JP6137490B2 - Method for predicting primary recrystallization texture and method for producing grain-oriented electrical steel sheet - Google Patents

Description

  The present invention relates to a technology for manufacturing a grain-oriented electrical steel sheet, and specifically relates to a method for predicting a texture of a steel sheet after primary recrystallization annealing and a method for producing a grain-oriented electrical steel sheet using the method.

  The grain-oriented electrical steel sheet is mainly used as a core material of a transformer, and is required to have excellent magnetic characteristics, particularly excellent iron loss characteristics. Therefore, the grain-oriented electrical steel sheet is highly aligned with the {110} <001> orientation, the so-called “Goss orientation”, by causing secondary recrystallization in finish annealing. . In order to further improve the magnetic properties, the orientation of the texture (primary recrystallization texture) of the steel sheet after primary recrystallization is controlled to an appropriate state. Specifically, {111} <112> ( Hereinafter, the strength of {411} <148> (hereinafter also referred to as “S orientation”) is increased, and the Goss grains phagocytose grains in these orientations to facilitate growth. It becomes important.

  As a method for improving the texture of primary recrystallized grains to an appropriate state, there are various methods such as increasing the temperature of cold rolling, increasing the grain size before cold rolling, etc. The actual situation is that a high value cannot be obtained over the entire length of the coil due to variations in manufacturing conditions. Factors that cause fluctuations in the density of the M and S orientations in the coil include, for example, temperature history during hot rolling and changes in the cold rolling speed (speed changes due to acceleration / deceleration, shape defects, ear cracks, etc. at both ends of the coil) ) Etc. Therefore, in order to obtain uniform magnetic properties in the coil, these must be kept constant, but it is not possible to eliminate temperature changes in the coil during hot rolling or to keep the rolling speed constant in cold rolling. It is almost impossible at present.

  Under these circumstances, measure the characteristics of the steel sheet at any stage during manufacturing, and feed back the results or adjust the manufacturing conditions to maintain the product quality constant. Various studies have been made. For example, in Patent Document 1, on the outlet side of the continuous annealing furnace, sensors capable of measuring the crystal grain size of the steel sheet online are provided at two or more locations in the width direction of the steel sheet. The method of measuring the fluctuation and feeding back the result to the upstream process is described in Patent Document 2, in which the primary recrystallized grain size is measured in the intermediate stage from the end of decarburization annealing to the start of final finish annealing. Based on the value, a method for producing a grain-oriented electrical steel sheet that performs feedback control to determine the heat treatment conditions of decarburization annealing performed thereafter, Patent Document 3 measures the coercive force of the steel sheet after primary recrystallization annealing, Depending on the deviation of the measured value from the target value, slab heating conditions, hot rolling conditions, hot rolled sheet annealing conditions, cold rolling conditions including intermediate annealing conditions, primary recrystallization annealing conditions, components of annealing separator Composition and secondary recrystallization annealing conditions A method for producing a grain-oriented electrical steel sheet that adjusts one or more of them and is excellent in magnetic properties is disclosed in Patent Document 4, in the stage after decarburization annealing, by the Fourier transform infrared absorption spectrum method (FT-IR). A method is disclosed in which the absorbance is calculated by measuring the infrared transmittance peak of at least one compound on the surface of the steel sheet, and the film adhesion of the final product is evaluated from the calculated value.

  Furthermore, in Patent Document 5, after degreasing treatment is performed before decarburization annealing, the concentration of the components in the steel on the surface of the steel sheet is measured, and the degree of atmospheric oxidation, annealing temperature, and annealing of decarburization annealing with respect to the surface concentration determined in advance. By substituting the above measured value into the relational expression consisting of the time and the amount of oxidation after decarburization annealing, the atmosphere oxidation degree, annealing temperature, and annealing time to obtain the desired amount of oxidation are calculated, and at least one of these is controlled. The method for producing a grain-oriented electrical steel sheet for controlling the oxidation amount in decarburization annealing is disclosed in Patent Document 6 in which the atmosphere gas in the heating zone is separated from the soaking zone in the decarburization annealing process of the grain-oriented electrical steel sheet. A method of manufacturing grain-oriented electrical steel sheets that stably builds film properties and magnetic properties by evaluating the oxide film after annealing with a fluorescent X-ray apparatus and managing these decarburized annealing atmosphere gases is also patented Reference 7 includes cold rolling passes In addition, a method is disclosed in which the iron loss of a steel sheet is measured online after the final pass, and the quality characteristics in the product are improved by adjusting the rolling conditions by feedback or feedforward based on the measurement result. .

JP 2007-146244 A Japanese Patent Laid-Open No. 03-294426 Japanese Patent Laid-Open No. 08-283855 JP 2004-191217 A JP-A-11-106826 Japanese Patent Laid-Open No. 10-219359 JP-A-10-195535

  However, the techniques of Patent Documents 1 and 2 mainly control the production conditions on the basis of the primary recrystallization grain size, and the technique of Patent Document 3 is based on the coercive force of the steel sheet after the primary recrystallization annealing. The technique for controlling the diameter and inhibitor inhibiting power, the technique of Patent Document 4 is for evaluating the film adhesion of the final product based on the form of the surface oxide, and the techniques of Patent Documents 5 and 6 are for decarburization annealing. This is intended to control the oxygen basis weight, and none of them focuses on the texture of the steel sheet after the primary recrystallization annealing.

