Iron-based powder mixture for powder metallurgy and method for producing iron-based sintered body
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Filing Date
- 2025-04-17
- Publication Date
- 2026-02-05
Abstract
Description
Iron-based mixed powder for powder metallurgy and method for producing iron-based sintered body
[0001] The present invention relates to an iron-based mixed powder for powder metallurgy, and more particularly to an iron-based mixed powder for powder metallurgy that can produce a sintered body having excellent strength at a low sintering temperature, and also to a method for producing an iron-based sintered body using the iron-based mixed powder for powder metallurgy.
[0002] Powder metallurgy products are generally produced by mixing raw material powders, filling a mold, and then compacting the mixture under pressure to form a compact, which is then sintered. The sintered compact may then be subjected to sizing, cutting, or heat treatment as necessary. For example, when producing iron-based powder metallurgy products, a mixed powder containing an iron-based powder, an alloy powder such as Cu powder or graphite powder, and a lubricant such as zinc stearate or ethylene bisstearamide is generally used as the raw material powder.
[0003] Such powder metallurgy technology allows parts with complex shapes to be manufactured with a shape very close to the target shape (a so-called near-net shape) and with high dimensional accuracy, thereby significantly reducing the cost required for cutting. Therefore, powder metallurgy products are used in a wide range of fields, and iron-based powder metallurgy products, in particular, are widely used for various mechanical and structural parts, including automotive parts, due to their excellent strength. In particular, iron-copper-carbon sintered materials are widely used as sintered metal materials with the most basic composition.
[0004] The Japanese Industrial Standard JIS Z 2500:2016, which is based on the international standard ISO 5755 and defines the specifications for sintered metal materials, specifies, as one of the iron-based materials for structural parts, a material having a chemical composition of 0.6% by mass or more and 0.9% by mass or less of C, 1.3% by mass or more and 3.0% by mass or less of Cu, 2% by mass or less of other trace elements, and the balance being Fe, and having a reference density of 7.0 g / cm. ３The standard describes the specifications for an iron-copper-carbon sintered body (material designation: P-JISZ2550-F-08C2-390) with a reference tensile strength of 480 MPa. The same standard also describes the specifications for an iron-copper-carbon heat-treated body (material designation: P-JISZ2550-F-08C2-620H) with a reference tensile strength of 690 MPa after the material has been austenitized, quenched, and tempered. Both of these materials are used for high-strength components.
[0005] For materials specified in the above standards, it is difficult to achieve the tensile strength specified as a reference value unless sintering is performed at 1100°C or higher to obtain a dense sintered body with a porosity of approximately 10% or less. For example, Non-Patent Document 1 describes a sintered body sintered at 1121°C with a density of 7.0 g / cm ３ The publication describes an iron-copper-carbon sintered material having a tensile strength of 500 MPa.
[0006] Michiru Kono and three others, "Powder and Powder Metallurgy," August 1984, Vol. 31, No. 6, pp. 189-195.
[0007] In powder metallurgy manufacturing processes, the sintering process in particular consumes a lot of energy because it uses an electric furnace, and emits more greenhouse gases than mixing and molding processes. Therefore, reducing greenhouse gas emissions in the sintering process is a challenge in the powder metallurgy field toward achieving carbon neutrality. One effective solution is thought to be lowering the sintering temperature than conventional methods.
[0008] Lowering the sintering temperature is also desirable from the perspective of extending the service life of manufacturing equipment used for sintering. In the manufacturing process of general powder metallurgy products, sintering is performed using a continuous sintering furnace called a belt furnace. In a belt furnace, sintering is performed continuously while parts are transported on a mesh belt, which has the advantages of excellent productivity and low running costs. If the sintering temperature of a belt furnace can be set to a temperature of 1150°C or less, it is expected that not only will greenhouse gas emissions be reduced, but the frequency of mesh belt replacement will also be reduced, further reducing running costs.
[0009] However, when a conventional iron-based mixed powder for powder metallurgy is used, if the sintering temperature is lowered to 1150°C or lower, it is difficult to produce an iron-copper-carbon sintered body having a tensile strength of 480 MPa or more and an iron-copper-carbon heat-treated body having a tensile strength of 690 MPa or more, as described above.
