JP2016069734A - Iron-based sintered alloy material for sliding member and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an iron-based sintered alloy material for a sliding member excellent in radial strength and wear resistance.SOLUTION: Iron based powder and solid lubricant powder excellent in sliding properties are subjected to ball mill treatment into iron based powder for raw material powder, further, as iron based powder for matrix formation, the iron based powder for raw material powder, or iron based powder, further powder for alloying, or further, hard grain powder are blended into mixed powder, the mixed powder is charged to a die and is subjected to press molding into a green compact, and the green compact is subjected to sintering treatment into an iron based sintered alloy material for a sliding member. The obtained iron based sintered alloy material has a structure where solid lubricant grains are included by 4.0 to 20.0% in mass%, and further, the structure including a dispersed region in which the solid lubricant grains are dispersed into a matrix phase is included by 25% or higher in area ratio to the whole structure other than the hard grains, and the solid lubricant grains are dispersed in such a manner that a dispersion degree reaches 0 to 20%, and also, the standard deviation reaches 3.5 or lower. Thus, the iron based sintered alloy material for a sliding member excellent in wear resistance without causing deterioration in its radial strength can be obtained.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an iron-based sintered alloy material suitable for a sliding member such as an internal combustion engine valve seat, and a method for producing the same, and more particularly to further improving wear resistance and crushing strength.

  The valve seat is press-fitted or joined to the cylinder head of the internal combustion engine, and serves to cool the combustion gas seal and the valve. The valve seat is hit by a valve, and is exposed to wear due to sliding, heating by combustion gas, corrosion by combustion products, and the like, so that it has been conventionally required to have excellent heat resistance and wear resistance. In recent years, sintered alloy materials have been applied to such valve seats that are required to have excellent heat resistance and wear resistance. Sintered alloy materials can easily produce metals and alloys that are difficult to obtain by ordinary melting methods, and because it is easy to combine functions, it is possible to manufacture parts with unique functions. Suitable for manufacturing difficult-to-work materials and parts with complex shapes.

  Recently, from the viewpoint of protecting the global environment, there are increasing demands for internal combustion engines for automobiles in addition to high performance, for improving fuel efficiency and purifying exhaust gas. In order to cope with such a demand, the operating condition of the internal combustion engine for automobiles is set to a severe condition, the combustion condition becomes severe, and the use environment of the valve seat used is further severe. Therefore, the conventional valve seat has a problem that the characteristics such as heat resistance and wear resistance are insufficient.

For such a problem, for example, Patent Document 1 describes a method of manufacturing a valve seat material for an internal combustion engine. In the technique described in Patent Document 1, ² to 20% by weight of hard particles having a Vickers hardness of 1500 kg / mm ² or more are added to a base metal powder, and alloyed by mechanical alloying. This is a method for manufacturing a valve seat material for an internal combustion engine in which a billet is formed by isostatic pressing and the billet is hot-extruded. According to the technique described in Patent Document 1, a valve seat material for an internal combustion engine in which hard particles such as alumina are uniformly dispersed in a base metal such as Fe can be manufactured in a size and shape close to a product.

  Patent Document 2 describes a method for producing a wear-resistant iron-based sintered alloy. In the technique described in Patent Document 2, a raw material powder in which copper is mainly compounded on the surface of iron powder or iron alloy powder is used, compacted, sintered, and subjected to Cu phase precipitation treatment on the sintered body. C: 0.3 to 2.5%, Cu: 1 to 8%, and one or more alloy elements of Mo, W, V, Nb, and Ta: 3 to 14%. The wear-resistant iron-based sintered alloy has a uniformly dispersed structure. In the technique described in Patent Document 2, a mechanical alloying method, a plating method, a partial alloying method, a method in which Cu is dissolved at the time of raw material atomization, and Cu is precipitated by a subsequent heat treatment are used. In particular, it is said that Cu powder is mechanically alloyed with iron powder or the like to obtain a raw material powder in which Cu is finely adhered mainly to the surface of Fe particles.

JP-A-62-270736 Japanese Unexamined Patent Publication No. 04-259351

  In the technique described in Patent Document 1, the base metal powder and the hard particle powder are alloyed by mechanical alloying. However, the technique described in Patent Document 1 requires hydrostatic pressing and further hot extrusion, and has a problem that the process is complicated and productivity is reduced. Furthermore, in the valve seat material manufactured by the technique described in Patent Document 1, it is difficult to obtain a sufficient improvement in wear resistance and a sufficient reduction in the opponent attack property under severe usage conditions in recent years. There is.

  Moreover, in the technique described in Patent Document 2, since the soft Cu phase is dispersed, the attack performance to the valve is improved. However, under recent severe use conditions, sufficient wear resistance is improved. There is a problem that it is difficult to expect.

