RU2494153C1 - Method of magnetothermal processing of anisotropic magnetically soft materials - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: performed are high-temperature annealing, curing, cooling to room temperature and processing in alternating magnetic field. In magnetic processing, strip plane deflects from magnetic field direction through 1° to 10° towards strip direction at magnetic field frequency of 0.05 to 1.0 Hz. Proposed method allows processing in continuous displacement of steel strip in process flow while strip angular deviation can be set by fitting guide rolls magnetothermal treatment furnace at different height.

EFFECT: improved magnetic properties of cold-rolled electric anisotropic steel.

2 cl, 2 dwg, 1 tbl

Description

The invention relates to metallurgy and can be used to improve the magnetic characteristics of cold rolled anisotropic electrical steel roll (Fe alloy ~ 3 wt.% Si with a body-centered cubic lattice).

The technological process for the production of electrical steel is very complicated [Cold-rolled electrical steel. Directory. Ed. B.V. Molotilova. M .: Metallurgy, 1989. 168 p.] And is aimed at obtaining the structure and crystallographic texture necessary to achieve the required operational properties.

These steels belong to soft magnetic materials, which are used as magnetic cores of generators, electric motors, transformers, relays, magnetic starters and other equipment. Improving their magnetic properties (increasing magnetic permeability and induction, reducing coercive force and energy loss during magnetization reversal) increases the efficiency of the listed equipment and allows to reduce its weight and dimensions.

One of the ways to improve the magnetic properties of soft magnetic materials is thermomagnetic treatment, carried out at a temperature not exceeding the Curie point, in the presence of an external magnetic field.

Various methods of thermomagnetic processing of soft magnetic materials are known.

Method for thermomagnetic processing of soft magnetic materials [A.S. SU No. 485155], including high-temperature annealing in a non-oxidizing medium, exposure and cooling to room temperature, thermomagnetic treatment in an alternating magnetic field. This method allows to increase the magnetic permeability (initial and maximum 2, 3 and 4 times, respectively), reduce the coercive force (by 50%) and electromagnetic losses (by 40%) of electrical steel.

Methods for thermomagnetic processing of soft magnetic materials [A.S. SU No. 5666886 and 626123], including the same operations, specify the thermomagnetic treatment modes (respectively, duration and temperature).

The listed methods of thermomagnetic processing were proposed for isotropic (textureless) material. Modern electrical anisotropic steel has a sharp texture {110} <001>, and thermomagnetic processing for it using these methods is ineffective [1. Kekalo I.B., Smirnova L.P., Kazadzhan L.B. The effect of thermomagnetic processing on the magnetic properties and domain structure of industrial transformer steel. Precision alloys. M .: Metallurgy. 1975. No2. S.157-162. 2. Shulika VV, Startseva I.E., Chistyakov V.K., Dragoshansky Yu.N. Anisotropy of the effect of thermomagnetic treatment in electrical steels. FMM. 1988.V. 66. Number 4. S.667-673.].

The effect of thermomagnetic treatment of anisotropic soft magnetic materials was proposed to be increased by increasing the frequency of the magnetic field [patent RU No. 2025504] or by introducing an additional operation before thermomagnetic processing — irradiation with accelerated inert gas ions [patent RU No. 2321644].

Closest to the physical nature of the present invention is a method of thermomagnetic processing of anisotropic magnetically soft materials [patent RU No. 2025504] in the form of a sharply textured electrical steel tape, which includes high-temperature annealing, exposure, cooling to room temperature and thermomagnetic processing in alternating magnetic field with a frequency of 0.2 -1.0 kHz, the direction of which coincides with the direction of rolling the tape (longitudinal direction, figure 1). This method allowed to reduce the magnetic loss (and hence the coercive force) of anisotropic electrical steel by only 10-15%.

The basis of the invention is the task of improving the magnetic characteristics of anisotropic magnetically soft materials by increasing the effect of thermomagnetic processing, namely increasing the ability of the material to induce uniaxial magnetic anisotropy during this treatment.

The problem is solved in that in the known method of processing anisotropic magnetically soft materials in the form of an electrical steel tape, including high-temperature annealing, exposure, cooling to room temperature and thermomagnetic processing in an alternating magnetic field, according to the invention, when thermomagnetic processing the tape is deviated from the direction of the magnetic field by angle φ around its transverse direction.

Wherein:

- the deviation angle φ is selected in the range from 1 to 10 °;

- the frequency of the magnetic field of 0.05-1.0 kHz.

