High strength steel plate, manufacturing method thereof, and rotor core

Abstract

To provide a high strength steel plate, etc. suitable for a rotary electric machine of an interior permanent magnet (IPM) system.SOLUTION: At least a part of bridge parts of electromagnetic steel plates is modified and the electromagnetic steel plates whose modification is terminated are laminated. Thus, short-circuit of a part of a magnetic line to draw a closed curve in a rotor core can be suppressed since permeability of the bridge parts becomes smaller than that in other parts in the rotor core concerning the present embodiment. Consequently, efficiency deterioration of a rotary electric machine of an interior permanent magnet (IPM) system can be suppressed.SELECTED DRAWING: Figure 1

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This international application claims priority based on Japanese Patent Application No. 2020-112817, filed with the Japan Patent Office on June 30, 2020, the entire contents of which are incorporated herein by reference. [Technical field]

[0002] The present disclosure relates to a manufacturing method for an interior permanent magnet (IPM) type rotor core. [Background technology]

[0003] 2. Description of the Related Art A rotor core for a rotating electric machine rotor is formed by laminating a number of electromagnetic steel plates in the thickness direction, as described in Patent Document 1, for example. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-6741 A Summary of the Invention [Problem to be solved by the invention]

[0005] In an interior permanent magnet (IPM) rotor, the permanent magnets are embedded in the rotor core, so some of the magnetic field lines are short-circuited inside the rotor core, drawing a closed curve, and do not reach, for example, the stator. This reduces the (apparent) permeance between the rotor and stator, reducing the efficiency of rotating electrical machines such as electric motors.

[0006] In view of the above, the present disclosure discloses an example of a manufacturing method for a rotor core that can suppress a decrease in efficiency of an interior permanent magnet (IPM) type rotating electric machine. [Means for solving the problem]

[0007] A manufacturing method of a rotor core (1) in which electromagnetic steel sheets (2) are laminated in the thickness direction and in which permanent magnets are embedded in parts thereof is preferably, for example, to melt at least parts of the bridge parts (4) of the electromagnetic steel sheets (2) together with a modifying metal or alloy to modify the part so that the magnetic permeability of the part is smaller than that of the other parts, and then to laminate the modified electromagnetic steel sheets (2).

[0008] As a result, in the rotor core 1, the magnetic permeability of the bridge portion 4 is smaller than that of other portions, so that it is possible to prevent a portion of the magnetic field lines from shorting out so as to draw a closed curve within the rotor core, and thus to prevent a decrease in the efficiency of an interior permanent magnet (IPM) type rotating electric machine.

[0009] The bridge portion is a portion of an electromagnetic steel sheet (also called a core sheet) that is generally called an "outer bridge" or "inner bridge (also called a "rib")" and is, for example, "a portion of the electromagnetic steel sheet (2) that connects an outer core that is on the outer periphery side of the magnet hole (3) in which the permanent magnet is embedded, and an inner core that is on the inner periphery side of the magnet hole."

[0010] Incidentally, the symbols in the above parentheses are examples showing the corresponding relationship with the specific configurations etc. described in the embodiments described below, and the present disclosure is not limited to the specific configurations etc. shown by the symbols in the above parentheses. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a front view of the rotor core according to the first embodiment. [Diagram 2] FIG. 2 is a partial enlarged view of the electromagnetic steel sheet according to the first embodiment. [Diagram 3] 1 is a process chart of a manufacturing method according to a first embodiment. [Figure 4] FIG. 2 is an explanatory diagram of a modification process according to the first embodiment. [Diagram 5] FIG. 4 is a diagram showing an example of a beam scanning method in the first embodiment. [Figure 6] FIG. 4 is an explanatory diagram of an insulating film forming step according to the first embodiment. [Figure 7] 1 is a process chart of a manufacturing method according to a second embodiment. [Figure 8] FIG. 11 is an explanatory view of a planarization step according to the second embodiment. [Figure 9] 11 is a process chart of a manufacturing method according to a third embodiment. [Figure 10] 13A to 13C are explanatory views of a recess forming step according to the second embodiment. [Explanation of symbols]

[0012] 1...Rotor core 2...Electromagnetic steel plate 3…Magnetic hole 4…Bridge section DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The following "embodiment of the invention" shows an example of an embodiment that falls within the technical scope of the present disclosure. In other words, the invention-specific matters described in the claims are not limited to the specific configurations and structures shown in the following embodiment.