  Therefore, the present inventors have solved the above-mentioned problems of the prior art, and can achieve further improvement in wear resistance without reducing the crushing strength, for sliding members such as valve seats for internal combustion engines. An object is to provide an iron-based sintered alloy material and a method for producing the same.

  In order to achieve the above-mentioned object, the present inventors diligently studied various factors affecting the wear resistance of the iron-based sintered alloy material. As a result, the inventors focused on solid lubricant particles having excellent sliding characteristics and came up with a large amount of solid lubricant particles. If a solid lubricant that improves sliding characteristics can be dispersed in a large amount in the base phase of the iron-based sintered alloy material, even if it is used under severe conditions such as a valve seat of an internal combustion engine, a large amount of hard particles are necessarily contained. The present inventors have conceived that the wear resistance can be remarkably improved without necessity.

  Therefore, we tried to add a large amount of solid lubricant particles up to 10% by mass in the base. However, the added solid lubricant particles are present at the metal powder (iron-based powder) boundary, and the addition of a large amount of solid lubricant particles inhibits the diffusion of elements in the sintering process, and the structure after the sintering process It has been found that a structure containing ferrite tends to be formed, resulting in a decrease in density and a decrease in hardness. For this reason, it has been found that the mere inclusion of a large amount of solid lubricant particles causes a decrease in strength (crushing strength), which is problematic.

  Therefore, the present inventors paid attention to a ball mill process which is a kind of mechanical alloying. A solid lubricant particle powder excellent in sliding characteristics is blended with iron base powder (iron powder) for base formation, and a ball mill treatment is applied, so that a large amount of solid lubricant particles are uniformly dispersed in the base. It was newly found that it can be made an iron-based powder.

  Further, the strength (compression strength) is reduced by using the iron-based powder in which a large amount of the solid lubricant particles obtained by applying this ball mill treatment is dispersed as a part or all of the iron-based powder for base formation. The present inventors have found that an iron-based sintered alloy material with significantly improved wear resistance can be produced without incurring the problem.

  The “ball mill treatment” here means, for example, a treatment using a vibration ball mill, a planetary ball mill or the like. For example, a metal ball and two or more kinds of metal powders are blended in a processing container of the mill. Is a process that continuously rotates and revolves, and repeatedly gives impact to the powder from the metal ball, and even in an equilibrium state, elements that do not dissolve in force can be forcibly dissolved, and an alloy can be formed without melting. Has been.

  First, the experimental results on which the present invention is based will be described.

Atomized pure iron powder or carbonyl iron powder was prepared as the base-forming iron-based powder, and MnS powder was prepared as the solid lubricant particle powder, and kneading treatment (ball mill treatment) was performed using a ball mill. The atomized iron powder or carbonyl iron powder and the MnS powder were blended as shown in Table 1. In this ball mill treatment, steel balls were used as the grinding media balls and the treatment time was 2 hours. The particle size of the iron powder as atomized was 91 μm, the particle size of the carbonyl iron powder was 5 μm, and the particle size of the MnS powder was 7 μm. The “particle diameter” here is a median diameter d ₅₀ measured using a laser diffraction scattering method.

  In addition, as shown in Japanese Patent No. 3486682, the used mill has guide vanes having an adjustable interval between the inner wall surface of the processing container and the processing container. A device that can store the grinding media ball and powder and is configured to be rotatable, and the grinding media ball can collide with the powder on the inner wall surface of the processing container and give the collision energy to the powder. is there.

  The sintered body obtained using the ball-milled powder was observed with an optical microscope (magnification: 500 times) while being polished. As a result, all sintered bodies using ball milled powders have a structure in which solid lubricant particles (gray part) are dispersed in the matrix phase (white part) (dispersion region) in an appropriate amount. I found out that

  In this dispersion region, when the amount of solid lubricant particles decreases (iron-based powder b0, FIG. 1 (b)), the thickness of solid lubricant particles (gray portion) dispersed in the matrix phase becomes thin, In addition, when iron-based powder having a smaller particle size is used (iron-based powder No. d0, FIG. 1 (c)), solid lubricant particles (gray portion) dispersed in the matrix phase are more densely dispersed. I also found out.

In addition, as shown in Table 1, about the iron-based powder (iron-based powder for raw material powder) obtained by ball milling the iron-based powder and the solid lubricant particle powder, the particle size ( When the median diameter d ₅₀ is measured, it can be seen that the ball mill treatment promotes the refinement of the powder as compared with the iron powder (particle diameter: 91 μm) as atomized.

