JP6941483B2 - Magnetostrictive member and its manufacturing method - Google Patents

Description

The present invention relates to a magnetostrictive member used for vibration power generation of a power source for an operation monitor of an industrial machine such as a compressor, lighting, a power source such as a remote control switch for home appliances and automobiles, or a driving element such as an ultrasonic motor or a displacement control linear actuator. The present invention relates to a magnetostrictive member used in the above, a magnetostrictive member used for a vibrator such as an acoustic element, and a method for manufacturing the same.

As the super-magnetostrictive material, a rare earth transition metal magnetostrictive material represented by Tb-Dy-Fe shown in Japanese Patent Publication No. 6-2635, Japanese Patent Publication No. 2002-531701 and Japanese Patent Publication No. 7-100839 is known. There is. The magnetostrictive amount of this type of magnetostrictive material exceeds 1000 ppm, and the magnetostrictive amount (30 ppm) of permendur (Fe50% -Co50% alloy) known as a magnetic material and the magnetostrictive alloy Alfel (Fe87% -Al13%) It is an order of magnitude larger than the amount of magnetostriction (70 ppm).

However, since this magnetostrictive material is made from an expensive rare earth transition metal, the magnetostrictive material itself is very expensive, and its structure is a Laves-type intermetallic compound, so it is very brittle and has a required shape. Difficult to process. Therefore, the fields of application are limited, and devices and actuators using this magnetostrictive material are not widely used.

On the other hand, although the amount of magnetostriction is not as large as that of Tb-Dy-Fe-based materials, the use of Fe-Ga-based alloys which show a large amount of magnetostriction of about 100 to 300 ppm and can be machined is being studied. As a material used for vibration power generation, a Fe-Ga alloy is convenient because it can be put into practical use if the amount of magnetostriction is about 100 to 300 ppm, and its performance as a precision actuator or a vibrator is sufficient.

Further, a magnetostrictive material such as a Tb-Dy-Fe-based material or a Fe-Ga-based alloy causes a large magnetostriction to appear in a specific direction of the crystal. A single crystal member with the same maximum orientation is optimal.

There are a bridgeman method, a pulling method, a zone melting method, etc. as a method for producing a single crystal, but since these single crystal production methods have extremely low productivity, a powder metallurgy method (Japanese Patent No. 3452210) and a quenching solidification method are used. Proposed a method for producing an alloy strip by Has been done. Further, as shown in Japanese Patent Publication No. 2012-500333, a method for producing a thin film by combining hot working and cold working has also been proposed.

The insides of the members manufactured by these various manufacturing methods are all polycrystalline, and it is impossible to match all the crystal orientations in the members with the orientations that maximize the magnetostriction, and the magnetostrictive characteristics are higher than those of single crystal members. There was a problem that it was inferior. In addition, there is a problem that only thin bands and thin films can be manufactured by the method of manufacturing alloy strips by the rapid cooling and solidification method or the method of manufacturing thin films by combining hot working and cold working, and the applicable range of members is limited. there were.

In addition, in the method of manufacturing parts by pressurizing and sintering flakes and powdered raw materials produced by the powder metallurgy method and the liquid quenching and solidifying method, special equipment such as atomizing equipment, quenching and solidifying equipment, and pressure sintering equipment are used. It is costly because it requires. Further, in the powder processing process, a special environment is required to prevent the deterioration of the magnetostrictive characteristics due to the mixing of foreign substances and impurities, which is also a factor of cost increase.

As a method for solving these problems, in Japanese Patent Application Laid-Open No. 2016-138028, a magnetostrictive member which is cheaper than the conventional single crystal manufacturing method and can be used for vibration power generation, has high performance, reliability, and versatility. And its manufacturing method are disclosed. However, since the ingot produced by the one-way solidification method is cut into strips, the cut strips are separated into individual single crystals at the grain boundaries, and then the magnetostrictive member is cut out by discharge processing, each single crystal is cut out. The yield rate of extracting the magnetostrictive member from the crystal was poor. Further, since Ga, which is a raw material of the magnetostrictive member, has a high rarity value and is expensive, there is room for manufacturing the magnetostrictive member at a lower cost.

Special Fair 6-2635 Gazette Special Table 2002-531701 Special Fair 7-100839 Gazette Japanese Patent No. 3452210 Japanese Patent No. 40533328 Japanese Patent No. 4814085 Special Table 2012-500333 Japanese Unexamined Patent Publication No. 2016-138028

The present invention has been made in order to solve the above-mentioned conventional problems, and is cheaper than the magnetostrictive member manufactured by the conventional single crystal manufacturing method and can be easily manufactured. It is an object of the present invention to provide a high-performance, highly reliable, and highly versatile magnetostrictive member that can be used as a power source for vibration power generation that extracts electric energy from the vibration of a motor or a drive element such as a displacement control actuator. Another object of the present invention is to provide a magnetostrictive member having less variation in magnetostrictive characteristics than a conventional magnetostrictive member.

