JPH04224629A - Manufacture of low core loss grain-oriented silicon steel sheet - Google Patents

Abstract

PURPOSE:To obtain a low core loss grain-oriented silicon steel sheet free from the deterioration in core loss even if it is subjected to high temp. stress relieving annealing and useful not only as a laminated iron core but also as a rolled iron core. CONSTITUTION:The surface of a grain-oriented silicon steel sheet finished with finish annealing is coated with an insulating film essentially consisting of phosphate and colloidal silica, and this insulating film is subjected to crystallization annealing treatment and is thereafter irradiated with EB in a direction crossing the rolling direction of the steel sheet to subdivide its magnetic domain.

Description

Description: [0001] The present invention relates to a method for producing grain-oriented silicon steel sheets, which achieves low core loss through magnetic domain refining, particularly by EB irradiation. [Prior Art] Unidirectional silicon steel sheets have secondary recrystallized grains of the product highly concentrated in the Goss orientation, a forsterite coating on the surface, and a thermal expansion coefficient on the surface. It is coated with a small insulating film and is manufactured through a complex and diverse process that requires strict control. These unidirectional silicon steel sheets are mainly used as iron cores for transformers and other electrical equipment, and their magnetic properties include high magnetic flux density (represented by the B8 value) and iron loss (W17/ 50) and an insulating film with good surface properties. Particularly in the wake of the energy crisis, the need to reduce power loss has become particularly strong, and the need for unidirectional silicon steel sheets with lower iron loss as core materials for transformers has become increasingly important. ing. Now, it is no exaggeration to say that the history of improving the iron loss of grain-oriented silicon steel sheets is the history of improving the Goss-oriented secondary recrystallized texture, and it is no exaggeration to say that the history of improving the iron loss of grain-oriented silicon steel sheets is the history of improving the Goss-oriented secondary recrystallized grains. As a method for this purpose, a method has been implemented in which primary recrystallized grain growth control agents such as AlN, MnS, and MnSe, so-called inhibitors are used to preferentially grow Goss-oriented secondary recrystallized grains. Recently, in addition to controlling the secondary recrystallization texture, laser irradiation on the steel plate surface has been developed.
Tadashi Ichiyama: Tetsu to Hagane, 69 (1983), P. 895
, Special Publication No. 57-2252, No. 57-53419,
58-24605 and 58-24606} or plasma irradiation {JP-A-62-96617
No. 62-151511, No. 62-152516, and No. 62-151517], an innovative method was proposed to introduce small local strains to subdivide magnetic domains and thereby reduce iron loss. ing. however,
Steel sheets manufactured according to these methods have the disadvantage that they cannot be used as materials for wound core transformers, which require high-temperature strain relief annealing, because minute strains disappear when heated to a high temperature range. [0004] As a method that does not cause deterioration of iron loss even when such high-temperature strain relief annealing is performed, there is a method of forming grooves or serrations on the surface of a finish annealed plate (Japanese Patent Publication No. 1973-
35679, JP-A No. 59-28525 and JP-A-59-28525
197520) or a method of forming a fine crystal grain region on the surface of a finish annealed plate (Japanese Patent Laid-Open No. 1975-130).
454), a method for forming a different thickness or defective region in a forsterite film (Japanese Patent Laid-Open No. 60-9247)
No. 9, No. 60-92480, No. 60-92481, and No. 60-258479), a method of forming a different composition region in a steel base, in a forsterite coating, or in a tension insulation coating (JP-A No. No. 60-103124 and No. 6
0-103182), etc. are known. However, all of these methods have complicated processes, have little effect on reducing iron loss, and have high manufacturing costs, so they have not yet been adopted industrially. However, unlike the above-mentioned known invention, the inventors have previously developed a laminated iron core by irradiating an electron beam (EB) on the insulation coating of a unidirectional silicon steel sheet in a direction perpendicular to the rolling direction. It has been disclosed that a low iron loss unidirectional silicon steel sheet that can be used for both wound cores can be manufactured (see, for example, Japanese Patent Laid-Open No. 186826/1983). However, as a material for wound core transformers, further improvements in properties have been desired. [0006] The present invention advantageously satisfies the above-mentioned requirements, and uses the EB method to create a steel core with excellent iron loss characteristics that is suitable not only for stacked cores but also for wound cores. The purpose of this study is to propose a new manufacturing method for unidirectional silicon steel sheets. [Means for Solving the Problems] In this invention, the reason why the EB method is used as a means of manufacturing a low core loss unidirectional silicon steel sheet by performing magnetic domain refining is that the EB method requires high vacuum. Although it has the major disadvantages of having to utilize it, on the other hand, it is possible to narrow down the beam, ■ it is easy to scan the beam, and ■ it has a deep beam penetration depth.
