Method for producing metal composite sintered compact and metal composite sintered compact

Abstract

To provide a method for producing a metal composite sintered compact which can sufficiently secure bonding strength and produce a hollow shape or a complex shape having a very small gap.SOLUTION: A method for producing a metal composite sintered compact comprises the steps of: preparing a kneaded compact of a metal powder and a binder; injection-molding the kneaded compact to produce a molded compact; degreasing the molded compact to remove the binder; sintering the molded compact from which the binder has been removed to obtain a sintered compact; polishing a joint surface of the sintered compact; preparing the plurality of sintered compacts and temporarily bonding the joint surfaces to each other; and diffusion sintering and bonding the temporarily bonded sintered compact.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a metal composite sintered body and a metal composite sintered body, and in particular to a method for producing a metal composite sintered body that can accurately produce sintered bodies having hollow spaces or complex shapes with intricate interiors, and a metal composite sintered body. [Background technology]

[0002] Conventionally, it is known that parts used in automobile parts and precision machinery are manufactured using a metal composite sintered body by powder metallurgy, in which metal powder is powder molded and then sintered to form a sintered body. Such parts used in automobile parts and precision machinery, such as sintered bodies of mechanical parts with complex shapes such as gears, joints, or cams, and sintered bodies of parts with complex partial shapes such as curved holes and elongated holes, cannot be obtained in the desired shape only by pressure molding using a powder molding die, so conventionally, sintered bodies with complex shapes have been manufactured by combining pressure molding and machining, for example, by the following method. First, a mixed powder of a metal powder as a raw material powder and a metal powder added as necessary is placed in a die and pressure molded to produce a molded body. Next, this molded body is sintered, and the obtained sintered body is machined to be molded into a desired shape. In other words, in the above manufacturing method, a complex shape is molded 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, there is a method for producing a metal composite sintered body by applying an adhesive coating liquid to the joining surface of an injection molded body obtained by metal powder injection molding and sintering the body in that state. As described in Patent Document 2, there is a method for producing a part with a complex shape by diffusion bonding the metal sintered bodies by fitting together a plurality of green bodies (molded products obtained by molding a mixture of metal powder and a binder using an injection molding machine) and degreasing and sintering them in a sintering furnace. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-236042 A [Patent Document 2] Patent Publication No. 2021-32622 Summary of the Invention [Problem to be solved by the invention]

[0005] However, according to the conventional manufacturing methods for metal composite sintered bodies described in Patent Documents 1 and 2, bonding is performed in the form of a molded body before degreasing, called a green body. Therefore, when the binder is removed after degreasing, shrinkage and deformation occur, resulting in uneven contact of the bonding surfaces and reduced bonding strength.

[0006] Furthermore, in conventional powder metallurgy manufacturing methods, a mold is used to form a compact, and so there is a problem in that the conventional manufacturing methods are unable to manufacture complex shapes, such as hollow shapes or shapes having extremely small gaps, which are difficult to mold using a mold.

[0007] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for manufacturing a metal composite sintered body, and a metal composite sintered body, which can ensure sufficient bonding strength and can be manufactured into hollow shapes or complex shapes having extremely small gaps. [Means for solving the problem]

[0008] The manufacturing method of the metal composite sintered body according to the present invention is characterized by comprising the steps of preparing a kneaded mixture of metal powder and a binder, injection molding the kneaded mixture to produce a molded body, 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 bonding surfaces of the sintered body, preparing a plurality of the sintered bodies and temporarily bonding the bonding surfaces together, and diffusion sintering the temporarily bonded sintered bodies to bond them.

[0009] In the method for producing a metal composite sintered body according to the present invention, it is preferable that the step of temporarily bonding the bonding surfaces includes a step of filling gaps between the temporarily bonded sintered bodies with a spacer material.

[0010] In the method for producing a metal composite sintered body according to the present invention, it is preferable that the sintering temperature in the diffusion sintering step is 1290°C to 1350°C.

[0011] In the method for producing a metal composite sintered body according to the present invention, it is preferable that the step of polishing the bonding surface sets the surface roughness of the bonding surface to Ra0.4 to Ra1.6.

[0012] In the method for producing a metal composite sintered body according to the present invention, it is preferable that the step of temporarily bonding the bonding surfaces uses an adhesive.

[0013] Furthermore, the metal composite sintered body according to the present invention is a metal composite sintered body obtained by joining a first member and a second member, each of which is a sintered body obtained by injection molding a mixture of metal powder and a binder, and which is characterized in that the tensile strength of the joining 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] In the metal composite sintered body according to the present invention, the tensile strength of the bonding surface is 768 N / mm 2 As described above, it is preferable that the metal powder is a precipitation hardening stainless steel.