[0010] The present invention has been made in view of the above-mentioned problems, and has an object to provide an iron-based mixed powder for powder metallurgy that can produce an iron-based sintered body having a tensile strength of 480 MPa or more and a heat-treated body having a tensile strength of 690 MPa or more, even when sintering is carried out at a low temperature of 950° C. or more and 1150° C. or less, preferably 950° C. or more and 1000° C. or less. A further object of the present invention is to provide a method for producing an iron-based sintered body obtained by sintering the iron-based mixed powder for powder metallurgy.
[0011] The present invention provides an iron-based mixed powder for powder metallurgy and a method for producing an iron-based sintered body that overcomes the above-mentioned problems of the prior art. The iron-based mixed powder for powder metallurgy according to the present invention contains a Cu alloy powder and a Cu powder having a predetermined apparent density. This makes it possible to produce a sintered body that has the same tensile strength as a conventional product, even when sintering is carried out at a lower sintering temperature than conventional products.
[0012] The gist and configuration of the present invention are as follows.
[0013] [1] An iron-based powder, a component composition containing 5 mass% or more and 30 mass% or less of Sn, the balance being Cu and unavoidable impurities, and a concentration of 0.5 g / cm ３ 4.0g / cm or more ３ Cu alloy powder having an apparent density of 0.5 g / cm ３ 4.0g / cm or more ３and graphite powder, wherein, relative to the total mass of the iron-based powder, the Cu alloy powder, the Cu powder, and the graphite powder, the Cu alloy powder is contained in an amount of 0.5 mass% or more, the Cu powder is contained in an amount of 0.5 mass% or more, the Cu alloy powder and the Cu powder are contained in an amount of 5.0 mass% or less, and the graphite powder is contained in an amount of 0.1 mass% or more and 1.0 mass% or less, and an amount of Sn relative to the total mass of the Cu alloy powder and the Cu powder is 5.0 mass% or more.
[0014] [2] A method for producing an iron-based sintered body, comprising a step of sintering a compact obtained by pressure-molding the iron-based mixed powder for powder metallurgy according to the above [1] at a sintering temperature of 950°C or more and 1150°C or less to obtain an iron-based sintered body.
[0015] [3] The method for producing an iron-based sintered body according to the above [2], wherein the sintering temperature is 950°C or higher and 1000°C or lower.
[0016] According to the iron-based mixed powder for powder metallurgy of the present invention, an iron-based sintered body with high strength can be obtained even when sintering is carried out at a temperature of 1150° C. or less, which makes it possible to reduce greenhouse gas emissions in the sintering process and also to extend the life of manufacturing equipment used for sintering.
[0017] Hereinafter, embodiments of the present invention will be described in detail. Note that the following description shows preferred embodiments of the present invention, and the present invention is not limited by the following description. In this specification, "%" regarding component compositions means "% by mass" unless otherwise specified.
[0018] [Iron-based mixed powder for powder metallurgy] An iron-based mixed powder for powder metallurgy in one embodiment of the present invention (hereinafter sometimes simply referred to as "mixed powder") contains, as essential components, an iron-based powder, a Cu alloy powder, a Cu powder, and a graphite powder. In other words, the iron-based mixed powder for powder metallurgy in one embodiment of the present invention is an iron-based mixed powder for powder metallurgy containing an iron-based powder, a Cu alloy powder, a Cu powder, and a graphite powder. Furthermore, the iron-based mixed powder for powder metallurgy in a preferred embodiment of the present invention can further contain, in addition to the above components, a lubricant and / or a machinability improver, as desired. These will be described below.
[0019] [Iron-based powder] The iron-based powder is not particularly limited and any iron-based powder can be used. Here, "iron-based powder" refers to a metal powder containing 50 mass% or more of Fe. Examples of iron-based powders include iron powder and alloy steel powder. Here, "iron powder" refers to a powder consisting of Fe and unavoidable impurities, and is generally referred to as "pure iron powder" in this technical field. "Alloy steel powder" refers to a powder consisting of Fe, alloy elements, and unavoidable impurities.
