Lubricant combinations, powder mixtures, combinations of raw materials for powder mixtures, and methods for manufacturing sintered bodies.

Abstract

To provide: a combination of lubricants capable of improving extractability of a compact and further capable of producing a sintered compact with suppressed poor appearance; a powder mixture containing the combination of the lubricants and a combination of raw materials for powder mixture; and a method for producing a sintered compact using the powder mixture or the combination of the raw materials for powder mixture.SOLUTION: A combination of lubricants comprises a lubricant A having a melting point of 60°C to 85°C and a metal soap-based lubricant B. When sieved using a JIS standard sieve, a proportion of particles having a particle size of 63 μm or less is 88 mass% or more relative to a total amount of the combination of the lubricants.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a combination of lubricants, a powder mixture, a combination of raw materials for the powder mixture, and a method for manufacturing a sintered body.

Background Art

[0002] Generally, lubricants are used for lubrication, for example, to reduce the 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 (powder lubricants) are used.

[0003] Among powder metallurgy methods, particularly in die forming, in order to reduce the friction between the die wall surface and the compacted powder, a powder mixture in which a powder lubricant is usually mixed into the raw material powder is generally used. The powder mixture is obtained by mixing a secondary raw material powder such as copper powder, graphite powder, powder for improving machinability, etc. and a powder lubricant with an iron-based powder as the main raw material powder.

[0004] Since the powder mixture contains a powder lubricant, powder properties such as fluidity and compactibility in the powder mixture are improved, and it becomes easier to extract the compression-molded compact from the die. Examples of powder lubricants 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 in consideration of its miscibility with the metal powder, powder properties when made into a powder mixture, extractability of the compact after compression molding, dissipation of the lubricant when sintering the compact, etc. Among these, zinc stearate is widely used as a lubricant from the viewpoints of relatively excellent lubricating properties and cost. Such lubricants are generally used by being premixed into the powder mixture. There is also a method of applying the lubricant to the die wall surface, but since special equipment is required, the manufacturing cost of the sintered body becomes relatively high.

[0006] However, metal soap-based lubricants, such as zinc stearate, have the problem of contaminating product surfaces, exhaust ducts, etc., during the sintering of compacted powders, and there is a desire to replace them with organic lubricants (wax-based lubricants). As organic lubricants, in addition to the lubricants described in Patent Documents 1 and 2, amide 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 [Overview of the project] [Problems that the invention aims to solve]

[0008] When a powder mixture with added lubricant is compression molded using a mold, it is desirable that the molded body be easy to remove from the mold, that is, that the molded body has excellent ejectability. Similarly, for sintered bodies formed by sintering the molded body, surface irregularities are prone to causing surface defects, so it is desirable that surface defects can be suppressed.

[0009] The present disclosure aims to provide a combination of lubricants that can improve the ejectability of molded articles and produce sintered articles with suppressed appearance defects, a combination of powder mixtures and raw materials for powder mixtures containing the lubricant combination, and a method for manufacturing sintered articles using the powder mixture or the combination of raw materials for powder mixtures. [Means for solving the problem]

