Metal composite sintered body

Abstract

The present invention provides a metal composite sintered body that can ensure sufficient bonding strength and can be manufactured in complex shapes, including hollow shapes and shapes with extremely small gaps. [Solution] A metal composite sintered body is formed by injection molding a mixture of metal powder and a binder, and then joining a first member and a second member, each made of a sintered body formed by injection molding, wherein the tensile strength of the joint surface between the first member and the second member is 80% or more of the tensile strength of the first member or the second member.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a metal composite sintered body and to a metal composite sintered body, and more particularly to a method for manufacturing a metal composite sintered body and a metal composite sintered body that can accurately manufacture sintered bodies with hollow or complex shapes with intricate interiors. [Background technology]

[0002] Conventionally, it is known that parts used in automobiles and precision machinery are manufactured using metal composite sintered bodies produced by powder metallurgy, a method in which metal powder is powder-molded and then sintered to form a sintered body. However, for sintered bodies of complex mechanical parts such as gears, couplings, or cams, or parts with complex partial shapes such as curved holes or elongated holes, the desired shape cannot be obtained by pressure molding using powder molding dies alone. Therefore, conventionally, sintered bodies with complex shapes have been manufactured by combining pressure molding and machining, for example, by the following method: First, a mixture of metal powder, which will be the raw material powder, and additional metal powder as needed, is placed in a mold and pressure-molded to produce a molded body. Next, this molded body is sintered, and the resulting sintered body is machined to form the desired shape. In other words, in the above manufacturing method, complex shapes are formed by machining after sintering.

[0003] Furthermore, various methods are known for obtaining sintered bodies with more complex shapes. For example, as described in Patent Document 1, a method is known for manufacturing a metal composite sintered body by applying an adhesive coating to the joint surface of an injection-molded body obtained by metal powder injection molding and then sintering it. Another method is known for manufacturing a complex-shaped part by diffusion bonding a metal sintered body by fitting together multiple green bodies (molded products formed using an injection molding machine by mixing a mixture of metal powder and a binder) with the green bodies and then degreasing and sintering them in a sintering furnace. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2010-236042 [Patent Document 2] Japanese Patent Publication No. 2021-32622 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, according to the conventional method for manufacturing metal composite sintered bodies described in Patent Documents 1 and 2 above, the joining is performed in the state of the molded body before degreasing, called the green body. As a result, when the binder is removed after degreasing, shrinkage and deformation occur, causing uneven contact at the joining surfaces and reducing the joint strength.

[0006] Furthermore, conventional powder metallurgy manufacturing methods involve using molds to produce molded bodies. This presents a problem in that complex shapes, such as hollow shapes or shapes with extremely small gaps, which are difficult to mold using molds, cannot be manufactured using conventional methods.

[0007] This invention has been made in view of the above circumstances, and aims to provide a method for manufacturing a metal composite sintered body and a metal composite sintered body that can ensure sufficient bonding strength and produce complex shapes such as hollow shapes and shapes with extremely small gaps. [Means for solving the problem]

[0008] A method for manufacturing a metal composite sintered body according to one embodiment is characterized by comprising the steps of: preparing a mixture of metal powder and a binder; manufacturing a molded body by injection molding the mixture; degreasing the molded body to remove the binder; sintering the molded body from which the binder has been removed to obtain a sintered body; polishing the joint surface of the sintered body; preparing a plurality of the sintered bodies and temporarily bonding the joint surfaces together; and joining the temporarily bonded sintered bodies by diffusion sintering.

[0009] Furthermore, in a method for manufacturing a metal composite sintered body according to one embodiment, the step of temporarily bonding the bonding surfaces together preferably includes a step of filling the gaps in the temporarily bonded sintered bodies with a spacer material.

[0010] Furthermore, in the method for manufacturing a metal composite sintered body according to one embodiment, the diffusion sintering step is preferably performed at a sintering temperature of 1290°C to 1350°C.

[0011] Furthermore, in the method for manufacturing a metal composite sintered body according to one embodiment, the step of polishing the joint surface is preferable if the surface roughness of the joint surface is Ra0.4 to Ra1.6.

[0012] Furthermore, in the method for manufacturing a metal composite sintered body according to one embodiment, it is preferable to use an adhesive in the step of temporarily bonding the joining surfaces together.

