JP2005015902A - Sintered compact with airtightness, and manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sintered compact capable of meeting the recent demand for a product requiring airtightness. <P>SOLUTION: In the airtight sintered compact 1 prepared by compacting and sintering a raw-material powder composed mainly of metal, the sintered compact contains 0.006 to 0.1 mass% carbon and 0.2 to 1.5 mass% phosphorus and also the sintered compact has ≤12% open porosity and ≤40μm average grain size and contains nitrogen, and further, a surface treatment layer 3 having airtightness is provided. Since, the percentage of the oxidation of phosphorus at sintering is decreased by a reducing effect by carbon, phosphorus lowers the melting point of the raw-material powder and promotes the formation of liquid-phase components and also the diffusion of iron and phosphorus is smoothly performed and phosphorus combines with iron and is allowed to enter into solid solution, by which the sintered compact minimal in pores and excellent in airtightness can be obtained. Further, the surface treatment layer 3 can be provided without performing sealing treatment. Owing to this surface treatment layer 3, airtightness can be secured. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hermetic sintered body and a method for producing the same.
[0002]
[Prior art]
In powder metallurgy, it is known that a raw material powder containing metal as a main raw material is compressed to form a green compact, and then this green compact is heated and sintered to form a sintered body of a predetermined shape. It has been.
[0003]
Thus, after the raw material powder is compression-molded, the sintered body to be sintered has a large number of pores. For this reason, when using sintered bodies for structural parts such as hydraulic pumps, variable valve timing mechanism housings, air conditioners, and compressors that generally require airtightness and pressure resistance, sealing treatment such as Cu or resin impregnation is conventionally used. Had gone. Further, when the Ni, Zn and Cr plating, TiN and CrN coating, which are surface treatments for improving the corrosion resistance and the surface hardness, are applied, the sealing treatment is necessary as a pretreatment for the surface treatment.
[0004]
In consideration of such problems, Patent Document 1 contains reduced iron powder and iron phosphide powder so that the amount of phosphorus is 0.5 to 2.0% by weight, and after this powder is compression molded. A sintered member having airtightness obtained by sintering has been proposed, and when this sintered member is used for an application requiring airtightness and pressure resistance, the sintered density is 7.0 g / cm.³It is described that the above is preferable.
[0005]
[Patent Document 1]
JP-A-55-122803
[0006]
[Problems to be solved by the invention]
However, in recent years, there has been a demand for higher performance and downsizing for components of pressure-resistant devices, and as a result, airtightness and high adhesion with the surface treatment layer are required. In the bonded body, it is difficult to obtain airtightness and adhesion to the surface treatment layer corresponding to this requirement.
[0007]
In addition, based on the prior art, the inventor conducted various experiments in order to obtain a sintered body having further airtightness and adhesion with the surface treatment layer and a method for producing the same. It has been found that the airtightness and the adhesion with the surface treatment layer cannot be effectively improved only by increasing the density.
[0008]
Then, an object of this invention is to provide the sintered compact which has airtightness, and its manufacturing method.
[0009]
[Means for Solving the Problems]
The airtight sintered body according to claim 1 is an airtight sintered body obtained by molding and sintering a raw material powder containing a metal as a main component in order to achieve the above object. Contains 0.006 to 0.1% by mass of carbon, 0.2 to 1.5% by mass of phosphorus, has an open porosity of 12% or less, an average crystal grain size of 40 μm or less, contains nitrogen, and has airtightness. A surface treatment layer is provided.
[0010]
Due to the reduction effect of carbon, the rate at which phosphorus oxidizes during sintering is small, so that phosphorus lowers the melting point of the raw material powder and promotes the formation of liquid phase components, and the diffusion of iron and phosphorus is performed smoothly. Is bonded to iron to form a solid solution, and a sintered body with few pores and excellent airtightness can be obtained.
[0011]
And if the carbon mix | blended as a raw material is less than 0.02 mass%, it cannot fully reduce phosphorus, and on the other hand, if carbon exceeds 0.2 mass%, austenite will be stabilized during sintering. In order to reduce the sintering speed, the amount of carbon blended as a raw material was set to 0.02 to 0.2% by mass. A part of the carbon becomes an oxide during the sintering and is lost from the sintered body. Therefore, the amount of carbon contained in the sintered body is set to 0.006 to 0.1% by mass.
