JP6317079B2 - Method for producing sintered oil-impregnated bearing - Google Patents

Description

The present invention relates to a method for producing a sintered oil-impregnated bearing made of a material containing a metal and using a fluorine-based lubricating oil as a lubricant, and in particular, decomposition of the fluorine-based lubricating oil by the Lewis acid catalytic ability of the metal contained in the material. It is related with the manufacturing method of the sintered oil-impregnated bearing which can improve durability by suppressing.

2. Description of the Related Art In recent years, small motors used in high-temperature environments such as around the engine of automobiles and ships, in an EGR (Exhaust Gas Recirculation) or ETC (Electronic Throttle Control) system, etc., have a high ambient temperature of 120 ° C. or more.
In a small motor used in such a high temperature environment, when a general-purpose lubricant based on hydrocarbon is used as a lubricant, a lubricant shortage due to evaporation (oil shortage) or a lubricant due to oxidation / polymerization This may cause solidification of the motor and reduce the durability of the motor.
Therefore, in such a small motor, a fluorine-based lubricating oil such as perfluoropolyether (PFPE) having excellent heat resistance as compared with the general-purpose lubricant is used as the lubricant (Patent Document 1). And Patent Document 2).
Particularly, “fomblin M series (trade name)” (manufactured by Solvay Specialty Polymer Co., Ltd.) having a linear structure is known as perfluoropolyether. This “fomblin M series” is not only excellent in thermal stability, evaporation characteristics and chemical stability, but also has a high viscosity index and a good yield in the manufacturing process, and is relatively inexpensive. It is often used in motors arranged in the environment.

JP 2003-147380 A Japanese Patent Laid-Open No. 5-240251

However, fluorine-based lubricating oils such as the above-mentioned “fomblin M series” have a property of reacting with a Lewis acid catalyst to cause rapid decomposition under a high temperature environment and evaporate while generating hydrogen fluoride.
Therefore, when a fluorine-based lubricating oil is used as a lubricant for a sintered oil-impregnated bearing made of a material containing a substance having a Lewis acid catalytic ability such as iron or other metals or graphite, the sliding surface of the sintered oil-impregnated bearing Due to the high heat generated in the fluorinated lubricant reacts with a substance having Lewis acid catalytic ability, hydrogen fluoride is generated, and the sliding surface of the sintered oil-impregnated bearing rapidly corrodes, resulting in abnormal sliding surfaces. Wear may occur.
For this reason, in sintered oil-impregnated bearings in which a fluorinated lubricant is used as a lubricant, it has been attempted to limit the material to a substance having a relatively low Lewis acid catalytic ability such as bronze. Sintered oil-impregnated bearings made only of materials with relatively low performance have low wear resistance and may cause abnormal wear depending on the conditions of use, especially when used around the engine of automobiles and ships. It has been confirmed that the wear and tear due to vibration is severe and the durability is not sufficient.
Therefore, for example, for sintered oil-impregnated bearings used around the engine of automobiles and ships, a material having Lewis acid catalytic ability such as iron or graphite is included in the material so that it can sufficiently withstand the impact caused by vibration. Inevitable.
An object of the present invention, the oil-impregnated sintered bearing which a fluorine-based lubricant with a lubricant, a fluorine-based lubricating oil, refrains from reacting with the metal having a Lewis acid catalyst ability contained in the material of the sintered oil-impregnated bearings That is.