[0013] Furthermore, the metal composite sintered body according to the present invention is a metal composite sintered body in which a first member and a second member are joined, each made of a sintered body formed by injection molding a mixture of metal powder and a binder, wherein the tensile strength of the joint surface between the first member and the second member is 80% or more of the tensile strength of the first member or the second member.

[0014] Furthermore, in the metal composite sintered body according to the present invention, the tensile strength of the joint surface is 768 N / mm². 2 The above is true, and the metal powder is preferably a precipitation-hardening stainless steel.

[0015] Furthermore, in the metal composite sintered body according to the present invention, the tensile strength of the joint surface is 416 N / mm². 2 The above is true, and the metal powder is preferably austenitic stainless steel.

[0016] Furthermore, in the metal composite sintered body according to the present invention, the tensile strength of the joint surface is 720 N / mm². 2 The above is true, and the metal powder is preferably martensitic stainless steel.

Advantages of the Invention

[0017] According to the method for manufacturing a metal composite sintered body and the metal composite sintered body according to the present invention, since it includes a step of polishing the bonding surface of the sintered body and a step of diffusion-sintering and bonding the temporarily adhered sintered bodies, it is possible to ensure the bonding strength of the bonding surface, and a sintered body having a complex shape such as a shape with a hollow or an extremely small gap can be obtained.

Brief Description of the Drawings

[0018] [Figure 1] Flow chart of the method for manufacturing a metal composite sintered body according to an embodiment of the present invention. [Figure 2] Conceptual diagram of a sintered body manufactured by the method for manufacturing a metal composite sintered body according to an embodiment of the present invention. [Figure 3] Conceptual diagram for explaining the step of temporarily bonding the bonding surfaces of the method for manufacturing a metal composite sintered body according to an embodiment of the present invention. [Figure 4] Conceptual diagram for explaining the step of filling a spacer material in the method for manufacturing a metal composite sintered body according to an embodiment of the present invention. [Figure 5] Conceptual diagram of a test piece for measuring the bonding shear strength of the metal composite sintered body according to the present embodiment. [Figure 6] Diagram showing the bonding surface of the test piece for measuring the bonding shear strength of the metal composite sintered body according to the present embodiment. [Figure 7] Graph showing the measurement results of the bonding shear strength of the metal composite sintered body according to the present embodiment. [Figure 8] Graph showing the measurement results of the tensile strength when the metal composite sintered body according to the present embodiment is composed of a precipitation hardening stainless steel. [Figure 9] Graph showing the measurement results of the tensile strength when the metal composite sintered body according to the present embodiment is composed of an austenitic stainless steel. [Figure 10] Graph showing the measurement results of the tensile strength when the metal composite sintered body according to the present embodiment is composed of a martensitic stainless steel. [Modes for carrying out the invention]

[0019] Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the drawings. Note that the following embodiments are not intended to limit the invention as described in each claim, and not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention.

[0020] Figure 1 is a flowchart of the manufacturing method of a metal composite sintered body according to an embodiment of the present invention; Figure 2 is a conceptual diagram of a sintered body manufactured by the manufacturing method of a metal composite sintered body according to an embodiment of the present invention; Figure 3 is a conceptual diagram for explaining the process of temporarily bonding the joining surfaces of the metal composite sintered body according to an embodiment of the present invention; Figure 4 is a conceptual diagram for explaining the process of filling spacer material in the manufacturing method of a metal composite sintered body according to an embodiment of the present invention; Figure 5 is a conceptual diagram of a test piece for measuring the joint shear strength of the metal composite sintered body according to this embodiment; Figure 6 is a diagram showing the joining surface of a test piece for measuring the joint shear strength of the metal composite sintered body according to this embodiment; Figure 7 is a graph showing the measurement results of the joint shear strength of the metal composite sintered body according to this embodiment; Figure 8 is a graph showing the measurement results of the tensile strength when the metal composite sintered body according to this embodiment is made of precipitation-hardening stainless steel; Figure 9 is a graph showing the measurement results of the tensile strength when the metal composite sintered body according to this embodiment is made of austenitic stainless steel; and Figure 10 is a graph showing the measurement results of the tensile strength when the metal composite sintered body according to this embodiment is made of martensitic stainless steel.

