JP2011052302A - Method for producing grain-oriented electromagnetic steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a grain-oriented electromagnetic steel sheet having excellent magnetic characteristic by using a material containing no inhibitor. <P>SOLUTION: The method for producing the grain-oriented silicon steel sheet in which a steel slab containing ≤7.0 mass% Si without any inhibitor is hot-rolled, a hot-rolled plate is annealed, and cold-rolled to the final thickness in one cold rolling, or the hot-rolled plate is annealed as necessary after the hot-rolling, and cold-rolled to the final thickness in two or more cold rolling including the intermediate annealing, and thereafter, the primary recrystallization annealing and the secondary recrystallization annealing are executed, the hot-rolled plate annealing with one cold-rolling or the intermediate annealing immediately before the final cold rolling with two or more cold-rolling comprises the soaking treatment of keeping the steel plate at the temperature of 750-1,200°C for 2-300sec, the quenching treatment of cooling the steel plate from 750°C to 400°C at the average cooling rate of 10-200°C/sec, and the strain imparting treatment of imparting strain corresponding to the rolling draft of 0.2-50% within 900 seconds after reaching 400°C. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties used for iron cores of transformers and other electrical equipment.

  As a method of improving the iron loss characteristics of the electrical steel sheet, a precipitate such as an inhibitor called Al, S, or Se is used, and {011} <100> oriented grains called goth oriented grains are used during final finish annealing. A technique is generally used in which the secondary recrystallization / growth preferentially increases the accumulation rate of the easy axis <100> in the rolling direction and improves the magnetic properties.

  On the other hand, techniques for preferentially growing the {011} plane using surface energy as a driving force without using an inhibitor are disclosed in Patent Documents 1-3. However, these techniques have a problem that, in principle, only the {011} plane can be selected, and goth grains having the <100> direction aligned in the rolling direction cannot be obtained. As a technique for solving this problem, Patent Document 4 discloses a technique for developing Goss-oriented grains by secondary recrystallization using a material that does not contain an inhibitor.

  By the way, in recent years, with the growing awareness of energy saving, there is a strong demand for grain-oriented electrical steel sheets that are more excellent in magnetic properties than ever before. In order to improve the magnetic properties, it is necessary to further increase the accumulation ratio of the easy axis <100> in the rolling direction. For this purpose, the texture of the steel sheet before and after the secondary recrystallization is appropriately set. It is important to control, that is, to increase the existence frequency of Goss orientation grains, and to increase the existence frequency of orientation grains such as {111} <112> orientation grains that are likely to be eroded by Goss orientation grains. Has been developed. For example, a technique for reducing the final cold rolling under high pressure, a technique for performing the final cold rolling warm, a technique for finely dispersing carbide in the steel plate before the final cold rolling, and the like can be mentioned.

  The inventors have further improved the texture of the steel sheet after the primary recrystallization in the method for producing a grain-oriented electrical steel sheet using a material that does not contain an inhibitor, thereby providing a steel sheet (product) after the secondary recrystallization annealing. Research has been conducted on how to improve the iron loss characteristics of steel. As a result, it has been found that by increasing the amount of solute carbon in the steel plate before the final cold rolling, the texture after the subsequent primary recrystallization is improved, and consequently the iron loss characteristics of the product are improved. It was. As a specific method, Patent Document 5 describes precipitation of solute carbon (aging precipitation) in steel while maintaining the steel sheet temperature at a low temperature from annealing immediately before final cold rolling to final cold rolling. It was proposed to increase the amount of solute carbon in the steel plate before the start of the final cold rolling.

JP-A 64-55339 Japanese Patent Laid-Open No. 02-57635 JP 07-197126 A JP 2000-129356 A JP 2003-253335 A

  However, maintaining the coil at a low temperature until just before the final cold rolling, especially maintaining the coil at a low temperature in the summer when the temperature in the factory is high, requires a huge cooling facility. In addition, there is a problem that it is difficult to implement on an industrial scale in terms of cost.