In order to solve the above-mentioned problems, a method for manufacturing a sintered oil-impregnated bearing according to the first invention includes a step of compressing raw material powder to obtain a green compact, and a sintered compact by sintering a compact. A step of nitriding the sintered body, and a step of impregnating the sintered body that has undergone the nitriding step with a fluorine-based lubricating oil. The raw material powder is subject to the nitriding treatment. A powder of a predetermined metal is included, and in the nitriding step, a nitride is formed by performing the nitriding process on the predetermined metal .
In the method for producing a sintered oil-impregnated bearing according to the first invention, the composition includes nitride formed by nitriding a predetermined metal contained in the raw material powder . As a result, in a high temperature environment, the Lewis acid (metal ion) of the metal (metal complex) contained in the sintered oil-impregnated bearing is transformed into nitrogen atoms (nitrogen forming nitrides) contained in the sintered oil-impregnated bearing by nitriding treatment. As a result, the fluorine-based lubricating oil reacts with the metal contained in the sintered oil-impregnated bearing (metal having Lewis acid catalytic ability). Hereinafter, “Lewis acid catalyzed reaction”) is suppressed. Therefore, decomposition of the fluorine-based lubricating oil is prevented, corrosion of the sliding surface of the sintered oil-impregnated bearing due to generation of hydrogen fluoride can be suppressed, and occurrence of abnormal wear of the sliding surface can be suppressed. Become.
In addition, in the method for producing a sintered oil-impregnated bearing according to the first invention, the Lewis acid catalytic reaction can be suppressed. As a result, a substance having high wear resistance such as iron (part 1) On the other hand, materials having high Lewis acid catalytic ability) and substances having characteristics as solid lubricants such as graphite (substance, substances having high Lewis acid catalytic ability) can be included in the material, and wear resistance Can be improved.
As described above, according to the method for manufacturing a sintered oil-impregnated bearing according to the first invention, the Lewis acid catalytic reaction can be suppressed, and the durability of the sintered oil-impregnated bearing can be improved.

Method for manufacturing an oil-impregnated sintered bearing according to the second invention is a method for producing a sintered oil-impregnated bearings according to the first invention, the nitriding treatment, characterized in that it is a gas nitrocarburizing treatment.
In the method for producing a sintered oil-impregnated bearing according to the second aspect of the invention, gas soft nitriding is performed on the metal contained in the sintered oil-impregnated bearing. Here, the gas soft nitriding treatment is a treatment for soft nitriding by diffusing carbon and nitrogen in a low temperature range, and is characterized by little occurrence of dimensional change and distortion in the object to be treated.
Specifically, in the gas soft nitriding treatment, the treatment temperature is set to around 570 ° C., and a gas obtained by mixing ammonia gas and carburizing gas is used as the main reaction gas. In the gas soft nitriding treatment, nitrides are formed in the object to be treated by the diffused nitrogen, and generally a compound layer (layer in which nitrides are formed) is formed on the outermost surface of the sintered oil-impregnated bearing. A diffusion layer (a layer in which nitrogen is dissolved) is formed inside the sintered oil-impregnated bearing.
As described above, according to the method for manufacturing a sintered oil-impregnated bearing according to the second invention, a sintered oil-impregnated bearing can be formed by a simpler method.

Method for manufacturing an oil-impregnated sintered bearing according to the third invention is a method for producing a sintered oil-impregnated bearings according to the first or second invention, the raw material powder, as a powder of said predetermined metal, iron powder It is included.
According to the method for manufacturing a sintered oil-impregnated bearing according to the third invention, the wear resistance can be further improved, and the durability can be further improved.

Method for manufacturing an oil-impregnated sintered bearing according to a fourth aspect of the present invention is the method for manufacturing an oil-impregnated sintered bearing according to any one of the invention first to third of the content of the powder of the predetermined metal in the raw material powder The amount is 1% by weight or more.
According to the method for manufacturing a sintered oil-impregnated bearing according to the fourth invention, the Lewis acid catalytic reaction can be sufficiently suppressed.

According to the method for producing a sintered oil-impregnated bearing according to the present invention, the Lewis acid catalytic reaction can be suppressed, and the durability of the sintered oil-impregnated bearing can be improved.

It is a figure which shows the structure of the sintered oil-impregnated bearing which concerns on an Example and a comparative example. It is a table | surface which shows the result of a corrosion progress test. It is a graph which shows the result of the corrosion progress test shown in FIG.

