JP5513096B2 - Sliding bearing and brass porous body manufacturing method - Google Patents

Description

  The present invention relates to a brass slide bearing and a brass porous body including a brass bush.

Brass is generally called brass and has excellent workability, thermal conductivity and corrosion resistance, and is relatively inexpensive. By using brass as a material and cutting it, The produced brass bush is widely used in industrial machines and the like.
By the way, since ordinary metal bushes cannot hold lubricating oil for a long period of time, it is necessary to lubricate them during use. It is hoped that.

In response to such a demand, an oil-free bushing in which a porous bush made of a porous body using a copper alloy is impregnated with a lubricating oil has been developed.
For example, Patent Documents 1 and 2 disclose bearing materials obtained by sintering a copper alloy containing graphite and tin.
Patent Document 3 discloses a bush made of a porous composite sintered alloy obtained by mixing individual metal powders of iron, copper, zinc, and tin. Patent Document 4 discloses a porous formed of copper powder and iron powder. A bushing made of a high quality composite sintered alloy is disclosed.

  Porous bushes such as those described above are generally porous by compacting a metal mixed powder and sintering the compact at a high temperature in a reducing atmosphere (for example, a mixed gas atmosphere of hydrogen and nitrogen) or a reduced pressure atmosphere. It is manufactured by obtaining a sintered body made of a sintered alloy and sizing the sintered body as necessary.

Japanese Patent No. 3803947 Japanese Patent No. 3835915 Japanese Patent No. 4213714 Patent No. 2832800

However, if sintering is performed in a reducing atmosphere or a reduced-pressure atmosphere, equipment costs and operating costs of the sintering furnace are required, and accordingly, it is expensive to manufacture a porous bush.
Here, it is considered that the manufacturing cost can be reduced by sintering the molded body made of the metal mixed powder in the air atmosphere, but the metal powder is oxidized and the sintering is not successful. Damage is likely to occur when sizing. In addition, it is difficult to obtain the original physical properties of the metal in the sintered body.

In addition, the oil-free bush using graphite has a problem of dust in the manufacturing process and a problem of contamination of sludge mixed with lubricating oil and carbon powder at the time of use of the product.
In view of the above problems, an object of the present invention is to provide a brass porous bearing and a brass porous body at low cost.

In order to achieve the above object, in the present invention, in a production method for producing a porous plain bearing mainly composed of brass, molding is performed by molding a green body by applying a pressure of 200 MPa to 800 MPa to brass powder. A step, a sintering step of heating and sintering the molded green body at 880 to 940 ° C., and a cutting step of cutting the sintered molded body were provided.
Moreover, in the manufacturing method which manufactures a brass porous body, the shaping | molding process which shape | molds a green body by applying the pressure of 200 MPa or more and 800 MPa or less with respect to brass powder, and heats and heats the shape | molded green body at 880-940 degreeC. And a sintering step to be set.

The sintering process is preferably performed in an air atmosphere.
It is preferable to use brass chips as the brass powder.
In addition, when using brass cuttings, it is preferable to arrange | equalize powder size as uniformly as possible.
Moreover, it is preferable to perform the mixing process which mixes a lubricant with brass powder prior to a forming process.

  Porous bearings and brass which are made of a porous sintered body mainly composed of brass powder, have fine pores with a pore diameter of 1 to 200 μm, and have a porosity (porosity) of 30 to 50 vol% by the above production method. A porous body can be realized.

According to the manufacturing method of the present invention, since the brass powders are sufficiently pressed together by pressure molding and then sintered, the brass powders are firmly bonded to each other, and the strength and ductility of the sintered body are sufficiently secured. can do.
Thereby, even in the cutting process, the sintered body can be processed without being damaged. Moreover, the outstanding physical property as a brass can also be hold | maintained.

And since sintering can reduce the installation cost and operating cost of a sintering furnace by performing sintering in air | atmosphere as mentioned above, it contributes to manufacturing a brass porous oil-impregnated bearing at low cost.
Moreover, it is suitable for manufacturing a porous sintered compact to use a brass chip as a main raw material especially among brass powders.
Furthermore, since brass chips are waste material and inexpensive, by using this as a main raw material, it is possible to manufacture a brass porous bearing at a lower cost and contribute to recycling of the material.

The porous bearing and the brass porous body manufactured by the manufacturing method of the present invention are porous bodies in which brass powders are sintered and pores are formed between the powders.
Therefore, an oil-free bearing can be obtained by filling the hole with a lubricant. Moreover, it is excellent in moisture absorption, sound absorption, vibration proofing, and heat dissipation. Furthermore, since it is compatible with plating, it can be applied as a functional part of various products.
Further, since it is not necessary to use carbon powder such as graphite, there is no contamination by carbon dust or sludge during use.

