JP2016141887A - Metal powder for powder metallurgy, compound, pelletized powder and sintered body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal powder for powder metallurgy capable of manufacturing a high density sintered body, a compound and a pelletized powder and the high density sintered body.SOLUTION: The metal powder for powder metallurgy contains Co as a main component, Cr of 10 to 35 mass%, Si of 0.2 to 3 mass% and contains a particle having a chemical composition containing a first element and a second element, which are two elements selected from a group of Ti, V, Y, Zr, Nb, Hf and Ta, of 0.01 to 0.5 mass% respectively, a first area and a second area having a larger volume than that of the first area as different structures each other with a relationship satisfying that (Si strength/Cr strength) in an EDX spectrum in the first area is larger than (Si strength/Cr strength) in the EDX spectrum in the second area.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a metal powder for powder metallurgy, a compound, a granulated powder, and 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. In particular, research on increasing the density of alloy powders containing Co as a main component is in progress.

JP 2012-87416 A

  The objective of this invention is providing the metal powder for powder metallurgy which can manufacture a high-density sintered compact, a compound and granulated powder, and a high-density sintered compact.

The above object is achieved by the present invention described below.
The metal powder for powder metallurgy of the present invention is mainly composed of Co,
Cr is contained in a proportion of 10% 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,
One element selected from the group consisting of Ti, V, Y, Zr, Nb, Hf and Ta is the first element, and one element selected from the group, the group in the periodic table of elements is When the element larger than the first element or the group in the periodic table of the elements is the same as the first element and the element in the periodic table of the elements 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,
The second element has a chemical composition containing 0.01% by mass or more and 0.5% by mass or less,
As a tissue different from each other, including a first region and a second region having a volume larger than that of the first region,
Among the EDX spectra acquired for the first region, the height of the peak of Cr included in the range of 5.3 keV to 5.5 keV is defined as the first Cr intensity, and the range is 1.6 keV to 1.8 keV. The height of the Si peak contained in the first Si intensity,
Among the EDX spectra acquired for the second region, the height of the Cr peak included in the range of 5.3 keV to 5.5 keV is the second Cr intensity, and is in the range of 1.6 keV to 1.8 keV. When the height of the Si peak contained in the second Si intensity,
2nd Si intensity | strength / 2nd Cr intensity | strength <1st Si intensity | strength / 1st Cr intensity | strength is included, It is characterized by including.

  Thus, when the metal powder for powder metallurgy is used for powder metallurgy, the second region acts to suppress significant growth, so that voids are less likely to occur in the sintered body, and the crystal grains The enlargement is suppressed, and a sintered body having high density and high mechanical properties can be obtained.

In the metal powder for powder metallurgy according to the present invention, the particles include a plurality of the second regions,
It is preferable that the first region is located at a boundary between the second regions.

  As a result, the sintering speed of the particles is hardly hindered by the first region, so that a sintered body having a particularly high relative density can be manufactured. Further, as a result, the first regions naturally maintain an appropriate distance, that is, a distance corresponding to the size of the second region. For this reason, the structure | tissue which originates in a 1st area | region can be disperse | distributed more uniformly in a sintered compact, and the fall of the mechanical characteristic of a sintered compact can be avoided.

In the metal powder for powder metallurgy according to the present invention, the second region is a crystal,
It is preferable that the particles include 1 to 20 second regions on average.

  As a result, the entire particle becomes a single crystal or a polycrystal close to a single crystal, and when subjected to firing, exhibits the same behavior as when the single crystal is subjected to firing. Accordingly, when such metal powder for powder metallurgy is fired, sintering proceeds at an excellent sintering rate derived from a single crystal. As a result, it is possible to manufacture a sintered body having a small relative void and a high relative density.

In the metal powder for powder metallurgy of the present invention, the average particle diameter of the particles is 0.5 μm or more and 30 μm or less,
The maximum diameter of the first region is preferably 5 nm or more and 150 nm or less.

  As a result, the size of the first region is optimal in obtaining the effect of obtaining a high-density sintered body.

In the metal powder for powder metallurgy of the present invention, Cr is contained in a proportion of 16% by mass to 35% by mass,
Si is contained in a ratio of 0.3% by mass to 2% by mass,
Mo is contained in a ratio of 3% by mass to 12% by mass,
The first element is included in a proportion of 0.01% by mass to 0.5% by mass,
It is preferable that the second element is contained at a ratio of 0.01% by mass to 0.5% by mass.
Thereby, the density of the sintered body to be manufactured can be further increased.

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 sintered body of the present invention is manufactured by sintering the metal powder for powder metallurgy of the present invention.
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. It is a figure which shows typically the structure | tissue of the particle | grains shown in FIG. It is a figure which expands and shows the range A of FIG. It is an example of the TEM image of the cross section of the particle | grains contained in the metal powder for powder metallurgy of this invention. It is the elements on larger scale of the range B enclosed with the broken line shown to Fig.4 (a), Comprising: It is an observation image when observing the same range B with a high angle annular dark field scanning transmission electron microscope. FIG. 6 is an EDX spectrum acquired for the first region shown in FIG. 5 and obtained by point analysis for a position corresponding to the first region shown in FIG. 5 (Position 1 in FIG. 6). FIG. 6 is an EDX spectrum acquired for the second region shown in FIG. 5 and obtained by point analysis with respect to a position (Position 2 in FIG. 7) corresponding to the second region shown in FIG. 5.

  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. According to such a powder metallurgy technique, 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.

  In the metal powder for powder metallurgy used for powder metallurgy, conventionally, attempts have been made to increase the density of a sintered body to be 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 chemical composition and crystal 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 is mainly composed of Co, Cr is contained in a ratio of 10 mass% to 35 mass%, and Si is 0.2 mass% to 3 mass%. %, And the first element described later is included in a ratio of 0.01% by mass to 0.5% by mass, and the second element described later is 0.01% by mass to 0.5% by mass. Particles having a chemical composition contained at a ratio of Moreover, this particle | grain contains the 1st area | region and the 2nd area | region whose volume is larger than a 1st area | region as mutually different crystal structures. Further, in the first region and the second region, the height of the peak of Cr included in the range of 5.3 keV to 5.5 keV in the EDX spectrum acquired for the first region is defined as the first Cr intensity. The Si peak height included in the range from 1.6 keV to 1.8 keV is defined as the first Si intensity, and the EDX spectrum acquired for the second region is in the range from 5.3 keV to 5.5 keV. When the height of the Cr peak contained in the sample is the second Cr intensity and the height of the Si peak contained in the range of 1.6 keV to 1.8 keV is the second Si intensity, the (first Si intensity / first Cr intensity) Strength)> (second Si strength / second Cr strength).

  According to the metal powder for powder metallurgy containing such particles, when the particles are sintered in the firing step, the sintering is promoted and the densification proceeds. 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 configuration of the metal powder for powder metallurgy according to the present embodiment will be further described in 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”.

  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 a diagram schematically showing the structure of the particles shown in FIG.

  The particles 1 shown in FIG. 1 are made of a Co-based alloy. And the particle | grains 1 contain the 1st area | region 11 and the 2nd area | region 12, as shown in FIG.

  Among these, at least one second region 12 may be included in the particle 1. FIG. 2 illustrates an example in which the particle 1 includes four second regions 12 as an example.

  Further, each of the second regions 12 is a single crystal, and the entire particle 1 is polycrystalline. Note that the boundaries between the second regions 12 are separated by linear grain boundaries 3.

