JP2003073755A - Porous metal-sintered compact for strengthening light alloy member, and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous metal-sintered compact for strengthening a light alloy member, which is superior in bondability, and provide a manufacturing method therefor. SOLUTION: This manufacturing method comprises mixing a graphite powder or further a fine particle powder for improving machinability, with an alloyed powder having such a particle size distribution as to pass a screen of 60 meshes and not to pass the screen of 350 meshes, to make a mixed powder, then charging the mixed powder into a die, molding it with compression to make a green compact, and sintering it. The porous metal-sintered compact has vacancy of 15-50% in an area rate, has the holes with more than 5 μm in diameter at the area rate of 80% or higher against the all holes area, and has radial crushing strength of 200 MPa or higher. The porous metal-sintered compact for strengthening the light alloy member, having superior bonding strength and superior strength of a composite member, can be obtained by cast-embedding the porous metal-sintered compact in the light alloy. A light alloy composite member is obtained by employing the same. The alloyed powder may include a stainless steel powder, an iron powder, and a copper powder, or a Fe-Cu alloyed powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used after being filled with a light alloy such as an aluminum alloy and used as a composite material, or a light alloy member such as an aluminum alloy. The present invention relates to a porous metal sintered body for reinforcing a light alloy member, and particularly to a porous metal sintered body and a porous metal sintered body suitable for reinforcing a part or the whole of a light alloy member such as an aluminum alloy used in an internal combustion engine. The present invention relates to a light alloy composite member using a body.

[0002]

2. Description of the Related Art In recent years, engines made of aluminum alloy have been becoming popular for the purpose of reducing the weight of engines and improving heat dissipation. However, the strength of aluminum alloy is lower than that of conventional cast iron.
There has been a problem that strength is insufficient in a member that is subjected to a high load at high temperature, such as a ring groove portion, a pin hole portion, and a lip portion of a piston.

In order to solve such a problem, for example, there has been proposed a structure in which a piston ring groove is provided with a wear ring made of a material having a strength higher than that of the piston material and the piston ring is supported by the wear ring. For example, in a diesel engine, a piston having a wear ring made of Ni-resist cast iron in a top ring groove has been proposed. However, since the Ni-resist cast iron wear ring is a cast product, the yield is low, the material cost is high, and the workability is poor, so that there is a problem that the cost is high overall. Further, in the Ni-resist cast iron wear ring, it is indispensable to perform alfin treatment in order to improve the castability of the aluminum alloy, and since it is an iron alloy, the density becomes high, which causes a problem that engine performance is deteriorated. It was

On the other hand, a light alloy composite member obtained by strengthening a light alloy such as an aluminum alloy with a reinforcing material such as whiskers or fibers has been receiving attention. These light alloy composite members may not always have satisfactory properties when used in a high temperature environment, and recently, a porous metal sintered body is used as a reinforcing material for the light alloy composite member. Is being done.

However, when a light alloy composite member using a porous metal sintered body as a reinforcement for a light alloy is used at a high temperature at which the strength of the light alloy remarkably decreases, the strength of the composite member is It will largely depend on the characteristics of the sintered body. However, conventionally, although the volume ratio of the porous metal sintered body, the alloying element, the size of the pores, etc. have been studied, the strength of the porous metal sintered body as a reinforcing material for the composite member is Little was considered.

Further, Japanese Patent Application Laid-Open No. 8-319504 discloses Cr,
2 to 70% of at least one of Mo, V, W, Mn and Si,
Carbon is 0.07 to 8.2%, iron-based raw material powder with unavoidable impurity composition is used to make a sintered body, and the hardness of the metal formed by cooling in gas and gas quenching is measured by the micro Vickers hardness.
A metal-sintered composite material has been proposed that has a porous metal sintered body set to Hv200 to 800 and a light metal that is impregnated into pores and solidified to secure seizure properties during sliding. However, in the porous metal sintered body described in JP-A-8-319504, a large amount of alloy elements such as Cr, Mo and V are added so that gas quenching is possible, and the light alloy contains It is economically disadvantageous for a reinforcing member that is used by being cast and wrapped.

[0007]

