JP6866696B2 - Non-oriented electrical steel sheet and its manufacturing method, and motor core and its manufacturing method - Google Patents

Description

The present invention relates to a non-oriented electrical steel sheet and a method for manufacturing the same, and a motor core and a method for manufacturing the same.

In recent years, especially in the field of electrical equipment such as rotating machines, small and medium-sized transformers, and electrical components, in the movement to protect the global environment represented by global _{power reduction, energy saving, CO 2 emission reduction, etc.} Therefore, the demand for higher efficiency and smaller size of motors is increasing more and more. In such a social environment, improving the performance of non-oriented electrical steel sheets used as the core material of motors is an urgent issue.

For example, in the automobile field, non-oriented electrical steel sheets are used as the core of a drive motor of a hybrid electric vehicle (HEV) or the like. The drive motors used in HEVs are in increasing demand for miniaturization due to restrictions on installation space and reduction of fuel consumption due to weight reduction.
With the demand for miniaturization of drive motors, it is necessary to increase the torque of the motors. Therefore, the non-oriented electrical steel sheet is required to further improve the magnetic flux density.
In addition, since the battery capacity mounted on an automobile is limited, it is necessary to reduce the energy loss in the motor. Therefore, non-oriented electrical steel sheets are required to further reduce iron loss.
Further, since the demand for high-speed rotation of the motor is increasing, improvement of magnetic characteristics at high frequencies (hereinafter, may be referred to as "high frequency characteristics") is also becoming important.

Further, conventionally, the electromagnetic steel sheet may be used after additional heat treatment. "Strain removal annealing" is known as a typical example. This is a heat treatment for finally removing unnecessary strain because the strain unavoidably introduced into the steel plate due to punching or the like when the steel plate is processed as an electric component worsens the iron loss. This heat treatment is applied to a member (steel plate blank) cut out from a steel plate or a motor core (for example, a stator core) in which members are laminated.
However, while strain-removing annealing has the effect of releasing strain and improving iron loss, at the same time, crystal orientation unfavorable for magnetic characteristics may develop and the magnetic flux density may decrease. Therefore, when particularly high magnetic characteristics are required, it is required to avoid a decrease in magnetic flux density due to strain relief annealing.

Against this background, in the technology of non-oriented electrical steel sheets, various efforts have been made in order to improve magnetic properties, such as control of metal structure such as crystal grain size and crystal orientation in steel sheet, and control of precipitates. (See, for example, Patent Documents 1 to 13).

Japanese Unexamined Patent Publication No. 05-279740 Japanese Unexamined Patent Publication No. 06-306467 JP-A-2002-348644 Japanese Unexamined Patent Publication No. 2011-11165 Japanese Unexamined Patent Publication No. 2006-045613 Japanese Unexamined Patent Publication No. 2006-045641 Japanese Unexamined Patent Publication No. 2006-219692 Japanese Unexamined Patent Publication No. 58-23410 Japanese Unexamined Patent Publication No. 11-124626 International Release 2012/029621 International Publication 2016/136095 Japanese Unexamined Patent Publication No. 03-223424 International Publication No. 2014/129034

Here, Patent Document 1 describes a steel strip having a specific chemical composition containing 4% <Si ≤ 8.0% and Al ≤ 2.0% in mass% at a rolling reduction of 5% or more and less than 40%. A non-oriented electrical steel sheet obtained through a process such as cold rolling is disclosed.
Further, in Patent Document 2, a steel strip containing a specific chemical composition containing Si ≦ 4.0 and Al ≦ 2.0% in mass% is cold-rolled at a rolling reduction of 5% or more and less than 40%. The non-oriented electrical steel sheet obtained through the above steps is disclosed.
However, the non-oriented electrical steel sheets disclosed in Patent Documents 1 and 2 have sufficient performance for a level requiring high magnetic characteristics, such as a core for a drive motor such as an HEV. There wasn't.

Further, Patent Document 3 has a specific chemical composition such as Si ≦ 0.4 _{, the value of the magnetic flux density B 25 at} a magnetic field strength of 2500 A / m is 1.70 T or more, and the magnetic field strength is 5000 A / m. A non-directional electromagnetic steel plate having a magnetic flux density B _{50 of 1.80 T or more is disclosed.} However, the non-oriented electrical steel sheet disclosed in Patent Document 3 has an Al content of 0.5% or less in mass% in order to avoid a significant adverse effect on the improvement _{of the magnetic flux density (B 25) in a low magnetic field.} It was limited and did not perform well for the levels that required high magnetic properties.
Patent Document 4 has a specific chemical composition such as 0.1% <Si ≤ 2.0% and Al ≤ 1.0, and specific production conditions such as a finishing hot spreading end temperature of 550 ° C to 800 ° C. The non-directional electromagnetic steel plate manufactured in the above is disclosed. However, the Al content is limited to 1.0% or less in mass%, which is not sufficient performance for the level requiring high magnetic properties. Further, even if it was manufactured by applying low-temperature hot-rolling to a hot-rolling temperature of 500 ° C. to 850 ° C., the expected effect was not obtained.

Patent Documents 5 to 7 have a specific chemical composition such as 0.05% to 4.0% (or 4.5%) of Si and 3.5% or less of Al in mass%, and the rolling direction. A non-oriented electrical steel sheet having excellent magnetic properties in the direction of 45 ° and having small in-plane anisotropy is disclosed.
However, the techniques described in Patent Documents 5 to 7 perform low-temperature hot-rolling at a hot-rolling temperature of 500 to 850 ° C., as in Patent Document 4, and are manufactured by applying such low-temperature hot-rolling. However, the expected effect was not obtained, and the performance was still not sufficient for the level requiring high magnetic properties. Further, the techniques described in Patent Documents 5 to 7 have not been sufficient in performance for the level required for iron loss at high frequencies.

Further, in Patent Document 8, the heating rate of finish annealing of a steel sheet having a chemical composition of 2.5% or more of Si and 1.0% or more of Al in mass% is controlled to 10 ° C./sec or more. , Techniques for improving magnetic properties are disclosed. However, in the current process based on continuous annealing, this degree of heating rate can be said to be a general technical range.
Patent Document 9 discloses a technique for avoiding deterioration of iron loss by slowing the heating rate of finish annealing to 40 ° C./sec because iron loss worsens if the heating rate of finish annealing is too fast. There is.
Patent Document 10 discloses a technique for controlling the texture and increasing the magnetic flux density by extremely increasing the heating rate of finish annealing to 100 ° C./sec. However, it has been pointed out that simply increasing the heating rate causes the magnetic characteristics to become unstable.
According to Patent Document 11, when the heating rate of finish annealing is high, the magnetic flux density becomes unstable. Therefore, in particular, appropriate heating in each temperature range of 600 ° C. to 700 ° C. and 700 ° C. to 760 ° C. A technique for avoiding destabilization of magnetic flux density by selecting a speed is disclosed.
Patent Documents 12 and 13 disclose techniques relating to semi-process non-oriented electrical steel sheets. Semi-process non-oriented electrical steel sheets are shipped after being recrystallized by finish annealing with strain applied, and then heat-treated by the steel sheet user to release the strain and obtain magnetic properties. It is a thing.
In particular, Patent Document 12 shows that it is effective to set the heating rate at the time of finish annealing to 5 ° C./sec to 40 ° C./sec in relation to Al nitride. Further, Patent Document 13 discloses a technique for improving the magnetic properties for a semi-process by increasing the heating rate up to 740 ° C. to 100 ° C./sec or more in low Al steel.
However, the conventional techniques have not been able to sufficiently meet the above-mentioned modern market needs in consideration of high frequency characteristics and magnetic characteristics after strain removal annealing.

As described above, the non-oriented electrical steel sheets disclosed in Patent Documents 1 to 13 have not sufficiently obtained the required magnetic properties.
As described above, the conventional non-oriented electrical steel sheet does not satisfy sufficient magnetic characteristics for a level requiring high magnetic characteristics, and further improvement of magnetic characteristics has been required.

The present invention has been made in view of the above circumstances, and the subject of the present invention is that the in-plane anisotropy is small, the iron loss is low, and the iron loss is high, in consideration of high frequency characteristics and magnetic characteristics after strain relief annealing. It provides a non-oriented electrical steel sheet having a magnetic flux density and excellent magnetic characteristics, and a method for manufacturing the same.