[0012]
Further, if the phosphorus is less than 0.2% by mass, the effect of airtightness cannot be obtained. On the other hand, if the phosphorus exceeds 1.5% by mass, the strength and toughness of the sintered body is reduced, and therefore included. Phosphorus was 0.2 to 1.5 mass%.
[0013]
Therefore, even if the green compact is molded at a lower pressure than before, a highly airtight sintered body can be obtained, and this sintered body has a small density and a light weight. For this reason, since the load of the molding die for molding the green compact is reduced, the durability of the molding die is also improved.
[0014]
The invention of claim 2 is the sintered body of claim 1, wherein the nitrogen amount of the sintered body is 60 to 300 ppm.
[0015]
In order to suppress the growth of iron powder crystals during sintering, the amount of nitrogen is preferably 60 ppm or more. On the other hand, if the amount of nitrogen exceeds 300 ppm, the progress of sintering is hindered by nitriding, and the strength rapidly decreases. Therefore, the above nitrogen amount is preferable.
[0016]
The invention of claim 3 is the sintered body of claim 1 or 2, wherein the sintered body has an oxygen content of 100 to 1000 ppm.
[0017]
In order to suppress the growth of iron powder crystals during sintering, the oxygen amount is preferably 100 ppm or more. On the other hand, if the oxygen amount exceeds 1000 ppm, the progress of the sintering is hindered by oxidation, and the strength rapidly decreases. Therefore, the oxygen amount is preferably set as described above.
[0018]
The invention according to claim 4 is the sintered body according to claims 1 to 3, wherein the surface treatment layer is formed by steam treatment.
[0019]
Airtightness can be ensured by steam treatment.
[0020]
According to a fifth aspect of the present invention, in the sintered body according to the first to third aspects, the surface treatment layer is formed by plating.
[0021]
Airtightness can be ensured by plating. Examples of the plating process include Ni, Zn, and Cr plating.
[0022]
The invention of claim 6 is the sintered body of claims 1 to 3, wherein the surface treatment layer is formed by a coating treatment.
[0023]
Airtightness can be ensured by the coating process. Examples of the coating treatment include TiN and CrN coatings.
[0024]
In order to achieve the above object, the method for producing a sintered body according to claim 7 pressurizes a raw material powder containing metal as a main component to form a green compact, and then sinters the green compact in an atmospheric gas. In the method for producing a sintered compact having airtightness, the reduced iron powder contains 40 mass% or more, phosphorus is 0.2 to 1.5 mass%, carbon is 0.02 to 0.2 mass%, and the atmosphere This is a method of forming a surface treatment layer having a gas tightness after sintering, wherein the gas contains 70% by volume or more of nitrogen.
[0025]
By using this method, strength and toughness are improved, and a sintered body having excellent adhesion to the surface treatment layer is obtained. This sintered body has adhesion to the surface treatment layer, and its surface. The treatment layer has airtightness.
[0026]
The invention of claim 8 is the method for producing the sintered body of claim 7, wherein the surface treatment layer is formed by steam treatment.
[0027]
According to this method, it is possible to perform a steam treatment with excellent adhesion without performing a sealing treatment as a pretreatment for the surface treatment.
[0028]
The invention of claim 9 is the method for producing the sintered body of claim 7, wherein the surface treatment layer is formed by plating.
[0029]
According to this method, plating having excellent adhesion can be provided without performing a sealing treatment as a pretreatment for the surface treatment.
[0030]
The invention of claim 10 is the method for producing a sintered body according to claim 7, wherein the surface treatment layer is formed by a coating treatment.
[0031]
According to this method, a coating having excellent adhesion can be provided without performing a sealing treatment as a pretreatment for the surface treatment.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 3 show an embodiment of the present invention.
[0033]
First, in the manufacturing method of the present invention, as shown in the flow chart of FIG. 1, raw material powder mainly composed of iron which is a metal is mixed (S1), and this raw material powder is compressed to form a green compact (S2). The green compact is sintered (S3) in a sintering furnace, and then surface treatment (S4) is performed to obtain the sintered body 1. In the present invention, it is preferable to use a predetermined amount or more of reduced iron powder as the raw material powder. The reduced iron powder can be reduced by various methods.
