Non-directional electromagnetic steel sheet

Abstract

This non-oriented electromagnetic steel sheet has a component composition comprising, in mass%, C at 0.0050% or less, Si at 2.0-5.0%, Mn at 2.0% or less, P at 0.20% or less, S at 0.0050% or less, Al at 2.0% or less, N at 0.0050% or less, Ti at 0.0030% or less, Nb at 0.0010% or less, V at 0.0050% or less, and O at 0.0050% or less. When an AC magnetic field is applied in the rolling direction (RD) in the steel sheet rolling plane, in the sheet width direction (TD), and in a direction (DD) which makes a 45° angle with the rolling direction such that the maximum magnetic flux density Bm becomes 1.5 T at a frequency of 50 Hz, and the zero peak values of magnetostriction in directions parallel to the respective magnetic field directions are denoted as λ / / H RD, λ / / H TD and λ / / H DD, the in-plane average value of magnetostriction λ / / H ave is 1.0×10-5 or less. The non-oriented electromagnetic steel sheet has excellent iron loss characteristics effective for improving electric motor efficiency.

Description

[Technical Field]

[0001] The present invention relates to a non-oriented electrical steel sheet, and more particularly to a non-oriented electrical steel sheet that exhibits excellent iron loss characteristics when used in the iron core of an electric motor (rotating machine) or the like. [Background technology]

[0002] In recent years, with the increasing demand for energy conservation in electrical equipment, there has been a strong demand for higher efficiency in electrical equipment. Accordingly, there is a growing demand for better magnetic properties in the non-oriented electrical steel sheets used in the iron cores of electric motors (motor cores).

[0003] A motor core consists of a stator core and a rotor core. In order to meet the recent demand for smaller size and higher output for HEV drive motors, etc., the non-oriented electrical steel sheets used in the stator core are strongly required to have excellent magnetic properties, such as high magnetic flux density and low iron loss.

[0004] The motor core is made by laminating multiple non-oriented electromagnetic steel sheets processed to the cross-sectional shape of the motor core and fixing them together by caulking, welding, bolting, etc. In addition to the above fixing, the stator core is fixed to the outer frame (case) by methods such as shrink fitting. Therefore, the motor core is subjected to some compressive stress due to the above fixing, etc., even when not excited.

[0005] It is known that when non-oriented electrical steel sheets are subjected to compressive stress, their iron loss increases due to magnetoelastic interaction. As increased iron loss reduces the efficiency of electric motors, it is desirable that non-oriented electrical steel sheets used in motor cores be less susceptible to compressive stress.

[0006] As a method for reducing the influence of the compressive stress, for example, Patent Document 1 discloses a method for reducing the magnetostriction constant λ 100 35×10 -6Furthermore, Patent Document 2 discloses a technique for suppressing deterioration of iron loss due to compressive stress by setting the average magnetostriction in the rolling direction and the direction perpendicular to the rolling direction after stress relief annealing in a non-oriented electrical steel sheet used in a stator to 5.0 × 10 or less. -6 The following technique is disclosed to obtain excellent magnetic properties. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-248559 [Patent Document 2] WO2018 / 179871 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the technology disclosed in the above Patent Document 1 does not provide a magnetostriction constant λ 100 In order to reduce this, it is necessary to adjust the balance between Si and Al, which makes it difficult to achieve both magnetostriction characteristics and iron loss characteristics of the motor core. Furthermore, according to the results of studies by the inventors, the technology disclosed in Patent Document 2 above has revealed that even if the average value of magnetostriction in the rolling direction and the direction perpendicular to the rolling direction is reduced, there are many cases in which the iron loss of the motor is not sufficiently reduced.

[0009] The present invention has been made in view of the above-mentioned problems of the conventional technology, and an object of the present invention is to provide a non-oriented electrical steel sheet having excellent iron loss characteristics that are effective in improving the efficiency of electric motors. [Means for solving the problem]

[0010] To solve the above problems, the inventors conducted extensive research, focusing on magnetostrictive deformation during the excitation process of the back yoke portion of the stator core. As a result, they discovered that it is possible to manufacture a motor with low iron loss and high efficiency by reducing the in-plane average value of magnetostriction in the rolling direction, the sheet width direction (direction perpendicular to the rolling direction), and the direction parallel to each magnetic field direction when an AC magnetic field is applied to the non-oriented electrical steel sheet used as the material for the motor core, and this led to the development of the present invention.

[0011] That is, the present invention provides a non-oriented electrical steel sheet having a chemical composition containing C: 0.0050 mass% or less, Si: 2.0 to 5.0 mass%, Mn: 2.0 mass% or less, P: 0.20 mass% or less, S: 0.0050 mass% or less, Al: 2.0 mass% or less, N: 0.0050 mass% or less, Ti: 0.0030 mass% or less, Nb: 0.0010 mass% or less, V: 0.0050 mass% or less, and O: 0.0050 mass% or less, with the balance being Fe and unavoidable impurities, Rolling direction within the rolling surface of the steel plate ( RD ), sheet width direction ( TD ) and the direction at an angle of 45° to the rolling direction ( DD ) at a frequency of 50Hz, the maximum magnetic flux density B m The zero-peak value of magnetostriction in the direction parallel to each magnetic field direction when an AC magnetic field of 1.5 T is applied is λ / / H RD , λ / / H TD and λ / / H DD When written as follows, the following equation (1) is obtained: The in-plane average value of magnetostriction λ defined in TIFF0007816516000001.tif32166 / / H ave is 1.0×10 -5 The non-oriented electrical steel sheet is characterized by the following:

