JP4232080B2 - Sliding member and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sliding member excellent in seizure resistance, wear resistance, strength, and the like, and a method for manufacturing the same.
[0002]
[Prior art]
From the viewpoint of weight reduction, high performance, recycling, and the like, various members are being shifted from those made of Fe-based materials to those made of light metals such as Al alloys and Mg alloys. However, instead of using the alloy materials as a whole, for various reasons such as strength, rigidity, slidability, and durability, it may be 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 in the cylinder liner that has become a sliding part, even though the exterior part is a die-cast molded product of an Al alloy. . However, such a cast iron sleeve is heavier than an Al alloy and has poor thermal conductivity. Moreover, interface peeling and the like occurred with the Al alloy, and this was not always preferable.
[0003]
Therefore, Japanese Patent Application Laid-Open No. 2000-204454 discloses that a ceramic fiber preform is cast into a cylinder liner portion that is a sliding portion to form a metal matrix composite material (MMC).
It is also considered that a porous sintered body obtained by sintering Fe-based powder is cast into the liner portion. For example, Japanese Patent Laid-Open No. 63-31947, Japanese Patent Laid-Open No. 3-189063, Japanese Patent Laid-Open No. 3-189066, Japanese Patent No. 3191665 have related disclosures. Further, although not a cylinder liner portion, a sliding member in which an Fe-based sintered body is inserted in the vicinity of a piston ring of a piston serving as a sliding portion is disclosed in JP-A-8-332562. Further, an Fe-based sintered body is disclosed in Japanese Patent Application Laid-Open No. 60-8293 as a general sliding member such as a bush.
[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 or strength.
The present invention has been made in view of such circumstances. That is, an object is to provide a new sliding member having excellent seizure resistance, wear resistance, strength, and the like. Moreover, it aims at providing the manufacturing method collectively.
[0005]
[Means for Solving the Problems and Effects of the Invention]
Therefore, the present inventor has eagerly studied to solve this problem, and while repeating trial and error, the Fe-based sintered body obtained by sintering Fe powder and WS ₂ powder has seizure resistance and wear resistance. It was found that it is superior to. The present invention has been completed by further developing it based on this finding.
(Sliding member)
That is, the sliding member of the present invention comprises tungsten (W), sulfur (S), carbon (C), the balance being iron (Fe) and unavoidable impurities, Fe—W phase consisting of Fe and W , Fe and W The Fe—S phase made of S is provided with at least a part of a sliding part dispersed in a base material made of Fe or an Fe alloy (Claim 1).
This sliding member exhibits excellent seizure resistance, wear resistance, strength, and the like. The reason is not necessarily clear, but it can be considered as follows.
At least in the sliding part, since the Fe—S phase having excellent slidability is dispersed in the base material, it is considered that the seizure resistance is improved. Moreover, since the hard Fe-S phase and Fe-W phase are also dispersed in the base material, it is considered that the wear resistance and strength of the sliding portion have been improved.
[0006]
The “Fe—W phase” 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” may be a compound of Fe and S, and the composition is not limited to FeS.
“Sliding member” as used in this specification includes bearings such as bushes, cylinder sleeves, ring groove members of pistons, etc., of course, including single items that require slidability and wear resistance, but are not limited thereto. . That is, a member or device incorporating these sliding members (single product) also corresponds to the sliding member referred to in the present invention. For example, a cylinder block in which a cylinder sleeve (which is 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 in the present invention. In short, any member having a portion (sliding portion) that can be a sliding surface in at least a part of the finished product is a sliding member in the present invention.
[0007]
(Sliding member manufacturing method)
In the sliding member of the present invention, it is preferable that the dispersion of each phase in the base material is fine and uniform. However, the specific dispersion form and dispersion method are not limited. For example, in advance, a Fe-W phase powder or a Fe-S phase powder is mixed in a Fe-based powder serving as a base material, and the mixed powder is sintered or the like. It is good also as a state which the phase disperse | distributed (premixing method). Further, Fe, W, and S, which are constituent elements of each phase, are given in a form different from that of each phase to be formed, and by reaction between Fe and W during heating and reaction between Fe and S, Fe— W phase or Fe-S phase may be precipitated in the substrate (in situ method).
