JP2013204144A - Motor rotor support and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotor support for a motor, which is suitable for an axial gap motor, and to provide a method for manufacturing the same.SOLUTION: A support for supporting a magnetic body arranged on the rotor of a motor is constituted of a non-magnetic cast steel which has a composition including, by mass, ≤0.3% of C, 0.1-2.0% of Si, 10-25% of Mn, 10-23% of Cr, and 0.3-0.8% of N, and optionally, one or more of 0.4-1.5% of V, ≤1.5% of Nb in terms of V+Nb, ≤0.02% of Al, ≤5.0% of Ni, ≤3.0% of Mo+1/2W, ≤3.0% of Co, and ≤0.01% of B, and the balance Fe with inevitable impurities. The support suitably has such characteristics that specific magnetic permeability is <1.005 and the 0.2% proof stress is ≥550 MPa at room temperature.

Description

  The present invention relates to a support used for a rotor of a motor and supporting a magnetic body disposed on the rotor, and a manufacturing method thereof.

Normally, rare earth magnets added with rare earth (rare earth) such as neodymium and dysprosium are used for motor magnets to exhibit high performance.
Patent Document 1 discloses an axial motor having a rotor provided with a plurality of permanent magnets having magnetic poles in a direction parallel to the rotation axis.
Patent Document 2 proposes a high-performance axial gap motor having a ferrite magnet instead of a rare earth magnet.

These axial type motors or axial gap motors have a rotor on which magnets are arranged, and the magnets are supported by a support included in the rotor. For this support, nonmagnetic steel made of austenitic stainless steel is generally used.
The support body is included in a rotor that rotates at high speed, and it is necessary to support the magnet and hold its position properly. For this reason, the support is required to have not only non-magnetic properties but also appropriate strength.
By the way, although austenitic stainless steel increases in strength by cold working, there is a problem that non-magnetic properties are impaired by work-induced transformation. For this reason, the process of obtaining a support body shape by machining from the raw material after hot forging is usually employed.

International Publication No. 2011/046108 JP 2011-010375 A

However, in the conventional manufacturing process, in order to obtain a product shape having a complicated shape, it is necessary to process the hot forging material by machining or wire cutting for a considerable time. Depending on the shape and size of the product, there are cases where processing takes as long as two weeks. Therefore, when mass production is considered, these become very big problems.
On the other hand, efficient production can be performed by obtaining the shape of the support body by casting a near net shape. However, cast products tend to have lower strength and ductility than forged steel products, and sufficient performance cannot be obtained with the same components as forged steel products.

  The present invention has been made against the background of the above circumstances, and provides a motor rotor support body made of a cast product that has high strength with nonmagnetic properties and can be efficiently manufactured, and a method for manufacturing the same. One of the purposes.

  That is, among the motor rotor supports of the present invention, the first present invention is a support that supports a magnetic body disposed on the rotor of the motor, and is composed of nonmagnetic cast steel. , By mass%, C: 0.3% or less, Si: 0.1-2.0%, Mn: 10-25%, Cr: 10-23%, N: 0.3-0.8% and the balance Has a composition comprising Fe and inevitable impurities.

  The motor rotor support according to the second aspect of the present invention is the above-described composition according to the first aspect of the present invention, wherein the composition further includes mass%, V: 0.4 to 1.5%, Ni: 5.0% or less, Mo + 1. / 2W: 3.0% or less, Co: 3.00% or less, B: One or two or more of selected elements of 0.01% or less are contained.

  The motor rotor support according to the third aspect of the present invention includes, in the second aspect of the present invention, at least V among the selected components, and further contains, by mass%, Nb at 1.5% or less in terms of V + Nb. It is characterized by.

  The motor rotor support according to the fourth aspect of the present invention is characterized in that, in any of the first to third aspects of the present invention, the composition further contains Al: 0.02% or less.

  The motor rotor support of the fifth aspect of the present invention is characterized in that, in any of the first to fourth aspects of the present invention, P and S in the inevitable impurities are each 0.03% or less.

  In the motor rotor support of the sixth aspect of the present invention, in any one of the first to fifth aspects of the present invention, the nonmagnetic cast steel is a precipitation hardening cast steel made of either or both of VN and NbN. Features.

