JP2004076136A - Sliding member and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sliding member which exhibits excellent seizure resistance, wear resistance or the like. <P>SOLUTION: At least a part of the sliding member is provided with a sliding part formed by dispersing an Fe-W phase consisting of Fe and W and an Fe-S phase consisting of Fe and S into a base material consisting of Fe or an Fe alloy. The Fe-S phase and Fe-W phase are hard, and at least the Fe-S phase has excellent slidability as well. The sliding member exhibits excellent seizure resistance and wear resistance. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sliding member having excellent seizure resistance, abrasion resistance, strength, and the like, and a method for manufacturing the same.
[0002]
[Prior art]
From the viewpoints of weight reduction, high performance, recycling, and the like, various members are shifting from Fe-based materials to light metals such as Al alloys and Mg alloys. However, instead of using the alloy material as a whole, for various reasons such as strength, rigidity, slidability, and durability, a composite material or a partially dissimilar material may be cast. Many.
For example, in the case of a cylinder block of an engine that is a sliding member, a cast iron sleeve has been cast into a cylinder liner that becomes a sliding portion even if the exterior part is a die-cast molded product of an Al alloy. . However, such a cast iron sleeve is heavier than the Al alloy and has poor thermal conductivity. In addition, interfacial peeling and the like also occurred with the Al alloy, which was not always preferable.
[0003]
Japanese Patent Application Laid-Open No. 2000-204454 discloses that a preform made of ceramic fiber is cast into a cylinder liner portion which is a sliding portion to form a metal matrix composite material (MMC).
It has also been considered to cast a porous sintered body obtained by sintering an Fe-based powder into a liner portion thereof. For example, JP-A-63-319947, JP-A-3-189063, JP-A-3-189066, and JP-A-3191665 have disclosures related thereto. Japanese Patent Application Laid-Open No. Hei 8-332562 discloses a sliding member in which an Fe-based sintered body is inserted into the vicinity of a piston ring of a piston serving as a sliding portion, not a cylinder liner portion. Further, as a general sliding member such as a bush, an Fe-based sintered body is disclosed in JP-A-60-8293.
[0004]
[Problems to be solved by the invention]
As described above, various sliding members have been conventionally proposed, but none of them is necessarily sufficient in terms of seizure resistance, wear resistance, strength, and the like.
The present invention has been made in view of such circumstances. That is, an object of the present invention is to provide a new sliding member having excellent seizure resistance, wear resistance, strength, and the like. It is another object of the present invention to provide a manufacturing method thereof.
[0005]
Means for Solving the Problems and Effects of the Invention
Therefore, the present inventor has conducted intensive research to solve this problem, and through repeated trial and error, the Fe-based sintered body obtained by sintering the Fe powder and the WS ₂ powder has been found to exhibit seizure resistance and wear resistance. Newly found to be excellent. The present invention has been completed based on this finding and further developing it.
(Sliding member)
That is, the sliding member of the present invention has at least a sliding portion in which the Fe-W phase composed of Fe and W and the Fe-S phase composed of Fe and S are dispersed in the base material composed of Fe or Fe alloy. It is provided in a part (claim 1).
This sliding member exhibits excellent seizure resistance, wear resistance, strength, and the like. The reason is not always clear, but at present it is considered as follows.
At least in the sliding portion, it is considered that the seizure resistance and the like have been improved because the Fe-S phase having excellent slidability is dispersed in the base material. In addition, since the hard Fe-S phase and the Fe-W phase are dispersed in the base material, it is considered that the wear resistance and the strength of the sliding portion are improved.
[0006]
The "Fe-W phase" mentioned here is sufficient if it is a (intermetallic) compound of Fe and W, and its composition is not limited to FeW. Similarly, the “Fe—S phase” is only required to be a compound of Fe and S, and its composition is not limited to FeS.
The term “sliding member” as used in the present specification includes, but is not limited to, a single product that requires slidability and wear resistance, such as a bearing such as a bush, a cylinder sleeve, and a ring groove member of a piston. . That is, members, devices, and the like incorporating these sliding members (single parts) also correspond to the sliding members in the present invention. For example, a cylinder block in which a cylinder sleeve (also a sliding member of the present invention) is cast, a piston in which a ring groove member is cast, and the like are also included in the sliding member of the present invention. In other words, at least a part of the finished product having a part (sliding part) that can be a sliding surface is a sliding member according to the present invention.
