JP3359449B2 - Manufacturing method of ultra high magnetic flux density unidirectional electrical steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing 2.5 to 4.0% of sulfur.
{110} used for iron cores such as transformers, including i
An object of the present invention is to provide a method for producing a high magnetic flux density unidirectional magnetic steel sheet in which the <001> orientation, that is, the Goss orientation, is highly developed.

[0002]

2. Description of the Related Art Generally, the magnetic properties of a grain-oriented electrical steel sheet are evaluated based on both iron loss properties and excitation properties. Increasing the excitation characteristics is effective in reducing the size of equipment that increases the design magnetic flux density. On the other hand, reducing the iron loss characteristics is effective in that when it is used as an electric device, heat loss is reduced and power consumption can be saved. further,
Aligning the <100> axis of the crystal grains of the product in the rolling direction can increase the magnetizing properties and lower the iron loss properties,
In recent years, many studies have been made particularly on this aspect, and various manufacturing techniques have been developed.

For example, Japanese Patent Publication No. 40-15644 discloses a method for producing a grain-oriented electrical steel sheet in order to obtain a high magnetic flux density. This is a production in which AlN + MnS is made to function as an inhibitor, and the rolling reduction in the final cold rolling step is more than 80%. {110} of the secondary recrystallized grains by the method <001> of the high degree of integration oriented electrical steel sheet B ₈ has a high magnetic flux density of more than 1.870T is obtained. However, the magnetic flux density B ₈ of the product based on the patent is at most about 1.95T 1.88, only shows the value of about 95% of the saturation magnetic flux density 2.03T of 3% Si steel. However, in recent years, social demands for energy savings and resource savings have become increasingly severe, and demands for reduction of iron loss and improvement of magnetic properties of the grain-oriented electrical steel sheets have also become fierce.

On the other hand, technically, as a technique for reducing iron loss, a method of subjecting a steel sheet to a laser treatment disclosed in Japanese Patent Publication No. 57-2252, and further a method of reducing the iron loss, further disclosed in Japanese Patent Publication No. 58-2569.
Various methods for subdividing magnetic domains, such as a method of applying a mechanical strain to a steel sheet, are disclosed in Japanese Patent Application Laid-Open Publication No. H11-157,878. When the magnetic domain is subdivided by the above-described method, the higher the magnetic flux density, the lower the iron loss characteristics tend to be. Therefore, the magnetic flux density B ₈ of the conventional grain-oriented electrical steel sheet is further increased,
At present, the appearance of means for approaching the saturation magnetic flux density of 2.03T of% Si steel is expected.

As means for achieving this goal, Japanese Patent Publication No. 58-50295 proposes a temperature gradient annealing method. B ₈ stably started in this way is now more products 1.95T is obtained. However, when this method is implemented with a factory-sized coil foam, there is a problem in industrial production because heating is performed from one end of the coil and the other end is cooled due to a temperature gradient, which is very thermal energy loss. there were.

Furthermore, a method of adding Bi in 100~5000g / T in molten steel is disclosed in JP-A 6-88171 JP, B ₈ is now more products 1.95T is obtained. However, in this method, when implemented in a coil form in plant size, there are secondary recrystallization portion unstable portions, the total length of the coil, over the entire width, industrially stable B ₈ is at all points There is a large problem that a product of 1.95T or more cannot be obtained.

[0007]

In the [0007] above conventional manufacturing method, B ₈ stable over coils entire length, the full width of the extremely high magnetic flux density ultra-high magnetic flux density grain-oriented electrical steel sheet as industrial production 1.95T It is difficult to obtain the above products,
The present invention provides a manufacturing method for solving the problem.

