JP6848597B2 - 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 rotary 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 a motor 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, conventionally, the electromagnetic steel sheet may be used after additional heat treatment. As a typical example, "Stress Relief Annealing (SRA)" is known. 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.

Against this background, in the technology of non-oriented electrical steel sheets, in order to improve magnetic properties, control of metal structure such as crystal grain size and crystal orientation in steel sheets as well as steel components, control of precipitates, etc. Various efforts have been made (see, for example, Patent Documents 1 to 12).

For example, Patent Document 1 discloses a non-oriented electrical steel sheet containing 0.10% to 0.30% of P in mass% and having a magnetic flux density _{of 1.70 T or more at B 50.}
Patent Documents 2 to 4 disclose a technique for controlling the crystal orientation after cold rolling and recrystallization annealing and improving the magnetic properties by segregating the contained P at the grain boundaries before cold rolling. ing.

Patent Document 5 has a specific chemical composition such as 0.1% <Si ≤ 2.0%, Al ≤ 1.0%, etc. in mass%, and the finishing hot spreading end temperature is 550 ° C. to 800 ° C., etc. Non-directional electromagnetic steel sheets manufactured under the specific manufacturing conditions of the above are disclosed.

Patent Documents 6 to 8 have a specific chemical composition such as 0.05% to 4.0% (or 4.5%) of Si and P ≦ 0.25% in mass%, and the hot rolling temperature. Disclosed is a non-oriented electrical steel sheet having a small in-plane anisotropy, which has improved magnetic properties in the 45 ° direction from the rolling direction by subjecting to low-temperature hot rolling at 500 ° C. to 850 ° C.

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. According to Patent Document 10, 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 11 and 12 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 11 shows that it is effective to set the heating rate at the time of finish annealing to 5 ° C./sec to 40 ° C./sec. Further, Patent Document 12 discloses a technique in which the magnetic properties for a semi-process are improved by increasing the heating rate up to 740 ° C. to 100 ° C./sec or more.

When a motor core is formed by using steel plates as described in Patent Documents 1 to 12, these steel plates are obtained by rotating a member cut out from the steel plate, for example, as described in Patent Documents 13 and 14. It is used as a motor core laminated in.

Japanese Patent No. 3870725 Japanese Unexamined Patent Publication No. 2012-036454 Japanese Unexamined Patent Publication No. 2005-20056 Japanese Unexamined Patent Publication No. 2016-21016 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. 11-124626 International Publication 2016/136095 Japanese Unexamined Patent Publication No. 03-223424 International Publication No. 2014/129034 Japanese Unexamined Patent Publication No. 2000-1533319 Japanese Unexamined Patent Publication No. 2000-094055

When laminating members cut out from steel sheets after rotating them, the accuracy and space factor of the thickness when laminating in the laminating axis direction, the fluctuation of magnetic characteristics around the laminating axis of the motor core after laminating, etc. It is being considered. However, it has been pointed out that the characteristics as a motor core may not be sufficiently improved even though the steel plates having good characteristics as a single steel plate are laminated.

Further, the strain-removing annealing described above has the effect of releasing strain and improving iron loss, but at the same time, a 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.

As described above, the conventional technology does not sufficiently meet the above-mentioned modern market needs in consideration of the magnetic characteristics after lamination and strain removal annealing as a motor core, and exhibits good practical characteristics. In addition, further improvement in magnetic characteristics has been required.

The present invention has been made in view of the above circumstances, and an object of the present invention is a non-oriented electrical steel sheet having excellent magnetic properties even after being laminated as a motor core and after being strain-removed and annealed. It provides a manufacturing method.

In order to obtain the above-mentioned non-oriented electrical steel sheet having excellent magnetic properties, the present inventors have made a steel sheet having a chemical composition with a large amount of P (for example, 0.021% by mass or more). The conditions for improving the degree of integration of the {100} orientation were examined. Pursuing that condition, in addition to increasing the degree of integration in the {100} orientation, increasing the degree of integration in the {210} <001> orientation in the surface layer of the steel sheet can be achieved after lamination as a motor core and strain removal annealing. It was found that there is a strong correlation with the improvement of magnetic characteristics in consideration of even magnetic characteristics.
Then, the conditions for obtaining a steel sheet having this characteristic were examined in detail. As a result, it was found that a non-oriented electrical steel sheet having the above magnetic characteristics can be obtained in a high P component steel sheet when the cold rolling reduction rate (reduction rate in cold rolling) is set to a specific range. Obtained. Similarly, it was found that a steel sheet having the above magnetic properties can be obtained even when the steel sheet after being cold-rolled at a cold rolling reduction ratio in a specific range is subjected to a recovery heat treatment by finish annealing. ..