[0034]
The inventor conducted various experiments in order to obtain a sintered body having excellent airtightness and a manufacturing method thereof, and as a result, the surface-treated layer was more airtight due to the relationship between the open porosity and the adhesion of the surface-treated layer. The present invention has been found to be obtained and can be obtained with a predetermined adhesion to the surface treatment layer. Further, it has been found that a sintered body having a small open porosity can be produced without increasing the sintering density, and has led to the present invention. It is a thing. In particular, it is possible to obtain airtightness even when the open porosity is relatively high.
[0035]
Below, an example of the experimental example which proves it is demonstrated.
[0036]
Experimental example
A plurality of iron-based sintered bodies 1 having different ratios of reduced iron powder in the raw material powder (Fe-0.6% P) are manufactured, the reduced iron powder is mixed with the raw material powder, and the rest is made of atomized iron powder. , 0.8 mass% phosphorus (P). In this case, phosphorus can be supplied by iron halide powder. Further, the raw material powder contains 0.1% by mass of graphite powder as carbon. In addition to the above raw material powder, Cu or the like may be mixed.
[0037]
And nitrogen atmosphere gas (N₂Base gas: N₂-3 vol% H₂) Or in a decomposed ammonia atmosphere gas (S3), and the open porosity of each sintered body 1 was measured. After the measurement, the sintered body 1 was subjected to a steam treatment as a surface treatment (S4).
[0038]
And the measurement of the average crystal grain diameter of the sintered compact 1, the amount of nitrogen, and the amount of oxygen, and the photography of the enlarged structure photograph of the sintered compact were performed, and also about the adhesiveness, the test was done, and the following things were found.
[0039]
It is confirmed from the enlarged structure photograph of the sintered body that the growth of the crystal of the iron powder is suppressed. This is because nitrogen is used as a nucleus by using nitrogen atmosphere gas as the atmosphere gas during sintering (S2). This is because the expansion of the iron powder crystals was suppressed. The amount of nitrogen is preferably 60 ppm or more because nitrogen serves as a nucleus during sintering to suppress the growth of iron crystal grains. On the other hand, if the amount of nitrogen exceeds 300 ppm, the progress of sintering is hindered by nitriding. And the strength rapidly decreases. The nitrogen amount is more preferably 70 to 200 ppm from the viewpoints of densification and strength.
[0040]
Oxygen is related to the suppression of iron crystal grain growth, and the oxygen content is preferably 100 ppm or more in order to suppress the growth of iron crystal grains. Therefore, the oxygen content is preferably 1000 ppm or less, and more preferably 200 to 700 ppm in terms of densification and strength.
[0041]
Since the average crystal grain size is largely related to the adhesion with the surface treatment layer, the average crystal grain size is preferably 40 μm or less. Furthermore, considering the adhesion with the surface treatment layer, the average crystal grain size is more preferably 25 μm or less.
[0042]
Moreover, the improvement of the toughness of a sintered compact was recognized by mixing 0.02-0.2 mass% of graphite powder with raw material powder. When the component analysis of the sintered body was performed, in the examples according to the present invention, the amount of carbon contained in the sintered body was 0.006 to 0.1% by mass. In an example, it becomes 0.001-0.004 mass%, and the thing of an Example has more carbon compared with a comparative example.
[0043]
The effect of the sintered body of the present invention manufactured as described above will be described with reference to the graph explanatory diagram of FIG. 3. When the green compact is formed from the raw material powder by the molding die on the horizontal axis, Shows the open porosity obtained by sintering the same-pressure powder on the vertical axis, the conventional product is shown by a broken line, the product of the present invention is shown by a solid line, and according to the product of the present invention at a low molding pressure, An airtight sintered body having a smaller open porosity than the product can be obtained.
[0044]
As described above, in the present invention, the generation of phosphorus oxides is suppressed, and phosphorus lowers the melting point of the raw material powder to promote the generation of liquid phase components, thereby obtaining a sintered body with few pores and excellent airtightness. It is done.