[0007]
(Method of manufacturing sliding members)
In the sliding member of the present invention, the finer and more uniform the dispersion of each phase in the base material, the more preferable. However, the specific dispersion form and dispersion method are not limited. For example, in advance, a powder to be an Fe-W phase and a powder to be an Fe-S phase are mixed in an Fe-based powder as a base material, and the mixed powder is sintered and the like, and each of the powders is added to the base material. The phase may be dispersed (premixing method). In addition, Fe, W, and S, which are constituent elements of each phase, are given in a form different from each phase to be formed, and a reaction between Fe and W during heating and a reaction between Fe and S cause Fe- The W phase or the Fe-S phase may be precipitated in the substrate (in-situ method).
[0008]
Of course, not only the sintering method, but also the respective phases may be dispersed and precipitated by a melting method. However, by using a powder metallurgy method such as a sintering method, it is easy to form a sliding portion in which each phase is finely dispersed. Further, the (near) net shape of the sliding member can be achieved.
Accordingly, the present invention provides a filling step in which a mixed powder obtained by mixing a base powder made of Fe powder and / or an Fe alloy powder and a reinforcing powder containing WS ₂ powder is filled in a molding die; It comprises a molding step of forming a powder compact by pressing, and a sintering step of heating the powder compact to form a sintered body, wherein Fe in the base powder and W in the reinforcing powder react. A sliding portion in which the Fe-W phase formed and the Fe-S phase formed by the reaction of Fe in the base powder and S in the reinforcing powder are dispersed in a base made of Fe or an Fe alloy The manufacturing method of the sliding member which can obtain the sintered body (Fe-based sintered body) provided at least in part (claim 6).
[0009]
The Fe-based sintered body here is not limited to a porous body, but by adjusting the pressing force during the forming step, an Fe-based porous sintered body can be easily obtained.
A cast member (sliding member) in which an Fe-based porous body is cast can be obtained by the following manufacturing method.
That is, an Fe-based porous body having at least a part of a sliding part in which a Fe-W phase composed of Fe and W and a Fe-S phase composed of Fe and S are dispersed in a substrate composed of Fe or an Fe alloy. Is a method for manufacturing a sliding member comprising a casting step of casting a sliding member.
[0010]
A representative example of the Fe-based porous body here is the above-described Fe-based porous sintered body, but may not be a sintered body. The casting step may be gravity casting, but high pressure casting such as die casting or molten metal forging is preferable because the impregnation of the molten metal into the Fe-based porous body becomes easy.
The sliding member of the present invention described above is not limited to one obtained by the sintering method, but may be one obtained by a melting method or the like.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in more detail with reference to embodiments. In addition, the content described below appropriately applies to any of the sliding member according to the present invention and the manufacturing method thereof.
(1) Structure of Sliding Part The sliding part according to the present invention is, as described above, formed by dispersing the Fe-W phase and the Fe-S phase in the Fe-based substrate.
The Fe-W phase is a compound having a composition such as FeW, FeW ₂ , Fe ₂ W, and Fe ₃ W ₂ . When the Fe-W phase is dispersed in the substrate in an amount of 0.1 to 10% by volume, and more preferably 1 to 5% by volume, it is preferable to improve wear resistance and strength. If the amount is too small, the effect is weak, and if it is too large, the opponent's aggressiveness is increased, which is not preferable.
FeS phase, for _example, FeS, is FeS _2, Fe 2 S, compounds having a composition such as Fe ₃ S. When the Fe-S phase is dispersed in the substrate in an amount of 0.1 to 20% by volume, and more preferably 2 to 10% by volume, it is preferable to improve seizure resistance and the like. If the amount is too small, the effect is thin, and if it is too large, the toughness is undesirably reduced.
[0012]
It is preferable that any of the phases is finely and uniformly dispersed in the base material, because seizure resistance, seizure resistance, strength, and the like can be improved, and falling off from the base material can be prevented. Specifically, the average particle size of each phase is preferably 50 μm or less, more preferably 10 μm or less.
The substrate may be pure Fe, but preferably contains various elements in appropriate amounts in order to improve the slidability and strength. Such elements include C, Mo, Cr, V, Mn, Cu, S, Ni, Co, W and the like. C enhances the solid solution of the base material, but when it is precipitated as graphite (graphite), the slidability can be further improved.
