JP2006022896A - Double-layered bearing material and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To finely grain crystals of a bearing alloy layer while keeping high bonding strength of the bearing alloy layer and a steel back metal layer in a double-layered bearing material formed by bonding the bearing alloy layer on the steel back metal layer. <P>SOLUTION: In this double-layered bearing material, a composition of the bearing alloy layer is composed of Sn of 0.5-12 mass%, Fe of 0.5-5 mass%, and Cu as remaining part, a Sn-Fe compound is separated out in the bearing alloy layer, and an average size of crystalline particles of the bearing alloy layer is 50 μm or less. The double-layered bearing material is manufactured by spraying and sintering the metallic powder for sintering on the steel back metal layer, then densifying the sintered layer to obtain an intermediate complex material, rolling the intermediate composite material with rolling reduction of 5% or more, and heating the same to 700-890°C. The crystals are distorted by the rolling, then the Sn-Fe compound is separated out while applying crystal distortion as nucleus in the heat treatment, and the Sn-Fe compound has a function for controlling the growth of crystals, and finely graining matrix. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multilayer bearing material obtained by joining a bearing alloy layer made of a copper alloy on a steel back metal layer, and more particularly to a material in which crystals of the bearing alloy layer are refined.

Some multi-layer bearing materials used in internal combustion engines such as automobiles, industrial machines, and agricultural machines have a bearing alloy layer made of a copper alloy such as bronze or phosphor bronze.
This bearing alloy layer is usually formed by sintering. According to Patent Document 1, the copper alloy powder for sintering dispersed on the steel back metal is heated and sintered (primary sintering) for 10 to 30 minutes in an electric furnace in a reducing atmosphere at 700 to 900 ° C., and thereafter The multi-layer bearing material is manufactured by performing primary rolling, secondary sintering, and secondary rolling.

In Patent Document 2, rapid heating is performed by high-frequency induction heating during sintering in order to reduce the crystal grains of a bearing alloy layer made of a sintered copper alloy. The heating temperature at this time is, for example, 750 to 1000 ° C. and 2 minutes or less, and the average equivalent phase of crystal grains of the bearing alloy layer is 5 to 50 μm.
Further, although not directly related to the present invention, Patent Document 3 discloses that Ag, Sn, Sb, In, Mn, Fe, Bi, Zn, Ni, and Ni in order to improve the seizure resistance of the bearing alloy layer. It is disclosed that at least one element selected from the group consisting of Cr is dissolved in a Cu matrix.
Japanese Patent No. 2769421 JP 2002-220631 A Japanese Patent Laid-Open No. 9-249924

  In recent years, an internal combustion engine or the like has been demanded to reduce the size and weight of a bearing device, and along with the increase in output of the internal combustion engine, the bearing surface pressure has been increased. In order to withstand high bearing surface pressure, it is necessary to increase the strength of the multilayer bearing material. For this purpose, it is necessary to increase the strength of the bearing alloy layer by making the crystal grains of the bearing alloy layer fine, and to increase the bonding strength between the steel back metal layer and the bearing alloy layer.

  Conventional multi-layer bearing materials generally heat-sinter copper alloy powder in an electric furnace. If the sintering temperature at this time is high, the bonding strength of the bearing alloy layer to the steel back metal layer However, the crystal grains of the bearing alloy layer become coarse. Conversely, when the sintering temperature is low, the crystal grains of the bearing alloy layer become fine, but the bonding strength of the bearing alloy layer to the steel back metal layer does not increase. As described above, in the case of sintering in a conventional electric furnace, it is difficult to satisfy both of making the crystal grains fine and increasing the bonding strength to the steel back metal layer. By the way, in what is heat-sintered with an electric furnace, as seen in Patent Document 1, it is generally performed that the sintering temperature is increased to 700 to 900 ° C. to give priority to the improvement of the joining strength with the steel backing metal. Yes.

  In Patent Document 2, the bonding strength between the bearing alloy layer and the steel back metal layer is not mentioned, but since the sintering temperature is high, it is considered that the bonding strength is also high. However, in this case, a rapid heating method using high-frequency induction heating has to be employed instead of a generally used heating method using an electric furnace, so that a new manufacturing facility is required. In addition, unlike the heating method using an electric furnace, the steel back metal layer itself is a heat source, so the sintering temperature must be controlled by detecting the temperature of the steel back metal layer itself, which is the heat source, not the ambient temperature. .