[Patent Document 1] Japanese Patent Application Laid-Open No. 8-31
When the porous reinforced sintered body described in 9504 is used by being wrapped in a light alloy and used, the bonding strength may fluctuate and boundary debonding may occur, and high bonding strength (adhesion) is not always stable. There was a problem that I could not get it. The present invention advantageously solves the above-mentioned problems of the prior art, and as a light alloy composite member filled with a light alloy to form a composite material, ensures high composite member strength even in a high temperature environment where the softening of the light alloy is remarkable. It is an object of the present invention to propose a porous metal sintered body for reinforcement of a light alloy composite member, which is capable of impregnating a light alloy. Further, the present invention, for reinforcement of the light alloy member, is cast in a light alloy member such as an aluminum alloy, and is suitable as a light alloy composite member for improving the strength of the member,
Porous metal sinter that has excellent impregnation with light alloys and excellent bondability with light alloy members, and light alloy composites using porous metal sinters so that the desired bonding strength can be stably ensured An object of the present invention is to provide a chemical conversion member and a manufacturing method thereof.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned objects, the present inventors have made a porous metal (iron-based) sintered body
As a kind of light alloy, it is used as a porous metal (iron-based) sintered body and the bonding strength between a porous metal (iron-based) sintered body and an aluminum alloy-made member when cast into an aluminum alloy member. Various factors affecting the tensile strength of the composite member filled (impregnated) with an aluminum alloy were thoroughly studied. As a result, a porous metal sintered body that is filled (impregnated) with an aluminum alloy or cast into an aluminum alloy member has a porosity of 15 to 50% and has a diameter of 5%.
Porosity over μm is 80% or more of the total porosity.
A light alloy with high tensile strength and high high-temperature hardness by using a porous metal sintered body that has a radial crushing strength of 200 MPa or more obtained according to the radial crushing strength test specified in SZ 2507. It was found that a composite member and a light alloy composite member having high bonding strength can be obtained.

First, a basic experiment conducted by the present inventor will be described. First, a porous metal (iron-based) sintered body was cast in an aluminum alloy member, and a tensile test piece including a joint boundary was taken. A tensile test was performed using these tensile test pieces to determine the bonding strength. The porosity of each porous metal (iron-based) sintered body was determined by density measurement. The relationship between the bonding strength and the porosity is shown in FIG. Boundary strength (σ)
Is the ratio to the desired boundary strength (σ _E ), the boundary strength ratio σ
Displayed as / σ _E. It means that when the boundary strength ratio is 1 or more, the boundary strength σ becomes a value equal to or larger than the desired boundary strength σ _E.

From FIG. 3, there is a large variation in the boundary strength ratio even with the same porosity. This is considered to be because the porosity was substituted by the density measurement, and the control of the porosity obtained by the density measurement alone represents a factor that affects the bonding strength of the porous metal (iron-based) sintered body. There will be no. Therefore, the present inventor examined the results of FIG. 3 in more detail, and even with the same porosity, there may be a large difference in the distribution and morphology of the pores, which is due to the light alloy member and the porous metal. It was thought that it had a great influence on the bonding strength with the sintered body. Even if the porosity is the same, the size and number of pores are different, for example,
In the porous metal sintered body having the pore distribution in the cross section schematically shown in FIGS. 2A and 2B, the sintered body having the pore distribution in FIG. 2B is a light alloy member. It was found that the joint strength with Furthermore, when casting light alloys, if the pores of the porous metal sintered body are fine, it is difficult for the light alloys to be impregnated into the pores, and in particular, the independent pores generated during sintering are impregnated with the light alloy. However, it was found that the bonding strength was significantly affected.

Therefore, the inventor of the present invention has found that a porous metal (iron-based) is used.
The cause of the formation of fine pores in the sintered body was further studied.
As a result, it was found that the bonding strength ratio is greatly influenced by the existence ratio of fine pores existing in the porous metal (iron-based) sintered body, particularly fine pores having a diameter of 5 μm or less. Ratio of fine porosity with a diameter of 5 μm or less and total porosity present in the porous metal sintered body, {(fine porosity with a diameter of 5 μm or less)
The relationship between / (total porosity)} × 100 (%) and the bonding strength ratio is shown in FIG. From Fig. 1, it can be seen that the fine pores with a diameter of 5 μm or less existing in the porous metal sintered body are
When it is less than%, the bonding strength ratio becomes 1 or more.
The joining strength ratio is shown based on the strength (boundary strength σ _E ) when the molten material (cast iron) is subjected to Alfin treatment. Here, the fine porosity and the total porosity with a diameter of 5 μm or less are obtained by polishing the cross section of the porous metal sintered body, measuring the area of the pores in the cross section with an image analyzer, and measuring the respective area ratios. The porosity was calculated.

Further, the particle size distribution of the alloy powder used has a great influence on the formation of fine pores in the porous metal sintered body,
In particular, in order to reduce the fine porosity of diameters of 5 μm or less to less than 20%, it was found that it is necessary to prevent the alloy powder used from mixing fine powder that passes through a # 350 sieve (-350 mesh). did. Further, the present inventor collected a tensile test piece in a state where the porous metal sintered body is filled with the aluminum alloy, and conducts a tensile test, to form a composite in the state where the porous metal sintered body is filled with the aluminum alloy. The tensile strength of the member was determined. Further, according to JIS Z 2507, the radial crushing strength of the porous metal sintered body was obtained, and the relationship between the tensile strength of the composite member and the radial crushing strength of the porous metal sintered body was obtained. As a result, it has a porosity of 15 to 50% and has a diameter of 5
Porosity over μm is 80% or more of the total porosity.
It was found that by setting the radial crushing strength obtained according to the radial crushing strength test specified in SZ 2507 to 200 MPa or more, a high-strength composite member is obtained and the high temperature hardness is further increased.

