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ADVANCED MATERIALS – THE KEY TO PROGRESS

VACODYM • VACOMAXPERMANENT MAGNETS

RARE-EARTH

RARE-EARTH PERMANENT MAGNETS2

The company

Vacuumschmelze

CONTENTS

1. Introduction P. 3

2. Product Range P. 4

3. Applications P. 6

4. Materials and Magnetic Properties P. 10

5. Corrosion Behaviour, Surface Protection and Coatings P. 40

6. Forms of supply P. 46

7. Glueing of RE Magnets P. 49

8. Integrated Management System P. 50

9. Safety Guidelines P. 51

10. Appendix – Technical Principles and Terms P. 52

11. Ductile Permanent Magnet Alloys and Magnetic Semi-Hard Materials P. 55

The company has a staff of approximately 4,500, is represented in 40 countries spread

across all continents and currently registers a turnover of more than € 350 million. The

headquarters and operational center of VAC is in Hanau, Germany. The company also

has production plants in Slovakia, Finland, Malaysia, and China.

0

100

200

300

400

500

600

700

800

1880 1900 1920 1940 1960 1980 2000 2020 2040 2060Year

Steel

AlNiCo

ferrite

SmCo5

Sm2Co17

NdFeB

Future possibilitiesof new materials

(BH)max = 485 kJ / m3

(Theoretical limits NdFeB)

(BH)max[kJ/m3]

RARE-EARTH PERMANENT MAGNETS 3

VacoDym • VacomaX

1. rare-earTh permanenT magneTs

VAC’s product range includes soft magnetic materials,semi-finished products and parts, inductive components,magnetic shieldings and various other materials withspecial physical properties as well as permanent magnets.Apart from the rare-earth permanent magnets, the spect-rum includes ductile permanent magnets and magneticallysemi-hard materials. The latter are characterized by low-cost forming capabilities and adjustable permanent magnetproperties.

We have been working on the magnetic properties of spe-cial metallic materials and their applications for over 70years. In 1973 we had already started producing perma-nent magnets on a rare-earth-cobalt base using powdermetallurgical methods. By finding optimum solutions inclose cooperation with our customers we have contributedstrongly to the widespread use of this new material group– available under the trade name VACOMAX®.

VACODYM® * is our trade name for neodymium-iron-boronmagnets. VACODYM has been produced on an industrialscale since 1986. Our materials have the highest energydensity available to date. All processing steps, from meltingthe alloy under vacuum to coating the finished parts, areperformed at our works, ensuring optimum material pro-perties throughout the entire production process. As theEuropean market leader today, we are among the world'stop-ranking producers of rare-earth permanent magnets.

The magnetic properties are largely determined by the pre-material and the production process. Magnets can beproduced in three different ways. These three methods areidentified by the letters HR, TP and AP in the alloy code.HR (high remanence) refers to isostatically pressedmagnets. In die-pressed design we differentiate betweenTP (transverse-pressed) and AP (axial-pressed). Detailson the available product options are given in Section 6.

We continously pursue intensive development to align ourrange of VACODYM alloys to market demands, forexample for electric drive systems for hybrid or electricvehicles in the field of electric mobility. Both coated anduncoated magnets are used in permanent magnetsynchronous machines, generally as embedded magnets.

In appropriate applications, the orientation profile of ouraxial-pressed (AP) magnets can enhance performance. Inaddition, we have added VACODYM 881 to our '8 Series'alloys. This new development features typical remanenceof 1.22 T (TP quality) and coercivity of 2,385 kA/m, placingit between the proven VACODYM 872 and VACODYM890 alloys. This series of alloys and the '6 Series,' alreadysuccessfully launched on the market and consisting ofVACODYM 633, 655, 669, 677 and 688, supply magnetsthat are particularly suitable for use in motor applicationsand can be used under normal ambient conditions withoutextra surface coating.

For systems with operating temperatures of up to150 °C, we developed the '7 Series' of alloys, comprisingVACODYM 722, 745, 764 and 776, which feature particu-larly high remanence induction values. Where optimumcorrosion resistance is an additional issue, the high-rema-nence VACODYM 837 and 854 from the '8 Series' are afurther option.

Cost-effective production processes, modern inspectiontechniques and a certified quality management systemcomplying with ISO 9001, ISO TS 16949 and ISO 14001are as much a matter of course as ongoing further trainingfor our staff and an active environmental protection policy. By continuing to build on our long-established foundations,we aim to remain your reliable and competent partner.

Fig 1: Development of energy densities (BH)max ofpermanent magnets and their potential

® = registered trademark of VACUUMSCHMELZE*) = licensor Hitachi Metals Ltd. (Japan)

1,50

1,45

1,40

1,35

1,30

1,25

1,20

1,15

1,10

1,05

1,00 800 1200 1600 2000 2400 2800 3200

Coercivity H (kA/m)cJ

Rem

anen

ce B

r (T)

745 TP 837 TP

633 TP

854 TP

655 TP

863 TP

669 TP

872 TP

881 TP890 TP

677 TP

688 TP

VACODYM

Demagnetizing field H

Indu

ctio

n


The product range of our rare earth magnets covers a carefully balanced program of materials with different magnetic properties. As a result, it isrelatively easy to select a material suitable for any specific application.

VACODYM is the permanent magnet material offering the highest energy densities currently available. The excellent magnetic properties of this materialgroup can be traced to the strongly magnetic matrix phase Nd2Fe14B featuring very high saturation polarization and high magnetic anisotropy. A ductileneodymium-rich bonding phase at the grain boundaries provides these magnets with good mechanical properties. Fig. 2 gives an overview of the typicalproperties of our VACODYM magnets.

VACOMAX is our permanent magnet material of rare earths and cobalt. These magnets feature especially high coercivities with simultaneous highsaturation and excellent temperature and corrosion stability. In Fig. 3 the typical demagnetization curves of VACODYM and VACOMAX are comparedwith the classic permanent magnet materials of AlNiCo and hard ferrite.

2. product range

Fig 2: Remanence Br and coercivity HcJ of trans-verse field pressed VACODYM magnets

Typical demagnetization curves ofVACODYM and VACOMAX in com-parison with AlNiCo and ferrite atroom temperature

Fig 3:

anisotropic ferrite

P P

H H

H P

P P

P

H H

H H

T

t

Melting of the alloyunder vacuum

Crushing

Milling

Alignment in magnetic field

Pressing

Magnetizing

Sintering, annealing

Machining, coating

Isostatic Die pressed

Transverse field (TP) Axial field (AP)


VACUUMSCHMELZE has many years of experience inthe production of permanent magnets and the design ofmagnetic circuits. Besides analytical methods, we utilizesophisticated computer programs to analyze and designmagnet systems. These include 2D and 3D field calculati-ons with finite element methods (FEM). Their use hassubstantially shortened the design phase of assemblies.As a result, besides single magnets, we are supplying anincreasing number of finished magnet assemblies tocustomers’ specifications.

Detailed information on these is given in our PD 004leaflet.

The use of soft magnetic materials as system components,e.g. VACOFLUX® and VACOFER®, enables us to meetcustomers’ specifications at a high quality level. In manycases optimum assembly and magnetization of thesystems is only possible when the magnets and the othersystem components are sourced and assembled at themagnet producer.

Magnets made of VACODYM and VACOMAX are produ-ced by sintering using powder metallurgy methods. Themain processing steps are given in Fig. 4. Depending onsize, shape, tolerances, batch size and magnetic require-ments, the parts are either cut from isostatically pressedblocks or are die pressed. During die-pressing, the powderparticles are aligned by strong magnetic fields parallel (axialfield for AP grades) or perpendicular (transverse fields forTP grades) to the direction of pressing depending on thegeometry of the part. Isostatically or transverse-fieldpressed parts have approximately 5 – 8 % higherremanence compared to axial-field pressed magnets.

The typical demagnetization curves of our rare-earthmagnets for various temperatures are available atleading FEM program manufacturers.

Fig. 4: production steps

® = registered trademark of VACUUMSCHMELZE

Fig 5: Example illustrating the volume reduction achieved with VACODYM andVACOMAX: each magnet is designed to produce a field of 100 mT at thereference point P = 5 mm from the surface of the pole

VACODYM

V = 0.27 cm3

Br = 1.40 T

VACOMAX

V = 0.70 cm3

Br = 0.95 T

Ferrite

V = 20.6 cm3

Br = 0.42 T

AlNiCo 500

V = 19.5 cm3

Br = 1.30 T

5 mm

P

P

P

P


Energy densities up to tenfold those of AlNiCo andhard ferrite not only enable a reduction in magnetvolume (see Fig. 5), but also the miniaturizationof systems and whole subassemblies, saving thecosts for return paths, coils etc.

Existing magnet systems can be improved inmany cases. In general, when using VACODYMor VACOMAX we recommend redesign of the pre-vious systems.

New design ideas can be utilized and new fieldsof applications are opened.

Servomotors, DC motors, linear motors and heavy-duty motors or engines (e.g. rail and ships’ engines,wind turbine and hydroelectric generator systems)predominantly utilize VACODYM magnets. In addi-tion, our Finnish subsidiary NEOREM Magnets spe-cializes in the production of large-size magnets andadvanced systems incorporating them (see alsowww.neorem.fi). VACOMAX continues to be the ma-terial of choice in special applications such as hightemperatures. A further important sector is that ofsmall and fractional HP motors, e.g. bell-type arma-ture and dental motors.

Compared to conventional magnet materials,

such as AlNiCo or hard ferrite, magnets of

VACODYM and VACOMAX display a number of

excellent magnetic properties, with the following

significant benefits in use:

3. applIcaTIons

moTors anD generaTors

Magnet track of a linear motor

•

•

•

Rotor of a servomotor


Sensors to measure engine, gear and wheel rotaryspeed (e.g. ABS systems), accelerations (e.g. ESP,airbag) or positions (e.g. throttle valve, injection sys-tems, camshaft, crankshaft, fuel gauges) are equip-ped with VACOMAX or VACODYM magnets,depending on the requirements for temperature andcorrosion stability.

