JP7147340B2 - Method for manufacturing non-oriented electrical steel sheet - Google Patents

Description

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

Electrical steel sheets used in electrical equipment and the like are required to be highly efficient from the viewpoint of energy saving.
For example, air conditioner compressors, various motors used in home appliances, drive motors, electric turbochargers, and electric compressors in automobiles are becoming smaller and more efficient, requiring high-speed rotation and high-frequency excitation. There is an increasing demand for non-oriented electrical steel sheets with low magnetic flux density and anisotropy.

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

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

In addition, as described in Patent Documents 3 and 4, a technique for improving magnetic properties by applying light reduction rolling before hot-rolled sheet annealing and performing strain-induced grain growth during hot-rolled sheet annealing is adopted. It is

In addition, in Patent Document 5, the grain growth of the hot-rolled sheet during self-annealing is uniformly coarsened by adding Sn to the grain size before cold rolling, and the synergistic control of the texture during finish annealing by adding Sn. Techniques for increasing the magnetic flux density by effect have been disclosed.

Patent Document 6 discloses a technique of defining the relationship between the final cold rolling reduction and the crystal grain size before cold rolling by a formula when manufacturing a thin non-oriented electrical steel sheet for high frequency with a thickness of 0.10 mm to 0.25 mm. It is In addition, the technology of performing hot-rolled sheet annealing and controlling 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 rate, and the production of non-oriented electrical steel sheets A technique to set the surface roughness Ra to 0.5 μm or less, measure the magnetism of the steel sheet 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 the magnetic flux Techniques for controlling the density ΔB50 to 0.08T or less have been proposed.
In Patent Document 7, 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%, the contents of Si, Al, and Mn satisfy the relationship of Si+2Al-Mn≧2, and the balance is Fe and inevitable impurity elements. A method for manufacturing a non-oriented electrical steel sheet by annealing a hot-rolled sheet, then subjecting it to cold rolling, recrystallization annealing, skin-pass rolling, and final annealing, wherein the hot-rolled sheet is annealed at an annealing temperature Th of 1,000. C. ≤ Th ≤ 1150°C and a cold rolling rate CR of 85% ≤ CR ≤ 93%, a method for producing a non-oriented electrical steel sheet with good all-around characteristics and workability is disclosed.
In Patent Document 8, in weight %, C ≤ 0.01%, Si: 0.1% to 2.0%, Al ≤ 2.0%, Si + 2Al: 0.1% to 2.50%, Mn < 1.0%, Ni: 0.1% to 4%, non-oriented electrical steel sheet with less anisotropy consisting of the balance Fe and unavoidable impurities, magnetic flux density B ₅₀ value minimum and maximum angular characteristics A non-oriented electrical steel sheet with little anisotropy, in which the difference in values is 0.025 T or less, is disclosed.

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

In Patent Document 10, after annealing the hot-rolled sheet at a temperature of 800 ° C. or higher, in one or two rolling steps including intermediate annealing, a reduction of at least 20% or more is performed in a temperature range of 50 ° C. or higher, and then A technique of performing finish annealing at a temperature of 850° C. or higher is disclosed.
Patent Literature 11 discloses a method of manufacturing a switched reluctance motor in which conditions such as temperature rise rate, steel sheet tension, atmosphere oxidizability, temperature drop rate, etc. are specified during final annealing.

Patent Literature 12 discloses a method of manufacturing a power steering modular motor having a low rotational speed, in which the conditions for final annealing are specified.
Patent Document 13 discloses a hot-rolled sheet annealing single cold-rolling method.

Japanese Patent Publication No. 57-43132 JP-A-62-54023 JP-A-2-213418 JP-A-3-211258 Japanese Patent Application Laid-Open No. 2002-294415 Japanese Patent Application Laid-Open No. 2001-295003 JP 2008-45151 A JP-A-8-246108 Japanese Patent Application Laid-Open No. 2001-49402 JP-A-2000-144348 JP-A-2005-240095 JP 2006-144036 A JP 2005-307258 A

However, the techniques of Patent Documents 1 and 2 are not as good as line annealing, and there is room for improvement in the in-plane anisotropy of the magnetic flux density. There is an increasing demand for reducing the anisotropy of the magnetic flux density when applying to a high-speed rotating machine reaching the following.

In the techniques of 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. , there is room for improving the uniformity of the magnetic flux flow when used in the frame core. Furthermore, when applied to high-speed rotating machines that reach 20,000 rpm or more and 200,000 rpm or less, which are being developed in recent years, there is a demand to reduce noise and vibration during use by reducing the anisotropy of the magnetic flux density. rising.

In the technique of Patent Document 5, there is room for improvement in the in-plane anisotropy of magnetic flux density. There is Furthermore, when applied to recent high-speed rotating machines, there is an increasing demand for reduction of noise and vibration during use due to the reduction of magnetic flux density anisotropy. In particular, in high-speed rotating machines that reach 20,000 to 200,000 rpm, which are being developed in recent years, there is an increasing demand for reducing the anisotropy of the magnetic flux density in terms of noise and vibration reduction.

In the technologies of Patent Documents 6, 7 and 8, the anisotropic magnetic flux density is used to reduce noise and vibration in high-speed rotating machines that reach 20,000 rpm or more and 200,000 rpm or less, which are being developed in recent years. There is an increasing demand for reducing

In the technique of Patent Document 9, as in Patent Document 6, there is room for reducing the in-plane anisotropy of the magnetic flux density of the final product even by the two-step method in which the process conditions are controlled. leave room for Furthermore, there is an increasing demand for reduction of anisotropy when applied to high-speed rotating machines reaching 20,000 to 200,000 rpm, which are being developed in recent years.

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 also room for reducing motor noise and vibration. Furthermore, there is an increasing demand for reduction of anisotropy when applied to high-speed rotating machines reaching 20,000 to 200,000 rpm, which are being developed in recent years.

In the technique of Patent Document 11, there is still room for manufacturing a non-oriented electrical steel sheet with small anisotropy when applied to a high-efficiency motor. Furthermore, there is an increasing demand for reducing anisotropy when applying this technology to high-speed rotating machines reaching 20,000 to 200,000 rpm, which are being developed in recent years.

