Non-oriented electrical steel sheet

Abstract

A non-oriented electrical steel sheet effective for reducing noise and vibration of an electric motor, the non-oriented electrical steel sheet having a component composition containing, in mass%, 0.0050% or less of C, 2.0-5.0% of Si, 2.0% or less of Mn, 0.20% or less of P, 0.0050% or less of S, 2.0% or less of Al, 0.0050% or less of N, 0.0030% or less of Ti, 0.0010% or less of Nb, 0.0050% or less of V, and 0.0050% or less of O, when an alternating-current magnetic field is applied at a frequency of 50 Hz and a maximum magnetic flux density Bm of 1.5 T in a rolling direction (RD), a plate width direction (TD), and a direction (DD) at an angle of 45 degrees with respect to the rolling direction in a rolling surface of a steel plate, zero-peak values of magnetostriction in directions perpendicular to the magnetic field direction and parallel to the rolling surface are denoted as [lambda] perpendicular to HRD, [lambda] perpendicular to HTD, and [lambda] perpendicular to HDD, respectively, [lambda] perpendicular to HRD, [lambda] perpendicular to HTD, and [lambda] perpendicular to HDD. The absolute value of the in-plane average value [lambda] perpendicular to Have of magnetostriction is 5 * 10 <-6 > or less.

Description

Technical Field

[0001] This invention relates to non-oriented electromagnetic steel sheets, and in particular to non-oriented electromagnetic steel sheets capable of reducing noise and vibration when used in the cores of electric motors (rotating machines), etc. Background Technology

[0002] In recent years, with the increasing demand for energy conservation in electrical equipment, there has been a strong requirement for higher efficiency in electrical equipment. Consequently, there is also a demand for superior magnetic properties in non-oriented electromagnetic steel sheets used in the cores of electric motors.

[0003] The motor core consists of a stator core and a rotor core. In order to meet the requirements of miniaturization and high output of HEV drive motors and the like in recent years, the non-oriented electromagnetic steel plates used for the stator core are strongly required to have excellent magnetic characteristics such as high magnetic flux density and low iron loss.

[0004] However, in recent years, the requirements for low noise and low vibration in HEV drive motors and the like have also increased. Causes of motor noise and vibration include cogging torque in the unexcited state and torque fluctuations in the excited state. Furthermore, the magnetostriction of the non-oriented electromagnetic steel sheet used as the core material of the motor is also known to contribute to motor noise and vibration.

[0005] The stator core of an electric motor is made by stacking two or more non-oriented electromagnetic steel plates that are machined into the cross-sectional shape of an electric motor core and fixing them together by riveting, welding, bolting, etc. When the stator core is energized, the non-oriented electromagnetic steel plates expand and contract due to magnetostriction. This expansion and contraction propagates from the stator core to the motor housing and is emitted as vibration sound.

[0006] Therefore, in order to reduce the noise and vibration of the electric motor caused by magnetostriction, it is preferable to minimize the magnetostriction of the non-oriented electromagnetic steel sheet used for the iron core. As a technique for reducing the magnetostriction of the non-oriented electromagnetic steel sheet, for example, Patent Document 1 discloses reducing the magnetostriction constant λ by adjusting the steel composition. 100 The technology.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2010-248559 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, in the technology disclosed in the aforementioned Patent Document 1, in order to reduce the magnetostriction constant λ 100The balance between Si and Al must be adjusted, presenting a challenge in simultaneously addressing the magnetostrictive properties and the iron loss characteristics of the motor core. Furthermore, even reducing the magnetostrictive constant λ presents its own limitations. 100 The problem is that the noise and vibration of the motor core may not be reduced.

[0012] The present invention was made in view of the above-mentioned problems existing in the prior art, and its purpose is to provide a non-oriented electromagnetic steel sheet with low magnetostriction that is effective in reducing the noise and vibration of electric motors.

[0013] Methods for solving problems

[0014] To address the aforementioned problems, the inventors conducted repeated and in-depth research focusing on the magnetostrictive deformation during the excitation process of the rear yoke of the stator core. The results showed that by reducing the in-plane average value of magnetostriction in directions perpendicular to and parallel to the rolling surface when an alternating magnetic field is applied to the non-oriented electromagnetic steel sheet used as the motor core material in the rolling direction, the sheet width direction (rolling right angle direction), and the direction at a 45° angle to the rolling direction, a low-noise, low-vibration motor can be manufactured, thus leading to the development of this invention.

[0015] That is, the present invention is a non-oriented electromagnetic steel sheet, comprising the following components: C: less than 0.0050 wt%, Si: 2.0-5.0 wt%, Mn: less than 2.0 wt%, P: less than 0.20 wt%, S: less than 0.0050 wt%, Al: less than 2.0 wt%, N: less than 0.0050 wt%, Ti: less than 0.0030 wt%, Nb: less than 0.0010 wt%, V: less than 0.0050 wt%, and O: less than 0.0050 wt%, with the balance being Fe and unavoidable impurities. The non-oriented electromagnetic steel sheet is characterized in that the rolling direction within the rolling surface of the steel sheet (… RD ), width direction ( TD and the direction at a 45° angle to the rolling direction ( DD A magnetic flux density B with a frequency of 50 Hz is applied to the surface. m The zero-peak values ​​of magnetostriction in directions perpendicular to the magnetic field and parallel to the rolling surface under an AC magnetic field of 1.5T are denoted as λ. ⊥H RD , λ ⊥H TD and λ ⊥H DD At that time, the in-plane average value λ of magnetostriction is defined by the following equation (1). ⊥H ave The absolute value is 5 × 10 -6 the following.