Furthermore, from the viewpoint that the texture change in the surface 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, it was confirmed that the degree of integration of the {210} <001> orientation in the surface layer of the steel sheet can be increased even when the high P component steel sheet is finished and hot-rolled at a low temperature. Similarly, it was confirmed that a steel sheet having the above-mentioned magnetic properties can be obtained even when the steel sheet after hot-rolling and cold-rolling at a low temperature is subjected to recovery heat treatment by finish annealing.

In addition, the case where the P content is low (for example, less than 0.021% by mass) was also examined. As a result, at least one of the conditions when the cold rolling reduction ratio is set to a specific range and when finishing hot rolling is performed at a low temperature is controlled, and further, the steel sheet after cold rolling is subjected to recovery heat treatment by finish annealing. It was found that a steel sheet having the above magnetic properties can be obtained even when the above-mentioned magnetic properties are applied.

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: 0.01% to 3.50%,
Al: 0.001% to 2.500%,
Mn: 0.01% to 3.00%,
P: 0.180% or less,
S: 0.0030% or less, and the balance: having a chemical composition containing Fe and impurities.
A non-oriented electrical steel sheet having a degree of integration of {210} <001> orientations of 6 or more in the surface layer from the surface of the steel sheet to the surface layer having a thickness of 1/10.
<2> The degree of integration of {210} <001> orientation in the surface layer (MS ₂₁₀ ) and the degree of integration of {210} <001> orientation in the central layer having a plate thickness of 1/5 to 1/2 of the plate thickness (MC). ₂₁₀ ) and
MS ₂₁₀ / MC ₂₁₀ > 1.50
The non-oriented electrical steel sheet according to <1>, which satisfies the relationship of.
<3> The non-oriented electrical steel sheet according to <1> or <2>, wherein the degree of integration of {100} <012> orientations in the surface layer is 6 or more.
_{<4> The ratio (B 50 / Bs) 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 is 0.870 or more <1> to <3>. The non-directional electromagnetic steel plate according to any one of the above items.
<5> were performed 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} ≧ 0.976 <1> ~ or <4> 1 The non-oriented electrical steel sheet described in the section.
<6> 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.
Any of <1> to <5> that satisfies at least one of the following conditions (a) and the following (b) and satisfies at least one of the following (c) and the following (d). The method for manufacturing a non-oriented electrical steel sheet according to item 1.
(A) Hot rolling process: Finish rolling in a temperature range of 500 ° C to 800 ° C (b) Cold rolling process: Cold rolling so that the total reduction ratio is 90% or more (c) P of steel sheet Content: Set the lower limit to 0.021% or more in mass% (d) Finish annealing step: After holding the steel sheet after the cold rolling step at 450 ° C to 600 ° C for 10 minutes or more, the temperature exceeds 600 ° C. <7> A motor core in which a non-directional electromagnetic steel sheet according to any one of <1> to <5> is laminated.
<8> A step of punching the non-oriented electrical steel sheet according to any one of <1> to <5> 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, it is possible to provide a non-oriented electrical steel sheet having excellent magnetic characteristics and a method for producing the same, even after laminating as a motor core and after strain removal and annealing.

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 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, {210} <001> direction, {100} <012> direction, etc.), the mirror index in the normal direction (rolling surface direction) of the rolled surface and the rolling direction are used. For the mirror exponents in the parallel directions (in-rolling plane direction), the directions within ± 5 ° are assumed to be the relevant directions.

<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: 0.01% to 3.50%, Al: 0.001% to 2.500%, Mn: It has a chemical composition containing 0.01% to 3.00%, P: 0.180% or less, S: 0.0030% or less, and the balance: Fe and impurities.

Further, the non-oriented electrical steel sheet according to the present embodiment has a degree of integration of {210} <001> orientation in the surface layer of 6 or more (this is a feature (A)).
The non-oriented electrical steel sheet according to the present embodiment has the above-mentioned characteristics, and therefore has excellent magnetic characteristics even after being laminated as a motor core and after being strain-removed and annealed. This will be described below.

The degree of integration of the {210} <001> orientation in the surface layer is 6 or more, which is an important feature in the non-oriented electrical steel sheet of the present embodiment. The {210} <001> orientation is an orientation close to the {110} <001> orientation used in grain-oriented electrical steel sheets, and is also an orientation that strengthens the in-plane anisotropy of magnetic characteristics. Therefore, in the non-oriented electrical steel sheet characterized by having a small in-plane anisotropy of magnetic characteristics, the orientation is usually suppressed.
In the non-oriented electrical steel sheet of the present embodiment, the degree of integration in the surface layer is defined as 6 or more for this {210} <001> orientation. It is preferably 8 or more, more preferably 10 or more. However, since the {210} <001> direction is a direction that strengthens the in-plane anisotropy as described above, it is better not to raise it too much. In this respect, the upper limit of the {210} <001> orientation is often 30 or less, preferably 25 or less.

