Sintered component and method for producing the same

Abstract

To provide a sintered component and a method for producing the same, capable of suppressing a crack that occurs at a recessed corner of a step in a green compact, as well as strength deficiency caused by insufficient density.SOLUTION: A sintered component is obtained by sintering a single green compact made of metal powder and having a step. On a surface of a recessed corner of the step, a brazing material permeates into a gap between the sintered metal powders.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a sintered member and a method for producing the same. [Background technology]

[0002] There is a known method for producing a sintered member by compressing metal powder such as Fe-based metal powder, for example, in a die with a lower punch and an upper punch to form a green compact, and sintering the green compact. For example, Patent Document 1 discloses a multi-stage molding device that forms a green compact having steps. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-091143 A Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors have found the following problems with respect to a sintered member obtained by sintering a powder compact having a step and a method for manufacturing the same. In a green compact having steps, cracks or insufficient density may occur at the recessed corners of the steps during compaction, which may result in defects such as insufficient strength in the sintered portion.

[0005] The present disclosure has been made in consideration of the above circumstances, and provides a sintered member and a manufacturing method thereof that can suppress cracks that occur at recessed corners of steps in a green compact and strength deficiencies due to insufficient density. [Means for solving the problem]

[0006] The sintered member according to one embodiment of the present disclosure comprises: A sintered member obtained by sintering a single powder compact made of metal powder and having a step, A brazing material permeates the gaps between the sintered metal powder particles on the surface of the recessed corner of the step.

[0007] In the sintered member according to one aspect of the present disclosure, the brazing material permeates into the gaps between the sintered metal powders on the surface of the recessed corner of the step, thereby eliminating cracks and insufficient density that occur in the recessed corner of the step during molding of the green compact, and suppressing insufficient strength of the sintered member obtained by sintering the green compact.

[0008] The metal powder may be an Fe-based metal powder, and the brazing material may be a Cu-Ni-Mn-based brazing material.

[0009] A method for producing a sintered member according to one embodiment of the present disclosure includes: providing a single compact of metal powder having a step; Placing a brazing material on a surface of the recessed corner of the step; and sintering the powder compact with the brazing material disposed thereon.

[0010] In a method for manufacturing a sintered member according to one aspect of the present disclosure, a brazing material is placed on the surface of a concave corner of a step of a powder compact, and the powder compact is sintered. Therefore, the molten brazing material penetrates into the gaps between the metal powders to be sintered on the surface of the concave corner during sintering. This eliminates cracks and insufficient density that occur in the concave corner of the step during molding of the powder compact, and suppresses insufficient strength of the sintered member obtained by sintering the powder compact.

[0011] The brazing material may be in a paste form, and may be disposed by applying the brazing material to the surface of the recessed corner of the step. With this configuration, the brazing material can be easily disposed on the surface of the recessed corner of the step.

[0012] The metal powder may be an Fe-based metal powder, and the brazing material may be a Cu-Ni-Mn-based brazing material. Effect of the Invention

[0013] The present disclosure provides a sintered member and a method for manufacturing the same that can suppress cracks that occur at recessed corners of steps in a green compact and strength deficiencies due to insufficient density. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a perspective view of a sintered member according to the first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of a sintered member according to the first embodiment. [Diagram 3] 3 is a flowchart showing a method for producing a sintered member according to the first embodiment. [Figure 4] 1 is a photograph of a cross-sectional structure of a recessed corner of a step in a sintered member according to an example. [Diagram 5] 13 is a cross-sectional structure photograph of a recessed corner of a step in a sintered member according to a comparative example. [Figure 6] 5 shows a backscattered electron image and element mapping images of Fe, Cu, Ni, Mn, and C in region VI of FIG. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, specific embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to the following embodiments. In addition, the following description and drawings are appropriately simplified for clarity of explanation.

[0016] (First embodiment) <Configuration of sintered parts> First, the configuration of the sintered member according to the first embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view of the sintered member according to the first embodiment. Fig. 2 is a cross-sectional view of the sintered member according to the first embodiment. The sintered member shown in Fig. 1 and Fig. 2 is, as an example, a sintered member for an automobile, more specifically, a planetary carrier.

[0017] Examples of sintered parts for automobiles to which this embodiment can be applied include engine parts such as pulleys, sprockets, oil pump parts, bearing caps for crankshafts and camshafts, manual transmission parts such as synchro hubs and shift fingers, and automatic transmission parts such as turbine hubs.

