Mixed powder for powder metallurgy

Abstract

To provide a mixed powder for powder metallurgy indicative of extractability and compressibility of a compact excellent not only at normal temperature but also after a rise in metal-mold temperature, using fatty acid amide as clean lubricant.SOLUTION: A mixed powder for powder metallurgy contains an iron-based powder, and fatty acid amide as a lubricant. The fatty acid amide contains saturated fatty-acid bisamide, saturated fatty-acid monoamide, and unsaturated fatty-acid amide. The unsaturated fatty-acid amide contains one or both of unsaturated fatty-acid bisamide and unsaturated fatty-acid monoamide. Provided that the addition quantities of saturated fatty-acid bisamide, saturated fatty-acid monoamide, unsaturated fatty-acid bisamide, and unsaturated fatty-acid monoamide are respectively indicated, in parts by weight relative to 100 pts. mass of the iron-based powder, as b1, b2, b3 and b4, the following expressions (1) to (3) are satisfied. 0<(b1)+(b2)+(b3)+(b4)≤2.0...(1), 0<(b1) / (b2)<0.45...(2), 0<[(b3)+(b4)] / [(b1)+(b2)+(b3)+(b4)]≤0.35...(3)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a powder mixture for powder metallurgy. [Background technology]

[0002] Powder metallurgy is a technology that creates parts with high dimensional accuracy by placing metal powder in a mold, compressing and solidifying it, and sintering it at high temperatures. With powder metallurgy, even parts with complex shapes can be formed with high dimensional accuracy, which significantly reduces cutting costs compared to shaping by machining or other methods. For this reason, powder metallurgy products are used in a wide range of applications, including in various machines and parts.

[0003] In powder metallurgy, a mixed powder for powder metallurgy (hereinafter sometimes referred to as a mixed powder) is used as a raw material powder, which is an iron-based powder that is the main raw material, mixed with alloy powders such as copper powder, graphite powder, and iron phosphide powder, powders for improving machinability such as MnS, and lubricants as needed.

[0004] The lubricant contained in the powder metallurgy mixture plays an extremely important role in manufacturing products by molding such a powder metallurgy mixture. The lubricant is required to reduce friction between particles contained in the powder mixture when the powder mixture is molded in a mold, and to reduce friction between the particles and the mold used for molding.

[0005] The effect of reducing friction between particles contained in the mixed powder when the mixed powder is compacted in a die is achieved, for example, by the presence of a lubricant between the particles during compaction. Reducing friction between particles promotes particle rearrangement, improving compactability. The effect of reducing friction between the particles and the die used in compaction is achieved, for example, by the presence of a lubricant on the die surface between the die and the particles. Reducing friction between the die and particles promotes particle rearrangement on the surface of the compact, improving compactability. These two effects enable the mixed powder to be compressed to a high density during compaction. Furthermore, reducing friction between the die and particles reduces friction between the die and the compact, and also improves the releasability of the compact from the die. The compact is removed from the die by, for example, pushing it out with a punch. However, high friction between the die and the compact can make it difficult to remove the compact from the die or can damage the surface of the compact.

[0006] Although the lubricant plays an important role during compaction and removal from the die as described above, it is required that the lubricant does not remain in the sintered body. Since the lubricant becomes unnecessary after the compact is removed from the die, it is desirable that the lubricant disappear during sintering of the compact, for example.

[0007] Incidentally, a component functioning as a binder may be added to a powder mixture for powder metallurgy. Here, the binder refers to a component that adheres additive components, such as alloying powder, to the surface of iron particles in the iron-based powder, which is the main component. A powder mixture obtained by simply mixing an iron-based powder with additive components, such as an alloying powder, a machinability-improving powder, and a lubricant, may experience segregation of each component after mixing. In particular, graphite powder, which is commonly used as an alloying powder, has a lower density than other components and therefore easily segregates when the mixed powder is fluidized or vibrated. To prevent this segregation, additive components may be attached to the particle surfaces of the iron-based powder via a binder. Such a powder mixture is sometimes referred to as a segregation-prevented powder. In a segregation-prevented powder, the additive components adhere to the iron-based powder, preventing the aforementioned segregation of the components.

[0008] Generally, lubricants have a stronger adhesive force than iron-based powders, which can cause a problem of impairing the flowability of the mixed powder. However, taking advantage of this adhesive force, compounds that also function as lubricants can be used as binders in segregation-prevented powders.