The present invention has been completed by further studies based on the above findings. That is, the first aspect of the present invention is a porous metal sintered body obtained by compacting and sintering a mixed powder containing an alloy powder, wherein the porous metal sintered body is
Porosity of 15 to 50% and diameter of the pores is 5 μm
Porous metal sinter for reinforcing light alloy members with excellent impregnation properties for light alloys, having pores exceeding 80% of the total porosity and radial crushing strength of 200 MPa or more Is. The radial crushing strength referred to in the present invention means a value obtained in accordance with the radial crushing strength test specified in JIS Z 2507.

In the first aspect of the present invention, the porous metal sintered body is composed of one or more selected from MnS, CaF, BN and enstatite having a particle size of 150 μm or less. It is preferable to contain 0.1 to 5 mass% of fine particles for improving machinability. Further, in the first aspect of the present invention, it is preferable that the porous metal sintered body is the porous stainless steel sintered body.

In the first aspect of the present invention, it is preferable to use a porous Fe-Cu-C type sintered body instead of the porous stainless steel sintered body. A second aspect of the present invention is a light alloy composite member in which a light metal alloy is impregnated into a porous metal sintered body obtained by compacting and sintering a mixed powder containing an alloy powder. The metal sintered body has a porosity of 15 to 50%, and the porosity exceeding 5 μm in diameter is 80% of the total porosity.
The light alloy composite member is characterized by having a radial crushing strength of 200 MPa or more, and in the second invention, the porous metal sintered body further has a particle diameter of 150 μm or less. It is preferable to contain 0.1 to 5 mass% of fine machinability-improving particles composed of one or more selected from MnS, CaF, BN, and enstatite. Further, in the second aspect of the present invention, it is preferable that the porous metal sintered body is a porous stainless steel sintered body. In the second aspect of the present invention, the porous stainless steel sintered body is a porous ferritic stainless steel sintered body, a porous martensitic stainless steel sintered body, or a porous austenitic stainless steel sintered body. Is preferred.

In the second aspect of the present invention, it is preferable to use a porous Fe-Cu-C type sintered body instead of the porous stainless steel sintered body, and in the second aspect of the present invention, Porous
It is preferable that the Fe-Cu-C based sintered body contains 2 to 6 mass% of Cu. In the third aspect of the present invention, the alloy powder is mixed with graphite powder and lubricant powder to form a mixed powder, the mixed powder is formed into a green compact, and then the green compact is formed. In the method for producing a porous metal sintered body by sintering to obtain a porous metal sintered body, the alloy powder is an alloy powder having a particle size distribution of −60 mesh to +350 mesh, and the sintering conditions for the sintering are The porosity of the porous metal sintered body is adjusted to 15 to 50 by adjusting.
%, And the radial crushing strength is 200 MPa or more, which is a method for manufacturing a porous alloy sintered body for light alloy member reinforcement excellent in impregnation of a light alloy, and in the third invention, The mixed powder further contains MnS, CaF, and BN having a particle size of 150 μm or less.
And one or two selected from enstatite
It is preferable that the machinability-improving fine particles of at least one kind are contained in an amount of 0.1 to 5 mass% with respect to the total amount of the mixed powder.

In a fourth aspect of the present invention, the alloy powder is mixed with graphite powder and lubricant powder to form a mixed powder, and the mixed powder is molded into a green compact having a predetermined shape. Then, the green compact is sintered to form a porous metal sintered body having a predetermined shape, and then a light alloy is impregnated to form a composite member. In the above, the alloy powder is an alloy powder having a particle size distribution of -60 mesh to +350 mesh and an apparent density of 2.6 or less, and the sintering conditions for the sintering are adjusted to obtain the porous sintered body. With a porosity of 15 to 50% and a radial crushing strength of 200 MPa or more, a method for manufacturing a light alloy composite member using a porous metal sintered body excellent in impregnation of a light alloy. Yes, the fourth
In the present invention, the mixed powder further contains fine particles for improving machinability, which are composed of one or more selected from MnS, CaF 2, BN and enstatite having a particle size of 150 μm or less. It is preferable to contain 0.1 to 5 mass% with respect to the total amount of the powder.

In the fourth aspect of the present invention, the alloy powder is preferably ferritic stainless steel powder, martensitic stainless steel powder or austenitic stainless steel powder, and in this case, the mixed powder is It is preferable that the graphite powder is contained in an amount of 1.0% by mass or less based on the total amount of the mixed powder. Further, in the fourth invention, the alloy powder is preferably iron powder and Cu powder, or Fe-Cu alloy powder, and in the fourth invention, the Cu powder, or
It is preferable to mix the Fe-Cu alloy powder so that the Cu content in the mixed powder is 2 to 6% by mass, and in the fourth aspect of the present invention, the mixed powder is the mixed graphite powder. It is preferable to contain 0.8 to 1.5 mass% with respect to the total amount.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The porous metal sintered body of the present invention is used as a composite member by filling a light alloy such as an aluminum alloy for reinforcing a light alloy member, or an aluminum alloy. It is preferable that the light alloy member is cast for use before use. The porous metal sintered body of the present invention is made into a product by molding a mixed powder obtained by mixing alloy powder, graphite powder and the like into a predetermined shape to obtain a green compact and then sintering the powder.

