JP2005060833A - Production method and sintering method for magnetostriction element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method and a sintering method for a magnetostriction element by which the generation of cavities is prevented, and yield can be improved. <P>SOLUTION: In a sintering stage for a compact finally made into a magnetostriction element, when the inside of a furnace is heated-up, in a temperature region where a hydride included in the compact is thermally decomposed and gaseous hydrogen is dissipated, the atmosphere in the furnace is sucked with a vacuum pump, the pressure in the furnace is held to the negative one, and the dissipation of hydrogen from the compact is promoted. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a magnetostrictive element and a method for sintering a sintered object including a hydride.

Conventionally, magnetostrictive elements have been used for linear actuators, vibrators, pressure torque sensors, vibration sensors, gyro sensors, and the like.
When this magnetostrictive element is used for a linear actuator, a vibrator, or the like, a driving force is generated by changing the size of the magnetostrictive element by changing the magnetic field to be applied.
When a magnetostrictive element is used for a pressure torque sensor, vibration sensor, gyro sensor, etc., the dimension of the magnetostrictive element changes due to externally applied pressure, and sensing is performed by detecting the magnetic permeability that changes accordingly. Is going.

  Such a magnetostrictive element is manufactured by forming a molded body by molding an alloy powder having a predetermined composition in a magnetic field, and then sintering the molded body in an inert gas atmosphere (for example, patents). Reference 1).

JP 2003-3203 A (page 4)

  In the sintering process of the magnetostrictive element, the molded body that becomes the magnetostrictive element is easily oxidized during the sintering, and discoloration or the like is likely to occur due to the radiant heat of the heater that is a heat source for sintering. Is housed in.

However, the conventional techniques as described above have the following problems.
In the case where a molded body to be a magnetostrictive element contains a hydride as a raw material, when the molded body is heated in the sintering process, the hydride is thermally decomposed to generate hydrogen, which is diffused from the molded body. If hydrogen is generated in a state where the molded body to be a magnetostrictive element is housed in a sealed container, the sealed container is filled with hydrogen and the vapor pressure increases, and eventually the hydrogen generated in the molded body is diffused out of the molded body. It becomes difficult to be done. In addition, as the sintering process proceeds, the solid phase reaction of the tissue starts from the surface of the molded body, which makes it more difficult for hydrogen generated in the molded body to go out.
As a result, in the finally obtained magnetostrictive element, a nest is generated due to gasified hydrogen bubbles, which causes a decrease in the strength of the magnetostrictive element, a decrease in magnetic characteristics, and the like, which is a factor of decreasing the yield. Such a tendency becomes more prominent as the molded body has a larger diameter.

  The present invention has been made based on such a technical problem, and an object of the present invention is to provide a method of manufacturing a magnetostrictive element and a method of sintering capable of preventing the formation of nests and improving the yield.

Conventionally, in the process of raising the temperature of the molded body in the furnace for sintering, the inside of the furnace is replaced with a non-oxidizing gas atmosphere such as an inert gas. However, the present inventors have found that the release of hydrogen gas from the molded body is promoted by reducing the pressure in the furnace to a certain temperature range and making it a substantially vacuum state.
The manufacturing method of the magnetostrictive element of the present invention based on this knowledge includes a step of forming a raw material alloy powder containing a hydride in a magnetic field to obtain a formed body, and reducing the atmosphere to a predetermined pressure or lower. A step of increasing the temperature to the first temperature, and a step of supplying a predetermined atmosphere after reaching the first temperature, increasing the atmosphere temperature to the second temperature, and sintering the compact. It is characterized by including.

Here, as the raw material alloy powder, the formula (1) RT _y (where R is one or more kinds of rare earth metals (however, the rare earth metal is a concept including Y), and T is one or more kinds of transition metals) And y is preferably 1 <y <4). R is preferably Tb and Dy, and R is a composition represented by the formula (2) Tb _a Dy _(1-a) , and a is in the range of 0.27 <a ≦ 0.50. Preferably there is.
Further, it is desirable to select Fe as T. A part of T may be substituted with Co and / or Ni.
When a compact in which the hydride is contained in the alloy powder is sintered, in the process, the hydride is thermally decomposed and hydrogen gas is released from the compact. At this time, since the pressure in the furnace is reduced to a predetermined pressure or less, the diffused hydrogen gas is not filled, and the diffusion of hydrogen from the molded body is not hindered.

