JP2005060811A - High-tensile non-oriented magnetic steel sheet and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-tensile non-oriented magnetic steel sheet which is excellent in both mechanical and magnetic properties which are required for a rotor of a rapidly spinning motor, and its production method. <P>SOLUTION: The high-tensile non-oriented magnetic steel sheet contains, by mass, 0.02-0.3% C, ≤2.0% Si, 1.0-3.0% Mn, ≤1.5% Al, ≤0.2% P, ≤0.02% S, ≤0.02% N and the balance substantially being Fe and impurities and has a thickness within the range of 0.15-1.0 mm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a non-oriented electrical steel sheet used for high-efficiency motors such as drive motors for electric vehicles, hybrid vehicles, and servo motors for robots, machine tools, etc., and in particular, rotation of a permanent magnet embedded motor that rotates at high speed. The present invention relates to a high-tensile non-oriented electrical steel sheet having excellent mechanical properties and magnetic properties suitable as a child, and a method for producing the same.

  Due to the recent increase in global environmental problems, energy conservation and environmental countermeasure technologies have been developed in many fields. The automobile field is no exception, and technologies for reducing exhaust gas and improving fuel efficiency are advancing rapidly. It is no exaggeration to say that electric vehicles and hybrid vehicles are the culmination of these technologies, and the performance of automobile drive motors (hereinafter referred to as drive motors) greatly affects automobile performance.

  Many drive motors use permanent magnets, and are composed of a stator (stator) portion provided with windings and a rotor (rotor) portion provided with permanent magnets. Recently, a shape in which a permanent magnet is embedded in a rotor (permanent magnet embedded type motor; IPM motor) has become mainstream as a drive motor. In addition, with the advancement of power electronics technology, the rotational speed can be arbitrarily controlled and tends to increase in speed. Therefore, the rate at which the iron core material is excited in the high frequency range of the commercial frequency (50 to 60 Hz) or higher is increasing, and not only the magnetic characteristic at the commercial frequency but also the improvement of the magnetic characteristic at 400 Hz to several kHz is required. It has become. Moreover, not only the centrifugal force at the time of high speed rotation but also the stress fluctuation accompanying the rotation speed fluctuation is always received, and the mechanical properties are required for the core material. In particular, since the IPM motor has a complicated rotor shape, the core material for the rotor needs to have mechanical characteristics sufficient to withstand centrifugal force and stress fluctuations even when stress concentration is taken into consideration. In the field of servo motors for robots and machine tools, stress fluctuations associated with fluctuations in the rotational speed are constantly applied, and it is expected that the rotational speed will increase as in the case of the drive motor.

  Conventionally, a stator of a drive motor has been manufactured mainly by stacking non-oriented electrical steel sheets that have been stamped, but a rotor has also been manufactured by a lost wax casting method or a sintering method. This is because the stator requires excellent magnetic properties and the rotor requires robust mechanical properties. However, since the eddy current loss increases in the above rotor, there is an essential problem that the motor efficiency is greatly reduced. Furthermore, since the motor performance is greatly influenced by the air gap between the rotor and the stator, the above-described rotor has a need for precision machining, and there is a problem that the manufacturing cost of the iron core is greatly increased. From the viewpoint of cost reduction, it is sufficient to use a punched electrical steel sheet, but no electrical steel sheet that combines the low eddy current loss required for the rotor with excellent mechanical properties has been found. .

  As an electrical steel sheet having excellent mechanical properties, for example, Patent Document 1 discloses mass% (hereinafter, “%” represents “mass%” unless otherwise indicated) in addition to 3.5 to 7% Si. Thus, a method of manufacturing an electrical steel sheet containing one or more of Ti, W, Mo, Mn, Ni, Co, and Al in a range not exceeding 20% has been proposed. Patent Document 2 contains B and a large amount of Ni in addition to 2.0 to 3.5% Si and 0.1 to 6.0% Mn, and has a crystal grain size of 30 μm or less. Electrical steel sheets have been proposed. These techniques mainly use solid solution strengthening as a steel strengthening mechanism. However, in the case of solid solution strengthening, the strength of the cold-rolled base material is increased at the same time, so that there is a drawback that cracks frequently occur during cold-rolling. For this reason, the yield of the steel sheet is extremely deteriorated, and the above-described problem of iron core manufacturing cost reduction cannot be overcome.

  Patent Document 3 and Patent Document 4 propose an electromagnetic steel sheet containing Nb, Zr, B, Ti, V, etc. in addition to 2.0 to 4.0% Si. These techniques utilize precipitation hardening in addition to solid solution strengthening by Si as a steel strengthening mechanism. However, since the Si content is essentially high, the occurrence of cracks during cold rolling has not been completely avoided, and it is difficult to reduce the plate thickness.

  Patent Documents 5 and 6 propose electromagnetic steel sheets containing Ti, Nb, V, P, or Ni after limiting Si and Al to 0.03 to 0.5%, respectively. These techniques utilize precipitation hardening of carbide and solid solution strengthening of P rather than solid solution strengthening by Si. However, in these technologies, the strength level required for a rotor of a drive motor to be described later cannot always be secured, and as shown in the examples, Ni content of 2.0% or more is essential, so that the alloy cost is low. There is a disadvantage that it is expensive.