[0013]
(2) Form of Sliding Section The sliding section is preferably made of an Fe-based porous body. In the case of a porous body, by adjusting the porosity, not only the weight, strength and the like can be adjusted, but also the use is expanded. For example, when the sliding surface is made of a porous material, fine pores on the surface serve as oil reservoirs, which can contribute to improvement in slidability. When casting (inserting) an Fe-based porous body, the molten metal is impregnated into the porous body, so that the porous body is firmly fixed in the casting by an anchor effect. Further, when the porous body is densely impregnated with the molten metal by, for example, high-pressure casting or the like, the heat transfer between them is improved.
It should be noted that the “porous body” referred to in the present specification does not need to be a completely porous body as a whole, but it is sufficient if at least a part thereof has a porous portion. For example, in some cases, it is preferable not to make the specific surface porous to prevent leakage of the impregnated molten metal.
[0014]
A typical example of a cast member in which such an Fe-based porous body is cast is a cylinder block. That is, by casting a cylindrical Fe-based porous body, an engine cylinder block (casting member) having an inner peripheral surface of the Fe-based porous body as a cylinder liner serving as a sliding surface is obtained. At this time, if the cylinder block is made of a light metal such as an Al alloy or a Mg alloy, it is possible to achieve both a reduction in the weight of the cylinder block as a whole and slidability in the cylinder liner.
[0015]
(3) Manufacturing Method By using the sintering method as described above, such a Fe-based porous body can easily be manufactured with a desired porosity.
The raw material powder used at that time comprises, for example, a base powder and a reinforcing powder. The base powder is Fe powder or Fe alloy powder as described above. The reinforcing powder is one or more of a W powder, a W alloy powder, a W compound powder, an S powder, a sulfide powder, and a compound powder of W and S. With WS ₂ powder strengthening powder, which is efficient because the W and S can be supplied at a time. The WS ₂ powder, for example, the whole of the mixed powder is taken as 100 mass%, 2-15 mass%, further may contain from 3 to 9 wt% preferred. If the amount is too small, the effects such as abrasion resistance and seizure resistance are thin, and if the amount is too large, the toughness decreases.
[0016]
Each powder may be an atomized powder, a reduced powder, or the like, and may have any particle shape. However, in consideration of producing an Fe-based porous sintered body, it is difficult to handle fine powder having a particle size that is too small. On the other hand, if the particle size is too large, it is difficult to finely and uniformly disperse each phase. Therefore, for example, it is preferable to use a powder having a particle size of about 1 to 200 μm. In particular, WS ₂ powder is preferably used 1~10μm powder.
It is preferable that the mixed powder appropriately contain a binder, a graphite powder, and the like. The binder may be a resin or wax, or a molding lubricant such as stearic acid or a stearic acid salt (eg, zinc stearate or lithium stearate).
[0017]
Since the molding pressure in the molding step varies depending on the desired porosity, the type of the added particles such as the binder and graphite, the mold surface roughness, and the like, it cannot be specified unconditionally. For example, when the volume ratio of the metal powder in the powder compact is 60 to 70% by volume, the molding pressure may be about 100 to 200 MPa.
The sintering step must be at a temperature at which the substrate powder sinters at least. Further, in this sintering step, the particles in the base powder and the particles in the reinforcing powder are sintered or a Fe-W phase or an Fe-S phase is formed by the reaction. Therefore, for example, it is preferable that the sintering temperature be 1000 to 1300 ° C.
[0018]
【Example】
Next, the present invention will be specifically described with reference to examples.
(Example 1)
An Al alloy engine block in which a cylinder sleeve made of an Fe-based porous sintered body was cast was manufactured as follows.
(1) producing the cylinder sleeve First, as raw materials, Fe powder: the (pure iron Kawasaki Steel Co. KIP240M), and WS ₂ powder (Nippon lubricant Ltd. Tanmikku, average particle size 1 [mu] m), and graphite (C), It was prepared with zinc stearate as a binder. These were mixed with a ball mill for 1 hour to obtain a mixed powder. The amount of this time, graphite: 1%, zinc stearate: 3%, WS ₂ powder: 6% or 9%, the balance of Fe powder (unit: mass%, hereinafter the same).
[0019]
Next, this was naturally filled into a molding die (die) having a cylindrical cavity (filling step).
The mixed powder filled in the mold was pressed from above and below by a hydraulic press to obtain a cylindrical powder compact. At this time, the pressure was 100 MPa. The obtained powder compact had an outer diameter of 100.4 mm × a height of 58 mm × a plate thickness of 3 mm.
This powder compact was placed in an electric furnace and heated at 1100 ° C. for 0.5 hour in a nitrogen atmosphere to be sintered (sintering step). Thus, an Fe-based porous sintered body having a porosity (porosity) of about 40% by volume was obtained.
