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

Abstract

A lubricant of the present invention includes a lubricant A, which has a melting point of 60–85°C, 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.

Description

Technical Field

[0001] The present disclosure relates to lubricants, combinations of lubricants, powder mixtures, combinations of raw materials for powder mixtures, and methods for manufacturing sintered compacts.

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 used. The powder mixture is obtained by mixing, for example, copper powder, graphite powder, powder for improving machinability, etc. as auxiliary raw material powders and powder lubricant with iron-based powder as the main raw material powder.

[0004] When 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), fatty acid amide-based lubricants, and mixtures of metal soap-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 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 them, zinc stearate is widely used as a lubricant from the viewpoints of relatively excellent lubricating properties and cost. Such lubricants are generally used after being previously mixed into the powder mixture. There is also a method of applying the lubricant to the die wall surface, but since a special device is required, the manufacturing cost of the sintered compact 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 Initiative] [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 lubricant and a combination of lubricants that can improve the ejectability of molded articles and produce sintered articles with suppressed surface defects, a powder mixture containing the lubricant or a combination of lubricants and a combination of raw materials for the powder mixture, and a method for manufacturing a sintered article using the powder mixture or a combination of raw materials for the powder mixture. [Means for solving the problem]

[0010] The specific means for achieving the aforementioned objectives are as follows: <1> A lubricant containing lubricant A having a melting point of 60°C to 85°C, wherein the proportion of particles with a particle size of 63 μm or less is 88% by mass or more of the total amount of lubricant. <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 described above. <3> The proportion of particles with a diameter larger than 150 μm is 5% by mass or less of the total amount of lubricant. <1> or <2> The lubricant described above. <4> Lubricant A has a melting point of 60°C to 85°C, It contains lubricant B, which is a fatty acid bisamide, A combination of lubricants in which 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. <5> The total content of lubricant A and lubricant B relative to the total amount of the lubricant combination is 60% by mass or more. <4> The lubricant combinations listed. <6> The proportion of lubricant particles with a particle size smaller than 10 μm is 10% by mass or more of the total amount of lubricant in the combination. <4> or <5> The lubricant combinations listed. <7> 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. <4> ~ <6> A combination of lubricants listed in any one of the following. <8> The melting point of the lubricant B is 140°C or higher and less than 150°C. <4> ~ <7> A combination of lubricants listed in any one of the following. <9> The lubricant B 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. <4> ~ <8> A combination of lubricants listed in any one of the following. <10> The lubricant A comprises at least one selected from the group consisting of erucic acid amide and oleic acid amide. The lubricant B comprises ethylenebisstearamide. <4> ~ <6> A combination of lubricants listed in any one of the following. <11> The mass ratio of lubricant A to lubricant B, i.e., lubricant A:lubricant B, is 1:9 to 9:1. <4> ~ <10> A combination of lubricants listed in any one of the following. <12> The proportion of particles with a particle size larger than 150 μm is 5% by mass or less of the total amount of the lubricant combination. <4> ~ <11> A combination of lubricants listed in any one of the following. <13> Raw material powder and <1> ~ <3> Any one of the lubricants or <4> ~ <12> A powder mixture containing any one of the lubricant combinations listed in the following. <14> Raw material powder and <1> ~ <3> Any one of the lubricants or <4> ~ <12> A combination of lubricants described in any one of the following, and a combination of raw materials for powder mixtures containing the above. <15> <13> The powder mixture described above or <14> 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 lubricant and a combination of lubricants that can improve the ejectability of molded articles and produce sintered articles with suppressed surface defects, a powder mixture and a combination of raw materials for the powder mixture containing the lubricant or the combination of lubricants, and a method for manufacturing a sintered article using the powder mixture or the combination of raw materials for the powder mixture. [Modes for carrying out the invention]

[0012] The following describes the lubricants, lubricant combinations, 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 the present disclosure, there may be multiple types of particles corresponding to each component. When there are multiple types of particles corresponding to each component, unless otherwise specified, the particle size of each component means the value for the mixture of the multiple types of particles.

[0013] [Lubricant] The lubricant of the present disclosure contains lubricant A with a melting point of 60°C to 85°C and is a lubricant in which 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.

[0014] By using the lubricant of the present disclosure, the extractability of the molded body can be improved, and a sintered body with suppressed appearance defects can be manufactured. More specifically, the lubricant of the present disclosure contains 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, 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. As a result, it is possible to manufacture a sintered body in which the surface unevenness is reduced and appearance defects are suppressed in the sintered body formed by sintering the molded body.

