METALLURGY. (!EON AND STEEL.) 



473 



instead of steam, a spray of water in a finely 

 divided (atomized) condition, together with the 

 air-blast, though the more equable action of 

 steain makes its use preferable in practice. 

 Mr. Jones claims as a marked advantage of his 

 invention that it allows the use of a grade of 

 pig-metal which shall be high enough in silicon 

 to avoid the presence of an objectionable per- 

 centage of sulphur, and yet, despite its greater 

 heating capacity, be under the easy control of 

 the operator. 



M. D. Chernoff read a paper before the Im- 

 perial Technical Society of St. Petersburg, on 

 his own observations, and those of Mr. Beck- 

 Gerhard, on the behavior of steel when sub- 

 jected to a destructive tensile strain. He had 

 noticed that, with cold-sheared samples of steel, 

 when the limits of elasticity were reached, 

 the scale on the specimens began to separate 

 in a peculiar manner, and the surfaces of the 

 samples were marked with curved lines of more 

 or less regularity. The appearance of the rays 

 on the polished surfaces of the steel reminded 

 him of some experiments made by M. Leger, 

 in which the lines of strains produced in glass 

 subjected to various pressures were made visi- 

 ble through the polarization of the light in 

 the regions strained. In view of these and 

 other similar observations, it occurred to M. 

 Chernoff that, as in glass-bearers, the lines of 

 strains assumed various curved forms, so, in 

 metal, similar actions took place, and became, 

 in part, manifested on the surface so soon as 

 the limits of elasticity were passed. In glass 

 the elastic limit coincides with that of ultimate 

 strength, so that it is impossible to fix the 

 waves of strain ; but in metals, the permanent 

 set will begin first where the strains are great- 

 est, and hence the deformation of surface 

 will follow the lines of maximum strain. Why 

 the regions of maximum strain should arrange 

 themselves in the form of curved rays in metals 

 is as difficult of explanation as the correspond- 

 ing phenomena in glass ; but M. Leger sug- 

 gests that the propagation of strains through 

 elastic substances may be of an undulatory 

 nature comparable to the propagation of sound. 

 M. Rgeshotarsky, repeating and extending the 

 experiments, found that the lines of strain were 

 manifested not only in punching, but in shear- 

 ing and in flattening with the steam-hammer. 



Walrand recommends for distinguishing iron 

 from steel in small pieces, a method by observ- 

 ing the fracture of a test-piece after heating 

 and allowing it to take a blue color. A slight 

 scratch should be made not far from the end of 

 the test-piece. Then heaj one end slowly and 

 uniformly to a dark-red color, and cool it in 

 water. During the cooling, while the piece is 

 still warm, it must be rubbed with a file from 

 time to time, until the shining metallic surface 

 laid bare, has assumed a dark yellow, or, bet- 

 ter, blue, color, when it is to be cooled quickly 

 and completely. The fractures of the piece 

 broken at the mark serve for comparison. Or- 

 dinary wrought-iron broken when cold appears 



fibrons or crystalline, but treated as above, its 

 fracture is dull, irregular, and of short fiber. 

 Hard and moderately hard steel are fine-grained ; 

 after the heating and subsequent treatment, 

 they have a shining, totally or partially smooth 

 fracture. Swedish iron has only traces of 

 fibers, and is hardly to be told from soft steel. 

 After treatment, the fibers become distinct, the 

 smooth appearance is lost, and the iron be- 

 comes so much the more distinguishable from, 

 soft steel treated in the same manner. 



While ordinary iron-rusts the ferrous and 

 ferric oxides spread and eat away the sub- 

 stance of the iron, the magnetic oxide Fe 3 O 4 

 is stable, and when of a certain thickness, ar- 

 rests the further oxidation of the metal. This 

 property is made use of in the Russianizing of 

 sheet-iron. In Prof. Barff's process for mag- 

 netic oxidizing the object is attained by ex- 

 posing iron to the action of steam with a high 

 temperature in a closed chamber. This pro- 

 cess has been improved upon by Mr. George 

 Bower, who substitutes highly heated air for 

 steam ; and further by his son, Mr. Anthony 

 S. Bower, to whom it occurred that the work 

 could be facilitated and made more effective 

 and less costly by substituting the internal ap- 

 plication of heat, and by a series of oxidizing 

 and* deoxidizing operations producing the coat- 

 ing of magnetic oxide simultaneously with the 

 action of heating. A furnace has been de- 

 vised in which this process is carried on on a 

 large scsfle. The duration of the treatment de- 

 pends upon the size, number, and intended use 

 of the articles. In the case of wrought-iron 

 and malleable steel, which are very sensitive 

 to oxidizing influences, this process operates 

 too rapidly, and the Barff method has been 

 found more satisfactory. The two inventors, 

 therefore, combined their methods, and a fur- 

 nace having the economic features of the Bower 

 furnace was designed to effect the Barff process. 

 By the Bower process, a coating of magnetic 

 oxide can be obtained in from three to eight 

 hours. The rustier the articles are, the more 

 effective and speedy is the process of oxidation. 



Prof. M. Keil has produced a composite ma- 

 terial of iron and steel, in which the valuable 

 qualities of the two substances are combined, 

 and the combination is made available for a 

 variety of uses. The principle of his process 

 is exemplified in a cast-iron mold divided cen- 

 trally by a thin sheet of iron, on one side of 

 which sheet fluid iron is poured, and on the 

 other side fluid steel. The dividing plate should 

 be thick enough to prevent the glowing masses 

 on either side from burning through it, and yet 

 so thin that those masses and it shall become 

 thoroughly welded together. The combination 

 has been produced in five shapes; steel by the 

 side of iron ; steel between two layers of iron ; 

 iron between two layers of steel; a core of 

 steel with a surrounding shell of iron; and a 

 core of iron with a surrounding shell of steel. 

 This steel-iron may be used for a great variety 

 of purposes in which the hard qualities of steel, 