Therefore, an oil-free bearing capable of maintenance-free can be manufactured, and can be used in the fields of automobiles and industrial machinery.
Moreover, according to the brass porous bearing of the present invention, since it has a fine hole with a hole diameter of 1 to 200 μm and a porosity of 30 to 50 vol%, it has a function of retaining lubricating oil in the hole for a long period of time. Have. Therefore, it can be used without lubrication for a long time.

It is process drawing which shows the manufacturing method of the brass porous bearing concerning embodiment. It is a figure explaining a pressure molding process. It is a figure explaining the drilling process and outer periphery cutting process of a sintered compact. It is a microscope picture of the brass chip used in the Example. It is a scanning electron micrograph of the sintered compact concerning an Example. It is a characteristic view which shows the strength test result of the sintered compact concerning an Example.

In the embodiment of the present invention, a brass porous sliding bearing (brass porous bush) is manufactured using brass powder as a main material.
Brass is an alloy mainly composed of copper Cu and zinc Zn, and the proportion of zinc in the alloy is 20% or more. Generally, as the proportion of zinc increases, hardness increases but brittleness also increases. In practice, the upper limit of the proportion of zinc is 45%.

Specifically, the following can be used as material symbols of the JIS standard.
C2600: Nanasan Brass (copper is about 70%, zinc is about 30%)
C2901: Hexagonal brass (copper is about 60%, zinc is about 40%)
C3604: Free-cutting brass Lead is added to improve machinability. (Copper 57-61%, lead 1.8-3.7%, iron 0.5% or less, iron + tin 1% or less, zinc remaining)
C3771: Brass for forging (copper is 57 to 61%, lead is 1 to 2.5%, iron + tin is 1% or less, zinc is the balance)
CAC201: Brass casting type 1
Drawing 1 is a flowchart showing the manufacturing method of the brass porous bearing concerning an embodiment.

Mixing step (S1):
First, a lubricant is added to brass chips and mixed with a powder mixer.
Here, suppose that the brass powder which generate | occur | produces when cutting a brass raw material is used as a brass powder. The average particle size of the brass chips used is preferably in the range of 0.5 to 2.0 mm. Here, the “average particle size” refers to the average of the maximum length of each brass chip.

Lubricant is an additive that reduces friction between the material and processing machine or particles of the material when processing the material, and it is not essential to add this to the brass chips. This is effective in favoring the pressure molding process.
Here, zinc stearate (Zn (OCOC ₁₇ H ₃₅ ) ₂ , melting point 115-125 ° C.) is used, and a small amount is mixed with the brass chips.

As the lubricant, the following can also be used.
Olefin waxes such as polyethylene wax and polypropylene wax Higher fatty acid esters such as butyl stearate, monoglyceride stearate, sorbitan ester stearate Bisamide lubricants such as ethylene bisamide Metal soap such as sodium stearate and calcium stearate Pressure molding process ( S2):
The above mixture in which a lubricant is mixed with brass chips is compression molded with a pressure molding machine (press).

FIG. 2 is a diagram illustrating the pressure molding process.
As shown in FIG. 2, with the lower punch 12 inserted into the die 10, the mixture 1 is filled, the upper punch 11 is lowered, and the pressure is applied to the mixture 1 as shown in FIG. 2 (b). Call.
As a result, the mixture 1 is compression-molded into a cylindrical shape that matches the internal shape of the die 10, and the green body 2 is produced.

As shown in FIG. 2C, the lower punch 12 is pushed up, and the green body 2 is taken out.
Since the lubricant (zinc stearate) is mixed in the filled mixture 1, when the upper punch 11 is pressed as described above, the brass chips are compressed while sliding against each other, and the pressure is uniformly applied to the whole. Take it.
In this step, it is preferable to pressurize at a pressure of 200 MPa or more so that the brass chips are sufficiently pressed together. This is because by performing pressure molding at a pressure of 200 MPa or more, brass chips are deformed, and adjacent powders are pressure-bonded to increase the contact area. On the other hand, in the green body 2, in order to ensure an appropriate gap between the brass chips, it is preferable to suppress the applied pressure in this step to 800 MPa or less.

It is considered that this applied pressure is preferably 300 MPa or more in order to more surely obtain the strength after sintering even in the range of 200 MPa or more and 800 MPa or less. Particularly, the preferable pressure is about 400 MPa.
Sintering step (S3):
The green body 2 formed into a cylindrical shape is sintered in an air atmosphere using a general batch furnace or a continuous open furnace (for example, a mesh belt type muffle sintering furnace). The sintering temperature is set in the range of 880 to 940 ° C.

