JP2020020005A - Method for manufacturing non-oriented silicon steel sheet - Google Patents

Abstract

To provide a method for manufacturing a non-oriented silicon steel sheet in which anisotropy of magnetic flux density in the entire circumferential direction is reduced.SOLUTION: The method for manufacturing non-oriented electromagnetic steel sheets includes the steps of: applying hot rolling to a slab; applying annealing to a hot-rolled sheet at 800-1,080°C for 5 seconds to 2 minutes; applying warm rolling at a rolling-reduction ratio of 3-75% in a temperature range of 400-700°C in a cooling process; and applying finish-annealing to a rolled sheet. When the magnetic flux densities at a magnetic field intensity of 5,000 A/m at 0°, 22.5°, 45°, 67.5°, 90° with respect to the rolling direction are defined as B, B, B, B, and B, respectively, an anisotropy index B50 defined by Equation (1) is equal to or less than 0.017. Bin Equation (1) is defined by Equation (2).SELECTED DRAWING: None

Description

  The present invention relates to a method for manufacturing a non-oriented electrical steel sheet.

Electrical steel sheets used for electrical equipment and the like are required to have high efficiency from the viewpoint of energy saving.
For example, compressors for air conditioners, various motors used in home appliances, and motors for driving motors, electric turbos, electric compressors, etc., use high-speed rotation and high-frequency excitation for miniaturization and high efficiency. There is an increasing demand for non-oriented electrical steel sheets having a low magnetic flux density and low anisotropy.

  Under such circumstances, various techniques have been conventionally employed with the aim of achieving a high magnetic flux density in the non-oriented electrical steel sheet.

Specifically, in order to improve magnetic properties while omitting hot-rolled sheet annealing, self-annealing is used, which replaces hot-rolled sheet annealing with the heat retained in the coil after finish hot rolling. For example, Patent Literature 1 describes a self-annealing technique.
Patent Literature 2 describes a technique for improving magnetic properties by finishing a hot-rolled finish at a high temperature without performing self-annealing and then setting a non-water injection time until winding.

  Further, as described in Patent Documents 3 and 4, a technology is employed in which light reduction rolling is performed before hot-rolled sheet annealing and strain-induced grain growth is performed during hot-rolled sheet annealing to improve magnetic properties. Have been.

  Patent Document 5 discloses that the grain growth of a hot-rolled sheet during self-annealing is uniformly increased by adding Sn to increase the crystal grain size before cold rolling, and the synergistic effect of controlling the texture during finish annealing by adding Sn. A technique for increasing the magnetic flux density by the effect is disclosed.

Patent Document 6 discloses a technique for defining a relationship between a final cold-rolling rate and a crystal grain size before cold-rolling by using an expression in producing a high-frequency thin non-oriented electrical steel sheet having a high frequency of 0.10 mm to 0.25 mm. Have been. In addition, hot-rolled sheet annealing, technology to control the grain size before cold rolling so as to satisfy a certain relational expression between the crystal grain size before cold rolling and the cold rolling reduction, furthermore, the non-oriented electrical steel sheet Technology for reducing surface roughness Ra to 0.5 μm or less, magnetism of steel sheet is measured every 22.5 °, and iron loss ΔW10 / 400, which is the difference between the maximum value and the minimum value, is 4.0 W / kg or less and magnetic flux A technique for controlling the density ΔB50 to 0.08T or less has been proposed.
Patent Document 7 discloses that, in mass%, C: 0.0005 to 0.010%, Mn: 0.05 to 1.5%, Si: 0.8 to 4.0%, Al: 0.1 to 4 0.0%, and the contents of Si, Al, and Mn satisfy the relationship of Si + 2Al-Mn ≧ 2, and the balance was obtained by hot rolling a steel material having a component composed of Fe and inevitable impurity elements. A method for producing a non-oriented electrical steel sheet in which a hot-rolled sheet is annealed, then cold-rolled, then recrystallized, and further subjected to final annealing through skin pass rolling, wherein the hot-rolled sheet has an annealing temperature Th of 1000. There is disclosed a method for producing a non-oriented electrical steel sheet having excellent circumferential properties and good workability, wherein the temperature is set to ≦ C ≦ Th ≦ 1150 ° C. and the rolling reduction CR of the cold rolling is set to 85% ≦ CR ≦ 93%.
Patent Document 8 discloses that C ≦ 0.01%, Si: 0.1% to 2.0%, Al ≦ 2.0%, Si + 2Al: 0.1% to 2.50%, Mn <% by weight. In a non-oriented electrical steel sheet containing 1.0%, Ni: 0.1% to 4%, and having a small amount of anisotropy, the balance being Fe and unavoidable impurities, the minimum value and the maximum value of the magnetic flux density _B50 value angular characteristic A non-oriented electrical steel sheet having a small anisotropy and having a value difference of 0.025T or less is disclosed.

  Patent Document 9 discloses that, in producing a non-oriented electrical steel sheet by the hot-rolled sheet annealing twice cold rolling method, the crystal grain size before the first cold rolling is controlled in a range of 10 to 60 μm, and the intermediate annealing is performed. A technique is disclosed in which the subsequent recrystallization rate is controlled in the range of 30 to 85% and the second cold rolling reduction is 3 to 30%.

In Patent Document 10, after hot-rolled sheet annealing at a temperature of 800 ° C. or more, in a rolling process including one or two times including intermediate annealing, a reduction of at least 20% or more is performed in a temperature range of 50 ° C. or more, A technique for performing finish annealing at a temperature of 850 ° C. or higher is disclosed.
Patent Literature 11 discloses a method for manufacturing a switch reluctance motor in which conditions such as a heating rate during finish annealing, a steel sheet tension, an oxidizing atmosphere, and a cooling rate are specified.

Patent Document 12 discloses a method of manufacturing a modular motor for power steering having a low rotation speed, in which finish annealing conditions are defined.
Patent Document 13 discloses a once-rolled hot-rolled sheet annealing cold rolling method.

JP-B-57-43132 JP-A-62-54023 JP-A-2-213418 JP-A-3-21258 JP 2002-294415 A JP 2001-295003 A JP 2008-45151 A JP-A-8-246108 JP 2001-49402 A JP 2000-144348 A JP 2005-240095 A JP 2006-144036 A JP 2005-307258 A

  However, the techniques of Patent Literature 1 and Patent Literature 2 do not extend to line annealing, and there is room for improvement in the in-plane anisotropy of the magnetic flux density. When applied to a high-speed rotating machine having the following requirements, there is an increasing demand for anisotropy reduction in magnetic flux density.

  In the techniques disclosed in Patent Documents 3 and 4, the hot-rolled sheet is subjected to light reduction and hot-rolled sheet annealing, and there is room for improvement in the in-plane anisotropy of the magnetic flux density. When used in a frame iron core, there is room for improving the uniformity of the flow of magnetic flux. Furthermore, when applied to a high-speed rotating machine that has recently been developed and reaches 20,000 to 200,000 rotations per minute, there is a need to reduce noise and vibration during use by reducing the anisotropy of magnetic flux density. Is growing.

  In the technique of Patent Document 5, there is room for improvement in the in-plane anisotropy of the magnetic flux density. For example, when used in a normal rotating machine, an EI core, or a frame iron core, there is room for further improving the uniformity of the magnetic flux flow. There is. Further, when applied to recent high-speed rotating machines, there is an increasing demand for reduction of noise and vibration during use due to reduction of anisotropy of magnetic flux density. In particular, in high-speed rotating machines that have been developed recently and reach 20,000 to 200,000 rotations per minute, demand for anisotropy reduction of magnetic flux density is increasing in terms of reduction of noise and vibration.

  The technologies of Patent Documents 6, 7, and 8 have recently been developed. In a high-speed rotating machine reaching 20,000 to 200,000 revolutions per minute, the anisotropic magnetic flux density is reduced in terms of noise and vibration reduction. There has been an increasing demand for reduced performance.

  In the technique of Patent Document 9, similarly to Patent Document 6, there is room for reducing the in-plane anisotropy of the magnetic flux density of the final product even by the twice method in which the process conditions are controlled, and the motor noise and vibration are improved. Also leave room. Furthermore, in the case of application to a high-speed rotating machine that has recently been developed and reaches 20,000 to 200,000 rotations per minute, there is an increasing demand for anisotropy reduction.

  In the technique of Patent Document 10, there is room for reducing the in-plane anisotropy of the magnetic flux density of the non-oriented electrical steel sheet subjected to hot-rolled sheet annealing, and there is room for reduction in motor noise and vibration improvement. Furthermore, in the case of application to a high-speed rotating machine that has recently been developed and reaches 20,000 to 200,000 rotations per minute, there is an increasing demand for anisotropy reduction.

  The technique of Patent Document 11 leaves room for manufacturing non-oriented electrical steel sheets having small anisotropy when applied to a high-efficiency motor. Further, in the case of this technology, there is an increasing demand for anisotropy reduction when it is applied to a high-speed rotating machine reaching 20,000 to 200,000 rotations per minute, which is being developed recently.

  The technique of Patent Document 12 is directed to a power steering modular motor having a low rotation speed, and the rotation speed of a general rotating machine is higher than that of the power steering, and there is an increasing demand for reducing noise and vibration. Furthermore, there is room for anisotropy reduction for higher-speed rotating machines that are being developed recently. For example, when applied to high-speed rotating machines that reach 20,000 to 200,000 rotations per minute, There is an increasing demand for anisotropy reduction.