In the light metal member reinforcing porous metal sintered body of the present invention, it is not necessary to particularly limit the material, and a material having characteristics such as strength matching the use environment can be appropriately selected. The light alloy member reinforcing porous metal sintered body of the present invention has an area ratio of
It has 15-50% vacancies. When the porosity is less than 15%, the molten metal of the light alloy does not impregnate the pores of the sintered body when it is cast in a light alloy member such as an aluminum alloy or filled with the light alloy, and the bonding strength is descend. On the other hand, the porosity is 50
When it exceeds%, there are too many pores and the strength is reduced, and it deforms during operation. Therefore, the porosity of the light alloy member-reinforcing porous metal sintered body is limited to the range of 15 to 50%.

Further, the porous metal sintered body for reinforcing a light alloy member of the present invention has 80% or more of the pores having a diameter exceeding 5 μm with respect to the total porosity. If the porosity exceeding 5 μm is less than 80% of the total porosity, that is, the diameter is 5
When the porosity of μm or less exceeds 20% with respect to the total porosity, the number of fine pores increases, and as shown in FIG. 1, the bonding strength decreases when the bonding strength ratio is less than 1. For this reason, the number of pores having a diameter of more than 5 μm is limited to 80% or more of the total porosity.

Further, the porous metal sintered body for reinforcing a light alloy member of the present invention is subjected to a radial crushing test stipulated in JIS Z 2507 from the viewpoint of securing the desired composite member strength and reinforcing the light alloy member. The obtained radial crushing strength shall be 200 MPa or more. If the radial crushing strength is less than 200 MPa, the strength is insufficient for reinforcing the light alloy member, and the light alloy member is deformed,
It causes problems such as cracking. Further, in the case of high pressure die casting or molten metal forging, problems such as cracks occurring before impregnation due to inability to withstand pressure occur. In the present invention, the radial crushing strength is used as an index of the strength of the porous metal sintered body, but when the tensile strength is used as the index of the strength, the material of the sintered body and the porosity are used. It is necessary to prepare a tensioning jig having a size corresponding to the above, and in the present invention, a radial crushing strength that allows evaluation with a simple jig is adopted because of the ease of evaluation.

Further, in the porous metal sintered body for reinforcing a light alloy member of the present invention, it is preferable to disperse fine particles for improving the machinability in the matrix in order to improve the machinability. The fine particles for improving machinability to be dispersed are preferably one or more selected from MnS, CaF ₂ , BN and enstatite. MnS, CaF ₂ , BN, and enstatite are all particles that improve machinability, and can be selected and contained as needed.

By uniformly dispersing such machinability-improving fine particles in the matrix, the cutting chips during cutting are divided into sizes determined by the distance between these fine particles. Therefore, the cutting resistance is kept low. The machinability improving fine particles dispersed in the matrix have a particle size of 150 μm.
It is preferable to use fine particles of m or less. If the particle size of the fine particles exceeds 150 μm, the bonding strength decreases. In addition,
It is preferably 5 to 100 μm.

The content of fine particles for improving the machinability dispersed in the matrix of the porous metal sintered body is 0.1 to 5% by mass.
It is preferable that If the content of the fine particles for improving the machinability is less than 0.1% by mass, the effect of improving the machinability cannot be recognized. On the other hand, if the content is more than 5% by mass, the adhesion strength with the matrix will decrease. Therefore, it is preferable that the machinability improving fine particles having a particle diameter of 150 μm or less are contained in the range of 0.1 to 5 mass%.

The porous metal sintered body for reinforcing the light alloy member is preferably a porous stainless steel sintered body.
When the sintered body is made of stainless steel having high oxidation resistance, oxidation of the sintered body during casting can be suppressed. Among stainless steels, it is more preferable to use martensitic stainless steel having high strength from the viewpoint of a reinforcing material.

Among the stainless steels, preferred martensitic stainless steels are SUS403, SUS410, and SU.
S 410S, SUS 420J1, SUS 420J2, SUS 431, SUS 440A, SUS
Examples are 440B and SUS 440C. Also, as ferritic stainless steel, SUS 405, SUS 410L, SUS 409, SUS 4
Examples are 09S, SUS 429, SUS 430, SUS 434 and SUS 436L.

Porous martensite type (ferrite type)
The stainless steel sintered body is, for example, in mass%, C: 0.1-
0.8%, Si: 1.0% or less, Mn: 2.0% or less, P: 0.1%
Hereinafter, it is preferable to have a composition containing S: 0.03% or less, Cr: 11.0 to 13.5%, and the balance being substantially Fe. Next, the reasons for limiting the composition of the porous martensite (ferrite) stainless steel sintered body will be described.