[0016]

[0017] The non-oriented electromagnetic steel sheet of the present invention is characterized in that, in addition to the above-mentioned composition, it also contains at least one of the following groups A to L.

[0018] Group A: Selected from at least one of Sn: 0.005–0.20% by mass and Sb: 0.005–0.20% by mass;

[0019] Group B: Selected from at least one of Ca: 0.0005–0.100% by mass, Mg: 0.0005–0.100% by mass, and REM: 0.0005–0.100% by mass;

[0020] Group C: Selected from at least one of Cr: 0.01–1.0 wt% and Cu: 0.01–1.0 wt%;

[0021] Group D: Ni: 0.01–1.0% by mass

[0022] Group E: Selected from at least one of Mo: 0.0005–0.1% by mass and W: 0.001–0.1% by mass;

[0023] Group F: Co: 0.01–1.0% by mass;

[0024] Group G: Selected from at least one of As: 0.001–0.05% by mass and B: 0.0001–0.005% by mass;

[0025] Group H: Pb: 0.00001–0.010% by mass;

[0026] Group I: Zn: 0.0001~0.02% by mass;

[0027] Group J: Ta: 0~0.0020% (mass);

[0028] • Group K: Selected from at least one of Zr: 0–0.0050% by mass, Se: 0–0.0050% by mass and Bi: 0–0.0020% by mass;

[0029] • Group L: Selected from at least one of Ge: 0 to 0.030 wt% and Ga: 0 to 0.030 wt%.

[0030] Invention Effects

[0031] According to the present invention, it is possible to manufacture an electric motor with low noise and low vibration. Attached Figure Description

[0032] Figure 1 This is a schematic diagram illustrating the structure of a toroidal iron core used for noise investigation.

[0033] Figure 2 This is a diagram showing the effect of a magnetic field applied in the thickness direction during final annealing on the magnetostriction of the product plate in a direction perpendicular to the magnetic field and parallel to the rolling surface.

[0034] Figure 3 It shows the in-plane average value λ of the magnetostriction of the workpiece plate in a direction perpendicular to the magnetic field direction and parallel to the rolling surface. ⊥H ave A diagram illustrating the impact of noise on a toroidal core. Detailed Implementation

[0035] First, the experiment that led to the development of this invention will be described.

[0036] A steel billet with the following composition—C: 0.001 wt%, Si: 3.2 wt%, Mn: 0.6 wt%, P: 0.01 wt%, S: 0.0020 wt%, Al: 0.50 wt%, N: 0.0015 wt%, Ti: 0.0010 wt%, Nb: 0.0001 wt%, V: 0.0005 wt%, and O: 0.0010 wt%, with the balance being Fe and unavoidable impurities—was hot-rolled to produce a hot-rolled sheet with a thickness of 1.8 mm. This hot-rolled sheet was then subjected to hot-rolled annealing at 950°C for 30 seconds, followed by pickling, a first cold rolling, an intermediate annealing at 900°C for 30 seconds, and a second cold rolling with a reduction rate set to 60%, to produce a cold-rolled sheet with a final thickness of 0.25 mm. Next, the aforementioned cold-rolled sheet is rapidly heated at an average heating rate of 100°C / s within a temperature range of 200°C to 700°C, and a DC magnetic field of varying magnitude is applied along the thickness of the sheet within the aforementioned temperature range. Then, it is heated from 700°C to 980°C without cooling, and a final annealing process of 980°C × 10s is performed.

[0037] A ring-shaped piece with an outer diameter of 80 mm and an inner diameter of 60 mm is cut from the final annealed steel sheet by punching. Figure 1 The test piece shown has eight notches on the outer periphery of the ring. Next, 100 of the above-mentioned annular test pieces are stacked along the thickness direction and fixed by V-shaped riveting at six points to create an annular iron core. Then, the above-mentioned annular iron core is hot-pressed into an aluminum alloy shell with a thickness of 3 mm and an inner diameter of 80 mm with a hot-press fit of 40 μm.

[0038] Then, as Figure 1 As shown, a primary winding and a secondary winding are wound on the aforementioned toroidal iron core, and then a magnetic flux density of 50Hz and a maximum magnetic flux density of B are applied. mExcitation was performed under a temperature of 1.5T. At this time, a noise meter was installed 50mm from the outer periphery of the shell to measure the noise level of the toroidal core.

[0039] Furthermore, using the rolling direction, the width direction, and the direction at a 45° angle to the rolling direction as the length direction, a rectangular test piece with a width of 30 mm and a length of 280 mm was cut from the aforementioned finally annealed steel plate. A strain gauge was used to measure the maximum magnetic flux density B applied along the length direction of the test piece at a frequency of 50 Hz. m The zero-peak value of magnetostriction in the direction perpendicular to each magnetic field direction and parallel to the rolling surface when energized by an AC magnetic field of 1.5T is applied. It should be noted that, in this invention, the zero-peak value of magnetostriction in the direction perpendicular to each magnetic field direction and parallel to the rolling surface when energized in the rolling direction, the plate width direction, and the direction at 45° to the rolling direction is denoted as λ. ⊥H RD , λ ⊥H TD and λ ⊥H DD .

[0040] Figure 2 The figure shows the magnitude of the DC magnetic field applied in the thickness direction during final annealing and the zero-peak value λ of the magnetostriction in the direction perpendicular to each magnetic field direction and parallel to the rolling surface, as determined by the method described above. ⊥H RD , λ ⊥H TD and λ ⊥H DD The relationship is shown in the figure. As the magnetic field applied in the thickness direction during the final annealing increases, the absolute value of the zero-peak value of the magnetostriction in the direction perpendicular to each magnetic field direction and parallel to the rolling surface of the product plate decreases.