  Next, the ball-milled powder (iron-based powder No. a0, No. b0, No. d0) is used as the iron-based powder for raw material powder, and the alloy powder and the hard particle powder are displayed on the iron-based powder for raw material powder. It mix | blended with the ratio shown in 2, and it mixed with the V-type mixer and was set as the mixed powder. In some cases, the above-mentioned ball-milled iron-based powder (iron-based powder for raw material powder) is further mixed with atomized iron powder (iron-based powder), alloy powder, and hard particle powder, mixed and mixed. Powdered. For comparison, solid iron powder, alloy powder, and hard particle powder were blended into atomized iron powder and mixed to obtain a mixed powder. The solid lubricant particles were MnS particles and blended so that the mass% with respect to the total amount of the mixed powder was 10%. Moreover, the blending amounts of the hard particle powder and the alloy powder were all the total, and the mass% with respect to the total amount of the mixed powder was 35.2%. In some cases, a mixed powder containing no hard particles was used.

  The blended hard particle powder is, by mass%, a Co-based intermetallic compound (hardness: 15% to 35% Mo-5 to 20% Ni-0.5 to 4% Si-15 to 35% Cr and the balance Co). 950-1150HV).

Subsequently, the obtained mixed powder was charged into a mold and press-molded at a pressure of green compact density: 7.0 g / cm ³ to obtain a green compact. The obtained green compact was sintered in a reducing atmosphere at a temperature of 1150 ° C. to obtain an iron-based sintered body (outer diameter 30 mmφ × inner diameter 18 mmφ × height 8 mm).

  The obtained iron-based sintered body is processed into a valve seat (size and shape: outer diameter φ30mm x inner diameter φ18mm x height 4mm) by cutting and grinding, and the crushing strength is obtained in accordance with the provisions of JIS Z 2507. It was.

  In addition, the obtained iron-based sintered body was cut into a valve seat (size and shape: outer diameter φ27.1 mm × inner diameter φ22.0 mm × height 6.5 mm) by cutting and grinding, and the single rig wear shown in FIG. A single rig wear test was conducted using a testing machine. After the valve seat 1 was press-fitted into the jig 2 corresponding to the cylinder head, the valve 4 was moved up and down by the crank mechanism while the valve 4 and the valve seat 1 were heated by the heat source 3 mounted on the testing machine, and the test was performed. The amount of wear was measured by the amount of valve sinking. The test conditions were as follows.

Test temperature: 300 ° C (sheet surface)
Test time: 4.5h
Cam rotation speed: 3000rpm
Valve speed: 20rpm
Spring load: 35kgf (345 N) (when set)
Valve material: T400 raised metal Lift amount: 7mm
Moreover, about the obtained sintered compact, after collect | recovering and grind | polishing the test piece for structure | tissue observation, a structure | tissue is observed using an optical microscope (magnification: 100-500 times), and it images and analyzes a solid, The area ratio with respect to the whole structure | tissue of the area | region (dispersion area | region) in which the lubricant particle was disperse | distributed in the base phase was computed, and it was set as the fraction of a dispersion | distribution area | region.

  The obtained results are shown in Table 3.

  Iron-based sintering obtained by using iron-based powder (iron-based powder for raw material powder) that has been ball milled and formulated with atomized pure iron powder or carbonyl iron powder and solid lubricant powder (MnS powder) The body (sintered body No.1, No.2, No.5) has the same amount of solid lubricant, but compared to a comparative material (sintered body No.3, MnS amount: 10%) that does not undergo ball milling. Both wear resistance and crushing strength are improved. In addition, the comparative example (sintered body No. 3, MnS amount: 10%) without increasing the amount of solid lubricant particles without ball milling is the conventional solid lubricant amount (MnS amount: 2%). Compared to the example (conventional example: sintered body No. 4), the wear resistance is improved, but the crushing strength is reduced.

  In addition, a sintered body (invention example) obtained by blending iron-base powder (iron-base powder for raw material powder) that has been subjected to ball milling by blending iron-base powder and solid lubricant particle powder is a solid lubricant. It has a structure having a dispersed region in which the agent particles are finely dispersed in the matrix phase. In contrast, in the sintered body using the iron-based powder not subjected to the ball mill treatment (comparative example, sintered body No. 3), the solid lubricant particles aggregated at the boundary of the base phase (base grain). Presents an organization.

  Thus, it was found that the sintered body in which the matrix phase and the solid lubricant particles exhibit a dispersed region becomes a sintered body with significantly improved wear resistance without showing a significant decrease in the crushing strength. .

  Furthermore, the total amount to be blended as iron-based powder shall be iron-based powder (iron-based powder for raw material powder) obtained by ball milling of iron-based powder and solid lubricant particle powder (mixed powder No. B) As a result, it has been found that both the wear resistance and the crushing strength of the sintered body are increased even when the amount of the solid lubricant is the same as compared with the case where a part of the iron-based powder not subjected to the ball mill treatment is blended.

