JP6992652B2 - Manufacturing method of electrical steel sheet and electrical steel sheet - Google Patents

Description

The present invention relates to an electromagnetic steel sheet and a method for manufacturing an electromagnetic steel sheet, and more particularly to a method for manufacturing an electromagnetic steel sheet in which an easily magnetized axis is inclined by 45 ° with respect to a rolling axis and integrated, and the electromagnetic steel sheet thereof.

Electrical steel sheets are used as a material for cores of electrical equipment. The electrical equipment includes, for example, a drive motor mounted on a hybrid vehicle, an electric vehicle, and a fuel cell vehicle, a small generator mounted on a two-wheeled vehicle and a household cogeneration system, and the like. These electric devices are required to have high energy efficiency, miniaturization and high output. Therefore, low iron loss and high magnetic flux density are required for electrical steel sheets used as cores of electrical equipment.

As a technique for reducing iron loss, techniques such as increasing the Si and Al contents, increasing the purity of the steel sheet, and reducing the thickness of the steel sheet have been adopted. On the other hand, recrystallization texture control is adopted as a technique for obtaining a high magnetic flux density. In the recrystallization texture control, the number of crystal grains including the easily magnetized axis is increased in the surface of the steel sheet. Specifically, in the recrystallization texture control, the {111} plane that does not include the easily magnetized axis is suppressed in the surface of the steel plate. Then, in the plate surface, the {110} surface and the {100} surface including the easily magnetized axis are increased. More specifically, in the rolling axis RD direction, a {100} <001> direction having an easy magnetization axis in two directions (hereinafter, also referred to as a Cube direction) and a {110} <with a one-way easy magnetization axis. 001> Increases the degree of integration of orientation (hereinafter, also referred to as Goss orientation). Such recrystallization texture control has been studied not only for so-called two-way electrical steel sheets and one-way electrical steel sheets, but also for non-oriented electrical steel sheets.

Recently, a motor using a split core has appeared for the purpose of improving the efficiency of the motor. In such a motor, the stator core is composed of a plurality of split cores. The plurality of divided cores are wound around the teeth portion and arranged in the circumferential direction of the stator core. At this time, the axis of the teeth portion extends in the radial direction of the stator core. In such a split core, it is preferable that the radial direction of the stator core (that is, the axial direction of the teeth portion) is the axial direction for easy magnetization in the teeth portion, and the circumferential direction of the stator core is the axial direction for easy magnetization in the yoke portion. Is preferable.

In the integrated stator core that does not use a split core, non-oriented electrical steel sheets in which the easily magnetized axes are not integrated in a specific direction are used. However, in the case of a stator core composed of split cores, it is possible to use an electromagnetic steel sheet in which the <100> orientation, which is the axis for easy magnetization, is integrated in a specific direction in the plate surface of the steel sheet. This is because the split core may be cut out from the electrical steel sheet so that the easily magnetized axes are integrated in the axial direction of the teeth portion. Therefore, a split core using a one-way electrical steel sheet or a two-way electrical steel sheet has been proposed.

However, one-way electrical steel sheets and two-oriented electrical steel sheets are very expensive. Therefore, as an electromagnetic steel sheet applicable to a split core instead of a unidirectional electromagnetic steel sheet or a bidirectional electromagnetic steel sheet, a method for manufacturing an electromagnetic steel sheet in which {100} <011> crystal orientations are integrated on the surface of the steel sheet is patented. It is proposed in Document 1.

The method for manufacturing an electromagnetic steel sheet proposed in Patent Document 1 is an α-γ transformation system, in which Si: 2.0% by mass or more and 4.0% by mass or less, or Al: 0.6% by mass or more and 3.0. A hot rolling process in which an ingot containing mass% or less and the balance of Fe and unavoidable impurities is used as a hot-rolled sheet, a cold rolling process in which a hot-rolled sheet is used as a cold-rolled steel sheet, and a cold-rolled steel sheet are finished and annealed. Has a process. Further, this manufacturing method does not have an annealing step between the hot rolling step and the cold rolling step. Further, the cumulative rolling reduction in the cold rolling process is set to 88% or more. It is described in Patent Document 1 that this makes it possible to manufacture an electromagnetic steel sheet in which {100} <011> crystal orientations are integrated on the surface of the steel sheet.

Japanese Unexamined Patent Publication No. 2017-193731

In the electromagnetic steel sheet disclosed in Patent Document 1, {100} <011> crystal orientations are accumulated on the surface of the steel sheet. That is, on the surface of the steel plate, the easy-magnetizing axis is inclined by 45 ° from the rolling axis RD and is integrated. Therefore, when the split core is manufactured using this magnetic steel sheet, the split core may be cut out by inclining the axis of the teeth portion by 45 ° from the rolling shaft RD. Therefore, as in Patent Document 1, an electromagnetic steel sheet in which the easily magnetized axis is inclined by 45 ° with respect to the rolled axis and integrated is also suitable for application to a split core.

By the way, in the method for manufacturing an electromagnetic steel sheet disclosed in Patent Document 1, the rolling reduction in the cold rolling process is as high as 88% or more. If the rolling reduction in the cold rolling process is high, it is necessary to increase the rolling reduction amount per pass of the rolling mill that carries out cold rolling. In this case, the load on the rolling mill that performs cold rolling becomes high. Considering operational stability, it is preferable that the load on the rolling mill that performs cold rolling can be suppressed.

Recently, there is a demand for miniaturization and high efficiency of motors. With the demand for miniaturization and high efficiency of motors, high magnetic flux density and low iron loss are required in a high frequency range of 1000 Hz or higher. Such magnetic characteristics (magnetic flux density and iron loss) in a high frequency range of 1000 Hz or higher have not been studied in Patent Document 1.

An object of the present disclosure is to obtain high magnetic flux density and low iron loss in a high frequency region without increasing the rolling reduction in the cold rolling process in the manufacturing process of electrical steel sheet, {100} <011> crystal. It is an object of the present invention to provide an electromagnetic steel sheet having a high degree of orientation integration and a method for manufacturing the electromagnetic steel sheet.

The electromagnetic steel sheet according to the present disclosure has a chemical composition of% by mass, C: 0.0050% or less, Si: 2.00 to 3.50%, Mn: 2.50 to 4.50%, P: 0.050. % Or less, S: 0.0050% or less, Al: 0.10% or less, N: 0.0025% or less, Ni: 0 to 1.000%, Cu: 0 to 0.100%, and the balance: Fe. The X-ray random intensity ratio of {100} <011> crystal orientation on the steel plate surface of the electromagnetic steel plate is 15.0 to 50.0, and the plane parallel to the steel plate surface at the center position of the plate thickness. The standard deviation when the average crystal grain size is standardized to 1.0 is 0.35 or less.

The method for manufacturing an electromagnetic steel plate according to the present disclosure includes a hot rolling step, a cold rolling step, an intermediate annealing step, a {100} <011> strain amount adjusting rolling step for orientation, and a finish annealing step.
In the hot rolling step, the chemical composition is mass%, C: 0.0050% or less, Si: 2.00 to 3.50%, Mn: 2.50 to 4.50%, P: 0.050%. Hereinafter, S: 0.0050% or less, Al: 0.10% or less, N: 0.0025% or less, Ni: 0 to 1.000%, Cu: 0 to 0.100%, and the balance: Fe and A slab composed of impurities is heated to 1000 to 1200 ° C., and the heated slab is hot-rolled to produce a steel sheet, and any of the following (1) and (2) is carried out.
(1) The finish rolling temperature in hot rolling is set to the _Ac3 transformation point or higher, and the temperature of the steel sheet after rolling in the final pass in hot rolling is cooled to 250 ° C. within 3 seconds after rolling in the final pass. do.
(2) The finish rolling temperature in hot rolling is set to _Acc3 transformation point −50 ° C. or lower, and after rolling in the final pass, the steel sheet is cooled at a cooling rate equal to or higher than the cooling rate.
In the cold rolling step, cold rolling is carried out at a rolling reduction of less than 50.0 to 85.0% without performing an annealing treatment on the steel sheet after the hot rolling step.
In the intermediate annealing step, the steel sheet after the cold rolling step is annealed at an intermediate annealing temperature of 500 ° C. to less than the _Ac1 transformation point.
{100} <011> In the alignment strain amount adjusting rolling step, cold rolling is carried out on the steel sheet after the intermediate annealing step at a rolling reduction of 5.0 to 15.0%.
In the finish annealing step, the steel sheet after the {100} <011> alignment strain adjustment rolling step is annealed at a finish annealing temperature of 500 ° C. to less than the _Ac1 transformation point.
By the above manufacturing process, the X-ray random intensity ratio of {100} <011> crystal orientation on the steel plate surface is 15.0 to 50.0, which is parallel to the steel plate surface at the center position of the plate thickness of the electromagnetic steel plate. An electromagnetic steel sheet having a standard deviation of 0.35 or less when the average crystal grain size is standardized to 1.0 on the surface is manufactured.

The electromagnetic steel sheet according to the present disclosure can increase the degree of integration of {100} <011> crystal orientation on the surface of the steel sheet without increasing the rolling reduction in the cold rolling process, and further suppresses the variation in crystal grain size. be able to. Therefore, a sufficient magnetic flux density and low iron loss can be realized especially in a high frequency region.

FIG. 1 is a perspective view of an electromagnetic steel sheet according to the present embodiment. FIG. 2 is a plan view of the electromagnetic steel sheet of FIG. FIG. 3 is a schematic diagram for explaining the recrystallization phenomenon. FIG. 4 is a schematic diagram for explaining strain-induced grain growth.

The present inventors have {100} < 011> We studied electrical steel sheets and their manufacturing methods that can sufficiently increase the degree of integration of grain orientation and realize sufficient magnetic flux density and low iron loss in the high frequency range of 1000 Hz or higher. As a result, the present inventors obtained the following findings.

The chemical composition of the electromagnetic steel sheet is, in terms of mass%, C: 0.0050% or less, Si: 2.00 to 3.50%, Mn: 2.50 to 4.50%, P: 0.050% or less, S. : 0.0050% or less, Al: 0.10% or less, N: 0.0025% or less, Ni: 0 to 1.000%, Cu: 0 to 0.100%, and the balance: Fe and impurities. It has a chemical composition. In this case, the Si content is as high as 2.00 to 3.50%, but the Mn content is also as high as 2.50 to 4.50%. Therefore, in the steel sheet having this chemical composition, the structure of the steel sheet in the hot rolling process can be austenite single phase or two phases of austenite and ferrite. In hot rolling, by cooling a steel sheet having a single-phase structure of austenite or a steel sheet having a two-phase structure of austenite and ferrite, the degree of integration of {100} <011> crystal orientation can be increased.

