METALLURGY. (METALS AS FUEL USE OF BLAST-FURNACE 



355 



acter of a steel chemically, and apparently me- 

 chanically, sai'e. In order to describe intelligibly 

 the structure of safe and dangerous steels, it is 

 necessary to consider the micrographic constitu- 

 ents of structural steel and the molecular mi- 

 grations of these constituents when at a red heat 

 the metallic mass is in a semiplastic condition. 

 The constituents of a typical micrographic steel 

 rail containing, approximately, besides the iron, 

 carbon 0.40, silicon 0.05, manganese 0.90, sulfur 

 0.00, phosphorus 0.00 per cent., together with 

 small percentages of arsenic and copper, are the 

 pale, simple constituent ferrite (in this case some- 

 what impure iron) ; the dark etching compound 

 constituent perlite, consisting of mixed granules 

 of iron and of a double carbide of iron and man- 

 ganese; and the dove-gray simple constituent sul- 

 M of manganese. In manganiferous steels these 

 constituents are completely differentiated visually 

 only under slow cooling from a full red heat. This 

 fact introduces the vital question of the migration 

 of constituents. Sulfid of manganese is not, un- 

 der working conditions, capable of migrating to 

 any appreciable extent. Thus it remains to con- 

 sider only the migrations of the ferrite and per- 

 lite. On heating the typical steel specified to 

 about 700 C., the compound constituent perlite 

 is converted, with absorption of heat, into the 

 simple constituent, martensite. Then the con- 

 stituents ferrite and martensite diffuse one into 

 the other till, at about 800 C., molecular equilib- 

 rium is eventually established. If, however, the 

 steel be cooled very slowly, the molecules of 

 martensite and ferrite will perfectly segregate in 

 the respective proportions of about 45 and 55 per 

 cent. Then, at about 640 C., the martensite wiH 

 decompose into the compound constituent per- 

 lite, which, owing to the presence of manganese, 

 will be granular and not laminated. On the 

 other hand, if the steel is somewhat quickly cooled 

 in air, the segregation of the constituents will be 

 imperfect, and the apparent proportion of perlite 

 relatively large, because, owing to the influence 

 of the manganese present, the phenomenon of con- 

 stitutional segregation is retarded. In a case in 

 which the rail was slowly cooled in the reheating 

 furnace during a period of fifty hours, the micro- 

 graph showed that the pale ferrite and dark 

 granular perlite had perfectly segregated mainly 

 in the form of thick, alternating laminae. This 

 structure must be regarded as highly dangerous, 

 because under vibration the adhesion between the 

 constituents is liable to loosen gradually and 

 finally to be destroyed. Nevertheless, mechanical 

 tests would inevitably reveal little difference in 

 the ductility of the two pieces of rail. These facts 

 give the clue to the direction in which the steel 

 microscopist must look for danger with reference 

 to rupture under vibration. To obtain complete 

 knowledge of the quality of the steel, three micro- 

 graphs should be taken, in three planes of section, 

 at right angles to one another namely, trans- 

 verse, longitudinal-horizontal, and longitudinal- 

 vertical sections. Usually the preparation of mi- 

 crographic sections has been too complex a work 

 for practical use in the shop, but the author has 

 devised a simpler method by which the micro- 

 graphs can be prepared in a very few minutes, 

 which is explained in his paper in Nature of 

 April 25, 1901. 



Metals as Fuel.- The use of metals as fuel 

 was treated in a thorough manner by Sir W. C. 

 Roberts- Austen in a lecture delivered at the Royal 

 Institution, Feb. 22. Treating the subject his- 

 torically, the author said that in smelting iron in 

 the old way carbon became associated with it, 

 and in its conversion into steel the iron had to 



be decarbonized. In doing this, inetallin^ists for 

 centuries truly burned some ol i he inn, it. self, 

 using it actually as fuel. The u c ,i mcln.U as* 

 fuel assumed magnificent proportion- i>i i|, haii'U 

 of Bessemer. Uis great service to i"hr ,(,.,! in- 

 dustry was in demonstrating the po-.-.ihiii 1 v .it 

 using metalloids and metals as fuel. In ;i. i ; >l,|<> 

 showing the amount of heat evolved hy binning 

 one gram each of certain elements, after carbon 

 and silicon, the first place is occupied by alumi- 

 num, which gives out 7,250 calories in the produc- 

 tion of A 2 O 3 or alumina. Other items in the table 

 are: 



This table indicates the advantages which cer- 

 tain metals possess over carbon for use as fuel. 

 The temperature at which such metals as can be 

 used for fuel begin to abstract oxygen from the 

 air depends on the method in which the metals are 

 prepared. Some metals can be made to take fire 

 and burn at ordinary temperatures. They are 

 said to be " pyrophoric." As far as the author is 

 aware, metals in this chemically active state have 

 not been used as fuel; neither has any use been 

 made of the allotropy of metals as enabling them 

 to be used for fuel. The burning of the metal 

 antimony plays an important part in the roasting 

 of silver ores. Aluminum w r as the metal the use 

 of which as fuel formed the chief subject of the 

 author's lecture. The starting-point of thte ex- 

 periments in this use was the discovery by Charles 

 and Alexandre Tissier in 1856 that aluminum de- 

 composes the oxids of lead and copper. These 

 experimenters, not using the metal in a finely di- 

 vided state, failed in the reduction of some of the 

 metals. At a meeting of the Royal Society in 

 June, 1894, Claude Vautier showed a few metals 

 which had been produced by this method, includ- 

 ing carbon-free chromium and manganese, and 

 gave an impulse to the movement. A lecture on 

 The Rarer Metals and their Alloys, delivered by 

 the author before the Royal Society in 1895, is 

 mentioned as the first occasion in which the re- 

 ducing action of aluminum was demonstrated on 

 a comparatively large scale, and was shown to 

 cover an extended series of metallic oxids. Since 

 that time great progress has been made, the most 

 noteworthy advance having been in the direction 

 of using aluminum for the sake of the heat af- 

 forded by its combustion as a true fuel. In this 

 combustion the oxygen is derived not from the 

 air, as when carbon is burned, but from a metallic 

 oxid; when the metals change places the alumi- 

 num is oxidized and the other metal set free from 

 its oxygen. 



Use of Blast-Furnace Gases. The inaugural 

 address of the new president of the British Iron 

 and Steel Institute, Mr. William Whitwell, was de- 

 voted mainly to a review of some of the many 

 problems in the iron and steel industries still 

 awaiting solution. There were two items of 

 waste in blast-furnace operations, the speaker 



