JP2009167482A - Method for producing connecting rod, and connecting rod - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a connecting rod in which the strength of a column part is increased, and whose thinning and lightening are possible while maintaining the rigidity and machinability of a large end part and a small end part, and to provide a connecting rod. <P>SOLUTION: The method for producing a connecting rod is characterized in that a column part, a large end part and a small end part in the cavity of a molding die are partitioned by a separator checking the movement of material powder, and the column part is packed with the material powder having strength higher than the material powder packed into the large end part and the small end part. The separator is composed of a plurality of slits narrower than the grain size of the material powder and elongating to the compressing direction, and is composed of Cu or Ag or Sn. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a connecting rod manufacturing method and a connecting rod. More specifically, the present invention relates to a sintered connecting rod formed by sintering forging material powder and a method for manufacturing the same.

  As is well known, the connecting rod is a member for connecting the piston of the reciprocating engine to the crankshaft, and includes a large end portion having a crankshaft hole, a small end portion having a piston pin hole, and a column portion connecting these. It is made up of. The connecting rod is a member that has a predetermined rigidity and fatigue strength and is required to be lightweight, and requires a high rigidity and good machinability at the large and small ends. Thinning and weight reduction by strengthening is required.

Patent Document 1 proposes a method of manufacturing a sintered connecting rod that satisfies the conflicting requirements with one kind of alloy powder. That is, in the green compact molding process, the density of the part that becomes the column part of the green compact is formed lower than the density of the part that becomes the large end part and the small end part, and the green compact is carburized in the sintering process. This is a method of performing a surface hardening treatment. According to this prior art, the low-density column part is carburized to a deeper part than the high-density large and small end parts, so that the large and small end parts that require machinability are not hardened. It is said that only the column portion where strength is required can be cured. However, there is a limit to satisfying these conflicting requirements with one kind of alloy powder, and there are cases where satisfactory characteristics cannot always be obtained for the column portion that requires strength.
JP 2007-284769 A

  The present invention has been made to solve the above-described problem, and is a connecting rod that can reduce the thickness and weight by increasing the strength of the column portion while maintaining the rigidity and machinability of the large end portion and the small end portion. It is an object to provide a manufacturing method and a connecting rod.

  The connecting rod manufacturing method of the present invention includes a powder filling step of filling a mold cavity with material powder, a pressure forming step of pressing the filled material powder to form a green compact, and the green compact And a forging step for forming a connecting rod coarse material by sintering and forging a method of manufacturing a connecting rod having a large end portion, a small end portion, and a column portion connecting the large end portion and the small end. In the powder filling step, a column region corresponding to the column portion of the cavity, a large end region corresponding to the large end, and a small end region corresponding to the small end are Partitioned by a separator that prevents the movement of the material powder, the column region is filled with a material powder that is stronger than the material powder that fills the large end region and the small end region, According to the flow of the material powder in the pressure molding step And form, and is characterized in that the melted or decomposed said sintering forging process.

  In the connecting rod manufacturing method of the present invention, the separator is composed of a plurality of slits that are narrower than the particle diameter of the material powder and extend in the compression direction, and the material is made of Cu, Ag, or Sn. It is desirable that it is either.

  The material powder filled in the column region of the cavity is desirably an Fe—C alloy powder containing at least one of Cu, Mo, and Ni.

  The connecting rod of the present invention is a connecting rod in which a large end portion, a small end portion, and a column portion connecting the large end portion and the small portion end are integrally formed by sintering. It is formed by using a material powder having a strength higher than that of the material powder forming the large end and the small end.

  According to the present invention, the column portion and the large and small end portions can be integrally sintered using material powders having different compositions, so that the column portion having high strength, high rigidity, and good machinability are obtained. A connecting rod that can be reduced in thickness and weight can be obtained.

  Further, since the separator according to the present invention is configured with a slit having a gap narrower than the particle size of the material powder, the material powder in the column region and the material powder in the large and small end regions are mixed with each other through the separator. There is nothing. Further, since the slit is formed so as to extend in the compression direction in the molding process, the separator can be deformed following plastic deformation and flow of the material powder due to pressurization. Therefore, since the material powder can be densified together with the separator, the strength of the boundary portion between the material powders having different compositions in the green compact can be made equal to other parts.

