ASTM A596/A596M-21

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: A596/A596M − 14 A596/A596M − 21
Standard Test Method for
Direct-Current Magnetic Properties of Materials Using the
Ballistic Point by Point (Ballistic) Method and Ring
Specimens
This standard is issued under the fixed designation A596/A596M; the number immediately following the designation indicates the year
of 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. 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 determination of the normal magnetization
curve and hysteresis loop 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 A34/A34M.
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. In most cases, equivalent results may be obtained using Test Method A773/A773M or
the test methods of IEC Publication 60404-4.
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 Fig. 1 and Sections 5, 6, 9, and 10. For the official
definitions see Terminology A340. Note that the term flux density used in this document is synonymous with the term magnetic
induction.
1.7 Warning—WarningMercury—Mercury has been designated by EPA and many state agencies as a hazardous material that can
cause central nervous system, kidney, and liver damage. Mercury, or its vapor, may be hazardous to health and corrosive to
materials. Caution should be taken when handling mercury and mercury-containing products. See the applicable product Material
Safety Data Sheet (MSDS) for details and EPA’s website (http://www.epa.gov/mercury/faq.htm ) for additional information. Users
should be aware that selling mercury or mercury-containing products, or both, in your state may be prohibited by state law.
This test method is under the jurisdiction of ASTM Committee A06 on Magnetic Properties and is the direct responsibility of Subcommittee A06.01 on Test Methods.
Current edition approved May 1, 2014Feb. 1, 2021. Published June 2014February 2021. Originally approved in 1969. Last previous edition approved in 20092014 as
ε1
A596/A596M–95(2009)A596/A596M – 14. . DOI: 10.1520/A0596_A0596M-14.10.1520/A0596_A0596M-21.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A596/A596M − 21
NOTE 1—
A —Multirange ammeter, main-magnetizing current circuit
A —Multirange ammeter, hysteresis-current circuit
N —Magnetizing (primary) winding
N —Flux-sensing (secondary) winding
F—Electronic integrator
R —Main current control rheostat
R —Hysteresis current control rheostat
S —Reversing switch
S —Shunting switch for hysteresis current control rheostat
FIG. 1 Basic Circuit Using Ring-Type Cores
1.8 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.
1.9 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.10 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
A34/A34M Practice for Sampling and Procurement Testing of Magnetic Materials
A340 Terminology of Symbols and Definitions Relating to Magnetic Testing
A341/A341M Test Method for Direct Current Magnetic Properties of Soft Magnetic Materials Using D-C Permeameters and the
Point by Point (Ballistic) Test Methods
A343/A343M Test Method for Alternating-Current Magnetic Properties of Materials at Power Frequencies Using Wattmeter-
Ammeter-Voltmeter Method and 25-cm Epstein Test Frame
A773/A773M Test Method for Direct Current Magnetic Properties of Low Coercivity Magnetic Materials Using Hysteresig-
raphs
2.2 IEC Standard:
Publication 60404-4 Ed. 2.2, Magnetic Materials—Part 4: Methods of Measurement of the D-C Magnetic Properties of
Magnetically Soft Materials, IEC, 2008
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036.
A596/A596M − 21
3. Significance and Use
3.1 Test methods using suitable ring-type specimens 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.
3.2 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.
3.3 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.
4. Interferences
4.1 This test method has several important requirements. Unless adequate inside diameter to outside diameter ratios are maintained
in the test specimens, the magnetic field strength will be excessively nonuniform throughout the test specimen and the measured
parameters cannot be represented as material properties.
4.2 The basic quality of materials having directionally sensitive properties cannot be tested satisfactorily with rings or laminations.
With them it is necessary to use Epstein specimens 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 acceptable minimum
width of strip used in such test specimens 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 Unless ring specimens are large in diameter, it is difficult to provide a sufficient number of primary turns needed to reach the
highest magnetic field strength. In general, magnetic materials tend to have nonuniform properties throughout the body of the test
specimen; for this reason, uniformly distributed test windings and uniform specimen cross-sectional area are highly desirable to
suppress nonuniform behavior to a tolerable degree.