  Patent Document 7 proposes a non-oriented electrical steel sheet for embedded permanent magnet motors with Si: 1.6 to 2.8% and limited crystal grain size, internal oxide layer thickness, and yield point. . However, at the yield point of the steel plate by this technique, the strength is insufficient as a rotor of a drive motor that rotates at high speed.

  As non-oriented electrical steel sheets specified in JIS C 2552, so-called high grade non-oriented electrical steel sheets (35A210, 35A230, etc.) have the highest alloy content and high strength. However, the mechanical property level is lower than that of the high-strength non-oriented electrical steel sheet, which is insufficient in strength as a rotor of a drive motor that rotates at high speed.

  Furthermore, these non-oriented electrical steel sheets according to the prior art have a ferrite single-phase structure because they have a material design with the use in the stator in mind. Therefore, the magnetic domain width is about several μm to several tens of μm, and even if the electrical resistance is increased and the plate thickness is reduced for the purpose of reducing eddy current loss, the eddy current loss is essentially large due to abnormal eddy current loss. is there.

JP 60-238421 A JP-A-1-162748 Japanese Patent Laid-Open No. 2-8346 JP-A-6-330255 JP 2001-234302 A JP 2002-146493 A JP 2001-172752 A

  The present invention has been made in view of the above problems, and provides a high-tensile non-oriented electrical steel sheet having excellent mechanical properties and magnetic properties, which is necessary as a rotor of a motor that rotates at high speed, and a method for producing the same. The main purpose is to do.

  The characteristics required for the rotor referred to in the present invention are mechanical characteristics of the electrical steel sheet, and mean the yield point and the tensile strength. This is intended not only to suppress rotor deformation during high-speed rotation, but also to suppress fatigue fracture caused by stress fluctuations. In the drive motors of recent electric vehicles and hybrid vehicles, the rotor receives a stress amplitude of about 150 MPa under an average stress of about 250 MPa. Therefore, from the viewpoint of suppressing rotor deformation, the yield point of the electromagnetic steel sheet needs to satisfy 400 MPa or more, and considering the safety factor, it is necessary to satisfy 500 MPa or more, and more preferably 550 MPa or more. From the viewpoint of suppressing fatigue failure in the stress state described above, the tensile strength of the electrical steel sheet is 550 MPa or more, preferably 600 MPa, and further considering the safety factor, 700 MPa or more is necessary.

  The second is the properties of the punched end face of the electrical steel sheet. Since it is premised on continuous punching into a complicated rotor shape, if the end face properties are inferior, it can be a starting point of fracture due to stress concentration. If cutting is performed after punching and lamination, the end face properties are improved, but it goes without saying that the cost increases. Even if the outer peripheral portion is cut, the punched end face inside the rotor, for example, the permanent magnet embedded portion, is often used as it is punched, and is particularly likely to be the starting point of fracture due to stress concentration. For these reasons, the end face properties are extremely important characteristics along with the mechanical characteristics of the steel sheet.

The third is eddy current loss of electrical steel sheets. The iron loss is composed of hysteresis loss due to irreversible domain wall motion and Joule heat (eddy current loss) due to eddy currents caused by magnetization change. Rated by iron loss. In a stator having a large magnetization change, it is appropriate to evaluate the iron loss of the iron core material by, for example, the total iron loss W _10/400 when the magnetization is forcibly changed from + 1.0T to -1.0T. is there. However, in the rotor, since the magnetic flux from the outside only enters and exits the state in which it is forcibly magnetized by the permanent magnet, the amount of change in magnetization is smaller than that of the stator. Furthermore, since the change in magnetization is from the state in which the domain wall is forcibly moved by the permanent magnet, the change in magnetization during use in the rotor is achieved by the rotation (rotation magnetization) of the magnetization in each magnetic domain. Hysteresis loss due to rotational magnetization is small, and it can be said that the generated loss is only eddy current loss. Therefore, it is recalled that even if the increase in hysteresis loss is allowed, the motor efficiency can be improved if the reduction in eddy current loss is achieved.

  Based on these ideas, the present inventors have conducted various studies on the influence of alloying elements on the properties of non-oriented electrical steel sheets, and as a result, are completely opposite to the technical recognition of conventional non-oriented electrical steel sheets. It has been found that by containing an appropriate amount of C, a non-oriented electrical steel sheet having mechanical properties suitable as a rotor for a motor rotating at high speed can be stably produced without breakage during cold rolling.

  That is, the present invention is, in mass%, C: 0.02% to 0.3%, Si: 2.0% or less, Mn: 1.0% to 3.0%, Al: 1.5% or less, P: 0.2% or less, S: 0.02% or less, N: 0.02% or less, the balance being substantially composed of Fe and impurities, and a thickness of 0.15 mm to 1.0 mm A high-tensile non-oriented electrical steel sheet is provided.

  In the present invention, the phrase “the balance consists essentially of Fe and impurities” means that it contains a case where other elements are contained within a range not impairing the effects of the present invention.

