to a white heat, not sufficient, however, to melt what may stil! remain of cast-iron.

After a proper annealing, the castings are covered with a film of oxide of iridescent colors-the yellow and azure blue predominating-which resembles that kind of Champlain iron ore called peacock, on account of its coloration.

Any adherent oxide is removed by another passage through the "tumblers," and the process of malleable iron making is finished. Any further grinding, polishing, boring, and adjusting which may be needed, is made in the same works.

The oxide of iron, or scales, employed, have parted with a portion of their oxygen during the annealing process, and the loss is made good by grinding the scales, and rusting them with a solution of sal ammoniac (hydrochlorate of aminonia). It seems to us possible to do without the expense of sal ammoniac, by wetting the powdered scales several times with water, stirring and drying them on the top of the annealing furnace. Among the products manufactured by the above mentioned firm, we have noticed hinges, entirely of cast-iron, and others with wrought iron pivots; patent elastic washers for railroad fish-plates, which prevent the nut from unscrewing, and keep it tight; castors for furniture, bolts, pulleys for cords of window sashes, keys, padlocks, screw presses, carriage parts, saddlery hardware, &c. &c. In fact, it would be necessary to make a catalogue with an index, of all of the patterns which were shown to us.

It is difficult to state the cost of malleable iron castings, since it depends to a great extent upon the size and the quantity of the articles. We may say, however, that being given a certain pattern, the malleable iron castings will cost from 70 to 80 per cent. more than ordinary castings from the same pattern. This increase of price is necessitated by more labor, the consumption of fuel for annealing, greater cost of pig metal employed, &c. &c.

To sum up, malleable iron castings are useful, whenever equal strength of material being not needed, the cost in labor, if made of wrought iron, would be too great; or when a casting is needed without the brittleness of common cast-iron. Scissors, sewing-machine parts, the butt-ends and guards, and many other parts of gun locks, ornaments, &c. &c., are made. in quantities from malleable iron castings. Even nails, of all sizes, are thus manufactured in England, and we are disposed to believe that, if made of good metal and well annealed, they may be at least equal to certain cut-nails produced from inferior plate, and the fibre of which has been broken by the concussion of the cutting machine.

Oxide of zinc has been proposed as a substitute for oxide of iron, under the plea that the operation is more rapid. A. A FESQUET.

BESSEMER STEEL.

IMPROVEMENTS IN THE PROCESS.

THE Bessemer process, as it was conducted several years since, has already been completely described in this work. The pig-metal still continues to be decarburized by the oxygen of a powerful blast, but the appliances and mode of operation have been modified.

It was thought, at the beginning, that it would be possible to use any kind of pig-metal for the manufacture of Bessemer steel, or homogeneous iron; and that the intense heat and blast would be sufficient to volatilize the impurities of the metal, i. e., sulphur and phosphorus. There was, indeed, little basis for this supposition in regard to sulphur, and not at all in regard to phosphorus, since phosphoric acid is one of the least volatile and most stable compounds known, and cannot be removed from the iron except by powerful bases, such as potassa and soda.

The doctoring by nitrate of soda, and other substances, has been tried on a large scale; but all manufacturers prefer to employ a pure pig-metal, comparatively free from sulphur and phosphorus, and holding a certain percentage of carbon and silicon, which are the two elements maintaining the combustion inside of the converting vessel.

The raw metal which, up to the present time, best fulfils the condition of purity with adaption to the Bessemer process, is the English product known as Cumberland pig. There is, however, little doubt that American pig-metal will be found as suitable for the purpose, when the proper inquiry shall be made.

The difficulty of producing a steel of the desired hardness, that is, holding a certain proportion of carbon, by arresting the blast at a certain period of the operation, has caused most manufacturers to entirely decarburize the metal in the converting vessel, and then to recarburize it to the proper degree by the addition of a proportion of Spiegeleisen calculated from the amount of carbon in the latter metal. This method gives much more certain results than by arresting the blast before entire decarburization is accomplished, the proper time being then guessed by fugitive differences in the color of the flame escaping from the mouth of the converter.

Spiegeleisen (mirror iron) is a white pig-metal presenting large facets in its fracture, and holding a variable proportion of

manganese and carbon, the latter in the combined state. Although nearly all of the manganese of this metal is found in the slags, the small proportion remaining with the steel appears greatly to improve its quality.

All of the trials made in various countries agree in this: that to be successful the Bessemer process for making steel requires a pig-metal of the first quality, and the addition of Spiegeleisen. The shape and disposition of the apparatus have also been modified, and we shall now examine these points.