In order to obtain the above-mentioned non-oriented electrical steel sheet having excellent magnetic properties, the present inventors improve the degree of integration in the {100} orientation in a steel sheet having a chemical composition with a large amount of Al (high Al component system). The conditions for this were examined. Pursuing that condition, in addition to increasing the degree of integration in the {100} orientation, reducing the degree of integration in the {223} <252> orientation in the intermediate layer of the steel sheet results in high-frequency characteristics and magnetism after strain relief annealing. It was found that it has a strong correlation with the improvement of magnetic characteristics considering even the characteristics. Then, the conditions for obtaining a steel sheet having this characteristic were examined in detail. As a result, in a high Al component steel sheet, when the mass ratio (Al / Si) of Al and Si is set to 0.5 or more and the cold rolling reduction rate (reduction rate in cold rolling) is set to a specific range. In addition, it was found that a steel sheet that solves the above problems can be obtained. Similarly, it was found that a steel sheet that solves the above problems can be obtained even when the steel sheet after cold stretching is rapidly heated by finish annealing.

Furthermore, from the viewpoint that the change in texture in the intermediate layer is related to the shear deformation due to rolling, detailed studies have been conducted on the control under hot rolling conditions. As a result, even when a steel sheet having a high Al component system and a mass ratio (Al / Si) of Al to Si of a specific value or more is finished and hot-rolled at a low temperature, the intermediate layer of the steel sheet , {223} <252> It was confirmed that the degree of integration of the orientation could be reduced.

That is, the present invention has been made based on these findings. That is, the gist of the present invention is as follows.

<1> By mass%,
C: 0.0030% or less,
Si: 0.0% to 3.5%,
Al: 1.0% to 3.5%,
Mn: 0.0% to 3.0%,
S: 0.0030% or less, and the balance: having a chemical composition containing Fe and impurities.
The mass ratio of Al / Si is 0.5 or more,
A non-oriented electrical steel sheet having a degree of integration of {223} <252> orientations of 6 or less in an intermediate layer having a plate thickness of 1/10 to 1/5.
<2> The non-oriented electrical steel sheet of <1> in which the maximum value of the degree of integration in the in-plane orientation of the {100} orientation in the intermediate layer is 11 or more.
_{<3> The maximum value (MI 100} ) of the degree of integration in the in-plane orientation of the {100} orientation in the intermediate layer and the degree of integration in the in-plane orientation of the {100} orientation in the surface layer from the steel plate surface to the plate thickness 1/10. The maximum value of (MS ₁₀₀ ) and the maximum value of the degree of integration in the in-plane orientation of the {100} orientation in the central layer of the plate thickness 1/5 to 1/2 of the plate thickness (MC ₁₀₀ ) are
MI ₁₀₀ > MS ₁₀₀ > MC ₁₀₀
The non-oriented electrical steel sheet according to <1> or <2>, which satisfies the relationship of.
_{<4> The ratio (B 50 / Bs) of the average magnetic flux density B 50 in} the all-circumferential direction and the saturated magnetic flux density Bs when excited with a magnetization force of 5000 A / m is 0.885 or more <1> to <3>. The non-directional electromagnetic steel plate according to any one of the above items.
<5> Of the magnetic flux densities in the five directions of 0 °, 22.5 °, 45 °, 67.5 °, and 90 ° with respect to the rolling direction, B _50max, which has the highest magnetic flux density, and B 50max, which has the highest magnetic flux density. Any one of <1> to <4> in which the value obtained by dividing the difference from the low B _{50 min} by the saturation magnetic flux density Bs is 0.015 or less [(B _50max −B _{50 min) / Bs ≦ 0.015)].} The non-directional electromagnetic steel plate described in the section.
<6> was carried flux density B _A of the steel sheet before carrying out the heat _treatment, and heating rate is 100 ° C. / hr, the maximum temperature is 800 ° C., and the holding time at 800 ° C. is a heat treatment under conditions of 2 hours when the magnetic flux density of the steel sheet after the _{B B,} the ratio between said _{B a} wherein _{B B is,} to satisfy the relationship of B B / _{B a} ≧ 0.98 <1> ~ or <5> 1 The non-directional electromagnetic steel sheet described in the section.
<7> A hot rolling step of hot rolling a slab having the chemical composition described in <1>, and
A cold rolling step of cold rolling on a steel sheet after the hot rolling step, and a cold rolling step.
It has a finish annealing step of finish annealing the steel sheet after the cold rolling step, and satisfies at least one of the following conditions (a), (b), and (c) <1> to <6>. The method for manufacturing a non-oriented electrical steel sheet according to any one of the above items.
(A) Hot rolling step: Finish rolling in a temperature range of 500 ° C to 800 ° C (b) Cold rolling step: Cold rolling so that the total rolling reduction is 90% or more (c) Finish annealing step : The steel sheet after the cold rolling process is finish-annealed so that the average heating rate in the temperature range of room temperature (25 ° C) to 800 ° C is 80 ° C / sec or more <8><1> to <6>. A motor core in which the non-directional electromagnetic steel sheet according to any one item is laminated.
<9> A step of punching the non-oriented electrical steel sheet according to any one of <1> to <6> to obtain a punched member.
The process of laminating the punched members and
A method for manufacturing a motor core.

According to the present invention, a non-oriented electrical steel sheet having low in-plane anisotropy, low iron loss, and high magnetic flux density and excellent magnetic properties in consideration of high frequency characteristics and magnetic characteristics after strain removal annealing. And its manufacturing method can be provided.

It is a perspective view which shows an example of the motor core which concerns on this embodiment. It is a perspective view which shows another example of the motor core which concerns on this embodiment.

Hereinafter, an example of a preferred embodiment of the present invention will be described in detail.
In the present specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.

In the present specification, when the terms "plate thickness 1/10", "plate thickness 1/5", and "plate thickness 1/2" are used, they indicate predetermined positions in the plate thickness direction from the surface of the steel plate.
The surface layer indicates a region from the surface of the steel sheet to the thickness of 1/10. The intermediate layer indicates a region from a plate thickness of 1/10 to a plate thickness of 1/5. The central layer indicates a region from a plate thickness of 1/5 to a plate thickness of 1/2.

In the present specification, for each direction (for example, {223} <252> direction, {100} direction, etc.), the mirror index in the normal direction of the rolling surface (rolling surface direction) and the direction parallel to the rolling direction. With respect to the mirror index (direction in the rolling plane), the direction within ± 5 ° is assumed to be the direction.

<Directional electromagnetic steel sheet>
(Characteristics of crystal orientation)
The non-oriented electrical steel sheet according to this embodiment has a mass% of C: 0.0030% or less, Si: 0.0% to 3.5%, Al: 1.0% to 3.5%, Mn: It has a chemical composition containing 0.0% to 3.0%, S: 0.0030% or less, and the balance: Fe and impurities.
The mass ratio of Al / Si is 0.5 or more.

Further, the non-oriented electrical steel sheet according to the present embodiment has an integration degree of {223} <252> orientation in the intermediate layer of 6 or less (this is a feature (A)).
The non-oriented electrical steel sheet according to the present embodiment has the above-mentioned characteristics, and is excellent in magnetic characteristics in consideration of high-frequency characteristics and magnetic characteristics after strain removal annealing. This will be described below.

The degree of integration of the {223} <252> orientation in the intermediate layer is 6 or less, which is an important feature in the non-oriented electrical steel sheet of the present embodiment. The {223} <252> orientation is relatively close to the {111} orientation, which is unfavorable for magnetic properties. The {223} <252> direction is a direction that should be suppressed so as to be naturally reduced.
Therefore, in the non-oriented electrical steel sheet of the present embodiment, the degree of integration of the {223} <252> orientation in the intermediate layer is defined as 6 or less. It is preferably 5 or less, more preferably 4 or less. The degree of integration of the {223} <252> orientation in the intermediate layer may be 0.

The {223} <252> orientation is also an intermediate orientation between the {111} <211> orientation and the {112} <110> orientation in which accumulation in high-purity steel proceeds by rolling. Therefore, conventionally, when the cold spreading reduction rate becomes high, the {223} <252> direction cannot be sufficiently lowered. Further, especially in the intermediate layer, since the additional shear deformation becomes large during rolling, the {223} <252> orientation is likely to occur. However, it was found that the accumulation of {223} <252> orientations can be suppressed under the conditions of a high Al component system and a high cold spreading reduction rate, and under the conditions of a high Al component system and rapid heating in finish annealing. It was also found that the accumulation of {223} <252> orientations can be suppressed even under the conditions of high Al component system and finishing heat spreading at low temperature (low temperature finishing heat spreading).