Hereinafter, embodiments of the sliding member according to the present invention will be described.
The sliding member according to the present invention is a variety of sliding members in which a thermally and chemically stable fluorine-based lubricating oil is used as a lubricant, particularly under special environments such as high temperature, low temperature, low pressure, and a chemical solvent atmosphere. The present invention can be applied to various sliding members (particularly heat-resistant metal sliding members) that constitute machinery that operates in a short time. Specifically, the sliding member according to the present invention is a sliding machine component that is required to be slidable (sliding member) among sintered machine parts manufactured by powder metallurgy, such as a sintered oil-impregnated bearing. It can be applied to various mechanical parts such as bearing members such as bearings and fluid dynamic pressure bearings, gears, hydraulic parts, pumps, prime movers, transmissions, turbines, air compressors, machine tools, refrigerators and the like.
In particular, the sliding member according to the present invention is suitable for application to a sintered oil-impregnated bearing forming a small motor used in a high temperature environment. In the following description, an embodiment in which the sliding member according to the present invention is applied to a sliding member manufactured by powder metallurgy is described.

(Configuration of sliding member)
First, the configuration of the sliding member according to this embodiment will be described.
The sliding member according to the present embodiment forms a compact by compressing raw material powder containing metal powder in a mold, and sintering the compact under a predetermined condition to form a sintered compact. The sintered body is formed by sizing (recompressing), washing, etc. and then impregnating with a lubricant (fluorine-based lubricating oil). In particular, the sliding member according to the present embodiment includes nitride (metal nitride) formed by nitriding a metal constituting the sliding member in the composition.
In addition, when applying the sliding member which concerns on this invention to a sintered oil-impregnated bearing, it is preferable to set it as an inside diameter relief bearing. An inner diameter escape bearing is formed between each bearing portion and a bearing portion that is formed at each end in the axial direction and rotatably supports the rotating shaft, and the inner diameter is compared with the inner diameter of each bearing portion. This refers to a sintered oil-impregnated bearing in which a large relief portion is integrally formed (see Japanese Patent Laid-Open No. 2-8302).

As the raw material powder for the sliding member, for example, an iron-based material containing iron and a copper-based material containing bronze can be used as known materials for the sliding member. In particular, for sliding members constituting small motors used in the vicinity of engines of automobiles and ships, etc., a material having high wear resistance such as iron or a solid such as graphite so that it can sufficiently withstand tapping wear caused by vibration. The use of a material having characteristics as a lubricant is essential. In this embodiment, the raw material powder is a mixture of iron, bronze and graphite.
Here, in order to obtain a sufficient effect of suppressing the Lewis acid catalytic reaction described later, the inclusion of a metal to be subjected to nitriding in the sliding member (a metal to be a target for forming a nitride by nitriding) The amount is preferably set to 1% by weight or more, preferably 10% by weight or more. In this embodiment, the metal to be subjected to nitriding is iron. Therefore, the raw material powder of the sliding member contains iron powder in an amount of 1% by weight or more, preferably 10% by weight or more.
Further, when graphite is included in the raw material powder of the sliding member, if the graphite content is excessive, the strength of the sliding member may be reduced. Therefore, in order to enhance the lubrication effect while maintaining sufficient strength, the content of graphite in the sliding member is in the range of 0.1 to 10% by weight, preferably in the range of 0.5 to 5% by weight. It is preferable to set to.

