JPH02200737A - Manufacture of low iron loss grain-oriented silicon steel sheet free from deterioration of properties caused by stress relieving annealing - Google Patents

Abstract

PURPOSE:To improve the iron loss of the silicon steel sheet by impressing ultrasonic vibration on the surface of a grain-oriented silicon steel sheet after subjected to secondary recrystallization annealing, locally removing an oxide layer thereon and thereafter subjecting the steel sheet to annealing treatment under prescribed conditions. CONSTITUTION:Ultrasonic vibration is impressed on the surface of a grain- oriented silicon steel sheet after subjected to secondary recrystallization annealing to locally remove an oxide layer on the surface of the above steel sheet. Next, the steel sheet is subjected to annealing treatment at >=950 deg.C in an inert gas atmosphere of <=-5 deg.C dew point. Thus, its iron loss is improved without the lowering of occupation rate and the deterioration of magnetic flux density.

Description

[Detailed Description of the Invention] (Industrial Application Field) Regarding the method of manufacturing a grain-oriented silicon steel sheet without deterioration of properties due to strain relief annealing, the technical contents described in this specification are as follows: By imparting non-uniformity to the oxide layer formed on the surface of the silicon steel sheet and forming areas on the surface where different tensions act or magnetically heterogeneous parts,
It is related to improving iron loss without causing property deterioration through strain relief annealing.

Grain-oriented silicon steel sheets are mainly used as iron cores for transformers and other electrical equipment, and their magnetization properties are excellent.
In particular, low iron loss (represented by Wl?/% value) is required.

For this purpose, the secondary recrystallized grains in the silicon steel sheet must be <001
．． >It is necessary to highly align the grain orientation in the rolling direction and to reduce as much as possible the impurities and precipitates present in the final product steel.

Grain-oriented silicon steel sheets manufactured under these considerations are
Through many improvement efforts to date, the iron loss value has been improved over the years, and recently products with a plate j so 0.30 threshold (I
l, tzs. A low core loss with a value of 1.05 W, ./kg has been obtained.

However, after the energy crisis a few years ago, electric power FM
The tendency to seek electrical equipment with less loss has become even stronger.
Unidirectional silicon steel sheets with even lower iron content are now required as core materials for these.

However, general methods for reducing iron loss in grain-oriented silicon steel sheets include increasing the St content, reducing the product thickness,
Refine secondary recrystallized grains, reduce impurity content,
Metallurgical methods are generally known, such as aligning secondary recrystallized grains with (110) (001) orientation to a higher degree, but these methods are no longer suitable for F of current production methods. It has reached its limit (1), and it is extremely difficult to improve beyond this point, and even if some improvement is recognized, the effective effect of iron loss improvement will be small compared to the efforts made.

(Prior art) Apart from the above-mentioned general method, Japanese Patent Publication No. 54-23647 discloses a method in which secondary recrystallization grains are made finer by forming a secondary recrystallization inhibiting region on the steel plate surface. A method is proposed. However, this method cannot be said to be practical because control of the secondary recrystallized grain size is not stable.

In addition, according to Special Publication No. 5B-5968,
After secondary recrystallization, a small ballpoint pen-shaped ball is applied to the surface of the steel plate.
Japanese Patent Publication No. 572252 discloses a technology that introduces micro-strain into the surface layer of a steel sheet to refine the width of the magnetic domain and reduce iron loss. This technology introduces high dislocation density regions into the surface layer of the steel sheet, refines the width of the magnetic domain, and reduces iron loss.
Each is proposed. Furthermore, JP-A-57-1888
A similar technique is also proposed in Japanese Patent No. 10 in which fine strain is introduced into the surface layer of a steel sheet by electric discharge coiling to refine the magnetic domain width and reduce iron loss.

All of these methods are performed after secondary recrystallization! ! This method aims to reduce the iron loss by making the magnetic domain width finer by introducing minute plastic strain into the surface layer of the steel plate.It is equally practical and has an excellent iron loss reduction effect. Strain relief annealing after punching, shearing, and winding of steel plates,
Seizing of the coating has the disadvantage that the effect of introducing plastic strain is diminished by the heat treatment.

