JPH04311576A - Production of grain-oriented silicon steel sheet in which property is not deteriorated by stress relieving annealing - Google Patents

Abstract

PURPOSE:To stably execute the fractionizing of a magnetic domain with a sufficiently high iron loss reducing effect without losing the above effect and without causing the remarkable deterioration in its magnetic flux density in a method for manufacturing a grain-oriented silicon steel sheet. CONSTITUTION:Oxide 2 on the surface of a grain-oriented silicon steel sheet 1 after secondary recrystallization annealing is locally removed. Next, the part at which the oxide 2 has been removed is subjected to alloy plating 3. After that, this steel sheet is subjected to heat treatment to change the stress of the alloy plating, and subsequently, this steel is coated with an insulating film 4.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for manufacturing grain-oriented silicon steel sheets with low iron loss, and more specifically, to a method for manufacturing grain-oriented silicon steel sheets with improved iron loss characteristics through magnetic domain refinement.
In particular, the purpose is to propose a manufacturing method in which the magnetic domain refining effect is not lost due to strain relief annealing required in winding transformers and the like.

Grain-oriented silicon steel sheets are mainly used as cores for transformers and other electrical equipment. The properties of such grain-oriented silicon steel sheets are defined by magnetic flux density and iron loss, and the higher the magnetic flux density (represented by the magnetic flux density B8 (T) at a magnetizing force of 800 A/m), the more desirable. Also, iron loss (1.7 T, 50 Hz iron loss W17/50
) is preferably lower.

0003

[Prior Art] Means for lowering the iron loss of grain-oriented silicon steel sheets include (1) increasing the silicon content; (2)
(3) Reduce the secondary recrystallized grains, (4) Reduce the impurity content, (5) Align the crystal orientation of the secondary recrystallized grains to the direction of the easy axis of magnetization, etc. , mainly metallurgical means were taken, but in recent years, in addition to such metallurgical means, 18
The magnetic domain refining method, which reduces the width of the 0 degree magnetic domain, has come to be used as an effective method. However, since this magnetic domain refining method utilizes local plastic strain, there remains the problem that the effect is lost when strain relief annealing, which is necessary for iron cores for wound transformers, etc., is applied. Therefore, a magnetic domain refining technology that does not use plastic strain is thought to be necessary, and various research and development efforts have been conducted.

[0004] Many techniques have already been disclosed as magnetic domain refining techniques in which the effects are not lost by strain relief annealing. For example, techniques that utilize elastic strain have been developed, and the oldest ones are Japanese Patent Publication No. 2-8027 and Japanese Patent Publication No. 2-802.
No. 8 discloses a technique that utilizes the tension effect of forsterite. Further, Japanese Patent Publication No. 2-5821 discloses a technique of forming localized foreign parts in forsterite and utilizing the elastic strain generated thereby. However, although all of these techniques are effective,
The effect is significantly smaller than that of magnetic domain refining technology that uses plastic strain. Also, a technique has been developed that utilizes the demagnetizing field of a locally placed foreign object. The oldest technology disclosed in Japanese Unexamined Patent Publication No. 60-89545 also describes a technique for subdividing magnetic domains by placing foreign matter locally inside the surface layer of the steel and utilizing the demagnetizing field of the foreign matter. Tokuko Showa 63-3
Publication No. 1527 also discloses a technique for subdividing magnetic domains by placing foreign matter locally inside the surface layer of the steel and utilizing the demagnetizing field of the foreign matter. In addition, Japanese Patent Application Laid-open No. 60-255296 discloses that a groove is locally formed inside the surface layer of the base metal and filled with metal.
Publication No. 2-54873 discloses a technique in which grooves are created in the surface layer of the base iron by pickling, and a phosphate coating is applied to the upper layer to inevitably fill the inside of the grooves. Although each of these techniques is effective, they have a major drawback in that the magnetic flux density equally decreases due to the formation of grooves inside the surface layer of the steel. Furthermore, Japanese Patent Publication No. 62-4875 proposed a method for localized placement of foreign matter without forming grooves.
Publication No. 5, Special Publication No. 62-33308 and Special Publication No. 6
Publication No. 2-56926 discloses a technique for thermally diffusing a colloid by attaching it, a technique for thermally diffusing a displacement-plated substance, and a technique for diffusing an attached substance using energy such as laser discharge machining. ing. However, all of these techniques have unstable effects because they attempt to infiltrate foreign matter into the steel base before secondary recrystallization annealing, and the effect of the magnetic domain refining of the diffused phase itself is not very large. For these reasons, the iron loss reduction effect is not as great as expected. Further, in Japanese Patent Application Laid-Open No. 62-51202, thermal diffusion of metal is performed locally on the plate after secondary recrystallization annealing, but the improvement effect is still not so great compared to other methods.