  In addition, the technique of Patent Document 7 is to measure the iron loss of the steel sheet between the cold rolling passes or after the final pass in order to make the texture constant, and control the rolling conditions. The recrystallization texture is formed at the time of primary recrystallization annealing, and it is difficult to absorb all fluctuations in the manufacturing conditions of the previous process only by the cold rolling process. Therefore, the effect obtained is also limited.

  The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to establish a method for accurately predicting the texture of a steel sheet after primary recrystallization annealing, and to use the above method. The object is to propose a method of stably producing a grain-oriented electrical steel sheet in which the primary recrystallization texture in the coil is made uniform and the variation in magnetic properties is small.

  The inventors have intensively studied to solve the above problems. As a result, as a method of predicting the texture of the steel sheet after primary recrystallization annealing, it is effective to measure some magnetic properties that have a correlation with the index representing the texture and to predict from the measurement results of the magnetic properties. In addition, as a method of controlling the predicted texture within a predetermined range, it is effective to adjust the heating rate of the heating process in the primary recrystallization annealing. It has been found that the recrystallized texture can be made preferable and uniform, and as a result, the degree of integration in the Goss orientation after the secondary recrystallization is increased over the entire length of the coil, and good magnetic properties can be obtained. Led to the development.

That is, the present invention measures the magnetic properties of the steel sheet after primary recrystallization annealing, and predicts the random strength ratio of the M orientation and S orientation of the texture of the steel sheet after primary recrystallization annealing from the measurement result. We propose a method for predicting the primary recrystallization texture. Here, the M direction indicates {111} <112>, and the S direction indicates {411} <148>.

  In the method for predicting a primary recrystallization texture of the present invention, the magnetic property is a magnetic flux density measured by changing the magnetization direction and the magnetization force with respect to the rolling direction.

Further, the present invention contains C: 0.002 to 0.10 mass%, Si: 2.0 to 8.0 mass%, and Mn: 0.005 to 1.0 mass%, with the balance being Fe and inevitable impurities. A hot-rolled sheet is obtained by hot-rolling a steel material having a composition as follows, and after hot-rolled sheet annealing or hot-rolled sheet annealing, it is cold-rolled twice or more with one or intermediate annealing. The directionality consisting of a series of steps in which a cold-rolled sheet with a final thickness is made, and after applying primary recrystallization annealing that also serves as primary recrystallization annealing or decarburization annealing, an annealing separator is applied to the steel sheet surface and finish annealing is performed. In the manufacturing method of the electrical steel sheet, the magnetic properties of the steel sheet after the primary recrystallization annealing are measured, and the random strength ratio of the M and S orientations of the texture of the steel sheet after the primary recrystallization annealing is predicted from the measurement results. M orientation of the texture and the predicted Random intensity ratio 5.0 to 6.2, so that the random intensity ratio of S orientation is in the range of 3.4 to 4.1, the heating rate between 500 to 700 ° C. in the heating process of the primary recrystallization annealing A method of manufacturing a grain-oriented electrical steel sheet characterized by controlling is proposed. Here, the M direction indicates {111} <112>, and the S direction indicates {411} <148>.

  The magnetic property in the method for producing a grain-oriented electrical steel sheet according to the present invention is a magnetic flux density measured by variously changing the magnetization direction and the magnetization force with respect to the rolling direction of the steel sheet.

  Moreover, the manufacturing method of the grain-oriented electrical steel sheet according to the present invention is characterized in that the temperature increase rate is feedback controlled based on a prediction result of a texture of the steel sheet after the primary recrystallization annealing.

  Moreover, the manufacturing method of the grain-oriented electrical steel sheet of the present invention is the above-mentioned primary recrystallization annealing, heated to a temperature of 700 ° C. or higher, cooled to 180 ° C. or lower, measured for magnetic properties, and then reheated to a soaking temperature. Then, the primary recrystallization annealing is completed.

  Moreover, the manufacturing method of the grain-oriented electrical steel sheet according to the present invention performs a holding treatment for holding for 0.5 to 5 seconds at any temperature between 200 to 500 ° C. in the heating process of the primary recrystallization annealing. It is characterized by that.

  The steel material used in the method for producing a grain-oriented electrical steel sheet according to the present invention further includes Al: 0.010-0.050 mass% and N: 0.003-0.020 mass% in addition to the above component composition. Or Al: 0.010-0.050 mass%, N: 0.003-0.020 mass%, Se: 0.003-0.030 mass% and / or S: 0.002-0.03 mass% It is characterized by containing.

  Further, the steel material used in the method for producing a grain-oriented electrical steel sheet according to the present invention includes Al, N, S and Se as inevitable impurities, Al: less than 0.01 mass%, N: less than 0.0050 mass%, S : Less than 0.0050 mass% and Se: less than 0.0030 mass%.

  Moreover, in addition to the said component composition, the said steel raw material used for the manufacturing method of the grain-oriented electrical steel sheet of this invention is further Ni: 0.010-1.50 mass%, Cr: 0.01-0.50 mass%, Cu : 0.01 to 0.50 mass%, P: 0.005 to 0.50 mass%, Sb: 0.005 to 0.50 mass%, Sn: 0.005 to 0.50 mass%, Bi: 0.005 to 0 .50 mass%, Mo: 0.005-0.100 mass%, B: 0.0002-0.0025 mass%, Te: 0.0005-0.0100 mass%, Nb: 0.0010-0.0100 mass%, V: 1 type or 2 types or more chosen from 0.001-0.010mass% and Ta: 0.001-0.010mass% are contained, It is characterized by the above-mentioned.

