118 Barrei"!', Brown & Hadfield — On the Electrical Conductivity and 



It is instructive to note the difference in this respect between the specimens 

 J 178 E and 1179 B. When the amounts of chromium and aluminium are nearly- 

 reversed, the hardness of the latter specimen is seen in its high coercive force and 

 low permeability. By comparing 1167 D, Table XI., witli 1178 B, Table XII., 

 we see that the addition of 1'75 per cent, of chromium to a low aluminium steel 

 more than doubles the hysteresis loss, whilst the coercive force is increased three 

 times. The large amount of aluminium in 1178 E lowers the coercive force, and 

 hence much reduces the hysteresis loss of this specimen. 



The addition of small percentages of copper does not seem to have much effect 

 on the magnetic properties of steel as is seen by comparing 1264 A and B in the 

 next Table, which are similar steels, except that 1264 B has about 1 per cent, more 

 copper. 



Table XIII. — Copper Steels. 



The large coercive force of these copper steels may be due to the high carbon or 

 manganese they contain, as will be seen by referring to the full analysis given in 

 Group 8. Another steel containing 14^ per cent, of copper with manganese and 

 chromium is given in Table XV. The B and H curves of these copper steels have 

 not been engraved, and it also seemed hardly worth while to determine their 

 hysteresis loss. 



Passing on to the effect produced by Chromium on the magnetic properties of 

 iron, we have examined two specimens of chromium steel, besides several other 

 chromium steels, containing nickel or tungsten in addition to chromium. The 

 percentage composition of these and other steels is given in the next table. 

 A nickel chromium steel, 1450, has already been given in Table VIII., p. 114; 

 comparing this with 1447 A and B (see p. 110), which have the same quantity 

 of nickel but no chromium, we find all three barely magnetic in a field of 45, in 

 the unan7icaled state, but magnetic in a field of 300, the induction of 1447 being 

 twice that of 1450, showing the effect of chromium. 



■ This specimen has also 1 per cent, of mauganese. 