The {210} <001> orientation is a crystal orientation that increases the in-plane anisotropy of the magnetic characteristics as described above. Therefore, conventionally, no technological development has been made to promote the formation of the {210} <001> orientation.
However, in the P-containing component system, the conditions for lowering the hot rolling finish temperature, at least one of the high-pressure lowering rate conditions in cold rolling, and the conditions for recovery annealing in finish annealing are set according to the P content. When applied, it was found that the accumulation of {210} <001> orientations increased mainly in the surface layer of the steel sheet, and that it had excellent magnetic properties even after being laminated as a motor core and after being strain-removed and annealed.

Under the above conditions, the reason why the {210} <001> orientation develops in the surface layer of the steel sheet is not clear, but it is presumed as follows.
In general, it is known that the dislocation structure at the time of processing and the crystal orientation after recrystallization differ from the central region of the sheet thickness because the surface layer of the steel sheet undergoes deformation including shear components during hot and cold drawing. Has been done.

On the other hand, P is considered to be an element having a strong interaction with dislocations. In addition to these, recovery annealing before recrystallization in finish annealing is considered to promote the development of {210} <001> orientation.
From these, considering the reason why the {210} <001> orientation develops in the surface layer of the steel sheet, the {210} <001> orientation is due to the interaction by P from the dislocation structure in a special deformed state including shear deformation. It is presumed that the formation of is promoted. Alternatively, it is speculated that the formation of {210} <001> orientation is promoted in the situation where relatively slow recrystallization such as sufficient recovery annealing proceeds from the dislocation structure in a special deformed state including shear deformation. Will be done.

In addition to the above features, the non-oriented electrical steel sheet of the present embodiment has an integration degree of {210} <001> orientation in the surface layer (MS ₂₁₀ ) and an integration degree of {210} <001> orientation in the central layer (MS 210). It is preferable that the MC ₂₁₀ ) _{satisfies the relationship of MS 210} / MC ₂₁₀ > 1.50 (this is a feature (B)).

The feature (B) is a feature (A) characterized by a change in the plate thickness direction. As described above, the non-oriented electrical steel sheet of the present embodiment has increased accumulation in the {210} <001> orientation in the surface layer. Since this phenomenon occurs in connection with additional shear deformation due to rolling (at least one of hot rolling and cold rolling), it is less likely to occur in the central layer where additional shear deformation does not act than in the surface layer. Therefore, the feature (B) is an inevitable result when it is manufactured through the rolling process, but it is also better to control it intentionally for the following reasons.
Since the {210} <001> orientation increases the in-plane anisotropy of the magnetic characteristics as described above, it is better not to increase it excessively with the non-oriented electrical steel sheet. On the other hand, as will be described later, this orientation is an effective orientation for improving the magnetic characteristics after lamination and strain removal annealing as a motor core, and in particular, only the surface layer has a {210} <001> orientation. Increasing the accumulation of these properties is advantageous for these properties. Details will be described later.
The degree of change in the degree of integration in the {210} <001> direction in the plate thickness direction is preferably _{2.00 or more for MS 210} / MC ₂₁₀ , and more preferably 2.50 or more. The upper limit of MS ₂₁₀ / MC ₂₁₀ is not particularly limited, but is often 5.00 or less, and preferably 4.00 or less.

Further, the non-oriented electrical steel sheet of the present embodiment preferably has an integration degree of {100} <012> orientation in the surface layer of 6 or more (this is a feature (C)).

It is well known that increasing the {100} orientation is advantageous for magnetic properties. However, conventionally, this orientation has been eroded by an orientation such as {111}, which is not preferable for the magnetic characteristics in the grain growth process, and cannot be sufficiently accumulated. On the other hand, in the non-oriented electrical steel sheet according to the present embodiment, the {210} <001> orientation is formed, so that the generation of an orientation unfavorable for the magnetic characteristics such as {111} is suppressed. Therefore, it is possible to prevent the orientations such as {111} from eclipsing the {100} orientation, and the degree of integration in the {100} <012> orientation in the surface layer tends to increase.
Therefore, one of the features of the non-oriented electrical steel sheet of the present embodiment is that the degree of integration of the {100} <012> orientation in the surface layer is 6 or more, and the magnetic characteristics are improved. It is preferably 7 or more, more preferably 8 or more. The upper limit of the degree of integration of the {100} <012> orientation in the surface layer is not particularly limited, but for example, it may be 30 or less.

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. When removing the surface layer, measurement test pieces having been reduced in thickness are prepared until the surface in the central plate thickness direction of the surface layer or the center layer of the original steel sheet becomes the surface.
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 each orientation in each layer is 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: 0.01% to 3.50%, Al: 0.001% to 2.500%, Mn: It has a chemical composition of 0.01% to 3.00%, P: 0.180% or less, S: 0.0030% or less, and the balance: Fe and impurities.