[0015] The lubricant of the present disclosure is preferably used, for example, for powder metallurgy. The lubricant of the present disclosure may also be used for applications other than powder metallurgy.

[0016] From the viewpoint of suitably suppressing appearance defects of the sintered body, 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 based on the total amount of the lubricant. In the present disclosure, the "proportion of particles with a particle size less than a specific particle size (for example, 63 μm or less)" can be derived by determining the proportion of particles passing through a sieve when sieving with a JIS standard sieve with a mesh opening of the specific particle size (for example, 63 μm), or by determining the integrated value (mass basis) of particles with a particle size less than the specific particle size (for example, 63 μm) after classification by a pneumatic classification method or the like and then measuring the particle size distribution.

[0017] The particle size used as the criterion for sieving or classification is not limited to 63 μm or less, but 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 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 90% by mass or more, 95% by mass or more, or 100% by mass, relative to the total amount of lubricant.

[0018] 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.

[0019] In the lubricant of this disclosure, the proportion of particles with a particle size larger than 150 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, from the viewpoint of effectively suppressing defects in the appearance of the sintered body. The proportion of the aforementioned particles may be 0% by mass or 0.5% by mass or more, based on the total amount of the lubricant. In this disclosure, the "percentage of particles with a particle diameter larger than a specific particle diameter (for example, larger than 150 μm)" can be derived by determining the percentage of particles that do not pass through a JIS standard sieve with an opening of the specific particle diameter (for example, 150 μm), or by determining the cumulative value (by mass) of particles with a particle size distribution of less than or equal to the specific particle diameter (for example, 150 μm) after classification by wind classification or the like, and then subtracting the obtained cumulative value (by mass) from 100% by mass.

[0020] If the lubricant of this disclosure consists of lubricant A, the proportion of particles with a particle size of 63 μm or less should be 88% by mass or more of the total amount of lubricant A. If the lubricant of this disclosure consists of lubricant A and lubricants other than lubricant A, the proportion of particles with a particle size of 63 μm or less should be 88% by mass or more of the total amount of lubricant A and lubricants other than lubricant A.

[0021] (Lubricant A) The lubricant of this disclosure comprises lubricant A having a melting point of 60°C to 85°C. The lubricant may contain one type of lubricant A, or it may contain two or more types of lubricant A. In this disclosure, the melting point is a value measured by differential scanning calorimetry (DSC).

[0022] 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, lubricant A preferably contains at least one of erucamide and oleamide, and more preferably erucamide.

[0023] The content of lubricant A may be 50% to 100% by mass, 70% to 100% by mass, or 90% to 100% by mass, relative to the total amount of lubricant.

[0024] (Lubricants other than lubricant A) The lubricant of this disclosure may contain lubricants other than lubricant A. Examples of lubricants other than lubricant A include fatty acid amides with a melting point exceeding 85°C, metal soap-based lubricants, etc. When using lubricants other than lubricant A, one type may be used alone, or two or more types may be used in combination.

[0025] 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.

[0026] Examples of metal soap-based lubricants include metal salts of fatty acids having 12 to 22 carbon atoms and at least one metal selected from the group consisting of lithium, magnesium, calcium, barium, zinc, and strontium.

[0027] The fatty acids having 12 to 22 carbon atoms may be saturated fatty acids or unsaturated fatty acids. The number of carbon atoms in the fatty acid may be 16 to 20 or 16 to 18.

[0028] 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.

[0029] Specific examples of metal soap-based lubricants include lithium stearate, calcium stearate, barium stearate, and zinc stearate.

[0030] The content of lubricants other than lubricant A relative to the total amount of lubricant may be greater than 0% by mass and 50% by mass or less, or 5% to 40% by mass, or 10% to 20% by mass. In this case, the total content of lubricant A and lubricants other than lubricant A should be 100% by mass.

[0031] [Combinations of lubricants] The lubricant combination of this disclosure comprises lubricant A, which has a melting point of 60°C to 85°C, and lubricant B, which is a fatty acid bisamide, wherein 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.

[0032] By using the lubricant combination disclosed herein, the fluidity of the powder mixture and the ease of removing the molded body can be improved, and a sintered body with suppressed surface defects can be manufactured. By combining lubricant A and lubricant B, the fluidity of the powder mixture can be improved while also improving the ease of removing the molded body.