[0008]

According to the present invention, as a result of repeated studies to solve the above-mentioned problems, the weight ratio of C: 0.10
% Or less, Si: 2.5 to 4.0%, Mn: 0.02 to
0.30%, one or two selected from S and Se
Total species: 0.001-0.040%, acid soluble Al:
0.010-0.065%, N: 0.0030-0.0
A hot-rolled sheet of unidirectional magnetic steel made of 200% as a basic component, with the balance being Fe and unavoidable impurities, is subjected to hot-rolled sheet annealing, and is subjected to one or more times or intermediate annealing.
In a method of manufacturing a grain-oriented electrical steel sheet by performing cold rolling more than once, decarburizing annealing, and then performing final finishing annealing, Bi is added to the composition of the material in an amount of 0.0005 to 0.05%.
Before decarburizing and annealing the strip rolled to the final thickness and containing it, at a heating rate of 100 ° C./sec or more and 700 ° C. or more in an atmosphere of PH ₂ O / P H ₂ of 0.4 or less. By rapidly heating to the temperature range,
Industrially stably B ₈ over the entire length of the coil, the total width is 1.
It has been found that a method for producing a grain-oriented electrical steel sheet having an extremely high magnetic flux density of 95 T or more can be obtained.

[0009] In addition, the above-mentioned rapid heating treatment is performed by using P H ₂ O
It has been found that a method for producing a grain-oriented electrical steel sheet having an extremely high magnetic flux density can be obtained by performing a heat treatment in a non-oxidizing atmosphere having / P H ₂ of 0.2 or less. Furthermore, it has been found that by incorporating the above two heat treatments as a temperature raising stage of decarburizing annealing, a unidirectional magnetic steel sheet having an extremely high magnetic flux density can be obtained by a method with a small number of steps.

The above-mentioned production method is characterized in that one or more components selected from Sb, Sn, Cu and Mo are contained in a weight ratio of 0.003 to 0.50%. It has been found that a method for producing a grain-oriented electrical steel sheet having an extremely high magnetic flux density can be obtained.

Hereinafter, the present invention will be described in detail. The present inventors have conducted various studies to increase the magnetic flux density of a so-called high magnetic flux density unidirectional magnetic steel sheet, and added a very small amount of Bi to a molten steel material for a unidirectional magnetic steel sheet having aluminum nitride as a main inhibitor. To produce a high magnetic flux density unidirectional electrical steel sheet of 1.95T or more and 2T, far exceeding the magnetic flux density B ₈ = 1.93T of the high magnetic flux density unidirectional electrical steel sheet currently commercially available. Successful.

However, it is very difficult with the above-mentioned method to industrially produce a high magnetic flux density unidirectional magnetic steel sheet of 1.95 T or more and 2 T or more. In other words, when manufacturing with a coil form, it is possible to obtain a high magnetic flux density unidirectional electrical steel sheet of not less than 1.95T and 2T far exceeding magnetic flux density B ₈ = 1.93T over the entire length and width of the coil. Was very difficult.

[0013] result of various studies in order to improve this, atmosphere and heating rate during heating in heat treatment and decarburization annealing before the decarburization annealing is ultra-high magnetic flux B ₈ is not less than 1.95T It has been found that it contributes greatly to obtaining a stable density.

A grain-oriented electrical steel sheet can be produced by sufficiently causing secondary recrystallization during the final annealing in the production process to obtain a so-called Goss texture. In order to obtain this Goss texture, the coarse growth of primary recrystallized grains is suppressed, and only the recrystallized grains having the {110} <001> orientation aligned with the rolling direction are selectively grown in a certain temperature range. In other words, it is necessary to make a base material for secondary recrystallization.
For this purpose, fine precipitates such as MnS, AlN, and Cu ₂ S must be uniformly dispersed in the material as an inhibitor (inhibitor) for the growth of primary recrystallized grains. Therefore, in the conventional manufacturing method, Bi was added to obtain a uniform and fine inhibitor effect as disclosed in JP-A-6-88171.

However, Bi metal has a melting point of about 270.
Due to the temperature of Bi, Bi is very unstable in a high temperature region around 1100 ° C where the secondary recrystallization is performed. For this reason, it has been discovered that a uniform fine state of an inhibitor such as AlN cannot be maintained in a high temperature range, and as a result, an ultra-high magnetic flux density of 1.95 T or more cannot be obtained stably.