C: 0.1% to 0.8% C is an element that increases the strength and hardness of the sintered body and facilitates the adjustment of dimensional accuracy.
It must contain at least 1%. If the content exceeds 0.8%, carbides are formed, the hardness increases and the radial crushing strength decreases. Therefore, C is preferably limited to 0.1 to 0.8%.

Si: 1.0% or less Si is an element that increases the strength of the sintered body, and it is preferable to contain Si in an amount of 0.3% or more. However, if it exceeds 1.0%, the sintered body tends to become brittle. Become. Therefore, Si is 1.0
% Or less is preferable. Mn: 2.0% or less Mn is an element that increases the strength of the sintered body, and is preferably contained in the present invention in an amount of 0.05% or more, but when it exceeds 2.0%, the sintered body tends to become brittle. Become. For this reason,
Mn is preferably 2.0% or less.

P: 0.1% or less If P is contained in excess of 0.1%, steadite carbides increase and the steel becomes brittle, so P is preferably limited to 0.1% or less. It is more preferably 0.05% or less. S: 0.03% or less S forms sulfides and reduces the ductility and toughness of the material, so it is preferable to reduce S as much as possible. Therefore, in the present invention, S is preferably 0.03% or less.

Cr: 11.0 to 13.5% Cr is a solid solution strengthening element, and is preferably contained in an amount of 11.0% or more in order to secure a desired strength. On the other hand, when the content exceeds 13.5%, precipitation of Cr carbide on the grain boundaries becomes remarkable and the strength decreases. Therefore, Cr is preferably limited to the range of 11.0 to 13.5%.

The balance other than the above components is substantially Fe. As inevitable impurities, N: 0.1% or less, S
e: 0.15% or less is acceptable. Further, as a preferable austenitic stainless steel, SUS 302, SUS 303, SUS
Examples include 304, SUS 304 L, SUS 316, SUS 317, and SUS 310S. The porous austenitic stainless steel sintered body is, for example, in mass%, C: 0.1 to 1.0%, Si: 1.0% or less, M
n: 2.0% or less, P: 0.1% or less, S: 0.03% or less, N
It is preferable to have a composition containing i: 5.0 to 15.0 and Cr: 15.0 to 25.0% with the balance being substantially Fe.

Next, the reasons for limiting the composition of the porous austenitic stainless steel sintered body will be described. C: 0.1 to 1.0% C is an element that increases the strength and hardness of the sintered body and facilitates the adjustment of the dimensional accuracy.
It must contain at least 1%. If the content exceeds 1.0%, carbides are formed, the hardness increases and the radial crushing strength decreases. Therefore, C is preferably limited to 0.1 to 1.0%.

Si: 1.0% or less Si is an element that increases the strength of the sintered body, and it is preferable to contain Si in an amount of 0.3% or more. However, if it exceeds 1.0%, the sintered body tends to become brittle. Become. Therefore, Si is 1.0
% Or less is preferable. Mn: 2.0% or less Mn is an element that increases the strength of the sintered body, and is preferably contained in the present invention in an amount of 0.05% or more, but when it exceeds 2.0%, the sintered body tends to become brittle. Become. For this reason,
Mn is preferably 2.0% or less.

P: 0.1% or less. If P is contained in excess of 0.1%, stedite carbide increases and the steel becomes brittle, so P is preferably limited to 0.1% or less. It is more preferably 0.05% or less. S: 0.03% or less S forms sulfides and reduces the ductility and toughness of the material, so it is preferable to reduce S as much as possible. Therefore, in the present invention, S is preferably 0.03% or less.

Ni: 5.0-15.0% Ni is an austenitizing element, and in the present invention, 5.0%.
It is preferable to contain the above. On the other hand, if the content exceeds 15.0%, the hardness decreases. Therefore, Ni is 5.0-15.0.
It is preferable to limit to the range of%. Cr: 15.0 to 25.0% Cr is a solid solution strengthening element, and is preferably contained in an amount of 15.0% or more in order to secure desired strength. On the other hand, if the content exceeds 25.0%, the precipitation of Cr carbide on the grain boundaries becomes remarkable and the wear resistance decreases. Therefore, Cr is 15.0 to 25.0%
It is preferable to limit the range.

In addition to the above components, there is no problem even if one or more of Mo, Ti, and Nb are contained in a total amount of 1% or less. The balance other than the above components is substantially Fe. As inevitable impurities, N: 0.1% or less, Se: 0.15
% Or less is acceptable. Further, in the present invention, a porous Fe-Cu-C based sintered body can be used instead of the above-mentioned porous stainless steel sintered body. The porous Fe-Cu-C based sintered body preferably contains 2 to 6 mass% of Cu. If the Cu content in the sintered body is less than 2% by mass, the joint strength will be reduced when cast in a light alloy member such as an aluminum alloy. On the other hand, if the content exceeds 6%, single pores are likely to be formed, and the impregnability of the light alloy deteriorates. For this reason,
In the present invention, the Cu content in the porous Fe-Cu-C system sintered body is
It is preferably limited to 2 to 6 mass%.

