VDM Report No. 27Soft magnetic Ni-Fe base alloys.

ThyssenKrupp VDMA company ofThyssenKrupp

Steel

TK

B, J

B

B

H

µ

S

R

-H C H C

-B S

-B R

B

H

VDM Report No. 27Soft magnetic Ni-Fe base alloys.Physical basics and specific applications.

Dr. Heike Hattendorf

ThyssenKrupp VDM GmbH58791 Werdohl

Contents.

Introduction 2

Physical basics

Magnetic variables 3

Exchange integral 5

Anisotropy constants 6

The Ni-Fe alloy system 8

Adjusting the properties

High permeabilities in high-nickel alloys 9

Permeability as a function of temperature 11

Effects on the shape of the hysteresis loop 12

- Hysteresis loop 14

- Flat loop 16

- Rectangular loop 16

- Lattice defects 17

Textures of medium-nickel alloys 18

Annealing under a longitudinal magnetic field 20

Ni-Fe alloy types

Ni-Fe alloys with a high nickel content 22

Ni-Fe alloys with a medium nickel content 25

Alloy production, processing and final anneal 28

Applications

Residual current circuit breakers 30

Relays for residual current circuit breakers 31

Transducers 32

Pulse transformers 33

Low-distortion transformers for modems 34

Shielding 35

Summary 36

List of variables and units used 37

Literature 40

Material tables 41

Forms supplied 45

Sales organisation 46

Imprint 49

2 Introduction.

Soft magnetic alloys have played a decisive rolein electrical engineering for over 100 years now.Typical applications include the pole pieces ofelectric motors, transformer sheet packs (Figure 1),shielding, and yokes and armatures in relays.Starting from the original pure iron, a large num-ber of soft magnetic alloy types have been devel-oped over time, each of them improving on spe-cific magnetic properties. Today, soft magneticalloys include:

- Fe-Si alloys - Fe-Ni alloys- Fe-Co alloys- amorphous alloys- nano-crystalline alloys, and- ferrites

This report describes the properties and applica-tion areas of nickel-iron alloys. It starts with abrief outline of the basics of magnetism.

Figure 1: Transformer station (5000/125 volt)from Augsburg, designed as a poster column,1900 (original).

(Photo: German Museum, Munich)

3Physical basics.Magnetic variables.

A magnetic field can be generated with the aidof a current-carrying conductor coil. If a softmagnetic material is introduced into the coil'sinterior, the magnetic field strength within thismaterial will be higher than the field in the coilwould be without the soft magnetic alloy [1], [2].In other words, the soft magnetic material actsas a sort of amplifier for the magnetic field. Theterm "magnetic field", however, requires furtherdefinition.

The magnetic field strength H describes thegenerating field which in the case of a current-carrying coil, for example, depends only on thecurrent and the coil geometry. To describe theamplifying effect, a further field parameter mustbe introduced, namely the magnetic flux densityB. The generating field is the same in the softmagnetic material and in air. The magnetic fluxdensity B is greater in the soft magnetic materialthan in air, depending on the effective amplifica-tion. B is the magnetic parameter, which is responsible for the induction of currents! Thequotient B/H indicates the absolute permeability. In practice, relative permeability is used morefrequently:

µ = B/µ0H where µ0 = magnetic field constant

= 1.257·10-4 Tcm/A.= 1.257·10-6 Tm/A.

H is measured in amperes / metre (A/m), B intesla (T). For a field in vacuum conditions µ = 1.For a field in air, µ ≈ 1. The difference betweenthe magnetic flux density B in a soft magneticmaterial and the magnetic flux density B0 in avacuum is designated the magnetic polarization J:

J = B - B0 = µµ0H -µ0H

Soft magnetic materials are characterized byhigh permeabilities, i.e. as a rule B0 can beneglected.

4

The relationship between B and H is not unique;and a plot of B versus H will take the shape of ahysteresis loop (Figure 2). As the magnetic fieldstrength H increases, B (or J) will reach saturati-on; the saturation flux density BS (or saturationpolarization JS) is obtained as a result. If themagnetic field strength is reduced to H = 0, theremanent magnetic flux density BR will remainwithin the material. The zero value of the mag-netic flux density is only reached with a negativeapplied magnetic field strength, the coerciveforce -HC. A further increase of H in the negativedirection yields B = -BR. As H increases in thepositive direction, B assumes the value 0 at HC

and finally saturation induction BS. The initialmagnetization curve is unique, which is why it isalso termed a virgin curve. If a specimen is runthrough multiple full remagnetization cycles with

a fixed peak value of magnetic field strength H,and the peak value of the magnetic flux density B is measured, and this process is repeated withvarious magnetic field strength values H, themeasured value pairs (H, B) will lie on the com-mutation curve which is practically identical withthe initial magnetization curve.

Applying magnetic field strength levels right upto the peak value of H during alternating mag-netization cycles will result in an amplitude per-meability µa [3] of

µa =

at the peak value of magnetic flux density B.

Special permeabilities which are frequently usedfor characterizing a material include the initialpermeability (amplitude permeability) µi for H →0,permeability µ4 at H = 4 mA/cm, and the maxi-mum permeability µmax.

Soft magnetic materials are used in alternatingfields with varying frequencies. As the frequencyincreases, the hysteresis loop widens, HC rises,and the permeabilities are reduced. It is there-fore important to differentiate between the valuesof the above mentioned variables according tothe frequency at which they have been mea-sured, i.e. at a quasi-static frequency close to 0 Hz or – as is often the case – at 50 Hz or evenhigher frequencies (Figure 3).

Each time the direction of magnetization is revers-ed, some useful energy is wasted in overcominginternal friction. This loss is proportional to thearea covered by the hysteresis loop. The areacovered by the magnetization curve yields theremagnetization loss per unit volume for a com-plete cycle [1].

o B dH =

Remagnetization loss can be broken down intovarious types. The hysteresis loss is the reduc-tion in area covered by the static hysteresis loop.Normal and anomalous eddy current losses andthe residual loss are the loss types that causethe hysteresis loop to widen at frequencies great-er than zero [4].

Soft magnetic materials can be readily remagnet-ized, i.e. their permeabilities are high, and both re-magnetization loss and the coercive force are low.

B

µo H

B, J

B

B

H

µ

Initial curve ≈ Commutation curve

S

R

-H C H C

-B S

-B R

B

H

Figure 2: The hysteresis loop.

B

H

Eddy current losses

Static hysteresis loop

50 Hz Hysteresis loop

Figure 3: Hysteresis loops for various frequencies (schematized).

hysteresis lossunit volume∫

ˆ

B = Magnetic flux densityH = Magnetic field strengthBR = RemanenceHC = Coercive force

5Physical basics.Exchange integral.

Soft magnetic materials are designated "ferro-magnetic" substances after their best-knownrepresentative, iron (Latin: ferrum). Other ferro-magnetic substances include Co, Ni, Cr, Mn andrare earths. The atoms of ferromagnetic sub-stances have a "magnetic moment", i.e. theyreact to an external magnetic field just like themagnetic needle of a compass. The magneticmoment is the sum total of the "magneticmoments" of all the electron spins (electron rotation around its own axis) and the angularmomentums of the electrons orbiting around thenucleus. The magnetic moment of ferromagneticelements in particular originates from the spin ofelectrons from open electron shells within atoms.

However, the presence of a magnetic moment ina material's atoms alone does not make it a fer-romagnetic substance. In a ferromagnet, themagnetic moments of the individual atoms arealigned in parallel by interaction energies ofinner-shell electrons, i.e. without an externalmagnetic field acting on the material (Figure 4).

This leads to spontaneous magnetization. Spinning a magnetic moment out of its parallelposition requires energy, the so-termed ex-change energy wA between two magneticmoments [1], [2]:

wA = IA S2

2(for small values)

where IA is the exchange integral, S the spinquantum number (proportional to the atom'smagnetic moment), and the angle betweentwo neighbouring magnetic moments. As thetemperature increases, thermal oscillation com-petes with the ferromagnetic tendency for spinsto align and causes them to fluctuate around theideal parallels. When the temperature risesbeyond the Curie temperature TC, thermal oscillation becomes so strong that the ferromag-netism is broken down. The directions of the atom-ic magnetic moments are then statistically distri-buted. In the presence of an external magneticfield, they tend to align in parallel to this field tosome extent, an effect called paramagnetism.

Figure 4: Orientation of magnetic moments in atoms in the ferromagnetic and paramagnetic states.

Ferromagnetism

Paramagnetism

The atoms of substances such as metals do notfollow a random orientation but are regularlyarranged on a crystal lattice. Figure 5 shows asimple two-dimensional case. If this is extendedinto the third dimension, a cubic lattice is obtain-ed. A large number of metals are arranged insuch a cubic lattice. For example, iron and Fe-Sialloys of a specific type are arranged in a body-centred cubic lattice, while nickel-iron alloys arearranged in another specific type, the face-cen-tred lattice. Although other crystalline magnetic

materials, such as ferrites, have a far more com-plex structure, the basics explained below for asimple cubic lattice apply to all of them.

In a cubic lattice, specific directions, e.g. theedges or diagonals, are characterized by theirsymmetry (Figures 5, 6). The magnetic momentsdo not follow a random orientation but specificpreferred directions, such as the edges or thediagonals. In the case of Fe and Ni-Fe with medi-um nickel contents, the preferred magnetic direc-tions are the cube edges, and for pure nickel thebody diagonals (Figure 6).

These are the easy magnetization directions.Changing the orientation of magnetic momentsfrom the preferred direction requires energy. Forexample, if a material is used in a 50 Hz trans-former, the orientation of its magnetic momentsis changed 100 times per second. The energyrequired for this is termed the crystal anisotropyenergy Ek. It can be described by the followingequation [1], [2]:

Ek/V = K1 (α12 α2

2+α22 α3

2+α12α3

2 ) + K2 α12 α2

2 α32

where α1, α2, α3 are the cosines of the angle be-tween the magnetization direction and the rele-vant cube edge, V is the volume unit, and K1, K2

are proportionality constants. K1 is significantlygreater than K2. In most cases, K1 will suffice todescribe experimental findings. The smaller theamount of K1, the lower the amount of energyrequired to deflect the magnetic moments from a preferred direction. If the cube edges are thepreferred directions, K1 is > 0; if the body diago-nals are the preferred directions, K1 < 0. If, forexample, the cube edges are the preferred direc-tions, then there are 3 preferred directions.

In specific cases, there is only one preferreddirection. This denotes a case of uniaxial an-isotropy energy EU, where the above formulaapplies in a simplified form [1]:

EU/V = KU sin2

KU is the uniaxial anisotropy constant, the en-closed angle between the preferred direction andthe magnetization direction. Such anisotropiescan be induced, for example, by magnetic fieldsduring annealing or, as described in the follow-ing, by stresses in the material.

6 Physical basics.Anisotropy constants.

Edge Diagonal

Edge

Preferred magnetic directions: Edges Diagonals

Figure 6: Preferred magnetic directions for K1 > 0 and K1 < 0.

Figure 5: A simple two-dimensional cubic lattice.

Preferreddirections

K > 01

Examples:Fe, 50% Ni-Fe

K > 01

Preferred directions

Example:Ni

7

Figure 7: Change of length when applying a magnetic field to a ferromagnetic specimen.

If a ferromagnet is magnetized, it undergoesminor changes in length. This phenomenon istermed magnetostriction [1] and it causes,among other things, the hum of transformers.Magnetostriction is measured as the relativechange in length in the direction of the magneticfield at saturation polarization (Figure 7). It variesas a function of the direction within the lattice.With cubic lattices, two constants are sufficient:λ100 in the cube edge directions and λ111 in thedirection of body diagonals. The two constantsmay differ considerably from each other. Fre-quently the mean magnetostriction constant λS isused for polycrystalline materials with statisticaldistribution of the grain directions. Magnetostric-tion may assume a negative value – as in thecase of pure nickel, where magnetization leads toa reduction in length – or a positive value – aswith Ni-Fe alloys with a medium nickel content.

In a material with positive magnetostriction, thedirection of tensile stress becomes the preferredmagnetic direction; with negative magnetostric-tion it becomes the most difficult direction, whilethe directions perpendicular to the direction oftensile stress become preferred magnetic direc-tions.

There is a further anisotropy energy, the stressanisotropy energy Eσ :

Eσ/V = 3/2 λS σ sin2 KU = 3/2 λS σ(for an isotropic polycrystalline material)

σ is the tensile stress, the angle of deflectionfrom the preferred direction. Internal stressesthat exist in every material, no matter howcarefully it has been treated, have the sameeffect as external stresses. However, if stressanisotropy energies do occur, they are lower, the smaller the values of the magnetostrictionconstants.

Soft magnetic materials are characterized by low hysteresis losses, high permeabilities andlow coercive forces. An essential prerequisite for achieving these properties is to keep all anisotropyenergies at the lowest possible level becausethey make remagnetizing more difficult. In otherwords, the crystal anisotropy constant K1 and themagnetostriction constants λ should be smalland internal stresses should be minimized bycareful treatment of the material. The relation-

ship between µ or HC and the anisotropy con-stants K is governed in many cases by the follow-ing proportionalities [1]:

HC ≈ K/JS , µ ≈ JS2/µ0K

where K can be one, or a sum, of the anisotropyconstants mentioned above. The permeabilitiesbehave in reverse proportion to the coercive force values.

J = Js

J = 0

∆l/2

∆l/2

H

Magnetostrictionconstant

λ 23

∆ll

=

l

To achieve good soft magnetic properties in amaterial, the anisotropy energies must be low[1], [2] (see section "Anisotropy constants"). Thisis the case where the crystal anisotropy constantK1 and the magnetostriction constants λ100 andλ111 are very small or close to zero. Figure 8 plotsthese constants as a function of the nickel con-tent in the Ni-Fe system.