Synchronous motors as main drives in electric andhybrid vehicles are also equipped with VACODYMmagnets.

VACODYM magnets are particularly suitable foractuators in engine management, small motors (e.g.steering boost), generators and for noise reductionsystems.

Different magnetic bearing principles have been de-veloped for turbo-molecular pumps, centrifuges etc.These employ ring magnets magnetized in eitheraxial or radial direction. The material is selectedaccording to customer’s specifications.

auTomoTIVe engIneerIng anD

sensors

permanenT magneT BearIngs

In precise analysis equipment in medical enginee-ring, more and more permanent magnet systemswith high remanent VACODYM grades are used inplace of superconducting and other electricallyexcited systems. The main advantages are the verylow energy consumption, savings in weight, and amaintenance-free construction.

mrI

(magneTIc resonance ImagIng)

Magnetic couplings are preferred in automation andchemical processing technology as they ensure per-manent hermetic separation of different media.Owing to increased temperature requirements,VACOMAX magnets are used for numerous appli-cations. VACODYM is recommended for lower ap-plication temperatures.

magneTIc couplIngs

Synchronous coupling with VACODYM magnets

Sensor modules with VACOMAX magnets for double clutch gear unit (by courtesy of Volkswagen AG)


Permanent magnetic beam guiding systems requirevery little maintenance and no power supply. Sys-tems using VACODYM or VACOMAX magnets haveproved invaluable in all applications where high fieldstrengths have to be achieved in special reactionchambers, e.g. in wigglers, undulators and multi-pole devices, as well as particle detectors.

To meet these requirements, we produce definedand carefully balanced compatible sets of magnetsexhibiting magnetic properties to tight tolerances,including the angle between the preferred magneticdirection and the geometry of the parts. Economicmanufacturing processes are available to produceparts with a large volume; in particular, we can pro-duce large magnet cross-sections with polesurfaces up to approx. 100 cm2.

Beam guIDIng sysTems,

WIgglers anD unDulaTors

Undulator system with VACODYM magnets

Mass spectrometer of INFICON GmbH with VACOMAX magnets


In this field the applications range from electronicscales and pulse meters to NMR (nuclear magneticresonance) analysis equipment. Depending on theconstruction principle, systems using armatures orrotors fitted with VACODYM or VACOMAX magnetsare selected.

measurIng InsTrumenTs

For the widely varying designs of Hall switches, po-larized relays, revolution counters, etc., magnets ormagnet assemblies incorporating VACODYM orVACOMAX are used depending on the specification.

sWITches anD relays

4. maTerIals anD magneTIc properTIes4.1 characTerIsTIc properTIes

1) Coding based on IEC 60404-8-1, the magnetic values usually exceed the IEC values

Table 1: CHARACTERISTIC PROPERTIES OF VACODYM AT ROOM TEMPERATURE (20 °C)

VACODYM 722 HR 380/87.5 15 1.47 14.7 1.42 14.2 915 11.5

VACODYM 745 HR 370/111.5 16 1.44 14.4 1.40 14.0 1115 14.0

VACODYM 510 HR 360/95.5 19 1.41 14.1 1.38 13.8 980 12.3

VACODYM 633 HR 315/127.5 20 1.35 13.5 1.29 12.9 1040 13.1

VACODYM 655 HR 280/167 21 1.28 12.8 1.22 12.2 990 12.4

VACODYM 677 HR 240/223 23 1.18 11.8 1.12 11.2 915 11.5

VACODYM 745 TP 355/111.5 - 1.41 14.1 1.37 13.7 1090 13.7

VACODYM 764 TP 335/127.5 17 1.37 13.7 1.33 13.3 1060 13.3

VACODYM 776 TP 305/167 18 1.32 13.2 1.28 12.8 1020 12.8

VACODYM 837 TP 335/127.5 25 1.37 13.7 1.33 13.3 1060 13.3

VACODYM 854 TP 310/167 26 1.32 13.2 1.28 12.8 1020 12.8

VACODYM 863 TP 295/200 27 1.29 12.9 1.25 12.5 995 12.5

VACODYM 872 TP 280/223 28 1.25 12.5 1.21 12.1 965 12.1

VACODYM 881 TP 265/238.5 29 1.22 12.2 1.18 11.8 945 11.9

VACODYM 890 TP 250/263 30 1.19 11.9 1.15 11.5 915 11.5

VACODYM 633 TP 305/127.5 - 1.32 13.2 1.28 12.8 1020 12.8

VACODYM 655 TP 280/167 - 1.26 12.6 1.22 12.2 970 12.2

VACODYM 669 TP 255/200 22 1.22 12.2 1.17 11.7 940 11.8

VACODYM 677 TP 240/223 - 1.18 11.8 1.13 11.3 915 11.5

VACODYM 688 TP 225/262.5 24 1.14 11.4 1.09 10.9 885 11.1

VACODYM 745 AP 325/111.5 16 1.34 13.4 1.31 13.1 1025 12.9

VACODYM 764 AP 305/135.5 17 1.30 13.0 1.27 12.7 995 12.5

VACODYM 776 AP 280/167 18 1.26 12.6 1.22 12.2 965 12.1

VACODYM 837 AP 300/135.5 25 1.30 13.0 1.26 12.6 995 12.5

VACODYM 854 AP 275/167 26 1.26 12.6 1.21 12.1 965 12.1

VACODYM 863 AP 250/200 27 1.21 12.1 1.17 11.7 925 11.6

VACODYM 872 AP 235/223 28 1.17 11.7 1.13 11.3 890 11.2

VACODYM 881 AP 230/238.5 29 1.14 11.4 1.10 11.0 875 11.0

VACODYM 890 AP 210/263 30 1.11 11.1 1.07 10.7 845 10.6

VACODYM 633 AP 280/135.5 20 1.26 12.6 1.22 12.2 965 12.1

VACODYM 655 AP 255/167 21 1.20 12.0 1.16 11.6 915 11.5

VACODYM 669 AP 225/200 22 1.16 11.6 1.12 11.2 885 11.1

VACODYM 677 AP 215/223 23 1.13 11.3 1.08 10.8 860 10.8

VACODYM 688 AP 200/262.5 24 1.08 10.8 1.03 10.3 830 10.4

HR

TP

AP

Pressingdirection Material Code1) See Page Remanence Coercivity

Br

typ.Tesla kG

Br

min.Tesla kG

HcB

typ.kA/m kOe


2) The maximum application temperature is governed by the layout of the system. The approx. values given refer to magnets operating in working points of B/uoH = -1 (max. energy product). Users are recommended to consult VAC on any application of VACODYM involving temperatures above 150 °C.

835 10.5 875 11 415 53 380 48 -0.115 -0.77 7.6 50 120

1065 13.4 1115 14 400 50 370 47 -0.115 -0.73 7.6 70 160

915 11.5 955 12 385 48 360 45 -0.115 -0.79 7.5 60 140

980 12.3 1275 16 350 44 315 40 -0.095 -0.65 -0.105 -0.55 7.7 110 230

925 11.6 1670 21 315 40 280 35 -0.090 -0.61 -0.100 -0.55 7.7 150 300

850 10.7 2230 28 270 34 240 30 -0.085 -0.55 -0.095 -0.50 7.7 190 370

1035 13.0 1115 14 385 48 355 45 -0.115 -0.73 7.6 70 160

1005 12.6 1275 16 360 46 335 42 -0.115 -0.70 -0.125 -0.59 7.6 100 210

970 12.2 1670 21 335 42 310 39 -0.110 -0.61 -0.120 -0.55 7.6 140 280

1010 12.7 1275 16 360 46 335 42 -0.110 -0.62 -0.120 -0.54 7.6 110 230

970 12.2 1670 21 335 42 310 39 -0.105 -0.60 -0.115 -0.53 7.7 150 300

950 11.9 2000 25 315 40 295 37 -0.100 -0.56 -0.110 -0.51 7.7 170 340

915 11.5 2230 28 300 38 280 35 -0.095 -0.53 -0.105 -0.49 7.7 190 370

900 11.3 2385 30 290 36 265 33.5 -0.093 -0.51 -0.103 -0.47 7.7 200 390

865 10.9 2625 33 270 34 250 31 -0.090 -0.50 -0.100 -0.46 7.7 220 430

970 12.2 1275 16 335 42 305 39 -0.095 -0.65 -0.105 -0.57 7.7 110 230

925 11.6 1670 21 305 39 280 35 -0.090 -0.61 -0.100 -0.55 7.7 150 300

875 11.0 2000 25 290 36 255 32 -0.085 -0.57 -0.095 -0.51 7.7 170 340

860 10.8 2230 28 270 34 240 30 -0.085 -0.55 -0.095 -0.50 7.7 190 370

830 10.4 2625 33 250 32 225 28 -0.080 -0.51 -0.090 -0.46 7.8 220 430

970 12.2 1115 14 340 43 325 41 -0.115 -0.73 7.6 80 180

955 12.0 1355 17 325 41 305 38 -0.115 -0.69 -0.125 -0.58 7.6 110 230

915 11.5 1670 21 305 38 280 35 -0.110 -0.61 -0.120 -0.55 7.6 150 300

950 11.9 1355 17 325 41 300 37 -0.110 -0.62 -0.120 -0.54 7.6 120 250

905 11.4 1670 21 305 38 275 35 -0.105 -0.60 -0.115 -0.53 7.7 160 320

875 11.0 2000 25 280 35 250 32 -0.100 -0.56 -0.110 -0.51 7.7 180 360

845 10.6 2230 28 260 33 235 30 -0.095 -0.53 -0.105 -0.49 7.7 200 390

830 10.4 2385 30 250 31.5 230 28.5 -0.093 -0.51 -0.103 -0.47 7.7 210 410

795 10.0 2625 33 235 29 210 26 -0.090 -0.50 -0.100 -0.46 7.7 230 440

915 11.5 1355 17 305 38 280 35 -0.095 -0.64 -0.105 -0.57 7.7 120 250

865 10.9 1670 21 275 35 255 32 -0.090 -0.61 -0.100 -0.55 7.7 160 320

820 10.3 2000 25 255 32 225 28 -0.085 -0.57 -0.095 -0.51 7.7 180 360

805 10.1 2230 28 240 30 215 27 -0.085 -0.55 -0.095 -0.50 7.7 200 390

770 9.7 2625 33 225 28 200 25 -0.080 -0.51 -0.090 -0.46 7.8 230 440

HcB

min.kA/m kOe

HcJ

min.kA/m kOe

(BH)max

typ.kJ/m3 MGOe

(BH)max

min.kJ/m3MGOe °F

TC (HcJ)typ.%/°C

Tmax2)