The technique of Patent Document 12 is intended for power steering modular motors with a low rotational speed, and general rotating machines have a higher rotational speed than power steering, and there is an increasing demand for reducing noise and vibration. Furthermore, there is room for reducing the anisotropy for rotating machines that rotate at higher speeds, which are being developed in recent years. Demand for reduction of anisotropy is increasing.

The technique of Patent Document 13 has room for reducing the in-plane anisotropy of the magnetic flux density, and for example, there is room for reducing the anisotropy when applied to high-speed rotating machines that are being developed in recent years. Furthermore, there is an increasing demand for reduction of anisotropy when applied to high-speed rotating machines reaching 200,000 rpm or more and 200,000 rpm or less, which are being developed recently.

As described above, 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 depending on the direction) with the conventional technology, and there is a demand for reducing the anisotropy of the magnetic flux density. rice field. When applied to the iron core of a rotating machine, it has been desired to reduce noise and vibration and improve the maximum rotational speed.
Against this background, the present inventors have found that by controlling the anisotropy of the magnetic flux density defined by a specific parameter, the torque fluctuation during rotation when applied to a rotating machine such as a motor is reduced, resulting in noise. It was found that the vibration is reduced and the maximum rotation speed can be increased.

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

式（１）
ここで、式（１）中、Ｂ_{５０ＡＶＥ}は、下記式（２）で規定される。

式（２）
＜２＞
前記温間圧延工程で前記温間圧延を施した前記温間圧延後の圧延板に、前記仕上焼鈍を施す前に、７００℃超１０８０℃以下の温度で５秒以上２分以下の中間焼鈍を施す中間焼鈍工程をさらに備え、前記中間焼鈍の冷却過程において４００℃以上７００℃以下の温度域で温間圧延を施す、請求項１に記載の無方向性電磁鋼板の製造方法。
＜３＞
前記無方向性電磁鋼板は、圧延方向での磁界強度５０００Ａ／ｍにおける磁束密度Ｂ_{５０（０°）}と、圧延方向に対して直角となる方向での磁界強度５０００Ａ／ｍにおける磁束密度Ｂ_{５０（９０°）}と、の算術平均である平均磁束密度Ｂ_{５０（ＬＣ）}が、１．６４Ｔ以上である＜１＞又は＜２＞に記載の無方向性電磁鋼板の製造方法。
Means for solving the above problems are as follows.
<1>
A hot-rolling step of hot-rolling the slab to form a hot-rolled steel sheet;
A hot-rolled sheet annealing step of subjecting the hot-rolled steel sheet to hot-rolled sheet annealing at 800 ° C. or higher and 1080 ° C. or lower for 5 seconds or more and 2 minutes or less;
A warm rolling step of performing warm rolling at a rolling reduction of 3% or more and 75% or less in a temperature range of 400°C or more and 700°C or less in the cooling process of hot-rolled sheet annealing;
A finish annealing step of applying finish annealing to the rolled plate after warm rolling;
with
A composition containing Si: 2.1 to 3.2%, Mn: 0.1 to 2.5%, Al: 0.3 to 1.2% in mass%, and the balance being Fe and impurities, The magnetic flux densities at a magnetic field strength of 5000 A / m in the directions of angles of 0 °, 22.5 °, 45 °, 67.5 ° and 90 ° with respect to the rolling direction are B _{50 (0 °)} and B _{50 (22.5°)} , B _{50 (45°)} , B _{50 (67.5°)} , and B _{50 (90°)} , the anisotropic index defined by the following formula (1) A method for producing a non-oriented electrical steel sheet, which produces a non-oriented electrical steel sheet having a B50 (anisotropy) of 0.017 or less.

formula (1)
Here, in formula (1), B _50AVE is defined by the following formula (2).

formula (2)
<2>
Before performing the finish annealing on the rolled sheet after the warm rolling that has been subjected to the warm rolling in the warm rolling step, intermediate annealing is performed at a temperature of more than 700 ° C. and 1080 ° C. or less for 5 seconds or more and 2 minutes or less. 2. The method for producing a non-oriented electrical steel sheet according to claim 1 , further comprising an intermediate annealing step of performing warm rolling in a temperature range of 400° C. or higher and 700° C. or lower in the cooling process of said intermediate annealing .
<3>
The non-oriented electrical steel sheet has a magnetic flux density B 50 (0°) at a magnetic field strength of 5000 A / m in the rolling direction and a magnetic flux density B _{50 (0 °)} at a magnetic field strength of 5000 A / m in a direction perpendicular to the rolling direction _90°) and an average magnetic flux density B50 _(LC) of 1.64 T or more.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method which manufactures 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 reduces noise and vibration by controlling torque fluctuations during motor rotation using the anisotropy of the magnetic flux density of a non-oriented electrical steel sheet. First, the results of experiments leading to this technical finding will be described.

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

Steel plate 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, 30% rolling (warm rolling) is performed in one pass to finish to a thickness of 1.4 mm, and then Cooled to room temperature. The rolling at this time was performed at a temperature at the entry side of the stand of 480°C and a temperature at the exit side of the stand of 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 maximum temperature reached by heat generated during the additional rolling was 75°C. After that, finish annealing was performed at 970° C. for 20 seconds.

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

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 then subjected to Epstein measurement to obtain an anisotropy index B50 (anisotropy).
B50 (anisotropy) of steel plate BA was 0.008, and B50 (anisotropy) of steel plate BB was 0.019.

Also, a stator was produced using steel plate BA or BB, and a high-tensile steel plate having a plate thickness of 0.35 mm and a tensile strength of 750 MPa was used for the rotor to produce a permanent magnet synchronous high-speed rotation motor with a maximum output of 5 kW.
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 rotation speed of each motor was changed was evaluated in units of 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 plate BA with a small anisotropy index B50 (anisotropy) has lower noise and vibration than the steel plate BB with a large anisotropy index B50 (anisotropy) in the entire rotation speed range. 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 the hot rolled steel sheet to a thickness of 2.0 mm, which is cooled to 600° C. Coiled on a coiler. From this hot-rolled steel sheet, two types of steel sheets DA and DB were produced by the following steps. Table 4 shows the chemical composition of the non-oriented electrical steel sheet obtained from the slab of steel type D.