In order to achieve the above object, the invention according to claim 1 of the present application is a steel ingot formed by a one-way solidification method and composed of one coarse crystal grain having a <100> orientation of crystals in the longitudinal direction. Fe-Ga-Cu alloy single crystal, or Fe-Ga-Cu alloy single crystal formed by separating into individual single crystals at the grain boundaries of a steel ingot composed of a plurality of coarse crystal grains. The Fe-Ga-Cu alloy is a magnetic strain member formed by cutting out by discharge processing at a position where the <100> orientation of the alloy crystal is aligned in a direction requiring magnetic strain of the magnetic strain member from the crystal. It is characterized by containing Ga: 17.5 to 23.5% and Cu: 0.04 to 2.4% in mass%, and the balance is composed of Fe and unavoidable impurities.

Further, in order to achieve the above object, in the invention according to claim 2 of the present application, the surface of the magnetostrictive member formed by cutting out by the electric discharge machining is subjected to the electric discharge machining by a polishing process that does not introduce strain into the magnetostrictive member. It is characterized in that it is a smooth surface from which minute irregularities generated at the time of the above are removed.

Further, in order to achieve the above object, the invention according to claim 3 of the present application contains Ga: 17.5 to 23.5% and Cu: 0.04 to 2.4% in mass%, and the balance is After holding the Fe-Ga-Cu alloy consisting of Fe and unavoidable impurities in the furnace above the melting temperature for a certain period of time, the molten alloy is pulled out of the furnace at a constant speed to solidify the molten alloy in one direction. After the step and the step of unidirectional solidification, when the solidified steel ingot obtained in the step of unidirectional solidification is composed of a plurality of coarse crystal grains, individual single crystals are formed at the grain boundaries. The <100> orientation of the single crystal obtained in the step of separating into the above and the step of solidifying in one direction or the step of separating into the individual single crystals is set in the direction requiring the magnetic strain of the magnetic strain member by discharge processing. It is characterized by consisting of a process of aligning and cutting out.

Further, in order to achieve the above object, in the invention according to claim 4 of the present application, the surface of the magnetostrictive member obtained by the step of cutting out by the electric discharge machining is subjected to a polishing treatment that does not introduce strain into the magnetostrictive member. The present invention is characterized by having a step of removing minute irregularities generated during the electric discharge machining to make the surface smooth.

Further, in order to achieve the above object, the invention according to claim 5 of the present application is characterized in that the constant speed is set to 20 mm / hour or less.

As described above, the magnetic strain member according to the present invention includes a step of manufacturing a unidirectional solidified steel ingot with a simple and inexpensive melting-casting facility, and a step of separating the manufactured unidirectional solidified steel ingot into individual single crystals. Since it is manufactured by a process of cutting out a magnetic strain member from the separated single crystal to the size and shape required for electric discharge machining, it can be manufactured very inexpensively and easily. Further, the magnetostrictive member manufactured by the above steps is characterized by high performance, high reliability, high versatility, and little variation in magnetostrictive characteristics.

An apparatus used in the present invention to melt a magnetostrictive alloy and solidify the melted magnetostrictive alloy in one direction. FIG. It is a vertical sectional view of the device which shows the process. It is a photograph of a unidirectional solidified steel ingot B separated into two solidified by the apparatus used in the present invention (FIG. 1), (I) is a front photograph of one solidified steel ingot B1, and (II) is a back surface thereof. The photograph, (III) is a plan photograph thereof, (IV) is a bottom photograph thereof, and (V) is a front photograph of the other solidified steel ingot B2.

Hereinafter, the present invention will be described in detail with reference to Examples shown in the drawings, but the present invention is not limited thereto. FIG. 1 is a device for melting a Fe-Ga-Cu alloy and unidirectionally solidifying the melted magnetostrictive alloy, and FIG. 1 in the figure is a tube furnace. Reference numeral 2 denotes a core tube vertically arranged in the center of the tubular furnace 1, and a heater 3 and a heat insulating material 4 made of electric resistors are installed so as to surround the core tube 2 on the outside of the core tube 2. Has been done.

