96 



Barrett, Brown & Hadfield — On the Electrical Conductivity and 



CLASS III. 

 Effect of three or more Elements added to Iron or Steel. 



This class exhibits the effect of the addition of three or four elements to 



steel. 



Group 23. — Cobalt-Manganese-Silicon Steels. 



Hitherto no alloys of steel have been examined containing cobalt ; the 

 effect on the conductivity produced by the addition of this element closely 

 resembles that produced by nickel, as will be seen by comparing this group with 

 Group 3, p. 78. 



The next specimens show the effect of adding copper to a nickel-manganese 

 steel and to a chromium-tungsten steel. 



Group 24. — Nickel-Manganese-Copper Steel. 



Group 25. — Chromium-Tungsten-Copper Steel, 



This alloy 1249 A was drawn into wire and its specific resistance directly 

 measured in the annealed state, together with its temperature coefiicient. The 

 specific resistance at 16° C. was found to be 31*6 microhms per c.c. As will 

 be seen, this result closely agrees with that deduced from its conductivity in the 

 form of a rod. The percentage variation of resistance of this alloy per 1^ C. was 

 found to be 0-204 between 10° and 150° C. 