In the electromagnetic steel sheet having the above-mentioned chemical composition, the X-ray random intensity ratio of {100} <011> crystal orientation on the surface of the steel sheet is set to 15.0 to 50.0. As shown in FIG. 1, the steel plate surface referred to in the present specification refers to the rolling shaft RD and the rolling shaft RD of the surface of the electromagnetic steel plate 1 when the rolling axis RD, the normal axis ND, and the plate width axis TD of the electromagnetic steel sheet 1 are defined. It is a surface including the plate width axis TD, and means a surface 10 having a normal axis ND as a normal. Here, the rolling axis RD, the normal axis ND, and the plate width axis TD are orthogonal to each other.

Further, in the electromagnetic steel sheet according to the present embodiment, the standard deviation when the average crystal grain size is standardized to 1.0 on the plane parallel to the steel plate plate surface at the center position of the plate thickness is set to 0.35 or less. Here, as shown in FIG. 1, the plane parallel to the steel plate surface at the center position of the plate thickness is T in the plate thickness direction from the steel plate plate surface 10 when the plate thickness of the electromagnetic steel plate 1 is defined as T (mm). At the center position of the plate thickness, which is the position of / 2, the surface 20 is parallel to the steel plate surface 10. Here, the surface 20 parallel to the surface of the steel plate is a cross section having the normal axis ND as the normal. Hereinafter, in the electromagnetic steel sheet 1, the surface 20 parallel to the steel plate surface 10 is also referred to as an “ND surface”.

The present inventors have found that if the variation in crystal grain size on the ND plane at the center position of the plate thickness is small, the iron loss is reduced in the high frequency region. The reason for this is not clear, but the following reasons can be considered. The size of the grain boundaries in the electrical steel sheet affects the movement of the domain wall. If the variation in crystal grain size on the ND plane at the center position of the plate thickness is large, the domain wall cannot move uniformly, and a region where the domain wall is difficult to move locally occurs. It is considered that such variation in the movement of the domain wall causes an abnormal eddy current loss and a hysteresis loss, and increases the iron loss. Variations in crystal grain size on the ND plane at the center of the plate thickness significantly increase iron loss, especially in the high frequency range of 1000 Hz and above.

In the electromagnetic steel plate of the present embodiment, the X-ray random intensity ratio of {100} <011> crystal orientation on the plate surface is 15.0 to 50.0, and the average crystal grain on the ND surface at the center position of the plate thickness. The standard deviation when the diameter is standardized to 1.0 is 0.35 or less. In this case, as shown in FIG. 2, on the steel plate surface 10 of the electrical steel sheet, the easily magnetized axis (<100>) can be integrated in the direction inclined by 45 ° from the rolling axis RD. Therefore, as shown in FIG. 2, the axis of the tooth portion of the split core 30 is parallel to the axis of easy magnetization, that is, the axis of the tooth portion of the split core 30 is tilted by 45 ° from the rolling axis RD to form the split core 30. By cutting out, the magnetic characteristics of the split core 30 can be sufficiently enhanced. Further, as described above, by sufficiently reducing the variation in crystal grain size on the ND plane at the center position of the plate thickness, it is possible to sufficiently reduce the iron loss in the high frequency region of 1000 Hz or higher.

The present inventors further investigated a method capable of manufacturing an electromagnetic steel sheet having the above-mentioned characteristics without increasing the rolling reduction in the cold rolling process to the level described in Patent Document 1. As a result, as an example, by carrying out the manufacturing process shown below, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface is 15.0 to 50.0, and the plate thickness. It has been found that an electromagnetic steel sheet having a standard deviation of 0.35 or less when the average crystal grain size on a plane parallel to the steel plate plate surface (ND plane) at the center position is standardized to 1.0 can be manufactured.

The method for manufacturing an electromagnetic steel plate of the present embodiment includes a hot rolling step, a cold rolling step, an intermediate annealing step, a {100} <011> strain amount adjusting rolling step for orientation, and a finish annealing step.

In the hot rolling step, the chemical composition is mass%, C: 0.0050% or less, Si: 2.00 to 3.50%, Mn: 2.50 to 4.50%, P: 0.050% or less. , S: 0.0050% or less, Al: 0.10% or less, N: 0.0025% or less, Ni: 0 to 1.000%, Cu: 0 to 0.100%, and the balance: Fe and impurities. The slab consisting of, is heated to 1000-1200 ° C. Then, hot rolling is performed on the heated slab to manufacture a steel sheet. In the hot rolling step, the following (1) or (2) is carried out.
(1) The finish rolling temperature in hot rolling is set to the _Ac3 transformation point or higher, and the temperature of the steel sheet is raised to 250 ° C. within 3 seconds after rolling the final pass for the steel sheet that has been rolled in the final pass in hot rolling. Cooling.
(2) The finish rolling temperature in hot rolling is set to the _Ac3 transformation point −50 ° C. or lower, and after rolling the final pass, the product is cooled at a cooling rate equal to or higher than the cooling rate.

Subsequently, in the cold rolling process, the steel sheet after the hot rolling process is cold rolled without annealing, and the rolling reduction in the cold rolling is set to less than 50.0 to 85.0%. do. In the cold rolling step of the present embodiment, the rolling reduction can be suppressed to less than 85%. Therefore, the load on the rolling mill used in the cold rolling process can be reduced.

In the present embodiment, the rolling reduction in the cold rolling step is suppressed, and the following manufacturing steps (A) to (C) are carried out in the order of (A) to (C) after the cold rolling step.
(A) Intermediate annealing process (B) {100} <011> Strain amount adjustment rolling process for orientation (C) Finish annealing process

In the intermediate annealing step of (A) above, the steel sheet after the cold rolling step is annealed at an intermediate annealing temperature of 500 ° C. to less than the _Ac1 transformation point.

In the {100} <011> alignment strain amount adjusting rolling step of (B) above, cold rolling is carried out on the steel sheet after the intermediate annealing step at a rolling reduction of 5.0 to 15.0%.

In the finish annealing step of (C) above, the steel sheet after the {100} <011> alignment strain amount adjusting rolling step is annealed at a finish annealing temperature of 500 ° C. to less than the _Ac1 transformation point.

By carrying out the above manufacturing process, in the electromagnetic steel sheet having the above chemical composition, the X-ray random intensity ratio of {100} <011> crystal orientation on the surface of the steel sheet becomes 15.0 to 50.0, and the sheet of the electromagnetic steel sheet becomes The standard deviation when the average crystal grain size is standardized to 1.0 on the plane parallel to the steel plate surface at the center position of the thickness is 0.35 or less. The reason for this is not clear, but the following reasons can be considered.

First, in the chemical composition of the electrical steel sheet of the present embodiment, not only the Si content is as high as 2.00 to 3.50%, but also the Mn content is as high as 2.50 to 4.50%. Si lowers the stacking defect energy of Fe. Therefore, in the above chemical composition, if the Mn content is low, Si reduces the stacking defect energy of Fe, and as a result, the slip system that can be active during rolling is limited. In this case, deformation occurs preferentially in the slippery <111> direction, and strain is concentrated and accumulated at the grain boundaries of {111} grains. Here, the {111} grain means a crystal grain whose crystal plane on the surface of the steel plate is {111}.

As described above, in the conventional electrical steel sheet, strain is concentrated and accumulated at the grain boundaries of {111} grains. Therefore, in the finish annealing step, as shown in FIG. 3, recrystallized grains 50 are nucleated and grown from the grain boundaries 40 of {111} grains. In this case, since the recrystallized grains 50 tend to be {111} grains, {111} grains grow and become dominant on the steel plate surface.

On the other hand, in the chemical composition of the present embodiment, not only the Si content but also the Mn content is high. Therefore, in the case of the chemical composition of the present embodiment, the stacking defect energy of Fe is higher than that of the above-mentioned electromagnetic steel sheet having a high Si content only. In this case, the slip system that can be active is not limited. In particular, in the cold rolling step and in the strain amount adjusting rolling step for {100} <011> orientation, not only {111} grains but also other grains including {100} <011> crystal orientation grains are strained. Is introduced. Here, the {100} <011> crystal orientation grain is a crystal grain in which the crystal grain on the steel plate plate surface is the {100} crystal plane and the <011> orientation is along the rolling axis RD.

As described above, in the present embodiment, in the steel sheet before the intermediate annealing step, strain is introduced not only to {111} grains but also to other crystal grains including {100} <011> crystal orientation grains. ing. For this steel sheet, in the intermediate annealing step of (A) above, the finish annealing temperature is set to 500 to less than the _Ac1 transformation point. In this case, it is possible to give a driving force for recrystallization to crystal grains other than {111} grains and to which strain has been introduced, and even in {100} <011> grains, recrystallization can occur. Occur. Therefore, by the intermediate annealing step of (A) above, the strain amount of each crystal grain can be reduced and {100} <011> crystal orientation grains can be left.

After the intermediate annealing step, in the {100} <011> alignment strain amount adjusting rolling step of (B) above, the steel sheet is cold-rolled at a rolling reduction of 5.0 to 15.0%. At this time, since the steel sheet of the present embodiment has a high Mn content as well as a Si content, strain is introduced into the crystal grains other than the {111} grains as described above. However, the {100} <011> crystal orientation grains are less likely to introduce strain than the {111} grains and other crystal grains. Therefore, the amount of strain introduced into the {100} <011> crystal orientation grains on the surface of the steel plate after the {100} <011> alignment strain adjustment rolling step is larger than that of other crystal grains such as {111} grains. There are few. As described above, in the {100} <011> alignment strain adjustment rolling step, an appropriate strain amount is introduced into each crystal grain in order to integrate the {100} <011> crystal orientation in the finish annealing step of the next step. Let me.