  The technique of Patent Document 13 has room for reducing in-plane anisotropy of magnetic flux density. For example, there is room for reduction of anisotropy when applied to a high-speed rotating machine that has recently been developed. Further, when applied to a high-speed rotating machine that has recently been developed and reaches 20,000 to 200,000 rotations per minute, there is a growing demand for anisotropy reduction.

As described above, in the related art, it is not easy to reduce the anisotropy of the magnetic flux density in the entire circumferential direction (that is, the difference in the magnitude of the magnetic flux density caused by the direction), and it is required to reduce the anisotropy of the magnetic flux density. Was. When applied to the iron core of a rotating machine, it has been required to achieve reduction of noise and vibration, improvement of the maximum number of revolutions, and the like.
In such a background, the present inventors control the anisotropy of the magnetic flux density defined by a specific parameter, thereby reducing the torque fluctuation during rotation when applied to a rotating machine such as a motor and reducing noise. It was also found that vibrations were reduced and that the maximum number of revolutions could be increased.

  The present invention has been made based on the above findings, and has as its object to provide a manufacturing method for manufacturing a non-oriented electrical steel sheet with reduced anisotropy of magnetic flux density in all circumferential directions.

Means for solving the above-mentioned problem are as follows.
<1>
Hot rolling the slab to a hot-rolled steel sheet,
Hot-rolled steel sheet, hot-rolled sheet annealing step of performing hot-rolled sheet annealing at 800 ° C or higher and 1080 ° C or lower for 5 seconds or more and 2 minutes or less;
In the cooling process of the hot-rolled sheet annealing, a warm rolling step of performing warm rolling at a rolling reduction of 3% to 75% in a temperature range of 400 ° C to 700 ° C,
Finish annealing step of performing finish annealing on the rolled sheet after warm rolling,
With
The magnetic flux densities at directions of 0 °, 22.5 °, 45 °, 67.5 °, and 90 ° with respect to the rolling direction at a magnetic field strength of 5000 A / m are represented by B50 _{(0 °)} and B50, respectively. When expressed as _{50 (22.5 °)} , B _{50 (45 °)} , B _{50 (67.5 °)} , and B _{50 (90 °)} , the anisotropy index defined by the following formula (1) A method for producing a non-oriented electrical steel sheet, wherein the non-oriented electrical steel sheet has a B50 (anisotropy) of 0.017 or less.

Equation (1)
Here, in the equation (1), _B50AVE is defined by the following equation (2).

Equation (2)
<2>
<1> The method for producing a non-oriented electrical steel sheet according to <1>, wherein the warm rolling is performed twice or more at a temperature of more than 700 ° C and not more than 1080 ° C with an intermediate annealing of 5 seconds or more and 2 minutes or less.
<3>
The non-oriented electrical steel sheets, the magnetic flux density _{B 50} in the magnetic field strength 5000A / m at the rolling direction _{(0 °),} the magnetic flux density _{B 50} in the magnetic field strength 5000A / m in a direction at right angles to the rolling direction _{( 90 °)} , wherein the average magnetic flux density B _{50 (LC)} , which is an arithmetic average of the non-oriented electrical steel sheet, is 1.64 T or more, according to <1> or <2>.
<4>
The non-oriented electrical steel sheet is, in mass%,
Si: 0.1% to 3.8%,
Mn: 0.1% to 2.5%,
Al: 0% to 2.5%,
The method for producing a non-oriented electrical steel sheet according to any one of <1> to <3>, wherein the balance is a composition comprising Fe and impurities.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of manufacturing the non-oriented electrical steel sheet which reduced the anisotropy of the magnetic flux density of all the circumferential directions is provided.

  The present invention is to reduce the noise and the vibration by controlling the torque fluctuation during the rotation of the motor by the anisotropy of the magnetic flux density of the non-oriented electrical steel sheet. First, the results of an experiment that led to this technical knowledge will be described.

(Experiment 1)
The slab of steel type B is subjected to rough hot rolling at a heating temperature of 1100 ° C., and then subjected to finish hot rolling at a finishing temperature of 900 ° C. to finish a hot-rolled steel sheet to a thickness of 2.0 mm and cool it to 650 ° C. Wound on a coiler. From the hot-rolled steel sheet, two types of steel sheets BA and BB were manufactured by the following steps. Table 1 shows the chemical composition of the non-oriented electrical steel sheet obtained from the steel type B slab.

The steel sheet BA was manufactured as follows.
The hot-rolled steel sheet is subjected to hot-rolled sheet annealing at 975 ° C. for 60 seconds, and in the cooling process after the hot-rolled sheet annealing, is subjected to 30% rolling (warm rolling) in one pass to finish to a thickness of 1.4 mm. Cooled to room temperature. In the rolling at this time, the temperature at the stand entrance was 480 ° C, and the temperature at the stand exit was 410 ° C.
After pickling, the warm-rolled sheet was subjected to additional rolling at 20 ° C. (rolling start temperature) to a thickness of 0.25 mm. The highest attainable temperature due to the heat generated during processing during the additional rolling was 75 ° C. Thereafter, finish annealing at 970 ° C. for 20 seconds was performed.

The steel plate BB was manufactured as follows.
The hot-rolled steel sheet was annealed at 975 ° C. for 60 seconds, and then cooled to room temperature. This hot rolled annealed sheet was pickled and then rolled at 20 ° C. (rolling start temperature) to a thickness of 0.25 mm. The maximum temperature due to the heat generated during processing during the rolling was 75 ° C. Thereafter, finish annealing at 970 ° C. for 20 seconds was performed.

The obtained steel sheets BA and BB were cut into Epstein samples at intervals of 22.5 ° from the rolling direction, subjected to strain relief annealing, and subjected to Epstein measurement to obtain an anisotropy index B50 (anisotropic).
The B50 (anisotropic) of the steel sheet BA was 0.008, and the B50 (anisotropic) of the steel sheet BB was 0.019.

Further, a stator was manufactured using a steel plate BA or BB, and a permanent magnet synchronous high-speed rotation motor with a maximum output of 5 kW using a high-strength steel plate having a thickness of 0.35 mm and a tensile strength of 750 MPa as a rotor was manufactured.
The noise when the rotation speed of each motor was changed was measured based on JIS Z8731 (1999). Table 2 shows the results.
Vibration when the number of rotations of each motor was changed was evaluated in unit dB based on JIS C1510 (1995) with a reference vibration acceleration of 10 ⁻⁵ m / s ² . Table 3 shows the results.

  From these results, the steel sheet BA having a small anisotropy index B50 (anistropy) has reduced noise and vibration in the entire rotation speed range as compared with the steel sheet BB having a large anisotropy index B50 (anisotropic). Can be confirmed.

(Experiment 2)
A slab of steel type D is subjected to rough hot rolling at a heating temperature of 1100 ° C., and then subjected to finish hot rolling at a finishing temperature of 890 ° C. to finish a hot-rolled steel sheet to a thickness of 2.0 mm and cool it to 600 ° C. Wound on a coiler. From the hot-rolled steel sheet, two types of steel sheets DA and DB were manufactured by the following steps. Table 4 shows the chemical composition of the non-oriented electrical steel sheet obtained from the steel type D slab.

The steel sheet DA was manufactured as follows.
The hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 950 ° C. for 30 seconds, and in a cooling process after the hot-rolled sheet annealing, was rolled by 30% in one pass, finished to a thickness of 1.4 mm, and then cooled to room temperature. In the rolling at this time, the temperature at the stand entrance was 295 ° C., and the temperature at the stand exit was 200 ° C.
After this pickled plate was pickled, additional rolling was performed at 26 ° C. (rolling start temperature) to a thickness of 0.25 mm. The highest attained temperature due to the heat generated during processing during the additional rolling was 80 ° C. Thereafter, finish annealing was performed at 970 ° C. for 30 seconds.

The steel plate DB was manufactured as follows.
The hot-rolled steel sheet is subjected to hot-rolled sheet annealing at 950 ° C. for 30 seconds, and in the cooling process after the hot-rolled sheet annealing, is subjected to 30% rolling (warm rolling) in one pass to finish to a thickness of 1.4 mm. Cooled to room temperature. In the rolling at this time, the stand entrance temperature was 550 ° C, and the stand exit temperature was 470 ° C.
After pickling, the warm-rolled sheet was subjected to additional rolling at 26 ° C. (rolling start temperature) to a thickness of 0.25 mm. The highest attained temperature due to the heat generated during processing during the additional rolling was 80 ° C. Thereafter, finish annealing was performed at 970 ° C. for 30 seconds.

The obtained steel plates DA and DB were cut into Epstein samples at intervals of 22.5 ° from the rolling direction, subjected to strain relief annealing, and subjected to Epstein measurement to obtain an anisotropy index B50 (anisotropic).
B50 (anisotropic) of the steel plate DA was 0.021, and B50 (anisotropic) of the steel plate DB was 0.007.