  The present invention has been made in view of the above circumstances, and its purpose is to maintain a good bonding strength between the bearing alloy layer and the steel back metal layer without performing rapid heating by high-frequency induction heating or the like, while bearing alloy An object of the present invention is to provide a multi-layer bearing material capable of refining the crystal of the layer and a method for producing the same.

  As a result of repeated experiments, the inventor added Fe to a Cu—Sn bearing alloy and precipitated the Sn—Fe compound by heat treatment, so that the Sn—Fe compound suppressed the growth of crystal grains, It was found that fine graining is effective. At the same time, the precipitation of the Sn—Fe compound occurs by applying strain to the crystal before the heat treatment, and when the crystal is not subjected to appropriate strain, is the precipitation of the Sn—Fe compound observed? In addition, it was investigated together that precipitation was insufficient even though precipitation was insufficient.

The present invention has been made on the basis of the experimental results as described above, and the multilayer bearing material has a composition of a bearing alloy layer of 0.5 to 12% by mass of Sn, 0.5 to 5% by mass of Fe, Sn—Fe compound is precipitated in the bearing alloy layer, and the average grain size of the bearing alloy layer is 50 μm or less. 1).
In the multilayer bearing material of the present invention, the Sn—Fe compound is precipitated in the bearing alloy layer, and the crystal of the bearing alloy layer is refined by the crystal grain growth inhibiting action of this compound, and the average is 50 μm or less. ing. And since the intensity | strength of a bearing alloy layer increases by refinement | miniaturization of this crystal | crystallization, it can be set as a high intensity | strength multilayer bearing material.

In the multilayer copper-based bearing material of the present invention, the bearing alloy layer further includes P in an amount of 0.2% by mass or less, at least one of Ni and Ag in a total amount of 5% by mass or less, and at least one of Pb and Bi. Can be contained in a total amount of 25% by mass or less (claim 2).
According to this, the strength of the bearing alloy layer can be further increased, and the corrosion resistance and lubricity can be increased.

Here, the reason for limitation for each of the above components will be described.
(1) Sn: 0.5 to 12% by mass
Sn strengthens the bearing alloy layer and serves as a nucleus for the formation of the Sn—Fe compound. If it is less than 0.5% by mass, the strength of the bearing alloy layer is insufficient, the precipitation of Sn—Fe compound is small, and the effect of crystal grain refinement cannot be obtained. Moreover, when it exceeds 12 mass%, a bearing alloy layer will become weak. Therefore, the Sn content is set to 0.5 to 12% by mass in order to improve the strength and crystal grain refinement of the bearing alloy layer.
(2) Fe: 0.5-5 mass%
Fe serves as a nucleus of formation of the Sn—Fe compound. If the amount is less than 0.5% by mass, precipitation of the Sn—Fe compound is small, and if it exceeds 5% by mass, the corrosion resistance of the bearing alloy layer is lowered. Therefore, the Fe content is set to 0.5 to 5% by mass in order to finely refine the crystals of the bearing alloy layer without impairing the corrosion resistance.
(3) Precipitation of Sn—Fe compound When the Sn—Fe compound is precipitated in the bearing alloy layer, the growth of crystal grains of the Cu matrix is suppressed and refined. When there is no generation of Sn—Fe compound, crystal grain refinement does not occur.
Incidentally, in Patent Document 3, it is described that Fe may be added as a selective element. However, since Fe is dissolved in a Cu matrix, there is no precipitation of Sn—Fe compound, and Sn— Refinement of Cu matrix crystals due to precipitation of Fe compounds has not been achieved.

(4) P: 0.2% by mass or less P strengthens the bearing alloy layer, but if it exceeds 0.2% by mass, the bearing alloy layer tends to become brittle. Therefore, P is preferably 0.2% by mass or less for strengthening the bearing alloy layer.
(5) Ni and Ag: 5% by mass or less in total amount Ni and Ag improve the corrosion resistance of the bearing alloy layer. When these elements exceed 5% by mass in total, the bearing alloy layer tends to become brittle. Moreover, since it is an expensive element, the cost is increased. Accordingly, the total amount of Ni and Ag is preferably 5% by mass or less.
(6) Pb and Bi: 25% by mass or less in total amount Pb and Bi increase the lubricity of the bearing alloy layer. When the total amount of these elements exceeds 25% by mass, the bearing alloy layer tends to become brittle. Accordingly, the total amount of Pb and Bi is preferably 25% by mass or less.