In the step of raising the molded body to the first temperature in a state where the atmosphere is reduced to a predetermined pressure or lower, it is preferable that the atmosphere is in a substantially vacuum state. Here, the substantially vacuum state means that the pressure is 2 × 10 ⁻⁵ Torr (1 Torr≈133.322 Pa) or less.
The first temperature is preferably set to 450 to 750 ° C., and more preferably set to 550 to 750 ° C.
The hydride contained in the molded body is thermally decomposed around 650 ° C. to generate hydrogen gas. For this reason, if the first temperature, which is the upper limit temperature for maintaining the atmosphere at a predetermined pressure or less, is a value below 450 ° C., it is not possible to promote the diffusion of hydrogen gas, and if the value exceeds 750 ° C., Sintered body density will fall.
The predetermined atmosphere supplied after reaching the first temperature is preferably a non-oxidizing gas. For example, an inert gas. Furthermore, supplying hydrogen gas or hydrogen gas and inert gas is also effective for improving the density of the sintered body finally obtained. When supplying hydrogen gas and an inert gas, it is preferable to set it as the mixed atmosphere of hydrogen gas and an inert gas at least 650 degreeC or more of a temperature rising process. This is to prevent oxidation due to a small amount of residual oxygen.
In addition, it is preferable to keep the atmospheric temperature substantially constant in the step of raising the atmospheric temperature to the second temperature and sintering the compact. The stable temperature which is kept substantially constant is preferably in the range of 1150 to 1230 ° C. When the stable temperature is lower than 1150 ° C., it is necessary to hold for a long time in order to remove internal strain, which is not efficient. On the other hand, when the stable temperature exceeds 1230 ° C., the sintered body may be melted because it is close to the melting point of the alloy represented by RT _y , and other phases such as other RT ₃ phases may precipitate. Because.

The present invention can also be understood as a method for sintering a sintered object containing a hydride. In this method, the object to be sintered is placed in a furnace, and the temperature in the furnace is increased to the first temperature in a state where the furnace is at a negative pressure, so that the hydride contained in the object to be sintered is thermally decomposed. The process of dissipating the generated hydrogen gas from the object to be sintered, and after reaching the first temperature, supplying a predetermined atmosphere in the furnace, raising the temperature in the furnace to the second temperature, And a step of sintering.
Setting the first temperature to be equal to or higher than the temperature at which thermal decomposition of the hydride begins is effective in reducing the incidence of nests in the sintered body.
Further, after reaching the first temperature, the temperature at which the predetermined atmosphere is supplied into the furnace is preferably 650 ° C. or higher.
In the step of sintering the molded body, it is preferable to maintain the temperature in the furnace within a predetermined temperature range for a predetermined time. In this step, it is preferable to supply a hydrogen gas atmosphere or a mixed atmosphere of hydrogen gas and inert gas into the furnace.
Such a sintered object is not limited to a material of a magnetostrictive element as long as it contains a hydride, but can include a Tb, Dy, and Fe, and can be formed into a molded body that becomes a magnetostrictive element by sintering. .

  According to the present invention, by keeping the furnace pressure low during the temperature rising process during sintering, it is possible to finally obtain a magnetostrictive element or the like without suppressing hydrogen dissipation from the compact during sintering. It is possible to prevent the formation of nests in the sintered object and to improve the yield.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
First, a method for manufacturing a magnetostrictive element in the present embodiment will be described.
In the present embodiment, it is represented by the formula (1) RT _y (where R is one or more rare earth metals, T is one or more transition metals, and y represents 1 <y <4). A magnetostrictive element is obtained by sintering the alloy powder having the composition.
Here, R represents one or more selected from lanthanoid series and actinoid series rare earth metals, and the rare earth metal is a concept including Y. Among these, as R, in particular, rare earth metals such as Nd, Pr, Sm, Tb, Dy, and Ho are preferable, and Tb and Dy are more preferable. These can be used in combination. T represents one or more transition metals. Among these, as T, transition metals such as Fe, Co, Ni, Mn, Cr, and Mo are particularly preferable, Fe, Co, and Ni are more preferable, and these can be mixed and used.