Further, a stator was manufactured using the steel plate DA or DB, and a permanent magnet synchronous brushless synchronous motor having an output of 200 W was manufactured. The steel plate was used for the stator, and the rotor was attached with a neodymium bonded magnet on the rotating shaft, and reinforced around the neodymium bonded magnet with carbon fiber to withstand high-speed rotation.
The noise when the rotation speed of each motor was changed was measured based on JIS Z8731 (1999). Table 5 shows the results.
Vibration when the number of rotations of each motor was changed was evaluated in unit dB based on JIS C1510 (1995) with a reference vibration acceleration of 10 ⁻⁵ m / s ² . Table 6 shows the results.

  From these results, the steel plate DB having a small anisotropy index B50 (anisotropic) has reduced noise and vibration in the entire rotation speed range as compared with the steel plate DA having a large anisotropy index B50 (anisotropic). Can be confirmed. The results are the same as those in Experiment 1 described above, and it has been confirmed that the effect of reducing noise and vibration by controlling the anisotropy index B50 (anisotropic) can be obtained regardless of the type of motor.

Next, a method for manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention and a non-oriented electrical steel sheet manufactured by this manufacturing method will be described in detail.
In addition, in this specification, unless otherwise specified, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit and an upper limit.

<Non-oriented electrical steel sheet>
A non-oriented electrical steel sheet manufactured by the method for manufacturing a non-oriented electrical steel sheet according to the present embodiment (hereinafter, also simply referred to as a “non-oriented electrical steel sheet according to the present embodiment”) is 0 ° with respect to the rolling direction. , 22.5 °, 45 °, 67.5 °, and 90 °, the magnetic flux densities at a magnetic field strength of 5000 A / m are B _{50 (0 °)} , B _{50 (22.5 °)} , When expressed as B _{50 (45 °)} , B _{50 (67.5 °)} , and B _{50 (90 °)} , the anisotropy index B50 (anisotropic) defined by the following formula (1) is 0.017. It is as follows.

Equation (1)

Here, in the equation (1), _B50AVE is defined by the following equation (2).

Equation (2)

-Anisotropy index B50 (anisotropic)
In the present embodiment, the anisotropy in the circumferential direction of the magnetic flux density is evaluated by Expression (1). That is, the anisotropy index B50 (anisotropic) defined by the expression (1) is 0 °, 22.5 °, 45 °, 67.5 °, and 90 ° with respect to the rolling direction. Of the magnetic flux density at a magnetic field intensity of 5000 A / m. When the anisotropy index B50 (anisotropy) defined by the expression (1) is 0.017 or less, the anisotropy of the magnetic flux density in all circumferential directions decreases.
Thus, when applied to a rotating machine such as a motor, the characteristics of the rotating core are improved, such as a reduction in torque fluctuation during rotation, a reduction in noise and vibration, and an increase in the maximum number of revolutions.
Also, when applied to other EI cores, picture frame cores, etc., the change in the ease of flow of the magnetic flux depending on the direction of the yoke is reduced, the iron core with high uniformity of the magnetic characteristics is obtained, and the magnetic attraction force is improved. The iron core characteristics can be improved, for example, the current can be reduced by improving the force.
The lower limit of the anisotropy index B50 (anisotropy) is 0 or more.

The anisotropy index B50 (anisotropy) is more preferably 0.015 or less, and still more preferably 0.013 or less, from the viewpoint of reducing the anisotropy of the magnetic flux density in all circumferential directions.
In addition, the lower limit of the anisotropy index B50 (anisotropic) is not particularly limited, but is preferably 0.003 or more, more preferably 0.005 or more, from the viewpoint of stable production.

The magnetic flux density is obtained by cutting an Epstein sample and measuring the magnetic flux density at a magnetic field intensity of 5000 A / m according to the Epstein method specified in JIS C2550-1.
The anisotropy index B50 (anisotropic) of the non-oriented electrical steel sheet can be controlled in the above range by producing the anisotropy index B50 (anisotropic) by the following method for manufacturing a non-oriented electrical steel sheet according to the present embodiment.

・ Average magnetic flux density B _{50 (LC)}
The non-oriented electrical steel sheet according to this embodiment has a magnetic flux density _{BB50 (0 °)} at a magnetic field strength of 5000 A / m in the rolling direction and a magnetic flux density at a magnetic field strength of 5000 A / m perpendicular to the rolling direction. The average magnetic flux density _{B50 ( LC)} , which is the arithmetic average of BB50 _{(90 °)} , is preferably higher, for example, 1.64T or more. When the average magnetic flux density B50 _(LC) is 1.64T or more, high magnetic flux density of the non-oriented electrical steel sheet is realized, and when applied to a rotating machine such as a motor, high-speed rotation and high-frequency excitation are realized. And high efficiency can be achieved.
Average magnetic flux density B50 _(LC) is more preferably 1.66 T or more, and still more preferably 1.68 T or more.
The upper limit of the average magnetic flux density B50 _(LC) is not particularly limited, but is preferably 1.90 T or less, more preferably 1.80 T or less, from the viewpoint of stably reducing anisotropy. .
The method for controlling the average magnetic flux density B50 _(LC) to be in the range of 1.64 T or more is not particularly limited. For example, the method is manufactured by the following method for manufacturing a non-oriented electrical steel sheet according to the present embodiment. Method.

_-Iron loss In the non-oriented electrical steel sheet according to the present embodiment, the iron loss ( _{W10 / 400} ) is preferably lower.
For example, the range is preferably 7.5 W / kg or more and 11.0 W / kg or less (more preferably 7.8 W / kg or more and 10.5 W / kg or less) for a 0.20 mm thick material. In a 0.25 mm-thick material, it is preferably 8.0 W / kg or more and 12.5 W / kg or less (more preferably, 8.5 W / kg or more and 11.5 W / k or less). In a 0.30 mm-thick material, It is preferably 11.0 W / kg or more and 15.0 W / kg or less (more preferably 11.5 W / kg or more and 13.5 W / kg or less). For a 0.35 mm thick material, 14.0 W / kg or more. It is preferably 20.0 W / kg or less (more preferably 14.5 W / kg or more and 18.0 W / kg or less). When the sheet thickness further increases, an appropriate iron loss range is determined accordingly. The lower limit of the iron loss is determined from the viewpoint of production stability such as cold rolling stability and obtaining stable characteristics. The upper limit of the iron loss is determined from characteristics determined for each sheet thickness required for a high-efficiency iron core.
As the iron loss, an iron loss generated when the sample is cut into an Epstein sample and the inverter excitation is measured by the Epstein method is used. Specifically, an iron loss W _10/400 (W / kg) when magnetized at a magnetic flux density of 1.0 T and a frequency of 400 Hz is used.

<Production method of non-oriented electrical steel sheet>
The manufacturing method of the non-oriented electrical steel sheet according to the present embodiment is to perform hot rolling on the slab, to perform a hot rolling step to make a hot-rolled steel sheet, and to hot-rolled steel sheet after hot rolling, at 800 ° C or more and 1080 ° C or less. In the hot-rolled sheet annealing step of performing hot-rolled sheet annealing for 5 seconds or more and 2 minutes or less, and in the cooling process of hot-rolled sheet annealing, a temperature reduction of 3% or more and 75% or less in a temperature range of 400 ° C or more and 700 ° C or less. The method includes a warm rolling step of performing cold rolling on a rolled sheet, and a finish annealing step of performing finish annealing on the rolled sheet after the warm rolling. Then, through these steps, a non-oriented electrical steel sheet in which the anisotropy index B50 (anisotropic) defined by the formula (1) is in the above range is manufactured.

  The warm rolling can be performed twice or more. The second and subsequent warm rolling may be performed by performing intermediate annealing in a temperature range sufficiently higher than the temperature range of the warm rolling, and may be performed in a temperature range of 400 ° C. or more and 700 ° C. or less in the cooling process.

  According to the method for manufacturing a non-oriented electrical steel sheet of the present embodiment, a non-oriented electrical steel sheet having improved magnetic flux density and reduced anisotropy of magnetic flux density can be obtained.

  Hereinafter, the method for manufacturing a non-oriented electrical steel sheet according to the present embodiment will be described in detail in the order of steps.

1. Hot Rolling Step In the method for producing a non-oriented electrical steel sheet of the present embodiment, first, a slab is subjected to hot rolling (hot rolling). The slab that can be used in the present embodiment and the chemical composition of the non-oriented electrical steel sheet and the like obtained from the slab will be described later in detail.
Various conditions of the hot rolling are not particularly limited, and may be performed according to known conditions. For example, a slab having a thickness of 150 to 300 mm is heated to 1000 to 1300 ° C., and is rolled to a thickness of 1 to 3 mm with the final temperature of the exit of the rolling stand being 800 to 1100 ° C. The steel sheet that has exited the rolling stand is cooled to 400 to 900 ° C. and wound around a coil.

2. Hot Rolled Sheet Annealing Step In the manufacturing method of the present embodiment, hot rolled sheet annealing is performed on the hot rolled steel sheet that has completed the hot rolling step.
Various conditions for hot-rolled sheet annealing are not particularly limited, and may be performed according to known conditions.
The maximum temperature is, for example, 800 ° C. to 1080 ° C., preferably 830 ° C. to 1050 ° C., and more preferably 850 ° C. to 1000 ° C. If the temperature is lower than 800 ° C., the effect is insufficient. If the temperature exceeds 1080 ° C., it is difficult to prevent the surface oxidation of the steel sheet.
The retention time is, for example, 5 seconds or more and 2 minutes or less, preferably 10 seconds or more and 90 seconds or less, and more preferably 15 seconds or more and 60 seconds or less.