[0041] in addition, Figure 3 The figure shows the average value λ of magnetostriction in the rolling plane of the product plate in a direction perpendicular to each magnetic field direction and parallel to the rolling plane, as defined by the following equation (1). ⊥H ave The relationship between the in-plane average value (also referred to as the "in-plane average value" in this invention) and the noise value measured using a toroidal iron core. As shown in the figure, the in-plane average value λ of magnetostriction... ⊥H ave The smaller the absolute value, the less noise.

[0042]

[0043] Although the in-plane average value λ of magnetostriction has not been fully elucidated... ⊥H aveThe inventors believe the following is the mechanism by which hot-pressed toroidal cores affect noise.

[0044] If an alternating current is used to excite the toroidal core, the circumference of the core is energized, resulting in radial expansion and contraction in a direction perpendicular to the magnetic field and parallel to the rolling plane due to magnetostriction. The angle between the circumferential direction of the toroidal core and the rolling direction of the original steel sheet varies depending on its position. Typically, the magnetostriction of non-oriented electromagnetic steel sheets is anisotropic within the rolling plane, thus the radial expansion and contraction varies depending on the circumferential position. Therefore, a large anisotropy in magnetostriction results in positions with large and small radial expansion and contraction in the circumferential direction of the toroidal core. It is argued that such non-uniformity disrupts the symmetry of the toroidal core's vibration, thus generating inherent vibration peaks that do not appear without the anisotropy of magnetostriction, leading to increased vibration and noise. Therefore, it is believed that in order to reduce the radial expansion and contraction of the toroidal core and thus reduce noise and vibration, the magnetostriction in the direction perpendicular to the magnetic field and parallel to the rolling surface should be reduced along the entire circumference of the toroidal core, that is, the in-plane average value λ of the aforementioned magnetostriction should be reduced. ⊥H ave The absolute value is valid.

[0045] This invention was developed based on the aforementioned new insights.

[0046] Next, the applications of the non-oriented electromagnetic steel sheet of the present invention will be described.

[0047] The non-oriented electromagnetic steel sheet of the present invention has the effect of suppressing the increase of noise and vibration caused by compressive stress based on magnetostriction. Considering this feature, it is effective for use in stator cores. However, it is not limited to application in rotor cores. Therefore, stator cores and rotor cores can be cut simultaneously from the non-oriented electromagnetic steel sheet of the present invention.

[0048] Next, the composition of the non-oriented electromagnetic steel sheet of the present invention will be described.

[0049] C: Less than 0.0050% by mass

[0050] Carbon (C) in the finished product is a harmful element that causes magnetic aging, forms carbides, and deteriorates iron loss characteristics. Therefore, the upper limit of C content in the raw material is limited to 0.0050% by mass, preferably 0.0040% by mass or less. It should be noted that there is no specific lower limit for C, but from the viewpoint of reducing decarburization costs in the refining process, it is preferably set to about 0.0001% by mass.

[0051] Si: 2.0–5.0% by mass

[0052] Si has the effect of increasing the resistivity of steel, reducing iron loss, and improving the strength of steel through solid solution strengthening, therefore it is contained at 2.0% by mass or more. On the other hand, when it exceeds 5.0% by mass, rolling becomes difficult, so the upper limit is set at 5.0% by mass. Preferably, it is in the range of 2.8% to 4.5% by mass. More preferably, it is in the range of 3.2% to 4.0% by mass.

[0053] Mn: less than 2.0% by mass

[0054] Like Si, Mn is an effective element for improving the resistivity and strength of steel. Additionally, Mn also improves hot workability. However, adding more than 2.0% by mass can cause slab cracking and other defects, deteriorating the operability of the steelmaking process; therefore, the upper limit is set at 2.0% by mass. A range of 0.1% to 1.5% by mass is preferred.

[0055] P: less than 0.20% by mass

[0056] P is a useful element for adjusting the strength (hardness) of steel. However, when it exceeds 0.20% by mass, the steel becomes brittle, and rolling becomes difficult. Therefore, the upper limit is set at 0.20% by mass. It should be noted that there is no specific lower limit, but from the viewpoint of reducing the cost of removing P in the refining process, it is preferably set at about 0.001% by mass. The preferred range is 0.01% to 0.1% by mass.

[0057] S: less than 0.0050% by mass

[0058] S is an element that forms fine precipitates and hinders grain growth during final annealing and stress-relief annealing, thus adversely affecting iron loss characteristics. This adverse effect becomes significant, especially when the content exceeds 0.0050% by mass; therefore, the upper limit is limited to 0.0050% by mass, preferably 0.003% by mass or less.

[0059] Al: less than 2.0% by mass

[0060] Like Si, Al is a useful element that increases the resistivity of steel and reduces iron loss. However, when the content exceeds 2.0% by mass, the steel becomes brittle, making rolling difficult. Therefore, the upper limit for Al is set at 2.0% by mass, preferably 1.5% by mass or less. It should be noted that when Al is too low, the effect of increasing resistivity becomes smaller, so it is preferable to contain 0.1% by mass or more.

[0061] N: less than 0.0050% by mass

[0062] Nitrogen (N) is an element that forms fine precipitates and hinders grain growth during final annealing and stress-relief annealing, thus adversely affecting iron loss characteristics. This adverse effect becomes significant, especially when the content exceeds 0.0050% by mass; therefore, the upper limit is limited to 0.0050% by mass, preferably 0.003% by mass or less.

[0063] Ti: less than 0.0030% by mass

[0064] Ti is also an element that forms fine precipitates and hinders grain growth during final annealing and stress-relief annealing, thus adversely affecting iron loss characteristics. This adverse effect becomes significant, especially when it exceeds 0.0030% by mass; therefore, the upper limit is limited to 0.0030% by mass, preferably below 0.002% by mass.