[0018] Furthermore, the sintered member according to the present embodiment is not limited to automotive parts, but may be a magnet, a motor core, a motor rotor, a reactor core, a cutting tool, etc. Furthermore, although the sintered member according to the present embodiment is an Fe-based sintered member, it may be a sintered member made of a metal material containing, for example, Cu, Ni, Co, Ti, W, Mo, etc. as a main component.

[0019] Naturally, the right-handed XYZ Cartesian coordinate system shown in Figures 1 and 2 is for the convenience of explaining the positional relationship of the components. In Figure 1 and other figures, the positive direction of the Z axis is vertically upward, and the XY plane is a horizontal plane, which is common to all the drawings. 2 corresponds to the cross-sectional view taken along line II-II in FIG.

[0020] The sintered member 10 shown in FIG. 1 and FIG. 1 and 2, the base portion 11 is a plate-like portion having a substantially square shape when viewed in the XY plane. Each of the four sides of the base portion 11 is curved so as to protrude outward. A circular through hole 11a is provided in the center of the base portion 11.

[0021] The steps 12 extend along the four sides of the base portion 11 and protrude in the positive direction of the Z axis. Both longitudinal ends of the steps 12 protrude toward the inside of the base portion 11 (toward the through hole 11a). A recessed corner 12a of the step 12 is rounded.

[0022] The sintered component 10 is obtained by sintering a single green compact made of metal powder and having steps, that is, the sintered component 10 is not obtained by brazing a plurality of green compacts or sintered bodies.

[0023] On the other hand, the sintered member 10 is manufactured by applying a brazing material to the surface of the recessed corner 12a of the step 12 in the green compact before sintering, and then sintering the compact. Therefore, as shown in Fig. 2, on the surface of the recessed corner 12a of the step 12 in the sintered member 10, a permeated portion 13 where the brazing material has permeated into the gap between the sintered metal powder particles is formed.

[0024] For example, a paste-like brazing material is applied to the surface of the recessed corner 12a of the step 12, and then the compact is sintered. The paste-like brazing material is a mixture of a brazing material powder made of a metallic material and an organic binder. Alternatively, a compact of the brazing material powder made of a metallic material may be placed on the surface of the recessed corner 12a. The average particle size D50 of the brazing material powder is not particularly limited, but is, for example, about 20 to 50 μm.

[0025] The brazing material is appropriately selected depending on the type of metal powder constituting the green compact. When the green compact is composed of Fe-based metal powder, for example, a Cu-Ni-Mn brazing material is selected. As the Fe-based metal powder constituting the green compact, for example, an Fe-based alloy containing small amounts of Cu and C is used. The average particle size D50 of the Fe-based metal powder constituting the green compact is not particularly limited, but is, for example, about 20 to 300 μm.

[0026] When the Cu-Ni-Mn brazing material melts and penetrates into the gaps between the Fe-based metal powders, its melting point rises due to a reaction with Fe, and it resolidifies. Therefore, it can remain on the surface of the recessed corner 12a of the step 12, eliminating cracks and insufficient density of the recessed corner 12a. Here, the brazing material may contain, in addition to the Cu-Ni-Mn brazing material powder, about 10% to 20% of the Fe-based metal powder that constitutes the green compact. The brazing filler metal is generally called a Cu-Ni-Mn brazing filler metal, but in some cases the Ni concentration is higher than the Cu concentration, and the brazing filler metal may be called a Ni-Cu-Mn brazing filler metal.

[0027] As described above, when manufacturing the sintered member 10, cracks or insufficient density may occur in the recessed corner portion 12a at the base of the step 12 during compaction of the green compact. However, in the sintered member 10 according to this embodiment, during sintering, the molten brazing material penetrates into the gaps between the metal powder particles to be sintered on the surface of the recessed corner 12a of the step 12. This eliminates cracks and insufficient density that occur at the recessed corner 12a of the step 12 during molding of the green compact, and suppresses insufficient strength of the sintered member 10 obtained by sintering the green compact.

[0028] Furthermore, increasing the density of the green compact improves the strength of the sintered member 10, but makes the green compact more susceptible to cracking during molding. In other words, even if the green compact is made more dense and cracks occur during molding, the brazing material penetrates during sintering to eliminate the cracks and insufficient density. Therefore, the density of the green compact can be increased to improve the strength of the sintered member 10.

[0029] The sintered member according to this embodiment is not limited in shape, use, etc., so long as it is a sintered single green compact made of metal powder and having a step. 1 and 2, the base portion 11 may be circular or have another shape in plan view. The through hole 11a provided in the base portion 11 is not essential, and the shape of the through hole 11a is not limited to a circle. The position, shape, number, etc. of the step 12 can also be changed as appropriate.

