Certain Chrome and Tungsten Steels. 747 



the magnetism was found to have fallen off slightly in each 

 case, by about 0'25 per cent. Neither percussion nor heating 

 and cooling was then found, however, to have any further 

 effect. 



On comparing among themselves the results obtained for 

 the four specimens, it is to be noticed first that while the 

 corrected residual magnetism diminishes with increasing- 

 tungsten content, the intrinsic residual magnetism is prac- 

 tically constant, while the percentage of tungsten increases 

 to 8*72, but falls off with further increase. The coercive 

 force is very nearly the same for all four specimens, being 

 only a little greater for higher percentages of tungsten, and 

 as might be expected from this similarity, the percentage 

 loss of magnetism is practically the same in the four cases. 

 Though the total percentage loss is the same however, there 

 is considerable variation in the loss due to the two causes, per- 

 cussion and change of temperature, the percentage loss by 

 percussion being least for the first specimen and increasing to 

 a maximum with the third, after which it falls off again, 

 while with the loss due to change of temperature, exactly 

 the reverse is the case. 



For the purpose of a satisfactory magnet which is to 

 resist both percussion and change of temperature, then, there 

 is very little to choose between the first three specimens, 

 though they are all superior to the fourth which has a lower 

 intrinsic residual magnetism, but if the effect of percussion 

 only need be considered the first is the best, while if the 

 magnet is to resist change of temperature only, the third is 

 the most satisfactory. 



Though none of these specimens is so satisfactory from 

 the point of view of permanency as the chrome-steel magnets 

 containing 8 per cent, chromium and upwards, they are all, 

 even after being submitted to shock and change of tempera- 

 ture, much superior in magnetic intensity to even the best of 

 the chrome steels. 



The most striking thing about the results obtained for 

 the four tungsten steels is, however, neither their residual 

 magnetism nor their coercive force, but the extraordinary 

 similarity between them. It seems very remarkable that 

 when quenched at 900° 0. a specimen containing as much 

 as 8*72 per cent, tungsten should be hardly superior to one 

 containing only 2'88 per cent., while one containing 11*65 

 per cent, is actually inferior. 



This investigation, then, as far as it has gone shows clearly 

 that when a tungsten steel is quenched from 900° C, no 

 -advantage is gained either in intensity or permanence of 



3C2 