[0012] The non-oriented electrical steel sheet of the present invention is characterized by containing, in addition to the above-mentioned chemical composition, at least one element selected from the following groups A to L. Note Group A: At least one selected from Sn: 0.005 to 0.20 mass% and Sb: 0.005 to 0.20 mass% Group B: at least one selected from Ca: 0.0005 to 0.100 mass%, Mg: 0.0005 to 0.100 mass%, and REM: 0.0005 to 0.100 mass% C group: at least one selected from Cr: 0.01 to 1.0 mass% and Cu: 0.01 to 1.0 mass% ·Group D; Ni:0.01~1.0mass% Group E: at least one selected from Mo: 0.0005 to 0.1 mass% and W: 0.001 to 0.1 mass% ·F group; Co:0.01~1.0mass% Group G: At least one selected from As: 0.001 to 0.05 mass% and B: 0.0001 to 0.005 mass% ·H group; Pb:0.00001~0.010mass% Ion group: Zn: 0.0001-0.02 mass% ·G group;Ta:0~0.0020mass% K group: at least one selected from Zr: 0 to 0.0050 mass%, Se: 0 to 0.0050 mass%, and Bi: 0 to 0.0020 mass% L group: at least one selected from Ge: 0 to 0.030 mass% and Ga: 0 to 0.030 mass% [Effects of the Invention]

[0013] According to the present invention, it is possible to manufacture a motor with low iron loss. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram illustrating the structure of a ring core used to examine iron loss. [Figure 2] 1 is a graph showing the effect of a magnetic field applied in the sheet thickness direction during finish annealing on magnetostriction of the product sheet in a direction parallel to the magnetic field direction. [Figure 3] 10 is a graph showing the influence of the in-plane average value λ / / H ave of magnetostriction in a direction parallel to the magnetic field direction of the product sheet on the hysteresis loss Whys of the ring core. DETAILED DESCRIPTION OF THE INVENTION

[0015] First, the experiment that led to the development of the present invention will be described. A steel slab containing 0.001 mass% C, 3.2 mass% Si, 0.6 mass% Mn, 0.01 mass% P, 0.0020 mass% S, 0.50 mass% Al, 0.0015 mass% N, 0.0010 mass% Ti, 0.0001 mass% Nb, 0.0005 mass% V, and 0.0010 mass% O, with the balance being Fe and unavoidable impurities, was hot-rolled to a thickness of 1.8 mm. The hot-rolled sheet was then annealed at 950°C for 30 seconds, pickled, and cold-rolled to a final thickness of 0.25 mm. Next, the cold-rolled steel sheet was rapidly heated at an average heating rate of 100°C / s in the temperature range from 200°C to 700°C, and a DC magnetic field of different magnitudes was applied in the thickness direction in the temperature range. After that, the steel sheet was heated from 700°C to 980°C without cooling, and then subjected to finish annealing at 980°C for 10 seconds.

[0016] From the steel sheet after the final annealing thus obtained, a ring-shaped test piece having an outer diameter of 80 mm and an inner diameter of 60 mm and having eight notches on the outer periphery of the ring as shown in Fig. 1 was punched. Next, 100 of the ring-shaped test pieces were stacked in the thickness direction and fixed with V-shaped crimps at six locations to prepare a ring core. Thereafter, the ring core was shrink-fitted into an aluminum alloy case having a thickness of 3 mm and an inner diameter of 80 mm with a shrink-fit allowance of 30 µm.

[0017] After that, as shown in Figure 1, the primary and secondary windings are wound around the ring core, and then the frequency is 50 Hz and the maximum magnetic flux density is B m Excitation at 1.5T, hysteresis loss W of the ring core hys Here, the hysteresis loss Whys The reason for measuring is that, although eddy current loss is affected by the excitation frequency, hysteresis loss can eliminate this effect and clarify the effect of magnetostriction.

[0018] Furthermore, rectangular test pieces 30 mm wide x 280 mm long were cut out from the steel sheets after the above-mentioned finish annealing so that the length directions were the rolling direction, the sheet width direction, and the direction forming an angle of 45° with the rolling direction. m When an AC magnetic field of 1.5 T was applied and magnetized, the zero-peak value of magnetostriction in a direction parallel to each magnetic field direction was measured using a laser Doppler vibrometer. In the present invention, when magnetization was performed in the rolling direction of the steel sheet, the sheet width direction, and the direction at an angle of 45° to the rolling direction, the zero-peak value of magnetostriction in a direction parallel to each magnetic field direction was measured as λ / / H RD , λ / / H TD and λ / / H DD It is written as follows.

[0019] Figure 2 shows the magnitude of the DC magnetic field applied in the thickness direction during finish annealing and the zero-peak value λ of magnetostriction in the direction parallel to each magnetic field direction measured using the method described above. / / H RD , λ / / H TD and λ / / H DD This figure shows that as the magnetic field applied in the thickness direction during finish annealing increases, the zero-peak value of magnetostriction in the direction parallel to each magnetic field direction of the product sheet decreases.