And in the sliding member which concerns on this embodiment, the nitriding process is performed to the metal (this embodiment iron) contained in a sliding member. Specifically, nitriding is performed on the metal contained in the sliding member by performing nitriding on the sintered body after sizing. Here, when nitriding was performed at any stage before sintering (before the compact was sintered), it was formed on the sliding member due to the high temperature of sintering performed thereafter. There is a risk that the nitride will decompose again. Therefore, it is preferable that the timing of nitriding the metal contained in the sliding member is after sintering (after the green compact has been sintered).
The nitriding treatment is a treatment in which nitrogen (N) penetrates and diffuses on the surface of the object to be processed to form a nitride (nitriding layer) on the surface, and nitrogen is dissolved in the object to be processed. Yes. As nitriding treatment, carbonitriding treatment, gas nitriding (HNTG) treatment, plasma nitriding (ion nitriding) treatment, salt bath soft nitriding (HNTT) treatment, sulfur nitriding treatment, gas soft nitriding treatment, etc. can be applied. is there.

The carbonitriding process is a process in which nitriding is performed simultaneously with carburizing. Specifically, in the carbonitriding process, nitriding is performed in a gas obtained by adding 0.5 to 1.0% ammonia gas (NH3) to a carburizing gas. At this time, the processing temperature is set to 700 to 900 ° C.
The gas nitriding (HNTG) treatment is a treatment for forming a nitrided layer by infiltrating and diffusing nitrogen (N) in the nascent stage generated by the decomposition of the ammonia gas (NH3) into the object to be treated. Specifically, in the gas nitriding treatment, nitriding is performed in an ammonia decomposition gas. At this time, the processing temperature is set to 500 to 550 ° C., and the processing time is set to 50 to 150 hours.
The plasma nitriding (ion nitriding) process is a kind of gas nitriding process performed in a reduced pressure (0.5 to 10 Torr) vacuum. Specifically, in plasma nitriding, a voltage (about 500 V) is applied in a vacuum furnace in a mixed gas atmosphere of low-pressure nitrogen (N2) and hydrogen (H2), with the object to be processed as a cathode and the furnace wall as an anode. Nitriding is performed by causing glow discharge and causing ions generated thereby to collide with the surface of the object to be processed. At this time, the processing temperature is set to 450 to 570 ° C.

The salt bath soft nitriding (HNTT) treatment is a kind of gas nitriding treatment performed in a low concentration chlorinated gas. Specifically, in the salt bath soft nitriding treatment, potassium cyanide, potassium carbonate, or the like is put in a titanium crucible and melted, and nitriding is performed while air is blown into the titanium crucible. At this time, the processing temperature is set to around 570 ° C., and the processing time is set to about 30 to 240 minutes.
The nitrosulphurizing treatment is a treatment for simultaneously permeating and diffusing nitrogen and sulfur into the object to be treated. Specifically, in the nitrosulphurizing treatment, a sulfur compound is added into a salt bath soft nitriding bath, and a nitrogen compound and a sulfur compound are simultaneously generated in the object to be treated.
Gas soft nitriding is a process in which soft nitriding is performed with gas. Specifically, in the gas soft nitriding treatment, a gas obtained by mixing ammonia gas and carburizing gas is used as the main reaction gas. At this time, the processing temperature is set to around 570 ° C. In gas soft nitriding, nitride is formed in the object to be processed by the diffused nitrogen, and generally a compound layer (layer in which nitride is formed) is formed on the outermost surface of the sliding member. A diffusion layer (a layer in which nitrogen is dissolved) is formed inside the member. As the carburizing gas, RX gas, carbon dioxide gas or the like is used.
Here, the gas soft nitriding treatment is characterized in that there are few dimensional changes and distortions of the object to be treated. Therefore, in the present embodiment, the metal contained in the sliding member is nitrided by gas soft nitriding.
In the gas soft nitriding treatment according to the present embodiment, a mixed gas of nitrogen (N 2) + ammonia gas (NH 3) + carbon dioxide gas (CO 2) is used as the main reaction gas. In the gas soft nitriding treatment, if the treatment time is too short (less than 60 minutes), the atmosphere in the furnace may not be stable, resulting in a non-uniform product. On the other hand, the treatment time is too long (180 minutes). Exceeding the upper limit), the compound layer becomes too thick and the outermost surface may be peeled off. Therefore, the treatment time in the gas soft nitriding treatment is preferably set within a range of 60 to 180 minutes. Furthermore, the treatment temperature in the gas soft nitriding treatment is preferably set in the range of 550 to 600 ° C, and preferably in the range of 570 to 590 ° C.

