KR100257792B1 - Cu sliding bearing material and internal combustion engine sliding bearing - Google Patents

Abstract

An object of the present invention is to provide a copper-based sliding bearing material and a sliding bearing for an internal combustion engine, which can obtain excellent scissor resistance without containing Pb and can make the overlay thin. Ag: 0.1 to 2%, Sn: 1 to 10%, the remainder is made of Cu and unavoidable impurities, and the Ag and Sn do not substantially form a second phase, and the Cu matrix It is characterized by a copper alloy that is completely or substantially dissolved in it.

Description

Copper sliding bearing material and sliding bearing for internal combustion engine

The present invention relates to a copper-based sliding bearing material and a sliding bearing for an internal combustion engine, and more particularly, to a copper-based sliding bearing material having a novel composition and structure used as internal combustion engine bearings such as engine main bearings and connecting rod bearings. And a sliding bearing such as a sliding bearing for an internal combustion engine and a connecting rod bearing.

Conventionally, a sliding bearing of a general internal combustion engine is Pb: about 8 to 35%, Sn: about 10% or less on a strip made of low carbon steel such as SAE 1010 or 1020, as described in Japanese Patent Application Laid-Open No. 60-145345. And so-called lining of a copper-based alloy composed of the remainder Cu.

Further, as described in detail in Japanese Patent Laid-Open No. 1-503150, in a bearing structure in which a Pb-Sn-based or Pb-Sn-Cu-based overlay is formed on a lining, Sn is diffused into the lining as a result. Since Sn is depleted and corrosion resistance to lubricating oil deteriorates rapidly, Ni-barrier by plating is interposed between the lining and the overlay. As a countermeasure for preventing corrosion deterioration caused by this lead, it is proposed in the above publication to refine the lead phase in the overlay.

The lining of the conventional over-retained kelmet bearings contains lead, but since lead is a soft metal and excellent in lubricity and familiarity, it becomes familiar with the scissor caused by Kelmet's Cu adhering to the opposite axis. Lead has been used for this purpose.

If the conventional sliding bearing is used for a long time in a deteriorated lubricating oil, when the lining is exposed, the lead phase in the lining is corroded and dissolved, resulting in a rough surface of the lining leading to the scissor. Alternatively, the gap is formed by the elution of the lead phase, so the strength of the lining is lowered, the lining is buckled, and a scissor occurs. In order to reduce the corrosion of such lead phases, measures have been taken such as making the lead phases fine. However, the countermeasures have been limited as long as the sliding bearing material contains lead.

In addition, when Kelmet is used for a long time in deteriorated lubricating oil, copper reacts with sulfur (S) in the lubricating oil to sulfide and copper sulfide is formed on the surface of the lining, thereby deteriorating corrosion resistance and wear resistance. Although Zn is added as a countermeasure, Zn hardly improves shear resistance.

In addition, the conventional overlay has a thickness of 20 μm or more so as to take familiarity with the shaft and to exhibit sliding resistance performance of the resistance of the resistance by itself. However, it goes without saying that thick plating should be avoided in terms of the cost of the sliding bearing material.

As another problem, the conventional nickel barrier cannot be used to prevent the diffusion of Sn, but in the stage where the nickel barrier is exposed by the wear of the overlay, a scissor is very likely to occur in the hard Ni exposed portion. Therefore, it has also been determined that this time is the bearing life. This problem of nickel barriers has been pointed out in the past, but it can be said that nickel barriers were inevitably used to prevent the diffusion of Sn.

The present invention provides a copper-based sliding bearing material and a sliding bearing for an internal combustion engine that can solve the above-mentioned problems.

1 is a graph showing the relationship between the Ag content and the area ratio of the Ag precipitated portion.

2 is a graph showing the relationship between Ag content and seizure load.

3 shows an SEM image of Ag of a copper-based material containing 4% Ag.

4 shows a stick slip tester.

5 is a diagram showing a scissors tester.