[0030] 2 is formed over the entire recessed corner 12a of the step 12 shown in Fig. 1, but it may be formed only in a part of the recessed corner 12a. For example, the penetrating portion 13 shown in Fig. 2 may be formed only in a part of the recessed corner 12a that is particularly likely to crack or have insufficient density. With this configuration, the amount of brazing material used can be reduced.

[0031] On the other hand, for example, permeation portion 13 may be formed in a wider range including recessed corner portion 12a so as to straddle from the inner surface of step 12 to the upper surface of base portion 11. That is, permeation portion 13 may be formed in a wider range than permeation portion 13 shown in FIG. Here, the penetration portion 13 shown in FIG. 2 is merely shown diagrammatically, and does not accurately show the range, depth, etc. of the penetration portion 13 into which the brazing material has penetrated.

[0032] <Method of manufacturing sintered member according to the first embodiment> Next, the method for producing a sintered member according to the first embodiment will be described with reference to Fig. 3. Fig. 3 is a flow chart showing the method for producing a sintered member according to the first embodiment. 3, a single green compact made of metal powder and having a step 12 is prepared (step ST1). The green compact having the step 12 is manufactured by, for example, multi-stage molding, although not particularly limited thereto.

[0033] Next, as shown in Fig. 3, a brazing material is placed on the surface of the reentrant corner 12a of the step 12 of the compact (step ST2). For example, the brazing material is placed on the surface of the reentrant corner 12a of the step 12 by applying a brazing material paste to the surface of the reentrant corner 12a. Alternatively, a compact of brazing material powder made of a metallic material may be placed on the surface of the reentrant corner 12a. By using a brazing material paste, the brazing material can be easily placed on the surface of the reentrant corner of the step.

[0034] Finally, as shown in Fig. 3, the powder compact with the brazing material disposed on the surface of the reentrant corner 12a is sintered (step ST3). For example, the powder compact is placed in a sintering furnace and sintered by heating to a predetermined temperature. By step ST3, the molten brazing material penetrates into the gaps between the metal powder particles to be sintered on the surface of the reentrant corner 12a, forming the penetrated portion 13 shown in Fig. 2.

[0035] As described above, in the method for producing a sintered member according to this embodiment, a brazing material is placed on the surface of the recessed corner 12a of the step 12 of the green compact (step ST2), and the green compact is sintered to obtain a sintered member 10 (step ST3). Therefore, during sintering, the molten brazing material penetrates into the gaps between the metal powder particles to be sintered on the surface of the recessed corner 12a, forming the penetrated portion 13 shown in Fig. 2. This eliminates cracks and insufficient density that occur at the recessed corner 12a of the step 12 during molding of the green compact, and suppresses insufficient strength of the sintered member 10 obtained by sintering the green compact. EXAMPLES

[0036] The sintered member 10 according to the first embodiment and the method for producing the same will be described in detail below with reference to examples. However, the sintered member 10 according to the first embodiment and the method for producing the same are not limited to the following examples.

[0037] <Example> First, a single green compact made of Fe-based alloy (Fe-2.0 mass % Cu-0.9 mass % C) powder and having a step 12 was prepared (step ST1). The green compact had the same shape as the sintered member 10 shown in Fig. 1 and Fig. 2, and was formed by multi-stage molding. Here, the green compact was formed so that a crack would occur at a predetermined recessed corner 12a in the step 12.

[0038] Next, a brazing material was placed on the surface of the recessed corner 12a of the step 12 of the compact (step ST2). Specifically, a brazing material paste was applied to the surface of the recessed corner 12a of the step 12. The brazing material paste was a mixture of Cu-Ni-Mn alloy (Cu-41.5% by mass Ni-15% by mass Mn-1.8% by mass Si-1.5% by mass B) powder and an organic binder. Furthermore, the brazing material further contained Fe alloy (Fe-2.0% by mass Cu-0.9% by mass C) powder constituting the compact. The mass ratio of the Cu-Ni-Mn alloy powder to the Fe alloy in the brazing material was 85:15.

[0039] Next, the green compact with the brazing material disposed on the surface of the reentrant corner 12a was sintered in a sintering furnace to obtain the sintered member 10 (step ST3). The sintering conditions were a temperature of 1120° C. and a time of 20 minutes. For the sintered component 10 obtained in step ST3, cross-sectional structure observation of the reentrant corner portion 12a and a torsion strength test were performed.

