JP6314866B2 - Method for producing metal powder for powder metallurgy, compound, granulated powder and sintered body - Google Patents

Description

The present invention relates to a metal powder for powder metallurgy, a compound, a granulated powder, and a method for producing a sintered body.

  In the powder metallurgy method, a composition including a metal powder and a binder is molded into a desired shape to obtain a molded body, and then the molded body is degreased and sintered to produce a sintered body. In the manufacturing process of such a sintered body, an atomic diffusion phenomenon occurs between the particles of the metal powder, and thereby the compact is gradually densified, resulting in sintering.

  For example, Patent Document 1 proposes a metal powder for powder metallurgy that includes at least one selected from the group consisting of Fe, Co, and Ni and unavoidable elements, including Zr and Si. According to the metal powder for powder metallurgy, the sinterability is improved by the action of Zr, and a high-density sintered body can be easily manufactured.

  In recent years, the sintered body thus obtained has been widely used for various machine parts, structural parts, and the like.

  However, depending on the application of the sintered body, further densification may be required. In such a case, the density is increased by performing additional processing such as hot isostatic pressing (HIP processing) on the sintered body. The cost cannot be avoided.

  Therefore, there is an increasing expectation for the realization of a metal powder capable of producing a high-density sintered body without performing additional processing.

JP 2012-87416 A

An object of the present invention is to provide a metal powder for powder metallurgy capable of producing a high-density sintered body, a compound and a granulated powder, and a method for producing a sintered body capable of producing a high-density sintered body. It is in.

The above object is achieved by the present invention described below.
The metal powder for powder metallurgy of the present invention contains Fe as a main component,
Cr is included in a proportion of 0.2% by mass to 35% by mass,
Si is contained in a proportion of 0.2% by mass or more and 3% by mass or less,
C is contained in a ratio of 0.005 mass% to 2 mass%,
Ti, V, Y, Zr, and one element selected from the group consisting of Nb and Hf as a first element, V, Z r, Nb, with one kind of element selected from the group consisting of Hf and Ta When the element in the periodic table of elements is larger than the first element or the element in the periodic table of elements is the same as the first element and the element in the periodic table of elements is larger than the first element is the second element. ,
The first element is included in a proportion of 0.01% by mass to 0.5% by mass,
Having particles containing the second element in a proportion of 0.01% by mass or more and 0.5% by mass or less;
The Cr content on the surface of the particles is 0.2 atomic% or more and 15 atomic% or less, and 70% or more and 170% or less of the Cr content at a position where the depth from the surface of the particles is 60 nm. It is characterized by being.
The metal powder for powder metallurgy of the present invention contains Fe as a main component,
Cr is contained in a ratio of 2% by mass to 32% by mass,
Si is contained at a ratio of 0.4 mass% or more and 1.5 mass% or less,
C is contained in a proportion of 0.01% by mass or more and 1.5% by mass or less,
Ti, V, Y, Zr, and one element selected from the group consisting of Nb and Hf as a first element, V, Z r, Nb, with one kind of element selected from the group consisting of Hf and Ta When the element in the periodic table of elements is larger than the first element or the element in the periodic table of elements is the same as the first element and the element in the periodic table of elements is larger than the first element is the second element. ,
The first element is included at a ratio of 0.03% by mass to 0.4% by mass,
Having particles containing the second element in a proportion of 0.03% by mass or more and 0.4% by mass or less;
The Cr content on the surface of the particles is 0.2 atomic% or more and 15 atomic% or less, and 70% or more and 170% or less of the Cr content at a position where the depth from the surface of the particles is 60 nm. It is characterized by being.
The metal powder for powder metallurgy of the present invention contains Fe as a main component,
Cr is included in a ratio of 6% by mass to 30% by mass,
Si is contained in a proportion of 0.5% by mass or more and 1% by mass or less,
C is contained at a ratio of 0.02 mass% to 1 mass%,
Ti, V, Y, Zr, and one element selected from the group consisting of Nb and Hf as a first element, V, Z r, Nb, with one kind of element selected from the group consisting of Hf and Ta When the element in the periodic table of elements is larger than the first element or the element in the periodic table of elements is the same as the first element and the element in the periodic table of elements is larger than the first element is the second element. ,
The first element is included in a proportion of 0.05% by mass or more and 0.3% by mass or less,
Having particles containing the second element in a proportion of 0.05% by mass or more and 0.3% by mass or less;
The Cr content on the surface of the particles is 0.2 atomic% or more and 15 atomic% or less, and 70% or more and 170% or less of the Cr content at a position where the depth from the surface of the particles is 60 nm. It is characterized by being.

  As a result, the particles of the metal powder for powder metallurgy have a thickness of the passive film derived from the oxide of Cr to a certain extent, and can suppress the sinterability of the particles from being lowered by the passive film. . As a result, since the particles are densified at the time of sintering, a high-density sintered body can be produced without additional processing.

In the metal powder for powder metallurgy according to the present invention, the Si content on the surface of the particles is preferably 155% to 800% of the Si content at a position where the depth from the surface of the particles is 60 nm. .
In the metal powder for powder metallurgy according to the present invention, the Si content on the surface of the particles is preferably 200% to 500% of the Si content at a position where the depth from the surface of the particles is 60 nm. .

  As a result, Si is segregated on the surface of the particles, and since this Si acts as a deoxidizing element that suppresses oxidation of Fe and Cr, a large amount of iron oxide is produced when the particles are sintered. And generation of chromium oxide can be suppressed. As a result, the particles are more excellent in sinterability, and a higher density sintered body can be produced.

In the metal powder for powder metallurgy according to the present invention, the ratio of the O content to the Si content on the surface of the particles is preferably 0.05 or more and 0.4 or less.
In the metal powder for powder metallurgy according to the present invention, the ratio of the O content to the Si content on the surface of the particles is preferably 0.1 or more and 0.35 or less.

  Thereby, even if Si segregates on the surface of the particles, the ratio of Si existing in the silicon oxide state can be sufficiently reduced. As a result, the deoxidation effect by Si can be more reliably exhibited while suppressing the decrease in sinterability due to the presence of a large amount of silicon oxide.

  In the metal powder for powder metallurgy according to the present invention, the Cr content on the surface of the particles is preferably smaller than the Cr content on the entire particles.

  Thereby, since it can suppress that the film thickness of the passive film formed in the surface of particle | grains becomes thick too much, the sinterability of particle | grains can be improved especially.

In the metal powder for powder metallurgy according to the present invention, a value X1 obtained by dividing the content of the first element by the atomic weight of the first element with respect to the value X2 obtained by dividing the content of the second element by the atomic weight of the second element. The ratio X1 / X2 is preferably 0.3 or more and 3 or less.
In the metal powder for powder metallurgy according to the present invention, a value X1 obtained by dividing the content of the first element by the atomic weight of the first element with respect to the value X2 obtained by dividing the content of the second element by the atomic weight of the second element. The ratio X1 / X2 is preferably 0.5 or more and 2 or less.
In the metal powder for powder metallurgy according to the present invention, a value X1 obtained by dividing the content of the first element by the atomic weight of the first element with respect to the value X2 obtained by dividing the content of the second element by the atomic weight of the second element. The ratio X1 / X2 is preferably 0.75 or more and 1.3 or less.

  Thereby, when the metal powder for powder metallurgy is fired, the balance between the precipitation amount of the first element carbide and the like and the precipitation amount of the second element carbide and the like can be optimized. As a result, since the voids remaining in the molded body can be sequentially discharged from the inside and discharged, the voids generated in the sintered body can be minimized. Therefore, a metal powder for powder metallurgy capable of producing a sintered body having high density and excellent sintered body characteristics can be obtained.

In the metal powder for powder metallurgy according to the present invention, the total content of the first element and the content of the second element is preferably 0.05% by mass or more and 0.8% by mass or less.
In the metal powder for powder metallurgy according to the present invention, the total content of the first element and the content of the second element is preferably 0.10% by mass or more and 0.6% by mass or less.
In the metal powder for powder metallurgy of the present invention, the total content of the first element and the content of the second element is preferably 0.12% by mass or more and 0.24% by mass or less.
As a result, the density of the sintered body to be manufactured becomes necessary and sufficient.

  In the metal powder for powder metallurgy of the present invention, the average particle size is preferably 0.5 μm or more and 30 μm or less.

  Thereby, since the void | holes which remain | survive in a sintered compact become very few, the sintered compact which was especially high-density and excellent in the mechanical characteristic can be manufactured.

The compound of the present invention comprises the metal powder for powder metallurgy of the present invention and a binder for binding particles of the metal powder for powder metallurgy.
Thereby, the compound which can manufacture a high-density sintered compact is obtained.

The granulated powder of the present invention is obtained by granulating the metal powder for powder metallurgy of the present invention.
Thereby, the granulated powder which can manufacture a high-density sintered compact is obtained.

The method for producing a sintered body of the present invention includes a step of molding a composition containing the metal powder for powder metallurgy of the present invention to obtain a molded body,
Firing the molded body to obtain a sintered body;
It is characterized by having .
Thereby, a high-density sintered compact is obtained.

It is a figure which shows typically the cross section of the particle | grains contained in embodiment of the metal powder for powder metallurgy of this invention. FIG. 2 is an enlarged view of a range A of the cross section of the particle shown in FIG. 1, for explaining a state in which depth direction analysis is performed by Auger electron spectroscopy using sputtering on the surface of the particle. Sample No. 1 is an Auger electron spectroscopic spectrum obtained from particles of metal powder for powder metallurgy 1. Sample No. It is an Auger electron spectroscopy spectrum obtained from the particle | grains of the metal powder for 23 powder metallurgy.

  Hereinafter, the metal powder for powder metallurgy, compound, granulated powder, and sintered body of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

[Metal powder for powder metallurgy]
First, an embodiment of the metal powder for powder metallurgy of the present invention will be described.

  In powder metallurgy, a composition containing a metal powder for powder metallurgy and a binder is molded into a desired shape, and then degreased and fired to obtain a sintered body having a desired shape. Such a powder metallurgy technique has an advantage that a sintered body having a complicated and fine shape can be manufactured with a near net shape (a shape close to the final shape) as compared with other metallurgical techniques.

  As metal powder for powder metallurgy used for powder metallurgy, attempts have been conventionally made to increase the density of a sintered body produced by appropriately changing the composition. However, since pores are easily formed in the sintered body, it was necessary to further increase the density of the sintered body in order to obtain mechanical properties equivalent to the melted material.

  For example, conventionally, the obtained sintered body may be further densified by performing additional processing such as hot isostatic pressing (HIP processing). However, such additional processing involves a lot of labor and cost, and is an obstacle when expanding the use of the sintered body.

  In view of the above problems, the present inventor has intensively studied the conditions for obtaining a high-density sintered body without performing additional processing. As a result, it has been found that the density of the sintered body can be increased by optimizing the structure of each particle contained in the metal powder, and the present invention has been completed.

  Specifically, the metal powder for powder metallurgy according to the present embodiment contains Fe as a main component, Cr is contained in a ratio of 0.2 mass% to 35 mass%, and Si is 0.2 mass%. It is contained in a proportion of 3% by mass or less, C is contained in a proportion of 0.005% by mass or more and 2% by mass or less, and a first element described later is contained in a proportion of 0.01% by mass or more and 2% by mass or less. The second element to be described later has particles containing 0.01% by mass or more and 2% by mass or less, and the Cr content on the surface of the particles is 60 nm deep from the particle surface. The metal powder is characterized by being 70% or more and 170% or less of the Cr content at the position. According to such a metal powder, the chemical composition and the particle structure are optimized, and as a result, densification during sintering can be particularly enhanced. As a result, a sufficiently high density sintered body can be manufactured without performing additional processing.

  Such a sintered body is excellent in mechanical properties. For this reason, a sintered compact can be widely applied also to the use to which external force is added, such as a machine part and a structural part, for example.

  The first element is one element selected from the group consisting of seven elements of Ti, V, Y, Zr, Nb, Hf and Ta, and the second element is the group consisting of the seven elements. Selected from the group consisting of the seven elements and the first element selected from the group consisting of the seven elements. And the element in the periodic table of the elements is the same element, and the period in the periodic table of the elements is larger than the first element.

  Hereinafter, the structure of the powder for powder metallurgy according to the present embodiment will be described in more detail. In the following description, the metal powder for powder metallurgy is also simply referred to as “metal powder”, and each of a large number of particles constituting the metal powder for powder metallurgy is also simply referred to as “particles”.

<Particle structure>
First, the structure of particles of metal powder for powder metallurgy according to the present embodiment will be described.

  FIG. 1 is a diagram schematically showing a cross section of particles included in an embodiment of the metal powder for powder metallurgy of the present invention, and FIG. 2 is an enlarged view of a range A of the cross section of the particles shown in FIG. It is a figure for demonstrating a mode that the depth direction analysis by the Auger electron spectroscopy which used sputtering together on the surface of particle | grains is performed.

  When the Cr content on the surface of the particle 1 is Cr (0) and the Cr content at the position where the depth from the surface of the particle 1 is 60 nm is Cr (60), Cr (0) is 0. It is 2 atomic% or more and 15 atomic% or less and 70% or more and 170% or less of Cr (60).

  It can be said that the particle 1 satisfying such a condition has a relatively constant Cr content from its surface to a depth of 60 nm. In such particles 1, the passive film derived from the oxide of Cr becomes thin to some extent, and it can be suppressed that the sinterability of the particles 1 is lowered by the passive film. As a result, since the particles 1 are densified at the time of sintering, a high-density sintered body can be manufactured without additional processing.

  Note that if Cr (0) falls below the lower limit or the ratio of Cr (0) to Cr (60) falls below the lower limit, the oxidation resistance on the surface of the particles 1 is lowered. When the oxidation resistance is lowered, the surface of the particle 1 is easily oxidized due to an environmental change. At this time, since the oxidation of the surface of the particles 1 tends to be non-uniform for each particle 1, the sinterability of each particle 1 varies and the densification of the sintered body is impaired. On the other hand, if Cr (0) exceeds the upper limit value or the ratio of Cr (0) to Cr (60) exceeds the upper limit value, the thickness of the passive film becomes too thick. For this reason, the passive film inhibits the sintering of the particles 1 and the densification of the sintered body is impaired.

