JP6519955B2 - Iron-based sintered sliding member and method of manufacturing the same - Google Patents

Description

  The present invention is, for example, a valve guide or valve seat of an internal combustion engine, a vane or roller of a rotary compressor, a sliding component of a turbocharger, and sliding like a driving part or sliding part of a vehicle, machine tool, industrial machine, etc. The present invention relates to a sliding member suitable for use in sliding parts or the like in which a high surface pressure acts on the surface, and in particular, a green compact obtained by compacting a raw material powder containing Fe as a main component was sintered The present invention relates to an iron-based sintered sliding member.

  Sintered members manufactured by powder metallurgy can be formed into a near net shape and are applied to various machine parts because they are suitable for mass production. In addition, since it is possible to easily obtain a special metallographic structure which can not be obtained by ordinary molten materials, it is also applied to various sliding parts as described above. That is, in a sintered member manufactured by the powder metallurgy method, a powder of a solid lubricant such as graphite or manganese sulfide is added to the raw material powder, and the solid lubricant is sintered by sintering under the condition that the solid lubricant remains. Can be dispersed in the metallographic structure, and thus, they are applied to various sliding parts (Patent Documents 1 to 3 and the like).

Unexamined-Japanese-Patent No. 04-157140 JP, 2006-052468, A JP, 2009-155696, A

  Heretofore, in a sintered sliding member, a solid lubricant such as graphite or manganese sulfide is applied in the form of powder and is left without being solid-solved during sintering. For this reason, the solid lubricant is localized in the pores and in the powder grain boundaries in the metallographic structure. Such solid lubricants are not bonded to the matrix in the pores and at the powder grain boundaries, and therefore, they are easily detached from the matrix at the time of sliding.

  When graphite is used as a solid lubricant, it is necessary not to dissolve graphite in the matrix at the time of sintering and to leave it as graphite liberated after sintering. For this purpose, the sintering temperature should be lower than in the case of general iron-based sintered alloys. For this reason, bonding between particles due to diffusion of the raw material powders is weakened, and the base strength tends to be low.

  On the other hand, solid lubricants such as manganese sulfide do not easily form a solid solution in the matrix at the time of sintering, and therefore can be sintered at a sintering temperature equivalent to that of a general iron-based sintered alloy. However, solid lubricant added in the form of powder exists between the raw material powders. For this reason, the diffusion of the raw material powders is inhibited, and the base strength becomes lower as compared with the case where the solid lubricant is not added. Then, the strength of the iron-based sintered member is reduced due to the reduction in the strength of the base, and the durability of the base at the time of sliding is reduced, and the abrasion tends to progress.

  Under such circumstances, according to the present invention, the solid lubricant is uniformly dispersed not only in the pores and the powder grain boundaries but also in the powder grains, and is firmly fixed to the matrix, and has excellent sliding characteristics. An object of the present invention is to provide an iron-based sintered sliding member excellent in mechanical strength.

In the first iron-based sintered sliding member of the present invention, the total composition is, by mass ratio, S: 0.2 to 3.24%, Cu: 3 to 10%, C: 0.2 to 2%, Remainder: It has a metal structure consisting of Fe and unavoidable impurities, and a matrix on which sulfide particles are precipitated and dispersed in grain boundaries and grains, and pores, C is given to the matrix, and the matrix And the mixed structure of any one of ferrite, pearlite and bainite, or a structure in which the copper phase is dispersed in any one of the ferrite, perlite and bainite, or a mixed structure thereof, The sulfide particles are dispersed at a ratio of 0.8 to 15.0% by volume with respect to the matrix , and in the sulfide particles, the area of the sulfide particles having a maximum equivalent diameter of 10 μm or more at a circle equivalent diameter is sulfide Whole particle Characterized in that account for more than 30% of the area.

In the second iron-based sintered sliding member of the present invention, the total composition is S: 0.2 to 3.24%, Cu: 3 to 10%, C: 0.2 to 3 in mass ratio. %, B: 0.03 to 0.62%, 7 parts: a metal structure consisting of Fe and incidental impurities, and a matrix on which sulfide particles are precipitated and dispersed in grain boundaries and grains, and pores And part or all of the C is dispersed as graphite in the pores, and the matrix is any one of ferrite, pearlite and bainite, or a mixed structure thereof, or any of the ferrite, pearlite and bainite The sulfide particles are dispersed in a ratio of 0.8 to 15.0% by volume with respect to the matrix, and the sulfide particles are dispersed in a structure in which a copper phase is dispersed in one or a mixture of these structures. In particles, equivalent circle diameter The area of the sulfide particles having a maximum particle size of 10 μm or more occupies 30% or more of the area of the entire sulfide particles.

First the second iron-based sintered sliding member, Mn in the impurity: a preferred embodiment in that it contains 0.02 to 1.20 wt%. Furthermore, it is preferable to contain 10% by mass or less of at least one of Ni and Mo.

The method for producing an iron-based sintered sliding member according to the present invention comprises, as an iron powder, at least one metal sulfide powder selected from iron sulfide powder, copper sulfide powder, molybdenum disulfide powder, and nickel sulfide powder. It is added so that the amount of S of powder becomes 0.2-3.24 mass%, copper powder or copper alloy powder is added so that the amount of Cu in raw material powder becomes 3-10 mass%, and graphite powder is added The raw material powder mixed and added at 0.2 to 2% by mass to the raw material powder is compacted in a die, and the obtained molded body is sintered at 1090 to 1300 ° C. in a non-oxidizing atmosphere. Grains of a matrix in which the copper phase is dispersed in any one of ferrite, pearlite and bainite, or a mixed structure thereof, or any one of the ferrite, pearlite and bainite, or a mixed structure thereof And precipitating sulfide particles within the crystal grains, giving the C in the base, in the sulfide particles, maximum particle size equivalent circle diameter is the area of the above sulfide particles 10 [mu] m, the total sulfide particles It is characterized in that it occupies 30% or more of the area .