Also, according to Japanese Patent Application Laid-Open No. 61-73886, the momentum 5
A technique has also been proposed in which the coating is removed using a vibrating body that is forced to move back and forth at a speed of more than
It has the disadvantage that its effect is largely lost by annealing at temperatures above 00°C.

In addition, if a minute plastic strain is introduced after the coating process, the C insulation coating must be reapplied to maintain insulation properties, which significantly increases the number of processes including the strain imparting process and the reapplying process, which increases costs. “Brings seven tsups.

In order to resolve the contradictions between these techniques, it has been proposed in Japanese Patent Laid-Open No. 6092481 to provide a defective portion to the forsterite coating.

As a method for forming such a defective part, the same publication describes the following:
Although a method in which forsterite is not partially formed and a method in which a defective portion is partially formed after formation are disclosed, the method that is actually advantageous for industrial application is:
This is a method in which forsterite is partially removed after it is formed.The reason for this is that methods that do not partially form forsterite use chemical means, that is, methods that inhibit the reaction, making process control difficult. This is because it is not of good quality.

On the other hand, methods for partially chipping forsterite after secondary recrystallization, that is, after forsterite formation, include chemical polishing, electrolytic polishing, mechanical polishing such as removal with a rotating disc-shaped grindstone, or removal with iron nails using light pressure. Furthermore, optical removal methods using a laser beam with adjusted output have been disclosed, but although each of these methods is effective in its own way, chemical polishing and electrolytic polishing significantly increase costs, and they also require a rotating disk. The use of a shaped grinding wheel is not suitable for industrial production because it is difficult to control the position to follow the disk height due to the surface texture, and furthermore, optical removal methods such as laser beams are expensive. expensive.

Although the method of removing the remaining iron nails using light pressure is low in cost, it is difficult to control the removal of only the forstiffi, so the surface of the bare iron is also removed, leaving no trace of removal. It is still difficult to implement this method industrially, since it causes the isthmus to bulge on both sides, resulting in adverse practical effects such as a significant decrease in the space factor.

In addition, a technology for forming grooves on the surface of a silicon steel sheet as a magnetic domain refining technology is disclosed in Japanese Patent Publication No. 50-35679,
-285,25, JP-A-59-197520, JP-A-61-117218 and JP-A-61-11.728
It is disclosed in various publications such as No. 4 and has become a widely known technique. However, since these techniques all utilize the phenomenon of magnetic domain refining caused by a demagnetizing field in the groove space, each method cannot withstand strain relief annealing. ), the mechanical properties deteriorate, and depending on the method of forming the grooves, the space factor can significantly deteriorate.

In this regard, the inventors previously proposed in Japanese Patent Application No. 63-311834 G a solution to the above-mentioned problem as "4" which was formed on the surface of a steel plate after finish annealing. We have proposed a method for producing grain-oriented silicon steel sheets in which the oxide layer of 1 is locally removed and polished by ultra-i wave vibration.

By using the above method, the B1゜ value is improved, the mechanical properties are improved, and there is almost no decrease in the pile ratio, and there is no deterioration of iron loss during strain relief annealing. It is easy to carry out, does not cause low operating efficiency, and it has become possible to obtain low iron I4 force oriented silicon steel sheets at low cost.

(Problems to be Solved by the Invention) This invention relates to the improvement of the above-mentioned manufacturing technology, and it is obvious that it is easy to implement and inexpensive in manufacturing, and does not cause a decrease in the occupancy rate. Low magnetic flux density P
We propose an advantageous manufacturing method for grain-oriented silicon steel sheets that makes it possible to further reduce core loss without causing any
The porpose is to do.

(Means for Solving the Problems) The present invention provides a method for solving the problem in areas where the tension of forsterite locally differs or in an oxide layer mainly composed of forsterite on the surface of a grain-oriented silicon steel sheet after secondary recrystallization. In this technology, a magnetic domain refining effect that can withstand strain relief annealing is achieved by forming a demagnetizing field, and in order to further improve magnetic properties, it is necessary to New finding that it is extremely effective to perform heat treatment under predetermined conditions after removing oxides from the surface of the board
I stand on this.