3. Warm Rolling Step In the manufacturing method of the present embodiment, after the hot rolled sheet annealing, warm rolling is performed in a cooling process of the hot rolled sheet annealing. Performing this warm rolling in the cooling process of the hot-rolled sheet annealing is a major feature of the manufacturing method of the present embodiment.
In this specification, warm rolling refers to rolling performed in a temperature range of 400 ° C. or more and 700 ° C. or less. In rolling, it is conceivable that the temperature of the steel sheet increases due to the heat generated during processing. However, in the above temperature range, generally, the heat removal by the rolling rolls is large, and the temperature of the steel sheet tends to decrease during rolling. Therefore, in the cooling process of hot-rolled sheet annealing, in order to perform rolling in the above temperature range, rolling should be started before the steel sheet temperature reaches 400 ° C.
The heating is preferably performed at 425 ° C to 650 ° C, more preferably at 450 ° C to 600 ° C. In the present embodiment, it is assumed that warm rolling is performed when both the entrance and exit temperatures of the rolling stand are within the above temperature range. This is because the steel sheet needs to satisfy the temperature range of the present embodiment, including the temperature change of the steel sheet due to the heat generated during processing and the removal of heat from the roll during warm rolling.

The warm rolling can be performed not only in one step in the cooling process of the hot-rolled sheet annealing described above, but also in two or more steps in addition to this.
When performing the second or subsequent warm rolling, the steel sheet that has been subjected to the first warm rolling is reheated to perform the warm rolling. At this time, the first time, the second time, and the third and subsequent warm rolling are distinguished by performing reheating before the warm rolling. Before the second and subsequent warm rolling, intermediate annealing described below may be performed. In this case, the second and subsequent warm rolling is performed in a temperature range of 400 ° C or more and 700 ° C or less in the cooling process of the intermediate annealing. It is also possible to carry out.

It is not clear why warm rolling is performed in the cooling process of hot-rolled sheet annealing to produce a non-oriented electrical steel sheet with reduced anisotropy of magnetic flux density in all circumferential directions, but it is not clear as follows. I guess.
The following three points are characteristic of the situation of the cooling process of hot-rolled sheet annealing. The first point is that the temperature of the surface layer of the steel sheet to be rolled is significantly lower than that of the center layer because of the cooling process. For example, it is considered that the temperature difference between the inner surface layer at the time of 700 ° C. in the cooling process of the steel sheet heated and maintained at 1000 ° C. is larger than the temperature difference of the inner surface layer at the time of 700 ° C. of the steel plate heated and maintained at 710 ° C. Can be Second, it is considered that if the immediately preceding heat treatment temperature is different, the state of the precipitate during cooling is different. In particular, in a heat treatment at a high temperature for a short time such as hot-rolled sheet annealing, the surface layer of the steel sheet is considered to be in an overheated state. Alternatively, it is conceivable that the form of the precipitate is largely changed, including nitriding. A third point is that the thickness of the steel sheet to be simply rolled is large. The inventors presume that this is because the effect of warm rolling becomes more remarkable because a thicker sheet has a larger thickness reduction even at the same reduction ratio.
In these circumstances, by performing rolling in the above range, the crystal rotation of the steel sheet surface layer and the central layer becomes special, and the cold rolling to be performed as necessary, and further the texture after finish annealing are carried out. It is considered that the anisotropy index B50 (anisotropy) defined by the form is satisfied.

The rolling reduction of the warm rolling is 3% or more and 75% or less, preferably 5% or more and 70% or less, and more preferably 10% or more and 65% or less. If it is less than 3%, the effect of reducing the anisotropy of the magnetic flux density cannot be obtained, so it is determined to be 3% or more. If it exceeds 75%, the anisotropy of the magnetic flux density increases, so it is set to 75% or less.
When performing the warm rolling in two or more times, the rolling reduction is obtained by converting the sum of the true strains imparted in each of the warm rolling. That is, assuming that the incoming side sheet thickness in one warm rolling is l ₀ and the outgoing side sheet thickness is l, the true strain imparted in one warm rolling is ln (l ₀ / l), and a plurality of times The true strain for warm rolling is summed. When the above-mentioned appropriate range of the rolling reduction of the warm rolling is 3% or more and 75% or less, the total true strain is 0.031 or more and 1.386 or less when converted to true strain.

4. Intermediate annealing step Intermediate annealing is a step of raising the temperature of a steel sheet to over 700 ° C. after warm rolling. The intermediate annealing may be performed by cooling the immediately preceding hot-rolled sheet (for example, cooling to about room temperature) and then reheating the sheet, or may be performed while maintaining the temperature of 400 ° C. or more after the warm rolling (for example, during warming). Intermediate annealing may be performed by reheating (without lowering the temperature from the end temperature of rolling). It is preferable that the temperature of the intermediate annealing be higher than 700 ° C. since the effect of improving the magnetic properties can be obtained well. The upper limit of the temperature of the intermediate annealing is preferably set to 1080 ° C. By setting the temperature to 1080 ° C. or lower, surface oxidation of the steel strip can be favorably prevented.
The retention time in the intermediate annealing is preferably from 5 seconds to 2 minutes, more preferably from 10 seconds to 90 seconds, even more preferably from 15 seconds to 60 seconds. When the intermediate annealing is performed two or more times, the holding time is a total time of each time. When the time is 5 seconds or longer, the effect of improving the magnetic properties can be favorably obtained. If the time is less than 2 minutes, the effect of improving the magnetic properties is not saturated, that is, annealing that does not contribute to the effect of improving the magnetic properties can be suppressed.

  When the warm rolling or the intermediate annealing is performed two or more times, the conditions for each time need not be the same, and may be different.

5. Cold Rolling Step In the present embodiment, cold rolling may be performed as necessary.
In this specification, cold rolling refers to rolling performed in a temperature range of less than 400 ° C. In consideration of the distinction from the above-mentioned warm rolling, the rolling in which at least one of the inlet and outlet temperatures of the rolling stand is less than 400 ° C. is determined to be cold rolling. The reaction is preferably carried out at 5 ° C to 250 ° C, more preferably at 25 ° C to 200 ° C, even more preferably at 35 ° C to 150 ° C. The lower limit of the temperature of the cold rolling is preferably the above range from the viewpoint of ensuring the rolling stability of the steel sheet, and the upper limit is preferably the above range from the viewpoint of extending the life of the roll and the lubricating oil and reducing the maintenance cost of the cold rolling mill. .
However, when the hardness of the steel sheet is high, the steel sheet is heated in a coil state by a known method such as hot bath heating with hot water, induction heating, or the like, in order to stabilize the rolling property, and the steel sheet at the entrance side of the rolling stand is heated. The temperature may be raised, for example, to 50 ° C. or higher. In this case, the temperature of the steel sheet at the exit side of the rolling stand may reach about 200 ° C. due to the heat generated during processing.
In addition, in order to reduce the hardness of the steel sheet by using the heat generated during processing and to improve the passability of the sheet material, the lubricating oil is reduced to promote the heat generated during processing, and the temperature of the steel sheet is raised up to 250 ° C. as an upper limit. May be performed.

Although various patterns are possible for the timing of performing the second and subsequent warm rolling and cold rolling, as described above, the warm rolling in the present embodiment is performed in a situation where the sheet thickness is large. Considering what should be done, it is advantageous to perform the second warm rolling before the cold rolling.
After completion of hot rolling, pickling may be performed in a process prior to cold rolling.

  The rolling reduction of the cold rolling is not particularly limited as long as the operation and effect of the present embodiment can be obtained, but is preferably 50% or more and 97% or less, and particularly preferably 60% or more and 88% or less. Is preferred. When the rolling reduction is 50% or more, it becomes easy to achieve appropriate magnetic properties after finish annealing. When the rolling reduction is 97% or less, the texture of the non-oriented electrical steel sheet can be appropriately controlled, and iron loss can be easily reduced.

  In the present embodiment, the thickness of the final rolled plate is preferably 0.10 mm or more and 0.65 mm or less after the above-mentioned warm rolling (and further cold rolling if necessary), and particularly preferably It is preferable that the thickness be not less than .15 mm and not more than 0.35 mm.

6. Finish Annealing Step In the finish annealing step, a finish annealing is performed on the rolled sheet that has been subjected to the warm rolling step (and further to the cold rolling step when cold rolling is performed).

  The conditions of the finish annealing are not particularly limited as long as the operation and effect of the present embodiment can be obtained. However, for the purpose of preventing oxidation during annealing to prevent an increase in iron loss and controlling crystal grains to reduce iron loss, it is preferable that the temperature is maintained in a temperature range of 700 ° C. or more and 1100 ° C. or less, and especially 750 ° C. or more. It is preferable to maintain the temperature in a temperature range of 1050 ° C. or lower. In this case, the holding time is preferably from 0.1 to 120 seconds, and more preferably from 10 to 60 seconds.

7. Other Steps The method for manufacturing a non-oriented electrical steel sheet according to the present embodiment is characterized in that, after the above-described finish annealing step, a coating liquid is applied to the steel sheet surface obtained by the above-mentioned finish annealing step and baked to form an insulating film. A film forming step may be provided. The conditions for forming the insulating film and the coating liquid are performed by a known method using commonly used materials.