  According to the present invention, the magnetic properties of the steel sheet after the primary recrystallization annealing are measured, the texture is predicted from the measurement results, and the primary recrystallization annealing is performed so that the predicted texture falls within a predetermined target range. Controls the rate of temperature rise in the heating process, making the primary recrystallized texture in the longitudinal direction in the coil uniform over the entire length of the coil, and thus stable production of grain-oriented electrical steel sheets with excellent magnetic properties and no variation. It becomes possible to do.

It is a graph which shows the influence of the temperature increase rate of cold rolling speed and primary recrystallization annealing on iron loss characteristics. It is a graph which shows the influence of the temperature increase rate of the cold rolling speed | velocity | rate and the primary recrystallization annealing which affects the random intensity ratio of M direction, and the random intensity ratio of S direction. It is a figure explaining the sensor used for the measurement of a magnetic characteristic in this invention. It is a graph which shows the influence of the magnetic flux density of a 45 degree direction from the rolling direction of the cold rolling speed and the rolling direction of a steel plate after primary recrystallization annealing on the random strength ratio of M direction and S direction.

First, an experiment that triggered the development of the present invention will be described.
Steel containing C: 0.065 mass%, Si: 3.44 mass%, Mn: 0.08 mass%, Al: 0.024 mass% and N: 0.008 mass%, and a steel slab by a continuous casting method After that, it was reheated to 1410 ° C. and hot-rolled to obtain a hot-rolled sheet having a thickness of 2.4 mm, and then the final sheet thickness of 0 mm was obtained by two cold rollings with intermediate annealing at 1120 ° C. × 80 seconds. A 23 mm cold rolled sheet was used. At this time, the rolling speed in the secondary cold rolling was divided into two conditions of 600 mpm and 20 mpm.
Next, primary recrystallization annealing was performed which also served as decarburization annealing in which decarburization was performed at 840 ° C. for 100 seconds in a humid atmosphere of 50 vol% H ₂ -50 vol% N ₂ and a dew point of 55 ° C. Under the present circumstances, the temperature increase rate between 500-700 degreeC in the heating process of primary recrystallization annealing was variously changed in the range of 20-350 degreeC / s.
Next, test pieces were collected from each steel plate after the primary recrystallization annealing, and the texture was measured. Here, the texture is measured by measuring an X-ray pole figure of the thickness center layer, and from the measurement data, a three-dimensional texture, specifically, a random intensity ratio in the M direction and a random value in the S direction. The intensity ratio was calculated.
Next, after applying and drying an annealing separator mainly composed of MgO on the surface of the steel sheet, a final annealing consisting of secondary recrystallization annealing and purification annealing of 1200 ° C. × 10 hr was performed. Then, after removing the unreacted annealing separator, an insulating film treatment agent was applied, and planarization annealing at 800 ° C. for 60 seconds was performed to double the baking.
Test pieces were collected from each steel plate obtained as described above, and the iron loss W _17/50 was measured according to JIS C2550.

  FIG. 1 shows the measurement result of the iron loss as a relationship between the rolling speed and the temperature increase rate of the primary recrystallization annealing. From this figure, when the rolling speed in the final cold rolling is 600 mpm or 20 mpm, the lowest iron loss value is about 0.80 W / kg, but the heating rate showing the lowest iron loss is It can be seen that the rolling speed is different from the range of 100 to 150 ° C./s at 20 mpm and 150 to 200 ° C./s at 600 mpm.

FIG. 2 shows the influence of the temperature increase rate of the primary recrystallization annealing and the rolling rate on the texture of the thickness center layer measured by X-ray. FIG. FIG. 2B shows an example in which the random intensity ratio in the S direction is used as the texture index, and the random intensity ratio in the S direction is used as the texture index.
From FIG. 2 (a), the random strength ratio in the M direction is higher at 20 mpm at the rolling speed of 600 mpm, and the random strength ratio in the M direction has a temperature increase rate of 100 at any rolling speed. It can be seen that there is almost no change below 100 ° C./s, but there is a tendency to continuously decrease above 100 ° C./s.
Further, from FIG. 2B, the random strength ratio in the S direction is slightly higher than 600 mpm at the rolling speed of 20 mpm, and the random strength ratio in the M direction is increased at any rolling speed. It can be seen that when the temperature rate is 100 ° C./s or less, the temperature increases as the temperature increase rate increases.

  As described above, in hot rolling, it is difficult to keep the temperature history and rolling history in the coil constant. In the final cold rolling, it is desirable to perform rolling with the rolling speed kept constant by the coil longitudinal method, but fluctuations in the rolling speed accompanying acceleration / deceleration are unavoidable at both ends of the coil unless continuous rolling is performed. In addition, in a defective shape part or an ear crack part existing in the coil, the rolling speed must be reduced and rolling is unavoidable. Such variations in manufacturing conditions within the coil have a subtle effect on the magnetic properties of the final product through changes in texture.

  However, from the results of the above experiment, the random strength ratio of the M and S orientations, that is, the primary recrystallization texture changes depending on the rolling speed of the final cold rolling, but also changes depending on the temperature increase rate of the primary recrystallization annealing. To do. This means that even if the primary recrystallization texture changes as the rolling speed changes in the final cold rolling, the texture is controlled within a certain range by adjusting the heating rate of the primary recrystallization annealing. It shows that you might get.