[0020] Also, in Figure 3, the following equation (1) is shown: The average value λ of magnetostriction in the rolling plane of the product sheet in the direction parallel to each magnetic field direction defined in TIFF0007816516000002.tif32166 / / H ave (In the present invention, this is also referred to as the "in-plane average value") and the hysteresis loss W measured with the ring core. hys From this figure, the in-plane average value of magnetostriction λ / / Have The smaller the hysteresis loss W hys It can be seen that is reduced.

[0021] In-plane average value of magnetostriction λ / / H ave However, the iron loss of the ring core after shrink fitting (hysteresis loss W hys Although the mechanism by which this influences the above-mentioned phenotype has not yet been fully elucidated, the inventors believe that this is as follows. When the ring core is excited with an AC current, it is excited in the circumferential direction, and expands and contracts in the magnetic field direction due to magnetostriction, causing compressive stress to act in the circumferential direction of the ring core. The angle between the circumferential direction of the ring core and the rolling direction of the raw steel sheet changes depending on the position. Generally, the magnetostriction of non-oriented electrical steel sheets is anisotropic within the rolling surface, so the compressive stress acting in the circumferential direction changes depending on the circumferential position. Therefore, for example, the magnetostriction λ in the direction parallel to the rolling direction / / H RD Even if the magnetostriction in the plate width direction λ / / H TD When the circumferential direction of the ring core is large, the compressive stress of magnetostriction increases at the position where the circumferential direction of the ring core is parallel to the sheet width direction, and it is thought that this increases the hysteresis loss. Therefore, in order to suppress the increase in hysteresis loss due to the compressive stress of magnetostriction, it is necessary to reduce the magnetostriction in the direction parallel to the magnetic field direction in all directions in the rolling surface, that is, to reduce the in-plane average value λ of the magnetostriction. / / H ave It is thought that reducing The present invention was developed based on the above novel findings.

[0022] Next, applications of the non-oriented electrical steel sheet of the present invention will be described. The non-oriented electrical steel sheet of the present invention is effective for use in stator cores because it has the characteristic of suppressing an increase in iron loss due to compressive stress caused by magnetostriction. However, this does not limit its application to rotor cores. Therefore, stator cores and rotor cores may be obtained simultaneously from the non-oriented electrical steel sheet of the present invention.

[0023] Next, the chemical composition of the non-oriented electrical steel sheet of the present invention will be described. C: 0.0050mass% or less The carbon contained in the product sheet is a harmful element that causes magnetic aging, forms carbides, and deteriorates iron loss characteristics. Therefore, the upper limit of carbon contained in the material is limited to 0.0050 mass%, preferably 0.0040 mass% or less. There is no particular lower limit for carbon, but from the viewpoint of reducing decarburization costs in the refining process, it is preferably set to about 0.0001 mass%.

[0024] Si: 2.0 to 5.0 mass% Si has the effect of increasing the resistivity of steel, reducing iron loss, and increasing the strength of steel through solid solution strengthening, so it is contained in an amount of 2.0 mass% or more. On the other hand, if it exceeds 5.0 mass%, rolling becomes difficult, so the upper limit is set to 5.0 mass%. The range of 2.8 to 4.5 mass% is preferable, and the range of 3.2 to 4.0 mass% is even more preferable.

[0025] Mn:2.0mass% or less Like Si, Mn is an element that is effective in increasing the resistivity and strength of steel. It also improves hot workability. However, addition of more than 2.0 mass% causes slab cracking and deteriorates the operability of the steelmaking process, so the upper limit is set to 2.0 mass%. The preferred range is 0.1 to 1.5 mass%.

[0026] P:0.20mass% or less P is a useful element used to adjust the strength (hardness) of steel. However, if the content exceeds 0.20 mass%, the steel becomes embrittled and rolling becomes difficult, so the upper limit is set to 0.20 mass%. There is no particular lower limit, but from the viewpoint of reducing the cost of dephosphorization in the refining process, it is preferably set to about 0.001 mass%. The range of 0.01 to 0.1 mass% is preferable.

[0027] S: 0.0050mass% or less S is an element that forms fine precipitates, inhibits grain growth during finish annealing and stress relief annealing, and adversely affects iron loss characteristics. In particular, if the S content exceeds 0.0050 mass%, the adverse effects become significant, so the upper limit is limited to 0.0050 mass%, preferably 0.003 mass% or less.

[0028] Al:2.0mass% or less Like Si, Al is a useful element that increases the resistivity of steel and reduces iron loss. However, if the Al content exceeds 2.0 mass%, the steel becomes embrittled and difficult to roll, so the upper limit of Al is set to 2.0 mass%. Preferably, it is 1.5 mass% or less. However, if the Al content is too low, the effect of increasing the resistivity is reduced, so it is preferable to contain 0.1 mass% or more.

[0029] N: 0.0050mass% or less N is an element that forms fine precipitates, inhibits grain growth during finish annealing and stress relief annealing, and adversely affects core loss characteristics. Since the adverse effects become particularly pronounced when the N content exceeds 0.0050 mass%, the upper limit is set to 0.0050 mass%, preferably 0.003 mass% or less.

[0030] Ti:0.0030mass% or less Ti is also an element that forms fine precipitates, inhibits grain growth during finish annealing and stress relief annealing, and adversely affects iron loss characteristics. In particular, if the Ti content exceeds 0.0030 mass%, the adverse effects become significant, so the upper limit is limited to 0.0030 mass%, preferably 0.002 mass% or less.