(C: 0.0030% or less)
C is a component that increases iron loss and causes magnetic aging. Therefore, 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: 0.01% to 3.50%)
As the content of Si increases, the magnetic flux density decreases. In addition, the hardness is increased and the punching workability is deteriorated. Further, in the manufacturing process itself of the non-oriented electrical steel sheet, workability such as cold spreading is lowered, and the cost is increased. Therefore, the upper limit of the Si content is 3.50% or less. The preferable upper limit of the amount of Si is 3.20% or less, and the more preferable upper limit is 3.00% or less. On the other hand, Si has the effect of increasing the electrical resistance of the steel sheet, reducing the eddy current loss, and reducing the iron loss. Therefore, the lower limit of the amount of Si is set to 0.01% or more. The preferable lower limit of the amount of Si is 0.10% or more, the more preferable lower limit is 0.50% or more, and further preferably 1.00% or more.

(Al: 0.001% to 2.500%)
Al is inevitably contained in ores, refractories, etc., and is also used for deoxidation. Taking this into consideration, the lower limit is set to 0.001% or more. Further, Al is a component having an action of reducing iron loss by increasing electric resistance and reducing eddy current loss, like Si. Therefore, Al may be contained in an amount of 0.200% or more. On the other hand, when the Al content increases, the saturation magnetic flux density decreases, which leads to a decrease in the magnetic flux density. Therefore, the upper limit of the Al content is set to 2.500% or less. It is preferably 2.000% or less.

(Mn: 0.01% to 3.00%)
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. For these purposes, Mn is contained in an amount of 0.01% 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 3.00% or less. The preferable upper limit of the amount of Mn is 2.50% or less, more preferably 2.00% or less.

(P: 0.180% or less)
P has the effect of increasing the strength without lowering the magnetic flux density. However, if P is excessively contained, the toughness of the steel is impaired, and the steel sheet is liable to break. Therefore, the upper limit of the amount of P is 0.180%. It is preferably 0.150% or less, more preferably 0.120% or less. The lower limit of the amount of P is not particularly limited, but it is 0.001% or more in consideration of the manufacturing cost.
Further, as described above, P is an element effective for increasing the degree of integration of the {210} <001> orientation in the surface layer. P in that the effect of having excellent magnetic characteristics (hereinafter, may be referred to as "specific magnetic characteristics") can be obtained more effectively even after being laminated as a motor core and after being strain-removed and annealed. The lower limit of the amount is preferably 0.021% or more, more preferably 0.041% or more, still more preferably 0.061% or more.

(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 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 sample for measurement is dissolved in an acid to prepare an acid solution, 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 0.870 or more. It is preferably 0.890 or more, more preferably 0.895 or more, still more preferably 0.900 or more. The upper limit is not particularly limited, but the closer it is to 1, the better, and for example, 0.980 or less can be mentioned.
Further, the average magnetic flux density B ₅₀ in the entire circumferential direction is preferably 1.75 (T) or more, preferably 1.80 (T) or more.

_{Here, the magnetic flux densities B 50} of the non-directional electromagnetic steel plate in the entire circumferential direction are 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.}

-Characteristics of laminated core-
As described above, the non-oriented electrical steel sheet according to the present embodiment has a higher degree of integration in the {210} <001> orientation in the surface layer than that of a normal steel sheet. At the same time, it promotes the accumulation of {100} <012> orientations in the surface layer. As a result, it is characterized in that it exhibits particularly preferable characteristics in the magnetic characteristics after lamination as a core and strain removal annealing. The reason for this is not clear, but I think it is as follows.

The reason why the magnetic characteristics of the core in which steel plates are laminated does not simply reflect the characteristics of a single steel plate is that the flow of magnetic flux in the core is not completely along the surface of the steel plate, and the steel plates are laminated. It is considered that this is because the flow of magnetic flux having a directional component is generated. In particular, the magnetic flux is likely to be disturbed in the vicinity of the upper and lower surfaces of the laminated core and in the place where the insulating film between the steel plates is peeled off due to the influence of caulking, and the magnetic flux of the component in the stacking direction is likely to be generated. In such a situation of magnetic flux flow, the magnetic flux shifts from a specific steel sheet to another steel sheet, and it is considered that the magnetic characteristics of the surface layer of the steel sheet in the plate thickness direction have an effect. That is, it is considered that the transition of the magnetic flux between the steel sheets is likely to occur because there is a certain degree of crystal orientation on the surface of the steel sheet in which the axis of easy magnetization is not limited to the surface of the steel sheet. It is considered that the {210} <001> direction effectively acts as such a direction.