In the alloy represented by the formula (1) RT _y , _y represents 1 <y <4. RT _y is y = 2, and the RT ₂ Laves type intermetallic compound formed by R and T is suitable for a magnetostrictive element because it has a high Curie temperature and a large magnetostriction value. Here, when y is 1 or less, the RT phase is precipitated by the heat treatment after sintering, and the magnetostriction value is lowered. When y is 4 or more, the RT ₃ phase or the RT ₅ phase increases and the magnetostriction value decreases. For this reason, in order to increase the RT ₂ phase, y is preferably in the range of 1 <y <4. R may be mixed with rare earth metals, and it is particularly preferable to mix Tb and Dy. In this case, in the alloy represented by the formula (2) Tb _a Dy _(1-a) , a is more preferably in the range of 0.27 <a ≦ 0.50. Thereby, an alloy of (Tb _a Dy _(1-a) ) T _y has a large saturation magnetostriction constant and a large magnetostriction value can be obtained. Here, when a is 0.27 or less, a sufficient magnetostriction value is not exhibited at room temperature or less, and when it exceeds 0.50, a sufficient magnetostriction value is not exhibited near room temperature. T is particularly preferably Fe, and Fe forms a Tb, Dy and (Tb, Dy) Fe ₂ intermetallic compound, and a sintered body having a large magnetostriction value and high magnetostriction characteristics is obtained. At this time, a part of Fe may be substituted with Co or Ni. However, Co increases the magnetic anisotropy but decreases the magnetic permeability. Ni lowers the Curie temperature, and as a result, lowers the magnetostriction value at room temperature and high magnetic field. Therefore, the proportion of Fe in T is 70 wt% or more, more preferably 80 wt% or more.

Moreover, it is preferable that a part or all of the alloy powder is a raw material to be subjected to hydrogen storage treatment. By occluding hydrogen in the alloy powder, the particles constituting the alloy powder are distorted and cracked due to the internal stress. For this reason, the alloy powder to be mixed is subjected to pressure when forming a compact, and is pulverized inside the mixed state to become fine, and when it is sintered, a dense high-density sintered body can be obtained. . Furthermore, since rare earths of Tb and Dy are easily oxidized, an oxide film having a high melting point is formed on the surface even if there is a slight amount of oxygen, and the progress of sintering is suppressed, but it is oxidized by occlusion of hydrogen. It becomes difficult. Therefore, a high-density sintered body can be manufactured by hydrogen storage treatment of a part of the alloy powder.
Here, the raw material for occluding hydrogen preferably has a composition represented by the formula (3) Dy _b T _(1-b) and b is 0.37 ≦ b ≦ 1.00. T may be Fe alone, or a part of Fe may be substituted with Co or Ni. Thereby, the sintered compact density of the alloy powder of a raw material can be made high.

Specific examples for obtaining the above alloy powder are as follows.
First, as one of raw materials, Tb, Dy, and Fe are weighed and melted in an inert atmosphere of Ar gas to produce an alloy (hereinafter referred to as “raw material A”). Here, the raw material A has a composition of, for example, Tb _0.4 Dy _0.6 Fe _1.94 . This raw material A is subjected to a heat treatment for annealing to make the concentration distribution of each metal element uniform during the manufacture of the alloy, and after annihilating the precipitated foreign phase, it is pulverized by, for example, an atomizer.

Also, as one of the raw materials, DyH ₂ and Fe are weighed and melted in an inert atmosphere of Ar gas to produce an alloy (hereinafter referred to as “raw material B”). Here, as the raw material B, the ratio of DyH ₂ and Fe is set so that, for example, the composition of Dy _2.0 Fe is obtained after hydrogen disappears during the sintering process. Similarly, the raw material B is pulverized by, for example, an atomizer.