[0031] Nb:0.0010mass% or less Like Ti, Nb forms fine precipitates that inhibit grain growth during finish annealing and stress relief annealing, adversely affecting iron loss characteristics. Since this adverse effect becomes significant when the Nb content exceeds 0.0010 mass%, the upper limit is set to 0.0010 mass%, and preferably 0.0005 mass% or less.

[0032] V:0.0050mass% or less Like Ti and Nb, V forms fine precipitates that inhibit grain growth during finish annealing and stress relief annealing, adversely affecting iron loss characteristics. Since this adverse effect becomes significant when V exceeds 0.0050 mass%, the upper limit is set to 0.0050 mass%, and preferably 0.0003 mass% or less.

[0033] O: 0.0050mass% or less O is a harmful element that forms oxide inclusions, inhibits grain growth, and increases iron loss. In particular, if the O content exceeds 0.0050 mass%, the above adverse effects become significant, so the upper limit is set to 0.0050 mass%, and preferably 0.0030 mass% or less.

[0034] The steel material used to manufacture the non-oriented electrical steel sheet of the present invention essentially consists of Fe and unavoidable impurities other than the above-mentioned components. However, depending on the required properties, the steel material may further contain the following components in addition to the above-mentioned components.

[0035] At least one selected from Sn: 0.005 to 0.20 mass% and Sb: 0.005 to 0.20 mass% Sn and Sb have the effect of improving the recrystallization texture and reducing iron loss. To obtain this effect, it is necessary to add 0.005 mass% or more of each. On the other hand, if each is added in excess of 0.20 mass%, the effect saturates. Therefore, it is preferable to add Sn and Sb in the range of 0.005 to 0.20 mass% each. More preferably, each should be added in the range of 0.01 to 0.10 mass%.

[0036] At least one selected from Ca: 0.0005 to 0.100 mass%, Mg: 0.0005 to 0.100 mass%, and REM: 0.0005 to 0.100 mass% Ca, Mg, and REM form stable sulfides and reduce fine sulfides, thereby promoting grain growth and improving iron loss characteristics. To achieve this effect, 0.0005 mass% or more of each element must be added. On the other hand, adding more than 0.100 mass% of each element actually deteriorates iron loss. Therefore, it is preferable to add Ca, Mg, and REM in the range of 0.0005 to 0.100 mass% each. More preferably, each element should be added in the range of 0.001 to 0.05 mass%.

[0037] Furthermore, the steel material used to manufacture the non-oriented electrical steel sheet of the present invention may further contain the following components in addition to the above-mentioned components, as appropriate. However, since the raw material costs of these components are relatively high, it is desirable to keep the addition amount to the minimum necessary.

[0038] At least one selected from Cr: 0.01 to 1.0 mass% and Cu: 0.01 to 1.0 mass% Like Si and Al, Cr and Cu increase the resistivity of steel and reduce iron loss. However, because their solid solution strengthening ability is weaker than that of Si and Al, they are preferably added when it is desired to reduce iron loss without reducing rollability. However, if the amount of each added is less than 0.01 mass%, the above effect is not fully achieved, while if the amount exceeds 1.0 mass%, the iron loss improvement effect saturates. Therefore, it is preferable to add Cr and Cu in the range of 0.01 to 1.0 mass% each.

[0039] Ni: 0.01 to 1.0 mass% Ni has a high solid solution strengthening ability and is an effective element for increasing the strength of steel. However, if the amount added is less than 0.01 mass%, the above effect is not sufficiently obtained, while if the amount added exceeds 1.0 mass%, raw material costs increase. Therefore, it is preferable to add Ni in the range of 0.01 to 1.0 mass%.

[0040] At least one selected from Mo: 0.0005 to 0.1 mass% and W: 0.001 to 0.1 mass% Mo and W have the effect of coarsening carbides and reducing iron loss. However, if the amount of Mo added is less than 0.0005 mass% or the amount of W added is less than 0.001 mass%, this effect is not sufficiently achieved. On the other hand, if the amount of Mo added exceeds 0.1 mass%, the iron loss improvement effect saturates. Therefore, it is preferable to add Mo and W in the ranges of 0.0005 to 0.1 mass% and 0.001 to 0.1 mass%, respectively.

[0041] Co: 0.01 to 1.0 mass% Co increases the magnetic moment of the Fe alloy, thereby increasing the magnetic flux density and reducing iron loss. However, if the amount added is less than 0.01 mass%, the above effects are not fully achieved, while if the amount added exceeds 1.0 mass%, the raw material cost increases. Therefore, it is preferable to add Co in the range of 0.01 to 1.0 mass%.

[0042] At least one selected from As: 0.001 to 0.05 mass% and B: 0.0001 to 0.005 mass% As and B are grain boundary segregation elements that have the effect of reducing iron loss by improving the texture. The above effect can be achieved by adding 0.001 mass% or more of As and 0.0001 mass% or more of B. However, As is also an element that can cause grain boundary embrittlement, and the above adverse effects become particularly pronounced when the content exceeds 0.05 mass%. Therefore, it is preferable to add As in the range of 0.001 to 0.05 mass%. Furthermore, when B exceeds 0.005 mass%, the adverse effect of inhibiting grain boundary migration becomes significant. Therefore, it is preferable to add B in the range of 0.0001 to 0.005 mass%.

