JP6341455B2 - Manufacturing method of iron-based sintered sliding member - Google Patents

Description

  The present invention slides like a driving part or sliding part of a valve guide or valve seat of an internal combustion engine, a vane or roller of a rotary compressor, a sliding part of a turbocharger, a vehicle, a machine tool, an industrial machine, etc. A powder metallurgy method for sintering a green compact obtained by compacting a raw material powder composed mainly of Fe, particularly for a sliding member suitable for a sliding component in which a high surface pressure acts on the surface The present invention relates to a method for manufacturing an iron-based sintered sliding member.

Sintered members by powder metallurgy can be shaped into a near net shape and are suitable for mass production, and are applied to various machine parts. In addition, since a special metal structure that cannot be obtained by a normal melted material can be easily obtained, the present invention is also applied to various sliding parts as described above. That is, in a sintered member by the powder metallurgy method, a solid lubricant powder such as graphite or manganese sulfide is added to the raw material powder and sintered under the condition that the solid lubricant remains, so that the solid lubricant becomes a metallographic structure. Since it can be dispersed therein, it is applied to various sliding parts (Patent Documents 1 to 3, etc.).

JP 04-157140 A JP 2006-052468 A JP 2009-155696 A

  Conventionally, in a sintered sliding member, a solid lubricant such as graphite or manganese sulfide is applied in the form of powder, and remains without being dissolved at the time of sintering. For this reason, the solid lubricant is unevenly distributed in the pores and at the powder grain boundaries. Since such a solid lubricant is not bonded to the base in the pores and at the powder grain boundary, the sticking property is low, and the solid lubricant is easily dropped from the base during sliding.

  Also, when graphite is used as a solid lubricant, it is necessary not to dissolve the graphite in the matrix during sintering, but to remain as free graphite after sintering. It must be lower than in the case of sintered alloys. For this reason, the bond between particles due to the diffusion of the raw material powders is weakened, and the base strength tends to be lowered.

  On the other hand, solid lubricants such as manganese sulfide are not easily dissolved in the matrix during sintering, and can be sintered at a sintering temperature equivalent to that of a general iron-based sintered alloy. However, the solid lubricant added in powder form exists between the raw powders. For this reason, the base strength is lowered as compared with the case where the diffusion of the raw material powders is inhibited and the solid lubricant is not added. Further, the strength of the iron-based sintered member is reduced due to the decrease in the base strength, and the durability of the base during sliding is reduced, so that the wear easily proceeds.

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

The method for producing an iron-based sintered sliding member of the present invention uses a raw material powder made of iron powder and iron sulfide powder, and the iron sulfide powder has an S amount of 3.24 to 8.10 mass of the raw material powder. %, The raw material powder is compacted in a mold, and the resulting molded body is sintered at 1000 to 1300 ° C. in a non-oxidizing atmosphere.

  In the manufacturing method of the iron-based sintered sliding member, copper powder or copper alloy powder is further added to the raw material powder, the Cu amount of the raw material powder is 20% by mass or less, and the sintering temperature is 1090. It is set as a preferable aspect that it is -1300 degreeC. Further, in place of the iron powder, an iron alloy powder containing at least one of Ni and Mo is used, and the amount of Ni and Mo in the raw material powder is 13% by mass or less. While adding, it is set as a preferable aspect that the amount of Ni of raw material powder is 13 mass% or less. Further, 0.2 to 2% by mass of graphite powder is added to the raw material powder, or 0.2 to 3% by mass of graphite powder is further added to the raw material powder, boric acid, boric oxide, boron nitride. The addition of one or more of boron halide, boron sulfide, and boron hydride powders in a preferred embodiment is preferred.

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

It is a drawing substitute photograph which shows an example of the metal structure of the iron-based sintered sliding member manufactured by this invention.

