JPH03287725A - Production of grain-oriented silicon steel sheet reduced in iron loss - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel sheet of low iron loss free from deterioration due to stress relief annealing by locally irradiating the surface of a finish-annealed grain-oriented silicon steel sheet surface of specific temp. with electron beam of high voltage and small electric current and also properly shifting this electron beam irradiation. CONSTITUTION:A slab of a silicon steel containing about 2.0-4.5wt.% Si is hot-rolled and cold-rolled and then subjected to recrystallization annealing and to finish annealing, and, if necessary, an insulation coating is formed on the surface. The temp. of the resulting grain-oriented silicon steel sheet is regulated to >=50 deg.C. The surface of this steel sheet is locally irradiated with electron beam. As this electron beam, the one produced at a voltage as high as about 65-500kV and an electric current as small as about 0.01-5mA is used, and the irradiation of this electron beam is shifted in a direction orthogonal to the rolling direction of the steel sheet. By the above procedure, a forsterite film on the above steel sheet can be pressed into ferrite together with the insulation coating, if necessary, by which a magnetic domain can be fractionized and iron loss can be reduced. By this method, the grain-oriented silicon steel sheet of low iron loss free from deterioration even if subjected to stress relief annealing can be obtained.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for manufacturing unidirectional silicon steel sheets with low core loss, and in particular, to a method for manufacturing unidirectional silicon steel sheets with low core loss, in particular, by press-fitting a coating on the surface of a steel sheet into a base steel, the magnetic domains are removed. This relates to a method of reducing iron loss by subdividing the iron.

Unidirectional silicon steel sheets are mainly used as iron cores for transformers and other electrical equipment, and are required to have excellent magnetization characteristics, that is, low iron loss (represented by Wlff/S). There is.

For this purpose, firstly, the secondary recrystallized grains in the steel sheet should be <001
＞It is necessary to highly align the oriented grains in the rolling direction,
Secondly, it is necessary to reduce as much as possible the impurities and precipitates present in the final product steel. The iron loss value of unidirectional silicon steel sheets manufactured under these considerations has been improved over the years due to numerous efforts to date. As the demand for equipment becomes stronger, there is a demand for the production of unidirectional silicon steel sheets with even lower iron loss as the iron core material for these devices.

(Prior art) By the way, in order to reduce the iron loss of unidirectional silicon tlAvi, (1) increase the Si content (2) reduce the thickness of the product plate (3) make the secondary recrystallized grains finer (4) ) Reduction of impurity content (5) (110) Mainly metallurgical methods are generally known, such as aligning secondary recrystallized grains with <001> orientation to a higher degree, but these methods are currently We have reached the limit of our production means, and it is extremely difficult to make any further improvements, and even if some improvement is made, the effect of iron loss improvement will be small compared to the efforts made. There is.

Apart from these methods, as disclosed in Japanese Patent Publication No. 54-23647, it has been proposed to make secondary recrystallized grains finer by forming a secondary recrystallized grain blocking region on the steel sheet surface. has been done. However, this technique cannot be said to be practical because control of the secondary recrystallized grain size is not stable.

On the other hand, Japanese Patent Publication No. 5B-5968 discloses a technique for reducing iron loss by introducing micro-strain into the surface of a steel plate after secondary recrystallization using a ballpoint pen-shaped ball to refine the width of the magnetic domain and reduce iron loss. No. 57-2252, No. 5753419, No. 58-24605, and No. 58-24605 or Tetsu to Tsuna, 69 (1983), P, 895
(Tasashi Ichiyama) irradiates the surface of the final product sheet with a laser beam at intervals of several strands almost perpendicular to the rolling direction to introduce high dislocation density regions on the surface of the steel sheet, thereby refining the width of the magnetic domains.
Techniques to reduce iron loss have also been proposed.

Furthermore, Japanese Patent Publication No. 57-188810 proposes a similar technique in which fine strain is introduced into the surface layer of a steel sheet by electrical discharge machining to refine the magnetic domain width and reduce iron loss. Also, recently, Japanese Patent Application Laid-open No. 62-96617, No. 62-15151
No. 1, No. 62-151516 and No. 62-15151
In each of the No. 1 publications, a method was proposed in which local microstrain was introduced into the surface of a steel sheet by plasma irradiation to subdivide the magnetic domain, thereby reducing iron loss.

All of these four methods aim to reduce iron loss by refining the magnetic domain width by introducing minute plastic strain to the surface of the base steel of the steel sheet after secondary recrystallization. Although it is practical and has an excellent iron loss reduction effect, the effect of introducing plastic strain is reduced by heat treatment such as strain relief annealing after punching, shearing, and winding of steel plates, and baking of other coatings. With drawbacks.

