JP4201330B2 - Sintering method for sintered composites - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a sintering joining method in which inner and outer members are fitted together and joined by sintering, and in particular, a sintered composite joining method for a sintered composite suitable when inner and outer members are joined by utilizing the sintering shrinkage of outer members. It is about.
[0002]
[Prior art]
This type of sintered joining method is simpler and more advantageous in terms of manufacturing cost than mechanical joining because the inner and outer members are joined in the sintering process. In this joining method, the inner and outer members may utilize the sintering shrinkage of the outer member, and when the inner member 20 and the outer member 25 are surface joined as shown in FIG. If the outer member 25 is compressed in the length direction when the green compact for the outer member is used, the outer member 25 is in close contact with the inner member 20 in the length direction. The both ends 25a, 25a are easily bonded to each other without being in close contact with the corresponding portion of the inner member 20, and the bonding strength is insufficient. This is likely to occur in a mode in which the size after sintering (cooled from the sintering temperature to room temperature) as the sintered material structure shrinks to about 0.3% or more with respect to the green compact size. The following Patent Document 1 solves the above-described problem by the configuration of FIG. (A) shows the state before sintering, and (b) shows the sintered composite after sintering. This joining feature is that the inner member 21 has a large diameter portion 21a, 21b corresponding to the inner circumference of both ends of the outer member 26, a small diameter portion 21c, a small diameter portion 21c, and the large diameter portions 21a, 21b. A gentle connecting portion 21d is formed. Then, in the process of fitting and sintering the inner member 21 to the outer member green compact 26A, the inner peripheral surface of the green compact 26A is deformed into a shape corresponding to the outer peripheral surface shape of the inner member 21 formed. By being sintered and joined to the outer peripheral surface of the inner member, unjoined portions are prevented from being generated as much as possible, and the joining strength is satisfied.
[0003]
[Patent Document 1]
Japanese Patent No. 3318213 (Pages 2 to 3, FIGS. 1 to 5)
[0004]
[Problems to be solved by the invention]
In the sintered joining method of the above-mentioned document 1, it is possible to moderately increase the joining strength of the inner and outer members by suppressing the diameter expansion of the outer member end in FIG. 5 (a), but the processing to the inner member becomes complicated, and the joining strength becomes smaller. Fluctuation easily occurs depending on the step size between the small portion and the large diameter portion, the inclination angle of the connecting portion, and the like. Further, as shown in FIG. 5B, the inner member 22 has a concave groove 23 communicating with the inside of the cylinder on the outer periphery, and the outer member 27 is in a form that covers the concave groove 23, it becomes difficult to apply. Normally, the outer member 27 contracts so as to escape into the groove 23 during the green compact sintering process, and both ends of the outer member do not adhere to the inner member 22 in the same manner as in FIG. In the case of a fluid passage, a gap is formed and becomes a cause of fluid leakage. Therefore, from the widespread use and mass productivity of sintered composites, it is effective to simplify the processing of the inner member applied for joining, or to have a groove for passage closed by the outer member. Moreover, it must be possible to ensure a strong bonding strength.
[0005]
The present invention has been devised from the above background. The purpose is for a sintered joining method that utilizes the shrinkage of the outer member due to sintering, the joining surface is a simple flat plate, and any aspect having a concave groove (annular or circular groove) in the middle of the joining surface. It is to make it easy to apply and to have excellent versatility and to improve the bonding strength.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is specified in the example of FIG. 1, in the sintered joining method of the sintered composite 1 in which the inner member 10 and the outer member 15 are fitted and joined by sintering, the outer member 15. Is obtained by sintering a cylindrical green compact 15A that has been compression-molded and has a dimensional shrinkage ratio of 0.3 to 0.8% due to sintering. By setting a relief step 10a at the location of the inner member 10 corresponding to the surface, fitting the inner member 10 into the cylinder of the green compact 15A, and dimensional shrinkage due to sintering of the green compact 15A, The both ends 15a of the outer member 15 are deformed so as to wrap around the edges of the step 10a of the inner member 10, respectively.