  Hereinafter, the metal structure of the iron-based sintered sliding member produced in the present invention and the basis for limiting the numerical values will be described. The iron-based sintered sliding member produced in the present invention contains Fe as a main component. Here, the main component means a component occupying a majority of the sintered sliding member, and in the present invention, the Fe content in the overall composition is 50 mass% or more, preferably 60 mass% or more. The metal structure is composed of iron bases (iron alloy bases) 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 voids between the powders when the raw material powder is compacted are left in the iron base formed by the combination of the raw material powders.

  Generally, iron powder contains about 0.03 to 0.9% by mass of Mn as an unavoidable impurity due to the manufacturing method, and the iron base therefore contains a small amount of Mn as an unavoidable impurity. And by giving S, sulfide particles, such as manganese sulfide, can be deposited in a matrix as a solid lubricant. Here, manganese sulfide precipitates finely in the matrix and is therefore effective in improving machinability, but is too fine to contribute to the sliding characteristics, so the sliding characteristics improving effect is small. For this reason, in the present invention, not only the amount of S which reacts with a very small amount of Mn contained in the base, but also S is added, and this S is combined with Fe as the main component to form iron sulfide. .

  Usually, the easiness of forming sulfide is higher as the difference in electronegativity is larger than S. The value of electronegativity (electronegativity by Pauling) is S: 2.58, Mn: 1.55, Cr: 1.66, Fe: 1.83, Cu: 1.90, Ni: 1.91. Since Mo: 2.16, sulfides are easily formed in the order of Mn> Cr> Fe> Cu> Ni> Mo. For this reason, when adding an amount of S that exceeds the amount of S that can combine with all the Mn contained in the iron powder to form MnS, a reaction with Fe as the main component occurs in addition to a reaction with a very small amount of Mn. Not only manganese sulfide, but also iron sulfide is deposited. Therefore, the sulfide precipitated in the matrix is mainly iron sulfide produced by Fe as a main component, and partly becomes manganese sulfide produced by Mn which is an inevitable impurity.

  Iron sulfide is a sulfide particle of a size suitable for improving sliding characteristics as a solid lubricant, and is formed by combining with Fe, which is the main component of the base, so that it can be uniformly deposited and dispersed in the base. .

  As described above, in the present invention, the amount of S to be combined with Mn contained in the matrix, and further, S is added and combined with Fe as the main component of the matrix to precipitate sulfide. However, if the amount of sulfide particles precipitated and dispersed in the matrix is less than 15% by volume, a certain level of lubrication effect can be obtained, but the sliding characteristics are deteriorated. On the other hand, if the amount of sulfide particles exceeds 30% by volume, the amount of sulfide with respect to the base becomes excessive, and the strength of the iron-based sintered sliding member decreases. Therefore, the amount of sulfide particles in the base is set to 15 to 30% by volume with respect to the base.

Although S has a low compounding force at room temperature, it is very reactive at high temperatures, and combines with not only metals but also nonmetallic elements such as H, O, and C. By the way, in the manufacture of sintered members, generally, a molding lubricant is added to the raw material powder, and so-called dewaxing is performed in which the molding lubricant is volatilized and removed in the temperature rising process of the sintering process. When applied in the form of powder, the molding lubricant is decomposed and combined with the components (mainly H, O, C) to be released, so that S necessary for iron sulfide formation is stably given. Is difficult. For this reason, S is provided in the form of iron sulfide powder . When S is applied in the form of these iron sulfide powders, it is present in the form of iron sulfide in the temperature range where the dewaxing step is performed (about 200 to 400 ° C.), so the component produced by decomposition of the molded lubricant Since no separation of S occurs, S necessary for the above iron sulfide formation can be stably provided.

In the present invention, since iron sulfide powder is used as the metal sulfide, if it exceeds 988 ° C. in the temperature rising process of the sintering process, an eutectic liquid phase of Fe—S is generated and becomes liquid phase sintering to form powder particles Promote the growth of the neck between. Further, since S diffuses uniformly from the eutectic liquid phase into the iron matrix, the sulfide particles can be uniformly precipitated and dispersed from the matrix.