  Therefore, an object of the present invention is to more stably maintain a high amount of solute carbon after annealing immediately before the final cold rolling, and, in turn, through the improvement of the steel sheet texture after the primary recrystallization, The object is to propose a method for producing grain-oriented electrical steel sheets that can advantageously improve the product magnetic properties after crystallization.

  The inventors have made extensive studies on a method for maintaining the amount of solute carbon immediately before the final cold rolling at a high level in place of the conventional technique for holding the coil at a low temperature. As a result, the existence state of the solute carbon is changed, that is, immediately after quenching in the annealing immediately before the final cold rolling, a straining treatment is performed to introduce a number of dislocations in the steel sheet, and the solute carbon is By trapping (fixing), the method of suppressing the precipitation of solute carbon from the annealing immediately before the final cold rolling to the start of the final cold rolling is extremely effective in securing the amount of solute carbon. The headline and the present invention were completed.

That is, the present invention contains C: 0.005-0.15 mass%, Si: 7.0 mass% or less and Mn: 0.005-3.0 mass%, and Al: less than 0.0100 mass%, S And Se are each reduced to 0.0050 mass% or less, and the steel slab consisting of Fe and inevitable impurities in the balance is hot-rolled and then hot-rolled sheet annealed to obtain the final sheet thickness by one cold rolling, In the method for producing a grain-oriented electrical steel sheet comprising a series of steps of performing primary recrystallization annealing and secondary recrystallization annealing, the hot-rolled sheet annealing is performed as follows:
(1) Soaking treatment that is maintained at a temperature of 750 to 1200 ° C. for 2 to 300 seconds;
(2) a rapid cooling process for cooling from 750 ° C. to 400 ° C. at an average cooling rate of 10 to 200 ° C./sec;
(3) A method for producing a grain-oriented electrical steel sheet, comprising: a strain imparting treatment that imparts a strain corresponding to a rolling reduction of 0.2 to 50% within 900 seconds after reaching 400 ° C.

Further, the present invention contains C: 0.005 to 0.15 mass%, Si: 7.0 mass% or less and Mn: 0.005 to 3.0 mass%, Al: less than 0.0100 mass%, S And Se are each reduced to 0.0050 mass% or less, and after the steel slab consisting of Fe and inevitable impurities is hot-rolled, it is subjected to hot-rolled sheet annealing as necessary, and two or more colds sandwiching the intermediate annealing. In the manufacturing method of the grain-oriented electrical steel sheet consisting of a series of steps of performing the final sheet thickness by rolling and then performing the primary recrystallization annealing and the secondary recrystallization annealing, the intermediate annealing before cold rolling to the final sheet thickness is
(1) Soaking treatment that is maintained at a temperature of 750 to 1200 ° C. for 2 to 300 seconds;
(2) a rapid cooling process for cooling from 750 ° C. to 400 ° C. at an average cooling rate of 10 to 200 ° C./sec;
(3) A method for producing a grain-oriented electrical steel sheet, comprising: a strain imparting treatment that imparts a strain corresponding to a rolling reduction of 0.2 to 50% within 900 seconds after reaching 400 ° C.

  In the steel slab in the present invention, in addition to the above component composition, Ni: 0.005-1.5 mass%, Sn: 0.005-0.50 mass%, Sb: 0.005-0.50 mass%, Cu : One or more selected from 0.005 to 1.5 mass%, P: 0.005 to 0.50 mass% and Cr: 0.005 to 1.5 mass% .

  According to the present invention, since the amount of solute carbon immediately before the final cold rolling can be maintained at a higher level as compared with the prior art that maintains the coil at a low temperature, the texture of the steel sheet after the primary recrystallization Can be stably controlled. As a result, a grain-oriented electrical steel sheet having excellent magnetic properties can be stably provided.

It is a figure explaining the annealing cycle just before the last cold rolling in this invention.