  The average number of the second regions 12 included in the cross section of the particle 1 is not particularly limited, but is preferably 1 or more and 20 or less, and more preferably 1 or more and 10 or less. Such a particle 1 can be said to be a single crystal or a polycrystal close to a single crystal as a whole, and when subjected to firing, exhibits the same behavior as when the single crystal is subjected to firing. Therefore, when the metal powder for powder metallurgy is fired, the sintering proceeds at an excellent sintering speed derived from the single crystal. As a result, it is possible to manufacture a sintered body having a small relative void and a high relative density.

  The average number of the second regions 12 in the cross section of the particle 1 is included in one particle 1 by observing those cross sections with an electron microscope with 10 or more particles 1 included in the metal powder as an observation target. The number of the second regions 12 is counted by visually observing the observation image, and the number is averaged over the entire observation target. Since the first region 11 and the second region 12 are accompanied by a difference in light and shade in the observation image of the electron microscope, based on that. It can be seen that different structures exist in the cross section of the particle 1.

  For example, a transmission electron microscope (TEM) is used as the electron microscope, and the second region 12 can be specified as a structure that occupies most of the cross section of the particle 1 when observed in a bright field image. In addition, when it is difficult to clearly identify the second region 12 in the bright field image, the identification may be facilitated by switching to the dark field image.

  The equivalent circle diameter of the second region 12 (the diameter of a circle having the same area as the cross section of the second region 12) is 1 of the equivalent circle diameter of the particle 1 (the diameter of a circle having the same area as the cross section of the particle 1). % Or more and less than 100%, more preferably 3% or more and 99.9% or less. When the ratio of the equivalent circle diameter of the second region 12 to the equivalent circle diameter of the particle 1 is within the above range, the second region 12 behaves predominantly in the sinterability of the particle 1 when subjected to firing. be able to. That is, since the particle 1 behaves like a single crystal particle, the sintering speed is increased, which greatly contributes to the improvement of the sintering density.

  The second region 12 is a crystal containing Co as a main component. The second region 12 occupies most of the cross section of the particle 1 (90% or more in area ratio). Therefore, the second region 12 affects the characteristics of the particles 1 (metal powder for powder metallurgy) and the sintered body produced from the particles 1.

  On the other hand, at least one first region 11 may be included in the particle 1. FIG. 3 illustrates an example in which one first region 11 is included in the range A of FIG. 2 as an example.

  In the range A shown in FIG. 3, the first region 11 having a volume smaller than that of the second region 12 exists. Due to the presence of the first region 11, the sintered body manufactured using the metal powder including the particles 1 has a high relative density and excellent mechanical properties.

  The first region 11 may be present inside the second region 12, but is preferably present at the boundary between the second regions 12, that is, at the grain boundaries 3. Thereby, since the sintering speed of the particles 1 is hardly hindered by the first region 11, a sintered body having a particularly high relative density can be manufactured.

  In addition, the shape of the first region 11 in the cross section of the particle 1 is not particularly limited, and may be any shape, but is preferably a circular shape, a polygonal shape, or a shape similar to these. By including the 1st area | region 11 of such a shape, the particle | grains 1 become the thing which was excellent in sinterability more, and the sintered compact manufactured using the metal powder containing this particle | grain 1 is more The relative density is high.

  In addition, the shape of the first region 11 is preferably a shape having a small aspect ratio. Specifically, the average value of the aspect ratios defined by the major axis / minor axis of the first region 11 is preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less. By including the first region 11 having such a shape, similarly to the above, the particles 1 are more excellent in sinterability, and are sintered using the metal powder including the particles 1. The body has a higher relative density.

  The major axis of the first region 11 is the maximum length that can be taken in the first region 11, and the minor axis is the maximum length that can be taken in the direction orthogonal to the major axis.

  Moreover, about the 1st area | region 11, the magnitude | size, distribution, etc. can also be specified by the surface analysis of qualitative analysis. Specifically, the presence of the first region 11 can be specified by finding a region where Si is segregated in an Si composition image obtained by an electron beam microanalyzer (EPMA).

  The maximum value (maximum diameter) of the equivalent circle diameter of the first region 11 (the diameter of a circle having the same area as the cross section of the first region 11) in one particle 1 is not particularly limited, but is 5 nm or more and 150 nm or less. Is preferably 10 nm or more and 120 nm or less. When the maximum diameter of the first region 11 is within the above range, the size of the first region 11 is optimal for achieving the effects as described above. That is, when the maximum diameter of the first region 11 is less than the lower limit value, the size of the first region 11 is insufficient, so that the effect of suppressing crystal enlargement when the particles 1 are fired is sufficient. On the other hand, if the maximum diameter of the first region 11 exceeds the upper limit, the mechanical properties of the sintered body may be deteriorated.

  The maximum diameter of the first region 11 can be obtained as the maximum value of the diameter of the circle having the same area as the area of the region where Si is segregated (projected area circle equivalent diameter) in the Si composition image.

  By the way, the 1st field 11 and the 2nd field 12 satisfy the relation mentioned below, when an EDX spectrum is acquired, respectively.

  First, in the EDX spectrum acquired for the first region 11, the height of the peak of Cr included in the range of 5.3 keV to 5.5 keV is defined as the first Cr intensity, and is 1.6 keV to 1.8 keV. The height of the Si peak included in the range is defined as the first Si intensity.

Moreover, the height of the peak of Cr contained in the range of 5.3 keV or more and 5.5 keV or less among the EDX spectrum acquired about the 2nd area | region 12 is made into 2nd Cr intensity | strength, and is 1.6 keV or more and 1.8 keV or less The height of the Si peak included in the range is defined as the second Si intensity.
At this time, the particle 1 satisfies the following formula [1].

Second Si strength / Second Cr strength <First Si strength / First Cr strength [1]
Further, the particle 1 preferably satisfies the following formula [2], and more preferably satisfies the following formula [3].

Second Si strength / Second Cr strength <First Si strength / First Cr strength <1 [2]
1.5 × second Si strength / second Cr strength <first Si strength / first Cr strength <0.8 [3]

  By satisfying the above relationship, the first region 11 acts to suppress the second region 12 from growing significantly when the particles 1 are subjected to firing. As a result, voids are less likely to occur in the sintered body, and enlargement of crystal grains is suppressed, and a sintered body having a high density and high mechanical properties can be obtained.

  4A is an example of a TEM image (bright field image) of the cross section of the particle 1, and FIG. 4B is a TEM image (dark image) of the cross section of the particle 1 shown in FIG. (Field image) is an example.

  In the TEM image (bright field image) shown in FIG. 4A, two second regions 12 included in the particle 1 are shown. In addition, a line based on the difference in shade indicated by an arrow in FIG. 4A is a grain boundary 3 located at the boundary between the two second regions 12.

  In addition, in the TEM image (dark field image) shown in FIG. 4B, one second region 12 located on the left of the two second regions 12 is shown in light color, while the right side One second region 12 located in the direction is shown in a dark color. Thus, by observing the second region 12 with a dark field image, the contrast between the two second regions 12 can be enhanced based on the difference in crystal orientation.

  Further, FIG. 5 is a partially enlarged view of a range B surrounded by a broken line shown in FIG. 4A, and is an observation image when the range B is observed with a high-angle annular dark field scanning transmission electron microscope. is there. In addition, dark portions indicated by arrows in FIG. Of the two first regions 11 shown in FIG. 5, one is located in the second region 12 and the other is located in the grain boundary 3.

  FIG. 6 is an EDX spectrum acquired for the first region 11 shown in FIG. 5 and obtained by point analysis with respect to a position corresponding to the first region 11 shown in FIG. 5 (Position 1 in FIG. 6). It is. Further, FIG. 7 is an EDX spectrum acquired for the second region 12 shown in FIG. 5 and obtained by point analysis with respect to a position (Position 2 in FIG. 7) corresponding to the second region 12 shown in FIG. It is.