  In addition, since the separator is made of a material having a melting point lower than the sintering temperature, such as Cu, Ag, Sn, etc., the separator component melts, diffuses, decomposes or disappears in the material powder in the sintering forging process. It does not reduce the strength. Accordingly, it is possible to obtain a connecting rod in which the bonding strength of the material powders having different compositions at the boundary portion between the column portion and the large and small end portions is stable.

  The manufacturing method of the connecting rod of the present invention can be carried out in the same manner as before except that a separator is mounted at a predetermined position of a molding die during powder molding and a plurality of material powders having different compositions are used. Therefore, the conventional line can be easily applied without drastically changing, and productivity is not hindered.

  The connecting rod manufacturing method of the present invention includes a powder filling step of filling a mold cavity with material powder, a pressure forming step of pressing the filled material powder to form a green compact, and sintering the green compact. And a sintering forging step of immediately forging and forging.

  A preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view schematically showing a molding die 1 according to the present embodiment. FIG. 2 is a schematic diagram illustrating an example of a separator.

  A cavity 10 corresponding to the outer shape of the connecting rod is formed in the molding die 1. The cavity 10 includes a large end region 12 corresponding to the large end portion of the connecting rod, a small end region 16 corresponding to the small end portion, and a column portion region 14 corresponding to the column portion. Grooves 18 and 18 for disposing the separator 2 are provided at the boundary between the large end region 12 and the column region 14 and at the boundary between the column region 14 and the small end region 16.

  In the powder filling process, first, separators 2 and 2 are provided upright in the grooves 18 and 18 of the molding die 1 to divide the cavity 10 into a large end region 12, a column region 14 and a small end region 16. . Next, a desired material powder is filled in each region. For example, the column region 14 is filled with Fe—C based alloy powder obtained by adding Cu, Ni, Mo or the like to the Fe—C based powder in order to increase the strength and reduce the thickness and weight. Further, in order to obtain high rigidity and good machinability, the large end region 12 and the small end region 16 are filled with a low C Fe—C-based powder having excellent powder compressibility and not high hardness. To do.

  In the pressure molding step, the filled material powder is pressed together with the separators 2 and 2 to form a green compact.

  In the sintering forging step, the green compact is heated and held at a predetermined temperature, and then sintered and forged to obtain a sintered forged body (a connecting rod coarse material). Furthermore, the desired connecting rod can be obtained by subjecting the obtained connecting rod crude material to coining, shot blasting and processing.

  Here, the separator 2 may be formed by forming a plurality of vertically long gaps (hereinafter referred to as slits) 24 on a foil or thin plate 22 made of Cu, Ag, Sn, or the like. The separator 2 formed in this manner can be deformed following the plastic deformation and flow of the material powder while partitioning the adjacent material powders so as not to be mixed in the pressure forming step. Accordingly, since the material powder can be densified together with the separator, the strength of the boundary portion between the material powder at the column portion and the material powder at the large and small end portions in the green compact can be made equal to other portions.

  Since the material powder at the boundary part is in close contact with each other through the slit 24, it can be sintered in the same manner as other parts by holding the green compact at a predetermined temperature. Further, since the separators 2 and 2 embedded in the green compact are made of Cu, Ag, Sn, or the like whose melting point is lower than the sintering temperature, Will not diffuse or disappear, and will not remain at the boundary between the column portion and the large and small end portions after sintering. Therefore, it does not cause a decrease in the strength of the boundary portion.

  In the separator 2 as described above, the thickness is desirably 1 to 100 μm. If it is less than 1 μm, it is difficult to form a slit, and if it exceeds 100 μm, densification of the material powder may be hindered. More preferably, it is 1-50 micrometers. The width w of the slit 24 is desirably set narrower than the minimum particle diameter of the material powder, and may be set to 5 to 40 μm, for example. If the slit width w is less than 5 μm, densification of the material powder at the boundary portion may be insufficient, and if it exceeds 40 μm, the adjacent material powder may be mixed, which is not appropriate. More preferably, it is 20-30 micrometers. It should be noted that the interval a between the slits 24 and 24 is preferably equal to the slit width w.