* Explanation of symbols for main parts of the drawings

1: test piece 2: heater

3: steel ball 5: hydraulic cylinder

6: oil supply pad 7: test piece

8: Disc 9: Balance Weight

10: load cell

First of the present invention, in a weight percentage, Ag: 0.1 to 2%, Sn: 1 to 10%, the remainder is composed of Cu and unavoidable impurities, the Ag and Sn is the second phase It is a copper-based sliding bearing material excellent in resistance to corrosion, characterized in that it is not substantially formed and is completely or substantially dissolved in a Cu matrix. The second aspect of the present invention is the above-described copper-based sliding bearing material and the thickness thereof. A sliding bearing for an internal combustion engine, comprising a soft metal having a thickness of 1 to 25 μm or comprising a solid lubricant and a resin, and a third aspect of the present invention is the sliding bearing material having the overlay interposed therebetween. It relates to a sliding bearing for an internal combustion engine, characterized in that the adhesive is directly bonded without.

Hereinafter, the configuration of the present invention will be described, but first, the alloy composition of the sliding bearing material according to the present invention will be described.

Ag contained in the copper-based alloy is uniformly finely dispersed in the Cu matrix, thereby improving the resistance to scissorization. In any case where the Ag content is less than 0.1% and more than 2%, the effect of improving the resistance to ashing is not exhibited. Preferable Ag content is 0.4 to 1%.

Next, Sn increases the hardness and strength of the Cu matrix by solid solution, and improves the corrosion resistance and the adhesion resistance. If the Sn content is less than 1%, there is no effect of improving the adhesion resistance, while if the Sn content is more than 10%, the copper alloy becomes too hard and the familiarity as a bearing is degraded, and the Cu ₃ Sn compound (ε phase) begins to precipitate. The resistance to deterioration is poor. Preferable Sn content is 2 to 7%.

0.5% or less of P may be added to the composition. P does not contribute to the sliding characteristics by itself, but improves the flow of the hot water as a deoxidizer during powder spraying to improve the properties of the powder and to allow sintering at a relatively low temperature. In addition, P acts as a deoxidizer at the time of manufacture of a casting material, and improves hot flow, and reduces casting defects. The amount of solute oxygen which can interfere with the precipitation of Ag and Sn during the use of the bearing is reduced by the addition of P, and the amount of Sn and Ag maintained in the solute state increases so that the resistance to shearing is good. Therefore, it is preferable to add P when there is much oxygen amount in a copper alloy. However, when P content exceeds 0.5%, a copper alloy will become hard and soft. Preferable P content is 0.05 to 0.15%.

Particularly preferred compositions are Cu-1% Ag-5% Sn in which the Ag and Sn contents exceed the equilibrium solid solution limit, and alloys forcing solid solution of these elements exhibit very excellent sliding characteristics.

Elements other than the said component are impurities, such as O, Fe, As, and Ni normally contained in copper. The fewer these elements are, the more preferable. In particular, oxygen may interfere with the precipitation of forced solid solution Ag (see FIG. 3 to be described later), and Pb causes corrosion by the S component in the lubricating oil. Since the other components do not bring about a beneficial effect, it is preferable to regulate them to about 1% or less in total. In addition, although the copper alloy of this invention does not contain Pb which is a soft metal as an essential component, it can mention that the sliding characteristic is very favorable, without Cu adhering to a counterpart material. However, Pb and Bi may be added to the copper alloy of 4% or less in order to provide free machinability.

Next, the structure of the copper alloy which concerns on this invention is demonstrated.

In the present Cu-Sn-Ag alloy, the solid-solution limit in the equilibrium state is about 2% Sn and about 0.2% Ag. Therefore, the alloy composition of the present invention extends from the content of these elements to less than the solubility limit.

It is important for these elements to be dissolved in the Cu matrix and finely dispersed at the electron microscope level in order to improve the sliding characteristics. In the present invention, the complete solid solution can not recognize the presence of the secondary phase by an electron microscope, and Cu, Sn, P is Ag, ε-CuSn _x (Cu ₃ Sn), η'-CuSn by EPMA. It is a structure in which it concentrates and distributes in secondary form, such as (Cu ₆ Sn ₅ ), and is not detected. In addition, in the present invention, it is necessary that the main components such as Cu, Sn, Ag, etc. do not substantially form the secondary phase, but it is not impeded that impurities form a small amount of inclusions or secondary phases.

In the present invention, the employment state is preferably full employment, but may be a practical employment state in which the secondary phase is hardly detected. Here, the practical solid solution state is specifically an X-ray photograph of each component such as Ag, and is an organization state in which the secondary image area in an arbitrary viewing field (1,000 times) is 5% or less.

