

METALLURGY. 



465 



manufacture of light castings, and for this reason 

 silicon irons are largely used in foundries mak- 

 ing that class of work. The percentage of sili- 

 con an iron may contain and yet retain sufficient 

 cohesive force for the work depends upon the 

 amount of other impurities present and the work 

 for which the iron is employed. For heavy 

 work, requiring great strength, it should contain 

 none. For light machinery it may contain from 

 \ to 1 per cent., and for stove plates, light bench 

 work, etc., from 2 to 8 per cent. 



Experimenting on iron with chromium and 

 tungsten, Prof. H. Behrens and M. Van Lingen, 

 of Delft, found in a ferrochrome with 13-3 Cr, 

 5'5 C, a ground mass which showed a hardness a 

 little superior to that of iron, and yielding iron 

 and chromium to hydrochloric acid. By treat- 

 ment with aqua regia the metal was disinte- 

 grated, and when observed under the microscope 

 showed well-defined monoclinic prisms, which 

 had a hardness between that of quartz and that 

 of topaz (7'5), and resisted the corrosive action 

 of aqua regia for a fortnight. After washing 

 with a heavy solution, the composition of this 

 compound was found to be 75 Fe, 16'8 Cr, 6'7 C. 

 Chromium steel, with 7'5 Cr, 2'5 C, was subjected 

 to the same treatment, and yielded grains and 

 small prisms of the same form arid hardness. 

 Analytical examination gave the result 73'5 Fe, 

 20 Cr, (5-7 C. From this the empiric formula 

 Cr 2 C 3 Fe 7 can be deduced. Similar crystals have 

 isolated from a ferrochrome with 50 per cent. 

 Cr, much chromium being dissolved in strong 

 hydrochloric acid. From ferrotungsten con- 

 taining much Mn and S beautiful rhombic octa- 

 hedra were obtained, containing 69 g 5 Fe, 28'9 W, 

 1'6 S; from another sample, poor in Mn and S, 

 similar crystals composed of 65-2 Fe. 28'6 W. 

 Both have a hardness superior to that of feldspar. 

 Evidently the great hardness of these alloys 

 must be ascribed to well-defined compounds of 

 the three elements, not, as heretofore, to allo- 

 tropic modifications of iron. The investigation 

 is to be extended to ferromanganese and to 

 bronzes containing Al and S. 



It is found by T. W. Hogg, of the Newburn 

 Steel Works, as the result of a large number of 

 experiments, that in the purer classes of iron the 

 tendency of carbon to be retained in a combined 

 state is prevented by the addition of 1 per cent, 

 of aluminum ; but every increase above that 

 percentage has an opposite tendency. It also 

 appears that the more rapidly cooled ferrocar- 

 bon alloys containing aluminum also contain a 

 larger proportion of graphite. 



In an investigation of the elongation produced 

 in soft iron by magnetization, Sidney J. Lochner 

 found that for a given magnetizing field differ- 

 ent elongations are produced, according as the 

 magnetizing current is applied suddenly or grad- 

 ually; and in the latter case it made a difference 

 whether the current had reached its final value 

 by increasing slowly, or by decreasing slowly from 

 a higher value. Another peculiarity observed, 

 was, that if the current was gradually increased 

 from zero, a maximum expansion was reached at 

 a certain point, after which a further increase of 

 the current produced a decrease in the elonga- 

 tion. If, however, instead of increasing the cur- 

 rent when the maximum was reached, it was 

 gradually decreased, it was possible to obtain a 

 VOL. xxxiv. 30 A 



still greater elongation. . The observations show 

 that the expansion is a function of the ratio be- 

 tween the diameter and length of the bar, and 

 that the elongation varies approximately direct- 

 ly as the square root of this ratio ; also that 

 the expansion varies as the permeability. The 

 amount of current required to produce the maxi- 

 mum expansion likewise depends on the ratio 

 between the diameter and the length. 



From his experiments as to the part performed 

 by transformations of iron and carbon in the 

 hardening of steel, M. Georges Charpy concludes 

 that hardening produces, among other modifica- 

 tions, a transformation of the iron (characterized 

 by the breaking strain) and a transformation of 

 the carbon (characterized by the variation of the 

 results by the Eggestz test). The transforma- 

 tion of the iron appears to have but a feeble in- 

 fluence on the breaking strain, whereas the trans- 

 formation of the carbon appears to be correlative 

 with the augmentation of hardness. 



The substitution of malleable castings for 

 wrought-iron work is becoming more common 

 in many English industries, and the production 

 of the castings has had a remarkable develop- 

 ment, with improvement in the quality and fine- 

 ness of the castings and diminished- cost. It is 

 now claimed that, for many purposes connected 

 with hardware industries, castings from soft 

 Scotch pigs are equal to forged wrought iron. 



In the steel process of E. Bertrand and 0. Thiel, 

 Kladno, Bohemia, open-hearth furnaces are ar- 

 ranged to work together so that one furnace 

 performs the melting of the metal, the oxidation 

 and removal of the silicon and of a part of the 

 carbon, and eventually of the phosphorus ; then 

 the metal so purified is let down into a second 

 open-hearth furnace, in which the process is 

 brought to an end, and the heat is finished in the 

 usual manner by the addition of ferromanga- 

 nese, spiegeleisen, etc. Arrangements of two or 

 three furnaces, at different levels, will be needed, 

 according to the relative percentages of silicon 

 and phosphorus in the metal. 



In the search for nonexpensive alloying sub- 

 stances which would harden steel as well as tung- 

 sten and at the same time give a metal less brit- 

 tle and more suited for forging, trials have been 

 made with uranium, cerium, and titanium ; but 

 the very high prices of those rare metals have 

 prevented their use in a commercial way. Very 

 good results have lately been obtained with mo- 

 lybdenum, which is closely similar to tungsten. 

 This has also been an expensive metal and hard 

 to obtain ; but by a newly patented process it 

 can now be obtained chemically pure from the 

 lime salt. The molybdenum is of from 96 to 98 

 per cent, purity, containing no other substances 

 than about 2 or 4 per cent, chemically bound 

 carbon. Only 50 per cent, of the proportion re- 

 quired when 'using tungsten resulted in a steel 

 of equal hardness. Molybdenum steel contain- 

 ing 2 per cent, molybdenum shows a silverlike 

 white color and a breaking surface smooth and 

 velvetlike and very homogeneous. 



It is shown, in a paper on the ' Soundness and 

 Working Qualities of Crucible Steel," by P. Korb 

 and Thomas Turner, that during the solidifica- 

 tion of a steel ingot two sets of forces are called 

 into play, which act in opposite directions. The 

 gas which is evolved tends to make the ingot 