-Changes in magnetic properties due to additional heat treatment (strain removal annealing)-
The non-oriented electrical steel sheet according to the present embodiment suppresses the decrease in magnetic flux density that occurs during the growth of recrystallized grains even when additional heat treatment (strain removal annealing) is performed at a low heating rate. It is something that can be done.
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 after a holding time at 800 ° C. were conducted to a heat treatment under conditions of 2 hours when the magnetic flux density of the steel sheet was _{B B,} the ratio of _{B B} and _{B a is,} B B / _{B a} ≧ 0.976 (preferably _B B / _{B a} ≧ 0.977, more preferably _B B / The relationship of B _A ≧ 0.978) 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 = 1.00} ) It 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 1.00.
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.

The conditions of the additional heat treatment that defines the non-oriented electrical steel sheet according to the present embodiment are set to specific values in the heating rate, the maximum temperature reached, and the holding time as described above. This uses values that are considered to be typical as conditions for strain relief annealing that are currently practically practiced. When the non-oriented electrical steel sheet according to the present embodiment is used for performing additional heat treatment, the effect of suppressing the decrease in magnetic flux density due to the additional heat treatment is limited to this value in terms of heating rate, maximum temperature reached, and holding time. However, it can be enjoyed within a wide range to some extent. For example, as conditions for additional heat treatment in which specific magnetic characteristics can be confirmed, the heating rate is 30 ° C./hr to 500 ° C./hr, the maximum temperature reached is 750 ° C. to 850 ° C., and the holding time at 750 ° C. or higher is 0.5 hours. A range of up to 100 hours can be mentioned.

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 at a low heating rate such as strain relief annealing, it is more advantageous than crystal grains having a {100} orientation, which is advantageous for magnetic properties. , Growth of crystal grains having other orientations (eg, {111}, {223}, {112}, etc.) becomes dominant. Since these orientations grow by eroding the {100} orientation in particular, the magnetic flux density of the conventional non-oriented electrical steel sheet is greatly reduced.

On the other hand, the non-oriented electrical steel sheet according to the present embodiment contains P, and further, at least one condition of the temperature condition of finish rolling in hot rolling and the reduction rate condition in cold rolling is a specific condition. At least one of the P content and the heating condition of finish annealing after cold rolling is controlled by a specific condition. As a result, the development of the {210} <001> orientation is promoted especially in the surface layer, and as a result, the development of the orientation such as {111} is suppressed. Therefore, in the grain growth by the additional heat treatment by slow heating after finish annealing, the growth in the orientation such as {111} is not dominant, and the crystal grains having the {100} orientation which is advantageous for increasing the magnetic flux density remain. It is presumed to grow and maintain a high magnetic flux density.

The effect on the selectivity of the grown grains by such additional heat treatment is that the heating rate is relatively high (for example, 10 ° C. per second) until the initial stage of grain growth (for example, the stage where the crystal grain size is 80 μm or less). Crystals generated at (10 ° C./sec) or higher) have a relatively low heating rate and a low temperature for a long time (for example, 1) in the late stage of grain growth (for example, the crystal particle size is more than 80 μm). The growth proceeded at about 100 ° C. (100 ° C./hr) or less per hour, and the holding time in the temperature range of 550 ° C. to 750 ° C., which is relatively low as the temperature range at which grain growth occurs, was 2 hours or more). It becomes noticeable in some cases.

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.
On the other hand, for example, in finish annealing (in rapid heating annealing), a steel sheet having a particle size of less than 20 μm, for example, a steel sheet in which an unrecrystallized structure remains, is grown to progress of recrystallization and grain growth, for example, about 50 μm. Even in the case, the preferable orientation selectivity is not lost.

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.

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.

<Manufacturing method of non-oriented electrical steel sheet>
As described above, the non-oriented electrical steel sheet according to the present embodiment contains P, and further contains at least one condition of the temperature condition of finish rolling in hot rolling and the reduction rate condition in cold rolling, and P. It is obtained by controlling at least one of the content condition and the recovery annealing condition of the finish annealing after cold rolling to a specific condition. 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: 0.01% to 3.50%, Al: 0. Heat a slab with (0.01% to 2.500%, Mn: 0.01% to 3.00%, P: 0.180% or less, S: 0.0030% or less, and balance: Fe and impurities). After the hot rolling process (hot rolling process) of hot rolling (hot rolling), the cold rolling process (cold rolling step) of cold rolling (cold rolling) on the steel sheet after the hot rolling process, and the cold rolling process. It has a finish annealing step of finish annealing on a steel sheet of the above.
Then, at least one of the following conditions (a) and the following (b) is satisfied, and at least one of the following (c) and the following (d) is satisfied.
(A) Hot rolling process: Finish rolling in a temperature range of 500 ° C to 800 ° C (b) Cold rolling process: Cold rolling so that the total reduction ratio is 90% or more (c) P of steel sheet Content: The lower limit is 0.021% or more in mass%. (D) Finish annealing step: After holding the steel sheet after the cold rolling step at 450 ° C to 600 ° C for 10 minutes or more, the temperature exceeds 600 ° C. To raise the temperature to finish annealing

Here, (a) and (b) are conditions for bringing the surface layer of the steel sheet into a special deformed state, and (c) and (d) are relatively slow in finish annealing after cold rolling. It is a condition for realizing the situation where the recrystallization progresses. By satisfying at least one condition of (a) and (b) and at least one condition of (c) and (d), the {210} <001> orientation in the surface layer after finish annealing. The degree of integration of the above is 6 or more (that is, the above-mentioned feature (A) is obtained), and it becomes possible to obtain a specific magnetic characteristic.

