JP2010002042A - Bearing made of sintered metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing made of sintered metal having a high corrosion resistance and also excellent in the slidability and wear resistance. <P>SOLUTION: The bearing of sintered metal includes an austenite series stainless steel structure and a manganese sulfide structure, and further includes a nickel structure, wherein the share to the whole of the nickel component contained in the nickel structure and austenite series stainless steel structure is adjusted to, for example between 13-35 wt.%, including the limits, while the share to the whole of the manganese sulfide structure is adjusted to, for example between 1.5-2.5 wt.%, including the limits. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sintered metal bearing, and more particularly to a sintered metal bearing that can be used in an environment where high corrosion resistance is required.

  Applications that require high corrosion resistance include, for example, bearings for fuel pumps of automobile engines. Recently, the appearance of sintered metal bearings with higher corrosion resistance is expected.

In other words, bio-gasoline including bioethanol has been developed in place of conventional fossil fuels such as petroleum for the purpose of reducing environmental burdens by reducing CO ₂ in recent years, and actually started to be introduced as engine oil for automobiles. However, this type of gasoline has a higher proportion of impurities such as organic acids than conventional fossil fuel-based gasoline. Therefore, a bearing having acid resistance (durability against acid corrosion) is required for a bearing for a fuel pump for pumping gasoline containing such a large amount of impurities to the engine.

As a bearing suitable for the corrosive environment, for example, a sintered metal bearing described in Patent Document 1 is known. That is, this sintered metal bearing contains Ni: 21-35%, Sn: 5-12%, C: 3-7%, P: 0.1-0.8%, the balance: Cu and inevitable A bearing made of a Cu-Ni-based sintered alloy having a component composition consisting of impurities, the inner surface of an open hole formed open to the surface of the bearing, at least around the opening of the open hole, and inside the bearing It has a structure in which an Sn high-concentration alloy layer containing Sn: 50% by mass or more is formed on the inner surfaces of the internal pores.
JP 2006-199977 A

  In the sintered alloy bearing described in Patent Document 1, the corrosion resistance is improved by forming a Sn high-concentration alloy layer in the opening portion and the periphery thereof, but basically a sintered alloy based on Cu. In the case of a bearing made of acid, the acid corrosion resistance, particularly durability against sulfidation corrosion is poor, and it is difficult to achieve sufficient improvement even if the composition and the blending ratio thereof are changed as described above.

  In addition, when used under gasoline immersion as described above, even if the bearing is impregnated with lubricating oil, it flows out of the bearing. Therefore, this type of bearing is required to have not only corrosion resistance but also high slidability and wear resistance even in an oil-free state.

  In view of the above circumstances, it is a technical problem to be solved by the present invention to provide a sintered metal bearing having high corrosion resistance and excellent slidability and wear resistance.

  The present invention has been made to solve the above problems. That is, the sintered metal bearing according to one aspect of the present invention is a sintered metal bearing having an austenitic stainless steel structure and a manganese sulfide structure, and further characterized by having a nickel structure.

  The sintered metal bearing having the above-described configuration can exhibit superior performance in terms of corrosion resistance, slidability, and wear resistance as compared to conventional sintered metal bearings for the following reasons. That is, austenitic stainless steel is an alloy structure of chromium with iron as a base material, and contains a considerable amount of nickel component, so it has excellent ability to form and repair chromium oxide passive film. Therefore, high corrosion resistance can be imparted to non-oxidizing acids, particularly sulfuric acid and sulfurous acid. In addition, since the manganese sulfide structure also functions as a solid lubricant, it is possible to obtain good slidability while using stainless steel as a base material, thereby reducing torque even in an oil-free state. In addition, in the present invention, since the nickel structure is provided separately from the austenitic stainless steel structure, the ability to form a passive film of chromium oxide can be further enhanced, and the corrosion resistance by the stainless steel structure can be enhanced. . Further, although the manganese sulfide structure itself is not excellent in acid corrosion resistance, providing the nickel structure as described above can protect the manganese sulfide structure and further improve the corrosion resistance of the entire bearing. The above effect can be obtained only by providing a nickel structure alone. Further, according to the nickel structure, the effect of suppressing the sliding wear can be obtained, so that the wear resistance can be improved.