[0014] In addition, arrows and diagonal lines indicating directions in each figure are provided to facilitate understanding of the relationship between the figures and the shapes of each member or part. Therefore, the invention shown in this disclosure is not limited to the directions indicated in each figure. Diagonal lines do not necessarily indicate cross-sectional views.

[0015] At least one of each of the members or parts described with a reference numeral is provided, unless otherwise specified by "one". In other words, unless otherwise specified by "one", two or more of the member may be provided. The rotor core etc. shown in this disclosure includes at least the components such as the members or parts described with a reference numeral, as well as the structural parts shown in the drawings.

[0016] (First embodiment) <1. Outline of rotor core> In this embodiment, an example of the manufacturing method of a rotor core according to the present disclosure is applied to a manufacturing method of a rotor core used in an electric motor for driving an electric vehicle. A rotor core 1 according to this embodiment is a rotor that rotates by electromagnetic force within a stator (also called a fixed part).

[0017] The rotor core 1 has a large number of electromagnetic steel plates (also called core sheets) 2 made of silicon steel plates as shown in Fig. 1, and these electromagnetic steel plates 2 are laminated in the thickness direction. The thickness direction refers to the plate thickness direction of each electromagnetic steel plate 2 (in Fig. 1, the direction perpendicular to the paper surface).

[0018] Permanent magnets (not shown) are embedded in the rotor core 1. For this purpose, a plurality of magnet holes 3 are provided in each electromagnetic steel sheet 2. Each magnet hole 3 is a through hole into which the permanent magnet is embedded. The type of permanent magnet embedded in each magnet hole 3 and the embedding method are not important.

[0019] <2. Rotor core manufacturing method> <2.1 Overview of manufacturing method> The rotor core 1 is manufactured, for example, according to the process chart shown in Fig. 3. That is, first, a rolled electromagnetic steel sheet, which is to serve as the material, is formed into a shape suitable for processing in the next process (S20) (pre-forming process: S10).

[0020] At least a portion of the bridge portion 4 (see FIG. 2) of each pre-formed magnetic steel sheet 2 is modified (modifying step: S20). The modification refers to a process in which the portion is melted together with a modifying metal or alloy to make the magnetic permeability of the portion smaller than that of the other portions.

[0021] The bridge portion 4 is a portion of the electromagnetic steel sheet 2 that is generally called an "outer bridge" or "inner bridge (also called a "rib")" and, as shown in Figure 2, refers to, for example, "a portion of the electromagnetic steel sheet 2 that connects an outer core 3A that is on the outer peripheral side of the magnet hole 3 in which a permanent magnet is embedded, and an inner core 3B that is on the inner peripheral side of the magnet hole 3."

[0022] 2, four magnet holes 3 are arranged in two rows. Therefore, the portion of the electromagnetic steel sheet 2 between the magnet holes 3 of the outer row and the magnet holes 3 of the inner row becomes an outer core 3A for the magnet holes 3 of the inner row, and becomes an inner core 3B for the magnet holes 3 of the outer row.

[0023] After the modification process, an electrical insulating film is formed on at least a part of the bridge portion 4 of each of the electromagnetic steel sheets 2 (insulating film forming process: S30), as shown in Fig. 3. Thereafter, each of the electromagnetic steel sheets 2 is press-formed into a predetermined shape by punching using a press machine (punching and forming process: S40).

[0024] The predetermined shape refers to, for example, the shape shown in Figure 1, specifically, the shapes of the multiple arc-shaped magnet holes 3, the circular outer peripheral shape, the inner peripheral shape into which the shaft is inserted, and the key groove provided in the inner peripheral shape.

[0025] That is, the magnet holes 3 are not formed in the steps prior to the punching and forming step (for example, the modification step), and are formed in the punching and forming step. Similarly, the circular outer shape of the magnetic steel sheet 2, i.e., the core sheet, is not formed either.

[0026] After the punching process, a predetermined number of the electromagnetic steel sheets 2 are stacked in the thickness direction (a "stacking process": S50). In the stacking process according to this embodiment, recesses (not shown) and protrusions (not shown) formed on the electromagnetic steel sheets 2 are press-fitted into each other and fixed.

[0027] <2.2 Details of main processes> <Modification process (see Figure 4)> The modification process according to this embodiment includes a powder coating process, a pre-heat treatment process, a melting modification process, and a post-heat treatment process, etc. The powder coating process is a process for coating a modifying metal or a modifying alloy (hereinafter, these metals are referred to as modifiers) on the melting area.

