JPH0969422A - Metallic magnetic material and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the title metallic magnetic material having excellent mass productivity and reliability without losing magnetic phase even if repeatedly exposed to heating and cooling steps. SOLUTION: An Sn-Ag eutectic alloy is melt-junctioned on the surface of a base substance made of austenite stainless steel to be annealed after heating at the temperature of 800-1200 deg.C. Through these procedures, the Sn diffused and infiltrated part of the austenite phase is transformed into ferrite phase thereby enabling magnetic parts 2 to be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metallic magnetic material having a non-magnetic portion and a magnetic portion and used for a brushless motor, an electromagnetic valve, an identification mark using magnetism, various sensors and the like, and a method for manufacturing the same. .

[0002]

2. Description of the Related Art Conventionally, as a disk of a brushless motor, a metal magnetic material composed of a substantially disk-shaped base body and magnetic portions arranged in the circumferential direction on the surface of the base body has been used. This metallic magnetic material is formed by joining a magnetic body as a magnetic portion to the surface of a non-magnetic base body.

However, the metal magnetic material formed by joining the magnetic bodies in this way has the drawbacks that the production is complicated and the magnetic body may peel off, resulting in low reliability. Therefore, conventionally, there has been a demand for a metal magnetic material in which a magnetic portion is selectively formed on the surface of a non-magnetic material without using bonding, and a method for producing such a metal magnetic material has been studied. .

For example, conventionally, non-magnetic (austenite)
Duplex stainless steel has been developed as a duplex metal having a structure in which a phase and a magnetic (ferrite) phase are finely mixed. However, this duplex stainless steel exhibits ferromagnetism as a whole, and the nonmagnetic portion and the magnetic portion cannot be arbitrarily arranged. There is also a method of applying a processing stress to austenitic stainless steel that is non-magnetic at room temperature to induce a martensitic structure and obtain ferromagnetism. However, this method has a drawback that it is difficult to control the generation amount of the martensite structure. Further, this method has a problem that the ferromagnetism disappears at a relatively low temperature.

Further, Japanese Patent Application Laid-Open No. 57-203747 proposes an alloy containing a predetermined amount of Mn and Co, controlling the Si content, and the balance being Fe.
The alloy can be partially heated by a laser or an electron beam and then annealed to partially obtain a magnetic phase.

[0006]

However, the alloy described in JP-A-57-203747 is complicated because it requires a large-scale device such as a laser device or an electron beam device to obtain a magnetic phase. There is a problem. In addition, this alloy has a drawback that the phase transformation from a non-magnetic phase to a magnetic phase is reversible, and the magnetic phase may disappear when used in an environment where heating and cooling are repeatedly performed. Further, this alloy has a drawback that it is necessary to irradiate a laser or an electron beam one by one, and mass productivity is poor.

The present invention was created in view of the above-mentioned problems of the conventional example, does not require a large-scale device such as a laser device or an electron beam device, is excellent in mass productivity, and can be heated and heated. It is an object of the present invention to provide a highly reliable metal magnetic material in which the magnetic phase does not disappear even after repeated cooling and a method for manufacturing the same.

[0008]

The above-mentioned problem is a metal magnetic material in which a magnetic phase is selectively formed on the surface layer of a base made of a non-magnetic metal containing Fe, and the base has an austenite phase at room temperature. And the magnetic phase is obtained by selectively introducing a non-magnetic element into the surface layer of the substrate to transform the austenite phase of the surface layer of the substrate into a ferrite phase. To do.

The substrate may be austenitic stainless steel or a two-phase metal having a mixed structure of an austenite phase and a ferrite phase. In addition, Sn can be used as the non-magnetic element. Second,
A step of depositing or welding Sn onto the surface of a base body containing a nonmagnetic metal containing Fe and having an austenite phase at room temperature; and heating the base body to 800 to 1200 ° C.
d diffusing (including permeating) n into the surface layer of the substrate,
After that, it is solved by a method for producing a metal magnetic material, which comprises a step of gradually cooling.

In the metallic magnetic material according to the present invention, a nonmagnetic element such as Sn is introduced into the surface layer of a substrate made of a nonmagnetic metal having an austenite phase, and the austenite phase in the surface layer of the substrate in the portion where the nonmagnetic element is introduced is changed. The magnetic phase is selectively formed on the surface layer of the substrate by transforming into the ferrite phase.
The nonmagnetic element is introduced by, for example, depositing or welding Sn or a Sn alloy on the surface of the substrate by printing, fusion bonding, or the like, and then heating to 800 to 1200 ° C. Further, Sn or Sn alloy powder may be attached to the substrate by a so-called cementate method, and the Sn may be diffused on the substrate surface by heating to a high temperature. Then, by heating and then gradually cooling, the austenite phase in the portion into which the non-magnetic element is introduced is transformed into a ferrite phase and becomes magnetic. In this way, the magnetic phase can be selectively formed on the surface layer of the substrate made of a non-magnetic metal.

