ASTM A596/A596M-95(2004)
(Test Method)Standard Test Method for Direct-Current Magnetic Properties of Materials Using the Ballistic Method and Ring Specimens
Standard Test Method for Direct-Current Magnetic Properties of Materials Using the Ballistic Method and Ring Specimens
SIGNIFICANCE AND USE
Test methods using suitable ring-type specimens4 are the preferred methods of determining the basic magnetic properties of a material caused by the absence of demagnetizing effects and are well suited for specification acceptance, service evaluation, and research and development.
Provided the test specimen is representative of the bulk material as is usually the case for thin strip and wire, this test is also suitable for design purposes.
When the test specimen is not necessarily representative of the bulk material such as a ring machined from a large forging or casting, the results of this test method may not be an accurate indicator of the magnetic properties of the bulk material. In such instances, the test results when viewed in context of past performance history will be useful for judging the suitability of the current material for the intended application.
SCOPE
1.1 This test method covers dc ballistic testing for the determination of basic magnetic properties of materials in the form of ring, toroidal, link, double-lapped Epstein cores, or other standard shapes which may be cut, stamped, machined, or ground from cast, compacted, sintered, forged, or rolled materials. It includes tests for normal induction and hysteresis taken under conditions of steep wavefront reversals of the direct-current magnetic field strength.
1.2 This test method shall be used in conjunction with Practice A 34/A 34M.
1.3 This test method is suitable for a testing range from very low magnetic field strength up to 200 or more Oe [15.9 or more kA/m]. The lower limit is determined by integrator sensitivity and the upper limit by heat generation in the magnetizing winding. Special techniques and short duration testing may extend the upper limit of magnetic field strength.
1.4 Testing under this test method is inherently more accurate than other methods. When specified dimensional or shape requirements are observed, the measurements are a good approximation to absolute properties. Test accuracy available is primarily limited by the accuracy of instrumentation.
1.5 This test method permits a choice of test specimen to permit measurement of properties in any desired direction relative to the direction of crystallographic orientation without interference from external yoke systems.
1.6 The symbols and abbreviated definitions used in this test method appear in and Sections 5, 6, 9, and 10. For the official definitions see Terminology A 340. Note that the term flux density used in this document is synonymous with the term magnetic induction.
1.7 The values stated in either customary (cgs-emu and inch-pound) units or SI units are to be regarded separately as standard. Within this test method, the SI units are shown in brackets except for the sections concerning calculations where there are separate sections for the respective unit systems. The values stated in each system are not exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with this method.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
Designation: A 596/A 596M – 95 (Reapproved 2004)
Standard Test Method for
Direct-Current Magnetic Properties of Materials Using the
Ballistic Method and Ring Specimens
ThisstandardisissuedunderthefixeddesignationA596/A596M;thenumberimmediatelyfollowingthedesignationindicatestheyear
of original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.
A superscript epsilon (ϵ) indicates an editorial change since the last revision or reapproval.
1. Scope 1.7 The values stated in either customary (cgs-emu and
inch-pound) units or SI units are to be regarded separately as
1.1 This test method covers dc ballistic testing for the
standard. Within this test method, the SI units are shown in
determination of basic magnetic properties of materials in the
brackets except for the sections concerning calculations where
form of ring, toroidal, link, double-lapped Epstein cores, or
there are separate sections for the respective unit systems. The
other standard shapes which may be cut, stamped, machined,
values stated in each system are not exact equivalents; there-
or ground from cast, compacted, sintered, forged, or rolled
fore, each system shall be used independently of the other.
materials. It includes tests for normal induction and hysteresis
Combiningvaluesfromthetwosystemsmayresultinnoncon-
taken under conditions of steep wavefront reversals of the
formance with this method.
direct-current magnetic field strength.
1.8 This standard does not purport to address all of the
1.2 This test method shall be used in conjunction with
safety concerns, if any, associated with its use. It is the
Practice A34/A34MA34/A34M.
responsibility of the user of this standard to establish appro-
1.3 Thistestmethodissuitableforatestingrangefromvery
priate safety and health practices and determine the applica-
lowmagneticfieldstrengthupto200ormoreOe[15.9ormore
bility of regulatory limitations prior to use.
kA/m]. The lower limit is determined by integrator sensitivity
and the upper limit by heat generation in the magnetizing
2. Referenced Documents
winding. Special techniques and short duration testing may
2.1 ASTM Standards:
extend the upper limit of magnetic field strength.
A34/A34M Practice for Sampling and Procurement Test-
1.4 Testing under this test method is inherently more accu-
ing of Magnetic Materials
rate than other methods. When specified dimensional or shape
A340 Terminology of Symbols and Definitions Relating to
requirements are observed, the measurements are a good
Magnetic Testing
approximationtoabsoluteproperties.Testaccuracyavailableis
A341/A341M Test Method for Direct Current Magnetic
primarily limited by the accuracy of instrumentation.