°C

TC (Br)typ.%/°C

typ.g/cm3

TC (HcJ)typ.%/°C

TC (Br)typ.%/°C

Energy densityTemperature coefficient20-100 °C 20-150 °C Density

Max.cont.-temperature


Material Curie Specific Specific Thermal Coefficient of thermal Young’s Bending Compressive Vickers Stress

temp. electr. heat con- expansion modulus strength strength hardness crack

resistance ductivity 20-100 °C resistance II c � c KIC °C �mm2/m J/(kg · K) W/(m·K) 10-6/K 10-6/K kN/mm2 N/mm2 N/mm2 HV N/mm3/2

VACODYM 310–370 350–550 5–15 4–9 -2–0 140–170 120–400 600–1250 500–700 80–180

VACOMAX Sm2Co17 800–850 0.65–0.95 300–500 5–15 8–12 10–14 140–170 80–150 400–900 550–750 30–60

VACOMAX SmCo5 700–750 0.4–0.7 300–500 5–15 4–10 10–16 100–130 90–180 600–1100 500–700 40–80

Table 3: CHARACTERISTIC PHYSICAL PROPERTIES OF VACODYM AND VACOMAX AT ROOM TEMPERATURE (20 °C)

1.4–1.6 (II c)1.2–1.4 (� c)

3) 3)

Material Remanence CoercivityCode1) Br Br HcB HcB HcJ

typ. min. typ. min. min. Tesla kG Tesla kG kA/m kOe kA/m kOe kA/m kOe

VACOMAX 240 HR 1.12 11.2 1.05 10.5 730 9.2 600 7.5 640 8.0

200/64

VACOMAX 225 HR 1.10 11.0 1.03 10.3 820 10.3 720 9.0 1590 20.0

190/159

VACOMAX 225 TP 1.07 10.7 1.03 10.3 790 9.9 720 9.0 1590 20.0

190/159

VACOMAX 225 AP 1.04 10.4 0.97 9.7 760 9.6 680 8.5 1590 20.0

170/159

VACOMAX 200 HR 1.01 10.1 0.98 9.8 755 9.5 710 8.9 995 12.5

180/100

VACOMAX 170 0.95 9.5 0.90 9.0 720 9.0 660 8.3 1195 15.0

160/120

VACOMAX 145 S 0.90 9.0 0.85 8.5 660 8.3 600 7.5 1990 25.0

140/2001) Coding based on IEC 60404-8-1, the magnetic values usually exceed the IEC values

E T D M 2 2 c t ( ( T T T T T t m t t t t t k M k M % % % % g ° °

2 3 2 2 – – – – 8 3 5

2 2 1 2 – – – – 8 3 6

2 2 1 2 – – – – 8 3 6

2 2 1 2 – – – – 8 3 6

2 2 1 2 – – – – 8 2 4

1 2 1 2 – – – – 8 2 4

1 2 1 1 – – – – 8 2 4

Table 2: CHARACTERISTIC MAGNETIC PROPERTIES OF VACOMAX AT ROOM TEMPERATURE (20 °C)

See Page

31

32

–

32

33

34

35

12 RARE-EARTH PERMANENT MAGNETS

3) II c: parallel to preferred magnetic direction� c: perpendicular to preferred magnetic direction

The values in the above table shall be regarded as typical values andnot as tolerance limits.

More information onmagnetization is givenin Section 4.4 frompage 37.

Energy density Temperature coefficient Density Max. 20-100 °C 20-150 °C continuous temperature (BH)max (BH)max TC (Br) TC (HcJ) TC (Br) TC (HcJ) T

2)max

typ. min. typ. typ. typ. typ. typ. kJ/m3 MGOe kJ/m3 MGOe %/°C %/°C %/°C %/°C g/cm3 °C °F

240 30 200 25 –0.030 –0.15 –0.035 –0.16 8.4 300 570

225 28 190 24 –0.030 –0.18 –0.035 –0.19 8.4 350 660

215 27 190 24 –0.030 –0.18 –0.035 –0.19 8.4 350 660

200 25 170 21 –0.030 –0.18 –0.035 –0.19 8.4 350 660

200 25 180 23 –0.040 –0.21 –0.045 –0.22 8.4 250 480

180 23 160 20 –0.040 –0.21 –0,045 –0.22 8.4 250 480

160 20 140 18 –0.040 –0.14 –0.045 –0.15 8.4 250 480

2) Customers are recommended to contact VAC before using VACOMAX in applications above 200 °C.

13RARE-EARTH PERMANENT MAGNETS

Material Hmag min.

kA/m kOe

VACODYM 2500 31

VACOMAX 225 3650 46

VACOMAX 240 2000 25

VACOMAX 145/170/200 2000 25

Table 4: INNER MAGNETIZING FIELD STRENGTHOF VACODYM AND VACOMAX


4.2 maTerIal graDes

VACODYM and VACOMAX are anisotropic materi-als with reversible permeability μrev < 1.1 at the wor-king point. The exact value depends on the materialgrade and the magnet geometry.

VACODYM and VACOMAX do not have openporosity, i.e. the pores are not interconnected.Therefore both materials can be utilized for vacuumapplications.

The following pages show demagnetization curvesof different grades at various temperatures. Additio-nally, the typical irreversible losses are given as afunction of temperature at different load lines. Thesecharts are based on HR or TP grades. Axial fieldpressed magnets have slightly reduced losses undercomparable conditions.

The diagrams of typical irreversible losses take ther-mal after-effects into consideration (logically, theseare not included in the demagnetization curves J(H)and B(H) shown). The resulting time and tempera-ture-dependend opposing field must be consideredin addition to the demagnetizing field determined bythe working point in question (see also Appendix10.1.2, p. 53).

It may be assumed for practical purposes that theseadditional opposing fields are in the range of approx.150 kA/m. Magnet dimensions incorporatingconsiderations of long-term stability should thereforebe based on the irreversible losses shown in thefollowing.

The measured curves refer to magnets whose mini-mum dimensions are 10 mm perpendicular to the di-rection of magnetization and 5 mm parallel to it.Smaller dimensions may deviate from the curvesshown.

VACODYM 722 HR

-0.5

20°C 60°C 80°C 100° C

120° C

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/µo ·H

kA/m -1400 -1200 -1000

-1.0 -1.5 -2.0 -4.0

H

0-800 -600 -400 -200

8

6

2

0

Typical demagnetization curves B(H) and J(H) at different temperatures

Typical irreversible losses at different working points as a function of temperature

Irrev

ersi

ble

loss

es (%

)

Temperature


VacoDym 722

4.2.1 sInTereD magneTs on a ndFeB Base

VACODYM 745 HR

-0,5

20° C

120° C

60° C 80° C 100° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

VACODYM 745 AP

-0,5

20° C

120° C

60° C 80° C 100° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

Typische EntmagnetisierungskurvenB(H) und J(H) beiverschiedenen Temperaturen

Typische irreversible Verluste fürverschiedene Arbeitspunkte inAbhängigkeit von der Temperatur

16



Irrev

ersi

ble

loss

es (%

)

Temperature

RARE-EARTH PERMANENT MAGNETS

VacoDym 745

sInTereD magneTs on a ndFeB Base

VACODYM 764 TP

-0,5 20°C C 120° C

150° C

80° C60°C 100°C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

VACODYM 764 AP

-0,520°C 80° C60°C 100°C 120° C

150° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0



S

VACODYM 764 AP

-0,520°C 80° C60°C 100°C 120° C

150° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

17



Irrev

ersi

ble

loss

es (%

)

Temperature


VacoDym 764


VACODYM 776 TP

-0,5

20° C

120° C 150° C

180° C

100° C60° C 80° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

VVAACCOODDYYMM 777766 AAPP

-0,5

20° C

120° C 150° C

180° C

80° C60° C 100° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

-10

-5

0

0 50 100 150 200

Temperatur

irrev

ersi

ble

Ver

lust

e (

%) VACODYM 776 TP

°C

B/µ0 · H = -20 -0,5 -1



18



Irrev

ersi

ble

loss

es (%

)

Temperature


VacoDym 776


VACODYM 510 HR

-0,5

20° C

120° C

60°C 80°C 100° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0



19



Irrev

ersi

ble

loss

es (%

)

Temperature


VacoDym 510


VACODYM 633 HR

-0,5 20° C 120° C

150° C

80° C 100° C60° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

VACODYM 633 AP

-0,5 20° C 120° 150° C100° C80° C60° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0



20



Irrev

ersi

ble

loss

es (%

)

Temperature


VacoDym 633


VACODYM 655 HR

-0,5

20° C

120° C 150° C

180° C

100° C60° C 80° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

VACODYM 655 AP

-0,5

20° C

120° C 150° C

180° C

80° C60° C 100° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0



21



Irrev

ersi

ble

loss

es (%

)