K1 passes through zero at approximately 75 %Ni, and the two magnetostriction constants λ100

and λ111 pass through zero at between 80 % and82 % Ni*). The anisotropy energies can thus bereduced to very low levels in the range of high-nickel Ni-Fe alloys which are characterized byhigh permeabilities, low coercive forces, lowhysteresis loss and a saturation polarizationbelow 1 T.

Other Ni-Fe alloys are positioned in the range ofapproximately 50 % Ni. This alloy group has thehighest saturation polarization among Ni-Fealloys. Permeabilities are lower than with 75 % to80 % nickel, because K1 is always greater than 0.In some cases permeabilities can be improvedby a specific treatment of the alloy.

8 The Ni-Fe alloy system.

Figure 8: Crystal anisotropy constant K1, magnetostriction constants λ100, λ111, saturation polarization JS andCurie temperature TC as a function of the nickel content (according to [5] [9]).

*) All units in % in the text denote % by mass.

quenched

cooled slowly

40 60 80 100

1

0

-1

-2

-3

20

0

-20

FeNi3

K i

n 10

W

s/cm

31

-3

in 1

0-6

100

111

Ni content in % by mass

JS

TC

40 60 80 100

Ni content in % by mass

J in

TS

600

400

200

0

1.6

1.4

1.2

1.0

0.8

0.6

0.4

9Adjusting the properties.High permeabilities in high nickel alloys.

Figure 9: The multicomponent system Ni, Fe + Cu (according to [10] – [12]).Curves for different cooling conditions from temperatures 900 °C.

Figure 8 shows that K1 and λ100 or λ111 in the two-component system nickel-iron never assume thevalue zero simultaneously. This can however beachieved by alloying with Cu, Mo or Cr. Unfortu-nately there is no way of reducing all magneto-striction constants to zero. It has been shownthough that the highest permeabilities can beachieved for λ100 ≈ 0 or λ111 ≈ 0.

Figure 9 presents the multicomponent system Ni,Mo, Fe + Cu ([10] -[12]). The K1 = 0 curves areplotted for various cooling conditions from tem-peratures 900 °C. K1 = 0 varies considerablyaccording to heat treatment. The curves shift tohigher molybdenum contents with slower coolingrates. The same effect can be achieved with atempering treatment at around 500 °C afterquick cooling from temperatures 900 °C. So itis possible to influence K1 subsequently and takeit down to zero by targeted heat treatment.

As the molybdenum content increases, the curves for K1 = 0 are shifted toward higher nickelcontents. Iron can be replaced with copper with-out any significant shift in the curves for K1 = 0.The behaviour of the magnetostriction constantsis exactly the reverse: their passage through zeroas a function of heat treatment varies by lessthan 0.05 % Ni. On the addition of molybdenum,the curves for λ100 or λ111 stay the same withnickel content. When iron is replaced with cop-per, their passage through zero shifts to lowernickel contents, i.e. there are many ways ofreducing K1 and one of the three magnetostric-tion constants to zero. The technically relevantalloys are positioned close to the curve for "Cooled quickly from 550 °C". A few examplescan be seen in Table 1. K1 is strongly influencedby heat treatment (Figure 8). This has specificconsequences:

Table 1: Alloys with λ111 ≈ 0 and K1 ≈ 0.

Composition Strip thickness 50 Hz permeabilitiesin mm µ4 µmax

Magnifer® 7904 80 % Ni, 5 % Mo, 0.065 200-300 000 320-420 000 bal. Fe

Magnifer® 7754 77 % Ni, 5 % Cu, 0.065 200-300 000 320-420 0004 % Mo, bal. Fe

Magnifer® 75 76 % Ni, 5 % Cu, 0.065 150-200 000 240-320 000 2 % Cr, bal. Fe

>~

>~

>~

10

Magnifer 7904 1200 °C - 4h - Cooling rate 0.9 °C/min

440 460 480 500 520

Perm

eabi

lity

Withdrawal temperature T in °CE

500 000

400 000

300 000

200 000

100 000

K = 01K < 01

µ max

µ 4

K > 01

Figure 10: µ4 and µmax as a function of the withdrawal temperature TE.

Figure 10 shows the permeabilities of toroidalstrip wound cores in an alloy with 80 % Ni, 5 %Mo, balance Fe. The toroidal strip wound coreswere annealed at 1200 °C, followed by cooling inthe furnace at a rate of 0.9 °C/min. They weretaken from the furnace at the withdrawal tempe-rature TE and then allowed to cool quickly in air.The permeability µ4 at 4 mA/cm and the maxi-mum permeability µmax depend strongly on TE.Missing the optimum withdrawal temperature byonly a few degrees will result in a significant dropin permeability. This means that the temperaturecontrol system of an annealing furnace mustmeet the highest requirements in terms of pre-cision, if maximum permeabilities are to beachieved outside the laboratory as well.

Further, it should be noted that the maximum isasymmetrical. At temperatures above the opti-mum withdrawal temperature, permeability willsuffer a sharp drop. At the maximum, K1 = 0, asFigure 8 shows, faster cooling in the furnace or ahigher withdrawal temperature TE will result in K1 > 0;with slower cooling or a lower TE, K1 < 0.

11Adjusting the properties.Permeability as a function of temperature.

Measuring temperature °C

Magnifer 7904 1200 °C - 4h - Cooling rate 0.9 °C/min

-20 0 20 40 60 80 100

Perm

eabi

lity

µ4

515 °C500 °C495 °C

490 °C

475 °C

460 °C

400 000

300 000

200 000

100 000

0

K = 01 T E

K < 01

K > 01

Figure 11: µ4 as a function of the measuring temperature and withdrawal temperature TE.

Roughly constant permeabilities and magneticflux densities between -25 °C and 80 °C areimportant for many applications. Figure 11shows the temperature dependence of permea-bility µ4 between -25 °C and 80 °C.

In the specimens taken at 495 °C, this tempera-ture dependance is less marked at higher mea-suring temperatures and shows a significantdrop at low measuring temperatures. K1 = 0 atthe maximum of this curve, greater than 0 in therange of the significant fall, and smaller than 0 inthe range of the less marked ˝flat˝ temperaturedependance. At lower withdrawal temperatures,the passage of K1 through zero shifts to lowertemperatures and so the flat section of the curvecovers an ever increasing measuring tempera-ture range. The dependence of permeability ontemperature decreases, but the permeabilitylevel drops as well. This means a compromisehas to be found for the individual application between a low dependence on temperature andhigh permeability.

Hysteresis loop

Flat RectangularRound

Figure 12: Hysteresis loop shapes.

Table 2: Hysteresis loop description by of BR/BM.

12 Adjusting the properties.Effects on the shape of the hysteresis loop.

Hysteresis loop shape BR/BM

Round approximately 0.6 – 0.7

Flat < 0.5

Square approximately 0.9

The hysteresis loop can have a variety of shapes(Figure 12). These are described by the ratioBR/BS or by the ratio BR/BM, which probably reflectspractical conditions more correctly. BM stands fora defined magnetic flux density ≈ BS (Table 2).<

13

B

B B

B

B

∆B

∆B

0.8 T

H

H

0.8 T 0.8 T

0.8 T

H H

Pulsating

Sinus-shaped (50 Hz)

Magnetic field strength H Rectangular loop Flat loop

t

B

5A/m

5A/m 5A/m

5A/m

t

Figure 13: Magnetic flux change in sinus-shaped current and pulsating DC with a flat and a rectangular hysteresis loop.

For residual current circuit breakers with pulsedcurrent sensitivity, a material with a flat loop isrequired, [11] [13], to ensure that pulsatingdirect currents also induce a sufficiently largemagnetic flux change in the core. Figure 13shows this for a toroidal strip wound core with arectangular and flat hysteresis loop respectively.With a pulsating direct current the hysteresisloop will run in the region above to the upperremanent magnetic flux density. During the period with no current, the magnetic flux densitydrops to the static remanent magnetic flux density from which the next pulse starts. For acore with a rectangular hysteresis loop, the staticremanent magnetic flux density is very high.Hence, in the case of pulsating direct current exci-

tation, the achievable change in magnetic fluxdensity or flux density swing ∆B is much smallerfor a core with a rectangular hysteresis loop thanfor a core with a flat loop. Compared to a sinus-shaped magnetic field strength of identical value,the change in magnetic flux density will be some-what smaller in a core with a flat loop than in acore with a more rectangular loop. With pulsatingdirect current, on the other hand, the magneticflux density swing is greater because the rema-nent magnetic flux density is lower.

The shape of the hysteresis loop can be influ-enced and varied over a wide range by means oftargeted heat treatment.

14

Weiss domains

Figure 14: A ferromagnetic specimen broken down into Weiss domains (according to [1], [2]).

Bloch w

allDomain

Domain

Figure 15: Rotation of the magnetization direction in a Bloch wall (according to [1], [2]).

Hysteresis loopIn the section "Exchange integral" it was men-tioned that all magnetic moments in a ferromagnet-ic material are parallel. Although this is correct,in reality it is somewhat more complex. The atom-ic magnetic moments are not polarized parallel to each other throughout the material but withinindividual regions – the Weiss domains (Figure14) [1], [2].

The individual Weiss domains have differentmagnetization directions. They are separatedfrom each other by Bloch walls (Figure 15). A Bloch wall is a transition area between twoWeiss domains in which the neighbouring spinmagnetic moments rotate gradually from themagnetization direction of one Weiss domain toanother. In a demagnetized specimen the Weissdomains are so arranged that their magneticmoments cancel each other (Figure 16, uppersection).

When an external magnetic field is applied to ademagnetized specimen, the favourably posi-tioned Weiss domains grow at the cost of theunfavourably positioned domains, i.e. the Blochwalls are forced to move (Figure 16). The speci-men shows a magnetic polarization J and mag-netic flux density B unequal to zero. Of coursereal materials usually have lattice defects suchas dislocations, grain boundaries and impuritiesthat impede the Bloch wall movement. Theseinclusions or defects are often referred to as pin-ning sites. With very small magnetic field strengths,a minor bulge in a Bloch wall between its pinningsites suffices as movement. Magnetization is stillreversible; if the magnetic field strength H dropsto zero, the magnetic polarization disappears(Figure 17). This phenomenon is termed reversi-ble Bloch wall movement.

With greater magnetic field strengths the Blochwalls gradually detach themselves from their pin-ning sites and move towards a new equilibriumposition. This movement can be observed: it is known as the Barkhausen jumps which can,for example, be clearly heard as clicks in a loud-speaker. The magnetization cycle has now reached the steep section of the hysteresis loop.If H drops to zero now, J assumes a value diffe-rent from zero. The Bloch wall movement is nowno longer reversible.

15

B, J = 0

B, J > 0

H > 0

H = 0

Demagnetized

Bloch wall

Weiß domain

Figure 16: Magnetization of a demagnetized ferromagnetic specimen.

With further increased magnetic field strengths,the magnetization direction within the individualWeiss domains also rotate out of the preferreddirection (spin rotation processes, Figure 17).The magnetization curve becomes flatter until, on completion of all spin rotation processes, itreaches the saturation polarization JS. If themagnetic field strength is now reduced to zero,the magnetization direction returns to the nearestpreferred direction and the formation of Blochwalls commences. The remanent polarization JR

remains within the material. On the application ofa magnetic field strength in the opposite direc-tion, further Bloch walls form. The total polariza-tion becomes zero again only with a sufficientlyhigh magnetic field strength -HC, (coercive force).If H is further increased in the negative direction,the same processes will take place in the otherdirection, and so on.

The magnetic field strength H required to causethe Bloch walls to bulge, loosen and move varieswith the number and type of lattice defects. Per-meability and coercive force increases with great-er numbers of Bloch wall pinning sites. Henceobstacles to Bloch wall movement must be avoided.

J

JR

S

-HC HC H

IrreversibleBloch wallmovement

Reversible Bloch wall movement

Spin rotation processes

Initial curve

J, B

Figure 17: The various types of Bloch wall movement through the hysteresis loop.

16

ˆ

Toroidal strip wound core Later magnetic flux direction

Preferred direction

= direction of the magnetic fieldapplied during annealing

= induced uniaxial anisotropy energy ~ Ku

Figure 18: Heat treatment under a magnetic field transverse to the later direction of magnetic flux (transverse fieldannealing).

Flat hysteresis loopA flat hysteresis loop is obtained, when the spinrotation processes that govern the flat section ofthe loop, start at a very early stage of the remag-netization cycle (Figure 17). This is the case witha preferred direction perpendicular to the latermagnetic flux direction, so most of the Weissdomains are magnetized perpendicular to thelater magnetization direction (Figure 18).

To achieve this in high-alloy nickel alloys it isnecessary to make sure that K1 ≈ 0, i.e. there isno preferred magnetization direction. Then thematerial should be heat treated at temperaturesbetween 300 and 350 °C for 1 to 1.5 hoursunder a magnetic field perpendicular to the laterflux direction (Figure 18). This treatment is ter-med transverse magnetic field annealing. Itgenerates uniaxial anisotropy with a correspon-dingly high uniaxial anisotropy constant KU trans-verse to the later flux direction.

Figure 19 shows how the magnetic flux density Bin a field with a peak value H = 15 mA/cm varieswith the transverse magnetic field annealing timetQ. With a sinus-shaped magnetic field strength itdecreases continuously, with pulsating directcurrent (index "stat") it reaches a maximum. Withlonger times tQ ∆Bstat also decreases because thehysteresis loop becomes too flat and permeabili-ties drop to very low values.