  In addition, nickel powder consisting of nickel structure that exhibits these excellent effects can be sintered at the sintering temperature of austenitic stainless steel powder. For example, austenitic stainless steel powder is mixed with manganese sulfide powder and nickel simple substance powder. And after sintering this after compacting, the sintered metal bearing which has the said structure | tissue can be obtained.

  Here, the ratio of the nickel component contained in the nickel structure and the austenitic stainless steel structure to the whole may be adjusted to 13 wt% or more and 35 wt% or less, and is adjusted to 13 wt% or more and 25 wt% or less. Furthermore, it may be adjusted to 15 wt% or more and 20 wt% or less. This is because if the ratio of the nickel component to the whole is less than 13 wt%, it becomes difficult to ensure the corrosion resistance and wear resistance that should be originally obtained by the nickel component. Moreover, if the content ratio of the nickel component exceeds 35 wt%, the ratio of the iron component as the main component is greatly reduced, and it becomes difficult to ensure the required strength and rigidity.

  Further, the ratio of the manganese sulfide structure to the whole may be adjusted to 0.5 wt% or more and 10 wt% or less, may be adjusted to 1.5 wt% or more and 2.5 wt% or less, and It may be adjusted to 6 wt% or more and 1.9 wt% or less. If it is less than 0.5 wt%, the effect of improving the sliding property due to the inclusion of manganese sulfide cannot be sufficiently obtained, and if the content ratio of manganese sulfide exceeds 10 wt%, the fluidity at the powder stage This is because the pressability deteriorates and it becomes difficult to mold. In addition, when used under high load and high speed rotation, such as a fuel pump for an automobile engine, the content ratio of at least the manganese sulfide structure is 1.5 wt% or more and 2.5 wt% or less. However, the above bearing can be used without any problem. Moreover, if it exists in the range of 1.6 wt% or more and 1.9 wt% or less, a dynamic friction coefficient can be made very small and the friction reduction effect by mix | blending manganese sulfide can be enjoyed to the maximum.

  The content ratio of the manganese sulfide structure can be determined in relation to the content ratio of the nickel component contained in the nickel structure or the austenitic stainless steel structure. That is, the more the manganese sulfide is contained, the higher the slidability can be. On the other hand, the corrosion resistance of manganese sulfide itself is not so high, so it is necessary to determine the content ratio of the nickel component according to the content ratio of manganese sulfide. is there. In this regard, the above content balance, that is, the content ratio of the nickel component is 13 wt% or more and 35 wt% or less, and the content ratio of the manganese sulfide structure is 1.5 wt% or more and 2.5 wt% or less, Both sliding characteristics can be exhibited at a high level.

  The solution to the above problem can also be achieved by a sintered metal bearing according to another aspect of the present invention. That is, this sintered metal bearing is a sintered metal bearing having an austenitic stainless steel structure and a manganese sulfide structure, and the proportion of the nickel component contained in the austenitic stainless steel structure is 13 wt%. % Or more and 35 wt% or less.

  Thus, the corrosion resistance of the austenitic stainless steel structure can be enhanced also by increasing the content ratio of the nickel component contained in the austenitic stainless steel structure. Therefore, it is possible to provide a sintered metal bearing that exhibits excellent acid corrosion resistance and wear resistance while imparting good sliding characteristics to reduce torque.

  Also in this case, similarly to the sintered metal bearing described above, the nickel component content is 13 wt% or more and 35 wt% or less, and the manganese sulfide structure content is 1.5 wt% or more and 2.5 wt% or less. By doing so, a sintered metal bearing excellent not only in corrosion resistance but also in sliding characteristics can be obtained.

  The sintered metal bearing according to the above description is excellent in sliding characteristics and wear resistance as well as acid corrosion resistance, and can be suitably used by being incorporated in a fuel pump of an automobile engine, for example. In this type of pump, for example, a low-quality fuel containing a high concentration organic acid or sulfur, such as bioethanol, may be used. Also shows high corrosion resistance. In addition, since it has excellent sliding characteristics and wear resistance, it can be used without problems even when used under high load and high speed rotation.

  As described above, according to the present invention, it is possible to provide a sintered metal bearing having high corrosion resistance and excellent slidability and wear resistance.

  Hereinafter, an embodiment of a sintered metal bearing according to the present invention will be described.

