JPH0776731A - Production of grain-oriented silicon steel sheet having crystal orientation accumulated in goss orientation - Google Patents

Abstract

PURPOSE:To stably produce a grain-oriented silicon steel sheet having crystal orientation accumulated in the Goss orientation by successively executing each treatment of hot rolling, cold rolling and annealing to a steel sheet having a specified compsn. under specified conditions. CONSTITUTION:Steel contg., by weight, <=0.01% C, 2.5 to 7% Si, <=0.01% Cu, <=0.01% S, <=0.01% Al and <=0.01% N is held to >=1000 deg.C. Next, it is subjected to hot rolling so as to regulate the finishing temp. into 700 to 950 deg.C and is thereafter subjected to primary cooling rolling or warm rolling at 70 to 90% draft. Furthermore, secondary and third cold rolling or warm rolling are executed via process annealing for two times. After that, it is annealed at 1000 to 1300 deg.C in a reducing atmosphere, or in a nonoxidizing atmosphere of <=0.5Pa oxygen partial pressure or in a vacuum of <=0.5Pa oxygen partial pressure. Thus, the grain oriented silicon steel sheet having crystal orientation accumulated in the Goss orientation and excellent in magnetic properties can stably be obtd. by annealing treatment in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain-oriented silicon steel sheet having a crystal orientation integrated in the Goss orientation.

[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 two.

The first method is to add a crystal grain growth inhibitor called an inhibitor such as Al or N, and utilize the crystal grain growth inhibitory effect of these elements and their fine precipitates.
A secondary recrystallized grain having a Goss structure is selectively grown (for example, Japanese Patent Publication No. 51-13469 and Japanese Patent Publication No. 40-15644).

The second method is the use of no inhibitor
The Goss grains are developed by simply combining rolling under specific conditions and heat treatment (see, for example, Japanese Patent Laid-Open No. 6-58242).
4-55339, JP-A-2-57635).

[0005]

Since the first method requires decarburization annealing and purification annealing, annealing at high temperature for a long time is indispensable. Therefore, it is inevitable that the manufacturing cost and the equipment cost increase. Further, 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.

On the other hand, the second method is advantageous over the first method in terms of manufacturing cost because decarburization annealing and purification annealing for removing the inhibitor are unnecessary. Further, according to this second method, even if the final plate thickness is 0.1 mm or less, Goss grain growth utilizing surface energy can be stably performed in a short time, and iron loss can be reduced. In this respect also, Advantage over method.

However, when the inventors of the present application made additional tests of the methods disclosed in JP-A-64-55339 and JP-A-2-57635, the Goss grain growth was extremely unstable and stable. It has proved difficult to obtain the desired quality.

In order to solve such a problem, the inventors of the present invention first sandwiched a steel sheet of 2.5 to 7 wt% Si having a specific composition with intermediate annealing without using an inhibitor.
An application was made for a method for producing a grain-oriented silicon steel sheet in which the crystal orientation is integrated in the Goss orientation by performing cold rolling twice and controlling the oxygen concentration in the atmosphere as the final annealing (Japanese Patent Application No. 4-185374). By using this method, a Goss structure can be formed more stably than in the past, but according to the experiments conducted by the inventors of the present application, it was confirmed that the samples formed under the manufacturing conditions that exhibit excellent magnetic characteristics it is recognized that the magnetic properties vary _in, B 8 (800A
The final annealing time is about 1 hour in order for 80% of all the samples to exhibit good magnetic characteristics such as a magnetic flux density of 1.85 or more when a DC magnetic field of 1 / m is applied). It has been found that the annealing treatment for a long time does not provide stable magnetic properties, and is still insufficient for obtaining a grain-oriented silicon steel sheet that is industrially stable and desired.

The present invention has been made in view of the above circumstances, and stably manufactures a grain-oriented silicon steel sheet having excellent magnetic characteristics having a crystal orientation integrated in the Goss orientation by a short-time annealing treatment. The purpose is to provide a method that can.

