JPH0776732A - Production of grain-oriented silicon steel sheet high in magnetic flux density - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel sheet capable of forming a stable Goss structure by final annealing in a short time and high in magnetic flux density. CONSTITUTION:Steel having a compsn. contg., by weight, <=0.01% C, 2.5 to 7% Si, <=0.01% S, <=0.01% Al, <=0.01% N, <=0.01% Cu, <=5ppm Nb, <=10ppm Sn and <=20ppm Ti and satisfying [Nb]+0.5X[Sn]+0.25-[Ti]<=8, and the balance Fe with inevitable impurities is held to >=1000 deg.C, is thereafter subjected to hot rolling at 700 to 950 deg.C finishing temp., is next subjected to cold rolling at 40 to 80% rolling ratio, is thereafter annealed at 1000 to 1300 deg.C for <=10min in a reducing atmosphere, in a nonoxidizing atmosphere of <=0.5Pa oxygen partial pressure or in a vacuum of <=0.5Pa oxygen partial pressure to obtain the grain-oriented silicon steel sheet high in magnetic flux density. Thus, the time of the final annealing is shortened, and continuous annealing can be effected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for economically and stably producing a grain-oriented silicon steel sheet having a crystallographic orientation integrated in the Goss orientation and a high magnetic flux density.

[0002]

BACKGROUND OF THE INVENTION Grained silicon steel sheets have better magnetic properties than non-oriented silicon steel sheets and are mainly used as transformer iron cores. {110} <0 by Goss
Since the invention of the method for producing a grain-oriented silicon steel sheet having crystal grains aligned in the 01> orientation, many methods for producing a grain-oriented silicon steel sheet having such a Goss structure have been proposed. These proposals are roughly classified into the following three.

The first method is a method called a double cold pressing method. This method is an improved method of the Goss method, in which Mn, Sb, S, Se, etc. are added in the steelmaking stage, and secondary recrystallization is performed by utilizing the grain growth suppression effect of these elements and their fine precipitates. It is also done. Specifically, C:
0.02-0.08 wt%, Si: 2.0-4.0 wt
%, Mn: about 0.2 wt%, S: 0.005-0.0
A steel ingot having a composition of 5 wt% is melted and rolled by hot rolling to a plate thickness of 2.0 to 3.0 mm, hot-rolled sheet is annealed, and then cold-rolled at a rolling ratio of about 70%. 85
Intermediate annealing of 0 to 1050 ° C. is performed, and the rolling ratio is 60 to
After cold rolling at 70%, decarburization annealing at 800 to 850 ° C, annealing at a temperature of 1100 ° C or higher for 5 to 50 hours for secondary recrystallization and removal of inhibitors (purification annealing), and Go
Ss grains are grown (for example, Japanese Patent Publication No. 51-13469).
issue).

The second method is a one-time cold pressing method. This method is a method in which the number of cold rolling is 1
It is known to have a higher degree of Goss grain accumulation than the chill-cold method. Specifically, C: 0.02-0.08 wt%, S
i: 2.0 to 4.0 wt%, Mn: about 0.2 wt%,
N: 0.01 to 0.05 wt%, Al: 0.1 wt% of a steel ingot having a composition and melted and hot rolled to a plate thickness of 2.
After rolling to 0 to 3.0 mm, hot-rolled sheet annealing is performed to perform AlN precipitation treatment, then cold rolling at a rolling rate of 80 to 95% is performed, followed by decarburization annealing, and then at 1200 ° C. Two
Secondary recrystallization and inhibitor removal (purification annealing) are performed by high temperature annealing for 0 hours to grow Goss grains (for example, Japanese Patent Publication No. 40-15644).

The third method is Go without the use of inhibitors.
This is a method for forming an ss structure (see, for example, JP-A-64-5
5339, JP-A-2-57635, etc.). This method simply develops Goss grains by combining rolling and heat treatment under specific conditions.

[0006]

As described above, the first,
Since the second method requires decarburization annealing and purification annealing, high temperature and long time annealing is indispensable. Therefore, the manufacturing cost,
Inevitably, equipment costs will increase.

If the final plate thickness is reduced to 0.20 mm or less in order to reduce iron loss, the secondary recrystallization phenomenon becomes unstable and it becomes difficult to occupy the entire surface with Goss grains. Therefore, at present, the production limit is about 0.23 mm in plate thickness.

Since the third method does not require decarburization annealing and purification annealing, it is more advantageous in manufacturing cost than the first and second methods. However, the inventors of the present application disclosed in JP-A-64-55339 and JP-A-2-57635.
When I did an additional test of the method disclosed in the issue,
It was found that the ss grain growth mechanism is extremely unstable, and it is not always possible to obtain a material entirely covered with Goss grains, and it is difficult to obtain stable quality. Stable Goss
Grain formation is indispensable for a grain-oriented silicon steel sheet in practical use, and even if it is used excluding the parts other than the Goss grains, the cost will be increased due to the decrease in yield.

