METALLURGY. 



441 



being the result of oxidation, it is probable that 



tin- nature of the surface to be heated, its free- 

 dom from any soiling, ami the length of time 

 during which it is heated, must exert a con- 

 siderable influence on the >hade produced. 



The apparatus of Henry II. Eames for the 

 extraction of iron consists of an endless belt or 

 baiid which has along its surface a series of 

 conducting strips, and which is made by means 

 of a series of rollers above and below it to as- 

 sume an undulating, corrugated, or serpentine 

 form. This band is placed in an inclined posi- 

 tion, so that the ores dropped upon it travel 

 naturally upon an inclined corrugated plane. 

 Means are provided for imparting to the strips 

 upon the band, or passing througn it, an electric 

 current. The ores or gangues are dropped upon 

 this c . irriigated band. The current passing 

 through the conducting strips crossing the same 

 causes the particles of iron on the band to at- 

 tach themselves to the conducting strips. At 

 the same time a stream of water is directed 

 upon the band, which, being inclined, flows in 

 the direction opposite to that in which the band 

 is traveling, and washes back the particles of 

 gold or copper or other metal composing the 

 gangue or sponges, which do not adhere to the 

 metal strips, and continue to flow back until 

 they are washed off from the lower end of the 

 band into a receptacle placed there to catch 

 them. The iron particles adhere to the strips 

 and travel with them to the other end of the 

 apparatus, when the circuit passing through 

 them is broken, and the iron particles fall. 



Under the title of special steels, M. Louis 

 Campredon includes all castings obtained from 

 steels that derive their special characteristic prop- 

 erties, ofiei, very remarkable, from the presence 

 of an additional foreign substance. Among 

 those best known and which have been found 

 highly serviceable are manganese steel, chrome 

 steel, aluminum steel, tungsten steel, copper steel, 

 silicon steel, nickel steel, etc. Manganese steel 

 is very fluid, and yields excellent castings without 

 blowholes. While the resistance is not very high 

 in the simply cast metal, it is imparted in a 

 very high degree by forging. When cold, this 

 steel is very hard, and can be worked only in the 

 mill, a quality which has stood in the way of 

 its introduction for many uses for which it 

 would be valuable as in agricultural machines, 

 wagon wheels, horseshoes, rotary axles, and 

 generally for all pieces exposed to wear by fric- 

 tion or to rupture by imimct. Aluminum steel 

 is sound, resisting, and elastic. It only requires 

 flame annealing, when ordinary steel would re- 

 quire an oxide annealing. Chrome steels are 

 employed in the manufacture of the hardest 

 projectiles intended to penetrate the thickest 

 armor plates. Nickel promotes the casting of 

 special steels which resist well the impact of pro- 

 jectiles, even chrome-steel projectiles. Among 

 the improvements that have been made and dif- 

 ficulties overcome during the past forty years 

 in the manufacture of cast steel, the author 

 mentions the adoption of a sufficiently refrac- 

 tory and plastic mixture, answering the double 

 purpose of obtaining clean castings with an 

 easily formed mold ; production of a fluid metal 

 yielding castings free from blow-holes; obtain- 

 ing an annealing sufficient to assure to the steel 



castings perfect homogeneity of grain ; better- 

 ing the quality of the metal until it b< 

 equal to that of forged steel ; preparat i 

 alloys or special combinations to meet certain 

 specified requirements. With crucible-.steel ap- 

 paratus light castings are generally obtained for 

 the manufacture of pieces which must possess 

 great resistance. The bulk of pieces of consider- 

 able or average weight are cast with Martin- 

 Siemens steel, the manufacture of which ha* 

 become regular and reliable. In < asting marine 

 propellers in one piece, serious difficulties are 

 met with from the unevenness of the contrac- 

 tion, which is liable to cause rupture during 

 cooling. To obviate this inconvenience, the 

 mold which contains the pattern of the pro- 

 peller is placed in a furnace maintained at the 

 same temperature, and the screw Is cast in the 

 same furnace in which it is annealed. The small 

 converter is an intermediary apparatus between 

 the crucible and the Martin furnace, suitable for 

 casting pieces too heavy for the former and 

 rather too light for the latter. In brief, the 

 studies of engineers and chemists, as also the 

 researches of steel manufacturers, have resulted 

 in the production of steel castings capable of 

 advantageously replacing the iron castings hith- 

 erto employed. 



An examination of manganese steel (10'C to 

 12-3 per cent, manganese), made by Mr. Tetskichi 

 Mukan, with a view to discovering the reason of 

 the remarkable toughening which sudden cool- 

 ing produces in the metal, enabled him to deter- 

 mine the following properties of the substance: 

 The specific gravity of manganese steel in the 

 suddenly cooled state is apparently greater than 

 that of the slowly cooled steel, while the opj>o- 

 site, in general, holds good of other metals ; the 

 hardness of the suddenly cooled specimen is 

 greater than that of the slowly cooled, just as in 

 the case of common steel. The hardness is. ac- 

 cording to the author, apparently conferred by 

 the hardening carbon ; the content of cement or 

 nonhardening carbon is rather large in man- 

 ganese steel. This, perhaps, is partly due to the 

 large proportion of manganese present. It is 

 the function of manganese to increase the pro- 

 portion of the so-called chemically combined 

 carbon. Manganese, however, besides doing this, 

 favors the retention of the carbon in the condi- 

 tion of cement or nonhardening carbon. The 

 characteristic features of the structure of man- 

 ganese steel are the parallel dark plates on its 

 surfaces, which are surrounded by the mother 

 mass. These appearances are often observed in 

 iron rich in manganese. It is clearly seen 

 under the microscope that the grains of the 

 suddenly cooled manganese are larger than 

 those of the slowly cooled. The ductility and 

 malleability of suddenly cooled manganese steel 

 can not be attributed to the condition of carbon, 

 for the carbon behaves as in common steel. 



In the discussion of a paper on chrome steel, 

 by Mr. Hadfleld, at the Iron and Steel Institute. 

 Prof. Roberts-Austen pointed out that the au- 

 thor's researches supported the views taken by 

 himself and Osmonds as to the dual form in 

 which iron exists. This appeared in the dia- 

 grams showing the rate of cooling, which ac- 

 companied the report. In these, when the cool- 

 ing was from a high temperature, 1,320 C., the 