[0010]

The present invention provides C:
0.01 wt% or less, Si: 2.5 to 7 wt%, Cu:
0.01 wt% or less, S: 0.01 wt% or less, Al:
After preparing a steel material containing 0.01 wt% or less and N: 0.01 wt% or less and holding the steel material at 1000 ° C. or higher,
Hot rolling is performed so that the finishing temperature becomes 700 to 950 ° C., then primary cold rolling or warm rolling is performed at a reduction rate of 70 to 90%, and then secondary annealing is performed through two intermediate annealings. Third cold rolling or warm rolling is performed, and then a reducing atmosphere or a non-oxidizing atmosphere having an oxygen partial pressure of 0.5 Pa or less,
Or 100 in a vacuum with an oxygen partial pressure of 0.5 Pa or less.
Goss characterized by annealing at a temperature of 0 to 1300 ℃
Provided is a method for manufacturing a grain-oriented silicon steel sheet having crystal orientations integrated in the orientation.

The inventors of the present invention have conducted extensive studies to obtain a grain-oriented silicon steel sheet having stable and high magnetic properties even when the final annealing time is short, and as a result, two intermediate annealings are carried out. By setting the rolling reduction of primary cold rolling or warm rolling to a high value of 70 to 90% among the cold rolling or the warm rolling of the number of times, Goss grains can be obtained by the final annealing for a short time within 30 minutes. It has been found that stable growth and stable high magnetic properties can be obtained. The present invention has been made based on such findings of the inventors of the present application.

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

Si has the effect of increasing the electric resistance and
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.

Cu is an element having a small solid solubility in α-iron, and is an element that 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 preferable to reduce the content to 0.01 wt% or less, which does not cause the above-mentioned inconvenience, and more preferably 0.005 wt% or less. However, the melting point of Cu is 1083.
C., which is a component that volatilizes by heat treatment at about 1000.degree. C. or higher, so even if it is contained in excess of 0.01 wt.%, It can be made 0.01 wt.% Or less by heat treatment for a relatively long time. However, extension of the heat treatment time is not preferable from the viewpoint of improving the efficiency of the process.

The amount of unavoidable impurity elements other than these elements is acceptable as long as it is contained in ordinary steel. However, the smaller amount is preferable from the viewpoint of further improving the magnetic properties and the like. In particular, Sn, which has a low solid solubility in α-iron, significantly inhibits the crystal grain growth when the Goss structure is formed by the final heat treatment like Cu, so its content is 0.01 wt%.
% Or less, preferably 0.005 wt% or less. 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 wt% or less. Furthermore, 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. In addition, it is preferable that Mn and P other than those described above among the basic elements of steel are as small as possible.

Next, the hot rolling conditions will be described. The molten steel having the above-mentioned 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 and subjected to hot rolling. Holding temperature before hot rolling is 1000 ℃
What has been specified above is 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 ° C.
This is to secure the hot rolling finishing temperature of. The hot rolling may be performed after heating the ingot or the slab to 1000 ° C or higher in a heating furnace, or may be performed after the 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 about 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 during hot rolling cannot be extinguished, the effect is not substantially exhibited. On the other hand, when the hot-rolled sheet annealing temperature exceeds 1100 ° C., it causes a high operating cost, which is a practical problem.

Next, cold rolling conditions and annealing conditions will be described. The hot rolled sheet produced as described above was pickled to remove the oxide layer formed on the surface, and then had a rolling reduction of 70.
Primary cold (or warm) rolling is performed at ˜90%. By performing the primary cold (or warm) rolling at such a high pressure reduction rate, it is possible to refine the crystal grains and to increase the density of (111) grains that are easily eroded by Goss grains, and to increase the density before the final annealing. The plate structure can be made suitable for Goss grain formation.

This will be described with reference to FIG. Figure 1
Is a summary of the results of X-ray diffraction of a sample obtained by subjecting a 3% Si steel having the composition shown in Table 2 to primary cold rolling, in which the horizontal axis represents the primary cold rolling rate and the vertical axis represents the reflection. The P value corresponding to the relative value of the peak integrated intensity is taken to show the change of the P value in each crystal plane. As shown in this figure, the P value of the (110) plane decreased slightly with the increase of the primary cold rolling rate, whereas the P value of the (111) plane increased sharply from around 70% rolling rate. I understand that If the primary rolling ratio is less than 70%, a desirable Goss structure cannot be obtained after the final annealing for a short time.

When a 3% Si hot-rolled sheet having a composition shown in Table 2 and having a plate thickness of 2.5 mm in FIG. 2 is cold-rolled three times at a reduction rate shown in Table 1 and rolled to 0.1 mm The relationship between the primary cold rolling rate and the value of B ₈ after the final annealing is shown. Here, the final annealing was performed at 1200 ° C. for 10, 30, and 60 minutes. From this figure, it is understood that by setting the primary cold rolling rate to 70% or more, B ₈ of 1.85 T or more can be obtained within the final annealing time of 30 minutes. In the case of warm rolling as well, the primary warm rolling rate may be 70% or more.