[0010] The specific means for achieving the aforementioned objectives are as follows: <1> Lubricant A has a melting point of 60°C to 85°C, It contains 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% by mass or more of the total amount of the lubricant combination. <2> The lubricant A comprises at least one selected from the group consisting of oleamide, erucamide, ricinoleamide, N-oleyloleamide, N-stearyloleamide, N-oleylstearateamide, N-stearylerucamide, N-oleylpalmitamide, N-oleylhydroxystearateamide, stearic acid, and N-oleylpalmitamide. <1> The lubricant combinations listed. <3> The aforementioned 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> The lubricant combinations listed. <4> When sieved using a JIS standard sieve with a mesh size of 150 μm, the percentage of particles that do not pass through the sieve is 5% by mass or less relative to the total amount of lubricant. <1> ~ <3> A combination of lubricants listed in any one of the following. <5> It further contains lubricant C, which is a fatty acid bisamide. <1> ~ <4> A combination of lubricants listed in any one of the following. <6> The melting point of the lubricant C is 140°C or higher and less than 150°C. <5> The lubricant combinations listed. <7> The lubricant C is methylenebisstearate, methylenebislaurate, methylenebishydroxystearate, ethylenebiscaprylate, ethylenebiscaprate, ethylenebislaurate, ethylenebisstearate, ethylenebisisostearate, ethylenebishydroxystearate, ethylenebisbehenamide, hexamethylenebisstearate, hexamethylenebisbehenamide, hexamethylenebishydroxystearate It comprises at least one selected from the group consisting of nitrate amide, butylene bishydroxystearamide, N,N'-distearyl adipic acid amide, N,N'-distearyl sebacinate amide, methylene bisoleamide, ethylene bisoleamide, ethylene biserucate amide, hexamethylene bisoleamide, N,N'-dioleyl adipic acid amide, N,N'-dioleyl sebacinate amide, m-xylylene bisstearamide, and N,N'-distearyl isophthalate amide. <5> The lubricant combinations listed. <8> Raw material powder and <1> ~ <7> A powder mixture containing any one of the lubricant combinations listed in the following. <9> Raw material powder and <1> ~ <7> A combination of lubricants described in any one of the following, and a combination of raw materials for powder mixtures containing the above. <10> <8> The powder mixture described above or <9> A method for producing a sintered body, comprising sintering a powder mixture obtained from the combination of raw materials for powder mixtures described above. [Effects of the Invention]

[0011] According to this disclosure, it is possible to provide a combination of lubricants that can improve the ejectability of molded articles and produce sintered articles with suppressed appearance defects, a combination of powder mixtures and raw materials for powder mixtures that include the lubricant combination, and a method for manufacturing sintered articles using the powder mixture or the combination of raw materials for powder mixtures. [Modes for carrying out the invention]

[0012] The following describes the combinations of lubricants, powder mixtures, combinations of raw materials for powder mixtures, and methods for manufacturing sintered bodies according to this disclosure. However, this disclosure is not limited to the following embodiments. In the following embodiments, the components (including elemental steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present invention. In this disclosure, the numerical range indicated using "~" represents a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples. In this disclosure, each component may contain multiple substances. If multiple substances exist for each component, the content or amount of each component means the total content or amount of those multiple substances unless otherwise specified. In this disclosure, each component may include multiple types of particles. If multiple types of particles exist for each component, the particle size of each component refers to the value for a mixture of such multiple types of particles, unless otherwise specified.

[0013] [Combinations of lubricants] The lubricant combination of this disclosure comprises lubricant A having a melting point of 60°C to 85°C and metal soap-based lubricant B, wherein when sieved using a JIS standard sieve, the proportion of particles with a particle size of 63 μm or less is 88% by mass or more of the total amount of the lubricant combination.

[0014] By using the combination of lubricants of the present disclosure, the extractability of the molded body can be improved, and furthermore, a sintered body with suppressed appearance defects can be manufactured. More specifically, the combination of lubricants of the present disclosure includes a lubricant A with a relatively low melting point, which makes it easier to extract the molded body from the mold, that is, the extractability of the molded body tends to be improved. Furthermore, when sieved, the proportion of particles with a particle size of 63 μm or less is 88% by mass or more based on the total amount of the lubricant. Thereby, in the sintered body obtained by sintering the molded body, it is possible to manufacture a sintered body in which the surface irregularities are reduced and appearance defects are suppressed.

[0015] When using lubricant A, the fluidity of the powder mixture tends to decrease slightly. By combining lubricant A with a metal soap-based lubricant B, the fluidity of the powder mixture can be greatly enhanced. Therefore, in the combination of lubricants of the present disclosure, the fluidity of the powder mixture tends to be good. By using lubricant A and the metal soap-based lubricant B in combination, the amount of the metal soap-based lubricant B used can be reduced.

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

[0017] In the combination of lubricants of the present disclosure, when sieved using a JIS standard sieve, the proportion of particles with a particle size of 63 μm or less is 88% by mass or more based on the total amount of the combination of lubricants. Thereby, in the sintered body obtained by sintering the molded body, it is possible to manufacture a sintered body in which the surface irregularities are reduced and appearance defects are suppressed. In the present disclosure, the proportion of particles with a particle size less than a specific particle size (for example, 63 μm or less) is defined as the proportion of particles passing through the sieve when the lubricant is sieved with a JIS standard sieve having a mesh size of the specific particle size (for example, 63 μm).