5. Apparatus
5.1 The apparatus shall consist of as many of the components described in 5.2 – 5.10 as are required to perform the desired test.
The basic circuit is shown in Fig. 1.
5.2 Balance and Scales:
5.2.1 The balance used to weigh the test specimen shall be capable of weighing to an accuracy of better than 60.1 % of the
specimen mass.
5.2.2 The micrometer, caliper, or other length-measuring device used in the determination of magnetic path length and
cross-sectional area shall be capable of measuring to an accuracy of better than 60.1 % of the measured values.
5.3 dc Power Supply—The preferred source of dc current is a high quality high-quality linear power supply of either unipolar or
bipolar operation. The power supply must exhibit high stability and very low ripple to achieve the most accurate results.
Programmable bipolar operational amplifier power supplies have proven to be very satisfactory for this type of testing. Other stable
sources of dc current such as storage batteries are permitted.
5.4 Main-Current-Control Rheostat R —When nonprogrammable sources of dc current such as storage batteries are used,
rheostats must be used to control the current. These rheostats must have sufficient power rating and heat-dissipating capability to
handle the largest test current without undesirable changes in resistance and, therefore, magnetizing current during conduct of the
test.
Lloyd, M. G., “Errors in Magnetic Testing with Ring Specimens,” Technical News Bulletin, National Institute for Standards and Technology, Vol 5, 1909, p. 435 (S108).
A596/A596M − 21
5.5 Hysteresis-Current-Control Rheostat R —The hysteresis-current-control rheostat, when required, must have the same power
rating and resistance as the main-current-control rheostat.
5.6 Main-Current Ammeter A —Measurement of the magnetizing current can be accomplished with either a dc ammeter or a
combination of a precision shunt resistor and dc voltmeter. The meters and shunt resistor, if used, must have an accuracy of at least
0.25 %. To improve test accuracy multirange digital ammeters or voltmeters are preferred. Autoranging capability is desirable for
convenience but is not essential for this test method. If analog meters are used, the ranges must be such that all test readings are
made in the upper two thirds of the scale.
5.7 Hysteresis-Current Ammeter, A —The hysteresis-current measuring system shall conform to the requirements in 5.6. In
general, a separate measuring system is not required since the main current ammeter (A ) can also be used to measure the hysteresis
current.
5.8 Reversing Switch, S —Because of the low resistance nature of the magnetizing circuit, it is imperative that high quality
switches be used. Changes in switch resistance upon reversal will cause deviation from the cyclically magnetized condition which,
if excessive, will impair test accuracy and precision. Experience has shown that mercury switches are the best suited for this
application. Knife blade switches or mechanical or electrically operated contactors can also be used provided the requirement for
uniform and equal contact resistance can be maintained. Because of the presence of leakage currents in the open condition, solid
state relays are not permitted. The difficulties inherent in the use of main current reversing switches can be minimized by use of
linear power supplies capable of accepting a remote programming signal. Such power supplies are permitted provided that the
magnetizing current is equal (to within 0.1 %) in either polarity when normal induction testing is conducted,testing in the SCM
condition, current reversals can be conducted with no overshoot or oscillation and the magnetizing current is truly zero for the zero
current programming signal.
5.9 Hysteresis Switch, S (When Required)—This switch shouldshall conform to requirements in 5.8.
5.10 Integrator, F—Because of their superior accuracy, stability, and ease of operation, electronic charge integrators are the
preferred means of measuring magnetic flux. Integrators using either operational amplifier and capacitor feedback (analog
integrator) or pulse counting are permitted. The accuracy of the integrator must be better than 1 % full scale. If analog display
meters are used to read the value of flux, the measurement should be made on the upper two thirds of the scale. Analog integrators
−6
must have drift adjust circuitry and the drift should not exceed 100 Maxwell-turns [10 Wb-turns] per minute on the most sensitive
range. It is also desirable that the integrator have appropriate scaling circuitry to permit direct reading of either flux (φ) or flux
density (magnetic flux, φ, or magnetic flux density, BB.).