  The sintered metal bearing according to the present invention is roughly divided into a sintered metal structure (first structure form) having an austenitic stainless steel structure, a manganese sulfide structure, and a nickel structure, and an austenitic stainless steel structure. Examples of the second structure form include a manganese sulfide structure and a structure in which the content ratio of the nickel component in the austenitic stainless steel is increased (13 wt% or more and 35 wt% or less).

[First organization form]
First, regarding the sintered metal bearing according to the first structure form, the austenitic stainless steel structure constituting the sintered metal structure contains at least 11 wt% or more of a chromium component and 8 wt% or more of a nickel component. The composition ratio is not particularly limited. Here, typical SUS304 (18Cr-8Ni) can be mentioned as an austenitic stainless steel.

  At this time, the proportion of the nickel component contained in the nickel structure and the austenitic stainless steel structure is 13 wt% or more and 35 wt% or less, preferably 13 wt% or more and 25 wt% or less, more preferably 15 wt% or more and 20 wt% or less. Thus, the content ratio of the nickel structure is adjusted. As an example, when SUS304 (containing 18 wt% Cr) is used as an austenitic stainless steel and the content ratio of manganese sulfide is 1.75 wt%, the content ratio of the nickel structure is 5.6 wt% or more and 29.5 wt%. % Is adjusted within the range. Of course, the nickel content can be lowered to increase the nickel content in the austenitic stainless steel, but in that case the chromium content should not be excessive (for example, in the stainless steel). It is preferable to determine the composition ratio of the stainless steel structure so that the proportion is 25 wt% or less. This is because chromium has a higher melting point than iron and nickel, and the sintering action may be insufficient at the sintering temperature of stainless steel.

  Moreover, the manganese sulfide structure | tissue which comprises a sintered metal structure with a stainless steel structure | tissue is mix | blended for the purpose of making it act as a solid lubricant. From this viewpoint, the proportion of the manganese sulfide structure in the whole is preferably 0.5 wt% or more and 10 wt% or less, more preferably 1.5 wt% or more and 2.5 wt% or less, and 1.6 wt% or more. More preferably, it is 1.9 wt% or less. This is because when the content of the manganese sulfide structure is less than 0.5% by weight, it is difficult to sufficiently exhibit the function as a solid lubricant. In addition, when the manganese sulfide structure is included exceeding 10% by weight, the effect of reducing the friction coefficient on the sliding surface (bearing surface) cannot be expected so much, or as described above, the formability is reduced or the stainless steel is reduced. This is because the bearing strength may be reduced due to a reduction in the steel structure.

  In addition to the above structure, other structures may be included. For example, a copper structure may be further included for the purpose of improving workability (formability). That is, the sintered metal bearing may be composed of a sintered metal structure having an austenitic stainless steel structure, a manganese sulfide structure, a nickel structure, and a copper structure.

The volume ratio (100−porosity [wt%]) of the sintered metal bearing having the above-described structure is preferably set according to the actual application, for example, 75 wt% or more and 95 wt% or less (which can be said by porosity). For example, it is set within a range of 5 wt% or more and 25 wt% or less. In addition, when used under a high load environment such as a fuel pump bearing for an automobile engine, the porosity should be as small as possible (for example, 5 wt% or more and 15 wt% or less) in order to increase the bearing strength. . Here, the “porosity” refers to the ratio of the total volume of the internal holes per unit volume of the sintered metal bearing, and is specifically calculated by the following equation.
Porosity [%] = 100−Density ratio [%] = {1− (ρ1 / ρ0)} × 100
ρ1: Density of sintered metal bearing (Refer to the JIS Z 2501 dry density column for the measurement method)
ρ0: True density of materials with the same composition as sintered metal bearings Porosity has been found to decrease almost linearly with increasing density ratio, thus obtaining porosity by determining density ratio Can do.

