JP3245893B2 - Fine grain tungsten alloy and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called heavy metal alloy containing W as a main component, and more particularly to a fine grain tungsten alloy produced by a solid phase sintering method and a method for producing the same. .

[0002] Tungsten alloys having a fine crystal grain are used, for example, as a material for a balancer utilizing a high specific gravity or a radiation shielding material.

[0003]

2. Description of the Related Art A so-called heavy metal alloy (not a cemented carbide such as WC) containing 90% or more of W and containing other alloying elements such as Ni, Fe, Cr, Re, and Cu has conventionally been sintered. It has been manufactured by the method. Typically, element powders such as pure W, pure Fe, and pure Ni are prepared as raw materials, and after these powders are mixed, CIP molding is performed. A molded body is sintered in an H ₂ atmosphere above 1400 ° C.. The sintering method at this time is a so-called liquid phase sintering method.
W has a very high melting point, but Ni-Fe generates a liquid phase at a relatively low temperature as compared with W. Therefore, at the time of sintering, Ni and Fe are alloyed to generate a liquid phase, and the liquid phase spreads all over the W particles, thereby obtaining a sintered body having a density of 99% or more.

[0004]

As described above, conventional heavy metal alloys have been manufactured by a liquid phase sintering method. Therefore, the Ostwald phenomena of W particles cannot be avoided during the liquid phase sintering process. Even if the particle size of the W raw material powder is about several μm, the size of the W particles reaches about 50 μm due to Ostwald growth in the liquid phase sintering process. Since the above reaction occurs very quickly, W
Abnormal growth of particles is hard to suppress. Even if the amount of liquid phase generated can be reduced in the laboratory and the time required for generating the liquid phase can be extremely shortened, it is extremely difficult to achieve the same results on an industrial scale. In addition, when the size of the material to be sintered is large, it is difficult to control such that the generation amount of the liquid phase is suppressed or the generation time is shortened.

Further, in order to produce a heavy metal alloy by the liquid phase sintering method, a combination of elements which generate a liquid phase at a lower melting point than W, such as a combination of Ni and Fe, is required. Become indispensable.

On the other hand, it is conceivable to produce a heavy metal alloy without using the liquid phase sintering method. However, as long as pure W, pure Ni, and pure Fe are used as raw materials, it is extremely difficult to produce them without using the liquid phase sintering method. The reason,
It is described below.

[0007] Heavy metal alloys have, as their microstructure, W particles having a W component of almost 100% (particle diameter of about 50%).
μm) and a matrix phase containing Ni, Fe, and W as main components. The matrix phase exists so as to surround the W particles. This structure guarantees good mechanical properties of the heavy metal alloy. If the matrix phase does not surround the periphery of the W particles, that is, if the structure has many portions where the W particles are in contact with each other, mechanical properties, particularly elongation, etc. The ductility decreases. In other words, because the matrix phase is uniformly present around the W particles,
It imparts ductility to heavy metal alloys. Pure W, Pure Ni,
If the sintering process of the mixed powder using pure Fe as a raw material is performed by solid-phase sintering, the formation of the matrix phase is insufficient, and the matrix phase cannot sufficiently surround the W particles. Therefore, it becomes an alloy with low ductility. For example, even if the component powder mixture is solidified by a method such as HIP or extrusion, it is difficult to produce a heavy metal alloy having excellent mechanical properties (particularly ductility) unless a liquid phase is generated.

In a laboratory, a pre-alloyed powder having a structure in which a matrix phase surrounds W particles is prepared,
The pre-alloy powder can be molded and solid-phase sintered. However, the sintered body structure of such a pre-alloy powder has high so-called contiguity (proximity between W particles) because the W particles are not spherical but polygonal.
For this reason, mechanical properties, especially ductility, tend to be inferior. In order to avoid this, it is necessary to generate a liquid phase only for a very short time. However, as described above, it is difficult to generate a liquid phase for a very short time at an industrial level. is there.

An object of the present invention is to provide a fine-grained tungsten alloy having fine crystal grains, high strength and moderate ductility.

Another object of the present invention is to provide a method for producing a fine-grained tungsten alloy as described above.

[0011]

The fine-grain tungsten alloy of the present invention comprises spherical W particles having a particle size of 7 μm or less,
at least one of i and Fe, and a matrix phase containing W as a main component. The content of the compound containing at least one of Ni and Fe and W is 5% by volume.
Is less than. The content of W is in the range of 50 to 97% by weight.

The method for producing a fine grain tungsten alloy of the present invention includes the following steps. (A) At least one powder of Ni powder and Fe powder and W powder are prepared, and the content of W is 50 to 97% by weight.
And then uniformly mixing.

(B) a step of subjecting the mixed powder to a mechanical alloying treatment in an atmosphere having an impurity gas component concentration of 500 ppm or less and at a treatment temperature of 80 ° C. or less.

(C) a step of deoxidizing the powder by exposing the powder subjected to mechanical alloying to a reducing atmosphere at 800 ° C. or higher for 10 minutes or more.

(D) A step of enclosing the deoxidized powder in a container in a vacuum. (E) a step of extruding the powder enclosed in the container at a temperature of 800 ° C. or higher and an extrusion ratio of 10 or higher.

[0016]

In the liquid phase sintering method, a combination of elements that generates a liquid phase at a lower melting point than W, such as a combination of Ni and Fe, is indispensable. However, according to the method including the mechanical alloying step and the extrusion processing step as in the present invention, a heavy metal alloy (W alloy) can be produced by solid-phase sintering without restriction on the combination of elements. However, simply performing mechanical alloying treatment on the W powder and another metal powder does not mean that a desired W alloy can be obtained. When W powder, Ni powder, and Fe powder are mechanically alloyed, an intermetallic compound (for example, W-Ni, W-Fe, or an intermetallic compound thereof with oxygen or carbon) between these metals is generated. Often done. Intermetallic compounds impair the mechanical properties (strength, elongation) of the material. Therefore, it is necessary to set the conditions of the mechanical alloying process so that the intermetallic compound cannot be formed, or to set the conditions of the subsequent processing.