[0008]
Of course, each phase may be dispersed and precipitated not only by the sintering method but also 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. Also, 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 Fe powder, WS ₂ powder, graphite powder, and a binder is filled in a molding die, and a molding step in which the mixed powder in the molding die is pressed to form a powder compact. And a Fe-W phase formed by reacting Fe in the Fe powder and W in the WS ₂ powder and the Fe powder. The sintered body comprising at least a part of a sliding portion in which Fe in the iron and Fe-S phase formed by reaction of S in the WS ₂ powder are dispersed in a base material made of Fe or an Fe alloy. It is good also as a manufacturing method of the sliding member from which (Fe-based sintered body) is obtained.
[0009]
The Fe-based sintered body here is not limited to a porous body, but an Fe-based porous sintered body can be easily obtained by adjusting the applied pressure during the molding process.
Moreover, the cast member (sliding member) which cast Fe-based porous body can be obtained by the following manufacturing method.
That is, an Fe-based porous body having at least a part of a sliding portion in which an Fe—W phase composed of Fe and W and an Fe—S phase composed of Fe and S are dispersed in a base material composed of Fe or an Fe alloy which is a method for producing a sliding member comprising a casting step of the sliding member by casting (claim 10).
[0010]
A typical example of the Fe-based porous body here is the aforementioned Fe-based porous sintered body, but it need not be a sintered body. The casting process may be gravity casting, but high pressure casting such as die casting or molten metal forging is preferable because the molten metal can be easily impregnated into the Fe-based porous body.
The sliding member of the present invention described above is not limited to that obtained by the above sintering method, but may be obtained by a melting method or the like.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in more detail with reference to embodiments. The contents described below appropriately correspond to both the sliding member and the manufacturing method thereof according to the present invention.
(1) Structure of sliding portion As described above, the sliding portion referred to in the present invention is formed by dispersing the Fe-W phase and the Fe-S phase in the Fe-based substrate.
FeW phase, FeW, a FeW _2, Fe ₂ W, compounds having a composition such as Fe ₃ W _2. When this Fe—W phase is dispersed in the base material in an amount of 0.1 to 10% by volume, more preferably 1 to 5% by volume, it is preferable for improving wear resistance and strength. If the amount is too small, the effect is thin.
The Fe—S phase is a compound having a composition such as FeS, FeS ₂ , Fe ₂ S, and Fe ₃ S, for example. When this Fe—S phase is dispersed in the base material in an amount of 0.1 to 20% by volume, more preferably 2 to 10% by volume, it is preferable for improving seizure resistance and the like. If the amount is too small, the effect is thin. If the amount is too large, the toughness is lowered, which is not preferable.
[0012]
Any phase is more preferably dispersed finely and uniformly in the base material because it can improve seizure resistance, seizure resistance, strength, and the like, and can prevent dropping from the base material. Specifically, the average particle size of each phase is preferably 50 μm or less, more preferably 10 μm or less.
The base material may be pure Fe, but it is preferable to contain appropriate amounts of various elements in order to improve slidability and strength. Examples of such elements include C, Mo, Cr, V, Mn, Cu, S, Ni, Co, and W. Note that C strengthens the base material by solid solution, but when it is precipitated as graphite (graphite), the slidability can be further improved.
[0013]
(2) Form of sliding portion The sliding portion is preferably made of an Fe-based porous material. In the case of a porous body, by adjusting the porosity, not only the weight, strength, etc. can be adjusted, but also the use is expanded. For example, when the sliding surface is made of a porous body, fine pores on the surface become an oil reservoir, which can contribute to improvement in slidability. Further, 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 the anchor effect. Furthermore, when the molten metal is densely impregnated into the porous body, for example, by high-pressure casting or the like, the heat transfer property between the two is improved.