{100} <011> In the alignment strain amount adjusting rolling step, the finish annealing step of (C) above is carried out on a steel sheet into which an appropriate strain amount has been introduced. In this case, it is considered that strain-induced grain growth (bulging) shown in FIG. 4, which is different from recrystallization as shown in FIG. 3, occurs. Specifically, as shown in FIG. 4, the grain boundary 80 of the {100} <011> crystal orientation grain 70 introduces a larger amount of strain than the {100} <011> crystal orientation grain 70 on the surface of the steel plate. It overhangs to the side of the crystal grain 60 and grows. Here, the crystal grains 60 are, for example, {111} grains. In the present embodiment, it is considered that the {100} <011> crystal orientation grains can be grown by the grain growth due to such bulging, and as a result, the degree of integration of the {100} <011> crystal orientation can be increased.

The rolling reduction of the cold rolling process is suppressed to less than 85.0%, and (A) intermediate annealing process, (B) {100} <011> strain amount adjustment rolling process for orientation, and (C) finish annealing process are performed. By implementing this, the variation in the crystal grain size of the electromagnetic steel sheet is further suppressed, and the standard deviation when the average crystal grain size is standardized to 1.0 on the surface parallel to the steel plate plate surface at the center position of the plate thickness is 0.35. It can be as follows. The reason for this is not clear, but the following reasons can be considered.

When the rolling reduction in the cold rolling process during the manufacturing process of the electromagnetic steel sheet with a high degree of integration of the conventional {100} <011> crystal orientation is set to 85.0% or more, the steel sheet is subjected to the finish annealing process of the next process. Abnormal grain growth may occur on the ND surface (plane parallel to the steel plate surface). In this case, the crystal grains are scattered on the ND surface. The following reasons can be considered as the reason for this. When the reduction ratio in the cold rolling process is 85.0% or more, the reduction ratio is extremely high, so that the strain is locally concentrated in the steel sheet before finish annealing, and the strain distribution in the steel sheet is extremely poor. It is uniform. When finish annealing is performed on a steel sheet having such a strain distribution, abnormal grain growth is likely to occur after recrystallization occurs. As a result, crystal grains may be scattered on the ND surface of the manufactured electrical steel sheet.

On the other hand, in the present embodiment, as described above, the rolling reduction in the cold rolling step is suppressed to less than 85.0%, and (A) the intermediate annealing step and (B) {100} <011> orientation. The strain amount adjusting rolling step and (C) finish annealing step are carried out.

By the intermediate annealing step of (A) above, the driving force for recrystallization can be applied to other crystal grains into which strain has been introduced in addition to the {111} grains. That is, recrystallization occurs even in the {100} <011> crystal orientation grain. Therefore, by the intermediate annealing step of (A) above, it is possible to reduce the strain amount of each crystal grain and leave {100} <011> crystal orientation grains. Then, in the {100} <011> alignment strain adjustment rolling step of (B) above, cold rolling is performed at a rolling reduction of 5.0 to 15.0%, so that the strain distribution is extremely non-uniform. The amount of strain accumulated in each crystal grain in the steel plate is adjusted to an appropriate amount while suppressing the formation. Then, in the finish annealing step of (C) above, grain growth due to bulging is expressed. Grain growth by bulging can suppress abnormal grain growth as compared with grain growth by recrystallization. As a result, it is considered that the variation in the crystal grain size of the manufactured electrical steel sheet can be suppressed.

The above mechanism is a hypothesis. However, even if other mechanisms are functioning, the rolling reduction in the cold rolling process is suppressed to less than 85.0%, and (A) intermediate annealing process, (B) {100} <011> alignment strain. By carrying out the quantity-adjusted rolling step and (C) finish annealing step, the degree of integration of {100} <011> crystal orientation is increased in the electromagnetic steel sheet having the above-mentioned chemical composition, and {100 on the rolled plate surface. } <011> The X-ray random intensity ratio of the crystal orientation was 15.0 to 50.0, and the average crystal grain size was standardized to 1.0 on the plane parallel to the steel plate surface at the center position of the plate thickness. It is also proved in the examples described later that the standard deviation of the case is 0.35 or less.

Based on the above findings, the electromagnetic steel sheet of the present embodiment completed by a technical idea different from the conventional one has a chemical composition of 0.0050% or less in C: 0.0050% or less and Si: 2.00 to 3.50% in mass%. , Mn: 2.50 to 4.50%, P: 0.050% or less, S: 0.0050% or less, Al: 0.10% or less, N: 0.0025% or less, Ni: 0 to 1. It consists of 000%, Cu: 0 to 0.100%, and the balance: Fe and impurities, and the X-ray random intensity ratio of {100} <011> crystal orientation on the steel plate surface of the electromagnetic steel plate is 15.0 to 50. It is 0.0, and the standard deviation when the average crystal grain size is standardized to 1.0 on the plane parallel to the steel plate plate surface at the center position of the plate thickness of the electromagnetic steel plate is 0.35 or less.

The above-mentioned chemical composition of the electromagnetic steel sheet of the present embodiment is an α-γ transformation system chemical composition. Here, the "chemical composition of the α _- γ transformation system" has an A3 transformation point in an equilibrium state _, the main phase of the microstructure becomes ferrite below the A3 transformation point _, and the main phase of the microstructure becomes ferrite above the A3 transformation point. It means a chemical composition in which the main phase of the microstructure becomes austenite.

The plate thickness of the electromagnetic steel sheet of the present embodiment may be 0.25 to 0.50 mm.

The method for manufacturing an electromagnetic steel plate according to the present embodiment includes a hot rolling step, a cold rolling step, an intermediate annealing step, a {100} <011> strain amount adjusting rolling step for orientation, and a finish annealing step.
In the hot rolling process, in terms of mass%, C: 0.0050% or less, Si: 2.00 to 3.50%, Mn: 2.50 to 4.50%, P: 0.050% or less, S: Consists of 0.0050% or less, Al: 0.10% or less, N: 0.0025% or less, Ni: 0 to 1.000%, Cu: 0 to 0.100%, and the balance: Fe and impurities. The slab is heated to 1000 to 1200 ° C., hot rolling is performed on the heated slab to produce a steel sheet, and any of the following (1) and (2) is carried out.
(1) The finish rolling temperature in hot rolling is set to the _Ac3 transformation point or higher, and the temperature of the steel sheet is raised to 250 ° C. within 3 seconds after rolling the final pass for the steel sheet that has been rolled in the final pass in hot rolling. Cooling.
(2) The finish rolling temperature in hot rolling is set to the _Ac3 transformation point −50 ° C. or lower, and after rolling in the final pass, the product is cooled at a cooling rate equal to or higher than the cooling rate.
In the cold rolling step, cold rolling is carried out at a rolling reduction of less than 50.0 to 85.0% without performing an annealing treatment on the steel sheet after the hot rolling step.
In the intermediate annealing step, the steel sheet after the cold rolling step is annealed at an intermediate annealing temperature of 500 ° C. to less than the _Ac1 transformation point.
{100} <011> In the alignment strain amount adjusting rolling step, cold rolling is carried out on the steel sheet after the intermediate annealing step at a rolling reduction of 5.0 to 15.0%.
In the finish annealing step, the steel sheet after {100} <011> alignment strain adjustment rolling is annealed at a finish annealing temperature of 500 ° C. to less than the _Ac1 transformation point.
By the above manufacturing process, the X-ray random intensity ratio of {100} <011> crystal orientation on the steel plate surface is 15.0 to 50.0, and the plane parallel to the steel plate surface at the center position of the plate thickness of the electromagnetic steel plate. In, an electromagnetic steel sheet having a standard deviation of 0.35 or less when the average crystal grain size is standardized to 1.0 is manufactured.

In the above-mentioned finish annealing step, the annealing treatment is carried out with the heating rate up to the finish annealing temperature set to less than 0.1 to 10.0 ° C./sec and the holding time of the steel sheet at the finish annealing temperature set to 10 to 120 seconds. You may.

Hereinafter, the electromagnetic steel sheet according to this embodiment will be described in detail. Unless otherwise specified, "%" for an element means mass%.

[Electromagnetic steel sheet according to this embodiment]
[Chemical composition]
The chemical composition of the electrical steel sheet according to this embodiment contains the following elements.

C: 0.0050% or less Carbon (C) is an impurity inevitably contained. That is, the C content is more than 0%. C forms fine carbides. Fine carbides inhibit the movement of the domain wall and inhibit the grain growth during the manufacturing process. In this case, the magnetic flux density decreases or the iron loss increases. Therefore, the C content is 0.0050% or less. The C content is preferably as low as possible. However, excessive reduction of C content increases manufacturing costs. Therefore, when considering the operation in industrial production, the lower limit of the C content is preferably 0.0001%, more preferably 0.0005%, still more preferably 0.0010%.

Si: 2.00-3.50%
Silicon (Si) increases the electrical resistance of steel and reduces iron loss. If the Si content is less than 2.00%, this effect cannot be obtained. On the other hand, if the Si content exceeds 3.50%, the magnetic flux density of the steel decreases. If the Si content exceeds 3.50%, the cold workability is further lowered, and the steel sheet may be cracked during cold rolling. Therefore, the Si content is 2.00 to 3.50%. The preferred lower limit of the Si content is 2.10%, more preferably 2.40%. The preferred upper limit of the Si content is 3.40%, more preferably 3.20%.

Mn: 2.50-4.50%
Manganese (Mn) increases the electrical resistance of steel and reduces iron loss. Mn further lowers the _Ac3 transformation point and enables the refinement of crystal grains by phase transformation in the component system of the electrical steel sheet of the present embodiment. As a result, in the electromagnetic steel sheet after the final manufacturing process, the random intensity ratio of the {100} <011> crystal orientation on the surface of the steel sheet can be increased. As described above, the Si content of the electrical steel sheet of the present embodiment is high. Si is an element that raises the _Ac3 transformation point. Therefore, in the present embodiment, by increasing the Mn content, the _Ac3 point is lowered, and the phase transformation in the hot rolling step is enabled. If the Mn content is less than 2.50%, the above effect cannot be obtained. On the other hand, if the Mn content is too high, MnS is excessively generated and the cold workability is deteriorated. Therefore, the Mn content is 2.50 to 4.50%. The preferred lower limit of the Mn content is 2.60%, more preferably 2.70%. The preferred upper limit of the Mn content is 4.40%, more preferably 4.30%.

P: 0.050% or less Phosphorus (P) is an impurity that is inevitably contained. That is, the P content is more than 0%. P segregates and lowers the workability of the steel. Therefore, the P content is 0.050% or less. The lower limit of the P content is preferably 0.040%, more preferably 0.030%. It is preferable that the P content is as low as possible. However, excessive reduction of P content increases the manufacturing cost. Considering the operation in industrial production, the preferable lower limit of the P content is 0.0001%, and more preferably 0.0003%.

