ASTM A773 A773M-2001 Standard Test Method for dc Magnetic Properties of Materials Using Ring and Permeameter Procedures with dc Electronic Hysteresigraphs.pdf

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1、Designation: A 773/A 773M 01Standard Test Method fordc Magnetic Properties of Materials Using Ring andPermeameter Procedures with dc ElectronicHysteresigraphs1This standard is issued under the fixed designationA773/A773M; the number immediately following the designation indicates the yearof original

2、 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method provides dc hysteresigraph procedures(B-H loop me

3、thods) for the determination of basic magneticproperties of materials in the form of ring, toroidal, link,double-lapped Epstein cores, or other standard shapes that maybe cut, stamped, machined, or ground from cast, compacted,sintered, forged, or rolled materials. It includes tests for normalinducti

4、on and hysteresis taken under conditions of continuoussweep magnetization. Rate of sweep may be varied, eithermanually or automatically at different portions of the curvesduring tracing. Total elapsed time for tracing a hysteresis loopis commonly 10 to 120 s per loop.1.2 The values and equations sta

5、ted in customary (cgs-emuand inch-pound) or SI units are to be regarded separately asstandard. Within th is 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

6、 two systems may result in noncon-formance with this standard.1.3 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

7、-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A 34/A 34M Practice for Sampling and Procurement Test-ing of Magnetic MaterialsA 341/A 341M Test Method for Direct Current MagneticProperties of Materials Using D-C Permeameters and theBallistic Test MethodsA 3

8、43/A 343M Test Method for Alternating-Current Mag-netic Properties of Materials at Power Frequencies UsingWattmeter-Ammeter-Voltmeter Method and 25-cm EpsteinTest FrameA 596/A 596M Test Method for Direct-Current MagneticProperties of Materials Using the Ballistic Method andRing Specimens2.2 Other:IE

9、C Publication 404-4: Magnetic MaterialsPart 4: Meth-ods of Measurement of dc Magnetic Properties of Iron andSteel (1995)33. Summary of Test Method3.1 As in making most magnetic measurements, a specimenis wound with an exciting winding (the primary) and a searchcoil (the secondary) for measuring the

10、change in flux. When anexciting current, I, is applied to the primary winding, amagnetic field, H, is produced in the coil, and this in turnproduces magnetic flux f in the specimen. In uniform speci-mens that do not contain air gaps, such as ring samples, all ofthe exciting current is used to magnet

11、ize 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 exciting coil A; andK = constant determined by the number of primary turnsthe magnetic path length of the specimen and systemof units.3.1.1 The

12、magnetic flux may be determined by integrationof the instantaneous electromotive force that is induced in thesecondary coil when the flux is increased or decreased by avarying H. The instantaneous voltage, e, is equal to:e 52NK1dfdt(2)or1This test method is under the jurisdiction of ASTM Committee A

13、06 onMagnetic Properties and is the direct responsibility of SubcommitteeA06.01 on TestMethods.Current edition approved June 10, 2001. Published September 2001. Originallyapproved in 1980. Last previous edition approved in 1996 as A 773 96.2For referenced ASTM standards, visit the ASTM website, www.

14、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 10036.1Copyright ASTM Inter

15、national, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.f51K1N*edtwhere:dt = time differential,N = number of turns, andK1=108for cgs-emu system, or K1= 1 for SI system.The flux f can be obtained if *edt can be determined. Thiscan be accomplished by several means

16、, as described in ASTMSTP 526. (1)4The most common method uses an electronicintegrator consisting of a high-gain dc amplifier with resistive-capacitive feedback. The relationship to * edt is:E 51RC*edt (3)where:E = output voltage, V;R = input resistance of the integrator in the secondarycircuit, V;

17、andC = the feedback capacitance, F.By combining the two equations:f5ERCK1Nor E 5fNK1RC(4)If the voltage, E, is applied to the Y axis of an X-Y recorder,the Y deflection of the pen is proportional to the flux, f.3.1.2 Measurements of magnetic field strength and flux bythe hysteresigraph method is ill

18、ustrated in the block diagram ofFig. 1. The system consists of a magnetizing power source, anexciting current controller, an electronic flux integrator, and adata recorder. As exciting current is applied to the coil, avoltage proportional to I is produced across the shunt resistorwhich is connected