Another method of manufacturing an iron-based sintered sliding member according to the present invention comprises adding iron powder, at least one metal sulfide powder of iron sulfide powder, copper sulfide powder, molybdenum disulfide powder, and nickel sulfide powder to iron powder. Add the copper powder or copper alloy powder such that the amount of S in the raw material powder is 0.2 to 3.24% by mass, and add the copper powder or the copper alloy powder so that the amount of Cu in the raw material powder is 3 to 10% by mass 0.2 to 2% by mass of the powder relative to the raw material powder, at least one of oxalic acid, borooxide, boron nitride, boron halide, boron sulfide and boron hydride powder 0.1 The ferrite is obtained by sintering at 1090 ° C. to 1300 ° C. in a non-oxidizing atmosphere, using the raw material powder to which 2.0 mass% is added and mixed, and compacting in a die and obtaining the formed body obtained. Perlite and / or bainite, or one of these Sulfide particles are precipitated in grain boundaries and grains of a mixed structure of the above, or any one of the above ferrite, pearlite and bainite, or a mixed phase of the copper phase in these mixed structures, and a part of the above C Or, the whole of the pores is dispersed as graphite, and in the above-mentioned sulfide particles, the area of the sulfide particles having a circle equivalent diameter and the maximum particle diameter of 10 μm or more occupies 30% or more of the entire area of the sulfide particles. I assume.

In the method of manufacturing an iron-based sintered sliding member described above, it is preferable to add copper powder or copper alloy powder to the raw material powder. Also, instead of using the iron powder, an iron alloy powder containing at least one of Ni and Mo is used, and the amount of Ni and Mo of the raw material powder is 10% by mass or less, and nickel powder is further added to the raw material powder. While adding, it is set as a preferable aspect that the amount of Ni of a raw material powder is 10 mass% or less .

  In the iron-based sintered sliding member of the present invention, metal sulfide particles mainly composed of iron sulfide are precipitated from the iron base and dispersed in the iron base, so that the sliding property is firmly fixed to the base, Excellent in mechanical strength.

It is a drawing substitute photograph (mirror polishing) which shows an example of the metal structure of the iron-based sintered sliding member of the present invention. It is a drawing substitute photograph (3%-nital corrosion) which shows an example of the metal structure of the iron-based sintered sliding member of the present invention.

  Hereinafter, the metal structure of the iron-based sintered sliding member of the present invention and the ground of numerical limitation will be described together with the operation of the present invention. The iron-based sintered sliding member of the present invention contains Fe as the main component. Here, the main component means a component that occupies the majority in the sintered sliding member, and in the present invention, the amount of Fe in the entire composition is 50% by mass or more, preferably 60% by mass or more. The metallographic structure is composed of an iron matrix (iron alloy matrix) in which sulfide particles mainly composed of Fe are dispersed and pores. The iron base is formed of iron powder and / or iron alloy powder. The pores are generated due to the powder metallurgy method, and the voids between the powder when the raw material powder is compacted remain in the iron base formed by the bonding of the raw material powder.

  In general, iron powder contains about 0.02 to 1.2% by mass of Mn due to the production method, so the iron base contains a trace amount of Mn as an unavoidable impurity. Therefore, by giving S to iron powder, sulfide particles such as manganese sulfide can be deposited in the base as a solid lubricant. Here, since manganese sulfide precipitates finely in the matrix, it is effective for improving the machinability, but it is too fine to improve the sliding characteristics. For this reason, in the present invention, not only the amount of S that reacts with Mn contained in a small amount in the matrix but also S is added, and this S is combined with Fe as the main component to form iron sulfide. .

  In general, the easiness of formation of sulfide is higher as the difference in electronegativity to S is larger. The electronegativity value (Poring electronegativity) is S: 2.58, Mn: 1.55, Cr: 1.66, Fe: 1.83, Cu: 1.90, Ni: 1.91 And Mo: 2.16, sulfides are easily formed in the order of Mn> Cr> Fe> Cu> Ni> Mo. For this reason, when S is added in an amount exceeding the amount of S capable of forming MnS by combining with all the Mn contained in iron powder, a reaction with Fe as the main component occurs in addition to the reaction with a slight amount of Mn. Not only manganese sulfide but also iron sulfide precipitates. Therefore, the sulfides deposited in the matrix are mainly composed of iron sulfide generated by Fe as the main component, and partly converted to manganese sulfide generated by Mn as the unavoidable impurity.

  Iron sulfide is a sulfide particle of a size suitable for improving sliding characteristics as a solid lubricant, and is formed in combination with Fe which is the main component of the matrix, so that it uniformly precipitates in the matrix including the inside of powder particles. It can be dispersed.

  As described above, in the present invention, the amount of S to be bound to Mn contained in the matrix and S are further given to be combined with Fe which is the main component of the matrix to precipitate sulfide. In order to obtain the effect of the sliding property improvement by the sulfide particles, the amount of the sulfide particles deposited and dispersed in the matrix needs to be 0.8% by volume. On the other hand, when the dispersion amount of sulfide particles is increased, the sliding property is improved, but the mechanical strength is lowered because the amount of iron base is reduced by the dispersion of the sulfide in the iron base. For this reason, when the amount of sulfide particles exceeds 15% by volume, the amount of sulfide with respect to the matrix becomes excessive, and the mechanical strength of the iron-based sintered sliding member significantly decreases. From this, the amount of sulfide particles in the matrix is 0.8 to 15% by volume with respect to the matrix.

