When the metal manganese was first discovered in 1774 by Frederick Gahn, the celebrated Swedish mineralogist and chemist, in reducing it from the natural oxide in a small crucible, nobody could have foreseen that the identical body, only combined with a few Per cent. of carbon and iron, would a hundred years hence, be produced in the largest blast furnaces, and at not very much greater cost than common crude iron. When this greyish-white and very brittle metal was first known, its properties seemed to render it unfit for any practical use, as it required a very great heat for its reduction from the ore, and when exposed to damp air, it would rapidly decay or crumble to pieces. Although the metal was known to exist to some extent in the so-called spiegeleisen, and although it was many years ago thought to be essential in the manufacture of the very best German shear steel, nobody took the trouble to produce metallic manganese on purpose. Oxidized manganese was, however, at an early date, a frequent admixture in the manufacture of ordinary cast steel or crucible steel, and by the Sheffield steelmakers particular cleansing or strengthening pro-perties were attributed to it, in more good belief than reality.
It was only after Valenciennes, in 1870, had succeeded in producing, in a magnesia crucible with a gas-furnace, pure manganese metal in the molten state from pure manganese hyperoxide, and had exhibited this to the French Academy, that fresh attention was directed upon this peculiar and, as is now generally acknowledged, highly useful metal. Thus, Dr. Percy, in 1873, proposed to employ manganese instead of nickel in the manufacture of German silver, an alloy which contains copper and zinc besides. At that time also Tamm was able to produce an alloy of manganese and iron, with 96 Per cent. of the former; while at Jauerburg, in Carniola, ferro-manganese, an alloy of iron with carbon and up to 30 Per cent. of manganese, had been successfully produced in the charcoal blast-furnace and on a large scale. Since then the production of either pure metal or of its alloys with iron has been attempted by many English and foreign metallurgists, and by the employment of very different methods. The palm must, however, be given to those who have succeeded in producing ferro-manganese, containing 80 to 90 Per cent. of the metal, by using the ordinary blastfurnace as a reductor and coke as fuel.
Such specimens were largely exhibited at the late Diisseldorf Provincial Exhibition by the Phoenix Iron Company of Ruhrort, and the Gutehoffhungs-Htitte of Oberhausen; while alloys of manganese with copper, zinc, tin, and lead were shown by the Brothers Heusler, of Dillenburg, in Nassau. They are remarkable for their extraordinary strength, toughness, and hardness, which may be produced at will by varying the quantities of the component metals.
When we look at the progress which the production of ferro-manganese-or, as we now may well call it, "crude manganese " - has made during the last few years, we find it to be quite astonishing. The reduction of manganese in combination with iron and carbon was attempted as long ago as 1865 by several metallurgists, such as Prieger, Bessemer, and others, who employed crucibles; and by Henderson, who used the Siemens furnace for this purpose; and while the latter succeeded in getting a compound with about 30 per cent., the crucible process was able to produce an alloy with 60 Per cent. of manganese, spiegeU eisen at that time hardly ever containing above 12 Per cent. of the metal. This was the state of the manufacture of manganese compounds when, at the Vienna International Exhibition in 1873, the Erainer Eisen- und Stahlwerks-Gesellschaft, of Laibach, in Carniola, produced specimens of spiegeleisen with nearly 20 per cent., and others of ferro-manganese of a far higher percentage, which were then considered as something quite wonderful among metallurgical products.
For, as was stated, they were products of the blast-furnace, and very many tons of these compounds could every day be tapped from the blast-furnaces of Jauerburg and Sava.