An annealing treatment under a magnetic fieldcan also produce uniaxial anisotropy in medium-nickel alloys all of which always have K1 > 0. A transverse magnetic field annealing, for exam-ple, will result in very flat loops with a higher fluxdensity swing than in the high-nickel alloys [11].

Rectangular hysteresis loopA rectangular hysteresis loop is obtained whenmagnetization (Figure 17) is more or less exclu-sively governed by Bloch wall movement andalmost no spin rotation processes are required.This is the case if there is a preferred directionparallel to the later magnetic flux direction. Suchan example will be discussed in the section onmedium-nickel alloys.

Magnifer 7904 F

0 0.5 1.0 1.5

600

400

200

0

B

∆B stat

t in hQ

B in

mT ˆ

Transverse field annealing at 340 °C for tQ

statMagnetic field strength = 15 mA/cm

H (50 Hz)∆H ˆ

Figure 19: B, ∆Bstat as a function of the annealing time tQ under a transverse field.ˆ

17Adjusting the properties.Lattice defects.

Perm

eabi

lity

Grain diameter in

Degree of purity

Figure 20: µ4 as a function of the degree of purity r (reciprocal of the volume in % take up by inclusions, accordingto JIS G 0555) and grain diameter.

δ = kTC

aK1

The magnetic field strength H required to causethe Bloch walls to bulge, detach from their pin-ning sites and move depends on the number andtype of lattice defects. These pinning sites shouldbe avoided because the greater the number ofthese obstacles to Bloch wall movement, thelower a material's permeability. Generally, thepermeability of a classic crystalline material willbe higher, the lower the amount of impurities(nonmagnetic inclusions) it contains, the greaterits grain size, and the smaller the number of dis-locations. This explains why, for example, defor-mation should be avoided.

The structure of a Bloch wall is influenced byinteraction of the anisotropy energy and theexchange energy. In a 180° Bloch wall, forexample, the magnetic polarization vector rotatestowards its new orientation along the length δ(Figure 15). The magnetic moments of two neighbouring atoms form the angle betweenthem. This increases their exchange energy wA,which increases along with . The smaller , thesmaller wA, but the thicker the Bloch wall. As the magnetic moments within the wall are not aligned in a preferred direction, i.e. the crystalanisotropy EK is not equal to zero, EK increaseswith the Bloch wall thickness and thus acts in theopposite direction. The optimum Bloch wallthickness δ is obtained when the total wall ener-gy assumes its minimum [1]. In this condition,the following relationship applies:

a lattice constant k Bolzmann's constantK1 crystal anisotropy constant TC Curie temperature

The smaller K1, the thicker and the more blurredthe Bloch wall. This relationship is relevant in thecontext of inclusions. Not all inclusions areequally important but it is mainly those whosediameter is roughly equal to the Bloch wallthickness δ that act as pinning sites. The signifi-cantly smaller or larger inclusions are "over-looked" [2], [11].

Soft magnetic materials are not just magneticallysoft but often mechanically soft as well. The 80 %NiMoFe alloy, for example, has a hardness ofonly 110 - 130 HV5 (Table 12) in the final annea-

led condition. However, greater hardness coup-led with good soft magnetic characteristics wouldbe desirable for components susceptible to wear,such as sound recording heads. This is achievedby alloying with Nb, Ti, Al, etc. Yet a targetedannealing treatment leads to the formation offine precipitates which have an adverse effect onpermeability. In high-nickel alloys with K1 ≈ 0 thiseffect is limited because the diameter of the pre-cipitates is significantly smaller than the Blochwall thickness [11].

The permeability of the alloy 80 % Ni, 4 % Mo,Fe is essentially determined by the grain size inthe final annealed condition. Figure 20 plots µ4

as a function of the grain size for heats with avarying degree of purity r (reciprocal of the vol-ume in % taken up by inclusions, according toJIS). All the points lie on one straight line, inde-pendent of the degree of purity.

The degree of purity of these heats is so highthat the direct importance of the few relevantinclusions (in this case those in the µm-range) in their role as pinning sites for the Bloch walls is insignificant when compared with the grainboundaries. Indirectly, however, the degree ofpurity is important, because heats of the highestdegree of purity always have the greatest grainsizes.

18 Adjusting the properties.Textures of medium-nickel alloys.

In medium-nickel alloys, the saturation flux den-sity reaches a maximum yet the crystal anisotro-py constant K1 is always greater than zero, i.e.the cube edges are preferred magnetizationdirections. Permeability is therefore generallylower than with high-nickel alloys. It can, how-ever, be increased via a specific texture [11].

The crystal lattice does not usually extend acrossthe material but only over a specific area i.e. thegrain. In the neighbouring grain it is turnedthrough an arbitrary angle [14] (Figure 21). In an isotropic texture, the cube edge directions arestatistically distributed in each grain within thelattices (Figure 22 left). In the second texture inFigure 22, all grains are oriented approximatelyin the same direction, i.e. the cube edge direc-tion [15]. This can be achieved by a specific rolling and annealing procedure.

If a cube edge direction – i.e. a preferred magne-tization direction – lies approximately in thedirection of magnetic flux, remagnetization up tohigh flux densities is governed by Bloch wallmovements. The result is a rectangular loop withhigh permeabilities (see section ”Rectangularhysteresis loop”). In an isotropic texture whereonly very few grains are aligned in the preferreddirection, the spin rotation processes commenceat an earlier stage. This results in a somewhatflatter loop (see section "Flat hysteresis loop")with somewhat lower permeabilities, because thespin rotation processes are energetically lessfavourable.

In nickel-iron alloys, various types of textures canbe generated (Figure 23): in the cubic texture[15] one side of the cube lies on the strip planeand one cube edge points to the rolling directionwhich later becomes the magnetic flux direction.In a further texture, the cube is rotated throughapprox. 27° about the rolling direction, but thecube edge pointing in the rolling direction/latermagnetic flux direction retains its orientation. It isnamed ”(210) [001] texture”. This terminologywill be used to designate this texture in the follo-wing text.

Figure 21: Grains and grain boundaries in crystalline materials.

Figure 22: Explaining the term "texture" (schematic, two-dimensional).

Figure 23: Textures of NiFe alloys.

Grain boundary

Grain

Rolling direction Magnetic flux direction

Cubic texture

Strip plane

[ ]001 Rolling direction Magnetic flux direction

Strip plane

[ ]001

27°

.

(210) [001] texture

19

If a material of a specific grain size is deformedby a strain of only some 30 - 60 %, then afterrecrystallization annealing in the range of 900 °C to 1050 °C, the material will have a fine-grained,approximately isotropic microstructure. The grainsize varies with the annealing temperature. Withhigher strains the intensity of cubic texture increases. Depending on the initial grain sizemainly the cubic texture is formed after strainsbetween 90 % and 96 % (Figure 24). The cubictexture will become more marked as the strainincreases.

If the material is annealed at temperatures bet-ween 1100 °C and 1200 °C, a second recrystal-lizing process [17], [18] – called secondaryrecrystallization – will take place after the forma-tion of the cubic texture. As a result, the cubictexture will be destroyed and a (210) [001] tex-ture with a millimetre-range grain size will be gene-rated instead. Excessively high strains will lead tocentimetre-range grain growth with varying,magnetically unfavourable orientation directions(coarse grain). Each of the textures is clearlyidentifiable by its very marked grain structure(Figure 25). The transition area between the indi-vidual texture types varies with the degree ofimpurity and the chemical composition of thealloy.

The highest permeabilities are achieved with atexture of the (210) [001] type. A coarse-grainedmicrostructure has lower permeabilities becausethe grain orientation does not follow a preferreddirection. Permeabilities in a fine-grained, isotro-pic microstructure are also lower because thegrain size is significantly smaller. A cubic texturegenerates a marked rectangular loop; onceagain, however, the very small grain size resultsin low permeabilities. Table 3 gives an overviewof how texture influences a 48 % nickel-ironalloy.

Primary recrystallization

900 - 1050 °C

2.0 2.5 3.0 3.5

80 85 90 95 97

25

20

15

10

900

850

800Initi

al g

rain

dia

met

er in

µm

Tem

pera

tur

of in

term

edia

te a

nnea

ling

in °

C

fine-grained

-In (l/lo)

cubic texture

increasing intensity

Final stain in %∆l lo

Figure 24: Primary recrystallization in medium-nickel alloys at temperatures of 1100°C – 1200°C (according to [16]).

Table 3: Effect of textures on Magnifer® 50 (48% Ni, bal. Fe; strip thickness 0.20 mm for RG and TG, and 0.10 mm for T).

Primary recrystallization Secondary recrystallization

1100 - 1200 °C

2.0 2.5 3.0 3.5

80 85 90 95 97

25

20

15

10

Initi

al g

rain

dia

met

er in

µm

fine-grained

-In (l/lo)

(210

) [00

1] p

refe

rred

coarse-grained

Final stain in %∆l lo

900

850

800

Tem

pera

tur

of in

term

edia

te a

nnea

ling

in °

C

Figure 25: Secondary recrystallization in medium-nickel alloys at temperatures of 1100 °C – 1200 °C (according to[16]).

20 mm

Structure µ4 µmax

RG Isotropic 9,900 82,000

TG Secondary-recrystallized (210) [001] texture 16,000 95,000

T Cubic texture BR/BM >0.95 <1,000 40,000

20 Adjusting the properties.Annealing under a longitudinal magnetic field.

The following section looks at the process ofannealing under a longitudinal magnetic fieldparallel to the later flux direction (Figure 26) [11],[19, 20], a process referred to as longitudinalmagnetic field anneal. The toroidal strip woundcores are strung onto an isolated electrical con-ductor through which current of a suitable inten-sity is conducted during the heat treatment.

A precondition for this treatment is that the uniaxial anisotropy constant KU induced underthe magnetic field can assume a value largerthan the crystal anisotropy constant K1.

Figure 27 plots a comparison of the uniaxial anisotropy constant KU and the crystal anisotropyconstant K1. With an annealing temperature of450 °C, KU reaches its maximum at approxi-mately 65 % Ni, which is where the differencebetween the Curie temperature and the temper-ing temperature is greatest. From approximately55 % Ni, K1 can be reduced to a value of K1 KU.

In addition to cause generation of uniaxial ani-sotropy, the magnetic field annealing also chan-ges the value of K1. The values of K1 and KU varywith the annealing temperature and time. K1

becomes smaller, the lower the annealing tem-perature and the longer the duration of theannealing treatment because its value shiftstoward the "cooled slowly" curve (Figure 27). By contrast, KU increases with decreased annea-ling temperatures and increased annealingtimes.

Toroidal strip wound core

Later magnetic flux direction

= magnetic field directionduring annealing

= preferred directionof induced uniaxial anisotropy energy,strength ~ KU

Current I

Figure 26: Heat treatment under a magnetic field parallel to the later direction of magnetic flux (longitudinalmagnetic field annealing).

<≈

21

At lower temperatures (approx. 420 °C) K1 < KU

for an alloy with 55 % Ni [11], [19, 20]. The pre-ferred direction is the direction of the magneticflux density. The hysteresis loop is rectangularbecause the spin rotation processes start at avery late stage in the cycle (Figure 28); The permeability µ4 is low.

Slightly higher temperatures generate a statewhere K1 ≈ KU. The hysteresis loop is round andpermeabilities are very high. At even higher tem-peratures, the loop is extremely flat, despite thelongitudinal field annealing. Permeabilities drop,and ∆B for pulsating direct current increases significantly. In these conditions, KU << K1 [13].

Annealing without a magnetic field produces verylow permeabilities in alloys with 53 % to 65 %nickel. Below the Curie point of approximately530 °C, a material with 55 % Ni is magnetized tosaturation in its Weiß regions. This means thatduring cooling it is exposed to magnetizationwhich has a different direction in each Curie-Weiss region. From this it follows that a magneticfield treatment is essential for these materials.What has been said previously about the influ-ence of texture also remains valid here: maximumpermeabilities can only be achieved where theoptimum (210) [001] texture has been formed.

quenched

cooled slowly

Ni content in % by mass

40 60 80 100

-3K

in 1

0 W

s/cm

3

1

0

-1

-2

-3

FeNi3

K1

K after annealing at 450 °C

U

Figure 27: Ku as a function of the nickel content (according to [6] - [9], [23]).

µ max

µ

max

4 µ

∆B for ∆H=20 A/m

∆B

in m

T

Annealing temperature in °C

after longitudinal field annealMagnifer 53

400 420 440 460 480 500

µ4

100 000

75 000

50 000

25 000

0

200 000

150 000

100 000

50 000

0

800

600

400

200

0

0.8

0.6

0.4

0.2

0

B /B R M

B /

B

R

M

Figure 28: µ4, µmax, BR/BM and ∆B as a function of the annealing temperature during longitudinal field treatment.

22 Ni-Fe alloy types.Ni-Fe alloys with a high nickel content.

This group includes the nickel-iron alloys with thehighest initial and maximum permeabilities. Theirsaturation flux density BS lies between 0.7 and 0.8 T.

The soft-magnetic nickel-iron alloy Magnifer7904 with approximately 80 % nickel and approx-imately 5 % molybdenum has the highest techni-cally achievable permeability values of all nickel-iron alloys - i.e. µ4 ≥ 240,000 for a strip thick-ness of 0.065 mm – also with very small coerciveforces of HC ≤ 1 A/m (Table 4, Figure 31). Magni-fer 75 alloy with 75 % Ni, 2 % Cr and 5 % Cu canreach initial permeabilities of µ4 = 150,000 in stripof 0.065 mm thickness (Table 5, Figure 31). Itsductility is superior to that of the alloy with 80 % Niand 5 % Mo (Table 10). Major application areasinclude toroidal wound strip cores for integratingcurrent transformers in residual current circuitbreakers, transducers, laminations for LF transfor-mers, electronic differential current switches, low-distortion transformers in modems, as well asstamped parts for relays, stepped motors, sen-sors and shielding cases (Figures 29, 30, 33,34, 37 and 38).