[0025]

[Table 1]

However, the primary cold (or warm) rolling rate is 9
When it exceeds 0%, an excessive load is applied to the cold rolling mill, which is not preferable in operation. In general, a cold rolling uses a lubricant, but the same effect can be obtained by rolling without lubrication without using a lubricant.

Intermediate annealing (primary annealing) is performed on the sheet rolled at such a reduction rate. At this time, the primary annealing is preferably performed at a temperature in the range of 600 to 900 ° C. If the annealing temperature is less than 600 ° C, complete recrystallization due to annealing cannot be performed. On the other hand, the annealing temperature is 9
When the temperature exceeds 00 ° C, recrystallization is achieved, but the annealing cost is inevitably high. Further, in order to carry out recrystallization in a short time and to secure the economical efficiency, particularly, 680 to
It is preferable to anneal at a temperature of 800 ° C. In this annealing, even if the surface of the steel sheet is slightly oxidized, it can be removed by pickling before cold (or warm) rolling that is performed later, so Goss of the crystal orientation during the third annealing (final annealing) There is no major problem in terms of securing the accumulation in the direction.
However, from the viewpoint of preventing the oxide film from being excessively generated, it is preferable to carry out the process in a non-oxidizing atmosphere or vacuum where oxygen partial pressure is as low as possible. There is no problem if the annealing time is usually 2 minutes or more. Such annealing treatment can be performed by batch annealing or continuous annealing in a box furnace.

Regarding the heating conditions in the annealing treatment, a heating rate of 200 to 500 ° C./minute and a holding time of 2 to 5 minutes are suitable for continuous annealing, and a heating rate of 4 to 20 for batch annealing.
C./minute and holding time of 1 to 10 hours are suitable. The cooling rate may be a cooling rate that is usually adopted as long as the strain due to heat shrinkage does not remain in the steel sheet. For example, 6
A cooling rate of 13.5 ° C / sec up to 00 ° C and 12 ° C / sec up to 300 ° C is adopted.

The steel sheet subjected to the primary annealing is subjected to secondary cold (or warm) rolling in the same direction as the primary cold (or warm) rolling. The rolling reduction in this case is preferably in the range of 20 to 80%. If the rolling reduction is less than 20% or more than 80%, the final accumulation of GOSS grains is not sufficient. The reason why the secondary rolling rate is allowed in such a wide range is that the primary rolling rate is defined in the narrow range as described above in the present invention. The cold rolling in this case can be carried out without lubrication or lubrication, like the primary cold rolling.

The secondary rolled sheet thus obtained is subjected to intermediate annealing (secondary annealing) again, and at this time as well as the primary annealing, a temperature of 600 to 900 ° C. is preferable. If the annealing temperature is less than 600 ° C, complete recrystallization due to annealing cannot be performed. On the other hand, if the annealing temperature exceeds 900 ° C., recrystallization is achieved, but the annealing cost will inevitably increase. Further, it is preferable to anneal at a temperature of 680 to 800 ° C. in order to carry out recrystallization in a short time and to secure economy. Even in this secondary annealing, some oxidation of the steel sheet surface is allowed for the same reason as in the primary annealing,
In this case as well, from the viewpoint of preventing the oxide film from being excessively generated, it is preferable to carry out in a non-oxidizing atmosphere or in a vacuum where oxygen partial pressure is as low as possible. As with the primary annealing, there is no problem if the secondary annealing time is usually 2 minutes or more. This secondary annealing treatment can also be performed by batch annealing or continuous annealing in a box furnace.

The steel sheet subjected to the secondary annealing is further subjected to tertiary cold (or warm) rolling. The reduction rate at this time is 50 to 9
0% is preferable. When the rolling reduction is less than 50% or more than 90%, the final accumulation of Goss grains is insufficient. Cold rolling in this case is also unlubricated, as in the case of primary and secondary cold rolling.
Either lubrication can be performed.

Final annealing (tertiary annealing) is performed on the thus obtained tertiary rolled plate. The temperature at this time is preferably 1000 to 1300 ° C. Annealing temperature is 100
If the temperature is lower than 0 ° 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.

