196 SUMMARY OF CURRENT RESEARCHES RELATING TO 



some other metal are heated in a mixture containing finely ground 

 aluminium. The effect is to form a coating of an aluminium-rich alloy 

 on the article treated. This coating possesses remarkable resistance to 

 oxidation on heating to high temperatures, and it is because of this 

 property that the process is known as " calorizing." The microstructure 

 of the coatings obtained on copper and other metals is described. 

 There is a clear line of division between the unchanged copper and the 

 alloy ; the alloy is richest in aluminium at the surface. 



Manganese Steel.*— J. H. Hall deals with the metallography as well 

 as the manufacture, properties and uses of manganese steel, which 

 commonly contains 9 to 14 p.c. manganese and 1 to 1*5 p.c. carbon. 

 In the cast condition manganese steel consists of a ground-mass 

 of austenite, containing manganiferous cementite in the form of a net- 

 work, needles, and small masses. The cementite is bordered by austenite 

 more or less transformed to troostite or sorbite. When the steel is 

 heated to a sufficiently high temperature (1000 to 1100° C), the cementite 

 is dissolved in the austenite. If the cooling is rapid, the cementite is 

 not liberated, but if the steel is cooled slowly, the cementite is liberated 

 in a structure resembling that of the cast material. When the tough, 

 quenched steel is reheated it becomes brittle owing to the separation of 

 cementite as a fine network, and needles at about 500° C. If heating at 

 500° to 600° 0. is prolonged for 24 hours, the austenite is transformed to 

 sorbite and the steel becomes strongly magnetic. 



Boron Steels. f—G. Hannesen has examined iron-boron alloys 

 containing up to 8*5 p.c. boron. The compound Fe 5 B 2 was found as 

 needle-shaped crystals of rhombic section, and is magnetic. By quench- 

 ing alloys containing - 4 to 2*0 p.c. boron a martensitic structure was 

 obtained, but in no case was an austenitic structure produced. 



Honeycombing in Steel. $— E. Crowe describes the structure of a 

 crust of solid steel which had formed to a thickness of 4 to 6 inches on 

 the top of the steel contained in a casting ladle, as a result of accidental 

 long delay in casting. The underside of this top crust was honeycombed 

 in a remarkable way. J. E. Stead puts forward the explanation that the 

 gases given off in solidification had collected underneath the crust 

 as bubbles, aud the steel continued to crystallize round these bubbles. 



Structure of Steel Castings.§ — J. H. Whiteley found two distinct 

 structures in a steel casting. On one side, large dendrites had formed, 

 while on the other side the structure was not dendritic but granular. 

 Examination of a number of castings, and experiments in which portions 

 of molten steel were cooled quickly or slowly, indicated that slow cooling 



* Journ. Soc. Cheru. Ind., xxxiv. (1915) pp. 57-60 (1 fig.). 



t Zeitschr. Anorg. Chem., lxxxix. (1914) pp. 257-78, through Journ. Soc. Cheru. 

 Ind., xxxiv. (1915) p. 84. 



t Iron and Coal Trades Rev., xc. (1915) p. 327 (2 figs.). 



§ Iron and Coal Trades Rev., lxxxix. (1914) p. 763 (Clev. Inst. Engineers. 

 Dec. 14, 1914). 