The surface opening ratio may be set according to the actual application. For example, in the case of the fuel pump application of the automobile engine described above, the surface opening ratio is considered in consideration of the usage mode under high load and high speed rotation. The rate should be set to 10% or less, preferably 5% or less. Here, “surface opening” refers to a portion where pores contained in a sintered metal bearing having a porous structure are opened on the outer surface. “Surface open area ratio” refers to the area ratio of surface open area to the unit area of the outer surface, and is measured and evaluated under the following conditions.
[measurement tool]
Metallic microscope: Nikon ECLIPSS ME600
Digital camera: Nikon DXM1200
Photography software: Nikon ACT-1 ver. 1
Image processing software: QUICK GRAIN made by Innotek
[Measurement condition]
Photography: Shutter speed 0.5 seconds Binary threshold: 235

  Further, the sintered metal bearing can take various shapes. Here, as a specific shape, for example, typical bearing shapes shown in FIGS. The sintered metal bearing 1 shown in FIG. 1 is a so-called sleeve shape, and has a substantially cylindrical shape having both an outer diameter and an inner diameter that are constant in the axial direction. Further, the sintered metal bearing 2 shown in FIG. 2 is a so-called spherical type, and the inner peripheral surface has a constant inner diameter dimension in the axial direction, while a part or the whole of the outer peripheral surface has a partial spherical shape. Is. Further, the sintered metal bearing 3 shown in FIG. 3 is a so-called flange shape, and one end in the axial direction of the sintered metal bearing having the shape (substantially cylindrical shape) shown in FIG. In this place, a flange portion 3a is provided at the location. These are appropriately selected and used according to the application, particularly the shape of the mounting parts of various devices to be assembled and the mounting mode.

  Here, the sintered metal bearing which concerns on the said structure | tissue form is manufactured by the method shown below, for example. That is, a step (a1) of compressing a mixed powder of austenitic stainless steel powder, manganese sulfide powder and nickel powder as raw materials into a predetermined shape, a step (b1) of sintering a green compact, It is manufactured through at least three steps of the step (c1) of sizing the bonded body.

  First, regarding the compacting step (a1), a raw material powder in which manganese sulfide powder and nickel powder are mixed with austenitic stainless steel powder with a V-type mixer or the like is prepared. The particle size of each powder used here is as shown below, for example. That is, austenitic stainless steel powder: particle size 150 μm or less, manganese sulfide powder: particle size 180 μm or less, nickel powder: particle size 100 μm or less are used. In this case, the particle size of the nickel powder is smaller than that of the austenitic stainless steel powder and smaller than that of the manganese sulfide powder. In the relationship between the austenitic stainless steel powder and the manganese sulfide powder, the particle size of the austenitic stainless steel powder is smaller than that of the manganese sulfide powder. Moreover, in the case of the said powder mixing, the mixing ratio of each powder is set according to the content rate of each component in the finished product mentioned above. For example, the ratio of the nickel component contained in the nickel powder and the austenitic stainless steel powder to the entire mixed powder is 13 wt% or more and 35 wt% or less, and the ratio of the manganese sulfide powder to the entire mixed powder is 1.5 wt%. Each powder is mixed so that it may become more than% and 2.5 wt% or less. At this time, the order of mixing is not particularly limited, and manganese sulfide powder mixed with nickel powder may be mixed with austenitic stainless steel powder. After mixing manganese sulfide powder with austenitic stainless steel powder, Nickel powder may be mixed. Of course, after mixing nickel powder with austenitic stainless steel powder, manganese sulfide powder may be mixed, or three kinds of powders may be mixed simultaneously. Furthermore, when mixing other types of powders, the mixing order is arbitrary.

  Next, a molding die having a powder filling space having a shape corresponding to the finished product (for example, the cylindrical shape shown in FIG. 1) is prepared, and the raw material powder is supplied to the filling space in the die at a predetermined pressure. By pressing, the compacting body of the shape corresponding to the said metal mold | die is obtained.

  Next, the green compact is heated to a sintering temperature (1100 ° C. to 1200 ° C.) of the metal powder as a main component, here austenitic stainless steel powder, and held for a predetermined time. As a result, the stainless steel powder and the manganese sulfide powder are sintered to each other, and the nickel powder is also sintered. Thus, the austenitic stainless steel structure, the manganese sulfide structure, and the nickel structure are sintered. A sintered body made of a metal structure can be obtained (sintering step (b1)).

  By carrying out sizing on the sintered body for the purpose of correcting the size or shape of the sintered body thus obtained (sizing step (c1)), a sintered metal bearing is completed. By this sizing, the sintered body is shaped into a size or shape according to the finished product, and the surface area ratio of the inner peripheral surface serving as the bearing surface is adjusted to a predetermined size (for example, 10% or less). In addition, for the purpose of reducing the number of surface apertures and individual opening areas on the inner peripheral surface, it is possible to perform rotational sizing together with or in place of the sizing. According to this sizing, the surface open area ratio of the inner peripheral surface is adjusted to be smaller (for example, 5% or less), whereby an oil film is formed on the sliding surface even with a relatively low viscosity fluid such as gasoline oil. Can be formed.