The present invention has been made in view of the above circumstances, and is based on a manufacturing method that does not use an inhibitor, and has a high magnetic flux density directionality capable of forming a stable Goss structure by short-time annealing. It is an object to provide a method for manufacturing a silicon steel sheet.

[0010]

Means and Action for Solving the Problems
In addition, C: 0.01 wt% or less, Si: 2.5 to 7 wt
%, S: 0.01 wt% or less, Al: 0.01 wt% or less, N: 0.01 wt% or less, Cu: 0.01 wt% or less, Nb: 5 ppm or less, Sn: 10 ppm or less, Ti: 2
0 ppm and [Nb] + 0.5 × [Sn] +0.25 [Ti] ≦ 8
(However, the concentration of each element is ppm.), A steel material containing the balance Fe and other unavoidable impurities was prepared, and after the steel material was maintained at 1000 ° C or higher, the finishing temperature was 700 to 950 ° C. Hot rolling, then rolling rate 4
1000 ~ 80% in a reducing atmosphere, a non-oxidizing atmosphere with an oxygen partial pressure of 0.5 Pa or less, or a vacuum with an oxygen partial pressure of 0.5 Pa or less.
Provided is a method for producing a grain-oriented silicon steel sheet having a high magnetic flux density, which is characterized by annealing at a temperature of 1300 ° C. for 10 minutes or less.

Second, C: 0.01 wt% or less, Si:
2.5-7 wt%, S: 0.01 wt% or less, Al:
0.01 wt% or less, N: 0.01 wt% or less, C
u: 0.01 wt% or less, Nb: 5 ppm or less, Sn: 1
0 ppm or less, Ti: 20 ppm, and [Nb] + 0.5 × [Sn] +0.25 [Ti] ≦ 8
(However, the concentration of each element is ppm.), Prepare a steel material consisting of the balance Fe and other unavoidable impurities, hold this steel material at 1000 ° C or higher, and then set the finishing temperature to 700 to 950 ° C. And then cold rolling at a rolling ratio of 80% or less, and then a reducing atmosphere or a non-oxidizing atmosphere with an oxygen partial pressure of 0.5 Pa or less, or an oxygen partial pressure of 0.5 Pa or less. In the vacuum of 1
Annealed at a temperature of 000 to 1300 ° C, and a rolling rate of 90
% Or more, and then 1000 to 13 in a reducing atmosphere, a non-oxidizing atmosphere with an oxygen partial pressure of 0.5 Pa or less, or a vacuum with an oxygen partial pressure of 0.5 Pa or less.
Provided is a method for producing a grain-oriented silicon steel sheet having a high magnetic flux density, which is characterized by annealing at a temperature of 00 ° C. for 10 minutes or less.

The inventors of the present invention firstly cold-rolled a steel sheet having a specific composition of 3% Si from 1 to 3 times without using an inhibitor, and as the final annealing, the oxygen concentration in the atmosphere was adjusted. Controlled and applied for a method for producing a grain-oriented silicon steel sheet in which the crystal orientation is integrated in the Goss orientation (Japanese Patent Application Nos. 4-185374 and 4-185375,
Japanese Patent Application No. 4-185376). These methods are different from the conventional method for producing grain-oriented silicon steel sheet that does not use inhibitors, and by using these methods, Goss
The tissue can be stably formed. In these applications, it is considered that there is no problem if the final annealing time is 3 minutes or more, but according to the experiments conducted by the inventors of the present application, the magnetic flux finally obtained when the time is shorter than 1 hour. It was found that the Goss structure is not always stable because the density tends to vary. By these methods as well, if the final annealing time is 1 hour or more, a Goss structure can be obtained sufficiently stably, but this not only increases the time required for production, but it also enables continuous annealing that enables highly efficient production. Is practically difficult to apply.

Therefore, the inventors of the present application have conducted research on a method capable of stably obtaining a Goss structure by a short-time annealing that can be applied to continuous annealing. The target of the final annealing time was set within 10 minutes which is considered to be the limit of continuous annealing.

In order to form a stable Goss structure in a short time in the final annealing, {110} <001> during annealing.
It suffices to promote grain boundary migration of crystal grains having an orientation or an orientation close thereto, and various methods have been studied. As a result, in the initial stage of grain boundary migration during final annealing, only the grains having the Goss structure coarsen with the help of surface energy, and the relatively small grains having an orientation other than the Goss orientation are gradually serially eroded. The phenomenon of grain growth is shown, and it has been found that the grain boundary migration of the crystal grains is promoted by removing such factors that hinder grain growth. In consideration of such a fact, a test was conducted to grasp the influence of the element, which was conventionally considered as an unavoidable impurity, on the grain boundary migration.
As a result, if Nb, Sn, and Ti are reduced to a certain amount or less, the grain boundary migration of the crystal grains having the {110} <001> orientation or an orientation close thereto is promoted, and the final annealing for a short time of 10 minutes or less is performed. The inventors have found that the Goss structure is stably formed, and have completed the present invention having the above-described structure.