  Here, Cu is less likely to form a sulfide at room temperature compared to Fe, but has a smaller standard free energy of formation at a high temperature than Fe at a high temperature, and tends to form a sulfide. In addition, since Cu has a small solid solubility limit in α-Fe and does not form a compound, Cu dissolved in γ-Fe at high temperature has a characteristic that Cu separates out into α-Fe in the cooling process. have. Therefore, Cu once solid-dissolved in the cooling process during sintering precipitates uniformly from the Fe matrix. At this time, Cu and sulfide form a metal sulfide (copper sulfide, iron sulfide and a composite sulfide of iron and copper) with Cu precipitated from this matrix as a core and sulfide particles (iron sulfide) around it Has an action of promoting the precipitation of Also, Cu diffuses into the iron matrix to strengthen it, and when C is contained in the iron matrix, the hardenability of the iron matrix is improved to refine the pearlite structure, thereby further strengthening the iron matrix Do. In the present invention, in order to actively utilize the action of these Cu, it is an essential element.

  Since Cu promotes the formation of sulfides, when the amount of S is larger than the amount of Cu, it precipitates in the form of copper sulfide or a complex sulfide of iron and copper in the iron base, but Cu When the amount of S is small compared to the amount, it precipitates and disperses in the iron base as a copper phase.

  S has a low compounding power at normal temperature, but is highly reactive at high temperature, and combines not only with metals but also with non-metallic elements such as H, O, and C. By the way, in production of a sintered member, generally, a forming lubricant is added to the raw material powder, and a so-called dewaxing step is performed in which the forming lubricant is volatilized and removed in the temperature raising process of the sintering step. Here, when S is applied in the form of a sulfur powder, the forming lubricant decomposes and combines with the components (mainly H, O, C) generated to be desorbed, so S necessary for the formation of iron sulfide described above It is difficult to give stable. For this reason, it is preferable to apply S in the form of metal sulfide powder such as iron sulfide powder and metal sulfide powder having a lower electronegativity than Fe, that is, copper sulfide powder, nickel sulfide powder, molybdenum disulfide powder and the like. . When S is applied in the form of these metal sulfide powders, it is formed in the form of metal sulfides in the temperature range (about 200 to 400 ° C.) where the dewaxing step is performed, so the formed lubricant is decomposed and produced Since it does not combine with any of the components, and the release of S does not occur, it is possible to stably provide S necessary for the formation of the above-mentioned iron sulfide.

  When iron sulfide powder is used as the metal sulfide, a eutectic liquid phase of Fe-S is generated when the temperature exceeds 988 ° C in the temperature rising process of the sintering process, resulting in liquid phase sintering and the growth of the neck between powder particles Promote. Further, since S diffuses uniformly from the eutectic liquid phase into the iron matrix, sulfide particles can be uniformly deposited and dispersed from the matrix.

  When copper sulfide powder is used as the metal sulfide, Cu generated by decomposition of the copper sulfide powder generates a Cu liquid phase, wets and covers the iron powder, and diffuses into the iron powder.

  When nickel sulfide powder or molybdenum disulfide powder is used as the metal sulfide powder, most of the metal components (Ni, Mo) generated by the decomposition of the metal sulfide powder are diffused to the iron base to form a solid solution. Contribute to the strengthening of the base. In addition, when used in combination with C, it contributes to the improvement of the hardenability of the iron base, refines the pearlite structure to increase the strength, and obtains high strength bainite or martensite at a normal cooling rate during sintering. Can. There are also cases where undecomposed nickel sulfide and molybdenum disulfide remain in a very small part, and nickel sulfide and molybdenum disulfide are precipitated, but also in this case, the added nickel sulfide powder and molybdenum disulfide Most of the powder is decomposed to contribute to the formation of iron sulfide, and nickel sulfide and molybdenum disulfide do not cause any problems because they have lubricity.

  The above-mentioned sulfide particles combine and precipitate Mn and Fe in the matrix with S, and thus precipitate out of the matrix and disperse uniformly. Therefore, the sulfide is firmly fixed to the base, and it becomes difficult to drop out. In addition, since sulfide is generated by precipitation from iron base, the diffusion of the raw material powders during sintering is not inhibited and the sintering is promoted by the Fe-S liquid phase and the Cu liquid phase. The diffusion is well performed, the strength of the iron base is improved, and the wear resistance of the iron base is improved.

  The sulfide deposited in the matrix preferably has a predetermined size, rather than a fine size, in order to exert a solid lubricating action in sliding with the other member. According to the study of the present inventors, it has been found that a sulfide particle having a maximum particle size of less than 10 μm can not sufficiently obtain a solid lubricating action. From this viewpoint, it is preferable that the area of the sulfide particles having a maximum particle size of 10 μm or more occupies 30% or more of the area of the entire sulfide particles in order to obtain a sufficient solid lubricating action.

  Cu may be applied in the form of copper sulfide powder as described above, but may be applied in the form of copper powder or copper alloy powder. That is, when iron sulfide powder, nickel sulfide powder and molybdenum disulfide powder are used as metal sulfide powder, Cu may be applied in the form of copper powder or copper alloy powder, and addition is made when copper sulfide powder is used. Alternatively, copper powder or copper alloy powder may be used. As described above, Cu has the effect of promoting the precipitation of sulfide particles, and in the case where the copper phase precipitates and disperses in the iron matrix, the soft copper phase acts to improve the compatibility with the other member. Have. However, when added in a large amount, the amount of the precipitated copper phase becomes excessive, and the strength of the iron-based sintered member decreases significantly. Therefore, the amount of Cu is 10% by mass or less in the entire composition.