[0007]
In the above-mentioned sintering joining method, both end joining surfaces of the green compact for the outer member are located at the corresponding step of the inner member and are in an unrestrained state. It deforms and bites into the inner member so as to wrap the step edge from the outside by the inner deformation. As a result, the bonding strength increases in proportion to the biting into the edge of the step at both ends of the outer member, and the force required for the separation (extraction) in the axial direction of the inner member can be increased. Further, in this method, the inner member has a configuration in which the step is formed at both ends of the outer periphery or in the middle of the outer periphery (FIGS. 1 and 2), and a configuration in which a groove for passage is formed in the middle of the outer periphery (FIG. 4) is also applicable. In addition, in an aspect in which the inner member is shorter than the outer member, the steps may be omitted by setting the dimensions of each part so that the step is configured by both end faces of the inner member (FIG. 3). For this reason, the method of the present invention has an advantage that the processing of the inner member is simple and the applicable sintered composite is not widely regulated in shape.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, the method of the present invention will be described in detail with reference to the drawings. 1 to 4 show four sintered composite structures to which the method of the present invention is applied. In each figure, (a) schematically shows the state before sintering in which the inner member is fitted in the cylinder of the outer member green compact, and (b) schematically shows the sintered composite after sintering. It shows. In the following description, after clarifying examples of the sintered composite body with reference to FIGS.
[0009]
(Sintered composite) The sintered joining method of the present invention is such that the green compact for the outer member is sintered in a state where the inner member is fitted in the cylinder, and the inner and outer surfaces are illustrated as shown in FIG. The present invention is applied to a sintered composite formed by joining and integrating the members exclusively by sintering shrinkage of the outer member. Here, the outer member is a green compact obtained by compression-forming various mixed powders used in the field of powder metallurgy, or is pre-sintered at a low temperature. It is preferable that the sintered dimensional shrinkage ratio as a green compact or a pre-sintered body is at least 0.3% or more. When the dimensional shrinkage is performed, for example, a low-density green compact, a green compact with a lot of fine powder, and a green compact in which a liquid phase is produced by sintering are referred to, and are brought close to the target shrinkage rate. The inner member may be a steel material, a melted material, a sintered material, or a green compact. In short, there is a relationship in which dimensional expansion relative to the outer member is caused by sintering (for example, if the green compact for the inner member is smaller than the sintered dimensional shrinkage rate of the green compact for the outer member). That's fine.
[0010]
(Basic Example) The sintered composite body 1 in FIG. 1 has a configuration in which the inner member 10 and the outer member 15 have substantially the same length, and the inner and outer members are integrated in appearance. In this case, the inner member 10 may have a cylindrical shape, and may further have a small-diameter extension on one or both end faces. In such a form, the inner member 10 and the outer member green compact 15A have substantially the same length, and therefore the outer circumferences of both ends of the inner member 10 correspond to the both-end joint surfaces of the green compact 15A. Accordingly, a step 10a having a small diameter is formed on the outer periphery of both ends of the inner member 10 so as to be in non-contact with the both-end joint surface of the green compact 15A. If the step 10a has the small diameter extension portion, the step between the inner member 10 and the extension portion, that is, the large diameter portion of the inner member 10 is set to the length dimension shown in FIG. But it doesn't matter. Both the above members are sintered by fitting the inner member 10 in the cylinder of the green compact 15A. Then, the green compact 15A shrinks in size and deforms so that both ends 15a of the outer member 15 wrap around the edge of the step 10a of the inner member 10, respectively. In the sintered composite 1 obtained after cooling, the joining strength of the inner and outer members becomes stronger in proportion to the amount of biting due to the deformation of both ends 15a.