[0020] The alloy steel powder is preferably at least one selected from the group consisting of pre-alloyed steel powder, partially diffusion-alloyed steel powder, and hybrid steel powder. Here, pre-alloyed steel powder refers to alloy steel powder in which alloying elements are pre-alloyed during melting, and is also called fully alloyed steel powder. Partial diffusion-alloyed steel powder refers to powder consisting of iron powder as nuclei and at least one alloying element particle attached to the surface of the iron powder, with the iron powder and the alloying element particle being diffusion-bonded. Furthermore, hybrid steel powder refers to powder in which alloying element particles are further diffusion-adhered to the surface of the pre-alloyed steel powder. The alloying elements used in the alloy steel powder and the alloying element particle can be, for example, one or more elements selected from the group consisting of C, Cu, Ni, Mo, Mn, Cr, V, and Si.
[0021] The iron-based powder can be produced by any method. For example, the iron-based powder may be a reduced iron-based powder, an atomized iron-based powder, or a mixture thereof. The reduced iron-based powder is an iron-based powder produced by reducing iron oxide. The atomized iron-based powder is an iron-based powder produced by an atomization method. Alternatively, the iron-based powder may be a powder in which alloy elements are diffused and attached to the surface of the reduced iron-based powder or the atomized iron-based powder.
[0022] The iron-based powder may be of any size, but it is preferable to use an iron-based powder having a median diameter D50 of 30 μm or more and 120 μm or less.
[0023] The mass ratio of the iron-based powder to the total mass of the iron-based powder, Cu alloy powder, Cu powder, and graphite powder is not particularly limited, but is preferably 86 mass % or more, and more preferably 90 mass % or more.
[0024] [Cu alloy powder] The Cu alloy powder in the mixed powder according to the present invention has a component composition containing 5 mass % or more and 30 mass % or less of Sn, the balance being Cu and unavoidable impurities, and a concentration of 0.5 g / cm ３ 4.0g / cm or more ３ The Cu alloy powder has the following apparent density:
[0025] As mentioned above, in the production of iron-copper-carbon sintered bodies using conventional techniques, sintering is carried out at temperatures exceeding 1150°C. This sintering temperature is higher than the melting point of Cu, which is 1083°C. This sintering temperature not only promotes sintering through liquid phase sintering, but also takes advantage of the hardenability of Cu, resulting in a high-strength sintered body. However, if the sintering temperature is lower than the melting point of Cu, the sintering promotion effect of liquid phase sintering cannot be obtained.
[0026] The mixed powder according to the present invention includes a Cu alloy powder having a composition comprising 5% to 30% by mass of Sn, which has a melting point of 232°C, with the remainder consisting of Cu and unavoidable impurities. The melting point of the Cu alloy powder is lower than that of Cu. Therefore, by using the mixed powder according to the present invention, it is possible to obtain a sintered body having a predetermined tensile strength even at low sintering temperatures due to the sintering promotion effect of liquid phase sintering. However, if the Sn content in the Cu alloy powder is too low, the sintering promotion effect of liquid phase sintering of the Cu alloy powder cannot be fully obtained. Therefore, the Sn content in the Cu alloy powder is set to 5% by mass or more, preferably 10% by mass or more. On the other hand, if the Sn content in the Cu alloy powder is too high, liquid phase sintering will begin at a temperature lower than the temperature at which self-diffusion between iron powder particles begins, resulting in the formation of voids between the iron-based powder particles and inhibiting sintering. Therefore, the Sn content in the Cu alloy powder is set to 30% by mass or less, preferably 20% by mass or less.
[0027] 0.5 g / cm ３ 4.0g / cm or more ３ The apparent density of Cu alloy powder is a property that affects the powder properties of the mixed powder and the tensile strength of the sintered body. However, if the apparent density of Cu alloy powder is too low, the flowability of the powder deteriorates, resulting in a significant decrease in the productivity of powder molding. Therefore, the apparent density of Cu alloy powder is set to 0.5 g / cm. ３ or more, preferably 1.0 g / cm ３ On the other hand, if the apparent density of the Cu alloy powder is too high, the particle shape becomes nearly spherical, and the contact area with the iron powder decreases, making it difficult to proceed with sintering, resulting in a low tensile strength of the sintered body. Therefore, the apparent density of the Cu alloy powder should be 4.0 g / cm or more. ３ Preferably, it is 2.0 g / cm or less. ３ The following applies.