[0005]

[Problem to be Solved by the Invention] To stably subdivide a magnetic domain that has a sufficiently large iron loss reducing effect without losing the effect even by strain relief annealing and without causing a significant decrease in magnetic flux density. It is an object of the present invention to propose a novel method for producing grain-oriented silicon steel sheets.

[0006]

[Means for Solving the Problems] This invention locally removes oxides on the surface of a grain-oriented silicon steel sheet after secondary recrystallization annealing, then performs alloy plating on the portion where the oxides are removed, and then A method for producing a grain-oriented silicon steel sheet whose properties do not deteriorate due to strain relief annealing, characterized in that the steel sheet is subjected to heat treatment to change the stress of the alloy plating, and then an insulating coating is applied to the steel sheet (first invention). It is.

[0007] Furthermore, the present invention locally removes oxides and insulating coatings on the surface of grain-oriented silicon steel coated with an insulating coating after secondary recrystallization annealing, and then injects an alloy into the removed portions of the oxides and insulating coating. A method for producing a grain-oriented silicon steel sheet whose properties do not deteriorate due to strain relief annealing, characterized by applying plating, then heat-treating the steel sheet to change the stress of the alloy plating, and then applying an insulating coating to the steel sheet. (Second invention).

An example of a steel plate obtained according to the manufacturing method of the present invention is shown in cross section in FIG. Substrate (oriented silicon steel plate)
Oxide 2 on one surface is locally removed, a plating alloy 3 is deposited on the removed portion, and an insulating film 4 is deposited covering the oxide 2 and plating alloy 3.

[0009]

[Operation] In this invention, the oxide present on the surface of the base steel after secondary recrystallization annealing is removed so as not to damage the base steel as much as possible, and further, the defective portions of the removed oxide are subjected to alloy plating. When alloy plating is further subjected to appropriate heat treatment, the stress applied to the surrounding area changes significantly due to an effect that is thought to be caused by alteration, that is, rearrangement of atoms from an amorphous state. Therefore, the same effect as applying strong strain locally can be obtained, and since the strain is not plastic strain, the effect will not be lost by subsequent annealing.

Further, the present invention will be specifically explained based on the order of the process. In this invention, a grain-oriented silicon steel plate after secondary recrystallization annealing is used. Grain-oriented silicon steel plate is
Prior to the secondary recrystallization annealing, an annealing separator, usually based on MgO, is applied to the surface in order to carry out the subsequent secondary recrystallization annealing at high temperature and the subsequent purification annealing, thus the secondary recrystallization annealing The surface of the subsequent steel plate is covered with an oxide film whose main component is forsterite. In this invention, this oxide film is locally removed. The shape of the removed portion is in the form of lines or rows of points,
It is desirable that the lines or rows are repeatedly arranged at an angle of 45 degrees or more, preferably at right angles, to the rolling direction of the steel plate, that is, the direction of the axis of easy magnetization. FIG. 2 shows a plan view of the form of the removed portions when they are arranged in parallel lines. Furthermore, it has been confirmed that it is effective if the removal width (W in FIG. 2) is 50 μm or more, but if it exceeds 0.5 mm, the appearance becomes poor and the magnetic flux density decreases significantly. Regarding the repetition interval (L in FIG. 2) between the removed parts, it is desirable that the interval be 2 mm or more when they are arranged in parallel lines, and the effect will be small if the interval exceeds 10 mm. It is sufficient to apply the removal portion to one side of the board surface, or it may be applied to both sides.

