JP6269601B2 - Rotating machine and manufacturing method thereof - Google Patents

Description

  The present invention relates to a rotating machine having a non-magnetic portion including an austenite phase formed by solid solution of nitrogen in a magnetic circuit of a rotating machine (referred to as “nitrogen-solved austenite phase” as appropriate), and a method for producing the same. .

  Rotating machines (also simply referred to as “motors”) need to effectively use the magnetic force supplied from magnetomotive sources (permanent magnets and electromagnets) in order to reduce size, increase output, or reduce loss. . For this reason, a magnetic circuit that efficiently guides the magnetic field lines generated by the magnetomotive source along a desired magnetic path is important. The magnetic circuit is mainly formed by a yoke (also simply referred to as “yoke”) made of a soft magnetic material (iron or iron alloy). For the purpose of forming a desired magnetic circuit or shielding leakage magnetic flux, A nonmagnetic portion (a region having a saturation magnetization or a permeability smaller than that of a soft magnetic material as a base material) may be partially provided in the yoke. There is a description related to this in Patent Document 1, for example. In the specification of the present application, not only the soft magnetic part but also the non-magnetic part is simply referred to as a “yoke”.

JP2013-143791A JP-A-6-79483

  In Patent Document 1, a part of the rotor core (the yoke) constituting the rotor (rotor) of the internal magnet type synchronous machine (IPM) (peripheral side of the slot of the bonded magnet to be injected and filled) has a permeability higher than the surroundings. It has been proposed to use a small low magnetic part (non-magnetic part). Patent Document 1 describes that such a low magnetic part can be formed by modifying a soft magnetic material constituting a rotor core to have an austenite structure.

  However, in Patent Document 1, based on the description in Patent Document 2, a carbon dioxide laser is irradiated to a processing part in which a Ni—Cr wire is arranged to partially melt the processing part, and the processing part is made of Ni and Cr ( A low magnetic part is formed as an alloy containing an austenite stabilizing element.

  An object of the present invention is to provide a rotating machine using a yoke having a new non-magnetic part, which is different from the conventional one, as a stator or a rotor, and a preferable manufacturing method thereof. To do.

  As a result of extensive research and trial and error, the present inventor has conducted a near-ultraviolet nanosecond pulse in a nitrogen-containing atmosphere to a part of the yoke constituting the rotating machine (a part to be processed). By irradiating with laser, we succeeded in producing a nonmagnetic part consisting of austenite phase in which nitrogen is supersaturated. By developing this result, the present invention described below has been completed.

《Rotating machine》
(1) A rotating machine according to the present invention is a rotating machine including a stator and a rotor that rotates relative to the stator, and the stator or the rotor is a yoke constituting a magnetic circuit. the provided,該継iron, and a non-magnetic portion saturation magnetization is smaller than the soft magnetic part and the soft magnetic portion made of an iron alloy, iron alloy, the whole 100% by mass, chromium (Cr) 0.01 to 2%, and the nonmagnetic part has an austenite phase in which the ferrite phase of the soft magnetic part is transformed by dissolving nitrogen (N) and is substantially free of nitride. Features.

(2) In the rotating machine of the present invention, at least one of the stator and the rotor includes a non-magnetic part including an austenite phase in which a relatively large amount of nitrogen (moreover, supersaturated nitrogen) is generated or maintained as a solid solution. With a yoke (including a rotor core, a field core, etc.). Since this nonmagnetic part is not what forms the nonmagnetic part by melting and solidifying the metal element that stabilizes the austenite phase as in the prior art, for example, while suppressing distortion and deformation associated with melting heating, It can be arranged with high precision even in a fine local site. As a result, the degree of freedom in setting the magnetic circuit, the dimensional accuracy of the yoke, and the like can be improved, and as a result, the performance and size of the rotating machine can be improved.

  Incidentally, the “austenite phase formed by dissolving N in solid solution” constituting the nonmagnetic portion according to the present invention means an austenite phase generated or maintained by dissolving a large amount of N as described above. However, a small amount of N is not simply dissolved in the austenite phase formed by composition adjustment (for example, alloying using an austenite stabilizing element) or the like. However, such an “austenite phase formed by dissolving N in solid solution” is impossible or impractical because it cannot be directly specified by structure (structure, composition, etc.) or characteristics.

  If the metal structure of the non-magnetic part is to be specified directly, “Austenitic phase in which N is supersaturated” is a subordinate concept included in “Austenitic phase formed by dissolving N”. Can be used. At this time, since the solid solubility limit may vary depending on the base material, the solid solution amount of N that becomes supersaturated cannot be specified in general. For example, the solid solution amount of N is 0.2 mass% or more, 0.4 It can be set to not less than mass%, more preferably not less than 0.6 mass%. In addition, it is usually not considered that the nonmagnetic part adjacent to the soft magnetic part has an austenite phase in which N is supersaturated and dissolved from the conventional technical common sense. Therefore, the non-magnetic portion according to the present invention and the conventional non-magnetic portion are clearly distinguished as “things” by the above expression.