Temperature


VacoDym 655


VACODYM 669 TP

-0,5

20° C

120° C 150° C 180° C80° C 100° C

210° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

VACODYM 669 AP

-0,5

20° C

150° C

180° C

80° C 100° C

210° C

120° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0



22



Irrev

ersi

ble

loss

es (%

)

Temperature


VacoDym 669


-2

VACODYM 677 HR

-0,5

20° C

120° C 150° C 180° C

210° C

100° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

VACODYM 677 AP

-0,5

20° C

150° C 180° C

210° C

100° C 120° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0



23



Irrev

ersi

ble

loss

es (%

)

Temperature


VacoDym 677


-2

VACODYM 688 TP

-0,5

20° C

120° C 150° C 180° C 210° C

240° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

-2

VACODYM 688 AP

-0,5

20° C

120° C 150° C 180° C 210° C

240° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0



24



Irrev

ersi

ble

loss

es (%

)

Temperature


VacoDym 688


VACODYM 837 AP

-0,520°C 60°C 80° C 100°C 120°C 150° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

VACODYM 837 TP

-0,520° C 80° C60°C 100°C 120°C 150° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

-10

-5

050 100 150 200 250

Temperatur

irreversibleVerluste(%)

VACODYM 837 TP

-1 -2

°C

- 0,5B/µ0 · H = 0



25



Irrev

ersi

ble

loss

es (%

)

Temperature


VacoDym 837


VACODYM 854 TP

-0,5

20° C

120° C 150° C 180° C80° C60° C 100° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

VACODYM 854 AP

-0,5

20° C

120° C 150° C 180° C80° C60° C 100° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

-10

-5

050 100 150 200 250

Temperatur

irreversibleVerluste(%)

VACODYM 854 TP

-1 -2

°C

- 0,5B/µ0 · H = 0



26



Irrev

ersi

ble

loss

es (%

)

Temperature


VacoDym 854


VACODYM 863 AP

-0,5

20° C

150° C180° C

80° C 100° C

210° C

120° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

VACODYM 863 TP

-0,5

20° C

120° 150° C 180° C80° C 100° C

210° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

-10

-5

0

50 100 150 200 250

Temperatur

irrev

ersi

ble

Ver

lust

e (

%)

VACODYM 863 TP

B/ 0 · H = 0 - 0,5 -1 -2

°C



27



Irrev

ersi

ble

loss

es (%

)

Temperature


VacoDym 863


-2

VACODYM 872 AP

-0,5

20° C

120° 150° C 180° C

210° C

100° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

VACODYM 872 TP

-0,5

20° C

120° 150° C 180° C

210° C

100° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

-10

-5

0

50 100 150 200 250Temperatur

irrev

ersi

ble

Ver

lust

e (

%)

VACODYM 872 TP

B/ 0 · H = 0 - 0,5 -1 -2

°C



-10

-5

0

50 100 150 200 250Temperatur

irrev

ersi

ble

Ver

lust

e (

%)

VACODYM 872 TP

B/ 0 · H = 0 - 0,5 -1 -2

°C

28



Irrev

ersi

ble

loss

es (%

)

Temperature


VacoDym 872


VACODYM 881 TP

50 1000

-5

-10

150 200Temperatur

irrev

ersib

le Ve

rluste

(%

)

250°C

-1 -2B/µ0 · H = 0 - 0,5

kOe - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

kA/m -1400 -1200 -1000 -800 -600 -400 -200 0

H

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

T kG

-8

-6

-4

-2

4

10

12

14

16

8

6

2

0

J,B

VACODYM 881 TP

B/µ ·H° -1,0

-0,5

-1,5 -2,0 -4,0

20°C

100°C 120°C 150°C 180°C

210°C

kOe - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

kA/m -1400 -1200 -1000 -800 -600 -400 -200 0

H

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

T kG

-8

-6

-4

-2

4

10

12

14

16

8

6

2

0

J,B

VACODYM 881 AP

B/µ ·H° -1,0

-0,5

-1,5 -2,0 -4,0

20°C

100°C 120°C 150°C 180°C

210°C

29

Irrev

ersi

ble

loss

es (%

)

Temperature


VacoDym 881




-2

VACODYM 890 AP

20° C

120° 150° C 180° C 210° C

240° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

-2

VACODYM 890 TP

-0,5

20° C

120° 150° C 180° C 210° C

240° C

-0,8

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

-2 0 - 18 -16 -14 -12 -10 -8 -6 -4 -2 0

-8

-6

-4

-2

4

10

12

14

16

T kG

J,B

kOe

B/ µo · H

kA/m -1400 -1200 -1000

-1,0 -1,5 -2,0 -4,0

H

0-800 -600 -400 -200

8

6

2

0

-10

-5

0

50 100 150 200 250

Temperatur

irrev

ersi

ble

Ver

lust

e (

%)

VACODYM 890 TP

B/ 0 · H = 0 - 0,5 -1 -2

°C



30



Temperature


Irrev

ersi

ble

loss

es (%

)

VacoDym 890




0 50 100

B/µ

0

-5

%

-10

150 200Temperatur

VACOMAX 240 HR

irrev

ersib

le Ve

rluste

250 300°C

0 · H = - 0,5

-1

-2

-4

31



Irrev

ersi

ble

loss

es (%

)

Temperature


VacomaX 240

4.2.2 sInTereD magneTs on a sm2co17 Base

AP



100 150 200

B/µ

0

0

-5

%

-10

250 300Temperatur

VACOMAX 225 HR

irrever

sible

Verlu

ste

350°C

0 · H = - 0,5

-1 -2-4

32



Irrev

ersi

ble

loss

es (%

)

Temperature


VacomaX 225

sInTereD magneTs on a sm2co17 Base



33




VACOMAX 200 HR

VACOMAX 200 HR

50 100

B/µ

-5

%

-10

0150 200

Temperatur

irrev

ersib

le Ve

rluste

250°C

0 · H = 0

- 0,5-1

-2-4

Irrev

ersi

ble

loss

es (%

)

Temperature

VacomaX 200

4.2.3 sInTereD magneTs on a smco5 Base



34




VACOMAX 170

50 100

B/µ-5

%

-10

0150 200

Temperatur

irrev

ersib

le Ve

rluste

250°C

0 · H = 0- 0,5

-1-2

-4

Irrev

ersi

ble

loss

es (%

)

Temperature

VacomaX 170

sInTereD magneTs on a smco5 Base



35




VACOMAX 145 S

50 100

B/µ

-5

%

-10

0150 200

Temperatur

irrev

ersib

le Ve

rluste

250°C

0 · H = 0- 0,5

-1

Irrev

ersi

ble

loss

es (%

)

Temperature

VacomaX 145

sInTereD magneTs on a smco5 Base


4.3 TemperaTure DepenDence

anD magneTIc losses

The magnetic properties of permanent magnetsdepend on the application temperature. The typicaldemagnetization curves of VACODYM andVACOMAX at different temperatures are shown on therelevant alloy pages (see pages 15-35). Whenselecting a material and the dimensions of a magnet,the characteristic magnetic values and the tempera-ture dependence must be considered (see section10.1 ”Technical Principles and Terms”).

The temperature dependence of the demagnetizationcurves causes changes in the flux density, commonlyreferred to as magnetic losses. These losses fall intotwo main categories: reversible losses and irreversiblelosses.

Reversible losses in the flux density are attributedto the temperature dependence of the saturation po-larization and are solely a function of alloy composi-tion. They are described by the temperature coefficientof the remanence; the mean value for each materialis given in tables 1 and 2.

If an application calls for temperature compensation,we recommend the use of a magnetic shunt made ofTHERMOFLUX®. This achieves temperature coeffi-cients of l TC l < 0.01 %/K in systems with slightly re-duced flux values in the range from 20 °C to 100 °C.

Irreversible losses result from demagnetization ofsmall areas of the magnet in opposing fields and/or arise in temperature, as well as changes in the micro-structure. Owing to demagnetization processes theyare dependent on the load line of the magnet and themaximum application temperature. The typicalirreversible losses to be expected for the variousmaterial types at different load lines B/μoH are givenin the applicable data sheets.

Irreversible changes can largely be avoided by meansof a stabilization process (aging). Users should contactVAC to obtain the optimum stabilization conditions foreach application. As a rule, it is adequate to heat themagnets to slightly above the maximum applicationtemperature for approximately one hour. Thispretreatment achieves good stabilization but at theexpense of the flux density which is reducedaccordingly by the irreversible changes. With thisprocedure the “thermal after-effects” (s. page 14) canbe anticipated.

Irreversible losses caused by magnetization reversalin small areas of the magnet can be eliminated byremagnetization.

To avoid undesired irreversible changes in the micro-structure which cannot be remedied by remagnetiza-tion, VACODYM magnets must not be heated above350°C and VACOMAX magnets not above 400 °C.

Chemical reactions with the immediate environmentor contact materials (e.g. adhesives) must beprevented. This applies especially to reactions withpotential hydrogen production (see section 5.1).Radioactive radiation over a longer period can causeirreversible magnetic losses.

VACOMAX can be used at temperatures down to thatof liquid helium (approximately 4 K). When usingVACODYM below approx. 150 K our technical staffshould be consulted.



4.4 magneTIzaTIon

oF rare-earTh maTerIals

Full magnetization is a precondition for achieving thetypical magnetic values that are listed in tables 1 and2 for the various materials. The required minimum fieldstrengths of the inner magnetizing field Hmag are ob-tained from the magnetization behavior of the materialin question. They are shown in table 4, page 13, andin fig. 6. To achieve the internal magnetizing field Hmag,the given external field Hext must be increased by thevalue of the demagnetizing field Ha which is deter-mined by the working point. In addition, care shouldbe taken that the magnetization field is maintained forlong enough to avoid demagnetizing eddy currents:

l Hext l = l Hmag l + l Ha l

Due to the high coercivities of VACODYM andVACOMAX, it is sometimes necessary to magnetizethe magnets outside the system. As a result, handlingthe magnets and assembly of systems is more difficultbut the actual magnetization is far easier. With VACO-DYM 510, 722/745 and also VACOMAX 240, caremust be taken to ensure that the working point of themagnet is sufficiently above the “knee” of the B(H)demagnetization curve (see section 10.1 of appendix“Technical Principles and Terms”), to prevent self-demagnetization of the magnet.

