352 BRUSH— DEVELOPMENT OF MAGNETIC SUSCEPTIBILITY 



the bars were again quenched. This was followed by very little, 

 if any, spontaneous generation of heat. 



Hardness was: Bar No. i, 37.4; Bar No. 7, 36.2. 



This shows a very considerable softening since the last quench- 

 ing, notwithstanding the large increase of magnetic susceptibility. 

 The softening may account for the absence of heat generation after 

 the quenching. 



The magnetic susceptibility of the cold quenched bars was almost 

 the same (slightly lower) as before quenching. 



360 380 400 



Hours of Heating 



Fig. 3. 



The ten bars were again heated, slowly this time, to 590° and 

 held nearly at that temperature until the 381st hour of total treat- 

 ment, as shown in Fig. 3. Susceptibility rose slightly, reaching its 

 highest value, 68.5. As this is comparable with the susceptibility of 

 ordinary steel, the manganese had apparently almost completely lost 

 its influence. 