  According to the present invention, by containing a predetermined amount of C as a steel component, the steel structure is changed from a ferrite single-phase structure of the prior art to a ferrite + martensite and / or bainite multiphase structure, a martensite or bainite single-phase structure. Since it is controlled, the strength of the steel sheet is increased. The steel structure is formed in the final finish continuous annealing and its cooling process. Therefore, unlike conventional electromagnetic steel sheets mainly composed of solid solution strengthening, it is possible to increase the strength of electromagnetic steel sheets without increasing the strength of the cold-rolled base material (that is, breaking of the steel sheets during cold rolling). It becomes possible. Furthermore, the electrical steel sheet whose structure is controlled by containing a predetermined amount of C as a steel component has a preferable end face property from the viewpoint of fatigue fracture suppression, and can effectively reduce eddy current loss.

  In the present invention, the ferrite + martensite and / or bainite double phase structure, the martensite or bainite single phase structure means (1) a ferrite and martensite double phase structure, and (2) a ferrite and bainite double phase structure. , (3) a multiphase structure of ferrite, martensite and bainite, (4) a martensite single phase structure, and (5) a bainite single phase structure.

In the said invention, it is preferable to contain at least 1 type of element selected from the element group which consists of Nb, Zr, Ti, V, Cr, Mo, and B by the following mass%.
Nb: 0.001% or more and less than 0.2%, Zr: 0.002 or more and less than 0.2%,
Ti: 0.001% or more and less than 0.2%, V: 0.001% or more and less than 0.25%,
Cr: 0.01% or more and less than 1.0%, Mo: 0.005% or more and less than 1.0%,
B: 0.0001% or more and less than 0.01%.

  This is because by containing Nb, Zr, Ti and V in the above range, fine carbonitrides can be formed and the strength of the steel sheet can be increased. Further, by containing Cr, Mo and B in the above range, the generation of pearlite is suppressed and the generation of martensite is promoted, so the strength of the steel sheet can be increased and eddy current loss can be reduced. .

  Moreover, in the said invention, it is preferable to contain at least any one of Cu and Ni in the range of 0.01%-0.5% by the mass%. This is because inclusion of Cu and Ni in the above range can increase the yield point and the tensile strength and improve the mechanical properties.

  Furthermore, in the above invention, it is preferable that at least one surface of the high-tensile non-oriented electrical steel sheet has an organic component insulating coating, an inorganic component insulating coating, or an organic-inorganic composite insulating coating. Insulation coating between laminated steel sheets improves when it has an inorganic component insulation coating, and both punchability and insulation between laminated steel plates improve when it has an organic-inorganic composite insulation coating. This is because the punching property is improved when it has.

  Moreover, in the said invention, it is preferable to have an adhesive insulating film on the surface of at least one side of the said high tension non-oriented electrical steel sheet. This is because the adhesive insulating film exhibits adhesiveness by heating and pressurizing after processing such as punching, and is effective in reducing vibration and noise. Moreover, it is because the adhesion force between steel plates can be increased without accompanying deterioration of magnetic properties due to caulking or welding.

  The present invention also includes, in mass%, C: 0.02% to 0.3%, Si: 2.0% or less, Mn: 1.0% to 3.0%, Al: 1.5% or less, P : 0.2% or less, S: 0.02% or less, N: 0.02% or less, and the steel ingot or steel slab, the balance of which is substantially made of Fe and impurities, is hot-rolled and necessary Depending on the hot-rolled sheet annealing, the sheet thickness is set within the range of 0.15 mm to 1.0 mm by performing cold rolling twice or more with one or intermediate annealing, and then the material during soaking There is provided a method for producing a high-tensile non-oriented electrical steel sheet, characterized by performing continuous annealing within a temperature range of 700 ° C to 1100 ° C.

  In the present invention, by containing a predetermined amount of C as a steel component, the steel structure is changed from a ferrite single phase structure of the prior art to a ferrite + martensite and / or bainite multiphase structure, a martensite or bainite single phase structure. Be controlled. Unlike conventional solid solution strengthening electrical steel sheets, in the present invention, the steel structure is formed by the final finish continuous annealing and its cooling process, so that the high strength of the cold rolled base metal Accordingly, it is possible to manufacture a high-strength non-oriented electrical steel sheet with high strength without causing a problem that the steel sheet breaks during cold rolling. Furthermore, the high-tension non-oriented electrical steel sheet whose structure is controlled as described above has good end face properties from the viewpoint of fatigue fracture suppression, and can effectively reduce eddy current loss. Furthermore, the high tension non-oriented electrical steel sheet which has sufficient intensity | strength can be manufactured by making the material temperature at the time of soaking of continuous annealing into the said range.

In the said invention, it is preferable that the said steel ingot or steel slab contains at least 1 type of element selected from the element group which consists of Nb, Zr, Ti, V, Cr, Mo, and B by the following mass%.
Nb: 0.001% or more and less than 0.2%, Zr: 0.002 or more and less than 0.2%,
Ti: 0.001% or more and less than 0.2%, V: 0.001% or more and less than 0.25%,
Cr: 0.01% or more and less than 1.0%, Mo: 0.005% or more and less than 1.0%,
B: 0.0001% or more and less than 0.01%.

