Lubricant combination, powder mixture, combination of raw materials for powder mixture, and method for manufacturing sintered body

Abstract

A lubricant of the present invention includes a lubricant A, which has a melting point of 60–85°C, and a metal soap-based lubricant B, and the ratio of particles with a particle size of 63 μm or less is at least 88 mass% with respect to the total amount of the lubricant combination when sifted using a JIS-standard sieve.

Description

[Technical field]

[0001] The present disclosure relates to lubricant combinations, powder mixtures, raw material combinations for powder mixtures, and methods for producing sintered bodies. [Background technology]

[0002] Lubricants are generally used for lubrication, for example, to reduce friction between solids in contact with each other. Examples of lubricants include liquid lubricating oils, semi-solid greases, solid lubricants, etc. For example, in powder metallurgy, solid lubricants in powder form (powdered lubricants) are used.

[0003] Among powder metallurgy methods, particularly in die compaction, a powder mixture in which a powdered lubricant is mixed into raw material powder is usually used to reduce friction between the die wall and the green compact. The powder mixture is a mixture of an iron-based powder as the main raw material powder, auxiliary raw material powders such as copper powder, graphite powder, and machinability improving powder, and lubricant powder.

[0004] By including a powdered lubricant in the powder mixture, the powder characteristics such as flowability and compactibility of the powder mixture are improved, and the compression-molded green compact can be easily removed from the die. Examples of lubricant powder include metal soap-based lubricants such as stearic acid and its metal salts, organic lubricants (wax-based lubricants), and fatty acid amide-based lubricants (see, for example, Patent Documents 1 and 2).

[0005] The lubricant is selected taking into consideration the mixability with the metal powder, the powder characteristics when the powder mixture is prepared, the extractability of the green compact after compression molding, the dissipation of the lubricant when the green compact is sintered, etc. Among them, zinc stearate is widely used as a lubricant because of its relatively excellent lubricating properties and cost. Such lubricants are generally mixed in the powder mixture before use. There is also a method in which the lubricant is applied to the wall surface of the die, but this requires special equipment, which increases the manufacturing cost of the sintered body.

[0006] However, metal soap-based lubricants, such as zinc stearate, have a problem of contaminating the product surface, exhaust ducts, etc., when sintering a green compact, and there is a demand for their replacement with organic lubricants (wax-based lubricants).As organic lubricants, in addition to the lubricants described in Patent Documents 1 and 2, amide-based compounds having long-chain alkyl groups have been proposed (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 4-136104 [Patent Document 2] Japanese Patent Application Publication No. 11-193404 [Patent Document 3] Special Publication No. 2008-513602 Summary of the Invention [Problem to be solved by the invention]

[0008] When the powder mixture to which the lubricant has been added is compression molded using a die, it is desirable that the molded body be easily removable from the die, i.e., that the molded body have excellent removable properties. Since the sintered body obtained by sintering the molded body is also prone to appearance defects due to the formation of irregularities on the surface, it is desirable that the appearance defects can be suppressed.

[0009] An object of the present disclosure is to provide a combination of lubricants capable of improving the extractability of a green body and producing a sintered body with reduced appearance defects, a combination of a powder mixture and a raw material for the powder mixture that includes the combination of lubricants, and a method for producing a sintered body using the powder mixture or the combination of raw materials for the powder mixture. [Means for solving the problem]