  The depth of 60 nm from the surface of the particle 1 is considered to have a low probability of contributing to sintering even when the metal powder is subjected to firing. In other words, the chemical composition at a position of a depth of 60 nm is considered to be close to the chemical composition inside the particle 1. For this reason, the fact that Cr (0) is approximately the same as that of Cr (60) means that a remarkably thick passive film is not formed on the surface of the particle 1, which means that the sinterability of the particle 1. It is thought that this is the reason why

  Such Cr (0) and Cr (60) can be obtained by depth direction analysis by Auger electron spectroscopy combined with sputtering. In this analysis, ions are collided with the surface of the particle 1 and the atomic layer is gradually peeled off, the particle 1 is irradiated with an electron beam, and the atom is identified and quantified based on the kinetic energy of Auger electrons emitted from the particle 1. I do. For this reason, the relationship between the depth from the surface of the particle 1 and the composition ratio can be obtained by converting the time required for sputtering into the thickness of the atomic layer peeled off by sputtering.

  The relationship between the depth and the composition ratio as described above can be obtained within a range of several hundred nm from the surface. At this time, it is sufficient that at least Cr (0) and Cr (60) satisfy the above relationship. For example, the Cr content at a depth of 30 nm from the surface of the particle 1 is 70% or more of Cr (60) 170 % Or less.

  Further, Cr (0) may be 0.2 atomic% or more and 15 atomic% or less, but is preferably 0.5 atomic% or more and 13 atomic% or less.

  Further, Cr (0) may be 70% or more and 170% or less of Cr (60), but is preferably 80% or more and 150% or less.

  Furthermore, when the Cr content in the entire particle 1 is Cr (w), the Cr content Cr (0) on the surface of the particle 1 may satisfy the relationship of Cr (0) <Cr (w). Preferably, it is more preferable to satisfy the relationship Cr (0) <0.8 × Cr (w). By satisfying such a relationship, the Cr content in the surface of the particle 1 can be made smaller than the Cr content in the entire particle 1. Thereby, compared with the film thickness of the passive film converted from the chemical composition of the whole particle 1, it can suppress that the film thickness of the passive film formed on the surface of the particle 1 becomes too thick. The sinterability of the particles 1 can be particularly enhanced.

  In addition, the content rate of Cr in the whole particle | grain 1 can be calculated | required with the analysis method mentioned later.

  Further, when the Si content on the surface of the particle 1 is Si (0) and the Si content at a position where the depth from the surface of the particle 1 is 60 nm is Si (60), Si (0) is It is preferable that it is 155% or more and 800% or less of Si (60), and it is more preferable that it is 200% or more and 500% or less.

  The particle 1 satisfying such a condition is that the Si content on the surface is 1.55 times or more larger than the Si content in the interior (depth of 60 nm). In such particles 1, it can be said that Si is segregated on the surface. Si is considered to exist on the surface of the particle 1 in a state such as silicon oxide. Since Si acts as a deoxidizing element that suppresses oxidation of Fe and Cr, generation of iron oxide and chromium oxide on the surface of the particle 1 can be suppressed. Moreover, even when oxygen is newly supplied when the particles 1 are sintered, it is possible to suppress the generation of a large amount of iron oxide or chromium oxide. As a result, the particles 1 are more excellent in sinterability, and a higher density sintered body can be produced.

  Further, Si present on the surface of the particles 1 acts to suppress the enlargement of crystal grains when the metal powder is subjected to firing. For this reason, the refinement | miniaturization of a crystal | crystallization is achieved and the sintered compact excellent in the mechanical characteristic can be manufactured.

  Further, Si (0) is preferably 15 atom% or more and 50 atom% or less, and more preferably 25 atom% or more and 45 atom% or less.

  Particles 1 satisfying such conditions can suppress the production of a large amount of iron oxide or chromium oxide. For this reason, the particle | grain 1 becomes what was excellent in sinterability, and can manufacture a higher density sintered compact.

  On the other hand, although Si is segregated on the surface of the particle 1, if a large amount is present in the state of silicon oxide, there is a risk of inhibiting the firing of the metal powder, like iron oxide and chromium oxide. .

  Considering this point, when the O content on the surface of the particle 1 is O (0), O (0) is preferably 0.05 times or more and 0.4 times or less that of Si (0). More preferably, they are 0.1 times or more and 0.35 times or less.

  Keeping the ratio of O (0) to Si (0) within the above range means that even if Si is segregated on the surface of the particles 1, the ratio of Si existing in the silicon oxide state is sufficiently increased. It leads to being lowered. Therefore, by keeping the ratio of O (0) to Si (0) within the above range, the deoxidation effect by Si is more reliably exhibited while suppressing the deterioration of sinterability due to the presence of a large amount of silicon oxide. Can be made. As a result, particles 1 having particularly high sinterability are obtained, and by using a metal powder containing the particles 1, a high-density sintered body can be produced.

  In addition, Si (0), Si (60) and O (0) described above can also be obtained by depth direction analysis by Auger electron spectroscopy combined with sputtering, similarly to Cr (0) and Cr (60). .

  As described above, a sintered body having excellent mechanical characteristics can be obtained by increasing the density of the sintered body. Such a sintered body can be widely applied to applications where a large external force is applied, such as mechanical parts and structural parts.

<Chemical composition of particles>
Next, an example of the overall chemical composition of the particles 1 will be described.

  Fe is a component (main component) having the highest content ratio among the chemical compositions of the particles 1 and greatly affects the characteristics of the sintered body. The Fe content in the entire particle 1 is 50% by mass or more.

(Cr)
Cr (chromium) is an element that imparts corrosion resistance to the sintered body to be produced. By using a metal powder containing Cr, a sintered body that can maintain high mechanical properties over a long period of time can be obtained.

  The Cr content in the particles 1 is 0.2% by mass or more and 35% by mass or less, preferably 2% by mass or more and 32% by mass or less, more preferably 6% by mass or more and 30% by mass or less. The

  When the Cr content is less than the lower limit, depending on the overall composition, the corrosion resistance of the manufactured sintered body may be insufficient. On the other hand, if the Cr content exceeds the upper limit, depending on the overall composition, the sinterability may be reduced, and it may be difficult to increase the density of the sintered body.

(Ni)
Ni (nickel) is an element that imparts corrosion resistance and heat resistance to the sintered body to be produced as necessary.

  The Ni content in the particles 1 is preferably 41% by mass or less, more preferably 10% by mass to 39% by mass, and still more preferably 12% by mass to 27% by mass. By setting the Ni content within the above range, a sintered body having excellent mechanical properties over a long period of time can be obtained.

  If the Ni content is less than the lower limit, depending on the overall composition, the corrosion resistance and heat resistance of the sintered body to be produced may not be sufficiently increased. On the other hand, the Ni content is not limited to the upper limit. If the value is exceeded, corrosion resistance and heat resistance may be deteriorated.

  Moreover, when the particle | grains 1 contain Ni and Mo, you may make it change the content rate of Cr suitably according to it.

  For example, when the Ni content is 7% by mass or more and 22% by mass or less and the Mo content is less than 1.2% by mass, the Cr content is 18% by mass or more and 20% by mass or less. More preferably. On the other hand, when the Ni content is 10% by mass or more and 22% by mass or less and the Mo content is 1.2% by mass or more and 5% by mass or less, the Cr content is 16% by mass or more. More preferably, it is less than 18% by mass.

  Further, when the Ni content is 0.05% by mass or more and 0.6% by mass or less, the Cr content is more preferably 10% by mass or more and 18% by mass or less.

(Si)
Si (silicon) is an element that imparts corrosion resistance and high mechanical properties to the sintered body to be produced. By using a metal powder containing Si, a sintered body that can maintain high mechanical properties over a long period of time is obtained. can get.

  The Si content in the particles 1 is 0.2% by mass or more and 3% by mass or less, preferably 0.4% by mass or more and 1.5% by mass or less, and more preferably 0.5% by mass or more. 1% by mass or less.

  If the Si content is lower than the lower limit, the effect of adding Si is dilute depending on the overall composition, and the corrosion resistance and mechanical properties of the manufactured sintered body may be reduced. On the other hand, if the Si content exceeds the upper limit, depending on the overall composition, Si becomes too much, so that corrosion resistance and mechanical properties may be deteriorated.

(C)
C (carbon) is used in combination with the first element and the second element to generate carbides of the first element, carbides of the second element, and the like as described above. Thereby, as mentioned above, a high-density sintered body can be obtained.

  The C content in the particles 1 is 0.005% by mass or more and 2% by mass or less, preferably 0.01% by mass or more and 1.5% by mass or less, more preferably 0.02% by mass or more. 1% by mass or less.

  If the C content is less than the lower limit, depending on the overall composition, a sufficient amount of carbides of the first element, carbides of the second element, and the like are difficult to be generated. May be insufficient. On the other hand, if the C content exceeds the upper limit, depending on the overall composition, C may be excessive with respect to the amounts of the first element and the second element, which may reduce the sinterability of the particles 1. is there.

  In addition, when the particle | grains 1 contain Ni, you may make it change the content rate of C suitably according to it.

  For example, when the Ni content is 7% by mass or more and 22% by mass or less, the C content is more preferably 0.005% by mass or more and 0.3% by mass or less.

  Moreover, when the Ni content is 0.05% by mass or more and 0.6% by mass or less, the C content is more preferably 0.15% by mass or more and 1.2% by mass or less.

  In addition, when the particle | grains 1 contain Ni, it is preferable to set the content rate of Ni to 0.05 mass% or more and 22 mass% or less. By adding Ni to the particles 1, the corrosion resistance and heat resistance of the sintered body to be produced can be further increased.

  If the Ni content is below the lower limit, depending on the overall composition, the corrosion resistance and heat resistance of the sintered body to be produced may not be sufficiently increased, while the Ni content exceeds the upper limit. If it exceeds the upper limit, the corrosion resistance and heat resistance may be lowered depending on the overall composition.

(First element and second element)
The first element and the second element precipitate carbides and oxides (hereinafter collectively referred to as “carbides and the like”). And this precipitated carbide | carbonized_material etc. are thought to inhibit the remarkable growth of a crystal grain, when a metal powder sinters. As a result, as described above, voids are less likely to occur in the sintered body, and the enlargement of crystal grains is prevented, and a sintered body having a high density and high mechanical properties can be obtained.

  In addition, as will be described in detail later, the precipitated carbides and the like promote the accumulation of silicon oxide at the grain boundaries, and as a result, the sintering is promoted and the density is increased while suppressing the enlargement of the crystal grains. .

  Incidentally, the first element and the second element are two elements selected from the group consisting of seven elements of Ti, V, Y, Zr, Nb, Hf, and Ta. It is preferable that an element belonging to Group 4A or Group 4A (Ti, Y, Zr, Hf) is included. By including an element belonging to Group 3A or 4A as at least one of the first element and the second element, oxygen contained as an oxide in the metal powder is removed, and the sinterability of the metal powder is particularly enhanced. Can do.

  Further, as described above, the first element may be one element selected from the group consisting of seven elements of Ti, V, Y, Zr, Nb, Hf and Ta, but preferably the seven elements In the group consisting of the elements, the element belongs to Group 3A or Group 4A of the long-period element periodic table. The elements belonging to Group 3A or Group 4A can remove oxygen contained in the metal powder as an oxide (act as a deoxidizing element), and can particularly enhance the sinterability of the metal powder. Thereby, the oxygen concentration remaining in the crystal grains after sintering can be reduced. As a result, the oxygen content of the sintered body can be reduced and the density can be increased. Moreover, since these elements are highly active elements, it is considered that rapid atomic diffusion is brought about. For this reason, this atomic diffusion becomes a driving force, the distance between the particles of the metal powder is efficiently reduced, and densification of the compact is promoted by forming a neck between the particles. As a result, the sintered body can be further densified.

  On the other hand, as described above, the second element is one element selected from the group consisting of seven elements of Ti, V, Y, Zr, Nb, Hf, and Ta, and the first element is Any element may be used as long as it is different, but it is preferably an element belonging to Group 5A of the periodic table of the long-period type element among the group of 7 elements. In particular, the elements belonging to Group 5A can efficiently precipitate the above-described carbides and the like, so that significant growth of crystal grains during sintering can be efficiently inhibited. As a result, the generation of fine crystal grains can be promoted, and the density of the sintered body can be increased and the mechanical properties can be improved.

  In addition, in the combination of the 1st element and 2nd element which consist of the above elements, each effect is exhibited, without mutually inhibiting. For this reason, such a metal powder containing the first element and the second element can produce a particularly high-density sintered body.

  More preferably, a combination in which the first element is an element belonging to Group 4A and the second element is Nb is employed.

More preferably, a combination in which the first element is Zr or Hf and the second element is Nb is employed.
By adopting such a combination, the above-described effect becomes more remarkable.

  In addition, when the first element is Zr in particular, Zr is a ferrite-forming element, so that a body-centered cubic lattice phase is precipitated. This body-centered cubic lattice phase is excellent in sinterability compared to other crystal lattice phases, and thus contributes to higher density of the sintered body.

  Note that the atomic radius of Zr is slightly larger than the atomic radius of Fe. Specifically, the atomic radius of Fe is about 0.117 nm, and the atomic radius of Zr is about 0.145 nm. For this reason, although Zr is solid-dissolved with respect to Fe, it does not reach a complete solid solution, and a part of Zr is precipitated as a carbide or the like. As a result, an appropriate amount of carbide or the like is precipitated, so that the enlargement of crystal grains can be effectively suppressed while promoting the sintering and increasing the density.

  When the second element is particularly Nb, the atomic radius of Nb is slightly larger than the atomic radius of Fe, but slightly smaller than the atomic radius of Zr. Specifically, the atomic radius of Fe is about 0.117 nm, and the atomic radius of Nb is about 0.134 nm. For this reason, although Nb dissolves in Fe, it does not reach a complete solid solution, and a part of Nb is precipitated as a carbide or the like. As a result, an appropriate amount of carbide or the like is precipitated, so that the enlargement of crystal grains can be effectively suppressed while promoting the sintering and increasing the density.

