JP4962516B2 - Method for producing grain-oriented electrical steel sheet - Google Patents

Description

  The present invention relates to a method for producing a grain-oriented electrical steel sheet that is suitable for applications such as iron core materials for transformers.

For grain-oriented electrical steel sheets, it is known as a common technique to preferentially recrystallize grains having Goss orientation during final finish annealing using precipitates called inhibitors. . For example, Patent Document 1 discloses a method of using AlN and MnS as an inhibitor, and Patent Document 2 discloses a method of using MnS and MnSe as an inhibitor, which are industrially put into practical use.
Further, for the purpose of enhancing the action of these inhibitors, Patent Document 3 discloses a method using Pb, Sb, Nb, Te, and Patent Document 4 discloses Zr, Ti, B, Nb, Ta. , V, Cr, and Mo are disclosed.

  Although the method using these inhibitors is an effective method for stably developing secondary recrystallized grains, slab heating at a high temperature of 1300 ° C or higher is required to finely disperse the inhibitor in steel. Met. In addition, since the inhibitor component causes deterioration of the magnetic properties after secondary recrystallization, a purification annealing process is required to remove the inhibitor, and the process is controlled at a high temperature of 1100 ° C or higher. There was a need to do.

  On the other hand, Patent Document 5 proposes a technique for developing Goss-oriented crystal grains by secondary recrystallization in a material that does not contain an inhibitor component. This method eliminates impurities such as inhibitor components as much as possible, and makes the grain boundary energy dependency of the grain boundary energy at the time of primary recrystallization obvious, without using an inhibitor. Is a technique for secondary recrystallization of grains having goth orientation, and the effect is called a texture inhibition effect. In the method of Patent Document 5, the step of purifying the inhibitor is unnecessary, so that the final finish annealing does not need to be performed at a high temperature, the inhibitor does not need to be finely dispersed in the steel, and high-temperature slab heating is not necessary. For this reason, this method has great advantages both in terms of manufacturing cost and equipment maintenance.

Japanese Patent Publication No.40-15644 Japanese Patent Publication No.51-13469 Japanese Patent Publication No.38-8214 JP-A-52-24116 JP 2000-129356 JP

  However, since the component system not containing an inhibitor has few precipitates that suppress grain growth, the grain size tends to increase due to grain growth during annealing, that is, the annealing temperature dependency is strong. For this reason, the grain size after hot-rolled sheet annealing and after recrystallization annealing also fluctuates due to slight variations in process conditions, specifically the annealing temperature, and the magnetic characteristics over the entire length of the product coil vary, The problem that good magnetic properties cannot be obtained as a whole coil has become apparent.

  The present invention advantageously solves the above-described problems, and an object of the present invention is to propose an advantageous method for producing a grain-oriented electrical steel sheet capable of achieving high-level stabilization of product magnetic properties.

  Now, as a result of intensive studies to solve the above problems, the inventors have added a small amount of a specific element, specified the ratio of impurities Al and N, and further increased the temperature during recrystallization annealing. It has been found that the intended purpose can be advantageously achieved by controlling the speed.

Hereinafter, experiments that have made the present invention successful will be described. Unless otherwise specified, “%” in relation to ingredients means mass%.
<Experiment 1>
C: 0.035 to 0.043%, Si: 3.23 to 3.30%, Mn: 0.06 to 0.09%, Sb: 0.027 to 0.045%, Cr: 0.02 to 0.06%, P: 0.012 to 0.015%, Al: 28 to 100 ppm, N: Steel slab containing 17-50ppm, S: 15-26ppm and Nb: 25-47ppm, the balance being Fe and unavoidable impurities is manufactured by continuous casting, and after slab heating at 1250 ° C, hot rolling Then, a hot-rolled sheet having a thickness of 2.3 mm was formed, and then annealed at 1050 ° C. for 15 seconds, followed by cold rolling to a final thickness of 0.23 mm. After applying recrystallization annealing in a soaking condition of 50% N ₂ -50% H ₂ at 850 ° C for 60 seconds, after applying an annealing separator mainly composed of MgO, 1200 Purification annealing was carried out at 10 ° C. for 10 hours. Thereafter, planarization annealing was performed at 900 ° C. for 15 seconds under the condition of forming a tension-imparting coating mainly composed of magnesium phosphate and boric acid.