[0028] The melting range is at least a part of the bridge portion 4, which is a target of modification. Note that "at least a part of the bridge portion 4" means "a part of each of the plurality of bridge portions 4" and does not mean "any bridge portion of the plurality of bridge portions 4."

[0029] Incidentally, each bridge portion 4 and each melting range are ranges that are appropriately determined by experiments or numerical simulations using a computer depending on the shape and size of the electromagnetic steel sheet 2 and the required magnetic specifications.

[0030] In the modification process, the magnet holes 3 have not yet been formed. Therefore, the bridge portions 4 in the modification process are portions that will become the bridge portions 4 when the magnet holes 3 are formed in the next or subsequent process.

[0031] In addition, in this specification, a "bridge portion 4" refers to any bridge portion among the multiple bridge portions 4. Similarly, a "magnet hole 3" refers to any magnet hole 3 among the multiple magnet holes 3. In other words, the bridge portion 4 and magnet hole 3 in this specification do not intend a specific bridge portion 4 and a specific magnet hole 3.

[0032] The pre-heat treatment step is a heating step in which at least the melting range of the electromagnetic steel sheet 2 after the powder coating step is heated to a predetermined temperature lower than the melting point of the electromagnetic steel sheet 2. The melting modification step is a step in which the melting range is heated together with a modifier to modify it.

[0033] In the melting and modifying process according to the present embodiment, a beam such as a laser beam or an electron beam is irradiated to melt the melting range. Hereinafter, a predetermined range including the part where the irradiation of the beam is started within the melting range and outside the bridge portion 4 is referred to as a start range.

[0034] In addition, the end range refers to a predetermined range including the part where the beam irradiation is completed within the melting range and outside the bridge portion 4. The start range and the end range are the parts outside the bridge portion 4.

[0035] In principle, the beam scanning direction is not important. In the bridge portion 4 on the outer periphery side (also called the outer bridge) according to this embodiment, as shown in Fig. 5, for example, the beam is scanned in a direction Did corresponding to the radial direction of the rotor core 1 while being scanned at high speed in a direction Cid corresponding to the circumferential direction of the rotor core 1. In Fig. 5, the reference numeral 5 indicates the melting range, that is, the irradiation range of the beam.

[0036] That is, in the outer bridge, the beam is scanned in the direction Did while vibrating at high speed in the direction Cid. Furthermore, in this embodiment, macroscopically, that is, ignoring the scanning in the direction Cid, the beam is scanned in the direction Did from the center side to the outer side of the rotor core 1.

[0037] In the bridge portion 4 (also called the inner bridge) on the inner circumference side according to the present embodiment, the beam is scanned at high speed in the direction Did while being scanned in a direction perpendicular to the direction Did. That is, the beam in the inner bridge is scanned in a direction perpendicular to the direction Did, macroscopically.

[0038] In addition, the macroscopic beam scanning direction is a direction approximately parallel to the direction from the magnet hole 3 toward the outer peripheral surface, or a direction approximately parallel to the direction from one magnet hole 3 to the other magnet hole 3 in two adjacent magnet holes 3.

[0039] The start range in this embodiment is the range on the side marked "Start" in FIG. 5, and the end range in this embodiment is the range on the side marked "End" in FIG. 5.

[0040] The start range and end range are ranges that are appropriately determined by experiments or numerical simulations using a computer depending on the shape and size of the electromagnetic steel sheet 2 and the required magnetic specifications.

[0041] The post-heat treatment process is a heat treatment process in which the cooling rate within the area heated in the melting and reforming process is maintained at or below a predetermined cooling rate. That is, in the pre-heat treatment process, the melting area is heated to a predetermined temperature below the melting point of the electrical steel sheet 2.

[0042] In the melting and modifying step, the portion irradiated with the beam has a temperature higher than the predetermined temperature, and the post-heat treatment step prevents the area heated in the pre-heat treatment step and the melting and modifying step from being suddenly cooled.

[0043] <Insulating film formation process (see Fig. 6)> The insulating coating according to this embodiment is formed on at least a part of the bridge portion 4, that is, on the melting area. Specifically, an organic resin is applied or sprayed onto the melting area, and then the resin is heated at approximately 100°C to 400°C.

[0044] The insulating coating is formed on at least one of the sheet surfaces (in this embodiment, only one surface) of the electromagnetic steel sheets 2. That is, the insulating coating is formed so that adjacent electromagnetic steel sheets 2 are electrically insulated from each other when a large number of electromagnetic steel sheets 2 are stacked.