The above sulfide particles are precipitated by bonding Mn, Fe, and S in the matrix to be precipitated and uniformly dispersed in the matrix. Therefore, the sulfide is firmly fixed to the base and is difficult to fall off. In addition, since sulfide is generated by precipitation from the iron base, it does not inhibit the diffusion of the raw material powders during sintering, and the sintering is promoted by the Fe-S liquid phase. This is done well, improving the strength of the iron base and improving the wear resistance of the iron base.

  In addition, since the sulfide which precipitates in a base | substrate exhibits a solid-lubricating effect | action in sliding with a counterpart member, it is preferable that it is a predetermined magnitude | size rather than a fine thing. From this viewpoint, it is preferable that the area of sulfide particles having a maximum particle diameter of 10 μm or more in terms of the equivalent circle diameter occupies 30% or more of the entire area of the sulfide particles. If the maximum particle size of the sulfide particles is less than 10 μm in terms of the equivalent circle diameter, it is difficult to sufficiently obtain a solid lubricating action. Moreover, even if the area of sulfide particles having a maximum equivalent particle diameter of 10 μm or more is less than 30% of the area of the entire sulfide particles, it is difficult to obtain a sufficient solid lubricating action.

  In general, an iron-based sintered alloy is used as an iron alloy by dissolving elements such as C, Cu, Ni, and Mo in the iron matrix to strengthen the iron matrix. Similarly, in the member, an element that strengthens the iron base can be added to form an iron alloy base. Among these elements, Ni and Mo do not inhibit the formation of sulfide particles mainly composed of iron sulfide from the relationship of electronegativity as described above. Cu has an effect of promoting the formation of sulfide particles mainly composed of iron sulfide. These elements have the effect of strengthening the base by solid solution in the iron base, and when used in combination with C, improve the hardenability of the iron base, refine the pearlite to increase the strength, or sinter It makes it easy to obtain high-strength bainite and martensite at normal cooling rates.

  At least one of Ni and Mo is a plain powder (nickel powder and molybdenum powder) or an alloy powder with other components (Fe-Mo alloy powder, Fe-Ni alloy powder, Fe-Ni-Mo alloy powder, Cu-Ni alloy powder, Cu-Mo alloy powder, etc.) can be added. However, these materials are expensive, and when added as a simple powder, if the amount of the component is excessive, an undiffused portion remains in the iron base, and a portion where no sulfide is deposited is generated. For this reason, it is preferable that Ni and Mo are each 13 mass% or less in the whole composition.

  Cu can be added in the form of a simple powder or an alloy powder with other components. As described above, Cu has an effect of promoting the precipitation of sulfide particles, and when the amount of Cu is larger than the amount of S, a soft free copper phase is precipitated in the iron base, and Improves familiarity. However, if added in a large amount, the amount of the free copper phase that precipitates becomes excessive, and the strength of the iron-based sintered member is significantly reduced. For this reason, it is preferable that the amount of Cu is 20 mass% or less in the whole composition.

  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 it is applied in the form of graphite powder. When the addition amount of C is less than 0.2% by mass, the ratio of ferrite having low strength becomes excessive, and the effect of addition becomes poor. On the other hand, when the addition amount is excessive, brittle cementite is precipitated in a network form. For this reason, in this invention, while containing 0.2-2.0 mass% of C, it is preferable that the whole quantity of C precipitates as a solid solution or metal carbide in a base | substrate.

  In addition, if C is not dissolved in the base and remains in the pores in the state of graphite, this graphite functions as a solid lubricant, and effects such as reduction of friction coefficient and suppression of wear are obtained, and sliding characteristics are improved. Can be improved. For this reason, in this invention, while containing 0.2-3.0 mass% of C, it is preferable that a part or all of C is disperse | distributing as graphite in a pore. 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 graphite to be dispersed becomes insufficient, and the effect of improving the sliding characteristics becomes insufficient. On the other hand, since the graphite remaining in the pores maintains the shape of the added graphite powder, the pores are prevented from being spheroidized by the graphite, and the strength tends to decrease. For this reason, the upper limit of the addition amount of C is set to 3.0 mass%.