Further, as one of the raw materials, Fe is subjected to a reduction treatment for removing oxygen in a hydrogen gas atmosphere, and then pulverized with, for example, an atomizer (hereinafter referred to as “raw material C”).
As the reducing atmosphere containing hydrogen gas used for the reduction treatment, hydrogen gas: argon (Ar) gas = X: In the formula (4) represented by 100−X, X (vol%) is 0 <X < 50 is preferable. Since Ar gas is an inert gas and does not oxidize R, it can be mixed with hydrogen gas to obtain an atmosphere having a reducing action. For this reason, in order to have a reducing action, X (vol%) is preferably at least 0 <X. Further, X (vol%) is preferably X <50 since the reducing action is saturated when 50 ≦ X.

Next, after the obtained raw materials A, B, and C are weighed, a raw material alloy powder having a composition of, for example, Tb _0.3 Dy _0.7 Fe _1.88 can be obtained by pulverizing and mixing.

In the present embodiment, the raw material alloy powder as described above is put into a mold, molded in a magnetic field of a predetermined strength, for example, 8 kOe, to obtain a molded body, and then the molded body is sintered in a furnace.
In this sintering step, the temperature in the furnace is changed with a predetermined profile as shown in FIG. In the first process of starting the sintering, the inside of the furnace is sucked with a vacuum pump to maintain the degree of vacuum above a predetermined level in order to promote the diffusion of hydrogen gas from the compact. The degree of vacuum is preferably 2 × 10 ⁻⁵ Torr (1 Torr≈133.322 Pa), for example.
Then, the temperature is increased at a predetermined temperature increase rate while maintaining the degree of vacuum until the temperature in the furnace reaches the predetermined temperature. Here, the upper limit temperature (first temperature) T1 for maintaining the degree of vacuum is preferably set to 450 to 750 ° C. The hydride contained in the molded body is thermally decomposed around 650 ° C. to generate hydrogen gas. For this reason, if the upper limit temperature T1 for maintaining the degree of vacuum is set to a value lower than 450 ° C., it is not possible to promote the diffusion of hydrogen gas. Moreover, if the upper limit temperature T1 is set to a value exceeding 750 ° C., the sintered body density is lowered.
This upper limit temperature T1 is preferably set in accordance with the size (cross-sectional area) of the compact to be sintered. Naturally, the larger the cross-sectional area of the molded body, the higher the upper limit temperature T1 is set in order to enhance the effect of promoting the diffusion of hydrogen gas.
Further, in the first process, it is preferable that the temperature in the furnace is continuously increased at a predetermined temperature increase rate without maintaining a constant temperature during the temperature increase. In this case, the temperature raising rate is preferably 3 to 20 ° C./min. When the rate of temperature rise is less than 3 ° C./min, the productivity is low, and when the rate of temperature rise exceeds 20 ° C./min, the temperature of the raw material powder formed in the furnace is not uniform and segregation or heterogeneous phase occurs.

In the sintering process, when the first process is completed, that is, when the temperature in the furnace reaches a preset upper limit temperature, the suction by the vacuum pump is stopped and the process proceeds to the second process.
In the second process, a hydrogen gas atmosphere or a mixed atmosphere of hydrogen gas and inert gas is supplied into the furnace, and the temperature rise is continued. Here, in the case of an alloy represented by RT _y constituting the molded body, a mixed atmosphere of hydrogen gas and inert gas (predetermined atmosphere) is reached in the furnace before reaching a predetermined temperature T2 that is equal to or higher than the upper limit temperature T1 in the temperature rising process. ). The predetermined temperature T2 for making the mixed atmosphere of hydrogen gas and inert gas is preferably at least 650 ° C. or higher. This is to prevent oxidation of the rare earth metal by the remaining trace amount of oxygen. In the case of a mixed atmosphere of hydrogen gas and inert gas, X in the formula (4) expressed as hydrogen gas: argon (Ar) gas = X: 100−X is 0 <X <50. preferable.
Also in the second step, it is preferable that the temperature rising rate in the furnace is 3 to 20 ° C./min. When the rate of temperature rise is less than 3 ° C./min, the productivity is low, and when the rate of temperature rise exceeds 20 ° C./min, the temperature of the raw material powder formed in the furnace is not uniform and segregation or heterogeneous phase occurs.