  The motor rotor support according to the seventh aspect of the present invention is that, in any one of the first to sixth aspects of the present invention, the relative permeability is less than 1.005, and the 0.2% proof stress at room temperature is 550 MPa or more. Characterize

  The motor rotor support according to the eighth aspect of the present invention is characterized in that, in any of the first to seventh aspects of the present invention, the magnetic body includes a rare earth magnet or a non-rare earth magnet.

  The motor rotor support according to the ninth aspect of the present invention is characterized in that, in the eighth aspect of the present invention, the non-rare earth magnet is a ferrite magnet.

  A motor rotor support according to a tenth aspect of the present invention is characterized in that, in any of the first to ninth aspects of the present invention, the magnetic body includes a dust core.

  The motor rotor support according to an eleventh aspect of the present invention is the motor rotor support according to any one of the first to tenth aspects of the present invention, wherein the nonmagnetic cast steel is manufactured by a near net shape casting method. .

  According to a twelfth aspect of the present invention, there is provided a method for manufacturing a motor rotor support, comprising: casting a raw material with the composition material according to any one of the first to sixth aspects of the invention; And an aging treatment.

  According to a thirteenth aspect of the present invention, there is provided a method for producing a motor rotor support according to the twelfth aspect of the present invention, wherein the solution treatment condition is 1000 to 1250 ° C., the holding time is 5 minutes or more, and the aging treatment condition is 600. -1000 degreeC and holding time are 30 minutes or more, It is characterized by the above-mentioned.

  According to a fourteenth aspect of the present invention, there is provided a motor rotor support manufacturing method according to the twelfth or thirteenth aspect of the present invention, wherein finishing is performed after the aging treatment.

In the present invention, the motor rotor support is constituted by the nonmagnetic cast steel having the above composition. Non-magnetic cast steel has good non-magnetic properties and also shows high strength at room temperature (for example, 5 ° C. to 30 ° C.).
The magnetic material can be supported without affecting the magnetism of the rotor due to the good non-magnetic properties in the present invention. Moreover, a magnetic body can be stably supported by having high intensity | strength.

  Next, this invention demonstrates the effect | action and limitation reason of each component in nonmagnetic cast steel. In addition, all content shown below is shown by the mass%.

C: 0.3% or less C contributes to increasing the strength by precipitation of VC or NbC, but if contained excessively, the ductility is lowered, so the upper limit is made 0.3%. For the same reason, it is desirable to set the upper limit to 0.25%. Moreover, in order to acquire the said effect | action, it is desirable to contain 0.01% or more.

N: 0.3-0.8%
When N is contained, VN and NbN are produced, and contribute to increasing the strength while maintaining ductility. For this reason, it contains 0.3% or more. However, if it is contained excessively, nitrogen causes blowhole generation, so the upper limit is made 0.8%. For the same reason, it is desirable to set the lower limit to 0.4% and the upper limit to 0.7%.

Si: 0.1 to 2.0%
Since Si is used as a deoxidizing material, it needs to contain 0.1%. However, since Si is a ferrite phase forming element, if it is contained excessively, the ferrite phase is precipitated and the cold workability is also deteriorated, so the upper limit is made 2.0%. For the same reason, it is desirable to set the lower limit to 0.3% and the upper limit to 1.0%.

Mn: 10-25%
Mn is an austenite phase-forming element and needs to be contained at 10% or more in order to increase the N solubility. However, since an intensity | strength will fall when it contains excessively, an upper limit shall be 25%. For the same reason, it is desirable to set the lower limit to 12% and the upper limit to 23%, and it is even more desirable to set the lower limit to 14% and the upper limit to 22%.

Cr: 10 to 23%
Cr needs to be contained in an amount of 10% or more in order to ensure corrosion resistance and increase N solubility. However, since Cr is a ferrite forming element, if it is excessively contained, the ferrite phase precipitates, so the upper limit is made 23%. For the same reason, it is desirable to set the lower limit to 12% and the upper limit to 22%, and it is more desirable to set the lower limit to 14% and the upper limit to 21%.

V: 0.4 to 1.5%
V is an element necessary for achieving higher strength while maintaining ductility by precipitation of VN, and is contained as desired. In order to obtain the effect, 0.4% or more is necessary. However, if the content is excessive, the ductility is deteriorated, so the upper limit is made 1.5%. For the same reason, it is desirable to set the lower limit to 0.5% and the upper limit to 1.0%.

