- Email: [email protected]
Influence of the cutting process on the magnetic properties of non-oriented electrical steels
Journal of Magnetism and Magnetic Materials 215}216 (2000) 100}102
In#uence of the cutting process on the magnetic properties of non-oriented electrical steels A. Schoppa*, J. Schneider, J.-O. Roth Department of Application EBG Bochum, Castroper Strasse 228, 44791 Bochum, Germany
Abstract The laminations for the cores used in electrical applications like motors, generators, ballasts are manufactured by punching, mechanical cutting or cutting by laser of coils of non-oriented fully processed electrical steels. The magnetic material close to the cutting edge is essentially in#uenced by these processes. Depending on the parameter, the magnetic properties can vary substantially. 2000 Elsevier Science B.V. All rights reserved. Keywords: Non-oriented electrical steel; Manufacturing process; Cutting; Electric motors; Magnetic properties
1. Introduction
2. Experimental
As well known the di!erent manufacturing processes like: punching, cutting, pressing during stacking of laminations to cores, welding, riveting or pressing of cores into the frames of electromagnetic devices deteriorate partly the magnetic properties of the used electrical steels. The punching or cutting process give the main contribution to the deterioration of the magnetic properties by manufacturing of magnetic components [1]. Previous works [2}4] demonstrate the general features of the changes of J vs. H and P vs. J upon cutting. How ever, there is no systematic study of the relationship between the deterioration of the magnetic properties, the type of alloys, the thickness of the material, rolling direction, grain size and other parameters like the operating range of induction and frequency. In this paper the authors will present some of the obtained results of such an extensive study of the in#uence of the cutting process on the magnetic properties of di!erent non-oriented fully processed electrical steels.
The investigations started with single strips of the dimension 160;30 mm. The magnetic properties of these samples were measured using a single-sheet testing device. Afterwards, the strips were cut into two strips with a width 160;15 mm and again measured in the mentioned device. To avoid the in#uence of the geometrical shape on the magnetic properties, the samples were put together into the testing device and measured simultaneously like a sample with a width 160;30 mm. This procedure was repeated several times to increase the characteristic parameter: cutting length per mass of the sample (¸"l/m). The testing method was exactly described in Ref. [3]. The measured magnetic data before and after cutting will give a volume-averaged quantitative value for the in#uence of the cutting length.
* Corresponding author. Tel.: #49-234-50851561; fax: #49234-50851042. E-mail address: [email protected] (A. Schoppa).
3. Results and discussion Figs. 1 and 2 illustrate the e!ect of increasing cutting length per mass of the sample on the characteristics of J vs. H and P vs. J for an FeSi 3.2-alloy. While the magnetic losses increase practically in the whole range of polarization, the most pronounced changes in J vs. H are observed in the range of polarization from 0.4 to 1.5 T. Similar curves were obtained for medium and low Sialloyed grades. Fig. 3 illustrates the increase of the
0304-8853/00/$ - see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 0 0 ) 0 0 0 7 7 - 9
A. Schoppa et al. / Journal of Magnetism and Magnetic Materials 215}216 (2000) 100}102
101
Fig. 3. Increase of the exciting "eld at 1.0 T upon increasing values of the speci"c cutting length ¸ for non-oriented electrical steels with a di!erent Si-content.
Fig. 1. In#uence of the speci"c cutting length on the characteristics of P vs. J (high Si-alloyed grade, 50 Hz, thickness 0.50 mm).
Fig. 4. Increase of the core loss at 1.0 T upon increasing values of the speci"c cutting length ¸ for non-oriented electrical steels with a di!erent Si-content.
Fig. 2. In#uence of the speci"c cutting length on the characteristics of J vs. H (high Si-alloyed grade, 50 Hz, thickness 0.50 mm).
exciting "eld upon increasing values of ¸ at J"1.0 T for non-oriented electrical steels with a di!erent Si-content. The increase of the necessary exciting "eld will become smaller for lower or higher values of polarization (see Fig. 2). The observed trend clearly indicate an increase of the exciting "eld strength with increasing Si-content and increasing values of ¸. The additional magnetic losses at J"1.0 T as a function of the Si-content and the parameter ¸ show a similar
102
A. Schoppa et al. / Journal of Magnetism and Magnetic Materials 215}216 (2000) 100}102
permeability grade (STABOCOR威400-50 AP) using a di!erent experimental method are presented in Ref. [5].