After the flattening annealing, the iron loss of the entire length of the coil was measured in advance with an in-line iron loss meter, and a total of 5 samples were collected: 3 places where the iron loss was bad in the full length measurement and 2 ends of the coil: 2 places.
The magnetic properties (magnetic flux density B ₈ ) of the obtained sample were measured by the method described in JIS C 2550, and the value having the worst magnetic properties among the five locations was taken as the representative value of the coil. In this method, when the variation in the magnetic characteristics is large, the representative value is deteriorated. Therefore, it can be considered that the variation in the coil can be quantified.

Although the obtained magnetic characteristics seemed to vary at first glance, a good correlation was obtained by arranging the ratio Al / N of Al and N in the steel slab component. The result is shown in FIG.
As can be seen from FIG. 1, when Al / N is decreased, the magnetic characteristics are deteriorated, and particularly when the Al / N is less than 1.4, the variation is increased. Even in the range where the magnetic flux density is high, when Al / N is less than 2.0, the magnetic flux density tends to decrease somewhat.

Therefore, further experiments were conducted to investigate the reason why Al / N has a correlation with the magnetic flux density.
Since a change in magnetic flux density was observed even when Al / N was around 2.0, Al and N present as impurities formed AlN (Al / N was 27 / 14≈1.93 by mass ratio). Presuming that the behavior of the compound might be involved, we experimented with various additions of nitride-forming elements.

<Experiment 2>
C: 0.045 to 0.062%, Si: 3.20 to 3.31%, Mn: 0.04 to 0.16%, Sb: 0.015 to 0.037%, Cr: 0.03 to 0.11%, Mo: 0.03 to 0.05%, Al: 55 to 97 ppm, N: Steel slabs containing 20 to 49 ppm (Al / N: 1.98 to 3.10) and S: 17 to 27 ppm, and further containing only about 50 ppm of one selected from Zr, Ti, Nb, B, and V, and these Zr Steel slabs that do not contain Ti, Nb, B, and V are manufactured by continuous casting, slab heated at 1250 ° C, then hot rolled into a 2.8mm thick hot rolled sheet, and then heated at 1100 ° C for 60 seconds. After hot-rolled sheet annealing, it was finished to a final sheet thickness of 0.30 mm by cold rolling. Then, after applying recrystallization annealing in a soaking condition of 50% N ₂ -50% H ₂ at 840 ° C. for 80 seconds, after applying an annealing separator mainly composed of MgO, 1200 Purification annealing was carried out at 10 ° C. for 10 hours. Thereafter, planarization annealing was performed at 900 ° C. for 15 seconds under the condition of forming a tension-imparting coating mainly composed of magnesium phosphate and boric acid.

  After flattening annealing, the iron loss of the entire length of the coil is measured in advance with an in-line iron loss meter, and a total of five samples are taken from within the coil using the same method as in Experiment 1, and the magnetic properties of the obtained sample are JIS C 2550 As a representative value of the coil, the value having the worst magnetic characteristics among the five locations was measured.

The obtained results are shown in FIG.
FIG. 2 shows that the magnetic flux density varies greatly depending on the trace element added with about 50 ppm. Here, secondary recrystallization did not appear in the Zr and Ti additive materials having a low magnetic flux density. Further, it has been clarified that when B, Nb, and V are added, the magnetic flux density is higher than when nothing is added.

As described above, the reason why the magnetic characteristics change due to the addition of a trace element is not necessarily clearly clarified, but the inventors consider as follows.
The thermodynamic stability of nitrides in trace additives and impurities has been investigated in detail, and it has been found that the stability varies depending on the element bound to nitrogen. In the element added in this experiment, the stability of the nitride is Zr, Ti, Al, B, Nb, V from the stable side.
According to the results of FIG. 2, the elements having poor magnetic characteristics are Zr and Ti whose nitrides are more stable than Al, and the elements having good magnetic characteristics are B, Nb and V whose nitrides are more unstable than Al. Met. From this, when Zr and Ti are present, it is presumed that N in the steel is combined with these elements and the formation of ZrN and TiN deteriorates the magnetic properties. Moreover, even if B, Nb, and V are present, N in the steel is considered to form a stable nitride with Al, and a nitride with B, Nb, and V is not formed.