Steel plate 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 the cooling process after the hot-rolled sheet annealing, rolling was performed by 30% in one pass to finish to a thickness of 1.4 mm, and then cooled to room temperature. The rolling at this time was performed at a temperature at the entry side of the stand of 295°C and a temperature at the exit side of the stand of 200°C.
After pickling, the rolled sheet was subjected to additional rolling at 26° C. (rolling start temperature) to a thickness of 0.25 mm. The maximum temperature reached by heat generated during the additional rolling was 80°C. After that, finish annealing was performed at 970° C. for 30 seconds.

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 hot-rolled sheet annealing, 30% rolling (warm rolling) is performed in one pass to finish to a thickness of 1.4 mm, and then Cooled to room temperature. In this rolling, the temperature on the entrance side of the stand was 550°C, and the temperature on the exit side of the stand 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 maximum temperature reached by heat generated during the additional rolling was 80°C. After that, finish annealing was performed at 970° C. for 30 seconds.

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

Also, a stator was produced using steel plate DA or DB, and a permanent magnet type synchronous brushless synchronous motor with an output of 200 W was produced. A steel plate was used for the stator, and for the rotor, a neodymium bond magnet was attached to the rotating shaft, and carbon fiber was wrapped around the neodymium bond magnet to reinforce it so as 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 rotation speed of each motor was changed was evaluated in units of 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 with a small anisotropy index B50 (anisotropy) has lower noise and vibration than the steel plate DA with a large anisotropy index B50 (anisotropy) in the entire rotation speed range. can be confirmed. This result is similar to that of Experiment 1 described above, and it was confirmed that the effect of reducing noise and vibration by controlling the anisotropy index B50 (anisotropy) 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 this specification, unless otherwise specified, the numerical range represented by "to" means a range including the numerical values before and after "to" as lower and upper limits.

式（１）
<Non-oriented electrical steel sheet>
A non-oriented electrical steel sheet manufactured by the method for manufacturing a non-oriented electrical steel 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°, respectively, at a magnetic field strength of 5000 A/m, B _50(0°) , B _50(22.5°) , When expressed as B50 _(45°) , B50( _67.5°) , and B50( _90°) , the anisotropy index B50 (anisotropy) defined by the following formula (1) is 0.017. It is below.

formula (1)

式（２） Here, in formula (1), B _50AVE is defined by the following formula (2).

formula (2)

・ Anisotropy index B50 (anisotropy)
In this embodiment, the anisotropy of the magnetic flux density in all circumferential directions is evaluated by Equation (1). That is, the anisotropy index B50 (anisotropy) defined by formula (1) is 0°, 22.5°, 45°, 67.5°, and 90° with respect to the rolling direction. , the difference in magnetic flux density at a magnetic field strength of 5000 A/m is indexed. When the anisotropy index B50 (anisotropy) defined by the formula (1) is 0.017 or less, the anisotropy of the magnetic flux density in all circumferential directions becomes small.
As a result, when applied to a rotating machine such as a motor, torque fluctuation during rotation is reduced, noise and vibration are reduced, and the characteristics of the rotating iron core are improved, such as increasing the maximum rotational speed.
In addition, when applied to other EI cores, frame cores, etc., changes in the ease of flow of magnetic flux due to the direction of the yoke are reduced, resulting in an iron core with highly uniform magnetic characteristics and improved magnetic attraction. Core properties can be improved, such as less current required due to increased force.
In addition, 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, 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 (anisotropy) is not particularly limited, but from the viewpoint of stable production, it is preferably 0.003 or more, more preferably 0.005 or more.

The magnetic flux density is determined by cutting an Epstein sample and measuring the magnetic flux density at a magnetic field strength of 5000 A/m according to the Epstein method defined in JIS C2550-1.
The anisotropy index B50 (anisotropy) of the non-oriented electrical steel sheet can be controlled within the above range by manufacturing the non-oriented electrical steel sheet according to the present embodiment described below.

・Average magnetic flux density B _{50 (LC)}
The non-oriented electrical steel sheet according to the present embodiment has a magnetic flux density B _{B50 (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 in a direction perpendicular to the rolling direction The average magnetic flux density B50 ( _LC) , which is the arithmetic mean of BB50 _(90°) , is preferably as high as possible, for example, 1.64 T or more. With an average magnetic flux density B50 _(LC) of 1.64 T or more, a 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. It is possible to achieve high efficiency.
The average magnetic flux density B50 _(LC) is more preferably 1.66T or higher, and even more preferably 1.68T or higher.
In addition, the upper limit of the average magnetic flux density B50 _(LC) is not particularly limited, but from the viewpoint of stably reducing the anisotropy, it is preferably 1.90 T or less, and more preferably 1.80 T or less. .
The method for controlling the average magnetic flux density B50 _(LC) in the range of 1.64 T or more is not particularly limited, but for example, the non-oriented electrical steel sheet manufacturing method according to the present embodiment described below. method.

- Iron loss In the non-oriented electrical steel sheet according to the present embodiment, the lower the iron loss ( _W10/400 ), the better.
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 plate thickness of 0.20 mm. 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) is preferable for a plate thickness of 0.25 mm, and for a plate thickness of 0.30 mm, 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), and 14.0 W/kg or more for a plate thickness of 0.35 mm. It is preferably 20.0 W/kg or less (more preferably 14.5 W/kg or more and 18.0 W/kg or less). If the plate thickness is further increased, an appropriate iron loss range is determined accordingly. The lower limit of iron loss is determined from the viewpoint of manufacturing stability such as obtaining cold rolling stability and stable properties. The upper limit of iron loss is determined from the characteristics determined for each plate thickness required for a high-efficiency core.
As the iron loss, the iron loss generated when an Epstein sample is cut and the inverter excitation is measured by the Epstein method is used. Specifically, the core 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.

<Manufacturing method of non-oriented electrical steel sheet>
The method for manufacturing a non-oriented electrical steel sheet according to the present embodiment includes a hot rolling step of hot rolling a slab to obtain a hot rolled steel sheet, and a hot rolled steel sheet after hot rolling at 800 ° C. or higher and 1080 ° C. or lower. In the hot-rolled sheet annealing step of performing hot-rolled sheet annealing for 5 seconds or more and 2 minutes or less at , and the cooling process of the hot-rolled sheet annealing, the temperature range of 400 ° C or higher and 700 ° C or lower with a rolling reduction rate of 3% or higher and 75% or lower A warm rolling step of subjecting the rolled plate to rolling and a finish annealing step of subjecting the rolled plate after warm rolling to finish annealing. Through these steps, a non-oriented electrical steel sheet having an anisotropy index B50 (anisotropy) defined by the formula (1) falling within the above range is produced.