S: 0.0050% or less Sulfur (S) is an impurity that is inevitably contained. That is, the S content is more than 0%. S forms a sulfide such as MnS. Sulfide impedes domain wall movement and reduces magnetic properties. If the S content exceeds 0.0050% in the chemical composition of the electrical steel sheet of the present embodiment (when an element other than S is within the range of the present embodiment), the generated sulfide deteriorates the magnetic properties. .. That is, the magnetic flux density decreases and the iron loss increases. Therefore, the S content is 0.0050% or less. The preferred upper limit of the S content is 0.0040%, more preferably 0.0030%. It is preferable that the S content is as low as possible. However, excessive reduction of the S content increases the manufacturing cost. Considering industrial production, the preferred lower limit of the S content is 0.0001%, more preferably 0.0003%.

Al: 0.10% or less Aluminum (Al) is an impurity. When the Al content exceeds 0.10%, the recrystallization temperature of the steel sheet rises in the chemical composition of the present embodiment (when an element other than Al is within the range of the present embodiment). In this case, the strain introduced during hot rolling is removed, and the austenite grains become coarse during hot rolling. As a result, it becomes difficult to obtain fine ferrite grains in the hot-rolled steel sheet, and in the electromagnetic steel sheet after the final manufacturing process, the random intensity ratio of the {100} <011> crystal orientation on the steel sheet surface decreases. Therefore, the Al content is 0.10% or less. The upper limit of the Al content is preferably 0.05%, more preferably 0.03% or less. The Al content may be 0%. That is, the Al content is 0 to 0.10%. However, excessive reduction of Al content increases the manufacturing cost. Therefore, when considering the operation in industrial production, the preferable lower limit of the Al content is 0.0001%, and more preferably 0.0003%.

N: 0.0025% or less Nitrogen (N) is an impurity that is inevitably contained. That is, the N content is more than 0%. N forms a fine nitride. Fine nitrides hinder the movement of the domain wall. Therefore, the magnetic flux density decreases and the iron loss increases. Therefore, the N content is 0.0025% or less. The preferred lower limit of the N content is 0.0020%, more preferably 0.0010%. The N content is preferably as low as possible. However, excessive reduction of N content increases the manufacturing cost. Therefore, considering industrial production, the preferable lower limit of the N content is 0.0001%.

The rest of the chemical composition of the electrical steel sheet according to this embodiment is Fe and impurities. Here, the impurities are mixed from ore, scrap, manufacturing environment, etc. as a raw material when the electromagnetic steel sheet according to the present embodiment is industrially manufactured, and have an adverse effect on the electromagnetic steel sheet according to the present embodiment. It means what is allowed within the range that does not give.

Impurities other than the above-mentioned impurities are, for example, O, Ti, V, W, Nb, Zr, Cr, Ca, and Mg. All of these elements may suppress grain growth. The preferable content of each of the above elements is 0.01% or less.

[About arbitrary elements]
The electromagnetic steel sheet according to this embodiment may further contain one or more selected from the group consisting of Ni and Cu instead of a part of Fe.

Ni: 0 to 1.000%
Nickel (Ni) is an optional element and may not be contained. That is, the Ni content may be 0%. When contained, Ni increases the electrical resistance of the steel sheet and reduces iron loss, similar to Mn. Ni further lowers the _A3 transformation point and enables the refinement of crystal grains by phase transformation in the chemical composition of the electrical steel sheet of the present embodiment. However, if the Ni content is too high, the product cost will be high because Ni is expensive. Therefore, the Ni content is 0 to 1.000. The lower limit of the Ni content is more than 0%, more preferably 0.100%, still more preferably 0.200%. The preferred upper limit of the Ni content is 0.900%, more preferably 0.850%.

Cu: 0 to 0.100%
Copper (Cu) is an optional element and may not be contained. That is, the Cu content may be 0%. When contained, Cu increases the electrical resistance of the steel sheet and reduces iron loss, similar to Mn. Cu further lowers the _A3 transformation point to enable the refinement of crystal grains by phase transformation in the chemical composition of the electrical steel sheet of the present embodiment. However, if the Cu content is too high, the recrystallization temperature rises and strain accumulation becomes difficult. In this case, {100} <011> crystal orientation grains cannot be highly integrated. Therefore, the Cu content is 0 to 0.100%. The lower limit of the Cu content is more than 0%, more preferably 0.010%, still more preferably 0.040%. The preferred upper limit of the Cu content is 0.090%, more preferably 0.080%.

[Measuring method of chemical composition of electrical steel sheet]
The chemical composition of the electrical steel sheet according to this embodiment is measured by an ICP emission spectroscopic analysis method based on JIS G 1258 (2014). Specifically, a faceted sample is collected from the central portion of the width of the electrical steel sheet and weighed. The collected sample is dissolved in acid to prepare an acid solution. Further, the residue is collected with filter paper and separately melted in alkali. Extract the melt with acid to make a solution. This solution is mixed with the above-mentioned acid solution to prepare a measurement solution. The measurement solution is measured by inductively coupled plasma mass spectrometry (ICP-MS method) according to JIS G 1258 (2014).

[Random X-ray intensity on the plate surface of electrical steel sheet]
Further, in the electromagnetic steel plate according to the present embodiment, the X-ray random intensity ratio of {100} <011> crystal orientation on the steel plate surface is 15.0 to 50.0. In this case, as shown in FIG. 2, the degree of integration in the <100> direction, which is the easy axis of magnetization, becomes sufficiently high in the direction inclined by 45 ° with respect to the rolling direction (RD) on the surface of the steel plate. Therefore, as shown in FIG. 2, if the split core 30 is cut out from the electrical steel sheet so that the axial direction of the teeth portion of the split core 30 is parallel to the axis inclined by 45 ° from the rolling shaft RD, the split core has a sufficient magnetic flux. It has a density and the iron loss is sufficiently low. Here, the steel plate plate surface is a surface of the electromagnetic steel plate including the rolling axis RD and the plate width axis TD, and has the normal axis ND as the normal line (reference numeral 10 in FIG. 1). Equivalent).

If the {100} <011> crystal orientation X-ray random intensity ratio on the steel plate surface is less than 15.0, the degree of integration of the easily magnetized shaft in the direction inclined by 45 ° with respect to the rolling shaft RD is too low. In this case, a sufficient magnetic flux density cannot be obtained in a direction inclined by 45 ° with respect to the rolling shaft RD, and the iron loss also increases. On the other hand, if the X-ray random intensity ratio of the {100} <011> crystal orientation on the surface of the steel sheet exceeds 50.0, the magnetic flux density of the electromagnetic steel sheet having the above chemical composition is saturated. Therefore, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface is 15.0 to 50.0. The preferred lower limit of the X-ray random intensity ratio is 17.0, more preferably 20.0. The preferred upper limit of the X-ray random intensity ratio is 47.0, more preferably 45.0.

The {100} <011> crystal orientation X-ray random intensity ratio on the surface of a steel plate is the {100} <011> crystal orientation of a standard sample (random sample) that does not have accumulation in a specific orientation in X-ray diffraction measurement. It is the ratio of the X-ray diffraction intensity of {100} <011> crystal orientation of the measured electromagnetic steel plate sample to the X-ray diffraction intensity of. That is, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface is expressed by the following equation.
X-ray random intensity ratio = (measured electromagnetic steel plate sample {100} <011> crystal orientation X-ray diffraction intensity) / standard sample {100} <011> crystal orientation X-ray diffraction intensity

The X-ray random intensity ratio of the {100} <011> crystal orientation on the surface of the steel plate can be measured by the following method. Crystal orientation distribution representing a three-dimensional texture calculated by the series expansion method based on the pole diagram of {200}, {110}, {310}, {211} of the α-Fe phase measured by the X-ray diffraction method. Obtained from a function (Orientation Distribution Function: ODF). The measurement by the X-ray diffraction method is performed at an arbitrary position between the plate thickness / 4 and the plate thickness / 2 of the magnetic steel sheet. At this time, the measurement surface is finished by chemical polishing or the like so as to be smooth.

[Granularity variation]
Further, in the electromagnetic steel plate in the present embodiment, the standard deviation when the average crystal grain size is standardized to 1.0 on the plane parallel to the steel plate plate surface (ND plane) at the center position of the plate thickness is 0.35 or less. be.

As described above, it is considered that the larger the variation of the crystal grains on the ND surface at the center position of the plate thickness of the magnetic steel sheet, the more the movement of the domain wall is hindered. That is, the larger the variation of the crystal grains (ferrite grains) on the ND surface at the center position of the plate thickness, the higher the iron loss especially in the high frequency region (1000 Hz or more).

In the electromagnetic steel plate according to the present embodiment, the variation of crystal grains on the ND surface at the center position of the plate thickness is small, and the standard deviation when the average crystal grain size is standardized to 1.0 is 0.35 or less. In this case, the domain wall can be smoothly moved in the entire steel sheet, and the iron loss can be kept low. Further, when the split core is formed from the electrical steel sheet by punching, sagging due to punching is less likely to occur, and the punching accuracy is improved. When the average crystal grain size on the ND surface at the center position of the plate thickness is standardized to 1.0, the preferable upper limit of the standard deviation is 0.30, and more preferably 0.25.

The standard deviation when the crystal grain size of the ND plane at the center position of the plate thickness is standardized to 1.0 can be obtained by the following method. A sample having a 30 mm × 30 mm square observation surface (the observation surface is an ND surface), which is a surface parallel to the steel plate surface at the center position of the plate thickness, is prepared at an arbitrary portion of the electromagnetic steel plate. After mirror-polishing the observation surface of the prepared sample, etching is performed on the mirror-polished observation surface using a nital solution. Crystal grains in an arbitrary observation field in the etched observation surface are observed with an optical microscope to generate a photographic image of the observation field. Crystal grains are specified for the generated photographic image using an image processing device, and the specified crystal grains are approximated to an ellipse by an ellipse approximation method. The average value of the major axis and the minor axis of the obtained ellipse is defined as the crystal grain size (μm) of the specified crystal grain. The above-mentioned observation field of view is selected so that the number of specified crystal grains is 2000 or more. The average value of the crystal grain size of the specified crystal grains is defined as the average crystal grain size (μm).