The present invention has been completed based on such findings and further studies. That is, the gist of the present invention is as follows.
(1) An iron-based sintered alloy material for a sliding member having a structure containing a matrix phase and solid lubricant particles or hard particles, the solid lubricant particles being 4.0% to 20.0% by mass. %, And the structure is a structure containing a dispersion region in which the solid lubricant particles are dispersed in the matrix phase and having a surface area ratio of 25% or more with respect to the entire structure excluding hard particles. An iron-based sintered alloy material for sliding members that combines high wear resistance and excellent crushing strength.
(2) The iron-based sintered alloy for a sliding member according to (1), wherein the dispersion degree of the solid lubricant particles in the dispersion region is 0 to 20% and the standard deviation is 3.5 or less. Wood.
(3) The iron-based sintered alloy material for a sliding member according to (1) or (2), wherein the solid lubricant particles are any of MnS particles, CaF ₂ particles, and talc.
(4) An iron-based sintered alloy material for a sliding member according to any one of (1) to (3), wherein the hard particles are contained in an amount of 5 to 65% by mass.
(5) In any one of (1) to (4), the hard particles are Co-based intermetallic compound particles, carbide-based hard particles, Fe-Mo-based intermetallic particles having a Vickers hardness of 500 to 1400 HV. An iron-based sintered alloy material for a sliding member, which is any one of compound particles.
(6) In any one of (1) to (5), the composition of the base part containing the base phase and the solid lubricant particles is in mass%, and contains C: 0.2 to 2.0%, S, Mn , Ni, Cr, Mo, Cu, Co, W, or V, containing a total of 40% or less of one or more selected from the group consisting of Fe and unavoidable impurities Iron-based sintered alloy material for sliding members.
(7) The iron-based sintered alloy material for a sliding member according to any one of (1) to (6), wherein the sliding member is a valve seat.

  According to the present invention, it is possible to easily and inexpensively manufacture an iron-based sintered alloy material for a sliding member such as a valve seat for an internal combustion engine, which is excellent in wear resistance, without being accompanied by a decrease in the crushing strength. Has an exceptional effect.

It is a microscope picture which shows an example of the dispersion | distribution area | region in the sintered compact obtained by using the iron base powder for raw material powders obtained by performing a ball mill process for pure iron powder and solid lubricant particle powder. (A) Iron-based powder No. a0, (b) Iron-based powder No. b0, (c) Iron-based powder No. d0. It is explanatory drawing which shows typically the outline | summary of the abrasion tester used for evaluation of abrasion resistance in an Example. It is explanatory drawing which shows typically the influence of the particle size of an iron-base powder and the amount of solid lubricant particles which has on the dispersion state (dispersion area | region) of a solid lubricant particle. It is a metallographic photograph which shows an example of the structure | tissue of the iron-based sintered alloy material obtained in the Example.

  The iron-based sintered alloy material (sintered body) for a sliding member of the present invention has a structure including a matrix phase and solid lubricant particles or hard particles, and the solid lubricant particles are contained in a mass% of 4.0 to Contains 20.0%. In addition, when containing hard particles, it is preferable to contain 5-65% by the mass% in a sintered compact. And the base part which consists of a base phase and a solid lubricant particle is the mass%, contains C: 0.2-2.0%, and is from among S, Mn, Ni, Cr, Mo, Cu, Co, W, V It is desirable to have a base composition composed of the balance of Fe and unavoidable impurities, including a total of 40% or less of one or more selected.

C: 0.2-2.0 mass%
C is an element having an action of increasing the strength and hardness of the sintered body and facilitating the diffusion of metal elements during sintering. In order to obtain such an effect, the content of 0.2% by mass or more is required. On the other hand, when the content exceeds 2.0% by mass, cementite is likely to be generated in the matrix, and a liquid phase is likely to occur during sintering, resulting in a decrease in dimensional accuracy. For this reason, C was limited to the range of 0.2 to 2.0 mass%. In addition, Preferably it is 0.4 mass% or more, More preferably, it is 0.8-1.4 mass%.

One or more selected from S, Mn, Ni, Cr, Mo, Cu, Co, W, and V: 40% by mass or less in total
S, Mn, Ni, Cr, Mo, Cu, Co, W, and V are all elements that increase the strength and hardness of the sintered body and further improve the wear resistance. In order to obtain such an effect, it is desirable to select at least one kind including the origin of the iron-based powder and the origin of the solid lubricant and to contain 0.5% by mass or more in total. On the other hand, when it contains exceeding 40 mass%, a moldability will fall and mechanical strength will also fall. Therefore, one or more selected from S, Mn, Ni, Cr, Mo, Cu, Co, W, and V are limited to a total range of 40% by mass or less. In addition, Preferably it is 2-10 mass%.