Further, according to the above manufacturing method, the degree of accumulation of {210} <001> orientation in the surface layer (MS ₂₁₀ ) and the accumulation of {210} <001> orientation in the central layer having a plate thickness of 1/5 to 1/2 of the plate thickness. Degree (MC ₂₁₀ )
MS ₂₁₀ / MC ₂₁₀ > 1.50
(That is, the above-mentioned feature (B) is further obtained).

Then, as the non-oriented electrical steel sheet obtained by the above manufacturing method, a steel sheet having an integration degree of {100} <012> orientation in the surface layer of 6 or more can be 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)
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 finish hot rolling becomes an effective control factor for increasing the degree of integration of {100} <012> orientation in the surface layer of the steel sheet recrystallized by cold rolling after hot rolling and finish annealing. obtain. For this purpose, the temperature of the finish hot spreading is preferably set to 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 temperature of finish rolling is generally about 850 ° C. to 950 ° C., and it is specified as the surface layer of the steel sheet by lowering the temperature of finish rolling as in the method for manufacturing non-oriented electrical steel sheet according to the present embodiment. The reason why the crystal orientation of is expressed is not clear, but it is considered as follows. As mentioned above, considering that it is caused by "shear deformation acting on the surface layer", it is considered that the same phenomenon is brought about in the surface layer of the hot-rolled steel sheet by lowering the rolling temperature in hot rolling. I can guess. Of course, it is not necessary that the orientation change in the surface layer by hot spreading becomes favorable for a specific magnetic property after cold rolling and finish annealing as it is. However, at least it is natural to think that the shear strain introduced into the surface layer at a relatively low temperature in hot spreading affects the crystal orientation generated after cold rolling and finish annealing. It is hoped that the changes in crystal orientation from hot spreading to cold spreading to annealing will be elucidated in the future.

(Cold rolling process)
Next, the steel sheet after hot rolling is cold rolled. The reduction rate of cold spreading is not particularly limited, but it 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 {210} <001> orientation on the surface layer 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 a specific crystal orientation. 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 surface 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 can be an effective control factor for obtaining a specific crystal orientation defined by the non-oriented electrical steel sheet according to the present embodiment. The heating conditions in the finish annealing step may be as follows.
In order to effectively obtain specific magnetic properties, finish annealing involves holding the steel sheet after the cold rolling process at 450 ° C. to 600 ° C. for 10 minutes or more, and then raising the temperature to over 600 ° C. for finish annealing. That's good. From the viewpoint of structural change of the steel sheet, this heat treatment process sufficiently restores the processed structure in the temperature range of 450 ° C. to 600 ° C. (heat treatment in this temperature range is sometimes referred to as "recovery annealing"). After that, recrystallization proceeds in a temperature range of more than 600 ° C. to further grow grains.
In addition, when the heating conditions in the 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 of the finish annealing is performed. When the condition is controlled to at least one of the case where the condition is set to this condition and the lower limit value of the P content is set to 0.021% or more, as described above, the non-directional electromagnetic steel having better magnetic characteristics is obtained. A steel plate is obtained.

The holding time in the recovery annealing may be 10 minutes or more, but from the viewpoint of preferably controlling the crystal orientation, the longer the holding time, the more preferably 30 minutes or more. It is preferably 2 hours or more. The upper limit of the holding time is not particularly set, but when BAF (Box Annealing Finance) annealing (batch annealing by a box annealing furnace) described later is applied, holding for a long time lowers the production efficiency, so it is preferably 20 hours or less, preferably. It is better to keep it within 10 hours.
The holding in the temperature range of 450 ° C. to 600 ° C. may be carried out as a separate step before the annealing for recrystallizing the steel sheet, or is carried out by controlling the temperature raising process in the annealing for recrystallizing the steel sheet. You may.
Considering that the holding time is at least 10 minutes, when the annealing for recrystallizing the steel sheet is a continuous annealing step, it can be said that batch annealing is performed as a separate step as a practical method.