Next, as a manufacturing method of the above-mentioned multi-layer bearing material, the present invention provides a sintered layer by dispersing and sintering a metal powder for sintering for forming a bearing alloy layer on a steel back metal layer, The sintered layer was densified to obtain an intermediate composite material, and the intermediate composite material was rolled at a rolling reduction of 5% or more, and then heated to 700 to 890 ° C. Item 3).
In other words, the multilayer bearing material of the present invention is intended to increase the bonding strength of the bearing alloy layer to the steel back metal layer when the bearing alloy layer is formed on the steel back metal layer by sintering in the production of the intermediate composite material. Furthermore, it can be sintered at a high temperature. In addition, the Sn—Fe compound can be uniformly precipitated in the bearing alloy layer, and the crystal of the bearing alloy layer can be finely divided to an average of 50 μm or less by the crystal grain growth inhibiting action of this compound. And since the strength of the bearing alloy layer is increased by the refinement of the crystal, it is possible to obtain a high-strength multilayer bearing material in combination with the increase in the bonding strength by performing the sintering at a high temperature. .
The sintering metal powder dispersed on the steel back metal layer can be a pre-alloy powder formed in advance from an alloy having the same composition as the bearing alloy layer.
In the present invention, the bearing alloy layer is mainly expressed as a sintered layer during the production of the multilayer bearing material.

The production method of the present invention will be described below.
In the production method of the present invention, first, metal powder for sintering is sprayed on the steel back metal layer, and this is sintered. Hereinafter, this sintering is referred to as primary sintering.
Since this primary sintering does not require rapid heating, it is possible to employ heating sintering by an electric furnace that has been generally used. The sintering temperature can be set to a high sintering temperature for the purpose of increasing the bonding strength of the bearing alloy layer. The sintering temperature suitable for increasing the bonding strength varies depending on the composition of the bearing alloy layer, but is generally 20 to 50 ° C. lower than the melting point.

When the metal powder used for sintering is a mixture of pure metal powders such as pure Cu powder, pure Sn powder, pure Fe powder, etc., these metal elements diffuse by sintering, and the Cu-Sn alloy Form. However, at practical sintering temperatures and times, Fe elements hardly diffuse into the Cu matrix, and it may be difficult to produce Sn—Fe compounds.
In order to solve this problem, pre-alloy powder is preferably used as the metal powder for sintering. The pre-alloy powder is a powder obtained by melting and mixing component elements having the same composition as the bearing alloy layer, and spraying gas or water. In this pre-alloy powder, the above-mentioned problems do not occur because the alloy itself is already made into a copper alloy and Fe is also dissolved in the Cu matrix.

  Immediately after the primary sintering, as shown in FIG. 2, the sintered layer A is porous. In FIG. 2, symbol B indicates a hole, and symbol C indicates a steel back metal layer. If rolling is performed in this porous state, non-uniform distortion occurs in the sintered layer, and as a result, the precipitation of the Sn—Fe compound becomes non-uniform. In order to avoid this, the sintered layer is densified by substantially eliminating voids in the sintered layer. In the present invention, the treatment for densification includes rolling for crushing the pores of the sintered layer to greatly reduce the porosity, and sintering for increasing the adhesion between the metal powders thereafter. including. The porosity of the intermediate composite material is preferably 5% or less. More preferably, it is 1% or less. Hereinafter, rolling and sintering for densification are referred to as primary rolling and secondary sintering, respectively. Here, the state of the crystal grains of the sintered layer immediately after the secondary sintering is shown in FIG.

  Next, an intermediate composite material formed by densification of the sintered layer, that is, an intermediate composite material obtained by joining the sintered layer onto the steel back metal layer is rolled at a reduction ratio of 5% or more. In terms of mass productivity, rolling is preferably performed by roll rolling. Here, the rolling reduction is a percentage of a value obtained by dividing the difference between the thickness of the intermediate composite material before rolling and the thickness of the intermediate composite material after rolling by the thickness of the intermediate composite material before rolling. This rolling gives crystal strain to the sintered layer. Hereinafter, this rolling for giving crystal strain is referred to as secondary rolling.