  As shown in these EDX spectrum examples, the first Si intensity / first Cr intensity in the EDX spectrum acquired for the first region 11 is greater than the second Si intensity / second Cr intensity in the EDX spectrum acquired for the second region 12. Is also getting bigger. Si accumulated at a high concentration in the first region 11 is considered to be contained in a state such as silicon oxide. For this reason, when the particle 1 is subjected to firing, the first region 11 is interposed between the crystals to be grown, so that further crystal growth can be suppressed. As a result, voids are less likely to occur in the sintered body, and enlargement of crystal grains is suppressed, and a sintered body having a high density and high mechanical properties can be obtained.

  When the first Si strength / first Cr strength is equal to or less than the second Si strength / second Cr strength, Si is accumulated in the first region 11 at a high concentration. Therefore, when the particles 1 are subjected to firing, the crystals may be enlarged. As a result, voids may be generated in the sintered body or the crystal grains may be enlarged.

  Moreover, it is preferable that the sintered compact manufactured using the metal powder for powder metallurgy of this invention does not contain a dendrite phase as much as possible.

  Here, the dendrite phase is a crystal structure grown in a dendritic shape, but if such a dendrite phase is contained in a large amount, the mechanical properties of the sintered body deteriorate. Therefore, reducing the dendrite phase content is effective in enhancing the mechanical properties of the sintered body. Specifically, the cross section of the sintered body is observed with a scanning electron microscope, and the area ratio occupied by the dendrite phase in the obtained observation image is preferably 20% or less, and more preferably 10% or less. . A sintered body satisfying such conditions is particularly excellent in mechanical properties.

  The area ratio described above is calculated as the ratio of the area occupied by the dendrite phase to the area of the observation image, and one side of the observation image is set to about 50 μm or more and 1000 μm or less.

Hereinafter, an example of the chemical composition of the particle 1 will be described in detail.
In the overall chemical composition of the particles 1, Co is an element (main component) having the highest content rate, and is an element that affects the characteristics of the sintered body. The Co 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. For this reason, for example, even when the obtained sintered body comes into contact with the skin, metal ions are more difficult to elute, so that a sintered body with higher compatibility with a living body can be obtained.

  The Cr content in the metal powder is 10% by mass or more and 35% by mass or less, preferably 16% by mass or more and 34% by mass or less, and more preferably 28% by mass or more and 33% by mass or less. When the Cr content is less than the lower limit, depending on the overall composition, the corrosion resistance of the manufactured sintered body becomes insufficient. On the other hand, if the Cr content exceeds the upper limit, depending on the overall composition, the sinterability may be reduced, making it difficult to increase the density of the sintered body.

(Mo)
The metal powder for powder metallurgy of the present invention may contain Mo (molybdenum) as necessary.

  Mo is an element that acts to further increase the corrosion resistance of the sintered body to be produced. That is, the corrosion resistance due to the addition of Cr can be further enhanced by the addition of Mo. This is considered to be due to the fact that the passive film mainly composed of an oxide of Cr is densified by adding Mo. Therefore, in the sintered body manufactured using the metal powder to which Mo is added, metal ions are more difficult to elute, and a sintered body with further improved compatibility with a living body can be obtained.

  The Mo content in the metal powder is preferably 3% by mass or more and 12% by mass or less, more preferably 4% by mass or more and 11% by mass or less, and further preferably 5% by mass or more and 9% by mass or less. . If the Mo content is below the lower limit, depending on the Cr or Si content, the amount of Mo relative to the Cr or Si will be relatively large, and the balance of the contained elements will be lost. There is a risk that the physical characteristics will deteriorate.

(Si)
Si (silicon) is an element that acts to enhance the mechanical properties of the sintered body to be produced. By adding Si, silicon oxide in which a part of Si is oxidized is generated in the alloy. Examples of silicon oxide include SiO and SiO ₂ . Such silicon oxide inhibits the metal crystal from becoming significantly enlarged when the metal crystal grows during sintering of the metal powder. For this reason, in the alloy to which Si is added, the particle size of the metal crystal is kept small, and the mechanical properties of the sintered body can be further enhanced. In particular, when a Si atom substitutes a Co atom as a substitutional element, the crystal structure is slightly distorted and the Young's modulus is increased. Therefore, by adding Si, excellent mechanical properties, particularly excellent Young's modulus can be obtained. As a result, a sintered body having higher deformation resistance can be obtained.

  The content of Si in the metal powder is 0.2% by mass or more and 3% by mass or less, preferably 0.3% by mass or more and 2% by mass or less, and 0.6% by mass or more and 0.9% by mass. % Or less is more preferable. If the Si content is lower than the lower limit, depending on the firing conditions, the amount of silicon oxide becomes too small, and the metal crystals may tend to enlarge during the sintering of the metal powder. On the other hand, when the Si content exceeds the upper limit, depending on the firing conditions, the amount of silicon oxide becomes excessive, so that a region in which silicon oxide is spatially continuously distributed tends to occur. In this region, there is a high possibility that the mechanical characteristics will deteriorate.

  Further, as described above, it is preferable that a part of Si is present in the state of silicon oxide, but the abundance thereof is such that the ratio of Si contained as silicon oxide with respect to the total amount of Si is 10 mass. % To 90% by weight, more preferably 20% to 80% by weight, more preferably 30% to 70% by weight, and more preferably 35% to 65% by weight. Is particularly preferred. By setting the ratio of Si contained as silicon oxide in the total Si within the above range, the sintered body has the effect of improving the mechanical properties as described above, while a certain amount of silicon oxide is present. By being present, the oxide amount of transition metal elements such as Co, Cr, and Mo contained in the sintered body can be sufficiently suppressed. That is, since Si is more easily oxidized than Co, Cr, and Mo, and the reduction reaction can be caused by the removal of oxygen bonded to these transition metal elements. This is because that is not silicon oxide is considered to be equivalent to causing a sufficient reduction reaction to the transition metal element. Therefore, when the ratio of Si contained as silicon oxide in Si is within the above range, the effect of high mechanical characteristics as described above is inhibited by the oxide of Co, Cr, or Mo in the sintered body. Is suppressed. As a result, a more reliable sintered body can be realized.

  In addition, it is considered that a certain amount of silicon oxide contributes to forming a chemically stable film together with chromium oxide and molybdenum oxide on the surface of the sintered body. For this reason, chemical stability is imparted to the surface of the sintered body, leading to a further increase in the corrosion resistance of the sintered body.

  Moreover, moderate hardness will be given with respect to a sintered compact by setting the ratio of Si contained as silicon oxide of Si in the said range. That is, it is considered that when a certain amount of Si that is not silicon oxide is present, at least one of Co, Cr, and Mo and Si form a hard intermetallic compound, which increases the hardness of the sintered body. Durability and abrasion resistance can be improved by increasing the hardness of the sintered body.

The intermetallic compound is not particularly limited, and an _{example, CoSi 2, Cr 3 Si,} MoSi 2, Mo 5 Si 3 and the like.

  In consideration of the amount of precipitation of the intermetallic compound, the ratio of Si content to the Mo content (Si / Mo) is preferably 0.05 or more and 0.2 or less in terms of mass ratio. More preferably, it is 0.15 or less. Thereby, higher mechanical properties (for example, a good balance between hardness and toughness) can be imparted to the sintered body.

  Further, as described above, silicon oxide is contained in the first region 11 at a high concentration. However, when the first region 11 is located at the grain boundary 3, the first regions 11 are naturally at an appropriate distance, that is, the first region 11. The distance corresponding to the size of the two regions 12 is maintained. For this reason, the structure | tissue originating in the 1st area | region 11 can be disperse | distributed more uniformly in a sintered compact. As a result, the probability that the structure derived from the first region 11 is spatially continuously distributed is reduced, and the deterioration of the mechanical properties of the sintered body can be avoided.

