JP5741308B2 - Manufacturing method of grain-oriented electrical steel sheet and material steel sheet thereof - Google Patents

Description

  The present invention relates to a method for producing a so-called grain-oriented electrical steel sheet, in which crystal grains are highly integrated in a Miller index, {110} on a plate surface, and <001> in a rolling direction, and a raw steel plate used for the production thereof. .

The grain-oriented electrical steel sheet is a soft magnetic material and is mainly used as an iron core of electrical equipment such as a transformer. This grain-oriented electrical steel sheet is obtained by performing secondary recrystallization annealing and highly accumulating crystal grains in {110} <001> orientation (hereinafter referred to as “Goss orientation”). It is known to show characteristics (for example, see Patent Document 1). In addition, as an index for evaluating the magnetic properties of the electromagnetic steel sheet, the iron loss per kg of the steel sheet when magnetized to 1.7 T with a magnetic flux density B ₈ at a magnetic field strength of 800 A / m and an alternating magnetic field with an excitation frequency of 50 Hz. W _17/50 is often used.

By the way, it is known that the magnetic properties of grain-oriented electrical steel sheets are improved by controlling the texture of the steel sheets before secondary recrystallization annealing, that is, after primary recrystallization annealing. For example, in Patent Document 2, the texture in the vicinity of the surface layer of the steel sheet after the primary recrystallization annealing is 10 from the direction of φ ₁ = 0 °, φ = 15 °, φ ₂ = 0 ° in Bunge's Euler angle display. Or a maximum orientation within 10 ° from the orientation of φ ₁ = 5 °, Φ = 20 °, φ ₂ = 70 °, and the texture of the central layer of the steel plate is also a Bunge Euler angle. A grain-oriented electrical steel sheet having excellent magnetic properties after secondary recrystallization annealing when it has a maximum orientation within 5 ° from the orientation of φ ₁ = 90 °, φ = 60 °, φ ₂ = 45 °. It is described that it is obtained.

  As one of the methods for controlling the texture of the steel sheet after the primary recrystallization annealing, it is known to control the reduction ratio of the final cold rolling. For example, in Patent Document 3, in order to stably manufacture a grain-oriented electrical steel sheet having excellent magnetic properties, it is preferable to control the rolling reduction ratio of the final cold rolling within a range of 70 to 91%. Have been described.

  The reason for controlling the rolling reduction within the above range is considered as follows. In general, the texture of the steel sheet after primary recrystallization is such that Goss orientation grains are strongly accumulated, and the matrix is that {111} <112> orientation grains are easy to grow. Ideal. It is known that the accumulation degree of {111} <112> oriented grains in the matrix is increased by increasing the rolling reduction of the final cold rolling, and the magnetic properties after secondary recrystallization are improved. On the other hand, since the Goss orientation grains decrease from the point when the rolling reduction of the final cold rolling exceeds about 65%, a good matrix is formed at a high pressure reduction exceeding 90%. Nevertheless, since the absolute amount of Goss orientation grains is insufficient, it is difficult to cause good secondary recrystallized grains.

Then, the technique which increases the Goss orientation grain of the steel plate after primary recrystallization is examined.
For example, Patent Document 4 discloses a technique in which heating to a temperature of 675 ° C. or higher in decarburization annealing also serving as primary recrystallization annealing is performed as rapid heating of 140 ° C./sec or higher. It is known that the accumulated energy of dislocations introduced in cold rolling has crystal orientation dependence and {111}>{110}> {100}. Since primary recrystallization uses the strain energy of dislocation as the driving force, {111} -oriented grains with large stored energy preferentially recrystallize, and {110} -oriented grains that are Goss oriented grains are relatively recrystallized. It is said that it is difficult to crystallize. Therefore, it is considered that the technique of Patent Document 4 promotes the recrystallization of Goss orientation grains by increasing the temperature rising rate in the primary recrystallization and reducing the orientation dependency of the recrystallization grains.
However, this technique has a problem that the texture of the matrix deteriorates on the contrary, and as a result, the history loss is deteriorated after the secondary recrystallization.