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

[0019] The particle size used as the criterion for sieving is not limited to 63 μm or less; it may be 50 μm or less, or 43 μm or less. For example, the proportion of particles with a particle size of 50 μm or less may be 88% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass, relative to the total amount of lubricant. The proportion of particles with a particle size of 43 μm or less may be 88% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass, relative to the total amount of lubricant.

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

[0021] In the lubricant combinations of this disclosure, the proportion 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, relative to the total amount of the lubricant combination, from the viewpoint of effectively suppressing defects in the appearance of the sintered body. The aforementioned proportion of particles may be 0% by mass or 0.5% by mass or more, relative to the total amount of the lubricant combination.

[0022] When the lubricant combination of the present disclosure consists of lubricant A and metal soap-based lubricant B, the proportion of particles with a particle size of 63 μm or less when sieved using a JIS standard sieve should be 88% by mass or more relative to the total amount of lubricant A and metal soap-based lubricant B. When the lubricant combination of the present disclosure consists of lubricant A, metal soap-based lubricant B and lubricant C described later, the proportion of particles with a particle size of 63 μm or less when sieved using a JIS standard sieve should be 88% by mass or more relative to the total amount of lubricant A, metal soap-based lubricant B and lubricant C described later.

[0023] In this disclosure, the lubricant combination may be a mixture of lubricants containing at least lubricant A and metal soap-based lubricant B, or it may be a combination of lubricants containing lubricant A and lubricants containing metal soap-based lubricant B prepared separately without mixing. For example, in the case of a combination of lubricants containing lubricant A and lubricants containing metal soap-based lubricant B prepared separately without mixing, the lubricant containing lubricant A and the lubricant containing metal soap-based lubricant B may be mixed when manufacturing the powder mixture. If necessary, lubricant C, etc., as described later, may be added to the mixture. The lubricant containing lubricant C, etc., may be prepared separately from the lubricant containing lubricant A and the lubricant containing metal soap-based lubricant B.

[0024] (Lubricant A) The lubricant combinations of this disclosure include lubricant A having a melting point of 60°C to 85°C. The lubricant combinations may include one type of lubricant A, or two or more types of lubricant A. In this disclosure, the melting point is a value measured by differential scanning calorimetry (DSC).

[0025] Lubricant A preferably contains at least one selected from the group consisting of oleamide, erucamide, ricinoleamide, N-oleyloleamide, N-stearyloleamide, N-oleylstearamide, N-stearylerucamide, N-oleylpalmitamide, N-oleylhydroxystearamide, stearic acid, and N-oleylpalmitamide, and more preferably contains at least one selected from the group consisting of oleamide, erucamide, ricinoleamide, stearic acid, and N-oleylpalmitamide. In particular, from the viewpoint of the ease of extraction of the molded article, it is more preferable to contain at least one of erucamide and oleamide.

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

[0027] (Metal soap-based lubricant B) The lubricant combinations of this disclosure include metal soap-based lubricants B. The lubricant combinations may include one type of metal soap-based lubricant B, or two or more types of metal soap-based lubricants B.

[0028] Examples of metal soap-based lubricants B include metal salts 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] Fatty acids having 12 to 22 carbon atoms may be saturated fatty acids with 12 to 22 carbon atoms, or unsaturated fatty acids with 12 to 22 carbon atoms. The number of carbon atoms in a fatty acid may be 16 to 20, or 16 to 18.

[0030] Examples of fatty acids with 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 metal soap-based lubricants B include lithium stearate, calcium stearate, barium stearate, and zinc stearate.

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

[0033] The mass ratio of lubricant A to metal soap-based lubricant B, which is lubricant A: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, from the viewpoint of balancing the fluidity of the powder mixture and the ease of extracting the molded product.

[0034] (Lubricant C) The lubricant combinations of this disclosure may include lubricant C, which is a fatty acid bisamide. The lubricant combinations may include one type of lubricant C, or two or more types of lubricant C.