  In addition, not only the form of metal sulfide powder but also simple powder (nickel powder and molybdenum powder) or alloy powder with other components (Fe-Mo alloy powder, Fe-Ni alloy powder, Fe-Ni) as Ni or Mo -It can add in the form of Mo alloy powder, Cu-Ni alloy powder, Cu-Mo alloy powder etc.). That is, when iron sulfide powder and copper sulfide powder are used as metal sulfide powder, at least one of Ni and Mo may be applied in the form of a simple powder or an alloy powder with other components, When using a nickel powder and a molybdenum disulfide powder, it is possible to additionally use a simple powder or an alloy powder with other components. As described above, Ni and Mo form a solid solution in the iron matrix to contribute to the strengthening of the iron matrix, and when used in combination with C, contribute to the improvement of the hardenability of the iron matrix and to make pearlite fine and strength High strength bainite and martensite can be obtained at a normal cooling rate during sintering. However, these materials are expensive, and when added as a single powder, when the amount of components is excessive, the undiffused part remains in the iron base and a part where sulfide precipitates is generated. . For this reason, it is preferable to make each of Ni and Mo 10% by mass or less in the entire composition.

  Generally, iron-based sintered alloys use C as a solid solution in iron-based to strengthen the iron-based, and C is added similarly in the iron-based sintered sliding member of the present invention. Can. When C is applied in the form of an alloy powder, the hardness of the alloy powder increases and the compressibility of the raw material powder decreases, so C is applied in the form of a graphite powder. When the addition amount of C is less than 0.2% by mass, the proportion of ferrite having low strength becomes excessive, and the addition effect becomes poor. On the other hand, when the addition amount is excessive, brittle cementite precipitates in the form of a network. Therefore, in the present invention, it is preferable to contain 0.2 to 2.0% by mass of C, and the whole amount of C is precipitated as a solid solution or metal carbide in the matrix.

  If C is not dissolved in the matrix and remains in the pores in the form of graphite, this graphite functions as a solid lubricant, and effects such as reduction of the friction coefficient and suppression of wear are obtained, and the sliding characteristics are It can be improved. Therefore, in the present invention, it is preferable that 0.2 to 3.0% by mass of C is contained, and part or all of C is dispersed in the pores as graphite. In this case, C is added in the form of graphite powder. When the addition amount of C is less than 0.2% by mass, the amount of dispersed graphite becomes scarce, and the effect of improving the sliding characteristics becomes insufficient. On the other hand, since the shape of the added graphite powder is maintained for the graphite remaining in the pores, the spheroidization of the pores is inhibited by the graphite, and the strength tends to be reduced. For this reason, the upper limit of the addition amount of C is 3.0 mass%.

  In order to cause C to remain in the pores in the form of graphite, 0.2 to 3.0% by mass of the graphite powder, boric acid, boric oxide, boron nitride, boron halide, boron sulfide, and the like in the raw material powder And 0.1 to 2.0% by mass of one or more powders of hydrides of boron and boron. These boron-containing powders have a low melting point and generate a liquid phase of boron oxide at about 500.degree. For this reason, in the process of raising the temperature of the green compact containing the graphite powder and the boron-containing powder in the sintering step, the boron-containing powder is melted and the surface of the graphite powder is wet and covered by the generated boron oxide liquid phase. For this reason, the diffusion of C of the graphite powder into the Fe matrix starting from about 800 ° C. when the temperature is further raised is prevented, and the graphite powder can be made to remain and be dispersed in the pores. The boron-containing powder is preferably used in an amount sufficient to cover the graphite powder, and even if added in excess, boron oxide remains in the matrix to cause a reduction in strength. It is good to set it as 2.0 mass%.

  The iron-based metallographic structure is a ferrite structure when C is not given. In addition, in the case of giving C, when C is left in the pores in the state of graphite, the metal structure of the iron base becomes ferrite. And, when a part or all of C is diffused to the iron base, the metal structure of the iron base becomes a mixed structure or pearlite of ferrite and perlite. When at least one of Cu, Ni, and Mo is used together with C, the iron-based metallographic structure is a mixed structure of ferrite and pearlite, a mixed structure of ferrite and bainite, a mixed structure of ferrite, pearlite and bainite, and pearlite It becomes a mixed structure of bainite, perlite, or metal structure of bainite. Furthermore, in the case where the amount of Cu is larger than the amount of S, a metallographic structure in which a copper phase is dispersed in the above-described iron-based metallographic structure is obtained.

  1 and 2 show an example of the metal structure of the iron-based sintered sliding member of the present invention, wherein 3% by mass of iron sulfide powder, 6% by mass of copper powder and 1% by mass of graphite powder are added to iron powder. Metal of iron-based sintered sliding member formed of S: 1.09% by mass, Cu: 6% by mass, C: 1% by mass and the balance being Fe and unavoidable impurities, using the added raw material powder It is an organization. FIG. 1 is a mirror picture taken at 100 ×, and FIG. 2 is a metallographic picture taken at 200 × of the same sample (3% —nital corrosion). From FIG. 1, the iron base is a white part, and the sulfide particles are a gray part. The pores are black parts. It can be seen from FIG. 1 that the sulfide particles (grey) are precipitated and dispersed in the iron base (white), and the adhesion to the base is good. The pores (black) have a relatively rounded shape, which is considered to be due to the generation of the Fe-S liquid phase and the Cu liquid phase. Further, FIG. 2 shows that the iron base has a mixed structure of fine pearlite and ferrite, and sulfide particles are precipitated and dispersed in this mixed structure. In this sample, the amount of sulfide is about 4.5% by volume with respect to the base excluding pores, and the amount of sulfide particles having a maximum particle diameter of 10 μm or more with respect to the amount of all sulfide particles is 45% It is an extent.