  As another method for increasing the Goss orientation grains of the steel sheet after the primary recrystallization, there is a method of coarsening the crystal grains of the intermediate annealing plate in a manufacturing method in which cold rolling is performed twice or more. In this method, in the primary recrystallization annealing, {111} -oriented grains that become the matrix of the steel sheet after the primary recrystallization are generated from the grain boundaries of the intermediate annealed plate, so the grain size of the intermediate annealed plate is increased. Reduced {111} oriented grains after primary recrystallization, relatively increased Goss oriented grains, and coarsened the grain size of the intermediate annealed plate, resulting in grain in the final cold rolling The aim is to increase the number of shear bands to be increased and increase the nucleation sites of Goss orientation grains in primary recrystallization.

Japanese Patent Publication No. 40-015644 JP 2001-060505 A Japanese Patent No. 4123653 Japanese Patent Publication No. 06-051887

  As a method of increasing the crystal diameter of the intermediate annealing plate, a method of increasing the intermediate annealing temperature to reduce the γ phase fraction in hot rolling is known. However, in the method of reducing the γ phase fraction, the hot rolled sheet structure tends to remain and secondary recrystallization becomes difficult. In addition, the method of increasing the intermediate annealing temperature has a problem that the coarsening of the inhibitor proceeds and secondary recrystallization becomes difficult. Therefore, it is considered that these methods for coarsening the crystal grains of the intermediate annealing plate are inappropriate as a technique for improving magnetic characteristics.

  Accordingly, an object of the present invention is to provide a method for producing a grain-oriented electrical steel sheet that is excellent in magnetic properties after secondary recrystallization, in which the Goss orientation grains of the steel sheet after primary recrystallization annealing are increased by a method different from the above-described prior art. In addition to proposing, it is to provide a raw steel plate used for its production.

  Inventors repeated earnest research toward development of the new technique which increases the Goss orientation grain of the steel plate after primary recrystallization annealing. As a result, in the method of producing a grain-oriented electrical steel sheet by the double cold rolling method, the yield stress YS at room temperature (25 ° C.) of the raw steel sheet before the primary cold rolling is reduced, so that the non-uniformity in the primary cold rolling Deformation can be suppressed, and the grain size of the intermediate annealed sheet can be increased. As a result, the absolute amount of Goss orientation grains in the steel sheet after primary recrystallization increases, and excellent magnetic properties are obtained after secondary recrystallization annealing. It discovered that the grain-oriented electrical steel sheet which can be obtained can be obtained, and developed this invention.

That is, the present invention relates to C: 0.02-0.15 mass%, Si: 2.5-4.0 mass%, Mn: 0.005-0.3 mass%, sol. Al: 0.01 to 0.05 mass%, N: 0.002 to 0.012 mass%, and one or two of S and Se are contained in a total of 0.05 mass% or less, with the balance being Fe and inevitable impurities In the manufacturing method of the grain-oriented electrical steel sheet in which the steel material is hot-rolled and then cold-rolled at least twice with intermediate annealing, primary recrystallization annealing, and finish annealing, Yield stress YS (MPa) is expressed by the following formula (1) in relation to the Si content (mass%) of the steel material;
124.32 × Si-12.45 ≦ YS ≦ 124.32 × Si + 127.55
... (1)
After adjusting to satisfy | fill, it is the manufacturing method of the grain-oriented electrical steel sheet characterized by performing primary cold rolling.

  In addition to the above component composition, the steel material in the method for producing a grain-oriented electrical steel sheet according to the present invention further includes Ni: 0.005-1.5 mass%, Sn: 0.005-0.50 mass%, Sb: 0.005. ~ 0.50 mass%, Cu: 0.005 to 1.5 mass%, P: 0.005 to 0.50 mass%, and Cr: 0.01 to 1.5 mass% It is characterized by containing.

Moreover, this invention is the raw steel plate before the primary cold rolling used for manufacture of the grain-oriented electrical steel sheet which is cold-rolled twice or more sandwiching the intermediate annealing, subjected to primary recrystallization annealing, and finish annealing after hot rolling. In the steel sheet, C: 0.02-0.15 mass%, Si: 2.5-4.0 mass%, Mn: 0.005-0.3 mass%, sol. Al: 0.01 to 0.05 mass%, N: 0.002 to 0.012 mass%, and one or two of S and Se are contained in a total of 0.05 mass% or less, with the balance being Fe and inevitable impurities The yield stress YS (MPa) and the Si content (mass%) are represented by the following formula (1):
124.32 × Si-12.45 ≦ YS ≦ 124.32 × Si + 127.55
... (1)
It is a raw material steel plate for grain-oriented electrical steel sheets characterized by satisfying the above.