Figure 29: Stamped core sheets in Magnifer® 7904 for low-distortion transmitters in modems.

Table 4: Alloys with approx. 80 % nickel. Further information is contained in the Magnifer® 7904, Magnifer® 8105data sheets and in the appropriate material tables.

Material Characteristic Magnetic Applicationsproperties properties

Magnifer® 79041) Bs = 0.74 T80 % Ni, 5 % Mo, bal. Fe

Magnifer® 7904 MP2401) Highest µ4 > 240,0002) Toroidal strip wound corespermeability for integrating current trans-

formers for residual currentcircuit breakers, transducers,laminations for LF transfor- mers, electronic differential current switches, low-distor-tion transformers in modems, as well as stamped partsfor relays, stepped motors,sensors and shielding

Magnifer® 7904 F 251) Flat loop ∆Bstat > 200 mT for Toroidal strip wound cores ∆Hstat = 15 mA/cm2) for residual current circuit

breakers with pulsed current sensitivity

Magnifer® 8105 Negative µ4 > 100,000 (DC) Stamped parts and magnetostriction Bs = 0.7 T shielding cases for

magnetic heads

Magnifer® 7904 MP H1 Hc < 1 A/m solid material

1) For further quality grades see appropriate material data sheets and/or tables. 2) Measured at 50Hz on toroidal strip cores of 0.065 mm thickness.

23

Figure 30: Toroidal strip cores in Magnifer® alloys.

B in

mT

ˆ

10 000

1 000

100

10

11 10 100 1 000

Magnifer d/mm7904 MP 0.06

75 ME 0.1053 MG 0.10

50 RG 0.1036 W 0.10

H in mA/cm

Figure 31: Magnetic flux density/Magnetic field strength curves for nickel-iron alloys.

Bsin

∆Bstat

∆Bdyn

B, ∆

B in

mT

ˆ

101 100

1000

10

100

Magnifer 7904 F 25 TK Strip thickness 0.065 mm

H, ∆H in mA/cmˆ

ˆ

Figure 32: Magnetic flux density/Magnetic field strength curves for Magnifer® 7904 F25 TK (80 % Ni, 5 % Mo, bal. Fe).

A transverse field annealing permits a flat hyste-resis loop with a very high unipolar flux densityswing to be generated for both alloys (Tables 4and 5, Figure 32). The indices "stat" and "dyn"stand for excitation via half-wave and full waverectified current respectively. The main applica-tion of these alloys is in the manufacture of inte-grating current transformers for residual currentcircuit breakers with pulsed current sensitivity.

By means of an annealing treatment all thesevariants can be produced in a grade with improv-ed temperature coefficient between -25 °C and80 °C (TC materials).

An increase of approximately 1 % in the nickelcontent of an 80 % nickel alloy produces anickel-iron alloy with negative saturation magne-tostriction – Magnifer 8105. The negative magne-tostriction increases this alloy's resistance tomechanical loads, e.g. when sealing it in synthet-ic resins. It is therefore mainly used in the manu-facture of shielding cases and pole pieces formagnetic heads in audio equipment (Table 4).

24

By alloying Magnifer 77 Ti Nb with niobium andtitanium, the usually very soft and therefore notparticularly wear-resistant nickel-iron alloys areimproved in terms of their mechanical properties.In addition to relatively high initial permeabilitiesof µ4 ≥ 40,000 and a coercive force of HC ≤2 A/m, high hardness and wear resistance areachieved as well as good corrosion behaviour incyclic climate conditions as per DIN VDE 664.This is due to the precipitation of fine inclusionscontaining titanium and niobium, which are res-ponsible for the rise in mechanical hardness. Themost important applications for this alloy includemagnet armatures and legs for release relays inresidual current circuit breakers (Figure 37) aswell as magnetic heads in audio and videoequipment.

Figure 33: Integrating current transformers made of Magnifer®

alloys for residual current circuit breakers.

Figure 34: Shielding made of Magnifer® alloys.

Table 5: Alloys with 75 % nickel. Further information is contained in the Magnifer® 75 data sheet and in the mater-ial tables.

HC < 2 A/m solid material

Magnifer® 75 MH 2

Material Characteristic Magnetic Applications properties properties

Magnifer® 751) BS = 0.8 T 76 % Ni, 2 % Cr, 5 % Cu,bal. Fe

Magnifer® 75 ME 81) High permeability, µ4 >150,000 (50Hz) Toroidal strip wound increased ductility (0.065 mm Bd.) cores for transducers,

µ4 > 80,000 (50Hz) laminations (0.20 mm strip) for LF transformers,

shielding

Magnifer® 75 F Flat loop ∆Bstat ≥ 200 mT for Toroidal strip wound ∆Hstat = 20 mA/cm2) cores

Magnifer® 77 TiNb So Precipitation- µ4 > 40,000 (DC) Stamped parts 77 % Ni, 5 % Cu, 1 % Ti hardening: HC ≤ 2 A/m for relays, 2 % Nb, bal. Fe HV = 150 - 200 BS = 0.7 T magnetic heads

finish annealed,fully aged, good corrosion behaviour

1) For further quality grades see appropriate material data sheets and/or tables.

25Ni-Fe alloy types.Ni-Fe alloys with a medium nickel content.

Magnifer 53 F Strip thickness 0.10 mm

B, ∆

B in

mT

ˆ

100

10 000

10101 100 1000

1 000

H, ∆H in mA/cmˆ

B

∆Bstat

sin

∆Bdyn

ˆ

Figure 35: Magnetic flux density – Magnetic field strength curves for Magnifer® 53 F (55 % Ni, bal. Fe).

Magnifer 53 with approximately 55 % Ni has asaturation polarization of 1.5 T. The alloy is usedexclusively for toroidal strip wound cores (seesection "Annealing under a longitudinal magneticfield") and is manufactured in a number of vari-ants (Table 6).

Magnifer 53 MG 60, for example, owes its highpermeability of µ4 = 60,000 (Figure 31) to longi-tudinal field annealing. This alloy is used for trans-ducer cores and integrating current transformersin residual current circuit breakers (Figures 30and 33).

The Magnifer 53 F variant has a flat hysteresisloop and thus a high unipolar flux density swing.This alloy is used for integrating current transfor-mers in residual current circuit breakers with pul-sed current sensitivity (Figures 33 and 35).

In the case of the Magnifer 54 F variant, trans-verse field annealing generates a particularly flathysteresis loop and thus high pulse permeability.This alloy is mainly used for magnetic cores inpulse transformers and thyristor choke coils(Figure 36).

At 1.55 T, the saturation polarization of Magnifer50 with 48 % Ni is the highest achievable withinthe nickel-iron alloy system. The alloy is pro-duced in several variants (Table 7). These aredistinguished by their varying microstructures,which are adjusted by means of targeted rollingand annealing processes (see section on "Textu-res of medium-nickel alloys").

After final annealing, variant RG forms an iso-tropic, relatively fine-grained microstructure with initial permeabilities of µ4 ≥ 8,000 and coercive

force of HC ≤ 5 A/m. Typical applications includerotor and stator plates, toroidal strip cores for LF transformers, choke coils and transformercores for residual current circuit breakers andshielding (Table 7, Figures 30, 33, 34).

With variant TG, the final anneal produces ananisotropic microstructure with coarser grainsand (210) [001] texture. This gives the alloy verygood permeabilities in the rolling direction, withµ4 ≥ 14 000 (Table 7). A special variant (RG S)which lie between the RG and TG can be pro-duced by taking account of the conditions of downstream processing requirements.

Material Characteristic Magnetic Applicationsproperties properties

Magnifer® 531) For toroidal strip wound BS = 1.5 T55 % Ni, bal. Fe cores only, annealed

under a magnetic field

Magnifer® 53 MG 601) Highest µ4 > 60,000 (50 Hz) Transducers, integratingpermeability (0.10 mm strip) current transformers for re-

sidual current circuit breakers

Magnifer® 53 F Flat loop ∆Bstat ≥ 200 mT for integrating current trans-∆Hstat = 50 mA/cm2) formers for residual current

circuit breakers with pulsed current sensitivity

Magnifer® 54 F High pulse µp > 4,000 Pulse transformers, permeability bei tp = 50 µs thyristor choke coils

Table 6: Alloys with 55 % nickel. Further information is contained in the Magnifer® 53 data sheet and in the material tables.

1) For further quality grades see appropriate material data sheets and/or tables.

26

Figure 37: Relay parts in Magnifer® alloys.

Table 8: Alloys with 40 % nickel.

Figure 36: Chokes and transformers.

Material Characteristic Magnetic Applicationsproperties properties

Magnifer® 50 BS = 1.55 T48 % Ni, bal. Fe

Magnifer® 50 RG1) Rotor grade, µ4 > 8,000 (50 Hz) Toroidal strip wound cores, fine-grained (0.20 mm strip) laminations for LF transformers, isotropic HC < 5 A/m storage chokes, integrating cur-microstructure rent transformers for residual

current circuit breakers

Magnifer® 50 RG S Special variant Properties improved Rotor, stator plates,between 50 RG over 50 RG shielding and 50 TG

Magnifer® 50 TG1) Transformer grade, µ4 ≥10,000 ( ≥14,000) Laminations, toroidal strip anisotropic (50 Hz, 0.20 mm strip) wound cores for LF transformers, microstructure transducers, integrating

current transformers

Magnifer® 50 T Cubic texture, Remanence ratio Toroidal strip wound cores for rectangular hyste- BR/BM > 0.95 chokes, memory cores, ris loop (0.10 mm strip) pulse transformers

Magnifer® 50 MH1) Solid material HC < 8 A/m (< 5 A/m) Stamped parts for relays, µ4 >100,000 (DC) clocks and watches, stepped HC < 2 A/m motors, inductive rotaryµmax < 160,000 (DC) sensors and electrovalves

Magnifer® 50 B So1 corrosion resistant in cyclic climate condi-tions warm, humid/ dry cold

Material Characteristic Magnetic Applicationsproperties properties

Magnifer® 4008 High resistivity BS = 0.8 T Stamped parts for relays, 48 % Ni, 8 % Cr of HC < 5 A/m clocks and watches, bal. Fe 0.96 Ω mm2/m µmax > 100,000 (DC) stepped motors,

shieldings

Table 7: Alloys with 48 % nickel. Further information is contained in the Magnifer® 50 datasheet and in the mate-rial tables.

1) For further quality grades see appropriate material data sheets and/or tables.

27

In variant T the final anneal produces a markedcubic texture which, in turn, leads to rectangularhysteresis loop. The ratio of the remanence tothe saturation flux density is greater than 0.95(Table 7).

Variant MH is manufactured as a solid material.It is used in the watches and clocks industry, forarmatures and magnetic yokes in relays as wellas for stepped motors in photo cameras, induc-tive rotary sensors for the automotive industry(ABS) and in electrovalves (Figures 37 and 38).Variant B So1 features improved corrosion re-sistance in a climate cycling test with alternatingwarm and humid / cold and dry phases [21, 22].

Magnifer 4008 with approx. 40 % Ni and approx.8 % Cr (Table 8, Figures 37 and 38) is anotheralloy that is produced as a solid material. It isused for stamped parts for relays, clocks andwatches, and stepped motors. At 0.8 T, its satu-ration flux density is comparable to that of high-nickel alloys, although its magnetic propertiesare somewhat reduced. On the other hand,Magnifer 4008 is much more favourably pricedthan a high-nickel alloy.

Alloy Magnifer 36 with 36 % nickel has a satu-ration polarization of 1.3 T and a high resistivityof ρ = 0,75 Ω. It is available in two variants (Table 9).

With the first variant, the increase in permeabilityin the magnetic field strength range of H = 4 mA/cm to H = 80 mA/cm is very small. Typicalapplications are laminations for LF transformers,and chokes.

The second variant has higher permeabilities andlower coercive forces (Figure 31). Major applica-tions include solid components for relays, poleshoes, as well as strip and sheet for shielding,e.g. for speedometers. In addition the alloy isused for manufacturing transducer cores.

Figure 38: Stepped motors in analog quartz watches. The yoke and armature are madefrom nickel-iron alloys.

ˆ

ˆˆ

Table 9: Alloys with 36 % nickel. Further information is contained in the Magnifer® 36 data sheet and in the material tables.

1) For further quality grades see appropriate material data sheets and/or tables.

Material Characteristic Magnetic Applicationsproperties properties

Magnifer® 36 high resistivity BS = 1.3 T36 % Ni, bal. Fe 75 Ω mm2/m

Magnifer®36 K1) Small permeability µ16 = 2,300 ± 200 (50 Hz) Laminations, toroidal stripincrease small permeability wound cores for LF transfor-

increase between mers, chokes H = 4 to 80 mA/cm

Magnifer®36 W1) higher permeability µ4 ≥ 5,000 (50 Hz, Laminations, toroidal strip 0.35 mm Bd.) wound cores for LF transfor-HC < 15 A/m mers, solid components for

relays, pole shoes, shielding transducer cores

28 Alloy production, processing and final annealing.

Table 10: Mechanical properties (approximate values) of Ni-Fe alloys.Condition: hard rolled with strain ≥ 50 %.