Since general brass melts at about 902 ° C., by sintering the green body within the range of the sintering temperature of 880 to 940 ° C. as described above, the brass chips contained in the green body 2 are mutually bonded. The porous sintered body 3 is manufactured by sintering so as to bond in the contact region. The organic component (stearic acid) contained in the green body 2 is burned off during the sintering.
In the sintered body 3 to be manufactured, the chips do not melt completely. Accordingly, the gaps between the brass chips remain as fine pores. The pore size is on the order of submillimeters.

Cutting process (S4)
FIG. 3 is a diagram for explaining drilling and peripheral cutting of the sintered body 3.
The sintered body 3 is held by a lathe chuck 21. While rotating the lathe chuck 21, the tip of the drill 22 is abutted along the central axis of the sintered body 3 and drilled. In addition, after drilling with a drill, you may process an internal diameter with a bite.

Next, the outer periphery is cut by feeding the tip of the cutting tool 23 against the outer periphery of the sintered body 3 by operating the table to which the cutting tool 23 is fixed while rotating the chuck 21 of the lathe.
Such cutting is generally the same as the processing method used when manufacturing a metal bush, and can be finished with high accuracy.

Therefore, the brass porous bearing 4 can be accurately sized through this cutting process.
Here, the cylindrical green body 2 and the sintered body 3 are produced, and then the cylindrical brass porous bearing 4 is obtained by cutting the green body 2 and the sintered body 3. The shape is not limited to a cylindrical shape. For example, by preparing the hollow cylindrical green body 2 and sintered body 3 by adjusting the shape of the die 10, the brass porous bearing 4 can be obtained by cutting the inner periphery and the outer periphery thereof. it can.

In addition, in order to accurately size the inner diameter and the outer diameter, a grinding process, a polishing process, and a rolling process may be performed in addition to the cutting process.
<Characteristics of brass porous bearing and porous body according to the present embodiment>
The brass porous bearing 4 obtained by the above manufacturing method has a porosity of 10 to 50 vol%.

The porosity can be calculated by measuring the volume and weight.
Porous bearings with a high porosity are light in weight and can retain a large amount of oil in the gap. Therefore, by immersing the brass porous bearing 4 in the lubricating oil, a large amount of lubricating oil is impregnated in the hole and lubrication is performed. Oil is retained in the holes. Therefore, it is possible to realize a bearing that can be used without lubrication for a long period (for example, 1000 hours).

Generally, in a metal sintered body, if the porosity is increased, the sintering is likely to be insufficient. Therefore, the conventional metal porous bearing has a porosity of about 10 to 30 vol%. Therefore, a porous bearing having a high porosity of 30 vol% or more can be obtained, so that more lubricant can be retained in the bearing. Moreover, since it does not contain carbon powder, it is not contaminated by carbon dust or sludge during use.
Moreover, the brass porous body obtained by the above production method is excellent in moisture absorption, sound absorption, vibration proofing, and heat dissipation, and also has good compatibility with plating. Therefore, the present invention can be applied not only to a plain bearing but also as a functional part of various products.

<Effects of manufacturing method of this embodiment>
(1) According to the manufacturing method of the present embodiment, brass chips are used as the main raw material, and the brass chips are inexpensive, such as about 1,000 yen / kg or less, so that an oil-impregnated bearing made of brass can be manufactured at low cost.
(2) According to the manufacturing method of this embodiment, the cutting process is provided after the sintering process.
In this cutting process, a brass porous bearing can be accurately sized by performing a hole raising process, an outer diameter process, or the like, as in a general bushing process.

(3) Generally, when metal powder is sintered, the metal material is sintered at a temperature close to its melting temperature (about 902 ° C. for brass) in order to diffuse the metal material. In addition, if the metal powder is oxidized during the sintering, diffusion is not successfully performed. In order to prevent this, the sintering is performed under a reduced pressure atmosphere or a reducing atmosphere such as a nitrogen atmosphere.
On the other hand, in the present embodiment, the brass chips are pressure-bonded to each other and sintered after securing a sufficient contact area with each other. The chips are not easily oxidized and the brass chips are firmly joined together. Therefore, sufficient strength of the sintered body 3 can be ensured.

Thereby, it is possible to size the sintered body 3 without damaging it in the cutting process. Moreover, the outstanding physical property as a brass is also hold | maintained.
Also, a brass porous bearing having a porosity as high as about 40 vol% and strength can be obtained relatively easily.
Moreover, the installation cost and operation cost of a sintering furnace can be reduced by performing a sintering process in air | atmosphere atmosphere using a general sintering furnace. Therefore, it contributes to manufacturing a brass oil-impregnated bearing at a low cost.

(4) Among brass powders, particularly brass chips are used as the main raw material, which is suitable for producing a porous sintered body.
[Example]
The components of the brass chips used as the main material are 57 to 61% Cu, 1.8 to 3.7% Pb, 0.5% Fe, 1.2% Fe + Sn, and the remainder Zn.

