114 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Metallography, etc. 



Quenching Velocities.* — C. Benedicks has carried out a lengthy 

 and painstaking investigation on the cooling power of liquids, on 

 quenching velocities, and on the constituents troostite and austenite. 

 From the results given by two different methods, in which the tem- 

 perature of a body heated by electrical energy and cooled by a flowing 

 liquid was measured, it is concluded that, as Le Chatelier had found 

 by another method, mercury is much inferior to water in cooling power, 

 that the main factor in the cooling power of a liquid is its latent heat 

 of vapour ; specific heat has a secondary influence ; conductivity for heat 

 and viscosity may probably be neglected. Experiments in which photo- 

 graphic time-temperature curves of small pieces of steel quenched in 

 water were taken, demonstrated that the time occupied in cooling 

 through a given range (700°-100° C.) is directly proportional to the 

 mass, but almost independent of the surface area of the specimen. 

 Speed of cooling is increased by raising the temperature from which 

 the sample is quenched. Troostite is held to be a solid colloid solution 

 of cementite in iron, and " osmondite " is a state with a maximum 

 content of troostite. For the detection of austenite, a new etching- 

 reagent, 5 p.c. alcoholic solution of metanitrobenzolsulphonic acid was 

 found to be useful. The preservation of austenite in carbon steel re- 

 quires a high mechanical pressure. 



Iron-Carbon Equilibrium.t — Gr. B. Upton proposes a greatly modified 

 iron-carbon diagram, based upon the experimental results obtained by 

 Carpenter, Wiist, Goerens, and others. The hypothesis of iron-graphite 

 as the stable system with iron-ironcarbide metastable, is considered to 

 be unnecessary. The phases crystallising from the melt are solid solu- 

 tion and graphite, forming a eutectic at 1145° C. of4 - 3 p.c. carbon. 

 At 1095° C. the inversion y + graphite to y + Fe 6 C, or Fe 6 C + 

 graphite occurs. At 800° C, Fe 6 C breaks up into Fe 3 C -f- y ; and at 

 G15°C, Fe 3 C decomposes into Fe 2 C -f Fe. The two new phases Fe 6 G 

 and Fe 2 C are introduced to account for the thermal critical points found 

 by Carpenter and Keeling in the neighbourhood of 800° and 600° C. 

 The existence of these compounds appears to be supported by the work 

 of Campbell and others on the chemical constitution of cast irons. 



The author deals in a very thorough manner with the various 

 phenomena (such as formation of temper-carbon) exhibited by the cast 

 irons, and accounts for all of them in his equilibrium diagram, which, 

 however, appears likely to meet with much well-founded criticism. 



Copper and Copper Alloys.^ — J- T. Milton discusses niirnerous cases 

 of abnormal behaviour, and indicates directions in which investigation 

 should be pursued. The effect of hot and cold work, and of anneal- 

 ing, is imperfectly understood. The influence of heat-treatment on the 



* Journ. Iron and Steel Inst., lxxvii. (1908) pp. 153-257 (51 figs.), 

 f Journ. Phys. Chem., xii. (1908) pp. 507-49 (13 figs.). 



% Ironmongers' Chronicle (Special Report Number, Institute of Metals, 

 Birmingham Meeting) lxi. (1908) pp. 11-15. 



