JP4412482B2 - Sintering container, magnetostrictive element manufacturing method - Google Patents

Description

  The present invention relates to a method of manufacturing a magnetostrictive element used for a linear actuator, a vibrator, a pressure torque sensor, a vibration sensor, a gyro sensor, and the like, and a sintering container suitable for use in manufacturing the magnetostrictive element.

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).
When the magnetostrictive material is fired and the obtained sintered body (magnetostrictive element) is evaluated, the evaluation parameters are mainly the sintered body density and the magnetostrictive value. As in the method disclosed in Patent Document 1, sintering is promoted and the density of the sintered body is improved when performed in a mixed gas atmosphere (reducing gas) of hydrogen gas and Ar gas during the heating process during firing. Can be made.

JP 2003-3203 A (page 4)

However, when firing is performed in a reducing gas that is a mixed atmosphere of hydrogen gas and Ar gas, the resulting sintered body has a large variation in the density of the sintered body. As a result, as shown in FIG. There was a problem that crack 2 occurred in 1. Since the sintered body 1 in which the crack 2 is generated cannot be shipped as a product as a matter of course, as a result, the yield of the magnetostrictive element is lowered.
The present invention has been made on the basis of such a technical problem, and provides a sintering container and a magnetostrictive element manufacturing method capable of suppressing variations in sintered body density and improving yield. Objective.

  The inventors of the present invention who have made extensive studies in order to solve the above-mentioned problems are located in the outer peripheral portion of the plurality of sintered bodies arranged in the sintering container in the sintering container used for firing. It was found that many cracks occurred in the sintered body. And at the time of firing, hydrogen contained in the alloy powder is released from the molded body in the process of obtaining the alloy powder constituting the molded body, and the release degree of the hydrogen depends on the position of the molded body in the sintering container. It was speculated that the difference may be the cause of cracks. That is, among a plurality of molded bodies arranged, the molded body positioned on the center side is surrounded by other molded bodies, whereas the molded body positioned on the outer periphery is a part of the periphery Are not adjacent to other shaped bodies. For this reason, compared with the molded body on the central part side surrounded by other molded bodies, the hydrogen concentration in the atmosphere does not increase so much compared to the central part side in the molded body on the outer peripheral part. As a result, it was thought that more hydrogen was released from the molded body (easily released).

The sintering container of the present invention made based on such inference is a sintering container for storing a sintering object that becomes a magnetic material containing hydrogen by sintering, and is partially A container body, a lid that closes the opening of the container body, and a setter that is provided in the container body and on which the object to be sintered is placed. Furthermore, this sintering container is positioned on the outer periphery of a plurality of sintering objects placed on the setter in order to suppress release of hydrogen from the sintering object positioned on the outer periphery on the setter. A shroud is provided so as to cover the object to be sintered. The shroud may have any shape. For example, the shroud has a rising portion that rises upward from the outer peripheral portion of the setter and an overhang portion that extends from the upper end portion of the rising portion toward the central portion of the container body. It can be made into a simple shape. By covering the object to be sintered with such a shroud, hydrogen released from the object to be sintered is prevented from widely dissipating, and the hydrogen concentration in the atmosphere around the object to be sintered is kept high. The release of hydrogen from the sintered object located on the outer periphery is suppressed.
This makes it possible to equalize the amount of hydrogen released during the firing process between the sintered object located on the outer peripheral portion in the container body and the sintered object located on the center side.
The sintered object can be various kinds of magnetic bodies, and in particular, the sintering container of the present invention is applied to a case where Tb, Dy, and Fe are contained and become a magnetostrictive element by sintering. It is preferable to do this. In this case, the shroud is preferably made of Mo.

