320 SUMMARY OF CURRENT RESEARCHES RELATING TO 



steel contains 1*0 to 1*6 p.c. carbon, and consists structurally of small 

 grains of cementite embedded in ferrite. Lamellar pearlite is wholly 

 absent. Zones rich in cementite alternate with zones containing 1 much 

 less cementite. It is shown that the damascene structure cannot be 

 obtained by prolonged heating at temperatures above the critical range. 

 Long heating below 700° C. is necessary to convert the cementite into 

 the desired form, while some previous treatment, _such as mechanical 

 working within a particular temperature range, appears to be required to 

 secure the remaining characteristics of damascene steel. 



Iron-carbon System.* — W. Guertler gives a critical account of the 

 researches of Wittorf and of Hanemann on the iron-carbon system, and 

 discusses the probability of the existence of the carbides FeC 2 and Fe 4 C. 



Hyper-eutectic Iron-carbon Alloys. f — H. Hanemann has heated 

 pure iron-carbon melts with excess of carbon (sugar-charcoal) to tem- 

 peratures ranging from 1200° to 2500° C. Most of the twenty-two 

 melts were cooled rapidly, others slowly. The structures are described 

 in tabular form. The maximum carbon-content, 18 "5 p.c, was found 

 in an alloy heated to 2500° C. In specimens quenched from tempera- 

 tures above 1400° C, graphite was found as a primary product, and 

 not as a decomposition-product of cementite. The so-called primary 

 cementite could only be obtained by extremely rapid cooling. In 

 quenched specimens the cementite crystallized radially from the centre. 

 "Wittorf's dendritic carbide, Fe 4 C, was shown to be austenite, as it was 

 converted into martensite by cooling in liquid air, and into pearlite by 

 annealing. 



Ternary Alloys of Iron, Carbon, and Phosphorus.^ — J. E. Stead 

 gives the results of a detailed microscopic study of a number of iron- 

 carbon-phosphorus alloys. An alloy containing 2 p.c. phosphorus and 

 " 12 p.c. carbon, was submitted to cementation, yielding a mass in which 

 the central portion remained unchanged, while the carbon in the outer 

 layer was raised to 1"3 p.c. Alloys containing 1*2 p.c. phosphorus 

 and varying amounts of carbon were prepared by fusion. Phosphorus- 

 rich pig irons, and an alloy containing ■ 3 p.c. carbon and ■ 5 p.c. 

 phosphorus were also studied. The ternary eutectic in grey cast iron 

 decomposes on cooling into the binary eutectic and pearlite or iron. In 

 the solidification of a low-carbon alloy containing 2 p.c. phosphorus, 

 crystallites free from carbon first form, and the ternary eutectic solidifies 

 last. On slow cooling, the carbide diffuses out of the eutectic, forms 

 a pearlite fringe round the eutectic, and throws some of the phosphide 

 out of solid solution. This phosphide appears as fine lamellre in jux- 

 taposition to the pearlite carbide. A fringe having a characteristic 

 structure and consisting of ferrite, carbide, and phosphide is thus 

 formed. The effect of carbon in diminishing the solid solubility of 

 iron-phosphide in iron, and the tendency of phosphorus to concentrate 

 in segregated areas free from carbon, are discussed and copiously 

 illustrated. 



* Int. Zeitschr. Metallographie, v. (1914) pp. 239-77 (30 figs.), 

 t Zeitschr. Anorg. Chem., lxxxiv. (1913) pp. 1-23 (31 figs.). 

 t Jouru. Soc. Chem. Ind., xxxiii. (1914) pp. 173-84 (44 figs.). 



