IN MANGANESE STEEL BY HEAT TREATMENT. 353 



At this stage it was thought that decalescence might possibly be 

 brought about by cautiously raising the temperature, and the effect 

 of doing so is shown in the great and nearly vertical drop in the sus- 

 ceptibilty curve. The stations in this part of the curve represent 

 observations at half-hour intervals, indicating two hours for the 

 total drop, with the temperature steadily rising to the maximum 

 of 692°. 



It seemed clear that decalescence was not taking place, because 

 loss of susceptibility was far too slow in time, and the maximum 

 temperature reached was not sufficiently high. Probably the man- 

 ganese was simply resuming its sway. 



The temperature was next rapidly lowered to 6o5°-590°, bringing 

 on a rapid recovery of magnetic susceptibility, amounting to 30 

 points in 21 hours as shown. 



Again the temperature was raised, but much more rapidly than 

 before, resulting in a much steeper drop in the curve, the observa- 

 tion stations shown representing only five-minute intervals. 



Seventh quenching: At the end of the curve shown in Fig. 3 the 

 steel bars were quenched at 687°. Subsequently there was no trace 

 of generation or absorption of heat. Hence it is virtually certain 

 there had been no decalescence. 



Hardness was: Bar No. i, 42; Bar No. 7, 41.8. 



Sir Robert Hadfield long ago assured me that the study o"f 

 manganese steel is full of surprises for the investigator. I have 

 experienced some of them, and hesitate at present to draw definite 

 conclusions from the results of the experiments just described. The 

 manner in which the manganese operates in completely obliterating 

 the magnetic quality of seven times its weight of iron is, so far as I 

 am aware, not yet known ; and the instability of the alloy or, prob- 

 ably, mixture of alloys, in which the carbon present may play an 

 important part, at about 600° temperature as herein shown, is most 

 remarkable and promises a fertile field for future investigation. 



I am contemplating the study of a similar ferro-manganese alloy 

 free from carbon. 



Cleveland, O., 

 April, 1918. 