[0010] Specific means for achieving the above object are as follows. <1> Lubricant A having a melting point of 60°C to 85°C; A metal soap-based lubricant B, A combination of lubricants in which, when sieved using a JIS standard sieve, the proportion of particles with a particle size of 63 μm or less is 88 mass % or more of the total amount of the combination of lubricants. <2> The lubricant A includes at least one selected from the group consisting of oleic acid amide, erucic acid amide, ricinoleic acid amide, N-oleyl oleic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide, N-oleyl palmitic acid amide, N-oleyl-hydroxystearic acid amide, stearic acid, and N-oleyl palmitamide. <1> A combination of lubricants as described in claim 1. <3> The metal soap-based lubricant B contains a metal salt of a fatty acid having 12 to 22 carbon atoms and at least one metal selected from the group consisting of lithium, magnesium, calcium, barium, zinc, and strontium. <1> or <2> A combination of lubricants as described in claim 1. <4> When sieved through a JIS standard sieve with 150 μm openings, the ratio of particles that do not pass through the sieve is 5 mass% or less based on the total amount of the lubricant. <1> ~ <3> 2. A lubricant combination according to any one of claims 1 to 11. <5> Further comprising lubricant C which is a fatty acid bisamide. <1> ~ <4> 2. A lubricant combination according to any one of claims 1 to 11. <6> The melting point of the lubricant C is 140° C. or higher and lower than 150° C. <5> A combination of lubricants as described in claim 1. <7> The lubricant C is selected from the group consisting of methylene bisstearic acid amide, methylene bislauric acid amide, methylene bishydroxystearic acid amide, ethylene biscaprylic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bisisostearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene bishydroxystearic acid amide, and the like. at least one selected from the group consisting of butylene bishydroxystearic acid amide, N,N'-distearyl adipamide, N,N'-distearyl sebacic acid amide, methylene bisoleic acid amide, ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipamide, N,N'-dioleyl sebacic acid amide, m-xylylene bisstearic acid amide, and N,N'-distearyl isophthalic acid amide. <5> A combination of lubricants as described in claim 1. <8> A raw material powder, <1> ~ <7> and a powder mixture comprising the lubricant combination according to any one of claims 1 to 5. <9> A raw material powder, <1> ~ <7> A combination of raw materials for a powder mixture comprising the lubricant combination described in any one of the above. <10> <8> or a powder mixture according to <9> A method for producing a sintered body, comprising sintering a powder mixture obtained from the combination of raw materials for the powder mixture described in claim 1. Effect of the Invention

[0011] According to the present disclosure, it is possible to provide a combination of lubricants capable of improving the extractability of a molded body and producing a sintered body with reduced appearance defects, a combination of a powder mixture and a raw material for the powder mixture that includes the combination of lubricants, and a method for producing a sintered body using the powder mixture or the combination of raw materials for the powder mixture. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The combination of lubricants, the powder mixture, the combination of raw materials for the powder mixture, and the method for producing a sintered body according to the present disclosure will be described below. However, the present disclosure is not limited to the following embodiments. In the following embodiments, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to the numerical values ​​and their ranges, and they do not limit the present invention. In the present disclosure, a numerical range indicated using "~" indicates a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in the present disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in the present disclosure. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with a value shown in the examples. In the present disclosure, each component may contain multiple substances corresponding to the component. When multiple substances corresponding to each component exist, the content or amount of each component means the total content or amount of the multiple substances, unless otherwise specified. In the present disclosure, particles corresponding to each component may include multiple types. When multiple types of particles corresponding to each component exist, the particle size of each component means the value for a mixture of the multiple types of particles, unless otherwise specified.

[0013] [Lubricant combination] The lubricant combination of the present disclosure includes lubricant A having a melting point of 60°C to 85°C and metal soap-based lubricant B, and when sieved using a JIS standard sieve, the proportion of particles having a particle diameter of 63 μm or less is 88 mass% or more of the total amount of the lubricant combination.

[0014] By using the combination of lubricants of the present disclosure, the ejectability of the compact can be improved, and a sintered body with reduced appearance defects can be produced. More specifically, the combination of lubricants of the present disclosure contains lubricant A with a relatively low melting point, which makes it easier to eject the compact from the die, that is, tends to improve the ejectability of the compact. Furthermore, when sieved, the ratio of particles with a particle size of 63 μm or less is 88 mass% or more relative to the total amount of the lubricant. This makes it possible to produce a sintered body obtained by sintering a compact, in which the surface irregularities are reduced and appearance defects are suppressed.

[0015] The use of lubricant A tends to slightly decrease the fluidity of the powder mixture. Combining lubricant A with metal soap-based lubricant B can greatly increase the fluidity of the powder mixture. Therefore, the combination of lubricants disclosed herein tends to improve the fluidity of the powder mixture. The combined use of lubricant A and metal soap-based lubricant B can reduce the amount of metal soap-based lubricant B used.

[0016] The lubricant combination of the present disclosure is preferably used for, for example, powder metallurgy. The lubricant combination of the present disclosure may be used for applications other than powder metallurgy.

[0017] In the lubricant combination of the present disclosure, when sieved using a JIS standard sieve, the ratio of particles having a particle size of 63 μm or less is 88 mass% or more relative to the total amount of the lubricant combination, which makes it possible to produce a sintered body obtained by sintering a compact, in which surface irregularities are reduced and appearance defects are suppressed. In the present disclosure, the percentage of particles having a particle size equal to or smaller than a specific particle size (e.g., equal to or smaller than 63 μm) refers to the percentage of particles that pass through a JIS standard sieve having openings equal to the specific particle size (e.g., 63 μm) when the lubricant is sieved through the sieve.