  In order to leave C in the pores in the state of graphite, the raw material powder contains 0.2 to 3.0% by mass of graphite powder, boric acid, boric oxide, boron nitride, boron halide, boron sulfide. In addition, it can be obtained by adding one or more of 0.1 to 2.0% by mass of boron hydride powder. These boron-containing powders have a low melting point and generate a liquid phase of boron oxide at about 500 ° C. For this reason, in the process of heating the green compact containing graphite powder and boron-containing powder in the sintering step, the boron-containing powder is melted and the surface of the graphite powder is wetted and covered by the generated boron oxide liquid phase. For this reason, the diffusion of C in the graphite powder into the Fe base starting from about 800 ° C. when the temperature is further increased is prevented, and the graphite powder can be retained and dispersed in the pores. The boron-containing powder is preferably an amount sufficient to cover the graphite powder, and even if excessively added, boron oxide remains in the matrix and causes a decrease in strength. It is good to set it as 2.0 mass%.

  The metal structure of the iron base becomes a ferrite structure when C is not given. In addition, when C is provided, when C is left in the pores in the form of graphite, the metal structure of the iron base becomes ferrite. When part and all of C is diffused into the iron base, the metal structure of the iron base becomes a mixed structure of ferrite and pearlite or pearlite. When at least one of Cu, Ni, and Mo is used together with C, the metal structure of the iron base 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 metallic structure of a mixed structure of bainite, pearlite, or bainite. Furthermore, when Cu is added and the amount of Cu is larger than the amount of S, a metal structure in which a free copper phase is dispersed in the metal structure of the iron base is obtained.

  As described above, the raw material powder is slidably fitted into a mold having a mold hole for shaping the outer peripheral shape of the product and the mold hole of the mold, and the lower end surface of the product is shaped. A lower punch that, in some cases, a core rod that shapes the inner peripheral shape of the product or a hollow portion, and an upper punch that fills a cavity formed with raw material powder and shapes the upper end surface of the product, and the lower punch After the raw material powder is compression-molded by the above method, it is molded into a molded body by a method (pushing method) of extracting from the mold hole of the mold.

  The obtained molded body is heated and sintered in a sintering furnace. 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, when the sintering temperature is lower than 1000 ° C., the Fe—S eutectic liquid phase is not generated, and the formation of sulfide mainly composed of iron becomes insufficient. Moreover, when using Cu as an additional additive element, since the melting point of Cu is 1084.5 ° C., the sintering temperature is preferably set to 1090 ° C. or higher in order to sufficiently generate a Cu liquid phase. On the other hand, when the sintering temperature is higher than 1300 ° C., the amount of liquid phase generated becomes excessive, and mold deformation is likely to occur. The sintering atmosphere may be a non-oxidizing atmosphere. However, since S easily reacts with H and O as described above, it is preferable to use an atmosphere with a low dew point.

[First embodiment]
Iron sulfide powder (S content: 36.47 mass%) was added to iron powder containing 0.03% by mass of Mn as a blending ratio (addition ratio) shown in Table 1 and mixed to obtain a raw material powder. . The raw material powder was molded at a molding pressure of 600 MPa to produce 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. Subsequently, it sintered at 1120 degreeC in non-oxidizing gas atmosphere, and the sintered member of sample numbers 01-08 was produced. Table 1 shows the overall composition of these samples.

  The volume% of sulfide in the metal structure is equal to the area ratio of sulfide in the metal structure cross section. For this reason, in the Example, in evaluating the volume% of the metal sulfide, the area% of the sulfide of the metal structure cross section was evaluated. That is, the obtained sample is cut, the cross section is mirror-polished, and the cross section is observed. Using image analysis software (WinROOF manufactured by Mitani Corporation), the area of the base portion and the area of sulfide are excluded. While measuring, the area% of the sulfide occupying the base was determined, and the area of the sulfide having a maximum particle size of 10 μm or more was measured to determine the ratio to the total sulfide area. In addition, the maximum particle diameter of each sulfide particle was measured by the equivalent circle diameter which calculated | required the area of each particle and converted into the diameter of a circle equal to this area. When sulfide particles are bonded, the combined sulfide is regarded as one sulfide, and the equivalent circle diameter is obtained from the area of the sulfide. These results are shown in Table 2.