[0009] Powder metallurgy mixtures are typically press-molded at pressures of 300 to 1000 MPa to obtain the desired part shape, followed by sintering at temperatures above 1000°C to obtain the final part shape. The total amount of lubricant and binder contained in the mixture is typically about 0.1 to 2 parts by mass per 100 parts by mass of iron-based powder. Because lubricants and binders have a lower density than iron-based powders, adding large amounts can reduce the density of the compact, resulting in a lower density of the sintered compact. Therefore, to increase the density of the compact, it is better to add less lubricant and binder. For example, using a binder that also has lubricating properties can reduce the total amount of binder and lubricant added to the mixture.

[0010] The lubricating performance of a lubricant is greatly influenced by the type of compounds contained in the lubricant. Fatty acid amides and fatty acid metal soaps are typical compounds commonly used as lubricants for powder metallurgy. Both fatty acid amides and fatty acid metal soaps are substances with excellent lubrication properties. However, fatty acid metal soaps can produce metal oxides during sintering, which can contaminate the surface of the sintered body and the sintering furnace. In contrast, fatty acid amides decompose during sintering, volatilizing all of their components, making them useful as clean lubricants that do not cause contamination.

[0011] For example, Patent Document 1 discloses the use of one or more selected from stearic acid, oleic acid monoamide, and stearic acid monoamide, and one or more selected from ethylene bisstearic acid amide and methylene bisstearic acid amide as a binder and lubricant.

[0012] Furthermore, Patent Document 2 discloses the use of a primary or secondary fatty acid amide in combination with an alkylenebisfatty acid amide or a secondary or tertiary polyhydroxy fatty acid amide.

[0013] Furthermore, Patent Document 3 discloses the use of a linear fatty acid bisamide and a linear fatty acid monoamide with an unsaturated fatty acid bisamide or a branched fatty acid bisamide or an unsaturated fatty acid monoamide in a predetermined ratio.

[0014] Furthermore, Patent Document 4 discloses the use of a lubricant in which an unsaturated fatty acid bisamide and a saturated hydroxy fatty acid are combined. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Japanese Patent Application Laid-Open No. 1993-148505 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-184708 [Patent Document 3] International Publication No. 2014 / 123106 [Patent Document 4] Japanese Patent Application Publication No. 2019-143200 Summary of the Invention [Problem to be solved by the invention]

[0016] In commercial powder metallurgy molding processes, hundreds to thousands of parts are molded continuously. During such continuous molding, the temperature of the mold gradually increases due to frictional heat. The degree of mold temperature increase varies depending on the mold and part shape, but for parts with large lateral areas, it can reach 70 to 80°C. Therefore, powder metallurgy lubricants are required to exhibit high lubricity not only at room temperature during the initial molding process, but also after the mold temperature has increased. However, Patent Documents 1 to 4 only describe the molding density and ejection force during molding at room temperature, and do not mention performance at elevated mold temperatures.

[0017] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a mixed powder for powder metallurgy which uses a fatty acid amide, which is a clean lubricant, and which exhibits excellent ejection and compressibility of molded products not only at room temperature but also after the mold temperature is elevated. [Means for solving the problem]

[0018] In order to achieve the above object, the mixed powder for powder metallurgy according to the present invention is as follows.

[0019] [1] an iron-based powder; a fatty acid amide as a lubricant, The fatty acid amides include saturated fatty acid bisamides, saturated fatty acid monoamides, and unsaturated fatty acid amides; The unsaturated fatty acid amide includes one or both of an unsaturated fatty acid bisamide and an unsaturated fatty acid monoamide, A mixed powder for powder metallurgy that satisfies the following formulas (1) to (3), where the amounts of the saturated fatty acid bisamide, the saturated fatty acid monoamide, the unsaturated fatty acid bisamide, and the unsaturated fatty acid monoamide added are represented by b1, b2, b3, and b4, respectively, in parts by weight relative to 100 parts by mass of the iron-based powder. 0<(b1)+(b2)+(b3)+(b4)≦2.0...Equation (1) 0<(b1) / (b2)<0.45...Equation (2) 0<[(b3)+(b4)] / [(b1)+(b2)+(b3)+(b4)]≦0.35...Equation (3)

[0020] The mixed powder for powder metallurgy according to the present invention may further be as follows.