Nb: Nb + V of 1.5% or less When Nb is contained, NbN is produced, and contributes to high strength by a synergistic effect with NV. However, if the content is excessive, the toughness deteriorates, so the upper limit is made 1.5% Nb + V. In addition, in order to fully obtain the said effect | action, it is desirable to contain 0.5% or more by Nb + V.

Al: 0.02% or less Al is added as a deoxidizing material. However, if excessively contained, nitrides are formed and the toughness is lowered.

Ni: 5.0% or less Ni is an austenite phase forming element, and is contained as desired. However, if it exceeds 5.0%, the strength decreases, so the upper limit is made 5.0%. In addition, when it contains if desired, in order to acquire the effect | action fully, containing 1.0% or more is desirable, and containing 1.5% or more is still more desirable. Ni may be inevitably mixed with scrap or the like, and may be contained in an amount of less than 1.0% as an unavoidable impurity.

Mo + 1 / 2W: 3.0% or less W and Mo are components that improve the strength, but if included excessively, the cold workability is deteriorated. It can contain in the following ranges. In addition, when it contains if desired, in order to fully obtain the effect | action, it is desirable to contain 0.5% or more.

Co: 3.00% or less Co is an austenite phase forming element. However, since it is an expensive component, it can be contained as desired up to 3.00%. In addition, when it contains if desired, in order to fully obtain the effect | action, it is desirable to contain 0.5% or more.

B: 0.01% or less B strengthens by solid solution and can be expected to be strengthened by fine nitrides, and improves strength and toughness. However, if contained excessively, it becomes coarse nitrides and causes toughness to decrease. Therefore, it can be contained within a range of 0.01% or less if desired. In addition, when making it contain depending on necessity, in order to fully obtain the effect | action, it is desirable to contain 0.001% or more.

Inevitable impurities P and S: 0.03% or less P and S that can be included as inevitable impurities affect toughness and hot workability. Therefore, it is desirable that P and S be 0.03% or less.

Relative permeability: less than 1.005 0.2% proof stress: 550 MPa or more The above-mentioned nonmagnetic cast steel desirably has a relative permeability of less than 1.005 and a 0.2% proof stress at room temperature of 550 MPa or more. . When the relative permeability is less than 1.005, no magnetic influence is exerted on the rotor. Further, when the 0.2% proof stress is 550 MPa or more, the magnetic body can be reliably supported, and the weight can be easily reduced. In the nonmagnetic steel, the elongation is desirably 5% or more. If the elongation is low, the material becomes brittle and the possibility of breakage increases during use. The elongation should be higher and more preferably 15% or more.

Manufacturing Process The motor rotor support of the present invention is made of cast steel obtained by casting.
As a casting method, a generally known method such as sand mold casting or precision casting can be appropriately employed. It is desirable to manufacture by near net shape, and examples thereof include a lost wax method and a shell mold method which are precision casting.

Solution treatment and aging treatment It is desirable that the produced cast steel is subjected to solution treatment and aging treatment. Note that depending on the strength required, only the solution treatment may be performed, and it is within the scope of the present invention to perform neither the solution treatment nor the aging treatment.

Solid solution treatment: 1000 to 1250 ° C. × 5 minutes or more Solid solution treatment conditions are not particularly limited, but 1000 to 1250 ° C., holding time is 5 minutes or more, and cooling methods include water cooling, oil cooling, and air cooling including fan cooling. Is done.

Aging treatment: 600 to 1000 ° C. × 30 minutes or more Further, after the solution treatment, the strength of the rotating support can be further increased by applying the aging treatment. Although the conditions of an aging treatment are not specifically limited, 600-1000 degreeC x 30 minutes or more can be illustrated.

Finishing The cast steel product can be made into a product shape by finishing. The content of the finishing process is not particularly limited, and a generally known method such as a cutting process or a polishing process can be appropriately employed.

  As described above, according to the present invention, there is an effect that a rotor support for a motor that can be manufactured by a casting method and has sufficient strength even in the centrifugal direction can be obtained.

It is a figure which shows the motor rotor support body of one Embodiment of this invention, (a) is a front view, (b) is the II sectional view taken on the line of (a). Similarly, it is a figure which shows the motor rotor support body which has arrange | positioned the permanent magnet, (a) is a front view, (b) is the II-II sectional view taken on the line of (a).