The crystal distortion given by secondary rolling becomes the nucleus of precipitation of the Sn—Fe compound. When the rolling reduction is less than 5%, the crystal strain becomes non-uniform, and as a result, the precipitation distribution of the Sn—Fe compound becomes non-uniform, so that the grain refinement during the subsequent heat treatment becomes non-uniform.
In order to more uniformly impart crystal strain to the sintered layer by secondary rolling, the rolling reduction is preferably 10% or more. There is no upper limit to the rolling reduction for uniformly giving crystal strain, but it is preferably 30% or less. The rolling reduction that can be given by one roll rolling is limited to 30%. Therefore, if the rolling reduction exceeds 30%, it is not necessary to carry out one rolling, and it is necessary to carry out a plurality of rollings. Because it brings about a rise in

  By this secondary rolling, uniform crystal strain can be applied to the sintered layer. Then, after the secondary rolling, the intermediate composite material is heat treated. This heat treatment is performed by heating the intermediate composite material to 700 to 890 ° C. By this heat treatment, a Sn—Fe compound is deposited on the sintered layer which is a copper alloy, and the crystal is refined as shown in FIG. The Sn—Fe compound starts to precipitate even at 650 ° C., but its distribution is non-uniform, and as a result, fine graining is also non-uniform (see FIG. 1B).

  Here, in FIG.1 (b) and (c), a black point shows the deposited Sn-Fe compound. In addition, at the magnification of the degree shown in FIGS. 1B and 1C, the deposited Sn—Fe compound cannot actually be seen, but is highlighted with black dots for easy understanding. is there. According to FIG. 1 (b), the Sn—Fe compound is non-uniformly precipitated in the sintered layer, but the crystal is refined at the portion where the non-uniform but the same compound is precipitated. However, it is understood that since the precipitation of the Sn—Fe compound is originally non-uniform, the grain refinement is also non-uniform.

  When the heat treatment temperature is 900 ° C. or higher, the precipitated Sn—Fe compound disappears, and the crystal grains of the sintered layer grow rapidly. For this reason, the heat treatment temperature for uniformly depositing the Sn—Fe compound and uniformly refining the crystal is set to 700 to 890 ° C. The heat treatment time is preferably 2 minutes or longer.

Examples of the present invention will be described below.
[Effects of secondary rolling and heat treatment]
(1) On a steel plate (JIS: SPCC) having a thickness of 1.5 mm, a prealloy powder having the composition shown in the following Table 1 is dispersed, and this is applied to a sintering temperature shown in Table 1 in an electric furnace in a reducing atmosphere. After performing primary sintering for 10 to 30 minutes, then cooling and performing primary rolling, secondary sintering is performed under the same conditions as primary sintering, and a densified intermediate composite material (porosity) 0.5%). Then, this intermediate composite material was subjected to secondary rolling at the rolling reduction shown in Table 1, followed by heat treatment at the temperature shown in Table 1 for 3 minutes to obtain Example Products 1 to 3.

  (2) Further, a prealloy powder having the composition shown in Table 1 is sprayed on a steel sheet (JIS: SPCC) having a thickness of 1.5 mm, and this is applied to a sintering temperature shown in Table 1 in an electric furnace in a reducing atmosphere. After performing primary sintering for 10 to 30 minutes, then cooling and performing primary rolling, secondary sintering is performed under the same conditions as primary sintering, and a comparative example product having a porosity of 0.5% 1-3 were obtained.

  (3) Next, with respect to Examples 1 to 3 and Comparative Examples 1 to 3 obtained as described above, the average crystal grain size of the bearing alloy layer is measured by the JIS 0501 copper grain size test method. In addition, the hardness of the bearing alloy layer was measured, and the results are shown in Table 1. Example product 1 and comparative product 1, Example product 2 and comparative product 2, Example product 3 and comparative product 3 are the composition of the bearing alloy layer, primary sintering, primary rolling and secondary sintering, respectively. These conditions are the same, and the difference lies in whether secondary rolling and subsequent heat treatment are performed.