Assuming that the total number of obtained crystal grains is n, the average crystal grain size is d (μm), and the crystal grain size of the i-th crystal grain is di (μm), the average crystal grain size is 1.0 from the following formula. The standard deviation s when standardized is obtained.

In the electromagnetic steel sheet according to the present embodiment having the above configuration, the X-ray random intensity ratio of {100} <011> crystal orientation on the surface of the steel sheet is 15.0 to 50.0. Therefore, a sufficient magnetic flux density can be obtained in a direction inclined by 45 ° with respect to the rolling shaft RD. Further, in this electromagnetic steel plate, the standard deviation when the average crystal grain size is standardized to 1.0 on the plane parallel to the steel plate plate surface at the center position of the plate thickness of the electromagnetic steel plate is 0.35 or less. Therefore, as described above, a sufficient magnetic flux density can be obtained especially in a high frequency region (1000 Hz or more) in a direction inclined by 45 ° with respect to the rolling shaft RD, and iron loss is sufficiently low.

The average crystal grain size is not particularly limited, but the average crystal grain size is preferably 70 to 100 μm. A more preferable lower limit of the average crystal grain size is 75 μm. A more preferable upper limit of the average crystal grain size is 90 μm.

[Preferable thickness of electrical steel sheet according to this embodiment]
The thickness of the electrical steel sheet according to this embodiment is not particularly limited. The preferred thickness of the electrical steel sheet is 0.25 to 0.50 mm. Normally, the thinner the plate, the lower the iron loss, but the lower the magnetic flux density. When the thickness of the electromagnetic steel sheet according to the present embodiment is 0.25 mm or more, the iron loss is lower and the magnetic flux density is higher. On the other hand, if the plate thickness is 0.50 mm or less, low iron loss can be maintained. Therefore, the preferable thickness of the electromagnetic steel sheet according to the present embodiment is 0.25 to 0.50 mm. The preferable lower limit of the plate thickness is 0.30 mm. In the electromagnetic steel sheet of the present embodiment, even if the plate thickness is as thick as 0.50 mm, a high magnetic flux density and a low iron loss can be obtained.

[Use of electrical steel sheets according to this embodiment]
The electrical steel sheet according to the present embodiment described above can be widely applied to applications requiring magnetic characteristics (high magnetic flux density and low iron loss). The uses of the electromagnetic steel sheet according to this embodiment are as follows, for example.
(A) Servo motors, stepping motors, compressors used in electrical equipment (B) Drive motors used in electric vehicles and hybrid vehicles. Here, the vehicle includes automobiles, motorcycles, railways, and the like.
(C) Generator (D) Iron cores, choke coils, reactors (E) current sensors for various purposes, etc.

The electrical steel sheet according to this embodiment can be applied to applications other than the above applications. The electrical steel sheet according to this embodiment is particularly suitable for use as a split core, and further suitable for a split core of a drive motor of an electric vehicle or a hybrid vehicle, which is applied in a high frequency range of 1000 Hz or higher.

[Manufacturing method of electrical steel sheet of this embodiment]
An example of a method for manufacturing an electromagnetic steel sheet according to the present embodiment will be described. The method for manufacturing an electromagnetic steel plate includes a hot rolling step, a cold rolling step, an intermediate annealing step, a {100} <011> strain amount adjusting rolling step for orientation, and a finish annealing step. Hereinafter, each step will be described in detail.

[Hot rolling process]
In the hot rolling step, a slab satisfying the above-mentioned chemical composition is hot-rolled to produce a steel sheet. The hot rolling step includes a heating step and a rolling step.

Slabs are manufactured by well-known methods. For example, molten steel is manufactured in a converter or an electric furnace. The manufactured molten steel is secondarily refined with a degassing facility or the like to obtain a molten steel having the above chemical composition. A slab is cast using molten steel by a continuous casting method or an ingot forming method. The cast slab may be block-rolled.

[Heating process]
In the heating step, the slab having the above-mentioned chemical composition is heated to 1000 to 1200 ° C. Specifically, the slab is placed in a heating furnace or a soaking furnace and heated in the furnace. The holding time at the above heating temperature in the heating furnace or the soaking furnace is, for example, 30 to 200 hours.

[Rolling process]
In the rolling step, the slab heated by the heating step is rolled a plurality of passes to manufacture a steel sheet. Here, "pass" means that the steel sheet passes through one rolling stand having a pair of work rolls and is subjected to rolling. Hot rolling is performed, for example, by performing tandem rolling using a tandem rolling mill including a plurality of rolling stands arranged in a row (each rolling stand has a pair of work rolls), and performing multiple pass rolling. Alternatively, reverse rolling with a pair of work rolls may be carried out to carry out rolling of a plurality of passes. From the viewpoint of productivity, it is preferable to carry out a plurality of rolling passes using a tandem rolling mill.

The finish rolling temperature FT of the steel sheet manufactured by the rolling process and the cooling conditions after the rolling process shall be any of the following (1) and (2).
(1) The finish rolling temperature FT in hot rolling is set to the _Ac3 transformation point or higher, and the temperature of the steel sheet after rolling in the final pass in hot rolling is cooled to 250 ° C. within 3 seconds after rolling in the final pass. do.
(2) The finish rolling temperature FT in hot rolling is set to _Acc3 transformation point −50 ° C. or lower, and after rolling in the final pass, the steel sheet is cooled at a cooling rate equal to or higher than the cooling rate. Here, in the present specification, the cooling rate in cooling is defined as 120 ° C./sec. In the condition (2), the temperature of the steel sheet may be cooled to 250 ° C. within 3 seconds after rolling the final pass.

In (1) and (2), the cooling method after the steel sheet temperature reaches 250 ° C. is not particularly limited. The steel sheet temperature means the surface temperature (° C.) of the steel sheet.

Here, the finish rolling temperature FT means the surface temperature (° C.) of the steel sheet on the exit side of the rolling stand for rolling down the final pass in the rolling process during the hot rolling process. The finish rolling temperature FT can be measured by, for example, a temperature gauge installed on the exit side of the rolling stand that reduces the final pass. The finish rolling temperature FT (° C) is, for example, the temperature measurement result of the portion excluding one division at the front end and one division at the rear end when the total length of the steel sheet is divided into 10 equal parts in the rolling direction. Means the average value of.

The temperature of the steel sheet 3 seconds after rolling the final pass is measured by the following method. In the hot rolling equipment line for electrical steel sheets, a cooling device and a transfer line (for example, a transfer roller) are arranged downstream of the hot rolling machine. A temperature gauge that measures the surface temperature of the steel sheet is placed on the exit side of the rolling stand that carries out the final pass of the hot rolling mill. Further, a plurality of temperature gauges are also arranged along the transfer line on the transfer roller arranged downstream of the rolling stand. The cooling device is located downstream of the rolling stand that carries out the final pass. A temperature gauge is placed on the entrance side of the water cooling device. The cooling device may be, for example, a well-known water cooling device or a well-known forced air cooling device. Preferably, the cooling device is a water cooling device. The coolant of the water cooling device may be water or a mixed fluid of water and air.

The temperature of the steel sheet is measured by a temperature gauge installed in the hot rolling equipment line. Then, the temperature of the steel sheet 3 seconds after the rolling of the final pass is obtained.

[About (1) Austenite single-phase hot rolling + quenching]
In (1) above, the finish rolling temperature FT is set to be equal to or higher than the _Ac3 transformation point. In this case, the structure of the steel sheet in hot rolling is austenite single phase. In the chemical composition of the steel sheet in this embodiment, the Mn content is as high as 2.50% or more. Therefore, the movement of grain boundaries is extremely slow during hot rolling. As a result, during hot rolling, the processed austenite with accumulated strain is maintained without recovery and recrystallization. Therefore, even in the structure of the steel sheet in which the rolling of the final pass of hot rolling is completed, the processed austenite in which the strain is accumulated is maintained.

Further, in (1), the temperature of the processed austenite single-phase steel sheet in which the rolling of the final pass is completed and the strain is accumulated is cooled to 250 ° C. within 3 seconds after the rolling of the final pass. In this case, recrystallization of processed austenite is suppressed in the hot-rolled steel sheet, and the processed austenite is transformed into ferrite by cooling. At this time, since the above-mentioned rapid cooling is performed, the strain is sufficiently maintained in the structure after transformation. Therefore, on the premise that the manufacturing conditions described later are satisfied, the X-ray random intensity ratio of the {100} <011> crystal orientation on the surface of the steel sheet is sufficiently high in the manufactured electromagnetic steel sheet.

[(2) Hot rolling in the two-phase region of austenite and ferrite]
In (2) above, the finish rolling temperature is set to the _Ac3 transformation point −50 ° C. or lower. In this case, the steel sheet is hot-rolled in the two-phase region (austenite and ferrite). Therefore, strain is accumulated in austenite and ferrite in the structure of the steel sheet. After the rolling of the final pass of hot rolling is completed, the steel sheet is cooled at a cooling rate (120 ° C./sec or more) equal to or higher than the cooling rate. In this case, in the steel sheet that has been hot-rolled in the two-phase region, the ferrite maintains its strain even after cooling. Further, as described above, since the Mn content in the component system of the present embodiment is as high as 2.50% or more, the movement speed of the grain boundaries is slow. Therefore, even when cooled by cooling or more, recovery and recrystallization of austenite particles in the structure are suppressed, and austenite is transformed into ferrite while the strain is accumulated. Therefore, even when (2) is carried out, the same hot-rolled steel sheet as in (1) can be manufactured. In (2), the cooling rate is not particularly limited as long as it is equal to or higher than the cooling rate. Therefore, in (2), even if the steel sheet temperature is cooled to 250 ° C. at an average cooling rate CR of 200 to 400 ° C./sec within 3 seconds after rolling in the final pass after the rolling in the two-phase region is completed. good.

A hot-rolled steel sheet is manufactured by the hot rolling process described above.

[Omission of annealing process after hot rolling process and before cold rolling process]
In the method for manufacturing an electromagnetic steel plate according to the present embodiment, the annealing step (generally called a hot-rolled plate annealing step) is not performed after the hot rolling step and before the cold rolling step. That is, the annealing step after the hot rolling step and before the cold rolling step is omitted. As described above, the chemical composition of the electrical steel sheet of the present embodiment has a high Mn content. Therefore, if the hot-rolled sheet annealing carried out in the conventional electromagnetic steel sheet is carried out, Mn segregates at the grain boundaries, and the workability of the steel sheet (hot-rolled steel sheet) after the hot rolling process is significantly deteriorated. Therefore, in the present embodiment, after the hot rolling step is completed, the hot rolling plate annealing step is omitted (that is, the hot rolling plate annealing is not carried out), and the cold rolling step is carried out.