  In the steel sheet according to the present invention, in addition to the above component composition, Ni: 0.005 to 1.5 mass%, Sn: 0.005 to 0.50 mass%, Sb: 0.005 to 0.50 mass%, Cu: It contains one or more selected from 0.005 to 1.5 mass%, P: 0.005 to 0.50 mass%, and Cr: 0.01 to 1.5 mass%.

According to the present invention, by reducing the yield stress of the raw steel sheet before the primary cold rolling, the texture of the steel sheet after the primary recrystallization is improved, and consequently the iron loss value after the secondary recrystallization annealing is low. It becomes possible to manufacture a grain-oriented electrical steel sheet having a high magnetic flux density. In particular, it is possible to stably manufacture a grain-oriented electrical steel sheet having an iron loss W _17/50 after secondary recrystallization annealing of 0.85 W / kg or less even at a sheet thickness of _{0.23 mm, which} is difficult to manufacture. It becomes.

It is a graph which shows the influence of the yield stress YS in 25 _degreeC of Si content of a steel raw material and the raw steel plate before a primary cold rolling which influences the iron loss _{W17 / 50} after secondary recrystallization.

  The steel material of the grain-oriented electrical steel sheet of the present invention includes C: 0.02-0.15 mass%, Si: 2.5-4.0 mass%, Mn: 0.005-0.3 mass%, sol. Al: 0.01 to 0.05 mass%, N: 0.002 to 0.012 mass%, and one or two of S and Se may be contained in a total composition of 0.05 mass% or less. is necessary. Hereinafter, the reason for limitation will be described.

C: 0.02-0.15 mass%
C is an element necessary for improving the hot-rolled sheet structure by utilizing the γ-α transformation during soaking of hot-rolled and hot-rolled sheet annealing. However, if it is less than 0.02 mass%, the effect of improving the hot-rolled sheet structure is small, and it becomes difficult to obtain a primary recrystallized texture containing many Goss orientation grains. On the other hand, when it exceeds 0.15 mass%, the load in decarburization annealing increases, decarburization becomes incomplete, and causes a magnetic aging in a product plate. Therefore, C is set to a range of 0.02 to 0.15 mass%. Preferably, it is the range of 0.04-0.08 mass%.

Si: 2.5-4.0 mass%
Si is an element effective for increasing the electrical resistance of steel and reducing eddy current loss that constitutes a part of iron loss. In the present invention, Si is added in an amount of 2.5 mass% or more. Further, if Si is less than 2.5 mass%, the presence of the α-γ transformation hinders secondary recrystallization in the final finish annealing, resulting in a problem that the magnetic properties are deteriorated. On the other hand, the iron loss reduction effect due to the addition of Si can be obtained up to 11 mass%, but if it exceeds 4.0 mass%, the workability is remarkably lowered and it is difficult to manufacture. Therefore, Si is set to a range of 2.5 to 4.0 mass%. Preferably, it is in the range of 3.0 to 3.5 mass%.

Mn: 0.005 to 0.3 mass%
Mn is an important element in the present invention that forms MnS and MnSe that act as an inhibitor that suppresses the growth of normal grains in the temperature rising process during secondary recrystallization annealing. However, if the Mn content is less than 0.005 mass%, a sufficient inhibitory force cannot be obtained because the absolute amount of the necessary inhibitor is insufficient. On the other hand, when the addition exceeds 0.3 mass%, it is necessary to increase the slab heating temperature before hot rolling to completely dissolve the inhibitor, or the inhibitor is coarsely precipitated and the inhibitory power becomes insufficient. . Therefore, Mn is in the range of 0.005 to 0.3 mass%. Preferably it is the range of 0.02-0.10 mass%.

sol. Al: 0.01-0.05 mass%
Al is an important element in the present invention that constitutes AlN that acts as an inhibitor that suppresses the growth of normal grains in the temperature rising process during secondary recrystallization annealing. However, the content of Al is sol. If it is less than 0.01 mass% with Al (acid-soluble Al), the absolute amount of the inhibitor is insufficient and the inhibitory power becomes insufficient. On the other hand, when it exceeds 0.05 mass%, AlN coarsely precipitates, and the suppression force is still insufficient. Therefore, sol. Al is in the range of 0.01 to 0.05 mass%. Preferably it is the range of 0.015-0.030 mass%.