  As shown in Table 1, the example products 1 to 3 subjected to the secondary rolling and the heat treatment had a very large crystal grain size of the bearing alloy layer compared to the comparative products 1 to 3 that did not. Finely, the average crystal grain size of the matrix is 50 μm or less. Then, by the refinement of the crystal, the hardness of the bearing alloy layer is higher in the example product 1 than in the comparative product 1, the example product 2 is higher than the comparative product 2, and the test product 3 is higher than the comparative product 3. It has become.

  From the above, when Fe is added to a Cu—Sn bearing alloy and primary sintering → primary rolling → secondary sintering → secondary rolling → heat treatment, the crystal of the bearing alloy layer is refined. It is understood. Furthermore, it is understood that when secondary rolling and heat treatment are performed, the finer the crystal, the better the content of Fe and Sn. In other words, when secondary rolling and heat treatment are performed, an amount of Sn—Fe compound corresponding to the content of Sn and Fe is uniformly deposited on the bearing alloy layer, and the amount of precipitation of the compound is reduced by the crystal growth inhibiting function of this compound. Corresponding crystal refinement is performed.

[Effects of additive elements and secondary rolling reduction and heat treatment temperature]
(1) A pre-alloy powder having the composition shown in the following Table 2 is dispersed on the same steel plate as described above, and this is applied in an electric furnace in a reducing atmosphere at a sintering temperature shown in Table 2 for 10 to 30 minutes. After performing primary sintering and then cooling and performing primary rolling, secondary sintering was performed under the same conditions as the primary sintering, and an intermediate composite material having a porosity of 0.5% was obtained. Next, the intermediate composite material was subjected to secondary rolling at the rolling reduction shown in Table 2 and then heat-treated at the temperature shown in Table 2 to obtain Example products 4 to 10 and Comparative product products 4 to 9. Got.

(2) Next, for the example products 4 to 10 and the comparative example products 4 to 9 obtained as described above, the average crystal grain size of the bearing alloy layer was measured and the hardness of the bearing alloy layer was measured. The results are shown in Table 2.
As is apparent from Table 2, in Comparative Examples 4 and 5 in which the bearing alloy layer does not contain Fe or Sn, the crystal grains are not affected even when the rolling reduction and heat treatment temperature of the secondary rolling are within the scope of the present invention. It is large and not refined. This is presumably because there is no precipitation of Sn—Fe compound during the heat treatment because Fe or Sn is absent, and therefore the crystal is not finely divided.
Further, even if the bearing alloy layer contains Fe and Sn, the comparative example product 6 in which the rolling reduction ratio of the secondary rolling is less than 5%, and the comparative example products 7 to 9 in which the heat treatment temperature is out of the upper and lower limits of the present invention. However, the crystal grains are large.

  However, the average crystal grain sizes of the comparative example products 6 and 7 are smaller than those of the other comparative example products. This is 3% in which the rolling reduction ratio of the comparative example product 6 is slightly lower than 5% of the example products 4 to 7, and the heat treatment temperature of the comparative example product 7 is 700 ° C. of the example products 4 to 7. In Comparative Examples 6 and 7, the Sn—Fe compound was slightly deposited in the heat treatment, but the average grain size was smaller than that of the other Comparative Examples. It seems that

  In Comparative Examples 8 and 9, the heat treatment temperatures were 900 ° C. and 925 ° C., which exceeded the upper limit of the heat treatment temperature of the present invention. Therefore, the Sn—Fe compound disappeared, and it seems that crystal grains grew. . On the other hand, in Example Product 9, heat treatment was performed at 890 ° C. At this temperature, crystal grain refinement is not impaired. However, as described above, in Comparative Product 8 in which the heat treatment temperature is 900 ° C., the crystals are coarsened.

In addition, based on the consideration about the above comparative example products 7 to 9, as a condition for making the precipitation of the Sn—Fe compound uniform and making the crystal finely uniform, the rolling reduction of the secondary rolling is 5%. As described above, the heat treatment temperature is set to 700 to 890 ° C.
On the other hand, in Example goods 4-10, the average crystal grain diameter is small and has become 50 micrometers or less. This is because by performing secondary rolling at a rolling reduction of 5% or more, uniform crystal distortion occurs in the entire sintered layer, and by performing heat treatment at 700 to 890 ° C., the Sn—Fe compound is uniform. It is confirmed that the crystals are uniformly refined.

