JPH0428836A - Sliding material - Google Patents

Abstract

PURPOSE:To reduce the wear amt. in a sliding material into a low one and to provide it with high loading capacity, by constituting a sliding material of a Cu base sintered alloy contg. Pb, In, Bi and Tl and letting the above Pb, etc., form a film as quasi-flaky fine grains. CONSTITUTION:This sliding material is constituted of a sintered allay contg. 5 to 60% soft metals of elements such as Pb, In, Bi and Tl having low solid soln. degree to Cu. The metals such as Pb are distributed into a Cu matrix as substantially quasi-flaky fine grains having <=10mum average grain size and show conformability, lubricity or the like. If required, the above compsn. is incorporated with <=15% Sn. The soft metals such as Pb form a film on the approximately whole face of the sliding face with the mating member under a boundary lubricating condition in the use. This sliding material is suitable for a bearing material for a high load-high output internal combustion engine and a bearing material used in a boundary lubricating area.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a sliding material used for main journal bearings of internal combustion engines, sliding bearings such as connecting rod bearings, bushings as general machine elements, etc. . More specifically, the present invention relates to a copper-based sintered sliding material containing copper as a main component and soft metals such as lead and indium as additive elements.

[Prior Art] Conventionally, the sliding material used for the above-mentioned purpose is generally a copper-lead based Kelmet alloy, and therefore an example of this copper-lead alloy will be mainly explained below.

Conventionally, copper-lead alloy bimetallic materials have been manufactured by scattering powder made by water or gas atomization onto an iron plate and sintering it in a reducing atmosphere. The copper-lead alloy used as a sliding bearing material is an alloy with lead that does not dissolve in copper, so lead acts as a type of inclusion, so the finer its distribution, the better the load capacity. is easily estimated.

However, in the conventional method, there is a limit to the size of the Pb phase that can be refined depending on the solidification rate of the powder, and a sufficiently refined sintered structure cannot be obtained even if the sintering temperature and time conditions are modified.

In recent years, the performance of internal combustion engines, including automobile engines, has improved significantly, and as a result, the load on bearings has become extremely severe.Currently, copper-lead alloys have been developed with a finer distribution of lead to create bearings that can withstand even higher loads. It became necessary to make something happen.

In copper-lead alloy bearing materials, it is well known that the lead phase dispersed within the copper matrix acts as a lubricating metal, but there are pros and cons as to whether it is better to have a finer or coarser distribution of lead. Yes, there is no clear answer yet.

There is US Patent No. 4,818,628 as a patent that discloses refining the lead layer of a copper-lead sintered alloy. In this patent, sintering is performed by induction heating at 650°C or higher and second stage heating at about 850°C in a furnace, and the average lead particle size is 8 μm or less. diameter is 4
It has been proposed to obtain a microstructure of 4 μm or less. This U.S. patent states that it is preferable that the raw material powder be 147 μm or less, and does not mention the powder manufacturing method, but considering the size of the powder, it is thought to be a common gas or water atomization method. . In addition, the above-mentioned U.S. Patent No. 4,818,628 discloses that when corrosion starts from cracks in the overlay and reaches the lead phase in Kelmet, if the lead phase is rough, corrosion tends to progress in the lead phase. Therefore, it is proposed to make the lead phase of Kelmet ground finer.

(Problem to be Solved by the Invention) The present inventor created a copper-lead sintered body by making the atomized alloy powder as fine as possible, and by devising sintering conditions to perform sintering while suppressing grain growth. We observed the organization and obtained the following findings. That is, the lead phase in the sintered body remains in a network shape solidified along the grain boundaries of the copper matrix. Although the performance of a sintered body having such a structure is improved to some extent by miniaturization, it is not possible to achieve performance that greatly exceeds conventional performance.

(Means for Solving the Problems) The present invention significantly improves the performance of the conventional sintered sliding materials as described above.

5 to 100% of one or more components selected from In, Bi, and TI
60% of the Pb, In, Bi, Tl
etc. are dispersed as substantially pseudo-flake-like fine particles with an average particle diameter of 10 μm or less, and are characterized by forming a film on substantially the entire surface of the sliding surface with the mating shaft under boundary lubrication conditions.