[0020]
(2) Manufacture of engine block The Fe-based porous sintered body was cast into an Al alloy (JIS ADC12) to manufacture an engine block. This casting was performed by die casting (casting step). The conditions of the die casting were a melt temperature of 680 ° C., a mold temperature of 250 ° C., a preheating of the formed body of 500 ° C., and a melt pressure of 65 MPa. The molten Al alloy had reached from the outer peripheral surface to the inner peripheral surface of the Fe-based porous sintered body.
The inner peripheral surface of the cylinder was finished by surface polishing.
[0021]
(Example 2)
(1) by using the raw material of Example 1 Fe-based porous sintered body, graphite: 0.7%, zinc stearate: 1% WS ₂ powder: in a proportion of Fe powder: 3%, and a balance Prepared mixed powder was prepared. The mixing method is the same as in Example 1.
As in Example 1, this mixed powder was filled in a mold and molded at 200 MPa. The obtained powder compact was heated and sintered at 1250 ° C. for 0.5 hour. The porosity of the thus obtained Fe-based porous sintered body was about 30% by volume.
[0022]
(2) Manufacture of engine block The Fe-based porous sintered body was cast into an Al alloy (JIS ADC12) to manufacture an engine block. This casting was performed by molten forging. The conditions for the molten metal forging were as follows: molten metal temperature: 680 ° C., mold temperature: 250 ° C., preheating of the molded body: 500 ° C., molten metal pressure: 100 MPa. Also at this time, the Al alloy melt had reached from the outer peripheral surface to the inner peripheral surface of the Fe-based porous sintered body.
And the inner peripheral surface of the cylinder was finished by honing.
[0023]
(Evaluation)
(1) Structure of Fe-based Porous Sintered Body The cross-sectional structure of the Fe-based porous sintered body of Example 1 was observed with a metallographic microscope and an X-ray microanalyzer (EPMA). FIGS. 1 and 3 show metal micrographs, and FIG. 2 shows the results of analysis of the structure by EPMA. 1 and 2 WS ₂ powder: is at 6% ones, 3 WS ₂ powder: is of 9%. FIG. 1A is a tissue photograph showing the dispersion state of each tissue, and FIG. 1B is a tissue photograph mainly showing an aggregated patchy tissue.
[0024]
From these photographs, WS ₂ many particles are decomposed to react with Fe of the base material powder, compound layer of Fe and W (Fe-W-phase) and the compound layer of Fe and S (Fe-S phase ). That is, the compound structure of Fe and W (white thin needles) forming a pearlite stripe pattern, the compound structure of Fe and S (light brown mass), and the patchy structure in which these structures are mixed are shown. Three species were observed. In addition, the existence rate of the patchy structure was rather low, and most of them were a lump or needle-like (or streak-like) having an average particle diameter of 10 μm or less, and a slightly cohesive structure was observed.
[0025]
Next, when the hardness of the cross-sectional structure portion (cylinder inner peripheral surface (liner) portion) was examined, the following results were obtained.
Coarse pearlite portion when blended WS ₂ powder 6%: 200~290MHv (25g)
Fine pearlite part: 190 to 280 MHv (25 g)
When ₂ % of WS2 powder is blended, coarse pearlite portion: 270 to 310 MHv (25 g)
Fine pearlite part: 190 to 280 MHv (25 g)
Coarse pearlite portion when not blended WS ₂ powder: 150~210MHv (25g),
Fine pearlite part: 180 to 230 MHv (25 g)
As described above, it has been found that the blending of the WS ₂ powder increases the hardness of the Fe portion and can improve the wear resistance and strength. In addition, it is considered that the reason why the hardness increased was that a reactant of W was formed in a thin portion in the Fe portion.
[0026]
(2) Seizure resistance of the cylinder block In order to examine the seizure of the sliding part (cylinder liner part) of the manufactured cylinder block, the following low-temperature scuff test was performed.
{Circle around (1)} The test conditions for Example 1 are as follows.