In addition, the example products 4 to 7 in which P, Ni, Ag, Pb, and Bi are added to the bearing alloy layer are the average crystal grains of the other example products 8 and 9, the example products 1 to 3 in Table 1, and the like. The diameter is the same. From this, it can be said that these additive elements do not have any adverse effect on crystal grain refinement. Therefore, the addition of P, Ni, Ag, Pb, and Bi can improve the corrosion resistance and lubricity of the bearing alloy layer without hindering crystal grain refinement.
In Example product 10 in which the rolling reduction of secondary rolling is 30%, the degree of crystal grain refinement is high. From this, it can be said that the rolling reduction has a great influence on the refinement of crystals (precipitation of Sn-Fe compound), and the higher the reduction ratio, the more the refinement (precipitation of Sn-Fe compound) is promoted.

[Bearing alloy layer joint strength]
(1) A prealloy powder having the composition shown in the following Table 3 is sprayed on a steel plate (JIS: SPCC) having a thickness of 1.5 mm, and this is applied to a sintering temperature shown in Table 3 in an electric furnace in a reducing atmosphere. After performing primary sintering for 10 to 30 minutes, then cooling and performing primary rolling, secondary sintering is performed under the same conditions as primary sintering, and a comparative example product having a porosity of 0.5% 10 and 11 were obtained.

  (2) Then, a shear test was performed on Example Product 1 in Table 1 and Comparative Product 10 and 11 described above in order to see the bondability of the bearing alloy layer to the steel plate (steel back metal layer). For this shear test, the test piece 1 shown in FIG. 3 was manufactured by processing the example product 1 and the comparative example products 10 and 11 described above. The test piece 1 is provided with two circular openings 2, and the two openings 2 are hooked on a tensile tester to pull the shear strength (bonding force) between the steel plate 3 and the bearing alloy layer 4. Was measured. The results of this test are shown in Table 3.

  As is clear from Table 3, in Comparative Example Product 10 in which the sintering temperature was 950 ° C., the bonding strength between the steel plate and the bearing alloy layer was high. However, the crystal grains of the bearing alloy layer have grown greatly. On the other hand, in Comparative Product 11 in which the sintering temperature is 850 ° C., the bonding strength between the steel plate and the bearing alloy layer is low, but the crystal grains of the bearing alloy layer are fine. As described above, the sintering temperature has a great influence on the bonding strength and the crystal grain size. If the sintering temperature is high, the bonding strength increases, but the crystal grain size increases. The particle size becomes smaller.

  On the other hand, in Example Product 1, the bonding strength between the steel plate and the bearing alloy layer is high, and the crystal grains of the bearing alloy layer are fine. In Example Product 1, since the sintering temperature was set as high as 950 ° C., the bonding strength between the steel plate and the bearing alloy layer was increased, and crystals were grown by using this high sintering temperature. This is because the crystals could be refined by subsequent secondary rolling and heat treatment.

[Elongation and fatigue resistance]
(1) A prealloy powder having the composition shown in the following Table 4 is sprayed on a steel sheet (JIS: SPCC) having a thickness of 1.5 mm, and this is applied to a sintering temperature shown in Table 4 in an electric furnace in a reducing atmosphere. After performing primary sintering for 10 to 30 minutes, then cooling and performing primary rolling, secondary sintering is performed under the same conditions as primary sintering, and an intermediate composite material having a porosity of 0.5% Got. As shown in Table 4, this intermediate composite material was subjected to secondary rolling at a reduction rate of 5.7% to obtain a comparative product 12.

  (2) A fatigue test was performed on Example Product 1 in Table 1, Comparative Product 10 and 11 in Table 3, and the above Comparative Product 12. The fatigue test was carried out by forming Example Product 1 and Comparative Product 10 to 12 into half bearings, respectively, and attaching them to a testing machine. The tester used was a bearing dynamic load tester that evaluates fatigue resistance based on impact load due to rotational load and contact per piece due to shaft deflection. The fatigue test conditions are as shown in Table 5 below.

  Further, the comparative product 12 was also subjected to the shear test described above, and at the same time, the elongation of the bearing alloy layer was measured. In addition, also when the shear test was done with respect to Example product 1 and Comparative product 10 and 11 in Table 4, the elongation of the bearing alloy layer was measured in the same manner.