Furthermore, the present invention is composed of a sintered alloy containing 5 to 60% of one or more components selected from Pb, In, Bi, and TI, and 15% or less of Sn, with the remainder consisting of Cu and inevitable impurities, The above-mentioned Pb, In, Bi, Tl, etc. are dispersed as substantially pseudo-flake-like fine particles with an average particle size of 10 μm or less, and under boundary lubrication conditions, a film is formed on almost the entire sliding surface with the mating shaft. It is characterized by

The present invention will be explained in detail below.

First, the composition of the sliding material of the present invention will be explained. The sliding material according to the present invention contains elements having low solid solubility in Cu, such as Pb, In, Bi, and Tl, as soft metals. These metals are distributed in the Cu matrix and exhibit conformability, lubricity, and the like.

If the content of soft metal is less than 5% (percentages are by weight unless otherwise specified), the above performance will be insufficient;
On the other hand, if the content exceeds 60%, the strength of the copper-lead alloy will be insufficient and the load capacity will be insufficient. Furthermore, as will be described later, in the present invention, since phases such as Pb and In are densely packed in fine shapes, if the content of Pb, In, Bi, TI, etc. is less than 5%, a soft phase is observed. is isolated, spread out and dispersed, and the effect of forming a continuous layer of lead etc. on the sliding surface according to the present invention cannot be achieved, so it is necessary to add the above-mentioned lower limit content of 5% or more. The soft metal content is preferably 5 to 30%, especially for fatigue resistance and high load purposes.
, more preferably 8 to 25%, and for the purpose of boundary lubrication, preferably 20 to 60%, more preferably 30 to 50%.

The remainder of the soft metal described above is Cu and impurities. C
u distributes the above-mentioned soft metal uniformly and finely as a matrix, firmly supports it, and plays the role of a good thermal conductor that dissipates heat generated by friction.

Here, in conventional atomized powder sintering, the content of PB is high (this results in lower strength of the material itself, poor fatigue resistance,
Although it cannot withstand sufficient use as a high-load application, the powder sintered body produced by the mechanical alloying method is
Since the substrate itself is strengthened, a high Pb content can be adopted.

Since this high pb is cheaper than Cu, it is also advantageous in terms of material cost.

Next, 15% or less of Sn can be further added to the above composition. Sn is a component that solid-solution strengthens the Cu base, and is 15
%, C
On the contrary, it makes the U-shaped fabric brittle. Preferably 0.5-12%
The Sn content is good.

In addition to the above-mentioned components, Sb, Fe, Ni, Mn, etc. may be added as hard components in small amounts of 5% or less each. These hard components strengthen the sintered body through dispersion strengthening and increase the load capacity. Further, known subcomponents of the Cu-based sliding material may be added as appropriate, for example, P to 1% or less, preferably 0.00%.
It may be added in an amount of 1 to 0.5%.

The sintered structure, which is the most characteristic feature of the present invention, will be explained below.

In conventional copper-lead alloys, the lead phase remains in the cast state, or the lead phase remelts during sintering and is redistributed along the copper grain boundaries, resulting in a net-like distribution. . However, the lead phase according to the present invention has no traces of such a casting/remelting structure (and exhibits a piece-like structure.
There is no similar example in lead alloys (found in graphite with an intermediate shape between Mg-added spheroidal graphite in cast iron and flaky graphite in ordinary gray cast iron (edited by the Japan Institute of Metals, "Revised 5th edition, Metal Handbook", p. 597). (Reference) This flake-like lead phase is generally flake-like (it does not have a net-like shape, it has a long shape, and the aspect ratio is not like that of a sphere), but it also has a jagged shape, They are called "pseudo" flakes because they have irregular shapes, such as shapes with small protrusions, locally thickened shapes, and shapes with branched ends.

The lead phase of the present invention has an average size of 10 μm or less in size.

The average size of the lead phase of 10 tLm or less, together with the above-mentioned flaky structure, is a necessary condition for achieving the lead film forming effect according to the present invention. When these conditions are met, the conventional reticulated lead phase surrounds the Cu grain boundaries, so typically 20~
The lead phase is dispersed at approximately the same intervals as the grain size of the cast solidified Cu phase, which is 40 μm. In the present invention, the lead phase has a piece-like shape that cannot be obtained in a cast structure, so the lead phase is much more densely packed than in the atomized powder, and the average interval between the lead phases is much narrower.