4. Conclusions The in#uence of the cutting process on the magnetic properties: magnetizing behaviour and losses, becomes very important for large values of ¸ and high Si-alloyed grades of non-oriented fully processed electrical steel, especially within an operating range of induction from 0.4 to 1.5 T. The deterioration of magnetic properties is caused by the induced internal mechanical stresses due to punching and cutting. The in#uenced zone is located nearby the cutting edge [6]. The grain size d of the investigated FeSi-alloys increase with the Si-content. The increase of d is higher for Si-contents above 1.5%. Keeping in mind this observation the realized trend with respect to the increase of the exciting "eld for a given magnetic induction and the increase of speci"c magnetic losses due to cutting, (see Figs. 3 and 4), implies that the e!ect of cutting will be higher for materials with large grains. A way to overcome the stress-induced changes of the magnetic properties is a stress-relief annealing of the cut or punched components.
Fig. 5. In#uence of the cutting length on the speci"c core losses for samples cut parallel and perpendicular to the rolling direction (high Si-alloyed grade, 50 Hz).
trend (see Fig. 4). The in#uence of the cutting length is remarkably smaller for strips cut perpendicular to the rolling direction compared to those cut parallel (see Fig. 5). The observed e!ects are smaller for a reduced thickness of the sheets (0.35 mm). The results for a high
References [1] A. Schoppa, J. Schneider, C.-D. Wuppermann, J. Magn. Magn. Mater. 215}216 (2000) 74. [2] T. Nakata et al., IEEE Trans. J. Magn. Japan 7 (6) (1992) 453. [3] K.-H. Schmidt, J. Magn. Magn. Mater. 2 (1}3) (1976) 136. [4] T. Belgrand, J. Phys. IV France 8 (1998). [5] A.J. Moses, N. Derebasi, G. Loisos, A. Schoppa, J. Magn. Magn. Mater. 215}216 (2000) 690. [6] R. Rygal, A.J. Moses, N. Derebasi, J. Schneider, A. Schoppa, J. Magn. Magn. Mater. 215}216 (2000) 687.
In#uence of the cutting process on the magnetic properties of non-oriented electrical steels A. Schoppa*, J. Schneider, J.-O. Roth Department of Application EBG Bochum, Castroper Strasse 228, 44791 Bochum, Germany
Abstract The laminations for the cores used in electrical applications like motors, generators, ballasts are manufactured by punching, mechanical cutting or cutting by laser of coils of non-oriented fully processed electrical steels. The magnetic material close to the cutting edge is essentially in#uenced by these processes. Depending on the parameter, the magnetic properties can vary substantially. 2000 Elsevier Science B.V. All rights reserved. Keywords: Non-oriented electrical steel; Manufacturing process; Cutting; Electric motors; Magnetic properties
1. Introduction
2. Experimental
As well known the di!erent manufacturing processes like: punching, cutting, pressing during stacking of laminations to cores, welding, riveting or pressing of cores into the frames of electromagnetic devices deteriorate partly the magnetic properties of the used electrical steels. The punching or cutting process give the main contribution to the deterioration of the magnetic properties by manufacturing of magnetic components [1]. Previous works [2}4] demonstrate the general features of the changes of J vs. H and P vs. J upon cutting. How ever, there is no systematic study of the relationship between the deterioration of the magnetic properties, the type of alloys, the thickness of the material, rolling direction, grain size and other parameters like the operating range of induction and frequency. In this paper the authors will present some of the obtained results of such an extensive study of the in#uence of the cutting process on the magnetic properties of di!erent non-oriented fully processed electrical steels.
The investigations started with single strips of the dimension 160;30 mm. The magnetic properties of these samples were measured using a single-sheet testing device. Afterwards, the strips were cut into two strips with a width 160;15 mm and again measured in the mentioned device. To avoid the in#uence of the geometrical shape on the magnetic properties, the samples were put together into the testing device and measured simultaneously like a sample with a width 160;30 mm. This procedure was repeated several times to increase the characteristic parameter: cutting length per mass of the sample (¸"l/m). The testing method was exactly described in Ref. [3]. The measured magnetic data before and after cutting will give a volume-averaged quantitative value for the in#uence of the cutting length.