[0045] <Punching molding process> After the modification process, each of the electromagnetic steel sheets 2 is press-formed into a predetermined shape by punching using a press machine. At this time, a trimming process is also performed to remove at least a part of at least one of the start range and the end range (in this embodiment, the start range and the end range).

[0046] Therefore, when the trimming step according to this embodiment is carried out, at least a part of the start range on one side and the end range on the other side across the bridge portion 4 is removed, and at least the bridge portion 4 remains.

[0047] 3. Features of the manufacturing method according to this embodiment In this embodiment, at least a portion of the bridge portion 4 of the electromagnetic steel sheet 2 is modified, and the modified electromagnetic steel sheet 2 is laminated. As a result, in the rotor core 1 according to this embodiment, the magnetic permeability of the bridge portion 4 is smaller than that of other portions, so that it is possible to prevent some of the magnetic field lines from shorting out so as to draw a closed curve within the rotor core 1. In turn, it is possible to prevent a decrease in the efficiency of an interior permanent magnet (IPM) type rotating electric machine.

[0048] In the modification process, the electromagnetic steel sheets 2 are heated and melted, which destroys the electrical insulation of the melted portions. However, in this embodiment, an electrical insulating film is formed on at least a portion of the bridge portion 4 after the modification process has been completed, which makes it possible to ensure electrical insulation between adjacent electromagnetic steel sheets 2.

[0049] However, since heat is not sufficiently transferred to the start range, there is a possibility that the fusion zone to be modified cannot be sufficiently melted. If the melting is insufficient, it is difficult to sufficiently contain the nonmagnetic modifier additive element as a modifier in the magnetic steel sheet 2, and therefore nonmagnetic modification failure is likely to occur.

[0050] Since the end region is the last to solidify, defects such as cracks and voids due to shrinkage are likely to occur in the end region. This may cause a decrease in strength in the end region. In other words, the start region and the end region are likely to be unsuitable regions for the rotor core 1.

[0051] In contrast, the present embodiment includes a trimming process for removing at least a portion of each of the start range and the end range, thereby removing areas from the electromagnetic steel sheet 2 that are prone to non-magnetic modification defects and areas where strength reduction may occur.

[0052] In this embodiment, the beam is scanned in a direction Did while oscillating at high speed in the direction Cid. In other words, the beam is scanned in a macroscopic scanning direction while oscillating at high speed in a direction perpendicular to the scanning direction of the beam.

[0053] Therefore, the magnetic steel sheet 2 manufactured by the manufacturing method according to this embodiment suppresses the occurrence of problems such as a magnetic short circuit phenomenon caused by insufficient nonmagnetic modification and insufficient strength of the magnetic steel sheet 2. As a result, the rotor core 1 according to this embodiment is capable of high-speed rotation.

[0054] In this embodiment, the modification step is carried out after a predetermined area including the melting area is heated to a predetermined temperature lower than the melting point of the electromagnetic steel sheet 2 (pre-heat treatment step). Therefore, the occurrence of cracks can be suppressed compared to the case where the temperature of only the melting area increases during the modification step.

[0055] In this embodiment, the cooling rate in the area heated in the melting and reforming process is kept at or below a predetermined cooling rate (post-heat treatment process). This prevents the heated area from being cooled suddenly, and therefore can prevent cracks from occurring due to a sudden shrinkage of the melting area.

[0056] Second embodiment In the manufacturing method according to this embodiment, a flattening step (S60) is carried out after the modification step and before the lamination step, as shown in Fig. 7. The flattening step is a pressing step in which the thickness dimension of a predetermined range, including the bridge portion 4, of the electromagnetic steel sheet 2 after the modification step is made equal to or smaller than the thickness dimension of the other portions.

[0057] That is, as shown in Fig. 8, the bridge portion 4 after the modification process, i.e., the melted area, has a larger thickness dimension and a convex shape compared to other areas. Therefore, in the flattening process, the area is pressed by a press machine to flatten the convex shape. This allows the electromagnetic steel sheets 2 to be appropriately stacked in the thickness direction when multiple electromagnetic steel sheets 2 are stacked.

[0058] In addition, the same components as those in the above-described embodiment are denoted by the same reference numerals as those in the above-described embodiment, and therefore, in this embodiment, duplicated explanations are omitted.