Below, the motor rotor support body of one Embodiment of this invention is demonstrated based on FIG.
The motor rotor support 1 of this embodiment is made of non-magnetic cast steel, and preferably has a relative permeability of less than 1.005, a 0.2% proof stress at room temperature of 550 MPa or more, and an elongation of 15% or more. It has the characteristics.

  The motor rotor support 1 has a bearing portion 3 which is formed in a thin disk shape as a whole and has a shaft hole 2 formed in the center. Ring-shaped ribs 4 are formed on the outer peripheral side of the bearing portion 3 at intervals, and an outer edge ring 5 is formed on the outermost peripheral edge. Further, 16 partition walls 6 are formed radially at equiangular intervals between the bearing portion 3, the ring-shaped rib 4 and the outer ring 5.

A space surrounded by the partition walls 6, 6, the ring-shaped rib 4, and the outer edge ring 5 is allocated to the magnet storage portion 7. A permanent magnet 10 having magnetic poles having different polarities on both axial surfaces is accommodated in the magnet accommodating portion 7. The permanent magnets 10 are arranged so that adjacent ones in the circumferential direction have magnetic poles having different polarities. A rotation shaft (not shown) can be attached to the shaft hole 2 of the motor rotor support 1 to be used as a motor rotor support provided for the rotor. In addition, you may use the motor rotor support body 1 as a rotor as it is.
In the above description, only the permanent magnet is described as the magnetic body supported by the motor rotor support body. However, the magnetic body may have a structure that supports a ferromagnetic body.

  The motor rotor support of this embodiment is not particularly limited in output, etc., but can be suitably used particularly for motors of 5 kW or more, can be mass-produced and can be manufactured at low cost, In particular, it can be used as a support suitable for a rotor of an axial gap motor.

Next, the manufacturing process of the motor rotor support will be described.
It melt | dissolves in melting furnaces generally used, such as an atmospheric high frequency furnace so that it may adjust to an above described composition. As the deoxidizer, commonly used ones such as Ca-Si can be appropriately used.
The obtained steel ingot is cast into a sand mold or a mold at a temperature sufficiently higher than the melting point.
As a casting method, a generally known method such as sand mold casting or precision casting can be appropriately employed. Precision casting is synonymous with near net shape casting, and the lost wax method is exemplified.

In casting, it is desirable to adopt a casting method in which hot water flows from the outer surface portion of the support body into the central portion so that the flow of hot water is not disturbed and casting defects do not occur.
In order to prevent casting defects from occurring at locations where the hot water flow stagnate, it is desirable to arrange hot water, chillers or the like to cause directional solidification. In addition, it is applicable to cover the hot metal surface with a heat insulating material immediately after casting.
It is also possible to appropriately prevent the occurrence of casting defects due to local solidification delay by arranging a metal cooling metal in the mold.

  By adopting the above casting method, it is possible to efficiently manufacture even a support having a complicated final shape. In this regard, the conventional integral molding by plastic working such as forging is disadvantageous in terms of manufacturing cost if cutting for obtaining the final shape, laser cutting, or the like is included.

The obtained cast steel product is subjected to only a solid solution treatment or a solid solution treatment and an aging treatment as desired.
The solution treatment can be performed under conditions of 1000 to 1250 ° C. and a holding time of 5 minutes or more.
The aging treatment can be performed under conditions of 600 to 1000 ° C. and a holding time of 30 minutes or more.

  Moreover, it is also possible to repair the casting defect which remained unavoidably by repair welding. A welding rod made of a common material is preferable as the welding material, but a welding rod for austenitic stainless steel may be used. After repair welding, stress relief annealing at 300 to 700 ° C. may be performed.

  Cast steel products can be finished to obtain the final product shape. Examples of the finishing process include cutting process and polishing process in this embodiment, but the type of the process is not particularly limited in the present invention.

The components shown in Table 1 (the balance is Fe and inevitable impurities, P is 0.025% or less, S is 0.005% or less) and dissolved in an atmospheric high-frequency furnace to form a gate, runner, weir, hot water, etc. Was cast into a sand mold with a near net shape, and a disk-shaped test material equivalent to the support was produced. For comparison, test samples of commercially available SUS304 stainless steel (steel No. 28) and commercially available SUS316 stainless steel (steel No. 27) were also obtained.
The manufactured disk-shaped test material was subjected to a water-cooling solution treatment under the conditions shown in Table 2 at 1050 to 1150 ° C., a holding time of 3 hours. After the solution treatment, an aging treatment was performed under the conditions shown in Table 2 at an aging temperature of 900 ° C. and a holding time of 1 hour. Test materials with a solid solution treatment were also prepared and compared with and without an aging treatment.