Either one of the above-mentioned porous metal sintered bodies is filled with a light alloy such as an aluminum alloy to form a light alloy composite member, or one of the above-mentioned porous metal sintered bodies. Can be used as a porous metal sintered body for reinforcing a light alloy member by casting in a light alloy such as an aluminum alloy. Next, a method for manufacturing the porous metal sintered body for reinforcing the light alloy member of the present invention will be described.

After alloy powder as raw material, graphite powder and lubricant powder are mixed to form a mixed powder, these mixed powders are charged into a mold and pressure-molded to obtain a green compact. The powder is sintered to form a porous metal sintered body. As the raw material powder, the alloy powder used passes through a 60-mesh sieve (hereinafter, also referred to as 60-mesh under or -60 mesh) and does not pass through a 350-mesh screen (hereinafter, 350-mesh over or + 350-mesh) It is preferable that the alloy powder has a grain size distribution adjusted.

The presence of particles of +100 mesh (which does not pass through a # 100 mesh sieve) lowers the powder compacting property of the mixed powder, making it difficult to obtain a powder compact having a desired density. Particles of 60 to +100 mesh are
If it is less than 40%, it can be molded, which is advantageous for forming a green compact having a desired porosity. On the other hand, the presence of particles of -350 mesh (passing through a sieve of # 350 mesh) increases the abundance of fine pores with a diameter of less than 5 μm
The boundary strength ratio tends to decrease.

There are no particular restrictions on the type of alloy powder used in the production of the porous metal sintered body for reinforcing the light alloy member. Depending on the application of the light alloy member, the alloy powder of the optimum material can be used as appropriate. In addition,
From the viewpoint of oxidation resistance when filling or casting with a light alloy, it is preferable to use stainless steel powder. As the stainless steel, any of martensite type, ferritic type and austenitic type is suitable. Further, iron powder and Cu powder or Fe-Cu alloy powder may be used instead of the stainless steel powder.

Further, for reinforcing each light alloy member, the porosity of the porous metal sintered body is adjusted to 15 by appropriately adjusting the sintering conditions.
It is preferable that the crushing strength is up to 50% and the crushing strength obtained by the crushing strength test specified in JIS Z 2507 has a strength of 200 MPa or more. The above-mentioned porous metal sintered body can be filled with a light alloy such as an aluminum alloy and used as a light alloy composite member.

Next, a method for manufacturing a light alloy composite member using the porous metal sintered body of the present invention will be described. In the present invention, the alloy powder is mixed with graphite powder and lubricant powder to form a mixed powder, and then the mixed powder is formed into a green compact having a predetermined shape, and then the green compact is baked. The porous metal sintered body is bonded to form a porous metal sintered body having a predetermined shape.

In the present invention, the alloy powder used as the raw material powder is prepared from the above-mentioned composition and is composed of martensitic stainless steel powder, ferritic stainless steel powder or austenitic stainless steel powder, or iron powder and Cu powder, or
Fe—Cu alloy powder is preferable. The Cu powder or the Fe-Cu alloy powder as the alloy powder is preferably blended so that the Cu content in the mixed powder is 2 to 6% by mass.

As described above, the alloy powder used passes through a 60-mesh sieve (hereinafter, also referred to as 60-mesh under or -60 mesh) and does not pass through a 350-mesh screen (hereinafter, 350-mesh over, Or +350
It is preferable to use steel powder adjusted to have a particle size distribution (also referred to as a mesh). The presence of particles of +100 mesh (which does not pass through a # 100 mesh sieve) reduces the powder compactibility of the mixed powder, making it difficult to obtain a powder compact with the desired density, which may shorten the mold life. However, if the particles of -60 to +100 mesh are less than 40% of the total powder, it is possible to mold and it is advantageous to obtain a green compact having a desired porosity. On the other hand, the presence of particles of -350 mesh (passing through a sieve of # 350 mesh) tends to increase the abundance of fine pores having a diameter of less than 5 µm and reduce the bonding strength ratio.

The alloy powder having the above-mentioned particle size distribution is further mixed with graphite powder, lubricant powder such as zinc stearate, and wax-based granulating powder to form a mixed powder. Graphite powder is added as an alloying element that increases the strength of the porous sintered body. When the alloy powder is stainless steel powder, the blending ratio of graphite powder is preferably 1.0 mass% with respect to the total amount of the mixed powder. The amount of graphite powder in the mixed powder is
If it exceeds 1.0% by mass, carbides increase, which hinders the properties of stainless steel, deteriorates machinability, and causes a liquid phase during sintering, resulting in many independent pores and a decrease in bonding strength. .