Under the above conditions, the reason why the accumulation of {223} <252> directions can be suppressed is not clear, but it is presumed as follows.
Generally, Si is known to have the effect of limiting the slip system of dislocations associated with deformation. However, the slip system changes when Al is contained in a high concentration. Then, it is considered that by increasing the heating rate at the time of recrystallization, the generation of nuclei in the {223} <252> orientation that should originally appear was suppressed, and the behavior was different from the conventional one. Further, when the cold rolling reduction ratio is high, the effect of suppressing the {223} <252> orientation works strongly, which is considered to be related to the change in the slip system of dislocations during rolling.
Further, it is considered that the same phenomenon occurs when a steel piece containing a high concentration of Al is subjected to finish heat spreading at a low temperature.

On the other hand, the reason why the accumulation of {223} <252> orientations is suppressed by increasing the heating rate of finish annealing is not clear, but it is considered as follows. In addition to the above-mentioned change in the slip system due to the high concentration of Al, the temperature rapidly exceeds the recrystallization start temperature, which weakens the orientation selectivity. It is presumed that the recrystallization of various orientations was started thereby, and the priority of the accumulation of {223} <252> orientations was suppressed.

The intermediate layer formed through additional shear deformation has a crystal orientation different from that of the adjacent surface layer and central layer, and exists in the intermediate layer when the crystal grain size is coarsened by strain relief annealing or the like. There was a situation in which the crystal grains to grow were easy to grow.
However, the non-oriented electrical steel sheet of the present embodiment is a case where grains are grown by strain relief annealing because the {223} <252> orientation, which is not preferable for the magnetic characteristics existing in the intermediate layer, is reduced. However, it is considered that the deterioration of the magnetic characteristics could be suppressed.

The non-oriented electrical steel sheet of the present embodiment further has a maximum value of the degree of integration in the in-plane orientation of the {100} orientation in the intermediate layer (hereinafter, the maximum value of the degree of integration may be referred to as "peak integration degree"). However, it is preferable that the value is 11 or more (this is a feature (B)).

It is well known that increasing the {100} orientation is advantageous for magnetic properties. However, conventionally, in the intermediate layer, since the {223} <252> orientation is not sufficiently reduced as described above, the accumulation in the {100} orientation cannot be sufficiently increased. As described above, for example, in a steel sheet of a high Al component system, the present embodiment obtained by controlling at least one of a high cold rolling reduction ratio, a condition of rapid heating in finish annealing, and a condition of low temperature finish hot rolling. In the intermediate layer of the non-oriented electrical steel sheet of the form, the development of {223} <252> orientation is suppressed. At the same time, the degree of integration in the {100} direction tends to increase. However, with respect to the {100} orientation, the distribution of the degree of integration in the plane is likely to change, and it is difficult to accurately represent the characteristics in a specific in-plane orientation. Therefore, in the non-oriented electrical steel sheet according to the present embodiment, the peak integration degree is set in the plane.
Therefore, in the non-oriented electrical steel sheet of the present embodiment, the peak integration degree in the {100} direction in the intermediate layer is preferably 11 or more. It is preferably 14 or more, more preferably 17 or more.

In addition to the above features, the non-oriented electrical steel sheet of the present embodiment has a peak integration degree of {100} orientation in the intermediate layer (MI ₁₀₀ ) and a peak integration degree of {100} orientation in the surface layer (MS _{100). ) And the peak integration degree (MC 100} ) in the {100} direction in the central layer _{may satisfy MI 100} > MS ₁₀₀ > MC ₁₀₀ (this is characterized by (C)).

The feature (C) is a feature (B) characterized by a change in the plate thickness direction. As described above, in the non-oriented electrical steel sheet of the present embodiment, the accumulation in the {223} <252> orientation is reduced in the intermediate layer. In addition, the accumulation in the {100} direction tends to increase accordingly. These phenomena occur in connection with additional shear deformation due to rolling (at least one of hot and cold rolling), but there is also material constraint due to rolls in the surface layer. Therefore, although it is not up to the intermediate layer, the {223} <252> orientation decreases and the {100} orientation tends to increase due to the occurrence of the shear deformation component. These phenomena in the surface layer are more likely to occur than in the central layer where no additional shear deformation acts.
When the texture change in the plate thickness direction has the above relationship, it is possible to avoid deterioration of magnetic characteristics due to grain growth in strain annealing and to obtain a steel sheet having excellent high frequency characteristics. The degree of this change is preferably 1.1 or more, more preferably 1.2 or more for _{MI 100} / MS ₁₀₀ or MI ₁₀₀ / MC _100.

The crystal orientation can be measured by the following method. The surface layer on one side is removed by performing mechanical polishing and chemical polishing on a steel plate sample of about 30 mm × 30 mm cut out from the steel plate. Next, measurement test pieces having been reduced in thickness until the central plate thickness direction position of the surface layer, intermediate layer or center layer of the original steel sheet becomes the surface are produced.
For each measurement test piece, polar diagrams of {200} plane, {110} plane, and {211} plane are measured by an X-ray diffractometer, and a crystal orientation distribution function ODF (Orientation Determination Function) in each layer is created. Based on this crystal orientation distribution function, the degree of integration of {223} <252> orientation and the degree of peak accumulation of {100} orientation in each layer are obtained.

Next, the reason for limiting the chemical composition of the non-oriented electrical steel sheet according to the present embodiment will be described. Regarding the composition of the steel sheet, "%" is "mass%".

The non-oriented electrical steel sheet according to this embodiment has a mass% of C: 0.0030% or less, Si: 0.0% to 3.5%, Al: 1.0% to 3.5%, Mn: It has a chemical composition of 0.0% to 3.0%, S: 0.0030% or less, and the balance: Fe and impurities.

(C: 0.0030% or less)
Since C is a component that increases iron loss and causes magnetic aging, the smaller the content of C, the better. Therefore, the content of C is set to 0.0030% or less. The preferable upper limit of the amount of C is 0.0025% or less, and more preferably 0.0020% or less. The lower limit of the C content is not particularly limited, but the C content is practically 0.0001% or more in consideration of the industrial purification technology, and 0.0005% or more in consideration of the manufacturing cost.

(Si: 0.0% to 3.5%)
When the content of Si increases, the magnetic flux density decreases and the hardness increases, which deteriorates the punching workability, and also in the manufacturing process of non-oriented electrical steel sheets, the workability such as cold spreading is improved. It will be reduced and the cost will be high. Therefore, the Si content is set to 3.5% or less. The preferable upper limit of the amount of Si is 3.2% or less, and the more preferable upper limit is 3.0% or less. On the other hand, Si may be 0%, but since it has an effect of increasing the electric resistance of the steel sheet, reducing the eddy current loss and reducing the iron loss, it may be added as necessary. The preferable lower limit of the amount of Si is 0.1% or more, the more preferable lower limit is 0.5% or more, and further preferably 1.0% or more.

(Al: 1.0% to 3.5%)
Like Si, Al is a component that has the effect of reducing iron loss by increasing electrical resistance and reducing eddy current loss, but compared to Si, it has less effect of increasing the hardness of the steel sheet. .. Therefore, Al needs to be contained in an amount of 1.0% or more. The preferable lower limit of the amount of Al is 1.2% or more, and the more preferable lower limit is 1.5% or more. On the other hand, when the Al content increases, the saturation magnetic flux density decreases, leading to a decrease in the magnetic flux density. Further, the yield ratio is reduced and the punching workability is also deteriorated. Therefore, the upper limit of the Al content is 3.5% or less. The preferable upper limit of the amount of Al is 3.0% or less, and the more preferable upper limit is 2.7% or less.

(Mass ratio of Al / Si)
When the mass ratio of Al / Si is increased, the peak integration degree in the {100} orientation increases, the integration degree in the {223} <252> orientation in the surface layer and the intermediate layer tends to decrease, and the magnetic flux becomes magnetic flux. Increases density. Therefore, the mass ratio of Si / Al is set to 0.5 or more. The mass ratio of Si / Al is preferably 0.7 or more, preferably 1.0 or more, and more preferably 1.2 or more.

(Mn: 0.0% to 3.0%)
Mn increases electrical resistance to reduce eddy current loss and suppresses precipitation of fine sulfides such as MnS, which are harmful to crystal grain growth. When Mn is contained for these purposes, it is preferable to contain Mn in an amount of 0.1% or more. The preferable lower limit of the amount of Mn is 0.15% or more. However, when the Mn content increases, the grain growth during annealing decreases and the iron loss increases. Therefore, the upper limit of the Mn content is set to 3.0% or less. The preferable upper limit of the amount of Mn is 2.5% or less, more preferably 2.0% or less.