* Corresponding author. Tel.: #49-234-50851561; fax: #49234-50851042. E-mail address: [email protected] (A. Schoppa).
3. Results and discussion Figs. 1 and 2 illustrate the e!ect of increasing cutting length per mass of the sample on the characteristics of J vs. H and P vs. J for an FeSi 3.2-alloy. While the magnetic losses increase practically in the whole range of polarization, the most pronounced changes in J vs. H are observed in the range of polarization from 0.4 to 1.5 T. Similar curves were obtained for medium and low Sialloyed grades. Fig. 3 illustrates the increase of the
0304-8853/00/$ - see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 0 0 ) 0 0 0 7 7 - 9
A. Schoppa et al. / Journal of Magnetism and Magnetic Materials 215}216 (2000) 100}102
101
Fig. 3. Increase of the exciting "eld at 1.0 T upon increasing values of the speci"c cutting length ¸ for non-oriented electrical steels with a di!erent Si-content.
Fig. 1. In#uence of the speci"c cutting length on the characteristics of P vs. J (high Si-alloyed grade, 50 Hz, thickness 0.50 mm).
Fig. 4. Increase of the core loss at 1.0 T upon increasing values of the speci"c cutting length ¸ for non-oriented electrical steels with a di!erent Si-content.
Fig. 2. In#uence of the speci"c cutting length on the characteristics of J vs. H (high Si-alloyed grade, 50 Hz, thickness 0.50 mm).
exciting "eld upon increasing values of ¸ at J"1.0 T for non-oriented electrical steels with a di!erent Si-content. The increase of the necessary exciting "eld will become smaller for lower or higher values of polarization (see Fig. 2). The observed trend clearly indicate an increase of the exciting "eld strength with increasing Si-content and increasing values of ¸. The additional magnetic losses at J"1.0 T as a function of the Si-content and the parameter ¸ show a similar
102
A. Schoppa et al. / Journal of Magnetism and Magnetic Materials 215}216 (2000) 100}102
permeability grade (STABOCOR威400-50 AP) using a di!erent experimental method are presented in Ref. [5].
4. Conclusions The in#uence of the cutting process on the magnetic properties: magnetizing behaviour and losses, becomes very important for large values of ¸ and high Si-alloyed grades of non-oriented fully processed electrical steel, especially within an operating range of induction from 0.4 to 1.5 T. The deterioration of magnetic properties is caused by the induced internal mechanical stresses due to punching and cutting. The in#uenced zone is located nearby the cutting edge [6]. The grain size d of the investigated FeSi-alloys increase with the Si-content. The increase of d is higher for Si-contents above 1.5%. Keeping in mind this observation the realized trend with respect to the increase of the exciting "eld for a given magnetic induction and the increase of speci"c magnetic losses due to cutting, (see Figs. 3 and 4), implies that the e!ect of cutting will be higher for materials with large grains. A way to overcome the stress-induced changes of the magnetic properties is a stress-relief annealing of the cut or punched components.
Fig. 5. In#uence of the cutting length on the speci"c core losses for samples cut parallel and perpendicular to the rolling direction (high Si-alloyed grade, 50 Hz).
trend (see Fig. 4). The in#uence of the cutting length is remarkably smaller for strips cut perpendicular to the rolling direction compared to those cut parallel (see Fig. 5). The observed e!ects are smaller for a reduced thickness of the sheets (0.35 mm). The results for a high
References [1] A. Schoppa, J. Schneider, C.-D. Wuppermann, J. Magn. Magn. Mater. 215}216 (2000) 74. [2] T. Nakata et al., IEEE Trans. J. Magn. Japan 7 (6) (1992) 453. [3] K.-H. Schmidt, J. Magn. Magn. Mater. 2 (1}3) (1976) 136. [4] T. Belgrand, J. Phys. IV France 8 (1998). [5] A.J. Moses, N. Derebasi, G. Loisos, A. Schoppa, J. Magn. Magn. Mater. 215}216 (2000) 690. [6] R. Rygal, A.J. Moses, N. Derebasi, J. Schneider, A. Schoppa, J. Magn. Magn. Mater. 215}216 (2000) 687.