[0065] Nb: less than 0.0010% by mass

[0066] Like Ti, Nb is an element that forms fine precipitates and hinders grain growth during final annealing and stress-relief annealing, thus adversely affecting iron loss characteristics. This adverse effect becomes significant, especially when it exceeds 0.0010% by mass; therefore, the upper limit is limited to 0.0010% by mass, preferably below 0.0005% by mass.

[0067] V: less than 0.0050% by mass

[0068] Like Ti and Nb, V is an element that forms fine precipitates and hinders grain growth during final annealing and stress-relief annealing, thus adversely affecting iron loss characteristics. This adverse effect becomes significant, especially when it exceeds 0.0050% by mass; therefore, the upper limit is limited to 0.0050% by mass, preferably below 0.0003% by mass.

[0069] O: less than 0.0050% by mass

[0070] O is a harmful element that forms oxide inclusions, hinders grain growth, and increases iron loss. In particular, the adverse effects become significant when the content exceeds 0.0050% by mass; therefore, the upper limit is set at 0.0050% by mass, preferably below 0.0030% by mass.

[0071] In the steel raw material used to manufacture the non-oriented electromagnetic steel sheet of the present invention, the balance other than the above-mentioned components is substantially Fe and unavoidable impurities. However, depending on the desired characteristics, the following components may also be appropriately included in addition to the above-mentioned components.

[0072] Selected from at least one of Sn: 0.005–0.20% by mass and Sb: 0.005–0.20% by mass.

[0073] Sn and Sb improve recrystallization texture and reduce iron loss. To achieve these effects, each needs to be added at least 0.005% by mass. On the other hand, even if each is added more than 0.20% by mass, the effects become saturated. Therefore, Sn and Sb are preferably added in the range of 0.005 to 0.20% by mass, respectively. More preferably, they are added in the range of 0.01 to 0.10% by mass, respectively.

[0074] Selected from at least one of Ca: 0.0005–0.100 wt%, Mg: 0.0005–0.100 wt%, and REM: 0.0005–0.100 wt%.

[0075] Ca, Mg, and REM have the effect of reducing fine sulfides by forming stable sulfides, thereby promoting grain growth and improving iron loss characteristics. To obtain the above effects, each needs to be added at least 0.0005% by mass. On the other hand, adding more than 0.100% by mass each will deteriorate iron loss. Therefore, Ca, Mg, and REM are preferably added in the range of 0.0005 to 0.100% by mass, respectively. More preferably, they are added in the range of 0.001 to 0.05% by mass, respectively.

[0076] In addition, the steel raw materials used to manufacture the non-oriented electromagnetic steel sheet of the present invention may appropriately contain the following components in addition to the above-mentioned components. However, the raw material cost of these components is relatively expensive, so it is preferable to keep the amount added to the minimum required.

[0077] Selected from at least one of Cr: 0.01–1.0 wt% and Cu: 0.01–1.0 wt%.

[0078] Like Si and Al, Cr and Cu increase the resistivity of steel and reduce iron loss. However, compared to Si and Al, their solid solution strengthening ability is weaker, so they are preferably added when it is desirable to reduce iron loss without compromising rollability. However, when the addition amount of each is less than 0.01% by mass, the above-mentioned effects cannot be fully obtained; on the other hand, when it exceeds 1.0% by mass, the iron loss improvement effect saturates. Therefore, Cr and Cu are preferably added in the range of 0.01 to 1.0% by mass, respectively.

[0079] Ni: 0.01~1.0% by mass

[0080] Ni is an element with strong solid solution strengthening ability and is effective in increasing the strength of steel. However, when the addition amount is less than 0.01% by mass, the above-mentioned effect cannot be fully obtained. On the other hand, when it exceeds 1.0% by mass, it leads to an increase in raw material costs. Therefore, it is preferable to add Ni in the range of 0.01% to 1.0% by mass.

[0081] Selected from at least one of Mo: 0.0005–0.1% by mass and W: 0.001–0.1% by mass.

[0082] Mo and W have the effect of coarsening carbides and thus reducing iron loss. However, when the amount of Mo added is less than 0.0005% by mass and the amount of W added is less than 0.001% by mass, the above-mentioned effect cannot be fully obtained. On the other hand, when the amount of Mo and W added exceeds 0.1% by mass, the above-mentioned iron loss improvement effect saturates. Therefore, it is preferable to add Mo and W in the range of 0.0005 to 0.1% by mass and 0.001 to 0.1% by mass, respectively.

[0083] Co: 0.01~1.0% by mass

[0084] Co increases the magnetic moment and flux density of Fe alloys, and reduces iron loss. However, when the addition amount is less than 0.01% by mass, these effects cannot be fully obtained; on the other hand, when it exceeds 1.0% by mass, the raw material cost increases. Therefore, it is preferable to add Co in the range of 0.01% to 1.0% by mass.

[0085] Selected from at least one of As: 0.001 to 0.05% by mass and B: 0.0001 to 0.005% by mass.

[0086] As and B are grain boundary segregation elements that reduce iron loss by improving texture. This effect is achieved by adding 0.001% by mass or more of As and 0.0001% by mass or more of B. However, As also contributes to grain boundary embrittlement, and this disadvantage becomes significant, especially when it exceeds 0.05% by mass. Therefore, it is preferable to add As in the range of 0.001 to 0.05% by mass. Furthermore, when B exceeds 0.005% by mass, its adverse effect on suppressing grain boundary migration increases. Therefore, it is preferable to add B in the range of 0.0001 to 0.005% by mass.

