JP4432789B2 - Method for producing grain-oriented electrical steel sheets with excellent magnetic properties - Google Patents

Description

  The present invention relates to a method for producing a grain-oriented electrical steel sheet suitable for iron core materials such as transformers and rotating machines.

  For grain-oriented electrical steel sheets, it is a common technique to use secondary precipitates called inhibitors to secondary recrystallize grains having Goss orientation during finish annealing. For example, a method using AlN and MnS described in Patent Document 1 and a method using MnS and MnSe described in Patent Document 2 are disclosed and industrially put into practical use.

  Although the method using these inhibitors is a useful method for stably developing secondary recrystallized grains, if the inhibitor remains after secondary recrystallization that has performed its function, it may cause deterioration of magnetic properties. Therefore, it is necessary to remove precipitates and inclusions such as inhibitors from the ground iron by setting the finish annealing (particularly the purification annealing performed in the latter half of the finish annealing) to a high temperature of 1100 ° C. or higher and controlling the atmosphere.

  In view of this, the present inventors have proposed, in Patent Document 3, Patent Document 4, etc., a technique for developing Goss-oriented crystal grains by secondary recrystallization in a material that does not contain an inhibitor-forming element. In this method, since the step of purifying the inhibitor is unnecessary, there is no need to increase the temperature of the purification annealing, and this method provides a great merit in terms of both cost and maintenance.

  Furthermore, since it is not necessary to finely disperse the inhibitor in the steel in the material that does not contain the inhibitor forming element, it is also necessary to heat the slab at a high temperature for the purpose of dissolving the inhibitor forming element, which has been essential in the past. This is also advantageous from the viewpoint of energy cost.

  In addition, when slab heating at high temperature is performed, the crystal grains become coarse and cause deterioration of the magnetic properties. Therefore, it is necessary to prevent the coarsening of the crystal grains by causing an appropriate amount of carbon in the steel to cause γ transformation. However, it is also possible not to contain carbon that is normally required in a component system that does not have an inhibitor forming element and does not require slab heating at a high temperature.

When carbon is not contained in this way, there is no need for decarburization in recrystallization annealing, so annealing in a dry atmosphere is possible. In this case, since it is reduced as much as possible the formation of SiO ₂ in the steel sheet surface layer, even with the use of MgO commonly used in annealing separator, it is possible to suppress the formation of forsterite coating. In such a case, since there is no hard SiO ₂ or forsterite coating on the steel sheet, there is an advantage that a grain-oriented electrical steel sheet having excellent punchability can be obtained, which was proposed in Patent Document 5.

In addition, Patent Document 6 and Patent Document 7 disclose application technologies of grain-oriented electrical steel sheets that do not contain an inhibitor-forming element.
Japanese Patent Publication No. 40-15644 Japanese Patent Publication No. 51-13469 JP 2000-129356 A Japanese Unexamined Patent Publication No. 2000-111982 JP 2002-220623 A JP 2001-158950 A JP 2003-34821 A Japanese Patent Laid-Open No. 2-200731

  However, a component system that does not contain an inhibitor is susceptible to the atmosphere of secondary recrystallization annealing, and there is a problem that the magnetic properties are not stable in some cases.

  The present invention aims to stabilize the magnetic properties of products in a grain-oriented electrical steel sheet that does not use an inhibitor.

  The present inventors have found a method for stabilizing the magnetic properties of a product by appropriately controlling the atmosphere of secondary recrystallization annealing, and have completed the method for producing a grain-oriented electrical steel sheet according to the present invention.

That is, the gist configuration of the present invention is as follows.
1. The steel slab containing C: 0.08% or less, Si: 2.0% to 8.0%, Mn: 0.005 to 1.0% by mass%, the balance being Fe and inevitable impurities, is hot. Rolled and annealed the obtained hot-rolled steel sheet (referred to as hot-rolled sheet annealing), or with or without cold rolling one or more times with intermediate annealing, followed by recrystallization In the manufacturing process of the grain-oriented electrical steel sheet to which annealing and secondary recrystallization annealing are performed, the component of the steel slab is reduced by mass ratio such that Al is 100 ppm or less and N, S, and Se are reduced to 50 ppm or less, and the secondary recrystallization. In the annealing, the temperature is raised to a temperature range of 825 to 1000 ° C. and held, and at least 20 hours after the secondary recrystallization temperature is reached, the annealing is performed at the secondary recrystallization temperature or higher. At that time, the secondary recrystallization annealing temperature T1 when the temperature reached 800 ° C., secondary recrystallization of steel plate When the time after 20 hours and t2 from the time reaching the time, the production method of the grain-oriented electrical steel sheet, which comprises a time more than 70% in the interval from t1 t2 with Ar atmosphere.
2. 2. The method for producing a grain-oriented electrical steel sheet according to 1, wherein decarburization annealing and purification annealing are performed after the secondary recrystallization annealing.
3. The steel pieces to be hot-rolled are further in terms of mass%: Ni: 0.010-1.50%, Cu: 0.01-0.50%, P: 0.005-0.50%, Sn: 0.005 -0.50%, Sb: 0.005-0.50%, Bi: 0.005-0.50%, Mo: 0.005-0.50%, and Cr: 0.005-0.50% The method for producing a grain-oriented electrical steel sheet according to 1 or 2, comprising one or more selected from the group consisting of:

