ASTM_A_773_-_A_773M_-_14.pdf

Designation:A773/A773M14Standard Test Method forDirect Current Magnetic Properties of Low CoercivityMagnetic Materials Using Hysteresigraphs1This standard is issued under the fixed designation A773/A773M;the number immediately following the designation indicates the yearof original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method provides dc hysteresigraph procedures(B-H loop methods)for the determination of basic magneticproperties of materials in the form of ring,spirally woundtoroidal,link,double-lapped Epstein cores,or other standardshapes that may be cut,stamped,machined,or ground fromcast,compacted,sintered,forged,or rolled materials.It in-cludes tests for normal induction and hysteresis loop determi-nation taken under conditions of continuous sweep magnetiza-tion.Rate of sweep may be varied,either manually orautomatically at different portions of the curves during mea-surement.1.2 The equipment and procedures described in this testmethod are most suited for soft and semi-hard materials withintrinsic coercivity less than about 100 Oersteds 8 kA/M.Materials with higher intrinsic coercivities should be testedaccording to Test Method A977/A977M.1.3 The values and equations stated in customary(cgs-emuand inch-pound)or SI units are to be regarded separately asstandard.Within this standard,SI units are shown in brackets.The values stated in each system may not be exact equivalents;therefore,each system shall be used independently of the other.Combining values from the two systems may result in noncon-formance with this standard.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2A34/A34M Practice for Sampling and Procurement Testingof Magnetic MaterialsA340 Terminology of Symbols and Definitions Relating toMagnetic TestingA341/A341M Test Method for Direct Current MagneticProperties of Materials Using D-C Permeameters and theBallistic Test MethodsA343/A343M Test Method for Alternating-Current Mag-netic Properties of Materials at Power Frequencies UsingWattmeter-Ammeter-Voltmeter Method and 25-cm Ep-stein Test FrameA596/A596M Test Method for Direct-Current MagneticProperties of Materials Using the Ballistic Method andRing SpecimensA977/A977M Test Method for Magnetic Properties of High-Coercivity Permanent Magnet Materials Using Hyster-esigraphsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 Other:IEC Publication 60404-4 Ed 2.2 Part 4:Methods ofMeasurement of d.c.Magnetic Properties of MagneticallySoft Materials(2008)33.Terminology3.1 DefinitionsThe terms and symbols used in this testmethod are defined in Terminology A340.4.Summary of Test Method4.1 A specimen is wound with a magnetizing winding(theprimary winding)and a search winding(the secondary wind-ing)for measuring the change in flux.When a magnetizingcurrent,I,is applied to the primary winding,a magnetic field,H,is produced in the coil.This in turn produces magnetic flux in the specimen and the changing flux induces a voltage inthe secondary winding which is integrated with respect to timeusing a fluxmeter.In specimens with uniform cross-sectionalarea that do not contain air gaps,such as rings,all of the1This test method is under the jurisdiction of ASTM Committee A06 onMagnetic Properties and is the direct responsibility of Subcommittee A06.01 on TestMethods.Current edition approved Oct.1,2014.Published October 2014.Originallyapproved in 1980.Last previous edition approved in 2009 as A773/A773M01(2009).DOI:10.1520/A0773_A0773M-14.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute,25 W.43rd St.,4thFloor,New York,NY 10036.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 magnetizing current is used to magnetize the specimen,and His proportional to I in accordance with the following equation:H 5 KI(1)where:H=magnetic field strength,Oe A/m;I=current in the magnetizing winding A;andK=constant determined by the number of primary turns themagnetic path length of the specimen and system ofunits.4.1.1 The magnetic flux may be determined by integrationof the instantaneous electromotive force that is induced in thesecondary winding when the flux is increased or decreased bya varying H.The instantaneous voltage,e,is equal to:e 5 2NK1ddt(2)or 51K1N*edtwhere:dt=time