(N)
The metal powder for powder metallurgy of the present invention may contain N (nitrogen) as necessary.

  N is an element that acts to enhance the mechanical properties of the sintered body to be produced. Since N is an austenitizing element, it acts to promote austenitization (face-centered cubic lattice formation) of the crystal structure of the sintered body and increase toughness.

  In addition, by including N, generation of a dendrite phase is suppressed in the sintered body, and the content rate of the dendrite phase becomes very small. From such a viewpoint, toughness can be increased.

  Therefore, the obtained sintered body has moderate hardness, high toughness, and low dendrite phase content. For this reason, such a sintered body is rich in impact resistance and the like.

The N content in the metal powder is preferably 0.09% by mass or more and 0.5% by mass or less, more preferably 0.12% by mass or more and 0.4% by mass or less, and 0.14% by mass. % To 0.25% by mass, more preferably 0.15% to 0.22% by mass. When the N content is less than the lower limit, depending on the composition of the alloy, the crystal structure of the sintered body may become insufficiently austenitized, and the toughness of the sintered body may be easily lowered. This is considered to be because an excessive hcp structure (ε phase) is precipitated in the sintered body. On the other hand, if the N content exceeds the upper limit, depending on the composition of the alloy, a large amount of various nitrides may be generated and the composition may be difficult to sinter. For this reason, there is a possibility that the sintered density of the sintered body is lowered and the corrosion resistance and mechanical properties are lowered. Examples of the generated nitride include Cr ₂ N.

  In particular, in the range of 0.15% by mass or more and 0.22% by mass or less, the austenite phase (face-centered cubic lattice phase) becomes particularly dominant, and a remarkable improvement in toughness is observed as the hardness decreases. When a sintered body manufactured using a metal powder containing N at such a content rate is subjected to crystal structure analysis by an X-ray diffraction method using CrKα rays, the main peak due to the austenite phase is very strong. On the other hand, the peak due to the hcp structure and other peaks are all 5% or less of the height of the main peak. This shows that the austenite phase is dominant.

  Further, the ratio of N content (N / Si) to Si content is preferably 0.1 or more and 0.8 or less, and more preferably 0.2 or more and 0.6 or less in terms of mass ratio. preferable. Thereby, it is possible to achieve both high mechanical properties and high corrosion resistance in the sintered body. That is, when an appropriate amount of Si is added, an appropriate amount of silicon oxide is generated and the amount of oxides of Co, Cr, and Mo is reduced, so that the mechanical properties are improved as described above, and the corrosion resistance on the surface is higher. Become. On the other hand, if the amount of Si added is too large, the amount of silicon oxide produced becomes too large, which may reduce the mechanical properties of the sintered body. Therefore, when N is added at a ratio within the above range, the high corrosion resistance due to the addition of Si and the above-described effect due to the addition of N can be exhibited without canceling each other, so that it is high. Both corrosion resistance and high mechanical properties can be achieved. This is thought to be because Si and a metal element such as Co produce a substitutional solid solution, whereas a metal element such as N and Co produces an interstitial solid solution and can coexist with each other. In addition, it is considered that the distortion of the crystal structure due to the solid solution of Si is also suppressed due to the solid solution of N, which is considered to prevent the deterioration of mechanical properties.

  When Si is added, the crystal structure is distorted as described above. However, in this state, hysteresis tends to occur in the behavior of thermal expansion and contraction. If there is a large hysteresis in the behavior of thermal expansion and contraction, the thermal characteristics of the sintered body may change over time.

  On the other hand, when N is added at the above-described ratio, N penetrates into the crystal structure and dissolves therein, so that distortion of the crystal structure is suppressed. As a result, hysteresis in the behavior of thermal expansion and contraction is suppressed, and the thermal characteristics of the sintered body can be stabilized.

  From the above, by appropriately adding Si and N, it is possible to stabilize the mechanical properties and the thermal properties of the sintered body, respectively.

  In addition, when the ratio of the content rate of N with respect to the content rate of Si is less than the said lower limit, depending on the composition of the alloy, the distortion of the crystal structure cannot be sufficiently suppressed, and the toughness and the like may be reduced. On the other hand, if it exceeds the upper limit, depending on the composition of the alloy, the composition becomes difficult to sinter, the sintered density of the sintered body is lowered, and the mechanical properties may be lowered.

(C)
The metal powder for powder metallurgy of the present invention may contain C (carbon) as necessary.

  C is an element that acts to enhance the mechanical properties of the sintered body to be produced. The addition of C increases the hardness and tensile strength of the sintered body. In addition, the mechanical properties of the sintered body can be improved by combining the C with the first element and the second element to generate carbides.

  The C content in the metal powder is preferably 1.5% by mass or less, and more preferably 0.7% by mass or less. If the C content exceeds the upper limit, depending on the composition of the alloy, the brittleness of the sintered body increases and the mechanical properties may deteriorate.

  Further, the lower limit value of the addition amount is not particularly set, but the lower limit value is preferably set to about 0.05% by mass in order to sufficiently exhibit the above-described effects.

  The C content is preferably about 0.02 to 0.5 times the Si content, more preferably about 0.05 to 0.3 times. By setting the ratio of C to Si within the above range, the adverse effects of silicon oxide and carbide on the hardness and mechanical properties of the sintered body can be minimized.

  Further, the N content is preferably about 0.3 to 10 times the C content, more preferably about 2 to 8 times. By setting the ratio of N to C within the above range, the balance between the hardness and mechanical properties of the sintered body can be optimized.

(First element and second element)
The first element and the second element are combined with oxygen or the like contained in the binder or metal powder in the molded body, and precipitate carbides and oxides (hereinafter collectively referred to as “carbides and the like”) in the alloy. . 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 carbide or the like promotes the accumulation of silicon oxide, thereby promoting the generation of the first region 11. As a result, it is possible to promote sintering and increase the density while suppressing the enlargement of 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. Elements belonging to Group 3A or Group 4A can remove oxygen contained in the metal powder as an oxide 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.

  Of these elements, 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.

  The content ratio 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 0.2% by mass or less, and more preferably 0.8% by mass. It is set to 05 mass% or more and 0.1 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 0.2% by mass or less, and more preferably 0.8% by mass. It is set to 05 mass% or more and 0.1 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 assumed 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 different from each other when the metal powder is sintered. . 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.

  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.

  The ratio of the content ratio of the first element and the content ratio of the second element is set in consideration of the mass number of the element selected as the first element and the mass number of the element selected as the second element. Is preferred.

  Specifically, the value obtained by dividing the content E1 (mass%) of the first element by the mass number of the first element is taken as an index X1, and the content E2 (mass%) of the second element is the mass number of the second element. The ratio X1 / X2 of the index X1 with respect to the index X2 is preferably 0.3 or more and 3 or less, more preferably 0.5 or more and 2 or less. More preferably, it is 75 or more and 1.3 or less. By setting X1 / X2 within the above range, it is possible to optimize the difference between the timing of precipitation of the first element carbide and the like and the timing of precipitation of the second element carbide and the like. 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. Further, since the balance between the number of atoms of the first element and the number of atoms of the second element is optimized, the effect brought about by the first element and the effect brought about by the second element are exhibited synergistically, A sintered body having a density 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 mass number of Zr is 91.2 and the mass number of Nb is 92.9, so E1 / E2 is 0.29. The above is preferably 2.95 or less, and more preferably 0.49 or more and 1.96 or less.