We advise users to contact VAC before magnetizingVACODYM and VACOMAX in a system.

Likewise: magnets made of VACODYM and especiallyof VACOMAX can only be completely reversed inexceptionally high magnetic fields (> approx. 100 kOe).

38

Magnetizing field strength(kA/m)



The magnetization behavior of VACODYM (figure 6a) and VACOMAX of the SmCo5 type (figure 6b) is based on theso-called 'nucleation mechanism'. The 'pinning mechanism' is characteristic of the VACOMAX type Sm2Co17. VACOMAX 240 (figure 6c) is easier to magnetize than VACOMAX 225 (figure 6d), due to a special heat treat.

DemagneTIzaTIon curVes oF VacoDym anD VacomaX

as a FuncTIon oF magneTIzIng FIelD sTrengTh hmag

Fig. 6:

a)

b)

39




c)

d)

VACODYM 6XX, 8XX

VACODYM 7XX

traditionalNdFeB

Exposure time (Days)

Wei

ght l

oss

(mg/

cm )2

1000

100

10

10 12 14 16 18 20 8 6 4

1

0.1

2 0


5. corrosIon BehaVIor,

surFace proTecTIon anD coaTIngs

Rare earth (RE) elements belong to the group ofignoble and thus highly reactive elements due totheir strongly negative electrochemical standardpotential (E0 = –2.2 to –2.5 V).

Their chemical reactivity is similar to that of alkalineearth metals such as magnesium. Under normalconditions the RE metals react slowly. Under con-ditions at higher temperatures and the presence ofwater or humidity, the reaction is more rapid, REhydroxide is formed and hydrogen is released. Thereleased hydrogen can then react with the free REmetal forming RE metal hydrides.

Adding a sufficient quantity of a more nobleelement such as cobalt nearly suppresses thereaction with water. This is the reason whyVACOMAX (SmCo5 or Sm2Co17) only exhibits slightsurface discoloration when exposed to high humidity(e.g. > 80 % relative humidity) and increasedtemperature (e.g. > 80 °C). No significant amountsof corrosion products were measured even afterlong exposure (e.g. > 1000 h).

The general situation is different with Nd-Fe-B mag-nets. Here, the individual magnet grains are heldtogether mechanically and bonded to each other bythe 'neodymium-rich' phase. This phase representsup to 5 % of the total volume of the material andbehaves like pure neodymium from a chemical pointof view in uncoated magnets.

5.1 corrosIon BehaVIor

This in turn leads to a high corrosion rate anddebris, which is neodymium hydroxide, andalso to magnet dust (loose Nd-Fe-B grains).Sections 5.2 to 5.4 describe means of pro-tecting these materials effectively in corrosiveoperating conditions.

As a result, intergranular decomposition of themagnet (see fig. 7) starts in combination withhigh humidity and temperature (e.g., in theHAST Highly Accelerated Stress Test acc. IEC68-2-66 at 130 °C / 95 % humidity and 2.6 bar).

The second generation of VACODYM materials suchas the 6-series and 8-series alloys do no longerallow this corrosion mechanism to occur.

Additions of carefully selected suitable elements(including cobalt) to the neodymium-rich phase haveimproved their corrosion behaviour and systemati-cally stopped intergranular corrosion in a warm,humid atmosphere. The corrosion behavior of suchVACODYM alloys is similar to that of pure ironmaterials (steel). A HAST shows negligiblecorrosion even after several weeks' exposure, withonly a dark grey shimmer visible on the materialsurface.

Like parts made of iron, VACODYM materialsgradually begin to rust (red rust) in cases wherehumidity turns to condensation. Here the corrosionproducts are mainly non-magnetic metal oxides orhydroxides. We recommend coating for applicationswhere dew formation occurs regularly (condensa-tion) and/or the parts are to be used in water or othercorrosive media.

In case of VACODYM high humidity, dew formationor sweat is already sufficient to cause corrosion. Wetherefore recommend using suitable gloves tohandle VACODYM magnets in all cases.

Fig. 7: Weight loss of VACODYM magnets in a HAST test similar toIEC 68-2-66 (130 °C; 95 % relative humidity; 2.6 bar pressure of vapour)


To protect uncoated magnets temporarily, e.g. duringtransport or storage, we have developed a passiva-tion method. This protects our RE-magnets, inclu-ding the more corrosion-sensitive VACODYM,sufficiently against temporary environmental influen-ces such as a rise in humidity. With this standardprocedure our magnets can be stored under normalambient conditions providing condensation can beprevented.

Passivation involves the application of an ultra-thinNd/Fe phosphate layer to the magnet surface.

This phosphate layer is only a few hundred nm thick(< 0.5 μm) and effectively protects magnetsagainst rust under normal climate conditions(T � 30 °C; rel. humidity < 70 %).

The thickness of the phosphate layer is within thespectrum of visible light wavelengths. Minor fluctua-tions in thickness and light incidence cause thesurface to appear in different colors. Magnetsnormally appear from light yellow or brownish toiridescent blue and grey. These colors are not an in-dication of corrosion (rust) but are the basiccolors of the phosphate coating.

5.2 Temporary corrosIon

proTecTIon anD

surFace passIVaTIon

5.3 surFace proTecTIon

proTecTIon agaInsT magneTIc

parTIcles

In many applications, the phosphate coating appliedin passivation is too thin to provide reliable long-termprotection for VACODYM magnets. For effectivecorrosion protection under application conditions, adifferent type of coating is often necessary.

The type and thickness of coating depends on pre-valent environmental influences in the application.Corrosion-proof coatings can be applied to magnetsdirectly after production and cleaning.

VACODYM and VACOMAX are sintered materials,thus it cannot be excluded that magnetic particlesare found on the surface. In certain applications (e.g.systems with small working air gaps) loose magneticparticles may affect the function and/or destroy themagnet assembly. Coating ensures that the magnetscan be cleaned thoroughly and are free of all depo-sits.

hanDlIng proTecTIon

Magnets are frequently mechanically stressedduring assembly or operation in an assembly. Insome circumstances, this may lead to chipping,particularly at sharp edges.

Each application of VACODYM and VACOMAXmust be evaluated to ascertain whether coating isnecessary and how the surface is to be protected.We have tested the behaviour of our permanentmagnets under widely varying conditions and will bepleased to advise you on the appropriate coating foryour application.

Users may also choose to apply surface protection tomagnets in the finished assembly. Proven methodsinclude protective wrap to which liquid anti-corrosioncompound is applied, molding or spraying the assem-bled magnets with resin, enclosing them in e.g.stainless steel casing or applying corrosion-proofcoatings such as paint or varnish to the assembly.

Depending on the application, surface coatings mayalso serve other purposes besides corrosionprotection:


5.4 Types oF coaTIngs

The coatings can be divided into two basic groups:metallic and organic. To meet special requirementsand on request, double coatings of metal/metal &metal/organic, and a number of special coatings areavailable.

meTallIc coaTIngs

As a rule, galvanic processes are used for metalliccoatings. Apart from our standard nickel or tin coating,on request we offer double coating of nickel + tin. Inaddition IVD-aluminium (Ion Vapor Deposition) coatingis also possible.

When selecting the type of metallic coating, the pos-sibility of a galvanic element formation in the assemblymust be taken into account where bedewing cannotbe excluded.

In addition, all galvanic coating processes generate asmall amount of hydrogen as a side reaction to metaldeposition. This hydrogen is absorbed by the surfacemagnetic material and may lead to irreversible lossesin NdFeB alloys with appropriate geometry. In thiscontext, unsuitable parts are miniature parts (weight< 0.5 g), thin-walled rings and ultra-thin magnets(thickness < 1.5 mm). In these cases, other coatingprocesses such as spray-coating should be selectedinstead of galvanization.

organIc coaTIngs

We offer a range of spray coatings with excellentcorrosion protection characteristics. Our newVACCOAT® epoxy resin coatings are particularlyuseful cost-effective alternatives to metallic coatings,especially for large magnets weighing approx. 25 gand over, which must usually be rack-coated whenmetallic coatings are selected. Spray coatings offersignificant advantages in terms of cost, coating quality,and resistance in corrosive testings.

Most applications can be served by our galvanic tin,galvanic nickel, IVD aluminium coatings and ourrecently introduced VACCOAT spray coatings. Thecoatings feature complementary properties.

All galvanic coating processes and the spray coatingsare applied at VACUUMSCHMELZE using the latestautomated technology, yielding cost effective solutionsthat offer high reproducibility and quality. Thedescribed properties can only be achieved in a care-fully controlled system which takes into considerationthe microstructure of the magnets, the mechanicalprocessing/machining, cleaning and coating.

IVD aluminium coating is performed by a subcon-tractor selected and qualified by VAC with great care.Appropriate quality assurance measures ensureconsistent quality in series production.

5.5 DescrIpTIon

oF The coaTIngs



This coating family is an in-house development thatsets new standards regarding corrosion protection,temperature resistance, coating application and thesubsequent processing of coated magnets intosystems. When cured, VACCOAT 20011 provideshigh-grade corrosion protection for VACODYM. At thesame time, before curing the coating film can alsoserve as a high-strength adhesive. A high-strengthadhesive bond forms during baking, giving a typicalshear strength of >15 N/mm2.