Furthermore, in Experiment 1, when Al / N is low, the reason why the magnetic properties deteriorated even in the presence of Nb is that the stoichiometric amount of N is excessive as compared with Al, and Nb remains bound to N. This is thought to be due to the formation of nitride.
From the extreme point of view, it is considered that the presence of nitrides of Zr, Ti, B, Nb, and V deteriorates the magnetic properties. Presumably, this is because the texture inhibition effect using the grain boundary energy difference between the crystal grains of the steel sheet as a driving force is diminished due to an increase in impurities such as nitride.

  In addition, when a small amount of B, Nb, or V is added, the reason why the magnetic characteristics are better than when it is desired to be added is not clear. However, it has been found that when these are added, the crystal grain size after recrystallization annealing is fine and uniform, which eliminates the effect of the size effect on the grain size and provides a texture inhibition effect. It is speculated that this has led to an improvement in magnetic properties. The effect of uniforming the particle size also contributes to the improvement of variations in magnetic properties within the same sample.

Based on the above results and considerations, further experiments were conducted to investigate the effect of particle size uniformity.
<Experiment 3>
C: 0.034%, Si: 3.30%, Mn: 0.07%, Sb: 0.030%, Sn: 0.059%, Cr: 0.05%, Al: 56ppm, N: 29ppm (Al / N: 1.93), S: 15ppm and Nb : A steel slab containing 35 ppm, the balance being Fe and inevitable impurities, manufactured by continuous casting, heated at 1150 ° C, then hot rolled into a hot rolled sheet of 3.0 mm thickness, then 950 ° C After 30 seconds of hot-rolled sheet annealing, the first sheet is cold rolled to an intermediate thickness of 1.8 mm. After 1000 seconds of intermediate annealing for 40 seconds, the second sheet is cold rolled to a final thickness of 0.23 mm. It was. Thereafter, recrystallization annealing was performed in a soaking condition of 50% N ₂ -50% H ₂ at 850 ° C. for 60 seconds. Under the present circumstances, the average temperature increase rate between 600-800 degreeC was changed variously.

  The recrystallized particle size of the obtained sample was measured, and the average particle size and its standard deviation were determined from the particle size distribution. The recrystallized grain size is measured by cutting a cross section perpendicular to the rolling direction of the sample, observing it with an optical microscope after etching with a nital solution, approximating the grains in the field of view with an ellipse approximation method by an image processing device, The average of the major and minor axes was taken as the particle size of the grains. Samples at that time were collected from both end portions and the central portion in the width direction of the produced recrystallized plate, and the observation location was the plate thickness full thickness. Samples were collected so that the number of particles observed was a total of at least 2000 at both ends and the center.

FIG. 3 shows the standard deviation when the average grain size is normalized to 1.0 in relation to the temperature increase rate of recrystallization annealing.
As shown in the figure, it can be seen that the standard deviation is smaller, that is, the variation in the particle size is smaller, as the average heating rate between 600 and 800 ° C. is faster.

Through the above experiments and considerations, the inventors have defined the ratio of Al and N present as impurities in a system in which a small amount of B, Nb, or V is added to a component system that does not contain an inhibitor, and again It was concluded that a grain-oriented electrical steel sheet with excellent magnetic properties can be obtained by controlling the rate of temperature rise during crystal annealing.
The present invention is based on the above findings.

That is, the gist configuration of the present invention is as follows.
1. In mass%, C: 0.10% or less, Si: 2.0-8.0%, and Mn: 0.005-1.0%, Al is reduced to 100 ppm or less, N, S, and Se are each reduced to 50 ppm or less, and the balance is Fe And after slab consisting of unavoidable impurities, hot-rolled, and subjected to hot-rolled sheet annealing as necessary, finish it to the final sheet thickness by performing cold rolling twice or more sandwiching once or intermediate annealing, Then, after performing recrystallization annealing, in the manufacturing method of grain oriented electrical steel sheet consisting of a series of steps to perform purification annealing,
The slab further contains one or more selected from B, Nb and V in a total range of 10 to 150 ppm, and the ratio of Al to N contained as impurities is expressed as Al / N by mass ratio. A method for producing a grain-oriented electrical steel sheet, wherein ≧ 1.4 and the average rate of temperature increase between 600 and 800 ° C. in recrystallization annealing is 15 ° C./s or more.