In order to improve this, the present inventors have focused on compensating for Bi instability by controlling the oxide film before the secondary recrystallization. In other words, by controlling the initial oxide film before starting decarburization annealing to be SiO ₂ rich, nitrogen absorption and denitrification during secondary recrystallization annealing are suppressed,
It was conceived to maintain a uniform and fine state of an inhibitor such as AlN as much as possible.

In order to control the SiO ₂ , P
It has been found that it is very effective to perform the heat treatment in an atmosphere having an oxygen potential of H ₂ O / P H ₂ of 0.4 or less in a short time. That is, in a temperature range of 700 ° C. or more in an atmosphere of PH ₂ O / P H ₂ of 0.4 or less, 10
This can be achieved by performing a rapid heating treatment at a heating rate of 0 ° C./second or more. In addition, the above-mentioned rapid heat treatment is carried out with PH ₂ O /
It was also found that the implementation of P H ₂ in a non-oxidizing atmosphere of 0.2 or less further improved the magnetic properties.

[0018]

Next, the reason why the steel composition and the manufacturing conditions are limited as described above in the present invention will be described in detail. The reasons for limiting the steel components are as follows. The upper limit of 0.10% for C is limited because if it is more than this, the time required for decarburization becomes longer and it is economically disadvantageous. The lower limit of Si is set to 2.5% in order to improve iron loss, but if it is too large, it is likely to crack during cold rolling and processing becomes difficult, so the upper limit is set to 4.0%.

Further, in order to produce a grain-oriented electrical steel sheet, the following component elements are added as ordinary inhibitor components. Mn, S and Se are manganese sulfide as an inhibitor and Mn: 0.02-0.3 in order to act as an auxiliary inhibitor by forming MnSe.
0%, a total of one or two selected from S and Se: 0.001 to 0.040% is required. Mn is manganese sulfide, in order to obtain an appropriate dispersion state of MnSe,
It was limited to 0.02 to 0.30%. One or two kinds selected from S and Se are manganese sulfide, Mn.
In order to obtain a proper dispersion state of Se, 0.001 to 0.0
Limited to 40%.

Further, in order to utilize aluminum nitride as an inhibitor, acid-soluble Al and N are added. Acid-soluble Al is limited to 0.010 to 0.065% in order to obtain an appropriate dispersion state of aluminum nitride. N is also 0.0030 in order to obtain a proper dispersion state of aluminum nitride.
Limited to ~ 0.0200%.

Bi, which is a feature of the present invention, is represented by Bi:
A very small range of 0.0005 to 0.05% is effective. If it is less than 0.0005%, the improvement of the magnetic flux density is slight, and if it exceeds 0.05%, the effect of improving the magnetic flux density is saturated and cracks occur at the end of the hot rolled sheet.
%.

In addition, Sb, Sn, Cu and M
one or more selected from the group consisting of 0.003 to 0.5
0% may be added. When the amount is outside the above range, an appropriate dispersion state of the precipitate cannot be obtained, so that the amount is limited. Next, a hot strip is obtained from the molten steel by a normal ingot casting method or a continuous casting method or hot rolling. When obtaining the hot strip, a strip casting method can be applied to the present invention.

Next, hot rolled sheet annealing is performed to precipitate AlN and the like. At this time, it is desirable to perform annealing at 950 to 1200 ° C. for 30 seconds to 30 minutes. Next, a strip having a final product thickness is obtained by rolling once, twice or more, or twice or more including intermediate annealing. When rolling two or more times, the first rolling preferably has a reduction of 5 to 50%. In the case where intermediate annealing is performed between two or more rollings, it is preferable to perform the intermediate annealing at 950 to 1200 ° C. for 30 seconds to 30 minutes.

In the above-mentioned rolling, the final rolling reduction in cold rolling to the final product thickness is desirably 85% or more. The lower limit of 85% is because below this, a Goss nucleus with a {110} <001> orientation having a high degree of integration in the rolling direction cannot be obtained. As a cold rolling method at this time, during the cold rolling, the final sheet thickness is obtained through each thickness step by a plurality of passes, but in order to improve the magnetic properties, at least one or more intermediate sheet thicknesses are required. At the stage, the steel sheet may have a thermal effect of maintaining the steel sheet at a temperature range of 100 ° C. or more for a time of 1 minute or more.