The “porous body” as used in the present specification does not necessarily have to be completely porous, and it is sufficient that at least a part of the porous body has a porous part. For example, it may be preferable not to make the specific surface porous in order to prevent leakage of the impregnated molten metal.
[0014]
A typical 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) is obtained in which the inner peripheral surface of the Fe-based porous body is a cylinder liner that is a sliding surface. At this time, if the cylinder block is made of a light metal such as an Al alloy or Mg alloy, both the weight reduction of the entire cylinder block and the slidability of the cylinder liner can be achieved.
[0015]
(3) Manufacturing method When the Fe-based porous body is sintered as described above, a desired porosity can be easily manufactured.
The raw material powder used at that time is composed of, 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 W powder, W alloy powder, W compound powder, S powder, sulfide powder, and W and S compound powder. When WS ₂ powder is used as the reinforcing powder, W and S can be supplied at a time, which is efficient. For example, the WS ₂ powder is preferably contained in an amount of 2 to 15% by mass, and more preferably 3 to 9% by mass, when the total amount of the mixed powder is 100% by mass. This is because if the amount is too small, effects such as wear resistance and seizure resistance are thin, and if the amount is too large, the toughness decreases.
[0016]
Each powder may be any atomized powder, reduced powder, etc., and the particle shape is not limited. However, considering the production of an Fe-based porous sintered body, it is difficult to handle fine powder having a too small particle size. On the other hand, if the particle size is too large, fine and uniform dispersion of each phase becomes difficult. 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 1 to 10 μm.
The mixed powder preferably contains a binder, graphite powder or the like as appropriate. The binder may be a molding lubricant such as stearic acid or a stearate (for example, zinc stearate or lithium stearate) in addition to a resin, a wax, or the like.
[0017]
In the molding process, the molding pressure cannot be generally specified because it varies depending on the desired porosity, the kind of additive particles such as binder and graphite, the surface roughness of the mold, and the like. For example, if the metal powder occupation volume ratio in the powder compact is 60 to 70% by volume, the compaction pressure may be about 100 to 200 MPa.
The sintering process must be at a temperature at which the substrate powder is at least sintered. Further, in this sintering step, the particles in the base powder and the particles in the reinforcing powder are sintered, or an Fe—W phase or an Fe—S phase is formed by a reaction. Therefore, for example, the sintering temperature is preferably 1000 to 1300 ° C.
[0018]
【Example】
Next, an Example is given and this invention is demonstrated concretely.
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) Manufacture of cylinder sleeve First, as a raw material, Fe powder (pure iron: Kawasaki Steel KIP240M), WS ₂ powder (Nippon Lubricant Co., Ltd. Tanmic, average particle size 1 μm), graphite (C), Prepared with binder zinc stearate. These were mixed with a ball mill for 1 hour to obtain a mixed powder. The compounding amounts at this time are graphite: 1%, zinc stearate: 3%, WS ₂ powder: 6% or 9%, and the balance: Fe powder (unit: mass%, the same applies hereinafter).
[0019]
Next, this was naturally filled into a mold (mold) having a cylindrical cavity (filling step).
The mixed powder filled in the mold was pressed from above and below with a hydraulic press to obtain a cylindrical powder compact. At this time, the applied pressure was 100 MPa. The obtained powder compact had an outer diameter of 100.4 mm, a height of 58 mm, and a plate thickness of 3 mm.
This powder compact was placed in an electric furnace and sintered by heating at 1100 ° C. for 0.5 hours in a nitrogen atmosphere (sintering step). Thus, an Fe-based porous sintered body having a porosity (porosity) of about 40% by volume was obtained.