The converting vessel or converter revolves on two trunnions (Fig. 608); one of them is hollow and connected by a coupling

Fig. 609

curved pipe along the lower part of the converter, and termi

nating in a metallic box beneath the apparatus. The other bears a strong pinion to which a revolving motion is given by a rack at the end of the piston rod of a double-acting waterpressure engine.

'The converter itself is an ellipsoidal vessel (Fig. 609), made of strong wrought-iron plate. The upper and lower parts are bolted together. On the top is an oblique mouth for receiving the charge of metal, for the escape of gases, and the running out of the steel. At the bottom a metallic box receives the blast and divides it through the tuyeres, five, six, or seven in number, and with five holes in each. The trunnions are fixed upon a large wrought-iron belt, about midway of the apparatus. The inside lining must be very carefully made; the refractory clay, strongly beaten into it, is mixed with a certain quantity of quartz, or ground firebrick free from scoriæ.

The hole of the tuyere is also made of firebricks, with all of the joints carefully luted. When the lining is dry a charcoal fire is built in it, and all cracks are closed. Afterwards a stronger fire is built, a certain blast is given, and the interior receives a glazing of common salt.

The ashes being removed, the converter is placed in a horizontal position, and the charge of pig-iron, previously smelted in a cupola, is run into it by means of a trough lined with sand. The charge is then level with the tuyeres, and the blast is turned on before the converter is made to revolve to its vertical position, which is slowly done. After fifteen to twenty minutes of blast, and when the long and blue flame of oxide of carbon has disappeared, the converter is swung again to a horizontal position in order to receive the additional charge of five to ten per cent. of Spiegeleisen. Having again been made to assume the vertical position, after five minutes more of blast, the steel is completed and run into a large ladle supported by a crane. From this ladle the ingot moulds are filled.

The blast, after the introduction of the Spiegeleisen, is intended to stir the mixture; but, as at the same time part of the carbon is burned off, it is necessary to add more Spiegeleisen than is needed for the desired per cent. of carbon in the steel. At the Belgian works of Seraing, no blast is let on after the introduction of the Spiegeleisen, and the mixture is considered sufficiently intimate after the several pourings into the converter, then into the casting ladle, and lastly into the ingots.

The steel poured into separate ingot moulds is apt to retain a certain amount of slags, and to be porous. The ingots are better when the moulds are in the form of siphons; the metal is more condensed and without admixture of slags, since they remain in the branch which receives the molten steel. These moulds are generally disposed as follows: a metallic platform is cast with deep grooves radiating from a centre, and the grooves and bottom of the central part are lined with small

bricks of fire clay. The moulds are of heavy cast iron, and present the shape of truncated quadrangular pyramids, the larger sections of which rest upon the metallic platform. Now, if we put one such mould over the central opening, and upon each outlet of the radiating grooves, the metal poured into the central mould will run into and fill the other moulds. All the slag remains in the central mould which, on this account, is a little higher than the others. When the steel has been sufficiently cooled off, the moulds are lifted by a crane.

Before rolling the steel the ingots are reheated and their cavities closed by condensing the metal under a steam hammer. The converters are made to receive from three to ten tons of molten pig-iron, which should, however, occupy but a small place in them; the reaction and the boiling are so violent that a part of the metal would be thrown out if there were not plenty of room. A six ton converter is eleven feet high, and five and a half feet in its widest diameter.

The oxidization of the silicon takes place before that of the carbon, and but little flame is therefore seen at the beginning of the operation. The silica unites with oxide of iron and forms a small quantity of slag. The pressure of the blast, for medium sized converters, is about fifteen pounds to the square inch.

The end of the decarburization is ascertained in different means: by viewing the flame through an optical instrument known as the spectroscope, which enables the observer to detect a certain line in the spectrum or image of the flame, the disappearance of which line marks, to within a few seconds, the conclusion of the process-by the sudden decrease of the long blue flame, and its appearance when viewed with the naked eye, or through different colored glasses superposed (blue and yellow), giving a dark neutral tint. Through these glasses the flame appears white as long as the decarburization is going on, and turns red when all the carbon has been burnt off.

Notwithstanding the care taken to stop the blast at the proper time, and to calculate the proportion of Spiegeleisen to be added, the steel produced requires to be classified afterwards. according to its chemical composition and physical properties. A small test ingot is cast at about the middle of the pouring, and its fracture examined. After having taken from it the necessary quantity of metal for the chemical determination of the carbon, it is hammered, bent, hardened, and tempered, and its tensile strength is also now and then ascertained. All of these tests give valuable information, and permit of the classification of the various grades of steel.

Nearly every steel works possesses its own mode of classifi cation, and we give below that used at the Belgian works of Seraing, near Liège.