<Method for manufacturing rotating machine>
(1) The present invention can be grasped not only as the rotating machine described above but also as a manufacturing method thereof. That is, the present invention irradiates a portion to be processed which is a part of a soft magnetic portion made of pure iron or an iron alloy while relatively moving a high energy beam in an atmosphere containing nitrogen. There may be provided a rotating machine manufacturing method comprising a reforming step of reforming at least a part of the constituting ferrite phase into an austenite phase, and the nonmagnetic portion described above is formed in the portion to be treated.

(2) The “processed part” is not limited to the outer surface side but may be the inner surface side as long as it can be irradiated with a high energy beam. The “high energy beam” is a light beam or electron beam having sufficient energy for dissolving N in the base material (soft magnetic material). In particular, when ablation is caused and austenitization with solute nitrogen is attempted, a high energy beam is a laser or electron that has both sufficient energy to cause ablation and a strong electric field that causes plasma around the irradiated area. A beam or the like is preferable.

  A “nitrogen-containing atmosphere” is an atmosphere in which nitrogen is present at the molecular or atomic level. Specifically, a nitrogen gas atmosphere composed only of nitrogen gas, a mixed gas atmosphere (including an air atmosphere) composed of nitrogen gas and an inert gas, a compound gas atmosphere containing a nitrogen compound, and the like. The reforming treatment according to the present invention is possible even in the atmosphere containing nitrogen. In this case, the nonmagnetic part can be formed more easily. However, when only N is dissolved, it is preferable that the above-described reforming step is performed in a nitrogen gas atmosphere or an atmosphere in which nitrogen gas is diluted with an inert gas. Note that the pressure (gas pressure) of the nitrogen-containing atmosphere does not have to be high and may be normal pressure (atmospheric pressure). The temperature of the nitrogen-containing atmosphere may also be room temperature (normal temperature).

<Others>
(1) In this specification, the reforming treatment for increasing the proportion of the austenite phase by dissolving N in the base material is also simply referred to as “nitriding” as appropriate.

(2) Unless otherwise specified, “x to y” in this specification includes a lower limit value x and an upper limit value y. Any numerical value included in various numerical values or numerical ranges described in the present specification can be newly established as a range such as “ab” as a new lower limit value or upper limit value.

It is an EPMA nitrogen mapping image of the sample which carried out the modification process. It is a dispersion | distribution figure which shows the relationship between nitrogen concentration (N solid solution amount) and an austenitization rate (fcc conversion rate). It is a dispersion | distribution figure which shows the relationship between nitrogen concentration (N solid solution amount) and a non-magnetization rate. It is an XRD profile image concerning each sample. It is a bar graph which shows the ratio of fcc (gamma phase) and bcc (alpha phase) which concern on each sample. It is a schematic diagram which shows the outline | summary of the simulation model which used a part of rotor core (IPP) for IPM as a nonmagnetic part. It is a graph which shows the relationship between the maximum torque increase rate and current amplitude which were obtained by the simulation.

  The contents described in this specification can be applied not only to the rotating machine of the present invention but also to the manufacturing method thereof. One or more components arbitrarily selected from the present specification may be added to the above-described components of the present invention. In this case, the components related to the manufacturing method are in a certain case (a situation where it is impossible or impractical (impossible / unpractical circumstances), etc.) In some cases, it can be a component of “things” as a product-by-process. Note that which embodiment is the best depends on the target, required performance, and the like.

《Rotating machine》
Various types are included in the rotating machine of the present invention. For example, the rotating machine may be an electric motor or a generator. The rotating machine may be a DC machine or an AC machine. The AC machine may be a synchronous machine, an induction machine, or a non-commutator machine (such as a brushless DC motor). In addition, when using a permanent magnet, an encapsulated type (IPM etc.) or a surface type (SPM etc.) may be sufficient. Furthermore, the rotor may be an inner rotor type or an outer rotor type.

  The rotating machine of the present invention has at least a stator (stator) and a rotor (rotor). In addition to these, the rotating machine of the present invention usually includes a rotating shaft (output shaft) that rotates integrally with the rotor, a bearing that pivots the rotating shaft, a housing (case) that supports or surrounds them. Note that the rotor according to the present invention may include an accessory member such as a rotating shaft.

  Usually, one of the rotor and the stator is an armature or a field, respectively, but the field magnetomotive source may be a permanent magnet or an electromagnet. Further, the rotor or the stator has a yoke for inducing magnetic flux generated from the armature or the field. In this yoke, iron loss such as hysteresis loss and eddy current loss occurs when the direction of the magnetic field changes periodically according to the rotation speed of the rotating machine. In order to reduce this iron loss (especially eddy current loss), the yoke is made of a composition-adjusted iron alloy or a thin electromagnetic steel plate (for example, a silicon steel plate whose surface is insulated) is laminated. A fixed laminated body is used, or a powder magnetic core obtained by press-molding iron-based (pure iron or iron alloy) particles coated with insulation is used. In the present invention, not only a soft magnetic part having a high magnetic flux density but also a non-magnetic part having a low magnetic flux density is referred to as “a yoke”. The yoke not only functions as a mere magnetic path, but may constitute the rotor body like a rotor core. The nonmagnetic part is usually arranged in contact with the soft magnetic part, but both may be integrated or separable. For example, a nonmagnetic part formed by modifying a part of the soft magnetic part is integrated with the soft magnetic part.