At the same time the system is protected effectivelyfrom corrosion by the coating, with corrosionprotection comparable to aluminium spray coating.The baked coating has a pencil hardness of at least4H and can be thermally stressed to approx. 200 °C.Visually high-quality layers of between 5 μm and40 μm can be applied in a single operation. Althoughthe standard color is black, other colors are available.The coating is abrasion-resistant and exhibitsexcellent electrical insulation behaviour. Similar toaluminium spray coating, the layers can be applied tothe magnets in either a continuous automatic processor a barrel-coating process.

VACCOAT 20021 was developed specifically for smallbarrel-coated magnets (< 10 g) and offers optimizedcorrosion protection and productivity.

The newest VACCOAT generation, VACCOAT 30033,was developed to maximize corrosion protection forRE magnets. In salt spray tests (DIN EN ISO 9227)and autoclave tests (130 °C / 100 % humidity / 2.7 barpressure), VACODYM magnets protected with thiscoating achieve corrosion-free testing times of over1,000 hours. These high results in both tests cannotbe matched by previous spray coatings or by metallicplating such as galvanic nickel / tin. Other properties(mechanical parameters, temperature and chemicalresistance) are comparable with VACCOAT 20011.This coating type is only available for continuousautomatic processing, and thus only for magnets withweight of > 5 g. This process ensures highreproducibility and process safety as well ascompliance with strict dimensional tolerances.

epoXy spray coaTIngs

VaccoaT

This stove-enamel finish filled with aluminium flakesshows resistance to climatic and salt spray tests atlevels similar to IVD aluminium. Even magnets with acoating thickness of only 5 μm withstand long-termautoclave and salt spray tests.

Compared to other spray coatings VACCOAT 10047provides a superior edge protection. The coating issuitable for application temperatures of up to 180 °Cin continuous operation.

Due to the excellent hardness of this stove-enamelfinish (typically 6-8 H pencil hardness), Al-spraycoating is not sensitive to mechanical damage.

An automated and highly cost-effective barrel-platingprocess is available for small parts.

IVD-alumInIum

IVD (= Ion Vapor Deposition) aluminium ensuresexcellent corrosion protection in both humid climatesand salt spray exposure. The cathodic protectionafforded by the aluminium coating permits continuoususe in water, for example. Furthermore, minor imperfections in the coating do notnoticeably impair corrosion resistance thanks to theelectrochemical protection provided by the aluminium.Because of the high ductility of the coating, mechani-cal loads merely cause deformation of the coatingsimilar to that shown by tin, and the protective effectremains unimpaired by damage to the coating. Incomparison to electroplated zinc layers, which are alsoused as cathodic protection for NdFeB, IVD aluminiumhas the following advantages:

• extremely high temperature resistance • no hydrogen embrittlement during coating process• no formation of loose white rust in corrosive atmosphere • excellent HAST resistance

Small parts (up to 25 g) are coated in a cost-effectivebarrel process. Heavy parts are handled as rackgoods. Contact marks caused by processing areprevented by special handling.

alumInIum spray coaTIngs

VaccoaT 10047


Galvanic tin plating provides good corrosionprotection against atmospheric influences, humidity,and weak acids and alkaline solutions. The tin platingapplied at VAC is dense and free of interconnectedpores. The typical plating thickness range formagnets is 15–30 μm. The finish of tin plating issilvery-white and slightly glossy.

No phase transitions occur between –40 °C and themelting point of 232 °C. The deposition process isoptimized by VAC for RE magnets especially toprevent hydrogen damage to the surface of themagnet during plating.

Small parts can be plated economically in a barrel.Larger parts are galvanized in a rack. The decision onwhich method to use is governed by the weight of thepart and/or the geometry (typical nominal values:< 25 g barrel; > 25 g rack).

The special merits of tin platings are their high resis-tance to environmental influences (e.g. 85 °C / 85 %relative humidity) as generally specified for electronicapplications. Tin is highly ductile and is almost free ofinternal stresses over a wide plating thickness range.Moreover, the process is highly reliable. There is norisk of cracking or flaking. Mechanical stress does notlead to chipping but merely to deformation of the tinplating, so that the magnetic material is still protectedsafely.

After thorough cleaning the tin plating is free of allresidues and thus provides an ideal surface for manyadhesives.

galVanIc-TIn galVanIc nIcKel

Galvanic nickel platings can be used as an alternativeto tin or as double plating in combination with tin.

In general, galvanic nickel provides superior protectionagainst a comparable plating thickness of tin. Theminimum plating thickness that we recommend forprotection against corrosion is 10 μm for nickel platingin comparison to15 μm for tin plating.

Because galvanic nickel platings are hard, abrasion-proof and easy to clean without residues, they are stillpopular today, especially for cleanroom applications.

VAC uses a special nickel plating process whichsupplies visually attractive semibright platings.


Table 5 compares the properties of the most impor-tant coatings and should be used as a guidelinewhen selecting surface protection for an application.It gives the minimum layer thickness of the variouscoatings and ensures adequate corrosion protectionin the majority of applications.

To meet more stringent requirements on corrosionprotection, the layer thickness must be adjustedaccordingly. Please note that improper handling mayharm the coating.

characTerIsTIcs

oF DIFFerenT coaTIngs

Micrograph of coverage with VACCOATat the edge of a magnet

1) Vickers hardness (nominal values) 2) Pencil hardness

Table 5: SURFACE COATINGS

tin (Sn) galvanic > 15 µm silver HV 101) humid atmosphere, < 160 °C electric motors, bright solvents sensor technology, mechanical engineering

nickel (Ni) galvanic > 10 µm silver HV 3501) humid atmosphere, < 200 °C clean-rooms, semibright solvents, small-sized motors, cooling lubricants linear motors, UHV undulators

epoxy automatic > 10 µm green > 4H2) humid atmosphere, < 200 °C applications spray coating spray coating salt spray test, with highestVACCOAT toxic gas test, corrosion 30033 solvents requirements

Surface Method Min. layer Colour Hardness Resistance Temperature Typical

thickness for to range application

corrosion examples

protection

aluminium IVD > 5 µm silver semibright HV 201) humid atmosphere, < 500 °C electric motors, (chromium VI salt spray test, sensor technology, free), yellow solvents aeronautic semibright applications (yellow chromated)

aluminium automatic > 5 µm yellow > 4H2) humid atmosphere, < 180 °C electric motors,spray coating spray coating semibright salt spray test, generators,VACCOAT toxic gas test, sensor technology,10047 solvents linear motors, motor vehicles

epoxy automatic > 10 µm black 4H2) humid atmosphere, < 200 °C segmented magnet spray coating spray coating salt spray test, systems, electric motors,VACCOAT toxic gas test, linear motors, 20011 / 20021 solvents motor vehicles


6. Forms oF supply

Magnets made of VACODYM and VACOMAX canbe supplied in magnetized or non-magnetized state.Normally the poles are not marked.

Owing to the magnetic anisotropy of VACODYM andVACOMAX, the parts are aligned along thepreferred direction relative to the geometry of thepart. The most common pole configurations areshown below:

Our experts with in-depth know-how will be pleasedto answer any questions on magnetizationtechniques. We have developed various packagingmethods for the delivery of magnetized parts whichcan – if necessary and in compliance with therigorous IATA regulations – be modified to meetindividual customers’ requirements for airfreight.Packaging should be agreed with the customer toensure efficient further processing upon delivery.

6.1 Types oF magneTIzaTIon

By leaving out the grinding process, competitivelypriced magnets with a pole surface of up to approx.6 cm2 can be die-pressed. Perpendicular to the di-rection of pressing, these netshape magnets exhibitthe tolerances as stated.

Owing to special die-pressing processes in the di-rection of pressing thickness tolerances of typically± 0.2 mm can be met at individually measured pointswithout subsequent grinding. Preferred shapes arecuboids and segments with typical thicknesses in therange of 2.2 to 8.0 mm. Our experts will gladly assistin the layout of the magnet geometry and the tole-rance of netshape magnets.

neTshape parTs

The pole surfaces of die-pressed sintered magnetsmade of VACODYM or VACOMAX usually need to beground. The tolerance after grinding is normally± 0.05 mm; values of ± 0.02 mm are possible.

The dimensions perpendicular to the direction ofpressing are largely determined by the dies and oftendo not require machining (netshape). Typicaltolerances for the sides of die pressed parts are:

If a non-pole-face surface requires machining,general tolerances as per DIN EN 2768 mK inconnection with tolerance levels as per DIN ISO8015 can usually be met. For shaped parts withmore complex geometry we usually offer a surfaceprofile tolerance. Tolerances for sliced parts are± 0.1 mm. On request, even tighter tolerances canbe met by grinding. If no tolerances are specified,we supply according to DIN ISO 2768 mK.