First, an experiment that triggered the development of the present invention will be described.
Steel slab containing C: 0.09 mass%, Si: 2.8 mass%, Mn: 0.03 mass%, Al: 0.0020 mass%, S: 0.0020 mass% and Se: 0.0001 mass% at 1200 ° C After heating, it was hot-rolled to obtain two types of A and B hot-rolled plates having a plate thickness of 2.0 mm. Next, the hot rolled sheet A is subjected to a soaking treatment that is held at 1000 ° C. for 60 seconds, followed by a rapid cooling process in which cooling is performed from 750 ° C. to 400 ° C. at an average cooling rate of 40 ° C./sec, and the steel plate temperature reaches 400 ° C. Then, hot-rolled sheet annealing comprising a series of steps of applying a strain applying treatment for applying a strain with a rolling reduction of 1% by rolling after 100 seconds was performed. On the other hand, the hot-rolled sheet of B was subjected to hot-rolled sheet annealing which was only subjected to the same soaking and quenching process as described above and not subjected to the strain imparting process.

  Next, in order to simulate the effect of aging in the factory in the summer, the steel sheets A and B after the hot-rolled sheet annealing are subjected to aging treatment that is held at 80 ° C. for 500 hours, and then cold-rolled once. Then, a cold rolled sheet having a final sheet thickness of 0.30 mm is formed, and after the primary recrystallization annealing also serving as decarburization annealing at 850 ° C. × 120 seconds, the secondary recrystallization annealing also serving as purification at 1200 ° C. × 15 hours is performed, and A , B2 types of grain-oriented electrical steel sheets were obtained.

These steel sheets were measured the magnetic properties in the rolling direction (B _8), B ₈ of the electromagnetic steel sheets from hot-rolled sheets of A 1.93 T, B ₈ of the electromagnetic steel sheets from hot-rolled sheets of B is 1.85T. From this result, towards the B ₈ of the electromagnetic steel sheets from hot-rolled sheets of A is higher than B ₈ of the electromagnetic steel sheets reasons obtained from hot-rolled sheets of B, the final cold rolling immediately before the annealing (in the experiment It was considered that the strain imparting process in the hot-rolled sheet annealing) suppressed the precipitation of carbon between the annealing and the start of the final cold rolling, and increased the amount of solute carbon before the final cold rolling.
The present invention has been developed based on the above novel findings.

Next, the component composition of the steel slab used as the raw material of the grain-oriented electrical steel sheet according to the present invention will be described.
C: 0.005-0.15 mass%
If C is less than 0.005 mass%, the effect of improving the primary recrystallization structure is small, and the effect of improving the magnetic properties cannot be obtained. On the other hand, if it exceeds 0.15 mass%, it becomes difficult to reduce the amount of C in the product to 0.0050 mass% or less at which magnetic aging does not occur. Therefore, C is in the range of 0.005 to 0.15 mass%. Preferably, it is the range of 0.01-0.10 mass%.

Si: 7.0 mass% or less Since Si is a useful element that increases the electrical resistance of steel and reduces iron loss, it is preferably contained in an amount of 2.0 mass% or more. However, if added over 7.0 mass%, the workability is remarkably lowered and it becomes difficult to cold-roll. Therefore, Si is set to 7.0 mass% or less. More preferably, it is the range of 2.0-4.0 mass%.

Mn: 0.005 to 3.0 mass%
Mn is an element useful for preventing hot brittleness due to S and improving hot workability, and it is necessary to contain 0.005 mass% or more. However, addition exceeding 3.0 mass% causes a decrease in magnetic flux density. Therefore, Mn is in the range of 0.005 to 3.0 mass%. Preferably, it is the range of 0.01-1.0 mass%.

Al: less than 0.0100 mass%, S, Se: each less than 0.0050 mass% The method for producing a grain-oriented electrical steel sheet according to the present invention is a technique for causing secondary recrystallization without using an inhibitor such as Al, S, or Se. It is. Therefore, in the present invention, Al, S and Se are elements that are positioned as inevitable impurities, and in order to cause good secondary recrystallization, Al is less than 0.0100 mass%, and S and Se are respectively It is necessary to limit to less than 0.0050 mass%. Preferably, Al is 0.0090 mass% or less, and S and Se are each 0.0040 mass% or less.