In this case, the transformation from the austenite phase to the ferrite phase is irreversible, and the magnetic phase does not disappear even if heating and cooling are repeated. Further, since the magnetic phase is formed by heat treatment, it is possible to treat a plurality of base materials at the same time, and mass productivity is excellent. When the temperature during the heat treatment is less than 800 ° C., the transformation from the austenite phase to the ferrite phase is not sufficient and the magnetic phase cannot be obtained. Also, the heat treatment temperature is 1200
If the temperature exceeds ℃, the metal material will be deformed. Therefore, it is necessary to set the heat treatment temperature to 800 to 1200 ° C.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. (First Embodiment) FIG. 1 is a plan view showing a first embodiment of a metal magnetic material according to the present invention. The present embodiment shows an example in which the present invention is applied to a sensor unit of an automobile ABS (anti-lock braking system) device.

The substrate 1 is made of SUS316 stainless steel in the shape of a disk, and on the surface thereof, substantially rectangular magnetic portions 2 are arranged at a constant pitch in the circumferential direction. The magnetic part 2 is made to be a magnetic phase by diffusing Sn on the surface of the substrate 1 and transforming the austenite phase of the surface layer of the substrate 1 into a ferrite phase. The sensor unit of the ABS device is composed of a base body 1 mounted so as to rotate together with a tire wheel, and a Hall element for magnetic detection mounted on the vehicle body side. In the ABS device configured as described above, while the tire wheel is rotating, the hall element outputs a pulse signal corresponding to the number of revolutions. When the brake is applied to lock the wheel, the pulse signal is stopped. The ABS device controls the braking force according to the output of the hall element to stop the vehicle safely.

In the sensor part of this ABS device, the magnetic part 2 is formed by the transformation from the austenite phase to the ferrite phase even when heated by the heat generated during braking, so the phase transformation is reversible. The magnetic phase does not disappear even if heating and cooling are repeated. Therefore, the metallic magnetic material according to this embodiment has high reliability.

The method of manufacturing the metallic magnetic material according to this embodiment will be described below. First, as the substrate 1, a disk-shaped austenitic stainless steel (SUS316) is prepared.
Then, in the portion of the surface of the substrate 1 that is to be the magnetic phase, S
The n-Ag eutectic alloy is melt-bonded. Note that, instead of the melt-bonding of the Sn-Ag eutectic alloy, a paste or the like containing Sn may be attached or welded to the surface of the substrate 1 by a printing method or the like.

Next, the substrate 1 is heated at a temperature of about 850 ° C. for about 15 minutes.
After heating for a minute, Sn is diffused and permeated into the surface layer of the substrate 1. After that, it is gradually cooled at a cooling rate of about 5 to 10 ° C./minute. As a result, the austenite phase of the surface layer of the substrate 1 at the portion where Sn diffuses and diffuses is transformed into a ferrite phase and becomes magnetic, and the metallic magnetic material of the present embodiment is completed. According to this manufacturing method, after the Sn—Ag eutectic alloy is melt-bonded to the surface of the disk-shaped substrate 1, heat treatment may be performed in a heating furnace, so that a large-scale device such as a laser device or an electron beam device can be used. In addition to being unnecessary, it is easy to manufacture a large number of metal magnetic materials at the same time, and mass productivity is excellent. Further, since the transformation from the austenite phase to the ferrite phase is irreversible, the magnetic phase does not disappear even if heating and cooling are repeated, and the reliability is high.

(Second Embodiment) FIG. 2 is a plan view showing a second embodiment of the present invention. This embodiment shows an example in which the present invention is applied to a disk of a brushless motor. The base 11 is SUS
It is made of 316 stainless steel and is formed into a disc shape. A fan-shaped magnetic portion 12 is provided on the surface of the base 11 along the circumferential direction. The widths of the magnetic portions 12 in the circumferential direction are gradually changed from a large size to a small size to a large size at regular intervals.

In the metallic magnetic material of this embodiment, Sn is diffused and permeated into the surface of the disk-shaped substrate 11 as in the first embodiment,
It is formed by transforming the austenite phase on the surface of the base 11 into a ferrite phase. In this embodiment, the same effect as in the first embodiment can be obtained, and in addition, since the width of the magnetic portion in the circumferential direction of the base 11 is changed stepwise, the rotation of the motor is smooth. Has the effect.

The present invention can be applied as a so-called tilt characteristic member whose magnetic characteristics change substantially continuously, other than the above-mentioned disk of the brushless motor. Hereinafter, the results of actually manufacturing the metal magnetic material according to the present invention and examining its characteristics will be described. First, a nonmagnetic austenitic stainless steel (SUS316) sintered metal material was used as a substrate, and a Sn-Ag eutectic alloy (nonmagnetic) was melt-bonded to a desired region on the surface of the substrate. After that, this substrate was heated to 850 to 1200 ° C., and heat treatment was performed to diffuse and permeate Sn and Ag into the substrate.