Material Tensile strength Yield strength Elongation Hardness (bal. Fe) Rm in N/mm2 RP0,2 in N/mm2 A5 in % HV5

Magnifer® 36 630 600 5 20036 % Ni

Magnifer® 50 750 700 4 20048 % Ni

Magnifer® 75 860 800 5 27076 % Ni, 5 % Cu, 2 % Cr

Magnifer® 7904 1 000 900 4 35080 % Ni, 5 % Mo

The alloys are melted in air or under vacuumconditions and then continuously cast into billets.These are hot rolled to approximately 4 mm thickstrip which is pickled and then surface ground ifrequired. Following this, the hot strip is cold rol-led. Depending on the final strip thickness andfinal strain, intermediate annealing may benecessary. The strip can be rolled down to foilthicknesses as small as 20 µm.

The strip serves as starting material for the pro-duction of toroidel strip wound cores, lamina-tions, relay components and shielding. All for-ming processes including turning, drilling, mil-ling, bending, punching and deep drawing arepossible. The mechanical properties of Ni-Fealloys are listed in Tables 10 to 12.

The best welding process is usually resistancespot welding, although in principle other pro-cesses are also applicable.

29

Table 11: Mechanical properties (aproximate values) of Ni-Fe alloys.Condition: deep-drawable and bendable.

After processing, Ni-Fe alloys require a (final)recrystallization anneal. Depending on the in-tended application, this is carried out at tempera-tures between 750 to 1300 °C in cracked ammo-nia or pure hydrogen with a dewpoint < -40 °C or– better – < -60 °C. Subsequently, a magneticfield annealing may be necessary. After the finalannealing, stresses leading to plastic deforma-tion must be avoided since this would lead to aconsiderable loss in magnetic properties.

Lattice defects should be kept to an absoluteminimum throughout all manufacturing and pro-cessing steps.

To reduce the number of dislocations and grainboundaries, a high annealing temperatureshould be chosen (grain growth) and the great-est possible care should be applied during thecooling phase and when handling the final-annealed material, e.g. by placing the parts in aprotective container (avoidance of deformationand internal stresses).

Non-magnetic inclusions such as slag particlesand oxides must be avoided at all cost, i.e. ele-ments such as O, C, S, Al, Mg should be limitedto the smallest possible amounts. Metallurgicalmeasures such as deoxidation, stirring withargon and degassing under vacuum allow a highdegree of purity to be achieved in the material atmelt stage.

Table 12: Mechanical properties (aproximate values) of Ni-Fe alloys.Condition: finish-annealed.

Material Tensile strength Yield strength Elongation Hardness (bal. Fe) Rm in N/mm2 RP0,2 in N/mm2 A5 in % HV5

Magnifer® 36 440 290 30 130-15036 % Ni

Magnifer® 50 530 280 40 120-13048 % Ni

Magnifer® 75 600 290 40 140-16076 % Ni, 5 % Cu, 2 % Cr

Magnifer® 7904 750 310 40 140-16080 % Ni, 5 % Mo

Material Tensile strength Yield strength Elongation Hardness (bal. Fe) Rm in N/mm2 RP0,2 in N/mm2 A5 in % HV5

Magnifer® 36 200 40 90-11036 % Ni

Magnifer® 50 530 220 40 100-12048 % Ni

Magnifer® 75 580 220 40 110-13076 % Ni, 5 % Cu, 2 % Cr

Magnifer® 7904 580 250 40 110-13080 % Ni, 5 % Mo

30 Applications.Residual current circuit breakers.

A residual current circuit breaker protects peopleand equipment in electrical installations. It consists of an integrating current transformerfor recording leakage currents, a release relay,and a latch (Figure 39) [24].

All the currents from all the current-carrying linesin the electrical installations are passed throughthe integrating current transformer. Under nor-mal, trouble-free operating conditions, the sumof all incoming and outgoing currents is equal tozero. Any current that leaks into the earth due toan insulation defect is missing in the integratingcurrent transformer, which is then magnetizedaccordingly. As a result, voltage is induced in thesecondary winding, and the release relay connect-ed up to the secondary circuit activates the latch.

Since a current integrating transformer shouldreact not only to sinus-shaped currents but alsoto pulsed currents, it requires a core with a flathysteresis loop (see section "Flat hysteresisloop"). In addition, low temperature dependencebetween -25 °C and 80 °C is important. Theenergy needed for activating the release relay isprovided directly by the leakage current. Theinductive impedance of the release relay and theintegrating current transformer is therefore com-pensated with the aid of a condenser, to get opti-mal sensitivity.

Depending on the sensitivity of the residual cur-rent circuit breaker, various materials can beused for the core of the integrating current trans-former. Circuit breakers with 300 mA or 500 mArated leakage current, for example, are madefrom Magnifer 53 or Magnifer 50, depending onthe release circuit design. Magnifer 7904 is usedfor rated leakage currents of 30 mA and 10 mAdue to its high permeability.

S

T

W

R

Figure 39: Design of a residual current circuit breaker (according to [24]).

L Latch R release relayC Integrating current transformer T Test key

131

Klappanker

YokeCoil

Pin

Coil current a I

NebenschlussSpring

Permanent magnet

armature

Figure 40: Schematic illustration of a polarized relay.

Applications.Relays for residual current circuit breakers.

Figure 41: B(H) curve of the soft magnetic circuit of a relay.

B

HU PH H

Pulled-in armature

Releasedarmature

Hysteresis loop2

1

43

Table 13: Relay materials.

Material BS in T HC in A/m µmax (DC, 1mm)

Magnifer® 50 MH or B So 1 1.5 < 5 100,000

Magnifer® 7904 0.74 < 1 350,000

Magnifer® 77 TiNb So 0.7 < 2 250,000

A relay is an electromechanical switch that changesa low release current into mechanical movement.For many applications, relays are made of pureiron or Fe with 3 % Si for economic reasons.However, components such as residual currentcircuit breakers operating independently of themains voltage require a relay with very low re-lease current (e.g. approx. 0.1 to 0.2 mW). Here,nickel-iron alloys are used. Polarized relays areused [4, 25, 26] in most cases. A polarized relayconsists of a soft-magnetic circuit formed by anarmature and a yoke. This circuit is premagnet-ized by a permanent magnet so that the armatureis kept in position on the yoke. A coil current Ia

weakens the magnetic flux in the permanentmagnet so that the armature – and thus the relay– is released. The electric energy input is increa-sed by a factor through the spring's energy storage (Figure 40).

With the armature pulled in, the relay is in state 1 as shown in Figure 41. The coil current Ia re-duces the magnetic field strength down to HU

(state 2), the armatures is released (state 3), thecurrent – and thus the leakage current – is inter-rupted (state 4). To cause the relay to open, themagnetic holding force FM must be smaller thanthe holding force FF of the spring [26].

FM = B2AFe/2µ0 AFe cross sectional area

µ0 magnetic field constant

At the same time, FM - FF must be big enough toavoid the relay being susceptible to vibrationsand external fields. In other words, the magneticflux density B and the difference ∆B to the cur-rent-carrying state should be as big as possible.In addition, a low releasing sensitivity is required,which means a small release current Ia ~ HP –HU, i.e. a large ∆B must be generated with anappropriately small HP – HU (Figure 41). It follows that the magnetic circuit must have thehighest possible effective permeability µ*.

B = µoµ*H 1/µ* = 1/µ + d/l Fe

d = Total air gapIFe = Length of the magnetic circuit µ = Permeability of the material

This means very small air gaps in the range ofapprox. 1 µm and high permeabilities for thearmature and yoke material. The permanent magnet (low permeability) is therefore by passedvia a shunt, and so the release magnetic flux

need not pass through it. This also serves toobviate the risk of demagnetizing or remagnet-izing the permanent magnet.

The armature and the yoke require a materialwith high permeability, low coercive force andhigh saturation flux density. The material mustmaintain stable properties for an extended periodof time. In addition, it must be mechanically hardenough to ensure that the pole surfaces are notdeformed during switching. Another essentialprerequisite is that such a material must be suffi-ciently resistant to corrosion in cyclic climateconditions as per DIN VDE 664. Table 13 belowlists the alloys used for this application.

HP D. C. field generated

by permanent magnet

HU resultant field

with release current

32 Applications.Transducers.

“ Transducers are required for converting currentsor voltages in energy distribution systems intovalues that can be measured by LF measuringequipment [27]. For the ideal transducer, thecurrent ratio is in inverse proportion to the turnsratio.

n2/n1 = I1/I2 (see Figure 42)

In reality, the ratio will be smaller becauseaccount has to be taken of scattering, losses andthe actual load. The required accuracy must beensured in the conversion of the values to bemeasured. For the magnetic material used, thismeans that the dependence of the permeabilityon the flux density should be reasonably con-stant in order to achieve linear conversion behav-iour and thus high accuracy. High permeabilityand high saturation flux density make a compactdesign possible. Scattering can be reducedthrough the use of toroidal strip wound cores.

For this application, Magnifer 75 and Magnifer53 have proved most successful. Magnifer 75 isfrequently also used in combination with Fe 3 %Si. In this case, Ni-Fe cores ensure the highestpermeability at small signals while Fe 3 % Sicores ensures high signals.

Transducers of the type shown in Figure 42 canonly measure alternating currents. In modernconverter connections of the type used, forexample, in drive technology and electric heatingsystems, mixed currents occur which compriseboth DC and AC components. Such currents aremeasured using current measuring modules(Figure 44) [28, 29] which incorporate a Hallprobe (Figure 43). In a magnetized Hall probe, a voltage is excited that is proportional to themagnetic field within the probe. This Hall voltageis used for triggering an electronic amplifierwhich feeds a current I2 to an additional windingon the core. The magnetic field generated by thiscurrent is then compensated to zero by theamplifier. As a result, I2 = n1 I1/n2 is fulfilled.Since the flux density is compensated to zero,the core operates close to the coercive forcelevel that causes an offset. High-permeabilitytoroids in high-nickel Ni-Fe alloys are thereforeparticularly well-suited to this application.

I2

An2

n2

n1

=I1

I2

n1

I1

Figure 42: Design of a transducer.

Current-measuring module

Submodule

I2

I

R

R

H

64

+

_

5

3

U+ B

U- B

RM

2

1

I1

Figure 43: Current measuring module with Hall probe and compensation winding.

Figure 44: Current-measuring module.

33

Thyristors in power electronics are triggered bypulse transformers (Figure 45). They transformthe trigger voltage pulses to the required levelwhile ensuring potential separation between thecontrol and power components [28, 29]. Normallyunipolar square wave voltage pulses have to betransformed. In the magnetic core magnetic fluxdensity swing ∆B starts from the remanent fluxdensity. The following holds [27]:

- n2 AFe B(t) = ∫ U dt

where

n2 = Number of turns in the secondary windingU = Secondary voltageAFe = Cross sectional areat = Time

With a given voltage-time integral, a large fluxdensity swing permits the use of cores with asmall cross section and/or a small number ofturns and this ensures compact design. At the same time, very low coupling capacity andleakage inductance are also achieved - an indi-spensable condition if the gate trigger current isto rise steeply. The main inductance LH of thetransformer is then calculated as:

LH = n22

µ0 µP AFe / lFe

where

µP = Pulse permeabilitylFe = Length of magnetic circuit

The number of turns n2 in the secondary windingfor the specified voltage-time integral must belarge enough to permit the main inductance tobe set to a minimum value. For this purpose,high pulse permeability is advantageous.

Materials for pulse transformers must have alarge usable magnetic flux density swing andhigh pulse permeability, such as Magnifer 54 Fwith a very flat hysteresis loop.

Applications.Pulse transformers.

Figure 45: Circuit board with pulse transformers in Magnifer® alloys.

34 Applications.Low-distortion transformerin modems.

A modem allows computers to communicateover ordinary analogue telephone lines. How-ever, the limited frequency range of the analoguenetwork means transmission rates higher than2400 Baud can only be achieved with specialcoding techniques. This calls for special low-distortion transformers. Low-distortion in thiscontext means, that a sinus signal to be trans-formed should have a very low harmonic con-tent. The total harmonic distortion (THD) of a signal is the logarithm of the sum of the powersof all harmonics frequencies above the funda-mental frequency to the power of the fundamen-tal frequency.

THD= 10 log (Pharmonics/Pfundamental waves)

Low-distortion transformers are made from high-nickel alloys. Signal distortion can be reduced bymeasures such as the use of small strip thick-nesses and low magnetic flux densities. Figure46 shows a typical curve of total harmonicdistortion as a function of the frequency forMagnifer 7904.

For modems with transmission rates of56 kBaud, for example THD values smaller than-80 dB at 200 Hz are required.

Frequency (Hz)

10 100 1 000 10 000 100 000

Tota

l har

mon

ic

dist

ortio

n (d

B)

0

- 20

- 40

- 60

- 80

- 100

- 120

Figure 46: Typical curve of "Total Harmonic Distortion" as a function of frequency for Magnifer® 7904, measuredon a transformer core package ED-8 (strip thickness 0.20 mm).

35

Equipment that generates or is susceptible tointerference signals must be shielded.

The shielding property is described by the shielding factor S [32].

S = | Ha / Hi |

(In [32] the reciprocal Q or aS = -ln |Q| is used.)

The function of a magnetic shield is explained inthe following using an (ideally, infinitely long)round cylinder with the radius R and wall thick-ness d (Figures 47 and 48). The interferencefield Ha runs vertical to the cylinder axis (trans-verse field). Two borderline cases will be descri-bed:

a) Frequency f → (or d >>δ )S can be described by approximation as:

κ = electric conductivity

δ is the skin depth of the field into the shield.Figure 47 shows the field lines.

