236 SUMMAHY OF CUKRENT EESEAKCHES. 



heating samples above 1000° C, allowing to cool slowly, and quenching 

 individual samples at various temperatures. Photomicrographs of all 

 the quenched samples are given. The microstructures of all samples 

 quenched above 900° or below 800 C° were as normally obtained with 

 pure iron, but those qu.enched between these temperature-limits showed 

 a peculiar "eutectoid" constituent, with double boundaries at the 

 junctions of many of the crystal boundaries. The composite character 

 of the constituent was always characteristic, the central structure being 

 more or less pearhtic, surrounded by a ferrite zone which connected 

 up in a definite manner with the adjacent crystal grains. The com- 

 position of the " eutectoid " has not been determined by the authors, 

 but a combination of sulphide, phosphide, and carbide is suggested. 

 Increasing the oxygen-content of the iron was not found to increase the 

 amount of the eutectoid. From the coincidence of the temperatures of 

 appearance and disappearance of the constituent with those of the 

 brittle range, it is considered very probable that the constituent is the 

 cause of the red-shortness shown by " Armco " iron. 



Fay, Hekry — Microscopic Examination of Steel. 



[A guide to others engaged iu the inspection of steel.] 



Wiley & Sons and Chapman & Hall : iv and 18 pp. (65 photos.). 