The method of the present invention basically employs a solid phase sintering method. Therefore, the alloy system is changed to Ni and F
There is no restriction that the combination must generate a liquid phase such as the combination with e.

In the method of the present invention, W particles are grown (Ostwald growth) in a solid phase, instead of in the presence of a liquid phase as in the prior art. Since the grain growth is in the solid phase, unnecessary growth of W particles is suppressed. Therefore, it is possible to obtain an alloy having a small W particle size and low contiguity, that is, excellent toughness. In particular, small crystal grains in the alloy are advantageous for improving the strength of the alloy, and a high-strength alloy can be obtained.

Although Ostwald ripening itself in the solid state is already known, a feature of the present invention is that the Ostwald ripening in the solid state and mechanical alloying of the W alloy are linked. .

The present inventors utilize the effect of supersaturated solid solution of constituent elements and the effect of promoting diffusion by introducing a large amount of lattice defects, which are one of the features of the mechanical alloying treatment, for the growth of W particles in heavy metal alloys. We considered whether we could do it. In other words, the W alloy was supersaturated into Ni by mechanical alloying, and thereafter, it was examined whether Ostwald growth of W particles could be caused by the diffusion phenomenon enhanced by mechanical alloying, for the W alloy. As a result, the inventors of the present application have found that this is possible depending on the conditions. In this respect, it can be said that the adoption of the mechanical alloying method and the adoption of the step of growing the W particles in the solid phase have a close relationship that is not indispensable to each other. The mere adoption of the mechanical alloying method and the knowledge of the Ostwald ripening phenomenon in the solid phase do not provide a fine-grained tungsten alloy as intended in the present invention. Note that it is not easy to include as much as 90% of W in Ni unless a mechanical alloying method is used.

In the present invention, the use of solid phase sintering is an essential requirement. This is because, even when W is grown small in Ostwald in the solid state, W particles grow larger if liquid phase sintering is performed thereafter. Therefore, for the present invention, mechanical alloying, solid phase sintering, and W particle growth in the solid phase are in a necessary relationship with each other.

The method and operation of the present invention will be described more specifically. In the present invention, for example, pure W, pure Ni, pure Fe
Is used as a raw material. After blending these powders so that the W content is 50 to 97% by weight, they are uniformly mixed in a dry system. Both Ni and Fe are not necessarily required, and a combination of W and Ni or a combination of W and Fe may be used. Alternatively, W-Ni, W-Fe, or Ni-Fe alloy powder may be used as one of the raw materials.

The greater the content of Ni or Fe, the easier it is to perform mechanical alloying. This is because the mechanical alloying phenomenon is more likely to occur when a large amount of powder (Ni or Fe) having high deformability is included. N
It is for this reason that many examples of mechanical alloying of Ni-based alloys and Fe alloys containing i or Fe as a main component have been reported. Therefore, the lower limit of the W content is not particularly significant. However, in the present invention, it is intended to obtain a W alloy containing the largest amount of W, and for this reason, the lower limit of the W content is set to 50% by weight. Needless to say, the smaller the W content, the easier it is to perform mechanical alloying.

On the other hand, if the alloy contains a large amount of W, for example, an alloy containing 80% by weight or more, it becomes difficult to perform mechanical alloying. The reason is that if there is a lot of W with low deformation performance, of the crushing and crimping actions that occur during mechanical alloying, only crushing will occur too much, and the balance between crushing and crimping will be lost, and composite formation will occur. This is because it becomes difficult to cause a so-called mechanical alloying phenomenon. Since powder hardens during mechanical alloying, pulverization occurs automatically without particularly setting the conditions in detail. From the common sense of mechanical alloying researchers, it seems that it is extremely difficult to perform mechanical alloying on an alloy system containing, for example, 80% by weight or more of W. As can be seen from the fact that many of the reported examples of mechanical alloying reported to date are Ni, Fe, Al, and Cu-based alloys, the inclusion of a large number of elements with high deformability indicates that the mechanical alloying phenomenon occurs. Conditions for expression. In experiments conducted by the inventor of the present application, when the W content exceeded 97% by weight, only the pulverizing effect was strong during mechanical alloying, and a favorable composite state could not be obtained.

W having low deformation performance and high hardness is not originally suitable for mechanical alloying. In fact, as a result of research conducted by the present inventor, the strength of the crimping force is Ni> Fe
> W, and it was found that the ease of mechanical alloying was also in this order. In other words, the easier the crimping is, the easier it is to perform mechanical alloying. In other words, W is an element that is difficult to perform mechanical alloying. Therefore, in order to perform mechanical alloying on W, it is necessary to find out mechanical alloying processing conditions that increase the pressure bonding action.

In order to facilitate mechanical alloying, it is effective to mix W-Ni or W-Fe with W powder. This is a method in which a part of the W element that is difficult to perform mechanical alloying is alloyed in advance with viscous Ni or Fe. Ni-Fe alloy powder may be used as a raw material in order to make the alloy state of Ni and Fe more uniform. If the impurity gas component is small, a vacuum atmosphere may be used as the atmosphere, or an Ar gas atmosphere and a vacuum atmosphere may be used alternately during mechanical alloying.

There are other reasons why it is difficult to perform mechanical alloying on W. That is, W easily forms an intermetallic compound with another element. Therefore, it is necessary to perform mechanical alloying so as to avoid generation of the intermetallic compound. As a result of research conducted by the inventor of the present application, after mechanical alloying, for example, FeWO
₄ and Ni ₂ W ₄ C were found to be formed.

The inventor of the present application has repeatedly studied the processing conditions of mechanical alloying. As a result, in the case of W alloys, in order to prevent the formation of intermetallic compounds during mechanical alloying, it is necessary to control the oxygen concentration of the atmosphere during mechanical alloying, control the temperature during processing, and adjust the processing time. Was found to be necessary. In the case of this alloy, the oxygen concentration in the atmosphere, which is one of the oxygen sources, is 5%.
00 ppm or less, more preferably 50 ppm
It is as follows. The processing temperature is desirably 80 ° C. or less. This temperature was measured by a thermocouple installed on the wall of the processing tank. If the processing temperature during mechanical alloying is high, or if the oxygen concentration in the atmosphere is high, in addition to the formation of intermetallic compounds, the formation reduces the ductility of the powder. And the mechanical alloying phenomenon is less likely to occur.