《Soft magnetic part》
The soft magnetic part constituting the yoke is made of pure iron or an iron alloy having a large saturation magnetization. Specifically, the soft magnetic part is mainly composed of a ferrite phase, and its saturation magnetization is preferably 1.5T or more, 1.6T or more, 1.7T or more, and further 1.8T or more.

  The iron alloy serving as the soft magnetic part preferably has a composition that can achieve both magnetic properties (high saturation magnetization) and electrical properties (reduction of eddy current loss). For example, the iron alloy preferably contains 1 to 8%, further 2 to 5% of Si. The iron alloy preferably contains Al in an amount of 0.2 to 5%, more preferably 0.5 to 2%. If the amount of Si or Al is too small, the effect of reducing the iron loss is poor, and if the amount of Si or Al is excessive, the saturation magnetization is lowered. In addition, unless otherwise indicated, each composition of the iron alloy as used in this specification is the mass ratio which made the whole 100 mass%, and the remainder is Fe and an unavoidable impurity.

  However, Si and Al are ferrite phase stabilizing elements, and Al easily forms a compound with N. For this reason, Si and Al tend to inhibit austenitization due to N solid solution. Therefore, when a part of the soft magnetic part mainly composed of the ferrite phase is modified to a nonmagnetic part mainly composed of the austenite phase, the iron alloy according to the present invention contains 0.1 to 7% or even 0% of Cr. It is preferable to contain 3 to 2%. In addition, in order to accelerate | stimulate austenitization by N solid solution, Cr may be contained in the iron alloy separately from the presence or absence of Si or Al. In any case, if Cr is too small, the effect of promoting austenite formation by N solid solution is poor, and if Cr is excessive, saturation magnetization is lowered.

《Nonmagnetic part》
The nonmagnetic part according to the present invention is a part (part of the yoke) having an austenite phase generated or maintained by N solid solution. By adjusting the amount of N solid solution contained in the nonmagnetic part and the proportion of the austenite phase generated (austenite ratio) accordingly, the magnetic properties (permeability, saturation magnetization, magnetic susceptibility, etc.) of the nonmagnetic part, that is, The demagnetization rate can be controlled. As a result, not only the simple distinction between magnetic and non-magnetic, but also the local area of the yoke can be controlled to a suitable saturation magnetization, magnetic permeability, etc., and the degree of freedom in forming the magnetic circuit can be increased.

The amount of N contained in the nonmagnetic part can be appropriately adjusted according to the specifications of the rotating machine or the yoke (magnetic characteristics required for the nonmagnetic part), the composition of the base material, etc., but at least less than the soft magnetic part. The amount of N that lowers the saturation magnetization and magnetic permeability of the magnetic part is necessary. Specifically, it is preferable that the N content is 0.2% or more, 0.5% or more, 0.8% or more, and further 0.9% or more, assuming that the entire nonmagnetic portion is 100% by mass. In addition, N amount as used in this specification is a value in a normal temperature range, and is specified based on the result of having analyzed a nonmagnetic part with the electron beam microanalyzer (EPMA). In addition, the fact that N contained in the nonmagnetic part is in a solid solution state means that when observing a profile obtained by X-ray diffraction (XRD), the fcc (γ phase) peak shifts to the lower angle side. In addition, it can be judged from the fact that no peaks related to nitrides (Fe ₃ N, Fe ₄ N, Cr ₂ N, CrN, etc.) are substantially observed.

  When the amount of N (also referred to as “N solid solution amount” or “N concentration”) is too small, the proportion of the ferrite phase (also referred to as “α phase” as appropriate) is large, and the substantial demagnetization is exhibited. This austenite phase (also referred to as “γ phase” as appropriate) cannot be obtained. On the other hand, when the amount of N becomes sufficiently large (for example, when N becomes a solid solution in a supersaturated state), austenitization in which the α phase of the bcc structure is transformed into the γ phase of the fcc structure (“fcc conversion” or “γ According to the degree, the portion to be processed has a metal structure in which an α phase and a γ phase are mixed, and the demagnetization proceeds. When the amount of N exceeds a predetermined value, most of the nonmagnetic portion becomes a γ phase and becomes almost nonmagnetic. Thus, the non-magnetic portion exhibits magnetic properties (permeability, saturation magnetization, etc.) according to the austenitization rate (referred to as “fcc conversion rate” as appropriate), which is the proportion of the γ phase in the metal structure.

  The austenite ratio (fcc conversion ratio), which is the ratio of the austenite phase to the entire metal structure of the nonmagnetic part, is 30% by volume (referred to as simply “%” as appropriate) or more, 50% or more, 80% or more, 90%. More preferably, it is 95% or more. Note that the fcc conversion rate referred to in this specification is calculated based on the ratio of the γ phase (fcc phase) obtained by analyzing the X-ray diffraction profile of the nonmagnetic portion by a Rietveld (Reitveld) analysis. Details regarding this point will be described later.

