Magnetic Permeability of various Alloys of Tron. 93 
Group 15.—MANGANESE-SILICON STEELS. 
Specific resistance 
Marks. Percentage Composition. Conductivity Copper = 100. (calculated) 
Mn Si C Unann. Ann. Unann. Ann. 
611 0:58 0°49 0:58 7:5 8:3 23:1 20°7 
1379 D 10:08 0:65 0:16 2°6 2°8 65°5 61:1 
601 2°00 4:25 0:40 2°3 2°5 73'8 68:4 
Other low manganese-silicon steels are given in Groups | and 8, Series B, from 
which 611 is transferred for comparison, and 1379 D is also transferred from 
Group 2, Series B. By comparing 601 with 687 in Group 14, or with 53 in Group 
2, p. 76, it will be seen how powerfully silicon affects the conductivity of steel. 
In the next group we see the effect of adding copper to manganese steel. 
Marks. 
Group 16.—-MANGANESE-CopPER STEELS. 
Percentage Composition. 
Conductivity Copper = 100. 
Specific resistance 
(calculated). 
1240 
1260 A 
Mn Cu | C 
2:0 15 =| (0:25 
8:0 2°75 | 0°64 
Unann. | Ant. 
5'8 6°8 
2°4 3°3 
Unann. Ann. 
29°5 sy) 
A! 51°8 
From Group 2 it will be seen that a steel (53), having 24+ per cent. of 
manganese, but no copper, has rather a lower conductivity than 1240 in 
the above table; the carbon it is true is rather lower in the latter specimen. 
We will now examine the effect of adding a second metal to the chromium 
steels. Here is a group of chromium-aluminium steels. 
Group 17.—Curomium-ALuMINIUM STEELS. 
Marks Percentage Compositi Conductivity C = 100 Specific resistance 
6 s Pp S1T10N. onductlyl ry opper = 6 (calculated). 
Cr Al C Unann. Ann. Unann. Ann. 
1178B 1:75 0:75 0-21 5:2 6:1 33:2 28:0 
1179B 3°50 1:00 0:46 3°4 3.8 49:9 45:0 
1178D 1°50 2°50 0:18 2-9 3:4 58°5 50°38 
1178E 1°50 4°50 0:22 oa) 2:5 778 68:4 
IP 2 