That is, this invention applies ultrasonic vibration to the surface of a grain-oriented silicon steel sheet after secondary recrystallization annealing, locally removes the oxide layer on the surface of the steel sheet, and then lowers the dew point to -5°C. A method for manufacturing a grain-oriented silicon steel sheet with low iron loss that does not cause property deterioration due to strain relief annealing, which comprises annealing at a temperature of 950°C or higher -4 in the following inert gas atmosphere (first invention)
It is.

Further, in this invention, prior to the annealing treatment described in J, dew point: 20
This is a manufacturing method (second invention) comprising performing an annealing treatment at a temperature of 600 to .9150°C in an inert gas atmosphere at a temperature of 600 to 9150°C.

This invention will be explained in detail below.

The material targeted by this invention is a grain-oriented silicon steel sheet whose surface is covered with an oxide layer containing forsterite as a main component and which has been subjected to secondary recrystallization annealing.

Now, in this invention, the oxide layer on the surface m1 of the steel plate is first locally removed, and in step 7 as a removal means,
It is important to use a processed terminal that has been subjected to ultrasonic vibration.

Beyond the processed terminal 11: The contact pressure against the I surface is
It is preferable to set it to about 40 kg/am” or less.
) is that when the contact pressure exceeds 40 kg/am, plastic strain is not introduced inside the steel plate, but the space factor decreases due to burrs of the surrounding steel, and furthermore, the processed edge deteriorates due to wear and tear. This is because it invites

Also, the ultrasonic conditions are frequency 710kHz or higher, amplitude = 5
It is preferable to use a vibration having a component perpendicular to the surface of the steel sheet with a vibration amplitude of 0 μ or less. This means that the frequency is 1
If the amplitude is less than 0 kHz, the effect is weak because the impact density of the vibration is small, whereas if the amplitude exceeds 50 μm, the impact force is too large, causing large distortion and deteriorating the magnetic flux density.

Furthermore, the processed terminal for applying ultrasonic vibration to the surface of the steel plate may be made of any material as long as it can locally remove the oxide layer, but diamond-based,
Diameter: 2m made of ceramic or cemented carbide
Cylindrical or hemispherical shapes of less than m are advantageously suitable.

In addition, it is preferable that the local removal of oxides be formed in continuous or non-continuous lines or points repeatedly in parallel across the rolling direction, and in particular, the direction is perpendicular to the rolling direction It is desirable that there be. Further, the interval between the parallel line groups is 1 to 30 am.

The width of the removed portion is preferably about 10 to 1000 microns. Furthermore, although it is sufficient to perform the removal treatment on one side, it goes without saying that the removal treatment may be performed on both sides.

Next, the steel plate from which the surface oxide layer has been locally removed as described above is subjected to heat treatment to improve its magnetic properties.

Figure 1 shows a grain-oriented silicon steel plate after secondary recrystallization (
Plate thickness: 0.111+nl11) The oxides on the surface are lined at intervals of 5+nm in the direction of the rolling force of the plate (vA width: 250/Im
) and then annealed for 1 hour at various temperatures in Ar with a dew point of -10''C, the results of investigating the effect of improving iron loss characteristics are shown.

As is clear from the figure, after removing oxides, the temperature exceeds 950℃.
By performing annealing at a temperature of -, the iron loss characteristics are significantly improved.

Figure 2 also shows the results of investigating changes in magnetic flux densities B and l when annealing was performed at 800 °C after oxide removal. A comparison is shown below.

As is clear from the figure, even when the oxides were removed by applying ultrasonic vibration according to the present invention, B8 decreased slightly, but was completely recovered by the subsequent annealing treatment.

In this regard, if the oxide is removed simply by pressure reduction, B
8 was significantly lowered, and therefore, even after subsequent annealing, a much lower B than the raw material could not be obtained.

In this way, after local removal of the oxide layer by applying ultrasonic vibration, annealing is performed at a temperature of 950°C or higher (preferably 1200°C or higher), thereby completely recovering the magnetic flux density and reducing iron loss. Significant improvements in properties are achieved.

In the above-mentioned annealing, the atmosphere needs to be inert. This is because the film deteriorates in an oxidizing atmosphere5.
This is because the magnetic properties deteriorate.

Furthermore, if the dew point of the atmosphere exceeds 15°C, the coating will deteriorate.
Since both adhesion and magnetic properties deteriorate, the dew point is -5℃.
It is necessary to do the following. Note that if the processing time is too short, a satisfactory effect will not be obtained, so the processing time should be 30 minutes.
It is preferable that the time is more than 1 minute.