[0021] [2] The fatty acid amide according to [1] above has a long-chain alkyl or alkenyl group having 11 to 21 carbon atoms. Mixed powder for powder metallurgy .

[0022] [3] The fatty acid amide according to [1] or [2] above, wherein the fatty acid amide is a derivative of lauric acid, palmitic acid, stearic acid, behenic acid, oleic acid, or erucic acid. Mixed powder for powder metallurgy .

[0023] [4] The composition according to any one of [1] to [3] above, further comprising at least one of carbon black, metal oxide fine particles, and metal soap as a flow improver. Mixed powder for powder metallurgy .

[0024] [5] The alloy powder according to any one of [1] to [3], further comprising one or both of an alloy powder and a machinability improver. Mixed powder for powder metallurgy .

[0025] [6] The method according to [4], further comprising one or both of an alloy powder and a machinability improver. Mixed powder for powder metallurgy .

[0026] [7] The method according to [5] above, wherein one or both of the alloying powder and the machinability improver are attached to the particle surface of the iron-based powder via the fatty acid amide. Mixed powder for powder metallurgy .

[0027] [8] The method according to [6] above, wherein one or both of the alloying powder and the machinability improver are attached to the particle surfaces of the iron-based powder via the fatty acid amide. Mixed powder for powder metallurgy . [Effects of the Invention]

[0028] The mixed powder for powder metallurgy of the present invention can provide a molded product with excellent ejection and compressibility not only at room temperature but also after the mold temperature is elevated. DETAILED DESCRIPTION OF THE INVENTION

[0029] A mixed powder for powder metallurgy according to an embodiment of the present invention will be described. Note that the following description exemplifies preferred embodiments of the present invention, and the present invention is not limited to these examples.

[0030] First, an outline of the mixed powder for powder metallurgy according to this embodiment will be described.

[0031] The powder mixture for powder metallurgy according to the present embodiment includes an iron-based powder and a fatty acid amide as a lubricant. The fatty acid amide includes saturated fatty acid bisamide, saturated fatty acid monoamide, and unsaturated fatty acid amide. The unsaturated fatty acid amide includes one or both of unsaturated fatty acid bisamide and unsaturated fatty acid monoamide.

[0032] In the mixed powder for powder metallurgy according to this embodiment, when the amounts of the saturated fatty acid bisamide, saturated fatty acid monoamide, unsaturated fatty acid bisamide, and unsaturated fatty acid monoamide added are denoted by b1, b2, b3, and b4, respectively, in parts by weight relative to 100 parts by mass of the iron-based powder, the following formulas (1) to (3) are satisfied.

[0033] 0<(b1)+(b2)+(b3)+(b4)≦2.0...Equation (1)

[0034] 0<(b1) / (b2)<0.45...Equation (2)

[0035] 0<[(b3)+(b4)] / [(b1)+(b2)+(b3)+(b4)]≦0.35...Equation (3)

[0036] The mixed powder for powder metallurgy according to this embodiment uses a fatty acid amide, which is a clean lubricant, and can achieve excellent ejection and compressibility of the molded product not only at room temperature but also after the mold temperature is increased.

[0037] The mixed powder for powder metallurgy according to this embodiment will be described in detail below.

[0038] The mixed powder for powder metallurgy according to this embodiment (hereinafter, sometimes simply referred to as the mixed powder) may further contain at least one of a flowability improver, an alloying powder, and a machinability improver, in addition to the iron-based powder and the fatty acid amide.

[0039] In this embodiment, the iron-based powder is a metal powder containing 50% by mass or more of Fe. In this embodiment, "iron powder" refers to a powder consisting of Fe and inevitable impurities. "Iron powder" is generally referred to as "pure iron powder" in this technical field.

[0040] The iron-based powder is not particularly limited and any iron-based powder can be used. Examples of iron-based powders include iron powder and alloy steel powder. As the alloy steel powder, any one can be used, such as pre-alloyed steel powder (fully alloyed steel powder) in which alloying elements are pre-alloyed during melting, partially diffused alloyed steel powder in which alloying elements are partially diffused into iron powder, and hybrid steel powder in which alloying elements are further partially diffused into pre-alloyed steel powder. As the alloying element, for example, one or more elements selected from the group consisting of C, Cu, Ni, Mo, Mn, Cr, V, and Si can be used.