6.2 DImensIonal Tolerances

Tolerance (mm)*

±0.10 . . . ±0.20

±0.15 . . . ±0.30

±0.25 . . . ±0.40

±0.30 . . . ±0.60

±0.45 . . . ±0.90

±0.80 . . . ±1.50

±1.50 . . . ±2.50

up to 7

7 – 15

15 – 25

25 – 40

40 – 60

60 –100

100 –150

* precise data on request

Pole arrangements top view side view

for rodsand rings:axial

for rings:radial

for rings:diametral

for segments:diametral

Nominal dimensionsperpendicular to thedirection of pressing (mm)


W

H

T

Re

M

A

(LxW)

DIMENSIONS OF DIE-PRESSED VACODYM AP-MAGNETS (AXIAL FIELD PRESSED)CRITERIA FOR ECONOMIC MAGNET GEOMETRIES

Dd

TA

w

M

D

TA

M

R

TA

W

M

e

L

W

H

T

Re

L

M

W

H

TRe

L

M

b

��

Shape Type Sketch Dimensions Dimensions Remarks economical possible economical

Ring AP D �120 mm D �180 mm only d �3 mm 1 mm �T �70 mm thickness T ground (D-d)/2 = w �3 mm A <15000 mm2

d/D �0.6 D/10 �T �D/2 A <9500 mm2

Disk AP D �100 mm D �140 mm only D/10 �T �D/2 1 mm �T �70 mm thickness T ground

Cuboid AP L �120 mm L �150 mm only LxW �9500 mm2 LxW �15000 mm2 thickness T ground T �55 mm 1 mm �T �70 mm T �0.15 �� L/W �5 0.5 � Re � 5.0 mm

Loaf AP L �120 mm L �150 mm thickness W �50 mm 2 mm �H �55 mm T and width W ground T �0.6 H 2 mm �H �20 mm 0.5 �L/W �5 0.5 � Re � 5.0 mm

Arc- AP L �120 mm L �150 mm thicknessSegment W �50 mm 1.5 mm �T �50 mm T and width W ground 2 mm �T 20 mm ß �150 ° ß �80 ° W �70 mm 0.5 �L/W �3 0.5 � Re � 5.0 mm

Shaped AP W �45 mm H, W �150 mm onlyPart H �35 mm A �15000 mm2 thickness T ground A �1500 mm2 1 mm �T �70 mm W/H �3 1.5 mm �T �30 mm T �0.1 A 0.5 � Re � 5.0 mm

48


Cuboid TP W �70 mm W �110 mm Thickness T (HR) 2 mm �T �100 mm 1 mm �T �140 mm cut or ground 10 mm �H �55 mm TxW � 13000 mm2 W/H �2.5 H �80 mm Re � 0.5 mm (TxW)

Ring TP 8 mm �D �70 mm 6 mm �D �120 mm only outer diameter D ground(diametral) d �3 mm d �1 mm (D-d)/2 = w �2 mm w �1.5 mm 0.1 �d/D �0.65 0.1 �d/D �0.8 3 mm �H �55 mm 2 mm �H �80 mm H �5w H �8w

Disk TP 8 mm �D �70 mm 5 mm �D �120 mm only diameter D ground(diametral) 5 mm �H �55 mm 2 mm �H �80 mm H �D/4

H

T

W

M

Re

H

D

M

d

H

D

M


DIMENSIONS OF DIE-PRESSED VACODYM TP MAGNETS (TRANSVERSE FIELD PRESSED) CRITERIA FOR ECONOMIC MAGNET GEOMETRIES

DIMENSIONS OF ISOSTATICALLY-PRESSED VACODYM HR MAGNETS (UNTREATED, UNPROCESSED) CRITERIA FOR ECONOMIC MAGNET GEOMETRIES


Cuboid HR W �110 mm W �110 mm unprocessed with T �250 mm T �800 mm 6 mm � contour tolerance, A �7000 mm2 A �7000 mm2 Re approx. 5 mm

Disk, HR D �70 mm D �90 mm unprocessed with rod L �250 mm L �800 mm 6 mm � contour tolerance

Shapes and dimensions also available in VACOMAX with moderate restrictions (appropriate to the magnet quality).

T

W

A

M

Re

L

D

A

M


7. glueIng oF re magneTs

The majority of RE magnets produced by VAC areassembled into magnet systems using adhesives.When selecting an adhesive the following should beconsidered:

• static and dynamic load

• thermal load (time-span/frequency/ temperature range)

• thermal expansion of both partners

• size of bonding area

• corrosive load (resistance of adhesive to atmosphere and chemicals)

• quality of bonding (coating, roughness, etc.)

• material matching regarding electrochemical potentials (corrosion due to voltaic cell formation)

• thickness of adhesive gap

In the following we offer some advice on adhesivesand accumulated glueing methods for magnetsbased on our extensive experience at VAC:

a) Adhesives with acid content must not be used withRE magnets, particularly not with VACODYM. Acidicproducts in connection with humidity lead to rapiddecomposition of the magnet material at theadhesive/magnet interface and will damage thebond. Such adhesive must even be avoided whenmagnets are coated.

b) When bonding large surfaces with iron or othersubstrates, the coefficients of thermal expansion ofthe RE magnet materials must be taken intoaccount. In particular, in connection with VACODYM,which has a negative coefficient of thermal expan-sion (-1 x 10-6/K) perpendicular to the direction ofmagnetization, and thus, as a rule, parallel to theglueing surface, stresses build up due to strainsresulting from fluctuations in temperature which theglue must absorb. Our team of magnet experts willbe pleased to advise you on this matter.

c) When preparing RE magnets for glueing, sandblasting should be avoided. This processing stepmight lead to loosening of the microstructure on thesurface of the sintered magnets. Our permanentmagnets are supplied in a ready-for-glueing state.The passivation applied after cleaning provides asuitable base for most adhesives. However, if apre-treatment step directly prior to glueing isconsidered important, we recommend cleaning theglueing surface with a solvent such as acetone orwhite spirit.

d) An adhesive selected for an uncoated magnet isnot automatically suitable for a coated magnet. Forsurfaces which are particularly difficult to glue, e.g.nickel plating, the market offers tailor-made adhesi-ves. With coated magnets care must be taken toensure that the adhesive does not attack the coatingor cause blisters. VAC has in-depth experience witha large number of adhesives and the mostcommonly used surfaces, and will be pleased to helpcustomers select the right adhesive for theirapplication.


Documentation of the quality, environmental and in-dustrial safety management system was integratedinto a corporate quality management system in2003. It is currently based on the following set ofstandards:

• ISO 9001• ISO/TS 16949• ISO 14001• OHSAS 18001• ISO/IEC 17025

8. InTegraTeD managemenT sysTem

Quality is an essential aspect of our corporate policy.In order to reliably realize the high quality of ourproducts and services based on a quality manage-ment system certified in accordance with DIN ENISO 9001 and ISO/TS 16949, we priorize closecooperation of all operational divisions. Our TotalQuality Management (TQM) process has undergonecontinuous advancement since its introduction asearly as 1994, based on business excellencemodels and our corporate goals.

Our quality management-related actions have theaim of fulfilling customers’ expectations andachieving high customer satisfaction, both internallyand externally. To further optimize VAC-internalprocesses – with the primary objective of furtherreducing costs – the Six-Sigma analysis wasintroduced in all our operations in 2002.

We achieve the product quality demanded by ourcustomers by defining and implementing targetedQM measures in product and process planning,strictly controlling raw material procurement, andintegrating test sequences into processes using astatistical process control system (SPC). Standardfeatures of our quality management system includecompliance with relevant process feasibilities(cpk values) and documentation of essential mag-netic and geometric properties. For complex tasksor especially rigorous requirements, we work withour clients to define a tailored quality assuranceprogram. By providing qualified technical advice, wehelp to design and implement high-quality and cost-effective products and services; we also draw upquality assurance agreements (QAA) on request.

Like most other permanent magnet materials, sinteredmagnets of rare earth alloys are brittle. AlthoughVACODYM is mechanically more stable thanVACOMAX, it is impossible to rule out fine hairlinecracks or chipped edges in magnets of either material.These have a negligible effect, however, on themagnetic and mechanical properties of the products.

Unless we have a special agreement with our custo-mer, our quality inspection allows mechanical surfacedamages (flaking, edge and corner chips) up to a totalof max. 2 % per pole surface. For small magnets witha pole surface of < 20 mm2, the permissible extent ofchipping must be defined jointly with the customer.Fine hairline cracks covering up to a third of the cross-sectional area affected will not be rejected as long asthe mechanical stability in accordance with theintended use is met. In serial production, exchange ofsamples has proved of value in the testing anddefinition of the visual quality of magnets.

Under normal manufacturing conditions, slightamounts of magnetic dust and material debris mayadhere to finished parts, in particular to uncoated andmagnetized parts. If this is not acceptable, a coatingresp. individual packaging is to be provided.

The final inspection of our magnets and assemblies isnormally based on a standardized fixed sampling rate.Unless otherwise agreed with customers, we test toDIN ISO 2859-1, AQL 0.65 with the c = 0 acceptancecriteria. By consistently employing the latest quality as-surance techniques, we are frequently able to agreeto even higher quality requirements on request. Forinstance, magnets for the automotive industry typicallyrequire an additional process capability value ofcpk � 1.33 for critical dimensional characteristics.

Acceptance conditions for special magnetic propertiescall for clearly defined test procedures and referencesamples. A further prerequisite, in particular forVACOMAX, is that the parts are supplied in themagnetized state.

With miniature magnets – dimensions less thanapprox. 2 mm – reduced magnetization is to beexpected owing to surface effects and depending onthe position of the working point. If you require moreinformation, please contact us.

8.1 QualITy managemenT

8.2 TechnIcal Terms

anD conDITIons oF sale


8.3 enVIronmenTal anD

saFeTy managemenT

We are committed to protecting our environment andto using the available natural resources as econo-mically as possible. This principle applies to our pro-duction processes as well as to our products. Weevaluate potential damage to the environment rightfrom the development stage of our products, with theaim of avoiding or minimizing any harmful effects byimplementing precautions that frequently exceedthose stipulated by law.

VAC environmental management assures that thestandard of EN ISO 14001 is effectively put intopractice. Technical and organizational means for thispurpose are regularly audited and are subject tocontinuous improvement.

A further goal in the design of our products, proces-ses and workplaces is the health and safety pro-tection of our staff and our partners based onOHSAS 18001. Here the applicable laws, standardsand regulations are taken into account together withstate-of-the-art expertise on occupational medicineand industrial science.

Magnetized rare-earth magnets of VACODYM andVACOMAX exhibit magnetic field and exert strong,attractive forces on iron and other magnetic partsin their vicinity. Consequently, they must behandled with care to avoid damage. Owing to theirstrong magnetic forces there is a risk of injurywhen handling larger magnets. They shouldalways be handled individually or with the aid offixtures. We recommend protective gloves to beworn as well as for handling of uncoatedVACOMAX and Ni-coated parts, especially forpeople with allergies to metals.

The magnetic fields can change or damage thecalibration of sensitive electronic devices and mea-suring instruments. Please note that magnetizedmagnets must be kept at a safe distance (e.g. over2 m) from pacemakers, computers, monitors and allmagnetic data storage media (such as floppy disks,credit cards, audio and video tapes etc.).