At high frequencies, the shielding effect is based on the eddy currents induced by the interferencefield; they displace the interference field from within the shield. In this case, good electric con-ductivity is essential for the shield, which is whycopper or aluminium are used for shielding high-frequency fields.

b) Frequency f ≈ 0 (or d << δ), and µ >> 1

Now S can be described by approximation as:

S = 1 + 1/2 µ d/R

The field lines are shown in Figure 48. The shiel-ding effect is based on the magnetic flux flowingvia the highly permeable and thus magneticallyconductive material. Because µ >> 1 the outerfield lines run almost vertically into the shieldingcylinder. Inside the cylinder they run almost par-allel to the cylinder surface. Inside, Hi is homoge-neous and parallel to the interference field Ha,without a shield present.

The shielding effect increases along with the per-meability. In cases like this, highly permeablematerials are used, especially nickel-iron alloys.

Shielding factors for Magnifer 36, Magnifer 50and Magnifer 7904 are set out in Table 14. Themeasurements were taken on cylinders with awall thickness of 0.35 mm.

Typical applications for shielding in nickel-ironalloys include sound recording heads, micro-phones, sensors and electron beam tubes. Thematerials are also used for cladding completeexamination rooms in hospitals where highlysensitive measuring equipment is used.

Tabelle 14: Shielding factor S of some soft magnetic materials, measured in the transverse field at 200 A/m oncylinders (length 300 mm, diameter 80 mm) with a wall thickness of 0.35 mm.

Material Chemical composition S

Magnifer® 36 36 % Ni, bal. Fe 60 60

Magnifer® 50 48 % Ni, bal. Fe 150 150

Magnifer® 7904 80 % Ni, 5 % Mo, bal. Fe 1 000

δ =exp ( ) 22nfµµ0 κ

S =1

2 2R d

µδ δ

8

. .

Hi = Field in the interior of the shieldHa = Interference field before the

shield

Figure 47: Field lines for a cylindrical shield in the case of high frequencies.

HaHi Ha

Hi

Figure 48: Field lines for a cylindrical shield in the case of a DC field.

Applications.Shielding.

36

There are two main groups of soft magneticnickel-iron alloys:

The first group comprises medium-nickel alloyswhose most important representatives areMagnifer 50 with 48 % nickel, balance iron andMagnifer 53 with approximately 55 % nickel,balance iron.

The second group is made up of high-nickelalloys, and their most important representativesare Magnifer 7904 with 80 % nickel, approxi-mately 5 % molybdenum and the balance iron,and Magnifer 75 with 76 % nickel, 2 % chromium,5 % copper and the balance iron.

They are used for:

- toroidal strip wound cores in integrating cur-rent transformers in residual current circuit breakers, transducers

- laminations for LF transformers, electronic differential current switches, low-distortion transformers in modems

- stamped and bent parts for relays, stepped motors, electrovalves, inductive rotary sensors,rotor sheets, stator sheets, magnetic heads

- shielding, storage chokes, and thyristor choke coils.

Summary.

37List of variables and units used.

ˆˆ

ˆˆ

<

Variable Unit NoteConcentration % Unless otherwise

specified, data given in percent indicate the percentage per mass

a Lattice constant m metre

A Cross sectional area m2

A5 Elongation % weight

B Magnetic flux density or induction T tesla 1 T = Vs/m2

mT 1mT = 0.001 T

BS Saturation flux density T

BM Magnetic flux density ≈ BS T

BO Magnetic flux density in vacuum T

BR Remanent magnetic flux density T

B Peak value of magnetic flux density T

Bsin Peak value of magnetic flux density Tin a sinus-shaped field

∆B Flux density swing Tin a pulsed magnetic field

∆Bstat Flux density swing Tin a half-wave rectified sinus-shaped field

∆Bdyn Flux density swing Tin a full-wave rectified sinus-shaped field

d Air gap or wall thickness m

E Energy J joule

Ek Crystal anisotropy energy J

Eu Uniaxial anisotropy energy J

Eσ Stress anisotropy energy J

F Force N newton

f Frequency Hz hertz 1 Hz = 1/s

H Magnetic field strength H = n1 I1 /lFe A/m, mA/cm 1 A/m = 10 mA/cm

H Peak value of magnetic field strength A/m

Hsin Peak value of magnetic field strength A/min a sinus-shaped field

∆Hstat Magnetic field strength swing of a half-wave A/mrectified sinus-shaped field

∆Hdyn Magnetic field strength swing of a full-wave A/mrectified sinus-shaped field

HV5 Vickers hardness at 49 N test force

HC Coercive force A/m

Hi Field in a shielding's interior A/m

Ha Interference field before shielding A/m

I Electric current A ampere

I1 Primary current A ampere

I2 Secondary current A ampere

IA Exchange integral J

J Magnetic polarization (induction) T tesla 1 T = Vs/m2

Variable Unit NoteJS Saturation polarization T tesla 1 T = Vs/m2

k Bolzmann's constant J/°C 1.38054 10-23 J/°C

K Anisotropy constant, single or total J/m3 1 J/m3 = 106 Ws/cm3

Ws/cm3

K1, K2 Crystal anisotropy constants J/m3 1 J/m3 = 106 Ws/cm3

Ws/cm3

KU Uniaxial anisotropy constant(s) J/m3

l Length m metrecm centimetre 1 cm = 0.01mmm millimetre 1 mm = 10-3 mµm micrometre 1 µm = 10-6 m

∆l Change in length m

l0 Initial length m

lFe Length of magnetic circuit m

L Inductivity L = n2 µ0 µ AFe /lFe H henry 1 H = 1 Tm2/A = 1 Vs/A

n Number of winding turns -

n1 Number of turns in primary winding -

n2 Number of turns in secondary winding -

P Power W watt 1W = 1 VA = 1 J/s

Q Reciprocal of shielding factor S -

r Degree of purity (reciprocal of the volumein % taken up by inclusions) according to JIS G 0555

R Radius m

Rm Tensile strength N/mm2 1 MPa = 106N/m2

MPa megapascal

Rp0,2% 0.2 % Proof stress MPa megapascal

S Spin quantum number -

S Shielding factor S = | Ha / Hi | -

t Time h hour 1 h = 3,600 ss second

tP Pulse duration s second 1 µs = 0.001sµs

T Temperature °C

TC Curie temperature °C

TE Withdrawal temperature °C

TM Measuring temperature °C

THD Total harmonic distortion -THD = 10 log ( Pharmonics/Pfundamental waves)

U Electric voltage V volt

V Unit volume m3 cubic metre

wA Exchange energy J

αi Cosine of the angle enclosed between -the magnetizing direction and the cube edges

δ Bloch wall thickness or depth of penetration m, µm

κ Conductivity 1/Ωm

38

39

Variable Unit Noteλ Magnetostriction constant -

λ100 Magnetostriction constant in the cube -edge directions

λ111 Magnetostriction constants in the direction -of body diagonals

λS Mean magnetostriction constant -

µ Relative permeability -

µ0 Magnetic field constant Tm/A 1.257·10-6 Tm/A

µa Amplitude permeability = B/µ0 H -

µi Initial permeability = amplitude permeability -for H → 0

µ4 Amplitude permeability at 4 mA/cm -

µ* Effective permeability of magnetic circuit - 1/µ* = 1/µ + d/lFe

(incl. air gaps)

µmax Maximum permeability -

µP Pulse permeability = ∆B/µ0∆H for an H- -pulse of the duration tP, pulse interval >>tP

µ∆ Permeability differential = dB/µ0dH -

Angle between two neighbouring -magnetic moments or angle between the preferred direction and the magnetizing direction

ρ Resistivity Ω mm2/m

σ Tensile stress N/m2

ˆ

40 Literature.

1) S. Chikazumi, Physics of Magnetism., Krieger-Verlag, Malabar, Florida

2) E. Kneller, Ferromagnetismus, Springer Verlag, Berlin/Göttin-gen/Heidelberg (1962)

3) IEC 404-6 oder DIN IEC 68(CO) 39 (1984), Verfahren zur Messung der magnetischen Eigenschaften von isotropen weichmagnetischen Nickel-Eisen-Legierungen der Typen E1, E3, E4

4) C. Heck, Magnetische Werkstoffe und ihre Anwendung, Hütig Verlag, (1967)

5) F. Hegg, Arch. Sci. phys. nat. 29 (1910), p. 592 ff; 30 (1910),p. 15 et seq.

6) K.E. Volk, Nickel- und Nickel-Legierungen, Springer Verlag, Berlin, Heidelberg, New York (1970) p. 55 et seq.

7) R.M. Bozorth, J.G. Walker, Phys. Rev. 89 (1953), p. 624 et seq.

8) I.M. Puzei, Fizika Metallov. i. Metallovedenie 11 (1961),p. 686 et seq.

9) R.C. Hall, J. Appl. Phys. 30 (1959), p. 816 et seq.

10) I.M. Puzei, B.V. Molotilov, Izvestijie Akademie Nauk SSR., Ser. Fiz. 22 (1958), p. 1244 et seq.

11) F. Pfeifer, C. Radeloff, JMMM 19 (1980), p. 190 et seq.

12) F. Pfeifer, Z. Metallkunde 57 (1966), p. 295 et seq.

13) F. Pfeifer, H. Wegerle in Berichte der Arbeitsgemeinschaft, Magnetismus Vol. 1, Verlag Stahleisen Düsseldorf (1983), p. 120 et seq.

14) G.E.R. Schulze, Metallphysik, Akademie Verlag Berlin (1974).

15) G. Gottstein, Rekristallisation metallischer Werkstoffe, Deutsche Gesellschaft für Metallkunde (1984).

16) B. Erpenbeck, Thesis, FH - Dortmund (1990)

17) G.W. Rathenau, J.F.H. Custers, Philips Res. Rep 4 (1949), p. 241 et seq.

18) E. Adler, H.G. Baer, Berichte der AG Magnetismus (1959) (AG Magnetismus, Düsseldorf 1960), p. 190 et seq.

19) F. Pfeifer, Z. Metallkunde 57 (1966), p. 240 et seq.

20) H. Hattendorf, B. Erpenbeck, Relation between texture and magnetic annealing of a 55 % Ni-Fe alloy, JMMM 112 (1992), p. 29 et seq.

21) B. Gehrmann, H. Hattendorf, A. Kolb-Telieps, W. Kramer, W. Möttgen, Corrosion behaviour of soft magnetic iron-nickel alloys, Materials and Corrosion 48 (1997), p. 535 et seq.

22) H. Hattendorf, A 48 % Ni-Fe alloy of low coercivity and improv-ed corrosion resistance in a cyclic damp heat test, JMMM 231 (2001), p. L29 et seq.

23) E.T. Ferguson, J. Appl. Phys. 29 (1958), p. 252 et seq.

24) G. Morgenthaler, L. Schreyer, R. Solleder, Fehlerstrom-Schutzschalter für eine zukunftssichere Schutztechnik, etc - Elektronische Zeitung 113 (1992), pp. 10 – 17

25) A. Heitbrink, Dissertation, Universität Duisburg, (1993)

26) H. Sauer, Relaisteil-Lexikon, Hütig Verlag, Heidelberg (1985)

27) K. Küpfmüller, Einführung in die theoretische Elektrotechnik, Springer Verlag, Berlin Heidelberg New York, (1984)

28) W. Kramer, Weichmagnetische Nickel-Eisen-Werkstoffe in induktiven Bauelementen für die Leistungselektronik, Seminar on Soft magnetic materials, TAW 1996

29) Datenblatt Strommessmodul, ThyssenKrupp VDM

30) Datenblatt Impulsübertrager, ThyssenKrupp VDM

31) Datenblatt Speicherdrosseln, ThyssenKrupp VDM

32) H. Kaden, Wirbelströme und Schirmung in der Nachrichten-technik, Springer-Verlag, Berlin Göttingen Heidelberg, (1959)

41

Magnifer 501)

1.3922 1.3926 1.3927

Ni 48 RNi 12 RNi 8 E 31 (F3)

17745 17405 17405 DIN IEC 740-2 (41301)

K94840/A 753

47.0 – 48.5

–

bal.

max. 0.05

max. 0.3 – 0.5

max. 0.3

max. 0.02

Mg max. 0.01

Rp 0.2 Rm A50 HV

700 750 4 200

280 530 30 125

Quality Permeability (min.) Coercivity

class µ4 µmax

MF 6 6000 70000 ≤ 8

MF 8 8000 70000 ≤ 8

MF 10 10000 80000 ≤ 5

MH 12 ≤ 12

MH 8 – – ≤ 8

MG 6 6000 70000 –

MG 10 10000 80000 –

Strip thickness ~ 0.2 mm

MT strip thickness 0.1 mm with cubic texture

1.55

470

+ 25

8.25

500

15

45

164

100 200 300 400 500

9.8 9.2 8.8 8.7 9.1

1440

–

good

good

Low coercive force, good permeability with low

hysteresis losses. High saturation induction.

Transformer, transducers, residual current circuit

breakers, relay and shielding components, memory

cores, pulse transformers, magnetic switches,

toroidal strip cores, laminations, stepped motors.

ThyssenKrupp VDM alloy

D Material No.

DIN designation

DIN standard

USA UNS/ASTM

Nickel

Chromium

Iron

Carbon

Manganese

Silicon

Aluminium

Other elements

50% cold worked

deep-drawing

Saturation induction (T)

Curie temperature (°C)

Saturation magnetostriction (10-6)

Density (g/cm3)

Specific heat (J/kgK)

Thermal conductivity (W/mK)

Resistivity (µΩ cm)

Modulus of electricity (kN/mm2)

Expansion coefficient from 20°C to

(10-6/K)

Melting point (°C)

Max. working temperature (°C)

Formability

Weldability

1) For further DIN material numbers see special

material data sheet.2) AC values after optimum heat treatment.