19、in series with the primary coil. This voltagedetermines the value of H.3.1.3 In the testing of hard magnetic materials, or softmagnetic materials in the form of wire, bars or rods, it isusually necessary to use a permeameter. This is shown in theblock diagram of Fig. 2. When using permeameters, the

20、valueof H in the gap is generally not proportional to I that flowsthrough the exciting coil of the yoke. In these cases, the valueof H is determined by integration of the electromotive forcethat is induced in an H coil (or Chattock potentiometer) or fromthe signal developed by a Hall probe which is

21、placed near thespecimen. When using an H coil, the determination of H isaccomplished with an H integrator in exactly the same manneras that used to determine flux with the B integrator described in3.1. When using a Hall sensor, the H values are determinedfrom the voltage output which is proportional

22、 to H. In somecases, the H versus I relationship may be sufficiently linearfrom 0 to the coercive field strength (Hc) of the material undertest. In such cases, it is acceptable to determine the secondquadrant of the hysteresis loop by determining H from thevalue of I in the exciting winding.4. Signi

23、ficance and Use4.1 Hysteresigraph testing permits more rapid and efficientcollection of dc hysteresis (B-H loop) data as compared to thepoint by point ballistic Test Methods A 341/A 341M andA 596/A 596M. The accuracy and precision of testing iscomparable to the ballistic methods. Hysteresigraphs are

24、 par-ticularly desirable for testing of semihard and hard magneticmaterials where either the entire second quadrant (demagneti-zation curve) or entire hysteresis loop is of primary concern.4.2 Provided the test specimen is representative of the bulksample or lot, this test method is well suited for

25、design,specification acceptance, service evaluation and research anddevelopment.5. Interferences5.1 Test methods using suitable ring-type specimens are thepreferred methods for determining the basic magnetic proper-ties of a material. However, this test method has severalimportant requirements. Unle

26、ss adequate inside diameter tooutside diameter ratios are maintained in the test specimens,the magnetic field strength will be excessively nonuniformthroughout the test material and the measured parameterscannot be represented as material properties. The basic quality4The boldface numbers in parenth

27、eses refer to the list of references at the end ofthis test method.FIG. 1 Block Diagram of Ring Test ApparatusA 773/A 773M 012of materials having directional sensitive properties cannot betested satisfactorily with punched rings or laminations. Withthem it is necessary to use Epstein specimens cut w

28、ith theirlengths in the direction of specific interest or use longlink-shaped or spirally wound core test specimens whose longdimensions are similarly oriented. The acceptable minimumwidth of strip used in such test specimens is also sensitive tothe material under test. At present, it is believed th

29、e siliconsteels should have a strip width of at least 3 cm 30 mm.Unless ring specimens are large, it is difficult to providesufficient magnetizing turns or current-carrying capacity toreach high magnetic field strengths. In general, magneticmaterials tend to have nonuniform properties throughout the

30、body of the test specimens; for this reason, uniformly distrib-uted test windings and uniform specimen cross-sectional areaare highly desirable to average nonuniform behavior to atolerable degree.5.2 When conducting permeameter tests on bars, rods, andother appropriate specimens, this test method co

31、vers a range ofmagnetic field strengths from about 0.05 Oe 4 A/m up toabout 20 000 Oe 1600 kA/m or more, depending on thespecimen geometry and the particular permeameter that isused. In general, the lower limit of magnetic field strength isdetermined by the area-turns of the H coil (or the sensitivi

32、ty ofthe Hall probe if it is used), the sensitivity of the integrator, andthe sensitivities of the measuring and recording components.The upper limitation in magnetic field strength is determinedby the type of permeameter appropriate for the specimen, thepower supply, and the heat generated in the y

33、oke windings.Recommendations of the useful range of magnetic fieldstrength for the various permeameters are shown in Table 1.Other types may be used with appropriate precautions.5.2.1 In general, permeameters do not maintain a uniformmagnetic field in either the axial or radial directions around the

34、test specimen. The field gradients in both of these directionswill differ in the various permeameters.Also the H-sensing andB-sensing coils of the different permeameters are not identicalin area, in turns, or in length or identically located. Althoughtest specimens are prepared to have uniform physi

35、cal crosssection, they may have undetected nonuniform magnetic prop-erties radially or axially along the specimen length adjacent tothe H or B coils. Some permeameters may also introduceclamping strains into the test specimen. For these reasons testresults obtained on a test specimen with one type o

36、f permeame-ter may not compare closely with those obtained on the samespecimen from another type permeameter, and both may differfrom more precise testing methods.5.2.2 The limitation in the B measurement by this testmethod is determined by the number of turns on the specimen,the cross-sectional are

37、a, the permeability, and the sensitivitiesof the B integrator and X-Y recorder. In general, normalinduction and hysteresis data may be determined from a fluxlinkage corresponding to 1000 Maxwell turns 105Weberturns to an upper induction that corresponds to the intrinsicsaturation for most materials.