[0021] As shown in Figure 1, the method for manufacturing a metal composite sintered body according to this embodiment includes the steps of: creating a kneaded mixture by kneading metal powder and a binder and then granulating it (S101); manufacturing a molded body by injection molding the kneaded mixture (S102); degreasing the molded body to remove the binder (S103); sintering the molded body from which the binder has been removed to obtain a sintered body (S104); polishing the joint surface of the sintered body (S105); preparing a plurality of sintered bodies and temporarily bonding the joint surfaces together (S106); joining the temporarily bonded sintered bodies by diffusion sintering (S107); and performing post-processing and inspection of the metal composite sintered body joined by diffusion sintering (S108).

[0022] The metal composite sintered body 10 manufactured by the manufacturing method of the metal composite sintered body according to this embodiment will be described in the case where the metal composite sintered body 10 is manufactured by planar contact having a plate-shaped first member 11 and a plate-shaped second member 12, as shown in Figure 2(a) (Embodiment 1). Furthermore, the case where a metal composite sintered body 10a is manufactured having a plate-shaped first member 11a and a plate-shaped second member 12a having a columnar portion 13, and slits 21 having a predetermined groove width G are formed along both ends, as shown in Figure 2(b) (Embodiment 2). The groove width G of the slits 21 of the metal composite sintered body 10 is formed to an extremely small width that cannot be formed by molding with a mold, for example, having a groove width of about 0.5 mm.

[0023] Step S101 involves mixing the metal powder and binder to create a paste. Various conventionally known metal powders can be used, but stainless steel powder made from precipitation-hardening stainless steel such as SUS630 is preferred. While various metal powders can be used, other suitable stainless steel powders include austenitic stainless steels such as SUS316, SUS304, and SUS316L, or martensitic stainless steels such as SUS420J2. The binder is an additive that provides the fluidity necessary for injection molding, as described later. A binder made from a general-purpose synthetic resin with added lubricants and plasticizers is preferred. The ratio of metal powder to binder can be adjusted as appropriate depending on the properties and shape of the metal composite sintered body to be manufactured, but a ratio of 60 vol% to 40 vol% is preferred.

[0024] The compound is prepared by adding a binder to metal powder, heating and pressurizing the mixture, then cooling and solidifying the mixture, which is then crushed and granulated, or granulated using a granulator to obtain a fluid compound.

[0025] The process of manufacturing a molded body by injection molding of a compound (S102) involves injecting the compound into a mold and then cooling and solidifying it to produce a molded body of a predetermined shape. The mold used for injection molding can be a conventional mold corresponding to the shape of the molded body, and in the manufacturing method of the metal composite sintered body according to this embodiment, the first members 11, 11a and the second members 12, 12a are manufactured by injection molding, respectively.

[0026] The step of degreasing the molded body to remove the binder (S103) is a step of removing the binder contained in the molded body to obtain a degreased body prior to sintering, which will be described later. This can be done by a heat degreasing treatment in which the molded body is heated under an inert gas flow to evaporate and thermally decompose the binder, or by a solvent degreasing treatment in which the binder is extracted with an organic solvent.

[0027] In the step of obtaining a sintered body by sintering the molded body from which the binder has been removed (S104), the degreased body is heated to approximately 1100°C to 1400°C in a vacuum, inert gas, and reducing gas atmosphere to sinter it. Any remaining binder contained in the degreased body is removed during the heating process by sintering. As the binder is removed from the molded body through degreasing and sintering in this way, the sintered body shrinks in dimensions by about 10% to 20% compared to the molded body.

[0028] The step of polishing the joint surfaces of the sintered bodies (S105) involves polishing each joint surface that is superimposed when multiple sintered bodies are joined to a predetermined surface roughness. Specifically, as shown in Figures 3(a) and (b), the joint surfaces 14 of the first members 11, 11a and the joint surfaces 15 of the column portion 13 of the second member 12 and the second member 12a are polished. At this time, it is preferable to polish the joint surfaces 14 and 15 so that the surface roughness Ra after polishing is between 0.4 and 1.6. Various conventional polishing methods can be used to polish the joint surfaces 14 and 15.

