Page:Encyclopædia Britannica, Ninth Edition, v. 13.djvu/366

350 IRON tion, and G is a small bed for heating scrap, &c., before its introduction into the main hearth D. Owing to the regene rator only heating up the blast, the waste gases escape at a much higher temperature than with a Siemens regene rator ; accordingly they may be advantageously utilized to produce steam. According to Perisse (from whose paper Journ. I. and S. Inst., 1878, 459 the cuts, ligs. 63 and 64 are taken) the average duration of a blow and subsequent operations in a 5-ton furnace is five to six hours when the metal is charged cold, whilst six to eight operations may ba made in twenty-four hours when it is previously melted in a spare hearth ; 250 kilos (about 5 cwts.) of Mons coal were consumed per hour, or about 6 tons per twenty-four hours for 20 tons and upwards of production (charged cold), or for 30 to 40 tons (charged with fluid metal). Phosphorus is not materially eliminated, because, as in the ordinary Bessemer and Siemens-Martin hearths, there is a silicious flux always present, owing to the nature of the lining ; this objection, however, is readily remediable by simply using a "basic" lining ( 37), when more or less complete dephosphorization results, just as is the case with the Pernot hearth when a large amount of fussd iron oxide is added, as in Krupp s dephosphorizing process. By omitting the movable bed, and substituting the ordinary fixed bed of a reheating furnace, the Ponsard forno-convertisseur becomes changed into the Ponsard reheating furnace ; the advan tages of this form of arrangement over that of Siemens s ivheater are said to be considerable saving of cost in construction and capa bility of producing steam by the waste heat. 41. Manufacture of Spiegeleisen and Ferro -manganese and Allied Substances. In all the above combination pro cesses which are successfully worked, the final stage is almost invariably the addition to more or less com pletely decarbonized molten iron of carbonized mangani ferous iron in definite proportion, so as to communicate a known amount of carbon (and also of manganese) to the mixture ; accordingly the preparation of Manganeisen (as such substances may be conveniently termed) is an im portant step in the steel making processes. When highly manganiferous iron ores, such as the Styrian spathose ores, are smelted in the ordinary way in a blast furnace, a large fraction of the manganese is not reduced, but passes away in the cinder ; by using a larger amount of fuel FIG. 64. Ponsard Forno-Convertisseur Longitudinal section. relatively to the burden, however, the quantity of manganese reduced and obtained in the pig iron is increased ; the hotter the blast the greater the richness in manganese of the pig, at least with the ores used in the Siegen district. At Nijne Tajilsk (Urals) a ferruginous manganese dioxide occurs of the following composition : Manganese dioxide 58 00 per cent. ,, sesquioxide 13 86 ,, Ferric oxide 15 33 ,, Silica 4-13 Water 8 68 ,, From this a fine brand of spiegeleisen is smelted. At Schisshyttan (Sweden) occurs a mixture of magnetite, manganiferous garnet, and knebelite (silicate of iron and manganese), of which mixed ore the average composition is Silica 25 88 percent. Ferrous oxide 54 57 , , Manganese oxide 17 17 ,, Alumina and calcium carbonate, &c 2 - 38 ,, Of late years this has been extensively used for manu facturing spiegeleisen (chiefly used for Swedish Bessemer iron) containing about 4 per cent, carbon and upwards of 10 of manganese, sometimes 15 or even more per cent, being present. These higher manganiferous irons show little or no magnetic action. During the early period of the development of the fused steel industry, the richer manganeisens (containing 15 per cent, and upward of manganese) used for crucible steels were themselves pre pared in crucibles, the term " ferro-manganese " being applied to these products, "spiegeleisen" indicating the less manganiferous pig containing some 6 or 7 per cent, of manganese prepared in the blast furnace ; subsequently, however, the blast furnace spiegel- eisens of commerce were prepared much richer in manganese than formerly, whilst ferro-manganese of 30 and upwards per cent, of manganese came into use prepared by Henderson s method, viz., by reducing upon the open hearth of a Siemens furnace a mixture of manganese carbonate (obtained from bleaching powder residues or " still -liquor ") and ferric oxide in presence of excess of carbon, a neutral or slight reducing flame being employed. The furnace bottom is made of coke ground up and consolidated, so as virtually to form a large carbon shallow crucible or basin, the finely divided mixture being put in and the temperature raised to a low red beat for some hours. A metallic sponge is obtained which subsequently runs down to a regulus when the temperature is raised to a full white. An important influence in the amount of manganese