[0043] Pb: 0.00001 to 0.010 mass% Pb is an element that disperses finely in steel as metallic inclusions and remains in the steel even after finish annealing, thereby acting as a starting point for stress concentration during punching, promoting crack propagation and suppressing die wear, thereby improving punchability. However, if the Pb content is less than 0.00001 mass%, the above-mentioned effect of improving punchability is not fully achieved, while if it exceeds 0.010 mass%, the grain growth suppression effect becomes too great and good iron loss properties cannot be obtained. Therefore, the Pb content is set to the range of 0.00001 to 0.010 mass%, preferably 0.00003 to 0.0050 mass%.

[0044] Zn: 0.0001 to 0.02 mass% Zn forms stable and coarse sulfides or oxides, which improves grain growth and reduces the pinning force of domain walls. To achieve these effects, Zn must be added in an amount of 0.0001 mass% or more. However, if Zn is added in an amount exceeding 0.02 mass%, the above effects saturate. Therefore, the Zn content is preferably in the range of 0.0001 to 0.02 mass%.

[0045] Ta: 0 to 0.0020 mass% Ta is an element effective in improving the workability and strength of steel, and can be added as needed. To reliably obtain the above effects, it is preferable to add 0.0001 mass% or more. On the other hand, Ta is an element that increases iron loss, and the above adverse effects become apparent particularly when the Ta content exceeds 0.0020 mass%, so the upper limit is preferably set to 0.0020 mass%. A more preferable range is 0.0003 to 0.0010 mass%.

[0046] At least one selected from Zr: 0 to 0.0050 mass%, Se: 0 to 0.0050 mass%, and Bi: 0 to 0.0020 mass% Zr, Se, and Bi can be added appropriately because they all disperse finely in the steel as inclusions, improving workability and refining grains to increase the strength of the steel. However, if Zr and Se exceed 0.0050 mass%, and Bi exceeds 0.0020 mass%, respectively, the grain growth suppression effect becomes too great and good core loss properties cannot be obtained. Therefore, the upper limits of these elements are preferably set at the above values. More preferably, Zr is in the range of 0.0005 to 0.0030 mass%, Se is in the range of 0.0001 to 0.0030 mass%, and Bi is in the range of 0.0001 to 0.0010 mass%.

[0047] At least one selected from Ge: 0 to 0.030 mass% and Ga: 0 to 0.030 mass% Ge and Ga are both elements that improve texture. To ensure the above effects, it is preferable to add 0.001 mass% or more of each. However, even if each is added in excess of 0.030 mass%, the above effects saturate, so the upper limit of each is preferably 0.030 mass%. More preferably, each is in the range of 0.003 to 0.010 mass%.

[0048] Next, the magnetostriction characteristics of the non-oriented electrical steel sheet of the present invention will be described. In-plane average value of magnetostriction λ / / H ave :1.0×10 -5 below In the back yoke of the stator core, the steel plate is mainly excited in the circumferential direction, so depending on its position, the back yoke is excited in all directions within the rolling surface of the steel plate. When the steel plate is excited, it expands and contracts in a direction parallel to the direction of excitation (magnetic field direction), so compressive stress acts in the circumferential direction on the back yoke. If the expansion and contraction in each direction within the rolling surface of the steel plate when excited is large, the compressive stress due to magnetostriction increases, and the iron loss of the motor core increases. As can be seen from Figure 3, the increase in iron loss occurs when the in-plane average value λ, which is the average value of magnetostriction in each direction within the rolling surface, is increased. / / H ave is 1.0×10 -5Therefore, in the present invention, the in-plane average value λ of magnetostriction is / / H ave to 1.0 x 10 -5 The in-plane average value of magnetostriction, λ / / H ave is 0.8×10 -5 If the value is less than this, the effect of reducing the compressive stress due to magnetostriction becomes even greater, which is effective in improving iron loss, and is therefore more preferable.

[0049] The in-plane average value λ of the above magnetostriction / / H ave is defined by the following equation (1). TIFF0007816516000003.tif32166Here, λ in the above formula / / H RD , λ / / H TD and λ / / H DD is the rolling direction in the rolling plane of the steel plate ( RD ), sheet width direction ( TD ) and the direction at an angle of 45° to the rolling direction ( DD ) at a frequency of 50Hz and a maximum magnetic flux density of B m These are the zero-peak values ​​of magnetostriction in the direction parallel to each magnetic field direction when excited at 1.5T.

[0050] Next, a method for producing a non-oriented electrical steel sheet according to the present invention will be described. In the production method described below, the steps other than finish annealing are merely examples of methods and conditions for producing a non-oriented electrical steel sheet according to the present invention, and production by different methods and conditions is not in any way excluded.

[0051] First, a steel having the aforementioned chemical composition suitable for the present invention is melted by a commonly known refining process using a converter, an electric furnace, a vacuum degasser, or the like, and then formed into a steel material (slab) by a continuous casting method or an ingot casting-blooming rolling method. This slab is then hot-rolled by a commonly known method and conditions to form a hot-rolled sheet.