The present invention will be described in detail below. The invention of the present application is based on Japanese Patent Application No. 4-185376 which is premised on one cold rolling among the above-mentioned prior applications.

First, the reasons for limiting the chemical components in the present invention will be described. It is preferable in terms of magnetic properties that C be reduced as much as possible in the steelmaking stage. C is 0.01 wt%
If it exceeds, magnetic properties will be significantly deteriorated. Therefore, the upper limit of C is specified to be 0.01 wt%.

Si has the effect of increasing the electrical resistance, and has the effect of 2.5
The inclusion of more than wt% eliminates the metallurgical transformation point and
It has the effect of making it a single phase. Further, since the magnetostriction becomes zero near 6.5 wt%, extremely excellent soft magnetic characteristics can be obtained. However, if it exceeds 7 wt%, the magnetostriction increases again, the magnetic characteristics deteriorate, and it becomes extremely brittle, which is not practical. Therefore, the Si content is 2.5 to 7 wt%
Stipulate in the range of.

S and N are typical elements contained in ordinary steel, but these elements inhibit grain growth in the form of solid solution and in the form of precipitates. It is preferable to reduce as much as possible. However, since extreme reduction in the steelmaking stage causes a cost increase, the upper limits of these contents are set to 0.01 wt% respectively as a range that does not hinder grain growth.

Al is an element having a wide solid solubility in α-iron and a strong affinity with oxygen. Therefore, when the Goss structure is formed by the final heat treatment, it reacts with a small amount of oxygen in the heat treatment atmosphere to form an oxide layer on the surface of the steel sheet, which hinders crystal grain growth due to surface energy. Therefore, the content of Al is specified to be 0.01 wt% or less so that such a disadvantage does not occur. The more preferable range of the Al content is 0.005 wt% or less. Since Al is usually added as a deoxidizer, it needs to be controlled particularly strictly.

Cu is an element having a small solid solubility in α-iron, and is an element which markedly inhibits the crystal grain growth when the Goss structure is formed by the final heat treatment. Further, Cu is contained in an amount of about 0.05 wt% at the steel making stage. Therefore, it is necessary to reduce the content to 0.01 wt% or less which does not cause the above-mentioned inconvenience. Preferably 0.005w
It is t% or less. However, since Cu has a melting point of 1083 ° C. and is a component that volatilizes by heat treatment at about 1000 ° C. or more, even if it is contained in excess of 0.01 wt%, it will be 0.01 wt% or less by heat treatment for a relatively long time. It is possible to However, extension of the heat treatment time is not preferable from the viewpoint of improving the efficiency of the process.

Nb, Sn, and Ti are usually contained as impurity elements, but all have a strong effect of delaying the grain growth of Goss grains at the time of final annealing, and Goss is obtained by the final annealing for a short time of 10 minutes or less. In order to form a stable structure without variation, it is necessary to adjust Nb to 5 ppm or less, Sn to 10 ppm or less, and Ti to 20 ppm or less after the composition adjustment during steelmaking.

Further, since they have the same action, when they are contained at the same time, it is necessary to define them by the total of them. Considering the degree of these actions, [Nb] + 0.5 × [ Sn] +0.25 [Ti] ≦ 8
(However, the concentration of each element is ppm.) Is required to be satisfied. If the above content and this formula are satisfied, the grain growth during the final annealing can be completed without variation within a short time of 10 minutes or less.

In order to specify these elements in the above range, it is important to sufficiently control the name components from the hot metal stage and to strictly control the scrap to be introduced even in the steel making stage.

Among the components mixed as impurities in the steel together with Nb, Sn and Ti, Mn, Cr and Ni are included.
However, even if the content is increased or decreased, the effect on grain growth during final annealing is small, and even if other characteristics are taken into consideration, the amount considered as inevitable impurities or normal impurities ( It was confirmed that an amount of about 0.01 to 0.05 wt%) is acceptable.

With respect to the unavoidable impurity elements other than these elements, the amount contained in ordinary steel is acceptable. However, the smaller amount is preferable from the viewpoint of further improving the magnetic properties and the like. Further, V, Zn, etc., which have a wide solid solubility in α-iron and have a strong affinity with oxygen, have the effect of inhibiting crystal grain growth due to surface energy like Al, and therefore their content is 0.01 wt. % Or less, preferably 0.005
Care must be taken to keep it below wt%. further,
Since O in steel affects the third-order recrystallization behavior, it is desirable to be as low as possible, preferably 0.008 wt% or less.