2. In the slab, Ni: 0.010 to 1.50%, Cr: 0.01 to 0.50%, Cu: 0.01 to 0.50%, P: 0.005 to 0.50%, Sn: 0.005 to 0.50%, Sb: 0.005 to 0.50 %, Bi: at least one selected from 0.005 to 0.50 % . The method for producing a grain-oriented electrical steel sheet according to 1, wherein the grain-oriented electrical steel sheet is produced.

3. The grain size distribution of recrystallized grains in the steel sheet after recrystallization annealing has a standard deviation of 0.3 or less when the average grain size is normalized to 1.0. Production method.

  According to the present invention, in a component system that does not contain an inhibitor, variation in magnetic characteristics in the longitudinal direction and width direction of the coil can be reduced, and as a result, good magnetic characteristics can be obtained as a whole product coil.

It is a diagram showing the relationship between the ratio Al / N and the magnetic flux density B ₈ of impurities Al and N in the steel. It is a diagram illustrating a relationship between the type and the magnetic flux density B ₈ of the added trace elements in the steel. It is the figure which showed the standard deviation when an average particle diameter is normalized to 1.0 with respect to the temperature increase rate of recrystallization annealing.

Hereinafter, the present invention will be specifically described.
First, the reason why the component composition of the slab is limited to the above range in the present invention will be described.
C: 0.10% or less When the C content exceeds 0.10%, it is difficult to reduce to 50 ppm or less where magnetic aging does not occur even if decarburization is performed. Therefore, the C content is limited to 0.10% or less.

Si: 2.0-8.0%
Si is an element necessary to increase the specific resistance of steel and improve iron loss. However, if it is less than 2.0%, its effect is poor. On the other hand, if it exceeds 8.0%, workability deteriorates and rolling becomes difficult. Therefore, the Si content is limited to a range of 2.0 to 8.0%.

Mn: 0.005 to 1.0%
Mn is an element necessary for improving the hot workability. However, if it is less than 0.005%, its effect is poor. On the other hand, if it exceeds 1.0%, the magnetic flux density of the product plate is lowered. Limited to 1.0% range.

Al: 100 ppm or less, and N, S, Se: 50 ppm or less In the present invention, the amount of Al is 100 ppm or less, and the amount of N, S, and Se is 50 ppm or less. Indispensable for recrystallization. Although it is desirable to reduce these components as much as possible from the viewpoint of magnetic characteristics, since the reduction of these components increases the cost, there is no problem even if they are left within the above range. Among these, since Al and Se are elements that are difficult to purify from the steel during the purification annealing, it is more desirable that Al is 80 ppm and Se is 20 ppm or less. In addition, it is difficult to completely remove N and S light elements at the time of adjusting the components before making the steel slab, and in the case where no special treatment is performed, it is generally left in the steel plate by about 20 ppm each. Is.

  Among these impurities, it is essential that the ratio of Al to N (Al / N) is 1.4 or more for the reasons described above, and it is more desirable to set Al / N to 2.0 or more, since the magnetic characteristics are improved. Further, as described above, since it is difficult to completely remove N, addition of a small amount of Al in the range of 100 ppm or less to satisfy Al / N ≧ 1.4 is not prevented.

One or more selected from B, Nb and V in total: 10 to 150 ppm
Furthermore, in order to sufficiently obtain the effect of improving the magnetic characteristics in the present invention, it is necessary to add 10 ppm or more of one or more of B, Nb and V. If each addition amount is less than 10 ppm, the effect of addition is small. Preferably, each is 20 ppm or more. However, these trace additive elements remain in the base iron even in the final product and cause deterioration of iron loss, so the total amount is limited to 150 ppm or less. From the viewpoint of suppressing iron loss deterioration, the total amount is desirably 50 ppm or less.

As described above, the essential element and the suppressing element have been described. In the present invention, at least one selected from Ni, Cr, Cu, P, Sn, Sb, and Bi is also used as the magnetic property improving element in the following range. It can be contained as appropriate.
Ni: 0.010 to 1.50%
Ni is an element that is useful for improving the magnetic properties by improving the hot-rolled sheet structure. However, if the addition amount is less than 0.010%, the effect of the addition is poor, while if it exceeds 1.50%, secondary recrystallization does not occur. It becomes stable and the magnetic properties deteriorate.