  The raw material powder is slidably fitted with a mold having a mold hole for molding the outer peripheral shape of the product and a mold hole of the mold as conventionally performed, and the lower end of the product is molded. The raw powder is compressed by the upper punch which is filled in the cavity formed by the punch and the core rod which forms the inner peripheral shape or the hollow portion of the product in some cases, and the upper end surface of the product and the lower punch. After being molded, it is molded into a molded body by a method of removing it from the mold hole of the mold (pressing method).

  The obtained molded body is heated in a sintering furnace to perform sintering. The heating and holding temperature at this time, that is, the sintering temperature has an important influence on the progress of sintering and the formation of sulfides. Here, since the melting point of Cu is 1084.5 ° C., the sintering temperature is made 1090 ° C. or more in order to generate a Cu liquid phase sufficiently. On the other hand, when the sintering temperature is higher than 1300 ° C., the amount of liquid phase generation is excessive, and it becomes easy to cause mold deformation. The sintering atmosphere may be any non-oxidizing atmosphere, but since S is likely to react with H and O as described above, it is preferable to use an atmosphere having a low dew point.

[First reference example ]
Iron sulfide powder (S content: 36.47 mass%) and copper powder are prepared for iron powder containing 0.03 mass% of Mn, and the compounding ratio (ratio) of iron sulfide powder is added as a ratio shown in Table 1 The mixture was mixed to obtain a raw material powder. Then, the raw material powder was molded at a molding pressure of 600 MPa, and a ring-shaped green compact having an outer diameter of 25.6 mm, an inner diameter of 20 mm, and a height of 15 mm was produced. Subsequently, it sintered at 1150 degreeC in non-oxidizing gas atmosphere, and produced the sintered member of sample number 01-15. The overall compositions of these samples are shown together in Table 1.

The volume percent of sulfide in the metallographic structure is equal to the area fraction of sulfide in the metallographic cross section. Therefore, in the first reference example , the area% of the sulfide in the cross section of the metallographic structure was evaluated in the evaluation of the volume% of the metal sulfide. That is, the obtained sample is cut, the cross section is mirror-polished, cross-sectional observation is performed, and the area of the base portion excluding pores and the area of sulfide are calculated using image analysis software (WinROOF manufactured by Mitani Corporation). The area% of total sulfide occupied in the base was measured to determine the area of sulfide having a maximum particle diameter of 10 μm or more, and the ratio to the area of total sulfide was determined. In addition, the maximum particle diameter of each sulfide particle | grains calculated | required the area of each particle | grain, and measured it by the equivalent circle diameter converted into the diameter of the circle | round | yen equal to this area. When sulfide particles were bonded, the bonded sulfide was regarded as one sulfide, and the equivalent circle diameter was determined from the area of this sulfide. The results are shown in Table 2.

With respect to a ring-shaped sintered member, using a heat-treated material of SCM 435H specified in JIS as a mating material, a ring-on-disk friction and wear tester under a load of circumferential speed 400 rpm and 5 kgf / cm ² A sliding test was conducted without lubrication, and the coefficient of friction was measured. Furthermore, as a mechanical strength, a radial crushing test was performed on the ring-shaped sintered member to measure the radial crushing strength. These results are also shown in Table 2.

  In addition, in the following evaluation, it judged as the sample which becomes a friction coefficient of 0.7 or less, and radial crushing strength 350 Mpa or more as a pass.

  As can be seen from Tables 1 and 2, the amount of S in the overall composition increases as the amount of addition of the iron sulfide powder increases, and the amount of precipitated sulfide increases. The proportion of sulfides having a maximum particle size of 10 μm or more increases as the amount of S increases. By such precipitation of sulfides, the coefficient of friction decreases as the amount of S in the overall composition increases. Since the addition of the iron sulfide powder generates a liquid phase at the time of sintering to promote sintering, the radial crushing strength increases. However, since the strength of the base decreases as the amount of sulfide deposited in the base increases, the amount of deposited sulfide is large in the region where the amount of S is large, so the radial crushing strength decreases.

  Here, in the sample of sample No. 02 in which the amount of S in the entire composition is less than 0.2 mass%, the amount of precipitated sulfide falls below 0.8 area% because the amount of S is scarce, and the improvement effect of the friction coefficient is poor. On the other hand, in the sample of sample No. 03 in which the amount of S in the entire composition is 0.2 mass%, the ratio of the amount of sulfide precipitation is 0.8 area% and the maximum particle diameter is 10 μm or more is It is 30 area%, and the coefficient of friction is improved to 0.7 or less. On the other hand, when the amount of S in the whole composition exceeds 3.24% by mass, the reduction in radial crushing strength becomes remarkable, and the radial crushing strength falls below 350 MPa. From the above, it was confirmed that a good coefficient of friction and strength can be obtained when the amount of S in the overall composition is in the range of 0.2 to 3.24 mass%.

[Second reference example ]
Iron sulfide powder (S content: 36.47 mass%) and copper powder are prepared for iron powder containing 0.8% by mass of Mn, and the compounding ratio (ratio) of iron sulfide powder is added as a ratio shown in Table 3 The mixture was mixed to obtain a raw material powder. Then, in the same manner as in the first reference example , molding and sintering were performed to prepare sintered members of sample numbers 16 to 30. The overall compositions of these samples are shown together in Table 3. With respect to these samples, in the same manner as in the first reference example , the ratio of the area of all sulfides and the area of sulfides having a maximum particle diameter of 10 μm or more to the area of all sulfides is measured. The strength was measured. The results are shown in Table 4.

The second reference example is an example where iron powder (Mn amount: 0.03 mass%) different from the iron powder used in the first reference example is used but the same tendency as the first reference example is used. It shows. That is, from Table 3 and Table 4, as the addition amount of iron sulfide powder increases, the amount of S in the whole composition increases and the amount of precipitation of sulfide increases. The proportion of sulfides having a maximum particle size of 10 μm or more increases as the amount of S increases. By such precipitation of sulfides, the coefficient of friction decreases as the amount of S in the overall composition increases. Since the addition of iron sulfide powder generates a liquid phase at the time of sintering to promote sintering, the radial crushing strength increases, but if the amount of sulfides deposited in the matrix increases, the matrix strength decreases. In the region where the amount of S is large, the precipitation amount of sulfide increases, the strength decreases, and the crushing strength decreases.

