Magnetic Permeabiliti/ of various Alloys of Iron. 



87 



curves show the resistances in the tinannealed condition. The effect of annealing 

 is to lower the curves in each case. Some of the irregularities observed, notably 

 the loop in the manganese steels, are smoothed out by annealing, and the position 

 of the copper steels would then be slightly below tliat of the tungsten steels 

 instead of above, as shown in fig. 6. It must be borne in mind that (1) owing to 

 small irregularities in the sectional area of the rods, and (2) the disturbing influence 

 caused by small variations in tlie amounts of carbon, silicon, and manganese 

 unavoidably present in the alloys, the curves here shown can only be regarded as 

 an approximate representation of the effect produced by varying amounts of 

 different elements on the conductivity of these alloys of iron. 



CLASS II. 

 Effect of two Elements added to Iron or Steel. 



We now come to specimens which exhibit the eff'ect of hvo elements added to 

 iron or steel ; and for the sake of comparison with the last group, which shows 

 the eft'ect of copper on the conductivity of steel, we will first give a specimen of 

 an iron alloy containing nickel as well as copper. The comj^arison is of interest, 

 as the alloy has practically the same amount of copper and carbon as 1263 C in 

 Group 8, only with 5 '75 of nickel added to it. 



Group 9. — Nickel- Copper Steel. 



It will be noticed that the addition of the nickel reduces the conductivity of 

 the alloy one-half compared with a similar copper steel without nickel. In like 

 manner, the addition of copper to a nickel steel reduces the conductivity of the 

 alloy when compared with a similar nickel steel without copper. This may be 

 seen upon referring to the nickel steel curve in Plate II. or fig. 6. We will now 

 take other double alloys of steel where nickel is one of the elements. 



Here is a group of alloys of nickel and chromium with iron, arranged in order 

 of conductivity. Their conductivity, it will be noticed, is considerably lower 

 than steels containing corresponding percentages of nickel alone. 