[0035] The melting point of lubricant C may be 140°C or higher but less than 150°C, or 140°C or higher but 148°C or lower.

[0036] Examples of lubricant C include methylenebisstearate, methylenebislaurate, methylenebishydroxystearate, ethylenebiscaprylate, ethylenebiscaprate, ethylenebislaurate, ethylenebisstearate, ethylenebisisostearate, ethylenebishydroxystearate, ethylenebisbehenamide, hexamethylenebisstearate, hexamethylenebisbehenamide, hexamethylenebis Examples include hydroxystearamide, butylene bishydroxystearamide, N,N'-distearyl adipic acid amide, N,N'-distearyl sebacinate amide, methylene bisoleamide, ethylene bisoleamide, ethylene biserucate amide, hexamethylene bisoleamide, N,N'-dioleyl adipic acid amide, N,N'-dioleyl sebacinate amide, m-xylylene bisstearamide, and N,N'-distearyl isophthalamide. Among these, lubricant C is more preferably ethylene bisstearamide from the viewpoint of the fluidity of the powder mixture.

[0037] When the lubricant combination 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 is, from the viewpoint of balancing the fluidity of the powder mixture and the ease of extraction of the molded product, preferably, lubricant A is at least one selected from the group consisting of erucic acid amide and oleic acid amide, metal soap-based lubricant B is zinc stearate, and lubricant C is ethylenebisstearamide.

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

[0039] The mass ratio of lubricant A to lubricant C, lubricant A: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, from the viewpoint of balancing the fluidity of the powder mixture and the ease of extracting the molded product.

[0040] The mass ratio of lubricant A to the total of metal soap-based lubricants B and C, i.e., lubricant A:metal soap-based lubricants B and 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 balancing the fluidity and compactibility of the powder mixture and the ease of extracting the molded product. The mass ratio of metal soap lubricant B to lubricant C, i.e., metal soap 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 balancing the fluidity and compactibility of the powder mixture and the ease of extraction of the molded product.

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

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

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

[0044] The content of other lubricants relative to the total amount of the lubricant combination may be greater than 0% by mass and 50% by mass or less, 5% by mass to 40% by mass, or 10% by mass to 20% by mass.

[0045] [Powder mixture] The powder mixture of this disclosure comprises a raw material powder and a combination of the lubricant of this disclosure described above. By using this powder mixture, the ejectability of the molded article can be improved, and a sintered article with suppressed surface defects can be manufactured. The powder mixture of this disclosure is preferably used, for example, for powder metallurgy.

[0046] Examples of raw material powders include main raw material powders containing iron as the main component, and auxiliary raw material powders that improve the properties of the sintered body. Furthermore, "containing iron as the main component" means that the iron content in the raw material powder is 50% by mass or more of the total raw material powder.

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

[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 this disclosure, the average particle diameter is the particle diameter (D50) at which the cumulative total from the smaller diameter side in the volume-based particle size distribution measured by laser diffraction is 50%.

[0049] Iron-based powder can be produced, for example, by atomizing molten iron or a molten iron alloy into fine particles, then reducing the fine particles, and finally grinding 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 include powders that improve the mechanical properties of the sintered body such as hardness and toughness, and powders that improve the machinability of the sintered body.

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

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

[0053] Examples of inorganic powders include 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; and powders of 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 raw material powder, the content of the main raw material powder is preferably 90 to 99 parts by mass, and more preferably 95 to 98 parts by mass.

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

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

[0058] (Other ingredients) The powder mixture of this disclosure may contain other components besides the raw material powder and the lubricant of this disclosure. Other components include binders. The inclusion of a binder in the powder mixture tends to suppress segregation, scattering, etc., of the raw material powder.

[0059] The binder is not particularly limited and includes polyolefins, acrylic resins, polystyrene, styrene-butadiene rubber, ethylene glycol distearate, epoxy resins, rosin esters, and the like.

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

[0061] The powder mixtures of the present disclosure are obtained by mixing raw material powders with the lubricant combination of the present disclosure and, if necessary, other components. The mixing of raw material powders with the lubricant combination of the present disclosure can be carried out using commonly used mixers such as impeller mixers, V-type mixers, and double-cone mixers (W-cones).