The temperature rise in the second process stops when the inside of the furnace reaches a preset temperature (second temperature) T3, and shifts to the third process.
In the third process, the temperature in the furnace is set to a stable temperature that is maintained in a substantially constant temperature range. This stable temperature is preferably in the range of 1150-1230 ° C. If the stable temperature is less than 1150 ° C., it takes a long time to remove internal strain, which is not efficient, and if the stable temperature exceeds 1230 ° C., it will be close to the melting point of the alloy represented by RT _y , so This is because the aggregate may melt and other phases such as other RT ₃ phases may precipitate.

Furthermore, in the third step of sintering, hydrogen gas in which hydrogen gas atmosphere or hydrogen gas: argon (Ar) gas = X: 1 in formula (5) represented by 1−X is such that 0 <X <0.5. It is preferable to carry out in a mixed atmosphere of inert gas.
R reacts very easily with oxygen to form a stable rare earth oxide. These oxides have low magnetic properties and do not exhibit magnetic properties that make them practical magnetic materials. In high-temperature sintering, even a slight amount of oxygen greatly reduces the magnetic properties of the sintered body. Therefore, in heat treatment such as sintering, an atmosphere containing hydrogen gas is particularly preferable. An atmosphere for preventing oxidation includes an atmosphere of an inert gas. However, it is difficult to completely remove oxygen with only an inert gas, and a rare earth metal having a high reactivity with oxygen forms an oxide. Therefore, in order to prevent oxidation of the rare earth metal, hydrogen gas and inert gas A mixed gas atmosphere is preferred.

  By passing through the first to third processes, the molded body can be sintered to obtain a sintered body. Thereafter, the magnetostrictive element can be obtained by subjecting this sintered body to an aging treatment and further dividing the sintered body into a predetermined size.

In the above-described sintering step, a molded body (sintering object) 100 that finally becomes a magnetostrictive element is sintered in a state of being accommodated in a sintering container 10 as shown in FIGS. The
As shown in FIGS. 2 and 3, the sintering container 10 includes a container body 11, a lid body 12, and a seal member 13.
The container body 11 and the lid body 12 are made of a material having high heat resistance and hardly causing a reaction with the raw material of the magnetostrictive element, for example, Mo.
Further, the sealing member 13 is used to close the container main body 11 and the lid body 12 when the container main body 11 is closed with the lid body 12, thereby making the inside of the sintering container 10 a sealed space. It is made of a high and flexible material such as Nb.

When the molded body 100 is sintered, a setter 15 that supports the molded body 100 is provided in the container body 11 of the sintering container 10 having the above-described configuration, and the molded body 100 is placed on the setter 15. Cover the lid 12 from above.
In this state, the sintering container 10 is placed in the furnace, and the furnace 100 is heated with a predetermined temperature profile to sinter the molded body 100 housed in the sintering container 10.

In the present embodiment, as the temperature of the molded body 100 accommodated in the sintering container 10 rises, the hydrogenated gas contained in the hydride contained in the raw material of the molded body 100 is thermally decomposed. In the temperature region where hydrogen gas is diffused, the furnace atmosphere is sucked by the vacuum pump, so that the pressure in the furnace, that is, the inside of the sintering vessel 10 is maintained at a negative pressure. Therefore, the release of hydrogen from the molded body 100 is promoted without being hindered. Thereby, hydrogen release can be completed before the solid-phase reaction of the surface of the molded object 100 starts. As a result, it is possible to prevent a nest from occurring in the finally obtained magnetostrictive element, to suppress a decrease in strength and magnetic characteristics of the magnetostrictive element and to improve its yield.
In addition, in the first process during sintering, the inside of the furnace is in a substantially vacuum state, so that oxidation of the molded body 100 can be prevented.

