92 Barrett, Brown & Haprienp—On the Electrical Conductivity and 
The carbon is high in all these specimens. In the first three specimens 
the percentages of manganese and of carbon remain about the same, the amount 
of chromium in each differing; the conductivity it will be seen is very low 
in all. 
From the chemical analysis we should expect to find the conductivity of 
1274 A higher than that of 1430, but the reverse is the case, confirmed after 
several trials. This is, no doubt, due to the difference in hardness, as the latter 
is distinctly softer to the file than the former. 
Annealing makes a great difference in the conductivity of these manganese 
chromium steels, e.g. 1430 in the unannealed state had a conductivity of 3-4, 
whilst in the annealed state it was 4:7, taking copper as 100. This difference 
is still more striking in the magnetic permeability of this specimen in the two 
states (see p. 114). The alloy, 1233 A, is enormously hard, and can hardly be 
touched by a file. 
The next is a series of manganese-tungsten steels. 
Group 14.—MancGanese-TuNGsTEN STEELS. 
Marks. | Percentage Composition. | Conductivity Copper = 100. | BP oe 
Mn W | C Unann. | Ann. | Unann. Ann. 
687 2:25 3°25 0-40 4:7 | 6-2 37-1 27-7 
683 3°25 LOO |} ay 3°8 | ya) 45:4 31°73 
1343 B 10°20 2°11 | 1:08 2°4 | 2°6 71:3 65°8 
1343 A 11:10 2°85 | 1°34 2°3 | 2°5 74:5 68°4 
Tungsten, it will be remembered, had the least effect of any element, so 
far tried, in reducing the conductivity of steel; the addition of manganese to 
the tungsten steels produces a great drop in the conductivity, as will be seen 
by comparing 687 above, with 1294H in Group 4. Compare also the man- 
ganese steel 53 in Group 2 with the specimen 687, having the same quantity 
of manganese and carbon; the effect of 314 per cent. of tungsten added to the 
latter raises the conductivity when both specimens are annealed. The same 
remarkable increase in conductivity will be seen by comparing 683 with 1381 in 
Group 2, Series B; in the former 10 per cent. of tungsten has been added to a 
manganese steel. Note also the effect of practically reversing the amounts of 
tungsten and manganese in the specimens 683 and 1343. 
The next group exhibits the effect of adding silicon to manganese steel. 