[0040] <Comparative Example> A sintered member was produced in the same manner as in the example, except that step ST2 was omitted. In this way, since no brazing material is used in the manufacture of the sintered member of the comparative example, the sintered member of the comparative example does not have the infiltrated portion 13 shown in FIG. 2 formed on the surface of the reentrant corner portion 12a. The sintered member according to the comparative example was also subjected to cross-sectional structure observation of the reentrant corner portion 12a and a torsion strength test.

[0041] <Cross-sectional structure observation results> Below, the results of cross-sectional structure observation of the sintered members according to the example and the comparative example will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a cross-sectional structure photograph of a recessed corner of a step in the sintered member according to the example. Fig. 5 is a cross-sectional structure photograph of a recessed corner of a step in the sintered member according to the comparative example. Fig. 4 and Fig. 5 are both backscattered electron images.

[0042] As shown in Fig. 4, in the sintered component 10 according to the example, the brazing material permeates the surface of the recessed corner 12a of the step 12, forming the permeated portion 13 shown in Fig. 2. It was also confirmed that the permeated portion 13 extends to the inside of the sintered component 10 along the crack that occurred during molding of the powder compact, and the crack has been eliminated.

[0043] On the other hand, as shown in FIG. 5, in the sintered member 10 according to the comparative example, cracks were found on the surface of the recessed corner 12a of the step 12. In addition, in FIG. 4, the brazing material remaining on the surface of the recessed corner portion 12a of the step 12 does not particularly need to be removed, but may be removed.

[0044] Here, Fig. 6 shows a backscattered electron image and element mapping images of Fe, Cu, Ni, Mn, and C in region VI of Fig. 4. The mapping images of each element were all measured by an EPMA (Electron Probe Micro Analyzer).

[0045] As shown in Fig. 6, the observation area shows three Fe-based alloy particles P1 to P3 that make up the compact, and it was confirmed that the Cu-Ni-Mn-based brazing filler metal has penetrated into the gaps between the Fe-based alloy particles P1 to P3. It is also presumed that the concentrations of Fe, Cu, Ni, Mn, etc. gradually change near the interfaces between the Fe-based alloy particles P1 to P3 and the brazing filler metal, causing mutual diffusion.

[0046] <Torsion strength test results> The average torsional strength of the ten samples of the sintered member 10 according to the embodiment was 9650 N·m. On the other hand, the average torsional strength of the ten samples of the sintered member according to the comparative example was 9320 N·m. Thus, the torsional strength of the sintered member 10 according to the embodiment was, on average, 300 Nm (3% or more) higher than the torsional strength of the sintered member according to the comparative example, and all samples met the standard value for torsional strength.

[0047] As described above, in the sintered member 10 according to the embodiment, during sintering, the molten brazing material penetrates into the gaps between the metal powder particles to be sintered on the surface of the recessed corner 12a of the step 12. This eliminates the cracks and insufficient density that occur at the recessed corner 12a of the step 12 during molding of the green compact, and suppresses insufficient strength of the sintered member 10 obtained by sintering the green compact.

[0048] Furthermore, in the sintered member 10 according to the embodiment, the density of the green compact was set high so that cracks would occur during molding. As described above, increasing the density of the green compact improves the strength of the sintered member 10. It was found that in the sintered member 10 according to the embodiment, even if the density of the green compact was increased and cracks occurred during molding, the brazing material penetrated during sintering and the cracks and insufficient density were eliminated. In other words, in the sintered member 10 according to the embodiment, the strength could be improved compared to conventional methods by increasing the density of the green compact.

[0049] The present disclosure is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present disclosure. [Explanation of symbols]

[0050] 10 Sintered parts 11 Base 11a Through hole 12 steps 12a Recessed corner 13 Penetration part P1~P3 Fe-based alloy particles

Claims

1. A sintered member obtained by sintering a single powder compact made of metal powder and having a step, A brazing material is permeated into gaps between the sintered metal powders on the surface of the recessed corner of the step. Sintered parts.

2. The metal powder is an Fe-based metal powder, The brazing material is a Cu-Ni-Mn based brazing material. The sintered part according to claim 1 .

3. providing a single compact of metal powder having a step; Placing a brazing material on a surface of the recessed corner of the step; and sintering the powder compact having the brazing material disposed thereon. A method for manufacturing a sintered part.

4. The brazing material is in a paste form, and the brazing material is disposed by applying the brazing material to a surface of the recessed corner portion of the step. The method for producing a sintered member according to claim 3.

5. The metal powder is an Fe-based metal powder, The brazing material is a Cu-Ni-Mn based brazing material. The method for producing a sintered member according to claim 3 or 4.

Images