In detail, as described later, Ag is concentrated on the surface to form an Ag-S compound during use of the bearing, and this phenomenon is considered to be the cause of the drastic improvement in the sliding performance of the sliding bearing material of the present invention. Since it is said solid solution state in a Cu matrix which enables formation of Ag-S compound, it is necessary to confirm solid solution state except the outermost surface of the lining in the sliding bearing in use. In addition, since the solid solution state is a necessary condition for improving the sliding characteristics during use of the bearing, the solid solution state should be realized at a shallow position of about 1 μm or less from the surface where bearing wear may occur. It will be apparent from the following description that Ag or the like may be precipitated inside the material in which the cooling rate becomes slow due to the effect.

In order to solidify Ag and Sn in the Cu matrix, the sintering of the copper alloy powder is preferably performed at 800 to 900 ° C, followed by quenching at a cooling rate of 50 ° C / min or more, or solution heat treatment under the same conditions. In addition, these elements need to be forcibly dissolved in the Cu matrix.

In the case of casting materials, the molten metal is introduced into a steel plate (SPCC) having a thickness of about 1.5 mm and preheated to about 500 to 600 ° C in N ₂ atmosphere, and then water cooled from the back plate of the steel plate at a cooling rate of 100 ° C / sec or more. It is preferable.

As described above, the content of Ag and Sn may be less than the solubility limit in the equilibrium state, but in order to prevent segregation of these elements, it is also preferable to quench rapidly.

Then, the sliding bearing using the sliding bearing material of this invention is demonstrated. This sliding bearing material can be used in all known forms such as using an overlay as in the prior art. However, a particularly advantageous use of the sliding material of the present invention having excellent sliding characteristics is as follows.

Since the sliding bearing material of the present invention does not need to be reinforced with a thick overlay as in the prior art, the overlay only needs to have a thickness necessary to achieve familiarity with the shaft, and the thickness thereof is 1 to 25 µm, preferably 2 to 2. 8 μm.

As the overlay, various metal overlays such as Pb-In-based, Pb-Sn-Cu-based, Pb-Sn-In-based, Pb-Sn-In-Cu-based alloy plating, Sn-based plating, and In-based plating can be used. In addition, it is also possible to use an overlay bonded by a solid lubricant such as MoS ₂ in a resin binder such as polyimide (PI), polyamide-imide (PAI), epoxy resin.

As described above, Sn in the overlay occurs in the lining during bearing use. In the present invention, the overlay only needs to have a function that takes a familiarity. Therefore, the overlay does not need to have long-term performance to cause Sn depletion. From this point of view, the nickel barrier is unnecessary and actively nickel By eliminating the barrier, it is possible to prevent the scissor caused by the exposed nickel barrier and rather to utilize the excellent scissor resistance of the exposed lining. In this sliding bearing, the surface of the copper-based sliding bearing material can be treated to improve adhesion to the overlay by etching, shot blasting, plating, or the like.

The phenomenon recognizable when using the copper-based material ① and the copper-based material ② for comparison as the bearing according to the present invention is as follows: (A) Solute Ag in the matrix is a sliding surface during the use of the bearing (temperature: 120 to 180 ° C). Precipitates and reacts with the S component in the lubricating oil to form a very thin film of Ag ₂ S, an Ag—S compound, (①); (B) Ag precipitation cannot be detected inside the lining 1 μm or more away from the sliding surface (①); (C) Ag precipitated as a second phase from the beginning of bearing use is so hard that its sliding characteristics are poor, and since the above described Ag ₂ S film is not widely formed in every corner in the sliding part, the sliding characteristics are not excellent (②). ; (D) The shape of (A) occurs even in the amount of Ag smaller than the equilibrium solid solution limit (①), etc.

A sintered material having a composition of Sn = 5%, P = 0.05%, Ag≤5% and the remainder of Cu was prepared by the same manufacturing method as in Example 1 described below, and the Ag precipitation area ratio was measured at 5 o'clock before using the bearing. One result is shown in FIG. 1, or the scissor load of this material is shown in FIG. 3 shows Ag phase (magnification 1000 times) by SEM with Ag = 4% and Ag precipitation area ratio = 4%. In FIG. 1 and FIG. 2, (a) the Caesar load increases dramatically with the Ag content at 1% or less in which Ag is completely dissolved; (B) When the Ag content exceeds 1.0%, forced employment becomes impossible, and precipitation of Ag starts, and accordingly, the scissor load gradually decreases; (C) At 2%, the upper limit of Ag content, 1% of Ag is present as a solute and the remaining 1% of Ag is present as a secondary phase. Even in this tissue state, the scissor load is maintained at a very high level by the action of solute Ag.