[0011] As a method for removing oxides, methods that leave large processing strains on the plate surface are not suitable. This is because, on the contrary, the magnetic properties are deteriorated. Also, it is necessary to avoid removing the base metal part as much as possible. This is because even locally removing the base metal portion causes a decrease in magnetic flux density. However, this involves very difficult problems in practice. This is because, in actual grain-oriented silicon steel sheets, the interface between the oxide and the base metal is not flat and is complicated. As a specific method for removing oxides in such an interface state, the most suitable method is to crush and remove oxides using a needle-shaped vibrator to which ultrasonic waves are applied as a processing end. In addition, oxides can be removed by irradiation with energy-controlled laser light or electron beam.

Next, the removed portion is plated with an alloy. The plating of this alloy and the subsequent heat treatment were the most difficult part of this invention, and are also the characteristics of this invention. It is important to select a plating alloy whose internal stress will change significantly through post-forming heat treatment, and which will not cause deterioration such as peeling even when subjected to strain relief annealing at approximately 800°C after forming the iron core. be. Such alloys include, for example, Ni-P, Ni-Co, Fe-Ni.
, Cu-Ni, Sn-Ni, etc. are suitable, especially N
i-P alloy plating is advantageously compatible with this invention.

[0013] In order to investigate the effect of heat treatment temperature on iron loss characteristics after alloy plating is applied by the method according to the present invention, the material after secondary recrystallization annealing was subjected to repeated intervals of 5 mm.
After oxide removal with a removal width of 0.2 mm was performed using a diamond needle to which ultrasonic waves were applied, Ni-P alloy plating was applied. The content of P in the alloy is 12wt%
The basis weight was 15 g/m2. After that 200 ~
Heat treatment was performed at various temperatures of 1000° C. for 3 minutes, and after further heat treatment, an insulating coat of phosphate was applied. The results thus obtained are shown graphically in FIG. From the same figure, it can be seen that if the heat treatment temperature is less than 500°C, the effect of reducing iron loss is not so great. On the other hand, if the heat treatment temperature exceeds 1000℃, it becomes impractical to carry out continuous heat treatment.
The heat treatment temperature is preferably in the range of 500 to 1000°C. More preferably, the temperature is in the range of 500 to 800°C.

[0014] Furthermore, if the heat treatment time is less than 3 minutes, a stable effect cannot be obtained, so it is preferable to carry out the heat treatment for 3 minutes or more. The upper limit is not particularly limited, but
For continuous industrial heat treatment, it is desirable to set the temperature to about 1000°C.

[0015] In the second invention, the oxide and the insulation coating on the surface of the grain-oriented silicon steel sheet provided with the insulation coating after the secondary recrystallization annealing are locally removed. In this way, the same effect can be obtained by applying an insulating coating to the surface of the steel sheet after secondary recrystallization annealing, then locally removing insulators and oxides, then applying alloy plating, and then applying heat treatment. It will be done.