N: 0.002-0.012 mass%
N is an element that combines with Al to form an inhibitor. However, if the content is less than 0.002 mass%, the inhibitory power is insufficient because the absolute amount of the inhibitor is insufficient. On the other hand, if it exceeds 0.012 mass%, void defects called blisters are produced during cold rolling. Therefore, N is set to a range of 0.002 to 0.012 mass%. Preferably, it is the range of 0.005-0.010 mass%.

S, Se: 1 type or 2 types in total 0.05 mass% or less S and Se are elements that combine with Mn to form an inhibitor, and are preferably contained in a total of 0.01 mass% or more. However, if the total content exceeds 0.05 mass%, the removal of S and the removal of Se in finish annealing (purification annealing) become incomplete, causing a reduction in iron loss characteristics. Therefore, in the present invention, S and Se are added in a total amount of 0.05 mass% or less. Preferably, it is the range of 0.01-0.03 mass%.

In addition to the above essential components, the grain-oriented electrical steel sheet of the present invention may further contain one or more selected from Ni, Sn, Sb, Cu, P and Cr.
Ni: 0.005-1.5 mass%
Since Ni is an austenite-generating element, it is an effective element for improving the hot rolled sheet structure by utilizing the γ-α transformation and improving the magnetic properties. However, if the content is less than 0.005 mass%, the effect of improving the magnetic properties is small. On the other hand, if the content exceeds 1.5 mass%, the workability is deteriorated and the productivity is deteriorated, or secondary recrystallization is not achieved. It becomes stable and the magnetic properties are lowered. Therefore, when adding Ni, it is preferable to set it as the range of 0.005-1.5 mass%.

Sn: 0.005-0.50 mass%, Sb: 0.005-0.50 mass%, Cu: 0.005-1.5 mass%, P: 0.005-0.50 mass%, and Cr: 0.01- 1.5 mass%
Sn, Sb, Cu, P and Cr are useful elements for improving the magnetic properties. However, if the content of any element is less than the above lower limit value, the effect of improving the magnetic properties is small. On the other hand, if the content exceeds the upper limit value, secondary recrystallization becomes unstable and the magnetic properties are reduced. It begins to decline. Therefore, Sn, Sb, Cu, P and Cr are Sn: 0.005-0.50 mass%, Sb: 0.005-0.50 mass%, Cu: 0.005-1.5 mass%, and P: It is preferable to add in the range of 0.005 to 0.50 mass% and Cr: 0.01 to 1.5 mass%.

  In the grain-oriented electrical steel sheet of the present invention, the balance other than the above essential components and optional additive components is Fe and inevitable impurities. However, addition of other elements is not rejected as long as the effects of the present invention are not impaired.

Next, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated.
The method for producing a grain-oriented electrical steel sheet according to the present invention first produces a steel material (slab) having the above composition, then reheats the steel material under normal conditions, hot-rolls and heats it. Let it be a sheet.
The hot-rolled sheet after hot rolling may be subjected to hot-rolled sheet annealing in order to recrystallize the unrecrystallized structure and improve the hot-rolled sheet structure, and the soaking temperature in that case is 800 to 1200 ° C. The soaking time is preferably in the range of 2 to 300 sec. If the soaking temperature is less than 800 ° C. or the soaking time is less than 2 seconds, an unrecrystallized structure remains, and thus the hot rolled sheet structure is not sufficiently improved. On the other hand, when the soaking temperature exceeds 1200 ° C. or the soaking time exceeds 300 sec, dissolution of AlN, MnSe, and MnS proceeds, and the inhibitor repressing power in the finish annealing is insufficient, so that secondary recrystallization hardly occurs. This is because the magnetic characteristics are deteriorated.