Further, as in the first reference example , in the sample of sample No. 17 in which the amount of S in the overall composition is less than 0.2% by mass, the amount of precipitated sulfide falls below 0.8 area% because the amount of S is scarce. , The improvement effect of the coefficient of friction is poor. On the other hand, in the sample of sample No. 18 in which the amount of S in the entire composition is 0.2 mass%, the amount of precipitation of sulfide is 0.8 area%, and the sulfide having a maximum particle diameter of 10 μm or more is occupied The percentage is 30%, and the coefficient of friction is improved to 0.7 or less. On the other hand, when the amount of S in the whole composition exceeds 3.24% by mass, the reduction in radial crushing strength becomes remarkable, and the radial crushing strength falls below 350 MPa. From the above, it was confirmed that a good coefficient of friction and strength can be obtained when the amount of S in the overall composition is in the range of 0.2 to 3.24 mass%.

[Third reference example ]
Iron sulfide powder (S content: 36.47 mass%) and copper powder are prepared for iron powder containing 0.03 mass% of Mn, and the compounding ratio (ratio) of copper powder is added as a ratio shown in Table 5 The mixture was mixed to obtain a raw material powder. Then, in the same manner as in the first reference example , molding and sintering were performed to prepare sintered members of sample numbers 31 to 40. The overall compositions of these samples are shown together in Table 5. With respect to these samples, in the same manner as in the first reference example , the ratio of the area of all sulfides and the area of sulfides having a maximum particle diameter of 10 μm or more to the area of all sulfides is measured. The strength was measured. These results are shown in Table 6. Tables 5 and 6 also show the results of the sample of sample No. 06 of the first reference example .

  From Tables 5 and 6, when the amount of added copper powder is changed to change the amount of Cu in the entire composition, precipitation of sulfide particles is promoted as the amount of Cu increases, and the amount of sulfide increases. The amount of sulfide particles having a maximum particle size of more than 10 μm is increasing, which results in a decrease in the friction coefficient. With respect to the radial crushing strength, as the amount of Cu increases, the amount of liquid phase generation increases to densify, and the action of matrix strengthening increases the amount of Cu up to 7% by mass. However, when the amount of Cu exceeds 7% by mass, the amount of free copper phase dispersed in the matrix increases, and the radial crushing strength decreases. And, when the amount of Cu exceeds 10% by mass, the reduction of the radial crushing strength becomes remarkable, and the radial crushing strength falls below 350 MPa. As described above, it has been confirmed that the addition of Cu accelerates the precipitation of sulfide particles to reduce the friction coefficient. However, when the amount of Cu exceeds 10% by mass, the decrease in strength becomes remarkable, so it was confirmed that when Cu is added, the upper limit should be 10% by mass.

[4th reference example ]
A copper sulfide powder (S content: 33.54 mass%) and a copper powder are prepared for an iron powder containing 0.03% by mass of Mn, and the compounding ratio (ratio) of the copper sulfide powder is shown in Table 7 It was added and mixed to obtain a raw material powder. Then, in the same manner as in the first reference example , molding and sintering were performed to prepare sintered members of sample numbers 41 to 54. The overall compositions of these samples are shown together in Table 7. With respect to these samples, in the same manner as in the first reference example , the ratio of the area of all sulfides and the area of sulfides having a maximum particle diameter of 10 μm or more to the area of all sulfides is measured. The strength was measured. The results are shown in Table 8.

The fourth reference example is an example where S is provided by copper sulfide powder instead of iron sulfide powder, but shows the same tendency as the first reference example . That is, from Table 7 and Table 8, as the addition amount of the copper sulfide powder increases, the amount of S in the whole composition increases and the amount of precipitation of sulfide increases. The proportion of sulfides having a maximum particle size of 10 μm or more increases as the amount of S increases. By such precipitation of sulfides, the coefficient of friction decreases as the amount of S in the overall composition increases. Since the addition of copper sulfide powder generates a liquid phase at the time of sintering to promote sintering, the radial crushing strength increases, but if the amount of sulfides deposited in the matrix increases, the matrix strength decreases. In the region where the amount of S is large, the amount of precipitation of sulfide increases, the strength decreases, and the radial crushing strength decreases.

Further, as in the first reference example , in the sample of sample No. 42 in which the amount of S in the overall composition is less than 0.2% by mass, the amount of precipitated sulfide is less than 0.8 area% because the amount of S is scarce. , The improvement effect of the coefficient of friction is poor. On the other hand, in the sample of sample No. 18 in which the amount of S in the entire composition is 3.24% by mass, the precipitation amount of sulfides is 15 area%, and the ratio of sulfides having a maximum particle diameter of 10 μm or more is 60% The coefficient of friction is improved to 0.6 or less. On the other hand, when the amount of S in the overall composition exceeds 3.24% by mass, the amount of sulfide occupied in the base exceeds 15% by area, and as a result, the reduction in radial crushing strength significantly falls below 350 MPa.

When S is provided by copper sulfide powder instead of iron sulfide powder, Cu formed by decomposition of copper sulfide powder has a function of promoting precipitation of sulfide particles, and when S is supplied by iron sulfide powder ( The amount of precipitation is larger than in the first embodiment, and the friction coefficient is smaller. In addition, since this Cu acts on the densification (promotion of sintering) by the liquid phase generation and the reinforcement of the matrix, the radial crushing strength is also higher than in the case of supplying S with iron sulfide powder (first reference example ) It is a high value.