In addition, for a ring-shaped sintered member, using a tempered material of SCM435H defined in JIS standard as a counterpart material, a ring-on-disk friction and wear tester under a load of peripheral speed 477 rpm, 5 kgf / cm ² A sliding test was conducted without lubrication, and the coefficient of friction was measured. Further, a crushing test was performed on the ring-shaped sintered member to measure crushing strength. These results are also shown in Table 2.

  In the following evaluation, a sample having a friction coefficient of 0.6 or less and a crushing strength of 150 MPa or more was judged as acceptable.

  From Tables 1 and 2, sulfide is precipitated by adding iron sulfide powder, and as the amount of iron sulfide powder added increases, the amount of S in the overall composition increases and the amount of sulfide deposited increases. ing. Further, the ratio of the sulfide having a maximum particle size of 10 μm or more increases as the amount of S increases. Is 10 μm or more. By precipitation of such sulfides, the coefficient of friction decreases as the amount of S in the overall composition increases. The crushing strength increases because the addition of iron sulfide powder generates a liquid phase during sintering and promotes sintering. However, when the amount of sulfide deposited in the base increases, the strength of the base decreases. Therefore, in a region where the amount of S is large, the amount of sulfide deposited increases and the strength of the base decreases and the crushing strength decreases.

  Here, in the sample of sample number 02 in which the amount of S in the entire composition is less than 3.24% by mass, the amount of sulfur is insufficient, so the amount of sulfide deposited is less than 15 area%, and the effect of improving the friction coefficient is poor. . In contrast, in the sample No. 03 having an S content of 3.24% by mass in the entire composition, the amount of sulfide deposited was 15% by area, and the area of the sulfide having a maximum particle size of 10 μm or more was totally sulfided. The ratio with respect to the area of the object exceeds 60%, and the friction coefficient is improved to 0.6. On the other hand, when the amount of S in the entire composition exceeds 8.1% by mass, the amount of sulfide occupying the base exceeds 30% by area. As a result, the reduction of the crushing strength becomes significant, and the crushing strength falls below 150 MPa. As described above, it was confirmed that a good friction coefficient and strength were obtained when the amount of S in the entire composition was in the range of 3.24 to 8.1 mass%.

  FIG. 1 shows the metal structure (mirror polishing) of the iron-based sintered sliding member of Sample No. 05. The iron base is the white part, and the sulfide particles are the gray part. The pores are black portions. As can be seen from FIG. 1, sulfide particles (gray) are precipitated and dispersed in the iron matrix (white), and the adhesion to the matrix is good. In addition, the sulfide particles are bonded to each other and grow to a certain size and are dispersed in the matrix in such a large form, so the action as a solid lubricant is great, contributing to the reduction of the friction coefficient. It is thought that. The pores (black) have a relatively round shape, which is considered to be due to the generation of the FeS liquid phase.

[Second Embodiment]
An iron powder containing 0.8% by mass of Mn was added with iron sulfide powder (S content: 36.47% by mass) in the mixing ratio shown in Table 3 and mixed to obtain a raw material powder. Then, in the same manner as in the first example, molding and sintering were performed to produce sintered members of sample numbers 09 to 16. The overall composition of these samples is also shown in Table 3. For these samples, in the same manner as in the first example, the ratio of the sulfide area and the area of the sulfide having a maximum particle size of 10 μm or more to the total sulfide area was measured, and the friction coefficient and the crushing strength were measured. The measurement was performed. These results are shown in Table 4.