As described above, in a sliding member used in a high temperature environment of about 120 ° C. or higher, when a general-purpose hydrocarbon-based lubricant is used as the lubricant, the lubricant by evaporation Insufficient oil (insufficient oil) or solidification of the lubricant due to oxidation / polymerization may occur, and seizure or abnormal wear may occur on the sliding surface of the sliding member. Therefore, in the present embodiment, perfluoropolyether, which is a lubricant excellent in stability (heat resistance) in a high temperature environment as a lubricant impregnated in the sliding member as compared with the general-purpose lubricant described above. Fluorine-based lubricating oil such as (PFPE) is used.
Examples of perfluoropolyethers include “Fonbrin M Series (trade name)” which is a linear fluoro oil manufactured by Solvay Specialty Polymer, and “Fonbrin Y Series (trade name)” which is a side chain fluoro oil. "Crytox (trade name)" which is a side chain type fluorine oil manufactured by DuPont, and "Demnam (trade name)" which is a linear type fluorine oil manufactured by Daikin Industries, Ltd.
“Fomblin Y Series” and “Crytox” have difficulties such as easy evaporation and low viscosity index, and “Demnam” has poor yield in the manufacturing process and unstable supply. There are difficulties. On the other hand, the “fomblin M series” is not only excellent in thermal stability, evaporation characteristics and chemical stability, but also has a high viscosity index and good yield in the production process and is relatively inexpensive. Therefore, it is preferable to use the “fomblin M series”.
In addition, in order to make up for the above-mentioned difficulties, there is also a product in which “Fomblin M Series” and side chain type fluorine oil are mixed and polytetrafluoroethylene: tetrafluoroethylene resin (PTFE) is added as a thickener. Exists. However, this product is more expensive than the “fomblin M series”, and it has been confirmed that the components of the “fomblin M series” react to cause corrosion on the sliding member. It can be said that it is scarce.

(Operation / effect of sliding member)
Next, the operation and effect of the sliding member according to this embodiment will be described.
As described above, in a sliding member used in a high-temperature environment, when a general-purpose hydrocarbon-based lubricant is used as a lubricant, a lubricant shortage due to evaporation (oil shortage) or oxidation / Solidification of the lubricant due to polymerization may occur, and seizure or abnormal wear may occur on the sliding surface of the sliding member.
In contrast, fluorine-based lubricants such as perfluoropolyethers are exposed to high temperature environments because they are superior in thermal stability, evaporation characteristics, chemical stability, etc. compared to the above-mentioned general-purpose lubricants. Even in such a case, evaporation and solidification (oxidation / polymerization) hardly occur, and seizure and abnormal wear on the sliding surface of the sliding member can be suppressed. And a fluorine-type lubricant coat | covers a sliding surface by couple | bonding firmly with the metal surface through the functional group couple | bonded with a metal, and improves the lubricity in the sliding surface of a sliding member.