(Relationship between Si, Al, and Mn contents)
It should be noted that (Si content) + (2 × Al content)-(Mn content) is 2.0% by mass between the mutual elements of the alloy element components Si, Al, and Mn. It is good to satisfy the above relationship. When (Si content) + (2 × Al content)-(Mn content) is less than 2.0%, the chemical composition system has α-γ transformation. Therefore, α-γ transformation may occur even during finish annealing in the manufacturing process of non-oriented electrical steel sheets, which may hinder the improvement of magnetic properties. Therefore, it is preferable to satisfy the above relationship.

(S: 0.0030% or less)
S is 0.0030% or less because it inhibits recrystallization and grain growth during finish annealing and the like due to fine precipitation of sulfides such as MnS. The preferred upper limit of the S content is 0.0020% or less, more preferably 0.0015% or less. The lower limit of the S content is not particularly limited, but the S content is practically 0.0001% or more in consideration of the industrial purification technology, and 0.0005% or more in consideration of the manufacturing cost.

(Fe and impurity elements)
The rest of the steel sheet is Fe and impurity elements. Here, the impurity element refers to a component contained in the raw material or a component mixed in the manufacturing process and not intentionally contained in the steel sheet.

The chemical composition is the composition of the steel components constituting the steel sheet. If the steel sheet used as the measurement sample has an insulating film or the like on the surface, the measurement is performed after removing the insulating film or the like.
Examples of the method for removing the insulating film of the non-oriented electrical steel sheet include the following methods.
First, the non-oriented electrical steel sheet having an insulating film, etc., aqueous sodium hydroxide (NaOH: 10 _{wt% +} H 2 O: 90 wt%) in 15 minutes at 80 ° C., immersion. Then, it is immersed in an aqueous sulfuric acid solution (H ₂ SO ₄ : 10% by mass + H ₂ O: 90% by mass) at 80 ° C. for 3 minutes. Thereafter, an aqueous solution of nitric acid _(HNO 3: 10 _{wt% +} H 2 O: 90 wt%) by normal temperature for 1 minute just under (25 ° C.), washed immersed in. Finally, dry with a warm air blower for a little less than 1 minute. As a result, a steel sheet from which the insulating film described later has been removed can be obtained.

The content ratio of each element in the steel plate can be measured by, for example, inductively coupled plasma mass spectrometry (ICP-MS method: Inductively Coupled Plasma-Mass Spectrometry). Specifically, first, a non-oriented electrical steel sheet to be measured is prepared. A part of the electrical steel sheet is cut into pieces and weighed, and this is used as a measurement sample. The measurement sample is dissolved in an acid to obtain an acid solution, and the residue is collected from a filter paper and 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 it if necessary, an ICP-MS measurement solution can be obtained.

(Magnetic characteristics of non-oriented electrical steel sheets)
The non-directional electromagnetic steel plate according to the present embodiment has excellent magnetic characteristics, _{and is the ratio of the average magnetic flux density B 50 in} the entire circumferential direction to the saturated magnetic flux density Bs when excited with a magnetization force of 5000 A / m (B). ₅₀ / Bs) is preferably 0.875 or more. It is preferably 0.880 or more, more preferably 0.885 or more, still more preferably 0.890 or more. The upper limit of B ₅₀ / Bs is not particularly limited, but the closer it is to 1, the better, and examples thereof include 0.980 or less.
Further, the magnetic flux density B _{50 on} average in the entire circumferential direction is preferably 1.75 (T) or more (preferably 1.80 (T) or more).

_{Here, the magnetic flux density B 50} of the non-directional electromagnetic steel plate on average in the entire circumferential direction is 22.5 °, 45 °, 67.5 °, and 90 ° with respect to the rolling direction (0 °) and the rolling direction. It is an average value of the magnetic flux density B _{50 in the five directions of.}

− In-plane anisotropy −
The non-oriented electrical steel sheet according to this embodiment is excellent in in-plane anisotropy of magnetic flux density. The non-directional electromagnetic steel plate according to the present embodiment has excellent in-plane anisotropy of magnetic flux density, and is 22.5 °, 45 °, 67.5 ° with respect to the rolling direction (0 °) and the rolling direction. , and out of the magnetic flux density at 5 direction of 90 °, and most flux density is high _{B 50Max,} the difference between the highest flux density is low _{B 50min,} less than a value obtained by dividing the saturation magnetic flux density Bs 0.018 [(B _50max -B _50min) / Bs good to be <0.018]. Preferably, 0.015 _{[(B 50max -B 50min) /Bs≦0.015} ], and more preferably 0.013 or less _{[(B 50max -B 50min) /Bs≦0.013} ].

-High frequency characteristics-
As described above, the non-oriented electrical steel sheet according to the present embodiment suppresses the accumulation in the {223} <252> orientation, which is not preferable for the magnetic characteristics, in the crystal orientation of the surface layer and the intermediate layer of the steel sheet. It also promotes accumulation in the {100} orientation, which is favorable for magnetic properties. Since the characteristic value changes greatly depending on the steel sheet composition and the degree of texture control, etc., it is not specified quantitatively, but it is said that the characteristic value is particularly preferable in the excitation situation at high frequency where the magnetic flux is concentrated near the surface layer of the steel sheet. It is a feature.

-Changes in magnetic properties due to additional heat treatment (strain removal annealing)-
The non-oriented electrical steel sheet according to the present embodiment can suppress the decrease in magnetic flux density that occurs during the growth of recrystallized grains even when additional heat treatment (strain removal annealing) is performed. Is.
For example, the magnetic flux density B _A of the steel sheet before carrying out the additional heat _treatment, and heating rate is 100 ° C. / hr, the maximum temperature is 800 ° C., and the holding time at 800 ° C. is a heat treatment under conditions of 2 hours embodiment when the magnetic flux density of the steel sheet after was _{B B,} the ratio of _{B B} and _{B a is,} B B / _{B a} ≧ 0.98 (preferably _B B / _{B a} ≧ 0.985, more preferably B _{The relationship of B} / B _A ≧ 0.99) can be satisfied.
_{Incidentally,} B B / _B upper limit of _A is not particularly specified, there is no characteristic degradation by the addition heat treatment _{(i.e., B B / B A = 1.0} ) that is also a reference to a target. However, in the non-oriented electrical steel sheet of the present embodiment, since the crystal orientation is controlled preferably to account for changes in the thickness direction, preferably the orientation grow preferentially for magnetic properties, B B _/ B _A is It may exceed 1.0.
Here, the measurement method of the magnetic flux density B _A and B _B before and after carrying out the additional heat treatment is the same as the aforementioned B _50.

As described above, even when the steel sheet according to the present embodiment is subjected to additional heat treatment (strain removal annealing), a decrease in magnetic flux density is suppressed as compared with the case where the conventional steel sheet is strained and annealed. The reason for this is not always clear, but I think it is as follows.

In conventional non-oriented electrical steel sheets, when grain growth is performed at a relatively low temperature by additional heat treatment such as strain relief annealing, the grain has a different orientation (than the crystal grain having the {100} orientation, which is considered to be advantageous for magnetic properties. For example, the growth of crystal grains having {111}, {223}, {112}, etc.) becomes dominant. Therefore, it is presumed that the magnetic flux density of the conventional non-oriented electrical steel sheet is significantly reduced.
In particular, the priority of growth due to such crystal orientation (for example, {111}, {223}, {112}, etc.) tends to cause a change in crystal orientation in the plate thickness direction. That is, it is considered that there is a high possibility that the orientation difference from the adjacent grains will be large, and that the crystal grains in the intermediate layer, which tend to have a high driving force for grain growth, are easily affected.

On the other hand, the non-oriented electrical steel sheet according to the present embodiment contains Al in a relatively high concentration, and further, the temperature conditions for finish rolling by hot rolling, high cold rolling reduction, and finish annealing after cold rolling. Control at least one of the heating conditions of. As a result, the steel sheet during the production of non-oriented electrical steel sheets (that is, after finish annealing) suppresses the accumulation in the {223} <252> orientation of the crystal orientation of the intermediate layer and enhances the accumulation in the {100} orientation. It is supposed to be. Therefore, in the orientation development in the grain growth by the additional heat treatment by the slow heating after the finish annealing, the growth in the {223} <252> orientation is not dominant. Then, since the crystal grains having an orientation advantageous for increasing the magnetic flux density (that is, the {100} orientation) are not eroded and the {100} orientation is predominantly present or grows, the high magnetic flux density is maintained. Presumed.
Depending on the conditions adopted for realizing the invention, the accumulation of at least one of the {111} direction and the {112} direction is also suppressed, which has a preferable effect on the magnetic flux density. Depending on the conditions, the accumulation of at least one of the {111} and {112} directions may increase, but the effect is compared to the effect obtained by controlling the {100} and {223} directions. small. Therefore, the effect obtained by the non-oriented electrical steel sheet of the present embodiment is not impaired.