  ADVANTAGE OF THE INVENTION According to this invention, in the raw material which does not have an inhibitor formation element, deterioration of the magnetic characteristic during secondary recrystallization annealing can be prevented effectively, and the grain-oriented electrical steel sheet which has the outstanding magnetic characteristic can be manufactured.

  First, experiments that have made the present invention successful will be described.

<Experiment 1>
By mass%: C: 0.0190%, Si: 3.25%, Mn: 0.06%, Sol. A steel slab containing Al: 58 ppm, N: 29 ppm, and S: 21 ppm (referred to as a steel slab) is manufactured by continuous casting, heated at 1200 ° C., and hot-rolled to a thickness of 2.4 mm. Then, after hot-rolled sheet annealing at 1050 ° C. for 45 seconds, it was finished to a thickness of 0.30 mm by cold rolling. Furthermore, after recrystallization annealing (primary recrystallization annealing) under a soaking condition of 910 ° C. for 10 seconds and in a dry nitrogen atmosphere, secondary recrystallization annealing was carried out at 875 ° C. for 75 hours.

In this secondary recrystallization annealing, the time when the annealing temperature reaches 800 ° C. is set as the start point (t1), and the temperature is further increased to reach the secondary recrystallization temperature. In the section to perform, the time which makes an annealing atmosphere Ar atmosphere was changed. At this time, the N ₂ atmosphere was used for the time other than the time for the Ar atmosphere. In the case of this experiment, the length of the section was 51 hours. Also, annealing was performed in an Ar atmosphere until the annealing temperature reached 800 ° C. and after 20 hours had passed since the secondary recrystallization temperature was reached.

Here, the secondary recrystallization temperature is defined as the lowest temperature at which secondary recrystallization is completed by soaking for 50 hours in an N ₂ atmosphere. Specifically, it was determined by the following measurement method.

A steel plate sample (steel plate after primary recrystallization) is placed in a static state in an annealing furnace having a temperature gradient with respect to the longitudinal direction of the furnace (for example, the low temperature side of the furnace is 800 ° C. and the high temperature side is 900 ° C.), and the N ₂ atmosphere Annealed under for 50 hours. As a result, the low temperature side is fine primary recrystallized grains that do not develop secondary recrystallization, and the high side is coarse secondary recrystallization that expresses secondary recrystallization. Approximately, the temperature corresponding to the boundary corresponds to the secondary recrystallization temperature. In the present invention, the sample obtained as described above is pickled and the secondary recrystallization structure is observed, and the portion corresponding to the lowest temperature at which the secondary recrystallization is developed over the entire plate width. The temperature inside the furnace was specified, and the secondary recrystallization temperature was used for convenience. This temperature is generally higher than 800 ° C.

  In the test material of this experiment, the secondary recrystallization temperature measured by the above method was 862 ° C.

  After secondary recrystallization annealing, the sample was sufficiently decarburized by performing flattening annealing in a humid atmosphere, and then magnetic measurement was performed by the method described in JIS C2550.

FIG. 1 shows the relationship between the magnetic properties (magnetic flux density B ₈ ) of the sample and the ratio of the time during which the Ar atmosphere was introduced in the elapsed time in the section from t1 to t2. From this figure, it can be seen that good magnetic properties can be obtained if the ratio of the time during which the Ar atmosphere is introduced is 70% or more of the elapsed time in the section.

  The magnetic properties of the steel sheet are good by annealing 70% or more of the time in the Ar atmosphere after reaching the secondary recrystallization temperature of the steel sheet after the annealing temperature reaches 800 ° C. until 20 hours later. The reason for this is not clear, but the inventors speculate as follows.