[0028] The apparent density of the Cu alloy powder is determined by the properties of the Cu alloy powder, such as the size and shape of each particle, the particle size distribution, etc. The apparent density can be controlled within the above range by adjusting the size, shape, particle size distribution, etc. of the Cu alloy powder.
[0029] [Cu powder] 0.5g / cm３ 4.0g / cm or more ３ Similar to the apparent density of Cu alloy powder, the apparent density of Cu powder also affects the powder properties of the mixed powder and the tensile strength of the sintered body. However, if the apparent density of Cu powder is too low, the powder fluidity deteriorates, resulting in a significant decrease in the productivity of powder molding. Therefore, the apparent density of Cu powder is set to 0.5 g / cm. ３ or more, preferably 1.0 g / cm ３ On the other hand, if the apparent density of the Cu powder is too high, the particle shape becomes nearly spherical, and the contact area with the iron powder decreases, making it difficult to proceed with sintering, resulting in a low tensile strength of the sintered body. Therefore, the apparent density of the Cu powder should be 4.0 g / cm ３ Preferably, it is 2.0 g / cm or less. ３ The following applies.
[0030] [Mass Ratio of Cu Alloy Powder and Cu Powder] Adjusting the mass ratio of the Cu alloy powder and Cu powder to the total mass of the iron-based powder, Cu alloy powder, Cu powder, and graphite powder to an appropriate range, where the Cu alloy powder, the Cu powder, and the graphite powder contain 0.5 mass% or more of Cu alloy powder, 0.5 mass% or more of Cu powder, and the total of the Cu alloy powder and Cu powder is 5.0 mass% or less, effectively improves the tensile strength of the sintered body. However, if the mass ratio of the Cu alloy powder and Cu powder to the total mass of the iron-based powder, Cu alloy powder, Cu powder, and graphite powder is too low, the sintering promotion effect of the Cu alloy powder and Cu powder due to liquid phase sintering cannot be sufficiently obtained, and the effect of improving hardenability due to Cu and Sn becomes insufficient. Therefore, the Cu alloy powder is contained in an amount of 0.5% by mass or more, preferably 2.0% by mass or more, relative to the total mass of the iron-based powder, Cu alloy powder, Cu powder, and graphite powder. Similarly, the Cu powder is contained in an amount of 0.5% by mass or more, preferably 2.0% by mass or more, relative to the total mass of the iron-based powder, Cu alloy powder, Cu powder, and graphite powder. On the other hand, if the total mass ratio of the Cu alloy powder and Cu powder to the total mass of the iron-based powder, Cu alloy powder, Cu powder, and graphite powder is too large, sintering expansion during liquid phase sintering becomes too large, significantly reducing the density after sintering and potentially resulting in deterioration of mechanical properties. Therefore, the total amount of the Cu alloy powder and Cu powder is contained in an amount of 5.0% by mass or less, preferably 4.0% by mass or less, relative to the total mass of the iron-based powder, Cu alloy powder, Cu powder, and graphite powder.
[0031] [Graphite Powder] The graphite powder is not particularly limited and any one can be used, but for example, it is preferable to use one or both of graphite powder and carbon black. As the graphite powder, either natural graphite powder or artificial graphite powder can be used.
[0032] The mixed powder according to the present invention, which contains 0.1 mass% or more and 1.0 mass% or less of graphite powder relative to the total mass of the iron-based powder, Cu alloy powder, Cu powder, and graphite powder, effectively improves the tensile strength of the sintered body. However, if the mass ratio of graphite powder relative to the total mass of the iron-based powder, Cu alloy powder, Cu powder, and graphite powder is too small, the effect of improving the tensile strength of the sintered body cannot be sufficiently obtained. Therefore, the graphite powder is contained in an amount of 0.1 mass% or more, preferably 0.4 mass% or more, relative to the total mass of the iron-based powder, Cu alloy powder, Cu powder, and graphite powder. On the other hand, if the mass ratio of graphite powder relative to the total mass of the iron-based powder, Cu alloy powder, Cu powder, and graphite powder is too large, hyper-eutectoid formation occurs, causing cementite to precipitate, which actually reduces strength. Therefore, the graphite powder is contained in an amount of 1.0 mass % or less, preferably 0.9 mass % or less, based on the total mass of the iron-based powder, Cu alloy powder, Cu powder, and graphite powder.