<Chemical composition of slab and non-oriented electrical steel sheet>
Next, the slab used in the method for manufacturing a non-oriented electrical steel sheet according to the present embodiment and the chemical composition of the non-oriented electrical steel sheet obtained by the manufacturing method will be described.
The chemical composition of the non-oriented electrical steel sheet obtained by the manufacturing method according to the present embodiment is not particularly limited as long as the effects of the present embodiment can be obtained, for example, a general non-oriented electrical steel sheet Can be used. Also, the chemical composition of the slab that can be used in the manufacturing method according to the present embodiment is the same as that of the non-oriented electrical steel sheet.
The chemical composition contains, by mass%, Si: 0.1% to 3.8%, Mn: 0.1% to 2.5%, and Al: 0% to 2.5%. Preferably, the balance is made of Fe and impurities.
Hereinafter, preferable contents of each component will be described. In the following, the content of each component is a value in mass%.

a. Si
It is preferable that the Si content be 0.1% or more and 3.8% or less.

  Since Si has an effect of increasing the specific resistance, it contributes to reducing iron loss. Therefore, from the viewpoint of reducing iron loss, the Si content is preferably set to 0.1% or more, particularly preferably 1.0% or more, particularly preferably 2.0% or more. On the other hand, from the viewpoint of improving magnetic properties and rolling manufacturability and suppressing an increase in the finish annealing temperature, the Si content is preferably set to 3.8% or less, among which 3.6% or less, particularly 3.4%. It is preferable to set the following.

b. Mn
It is preferable that the Mn content be 0.1% or more and 2.5% or less.

  Since Mn also has the effect of increasing the specific resistance, it contributes to reducing iron loss. Therefore, from the viewpoint of reducing iron loss, the Mn content is preferably set to 0.1% or more, more preferably 0.2% or more, particularly preferably 0.5% or more. If the content is too large, the recrystallized structure is refined and iron loss is increased. Therefore, the content is preferably 2.5% or less, more preferably 1.3% or less, and further preferably 1.0% or less.

c. Al
The slab in the present embodiment and the non-oriented electrical steel sheet obtained by the present embodiment may not intentionally contain Al or may intentionally contain Al. Preferably, the Al content is 0% or more and 2.5% or less.

  When Al is contained, from the viewpoint of reducing iron loss, the Al content is preferably 0.1% or more and 2.5% or less, more preferably 0.3% or more and 2.3% or less, particularly 0.1% or less. It is preferable that the content be 9% or more and 2.0%.

d. Remainder The remainder is Fe and impurities.

  The slab in the manufacturing method of the present embodiment and the non-oriented electrical steel sheet obtained by the present embodiment may include impurities that are various elements that can be mixed as long as the effects of the present embodiment are not impaired. Examples of the impurities include Ti, Nb, As, Zr, and P in addition to C, N, and S.

  The C content is preferably 0% or more and 0.003% or less from the viewpoint of improving magnetic properties, and particularly preferably 0% or more and 0.002% or less, particularly 0% or more and 0.001% or less. preferable. By setting the content to 0.001% or less, particularly excellent magnetic characteristics can be obtained.

  The N content is preferably 0% or more and 0.003% or less from the viewpoint of improving magnetic properties, and particularly preferably 0% or more and 0.002% or less, particularly 0% or more and 0.001% or less. preferable. By setting the content to 0.001% or less, particularly excellent magnetic characteristics can be obtained.

  The S content is preferably 0% or more and 0.003% or less from the viewpoint of improving magnetic properties, and particularly preferably 0% or more and 0.002% or less, particularly 0% or more and 0.001% or less. preferable. By setting the content to 0.001% or less, particularly excellent magnetic characteristics can be obtained.

  The Ti content is preferably 0% or more and 0.004% or less, particularly preferably 0% or more and 0.003% or less, from the viewpoint of improving magnetic properties. In order to obtain particularly excellent magnetic properties, it is particularly preferable that the content be 0% or more and 0.002% or less.

  The Nb content is preferably 0% or more and 0.003% or less from the viewpoint of improving magnetic properties, and particularly preferably 0% or more and 0.002% or less, particularly 0% or more and 0.001% or less. preferable. By setting the content to 0.001% or less, particularly excellent magnetic characteristics can be obtained.

  From the viewpoint of improving magnetic properties, the As content is preferably 0% or more and 0.003% or less, and particularly preferably 0% or more and 0.002% or less, particularly 0% or more and 0.001% or less. preferable. By setting the content to 0.001% or less, particularly excellent magnetic characteristics can be obtained.

  The Zr content is preferably 0% or more and 0.003% or less from the viewpoint of improving magnetic properties, and particularly preferably 0% or more and 0.002% or less, particularly 0% or more and 0.001% or less. preferable. By setting the content to 0.001% or less, particularly excellent magnetic characteristics can be obtained.

  The P content is preferably 0% or more and 0.25% or less, and more preferably 0% or more and 0.15% or less, from the viewpoint of improving magnetic properties. In order to obtain particularly excellent magnetic properties, the content is particularly preferably 0% or more and 0.10% or less, and more preferably 0% or more and 0.05% or less.

  From the viewpoint of improving magnetic properties, the content of the entire impurity is preferably 0% or more and 0.1% or less, and particularly preferably 0% or more and 0.05% or less.

-Chemical composition measurement method-
The slab in the production method of the present embodiment, and the content of each element in the non-oriented electrical steel sheet obtained by the present embodiment, depending on the type of element, using a general method, under general measurement conditions Can be measured.

  The contents of Si, Mn, Al, Ti, Nb, and Zr can be measured using, for example, an ICP-MS method (inductively coupled plasma mass spectrometry). The As content can be measured, for example, by the AA method (flameless atomic absorption method). The contents of C and S can be measured by, for example, a combustion infrared absorption method. The N content can be measured by a heat melting-heat conduction method.

  If no insulating coating or other layers are formed on the non-oriented electrical steel sheet obtained by the production method of the present embodiment, a part of the non-oriented electrical steel sheet is cut and weighed to obtain a measurement sample. . When the insulating coating and other layers are formed on the non-oriented electrical steel sheet, after removing the insulating coating and other layers in advance by a general method, a part of the non-oriented electrical steel sheet is cut off. Weigh and use as a sample for measurement.

  When the ICP-MS method is used, the above-described sample for measurement is dissolved in an acid, and if necessary, heated to obtain an acid solution. The residue dissolved in the acid is recovered by filter paper and separately melted in an alkali or the like, and the melt is extracted with an acid to form a solution. The solution and the acid solution are mixed together and, if necessary, diluted to obtain a solution for ICP-MS measurement.

  The present invention is not limited to the embodiments described above. The above-described embodiment is an exemplification, and any configuration having substantially the same configuration as the technical idea described in the claims of the present invention and having the same effect can be obtained. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be specifically described by way of examples and comparative examples. It should be noted that the conditions of the examples are examples adopted for confirming the feasibility and effects of the present invention, and the present invention is not limited to the conditions of the examples. The present invention can employ various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Evaluation method)
Here, various characteristics used for evaluation in Examples and Comparative Examples will be described.

・ Iron loss As the iron loss of the non-oriented electrical steel sheet, cut into Epstein samples and use the iron loss generated when the inverter is excited. Specifically, an iron loss W _10/400 (W / kg) when magnetized at a magnetic flux density of 1.0 T and a frequency of 400 Hz is used. The measurement is performed by the Epstein method specified in JIS C2550-1.

-Magnetic flux density The magnetic flux density at a magnetic field intensity of 5000 A / m is measured by the following method. An Epstein sample is cut, and magnetic measurement is performed using the sample according to the Epstein method specified in JIS C2550-1.

-Motor for noise and vibration measurement One of the following two types of motors is manufactured from non-oriented electrical steel sheets for evaluation, and noise and vibration are measured.
Motor A: A permanent magnet synchronous high-speed motor with a maximum output of 5 kW using a high-strength steel plate having a thickness of 0.35 mm and a tensile strength of 750 MPa for the rotor, the stator being made of a non-oriented electrical steel sheet for evaluation, and a motor B : The stator was made of a non-oriented electrical steel sheet for evaluation, the rotor was attached with a neodymium bonded magnet on the rotating shaft, and wrapped around the neodymium bonded magnet with carbon fiber to withstand high-speed rotation and reinforced. Magnet synchronous brushless synchronous motor

-Noise The noise when the measuring motor is rotated at 400,000 rpm is measured based on JIS Z8731 (1999).

Vibration Vibration when the measuring motor is rotated at 400,000 rpm is evaluated based on JIS C1510 (1995) with a reference vibration acceleration of 10 ⁻⁵ m / s ² in units of dB.