In addition, the present invention provides a step of forming a raw material powder in a magnetic field to obtain a hydrogen-containing molded body, a plurality of molded bodies arranged side by side in a container, and a molded body positioned on the outer periphery from the molded body. And a step of sintering in a state of being covered with a shroud for suppressing the release of hydrogen. In this case, the molded body contains Tb, Dy, and Fe, and can be a magnetostrictive element by sintering. Such a method is particularly effective for preventing the generation of cracks when a molded body containing 500 ppm or more of hydrogen is sintered.
Furthermore, in the step of sintering the molded body, a hydrogen-containing body having a hydrogen content higher than that of the molded body is arranged in the vicinity of the molded body located on the outer peripheral portion among the plurality of molded bodies accommodated in the container. In this state, the molded body can be sintered. Thereby, at the time of baking, the hydrogen released from the hydrogen-containing body can keep the hydrogen concentration in the atmosphere around the object to be sintered high, and can suppress the release of hydrogen from the molded body located on the outer peripheral portion. Further, when hydrogen release is excessively suppressed by this, in the step of sintering the molded body, the hydrogen content is lower than the molded body and the hydrogen-containing body between the molded body and the hydrogen-containing body, In addition, the molded body may be sintered in a state where a hydrogen storage body capable of storing hydrogen is disposed. Thereby, hydrogen discharge | release from the molded object located in an outer peripheral part can be adjusted by occluding a part of hydrogen discharge | released from a hydrogen containing body with a hydrogen storage body.

  According to the present invention, by providing the shroud, it is possible to suppress excessive hydrogen release from the molded body (sintering object) located on the outer peripheral portion of the container body of the sintering container, and the sintered body. It becomes possible to prevent a decrease in density. Thereby, it is possible to equalize the hydrogen release amount among a plurality of molded bodies that are fired simultaneously in the sintering container, and to suppress the generation of cracks. As a result, the yield of magnetostrictive elements can be improved and the quality can be stabilized.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Magnetostrictive elements used for linear actuators, vibrators, pressure torque sensors, vibration sensors, gyro sensors, etc. are represented by the formula (1) RT _y (where R is one or more rare earth metals and T is one or more transition metals). And y represents 1 <y <4).
Here, R represents one or more selected from lanthanoid series and actinoid series rare earth metals 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 decreases, the RT ₂ phase corresponding to the main phase decreases and the magnetostriction value decreases. When y is 4 or more, the RT ₃ phase increases and the magnetostriction value decreases. For this reason, in order to increase the RT ₂ rich phase, y is preferably in the range of 1 <y <4.

Two or more rare earth metals may be used for R, and it is particularly preferable that Tb and Dy are used and the composition is represented by the formula (2) Tb _a Dy _(1-a) . 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. For this reason, if the magnetostrictive element is used near room temperature, a is preferably 0.27 <a ≦ 0.50.
When a is 0.50 or less, when a sensor such as a torque sensor is configured using this magnetostrictive element, the inductance changes according to the ambient temperature, and the inductance decreases particularly in a low temperature region. Therefore, when a is in the range of 0.50 <a ≦ 1.00, a stable temperature characteristic can be obtained in which there is little change in inductance due to temperature change. Here, a includes a = 1.00, that is, a case where Dy is not contained. That is, a may be appropriately selected according to the environment in which the magnetostrictive element can be assumed to be used.

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 and Ni. However, Co increases magnetic anisotropy but decreases magnetic permeability, and Ni lowers the Curie temperature. In order to reduce the magnetostriction value at room temperature and high magnetic field, Fe is 70 wt% or more, more preferably 80 wt% or more.

Details of the flow of the manufacturing process of the magnetostrictive element as described above are as follows.
In this embodiment, the magnetostrictive element is prepared by mixing three kinds of raw material powders having different compositions as disclosed in JP-A-2002-129274. In addition, it is preferable that a part of the alloy powder to be a raw material powder contains a raw material to be subjected to hydrogen storage treatment. By storing hydrogen in the alloy powder, distortion occurs and cracks occur 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 subjecting a part of the alloy powder to hydrogen storage treatment.
Here, the raw material for storing hydrogen preferably has a composition represented by the formula (3) Dy _b T _(1-b) and b is expressed as 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.

First, as one of the 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 _1.95 . This raw material A is annealed by stabilizing it at 1170 ° C. for 20 hours to make the concentration distribution of each metal element uniform during the production of the alloy, and after erasing the precipitated foreign phase, it is pulverized by, for example, a brown mill To obtain coarse powder. And this coarse powder removes the thing of 2 mm or more with a mesh.
Further, as one of the raw materials, Dy 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, the raw material B has a composition of, for example, Dy _2.0 Fe. This raw material B is heat-treated at 150 ° C. for 1 hour in a hydrogen atmosphere (hydrogen concentration 80%), and pulverized by storing, for example, about 18000 ppm of hydrogen to obtain a pulverized powder. And the thing of 2 mm or more is removed with a mesh from the obtained pulverized powder.
Furthermore, as one of the raw materials, Fe is heat-treated at 300 ° C. for 1 hour in a hydrogen gas atmosphere to reduce oxygen from, for example, about 3000 ppm to about 1500 ppm by reduction, and then pulverized by, for example, an atomizer. (Hereinafter referred to as “raw material C”).