[0033] In this disclosure, the lubricant combination may be a mixture of lubricants containing at least lubricant A and lubricant B, or it may be a combination of lubricants containing lubricant A and lubricants containing lubricant B prepared separately without mixing. For example, in the case of a combination of lubricants containing lubricant A and lubricants containing lubricant B prepared separately without mixing, the lubricants containing lubricant A and lubricants containing lubricant B may be mixed when producing the powder mixture.

[0034] In the lubricant combinations of this disclosure, 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.

[0035] The particle size used as the standard for sieving or classification is not limited to 63 μm or less; it may be 50 μm or less, or 43 μm or less.

[0036] In the lubricant combinations of this disclosure, the proportion of particles with a particle size larger than 150 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 effectively suppressing defects in the appearance of the sintered body. The proportion of the aforementioned particles may be 0% by mass or 0.5% by mass or more, based on the total amount of the lubricant combination.

[0037] The composition of lubricant A included in the lubricant combination of this disclosure is the same as the composition of lubricant A included in the lubricant of this disclosure described above, so no explanation is given.

[0038] (Lubricant B) The lubricant combinations of this disclosure include lubricant B, which is a fatty acid bisamide. The lubricant combinations may include one type of lubricant B, or two or more types of lubricant B.

[0039] The melting point of lubricant B may be 140°C or higher but less than 150°C, or 140°C or higher but 148°C or lower.

[0040] Examples of lubricant B 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 sebacin acid amide, methylene bisoleamide, ethylene bisoleamide, ethylene biserucic acid amide, hexamethylene bisoleamide, N,N'-dioleyl adipic acid amide, N,N'-dioleyl sebacin acid amide, m-xylylene bisstearamide, and N,N'-distearyl isophthalamide. Among these, lubricant B is more preferably ethylene bisstearamide from the viewpoint of the fluidity of the powder mixture.

[0041] A preferred combination of lubricant A and lubricant B is one in which, from the viewpoint of balancing the fluidity of the powder mixture and the ease of extraction of the molded product, lubricant A preferably contains at least one selected from the group consisting of erucic acid amide and oleic acid amide, and lubricant B preferably contains ethylenebisstearic acid amide. The total content of erucic acid amide and oleic acid amide in lubricant A is preferably 50% to 100% by mass, more preferably 70% to 100% by mass, and even more preferably 90% to 100% by mass. The content of ethylenebisstearate in lubricant B is preferably 50% to 100% by mass, more preferably 70% to 100% by mass, and even more preferably 90% to 100% by mass.

[0042] The mass ratio of lubricant A to lubricant B, lubricant A:lubricant B, 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 of the powder mixture and the ease of extracting the molded product.

[0043] The combined content of lubricant A and lubricant B relative to the total amount of lubricant combination is preferably 50% to 100% by mass. Alternatively, the combined content of lubricant A and lubricant B may be 60% to 95% by mass, or 80% to 90% by mass. From the viewpoint of improving the fluidity of the powder mixture and reducing graphite segregation, the total content of lubricant A and lubricant B in the lubricant combination is preferably 60% by mass or more, more preferably 70% to 100% by mass, even more preferably 80% to 100% by mass, and particularly preferably 90% to 100% by mass.

[0044] The proportion of lubricant particles with a particle size smaller than 10 μm is preferably 10% by mass or more, more preferably 15% to 50% by mass, even more preferably 20% to 40% by volume, and particularly preferably 25% to 35% by mass, relative to the total amount of lubricant combined. A proportion of lubricant particles with a particle size smaller than 10 μm of 10% by mass or more tends to reduce graphite segregation.

[0045] (Other lubricants) The lubricant combinations of this disclosure may include lubricants other than lubricant A and lubricant B. Examples of other lubricants include amide lubricants other than lubricant A and lubricant B, and the aforementioned metal soap lubricants. Examples of amide lubricants other than lubricant A and lubricant B include fatty acid amides with a melting point exceeding 85°C. Other lubricants may be used individually or in combination of two or more types.

[0046] The content of other lubricants relative to the total amount of 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. In this case, the total content of lubricant A, lubricant B, and other lubricants should be 100% by mass. The content of other lubricants relative to the total amount of lubricant combination is preferably 40% by mass or less, more preferably 0% to 30% by mass, even more preferably 0% to 20% by mass, and particularly preferably 0% to 10% by mass, from the viewpoint of fluidity of the powder mixture and reduction of graphite segregation.

[0047] [Powder mixture] The powder mixture of this disclosure comprises a raw material powder and the lubricant of this disclosure as described above or a combination of the lubricants of this disclosure as 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.