[0041] Any iron-based powder can be used, such as reduced iron-based powder produced by reducing iron oxide, or atomized iron-based powder produced by atomization.

[0042] The particle diameter of the iron-based powder is not particularly limited, but the particle diameter of the iron-based powder is the median diameter (50% particle diameter: D 50 ) is preferably 30 to 120 μm.

[0043] The ratio of the mass of the iron-based powder to the total mass of the mixed powder is not particularly limited, but is preferably 86 mass % or more, and more preferably 90 mass % or more, of the total mass of the mixed powder.

[0044] The mixed powder according to this embodiment contains a fatty acid amide as a lubricant. The mixed powder according to this embodiment contains a saturated fatty acid bisamide, a saturated fatty acid monoamide, and an unsaturated fatty acid amide as the fatty acid amide as a lubricant. The unsaturated fatty acid amide includes one or both of an unsaturated fatty acid bisamide and an unsaturated fatty acid monoamide.

[0045] In the mixed powder according to this embodiment, when the amounts of saturated fatty acid bisamide, saturated fatty acid monoamide, unsaturated fatty acid bisamide, and unsaturated fatty acid monoamide added are represented by b1, b2, b3, and b4, respectively, in parts by weight relative to 100 parts by mass of the iron-based powder, the mixed powder satisfies the above-mentioned formulas (1) to (3).

[0046] That is, the total amount of b1, b2, b3, and b4 is preferably greater than 0 parts by mass and equal to or less than 2.0 parts by mass relative to the iron-based powder (see formula 1). When the total amount is within this range, the compaction density is increased when the mixed powder is compression-molded. However, if the total amount exceeds 2.0 parts by mass, the compaction density during compression may decrease.

[0047] The ratio of b1 to b2 is preferably greater than 0 and less than 0.45 (see formula 2). When the ratio of b1 to b2 is within this range, the molding density during room temperature molding and after the mold temperature is increased can be increased, and the ejection force of the molded body from the mold can be reduced.

[0048] The ratio of the total amount of b3 and b4 to the total amount of b1, b2, b3, and b4 is preferably greater than 0 and not greater than 0.35. When the ratio of the total amount of b3 and b4 is within this range, the molding density after the mold temperature has increased can be increased and the ejection force of the molded body from the mold can be reduced. If the ratio of the total amount of b3 and b4 is too high, the molding density after the mold temperature has increased can be reduced and the ejection force can be increased.

[0049] The fatty acid amide preferably has a long-chain alkyl or alkenyl group having 11 or more carbon atoms. This is because lubricity cannot be maintained if the alkyl or alkenyl chain is too short. Furthermore, from the viewpoint of easy availability, the number of carbon atoms in the alkyl or alkenyl chain of the fatty acid amide is preferably 21 or less. Specifically, the fatty acid amide is preferably an amide made from saturated or unsaturated fatty acids such as lauric acid, palmitic acid, stearic acid, behenic acid, oleic acid, or erucic acid. That is, specifically, the fatty acid amide is preferably a derivative of lauric acid, palmitic acid, stearic acid, behenic acid, oleic acid, or erucic acid.

[0050] The flow improver is carbon black, metal oxide fine particles, or metal soap. The mixed powder according to this embodiment preferably contains at least one of carbon black, metal oxide fine particles, and metal soap as the flow improver. This improves the flowability of the mixed powder, making it easier to insert into a mold during compression molding. Furthermore, the moldability during compression molding is improved.

[0051] The alloying powder is used to improve the strength of a compact of the mixed powder. There are no particular limitations on the alloying powder, and any powder that can become an alloying component can be used. For example, the alloying powder can be one or more powders selected from the group consisting of C, Cu, Ni, Mo, Mn, Cr, V, and Si. When C is used as an alloying component, it is preferable to use graphite powder as the alloying powder.

[0052] When a mixed powder containing an alloying powder is sintered, the alloying elements dissolve in the iron to form an alloy, and therefore the strength of the final sintered body can be improved by using the alloying powder.

[0053] The machinability improver may be, for example, one or more selected from the group consisting of MnS, CaF2, and talc. By adding the machinability improver, the machinability (processability) of the finally obtained sintered body can be improved.