[0045]
In addition, the open porosity in this invention is calculated by the sintered metal material-density, oil content, and open porosity test method of JIS Z 2501 (2000). The outline of this test method will be described. As an apparatus, an analytical balance having a sufficient measurement capacity and accuracy within 0.01%, a Soxhlet extractor (exemplified in FIG. 1 of JIS Z 2501), a test piece A jig for measuring the mass in the air and liquid (liquid is generally water) (illustrated in Attached Figure 2 to Attached Figure 4 of JIS Z 2501), and a test piece and a jig for achieving it are sufficient. A container containing distilled water containing 0.05 to 0.10 vol% of surfactant, or preferably degassed water, a vacuum oil retaining device, and an impregnating oil of known density Use a thermometer with an accuracy of ± 0.5 ° C. The test specimen is usually tested as a whole specimen. If this is not possible, the specimen may be cut or broken into small pieces for ease of operation. It can also be applied to testing only representative parts of parts. When the mass of the test piece is less than 5 g, an average value is obtained by collecting and measuring several test pieces. The surface of the specimen shall be free from dirt, oil and other foreign matter. Excess surface oil must not adhere to the surface of the specimen. When removing excess oil with an oil absorbent, care must be taken not to remove the oil in the pores. The test method consists of (7-1) weighing the weight of the test piece as received as the first mass measurement of the test piece, m₁(Initial mass of test piece: unit g) is obtained. When it is known that the test piece does not contain oil, it was described in “(7-2) Oil removal of test piece with solvent” and “(7-3) Mass measurement of dry test piece” described later. The method can be omitted.
[0046]
(7-2) In order to remove the oil from the thin-walled test piece at a normal density by immersing in the solvent for about 3 hours as the oil removal of the test piece with the solvent, approximately 10 solvent changes are required. Thick and high density specimens may be immersed for up to 24 hours. Extraction is continued until the mass after evaporation of the pore solvent is constant. Dry until the specimen is of constant mass (the mass reduction in the last extraction should not exceed 0.01%). The drying temperature is set 20 ° C. higher than the boiling point of the solvent, and then the mass is measured after cooling in a desiccator. Select a solvent that completely dissolves the oil. It needs to be tested separately. In the test report, specify the name of the solvent used. In practice, other methods of removing the oil may be performed (eg, heating in a protective atmosphere). In case of debate, the Soxhlet extraction method should be consulted. (7-3) For measuring the mass of a dry test piece, the test piece is deoiled and weighed after drying, m₂(Mass of test piece after degreasing and drying: unit g) is obtained.
[0047]
For complete impregnation (for measuring open porosity), immerse the specimen in oil in a suitable container that can withstand vacuum conditions. Reduce oil surface pressure up to 70 kPa. Continue vacuuming until the oil surface is free of bubbles. Return the vacuum to ambient pressure. The specimen may be kept immersed in the oil for 10 minutes. The oil must never mix with water or wet the porous metal. Remove specimen from oil, drain and remove excess surface oil. In this case, excess surface oil should not adhere to the surface of the test piece. When removing excess oil with an oil absorbent, care must be taken not to remove even the oil in the pores. To measure the mass of a fully impregnated test piece, weigh the test piece after complete impregnation, m₃(Mass of test piece after complete impregnation: unit g) is obtained. To measure the volume of the test piece, weigh in the air to determine the volume V of the test piece, m_a(Air mass of impregnated test piece and support jig (for example, suspension wire): unit g) is obtained, and then the known density ρ_WSoak in water or liquid_W(Mass in water of impregnated test piece and supporting jig (for example, suspension wire): unit g) is obtained. Volume Vcm³Is calculated by the following equation.
[0048]
V = (m_a-M_W) / Ρ_W
For porous metals, it is important that the liquid used is not absorbed by the pores. For this, the pores are impregnated with oil. In general, it is desirable to make the mass and volume of the jig as small as possible. In measuring the volume, the test piece is hung with a thin wire, and the total mass of the test piece and the wire is weighed in the air and in water. Although tolerance is caused by the accumulation of the wire in the water, there is no problem because it is smaller than the volume of the test piece. This permissible error can be grasped by weighing the underwater mass and then weighing the water accurately. Another method is to measure the length of the underwater portion if the volume of the unit length of the wire is known. It is confirmed that no bubbles are generated from the surface of the test piece and the holding jig. It is possible to add 0.05 to 0.10 vol% of surfactant in water. The test piece and water are at the same temperature. The normal test temperature is 18-22 ° C, and the density of pure water in this range_WIs 0.0998 g / cm³It is.
