Magnetic Permeability of various Alloys of Iron. 1138 
There is, however, this difference; the first flexure in the magnetic properties of 
the curve appears to take place at about 4 per cent., whereas the first flexure in 
the mechanical properties takes place a little under 8 per cent. ; the second flexure 
occurs at about 24 and 20 per cent. respectively. ‘This is better seen by referring 
to the hysteresis loss in Table VII. These slight differences, probably due to 
differences in heat treatment, will doubtless be cleared up by further experiments, 
when a more complete set of these nickel steels has been prepared for the deter- 
mination of their magnetic properties. 
The effect on the magnetic and mechanical properties produced by the prior 
heat treatment, to which these steels have been subjected, is most marked, 
especially in certain percentages of nickel.* This is well seen from Table VI. 
The specimens containing 12°7 and 12:1 per cent. of nickel were only slightly 
magnetic in the unannealed condition, in a field of 45, whereas they were fairly 
magnetic when annealed. In much stronger fields, however, their magnetisation 
in both physical states rises considerably, and soon much exceeds that of the 
higher nickel steels, which are saturated in lower fields. The permeability and 
the hysteresis loss of several of the nickel steels is shown on the next Table. 
Taste VII.—WMickel Steels. 
' / y Percentage of ‘ ce Energy esa 
lens. Nickel. fe HOP UES B. per cycle. 
Iron 0:0 1560 11090 
1287 D 1°92 1290 15760 
pat Lt 3°82 1280 16340 
1267 B 4:75 140 41000 
1287 I 11°39 | 120 338000 
1447 B 12:1 115 22500 
» Unann. <5 0 — 
1447 A 12-7 60 25000 
> Unann. 96 0) 900 
1287 K 19°64 96 | 38000 
» Unann. 99 60 36130 
1287 L 24°5 50 22850 
( 1449 31-4 | 365 | 930 
{ » unann. re 300 2420 
* This subject, as is well known, was first investigated by the late Dr. Hopkinson, who discovered 
that steels containing from 43 per cent. of nickei and upwards could exist in a stable magnetisable or non- 
magnetisable state, according to the prior temperature to which they had been subjected. Dr. Hopkinson 
also found that nickel steels, up to 43 per cent., were capable of higher magnetisation than wrought iron, 
in fields of from 80 to 50 C. G. S, units: see Proc. Royal Society for 1889 and 1890. 