It is also possible to divide the warm rolling into two or more times. In the second and subsequent warm rollings, intermediate annealing may be performed in a temperature range sufficiently higher than the temperature range of the warm rolling, and the cooling process may be performed in a temperature range of 400°C or higher and 700°C or lower.

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

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

2. Hot-rolled sheet annealing process In the manufacturing method of this embodiment, the hot-rolled steel sheet that has completed the hot rolling process is subjected to hot-rolled sheet annealing.
Various conditions for hot-rolled sheet annealing are not particularly limited, and the annealing may be carried out according to known conditions.
The maximum temperature is, for example, 800°C or higher and 1080°C or lower, preferably 830°C or higher and 1050°C or lower, more preferably 850 or higher and 1000°C or lower. If it is less than 800°C, the effect is insufficient, and if it exceeds 1080°C, it becomes difficult to prevent surface oxidation of the steel sheet.
The holding time is, for example, 5 seconds or more and 2 minutes or less, preferably 10 seconds or more and 90 seconds or less, more preferably 15 seconds or more and 60 seconds or less.

3. Warm Rolling Step In the manufacturing method of the present embodiment, warm rolling is performed in the cooling process of hot-rolled sheet annealing after hot-rolled sheet annealing. Carrying out this warm rolling in the cooling process of the hot-rolled sheet annealing is a major feature of the production method of the present embodiment.
In this specification, warm rolling refers to rolling performed in a temperature range of 400°C or higher and 700°C or lower. In rolling, the temperature of the steel sheet may rise due to heat generated by working, but if the temperature is within the above temperature range, heat removal by the rolling rolls is generally large, and the steel sheet temperature tends to decrease during rolling. Therefore, in the cooling process of hot-rolled sheet annealing, rolling should be started before the steel sheet temperature reaches 400° C. in order to perform rolling within the above temperature range.
The temperature is preferably 425° C. or higher and 650° C. or lower, more preferably 450° C. or higher and 600° C. or lower. In this embodiment, it is assumed that warm rolling is performed when both the temperatures at the entry side and the exit side of the rolling stand are within the above temperature range. This is because the steel sheet must satisfy the temperature range of the present embodiment, including the temperature change of the steel sheet due to the heat generated during warm rolling and the heat removal of the rolls.

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.
When the second and subsequent warm rolling is performed, the steel sheet that has completed the first warm rolling is reheated to perform the warm rolling. At this time, the first and second warm rollings, and the third and subsequent warm rollings are distinguished by reheating before the warm rolling. Intermediate annealing, which will be described later, may be performed before the second and subsequent warm rolling. It is also possible to implement in

The reason why it is possible to produce a non-oriented electrical steel sheet with reduced anisotropy of magnetic flux density in all circumferential directions by performing warm rolling in the cooling process of hot-rolled sheet annealing is not clear, but it is as follows. I'm guessing.
The following three points can be cited as characteristics 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 rolled steel sheet is significantly lower than that of the central layer because of the cooling process. For example, it is thought that the temperature difference between the surface and inner layers at 700°C of a steel sheet heated and held at 710°C is greater than the temperature difference between the surface and inner layers at 700°C in the cooling process of a steel plate heated and held at 1000°C. be done. The second point is that if the heat treatment temperature immediately before is different, the state of precipitates during cooling is considered to be different. Especially in high-temperature, short-time heat treatment 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 morphology of the precipitate has changed significantly, including nitriding. Furthermore, the third point is that the plate thickness of the simply rolled steel plate is thick. The inventors presume that the effect of warm rolling is more pronounced because the amount of reduction in thickness is greater for thicker steels, even at the same rolling reduction.
Under these circumstances, by performing rolling within the above range, the crystal rotation of the surface layer and center layer of the steel sheet becomes special, and the cold rolling performed as necessary and the texture after finish annealing are improved. It is considered that the anisotropy index B50 (anisotropy) defined by the morphology is satisfied.

The rolling reduction of warm rolling is 3% or more and 75% or less, preferably 5% or more and 70% or less, 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 set to 3% or more. If it exceeds 75%, the anisotropy of the magnetic flux density increases, so it is set to 75% or less.
When the warm rolling is performed in two or more steps, the rolling reduction is obtained by converting the total true strain imparted in each warm rolling. That is, when the entry side plate thickness in one warm rolling is l ₀ and the delivery side plate thickness is l, the true strain imparted in one warm rolling is ln (l ₀ /l), and a plurality of times Sum the true strain for warm rolling. The appropriate range of rolling reduction in warm rolling described above of 3% or more and 75% or less is equivalent to a total true strain of 0.031 or more and 1.386 or less when converted to true strain.

4. Intermediate Annealing Step Intermediate annealing is the step of raising the temperature of the steel sheet above 700° C. after warm rolling. Intermediate annealing may be carried out by cooling the immediately preceding warm-rolled sheet (for example, cooling to about room temperature) and then reheating it, or while maintaining a temperature of 400 ° C. or higher after warm rolling (for example, warm Intermediate annealing may be performed by reheating without lowering the temperature from the end temperature of rolling. It is preferable to set the temperature of the intermediate annealing to over 700° C. so that the effect of improving the magnetic properties can be satisfactorily obtained. The upper limit of the intermediate annealing temperature is preferably 1080°C. By setting the temperature to 1080°C or less, it is possible to satisfactorily prevent surface oxidation of the steel strip.
The holding time in the intermediate annealing is preferably 5 seconds or more and 2 minutes or less, more preferably 10 seconds or more and 90 seconds or less, and still more preferably 15 seconds or more and 60 seconds or less. When intermediate annealing is performed twice or more, the retention time is the total time of each time. If the time is 5 seconds or more, the effect of improving the magnetic properties can be satisfactorily obtained, so the time of 5 seconds or more is preferable. If the time is 2 minutes or less, the effect of improving the magnetic properties does not saturate, that is, annealing, which contributes little to the effect of improving the magnetic properties, can be suppressed, so the time is preferably 2 minutes or less.