  The second example is an example in which an iron powder having an Mn amount different from the iron powder (Mn amount: 0.03 mass%) used in the first example is used, but the same tendency as the first example is exhibited. Show. That is, from Tables 3 and 4, as the amount of iron sulfide powder added increases, the amount of S in the overall composition increases and the amount of sulfide deposited increases. In addition, the ratio of the sulfide having a maximum particle size of 10 μm or more increases with an increase in the amount of S. When the amount of S is 8.10%, which is the upper limit of the present invention, most of the largest particles of sulfides. The diameter is 10 μm or more. By precipitation of such sulfides, the friction coefficient decreases as the amount of S in the overall composition increases. Addition of iron sulfide powder generates a liquid phase during sintering and promotes sintering, so the crushing strength increases. However, as the amount of sulfide precipitated in the matrix increases, the strength of the matrix decreases. In the region where the amount of S is large, the amount of sulfide deposited is large and the strength is lowered, so that the crushing strength is lowered.

  Similarly to the first example, in the sample of Sample No. 10 in which the amount of S in the entire composition is less than 3.24% by mass, the amount of S deposited is less than 15 area% because the amount of S is insufficient. The effect of improving the coefficient of friction is poor. On the other hand, in the sample of Sample No. 11 in which the amount of S in the entire composition is 3.24% by mass, the amount of sulfide deposited is 15 area% and the area of sulfide having a maximum particle size of 10 μm or more Is 60%, and the friction coefficient is improved to 0.6 or less. On the other hand, when the amount of S in the entire composition exceeds 8.1% by mass, the amount of sulfide occupying the base exceeds 30% by area. As a result, the reduction of the crushing strength becomes significant, and the crushing strength falls below 150 MPa. As described above, it was confirmed that a good friction coefficient and strength were obtained when the amount of S in the entire composition was in the range of 3.24 to 8.1 mass%.

[Third embodiment]
While adding 15 mass% iron sulfide powder and copper powder to the iron powder used in 1st Example, it changed into the addition ratio (compounding ratio) of the copper powder shown in Table 5, and added and mixed. Raw material powder was obtained. Then, in the same manner as in the first example, molding and sintering were performed to produce sintered members of sample numbers 31 to 35. Table 5 shows the overall composition of these samples. For these samples, in the same manner as in the first example, the ratio of the sulfide area and the area of the sulfide having a maximum particle size of 10 μm or more to the total sulfide area was measured, and the friction coefficient and the crushing strength were measured. The measurement was performed. These results are shown in Table 6. Table 6 also shows the results of the sample No. 05 of the first embodiment (example not including copper powder).

  From Tables 5 and 6, when the amount of Cu powder is changed to change the amount of Cu in the overall composition, precipitation of sulfide particles is promoted and the amount of sulfide increases as the amount of Cu increases. At the same time, the amount of sulfide particles exceeding 10 μm tends to increase, and thus the friction coefficient tends to decrease. As the Cu content increases, the crushing strength increases as the amount of liquid phase increases and becomes dense, and the Cu content increases up to 15% by mass due to the effect of strengthening the base. However, if the amount of Cu exceeds 15% by mass, the amount of free copper phase dispersed in the matrix increases and the crushing strength decreases. If the amount of Cu exceeds 20% by mass, the crushing strength decreases to 150 MPa. Below.

  From the above results, it was confirmed that the addition of Cu promotes the precipitation of sulfide particles and can reduce the friction coefficient. However, when the amount of Cu exceeds 20% by mass, the strength is remarkably reduced. Therefore, when Cu is added, it is also confirmed that the upper limit is preferably 20% by mass or less.

[Fourth embodiment]
While adding 15 mass% iron sulfide powder, 10 mass% copper powder, and nickel powder to the iron powder used in 1st Example, it changes into the ratio (mixing ratio) of the nickel powder shown in Table 7. Were added and mixed to obtain a raw material powder. Then, in the same manner as in the first example, molding and sintering were performed to produce sintered members of sample numbers 36 to 40. The overall composition of these samples is also shown in Table 7. For these samples, in the same manner as in the first example, the ratio of the sulfide area and the area of the sulfide having a maximum particle size of 10 μm or more to the total sulfide area was measured, and the friction coefficient and the crushing strength were measured. The measurement was performed. These results are shown in Table 8. Table 8 also shows the results of the sample No. 32 (example not including nickel powder) of the third example.