First Embodiment
Iron sulfide powder (S content: 36.47 mass%), copper powder and graphite powder are prepared for iron powder containing 0.03% by mass of Mn, and the compounding ratio (ratio) of iron sulfide powder is shown in Table 9 It was added as a proportion and mixed to obtain a raw material powder. Then, in the same manner as in the first reference example , molding and sintering were performed to prepare sintered members of sample numbers 55 to 64. The overall compositions of these samples are shown together in Table 9. With respect to these samples, in the same manner as in the first reference example , the ratio of the area of all sulfides and the area of sulfides having a maximum particle diameter of 10 μm or more to the area of all sulfides is measured. The strength was measured. These results are shown in Table 10. Tables 9 and 10 also show the results of the sample of sample No. 06 of the first reference example .

The first embodiment is an example in which C is provided to the iron-based sintered sliding member, and the total amount of C is provided as a solid solution in the iron base. The sample of sample No. 06 of the first reference example does not contain C, and the iron-based metal structure is a ferrite structure of low strength. Here, when graphite powder is added to impart C, the pearlite phase which is harder than the ferrite phase in the metal structure of the iron matrix disperses in the ferrite structure, and the radial crushing strength increases and the friction coefficient becomes descend. Then, as the amount of C increases, the amount of the pearlite phase increases and the ferrite phase decreases, and when the amount of C is about 1% by mass, the metal structure of the iron base becomes the entire pearlite structure. For this reason, while C amount increases to 1 mass%, while a radial crushing strength increases with the increase in C amount, a friction coefficient falls. On the other hand, when the amount of C exceeds 1% by mass, high and brittle cementite precipitates in the pearlite structure, and the radial crushing strength decreases and the friction coefficient increases. When the amount of C exceeds 2% by mass, the amount of cementite precipitated in the pearlite structure becomes excessive and the radial crushing strength significantly decreases, and the radial crushing strength becomes a value below 350 MPa.

  As described above, the strength can be improved by adding C and causing solid solution in the iron matrix, but if the amount of C exceeds 2% by mass, the upper limit is 2% by mass or less because the friction coefficient increases with the decrease in strength. It was confirmed that it is preferable to

[ Fifth reference example ]
In the sample of sample No. 06 of the first reference example , as shown in Table 11, iron sulfide powder (S amount: 36.47% by mass) is replaced with molybdenum disulfide powder (S amount: 40.06% by mass) A raw material powder was prepared using the same amount (3% by mass) and formed and sintered in the same manner as in Example 1 to prepare a sintered member of Sample No. 65. The overall composition of this sample is shown together in Table 11. With respect to this sample, in the same manner as in the first reference example , the ratio of the area of all sulfides and the area of sulfides having a maximum particle diameter of 10 μm or more to the area of all sulfides is measured. Measurements were taken. The results are shown in Table 12. Tables 11 and 12 also show the results of the sample of sample No. 06 of the first embodiment.

  As can be seen from Table 11 and Table 12, the amount of S of molybdenum disulfide is larger than the amount of S of iron sulfide, so when molybdenum disulfide powder is added in the same amount as iron sulfide powder, it is in the whole composition As the amount of S increases and the amount of sulfide increases, the sulfide having a maximum particle diameter of 10 μm or more increases. For this reason, the coefficient of friction is reduced. Further, as a result of decomposition of the molybdenum disulfide powder, Mo generated by diffusion being diffused to the iron matrix to form a solid solution and acting on strengthening of the iron matrix, improvement in radial crushing strength is observed. As described above, it was confirmed that the use of molybdenum disulfide powder instead of iron sulfide powder has the effect of reducing the friction coefficient equal to or higher than that of iron sulfide powder. Moreover, it was confirmed that the strength of the iron matrix is improved by increasing the solid solution of Mo in the iron matrix to increase the radial crushing strength.

Sixth reference example
As shown in Table 13, the raw material powder added by adding 2 wt% of nickel powder to the sample of the sample No. 06 of the first reference example was prepared, as in the first reference example, molding, sintering The sample No. 66 sintered member was manufactured. The overall composition of this sample is shown together in Table 13. With respect to this sample, in the same manner as in the first reference example , the ratio of the area of all sulfides and the area of sulfides having a maximum particle diameter of 10 μm or more to the area of all sulfides is measured. Measurements were taken. The results are shown in Table 14. Tables 13 and 14 also show the results of the sample of sample No. 06 of the first reference example .

  As can be seen from Tables 13 and 14, when nickel powder is added to the raw material powder to give Ni in the overall composition, the iron base is strengthened by Ni and the crush strength is increased. Note that Ni does not affect the amount of sulfide and the amount of sulfide having a maximum particle diameter of 10 μm or more, and the coefficient of friction is equivalent to that of the sample No. 06 to which Ni is not added. As described above, it was confirmed that the strength of the iron matrix is improved and the radial crushing strength is increased by causing Ni to be solid-solved in the iron matrix.

Second Embodiment
As shown in Table 15, a raw material powder was prepared by adding 0.5 mass% of boron oxide powder to the sample (graphite powder: 1 mass%) of sample No. 59 of the first embodiment , In the same manner as in the reference example , molding and sintering were performed to prepare a sintered member of sample number 67. The overall composition of this sample is shown together in Table 15. With respect to this sample, in the same manner as in the first reference example , the ratio of the area of all sulfides and the area of sulfides having a maximum particle diameter of 10 μm or more to the area of all sulfides is measured. Measurements were taken. The results are shown in Table 16. Tables 15 and 16 also show the results of the sample of sample No. 59 of the first embodiment .