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

5. Cold Rolling Step In the present embodiment, cold rolling may be performed as necessary.
As used herein, cold rolling refers to rolling performed in a temperature range of less than 400°C. Considering the distinction from warm rolling described above, cold rolling is defined as rolling in which at least one of the temperature at the entry side and the exit side of the rolling stand is less than 400°C. It is preferably 5° C. or higher and 250° C. or lower, more preferably 25° C. or higher and 200° C. or lower, still more preferably 35° C. or higher and 150° C. or lower. The lower limit of the cold rolling temperature is preferably the above range from the viewpoint of ensuring rolling stability of the steel sheet, and the upper limit is preferably the above range from the viewpoint of extending the life of the rolls and lubricating oil and reducing the maintenance cost of the cold rolling mill. .
However, in the case of a steel plate with high hardness, the steel plate is heated in a coil state by a known method such as hot bath heating with hot water or induction heating, and the steel plate is heated at the entry side of the rolling stand to stabilize rolling performance. The temperature may be increased, for example, to 50° C. or higher. In this case, the temperature of the steel sheet on the delivery side of the rolling stand may reach about 200° C. due to heat generated during processing.
In order to reduce the hardness of the steel sheet by utilizing the heat generated during working and improve the threadability of the thin sheet material, the amount of lubricating oil is reduced to promote the heat generated during working, and the temperature of the steel sheet is raised up to 250°C. may be performed.

Various patterns are possible for the timing of performing the second and subsequent warm rollings and cold rollings. It is advantageous to carry out the second warm rolling prior to the cold rolling.
After completion of hot rolling, pickling may be performed in a process prior to cold rolling.

The reduction ratio of cold rolling is not particularly limited as long as the effects of the present embodiment can be obtained, but it is preferably 50% or more and 97% or less, especially 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. Moreover, since 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, it is preferable that the thickness of the final rolled sheet is 0.10 mm or more and 0.65 mm or less after the above warm rolling (and further cold rolling if necessary). 0.15 mm or more and 0.35 mm or less.

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

The finish annealing conditions are not particularly limited as long as the effects of the present embodiment can be obtained. However, in order to prevent oxidation during annealing to prevent an increase in iron loss and to control crystal grains to reduce iron loss, it is preferable to keep the temperature in the range of 700 ° C. or higher and 1100 ° C. or lower, especially 750 ° C. or higher. It is preferable to keep the temperature within a temperature range of 1050° C. or lower. The holding time at that time is preferably 0.1 seconds or more and 120 seconds or less, and preferably 10 seconds or more and 60 seconds or less.

7. Other steps In the method for manufacturing a non-oriented electrical steel sheet of the present embodiment, after the finish annealing step, a coating liquid is applied to the surface of the steel sheet obtained by the finish annealing step, and baked to form an insulation coating. You may have a film formation process. The conditions for forming the insulating film and the coating liquid are determined by a known method using commonly used materials.

<Chemical composition of slab and non-oriented electrical steel sheet>
Next, the chemical composition of the slab used in the manufacturing method of the non-oriented electrical steel sheet according to this embodiment and 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. The chemical composition of the mother steel sheet in 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 Si: 0.1% or more and 3.8% or less, Mn: 0.1% or more and 2.5% or less, and Al: 0% or more and 2.5% or less in mass %. , the balance of which is preferably Fe and impurities.
Preferred contents of each component are described below. Below, the content of each component is a value in mass %.

a. Si
The Si content is preferably 0.1% or more and 3.8% or less.

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

b. Mn
The Mn content is preferably 0.1% or more and 2.5% or less.

Since Mn also has the effect of increasing the specific resistance, it contributes to the reduction of iron loss. Therefore, from the viewpoint of iron loss reduction, the Mn content is preferably 0.1% or more, more preferably 0.2% or more, and more preferably 0.5% or more. If the amount is too high, the recrystallized structure is refined and the core loss is increased.

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

When Al is contained, 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 0.3% or more, from the viewpoint of iron loss reduction. It is preferable to make it 9% or more and 2.0%.

d. Balance The balance 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 contain impurities, which are various elements that can be mixed within the range that does not impair the effects of the present embodiment. Impurities include C, N, S, Ti, Nb, As, Zr, P, and the like.

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

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

From the viewpoint of improving the magnetic properties, the S content is preferably 0% or more and 0.003% or less, especially 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 properties can be obtained.

The Ti content is preferably 0% or more and 0.004% or less, more 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.

From the viewpoint of improving magnetic properties, the Nb content is preferably 0% or more and 0.003% or less, especially 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 properties can be obtained.

From the viewpoint of improving the magnetic properties, the As content is preferably 0% or more and 0.003% or less, especially 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 properties can be obtained.

From the viewpoint of improving the magnetic properties, the Zr content is preferably 0% or more and 0.003% or less, especially 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 properties can be obtained.

The P content is preferably 0% or more and 0.25% or less, 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 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 all impurities is preferably 0% or more and 0.1% or less, and more preferably 0% or more and 0.05% or less.

-Method for measuring chemical composition-
The content of each element in the slab in the production method of the present embodiment and in the non-oriented electrical steel sheet obtained by the present embodiment is determined according to the type of element using a general method and under general measurement conditions. can be measured.

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

When the non-oriented electrical steel sheet obtained by the manufacturing method of the present embodiment is not formed with an insulating coating or other layers, a part of the non-oriented electrical steel sheet is cut into facets and weighed to obtain a measurement sample. . When an insulating coating or other layers are formed on the non-oriented electrical steel sheet, after removing the insulating coating or other layers in advance by a general method, cut a part of the non-oriented electrical steel sheet into a facet shape. Weigh and use as a sample for measurement.

When using the ICP-MS method, the measurement sample is dissolved in an acid, and heated as necessary to obtain an acid solution. Then, the residue when dissolved in the acid is recovered by filter paper, separately melted in an alkali or the like, and the melt is extracted with an acid to form a solution. By mixing the solution and the acid solution and diluting the mixture as necessary, a solution for ICP-MS measurement can be obtained.

The invention is not limited to the embodiments described above. The above-described embodiment is an example, and any device that has substantially the same configuration as the technical idea described in the claims of the present invention and produces the same effect is the present invention. It is included in the technical scope of the invention.