In addition to this, in a steel sheet containing a relatively high concentration of Al, as a result of controlling at least one of the finish hot spreading condition, the cold rolling reduction rate and the finish annealing condition within a specific range, in particular, nitride in the steel sheet. The object is relatively coarse and has a low number density. It is possible that the nitride thus controlled has an advantageous effect on the selective growth in a specific direction during grain growth at low temperature including slow heating. For example, in the non-directional electromagnetic steel plate according to the present embodiment, in addition to the texture, the nitride is coarse and the number density is low, and the slow heating grain growth property is appropriately controlled, so that the initial stage (crystal grain size). For example, a crystal generated at a relatively high heating rate (for example, about 10 ° C. (10 ° C./sec) or more per second) at a stage of 80 μm or less) is produced in a grain growth stage (as a crystal particle size, the crystal particle size). For example, at a stage of more than 80 μm), the heating rate is relatively low and the temperature is low (for example, about 100 ° C. (100 ° C./hr) or less per hour, and the temperature range in which grain growth and nitride coarsening occur is relatively low. The growth is progressing in the holding time in the temperature range of 550 ° C. to 750 ° C. for 2 hours or more). As a result, it is considered that the effect of preferentially and selectively growing crystal grains in a specific orientation is enhanced.
In the above, the effect of the preferable selection of the crystal orientation on the grain growth was described by the orientation change at around 80 μm, but this effect was set to more than 80 μm, for example 100 μm or more, for example, in finish annealing (in rapid heating annealing). Even in the steel sheet, further grain growth from the steel sheet, for example, preferably orientation selectivity of 200 μm or more is not lost.

The crystal grain size is measured as follows.
The test piece is cut so that the cross section of the plate thickness can be observed, and the grain boundaries are corroded and expressed by nightal etching. After that, the metal structure of the plate thickness cross section is photographed with an optical microscope, and the crystal grain size of 100 or more crystal grains is calculated by the line segment method (drawing a straight line on the photograph of the metal structure and calculating from the number of intersections between the straight line and the grain boundary). ) To determine the average grain size.

<Manufacturing method of non-oriented electrical steel sheet>
As described above, the non-oriented electrical steel sheet according to the present embodiment contains Al in a relatively high concentration, and further, the temperature condition of finish rolling by hot rolling, the reduction rate condition by cold rolling, and cold rolling. It can be obtained by controlling at least one of the heating conditions for the subsequent finish annealing under the conditions described below. The following method is mentioned as an example of a preferable manufacturing method of the non-oriented electrical steel sheet according to the present embodiment.
Hereinafter, an example of a preferable manufacturing method of the non-oriented electrical steel sheet according to the present embodiment will be described.

An example of a suitable manufacturing method for the non-directional electromagnetic steel sheet of the present embodiment is the above-mentioned chemical composition (in mass%, C: 0.0030% or less, Si: 0.0% to 3.5%, Al: 1). Hot rolling (hot rolling) of slabs having 0.0% to 3.5%, Mn: 0.0% to 3.0%, S: 0.0030% or less, balance: Fe and impurities) A process (hot rolling process), a cold rolling process (cold rolling process) of cold rolling (cold rolling) on a steel sheet after a hot rolling process, and a finish annealing process of finishing annealing on a steel sheet after a cold rolling process. , Have.
Then, at least one of the following conditions (a), (b) and (c) is satisfied.
(A) Hot rolling step: Finish rolling in a temperature range of 500 ° C to 800 ° C (b) Cold rolling step: Cold rolling so that the total rolling reduction is 90% or more (c) Finish annealing step : Finish-anneal the steel sheet after the cold rolling process so that the average heating rate in the temperature range of room temperature (25 ° C) to 800 ° C is 80 ° C / sec or more.

Moreover, as another example of the more preferable manufacturing method of the non-oriented electrical steel sheet of this embodiment, the following methods (1) to (4) can be mentioned.

(1) The hot rolling process is a process of performing finish rolling in a temperature range of 500 ° C. to 800 ° C., and the cold rolling process is a total of cold rolling (cold rolling) on a steel sheet after hot rolling. This is a step of cold rolling so that the rolling reduction is 90% or more.

(2) The cold rolling step is a step of cold rolling a steel sheet after hot rolling so that the total reduction ratio in cold rolling (cold rolling) is 90% or more, and the finish annealing step is a step of cold rolling. This is a step of finish annealing the steel sheet after the cold rolling step so that the average heating rate at room temperature (25 ° C.) to 800 ° C. is 80 ° C./sec or more.

(3) The hot rolling process is a process of performing finish rolling in a temperature range of 500 ° C. to 800 ° C., and the finish annealing process is a process of applying a steel sheet after the cold rolling process to a temperature of room temperature (25 ° C.) to 800 ° C. This is a step of finish annealing so that the average heating rate in the region is 80 ° C./sec or more.

(4) The hot rolling process is a process of performing finish rolling in a temperature range of 500 ° C. to 800 ° C., and the cold rolling process is a total of cold rolling (cold rolling) on a steel sheet after hot rolling. It is a step of cold rolling so that the rolling reduction is 90% or more, and the finish annealing step is an average heating rate of 80 in the temperature range of room temperature (25 ° C.) to 800 ° C. on the steel sheet after the cold rolling step. This is a step of finish annealing so that the temperature is equal to or higher than ° C./sec.

Then, the non-oriented electrical steel sheet obtained by the above-mentioned manufacturing method has a degree of integration of {223} <252> orientation in the intermediate layer of the steel sheet reduced to 6 or less (that is, the above-mentioned feature (A) can be obtained. ). It is considered that this is because, as described above, the slip deformation related to the shear deformation, which acts particularly strongly on the intermediate layer, is appropriately controlled.

Further, by the above manufacturing method, a steel sheet having a peak integration degree of {100} orientation in the intermediate layer of 11 or more can be obtained (that is, the above-mentioned feature (B) is further obtained).
Furthermore, the peak accumulation of {100} orientation in the intermediate layer (MI ₁₀₀ ), the peak integration of {100} orientation in the surface layer (MS ₁₀₀ ), and the peak integration of {100} orientation in the central layer (MC ₁₀₀ ). However, a _{steel sheet satisfying MI 100} > MS ₁₀₀ > MC ₁₀₀ is obtained (that is, the above-mentioned feature (C) is further obtained).

Hereinafter, each step in an example of a preferable production method will be collectively described.

(Hot rolling process)
Specifically, first, a slab having the above-mentioned chemical composition is roughly rolled to a desired thickness (hereinafter, may be referred to as "crude hot rolling"). It is preferable that the reduction rate from crude heat spreading to cold spreading is high in terms of reducing the degree of integration of the {223} <252> orientation of the intermediate layer. Therefore, it is preferable to apply the rough heat spreading to the slab so that the thickness after the rough heat spreading becomes, for example, 10 mm or more (preferably 15 mm or more).
The heating temperature of the slab before hot spreading is not particularly limited, but it is preferably 1000 ° C. to 1300 ° C. from the viewpoint of cost and the like.

After rough hot rolling is applied to the heated slab, finish rolling (hereinafter, may be referred to as "finish hot rolling") is performed. The temperature condition of the finish hot-rolling is not particularly limited, but the finish hot-rolling temperature has low in-plane anisotropy, low iron loss and high magnetic flux density in consideration of high frequency characteristics and magnetic characteristics after strain removal annealing. It can be an effective control factor for obtaining excellent magnetic characteristics (hereinafter, may be referred to as "specific magnetic characteristics") having the above. In order to effectively obtain a specific magnetic property, the temperature of the finish heat spreading is preferably 500 ° C. to 800 ° C. From the viewpoint of rollability, the preferable lower limit of the temperature of hot rolling for finishing is 550 ° C. or higher, more preferably 600 ° C. or higher. The preferred upper limit of the temperature of the finish hot spreading is 750 ° C. or lower, more preferably 700 ° C. or lower.