  When the first element is Hf and the second element is Nb, the mass number of Hf is 178.5 and the mass number of Nb is 92.9, so E1 / E2 is 0.58. It is preferably 5.76 or less and more preferably 0.96 or more and 3.84 or less.

  When the first element is Ti and the second element is Nb, the mass number of Ti is 47.9 and the mass number of Nb is 92.9, so E1 / E2 is 0.15. It is preferably 1.55 or less and more preferably 0.26 or more and 1.03 or less.

  When the first element is Nb and the second element is Ta, the mass number of Nb is 92.9 and the mass number of Ta is 180.9. Therefore, E1 / E2 is 0.15. It is preferably 1.54 or more and more preferably 0.26 or more and 1.03 or less.

  When the first element is Y and the second element is Nb, the mass number of Y is 88.9 and the mass number of Nb is 92.9, so E1 / E2 is 0.29. It is preferably 2.87 or less and more preferably 0.48 or more and 1.91 or less.

  Further, when the first element is V and the second element is Nb, the mass number of V is 50.9 and the mass number of Nb is 92.9, so E1 / E2 is 0.16. It is preferable that it is 1.64 or more and more preferably 0.27 or more and 1.10 or less.

  When the first element is Ti and the second element is Zr, the mass number of Ti is 47.9 and the mass number of Zr is 91.2. Therefore, E1 / E2 is 0.16. It is preferably 1.58 or more and more preferably 0.26 or more and 1.05 or less.

  When the first element is Zr and the second element is Ta, the mass number of Zr is 91.2 and the mass number of Ta is 180.9, so E1 / E2 is 0.15. It is preferably 1.51 or more and more preferably 0.25 or more and 1.01 or less.

  When the first element is Zr and the second element is V, the mass number of Zr is 91.2 and the mass number of V is 50.9, so E1 / E2 is 0.54. It is preferably 5.38 or less and 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.

  Further, the content ratio E1 of the first element and the content ratio E2 of the second element are as described above, respectively, and the total of these is preferably 0.05% by mass or more and 0.6% by mass or less, It is more preferably 0.10% by mass or more and 0.48% by mass or less, and further 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, by adding appropriate amounts of the first element and the second element, the carbide of the first element, the carbide of the second element, and the like become “nuclei” at the grain boundaries in the sintered body, and the silicon oxide Accumulation is thought to occur. Accumulation of silicon oxide reduces the oxide concentration at other sites, thereby promoting sintering. As a result, it is considered that the densification of the sintered body is further promoted.

  Furthermore, since the accumulated silicon oxide easily moves to the triple point of the crystal grain boundary in the process of firing the metal powder, crystal growth at this point is suppressed (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.

  Further, the accumulated silicon oxide tends to be located at the triple point of the grain boundary as described above, and therefore tends to be formed into a granular shape. Therefore, the sintered body has such a granular shape, the first region 11 having a relatively high silicon oxide content rate, and the second region having a silicon oxide content rate relatively lower than that of the first region 11. 12 is easily formed. The presence of the first region 11 makes it possible to reduce the oxide concentration inside the crystal and suppress the remarkable growth of crystal grains as described above.

  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, it is possible to achieve both an increase in hardness and a decrease in toughness when C is added and an increase in density caused by the addition of the first element and the second element. Can do. As a result, a metal powder capable of producing a sintered body having excellent mechanical properties such as tensile strength and toughness can be obtained.

(Other elements)
The particles 1 may contain at least one of Fe, Ni, Mn, W, and S as necessary in addition to the elements described above. In addition, these elements may be inevitably included.

Fe is an element that imparts high mechanical properties to the sintered body to be produced.
Although the content rate of Fe in a metal powder is not specifically limited, It is preferable that it is 0.01 to 25 mass%, and it is more preferable that it is 0.03 to 5 mass%. By setting the Fe content within the above range, a sintered body having high density and excellent mechanical properties can be obtained.

Ni is an element that imparts high toughness to the manufactured sintered body.
Although the content rate of Ni in a metal powder is not specifically limited, It is preferable that it is 0.01 to 40 mass%, and it is more preferable that it is 0.02 to 37 mass%. By setting the Ni content within the above range, a sintered body having high density and excellent toughness can be obtained.

  Mn, like Si, 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 a metal powder is not specifically limited, It is preferable that it is 0.05 to 1.5 mass%, and it is more preferable that it is 0.1 to 1 mass%. By setting the Mn content within the above range, a sintered body having a high density and excellent mechanical properties can be obtained. Further, the mechanical strength can be increased while suppressing the reduction in elongation. Furthermore, an increase in brittleness at a high temperature (during red heat) can be suppressed.

  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 If the upper limit is exceeded, corrosion resistance and mechanical properties may be deteriorated.

W is an element that enhances the heat resistance of the sintered body to be produced.
Although the content rate of W in a metal powder is not specifically limited, It is preferable that they are 1 mass% or more and 20 mass% or less, and it is more preferable that they are 2 mass% or more and 16 mass% or less. By setting the W content in the above range, the heat resistance of the sintered body can be further enhanced without causing a significant decrease in the density of the sintered body to be produced.

S is an element that enhances the machinability of the sintered body to be produced.
Although the content rate of S in a metal powder is not specifically limited, It is preferable that it is 0.5 mass% or less, and it is more preferable that it is 0.01 mass% or more and 0.3 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.

  In addition, B, Se, Te, Pd, or the like may be added to the particles 1. 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. Specifically, for example, Li, Be, Na, Mg, P, K, Ca, Sc, Zn, Ga, Ge, Ag, In, Sn , Sb, Os, Ir, Pt, Au, Bi and the like. The amount of these impurities mixed is preferably set so that each element is less than the contents of Co, Cr, Si, the first element and the second element. 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 particles 1 at this level, the sinterability becomes high, and a sintered body having 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.

  Co is a component (main component) having the highest content in the alloy constituting the metal powder for powder metallurgy of the present invention, and has a great influence on the properties of the sintered body. The content of Co is not particularly limited, but is preferably 50% by mass or more, and more preferably 55% by mass or more and 67.5% by mass or less.

The composition ratio of the particles 1 is, for example, iron and steel-atomic absorption spectrometry defined in JIS G 1257 (2000), iron and steel-ICP emission spectroscopy 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.

  In addition, 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 particles 1 are preferably contained in the metal powder for powder metallurgy in a number ratio of 50% or more, and more preferably 60% or more. According to such metal powder for powder metallurgy, the above-described effects can be more reliably exhibited, and a sintered body having high density and excellent mechanical properties can be more reliably produced.

  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. .

  Moreover, it is preferable that the metal powder for powder metallurgy of this invention contains the chemical component of the cobalt chromium alloy prescribed | regulated, for example to JIST6115 (2013).

  The “chemical component” refers to a chemical component defined in JIS T 6115 (2013). Specifically, for example, it refers to a combination of elements contained in the content (unit: mass%) defined in 4.3 of JIS T 6115 (2013).

[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 molten metal is cooled very quickly, the particles 1 having the same size of the second region 12 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, 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 size of the granulated powder is not particularly limited, but is preferably about 10 μm to 200 μm, more preferably about 20 μm to 100 μm, and more preferably about 25 μm to 60 μm. 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 to 1000 MPa. 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 about 980 ° C. or higher and 1450 ° C. or lower as an example. The temperature is preferably about 1050 ° C. or higher and 1350 ° 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 probably because the alloy composition and the crystal structure of the particles were optimized, so that the sinterability of the metal powder was improved 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 it varies slightly depending on the composition of the metal powder for powder metallurgy, the surface Vickers hardness is expected to be 300 or more and 780 or less as an example. Further, it is expected to be preferably 340 or more and 600 or less. Since the sintered body having such hardness has both wear resistance and impact resistance, the sintered body has particularly high durability.