Next, the magnetic properties of the steel sheet after the primary recrystallization annealing obtained in the above experiment were measured, and the relationship with the texture (random strength ratio of M orientation and S orientation) was examined.
Here, in the measurement of the magnetic characteristics, a primary coil for excitation and a secondary coil for output are wound around a U-shaped yoke (core) disclosed in Patent Document 1, as shown in FIG. The sensor is held at a height of 5 mm on the surface of the steel sheet, and the magnetic flux density B is changed by changing the angle and magnetization force of the magnetization direction (core length direction) with respect to the rolling direction in the steel sheet surface. It was measured. The width of the U-shaped core (W in FIG. 3B) is 300 mm, and the length of the U-shaped core (L in FIG. 3A) is 300 mm. It becomes the range of xL.

About the measurement result of the magnetic flux density B measured by the above-mentioned various directions and magnetizing forces, the correlation between the random intensity ratio of the M direction and the S direction was investigated. As a result, as shown in FIG. 4A, the random intensity ratio in the M direction is the magnetic flux density B ₁ when the magnetization direction is shifted by 45 ° from the rolling direction (the magnetic flux density when the magnetization force is 100 A / m ( T)) and a good correlation were observed. And from the comparison with FIG. 1, the random strength ratio in the M direction of the test piece in which the iron loss of the product plate stably shows a low value (W _17/50 ≦ 0.82 W / kg) is 5.0 to It was found to be within the range of 6.2. On the other hand, as shown in FIG. 4 (b), the random intensity ratio in the S direction is determined by the magnetic flux density B _{5 in the} direction in which the magnetization direction is shifted by 45 ° from the rolling direction (magnetic flux density when the magnetization force is 500 A / m (T )) And good correlation. And from the comparison with FIG. 1, the random strength ratio of the S orientation of the test piece in which the iron loss of the product plate stably shows a low value (W _17/50 ≦ 0.82 W / kg) is 3.4 to It was found to be within the range of 4.1.

From the above results, as an index of the texture of the steel sheet after the primary recrystallization annealing that affects the iron loss characteristics of the grain-oriented electrical steel sheet, the random strength ratio of the M orientation and the S orientation is measured, and after the primary recrystallization annealing. As magnetic properties of the steel sheet, the magnetic flux density in various directions and various magnetizing forces with respect to the rolling direction is measured, and the measurement conditions of the magnetic properties having the best correlation among them are found, and after the primary recrystallization in those conditions By measuring the magnetic properties of the steel sheet, it is possible to predict the texture of the steel sheet, and further, based on the predicted texture of the steel sheet, the iron loss characteristics of the predicted texture of the steel sheet are best. It was found that the grain-oriented electrical steel sheet having excellent iron loss characteristics can be stably produced by adjusting the temperature increase rate of the primary recrystallization annealing so as to be within the predetermined range.
The present invention has been developed based on the above novel findings.

In the above experiment, the random intensity ratio of the M direction and the S direction is used as the texture index. However, any other index may be used as long as it is a texture index correlated with the magnetic characteristics. .
In the above experiment, as magnetic properties of the steel sheet after the primary recrystallization, the magnetic flux densities B ₁ and B _{5 in the} direction of 45 ° from the rolling direction were measured. However, the magnetic density is not limited to the above magnetic flux density. Any magnetic characteristic may be used as long as it is related to an index representing a texture such as a random intensity ratio of the M direction and the S direction.
The sensor used for measuring the magnetic characteristics is not limited to the sensor shown in FIG. 3 in which a primary coil for excitation and a secondary coil for output are wound around a U-shaped yoke (core). For example, a solenoid coil type sensor may be used, and other types of sensors may be used.

Next, the component composition of the steel material (slab) used for manufacture of the grain-oriented electrical steel sheet of the present invention will be described.
C: 0.002-0.10 mass%
If C is less than 0.002 mass%, the grain boundary strengthening effect of C is lost, and the slab is cracked, resulting in problems in production. On the other hand, when it exceeds 0.10 mass%, it becomes difficult to reduce to 0.005 mass% or less in which demagnetization annealing does not cause magnetic aging. Therefore, C is preferably in the range of 0.002 to 0.10 mass%. More preferably, it is the range of 0.010-0.080 mass%.

Si: 2.0 to 8.0 mass%
Si is an element necessary for increasing the specific resistance of steel and reducing iron loss. If the effect is less than 2.0 mass%, it is not sufficient. On the other hand, if it exceeds 8.0 mass%, the workability deteriorates and it is difficult to roll and manufacture. Therefore, Si is preferably in the range of 2.0 to 8.0 mass%. More preferably, it is the range of 2.5-4.5 mass%.

Mn: 0.005 to 1.0 mass%
Mn is an element necessary for improving the hot workability of steel. If the effect is less than 0.005 mass%, it is not sufficient. On the other hand, if it exceeds 1.0 mass%, the magnetic flux density of the product plate is lowered. Therefore, Mn is preferably in the range of 0.005 to 1.0 mass%. More preferably, it is the range of 0.02-0.20 mass%.

Components other than C, Si and Mn are different depending on whether or not an inhibitor is used in order to cause secondary recrystallization.
First, when an inhibitor is used to cause secondary recrystallization, for example, when an AlN-based inhibitor is used, Al and N are changed to Al: 0.010 to 0.050 mass%, N: 0.003, respectively. It is preferable to make it contain in the range of -0.020 mass%. Moreover, when using a MnS * MnSe type | system | group inhibitor, it is preferable to contain S: 0.002-0.030mass% and / or Se: 0.003-0.030mass%. When the amount of each additive is less than the above lower limit value, the inhibitor effect cannot be sufficiently obtained. On the other hand, when the amount exceeds the upper limit value, the inhibitor component remains undissolved during slab heating, resulting in a decrease in magnetic properties. . AlN and MnS / MnSe inhibitors may be used in combination.