  This is because, as described above, by containing Nb, Zr, Ti and V in the above range, fine carbonitride can be formed and the strength of the steel sheet can be increased. Further, by containing Cr, Mo and B in the above range, the generation of pearlite is suppressed and the generation of martensite is promoted, so the strength of the steel sheet can be increased and eddy current loss can be reduced. .

  Moreover, in the said invention, it is preferable that the said steel ingot or steel slab contains at least any one of Cu and Ni in the range of 0.01%-0.5% by the mass%. This is because inclusion of Cu and Ni in the above range can increase the yield point and the tensile strength and improve the mechanical properties.

  ADVANTAGE OF THE INVENTION According to this invention, the high tension non-oriented electrical steel sheet which has the outstanding mechanical characteristic and magnetic characteristic required as a rotor of the motor which rotates at high speed can be manufactured stably, without causing a great cost increase. Therefore, it can sufficiently cope with the speed increase in the drive motor field of electric vehicles and hybrid vehicles, and its industrial value is extremely high.

  The present invention includes a high-tensile non-oriented electrical steel sheet and a method for producing the same. Hereinafter, each will be described in detail. “%” Indicating the content of each element in the steel means “% by mass” unless otherwise specified.

A. First, the high-tensile non-oriented electrical steel sheet of the present invention will be described.

  The high-tensile non-oriented electrical steel sheet of the present invention is in mass%, C: 0.02% to 0.3%, Si: 2.0% or less, Mn: 1.0% to 3.0%, Al: 1.5% or less, P: 0.2% or less, S: 0.02% or less, N: 0.02% or less, the balance being substantially made of Fe and impurities, and a plate thickness of 0.15 mm It is characterized by being in the range of -1.0 mm.

  Non-oriented electrical steel sheets used for rotors of conventional electric vehicles and drive motors of hybrid vehicles have a ferrite single-phase structure. In the present invention, ferrite is added by adding a predetermined amount of C as a steel component. The steel structure is controlled not to a single phase structure but to a ferrite + martensite and / or bainite double phase structure, a martensite or bainite single phase structure. This steel structure is formed in the final finish continuous annealing and its cooling process. Therefore, in the past, since the electromagnetic steel sheet was strengthened using solid solution strengthening, the cold-rolled base material was also strengthened at the same time, and the inconvenience that the steel sheet was cracked during cold rolling occurred. As mentioned above, since the steel structure is formed in the final finish continuous annealing and its cooling process, the strength of the cold-rolled base metal is increased, that is, the steel sheet is broken during cold rolling. Without being accompanied, it is possible to increase the strength of the high-tensile non-oriented electrical steel sheet.

  Further, as a characteristic necessary for use as a rotor, there is a property of a punched end face of an electromagnetic steel sheet. In general, the electromagnetic steel sheet is premised on continuous punching into a complicated rotor shape. Therefore, when the end face properties are inferior, it can be a starting point of fracture due to stress concentration. Further, if cutting is performed after punching, the end face properties are improved, but the cost is increased. In addition, even if the outer periphery of the electrical steel sheet is cut after punching, the punched end face inside the rotor, for example, the permanent magnet embedded part, is often used as punched, which is the starting point of fracture due to stress concentration. Cheap.

  Therefore, the inventors investigated the influence of the steel composition on the punched end face properties. FIG. 1 is a graph showing a high tensile strength of ferrite, martensite and bainite multiphase structures containing C: 0.09%, Si: 0.9%, Mn: 2.5%, and Al: 0.05% of the present invention. This is a punched end face property of a grain-oriented electrical steel plate (steel plate A) and 35A230 (steel plate B) according to the prior art defined in JIS C2552. As is clear from the shape of the boundary between the shear plane and the fracture surface shown in FIG. 1, the steel sheet A of the present invention has better end face properties.

  Furthermore, as a characteristic necessary for use as a rotor, there is an eddy current loss of an electromagnetic steel sheet. Iron loss is composed of hysteresis loss due to irreversible domain wall motion and Joule heat (eddy current loss) due to eddy currents caused by magnetization changes. The iron loss of electrical steel sheets is the sum of these totals. It is evaluated by iron loss. The rotor has only a magnetic flux from the outside in a state where it is forcibly magnetized by the permanent magnet, and therefore the amount of magnetization change is smaller than that of the stator. Furthermore, since the change in magnetization is from the state in which the domain wall is forcibly moved by the permanent magnet, the change in magnetization during use of the rotor is achieved by rotation (rotational magnetization) of magnetization in each magnetic domain. Hysteresis loss due to rotational magnetization is small, and it can be said that the generated loss is only eddy current loss. Therefore, it is recalled that even if the increase in hysteresis loss is allowed, the motor efficiency can be improved if the reduction in eddy current loss is achieved.