Reference numeral 5 denotes a crucible arranged in the core tube 2, which is placed on the crucible support base 6, and the crucible support 6 is configured to move up and down in the vertical direction by the lifting device 7 via the crucible support rod 8. There is. Reference numeral 9 is an electric heat pair inserted inside and outside the core tube 2, and reference numeral 10 is a vacuum exhaust pipe. One end side of the vacuum exhaust pipe 10 communicates with a vacuum pump (not shown) and the other end side communicates with the core pipe 2. , The inside of the core tube 2 can be put into a vacuum state or an atmosphere state by various gases with the above-mentioned vacuum pump.

Therefore, in the tubular furnace 1 shown in FIG. 1, the magnetostrictive alloy material A is put in the crucible 5 installed in the core tube 2, and the magnetostrictive alloy material A in the crucible 5 is put in the heater 3 installed in the tubular furnace 1. Is heated above its melting temperature to bring it into a melting state (see I in FIG. 1). Then, the magnetostrictive alloy material Aa in the molten state is held in the tubular furnace 1 in which the temperature inside the furnace is kept constant for a certain period of time. In this case, the temperature inside the tube furnace 1 may be kept constant, and it is not necessary to control the temperature in a complicated manner.

After holding the molten magnetic strain alloy material Aa in the tubular furnace 1 for a certain period of time, the crucible support 6 is lowered by the elevating device 7, and the crucible 5 and the inside of the crucible 5 are placed on the crucible support 6. The magnetic strain alloy material Aa in the molten state is gradually pulled out from the inside of the tube furnace 1 to the outside of the tube furnace 1 (see II in FIG. 1).

By gradually pulling out the magnetostrictive alloy material Aa from the inside of the tubular furnace 1 to the outside of the tubular furnace 1 and downward by the elevating device 7, the magnetostrictive alloy material Aa in the rutsubo 5 solidifies in one direction from the lower part to the upper part of the rutsubo 5. Therefore, crystal growth occurs in the direction of the <100> orientation of the crystal having the maximum magnetostriction, and a columnar crystal (single crystal D) having the <100> orientation of the crystal in the longitudinal direction of the ingot B is obtained.

Further, by pulling out the magnetostrictive alloy material Aa in the molten state from the inside of the furnace to the outside of the furnace at a sufficiently slow speed, the magnetostrictive alloy material Aa solidifies at a very slow speed, so that coarse crystal grains can be obtained. In order to obtain sufficiently coarse crystal grains, it is desirable that the descent rate of the material is 20 mm / hour or less. The material descent speed may be constant during operation.

In the present invention, a temperature gradient is provided in a furnace such as a single crystal manufacturing apparatus, a highly accurate position control mechanism and control device for controlling material movement according to crystal growth, or a crystal growth direction is controlled. The delicate control required to produce a conventional single crystal, such as the operation of bringing the seed crystal into contact with the surface of the molten metal in the early stage of solidification of the material and the use of a specially shaped lube to limit nuclear growth. And the mechanism for that is not required, and the manufacturing mechanism can be a simple and inexpensive facility.

FIGS. 2 (I) to 2 (V) are photographs showing the appearance of the steel ingot B of the Fe-Ga-Cu magnetostrictive alloy material A solidified by the unidirectional solidifying device after polishing the surface. , The ingot B is in a state of being separated into two ingots B1 and B2 along the grain boundary C. FIG. 2 (I) is a front photograph of one of the ingots B1, (II) is a rear view photograph of the ingot B1, (III) is a plan photograph of the ingot B1, and (IV) is a bottom photograph of the ingot B1. Further, FIG. 2 (V) is a front view of the other steel ingot B2.

As shown in FIGS. 2 (I) to 2 (V), the steel ingots B1 and B2 are formed of a plurality of large single crystals D. The lines C visible on the surfaces and fracture surfaces of the steel ingots B1 and B2 are the boundaries of the individual single crystals D, that is, the grain boundaries.

As described above, it was found that the Fe-Ga-Cu alloy obtained by adding Cu to the Fe-Ga alloy has a much weaker grain boundary bonding force than the Fe-Ga alloy. This is because Fe-Cu alloys are separated into two phases and segregation is strongly generated. Therefore, in a solidification process in which solidification proceeds very slowly such as unidirectional solidification, Cu segregates at the grain boundaries C and grains. This is probably because it makes the world vulnerable.

Therefore, as described in Patent Document 8, it is possible to easily separate individual single crystals D at grain boundaries C without cutting them into strips of a required size from the steel ingot B. Then, the magnetostrictive member according to the present invention can be obtained by cutting out the separated single crystal D by aligning the direction requiring magnetostriction with the <100> direction of the single crystal D by electric discharge machining.