[0087] Pb: 0.00001~0.010% by mass

[0088] Pb is an element that is finely dispersed in steel as a metallic inclusion and remains in the steel after final annealing. It thus becomes a stress concentration point during blanking, promoting cracking and inhibiting die wear, thereby improving blanking performance. However, when Pb is less than 0.00001% by mass, the aforementioned improvement in blanking performance cannot be sufficiently obtained. On the other hand, when it exceeds 0.010% by mass, the grain growth inhibition becomes too large, resulting in poor iron loss. Therefore, the range is set to 0.00001 to 0.010% by mass, preferably 0.00003 to 0.0050% by mass.

[0089] Zn: 0.0001~0.02% by mass

[0090] Zn has the effect of forming stable and coarse sulfides or oxides, improving grain growth, or reducing the pinning force of magnetic domain walls. To obtain these effects, it is necessary to add more than 0.0001% by mass of Zn. However, even if more than 0.02% by mass is added, the above effects saturate. Therefore, Zn is preferably set in the range of 0.0001% to 0.02% by mass.

[0091] Ta: 0~0.0020% of mass

[0092] Ta is an effective element for improving the workability and increasing the strength of steel, and can be added appropriately. To reliably obtain the above effects, it is preferable to add 0.0001% by mass or more. On the other hand, Ta is an element that increases iron loss, and the above-mentioned adverse effects become significant, especially when it exceeds 0.0020% by mass. Therefore, the upper limit is preferably set at 0.0020% by mass. More preferably, it is in the range of 0.0003 to 0.0010% by mass.

[0093] Selected from at least one of Zr: 0–0.0050% by mass, Se: 0–0.0050% by mass, and Bi: 0–0.0020% by mass.

[0094] Zr, Se, and Bi are all elements that are finely dispersed in steel as inclusions, improving workability while refining grain size and thus increasing steel strength. Therefore, they can be added appropriately. However, when Zr and Se exceed 0.0050% by mass and Bi exceeds 0.0020% by mass, the grain growth inhibition becomes too great, resulting in poor iron loss. Therefore, the above values ​​are preferably set as upper limits. More preferably, the ranges are Zr: 0.0005–0.0030% by mass, Se: 0.0001–0.0030% by mass and Bi: 0.0001–0.0010% by mass.

[0095] Selected from at least one of Ge: 0 to 0.030 wt% and Ga: 0 to 0.030 wt%.

[0096] Both Ge and Ga are elements that improve texture. To reliably obtain the above effects, it is preferable to add 0.001% by mass or more of each. On the other hand, even if more than 0.030% by mass is added, the above effects will saturate, so the upper limit is preferably set to 0.030% by mass. More preferably, it is in the range of 0.003 to 0.010% by mass.

[0097] Next, the magnetostrictive properties of the non-oriented electromagnetic steel sheet of the present invention will be explained.

[0098] In-plane average value λ of magnetostriction ⊥H ave Absolute value: 5 × 10-6 the following

[0099] In the rear yoke of the stator core, the steel plate is primarily magnetized in the circumferential direction. Therefore, the rear yoke is magnetized in all directions within the rolled surface of the steel plate, depending on its position. When the steel plate is magnetized, it elongates and contracts in directions perpendicular to the magnetization direction (magnetic field direction) and parallel to the rolled surface. If the magnetostriction in all directions within the rolled surface of the steel plate is large during magnetization, the radial expansion and contraction, perpendicular to the magnetization direction, becomes uneven depending on the position of the rear yoke. Consequently, during magnetization, a peak of inherent vibration that does not occur without the unevenness caused by magnetostriction is generated, increasing the vibration of the motor core and increasing noise. Specifically, the average value λ of the magnetostriction... ⊥H ave The absolute value exceeds 5 × 10 -6 At times, such as Figure 3 As shown, the noise increases significantly. Therefore, in this invention, the average value λ of the magnetostriction is... ⊥H ave The absolute value is limited to 5 × 10 -6 The following should be noted: the average value λ of magnetostriction... ⊥H ave The absolute value is 3 × 10 -6 The vibration suppression effect of the motor core is further enhanced in the following cases, making it even more preferable.

[0100] The in-plane average value λ of the above magnetostriction ⊥H ave Defined by the following equation (1).

[0101]

[0102] Here, λ in the above formula ⊥H RD , λ ⊥H TD and λ ⊥H DD The rolling direction within the rolling surface of the steel plate ( RD ), plate width direction ( TD and the direction at a 45° angle to the rolling direction ( DD At a frequency of 50Hz and a maximum magnetic flux density of B m The zero-peak value of magnetostriction in the direction perpendicular to each magnetic field direction and parallel to the rolling surface when energized under the condition of 1.5T.

[0103] Next, the manufacturing method of the non-oriented electromagnetic steel sheet of the present invention will be described. It should be noted that in the manufacturing method described below, the processes other than the final annealing are examples of the methods and conditions for manufacturing the non-oriented electromagnetic steel sheet of the present invention, and different methods and conditions are not excluded from the manufacturing process.

[0104] First, steel having the composition conforming to the present invention is smelted using a commonly known refining process such as a converter, electric furnace, or vacuum degassing device. Then, steel raw material (slab) is produced by continuous casting or ingot-slab rolling. The slab is then hot-rolled using commonly known methods and conditions to produce a hot-rolled plate.