  Then, next, the present inventors investigated the influence of the steel composition on the eddy current loss. FIG. 2 shows a ferrite containing C: 0.02 to 0.3%, Si: 2.0% or less, Mn: 1.0% to 3.0%, Al: 1.5% or less of the present invention. A high-tensile non-oriented electrical steel sheet having a martensite and / or bainite double-phase structure, a martensite or bainite single-phase structure and a thickness of 0.35 mm, and C: 0.002 to 0.003%, Si: 0.00. Non-directional electromagnetic according to the prior art with a plate thickness of 0.35 mm, which is a ferrite single-phase structure containing 3-3.2%, Mn: 0.15-0.9%, Al: 0.2-2.0% It is a graph which shows the relationship between an eddy current loss and an electrical resistance about a steel plate. Here, the eddy current loss uses values at a maximum magnetic flux density of 0.5 T and an excitation frequency of 1500 Hz. As is clear from FIG. 2, the eddy current loss is reduced by increasing the electric resistance. However, even with the same electric resistance, the high-tensile non-oriented electrical steel sheet of the present invention is more effective than the conventional technique. It became lower than the grain-oriented electrical steel sheet.

FIG. 3 shows a ferrite + martensite and / or bainite multiphase structure containing C: 0.09%, Si: 0.9%, Mn: 2.5%, and Al: 0.05% of the present invention. , A high-tensile non-oriented electrical steel sheet having a single-phase structure of martensite or bainite, and ferrite containing C: 0.002%, Si: 2.0%, Mn: 0.2%, Al: 0.3% It is a graph which shows the relationship between an eddy current loss and plate | board thickness about the non-oriented electrical steel plate of the prior art which is a single phase structure. The electrical resistance is about 40 Ωm × 10 ⁻⁸ and is almost the same for all steel types. As shown in FIG. 3, even with the same plate thickness, the high-tensile non-oriented electrical steel sheet of the present invention has a lower eddy current loss than the conventional non-oriented electrical steel sheet. Note that FIG. 3B is an enlarged view of the thin plate thickness range.

  From the above, in the present invention, by containing a predetermined amount of C as a steel component, the high-tensile non-oriented electrical steel sheet whose structure is controlled as described above has a good end face property from the viewpoint of suppressing fatigue fracture. It has been found that eddy current loss can be effectively reduced.

  As described above, the present invention is characterized by containing a predetermined amount of C as a steel component. However, in order to effectively bring out the effect and satisfy other characteristics necessary for the electromagnetic steel sheet, it will be described later. Thus, it is necessary to limit the steel component, the plate thickness, and the like. Hereinafter, the steel component, plate thickness, and insulating coating in the high-tensile non-oriented electrical steel sheet of the present invention will be described.

1. Steel composition ・ C
C is an essential element for obtaining desired strength, eddy current loss, and punched end face properties by controlling the structure. Moreover, there is also an effect of increasing the strength of the steel sheet by forming fine carbides. The content of C may be determined according to the target strength level, but in order to achieve the strength required as a rotor of a motor that rotates at high speed, which is the object of the present invention, it is necessary to contain 0.02% or more. And preferably 0.04% or more. In addition, the upper limit value of the C content is set to 0.3% from the viewpoint of weldability deterioration in the continuous annealing line at the time of manufacturing the electrical steel sheet.

・ Si
Si is an element having an effect of increasing electric resistance and reducing eddy current loss. However, when Si is contained in a large amount, cracking of the steel sheet is induced during cold rolling, and the production cost increases due to a decrease in yield. Therefore, the Si content is 2.0% or less. Moreover, when Si is used as a deoxidizer, it is necessary to contain 0.01% or more, but since Al may be used as a deoxidizer, the lower limit of the Si content is not particularly defined. And

・ Mn
Mn, like Si, has the effect of increasing electrical resistance and reducing eddy current loss. Since the effect of Mn is smaller than that of Si, it is necessary to contain 1.0% or more to obtain this effect. On the other hand, when Mn is contained in a large amount, the alloy cost increases, so the upper limit of the Mn content is set to 3.0%.

・ Al
Al, like Si, has the effect of increasing electrical resistance and reducing eddy current loss. However, if a large amount of Al is contained, the alloy cost increases, so the Al content is 1.5% or less. In addition, when Al is used as a deoxidizing agent, it is necessary to contain 0.01% or more, but since Si may be used as a deoxidizing agent, there is no particular lower limit for the Al content. And

・ P
P has the effect of increasing the strength of the steel sheet by solid solution strengthening. However, when P is contained in a large amount, cracking of the steel sheet is induced during cold rolling. Therefore, the P content is 0.2% or less.

・ S
S is an impurity inevitably mixed in the steel, but since the cost increases in order to reduce the S content in the steelmaking stage, the upper limit of the S content is 0.02%.

・ N
N has the effect of forming fine precipitates and increasing the hardness of the steel sheet. However, when a large amount of N is contained, cracking of the steel sheet is induced during cold rolling. Therefore, the N content is 0.02% or less.

-Other components In this invention, in addition to said steel component, at least 1 type of element selected from the element group which consists of Nb, Zr, Ti, V, Cr, Mo, and B can be contained suitably.