[0059] Third embodiment In the manufacturing method according to this embodiment, a recess forming step (S70) is performed before the modification step, as shown in Fig. 9. The recess forming step is a step of recessing at least a part of the bridge portion 4 or a predetermined range including the bridge portion 4 (the melted range in this embodiment) in the thickness direction by a press, as shown in Fig. 10.

[0060] In this embodiment, a modifier is applied to the recessed portion, and the recessed portion is modified. The recessed portion is at least one of the one side and the other side in the thickness direction (the one side and the other side in FIG. 10).

[0061] Therefore, in this embodiment, the melted area can be maintained in a recessed state even after the modification process is completed. Therefore, even if the electrical insulation of the melted area is destroyed, it may be possible to ensure electrical insulation between adjacent magnetic steel sheets 2. As a result, it may be possible to omit the insulating film forming process.

[0062] In Fig. 9, the insulating film forming step is omitted for the above-mentioned reason, but the insulating film forming step may be performed in this embodiment as well. The same components as those in the above-mentioned embodiment are denoted by the same reference numerals as those in the above-mentioned embodiment. Therefore, in this embodiment, duplicated explanations are omitted.

[0063] In this regard, when the one and other sides in the thickness direction are recessed, the recessed state of the one and other sides in the thickness direction of the melted range can be maintained even after the modification process is completed. In this case, the flattening process can be omitted.

[0064] (Fourth embodiment) This embodiment is an example related to a configuration for ensuring electrical insulation between adjacent electromagnetic steel sheets 2. That is, when one of two stacked adjacent electromagnetic steel sheets 2 is designated as the first electromagnetic steel sheet 2, the other electromagnetic steel sheet 2 is designated as the second electromagnetic steel sheet 2, the bridge portion 4 of the first electromagnetic steel sheet 2 is designated as the first bridge portion, the bridge portion 4 of the second electromagnetic steel sheet 2 is designated as the second bridge portion, and an imaginary plane perpendicular to the stacking direction is designated as a projection plane, in the stacking process according to this embodiment, the sheets are stacked such that the first bridge portion projected onto the projection plane is shifted with respect to the second bridge portion projected onto the projection plane.

[0065] This prevents adjacent modified portions, i.e., adjacent portions where electrical insulation has been destroyed, from coming into contact with each other, so that even if electrical insulation is destroyed by the modification, it may be possible to ensure electrical insulation between adjacent magnetic steel sheets 2. As a result, it may be possible to omit the insulating film forming step.

[0066] Fifth embodiment As described above, a modified portion is provided in a part of the bridge portion 4 made of silicon steel plate, which is modified by heating together with a modifier (e.g., nickel or chromium). An austenite phase is formed in the modified portion, and the magnetic permeability is smaller than that of other portions.

[0067] Here, in rotor core 1 rotating at high speed, centrifugal force generates large tensile stress in bridge portion 4 (see Fig. 1), so the bridge portion needs to have a stronger tensile strength. If part of the bridge portion is modified by laser melting to increase its strength, the modified portion may become stronger, but the bridge portion is configured with an arrangement of weak silicon steel plate, strong modified portion, and weak silicon steel plate portion in that order. Therefore, if pulled in the direction of this arrangement, the relatively weak silicon steel plate will eventually break, and so it was thought that even if the bridge portion was partially modified, it would not be effective in improving the tensile strength.

[0068] However, the inventors of the present application have discovered that by subjecting at least the modified portion to press processing after the modification process, i.e., a flattening process in which mechanical pressure is applied to the modified portion, the tensile strength of the entire bridge portion 4, including the modified portion, is improved.

[0069] In other words, the inventors discovered that "a silicon steel sheet manufactured by a manufacturing method including the manufacturing method according to the second embodiment becomes a high-strength steel sheet having improved tensile strength compared to a normal silicon steel sheet to which this manufacturing method is not applied."

[0070] That is, when at least a part of the bridge portion 4 of the electrical steel sheet 2 made of silicon steel sheet is provided with a modified portion that satisfies the following requirements, the tensile strength is improved compared to that of an ordinary silicon steel sheet.

[0071] The requirement is that the modified portion is "a modified portion that is irradiated with a laser beam or an electron beam, melted and modified together with a modifying metal or a modifying alloy, and then pressed." Preferably, at least a part of the modified portion extends from one surface to the other surface in the thickness direction of the silicon steel plate.

