IN MANGANESE STEEL BY HEAT TREATMENT. 



351 



of susceptibility at this higher temperature, until it reaches nearly 

 double the value it had at the end of the previous treatment. 



Fig. 2 shows that at the 260-hour point of total treatment the 

 temperature was quickly raised about 25°, i. e., to 619°, and con- 

 tinued at that point about ten hours. This moderate rise in tem- 

 perature brought about a sudden and very considerable fall in sus- 

 ceptibility, approaching stability at the end of the ten hours. 



Hours of Heating 

 Fig. 2. 



When the temperature was next quickly lowered to its former 

 value and then continued to the end of the experiment, 175 hours 

 (340 hours total), there was at first a sudden rise of susceptibility, 

 followed by steady growth as before. All these changes are clearly 

 shown in Fig. 2. 



Great sensitiveness to temperature change is indicated at about 

 600°. 



Sixth quenching: At the end of 344 hours, total, of treatment, 