  In the secondary recrystallization process of grain-oriented electrical steel sheets, when the temperature of the steel sheet is gradually raised and secondary recrystallization starts when a certain temperature is reached, the temperature at this time is usually secondary recrystallization. It is called temperature. However, in actuality, secondary recrystallization does not appear at the moment when this secondary recrystallization temperature is reached, but starts to develop after a certain incubation period. As a result of intensive studies, this incubation period has been found to vary depending on the components of the steel slab and various process conditions, but in a component system that does not contain an inhibitor, it is approximately 10 to 20 hours. That is, it can be said that, after 20 hours from the arrival of the secondary recrystallization temperature, secondary recrystallization has started almost under any condition as long as it is within the component range of the present invention.

In a grain-oriented electrical steel sheet using a normal inhibitor, it is known that the atmosphere immediately before secondary recrystallization greatly affects the magnetism of the steel sheet. For example, in Patent Document 8, etc., NH ₃ is introduced in the initial heating process of secondary recrystallization annealing to nitride a steel sheet, thereby forming an inhibitor mainly composed of (Al, Si) N or strengthening an existing inhibitor. A technique for improving magnetic characteristics is disclosed. However, in a component system that does not use an inhibitor as in the present technology, a precipitate is formed at the grain boundary by nitriding, so that the texture inhibition effect based on the grain boundary energy (the crystal that the texture itself has) The effect of suppressing grain growth) is impaired, and as a result, the magnetism deteriorates. Therefore, not only the NH ₃ atmosphere but also the N ₂ atmosphere causes nitridation, which is not preferable.

In addition, as an atmosphere conventionally used in secondary recrystallization annealing, there is another H ₂ atmosphere. However, in a component system that does not use an inhibitor, when an H ₂ atmosphere is introduced, grain growth is promoted and normal grain growth seems to have occurred. As a result, secondary recrystallization does not appear, or even if it appears, the crystal orientation becomes uneven and the magnetic properties become insufficient.

  Therefore, in the present invention, if the annealing atmosphere immediately before the secondary recrystallization, that is, after reaching 800 ° C. at which nitriding or normal grain growth is likely to occur until the start of the secondary recrystallization is an Ar atmosphere, the above-described precipitation is performed. Formation of grains and grain growth can be avoided, and the texture inhibition effect can be maintained until secondary recrystallization starts, and the magnetic properties can be improved. The present invention is based on the above findings.

  Next, the reasons for limiting the configuration requirements of the present invention will be described. First, the steel composition as a starting material will be described. The steel composition is expressed by mass ratio (mass% or mass ppm).

C: 0.08% or less When C exceeds 0.08%, it is difficult to reduce it to 50 ppm or less at which magnetic aging does not occur even if decarburization is performed, so it is limited to 0.08% or less.

Si: 2.0 to 8.0%
Si is an element necessary for increasing the specific resistance of steel and improving iron loss, but if it is less than 2.0%, there is no effect, and if it exceeds 8.0%, the workability of steel deteriorates. Since rolling becomes difficult, it is limited to 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%, there is no effect, and if it exceeds 1.0%, the magnetic flux density of the product plate decreases. -1.0%.

Al: 100 ppm or less, N, S, Se: 50 ppm or less for each of them As an inhibitor forming element, Al is reduced to 100 ppm or less, and each of N, S, and Se is also reduced to 50 ppm or less, in order to favorably secondary recrystallize the steel sheet. It is effective in. Such components are desirably reduced as much as possible from the viewpoint of magnetic properties, and more preferably 70 ppm or less for Al. However, since the cost may increase in order to reduce such components, there is no problem even if it remains within the above range.

  Reduction of other nitride forming elements such as Ti, Nb, B, and V to 50 ppm or less is effective in preventing deterioration of iron loss and ensuring good workability.