(Example 1)
The slab of steel type A was hot-rolled at a heating temperature of 1100 ° C. and a finishing temperature of 900 ° C., finished to a thickness of 2.0 mm, cooled to 700 ° C., and wound around a coiler. Table 7 shows the chemical composition of the non-oriented electrical steel sheet obtained from the steel type A slab.
The hot-rolled steel sheet is subjected to hot-rolled sheet annealing at 950 ° C. for 30 seconds. When the temperature reaches 540 ° C. in the cooling process after the hot-rolled sheet annealing, the steel sheet is subjected to a 25% reduction in one pass and rolled at 470 ° C. (warm rolling) ) Was finished, finished to a thickness of 1.5 mm, and then cooled to room temperature.
After pickling, the warm-rolled sheet was cold-rolled (rolling start temperature: 25 ° C., maximum temperature: 70 ° C.) to a thickness of 0.25 mm, and subjected to finish annealing at 900 ° C. for 30 seconds (steel sheet No. A-). 1).

Further, the hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 950 ° C. for 30 seconds under the same conditions as described above until wound into a coiler, and then cooled to room temperature. The hot-rolled annealed sheet was reheated to 540 ° C., subjected to 25% reduction in one pass at a rolling start temperature of 540 ° C., rolled at 470 ° C. (warm rolling), finished to a thickness of 1.5 mm, and then to room temperature. Cool.
After pickling, the warm-rolled sheet was cold-rolled (rolling start temperature: 25 ° C., maximum temperature: 70 ° C.) to a thickness of 0.25 mm, and subjected to finish annealing at 900 ° C. for 30 seconds (steel sheet No. A-). 2).

  Further, the hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 950 ° C. for 30 seconds under the same conditions as described above until wound into a coiler, and then cooled to room temperature. After pickling, the hot-rolled annealed sheet was cold-rolled (rolling start temperature: 25 ° C., maximum temperature: 70 ° C.) to a thickness of 0.25 mm, and finish-annealed at 900 ° C. for 30 seconds (Steel sheet No. A-). 3).

Epstein samples were cut out from each of the obtained non-oriented electrical steel sheets at intervals of 22.5 ° from the rolling direction, subjected to strain relief annealing, and then subjected to Epstein measurement.
A motor A was manufactured using these steel plates as a stator, and noise and vibration at 400,000 rpm were measured. The noise was 80 dB or less and the vibration was 70 dB or less.
Table 8 shows the magnetic measurement results and the motor noise and vibration measurement results of the example and the comparative example.

As can be seen from Table 8, in this embodiment, the value of the anisotropy B50 (anisotropic) of the magnetic flux density is 0.011, which is smaller than that of the comparative example.
In this embodiment, the average magnetic flux density B _{50 (LC),} which is the arithmetic average of the magnetic flux density B _{50 (0 °) in the} rolling direction and the magnetic flux density B _{50 (90 °)} in the direction perpendicular to the rolling direction, is compared. Higher than the example.
Further, in the present embodiment, the noise of the motor A at 400,000 rpm is 80 dB or less and the vibration is 70 dB or less, and it can be seen that the noise and the vibration at the high speed rotation of the motor A are reduced as compared with the comparative example.
In addition, even if rolling is performed under the same warm rolling conditions, the effect of the present disclosure is lost when the temperature of the steel sheet is once cooled to room temperature after hot-rolled sheet annealing. It can be seen from the measurement results of the magnetic characteristics, motor noise and vibration of A-2.
As described above, according to the present embodiment, it is possible to manufacture a non-oriented electrical steel sheet having high magnetic flux density and small anisotropy of magnetic flux density. In addition, the iron loss value W _10/400 is as low as 9.63 W / kg, which is excellent.

(Example 2)
The slab of steel type B was subjected to hot rolling at a heating temperature of 1100 ° C. and a finishing temperature of 900 ° C. to finish the slab to a thickness of 2.0 mm, cooled to 650 ° C., and wound around a coiler. Table 9 shows the chemical composition of the non-oriented electrical steel sheet obtained from the steel type B slab.
The hot-rolled steel sheet is subjected to hot-rolled sheet annealing for 60 seconds while changing the temperature, and in the cooling process after the hot-rolled sheet annealing, is subjected to 30% 1-pass reduction at 480 ° C and rolled at 410 ° C (warm rolling). Was completed, and finished to a thickness of 1.4 mm, and then cooled to room temperature.
After pickling, the warm-rolled sheet was cold-rolled (rolling start temperature: 20 ° C., maximum temperature: 75 ° C.) to a thickness of 0.25 mm, and subjected to finish annealing at 970 ° C. for 20 seconds (steel sheet No. B-). 1-6).

  Further, a hot-rolled steel sheet was subjected to a hot-rolled sheet annealing for 60 seconds at a different temperature and then cooled to room temperature under the same conditions as above until winding into a coiler. After pickling, the hot-rolled annealed sheet was cold-rolled (rolling start temperature: 20 ° C., maximum temperature: 75 ° C.) to a thickness of 0.25 mm, and subjected to finish annealing at 970 ° C. for 20 seconds (steel sheet No. B-). 7-12).

The obtained non-oriented electrical steel sheet was cut into Epstein samples every 22.5 ° from the rolling direction, subjected to strain relief annealing, and then subjected to Epstein measurement.
A motor A was manufactured using these steel plates as a stator, and noise and vibration at 400,000 rpm were measured. The noise was 80 dB or less and the vibration was 70 dB or less.
Table 10 shows the magnetic measurement results and the motor noise and vibration measurement results of the example and the comparative example.

According to Table 10, according to the hot-rolled sheet annealing temperature of this example, B50 ( _LC) is improved as compared with the comparative example, and a non-oriented electrical steel sheet having small anisotropy B50 (anisotropic) of magnetic flux density is obtained. You can see that you can do it. Further, the value W _{10/400 of the} iron loss is as low as 9.65 W / kg or less, which is excellent.
Further, in this embodiment, as a result of reducing the anisotropy of the magnetic flux density, the noise of the motor A at 400,000 rpm is less than 80 dB and the vibration is 70 dB smaller than that of the comparative example. It can be seen that the vibration has been reduced.

(Example 3)
The slab of steel type C was hot-rolled at a heating temperature of 1100 ° C. and a finishing temperature of 910 ° C., finished to a thickness of 2.0 mm, cooled to 650 ° C., and wound around a coiler. Table 11 shows the chemical composition of the non-oriented electrical steel sheet obtained from the steel type C slab.
The above hot-rolled steel sheet is subjected to hot-rolled sheet annealing at 950 ° C. for a different holding time, and in the cooling process after hot-rolled sheet annealing, is subjected to a 30% reduction in one pass at 460 ° C. and rolled at 405 ° C. (warm rolling) ), And finished to a thickness of 1.4 mm, and then cooled to room temperature.
After pickling, the warm-rolled sheet was cold-rolled (rolling start temperature 27 ° C., maximum temperature 80 ° C.) to a thickness of 0.25 mm, and subjected to finish annealing at 970 ° C. for 30 seconds (steel sheet No. C-). 1-6).

A hot-rolled steel sheet at 950 ° C. was subjected to a different holding time for a hot-rolled steel sheet under the same conditions as above until winding into a coiler, and then cooled to room temperature.
After pickling, the hot-rolled annealed sheet was cold-rolled (rolling start temperature 27 ° C., maximum temperature 80 ° C.) to a thickness of 0.25 mm, and finish-annealed at 970 ° C. for 30 seconds (steel No. C-). 7-12).

Epstein samples were cut out from the obtained non-oriented electrical steel sheet at intervals of 22.5 ° from the rolling direction, subjected to strain relief annealing, and then subjected to Epstein measurement.
A motor A was manufactured using these steel plates as a stator, and noise and vibration at 400,000 rpm were measured. The noise was 80 dB or less and the vibration was 70 dB or less.
Table 12 shows the magnetic measurement results and the motor noise and vibration measurement results of the example and the comparative example.

According to Table 12, according to the hot-rolled sheet annealing time of this example, B50 ( _LC) is improved as compared with the comparative example, and a non-oriented electrical steel sheet having a small anisotropy B50 (anisotropic) of magnetic flux density is obtained. You can see that you can do it. In addition, the iron loss value W10 / ₄₀₀ is as low as 9.64 W / kg or less, which is excellent.
Further, in this embodiment, as a result of reducing the anisotropy of the magnetic flux density, the noise of the motor A at 400,000 rpm is less than 80 dB and the vibration is 70 dB smaller than that of the comparative example. It can be seen that the vibration has been reduced.

(Example 4)
The slab of steel type D was hot-rolled at a heating temperature of 1100 ° C. and a finishing temperature of 890 ° C., finished to a thickness of 2.0 mm, cooled to 600 ° C., and wound around a coiler. Table 13 shows the chemical composition of the non-oriented electrical steel sheet obtained from the steel type D slab.
The hot-rolled steel sheet is subjected to hot-rolled sheet annealing at 950 ° C. for 30 seconds, the rolling start temperature and the rolling end temperature are changed in the cooling process after the hot-rolled sheet annealing, and the rolling is performed by 30% reduction in one pass. Finished to 1.4 mm thickness and then cooled to room temperature.
In this experiment, the conditions were set so that the rolling after the hot-rolled sheet annealing included a mode satisfying the range of the warm rolling according to the present disclosure and a mode not satisfying the range.
After pickling, this rolled sheet was cold-rolled (rolling start temperature 26 ° C., maximum temperature 80 ° C.) to a thickness of 0.25 mm, and subjected to finish annealing at 970 ° C. for 30 seconds (steel sheet No. D-1 to No. D-1). 6).