[0016]

[Example] Example 1 C: 0.06wt% (hereinafter simply expressed as %), Si: 3.
2%, Mn: 0.07%, Se: 0.020%, and Sb: 0.018%, and the remainder is substantially Fe.
A silicon steel slab having the composition was heated at 1350° C. for a period of time and then hot-rolled to obtain a hot-rolled plate. then 100
After uniform annealing at 0°C for 2 minutes, cold rolling was performed twice with intermediate annealing at 1000°C for 2 minutes to a thickness of 0.20 mm.
The final cold-rolled sheet was obtained. Then, after decarburization and primary recrystallization annealing in wet hydrogen at 820°C, MgO
Apply an annealing separator mainly composed of
A purification annealing with a secondary recrystallization annealing was performed for an hour. The oxides on the surface of the steel plate were removed in a linear manner using a diamond needle to which ultrasonic waves were applied. The removal width at this time was 0.3 mm, and the lines were arranged as parallel lines repeatedly perpendicular to the plate rolling direction. The repeat interval is 4 mm. Various alloy platings were applied to the removed wire at a rate of 10 g/m2. After this alloy plating, the steel plate was heat treated at 300 to 900°C for 3 minutes. Furthermore, an insulating film containing phosphate and colloidal silica as main components was formed on the surface of the steel plate. After that 80
The final product was subjected to strain relief annealing for 3 hours in a N2 atmosphere at 0°C. Table 1 shows the results of measuring the iron loss characteristics of the thus obtained product after plating treatment and of the final product.

[0017]

Example 2 C: 0.07%, Si: 3.2%, Mn: 0.07%
, Se: 0.020%, Al: 0.024%, N:
A silicon steel slab containing 0.008%
After heating at ℃ for 1 hour, hot rolling was performed to obtain a hot rolled sheet. After that, after uniform annealing at 1100℃ for 2 hours, 300℃
The thickness is 0.2 by cold rolling with aging treatment in between.
A final cold-rolled sheet of mm was obtained.

After decarburization and primary recrystallization annealing in wet hydrogen at 820°C, an annealing separator containing MgO as a main component was applied to the surface of the steel sheet, and secondary recrystallization was performed at 1200°C for 5 hours. Crystal annealing was performed as purification annealing. Further, an insulating coating containing phosphate and colloidal silica as main components was formed on the surface of the steel plate.

Subsequently, the oxide and insulating coating on the surface of the steel plate were removed using a diamond needle applied with ultrasonic waves. The removal width at this time was 0.3 mm, and the lines were arranged as parallel lines repeatedly perpendicular to the plate rolling direction. Repeat interval is 5
It is mm. 10g of various alloy platings are applied to the wire after removal.
It was applied at a rate of m2. After this alloy plating, 300
Heat treatment was performed at ~900°C for 3 minutes. After that 80
The final product was subjected to strain relief annealing for 3 hours in a N2 atmosphere at 0°C. Table 2 shows the results of measuring the iron loss characteristics of the final product thus obtained.

[0021]

[0022]

According to the present invention, a grain-oriented silicon steel sheet whose magnetic properties do not deteriorate even after strain relief annealing can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an example of a grain-oriented silicon steel sheet obtained according to the manufacturing method of the present invention.

FIG. 2 is a plan view showing the manner in which oxides are removed from the surface of a steel plate.

FIG. 3 is a graph showing the effect of heat treatment temperature on core loss characteristics after alloy plating.

[Explanation of symbols]

1 Subway 2 Oxide 3 Plating alloy 4 Insulating film W Removal width L　Repetition interval

Claims (2)

[Claims] Claim 1: After secondary recrystallization annealing, oxides on the surface of a grain-oriented silicon steel sheet are locally removed, then alloy plating is applied to the areas where the oxides are removed, and then this steel sheet is heat-treated to form an alloy. A method for producing a grain-oriented silicon steel sheet whose properties do not deteriorate due to strain relief annealing, the method comprising applying an insulating coating to the steel sheet after changing the plating stress. Claim 2: After secondary recrystallization annealing, the oxide and insulation coating on the surface of the grain-oriented silicon steel coated with insulation are locally removed, and then alloy plating is applied to the areas where the oxide and insulation coating have been removed. A method for producing a grain-oriented silicon steel sheet whose properties do not deteriorate due to strain relief annealing, the method comprising: heat-treating the steel sheet to change the stress of the alloy plating, and then applying an insulating coating to the steel sheet.