  The content of the first element in the metal powder is 0.01% by mass or more and 0.5% by mass or less, preferably 0.03% by mass or more and 0.4% by mass or less, and more preferably 0.8% by mass. It is set to 05 mass% or more and 0.3 mass% or less. When the content of the first element is below the lower limit, depending on the entire composition, the effect of adding the first element becomes dilute, so that the density of the sintered body to be manufactured becomes insufficient. On the other hand, if the content of the first element exceeds the upper limit, depending on the overall composition, the first element will be too much, so that the ratio of the above-described carbides will be too much, and the densification will be impaired. .

  The content ratio of the second element in the metal powder is 0.01% by mass or more and 0.5% by mass or less, preferably 0.03% by mass or more and 0.4% by mass or less, and more preferably 0.8% by mass. It is set to 05 mass% or more and 0.3 mass% or less. If the content ratio of the second element is less than the lower limit, depending on the entire composition, the effect of adding the second element becomes dilute, so that the density of the sintered body to be manufactured becomes insufficient. On the other hand, if the content ratio of the second element exceeds the upper limit, depending on the entire composition, the second element becomes too much, so that the ratio of the above-mentioned carbides and the like becomes too large, and the densification is impaired. .

  In addition, as described above, the first element and the second element each precipitate carbide or the like. However, as described above, the element belonging to the 3A group or the 4A group is selected as the first element, and the second element is described above. Thus, when an element belonging to the group 5A is selected, it is estimated that the timing at which the carbide of the first element precipitates and the timing at which the carbide of the second element precipitates are appropriately shifted when the metal powder is sintered. The Since the timing of precipitation of carbides and the like is shifted in this way, the sintering proceeds gradually, so that it is considered that the formation of pores is suppressed and a dense sintered body can be obtained. That is, it is considered that the presence of both the first element carbide and the second element carbide makes it possible to suppress the enlargement of crystal grains while achieving higher density.

  Note that, due to such a timing shift, the first element carbides and the second element carbides precipitated in the particles 1 are also mutually exclusive. That is, the first element carbide and the second element carbide rarely precipitate at the same position, and most of them are separated from each other. And since both the carbide | carbonized_material of such a 1st element, the carbide | carbonized_material of a 2nd element, etc. exist, when the particle | grain 1 sinters, the enlargement of a crystal grain will be suppressed more reliably. The density of the sintered body is increased.

  Furthermore, since the carbides of the first element and the carbides of the second element are precipitated in a state of being separated from each other, the effect that the enlargement of crystal grains is suppressed is exhibited evenly in the particles 1. That is, from this viewpoint, the densification of the sintered body is particularly promoted.

  In addition, in the particles 1, it is considered that the carbide of the first element, the carbide of the second element, and the like become “nuclei” and silicon oxide accumulates. Since silicon oxide accumulates at the crystal grain boundaries, the oxide concentration inside the crystal decreases, so that sintering is promoted. As a result, it is considered that when the particles 1 are sintered, the densification of the sintered body is further promoted.

  And since such a particle | grain 1 can aim at densification of a sintered compact when it uses for powder metallurgy, a high-density sintered compact can be manufactured, without performing an additional process. When the particles 1 are subjected to powder metallurgy, it is considered that carbides and the like move to the grain boundaries of the metal crystals in the sintered body. And the carbide | carbonized_material etc. which moved to the triple point of a crystal grain boundary suppress the crystal growth in this point (pinning effect). As a result, remarkable growth of crystal grains is suppressed, and a sintered body having finer crystals can be obtained. Such a sintered body has particularly high mechanical properties.

The ratio of the content ratio of the first element and the content ratio of the second element is preferably set in consideration of the atomic weight of the first element and the atomic weight of the second element.

Specifically, the value obtained by dividing the content E1 (mass%) of the first element by the atomic weight of the first element is X1, and the content E2 (mass%) of the second element is divided by the atomic weight of the second element. When the value is X2, X1 / X2 is preferably 0.3 or more and 3 or less, more preferably 0.5 or more and 2 or less, and further preferably 0.75 or more and 1.3 or less. . By setting X1 / X2 within the above range, the balance between the precipitation amount of the first element carbide and the like and the precipitation amount of the second element carbide and the like can be optimized. Thereby, since the void | hole remaining in a molded object can be discharged | emitted as it sweeps out sequentially from an inner side, the void | hole produced in a sintered compact can be suppressed to the minimum. Therefore, by setting X1 / X2 within the above range, a metal powder capable of producing a sintered body having high density and excellent mechanical properties can be obtained.

  Here, regarding a specific combination example of the first element and the second element, based on the above-described range of X1 / X2, the ratio E1 / E2 of the content ratio E1 of the first element and the content ratio E2 of the second element calculate.

For example, when the first element is Zr and the second element is Nb, the atomic weight of Zr is 91.2 and the atomic weight of Nb is 92.9, so E1 / E2 is 0.29 or more and 2 It is preferably .95 or less, more preferably 0.49 or more and 1.96 or less.

When the first element is Hf and the second element is Nb, the atomic weight of Hf is 178.5, and the atomic weight of Nb is 92.9, so E1 / E2 is 0.58 or more and 5 Is preferably .76 or less, more preferably 0.96 or more and 3.84 or less.

When the first element is Ti and the second element is Nb, the atomic weight of Ti is 47.9 and the atomic weight of Nb is 92.9, so E1 / E2 is 0.15 or more and 1 Is preferably .55 or less, more preferably 0.26 or more and 1.03 or less.

When the first element is Nb and the second element is Ta, the atomic weight of Nb is 92.9 and the atomic weight of Ta is 180.9, so E1 / E2 is 0.15 or more and 1 Is preferably .54 or less, more preferably 0.26 or more and 1.03 or less.

When the first element is Y and the second element is Nb, the atomic weight of Y is 88.9, and the atomic weight of Nb is 92.9, so E1 / E2 is 0.29 or more and 2 It is preferably 0.87 or less, and more preferably 0.48 or more and 1.91 or less.

When the first element is V and the second element is Nb, the atomic weight of V is 50.9 and the atomic weight of Nb is 92.9, so E1 / E2 is 0.16 or more and 1 .64 or less, more preferably 0.27 or more and 1.10 or less.

Further, when the first element is Ti and the second element is Zr, the atomic weight of Ti is 47.9 and the atomic weight of Zr is 91.2. Therefore, E1 / E2 is 0.16 or more and 1 Is preferably .58 or less, more preferably 0.26 or more and 1.05 or less.

When the first element is Zr and the second element is Ta, the atomic weight of Zr is 91.2 and the atomic weight of Ta is 180.9. Therefore, E1 / E2 is 0.15 or more and 1 0.51 or less, more preferably 0.25 or more and 1.01 or less.

When the first element is Zr and the second element is V, the atomic weight of Zr is 91.2 and the atomic weight of V is 50.9, so E1 / E2 is 0.54 or more and 5 .38 or less, more preferably 0.90 or more and 3.58 or less.

  In addition, E1 / E2 can be calculated in the same manner as described above for combinations other than those described above.

  The total of the content ratio E1 of the first element and the content ratio E2 of the second element is preferably 0.05% by mass or more and 0.8% by mass or less, and more preferably 0.10% by mass or more and 0.6% by mass. % Or less, more preferably 0.12% by mass or more and 0.24% by mass or less. By setting the sum of the content ratio of the first element and the content ratio of the second element within the above range, it is necessary and sufficient to increase the density of the manufactured sintered body.

  Further, when the total ratio of the content ratio of the first element and the content ratio of the second element with respect to the Si content ratio is (E1 + E2) / Si, (E1 + E2) / Si is 0.1 to 0.7 in terms of mass ratio. Or less, more preferably from 0.15 to 0.6, and even more preferably from 0.2 to 0.5. By setting (E1 + E2) / Si within the above range, the reduction in toughness when Si is added is sufficiently compensated by the addition of the first element and the second element. As a result, it is possible to obtain a metal powder capable of producing a sintered body having excellent mechanical properties such as toughness and excellent corrosion resistance derived from Si, despite its high density. In addition, in the particle 1, silicon oxide having the first element carbide or the like or the second element carbide or the like as a nucleus is necessary and sufficiently accumulated. In addition to Fe and Cr, elements such as Ni are contained in the particle 1. When it is contained, those oxidation reactions are easily suppressed. For this reason, also from this viewpoint, the sinterability of the particles 1 is increased, and a sintered body having a higher density and excellent mechanical properties and corrosion resistance can be obtained.

  Further, when the total ratio of the content ratio of the first element and the content ratio of the second element to the content ratio of C is (E1 + E2) / C, (E1 + E2) / C is preferably 1 or more and 16 or less. It is more preferably 2 or more and 13 or less, and further preferably 3 or more and 10 or less. By setting (E1 + E2) / C within the above range, both increase in hardness and reduction in toughness when C is added and high density brought about by the addition of the first element and the second element are compatible. Can be made. As a result, particles 1 capable of producing a sintered body having excellent mechanical properties such as tensile strength and toughness can be obtained.

  The metal powder only needs to contain two kinds of elements selected from the group consisting of the seven elements, but the elements are selected from this group and are different from the two kinds of elements. May further be included. That is, the metal powder may contain three or more elements selected from the group consisting of the seven elements. As a result, the effect described above can be further enhanced, although it differs somewhat depending on the combination.

(Other elements)
The particle | grains 1 may contain at least 1 sort (s) of W, Co, Mn, Mo, Cu, N, and S as needed other than these elements. In addition, these elements may be inevitably included.

W is an element that enhances the heat resistance of the sintered body to be produced.
The content of W in the metal powder is 0.5% by mass or more and 20% by mass or less, preferably 1% by mass or more and 10% by mass or less, more preferably 5% by mass or more and 7% by mass or less. The When the W content is below the lower limit, depending on the overall composition, the heat resistance of the sintered body cannot be sufficiently increased. For example, when a tool is produced using the obtained sintered body, the temperature is high. There is a risk that the hardness, softening resistance, and wear resistance of the tool below will decrease. On the other hand, if the W content exceeds the upper limit, depending on the overall composition, mechanical properties such as toughness of the sintered body may be reduced, and there may be a problem such as chipping in the tool.

Co is an element that enhances the heat resistance of the sintered body to be produced.
Although the content rate of Co in a metal powder is not specifically limited, It is preferable that they are 3 mass% or more and 12 mass% or less, and it is more preferable that they are 4.5 mass% or more and 10.5 mass% or less. By setting the content ratio of Co within the above range, the heat resistance of the sintered body can be further enhanced without causing a significant decrease in the density of the manufactured sintered body. In particular, since the decrease in hardness and softening resistance at high temperatures can be suppressed, for example, when a tool is manufactured using the obtained sintered body, a high-speed tool capable of cutting at a higher speed can be easily obtained. Can be manufactured.

Mn is an element that imparts corrosion resistance and high mechanical properties to the sintered body to be produced.
Although the content rate of Mn in the particle | grains 1 is not specifically limited, It is preferable that it is 0.01 to 3 mass%, and it is more preferable that it is 0.05 to 1 mass%. By setting the content of Mn within the above range, a sintered body having a higher density and excellent mechanical properties can be obtained.

  If the Mn content is less than the lower limit, depending on the overall composition, the corrosion resistance and mechanical properties of the sintered body to be produced may not be sufficiently improved, whereas the Mn content is When the upper limit is exceeded, depending on the overall composition, corrosion resistance and mechanical properties may be deteriorated.

Mo is an element that enhances the corrosion resistance of the sintered body to be produced.
The content of Mo in the particles 1 is not particularly limited, but is preferably 1% by mass to 5% by mass, more preferably 1.2% by mass to 4% by mass, and more preferably 2% by mass to 3%. More preferably, it is at most mass%. By setting the Mo content in the above range, the corrosion resistance of the sintered body can be further enhanced without causing a significant decrease in the density of the sintered body to be produced.

Cu is an element that enhances the corrosion resistance of the sintered body to be produced.
Although the content rate of Cu in the particle | grains 1 is not specifically limited, It is preferable that it is 5 mass% or less, and it is more preferable that it is 1 mass% or more and 4 mass% or less. By setting the Cu content within the above range, the corrosion resistance of the sintered body can be further enhanced without causing a significant decrease in the density of the sintered body to be produced.

  When the Ni content is 0.05% by mass or more and 0.6% by mass or less, the Cu content is preferably less than 1% by mass, and less than 0.1% by mass. More preferred. Further, in this case, it is more preferable that Cu is not substantially contained (less than 0.01% by mass) except for an unavoidable content. Although a detailed reason is unknown, it is because there exists a possibility that the effect as mentioned above which a 1st element and a 2nd element bring about may be diluted by containing Cu.

N is an element that enhances mechanical properties such as yield strength of the sintered body to be produced.
The N content in the particles 1 is not particularly limited, but is preferably 0.03% by mass or more and 1% by mass or less, more preferably 0.08% by mass or more and 0.3% by mass or less. More preferably, the content is 1% by mass or more and 0.25% by mass or less. By setting the N content within the above range, mechanical properties such as yield strength of the sintered body can be further enhanced without causing a significant decrease in the density of the sintered body to be produced.

  In order to manufacture the particles 1 to which N is added, for example, a method using a nitrided raw material, a method of introducing nitrogen gas into the molten metal, a method of nitriding the manufactured metal powder, and the like are used. It is done.

S is an element that enhances the machinability of the sintered body to be produced.
The S content in the Fe-based alloy is not particularly limited, but is preferably 0.5% by mass or less, and more preferably 0.01% by mass or more and 0.3% by mass or less. By setting the S content within the above range, the machinability of the manufactured sintered body can be further improved without causing a significant decrease in the density of the manufactured sintered body. Therefore, a desired shape can be cut out by cutting the obtained sintered body.

  In addition, B, Se, Te, Pd, Al, or the like may be added to the Fe-based alloy. In that case, the content of these elements is not particularly limited, but is preferably less than 0.1% by mass, and preferably less than 0.2% by mass in total. In addition, these elements may be inevitably included.