  In addition, the sintered body has a sufficiently high density and mechanical properties without any additional treatment. However, in order to further increase the density and improve the mechanical properties, various additional treatments are performed. You may make it give.

  As this additional process, for example, an additional process for increasing the density, such as the HIP process described above, may be used. Various quenching processes, various sub-zero processes, various tempering processes, various annealing processes, etc. Good. These additional processes may be performed independently or 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 changes slightly 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, sufficient effects 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, Plant parts such as thermal power plants, hydroelectric power plants, refineries, chemical complexes, watch parts, metal tableware, jewelry, ornaments such as eyeglass frames, surgical instruments, artificial bones, artificial teeth, artificial roots In addition to medical devices such as orthodontic parts, it is used for 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 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: 1300 ℃
-Firing time: 3 hours (holding time at the firing temperature)
・ Baking atmosphere: Argon atmosphere

(Sample Nos. 2 to 29)
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. The sintered body of 29 was subjected to HIP treatment under the following conditions after firing. Sample No. The sintered bodies 14 to 16 were obtained using metal powders manufactured by the gas atomization 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 No. 30)
[1] First, a metal powder having the composition shown in Table 2 was sampled. 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

  [6] Next, a solution heat treatment and a precipitation hardening heat treatment were sequentially performed on the obtained sintered body under the following conditions.

<Solution heat treatment conditions>
・ Heating temperature: 1050 ° C
・ Heating time: 10 minutes ・ Cooling method: Water cooling

<Precipitation hardening heat treatment conditions>
・ Heating temperature: 480 ℃
・ Heating time: 60 minutes ・ Cooling method: Air cooling

(Sample Nos. 31-40)
Except for changing the composition of the metal powder for powder metallurgy as shown in Table 2, each sample No. In the same manner as in the case of 30, a sintered body was obtained. Sample No. About 40 sintered bodies, after firing, HIP treatment was performed under the following conditions.

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

In Table 2, 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 2 was omitted.

2. Evaluation of metal powder (Zr—Nb system) With respect to the cross section of the particles of the metal powder for powder metallurgy, the crystal structure was evaluated by TEM.

  As a result, in the metal powder for powder metallurgy corresponding to the example, the presence of two different regions in the particles, that is, the first region and the second region, was recognized. Further, EDX spectra were obtained for these regions, and “first Si intensity / first Cr intensity” and “second Si intensity / second Cr intensity” were calculated.

The calculation results are shown in Tables 3 and 4.
As is apparent from Tables 3 and 4, it was confirmed that the metal powder for powder metallurgy corresponding to the examples satisfied the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength”. It was.

  In the metal powder for powder metallurgy corresponding to the examples, the maximum diameter of the first region is 5 nm or more and 150 nm or less, and the equivalent circle diameter of the second region is 3% or more of the equivalent circle diameter of the particles. It was less than 100%. Furthermore, the average number of the second regions per particle was 1 or more and 20 or less.

  In addition, in the metal powder for powder metallurgy corresponding to the Examples, particles having the above-described characteristics contained 50% or more in number ratio.

  On the other hand, among the metal powders for powder metallurgy corresponding to the comparative example, there was a powder containing particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength”. The abundance ratio of the particles was 10% or less.

  In addition, the first region contained in the particles had a maximum diameter of 200 nm to 500 nm and was very large. Although the reason for this is not clear, since both the first element and the second element are not included, there is no nucleus for silicon oxide to accumulate, and therefore, some crystal dislocations. When this occurs, it becomes the nucleus that promotes the accumulation of silicon oxide, and the first region is thought to be enlarged.

  Further, the average number of the second regions contained in the particles was 20 or more, which was a polycrystal close to a microcrystal.

3. Evaluation of Sintered Body (Zr—Nb System) 3.1 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 3 and 4.

3.2 Evaluation of hardness Each sample No. shown in Tables 1 and 2 was used. 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 measured hardness was evaluated according to the following evaluation criteria.

<Vickers hardness evaluation criteria>
A: Vickers hardness is 300 or more F: Vickers hardness is less than 300 Tables 3 and 4 show the evaluation results.

3.3 Evaluation of tensile strength, 0.2% proof stress and elongation 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>
A: Tensile strength of the sintered body is 695 MPa or more B: Tensile strength of the sintered body is 685 MPa or more and less than 695 MPa C: Tensile strength of the sintered body is 675 MPa or more and less than 685 MPa D: Sintering The tensile strength of the body is 665 MPa or more and less than 675 MPa E: The tensile strength of the sintered body is 655 MPa or more and less than 665 MPa F: The tensile strength of the sintered body is less than 655 MPa

<Evaluation criteria for 0.2% proof stress>
A: 0.2% yield strength of the sintered body is 490 MPa or more B: 0.2% yield strength of the sintered body is 480 MPa or more and less than 490 MPa C: 0.2% yield strength of the sintered body is 470 MPa or more and less than 480 MPa D: The 0.2% yield strength of the sintered body is 460 MPa or more and less than 470 MPa E: The 0.2% yield strength of the sintered body is 450 MPa or more and less than 460 MPa F: The 0.2% yield strength of the sintered body is Less than 450 MPa

<Evaluation criteria for elongation>
A: Elongation of sintered body is 16% or more B: Elongation of sintered body is 14% or more and less than 16% C: Elongation of sintered body is 12% or more and less than 14% D: Sintered body E: The elongation of the sintered body is 8% or more and less than 10% F: The elongation of the sintered body is less than 8% The above evaluation results are shown in Tables 3 and 4 Show.

3.4 Evaluation of fatigue strength 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 430 MPa or more B: The fatigue strength of the sintered body is 410 MPa or more and less than 430 MPa C: The fatigue strength of the sintered body is 390 MPa or more and less than 410 MPa D: The fatigue of the sintered body The strength is 370 MPa or more and less than 390 MPa E: The fatigue strength of the sintered body is 350 MPa or more and less than 370 MPa F: The fatigue strength of the sintered body is less than 350 MPa The above evaluation results are shown in Tables 3 and 4.

  As is apparent from Tables 3 and 4, 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. 41 to 69)
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.

5. Evaluation of metal powder (Hf—Nb system) With respect to the cross section of the particles of the metal powder for powder metallurgy, the crystal structure was evaluated by TEM.

  As a result, the metal powders for powder metallurgy corresponding to the examples all include particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” in a number ratio of 50% or more. It was recognized that Further, the maximum diameter of the first region in the particles was 5 nm or more and 150 nm or less, and the equivalent circle diameter in the second region was 3% or more and less than 100% of the equivalent circle diameter of the particles. Furthermore, the average number of the second regions per particle was 1 or more and 20 or less.

  On the other hand, in the metal powder for powder metallurgy corresponding to the comparative example, the abundance ratio of particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” is 10% or less, Further, the maximum diameter of the first region in the particles was 200 nm or more and 500 nm or less.

6). Evaluation of Sintered Body (Hf—Nb System) 6.1 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 6 shows the calculation results.

6.2 Evaluation of hardness Each sample No. shown in Table 5 The Vickers hardness of the sintered body was measured according to the method of the Vickers hardness test specified in JIS Z 2244 (2009).

Then, the measured hardness was evaluated according to the evaluation criteria described in 3.2.
The evaluation results are shown in Table 6.

6.3 Evaluation of tensile strength, 0.2% proof stress and elongation Each sample No. shown in Table 5 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).

The measured physical property values were evaluated according to the evaluation criteria described in 3.3.
The evaluation results are shown in Table 6.