[0049]
Based on the numerical value obtained by the above measurement, the dry density is obtained by the following equation.
[0050]
Dry density (g / cm³) = M₂/ V
Moreover, an open porosity is calculated | required by the following formula.
[0051]
Open porosity (vol%) = (m₃-M₂) / (Ρ₂V) × 100
Ρ₂Is the density of the oil used for impregnation.
[0052]
In the present invention, it was found that the open porosity was set to 12% or less, and it was possible to ensure airtightness by combining with the surface treatment layer. Then, a surface treatment layer by various plating such as Ni plating, Zn plating or Cr plating, a surface treatment layer by various alloy coating such as TiN coating or CrN coating, a surface treatment layer which is a surface coating by steam treatment, or the like may be used. The adhesion between the sintered body 1 and the surface treatment layer 3 will be described with reference to the drawings. FIG. 2 is a cross-sectional explanatory view of the main part of the sintered body 1. In the crystal grain 4 formed by providing the surface treatment layer 3 by treatment or the like and sintering the raw material powder, the surface treatment layer 3 enters the boundary, that is, the crystal grain boundary 5, and the surface treatment layer 3 entering the crystal grain boundary 5 is The surface is shaped like a wedge, and the surface treatment layer 3 adheres to the surface of the sintered body 1. That is, if the surface treatment layer 3 is formed by steam treatment, a film of iron trioxide is formed in a close contact state. Further, even in the pores 6 on the surface of the sintered body 1, the surface treatment layer 3 enters the crystal grain boundaries 5 of the pores 6, and the surface treatment layer 3 that has entered the crystal grain boundaries 5 has a shape that is driven with a wedge, The surface treatment layer 3 adheres to the sintered body 1. Since the number of crystal grain boundaries 5 per unit area is larger when the average crystal grain size is smaller, the adhesion is excellent.
[0053]
In addition, as surface treatment, coating such as Zn, Cr, Ni, Ag plating, TiN, CrN, TiC, TiCN, DLC (diamond-like carbon) may be performed. These surface treatment layer 3 and sintered body 1 A predetermined adhesion can be obtained and airtightness can be secured by the surface treatment layer 3.
[0054]
In addition, in the raw material powder, reduced iron powder has the advantages of reduced open porosity and low cost, while compared to other iron powders, the strength and compressibility are low, and the atomized iron powder has high strength, Although it has the advantages of high compressibility and low cost, the effect of reducing open porosity is low, and carbonyl iron powder has the advantages of high strength and low open porosity, but has the disadvantage of low compressibility and high cost. From the viewpoint of reduction of open porosity and low cost, it is preferable to use 40% by mass or more of reduced iron powder.
[0055]
Thus, in the present embodiment, corresponding to claim 1, in the sintered body 1 having airtightness formed by molding and sintering the raw material powder mainly composed of metal, the raw material powder is reduced iron powder. 40 mass% or more, 0.006 to 0.1 mass% of carbon and 0.2 to 1.5 mass% of phosphorus, open porosity of 12% or less, average crystal grain size of 40 μm or less, nitrogen Since the surface treatment layer 3 having airtightness is provided, because of the reduction effect of carbon, the ratio of phosphorous oxidation during sintering is small. While promoting the formation, the diffusion of iron and phosphorus is performed smoothly, phosphorus binds to iron and forms a solid solution, and a sintered body with few pores and excellent airtightness can be obtained without sealing treatment. The surface treatment layer 3 can be provided, and the surface treatment layer 3 It is possible to ensure the sex. And if the carbon mix | blended as a raw material is less than 0.02 mass%, it cannot fully reduce phosphorus, and on the other hand, if carbon exceeds 0.2 mass%, austenite will be stabilized during sintering. In order to reduce the sintering speed, the amount of carbon blended as a raw material was set to 0.02 to 0.2% by mass. A part of the carbon becomes an oxide during the sintering and is lost from the sintered body. Therefore, the amount of carbon contained in the sintered body is set to 0.006 to 0.1% by mass. Further, if the phosphorus is less than 0.2% by mass, the effect of airtightness cannot be obtained. On the other hand, if the phosphorus exceeds 1.5% by mass, the strength and toughness of the sintered body is reduced, and therefore included. Phosphorus was 0.2 to 1.5 mass%.