The annealing treatment referred to here means, for example, a heat treatment in which the temperature rise temperature is equal to or lower than the _Ac1 transformation point and is 300 ° C. or higher.

[Cold rolling process]
A cold rolling process is performed on a steel sheet manufactured by the hot rolling process without performing an annealing process. Cold rolling is performed, for example, by performing tandem rolling using a tandem rolling mill including a plurality of rolling stands arranged in a row (each rolling stand has a pair of work rolls), and performing multiple pass rolling. May be good. Further, reverse rolling may be carried out by a Zendimia rolling mill or the like having a pair of work rolls, and rolling of one pass or a plurality of passes may be carried out. From the viewpoint of productivity, it is preferable to perform rolling of multiple passes using a tandem rolling mill.

In the cold rolling process, cold rolling is performed without performing annealing treatment during cold rolling. For example, when reverse rolling is carried out and cold rolling is carried out in a plurality of passes, cold rolling is carried out in multiple passes without annealing treatment between the passes of cold rolling. .. In addition, cold rolling may be carried out with only one pass using a reverse type rolling mill. Further, when cold rolling is carried out using a tandem rolling mill, cold rolling is carried out continuously in a plurality of passes (passes at each rolling stand).

In the present embodiment, the rolling reduction ratio RR1 in the cold rolling process is set to less than 50.0 to 85.0%. Here, the rolling reduction ratio RR1 in the cold rolling process is defined as follows.
Rolling ratio RR1 (%) = (1-Steel sheet thickness after rolling in the final pass in the cold rolling process / Steel sheet thickness before cold rolling in the first pass in the cold rolling process) x 100

In the present embodiment, the rolling reduction ratio RR1 in the cold rolling process can be suppressed to less than 85.0%. Therefore, the rolling reduction in the cold rolling process can be suppressed.

[Intermediate annealing process]
In the intermediate annealing step, the steel sheet after the cold rolling step is annealed at an intermediate annealing temperature T1 of 500 ° C. to less than the _Ac1 transformation point.

[Intermediate annealing temperature T1]
If the intermediate annealing temperature T1 is less than 500 ° C., the strain introduced by the cold rolling step cannot be sufficiently reduced. In this case, the degree of integration of the {100} <011> crystal orientation decreases, and the crystal grains on the ND plane at the center position of the plate thickness also vary. As a result, the X-ray random intensity ratio of {100} <011> crystal orientation on the steel plate surface of the electromagnetic steel plate is out of the range of 15.0 to 50.0, and the steel plate surface at the center position of the plate thickness of the electromagnetic steel plate In parallel planes, the standard deviation when the average crystal grain size is standardized to 1.0 exceeds 0.35. On the other hand, if the intermediate annealing temperature T1 exceeds the _Acc1 point, a part of the structure of the steel sheet is transformed into austenite, and the strain in the steel sheet is excessively reduced. Therefore, the intermediate annealing temperature T1 is from 500 ° C. to less than the _Ac1 transformation point. The preferred lower limit of the intermediate annealing temperature T1 is 550 ° C, more preferably 570 ° C.

Here, the intermediate annealing temperature T1 (° C.) is the plate temperature (temperature on the surface of the steel plate) in the vicinity of the extraction port of the annealing furnace. The plate temperature of the annealing furnace can be measured by a temperature gauge arranged at the annealing furnace extraction port.

The holding time at the intermediate annealing temperature T1 in the intermediate annealing step may be a time well known to those skilled in the art. The holding time at the intermediate annealing temperature T1 is, for example, 1 to 30 seconds. However, the holding time at the intermediate annealing temperature T1 is not limited to this. Further, the rate of temperature rise up to the intermediate annealing temperature T1 may be a well-known condition. The rate of temperature rise up to the intermediate annealing temperature T1 is, for example, 10.0 to 20.0 ° C./sec. However, the rate of temperature rise up to the intermediate annealing temperature T1 is not limited to this.

The atmosphere at the time of intermediate annealing is not particularly limited, but for example, an atmosphere gas (drying) containing 20% H ₂ and having the balance of N ₂ is used for the atmosphere at the time of intermediate annealing. The cooling rate of the steel sheet after intermediate annealing is not particularly limited. The cooling rate is, for example, 5.0 to 50.0 ° C./sec.

[{100} <011> Strain amount adjustment rolling process for orientation]
The {100} <011> alignment strain amount adjusting rolling step is carried out on the steel sheet after the intermediate annealing step is completed. Specifically, the steel sheet after the intermediate annealing step is rolled (cold rolled) at room temperature and in the air. For cold rolling here, for example, a reverse rolling mill represented by the above-mentioned Zendimia rolling mill or a tandem rolling mill is used.

{100} <011> In the alignment strain amount adjusting rolling step, cold rolling is carried out without performing annealing treatment during cold rolling. For example, when reverse rolling is carried out and cold rolling is carried out in a plurality of passes, cold rolling is carried out in multiple passes without annealing treatment between the passes of cold rolling. .. In addition, cold rolling may be carried out with only one pass using a reverse type rolling mill. Further, when cold rolling is carried out using a tandem rolling mill, cold rolling is carried out continuously in a plurality of passes (passes at each rolling stand).

{100} <011> The rolling reduction ratio RR2 in the alignment strain adjustment rolling step is 5.0 to 15.0%. Here, the rolling reduction RR2 in the {100} <011> strain-imparting rolling step for orientation is defined as follows.
Reduction rate RR2 (%) = (1-Thickness of steel sheet after rolling in the final pass / Thickness of steel sheet before rolling in the first pass) x 100

{100} <011> The number of cold rolling passes in the strain adjustment rolling process for orientation may be only one pass (that is, only one rolling) or multiple passes. good.

As described above, in the present embodiment, after strain is introduced into the steel sheet by the hot rolling step and the cold rolling step, the strain introduced into the steel sheet by the intermediate annealing step is temporarily reduced. Then, the {100} <011> alignment strain amount adjusting rolling step is carried out. As a result, while reducing the strain introduced excessively by the cold rolling process in the intermediate annealing process, the {111} grains preferentially recrystallize in the surface of the steel sheet plate by performing the intermediate annealing process. Is suppressed, and {100} <011> crystal orientation grains remain. Then, in the {100} <011> alignment strain amount adjusting rolling step, an appropriate strain amount is introduced into each crystal grain in the steel sheet, so that grain growth due to bulging is likely to occur in the finish annealing step of the next step. do.

[Finishing annealing process]
In the finish annealing step, the finish annealing temperature T2 is set to 500 ° C. to less than the _Ac1 transformation point with respect to the steel sheet after the {100} <011> alignment strain amount adjusting rolling step.

[About finish annealing temperature T2]
If the finish annealing temperature T2 is less than 500 ° C., the grain growth of {100} <011> crystal orientation grains due to bulging does not occur sufficiently. In this case, the degree of integration of {100} <011> crystal orientation decreases, and the crystal grains on the ND plane also vary. As a result, the X-ray random intensity ratio of {100} <011> crystal orientation on the steel plate surface of the electromagnetic steel plate is out of the range of 15.0 to 50.0, and the surface parallel to the steel plate surface at the center position of the plate thickness. The standard deviation when the average crystal grain size is standardized to 1.0 exceeds 0.35. On the other hand, if the finish annealing temperature T2 exceeds the _Ac1 point, a part of the structure of the steel sheet is transformed into austenite, and grain growth due to bulging does not occur. As a result, the X-ray random intensity ratio of {100} <011> crystal orientation on the steel plate surface of the electromagnetic steel plate is out of the range of 15.0 to 50.0, and the surface parallel to the steel plate surface at the center position of the plate thickness. The standard deviation when the average crystal grain size is standardized to 1.0 exceeds 0.35. Therefore, the finish annealing temperature T2 is from 500 ° C. to less than the _Ac1 transformation point. The preferred lower limit of the finish annealing temperature T2 is 550 ° C, more preferably 570 ° C.

Here, the finish annealing temperature T2 (° C.) is the plate temperature (the temperature of the surface of the steel plate) in the vicinity of the extraction port of the annealing furnace. The furnace temperature of the annealing furnace can be measured by a temperature gauge arranged at the annealing furnace extraction port.

The rate of temperature rise up to the finish annealing temperature T2 in the finish annealing step may be any rate as known to those skilled in the art, and the holding time Δt2 at the finish annealing temperature T2 may be a time well known to those skilled in the art. ..

The atmosphere during the finish annealing process is not particularly limited. For the atmosphere at the time of the finish annealing step, for example, an atmosphere gas (drying) containing 20% H ₂ and the balance being N ₂ is used. The cooling rate of the steel sheet after finish annealing is not particularly limited. The cooling rate is, for example, 5 to 20 ° C./sec.

[Retention time Δt2]
The preferable holding time Δt2 at the finish annealing temperature T2 in the finish annealing step is 10 to 120 seconds. When the holding time Δt2 is 10 to 120 seconds, bulging causes sufficient grain growth of {100} <110> grains. In this case, the degree of integration of the {100} <011> crystal orientation is increased, and the crystal grains on the ND plane at the center position of the plate thickness are less likely to vary. The lower limit of the holding time Δt2 is more preferably 12 seconds, still more preferably 15 seconds. A more preferable upper limit of the holding time Δt2 is 100 seconds, and even more preferably 90 seconds.

Here, the holding time Δt2 (seconds) means the holding time after the steel sheet temperature reaches the finish annealing temperature.

[About temperature rise rate TR2]
The preferred temperature rise rate TR2 up to the finish annealing temperature T2 in the finish annealing step is 0.1 to less than 10.0 ° C./sec. When the temperature rise rate TR2 is 0.1 to 10.0 ° C./sec, grain growth due to bulging sufficiently occurs. In this case, the degree of integration of the {100} <011> crystal orientation is increased, and the crystal grains on the ND plane at the center position of the plate thickness are less likely to vary.

The temperature rise rate TR2 is obtained by the following method. A thermocouple is attached to a steel sheet having the above chemical composition and obtained by carrying out from the above hot rolling step to the {100} <011> alignment strain amount adjusting rolling step to obtain a sample steel sheet. The temperature of the sample steel sheet to which the thermocouple is attached is heated, and the time from the start of the temperature increase to the arrival of the finish annealing temperature T2 is measured. The temperature rise rate TR2 is obtained based on the measured time.