The grain-oriented electrical steel sheet according to the present invention contains at least one selected from Ni, Sn, Sb, Cu, P and Cr in addition to the essential components and inhibitor components described above. Sn: 0.005-0.50 mass%, Sb: 0.005-0.50 mass%, Cu: 0.005-1.5 mass%, P: 0.005-0.50 mass%, Cr: 0.005 It can add in the range of -1.5 mass%.
Ni is an element having the effect of improving the hot rolled sheet structure and improving the magnetic properties. However, if the content is less than 0.005 mass%, the above effect is small. On the other hand, if the content exceeds 1.5 mass%, the secondary recrystallization becomes unstable, and the magnetic properties deteriorate. Therefore, Ni is preferably added in the range of 0.005 to 1.5 mass%.
Sn, Sb, Cu, P, and Cr are elements that are effective for improving the iron loss. If any of these elements does not satisfy the above lower limit value, the effect of improving the iron loss is small. Development of secondary recrystallized grains is inhibited. Therefore, it is preferable to add Ni, Sn, Sb, Cu, P, and Cr in the above ranges, respectively.

  In the grain-oriented electrical steel sheet of the present invention, the balance other than the above components is Fe and inevitable impurities. However, as described above, since the present invention is a technique that does not use an inhibitor, the reduction in iron loss can be achieved even for the nitride forming elements Ti, Nb, B, Ta, V, etc., which have been added in the prior art. From the viewpoint of prevention, it is desirable to reduce each to 0.0050 mass% or less.

Next, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated.
In producing the grain-oriented electrical steel sheet of the present invention, the steel adjusted to the above-mentioned preferred component composition is melted by a known method using a converter, an electric furnace, or the like, and further subjected to vacuum treatment, if necessary. The steel slab is preferably produced using a conventional ingot-making method or continuous casting method. Thereafter, the steel slab is subjected to hot rolling. At this time, either a normal method of reheating in a heating furnace and then hot rolling, or a method of hot rolling immediately after casting without reheating is performed. May be adopted.

  In addition, the heating temperature in the case of reheating the slab is such that the inhibitor component that is inevitably mixed partially dissolves and avoids the adverse effects caused by precipitation in the subsequent process, and the primary recrystallization after the final cold rolling. In order to make the crystal structure obtained by annealing fine and uniform, the temperature is preferably 1250 ° C. or lower. Also, from the viewpoint of reducing the amount of scale generated during slab heating, the slab heating temperature is preferably as low as possible.

  The hot rolling conditions for obtaining a hot-rolled sheet from the steel slab may be performed according to a conventional method, and there is no particular limitation. However, the finish rolling finish temperature is 700 to 1000 ° C, and the coil winding temperature is 500 to 700 ° C. The range is preferable.

  The hot-rolled sheet after the hot rolling is then subjected to hot-rolled sheet annealing and then cold-rolled once to finish to the final sheet thickness by one cold rolling, or hot-rolled sheet as necessary After annealing, the final thickness is finished by two or more cold rollings with intermediate annealing. For example, a cold-rolled sheet is obtained by a cold-rolling two-time method in which the final sheet thickness is finished by two cold rollings with intermediate annealing or a cold-rolling three-time method in which the final sheet thickness is finished by three cold rollings with intermediate annealing. Is preferable.

Here, in the production method of the present invention, the most important point is annealing immediately before the final cold rolling, that is, in the case of the cold rolling one-time method, hot-rolled sheet annealing, the cold-rolling two-time method or the cold-rolling three-time method. In the above case, in the intermediate annealing immediately before the final cold rolling, heat treatment consisting of the processing steps shown in FIG.
(1) Soaking treatment that is maintained at a temperature of 750 to 1200 ° C. for 2 to 300 seconds;
(2) a rapid cooling process for cooling from 750 ° C. to 400 ° C. at an average cooling rate of 10 to 200 ° C./sec;
(3) a strain imparting treatment that imparts a strain corresponding to a rolling reduction of 0.2 to 50% within 900 seconds after reaching 400 ° C .;
It is to give the annealing which consists of. Hereinafter, the reason for limiting the annealing conditions will be described.

