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Phenomenon of anisotropy in Fe-based commercial soft magnetic materials
MiNI Journal of Magnetism and Magnetic Materials 112 (1992) 251-252 North-Holland
/H,,m
Phenomenon of anisotropy in Fe-based commercial soft magnetic materials M a r i a n Soifiski Materials Engineering Centre, Technical Unit ersiO' of Czestochowa, Czqstochowa, Poland
The main aim of this contribution is to investigate the directional (anisotropic) properties of oriented and non-oriented electrical steel sheets. The suggested method of the determination of angular dependencies avoiding the necessity of taking many measurements of the Epstein frame becomes very useful, especially for users of all electrical sheets.
1. Introduction
2. Results
The main aim of this contribution is to investigate the directional (anisotropic) properties of oriented and non-oriented electrical steel sheets. Such properties as induction, core loss and apparent core loss can be used as a basic function when classifying magnetic exploited in building various electrical devices. Knowledge of the parameters is important in establishing which materials are best fitted for a given technological application in the electrical and power electronic industry. Directional properties of magnetic soft materials are strongly dependent on their crystalline structure, a phenomenon reflected in the classification of these materials. Building economical electrical devices, saving electrical energy requires significant changes in their design. More attention should be paid in designing magnetic circuits exploiting the phenomenon of anisotropy of ferromagnetic materials.
Magnetic cores of almost all electrical devices are made of soft magnetic materials, i.e. with a small coercive force, easy to magnetize to saturation. Silicon and silicon-free electrical sheets are usually used in industry, whcreas amorphous ribbons and rapidly quenched iron-silicon alloys seem to be the material for the future. Isotropic sheets that are used in electrical motors of small and average power and should possess a high working induction and small anisotropy. The magnetic cores used in current transformers and electronic systems are produced from materials with a small coercive force and with high magnetic permeability in the initial part of the magnetization curve. In electrical appliances meant to work at high frequencies or at risk of sudden impulse changes of the magnetic field, thin electrical sheets are used. The anisotropic sheets used in producing transformers and large generators shouid, most importantly, have high induction and small core loss. Construction of such magnetic cores, due to the directional properties of the materials, guarantees that the magnetic flux flows along the direction of easy magnetization which is the reason why we use ceres made of cornered and
Correspondence to: Dr. M. Soifiski, Materials Engineering Centre, Technical University of Czestochowa, Cz~stochowa, Poland.
0304-8853/92,/$05.00 © 1992 - Elsevier Science Publishers B.V. All rights reserved
252
M. Soitlski / Anisotropy in Fe-based commercial soft magnetic materials
Table 1 Anisotropic properties of electrical sheets Designation
HI-B
M4
oriented thin gauge
M5
M6
thin gauge
M7
M9
M43
M45
M47
Degree of orientation Rank Correlation in anisotropy of magnetic flux density
97% 1
95% 2
90% 3
87% 4
85% 5
75% 6
65% 7
45% 8
1(1% 9
10% 10
9% 11
1
2
6
3
4
8
5
7
10
11
segmented sheets in transformers and electrical motors, respectively. Anisotropy of magnetic ptoperties of ferromagnets investigated here is strongly correlated to their crystalline structure. This can be seen from the data given in table 1 showing correlation ranks. The properties are ordered according to the degree of the crystalline orientation. The correlation rank coefficient for the above pairs is 0.96. The coefficient of consistence of the whole test described in ref. [1] equals 0.88, and the data show a strong dependence between the variables given in table 1. Thus when we have one datum, e.g. degree of orientation in magnetic materials, we can determine - on the basis of the results of research presented in ref. [1] and with great probability - other magnetic values such as: induction, magnetic field intensity, permeability, coercive force, demagnetization of the sample, magnetostrictive elongation, apparent core loss, core loss, some mechanical and electrical properties, etc. Ref. [1] also suggests a new instrumentation approach for all soft magnetic materials. The properties along the rolling or casting direction of material should be determined in one test in a standard frame or in a wound sample. The direction magnetically distinguished and the degree of orientation should be determined by means of one anisometric method and not of many measurements of samples differing in the cutting anule r e l a t i v e to t h e ~:~v, rcdllng dlr~c, t l n n
N n th,~
basis of developed dependencies [1], it is possible with a high probability of 0.88 to determine the directional changes of the parameters listed above. Graphic approximation of the data for the given angles ~ represents a new approach of angular dependencies and it shows very useful
9
changes of many particular properties under the influence of the magnetization direction.
3. Concluding remarks The electrical sheets are characterized by the anisotropy of magnetic parameters resulting from the crystalline structure of the material. The oriented transformer sheets display the so-called Goss texture and the anisotropy resulting from this texture is smaller than in the case of the F e - S i monocrystallites. Isotropic silicon sheets with weak Goss texture and isotropic silicon-free sheets with mixed texture possess one order smaller grain orientation. A different anisotropy present in amorphous materials is the induced uniaxial anisotropy. The parameter is two order smaller in the Fe-based amorphous ribbons than the respective value in strongly oriented electrical sheets. MicrocrystaUine tapes present even smaller values. The suggested method of determining angular dependencies avoiding the necessity of taking many measurements of the Epstein frame becomes very useful, especially for users of electrical sheets. The demand for energy-saving electrical machines calls tor radical changes in the design, therefore the engineers should - to a greater extent than they do presently - take into account the apisotropic properties of soft magnetic materials.