[0015] In the metal composite sintered body according to the present invention, the tensile strength of the bonding surface is 416 N / mm 2 As described above, it is preferable that the metal powder is an austenitic stainless steel.

[0016] In the metal composite sintered body according to the present invention, the tensile strength of the bonding surface is 720 N / mm 2 As described above, it is preferable that the metal powder is a martensitic stainless steel. Effect of the Invention

[0017] The manufacturing method of the metal composite sintered body and the metal composite sintered body of the present invention include a process of polishing the joining surfaces of the sintered bodies and a process of diffusion sintering and joining the temporarily bonded sintered bodies, so that the joining strength of the joining surfaces can be ensured and sintered bodies with complex shapes, such as hollow spaces or shapes with extremely small gaps, can be obtained. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a flow diagram of a method for producing a metal composite sintered body according to an embodiment of the present invention. [Diagram 2] 1 is a conceptual diagram of a sintered body manufactured by a method for manufacturing a metal composite sintered body according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a conceptual diagram for explaining a step of temporarily bonding bonding surfaces together in the manufacturing method of the metal composite sintered body according to the embodiment of the present invention. [Figure 4] FIG. 4 is a conceptual diagram for explaining a step of filling a spacer material in the manufacturing method of the metal composite sintered body according to the embodiment of the present invention. [Diagram 5] FIG. 2 is a conceptual diagram of a test piece for measuring the joint shear strength of the metal composite sintered body according to the embodiment. [Figure 6] FIG. 2 is a diagram showing a joint surface of a test piece for measuring the joint shear strength of the metal composite sintered body according to the embodiment. [Figure 7] 4 is a graph showing the measurement results of the joint shear strength of the metal composite sintered body according to the embodiment. [Figure 8] 4 is a graph showing the measurement results of tensile strength when the metal composite sintered body according to the embodiment is made of precipitation hardening stainless steel. [Figure 9] 4 is a graph showing the measurement results of tensile strength when the metal composite sintered body according to the embodiment is made of austenitic stainless steel. [Figure 10] 4 is a graph showing the measurement results of tensile strength when the metal composite sintered body according to the embodiment is made of martensitic stainless steel. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Preferred embodiments for carrying out the present invention will be described below with reference to the drawings. Note that the following embodiments do not limit the inventions according to the claims, and all of the combinations of features described in the embodiments are not necessarily essential to the solution of the invention.

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

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

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

[0023] In the step (S101) of preparing a kneaded product of metal powder and binder, the metal powder and the binder are kneaded to prepare a kneaded product. As the metal powder, various metal powders known in the art can be used, but for example, stainless steel powder made of precipitation hardening stainless steel such as SUS630 is preferably used. As the metal powder, various metal powders can be used, but as the stainless steel powder, austenitic stainless steel such as SUS316, SUS304, SUS316L, or martensitic stainless steel such as SUS420J2 can be used. In addition, the binder is an additive that provides the necessary fluidity for injection molding, which will be described later, and is preferably a binder made of a general-purpose synthetic resin to which a lubricant and a plasticizer have been added. The ratio of the metal powder to the binder can be appropriately adjusted depending on the properties and shape of the metal composite sintered body to be manufactured, but for example, it is preferable to set the ratio of the metal powder to the binder to 60 vol%:40 vol%.

[0024] The kneaded material is prepared by adding a binder to metal powder, kneading the mixture under heating and pressure, and then cooling and solidifying the kneaded material, which is then pulverized and granulated or granulated in a granulator to obtain a kneaded material having flowability.

[0025] In the step (S102) of injection molding the kneaded mixture to manufacture a molded body, the kneaded mixture is injection molded into a metal mold, and then cooled and solidified to manufacture a molded body of a predetermined shape. The metal mold used for injection molding can be a metal mold corresponding to the shape of a conventionally known molded body, and in the method for manufacturing a metal composite sintered body according to this embodiment, the first members 11, 11a and the second members 12, 12a are each manufactured by injection molding.

[0026] The step (S103) of degreasing the green body to remove the binder is a step of removing the binder contained in the green body to obtain a degreased body prior to sintering, which will be described later. A thermal degreasing process in which the green body is heated under an inert gas flow to evaporate and pyrolyze the binder, or a solvent degreasing process in which the binder is extracted with an organic solvent, etc., are carried out.

[0027] In the process (S104) of sintering the green body from which the binder has been removed to obtain a sintered body, the degreased body is heated to about 1100°C to 1400°C in a vacuum, inert gas, or reducing gas atmosphere and sintered. Note that any binder remaining in the degreased body is removed in the process of heating by sintering. As the binder is removed from the green body through degreasing and sintering in this way, the dimensions of the sintered body shrink by about 10% to 20% compared to the green body.