The hot-rolled sheet that has been hot-rolled or subjected to hot-rolled sheet annealing is then made into a cold-rolled sheet having a final thickness by cold rolling two or more times with intermediate annealing interposed therebetween.
Here, the feature of the present invention is that the yield stress YS of the raw steel plate before the primary cold rolling is reduced at room temperature (25 ° C.), the non-uniform deformation in the primary cold rolling is suppressed, and the grain size of the intermediate annealing plate is reduced. By coarsening, the strength of Goss orientation grains in the steel sheet after the primary recrystallization is increased, thereby imparting excellent magnetic properties to the steel sheet after the secondary recrystallization. However, the yield stress has an appropriate range according to the Si content, and good iron loss characteristics cannot be obtained if it is too high or too low. The reason will be described below.

  A to D steel materials (slabs) having component compositions with different Si contents shown in Table 1 were heated to 1350 ° C. and hot-rolled to obtain a hot-rolled sheet having a thickness of 2.4 mm. Next, the hot-rolled sheet was subjected to hot-rolled sheet annealing at 1000 ° C. × 40 sec, and then annealed in a dry nitrogen atmosphere maintained at a temperature of 700 ° C. for various periods of time, yielding of the steel sheet before primary cold rolling The stress YS was changed variously. After that, a primary cold rolling is performed to obtain a cold rolled sheet having an intermediate sheet thickness of 1.5 mm, an intermediate annealing at 1050 ° C. × 80 sec is performed, and then a second cold rolling is performed to obtain a cold rolled sheet having a final sheet thickness of 0.23 mm. It was. Then, after performing primary recrystallization annealing also serving as decarburization at 800 ° C. × 120 sec, an annealing separator mainly composed of MgO is applied to the steel sheet surface, and purification annealing and secondary recrystallization annealing at 1150 ° C. × 50 hr are performed. A grain-oriented electrical steel sheet was prepared by performing finish annealing that also served as a steel.

Table 1 shows the iron loss value W _17/50 of the _grain- oriented electrical steel sheet obtained as described above and the yield stress YS at room temperature (25 ° C.) of the raw steel sheet before the primary cold rolling. Moreover, in FIG. 1, the result of the same table _| surface is the result of arranging the relationship between the _iron loss value W _17/50 , the Si content in the steel material, and the yield stress YS of the material steel plate before the primary cold rolling. Indicated. From FIG. 1, the Si content (mass%) of the steel material and the yield stress YS (MPa) at room temperature of the material steel plate before the primary cold rolling are expressed by the following equation (1):
124.32 × Si-12.45 ≦ YS ≦ 124.32 × Si + 127.55
... (1)
It can be seen that in the range satisfying this relationship, excellent iron loss characteristics with an iron loss value W _17/50 after secondary recrystallization annealing of 0.85 W / kg or less can be obtained.

Here, the reason why the iron loss characteristic is improved when the yield stress YS of the raw steel sheet before primary cold rolling satisfies the above formula (1) according to the Si content is still sufficiently clear. I don't think so.
When the yield stress YS is high, the iron loss characteristics tend to deteriorate (iron loss increases), but by reducing YS so as to satisfy Equation (1), nonuniform deformation in primary cold rolling is suppressed. Thus, the grain size of the intermediate annealed plate becomes coarse and becomes sized, and as a result, the absolute amount of Goss orientation grains in the steel sheet after primary recrystallization increases, and the iron loss characteristics after secondary recrystallization can be improved. .
However, when YS is further reduced and falls below the formula (1), a structure in which strain is difficult to accumulate is obtained, so that the hot-rolled sheet structure is not sufficiently destroyed in the primary cold rolling, and the aggregate of the primary recrystallized sheets In the structure, {110} <001> orientation grains, which are orientations unnecessary for secondary recrystallization, remain, so that iron loss characteristics deteriorate.