In the first process (temperature raising process), the difference in the amount of hydrogen generated was examined when the furnace was in a substantially vacuum state and when the furnace was in an inert gas (Ar gas) atmosphere. The results are shown below.
First, as raw material A, Tb, Dy, and Fe were weighed and melted in an inert atmosphere of Ar gas to produce an alloy having a composition of Tb _0.4 Dy _0.6 Fe _1.94 . Then, the raw material A was subjected to a heat treatment for annealing, to make the concentration distribution of each metal element uniform during the manufacture of the alloy, and to dissipate the precipitated foreign phase, and then pulverized with an atomizer. As a raw material B, DyH ₂ and Fe were weighed at a predetermined ratio and melted in an inert atmosphere of Ar gas. The ratio of DyH ₂ and Fe was set so that the composition of Dy _2.0 Fe was obtained after hydrogen disappeared during the sintering process. The obtained alloy having the composition of Dy _2.0 Fe was similarly pulverized with an atomizer. As a raw material C, Fe was subjected to a reduction treatment for removing oxygen in a hydrogen gas atmosphere, and then pulverized with an atomizer.
Subsequently, the obtained raw materials A, B, and C were weighed and then pulverized and mixed to obtain an alloy powder having a composition of Tb _0.3 Dy _0.7 Fe _1.88 .
The obtained alloy powder was put in a mold and molded in a magnetic field of 8 kOe to obtain a molded body 100. The molded body 100 was a stick having a diameter of 7 mm and a length of 100 mm. In this state, the amount of hydrogen contained in the material was 2.03 g (= 22.74 Nl (normal liter: volume at room temperature)).
The obtained molded body 100 is placed in a sintering container 10 (internal dimensions: width 170 mm × length 240 mm × height 60 mm), and the temperature is increased from 20 ° C. at a temperature increase rate of 8.5 ° C./min in a furnace. The temperature was raised to 1000 ° C.
Here, in Example 1, the furnace pressure at the time of temperature rise was set to a substantially vacuum state of 2 × 10 ⁻⁵ Torr (1 Torr≈133.322 Pa), and in the comparative example, the inside of the furnace was set to an Ar atmosphere. The amount of hydrogen generated inside was detected.

FIG. 4 shows the result.
As shown in FIG. 4, in the comparative example in which the Ar atmosphere is used, hydrogen is generated in a wide temperature range ranging from 500 to 900 ° C., whereas in Example 1 in a substantially vacuum state, the temperature is 500 to 750 ° C. It can be seen that a larger amount of hydrogen is generated in the temperature range, and that a particularly large amount of hydrogen is generated around 600 ° C.

In addition, using the sintering container 10 as described above, the occurrence of nests in the magnetostrictive element was confirmed, and the results are shown below.
First, as described above, 773 g of Tb _0.4 Dy _0.6 Fe _1.94 , 101 g of raw material B described later, and 46 g of Fe as raw material C were used as the raw material A of the raw material powder alloy. By pulverizing and mixing these raw materials A, B, and C, a raw material alloy powder having a composition of Tb _0.3 Dy _0.7 Fe _1.88 was obtained, and the obtained alloy powder was put into a mold and molded in a magnetic field of 8 kOe. As a result, a molded body 100 was obtained. The molded body 100 was a stick having a diameter of 7 mm and a length of 100 mm. As in Example 1, the raw material B is obtained by weighing DyH ₂ and Fe at a predetermined ratio so that the composition of Dy _2.0 Fe is obtained after hydrogen disappears during the sintering process.
The obtained molded body 100 was placed in a sintering container 10 and heated in a furnace with a temperature profile as shown in FIG.
At this time, the internal dimensions of the container body 11 of the sintering container 10 were 170 mm wide × 240 mm long × 60 mm high.

Here, in the first step of the temperature profile shown in FIG. 1, an upper limit temperature T1 that continues to maintain a vacuum degree equal to or higher than a predetermined value,
Condition 1: T1 = 600 ° C.
Condition 2: T1 = 650 ° C.
Condition 3: T1 = 660 ° C.
Condition 4: T1 = 700 ° C.
Condition 5: T1 = 750 ° C.
The 5 types were as follows.
In the third step, the stable temperature to be maintained was 1230 ° C.

In this manner, 80 molded bodies 100 were fired under conditions 1 to 5, and the number of sintered bodies in which nests were generated was counted in the obtained sintered bodies.
The result is shown in FIG.
As shown in FIG. 5, the nest generation rate (= number of sintered bodies with nests / 80) is 4% under the condition 1 where T1 = 600 ° C., and 1 under the condition 2 where T1 = 650 ° C. 5%, 1% for Condition 3 with T1 = 660 ° C., 0% for Condition 4 with T1 = 700 ° C. and Condition 5 with T1 = 750 ° C.
Thereby, the upper limit temperature T1 that continues to maintain a vacuum level higher than a predetermined value while raising the temperature is set to a temperature T1 = 650 ° C. or higher at which thermal decomposition of the hydride starts, so that the incidence of nests is reduced. It is apparent that the nest generation rate is further reduced by setting the temperature T1 to around 700 ° C. or higher.