Soaking treatment The soaking temperature is in the range of 750 to 1200 ° C. If the temperature is lower than 750 ° C., the recrystallization of the hot-rolled sheet or the final cold-rolled sheet does not proceed sufficiently, and the non-recrystallized structure remains in part, so that the steel sheet structure after the primary recrystallization can be made fine and sized. This is because the growth of the secondary recrystallized structure is hindered and the magnetic properties of the product are deteriorated. On the other hand, when the soaking temperature exceeds 1200 ° C., impurity components such as inhibitors that are inevitably mixed are re-dissolved and re-precipitated non-uniformly during cooling, so that the steel sheet structure after primary recrystallization is grain-sized. This is because the growth of the secondary recrystallized structure is hindered and the magnetic properties of the product plate are deteriorated. Preferably, it is the range of 900-1100 degreeC.
The holding time at the soaking temperature is in the range of 2 to 300 seconds. If the holding time is less than 2 seconds, an unrecrystallized structure still remains, and it becomes difficult to refine and size the primary recrystallized structure, and the magnetic properties of the product plate are deteriorated. On the other hand, if the holding time exceeds 300 sec, the annealing effect is saturated and only the cost is increased. Preferably, it is the range of 10-200 sec.

Rapid Cooling Treatment The rapid cooling treatment following the soaking process requires cooling from 750 ° C. to 400 ° C. at an average cooling rate of 10 to 200 ° C./sec. When the average cooling rate is less than 10 ° C./sec, C dissolved in the steel is precipitated as carbide and the amount of dissolved carbon is reduced, so that the primary recrystallization texture deteriorates, and the product plate This is because the magnetic properties deteriorate. On the other hand, when the average cooling rate exceeds 200 ° C./sec, a hard martensite phase is generated, so that the primary recrystallization structure is deteriorated and the magnetic properties of the product are deteriorated. Preferably, the average cooling rate from 700 ° C. to 400 ° C. is in the range of 15-100 ° C./sec.

In the annealing immediately before the final cold rolling according to the present invention, the steel sheet temperature reaches 400 ° C. in the rapid cooling treatment, and within 900 sec, it corresponds to a rolling reduction ratio of 0.2 to 50% by some method. It is necessary to perform a strain imparting process for imparting strain. By this straining treatment, a number of dislocations are introduced into the steel sheet, and the solid solution carbon in the steel is fixed to the dislocation, and after the annealing immediately before the final cold rolling to the final cold rolling, As a result, the amount of dissolved carbon immediately before the final cold rolling is kept high, so that the primary recrystallization texture is improved and the magnetic properties of the product plate are improved. Will improve.
Here, the reason why the upper limit of the strain imparting temperature is set to 400 ° C. is that at a temperature exceeding 400 ° C., the strain imparting effect is reduced because recovery occurs even when strain is imparted. Moreover, after reaching 400 ° C., the reason for imparting strain within 900 sec is that if it exceeds 900 sec, the solute carbon is precipitated as carbide and the amount of solute carbon is reduced, and the effect of imparting strain is sufficiently obtained. Because it is not possible.

  Further, the reason why the amount of strain to be applied is 0.2 to 50% in terms of rolling reduction is that if the amount of strain is less than 0.2% in terms of rolling reduction, the number of dislocations to be introduced is small, so that strain is applied. This is because the effect of imparting the strain is saturated and the cost is increased if it exceeds 50%. In addition, since the purpose of imparting strain is to introduce dislocations, the strain imparting method is not particularly limited as long as strain (dislocation) corresponding to 0.2 to 50% in terms of rolling reduction can be introduced. Therefore, in addition to the rolling method, a method of repeatedly bending may be used, but the rolling method is preferable in terms of cost.