  The magnetic level of the non-magnetic part is indicated by, for example, a non-magnetization rate. The demagnetization ratio is calculated by φ = 100 × (H0−H1) / H0, where H0: saturation magnetization of the soft magnetic part and H1: saturation magnetization of the nonmagnetic part. The demagnetization rate referred to in this specification is also a value in the normal temperature range, and the saturation magnetization of each part is obtained from a magnetic property evaluation apparatus such as a vibrating sample magnetometer (VSM) at normal temperature. Such a demagnetization rate (φ) is preferably 20% or more, 50% or more, 80% or more, 95% or more, or 98% or more, for example.

  The form (shape, size, etc.) of the non-magnetic part is adjusted according to the specifications of the rotating machine or the yoke. When the manufacturing method of the present invention is used, for example, the minimum width of the nonmagnetic portion can be set to about 1 μm and the maximum depth thereof can be set to about 1 mm. Therefore, the width of the nonmagnetic part is preferably 1 μm to 10 mm, and further preferably 10 μm to 1 mm. The depth of the nonmagnetic part is preferably 10 μm to 1 mm, and further preferably 30 μm to 500 μm, for example. As described above, the nonmagnetic portion according to the present invention can be finely arranged in the yoke (soft magnetic portion) while ensuring a sufficient depth.

"Production method"
(1) Various methods for forming the nonmagnetic portion according to the present invention are conceivable. However, by performing a modification step (or irradiation step) of irradiating a high energy beam in an atmosphere containing nitrogen to a portion to be processed which is a part of a soft magnetic portion made of pure iron or an iron alloy, for example, Even a local nonmagnetic portion can be formed efficiently.

  Such a reforming step is a step of causing ablation to occur in a processing target portion by irradiation with a high energy beam, mixing emitted particles generated at that time and nitrogen in the atmosphere, and re-depositing them. (Ablation step) is preferable. Modification by ablation is different from conventional modification by local heating (and melting) as in the past. Thermal distortion and mechanical properties (hardness, strength, etc.) are applied to the treated part (non-magnetic part) or its surroundings. It is also possible to hardly cause a decrease or the like.

  Furthermore, it is possible to adjust the surface form of the processing target part by controlling the amount of redeposition of emitted particles or the like generated by ablation. For example, by limiting the redeposition amount, it becomes possible to make the outermost surface portion of the portion to be processed (nonmagnetic portion) concave. Thereby, the additional process of the surface part performed after the modification process, the insulation process, and the like can be omitted. Specifically, when modifying the surface of a laminated plate (plate electromagnetic steel sheet, etc.) used in a laminated manner, the outermost surface area of the non-magnetic part is made a slight concave shape, so that even after modification A highly accurate laminate can be obtained. In addition, even when modifying a laminated plate with a high-resistance coating (insulating coating) formed on its surface to reduce eddy current loss, etc., the nonmagnetic portion has a concave surface, which makes it nonmagnetic. As a result of the formation of a substantial insulating layer (air gap) in the vicinity of the surface of the part, an electrical short circuit in the nonmagnetic part can be suppressed even after the modification.

(2) Hereinafter, the case where at least a part of the ferrite phase constituting the part to be treated is transformed into an austenite phase by ablation to form a nonmagnetic part will be described in detail.

  First, ablation is a well-known technical term. By ablation, atoms and the like constituting the processing target are released by vaporization, evaporation, evaporation, scattering, and the like. The particles thus released (referred to as “emitted particles” where appropriate) can take various forms such as atoms, molecules, ions, electrons, photons, radicals, and clusters. Then, a reaction field in which the emitted particles and the atmospheric gas (nitrogen) in the vicinity of the processing target portion are mixed can be generated in the processing target portion where the ablation occurs (referred to as “ablation portion” as appropriate) or in the vicinity thereof. .

  The above-mentioned phenomenon occurs almost continuously one after another as the irradiation area of the high-energy beam moves on the processing target, and there are a large number of emitted particles and atmospheric nitrogen that generate reaction fields in the processing target and its vicinity. It becomes a state. The reaction field composed of the emitted particles and the ambient nitrogen is redeposited (filled) in a state where nitrogen is dissolved in the portion to be processed or in the vicinity thereof. By repeating such a phenomenon, it is considered that nitrogen is sufficiently introduced deep inside and a fine austenite phase in which nitrogen is dissolved is formed.

  If such ablation is used, unlike the conventional case of melting and heating, the non-magnetic part and the soft magnetic part around the non-magnetic part are hardly affected. For this reason, it becomes easy to demagnetize only a necessary portion without changing the composition or structure of the soft magnetic portion adjacent to the nonmagnetic portion. Further, by utilizing ablation, a nitrogen solid solution austenite phase composed of a fine metal structure can be generated in a single step substantially in a short time with respect to a base material in a wide composition range. And a nonmagnetic part can be made into a desired form by controlling the locus | trajectory of the irradiation area | region of a high energy beam. For example, it is possible to form non-magnetic parts in various forms such as flat, curved, curved (including straight), and dotted (including multiple spots such as spots) regardless of whether they are wide or narrow. is there. Furthermore, as long as the high energy beam reaches the target portion, it is possible to form a nonmagnetic portion in a recessed region, a recessed region, an undercut region, or the like.

