Magnetic member and manufacturing method thereof, and additive manufacturing powder

Abstract

To provide a magnetic member having high magnetic properties and including a non-magnetic part.SOLUTION: The present invention provides a magnetic member including a soft magnetic part comprising a first iron substrate, a non-magnetic part comprising a second iron substrate, and an intermediate part comprising a third iron substrate, the intermediate part being integrated with the soft magnetic part and the non-magnetic part. The third iron substrate has a component composition different from that of each of the first iron substrate and the second iron substrate. The intermediate part is a non-magnetic part. The intermediate part is, for example, substantially an austenite single phase. Such an intermediate part is formed on the soft magnetic part or on the non-magnetic part by an additive manufacturing method such as a directed energy deposition method and a powder bed fusion method. The soft magnetic part and the non-magnetic part may be additive manufactured together with the intermediate part. For example, powder (intermediate powder) used in additive manufacturing for the intermediate part preferably has such a composition that the total amount of a ferrite stabilization element is less than that of a ferrite stabilization element in the first iron substrate and the total amount of an austenite stabilization element is more than that of an austenite stabilization element in the second iron substrate.SELECTED DRAWING: Figure 3B

Description

[Technical Field]

[0001] The present invention relates to a magnetic member having a soft magnetic portion and a non-magnetic portion. [Background technology]

[0002] By providing a non-magnetic (including weakly magnetic and low-magnetic) region (non-magnetic part) in part of a magnetic component used in a magnetic field, it is possible to improve the performance, reduce loss, and increase the efficiency of electromagnetic equipment.

[0003] For example, in the rotor or stator of a magnet-embedded electric motor (motor, generator), the narrow bridge portions on the outer periphery of the slots that house the permanent magnets (magnetomotive sources) are demagnetized to reduce ineffective magnetic flux that does not contribute to rotational torque. Such demagnetization is described, for example, in the following patent documents: [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5272713 [Patent Document 2] Patent No. 3868019 [Patent Document 3] JP 6-140216 [Patent Document 4] Patent No. 4626683 [Non-patent literature]

[0005] [Non-Patent Document 1] Japan Institute of Metals 2023 Spring Conference, No.235 [Non-patent document 2] Journal of Laser Processing Society, Vol. 29, No. 2, (2022), pp. 98-102. Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, a nonmagnetic portion is formed by partially removing the ferromagnetic material on the surface layer of a multilayer material in which a nonmagnetic material is sandwiched between ferromagnetic materials. In Patent Document 2, a weakly magnetic portion is formed by locally heating a ferromagnetic martensitic stainless steel obtained by annealing. In Patent Document 3, a nonmagnetic portion and a ferromagnetic portion coexist by combining austenite formation by heating and deformation-induced martensite formation by cold working. In Patent Document 4, a nonmagnetic portion is formed by embedding a nonmagnetic alloy or stainless steel in part of an electromagnetic steel sheet.

[0007] In Non-Patent Document 1, a non-magnetic portion is formed by melting and reacting a Ni-Cr-Fe-B alloy on a part of an electrical steel sheet, while in Non-Patent Document 2, a non-magnetic portion is formed by reacting Cu on a part of an electrical steel sheet.

[0008] None of the documents focuses on the magnetic properties, component composition, metal structure, etc. near the boundary between the soft magnetic portion (ferromagnetic portion) and the non-magnetic portion. Furthermore, none of the documents mentions additive manufacturing of the area near the boundary between the soft magnetic portion and the non-magnetic portion using powder with a different component composition.

[0009] The present invention has been made in view of the above circumstances, and has an object to provide a new magnetic member or the like having a soft magnetic portion and a non-magnetic portion. [Means for solving the problem]

[0010] Through extensive research, the inventors came up with the idea of ​​forming a desired intermediate portion between a soft magnetic portion and a non-magnetic portion, and succeeded in realizing this idea. By expanding on this result, the present invention, which will be described below, was completed.

[0011] <Magnetic member> The present invention comprises a soft magnetic portion made of a first iron substrate, a non-magnetic portion made of a second iron substrate, and an intermediate portion made of a third iron substrate and integrated with the soft magnetic portion and the non-magnetic portion, wherein the third iron substrate has a different component composition from the first iron substrate and the second iron substrate, and the intermediate portion is a non-magnetic magnetic member.

[0012] In the magnetic member of the present invention, the area between the soft magnetic portion and the non-magnetic portion (intermediate portion) is non-magnetic, thereby preventing deterioration of magnetic properties and mechanical properties that may occur due to the mixing of soft magnetic and non-magnetic phases and grain refinement.