Next, after the obtained raw materials A, B, and C were weighed, this was pulverized and mixed with an atomizer in an inert atmosphere of Ar gas to obtain an alloy powder having a composition of, for example, Tb _0.6 Dy _0.4 Fe _1.88 ( Raw material powder).
Thereafter, the obtained alloy powder is put into a mold and molded at a pressure of 8 ton / cm ^{2 in} a predetermined magnetic field, for example, 12 kOe, to obtain a molded body. At this time, the alloy powder is moved inside the pipe filled with nitrogen gas to prevent oxidation. It is also effective to supply perfluoropolyether vapor or the like to improve the fluidity of the alloy powder.

And the obtained molded object is heated up with a predetermined | prescribed temperature profile in a furnace, and a sintered compact is obtained.
Sintering is preferably carried out by raising the temperature of the formed raw material powder in a furnace to a stable temperature that keeps the temperature substantially constant. This stable temperature is preferably in the range of 1150 to 1300 ° C. When the stable temperature is less than 1150 ° C., sintering is not promoted, so the main phase particle size is reduced and the magnetostriction value is lowered. When the stable temperature exceeds 1300 ° C., the melting point of the alloy expressed by RT _y is close to the melting point. This is because the sintered body may melt. Moreover, a temperature increase rate is 3-20 degrees 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 diffusion of atoms becomes insufficient, causing segregation and heterogeneous phases.
By the way, R reacts very easily with oxygen to form a stable rare earth oxide. These oxides have low magnetic properties but do not exhibit magnetic properties that make them practical magnetic materials. In high-temperature sintering, even with a slight amount of oxygen, the magnetic properties of the sintered body are greatly reduced. Therefore, in heat treatment such as sintering, an atmosphere containing hydrogen gas is particularly preferable. In addition, as an atmosphere for preventing oxidation, there is an atmosphere of an inert gas. However, it is difficult to completely remove oxygen with an inert gas alone, and a rare earth metal having a high reactivity with oxygen forms an oxide. In order to prevent oxidation, an atmosphere of a mixed gas of hydrogen gas and inert gas 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, it is preferable that X (vol%) is at least 0 <X. Further, X (vol%) is preferably X <50 since the reducing action is saturated when 50 ≦ X. Therefore, sintering is performed in a hydrogen gas atmosphere or a mixed atmosphere of hydrogen gas and inert gas in which X in Formula (4) expressed as hydrogen gas: argon (Ar) gas = X: 100-X is 0 <X <50 Preferably it is carried out below. In particular, it is preferable that the temperature is initially raised in an Ar gas atmosphere, hydrogen is introduced in the middle of the temperature rise, firing is performed in a mixed atmosphere of hydrogen gas and Ar gas, and then an Ar gas atmosphere is obtained.

  A magnetostrictive element can be obtained by performing an aging treatment on the sintered body thus obtained and then dividing the sintered body into a predetermined size.

1 and 2 are views for explaining the configuration of the sintering container 10 used in the manufacturing process of the magnetostrictive element as described above. FIG. 1 is a perspective view showing the appearance of the sintering container 10. 2 is a cross-sectional view in a state in which a compact (sintering object) 100 is housed in the sintering container 10.
In the present embodiment, the molded body 100 that finally becomes a magnetostrictive element is sintered in a state of being housed in a sintering container (container) 10.
As shown in FIG. 1, a sintering container 10 is made of Mo (molybdenum) and includes a container body 11 that opens upward, and a lid body 12 that detachably closes the opening of the container body 11. Yes.

As shown in FIG. 2, a setter 20 that supports the molded body 100 during sintering is provided in the container body 11.
The setter 20 is disposed along the bottom surface of the container main body 11 and can hold a plurality of molded bodies 100 side by side on the top surface thereof.
Such a setter 20 is preferably formed of a material that hardly reacts with the molded body 100. Furthermore, it is preferable to form the setter 20 with a material having a temperature (reaction temperature) that causes a sintering reaction with the molded body 100 lower than a temperature at which the molded body 100 contracts during sintering. Examples of such a material include CaO and Dy ₂ O ₃ , and it is particularly preferable to form the setter 20 with Dy ₂ O ₃ .