As described above, in the present invention, it is an essential matter to reduce the yield stress at room temperature of the raw steel plate before the primary cold rolling. There are various methods for reducing the yield stress at room temperature of the raw steel sheet before the primary cold rolling. For example, a material steel sheet (hot rolled sheet or hot rolled sheet annealed sheet) before the primary cold rolling is subjected to A The simplest method is a method in which annealing is performed for a long time at a temperature immediately below _one transformation point to promote spheroidization and disappearance of pearlite. As specific annealing conditions, it is preferable to perform box annealing at a temperature of 500 to 750 ° C. and holding for 0.2 to 480 hours. However, since annealing for a long time hinders productivity, it is more preferably set to 120 hr or less.

  As described above, the hot-rolled sheet in which the yield stress is controlled within a predetermined range is subjected to primary cold rolling to obtain a cold-rolled sheet having an intermediate sheet thickness, but the primary cold-rolling conditions are not particularly limited, What is necessary is just to perform by a well-known method normally.

The primary cold-rolled steel sheet is then subjected to intermediate annealing before the final cold rolling, but the annealing is performed in the range of a soaking temperature of 800 to 1200 ° C. and a soaking time of 2 to 300 seconds, and cooling after annealing is performed. , 800-400 ° C. is preferably quenched at a cooling rate of 10-200 ° C./s.
If the soaking temperature is less than 800 ° C. or the soaking time is less than 2 seconds, an unrecrystallized structure remains, so the steel sheet after the primary recrystallization cannot be made into a coarse sized structure, and the steel sheet after the primary recrystallization. Since the degree of accumulation of the Goss orientation grains cannot be increased, the magnetic properties after secondary recrystallization are reduced. On the other hand, when the soaking temperature is 1200 ° C. or the soaking time exceeds 300 seconds, the dissolution of AlN, MnSe, and MnS proceeds, the inhibitor's inhibitory power becomes insufficient, and secondary recrystallization hardly occurs. It is because it causes the fall of.
Moreover, when the cooling rate in the section of 800 to 400 ° C. in the cooling after the intermediate annealing is less than 10 ° C./sec, the coarsening of the carbide proceeds, and the texture improvement in the subsequent final cold rolling or primary recrystallization annealing The effect is weakened and the magnetic properties are degraded. On the other hand, when the cooling rate in the section of 800 to 400 ° C. exceeds 200 ° C./sec, the hard martensite phase increases, and the steel sheet structure after the primary recrystallization annealing cannot be made the desired structure. As a result, the magnetic characteristics are still deteriorated.

  The rolling reduction of the subsequent final cold rolling is preferably performed in the range of 60 to 95%. When the rolling reduction in the final cold rolling is less than 60%, the growth of Goss orientation grains in secondary recrystallization such as {554} <225> orientation grains and {12 4 1} <014> orientation grains in the primary recrystallization plate This is because the formation of advantageous orientation grains is not sufficient, while when it exceeds 95%, the absolute amount of Goss orientation grains serving as the nucleus of secondary recrystallization is insufficient.

The cold-rolled sheet having the final thickness is preferably subjected to primary recrystallization annealing that also serves as decarburization in a wet hydrogen atmosphere at a soaking temperature of 700 to 1000 ° C.
When the soaking temperature in the primary recrystallization annealing is less than 700 ° C., an unrecrystallized structure remains, and a desired uniform primary recrystallization grain size cannot be obtained. On the other hand, when the soaking temperature exceeds 1000 ° C., secondary recrystallization occurs and there is a possibility that Goss orientation grains may be generated.

  Then, it is preferable to apply secondary recrystallization annealing (finish annealing) after applying an annealing separator mainly composed of MgO to the steel sheet surface according to a conventional method. Moreover, this secondary recrystallization annealing can also be performed also as purification annealing by performing in a hydrogen atmosphere.

  The steel sheet that has been secondarily recrystallized by finish annealing is preferably a grain-oriented electrical steel sheet (product board) through an insulating coating application process for applying and baking an insulating coating and a flattening annealing process.

In the method for producing a grain-oriented electrical steel sheet of the present invention, it is possible to perform a nitriding treatment in which N is contained in the steel during the period from the first recrystallization annealing to the finish annealing and the second recrystallization. is there. As the method, a known technique in which heat treatment is performed in an NH ₃ atmosphere after primary recrystallization annealing, nitride is contained in an annealing separator, or the atmosphere before the final annealing is used as a nitriding gas can be applied. .