  From Table 7 and Table 8, when the amount of Ni in the overall composition is changed by changing the amount of nickel powder added, the crushing strength increases until the amount of Ni reaches 5% by mass due to the effect of base strengthening as the amount of Ni increases. To do. However, as the amount of Ni increases, the amount of Ni-rich phase (high Ni concentration phase) that remains without being diffused in the iron base increases and the strength decreases, so that it exceeds 5 mass% to 10 mass%. The effect of strengthening the base and the influence of the Ni-rich phase balance and the crushing strength is equal. And when Ni amount exceeds 10 mass%, the influence of a Ni rich phase will become large and the crushing strength will reduce. On the other hand, as the amount of Ni increases, the Ni-rich phase in which the precipitation of sulfide is poor increases, so the coefficient of friction gradually increases. However, when the amount of Ni exceeds 13% by mass, the Ni-rich phase increases too much, so the friction coefficient increases remarkably and exceeds 6.

  As described above, it is confirmed that the strength can be improved by the addition of Ni. However, it is confirmed that the upper limit is preferably 13% by mass or less because the friction coefficient increases with a decrease in strength when the Ni content exceeds 13% by mass. It was. Moreover, from this 4th Example, it was confirmed that intensity | strength can be improved by adding Ni in 13 mass% or less.

[Fifth embodiment]
While adding 15 mass% iron sulfide powder, 10 mass% copper powder, and graphite powder to the iron powder used in 1st Example, it changed into the ratio (compounding ratio) of the graphite powder addition shown in Table 9. Were added and mixed to obtain a raw material powder. Then, in the same manner as in the first example, molding and sintering were performed to produce sintered members of sample numbers 41 to 51. The overall composition of these samples is also shown in Table 9. For these samples, in the same manner as in the first example, the ratio of the sulfide and the ratio of the sulfide having the maximum particle size of 10 μm or more to the total sulfide was measured, and the friction coefficient and the crushing strength were measured. went. These results are shown in Table 10. Table 10 also shows the results of the sample of sample number 32 of the third embodiment (example not including graphite powder).

  The fifth embodiment is an example in which C is given to the iron-based sintered sliding member and the entire amount of C is given as a solid solution in the iron base. The sample of Sample No. 32 in the third example does not contain C, and the metal structure of the iron base is a ferrite structure with low strength. Here, when C is added by adding graphite powder, a pearlite phase that is harder and stronger than the ferrite phase is dispersed in the ferrite structure in the metal structure of the iron base, and the crushing strength is increased, and the friction coefficient is increased. descend. As the amount of C increases, the amount of pearlite phase increases and the ferrite phase decreases, and when the amount of C is about 1% by mass, the iron-base metal structure becomes the entire pearlite structure. For this reason, when the amount of C is up to 1% by mass, the crushing strength increases as the amount of C increases, and the friction coefficient decreases. On the other hand, when the amount of C exceeds 1% by mass, high and brittle cementite is precipitated in the pearlite structure, the crushing strength is reduced, and the friction coefficient is increased. When the amount of C exceeds 2% by mass, the amount of cementite precipitated in the pearlite structure becomes excessive, the crushing strength is remarkably reduced, and the crushing strength is lowered as compared with the sample of sample number 32 where C is not added. At the same time, the coefficient of friction is increased to a value exceeding 0.6.

  As described above, the strength can be improved by adding C and dissolving in the iron base. However, if the amount of C exceeds 2% by mass, the friction coefficient increases as the strength decreases, so the upper limit is 2% by mass or less. It was confirmed that it was preferable to make it.