  Since a high energy (convergent) beam is used, the size (width) and depth of the non-magnetic portion can be controlled in units of mm or μm. Assuming that the non-magnetic part effectively acts in the magnetic circuit (can be a substantial magnetic resistance), for example, the non-magnetic part has a minimum width of 1 mm or less, 100 μm or less, 10 μm or less, or 1 μm or less. It can have a range. The nonmagnetic portion can have a depth from the outermost surface of 10 μm or more, 100 μm or more, 500 μm or more, or 1 mm or more. Incidentally, since the thickness of the electromagnetic steel sheet is usually about 0.2 to 0.5 mm, it can be a non-magnetic portion penetrating the entire thickness direction by ablation using a high energy beam.

  The width of the nonmagnetic portion is the length in the direction orthogonal to the longitudinal direction (extending direction of the locus of the high energy beam). The depth of the nonmagnetic portion is a length from the deepest portion where the N amount is larger than that of the soft magnetic portion to the outermost surface based on an EPMA image obtained by observing a cross section of the nonmagnetic portion. The two-dimensional or three-dimensional form of the nonmagnetic part can be easily adjusted by adjusting the power density, beam diameter, focal point, nitrogen-containing atmosphere, etc. of the high energy beam. The redeposition amount can be adjusted by appropriately adjusting the fluence, scanning speed, focus position, and the like.

(3) Hereinafter, specific conditions at the time of reforming treatment by causing ablation with a high energy beam will be described.

  In order to generate ablation, it is necessary to instantaneously apply high energy to the target portion of the base material. That is, it is necessary to irradiate the processing target portion of the base material with a high energy beam having a high energy density (fluence) exceeding the ablation threshold. As such a high energy beam, a pulse laser with a short pulse width is suitable.

  If the output, the oscillation frequency, etc. of the laser oscillation device are constant, the laser beam having a higher fluence can be irradiated to the processing portion as the pulse width is shorter. Moreover, when the pulse width is short, thermal diffusion outside the irradiation area is suppressed, and ablation is promoted and thermal influence on the base material can be suppressed. Specifically, the pulse width of the pulse laser is preferably 10 ps to 100 ns, and more preferably 1 to 50 ns. If the pulse width is too large, it becomes difficult to obtain the fluence necessary for ablation. If the pulse width is too small (for example, about 150 fs where multiphoton absorption occurs), the form of energy application by the laser light changes, and the modification process according to the present invention is performed. The necessary reaction field may not be formed.

Speaking a pulsed laser power density (fluence), for ^example, when 0.3MW / cm ² ~30GW / cm 2 further is a ^3MW / cm ^{2 ~3GW} / cm 2 preferably. The output density affects the depth of the nonmagnetic part. When the output density is small, the nonmagnetic part becomes shallow, and when the output density is large, the thermal influence on the base material becomes large. Incidentally, the output density is obtained by dividing the laser output by the laser spot area.

  Further, the shorter the wavelength of the pulse laser, the higher the absorption rate of the laser beam by the base material, thereby promoting ablation and suppressing alteration of the non-ablation part. In addition, by appropriately adjusting the wavelength of the pulse laser, it becomes easy to form a nonmagnetic portion having a sufficient depth. The wavelength of such a pulse laser is preferably in the ultraviolet region (including the near ultraviolet region) shorter than the infrared region and further shorter than the visible region. Specifically, the wavelength of the pulse laser is preferably 700 nm or less, 550 nm or less, and further 380 nm or less. The wavelength of the pulse laser is preferably 190 nm or more, more preferably 320 nm or more. When the wavelength of the pulse laser is too small, the absorption of the laser by the atmospheric gas is not preferable.

Specific examples of such a pulse laser include excimers (excitation dimers) such as F ₂ (wavelength 157 nm), ArF (wavelength 193 nm), KrF (wavelength 248 nm), XeCl (wavelength 308 nm), and XeF (wavelength 351 nm). ) Excimer laser, and YAG laser that can oscillate a short wavelength.

  When a pulse laser is used as a high energy beam, it is easy to form a continuous non-magnetic portion by partially overlapping (overlapping) irradiation regions of adjacent pulsed light that oscillate. The ratio of overlapping the pulse wave irradiation area (pulse wrap ratio) is the oscillation frequency of the pulse laser, the relative movement speed with respect to the processing target (referred to as “scanning speed” as appropriate), and the size of the irradiation area on the outermost surface of the processing target. (Or the focal position of the pulse laser) or the like. Since it depends on the characteristics of the pulse laser, the pulse wrap rate is preferably less than 10 to 100%, and more preferably 20 to 95%. If the pulse wrap rate is too low, it is difficult to form a continuous nonmagnetic portion, and it is easy to perform removal processing. If the pulse wrap rate is excessive, it is difficult to improve the efficiency of the reforming process and to homogenize the nonmagnetic part.