The molten steel having such a composition is
Basically, a steel sheet is made by the same manufacturing method as the method described in Japanese Patent Application No. 4-185376. That is, first, a steel having such a composition is cast into an ingot or made into a slab by a continuous casting method, and then this ingot or slab is kept at a temperature of 1000 ° C. or higher,
Used for hot rolling. Hold temperature before hot rolling is 1000
The temperature above 700 ° C. is defined as the promotion of recrystallization during hot rolling in the preceding stage of the rough rolling mill or finishing hot rolling mill, and 700 to 950
This is to ensure the hot rolling finishing temperature of ℃. In the hot rolling, the ingot or slab is heated to 1000 ° C in a heating furnace.
It may be carried out after heating above, or may be carried out after continuous casting by direct rolling while keeping the slab temperature at 1000 ° C. or higher.

The finishing temperature of hot rolling is 700 to 95.
It must be in the range of 0 ° C. Finishing temperature is 700
If the temperature is lower than ℃, the rolling load of hot rolling becomes too large, which is not preferable in manufacturing, and adversely affects the final growth of Goss grains. Further, in order to make the finishing temperature higher than 950 ° C., it is necessary to set the initial temperature of the ingot or slab to a high value, which is disadvantageous in manufacturing cost.

The plate thickness of the hot rolled plate varies depending on the desired plate thickness of the final product, but is generally about 1.6 mm to 5.0 mm. The hot-rolled sheet thus produced is wound up according to a conventional method, but the winding temperature is preferably 560 to 800 ° C. If the coiling temperature is lower than 560 ° C, it is practically difficult to cool on the run-out table after the hot rolling is completed, while if the coiling temperature exceeds 800 ° C, the surface during coiling cooling Pickling deteriorates due to oxidation,
Not practical.

The wound hot rolled coil may be annealed in a continuous furnace or a batch furnace, if necessary.
The hot rolled sheet annealing temperature at this time is preferably 700 to 1100 ° C. When the hot-rolled sheet annealing temperature is less than 700 ° C,
Since the processed structure formed at the time of hot rolling cannot be eliminated, its effect does not substantially appear. On the other hand, when the hot rolled sheet annealing temperature exceeds 1100 ° C, it causes a high operating cost. It becomes a problem in practical use.

The hot-rolled sheet thus obtained is subjected to primary cold rolling according to a conventional method. The rolling rate of this cold rolling is 40
-80%. If the rolling ratio is less than 40%, it is difficult to roll from the normal hot-rolled sheet thickness to the final product sheet thickness (usually 1.0 mm or less), and the effect of surface energy becomes relatively small. Therefore, sufficient grain growth cannot be caused even by subsequent annealing. Further, if the rolling ratio exceeds 80%, the development of Goss grains is not sufficient, and the rolling load becomes large, which is not a good measure.

However, as will be described later, when secondary cold rolling is performed, the secondary cold rolling is performed at a large rolling rate,
It is not always necessary to specify the lower limit of the rolling rate as described above. However, even when the secondary cold rolling is performed, it is preferable to perform rolling at a rolling rate of 30% or more in order to exert the effect of surface energy to some extent during the primary annealing.

In general, a lubricant is used in cold rolling, but the same effect can be obtained by rolling without lubrication without lubrication. The primary cold-rolled sheet thus obtained is annealed at 1000 to 1300 ° C. Annealing temperature is 1
If the temperature is less than 000 ° C, the desired Goss structure cannot be obtained because the driving force for crystal grain growth utilizing surface energy is insufficient. On the other hand, if the annealing temperature exceeds 1300 ° C., the energy cost required for such high temperature heating becomes substantially too large, which causes a practical problem.

This annealing is carried out in an atmosphere which contains hydrogen in a necessary amount or more and which has a substantially reducing property, or when nitrogen or A is used.
It is necessary to carry out in a non-oxidizing atmosphere composed of an inert gas such as r having an oxygen partial pressure of 0.5 Pa or less or in a vacuum having an oxygen partial pressure of 0.5 Pa or less. This is to prevent the formation of an oxide film on the surface of the steel sheet that hinders the integration of the crystal orientation in the Goss orientation. When oxygen is contained in vacuum or in an inert gas atmosphere to an extent that the oxygen partial pressure exceeds 0.5 Pa, an oxide film is formed on the surface of the steel sheet, and the above effects cannot be obtained. The annealing time is 10 minutes or less. That is, in the method of Japanese Patent Application No. 4-185376, in order to form a sufficiently stable Goss structure as described above, 1
An annealing time of more than an hour is required, but in the present invention, Nb,
Since the amounts of Sn and Ti are regulated within a specific range, the annealing time for forming a sufficiently stable Goss structure may be 10 minutes or less. In addition, depending on the temperature of this annealing, Nb, S
The actions of n and Ti are naturally different, and if the temperature is high, grain growth is completed in a shorter time. However, in the present invention, the annealing time of 10 minutes or less at a temperature range of 1000 to 1300 ° C., which is the temperature range of tertiary annealing, regardless of temperature It is possible to obtain a sufficiently stable Goss organization. The lower limit is not particularly limited, but a sufficient Goss structure is formed even for about 3 minutes.