■This is because it has many advantages, including a good beam energy effect. Furthermore, in recent EB technology, high voltage and small current EB has been developed, and it has become possible to irradiate unidirectional silicon steel sheets with an insulating coating continuously and extremely efficiently at high speed. Now, as the cross section of a normal grain-oriented silicon steel sheet is schematically shown in FIG. An insulating film 3 is coated. This insulating film 3 is normally amorphous in the state of coating and baking treatment. Next, FIG. 2 is a schematic diagram showing a cross section of a steel plate when the magnetic domain refining technique using EB irradiation is applied. As shown in the figure, by applying EB irradiation (in a direction perpendicular to the rolling direction) on the insulating coating 3 and locally introducing minute strain, the magnetic domains can be subdivided, thereby achieving low iron loss. . For wound core materials, it is essential that the magnetic domain refining effect does not disappear even after strain relief annealing. For this purpose, it is necessary to apply strong EB irradiation to deepen the press-fit area of the steel plate. However, when the EB power density is increased and irradiated strongly, the steel plate is bent at the EB irradiation position, as shown in Figure 3, and even if magnetic domain refining is performed, the space factor is poor due to the unevenness of the steel plate. It can no longer be used as a product for rolled iron cores. In this regard, the inventors discovered that when EB irradiation is performed after crystallizing the insulating film, the irradiation effect is accelerated and irradiation scratches are effectively introduced into the insulating film (from the forsterite film to the ground). As a result, magnetic domain refinement is effectively carried out, and in this case, E as shown in Figure 3
It was newly discovered that no unevenness was observed on the steel plate 4 due to B irradiation. Furthermore, after such EB irradiation, if the EB irradiation position is pickled or electrolytically etched and then further coated, the effect of improving the magnetic properties will be further enhanced. The present invention is based on the above findings. In other words, the present invention provides an insulating film that is mainly composed of phosphate and colloidal silica, after forming an insulating film mainly composed of phosphate and colloidal silica on the forsterite film of a grain-oriented silicon steel sheet that has been subjected to finish annealing to have a forsterite film on its surface. This is a method for producing a unidirectional silicon steel sheet with low core loss, which comprises performing a crystallization annealing treatment on the coating, and then performing EB irradiation in a direction transverse to the rolling direction of the steel sheet to subdivide the magnetic domains. [Operation] Crystallization of the insulating film is achieved by annealing at a temperature of 800° C. or higher for 10 to 300 minutes. For this annealing method, a conventionally known method may be applied as is. The degree of crystallization was determined by X-ray diffraction as Mg2P2O7.
When the peak of is detected, sufficient EB irradiation effect appears. The EB irradiation at this time may be the same as for stacked iron cores, but the irradiation dot spacing should be narrowed to about 1.2 to 3 times (100 to 2
00 μm), and finer irradiation intervals of 2 to 10 mm.
It is more effective if the amount is reduced. [Example] Material component (a) C: 0.078%, Si
:3.36%, Mn:0.078%, Al:0.02
6%, Se: 0.020% and Mo: 0.013
%, Material component (b) C: 0.044%, Si: 3.42
%, Mn: 0.072%, Se: 0.018%, S
A hot rolled sheet containing 0.025% b and 0.015% Mo was cold rolled twice with intermediate annealing at about 1000° C. in between to obtain a final product sheet with a thickness of 0.23 mm. After decarburization and primary recrystallization annealing in wet hydrogen at 840°C, an annealing separator containing MgO as a main component was applied to the surface of the steel plate, and (a) was annealed at 10°C/h from 850°C. 11
Temperature raised to 00℃, (b) 2 for 50h at 850℃
After performing secondary recrystallization annealing to develop Goss-oriented secondary recrystallized grains, annealing treatment was performed in dry H2 at 1200°C. [0016] Thereafter, an insulating film containing phosphate and colloidal silica as main components was formed on the surface of the steel plate. after that
Crystallization annealing of the insulating film at 800°C x 2h (A)
, or did not apply (B), then EB under the following conditions
Irradiation was performed. - EB irradiation (single-sided irradiation) with accelerating voltage: 200 kV, current: 1.0 mA, dot spacing: 150 μm, and spacing: 7 mm. After that, strain relief annealing was performed at 800°C for 2 hours. Table 1 shows the results of investigating the magnetic properties of the product thus obtained. *Measurement of irregularities using a three-dimensional roughness meter ○ Unevenness 2 μm or less Δ Unevenness 2 to 10 μm [Effects of the Invention] Thus, according to the present invention, the iron loss property is excellent, and this property can be improved by strain relief annealing. It is possible to stably produce unidirectional silicon steel sheets that do not deteriorate.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a typical unidirectional silicon steel plate.

FIG. 2 is a cross-sectional view of a grain-oriented silicon steel sheet to which magnetic domain refining technology using EB irradiation is applied.

FIG. 3 is a cross-sectional view of a grain-oriented silicon steel sheet when the EB power density of high voltage and small current is increased and intense irradiation is performed.

[Explanation of symbols]

1 Subway 2 Forsterite coating 3 Insulating coating 4 Steel plate

Claims (1)

[Claims] Claim 1: An insulating film containing phosphate and colloidal silica as main components is formed on the forsterite film of a grain-oriented silicon steel sheet which has been subjected to finish annealing to have a forsterite film on its surface. A method for producing a unidirectional silicon steel sheet with low iron loss, characterized in that the film is subjected to crystallization annealing treatment, and then EB irradiation is performed in a direction transverse to the rolling direction of the steel sheet to subdivide the magnetic domains.