The alloy powder is iron powder and Cu powder, or Fe.
In the case of -Cu alloy powder, the blending ratio of graphite powder is preferably 0.8 to 1.5 mass% with respect to the total amount of the mixed powder. If the content of graphite powder in the mixed powder is less than 0.8% by mass, it becomes difficult to secure the desired strength, while if it exceeds 1.5% by mass,
Carbide increases and deteriorates the characteristics of the sintered body,
A liquid phase is generated during sintering, a large number of independent voids are generated, and the bonding strength is reduced.

The particle size of the graphite powder is preferably 0.1-10 μm. If it is less than 0.1 μm, handling becomes difficult, and if it exceeds 10 μm, uniform dispersion becomes difficult. The mixed powder described above is charged into a mold and pressure-molded to obtain a green compact having a predetermined shape substantially equal to the predetermined shape. The method for molding the green compact is not particularly limited, but it is preferable to use a molding press or the like. The green compact molded into a predetermined shape is then sintered to obtain a porous metal sintered body having a predetermined shape. The sintering conditions are adjusted so that the porosity of the porous metal sintered body is 15 to 50%, and the radial crushing strength determined by the radial crushing strength test specified in JIS Z 2507 is 200 MPa.
It is preferable to have the above strength.

The thus obtained porous sintered body having a predetermined shape was mounted on a corresponding portion of a mold for forming a light alloy member, and a molten light alloy such as molten aluminum alloy was poured into the mold, A light alloy composite member in which a sintered body is cast-in is manufactured by high pressure die casting or molten metal forging. As a result, the molten metal penetrates into the pores of the sintered body and the joining with the light alloy member is completed. Then, the light alloy composite member is cut into a member having a predetermined size.

[0051]

[Example] (Example 1) In addition to the alloy powder shown in Table 1, graphite powder,
Lubricant powder was added, mixed, and kneaded to form a mixed powder, which was then filled in a die and pressure-molded by a molding press to obtain a green compact having a substantially predetermined size. As shown in Table 1, the alloy powder is
The particles were classified in advance and the particle size distribution was adjusted. In Table 1, the apparent density is also shown for reference. In addition, Table 1 shows an example of the particle size distribution of the used steel powders A and D for reference.

Next, these green compacts were sintered at 1100 to 1200 ° C. to obtain a porous metal sintered body containing pores shown in Table 2.
The total porosity was determined by measuring the density. The density was measured by the Archimedes method. The ratio of the micropores to the total pores is the total area of the micropores with a diameter of 5 μm or less and the total pores obtained by imaging the structure of the cross section of the porous metal sintered body in the pressing direction with a metallurgical microscope. The area was calculated by (total area of fine pores with a diameter of 5 μm or less) / (total area of pores). The measurement points were set at 3 points on the circumference.

Further, test pieces were sampled from these porous metal sintered bodies and a radial crushing strength test was carried out in accordance with JIS Z 2507 to determine the radial crushing strength. Next, these porous metal sintered bodies were mounted on the reinforcing material charging position of the mold for forming the light alloy member. Then, a molten aluminum alloy (JIS AC8A) was poured into the mold, and then forged by a molten metal to cast a reinforcing porous metal sintered body into a composite member having a predetermined size.

From these composite members, a tensile test piece including a joint boundary was sampled and a tensile test was conducted to determine the joint strength, and the impregnation property of the aluminum alloy (light alloy) was evaluated. The tensile test piece was sampled in a direction perpendicular to the axis of the test piece and including the boundary surface. The bonding strength σ was evaluated by a ratio of a desired bonding strength σ _E (bonding strength of a molten material subjected to Alfin treatment) and a bonding strength ratio σ / σ _E.

Tensile test pieces and high temperature hardness test pieces were sampled from these composite members and subjected to a tensile test and 300 ° C.
The high temperature hardness test was performed to determine the tensile strength σ _TS and the high temperature hardness Hv ₃₀₀ . These tensile strength and high temperature hardness, tensile strength of these tensile strength sigma _TS and high-temperature hardness Hv ₃₀₀ aluminum alloy (AC8A) (σ _{TS) Al} and 30
Hardness at 0 ° C (Hv ₃₀₀ ) Ratio to _Al , tensile strength ratio σ
_TS / (σ _TS ) _Al and high temperature hardness ratio Hv ₃₀₀ / (Hv ₃₀₀ ) _Al were evaluated.

The results obtained are shown in Table 2.

[0057]

[Table 1]

[0058]

[Table 2]

Each of the examples of the present invention is a porous metal sintered body for reinforcing a light alloy member having a high radial crushing strength of 200 MPa or more and a high joint strength ratio of 1.0 or more, and a light alloy composite member using the same. ing. On the other hand, Comparative Examples out of the scope of the present invention have low radial crushing strength or low bonding strength ratio,
Despite the same porosity as in the example of the present invention, the composite member was inferior in bondability.