3 shows an example of the precipitation form of the Ag secondary phase.

On the other hand, Sn is excellent in sliding characteristics if it is a solute element of Cu matrix, but worsening of sliding characteristics because it becomes hard and fragile when precipitated as secondary phase even before the bearing is used. In the copper-based alloy having a structure characterized by the present invention, solute Sn precipitates on the sliding surface during use of the bearing, and Ag also precipitates together at the place where Sn precipitates. Thus, a compound such as _{Ag 2 S, Ag 3 Sn,} SnS is formed on the sliding surface as the second phase, these compounds are estimated to that improve the sliding characteristics.

Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1

The molten copper alloy whose composition is shown in Table 1 was powdered by spraying, and after that, a powder having a particle size of 150 µm was sprayed onto the back plate (SPCC, thickness = 1.4 mm) so as to have a thickness of about 0.6 mm, and then compressed. Without sintering at 850 DEG C in a hydrogen gas atmosphere. Thereafter, quenching was performed at a cooling rate of 50 deg. C / min. Then, the sintered layer was compressed so that the whole thickness might be 1.5 mm. Then, it sintered again in 850 degreeC and hydrogen gas atmosphere, and it quenched at the cooling rate of 50 degreeC / min after that. A sample (thickness 1.5 mm) prepared by grinding the sintered material to a surface roughness of 0.5 탆 was used for a stick slip test explaining the method in FIG. This test is suitable for examining the tendency of the scissor to occur due to adhesion. In FIG. 4, (1) is a test piece, (2) is a heater, (3) is a steel sphere which moves a sample surface, applying a load. The test conditions are as follows.

(A) Load (W): 500g

(B) Steel ball cross section radius: 4mm

(C) Steel roasting speed: 3.6mm / min

(D) Steel roasting distance: 20mm

(E) Maximum heating temperature by heater: 200 ℃

(F) Determination of copper-bonded surface: by steel sphere surface photograph

The results of the stick slip test are shown in Table 1.

In Table 1, Comparative Example 6 is pure copper, and the adhesion area of the test piece is large, and adhesion of the test piece occurs at low temperature. In Comparative Example 7 in which a small amount of Ag and P were added, adhesion tendency was somewhat suppressed. When a large amount of Sn is added (Comparative Examples 8 and 10), the adhesion tendency is further suppressed. When Pb and Sn are added in combination (Comparative Example 9), adhesion is completely suppressed. In contrast, in Examples 1 to 5 of the present invention, adhesion is completely suppressed even if Pb is not added.

Example 2

The copper alloy sintered material of the composition shown in Table 2 was manufactured by the method similar to Example 1. The resistance of the obtained sintered material was examined by a pin-on disk tester shown in FIG. In Fig. 5, reference numeral 5 denotes a hydraulic cylinder, numeral 6 a lubrication pad, numeral 7 a test piece, numeral 8 a disk to be a sliding material, and numeral 9 a balance weight of a hydraulic cylinder. Denoted at 10 is a load cell.

The test conditions are as follows.

(A) Sliding speed: 15m / sec

(B) Load: Load increase (step type), 600 N / min

(C) oil type: 10W-30

(D) Oil temperature: room temperature

(E) Relative material: S55 (quenched (Hv = 550-650), roughness 0.5-0.8 μmRz

(F) Test piece: area-1 cm ² , roughness-1.0 to 1.5 μmRz

The resistance test results are shown in Table 2.

In Table 2, the comparative example 20 is a typical composition example of the conventional Kelmet, and compared with this performance, it turns out that the resistance of the Examples 11-15 of this invention improves twice as fast. In particular, it is noted that the material of the embodiment of the present invention is excellent in the resistance to resistance even though it does not contain Pb.

In the addition of Ag (Comparative Example 17) and Sn (Comparative Example 18), the resistance to aging is better than that of pure copper (Comparative Example 16), but the degree is slight. In the addition of Ag and Sn (Comparative Example 19), the resistance to aging is also improved, but if P is insufficient, the degree is small. In Comparative Example 21, since the Ag content is excessive, the resistance to aging was not sufficient.