Then, the substrate after the heat treatment is heated to about 5 to 10 ° C.
It was gradually cooled to room temperature at a cooling rate of / min. As a result, the portion where the non-magnetic element penetrated was transformed into a ferromagnetic ferrite phase at room temperature, and a magnetic phase could be obtained. It should be noted that the portion of the base body where the non-magnetic element has not penetrated remains non-magnetic. FIG. 3 is a photograph (magnification: 50 times) showing a metal structure in a cross section of a metal material (hereinafter, referred to as an embodiment) which has been subjected to a treatment of diffusing and permeating a nonmagnetic element into the surface layer, and FIG. 4 is a cross section of the same embodiment. Photograph showing the metallographic structure (magnification: 2
FIG. 5 is a photograph (magnification: 50 times) showing a metal structure in a cross section of a metal material (hereinafter, referred to as a comparative example) which is not subjected to a treatment for diffusing and permeating a non-magnetic element into the surface layer.
As is clear from FIGS. 3 to 5, it can be seen that the crystal state is changed in the portion where the non-magnetic element is diffused and permeated. In addition, in FIGS. 3 to 5, innumerable black dots are holes existing in the sintered metal.

FIG. 6 is a diagram showing the results of examining the crystal structures of the surfaces of the metal materials of the embodiment and the comparative example using the X-ray diffractometer. As is clear from this figure, for the metal material of the embodiment, a diffraction peak due to BCC (body centered cubic lattice) and a slight diffraction peak due to the (111) crystal structure of FCC (face cubic lattice) were detected. Further, for the untreated product, only the FCC diffraction peak was detected. From this, it was confirmed that a ferromagnetic phase was formed in the metal material of the embodiment.

Next, a vibrating sample type magnetometer (VSM)
Was used to measure the room temperature magnetic characteristics of the embodiment and the comparative example formed by using the substrate cut out from the same sintered material. The results are shown in Table 1 below.

[0023]

[Table 1]

In FIGS. 7 and 8, the horizontal axis represents magnetic field strength and the vertical axis represents magnetic flux density, and the vibration sample type magnetic measurement apparatus is used for the embodiment (FIG. 7) and the comparative example (FIG. 7). It is a figure which shows the result of having investigated the magnetization characteristic of 8). As shown in FIGS. 7 and 8 and Table 1 above, the magnetization and saturation magnetic flux density of the embodiment were about 100 times that of the comparative example.

[0025]

As described above, according to the present invention, a magnetic phase is formed by introducing a nonmagnetic element into the surface layer of a nonmagnetic metal containing Fe and transforming the austenite phase into a ferrite phase. Therefore, the magnetic phase does not disappear even if heating and cooling are repeated, and the reliability is high.

Further, in the method of the present invention, Sn is adhered to the surface of a substrate made of a non-magnetic metal having an austenite phase, and then the Sn is diffused by heat treatment to convert the austenite phase of the surface layer of the substrate into a ferrite phase. Since the magnetic phase is formed by transformation, a large-scale device such as a laser device or an electron beam device is unnecessary, and
Since a large number of substrates can be processed at the same time, the mass productivity is excellent.

[Brief description of drawings]

FIG. 1 is a plan view showing a first embodiment of the present invention.

FIG. 2 is a plan view showing a second embodiment of the present invention.

FIG. 3 is a photograph showing the metal structure of the embodiment (magnification: 50).
Times).

FIG. 4 is a photograph (magnification: 200 times) showing the metal structure of the same embodiment.

FIG. 5 is a photograph showing a metal structure of a comparative example (magnification: 50 times).
It is.

FIG. 6 is a diagram showing the results of examining the crystal structures of the surfaces of the embodiment and the comparative example using an X-ray diffractometer.

FIG. 7 is a diagram showing a result of examining the magnetization characteristic of the embodiment.

FIG. 8 is a diagram showing a result of examining magnetization characteristics of a comparative example.

[Explanation of symbols]

 1,11 Base 2,12 Magnetic part

Claims (5)

[Claims] 1. A metal magnetic material in which a magnetic phase is selectively formed on a surface layer of a base made of a non-magnetic metal containing Fe, wherein the base has an austenite phase at room temperature, and the magnetic phase is A metal magnetic material characterized in that a non-magnetic element is selectively introduced into the surface layer of a substrate to transform the austenite phase of the surface layer of the substrate into a ferrite phase. 2. The magnetic metal material according to claim 1, wherein the substrate is made of austenitic stainless steel. 3. The metal magnetic material according to claim 1, wherein the base is made of a two-phase metal having a mixed structure of an austenite phase and a ferrite phase. 4. The metal magnetic material according to claim 1, wherein the non-magnetic element is Sn. 5. A step of adhering or fusing Sn to the surface of a substrate made of a nonmagnetic metal containing Fe and having an austenite phase at room temperature, and heating the substrate to 800 to 1200 ° C. 2. A method for producing a metal magnetic material, comprising: a step of diffusing into the surface layer of 1. and a step of gradually cooling thereafter.