If the oxygen concentration is high, there is also a disadvantage that the mechanical properties, particularly ductility, of the finally produced extruded material are impaired. If the mechanical alloying temperature is high, the adhesion of the mechanical alloying powder to the ball surface and the inner wall of the processing vessel during the mechanical alloying process becomes excessive. In extreme cases, the adhesion powder may strip off the material of the ball and the inner wall (often steel or ceramics), and the stripped-off material may enter the mechanical alloying powder as contamination. Occurs. This contamination causes deterioration of the properties of the extruded material. In many cases, Fe, C, Cr, and oxygen are mixed into the mechanical alloying powder. Therefore, if mechanical alloying is continued, the contaminants may form intermetallic compounds or cause voids in the extruded material. Deteriorate characteristics.

If mechanical alloying is performed on the powder, the powder reaches saturation hardness after a certain period of time. It has been found that the desired processing time for mechanical alloying is about two to three times the time required for the powder to reach saturation hardness. If the mechanical alloying treatment is performed for longer than this time, the cleanliness of the powder is lowered, and the formation of intermetallic compounds is likely to occur. Therefore, it is desirable that the time of the mechanical alloying process be at most 200 hours or less.

When the powder is mechanically alloyed, factors that may affect the mechanical alloying properties of the powder include, besides the processing temperature, the processing time and the atmosphere, the weight ratio of ball / powder, drum or agitator. The rotation speed of the powder, the shape and size of the powder itself, the hardness of the powder, and the like can be considered. Researchers are currently studying which of these many factors will effectively affect mechanical alloying phenomena, and in general, which factors are still effective Is not determined. Rather, it can be said that it is necessary to find the effective factors for the powders to be mechanically alloyed and find the optimum conditions. This is because, as described above, Ni, Fe, and W are different in the likelihood of the pressure bonding phenomenon. Also,
This is because the ease with which a harmful phase is formed differs depending on the alloy.

When Ni powder, Fe powder and W powder are used as raw material powders, instead of separately putting the raw material powders in a mechanical alloying apparatus and immediately performing mechanical alloying, the mechanical alloying process is performed before mechanical alloying. It is necessary to premix. In this case, it may be performed continuously using the same device as the mechanical alloying,
After mixing using another apparatus, the mixed powder may be taken out of the apparatus, and then mechanical alloying may be performed. If the mixing before mechanical alloying is insufficient, the following problems occur.

In the initial stage of mechanical alloying, the W powder particles occupying the majority of the mixed powder collide with each other, and the W particles are strongly subjected to work hardening to promote the pulverizing action, and the W particles become small. Becomes susceptible to oxidizing action. In other words, the W powder particles do not collide with the Ni powder, so that W is not taken into Ni.

[0034] The Ni powders are likely to collide with each other, so that the Ni powders having a strong pressing effect grow coarsely without taking in the W particles. Even if some of the W particles enter Ni, the compressive action of the Ni powder is large, so the W particles themselves are also taken into the coarse Ni powder and do not become smaller than the original particles. The alloying phenomenon is less likely to occur. Here, the mechanical alloying phenomenon refers to a phenomenon in which W particles are dispersed and compounded uniformly and finely (in many cases, in a lamellar shape) in Ni.

In order to avoid the above problems, it is necessary to pre-mix the raw material powder before performing the mechanical alloying. Mixing of the powders may be by any method. For example, it is effective to use a ball mill in an Ar gas atmosphere for 30 minutes to 1 hour.

The powder subjected to mechanical alloying is
In order to remove the oxygen component and facilitate the subsequent sintering phenomenon, it is exposed to a high temperature of 800 ° C. or more in a reducing atmosphere such as hydrogen. Even without performing this process, it is possible to produce a W alloy having fine W particles.
However, if annealing is not performed in a hydrogen atmosphere, oxygen will remain and an intermetallic compound will be formed. If the oxygen concentration is high, the sintering phenomenon will be hindered. Therefore, it is desirable to perform hydrogen reduction in order to produce a high-density sintered body. The mechanically alloyed powder usually contains oxygen as an impurity, and the amount of oxygen varies depending on the composition and mechanical alloying conditions. After the hydrogen reduction treatment, the powder is annealed in a vacuum at 800 ° C. or higher in order to remove a hydrogen component from the powder. Annealing of the powder in hydrogen and annealing of the powder in vacuum may be performed after the powder is formed by a cold forming method such as CIP. That is more convenient in terms of handling. In addition, of the above annealing, annealing in vacuum may be performed after extrusion molding described later.

The powder (mechanical alloying powder) subjected to the above treatment is filled in a container in a vacuum, and the container is sealed to be airtight. At this time, it is desirable to seal the powder after sufficiently heating it to remove the adsorbed components on the surface of the powder before sealing. The heating temperature is desirably 300 ° C. or higher. This heat treatment may be performed in combination with the above-described dehydrogenation treatment.

The powder sealed in the container is extruded at a temperature of 800 ° C. or more and an extrusion ratio of 10 or more.
The reason for setting the extrusion ratio to 10 or more is that if the extrusion ratio is low, the thin oxidized phase on the surface of the mechanical alloying W powder cannot be destroyed, and a firmly fixed state between the powders cannot be obtained. The extrusion temperature needs to be determined in consideration of the annealing temperature described later. Therefore, the upper limit of the extrusion temperature is also determined in consideration of the target structure and the annealing temperature.

The solidified material of the extruded powder is an alloy having small crystal grains as it is. That is,
This is a W alloy in which W is uniformly compounded with other alloy elements and has no W particles having a diameter of 3 μm or more.