6.4 Evaluation of fatigue strength Each sample No. shown in Table 5 The fatigue strength of the sintered body was measured in the same manner as in 3.4.

Then, the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
The evaluation results are shown in Table 6.

  As can be seen from Table 6, 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.

  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.

7). Production of sintered body (Ti-Nb system) (Sample No. 70-79)
Except for changing the composition and the like of the metal powder for powder metallurgy as shown in Table 7, 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. 80)
Metal powder, Ti powder having an average particle diameter of 40 μm, and 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 7.

  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 7, 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 7 was omitted.

8). Evaluation of metal powder (Ti-Nb system) With respect to the cross section of the particles of the metal powder for powder metallurgy, the crystal structure was evaluated by TEM.

  As a result, the metal powders for powder metallurgy corresponding to the examples all include particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” in a number ratio of 50% or more. It was recognized that Further, the maximum diameter of the first region in the particles was 5 nm or more and 150 nm or less, and the equivalent circle diameter in the second region was 3% or more and less than 100% of the equivalent circle diameter of the particles. Furthermore, the average number of the second regions per particle was 1 or more and 20 or less.

  On the other hand, in the metal powder for powder metallurgy corresponding to the comparative example, the abundance ratio of particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” is 10% or less, Further, the maximum diameter of the first region in the particles was 200 nm or more and 500 nm or less.

9. Evaluation of Sintered Body (Ti-Nb System) 9.1 Evaluation of Relative Density Each sample No. shown in Table 7 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 8 shows the calculation results.

9.2 Evaluation of Hardness Each sample No. shown in Table 7 The Vickers hardness of the sintered body was measured according to the method of the Vickers hardness test specified in JIS Z 2244 (2009).

Then, the measured hardness was evaluated according to the evaluation criteria described in 3.2.
The evaluation results are shown in Table 8.

9.3 Evaluation of tensile strength, 0.2% proof stress and elongation Each sample No. shown in Table 7 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).

The measured physical property values were evaluated according to the evaluation criteria described in 3.3.
The evaluation results are shown in Table 8.

9.4 Evaluation of Fatigue Strength Each sample No. shown in Table 7 The fatigue strength of the sintered body was measured in the same manner as in 3.4.

Then, the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
The evaluation results are shown in Table 8.

  As can be seen from Table 8, 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. 81-90)
Except for changing the composition and the like of the metal powder for powder metallurgy as shown in Table 9, 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 9, 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 9 was omitted.

11. Evaluation of metal powder (Nb-Ta series) With respect to the cross section of the particles of the metal powder for powder metallurgy, the crystal structure was evaluated by TEM.

  As a result, the metal powders for powder metallurgy corresponding to the examples all include particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” in a number ratio of 50% or more. It was recognized that Further, the maximum diameter of the first region in the particles was 5 nm or more and 150 nm or less, and the equivalent circle diameter in the second region was 3% or more and less than 100% of the equivalent circle diameter of the particles. Furthermore, the average number of the second regions per particle was 1 or more and 20 or less.

  On the other hand, in the metal powder for powder metallurgy corresponding to the comparative example, the abundance ratio of particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” is 10% or less, Further, the maximum diameter of the first region in the particles was 200 nm or more and 500 nm or less.

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 10 shows the calculation results.

12.2 Evaluation of Hardness Each sample No. shown in Table 9 The Vickers hardness of the sintered body was measured according to the method of the Vickers hardness test specified in JIS Z 2244 (2009).

Then, the measured hardness was evaluated according to the evaluation criteria described in 3.2.
Table 10 shows the evaluation results.

12.3 Evaluation of tensile strength, 0.2% proof stress and elongation Each sample No. shown in Table 9 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).

The measured physical property values were evaluated according to the evaluation criteria described in 3.3.
Table 10 shows the evaluation results.

12.4 Evaluation of Fatigue Strength Each sample No. shown in Table 9 The fatigue strength of the sintered body was measured in the same manner as in 3.4.

Then, the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
Table 10 shows the evaluation results.

  As is clear from Table 10, 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. 91 to 100)
Except for changing the composition of the metal powder for powder metallurgy as shown in Table 11, 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 11, 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 11 was omitted.

14 Evaluation of metal powder (Y-Nb system) With respect to the cross section of the particles of the metal powder for powder metallurgy, the crystal structure was evaluated by TEM.

  As a result, the metal powders for powder metallurgy corresponding to the examples all include particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” in a number ratio of 50% or more. It was recognized that Further, the maximum diameter of the first region in the particles was 5 nm or more and 150 nm or less, and the equivalent circle diameter in the second region was 3% or more and less than 100% of the equivalent circle diameter of the particles. Furthermore, the average number of the second regions per particle was 1 or more and 20 or less.

  On the other hand, in the metal powder for powder metallurgy corresponding to the comparative example, the abundance ratio of particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” is 10% or less, Further, the maximum diameter of the first region in the particles was 200 nm or more and 500 nm or less.

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 12 shows the calculation results.

15.2 Evaluation of Hardness Each sample No. shown in Table 11 The Vickers hardness of the sintered body was measured according to the method of the Vickers hardness test specified in JIS Z 2244 (2009).

Then, the measured hardness was evaluated according to the evaluation criteria described in 3.2.
The evaluation results are shown in Table 12.

15.3 Evaluation of tensile strength, 0.2% proof stress and elongation Each sample No. shown in Table 11 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).

The measured physical property values were evaluated according to the evaluation criteria described in 3.3.
The evaluation results are shown in Table 12.

15.4 Evaluation of Fatigue Strength Each sample No. shown in Table 11 The fatigue strength of the sintered body was measured in the same manner as in 3.4.

Then, the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
The evaluation results are shown in Table 12.

  As apparent from Table 12, 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.

16. Production of sintered body (V-Nb system) (Sample Nos. 101 to 110)
Except for changing the composition and the like of the metal powder for powder metallurgy as shown in Table 13, 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 13, 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 13 was omitted.

17. Evaluation of metal powder (V-Nb system) With respect to the cross section of the particles of the metal powder for powder metallurgy, the crystal structure was evaluated by TEM.

  As a result, the metal powders for powder metallurgy corresponding to the examples all include particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” in a number ratio of 50% or more. It was recognized that Further, the maximum diameter of the first region in the particles was 5 nm or more and 150 nm or less, and the equivalent circle diameter in the second region was 3% or more and less than 100% of the equivalent circle diameter of the particles. Furthermore, the average number of the second regions per particle was 1 or more and 20 or less.

  On the other hand, in the metal powder for powder metallurgy corresponding to the comparative example, the abundance ratio of particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” is 10% or less, Further, the maximum diameter of the first region in the particles was 200 nm or more and 500 nm or less.

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 14 shows the calculation results.

18.2 Evaluation of Hardness Each sample No. shown in Table 13 The Vickers hardness of the sintered body was measured according to the method of the Vickers hardness test specified in JIS Z 2244 (2009).

Then, the measured hardness was evaluated according to the evaluation criteria described in 3.2.
The evaluation results are shown in Table 14.

18.3 Evaluation of tensile strength, 0.2% proof stress and elongation Each sample No. shown in Table 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).

The measured physical property values were evaluated according to the evaluation criteria described in 3.3.
The evaluation results are shown in Table 14.

18.4 Evaluation of fatigue strength Each sample No. shown in Table 13 The fatigue strength of the sintered body was measured in the same manner as in 3.4.

Then, the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
The evaluation results are shown in Table 14.

  As is clear from Table 14, 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.

19. Production of sintered body (Ti-Zr system) (Sample Nos. 111 to 120)
Except for changing the composition of the metal powder for powder metallurgy as shown in Table 15, 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 15, 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 15 was omitted.