[0062] The combination of raw materials for powder mixtures of this disclosure includes a raw material powder and a combination of lubricants of this disclosure. The combination of raw materials for powder mixtures of this disclosure may be a mixture of the raw material powder and the combination of lubricants. Alternatively, it may be a combination of the raw material powder and the combination of lubricants of this disclosure prepared separately without mixing, or the raw material powder and the combination of lubricants of this disclosure may be mixed and used when manufacturing a molded article. The preferred conditions for the combination of raw materials for the powder mixtures of this disclosure are the same as those for the powder mixtures of this disclosure described above, and therefore their explanation is omitted.

[0063] [Method for manufacturing sintered bodies] The method for manufacturing a sintered body according to the present disclosure is a method for manufacturing a sintered body by sintering a powder mixture obtained from the aforementioned powder mixture or a combination of raw materials for the aforementioned powder mixture. The method for manufacturing a sintered body according to the present disclosure preferably includes filling a powder mixture into a mold, compressing the powder mixture filled into the mold to form a molded body, and sintering the molded body removed from the mold.

[0064] The method for manufacturing a sintered body according to this disclosure makes it possible to improve the ease of removing the molded body by using the aforementioned powder mixture, and to manufacture a sintered body with suppressed surface defects.

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

[0066] In the method for manufacturing a sintered body according to this disclosure, a sintered body is manufactured by sintering a powder mixture, preferably by sintering a molded body extracted from a mold. The conditions for sintering the powder mixture or the molded body are not particularly limited, and a conventional sintering method can be employed. [Examples]

[0067] The present disclosure will be described in more detail below based on the following examples. However, the present invention is not limited to the following examples.

[0068] [Examples 1-50 and Comparative Examples 1-120] As the main raw material powder, atomized iron powder for powder metallurgy with an average particle size of 75 μm was prepared, and as secondary raw material powders, electrolytic copper powder with an average particle size of 30 μm and graphite powder with an average particle size of 10 μm were prepared. 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) or a lubricant mixture of lubricant A, metal soap-based lubricant B and lubricant C, as shown in Tables 1 to 3 and below, was added to 97.5 parts by mass of iron powder, 1.5 parts by mass of copper powder and 1.0 part by mass of graphite powder. In each example and comparative example, a lubricant mixture was used in which, when sieved using a JIS standard sieve, the proportion of particles with a particle size of 63 μm or less was the value shown in Tables 1 to 3 relative to the total amount of lubricant. The proportions of lubricant A, metal soap-based lubricant B and lubricant C in each example and comparative example are shown in Tables 1 to 3. Subsequently, the mixture of raw material powder and lubricant was placed in a V-type mixer and mixed for 30 minutes to obtain the powder mixtures for each example and each comparative example. <Lubricant A> Erucic acid amide (melting point: 78°C~81°C) Oleamide (melting point: 75°C) <Metal soap-based lubricant B (referred to as Lubricant B in the table)> Zinc stearate <Lubricant C> Ethylene bis-stearamide (melting point: 145°C)

[0069] (Fluidity of powder mixtures) The fluidity of the powder mixtures obtained in each example and comparative example was evaluated according to the fluidity test method specified in JIS Z 2502 (2012). The evaluation criteria are as follows. -Evaluation Criteria- A powder mixture flowed within 30 seconds. B. The powder mixture flowed between 30 and 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. A rating of A or B indicates good fluidity of the powder mixture.

[0070] (Compactness of powder mixtures) The compaction properties of the powder mixtures obtained in each example and comparative example were evaluated by supplying 7 g of the powder mixture into a mold, then forming a cylindrical molded body with a diameter of 11.3 mm at a molding pressure of 700 MPa, and the evaluation was carried out according to the following criteria. -Evaluation Criteria- The density of the cylindrical molded body is 7.10 g / cm³. 3 That was all. The density of the cylindrical molded body is 7.06 g / cm³. 3 More than 7.10g / cm 3 It was less than [amount missing]. The density of the cylindrical molded body is 7.06 g / cm³. 3 It was less than [amount missing]. The results are shown in Tables 1 to 3. A rating of A or B indicates good compaction of the powder mixture.