[0029] The step of preparing multiple sintered bodies and temporarily bonding the joining surfaces together (S106) involves temporarily bonding the joining surfaces, which have been polished to a predetermined surface roughness, using an adhesive to fix them in place so that they do not move during the diffusion sintering process described later. Any adhesive can be used as long as it can be removed by heating during diffusion sintering, and various conventionally known adhesives can be used. The adhesive may be applied uniformly to the entire joining surface, or it may be applied in dots at predetermined intervals on the joining surface. Any adhesive can be used in the step of temporarily bonding the joining surfaces together (S106) as long as it can bond the polished joining surfaces together, but for example, an anaerobic adhesive is preferable.

[0030] Furthermore, as shown in Figure 4, in the metal composite sintered body 10a according to Embodiment 2, which has a slit 21 between the first member 11a and the second member 12a, it is preferable to fill the slit 21 with a spacer material 30 when temporarily bonding the first member 11a and the second member 12a. The spacer material 30 is filled to prevent the first member 11a and the second member 12a from tilting relative to each other during diffusion sintering, which would prevent the formation of a slit with a predetermined groove width. Alumina powder is preferably used for this purpose. In addition, the spacer material 30 is not limited to alumina powder; for example, ceramic powder can also be used to obtain a similar effect.

[0031] The step of joining the temporarily bonded sintered bodies by diffusion sintering (S107) is a step of joining the temporarily bonded sintered bodies together by sintering them again. Specifically, the sintering temperature for diffusion sintering is preferably set to 1290°C to 1350°C. At this time, since the sintered bodies have been degreased and sintered once, there is almost no remaining binder, so it is possible to minimize dimensional changes and deformation due to diffusion sintering.

[0032] The process of post-processing and inspection of the metal composite sintered body joined by diffusion sintering (S108) is a process of post-processing and inspection of the metal composite sintered body 10 joined by diffusion sintering. Specifically, this involves heat treatment of the metal composite sintered body 10, polishing to ensure dimensional accuracy, etc. [Examples]

[0033] Next, the present invention will be described in more detail with reference to examples.

[0034] [Shear strength test] The shear strength of the metal composite sintered body obtained by the manufacturing method of the metal composite sintered body according to this embodiment was measured. The example used for measuring the shear strength was a metal composite sintered body obtained by joining flat plate pieces 40 of stainless steel (SUS630) sintered body by diffusion sintering, as shown in Figure 5. For the measurement of shear strength, as shown in Figure 6, the surface roughness of the joining surface 41 of the flat plate pieces 40 was set to Ra0.4 for Example 1, Ra0.8 for Example 2, Ra1.6 for Example 3, and Ra3.2 for Comparative Example 1, and diffusion sintering was performed. The adhesive used for temporary bonding of the joining surfaces was Aron Alpha Jelly, manufactured by Konishi Co., Ltd., as an anaerobic adhesive.

[0035] Furthermore, for Examples 1 to 3 and Comparative Example 1, diffusion sintering was performed at sintering temperatures of 1230°C, 1260°C, 1290°C, 1320°C, and 1350°C, and the shear strength of the joint surface was measured for each example and comparative example. For the shear strength test, a test piece as shown in Figure 5 was cut from the first member 11 and second member 12 (4 mm × 2 mm × 13 mm) shown by the dotted line in Figure 2(a). The second member 12 side was held axially, and pressure was applied upward to the surface of the first member 11 side to apply force to the joint surface 41 and determine the shear strength. The shear test was performed at a speed of 1 mm / min.

[0036] As shown in Figure 7, Examples 1 and 2 achieved a shear strength of 80% or more of the unjoined, one-piece sintered body when the diffusion sintering temperature was between 1290°C and 1350°C (one-piece strength 600 N / mm²). 2 ±20 N / mm 2 It was confirmed that the material possessed a shear strength of ). Furthermore, in Example 3, it was confirmed that the material had sufficient shear strength, exceeding 80% of the shear strength of the integrated sintered body at temperatures of 1320°C or higher. In contrast, in Comparative Example 1, the shear strength was below 50% of the integrated body's shear strength at all diffusion sintering temperatures, confirming that it did not possess sufficient shear strength.

[0037] Further, when visually inspecting the joint surfaces of Examples 1 to 3 and Comparative Example 1, the joint surface could not be confirmed for the sintering temperatures of diffusion sintering in Example 1 ranging from 1290°C to 1350°C, whereas the joint surface was confirmed or it was confirmed to be in an unjoined state at the other sintering temperatures of diffusion sintering.