  The cold-rolled sheet subjected to the heat treatment is then subjected to final cold rolling to a final thickness, and then subjected to primary recrystallization annealing and secondary recrystallization annealing to obtain a grain-oriented electrical steel sheet. The annealing temperature for primary recrystallization annealing is preferably in the range of 700 to 1000 ° C. In addition, this primary recrystallization annealing may be performed in a wet hydrogen atmosphere also as decarburization annealing. Further, the subsequent secondary recrystallization annealing is preferably performed in a temperature range of 700 to 1250 ° C. At this time, in order to prevent the steel plates from fusing together, a known annealing separation such as MgO on the steel plate surface before annealing is performed. It is preferable to apply an agent. In addition, this secondary recrystallization annealing may be performed in the hydrogen atmosphere also as purification annealing.

The steel sheet after the secondary recrystallization annealing is then straightened by flattening annealing, and further to the above flattening annealing, for the purpose of improving iron loss, the steel sheet surface is subjected to an insulating coating that gives tension. Preferably it is a product.
In addition, in the manufacturing method of the grain-oriented electrical steel sheet according to the present invention, it is needless to say that a known magnetic domain refinement technique may be applied in any step from the cold rolling to commercialization. .

C: 0.01 mass%, Si: 3.8 mass%, Mn: 1.0 mass%, Al: 0.0080 mass%, S: 0.0002 mass%, Se: 0.0010 mass%, the balance being Fe and inevitable A steel slab composed of mechanical impurities was heated to 1100 ° C. and hot-rolled to obtain a hot-rolled sheet having a thickness of 2.0 mm. Next, the hot-rolled sheet was subjected to hot-rolled sheet annealing that was maintained at a soaking temperature of 1000 ° C. for 30 seconds, and then cold-rolled to obtain a cold-rolled sheet having a thickness of 1.6 mm. After performing an intermediate annealing consisting of soaking conditions, rapid cooling conditions, and strain imparting conditions, final cold rolling was performed to obtain a cold-rolled sheet having a sheet thickness of 0.22 mm. In the final cold rolling, in order to prevent brittle fracture due to the high Si content, the steel plate temperature was heated to 200 ° C. × 1 hr before rolling and immediately rolled to the final plate thickness.
Next, the final cold-rolled sheet is subjected to primary recrystallization annealing at 800 ° C. for 10 seconds, and then an annealing separator mainly composed of MgO is applied to the surface of the steel sheet to perform secondary re-treatment that also serves as purification at 1150 ° C. × 50 hours. Crystal annealing was performed to obtain a final grain-oriented electrical steel sheet.

The results of measuring the magnetic properties (B ₈ ) in the rolling direction of the grain-oriented electrical steel sheet obtained as described above are also shown in Table 1. From Table 1, it can be seen that all the steel sheets of the inventive examples manufactured by the method suitable for the present invention have excellent magnetic properties (B ₈ ) of 1.91 T or more. This is because the precipitation (aging) of carbon between the annealing and the final cold rolling is suppressed by the strain imparting treatment in the annealing immediately before the final cold rolling (intermediate annealing in the present embodiment), so that solid solution carbon This is probably because the amount increased.

  C: 0.03 mass%, Si: 3.0 mass%, Mn: 0.01 mass%, Al: 0.0010 mass%, S: 0.0020 mass%, Se: 0.0010 mass%, and further in Table 2 A steel slab containing the indicated additive components, the balance being Fe and inevitable impurities, was heated to 1250 ° C. and then hot rolled to obtain a hot rolled sheet having a sheet thickness of 3.0 mm. Thereafter, the hot-rolled sheet was formed into a cold-rolled sheet having a thickness of 2.0 mm by the first cold rolling without annealing the hot-rolled sheet.

Next, after the first intermediate annealing at 900 ° C. × 30 sec is performed on the cold-rolled sheet, a cold-rolled sheet having a thickness of 1.5 mm is formed by the second cold rolling, and then the following conditions 1 and 2 are satisfied. A second intermediate annealing was performed.
Condition 1: After soaking at 1100 ° C. × 10 sec, quench from 750 ° C. to 400 ° C. at 80 ° C./sec, and give a rolling strain of 5% reduction 30 sec after reaching 400 ° C.
Condition 2: After soaking at 1100 ° C. × 10 sec, quench from 80 ° C. to 400 ° C. at 80 ° C./sec, and after reaching 400 ° C., give a rolling strain of 15% reduction after 500 sec.
Condition 3: After soaking at 1100 ° C. × 10 sec, rapid cooling from 750 ° C. to 400 ° C. at 80 ° C./sec (no strain imparting treatment).