  In the base portion of the sintered body made of the base phase and the solid lubricant particles, the remainder other than the above components is made of Fe and inevitable impurities.

The sintered body for a sliding member of the present invention (iron-based sintered alloy material) has the above-described base part composition, and removes hard particles from a dispersed region (structure) in which solid lubricant particles are dispersed in the base phase. It has a structure containing 25% or more in area ratio with respect to the whole structure, and has a density: 6.3 g / cm ³ or more and a crushing strength: 45 MPa or more.

  If the total amount of the dispersed regions is less than 25% in terms of the area ratio with respect to the entire structure excluding the hard particles, the solid lubricant particles are unevenly distributed and a desired crushing strength cannot be ensured. In addition, the area ratio of a dispersion | distribution area | region is determined by the compounding quantity of the iron-base powder for raw material powder which performed the ball mill process. For this reason, the dispersion region is limited to 25% or more in terms of the area ratio with respect to the entire structure excluding hard particles.

  Further, in the iron-based sintered alloy material for sliding members of the present invention, in the dispersion region having the area ratio in the above range, the solid lubricant particles present in the dispersion region have a dispersity of 0 to 20%. And the standard deviation is 3.5 or less. When the degree of dispersion of the solid lubricant particles present in the dispersion region exceeds 20%, the density and the crushing strength decrease. Further, when the standard deviation of the dispersity is larger than 3.5, the dispersion of the solid lubricant particles is not uniform and unevenly distributed, and it is not possible to secure excellent wear resistance and superior crushing strength as compared with the prior art.

  The “dispersion degree of the solid lubricant particles” as used herein designates an arbitrary range of 100 × 100 μm in the dispersion region, and the range is divided into five parts equally in the vertical and horizontal directions. Measured area ratio of solid lubricant particles in each section in a total of 25 sections, and divided the area ratio in each section obtained by the area ratio of all sections (sum of area ratio in each section). (%). Therefore, 0% is obtained when no solid lubricant particles are present in the compartment. Then, the standard deviation of the degree of dispersion in each obtained section (total of 25 sections) is obtained. When the standard deviation of the dispersion degree exceeds 3.5, the dispersion of solid lubricant particles is uneven and unevenly distributed.

  The sintered body having such a structure can disperse a large amount of solid lubricant particles having excellent sliding characteristics and finely in the base of the sintered body, resulting in a decrease in the crushing strength. The wear resistance is remarkably improved without any problems.

  Next, a preferred method for producing the iron-based sintered alloy material for sliding members of the present invention will be described.

  In a preferred method for producing an iron-based sintered alloy material for a sliding member of the present invention, first, a solid lubricant powder excellent in sliding properties is first blended with a base-forming iron-based powder used as a raw material powder, A ball mill treatment is performed to prepare an iron-based powder for raw material powder. Here, as the iron-based powder for forming the base, pure iron powder, alloy steel powder having an alloy element amount of 5% by mass or less, Cr steel powder, etc. can be exemplified, and in the present invention, depending on the desired base composition, You can select and apply. In particular, it is preferable to use atomized pure iron powder from the viewpoint of improvement of crushing strength and manufacturing cost.

  In the present invention, the solid lubricant particle powder is mixed with the iron-base powder in a predetermined amount and is previously subjected to the above-described ball mill treatment and included in the iron-base powder for raw material powder. When the solid lubricant particle powder not subjected to the ball mill treatment is blended, the aggregation is remarkable, the diffusion of elements in the sintering treatment is inhibited, the generation of ferrite is promoted, and the property improvement corresponding to the content cannot be expected.

  The iron-base powder for raw material powder obtained by such treatment is blended as a part or all of the iron-base powder for base formation. When the iron-based powder for raw material powder obtained by the ball mill treatment is blended as part of the iron-based powder for base formation, the above-mentioned treatment is not performed, for example, formation of a base such as iron powder as atomized Needless to say, the iron-based powder for use is blended.

  The average particle size of the base-forming iron-based powder to be used is not particularly limited, but affects the structure of the obtained iron-based powder for raw material powder. The smaller the particle size of the iron-based powder, the finer the solid lubricant particles are dispersed in the matrix phase. However, the smaller the particle size of the iron-based powder, the lower the fluidity of the mixed powder, leading to a decrease in productivity. For this reason, in order to finely disperse the solid lubricant particles in the matrix phase, the average particle diameter of the iron-based powder is in the range of 30 to 150 μm, corresponding to the particle diameter of the solid lubricant particles. It is preferable.