In the container main body 11, a shroud 30 is provided along a pair of outer portions 20 a and 20 b facing each other in the setter 20.
In the process of firing the molded body 100, hydrogen occluded in the molded body 100 is released. The shroud 30 is provided for the purpose of suppressing the hydrogen released from the molded body 100 from widely diffusing into the sintering container 10. Therefore, the shroud 30 is an overhang extending upward from the outer side portions 20a and 20b of the setter 20 and being bent in a substantially L shape from the upper end portion of the rising portion 30a and extending inward of the container body 11. Part 30b. The shroud 30 is preferably formed of Mo, for example, like the container body 11 and the like.
In the present embodiment, the shroud 30 is arranged along the two outer portions 20a and 20b facing each other in the setter 20, but the present invention is not limited to this, and the shroud 30 is disposed on the entire circumference of the setter 20. It may be provided.

  A large amount of hydrogen released from the molded body 100 by such a shroud 30 stays in the end region S surrounded by the rising portion 30a and the overhang portion 30b. Thereby, the hydrogen concentration in this edge part area | region S becomes higher than the case where the shroud 30 is not provided, and discharge | release of hydrogen from the molded object 100 is suppressed. As a result, it can be expected that the amount of released hydrogen from the plurality of molded bodies 100 on the setter 20 is equalized.

  Moreover, as shown in FIG. 3, the molded object 100 can be piled up in multiple stages in the container main body 11, and baking can also be performed. In this case, a mesh-like partition plate 40 is provided in the container main body 11, and the setter 20 and the shroud 30 are set on the partition plate 40.

Further, when firing, as shown in FIG. 4, along the outer side portions 20 c and 20 d (parts not covered by the shroud 30) of the setter 20 on the two sides of the setter 20 where the shroud 30 is not provided. Thus, it is preferable to set the hydrogen generator 200 having a higher hydrogen content (concentration) than the molded body 100. By releasing hydrogen from the hydrogen generator 200 in the firing process, the hydrogen concentration in the end region S is increased and the release of hydrogen from the molded body 100 is suppressed.
As such a hydrogen generator 200, it is preferable to use a sintered body in which hydrogen is occluded. This is because such a sintered body can repeatedly occlude hydrogen and can be used repeatedly.
Here, assuming that the hydrogen content in the molded body 100 is, for example, 2000 ppm, the hydrogen content of the hydrogen generator 200 is preferably about 3000 to 20000 ppm, for example, about 14000 ppm.

  Further, as shown in FIG. 5, when hydrogen released from the hydrogen generator 200 excessively suppresses hydrogen release from the molded body 100 located in the end region S, the hydrogen generator 200 and the molded body. You may make it arrange | position the hydrogen storage body 300 between 100. FIG. As this hydrogen storage body 300, it is preferable to use a sintered body capable of storing hydrogen.

As described above, by providing the shroud 30 so as to cover the outer portion of the setter 20, excessive hydrogen release from the molded body 100 in the end region S can be suppressed. Furthermore, by setting the hydrogen generator 200 having a hydrogen content higher than that of the molded body 100, the hydrogen concentration in the end region S is further increased by the hydrogen released from the hydrogen generator 200 during the firing process. The release of hydrogen can also be suppressed. In this way, excessive hydrogen release from the molded body 100 in the end region S can be suppressed, and a decrease in the density of the sintered body can be prevented. In addition, when the hydrogen generator 200 is set, when hydrogen release from the molded body 100 located in the end region S is excessively suppressed, the hydrogen storage body 300 is interposed between the hydrogen generator 200 and the molded body 100. By arranging and appropriately storing the hydrogen released from the hydrogen generator 200, it is possible to prevent the hydrogen release from the molded body 100 from being excessively suppressed.
By doing in this way, hydrogen discharge | release amount can be equalized among the some molded object 100 baked simultaneously in the sintering container 10, and it becomes possible to suppress generation | occurrence | production of a crack. As a result, the yield of magnetostrictive elements can be improved and the quality can be stabilized.