[0054] The alloying powder and the machinability improver do not necessarily need to be contained, and the lower limit of the total amount of the alloying powder and the machinability improver per 100 parts by mass of the iron-based powder can be set to 0 parts by mass.

[0055] When one or both of an alloying powder and a machinability improver are added to the mixed powder, the amounts of the alloying powder and the machinability improver added are not particularly limited and can be any amount. The total amount of the alloying powder and the machinability improver is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the iron-based powder. By keeping the total amount of the alloying powder and the machinability improver within the above range, the density of the sintered body can be further increased, and the strength of the sintered body can be further improved.

[0056] When alloying powder and machinability improver are contained, the total amount thereof is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more. By keeping the total amount of alloying powder and machinability improver within the above range, the effect of adding these components can be further enhanced.

[0057] The method for producing the mixed powder will be described below.

[0058] The mixed powder of the present invention is not particularly limited and can be produced by any method. For example, the iron-based powder, lubricant (fatty acid amide), flowability improver, alloying powder, and machinability improver can be mixed using a mixer to produce the mixed powder. The addition and mixing of the components can be carried out in one go, or in two or more separate steps.

[0059] When adhering an alloying powder or a machinability improver to the particle surfaces of an iron-based powder, for example, the iron-based powder and a lubricant (fatty acid amide) are heated and mixed with the alloying powder or the machinability improver as follows, and the lubricant is used as a binder to adhere the powder. That is, one or both of the alloying powder and the machinability improver are stirred and mixed together with the lubricant and the iron-based powder. This allows the alloying powder or the machinability improver to adhere to the particle surfaces of the iron-based powder via the fatty acid amide. Hereinafter, mixing by stirring will be simply referred to as "mixing" or "mixing." In this case, the powders being mixed may be heated to or above the melting point of the lubricant while being mixed, and then gradually cooled while being mixed.

[0060] When the above-described heating and mixing is performed and at least one of carbon black, metal oxide, and metal soap is added, it is preferable to adhere one or both of the alloying powder and the machinability improver to the particle surfaces of the iron-based powder as described above, and then further add and mix at least one of carbon black, metal oxide, and metal soap. The mixing operation after adding at least one of carbon black, metal oxide, and metal soap is performed at a temperature below the melting point of the lubricant so as not to melt the lubricant (fatty acid amide) that has already been fixed.

[0061] There are no particular limitations on the mixing method or mixing device used to produce the mixed powder. Any mixing device, including various known mixers, can be used to produce the mixed powder. Examples of mixing devices include a V-type mixer, a high-speed bottom-stirring mixer, an inclined rotating pan mixer, a rotating hoe mixer, and a conical planetary screw mixer. Two or more of these mixing devices may be used in combination.

[0062] It should be noted that the heating and mixing is not essential. That is, the mixed powder may be produced by mixing all the components at room temperature without performing any heating and mixing. [Example]

[0063] [Experimental Example 1] The components were charged into a V-type mixer according to the formulation shown in Table 1 and mixed for 10 minutes to produce each mixed powder according to Experimental Example 1. These mixed powders were then compression molded to obtain compacts. In Table 1, the blended amount of the iron-based powder is defined as 100 parts by mass, and the blended amounts of the other components are shown as amounts (parts by mass) relative to 100 parts by mass of the iron-based powder.

[0064] [Table 1]

[0065] In Table 1, items “(b1)+(b2)+(b3)+(b4)” and “(b1) / (b2)” The underlined values ​​in "[(b3)+(b4)] / [(b1)+(b2)+(b3)+(b4)]" indicate that the values ​​of these items do not satisfy any of the above formulas (1) to (3) and do not satisfy the requirements of this embodiment.

[0066] The iron-based powder used was iron powder (pure iron powder) manufactured by atomization (JIP301A manufactured by JFE Steel Corporation). The median diameter of this iron powder was 80 μm. This median diameter was measured using a laser diffraction particle size distribution analyzer.

[0067] Copper powder and graphite powder were used as alloying powders.

[0068] The median diameters of the fatty acid amide powder used as a lubricant and the alloying powder were measured in the same manner as for the iron powder. The median diameter of the copper powder used as the alloying powder was 25 μm. The median diameter of the graphite powder was 4.2 μm.

