Properties of the Alloys of Cast-iron and Aluminium. 615 



§ VI. Experiments on the Changes in the B and T curves 

 due to successive Heatings and Coolings. 



The magnetic properties of the specimen change to some 

 extent after heating to a high temperature. 



The difference between two successive B and T curves 

 (H = a constant) is much smaller for strong than for weak 

 tields. 



In all the cases tried the characteristic form of the curve 

 was maintained. The nature of this change can be seen from 

 a consideration of the curves shown on fig. 3. 



The curves A and B were obtained from double reversal 

 throws taken simultaneously with the hysteresis loops for 

 rising temperatures. 



They were plotted from readings which are indicated on 

 the diagram thus X . 



In the figures T stands for the temperature in degrees 

 centigrade, B for the maximum induction reached at each 

 reversal, and H for the field-strength in c.G.s. units. 



H=8'2 c.G.s. units. 



H=3 48 c.G.s. units. 



T. 



B. 



T. 



B. 



24: 



3137 



24 



1364 



159 



3137 



146 



1463 



226 



3223 



157 



1487 



311 



3337 



165 



1535 



361 



3376 



204 



1621 



370 



3376 



228 



1697 



381 



3261 



307 



1955 



392 



2939 



312 



2021 



416 



2644 



370 



2269 



449 



2584 



382 



2241 



502 



2331 



392 



2035 



527 



2195 



415 



1858 



569 



1708 



500 



1522 



582 



1389 



570 



442 



587 



1257 



594 



248 



602 



628 



640 



106 



642 



221 







The specimen was then heated to 800° C, and double 

 reversal throws were taken for fields of 8'2 and 3*48 units 

 during cooling. 



The values obtained are indicated thus * in fig. 3. 



It will be seen that the magnetic properties have changed 

 considerably owing to the repeated heatings and coolings. 