The final annealing is carried out in an atmosphere containing hydrogen in a necessary amount or more and having a substantially reducing property, or is mainly composed of an inert gas such as nitrogen or Ar, and an oxygen partial pressure of 0. Non-oxidizing atmosphere of 5 Pa or less or oxygen partial pressure is 0.5
It is necessary to carry out in a vacuum of 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.

FIG. 3 shows the reduction ratio of primary rolling, the value of B ₈ and its variation when the final rolling was performed at 1200 ° C. for 3 minutes, 5 minutes, and 10 minutes on the sample rolled under the same conditions as in Table 1. It shows the relationship with. Here, 20 for each temperature
The result of having measured the sample of a book is shown. As is clear from this figure, if the reduction ratio of the primary cold rolling is in the range of 70 to 90%, even if the annealing time is as short as 3 to 10 minutes, B
The variation in the value of ₈ is small, and a stable high magnetic flux density can be obtained. As described above, in the present invention, a grain-oriented silicon steel sheet having a high magnetic flux density can be stably obtained with a final annealing time of approximately 3 minutes or more, and sufficiently good magnetic properties can be obtained by short-time annealing within 30 minutes. Obtained stably and excellent in economic efficiency.

The above-mentioned warm rolling is about 200 to 400.
Rolling performed at ℃. All the steel sheets produced by the method of the present invention have stable Goss grains within a short time of 30 minutes, and have excellent magnetic properties with B ₈ of 1.85 T or more in the case of 3% Si steel. Obtained.

[0036]

【Example】

Example 1 Steel having the chemical composition shown in Table 2 (Si:
3.02%), the finishing temperature is 810 ° C., the winding temperature is 6
Hot rolling was performed under the conditions of 40 ° C. and a finished plate thickness of 2.0 mm.

[0037]

[Table 2]

The hot-rolled sheet thus produced was pickled to remove a surface oxide film, then primary cold-rolled at a reduction rate of 40 to 90%, and then the steel sheet was placed in a 100% nitrogen atmosphere. Was subjected to a primary annealing treatment at 800 ° C. for 2 minutes.

Next, 40 to 9 for the steel sheet after the primary annealing.
Secondary cold rolling was performed at a reduction rate of 0%, and then secondary annealing treatment was performed under the same conditions as the primary annealing. Then, tertiary cold rolling was performed on the steel sheet after the secondary annealing to give a final thickness of 0.1 mm. Then 0.5 for these steel sheets
3 minutes, 10 minutes, 30 minutes, 1 minute at 1200 ° C in vacuum below P
A third annealing (final annealing) was performed for a time.

The B ₈ of the steel sheet obtained as described above was measured using a DC magnetic measuring device. The values of B ₈ after the third annealing when the reduction ratios of the primary and secondary cold rolling in this case are variously changed are shown in FIGS. 4 to 6
Correspond to tertiary annealing times of 10 minutes, 30 minutes, and 60 minutes, respectively.

From these figures, if the final annealing time is about 10 minutes, B ₈ will be obtained if the reduction ratios of the primary cold rolling and the secondary cold rolling are set to 70 to 90% and 20 to 80%, respectively. It exhibits magnetic properties of 1.85 T or more, and particularly, the reduction rates of primary cold rolling and secondary cold rolling are 75 to 95% and 20 to 20%, respectively.
It was confirmed that at 50%, excellent properties of 1.88 T or more were exhibited. [Example 2] The same hot-rolled sheet as in Example 1 was used, and this steel sheet was pickled and then subjected to 75% nitrogen +25 at a reduction rate shown in Table 3.
Primary cold rolling and secondary cold rolling were performed by sandwiching primary annealing (intermediate annealing) at 800 ° C. for 2 minutes in hydrogen. After this,
Secondary annealing was performed under the same conditions as the primary annealing. Then, these steel plates are subjected to tertiary cold rolling to 0.08 mm,
Further, in a 100% hydrogen atmosphere, 1200 ° C. × 0 minutes, 3 minutes,
5 minutes, 10 minutes, 20 minutes, 30 minutes tertiary annealing (final annealing)
(Samples A and B).

