JPH0525687A - Sliding member - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a sliding bearing provided with a surface layer having excellent wear resistance. [Structure] The surface layer 3 is composed of an aggregate of columnar crystals 4 of Pb alloy. The alloy element concentration in the outer peripheral region a of each columnar crystal 4 is made higher than the alloy element concentration in the inner region b excluding the outer peripheral region a. As a result, the metal structure becomes dense in the outer peripheral region a, so that the hardness is increased. When the sliding surface is formed by the end face of the columnar body 5 of each columnar crystal 4 during the progress of wear of the surface layer 3, the high hardness formed by the outer peripheral region a of each columnar crystal 4 on the sliding surface. The reticulated portions C are dispersed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member, and more particularly to a sliding member having a substrate and an alloy surface layer formed on the substrate and having a sliding surface with a mating member.

[0002]

2. Description of the Related Art Heretofore, as a sliding member of this kind, a sliding bearing in which the surface layer is made of a Pb-Sn alloy has been known (see JP-A-56-96088).

[0003]

This type of sliding bearing is
It is applied to the crankshaft journal part of the engine, the large end part of the connecting rod, etc., but under the current circumstances where the engine tends to be high speed and high output, the surface layer of the conventional plain bearing is wear resistant. There is a problem that is scarce.

The present invention has been made in view of the above circumstances, and an object thereof is to provide the sliding member in which the wear resistance of the surface layer is improved by specifying the structure of the surface layer.

[0005]

The present invention provides a sliding member comprising a substrate and an alloy surface layer formed on the substrate and having a sliding surface with a mating member, wherein the surface layer is It has a plurality of columnar crystals extending from the substrate, and the alloy element concentration in the outer peripheral region of each columnar crystal is higher than the alloy element concentration in the inner region excluding the outer peripheral region.

[0006]

1 and 2, a sliding bearing 1 as a sliding member is applied to a journal portion of a crankshaft in an engine, a large end portion of a connecting rod, and the like.
It consists of first and second halves 1 ₁ and 1 ₂ . Both halves 1 ₁ ,
1 ₂ has the same structure, and includes a substrate 2 and an alloy surface layer 3 formed on the substrate 2 and having a sliding surface 3a with the mating member x. The substrate 2 comprises a back metal 2 ₁ and a lining layer 2 ₂ which is formed on the surface of the back metal 2 ₁ and supports the surface layer 3. Cu between the back metal 2 ₁ and the lining layer 2 ₂
Plating layer, also between the lining layer 2 ₂ and the surface layer 3 provided as necessary Ni Mekkibariya layer, respectively.

The back metal 2 ₁ is made of a rolled steel plate, and its thickness is determined by the set thickness of the slide bearing 1. Lining layer 2 ₂ Cu, Cu alloy, Al, is composed of Al-based alloy, its thickness is 50 to 500 [mu] m, usually 30
It is about 0 μm. The surface layer 3 is made of Pb alloy,
Its thickness is 5 to 50 μm, usually about 20 μm.

The Pb alloy forming the surface layer 3 is 80-9.
It contains 0% by weight of Pb and 3 to 20% by weight of Sn, and if necessary Cu, In, Ag, Tl, Nb, Sb, N.
10% by weight or less of at least one selected from i, Cd, Te, Bi, Mn, Ca, and Ba.

Cu, Ni, and Mn have the function of improving the hardness of the surface layer 3, but if the content thereof exceeds 10% by weight, the hardness becomes too high and the initial conformability deteriorates.
When Cu or the like is added, the hardness Hmv of the surface layer 3 is 1
It is desirable to adjust the content so as to be 5 to 25.

In, Ag, Tl, Nb, Sb, Cd, T
e, Bi, Ca, and Ba have the function of softening the surface layer 3 to improve the initial conformability, but when the content thereof exceeds 10% by weight, the strength of the surface layer 3 decreases. When adding In or the like, it is desirable to adjust the content so that the hardness Hmv of the surface layer 3 becomes 8 to 15.