20. Evaluation of metal powder (Ti-Zr system) With respect to the cross section of the particles of the metal powder for powder metallurgy, the crystal structure was evaluated by TEM.

  As a result, the metal powders for powder metallurgy corresponding to the examples all include particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” in a number ratio of 50% or more. It was recognized that Further, the maximum diameter of the first region in the particles was 5 nm or more and 150 nm or less, and the equivalent circle diameter in the second region was 3% or more and less than 100% of the equivalent circle diameter of the particles. Furthermore, the average number of the second regions per particle was 1 or more and 20 or less.

  On the other hand, in the metal powder for powder metallurgy corresponding to the comparative example, the abundance ratio of particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” is 10% or less, Further, the maximum diameter of the first region in the particles was 200 nm or more and 500 nm or less.

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.
Table 16 shows the calculation results.

21.2 Evaluation of Hardness Each sample No. shown in Table 15 The Vickers hardness of the sintered body was measured according to the method of the Vickers hardness test specified in JIS Z 2244 (2009).

Then, the measured hardness was evaluated according to the evaluation criteria described in 3.2.
The evaluation results are shown in Table 16.

21.3 Evaluation of Tensile Strength, 0.2% Yield Strength and Elongation Each sample No. shown in Table 15 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).

The measured physical property values were evaluated according to the evaluation criteria described in 3.3.
The evaluation results are shown in Table 16.

21.4 Fatigue Strength Evaluation Each sample No. shown in Table 15 The fatigue strength of the sintered body was measured in the same manner as in 3.4.

Then, the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
The evaluation results are shown in Table 16.

  As is clear from Table 16, 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.

22. Production of sintered body (Zr-Ta series) (Sample Nos. 121 to 130)
Except for changing the composition and the like of the metal powder for powder metallurgy as shown in Table 17, 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 17, 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 17 was omitted.

23. Evaluation of metal powder (Zr-Ta system) With respect to the cross section of the particles of the metal powder for powder metallurgy, the crystal structure was evaluated by TEM.

  As a result, the metal powders for powder metallurgy corresponding to the examples all include particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” in a number ratio of 50% or more. It was recognized that Further, the maximum diameter of the first region in the particles was 5 nm or more and 150 nm or less, and the equivalent circle diameter in the second region was 3% or more and less than 100% of the equivalent circle diameter of the particles. Furthermore, the average number of the second regions per particle was 1 or more and 20 or less.

  On the other hand, in the metal powder for powder metallurgy corresponding to the comparative example, the abundance ratio of particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” is 10% or less, Further, the maximum diameter of the first region in the particles was 200 nm or more and 500 nm or less.

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.
Table 18 shows the calculation results.

24.2 Evaluation of Hardness Each sample No. shown in Table 17 The Vickers hardness of the sintered body was measured according to the method of the Vickers hardness test specified in JIS Z 2244 (2009).

Then, the measured hardness was evaluated according to the evaluation criteria described in 3.2.
The evaluation results are shown in Table 18.

24.3 Evaluation of tensile strength, 0.2% proof stress and elongation Each sample No. shown in Table 17 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).

The measured physical property values were evaluated according to the evaluation criteria described in 3.3.
The evaluation results are shown in Table 18.

24.4 Evaluation of Fatigue Strength Each sample No. shown in Table 17 The fatigue strength of the sintered body was measured in the same manner as in 3.4.

Then, the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
The evaluation results are shown in Table 18.

  As is clear from Table 18, 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. 131 to 140)
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.

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.

26. Evaluation of metal powder (Zr-V system) With respect to the cross section of the particles of the metal powder for powder metallurgy, the crystal structure was evaluated by TEM.

  As a result, the metal powders for powder metallurgy corresponding to the examples all include particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” in a number ratio of 50% or more. It was recognized that Further, the maximum diameter of the first region in the particles was 5 nm or more and 150 nm or less, and the equivalent circle diameter in the second region was 3% or more and less than 100% of the equivalent circle diameter of the particles. Furthermore, the average number of the second regions per particle was 1 or more and 20 or less.

  On the other hand, in the metal powder for powder metallurgy corresponding to the comparative example, the abundance ratio of particles satisfying the relationship of “second Si strength / second Cr strength <first Si strength / first Cr strength” is 10% or less, Further, the maximum diameter of the first region in the particles was 200 nm or more and 500 nm or less.

27. Evaluation of sintered body (Zr-V system) 27.1 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 20 shows the calculation results.

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

Then, the measured hardness was evaluated according to the evaluation criteria described in 3.2.
Table 20 shows the evaluation results.

27.3 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).

The measured physical property values were evaluated according to the evaluation criteria described in 3.3.
Table 20 shows the evaluation results.

27.4 Evaluation of Fatigue Strength Each sample No. shown in Table 19 The fatigue strength of the sintered body was measured in the same manner as in 3.4.

Then, the measured fatigue strength was evaluated according to the evaluation criteria described in 3.4.
Table 20 shows the evaluation results.

  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.

28. Evaluation of Specularity of Sintered Body 28.1 Evaluation of Porosity near and Inside Surface First, sample Nos. Shown in Table 21 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.
Table 21 shows the above calculation results.

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: Specularity of the surface is low (mirror glossiness 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 21.

  As is clear from Table 21, it was confirmed that the sintered body corresponding to the example had 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 3 grain boundary 11 first region 12 second region

Claims (8)

Co is the main component,
Cr is contained in a proportion of 10% 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,
One element selected from the group consisting of Ti, V, Y, Zr, Nb, Hf and Ta is the first element, and one element selected from the group, the group in the periodic table of elements is When the element larger than the first element or the group in the periodic table of the elements is the same as the first element and the element in the periodic table of the elements 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,
The second element has a chemical composition containing 0.01% by mass or more and 0.5% by mass or less,
As a tissue different from each other, including a first region and a second region having a volume larger than that of the first region,
Among the EDX spectra acquired for the first region, the height of the peak of Cr included in the range of 5.3 keV to 5.5 keV is defined as the first Cr intensity, and the range is 1.6 keV to 1.8 keV. The height of the Si peak contained in the first Si intensity,
Among the EDX spectra acquired for the second region, the height of the Cr peak included in the range of 5.3 keV to 5.5 keV is the second Cr intensity, and is in the range of 1.6 keV to 1.8 keV. When the height of the Si peak contained in the second Si intensity,
2. Metal powder for powder metallurgy, characterized in that it contains particles satisfying the relationship of second Si strength / second Cr strength <first Si strength / first Cr strength. The particle includes a plurality of the second regions,
The metal powder for powder metallurgy according to claim 1, wherein the first region is located at a boundary between the second regions. The second region is a crystal;
3. The metal powder for powder metallurgy according to claim 1, wherein the particles include one or more and 20 or less of the second regions on average. The average particle size of the particles is 0.5 μm or more and 30 μm or less,
The metal powder for powder metallurgy according to any one of claims 1 to 3, wherein a maximum diameter of the first region is 5 nm or more and 150 nm or less. Cr is contained in a proportion of 16% by mass to 35% by mass,
Si is contained in a ratio of 0.3% by mass to 2% by mass,
Mo is contained in a ratio of 3% by mass to 12% by mass,
The first element is included in a proportion of 0.01% by mass to 0.5% by mass,
The metal powder for powder metallurgy according to any one of claims 1 to 4, wherein the second element is contained in a proportion of 0.01 mass% or more and 0.5 mass% or less.   A compound comprising: the metal powder for powder metallurgy according to any one of claims 1 to 5; and a binder that binds 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 5.   A sintered body produced by sintering the metal powder for powder metallurgy according to any one of claims 1 to 5.

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