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10、 INTERNATIONAL ELECTROTECHNICAL COMMISSION R ICS 29.030 PRICE CODE ISBN 2-8318-1037-7 Registered trademark of the International Electrotechnical Commission 2 TR 62517 IEC:2009(E) CONTENTS FOREWORD.4 INTRODUCTION.6 1 Scope.7 2 Effective magnetizing field strength 7 3 Initial magnetization state.8 4 M
11、agnetizing behaviour of permanent magnets8 4.1 General .8 4.2 Nucleation type magnets, sintered Ferrites, RE-Fe-B, SmCo 5 .9 4.2.1 General .9 4.2.2 Initial magnetization curve after final heat treatment9 4.2.3 Approach to saturation after final heat treatment .9 4.2.4 Coercivity mechanism of nucleat
12、ion type magnets.11 4.2.5 Reversing the magnetization after magnetic saturation12 4.3 Pinning type magnets, Sm 2 Co 17 13 4.3.1 General .13 4.3.2 Initial magnetization curve.13 4.3.3 Approach to saturation 14 4.3.4 Coercivity mechanism of pinning type magnets15 4.4 Single domain particle magnets.16
13、4.4.1 General .16 4.4.2 Single domain particle magnets based on magnetocrystalline anisotropy .16 4.4.3 Alnico and CrFeCo magnets 16 5 Conclusions17 Bibliography19 Figure 1 Principal magnetizing behaviour of RE-TM magnets after final heat treatment 8 Figure 2 Magnetizing behaviour of sintered Nd-Dy-
14、Fe-B magnets 9 Figure 3 Magnetizing behaviour of sintered Nd-Dy-Fe-B magnets with various remanence B rand coercivity H cJvalues after final heat treatment 11 Figure 4 Magnetizing behaviour of sintered Nd-Dy-Fe-B magnets with various remanence B rand coercivity H cJvalues after magnetic saturation i
15、n the reverse direction12 Figure 5 Magnetizing behaviour of sintered Sm 2 Co 17magnets with a coercivity H cJof about 800 kA/m.13 Figure 6 Magnetizing behaviour of sintered Sm 2 Co 17magnets with a coercivity H cJof about 2 800 kA/m14 Figure 7 Magnetizing behaviour of sintered Sm-Co magnets with var
16、ious remanence B rand coercivity H cJvalues, left: after final heat treatment and right: after magnetic saturation in the reverse direction.15 Figure 8 Magnetization behaviour of bonded anisotropic HDDR RE-Fe-B magnets compared to a sintered anisotropic RE-Fe-B magnet 16 TR 62517 IEC:2009(E) 3 Table
17、 1 The recommended internal magnetizing field strengths, H mag , to achieve complete saturation for modern permanent magnets, starting from the initial state after the final heat treatment.18 4 TR 62517 IEC:2009(E) INTERNATIONAL ELECTROTECHNICAL COMMISSION _ MAGNETIZING BEHAVIOUR OF PERMANENT MAGNET
18、S FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all questions concerning standardization in t
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29、ly published as an International Standard, for example “state of the art“. IEC 62517, which is a technical report, has been prepared by IEC technical committee 68: Magnetic alloys and steels. The text of this technical report is based on the following documents: Enquiry draft Report on voting 68/377
30、/DTR 68/384/RVC Full information on the voting for the approval of this technical report can be found in the report on voting indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. TR 62517 IEC:2009(E) 5 The committee has decided that the c
31、ontents of this publication will remain unchanged until the maintenance result date indicated on the IEC web site under “http:/webstore.iec.ch“ in the data related to the specific publication. At this date, the publication will be reconfirmed, withdrawn, replaced by a revised edition, or amended. A
32、bilingual version of this publication may be issued at a later date. 6 TR 62517 IEC:2009(E) INTRODUCTION The full performance of a permanent magnet can only be obtained if it is magnetized properly to saturation. In IEC 60404-5 a definition of the saturation of a permanent magnet is given. According
33、ly, a magnet is defined as saturated at a magnetizing field strength H 1if a 50 % higher field strength leads to an increase of (BH) maxor H cBof less than 1 %. However, such a definition cannot explain the substantial differences in the magnetizing behaviour of modern permanent magnets which is mai
34、nly determined by their coercivity mechanisms. Unfortunately the variety of magnetizing behaviours cannot be accommodated by a simple recommendation such as “magnetize with magnetizing field strengths of three to five times the coercivity H cJ ”. In particular for RE permanent magnets with high coer
