466 



METALLURGY. 



spongy, and if the steel be poured when just 

 melted, before being killed, the upper surface of 

 the ingot is curved and there is no sign of pipe. 

 On the other hand, the contraction of well-melt- 

 ed metal causes the ingot to pipe, and if the cav- 

 ity is too deep the steel is always inferior. The 

 success of the operation, therefore, depends upon 

 the proper balancing of these opposite tenden- 

 cies. Steel which has been well melted, but 

 which has been poured at too low a temperature, 

 has a very small pipe in the ingot, while the top 

 is level instead of being concave. The upper 

 portion of the ingot is also permeated with blow- 

 holes, etc. ; owing to the low temperature em- 

 ployed, the steel was not sufficiently fluid to 

 allow of the free escape of gas. Steel which con- 

 tains much carbon is less subject to blowholes 

 than milder material, while rnetal that solidifies 

 quickly is much less liable to retain gas in this 

 form than steel that passes through an interme- 

 diate pasty condition before it becomes solid. 

 Mild steel is also frequently "lively" when 

 teemed rapidly, emitting sparks, and rising in 

 the molds. If this takes place to any considera- 

 ble extent the metal is almost useless. This dif- 

 ficulty is often met with in Bessemer steel, but 

 can be prevented by adding a trace of silicon. 



The Walrand-Legenisiel process for steel cast- 

 ings consists of adding to the metal at the 

 end of the ordinary blow a definite quantity of 

 melted ferrosilicon, then making the afterblow, 

 turning down when the extra silicon has been 

 burned out, and incorporating the ordinary final 

 additions of ferromanganese, etc., as circum- 

 stances required. The advantages of this pro- 

 cess are, first, that an ordinary Bessemer pig can 

 be used with a 2 to 3 per cent, silicon, thus 

 insuring a steel perfectly free from carbon ; sec- 

 ond, that the combination of the added silicon 

 produces such a large amount of heat at the 

 right time, and so rapidly, that the metal be- 

 comes very fluid ; third, that as the silicon 

 burns to a solid it leaves the metal free from 

 gas, and gas cavities ; fourth, that, in consequence 

 of the metal being so fluid and already free 

 from oxide of iron, the ferromanganese or other 

 substances added, such as aluminum, are more 

 effective and remain in the finest steel ; and, 

 fifth, that in consequence of the fluidity of the 

 metals much more time and facility are given 

 for casting operations. The system is, however, 

 confessedly expensive. 



In a paper on " The Dangerous Working Heat 

 of Mild Steel and the Effect of Annealing and 

 Air Cooling," Joseph Nodder, having reference 

 to marine work only, shows that in the tests of 

 steel for boiler purposes, made in 1880, iron and 

 Bessemer and Siemens steels all manifested the 

 same characteristics when pulled at a tempera- 

 ture of from 400 to 600, viz. : that the tensile 

 strength was rapidly increased and the elonga- 

 tion was rapidly decreased at these tempera- 

 tures, that of 400 giving the best results. 

 When the temperature was carried beyond 600 

 there was a corresponding decrease of tensile 

 and an increase of elongation : and when below 

 400 also an increase of elongation and decrease 

 of tensile, until the normal condition was reached 

 at about 150. Mr. Stromeyer. of Lloyd's sur- 

 vey, in 1886. named from 470 to 600 as the 

 temperature of most risk in working iron and 



steel. Later experiments placed the dangerous 

 heat nearer 400. It is plain that unequal heat- 

 ing, and especially the heat of between 400 and 

 000, places the best steel in a dangerous con- 

 dition, which can be removed only by a final 

 annealing. 



For the elimination of blowholes in steel in- 

 gots, J. L. Lebenius recommends that the liquid 

 steel be brought, immediately at the close of 

 casting, under the influence of centrifugal force. 

 As the steel solidifies, the gases which have 

 been dissolved in it are liberated, and only if an 

 adequate centrifugal force is acting upon the 

 metal are they forced toward the center of rota- 

 tion. A machine has been constructed to efl'ect 

 this. 



In Sweden, according to Mr. Erick Olden- 

 styerna, for the manufacture of hard, first-class 

 tool steel, pig iron as low as possible in phos- 

 phorusmade from the most nonphosphoric 

 ores obtainable is used. It is preferred to keep 

 the phosphorus under O03 per cent. The sul- 

 phur in the pig iron has not quite as much 

 effect on the hard steel as it has on the soft 

 steel, but should not be more than 0'02 per cent. 

 A good steady heat is kept in the furnace during 

 the process of melting, in order to get the steel, 

 if possible, entirely free from gas at tapping, 

 without too hiiih a percentage of silicon. If the 

 steel is coming from the furnace too hot. so that 

 piping is to be feared, it is either kept long 

 enough in the ladle to sink to the proper tem- 

 perature, or the " De Laval " heat rings are used. 

 These are iron rings lined with fireproof mate- 

 rial heated to a very high temperature, which 

 are placed on top of "the molds, and, in casting, 

 are filled with steel, which remains melted in 

 them, and sinks until the ingot below the ring 

 is solidified. Probably the danger most difficult 

 to avoid in the making of hard steel is that of 

 getting it too hot, which renders it liable to sur- 

 face blowholes. 



The relative resistances of the hardest steel 

 and the hardest stone under pressure have been 

 investigated in the Vienna Technological Mu- 

 seum of Commerce. Tubes made of corundum 

 and of finest steel '39 inch diameter were sub- 

 jected to the test. Corundum broke under a 

 weight of 118 hundredweight, while steel re- 

 sisted up to 844 hundredweight. 



A process for improving the quality of steel 

 armor plates, described by L. Gram bow, consists 

 in the combination of the three operations in the 

 order indicated : of hardening the plates by com- 

 pletely immersing them after they have been 

 raised to a temperature at which the molecules 

 have acquired the capability of ready rearrange- 

 ment in oil, water, or other medium : of anneal- 

 ing them at a temperature as high as possible 

 without reaching the temperature at which t In- 

 capability of arrangement begins ; and of hard- 

 ening them on one side or face at the same or at 

 a lower temperature than that specified in the 

 preceding operation. 



Gold and Silver. In extracting gold and 

 silver from roasted pyritons and arsenious ores, 

 B. Mierisch, of Managua, Nicaragua, causes hypo- 

 chlorites and chlorates to act in a nascent state 

 by mixing the ore with sodium hydrate and 

 then treating the mixture with chlorine. The 

 admixture of sodium sulphate to the concen- 