As described above, the strip rolled to the final product thickness is subjected to a heat treatment. In this heat treatment, rapid heating to a temperature range of 700 ° C. or more at a heating rate of 100 ° C./sec or more in an atmosphere of PH ₂ O / P H ₂ of 0.4 or less to optimally form an oxide film. Must be implemented. PH ₂ O /
In an atmosphere where PH ₂ is 0.4 or less, it is necessary to perform annealing in a short time because formation of SiO ₂ is not appropriate.
When the lower limit of the heating rate at this time is 100 ° C./sec, below this, the formation of SiO ₂ is not appropriate, and during the subsequent secondary recrystallization, AlN and the like in the steel significantly affect the influence of the nitrogen atmosphere from the steel sheet surface. This is limited because it is easy to receive and it is not possible to stably obtain an ultra-high magnetic flux density.

It is also possible to improve the primary recrystallization texture by this rapid heating treatment and to stabilize the secondary recrystallization. In addition, the lower limit of the heating temperature range was set to 700 ° C. in order to improve the formation of SiO ₂ . After the heating, normal cooling is performed, and then the decarburization annealing step is carried.
It is desirable that the cooling at this time be as fast as possible.

Further, in the above-mentioned rapid heating treatment, PH ₂ O /
By P H ₂ is combined with a non-oxidizing atmosphere of 0.2 or less, ultra-high magnetic flux density grain-oriented electrical steel sheet is obtained further. The upper limit of P H ₂ O / P H ₂ , 0.2, was limited above this value because the optimum amount of SiO ₂ was reduced. The non-oxidizing atmosphere refers to an inert gas such as N ₂ or Ar or a reducing atmosphere containing a small amount of H ₂ .

The above-mentioned rapid heating treatment is performed separately from the decarburization annealing to be performed next. However, since the number of steps is smaller when incorporated into the decarburization annealing step as the temperature raising step of decarburization annealing. desirable. Next, decarburization annealing is performed in a wet hydrogen atmosphere.
At this time, the carbon content is set to 0.1 in order not to deteriorate the magnetic characteristics of the product.
005% or less. Here, when the slab heating temperature in hot rolling is low, nitriding treatment may be added in an ammonia atmosphere. According to the above manufacturing method, the amount of SiO _{2 in} the oxide film after the decarburizing annealing becomes appropriate. Here, the appropriate amount of SiO ₂ means the SiO _{2 in} the oxide film.
₂ means that the ratio is 50% or more.

Further, by applying an annealing separator such as MgO and performing finish annealing at 1100 ° C. or more for secondary recrystallization and purification, a secondary film having a good film such as forsterite formed on the steel sheet surface is formed. Obtain recrystallized grains. Next, a unidirectional magnetic steel sheet having extremely low iron loss characteristics is manufactured by further applying an insulating film on a film such as forsterite. In addition, in order to further improve iron loss in the obtained product, it is desirable to subject the above-described grain-oriented electrical steel sheet to a treatment for subdividing magnetic domains.

[0030]

【Example】

Example 1 A hot-rolled sheet containing the chemical components shown in Table 1 and hot-rolled to a thickness of 2.3 mm was annealed at 1100 ° C. for 1 minute. Then, it was rolled to a final thickness of 0.22 mm by cold rolling.

Further, when the obtained strip was decarburized and annealed, the atmosphere was carried out under the conditions shown in Table 2 at the temperature raising stage. The heating rate at this time was 840 ° C. under the conditions shown in Table 3.
Until heated. Thereafter, decarburizing annealing was performed in wet hydrogen at a uniform temperature of 840 ° C., and after applying MgO powder, high-temperature annealing was performed at 1200 ° C. for 10 hours in a hydrogen gas atmosphere. Excess MgO of the obtained steel sheet was removed, and an insulating film was applied on the formed forsterite film.