  Further, the particles 1 may contain impurities. Examples of the impurities include all elements other than the elements described above. For example, Li, Be, Na, Mg, P, K, Ca, Sc, Zn, Ga, Ge, Ag, In, Sn, Sb, Os, Ir, Pt, Au, Bi, etc. are mentioned. The amount of these impurities mixed is preferably smaller than the content of the constituent elements of the Fe-based alloy described above. The amount of these impurities mixed is preferably set so that each element is less than 0.03% by mass, and more preferably set to be less than 0.02% by mass. Further, the total amount is preferably less than 0.3% by mass, and more preferably less than 0.2% by mass. In addition, as long as the content rate is in the above range, these elements may be intentionally added because the effects as described above are not inhibited.

  On the other hand, O (oxygen) may be added intentionally or inevitably mixed, but the amount is preferably about 0.8% by mass or less, and about 0.5% by mass or less. More preferably. By keeping the amount of oxygen in the metal powder at this level, the sinterability becomes high, and a sintered body having a high density and excellent mechanical properties can be obtained. The lower limit is not particularly set, but is preferably 0.03% by mass or more from the viewpoint of ease of mass production.

The chemical composition of the particle 1 is, for example, an iron and steel-atomic absorption spectrophotometric method defined in JIS G 1257 (2000), an iron and steel-ICP emission spectroscopic method defined in JIS G 1258 (2007), JIS G 1253 (2002) stipulated in iron and steel-spark discharge optical emission spectrometry, JIS G 1256 (1997) stipulated in JIS G 1256 (1997), JIS G 1211-G 1237 It can be specified by weight, titration, absorptiometry and the like. Specifically, for example, a solid emission spectroscopic analyzer manufactured by SPECTRO (spark discharge optical spectroscopic analyzer, model: SPECTROLAB, type: LAVMB08A) and an ICP apparatus (CIROS120 type) manufactured by Rigaku Corporation are exemplified.
JIS G 1211 to G 1237 are as follows.

JIS G 1211 (2011) Iron and steel-carbon determination method JIS G 1212 (1997) Iron and steel-silicon determination method JIS G 1213 (2001) Manganese determination method in iron and steel JIS G 1214 (1998) Iron and steel -Phosphorus determination method JIS G 1215 (2010) Iron and steel-sulfur determination method JIS G 1216 (1997) Iron and steel-nickel determination method JIS G 1217 (2005) Iron and steel-chromium determination method JIS G 1218 (1999) Iron And steel-molybdenum determination method JIS G 1219 (1997) Iron and steel-copper determination method JIS G 1220 (1994) Iron and steel-tungsten determination method JIS G 1221 (1998) Iron and steel-vanadium determination method JIS G 1222 (1999) ) Iron and steel-Cobalt determination method JIS G 1223 (1997) Iron and steel-titanium determination method JIS G 1224 (2001) Aluminum and iron in steel determination method JIS G 1225 (2006) Iron and steel-arsenic determination method JIS G 1226 (1994) Iron and steel Tin determination method JIS G 1227 (1999) Boron determination method in iron and steel JIS G 1228 (2006) Iron and steel-nitrogen determination method JIS G 1229 (1994) Steel-lead determination method JIS G 1232 (1980) In steel JIS G 1233 (1994) Steel-selenium quantification method JIS G 1234 (1981) Tellurium quantification method in steel JIS G 1235 (1981) Antimony quantification method in iron and steel JIS G 1236 (1992) Tantalum determination method JIS G 1237 ( 1997) Iron and steel-niobium determination method

  Further, when specifying C (carbon) and S (sulfur), in particular, an oxygen stream combustion (high frequency induction furnace combustion) -infrared absorption method defined in JIS G 1211 (2011) is also used. Specifically, a carbon / sulfur analyzer manufactured by LECO, CS-200 may be mentioned.

  Furthermore, when specifying N (nitrogen) and O (oxygen), in particular, a method for determining nitrogen in iron and steel specified in JIS G 1228 (2006), oxygen in a metal material specified in JIS Z 2613 (2006). A quantitative method is also used. Specific examples include an oxygen / nitrogen analyzer manufactured by LECO, TC-300 / EF-300.

  Moreover, it is preferable that as many particles 1 as described above are contained in the metal powder for powder metallurgy as much as possible, specifically, the number ratio is preferably 50% or more, and more preferably 60% or more. More preferably. According to such a metal powder for powder metallurgy, the above-described effects brought about by the particles 1 are more reliably exhibited.

  In addition, the said ratio can be calculated | required by extracting 20 or more particles in the metal powder for powder metallurgy arbitrarily, and how many particles 1 are mentioned above among these.

  The average particle size of the metal powder for powder metallurgy of the present invention is preferably 0.5 μm or more and 30 μm or less, more preferably 1 μm or more and 20 μm or less, and further preferably 2 μm or more and 10 μm or less. By using the metal powder for powder metallurgy having such a particle size, the number of voids remaining in the sintered body is extremely reduced, and thus a sintered body having a particularly high density and excellent mechanical properties can be produced. .

  The average particle size is obtained as the particle size when the cumulative amount is 50% from the small diameter side in the cumulative particle size distribution on a mass basis obtained by the laser diffraction method.

  In addition, when the average particle diameter of the metal powder for powder metallurgy is below the lower limit, in the case of a shape that is difficult to mold, there is a possibility that the moldability is lowered and the sintered density is lowered, and the upper limit is exceeded. Since the gaps between the particles become large during molding, the sintered density may also decrease.

  The particle size distribution of the metal powder for powder metallurgy is preferably as narrow as possible. Specifically, when the average particle size of the metal powder for powder metallurgy is within the above range, the maximum particle size is preferably 200 μm or less, and more preferably 150 μm or less. By controlling the maximum particle size of the metal powder for powder metallurgy within the above range, the particle size distribution of the metal powder for powder metallurgy can be narrowed, and the density of the sintered body can be further increased.

  The maximum particle size refers to the particle size when the cumulative amount is 99.9% from the small diameter side in the cumulative particle size distribution on a mass basis obtained by the laser diffraction method.

  Further, when the short diameter of the metal powder metal powder powder powder is S [μm] and the long diameter is L [μm], the average aspect ratio defined by S / L is about 0.4 or more and 1 or less. It is preferable that it is about 0.7 or more and 1 or less. Since the metal powder for powder metallurgy having such an aspect ratio has a shape that is relatively close to a spherical shape, the filling rate when formed is increased. As a result, the sintered body can be further densified.

  The major axis is the maximum length that can be taken in the projected image of the particle, and the minor axis is the maximum length that can be taken in the direction orthogonal to the major axis. Moreover, the average value of aspect ratio is calculated | required as an average value of the value of the aspect ratio measured about 100 or more particle | grains.

Moreover, the tap density of the metal powder for powder metallurgy of the present invention is preferably 3.5 g / cm ³ or more, more preferably 4 g / cm ³ or more. When the metal powder for powder metallurgy has such a large tap density, the filling property between the particles is particularly high when obtaining a compact. For this reason, a particularly dense sintered body can be finally obtained.

The specific surface area of the metal powder for powder metallurgy of the present invention is not particularly limited, but is preferably 0.1 m ² / g or more, and more preferably 0.2 m ² / g or more. Thus, if it is a metal powder for powder metallurgy with a large specific surface area, since surface activity (surface energy) will become high, it can sinter easily even if provision of less energy. Therefore, when the molded body is sintered, a difference in sintering speed hardly occurs between the inside and the outside of the molded body, and it is possible to suppress a decrease in the sintered density due to remaining voids on the inside. .

[Method for producing sintered body]
Next, a method for producing a sintered body using such metal powder for powder metallurgy according to the present invention will be described.

  The method for producing a sintered body includes [A] a composition preparation step for preparing a composition for producing a sintered body, [B] a molding step for producing a molded body, and [C] a degreasing step for performing a degreasing treatment. And [D] a firing step for firing. Hereinafter, each process will be described sequentially.

[A] Composition Preparation Step First, the metal powder for powder metallurgy of the present invention and a binder are prepared and kneaded with a kneader to obtain a kneaded product (composition).

  In the kneaded product (the embodiment of the compound of the present invention), the metal powder for powder metallurgy is uniformly dispersed.

  The metal powder for powder metallurgy of the present invention is produced by various powdering methods such as an atomizing method (for example, a water atomizing method, a gas atomizing method, a high-speed rotating water atomizing method, etc.), a reduction method, a carbonyl method, and a pulverizing method. .

  Among these, the metal powder for powder metallurgy of the present invention is preferably manufactured by an atomizing method, and more preferably manufactured by a water atomizing method or a high-speed rotating water atomizing method. The atomizing method is a method for producing a metal powder by causing molten metal (molten metal) to collide with a fluid (liquid or gas) jetted at high speed, thereby pulverizing and cooling the molten metal. By producing metal powder for powder metallurgy by such an atomizing method, extremely fine powder can be produced efficiently. Moreover, the particle shape of the obtained powder becomes close to a spherical shape due to the effect of surface tension. For this reason, a thing with a high filling rate is obtained when shape | molding. That is, a powder capable of producing a high-density sintered body can be obtained. Furthermore, since the cooling rate of the molten metal becomes very fast, the particles 1 in which the second region P2 and the third region P3 are more uniformly distributed can be obtained.

In addition, when the water atomizing method is used as the atomizing method, the pressure of water sprayed toward the molten metal (hereinafter referred to as “atomized water”) is not particularly limited, but is preferably 75 MPa or more and 120 MPa or less (750 kgf). / Cm ² or more and 1200 kgf / cm ² or less), more preferably 90 MPa or more and 120 MPa or less (900 kgf / cm ² or more and 1200 kgf / cm ² or less).

  The temperature of the atomized water is not particularly limited, but is preferably about 1 ° C. or higher and 20 ° C. or lower.

  Furthermore, atomized water is often sprayed in a conical shape having an apex on the molten metal drop path and the outer diameter gradually decreasing downward. In this case, the apex angle θ of the cone formed by the atomized water is preferably about 10 ° to 40 °, more preferably about 15 ° to 35 °. Thereby, the metal powder for powder metallurgy having the composition as described above can be reliably produced.

  Moreover, according to the water atomization method (especially high-speed rotation water flow atomization method), a molten metal can be cooled especially rapidly. For this reason, a high quality powder is obtained in a wide alloy composition.

Further, the cooling rate when the molten metal is cooled in the atomizing method is preferably 1 × 10 ⁴ ° C./s or more, and more preferably 1 × 10 ⁵ ° C./s or more. Such rapid cooling provides a homogeneous metal powder for powder metallurgy. As a result, a high-quality sintered body can be obtained. In addition, the crystalline volume occupation rate as described above in the particle 1 varies depending on conditions (for example, alloy composition, manufacturing conditions, etc.) when manufacturing the metal powder for powder metallurgy. For example, when the cooling rate is increased (for example, 1 × 10 ⁵ ° C./s or more), amorphous or metallic glass is slightly increased, and when the cooling rate is lowered (for example, 1 × 10 ⁴ ° C./s or more 1 × In the case of less than 10 ⁵ ° C / s), the crystallinity tends to be slightly increased.

  In addition, you may classify with respect to the metal powder for powder metallurgy obtained in this way as needed. Examples of classification methods include sieving classification, inertia classification, dry classification such as centrifugal classification, and wet classification such as sedimentation classification.

  On the other hand, examples of the binder include polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymers, acrylic resins such as polymethyl methacrylate and polybutyl methacrylate, styrene resins such as polystyrene, polyvinyl chloride, and polyvinylidene chloride. Various resins such as polyesters such as polyamide, polyethylene terephthalate, polybutylene terephthalate, polyether, polyvinyl alcohol, polyvinylpyrrolidone or copolymers thereof, various waxes, paraffin, higher fatty acids (eg stearic acid), higher alcohols, Examples include various organic binders such as higher fatty acid esters and higher fatty acid amides. Among these, one kind or a mixture of two or more kinds can be used.

  Further, the content of the binder is preferably about 2% by mass or more and 20% by mass or less, more preferably about 5% by mass or more and 10% by mass or less of the entire kneaded product. When the content of the binder is within the above range, a molded body can be formed with good moldability, the density can be increased, and the shape stability of the molded body can be made particularly excellent. This also optimizes the difference in size between the molded body and the degreased body, the so-called shrinkage rate, and prevents the dimensional accuracy of the finally obtained sintered body from being lowered. That is, a sintered body with high density and high dimensional accuracy can be obtained.

  Moreover, a plasticizer may be added to the kneaded material as necessary. Examples of the plasticizer include phthalic acid esters (eg, DOP, DEP, DBP), adipic acid esters, trimellitic acid esters, sebacic acid esters, and the like, and one or more of these are mixed. Can be used.

  Furthermore, in addition to the metal powder for powder metallurgy, the binder, and the plasticizer, various additives such as a lubricant, an antioxidant, a degreasing accelerator, and a surfactant may be added to the kneaded material as necessary. it can.

  The kneading conditions vary depending on various conditions such as the metal composition and particle size of the metal powder for powder metallurgy used, the composition of the binder, and the blending amount thereof. For example, kneading temperature: 50 ° C. or more and 200 ° C. Or less, kneading time: about 15 minutes or more and 210 minutes or less.

  Further, the kneaded product is formed into pellets (small lumps) as necessary. The particle size of the pellet is, for example, about 1 mm to 15 mm.

  Depending on the molding method described later, a granulated powder may be produced instead of the kneaded product. These kneaded materials, granulated powders, and the like are examples of compositions that are subjected to the molding step described later.

  In the embodiment of the granulated powder of the present invention, the metal powder for powder metallurgy of the present invention is granulated to bind a plurality of metal particles with a binder.

  Examples of the binder used in the production of the granulated powder include polyolefins such as polyethylene, polypropylene and ethylene-vinyl acetate copolymer, acrylic resins such as polymethyl methacrylate and polybutyl methacrylate, styrene resins such as polystyrene, Various resins such as polyesters such as vinyl chloride, polyvinylidene chloride, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyether, polyvinyl alcohol, polyvinyl pyrrolidone or copolymers thereof, various waxes, paraffin, higher fatty acids (eg, stearin) Acid), higher alcohols, higher fatty acid esters, higher fatty acid amides, and other organic binders. Among these, one or a mixture of two or more can be used.

