MAGNET STEELS AND PERMANENT MAGNETS 



397 



It is felt that these pouits lie closely enough along the straight line in 

 that figure to warrant the use of Br lie as a criterion of magnetic 

 quality of magnet steel for all practical purposes. In cases where 

 very accurate comparisons are required, it may be necessary to go to 

 the greater trouble of determining {BII)max- 



0.2 



04 0.6 0.8 



(BH)max X 10"^ 



1,0 



1.2 



Fig. 11 — Relation between the quantity Br X Tic and Evershed's criterion, {BH)max- 



Referring to a previous mention of optimum hardening temperatures, 

 it will be understandable now to state that the optimum hardening 

 temperature for a given type of steel is that temperature at which a 

 maximum value of (BH)max is obtained, or practically speaking, a 

 maximum value of Br He. 