[0018] When sieved using a JIS standard sieve, the proportion of particles having a particle size of 63 μm or less may be 90 mass % or more, 95 mass % or more, or may be 100 mass % based on the total amount of the lubricant combination, from the viewpoint of suitably suppressing poor appearance of the sintered body.

[0019] The particle size used as the basis for sieving is not limited to 63 μm or less, and may be 50 μm or less, or 43 μm or less. For example, the ratio of particles having a particle size of 50 μm or less may be 88 mass% or more, 90 mass% or more, 95 mass% or more, or 100 mass% based on the total amount of the lubricant. The ratio of particles having a particle size of 43 μm or less may be 88 mass% or more, 90 mass% or more, 95 mass% or more, or 100 mass% based on the total amount of the lubricant.

[0020] The JIS standard sieve complies with JIS-Z-8801-1:2006 and corresponds to ISO3310-1:2000. When using ISO3310-1:2000, it is preferable to use a sieve with square mesh, as in JIS-Z-8801-1:2006.

[0021] In the lubricant combination of the present disclosure, the ratio of particles that do not pass through a JIS standard sieve with a mesh size of 150 μm (preferably 100 μm, more preferably 80 μm) is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, based on the total amount of the lubricant combination, from the viewpoint of suitably suppressing the appearance defect of the sintered body. The ratio of the above-mentioned particles may be 0% by mass or 0.5% by mass or more, based on the total amount of the lubricant combination.

[0022] When the combination of lubricants disclosed herein is composed of lubricant A and metal soap-based lubricant B, the ratio of particles having a particle diameter of 63 μm or less when sieved using a JIS standard sieve may be 88% by mass or more relative to the total amount of lubricant A and metal soap-based lubricant B. When the combination of lubricants disclosed herein is composed of lubricants such as lubricant A, metal soap-based lubricant B, and lubricant C described below, the ratio of particles having a particle diameter of 63 μm or less when sieved using a JIS standard sieve may be 88% by mass or more relative to the total amount of lubricant A, metal soap-based lubricant B, and lubricant C described below.

[0023] In the present disclosure, the combination of lubricants may be a mixture of lubricants containing at least lubricant A and metal soap-based lubricant B, or may be a combination of a lubricant containing lubricant A and a lubricant containing metal soap-based lubricant B, which are prepared without mixing. For example, in the case of a combination of a lubricant containing lubricant A and a lubricant containing metal soap-based lubricant B, which are prepared without mixing, the lubricant containing lubricant A and the lubricant containing metal soap-based lubricant B may be mixed when producing a powder mixture. If necessary, lubricant C, etc., which will be described later, may be added to the mixture. A lubricant containing lubricant C, etc. may be prepared without mixing with a lubricant containing lubricant A and a lubricant containing metal soap-based lubricant B.

[0024] (Lubricant A) The lubricant combination of the present disclosure includes a lubricant A having a melting point of 60° C. to 85° C. The lubricant combination may include one type of lubricant A, or may include two or more types of lubricants A. In this disclosure, melting points are values ​​measured by differential scanning calorimetry (DSC).

[0025] The lubricant A preferably contains at least one selected from the group consisting of oleic acid amide, erucic acid amide, ricinoleic acid amide, N-oleyl oleic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide, N-oleyl palmitic acid amide, N-oleyl-hydroxystearic acid amide, stearic acid, and N-oleyl palmitamide, and more preferably contains at least one selected from the group consisting of oleic acid amide, erucic acid amide, ricinoleic acid amide, stearic acid, and N-oleyl palmitamide. Among these, it is more preferable to contain at least one of erucic acid amide and oleic acid amide from the viewpoint of the ejection property of the molded body.

[0026] The content of lubricant A may be 10% by mass to 90% by mass, 20% by mass to 70% by mass, or 30% by mass to 50% by mass relative to the total amount of the combination of lubricants.

[0027] (Metal soap-based lubricant B) The lubricant combination of the present disclosure includes a metal soap-based lubricant B. The lubricant combination may include one type of metal soap-based lubricant B, or may include two or more types of metal soap-based lubricants B.