In this embodiment, the ingot B is composed of a plurality of coarse crystal grains, but when the ingot B is composed of one coarse crystal grain (single crystal D). It is not necessary to separate as described above, and the magnetostriction according to the present invention is obtained by cutting out from the steel ingot B (single crystal D) by aligning the direction requiring magnetostriction with the <100> orientation of the single crystal D. A member is obtained.

Therefore, in the manufacturing process of the magnetostrictive member according to the present invention, the step of cutting out the steel ingot B into a strip shape as described in Patent Document 8 can be omitted, so that the magnetostrictive member can be easily formed as compared with the conventional case. Can be manufactured. Further, since the above step of cutting out the steel ingot B into strips can be omitted, it is not necessary to unnecessarily divide the individual single crystal D, and the magnetostrictive member can be cut out into the shape with the best yield, so that the yield loss Can be reduced, and the magnetostrictive member can be manufactured at a lower cost than before.

Further, as shown in the following examples, the magnetostrictive member according to the present invention made of the Fe-Ga-Cu alloy obtained by adding Cu to the Fe-Ga alloy has a higher Ga ratio than the Fe-Ga-Cu alloy. It is possible to obtain a magnetostrictive amount that is almost the same as that of a magnetostrictive member made of a −Ga alloy. Therefore, even if the Fe-Ga alloy has a low Ga ratio, a sufficient amount of magnetostriction can be obtained by adding Cu, so that the magnetostrictive member can be manufactured at a lower cost than before.

Further, in the Fe-Ga alloy containing almost no Cu, there is a large difference in the amount of magnetostriction between the magnetostrictive members having the same constituent components, whereas in the Fe-Ga-Cu alloy, the magnetostrictive members having the same constituent components have a large difference. There is little variation in the amount of magnetostriction and the magnetostrictive characteristics are stable. Therefore, from the Fe-Ga-Cu alloy, a magnetostrictive member having higher reliability than that from the Fe-Ga alloy can be obtained.

Hereinafter, as an example, a magnetostrictive member according to the present invention made of a Fe-Ga-Cu alloy, a magnetostrictive member made of a Fe-Ga alloy commercially available in the United States, which is currently the only conventional material available, and Cu as a comparative example are inevitable. Table 1 shows the measurement results of the magnetostrictive member made of Fe-Ga alloy contained at the target impurity level. The numerical values shown in Table 1 indicate that the magnetostrictive members (test pieces) of the example, the conventional material, and the comparative example are installed in the solenoid coil, and a current is passed through the solenoid coil to generate a magnetic field in the coil, which is generated in the magnetostrictive member. It is a numerical value when the amount of magnetostriction to be applied is measured with a strain gauge.

The magnetostrictive member (test piece) used for the measurement was cut out into dimensions of width 6 mm × thickness 0.5 mm × length 16 mm by electric discharge machining. The magnetostrictive member of the conventional material 1 is cut out from a columnar crystal polycrystal, and the magnetostrictive member according to Examples and Comparative Examples is cut out from a single crystal. Further, at the time of cutting out, the single crystal was cut out with the <100> orientation aligned in the longitudinal direction of the magnetostrictive member requiring magnetostriction. Then, the amount of magnetostriction in the longitudinal direction was measured by matching the longitudinal direction of the magnetostrictive member with the direction of the magnetic field lines.

Although the magnetostrictive members according to the conventional material 1, Comparative Example 2 and Comparative Example 3 are cut out from the same steel ingot, there is a large difference in the amount of magnetostriction between the magnetostrictive members (test pieces). On the other hand, the magnetostrictive members according to Examples 1 to 3 having a Cu ratio of 0.04% by mass or more all show a magnetostrictive amount substantially equal to the magnetostrictive amount of the magnetostrictive member having good magnetostrictive characteristics according to the conventional material 1. , There is almost no difference between the magnetostrictive members. In this way, by adding Cu to the Fe-Ga alloy to obtain a Fe-Ga-Cu alloy having a Cu ratio of 0.04% by mass or more, the effect of preventing a large variation in the amount of magnetostriction between the magnetostrictive members can be obtained. At the same time, a highly reliable magnetostrictive member can be obtained.

Further, the magnetostrictive members according to Examples 1 to 5 made of Fe-Ga-Cu alloy having a Cu ratio of 0.04% by mass or more showed almost the same amount of magnetostriction even though the Ga ratio was different. .. That is, even if the Fe-Ga alloy has a slightly different Ga ratio, by adding Cu to obtain a Fe-Ga-Cu alloy having a Cu ratio of 0.04% by mass or more, a high level (magnetostriction amount of 240 ppm) is obtained. It is possible to obtain a magnetostrictive member having stable magnetostrictive characteristics (before and after).