The present invention has been described in detail above using the lead phase as an example, but even when indium, bismuth, thallium, etc. are added elements, copper can be used as a hard metal by the mechanical alloying method.
Indium etc. act as a ductile metal,
Due to the NG effect, it is possible to create a structure in which indium and the like are so finely dispersed that they cannot be detected with an optical microscope. Note that the mechanical alloying method referred to in this application is a general term for mechanical alloying in a narrow sense and mechanical grinding.

In order to create the above-described structure, it is necessary to sinter the powder obtained by a method for creating an ultrafine structure such as a mechanical alloying method. Since the surface of the powder obtained by this method is very active, care must be taken in the sintering atmosphere conditions when performing sintering. Sintering can be performed by a process of primary sintering on a backing metal, pressing down of the secondary sintered powder onto the backing metal, and secondary sintering.

Hereinafter, the present invention will be further explained using a mechanically alloyed powder sintered material as an example.

[Effect]

When we observed the friction surfaces of the mechanically alloyed powder sintered material and the atomized powder sintered material after sliding them for a certain period of time, we found that the surface of the atomized powder sintered material had a copper matrix metallic luster after the sliding test. However, in the case of the mechanically alloyed powder sintered material, a number of black stripes extending in the direction of friction were observed. Electron microscopy, lead line analysis, and EPMA observation of the boundaries of these black stripes indicate that the black stripes that appear on the mechanically alloyed powder sintered material are lead, and that they cover the surface in the friction direction. Do you get it.

It is generally known that lead oozes out onto the surface of Kelmet alloys, but in conventional atomized powder sintered materials, as in this mechanically alloyed powder sintered material, lead oozes out from a large portion of the entire friction surface. It wasn't enough to cover it.

This sliding test used kerosene with low viscosity as the lubricant, and the speed was slow at 0.5 m/s, so the experiment was conducted in the boundary lubrication region. Therefore, it is thought that there was a part where the shaft and the test piece were in solid contact, and lead seeped out at that part.

Because the distribution of lead in the base is different between mechanically alloyed powder sintered material and atomized powder sintered material, the way it seeps out and the way it flows in the sliding direction and covers the friction surface have different results. I'm inviting you.

Figure 3 shows the results of observing lead seepage on the surfaces of mechanically alloyed powder sintered material and atomized powder sintered material, respectively.
A) to (D) and FIGS. 4(A) to (D). In the figure, A, B, C, and D are respectively 10 minutes later, 30 minutes later, and 60 minutes later.
After 120 minutes.

Mechanical alloyed powder sintered materials with a fine lead distribution will seep out onto the friction surface even after less than 10 minutes of sliding time (see Figure 3 (A)), and lead will flow on the surface. However, the nearby lead seeps out and connects to the flow, and the connections grow one after another and appear as a single line in the direction of friction.
The striped pattern gathers and gradually grows into a striped pattern that covers a considerable portion of the entire friction surface (see Fig. 3 (D)).

On the other hand, in the atomized powder sintered material, most of the sliding surface is exposed as a copper base, and only a few PB streaks are observed. The area ratio of the PB streaks seen from the sliding surface is only around 40% (when PB is increased by 30%).

On the other hand, in the mechanically alloyed sintered material as in the present application, a considerable portion of the sliding surface is covered with PB as described above. In this application, the area ratio of PB viewed from the sliding surface is approximately 5 in steady sliding state.
0% to about 100%. This area ratio is the combined pb
Although it depends on the amount, it is usually 80 to 95%.

From the above observation results, it can be seen that the dense presence of the lead phase essentially increases the lead seepage area and plays an important role in covering almost the entire sliding surface with lead. In order to make the lead phase dense as described above, it is necessary to limit the amount of lead added and the size and shape of the lead phase as defined by the present invention.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

〔Example〕

Copper-lead alloy powder containing 30% lead made by water atomization is processed using a high-energy ball mill using stainless steel balls (
Attritor) and mechanical alloying was performed for 50 hours to produce a fine alloy powder. Sono composition is 31.6%P
b, 0.91% Sn, Fe<0.055. Ni<0.0
5%.

Sb<0.05%, balance Cu. As a result of examining the lead distribution using EPMA and electron micrographs of the alloy powder after atomization and the alloy powder after 50 hours of mechanical alloying, it was found that the structure of the mechanically alloyed alloy powder was so fine and uniform that the distribution of lead could hardly be discerned. It had become.