[0011]
The sintered composite 2 in FIG. 2 is configured such that the inner member 11 is longer than the outer member 16 and the outer member 16 is mounted at an arbitrary position in the outer peripheral longitudinal direction of the inner member 11. In this case, the inner member 11 may have a cylindrical shape or may have a small diameter extension portion on one or both end faces. In such a form, since both ends of the green compact 16A for the outer member face the outer peripheral surface of the inner member 11, an annular step 11a is provided around the outer surface of the inner member 11 facing the surface. . The step 11a is formed so that both ends of the green compact 16A are accommodated within the groove width, that is, both end joint surfaces of the green compact 16A are in an unconstrained state. Similarly to the above, when the inner member 11 is fitted into the cylinder of the green compact 16A and sintered, the green compact 16A shrinks in size and the both ends 16a side of the outer member 16 are inside. It deform | transforms so that the level | step difference 11a edge part of the material 11 may be wrapped, respectively. In the sintered composite 2, the bonding strength of the inner and outer members is increased according to the amount of biting due to the deformation.
[0012]
(Modification) The sintered composite 3 of FIG. 3 has a configuration in which the inner member 12 is accommodated in the cylinder of the outer member 17 with respect to FIG. In this case, the inner member 12 may be cylindrical, and may further have a small-diameter extension on one or both end faces. In such a form, the both ends of the inner member 12 are located on the inner side of the both end joint surfaces of the green compact 17A, and the presence of the virtual steps corresponding to the steps described above does not require the step processing according to the invention. Then, when both members are sintered by fitting the inner member 12 into the cylinder of the green compact 17A, the green compact 17A shrinks in size, and both ends 17a side of the outer member 17 are the end face edges of the inner member 12. Deform to wrap each part. In the sintered composite 3 obtained after cooling, the joining strength of the inner and outer members is increased in proportion to the amount of biting due to the deformation of both ends 17a.
[0013]
On the other hand, in the sintered composite 4 of FIG. 4, the inner member 13 is cylindrical with respect to FIG. 2, and the annular groove 14 and the groove 14 communicate with the inside of the cylinder on the outer periphery. It is a form which has the through-hole 15. In this case, the inner member 13 may have an extension on one or both end faces. In such a form, both ends of the outer member green compact 18A face the outer peripheral surface of the inner member 11, so that an annular step 13a is provided on the outer periphery of the inner member 13 around the surface facing each other. The step 13a is formed with a dimension that takes into account the amount of deformation in which both ends of the green compact 18A fit within the groove width, that is, the green compact 18A slightly deforms toward the concave groove 14 during sintering. . In the same manner as described above, when the inner member 13 is fitted into the cylinder of the green compact 18A and sintered, the green compact 18A shrinks in size and the intermediate portion of the outer member 18 is recessed. The groove 14 is deformed, and the both ends 18a are deformed so as to wrap around the edge of the corresponding step 13a of the inner member 13, respectively. For this reason, as for the sintered composite 4, the joint strength of the inner and outer members is increased according to the amount of biting caused by the deformation.
[0014]
(Embodiment) An embodiment of the above-described sintered joining method will be described with reference to FIGS.
(1) In FIG. 1, a mixed powder of weight ratio (alloy iron powder in which 2% Ni powder is adhered and diffused to 1.5% Mo alloy powder) + 0.6% graphite is prepared, and the mixed powder is compacted. Compression molding was performed so that the body density was 6.8 g / cm ³ . The inner member 10 is prepared as a green compact for the inner member by preparing a mixed powder composed of iron powder + 1.5% copper powder + 0.6% graphite powder in a weight ratio, and the mixed powder has a green compact density of 6.5 g / and compression molded so as to be cm ^3. Then, the inner member 10 was fitted into the cylinder of the green compact 15A and sintered in a 1130 ° C. reducing gas atmosphere. The dimensional shrinkage ratio (shrinkage due to sintering) of the outer member 15 was about 0.3%. In addition, as a comparative example, what used the inner member 10 which does not provide the level | step difference 10a was used, and other than that used the same thing, and sintered on the same conditions. Thirty examples and comparative examples were produced. Then, a load was applied to the inner member in a state where the outer member was fixed, and the evaluation was performed based on the load when the joining of both members was broken. As a result, the bonding strength was 2.5 times or more stronger in the example than in the comparative example, confirming the effectiveness of the invention.
