Certain Chrome and Tungsten Steels. 743 



state was reached, without any long interval o£ time elapsing 

 between heatings. 



When the six specimens were re-tested after the lapse of a 

 month, the magnetism of specimen I. was found to have 

 deteriorated slightly, by less than 1 per cent., while that of 

 specimen Y. had gained about 0*4 per cent., the magnetism 

 of the other specimens remaining unaltered, but neither 

 percussion nor heating and cooling then produced any further 

 change, and when the specimens were tested again some 

 three or four months later the same constant value was 

 maintained in each case. 



In comparing the results obtained for the six specimens 

 (see Table I.), it will be noticed first, that while the corrected 

 values of the residual magnetism diminish steadily with 

 increasing percentage of chromium, the intrinsic residual 

 magnetism at first increases, and then steadily falls off, the 

 specimen containing 8 per cent, having the largest value. 

 The values of the coercive force also increase to a maximum 

 and then fall off with increasing chrome content, but the 

 maximum in this case is only reached with the fifth specimen 

 of the series. 



Specimen I., which has a coercive force of only 28 C.G.S. 

 units, loses by percussion and thermal treatment 16*3 per 

 cent, of its magnetism. Specimen II. loses 10*6 per cent., 

 and specimen III., which has the greatest intrinsic residual 

 magnetism both before and after treatment, loses 55 per 

 cent. The next two specimens retain a very great proportion 

 of their magnetism, losing only 3 and 2*8 per cent, respec- 

 tively ; but while specimen IV. is, after treatment, nearly as 

 magnetic as specimen II., specimen V. is considerably less 

 so. The last specimen of all, specimen VI., is less magnetic 

 still, and loses nearly 7 per cent, of its magnetism in 

 maturing. 



Considering them from the point of view of satisfactory 

 magnets then, specimens I. and VI. would be at once 

 discarded as being both less strongly magnetic and less 

 permanent than some of the others. From the point of view 

 of retentivity, specimens IV. and V. are almost equally good ; 

 but as the amount of magnetism held by IV. is considerably 

 greater than that held by V., the former makes undoubtedly 

 the superior magnet. Specimen III. retains most magnetism 

 of all, and, though it loses over 5 per cent, in maturing, 

 is still, even after that, more magnetic than any of the others. 

 Specimen II. is originally much more magnetic than IV. 

 and not much less so than III., but, losing over 10 per cent, 

 of its magnetism on being submitted to percussion and 