The maximum temperature reached by the soaking temperature of the finish annealing after the above-mentioned recovery annealing or when the recovery annealing is not performed on the high P component steel sheet may be a temperature equal to or higher than the recrystallization temperature, but is a number like continuous annealing. When the holding temperature is within minutes, the temperature is set to 800 ° C. or higher so that sufficient grain growth can occur and iron loss can be reduced. From this point of view, it is preferably 850 ° C. or higher.
Alternatively, if a process that can be retained for several hours, such as batch annealing, is applied, the temperature may be 680 ° C or higher. Generally, when a steel sheet having a low C content and a high cold flux reduction ratio, such as the non-oriented electrical steel sheet according to the present embodiment, is annealed by slow heating such as batch annealing, the direction is {111}. The typical orientation is easy to develop, and there is a concern that the magnetic flux density will decrease. However, in the non-oriented electrical steel sheet according to the present embodiment, as described above, preferential growth in the {111} direction at the grain growth stage is suppressed, so that a high magnetic flux density can be obtained even in batch annealing.

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. Therefore, the soaking temperature of the finish annealing is not sufficient from the viewpoint of grain growth, and there is no problem even if it is lower than the above temperature (800 ° C. for continuous annealing and 680 ° C. for batch annealing). In this case, the effect of avoiding the inferior magnetic properties due to the additional heat treatment is remarkably exhibited. In this case, it is possible to have the characteristic crystal orientation of the non-oriented electrical steel sheet according to the present embodiment even if the unrecrystallized structure remains in a part. The lower limit temperature of the soaking temperature is 640 ° C. or higher. 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 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, preferably 1050 ° C. or lower in continuous annealing in consideration of the load of the annealing furnace. Further, in batch annealing, the temperature is often 800 ° C. or lower, preferably 750 ° C. or lower.

The soaking heat holding time may be set in consideration of particle size, iron loss, magnetic flux density, strength, and the like. For example, continuous annealing may be performed for 5 sec to 120 sec, and batch annealing may be performed for 1 hour to 20 hours.

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.

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

According to this embodiment, a non-oriented electrical steel sheet having excellent 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. The punching member 11 is not limited to the shape, number, number of layers, etc. shown in FIG. 2, and may be designed according to the purpose.

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 a low iron loss and a 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 or after the laminating process, the heating rate is 30 ° C./hr to 500 ° C./hr, the maximum reaching temperature is in the temperature range of 750 ° C. to 850 ° C., and 750 ° C. It has a heat treatment step of heat-treating under the condition of the above holding time of 0.5 hour to 100 hours.

That is, the motor core according to the present embodiment has a holding time under specific conditions (heating rate: 30 ° C./hr to 500 ° C./hr, maximum reached temperature: 750 ° C. to 850 ° C., 750 ° C. or higher) after laminating the punched members. : 0.5 hours to 100 hours) may be subjected to heat treatment (strain removal annealing). 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 step in the steel sheet manufacturing process generally carried out at a heating rate of about several tens of degrees / sec. However, 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 this decrease in magnetic flux density. Depending on the conditions, the magnetic flux density may increase. Regarding the heating rate of strain-removing annealing that can enjoy specific magnetic characteristics, the upper limit is 500 ° C./hr or less in consideration of the capacity of the strain-removing annealing equipment. The lower limit is 30 ° C./hr or more in consideration of the production efficiency of strain relief annealing. 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-rolling 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 has the above conditions (heating rate: 30 ° C./hr to 500 ° C./hr, maximum ultimate temperature: 750 ° C. to 850 ° C., It is preferable to carry out the heat treatment (holding time at 750 ° C. or higher: 0.5 hours to 100 hours).
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 the core material of the motor, even after punching into a desired shape and then performing strain relief annealing, the magnetic flux density B ₅₀ is lowered and the iron loss is reduced. It has the advantage of suppressing deterioration. Further, even after laminating as a motor core, a decrease in magnetic flux density is suppressed. Therefore, since the non-oriented electrical steel sheet according to the present embodiment has excellent practical characteristics, it can sufficiently meet the urgent demand for high efficiency and miniaturization in the field of electrical equipment, and its industrial value is extremely high. It is a thing.

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 hot spreading is performed at the temperatures 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 0.35 mm. The steel sheet after cold rolling is subjected to finish annealing at the recovery annealing temperature (recovery annealing holding time is 600 min) and continuous annealing finish soaking temperature (both soaking time is 30 sec) shown in Table 1. Obtain a steel plate. In addition, "omission" described in the recovery annealing temperature column indicates that recovery annealing has not been performed.

The surface layer and the central layer of the obtained steel sheet were observed according to the method described above, and the degree of integration of the {210} <001> orientation in the surface layer (surface layer {210} <001> (MS ₂₁₀ )) and the central layer. Measured the degree of integration of {210} <001> orientation (central layer {210} <001> (MC ₂₁₀ )) and the degree of integration of {100} <012> orientation in the surface layer (surface layer {100} <012>). To do. The results are shown in Table 1. _{Further, the magnetic flux density B 50 of the} average circumference, the ratio of the magnetic flux density B ₅₀ to the saturated magnetic flux density Bs (B ₅₀ / Bs), and the iron loss (W _10/400 ) are measured. Further, the average crystal grain size (particle size) is measured according to the method described above.