[0015]
(2) In FIG. 4, the green compact 18A for the outer member is prepared by setting the weight ratio to copper powder + 10% tin powder and mixing and pulverizing to a predetermined particle diameter. It compression-molded so that it might be 6.0 g / cm < ³ >. As shown in FIG. 4A, the inner member 13 is formed with annular passage grooves 14 and through holes 15 on the outer periphery using a cylindrical member of S45C steel, and an annular step 13a having a groove width of 3 to 4 mm. Formed. Then, the inner member 13 was fitted into the cylinder of the green compact 18A and sintered in a reducing gas atmosphere at 780 ° C. The dimensional shrinkage ratio (shrinkage due to sintering) of the outer member 18 was about 0.8%. In addition, as a comparative example, what used the inner member 13 which does not provide the level | step difference 13a was used, and other than that used the same thing, and sintered on the same conditions. Thirty examples and comparative examples were produced. Then, a load was applied to the inner member in a state where the outer member was fixed, and the evaluation was performed based on the load when the joint between both members was broken. As a result, the bonding strength of the example was twice or more stronger than that of the comparative example, confirming the effectiveness of the invention. In addition, as a result of closing the cylinder one end side of the inner member 13 and applying water pressure from the other end side to examine liquid leakage, when the water pressure is 100 kgf / cm ² or more, the comparative example is that of the outer member 18 and the groove 14. Water leakage was observed from the beginning, but no leakage was observed in the examples.
[0016]
As described above, the present invention can be variously modified or developed as long as the requirements specified in the claims are satisfied. As an example, the outer member may be a cylindrical shape, and may have a flange portion, a projecting piece, or the like on the outer periphery.
[0017]
【The invention's effect】
As described above, the sintered joining method of the present invention is a form in which the inner and outer members are joined by utilizing the sintering shrinkage of the outer member, and the joining surface of the inner and outer members is a simple flat surface, and the inner member outer periphery has a concave groove. Even if it has, when the joint surface of both ends of the compact for outer member shrinks due to sintering, it bites into the inner member so as to wrap the step edge of the inner member from the outside, making sure that both members are in close contact To increase the bonding force. Also, compared to the method of Document 1, the processing of the inner member is extremely simple and suitable for mass productivity, and it is applicable to an aspect having a concave groove on the outer periphery of the inner member, so that it has versatility. Since the joining force at both ends of the material is particularly increased, it has advantages such as excellent reliability.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a first embodiment to which a method of the present invention is applied before and after sintering.
FIG. 2 is a schematic view showing a second embodiment to which the method of the present invention is applied before and after sintering.
FIG. 3 is a schematic view showing a modification of the first embodiment before and after sintering.
FIG. 4 is a schematic diagram showing a modification of the second embodiment before and after sintering.
FIG. 5 is a schematic diagram for explaining a conventional problem.
FIG. 6 is a schematic view showing a conventional example of a sintering joining method before and after sintering.
[Explanation of symbols]
1 to 4 ... Sintered composites 10 to 13 ... Inner member 14 ... Groove 15 ... Through holes 10a, 11a, 13a ... Escape steps 15 to 18 ... Outer members 15A to 18A ... Outer member green compacts 15a to 18a ... both ends

Claims (1)

In the sintered joining method of the sintered composite, in which the inner member and the outer member are fitted and joined by sintering,
The outer member is obtained by sintering a cylindrical green compact that is compression-molded, and the dimensional shrinkage due to sintering is 0.3 to 0.8% .
Dimensional shrinkage due to sintering of the green compact by setting a relief step at the location of the inner member corresponding to the joint surface of both ends of the green compact, and fitting the inner member into the cylinder of the green compact By the above, the both ends of the outer member are deformed so as to wrap around the step edges of the inner member, respectively.

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