Investigation of the properties of chilled cast iron as a material for permanent magnets . e above statements we have outlined only a fewof the many cases where permanent magnets areemployed, and where constancy is desiraDle, andsometimes absolutely essential. Prof. C. E. Freeman, of Armour Institute ofTechnology, made some experiments along the lines ofthis thesis but did not test any of the magnetswhich he made. It v/as, therefore, at his suggestion that we tookup this subject. It is interesting to note here that only those metalswhich have an atomic weight of 5^ to 5R are magnetic,or are ca
Investigation of the properties of chilled cast iron as a material for permanent magnets . e above statements we have outlined only a fewof the many cases where permanent magnets areemployed, and where constancy is desiraDle, andsometimes absolutely essential. Prof. C. E. Freeman, of Armour Institute ofTechnology, made some experiments along the lines ofthis thesis but did not test any of the magnetswhich he made. It v/as, therefore, at his suggestion that we tookup this subject. It is interesting to note here that only those metalswhich have an atomic weight of 5^ to 5R are magnetic,or are capable of being magnetized. All permanent magnets new in use are made of temperedsteel and it is evident that if we r^.re aDle to makethese magnets of cast iron the cost of productionwill De much reduced. As we have stated before the retentivity of a magnetseems to depend only on the physical hardness of thematerial of which it is composed. Hence if we areto mahe permanent magnets of cast iron some processmust De used to harden the iron. indicafelpDy theSity ln ttle sPeclnen unaer ^sz a. It was with, this object in vievr that we started to work. The first thing that presented itself was the calibration of the various instruments to De usedin this test. The specimens were to De tested Dy means ofan Esterline Permeameter. A description of thisinstrument will not be out of place here. This Permeameter was invented Dy , of Purdue University, ahfl is manufacturedDy the Central LaDoratory Supply Co.,of Lafayette, apparatus consists essentially of two poles ofhigh,grade,soft gweedish, iron, between which rotatesan armature would with many turns of fine,silkinsulated, wire. The armature was designed to be drivenoy a small induction motor. An induction was usedbecause of its good regulation, out it was foundthat the regulation of the ordinary generating unitwas not close enough to be used with a scientificinstrument. Tt would probaDly be sufficiently accuratefor com
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