[0033] [Sn content in the total mass of Cu alloy powder and Cu powder] The Sn content in the total mass of Cu alloy powder and Cu powder is 5.0 mass% or more. Adjusting the Sn content in the total mass of Cu alloy powder and Cu powder within an appropriate range effectively improves the tensile strength of the sintered body. However, if the Sn content in the total mass of Cu alloy powder and Cu powder is too low, the sintering promotion effect of liquid phase sintering of Cu alloy powder and Cu powder cannot be sufficiently obtained, and the effect of improving hardenability by Cu and Sn becomes insufficient. Therefore, the Sn content in the total mass of Cu alloy powder and Cu powder is 5.0 mass% or more, preferably 7.5 mass% or more. The Sn content in the total mass of Cu alloy powder and Cu powder can be 30 mass% or less.
[0034] [Auxiliary Raw Materials (Optional Components)] The mixed powder according to the present invention, which contains an iron-based powder, a Cu alloy powder, a Cu powder, and a graphite powder, can be used as is, or a lubricant may be further added. The inclusion of a lubricant facilitates the removal of the compact from the die. Examples of lubricants include, but are not limited to, metal soaps (e.g., zinc stearate, lithium stearate), and amide waxes (e.g., ethylene bisstearamide). The lubricant is preferably in powder form. When a lubricant is used, it is preferable to add 0.3 parts by mass or more and 1.0 parts by mass or less of the lubricant per 100 parts by mass of the total of the iron-based powder, the Cu alloy powder, the Cu powder, and the graphite powder.
[0035] The mixed powder according to the present invention may further contain a powder for improving machinability. The powder for improving machinability is not particularly limited, and examples thereof include MnS powder and oxide powder. When using a powder for improving machinability, it is preferable to add 0.1 parts by mass or more and 0.7 parts by mass or less of the powder for improving machinability to 100 parts by mass of the total of the iron-based powder, Cu alloy powder, Cu powder, and graphite powder.
[0036] [Method for Producing Mixed Powder] The method for producing the mixed powder is not particularly limited, and any method can be used. The mixed powder can be produced, for example, by mixing a Cu alloy powder, a Cu powder, and a graphite powder with an iron-based powder so that the mass ratio is as described above. The mixing can be performed by any method. For example, mixing can be performed using a V-type mixer, a double-cone mixer, a Henschel mixer, a Nauta mixer, or the like. During mixing, machine oil or the like may be added to prevent segregation of the Cu alloy powder, the Cu powder, and the graphite powder. Alternatively, the iron-based powder, the Cu alloy powder, the Cu powder, and the graphite powder may be filled into a mold for pressure molding so that the mass ratio is as described above to produce the mixed powder.
[0037] [Method for manufacturing an iron-based sintered body] A method for manufacturing an iron-based sintered body in another embodiment of the present invention comprises a step of obtaining an iron-based sintered body by sintering a compact obtained by pressure-molding the iron-based mixed powder for powder metallurgy at a sintering temperature of 950° C. or more and 1150° C. or less. Also, in a method for manufacturing an iron-based sintered body in a preferred embodiment of the present invention, the sintering temperature is 950° C. or more and 1000° C. or less. These will be explained below.
[0038] [Pressure Molding] After adding auxiliary materials (lubricant, machinability improving powder) to the above mixed powder as needed, the mixture is pressure molded into a desired shape to form a compact. The pressure molding method is not particularly limited, and any method can be used, for example, a method in which the mixed powder is filled into a mold and pressure molded. A lubricant can also be applied or attached to the mold, and the amount of lubricant in this case is preferably 0.3 parts by mass or more and 1.0 parts by mass or less per 100 parts by mass of the total of the iron-based powder, Cu alloy powder, Cu powder, and graphite powder.
[0039] The molding pressure when forming a green body by pressure molding can be set to 400 MPa or more and 1000 MPa or less. However, if the molding pressure exceeds 600 MPa, wear on the mold increases, leading to an increase in manufacturing costs, so the molding pressure is preferably set to the range of 400 MPa or more and 600 MPa or less. The iron-based mixed powder for powder metallurgy according to the present invention can produce a green body with a density (compressed density) of 7.1 g / cm under a molding pressure of 588 MPa, for example. ３ It can be more than that.