In the above embodiment, the sintering container 10 can have any other configuration as long as it can accommodate the molded body 100 during sintering and can be inserted and removed before and after sintering. Also good.
In addition to this, as long as it does not depart from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

It is a figure which shows the temperature profile in the sintering process in this Embodiment. It is a perspective developed view which shows the structure of the container for sintering used at a sintering process. It is sectional drawing of the container for sintering. It is a figure which shows the difference in the amount of hydrogen generation from a molded object when it is set as a substantially vacuum state, and when it is set as inert gas atmosphere. It is a figure which shows the relationship between the upper limit temperature which maintains a substantially vacuum state, and the incidence of a nest.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Sintering container, 11 ... Container main body, 12 ... Cover body, 100 ... Molded object (sintering object), T1 ... Upper limit temperature (first temperature), T3 ... Temperature (second temperature)

Claims (15)

Forming a raw material alloy powder containing hydride in a magnetic field to obtain a formed body;
Raising the molded body to a first temperature in a state where the atmosphere is reduced below a predetermined pressure;
After reaching the first temperature, supplying a predetermined atmosphere, raising the atmosphere temperature to a second temperature, sintering the molded body,
A method of manufacturing a magnetostrictive element comprising:   2. The method of manufacturing a magnetostrictive element according to claim 1, wherein the first temperature is not lower than 450 ° C. and lower than 750 ° C. 3.   2. The method of manufacturing a magnetostrictive element according to claim 1, wherein in the step of raising the temperature to the first temperature, the atmosphere is in a substantially vacuum state.   The method of manufacturing a magnetostrictive element according to claim 1, wherein the predetermined atmosphere supplied after reaching the first temperature is a non-oxidizing gas atmosphere.   2. The method of manufacturing a magnetostrictive element according to claim 1, wherein the second temperature is 1150 ° C. or more and 1230 ° C. or less. The raw material alloy powder is represented by the formula (1) RT _y (where R is one or more rare earth metals (wherein the rare earth metal is a concept including Y), and T is one or more transition metals, 2. The method of manufacturing a magnetostrictive element according to claim 1, wherein y has a composition represented by 1 <y <4).   The method for manufacturing a magnetostrictive element according to claim 6, wherein R is Tb and Dy. The R is a composition represented by the formula (2) Tb _a Dy _(1-a) , wherein a is in a range of 0.27 <a ≦ 0.50. A method of manufacturing a magnetostrictive element.   The method of manufacturing a magnetostrictive element according to claim 6, wherein the T is Fe. A method for sintering a sintered object including a hydride,
By putting the sintering object in a furnace and raising the temperature in the furnace to the first temperature with the inside of the furnace at a negative pressure, by thermal decomposition of the hydride contained in the sintering object Dissipating the generated hydrogen gas from the object to be sintered;
After reaching the first temperature, supplying a predetermined atmosphere in the furnace, raising the temperature in the furnace to a second temperature, and sintering the object to be sintered;
A sintering method comprising:   The sintering method according to claim 10, wherein the first temperature is equal to or higher than a temperature at which thermal decomposition of the hydride starts.   11. The sintering method according to claim 10, wherein after reaching the first temperature, a temperature at which a predetermined atmosphere is supplied into the furnace is 650 ° C. or more.   The sintering method according to claim 10, wherein in the step of sintering the molded body, the temperature in the furnace is maintained in a predetermined temperature range for a predetermined time.   The sintering method according to claim 10, wherein in the step of sintering the molded body, a hydrogen gas atmosphere or a mixed atmosphere of hydrogen gas and inert gas is supplied into the furnace.   The sintering method according to claim 10, wherein the object to be sintered includes Tb, Dy, and Fe, and is a molded body that becomes a magnetostrictive element by sintering.

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