In the electromagnetic steel sheet manufactured by the above manufacturing process, the X-ray random intensity ratio of {100} <011> crystal orientation on the steel sheet surface is 15.0 to 50.0, and at the center position of the plate thickness of the electromagnetic steel sheet. The standard deviation when the average crystal grain size is standardized to 1.0 on the plane parallel to the surface of the steel plate is 0.35 or less. Therefore, even if the rolling reduction in the cold rolling process is not as high as 85.0% or more, it is possible to have a high magnetic flux density sufficient for use in the split core and to reduce iron loss especially in the high frequency range of 1000 Hz. Electromagnetic steel sheet can be manufactured.

[Other processes]
The method for manufacturing electrical steel sheets according to this embodiment is not limited to the above manufacturing process.

For example, among the above manufacturing steps, the shot blasting step and / or the pickling step may be carried out after the hot rolling step and before the cold rolling step. In the shot blasting process, shot blasting is performed on the steel sheet after the hot rolling process to destroy and remove the scale formed on the surface of the steel sheet after the hot rolling process. In the pickling process, the steel sheet after the hot rolling process is pickled. For the pickling treatment, for example, an aqueous hydrochloric acid solution is used as a pickling bath. Pickling removes the scale formed on the surface of the steel sheet. The shot blasting step may be carried out after the hot rolling step and before the cold rolling step, and then the pickling step may be carried out. Further, it is not necessary to carry out the pickling step and the shot blasting step after the hot rolling step and before the cold rolling step. It is not necessary to carry out the shot blasting step and the pickling treatment after the hot rolling step and before the cold rolling step. The shot blasting step and the pickling step are arbitrary steps. Therefore, it is not necessary to carry out the shot blasting step and the pickling step after the hot rolling step and before the cold rolling step.

In the method for manufacturing electrical steel sheets according to the present embodiment, a coating step may be further carried out after the finish annealing step. In the coating process, an insulating coating is applied to the surface of the steel sheet after the finish annealing process.

The type of insulating coating is not particularly limited. The insulating coating may be an organic component or an inorganic component, and the insulating coating may contain an organic component and an inorganic component. The inorganic component is, for example, heavy chromic acid-boric acid type, phosphoric acid type, silica type and the like. The organic component is, for example, a general acrylic-based, acrylic-styrene-based, acrylic-silicon-based, silicon-based, polyester-based, epoxy-based, or fluorine-based resin. Considering the coatability, the preferable resin is an emulsion type resin. An insulating coating that exhibits adhesiveness by heating and / or pressurizing may be applied. The insulating coating having adhesive ability is, for example, an acrylic-based, phenyl-based, epoxy-based, or melamine-based resin.

The coating process is an arbitrary process. Therefore, it is not necessary to carry out the coating step after the finish annealing step.

The electrical steel sheet according to this embodiment is not limited to the above-mentioned manufacturing method. The {100} <011> crystal orientation X-ray random intensity ratio on the steel plate surface is 15.0 to 50.0, and the average crystal grain is on the plane parallel to the steel plate surface at the center position of the plate thickness of the electromagnetic steel plate. If the standard deviation when the diameter is standardized to 1.0 is 0.35 or less, the method is not limited to the above manufacturing method.

Hereinafter, specific examples of the present invention will be described by exemplifying examples. The present invention is not limited to the examples described below.

[Example 1]
A molten steel having the chemical composition shown in Table 1 was produced.

In the chemical composition of the above steel grades, the contents of O, Ti, V, Nb and Z were at the impurity level (0.01% or less). When the Ni and Cu columns in Table 1 are blank, it indicates that Ni and Cu were at the impurity level (Ni: 30 ppm or less, Cu: 20 ppm or less).

A slab was manufactured using molten steel. The slab was placed in a heating furnace and heated. A hot rolling process was carried out on the slab after heating to produce a hot-rolled steel sheet having a plate thickness of 2.0 mm. At this time, in each test number, either (1) hot rolling with austenite single phase + quenching, or (2) hot rolling with two phases of austenite and ferrite + cooling at a cooling rate higher than cooling rate. Was carried out. In the "condition" column of the "hot rolling process" in Table 2, "1" indicates that rolling was performed under the condition of (1) above, and "2" indicates that rolling was performed under the condition of (2) above. Indicates that rolling has been performed. When (1) was carried out, the temperature of the steel sheet 3 seconds after the finish rolling was completed was also measured. Table 2 shows the finish rolling temperature FT (° C.) and the steel sheet temperature (° C.) after 3 seconds when (1) was carried out.

Subsequently, in the test numbers 1 to 25, the cold rolling step was carried out on the hot-rolled steel sheet without performing the annealing treatment. On the other hand, in Test No. 26, the steel sheet after the hot rolling step was subjected to an annealing treatment of holding it at an annealing temperature of 600 ° C. for 60 seconds, and then a cold rolling step was carried out. Table 2 shows the rolling reduction ratio RR1 (%) in the cold rolling process at each test number.

Subsequently, an intermediate annealing step was carried out on the steel sheets of each test number after the cold rolling step. The intermediate annealing temperature T1 in the intermediate annealing step is as shown in Table 2. In test number 26, the experiment was terminated because cracks were observed in the steel sheet after the cold rolling process. In test number 26, since the annealing treatment was performed after the hot rolling process and before the cold rolling process, Mn segregated at the grain boundaries due to the annealing treatment, and as a result, the workability of the steel sheet deteriorated and cracks occurred. It is probable that it was done.

A strain amount adjusting rolling step for {100} <011> orientation was carried out on the steel sheets of each test number after the intermediate annealing treatment. {100} <011> The rolling reduction ratio RR2 (%) in the alignment strain adjustment rolling step is as shown in Table 2.

{100} <011> Adjustment of strain amount for orientation A finish annealing step was carried out on the steel sheets of each test number after the rolling step. The finish annealing temperature T2 in the finish annealing step is as shown in Table 2. The temperature rising rate TR2 was 0.1 to 10.0 ° C./sec, and the holding time Δt2 was 10 to 120 sec.

The electromagnetic steel sheets of each test number were manufactured by the above manufacturing method. The chemical composition of the manufactured electrical steel sheet was analyzed by the above-mentioned ICP-MS method. As a result, the chemical composition of each steel type was the same as the value shown in Table 1.

[Evaluation test]
The following evaluation tests were carried out on the electrical steel sheets of each test number.

[{100} <110> X-ray random intensity measurement test of crystal orientation]
A sample was taken from the steel plate of each test number, and the surface was mirror-polished. Among the mirror-polished regions, any region where the pixel measurement interval was 1/5 or less of the average crystal grain size and 5000 or more crystal grains could be measured was selected. EBSD measurements were performed in the selected regions to obtain pole figures of {200}, {110}, {310}, {211}. Using these extreme point diagrams, the ODF distribution representing the three-dimensional aggregate structure calculated by the series expansion method was obtained. From the obtained ODF, the X-ray random intensity ratio of {100} <011> crystal orientation was obtained. Table 2 shows the X-ray random intensity ratio of the obtained {100} <011> crystal orientation.

[Particle variation measurement test]
A sample having a square observation surface of 3 mm × 3 mm (the observation surface corresponds to the ND surface) at the center position of the plate thickness and parallel to the surface of the steel plate was prepared at an arbitrary part of the electromagnetic steel sheet of each test number. After the prepared observation surface was mirror-polished, the mirror-polished observation surface was etched with a nital solution. Among the etched observation surfaces, an arbitrary observation field of view was observed with an optical microscope to generate a photographic image containing 2000 or more identifiable crystal grains. Crystal grains were identified from the generated photographic image using an image processing device, and the identified crystal grains were approximated to an ellipse by an ellipse approximation method. The average value of the major axis and the minor axis of the obtained ellipse was defined as the crystal grain size (μm) of the specified crystal grains. The observation field of view was selected so that the number of specified crystal grains was 2000 or more. The average value of the crystal grain size of the specified crystal grains was defined as the average crystal grain size (μm). The total number of obtained average crystal grains was n, the average crystal grain size was d, the crystal grain size of the _i -th crystal grain was di, and the average crystal grain size was standardized to 1.0 from the following formula. The standard deviation s of the time was obtained. The obtained standard deviations s are shown in Table 2.

[Magnetic flux density measurement test in the direction of 45 ° from the rolling axis RD]
From the electromagnetic steel sheets of each test number, a single plate test piece of 55 mm × 55 mm was produced by punching. Using a single-plate magnetic measuring instrument, the magnetic flux density B ₅₀ (45 °) in the 45 ° direction from the rolling shaft RD was measured by the above method. The magnetic field at the time of measurement was 5000 A / m. The obtained magnetic flux density B ₅₀ (45 °) is shown in Table 2.

[Iron loss W _10/1000 at 1000 Hz]
From the electromagnetic steel sheets of each test number, a single plate test piece of 55 mm × 55 mm was produced by punching. Using a single plate magnetic measuring instrument, the iron loss W _10/1000 (W / kg) of the single plate test piece magnetized at a frequency of 1000 Hz and a maximum magnetic flux density of 1.0 T was measured. The results obtained are shown in Table 2.

[Punching accuracy evaluation test]
A punching accuracy evaluation test was carried out by the following method. The burr height was measured at the punched end face according to the method for measuring the burr height described in JIS C2550-2 (2011) 4.5.

[Evaluation results]
The evaluation results are shown in Table 2. With reference to Table 2, the chemical compositions of test numbers 1 to 11 were appropriate and the production conditions were also appropriate. Therefore, in the manufactured electromagnetic steel sheet, the X-ray random intensity ratio of {100} <011> crystal orientation on the steel sheet surface is 15.0 to 50.0, and the surface parallel to the steel plate surface at the center position of the plate thickness. When the average crystal grain size was standardized to 1.0, the standard deviation was 0.35 or less. As a result, the magnetic flux density B ₅₀ (45 °) was 1.650 T or more, and a high magnetic flux density was obtained. Further, the iron loss W _10/1000 was 95 W / kg or less, and a low iron loss was obtained. Further, the burr height in the punching dimensional accuracy evaluation test was 50 μm or less, and excellent dimensional accuracy was obtained.

On the other hand, in Test No. 12, the Mn content was too low. Therefore, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface was low. As a result, the magnetic flux density B ₅₀ (45 °) was less than 1.650 T.