Furthermore, in this invention, prior to the above annealing treatment, the dew point:
600~950" in an inert gas atmosphere at 20℃ or higher
By applying annealing treatment over a temperature range of -
It is possible to improve the iron loss characteristics of the layer.

Figure 1 shows the result of investigating the iron In properties when annealing was performed at 700°C for 13 minutes in an Ar atmosphere with a dew point of 30°C before the annealing shown with * in Figure 1. Also listed in

As shown in the figure, by performing annealing at 700° C. prior to annealing at 950° C. or higher, improvement in the core loss characteristics of the negative layer was achieved.

The annealing treatment prior to the above-described annealing at 950°C or higher is performed at a treatment temperature of 650 to 950°C (preferably 700 to 850°C).
℃), atmosphere: inert, atmosphere dew point = 20"C or higher. This means that the processing temperature is 650℃.
If less than 950
This is because if the temperature exceeds .degree. C., both iron loss and magnetic flux density deteriorate, and the effect of improving the iron 1 member cannot be obtained unless the atmospheric gas is inert and the atmospheric dew point is 20.degree. C. or higher.

Here, the reason why the iron loss characteristics change due to the annealing treatment described in 1-2 is that, although it has not yet been clearly elucidated, This is thought to be due to the subsequent high'/Fi annealing, which transformed the material into a material that forms a strong demagnetizing field.

(Example) After secondary recrystallization, the oxide layer on the surface of the swimming plate (17 mm: 0.20 m weight) was removed so that the tip was 1. Orrunφ annealed diamond is used as an ultrasonic vibration processing terminal, contact pressure: 30kg/M”
A conditioner with a frequency of 20klLz and an amplitude of 20μm was used to remove the force in parallel lines with an interval of 1mm in the direction of pressure and perpendicular force.

Then, annealing treatment was performed under various conditions shown in Table 1.

Table 1 also shows the results of investigating the magnetic properties of the product board obtained in the above manner.

For comparison, the same table also shows cases where oxide removal was performed using a sharply pointed cemented carbide terminal (1,0+nmφ) and cases where annealing treatment was performed without such oxide removal treatment. The survey results for those cases are also shown.

As is clear from the table, according to the present invention, by applying long sonic vibration to locally remove surface oxides and then performing a prescribed annealing treatment, iron can be processed without deterioration of magnetic flux density. A significant improvement in loss characteristics has been achieved.

Thereafter, heat treatment was performed at 800° C. for 13 hours in N7 to examine the effects of stop annealing (and roughness), but there was no change in the properties of each product sheet.

(Effects of the Invention) Thus, according to the present invention, it is possible to easily and inexpensively obtain a grain-oriented silicon steel sheet with extremely low iron loss without the conventionally unavoidable decrease in space factor and deterioration in magnetic flux density. be able to.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the annealing temperature and iron loss value after locally removing surface oxides. It is a graph showing a comparison of magnetic flux densities before and after annealing treatment when objects are removed. Fig. 1 Ar medium firing anchor, 1 hour firing at 700℃td, p, 3piC, 36tFrLl':
Ii 1゜1 hour bladder protection

Claims (1)

[Claims] 1. After applying ultrasonic vibration to the surface of a grain-oriented silicon steel sheet after secondary recrystallization annealing to locally remove the oxide layer on the surface of the steel sheet, dew point: -5 1. A method for producing a grain-oriented silicon steel sheet with low iron loss, which does not suffer from characteristic deterioration due to strain relief annealing, the method comprising performing an annealing treatment at a temperature of 950° C. or higher in an inert gas atmosphere of 30° C. or lower. 2. Apply ultrasonic vibration to the surface of the grain-oriented silicon steel sheet after secondary recrystallization annealing to locally remove the oxide layer on the surface of the steel sheet, and then heat it in an inert gas atmosphere with a dew point of 20°C or higher. The process is characterized by annealing at a temperature of 600 to 950°C, followed by annealing at a temperature of 950°C or higher in an inert gas atmosphere with a dew point of -5°C or lower. A method for producing iron loss grain-oriented silicon steel sheets.