The results of X11 diffraction of the mechanically alloyed alloy powder showed that no change in the peak position of each lattice plane was observed for both the copper partner and the lead phase, indicating that copper and lead were not alloyed to the extent of atomic substitution. .

The alloy powder obtained in this way was made into a disc-shaped compact with a diameter of 13φ and a thickness of about 3mm under a pressure of 4 to 5 tons/cm" and sintered at 700°C for 60 minutes in a hydrogen gas reducing atmosphere. A copper-lead sintered body was obtained.

A sintered body was also made under the same conditions using atomized alloy powder that had not been mechanically alloyed and used as a comparison material.

FIGS. 1 and 2 show optical micrographs of the sintered structure of the mechanically alloyed alloy powder and the sintered structure of the atomized alloy powder, respectively. The mechanically alloyed powder has a very fine sintered structure, and the atomized powder sintered material has a PB network structure. As a result of image analysis of these structures, it was found that the average area and average particle size of the lead phase in the mechanically alloyed sintered material were approximately 1/3 and 1/8, respectively.

(Leaving space below) Table 1: Average area, average particle size, and hardness of the lead phase determined by image analysis The hardness measured as a representative mechanical property of the mechanically alloyed powder sintered material is higher than that of the atomized powder sintered material. It is higher than that, and it is recognized that it is strengthened by making the PB dispersed particles finer.

Furthermore, using a cylindrical plate testing machine, the friction coefficient and amount of wear were measured under the following conditions.

Lubricating oil: Kerosene Bath temperature: Room temperature Shaft: 545C hardened material (diameter 45 mm) Shaft surface roughness:
RZ0.8 μm Load: 9 kg Shaft rotation speed: 273 rpm Speed: 0.5 m/sec Time: 126 minutes Figure 5 shows the wear amount of the atomized powder sintered material and the mechanically alloyed powder sintered material for 30% Pb-Cu. The seepage area ratio of pb is shown in FIG. The wear amount of the mechanically alloyed powder sintered material is clearly lower than that of the atomized powder sintered material, and the seepage area ratio in a steady state is also extremely high.

Therefore, mechanically alloyed powder sintered materials have excellent wear resistance, and this is because when solid contact occurs between the shaft and bearing, the temperature rises at the contact area and lead seeps out, suppressing wear. It is believed that there is.

[Effects of the Invention] As explained above, the material properties of the sintered material of the present invention are low wear and high load capacity, and during the use of the bearing, soft metals such as lead spread over almost the entire contact surface of the bearing. The feature is that it covers. Therefore, the sliding material of the present invention is suitable as a bearing material for a high-load, high-output internal combustion engine or a bearing material used in a boundary lubrication region.

[Brief explanation of drawings]

Figure 1 is a metallurgical micrograph of the sintered material of the present invention, Figure 2 is a metallurgical microscope photograph of a conventional sintered material, and Figures 3 (A) to (D)
) is a metallurgical micrograph showing the PB structure on the surface of the sliding material of the present invention after sliding. Figures 4 (A) to (D) show the PB structure on the surface of the conventional sliding material after sliding. The observed metallographic micrographs, Figure 5 is a graph showing the wear amount of the mechanically alloyed powder sintered material and the atomized powder sintered material, and Figure 6 shows the PB of the mechanically alloyed powder sintered material and the atomized powder sintered material. It is a graph showing seepage area ratio. Patent applicant: Taiho Kogyo Co., Ltd.

Claims (2)

[Claims] 1. It is composed of a sintered alloy containing 5 to 60% of one or more components selected from Pb, In, Bi, and Tl, with the remainder consisting of Cu and inevitable impurities, and the Pb, In,
Bi, Tl, etc. are dispersed as substantially pseudo-fine particles with an average particle diameter of 10 μm or less, and a film is formed on almost the entire sliding surface with the mating shaft under boundary lubrication conditions. sliding material. 2. It is composed of a sintered alloy containing 5 to 60% of one or more components selected from Pb, In, Bi, and Tl and 15% or less of Sn, with the remainder consisting of Cu and inevitable impurities, and the Pb, In , Bi, Tl, etc. have an average particle size of 1
A sliding material characterized in that it is dispersed as substantially pseudo-flake-like fine particles of 0 μm or less, and forms a film on substantially the entire sliding surface with a mating shaft under boundary lubrication conditions.