby obtained of the nature of the steel and the purposes for which it is suitable. As a rule, the steel produced at the Neuberg works welds with great facility, and, in fact, all the tires produced here are welded as in the case of iron. A table of the tensile strengths and other properties of steel, of the various classes below No. 2, is exhibited, and is as follows:

Tensile strength and ather properties of steel.

[blocks in formation]

The softest grade is used for wire, sheet steel, &c., and the higher numbers for boiler plate, gun barrels, axles, tires, tools, and cutlery, according to the hardness required.

A printed list gives the price of the steel in various forms delivered at the works, which, reduced to gold dollars, is as follows: ingots, $77 50; bars, $138; boiler plate, $145 50; tires, $155 50. These prices are little above those charged in England, where coal is abundant and an inferior quality of metal produced.

PRUSSIA.

In other countries than Sweden and Austria, we find nothing that presents any remarkable feature not to be found in English practice. Of course, Krupp is far ahead of all others in respect to the size of the masses

« AnteriorContinuar »