[0069] The fatty acid amides used were as follows: Ethylene bisstearic acid amide as saturated fatty acid bisamide; , ethylene bisbehenamide As the saturated fatty acid monoamide, lauric acid amide, palmitic acid amide, stearic acid amide or behenic acid amide was used. As the unsaturated fatty acid bisamide, Ethylene bis oleamide or ethylene bis erucamide As the unsaturated fatty acid monoamide, Erucamide or oleamidewas used.

[0070] Each mixed powder was compression molded in a mold, and the ejection force and green density were evaluated. The evaluation results are also shown in Table 1.

[0071] The ejection force was evaluated using the following procedure. Cylindrical compacts with a diameter of 11.3 mm and a height of 10 mm were produced using each mixed powder at a compaction pressure of 686 MPa according to the method specified in JPMA P 13-2022. A heater was attached to the die to adjust the die temperature to 30°C and 70°C. The maximum load applied when ejecting from the die was taken as the ejection force. The lower the ejection force, the better the ejection performance. The die temperature of 70°C simulates the rise in die temperature due to frictional heat during continuous compaction in a commercial powder metallurgy molding process.

[0072] The green density was calculated from the dimensions and weight of the green body according to the method specified in JIS Z 2508: 2020. The higher the green density, the better the compressibility of the mixed powder.

[0073] The compacts Nos. 1 to 13 according to this embodiment (corresponding to examples) were superior in either or both of ejection property and compressibility compared to the compacts Nos. 14 to 16 which did not satisfy the requirements of this embodiment.

[0074] In particular, when focusing on the compaction characteristics (70°C) after the mold temperature has increased, the compacts Nos. 1 to 13 according to this embodiment exhibit excellent ejection properties and compressibility even after the mold temperature has increased.

[0075] [Experimental Example 2] As in Experimental Example 1, the components were charged into a V-type mixer according to the formulation shown in Table 2 and mixed for 10 minutes to produce mixed powders according to Experimental Example 2. These mixed powders were then compression-molded to obtain green bodies. In Table 2, the blended amount of the iron-based powder is defined as 100 parts by mass, and the blended amounts of the other components are shown as the amounts (parts by mass) relative to 100 parts by mass of the iron-based powder. As in Table 1, values ​​in Table 2 that do not satisfy the requirements of this embodiment are underlined.

[0076] [Table 2]

[0077] The fatty acid amides used were as follows: As the saturated fatty acid bisamide, ethylene bisstearic acid amide was used; As the saturated fatty acid monoamide, stearic acid amide or behenic acid amide was used; As the unsaturated fatty acid bisamide, Ethylenebisoleamide As the unsaturated fatty acid monoamide, Erucamide or oleamide was used.

[0078] Each mixed powder was compression molded in a mold, and the ejection force and the density of the green body were evaluated in the same manner as in Experimental Example 1. These evaluation results are also shown in Table 2.

[0079] The compacts Nos. 17, 19, 21, and 23 according to this embodiment were superior in either or both of ejection property and compressibility compared to the compacts Nos. 18, 20, 22, and 24 which did not satisfy the requirements of this embodiment.

[0080] In particular, when focusing on the compaction characteristics (70°C) after the mold temperature is increased, the compacts Nos. 17, 19, 21, and 23 according to this embodiment show excellent ejection properties and compressibility even after the mold temperature is increased, compared to Nos. 18, 20, 22, and 24, which have the same conditions except for the conditions related to "(b1) / (b2)."

[0081] [Experimental Example 3] As in Experimental Examples 1 and 2, the components were charged into a V-type mixer according to the formulations shown in Table 3 and mixed for 10 minutes to produce mixed powders according to Experimental Example 3. These mixed powders were then compression-molded to obtain compacts. In Table 3, the amount of iron-based powder is defined as 100 parts by mass, and the amounts of the other components are shown as parts by mass relative to 100 parts by mass of the iron-based powder. Unlike Experimental Examples 1 and 2, Experimental Example 3 further contained carbon black, a metal oxide (titanium oxide: TiO2 or silica: SiO2), or a metal soap (zinc stearate or lithium stearate) as a flow improver. As in Table 1, values ​​in Table 3 that do not satisfy the requirements of this embodiment are underlined.