EXAMPLES Hereinafter, the present invention will be described in detail by way of examples and comparative examples. It should be noted that the conditions of the examples are examples adopted to confirm the feasibility and effect of the present invention, and the present invention is not limited to the conditions of the examples. Various conditions can be adopted in the present invention as long as the objects of the present invention are 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, the iron loss generated when the Epstein sample is cut and excited by the inverter is used. Specifically, the core 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 defined in JIS C2550-1.

- Magnetic flux density Magnetic flux density at a magnetic field strength 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 defined in JIS C2550-1.

- Noise and vibration measurement motor One of the following two types of motors is manufactured using non-oriented electrical steel sheets for evaluation, and noise and vibration are measured.
Motor A: Permanent magnet synchronous high-speed rotation motor with a maximum output of 5 kW, with a stator made of a non-oriented electromagnetic steel sheet for evaluation and a rotor made of a high-tensile steel sheet with a plate thickness of 0.35 mm and a tensile strength of 750 MPa. : The stator is made of a non-oriented magnetic steel sheet for evaluation, the rotor is a neodymium bond magnet attached to the rotating shaft, and carbon fiber is wrapped around the neodymium bond magnet to withstand high-speed rotation. Magnetic Synchronous Brushless Synchronous Motor

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

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

(Example 1)
A 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 then coiled on 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, and when the temperature reaches 540 ° C. in the cooling process after hot-rolled steel annealing, 25% reduction is applied in one pass and rolled at 470 ° C. (warm rolling ), finished to a thickness of 1.5 mm, and then cooled to room temperature.
After pickling the warm-rolled sheet, it 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 plate No. A- 1).

Further, the hot-rolled steel sheet was subjected to hot-rolled steel annealing at 950° C. for 30 seconds under the same conditions as above until it was wound on a coiler, and then cooled to room temperature. This hot-rolled and annealed sheet is reheated to 540°C, subjected to 25% reduction in one pass at the rolling start temperature of 540°C, finished rolling (warm rolling) at 470°C, finished to a thickness of 1.5 mm, and then cooled to room temperature. cooled.
After pickling the warm-rolled sheet, it 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 plate No. A- 2).

Furthermore, the hot-rolled steel sheet under the same conditions as above until being wound on a coiler was subjected to hot-rolled steel annealing at 950° C. for 30 seconds, and then cooled to room temperature. After pickling the hot-rolled and annealed sheet, it was subjected to cold rolling (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 plate 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 produced using these steel plates for a stator, and noise and vibration were measured at 400,000 rpm.
Table 8 shows the magnetic measurement results and motor noise and vibration measurement results for the examples and comparative examples.

As can be seen from Table 8, the anisotropy B50 (anisotropy) of the magnetic flux density in this example is 0.011, which is smaller than in the comparative example.
In addition, in this example, the average magnetic flux density _{B50 (LC)} , which is the arithmetic mean value of the magnetic flux density B50 _(0°) in the rolling direction and the magnetic flux density _{B50 (90°)} in the direction perpendicular to the rolling direction, is compared. higher than the example.
In this example, the noise of the motor A at 400,000 rpm was 80 dB or less, and the vibration was 70 dB or less.
Further, even if the steel sheet is rolled under the same warm rolling conditions, the effect of the present disclosure is lost once the temperature of the steel sheet is cooled down to room temperature after hot-rolled steel annealing. It can be seen from the magnetic properties of A-2, the noise of the motor, and the vibration measurement results.
As described above, according to this embodiment, it is possible to manufacture a non-oriented electrical steel sheet with high magnetic flux density and low anisotropy of magnetic flux density. In addition, the iron loss value W10/400 is also low at _9.63 W/kg, which is excellent.

(Example 2)
A slab of steel type B 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 650°C, and wound on a coiler. Table 9 shows the chemical composition of the non-oriented electrical steel sheet obtained from the slab of steel type B.
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, 1-pass reduction of 30% at 480 ° C. and rolling at 410 ° C. (warm rolling) was finished, finished to a thickness of 1.4 mm, and then cooled to room temperature.
After pickling the warm-rolled sheet, it was cold-rolled (rolling start temperature 20°C, maximum temperature 75°C) to a thickness of 0.25 mm, and was subjected to finish annealing at 970°C for 20 seconds (steel plate No. B- 1-6).

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

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

From Table 10, according to the hot-rolled sheet annealing temperature of this example, B50 ( _LC) is improved over that of the comparative example, and a non-oriented electrical steel sheet with a small anisotropy B50 (anisotropy) of magnetic flux density can be obtained. I know you can do it. In addition, the iron loss value W _10/400 is excellent, being as low as 9.65 W/kg or less.
In addition, 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 80 dB or less, and the vibration is 70 dB, which is smaller than the comparative example. and vibration are reduced.

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

In addition, the hot-rolled steel sheet under the same conditions as above until being wound on a coiler was subjected to hot-rolled steel annealing at 950° C. with different retention times, and then cooled to room temperature.
After pickling the hot-rolled annealed sheet, it was cold-rolled (rolling start temperature 27°C, maximum temperature 80°C) to a thickness of 0.25 mm, and was subjected to finish annealing at 970°C for 30 seconds (steel plate 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 produced using these steel plates for a stator, and noise and vibration were measured at 400,000 rpm.
Table 12 shows the magnetic measurement results and the motor noise and vibration measurement results of the example and the comparative example.

From Table 12, according to the hot-rolled sheet annealing time of this example, B50 ( _LC) is improved over that of the comparative example, and a non-oriented electrical steel sheet with a small magnetic flux density anisotropy B50 (anisotropy) can be obtained. I know you can do it. In addition, the iron loss value W _10/400 is also low at 9.64 W/kg or less, which is excellent.
In addition, 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 80 dB or less, and the vibration is 70 dB, which is smaller than the comparative example. and vibration are reduced.

(Example 4)
A 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 then wound on a coiler. Table 13 shows the chemical composition of the non-oriented electrical steel sheet obtained from the slab of steel type D.
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, the rolling start temperature and rolling end temperature are changed to reduce 30% in one pass, and the rolled sheet is obtained. It was finished to a thickness of 1.4 mm and then cooled to room temperature.
In this experiment, conditions were set so that the rolling after the hot-rolled sheet annealing includes a mode that satisfies the range of warm rolling according to the present disclosure and a mode that does not satisfy the range.
After pickling the rolled sheet, it was subjected to cold rolling (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 plate No. D-1 to 6).

