Graded Series of Chrome Steels at Low Temperatures, 841 



condition, the maximum residual magnetism is attained with 

 the lowest percentage of chromium, and every additional 

 amount of chromium produces a diminution in its value. 

 A similar regular change takes place also in the values of 

 the coercive force, but the value in the quenched condition 

 is invariably much greater than the value in the annealed 

 state. 



Table VII. 



1 per cent. Cr 



4*05 per cent. Cr 



.Residual Magnetism. 



Coercive Force. 



Annealed. 



Quenched. 



Annealed. 



Quenched. 



28 

 39 

 46 

 54 

 56 

 44 



400 

 500 

 660 

 510 

 490 

 440 



660 

 600 

 580 

 435 

 340 

 320 



5 

 21 

 20 

 19 

 17 

 15 



8 per cent. Cr 



12 per cent. Cr 



16 per cent. Cr 



20 per cent. Cr. 





Coming now to a comparison of the effects produced by 

 lowering the temperature of the different specimens, we find 

 that these effects are on the whole very similar. Considering 

 the quenched specimens first, we see indeed that they behave, 

 so far as the range examined goes, in exactly the same 

 manner, the curve taken at the temperature of liquid air 

 lying in each case below that taken at room-temperature, 

 and the curves taken at room-temperature before and after 

 immersion in liquid air exactly coinciding. 



The specimens in the annealed state, however, show some 

 slight differences in behaviour, for while the effect of 

 lowering the temperature to —190° C. is in each case to 

 diminish the susceptibility for low fields and to increase 

 it for high fields, there are considerable variations in the 

 value of the magnetizing force for which crossing of 

 the curves taken at the two temperatures occurs, the 

 actual values of the field-strength corresponding to the 

 crossing point being 8, 70, 102, 125, 95, and 65 c.G.s. units 

 for the specimens containing respectively 1 per cent., 4*05 

 per cent., 8 per cent., 12 per cent., 16 per cent., and 20 per 

 cent, chromium. As the chrome content increases from 

 1 per cent, to 12 per cent., that is to say, higher and higher 

 values of the magnetizing force are required to produce 

 crossing of the curves. Further additions of chromium 