The surface layer 3 is formed by an electroplating method, and the plating liquid is 40 to 1 per liter.
80 g Pb ²⁺ , 1.5-35 g Sn per liter
^2+, borofluoride based plating solution comprising the following Cu ²⁺ 15 g per liter, are used as occasion demands. The temperature of the plating solution is 10 to 35 ° C and the cathode current density is 3 to 15 A / d.
m ² respectively.

FIG. 3 is an electron micrograph (× 10,000) showing the crystal structure of the Pb alloy on the sliding surface 3a. Figure 4
Is an electron micrograph (5,000 times) showing the crystal structure of the Pb alloy when the surface layer 3 is longitudinally cut, and FIG. 5 corresponds to the partially enlarged electron micrograph of FIG. The surface layer 3 is made of a Pb alloy containing 8 wt% Sn and 2 wt% Cu. The surface layer 3 was formed on the Cu alloy lining layer 2 ₂ , and the cathode current density in the electroplating process for forming the surface layer 3 was set to 6 A / dm ² .

[0013] As shown in FIG. 6, the surface layer 3 is a columnar structure 4 assembly of the Pb alloy extending from the lining layer 2 _2, each columnar crystal 4 and the columnar body 5, the columnar body 5 And the columnar crystals 4 adjacent to each other are grown in a state in which they are in close contact with each other or one of them penetrates into the other.

As clearly shown in FIG. 7, in each columnar crystal 4, the alloying element concentration (C
u, Sn concentration) is higher than the alloying element concentration in the inner region b except the outer peripheral region a.

In such a concentration distribution of the alloy element, the current density in the outer peripheral region a becomes higher than that in the inner region b due to the end effect produced during the electroplating process, and Sn is segregated in the outer peripheral region a. It seems to occur.

As a result, the metal structure becomes dense in the outer peripheral region a, so that the hardness is increased and therefore the surface layer 3 is formed.
When the sliding surface 3a is formed by the end surface of the columnar main body 5 during the progress of wear of the sliding surface 3a, as shown in FIG.
Since the highly hard mesh portion C formed by the outer peripheral region a of each columnar crystal 4 is dispersed in the surface layer 3, the wear resistance of the surface layer 3 is improved.

FIG. 8 is an X-ray diffraction diagram of the Pb alloy crystal in the surface layer 3, and only the diffraction peaks of the (200) plane and the (400) plane are recognized by the Miller index.

Here, the orientation index Oe is used as an index representing the orientation of the crystal plane, (However, hkl is Miller index, Ihkl is (hkl)
The integrated intensity of the plane, ΣIhkl is defined as the sum of Ihkl), and the closer the orientation index Oe is to 100% in the (hkl) plane, the more the crystal plane oriented in the direction orthogonal to the (hkl) plane. There will be many.

The (200) plane and (40) of the Pb alloy crystal
Table 1 shows the integrated intensity Ihkl and the orientation index Oe on the (0) plane.

[0020]

[Table 1] From Table 1, the orientation index Oe in the (h00) plane of the Pb alloy crystal is 100%, and therefore the Pb alloy crystal is
Crystal planes oriented in the respective axis directions on the crystal axes a, b, c
That is, it has a (h00) plane.

When the crystal plane is oriented in the direction orthogonal to the (h00) plane as described above, the crystal structure of the Pb alloy is a face-centered cubic structure, so that the atomic density in the orientation direction becomes high. The hardness of No. 3 is increased, and the wear resistance thereof is improved.

Table 2 compares the composition of the surface layer, the orientation index Oe in the (h00) plane, the alloying element concentration, etc. in various slide bearings.

[0023]

[Table 2] The present invention (1) corresponds to the Pb alloy (FIGS. 3 to 5) in the present invention. The surface layers of both Comparative Examples (1) and (2) are formed of granular crystals.

FIG. 9 shows the wear test results of the present inventions (1) to (4) and comparative examples (1) and (2).