Nb, Zr, Ti and V:
Nb, Zr, Ti, and V are elements that form fine carbonitrides to increase the strength of the steel sheet, and may be contained as necessary. When these elements are contained, the contents of Nb, Ti and V are preferably 0.001% or more, and the Zr content is preferably 0.002% or more. On the other hand, when these elements are contained in a large amount, not only the effect of increasing the strength of the steel sheet is saturated but also the steel sheet may be cracked during cold rolling, so the contents of Nb, Zr and Ti are It is preferable to be less than 0.2%. Moreover, since V is less effective in increasing the strength of the steel sheet than Nb, Zr and Ti, the V content is preferably less than 0.25%.

Cr, Mo and B:
Cr, Mo and B are effective elements for increasing the strength of steel sheets and reducing eddy current loss by suppressing the formation of pearlite and promoting the formation of martensite. Good. When these elements are contained, the Cr content is preferably 0.01% or more, the Mo content is preferably 0.005% or more, and the B content is preferably 0.0001% or more. On the other hand, even if these elements are contained in a large amount, the effect of increasing the strength of the steel sheet is saturated and the cost is increased. Therefore, the Cr content is preferably less than 1.0%, the Mo content is less than 1.0%, and the B content is preferably less than 0.01%.

Cu and Ni:
Cu and Ni are elements having an effect of increasing the yield point and tensile strength of the steel sheet, and may be contained in the range of 0.01% to 0.5%.

Co and W:
Co and W have an effect of improving the yield point and tensile strength of the steel sheet, and may be contained as necessary. The Co and W contents are preferably 1% or less from the viewpoints of alloy cost and cold rollability.

Ca:
Ca is effective for deoxidation and desulfurization, and may be contained at 0.01% or less.

2. Plate Thickness In the present invention, it is preferable to reduce eddy current loss in order to use an electromagnetic steel plate as a rotor. In order to reduce the eddy current loss, it is extremely effective to reduce the thickness of the electromagnetic steel sheet. Therefore, in the present invention, the thickness of the high-tensile non-oriented electrical steel sheet is 1.0 mm or less, preferably 0.8 mm. The following. Thus, from the viewpoint of reducing eddy current loss, it is preferable that the plate thickness is thin. However, since automatic caulking becomes difficult, the lower limit value of the plate thickness is set to 0.15 mm. In the present invention, the eddy current loss is reduced by controlling the steel structure not to ferrite single phase structure but to ferrite + martensite and / or bainite double phase structure, martensite or bainite single phase structure. Such structure control and the above-described thinning of the plate thickness effectively reduce eddy current loss. Although details of this reason are not clear, it is speculated that the domain structure is refined by the structure control according to the present invention as compared with the non-oriented electrical steel sheet according to the prior art.

3. Insulating Coating In the present invention, it is preferable that at least one surface of the high-tensile non-oriented electrical steel sheet has any one of an organic component insulating coating, an inorganic component insulating coating, and an organic-inorganic composite insulating coating. Insulation coating between laminated steel sheets improves when it has an inorganic component insulation coating, and both punchability and insulation between laminated steel plates improve when it has an organic-inorganic composite insulation coating. This is because the punching property is improved when it has.

  As an inorganic component used for such an insulating film, for example, a commonly used composite of dichromate and boric acid, or a composite of phosphate and silica can be used.

  Examples of the organic component used for the insulating coating include acrylic resin, acrylic styrene resin, alkyd resin, polyester resin, silicone resin, fluororesin, polyolefin resin, styrene resin, vinyl acetate resin, epoxy resin, phenol resin, and urethane. Examples thereof include resins and melamine resins. These resins may be used alone or in combination of two or more.

  As the organic-inorganic composite insulating film, a mixture of the above-mentioned inorganic component and organic component can be used.

  Moreover, in this invention, it is preferable to have an adhesive insulating film on the surface of at least one side of a high tension non-oriented electrical steel sheet. This is because the adhesive insulating film exhibits adhesiveness by heating and pressurizing after processing such as punching, and is effective in reducing vibration and noise. Moreover, it is because the adhesion force between steel plates can be increased without accompanying deterioration of magnetic properties due to caulking or welding.

  As a material used for such an adhesive insulating film, a room temperature drying type or heat curing type organic resin, for example, an epoxy resin, a phenol resin, an acrylic resin, a melamine resin, or the like is preferable. These resins may be used alone or in combination of two or more.

B. Next, the manufacturing method of the high tension non-oriented electrical steel sheet of the present invention will be described.

  The manufacturing method of the high-strength non-oriented electrical steel sheet of the present invention is mass%, C: 0.02% to 0.3%, Si: 2.0% or less, Mn: 1.0% to 3.0%. , Al: 1.5% or less, P: 0.2% or less, S: 0.02% or less, N: 0.02% or less, with the balance being substantially made of Fe and impurities. The piece is subjected to hot rolling, hot-rolled sheet annealing is performed as necessary, and the sheet thickness is 0.15 mm to 1.0 mm by performing cold rolling twice or more sandwiching one time or intermediate annealing. Within the range, the material temperature during soaking is then continuously annealed within the range of 700 ° C to 1100 ° C.