[0082] [Table 3]

[0083] The fatty acid amides used were as follows: Ethylene bisstearic acid amide as saturated fatty acid bisamide; , ethylene bisbehenamide As the saturated fatty acid monoamide, lauric acid amide, palmitic acid amide, stearic acid amide or behenic acid amide was used. As the unsaturated fatty acid bisamide, Ethylene bis oleamide or ethylene bis erucamide As the unsaturated fatty acid monoamide, Erucamide or oleamide was used.

[0084] The powder properties of each mixed powder were evaluated, including apparent density and flowability, and the results are also shown in Table 3.

[0085] The apparent density was evaluated using a funnel with a diameter of 2.5 mm according to the method specified in JIS Z 2504: 2020. The larger the apparent density, the better the quality.

[0086] The flowability was measured using a funnel with an orifice diameter of 2.5 mm, according to the method specified in JIS Z 2502: 2020, to measure the time it took for 50 g of the mixed powder to flow down. The shorter the time it took for the mixed powder to flow down, the better the flowability.

[0087] Each mixed powder was compression molded in a mold, and the ejection force and the density of the green body were evaluated in the same manner as in Experimental Example 1. These evaluation results are also shown in Table 3.

[0088] By adding carbon black, metal oxide, or metal soap as a flow improver, the powders showed good apparent density and flowability. For powders with flowability issues, the method specified in JIS Z 2502:2020 may not allow measurement because the powder does not come out of the funnel. However, the flowability of all mixed powders No. 25 to 40 could be measured, so it can be said that they showed good flowability.

[0089] Furthermore, the compacts Nos. 25 to 28, 30 to 33, 35, 36, 38, and 39 according to this embodiment were superior in at least one of ejection property and compressibility compared to the compacts Nos. 29, 34, 37, and 40 which did not satisfy the requirements of this embodiment.

[0090] Focusing particularly on the compaction characteristics (70°C) after the mold temperature is increased, the compacts Nos. 25 to 28, 30 to 33, 35, 36, 38, and 39 according to this embodiment are superior in at least ejection properties to the compacts Nos. 29, 34, 37, and 40, which do not meet the requirements of this embodiment, although some of them have the same compressibility after the mold temperature is increased.

[0091] [Experimental Example 4] As in Experimental Example 3, the components were charged into a V-type mixer according to the formulation shown in Table 4 and mixed for 10 minutes to produce mixed powders according to Experimental Example 4. These mixed powders were then compression-molded to obtain green bodies. In Table 4, the blending amount of the iron-based powder is defined as 100 parts by mass, and the blending amounts of the other components are shown as the amounts (parts by mass) relative to 100 parts by mass of the iron-based powder. Unlike Experimental Example 3, Experimental Example 4 further added manganese sulfide (MnS) as a machinability improver.

[0092] [Table 4]

[0093] The fatty acid amides used were as follows: As the saturated fatty acid bisamide, ethylene bisstearic acid amide or methylene bisstearic acid amide was used; As the saturated fatty acid monoamide, lauric acid amide, stearic acid amide or behenic acid amide was used; As the unsaturated fatty acid bisamide, Ethylenebisoleamide As the unsaturated fatty acid monoamide, Erucamide or oleamide was used.

[0094] In addition, carbon black, metal oxide (silica: SiO2) or metal soap (zinc stearate or lithium stearate) is added as a flow improver.

[0095] The apparent density and fluidity of the mixed powder, and the ejection force and density of the compact were evaluated in the same manner as in Experimental Example 3. Table 4 also shows the results of these evaluations.

[0096] In this experimental example, a machinability improving agent was newly added, but the mixed powders Nos. 41, 43, 45, and 47 according to this embodiment exhibited good apparent density and fluidity. Furthermore, the compacts Nos. 41, 43, 45, and 47 according to this embodiment were superior in at least one of ejection property and compressibility to the compacts Nos. 42, 44, 46, and 48, which did not satisfy the requirements of this embodiment.

[0097] In particular, when focusing on the compacted powder characteristics (70°C) after the mold temperature is increased, the compacts Nos. 41, 43, 45, and 47 according to this embodiment have at least superior ejection properties after the mold temperature is increased compared to the compacts Nos. 42, 44, 46, and 48, which do not meet the requirements of this embodiment, although some of them have equivalent compressibility.