The annealed plate thus obtained has a Goss structure even if it is as it is, and exhibits a high magnetic flux density. However, by further performing the secondary cold rolling and the secondary annealing, the Goss structure is more stably formed. It is possible to obtain high magnetic properties.

The rolling ratio of the secondary cold rolling needs to be 90% or more. If it is less than 90%, the final accumulation of Goss grains is not sufficient. This cold rolling can be carried out with or without lubrication as in the primary cold rolling.

The secondary cold-rolled sheet thus obtained had 10
Secondary annealing is performed at 00 to 1300 ° C. Also in this case, if the annealing temperature is lower than 1000 ° C., the driving force for crystal grain growth utilizing surface energy is not sufficient, so that a desired Goss structure cannot be obtained. On the other hand, if the annealing temperature exceeds 1300 ° C., the energy cost required for such high temperature heating becomes substantially too large, which causes a practical problem. For the same reason as the above-described primary annealing, this annealing must be performed in a reducing atmosphere, a non-oxidizing atmosphere with an oxygen partial pressure of 0.5 Pa or less, or a vacuum with an oxygen partial pressure of 0.5 Pa or less. That is, also in this case, if an oxide film is formed on the surface of the steel sheet, the grain growth property is hindered, and finally a satisfactory Go
This is because the accumulation of ss grains cannot be obtained. The annealing time is 10 minutes or less as in the case of the primary annealing described above. When performing the secondary annealing as described above, the time for the primary annealing is not particularly specified.

In the steel sheet obtained by the method of the present invention, Goss grains grow sufficiently stably even in the final annealing for a short time as described above, and a magnetic field of 800 A / m is applied at a direct current in a composition of 3% Si. The magnetic flux density B ₈ is 1.6 T or more in one cold rolling, and 1.85 in cold rolling.
It exhibits excellent magnetic properties of T or higher. This value is lower than when the three-rolling method and the two-rolling method are adopted, but the production can be performed at a lower cost than those cases, and the efficiency is high even when rolling is performed. If B ₈ is further reduced, there is a possibility that the iron core may be enlarged and the iron loss may be increased when applied to electric equipment.

As described above, the steel sheet having excellent characteristics can be produced by the short-term final annealing as in the present invention.
For steel of a specific composition, it is preferable that selective grain growth occurs in a preferred crystal orientation due to surface energy during primary annealing after primary cold rolling, and further strong working is performed in secondary cold rolling. A texture is formed, and Goss is formed by the grain growth utilizing the surface energy of the secondary annealing.
This is because the selective grain growth of grains rapidly occurs.

[0039]

【Example】

[Example 1] Steel having a chemical composition with Nb changed shown in Table 1 was melted to form a slab, and hot rolling was performed at a finishing temperature of 800 ° C to a plate thickness of 1.2 mm. After removing the scale layer on the surface by pickling, cold rolling was performed to a plate thickness of 0.3 mm (reduction rate 75%). Then, in a hydrogen atmosphere with a dew point of -50 ° C and an oxygen concentration of 1.5 ppm, the heating rate is 200 ° C.
Annealing was performed at 1200 ° C. for 10 minutes / minute.

[0040]

[Table 1]

These samples were made to have a width of 10 mm and a length of 100 m.
The sample was cut into m pieces, heat-treated at 800 ° C. for 2 minutes in a nitrogen atmosphere to remove cutting strain, and subjected to magnetic measurement. Here, the magnetic flux density B ₈ to which a direct current magnetic field of 800 A / m after the demagnetizing field correction was applied was obtained. The results are shown in Table 2.

[0042]

[Table 2]

As shown in Table 2, when Nb is 0.0005% or less, that is, 5.0 ppm or less, the final annealing is 1
High B _{8 of} 1.60T or more, even for a short time of 0 minutes
It was confirmed that The high magnetic flux density was obtained because the Goss structure was stably formed. [Example 2] Steels having chemical compositions in which Sn shown in Table 3 was changed were melted to form slabs, and hot rolling was performed at a finishing temperature of 800 ° C to a plate thickness of 1.5 mm. After removing the scale layer on the surface by pickling, cold rolling was performed to a plate thickness of 0.3 mm (reduction rate 80%). Then, in a hydrogen atmosphere with a dew point of -50 ° C and an oxygen concentration of 2.5 ppm, the heating rate is 400 ° C.
Annealing was performed at 1180 ° C. for 10 minutes / minute.