DC values on request.

Specification

Chemical composition in %

Mechanical values (N/mm2, %)

Magnetic properties2)

Processing

Material characteristics

Typical applications

Magnifer 361)

1.3910 1.3911

Ni 36 RNi 24

17445 17405/17445

A 753

35.0 – 37.0

–

bal.

max. 0.05

max. 1.0

max. 0.3

max. 0.02

Mg max. 0.01

Rp 0.2 Rm A50 HV

600 630 5 200

290 ≥ 440 30 140

Quality Permeability (min.) Coercivity

class µ16 µmax

MD 1 2000±200 – –

MD 1a 2300±200 – –

MD 3 2900 20000 ≤ 16

MD 5 µ4 5000 25000 ≤ 12

Strip thickness 0.3 mm

1.3

250

+ 20

8.1

515

12.5

75

140

100 200 300 400 500

1.2 2.2 5.5 8.2 10.0

1450

–

good

good

High resistivity, good permeability with low

hysteresis losses at high frequencies.

Transformer, transducers, residual current circuit

breakers, relay and shielding components.

Physical properties at room temperature

Material tables.Soft magnetic alloys.

42

ThyssenKrupp VDM alloy

D Material No.

DIN designation

DIN standard

USA UNS/ASTM

Nickel

Chromium

Iron

Carbon

Manganese

Silicon

Aluminium

Other elements

50% cold worked

deep-drawing

Saturation induction (T)

Curie temperature (°C)

Saturation magnetostriction (10-6)

Density (g/cm3)

Specific heat (J/kgK)

Thermal conductivity (W/mK)

Resistivity (µΩ cm)

Modulus of electricity (kN/mm2)

Expansion coefficient from 20°C to

(10-6/K)

Melting point (°C)

Max. working temperature (°C)

Formability

Weldability

1) For further DIN material numbers see special

material data sheet.2) AC values after optimum heat treatment.

DC values on request.

Specification

Chemical composition in %

Mechanical values (N/mm2, %)

Magnetic properties2)

Processing

Material characteristics

Typical applications

Magnifer 531)

2.4420

NiFe 44

17745

–

54.0 – 56.0

–

bal.

max. 0.05

max. 0.5

max. 0.3

max. 0.005

–

Rp 0.2 Rm A50 HV

– – – –

– – – –

Quality Permeability (min.) Coercivity

class µ4 µmax

MG 40 40000 100000 2

MG 60 60000 130000 1.2

Strip thickness 0.1 mm

1.5

530

+ 25

8.3

500

16.5

45

–

100 200 300 400 500

10.6 10.6 10.7 10.7 10.8

1445

–

good

High permeability, high saturation induction.

Transducers, transformer, residual current circuit

breakers, toroidal strip wound cores for special

applications.

Magnifer 751)

2.4501 (2.4591) (2.4592)2.45952.4596

NiFe16CuCr (E3) (E4) RNi 2 RNi 5 E 11

17745 (41301) (41301) 17405 17405 DINIEC740-2

(E DIN40006)

N14076/A 753

bal.

1.5 – 2.5

15.0 – 17.0

max. 0.05

max. 1.0

max. 0.3

–

Cu 4.0 – 6.0

Rp 0.2 Rm A50 HV

800 860 5 270

290 600 40 150

Quality Permeability (min.) Coercivity

class µ4 µmax

ME 4 40000 115000 –

ME 6 60000 140000 –

ME 8 80000 175000 –

MH 2 – – ≤ 2

Strip thickness

0.8

400

+ 1

8.6

460

17

55

–

100

12.5

~ 1450

–

good

good

High permeability, low coercive force.

Transducers, transformer, residual current circuit

breakers, relay and shielding components, toroidal

strip wound cores.

Physical properties at room temperature

43

Magnifer 77 TiNb

–

–

–

–

–

77.0 – 78.5

–

bal.

max. 0.05

–

max. 0.5

–

Cu 4.0 – 5.0; Mo max. 0.2; Ti 0.5 – 1.0; Nb 1.0 – 2.0

Rp 0.2 Rm A50 HV

1030 1050 3 300

1210 1240 1 350

250 640 40 140

Quality Permeability (min.) Coercivity

class µ16 µmax

– 65 000 250 000 1.5

– – – –

– – – –

– – – –

– – – –

– – – –

– – – –

Strip thickness 1.0 mm

–

–

–

–

8.7

–

25

40

–

100 200 300 400 500

12.7 – – – –

–

–

–

–

Precipitation-hardenable alloy with good corrosion

behaviour.

Stamped parts for relays, magnetic heads.

ThyssenKrupp VDM alloy

D Material No.

DIN designation

DIN standard

USA UNS/ASTM

Nickel

Chromium

Iron

Carbon

Manganese

Silicon

Aluminium

Other elements

50% cold worked

80% cold worked

deep-drawing

Saturation induction (T)

Curie temperature (°C)

Saturation magnetostriction (10-6)

Density (g/cm3)

Specific heat (J/kgK)

Thermal conductivity (W/mK)

Resistivity (µΩ cm)

Modulus of electricity (kN/mm2)

Expansion coefficient from 20°C to

(10-6/K)

Melting point (°C)

Max. working temperature (°C)

Formability

Weldability

1) For further DIN material numbers see special

material data sheet.2) AC values after optimum heat treatment.

DC values on request.

Specification

Chemical composition in %

Mechanical values (N/mm2, %)

Magnetic properties2)

Processing

Material characteristics

Typical applications

Magnifer 79041)

2.4545

NiFe 15 Mo

17745

N14080/A 753

79.5 – 81.0

–

bal.

max. 0.05

max. 0.8

max. 0.5

–

Mo 4.0 – 6.0

Rp 0.2 Rm A50 HV

900 1000 4 350

310 750 40 150

Quality Permeability (min.) Coercivity

class µ4 µmax

MP 130 130000 275000 –

MP 160 160000 300000 –

MP 200 200000 350000 –

MP 240 240000 400000 –

MP 280 280000 420000 –

Strip thickness 0.06 mm

0.8

410

+ 1

8.7

460

17

55

–

100 200 300 400 500

12.0 12.8 13.0 13.6 14.3

~ 1440

–

good

good

High initial permeability and maximum permeability

with minimum hysteresis losses.

Transducers, transformers, residual current circuit

breakers, memory cores, pulse transformer, chokes,

stepped motors, toroidal strip wound cores, laminati-

ons.

Physical properties at room temperature

44

ThyssenKrupp VDM alloy

D Material No.

DIN designation

DIN standard

USA ASTM

Nickel

Chromium

Iron

Carbon

Manganese

Silicon

Aluminium

Other elements

50% cold worked

deep-drawing

Saturation induction (T)

Curie temperature (°C)

Saturation magnetostriction (10-6)

Density (g/cm3)

Specific heat (J/kgK)

Thermal conductivity (W/mK)

Resistivity (µΩ cm)

Modulus of electricity (kN/mm2)

Expansion coefficient from 20°C to

(10-6/K)

Melting point (°C)

Max. working temperature (°C)

Formability

Weldability

Specification

Chemical composition in %

Mechanical values (N/mm2, %)

Magnetic properties2)

Processing

Material characteristics

Typical applications

Magnifer 8105

–

–

–

–

80.0 – 82.0

–

bal.

–

max. 0.8

–

–

Mo 5.0 – 6.0

Rp 0.2 Rm A50 HV

1250 1250 3 350

310 700 30 140 – 180

Quality Permeabilität (min.) Coercivity

class µ4 µmax

100000 200000 1

Strip thickness 0.55 mm

0.72

420

- 1

8.7

–

17

60

–

100 200 300 400 500

12.0

~ 1450

–

good

good

Negative magnetostriction.

Stamped parts and housings for magnetic heads.

Physical properties at room temperature

45

AvailabilitySoft magnetic NiFe base alloys are available in the followingstandard product forms:

Rod & barConditions:forged, rolled, drawn,thermally treated,descaled or pickled, machined, peeled or ground

Product Forged1) Rolled1) Drawn1)

mm mm mm

Rod (O. D.) ≤ 600 8 – 100 12 – 65

Bar, square (a) 40 – 600 15 – 280 not standard

Bar, flat (a x b) (40 – 80) (5 – 20) (10 – 20)x x x(200 – 600) (120 – 600) (30 – 80)

Bar, hexagonal (s) 40 – 80 13 – 41 ≤ 50

inches inches inches

Rod (O. D.) ≤ 24 5/16 – 4 1/2 – 2 1/2

Bar, square (a) 15/8 – 24 10/16 – 11 not standard

Bar, flat (a x b) (15/8 – 31/8) (3/16 – 3/4) (3/8 – 3/4)x x x

(8 – 24) (43/4 – 24) (11/4 – 31/8)

Bar, hexagonal (s) 15/8 – 31/81/2 – 15/8 ≤ 2

1) other sizes and conditions subject to special enquiry

Thickness Width Coil I.D.mm mm mm

> 0.02 – ≤ 0.10 14 – 200 3) 300 400

> 0.10 – ≤ 0.20 14 – 350 3) 300 400 500

> 0.20 – ≤ 0.25 14 – 750 4) 400 500 600

> 0.25 – ≤ 0.60 16 – 750 4) 400 500 600

> 0.60 – ≤ 1.0 18 – 750 4) 400 500 600

> 1.00 – ≤ 2.0 15 – 750 4) 400 500 600

> 2.00 – ≤ 3.0 (3.5) 2) 25 – 750 4) 400 500 600

Strip1)

Conditions:cold rolled,thermally treated and pickled or bright annealed 2)

inches inches inches

> 0.0008 – ≤ 0.004 0.16 – 8 3) 12 16

> 0.0046 – ≤ 0.008 0.16 – 14 3) 12 16 20

> 0.0086 – ≤ 0.010 0.16 – 30 4) 16 20 24

> 0.0106 – ≤ 0.024 0.20 – 30 4) 16 20 24

> 0.0246 – ≤ 0.040 0.32 – 30 4) 16 20 24

> 0.0406 – ≤ 0.080 0.60 – 30 4) 16 20 24

> 0.0806 – ≤ 0.120 2) 1.00 – 30 4) 16 20 24≤ 0.140 2)

1) Cut-to-length available in lengths from 250 to 4000 mm (10 to 158 in.)2) Maximum thickness: bright annealed – 3 mm (0.120 in.),

cold rolled only – 3.5 mm (0.140 in.)3) Wider widths up to 730 mm (29 in.) subject to special enquiry4) Wider widths subject to special enquiry

WireConditions:bright drawn, 1/4 hard to hard, bright annealed

Dimensions:0.01 – 12.0 mm (0.0004 – 0.47 in.) diameter,in coils, pay-off packs, on spools and spiders

Welded tube and pipeWelded tubes and pipes are obtainable from qualified manu-facturers using ThyssenKrupp VDM semi-fabricated products.

Toroidal strip wound cores, relay parts, laminations andother stamped parts. Dimension on demand.

Forms supplied.

ThyssenKrupp VDM sales offices, subsidiaries and representations.

46

Germany

BerlinThyssenKrupp VDM GmbHWittestraße 4913509 BerlinTel. +49 (030) 4 32 40 36Fax +49 (030) 4 35 29 68E-Mail: sdueren@tks-vdm.

thyssenkrupp.com

DresdenThyssenKrupp VDM GmbHOskar-Röder-Straße 301237 DresdenTel. +49 (0351) 2 52 28 06Fax + 49 (0351) 2 52 28 07E-Mail: rsimmchen@tks-vdm.

thyssenkrupp.com

NurembergThyssenKrupp VDM GmbHDieselstraße 5590441 NürnbergTel. +49 (0911) 6 63 26 00Fax +49 (0911) 6 63 26 01E-Mail: dgoertz@tks-vdm.

thyssenkrupp.com

StuttgartThyssenKrupp VDM GmbHAm Ostkai 1570327 StuttgartTel. +49 (0711) 9 32 88-36Fax +49 (0711) 9 32 88-37E-Mail: hstegmaier@tks-vdm.

thyssenkrupp.com

Werdohl – Northern OfficeThyssenKrupp VDM GmbHPlettenberger Straße 2Postfach 182058778 WerdohlTel. +49 (02392) 55-2376Fax +49 (02392) 55-2526E-Mail: jleonhardt@tks-vdm.

thyssenkrupp.com

Werdohl – Western OfficeThyssenKrupp VDM GmbHPlettenberger Straße 2Postfach 182058778 WerdohlTel. +49 (02392) 55-2790Fax +49 (02392) 55-2526E-Mail: rpechan@tks-vdm.

thyssenkrupp.com

Europe

Belgium/LuxembourgS.A. ThyssenKrupp VDM BelgiumN.V.Avenue du Champ de Mai, 14Bte 34Résidence SaturneB-1410 WaterlooTel. +32 (2) 3 54 29 00Fax +32 (2) 3 54 36 26E-Mail: thyssenkruppvdm@

skynet.be

BulgariaThyssenKrupp VDM Austria GmbHParensov Str. 26BG-1000 SofiaTel. +359 (2) 9 89 16 77

9 88 65 22Fax +359 (2) 9 89 16 77E-Mail: dikov-kruppvdm@inet.bg

DenmarkThyssenKrupp MaterialsDenmark A/SAgenavej, 31DK-2670 GreveTel. +45 (43) 95 07 21Fax +45 (43) 95 07 01E-Mail: wg@thyssen.dk