[0028] In the step (S105) of polishing the bonding surfaces of the sintered bodies, the bonding surfaces that are overlapped when bonding a plurality of sintered bodies are polished to a predetermined surface roughness. Specifically, as shown in Figs. 3(a) and (b), the bonding surfaces 14 of the first members 11, 11a and the bonding surfaces 15 of the second member 12 and the column portion 13 of the second member 12a are polished. At this time, it is preferable to polish the bonding surfaces 14, 15 so that the surface roughness Ra after polishing is 0.4 to 1.6. Note that the polishing of the bonding surfaces 14, 15 can be performed by various conventionally known polishing methods.

[0029] In the step (S106) of preparing a plurality of sintered bodies and temporarily bonding the bonding surfaces together, the bonding surfaces polished to a predetermined surface roughness are temporarily bonded together using an adhesive, and the sintered bodies are fixed so as not to move during the diffusion sintering described below. Any adhesive may be used as the adhesive as long as it can be removed by heating during diffusion sintering, and various conventionally known adhesives may be used. In addition, the adhesive may be applied uniformly over the entire bonding surfaces, or may be applied in dots at predetermined intervals on the bonding surfaces. The adhesive used in the step (S106) of temporarily bonding the bonding surfaces together may be any adhesive as long as it can bond the polished bonding surfaces together, but it is preferable to use, for example, an anaerobic adhesive.

[0030] As shown in Fig. 4, the metal composite sintered body 10a according to the second embodiment having a slit 21 between the first member 11a and the second member 12a is preferably filled with a spacer material 30 in the slit 21 when the first member 11a and the second member 12a are temporarily bonded. The spacer material 30 is filled to prevent the first member 11a and the second member 12a from being tilted relative to each other during diffusion sintering, which would prevent a slit of a predetermined groove width from being formed, and is preferably made of alumina powder or the like. The spacer material 30 is not limited to alumina powder, and the same effect can be obtained by using, for example, ceramic powder.

[0031] The step (S107) of diffusion sintering and bonding the temporarily bonded sintered bodies is a step of re-sintering the temporarily bonded sintered bodies to bond them together. Specifically, the sintering temperature for the diffusion sintering is preferably 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 deformations due to diffusion sintering.

[0032] The step (S108) of post-processing and inspecting the metal composite sintered body joined by diffusion sintering is a step of post-processing and inspecting the metal composite sintered body 10 joined by diffusion sintering. Specifically, the metal composite sintered body 10 is subjected to a heat treatment and polished to ensure dimensional accuracy. EXAMPLES

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

[0034] [Shear strength test] A test was carried out to measure the joint shear strength of the metal composite sintered body obtained by the manufacturing method of the metal composite sintered body according to the present embodiment. The embodiment used for the measurement of the shear strength was a metal composite sintered body in which flat pieces 40 of sintered bodies of stainless steel (SUS630) were joined by diffusion sintering as shown in FIG. 5. For the measurement of the shear strength, in the embodiments 1 to 3 and the comparative example 1, the surface roughness of the joint surface 41 of the flat pieces 40 was Ra0.4 in the embodiment 1, Ra0.8 in the embodiment 2, Ra1.6 in the embodiment 3, and Ra3.2 in the comparative example 1, as shown in FIG. 6, and diffusion sintering was carried out. The adhesive used for the temporary adhesion of the joint surfaces was an anaerobic adhesive, Aron Alpha Jelly manufactured by Konishi Co., Ltd.

[0035] In addition, in 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 FIG. 5 was cut out from the first member 11 and the second member 12 (4 mm x 2 mm x 13 mm) shown by the dotted lines in FIG. 2(a), and the second member 12 side was held in the axial direction, and the surface on the first member 11 side was pressed upward to apply force to the joint surface 41 to determine the shear strength. The shear test was performed at a speed of 1 mm / min.

[0036] As shown in FIG. 7, in Examples 1 and 2, the sintering temperature of the diffusion sintering was 1290°C to 1350°C, and the shear strength of the sintered body of the unbonded monolith was 80% or more (the strength of the monolith was 600 N / mm 2 ±20N / mm 2 It was confirmed that Example 3 had a shear strength of 80% or more of the shear strength of the one-piece sintered body at 1320°C or higher, which was sufficient. In contrast, Comparative Example 1 had a shear strength of less than 50% of the one-piece shear strength at all sintering temperatures for diffusion sintering, which was confirmed to be insufficient.

[0037] In addition, when the bonding surfaces of Examples 1 to 3 and Comparative Example 1 were visually inspected, the bonding surfaces could not be observed when the sintering temperature of the diffusion sintering in Example 1 was 1290°C to 1350°C, whereas the bonding surfaces could be observed or the bonding surfaces were not yet bonded when the sintering temperature of the diffusion sintering in the remaining Examples 1 to 3 was 1290°C to 1350°C.