Cr: 0.01 to 0.50%, Cu: 0.01 to 0.50%, P: 0.005 to 0.50%
All of these elements are useful elements for improving iron loss, but if they do not reach the lower limit, the effect of addition is poor.On the other hand, if the upper limit is exceeded, the growth of secondary recrystallized grains is suppressed, rather magnetic properties. Cause deterioration.

Sn: 0.005-0.50%, Sb: 0.005-0.50%, Bi: 0.005-0.50 %
These elements are also useful elements for improving the magnetic properties. However, when the lower limit is not reached, the effect of addition is poor.On the other hand, when the upper limit is exceeded, the development of secondary recrystallized grains is suppressed, and rather the deterioration of the magnetic properties. Invite.

Next, the manufacturing process of the present invention will be described.
The molten steel adjusted to the above preferred component composition is made into a slab by a normal ingot-making method or a continuous casting method. Further, a thin cast piece having a thickness of 100 mm or less may be manufactured by a direct casting method. In the case of a slab, it is heated and rolled by a normal method, but may be immediately subjected to hot rolling without heating after casting. In the case of a thin slab, hot rolling may be performed, or the hot rolling may be omitted and the process may proceed as it is. Since the slab heating temperature before hot rolling is a component system that does not contain an inhibitor component with reduced Al, N, S, and Se, it does not require high-temperature annealing to dissolve the inhibitor, which has been essential in the past. In view of cost, a low temperature of 1250 ° C. or lower is desirable.

  Next, hot-rolled sheet annealing is performed as necessary. The hot-rolled sheet annealing temperature for obtaining good magnetic properties is preferably about 800 to 1150 ° C. If the hot-rolled sheet annealing temperature is less than 800 ° C., a band structure in hot rolling remains, and it becomes difficult to realize a sized primary recrystallized structure, which hinders the development of secondary recrystallization. On the other hand, when the hot-rolled sheet annealing temperature exceeds 1150 ° C., the grain size after the hot-rolled sheet annealing is excessively coarsened, which is extremely disadvantageous for realizing a sized primary recrystallized structure.

  After hot-rolled sheet annealing, re-annealing is performed after performing cold rolling twice or more sandwiching once or intermediate annealing. Cold rolling is performed by raising the temperature to 100 to 300 ° C., or performing aging treatment at 100 to 300 ° C. once or a plurality of times during the cold rolling in order to improve magnetic properties. It is advantageous.

  Recrystallization annealing is performed in a wet atmosphere when decarburization is required, but may be performed in a dry atmosphere when decarburization is not required. The soaking temperature in this recrystallization annealing is not particularly limited as long as it is equal to or higher than the recrystallization temperature, but there is a concern that annealing at an excessively high temperature results in a coarse crystal grain size and unstable secondary recrystallization. Therefore, the upper limit of the annealing temperature is preferably about 1050 ° C. In addition, after recrystallization annealing, you may use together the technique which increases Si amount by a siliconization method.

In the present invention, in the above-described recrystallization annealing step, it is important that the average rate of temperature increase from 600 ° C. to 800 ° C. is 15 ° C./s or more.
This is because if the average value of the heating rate is less than 15 ° C./s, as shown in FIG. 3, the standard deviation when the average particle size is normalized to 1.0 increases, that is, the variation in particle size. This is because the excellent magnetic properties cannot be stably obtained.
The upper limit value of the average temperature increase rate is not particularly limited and is preferably as large as possible. However, from the viewpoint of temperature control, it is preferable to adjust the temperature increase rate within a range of 300 ° C./s or less.

After that, when forming a forsterite film with an emphasis on iron loss, a secondary recrystallized structure is developed by applying a final annealing after applying an annealing separator mainly composed of MgO. A coating can be formed.
On the other hand, if the forsterite film is not formed with emphasis on the punching processability, the main component is silica or alumina that inhibits the formation of the forsterite film even if it is used or not. Use things. When these annealing separators are applied, it is effective to perform electrostatic coating that does not carry moisture, and a heat-resistant inorganic material sheet (silica, alumina, mica) may be used.