Example 3

By the method similar to Example 1, the copper-type sliding bearing material of the composition shown in Table 3 was prepared, and the sliding bearing for connecting rod bearing of the turbocharger diesel engine (2,400 cc exhaust volume) was produced. The back plate used was a steel plate (SPCC, thickness = 1.2 mm), the lining thickness was 0.3 mm, and an overlay was directly deposited on the lining surface without intervening a nickel barrier. The method of forming the overlay was performed by a method in which a metal overlay was combined with electrophoresis of a fluorinated bath and diffusion of In, and the solid lubricant-based overlay was performed by a scissor mixture with a resin. Sliding characteristics of each sliding bearing were evaluated by the following method.

(A) Speed: 4000rpm

(B) Bearing surface pressure: 450, 600, 700kg / cm ²

(C) oil species: 100W-30, CD

(D) Oil temperature: 125 ° C

(E) Test time: 400h

Evaluation of test results: measuring the amount of wear and calculating the average value; Surface state-The thing which was reusable by visual observation was made into pass ((circle)) and the impossible thing was rejected (x).

The test results are shown in Table 3. Test conditions are as follows.

(A) Engine: L4.2 diesel with T / C

(B) Speed: 4,000rpm

(C) Bearing surface pressure: 45, 60kg / cm ²

(D) Oil type: 10W-3a

(E) Oil temperature: 125 ℃

(F) Test time: 400h

In Table 3, the comparative example 34 is a conventional overlay attached kelmit bearing and the comparative example which made the thickness of the overlay thin enough to have familiarity, and a scissor arises in this experimental condition. On the other hand, a small amount (0.05%) of Ag is added and the comparative example 35 except Pb is more likely to produce a scissor. In the comparative example 36 which further increased Ag content and added a large amount of Sn, and the comparative example 37 which added only a large amount of Ag, it is hard to produce a scissor.

Compared with these comparative examples, in the embodiment of the present invention, the amount of wear is very small and the resistance to resistance is excellent. In particular, the amount of Sn is very at least excellent in performance (Examples 22 and 24).

As described above, the Cu-Sn-Ag-based copper alloy according to the present invention has a very excellent resistance to the desirability required as a sliding bearing and a lead-free material or a lead-free material without Pb that causes corrosion by heat deteriorated lubricant. It is characterized by a small material.

In addition, it is known that the copper alloy of this composition system is conventionally used as a spring, a contact material or an electrical component (for example, Japanese Patent Laid-Open Nos. 49-75417, 50-77216, and 2-228439). The material of the present invention using Ag and Sn secondary phases precipitated on the sliding surface during use as a forced solid-state bearing during use is improved in terms of metal structure control technology. It is a material to be noted.

Claims (10)

By weight percentage, Ag: 0.1 to 2%, Sn: 1 to 10%, the remainder is composed of Cu and unavoidable impurities, the Ag and Sn is substantially formed in the Cu matrix without forming a second phase A copper-based sliding bearing material, characterized in that it is in a completely or substantially solid state and is excellent in resistance to resistance to oxidation. The copper-based sliding bearing material according to claim 1, further comprising 0.5% or less of P in weight percentage. The copper-based sliding bearing material according to claim 1 or 2, wherein the Ag content is 0.4 to 1%. The copper-based sliding bearing material according to claim 1 or 2, wherein the Sn content is 2 to 7%. The copper-based sliding bearing material according to claim 2, wherein the P content is 0.05 to 0.15%. The copper-based sliding bearing material according to claim 1, wherein at least one of Pb and Bi is contained in a weight percentage of 4% or less. A sliding bearing for an internal combustion engine comprising the copper-based sliding bearing material according to claim 2 and an overlay made of a soft metal having a thickness of 1 to 24 µm or a solid lubricant and a resin. The sliding bearing for an internal combustion engine according to claim 7, wherein said copper-based sliding bearing material contains at least one of Pb and Bi in a weight percentage of 4% or less. The sliding bearing for an internal combustion engine according to claim 7 or 8, wherein the overlay is directly bonded to the bearing material without interposing an intermediate layer. The sliding bearing for an internal combustion engine according to claim 7 or 8, wherein said completely or substantially solid solution state is maintained outside of the sliding surface with the shaft.

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