The essence of the invention is as follows. It is known that the largely positive effect of thermomagnetic treatment in an alternating magnetic field is due to the reorientation of the axes of the pairs of the nearest atoms of the dissolved elements in the alloy and the interaction of the atoms of the dissolved elements with oscillating boundaries of the magnetic domains [1. Zaykova V.A., Startseva I.E., Filippov B.N. Domain structure and magnetic properties of electrical steel. M .: Nauka, 1992.270 s .; 2. V.V. Governors and others. Formation of the properties of ferromagnetic alloys during thermomagnetic and thermomechanical treatments. Physics of metals and metal science. 2004.V. 98. No. 1. S.31-37]. The magnetic field tends to reorient the axis of pairs of the nearest atoms of the dissolved elements (in the Fe alloy ~ 3% Si are mainly silicon atoms) so that the angle between the axis of the pairs and the direction of the magnetic field (magnetic field vector) is minimal. This is possible by jumping silicon atoms from the central nodes of the body-centered cubic lattice to its vertices. This process occurs due to the inevitable presence of thermal vacancies in the alloy. The state of silicon atoms when they are at the vertices of a cubic lattice is nonequilibrium. In an alternating magnetic field, the boundaries of magnetic domains clear their oscillation zone from various types of inhomogeneities (atoms of dissolved elements, impurities and defects in the crystal structure) due to magnetoelastic interaction with them. In this case, more “clean” zones are formed. Heterogeneities accumulate at the extreme positions of domain walls, forming narrow “dirty” zones, elongated along the direction of the magnetic field and alternating with “clean” zones. The presence of "clean" areas increases the magnetic permeability, reduces the coercive force and magnetic losses due to the destabilization of the magnetic domain structure [V.V. Governors and others. The effect of cyclic temperature changes near the Curie point on the effects of thermomagnetic treatment of soft magnetic alloys. Physics of metals and metal science. 2008.V. 106. Number 4. S.367-370].

In the isotropic polycrystalline alloy Fe ~ 3% Si, the axis of pairs of the nearest silicon atoms are randomly located relative to the applied magnetic field, and in the anisotropic alloy with the (110) [001] texture, they lie along the magnetic field. Therefore, the effects of thermomagnetic processing will be different: in the first case, it will be significantly higher, since the majority of silicon atoms will be exposed to the process of "moving - clearing". In anisotropic material, their position along the field is stable. This equilibrium can be violated by deviating [001] from the direction of the magnetic field. In reality, this can be done by deflecting the plane of the tape (plane (110)) around its transverse direction [110] from the direction of the magnetic field. As a result, the “moving-clearing” mechanism will be launched and the effect of thermomagnetic processing will increase.

Figure 1 shows the designation of the directions in the tape of cold rolled anisotropic electrical steel coil: NP - rolling direction, direction of movement of the tape, longitudinal direction, [001]; PN - transverse direction, [110]; (110) - plane of the tape, plane of rolling.

Figure 2 - arrangement of the tape of electrical steel in the furnace during thermomagnetic processing according to the proposed method.

The method was carried out on the widely used magnetically soft alloy Fe - 3% Si. A large single crystal (110) [001] was cut from a finished steel strip 0.5 mm thick. It was 70% rolled along [001] to a thickness of 0.15 mm and annealed at 770 ° C for 20 minutes. As a result, a grain of 0.02 mm and a sharp texture {110} <001> were obtained in a thin plate. The plate was cut into samples 0.15 × 5 × 100 mm in size, elongated along [001]. This method of sample preparation made it possible to obtain strictly identical samples (from one single crystal, with simultaneous processing) and to minimize the possible spread of experimental data. Thermomagnetic treatment was carried out at 500 ° C for 15 min with cooling in an alternating magnetic field of industrial frequency and an amplitude of 10 kA / m. Moreover, the field direction coincided with the direction [001] of the textured samples (φ = 0), or was deviated from it by φ = ± 8 °. On samples processed according to the first embodiment, a known method of thermomagnetic processing was implemented. After thermomagnetic treatment, the coercive force of the H samples was determined _{from the} magnetic hysteresis loops taken with a device based on the F-190 photovoltaic compensation microwebermeter.

The table shows the change in H _{from the} Fe - 3 wt.% Si alloy for different thermomagnetic treatment options. The gain in the reduction of H _with the proposed method is 2-3 times more compared to the known one.

It should be noted that thermomagnetic treatment according to the proposed method can also be subjected to coarse-grained, sharp-textured, soft magnetic materials.

The proposed method of thermomagnetic processing of soft magnetic materials is very technological: allows processing in the process of continuous movement of steel tape 1 in the process stream; the angular deviation φ of the tape can be set by installing the guide rollers 2 in the furnace 3 for thermomagnetic processing at different heights (figure 2).

Table The influence of processing methods on N _{with an} alloy of Fe - 3 wt.% Si Processing method φ, ° N _s , A / m Change N _s ,% Before TMT After TMT Famous 0 24.8 22.4 -9.8 Proposed -8 24.8 17.6 -29.0 +8 24.0 19,2 -20.0

Claims (2)

1. The method of thermomagnetic processing of anisotropic soft magnetic materials in the form of a tape of electrical steel, including high-temperature annealing, exposure, cooling to room temperature and processing in an alternating magnetic field, characterized in that when processing in a magnetic field, the plane of the tape is deviated from the direction of the magnetic field by an angle of range from 1 ° to 10 ° in the direction of movement of the tape. 2. The method according to claim 1, characterized in that the frequency of the magnetic field is 0.05-1.0 kHz.

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