As a result of further research by the present inventor,
It has been found that when the above-mentioned material is annealed, a two-phase alloy consisting of pure W particles and a matrix phase similar to a normal heavy metal alloy can be obtained. It has also been found that the size of W particles can be made extremely small according to the annealing conditions, unlike the conventional case. It has also been found that the generation of such fine W particles occurs at 1000 ° C. or higher. Needless to say, the growth of W does not occur at a temperature below a certain temperature and does not occur at a temperature above a certain temperature, but rather occurs slightly at a low temperature when viewed from a microscopic viewpoint. However, it has been found that this growth easily occurs at a temperature of 1000 ° C. or higher. When the annealing temperature was 1200 ° C., the diameter of the obtained W particles was 0.2 to 3 μm. Annealing temperature 135
When set to 0 ° C., the diameter of the obtained W particles is 0.5 to
It was 4 μm. The W particles obtained at this time are formed by Ostwald ripening, and thus the W particles are basically spherical. Such a tissue is quite different from a tissue made by other methods. For example, in a method of solid-phase sintering a powder in which a Ni or Fe element surrounds the periphery of a W particle, the W particle basically does not grow, so the shape of the W particle is polygonal. It is. As described above, regarding the shape of the W particle,
A spherical shape has better mechanical properties than a polygonal shape. Further, from the viewpoint of the consistency with the matrix phase, it is better to grow W particles rather than to keep the W particles in a polygonal shape without growing them.

In the above description, annealing was performed after extrusion. However, annealing may be performed before extrusion. This annealing can be performed, for example, concurrently with the dehydrogenation treatment. In this case, an extrusion process is added after the growth of the W particles. Therefore, even if the W particles are once precipitated in a spherical shape, they become elliptical particles having a high aspect ratio by extrusion. For example, the minor axis diameter of the ellipsoidal W particles is 4 μm or less, and the ratio of the major axis diameter to the minor axis diameter is 2 or more. Such an ellipsoidal W particle has a characteristic of higher hardness than usual. It was found that W particles of a normal heavy metal alloy had a micro Vickers hardness of 300 units, whereas W particles deformed into an ellipsoidal shape had a micro Vickers hardness of 400 units.

The size of the particles can be changed by changing the annealing temperature, and the above-mentioned extrusion temperature is also determined from this viewpoint. That is, if annealing is performed after the extrusion to grow the W particles large, it is necessary to set the temperature at the time of the extrusion to a temperature or lower at which precipitation of W occurs remarkably. As a result of research conducted by the inventor of the present invention, the upper limit of the temperature at which no remarkable growth of W (of course, microscopically growing) is observed, that is, the upper limit of the extrusion temperature is 1150 ° C. I understand. At temperatures higher than this, W particles grow. On the other hand, if the annealing is performed before the extrusion, the extrusion temperature needs to be 1430 ° C. or less at the highest. This is because W particles grow remarkably above this temperature. Even if the W particles grow as much as a normal heavy metal alloy, it does not impair the properties. However, since the object of the present invention is to obtain a fine-grained tungsten alloy, a temperature of 1430 ° C. or lower is desirable to achieve this object.
The fine crystal grain W alloy obtained as described above may contain a small amount of a compound of W and Fe or a compound of W and Ni during heat treatment, but the content is less than 5% by volume. When the content of this compound is 5% by volume or more, the mechanical properties become poor.

Post processing (hot forging, swaging, etc.) can also be performed on the heavy metal alloy produced by extrusion. At that time, it is possible to freely select whether annealing is performed after the post-processing or annealing before the post-processing.
In other words, it is the same as the relationship between the above-described annealing and extrusion.

The heavy metal alloy produced as described above has a form in which W particles are present in the matrix. In such a structure, it was found that it is better to rapidly cool the cooling rate during the last annealing (preferably heating to 900 ° C. or more) in order to improve the mechanical properties. The reason for this is not necessarily clear, but is presumably because the rapid cooling removes impurity components (P, S, etc.) from the interface between the W particles and the matrix phase or the interface between the W particles. The quenching method includes various methods such as water quenching, oil quenching, and introduction of a forced cooling gas. In addition, simply annealing after quenching and then cooling in a furnace is useful because it has the effect of changing the shape of microvoids and promoting the sintering phenomenon.

The tungsten alloy of the present invention has small crystal grains, but basically contains the same elements as ordinary heavy metal alloys. Therefore, it is possible to improve the mechanical properties of the alloy as is generally performed with heavy metal alloys. For example, Re, Co, Cr, Mo, Cu
Or strengthening the alloy by post-processing by forging or swaging. With the addition of Re, W is hardened, the strength increases, and solid solution strengthening also occurs.

Since the alloy of the present invention has small crystal grains, its tensile strength shows a higher value than that of a normal heavy metal alloy. In the case of a normal heavy metal alloy, the tensile strength is 90 kg / mm ² and the elongation is about 20%. The alloys of the present invention may have slightly lower elongation values, but exhibit higher tensile strength values.

However, one thing to note here is the relationship between the extrusion temperature and the annealing temperature of the extruded material (of course,
It is irrelevant if the extruded material is used without annealing.) If the mechanical alloying powder is insufficiently reduced or the mechanically alloyed powder is extruded without reduction to produce an extruded material, the subsequent annealing temperature is (extrusion temperature + 50 ° C). Must not be exceeded. If the temperature is exceeded, void defects are formed in the extruded material, and mechanical properties, particularly, ductility are deteriorated.

Thus, for example, when annealing at 1350 ° C., the voids formed in the material extruded at 1150 ° C. are larger and larger than the voids formed in the material extruded at 1250 ° C. . In this case, 1
At 250 ° C., void formation is no longer as pronounced as the 1150 ° C. material. However, since the formation of voids is also determined in relation to the cleanliness of the mechanically alloyed powder (mainly unreduced components are the source of contamination), it is generally better not to exceed (extrusion temperature + 50 ° C). .

The extruding temperature is 800 ° C. or more when the extrusion ratio is 10 or more, and preferably 1130 ° C. or more. This is because the extruded material is microscopically composed of W grains and a matrix phase without annealing, but since this structure is extremely small at a low extrusion temperature, for example, the tensile strength is 2%.
Higher than 100 kg / mm ² , but low elongation (<1
0%).