  On the other hand, when an inhibitor is not used to cause secondary recrystallization, the content of Al, N, S and Se, which are the above-described inhibitor generating components, is reduced as much as possible, Al: less than 0.01 mass%, N : It is preferable to use a steel material reduced to less than 0.0050 mass%, S: less than 0.0050 mass%, and Se: less than 0.0030 mass%.

  The steel material used for the grain-oriented electrical steel sheet of the present invention is the balance of Fe and inevitable impurities other than the above components. For the purpose of improving magnetic properties, Ni: 0.010 to 1.50 mass%, Cr : 0.01 to 0.50 mass%, Cu: 0.01 to 0.50 mass%, P: 0.005 to 0.50 mass%, Sb: 0.005 to 0.50 mass%, Sn: 0.005 to 0 .50 mass%, Bi: 0.005-0.50 mass%, Mo: 0.005-0.100 mass%, B: 0.0002-0.0025 mass%, Te: 0.0005-0.010 mass%, Nb: One or two selected from 0.0010 to 0.010 mass%, V: 0.001 to 0.010 mass%, and Ta: 0.001 to 0.010 mass% The above may be contained.

Next, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated.
The steel material (slab) used for the production of the grain-oriented electrical steel sheet of the present invention is prepared by melting the steel having the above-described component composition by a conventional refining process, and then performing a conventionally known ingot-bundling rolling method or continuous casting. You may manufacture by a method, and you may manufacture as a thin cast piece of thickness of 100 mm or less by a direct casting method. The slab is charged into a heating furnace or the like according to a conventional method, and reheated to a temperature of about 1400 ° C. when it contains an inhibitor component, while it is 1300 ° C. or less when it does not contain an inhibitor component. After reheating, it is preferably subjected to hot rolling. In addition, when not containing an inhibitor component, you may use for a hot rolling immediately after continuous casting, without reheating. In the case of a thin slab, the hot rolling may be omitted and the process may proceed as it is.

  Next, the hot-rolled hot-rolled sheet is subjected to hot-rolled sheet annealing as necessary. The temperature of this hot rolled sheet annealing is preferably in the range of 800 to 1150 ° C. in order to obtain good magnetic properties. If it is less than 800 degreeC, the band structure formed by hot rolling will remain, it will become difficult to obtain the primary recrystallized structure of a sized grain, and development of a secondary recrystallized grain will be inhibited. On the other hand, when the temperature exceeds 1150 ° C., the grain size after the hot-rolled sheet annealing is excessively coarsened, so that it becomes difficult to obtain a primary recrystallized structure of sized particles.

  The hot-rolled sheet after hot-rolling or after hot-rolled sheet annealing is made into a cold-rolled sheet having a final thickness by one or more cold rollings or two or more cold rollings sandwiching intermediate annealing. The annealing temperature of the intermediate annealing is preferably in the range of 900 to 1200 ° C. When the temperature is lower than 900 ° C., the recrystallized grains after the intermediate annealing become finer, and the Goss nuclei in the primary recrystallized structure are reduced to deteriorate the magnetic properties of the product plate. On the other hand, when the temperature exceeds 1200 ° C., the crystal grains become too coarse as in the hot-rolled sheet annealing, and it becomes difficult to obtain a primary recrystallized structure of the sized grains.

  In addition, cold rolling (final cold rolling) with a final thickness increases the steel sheet temperature during cold rolling to 100 to 300 ° C. in order to improve the primary recrystallization texture and improve the magnetic properties. It is effective to perform so-called warm rolling, or to perform aging treatment once or a plurality of times at a temperature of 100 to 300 ° C. during the cold rolling.

  The cold-rolled sheet having the final thickness is then subjected to primary recrystallization annealing that also serves as primary recrystallization annealing or decarburization annealing. This step is the most important step in the present invention. In order to control the primary recrystallization texture within a predetermined range, the heating rate between 500 and 700 ° C. in the heating process is in the range of 40 to 300 ° C./s. In particular, it is necessary to rapidly heat at an appropriate rate based on the measurement result of the texture of the steel sheet after the primary recrystallization annealing. When the rate of temperature rise is lower than 40 ° C./s, the strength of Goss orientation grains becomes too low. On the other hand, when it exceeds 300 ° C./s, the random strength ratio of M orientation decreases too much, which is good in both cases. This is because magnetic characteristics cannot be obtained. In addition, the annealing temperature of the primary recrystallization annealing is desirably in the range of 750 to 900 ° C. In addition, when serving also as decarburization annealing, the range of 750 to 900 ° C. is desirable from the viewpoint of ensuring decarburization. .

  The rapid heating means in the primary recrystallization annealing is not particularly limited, but an electric heating method or an induction heating method is preferable because the temperature raising rate can be easily and quickly changed.