  As described above, the separator according to this embodiment has an excellent separation function for accurately separating different material powders in the powder filling process and the pressure molding process, and is different in composition because it disappears by melting or decomposition in the sintering forging process. High joint strength between sintered alloys is not hindered. Therefore, such a separator is suitable for manufacturing a connecting rod using a plurality of material powders having different compositions.

(Example)
Using a separator in which a plurality of slits having a width w: 30 μm and a spacing a: 50 μm are formed in a copper foil (melting point: 1084.5 ° C.) having a thickness of 0.05 mm, the column region and the large end region of the mold cavity A small edge region was partitioned. The column part region was filled with Fe-0.6C-2.5Cu-1.5Mo as a material powder, and the large end region and the small end region were filled with Fe-0.55C-2Cu. In addition, a numerical value is the mixture ratio (mass%) of the said component powder when the whole material powder is set to 100.

Next, these material powders were pressed together with a separator at 6 ton / cm ² to obtain a green compact. Subsequently, the obtained green compact was held at 1150 ° C. for 10 minutes and immediately forged to obtain a connecting rod crude material of the example.
(Comparative example)
It is the conventional connecting rod which consists of one type of material powder which does not use a separator. A comparative connecting rod coarse material was obtained in the same manner as in the example except that a mold having the same shape as in the example was used and the cavity was filled with Fe-0.55C-2Cu as a material powder.
(Evaluation)
The hardness of the column part of the connecting rod coarse material of the example is Hv450 or more, and a remarkable effect by adding a reinforcing component, particularly Mo, was recognized. Further, the hardness of the large and small end portions was Hv300 or less, and it was confirmed that the machinability was good as in the conventional case.

Fatigue strength at 10 ⁷ times column portion of the connecting rod of the embodiment is 450 MPa, the fatigue strength at 10 ⁷ times column portion of the connecting rod of the comparative example was 340 MPa.

  As described above, by using a high-strength material powder for the column portion, the hardness of the column portion can be improved by 50% or more and the fatigue strength can be improved by 30% or more in the embodiment as compared with the conventional one. Therefore, it was confirmed that the connecting rod according to the present example can be reduced in weight by reducing the thickness of the column portion compared to the conventional connecting rod. In the connecting rod of the example, no separator was observed at the boundary portion between the column portion and the large end portion and the small end portion.

  The present invention is not limited to the above-described embodiments and examples, and can be modified without departing from the gist of the present invention.

  For example, in the embodiment, the material powder for filling the column region of the mold cavity and the material powder for filling the large / small end region are two kinds of powders having different compositions. Three types of material powders having different compositions may be used, assuming that the filling powder and the filling powder in the small end region have different compositions.

  The present invention is suitable for use in a sintered connecting rod formed by sintering material powder.

It is a plane schematic diagram which shows the shaping die of embodiment. It is explanatory drawing which shows an example of a separator typically.

Explanation of symbols

1: Mold 10: Cavity 12: Large end region 14: Column region 16: Small end region 2: Separator 24: Slit

Claims (5)

A powder filling process for filling the mold cavity with material powder;
A pressure forming step of pressing the filled material powder to form a green compact;
A sintering forging step of sintering the green compact to form a connecting rod coarse material;
A connecting rod having a large end, a small end, and a column portion connecting the large end and the small end,
In the powder filling step, the material powder moves between a column portion region corresponding to the column portion of the cavity, a large end region corresponding to the large end portion, and a small end region corresponding to the small end portion. The column portion region is filled with a material powder having a strength higher than that of the material powder filled in the large end region and the small end region,
The separator is a method for producing a connecting rod, wherein the separator is deformed in accordance with the flow of the material powder in the pressure forming step and is melted or decomposed in the sintering forging step.   The method of manufacturing a connecting rod according to claim 1, wherein the separator has a plurality of slits that are narrower than the particle diameter of the material powder and extend in the compression direction.   The method for manufacturing a connecting rod according to claim 1, wherein the separator is made of any one of Cu, Ag, and Sn.   The material powder with which the said column part area | region of the said cavity is filled is Fe-C type-alloy powder containing at least 1 or more types of Cu, Mo, and Ni, As described in any one of Claims 1-3. A method for manufacturing a connecting rod. A connecting rod formed by integrally sintering a large end, a small end, and a column portion connecting the large end and the small end,
The column part is formed using a material powder having a strength higher than that of the material powder forming the large end part and the small end part.

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