A method has been proposed in which iron loss does not deteriorate even when such high-temperature strain relief annealing is performed. For example, a method of forming grooves or serrations on the surface of a finish annealed plate (Japanese Patent Publication No. 50
-35679, JP-A-59-28525 and JP-A-59-28525
-197520), a method for forming fine recrystallized grain regions on the surface of a finish annealed plate (Japanese Unexamined Patent Publication No. 56-1304
54), a method of forming a different thickness or a defective region in a forsterite film (see Japanese Patent Application Laid-open Nos. 60-92479, 60-92480, 60-92481, and 60-258479). , a method for forming regions of different compositions in the substructure, in the forsterite coating, or in the tension insulation coating (JP-A-60-103124 and JP-A-60-103124)
103182), etc.

However, these methods have not been adopted industrially because the process is complicated, the effect of reducing iron loss is small, and the manufacturing cost is high.

(Problems to be Solved by the Invention) The present invention provides a low core loss unidirectional structure in which the core loss reduced by magnetic domain refining does not deteriorate even after strain relief annealing, and stable manufacturing is possible. The purpose of this paper is to propose an advantageous method for manufacturing raw steel sheets.

(Means for Solving the Problems) This invention aims to increase the temperature of a unidirectional silicon steel sheet after finish annealing to 50°C or higher, and to apply an electron beam generated at a high voltage and a small current to the surface of the copper sheet. A method for producing a low core loss unidirectional silicon steel sheet, characterized in that the coating on the surface of the copper sheet is press-fitted into the base steel by locally irradiating the copper sheet and moving the sheet in a direction perpendicular to the rolling direction of the sheet. It is.

The unidirectional silicon steel sheet after finish annealing that is the object of this invention has a forsterite coating on its surface, but a material in which an insulating coating is further formed on the forsterite coating is also suitable.

Such an insulating film is preferably formed by a coating containing phosphate and colloidal silica as main components.

In order to press-fit the forsterite coating and the insulating coating deep into the steel base in minute areas lined up in a direction perpendicular to the rolling direction of the steel plate, a high voltage and small current electron beam (hereinafter referred to as EB) is used. It becomes possible only when you use it. That is, especially high voltage (about 65 to 500 kV)
When using EB with a large and small current (approximately 0.01~5+aA), the pressing force in the thickness direction is stronger than other methods (laser, plasma, mechanical methods, etc.).
Moreover, since it can be press-fitted with the narrowest width, it is possible to press it into the base iron without losing the underlying forsterite coating and insulation coating.

Further, as the silicon-containing steel which is the material of this invention, any conventionally known compositions are suitable, but typical compositions are as follows.

C: 0.01 to 0.10 wtχ (hereinafter simply expressed as %)
C is a component useful not only for uniform refinement of the structure during hot rolling and cold rolling, but also for the development of Goss orientation, and its content is preferably at least 0.01%. However, 0.1
If the content exceeds 0%, the Goss orientation will be disturbed, so the upper limit is preferably about 0.10%.

Si: 2.0 to 4.5% St increases the specific resistance of the steel sheet and effectively contributes to reducing iron loss, but if it exceeds 4.5%, cold rollability is impaired;
If it is less than 0%, not only will the resistivity decrease, but also randomization of crystal orientation will occur due to α-γ transformation during the final high-temperature annealing performed for secondary recrystallization and purification, resulting in a sufficient iron loss improvement effect. is not obtained, the amount of Si is preferably about 2.0 to 4.5%.

Mn: 0.02 to 0.12% Mn is at least 0.02% to prevent hot embrittlement.
%, but if it is too large, the magnetic properties will deteriorate, so it is preferable to set the upper limit at about 0.12%.

As inhibitors, so-called MnS, MnSe
There are two types: the AIN system and the AIN system.

In the case of MnS SMnSe, at least one selected from S and Se: 0.005 to 0.06% 5SSe is an inhibitor that controls secondary recrystallization of grain-oriented silicon steel sheets. It is a powerful ingredient. From the viewpoint of securing suppressive power, at least 0.005% is required, but if it exceeds 0.06%, the effect will be impaired, so the upper and lower limits are about 0.01% and 0.06%, respectively. It is preferable to do so.

In the case of AIN type, Al: 0.005 to 0.10%, N: 0.
The ranges of 004% to 0.015% AI and N were also set to the above ranges for the same reason as in the case of the MnS and MnSe systems mentioned above. Here the MnS mentioned above,
MnSe type and AIN type can be used together.

In addition to the above-mentioned S, Se, and ^1, inhibitor components include Cu, Sn, Cr, Ge, Sb, Mo,
Since Te, Bi, P, etc. are also advantageously compatible, small amounts of each can also be included. Here, the preferred content ranges of the above components are Cu, Sn, and Cr, respectively:
0.01-0.15%, GeSb, Mo, Te,
Bi: 0.005~0.1%, P: 0.01~
0.2%, and each of these inhibitor components can be used alone or in combination.