  Furthermore, a plurality of artificial grooves are formed on the steel plate surface during the primary recrystallization annealing after the final cold rolling, the plasma jet or laser irradiation is linearly applied to the steel plate surface after the flattening annealing, It is also possible to reduce the iron loss by applying a magnetic domain subdividing process that gives a linear dent.

  C: 0.05 mass%, Si: 3.0 mass%, Mn: 0.10 mass%, sol. A slab containing Al: 0.02 mass%, N: 0.01 mass%, S: 0.0030 mass% and Se: 0.030 mass%, with the balance being composed of Fe and unavoidable impurities at 1400 ° C. After heating, hot-rolled to a hot-rolled sheet having a thickness of 2.2 mm, and then subjected to hot-rolled sheet annealing at 1000 ° C. × 40 sec, and then annealed by changing the holding time at 700 ° C. in a dry nitrogen atmosphere. The yield stress YS at 25 ° C. of the raw steel plate before the primary cold rolling was variously changed. Next, primary cold rolling is performed to obtain a cold rolled sheet having an intermediate sheet thickness of 1.7 mm, intermediate annealing at 1050 ° C. × 80 sec is performed, and then secondary cold rolling (final cold rolling) is performed to obtain a final sheet thickness of 0. A 23 mm cold rolled sheet was used. After that, this cold-rolled sheet was subjected to primary recrystallization annealing that also served as decarburization at 800 ° C. for 150 seconds, and after applying and drying an annealing separator mainly composed of MgO on the steel plate surface, purification at 1150 ° C. for 50 hours was performed. A secondary recrystallization annealing (finish annealing) was also performed to obtain a grain-oriented electrical steel sheet.

Test pieces were collected from the various _grain- oriented electrical steel sheets obtained as described above, and magnetic properties (iron loss W _17/50 , magnetic flux density B ₈ ) were measured. Table 2 shows the yield stress YS at room temperature (25 ° C.) of the steel sheet before primary cold rolling and the magnetic properties of the steel sheet after secondary recrystallization, along with the upper and lower limits of the above-mentioned formula (1). It was.

From Table 2, in the steel sheet where the yield stress YS of the raw steel sheet before the primary cold rolling satisfies the formula (1), the iron loss W _17/50 is a low iron loss of 0.85 W / kg or less. .
On the other hand, Y.S. deviates from the upper limit of the expression (1). In the steel plates 1 to 3, the low iron loss is not obtained. This is because, in a steel sheet with a high yield stress YS before primary cold rolling, dislocation tangles are promoted by processing strain in primary cold rolling, the nucleation sites of recrystallization increase, and the grain size of the intermediate annealing plate increases. It is estimated that it was made finer. As a result, the decrease in the absolute amount of Goss orientation grains in primary recrystallization annealing reduces the probability that sharp Goss orientation nuclei survive in the initial stage of secondary recrystallization annealing, and the integration of Goss orientation after secondary recrystallization. It is presumed that the degree of the magnetic field decreased and the magnetic characteristics were deteriorated.
On the other hand, No. where YS deviates from the lower limit of the expression (1). This is because the steel sheet No. 10 was not sufficiently destroyed in the hot-rolled sheet structure in the primary cold rolling, and {110} <001>, which is an orientation unnecessary for the secondary recrystallization, remained in the primary recrystallization texture. it is conceivable that.

  A slab containing Si: 3.5 mass%, N: 0.01 mass%, S: 0.0040 mass% and Se: 0.03 mass%, and other components having a composition shown in Table 3 was heated to 1350 ° C. Then, it is hot-rolled to obtain a hot-rolled sheet having a thickness of 2.2 mm, subjected to hot-rolled sheet annealing at 1000 ° C. × 40 sec, and then annealed at 700 ° C. × 120 hr in a dry nitrogen atmosphere to perform primary cooling. Yield stress YS of the raw steel plate before hot rolling was reduced. After that, the steel sheet was subjected to primary cold rolling to an intermediate thickness of 1.7 mm, subjected to intermediate annealing at 1050 ° C. × 80 sec, and then subjected to secondary cold rolling (final cold rolling) to a thickness of 0.23 mm. The cold-rolled sheet was used. Next, this cold-rolled sheet is subjected to primary recrystallization annealing also serving as decarburization at 800 ° C. for 150 seconds, and after applying an annealing separator mainly composed of MgO to the steel sheet surface, it also serves as purification at 1150 ° C. for 50 hours. Secondary recrystallization annealing (finish annealing) was performed to obtain a grain-oriented electrical steel sheet.