[0050]

【Example】

Example 1 Pure W powder and pure Ni powder were mixed in a weight ratio of W: Ni = 9: 1.
And mixed in an Ar atmosphere using a ball mill. The total weight of the powder was 2 kg. 3
After mixing for 0 minutes, the mixed powder was transferred to an attritor and subjected to a mechanical alloying treatment for 10 hours.
The atmosphere gas at this time was Ar, and the impurity oxygen concentration was 8
The condition was set to 0 ppm. Regarding the temperature of the mechanical alloying treatment, two conditions were set. First
Is a temperature of 60 ° C. or lower, and the powder obtained at this processing temperature is referred to as a 60 ° C. processed powder. The second condition is 100
The processing temperature is １２０120 ° C., and the powder obtained at this processing temperature is referred to as a 120 ° C. processed powder. The rotation speed of the agitator was performed under the same conditions of 175 rotations / minute.

It was found that the two types of powders obtained by the above-described treatment were coarse powders having +150 mesh at 10% or more. Raw W powder and pure Ni
Since the particle size of the powder was about several μm, it is considered from the observation results of the powder after the treatment that the pressing action was sufficiently performed at the time of mechanical alloying. Observation of these treated powders with an optical microscope revealed that W and Ni were in a composite state.

The powder treated at 60 ° C. and the powder treated at 120 ° C.
It was analyzed and identified by the line diffraction method. FIG. 1 shows the result of X-ray diffraction of the powder treated at 60 ° C. In this diffraction result, a peak of (Ni, Fe) other than a peak of W is observed. FIG.
The result of having analyzed the powder processed at 0 degreeC by EDX is shown. ED
In the X analysis, W and Ni were detected. Fe was not detected. Therefore, (Ni, Fe) is Ni having substantially the same structure and lattice constant as (Ni, Fe), or reflects the Fe component slightly mixed as an impurity from the inner wall of the attritor processing tank. It appears to be. In any case, most of the structure in the alloy is substantially composed of W and Ni, and it can be seen that there is no compound between W and Ni.

FIG. 3 shows the result of X-ray diffraction of the powder treated at 120 ° C. As can be seen from this diffraction result, 120
The ° C treated powder contained about 20% by volume of Ni ₂ W ₄ C.

The oxygen concentration of the treated powder was 0.6% by weight for the powder treated at 60 ° C., and 1.0% for the powder treated at 120 ° C.
It was 6% by weight. That is, the higher the processing temperature, the higher the oxygen contamination.

[0055] 2 types of processing powder thus obtained, after 3 hours at a temperature of 1300 ° C. in a hydrogen stream (dew point -30 ℃), 10 ^- 950 ℃ during ⁴ torr of vacuum
Temperature for 2 hours. These two powders, furthermore, 10 ^- was held 3 hours at a temperature of 500 ° C. during ⁴ torr vacuum, hermetically sealed and filled into a mild steel container. Further, the powder sealed in the container was extruded at a temperature of 1150 ° C. and an extrusion ratio of 12.

When the extruded material thus obtained was observed with an optical microscope, it was found that W was uniformly and finely compounded in the Ni matrix, and no spherical W particles having a particle diameter (diameter) of 2 μm or more were observed. Was.

When the extruded material was subjected to vacuum annealing at a temperature of 1350 ° C. for 2 hours, W particles were deposited and grown. Observation of this structure using an optical microscope revealed that W
It consisted of particles and a matrix phase. The analysis result revealed that the matrix phase contained Ni and W. The shape of the W particles was spherical, and the particle size was 1 to 3 μm. In the powder subjected to mechanical alloying at 120 ° C., particulate foreign matter was observed at a portion considered to be a powder grain boundary.

From two kinds of annealed extruded material, a test piece (cross section
φ4 mm), and a tensile test was performed at room temperature.
In the case of the material treated at 60 ° C., the tensile strength is 160.2 kg /
mm ^TwoAnd the elongation was 17.4%. In contrast
In the case of a 120 ° C. treated material, on average, the tensile strength is
140kg / mm^TwoAnd the elongation was 4%. this
From the results, the mechanics for the compound containing W and Ni
Effect of processing temperature of cal alloying on mechanical properties
It was confirmed that it had an effect. Similarly, W-50Ni powder
And pure W powder and pressed under the same conditions as the powder treated at 60 ° C.
A material was produced. As a result, the tensile strength was 162.1 kg.
/ Mm^TwoAnd the elongation was 10%.

Example 2 2 kg of pure W powder and pure Fe were mixed at a weight ratio of W: Fe = 9: 1, and then mixed in an Ar atmosphere using a ball mill. After mixing for 30 minutes, the mixed powder was transferred to an attritor and subjected to a mechanical alloying treatment for 10 hours. The atmosphere gas at this time was Ar. Regarding impurity oxygen concentration, 100ppm, 600p
The test was performed under three conditions of pm and 3500 ppm. The temperature of the mechanical alloying treatment is set to 60 ° C. or less, and the rotation speed of the ball mill is 175 rotations /
Minutes.

The particle sizes of three kinds of powders having different oxygen concentrations were investigated. The treated powder having an oxygen concentration of 3500 ppm is finer than the other two kinds of powder, and 98% of the powder is-
It was 250 mesh. +250 for the other two powders
It was a coarse powder having a mesh of 20% or more. Since the particle diameters of the raw material pure W powder and pure Fe powder were both about several μm, the oxygen concentration was 600 ppm and 100 pp.
With respect to the two types of treated powders m, it is recognized that the pressure bonding operation was sufficiently performed during mechanical alloying.
However, with respect to the treated powder having an oxygen concentration of 3500 ppm, it is considered that the pressing action was not sufficient, and only the pulverization occurred strongly.

According to an optical microscope, an oxygen concentration of 3500 p
pm of the treated powder, W and F
Although a region where e was compounded was present, most of the powder was composed of a non-composite portion which remained W powder and Fe powder.

Oxygen concentration 600 ppm and 100 ppm
Were analyzed and identified by X-ray diffraction. FIG. 4 shows an X-ray diffraction result of the treated powder having an oxygen concentration of 600 ppm. The diffraction results include F
An eWO ₄ peak is seen. On the other hand, oxygen concentration 100p
In the case of the pm treated powder, no peak other than W and Fe was observed.