  In addition, in the example of the manufacturing process according to the first structural form described above, a case where manganese sulfide powder is first prepared and mixed with stainless steel powder and nickel powder has been described, but instead of this, sulfur powder and manganese powder are used. The mixed powder is mixed with stainless steel powder and nickel powder to prepare a raw material powder, which is sintered to obtain a sintered body having a stainless steel structure, a manganese sulfide structure, and a nickel structure ( A sintered metal bearing) can be obtained. This is because by heating to the sintering temperature of stainless steel, sulfur and manganese in the green compact can react, and a manganese sulfide structure can be generated simultaneously with sintering. Of course, it is possible to adopt the same means in the manufacturing process example of the second structure form to be described later.

[Second organization form]
Next, the sintered metal bearing according to the second structure form will be described. The austenitic stainless steel structure constituting this sintered metal bearing contains at least 11 wt% or more of a chromium component and 13 wt% or more of a nickel component. Also, those having a higher nickel component content are used. In addition, although it does not specifically limit about composition ratios other than the above, If the content rate of a chromium component is too large, the content rate of an iron component will become small as a result. Therefore, when importance is attached to ensuring the bearing strength and rigidity, the content ratio of the chromium component should be suppressed to 25 wt% or less.

  Moreover, the manganese sulfide structure | tissue which comprises a sintered metal structure | tissue with a stainless steel structure | tissue is mix | blended for the purpose of making it act as a solid lubricant like a 1st structure | tissue form. Therefore, the ratio of the manganese sulfide structure to the whole is preferably 0.5 wt% or more and 10 wt% or less, more preferably 1.5 wt% or more and 2.5 wt% or less, and 1.6 wt% or more and 1 wt% or less. More preferably, it is 9 wt% or less. Accordingly, the proportion of the nickel component contained in the austenitic stainless steel structure in the entire bearing is 13 wt% or more and 35 wt% or less, preferably 13 wt% or more and 25 wt% or less, more preferably 15 wt% or more and 20 wt% or less. It is preferable to adjust the content ratio of the nickel component so that Other matters related to the finished product (addition of other components, porosity, surface area ratio) are the same as those in the first structural form. The specific shapes that can be taken are also the same as the first tissue form described above.

  The sintered metal bearing according to the above structure is manufactured by, for example, the following method. That is, a step (a2) of compressing and molding a mixed powder of austenitic stainless steel powder and manganese sulfide powder as raw materials into a predetermined shape, a step (b2) of sintering a green compact, and a sintered body It is manufactured through at least three steps of the sizing step (c2).

  First, regarding the compacting step (a2), a raw material powder in which manganese sulfide powder is mixed with austenitic stainless steel powder with a V-type mixer or the like is prepared. The matters relating to the particle size of each powder (austenitic stainless steel powder and manganese sulfide powder) at this time are as described in the first structural form. Moreover, in the case of the said powder mixing, the mixing ratio of each powder is set according to the content rate of each component in the finished product mentioned above. For example, the ratio of the nickel component contained in the austenitic stainless steel powder to the entire mixed powder is 13 wt% or more and 35 wt% or less, and the ratio of the manganese sulfide powder to the entire mixed powder is 1.5 wt% or more 2 Both powders are mixed so as to be 5 wt% or less.

  Next, a molding die having a powder filling space having a shape corresponding to the finished product (for example, the cylindrical shape shown in FIG. 1) is prepared, and the raw material powder is supplied to the filling space in the die at a predetermined pressure. By pressing, the compacting body of the shape corresponding to the said metal mold | die is obtained.

  Next, the green compact is heated to a sintering temperature (1100 ° C. to 1200 ° C.) of the metal powder as a main component, here austenitic stainless steel powder, and held for a predetermined time. As a result, the stainless steel powder and the manganese sulfide powder are sintered with each other, whereby a sintered body made of a sintered metal structure having an austenitic stainless steel structure and a manganese sulfide structure can be obtained (baked). Step (b2)).