[0048] 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.

[0049] 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.

[0050] 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%.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] Examples of metal powders include copper, nickel, chromium, molybdenum, tin, vanadium, and manganese.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] With respect to 100 parts by mass of raw material powder, the content of lubricant and the content of lubricant combination are 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, respectively.

[0060] (Other ingredients) The powder mixture of this disclosure may contain other components besides the raw material powder, the lubricant of this disclosure, and combinations of the lubricants of this disclosure. Examples of other components include binders. The inclusion of a binder in the powder mixture tends to suppress segregation, scattering, etc., of the raw material powder.

[0061] 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.

[0062] 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.

[0063] The powder mixtures of the present disclosure are obtained by mixing raw material powders with the lubricant of the present disclosure or a combination of the lubricants of the present disclosure and, if necessary, other components. The mixing of raw material powders with the lubricant of the present disclosure or a combination of the lubricants of the present disclosure can be carried out using commonly used mixers such as a vane mixer, a V-type mixer, or a double-cone mixer (W-cone).

[0064] The combination of raw materials for powder mixtures of this disclosure includes raw material powder and the lubricant of this disclosure or a combination of the lubricants of this disclosure. The combination of raw materials for powder mixtures of this disclosure may be a mixture of raw material powder and lubricant or a mixture of raw material powder and lubricant. Alternatively, it may be a combination of raw material powder and the lubricant of this disclosure or a combination of the lubricants of this disclosure prepared separately without mixing, and the raw material powder and the lubricant of this disclosure or a combination of the 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.

[0065] [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.

[0066] 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.

[0067] 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.

[0068] 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]

[0069] 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.

[0070] [Examples 1-14 and Comparative Examples 1-14] 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 lubricant A or a mixture of lubricant A and lubricant B shown in Table 1 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, lubricant A and lubricant mixture were used in which the proportion of particles with a particle size of 63 μm or less, when sieved using a JIS standard sieve, was the value shown in Table 1 relative to the total amount of lubricant. The proportions of lubricant A and lubricant B in each example and comparative example are shown in Table 1. After that, the mixture of raw material powder and lubricant was put into a V-type mixer and mixed for 30 minutes to obtain the powder mixture for each example and comparative example. <Lubricant A> Erucic acid amide (melting point: 78°C~81°C) Oleamide (melting point: 75°C) <Lubricant B> Ethylene bis-stearamide (melting point: 145°C)

[0071] (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. The 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 Table 1. A rating of A or B indicates good fluidity of the powder mixture.

[0072] (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 performing the evaluation based on 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 Table 1. A rating of A or B indicates good compaction of the powder mixture.

[0073] (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 powder mixture described above 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 Table 1. A rating of A or B indicates good extractability of the cylindrical molded body.

[0074] (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 Table 1. A rating of A indicates that the sintered body has a good appearance.

[0075] [Table 1]

[0076] As shown in Table 1, by using the powder mixtures of Examples 1 to 14, it was possible to manufacture sintered bodies with excellent ejectability and suppressed surface defects.

[0077] [Examples 15-90 and Comparative Examples 15-36] 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 lubricant A, a lubricant mixture of lubricant A and lubricant B, or a lubricant mixture of lubricants A to C, as shown in Table 2 and below, were 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, lubricant A and lubricant mixtures were 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 2 to 5 relative to the total amount of lubricant. The proportions of lubricant A, lubricant B, and lubricant C in each example and comparative example are as shown in Tables 2 to 5. After that, the mixture of raw material powders and lubricants was put into a V-type mixer and mixed for 30 minutes to obtain the powder mixtures of each example and comparative example. In Table 2, the mixing ratio of lubricant A is the ratio of lubricant A to the total of lubricant A and lubricant B, and the mixing ratio of lubricant B is the ratio of lubricant B to the total of lubricant A and lubricant B. The total content of (lubricant A + lubricant B) is the total content of (lubricant A + lubricant B) to the total of lubricant A, lubricant B, and lubricant C, and the content of lubricant C is the content of lubricant C to the total of lubricant A, lubricant B, and lubricant C. <Lubricant A> Erucic acid amide (melting point: 78°C~81°C) Oleamide (melting point: 75°C) <Lubricant B> Ethylene bis-stearamide (melting point: 145°C) <Lubricant C (Lubricant other than Lubricant A)> Stearic acid amide (melting point: 98°C~102°C)

[0078] The fluidity and compaction properties in Tables 2, 4, and 5 were evaluated using the methods described above. Graphite segregation in Tables 2 and 3 was evaluated using the following methods.