Example 3 Pure W powder and pure Ni powder were mixed in a weight ratio of W: Ni = 92:
After mixing 3 kg so as to be 8, the mixture was mixed in an Ar atmosphere using a ball mill. After mixing for 30 minutes, the mixed powder was transferred to another ball mill and subjected to mechanical alloying for 50 hours. Atmospheric gas at this time was Ar, and the impurity oxygen concentration was set to 80 ppm. The temperature during the treatment was set to 71 ° C. or less.

Separately from the above treatment, after blending W and Ni, the W powder and the Ni powder are immediately inserted into the treatment tank without mixing, and the mechanical alloying treatment is performed under the same conditions as above. Done.

The two types of treated powder thus obtained are represented by +
It was found that 150 mesh was a coarse powder containing 10% or more. Since the particle diameters of the pure W powder and the pure Ni powder as the raw materials were on the order of several μm, it is considered that both of the two types of treated powders sufficiently performed the press-bonding action during mechanical alloying.

The two kinds of treated powders were observed under an optical microscope. In the case of the treated powder obtained by premixing the W powder and the Ni powder, a composite structure was observed. On the other hand, in the case of the processed powder that has not been pre-mixed, a region of pure Ni that partially contains unmilled W particles and that is insufficiently complexed exists over a width of about 10 × 20 μm. Was observed. This region remained after annealing in hydrogen and vacuum at 900 ° C. and after extrusion at a temperature of 1020 ° C. and an extrusion ratio of 12, and a uniform structure could not be obtained.

Example 4 Pure W powder and pure Ni powder were mixed in a weight ratio of W: Ni = 9: 1.
And 5: 5 were blended in 3 kg each, and then each powder was mixed in an Ar atmosphere using a ball mill. After mixing for 30 minutes, each of the two mixed powders was transferred to an attritor, and subjected to a mechanical alloying treatment for 10 hours. Atmospheric gas at this time was Ar, and the impurity oxygen concentration was set to 80 ppm. The temperature during the mechanical alloying treatment was set to 60 ° C. or less, and the rotation speed of the agitator was set to 175 rotations / minute.

After the two kinds of treated powders thus obtained were kept at a temperature of 980 ° C. for 3 hours in a hydrogen stream,
10 ^- 2 during the ⁴ torr vacuum at a temperature of 980 ° C.
Hold for hours. Furthermore, the powder 10 ^- After 3 hours at a temperature of 500 ° C. at ⁴ torr in a vacuum, hermetically sealed and filled into a mild steel container. Further, the powder sealed in the container was extruded at an extrusion ratio of 6 and 12 at a temperature of 950 ° C.

In the extruded material having an extrusion ratio of 6, rows of holes were found parallel to the extrusion direction, and the densification was insufficient. On the other hand, in the extruded material having an extrusion ratio of 12, such pores were not observed in both materials regardless of the mixing ratio of W and Ni. Observation of the structure of the obtained extruded material showed that W was in a state of being uniformly and finely complexed in Ni as a matrix phase, and island-like W particles (such as those found in a normal heavy metal alloy). Particles having a particle size of 2 μm or more) were not observed.

Example 5 Among the extruded materials obtained in Example 4, the extruded material having a W: Ni compounding ratio of 5: 5 was used at 1200 ° C. and 1350 ° C.
Annealing was carried out under different temperature conditions for 2 hours.
After annealing, particles were precipitated. In the case of the 1200 ° C. annealed material, the particle diameter (particle diameter) was 0.2 to 2.5 μm. In the case of the 1350 ° C. annealed material, the diameter (particle size) of the particles was 0.5 to 3 μm.

FIG. 5 is a graph showing the relationship between the temperature of the annealed material at 1200 ° C.
3 shows a micrograph of a structure observation of M. EDX analysis revealed that the precipitated particles were W. 1350
The W particles grew in the annealed material at ° C. Further, each W particle was not a polygonal shape but a rounded spherical shape.

Example 6 In the extruded material obtained in Example 4, the ratio of W: Ni was 9:
For one extruded material, 1200 ° C and 1350 ° C
Annealing was performed for two hours under two temperature conditions. As a result of this annealing, particles are precipitated, and the diameter (particle size) of the particles in the 1200 ° C. annealed material is 0.2 to 3 μm.
In the case of the 350 ° C. annealed material, the particle diameter (particle size) is 1 to 4 μ
m. The structure of the annealed material was observed by SEM.
The observation results are shown in FIG. 6 and FIG. EDX
From the result of the analysis, it was found that the precipitated particles were W. Since W was precipitated and grown in the annealed material at 1350 ° C., each W particle was in contact with each other, but each particle was not a polygon but a rounded particle.

Example 7 Pure W powder and pure Ni powder were mixed in a weight ratio of W: Ni = 8: 2.
Then, the powder was mixed in an Ar atmosphere using a ball mill. After mixing for 30 minutes, the mixed powder was transferred to an attritor and subjected to mechanical alloying for 10 hours. Atmospheric gas at this time was Ar, and the impurity oxygen concentration was set to 80 ppm. The temperature during the treatment should be 60 ° C or less,
The agitator rotation speed was set to 200 rotations / minute.

The powder subjected to mechanical alloying was subjected to CIP molding at a molding pressure of 6000 kg / cm ² to produce a molded material. The size of the molding material was φ60 × 70 mm. After the molding material was held 3 hours at a temperature of 950 ° C. in a hydrogen gas stream, 10 ^- 95 during ⁴ torr of vacuum
It was kept at a temperature of 0 ° C. for 2 hours. For comparison, powders not subjected to annealing in hydrogen and in vacuum were prepared.

[0075] These two powder 10 ^- After 3 hours at a temperature of 500 ° C. at ⁴ torr in a vacuum, hermetically sealed and filled into a mild steel container. Further, the powder sealed in this container was extruded at an extrusion ratio of 1150 ° C.
Extruded at 2.