By carrying out sizing on the sintered body for the purpose of correcting the size or shape of the sintered body thus obtained (sizing step (c2)), a sintered metal bearing is completed. Also in this form of structure, it is also possible to carry out rotational sizing together with or in place of the sizing for the purpose of adjusting the surface area ratio of the inner peripheral surface to be small.

  The sintered metal bearing according to the above description has excellent corrosion resistance in a corrosive environment, particularly in a sulfuric acid corrosive environment, and has excellent sliding properties and wear resistance in an oil-free state. It can be suitably used for an application under immersion in a corrosive fluid such as a fuel pump.

  FIG. 4 shows an example of the above application, and shows a cross-sectional view of a fuel pump 11 of an automobile engine incorporating a sintered metal bearing 1 according to the present invention. This fuel pump 11 is for pumping gasoline as fuel to a separately installed automobile engine, and is driven to rotate by a casing 12, a motor 13 disposed in the casing 12, and the motor 13. An impeller 15 attached to one end of the shaft 14 is mainly provided. Further, sintered metal bearings 1 and 2 having the shapes shown in FIGS. 1 and 2, for example, are attached to the casing 12, and both ends in the axial direction from the motor 13 by the sintered metal bearings 1 and 2. The shaft 14 that protrudes in the direction is supported in rotation. In the fuel pump 11 according to the above configuration, when the motor 13 is driven to rotate, gasoline 16 is taken into the fuel pump 11 from the opening on the impeller 15 side. The gasoline 16 taken into the fuel pump 11 rotates with the gap formed between the outer peripheral surface of the impeller 15 and the motor 13 and the inner peripheral surface of the casing 12 and the sintered metal bearings 1 and 2. It is fed into the automobile engine through an opening formed on the side opposite to the impeller 15 through a gap formed with the shaft 14.

  In this way, even in an environment where the fuel is always in contact with gasoline 16, the sintered metal bearings 1 and 2 according to the present invention have excellent acid corrosion resistance, thereby reliably preventing deterioration of bearing performance due to corrosion. it can. In addition, since the sintered metal bearings 1 and 2 are excellent in sliding characteristics and wear resistance, high bearing performance is exhibited over a long period of time even in an environment where gasoline 16 always passes through the bearing gap as described above. It becomes possible to do.

  In the above application example, the case where it is used without oil is taken up. Of course, it is not limited to use without oil, but it can also be used in a state impregnated with lubricating fluid such as lubricating oil or lubricating grease. It is.

It is sectional drawing which shows an example of the shape of the sintered metal bearing which concerns on this invention. It is sectional drawing which shows the other example of the shape of the sintered metal bearing which concerns on this invention. It is sectional drawing which shows the other example of the shape of the sintered metal bearing which concerns on this invention. It is the figure which showed the example of a use of the sintered metal bearing which concerns on this invention, Comprising: It is sectional drawing of the fuel pump of the automobile engine incorporating this bearing.

Explanation of symbols

1, 2, 3 Sintered metal bearing 11 Fuel pump 12 Casing 13 Motor 14 Rotating shaft 15 Impeller 16 Gasoline

Claims (7)

  A sintered metal bearing having an austenitic stainless steel structure and a manganese sulfide structure, and further having a nickel structure.   2. The sintered metal bearing according to claim 1, wherein a ratio of a nickel component contained in the nickel structure and the austenitic stainless steel structure to the whole is adjusted to 13 wt% or more and 35 wt% or less.   The sintered metal bearing according to claim 1 or 2, wherein a ratio of the manganese sulfide structure to the whole is adjusted to 0.5 wt% or more and 10 wt% or less.   The sintered metal bearing according to claim 3, wherein a ratio of the manganese sulfide structure to the whole is adjusted to 1.5 wt% or more and 2.5 wt% or less.   A sintered metal bearing having an austenitic stainless steel structure and a manganese sulfide structure, wherein the proportion of the nickel component contained in the austenitic stainless steel structure is adjusted to 13 wt% or more and 35 wt% or less. Sintered metal bearings.   The sintered metal bearing according to claim 5, wherein a ratio of the manganese sulfide structure to the whole is adjusted to 1.5 wt% or more and 2.5 wt% or less.   The sintered metal bearing according to any one of claims 1 to 6, wherein the sintered metal bearing is used by being incorporated in a fuel pump of an automobile engine.

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