[0013] Furthermore, by providing the intermediate portion, the degree of freedom in the shape and arrangement of the soft magnetic portion and the non-magnetic portion can be increased, and the degree of freedom in the design of the magnetic member and magnetic circuit can also be increased.

[0014] 《Manufacturing method》 The present invention can also be understood as a method for manufacturing a magnetic member. For example, the present invention may be a method for manufacturing a magnetic member in which an intermediate portion is formed on a soft magnetic portion or a non-magnetic portion by directed energy deposition (DED) or powder bed fusion (PBF). The soft magnetic portion and / or the non-magnetic portion may also be additively manufactured by DED or PBF.

[0015] Powder for additive manufacturing The present invention may be understood as a powder used for such additive manufacturing. Such powder for additive manufacturing may be a single type of powder or a mixed powder blended to a desired composition.

[0016] "others" (1) The magnetic component may be entirely additively manufactured, or may be partially additively manufactured by combining it with a cast or sintered component. The term "additively manufactured product" as used herein includes both. Some additive manufacturing processes include modification, repair, and buildup.

[0017] In addition to DED and PBF, additive manufacturing (AM) processes that involve repeated layering include binder jetting, material jetting, material extrusion, vat photopolymerization, and sheet lamination. These methods can also be used as appropriate. However, DED and PBF are more suitable for the industrial production of magnetic components made of iron substrates.

[0018] The heat sources used to melt the powder (additive manufacturing powder) used in DED and PBF include laser beams, electron beams, and plasma arcs. A laser beam is a typical and versatile heat source. This specification mainly focuses on L-DED (LMD) and L-PBF, which use laser beams.

[0019] (2) The "iron base material" referred to in this specification may contain Fe, but it does not have to be primarily composed of Fe. Specifically, the iron base material may contain more than 50% by mass, 60% by mass or more, or even 70% by mass or more of Fe based on the total mass of the iron base material.

[0020] (3) 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 the various numerical values ​​or numerical ranges described in this specification may be used as a new lower limit or upper limit value to create a new range such as "a to b." Also, "x to y μm" in this specification means x μm to y μm. The same applies to other unit systems. [Brief explanation of the drawings]

[0021] [Figure 1A] 1 shows an SEM image and EDS analysis results for the vicinity of the middle part of Sample 1. [Figure 1B] The IPF and phase distribution map of the metal structure are shown. [Figure 2A] 1 shows an SEM image and EDS analysis results for the vicinity of the middle part of Sample 2. [Figure 2B]The IPF and phase distribution map of the metal structure are shown. [Figure 3A] 1 shows an SEM image and EDS analysis results for the vicinity of the middle part of Sample 3. [Figure 3B] The IPF and phase distribution map of the metal structure are shown. [Figure 4A] 1 shows an SEM image and EDS analysis results for the vicinity of the middle part of Sample 4. [Figure 4B] The IPF and phase distribution map of the metal structure are shown. DETAILED DESCRIPTION OF THE INVENTION

[0022] The components of the present invention may be supplemented with one or more components arbitrarily selected from the present specification. The contents described in this specification apply not only to the magnetic member, but also to the manufacturing method thereof (additive manufacturing method), powder for additive manufacturing, etc., as appropriate.

[0023] 《Soft magnetic part》 The first ferrous substrate constituting the soft magnetic portion may be made of pure iron or an iron alloy, and may contain a ferrite stabilizing element (Si, Al, Cr, Mo, etc.).

[0024] In particular, Si contributes to suppressing the austenite transformation of the iron substrate, highly orienting the crystal grains, and increasing the electrical resistivity (resistivity) and magnetic properties (magnetic permeability), etc. However, if there is too much Si, the iron substrate becomes embrittled and prone to cracking, etc.

[0025] The Si content of the ferrous base material (100%) is preferably, for example, 1 to 6.5% or 2 to 4%. Unless otherwise specified, the chemical composition (composition) referred to in this specification is a mass percentage relative to the entire object (100% by mass) and is expressed as "%" or numerical values ​​only. The composition should be determined in a range where the analysis results by energy dispersive X-ray spectroscopy (EDS) or electron probe microanalyzer (EPMA) are stable (the same applies to other parts).