[0056]
Therefore, even if the green compact is molded at a lower pressure than before, a highly airtight sintered body can be obtained, and this sintered body has a small density and a light weight. For this reason, since the load of the molding die for molding the green compact is reduced, the durability of the molding die is also improved.
[0057]
In this way, in this embodiment, since the nitrogen content of the sintered body 1 is 60 to 300 ppm, corresponding to claim 2, the growth of iron powder crystals during sintering is suppressed, and the surface A sintered body 1 having excellent adhesion to the treatment layer 3 can be obtained.
[0058]
In this way, in this embodiment, since the amount of oxygen in the sintered body 1 is 100 to 1000 ppm corresponding to claim 3, the growth of iron crystal grains during sintering is suppressed, and the open porosity is reduced. A low sintered body 1 can be obtained.
[0059]
In this way, in this embodiment, since the surface treatment layer 3 is formed by the steam process corresponding to the fourth aspect, the airtightness can be ensured by the steam process.
[0060]
In this way, in this embodiment, since the surface treatment layer 3 is formed by the plating process corresponding to the fifth aspect, airtightness can be ensured by the plating process.
[0061]
In this way, in this embodiment, since the surface treatment layer 3 is formed by the coating process corresponding to the sixth aspect, airtightness can be ensured by the coating process.
[0062]
Thus, in the present embodiment, corresponding to claim 7, after forming the green compact by pressurizing the raw material powder containing metal as a main component, the hermeticity of sintering the green compact in the atmosphere gas. In the manufacturing method of the sintered body 1 having 40% by mass or more of reduced iron powder, 0.2 to 1.5% by mass of phosphorus, 0.02 to 0.2% by mass of carbon, and the atmosphere gas is 90%. Since it is a method of forming the surface treatment layer 3 containing nitrogen in a volume% or more and having airtightness after sintering, the sintered body 1 is improved in strength and toughness and excellent in adhesion to the surface treatment layer 3. The sintered body 1 has adhesiveness with the surface treatment layer 3 and is airtight with the surface treatment layer 3.
[0063]
In this way, in this embodiment, since the surface treatment layer 3 is formed by the steam treatment in correspondence with the eighth aspect, the steam having excellent adhesion without performing the sealing treatment as the pretreatment of the surface treatment. Processing can be performed.
[0064]
In this way, in this embodiment, since the surface treatment layer 3 is formed by plating in accordance with claim 9, plating with excellent adhesion without performing sealing treatment as a pretreatment of the surface treatment. Can be provided.
[0065]
In this way, in this embodiment, since the surface treatment layer 3 is formed by a coating process corresponding to claim 10, the coating having excellent adhesion without performing a sealing process as a pretreatment of the surface treatment. Can be provided.
[0066]
In addition, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible. For example, the surface treatment layer can be applied to various types, and the plating material and the coating material exemplified as the surface treatment layer can be appropriately selected.
[0067]
【The invention's effect】
The sintered body having airtightness according to claim 1 is a sintered body having airtightness formed by molding and sintering a raw material powder mainly composed of a metal. 0.1% by mass, 0.2 to 1.5% by mass of phosphorus, an open porosity of 12% or less, an average crystal grain size of 40 μm or less, nitrogen, and a surface treatment layer having airtightness were provided. Thus, a surface treatment layer can be provided without sealing, and airtightness can be secured by this surface treatment layer.
[0068]
In addition to the effect of claim 1, the invention of claim 2 is such that the sintered body has a nitrogen content of 60 to 300 ppm, and can suppress the growth of iron powder crystals during sintering. A sintered body having excellent adhesion to the surface treatment layer can be obtained.
[0069]
Moreover, in addition to the effect of Claim 1 or 2, the invention of Claim 3 has an oxygen content of 100 to 1000 ppm in the sintered body, so that a denser sintered body can be obtained.
