ASTM A341/A341M-00(2011)

Permeameters require the use of yokes to complete the magnetic circuit and are therefore inherently less accurate than ring test methods. Refer to Test Method A596/A596M for further details on ring test methods. However, when testing certain shapes as bars or when magnetic field strength in excess of 200 Oe [15.9 or more kA/m] are required, permeameters are the only practical means of measuring magnetic properties.

This test method is suitable for specification acceptance, service evaluation, research and development and design.

When the test specimen is fabricated from a larger sample and is in the same condition as the larger sample, it may not exhibit magnetic properties representative of the original sample. In such instances the test results, when viewed in context of past performance history, will be useful for judging the suitability of the material for the intended application.

1.1 This test method provides dc permeameter tests for the basic magnetic properties of materials in the form of bars, rods, wire, or strip specimens which may be cut, machined, or ground from cast, compacted, sintered, forged, extruded, rolled, or other fabricated materials. It includes tests for determination of the normal induction under symmetrically cyclically magnetized (SCM) conditions and the hysteresis loop (B-H loop) taken under conditions of rapidly changing or 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 covers a range of magnetic field strength in the specimen from about 0.05 Oe [4 A/m] up to above 5000 Oe [400 kA/M] through the use of several permeameters. The separate permeameters cover this test region in several overlapping ranges.

1.4 Normal induction and hysteresis properties may be determined over the flux density range from essentially zero to intrinsic saturation for most materials.

1.5 Recommendations of the useful magnetic field strength range for each of the permeameters are shown in Table 1 . Also, see Sections 3 and 4 for general limitations relative to the use of permeameters.

1.6 The symbols and abbreviated definitions used in this test method appear with Fig. 1 and in appropriate sections of this document. 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 WarningMercury 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.

1.8 The values and equations stated in customary cgs-emu and inch-pound or SI units are to be regarded separately as standard. Within this standard, 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 may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with this standard.

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 and health practices and determine the applicability of regulatory limitations prior to use.

TABLE 1 Permeameters

^A Although the permeameters are capable of being used at the lower end of the measurement range, the measurement accuracy is reduced.

^B Imagnetizing current; HCfixed H coil; FCflip coil; HPHall probe; RCCRogowski-Chattock coil.

^C Fahy permeameters require a standard of known magnetic properties for calibration of the H coil.

Note—
A₁Multirange ammeter (main current)
A₂Multirange ammeter (hysteresis current)
BFlux density test position for Switch S₃
FElectronic Integrator
HMagnetic field strength test position for Switch S₃
N₁Magnetizing coil
N₂Flux sensing (B) coil
N₃Magnetic field strength sensing coil
R₁Main current control rheostat
R₂Hysteresis current control rheostat
S₁Reversing switch for magnetizing current
S₂Shunting switch for hysteresis current control rheostat
S₃Integrator selector switch
SPSpecimen