  Among these, as a binder, what contains polyvinyl alcohol or polyvinylpyrrolidone is preferable. Since these binder components have high binding properties, a granulated powder can be efficiently formed even in a relatively small amount. In addition, since it has high thermal decomposability, it can be reliably decomposed and removed in a short time during degreasing and firing.

  Further, the content of the binder is preferably about 0.2% by mass or more and 10% by mass or less, more preferably about 0.3% by mass or more and 5% by mass or less of the whole granulated powder. More preferably, it is 3 mass% or more and 2 mass% or less. When the content of the binder is within the above range, the granulated powder is efficiently formed while suppressing remarkably large particles from being granulated or from leaving a large amount of non-granulated metal particles. be able to. Moreover, since the moldability is improved, the shape stability of the molded body can be made particularly excellent. In addition, by setting the binder content within the above range, the difference in size between the molded body and the degreased body, the so-called shrinkage rate, is optimized to prevent the dimensional accuracy of the finally obtained sintered body from being lowered. can do.

  Furthermore, various additives, such as a plasticizer, a lubricant, an antioxidant, a degreasing accelerator, and a surfactant, may be added to the granulated powder as necessary.

  On the other hand, examples of the granulation treatment include a spray drying (spray drying) method, a rolling granulation method, a fluidized bed granulation method, and a rolling fluidization granulation method.

  In the granulation treatment, a solvent that dissolves the binder is used as necessary. Examples of such solvents include water, inorganic solvents such as carbon tetrachloride, ketone solvents, alcohol solvents, ether solvents, cellosolve solvents, aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, aromatic solvents. Organic solvent such as aromatic heterocyclic compound solvent, amide solvent, halogen compound solvent, ester solvent, amine solvent, nitrile solvent, nitro solvent, aldehyde solvent, etc. are selected from these One kind or a mixture of two or more kinds is used.

  The average particle diameter of the granulated powder is not particularly limited, but is preferably about 10 μm or more and 200 μm or less, more preferably about 20 μm or more and 100 μm or less, and further preferably about 25 μm or more and 60 μm or less. The granulated powder having such a particle size has good fluidity and can more accurately reflect the shape of the mold.

  The average particle size is obtained as the particle size when the cumulative amount is 50% from the small diameter side in the cumulative particle size distribution on a mass basis obtained by the laser diffraction method.

[B] Molding Step Next, the kneaded product or the granulated powder is molded to produce a molded body having the same shape as the intended sintered body.

  The production method (molding method) of the molded body is not particularly limited. For example, various molding methods such as a compacting (compression molding) method, a metal powder injection molding (MIM) method, and an extrusion molding method are used. Can be used.

Among these, the molding conditions in the case of the compacting method vary depending on various conditions such as the composition and particle size of the metal powder for powder metallurgy used, the composition of the binder, and the blending amount thereof, but the molding pressure is 200 MPa or more and 1000 MPa or less. It is preferably about (2 t / cm ² or more and 10 t / cm ² or less).

Further, although the molding conditions in the metal powder injection molding method vary depending on various conditions, the material temperature is about 80 ° C. to 210 ° C., and the injection pressure is 50 MPa to 500 MPa (0.5 t / cm ^{2 to} 5 t / cm ^2). The following is preferable.

In addition, although the molding conditions in the extrusion molding method vary depending on various conditions, the material temperature is about 80 ° C. to 210 ° C., and the extrusion pressure is 50 MPa to 500 MPa (0.5 t / cm ^{2 to} 5 t / cm ² ). It is preferable that it is about.

  The molded body thus obtained is in a state where the binder is uniformly distributed in the gaps between the plurality of particles of the metal powder.

  In addition, the shape dimension of the molded object produced is determined in consideration of the shrinkage | contraction part of the molded object in a subsequent degreasing process and a baking process.

[C] Degreasing process Next, the obtained molded body is subjected to a degreasing treatment (debinding treatment) to obtain a degreased body.

  Specifically, the molded body is heated to decompose the binder, thereby removing the binder from the molded body and performing a degreasing process.

  Examples of the degreasing treatment include a method of heating the molded body, a method of exposing the molded body to a gas that decomposes the binder, and the like.

  When using the method of heating the molded body, the heating condition of the molded body is preferably about 100 ° C. or higher and 750 ° C. or lower × 0.1 hour or longer and 20 hours or shorter, although it varies slightly depending on the composition and blending amount of the binder. 150 ° C. or more and 600 ° C. or less × 0.5 hours or more and 15 hours or less is more preferable. Thereby, degreasing | defatting of a molded object can be performed sufficiently and necessary, without sintering a molded object. As a result, it is possible to reliably prevent a large amount of binder component from remaining inside the degreased body.

  The atmosphere for heating the molded body is not particularly limited, and is a reducing gas atmosphere such as hydrogen, an inert gas atmosphere such as nitrogen or argon, an oxidizing gas atmosphere such as air, or these atmospheres. The reduced pressure atmosphere etc. which reduced pressure is mentioned.

On the other hand, examples of the gas that decomposes the binder include ozone gas.
In addition, such a degreasing process is performed by dividing into a plurality of processes (steps) having different degreasing conditions, so that the binder in the molded body can be decomposed and removed more quickly and not to remain in the molded body. Can do.

  Moreover, you may make it perform machining, such as cutting, grinding | polishing, and cutting | disconnection with respect to a degreased body as needed. Since the degreased body is relatively low in hardness and relatively rich in plasticity, it can be easily machined while preventing the shape of the degreased body from collapsing. According to such machining, a sintered body with high dimensional accuracy can be easily obtained finally.

[D] Firing step The degreased body obtained in the step [C] is fired in a firing furnace to obtain a sintered body.

  By this sintering, the metal powder for powder metallurgy is diffused at the interface between the particles, resulting in sintering. At this time, the degreased body is quickly sintered by the mechanism described above. As a result, an entirely dense and dense sintered body can be obtained.

  The firing temperature varies depending on the composition, particle size and the like of the metal powder for powder metallurgy used for the production of the molded body and the degreased body, but is set to about 980 ° C. or higher and 1330 ° C. or lower as an example. The temperature is preferably about 1050 ° C. or higher and 1260 ° C. or lower.

  The firing time is 0.2 hours or more and 7 hours or less, and preferably 1 hour or more and 6 hours or less.

  In the firing step, the sintering temperature or a firing atmosphere described later may be changed during the firing process.

  By setting the firing conditions in such a range, it is possible to sufficiently sinter the entire degreased body while preventing the sintering from proceeding excessively to cause oversintering to enlarge the crystal structure. As a result, a sintered body having a high density and particularly excellent mechanical properties can be obtained.

  Moreover, since the firing temperature is relatively low, the heating temperature in the firing furnace can be easily controlled, and thus the temperature of the degreased body is also likely to be constant. As a result, a more uniform sintered body can be produced.

  Furthermore, since the firing temperature as described above is a firing temperature that can be sufficiently realized in a general firing furnace, an inexpensive firing furnace can be used and a running cost can be suppressed. In other words, when the firing temperature is exceeded, it is necessary to use an expensive firing furnace using a special heat-resistant material, and the running cost may be increased.

  Further, the atmosphere during firing is not particularly limited, but in consideration of preventing significant oxidation of the metal powder, a reducing gas atmosphere such as hydrogen, an inert gas atmosphere such as argon, or these atmospheres The reduced pressure atmosphere etc. which reduced pressure is preferably used.

  The sintered body thus obtained has a high density and excellent mechanical properties. That is, a sintered body produced by molding a composition containing the metal powder for powder metallurgy of the present invention and a binder and then degreasing and sintering the sintered body is obtained by sintering a conventional metal powder. The relative density is higher than Therefore, according to the present invention, a high-density sintered body that could not be reached without additional processing such as HIP processing can be realized without additional processing.

  Specifically, according to the present invention, although it varies slightly depending on the composition of the metal powder for powder metallurgy, an improvement in relative density of 2% or more can be expected as an example.

  As a result, the relative density of the obtained sintered body can be expected to be 97% or more as an example (preferably 98% or more, more preferably 98.5% or more). A sintered body having a relative density in such a range is excellent in mechanical properties comparable to a smelting material, although it has a shape that is almost as close as the target shape by using powder metallurgy technology. Since it has characteristics, it can be applied to various machine parts and structural parts with little post-processing.

  In addition, the sintered body produced by molding, degreasing and sintering the composition containing the metal powder for powder metallurgy of the present invention and the binder has the conventional tensile strength and 0.2% proof stress. It becomes larger than the tensile strength and 0.2% proof stress of the sintered body similarly sintered using metal powder. This is presumably because the alloy composition and particle structure were optimized to enhance the sinterability of the metal powder, and the mechanical properties of the sintered body produced thereby were improved.

  Further, the sintered body manufactured as described above has a high hardness surface. Specifically, although slightly different depending on the composition of the metal powder for powder metallurgy, for example, in the case of a composition according to austenitic stainless steel, the surface Vickers hardness is expected to be 140 or more and 500 or less. Further, it is expected to be preferably 150 or more and 400 or less. For example, in the case of a composition according to martensitic stainless steel, the surface Vickers hardness is expected to be 570 or more and 1200 or less. Further, it is expected to be preferably 600 or more and 1000 or less. The sintered body having such hardness has particularly high durability.

  Note that the sintered body has a sufficiently high density and mechanical properties without any additional treatment, but various additional treatments are required to further increase the density and improve the mechanical properties. You may make it give.

  As this additional process, for example, an additional process for increasing the density like the HIP process described above may be used, and various quenching processes, various sub-zero processes, various tempering processes, etc. may be used. These additional processes may be performed independently, or a plurality of additional processes may be performed in combination.

  In the above-described firing step and various additional treatments, the light element in the metal powder (in the sintered body) volatilizes, and the composition of the finally obtained sintered body slightly changes from the composition in the metal powder. Sometimes it is.

  For example, although C varies depending on the process conditions and processing conditions, the content in the final sintered body is within the range of 5% to 100% of the content in the metal powder for powder metallurgy (preferably 30). % In the range of not less than 100% and not more than 100%).

  O also varies depending on process conditions and processing conditions, but the content in the final sintered body is in the range of 1% to 50% of the content in the metal powder for powder metallurgy (preferably 3 % In the range of not less than 50% and not more than 50%).

  On the other hand, as described above, the manufactured sintered body may be subjected to the HIP process as part of an additional process performed as necessary. However, even if the HIP process is performed, a sufficient effect may not be exhibited. Many. In the HIP process, the sintered body can be further densified, but the sintered body obtained by the present invention has already been sufficiently densified at the end of the firing step. For this reason, even if the HIP process is further performed, it is difficult to further increase the density.

  In addition, in the HIP process, it is necessary to pressurize the object to be processed through a pressure medium, so that the object to be processed is contaminated, or the composition and physical properties of the object to be processed are unintentionally changed due to the contamination. There is a possibility that the object to be treated may be discolored due to contamination. Further, when the pressure is applied, residual stress is generated or increased in the object to be processed, and as this is released over time, there is a risk of causing problems such as deformation and a decrease in dimensional accuracy.

  On the other hand, according to the present invention, since a sufficiently high density sintered body can be manufactured without performing such HIP treatment, the same high density and high strength as in the case of performing HIP treatment. It is possible to obtain a sintered body that has been made into a uniform shape. Such a sintered body has less contamination, discoloration, unintended composition and change in physical properties, etc., and less defects such as deformation and deterioration of dimensional accuracy. Therefore, according to the present invention, a sintered body having high mechanical strength and dimensional accuracy and excellent durability can be efficiently produced.

  In addition, the sintered body produced according to the present invention requires almost no additional treatment for the purpose of improving mechanical properties, and therefore the composition and crystal structure are likely to be uniform throughout the sintered body. For this reason, structural isotropy is high, and it becomes the thing excellent in the durability with respect to the load from all directions irrespective of a shape.

  In the sintered body manufactured in this way, it is recognized that the porosity in the vicinity of the surface is often relatively smaller than the porosity in the interior. The reason for this is not clear, but it can be mentioned that the addition of the first element and the second element makes it easier for the sintering reaction to proceed in the vicinity of the surface than in the molded body. .

  Specifically, when the porosity near the surface of the sintered body is A1, and the porosity inside the sintered body is A2, A2-A1 is 0.1% or more and 3% or less. Preferably, it is 0.2% or more and 2% or less. A sintered body in which A2-A1 is in such a range has the necessary and sufficient mechanical strength, while allowing the surface to be easily flattened. That is, a surface having high specularity can be obtained by polishing the surface of the sintered body.

  Such a highly specular sintered body has not only high mechanical strength but also excellent aesthetics. For this reason, this sintered compact is used suitably also for the use as which the outstanding aesthetic appearance is requested | required.

  Note that the porosity A1 in the vicinity of the surface of the sintered body refers to a porosity within a range of a radius of 25 μm centering on a position at a depth of 50 μm from the surface in the cross section of the sintered body. Further, the porosity A2 inside the sintered body refers to a porosity within a range of a radius of 25 μm around a position of a depth of 300 μm from the surface in the cross section of the sintered body. These porosity ratios are values obtained by observing the cross section of the sintered body with a scanning electron microscope and dividing the area of the pores existing in the range by the area of the range.

  As mentioned above, although the metal powder for powder metallurgy, compound, granulated powder, and sintered compact of this invention were demonstrated based on suitable embodiment, this invention is not limited to these.

  In addition, the sintered body of the present invention includes, for example, parts for transportation equipment such as parts for automobiles, parts for bicycles, parts for railway vehicles, parts for ships, parts for aircraft, parts for space transport aircraft (for example, rockets). , Parts for electronic devices such as parts for personal computers, parts for mobile phones, parts for electrical equipment such as refrigerators, washing machines, air conditioners, machine parts such as machine tools and semiconductor manufacturing equipment, nuclear power plants, It is used for plant parts such as thermal power plants, hydroelectric power plants, refineries, chemical complexes, clock parts, metal tableware, jewelry, decorative items such as eyeglass frames, and all structural parts.