[0028] The metal soap-based lubricant B may be, for example, a metal salt of a fatty acid having 12 to 22 carbon atoms and at least one metal selected from the group consisting of lithium, magnesium, calcium, barium, zinc, and strontium.

[0029] The fatty acid having 12 to 22 carbon atoms may be a saturated fatty acid having 12 to 22 carbon atoms, or an unsaturated fatty acid having 12 to 22 carbon atoms. The number of carbon atoms in the fatty acid may be 16 to 20, or 16 to 18.

[0030] Examples of fatty acids having 12 to 22 carbon atoms include saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid, and unsaturated fatty acids such as linoleic acid, linolenic acid, oleic acid, and erucic acid.

[0031] Specific examples of the metal soap-based lubricant B include lithium stearate, calcium stearate, barium stearate, and zinc stearate.

[0032] The content of metal soap-based lubricant B may be 1 mass% to 90 mass%, 10 mass% to 90 mass%, 30 mass% to 80 mass%, or 50 mass% to 70 mass% relative to the total amount of the combination of lubricants.

[0033] From the viewpoint of the balance between the fluidity of the powder mixture and the extractability of the compact, the mass ratio of lubricant A to metal soap-based lubricant B is preferably 1:9 to 9.9:0.1, more preferably 1:9 to 9:1, even more preferably 2:8 to 8:2, and particularly preferably 3:7 to 7:3.

[0034] (Lubricant C) The lubricant combination of the present disclosure may include a lubricant C that is a fatty acid bisamide. The lubricant combination may include one lubricant C or may include two or more lubricants C.

[0035] The melting point of the lubricant C may be 140°C or more and less than 150°C, or may be 140°C or more and 148°C or less.

[0036] Examples of the lubricant C include methylene bisstearic acid amide, methylene bislauric acid amide, methylene bishydroxystearic acid amide, ethylene biscaprylic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bisisostearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene bi Examples of the lubricant C include s-hydroxystearic acid amide, butylene bis-hydroxystearic acid amide, N,N'-distearyl adipamide, N,N'-distearyl sebacic acid amide, methylene bis-oleic acid amide, ethylene bis-oleic acid amide, ethylene bis-erucic acid amide, hexamethylene bis-oleic acid amide, N,N'-dioleyl adipamide, N,N'-dioleyl sebacic acid amide, m-xylylene bis-stearic acid amide, and N,N'-distearyl isophthalic acid amide. Among these, it is more preferable that the lubricant C contains ethylene bis-stearic acid amide from the viewpoint of the flowability of the powder mixture.

[0037] When the combination of lubricants includes lubricant A, metal soap-based lubricant B, and lubricant C, a preferred combination of lubricant A, metal soap-based lubricant B, and lubricant C, from the viewpoint of the balance between the fluidity of the powder mixture and the extractability of the compact, is such that lubricant A is at least one selected from the group consisting of erucamide and oleamide, metal soap-based lubricant B is zinc stearate, and lubricant C is ethylene bisstearamide.

[0038] The content of lubricant C may be 1 mass% to 90 mass%, 10 mass% to 90 mass%, 30 mass% to 80 mass%, or 50 mass% to 70 mass% relative to the total amount of the combination of lubricants.

[0039] From the viewpoint of the balance between the fluidity of the powder mixture and the extractability of the compact, the mass ratio of lubricant A to lubricant C is preferably 1:9 to 9.9:0.1, more preferably 1:9 to 9:1, even more preferably 2:8 to 8:2, and particularly preferably 3:7 to 7:3.

[0040] The mass ratio of lubricant A to the sum of metal soap-based lubricant B and lubricant C, i.e., lubricant A:total of metal soap-based lubricant B and lubricant C, is preferably 1:9 to 9:1, more preferably 2:8 to 8:2, and even more preferably 3:7 to 7:3, from the viewpoint of the balance between the fluidity and compactibility of the powder mixture and the ejection ability of the compact. The mass ratio of metal soap-based lubricant B to lubricant C, metal soap-based lubricant B:lubricant C, is preferably 1:9 to 9:1, more preferably 2:8 to 8:2, and even more preferably 3:7 to 7:3, from the viewpoint of the balance between the fluidity and compactibility of the powder mixture and the extractability of the compact.

[0041] The total content of lubricant A, metal soap-based lubricant B, and optionally contained lubricant C in the total amount of the combined lubricants is preferably 50% by mass to 100% by mass. The total content of lubricant A, metal soap-based lubricant B, and optionally contained lubricant C may be 60% by mass to 95% by mass, or 80% by mass to 90% by mass.