[0020]
(2) Production of engine block The engine block was produced by casting the Fe-based porous sintered body into an Al alloy (JIS ADC12). This casting was performed by die casting (casting process). The die casting conditions were as follows: molten metal temperature 680 ° C., mold temperature 250 ° C., compact preheating 500 ° C., and molten metal pressure 65 MPa. In addition, the Al alloy molten metal reached from the outer peripheral surface of the Fe-based porous sintered body to the inner peripheral surface.
The cylinder inner peripheral surface was finished by surface polishing.
[0021]
(Example 2)
(1) Production of Fe-based porous sintered body Using raw materials of Example 1, blended in proportions of graphite: 0.7%, zinc stearate: 1%, WS ₂ powder: 3% and balance: Fe powder. The prepared mixed powder was prepared. The mixing method is the same as in Example 1.
In the same manner 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. Thus, the porosity of the obtained Fe-based porous sintered body was about 30% by volume.
[0022]
(2) Production of engine block The engine block was produced by casting the Fe-based porous sintered body into an Al alloy (JIS ADC12). This cast casting was performed by molten metal forging. The conditions of the molten metal forging were a molten metal temperature of 680 ° C., a mold temperature of 250 ° C., a compact preheating of 500 ° C., and a molten metal pressure of 100 MPa. Also at this time, the Al alloy molten metal reached the inner peripheral surface from the outer peripheral surface of the Fe-based porous sintered body.
And the cylinder inner peripheral surface was finished by honing.
[0023]
(Evaluation)
(1) Structure of Fe-based porous sintered body The cross-sectional structure obtained by cutting the Fe-based porous sintered body of Example 1 was observed with a metal microscope and an X-ray microanalyzer (EPMA). The metal micrographs are shown in FIGS. 1 and 3, and the results of analysis of the structure by EPMA are shown in FIG. 1 and 2 are for WS ₂ powder: 6%, and FIG. 3 is for WS ₂ powder: 9%. FIG. 1 (a) is a tissue photograph showing the dispersed state of each tissue, and FIG. 1 (b) is a tissue photograph mainly showing aggregated patchy tissue.
[0024]
From these photographs, most of the WS ₂ particles are decomposed and react with Fe in the base powder, and a compound layer of Fe and W (Fe—W phase) and a compound layer of Fe and S (Fe—S phase). ). That is, a compound structure of Fe and W (white thin needles) forming a pearlite stripe pattern, a compound structure of Fe and S (light brown lump), and a patchy structure in which these structures are mixed Three species were observed. In addition, the abundance of the patchy tissue was somewhat low, and most of them were massive or needle-like (or streak) having an average particle size of 10 μm or less, and a slightly aggregated tissue 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: 190-280 MHv (25 g)
Coarse pearlite part when 9% WS ₂ powder is blended: 270 to 310 MHv (25 g)
Fine pearlite part: 190-280 MHv (25 g)
Coarse pearlite part when WS ₂ powder is not blended: 150-210 MHv (25 g),
Fine pearlite part: 180-230MHv (25g)
Thus, it has been found that by adding WS ₂ powder, the hardness of the Fe portion increases, and the wear resistance and strength can be improved. The reason why the hardness was increased is thought to be because the W reactant was formed in a thin thread form in the Fe portion.
[0026]
(2) Seizure resistance of cylinder block In order to examine the seizure property in the sliding part (cylinder liner part) of the manufactured cylinder block, the following low temperature scuff test was conducted.
(1) The test conditions for Example 1 are as follows.
Experimental temperature: 70 ° C., load: 3 kgf (29.4 N), time: rotation speed until seizure: 500 rpm, hertz pressure: 20 kgf / mm ² (196 MPa)
Lubrication method: Apply gasoline engine oil quantitatively (0.13mg / cm ² )
Cylinder bore diameter: φ96mm (inner peripheral surface: surface polishing)
Piston ring diameter: φ96mm, ring barrel diameter: 11.3mm
[0027]
The above test was performed three times for each of the WS ₂ powder: 6% blended, the WS ₂ powder: 9% blended, and the WS ₂ powder not blended as described in Example 1 above. Then, the time until seizure occurred for each test piece was measured, and the average was obtained and shown in FIG. As is apparent from this graph, the seizing time is extended by adding WS ₂ powder, and in particular, the extension is large when WS _{2 is} 9% by mass.