[0026] 《Non-magnetic part》 The ferrous base material constituting the non-magnetic portion preferably contains an austenite stabilizing element (Ni, Mn, Cu, C, etc.). The composition of the non-magnetic portion may be, for example, a composition (Ni equivalent - Cr equivalent) that allows a stable austenite phase to be obtained on the Schaeffler structural diagram. Austenitic stainless steel is a typical example of the ferrous base material.

[0027] "Middle section" The intermediate portion is located near the boundary between the soft magnetic portion and the non-magnetic portion, and is a region where the composition is clearly different from those of the other portions (a region where the composition is changing). The difference (change) in the composition can be determined, for example, from the results of EDS analysis.

[0028] The intermediate portion should preferably be non-magnetic (including weakly magnetic). Depending on the specifications of the magnetic member, the boundary between the soft magnetic region and the non-magnetic region becomes clear, thereby improving the performance of the magnetic member.

[0029] (1) Organization The ferrous base material constituting the intermediate portion is, for example, generally composed of a single austenite phase throughout, and may contain a small amount of ferrite near the interface or in a small area, which does not substantially affect the magnetic properties.

[0030] The metal structure can be identified, for example, based on an inverse pole figure (IPF) orientation map obtained by electron backscattered diffraction pattern (EBSD) analysis. EBSD also reveals the metal phases (α and γ phases) and whether the intermediate portion is a single phase or a mixed phase.

[0031] (2) Composition The specific composition of the intermediate portion (iron III substrate) is not important as long as it can be distinguished from the soft magnetic portion (iron I substrate) and the non-magnetic portion (iron II substrate). The composition may be substantially uniform in the intermediate portion, or it may change continuously or stepwise (multilayered) between the soft magnetic portion and the non-magnetic portion. The composition of each portion is determined by averaging the concentration changes of each element (analysis results of EDS or EPMA) at multiple measurement points within the extracted range (section).

[0032] Powder for additive manufacturing The powder used for additive manufacturing of the intermediate part (referred to as "intermediate powder" as appropriate) can be any manufacturing process or particle form (shape, size, etc.). The powder can be atomized powder or pulverized powder. It can also be a type of alloy powder, mixed powder, granulated powder, etc.

[0033] The intermediate powder may be, for example, a powder having a smaller total amount of ferrite stabilizing elements than the ferrous base material and a larger total amount of austenite stabilizing elements than the ferrous base material.

[0034] The chemical composition of the intermediate part formed by additive manufacturing using intermediate powder is not necessarily the same as the component composition (mixture) of the intermediate powder. Because the intermediate part (ferrous iron base material) is located between the soft magnetic part (ferrous iron base material) and the non-magnetic part (ferrous iron base material), its chemical composition is influenced by at least one of them.

[0035] The intermediate powder may contain, for example, 30 to 75%, 35 to 70%, or 40 to 65% Ni based on the total weight of the powder, and 0.5 to 20%, 1 to 10%, or 2 to 5% Mn. Ni and Mn stabilize the non-magnetic austenite phase (FCC).

[0036] Furthermore, the intermediate powder may contain 1 to 25% or 5 to 20% Cr. An appropriate amount of Cr can contribute to stabilizing the austenite phase. On the other hand, the intermediate powder may contain ferrite stabilizing elements (e.g., metal elements such as Mo, W, Ti, Nb, and V) in a total amount of, for example, 3% or less, 2% or less, or even 1% or less. The intermediate powder may also contain ferrite stabilizing elements such as Si and Al in a total amount of, for example, 1% or less, or even 0.5% or less. Furthermore, the intermediate powder may also contain impurity elements (e.g., non-metallic elements such as C, P, O, and N), but the total amount thereof should be, for example, 1% or less, or even 0.5% or less. If the C content increases, it becomes difficult to form the metal structure of the intermediate portion into an austenite phase due to carbide precipitation, etc.

[0037] The composition of the intermediate powder and the ferric base material can also be determined using Gibbs free energy. For example, the Gibbs free energy (G BCC ) and the Gibbs free energy (G FCC ) and the difference (dG=G BCC -G FCC ) is preferably −2900 J / mol or more, −2700 J / mol or more, or even −2500 J / mol or more. The intermediate powder preferably has a composition that allows such a ferric iron base material to be obtained.

[0038] <Magnetic member> The magnetic member constitutes, for example, a yoke or a core. The yoke or core is, for example, a rotor or stator of an electric motor (including a generator), a core for a transformer, etc. The electric motor is, for example, a synchronous motor or a DC motor equipped with a permanent magnet, or an induction motor or a switched reluctance motor (SR motor) without a permanent magnet. [Example]

[0039] An additive manufacturing object (sample) made of an iron alloy (iron substrate) was fabricated by LMD (L-DED), and its component composition, metal structure (crystal grains, metal phase), properties, etc. The present invention will be described in more detail based on these specific examples.