(Function) Next, this invention will be specifically described based on experimental examples.

C: 0.046%, Si: 3.46%, Mn:
0.072%, Se: 0.022%, Sb: 0
．． A silicon steel slab containing 0.026% and Mo: 0.013%, the remainder being substantially Fe, was heated at 1360°C for 5
After heating for several hours, it was hot-rolled into a 2.6 anO hot-rolled plate with a thickness of 2.6 anO, and then cold-rolled twice with an intermediate annealing at 950°C for 12 minutes to form a final cold-rolled plate with a thickness of 0.20 mm. did. Next, after performing primary recrystallization annealing which also serves as decarburization in a wet hydrogen atmosphere at 830"C, a slurry coating of an annealing separator mainly composed of MgO is applied to the surface of the steel sheet, and then annealing at 860"C for 55 minutes.
After performing secondary recrystallization annealing for 0 hours to preferentially grow Goss-oriented secondary recrystallized grains, annealing was performed for 5 hours in a dry hydrogen atmosphere at 1220°C.
Subjected to time purification annealing. Next, an insulating film containing phosphate and colloidal silica as main components was formed on the surface of the steel plate, and then EB with a beam diameter of 1.5 mm was generated at 150 kV and 1.3 mA at temperatures ranging from room temperature to 800°C. Irradiation was applied to both sides of a copper plate at 511III+ intervals or to one side of an m plate at 10 mm intervals in a direction perpendicular to the rolling direction under conditions where the steel plate temperature was varied over a range of temperatures. Thereafter, the samples irradiated on both sides were subjected to strain relief annealing at 800° C. for 3 hours. Similar experiments were also conducted using a comparative material that was not subjected to EB irradiation.

The iron loss characteristics (Wl'l/%. value) of each steel plate thus obtained are summarized in FIG. In the same figure, in the case of a steel plate that is not subjected to EB irradiation, the iron loss characteristics hardly change even if the temperature of the steel plate is changed. On the other hand, it is noteworthy that the iron loss characteristics of EB irradiated materials change significantly. That is, in the EB irradiated material, the iron loss characteristics are further improved at a steel plate temperature of 50° C. or higher for both the single-sided irradiated material and the double-sided irradiated material. Preferably, the iron loss characteristics are good in the temperature range of 150 to 750°C.

Although the reason why EB irradiation improves the iron loss characteristics when the temperature of the steel plate is elevated is not completely clear, it is clear that when EB irradiation is performed while the steel plate is thermally expanded, the magnetic domain It is possible to effectively perform subdivision and is considered to be effective in improving iron loss characteristics. Therefore, this invention is completely unexpected from known documents.
The effect and idea are new.

When heating a steel plate when irradiating this EB, it is preferable to uniformly heat the steel plate across the width of the plate in advance, and conventionally known methods such as resistance heating, infrared heating, etc. can be used for this purpose. Moreover, when carrying out in a continuous system, roll heating etc. are also suitable.

(Example) Steel plate with two types of component compositions, namely (A) C: 0.071%, Si23
．． 39%, Mn: 0.081%, ^1
: 0.025%, Se: 0.025%, Cu
: 0.068%, Mo: 0.013%, and (B) C: 0.044%, Si: 3.39%
, Mn: 0.066%, Se: 0.022%,
A finish annealed silicon steel plate (each plate thickness 0.23 mm) containing Sb: 0.023% and Mo: 0.013% was coated with forsterite, and on top of that was a coating containing phosphate and colloidal silica as main components. A steel plate coated with an insulating coating was irradiated with EB in dots on one side and both sides.

The EB irradiation conditions are: acceleration voltage: 175 to ν, acceleration current: 1.3mA, beam diameter: 0.13mmφ, beam spot spacing: 300μm (both sides) and 350μm.
(single side), scanning interval: 5mm (both sides) and 10 mm (single side). Further, the temperature of the steel plate at this time was 200°C.

Note that the double-sided irradiated material was subjected to strain relief annealing at 800° C. for 3 hours.

The magnetic properties of the fil plate thus obtained (Boo, 'A
r,ys. ) are shown in Table 1.

Table 1 By doing so, a unidirectional silicon steel sheet with further reduced iron loss can be obtained.

[Brief explanation of drawings]

FIG. 1 is a graph showing the influence of steel plate temperature on the iron loss characteristics of EB irradiated material and non-EB irradiated material. (Effect of the invention)

Claims (1)

[Claims] 1. The temperature of the unidirectional silicon steel plate after final annealing is 50℃.
On the other hand, by locally irradiating the surface of this steel plate with an electron beam generated with high voltage and small current and moving it in a direction perpendicular to the rolling direction of this steel plate, the film on the surface of this steel plate can be removed. A method for producing a low iron loss unidirectional silicon steel sheet, which is characterized by press-fitting it into a base steel.