  Non-oriented electrical steel sheets used for rotors of conventional electric vehicles and drive motors of hybrid vehicles have a ferrite single-phase structure. In the present invention, ferrite is added by adding a predetermined amount of C as a steel component. The steel structure is controlled not to a single phase structure but to a ferrite + martensite and / or bainite double phase structure, a martensite or bainite single phase structure. This steel structure is formed in the final finish continuous annealing and its cooling process. Therefore, in the past, since the electromagnetic steel sheet was strengthened using solid solution strengthening, the cold-rolled base material was also strengthened at the same time, and the inconvenience that the steel sheet cracked during cold rolling occurred. As mentioned above, since the steel structure is formed in the final finish continuous annealing and its cooling process, the strength of the cold-rolled base metal is increased, that is, the steel sheet is broken during cold rolling. Without being accompanied, it becomes possible to manufacture a high-strength non-oriented electrical steel sheet with increased strength. Furthermore, the high-tensile non-oriented electrical steel sheet whose structure is controlled as described above has good end face properties from the viewpoint of suppressing fatigue fracture, and can effectively reduce eddy current loss.

  The steel having the above chemical composition can be made into a slab by a known method such as a continuous casting method or a method of rolling a steel ingot. This slab may be charged in a heating furnace and hot-rolled, and when the slab temperature is high, it may be hot-rolled without being charged in the heating furnace. Although it does not specifically limit as slab heating temperature, It is preferable to set it as 1000-1300 degreeC from a viewpoint of cost and hot rolling property, More preferably, it is 1050-1250 degreeC.

  The hot rolling is not particularly limited, and may be performed according to known conditions such as a finishing temperature of 700 to 950 ° C. and a winding temperature of 750 ° C. or less.

  In the present invention, after the hot rolling, the steel plate is finished to a predetermined thickness by cold rolling. When finishing to a predetermined plate thickness, it may be finished to a predetermined plate thickness by a single cold rolling, or may be finished to a predetermined plate thickness by two or more cold rollings including intermediate annealing. Moreover, you may perform hot-rolled sheet annealing before cold rolling as needed. The hot-rolled sheet annealing temperature and intermediate annealing temperature are preferably 600 ° C. or higher regardless of continuous annealing or box annealing. In the present invention, since it is important to contain 0.02% or more, preferably 0.04% or more of C in the steel sheet, a special process such as decarburization annealing is not required.

  After the cold rolling, continuous annealing is performed. In the present invention, the material temperature during soaking is set in the range of 700 ° C to 1100 ° C. This is because if the material temperature is less than 700 ° C., sufficient strength may not be obtained. On the other hand, the operation under the condition that the material temperature exceeds 1100 ° C. is not practical in terms of equipment. Although continuous annealing conditions other than the above may be in accordance with known conditions, it is necessary to control the cooling rate at 750 ° C. or lower to 15 ° C./second or higher.

  Furthermore, in the present invention, after the above-described continuous annealing, according to a conventional method, at least one surface of the steel plate is coated with any one of an organic component insulating coating, an inorganic component insulating coating, and an organic inorganic composite insulating coating. It is desirable to do. Insulation coating between laminated steel sheets improves when it has an inorganic component insulation coating, and both punchability and insulation between laminated steel plates improve when it has an organic-inorganic composite insulation coating. This is because the punching property is improved when it has.

  Further, an adhesive insulating film may be coated on at least one surface of the steel plate. This is because the adhesive insulating film exhibits adhesiveness by heating and pressurizing after processing such as punching, and is effective in reducing vibration and noise. Moreover, it is because the adhesion force between steel plates can be increased without accompanying deterioration of magnetic properties due to caulking or welding.

  In addition, since it is the same as that of what was described in "A. high tension non-oriented electrical steel sheet" mentioned above about the steel component of a high tension non-oriented electrical steel sheet, description here is abbreviate | omitted.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

  Steels having various chemical compositions as shown in Table 1 are vacuum-melted, heated to 1150 ° C., finish-rolled at 820 ° C., wound at 580 ° C., and hot rolled with a thickness of 2.0 mm. A steel plate was obtained. This hot-rolled steel sheet is cold-rolled to an intermediate plate thickness, and then subjected to intermediate annealing by box annealing soaking in a hydrogen atmosphere for 10 hours, or intermediate annealing by continuous annealing soaking at 1000 ° C. for 60 seconds, and the second time The product thickness was finished by cold rolling. Also, some hot-rolled steel sheets are subjected to hot-rolled sheet annealing by box annealing soaking in a hydrogen atmosphere for 10 hours, or by hot-rolling sheet annealing by continuous annealing soaking at 1000 ° C. for 60 seconds. Finished to product thickness by cold rolling. Furthermore, some hot-rolled steel sheets were finished to product sheet thickness by a single cold rolling without being subjected to hot-rolled sheet annealing. Thereafter, continuous annealing was performed, which was held at various temperatures for 30 seconds and cooled at 25 ° C./second. The steel plates of Examples 1 to 35 have a ferrite + martensite and / or bainite double phase structure, and a martensite or bainite single phase structure, and the steel plates of Comparative Examples 2 to 5 and Comparative Examples 7 to 14 have a ferrite single phase structure. It was. Table 2 shows conditions for cold rolling, intermediate annealing or hot rolled sheet annealing.