[0044]

[Table 3]

These samples were made to have a width of 10 mm and a length of 100 m.
m, and subjected to a heat treatment at 800 ° C. for 2 minutes in a nitrogen atmosphere to remove cutting strain, and subjected to magnetic measurement,
B ₈ after the correction of the demagnetizing field was obtained. The results are shown in Table 4.

[0046]

[Table 4]

As shown in Table 4, when Sn is 0.0010% or less, that is, 10 ppm or less, the final annealing is 10
It was confirmed that a high B _{8 of} 1.60 T or more could be obtained even for a short time of minutes. The high magnetic flux density was obtained because the Goss structure was stably formed. [Example 3] Steels having different chemical compositions as shown in Table 5 were melted to form slabs, and hot rolling was performed at a finishing temperature of 850 ° C to a plate thickness of 1.8 mm. After removing the scale layer on the surface by pickling, cold rolling was performed to a plate thickness of 0.5 mm (reduction ratio: 72.2%). Then, dew point -50 ℃,
Heating rate 40 in a hydrogen atmosphere with an oxygen concentration of 1.5 ppm
Annealing was performed at 1200C for 10 minutes at 0C / min.

[0048]

[Table 5]

These samples were made to have a width of 10 mm and a length of 100 m.
m, and subjected to a heat treatment at 800 ° C. for 2 minutes in a nitrogen atmosphere to remove cutting strain, and subjected to magnetic measurement,
B ₈ after the correction of the demagnetizing field was obtained. The results are shown in Table 6.

[0050]

[Table 6]

As shown in Table 6, when Ti is 0.0020% or less, that is, 20 ppm or less, the final annealing is 10
It was confirmed that a high B _{8 of} 1.60 T or more could be obtained even for a short time of minutes. The high magnetic flux density was obtained because the Goss structure was stably formed. [Example 4] A steel having a chemical composition containing two kinds of Nb, Sn, and Ti shown in Table 7 was melted to form a slab, and hot rolling was performed at a finishing temperature of 780 ° C to a plate thickness of 1.5 mm. It was After removing the scale layer on the surface by pickling, plate thickness 0.35
Cold rolling was performed up to mm (reduction ratio 76.7%). After that, annealing was performed at 1200 ° C. for 10 minutes at a heating rate of 200 ° C./min in a hydrogen atmosphere having a dew point of −50 ° C. and an oxygen concentration of 1.5 ppm.

[0052]

[Table 7]

These samples are 10 mm wide and 100 m long.
m, and subjected to a heat treatment at 800 ° C. for 2 minutes in a nitrogen atmosphere to remove cutting strain, and subjected to magnetic measurement,
B ₈ after the correction of the demagnetizing field was obtained. The result is [Nb] +
The results are summarized in Table 8 as 0.5 [Sn] +0.25 [Ti] (ppm).

[0054]

[Table 8]

As shown in Table 8, [Nb] +0.5 [S
If n] +0.25 [Ti] is 8 or less, high B of 1.60 T or more even if the final annealing is as short as 10 minutes.
It was confirmed that ₈ was obtained. The high magnetic flux density was obtained because the Goss structure was stably formed. [Example 5] Steels having chemical compositions in which Mn, Cr, and Ni shown in Table 9 were changed were melted to form slabs, and the finishing temperature was 85.
Hot rolling was performed at 0 ° C. to a plate thickness of 1.5 mm. After removing the scale layer on the surface by pickling, the plate thickness is 0.35 mm
Primary cold rolling was performed (reduction ratio 76.7%). Then, annealing was performed at 1200 ° C. for 10 minutes at a heating rate of 400 ° C./min in a hydrogen atmosphere having a dew point of −50 ° C. and an oxygen concentration of 1.5 ppm.

[0056]

[Table 9]

These samples were made to have a width of 10 mm and a length of 100 m.
m, and subjected to a heat treatment at 800 ° C. for 2 minutes in a nitrogen atmosphere to remove cutting strain, and subjected to magnetic measurement,
B ₈ after the correction of the demagnetizing field was obtained. The results are shown in Table 10.

[0058]

[Table 10]

As shown in Table 10, it was confirmed that the magnetic flux density of Mn, Cr, and Ni contained as impurities hardly changed even if the contents changed. That is, it was found that these elements do not adversely affect Goss texture formation. [Example 6] Steel having a chemical composition with Nb changed shown in Table 1 was melted to form a slab, and hot rolling was performed at a finishing temperature of 800 ° C to a plate thickness of 2.0 mm. After removing the scale layer on the surface by pickling, cold rolling was performed to a plate thickness of 1.2 mm (reduction rate 40%). Then, in a hydrogen atmosphere with a dew point of -50 ° C and an oxygen concentration of 1.5 ppm, the heating rate is 200 ° C.
Annealing was performed at 1200 ° C. for 10 minutes / minute. Furthermore, cold rolling was performed to a plate thickness of 0.1 mm (reduction ratio 91.7).
%), Followed by annealing at 1200 ° C. for 10 minutes at a heating rate of 200 ° C./min in a hydrogen atmosphere having a dew point of −50 ° C. and an oxygen concentration of 1.5 ppm.

