258 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Metallography, etc. 



Heat-treatment of Steel Locomotive Axles by Water- and Oil- 

 quenching.* — The results obtained bj water-quenching and by oil- 

 quenching of two axle forgings, both from the same steel-melt con- 

 taining 0*6 p.c. carbon, have been compared by C. D. Young. The 

 mechanical properties of the two axles after treatment were generally 

 similar, except that water-quenching gave a higher elastic limit. The 

 structure of each axle (illustrated by photomicrographs) showed charac- 

 teristic differences. The water-quenched axle had an irregular sorbitic 

 structure, with very little ferrite network, while the oil-quenched axle 

 showed a more regular structure, with a moderately thick network of 

 ferrite. The assembling of the ferrite, liberated in passing through the 

 critical range, is restricted to a less extent during the less rapid cool- 

 ing of oil-quenching. 



Splitting of Brass Condenser Tubes.f — The results of an investi- 

 gation into the causes of spontaneous cracks or splits in brass condenser 

 tubes are set forth by A. E. White. The phenomenon is ascribed to the 

 existence of a state of molecular strain in the metal due to insufficient 

 annealing between the drawings during manufacture, or to incomplete 

 anneaHng after the final drawing. The most suitable composition of 

 brass and the proper treatment, thermally and mechanically, during 

 manufacture into tubes, to obtain a final product which will be in a 

 state of equilibrium free from mechanical strains, are considered in detail. 

 The guidance given by a study of microstructure in determining the 

 requisite heat-treatment is illustrated by a complete series of photo- 

 micrographs showing changes in structure of a drawn tube after anneal- 

 ing at varying temperatures, followed by different rates of cooling. No 

 change is effected by anneahng below 400° C. Above 400° C. the dis- 

 torted crystallization is broken up and replaced by a fine equi-axed 

 crystallization showing no distortion. With increase of temperature up 

 to 800° C. this crystallization becomes progressively coarser. Above 

 800° C. the structures show characteristic " burnt " crystals. A special 

 etching reagent, consisting of hydrogen peroxide and ammonia, was 

 employed. 



It is recommended that a microscopical examination should be in- 

 cluded in the specifications to be fulfilled by condenser tubes before 

 being accepted for service. Microsections of the tubes at a magnifica- 

 tion of 75 diam. should show no strains and no grain larger than ^ in. 

 diam. 



Recrystallization of Deformed Low-carbon Steel as a Factor in 

 the Failure of Boiler Tubes. | — It is well known that recrystallization 



* Proc. Amer. Soc. for Testing Materials, xvi. pt. 2 (1916) pp. 53-64 (5 figs.), 

 t Proc. Amer. Soc. for Testing Materials, xvi. pt. 2 (1916) pp. 152-67 (7 figs.). 

 X Proc. Amer. Soc. for Testing Materials, xvi. pt, 2 (1916) pp. 80-110 (24 figs.). 