Properties of Materials Using dc Permeameters and the
1.5 This test method permits a choice of test specimen to
Ballistic Test Methods
permit measurement of properties in any desired direction
A343/A343M Test Method for Alternating-Current Mag-
relative to the direction of crystallographic orientation without
netic Properties of Materials at Power Frequencies Using
interference from external yoke systems.
theWattmeter-Ammeter-VoltmeterMethodand25-cmEp-
1.6 Thesymbolsandabbreviateddefinitionsusedinthistest
stein Test Frame
method appear in Fig. 1 and Sections 5, 6, 9, and 10. For the
A773/A773M Test Method for dc Magnetic Properties of
official definitions see TerminologyA340A340. Note that the
Materials Using Ring and Permeameter Procedures with
termfluxdensityusedinthisdocumentissynonymouswiththe
dc Electronic Hysteresigraphs
term magnetic induction.
This test method is under the jurisdiction of ASTM Committee A06 on
MagneticPropertiesandisthedirectresponsibilityofSubcommitteeA06.01onTest
Methods. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2004. Published October 2004. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1969. Last previous edition approved in 1999 as A596/A596–95 Standards volume information, refer to the standard’s Document Summary page on
(1999). the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
A 596/A 596M – 95 (2004)
maintained in the test specimens, the magnetic field strength
will be excessively nonuniform throughout the test specimen
andthemeasuredparameterscannotberepresentedasmaterial
properties.
4.2 The basic quality of materials having directionally
sensitivepropertiescannotbetestedsatisfactorilywithringsor
laminations. With them it is necessary to use Epstein speci-
mens cut with their lengths in the direction of specific interest
or to use long link-shaped or spirally wound toroidal core test
specimens whose long dimensions are similarly located. The
acceptableminimumwidthofstripusedinsuchtestspecimens
is also sensitive to the material under test. At present, it is
believed that the grain-oriented silicon steels should have a
strip width of at least 3 cm [30 mm].
4.3 Unlessringspecimensarelargeindiameter,itisdifficult
toprovideasufficientnumberofprimaryturnsneededtoreach
the highest magnetic field strength. In general, magnetic
NOTE 1—
materials tend to have nonuniform properties throughout the
A —Multirange ammeter, main-magnetizing current circuit
A —Multirange ammeter, hysteresis-current circuit body of the test specimen; for this reason, uniformly distrib-
N —Magnetizing (primary) winding
uted test windings and uniform specimen cross-sectional area
N —Flux-sensing (secondary) winding
are highly desirable to suppress nonuniform behavior to a
F—Electronic integrator
tolerable degree.
R —Main current control rheostat
R —Hysteresis current control rheostat
5. Apparatus
S —Reversing switch
5.1 The apparatus shall consist of as many of the compo-
S —Shunting switch for hysteresis current control rheostat
nents described in 5.2-5.10 as are required to perform the
FIG. 1 Basic Circuit Using Ring-Type Cores
desired test. The basic circuit is shown in Fig. 1.
5.2 Balance and Scales:
2.2 IEC Standard:
5.2.1 The balance used to weigh the test specimen shall be
Publication 404-4, Magnetic Materials—Part 4: Methods of
capable of weighing to an accuracy of better than 0.1%.
Measurement of the D-C Magnetic Properties of Solid
3 5.2.2 The micrometer, caliper, or other length-measuring
Steels, IEC, 1982
device used in the determination of magnetic path length and
3. Significance and Use cross-sectional area shall be capable of measuring to an
4 accuracy of better than 0.1%.
3.1 Test methods using suitable ring-type specimens are
5.3 dc Power Supply—The preferred source of dc current is
the preferred methods of determining the basic magnetic
a high quality linear power supply of either unipolar or bipolar
properties of a material caused by the absence of demagnetiz-
operation. The power supply must exhibit high stability and
ing effects and are well suited for specification acceptance,
very low ripple to achieve the most accurate results. Program-
service evaluation, and research and development.
mable bipolar operational amplifier power supplies have
3.2 Provided the test specimen is representative of the bulk
proven to be very satisfactory for this type of testing. Other
material as is usually the case for thin strip and wire, this test
stable sources of dc current such as storage batteries are
is also suitable for design purposes.
permitted.
3.3 Whenthetestspecimenisnotnecessarilyrepresentative
5.4 Main-Current-Control Rheostat R —When nonpro-
of the bulk material such as a ring machined from a large
grammable sources of dc current such as storage batteries are
forgingorcasting,theresultsofthistestmethodmaynotbean
used, rheostats must be used to control the current. These
accurate indicator of the magnetic properties of the bulk
rheostatsmusthavesufficientpowerratingandheat-dissipating
material. In such instances, the test results when viewed in
capabilitytohandlethelargesttestcurrentwithoutundesirable
context of past performance history will be useful for judging
changes in resistance and, therefore, magnetizing current
the suitability of the current material for the intended applica-
during conduct of the test.
tion.
5.5 Hysteresis-Current-Control Rheostat R —The
4. Interferences hysteresis-current-control rheostat, when required, must have
the same power rating and resistance as the main-current-
4.1 This test method has several important requirements.
control rheostat.