[0052] Among the elements that may be contained in the steel material used in the present invention, elements such as Cu, Sn, Ni, Cr, and Mo are elements that are introduced from scrap, the raw material, when steel is melted in an electric furnace. Therefore, when using electric furnace steel, it is not necessary to reduce or even add these elements, which contributes to reducing raw material and refining costs. Furthermore, the casting and hot rolling of the melted steel may be performed using a thin slab caster in which a continuous casting machine and a hot rolling mill are directly connected. A thin slab caster can cast thin slabs with a thickness of 200 mm or less, which can then be immediately hot rolled in a hot rolling mill directly connected to the casting equipment, thereby enabling a thinner finished thickness than conventional hot rolling. This reduces the rolling load in the subsequent cold rolling, improving productivity, and the texture is improved by reducing the cold rolling reduction, which is also effective in reducing iron loss.

[0053] The hot-rolled sheet may be subjected to hot-rolled sheet annealing as required, and in this case, the soaking temperature is preferably in the range of 800 to 1100°C. If the temperature is less than 800°C, the effect of hot-rolled sheet annealing is small and the magnetic property improvement effect is not sufficiently obtained. On the other hand, if the temperature exceeds 1100°C, it may be disadvantageous in terms of production costs and may promote brittle fracture (sheet breakage) during cold rolling.

[0054] The hot-rolled sheet after the hot rolling or hot-rolled sheet annealing is then cold-rolled once or twice or more times with intermediate annealing in between to form a cold-rolled sheet of the final thickness. In this case, the cold-rolling to the final thickness is preferably warm-rolled, in which the steel sheet temperature is increased to 200°C or higher, in order to increase the magnetic flux density.

[0055] The final plate thickness (product plate thickness) is preferably in the range of 0.1 to 0.3 mm, because if it is less than 0.1 mm, productivity decreases, while if it exceeds 0.3 mm, the iron loss reduction effect is small.

[0056] The cold-rolled sheet having the final thickness is then subjected to finish annealing, preferably continuous annealing at a temperature of 700 to 1100°C for 1 to 300 seconds. If the soaking temperature is less than 700°C, recrystallization does not proceed sufficiently, and good magnetic properties cannot be obtained. In addition, the shape correction effect of continuous annealing is not fully achieved. On the other hand, if the temperature exceeds 1100°C, the crystal grains become coarse, and the strength of the steel sheet decreases.

[0057] In addition, in the heating process of the above-mentioned finish annealing, it is preferable to rapidly heat the material in the temperature range from 200°C to 700°C at a rate of 100°C / s or more. By setting the heating rate to 100°C / s or more, the nucleation orientation of primary recrystallized grains is randomized, and the in-plane average value λ of magnetostriction is reduced. / / H ave If the heating rate is less than 100°C / s, the above-mentioned randomization effect cannot be sufficiently obtained. Preferably, it is 500°C / s or more. Although there is no particular upper limit to the heating rate, a heating rate of about 2000°C / s is preferable from the viewpoint of saturating the magnetostriction reduction effect even if the heating rate is increased above 2000°C / s and suppressing excessive energy consumption.

[0058] Here, what is important in the present invention is that it is necessary to apply a DC magnetic field in the thickness direction in the temperature range of 200°C to 700°C during the heating process of the above-mentioned finish annealing. Since primary recrystallization of the cold-rolled structure occurs at temperatures above 500°C, especially above 600°C, when a DC magnetic field is applied in the thickness direction in the temperature range of 500°C to 700°C, nucleation of crystal orientations with an easy axis of magnetization in the thickness direction is preferential, and the easy axis of magnetization in the rolled surface becomes random, resulting in the in-plane average value λ of magnetostriction. / / H ave can be made smaller.

[0059] The temperature range in which the DC magnetic field is applied is set to a value equal to or less than the in-plane average value λ of the magnetostriction due to the DC magnetic field. / / H aveFrom the viewpoint of sufficiently ensuring the effect of reducing the magnetic field strength, suppressing the magnetic field force generated in the steel sheet by the DC magnetic field, and preventing the steel sheet from deviating from the conveying line, it is preferable to set the temperature at 600°C or higher, at which the spontaneous magnetization of the steel is reduced. The strength of the applied magnetic field must be 1 T or higher, and to further enhance the above effect, it is preferably 5 T or higher.

[0060] Next, the steel sheet after the above-mentioned finish annealing is preferably coated with an insulating coating on the surface of the steel sheet to ensure insulation when the steel sheets are stacked for use. For this insulating coating, it is desirable to select an organic coating containing a resin if good punchability is desired, while on the other hand, it is desirable to select a semi-organic or inorganic coating if weldability is important.

[0061] When manufacturing a stator core using the non-oriented electrical steel sheet of the present invention as an iron core material, the steel sheet after finish annealing is generally processed into a core shape by punching or the like, stacked, and fixed to assemble the stator core, and then stress relief annealing is performed. This stress relief annealing is preferably performed in an inert gas atmosphere under conditions of 780 to 950°C for 0.1 to 10 hours. If the stress relief annealing temperature is less than 780°C, the iron loss improvement effect of stress relief annealing is small, while if it exceeds 950°C, it becomes difficult to ensure insulation between the stacked steel sheets. [Example]

[0062] A steel slab containing 0.001 mass% C, 3.4 mass% Si, 0.4 mass% Mn, 0.01 mass% P, 0.0020 mass% S, 0.80 mass% Al, 0.0015 mass% N, 0.0010 mass% Ti, 0.0001 mass% Nb, 0.0005 mass% V, and 0.0010 mass% O, with the balance being Fe and unavoidable impurities, was hot-rolled to a thickness of 1.8 mm. The hot-rolled sheet was then annealed at 950°C for 30 seconds, pickled, cold-rolled for the first time, intermediate-annealed at 900°C for 30 seconds, and cold-rolled for the second time with a rolling reduction of 60% to a final thickness of 0.25 mm. The cold-rolled sheet was then rapidly heated in the temperature range from 200°C to 700°C at an average heating rate of 1000°C / s, and a DC magnetic field of varying magnitudes from 0 to 20 T was applied in the thickness direction within the temperature range.The sheet was then heated from the 700°C temperature to 980°C without cooling, and subjected to finish annealing at 980°C for 10 seconds.An insulating coating was then formed to produce a product sheet.