FIG. 4 also shows the Vickers hardness of each cylinder liner (sliding surface). As is clear from this, the hardness of the WS ₂ powder is improved, and not only seizure resistance but also abrasion resistance can be expected.
[0028]
(2) Test conditions for Example 2 are as follows.
Experimental temperature: 70 ° C., load: 3 kgf (29.4 N), time: rotation speed until seizure: 500 rpm, hertz pressure: 20 kgf / mm ² (196 MPa)
Lubrication method: Diesel engine oil is applied in a fixed amount (0.13 mg / cm ² )
Cylinder bore diameter: φ96mm (inner peripheral surface: honing)
Piston ring diameter: φ96mm, ring barrel diameter: 11.3mm
[0029]
WS ₂ powder described in Example 2 above: 3% blended, one blended with various other powders instead of WS ₂ powder, and one using a cast iron sleeve, the above test was performed twice. . Similarly in this case, the time until seizure occurred for each test piece was measured, and the average was obtained and shown in FIG. As is apparent from this graph, when WS ₂ powder was blended, the seizure time was significantly increased as compared with the case where other powders were blended. Moreover, the degree is far superior to that of conventional cast iron sleeves.
[Brief description of the drawings]
FIG. 1 is a structure photograph of a Fe-based porous sintered body (WS ₂ powder: 6% blended) according to Example 1 of the present invention by a metallographic microscope, and FIG. 1 (a) shows a dispersion state of each structure. The figure (b) shows the aggregated patchy tissue.
FIG. 2 is a photograph showing an analysis result of the structure of the Fe-based porous sintered body (WS ₂ powder: 6% blended) by EPMA.
FIG. 3 is a structural photograph taken by a metallographic microscope of an Fe-based porous sintered body (WS ₂ powder: 9% blended) according to Example 1 of the present invention.
FIG. 4 is a graph showing seizure resistance and hardness of a cylinder block according to Example 1 of the present invention.
FIG. 5 is a graph showing seizure resistance of a cylinder block according to Example 2 of the present invention.

Claims (10)

Tungsten (W), sulfur (S), carbon (C) and the balance consisting of iron (Fe) and inevitable impurities,
A slide comprising at least a part of a sliding portion in which an Fe—W phase composed of Fe and W and an Fe—S phase composed of Fe and S are dispersed in a base material composed of Fe or an Fe alloy. Moving member.   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 in 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. 5. The Fe-based porous body is an Fe-based porous sintered body obtained by sintering a mixed powder obtained by mixing Fe powder, WS ₂ powder, graphite powder, and a binder. Sliding member. The cast member, the sliding member according to claim 3 or 4, the Fe-based porous body is intended that cast in an Al alloy or a Mg alloy. A filling step of filling a mold with mixed powder obtained by mixing Fe powder, WS ₂ powder, graphite powder and binder;
A molding step of pressing the mixed powder in the mold to form a powder compact;
It comprises a sintering step in which the powder compact is heated to form a sintered body,
And Fe-S phase Fe and the WS ₂ Fe-W phase W in is Deki reacts powder and the Fe powder of Fe and S of the WS ₂ powder of said Fe powder has Deki reacted A method for producing a sliding member, comprising: the sintered body having at least a part of a sliding portion dispersed in a base material made of Fe or Fe alloy. The mixed powder, when the entirety is taken as 100 mass%, the manufacturing method of the slide member according to claim 7 including WS ₂ powder 2-15 mass%.   The said powder compact is a manufacturing method of the sliding member of Claim 7 whose occupation volume ratio of a metal powder is 60-70 volume%.   A Fe-based porous body provided with at least a part of a sliding portion 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. The manufacturing method of the sliding member characterized by consisting of the casting process which makes a sliding member into.

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