On the other hand, if Cu is excessively added, the Cu single phase or the Cu compound phase is dispersed and precipitated as foreign matter in the Fe-Ga alloy matrix in an island shape, which deteriorates the magnetostrictive property. Even if the Cu ratio of the member was increased to 2.4% by mass, no precipitate phase was observed that deteriorated the magnetostrictive characteristics. Therefore, it is desirable that the Cu ratio of the magnetostrictive member according to the present invention is 2.4% by mass or less.

The Ga ratio of the magnetostrictive member according to the second embodiment is 17.7% by mass, which is considerably smaller than the Ga ratio of the magnetostrictive member according to the conventional material 1, but it is equivalent to the magnetostrictive member according to the conventional material 1 by adding Cu. The amount of magnetostriction is generated. Therefore, even if the Ga ratio of the Fe-Ga alloy is reduced, a sufficient amount of magnetostriction can be obtained by adding Cu to obtain a Fe-Ga-Cu alloy having a Cu ratio of 0.04% by mass or more. It is possible to significantly reduce the content of Ga, which has a high rarity value and is expensive, and it is possible to manufacture a high-performance magnetostrictive member at a lower cost than before.

According to the research by the inventors, it is found that good magnetostrictive characteristics can be obtained when the upper limit of the Ga ratio of the Fe-Ga-Cu alloy of the magnetostrictive member according to the present invention is up to 23.5% by mass. ing. Since Ga is expensive, it is not a good idea to increase the content ratio from the viewpoint of cost effectiveness.

After the magnetostrictive member is cut out by the electric discharge machining, the machined surface is polished while paying close attention so as not to introduce strain into the magnetostrictive member. Specifically, it includes, but is not limited to, electrolytic polishing, chemical polishing, or polishing with wet emery paper and buff. Then, by these polishing treatments, minute irregularities generated during electric discharge machining are smoothly removed. Since the polishing treatment as described above does not cause disturbance in the crystal orientation of the surface of the magnetostrictive member, the surface of the magnetostrictive member can be polished while preventing deterioration of the magnetostrictive characteristics.

1 Tube furnace 2 Core tube 3 Heater 4 Insulation material 5 Crucible 6 Crucible support 7 Lifting device 8 Crucible support rod 9 Electric heat pair 10 Vacuum exhaust pipe A Magnetic strain alloy material Aa Molten magnetic strain alloy material B Steel ingot C Grain boundary D Single crystal

Claims (5)

Single crystal of Fe-Ga-Cu alloy of steel ingot composed of one coarse crystal grain formed by unidirectional solidification method and having <100> orientation of crystal in the longitudinal direction, or a plurality of coarse crystal grains From the single crystal of the Fe-Ga-Cu alloy formed by separating into individual single crystals at the grain boundaries of the steel ingot composed of, the <of the alloy crystal in the direction requiring magnetic strain of the magnetic strain member. 100> A magnetic strain member formed by cutting out by discharge processing at positions where the orientations are aligned, and the Fe-Ga-Cu alloy has a mass% of Ga: 17.5 to 23.5% and Cu: 0.04. A magnetic strain member containing up to 2.4% and having a balance composed of Fe and unavoidable impurities. The surface of the magnetostrictive member formed by cutting out by the electric discharge machining is a smooth surface from which minute irregularities generated during the electric discharge machining have been removed by a polishing process that does not introduce strain into the magnetostrictive member. The magnetostrictive member according to claim 1. Fe-Ga-Cu alloy containing Ga: 17.5 to 23.5% and Cu: 0.04 to 2.4% by mass% and the balance consisting of Fe and unavoidable impurities is placed in a furnace above the melting temperature. Obtained by a step of pulling the molten alloy out of the furnace at a constant speed after holding for a certain period of time to solidify the molten alloy in one direction, and a step of solidifying in the one direction after the step of solidifying in one direction is completed. When the solidified steel ingot is composed of a plurality of coarse crystal grains, it is separated into individual single crystals at grain boundaries and the one-way solidification step or the individual single crystals. A method for manufacturing a magnetic strain member, which comprises a step of cutting out a single crystal obtained in the step by aligning the <100> orientations of the crystals in a direction requiring magnetic strain of the magnetic strain member by discharge processing. The surface of the magnetostrictive member obtained by the step of cutting out by the electric discharge machining is subjected to a polishing treatment that does not introduce strain into the magnetostrictive member, thereby removing minute irregularities generated during the electric discharge machining and smoothing the surface. The method for manufacturing a magnetostrictive member according to claim 3, further comprising the step of claim 3. The method for manufacturing a magnetostrictive member according to claim 3 or 4, wherein the constant speed is 20 mm / hour or less.

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