The wear test was carried out for a constant sliding distance by rubbing each slide bearing on the rotary shaft and setting the load on the slide bearing as a sine full wave dynamic load synchronized with the rotary shaft. .

The test conditions are as follows. Rotating shaft material JIS S48C material with nitriding treatment, rotating shaft rotation speed 3000 rpm, maximum load surface pressure 600 kg / cm ² (bearing projected area: width x diameter), sliding distance 2.5 x 10 ³ k
m, lubrication temperature 120 ° C, lubrication pressure 3 kg / cm ² .

As is apparent from FIG. 9, the inventions (1) to (1) to
In (4), after each quadrangular pyramidal crystal 6 is worn, the highly hard mesh portion C is dispersed on the sliding surface 3a, and the orientation index Oe in the (h00) plane is 10
Since it is 0%, the surface layer 3 exhibits excellent wear resistance as compared with Comparative Examples (1) and (2).

At the initial stage of sliding, since the sliding surface 3a is formed of the quadrangular pyramidal crystal 6, the sliding surface 3a is formed.
The surface area of a is enlarged so that the surface layer 3 has sufficient oil retaining property, and the vertex d side of the quadrangular pyramidal crystal 6 is preferentially worn to improve the initial conformability. This is effective in avoiding the occurrence of image sticking. Such sliding characteristics are also obtained when the tip of the columnar crystal 4 is formed of a quadrangular pyramid truncated crystal.

Those in which the columnar crystals 4 form a part of the surface layer 3 are also included in the present invention. In this case, the area ratio of the end faces of the columnar crystals 4 on the sliding surface 3a is set to 50% or more.

As described above, the inclination of the columnar crystals 4 becomes a problem in order to obtain excellent sliding characteristics.

Therefore, as shown in FIGS. 6 and 10, an imaginary plane F along the sliding surface 3a is defined in the columnar crystal 4, and the center line of the columnar crystal 4, that is, a quadrangular pyramidal crystal 6 in the illustrated example. If the inclination angle formed by a straight line g passing through the apex d and the central portion k of the bottom surface with respect to a reference line h passing through the central portion k of the bottom surface and perpendicular to the virtual plane F is defined as θ, the inclination angle θ of the columnar crystal 4 is 0 °. ≦ θ ≦ 30 ° is set. When the inclination angle θ becomes θ> 30 °, the wear resistance of the surface layer 3 decreases.

The present invention is not limited to sliding bearings, but can be applied to other sliding members.

[0033]

According to the present invention, by specifying the structure of the surface layer as described above, it is possible to provide a sliding member having improved wear resistance of the surface layer.

[Brief description of drawings]

FIG. 1 is an exploded plan view of a plain bearing.

2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a micrograph showing a crystal structure of a Pb alloy on a sliding surface.

FIG. 4 is a micrograph showing a crystal structure of a Pb alloy when a surface layer is longitudinally cut.

FIG. 5 is a partially enlarged micrograph of FIG.

FIG. 6 is a schematic perspective view of a main part of a surface layer.

7 is a sectional view taken along line 7-7 of FIG.

FIG. 8 is an X-ray diffraction diagram of Pb alloy crystals in the surface layer.

FIG. 9 is a graph showing a result of a wear test.

FIG. 10 is an explanatory diagram showing a tilt angle measuring method for columnar crystals.

[Explanation of symbols]

 1 Sliding Bearing (Sliding Member) 2 Substrate 3 Surface Layer 3a Sliding Surface 4 Columnar Crystal a Perimeter Area b Inner Area

Claims (1)

Claim: What is claimed is: 1. A substrate (2) and an alloy surface layer (3) formed on the substrate (2) and having a sliding surface (3a) with a mating member (x). In the provided sliding member, the surface layer (3) has a plurality of columnar crystals (4) extending from the substrate (2), and an alloy element in an outer peripheral region (a) of each columnar crystal (4). A sliding member characterized in that the concentration is higher than the alloying element concentration in the inner region (b) excluding the outer peripheral region (a).