[0070]
In addition to the effects of claims 1 to 3, the invention of claim 4 is such that the surface treatment layer is formed by steam treatment, and airtightness can be secured by the steam treatment.
[0071]
Moreover, in addition to the effect of Claims 1-3, invention of Claim 5 is the said surface treatment layer formed by the plating process, and can ensure airtightness by the plating process.
[0072]
In addition to the effects of the first to third aspects, the sixth aspect of the invention is such that the surface treatment layer is formed by a coating treatment, and airtightness can be secured by the coating treatment.
[0073]
The method for producing a sintered body according to claim 7 is an airtight sintering method in which a raw powder mainly composed of metal is pressed to form a green compact, and then the green compact is sintered in an atmospheric gas. In the method for producing a body, nitrogen containing reduced iron powder in an amount of 40% by mass or more, phosphorus in an amount of 0.2 to 1.5% by mass, carbon in an amount of 0.02 to 0.2% by mass and the atmospheric gas in an amount of 70% by volume or more. Is a method of forming a surface treatment layer having airtightness after sintering, and a sintered body with improved strength and toughness and excellent adhesion to the surface treatment layer is obtained. The surface-treated layer has adhesiveness, and the surface-treated layer has airtightness.
[0074]
Moreover, in addition to the effect of Claim 7, since the surface treatment layer is formed by steam treatment, the invention of claim 8 is a steam having excellent adhesion without performing a sealing treatment as a pretreatment of the surface treatment. Processing can be performed.
[0075]
Further, in addition to the effect of claim 7, the invention of claim 9 forms the surface treatment layer by plating, so that plating with excellent adhesion without performing sealing treatment as a pretreatment of the surface treatment. Can be provided.
[0076]
Moreover, in addition to the effect of Claim 7, the invention of Claim 10 forms the surface treatment layer by a coating treatment. Therefore, the coating has excellent adhesion without performing a sealing treatment as a pretreatment of the surface treatment. Can be provided.
[Brief description of the drawings]
FIG. 1 is a flowchart for explaining a manufacturing method according to an embodiment of the present invention.
FIG. 2 is a cross-sectional explanatory view of the main part of the sintered body, partially enlarged.
FIG. 3 is a graph explanatory view showing the relationship between the compacting pressure of the green compact and the open porosity of the sintered body.
[Explanation of symbols]
1 Sintered body
3 Surface treatment layer

Claims (10)

In a sintered body having airtightness formed by molding and sintering a raw material powder containing a metal as a main component, carbon is contained in an amount of 0.006 to 0.1% by mass and phosphorus is contained in an amount of 0.2 to 1.5% by mass. An airtight sintered body comprising an air-tight surface treatment layer having an open porosity of 12% or less, an average crystal grain size of 40 μm or less, containing nitrogen. The sintered body having airtightness according to claim 1, wherein the sintered body has a nitrogen amount of 60 to 300 ppm. The sintered body having airtightness according to claim 1 or 2, wherein the sintered body has an oxygen content of 100 to 1000 ppm. The sintered body having airtightness according to any one of claims 1 to 3, wherein the surface treatment layer is formed by steam treatment. The sintered body having airtightness according to any one of claims 1 to 3, wherein the surface treatment layer is formed by plating. The sintered body having airtightness according to any one of claims 1 to 3, wherein the surface treatment layer is formed by a coating treatment. In the manufacturing method of a hermetic sintered body in which a green compact is formed by pressurizing a raw material powder containing metal as a main component, and the green compact is sintered in an atmospheric gas, the raw material powder is reduced 40 mass% or more of iron powder, 0.2 to 1.5 mass% of phosphorus, 0.02 to 0.2 mass% of carbon, the atmosphere gas contains nitrogen of 70 volume% or more, and airtight after sintering A method for producing a hermetic sintered body, characterized by forming a surface treatment layer having properties. The method for producing a sintered body having adhesiveness with a surface treatment layer according to claim 7, wherein the surface treatment layer is formed by steam treatment. The method for producing a sintered body having adhesiveness with a surface treatment layer according to claim 7, wherein the surface treatment layer is formed by plating. The method for producing a sintered body having adhesiveness with a surface treatment layer according to claim 7, wherein the surface treatment layer is formed by a coating treatment.

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