The obtained steel sheet was evaluated for mechanical properties, magnetic properties, and fatigue properties. Mechanical properties were evaluated by a yield test: YP and a tensile strength: TS in a tensile test using a JIS No. 5 test piece. Here, the yield point with high reading accuracy was adopted as the yield point. The magnetic properties were evaluated by an Epstein test defined in JIS C 2550. As the magnetic characteristics, the maximum magnetic flux density: 0.5T, the excitation frequency: 1500 Hz, and the eddy current loss: We _5/1500 were used and calculated from the measured values at various frequencies by the frequency separation method. Further, in the fatigue test, a test piece was collected by punching, and subjected to a single swing electromagnetic resonance test at a frequency of 60 Hz while being punched without grinding the end face. Considering the safety factor with respect to the stress state of the drive motor, it was judged that the one that did not undergo fatigue failure under the conditions of average stress: 300 MPa and stress amplitude: 180 MPa. Number of repetitions is carried out until ^107, was judged by the presence or absence of breakdown in this repetition number. Table 2 shows the results.

  Since Comparative Example 1 and Comparative Example 6 have high contents of Si, P, Al, etc., they broke during cold rolling. In Comparative Examples 2 to 5 and Comparative Examples 7 to 14, the C content was below the range defined in the present invention, and both the yield point (YP) and the tensile strength (TS) were low. On the other hand, in Examples 1-35, the yield point (YP) and the tensile strength (TS) showed the excellent value. FIG. 4 is a graph showing the balance between mechanical properties and magnetic properties of the example and the comparative example. As is apparent from FIG. 4, it was found that the example had excellent magnetic properties and mechanical properties. Further, in Examples 1 to 35, since fatigue failure did not occur even under the above-described stress conditions, it was found that the end face properties were good simultaneously with excellent mechanical properties.

It is a photograph which shows the punching end surface property of a non-oriented electrical steel sheet. It is a graph which shows the relationship between an electrical resistance and eddy current loss. It is a graph which shows the relationship between plate | board thickness and eddy current loss. It is a graph which shows the balance of the magnetic characteristic and mechanical characteristic of a non-oriented electrical steel sheet.

Claims (8)

In mass%, C: 0.02% to 0.3%, Si: 2.0% or less, Mn: 1.0% to 3.0%, Al: 1.5% or less, P: 0.2% Hereinafter, S: 0.02% or less, N: 0.02% or less is contained, the balance is substantially made of Fe and impurities, and the plate thickness is in the range of 0.15 mm to 1.0 mm. High tension non-oriented electrical steel sheet. 2. The high-tensile non-directional electromagnetic according to claim 1, comprising at least one element selected from the group consisting of Nb, Zr, Ti, V, Cr, Mo and B in the following mass%. steel sheet.
Nb: 0.001% or more and less than 0.2%, Zr: 0.002 or more and less than 0.2%,
Ti: 0.001% or more and less than 0.2%, V: 0.001% or more and less than 0.25%,
Cr: 0.01% or more and less than 1.0%, Mo: 0.005% or more and less than 1.0%,
B: 0.0001% or more and less than 0.01%. The high-strength non-oriented electrical steel sheet according to claim 1 or 2, characterized by containing at least one of Cu and Ni in a range of 0.01% to 0.5% by mass%. . 2. The high-strength non-oriented electrical steel sheet has one of an organic component insulating coating, an inorganic component insulating coating, and an organic-inorganic composite insulating coating on at least one surface thereof. The high-tensile non-oriented electrical steel sheet according to any one of claims 3 to 3. The high-tensile non-oriented electrical steel sheet according to any one of claims 1 to 3, further comprising an adhesive insulating coating on at least one surface of the high-tension non-oriented electrical steel sheet. . In mass%, C: 0.02% to 0.3%, Si: 2.0% or less, Mn: 1.0% to 3.0%, Al: 1.5% or less, P: 0.2% In the following, S: 0.02% or less, N: 0.02% or less is contained, and the steel ingot or steel slab, the balance of which is substantially made of Fe and impurities, is hot-rolled, and if necessary, hot rolled Plate annealing is performed, and cold rolling is performed twice or more with one or intermediate annealing, so that the plate thickness is in the range of 0.15 mm to 1.0 mm, and then the material temperature during soaking is 700 ° C. to The manufacturing method of the high tension non-oriented electrical steel sheet characterized by performing continuous annealing within the range of 1100 degreeC. The steel ingot or steel slab contains at least one element selected from the element group consisting of Nb, Zr, Ti, V, Cr, Mo, and B in the following mass%. The manufacturing method of the high tension non-oriented electrical steel sheet of description.
Nb: 0.001% or more and less than 0.2%, Zr: 0.002 or more and less than 0.2%,
Ti: 0.001% or more and less than 0.2%, V: 0.001% or more and less than 0.25%,
Cr: 0.01% or more and less than 1.0%, Mo: 0.005% or more and less than 1.0%,
B: 0.0001% or more and less than 0.01%. The said steel ingot or steel slab contains at least any one of Cu and Ni in the range of 0.01%-0.5% by the mass%, The Claim 6 or Claim 7 characterized by the above-mentioned. Manufacturing method for high-strength non-oriented electrical steel sheets.

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