Ni: 0.010 to 1.50%, Cu: 0.01 to 0.50%, P: 0.005 to 0.50%, Sn: 0.005 to 0.50%, Sb: 0.005 0.50%, Bi: 0.005-0.50%, Mo: 0.005-0.50%, Cr: 0.005-0.50%
From the viewpoint of improving magnetic properties, one or more selected from the above elements can be contained. First, Ni can be contained in order to improve the hot rolled sheet structure and improve the magnetic properties. If the content is less than 0.010%, the amount of improvement in magnetic properties is small, and if it exceeds 1.50%, secondary recrystallization becomes unstable and the magnetic properties deteriorate. The range. Further, Cu: 0.01 to 0.50% and P: 0.005 to 0.50% can be contained for the purpose of improving magnetic properties, particularly iron loss. When these contents are less than the respective lower limit amounts, there is no effect of improving iron loss, and when the upper limit amount is exceeded, the development of secondary recrystallized grains is suppressed. Furthermore, for the purpose of improving the magnetic flux density, Sn: 0.005 to 0.50%, Sb: 0.005 to 0.50%, Bi: 0.005 to 0.50%, Mo: 0.005 to 0 .50%, Cr: 0.005 to 0.50% can be contained. When these contents are less than the respective lower limit amounts, there is no effect of improving iron loss, and when the upper limit amount is exceeded, the development of secondary recrystallized grains is suppressed.

  The balance of steel is iron and inevitable impurities.

  The molten steel having the above composition is cast into a steel slab, but a slab may be produced by a normal ingot-making method or a continuous casting method, or a thin slab having a thickness of 100 mm or less may be produced by a direct casting method. Good. The steel slab is heated and hot rolled by a normal method, but may be immediately hot rolled without being heated 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 does not require high-temperature annealing for dissolving the inhibitor, which has been indispensable in the past, a low temperature of 1250 ° C. or lower is desirable in terms of cost.

  Next, hot-rolled sheet annealing is performed as necessary. In order to highly develop a goth structure in the product plate, the hot-rolled sheet annealing temperature is preferably 800 ° C. or higher and 1100 ° C. or lower. 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 primary recrystallized structure of sized particles, thereby inhibiting the development of secondary recrystallization. When the hot-rolled sheet annealing temperature exceeds 1100 ° C., the grain size after the hot-rolled sheet annealing is excessively coarsened, which is extremely disadvantageous in realizing a primary recrystallized structure of sized particles.

  After hot-rolled sheet annealing, it is subjected to recrystallization annealing after performing cold rolling at least once with intermediate annealing as necessary. It is preferable that the temperature of this cold rolling is preferably raised to 100 ° C. to 250 ° C. and / or that the aging treatment in the range of 100 ° C. to 250 ° C. is performed once or a plurality of times during the cold rolling. It is effective in developing the tissue.

  The 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. In addition, the magnetic flux density can be improved by performing secondary recrystallization with the C content remaining at 100 to 250 ppm after recrystallization annealing. After recrystallization annealing, a technique for increasing the amount of Si by a siliconization method may be used in combination. Then, if necessary, an annealing separator is applied, followed by secondary recrystallization annealing to develop secondary recrystallization.

  The secondary recrystallization annealing includes a process of raising the temperature to the secondary recrystallization temperature or higher. In addition, when the secondary recrystallization annealing is performed, a process of holding within a temperature range of 825 to 1000 ° C. is always performed. Here, holding means maintaining within the above temperature range, and the temperature can be freely changed within the temperature range. If the holding temperature is less than 825 ° C., it is difficult to sufficiently advance secondary recrystallization over the entire steel sheet, and good magnetic properties cannot be obtained. If the holding temperature exceeds 1000 ° C., the desired orientation (Goth orientation) And secondary recrystallization in an orientation other than (Cube orientation), the magnetic properties are deteriorated.

The holding time in this temperature range is preferably 10 hours or longer. Also,
More preferably, it is 100 hours or less.

In the present invention, the atmosphere in the secondary recrystallization annealing is particularly important. After the annealing temperature reaches 800 ° C. (t1), the secondary recrystallization temperature of the steel sheet is reached 20 hours later (t2). In the section up to 70%, it is indispensable to improve the magnetic characteristics by setting the Ar atmosphere to 70% or more of the time ratio in the section. When an atmosphere other than Ar is used in a part of the section from t1 to t2, an atmosphere other than Ar may be introduced at any timing, as estimated from the mechanism described above. That is, the section may be introduced in the first half, in the second half, or may be introduced in several times. However, since the introduction before the secondary recrystallization has some influence on the precipitates and the particle size and may affect the magnetic properties, it is desirable to introduce it in the latter half. Examples of the atmosphere other than Ar applied to the section from t1 to t2 include, but are not limited to, N ₂ gas, H ₂ gas, and the like. There is no problem even if impurities that are inevitable industrially are included as long as the effect can be sufficiently exhibited. If Ar is 90% or more in terms of partial pressure, it is regarded as an Ar atmosphere here.