[0079] (Evaluation of graphite segregation) The graphite segregation in each example and comparative example was evaluated by examining the surface of the cylindrical molded body used for evaluating compaction, which was formed using the aforementioned powder mixture, with an optical microscope, and evaluating it based on the following criteria. -Evaluation Criteria- A. No graphite segregation of 50 μm or more. B. There is graphite segregation of 50 μm to 100 μm. There is graphite segregation larger than 100 μm. The results are shown in Tables 2 and 3. A rating of A or B indicates a good evaluation of graphite segregation.

[0080] [Table 2]

[0081] As shown in Table 2, a combined content of lubricant A and lubricant B relative to the total amount of lubricant of 60% by mass or more made it possible to achieve both high fluidity and reduced graphite segregation.

[0082] [Table 3]

[0083] As shown in Table 3, reducing graphite segregation was possible by ensuring that the proportion of lubricant particles smaller than 10 μm was 10% by mass or more.

[0084] [Table 4]

[0085] [Table 5]

[0086] As shown in Tables 4 and 5, the compaction performance was good when the proportion of particles with a particle size of 63 μm or less was 88% by mass or more of the total amount of lubricant. On the other hand, as shown in Table 5, even when the proportion of particles with a particle diameter smaller than 80 μm was relatively high at 95% by mass, it was found that the compaction evaluation was poor if the proportion of particles with a particle diameter of 63 μm or less was less than 88% by mass. From these results, it was found that using the proportion of particles with a particle diameter of 63 μm or less as a criterion is important for evaluating compaction.

[0087] The disclosure of PCT / JP2021 / 022394, filed on 11 June 2021, is incorporated herein by reference in its entirety. 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 lubricant B, which is a fatty acid bisamide, The total content of lubricant A and lubricant B relative to the total amount of the combined molding lubricant is 60% by mass or more. A combination of molding lubricants for metal powder metallurgy in which 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 molding lubricant combination.

2. Lubricant A has a melting point of 60°C to 85°C, It contains lubricant B, which is a fatty acid bisamide, 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 molding lubricant combination. A combination of molding lubricants for metal powder metallurgy in which the proportion of particles with a particle size smaller than 10 μm is 10% by mass or more of the total amount of the molding lubricant combination.

3. The combination of a molding lubricant for metal powder metallurgy according to claim 1 or claim 2, wherein 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.

4. The combination of molding lubricants for metal powder metallurgy according to claim 1 or claim 2, wherein the melting point of lubricant B is 140°C or higher and less than 150°C.

5. The lubricant B is methylenebisstearate, methylenebislaurate, methylenebishydroxystearate, ethylenebiscaprylate, ethylenebiscaprate, ethylenebislaurate, ethylenebisstearate, ethylenebisisostearate, ethylenebishydroxystearate, ethylenebisbehenamide, hexamethylenebisstearate, hexamethylenebisbehenamide, hexamethylenebishydroxystearate, butylenebishydroxys A combination of forming lubricants for metal powder metallurgy according to claim 1 or claim 2, comprising at least one selected from the group consisting of thearic acid amide, N,N'-distearyl adipic acid amide, N,N'-distearyl sebacin 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 sebacin acid amide, m-xylylene bisstearic acid amide, and N,N'-distearyl isophthalic acid amide.

6. The lubricant A comprises at least one selected from the group consisting of erucic acid amide and oleic acid amide. The lubricant B is a combination of the molding lubricants for metal powder metallurgy according to claim 1 or claim 2, wherein the lubricant B comprises ethylenebisstearamide.

7. The combination of molding lubricants for metal powder metallurgy according to claim 1 or claim 2, wherein the mass ratio of lubricant A to lubricant B, i.e., lubricant A:lubricant B, is 1:9 to 9:

1.

8. The combination of molding lubricants for metal powder metallurgy according to claim 1 or claim 2, wherein the proportion of particles with a particle diameter larger than 150 μm is 5% by mass or less of the total amount of the combination of molding lubricants.

9. A powder mixture comprising a raw material powder and a combination of a forming lubricant for metal powder metallurgy according to claim 1 or claim 2.

10. A combination of raw materials for a powder mixture, comprising a raw material powder and a combination of a molding lubricant for metal powder metallurgy according to claim 1 or claim 2.

11. A method for producing a sintered body by sintering the powder mixture described in claim 9.

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

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