[0105] It should be noted that among the elements that can be contained in the steel raw materials used in this invention, Cu, Sn, Ni, Cr, and Mo are elements that are mixed in from the scrap used as raw materials during the electric furnace steelmaking process. Therefore, when using electric furnace steel, it is not necessary to reduce these elements, nor is it necessary to add them, thus helping to reduce raw material costs and refining costs. Furthermore, the casting and hot rolling of the smelted steel can also be performed using a thin slab continuous casting machine that is directly connected to a hot rolling mill. The thin slab continuous casting machine can cast thin slabs with a thickness of 200 mm or less, and then immediately hot-roll them using a hot rolling mill directly connected to the casting equipment, thus achieving a thinner finished product compared to conventional hot rolling. Therefore, the rolling load in the subsequent cold rolling is reduced, productivity is increased, and the texture is improved by reducing the cold rolling reduction rate, thus effectively reducing iron loss.

[0106] The hot-rolled sheet can be annealed as needed, and the soaking temperature is preferably set in the range of 800 to 1100°C. Below 800°C, the annealing effect is small, and the improvement in magnetic properties cannot be fully achieved. On the other hand, above 1100°C, manufacturing costs may become unfavorable, or brittle fracture (sheet breakage) may be promoted during cold rolling.

[0107] Then, the hot-rolled sheet, after being hot-rolled or annealed, is cold-rolled to its final thickness through one cold rolling or two or more cold rolling processes with intermediate annealing. At this point, from the viewpoint of increasing magnetic flux density, it is preferable to use warm rolling, in which the steel sheet temperature is raised to 200°C or higher, to produce the final thickness of the cold-rolled sheet.

[0108] It should be noted that the final plate thickness (product plate thickness) is preferably set in the range of 0.1 to 0.3 mm. This is because when it is less than 0.1 mm, the productivity decreases, and on the other hand, when it exceeds 0.3 mm, the effect of reducing iron loss is small.

[0109] Then, the cold-rolled sheet to the final thickness is subjected to final annealing, preferably set as continuous annealing at a temperature of 700–1100°C for 1–300 s. This is because when the soaking temperature is below 700°C, recrystallization will not occur sufficiently, resulting in poor magnetic properties, and the shape correction effect brought about by continuous annealing cannot be fully obtained. On the other hand, above 1100°C, the grains coarsen, and the strength of the steel sheet decreases.

[0110] Furthermore, during the final annealing process described above, it is preferable to perform rapid heating at a rate of 100°C / s or higher within a temperature range of 200°C to 700°C. By maintaining a heating rate of 100°C / s or higher, the nucleation orientation of the primary recrystallized grains can be randomized, reducing the in-plane average value λ of the magnetostriction. ⊥H ave The absolute value of the heating rate. When the heating rate is less than 100°C / s, the above-mentioned randomization effect cannot be fully obtained. Preferably, it is 500°C / s or more. It should be noted that there is no specific upper limit for the heating rate, but from the viewpoint that even if the heating rate is increased to more than 2000°C / s, the magnetostriction reduction effect will saturate, and from the viewpoint of suppressing excessive energy consumption, it is preferred to set it to about 2000°C / s.

[0111] Importantly, in this invention, it is necessary to apply a DC magnetic field in the thickness direction within a temperature range of 200°C to 700°C during the final annealing heating process described above. Primary recrystallization of the cold-rolled microstructure occurs at temperatures above 500°C, particularly above 600°C. Therefore, if a DC magnetic field is applied in the thickness direction within a temperature range of 500°C to 700°C, crystals with easy magnetization axes in the thickness direction preferentially nucleate, and the easy magnetization axes in the rolling plane are randomized, further reducing the in-plane average value λ of magnetostriction. ⊥H ave The absolute value of.

[0112] It should be noted that the in-plane average value λ, which fully ensures the magnetostriction caused by the DC magnetic field, is... ⊥H ave From the viewpoint of reducing the absolute value of the magnetic field and suppressing the magnetic force generated on the steel plate by the DC magnetic field, thus preventing the steel plate from detaching from the transport line, the temperature range in which the DC magnetic field is applied is preferably set to 600°C or higher, at which the spontaneous magnetization of the steel decreases. The strength of the applied magnetic field needs to be 1T or higher, and to further improve the above effect, it is preferably set to 5T or higher.

[0113] Next, to ensure insulation when the steel plates are stacked, the steel plates after final annealing are preferably coated with an insulating film. Regarding this insulating film, to ensure good punching performance, an organic film containing resin is preferred; on the other hand, to emphasize weldability, a semi-organic film or an inorganic film is preferred.

[0114] It should be noted that when the non-oriented electromagnetic steel sheet of the present invention is used as the core material to manufacture the stator core, the steel sheet after final annealing is usually processed into the core shape by punching or other processes, then stacked, fixed, and assembled into the stator core before stress-relief annealing is performed. This stress-relief annealing is preferably carried out in an inert gas atmosphere at 780–950°C for 0.1–10 hours. This is because when the stress-relief annealing temperature is below 780°C, the improvement in iron loss caused by stress-relief annealing is small; on the other hand, when the temperature exceeds 950°C, it is difficult to ensure insulation between the stacked steel sheets.

[0115] Example 1

[0116] A steel billet containing C: 0.001 wt%, Si: 3.4 wt%, Mn: 0.4 wt%, P: 0.01 wt%, S: 0.0020 wt%, Al: 0.80 wt%, N: 0.0015 wt%, Ti: 0.0010 wt%, Nb: 0.0001 wt%, V: 0.0005 wt%, and O: 0.0010 wt%, with the balance being Fe and unavoidable impurities, is hot-rolled to produce a hot-rolled sheet with a thickness of 1.8 mm. This hot-rolled sheet is then subjected to hot-rolled annealing at 950°C for 30 seconds, followed by pickling, a first cold rolling, an intermediate annealing at 900°C for 30 seconds, and a second cold rolling with a reduction of 60%, to produce a cold-rolled sheet with a final thickness of 0.25 mm. Then, the cold-rolled sheet is rapidly heated at an average heating rate of 1000°C / s within a temperature range of 200°C to 700°C, and a DC magnetic field of varying magnitude from 0 to 20T is applied in the thickness direction within the aforementioned temperature range. Then, it is heated from 700°C to 980°C without cooling, and a final annealing is performed at 980°C for 10 seconds. Finally, an insulating film is applied to form the finished sheet.