[0040] <<Sample Preparation>> (1) Raw material powder The raw material powders used were Fe-3Si powder (particle size: 45-105 μm), SUS316 powder (Fe-17Cr-12Ni-2.5Mo powder / particle size: 45-105 μm), and pure Ni powder (particle size: 74-104 μm). The powder composition is shown as a numerical value only, in terms of mass% (remainder: Fe) relative to the total powder.

[0041] The particle size was determined by classification (sieving) using a mesh. Particle size: x to y (μm) means that the particles are of a size that does not pass through a sieve with a mesh opening of x (μm) but passes through a sieve with a mesh opening of y (μm).

[0042] The soft magnetic portion was manufactured using Fe-3Si powder, and the non-magnetic portion was manufactured using SUS316 powder as is. The middle portion was manufactured using a mixed powder (intermediate powder) with the composition shown in Table 1. The mixed powder was prepared by weighing out SUS316 powder and pure Ni powder and then mixing them (rotation mixing at 45 rpm for 1 hour). For sample 1, the middle portion was manufactured using only SUS316 powder as is. Note that the amount of Ni (austenite stabilizing element) contained in the intermediate powder was increased in order from sample 1 to sample 4.

[0043] (2) Additive Manufacturing Powder for additive manufacturing (also called raw material powder) placed in the powder feeder (powder box) of the LMD device (laser processing test machine manufactured by Enshu Co., Ltd.) was supplied to the powder nozzle using carrier gas (Ar).

[0044] The laser (YLS-4000CW manufactured by IPG Corporation) irradiation conditions were as follows: For the non-magnetic part (SUS316) and the intermediate part, the laser output was 750 W and the scanning speed was 25 mm / s. For the soft magnetic part (Fe-3Si), the laser output was 950 W and the scanning speed was 40 mm / s.

[0045] For each part, the beam diameter (spot diameter): 2.0 mm (diameter), powder supply rate: 0.08 g / s, scanning pitch (x direction): 0.5 mm, layer pitch (z direction / modeling direction): 0.3 mm, and carrier gas (Ar) flow rate: 25 L / min (common conditions).

[0046] Under these conditions, the soft magnetic part, intermediate part, and non-magnetic part were layered on a substrate (SS400 / 100 × 100 × 10 mm thick) in room temperature air, starting from the bottom (substrate side), to obtain a cubic sample (10 mm × 10 mm × 10 mm).

[0047] In this process, the soft magnetic portion was laminated 17 times, the intermediate portion 2 times, and the non-magnetic portion 17 times, each laminated in the z direction (lamination direction). The raw material powder was changed for each portion. However, as mentioned above, the intermediate portion and non-magnetic portion of Sample 1 were molded using the same SUS316 powder.

[0048] Observation, Measurement, and Analysis The area between the non-magnetic and soft magnetic parts (near the middle part) was observed, measured, and analyzed. The results for Samples 1 to 4 are shown in Figures 1A to 4B (Sample 1: Figure 1, Sample 2: Figure 2, Sample 3: Figure 3, Sample 4: Figure 4), respectively. Specific details are as follows.

[0049] (1) Observation The images observed by a scanning electron microscope (SEM) are shown in Figures 1A, 2A, 3A, and 4A, respectively.

[0050] (2) Ingredient composition Using an energy dispersive X-ray analyzer (EDS), measurements were taken near the center of each sample, roughly along the center line of the SEM image. The measurement results for each sample are also shown in Figures 1A, 2A, 3A, and 4A. The specific component compositions at measurement points (11, 12, 21, 22, 31, and 34) extracted from the center of each sample are also shown in Table 1.

[0051] (3) Metal structure and crystal structure The metallographic structure (grains) and crystalline structure (phases) of each part were analyzed using an electron backscatter diffraction (EBSD: MSC-2200, manufactured by TSL Solutions, Inc.). The inverse pole figure orientation maps (IPFs) and phase distribution maps obtained in this way are shown in Figures 1B, 2B, 3B, and 4B, respectively. The phase (FCC or BCC) at each measurement point is also listed in Table 1. For reference, Table 1 also shows the phase (FCC) obtained when molding only the intermediate powder.