[0042] (Other lubricants) The lubricant combination of the present disclosure may include lubricants other than lubricant A, metal soap-based lubricant B, and lubricant C. Examples of lubricants other than lubricant A include fatty acid amides having a melting point of more than 85° C. When using other lubricants, one type may be used alone, or two or more types may be used in combination.

[0043] Examples of fatty acid amides having a melting point exceeding 85°C include lauric amide, palmitic amide, stearic amide, behenic amide, hydroxystearic amide, N-lauryl lauric amide, N-palmityl palmitic amide, N-stearyl stearic amide, and N-stearyl-hydroxystearic amide.

[0044] The content of the other lubricant relative to the total amount of the combination of lubricants may be more than 0 mass% and not more than 50 mass%, may be 5 mass% to 40 mass%, or may be 10 mass% to 20 mass%.

[0045] [Powder mixture] The powder mixture of the present disclosure includes a raw material powder and the combination of the lubricants of the present disclosure. By using this powder mixture, it is possible to improve the ejection property of a compact and to produce a sintered body with reduced appearance defects. The powder mixture of the present disclosure is preferably used for powder metallurgy, for example.

[0046] Examples of the raw material powder include a main raw material powder containing iron as a main component, and an auxiliary raw material powder that improves the properties of the sintered body. Incidentally, containing iron as a main component means that the content of iron in the raw material powder is 50 mass % or more of the entire raw material powder.

[0047] Examples of the main raw material powder include iron-based powders such as pure iron powder and iron-based alloy powder, which may contain inevitable impurities (oxygen, silicon, carbon, manganese, etc.). The main raw material powder may be used alone or in combination of two or more kinds.

[0048] The average particle size of the main raw material powder is preferably 30 μm to 150 μm, and more preferably 50 μm to 100 μm. In the present disclosure, the average particle size is the particle size (D50) at which the cumulative amount from the small diameter side reaches 50% in the volume-based particle size distribution measured by a laser diffraction method.

[0049] The iron-based powder can be produced, for example, by atomizing molten iron or a molten iron alloy into fine particles, reducing the fine particles, and then pulverizing them.

[0050] The auxiliary raw material powder is not particularly limited as long as it is a raw material powder that can improve the properties of the sintered body, and examples of the auxiliary raw material powder include powders that improve the mechanical properties of the sintered body, such as hardness and toughness, and powders that increase the machinability of the sintered body.

[0051] Examples of the auxiliary raw material powder include metal powders and inorganic powders other than the main raw material powder. The auxiliary raw material powders may be used alone or in combination of two or more kinds.

[0052] Examples of the metal powder include powders of copper, nickel, chromium, molybdenum, tin, vanadium, manganese, and the like.

[0053] Examples of inorganic powders include powders of sulfides such as manganese sulfide and manganese disulfide; nitrides such as boron nitride; oxides such as boric acid, magnesium oxide, potassium oxide and silicon oxide; graphite such as natural graphite and artificial graphite; phosphorus; and sulfur.

[0054] The average particle size of the auxiliary raw material powder is preferably 2 μm to 100 μm, and more preferably 5 μm to 50 μm.

[0055] Of 100 parts by mass of the raw material powder, the content of the main raw material powder is preferably 90 parts by mass to 99 parts by mass, and more preferably 95 parts by mass to 98 parts by mass.

[0056] In 100 parts by mass of the raw material powder, the content of the auxiliary raw material powder is preferably 1 part by mass to 10 parts by mass, and more preferably 2 parts by mass to 5 parts by mass.

[0057] The content of the lubricant combination relative to 100 parts by mass of the raw material powder is preferably 0.1 parts by mass to 2.0 parts by mass, more preferably 0.2 parts by mass to 1.5 parts by mass, and even more preferably 0.3 parts by mass to 1.0 part by mass.

[0058] (Other Ingredients) The powder mixture of the present disclosure may contain other components other than the raw material powder and the combination of lubricants of the present disclosure. The other components include a binder. By including a binder in the powder mixture, segregation, scattering, etc. of the raw material powder tends to be suppressed.

[0059] The binder is not particularly limited, and examples thereof include polyolefin, acrylic resin, polystyrene, styrene-butadiene rubber, ethylene glycol distearate, epoxy resin, and rosin ester.