[0071] (Extractability of cylindrical molded bodies) The ejectability of the cylindrical molded bodies in each example and comparative example was evaluated by measuring the ejection pressure when removing the cylindrical molded bodies used to evaluate the compaction properties of the aforementioned powder mixture from the mold, based on the following criteria. -Evaluation Criteria- A. The extraction pressure was 8 MPa or less. B. The extraction pressure was between 8 MPa and 15 MPa. The extraction pressure was over 15 MPa. The results are shown in Tables 1 to 3. A rating of A or B indicates good extractability of the cylindrical molded body.

[0072] (Evaluation of appearance) The appearance of each example and comparative example was evaluated by visually inspecting the surface of a sintered body, which was obtained by firing the cylindrical molded body used for evaluating the compaction of the aforementioned powder mixture at approximately 1100°C in nitrogen, and evaluating it based on the following criteria. -Evaluation Criteria- No surface roughness caused by surface irregularities was observed on the surface of the sintered body. Roughness caused by surface irregularities was observed on the surface of the C sintered body. The results are shown in Tables 1 to 3. A rating of A indicates 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 manufacture sintered bodies with excellent ejectability and suppressed surface defects.

[0077] All documents, patent applications, and technical standards described herein are incorporated by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

Claims

1. Lubricant A has a melting point of 60°C to 85°C, It contains a metal soap-based lubricant B, which is a metal salt of a fatty acid having 12 to 22 carbon atoms and a metal, A combination of powdered lubricants used in powder metallurgy mold forming methods, in which, when sieved using a JIS standard sieve, the proportion of particles with a particle size of 63 μm or less is 88% by mass or more of the total amount of the lubricant combination.

2. The combination of lubricants according to claim 1, wherein the lubricant A comprises at least one selected from the group consisting of N-oleyloleamide, N-stearyloleamide, N-oleylstearateamide, N-stearylerucamide, N-oleylpalmitamide, N-oleylhydroxystearateamide, and N-oleylpalmitamide.

3. The combination of lubricants according to claim 1 or claim 2, wherein the metal soap-based lubricant B comprises 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.

4. The combination of lubricants according to any one of claims 1 to 3, wherein the fatty acid having 12 to 22 carbon atoms is lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, linoleic acid, linolenic acid, oleic acid, or erucic acid.

5. The lubricant combination according to any one of claims 1 to 4, wherein the proportion of particles that do not pass through a JIS standard sieve with a mesh size of 150 μm when sieved is 5% by mass or less of the total amount of lubricant.

6. A combination of lubricants according to any one of claims 1 to 5, further comprising lubricant C, which is a fatty acid bisamide.

7. The lubricant combination according to claim 6, wherein the melting point of the lubricant C is 140°C or higher and less than 150°C.

8. The lubricant C is methylenebisstearate, methylenebislaurate, methylenebishydroxystearate, ethylenebiscaprylate, ethylenebiscaprate, ethylenebislaurate, ethylenebisstearate, ethylenebisisostearate, ethylenebishydroxystearate, ethylenebisbehenamide, hexamethylenebisstearate, hexamethylenebisbehenamide, hexamethylenebishydroxystearate, butylene The combination of lubricants according to claim 6, comprising at least one selected from the group consisting of bishydroxystearamide, N,N'-distearyl adipic acid amide, N,N'-distearyl sebacinate amide, methylene bisoleamide, ethylene bisoleamide, ethylene biserucate amide, hexamethylene bisoleamide, N,N'-dioleyl adipic acid amide, N,N'-dioleyl sebacinate amide, m-xylylene bisstearamide, and N,N'-distearyl isophthalamide.

9. A powder mixture comprising a raw material powder and a combination of the lubricant described in any one of claims 1 to 8.

10. A combination of raw materials for a powder mixture, comprising a raw material powder and a combination of the lubricant described in any one of claims 1 to 8.

11. A method for producing a sintered body, comprising sintering a powder mixture obtained from the powder mixture described in claim 9 or the combination of raw materials for the powder mixture described in claim 10.

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