558 SUMMARY OF CUERENT RESEARCHES RELATING TO 



Influence of Nitrogen on Cementation of Steel.* — J. Kirner has 

 investigated the efficiency of two nitrogenous case-hardening* materials, 



and a third containing alkali carbonates but very little nitrogen. From 

 600° to Nf)0° C. cementation proceeded actively with the nitrogenous 

 materials. At 900° C. their action was uncertain, while above 1)50° C. 

 the rate of cementation again increased. With the nitrogen-free material 

 the rate of cementation steadily rose with the temperature. When the 

 nitrogenous materials were used at temperatures between 600° and 

 ■850° C. the nitrogen content of the outer layer of the steel rose to 

 0*6 p.c, diminishing, however, at higher temperatures. A new con- 

 stituent, named " Flavite," was detected in the slowly cooled steel of 

 high nitrogen content. Flavite goes into solution above the critical 

 temperature, and is not observed in quenched specimens. 



Influence of Manganese on Mild Steel. f — G. Lang has examined 

 eleven mild steels containing 0'3 to 2*5 p.c. manganese, the carbon 

 content being 0*09 to 0*12 p.c. Mechanical tests were made on rod, 

 in three states, as rolled, quenched from 900° C. and slowly cooled from 

 900° C. Magnetic and electrical tests were also made. Tensile strength 

 and hardness were raised by increase of manganese, and in general the 

 addition of manganese up to 1'5 p.c. appeared to improve the properties 

 of the alloys. 



Iron-carbon System."}: — A. Baykoff considers as untenable the view 

 that in the iron-carbon diagram there are two distinct branches, corre- 

 sponding to the separation of cementite and of graphite from the melt. 

 Cementite and graphite must therefore separate along the same line of 

 the diagram, and from this it follows that cementite is a solid solution 

 and not a compound. Determinations of heat of combustion of pure iron 

 and of cementite, by burning in oxygen in a Berthelot bomb, have con- 

 firmed the author's view of the constitution of cementite, since that body 

 is shown to have a negligible heat of formation. An interpretation of 

 the iron-carbon diagram, involving the separation from the melt, at the 

 carbon-rich end, of mixed crystals of iron and carbon, is advanced. The 

 name " moissanite " is given to these mixed crystals, the carbon-content 

 of which may vary through the range 100 to 6 ■ 66 p.c. (pure carbon to 

 cementite). 



In a footnote, H. le Chatelier points out that BaykofFs conclusion is 

 in disagreement with the experimental results obtained by Moissan, who 

 found graphite and cementite, but no intermediate sobd solutions, in 

 high-carbon alloys. 



Iron-antimony Alloys. §— A. Portevin has determined the critical 

 points of five alloys containing 1*19 to 9 '20 p.c. antimony, with little 

 carbon. The results indicate a tendency of antimony to raise the critical 

 points of iron slightly. For microscopical examination, the alloys were 

 etched with copper-potassium chloride solution acidified with hydro- 

 chloric acid. A white constituent first appeared in the alloy containing 

 6 - 5 p.c. antimony. 



* Metallurgie, viii. (1911) pp. 72-7 (15 figs.), 

 t Metallurgie, viii. (1911) pp. 15-21, 49-53 (25 figs.). 

 t Rev. Metallurgie, viii. (1911) pp. 315-19 (2 figs.). 

 § Rev. Metallurgie, viii. (1911) pp. 312-14 (3 figs). 