Further, the hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 950 ° C. for 30 seconds under the same conditions as described above until wound into a coiler, and then cooled to room temperature.
After pickling, the hot-rolled annealed sheet was cold-rolled (rolling start temperature: 26 ° C., maximum temperature: 80 ° C.) to a thickness of 0.25 mm and finish-annealed at 970 ° C. for 30 seconds (steel No. D-). 7).

The obtained non-oriented electrical steel sheet was cut into Epstein samples every 22.5 ° from the rolling direction, subjected to strain relief annealing, and then subjected to Epstein measurement.
A motor A was manufactured using these steel plates as a stator, and noise and vibration at 400,000 rpm were measured. The noise was 80 dB or less and the vibration was 70 dB or less.
Table 14 shows the magnetic measurement results and the motor noise and vibration measurement results of the example and the comparative example.

According to Table 14, according to the warm rolling temperature of the present example, B50 ( _LC) is improved as compared with the comparative example, and a non-oriented electrical steel sheet having small anisotropy B50 (anisotropic) of magnetic flux density can be obtained. I understand. In addition, the value W _{10/400 of} iron loss is as low as 9.76 W / kg or less, which is excellent.
Further, in this embodiment, as a result of reducing the anisotropy of the magnetic flux density, the noise of the motor A at 400,000 rpm is less than 80 dB and the vibration is 70 dB smaller than that of the comparative example. It can be seen that the vibration has been reduced.

(Example 5)
The slab of steel type E was hot-rolled at a heating temperature of 1100 ° C. and a finishing temperature of 885 ° C., finished to a thickness of 2.0 mm, cooled to 600 ° C., and wound around a coiler. Table 15 shows the chemical composition of the non-oriented electrical steel sheet obtained from the steel type E slab.
The hot-rolled steel sheet is subjected to hot-rolled sheet annealing at 900 ° C. for 30 seconds, and in the cooling process after the hot-rolled sheet annealing, is subjected to rolling at 550 ° C. in one pass while changing the rolling reduction, and is rolled at 400 ° C. or more (warm rolling). ) Was completed to finish a rolled plate, and then cooled to room temperature.
After pickling this warm-rolled sheet, it was cold-rolled (rolling start temperature 30 ° C., maximum temperature 78 ° C.) to a thickness of 0.25 mm, and subjected to finish annealing at 900 ° C. for 30 seconds (steel sheet No. E-). 1-6).

Further, the hot-rolled steel sheet was subjected to the hot-rolled sheet annealing at 900 ° C. for 30 seconds under the same conditions as described above until wound into the coiler, and then cooled to room temperature.
After pickling the hot-rolled annealed sheet, it was cold-rolled (rolling start temperature 30 ° C., maximum temperature 78 ° C.) to a thickness of 0.25 mm, and was subjected to finish annealing at 900 ° C. for 30 seconds (steel sheet No. E- 7).

The obtained non-oriented electrical steel sheet was cut into Epstein samples every 22.5 ° from the rolling direction, subjected to strain relief annealing, and then subjected to Epstein measurement.
A motor B was manufactured using these steel plates for the stator, and noise and vibration at 400,000 rpm were measured. The noise was 80 dB or less and the vibration was 70 dB or less.
Table 16 shows the magnetic measurement results and the motor noise and vibration measurement results of the example and the comparative example.

From Table 16, according to the rolling reduction at the time of the warm rolling in the present example, a non-oriented electrical steel sheet having improved B50 ( _{LC) and} smaller anisotropy B50 (anisotropic) of the magnetic flux density than the comparative example was obtained. It can be seen that it can be obtained. In addition, the value of iron loss _10/400 is 9.73 W / kg or less, which is excellent.
Further, in this embodiment, as a result of reducing the anisotropy of the magnetic flux density, the noise of the motor B at 400,000 rpm is less than 80 dB and the vibration is 70 dB smaller than that of the comparative example. It can be seen that the vibration has been reduced.

(Example 6)
The slab of steel type F was hot-rolled at a heating temperature of 1100 ° C. and a finishing temperature of 875 ° C., finished to a thickness of 1.8 mm, cooled to 500 ° C., and wound around a coiler. Table 17 shows the chemical composition of the non-oriented electrical steel sheet obtained from the steel type F slab.
The hot-rolled steel sheet is subjected to hot-rolled sheet annealing at 950 ° C. for 10 seconds. When the temperature reaches 600 ° C. in the cooling process after hot-rolled sheet annealing, the steel sheet is subjected to a 17% reduction in one pass and rolled at 470 ° C. (warm rolling) )), The temperature was immediately increased, intermediate annealing was performed at 950 ° C. for 10 seconds, and then cooled to room temperature to obtain a 1.5 mm thick intermediate annealed plate.
After pickling, the intermediate annealed sheet was cold-rolled (rolling start temperature 35 ° C., maximum temperature 95 ° C.) to a thickness of 0.25 mm, and subjected to finish annealing at 900 ° C. for 20 seconds (steel sheet No. F-1). ).

Further, the hot-rolled steel sheet subjected to the same conditions as described above until it is wound into the coiler is subjected to hot-rolled sheet annealing at 950 ° C. for 10 seconds, once cooled to room temperature (25 ° C.), and reheated to reach 600 ° C. At this point, the rolling (warm rolling) was completed at 470 ° C. by applying 17% reduction in one pass, the temperature was immediately raised, intermediate annealing was performed at 950 ° C. for 10 seconds, and then cooled to room temperature to obtain a 1.5 mm thick steel sheet. An intermediate annealed plate was obtained.
After pickling, the intermediate annealed sheet was cold-rolled (rolling start temperature 35 ° C., maximum temperature 95 ° C.) to a thickness of 0.25 mm, and subjected to finish annealing at 900 ° C. for 20 seconds (steel sheet No. F-2). ).

Further, the hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 950 ° C. for 20 seconds under the same conditions as described above until wound into a coiler, and then cooled to room temperature.
After pickling, the hot-rolled annealed sheet was cold-rolled (rolling start temperature 35 ° C., maximum temperature 95 ° C.) to a thickness of 0.25 mm, and finish-annealed at 900 ° C. for 20 seconds (Steel Sheet No. F). -3).

The obtained non-oriented electrical steel sheet was cut into Epstein samples every 22.5 ° from the rolling direction, subjected to strain relief annealing, and then subjected to Epstein measurement.
A motor B was manufactured using these steel plates for the stator, and noise and vibration at 400,000 rpm were measured. The noise was 80 dB or less and the vibration was 70 dB or less.
Table 18 shows the magnetic measurement results and the motor noise and vibration measurement results of the example and the comparative example.

From Table 18, according to the hot rolling between the two hot-rolled sheet annealings and the two hot-rolled sheet annealings of the present example, B50 _(LC) was improved as compared with the comparative example, and the anisotropy was improved. It can be seen that a non-oriented electrical steel sheet having a small B50 (anisotropic) can be obtained. In addition, the iron loss value W _10/400 is as low as 9.73 W / kg, which is excellent.
Further, in this embodiment, as a result of reducing the anisotropy of the magnetic flux density, the noise of the motor B at 400,000 rpm is less than 80 dB and the vibration is 70 dB smaller than that of the comparative example. It can be seen that the vibration has been reduced.

(Example 7)
The slab of steel type G was hot-rolled at a heating temperature of 1100 ° C. and a finishing temperature of 875 ° C., finished to a thickness of 1.8 mm, cooled to 500 ° C., and wound around a coiler. Table 19 shows the chemical composition of the non-oriented electrical steel sheet obtained from the steel type G slab.
The hot-rolled steel sheet was subjected to annealing 1 by changing the temperature and time to perform hot-rolled sheet annealing according to the present disclosure and non-annealing, and in the cooling process, rolling 1 was performed by changing the rolling temperature and the rolling reduction. .
This rolled sheet was subjected to intermediate annealing by changing the temperature and time, and the temperature of annealing 1 and the subsequent combination of the temperature and rolling reduction of rolling 1 and the intermediate annealing temperature were changed. After the intermediate annealing, it was cooled to room temperature to obtain an intermediate annealed plate. Table 20 shows the conditions.
After pickling, the intermediate annealed sheet was cold-rolled (rolling start temperature 25 ° C., maximum temperature 80 ° C.) to a thickness of 0.25 mm, and subjected to finish annealing at 900 ° C. for 20 seconds (steel sheet No. G-1). ~ 29).

The obtained non-oriented electrical steel sheet was cut into Epstein samples every 22.5 ° from the rolling direction, subjected to strain relief annealing, and then subjected to Epstein measurement.
A motor B was manufactured using these steel plates for the stator, and noise and vibration at 400,000 rpm were measured. The noise was 80 dB or less and the vibration was 70 dB or less.
Table 20 shows the magnetic measurement results and the motor noise and vibration measurement results of the example and the comparative example.

From Table 20, by controlling the hot-rolled sheet annealing including the rolling under the conditions of the present example, B50 ( _LC) is improved and the anisotropy B50 (anisotropic) of the magnetic flux density is small compared to the comparative example. It can be seen that a conductive magnetic steel sheet can be obtained. Further, the iron loss value W10 / ₄₀₀ is as low as 9.78 W / kg or less, which is excellent.
Further, in this embodiment, as a result of reducing the anisotropy of the magnetic flux density, the noise of the motor B at 400,000 rpm is less than 80 dB and the vibration is 70 dB smaller than that of the comparative example. It can be seen that the vibration has been reduced.