In the extruded material of the powder not subjected to the annealing treatment, a row of foreign particles was observed parallel to the extrusion direction, and the old powder grain boundary was confirmed. On the other hand, no such row of particles was found in the extruded material of the annealed powder. Observation of the structure of the obtained extruded material showed that W and Ni were uniformly and finely complexed, and spherical W particles (particle diameter of 2 μm) as seen in a normal heavy metal alloy.
Above) were not seen.

When the extruded material was subjected to vacuum annealing at 1350 ° C. for 2 hours, W particles precipitated and grew.
Observation of this structure with an optical microscope revealed that the diameter was 3 mm.
It consisted of W particles of μm or less and a matrix phase.
Analysis revealed that the matrix phase contained Ni and W.

Test pieces (cross section φ4 mm) were cut out from two kinds of extruded materials annealed at 1350 ° C. and subjected to a tensile test at room temperature. In the case of extruded material annealed in hydrogen and vacuum, on average, the tensile strength is 160.2 kg
/ Mm ² and the elongation was 17.8%. On the other hand, in the case of the extruded material which was not annealed in hydrogen and vacuum, after tensile annealing at 1350 ° C., the tensile strength was 126 kg / mm ² on average and the elongation was 4%. Void formation was observed in the tissue. From these results, the effects of annealing in hydrogen and annealing in vacuum were confirmed. In addition, when a tensile test was performed on the material that was not subjected to the final 1350 ° C. annealing, the tensile strength was 190.5 kg / mm ² and the elongation was 6.
6%. In this structure, no void was observed in the 1350 ° C. annealed material.

The annealed material obtained by annealing hydrogen and the vacuum annealed material at 1350 ° C. was further annealed at 1000 ° C. × 2 hours, and then cooled in water. A test specimen was cut out from the quenched material and a tensile test was performed. As a result, the tensile strength is 160.7 kg / mm ² ,
The elongation was 18.1%. From this result, the effect of rapid cooling after annealing was confirmed.

Annealed, extruded, and re-annealed in the same manner as described above in Example 2 for the treated powder in an impure gas containing 600 ppm of FeWO ₄ and an oxygen concentration of about 20% by volume. Strength is 120kg / mm
² , and the elongation was 1%. The material subjected to annealing, extruding, and re-annealing in the same manner for the treated powder in a 100 pm impurity gas containing no FeWO ₄ has a tensile strength of 162 kg / mm ² and an elongation of 1%.
6.2.

Experimental Example 8 3 kg of pure W powder, pure Ni powder, Re powder and Cr powder were blended in a weight ratio of W: Ni: Re: Cr = 80: 13: 6: 1, and the powder was then ball milled. A using
The mixture was mixed in an atmosphere. After performing this mixing process for 30 minutes, the mixed powder was transferred to an attritor and subjected to a mechanical alloying process for 60 hours. At this time, the atmosphere gas was Ar, and the impurity oxygen concentration was adjusted to 80 ppm or less. The temperature during the processing was 60 ° C. or less, and the rotation speed of the agitator was 200 rotations / minute.

The treated powder thus obtained was kept at a temperature of 1000 ° C. for 3 hours in a hydrogen stream,
^- was held for 2 hours at a temperature of 1350 ° C. in a ⁴ torr vacuum. When this powder was observed with an optical microscope,
W particles were precipitated and grown in each powder.

[0083] The powder 10 ^- After 3 hours at a temperature of 500 ° C. in a vacuum of ⁴ torr, hermetically sealed and filled into a mild steel container. 12 powders sealed in a container
It was extruded at an extrusion ratio of 14 at a temperature of 50 ° C.

Observation of the extruded material showed that W of 3 μm or less
The particles extended in the extrusion direction and had an aspect ratio of 3 or more. The micro Vickers hardness of the extruded material was 430.

The extruded material was subjected to vacuum annealing at a temperature of 1200 ° C. for 2 hours and then quenched in water. A test piece (cross-section φ4 mm) was cut out from the quenched material, and a tensile test was performed at room temperature. As a result, on average, the tensile strength was 172 kg / mm ² and the elongation was 12.0%.

W: Ni: Mo: Co is 90: 6: 3: 1
A quenched material was prepared in the same manner as described above for the mixed powder described above, and a tensile test was performed on the quenched material.
As a result, the tensile strength was 170.1 kg / mm ² and the elongation was 13.2%.

Example 9 Pure W powder, pure Ni powder and pure Fe powder were mixed in a weight ratio of W:
After 3 kg of Ni: Fe was mixed at 94: 4: 2, the powder was mixed in an Ar atmosphere using a ball mill. After performing this mixing process for 60 minutes, the mixed powder was transferred to an attritor and subjected to a mechanical alloying process for 50 hours. At this time, the atmosphere gas was Ar, and the impurity oxygen concentration was set to 70 ppm. The temperature during the treatment was set to 50 ° C. or less, and the rotation speed of the agitator was set to 175 rotations / minute.

The thus-obtained treated powder is kept at a temperature of 1000 ° C. for 3 hours in a hydrogen stream, and thereafter, 10 ⁻⁴
The temperature was kept at 1000 ° C. for 2 hours in a torr vacuum. Furthermore, the powder 10 ^- After 3 hours at a temperature of 400 ° C. at ⁴ torr in a vacuum, hermetically sealed and filled into a mild steel container. Further, the powder enclosed in the container was extruded at an extrusion ratio of 16 at a temperature of 1250 ° C.

When the obtained extruded material was observed, W, N
i and Fe are uniformly and finely compounded,
W was uniformly compounded in the matrix phase. No island-like W particles (having a particle size of 2 μm or more) as seen in a normal heavy metal alloy were found.

After the mild steel container was removed from the extruded material, annealing was performed at 1350 ° C. for 2 hours in a vacuum, and W particles precipitated and grew. 4 μm for W particles
It had the following particle size:

A test piece (cross section φ4 mm) was cut out from the extruded material and subjected to a tensile test at room temperature. As a result, on average, the tensile strength was 160.2 kg / mm ² and the elongation was 16.2%.