[0052] "evaluation" The following can be seen from the microstructural morphology of each sample shown in Table 1 and the figures: BCC and martensite, which exhibit magnetic properties, appeared in the middle of Sample 1 and Sample 2. This is thought to be because Region A in Figure 1B and Region B in Figure 2B became a mixed phase of FCC and BCC.

[0053] The middle sections of Samples 3 and 4 were almost entirely nonmagnetic FCC. Although very thin, discontinuous mixed-phase sections were observed in areas C indicated by the arrows in Figure 3B and D indicated by the arrows in Figure 4B, they did not affect the magnetic properties.

[0054] Therefore, it was found that if intermediate powder with an appropriate component composition is used, an intermediate portion that is almost entirely nonmagnetic can be formed between the soft magnetic portion and the nonmagnetic portion.

[0055] 《Consideration》 Using multi-component thermodynamic analysis software (Thermo-Calc, database TCFE7), the Gibbs free energy and Curie temperature were calculated from the component compositions shown in Table 1. Based on these results, the mechanism or control involved in the structure formation of the intermediate region was discussed as follows.

[0056] (1) Gibbs free energy Considering the deformation-induced martensitic transformation, the free energy (G BCC ) and the free energy (G FCC ) was calculated.

[0057] The difference between them (dG=G BCC -G FCC ) are also shown in Table 1. As Ni increases, dG increases (G FCC This suppresses the phase transformation (ferrite phase ⇔ austenite phase) and stabilizes the austenite phase (FCC).

[0058] dG is negative (G BCC <G FCC The reason why FCC appears even in the case of LMD (L-DED) is that, unlike general melting processes, the objects obtained by LMD (L-DED) have a high cooling rate (10 3 ~10 6 This is thought to be because diffusional transformation (FCC to BCC) does not occur in the low temperature range due to solidification at a rate of 100°C / s. Also, the lower the temperature, the greater the negative driving force required for the progression of diffusionless transformation (martensitic transformation). Therefore, as long as dG, which indicates the driving force, is greater than a certain value (threshold value), FCC appears stably even if dG<0.

[0059] As can be seen by comparing dG at measurement points 21, 22, and 12, in the intermediate range of composition satisfying -2900 J / mol ≦ dG and even -2800 J / mol ≦ dG, neither BCC nor deformation-induced martensite appeared, and FCC was the stable phase.

[0060] (2) Curie temperature The Curie temperature calculated based on the component composition of the intermediate portion is also shown in Table 1. If the Curie temperature is equal to or higher than the Curie temperature shown in Table 1, the intermediate portion becomes non-magnetic.

[0061] Table 1 shows that unless the composition is similar to that of the intermediate powder of Sample 3 or Sample 4 (for example, Ni≧40 mass%), all of them become nonmagnetic near room temperature (and even above 0° C.).

[0062] From the above, it was confirmed that it is possible to form an intermediate portion that is almost entirely nonmagnetic between the soft magnetic portion and the nonmagnetic portion. A magnetic component made of such a formed body can exhibit high performance by effectively utilizing magnetic flux.

[0063] [Table 1]

Claims

1. a soft magnetic portion made of a first ferrous substrate; a non-magnetic portion made of a ferrous base material; an intermediate portion made of a ferrous base material and integrated with the soft magnetic portion and the non-magnetic portion; the ferric iron substrate has a different component composition from the ferrous iron substrate and the ferric iron substrate; The intermediate portion is a non-magnetic magnetic member.

2. 2. The magnetic member according to claim 1, wherein the intermediate portion is substantially made of a single austenite phase.

3. The magnetic member according to claim 1 , wherein the intermediate portion is formed by a layered manufacturing process.

4. The ferric iron substrate has a Gibbs free energy (G BCC ) and the Gibbs free energy (G FCC ) and the difference (dG = G BCC -G FCC 4. The magnetic member according to claim 1, having a component composition in which the value of .theta.

5. 2. A method for manufacturing a magnetic member according to claim 1, comprising: The method for manufacturing a magnetic member, wherein the intermediate portion is formed on the soft magnetic portion or the non-magnetic portion by directed energy deposition or powder bed fusion.

6. 6. The method for manufacturing a magnetic member according to claim 5, wherein the powder for additive manufacturing is used for additive manufacturing of the intermediate portion.

7. The powder for additive manufacturing according to claim 6, which has a composition in which the total amount of ferrite stabilizing elements is smaller than that of the first iron base material and the total amount of austenite stabilizing elements is larger than that of the second iron base material.

8. The powder for additive manufacturing according to claim 6 or 7, containing 30 to 75 mass% of Ni with respect to the entire powder.

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