[0060] When the powder mixture of the present disclosure contains a binder, the content of the binder is preferably 0.01 part by mass to 1.0 part by mass, and more preferably 0.1 part by mass to 1.0 part by mass, relative to 100 parts by mass of the raw material powder.

[0061] The powder mixture of the present disclosure can be obtained by mixing the raw material powder, the lubricant combination of the present disclosure, and other components as necessary. The raw material powder and the lubricant combination of the present disclosure can be mixed using a commonly used mixer such as a vane mixer, a V-type mixer, or a double cone mixer (W-cone).

[0062] The combination of raw materials for powder mixtures of the present disclosure includes raw material powders and a combination of lubricants of the present disclosure. The combination of raw materials for powder mixtures of the present disclosure may be a mixture of raw material powders and a combination of lubricants. Alternatively, the raw material powders and the combination of lubricants of the present disclosure may be a combination of raw material powders and lubricants prepared without mixing, and the raw material powders and the combination of lubricants of the present disclosure may be mixed and used when producing a compact. The preferred conditions for the combination of raw materials for the powder mixture of the present disclosure are similar to those for the powder mixture of the present disclosure described above, and therefore the description thereof will be omitted.

[0063] [Method for producing sintered body] The method for producing a sintered body according to the present disclosure is a method for producing a sintered body by sintering the above-described powder mixture according to the present disclosure or a powder mixture obtained from a combination of raw materials for the powder mixture according to the present disclosure. The method for producing a sintered body of the present disclosure preferably includes filling a powder mixture into a die, compression-molding the powder mixture filled in the die into a green body, and sintering the green body removed from the die.

[0064] In the method for producing a sintered body disclosed herein, the use of the above-mentioned powder mixture can improve the extractability of the molded body, and also makes it possible to produce a sintered body with reduced appearance defects.

[0065] In the method for producing a sintered body according to the present disclosure, the powder mixture filled in a mold may be compression molded. The molding temperature, molding pressure, etc. are not particularly limited, and may be appropriately adjusted depending on the composition of the powder mixture, the amount added, the shape inside the mold, etc.

[0066] In the method for producing a sintered body of the present disclosure, a sintered body is produced by sintering a powder mixture, and preferably, a sintered body is produced by sintering a molded body extracted from a die. The conditions for sintering the powder mixture or the molded body are not particularly limited, and a typical sintering method can be used. EXAMPLES

[0067] The present disclosure will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0068] [Examples 1 to 50 and Comparative Examples 1 to 120] As the main raw material powder, an atomized iron powder for powder metallurgy having an average particle size of 75 μm, an electrolytic copper powder having an average particle size of 30 μm, and a graphite powder having an average particle size of 10 μm were prepared as the auxiliary raw material powder. Next, 0.8 parts by mass of a lubricant mixture of lubricant A and metal soap-based lubricant B (referred to as "lubricant B" in the tables) shown in Tables 1 to 3 and below, or a lubricant mixture of lubricant A, metal soap-based lubricant B, and lubricant C, was added to 97.5 parts by mass of iron powder, 1.5 parts by mass of copper powder, and 1.0 parts by mass of graphite powder. In each example and each comparative example, a lubricant mixture was used in which the ratio of particles having a particle size of 63 μm or less to the total amount of lubricant when sieved using a JIS standard sieve is the numerical value shown in Tables 1 to 3. The ratios of lubricant A, metal soap-based lubricant B, and lubricant C in each example and each comparative example are as shown in Tables 1 to 3. Thereafter, the mixture of raw material powder and lubricant was charged into a V-type mixer and mixed for 30 minutes to obtain a powder mixture for each of the examples and comparative examples. <Lubricant A> Erucamide (Melting point: 78℃~81℃) Oleic acid amide (melting point: 75°C) <Metal soap-based lubricant B (lubricant B in the table)> Zinc stearate <Lubricant C> Ethylene bis stearic acid amide (melting point: 145°C)

[0069] (Flowability of powder mixture) The fluidity of the powder mixtures obtained in each Example and Comparative Example was evaluated by the fluidity test method specified in JIS Z 2502 (2012). The evaluation criteria are as follows. -Evaluation criteria- A The powder mixture flowed within 30 seconds. B The powder mixture flowed in more than 30 seconds but not more than 35 seconds. C. The powder mixture did not flow or the powder mixture flowed in more than 35 seconds. The results are shown in Tables 1 to 3. If the powder mixture is rated A or B, the fluidity of the powder mixture is good.