Further, the hot-rolled steel sheet was subjected to hot-rolled steel annealing at 950° C. for 30 seconds under the same conditions as above until it was wound on a coiler, and then cooled to room temperature.
After pickling the hot-rolled and annealed sheet, it was subjected to cold rolling (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 plate No. D- 7).

The obtained non-oriented electrical steel sheet was cut into Epstein samples at intervals of 22.5° from the rolling direction, subjected to strain relief annealing, and then subjected to Epstein measurement.
A motor A was produced using these steel plates for a stator, and noise and vibration were measured at 400,000 rpm.
Table 14 shows the magnetic measurement results and motor noise and vibration measurement results for the examples and comparative examples.

From Table 14, according to the warm rolling temperature of this example, B50 ( _LC) is improved and a non-oriented electrical steel sheet with a small magnetic flux density anisotropy B50 (anisotropy) can be obtained. I understand. In addition, the iron loss value W _10/400 is also low at 9.76 W/kg or less, which is excellent.
In addition, 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 80 dB or less, and the vibration is 70 dB, which is smaller than the comparative example. and vibration are reduced.

(Example 5)
A 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 then wound on a coiler. Table 15 shows the chemical composition of the non-oriented electrical steel sheet obtained from the slab of steel type E.
The hot-rolled steel sheet is subjected to hot-rolled sheet annealing at 900 ° C. for 30 seconds, and in the cooling process after hot-rolled sheet annealing, rolling is performed at 550 ° C. in one pass while changing the rolling reduction rate, and rolling at 400 ° C. or higher (warm rolling ) to finish the rolled plate and then cooled to room temperature.
After pickling the warm-rolled 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 plate No. E- 1-6).

Further, the hot-rolled steel sheet was subjected to hot-rolled steel annealing at 900° C. for 30 seconds under the same conditions as above until it was wound on a coiler, and then cooled to room temperature.
After pickling the hot-rolled and 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 plate No. E- 7).

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

From Table 16, according to the rolling reduction during warm rolling of this example, the B50 ( _LC) is improved and the anisotropy B50 (anisotropy) of the magnetic flux density is smaller than that of the comparative example. I know you can get it. In addition, the value of iron loss _10/400 is low and excellent at 9.73 W/kg or less.
In addition, 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 80 dB or less, and the vibration is 70 dB, which is smaller than the comparative example. and vibration are reduced.

(Example 6)
A 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 then wound on a coiler. Table 17 shows the chemical composition of the non-oriented electrical steel sheet obtained from the slab of steel type F.
The hot-rolled steel sheet is subjected to hot-rolled sheet annealing at 950 ° C. for 10 seconds, and when the temperature reaches 600 ° C. in the cooling process after hot-rolled steel annealing, 17% reduction is applied in one pass and rolled at 470 ° C. (warm rolling ), the temperature was immediately raised to perform intermediate annealing at 950° C. for 10 seconds, followed by cooling to room temperature to obtain an intermediate annealed sheet with a thickness of 1.5 mm.
After pickling the intermediate annealed sheet, it was subjected to cold rolling (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 plate No. F-1 ).

In addition, the hot-rolled steel sheet under the same conditions as the above before being wound on the coiler was subjected to hot-rolled steel annealing at 950 ° C. for 10 seconds, cooled to room temperature (25 ° C.) once, and reheated to reach 600 ° C. At that point, a 17% reduction was applied in one pass, rolling (warm rolling) was completed at 470°C, the temperature was immediately raised to 950°C for 10 seconds, and intermediate annealing was performed. An intermediate annealed sheet was obtained.
After pickling the intermediate annealed sheet, it was cold-rolled (rolling start temperature 35°C, maximum temperature 95°C) to a thickness of 0.25 mm, and was 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 steel annealing at 950° C. for 20 seconds under the same conditions as above until it was wound on a coiler, and then cooled to room temperature.
After pickling the hot-rolled and annealed sheet, it was subjected to cold rolling (rolling start temperature of 35°C, maximum temperature of 95°C) to a thickness of 0.25 mm, and finish annealing at 900°C for 20 seconds (steel sheet No. F -3).

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

From Table 18, according to the two hot-rolled sheet annealings of this example and the warm rolling between the two hot-rolled sheet annealings, the B _{50 (LC)} is improved more than the comparative example, and the anisotropic It can be seen that a non-oriented electrical steel sheet with a small B50 (anisotropy) can be obtained. In addition, the iron loss value W10/400 is also low at _9.73 W/kg, which is excellent.
In addition, 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 80 dB or less, and the vibration is 70 dB, which is smaller than the comparative example. and vibration are reduced.

(Example 7)
A slab of steel grade 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 then coiled on a coiler. Table 19 shows the chemical composition of the non-oriented electrical steel sheet obtained from the slab of steel type G.
The hot-rolled steel sheet was subjected to annealing 1 by changing the temperature and time, and subjected to hot-rolled steel annealing according to the present disclosure and non-annealing, and in the cooling process, rolling 1 was performed by changing the reduction temperature and reduction rate. .
This rolled sheet was subjected to intermediate annealing while changing the temperature and time, and the combination of the temperature of annealing 1, the temperature and reduction ratio of subsequent rolling 1, and the intermediate annealing temperature were changed. After the intermediate annealing, it was cooled to room temperature to obtain an intermediate annealed sheet. Table 20 shows the conditions.
After pickling the intermediate annealed sheet, it was subjected to cold rolling (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 plate No. G-1 ~29).

The obtained non-oriented electrical steel sheet was cut into Epstein samples at intervals of 22.5° from the rolling direction, subjected to strain relief annealing, and then subjected to Epstein measurement.
A motor B was produced using these steel plates for a stator, and noise and vibration were measured at 400,000 rpm.
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 sandwiching rolling to the conditions of this example, B50 ( _LC) is improved over the comparative example, and the anisotropy B50 (anisotropy) of the magnetic flux density is small. It can be seen that a flexible electrical steel sheet can be obtained. In addition, the iron loss value W _10/400 is also low at 9.78 W/kg or less, which is excellent.
In addition, 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 80 dB or less, and the vibration is 70 dB, which is smaller than the comparative example. and vibration are reduced.