Though these statements met at first with some incredulity, it was nevertheless confirmed that the technical managers of the company, Von Banz and Luckmann, had indeed succeeded in employing the ordinary blast-furnace, with charcoal as fuel, for the production of the above-named compounds from a mixture of calcined carbonates and hydrates of iron, with manganese ore from Vigunsza. The samples showed the characteristics of spiegeleisen up to a content of 20 Per cent. of manganese; above this, they lost all crystalline appearance, and became non-magnetic, with an almost homogeneous or finegrained fracture. Some of these samples, taken at the Exhibition, gave by analysis, in 100 parts-
This great success stimulated the managers of the Reschitsa Iron Works, in Hungary, to imitate the process, and after a good deal of trouble they were able to produce, with a slag containing principally lime, manganese, iron, and alumina, and only slightly above 20 Per cent. of silica, a compound with over 35 Per cent. of metallic manganese. At the same time, in 1874, Jordan, at the St. Louis Iron Works, near Marseilles, also succeeded in getting from the blast-furnace ferro-manganese with 20 to 25 per cent. At Terrenoire the Siemens furnace had been tried, since about 1868, in such a manner that bricks were made from an intimate mixture of calcareous manganese oxide with pounded Mokta iron ore, fine coal, and pitch, which bricks were then burned and strongly heated in the Siemens furnace with an addition of spiegeleisen,when alloys with 60 Per cent. could be obtained. The blast-furnace process at Terrenoire, has, however, only been in use since 1877; and though over 3 tons of coke are required for 1 ton of ferro-manganese, an alloy containing 72 to 74 and even 80 Per cent. of manganese can be now made there, when a very basic and refractory green manganese slag is aimed at.
At the Dusseldorf Exhibition of 1880, the Phoenix Company of Ruhrort exhibited specimens of ferro-manganese from the blast-furnace, made with coke and an extremely basic slag, in which silica is mostly replaced by alumina. They contained from 22 up to 77 and 80 Per cent. of manganese, while the Gutehofihungs-Hutte of Oberhausen was able to show samples containing 75. Per cent. of manganese with about 5 Per cent. of carbon, and, besides iron, only traces of sulphur and phosphorus.
Such is the present state of manufacture of "crude manganese," which will find a still larger use in the metallurgy of steel the more the basic Bessemer process spreads, as its addition is necessary to restore to the overblown iron the required amount of carbon, and to free it by the aid of manganese from its last traces of sulphur, which are left even after phosphorus is entirely eliminated. The success of the blast-furnace process depends, next to.a high, tem-perature, and to an extremely basic slag with very little silica, to an intimate mixture of the oxides of iron and manganese as it is found in the natural carbonate ore or the knebelite ore of Sweden, which is a silicate of equal proportions of protoxide of iron and manganese. Whenever the mixture is artificial, the most intimate contact must be looked for, because the reduction of manganese is much more owing to the action of metallic iron than to that of carbon, the former playing an intermediate role because it it is easily reduced by carbon, and then helps to render the manganese metallic. (Sci Amer, Sup.)
For the preparation of crude manganese, ores are mostly used which contain the manganese in the form of dioxide (MnO2) or its hydrate (MnH2O3). These compounds are reduced. in the blast-furnace, by the rising current of gases, to manganic oxide (Mn2O3) or manganous-manganic oxide (Mn3O4), a corresponding quantity of carbon monoxide being oxidized to dioxide. This oxidation is accompanied by a considerable development of heat. The high temperature thus produced in the upper part of the furnace rapidly destroys its walls and fittings, causes more fuel to be consumed, and greatly interferes with the proper course of the process; nor can the issuing current of gases be utilized any further, on account of a large amount of carbon dioxide. To obviate these .difficulties, Lederer recommends to subject the manganese ores to a reducing process before they are brought into the furnace. Of the two ways in which this can be effected, that one is preferable which consists in exposing the ore to the action of a current of gas containing carbon monoxide at a temperature of about 572° F. (300° C). The apparatus necessary for this is simple.
It requires a furnace in which the ores are brought into contact with the reducing gases,'and, as such, a cupola furnace with an inclined sole is best, the gases entering at the lower end and the ores advancing towards the draught. For the reduction, the gases issuing from the blast-furnace itself are most profitably used, since they have retained all carbon monoxide, if the manganese ores have been prepared in the manner stated. The reduction beginning about 392° F. (200° C), a special heating arrangement is not even necessary, because the furnace-gases are hotter than the above temperature. At most, at the commencement, the furnace may be heated up by burning the gases in it; afterwards, however, the atmospheric air is to be excluded, so that the gases can exert their reducing action upon the ore. (Chem. Centr. Biat.)