[0070] (Consolidation of powder mixtures) The compactibility of the powder mixtures obtained in each Example and Comparative Example was evaluated by feeding 7 g of the powder mixture into a mold, molding a cylindrical body with a diameter of 11.3 mm at a molding pressure of 700 MPa, and then evaluating the compactibility based on the following criteria. -Evaluation criteria- A: The density of the cylindrical compact is 7.10 g / cm 3 That was all. B The density of the cylindrical compact is 7.06 g / cm 3 More than 7.10g / cm 3 It was less than. C The density of the cylindrical compact is 7.06 g / cm 3 It was less than. The results are shown in Tables 1 to 3. If the powder mixture is rated A or B, the compactibility of the powder mixture is good.

[0071] (Removability of cylindrical molded body) The ejection properties of the cylindrical compacts in each Example and Comparative Example were evaluated based on the following criteria by measuring the ejection pressure when the cylindrical compacts used to evaluate the compactibility of the powder mixture described above were ejected from the die. -Evaluation criteria- A The ejection pressure was 8 MPa or less. B The ejection pressure was more than 8 MPa and less than 15 MPa. C The ejection pressure was over 15 MPa. The results are shown in Tables 1 to 3. If the evaluation was A or B, the extractability of the cylindrical molded article was good.

[0072] (Appearance evaluation) The appearance of each example and comparative example was evaluated by visually inspecting the surface of the sintered body obtained by sintering the cylindrical molded body used to evaluate the compactibility of the powder mixture described above at approximately 1100°C in nitrogen, and evaluating it based on the following criteria. -Evaluation criteria- No roughness due to surface irregularities was observed on the surface of the sintered body A. C Roughness due to surface unevenness was observed on the surface of the sintered body. The results are shown in Tables 1 to 3. Evaluation A means that the appearance of the sintered body is good.

[0073] [Table 1]

[0074] [Table 2]

[0075] [Table 3]

[0076] As shown in Tables 1 to 3, by using the powder mixtures of Examples 1 to 36, it was possible to produce sintered bodies with excellent compact extractability and suppressed defects in appearance.

[0077] All publications, patent applications, and standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or standard was specifically and individually indicated to be incorporated by reference.

Claims

1. a lubricant A having a melting point of 60°C to 85°C, and a metal soap-based lubricant B, and when sieved using a JIS standard sieve, the proportion of particles having a particle diameter of 63 µm or less is 88% by mass or more based on the total amount of the lubricant combination, the lubricant A contains at least one selected from the group consisting of oleic acid amide, erucic acid amide, ricinoleic acid amide, stearic acid, and N-oleyl palmitamide, the metal soap-based lubricant B contains at least one selected from the group consisting of lithium stearate, calcium stearate, barium stearate, and zinc stearate, and is a powdery lubricant combination used by being mixed into raw material powder in a powder metallurgy die forming method.

2. The combination of lubricants according to claim 1, wherein the proportion of particles that do not pass through the sieve when sieved with a JIS standard sieve having an opening of 150 µm is 5% by mass or less based on the total amount of the lubricant.

3. The combination of lubricants according to claim 1 or claim 2, further comprising a lubricant C which is a fatty acid bisamide.

4. The combination of lubricants according to claim 3, wherein the melting point of the lubricant C is 140°C or higher and less than 150°C.

5. The lubricant C is selected from the group consisting of methylene bisstearic acid amide, methylene bislauric acid amide, methylene bishydroxystearic acid amide, ethylene biscaprylic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bisisostearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene bishydroxystearic acid amide, butylene bishydroxystearic acid amide, N,N'-distearyl adipic acid amide, N,N'-distearyl sebacic acid amide, methylene bisoleic acid amide, ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipic acid amide, N,N'-dioleyl sebacic acid amide, m-xylylene bisstearic acid amide, and N,N'-distearyl isophthalic acid amide The combination of lubricants according to claim 3, which contains at least one selected.

6. ​ A powder mixture comprising a raw material powder and a combination of lubricants according to any one of claims 1 to 5.

7. A combination of raw materials for a powder mixture comprising a raw material powder and a combination of lubricants according to any one of claims 1 to 5.

8. A method for manufacturing a sintered body by sintering a powder mixture obtained from the powder mixture according to claim 6 or the combination of raw materials for the powder mixture according to claim 7.

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