From these test materials, at room temperature, a tensile test, a relative permeability measurement by a magnetic balance method, and an evaluation of immersion corrosion resistance were performed.
A test material having a composition outside the scope of the present invention was also prepared as a comparative material.
In addition, in the tensile test, the test which measures the tensile property in room temperature by JISZ2241 was implemented using the JIS14A test piece of JISZ2201 as a tensile test piece.
The immersion corrosion resistance was evaluated by immersing the test material in normal temperature tap water for 10 days, visually observing no clear rust as ◎, slightly rusting as ○, and rusting as x on the entire surface.

The test results are shown in Table 2. In comparison with the comparative material, depending on the element outside the component range of the present invention, there are those with low strength, high relative permeability, and insufficient corrosion resistance, and the present invention examples sufficiently satisfy these characteristics. I understand that.
Moreover, it turns out that the example of this invention has shown the intensity | strength higher than SUS304 type stainless steel or SUS316 type stainless steel.

From the above, the developed material of the present invention has sufficient strength, non-magnetism and corrosion resistance even if the support is manufactured by casting, and can be manufactured with a near net shape, so it is less expensive than the conventional manufacturing method. Can be manufactured.
Moreover, according to the precision casting method such as the lost wax method, it is possible to obtain a cast product that is closer to the product shape and has a clean casting surface, and thus can be said to be suitable for manufacturing a support having a complicated shape.

DESCRIPTION OF SYMBOLS 1 Motor rotor support body 2 Shaft hole 3 Bearing part 4 Ring-shaped rib 5 Outer ring 6 Partition wall 7 Magnet accommodating part 10 Permanent magnet

Claims (14)

  A support for supporting a magnetic body disposed on a rotor of a motor, which is made of nonmagnetic cast steel, and the nonmagnetic cast steel is in mass%, C: 0.3% or less, Si: 0.1-2 Motor rotor characterized by having a composition of 0.0%, Mn: 10 to 25%, Cr: 10 to 23%, N: 0.3 to 0.8%, and the balance consisting of Fe and inevitable impurities Support.   In addition to the above composition by mass, V: 0.4 to 1.5%, Ni: 5.0% or less, Mo + 1 / 2W: 3.0% or less, Co: 3.00% or less, B: 0.0. The motor rotor support according to claim 1, wherein the motor rotor support comprises one or two or more of selected components composed of 01% or less.   3. The motor rotor support according to claim 1, wherein among the selected components, at least V is contained, and further, by mass%, Nb is contained by 1.5% or less in terms of V + Nb.   The motor rotor support according to any one of claims 1 to 3, wherein the composition further contains Al: 0.02% or less in terms of mass%.   The motor rotor support according to any one of claims 1 to 4, wherein P and S in the inevitable impurities are each 0.03% or less.   6. The motor rotor support according to claim 1, wherein the nonmagnetic cast steel is a precipitation hardening cast steel made of either or both of VN and NbN.   The motor rotor support according to claim 1, wherein the relative permeability is less than 1.005, and the 0.2% proof stress at room temperature is 550 MPa or more.   The motor / motor rotor support according to claim 1, wherein the magnetic body includes a rare earth magnet or a non-rare earth magnet.   9. The motor rotor support according to claim 8, wherein the non-rare earth magnet is a ferrite magnet.   The motor rotor support according to any one of claims 1 to 9, wherein the magnetic body includes a dust core.   The motor rotor support according to any one of claims 1 to 10, wherein the nonmagnetic cast steel is manufactured by a near net shape casting method.   A method for producing a motor rotor support, comprising casting a shaped material with the composition material according to claim 1 and subjecting the shaped material to a solution treatment and / or an aging treatment. The solution treatment conditions are 1000 to 1250 ° C., holding time of 5 minutes or more,
The method for producing a motor rotor support according to claim 12, wherein the aging treatment conditions are 600 to 1000 ° C and the holding time is 30 minutes or more.   The method of manufacturing a motor rotor support according to claim 12 or 13, wherein finishing is performed after the aging treatment.

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