746 Dr. Margaret Moir on Permanent Magnetism of 



It is well known that the hardness of tungsten steels 

 varies very considerably with the temperature at which 

 quenching occurs, and that to obtain a complete record of 

 the behaviour of the steels as permanent magnets, it would 

 be necessary to examine them in the different conditions of 

 hardness brought about by quenching at various temperatures. 

 It was decided therefore to commence the investigation by 

 quenching the steels from 900° 0. and examining them in 

 that condition, and only the results thus obtained are included 

 in the present paper. 



The procedure in the case of these steels was exactly 

 similar to that in the case of the chrome steels. After being 

 quenched from 900° C. and tested for hysteresis, the speci- 

 mens were magnetized, and the loss of magnetism due to 

 percussion and heating and cooling observed. The chief 

 results obtained are shown in Table V. 



Table V. 

















Percentage 



















loss 



(E 



CO 



O 



© 



g 



'© 



© 



ft 



w 



© n 



1 IP 

 Z> p 



a J 



1 1 



Intrinsic 



Residual 



Magnetism 



© 



.t © 

 © © 



© o 

 o pa 



u o 

 © "S 



■si 



M ©■ 



I after 



heating and 



cooling. 



.2 



© 



ft 



S3 .5 

 OS o 



© § 



ri tic 

 | * 

 ° c 

 H © 

 © 



© 



ft 



A ... 



2-88 



735 



472 



35 



466 



430 



1-3 



7-6 



8 9 



B ... 



5-85 



726 



472 



35 



459 



431 



2-8 



59 



8-7 



O ... 



8-72 



720 



474 



37-5 



456 



432 



3-8 



51 



8:9 



D ... 



11-65 



685 



448 



37-5 



435 



408 



2-9 



60 



8'9 



The first specimen required 20, the second 30, and the 

 other two 40 falls each before a constant state was reached. 

 The last specimen when left for one day after having been 

 given 30 falls, had its magnetism spontaneously increased 

 by about 5 c.G.s. units, but other 10 falls wiped out this 

 increase, and brought about the state where further falls 

 ceased to affect it. In the case of each specimen, three 

 successive heatings and coolings were sufficient to set up a 

 cyclic state in which the loss of magnetism due to heating 

 was exactly balanced by the gain due to cooling. 



After this state of constancy was reached, each specimen 

 was laid aside for a month, and then tested once more, when 