[Sixth embodiment]
To the iron powder used in the first example, 15% by mass of iron sulfide powder, 10% by mass of copper powder, 0.5% by mass of boron oxide powder and graphite powder were added. The raw material powder was obtained by changing the addition ratio (blending ratio) and mixing. Then, in the same manner as in the first example, molding and sintering were performed to produce sintered members of sample numbers 52 to 62. Table 11 shows the overall composition of these samples. For these samples, in the same manner as in the first example, the ratio of the sulfide area and the area of the sulfide having a maximum particle size of 10 μm or more to the total sulfide area was measured, and the friction coefficient and the crushing strength were measured. The measurement was performed. These results are shown in Table 12. Table 12 also shows the results of the sample No. 32 (example not including graphite powder) of the third example.

  The sixth embodiment is an example in which C is given to the iron-based sintered sliding member and C is not diffused to the iron base, but remains in the pores and used as a solid lubricant. From Table 11 and Table 12, when the amount of graphite powder added is changed to change the amount of C in the overall composition, the graphite powder dispersed in the pores acts as a solid lubricant as the amount of C increases, and the coefficient of friction is descend. On the other hand, the crushing strength decreases because the amount of the weight base that increases the amount of graphite powder decreases. And when the addition amount of graphite powder exceeds 3 mass%, the crushing strength will fall remarkably and will be the value less than 150 MPa.

  As described above, when graphite powder is added and left in the pores, it is effective in reducing the friction coefficient. However, if the amount of C exceeds 3% by mass, the strength is significantly reduced, so the upper limit is set. It was confirmed that the content is preferably 3% by mass or less.

  In the manufacturing method of the iron-based sintered sliding member of the present invention, metal sulfide particles mainly composed of iron sulfide are precipitated and dispersed in the iron base from the iron base, and are firmly fixed to the base. Since it has excellent sliding characteristics and strength, it can be applied to the production of various sliding parts.

Claims (9)

  A raw material powder composed of iron powder and iron sulfide powder is used, and the iron sulfide powder is added and mixed so that the S amount of the raw material powder is 3.24 to 8.10% by mass. A method for producing an iron-based sintered sliding member, characterized in that the green compact is compacted and sintered at 1000 to 1300 ° C. in a non-oxidizing atmosphere.   The copper powder or copper alloy powder is further added to the raw material powder, the Cu amount of the raw material powder is 20% by mass or less, and the sintering temperature is 1090 to 1300 ° C. Method for manufacturing an iron-based sintered sliding member.   3. An iron alloy powder containing at least one of Ni and Mo is used in place of the iron powder, and the amount of Ni and Mo in the raw material powder is 13% by mass or less. Manufacturing method of iron-based sintered sliding member.   The method for producing an iron-based sintered sliding member according to claim 1 or 2, wherein nickel powder is further added to the raw material powder, and the amount of Ni in the raw material powder is 13 mass% or less. In addition to adding 0.2 to 2% by mass of graphite powder to the raw material powder, copper powder or copper alloy powder is added so that the Cu amount of the raw material powder is 10 to 20% by mass, and the sintering temperature is 1090. It is -1300 degreeC , The manufacturing method of the iron-based sintered sliding member in any one of Claims 1-4 characterized by the above-mentioned. An iron alloy powder containing Ni is used instead of the iron powder, and 0.2 to 2% by mass of graphite powder is further added to the raw material powder, so that the amount of Ni in the raw material powder is 5 to 13% by mass (5% The manufacturing method of the iron-based sintered sliding member according to any one of claims 1 to 4, wherein Further, 0.2 to 2% by mass of graphite powder is added to the raw material powder, and Ni powder is added so that the amount of Ni in the raw material powder is 5 to 13% by mass (excluding 5%). The manufacturing method of the iron-based sintered sliding member according to any one of claims 1 to 4. The copper powder or the copper alloy powder is added to the raw material powder so that the Cu amount of the raw material powder is 10 to 20% by mass, and the sintering temperature is 1090 to 1300 ° C. The manufacturing method of the iron-based sintered sliding member as described in any one of. 0.1 to 2.0% by mass of one or more of boric acid, boric oxide, boron nitride, boron halide, boron sulfide and boron hydride powder, It adds, The manufacturing method of the iron-based sintered sliding member in any one of Claims 1-8 characterized by the above-mentioned.