542 SUMMARY OF CUREENT RESEARCHES RELATING TO 



crystals in a magnified image of the heat-relief projected upon the 

 screen bj means of a projecting Microscope. The total area, measured 

 by a planimeter, was divided by the number of crystals in it. The 

 comparative vagueness of the slip bands observed in specimens which 

 had been maintained at a high temperature for some time after straining, 

 is ascribed to the volatilization of metal from the surface in the high 

 vacuum employed. 



Crystallization of Steel.* — F. Giolitti's experiments lead him to 

 differ fi'om Belaiew as to the process of crystallization in steel, which 

 would rather appear to consist in the formation of mixed crystals from 

 the melt, and the subsequent separation of the ferrite or cementite from 

 the mixed crystals. Slow cooling after eight hours heating at 1000" C. 

 favours the formation of Widmannstatten's figures in steel containing 

 0*32 p.c. carbon, while rapid cooling renders them less perfect. 



Microstructure of Steels.f — Bres describes the microstructure of 

 four steels, each containing about 2 * 6 p.c. nickel, * 6 p.c. chromium, 

 • 2 p.c. carbon. In spite of their similarity in composition and heat- 

 treatment, their mechanical properties differed widely, and corresponding 

 differences were found in their microstructure. In the cast condition, 

 one of the steels consisted of large areas of ferrite and well -formed 

 pearlite. The pearlite in the other steels was more finely divided and 

 confused in structure. These differences were found to persist after 

 rolling at a high temperature, and throughout an experimental series 

 of hent-treatments. It appears that in steels of similar composition, 

 differences in initial structure, which cannot be removed by mechanical 

 or thermal treatment, may occur. 



A. Porte vin J has examined the two steels which differed most 

 widely after forging and annealing, and gives photomicrographs illustrat- 

 ing the marked difference in microstructure at high magnification. 



Influence of Phosphorus upon the Properties of Mild Steel. § 

 E. d'Amico has studied numerous properties, including microstructure, 

 of twelve mild steels containing 0*01 to 1 • 21 p.c. phospliorus, the 

 carbon being about 0" 13 p.c. Specimens were examined as rolled, after 

 annealing and after quenching. Phosphorus above 0*6 p.c. caused 

 irregularity in the distribution of the ferrite and pearlite. The ferrite 

 crystals were large in the phosphorus-rich alloys. Surrounding each 

 pearlite mass, in the phosphorus-rich alloys, was a zone of ferrite dis- 

 tinguishable from tlie remainder of the ferrite by its lower level in etched 

 specimens. It is suggested that the zone is more rich in phosphorus 

 than the rest of the ferrite. 



Influence of Heat-treatment upon Cold-worked Mild Steel.||— P. 

 Goerens has studied the microstructure, in addition to numerous other 



* Atti Accad. Sci, Torino, xlviii. (1912-13) pp. 413-33, through Science Abstracts, 

 Section A, xvi. (1913) p. 393. 



t Rev. Metallurgie, x. (1913) pp. 797-807 (18 figs.). 

 : Rev. Metallurgie, x. (1913) pp. 808-10 (2 figs.). 

 § Ferrum, x. (1913) pp. 289-304 (33 figs.). 

 11 Ferrum, x. (1913) pp. 226-33, 260-70 (21 figs.). 