Now, since the effect by providing the shroud 30 was confirmed, the result is 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 _1.95 . Then, the raw material A is subjected to a heat treatment for annealing at 1170 ° C. (stabilization time 20 hours), the concentration distribution of each metal element at the time of manufacturing the alloy is made uniform, and the precipitated heterogeneous phase disappears. To obtain a coarse powder. The obtained coarse powder was passed through a sieve having an opening of 2 mm to remove coarse powder having a particle diameter of 2 mm or more.
As raw material B, Dy and Fe were weighed and melted in an inert atmosphere of Ar gas to produce an alloy having a composition of Dy _2.0 Fe. And this alloy was heat-treated in a hydrogen atmosphere (concentration 80%) at 150 ° C. (stabilization time 1 hr) and occluded about 18000 ppm of hydrogen, whereby the alloy was pulverized to obtain pulverized powder. The pulverized powder was passed through a sieve having an opening of 2 mm to remove coarse powder having a particle diameter of 2 mm or more.
As the raw material C, Fe powder was used, and this Fe powder was subjected to reduction treatment (300 ° C., stabilization time 1 hr) for removing oxygen in a hydrogen gas atmosphere.

Subsequently, the obtained raw materials A, B, and C were weighed, mixed, and then finely pulverized with an atomizer in Ar gas to obtain an alloy powder having a composition of Tb _0.34 Dy _0.66 Fe _1.88 .
The obtained alloy powder was put into a mold and molded at a molding pressure of 5 ton / cm ² in a magnetic field of 12 kOe to obtain a molded body. At this time, when filling the alloy powder with the mold, the alloy powder was moved through the pipe filled with N ₂ gas. The magnetic field was applied in a direction perpendicular to the pressure direction (so-called transverse magnetic field). The size of the compact was a cylindrical shape with a diameter of 3 mm and a length of 16 mm.

  The obtained molded body was placed in a sintering container as shown in FIG. 3, heated in a furnace, and fired in a stable temperature zone of 1236 ° C. to obtain a sintered body (magnetostrictive element). At this time, 480 molded bodies were accommodated in a three-stage stack in the sintering container. The atmosphere in the furnace is initially Ar gas, hydrogen is introduced in the middle of the temperature rise, and a mixed atmosphere of 35 vol% hydrogen gas and 65 vol% Ar gas is evacuated when reaching 1217 ° C. The gas was replaced with Ar gas, and the temperature was raised to 1236 ° C.

Here, at the time of firing, a shroud as shown in FIG. 3 was set in the sintering container, and among the molded bodies arranged on the setter, the side and upper side of the molded body on the outer side were covered. (Condition 1).
For comparison, firing was performed in the same manner even when the compacts were arranged on the setter in the sintering container without using the shroud as shown in FIG. 3 (Comparative condition 1).

About the obtained sintered compact, the sintered compact density, the magnetostriction value, and the external appearance were evaluated. The sintered body density was measured by the Archimedes method, and the average value, σ value, and yield (ratio of the sintered body density not less than the reference value (95% of the theoretical density)) were obtained. Further, the magnetostriction value was measured by a pressurization type magnetostriction value measuring apparatus, and the average value, σ value, and yield were obtained. As for the appearance, the presence or absence of cracks was visually checked, and those without cracks were regarded as non-defective products, and the yield was determined.
Table 1 shows the results.

  As shown in Table 1, in the condition 1 using the shroud, the sintered body density was higher and the yield was improved compared to the comparative condition 1 in which the shroud was not used. However, it was recognized that some of the sintered bodies located on the outer side of the uppermost layer in the sintering container still have a low sintered body density. In condition 1, the magnetostriction value was the same as in comparative condition 1, and no appearance cracks were observed. Thus, it was confirmed that the density of the sintered body can be improved and equalized by using the shroud. This suggests that hydrogen release from the molded body is suppressed by the shroud.

Next, since it confirmed about the effect at the time of using a hydrogen generator, the result is shown below.
A molded body obtained in the same manner as in Example 1 was fired under the same conditions as in Example 1 to obtain a sintered body. At this time, a shroud as shown in FIG. 4 was set in the sintering container so as to cover the side and the upper side of the outer side of the molded body arranged on the setter. Further, a hydrogen generator was set at a position along the inner wall surface of the container body as shown in FIG. 4 (condition 2). As this hydrogen generator, a sintered body having a composition of Tb _0.34 Dy _0.66 Fe _1.87 and having a size of 10 × 10 × 8 mm in which about 14000 ppm of hydrogen was occluded was used. Further, in the container main body, 30 g of hydrogen generators were arranged in the uppermost stage, and 5 g of hydrogen generators were arranged in the remaining two stages.