  The purification annealing (finish annealing) is desirably performed at 800 ° C. or higher for secondary recrystallization. Further, in order to complete the secondary recrystallization, it is desirable to hold at a temperature of 800 ° C. or higher for 20 hours or longer. If the forsterite film is not formed with emphasis on punchability, secondary recrystallization should be completed, so the holding temperature is preferably about 850 to 950 ° C., and finish annealing is finished at the holding stage. It is also possible. When placing importance on iron loss or forming a forsterite film to reduce transformer noise, it is desirable to raise the temperature to about 1200 ° C.

  After the purification annealing, water washing, brushing, pickling or the like is performed in order to remove the unreacted annealing separation agent that has adhered. Thereafter, it is effective to correct the shape by performing flattening annealing in order to reduce iron loss.

  In addition, when laminating | stacking and using a steel plate, in order to improve an iron loss, it is effective to give an insulating coating to the steel plate surface before or after planarization annealing. In order to reduce iron loss, this insulating coating is desirably a coating that can impart tension to the steel sheet. Inorganic coating is deposited on the steel sheet surface by a tension coating application method, physical vapor deposition method, or chemical vapor deposition method using a binder. When the coating method is employed, a coating film having excellent adhesion can be obtained, and the iron loss reduction effect can be improved.

Example 1
C: 0.018-0.023%, Si: 3.20-3.40%, Mn: 0.10-0.15%, Cr: 0.03-0.05%, Al: 30-140ppm and N: 29-50ppm, Al / N ratio is shown in Table 1. The steel slab containing the amount of Nb shown in Table 1 and the balance being Fe and inevitable impurities is manufactured by continuous casting, heated at 1200 ° C., and then hot-rolled. A hot-rolled sheet with a thickness of 2.2 mm was obtained, followed by hot-rolled sheet annealing at 1060 ° C. for 40 seconds, followed by cold rolling to a final sheet thickness of 0.23 mm. Thereafter, recrystallization annealing was performed at 820 ° C. for 90 seconds in a humid atmosphere of 25% N ₂ -75% H ₂ . At this time, the average rate of temperature increase between 600 and 800 ° C. was 36 ° C./s. The standard deviation of the recrystallized grain size distribution was about 0.21 in all cases. Next, after applying an annealing separator mainly composed of MgO, purification annealing was performed at 1200 ° C. for 10 hours. Then, planarization annealing was performed at 1200 ° C. for 60 seconds, and TiN was vapor-deposited on the surface of the steel sheet by chemical vapor deposition to form a coating.

After the flattening annealing, the iron loss of the entire length of the coil was measured in advance with an in-line iron loss meter, and a total of 5 samples were collected: 3 places where the iron loss was bad in the full length measurement and 2 ends of the coil: 2 places.
The magnetic properties (magnetic flux density B ₈ ) of the obtained sample were measured by the method described in JIS C 2550, and the value having the worst magnetic properties among the five locations was taken as the representative value of the coil. In this method, when the variation in the magnetic characteristics is large, the representative value is deteriorated. Therefore, it can be considered that the variation in the coil can be quantified.
The obtained results are also shown in Table 1.

  As is apparent from the table, it is understood that good magnetic properties can be obtained by adding an appropriate amount of Nb as a trace element and adjusting the Al / N ratio within an appropriate range.

Example 2
Steel slabs having the composition shown in Table 2 were manufactured by continuous casting, heated to 1200 ° C., and hot-rolled into 2.8 mm thick hot-rolled sheets. Then, the intermediate plate thickness was 2.0 mm by the first cold rolling, and after the intermediate annealing at 1000 ° C. for 40 seconds, the final thickness was 0.23 mm by the second cold rolling. Thereafter, recrystallization annealing was performed at 830 ° C. for 60 seconds in a wet atmosphere of 40% N ₂ -60% H ₂ . At this time, the average rate of temperature increase between 600 and 800 ° C. was 70 ° C./s. The standard deviation of the recrystallized grain size distribution was about 0.19 for all. Next, after applying an annealing separator mainly composed of MgO, purification annealing was performed at 1250 ° C. for 10 hours. At that time, out of the 10-hour retention, the latter half 5 hours was an Ar atmosphere, and the rest was a hydrogen atmosphere. Thereafter, flattening annealing was performed at 900 ° C. for 15 seconds under the condition of forming a tension-imparting coating mainly composed of magnesium phosphate and boric acid.