On the other hand, a fluorine-based lubricant has a property of reacting with a Lewis acid catalyst and rapidly decomposing in a high temperature environment and evaporating while generating hydrogen fluoride. Therefore, when fluorine-based lubricating oil is used as a lubricant for a sliding member made of a material containing a Lewis acid catalytic substance such as iron or other metals or graphite, it is generated on the sliding surface of the sliding member. Due to the high heat, the fluorine-based lubricating oil reacts with a substance having Lewis acid catalytic ability and evaporates while generating hydrogen fluoride. As a result, the sliding surface of the sliding member rapidly corrodes and slides. Abnormal wear of the moving surface may occur.
In contrast, in the sliding member according to the present embodiment, the metal contained in the sliding member is subjected to nitriding treatment, whereby nitride is formed and nitrogen is contained in the composition of the sliding member. It is dissolved. Thereby, in a high temperature environment, the Lewis acid (metal ion) of the metal (metal complex) contained in the sliding member is converted into nitrogen atoms (nitrogen atoms forming a nitride, Alternatively, a solid solution of nitrogen atoms) is captured and inactivated, and as a result, the reaction between the fluorine-based lubricating oil and the metal (metal having Lewis acid catalytic ability) contained in the sliding member (hereinafter referred to as “ "Lewis acid catalyzed reaction"). Accordingly, decomposition of the fluorine-based lubricating oil is prevented, corrosion of the sliding surface of the sliding member due to generation of hydrogen fluoride can be suppressed, and occurrence of abnormal wear of the sliding surface can be suppressed. .

Here, in order to obtain a sufficient effect of suppressing the Lewis acid catalytic reaction, the content of a metal to be subjected to nitriding treatment in the sliding member (a metal to be a target for forming a nitride by nitriding treatment), Alternatively, the content of nitride formed in the sliding member by nitriding treatment is preferably set to 1% by weight or more, preferably 10% by weight or more.
Moreover, in this embodiment, since the raw material powder of a sliding member uses what mixed iron, bronze, and graphite, iron nitride is formed as a nitride in a sliding member. However, as a raw material powder for the sliding member, a powder containing one or more of iron, copper, aluminum, magnesium, calcium, niobium, barium and gallium may be used. The nitride to be used includes one or more of metal nitrides such as iron nitride, copper nitride, aluminum nitride, magnesium nitride, calcium nitride, niobium nitride, barium nitride, and gallium nitride.

As described above, the sliding member according to the present embodiment includes nitride (metal nitride) formed by nitriding the metal constituting the sliding member in the composition. As a result, the Lewis acid catalytic reaction can be suppressed in a high temperature environment, and the occurrence of abnormal wear on the sliding surface can be suppressed.
Further, in the sliding member according to the present embodiment, as a result of suppressing the Lewis acid catalytic reaction, a substance having high wear resistance such as iron (to the contrary, a high Lewis acid is used so that it can sufficiently withstand tapping wear due to vibration. Materials having catalytic ability) and substances having characteristics as solid lubricants such as graphite (on the other hand, substances having high Lewis acid catalytic ability) can be included in the material, and the wear resistance of the sliding member can be increased. It becomes possible to improve.
In particular, in the sliding member according to the present embodiment, since the metal contained in the sliding member is subjected to nitriding treatment by gas soft nitriding treatment, the sliding member can be formed by a simpler method. Become.
As described above, according to the sliding member according to the present embodiment, the Lewis acid catalytic reaction can be suppressed, and the durability of the sliding member can be improved.

Next, examples of the present invention will be described.
As examples of the present invention, sintered oil-impregnated bearings subjected to gas soft nitriding were prepared, and as comparative examples 1 and 2, sintered oil-impregnated bearings not subjected to gas soft nitriding were prepared. And about each sintered oil-impregnated bearing, the corrosion progress test was done.
FIG. 1 is a diagram showing a configuration of a sintered oil-impregnated bearing according to Examples and Comparative Examples. FIG. 2 is a table showing the results of the corrosion progress test. FIG. 3 is a graph showing the results of the corrosion progress test shown in FIG.
(Configuration of each oil-impregnated bearing)
As shown in FIG. 1, each sintered oil-impregnated bearing (Example, Comparative Examples 1 and 2) uses a mixed powder of iron, bronze, and graphite as a raw powder, and compresses the raw powder in a mold. It is formed by forming a compact and sintering the compact under a predetermined condition. Each sintered oil-impregnated bearing is formed by the powder metallurgy method described in the above embodiment.
At this time, the sintered oil-impregnated bearing according to the example is subjected to gas soft nitriding treatment on the sintered body, and thereafter impregnated with “Fomblin M30” (manufactured by Solvay Specialty Polymers Japan Co., Ltd.) as a lubricant. .
On the other hand, in the sintered oil-impregnated bearing according to Comparative Example 1, the sintered body is not subjected to gas nitriding treatment and is not impregnated with a lubricant.
Further, in the sintered oil-impregnated bearing according to Comparative Example 2, the sintered body was not subjected to gas nitriding treatment, and “fomblin M30” was impregnated as a lubricant.