Test pieces were collected from the various _grain- oriented electrical steel sheets obtained as described above, and magnetic properties (iron loss W _17/50 , magnetic flux density B ₈ ) were measured. Table 3 shows the yield stress YS at room temperature (25 ° C.) of the steel sheet before primary cold rolling and the magnetic properties of the steel sheet after secondary recrystallization, along with the upper and lower limits of the above-described equation (1). It was.
No. in Table 3 Nos. 1 to 5 are examples in which the C content was changed. It can be seen that the magnetic properties are good in the range of 2 to 4, that is, in the range of C: 0.02 to 0.15 mass%. No. The reason why the steel sheet No. 1 is inferior in magnetic properties is considered to be that since the C content is small, the γ-α transformation does not occur during hot rolling, and the effect of improving the steel sheet texture after primary recrystallization is weak. No. The reason why the steel sheet No. 5 is inferior in magnetic properties is that the C content is high, the texture of the steel sheet after the primary recrystallization was not improved, and the decarburization in the primary recrystallization annealing was incomplete. it is conceivable that.
No. 6 to 27 are those in which the C content is 0.05 to 0.08 mass%, and the contents of Mn, Al, Sn, Sb, P, Ni, Cu and Cr are changed. Since it is within the range, good magnetic properties are obtained.

Claims (4)

C: 0.02-0.15 mass%, Si: 2.5-4.0 mass%, Mn: 0.005-0.3 mass%, sol. Al: 0.01 to 0.05 mass%, N: 0.002 to 0.012 mass%, and one or two of S and Se are contained in a total of 0.05 mass% or less, with the balance being Fe and inevitable impurities In the manufacturing method of the grain-oriented electrical steel sheet, after hot rolling the steel material to be cold-rolled twice or more sandwiching the intermediate annealing, primary recrystallization annealing, and finish annealing,
After adjusting the yield stress YS (MPa) of the material steel plate before the primary cold rolling to satisfy the following formula (1) in relation to the Si content (mass%) of the steel material, the primary cold rolling is performed. A method for producing a grain-oriented electrical steel sheet.
124.32 × Si-12.45 ≦ YS ≦ 124.32 × Si + 127.55
... (1) In addition to the above component composition, the steel material further includes Ni: 0.005-1.5 mass%, Sn: 0.005-0.50 mass%, Sb: 0.005-0.50 mass%, Cu: 0.00. 2 or more types selected from 005 to 1.5 mass%, P: 0.005 to 0.50 mass%, and Cr: 0.01 to 1.5 mass%. The manufacturing method of the grain-oriented electrical steel sheet described in 1. After the hot rolling, it is a raw steel plate before the primary cold rolling used for manufacturing the grain-oriented electrical steel sheet that is cold-rolled two or more times with intermediate annealing, primary recrystallization annealing, and finish annealing, , C: 0.02-0.15 mass%, Si: 2.5-4.0 mass%, Mn: 0.005-0.3 mass%, sol. Al: 0.01 to 0.05 mass%, N: 0.002 to 0.012 mass%, and one or two of S and Se are contained in a total of 0.05 mass% or less, with the balance being Fe and inevitable impurities A material steel sheet for grain-oriented electrical steel sheets, wherein the yield stress YS (MPa) and the Si content (mass%) satisfy the following formula (1):
124.32 × Si-12.45 ≦ YS ≦ 124.32 × Si + 127.55
... (1) In addition to the above component composition, the steel sheet further includes Ni: 0.005-1.5 mass%, Sn: 0.005-0.50 mass%, Sb: 0.005-0.50 mass%, Cu: 0.005. 1 to 2 or more types chosen from -1.5 mass%, P: 0.005-0.50mass%, and Cr: 0.01-1.5mass%, It is characterized by the above-mentioned. The material steel sheet for grain-oriented electrical steel sheets described.

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