These samples were made 10 mm wide and 100 m long.
m, and subjected to a heat treatment at 800 ° C. for 2 minutes in a nitrogen atmosphere to remove cutting strain, and subjected to magnetic measurement,
B ₈ after the correction of the demagnetizing field was obtained. The results are shown in Table 11.

[0061]

[Table 11]

As shown in Table 11, Nb is 0.0005%
If it is less than or equal to 5.0 ppm, that is, if the final annealing is as short as 10 minutes, a high B of 1.85 T or more is obtained.
It was confirmed that ₈ was obtained. The high magnetic flux density was obtained because the Goss structure was stably formed. [Example 7] Steels having chemical compositions shown in Table 3 with Sn changed were formed into slabs, and hot-rolled at a finishing temperature of 800 ° C to a plate thickness of 2.5 mm. After removing the scale layer on the surface by pickling, cold rolling was performed to a plate thickness of 1.1 mm (reduction rate 56%). Then, in a hydrogen atmosphere with a dew point of -50 ° C and an oxygen concentration of 2.5 ppm, the heating rate is 400 ° C.
Annealing was performed at 1180 ° C. for 10 minutes / minute. Furthermore, cold rolling was performed to a plate thickness of 0.1 mm (reduction ratio 90.9
%), Followed by annealing at 1200 ° C. for 10 minutes at a heating rate of 200 ° C./min in a hydrogen atmosphere having a dew point of −50 ° C. and an oxygen concentration of 1.5 ppm.

These samples were set to have a width of 10 mm and a length of 100 m.
m, and subjected to a heat treatment at 800 ° C. for 2 minutes in a nitrogen atmosphere to remove cutting strain, and subjected to magnetic measurement,
B ₈ after the correction of the demagnetizing field was obtained. The results are shown in Table 4.

[0064]

[Table 12]

As shown in Table 12, Sn is 0.0010%.
Below, that is, below 10 ppm, the final annealing is 1
High B _{8 of} 1.85T or more even for a short time of 0 minutes
It was confirmed that The high magnetic flux density was obtained because the Goss structure was stably formed. [Example 8] Steels having chemical compositions with different Ti shown in Table 5 were melted to form slabs, and hot rolling was performed at a finishing temperature of 850 ° C to a plate thickness of 2.5 mm. After removing the scale layer on the surface by pickling, cold rolling was performed to a plate thickness of 1.5 mm (reduction rate 40%). Then, in a hydrogen atmosphere with a dew point of -50 ° C and an oxygen concentration of 1.5 ppm, the heating rate is 400 ° C.
Annealing was performed at 1200 ° C. for 10 minutes / minute. Further, cold rolling was performed to a plate thickness of 0.1 mm (reduction ratio 93.3).
%), Followed by annealing at 1200 ° C. for 10 minutes at a heating rate of 200 ° C./min in a hydrogen atmosphere having a dew point of −50 ° C. and an oxygen concentration of 1.5 ppm.

These samples were made to have a width of 10 mm and a length of 100 m.
m, and subjected to a heat treatment at 800 ° C. for 2 minutes in a nitrogen atmosphere to remove cutting strain, and subjected to magnetic measurement,
B ₈ after the correction of the demagnetizing field was obtained. The results are shown in Table 13.

[0067]

[Table 13]

As shown in Table 13, Ti is 0.0020%.
Below, that is, below 20 ppm, the final annealing is 1
High B _{8 of} 1.85T or more even for a short time of 0 minutes
It was confirmed that The high magnetic flux density was obtained because the Goss structure was stably formed. [Example 9] Steels having chemical components containing two kinds of Nb, Sn, and Ti shown in Table 7 were melted to form slabs, and hot rolling was performed at a finishing temperature of 780 ° C to a plate thickness of 2.0 mm. It was After removing the scale layer on the surface by pickling, the plate thickness is 1.5 m
Cold rolling was performed to m (reduction rate 25%). Then, in a hydrogen atmosphere with a dew point of −50 ° C. and an oxygen concentration of 1.5 ppm,
Annealing was performed at 1200 ° C for 10 minutes at a heating rate of 200 ° C / minute. Further, cold rolling was performed to a plate thickness of 0.12 mm (reduction rate 92%), and then in a hydrogen atmosphere with a dew point of -50 ° C and an oxygen concentration of 1.5 ppm, at a heating rate of 200 ° C / minute and 1200 ° C for 10 minutes. Was annealed.

