100 SUMMARY OF QUERENT RESEARCHES RELATING TO 



(6) That good open-heartli steel with 0*23 p.c. carbon maybe heated 

 to close upon its burning-point without becoming brittle, and that it 

 only becomes truly burnt when intergranular separation is effected. 



(7) That when solid steel is partially decarburised by oxidising 

 agents at between 700° and 800°, an envelope of pure iron forms at the 

 surface, and the grains in this layer assume a columnar structure radiating 

 from the outside to a point below where there is carbon. 



(8) That by strongly etching pure iron, or iron containing much 

 phosphorus, aluminium, or silicon, the cubical crystals of pure iron are 

 readily developed. 



(9) That by mechanically testing micro-sections of pure iron by the 

 method of fracture, it seems to follow that the smaller aud finer the grain 

 the safer the structure. 



(10) That soft steel plates treated under certain conditions develope 

 a most peculiar crystalline structure, whose cleavage lines are invariably 

 at an angle of 45° to the direction in which the plates are rolled. This 

 extraordinary development is sometimes destroyed by close annealing 

 for 36 to 48 hours; but it is invariably destroyed by heating to 900° C, 

 and the steel then becomes exceedingly tough. 



Constitution of Steel considered as an Alloy of Iron and Carbon.* 

 — Albert Sauveur argues that the formation of a cryohydrate and of an 

 eutectic alloy are analogous phenomena ; the only difference being that 

 the former takes place at ordinary temperatures, and the other at high 

 temperatures. The result in each case is a mechanical compound in 

 which the constituents are juxtaposed in minute crystals and in definite 

 proportions. He illustrates his reasonings by the solubility curve of 

 sodium chloride in water, and by the cooling curve of the alloy of iron 

 and carbon (Le. steel). A plate of 16 figures reproduces the microstruc- 

 ture of the alloy. He quotes Ponsot's opinion f that the name " cryo- 

 hydrate " should be abandoned, as being inapplicable to a mechanical 

 mixture, and should be replaced by " cryosel." 



Allotropic Iron and Carbon4 — E. H. Sauiter's researches are in- 

 tended as an unbiassed contribution towards the controversy encircling 

 the cause of the glass-hardness of quenched carbon steel. His results 

 were obtained by hot-etching on specimens of metal selected for their 

 freedom from mechanical treatment — in other words, specimens in which 

 the normal structure would be as perfect as possible. His investigations 

 were arranged in three sections : — ■ 



i. The structure of pure carbonless iron at a bright red heat. (The 

 cubical crystals of cold iron became replaced by rhombohedral crystals 

 in the hot specimen, showing that iron is dimorphous.) 



ii. The structure of pure carbon-iron compounds at a bright red 

 heat. (There was a marked reduction in the size of the amorphous 

 carbon grains, as compared with their cold state.) 



iii. The effect of moderate quantities of sulphur, phosphorus, and 

 manganese on the structure of carbonless iron at a bright red heat. 



The dimorphism of section i. and the reduced amorphism of section ii. 



* Metallographist, 1898, pp. 210-29 (1 pi. and 3 figs.). 



t 'Kecherches sur la congelation des solutions aqueuees etendues,' Paris, 1896 



t Metallographist, 1S98, pp. 251-8 (7 figs.). 