[0117] From the resulting sheet, a ring-shaped part with an outer diameter of 80mm and an inner diameter of 60mm is punched out. Figure 1 As shown, after creating test pieces with notches at eight locations on the outer periphery of the ring, 100 sheets are stacked along the thickness direction and fixed by V-shaped riveting at six points to form a ring-shaped iron core. Next, the ring-shaped iron core is hot-pressed with a fit of 40 μm onto an austenitic stainless steel shell with a thickness of 3 mm and an inner diameter of 80 mm. Then, as... Figure 1As shown, primary and secondary windings are wound on a toroidal iron core after hot pressing and bonding, and then a magnetic flux density of 50Hz and a maximum magnetic flux density of B is applied. m Excitation was performed at a temperature of 1.5T. A noise meter was then placed 50mm from the outer periphery of the casing to measure the noise of the toroidal core during excitation. It should be noted that the noise level varies depending on the plate thickness and the size of the toroidal core. For the toroidal core made from a 0.25mm thick plate, a noise level below 40dBA is considered excellent.

[0118] Furthermore, rectangular test pieces with a width of 30 mm and a length of 280 mm were cut from the aforementioned product plate, with the rolling direction, plate width direction, and a 45° direction from the rolling direction as the length direction. A strain gauge was used to measure the maximum magnetic flux density B at a frequency of 50 Hz along the length direction. m The zero-peak value λ of magnetostriction in the direction perpendicular to the magnetic field and parallel to the rolling surface when excited at 1.5T. ⊥H RD , λ ⊥H TD and λ ⊥H DD The in-plane average value λ of magnetostriction is obtained by the following equation (1). ⊥H ave .

[0119]

[0120] The results of the above measurements are shown in Table 1. As can be seen from the table, the toroidal cores made using non-oriented electromagnetic steel sheets manufactured under conditions conforming to the present invention all exhibit excellent noise characteristics.

[0121]

[0122] Example 2

[0123] A hot-rolled sheet with a thickness of 1.8 mm is produced by hot rolling a steel billet containing the various components shown in Table 2, with the balance consisting of Fe and unavoidable impurities. Next, the hot-rolled sheet is subjected to hot-rolled annealing at 950°C for 30 seconds, followed by pickling, a first cold rolling, an intermediate annealing at 900°C for 30 seconds, and a second cold rolling with a reduction rate of 55%, resulting in a cold-rolled sheet with a final thickness of 0.25 mm. The cold-rolled sheet is then rapidly heated at an average heating rate of 1000°C / s within a temperature range of 200°C to 700°C, while applying various DC magnetic fields of magnitude ranging from 0 to 8 T in the thickness direction within this temperature range. Then, it is heated from 700°C to 980°C without cooling, undergoing a final annealing at 980°C for 10 seconds, and finally coated with an insulating film to produce the finished sheet.

[0124] From the resulting sheet, a ring-shaped part with an outer diameter of 80mm and an inner diameter of 60mm is punched out. Figure 1 As shown, after creating test pieces with notches at eight locations on the outer periphery of the ring, 100 sheets were stacked along the thickness direction and fixed by welding at six points to form a ring-shaped iron core. Next, the ring-shaped iron core was hot-pressed with a fit of 40 μm onto an austenitic stainless steel shell with a thickness of 3 mm and an inner diameter of 80 mm. Then, as... Figure 1 As shown, the primary and secondary windings are wound on the toroidal core after the above hot-pressing process, and then a magnetic flux density of 50Hz and a maximum magnetic flux density of B are applied. m Excitation was performed under a temperature of 1.5T, and the iron loss W was measured under this condition. 15 / 50 When the iron loss is below 20.0 W / kg, it is evaluated as having good iron loss characteristics. Furthermore, a noise meter was installed at a position 50 mm from the outer periphery of the casing to measure the noise during excitation, and when the noise is below 40 dBA, it is evaluated as having excellent noise characteristics.

[0125] Furthermore, rectangular test pieces with a width of 30 mm and a length of 280 mm were cut from the aforementioned product plate, with the rolling direction, plate width direction, and a 45° direction from the rolling direction as the length direction. A strain gauge was used to measure the maximum magnetic flux density B at a frequency of 50 Hz along the length direction. m The zero-peak value λ of magnetostriction in the direction perpendicular to the magnetic field and parallel to the rolling surface when excited at 1.5T. ⊥H RD , λ ⊥H TD and λ ⊥H DD The in-plane average value λ of magnetostriction is obtained by the following equation (1). ⊥H ave .

[0126]

[0127] The results of the above measurements are shown in Table 2. As can be seen from the table, the toroidal cores made using non-oriented electromagnetic steel sheets manufactured under conditions conforming to the present invention, using steel raw materials with a composition conforming to the present invention, all exhibit excellent iron loss characteristics and noise characteristics. It should be noted that the steel sheet of No. 20 (comparative example) in Table 2 fractured during cold rolling and therefore could not be made into a finished product.