[0092]

As described above, according to the present invention,
A tungsten alloy having fine crystal grains can be manufactured efficiently. Since tungsten alloy has fine crystal grains, it has high strength and moderate ductility. Such a fine-grained tungsten alloy can be advantageously used for members requiring a high specific gravity and good mechanical properties and members requiring a radiation shielding effect.

[Brief description of the drawings]

FIG. 1 shows that the weight ratio of W and Ni is 9: 1 and 6
It is a figure which shows the X-ray diffraction result of the powder which performed mechanical alloying at 0 degreeC.

FIG. 2: W: Ni weight ratio is 9: 1, 60 ° C.
Cross section of powder that has been mechanically alloyed by EDX
FIG. 4 is a diagram showing the result of elemental analysis at.

FIG. 3 shows that the weight ratio of W and Ni is 9: 1,
FIG. 3 is a view showing an X-ray diffraction result of a powder that has been subjected to mechanical alloying at ° C.

FIG. 4 is a view showing an X-ray diffraction result of a powder subjected to mechanical alloying in an atmosphere in which the weight ratio of W and Fe is 9: 1 and the impurity oxygen concentration is 600 ppm.

FIG. 5 is a mechanical alloying powder having a composition of 5: 5 in weight ratio of W and Ni, and a material obtained through an annealing process in hydrogen, an annealing process in a vacuum, an extrusion process, and an annealing process at 1200 ° C. 5 is a micrograph showing the structure of Example 1.

FIG. 6 is a mechanical alloying powder having a composition in which the weight ratio of W and Ni is 9: 1, and a material obtained through a process of annealing in hydrogen, annealing in vacuum, extrusion and annealing at 1200 ° C. 5 is a micrograph showing the structure of Example 1.

FIG. 7 is a mechanical alloying powder having a composition in which the weight ratio of W and Ni is 9: 1, and a material obtained through an annealing process in hydrogen, an annealing process in a vacuum, an extrusion process, and an annealing process at 350 ° C. 5 is a micrograph showing the structure of Example 1.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI B22F 3/20 B22F 3/20 B C21D 3/02 C21D 3/02 C22C 1/04 C22C 1/04 D (56) References Special features JP-A-59-25950 (JP, A) JP-A-3-293978 (JP, A) JP-A-54-99719 (JP, A) JP-A-58-189307 (JP, A) JP-A-61-264142 (JP, A) JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 27/04 B22F 1/00-3/20 C22C 1/04

Claims (17)

(57) [Claims] 1. A compound comprising spherical W particles having a particle diameter of 7 μm or less, at least one of Ni and Fe, and a matrix phase containing W as a main component, the compound containing at least one of Ni and Fe and W. A fine-grained tungsten alloy, wherein the content is less than 5% by volume and the W content is in the range of 50-97% by weight. 2. The spherical W particle has an elliptical shape, and the minor axis diameter of the elliptical W particle is 4 μm or less, and the ratio of the major axis diameter to the minor axis diameter is 2 or more. The fine-grained tungsten alloy according to claim 1, wherein 3. The composition of the matrix phase is Ni—Fe.
The fine-grained tungsten alloy according to claim 1, which is -W. 4. The fine-grain tungsten alloy according to claim 1, wherein the W particles include at least one element selected from the group consisting of Re, Co, Cr, and Mo. 5. The matrix phase comprises Re, Co, C
The fine-grained tungsten alloy according to claim 1, comprising at least one element selected from the group consisting of r and Mo. 6. The fine-grained tungsten alloy according to claim 1, wherein the W has a particle size of less than 3 μm, and the W element is uniformly compounded with another alloy element in a matrix phase. 7. (a) At least one of Ni powder and Fe powder and W powder are prepared, and the content of W is 5
A step of blending the mixture so as to have a concentration of 0 to 97% by weight, and then uniformly mixing;
A step of performing a mechanical alloying treatment in an atmosphere of 00 ppm or less and at a processing temperature of 80 ° C or less, and (c) subjecting the powder subjected to mechanical alloying to 800 ° C.
A step of deoxidizing the powder by exposing the powder to the reducing atmosphere for 10 minutes or more; (d) enclosing the deoxidized powder in a container in a vacuum; (e) a container Extruding the powder enclosed therein at a temperature of 800 ° C. or more and an extrusion ratio of 10 or more, a method for producing a fine-grained tungsten alloy. 8. A powder subjected to mechanical alloying at a temperature of 800 ° C. between the step (c) and the step (d).
The method for producing a fine-grained tungsten alloy according to claim 7, further comprising a step of exposing to a vacuum for 10 minutes or more. 9. After the step (e), the extruded extruded material is at least 1000 ° C. and the extrusion temperature is 50 ° C.
The method for producing a fine-grained tungsten alloy according to claim 7, comprising a step of annealing at a temperature not exceeding. 10. The production of a fine-grained tungsten alloy according to claim 7, further comprising a step of cold-forming the mechanically alloyed powder between the step (b) and the step (c). Method. 11. The method according to claim 7, further comprising, after the step (e), removing a portion of the container of the extruded extruded material, and thereafter exposing the extruded material to a vacuum of 800 ° C. or more for 10 minutes or more. 3. The method for producing a fine-grained tungsten alloy according to 1.). 12. Prior to the step (e), 10
The method for producing a fine-grained tungsten alloy according to claim 7, further comprising a step of annealing at a temperature of 00 ° C or higher. 13. The method for producing a fine-grained tungsten alloy according to claim 7, wherein the powder to be mixed includes pure W powder, pure Ni powder and pure Fe powder. 14. Powder to be compounded is pure Re powder, pure Mo
The method for producing a fine-grained tungsten alloy according to claim 7, comprising at least one kind of powder selected from the group consisting of powder, pure Cu powder, pure Cr powder, and pure Co powder. 15. The method for producing a fine-grained tungsten alloy according to claim 9, further comprising a step of quenching the extruded material after the annealing step. 16. The method according to claim 12, further comprising a step of quenching the powder after the annealing step. 17. The powder to be compounded is W-Ni alloy powder, W
The method for producing a fine-grained tungsten alloy according to claim 7, comprising at least one kind of powder selected from the group consisting of -Fe alloy powder and Ni-Fe alloy powder.