[0063] From the product plate thus obtained, a ring-shaped test piece with an outer diameter of 80 mm and an inner diameter of 60 mm, and eight notches on the outer periphery of the ring as shown in Figure 1, was punched out, and 100 sheets were stacked in the thickness direction and fixed with V-shaped rivets in six places to form a ring core. Next, the ring core was shrink-fitted into an aluminum alloy case with a thickness of 3 mm and an inner diameter of 80 mm with a shrink-fitting allowance of 30 μm. After that, the primary and secondary windings were wound around the shrink-fitted ring core as shown in Figure 1, and then it was tested at a frequency of 50 Hz and a maximum magnetic flux density B m Hysteresis loss W when excited at 1.5T hys The hysteresis loss W hys Although this differs depending on the plate thickness, for the above ring core made from a product plate with a plate thickness of 0.25 mm, a value of 2.00 W / Kg or less can be judged to be good.

[0064] In addition, rectangular test pieces with a width of 30 mm and a length of 280 mm were cut out from the above product plate so that the length direction was the rolling direction, the plate width direction, and a direction at 45° from the rolling direction. m Zero-peak value λ of magnetostriction in the direction parallel to the magnetic field when a magnetic field of 1.5 T is applied / / H RD , λ / / H TD and λ / / H DD was measured using a laser Doppler vibrometer, and the in-plane average value of magnetostriction λ / / H ave was calculated using the following equation (1). TIFF0007816516000004.tif32166

[0065] The results of the above measurements are shown in Table 1. From this table, it can be seen that all of the ring cores made using non-oriented electrical steel sheets manufactured under conditions compatible with the present invention have excellent iron loss characteristics.

[0066] [Table 1] [Example]

[0067] A steel slab containing the various components shown in Table 2, with the remainder consisting of Fe and unavoidable impurities, was hot-rolled to a thickness of 1.8 mm. The hot-rolled sheet was then annealed at 950°C for 30 seconds, pickled, cold-rolled for the first time, intermediate-annealed at 900°C for 30 seconds, and cold-rolled for the second time with a reduction of 55% to obtain a cold-rolled sheet with a final thickness of 0.25 mm. The cold-rolled sheet was then rapidly heated from 200°C to 700°C at an average heating rate of 1000°C / s, and a DC magnetic field of various magnitudes in the thickness direction within the range of 0 to 8 T was applied within the temperature range. The sheet was then heated from the 700°C temperature to 980°C without cooling, subjected to a final annealing at 980°C for 10 seconds, and then coated with an insulating coating to obtain a finished sheet.

[0068] From the product plate thus obtained, ring-shaped test pieces with an outer diameter of 80 mm and an inner diameter of 60 mm, each with eight notches on the outer periphery of the ring as shown in Figure 1, were punched out, and 100 of these were stacked in the thickness direction and fixed by welding in six places to form a ring core. Next, the ring core was shrink-fitted into an aluminum alloy case with a thickness of 3 mm and an inner diameter of 80 mm with a shrink-fitting allowance of 30 μm. After that, a primary winding and a secondary winding were wound around the shrink-fitted ring core as shown in Figure 1, and then the ring core was subjected to a test at a frequency of 50 Hz and a maximum magnetic flux density B m Hysteresis loss W when excited at 1.5T hys The hysteresis loss W hys Those having a core loss of 2.00 W / Kg or less were evaluated as having good core loss.

[0069] In addition, rectangular test pieces with a width of 30 mm and a length of 280 mm were cut out from the above product plate so that the length direction was the rolling direction, the plate width direction, and a direction at 45° from the rolling direction. m Zero-peak value λ of magnetostriction in the direction parallel to the magnetic field when an AC magnetic field of 1.5 T is applied / / H RD , λ / / H TD and λ / / H DD was measured using a laser Doppler vibrometer, and the in-plane average value of magnetostriction λ / / H ave was calculated using the following equation (1). TIFF0007816516000006.tif32166

[0070] The results of the above measurements are shown in Table 2. From this table, it can be seen that all of the ring cores manufactured using steel materials having compositional elements compatible with the present invention and non-oriented electrical steel sheets manufactured under conditions compatible with the present invention have excellent iron loss characteristics. Note that steel sheet No. 20 (comparative example) in Table 2 broke during cold rolling and could not be used as a finished sheet.