The reason why specific magnetic properties are exhibited by lowering the temperature of finish rolling is not clear, but as mentioned above, the slip of dislocations due to the high Al component system related to "shear deformation acting on the intermediate layer". Considering that it is caused by the behavior of system change and additional shear deformation, it can be inferred that the same phenomenon is caused in the intermediate layer of the hot-rolled steel sheet by lowering the rolling temperature in hot rolling. Of course, the orientation change in the intermediate layer in hot-rolling does not necessarily have to be favorable for specific magnetic properties after cold-rolling and finish annealing, but at least at relatively low temperatures in hot-rolling. It is natural to think that the shear strain introduced into the intermediate layer affects the crystal orientation generated after cold spreading and finish annealing. We hope that the changes in crystal orientation during the process from hot spreading to cold rolling to finish annealing will be elucidated in the future.

(Cold rolling process)
Next, the steel sheet after hot rolling is cold rolled. The total reduction rate of cold spreading is not particularly limited, but the total reduction rate of cold spreading can be an effective control factor for obtaining specific magnetic properties. In order to effectively obtain this specific magnetic property, cold rolling is applied to the hot-rolled steel sheet so that the total reduction rate in the cold-rolling process (total reduction rate of cold-rolling) is 90% or more. Is good. The total reduction rate is preferably 92% or more in terms of developing the {100} orientation and improving the magnetic characteristics. The upper limit of the total reduction rate of cold rolling is preferably 99% or less, but is preferably 95% or less from the viewpoint of manufacturing.

As mentioned above, the high pressure reduction rate in cold rolling can be an important factor in the development of specific magnetic properties. The method for producing non-oriented electrical steel sheets of the present embodiment is not particularly limited, but in order to impart sufficient shear deformation to the intermediate layer, rolling is performed with low lubrication, small diameter roll, and high strain rate (1 pass large pressure reduction). It is considered effective to carry out. This is expected to have a similar effect on heat spreading.

(Finish annealing process)
Next, the steel sheet after cold stretching is subjected to finish annealing. The heating conditions in the finish annealing step are not particularly limited, but can be an effective control factor for obtaining specific magnetic properties. The heating conditions in the finish annealing step are preferably as follows.
In order to effectively obtain specific magnetic properties, finish annealing is performed so that the average heating rate (C) in the temperature range of room temperature (25 ° C.) to 800 ° C. is satisfied at 80 ° C./sec or more. Is good.
Even when the heating conditions for finish hot-rolling are controlled to at least one of the above-mentioned specific temperature ranges and the cold-rolling reduction ratio is set to the above-mentioned specific range, the heating conditions for finish annealing can be set. Under this condition, as described above, a non-oriented electrical steel sheet having better magnetic characteristics can be obtained.

In the finish annealing, the crystal orientation is preferably controlled by setting the average heating rate in the heating process from room temperature (25 ° C.) to 800 ° C. to 80 ° C./sec or more, and specific magnetic characteristics can be effectively obtained. The upper limit of the heating rate is not particularly set, but if the heating rate is too high, specific magnetic characteristics tend to become unstable. Therefore, the upper limit of the heating rate is preferably suppressed to about 500 ° C./sec or less. If this heating is slow heating, it becomes difficult to obtain specific magnetic characteristics. It is preferably 100 ° C./sec or higher, more preferably 400 ° C./sec or higher.

The reason why specific magnetic properties are effectively exhibited by increasing the heating rate of finish annealing is unknown, but it is considered to indicate the importance of controlling the timing of recrystallization (nucleation). That is, conventionally, the {223} <252> orientation is an orientation in the vicinity of the {111} orientation, and it has not been easy to reduce this with Si steel. This indicates that the {223} <252> orientation is relatively easy to recrystallize. In general, the {111} orientation is known to be relatively easy to recrystallize because dislocation accumulation due to deformation is likely to occur. It is considered that the {223} <252> direction, which is a direction in the vicinity of the {111} direction, has the same characteristics.
In the non-oriented electrical steel sheet according to the present embodiment, the crystal orientation and the amount of accumulated dislocations after deformation due to the change of the slip system due to Al and shear deformation are also different from the case of simple Si steel, and the {223} <252> orientation. The predominance of recrystallization seems to be diminishing. Then, it is kept at a high temperature in a state where the driving energy for recrystallization remains high (the dislocation density remains high) by further rapid heating. As a result, it is considered that the effect of promoting the generation of orientations that are originally difficult to recrystallize and suppressing the {223} <252> orientation can be enhanced to the extent that it is practically meaningful.

The soaking temperature of the finish annealing is preferably in the range of 800 ° C. to 1200 ° C. when the finish annealing has a sufficiently low iron loss. The lower limit temperature of soaking heat may be a temperature equal to or higher than the recrystallization temperature, but by setting it to 800 ° C. or higher, sufficient grain growth can be caused and iron loss can be reduced. From this point of view, the lower limit of the soaking temperature is preferably 850 ° C. or higher.
Further, if the crystal grains are finally grown by additional heat treatment by slow heating such as strain relief annealing, the iron loss after the additional heat treatment can be reduced, so that the soaking temperature of the finish annealing is set from the viewpoint of grain growth. There is no problem even if the temperature is lower than 800 ° C, which is not sufficient. In this case, the effect of avoiding the inferior magnetic flux density due to the additional heat treatment is remarkably exhibited. In this case, even if the unrecrystallized structure remains in a part, it is possible to have the characteristic crystal orientation of the non-oriented electrical steel sheet according to the present embodiment, and the lower limit temperature is, for example, 640 ° C. or higher. Can be mentioned. A steel sheet having a fine crystal structure or a partially unrecrystallized structure by lowering the finish annealing temperature is also useful as a high-strength non-directional electromagnetic steel sheet because of its high strength.
On the other hand, the upper limit of the soaking temperature is preferably 1200 ° C. or lower in consideration of the load of the annealing furnace, preferably 1050 ° C.

Further, the soaking heat holding time may be set in consideration of the particle size, iron loss, magnetic flux density, strength, etc., and can be, for example, 5 sec or more as a guide. On the other hand, if it is 120 sec or less, the crystal grain growth becomes appropriate. Therefore, the soaking heat holding time is preferably set to 5 sec to 120 sec. Within this range, for example, when grain growth is carried out by performing additional heat treatment by slow heating thereafter, a crystal orientation having an effect of avoiding inferior magnetic properties tends to remain.
The cooling conditions after annealing may be normal conditions and are not particularly limited. Further, the method of controlling the heating rate at the time of finish annealing heating is also not particularly limited, and for example, a direct energization heating method or a dielectric heating method can be preferably used.

In order to obtain the non-oriented electrical steel sheet according to the present embodiment, other steps similar to the conventional non-oriented electrical steel sheet manufacturing process may be provided in addition to the above steps. As each condition of the other steps, the same conditions as those of the conventional non-oriented electrical steel sheet manufacturing process may be adopted. Specifically, for example, it may have an insulating film forming step of providing an insulating film on the surface of the steel sheet (non-oriented electrical steel sheet) after the finish annealing step.

Further, the non-oriented electrical steel sheet according to the present embodiment may have an insulating film on the surface of the steel sheet. The insulating film formed on the surface of the non-oriented electrical steel sheet according to the present embodiment is not particularly limited, and may be selected from known ones according to the intended use and the like. For example, the insulating film may be either an organic film or an inorganic film. Examples of the organic film include polyamine resin; acrylic resin; acrylic styrene resin; alkyd resin; polyester resin; silicone resin; fluororesin; polyolefin resin; styrene resin; vinyl acetate resin; epoxy resin; phenol resin; urethane resin; melamine. Examples include resin. Examples of the inorganic film include a phosphate film; an aluminum phosphate film and the like. Further, an organic-inorganic composite film containing the above resin and the like can be mentioned.
The thickness of the insulating film is not particularly limited, but the film thickness per one side is preferably 0.05 μm to 2 μm.

The method for forming the insulating film is not particularly limited, but for example, a composition for forming an insulating film in which the above resin or an inorganic substance is dissolved in a solvent is prepared, and the composition for forming the insulating film is uniformly applied to the surface of the steel sheet by a known method. An insulating film can be formed by applying to.

The thickness of the non-oriented electrical steel sheet according to the present embodiment may be appropriately adjusted according to the intended use and the like, and is not particularly limited, but is 0.10 mm to 0.50 mm from the viewpoint of manufacturing. It is preferably 0.15 mm to 0.50 mm. In particular, from the viewpoint of the balance between magnetic characteristics and productivity, 0.15 mm to 0.35 mm is preferable.

The non-oriented electrical steel sheet according to the present embodiment can be obtained by the manufacturing method having the above steps.

The non-oriented electrical steel sheet of the present embodiment is not particularly limited in its manufacturing method as long as a steel sheet having an integration degree of the {223} <252> orientation of the intermediate layer of 6 or less can be obtained. Needless to say.