In test number 13, the Mn content was too high. Therefore, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface was low. The magnetic flux density B ₅₀ (45 °) was less than 1.650 T, the iron loss W _10/1000 exceeded 95 W / kg, and the burr height in the punching dimensional accuracy evaluation test exceeded 50 μm. It is probable that the grain growth property was low because a large amount of MnS was precipitated during the manufacturing process.

In test number 14, the Si content was too low. Therefore, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface was low. Therefore, the magnetic flux density B ₅₀ (45 °) was less than 1.650 T. Further, since the Si content was low, the iron loss W _10/1000 exceeded 95 W / kg, and the burr height in the punching dimensional accuracy evaluation test exceeded 50 μm.

In test number 15, the Si content was too _high and there was no A3 transformation point. Therefore, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface was low. Therefore, the magnetic flux density B ₅₀ (45 °) was less than 1.650 T.

In test number 16, when the hot rolling step was carried out under condition 1, the finish rolling temperature FT was too low. Therefore, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface was low. As a result, the magnetic flux density B ₅₀ (45 °) was less than 1.650 T, and the iron loss W _10/1000 exceeded 95 W / kg.

In test number 17, when the hot rolling step was carried out under condition 1, the temperature of the steel sheet 3 seconds after the end of rolling exceeded 250 ° C. Therefore, the strain was not sufficiently accumulated, and the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface was low. As a result, the magnetic flux density B ₅₀ (45 °) was less than 1.650 T, and the iron loss W _10/1000 exceeded 95 W / kg.

In test number 18, the rolling reduction in the cold rolling process was too low. Therefore, the X-ray random intensity ratio was too low. Further, the standard deviation when the average crystal grain size was standardized to 1.0 on the plane parallel to the steel plate plate surface at the center position of the plate thickness exceeded 0.35, and the particle size variation occurred. As a result, the magnetic flux density B ₅₀ (45 °) was less than 1.650 T, and the magnetic flux density was low. Further, the iron loss W _10/1000 exceeded 95 W / kg, and the iron loss was high. Further, the burr height in the punching dimensional accuracy evaluation test exceeded 50 μm, and the dimensional accuracy was low.

In test number 19, the rolling reduction in the cold rolling process was too high. Therefore, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface was low. Further, the standard deviation when the average crystal grain size was standardized to 1.0 on the plane parallel to the steel plate plate surface at the center position of the plate thickness exceeded 0.35, and the particle size variation occurred. As a result, the magnetic flux density B ₅₀ (45 °) was less than 1.650 T, and the iron loss W _10/1000 exceeded 95 W / kg. Further, the burr height in the punching dimensional accuracy evaluation test exceeded 50 μm, and the dimensional accuracy was low. {111} grains are excessively generated in the intermediate annealing step after the cold rolling step, and strain-induced grain growth is desired. {100} <011> Crystal orientation grains are {100} <011> Before the strain adjustment rolling step for orientation It is probable that it did not exist sufficiently in.

In test number 20, the intermediate annealing temperature T1 in the intermediate annealing step was too low. Therefore, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface was too low. Further, the standard deviation when the average crystal grain size was standardized to 1.0 on the plane parallel to the steel plate plate surface at the center position of the plate thickness exceeded 0.35, and the particle size variation occurred. As a result, the magnetic flux density B ₅₀ (45 °) was less than 1.650 T, and the magnetic flux density was low. Further, the iron loss W _10/1000 exceeded 95 W / kg, and the iron loss was high. Further, the burr height in the punching dimensional accuracy evaluation test exceeded 50 μm, and the dimensional accuracy was low.

In test number 21, the intermediate annealing temperature T1 in the intermediate annealing step was too high. Therefore, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface was too low. Further, the standard deviation when the average crystal grain size was standardized to 1.0 on the plane parallel to the steel plate plate surface at the center position of the plate thickness exceeded 0.35, and the particle size variation occurred. As a result, the magnetic flux density B ₅₀ (45 °) was less than 1.650 T, and the magnetic flux density was low. Further, the iron loss W _10/1000 exceeded 95 W / kg, and the iron loss was high. Further, the burr height in the punching dimensional accuracy evaluation test exceeded 50 μm, and the dimensional accuracy was low.

In test number 22, the rolling reduction ratio RR2 in the {100} <011> alignment strain amount adjusting rolling step was too low. Therefore, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface was too low. Further, the standard deviation when the average crystal grain size was standardized to 1.0 on the plane parallel to the steel plate plate surface at the center position of the plate thickness exceeded 0.35, and the particle size variation occurred. As a result, the magnetic flux density B ₅₀ (45 °) was less than 1.650 T, and the magnetic flux density was low. Further, the iron loss W _10/1000 exceeded 95 W / kg, and the iron loss was high. Further, the burr height in the punching dimensional accuracy evaluation test exceeded 50 μm, and the dimensional accuracy was low.

In test number 23, the rolling reduction ratio RR2 in the {100} <011> alignment strain amount adjusting rolling step was too high. Therefore, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface was too low. Further, the standard deviation when the average crystal grain size was standardized to 1.0 on the plane parallel to the steel plate plate surface at the center position of the plate thickness exceeded 0.35, and the particle size variation occurred. As a result, the magnetic flux density B ₅₀ (45 °) was less than 1.650 T, and the magnetic flux density was low. Further, the iron loss W _10/1000 exceeded 95 W / kg, and the iron loss was high. Further, the burr height in the punching dimensional accuracy evaluation test exceeded 50 μm, and the dimensional accuracy was low.

In test number 24, the finish annealing temperature T2 in the finish annealing step was too low. Therefore, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface was too low. Further, the standard deviation when the average crystal grain size was standardized to 1.0 on the plane parallel to the steel plate plate surface at the center position of the plate thickness exceeded 0.35, and the particle size variation occurred. As a result, the magnetic flux density B ₅₀ (45 °) was less than 1.650 T, and the magnetic flux density was low. Further, the iron loss W _10/1000 exceeded 95 W / kg, and the iron loss was high. Further, the burr height in the punching dimensional accuracy evaluation test exceeded 50 μm, and the dimensional accuracy was low.

In test number 25, the finish annealing temperature T2 in the finish annealing step was too high. Therefore, the X-ray random intensity ratio of the {100} <011> crystal orientation on the steel plate surface was too low. Further, the standard deviation when the average crystal grain size was standardized to 1.0 on the plane parallel to the steel plate plate surface at the center position of the plate thickness exceeded 0.35, and the particle size variation occurred. As a result, the magnetic flux density B ₅₀ (45 °) was less than 1.650 T, and the magnetic flux density was low. Further, the iron loss W _10/1000 exceeded 95 W / kg, and the iron loss was high. Further, the burr height in the punching dimensional accuracy evaluation test exceeded 50 μm, and the dimensional accuracy was low.

The embodiment of the present invention has been described above. However, the embodiments described above are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and the above-mentioned embodiment can be appropriately modified and carried out within a range not deviating from the gist thereof.

Claims (4)

It ’s an electromagnetic steel sheet,
The chemical composition is
By mass%,
C: 0.0050% or less,
Si: 2.00-3.50%,
Mn: 2.50-4.50%,
P: 0.050% or less,
S: 0.0050% or less,
Al: 0.10% or less,
N: 0.0025% or less,
Ni: 0 to 1.000%,
Cu: 0 to 0.100% and
Remaining: Fe and impurities,
Consists of
The X-ray random intensity ratio of {100} <011> crystal orientation on the steel plate surface of the electrical steel sheet is 15.0 to 50.0.
The standard deviation when the average crystal grain size is standardized to 1.0 on the plane parallel to the steel plate surface at the center position of the plate thickness of the electromagnetic steel plate is 0.35 or less.
An electromagnetic steel sheet characterized by this. The electromagnetic steel sheet according to claim 1.
The thickness of the electromagnetic steel sheet is 0.25 to 0.50 mm.
An electromagnetic steel sheet characterized by this. The chemical composition is
By mass%,
C: 0.0050% or less,
Si: 2.00-3.50%,
Mn: 2.50-4.50%,
P: 0.050% or less,
S: 0.0050% or less,
Al: 0.10% or less,
N: 0.0025% or less,
Ni: 0 to 1.000%,
Cu: 0 to 0.100% and
Remaining: Fe and impurities,
The slab made of the material was heated to 1000 to 1200 ° C., and the heated slab was hot-rolled to produce a steel sheet.
(1) The finish rolling temperature in the hot rolling is set to the _Ac3 transformation point or higher, and the steel sheet temperature is set within 3 seconds after the rolling of the final pass for the steel sheet in which the rolling of the final pass in the hot rolling is completed. Cool to 250 ° C,
(2) The finish rolling temperature in the hot rolling is set to the _Ac3 transformation point −50 ° C. or lower, and after rolling the final pass, the product is cooled at a cooling rate equal to or higher than the cooling rate.
Hot rolling process and
A cold rolling step in which cold rolling is carried out at a rolling reduction of less than 50.0 to 85.0% without performing an annealing treatment on the steel sheet after the hot rolling step.
An intermediate annealing step in which the steel sheet after the cold rolling step is annealed at an intermediate annealing temperature of 500 ° C. to less than the _Ac1 transformation point.
The {100} <011> strain amount adjusting rolling step for orientation, in which cold rolling is performed on the steel sheet after the intermediate annealing step at a rolling reduction of 5.0 to 15.0%, and
The {100} <011> alignment strain amount adjustment The steel sheet after rolling is provided with a finish annealing step of performing an annealing treatment at a finish annealing temperature of 500 ° C. to less than the _Ac1 transformation point.
The {100} <011> crystal orientation X-ray random intensity ratio on the steel plate surface is 15.0 to 50.0, and the average crystal is formed on the plane parallel to the steel plate surface at the center position of the electromagnetic steel plate thickness. Manufacture electromagnetic steel sheets with a standard deviation of 0.35 or less when the particle size is standardized to 1.0.
A method for manufacturing electrical steel sheets, which is characterized by this. The method for manufacturing an electromagnetic steel sheet according to claim 3.
In the finish annealing step, the annealing process is performed by setting the temperature rise rate to the finish annealing temperature to less than 0.1 to 10.0 ° C./sec and the holding time of the steel sheet at the finish annealing temperature to 10 to 120 seconds. implement,
A method for manufacturing electrical steel sheets, which is characterized by this.

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