This section is from "Scientific American Supplement Volumes 275, 286, 288, 299, 303, 312, 315, 324, 344 and 358". Also available from Amazon: Scientific American Reference Book.
|Ordinary Bronze||90||10||20 kil.||4.00|
|Bronze with Manganese,||A,||90||10||0.5||24 kil.||15.00|
The White Brass Co., of London, exhibited at Paris, in 1878, manganese bronzes of four grades of durability, destined for different uses and corresponding to about 20 to 25 kilos of the limit of elasticity, and 36 to 37 kilos of resistance to fracture; the number 0 is equivalent after rolling to a resistance to fracture of 46.5 kilos, and 20 to 25 per cent. of elongation.
Such results show beyond contradiction the great interest there is in economically producing alloys of copper, manganese, tin, zinc, etc. In addition, they may be added to metallic fusions, for deoxidizing and also to communicate to the commercial alloys (such as bronze, brass, etc.) the greatest degree of resistance and tenacity.
While many investigators have tried to form alloys of copper and manganese by combining them in the metallic state (that is to say, by the simultaneous reduction of their oxides), the Hensler Bros., of Dillenburg, have found it best to first prepare the metallic manganese and then to alloy it in proper proportions with other metals. Their method consisted of reducing the pure pyrolusite in large plumbago crucibles, in the presence of carbon and an extra basic flux; the operation was carried on in a strong coke fire, and at the end of about six hours the crude manganese is poured out, having the following composition:
By refining, the manganese can be brought up to 94 to 95 per cent. of purity. It is from this casting of pure manganese that is obtained the substance used as a base for the alloys. This metal is white, crystalline, when exposed to the damp air slowly oxidizes, and readily combines with copper to form the cupro-manganese of the variety having the composition -
Cast in ingots or in pigs it becomes an article of commerce which may be introduced in previously determined proportions into bronze, gun metal, bell metal, brass, etc. It may also be used, as we have already mentioned, for the refining of copper according to Manhès's process.
Tests made from this standpoint at the works of Mansfield have shown that the addition of 0.45 per cent. of cupro-manganese is sufficient to give tenacity to the copper, which, thus treated, will not contain more than 0.005 to 0.022 of oxygen, the excess passing off with the manganese into the scorias.
On the other hand, the addition of cupro-manganese is recommended, when it is desirable to cast thin pieces of the metal, such as tubes, caldrons, kitchen utensils, which formerly could only be obtained by beating and stamping.
The tenacity obtained for tubes of only three centimeters in diameter and 1.75 millimeters in thickness is such that they are able to withstand a pressure of 1,100 pounds to the square inch.
The manganese bronze, which we have previously referred to, and which is used by the White Brass Company of London, is an alloy of copper, with from one to ten per cent. of manganese; the highest qualities of resistance, ductility, tenacity, and durability are obtained with one to four per cent. of manganese, while with twelve per cent. the metal becomes too weak for industrial uses.
The preceding table gives some of the experimental results obtained with the testing machine at Friedrich-Wilhelmshütte on the crude cast ingots; the resistance is increased, as with copper, by rolling or hammering.
The manganese German silver consists of
But as this alloy often breaks in rolling, the preference is given to the following proportions:
This results in a white, ductile metal, which is easily worked and susceptible of receiving a beautiful polish, like the alloys of nickel, which it may in time completely replace.
The bronzes of manganese, tin, and zinc were perhaps the first upon which important investigations were made; they were obtained by adding to an alloy of copper, zinc, and tin (ordinary bronze) a definite quantity of the cupro-manganese of the type indicated above (Cu 70, Mn 30). By this means the resistance is increased fully nine per cent., probably in the same way as the copper, that is, by the deoxidizing effect of the manganese, as both the copper and the tin are always more or less oxidized in ordinary bronzes.
Manganese combines with tin just the same as it does with copper, and the proportion which is recommended as giving the highest resistances is three to six per cent. of cupro-manganese.
However, notwithstanding the use of cupro-manganese, the tin, as in ordinary bronzes, has a tendency to liquate in those portions of the mould which are the hottest, and which become solid the last, especially in the case of moulds having a great width.
From a series of experiments made at Isabelle Hütte, it has been found that the metal which has the greatest resisting qualities was obtained from
5 per cent. of cupro-manganese = manganese 1.00 remaining in the metal.
The best method of procedure is first to melt the copper in a crucible, and then to add the tin and the zinc; finally the cupro-manganese is added just at the moment of pouring, as in the Manhès process; then the reaction on the oxides is very effective, there is a boiling with scintillation similar to the action produced in the Bessemer and Martin process when ferro-manganese is added to the bath of steel.
The following are some of the results obtained from thirteen alloys obtained in this manner. These samples were taken direct from the casting and were tested with the machine at Friedrich-Wilhelms-hütte, and with the one at the shops of the Rhine Railroad. Their resistance was considerably increased, as with the other alloys, by rolling or hammering.
|Numbers.||Nature of mould.||Copper||Tin.||Zinc.||Cupro-|
( 8 Pb)
The results of the tests of ductility which are here given, with reference to the cupro-manganese, manganese bronze, the alloys with zinc and tin, are taken from M.C. Hensler's very valuable communication to the Berlin Society for the Advancement of the Industrial Arts.
These various alloys, as well as the phosphorus bronze, of which we make no mention here, are at present very largely used in the manufacture of technical machines, as well as for supports, valves, stuffing-boxes, screws, bolts, etc., which require the properties of resistance and durability. They vastly surpass in these qualities the brass and like compounds which have been used hitherto for these purposes. - Bull. Soc. Chim., Paris, xxxvi. p. 184.
See Engineering, May 27, 1881