6. Test Specimen
6.1 When the test specimen represents a test lot of material, its selection shall conform to the requirements of Practice A34/A34M
or of an individual specification.
6.2 To qualify as a test specimen suitable for evaluation of material properties the effective ratio of mean diameter to radial width
shall be not less than 10 to 1 (or an inside diameter to outside diameter ratio not less than 0.82). When the test specimen has smaller
ratios than the above requirements, the test results should not be represented as material properties but should be called core
properties because of nonuniform flux distribution.
6.3 When link, oval-shaped, or rectangular test specimen forms are used, the requirements of 6.2 apply to the end or corner
sections where flux crowding occurs. When straight-sided test specimens are very long relative to the length of the corner or end
sections, they are suitable for basic material properties evaluation with relatively unoriented materials provided the uncertainty in
determination of true-path (effective) length is less than 5 % of the total path length. When this uncertainty in path length (shortest
or longest relative to the mean-path length) exceeds 5 %, the test values should be reported as core properties and not basic material
properties.
6.4 The test specimen may be constructed of solid, laminated, or strip materials and in any of the shapes described in 1.1.
6.5 Test specimen cores made from strip may be laminated, machined, spirally wound, or Epstein specimens (the method of
A596/A596M − 21
selection for Epstein specimens is described in Test Method A343/A343M, Annex A3). When the material is to be tested half
transverse and half longitudinal, the material shall be cut into Epstein strips or square laminations of adequate dimensional ratio.
6.6 Test specimens used for basic material evaluation shall be cut, machined, ground, slit, or otherwise formed to have a cross
section that remains sufficiently uniform that its nonuniformity will not materially affect the accuracy of establishing and measuring
magnetic flux density, B, or magnetic field strength, H, in the test specimen.
6.7 When required for material properties development, the test specimen shall have received a stress relief or other heat treatment
after preparation. This heat treatment is subject to agreement between manufacturer and purchaser, manufacturer’s
recommendation, or the recommended heat treatment provided by the appropriate ASTM standard for the material. The heat
treatment used shall be reported with the magnetic test results.
7. Calibration of Integrator
7.1 Practical operating experience has shown that provided a proper warmup period is allowed, electronic integrators require
infrequent calibration. Calibration is not an integral part of this test method. When calibration is required, it can be accomplished
with either a mutual inductor or a volt-second source. Because of their traceability to the fundamental units of voltage and time,
volt-second sources are the preferred means of calibration. The accuracy of either the mutual inductor or volt-second source must
be better than the rated full-scale accuracy of the integrator.
8. Procedure
8.1 In Fig. 1, the dc power source supplies magnetizing current measured by ammeter A or A . Rheostats R and R and switches
1 2 1 2
S and S determine the magnitude and direction of the current as required by various operations. In general, three types of
1 2
switching operations are required in ballistic testing. required. One is reversal of magnetizing current direction without change ofin
magnitude as required for establishing a symmetrically cyclically magnetized condition and in normal induction tests. (SCM)
condition. This is accomplished by throwing switch S from one side to the other. A second is reduction of magnitude of
magnetizing current without change of direction.polarity. This operation is required to measure points on the hysteresis loop in the
first quadrant. This is done by opening switch S . The third operation combines reversal of magnetizing current directionpolarity
with a reduction in its magnitude. This operation is required to measure points on the hysteresis loop in the second and third
quadrants. Obtain this reversal and reduction by simultaneously throwing switch S from one side to the other and opening switch
S . Use care to be sure S is opened before S is reclosed for reversal. When determining the hysteresis loop, switches S and S
2 2 1 1 2
must be operated to traverse the loop in the same direction between successive measurements so as to preserve the cyclically
magnetized state of the test specimen.
8.2 Demagnetize the test specimen immediately before testing. To demagnetize with direct current, first establish a magnetic field
strength sufficiently large to cause the magnetic flux density in the specimen to reach a value greater than the knee of the normal
induction or magnetization curve. Then slowly reduce the magnetizing current to zero while simultaneously operating the reversing
switch at one half second or longer intervals. An auxillaryauxiliary circuit using a time de
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