Next, examples of the present invention will be described.
1. Production of sintered body (Zr-Nb system) (Sample No. 1)
[1] First, a metal powder having the composition shown in Table 1 manufactured by the water atomization method was prepared. The metal powder had an average particle size of 4.05 μm, a tap density of 4.15 g / cm ³ , and a specific surface area of 0.21 m ² / g.

  The powder composition shown in Table 1 was identified and quantified by inductively coupled plasma emission spectrometry (ICP analysis). For ICP analysis, an ICP device (CIROS120 type) manufactured by Rigaku Corporation was used. For carbon identification and quantification, a carbon / sulfur analyzer (CS-200) manufactured by LECO was used. Further, an oxygen / nitrogen analyzer (TC-300 / EF-300) manufactured by LECO was used for identification and quantification of O.

[2] Next, the metal powder and a mixture of polypropylene and wax (organic binder) were weighed and mixed so that the mass ratio was 9: 1 to obtain a mixed raw material.
[3] Next, the mixed raw material was kneaded with a kneader to obtain a compound.

  [4] Next, this compound was molded by an injection molding machine under the molding conditions shown below to produce a molded body.

<Molding conditions>
-Material temperature: 150 ° C
Injection pressure: 11 MPa (110 kgf / cm ² )

  [5] Next, the obtained molded body was subjected to heat treatment (degreasing treatment) under the following degreasing conditions to obtain a degreased body.

<Degreasing conditions>
・ Degreasing temperature: 500 ° C
・ Degreasing time: 1 hour (holding time at degreasing temperature)
・ Degreasing atmosphere: Nitrogen atmosphere

  [6] Next, the obtained degreased body was fired under the firing conditions shown below. This obtained the sintered compact. The shape of the sintered body was a cylindrical shape having a diameter of 10 mm and a thickness of 5 mm.

<Baking conditions>
・ Baking temperature: 1200 ℃
-Firing time: 3 hours (holding time at the firing temperature)
・ Baking atmosphere: Argon atmosphere

(Sample Nos. 2 to 30)
Except for changing the composition and the like of the metal powder for powder metallurgy as shown in Table 1, each sample No. A sintered body was obtained in the same manner as in the method for producing a sintered body of No. 1. Sample No. About 30 sintered compacts, the HIP process was performed on the following conditions after baking. Sample No. The sintered bodies 18 to 20 were obtained using metal powders produced by the gas atomizing method. In Table 1, “gas” is written in the remarks column.

<HIP processing conditions>
・ Heating temperature: 1100 ° C
・ Heating time: 2 hours ・ Pressure: 100 MPa

In Table 1, each sample No. Among these sintered bodies, those corresponding to the present invention are referred to as “Examples”, and those not corresponding to the present invention are referred to as “Comparative Examples”.
Each sintered body contained a small amount of impurities, but the description in Table 1 was omitted.

(Sample Nos. 31-48)
Except for changing the composition of the metal powder for powder metallurgy as shown in Table 2, each sample No. A sintered body was obtained in the same manner as in the method for producing a sintered body of No. 1. Sample No. About 48 sintered compacts, after baking, the HIP process was performed on condition of the following. Sample No. The sintered bodies 41 to 43 are obtained by using metal powders produced by the gas atomizing method. In Table 2, “gas” is written in the remarks column.

<HIP processing conditions>
・ Heating temperature: 1100 ° C
・ Heating time: 2 hours ・ Pressure: 100 MPa

In Table 2, each sample No. Among these sintered bodies, those corresponding to the present invention are referred to as “Examples”, and those not corresponding to the present invention are referred to as “Comparative Examples”.
Each sintered body contained a small amount of impurities, but the description in Table 2 was omitted.

(Sample Nos. 49-66)
Except for changing the composition and the like of the metal powder for powder metallurgy as shown in Table 3, each sample No. A sintered body was obtained in the same manner as in the method for producing a sintered body of No. 1. Sample No. The sintered body of No. 66 was subjected to HIP treatment under the following conditions after firing. Sample No. The sintered bodies 59 to 61 were obtained using metal powders produced by the gas atomizing method. In Table 3, “gas” is written in the remarks column.

<HIP processing conditions>
・ Heating temperature: 1100 ° C
・ Heating time: 2 hours ・ Pressure: 100 MPa

In Table 3, each sample No. Among these sintered bodies, those corresponding to the present invention are referred to as “Examples”, and those not corresponding to the present invention are referred to as “Comparative Examples”.
Each sintered body contained a small amount of impurities, but the description in Table 3 was omitted.

(Sample No. 67)
[1] First, a metal powder having the composition shown in Table 4 was added to Sample No. As in the case of 1, it was produced by the water atomization method.

  [2] Next, the metal powder was granulated by spray drying. The binder used at this time was polyvinyl alcohol, and the amount used was 1 part by mass with respect to 100 parts by mass of the metal powder. Moreover, 50 mass parts solvent (ion-exchange water) was used with respect to 1 mass part of polyvinyl alcohol. This obtained the granulated powder with an average particle diameter of 50 micrometers.

  [3] Next, this granulated powder was compacted under the molding conditions shown below. A press molding machine was used for this molding. Moreover, the shape of the molded body to be produced was a 20 mm square cube shape.

<Molding conditions>
・ Material temperature: 90 ℃
Molding pressure: 600 MPa (6 t / cm ² )

  [4] Next, the obtained molded body was subjected to heat treatment (degreasing treatment) under the following degreasing conditions to obtain a degreased body.

<Degreasing conditions>
・ Degreasing temperature: 450 ° C
・ Degreasing time: 2 hours (holding time at the degreasing temperature)
・ Degreasing atmosphere: Nitrogen atmosphere

  [5] Next, the obtained degreased body was fired under the firing conditions shown below. This obtained the sintered compact.

<Baking conditions>
・ Baking temperature: 1200 ℃
-Firing time: 3 hours (holding time at the firing temperature)
・ Baking atmosphere: Argon atmosphere

(Sample No. 68-85)
Except for changing the composition of the metal powder for powder metallurgy as shown in Table 4, sample No. As in the case of No. 67, a sintered body was obtained. Sample No. About 85 sintered compacts, the HIP process was performed on the following conditions after baking.

<HIP processing conditions>
・ Heating temperature: 1100 ° C
・ Heating time: 2 hours ・ Pressure: 100 MPa

In Table 4, each sample No. Among these metal powders for powder metallurgy and sintered bodies, those corresponding to the present invention are referred to as “Examples”, and those not corresponding to the present invention are referred to as “Comparative Examples”.
Each sintered body contained a small amount of impurities, but the description in Table 4 was omitted.

(Sample No. 86-101)
Except for changing the composition and the like of the metal powder for powder metallurgy as shown in Table 5, each sample No. A sintered body was obtained in the same manner as in the method for producing a sintered body of No. 1.

In Table 5, each sample No. Among these sintered bodies, those corresponding to the present invention are referred to as “Examples”, and those not corresponding to the present invention are referred to as “Comparative Examples”.
Each sintered body contained a small amount of impurities, but the description in Table 5 was omitted.

2. Evaluation of metal powder (Zr—Nb system) Sample No. corresponding to Example The depth direction analysis by the Auger electron spectroscopy which used sputtering together about the particle | grains of the metal powder for powder metallurgy of 1 was performed.

  Then, the sputtering time is converted into the depth from the particle surface, and this is plotted on the horizontal axis, and the analysis results are plotted with the atomic content by Auger electron spectroscopy as the vertical axis. Obtained.

  Sample No. FIG. 3 shows an Auger electron spectroscopy spectrum obtained from the particles of the metal powder for powder metallurgy No. 1. Note that the four straight lines drawn to the left and right so as to overlap the spectrum are the sample numbers. Each content of Fe, Cr, Si, and O in one whole particle is shown.

  As is clear from FIG. In one particle, the Cr content hardly varies between the surface (depth 0 nm) and the depth 60 nm. Therefore, the Cr content Cr (0) on the surface of the particles is within the range of 70% to 170% of the Cr content Cr (60) at a depth of 60 nm from the particle surface. Is recognized.

  It is also recognized that the Cr content Cr (0) on the surface of the particles is within the range of 0.2 atomic% to 15 atomic%.

  On the other hand, sample No. corresponding to the comparative example. Similarly, 23 metal powder particles for powder metallurgy were analyzed in the depth direction by Auger electron spectroscopy combined with sputtering.

  Sample No. FIG. 4 shows an Auger electron spectroscopic spectrum obtained from the particles of 23 metal powders for powder metallurgy. Note that the four straight lines drawn to the left and right so as to overlap the spectrum are the sample numbers. The respective contents of Fe, Cr, Si and O in the entire 23 particles are shown.

  As is clear from FIG. In the case of 23 particles, it can be seen that the Cr content varies relatively greatly from the surface to a depth of 60 nm.

  Also, it is recognized that the Cr content Cr (0) on the surface of the particles is more than 15 atomic%.

Sample No. 1 and sample no. Sample No. other than 23 Similarly, the Cr content was determined for each of the particles.
The obtained content rates are shown in Tables 6 and 10.

In addition, each sample No. The Si content Si (0) on the particle surface, the Si content Si (60) at a depth of 60 nm from the particle surface, and the O content O (0) on the particle surface. Asked.
The obtained content rates are shown in Tables 6 and 10.

3. Evaluation of Sintered Body (Zr-Nb System) 3.1 Evaluation of Relative Density Each sample No. shown in Tables 1-5. According to the method of measuring the density of the sintered metal material defined in JIS Z 2501 (2000), the sintered density was measured and the powder used to manufacture each sintered body The relative density of each sintered body was calculated with reference to the true density of the metal powder for metallurgy.
The calculation results are shown in Tables 6-10.

3.2 Evaluation of Vickers Hardness Each sample No. shown in Tables 1-4. The Vickers hardness of the sintered body was measured according to the test method of the Vickers hardness test specified in JIS Z 2244 (2009).
The measurement results are shown in Tables 6-9.

3.3 Evaluation of Tensile Strength, 0.2% Yield Strength and Elongation Each sample No. shown in Tables 1-4 is shown. With respect to the sintered body, tensile strength, 0.2% proof stress and elongation were measured according to the metal material tensile test method defined in JIS Z 2241 (2011).
And about these measured physical-property values, it evaluated in accordance with the following evaluation criteria.

<Evaluation criteria for tensile strength (Tables 6 and 9)>
A: Tensile strength of the sintered body is 520 MPa or more B: Tensile strength of the sintered body is 510 MPa or more and less than 520 MPa C: Tensile strength of the sintered body is 500 MPa or more and less than 510 MPa D: Sintering The tensile strength of the body is 490 MPa or more and less than 500 MPa E: The tensile strength of the sintered body is 480 MPa or more and less than 490 MPa F: The tensile strength of the sintered body is less than 480 MPa

<Evaluation criteria for tensile strength (Tables 7 and 8)>
A: Tensile strength of the sintered body is 560 MPa or more B: Tensile strength of the sintered body is 550 MPa or more and less than 560 MPa C: Tensile strength of the sintered body is 540 MPa or more and less than 550 MPa D: Sintering The tensile strength of the body is 530 MPa or more and less than 540 MPa E: The tensile strength of the sintered body is 520 MPa or more and less than 530 MPa F: The tensile strength of the sintered body is less than 520 MPa

<Evaluation criteria for 0.2% proof stress (Tables 6 and 9)>
A: 0.2% yield strength of the sintered body is 195 MPa or more B: 0.2% yield strength of the sintered body is 190 MPa or more and less than 195 MPa C: 0.2% yield strength of the sintered body is 185 MPa or more and less than 190 MPa D: 0.2% proof stress of the sintered body is 180 MPa or more and less than 185 MPa E: 0.2% proof stress of the sintered body is 175 MPa or more and less than 180 MPa F: 0.2% proof stress of the sintered body is Less than 175 MPa

<Evaluation criteria for 0.2% proof stress (Tables 7 and 8)>
A: The 0.2% yield strength of the sintered body is 225 MPa or more B: The 0.2% yield strength of the sintered body is 220 MPa or more and less than 225 MPa C: The 0.2% yield strength of the sintered body is 215 MPa or more and less than 220 MPa D: The 0.2% yield strength of the sintered body is 210 MPa or more and less than 215 MPa E: The 0.2% yield strength of the sintered body is 205 MPa or more and less than 210 MPa F: The 0.2% yield strength of the sintered body is Less than 205 MPa

<Evaluation criteria for elongation>
A: Elongation of sintered body is 48% or more B: Elongation of sintered body is 46% or more and less than 48% C: Elongation of sintered body is 44% or more and less than 46% D: Sintered body E: The elongation of the sintered body is 40% or more and less than 42% F: The elongation of the sintered body is less than 40%

  The above evaluation results are shown in Tables 6-9. As described above, the evaluation criteria differ between Tables 6 and 9 and Tables 7 and 8, depending on the physical property values.

3.4 Evaluation of Fatigue Strength Each sample No. shown in Tables 1 to 4 was used. The fatigue strength of the sintered body was measured.

The fatigue strength was measured according to a test method defined in JIS Z 2273 (1978). The applied waveform of the load corresponding to the repetitive stress was a double sine wave, and the minimum maximum stress ratio (minimum stress / maximum stress) was 0.1. The repetition frequency was 30 Hz, and the number of repetitions was 1 × 10 ⁷ times.
And the measured fatigue strength was evaluated according to the following evaluation criteria.

<Fatigue strength evaluation criteria>
A: The fatigue strength of the sintered body is 260 MPa or more B: The fatigue strength of the sintered body is 240 MPa or more and less than 260 MPa C: The fatigue strength of the sintered body is 220 MPa or more and less than 240 MPa D: The fatigue of the sintered body Strength: 200 MPa or more and less than 220 MPa E: Fatigue strength of sintered body is 180 MPa or more and less than 200 MPa F: Fatigue strength of sintered body is less than 180 MPa The above evaluation results are shown in Tables 6-9.

  As is clear from Tables 6 to 10, the sintered body corresponding to the example has a higher relative density than the sintered body corresponding to the comparative example (excluding the sintered body subjected to HIP treatment). Was recognized. It was also recognized that there were significant differences in properties such as tensile strength, 0.2% proof stress and elongation.