FIG. 4 is a photomicrograph of brass chips used as the main raw material.
As shown in the figure, the shape of each chip is a flat bar, and the size is 1.5 mm in average length and 120 μm in average thickness.
The brass chips and zinc stearate are mixed at a weight ratio of 180: 1, and cylindrical firing is performed under conditions that are considered optimal (pressure 400 Mpa, pressure 910 ° C., sintering time 10 hours). A ligated sample (Φ20 mm, length 50 mm) was prepared.

FIG. 5 is a scanning electron micrograph of the sintered body.
As shown in this figure, in this sintered body, the shape of each chip is not a rod shape, but is compressed and deformed so that the contact area between adjacent chips becomes large. Adjacent chips are sintered together.
As a result of measuring the pore size (pore diameter) of this sintered body sample, the pore diameter was distributed in the range of 5 to 105 μm, and the average pore diameter was 25 μm.

Since the pores are connected to each other, the lubricating oil can be soaked into the inside.
In addition, although a pore diameter and a porosity are fluctuate | varied with pressurization conditions, the brass porous bearing manufactured by the manufacturing method of the said embodiment exists in the range whose pore diameter is 1-200 micrometers.
<Porosity and strength test of sintered body>
As a comparative example with respect to the above-described example, a sintered body sample was produced by using the above-mentioned brass chips and changing the pressing conditions and the sintering temperature.

And the porosity measurement and the strength test were performed about each sintered compact sample of an Example and a comparative example.
In the sintered body sample of the example, the porosity was 36%.

  In the strength test, while testing the cylindrical sintered body sample in the axial direction, the nominal strain (value obtained by dividing the change in length by the original length) and the nominal stress (load applied to the test piece are tested. And the value divided by the cross-sectional area of the piece).

FIG. 6 is a characteristic diagram showing a strength test result of the sintered body according to the example.
As shown in the figure, in the sintered body sample of the example, the nominal stress monotonously increases to about 140 MPa until the nominal strain reaches approximately 0.8. This means that the sintered body sample does not break even when it is subjected to a large deformation, that is, the sintered body sample has sufficient strength and ductility to withstand cutting, and also has strength and ductility as a bearing material. It shows that it has.

Actually, the sintered compact sample of the example was able to produce a brass porous bearing without being broken by cutting into a cylindrical shape with a lathe.
In addition, the sintered compact sample in which the pressure at the time of compression and pressurization is in the range of 200 MPa to 800 MPa and the sintering temperature is in the range of 880 ° C. to 940 ° C. has a porosity of 10 to 50 vol. % Deformation and showed large deformation without breaking in the compression test.

On the other hand, in the sintered body sample of the comparative example in which the pressure during compression and pressurization is less than 200 MPa, brittle fracture occurred before the nominal strain reached 0.8 in the strength test. In addition, breakage occurred when cutting with a lathe.
The comparative sintered body sample sintered at a sintering temperature of less than 880 ° C. also suffered brittle fracture before the nominal strain reached 0.8 in the strength test, and was damaged when cut with a lathe.

From the above results, in Examples, it was possible to realize a brass porous bearing having high porosity and strength in spite of sintering brass powder in the atmosphere. It is considered that this is because pressure molding was carried out with the material and the sintering conditions were optimized at a sintering temperature of 880 ° C. or higher.
The use of brass chips having a flat bar shape as the main material brass powder is considered to have contributed to the realization of a brass porous bearing having high porosity and strength.

  The brass bearing according to the present invention is inexpensive and suitable as an oil-free bearing. Moreover, it is useful not only as a sliding bearing but as a functional part of various products such as industrial machines and electrical equipment.

1 Mixture 2 Green Body 3 Sintered Body 4 Brass Porous Bearing 10 Die 11 Upper Punch 12 Lower Punch 21 Chuck 22 Drill 23 Bit

Claims (5)

A manufacturing method for manufacturing a porous plain bearing made of brass,
A molding step of molding a green body by applying a pressure of 200 MPa to 800 MPa for brass powder,
A firing step of heating and firing the molded green body at 880 to 940 ° C. in an air atmosphere ;
A method for manufacturing a sliding bearing, comprising: a cutting step of cutting the fired molded body. The brass powder is
The method for manufacturing a plain bearing according to claim 1, wherein the method is brass chips. The particle size of the brass powder is
The sliding bearing manufacturing method according to claim 1, wherein the manufacturing method is 0.5 mm or more and 2.0 mm or less. Prior to the molding process,
The manufacturing method of the sliding bearing in any one of Claims 1-3 provided with the mixing process which mixes a lubricant with brass powder. A production method for producing a porous brass porous body mainly composed of brass,
A molding step of molding a green body by applying a pressure of 200 MPa to 800 MPa for brass powder,
And a sintering step in which the molded green body is heated and sintered at 880 to 940 ° C. in an air atmosphere .