  FIG. 3 schematically shows the influence of the particle size of the iron-based powder and the amount of solid lubricant particles on the dispersion state of the solid lubricant particles after the ball mill treatment. When the particle size of the iron-based powder is larger than that of the solid lubricant particle powder and the amount of the solid lubricant particle is large, a large amount of solid lubricant particles existed between the iron-based powder particles in the conventional kneading. In contrast to the dispersion state, when the ball mill treatment is performed as in the present invention, a solid dispersion particle (structure) in which the solid lubricant particles are dispersed in the base phase due to the iron-based powder is shown. When the amount of solid lubricant particles is small, the thickness of the dispersed solid lubricant particles becomes thin. On the other hand, when the particle size of the iron-based powder is reduced to a particle size comparable to that of the solid lubricant particles, a dispersed region (structure) in which the solid lubricant particles are finely dispersed in the matrix phase is exhibited. FIG. 3 also shows an example of an optical micrograph of the powder cross section after the ball mill treatment.

  In the present invention, iron-base powder (iron-base powder for raw material powder) that has been subjected to the ball mill treatment as described above is used as part or all of the base-forming iron-base powder. Thereby, both the crushing strength and the wear resistance of the obtained sintered body are significantly improved.

  In the present invention, the apparatus used for the ball mill treatment is not particularly limited, and any known ball mill treatment apparatus such as a vibration ball mill or a planetary ball mill can be applied.

  If the ball mill treatment is performed, the powder having sufficient desired structure (iron-based powder for raw material powder) can be obtained by the treatment within 8 hours. Here, the “desired structure” refers to a structure in which a dispersed region (structure) in which solid lubricant particles are dispersed in a matrix phase derived from an iron-based powder occupies the entire region. Note that the longer the treatment time, the greater the proportion of the dispersed region in which the solid lubricant particles are finely dispersed in the matrix phase. In addition, the treatment for a long time exceeding 8 hours is not preferable because the powder becomes fine and is easily activated. For this reason, it is preferable to limit the processing time of the ball mill process to 8 hours or less.

  The amount of the solid lubricant particle powder to be blended is not particularly limited when the ball mill treatment is performed, but the amount of the solid lubricant particle necessary when it becomes a sintered body can be easily supplied. It is preferable to use a fixed amount.

  In the present invention, the iron-base powder (iron-base powder for raw material powder) that has been subjected to the ball mill treatment as described above is used as part or all of the base-forming iron-base powder to obtain a mixed powder. By using such a mixed powder, both the crushing strength and the wear resistance of the obtained sintered body are significantly improved.

  In the present invention, the iron-based powder subjected to ball milling (iron-based powder for raw material powder) is 25% or more by mass% with respect to the total amount of the iron-based powder for forming the base phase, and is sintered. And blended so as to contain 4.0 to 20.0% by mass of solid lubricant particles. The amount of iron-based powder that has been ball milled (iron-based powder for raw material powder) is mass% based on the total amount of iron-based powder for forming the base phase. The blending amount of the powder (iron-based powder for raw material powder) is small, and it is difficult to form a structure having a desired dispersion region, and the desired crushing strength and wear resistance as a sintered body cannot be ensured.

  On the other hand, if the solid lubricant particles are in mass% in the sintered body and less than 4.0%, the amount of solid lubricant particles is insufficient, and the desired wear resistance of the sintered body cannot be ensured. On the other hand, if it exceeds 20.0%, the amount of solid lubricant particles in the sintered body becomes too large, and the crushing strength decreases. For this reason, it is preferable to mix | blend so that the compounding quantity of solid lubricant particle powder may be 4.0-20.0% by the mass% with respect to the whole quantity of a sintered compact.

Examples of the solid lubricant particle powder include MnS powder, CaF ₂ powder, talc, etc., and any of them can be applied according to desired characteristics, but in particular from the viewpoint of wear resistance and manufacturing cost, MnS powder should be used. Is preferred.

  Needless to say, the mixed powder is further mixed with an alloy powder or a hard particle powder in addition to these base-forming iron-based powders so as to have a desired sintered body composition. Examples of alloy powders blended into the mixed powder as one of the raw material powders include graphite powder, Ni powder, Co powder, and Cu powder. The blending amount of the alloy powder is the base part in the desired sintered body. It determines suitably so that it may become a composition.

  In the present invention, the hard particle powder blended in the mixed powder as one of the raw material powders may be any one of Co-based intermetallic compound particle powder, carbide-based hard particle powder, and Fe-Mo-based intermetallic compound particle powder. preferable.