[0038] [Tensile Strength Test] Next, a measurement test of the tensile strength of the metal composite sintered body obtained by the manufacturing method of the metal composite sintered body according to the present embodiment was conducted. In the examples used for the measurement of the tensile strength, as the metal powder, in Example 4, SUS630, which is a precipitation hardening stainless steel, was used; in Example 5, SUS316, which is an austenitic stainless steel, was used; and in Example 6, SUS420J2, which is a martensitic stainless steel, was used. Further, in Examples 4 to 6, a metal composite sintered body in which round bar-shaped test pieces were joined by diffusion sintering was used. The test pieces used were cylindrical test pieces with a diameter of φ9 mm and a length of 22 mm. In Examples 4 to 6, diffusion sintering was performed with the surface roughness of the joint surface of the test pieces being Ra0.4. Furthermore, in the diffusion sintering of Examples 4 to 6, the sintering temperatures of 1290°C, 1320°C, and 1350°C were used respectively to measure the tensile strength. The adhesive used for the temporary adhesion between the joint surfaces was an anaerobic adhesive, manufactured by Konishi Co., Ltd., in the form of Aron Alpha Zelly.

[0039] As shown in FIG. 8, in Example 4, in all cases where the sintering temperature was 1290°C, 1320°C, and 1350°C in the tensile strength test, it was confirmed that the strength was 80% or more of the base material strength (960 N / mm 2 ), that is, 768 N / mm 2 ). As shown in FIG. 9, in Example 5, in all cases where the sintering temperature was 1290°C, 1320°C, and 1350°C in the tensile strength test, it was confirmed that the strength was 80% or more of the base material strength (520 N / mm 2 ), that is, 416 N / mm 2 ). Also, as shown in FIG. 10, in Example 6, in all cases where the sintering temperature was 1290°C, 1320°C, and 1350°C in the tensile strength test, it was confirmed that the strength was 80% or more of the base material strength (900 N / mm 2 ), that is, 720 N / mm2 It was confirmed that it possesses the strength of ).

[0040] Thus, it was confirmed that the metal composite sintered body according to this embodiment, when subjected to diffusion sintering at a sintering temperature of 1290°C to 1350°C with a surface roughness of Ra0.4 at the joint surface, has a tensile strength of 80% or more of the base material strength.

[0041] As described above, the manufacturing method and the metal composite sintered body according to this embodiment are performed by grinding the joint surface of the sintered body after it has been sintered once, and then joining by diffusion sintering. This makes it possible to suppress dimensional changes and deformation during diffusion joining and to ensure strength equivalent to that of the base material. Furthermore, the manufacturing method of the metal composite sintered body according to this embodiment not only suppresses dimensional changes and deformation as described above, but also ensures joint strength, making it possible to manufacture hollow shapes and complex shapes with extremely small gaps.

[0042] Furthermore, the present invention is not limited to joining sintered stainless steel bodies as described above; sintering may also be performed using various materials conventionally used as sintered bodies. It is clear from the claims that such modified or improved forms may also be included within the technical scope of the present invention. [Explanation of Symbols]

[0043] 10 Metal composite sintered body, 11 First member, 12 Second member, 13 Column section, 14, 15, 41 Joining surface, 20 Hollow section, 30 Spacer material, 40 Flat piece, G groove width.

Claims

1. A metal composite sintered body is formed by joining together a first member and a second member, which are made of a sintered body formed by injection molding of a mixture of metal powder and a binder, A metal composite sintered body characterized in that the tensile strength of the joint surface between the first member and the second member is 80% or more of the tensile strength of the first member or the second member.

2. In the metal composite sintered body according to claim 1, The tensile strength of the aforementioned joint surface is 768 N / mm². ２ That's all. The metal composite sintered body is characterized in that the metal powder is a precipitation-hardening stainless steel.

3. In the metal composite sintered body according to claim 1, The tensile strength of the aforementioned joint surface is 416 N / mm². ２ That's all. The metal composite sintered body is characterized in that the metal powder is austenitic stainless steel.

4. In the metal composite sintered body according to claim 1, The tensile strength of the aforementioned joint surface is 720 N / mm². ２ That's all. The metal composite sintered body is characterized in that the metal powder is martensitic stainless steel.

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