MancJicster Memoirs, Vol. h. (191 1), No. 24. 9 



junctions in rectangular forms, the meeting lines of the 

 columnar formation constitute a great weakness to the 

 casting, which is removed by annealing when the casting 

 is reheated through a certain range of temperature, and 

 kept at a certain heat for a certain length of time, accord- 

 ing to the composition of the steel and the nature of the 

 mecham'cal properties required from the material of the 

 casting. 



The influence of heat treatment upon the crystalline 

 structure of steel was perhaps most generally made known 

 through the researches of Brinell, and the publicity given 

 to his experiments by the exhibit of the Fagersta Com- 

 pany in the Swedish section of the Paris Exhibition of 

 1900. A copy of Brinell's chart, showing a graphical 

 representation of the changes of fracture and carbon in 

 steel containing 075 per cent, of carbon while heating 

 and cooling, and dated Fagersta, 1898, lies before you. 

 In this chart Brinell shows that however coarsely crystal- 

 line the texture of the steel might be, on heating the 

 same to the temperature which he calls the " moderate 

 hardening heat IF," corresponding to the temperature at 

 which the carbon of the steel suddenly passes from the 

 carbide or cement state into the hardening state, the steel 

 assumes the finest structure that it is capable of receiving. 

 (Stead referring to this particular chart assumes IF to be 

 about /So'-'C). If the steel is heated beyond the temper- 

 ature 11^, the crystals begin to grow and get the coarser 

 the higher the heat attained. The structure can, however, 

 be restored to the desired fineness by allowing the steel 

 to cool below a temperature denoted as the " annealing 

 heat F," and then to be re-heated to W. The annealing heat 

 F denotes the temperature at which the carbon in steel 

 containing hardening carbon has, during cooling as well 

 as heating, the greatest tendency to pass into cement 