In the sample of sample number 59, as described in the first embodiment, C provided in the form of graphite powder is diffused to the iron base to form a pearlite structure, and the iron base is strengthened. On the other hand, in the sample of sample No. 67 in which boron oxide powder is added to the raw material powder, diffusion of C imparted in the form of graphite powder to the iron base is suppressed by boron oxide, and the added graphite powder serves as a graphite phase. It remains inside and disperses, and the iron base is ferrite. The state of formation of sulfide does not change regardless of the presence or absence of boron oxide. For this reason, in the sample of sample No. 67 to which boron oxide is added, although the radial crushing strength decreases because there is no strengthening effect of iron base by C, the coefficient of friction is reduced by dispersing the graphite phase functioning as a solid lubricant. It is done. As described above, it was confirmed that the friction coefficient can be further reduced by dispersing C in the pores as a graphite phase.

  In the iron-based sintered sliding member of the present invention, metal sulfide particles mainly composed of iron sulfide are precipitated from the iron base and dispersed in the iron base, so that the sliding property is firmly fixed to the base, It is applicable to various sliding parts from being excellent in mechanical strength while being excellent.

Claims (8)

The entire composition consists of S: 0.2 to 3.24%, Cu: 3 to 10%, C: 0.2 to 2% by mass ratio, the balance: Fe and incidental impurities, and the sulfide particles are crystals. It has a metallographic structure consisting of pores that are precipitated and dispersed in grain boundaries and grains, and
The C is given to the base,
The base comprises a structure in which a copper phase is dispersed in any one of ferrite, perlite and bainite, or a mixed structure thereof, or any one of the ferrite, perlite and bainite, or a mixed structure thereof ,
The sulfide particles are dispersed at a ratio of 0.8 to 15.0% by volume with respect to the matrix,
In the above-mentioned sulfide particles, the area of sulfide particles having a circle equivalent diameter and a maximum particle diameter of 10 μm or more occupies 30% or more of the area of the entire sulfide particles. Overall composition is S: 0.2 to 3.24%, Cu: 3 to 10%, C: 0.2 to 3%, B: 0.03 to 0.62%, balance: Fe and the mass ratio It has a metal structure which consists of unavoidable impurities and has a matrix in which sulfide particles are precipitated and dispersed in grain boundaries and grains, and pores.
Some or all of the C is dispersed in the pores as graphite,
The base comprises a structure in which a copper phase is dispersed in any one of ferrite, perlite and bainite, or a mixed structure thereof, or any one of the ferrite, perlite and bainite, or a mixed structure thereof ,
The sulfide particles are dispersed at a ratio of 0.8 to 15.0% by volume with respect to the matrix,
In the above-mentioned sulfide particles, the area of sulfide particles having a circle equivalent diameter and a maximum particle diameter of 10 μm or more occupies 30% or more of the area of the entire sulfide particles.   The iron-based sintered sliding member according to claim 1 or 2, wherein the impurity contains Mn: 0.02 to 1.2% by mass.   The iron-based sintered sliding member according to any one of claims 1 to 3, wherein each of at least one of Ni and Mo is contained at 10% by mass or less. In the iron powder, at least one metal sulfide powder of iron sulfide powder, copper sulfide powder, molybdenum disulfide powder, and nickel sulfide powder, and the amount of S in the raw material powder is 0.2 to 3.24% by mass And copper powder or copper alloy powder is added so that the amount of Cu in the raw material powder is 3 to 10% by mass, and 0.2 to 2% by mass of the graphite powder is added to the raw material powder. Any one of ferrite, pearlite and bainite, or any one of these, by sintering the molded body obtained in the non-oxidative atmosphere at 1090 ° C. to 1300 ° C. using the mixed raw material powder and compacting in a die. Or sulfide grains are precipitated in grain boundaries and grains of a matrix in which a copper phase is dispersed in the mixed structure of the above, or any one of the above ferrite, pearlite and bainite, or mixed structures thereof, Gives the serial C in said base,
In the above-mentioned sulfide particles, the area of sulfide particles having a circle equivalent diameter and a maximum particle diameter of 10 μm or more occupies 30% or more of the area of the entire sulfide particles, and the iron-based sintered sliding member is produced. Method. In the iron powder, at least one metal sulfide powder of iron sulfide powder, copper sulfide powder, molybdenum disulfide powder, and nickel sulfide powder, and the amount of S in the raw material powder is 0.2 to 3.24% by mass The copper powder or copper alloy powder is added so that the amount of Cu in the raw material powder is 3 to 10% by mass, and the graphite powder is 0.2 to 2% by mass with respect to the raw material powder , boric acid, At least one of 0.1 to 2.0% by mass of powders of boride oxides, nitrides of boron, halides of boron, sulfides of boron and hydrides of boron are added and mixed. By compacting in a die and sintering the obtained compact at 1090 ° C. to 1300 ° C. in a non-oxidizing atmosphere, any one of ferrite, pearlite and bainite, or a mixed structure thereof, or the above ferrite , Parla Sulfide particles are precipitated in the grain boundaries and grains of the matrix in which the copper phase is dispersed in any one of itite and bainite or their mixed structure, and a part or all of the C is made into graphite in the pores Disperse,
In the above-mentioned sulfide particles, the area of sulfide particles having a circle equivalent diameter and a maximum particle diameter of 10 μm or more occupies 30% or more of the area of the entire sulfide particles, and the iron-based sintered sliding member is produced. Method.   7. The iron powder according to claim 5, wherein an iron alloy powder containing at least one of Ni and Mo is used instead of the iron powder, and Ni and Mo in the raw material powder are each 10% by mass or less. Method of manufacturing iron-based sintered sliding member   The iron-based sintered sliding member according to any one of claims 5 to 7, wherein nickel powder is further added to the raw material powder, and the amount of Ni in the raw material powder is 10% by mass or less. Production method.