FinlandOy Cronimo AbKarhutie 6FIN-01900 NurmijärviTel. +358 (9) 2 76 42 10Fax +358 (9) 2 76 42 21 50 E-Mail: sales@cronimo.fi

FranceThyssenKrupp VDM SARL30, Bd BelleriveF-92566 Rueil Malmaison CEDEXTel. +33 (1) 41 39 04 20Fax +33 (1) 47 16 78 20/14E-Mail: s.central@kruppvdm.fr

GreeceINTERAG Ltd.P.O. Box 650608, Pambouki Str.GR-15410 Psychico (Athens)Tel. +30 (10) 6 83 95 35Fax +30 (10) 6 83 95 36

Europe

Great Britain ThyssenKrupp VDM U.K. Ltd.111, Hare LaneClaygate-Esher, Surrey KT10 OQYTel. +44 (1372) 46 71 37Fax +44 (1372) 46 63 88E-Mail: info@tks-vdmuk.

thyssenkrupp.com

ItalyThyssenKrupp VDM Italia SrlVia Milanese 20I-20099 Sesto San Giovanni (Mi)Tel. +39 (02) 2 41 04 61Fax +39 (02) 24 10 46 29E-Mail: cquva@tin.it

NetherlandsThyssenKrupp VDM Nederland B.V.Stationsweg 4NL-3311 JW DordrechtP.O. Box 750NL-3300 AT DordrechtTel. +31 (78) 6 31 69 66Fax +31 (78) 6 31 58 57E-Mail: info@tks-vdmnl.

thyssenkrupp.com

NorwayA/S Stavanger RoerhandelGamle Forusvei 53P.O. Box 184N-4033 ForusTel. +47 (51) 81 85 00Fax +47 (51) 81 86 00

Austria/Central and Eastern EuropeThyssenKrupp VDM Austria GmbHTenschertstraße 3A-1230 WienTel. +43 (1) 6 15 06 00Fax +43 (1) 6 15 36 00E-Mail: office@krupp-vdm.at

Germany

Head OfficeThyssenKrupp VDM GmbHPlettenberger Straße 2Postfach 182058778 WerdohlTel. +49 (02392) 55-0Fax +49 (02392) 55-2217E-Mail: info@tks-vdm.

thyssenkrupp.comwww.thyssenkruppvdm.de

47

Europe

RomaniaThyssenKrupp VDM Austria GmbHStr. Stanislas Cihoschi, Nr.10Et.3, Ap. 10, Sector 1RO-010593 Bukarest Tel. +40 (21) 6 10 77 05Fax +40 (21) 2 11 99 44E-Mail: kruppvdm@fx.ro

Russian FederationThyssenKrupp AGRepräsentanz in der Russischen FöderationKrasnopresnenskaja nab 12Internationales Handelszentrum(CMT)Büro 1209GUS-123610 MoskauTel. +7 (502) 2 58 20 74Fax +7 (502) 2 58 20 76E-Mail: errmann@thyskrupp.wtt.ru

SwedenESMA ABDomnarvsgatan 8P.O. Box 8027S-16308 Spanga/StockholmTel. +46 (8) 4 74 42 00Fax +46 (8) 4 74 42 60E-Mail: angelika.andersson@

esma.se

SwitzerlandThyssenKrupp VDM (Schweiz) AGLange Gasse 90P.O. BoxCH-4002 BaselTel. +41 (61) 2 05 84 88Fax +41 (61) 2 05 84 15E-Mail: raoul.roth@thyssenkruppvdm.ch

Spain/PortugalThyssenKrupp VDM IbéricaCalvet, 30-32, 2°, 1.a

E-08021 BarcelonaTel. +34 (93) 2 00 90 11Fax +34 (93) 2 00 22 54E-Mail: info@tks-vdmes.

thyssenkrupp.com

TurkeyAkkurt A.S.Ahmediye KöyüTR-34904 B. Cekmece-IstanbulTel. +90 (212) 8 87 14 15 – 17Fax +90 (212) 8 87 10 79E-Mail: akkurt@ibm.net

North and Middle America

CanadaThyssenKrupp VDM Canada Ltd.Suite 20311 Allstate ParkwayMarkham, Ontario L3R 9T8Tel. +1 (905) 477-2064Fax +1 (905) 477-2817E-Mail: hklein@thyssenkruppvdm.ca

USAThyssenKrupp VDM USA, Inc.306 Columbia TurnpikeFlorham Park, N.J. 07932Tel. +1 (973) 236-1664Fax +1 (973) 236-1960E-Mail: vdmtech@vdmt.com

MexicoThyssenKrupp VDM de México S.A.de C.V.Bulevard Manuel AvilaCamacho No. 80 PH-ALomas de SoteloNaucalpanEdo. de MéxicoC.P. 53390 MéxicoTel. +52 (55) 57-14 71Fax +52 (55) 57-14 76E-Mail: kruppvdm@prodigy.net.mx

South America

ArgentinaWalvoss S.R.L.Humberto 1° 1333C 1103 ADA Buenos AiresTel. +54 (11) 43 04 87 70Fax +54 (11) 43 05 06 91E-Mail: wvsponte@pinos.com

BrazilIMS DO BRASIL LTDA.Av. Macuco, 726 – Cjs. 2002/2003 04523-001 Sáo Paulo-SPTel. +55 (11) 5054 - 6992Fax +55 (11) 5054 - 6886E-Mail: sergio.consolin@ims

group.com.br

ChileACERIMPEXHuérfanos 1160Oficina 1013Santiago – Centro Tel. +56 (2) 688 82 72Fax +56 (2) 699 03 19E-Mail: rubenreyesd@terra.cl

ColombiaHERGUT Ltda.CRA 43 A No. 1Sur-31, Of. 208MedellinTel. +57 (4) 266-17 37/17 57Fax +57 (4) 268-61 92

Ecuador Importadora Schiller Cia. Ltda.Santa Rosa Oe7-178 y Pasaje HerreraQuitoTel. +593 (2) 2 54 77 60Fax +593 (2) 2 56 27 88E-Mail: schiller@interactive.net.ec

PeruAMSET E.I.R.L.José Maria Eguren(Chumbiongo) 107,Dpto. 302Miraflores (Lima 18)Tel. +51 (1) 440 49 53Fax +51 (1) 442 12 33

UruguayFierro Vignoli S.A.Av. Urugay 1274/76MontevideoTel. +598 (2) 91 45 60Fax +598 (2) 92 12 30

South America

VenezuelaGUNZ S.R.L.2da. Av c/c 1ra. Transversal.,Edf. La Pradera, Torre B.Piso 9, P.H. 90-B, Urb. Los Palos Grandes,Caracas 1060Tel. +58 (2) 284-24 96Fax +58 (2) 978-12 85E-Mail: gunz-mse@etheron.net

Africa

EgyptOSAB TradeDr. O. Abbas6, El Nil El Abiad St.Lebanon SquareGiza/CairoTel. +20 (2) 303 46 33Fax +20 (2) 346 08 00

Samir L.W. El AyoubiP.O. Box Maadi 191House 30, Street 11Maadi-CairoTel. +20 (2) 350-21 12Fax +20 (2) 378-31 15

NigeriaBetcy Investment LimitedBetcy HouseBlock 14, Plot 241,Amuwo Odofin/Festac Access RoadP.O. Box 33743792 Festac TownTel. +234 (1) 589 05 52/53Fax +234 (1) 588 29 69E-Mail: betcygp@gacom.net

South AfricaThyssenKrupp VDM SA (PTY) LTD36, Crucible RoadHeriotdale 2094Johannesburg 2000Tel. +27 (11) 626-3370-306 Fax +27 (11) 626-2191E-Mail: heath@intecom.co.za

48

Middle East

Israel Middle East Metals Ltd.1, Korazin St.P.O. Box 87053583 GivatayimTel. +972 (3) 571 53 74/69Fax +972 (3) 571 53 71E-Mail: isbrildo@netvision.net.il

JordanInternational Technical Construction Co.P.O. Box 95 02 79AmmanTel. +962 (6) 551 49 63Fax +962 (6) 553 70 69E-Mail: itcc@go.com.jo

U. A. E.Eastern Union CorporationP.O. Box 3489Tourist Club AreaAbu DhabiTel. +971 (2) 78 24 62Fax +971 (2) 77 19 58

India

Variety (Agents) Private Ltd.301, Kakad Chambers132, Dr. Annie Besant RoadWorli, Mumbai – 400018Tel. +91 (22) 24 93-26 91Fax +91 (22) 24 95-05 78E-Mail: variety@bom3.vsnl.net.in

Asia

HongkongThyssenKrupp VDM Hongkong Ltd.Rooms 715-737, 7/F. Sun Hung Kai Centre30 Harbour Road, WanchaiHong KongTel. +852 31 81 78 00Fax +852 25 27 20 45E-Mail: info@tks-vdmhk.

thyssenkrupp.com

JapanThyssenKrupp VDM Japan K.K.Fukide Build. 7F1-13 Toranomon 4-chomeMinato-kuTokyo 105-0001Tel. +81 (3) 5472 2651Fax +81 (3) 5472 1564E-Mail: vdmj-t.k@galaxy.ocn.ne.jp

PhilippinesMESCO Inc.MESCO BuildingReliance Corner Brixton Streets1603 Pasig City, Metro ManilaTel. +63 (2) 631 1775-85Fax +63 (2) 631 4028

635 0036E-Mail: mescophil@skyinet.net

Singapore, Malaysia, IndonesiaFirsttech Distribution Pte. LtdNo. 10 Ubi Crescent #07-11Ubi TechParkSingapore 408564Tel. +65 68 46 88 22Fax +65 68 46 88 33E-Mail: Daniel.Lo@FIRSTTECH.

com.sg

South KoreaThyssenKrupp VDM Korea Co., Ltd.#12 13, Hyundai Office B/D9-4 Sunai-dong, Bundang-guSungnam-siKyunggido 463-020Tel. +82 (31) 711 15 83Fax +82 (31) 717 15 83E-Mail: michoi@tks-vdmkr.

thyssenkrupp.com

Taiwan Far East Alloy Corporation2F-2, No. 29-1, Lane 169Kang Ning St., Shih-Chih CityTaipai HsienTel. +886 (2) 26 95 30 33Fax +886 (2) 26 95 07 66E-Mail: sales@fea.com.tw

Asia

ThailandSahakol Trading Co. Ltd.128/113 9th FL, Payatai Plaza BuildingPayatai RoadBangkok 10400Tel. +66 (2) 216 57 47- 8Fax +66 (2) 216 57 21E-Mail: sahakol@loxinfo.co.th

Vietnam ThyssenKrupp AGRepresentative Office VietnamHanoi OfficeSuite 503, 5th FloorHanoi Central Office Building44B Ly Thuong Kiet StreetHoan Kiem DistrictHanoiTel. +84 (4) 934 70 43Fax +84 (4) 934 70 46E-Mail:doan@thyssenkrupp.com.vn

ThyssenKrupp AGRepresentative Office Ho Chi Minh R. 906, S Floor, Saigon Trade Centre37 Ton Duc Thang, District 1Ho Chi Minh CityTel. +84 (8) 910 24 38Fax +84 (8) 910 24 40E-Mail: thyssenkrupp@hcm.vnn.vn

Peoples Republic of ChinaThyssenKrupp VDM Hongkong Ltd.Beijing Representative OfficeUnit 8A, 22/F. China Life TowerNo. 16 Chaoyangmenwai AvenueChaoyang DistrictBeijing 100020Tel. +86 (10) 85 25 29 99Fax +86 (10) 85 25 21 61E-Mail: vdm.beijing@

thyssenkrupp.com.cn

ThyssenKrupp VDM Hongkong Ltd.Shanghai Representative OfficeUnit 2009, 20/F. China MerchantsTower161 Lujiazui Dong Road, Pu DongShanghai 200120Tel. +86 (21) 38 78 47 00Fax +86 (21) 58 82 95 89E-Mail: vdm.shanghai@

thyssenkrupp.com.cn

Asia

Peoples Republic of Chinaand HongkongFordley Development LtdRm 705-707, Yu Sung BoonBuilding107-111 Des Voeux Road CentralHong KongTel. +852 25 41 00 00Fax +852 28 54 19 42E-Mail: desmond@fordley.com.hk

Australia

ThyssenKrupp VDM Australia Pty.Ltd.724 Springvale RoadP.O. Box 271Mulgrave, Victoria 3170Tel. +61 (3) 95 61 13 11Fax +61 (3) 95 61 44 65E-Mail: cnicola@vdm.

thyssenkrupp.com.au

VDM Report No. 27Soft magnetic Ni-Fe base alloys

Published by:ThyssenKrupp VDM GmbHPlettenberger Strasse 258791 WerdohlP.O. Box 182058778 WerdohlGermanyPhone: +49 (2392) 55-0Fax: +49 (2392) 55-2217Email: info@tks-vdm.thyssenkrupp.comwww.thyssenkruppvdm.com

The information and recommendations in this bro-chure are based on practical experience and ourown research and development results at the timeof going to press. They may be changed at anytime in the interest of the ongoing improvementand further development of our materials.

While every care has been taken to ensure that thetechnical information in this brochure is correct andup to date, we do not guarantee that it is accurate.Product deliveries and services are subject exclu-sively to our General Terms and Conditions.

June 2004

Imprint.

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ThyssenKrupp VDM GmbHPlettenberger Strasse 258791 WerdohlP.O. Box 18 2058778 WerdohlGermanyPhone: +49 (23 92) 55-0Fax: +49 (23 92) 55-22 17E-Mail: info@tks-vdm.thyssenkrupp.comwww.thyssenkruppvdm.com