  On the other hand, when the respective physical property values were compared between the sintered body corresponding to the example and the sintered body subjected to the HIP treatment, it was recognized that both were comparable.

4). Production of sintered body (Hf-Nb system) (Sample Nos. 102 to 145)
Except for changing the composition of the metal powder for powder metallurgy as shown in Tables 11 to 14, sample No. A sintered body was obtained in the same manner as in the method for producing a sintered body of No. 1.

  In Tables 11 to 14, each sample No. Among these sintered bodies, those corresponding to the present invention are referred to as “Examples”, and those not corresponding to the present invention are referred to as “Comparative Examples”.

  Moreover, although each trace body contained the trace amount impurity, description to Tables 11-14 was abbreviate | omitted.

5. Evaluation of metal powder (Hf-Nb system) The Cr content Cr (0) on the particle surface, the Cr content Cr (60) at a depth of 60 nm from the particle surface, the Si content Si (0) on the particle surface, The Si content Si (60) at a depth of 60 nm from the surface and the O content O (0) on the surface of the particles were determined.

Tables 15 and 18 show the obtained content rates.
As is clear from Tables 15 and 18, in the metal powder particles corresponding to the examples, the Cr content Cr (0) on the surface is the Cr content Cr (60) at a depth of 60 nm from the particle surface. It is recognized that it is within the range of 70% or more and 170% or less.

  It is also recognized that the Cr content Cr (0) on the surface of the particle 1 is within the range of 0.2 atomic% to 15 atomic%.

6). Evaluation of Sintered Body (Hf-Nb System) 6.1 Evaluation of Relative Density Each sample No. shown in Tables 11-14. According to the method of measuring the density of the sintered metal material defined in JIS Z 2501 (2000), the sintered density was measured and the powder used to manufacture each sintered body The relative density of each sintered body was calculated with reference to the true density of the metal powder for metallurgy.
The calculation results are shown in Tables 15-18.

6.2 Evaluation of Vickers Hardness Each sample No. shown in Tables 11-14. The Vickers hardness of the sintered body was measured according to the test method of the Vickers hardness test specified in JIS Z 2244 (2009).
The measurement results are shown in Tables 15-18.

6.3 Evaluation of tensile strength, 0.2% proof stress and elongation Each sample No. shown in Tables 11-13. With respect to the sintered body, tensile strength, 0.2% proof stress and elongation were measured according to the metal material tensile test method defined in JIS Z 2241 (2011).

And each sample No. described in Table 11 is. The physical property values of the sintered bodies were evaluated according to the evaluation criteria applied to Tables 6 and 9 described above, and each sample No. described in Tables 12 and 13 was used. The physical properties of the sintered body were evaluated according to the evaluation criteria applied to Tables 7 and 8 described above.
The above evaluation results are shown in Tables 15-17.

  As is clear from Tables 15 to 18, it was confirmed that the sintered body corresponding to the example had a higher relative density than the sintered body corresponding to the comparative example. It was also recognized that there were significant differences in properties such as tensile strength, 0.2% proof stress and elongation.

7). Production of sintered body (Ti-Nb system) (Sample Nos. 146 to 155)
Except for changing the composition of the metal powder for powder metallurgy as shown in Table 19, each sample No. A sintered body was obtained in the same manner as in the method for producing a sintered body of No. 1.

(Sample No. 156)
A metal powder having an average particle diameter of 4.62 μm, a Ti powder having an average particle diameter of 40 μm, and an Nb powder having an average particle diameter of 25 μm were mixed to prepare a mixed powder. In addition, in preparation of mixed powder, each mixing amount of metal powder, Ti powder, and Nb powder was adjusted so that the composition of mixed powder might become a composition shown in Table 19.

  Next, using this mixed powder, sample No. A sintered body was obtained in the same manner as in the method for producing a sintered body of No. 1.

In Table 19, each sample No. Among these sintered bodies, those corresponding to the present invention are referred to as “Examples”, and those not corresponding to the present invention are referred to as “Comparative Examples”.
Each sintered body contained a small amount of impurities, but the description in Table 19 was omitted.

8). Evaluation of metal powder (Ti-Nb system) The Cr content Cr (0) on the particle surface, the Cr content Cr (60) at a depth of 60 nm from the particle surface, the Si content Si (0) on the particle surface, The Si content Si (60) at a depth of 60 nm from the surface and the O content O (0) on the surface of the particles were determined.

  As a result, in the metal powder particles corresponding to the examples, the Cr content Cr (0) on the surface is 70% to 170% of the Cr content Cr (60) at a depth of 60 nm from the particle surface. It was within the range.

  Further, the Cr content Cr (0) on the surface of the particles was within the range of 0.2 atomic% to 15 atomic%.

  On the other hand, in the metal powder particles corresponding to the comparative example, the Cr content Cr (0) on the surface was out of the above range.

9. Evaluation of Sintered Body (Ti-Nb System) 9.1 Evaluation of Relative Density Each sample No. shown in Table 19 According to the method of measuring the density of the sintered metal material defined in JIS Z 2501 (2000), the sintered density was measured and the powder used to manufacture each sintered body The relative density of each sintered body was calculated with reference to the true density of the metal powder for metallurgy.
Table 20 shows the calculation results.

9.2 Evaluation of Vickers Hardness Each sample No. shown in Table 19 The Vickers hardness of the sintered body was measured according to the test method of the Vickers hardness test specified in JIS Z 2244 (2009).
Table 20 shows the measurement results.

9.3 Evaluation of tensile strength, 0.2% proof stress and elongation Each sample No. shown in Table 19 With respect to the sintered body, tensile strength, 0.2% proof stress and elongation were measured according to the metal material tensile test method defined in JIS Z 2241 (2011).

Then, these measured physical property values were evaluated according to the evaluation criteria applied to Tables 6 and 9 described above.
The above evaluation results are shown in Table 20.

  As is clear from Table 20, the sintered body corresponding to the example was found to have a higher relative density than the sintered body corresponding to the comparative example. It was also recognized that there were significant differences in properties such as tensile strength, 0.2% proof stress and elongation.

10. Production of sintered body (Nb-Ta series) (Sample Nos. 157 to 166)
Except for changing the composition and the like of the metal powder for powder metallurgy as shown in Table 21, each sample No. A sintered body was obtained in the same manner as in the method for producing a sintered body of No. 1.

In Table 21, each sample No. Among these sintered bodies, those corresponding to the present invention are referred to as “Examples”, and those not corresponding to the present invention are referred to as “Comparative Examples”.
Each sintered body contained a small amount of impurities, but the description in Table 21 was omitted.

11. Evaluation of metal powder (Nb-Ta system) The Cr content Cr (0) on the particle surface, the Cr content Cr (60) at a depth of 60 nm from the particle surface, the Si content Si (0) on the particle surface, The Si content Si (60) at a depth of 60 nm from the surface and the O content O (0) on the surface of the particles were determined.

  As a result, in the metal powder particles corresponding to the examples, the Cr content Cr (0) on the surface is 70% to 170% of the Cr content Cr (60) at a depth of 60 nm from the particle surface. It was within the range.

  Further, the Cr content Cr (0) on the surface of the particles was within the range of 0.2 atomic% to 15 atomic%.

  On the other hand, in the metal powder particles corresponding to the comparative example, the Cr content Cr (0) on the surface was out of the above range.

12 Evaluation of Sintered Body (Nb-Ta System) 12.1 Evaluation of Relative Density According to the method of measuring the density of the sintered metal material defined in JIS Z 2501 (2000), the sintered density was measured and the powder used to manufacture each sintered body The relative density of each sintered body was calculated with reference to the true density of the metal powder for metallurgy.
Table 22 shows the calculation results.

12.2 Evaluation of Vickers Hardness Each sample No. shown in Table 21 The Vickers hardness of the sintered body was measured according to the test method of the Vickers hardness test specified in JIS Z 2244 (2009).
The measurement results are shown in Table 22.

12.3 Evaluation of tensile strength, 0.2% proof stress and elongation Each sample No. shown in Table 21 With respect to the sintered body, tensile strength, 0.2% proof stress and elongation were measured according to the metal material tensile test method defined in JIS Z 2241 (2011).

Then, these measured physical property values were evaluated according to the evaluation criteria applied to Tables 6 and 9 described above.
The above evaluation results are shown in Table 22.

  As is clear from Table 22, the sintered body corresponding to the example was found to have a higher relative density than the sintered body corresponding to the comparative example. It was also recognized that there were significant differences in properties such as tensile strength, 0.2% proof stress and elongation.

13. Production of sintered body (Y-Nb system) (Sample Nos. 167 to 177)
Except for changing the composition of the metal powder for powder metallurgy as shown in Table 23, each sample No. A sintered body was obtained in the same manner as in the method for producing a sintered body of No. 1.

In Table 23, each sample No. Among these sintered bodies, those corresponding to the present invention are referred to as “Examples”, and those not corresponding to the present invention are referred to as “Comparative Examples”.
Each sintered body contained a small amount of impurities, but the description in Table 23 was omitted.

14 Evaluation of metal powder (Y-Nb system) The Cr content Cr (0) on the particle surface, the Cr content Cr (60) at a depth of 60 nm from the particle surface, the Si content Si (0) on the particle surface, The Si content Si (60) at a depth of 60 nm from the surface and the O content O (0) on the surface of the particles were determined.

  As a result, in the metal powder particles corresponding to the examples, the Cr content Cr (0) on the surface is 70% to 170% of the Cr content Cr (60) at a depth of 60 nm from the particle surface. It was within the range.

  Further, the Cr content Cr (0) on the surface of the particles was within the range of 0.2 atomic% to 15 atomic%.

  On the other hand, in the metal powder particles corresponding to the comparative example, the Cr content Cr (0) on the surface was out of the above range.

15. Evaluation of Sintered Body (Y-Nb System) 15.1 Evaluation of Relative Density According to the method of measuring the density of the sintered metal material defined in JIS Z 2501 (2000), the sintered density was measured and the powder used to manufacture each sintered body The relative density of each sintered body was calculated with reference to the true density of the metal powder for metallurgy.
Table 24 shows the calculation results.

15.2 Evaluation of Vickers Hardness Each sample No. shown in Table 23 The Vickers hardness of the sintered body was measured according to the test method of the Vickers hardness test specified in JIS Z 2244 (2009).
The measurement results are shown in Table 24.

15.3 Evaluation of tensile strength, 0.2% proof stress and elongation Each sample No. shown in Table 23 With respect to the sintered body, tensile strength, 0.2% proof stress and elongation were measured according to the metal material tensile test method defined in JIS Z 2241 (2011).

Then, these measured physical property values were evaluated according to the evaluation criteria applied to Tables 6 and 9 described above.
The above evaluation results are shown in Table 24.

  As is clear from Table 24, it was recognized that the sintered body corresponding to the example had a higher relative density than the sintered body corresponding to the comparative example. It was also recognized that there were significant differences in properties such as tensile strength, 0.2% proof stress and elongation.

16. Production of sintered body (V-Nb system) (Sample Nos. 178 to 187)
Except for changing the composition of the metal powder for powder metallurgy as shown in Table 25, each sample No. A sintered body was obtained in the same manner as in the method for producing a sintered body of No. 1.

In Table 25, each sample No. Among these sintered bodies, those corresponding to the present invention are referred to as “Examples”, and those not corresponding to the present invention are referred to as “Comparative Examples”.
Each sintered body contained a small amount of impurities, but the description in Table 25 was omitted.

17. Evaluation of metal powder (V-Nb system) The Cr content Cr (0) on the particle surface, the Cr content Cr (60) at a depth of 60 nm from the particle surface, the Si content Si (0) on the particle surface, The Si content Si (60) at a depth of 60 nm from the surface and the O content O (0) on the surface of the particles were determined.

  As a result, in the metal powder particles corresponding to the examples, the Cr content Cr (0) on the surface is 70% to 170% of the Cr content Cr (60) at a depth of 60 nm from the particle surface. It was within the range.

  Further, the Cr content Cr (0) on the surface of the particles was within the range of 0.2 atomic% to 15 atomic%.

  On the other hand, in the metal powder particles corresponding to the comparative example, the Cr content Cr (0) on the surface was out of the above range.

18. Evaluation of Sintered Body (V-Nb System) 18.1 Evaluation of Relative Density According to the method of measuring the density of the sintered metal material defined in JIS Z 2501 (2000), the sintered density was measured and the powder used to manufacture each sintered body The relative density of each sintered body was calculated with reference to the true density of the metal powder for metallurgy.
Table 26 shows the calculation result.

18.2 Evaluation of Vickers Hardness Each sample No. shown in Table 25 The Vickers hardness of the sintered body was measured according to the test method of the Vickers hardness test specified in JIS Z 2244 (2009).
The measurement results are shown in Table 26.

18.3 Evaluation of Tensile Strength, 0.2% Yield Strength and Elongation Each sample No. shown in Table 25 With respect to the sintered body, tensile strength, 0.2% proof stress and elongation were measured according to the metal material tensile test method defined in JIS Z 2241 (2011).

Then, these measured physical property values were evaluated according to the evaluation criteria applied to Tables 6 and 9 described above.
The above evaluation results are shown in Table 26.

  As is clear from Table 26, it was recognized that the sintered body corresponding to the example had a higher relative density than the sintered body corresponding to the comparative example. It was also recognized that there were significant differences in properties such as tensile strength, 0.2% proof stress and elongation.

19. Production of sintered body (Ti-Zr system) (Sample Nos. 188 to 197)
Except for changing the composition and the like of the metal powder for powder metallurgy as shown in Table 27, each sample No. A sintered body was obtained in the same manner as in the method for producing a sintered body of No. 1.

In Table 27, each sample No. Among these sintered bodies, those corresponding to the present invention are referred to as “Examples”, and those not corresponding to the present invention are referred to as “Comparative Examples”.
Each sintered body contained a small amount of impurities, but the description in Table 27 was omitted.

20. Evaluation of metal powder (Ti-Zr system) The Cr content Cr (0) on the particle surface, the Cr content Cr (60) at a depth of 60 nm from the particle surface, the Si content Si (0) on the particle surface, The Si content Si (60) at a depth of 60 nm from the surface and the O content O (0) on the surface of the particles were determined.