  Here, what is important in the present invention is that the annealing speed in the primary recrystallization annealing is determined by measuring the random strength ratio of the M and S orientations in the texture of the steel sheet after the primary recrystallization annealing, and depending on the value. The relationship between the rate of temperature rise and iron loss, the relationship between the rate of temperature rise and the random strength ratio of the M and S orientations, and the magnetic properties after the primary recrystallization annealing and M From the relationship between the azimuth and S orientation random intensity ratios, the M orientation random intensity ratio is in the range of 5.0 to 6.2, and the S orientation random intensity ratio is in the range of 3.4 to 4.1. It is important to adjust. This is because by controlling to the above range, the primary recrystallization texture is improved and good magnetic properties can be obtained in the product plate. Preferably, the random intensity ratio in the M direction is in the range of 5.0 to 6.0, and the random intensity ratio in the S direction is in the range of 3.7 to 4.0.

  The annealing rate in the primary recrystallization annealing is preferably feedback controlled so that the texture predicted based on the measurement result of the magnetic properties of the steel sheet after the primary recrystallization annealing falls within a predetermined range. Here, the predetermined range refers to an appropriate range of an index representing the texture of the steel sheet after primary recrystallization annealing, in which the magnetic properties of the product plate after secondary recrystallization are good.

  In the method for producing a grain-oriented electrical steel sheet according to the present invention, in the primary recrystallization annealing, the steel sheet is once heated to a temperature of 700 ° C. or higher to be primary recrystallized, and then cooled to 180 ° C. or lower to obtain a magnetic property. A method of measuring and then reheating to a soaking temperature and performing holding annealing to complete primary recrystallization annealing may be employed. This allows feedback control to be applied in a short time to the subsequent part, so that it is possible to respond with high responsiveness to short cycle fluctuations in the previous process, such as temporary deceleration in cold rolling due to surface defects, etc. become able to.

  Moreover, in the manufacturing method of the grain-oriented electrical steel sheet according to the present invention, the holding is performed for a short time of 0.5 seconds to 5 seconds at any temperature between 200 to 500 ° C. in the heating process of the primary recrystallization annealing. It is preferable to perform the treatment. In the recovery during the holding process, the <111> // ND orientation having a high strain energy is preferentially restored, so that the recrystallization driving force of the <111> // ND orientation is selectively reduced, and other orientations are obtained. Will be recrystallized. As a result, the Goss orientation strength can be increased. If the holding time is less than 0.5 seconds, the effect of the holding process cannot be obtained. On the other hand, if it exceeds 5 seconds, the recovery proceeds too much, and the M direction and the S direction decrease. Note that the holding temperature does not need to be maintained at a constant temperature, and can be considered constant as long as the change is within ± 10 ° C. with respect to the holding temperature.

  Further, the heating process may be divided into two stages, ie, a recovery process from normal temperature to the holding treatment temperature and a recrystallization process from the holding treatment temperature to 700 ° C., and may be heated separately. In this case, by changing the holding temperature, the rate of temperature increase from 500 ° C. to 700 ° C. can be changed to a range of 40 to 300 ° C./s while keeping the line speed constant.

In addition, when performing decarburization annealing in the said primary recrystallization annealing, it is also possible to combine the following techniques.
(1) The decarburization annealing is divided into a plurality of stages, and the oxides on the surface layer are reduced using the final stage as a reducing atmosphere to improve the protective properties of the coating and improve the magnetic properties and coating.
(2) A nitriding treatment is performed during decarburization annealing or after decarburization annealing to reinforce inhibitor inhibitory force and improve magnetic properties.

The primary recrystallized annealed steel sheet is then coated with an annealing separator mainly composed of MgO on the steel sheet surface, wound on a coil, then subjected to finish annealing, and a secondary recrystallized structure highly accumulated in the Goss orientation. The forsterite film is formed.
In the finish annealing, it is preferable to heat to a temperature of 800 ° C. or higher for secondary recrystallization and to a temperature of about 1100 ° C. to complete the secondary recrystallization. Further, after that, in order to form a forsterite film and perform a purification treatment, it is preferable to continue heating to a temperature of about 1200 ° C.

  After the finish annealing, it is effective to perform flattening annealing for shape correction after performing water washing, brushing, pickling, etc. to remove the unreacted annealing separator adhering to the steel sheet surface. is there. This is because iron loss characteristics may be deteriorated due to shape defects such as coil curl and buckling in the finish annealing.

  When the grain-oriented electrical steel sheets of the present invention are laminated and used, it is effective to form an insulating film on the steel sheet surface at the same time as the flattening annealing or before or after that. . In particular, in order to reduce iron loss, it is preferable to apply a tension-imparting type insulating coating that applies tension to the surface of the steel sheet. In addition to the method of forming a normal forsterite base film and then applying and baking a silicic acid-based tension insulating film, the tension imparting film can be formed by physical vapor deposition or chemical vapor deposition. A method of forming an inorganic film on the surface of the steel sheet may be employed.

  In addition, the grain-oriented electrical steel sheet of the present invention is preferably subjected to a magnetic domain refinement treatment in order to further reduce iron loss. As a method of subdividing the magnetic domain, a generally practiced method, for example, irradiating the surface of the final product plate with an electron beam, laser, plasma, etc., to form a linear or dotted thermal strain region or impact strain region. A method of forming, a method of forming a strain region on the surface of the final product plate using a roller or the like, a method of forming a groove by etching in a subsequent intermediate process on a steel plate surface cold-rolled to the final plate thickness, etc. Can be used.