According to this embodiment, a non-oriented electrical steel sheet having the above-mentioned specific magnetic characteristics can be obtained. Therefore, the non-oriented electrical steel sheet according to the present embodiment can be suitably applied as various core materials of electrical equipment, particularly as core materials of motors such as rotary machines, small and medium-sized transformers, and electrical components.
Hereinafter, a case where the non-oriented electrical steel sheet according to the present embodiment is applied as a motor core will be described.

<Motor core and its manufacturing method>
Examples of the motor core according to the present embodiment include a form in which non-oriented electrical steel sheets according to the present embodiment are laminated. Specific examples thereof include a motor core in which a non-oriented electrical steel sheet according to the present embodiment is punched to create a punched member (steel sheet blank), and the punched member is laminated and integrated. For example, examples of the motor core according to the present embodiment include the motor cores shown in FIGS. 1 and 2.

FIG. 1 is a schematic view showing an example of a motor core according to the present embodiment. The motor core 100 is formed as a laminated body 21 in which a plurality of punched members 11 of non-oriented electrical steel sheets are laminated and integrated. As shown in FIG. 1, the punching member 11 is formed with six rectangular notches 13 for embedding a permanent magnet. The notches 13 are formed in the punched member 11 at six locations, but the notch 13 is not limited to this. When the permanent magnets are embedded in the notch 13, the notches 13 may be provided at an even number of positions so that the adjacent permanent magnets have opposite magnetic poles.

FIG. 2 is a schematic view showing another example of the motor core according to the present embodiment. As shown in FIG. 2, the motor core 300 is formed as a laminated body 33 in which a plurality of punching members 31 of non-oriented electrical steel sheets are laminated and integrated. The punching member 31 is formed with a yoke portion 37 on the outer peripheral side and a teeth portion 35 protruding inward in the radial direction from the inner peripheral surface of the yoke portion 37.

Although the motor cores shown in FIGS. 1 and 2 have been described above, the motor cores according to the present embodiment are not limited thereto.

Next, a method of manufacturing the motor core will be described.
The method for manufacturing the motor core according to the present embodiment is not particularly limited, and the motor core may be manufactured by a manufacturing method usually industrially adopted.
Hereinafter, an example of a preferable manufacturing method of the motor core according to the present embodiment will be described.
An example of a preferable manufacturing method of the motor core according to the present embodiment includes a punching step of performing a punching process on the non-oriented electrical steel sheet according to the present embodiment to obtain a punched member, and a laminating step of laminating the punched members. ..

(Punching process)
First, the non-oriented electrical steel sheet of the present embodiment is punched into a predetermined shape according to a purpose, and a predetermined number of punched members are produced according to the number of laminated sheets. The method for producing the punched member by punching the non-oriented electrical steel sheet is not particularly limited, and any conventionally known method may be adopted.
The punched member may form an uneven portion for laminating and fixing the punched member when it is punched into a predetermined shape.

(Laminating process)
A motor core can be obtained by laminating the punching members created in the punching process.
The method of fixing the laminated punching members is not particularly limited, and any conventionally known method may be adopted. For example, a known adhesive may be applied to the punched member to form an adhesive layer, and the punched member may be fixed via the adhesive layer. Further, caulking may be applied to mechanically fit and fix the uneven portions formed on the respective punched members to each other.

Through the above steps, the motor core according to the present embodiment can be obtained. Since the motor core according to the present embodiment is manufactured by using the non-oriented electrical steel sheet according to the present embodiment, it has low in-plane anisotropy, low iron loss, and high magnetic flux density.

Further, another example of a preferable manufacturing method of the motor core according to the present embodiment is a punching step of performing a punching process on the non-oriented electrical steel sheet according to the present embodiment to obtain a punched member, and a laminating step of laminating the punched member. After the punching process and before the laminating process or after the laminating process, the heating rate is 500 ° C./hr or less, the maximum reaching temperature is in the temperature range of 750 ° C. to 850 ° C., and the holding temperature is 750 ° C. or higher. It has a heat treatment step of heat-treating under the condition of a time of 0.5 hours to 100 hours.

That is, in the motor core according to the present embodiment, after laminating the punched members, the holding time under specific conditions (heating rate: 500 ° C./hr or less, maximum reaching temperature: 750 ° C. to 850 ° C., 750 ° C. or higher: 0.5) Heat treatment (strain removal annealing) may be performed in (hours to 100 hours). Further, in this heat treatment, the punched member before laminating the punched member may be subjected to the heat treatment under the above specific conditions.

Since the motor core itself does not have a thin shape like a steel sheet, the heating of the strain removing annealing of the motor core is the heat treatment in the finish annealing process in the steel sheet manufacturing process generally carried out at a heating rate of about several tens of degrees / sec. Is different, and it has to be very slow, about several hundred degrees Celsius / hr. As described above, when the crystal grains are grown at such a low heating rate, an orientation unfavorable for the magnetic characteristics develops, so that the magnetic flux density is lower than when the crystal grains are grown at a high heating rate. .. However, in the motor core using the non-oriented electrical steel sheet according to the present embodiment, it is possible to suppress a decrease in the magnetic flux density even when the crystal grains are grown at a low heating rate. Depending on the conditions, the magnetic flux density may increase. The upper limit of the heating rate of the strain-removing annealing capable of suppressing the decrease in the magnetic flux density due to the strain-removing annealing is, for example, 500 ° C./hr or less in consideration of the capacity of the strain-removing annealing equipment. Considering the production efficiency of strain relief annealing, the lower limit is, for example, 30 ° C./hr or more. In addition, if the heating rate is about 50 ° C./hr to 200 ° C./hr, in which strain removal annealing of the motor core is generally performed, the merit of using the non-oriented electrical steel sheet according to the present embodiment is fully exhibited. To.

Although it depends on the steel composition and the hot spreading conditions, the maximum temperature reached and the holding time at 750 ° C. or higher are the targets for obtaining an appropriate crystal grain size. When the maximum temperature reached is 750 ° C. or higher, or the holding time at 750 ° C. or higher is 0.5 hours or longer, crystal grain growth occurs, specific magnetic characteristics can be effectively obtained, and sufficient magnetism required for a motor core is obtained. Characteristics (especially low iron loss) can be obtained. Further, when the maximum temperature reached is 850 ° C. or lower, or the holding time at 750 ° C. or higher is 100 hours or less, the crystal grain growth becomes appropriate, the magnetic flux density is improved, and low iron loss can be achieved.

Therefore, in terms of avoiding deterioration of magnetic characteristics, the method for manufacturing a motor core according to the present embodiment is performed under the above conditions (heating rate: 500 ° C./hr or less, maximum temperature reached: 750 ° C. to 850 ° C., 750 ° C. or higher). Retention time: 0.5 hours to 100 hours) is preferable.
By performing this heat treatment, unnecessary strain is released in the motor core, and iron loss can be reduced. Since the motor core of the present embodiment uses the non-oriented electrical steel sheet according to the present embodiment, a high magnetic flux density is maintained even after the heat treatment, and an excellent motor core can be obtained.

From the above, the non-oriented electrical steel sheet according to the present embodiment is useful as a core material because it has excellent magnetic properties. Further, when the non-oriented electrical steel sheet according to the present embodiment is applied to a motor core material, the magnetic flux density B ₅₀ is lowered and the iron loss is deteriorated even after punching into a desired shape and then performing strain relief annealing. Has the advantage of being suppressed. Therefore, the non-oriented electrical steel sheet according to the present embodiment can sufficiently meet the urgent demand for high efficiency and miniaturization in the field of electrical equipment, and its industrial value is extremely high.

Hereinafter, the present invention will be specifically described by exemplifying examples, but the present invention is not limited thereto. It is clear that a person skilled in the art can come up with various modifications or modifications within the scope of the ideas described in the claims, which naturally belong to the technical scope of the present invention. It is understood as a thing.