Rare-earth magnets may generate large sparks onimpact. Never handle them in an explosive atmo-sphere.

Unprotected VACODYM and VACOMAX magnetsmust not be exposed to hydrogen. Its adsorptiondestroys the microstructure and leads to disinte-gration. The only effective protection is gas-proofencapsulation of the magnets.

Machining of magnets requires special safetyprecautions for the grinding slurry. For VACOMAXin particular, legal regulations regarding the hand-ling of Co-containing dust have to be observed.The EG Safety Data Sheets provide more compre-hensive information on the safety aspects involvedwhen handling VACODYM and/or VACOMAXmagnets.

9. saFeTy guIDelInes


10. appenDIX

The behavior of a magnetic material in a magneticfield is characterized by the correlation betweenmagnetic flux density (induction) B and magneticfield strength H (B(H) hysteresis loop). The samecorrelation can be described by the polarization J(J(H) hysteresis loop, Fig. I). The flux density B andthe polarization J are given by

The first quadrant of the hysteresis loop describesthe magnetization behavior of the material: whenapplying a magnetic field H, the flux density B of anon-magnetized material varies along the virgincurve (cf. Fig. I).

When all magnetic moments are oriented parallel tothe external magnetic field, the polarization J is at itsmaximum value, the saturation polarization Js(J = Js = const.). The flux density B, however, conti-nues to increase linearly with the field strength H.

The minimum field strength required to attain satu-ration polarization is referred to as the saturationfield strength Hs. If – in the magnetized state – themagnetic field strength is reduced, the flux densitychanges in accordance with the hysteresis loop andat H = 0 attains residual flux density (remanence) Br(intersection of the hysteresis loop with ordinate).

In the strongly anisotropic RE permanent magnetsdescribed here the remanence Br is in the same orderof magnitude as the saturation polarization Js :

10.1 TechnIcal BasIcs anD Terms

10.1.1 hysTeresIs loop

B = μ0H + J

Br ≈ Js

Fig. I

virgin cu

rve


The most effective use of a permanent magnet in sta-tic systems is when the working point P lies in the(BH)max point. In practice, shearing in the magneticcircuit should be selected so that the working point isat exactly this position or, preferably, just above it, i.e.is in slightly lower opposing field strengths.

For dynamic systems with changing operating straightlines (e.g. motors), shearing should be selected so thatthe working point of the magnet remains within thestraight line range of the demagnetization curve. Thereason is to ensure high stability with respect to outsidefield and temperature influences. The working pointshifts to higher opposing field strengths, e.g. from P1 toP2 if the air gap in a magnet system is increased. If thechange is reversed the original working point P1 canonly be reproduced if P2 is within the linear section ofthe demagnetization curve. However, if P2 is below theknee of the demagnetization curve, as shown in Fig. III,irreversible losses arise. The working point shifts to P3on a parallel inner return path with a correspondinglylower flux density. The rise of this return path is referredto as permanent permeability.

The second quadrant of the hysteresis loop describesthe demagnetization behavior of the material. Themost important characteristic terms of permanentmagnets which are operated exclusively in opposingfields (see “working point” for further details) aredetermined from the demagnetization curve.

The most important characteristic terms of apermanent magnet are:

– Remanence

This is obtained as described above from the inter-section of the hysteresis loop and the ordinate(at H = 0 we have Br = Jr).

– Coercivity

The field strengths at which the flux density B or thepolarization J reach zero are referred to as coercivitiesof flux density HcB or polarization HcJ respectively(intersection of the hysteresis loops B(H) and J(H) withthe abscissa).

– Energy Density

The product of the related values from flux density Band field strength H can be attained from any pointalong the demagnetization curve (see Fig. II). This pro-duct represents the energy density and passesthrough a maximum value between remanence andcoercivity, the maximum energy density (BH)max. As arule this value is used to grade permanent magnetmaterials.

– Working Point

The magnetic field originating from the poles of apermanent magnet has a demagnetizing effect as itis in the opposing direction to polarization J. Theoperational state of a permanent magnet is conse-quently always in the range of the demagnetizationcurve. The pair of values (Ba, Ha) applying to therelevant operational state is referred to as workingpoint P. The position of P depends on the geometryof the magnet or, in magnetic circuits with softmagnetic flux conductors, on the ratio of air-gaplength to magnet length. P is obtained from theintersection of the working or shearing lines with theB(H) curve (see point P1 in Fig. III).

10.1.2 DemagneTIzaTIon curVe

Fig. II

Fig. III

Fig. IV


The demagnetization curves of permanent magnetsare temperature-dependent.

This dependency is characterized by the tempera-ture coefficients of the remanent flux density TC(Br)and the coercivity TC(HcJ):

A change in temperature causes the working pointto shift on the working line (see fig. IV). As long asthe working point stays within the linear region of thedemagnetization curve, the changes in flux densityare reversible, i.e. after cooling the flux densityreturns to its original value. In all other cases anychange in flux density is irreversible (irreversiblemagnetic losses) and can only be reversed byremagnetization.

To avoid irreversible changes in the flux densitythrough temperature fluctuations, the working pointmust remain within the linear section of the demag-netization curve over the entire temperature rangein which the magnet is to be used.

A permanent magnet can be completely demagneti-zed by heating to temperatures above the Curietemperature Tc. After cooling to the initial tempera-ture the former state of magnetization can be repro-duced by remagnetizing providing heating has notcaused changes in the microstructure (see page 36).In contrast, thermal demagnetization may not beperformed on VACOMAX because the range ofCurie temperature in these alloys is substantiallyhigher and at temperatures greater than 700 °Cphase transitions occur which may destroy thepermanent magnet properties irreversibly.

10.1.3 InFluence oF TemperaTure

TC(Br) = ––– · ––– · 100 (%/K)1 dBrBr dT

TC(HcJ) = ––– · ––––– ·100 (%/K)1 dHcJHcJ dT

Unit and SI units1) Conversionsymbol table

flux density B T (Tesla) 1 T = 1 Vs/m2 = 10 kG (Induction) (Kilogauss)

Polarization J T (Tesla) s. flux density B

Magnetic field A/m 1 A/cm = 0.4 � Oe strength H � 1.257 Oe (Oersted)

Energy density kJ/m3 1 kJ/m3 = 0.126 MGOe(BH)max(Max. energy product)

Magnetic Wb (Weber) 1 Wb = 1 Vs = Flux � 108 Mx (Maxwell)

The most important magnetic sizes, their units and

conversions are as follows:

magneTIc Values

anD unITs

1) Basic units in SI systems: meter, kilogram, second, Ampere. The unitsGauss, Oested or Maxwell in the conversion table refer to the cgs or Gaus-sian system with the basic units centimeter, gram and second.

55

Material CROVAC® CROVAC CROVAC CROVAC MAGNETO®- VACOZET® SEMIVAC® SENSOR®- 12/160 16/160 12/500 16/550 FLEX 35U 258 90 VAC

Main components FeCrCo CoFeV CoFeNi FeCrCoNiMo FeNiAlTi

Variant isotropic • •

anisotropic • • • • • •

Product wire • • •

Options strip • • • • • • •

wire • •

strip • • • • •

Remanence (T) 0.85-0.95 0.80-0.90 1.15-1.25 1.10-1.20 0.80-0.90 1.30-1.50 0.90-1.30 1.30-1.60

Coercivity(kA/m) 36-42 39-45 47-55 53-61 25-30 2.0-3.2 4-10 1.5-2.6

Coercivity tolerance(kA/m) +/- 2 +/- 2 +/- 3 +/- 3 +/- 1.5 +/- 0.15 +/- 0.5 +/- 0.15

Energy density(BH)max (kJ/m3) 13 15 35 37 12 2.5 5 3

Density (g/cm3) 7.6 8.1 8.1 7.85 7.65

Curie temperature (°C) 640 700 800 700 630

Max. applicationtemperature (°C) 480 500 400 450 300

TK (BR) -25 °C - 250 °C (%/K) – 0.03 -0.01

Therm. expansion(RT-100 °C) (10-6/K) 10 11 11

El. resistivity(�mm2/m) 0.7 0.65 0.15

Vickers hardness HV as rolled 330 480 400

soft annealed 230

heat treated 480 900 600 700 600

Tensile strength RM as rolled (MPa) 1150 1850 1700

soft annealed (MPa) 620

heat treated (MPa) 1500

Elongation as rolled (%) 2 1.5 3

soft annealed (%) 20

heat treated (%) 0.5

The elongation is given for AL50 (strips) rsp. AL100 (wire).The above mechanical properties are given as related values.

A detailed description of these materials is included in our leaflet PD-003, which is available on request.


11. DUCTILE PERMANENT MAGNET ALLOYS AND SEMI-HARD MATERIALS (MAGNETIC AND MECHANICAL PROPERTIES)


VAC SALES USA LLC

2935 DOLPHIN DRIVE / SUITE 102ELIZABETHTOWN, KY 42701 PHONE +1 270 769-1333FAX +1 270 765 [email protected]

VACUUMSCHMELZE GMBH & CO. KG

GRÜNER WEG 37D 63450 HANAU / GERMANYPHONE +49 6181 38 0FAX +49 6181 38 [email protected]

VACUUMSCHMELZE SINGAPORE PTE LTD

1 TAMPINES CENTRAL 5, #06-10/11CPF TAMPINES BUILDINGSINGAPORE 529508PHONE +65 63 91 26 00FAX +65 63 91 26 [email protected]

PD002 – Edition 2012

© VACUUMSCHMELZE GmbH & Co.KG 2012. All rights reserved.

All materials marked® are registered trademarks of VACUUMSCHMELZE GmbH & Co.KG.

ADVANCED MATERIALS – THE KEY TO PROGRESS

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