  C: 0.070 mass%, Si: 3.43 mass%, Mn: 0.08 mass%, Al: 0.025 mass%, Se: 0.025 mass%, and N: 0.01 mass%, with the remainder being Fe and inevitable A steel slab made of mechanical impurities is manufactured by a continuous casting method, reheated to a temperature of 1420 ° C., and then hot-rolled to form a hot-rolled sheet having a thickness of 2.4 mm, which is 1000 ° C. × 50 seconds. After annealing, the intermediate sheet thickness is set to 1.8 mm by primary cold rolling, and after intermediate annealing at 1100 ° C. × 20 seconds, secondary cold rolling is performed to obtain a cold rolled sheet having a final sheet thickness of 0.23 mm. It was.

Then, the primary recrystallization annealing which served as the decarburization annealing was performed. At this time, the heating conditions for the primary recrystallization annealing were the following four conditions.
Condition 1: After heating at a heating rate of 500 to 700 ° C. in the heating process at 100 ° C./s (constant), 800 ° C. × 100 in a wet atmosphere of 60 vol% H ₂ -40 vol% N ₂ and a dew point of 60 ° C. A primary recrystallization annealing is performed, which also serves as a decarburization annealing that decarburizes in seconds.
Condition 2: The magnetic properties (magnetic flux density) after the completion of primary recrystallization annealing are measured under the above condition 1, and the primary recrystallization texture (random intensity ratio of M and S orientations) is predicted from the measurement results. From the relationship between the prediction result and the temperature increase rate of the primary recrystallization annealing obtained in advance and the random intensity ratio of the M orientation and the S orientation, the random intensity ratio of the M orientation is 5.0 to 6.2, and the S orientation is In order to keep the random intensity ratio within the range of 3.4 to 4.1, the temperature rising rate between 500 to 700 ° C. is feedback controlled within the range of 40 to 300 ° C./s.
Condition 3: A retention treatment is performed for 1 second at a temperature of 400 ° C. during the heating process of Condition 2 above.
Condition 4: After heating from room temperature to 700 ° C. under the above condition 1, the temperature is once lowered to 100 ° C., reheated again at a heating rate of 30 ° C./s, and decarburized at 800 ° C. × 100 seconds. When performing primary recrystallization annealing also serving as decarburization annealing, the magnetic properties (magnetic flux density) of the steel sheet are measured when the temperature is lowered to 100 ° C., and the primary recrystallization texture (of M and S orientations) is determined from the measurement result. Random intensity ratio), and the relationship between the prediction result and the temperature increase rate of primary recrystallization annealing obtained in advance and the random intensity ratio of the M and S orientations is 5. The heating rate between 500 and 700 ° C. when heating from room temperature to 700 ° C. is set to 40 to 300 so that the random intensity ratio of 0 to 6.2 and S orientation falls within the range of 3.4 to 4.1. Feedback control is performed within the range of ° C / s.

Thereafter, a slurry-like MgO-based annealing separator was applied to the surface of the steel sheet, dried, wound on a coil, and then subjected to finish annealing comprising secondary recrystallization annealing and purification annealing at 1200 ° C. × 10 hr. The atmosphere for the above finish annealing was H ₂ gas at 1200 ° C., N ₂ gas at the time of temperature rise (including secondary recrystallization annealing) and at the time of temperature fall. Then, after removing the unreacted annealing separator, an insulating coating solution was applied, passed through a flattening annealing line for shape correction, and baked under conditions of 800 ° C. × 1 min to obtain a product coil. Next, the product coil is divided into 6 equal parts in the length direction, and test pieces are collected from a total of 7 points including the coil rear end and the dividing point, and the iron loss W _17/50 is measured by a method according to JIS C2550. The maximum value (worst value) and the minimum value (best value) were determined.
The results are shown in Table 1. From the same table, by measuring the texture after primary recrystallization annealing, adjusting the temperature increase rate of primary recrystallization annealing based on the results, and keeping the texture after primary recrystallization annealing within a predetermined range It is possible to stably obtain a grain-oriented electrical steel sheet having low iron loss and small variations in iron loss within the coil. In particular, it can be seen that the iron loss characteristics are further improved when the retaining treatment is performed during the heating under the above conditions.

A steel slab having the composition shown in Table 2 with the balance being Fe and inevitable impurities is manufactured by a continuous casting method, reheated to a temperature of 1380 ° C., and then hot-rolled to a thickness of 2.0 mm. The hot rolled sheet was subjected to hot rolled sheet annealing at 1030 ° C. for 10 seconds, and then cold rolled to finish a cold rolled sheet having a final sheet thickness of 0.23 mm.
Then, after heating at a heating rate of 500 to 700 ° C. in a heating process at 100 ° C./s (constant), in a humid atmosphere of 60 vol% H ₂ -40 vol% N ₂ and a dew point of 60 ° C., 840 ° C. × 100 sec. Primary recrystallization annealing was also performed, which also served as decarburization annealing for decarburization. At this time, the magnetic properties (magnetic flux density) of the steel sheet after the primary recrystallization annealing are measured, and the primary recrystallization texture (random strength ratio of M orientation and S orientation) is predicted from the measurement result, and the prediction result, From the relationship between the temperature increase rate of the primary recrystallization annealing obtained in advance and the random intensity ratio of the M and S orientations, the random intensity ratio of the M orientation is 5.0 to 6.2, and the random intensity ratio of the S orientation is The temperature increase rate between 500-700 degreeC was adjusted so that it might be settled in the range of 3.4-4.1.
Thereafter, a slurry-like MgO-based annealing separator was applied to the surface of the steel sheet, dried, wound on a coil, and then subjected to finish annealing consisting of secondary recrystallization annealing and purification annealing at 1220 ° C. × 4 hr. The atmosphere for finish annealing was H ₂ gas at 1200 ° C., Ar gas at the time of temperature rise (including secondary recrystallization annealing) and at the time of temperature fall. Then, after removing the unreacted annealing separator, the insulating coating solution is applied and dried, and passed through a flattening annealing line for shape correction, and baked under conditions of 800 ° C. × 1 min. did. Next, the product coil is divided into 6 equal parts in the length direction, test pieces are collected from a total of 7 points of the coil rear end and the dividing point, and the iron loss W _17/50 is measured according to JIS C2550, The maximum value (worst value) and the minimum value (best value) were determined.