(Example 8)
The slab of steel type H is roughly hot-rolled at a heating temperature of 1100 ° C., then hot-rolled at a finishing temperature of 875 ° C., finished to a thickness of 1.5 mm, cooled to 500 ° C., and wound into a coiler. Was. Table 21 shows the chemical composition of the non-oriented electrical steel sheet obtained from the steel type H slab.
The hot-rolled steel sheet is subjected to hot-rolled sheet annealing at 950 ° C. for 20 seconds. When the temperature reaches 445 ° C. in the cooling process after the hot-rolled sheet annealing, a 33% reduction is performed in one pass and rolling is performed at 405 ° C. (warm rolling) ), Cooled to room temperature, and wound up. The warm-rolled sheet was heated again, subjected to intermediate annealing at 900 ° C. for 5 seconds, and then cooled to room temperature to obtain a 1.0-mm thick intermediate-annealed sheet.
After pickling, the intermediate annealed sheet was cold-rolled (rolling start temperature 28 ° C., maximum temperature 85 ° C.) to a thickness of 0.25 mm, and finish annealed at 925 ° C. for 15 seconds (steel sheet No. H-). 1).

Further, the hot-rolled steel sheet subjected to the same conditions as above before winding into a coiler is subjected to hot-rolled sheet annealing at 950 ° C. for 20 seconds, once cooled to room temperature (25 ° C.), and reheated to reach 445 ° C. At that time, the rolling (warm rolling) was completed at 405 ° C. by applying a 33% reduction in one pass, cooled to room temperature, and wound up. The rolled sheet was heated again and subjected to intermediate annealing at 900 ° C. for 5 seconds, and then cooled to room temperature to obtain a 1.0 mm thick intermediate annealed sheet.
After pickling, the intermediate annealed sheet was cold-rolled (rolling start temperature: 35 ° C., maximum temperature: 95 ° C.) to a thickness of 0.25 mm, and subjected to finish annealing at 900 ° C. for 20 seconds (steel sheet No. H-2). ).

Further, the hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 950 ° C. for 20 seconds under the same conditions as above until winding into a coiler, cooled to room temperature, and then 33% cold-rolled in one pass (rolling start temperature 25 ° C.). , A maximum temperature of 65 ° C) and a thickness of 1.0 mm.
Next, the temperature of the cold-rolled sheet was raised again, intermediate annealing was performed at 900 ° C. for 5 seconds, and then cooled to room temperature.
After pickling, the intermediate annealed sheet was cold-rolled (rolling start temperature 28 ° C., maximum temperature 85 ° C.) to a thickness of 0.25 mm, and finish annealed at 925 ° C. for 15 seconds (steel sheet No. H-). 3).

The obtained non-oriented electrical steel sheet was cut into Epstein samples every 22.5 ° from the rolling direction, subjected to strain relief annealing, and then subjected to Epstein measurement.
A motor B was prepared by using these steel plates for the stator, and noise and vibration at 400,000 rpm were measured. The noise was 80 dB or less, and the vibration was 70 dB or less.
Table 22 shows the magnetic measurement results and the motor noise and vibration measurement results of the example and the comparative example.

As shown in Table 22, when the steel sheet is subjected to warm rolling until it reaches room temperature in the cooling process after the first hot-rolled sheet annealing in this example, B50 _(LC) is improved as compared with the comparative example, It can be seen that a non-oriented electrical steel sheet having a small anisotropic B50 (anisotropic) can be obtained. In addition, the iron loss value W _10/400 is as low as 9.43 W / kg, which is excellent.
Further, in this embodiment, as a result of reducing the anisotropy of the magnetic flux density, the noise of the motor B at 400,000 rpm is less than 80 dB and the vibration is 70 dB smaller than that of the comparative example. It can be seen that the vibration has been reduced.

(Example 9)
The slab of steel type G was subjected to rough hot rolling at a heating temperature of 1100 ° C., and then subjected to finish hot rolling at a finishing temperature of 880 ° C. to finish a rolled plate to a thickness of 2.5 mm and cooled it to 550 ° C. on a ROT. Later, it was wound on a coiler. Table 23 shows the chemical composition of the non-oriented electrical steel sheet obtained from the steel type G slab.
The steel sheet No. shown in Table 24. G-1 to steel sheet No. As in G-6, hot-rolled sheet annealing, subsequent rolling (20% reduction), intermediate annealing, and rolling following intermediate annealing (25% reduction) were performed, wound around a coil, and cooled to room temperature.
After pickling, the rolled sheet was cold-rolled at 25 ° C. (rolling start temperature) to a thickness of 0.25 mm, and subjected to finish annealing at 925 ° C. for 15 seconds.

The obtained non-oriented electrical steel sheet was cut into Epstein samples every 22.5 ° from the rolling direction, subjected to strain relief annealing, and then subjected to Epstein measurement.
A motor B was manufactured using these steel plates for the stator, and noise and vibration at 400,000 rpm were measured. The noise was 80 dB or less and the vibration was 70 dB or less.
Table 25 shows the magnetic measurement results and the motor noise and vibration measurement results of the example and the comparative example.

According to Tables 24 and 25, in the cooling process after both the first and second annealing or the first or second annealing in this example, the steel sheet was subjected to warm rolling until it reached room temperature. For example, it can be seen that a non-oriented electrical steel sheet having a higher B50 _(LC) and a smaller anisotropy B50 (anisotropy) than the comparative example can be obtained. Further, the iron loss value W10 / ₄₀₀ is as low as 9.55 W / kg or less, which is excellent.
In this embodiment, as a result of reducing the anisotropy of the magnetic flux density, the noise of the motor B at 400,000 rpm is less than 80 dB and the vibration is 70 dB smaller than that of the comparative example at 400,000 rpm. It can be seen that is reduced.
Particularly noteworthy is the steel sheet No. which was subjected to warm rolling after the first and second annealing. G-1 and the steel sheet No. warm-rolled after the first hot-rolled sheet annealing. In G-2, the value of anisotropy B50 (anisotropic) shows excellent low anisotropy of 0.008 or less, the magnetic flux density B50 _(LC) shows a value of _1.70T , and _{W10 / 400} is It shows an excellent value of 9.39 W / kg or less, the result of noise measurement by the motor B shows an excellent value of 74 dB or less, and the result of vibration measurement shows an excellent value of 63 dB or less.
The steel sheet No. was cooled to room temperature after the first hot-rolled sheet annealing, and subjected to warm rolling in the cooling process after the second annealing. G-3 and steel sheet No. In G-5, the anisotropy B50 (anisotropy) was changed to steel sheet No. G-1 and steel sheet No. The noise measurement result and the vibration measurement result by the motor B are 79 dB and 69 dB, respectively, which are very close to the acceptable value line.
The inventors presume that this indicates that the effect of the present disclosure is more apparent when warm rolling is performed on a thick steel plate.

  As described above, according to the present invention, it is possible to obtain a non-oriented electrical steel sheet with less noise and vibration even at higher rotation speeds.

Claims (4)

Hot rolling the slab to a hot-rolled steel sheet,
A hot-rolled sheet annealing step of performing hot-rolled sheet annealing at 800 ° C. or more and 1080 ° C. or less for 5 seconds or more and 2 minutes or less,
In the cooling process of the hot-rolled sheet annealing, a warm rolling step of performing warm rolling at a rolling reduction of 3% to 75% in a temperature range of 400 ° C to 700 ° C,
Finish annealing step of performing finish annealing on the rolled sheet after warm rolling,
With
The magnetic flux densities at directions of 0 °, 22.5 °, 45 °, 67.5 °, and 90 ° with respect to the rolling direction at a magnetic field strength of 5000 A / m are represented by B50 _{(0 °)} and B50, respectively. When expressed as _{50 (22.5 °)} , B _{50 (45 °)} , B _{50 (67.5 °)} , and B _{50 (90 °)} , the anisotropy index defined by the following formula (1) A method for producing a non-oriented electrical steel sheet, wherein the non-oriented electrical steel sheet has a B50 (anisotropic) of 0.017 or less.

Equation (1)
Here, in the equation (1), _B50AVE is defined by the following equation (2).

Equation (2)   The method for producing a non-oriented electrical steel sheet according to claim 1, wherein the warm rolling is performed twice or more at a temperature of more than 700 ° C and not more than 1080 ° C with an intermediate annealing of 5 seconds or more and 2 minutes or less. The non-oriented electrical steel sheets, the magnetic flux density _{B 50} in the magnetic field strength 5000A / m at the rolling direction _{(0 °),} the magnetic flux density _{B 50} in the magnetic field strength 5000A / m in a direction at right angles to the rolling direction ₍ and _{90 °),} is the arithmetic mean is a mean magnetic flux density _{B 50} of _(LC), the manufacturing method of the non-oriented electrical steel sheet according to claim 1 or claim 2 is at least 1.64T. The non-oriented electrical steel sheet is, in mass%,
Si: 0.1% to 3.8%,
Mn: 0.1% to 2.5%,
Al: 0% to 2.5%,
The method for producing a non-oriented electrical steel sheet according to any one of claims 1 to 3, wherein the balance is a composition comprising Fe and impurities.