FIGS. 2 to 4 show examples of a section from time t1 when the annealing temperature reaches 800 ° C. to time t2 20 hours after reaching the secondary recrystallization temperature of the steel sheet in the secondary recrystallization annealing. The subsequent high-temperature treatment in FIG. 3 is so-called purification annealing. However, as already described, since the high temperature purification annealing is not required in the component system of the present invention, the purification annealing may be performed continuously at the same temperature as the secondary recrystallization annealing temperature, or the purification annealing is omitted. May be. Secondary recrystallization annealing or subsequent purification annealing is also collectively referred to as finish annealing.

  After secondary recrystallization annealing, flattening annealing is performed, and at that time, it is effective to reduce the iron loss by applying tension to correct the shape. Further, planarization annealing may be performed in a humid atmosphere to serve as decarburization. Furthermore, decarburization annealing may be performed independently before planarization annealing, or purification annealing at high temperature may be performed.

  In the case of using laminated steel plates, in order to improve iron loss, it is effective to apply an insulating coating to the steel plate surface after planarization annealing. In order to ensure good punchability, an organic coating containing a resin is desirable, and when emphasis is placed on weldability, it is desirable to apply a semi-organic or inorganic coating.

  The grain-oriented electrical steel sheet in the present invention means an electrical steel sheet in which secondary recrystallization has occurred. Therefore, not only the Goss direction but also the Cube direction (<100> <001> direction or <100> <011> direction) is subjected to secondary recrystallization, and the like is also within the scope of the claims of this patent.

  A steel slab containing the components shown in Table 1 was manufactured by continuous casting, and after heating the slab at 1200 ° C., it was finished to a thickness of 2.2 mm by hot rolling, and then hot-rolled for 30 seconds at 1075 ° C. After annealing, it was finished to a thickness of 0.27 mm by cold rolling. Furthermore, after recrystallization annealing was performed at 900 ° C. for 10 seconds under a dry nitrogen atmosphere, secondary recrystallization annealing was performed at 875 ° C. for 50 hours.

In this secondary recrystallization annealing, the time during which the Ar atmosphere is used is changed from the time when the annealing temperature reaches 800 ° C. until the secondary recrystallization temperature of the steel sheet reaches 20 hours (t2). (Pattern of FIG. 2), and shown in Table 2 as the ratio of Ar introduction time. At this time, an N ₂ atmosphere was applied during the time when Ar was not used, and this N ₂ was introduced at the timing when the secondary recrystallization annealing temperature reached 800 ° C. The secondary recrystallization temperature is determined by annealing the steel sheet sample after recrystallization annealing in a furnace (780 to 900 ° C.) with a temperature gradient in the longitudinal direction, pickling the sample, observing the structure, It was investigated whether the next recrystallization started. The results are also shown in Table 2. Annealing was performed in an Ar atmosphere until the annealing temperature reached 800 ° C. and after 20 hours had passed since the secondary recrystallization temperature was reached.

  Thereafter, planarization annealing was performed in a humid atmosphere, the sample was sufficiently decarburized, and then magnetic measurement was performed by the method described in JIS C2550.

  The obtained magnetic properties are shown in Table 2. As can be seen from the table, good magnetic properties can be obtained within the scope of the present invention.

  A steel slab containing the components shown in Table 3 was manufactured by continuous casting, and the slab was heated at 1200 ° C., then finished to a thickness of 2.4 mm by hot rolling, and then hot rolled at 1000 ° C. for 60 seconds. After annealing, it was finished to a thickness of 0.30 mm by cold rolling. Furthermore, after recrystallization annealing was performed at 900 ° C. for 10 seconds under a dry nitrogen atmosphere, secondary recrystallization annealing was performed to hold at 900 ° C. for 50 hours.

  In this secondary recrystallization annealing, the atmosphere was all Ar. Therefore, the section from t1 to t2 was also annealed in an Ar atmosphere (pattern in FIG. 2). The secondary recrystallization temperature is obtained by annealing a steel plate sample (after recrystallization annealing) in a furnace (780 to 900 ° C.) with a temperature gradient in the longitudinal direction, pickling the sample, observing the structure, and from what temperature It was investigated whether secondary recrystallization had started. The results are also shown in Table 3.

  Thereafter, planarization annealing was performed in a humid atmosphere, the sample was sufficiently decarburized, and then magnetic measurement was performed by the method described in JIS C2550.