Re[erence [1] A.J. Moses and M. Soinski, Int. Rep. Technical University of Czestochowa, Cz~stochowa (1990).
/H,,m
Phenomenon of anisotropy in Fe-based commercial soft magnetic materials M a r i a n Soifiski Materials Engineering Centre, Technical Unit ersiO' of Czestochowa, Czqstochowa, Poland
The main aim of this contribution is to investigate the directional (anisotropic) properties of oriented and non-oriented electrical steel sheets. The suggested method of the determination of angular dependencies avoiding the necessity of taking many measurements of the Epstein frame becomes very useful, especially for users of all electrical sheets.
1. Introduction
2. Results
The main aim of this contribution is to investigate the directional (anisotropic) properties of oriented and non-oriented electrical steel sheets. Such properties as induction, core loss and apparent core loss can be used as a basic function when classifying magnetic exploited in building various electrical devices. Knowledge of the parameters is important in establishing which materials are best fitted for a given technological application in the electrical and power electronic industry. Directional properties of magnetic soft materials are strongly dependent on their crystalline structure, a phenomenon reflected in the classification of these materials. Building economical electrical devices, saving electrical energy requires significant changes in their design. More attention should be paid in designing magnetic circuits exploiting the phenomenon of anisotropy of ferromagnetic materials.
Magnetic cores of almost all electrical devices are made of soft magnetic materials, i.e. with a small coercive force, easy to magnetize to saturation. Silicon and silicon-free electrical sheets are usually used in industry, whcreas amorphous ribbons and rapidly quenched iron-silicon alloys seem to be the material for the future. Isotropic sheets that are used in electrical motors of small and average power and should possess a high working induction and small anisotropy. The magnetic cores used in current transformers and electronic systems are produced from materials with a small coercive force and with high magnetic permeability in the initial part of the magnetization curve. In electrical appliances meant to work at high frequencies or at risk of sudden impulse changes of the magnetic field, thin electrical sheets are used. The anisotropic sheets used in producing transformers and large generators shouid, most importantly, have high induction and small core loss. Construction of such magnetic cores, due to the directional properties of the materials, guarantees that the magnetic flux flows along the direction of easy magnetization which is the reason why we use ceres made of cornered and
Correspondence to: Dr. M. Soifiski, Materials Engineering Centre, Technical University of Czestochowa, Cz~stochowa, Poland.
0304-8853/92,/$05.00 © 1992 - Elsevier Science Publishers B.V. All rights reserved
252
M. Soitlski / Anisotropy in Fe-based commercial soft magnetic materials
Table 1 Anisotropic properties of electrical sheets Designation
HI-B
M4
oriented thin gauge
M5
M6
thin gauge
M7
M9
M43
M45
M47
Degree of orientation Rank Correlation in anisotropy of magnetic flux density
97% 1
95% 2
90% 3
87% 4
85% 5
75% 6
65% 7
45% 8
1(1% 9
10% 10
9% 11
1
2
6
3
4
8
5
7
10
11
segmented sheets in transformers and electrical motors, respectively. Anisotropy of magnetic ptoperties of ferromagnets investigated here is strongly correlated to their crystalline structure. This can be seen from the data given in table 1 showing correlation ranks. The properties are ordered according to the degree of the crystalline orientation. The correlation rank coefficient for the above pairs is 0.96. The coefficient of consistence of the whole test described in ref. [1] equals 0.88, and the data show a strong dependence between the variables given in table 1. Thus when we have one datum, e.g. degree of orientation in magnetic materials, we can determine - on the basis of the results of research presented in ref. [1] and with great probability - other magnetic values such as: induction, magnetic field intensity, permeability, coercive force, demagnetization of the sample, magnetostrictive elongation, apparent core loss, core loss, some mechanical and electrical properties, etc. Ref. [1] also suggests a new instrumentation approach for all soft magnetic materials. The properties along the rolling or casting direction of material should be determined in one test in a standard frame or in a wound sample. The direction magnetically distinguished and the degree of orientation should be determined by means of one anisometric method and not of many measurements of samples differing in the cutting anule r e l a t i v e to t h e ~:~v, rcdllng dlr~c, t l n n
N n th,~
basis of developed dependencies [1], it is possible with a high probability of 0.88 to determine the directional changes of the parameters listed above. Graphic approximation of the data for the given angles ~ represents a new approach of angular dependencies and it shows very useful
9
changes of many particular properties under the influence of the magnetization direction.
3. Concluding remarks The electrical sheets are characterized by the anisotropy of magnetic parameters resulting from the crystalline structure of the material. The oriented transformer sheets display the so-called Goss texture and the anisotropy resulting from this texture is smaller than in the case of the F e - S i monocrystallites. Isotropic silicon sheets with weak Goss texture and isotropic silicon-free sheets with mixed texture possess one order smaller grain orientation. A different anisotropy present in amorphous materials is the induced uniaxial anisotropy. The parameter is two order smaller in the Fe-based amorphous ribbons than the respective value in strongly oriented electrical sheets. MicrocrystaUine tapes present even smaller values. The suggested method of determining angular dependencies avoiding the necessity of taking many measurements of the Epstein frame becomes very useful, especially for users of electrical sheets. The demand for energy-saving electrical machines calls tor radical changes in the design, therefore the engineers should - to a greater extent than they do presently - take into account the apisotropic properties of soft magnetic materials.
Re[erence [1] A.J. Moses and M. Soinski, Int. Rep. Technical University of Czestochowa, Cz~stochowa (1990).