Table 4 shows the results of the fatigue test, the shear test results, and the elongation measurement results.
In general, not only for bearing alloys, but as a characteristic of metals, the impact of ductility such as elongation is large for impact loads, and the higher the ductility, the higher the impact resistance. From this, in a fatigue test using a bearing dynamic load tester, the better the ductility (elongation), the better the fatigue resistance.
Since the crystal of the bearing alloy layer is refined, the example product 1 has high hardness and high strength. Also, the elongation is the same as that of the comparative example product 10 having low hardness, and the ductility is also high. Are better. For this reason, the example product 1 exhibits excellent fatigue resistance in combination with the sintering temperature of 950 ° C. and the high bonding strength of the bearing alloy layer.

  On the other hand, the comparative product 10 has a sintering temperature of 950 ° C., which is the same as that of the product 1 of Example, and the bonding strength between the steel plate and the bearing alloy layer is high, but the crystal grain size is large (the strength of the bearing alloy layer is high). Low), so it is inferior in fatigue resistance. Since the comparative example product 11 has a sintering temperature as low as 850 ° C., the crystal grain size of the bearing alloy layer is small, but since the bonding strength between the steel plate and the bearing alloy layer is low, the fatigue resistance is a comparative example product. It is even lower than 10.

  Moreover, the comparative example product 12 is not subjected to subsequent heat treatment while being subjected to cold secondary rolling. For this reason, work hardening due to cold secondary rolling remains in the bearing alloy layer as it is, the hardness thereof is the same as that of Example Product 1, and the shear strength is also that of Example Product 1 (sintering temperature is the same). ). However, since the comparative example product 12 is not heat-treated, the bearing alloy layer has no crystal grain refinement (the strength of the bearing alloy layer is low), and the ductility is low, so the fatigue resistance is low. .

The present invention is not limited to the above-described example and can be modified and expanded as follows.
After the crystal is refined by primary sintering → primary rolling → secondary sintering → secondary rolling → heat treatment, cold tertiary rolling may be further performed to work harden the bearing alloy layer. In this case, the bearing alloy layer having finely divided crystals has a high degree of deformation resistance to rolling, and if the rolling rate is the same, the degree of work hardening is higher than that of the case where heat treatment for fine graining is not performed. Becomes higher. In other words, if the same hardness is to be obtained, a small reduction ratio is sufficient for the bearing alloy layer crystal of the present invention that is made finer, and therefore the bearing alloy layer has a small decrease in ductility. Less impact degradation is required.
An adhesive layer such as a Cu plating layer for increasing the bonding strength of the bearing alloy layer may be provided on the surface of the steel back metal layer.

(A) after secondary sintering, (b) after heat treatment at 650 ° C., (c) is a schematic diagram showing the state of crystal grains of the bearing alloy layer (sintered layer) after heat treatment at 700 to 890 ° C. Schematic diagram of bearing alloy layer (sintered layer) immediately after secondary sintering The test piece which performs a shear test is shown, (a) is a top view, (b) is a side view.

Explanation of symbols

  In the drawings, 3 is a steel plate (steel back metal layer), and 4 is a bearing alloy layer.

Claims (4)

In a multi-layer bearing material configured by joining a bearing alloy layer made of a copper alloy on a steel back metal layer,
The composition of the bearing alloy layer includes 0.5 to 12% by mass of Sn and 0.5 to 5% by mass of Fe mainly composed of Cu,
A multi-layer bearing material, wherein a compound of Sn-Fe is precipitated in the bearing alloy layer, and the average grain size of the bearing alloy layer is 50 μm or less.   The bearing alloy layer further includes P in an amount of 0.2% by mass or less, at least one of Ni and Ag in a total amount of 5% by mass or less, and at least one of Pb and Bi in a total amount of 25% by mass or less. The multilayer bearing material according to claim 1. In the method for producing a multilayer bearing material according to claim 1 or 2,
A metal powder for sintering for forming the bearing alloy layer is dispersed on the steel back metal layer and sintered to provide a sintered layer, and the sintered layer is densified to form an intermediate composite material. A method for producing a multilayer bearing material, wherein the intermediate composite material is rolled at a rolling reduction of 5% or more and then heat-treated at 700 to 890 ° C. 4. The method for producing a multi-layer bearing material according to claim 3, wherein the sintering metal powder dispersed on the steel back metal layer is a pre-alloy powder previously formed from an alloy having the same composition as the bearing alloy layer.

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