[0042]

[Table 3]

FIG. 7 shows the cumulative annealing time of these steel sheets.
The average grain size of the Goss grains is shown, and FIG. 8 shows the surface occupancy of the Goss grains of these steel sheets with respect to the cumulative annealing time. As shown in these figures, sample A having a high primary cold rolling rate of 80%
Indicates that the Goss grains cover the surface of the sample in a short time, whereas in sample B in which the primary cold rolling rate was set as low as 40%, (11
In addition to 0 grains, (100) grains and (111) grains were also present. As a result of measuring B ₈ of these samples using a DC magnetometer, Sample A in which Goss grains covered 100% of the sample surface showed an extremely high value of 1.91T, whereas Sample B showed It was a slightly low value of 1.62T. Further, as a result of observing the crystal grains at each annealing time, it was confirmed that Sample B had a slow Goss grain growth rate. Thus, it was confirmed that the rolling reduction of primary cold rolling has an important effect on the final structure. Example 3 Steel having the chemical composition shown in Table 4 (Si:
6.58%), the finishing temperature is 820 ° C., the winding temperature is 6
Hot rolling was performed under the conditions of 40 ° C. and finished plate thickness of 2.5 mm.

[0044]

[Table 4]

The hot-rolled sheet thus produced was pickled to remove the surface oxide film, and then warm-rolled three times at 300 ° C. at a rolling reduction shown in Table 5 to give a final sheet thickness of 0. It was set to 0.1 mm. Between these warm rollings, primary and secondary annealing treatments were performed at 800 ° C. for 2 minutes in a 100% nitrogen atmosphere. After tertiary cold rolling, 0.5 for these steel sheets
Third annealing (final annealing) was performed at a temperature of 1200 ° C. in a vacuum of Pa or less for 10 minutes (Samples C, D, and E).

[0046]

[Table 5] Table 6 shows the magnetic properties of the sample thus produced and the Goss grain occupied area ratio on the sample surface.

[0047]

[Table 6]

As is clear from this table, 6.5% Si
Also in steel, Goss grains are likely to be formed when the rolling reduction during primary cold rolling is 70% or more, and B ₈ also has a high value as 1.62T and 6.5% Si, and has excellent soft magnetic properties. It was confirmed that

[0049]

EFFECTS OF THE INVENTION According to the present invention, a grain-oriented silicon steel sheet having excellent magnetic characteristics having a crystal orientation integrated in the Goss orientation,
A method that can be stably manufactured by a short-time annealing treatment within 30 minutes is provided.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the rolling reduction of primary cold rolling and the P value of each peak in X-ray diffraction.

FIG. 2 is a diagram showing the relationship between the reduction rate of primary cold rolling and the value of B ₈ after final annealing.

FIG. 3 is a diagram showing a relationship between a primary rolling reduction ratio, a value of B ₈ and its variation when the final annealing is performed at 1200 ° C. for 3 to 10 minutes.

FIG. 4 is a diagram showing the value of B ₈ after final annealing at 1200 ° C. for 10 minutes when various reduction ratios of primary and secondary cold rolling were changed.

FIG. 5 is a diagram showing the value of B ₈ after final annealing at 1200 ° C. for 30 minutes when various reduction ratios of primary and secondary cold rolling were variously changed.

FIG. 6 is a diagram showing the value of B ₈ after final annealing at 1200 ° C. for 60 minutes when various reduction ratios of primary and secondary cold rolling were changed.

FIG. 7 is a diagram showing a surface structure after annealing for 30 minutes of a sample cold-rolled under the conditions of the present invention and a sample cold-rolled under conditions outside the range.

FIG. 8 is a diagram showing the relationship between the final annealing time and the average particle size of Goss grains.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayoshi Oikawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Steel Pipe Co., Ltd. (72) Inventor Akira Hiroso 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Tube Co., Ltd. (72) Inventor Yasushi Tanaka 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Tube Co., Ltd. (72) Inventor Misao Namikawa 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Inside Steel Pipe Co., Ltd.

Claims (1)

[Claims] 1. C: 0.01 wt% or less, Si: 2.5
~ 7 wt%, Cu: 0.01 wt% or less, S: 0.01
wt% or less, Al: 0.01 wt% or less, N: 0.01
Prepare a steel material containing less than wt% and heat this steel material at 1000 ° C.
After the above holding, hot rolling is performed so that the finishing temperature becomes 700 to 950 ° C., then primary cold rolling or warm rolling is performed at a rolling reduction of 70 to 90%, and then two intermediate annealings are performed. Through the secondary and tertiary cold rolling or warm rolling,
Thereafter, it is annealed at a temperature of 1000 to 1300 ° C. in a reducing atmosphere or a non-oxidizing atmosphere 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, and integrated in the Goss orientation. Of manufacturing a grain-oriented silicon steel sheet having the above crystal orientation.