For the crystal grain size, the metal structure of the plate thickness cross section developed by corroding the grain boundaries by nightal etching was photographed with an optical microscope, and a linear method for 100 or more crystal grains (a straight line was drawn in the photograph of the metal structure). Calculated from the number of intersections between the straight line and the grain boundary).
Further, among the obtained steel sheets, for a material having a comparatively low soaking temperature for finish annealing, 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 removal annealing is performed, and the change in magnetic flux density 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.
In the table, B _B represents the magnetic flux density after SRA, and B _A represents the magnetic flux density before SRA.

Further, the obtained steel sheets are laminated by the following method, _{and the ratio (B 50} / Bs) of _{the magnetic flux density B 50} after the lamination to the saturated magnetic flux density Bs is measured.
Prepare a steel plate blank punched into the shape of the motor core with a die. In order to fix the laminated steel plate blanks together, caulking is performed to form a motor core. After that, the back yoke portion of the motor is wound with a primary: 100 turns and a secondary: 100 turns, and B ₅₀ and Bs are measured _{to calculate (B 50} / Bs).

The example of the invention corresponding to the non-oriented electrical steel sheet 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-oriented electrical steel sheet of the present embodiment. It can be seen that the change in magnetic flux density due to the ratio to the magnetic flux density Bs (B ₅₀ / Bs), the iron loss (W _10/400 ), and the strain removal annealing (SRA) shows good results.

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

Claims (7)

By mass%
C: 0.0030% or less,
Si: 0.01% to 3.50%,
Al: 0.001% to 2.500%,
Mn: 0.01% to 3.00%,
P: 0.180% or less,
S: 0.0030% or less, and
Remaining: Has a chemical composition of Fe and impurities,
The degree of integration of the {210} <001> orientation in the surface layer from the steel plate surface to the plate thickness 1/10 is 6 or more.
The degree of integration of {210} <001> orientation in the surface layer (MS ₂₁₀ ) and the degree of integration of {210} <001> orientation in the central layer of 1/5 to 1/2 of the plate thickness (MC ₂₁₀ ). But,
MS ₂₁₀ / MC ₂₁₀ > 1.50
Non-oriented electrical steel sheet that meets the relationship. By mass%
C: 0.0030% or less,
Si: 0.01% to 3.50%,
Al: 0.001% to 2.500%,
Mn: 0.01% to 3.00%,
P: 0.180% or less,
S: 0.0030% or less, and
Remaining: Has a chemical composition of Fe and impurities,
The degree of integration of the {210} <001> orientation in the surface layer from the steel plate surface to the plate thickness 1/10 is 6 or more.
{100} <012> orientation non-oriented electrical steel sheet integration degree Ru der 6 or more in the surface layer. By mass%
C: 0.0030% or less,
Si: 0.01% to 3.50%,
Al: 0.001% to 2.500%,
Mn: 0.01% to 3.00%,
P: 0.180% or less,
S: 0.0030% or less, and
Remaining: Has a chemical composition of Fe and impurities,
The degree of integration of the {210} <001> orientation in the surface layer from the steel plate surface to the plate thickness 1/10 is 6 or more.
Entire circumference ratio of the direction the average of the magnetic flux density _{B 50} and the saturation magnetic flux density Bs _(B 50 / Bs) is non-oriented electrical steel sheet Ru der than 0.870 in the case of excitation in the magnetizing force 5000A / m. By mass%
C: 0.0030% or less,
Si: 0.01% to 3.50%,
Al: 0.001% to 2.500%,
Mn: 0.01% to 3.00%,
P: 0.180% or less,
S: 0.0030% or less, and
Remaining: Has a chemical composition of Fe and impurities,
The degree of integration of the {210} <001> orientation in the surface layer from the steel plate surface to the plate thickness 1/10 is 6 or more.
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} ≧ 0.976. A hot rolling step of hot rolling a slab having the chemical composition according to any one of claims 1 to 4.
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.
Any one of claims 1 to 4 that satisfies at least one of the following conditions (a) and (b) and satisfies at least one of the following (c) and the following (d). A method for manufacturing a non-oriented electrical steel sheet according to.
(A) Hot rolling process: Finish rolling in a temperature range of 500 ° C to 800 ° C (b) Cold rolling process: Cold rolling so that the total reduction ratio is 90% or more (c) P of steel sheet Content: The lower limit is 0.021% or more in mass%. (D) Finish annealing step: After holding the steel sheet after the cold rolling step at 450 ° C to 600 ° C for 10 minutes or more, the temperature exceeds 600 ° C. To raise the temperature to finish annealing A motor core in which non-oriented electrical steel sheets according to any one of claims 1 to 4 are laminated. A step of punching a non-oriented electrical steel sheet according to any one of claims 1 to 4 to obtain a punched member.
The process of laminating the punched members and
A method for manufacturing a motor core.

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