38、FIG. 2 Block Diagram of Permeator Test ApparatusTABLE 1 Permeameters Recommended for Use WithHysteresigraphsNOTEOther permeameters may be suitable for use with dc hysteresi-graphs where appropriate modifications are made. Refer to Test MethodA 341/A 341M for other permeameters.Permeameter Magnetic F

39、ield Strength Range H MeasurementDeviceOe kA/mBabbit (2,3) 40/100 3.2/8 current, H coilFahy Simplex (4,5,6) 0.1/300 0.008/24 H coilFahy Simplex SuperH Adapter (6)100/2500 8/200 H coilIEC Type A 12/2500 1/200 H coil, Hall probeIEC Type B 12/620 1/50 H coilIsthmus (6, 7) 100/20 000 + 8/1600 + H coil,

40、Hall probeA 773/A 773M 0135.2.3 Some permeameters use compensation coils and re-quire continual adjustment of the current flowing through thesecoils. This may not be compatible with commercially availablehysteresigraphs and can be a source of significant error.5.2.4 The magnetic test results, partic

41、ularly for high perme-ability alloys, may not exactly agree with test results obtainedby the ballistic methods, Test Methods A 341/A 341M andA 596/A 596M. This is due to the influence of eddy currentsand the different nature of the magnetizing waveform betweenhysteresigraph and ballistic testing.6.

42、Apparatus6.1 The apparatus shall consist of as many of the compo-nents described in 6.2-6.6 as required to perform the tests.6.1.1 All apparatus used in this test method shall be cali-brated against known standards to ensure the accuracy limitsgiven below.6.2 Balance or Scales:6.2.1 The balance or s

43、cales used to weigh the test specimenshall be capable of weighing to an accuracy of 0.2 %.6.2.2 The micrometer or dimensional measuring scales usedto determine specimen dimensions for calculation of cross-sectional area shall be capable of measuring to an accuracy ofat least 0.1 %.6.3 Magnetizing Po

44、wer SourceThe power source mayrange from simple batteries to sophisticated regulated, low-ripple, protected, programmable types. It shall have sufficientcapacity to produce the maximum currents required for mag-netization of the specimen under test.6.4 Exciting Current ControllerInstantaneous value

45、ofmagnetizing current, and its rate of change, may be controlledentirely manually by means of rheostats, potentiometers,shunts, reversing switches, and so forth; semiautomatically bymeans of variable-speed motors or sweep generators, and soforth; or entirely automatic by means of rate sensors, and s

46、oforth. In all cases, components shall be capable of carrying therequired currents without overheating, and controls shall be ofsuch design that magnetizing current may be increased ordecreased in a uniform manner so that smooth traces areplotted on the X-Y recorder.6.5 B or H IntegratorThe flux int

47、egrator(s) may be any ofthe types described in ASTM STP 526 (or other) and shouldhave sufficient sensitivity, stability, linearity, and freedom fromdrift to ensure an accuracy of at least 0.5 % of full scale.6.6 Data RecorderThe B and H values can be recordedand displayed by either analog or digital

48、 X-Y chart recorders,dataloggers, or computers. The recording device shall becapable of resolving B or H values of 1 % of the full-scalevalue. For analog to digital converters, twelve-bit resolution isdesirable.7. Test Specimens for Ring-Type Measurements7.1 The specifications in 7.2-7.8 cover the g

49、eneral case forspecimens in which magnetic field strength is proportional tothe exciting current, that is, H = kI.7.2 When the test specimen represents a test lot of material,its selection shall conform to the requirements of PracticeA 34/A 34M or of an individual specification.7.3 To qualify as a test specimen suitable for evaluation ofmaterial properties, the effective ratio of mean diameter toradial width shall be not less than 10 to 1 (or an inside diameterto outside diameter ratio not less than 0.82). When the testspecimen has smaller ratios than the above re