  As Co-based intermetallic compound particles, the hardness is 950 to 1150 HV in terms of Vickers hardness, 0.5 to 4.0% Si-15 to 35% Cr-15 to 35% Mo-5 to 20% Ni- Co-based intermetallic compound particles having a composition comprising the balance Co have a composition of 0.5 to 4.0% Si-5.0 to 20% Cr-20 to 40% Mo-balance Co having a Vickers hardness of 650 to 850 HV. Co-based intermetallic compound particles having a hardness of 950 to 1150 HV in terms of Vickers hardness, 2.0 to 5.0% Si-3.0 to 10.0% Cr-3.0 to 15.0% Fe-35.0 to 47.0% Mo-balance Examples thereof include Co-based intermetallic compound particles having a composition of Co.

  Further, as the carbide-based hard particles, the hardness is 500 to 700 HV in terms of Vickers hardness, 0.2% to 2.0% C-2 to 10% Cr-2 to 10% Mo-2 to 10% W- in mass%. Examples thereof include carbide-based hard particles having a composition of 0.2 to 5.0% V-balance Fe. Moreover, as Fe-Mo type | system | group intermetallic compound particle | grains, the Fe-Mo type | system | group intermetallic compound particle | grains which have a composition which consists of 40-70% Mo- remainder Fe whose hardness is 1000-1400HV by Vickers hardness can be illustrated. Among these, a Co-based intermetallic compound powder having a Vickers hardness of 950 to 1150 HV is more preferable from the viewpoint of wear resistance.

  In addition, it is preferable to mix | blend with powder mixture so that the compounding quantity of hard particle powder may be 5 to 65% by the mass% in a sintered compact. When the blending amount of the hard particle powder is less than 5% by mass% in the sintered body, it becomes difficult to ensure desired wear resistance. On the other hand, if it is more than 65% by mass% in the sintered body, the mechanical strength of the sintered alloy material is lowered. For this reason, it is preferable that the compounding amount of the hard particles is 5 to 65% by mass% in the sintered body.

Next, the mixed powder blended as described above is filled in a mold, and then compressed and molded by a molding press or the like to obtain a green compact with a predetermined density. The density of the green compact need not be particularly limited, but is preferably 6.3 g / m ³ or more from the viewpoint of securing a desired sintered body density. Next, the obtained green compact is heated and sintered in a temperature range of 1100 to 1200 ° C. in a protective atmosphere such as ammonia decomposition gas and vacuum to obtain an iron-based sintered alloy material.

  In addition, although 1P1S process which performs shaping | molding P and sintering S once may be sufficient, it is more preferable to set it as 2P2S process which repeats shaping | molding P and sintering S twice. Moreover, it is good also as 1F1S process which replaces with press forming and sets it as the forging F.

The iron-based sintered alloy material (sintered body) obtained by the preferred manufacturing method described above has the above-described composition and the above-described structure, density: 6.3 g / cm ³ or more, and crushing strength: 45 MPa or more. Thus, a sintered body with significantly improved wear resistance is obtained without causing a reduction in the crushing strength.

  In the present invention, the iron-based sintered alloy material described above can be used as a sliding member such as a valve seat for an internal combustion engine having a predetermined size and shape by processing such as cutting and grinding.

  Hereinafter, the present invention will be described based on examples.

  Atomized pure iron powder or carbonyl pure iron powder as the base-forming iron-based powder and MnS particle powder as the solid lubricant particle powder are mixed in the amounts shown in Table 4 and charged into the processing container of the mill. A ball mill treatment was performed to obtain an iron-based powder (MA powder) for raw material powder. The ball mill treatment was performed using a mill having the same principle as that of the apparatus described in Japanese Patent No. 3486682. In addition, the rotation speed of the processing container was 800 rpm, and the processing time of the ball mill processing was 2 h. Note that pure iron powder (atomized pure iron powder) and alloy steel powder not subjected to ball mill treatment were also prepared as iron-base powders for base formation. The average particle size of each powder was measured by a laser diffraction method.

  Next, alloy powder, hard particle powder, or base formation iron base powder is further blended in the types and amounts shown in Table 5 and mixed in a V-type mixer to the prepared iron powder for raw powder. Kneaded to obtain a mixed powder. The blending amount is shown in mass% with respect to the total amount of the mixed powder. In some cases, the solid lubricant powder was blended into the mixed powder as it was.

  The hardness of the hard particle powder is measured in accordance with JIS Z 2244, with five or more particles measured at a load of 100 gf, and the average value is shown as the hardness HV of the hard particle powder.

  Subsequently, these mixed powders were filled into a mold and compressed and molded by a molding press to obtain a green compact having the density shown in Table 6. Subsequently, these green compacts were sintered in a protective atmosphere under the conditions shown in Table 6 to obtain iron-based sintered alloy materials. The forming / sintering process was a 1P1S process.