[0071] [Table 2-1]

[0072] [Table 2-2]

[0073] [Table 2-3]

[0074] [Table 2-4]

[0075] [Table 2-5]

[0076] [Table 2-6] [Example]

[0077] C:0.0015mass%, Si:3.4mass%, Mn:0.7mass%, P:0.020mass%, S:0.0005mass%, Al:1.0mass%, N:0.0020mass%, Ti:0.0020 mass%, Nb:0.0001mass%, V:0.0002mass%, O:0.0010mass%, Sn:0.01mass%, Cu:0.05mass%, Ni:0.05mass%, Cr:0.02mass, Steel containing 0.02% Mo, 0.0003% B, 0.0001% Pb, 0.0003% As, 0.0020% Zn, 0.0030% Co, and 0.0030% Ga was melted in an electric furnace, cast into a 100 mm thick thin slab using a thin slab continuous caster directly connected to a hot rolling mill, and then hot rolled into a 0.8 mm thick hot-rolled sheet. The hot-rolled sheet was then annealed at 1000°C for 30 seconds, pickled, and cold-rolled to a final thickness of 0.25 mm. Next, the cold-rolled sheet was rapidly heated in the temperature range from 200°C to 700°C at an average heating rate of 1000°C / s, and a DC magnetic field of 5 T was applied in the sheet thickness direction in the above temperature range. Thereafter, the sheet was heated from the above temperature of 700°C to 1000°C without cooling, and subjected to finish annealing at 1000°C for 10 seconds. After that, an insulating coating was formed to produce a product sheet.

[0078] From the product plate thus obtained, a ring-shaped test piece with an outer diameter of 80 mm and an inner diameter of 60 mm, and eight notches on the outer periphery of the ring as shown in Figure 1, was punched out, and then 100 sheets were stacked in the thickness direction and fixed by welding in six places to form a ring core. Next, the ring core was shrink-fitted into an aluminum alloy case with a thickness of 3 mm and an inner diameter of 80 mm with a shrink-fitting allowance of 30 μm. After that, a primary winding and a secondary winding were wound around the shrink-fitted ring core as shown in Figure 1, and then it was tested at a frequency of 50 Hz and a maximum magnetic flux density B m Hysteresis loss W when excited at 1.5T hys The hysteresis loss W hys Those having a core loss of 2.00 W / Kg or less were evaluated as having good core loss.

[0079] In addition, rectangular test pieces with a width of 30 mm and a length of 280 mm were cut out from the above product plate so that the length direction was the rolling direction, the plate width direction, and a direction at 45° from the rolling direction. m Zero-peak value λ of magnetostriction in the direction parallel to the magnetic field when an AC magnetic field of 1.5 T is applied / / H RD , λ / / H TD and λ / / H DD was measured using a laser Doppler vibrometer, and the in-plane average value of magnetostriction λ / / H ave was calculated using the following equation (1). TIFF0007816516000013.tif32166

[0080] The results of the above measurements are shown in Table 3. From this table, it can be seen that all of the ring cores manufactured using steel materials having compositional elements compatible with the present invention and non-oriented electrical steel sheets manufactured under conditions compatible with the present invention have excellent iron loss characteristics.

[0081] [Table 3]

Claims

1. A non-oriented electrical steel sheet having a component composition containing C: 0.0050 mass% or less, Si: 2.0 to 5.0 mass%, Mn: 2.0 mass% or less, P: 0.20 mass% or less, S: 0.0050 mass% or less, Al: 0.5 to 2.0 mass%, N: 0.0050 mass% or less, Ti: 0.0030 mass% or less, Nb: 0.0010 mass% or less, V: 0.0050 mass% or less, and O: 0.0050 mass% or less, with the balance being Fe and unavoidable impurities, The rolling direction in the steel plate rolling plane ( ＲＤ ), plate width direction ( ＴＤ ) and a direction forming an angle of 45° with the rolling direction ( ＤＤ ) at a frequency of 50 Hz, the maximum magnetic flux density B ｍ The zero-peak value of magnetostriction in the direction parallel to each magnetic field direction when an AC magnetic field of 1.5 T is applied is λ ／／Ｈ ＲＤ , λ ／／Ｈ ＴＤ and λ ／／Ｈ ＤＤ When expressed as above, the in-plane average value of magnetostriction λ defined by the following formula (1) ／／Ｈ ａｖｅ is 0.85 x 10 －５ A non-oriented electrical steel sheet characterized by the following: Note

2. The non-oriented electrical steel sheet according to claim 1, further comprising, in addition to the above-mentioned composition, at least one component selected from the following groups A to L: Note Group A: At least one selected from Sn: 0.005 to 0.20 mass% and Sb: 0.005 to 0.20 mass% Group B: at least one selected from Ca: 0.0005 to 0.100 mass%, Mg: 0.0005 to 0.100 mass%, and REM: 0.0005 to 0.100 mass% C group: at least one selected from Cr: 0.01 to 1.0 mass% and Cu: 0.01 to 1.0 mass% ・Group D; Ni: 0.01 to 1.0 mass% Group E: At least one selected from Mo: 0.0005 to 0.1 mass% and W: 0.001 to 0.1 mass% ・F group; Co: 0.01 to 1.0 mass% Group G: At least one selected from As: 0.001 to 0.05 mass% and B: 0.0001 to 0.005 mass% ・H group; Pb: 0.00001 to 0.010 mass% ・Group I; Zn: 0.0001 to 0.02 mass% ・G group; Ta: 0 to 0.0020 mass% K group: at least one selected from Zr: 0 to 0.0050 mass%, Se: 0 to 0.0050 mass%, and Bi: 0 to 0.0020 mass% L group: at least one selected from Ge: 0 to 0.030 mass% and Ga: 0 to 0.030 mass%

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