  The measurement results are shown in Table 2. From this, the temperature increase rate in the heating process of the primary recrystallization annealing of the cold rolled sheet having the component composition suitable for the present invention is adjusted based on the prediction result of the primary recrystallization texture so that the texture falls within the appropriate range. By doing so, it is understood that a method electrical steel sheet having low iron loss and uniform iron loss characteristics in the coil longitudinal direction can be obtained.

  According to the technique of the present invention, it is possible to control the texture of the steel sheet after the primary recrystallization annealing. Therefore, it can be applied to the texture control of, for example, a steel sheet for automobiles and a steel sheet for cans.

Claims (10)

Measuring the magnetic properties of the steel sheet after primary recrystallization annealing, and predicting the random strength ratio of M orientation and S orientation of the texture of the steel sheet after primary recrystallization annealing from the measurement results How to predict the organization. Here, the M direction indicates {111} <112>, and the S direction indicates {411} <148>. The method for predicting a primary recrystallization texture according to claim 1, wherein the magnetic property is a magnetic flux density measured by variously changing a magnetization direction and a magnetization force with respect to a rolling direction. C: Steel containing 0.002 to 0.10 mass%, Si: 2.0 to 8.0 mass% and Mn: 0.005 to 1.0 mass% , the balance being composed of Fe and unavoidable impurities The material is hot-rolled to form a hot-rolled sheet, and after the hot-rolled sheet annealing is performed or after the hot-rolled sheet annealing, the final sheet thickness is cooled by one or more cold rollings sandwiching the intermediate annealing. In the manufacturing method of grain-oriented electrical steel sheet consisting of a series of steps of applying annealing separator to the steel sheet surface and finishing annealing after applying primary recrystallization annealing that also serves as primary recrystallization annealing or decarburization annealing ,
The magnetic properties of the steel sheet after the primary recrystallization annealing are measured, and the random strength ratio of the M orientation and S orientation of the texture of the steel sheet after the primary recrystallization annealing is predicted from the measurement result, and the predicted M of the texture Temperature rise between 500-700 ° C. in the heating process of primary recrystallization annealing so that the random strength ratio of the orientation is in the range of 5.0 to 6.2 and the random strength ratio of the S orientation is in the range of 3.4 to 4.1. A method for producing a grain-oriented electrical steel sheet, characterized by controlling speed. Here, the M direction indicates {111} <112>, and the S direction indicates {411} <148>. 4. The method for producing a grain-oriented electrical steel sheet according to claim 3 , wherein the magnetic property is a magnetic flux density measured by variously changing the magnetization direction and the magnetizing force with respect to the rolling direction of the steel sheet. The method for producing a grain-oriented electrical steel sheet according to claim 3 or 4 , wherein the temperature rise rate is feedback controlled based on a prediction result of a texture of the steel sheet after primary recrystallization annealing. After heating to a temperature of 700 ° C. or higher by the primary recrystallization annealing, cooling to 180 ° C. or lower, measuring magnetic properties, and then reheating to a soaking temperature to complete the primary recrystallization annealing. The manufacturing method of the grain-oriented electrical steel sheet according to any one of claims 3 to 5 . Any one of claims 3 to 6, characterized by applying retention process to hold either 0.5 seconds 5 seconds or less at a temperature between 200 to 500 ° C. in the heating process of the primary recrystallization annealing 1 The manufacturing method of the grain-oriented electrical steel sheet as described in a term. The steel material further contains Al: 0.010 to 0.050 mass% and N: 0.003 to 0.020 mass% in addition to the above component composition, or Al: 0.010 to 0.050 mass%. , N: 0.003~0.020mass%, Se: 0.003~0.030mass% and / or S: any of claims 3-7, characterized in that it contains 0.002～0.03Mass% A method for producing the grain-oriented electrical steel sheet according to claim 1. In the steel material, as inevitable impurities, Al, N, S, and Se are respectively Al: less than 0.01 mass%, N: less than 0.0050 mass%, S: less than 0.0050 mass%, and Se: less than 0.0030 mass%. method for producing a grain-oriented electrical steel sheet according to any one of claims 3-7, characterized in that it contains. In addition to the above component composition, the steel material further includes Ni: 0.010 to 1.50 mass%, Cr: 0.01 to 0.50 mass%, Cu: 0.01 to 0.50 mass%, P: 0.00. 005 to 0.50 mass%, Sb: 0.005 to 0.50 mass%, Sn: 0.005 to 0.50 mass%, Bi: 0.005 to 0.50 mass%, Mo: 0.005 to 0.100 mass% , B: 0.0002 to 0.0025 mass%, Te: 0.0005 to 0.0100 mass%, Nb: 0.0010 to 0.0100 mass%, V: 0.001 to 0.010 mass%, and Ta: 0.001. The method for producing a grain-oriented electrical steel sheet according to claim 8 or 9 , comprising one or more selected from ˜0.010 mass%.

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