[0072] Here, when the tensile strength of the inner bridge (rib) 4 in Figure 2 was measured, the tensile strength was 874 MPa in the case of only the silicon steel plate without the modified portion, but in this embodiment, the tensile strength was significantly improved to 1033 MPa.

[0073] (Other embodiments) In the above embodiment, the melting area is irradiated with a beam to heat and melt the area. However, the present disclosure is not limited to this. That is, the present disclosure may be modified by heating and melting the area by, for example, electrical heating.

[0074] In the insulating coating step according to the embodiment described above, an insulating coating is formed on at least a part of the bridge portion 4, i.e., the melting range. However, the present disclosure is not limited to this. That is, the present disclosure may be, for example, a case in which an insulating coating is formed on the entire electromagnetic steel sheet 2 in the insulating coating step, or a case in which an insulating coating is formed only in a range of the melting range excluding a start range and an end range.

[0075] In the trimming process according to the above embodiment, the start range and the end range are removed. However, the present disclosure is not limited thereto. That is, the present disclosure may be applicable to, for example, a case where only the start range is removed or only the end range is removed in the trimming process.

[0076] The trimming step according to the embodiment described above is performed by punching using a press machine. However, the present disclosure is not limited to this. That is, in the present disclosure, the trimming step may be performed by, for example, cutting.

[0077] In the above-described embodiment, the pre-heat treatment step and the post-heat treatment step are included. However, the present disclosure is not limited thereto. That is, the present disclosure may be, for example, a manufacturing method in which at least one of the pre-heat treatment step and the post-heat treatment step is eliminated.

[0078] The pre-heat treatment process and the post-heat treatment process according to the above-described embodiment are measures to suppress the occurrence of cracks. However, the present disclosure is not limited thereto. That is, the present disclosure may, for example, carry out a demagnetizing heat treatment in addition to the crack prevention measures by those heat treatments.

[0079] The beam scanning method is not limited to the above. That is, for example, as shown in Fig. 5, the disclosure in the bridge portion 4 on the outer periphery side (also called the outer bridge) may be, for example, a case in which the beam scans in the direction Cid while vibrating at high speed in the direction Did, or a case in which the macroscopic beam scans in the direction Did from the outer side of the rotor core 1 toward the center outer side.

[0080] In the first embodiment described above, the punching and forming step (S40) is performed after the insulating film forming step (S30). However, the present disclosure is not limited to this. That is, in the present disclosure, for example, the insulating film forming step (S30) may be performed after the punching and forming step (S40).

[0081] In the first embodiment described above, the insulating coating forming step (S30) is performed after the modification step (S20). However, the present disclosure is not limited to this. That is, the present disclosure may perform, for example, a powder removing step for removing the remaining modifier before or after the post-heat treatment step.

[0082] The modified portion according to the above embodiment is configured such that at least a part of the modified portion reaches from one surface to the other surface in the thickness direction of the silicon steel plate. However, the present disclosure is not limited thereto. That is, the present disclosure may be configured such that, for example, the modified portion does not reach from one surface to the other surface in the thickness direction of the silicon steel plate.

[0083] Furthermore, the present disclosure is not limited to the above-mentioned embodiments as long as it is consistent with the gist of the disclosure described in the above-mentioned embodiments. Therefore, the present disclosure may be a configuration in which at least two of the above-mentioned embodiments are combined, or a configuration in which any of the components illustrated or the components described with reference numerals in the above-mentioned embodiments are eliminated.

Claims

1. A high-strength steel plate having a modified portion obtained by irradiating a silicon steel plate with a laser beam or an electron beam in the thickness direction, melting and solidifying a part of the silicon steel plate together with a modifier, and then pressing the melted and solidified part.

2. The high-strength steel plate according to claim 1 , wherein at least a part of the modified portion extends from one surface to the other surface in a thickness direction of the silicon steel plate.

3. A manufacturing method for high strength steel plate, comprising irradiating a silicon steel plate with a laser beam or an electron beam in the thickness direction to melt and solidify a part of the silicon steel plate together with a modifier, and then pressing the modified part.

4. The method for producing a high strength steel plate according to claim 3 , wherein the modified portion contains an austenite phase.

5. A rotor core formed by laminating the high-strength steel plates according to claim 1 or 2 in a thickness direction and having permanent magnets embedded in a portion thereof, At least a portion of the bridge portion of the rotor core is made of the modified portion.

6. 6. The rotor core according to claim 5, wherein a start range and an end range of irradiation of the laser beam or the electron beam in the high-strength steel plate are set to be outside the bridge portion.

Images