35、civity H cJthis simplification would lead to unacceptable overestimations of the required magnetizing field strengths. TR 62517 IEC:2009(E) 7 MAGNETIZING BEHAVIOUR OF PERMANENT MAGNETS 1 Scope It is within the scope of this technical report to describe the magnetizing behaviour of permanent magnets
36、in detail. Firstly, in Clause 3 the relationship between the applied magnetic field strength and the effectively acting internal field strength is reviewed. In Clause 4 the initial state prior to magnetization is discussed. Then, in the main Clause 5, the magnetizing behaviour of all common types of
37、 permanent magnets is outlined. The clause is subdivided according to the dominant coercivity mechanisms, namely the nucleation type for sintered Ferrites, RE-Fe-B and SmCo 5magnets, the pinning type for carbon steel and Sm 2 Co 171magnets and the single domain type for nano-crystalline RE-Fe-B, Aln
38、ico and Cr- Fe-Co magnets. Finally, the recommended magnetizing field strengths for modern permanent magnets are compiled in a comprehensive table. 2 Effective magnetizing field strength For magnetization of permanent magnets, the internal magnetic field strength H intin the magnet is the critical p
39、arameter. The internal field strength is determined by the applied field strength H appland the self-demagnetizing field strength H demagof the magnet or the magnet assembly. The self-demagnetizing field strength depends on the dimensions of the magnet or the load line of a magnet assembly and the p
40、olarization of the magnet material, see equation (1): H int= H appl H demag= H appl NJ/ 0(1) N denotes the demagnetization coefficient and J the polarization of the magnet material. Most advanced magnets are magnetized by a short pulse field, achieved by discharging a capacitor bank through a copper
41、 coil. The duration of the field pulse must last sufficiently long, in order to overcome the eddy currents at the surface of the magnets, in particular for large blocks. In general, a pulse duration of 5 ms to 10 ms is sufficient for complete penetration. The penetration depth , see equation (2), de
42、pends on the electrical resistance , the permeability of the magnet material and the frequency f of the field pulse 1 2 : = K f (2) K denotes a constant. Preferably, magnets will be magnetized after assembly, since handling of unmagnetized magnets is easier and prevents contamination by ferromagneti
43、c particles. In addition chipping of magnet-edges due to the mutual attraction of magnet parts is avoided. _ 1The composition Sm 2 Co 17is used as the generic name for a series of binary and multiphase alloys with transition elements such as Fe, Cu and Zr replacing Co, see also IEC 60404-8-1; 2 nded
44、ition 2001. 2The figures in brackets refer to the Bibliography. 8 TR 62517 IEC:2009(E) 3 Initial magnetization state For nucleation type ferrite, SmCo5 and REFeB magnets, the initial state prior to magnetizing is usually the state after the final heat treatment, i.e. after sintering. This state show
45、s no net remanent magnetization and is often called the thermally demagnetized, or virgin, state. Ferrite and REFeB magnets, once magnetized, may be reset to the initial state by heating them to above the Curie temperature. This will return them to the thermally demagnetized state without permanent
46、loss of properties. SmCo 5magnets can be reset to the initial state only by repeating the full final heat treatment. To prevent chemical changes which can lead to surface damage and permanent loss of properties, rare earth magnets shall be protected in an inert atmosphere during this procedure. For
47、anisotropic Alnico and CrFeCo magnets, where heat treatment in a magnetic field and tempering are involved, some residual magnetization may remain in the magnets. These magnets may be completely demagnetized from any degree of magnetization by applying a slowly reducing alternating magnetic field. T
48、he same holds for any pinning or single domain type magnet such as Sm 2 Co 17and rapidly quenched or HDDR-treated REFeB magnets. 4 Magnetizing behaviour of permanent magnets 4.1 General The magnetizing behaviour of permanent magnets is closely related to their coercivity mechanisms, therefore they n
49、eed to be discussed. Modern permanent magnets may be divided into three groups with respect to their coercivity mechanism. The principal magnetization behaviour for these groups, the nucleation type, the pinning type and the single domain particle type is illustrated in Figure 1. 0,0 0,5 1,0 0 500 1000 field strength H in kA/m polarization in T sintered anisotropic Nd-Fe-B magnet rapidly solidified Nd-Fe-B ribbon 0,0 0,5 1,0 0 1000 2000 3000 f