This pulse wrap rate is calculated by (r / d) × 100 (%) (d: beam diameter, r: overlap diameter of adjacent pulse waves). Here, the beam diameter (d) is a width (diameter) when the beam intensity is 1 / e ² level of the peak intensity value measured on a plane orthogonal to the laser axis. The overlapping diameter (r) of adjacent pulse waves is dR (R: distance between the centers of adjacent beams).

  The oscillation frequency, scanning speed, focus position, and the like are adjusted based on the pulse wrap ratio. An example is as follows. For example, the oscillation frequency is preferably 1 to 500 kHz, and more preferably 2 to 100 kHz. If the oscillation frequency is too low, the scanning speed must be lowered, and the processing efficiency cannot be improved. If the oscillation frequency is excessive, the laser fluence generally decreases, and it becomes difficult to form a homogeneous nonmagnetic portion.

  The scanning speed is preferably 0.1 to 5000 mm / s, more preferably 1 to 1000 mm / s, for example. If the scanning speed is too low, the efficiency of the process cannot be improved. If the scanning speed is too high, it is difficult to form a homogeneous non-magnetic portion as in the case where the correlated oscillation frequency is too high.

  The irradiation range of each pulse light varies depending on the focal position of the pulse laser. The focal position may be on the outermost surface of the part to be processed of the base material or may be shifted from the outermost surface. However, the output density at the irradiated area decreases as the focal point moves away from the pulse laser irradiated area (the outermost surface of the processed area), affecting the stability of processing near the irradiated area and the nonmagnetic area depth. To do. This tendency is more conspicuous as the laser is condensed to form a fine spot diameter at the irradiated portion.

  Irradiation with a high energy beam may be performed in a closed atmosphere such as a chamber, but may be performed in an open atmosphere. If a laser is used as the high energy beam, it is possible even in an air atmosphere at room temperature and pressure, which is an open atmosphere. However, in order to control the amount of dissolved nitrogen while avoiding generation of unnecessary compounds, etc., it is preferable to carry out in a nitrogen gas atmosphere or a mixed gas atmosphere in which nitrogen gas is diluted with an inert gas. Specifically, nitrogen gas or the like may be sprayed from above or from the side of the processing target. By adjusting the gas blowing direction, it is possible to suppress the debris caused by ablation. For example, by making the blowing direction coaxial with the optical axis of the high energy beam, the controllability of the nitrogen-containing atmosphere can be increased, and the homogeneity of the nonmagnetic part can be improved.

[First embodiment]
《Sample preparation》
(1) Test material (base material)
A plurality of test materials (15.0 × 9.0 × 7.5 mm) cut out from a plate material of SUS430 (JIS) were prepared.

(2) Modification process (demagnetization treatment, nitriding treatment)
As a high energy beam, a pulse laser having a wavelength in the near ultraviolet region and a pulse width of nanosecond level (this laser is simply referred to as “near ultraviolet nanosecond laser”) was prepared. Using this laser, irradiation was performed while spraying a nitrogen-containing gas to the treated portion of each specimen. Irradiation conditions are as follows: wavelength: 355 nm, pulse width: <20 ns, output: 0.6 W (output density: 150 MW / cm ² ), scanning speed: 2 mm / s, focal position: on the outermost surface of the specimen to be processed (Defocus distance: 0 μm, that is, just focus). However, the irradiation conditions were finely adjusted for each sample.

  The gas was blown onto the portion to be processed from above along the optical axis of the near ultraviolet nanosecond laser. At this time, a mixed gas obtained by diluting nitrogen gas with argon gas (dilution gas) was used. In addition, the nitrogen concentration (N solid solution amount) introduce | transduced into a test material was adjusted by changing suitably the nitrogen concentration in these gas.

  Further, the laser irradiation was performed with the pulse wrap rate calculated by the above-described method being 85%, and the locus of the irradiation area of each laser beam on the surface of the processing target was a parallel straight line with an interval of 3 to 7 μm. Thereby, the to-be-processed part irradiated with the laser was completely modified.

《Analysis of processed parts》
(1) EPMA
The processed part of each sample was analyzed with an electron beam microanalyzer (EPMA). The N concentration (N solid solution amount) of each processed part thus obtained was determined. As an example, FIG. 1 shows a nitrogen mapping image related to a portion to be processed of a sample having an N concentration of 0.9 mass%.

(2) XRD
An analysis by XRD (FeKα radiation source) was performed on a portion to be treated of each sample (specifically, a portion 10 μm from the outermost surface). Then, using the fcc (γ phase) peak and the bcc (α phase) peak appearing in the X-ray diffraction profile of each sample, the proportion of the γ phase (fcc conversion rate) in the treated portion of each sample was quantified. . The fcc conversion rate was calculated by the Rietveld method. More specifically, the fcc conversion rate was calculated by Rietveld analysis software: Rietan-FP on the premise of a two-phase mixed model of α phase and γ phase. At this time, an extended divided pseudo-voice function was used as the fitting function. The relationship between the fcc conversion rate and the N concentration of each sample thus obtained is shown in FIG.