[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 this embodiment was performed. In the examples used for measuring the tensile strength, as the metal powder, Example 4 used SUS630, which is a precipitation hardening stainless steel, Example 5 used SUS316, which is an austenitic stainless steel, and Example 6 used SUS420J2, which is a martensitic stainless steel. Furthermore, in Examples 4 to 6, a metal composite sintered body was used in which a round bar-shaped test piece was joined by diffusion sintering. The test piece was a cylindrical test piece of φ9 mm × 22 mm, and in Examples 4 to 6, the surface roughness of the joint surface of the test piece was Ra0.4 and diffusion sintering was performed. Furthermore, the sintering temperatures in the diffusion sintering in Examples 4 to 6 were 1290 ° C, 1320 ° C, and 1350 ° C, respectively, and the tensile strength was measured. In addition, the adhesive used for temporary adhesion between the joint surfaces was an anaerobic adhesive, Aron Alpha Jelly manufactured by Konishi Co., Ltd.

[0039] As shown in FIG. 8, in the tensile strength test of Example 4, in all cases where the sintering temperatures were 1290°C, 1320°C, and 1350°C, the base material strength (960 N / mm 2 ) 80% or more 768N / mm 2 9, it was confirmed that Example 5 had a base material strength of 520 N / mm 3 in all cases where the sintering temperatures were 1290°C, 1320°C, and 1350°C. 2 ) or more (416N / mm 2 10, it was confirmed that Example 6 had a base material strength of 900 N / mm 3 in all cases where the sintering temperatures were 1290°C, 1320°C, and 1350°C. 2 ) or more (720N / mm 2) strength.

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

[0041] In this way, according to the manufacturing method of the metal composite sintered body and the metal composite sintered body of the present embodiment, the bonding surface of the sintered body that has been sintered once is polished, and then the bonding is performed by diffusion sintering, so that dimensional changes and deformation during diffusion bonding can be suppressed and strength equivalent to that of the base material can be ensured. Furthermore, according to the manufacturing method of the metal composite sintered body of the present embodiment, in addition to suppressing dimensional changes and deformation as described above, the bonding strength can also be ensured, so that hollow shapes and complex shapes with extremely small gaps can be manufactured.

[0042] The present invention is not limited to the joining of the above-mentioned stainless steel sintered bodies, but may be performed using various materials that are conventionally used for sintered bodies. It is clear from the claims that such modified or improved embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0043] 10 metal composite sintered body, 11 first member, 12 second member, 13 column portion, 14, 15, 41 joint surface, 20 hollow portion, 30 spacer material, 40 flat plate piece, G groove width.

Claims

1. A step of preparing a mixture of metal powder and a binder; A step of producing a molded body by injection molding the kneaded mixture; degreasing the compact to remove the binder; sintering the compact from which the binder has been removed to obtain a sintered body; polishing the bonding surface of the sintered body; preparing a plurality of the sintered bodies and temporarily bonding the bonding surfaces together; and bonding the temporarily bonded sintered bodies by diffusion sintering.

2. The method for producing a metal composite sintered body according to claim 1, A method for manufacturing a metal composite sintered body, characterized in that the step of temporarily bonding the bonding surfaces includes a step of filling gaps between the temporarily bonded sintered bodies with a spacer material.

3. The method for producing a metal composite sintered body according to claim 1, The method for producing a metal composite sintered body, wherein the diffusion sintering step is performed at a sintering temperature of 1290°C to 1350°C.

4. The method for producing a metal composite sintered body according to claim 1, A method for producing a metal composite sintered body, wherein the step of polishing the joining surface sets the surface roughness of the joining surface to Ra 0.4 to Ra 1.

6.

5. The method for producing a metal composite sintered body according to claim 1, A method for producing a metal composite sintered body, wherein the step of temporarily bonding the bonding surfaces together is performed using an adhesive.

6. A metal composite sintered body obtained by joining a first member and a second member, each of which is a sintered body obtained by injection molding a mixture of a metal powder and a binder and then sintering the mixture, 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.

7. The metal composite sintered body according to claim 6, The tensile strength of the joint surface is 768 N / mm ２ That's all. A metal composite sintered body, wherein the metal powder is a precipitation hardening stainless steel.

8. The metal composite sintered body according to claim 6, The tensile strength of the joint surface is 416 N / mm ２ That's all.

2. A metal composite sintered body, wherein the metal powder is an austenitic stainless steel.

9. The metal composite sintered body according to claim 6, The tensile strength of the joint surface is 720 N / mm ２ That's all.

2. A metal composite sintered body, wherein the metal powder is a martensitic stainless steel.

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