Further, as condition 3, as shown in FIG. 5, in addition to condition 2, the composition of Tb _0.34 Dy _0.66 Fe _1.87 is used as a hydrogen occlusion body at a position adjacent to the inner peripheral side of the container body with respect to the hydrogen generator. The sintered body having a size of 10 × 10 × 8 mm and not storing hydrogen was disposed.

The sintered body thus obtained was evaluated for the sintered body density, magnetostriction value, and appearance.
As shown in Table 1, in the condition 2 using the hydrogen generator, both the average value and the σ value are improved, and the yield is 100, as compared with the condition 1 of Example 1 using only the shroud. %. In condition 2, the magnetostriction value was equivalent to that in comparative condition 1. However, in the condition 2, the appearance of appearance cracks was partially recognized.
On the other hand, in condition 3 using a hydrogen occlusion body in addition to the hydrogen generator, both the sintered body density and the magnetostriction value were equal to or greater than those in condition 2, and no appearance cracks were observed.
Thus, it was confirmed that the density of the sintered body can be equalized by releasing hydrogen from the hydrogen generator during firing. Further, it was suggested that the condition 2 leads to generation of cracks in the sintered body when hydrogen release from the hydrogen generating body is excessive. Furthermore, it was confirmed that, under condition 3, hydrogen released from the hydrogen generator was occluded by the hydrogen occlusion body, so that the sintered body density was equalized and cracks were prevented from occurring.

Further, similarly to the above condition 2, a hydrogen generator in which about 6000 ppm of hydrogen was occluded was set in the sintering container in which the shroud was set as shown in FIG. Condition 4).
The sintered body thus obtained was evaluated for the sintered body density, magnetostriction value, and appearance.
As shown in Table 1, under condition 4, the occurrence of external cracks was reduced as compared with condition 2 using a hydrogen generator storing 14000 ppm of hydrogen.
Thus, even when only the hydrogen generator was used, it was confirmed that by appropriately setting the hydrogen storage amount, crack generation can be suppressed while equalizing the sintered body density.

It is a perspective view which shows the external appearance of the container for sintering in this Embodiment. It is sectional drawing of the container for sintering, (a) is arrow sectional drawing of (b), (b) is a front sectional view. It is a front sectional view which shows the structure of the container for sintering in the case of making a molded object into a multistage stack. It is a plane sectional view showing an example in which a hydrogen generator is arranged. It is a plane sectional view showing an example in which a hydrogen generator and a hydrogen storage body are arranged. It is a microscope picture of the magnetostrictive element in which the crack produced.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Sintering container (container), 11 ... Container main body, 12 ... Lid body, 20 ... Setter, 30 ... Shroud, 30a ... Rising part, 30b ... Overhang part, 100 ... Molded object (sintering object), 200: Hydrogen generator, 300: Hydrogen storage body, S: End region

Claims (6)

A sintering container for storing a sintering object to be a magnetic body containing hydrogen by sintering,
A container body opened in part,
A lid for closing the opening of the container body;
A setter that is provided in the container body and on which the object to be sintered is placed;
In order to suppress the release of hydrogen from the sintering object located on the outer periphery on the setter, the sintering located on the outer periphery among the plurality of sintering objects placed on the setter. A shroud provided to cover the object;
A sintering container comprising: The shroud rises upward from the outer periphery of the setter; and
An overhang portion extending from an upper end portion of the rising portion toward a central portion of the container body;
The sintering container according to claim 1, comprising: The sintered object contains Tb, Dy, Fe, and becomes a magnetostrictive element by sintering.
The sintering container according to claim 1 or 2, wherein the shroud is made of Mo. Forming a raw material powder in a magnetic field to obtain a molded body containing hydrogen;
A step of storing a plurality of the molded bodies side by side in a container, and sintering the molded body located on the outer peripheral portion in a state of being covered with a shroud for suppressing release of hydrogen from the molded body;
A method of manufacturing a magnetostrictive element comprising: The method of manufacturing a magnetostrictive element according to claim 4 , wherein the formed body contains Tb, Dy, and Fe, and becomes a magnetostrictive element by sintering. 6. The method of manufacturing a magnetostrictive element according to claim 4 , wherein the molded body contains 500 ppm or more of hydrogen.

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