  As a result, in the metal powder particles corresponding to the examples, the Cr content Cr (0) on the surface is 70% to 170% of the Cr content Cr (60) at a depth of 60 nm from the particle surface. It was within the range.

  Further, the Cr content Cr (0) on the surface of the particles was within the range of 0.2 atomic% to 15 atomic%.

  On the other hand, in the metal powder particles corresponding to the comparative example, the Cr content Cr (0) on the surface was out of the above range.

21. Evaluation of Sintered Body (Ti-Zr System) 21.1 Evaluation of Relative Density According to the method of measuring the density of the sintered metal material defined in JIS Z 2501 (2000), the sintered density was measured and the powder used to manufacture each sintered body The relative density of each sintered body was calculated with reference to the true density of the metal powder for metallurgy.
The calculation results are shown in Table 28.

21.2 Evaluation of Vickers Hardness Each sample No. shown in Table 27 The Vickers hardness of the sintered body was measured according to the test method of the Vickers hardness test specified in JIS Z 2244 (2009).
The measurement results are shown in Table 28.

21.3 Evaluation of Tensile Strength, 0.2% Yield Strength and Elongation Each sample No. shown in Table 27 With respect to the sintered body, tensile strength, 0.2% proof stress and elongation were measured according to the metal material tensile test method defined in JIS Z 2241 (2011).

Then, these measured physical property values were evaluated according to the evaluation criteria applied to Tables 6 and 9 described above.
The above evaluation results are shown in Table 28.

  As is clear from Table 28, it was confirmed that the sintered body corresponding to the example had a higher relative density than the sintered body corresponding to the comparative example. It was also recognized that there were significant differences in properties such as tensile strength, 0.2% proof stress and elongation.

22. Production of sintered body (Zr-Ta series) (Sample No. 198-212)
Except for changing the composition and the like of the metal powder for powder metallurgy as shown in Tables 29 and 30, Sample No. A sintered body was obtained in the same manner as in the method for producing a sintered body of No. 1.

  In Tables 29 and 30, each sample No. Among these sintered bodies, those corresponding to the present invention are referred to as “Examples”, and those not corresponding to the present invention are referred to as “Comparative Examples”.

  Each sintered body contained a small amount of impurities, but the description in Tables 29 and 30 was omitted.

23. Evaluation of metal powder (Zr-Ta system) The Cr content Cr (0) on the particle surface, the Cr content Cr (60) at a depth of 60 nm from the particle surface, the Si content Si (0) on the particle surface, The Si content Si (60) at a depth of 60 nm from the surface and the O content O (0) on the surface of the particles were determined.

  As a result, in the metal powder particles corresponding to the examples, the Cr content Cr (0) on the surface is 70% to 170% of the Cr content Cr (60) at a depth of 60 nm from the particle surface. It was within the range.

  Further, the Cr content Cr (0) on the surface of the particles was within the range of 0.2 atomic% to 15 atomic%.

  On the other hand, in the metal powder particles corresponding to the comparative example, the Cr content Cr (0) on the surface was out of the above range.

24. Evaluation of Sintered Body (Zr-Ta System) 24.1 Evaluation of Relative Density According to the method of measuring the density of the sintered metal material defined in JIS Z 2501 (2000), the sintered density was measured and the powder used to manufacture each sintered body The relative density of each sintered body was calculated with reference to the true density of the metal powder for metallurgy.
The calculation results are shown in Tables 31 and 32.

24.2 Evaluation of Vickers Hardness Each sample No. shown in Table 29 The Vickers hardness of the sintered body was measured according to the test method of the Vickers hardness test specified in JIS Z 2244 (2009).
The measurement results are shown in Table 31.

24.3 Evaluation of tensile strength, 0.2% proof stress and elongation Each sample No. shown in Table 29 With respect to the sintered body, tensile strength, 0.2% proof stress and elongation were measured according to the metal material tensile test method defined in JIS Z 2241 (2011).

Then, these measured physical property values were evaluated according to the evaluation criteria applied to Tables 6 and 9 described above.
The above evaluation results are shown in Table 31.

  As is clear from Tables 31 and 32, the sintered body corresponding to the example was found to have a higher relative density than the sintered body corresponding to the comparative example. It was also recognized that there were significant differences in properties such as tensile strength, 0.2% proof stress and elongation.

25. Production of sintered body (Zr-V system) (Sample Nos. 213 to 227)
Except for changing the composition and the like of the metal powder for powder metallurgy as shown in Tables 33 and 34, Sample No. A sintered body was obtained in the same manner as in the method for producing a sintered body of No. 1.

  In Tables 33 and 34, each sample No. Among these sintered bodies, those corresponding to the present invention are referred to as “Examples”, and those not corresponding to the present invention are referred to as “Comparative Examples”.

  Each sintered body contained a small amount of impurities, but the description in Tables 33 and 34 was omitted.

26. Evaluation of metal powder (Zr-V system) The Cr content Cr (0) on the particle surface, the Cr content Cr (60) at a depth of 60 nm from the particle surface, the Si content Si (0) on the particle surface, The Si content Si (60) at a depth of 60 nm from the surface and the O content O (0) on the surface of the particles were determined.

  As a result, in the metal powder particles corresponding to the examples, the Cr content Cr (0) on the surface is 70% to 170% of the Cr content Cr (60) at a depth of 60 nm from the particle surface. It was within the range.

  Further, the Cr content Cr (0) on the surface of the particles was within the range of 0.2 atomic% to 15 atomic%.

  On the other hand, in the metal powder particles corresponding to the comparative example, the Cr content Cr (0) on the surface was out of the above range.

27. Evaluation of Sintered Body (Zr-V System) 27.1 Evaluation of Relative Density Each sample No. shown in Tables 33 and 34 According to the method of measuring the density of the sintered metal material defined in JIS Z 2501 (2000), the sintered density was measured and the powder used to manufacture each sintered body The relative density of each sintered body was calculated with reference to the true density of the metal powder for metallurgy.
The calculation results are shown in Tables 35 and 36.

27.2 Evaluation of Vickers Hardness Each sample No. shown in Table 33 The Vickers hardness of the sintered body was measured according to the test method of the Vickers hardness test specified in JIS Z 2244 (2009).
The measurement results are shown in Table 35.

27.3 Evaluation of tensile strength, 0.2% proof stress and elongation Each sample No. shown in Table 33 With respect to the sintered body, tensile strength, 0.2% proof stress and elongation were measured according to the metal material tensile test method defined in JIS Z 2241 (2011).

Then, these measured physical property values were evaluated according to the evaluation criteria applied to Tables 6 and 9 described above.
The above evaluation results are shown in Table 35.

  As apparent from Tables 35 and 36, the sintered body corresponding to the example was found to have a higher relative density than the sintered body corresponding to the comparative example. It was also recognized that there were significant differences in properties such as tensile strength, 0.2% proof stress and elongation.

28. Evaluation of Specularity of Sintered Body 28.1 Evaluation of Porosity near Surface and Inside First, sample Nos. Shown in Table 37 were used. The sintered body was cut and the cross section was polished.

Next, the porosity A1 in the vicinity of the surface and the internal porosity A2 were calculated, and A2-A1 was calculated.
The above calculation results are shown in Table 37.

28.2 Evaluation of Specular Gloss First, sample No. The sintered body was subjected to barrel polishing treatment.

  Next, the specular gloss of the sintered body was measured in accordance with the specular gloss measurement method defined in JIS Z 8741 (1997). The incident angle of light with respect to the surface of the sintered body was 60 °, and glass having a specular gloss of 90 and a refractive index of 1.500 was used as a reference surface for calculating the specular gloss. Then, the measured specular gloss was evaluated according to the following evaluation criteria.

<Evaluation criteria for specular gloss>
A: Specularity of the surface is very high (specular gloss is 200 or more)
B: High specularity of the surface (specular gloss is 150 or more and less than 200)
C: Specularity of the surface is slightly high (specular gloss is 100 or more and less than 150)
D: Specularity of the surface is slightly low (specular gloss is 60 or more and less than 100)
E: The surface specularity is low (specular gloss is 30 or more and less than 60)
F: The surface specularity is very low (specular gloss is less than 30)
The above evaluation results are shown in Table 37.

  As is clear from Table 37, it was recognized that the sintered body corresponding to the example had a higher specular gloss than the sintered body corresponding to the comparative example. This is considered to be due to the fact that the ratio of regular reflection is increased while light scattering is suppressed due to the particularly small porosity in the vicinity of the surface of the sintered body.

1 particle

Claims (18)

Fe is included as a main component,
Cr is included in a proportion of 0.2% by mass to 35% by mass,
Si is contained in a proportion of 0.2% by mass or more and 3% by mass or less,
C is contained in a ratio of 0.005 mass% to 2 mass%,
Ti, V, Y, Zr, and one element selected from the group consisting of Nb and Hf as a first element, V, Z r, Nb, with one kind of element selected from the group consisting of Hf and Ta When the element in the periodic table of elements is larger than the first element or the element in the periodic table of elements is the same as the first element and the element in the periodic table of elements is larger than the first element is the second element. ,
The first element is included in a proportion of 0.01% by mass to 0.5% by mass,
Having particles containing the second element in a proportion of 0.01% by mass or more and 0.5% by mass or less;
The Cr content on the surface of the particles is 0.2 atomic% or more and 15 atomic% or less, and 70% or more and 170% or less of the Cr content at a position where the depth from the surface of the particles is 60 nm. A metal powder for powder metallurgy characterized by Fe is included as a main component,
Cr is contained in a ratio of 2% by mass to 32% by mass,
Si is contained at a ratio of 0.4 mass% or more and 1.5 mass% or less,
C is contained in a proportion of 0.01% by mass or more and 1.5% by mass or less,
Ti, V, Y, Zr, and one element selected from the group consisting of Nb and Hf as a first element, V, Z r, Nb, with one kind of element selected from the group consisting of Hf and Ta When the element in the periodic table of elements is larger than the first element or the element in the periodic table of elements is the same as the first element and the element in the periodic table of elements is larger than the first element is the second element. ,
The first element is included at a ratio of 0.03% by mass to 0.4% by mass,
Having particles containing the second element in a proportion of 0.03% by mass or more and 0.4% by mass or less;
The Cr content on the surface of the particles is 0.2 atomic% or more and 15 atomic% or less, and 70% or more and 170% or less of the Cr content at a position where the depth from the surface of the particles is 60 nm. A metal powder for powder metallurgy characterized by Fe is included as a main component,
Cr is included in a ratio of 6% by mass to 30% by mass,
Si is contained in a proportion of 0.5% by mass or more and 1% by mass or less,
C is contained at a ratio of 0.02 mass% to 1 mass%,
Ti, V, Y, Zr, and one element selected from the group consisting of Nb and Hf as a first element, V, Z r, Nb, with one kind of element selected from the group consisting of Hf and Ta When the element in the periodic table of elements is larger than the first element or the element in the periodic table of elements is the same as the first element and the element in the periodic table of elements is larger than the first element is the second element. ,
The first element is included in a proportion of 0.05% by mass or more and 0.3% by mass or less,
Having particles containing the second element in a proportion of 0.05% by mass or more and 0.3% by mass or less;
The Cr content on the surface of the particles is 0.2 atomic% or more and 15 atomic% or less, and 70% or more and 170% or less of the Cr content at a position where the depth from the surface of the particles is 60 nm. A metal powder for powder metallurgy characterized by   The Si content on the surface of the particle is 155% or more and 800% or less of the Si content at a position where the depth from the surface of the particle is 60 nm. Metal powder for powder metallurgy.   The content rate of Si in the surface of the particle is 200% or more and 500% or less of the content rate of Si at a position where the depth from the surface of the particle is 60 nm. Metal powder for powder metallurgy.   The metal powder for powder metallurgy according to any one of claims 1 to 5, wherein a ratio of an O content rate to a Si content rate on the surface of the particles is 0.05 or more and 0.4 or less.   The metal powder for powder metallurgy according to any one of claims 1 to 5, wherein a ratio of an O content ratio to a Si content ratio on the surface of the particles is 0.1 or more and 0.35 or less.   The metal powder for powder metallurgy according to any one of claims 1 to 7, wherein a content ratio of Cr on a surface of the particle is smaller than a content ratio of Cr in the entire particle. The ratio X1 / X2 of the value X1 obtained by dividing the content of the first element by the atomic weight of the first element with respect to the value X2 obtained by dividing the content of the second element by the atomic weight of the second element is 0.3 or more The metal powder for powder metallurgy according to any one of claims 1 to 8, which is 3 or less. The ratio X1 / X2 of the value X1 obtained by dividing the content of the first element by the atomic weight of the first element with respect to the value X2 obtained by dividing the content of the second element by the atomic weight of the second element is 0.5 or more The metal powder for powder metallurgy according to any one of claims 1 to 8, which is 2 or less. The ratio X1 / X2 of the value X1 obtained by dividing the content of the first element by the atomic weight of the first element with respect to the value X2 obtained by dividing the content of the second element by the atomic weight of the second element is 0.75 or more The metal powder for powder metallurgy according to any one of claims 1 to 8, which is 1.3 or less.   12. The metal powder for powder metallurgy according to claim 1, wherein the total content of the first element and the content of the second element is 0.05% by mass or more and 0.8% by mass or less. .   The metal powder for powder metallurgy according to any one of claims 1 to 11, wherein the total content of the first element and the content of the second element is 0.10% by mass or more and 0.6% by mass or less. .   The metal powder for powder metallurgy according to any one of claims 1 to 11, wherein the total content of the first element and the content of the second element is 0.12% by mass or more and 0.24% by mass or less. .   The metal powder for powder metallurgy according to any one of claims 1 to 14, having an average particle size of 0.5 µm or more and 30 µm or less.   A compound comprising: the metal powder for powder metallurgy according to any one of claims 1 to 15; and a binder for binding particles of the metal powder for powder metallurgy.   A granulated powder obtained by granulating the metal powder for powder metallurgy according to any one of claims 1 to 15. Forming a composition containing the metal powder for powder metallurgy according to any one of claims 1 to 15 to obtain a molded body;
Firing the molded body to obtain a sintered body;
A method for producing a sintered body, comprising:

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