  Then, after aging treatment was performed for 1000 hours at 70 ° C. simulating aging in a factory in summer, the final cold rolling was performed to obtain a cold-rolled sheet to a thickness of 0.20 mm, and then 900 ° C. × 10 sec. After primary recrystallization annealing that also serves as decarburization of steel, after applying an annealing separator mainly composed of MgO to the surface of the steel sheet, secondary recrystallization annealing that also serves as purification at 1200 ° C. × 15 hr is performed, and directional electromagnetic A steel plate was obtained.

The measurement results of the magnetic properties (B ₈ ) in the rolling direction of the grain-oriented electrical steel sheets obtained as described above are also shown in Table 2. From Table 2, it can be seen that, in any of the components, B ₈ is superior in the condition 1 (invention example) imparted with rolling strain. This is because the carbon deposition (aging) after annealing to the final cold rolling was suppressed by the strain imparting treatment in the annealing before the final cold rolling (second annealing in the present example). As a result, it is considered that the amount of solute carbon before the final cold rolling increased.

Claims (3)

C: 0.005 to 0.15 mass%, Si: 7.0 mass% or less and Mn: 0.005 to 3.0 mass%, Al: less than 0.0100 mass%, and S and Se are each set to 0.00. The steel slab is reduced to 0050 mass% or less, and the balance is Fe and inevitable impurities. After hot rolling, hot-rolled sheet annealing is performed to obtain a final sheet thickness by one cold rolling, followed by primary recrystallization annealing and two steps. In the manufacturing method of the grain-oriented electrical steel sheet comprising a series of steps for performing the next recrystallization annealing, the hot-rolled sheet annealing is performed as follows:
(1) Soaking treatment that is maintained at a temperature of 750 to 1200 ° C. for 2 to 300 seconds;
(2) a rapid cooling process for cooling from 750 ° C. to 400 ° C. at an average cooling rate of 10 to 200 ° C./sec;
(3) A method for producing a grain-oriented electrical steel sheet, comprising: a strain imparting process that imparts a strain corresponding to a rolling reduction of 0.2 to 50% within 900 seconds after reaching 400 ° C. C: 0.005 to 0.15 mass%, Si: 7.0 mass% or less and Mn: 0.005 to 3.0 mass%, Al: less than 0.0100 mass%, and S and Se are each set to 0.00. The steel slab is reduced to 0050 mass% or less, and the balance is made of Fe and unavoidable impurities. After hot rolling, hot-rolled sheet annealing is performed as necessary, and the final sheet thickness is obtained by two or more cold rollings sandwiching the intermediate annealing. Then, in the method for producing a grain-oriented electrical steel sheet comprising a series of steps for performing primary recrystallization annealing and secondary recrystallization annealing, intermediate annealing before cold rolling to be the final sheet thickness is as follows.
(1) Soaking treatment that is maintained at a temperature of 750 to 1200 ° C. for 2 to 300 seconds;
(2) a rapid cooling process for cooling from 750 ° C. to 400 ° C. at an average cooling rate of 10 to 200 ° C./sec;
(3) A method for producing a grain-oriented electrical steel sheet, comprising: a strain imparting process that imparts a strain corresponding to a rolling reduction of 0.2 to 50% within 900 seconds after reaching 400 ° C. In addition to the above component composition, the steel slab further includes Ni: 0.005-1.5 mass%, Sn: 0.005-0.50 mass%, Sb: 0.005-0.50 mass%, Cu: 0.00. It contains one or more selected from 005 to 1.5 mass%, P: 0.005 to 0.50 mass% and Cr: 0.005 to 1.5 mass%. Or the manufacturing method of the grain-oriented electrical steel sheet of 2.

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