Unless adequate inside diameter to outside diameter ratios are
5.6 Main-Current Ammeter A —Measurement of the mag-
netizing current can be accomplished with either a dc ammeter
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
oracombinationofaprecisionshuntresistoranddcvoltmeter.
4th Floor, New York, NY 10036.
The meters and shunt resistor, if used, must have an accuracy
Lloyd, M. G., “Errors in Magnetic Testing with Ring Specimens,’’ Technical
of at least 0.25%. To improve test accuracy multirange digital
News Bulletin, National Institute for Standards andTechnology,Vol 5, 1909, p. 435
(S108). ammeters or voltmeters are preferred. Autoranging capability
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
A 596/A 596M – 95 (2004)
is desirable for convenience but is not essential for this test corner sections where flux crowding occurs. When straight-
method.Ifanalogmetersareused,therangesmustbesuchthat sided test specimens are very long relative to the length of the
all test readings are made in the upper two thirds of the scale. corner or end sections, they are suitable for basic material
5.7 Hysteresis-Current Ammeter, A —The hysteresis- properties evaluation with relatively unoriented materials pro-
current measuring system shall conform to the requirements in vided the uncertainty in determination of true-path (effective)
5.6. In general, a separate measuring system is not required length is less than 5% of the total path length. When this
since the main current ammeter (A ) can also be used to uncertainty in path length (shortest or longest relative to the
measure the hysteresis current. mean-path length) exceeds 5%, the test values should be
5.8 Reversing Switch, S —Because of the low resistance reported as core properties and not basic material properties.
nature of the magnetizing circuit, it is imperative that high 6.4 Thetestspecimenmaybeconstructedofsolidlaminated
quality switches be used. Changes in switch resistance upon or strip materials and in any of the shapes described in 1.1.
reversal will cause deviation from the cyclically magnetized 6.5 Test specimen cores made from strip may be laminated,
condition which, if excessive, will impair test accuracy and machined, spirally wound, or Epstein specimens (the method
precision. Experience has shown that mercury switches are the of selection for Epstein specimens is described inTest Method
best suited for this application. Knife blade switches or A343/A343MA343/A343M, Appendix 3). When the mate-
mechanical or electrically operated contractors can also be rial is to be tested half transverse and half longitudinal, the
used provided the requirement for uniform and equal contact materialshallbecutintoEpsteinstripsorsquarelaminationsof
resistance can be maintained. Because of the presence of adequate dimensional ratio.
leakagecurrentsintheopencondition,solidstaterelaysarenot 6.6 Test specimens used for basic material evaluation shall
permitted. The difficulties inherent in the use of main current be cut, machined, ground, slit, or otherwise formed to have a
reversing switches can be minimized by use of linear power cross section that remains sufficiently uniform that its nonuni-
supplies capable of accepting a remote programming signal. formity will not materially affect the accuracy of establishing
Such power supplies are permitted provided that the magne- andmeasuringfluxdensity, B,ormagneticfieldstrength, H,in
tizingcurrentisequal(towithin0.1%)ineitherpolaritywhen the test specimen.
normal induction testing is conducted, current reversals can be 6.7 When required for material properties development, the
conductedwithnoovershootoroscillationandthemagnetizing test specimen shall have received a stress relief or other heat
current is truly zero for the zero current programming signal. treatment after preparation. This heat treatment is subject to
5.9 Hysteresis Switch, S (When Required)—This switch agreementbetweenmanufacturerandpurchaser,manufacturers
should conform to requirements in 5.8. recommendation,ortherecommendedheattreatmentprovided
5.10 Integrator, F—Because of their superior accuracy, by the appropriate ASTM standard for the material. The heat
stability, and ease of operation, electronic charge integrators treatment used shall be reported with the magnetic test results.
are the preferred means of measuring magnetic flux. Integra-
7. Calibration of Integrator
tors using either operational amplifier and capacitor feedback
7.1 Practical operating experience has shown that provided
(analog integrator) or pulse counting are permitted. The accu-
racy of the integrator must be better than 1% full scale. If a proper warmup period is allowed, electronic integrators
require infrequent calibration and unlike ballistic galvanom-
analog display meters are used to read the value of flux, the
measurement should be made on the upper two thirds of the eters, calibration is not an integral part of this test method.
When calibration is required, it can be accomplished with
scale. Analog integrators must have drift adjust circuitry and
−6
thedriftshouldnotexceed100Maxwell-turns[10 Wb-turns] either a mutual inductor or a volt-second source. Because of
their traceability to the fundamental units of voltage and time,
per minute on the most sensitive range. It is also desirable that
theintegratorhaveappropriatescalingcircuitrytopermitdirect volt-secondsourcesarethepreferredmeansofcalibration.The
accuracy of either the mutual inductor or volt-second source
reading of either flux (φ) or flux density (B). Ballistic galva-
must be better than the rated full-scale accuracy of the
nometers or moving coil fluxmeters are allowed provided the
integrator.
1% full-scale accuracy requirement is met.
6. Test Specimen 8. Procedure
6.1 When the test specimen represents a test lot of material, 8.1
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