<Example 1>
The slab having the chemical composition shown in Table 1 is subjected to rough heat spreading so as to have a thickness of 40 mm. Then, finish heat spreading (finishing heat spreading temperature) is performed at the temperature shown in Table 1. The steel sheet after hot-spreading is cold-rolled at the total reduction rate (total cold-rolling rate) shown in Table 1. The thickness of the finished hot-rolled steel sheet is adjusted so that the thickness of the steel sheet after cold-rolling according to the total cold-rolling ratio in Table 1 is 0.25 mm. The cold-rolled steel sheet is finish-annealed at the average heating rate and soaking temperature shown in Table 1 (the soaking time is 30 seconds) to obtain a steel sheet.
The surface layer, intermediate layer, and central layer of the obtained steel sheet were observed according to the method described above, and the degree of integration in the {223} <252> orientation in the intermediate layer (intermediate layer {223}) and {in the intermediate layer { Maximum value of integration in in-plane orientation of 100} orientation (intermediate layer {100}), maximum value of integration in in-plane orientation of surface layer {100} orientation (surface layer {100}), {in the central layer { The maximum value of the degree of integration (central layer {100}) in the in-plane orientation of the 100} orientation is measured. The results are shown in Table 2.
The ratio of the magnetic flux density _{B 50} of the total circumference average, the magnetic flux density _{B 50} and the saturation magnetic flux density Bs _(B 50 / Bs), in-plane anisotropy of the magnetic flux density _{(B 50max -B 50min / B s} ), and Measure the iron loss (W _10/400). Further, the average crystal grain size (particle size) is measured according to the method described above.
Further, among the obtained steel sheets, for a material in which the soaking temperature of finish annealing was a comparatively low temperature, the heating rate was 100 ° C./hr, the maximum reaching temperature was 800 ° C., and the holding time at 800 ° C. was 2 hours. , Strain relief annealing (SRA) is performed, and the change in magnetic flux density ( _BB / B _A ) due to additional heat treatment at a low heating rate is evaluated. The results are shown in Table 2.

Here, B _{50, which} is the average of all circumferences, is the average magnetic flux density in the entire circumference direction when excited with a magnetization force of 5000 A / m. Specifically, the direction along the rolling direction (0 °), the direction forming an angle of 22.5 ° with the direction along the rolling direction, the direction forming an angle of 45 ° with the direction along the rolling direction, and the direction along the rolling direction. It is an average value _{of B 50} measured in five directions (90 °) in a direction forming an angle of 67.5 ° and a direction perpendicular to the rolling direction.
The iron loss of the all-around average is _{an average value when the magnetic flux density B 50} of the all-around average is measured in the same direction as the measurement direction, and is iron under the conditions of a maximum magnetic flux density of 1.0 T and a frequency of 400 Hz. It is measured as a loss (W _10/400).
The in-plane anisotropy of the magnetic flux density, B _{50max, is a value obtained by measuring B 50} in the above five directions (0 °, 22.5 °, 45 °, 67.5 ° C, and 67.5 ° C with respect to the rolling direction). of 90 5 direction B ₅₀ value of °), indicating a high value of the most magnetic flux density. Further, B _{50 min} represents the value having the lowest magnetic flux density among the above five directions.
B _B represents the magnetic flux density after SAR, and B _A represents the magnetic flux density before SAR.

The example of the invention corresponding to the non-directional electromagnetic steel plate of the present embodiment is saturated with the magnetic flux density B _{50 and the magnetic flux density B 50} of the overall circumference average as compared with the comparative example which is outside the range of the non-directional electromagnetic steel plate of the present embodiment. the magnetic flux density by the ratio _(B 50 / Bs), in-plane anisotropy of the magnetic flux density _{(B 50max -B 50min / Bs)} , iron loss _{(W 10/400),} and stress relief annealing (SRA) of the magnetic flux density Bs It can be seen that the changes show good results.
Therefore, the motor cores using the steel plates of these invention examples show better motor efficiency than the cores using the steel plates of the comparative examples.

11, 31 punched members, 21, 33 laminates, 13 notches, 35 teeth, 37 yokes, 100, 300 motor cores

Claims (8)

By mass%
C: 0.0030% or less,
Si: 0.0% to 3.5%,
Al: 1.0% to 3.5%,
Mn: 0.0% to 3.0%,
S: 0.0030% or less, and
Remaining: Has a chemical composition of Fe and impurities,
The mass ratio of Al / Si is 0.5 or more,
The degree of integration of the {223} <252> orientation in the intermediate layer having a plate thickness of 1/10 to 1/5 is 6 or less.
Non-oriented electrical steel sheet Ru der maximum of 11 or more degree of integration in the in-plane orientation of {100} orientation in the intermediate layer. By mass%
C: 0.0030% or less,
Si: 0.0% to 3.5%,
Al: 1.0% to 3.5%,
Mn: 0.0% to 3.0%,
S: 0.0030% or less, and
Remaining: Has a chemical composition of Fe and impurities,
The mass ratio of Al / Si is 0.5 or more,
The degree of integration of the {223} <252> orientation in the intermediate layer having a plate thickness of 1/10 to 1/5 is 6 or less.
The maximum value of the degree of integration in the in-plane orientation of the {100} orientation in the intermediate layer (MI ₁₀₀ ) and the maximum value of the degree of integration in the in-plane orientation of the {100} orientation in the surface layer from the steel plate surface to the plate thickness 1/10. (MS _{100 ) and the maximum value (MC 100} ) of the degree of integration in the in-plane orientation of the {100} orientation in the central layer of the plate thickness 1/5 to 1/2 of the plate thickness are
MI ₁₀₀ > MS ₁₀₀ > MC ₁₀₀
Non-oriented electrical steel sheet that meets the relationship. By mass%
C: 0.0030% or less,
Si: 0.0% to 3.5%,
Al: 1.0% to 3.5%,
Mn: 0.0% to 3.0%,
S: 0.0030% or less, and
Remaining: Has a chemical composition of Fe and impurities,
The mass ratio of Al / Si is 0.5 or more,
The degree of integration of the {223} <252> orientation in the intermediate layer having a plate thickness of 1/10 to 1/5 is 6 or less.
Non-oriented electrical steel sheet according Ru der ratio _(B 50 / Bs) is 0.885 or more and the total circumferential average magnetic flux density _{B 50} and the saturation magnetic flux density Bs in the case of excitation in the magnetizing force 5000A / m. By mass%
C: 0.0030% or less,
Si: 0.0% to 3.5%,
Al: 1.0% to 3.5%,
Mn: 0.0% to 3.0%,
S: 0.0030% or less, and
Remaining: Has a chemical composition of Fe and impurities,
The mass ratio of Al / Si is 0.5 or more,
The degree of integration of the {223} <252> orientation in the intermediate layer having a plate thickness of 1/10 to 1/5 is 6 or less.
To the rolling direction, 0 °, 22.5 °, 45 °, 67.5 °, and out of the magnetic flux density in the 5 direction of 90 °, most magnetic flux density is high _{B 50max,} most magnetic flux density is low _{B 50min} the difference of the saturation magnetic flux density divided by the Bs is 0.015 _{[(B 50max -B 50min) /Bs≦0.015} )] non-oriented electrical steel sheet Ru der with. By mass%
C: 0.0030% or less,
Si: 0.0% to 3.5%,
Al: 1.0% to 3.5%,
Mn: 0.0% to 3.0%,
S: 0.0030% or less, and
Remaining: Has a chemical composition of Fe and impurities,
The mass ratio of Al / Si is 0.5 or more,
The degree of integration of the {223} <252> orientation in the intermediate layer having a plate thickness of 1/10 to 1/5 is 6 or less.
Steel sheet after the magnetic flux density B _A before the steel _sheet, and heating rate is 100 ° C. / hr, the maximum temperature is 800 ° C., and the holding time at 800 ° C. were conducted to a heat treatment under conditions of 2 hours to carry out heat treatment when the magnetic flux density was _{B B,} the ratio _{B B} and the _{B a is} the non-oriented electrical steel sheet you satisfy the relation B B / _{B a} ≧ 0.98. A hot rolling step of hot rolling a slab having the chemical composition according to any one of claims 1 to 5.
A cold rolling step of cold rolling on a steel sheet after the hot rolling step, and a cold rolling step.
Any of claims 1 to 5 , which has a finish annealing step of finish annealing the steel sheet after the cold rolling step, and satisfies at least one of the following conditions (a), (b), and (c). The method for manufacturing a non-oriented electrical steel sheet according to item 1.
(A) Hot rolling step: Finish rolling in a temperature range of 500 ° C to 800 ° C (b) Cold rolling step: Cold rolling so that the total rolling reduction is 90% or more (c) Finish annealing step : Finish-anneal the steel sheet after the cold rolling process so that the average heating rate in the temperature range of room temperature (25 ° C) to 800 ° C is 80 ° C / sec or more. A motor core in which non-oriented electrical steel sheets according to any one of claims 1 to 5 are laminated. A step of punching a non-oriented electrical steel sheet according to any one of claims 1 to 5 to obtain a punched member.
The process of laminating the punched members and
A method for manufacturing a motor core.

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