[0040] [Sintering] The resulting molded body is then sintered at a sintering temperature of 950°C or higher and 1150°C or lower to obtain an iron-based sintered body. If the sintering temperature is too low, sintering due to iron self-diffusion does not proceed easily, and the desired tensile strength cannot be obtained. Therefore, the sintering temperature is set to 950°C or higher. On the other hand, if the sintering temperature is too high, more energy is consumed and greenhouse gas emissions also increase. Therefore, the sintering temperature is set to 1150°C or lower, and preferably 1000°C or lower. There are no particular limitations on the sintering method, and any method can be used.
[0041] The sintering time is preferably 15 minutes or more and 50 minutes or less. Within this range, insufficient sintering and insufficient strength can be avoided, and manufacturing costs can be reduced. If the cooling rate during cooling after sintering is too low, quenching cannot be performed sufficiently, and tensile strength may decrease. Therefore, the cooling rate is preferably 20°C / min or more. On the other hand, if the cooling rate during cooling after sintering is too high, additional equipment to accelerate the cooling rate is required, increasing manufacturing costs. Therefore, the cooling rate is preferably 40°C / min or less. If a lubricant is used, a degreasing process may be added before sintering, in which the temperature is maintained at 400°C or more and 700°C or less for a certain period of time to decompose and remove the lubricant. Manufacturing conditions and equipment for the sintered body other than those described above are not particularly limited, and known methods can be used.
[0042] [Heat Treatment] The obtained iron-based sintered body can be further subjected to heat treatment. By performing heat treatment, the strength of the sintered body can be further increased. As the heat treatment, a treatment accompanied by rapid cooling is preferably performed, and for example, strengthening treatments such as carburizing and quenching, bright quenching, induction hardening, and carbonitriding heat treatment can be performed. Furthermore, the sintered body after rapid cooling may be subjected to a recovery treatment for impact resistance such as tempering. The tempering temperature is preferably about 100°C or higher and 300°C or lower.
[0043] Next, the present invention will be described in more detail based on examples. The following examples are intended to illustrate preferred examples of the present invention, but the present invention is not limited to these examples.
[0044] An iron-based mixed powder for powder metallurgy was prepared according to the following procedure, and an iron-based sintered body and a heat-treated body were manufactured using the obtained iron-based mixed powder for powder metallurgy, and were then evaluated.
[0045] Preparation of Iron-Based Mixed Powder for Powder Metallurgy: An iron-based powder (JIP301A pure iron powder manufactured by JFE Steel Corporation) produced by atomization, a Cu alloy powder having a component composition containing Sn in the mass percentages shown in Table 1, with the balance consisting of Cu and unavoidable impurities, and an apparent density shown in Table 1, a Cu powder having an apparent density shown in Table 1, and graphite powder were prepared. In addition to these powders, Sn powder was also prepared for comparison. Next, the iron-based powder, Cu alloy powder, Cu powder, Sn powder, and graphite powder (hereinafter, these powders may be collectively referred to as "main components") were blended so that the mass ratios of the Cu alloy powder, Cu powder, graphite powder, and Sn powder to the total mass were as shown in Table 1. Next, 0.8 parts by mass of zinc stearate was added as a lubricant to a total of 100 parts by mass of the blended powders, and the mixture was mixed using a double-cone mixer to obtain an iron-based mixed powder for powder metallurgy. Table 1 shows the amount of Sn relative to the total mass of the Cu alloy powder, Cu powder, and Sn powder.
[0046] Next, the obtained mixed powder was pressure-molded into a tensile test piece with a width of 6 mm and a height of 5 mm as specified in Japanese Industrial Standard JIS Z 2550, and a rectangular parallelepiped test piece with a size of 10 mm x 10 mm x 55 mm as specified in the same standard. The density of all the compacts was 7.1 g / cm. ３ Next, the obtained molded body was placed in an RX atmosphere (N ２ -32% by volume H ２ -24% by volume CO -0.3% by volume CO ２ ) at a sintering temperature of 950°C, 1000°C or 1150°C for a holding time of 20 minutes to obtain an iron-based sintered body.