Experimental temperature: 70 ° C., load: 3 kgf (29.4 N), time: rotation until baking: 500 rpm, Hertz pressure: 20 kgf / mm ² (196 MPa)
Lubrication method: Gasoline engine oil is applied quantitatively (0.13 mg / cm ² )
Cylinder bore diameter: 96 mm (inner surface: surface polishing)
Piston ring diameter: φ96 mm, ring barrel diameter: 11.3 mm
[0027]
The above test was performed three times for each of the WS ₂ powder: 6% blend, the WS ₂ powder: 9% blend, and the WS ₂ powder not blended described in Example 1 above. Then, the time until the occurrence of seizure was measured for each test piece, and the average was determined, and the result was shown in FIG. As is clear from this graph, the seizure time is extended by blending the WS ₂ powder, and especially when WS _{2 is} 9 mass%.
FIG. 4 also shows the Vickers hardness of each cylinder liner (sliding surface). As is clear from this, the hardness is improved by blending the WS ₂ powder, and not only seizure resistance but also abrasion resistance can be expected to be improved.
[0028]
{Circle around (2)} The test conditions for Example 2 are as follows.
Experimental temperature: 70 ° C., load: 3 kgf (29.4 N), time: rotation until baking: 500 rpm, Hertz pressure: 20 kgf / mm ² (196 MPa)
Lubrication method: Diesel engine oil is applied quantitatively (0.13 mg / cm ² )
Cylinder bore diameter: φ96mm (inner surface: honing)
Piston ring diameter: φ96 mm, ring barrel diameter: 11.3 mm
[0029]
The above test was carried out twice for each of the WS ₂ powder: 3% compound described in the above Example 2, the compound containing various other powders instead of the WS ₂ powder, and the cast iron sleeve. . In this case, similarly, the time required for the occurrence of seizure was measured for each test piece, and the average was calculated, and the average was shown in FIG. As is clear from this graph, when the WS ₂ powder was blended, the seizure time was greatly extended as compared with the case where other powders were blended. In addition, the degree of the performance greatly exceeded that of the conventional cast iron sleeve.
[Brief description of the drawings]
Fe-based porous sintered body according to Example 1 of the present invention (WS ₂ powder: 6% formulation) A structural photograph by the metallurgical microscope, FIG. (A) is a dispersion state of the tissue (B) shows the aggregated patchy tissue.
[2] The Fe-based porous sintered body: a photograph showing the results of an analysis of tissues by EPMA of (WS ₂ powder 6% formulation).
[Figure 3] Fe-based porous sintered body according to Example 1 of the present invention (WS ₂ powder: 9% formulation) is a structural photograph by a metal microscope.
FIG. 4 is a graph showing seizure resistance and hardness of the cylinder block according to the first embodiment of the present invention.
FIG. 5 is a graph showing seizure resistance of a cylinder block according to Embodiment 2 of the present invention.

Claims (9)

At least one sliding portion is formed by dispersing a Fe—W phase composed of iron (Fe) and tungsten (W) and a Fe—S phase composed of Fe and sulfur (S) in a base material composed of Fe or an Fe alloy. A sliding member provided in a portion. The sliding member according to claim 1, wherein the sliding portion is made of an Fe-based porous body. The sliding member according to claim 2, comprising a cast member into which the Fe-based porous body is cast. The Fe-based porous body is cylindrical,
The sliding member according to claim 3, wherein the cast member is a cylinder block of an engine having an inner peripheral surface of the cast Fe-based porous body as a cylinder liner. The Fe-based porous body is an Fe-based porous sintered body obtained by sintering a mixed powder obtained by mixing a base powder made of Fe powder and / or Fe alloy powder and a reinforcing powder containing WS ₂ powder. Item 5. The sliding member according to any one of Items 2 to 4. A filling step of filling a mold with a mixed powder obtained by mixing a base powder composed of Fe powder and / or Fe alloy powder and a reinforcing powder containing WS ₂ powder;
Pressing the mixed powder in the mold to form a powder compact,
A sintering step of heating the powder compact to form a sintered body,
The Fe-W phase formed by the reaction of Fe in the base powder and W in the reinforcing powder and the Fe-S phase formed by the reaction of Fe in the base powder and S in the reinforcing powder Characterized by comprising the sintered body having at least a part of a sliding part dispersed in a base material made of Fe or an Fe alloy. The method for manufacturing a sliding member according to claim 6, wherein the mixed powder contains ₂ to 15% by mass of WS2 powder when the whole is 100% by mass. The method according to claim 6, wherein the mixed powder further includes a graphite powder and / or a binder. A Fe-based porous body having at least a part of a sliding part in which a Fe-W phase composed of Fe and W and a Fe-S phase composed of Fe and S are dispersed in a base material composed of Fe or Fe alloy is cast. A method for manufacturing a sliding member, comprising:

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