After the flattening annealing, the iron loss of the entire length of the coil was measured in advance with an in-line iron loss meter, and a total of 5 samples were collected: 3 places where the iron loss was bad in the full length measurement and 2 ends of the coil: 2 places.
The magnetic properties (magnetic flux density B ₈ , W _17/50 ) of the obtained sample were measured by the method described in JIS C 2550, and the value having the worst magnetic properties among the five locations was taken as the representative value of the coil. In this method, when the variation in the magnetic characteristics is large, the representative value is deteriorated. Therefore, it can be considered that the variation in the coil can be quantified.
The obtained results are also shown in Table 2.

  As is clear from the table, good magnetic properties were obtained in any of the invention examples in which the component composition satisfied the proper range of the present invention.

Example 3
C: 0.082%, Si: 3.30%, Mn: 0.07%, Cr: 0.05%, P: 0.012%, Sn: 0.054%, Sb: 0.035%, Al: 70ppm, N: 32ppm (Al / N = 2.19) and A steel slab containing V: 40 ppm, the balance being Fe and inevitable impurities was manufactured by continuous casting, and after heating the slab at 1200 ° C., a hot rolled sheet having a thickness of 2.7 mm was formed by hot rolling. Next, after hot-rolled sheet annealing at 950 ° C. for 30 seconds, a final sheet thickness of 0.30 mm was finished by warm rolling at 150 ° C. Thereafter, recrystallization annealing was performed at 835 ° C. for 90 seconds in a humid atmosphere of 60% N ₂ -40% H ₂ . At this time, the average heating rate between 600 and 800 ° C. was variously changed as shown in Table 3. Next, after applying an annealing separator mainly composed of MgO, purification annealing was performed at 1200 ° C. for 25 hours. Thereafter, flattening annealing was performed at 900 ° C. for 15 seconds under the condition of forming a tension-imparting coating mainly composed of magnesium phosphate and boric acid.

After the flattening annealing, the iron loss of the entire length of the coil was measured in advance with an in-line iron loss meter, and a total of 5 samples were collected: 3 places where the iron loss was bad in the full length measurement and 2 ends of the coil: 2 places.
The magnetic properties (magnetic flux density B ₈ , W _17/50 ) of the obtained sample were measured by the method described in JIS C 2550, and the value having the worst magnetic properties among the five locations was taken as the representative value of the coil. In this method, when the variation in the magnetic characteristics is large, the representative value is deteriorated. Therefore, it can be considered that the variation in the coil can be quantified.
The results obtained are also shown in Table 3.

  As is apparent from the table, it is understood that good magnetic properties can be obtained by setting the average temperature rising rate between 600 and 800 ° C. in the recrystallization annealing step to 15 ° C./s or more.

Claims (3)

In mass%, C: 0.10% or less, Si: 2.0-8.0%, and Mn: 0.005-1.0%, Al is reduced to 100 ppm or less, N, S, and Se are each reduced to 50 ppm or less, and the balance is Fe And after slab consisting of unavoidable impurities, hot-rolled, and subjected to hot-rolled sheet annealing as necessary, finish it to the final sheet thickness by performing cold rolling twice or more sandwiching once or intermediate annealing, Then, after performing recrystallization annealing, in the manufacturing method of grain oriented electrical steel sheet consisting of a series of steps to perform purification annealing,
The slab further contains one or more selected from B, Nb and V in a total range of 10 to 150 ppm, and the ratio of Al to N contained as impurities is expressed as Al / N by mass ratio. A method for producing a grain-oriented electrical steel sheet, wherein ≧ 1.4 and the average rate of temperature increase between 600 and 800 ° C. in recrystallization annealing is 15 ° C./s or more. In the slab, Ni: 0.010 to 1.50%, Cr: 0.01 to 0.50%, Cu: 0.01 to 0.50%, P: 0.005 to 0.50%, Sn: 0.005 to 0.50%, Sb: 0.005 to 0.50 %, Bi: 0.005 to 0.50 % . The method for producing a grain-oriented electrical steel sheet according to claim 1, comprising at least one selected from 0.005 to 0.50 % .   3. The grain-oriented electrical steel sheet according to claim 1 or 2, wherein the grain size distribution of the recrystallized grains of the steel sheet after recrystallization annealing has a standard deviation of 0.3 or less when the average grain size is normalized to 1.0. Manufacturing method.

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