(3) Saturation magnetization Saturation magnetization (H1) related to the treated portion of each modified sample was measured by VSM. Further, the saturation magnetization (H0) of the sample before the treatment was measured in the same manner. FIG. 3 shows the relationship between the demagnetization ratio (φ = 100 × (H0−H1) / H0) calculated for each sample and the N concentration. The saturation magnetization was obtained by conversion from the measurement result of VSM at room temperature and the density of the base material (untreated).

<Evaluation>
(1) As can be seen from FIG. 1, it can be seen that the portion to be treated has been modified from the outermost surface to a depth of about 150 μm. Further, about 0.9% by mass of N was introduced into the treated portion.

  As is apparent from FIG. 2, the fcc conversion rate monotonously increases with respect to the N concentration (N solid solution amount). When the N concentration is 0.9 mass%, the fcc conversion rate is almost 100%. I found out that

(2) As can be seen from FIG. 3, the demagnetization rate increases as the N concentration increases. When the N concentration is 0.6% by mass, the demagnetization rate is 80% and the N concentration is 0.9% by mass. It was also found that the non-magnetization rate was almost 100% at the time of%.

  2 and FIG. 3 together, it can be seen that both the fcc conversion rate and the non-magnetization rate increase as the N concentration increases, and there is a correlation between the fcc conversion rate and the non-magnetization rate. . However, when the N concentration is 0.1% by mass (<0.2% by mass), which is not more than the solid solubility limit (0.2% by mass), even if the γ phase is formed, the portion to be treated is substantially It was also revealed that no magnetization (reduction in saturation magnetization / demagnetization) occurred. Therefore, by setting the N concentration to a predetermined value or higher (so that N is dissolved in supersaturation), it is possible to reliably demagnetize the portion to be processed and to control the nonmagnetic level by adjusting the N concentration. It became clear.

Incidentally, from the X-ray diffraction profile for each sample, not only does the bcc peak decrease and the fcc peak increases as the N concentration increases, but the peak shifts to the lower angle side as the N concentration increases. all right. Furthermore, the profile of each sample, the peak of the nitride _{(Fe 3 N, Fe 4 N} , Cr 2 N, CrN , etc.) was not substantially observed. From these facts, it can be said that almost all of the N introduced into the treated portion is in a solid solution state, and the α phase in the base material is transformed into a γ phase (austenitized) due to an increase in the amount of N solution.

[Second Embodiment]
(1) Manufacture of sample A sample material having an alloy composition shown in Table 1 was prepared in place of the base material used in the first example. For sample 3 and sample C3 (no modification treatment), commercially available electrical steel sheets were used. Each of these test materials (excluding the sample C3) was subjected to the same modification treatment as in the first example to obtain each sample in which the portion to be treated was nitrided.

(2) Analysis / Evaluation of Processed Parts The processed parts of each sample were subjected to XRD analysis in the same manner as in the first embodiment, and the profiles obtained for each sample are shown in FIG. Further, the ratio of fcc (γ phase) and bcc (α phase) calculated in the same manner as in Example 1 based on the profile of each sample is shown in FIG.

  If the fcc conversion rate is close to 100%, fitting necessary for Rietveld analysis becomes difficult, and high-precision calculation of the fcc conversion rate is not easy. Therefore, in this specification, when the bcc peak is a noise level and only the fcc peak is observed, even if the fcc conversion rate is substantially 100%, the fcc conversion rate is expressed as> 95%.

For each sample, the saturation magnetization (Bs) was measured in the same manner as in the first example, and the magnetization (B ₅ k) when a magnetic field of 5 kA / m was applied was measured. This magnetization (B ₅ k) indicates the magnetic permeability of each sample. These measurement results are also shown in Table 1.

  From FIG. 4, a peak shift to the low angle side was observed by the reforming treatment, and almost all of the N introduced into the treated portion was in a solid solution state, and the α phase in the base material was transformed into a γ phase. It can be seen that (austenitized).

  The following can be seen from Table 1 and FIG. First, as can be seen from Sample 1 and Sample 2, it can be seen that Sample 1 made of substantially pure iron (the ferrite phase is almost 100%) is sufficiently austenitized by the modification treatment. However, as shown in Sample 2, when a small amount of Cr is contained, austenitization due to N solid solution is further promoted, and the non-magnetization rate is greatly improved.

  Such a tendency is the same in Samples 3 to 5 containing Si or Al as a ferrite phase stabilizing element. That is, as can be seen by comparing Samples 3 to 5, Sample C1, and Sample C3, in the case of a soft magnetic material made of an iron alloy containing Si or Al, in order to achieve austenite (demagnetization) by N solid solution, It can be seen that it is particularly preferable that a small amount of Cr is contained.