Table 2 shows the magnetic flux density of the obtained product. The magnetic flux density was measured at three points at both edges and the center of a product coil having a width of 1000 mm. According to the present invention, a grain-oriented electrical steel sheet having an ultra-high magnetic flux density with a B ₈ of 1.95 T or more stably in the width direction is obtained.

[0033]

[Table 1]

[0034]

[Table 2]

Example 2 A molten steel containing the composition shown in Table 3 was cast for 15 tons, heated to a slab, and then hot-rolled to obtain a 2.3 mm hot-rolled steel sheet. This was annealed at 1000 ° C. for 4 minutes and rolled to 1.55 mm. This is 1120 ° C
For 5 minutes, followed by pickling, followed by cold rolling to a thickness of 0.22 mm. Further, when the obtained strip is decarburized and annealed, a heating rate of 300 ° C. /
s, atmosphere 840 under the condition of PH ₂ O / P H ₂ of 0.05
Heated to ° C. Thereafter, decarburization annealing was performed in wet hydrogen at a uniform temperature of 840 ° C.

Next, after applying MgO powder, high-temperature annealing was performed at 1200 ° C. for 10 hours in a hydrogen gas atmosphere. Excess MgO of the obtained steel sheet was removed, and an insulating film was applied on the formed forsterite film. When 8000 m of the product coil obtained as described above is deployed,
The magnetic flux density was measured at each position of m, 4000 m, and 7800 m. The result was B ₈ = 1.97 T (100 m), 1.9.
8T (4000m) and 1.98T (7800m). B ₈ stably over the coil entire length by the present invention is oriented electrical steel sheet with ultra-high magnetic flux density of more than 1.95T was obtained. Further, the steel sheet obtained above was subjected to laser treatment. At this time, the _iron loss value is W _{17/5 0} = 0.68 W / kg.
(100m), 0.64W / kg (4000m), 0.6
It was 2 W / kg (7800 m), and very good iron loss characteristics were obtained.

[0037]

[Table 3]

[0038]

According to the present invention, a grain-oriented electrical steel sheet having a good ultra-high magnetic flux density can be produced industrially stably, so that the industrial contribution is extremely large.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunihide Takashima 20-1 Shintomi, Futtsu City Nippon Steel Corporation Technology Development Division (56) References JP-A-11-61356 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) C21D 8/12 C22C 38/00 303 C22C 38/60 H01F 1/16

Claims (4)

(57) [Claims] 1. A weight ratio of C: 0.10% or less, Si: 2.5 to 4.0%, Mn: 0.02 to 0.30%, one or more selected from S and Se or The sum of the two:
0.001-0.040%, acid-soluble Al: 0.010-0.065%, N: 0.0030-0.0200%, with the balance being one-way electromagnetic consisting of Fe and unavoidable impurities. Hot-rolled steel sheet is subjected to hot-rolled sheet annealing, cold-rolled one or more times or two or more times including intermediate annealing, decarburized annealing, and final finish annealing to be unidirectional. In the method of manufacturing an electrical steel sheet, Bi is contained in the composition of the material in an amount of 0.0005 to 0.05%,
Prior to decarburizing annealing of the strip rolled to the final thickness, the strip is rolled in an atmosphere having a PH ₂ O / PH ₂ of 0.4 or less.
A method for producing a grain-oriented electrical steel sheet having an extremely high magnetic flux density, characterized by rapidly heating at a heating rate of 0 ° C / sec or more to a temperature range of 700 ° C or more. 2. The heat treatment according to claim 1, wherein the heat treatment is carried out in an atmosphere in which PH ₂ O / P H ₂ is 0.2 or less.
The described method. 3. The method according to claim 1, wherein the heat treatment is performed as a temperature raising step of the decarburizing annealing. 4. An amount of one or more selected from Sb, Sn, Cu and Mo in a weight ratio of 0.003 to 0.50%
The method according to claim 1, wherein the compound is contained.