ASTM A977-97
(Test Method)Standard Test Method for Magnetic Properties of High-Coercivity Permanent Magnet Materials Using Hysteresigraphs
Standard Test Method for Magnetic Properties of High-Coercivity Permanent Magnet Materials Using Hysteresigraphs
SCOPE
1.1 This test method describes how to determine the magnetic characteristics of magnetically hard materials (permanent magnets), particularly their initial magnetization, demagnetization, and recoil curves and such quantities as the residual induction, coercive fields, knee field, energy products, and recoil permeability. This test method is suitable for all materials processed into bulk magnets by an common fabrication technique (casting, sintering, rolling, molding, and so forth), but not for thin films or for magnets that are very small or of unusual shape. Uniformity of composition, structure, and properties throughout the magnet volume is necessary to obtain repeatable results. Particular attention is paid to the problems posed by modern materials combining very high coercivity with high saturation induction, such as the rare-earth magnets, for which older test methods (see Test Method A341) are unsuitable. An applicable international standard is IEC Publication 404-5.
1.2 The magnetic system (circuit) in a device or machine generally comprises flux-conducting and nonmagnetic structural members with air gaps in addition to the permanent magnet. The system behavior depends on properties and geometry of all these components and on the temperature. The tests described here measure only the properties of the permanent magnet material. The basic test method incorporates the magnet specimen in a magnetic circuit with a closed flux path. Test methods using ring samples or frames composed entirely of the magnetic material to be characterized, as commonly used to magnetically soft materials, are not applicable to permanent magnets.
1.3 This test method shall be used in conjunction with Practice A 34.
1.4 the preferred units and the corresponding values appearing in this test method are customary (cgs-emu) units. SI units are indicated in parentheses. When necessary, derivations of separate equations, conversion factors or the inclusion of SI values, or both, in the text of tables is specified in the text.
1.5 The names and symbols of magnetic quantities used in this test method, summarized in Table 1, are the currently preferred by U.S. industry.
1.6 This test method is useful for magnet materials having Hci values between 100 Oe and 35 kOe (8 kA/m and 2.8 MA/m), and Br values in the approximate range from 500 G to 20 kG (50 mT to 2T). High coercivity rare-earth magnet test specimens may require much higher magnetizing fields that iron-core electromagnets can product. Such samples must be premagnetized externally and transferred into the measuring yoke. Typical values of the magnetizing fields, Hmag, required for saturating magnet materials are shown in Table 1.
1.7 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.
General Information
Relations
Standards Content (Sample)
Designation: A 977 – 97 An American National Standard
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Magnetic Properties of High-Coercivity Permanent Magnet
1
Materials Using Hysteresigraphs
This standard is issued under the fixed designation A 977; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope this test method, summarized in Table 1, are those currently
preferred by U.S. industry.
1.1 This test method describes how to determine the mag-
1.6 This test method is useful for magnet materials having
netic characteristics of magnetically hard materials (permanent
H values between about 100 Oe and 35 kOe (8 kA/m and 2.8
ci
magnets), particularly their initial magnetization, demagneti-
MA/m), and B values in the approximate range from 500 G to
r
zation, and recoil curves and such quantities as the residual
20 kG (50 mT to 2 T). High-coercivity rare-earth magnet test
induction, coercive fields, knee field, energy products, and
specimens may require much higher magnetizing fields than
recoil permeability. This test method is suitable for all materi-
iron-core electromagnets can produce. Such samples must be
als processed into bulk magnets by any common fabrication
premagnetized externally and transferred into the measuring
technique (casting, sintering, rolling, molding, and so forth),
yoke. Typical values of the magnetizing fields, H , required
but not for thin films or for magnets that are very small or of mag
for saturating magnet materials are shown in Table 1.
unusual shape. Uniformity of composition, structure, and
properties throughout the magnet volume is necessary to obtain
repeatable results. Particular attention is paid to the problems
TABLE 1 Symbols, Quantities, and Units
posed by modern materials combining very high coercivity
NOTE 1—IEC nomenclature calls B “remanence,” when B represents
r r
with high saturation induction, such as the rare-earth magnets,
the B at H 5 0 of the outermost hysteresis loop, and it calls B “remanent
r
for which older test methods (see Test Method A 341) are
magnetic induction” for B at H 5 0 at smaller loops.
unsuitable. An applicable international standard is IEC Publi-
Customary
Symbol Quantity SI Unit
cation 404-5.
cgs-emu
1.2 The magnetic system (circuit) in a device or machine
2 2
A Cross section of search coil m cm
t
generally comprises flux-conducting and nonmagnetic struc-
B Magnetic induction at BH TG
d max
B Magnetic induction at low point of TG
tural members with air gaps in addition to the permanent rec
recoil loop
magnet. The system behavior depends on properties and
B Magnetic induction at remanence T G
r
geometry of all these components and on the temperature. The
d Diameter of pole piece m cm
l
d Diameter of homogeneous field m cm
tests described here measure only the properties of the perma- 2
H Magnetic field strength at BH A/m Oe
d max
nent magnet material. The basic test method incorporates the
H Magnetic field strength at low point of A/m Oe
p
magnetic specimen in a magnetic circuit with a closed flux
recoil loop
l Distance between pole faces m cm
path. Test methods using ring samples or frames composed
l Length of test sample m cm
r
entirely of the magnetic material to be characterized, as
N Number of turns of test coil
commonly used for magnetically soft materials, are not appli-
e Voltage induced in test coil V V
d Total air gap between test sample and mcm
cable to permanent magnets.
pole faces
1.3 This test method shall be used in conjunction with
-7
μ A constant with value μ 5 4p 10
0 0
Practice A 34. H/m
μ Recoil permability
rec
1.4 The preferred units and the corresponding values ap-
pearing in this test method are customary (cgs-emu) units. SI
units are indicated in parentheses. When necessary, derivations
1.7 This standard does not purport to address all of the
of separate equations, conversion factors or the inclusion of SI
safety concerns, if any, associated with its use. It is the
values, or both, in the text of tables is specified in the text.
responsibility of the user of this standard to establish appro-
1.5 The names and symbols of magnetic quantities used in
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1
This test method is under the jurisdiction of ASTM Committee A-16 on
Magnetic Properties and is the direct responsibility of Subcommittee A06.01 on Test
2. Referenced Documents
Methods.
Current edition approved Oct. 10, 1997. Published November 1998. 2.1 ASTM Standards:
1
---------------------- Page: 1 ----------------------
A 977
A 34 Practice for Procurement Testing and Sampling of 3.
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.