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

In addition, the hot-rolled steel sheet under the same conditions as the above before being wound on the coiler was subjected to hot-rolled steel annealing at 950°C for 20 seconds, cooled to room temperature (25°C) once, and then reheated to reach 445°C. At this point, the roll was subjected to a reduction of 33% in one pass, rolled (warm rolled) at 405° C., cooled to room temperature, and coiled. The rolled sheet was again heated to 900° C. for 5 seconds for intermediate annealing, and then cooled to room temperature to obtain an intermediate annealed sheet having a thickness of 1.0 mm.
After pickling the intermediate annealed sheet, it was subjected to cold rolling (rolling start temperature 35° C., maximum temperature 95° C.) to a thickness of 0.25 mm, and was subjected to finish annealing at 900° C. for 20 seconds (steel plate No. H-2 ).

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

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

From Table 22, if warm rolling is performed until the steel sheet reaches room temperature in the cooling process after the first hot-rolled sheet annealing in this example, B50 _(LC) is improved compared to the comparative example, and it is different. It can be seen that a non-oriented electrical steel sheet with a small anisotropy (B50) can be obtained. In addition, the core loss value W10/400 is also low at _9.43 W/kg, which is excellent.
In addition, 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 80 dB or less, and the vibration is 70 dB, which is smaller than the comparative example. and vibration are reduced.

(Example 9)
A slab of steel grade G was subjected to rough hot rolling at a heating temperature of 1100°C, followed by finish hot rolling at a finishing temperature of 880°C to finish the rolled plate to a thickness of 2.5 mm, which was cooled to 550°C on the ROT. After that, it was wound on a coiler. Table 23 shows the chemical composition of the non-oriented electrical steel sheet obtained from the slab of steel type G.
Steel plate No. shown in Table 24. Steel plate No. from G-1. As in G-6, the hot-rolled sheet was annealed, followed by rolling (20% reduction), intermediate annealing, rolling (25% reduction) subsequent to intermediate annealing, coiled, and cooled to room temperature.
After pickling, the rolled sheet was subjected to cold rolling 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 at intervals of 22.5° from the rolling direction, subjected to strain relief annealing, and then subjected to Epstein measurement.
A motor B was produced using these steel plates for a stator, and noise and vibration were measured at 400,000 rpm.
Table 25 shows the magnetic measurement results and the motor noise and vibration measurement results of the example and the comparative example.

From Tables 24 and 25, in the cooling process after both the first and second annealing, or after the first or second annealing in this example, warm rolling was performed until the steel sheet reached room temperature. It can be seen that a non-oriented electrical steel sheet having an improved B50 _(LC) and a small anisotropy B50 (anisotropy) can be obtained. In addition, the core loss value W10/400 is also excellent, being as low as _9.55 W/kg or less.
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 80 dB or less, and the vibration is 70 dB, which is smaller than the comparative example. is reduced.
Of particular note is steel plate No. 1, which was warm-rolled after the first and second annealing. Steel sheet No. G-1 and warm-rolled after the first hot-rolled sheet annealing. In G-2, the value of anisotropy B50 (anisotropy) is 0.008 or less, showing excellent low anisotropy, the magnetic flux density B _{50 (LC)} shows a value of 1.70T, and W _10/400 is Excellent values of 9.39 W/kg or less are shown, noise measurement results of motor B are 74 dB or less, and vibration measurement results are 63 dB or less.
Steel sheet No. 1 was cooled to room temperature after the first hot-rolled sheet annealing, and warm-rolled during the cooling process after the second annealing. G-3 and steel plate No. In G-5, the anisotropic B50 (anisotropy) is the steel plate No. G-1 and steel plate No. It is 0.015 larger than G-2, and the noise measurement result and vibration measurement result of motor B are 79 dB and 69 dB, respectively, which are just above the acceptable value line.
The inventors speculate that this indicates that the effects of the present disclosure are more clearly manifested when a thick steel plate is subjected to warm rolling.

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

Claims (3)

A hot-rolling step of hot-rolling the slab to form a hot-rolled steel sheet;
A hot-rolled sheet annealing step of subjecting the hot-rolled steel sheet to hot-rolled sheet annealing at 800 ° C. or higher and 1080 ° C. or lower for 5 seconds or more and 2 minutes or less;
A warm rolling step of performing warm rolling at a rolling reduction of 3% or more and 75% or less in a temperature range of 400°C or more and 700°C or less in the cooling process of hot-rolled sheet annealing;
A finish annealing step of applying finish annealing to the rolled plate after warm rolling;
with
A composition containing Si: 2.1 to 3.2%, Mn: 0.1 to 2.5%, Al: 0.3 to 1.2% in mass%, and the balance being Fe and impurities, The magnetic flux densities at a magnetic field strength of 5000 A / m in the directions of angles of 0 °, 22.5 °, 45 °, 67.5 ° and 90 ° with respect to the rolling direction are B _{50 (0 °)} and B _{50 (22.5°)} , B _{50 (45°)} , B _{50 (67.5°)} , and B _{50 (90°)} , the anisotropic index defined by the following formula (1) A method for producing a non-oriented electrical steel sheet, which produces a non-oriented electrical steel sheet having a B50 (anisotropy) of 0.017 or less.

Formula (1)
Here, in formula (1), B _50AVE is defined by the following formula (2).

Formula (2) Before performing the finish annealing on the rolled sheet after the warm rolling that has been subjected to the warm rolling in the warm rolling step, intermediate annealing is performed at a temperature of more than 700 ° C. and 1080 ° C. or less for 5 seconds or more and 2 minutes or less. 2. The method for producing a non-oriented electrical steel sheet according to claim 1 , further comprising an intermediate annealing step of performing warm rolling in a temperature range of 400° C. or higher and 700° C. or lower in the cooling process of said intermediate annealing . The non-oriented electrical steel sheet has a magnetic flux density B 50 (0°) at a magnetic field strength of 5000 A / m in the rolling direction and a magnetic flux density B _{50 (0 °)} at a magnetic field strength of 5000 A / m in a direction perpendicular to the rolling direction _90°) and an average magnetic flux density B50 _(LC) of 1.64 T or more.