(Conditions for gas soft nitriding)
In the gas soft nitriding treatment applied to the sintered oil-impregnated bearing according to the example, a mixed gas of nitrogen (N2) + ammonia gas (NH3) + carbon dioxide gas (CO2) is used as the main reaction gas. , The treatment was performed at a treatment temperature of 580 ° C. for 90 minutes.
(Test method)
Each sintered oil-impregnated bearing (Example, Comparative Examples 1 and 2) was left in a high-temperature environment of 200 ° C., and the change in the outer diameter was measured at regular intervals.
Here, in the case of sintered oil-impregnated bearings, when the fluorine-based lubricant is decomposed, the bearing material is corroded by the generated hydrofluoric acid, the outer diameter increases, and the original shape can be maintained as corrosion progresses. It disappears and eventually collapses. Accordingly, in a sintered oil-impregnated bearing, the degree of progress of corrosion can be confirmed by measuring a change in the outer diameter of the sintered oil-impregnated bearing.

(Test results)
As shown in FIGS. 2 and 3, in the sintered oil-impregnated bearing according to Comparative Example 1, an increase in the outer diameter of about 0.1% occurs when 3000 hours have passed, but collapse occurs. Not. This is presumably because the sintered oil-impregnated bearing according to Comparative Example 1 is not impregnated with fluorine-based lubricating oil, so that hydrofluoric acid is not generated due to decomposition of the fluorine-based lubricating oil.
In the sintered oil-impregnated bearing according to Comparative Example 2, the outer diameter dimension increased rapidly after 500 hours passed, and when the 1500 hour passed, an increase in outer diameter dimension of about 5% occurred, and 2000 hours passed. At that time, the test piece collapsed, and thereafter measurement was impossible.
In the sintered oil-impregnated bearing according to the example, an increase in the outer diameter of about 0.6% has occurred when 3000 hours have passed, but no collapse has occurred.
As described above, in the sintered oil-impregnated bearing according to the example, the decomposition of the fluorine-based lubricating oil is greatly suppressed as compared with the sintered oil-impregnated bearing according to Comparative Example 2 in which the gas soft nitriding treatment is not performed. I understand that. In particular, it can be seen that in the sintered oil-impregnated bearing according to the example, the decomposition of the fluorine-based lubricating oil is suppressed to the same extent as the sintered oil-impregnated bearing according to Comparative Example 1 that is not impregnated with the fluorine-based lubricating oil.

Claims (4)

A step of compression molding raw material powder to obtain a green compact;
Sintering the compact to obtain a sintered body;
A nitriding step for nitriding the sintered body;
Impregnating the sintered body that has undergone the nitriding step with a fluorine-based lubricating oil,
The raw material powder includes a powder of a predetermined metal to be subjected to the nitriding treatment,
Wherein the nitriding step, by the the nitriding process is performed on the predetermined metal, the production method of the oil-impregnated sintered bearing, wherein the nitride is formed. The method of manufacturing a sintered oil-impregnated bearing according to claim 1, wherein the nitriding treatment is a gas soft nitriding treatment. Wherein the raw material powder, as a powder of said predetermined metal, the production method of the oil-impregnated sintered bearing according to claim 1 or 2, characterized in that it contains the iron powder. The method for producing a sintered oil-impregnated bearing according to any one of claims 1 to 3, wherein a content of the powder of the predetermined metal in the raw material powder is 1% by weight or more.

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