[0128]

[0129]

[0130]

[0131]

[0132]

[0133]

[0134] Example 3

[0135] Using an electric furnace, a mixture containing C: 0.0015 wt%, Si: 3.4 wt%, Mn: 0.7 wt%, P: 0.020 wt%, S: 0.0005 wt%, Al: 1.0 wt%, N: 0.0020 wt%, Ti: 0.0020 wt%, Nb: 0.0001 wt%, V: 0.0002 wt%, O: 0.0010 wt%, Sn: 0.01 wt%, Cu: 0.05 wt%, Ni: 0.05 wt%, and C... Steel with a composition of r: 0.02% by mass, Mo: 0.02% by mass, B: 0.0003% by mass, Pb: 0.0001% by mass, As: 0.0003% by mass, Zn: 0.0020% by mass, Co: 0.0030% by mass, and Ga: 0.0030% by mass was smelted and then cast into thin slabs with a thickness of 100 mm using a thin slab continuous casting machine that directly connects a continuous casting machine and a hot rolling mill. These slabs were then hot-rolled to produce a hot-rolled plate with a thickness of 0.8 mm. Next, the hot-rolled plate was annealed at 1000°C for 30 seconds, then pickled, and finally cold-rolled to produce a cold-rolled plate with a final thickness of 0.25 mm. The cold-rolled plate was then rapidly heated at an average heating rate of 1000°C / s within a temperature range from 200°C to 700°C, while a DC magnetic field of 5 T was applied along the thickness direction within this temperature range. Then, starting from the above-mentioned temperature of 700°C, it is heated to 1000°C without cooling, and a final annealing of 1000°C × 10s is performed. Then, an insulating film is applied to form the product board.

[0136] From the resulting sheet, a ring-shaped part with an outer diameter of 80mm and an inner diameter of 60mm is punched out. Figure 1 As shown, after creating test pieces with notches at eight locations on the outer periphery of the ring, 100 sheets were stacked along the thickness direction and fixed by welding at six points to form a ring-shaped iron core. Next, the ring-shaped iron core was hot-pressed with a fit of 40 μm onto an austenitic stainless steel shell with a thickness of 3 mm and an inner diameter of 80 mm. Then, as... Figure 1 As shown, the primary and secondary windings are wound on the toroidal core after the above hot-pressing process, and then a magnetic flux density of 50Hz and a maximum magnetic flux density of B are applied. m Excitation was performed under a temperature of 1.5T, and the iron loss W was measured under this condition. 15 / 50 When the iron loss is below 20.0 W / kg, it is evaluated as having good iron loss characteristics. Furthermore, a noise meter was installed at a position 50 mm from the outer periphery of the casing to measure the noise during excitation, and when the noise is below 40 dBA, it is evaluated as having excellent noise characteristics.

[0137] Furthermore, rectangular test pieces with a width of 30 mm and a length of 280 mm were cut from the aforementioned product plate, with the rolling direction, plate width direction, and a 45° direction from the rolling direction as the length direction. A strain gauge was used to measure the maximum magnetic flux density B along the length direction of the test piece at a frequency of 50 Hz. m The zero-peak value λ of magnetostriction in the direction perpendicular to the magnetic field and parallel to the rolling surface when excited at 1.5T. ⊥H RD , λ ⊥H TD and λ ⊥H DD The in-plane average value λ of magnetostriction is obtained by the following equation (1). ⊥H ave .

[0138]

[0139] The results of the above measurements are shown in Table 3. As can be seen from the table, the toroidal cores made using non-oriented electromagnetic steel sheets manufactured under conditions conforming to the present invention, and using steel raw materials with a composition conforming to the present invention, all exhibit excellent iron loss characteristics and noise characteristics.

[0140]

Claims

1. A non-oriented electromagnetic steel sheet, comprising a composition of C: less than 0.0050 wt%, Si: 2.0-5.0 wt%, Mn: less than 2.0 wt%, P: less than 0.20 wt%, S: less than 0.0050 wt%, Al: less than 2.0 wt%, N: less than 0.0050 wt%, Ti: less than 0.0030 wt%, Nb: less than 0.0010 wt%, V: less than 0.0050 wt%, and O: less than 0.0050 wt%, with the balance being Fe and unavoidable impurities, characterized in that... The rolling direction within the rolling surface of the steel plate ( RD ), width direction ( TD and the direction at a 45° angle to the rolling direction ( DD A magnetic flux density B with a frequency of 50 Hz is applied to the surface. m The zero-peak values ​​of magnetostriction in directions perpendicular to the magnetic field and parallel to the rolling surface under an AC magnetic field of 1.5T are denoted as λ. ⊥H RD , λ ⊥H TD and λ ⊥H DD At that time, the in-plane average value λ of magnetostriction is defined by the following equation (1). ⊥H ave The absolute value is 5 × 10 -6 the following, 。 2. The non-oriented electromagnetic steel sheet according to claim 1, characterized in that, In addition to the aforementioned composition, it also contains at least one of the following groups A to L. Group A: Selected from at least one of Sn: 0.005–0.20% by mass and Sb: 0.005–0.20% by mass; Group B: Selected from at least one of Ca: 0.0005–0.100% by mass, Mg: 0.0005–0.100% by mass, and REM: 0.0005–0.100% by mass; Group C: Selected from at least one of Cr: 0.01–1.0 wt% and Cu: 0.01–1.0 wt%; Group D: Ni: 0.01–1.0% by mass Group E: Selected from at least one of Mo: 0.0005–0.1% by mass and W: 0.001–0.1% by mass; Group F: Co: 0.01–1.0% by mass; Group G: Selected from at least one of As: 0.001–0.05% by mass and B: 0.0001–0.005% by mass; Group H: Pb: 0.00001–0.010% by mass; Group I: Zn: 0.0001~0.02% by mass; Group J: Ta: 0~0.0020% (mass); • Group K: Selected from at least one of Zr: 0–0.0050% by mass, Se: 0–0.0050% by mass and Bi: 0–0.0020% by mass; • Group L: Selected from at least one of Ge: 0 to 0.030 wt% and Ga: 0 to 0.030 wt%.

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