[0098] [Experimental Example 5] Each component was mixed in a high-speed bottom-stirring mixer according to the formulation shown in Table 5 to produce each mixed powder according to Experimental Example 5, and these mixed powders were then compression-molded to obtain a green body. In Table 5, the amount of iron-based powder is defined as 100 parts by mass, and the amounts of the other components are shown as the amounts (parts by mass) relative to 100 parts by mass of the iron-based powder. In Experimental Example 5, unlike Experimental Example 3, the lubricant was added in two separate additions.

[0099] [Table 5]

[0100] The fatty acid amides used were as follows: Ethylene bisstearic acid amide as saturated fatty acid bisamide; or ethylene bisbehenamide As the saturated fatty acid monoamide, stearic acid amide or behenic acid amide was used. As the unsaturated fatty acid bisamide, Ethylenebisoleamide As the unsaturated fatty acid monoamide, Erucamide or oleamide was used.

[0101] In addition, carbon black or metal soap (zinc stearate or lithium stearate) is added as a flow improver.

[0102] The lubricant was added as follows. First, the alloying powder and a portion of the lubricant (the amount listed in the "primary addition amount" column in Table 5) were added to the iron-based powder in a high-speed bottom-stirring mixer, and the mixture was heated and mixed for 20 minutes at a temperature higher than the melting points of all compounds contained in the primary lubricant. The mixture was then cooled to a temperature lower than the melting points. Subsequently, a portion of the lubricant (the amount listed in the "secondary addition amount" column in Table 5) and the flowability improver were added, and the mixture was mixed at room temperature for 1 minute to obtain a mixed powder according to Experimental Example 5.

[0103] The apparent density and fluidity of the mixed powder, and the ejection force and density of the compact were evaluated in the same manner as in Experimental Example 3. Table 5 also shows the results of these evaluations.

[0104] The compacts Nos. 49, 51, and 53 according to this embodiment were superior in ejection property and compressibility after the mold temperature was increased (to 70° C.) compared to the compacts Nos. 50, 52, and 54 which did not satisfy the requirements of this embodiment.

[0105] In this manner, a mixed powder for powder metallurgy can be provided.

[0106] It should be noted that the embodiments disclosed in this specification are merely examples, and the present invention is not limited to these embodiments, and can be modified as appropriate within the scope of the purpose of the present invention. [Industrial Applicability]

[0107] The present invention is applicable to mixed powders for powder metallurgy.

Claims

1. an iron-based powder; a fatty acid amide as a lubricant, The fatty acid amides include saturated fatty acid bisamides, saturated fatty acid monoamides, and unsaturated fatty acid amides; The unsaturated fatty acid amide includes one or both of an unsaturated fatty acid bisamide and an unsaturated fatty acid monoamide, the saturated fatty acid bisamide is ethylene bisstearic acid amide, methylene bisstearic acid amide, or ethylene bisbehenic acid amide; the saturated fatty acid monoamide is lauric acid amide, palmitic acid amide, stearic acid amide, or behenic acid amide; the unsaturated fatty acid bisamide is ethylene bisoleamide or ethylene biserucamide, the unsaturated fatty acid monoamide is erucic acid amide or oleic acid amide; A mixed powder for powder metallurgy, wherein the amounts of the saturated fatty acid bisamide, the saturated fatty acid monoamide, the unsaturated fatty acid bisamide, and the unsaturated fatty acid monoamide added are denoted by b1, b2, b3, and b4, respectively, in parts by mass relative to 100 parts by mass of the iron-based powder, and the mixed powder for powder metallurgy satisfies the following formulas (1) to (3): 0<(b1)+(b2)+(b3)+(b4)≦2.0...Formula (1) 0<(b1) / (b2)<0.45...Formula (2) 0.13≦[(b3)+(b4)] / [(b1)+(b2)+(b3)+(b4)]≦0.35...Formula (3)

2. 2. The mixed powder for powder metallurgy according to claim 1, further comprising at least one of carbon black, metal oxide fine particles, and metal soap as a flowability improver.

3. 3. The mixed powder for powder metallurgy according to claim 1, further comprising one or both of an alloying powder and a machinability improver.

4. 4. The mixed powder for powder metallurgy according to claim 3, wherein one or both of said alloying powder and said machinability improver are adhered to the particle surfaces of said iron-based powder via said fatty acid amide.

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