  The obtained magnetic properties are shown in Table 3. As can be seen from the table, good magnetic properties can be obtained within the scope of the present invention.

  A steel slab having the components A and B shown in Table 1 was produced by continuous casting. After heating the slab at 1200 ° C., it was finished to a thickness of 2.6 mm by hot rolling, and then at 1000 ° C. for 30 seconds. After hot-rolled sheet annealing, it was finished to a thickness of 1.8 mm by cold rolling. Then, after performing intermediate annealing for 60 seconds at 1025 ° C., it was finished to a thickness of 0.27 mm by warm rolling at 150 ° C. Furthermore, after recrystallization annealing is performed at 860 ° C. for 75 seconds under a wet nitrogen-hydrogen mixed atmosphere, secondary recrystallization annealing is performed at 900 ° C. for 75 hours and then at 1150 ° C. for 5 hours. did.

In this secondary recrystallization annealing, the time from which the annealing temperature reaches 800 ° C. (t1) to 20 hours after the secondary recrystallization temperature of the steel sheet is reached (t2) indicates the time for using the Ar atmosphere. 4 was changed (similar to the pattern of FIG. 3, but the first stage was not slow heating but soaking). At this time, the N ₂ atmosphere was applied during the time when Ar was not used, and this N ₂ was introduced at the timing when the Ar atmosphere was introduced from t1 and the time determined by the Ar introduction time ratio shown in Table 4 had elapsed. However, when the Ar introduction time ratio was 0%, an N ₂ atmosphere was introduced from the time t1. The N ₂ atmosphere was used until the annealing temperature reached 800 ° C. and 20 hours after the secondary recrystallization temperature was reached, and annealing was performed in a hydrogen atmosphere at 1050 ° C. or higher. Then, planarization annealing was performed in a dry atmosphere, and then magnetic measurement was performed by the method described in JIS C2550. The obtained magnetic properties are shown in Table 4. As can be seen from the table, good magnetic properties can be obtained within the scope of the present invention.

  According to the present invention, excellent magnetic properties can be obtained without deteriorating magnetic properties during secondary recrystallization annealing using materials having various characteristic and productivity advantages that do not have inhibitor forming elements. The grain-oriented electrical steel sheet can be manufactured.

At the time of secondary recrystallization annealing, an Ar atmosphere in a section from t1 (when the annealing temperature reaches 800 ° C.) to t2 (20 hours after the annealing temperature reaches the secondary recrystallization temperature of the steel plate) It is the figure which showed the relationship between the ratio of the time which introduce | transduced, and the magnetic characteristic of a steel plate. It is the figure which showed an example of the area from t1 to t2 at the time of secondary recrystallization annealing. It is the figure which showed another example of the area from t1 to t2 at the time of secondary recrystallization annealing. It is the figure which showed another example of the area from t1 to t2 at the time of secondary recrystallization annealing.

Claims (3)

The steel slab containing C: 0.08% or less, Si: 2.0% to 8.0%, Mn: 0.005 to 1.0% by mass%, the balance being Fe and inevitable impurities, is hot. Directionality of rolling and rolling the obtained hot-rolled steel sheet with or without annealing, or performing cold rolling at least twice with intermediate annealing, followed by recrystallization annealing and secondary recrystallization annealing In the manufacturing process of electrical steel sheets,
While reducing the component of the steel slab by mass ratio to 100 ppm or less of Al, N, S, and Se to 50 ppm or less, and raising the temperature to a temperature range of 825 to 1000 ° C. in the secondary recrystallization annealing, At least 20 hours after the secondary recrystallization temperature is reached, annealing is performed at the secondary recrystallization temperature or higher. At that time, the time when the secondary recrystallization annealing temperature reaches 800 ° C. is t1, the secondary recrystallization temperature of the steel sheet. A method for producing a grain-oriented electrical steel sheet, characterized in that when a time point 20 hours after the arrival time is t2, 70% or more of the time in a section from t1 to t2 is an Ar atmosphere.   The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein decarburization annealing and purification annealing are performed after the secondary recrystallization annealing.   The steel pieces to be hot-rolled are further in terms of mass%: Ni: 0.010-1.50%, Cu: 0.01-0.50%, P: 0.005-0.50%, Sn: 0.005 -0.50%, Sb: 0.005-0.50%, Bi: 0.005-0.50%, Mo: 0.005-0.50%, and Cr: 0.005-0.50% The method for producing a grain-oriented electrical steel sheet according to claim 1, comprising one or more selected from the group consisting of:

Images