  However, when a large amount of Cr is contained in the base material as in sample C2, austenitization (demagnetization) due to N solid solution is promoted, but the saturation magnetization is less than 1.5T. Therefore, it can be said that the yoke of the rotating machine preferably has a nonmagnetic part modified by dissolving N in a part of the base material (soft magnetic part) as shown in Samples 1 to 5.

[Third embodiment]
A model was prepared in which a part to be modified was placed on a part of the yoke constituting the rotating machine, and the effect of the modification (demagnetization) was confirmed by simulation. Specifically, it is as follows.

(1) Model A 4-pole internal magnet type motor (synchronous motor / IPM) as shown in FIG. 6 was used as a target model. The non-magnetic portion is arranged on the outer peripheral side of the slot of the rotor core (the yoke / soft magnetic portion) that encloses the permanent magnet to be processed and the adjacent end side of the pair of permanent magnets that constitute each pole. . The rotor core was made of a laminate in which 128 sheets of magnetic steel sheets (ferrite phase: 100%, saturation magnetization: 2.12T) having a thickness of 0.35 mm were laminated, and an outer diameter: 60 mm × axial length: 45 mm was assumed. The nonmagnetic part was formed so as to penetrate the entire thickness direction (axial direction of the laminate) at a predetermined position of each electromagnetic steel sheet. The permanent magnet was rectangular in cross section (3 × 6 mm) and the axial length was the same as that of the rotor core. The permanent magnet was assumed to be a rare earth sintered magnet, with magnetic properties of 860000 A / m and magnetic permeability of 1.05.

(2) Simulation The saturation magnetization (H1) of the processing target part is demagnetized at a predetermined ratio (10%, 30% or 70%) with respect to the saturation magnetization (H0) of the base material (reference material) before processing ( For each case of demagnetization, the relationship between the maximum torque and the current amplitude was calculated. FIG. 7 shows the relationship between the change rate of the maximum torque (maximum torque increase rate) and the current amplitude when the treated part is demagnetized with respect to the case where the treated part is not demagnetized (modified). The current amplitude is an effective value of the current input to the phase coil of the stator.

  As shown in FIG. 7, when compared with operating points that should be considered most (for example, urban fuel efficiency operating points) as drive motors mounted on automobiles, etc., the properly disposed processing parts are modified to be non-magnetic. It turns out that the maximum torque at a predetermined operating point can be increased by about 2 to 20%. It was also found that the maximum torque increases according to the magnitude of demagnetization (demagnetization ratio) of the portion to be processed, and increases rapidly when the demagnetization is 30% or more.

  Thus, it turns out that the characteristic of a rotary machine can be improved significantly by making only a part (local part) of the yoke which consists of a ferrite phase into the nonmagnetic part austenitized by N solid solution.

Claims (11)

A stator,
A rotor that rotates relative to the stator;
A rotating machine comprising:
The stator or the rotor includes a yoke constituting a magnetic circuit,
The yoke has a soft magnetic part made of an iron alloy and a nonmagnetic part having a saturation magnetization smaller than that of the soft magnetic part,
The iron alloy includes 0.01 to 2% of chromium (Cr) with the whole being 100% by mass,
The rotating machine characterized in that the nonmagnetic part has an austenite phase in which nitrogen (N) is dissolved and the ferrite phase of the soft magnetic part is transformed, and is substantially free of nitride .   The rotating machine according to claim 1, wherein the soft magnetic part has a saturation magnetization of 1.5 T or more.   3. The rotating machine according to claim 1, wherein the iron alloy includes 1 to 8% of silicon (Si) with 100% by mass (hereinafter simply referred to as “%”) as a whole.   The said iron alloy is a rotary machine in any one of Claims 1-3 which makes the whole 100 mass% and contains aluminum (Al) 0.2-5%. The rotating machine according to any one of claims 1 to 4, wherein the iron alloy includes 0.1 to 0.5 % of chromium (Cr) with the whole as 100 mass%.   2. The rotating machine according to claim 1, wherein the nonmagnetic part includes 100% by mass as a whole and N is 0.2% by mass or more.   The rotating machine according to claim 1, wherein the nonmagnetic part has an austenitization ratio (fcc ratio) that is a ratio of the austenite phase to the entire metal structure of the nonmagnetic part is 30% by volume or more. The rotating machine according to any one of claims 1 to 7, wherein the non-magnetic portion has a non-magnetization ratio (φ) obtained by the following formula of 20% or more.
φ = 100 × (H0−H1) / H0,
H0: Saturation magnetization of soft magnetic part, H1: Saturation magnetization of nonmagnetic part The rotating machine according to claim 1 , wherein the nonmagnetic part has a width of 1 μm to 10 mm or a depth of 10 μm to 1 mm .   The rotating machine according to claim 1, wherein the yoke is made of a laminate of electromagnetic steel sheets. By irradiating a processed part which is a part of a soft magnetic part made of pure iron or an iron alloy while relatively moving a high energy beam in an atmosphere containing nitrogen, the ferrite phase constituting the processed part Comprising a reforming step of reforming at least part of the austenite phase
A method of manufacturing a rotating machine, wherein the nonmagnetic part according to any one of claims 1 to 10 is formed in the part to be treated.