METALLURGY. 



459 



ing of different kind? of ores necessitate the con- 

 >i met ion of different kinds of furnaces. As a rule, 

 the magnetization takes place the more readily the 

 more the ore is in the form of small but solid 

 pieces but uniformity of size is still more impor- 

 tant. The magnetized ores, after the roasting, 

 must be submitted to concentration, which may. in 

 the first instance, be mechanical, to separate from 

 each other the ore particles of different sizes, and 

 then magnetic, or it might be magnetic from the 

 beginning. This must depend largely on whether 

 or to what extent the ores include constituents not 

 containing iron and iron oxides. In blast-furnace 

 practice the pieces should be about the size of hens' 

 eggs; while small and even pulverulent ore may be 

 utilized in the open hearth. In the discussion of 

 this paper in the Iron and Steel Institute Mr. S. P. 

 Martin spoke of the Davis-Colby kiln used in the 

 United States as enabling sulphurous magnetic ore 

 to be separated. 



In a process for the magnetization and concen- 

 tration of iron ores, described by Prof. Phillips be- 

 fore the American Institute of Mining Engineers, 

 pieces of hematite ore the size of an egg are heated 

 to redness, and carbonic oxide or producer gas is 

 parsed over them: when they become more or less 

 magnetic, and if only a small portion of the sesqui- 

 oxide is converted into magnetic oxide, a strong 

 magnet will remove the whole of the iron ore from 

 the gangue. As an average result of a working of 

 this process, it is represented that fossiliferous red 

 ore, containing 40 per cent, iron and 30 per cent, 

 insoluble matter, was concentrated so as to produce 

 an ore with 58 per cent, iron and 28 per cent, in- 

 soluble matter. The best result was the obtaining 

 of 1 ton of concentrates from 2 tons of ore, and the 

 worst of 1 ton from 10. It is believed that the 

 process will be found important in the working of 

 the red and brown iron ores of the South. 



A paper by Mr. II. I). Hillard. of Xew Jersey, 

 read in the Iron and Steel Institute, dwelt upon 

 the evil effects of sand in pig iron and the de- 

 sirability of avoiding it. An increasing demand, 

 the author said, is arising for sand-free pig iron for 

 the basic open-hearth steel process. Sand is. chem- 

 ically speaking, silica, and in the basic open-hearth 

 process silica in the furnace is the troublesome 

 agent. The sand in the pigs begins the destruction 

 of the bottom of the furnace as soon as it is brought 

 in contact with it at a sufficiently high temperature. 

 It is evident that a great reduction of labor about 

 the blast furnace could be effected by the use of a 

 mechanical appliance. Such an appliance is de- 

 scribed in the author's paper. 



Experiments made by Thomas "Wrightson, M. P., 

 and repeated many times in order to ascertain 

 whether the welding of iron is attended with a fall 

 of temperature, as in the regelation of ice, appear 

 to show that the application of pressure to plastic 

 iron heated within the range of temperature at 

 which it could be welded is certainly attended 

 with that effect. The welding of iron and the 

 regelation of ice would thus appear to be analogous 

 phenomena. 



The failure of any rail, however perfect, is, in the 

 opinion of Mr. Beaumont, as expressed in a paper 

 read at the British Association, chiefly a question 

 of the number of trains passing over it. The result 

 of the rolling is a gradual compression of the upper 

 part of the rails, and this produces internal str 

 that are cumulative and reach great magnitude. 

 That which takes place in the material of a rail 

 head under the action of very heavy rolling loads 

 at high speed is precisely that which is purposely 

 brought into use every day in iron works, but the 

 effect is obscured by the slowness of the growth and 

 transmission of the forces which are ultimately de- 



structive. When a piece of iron or steel is sub- 

 jected to pressures exceeding the limit of elastic 

 compression by a rolling or hammering action or 

 by both combined, the result is spreading of the 

 material and general change of the dimen- 

 This is equally the case with a plate hammered or 

 rolled on one side while resting on a flat surface. 

 Generally the material thus changed in form suffers 

 permanently no greater stresses than tlir.se within 

 its elastic limit of compression or expansion. When, 

 however, the material is not free to flow or to change 

 its form in the direction in which the s\ 

 up would act. the effect of continued work on the 

 surface is the growth of compressive stress exceed- 

 ing elastic resistance. In the case of railway rails 

 the freedom for the flow of material is very limited. 

 Hardening of the surface takes place and destruc- 

 tive compression of the surface material is set up. 

 If the material be cast iron the destructive com- 

 pression causes crumbling of the superficial parts 

 and the consequent relief of the material immedi- 

 ately below it from stress beyond that of elastic 

 compression, but when the material is that of steel 

 rails the stress accumulates, which gives rise to 

 molecular stresses analogous to those which, on the 

 compressive side or inner curve of a bar bent on 

 itself, originate transverse flaws on that side. This 

 condition of compression exists along the whole 

 length of a rail, so that when its magnitude is suf- 

 ficient to originate crumbling or minute flaws, any 

 unusual impact, stress, or a stress in the direction 

 opposite to that brought about by the usual rolling 

 load, the rail may break in two or into numerous 

 pieces. Various criticisms were made during the 

 discussion on this paper at different points in Mr. 

 Beaumont's exposition, to which he replied that he 

 had submitted facts and not speculations to explain 

 the breakage of rails. There was much yet to learn, 

 and he had put forward his paper mainly with a 

 view to raising discussion. 



It is well known that the brittleness of steel due 

 to the presence of phosphorus is more marked when 

 the percentage of carbon is high than when but lit- 

 tle carbon is present, and that with the same per- 

 centage of carbon the brittleness is more .parked 

 when the metal is hardened than when it is in its 

 annealed or normal state. Since the fact suggested 

 that there might be some relationship between the 

 carbon and phosphorus in steel, and that the chem- 

 ical condition in which phosphorus exists in steel 

 may be capable of being changed by varying the 

 heat treatment, an investigation was undertaken 

 by E. D. Campbell and S. C. Babcock to determine 

 whether phosphorus might exist in steel in two 

 forms. It was found that with low percentage of 

 carbon the effect of high treatment upon the solu- 

 bility of phosphorus is slight, and probably if car- 

 bon were entirely absent there would be no effect: 

 that with increase of carbon the effect of harden- 

 ing is to diminish the solubility of the phosphorus : 

 and that with high percentage of carbon the solu- 

 bility is increased by slow cooling. These three 

 facts, the authors observe, point very strongly to 

 the probable formation, at a very high temperature, 

 of a compound of difficult solubility of iron with 

 carbon and phosphorus, which is transformed on 

 slow cooling into an easily soluble substance. 



In a paper contributed to the English Iron and 

 Steel Institute in ISSs. Messrs. Ilarbord and Tucker 

 showed that a large quantity of arsenic in steel is 

 injurious. The results of experiments made since 

 on the effect of small quantities were communicated 

 by Mr. J. E. Stead to the Institute at its spring 

 meeting (1895). The general conclusions drawn by 

 the author are that between O'lO and 0-15 per cent, 

 of arsenic has no material effect upon the mechan- 

 ical properties of steel used for structural purposes. 