These samples were made to have a width of 10 mm and a length of 100 m.
m, and subjected to a heat treatment at 800 ° C. for 2 minutes in a nitrogen atmosphere to remove cutting strain, and subjected to magnetic measurement,
B ₈ after the correction of the demagnetizing field was obtained. The result is [Nb] +
The results are summarized in Table 14 as 0.5 [Sn] +0.25 [Ti] (ppm).

[0070]

[Table 14]

As shown in Table 14, [Nb] +0.5
It was confirmed that if [Sn] +0.25 [Ti] is 8 or less, a high B _{8 of} 1.85 T or more can be obtained even if the final annealing is as short as 10 minutes. The high magnetic flux density was obtained because the Goss structure was stably formed. [Example 10] Steels having chemical compositions in which Mn, Cr, and Ni shown in Table 9 were changed were melted to form slabs, and the finishing temperature was 8
Hot rolling was performed at 50 ° C. to a plate thickness of 2.0 mm. After removing the scale layer on the surface by pickling, plate thickness 1.0 mm
Primary cold rolling was performed up to 50% (reduction rate). afterwards,
Annealing was performed at 1200 ° C. for 10 minutes at a heating rate of 400 ° C./min in a hydrogen atmosphere having a dew point of −50 ° C. and an oxygen concentration of 1.5 ppm. Further, cold rolling was performed to a plate thickness of 0.08 mm (reduction rate 92%), and then a heating rate of 200 ° C./in a hydrogen atmosphere with a dew point of −50 ° C. and an oxygen concentration of 1.5 ppm.
Annealing was performed at 1200 ° C. for 10 minutes.

These samples were made to have a width of 10 mm and a length of 100 m.
m, and subjected to a heat treatment at 800 ° C. for 2 minutes in a nitrogen atmosphere to remove cutting strain, and subjected to magnetic measurement,
B ₈ after the correction of the demagnetizing field was obtained. The results are shown in Table 15.

[0073]

[Table 15]

As shown in Table 15, it was confirmed that the magnetic flux density of Mn, Cr, and Ni contained as impurities hardly changed even if the contents were changed. That is, it was found that these elements do not adversely affect Goss texture formation.

[0075]

According to the present invention, a stable Goss structure can be formed by final annealing for a short time of 10 minutes or less, and as a result, a method for producing a grain-oriented silicon steel sheet having a high magnetic flux density is provided. . Since the final annealing can be shortened, the final annealing can be performed by continuous annealing.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Tanaka 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. Nippon Steel Tube Co., Ltd.

Claims (2)

[Claims] 1. C: 0.01 wt% or less, Si: 2.5
~ 7 wt%, S: 0.01 wt% or less, Al: 0.01
wt% or less, N: 0.01 wt% or less, Cu: 0.0
1 wt% or less, Nb: 5 ppm or less, Sn: 10 ppm or less, Ti: 20 ppm, and [Nb] + 0.5 × [Sn] +0.25 [Ti] ≦ 8.
(However, the concentration of each element is ppm.), A steel material containing the balance Fe and other unavoidable impurities was prepared, and after the steel material was maintained at 1000 ° C or higher, the finishing temperature was 700 to 950 ° C. Hot rolling, then rolling rate 4
1000 ~ 80% in a reducing atmosphere, a non-oxidizing atmosphere with an oxygen partial pressure of 0.5 Pa or less, or a vacuum with an oxygen partial pressure of 0.5 Pa or less.
A method for producing a grain-oriented silicon steel sheet having a high magnetic flux density, which comprises annealing at a temperature of 1300 ° C. for 10 minutes or less. 2. C: 0.01 wt% or less, Si: 2.5
~ 7 wt%, S: 0.01 wt% or less, Al: 0.01
wt% or less, N: 0.01 wt% or less, Cu: 0.0
1 wt% or less, Nb: 5 ppm or less, Sn: 10 ppm or less, Ti: 20 ppm, and [Nb] + 0.5 × [Sn] +0.25 [Ti] ≦ 8.
(However, the concentration of each element is ppm.), Prepare a steel material consisting of the balance Fe and other unavoidable impurities, hold this steel material at 1000 ° C or higher, and then set the finishing temperature to 700 to 950 ° C. And then cold rolling at a rolling ratio of 80% or less, and then a reducing atmosphere or a non-oxidizing atmosphere with an oxygen partial pressure of 0.5 Pa or less, or an oxygen partial pressure of 0.5 Pa or less. In the vacuum of 1
Annealed at a temperature of 000 to 1300 ° C, and a rolling rate of 90
% Or more, and then 1000 to 13 in a reducing atmosphere, a non-oxidizing atmosphere with an oxygen partial pressure of 0.5 Pa or less, or a vacuum with an oxygen partial pressure of 0.5 Pa or less.
A method for producing a grain-oriented silicon steel sheet having a high magnetic flux density, which comprises annealing at a temperature of 00 ° C. for 10 minutes or less.