[0047] Production of Heat-Treated Body: Rectangular specimens from the obtained iron-based sintered bodies were machined into round bar tensile test specimens with a diameter of 4.75 mm as specified in Japanese Industrial Standard JIS Z 2550. Next, some of the obtained round bar tensile test specimens were gas carburized at a carbon potential of 0.8 mass %, at a holding temperature of 870°C for a holding time of 60 minutes, and then oil quenched at a temperature of 60°C and tempered at a holding temperature of 200°C for a holding time of 60 minutes to obtain heat-treated bodies. Note that "carbon potential" is an index that indicates the carburizing ability of the atmosphere in which steel is heated, and is expressed as the carbon concentration on the surface of the steel when equilibrium is reached with the gas atmosphere at that temperature.
[0048] The densities of the evaluated compacts and iron-based sintered bodies were measured in accordance with Japanese Industrial Standard JIS Z 2501. The tensile strengths of the iron-based sintered bodies and heat-treated bodies were measured in accordance with Japanese Industrial Standard JIS Z 2241. The obtained evaluation results are shown in Table 1.
[0049]
[0050] Among the examples shown in Table 1, Nos. 1 to 7, 9, and 11 to 29 are examples sintered at a sintering temperature of 1000°C, No. 8 at a sintering temperature of 950°C, and No. 10 at a sintering temperature of 1150°C. Nos. 1 to 18 are inventive examples in which the Sn content of the Cu alloy powder, the apparent density of the Cu alloy powder and Cu powder, the mass ratio of the Cu alloy powder and Cu powder, and the Sn content in the total mass of the Cu alloy powder and Cu powder are within the ranges of the present invention. Nos. 19 to 28 are comparative examples in which any of the Sn content of the Cu alloy powder, the apparent density of the Cu alloy powder and Cu powder, the mass ratio of the Cu alloy powder and Cu powder, and the Sn content in the total mass of the Cu alloy powder and Cu powder are outside the ranges of the present invention. No. 29 is a comparative example in which 1.8 mass % of Cu powder and 0.2 mass % of Sn powder were blended instead of the Cu alloy powder.
[0051] According to Table 1, in the invention examples No. 1 to 18, the density of the iron-based sintered body was 7.0 g / cm at a low sintering temperature of 950°C, 1000°C, or 1150°C. ３Furthermore, the iron-based sintered body achieved a tensile strength of 480 MPa or more, and the heat-treated body achieved a tensile strength of 690 MPa or more, both of which achieved the reference values for tensile strength specified in the aforementioned Japanese Industrial Standard JIS Z 2500:2016. In contrast, in Comparative Examples Nos. 19 to 29, the tensile strength was 6.9 g / cm at a sintering temperature of 1000°C. ３ 7.0g / cm or more ３ Although iron-based sintered bodies having the following densities were obtained, the tensile strengths of the iron-based sintered bodies and the heat-treated bodies were lower than the above reference values.
Claims
1. An iron-based powder, a component composition containing 5 mass% to 30 mass% Sn, the balance being Cu and unavoidable impurities, and a density of 0.5 g / cm ３ 4.0g / cm or more ３ Cu alloy powder having an apparent density of 0.5 g / cm ３ 4.0g / cm or more ３ and graphite powder, wherein, relative to the total mass of the iron-based powder, the Cu alloy powder, the Cu powder, and the graphite powder, the Cu alloy powder is contained in an amount of 0.5 mass% or more, the Cu powder is contained in an amount of 0.5 mass% or more, the Cu alloy powder and the Cu powder are contained in an amount of 5.0 mass% or less, and the graphite powder is contained in an amount of 0.1 mass% or more and 1.0 mass% or less, and an amount of Sn relative to the total mass of the Cu alloy powder and the Cu powder is 5.0 mass% or more.
2. A method for producing an iron-based sintered body, comprising a step of sintering a compact obtained by pressing the iron-based mixed powder for powder metallurgy according to claim 1 at a sintering temperature of 950°C or more and 1150°C or less to obtain an iron-based sintered body.
3. The method for producing an iron-based sintered body according to claim 2, wherein the sintering temperature is 950°C or higher and 1000°C or lower.