  A sample for analysis was collected from the obtained iron-based sintered alloy material (sintered body), and the content of each element was determined by quantitative analysis using X-rays with respect to the base part to obtain a base part composition. The base part structure refers to a composition composed of a base phase and solid lubricant particles. In addition, a specimen for tissue observation is collected from the obtained sintered body, polished, and observed with an optical microscope (magnification: 100 to 500 times). did. From the obtained structure photograph, the dispersion state of the matrix phase and the solid lubricant particles and the fraction of each structure were calculated by image processing.

  That is, for the obtained sintered body, first, the structure fraction of the dispersed region in which the solid lubricant particles were dispersed in the matrix phase was determined by the area ratio with respect to the entire structure excluding the hard particles. Here, “the entire structure excluding hard particles” means the entire matrix phase derived from the iron-based powder. Next, for each of these dispersed regions, the range of 100 × 100 μm was equally divided into 5 parts vertically and horizontally, and the area ratio of the solid lubricant particles was determined in each of the divided sections (25 sections in total). The area ratio was divided by the area ratio of all the sections (the sum of the area ratios in each section) to obtain the degree of dispersion (%) of the solid lubricant particles in the sections. And the standard deviation value of the dispersion degree in all the obtained divisions was calculated | required. For the sintered body in which no dispersion region was observed, the dispersity and the standard deviation value of the dispersity were similarly obtained and used as reference values.

  One example of the structure of the obtained iron-based sintered alloy material (sintered body) (sintered body No. 11, No. 12, No. 13, No. 21) is shown in FIG.

  Moreover, a test piece was collected from the obtained sintered body, and the density was measured by the Archimedes method.

  In addition, a test piece was collected from the obtained sintered body in accordance with the provisions of JIS Z 2507, and the crushing strength was measured.

  Further, the obtained sintered body is cut and ground into a valve seat (size and shape: outer diameter 27.1 mmφ × inner diameter 22.0 mmφ × height 6.5 mm), and the unit rig testing machine shown in FIG. 2 is used. A single rig wear test was conducted to evaluate the wear resistance. The test method is as follows.

  After the valve seat 1 was press-fitted into the jig 2 corresponding to the cylinder head, the valve 4 was moved up and down by the crank mechanism while the valve 4 and the valve seat 1 were heated by the heat source 3 mounted on the testing machine, and the test was performed. In addition, the amount of wear of the valve seat was measured after the test. The test conditions were as follows.

Test temperature: 300 ° C (sheet surface)
Test time: 4.5h
Cam rotation speed: 3000rpm
Valve speed: 20rpm
Spring load: 35kgf (345N) (when set)
Lift amount: 7mm
The results obtained are shown in Table 6.

  In all of the examples of the present invention, the desired structure is formed, the crushing strength is 45 MPa or more, the wear amount is small, and the crushing strength is significantly reduced as compared with the same solid lubricant particle amount. Wear resistance is improved. On the other hand, in the comparative example outside the scope of the present invention, the desired dispersion region (structure) is not formed, and the crushing strength is reduced or the wear resistance is reduced.

1 Valve seat 2 Jig 3 Heat source 4 Valve

Claims (7)

An iron-based sintered alloy material for a sliding member having a structure including a matrix phase and solid lubricant particles or hard particles,
The solid lubricant particles contain 4.0 to 20.0% by mass,
Excellent wear resistance characterized in that the structure is a structure containing a dispersion region in which the solid lubricant particles are dispersed in the matrix phase in an area ratio of 25% or more with respect to the entire structure excluding hard particles. An iron-based sintered alloy material for sliding members that combines excellent crushing strength.   2. The iron-based sintered alloy material for a sliding member according to claim 1, wherein a dispersion degree of the solid lubricant particles in the dispersion region is 0 to 20% and a standard deviation thereof is 3.5 or less. The iron-based sintered alloy material for a sliding member according to claim 1 or 2, wherein the solid lubricant particles are any one of MnS particles, CaF ₂ particles, and talc.   The iron-based sintered alloy material for a sliding member according to any one of claims 1 to 3, wherein the hard particles are contained in an amount of 5 to 65% by mass.   The hard particles are any one of Co-based intermetallic compound particles, carbide-based hard particles, and Fe-Mo-based intermetallic compound particles having a Vickers hardness of 500 to 1400 HV. The iron-based sintered alloy material for sliding members according to any one of 4 to 4.   The composition of the matrix part including the matrix phase and the solid lubricant particles is in mass%, C: 0.2 to 2.0%, S, Mn, Ni, Cr, Mo, Cu, Co, W, V 6. The sliding member according to claim 1, comprising one or two or more selected from among a total of 40% or less and having a composition composed of the remaining Fe and unavoidable impurities. Iron-based sintered alloy material.   The iron-based sintered alloy material for a sliding member according to any one of claims 1 to 6, wherein the sliding member is a valve seat.