Further, in all the examples of the present invention, the tensile strength ratio σ
_TS/ (σ_TS)_Al, And high temperature hardness ratio Hv ₃₀₀/ (Hv₃₀₀)_AlBut
It is 1 or more, compared to aluminum alloy alone,
Becomes a light alloy composite member with high strength and high temperature hardness
You can see that On the other hand, radial crushing strength is less than 200 MPa
In all the comparative examples out of the light range, the tensile strength ratio σ_TS/
(σ_TS)_AlIs less than 1, it shows only low composite member strength.
Yes.

Samples No. 24 and No. 25 are Cu in the sintered body.
Since the content exceeds 6% and the amount of fine voids is outside the range of the present invention, the bonding strength ratio is lowered. Also, the sample
No. 8 was considered difficult to mold because the surface pressure was excessive and the mold cracked and the mold life was shortened. (Example 2) Alloy powder A (SUS 304) shown in Table 1
Graphite powder with the content shown in Table 1, fine particle powder with the types, particle sizes and contents shown in Table 3 for improving machinability, and lubricant powder are added and mixed, and kneaded to form a mixed powder. It was filled in a mold and pressure-molded by a molding press to obtain a green compact having a substantially predetermined size.

Next, these green compacts were sintered at 1000 to 1200 ° C. to obtain a porous austenitic stainless steel sintered body containing pores shown in Table 3. The total porosity of the sintered body is
As in Example 1, the porosity was determined by measuring the density. Further, test pieces were sampled from these sintered bodies (porous austenitic stainless steel sintered bodies), and the ratio of fine pores to total pores and radial crushing strength were determined as in Example 1. .

Next, these sintered bodies were mounted on the reinforcing material charging position of the mold for forming the light alloy member. Then, an aluminum alloy melt (JIS AC8A) was poured into the mold, and then the melt forging was performed to cast a reinforcing porous metal sintered body into a composite member having a predetermined size. From these composite members, similarly to the example, a tensile test piece including a bonding boundary was sampled and a tensile test was performed to determine the bonding strength.
The impregnability of (light alloy) was evaluated. In addition, the sampling direction of the tensile test piece was the direction including the boundary surface perpendicular to the axis of the test piece, as in Example 1. The bonding strength σ was evaluated by the bonding strength ratio σ / σ _E , as in Example 1.

[0064]

[Table 3]

The examples of the present invention each had a high radial crushing strength of 200 MPa or more, even if they contained fine particles for improving machinability.
A porous metal sintered body for reinforcing a light alloy member having a high bonding strength ratio of 0 or more and a light alloy composite member using the same.

[0066]

EFFECTS OF THE INVENTION According to the present invention, it is possible to stably produce a porous metal sintered body for reinforcing light alloy members, which has excellent radial crushing strength and excellent bondability after casting and has a remarkable industrial effect. Play.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of the micropore ratio on the joint strength ratio after casting.

FIG. 2 is an explanatory view schematically showing an example of a distribution state of pores in a sintered body.

FIG. 3 is a graph showing the relationship between the porosity and the bonding strength ratio between a conventional porous metal sintered body after casting and an aluminum alloy material.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02F 3/00 302 F02F 3/00 302Z

Claims (14)

[Claims] 1. A porous metal sintered body obtained by compacting and sintering a mixed powder containing an alloy powder, wherein the porous metal sintered body has a porosity of 15 to 50%. , And the diameter of the holes is 5
Porous metal sinter for reinforcing light alloy members with excellent impregnation properties for light alloys, characterized by having 80% or more of pores with a total porosity of more than μm and radial crushing strength of 200 MPa or more. body. 2. The particle size of the porous metal sintered body is 150 μm.
0.1 to 5 mass% of fine particles for improving machinability consisting of one or more selected from the group consisting of m or less of MnS, CaF ₂ , BN and enstatite are contained. A porous metal sintered body for reinforcing the light alloy member described. 3. The porous metal sintered body for reinforcing a light alloy member according to claim 1, wherein the porous metal sintered body is a porous stainless steel sintered body. 4. The porous metal calcination for reinforcing a light alloy member according to claim 3, wherein the porous stainless steel sintered body is replaced with a porous Fe—Cu—C system sintered body. Union. 5. A composite member obtained by impregnating a porous metal sintered body obtained by compacting and sintering a mixed powder containing an alloy powder with a light alloy, wherein the porous metal sintered body comprises: Porosity of 15 to 50%, of which 80% or more of the total pores have a diameter of 5 μm and a radial crushing strength of 200 MPa.
A light alloy composite member characterized by the above. 6. The alloy powder is mixed with graphite powder and lubricant powder to form a mixed powder, the mixed powder is formed into a green compact, and then the green compact is sintered. In the method for producing a porous metal sintered body to be a porous metal sintered body, the alloy powder is an alloy powder having a particle size distribution of -60 mesh to +350 mesh, and the sintering conditions for the sintering are adjusted, The porosity of the porous metal sintered body is 15 to 50%, and the radial crushing strength is 200M.
A method for producing a porous sintered body for reinforcing a light alloy member, which is excellent in impregnation property of a light alloy, characterized by having Pa or more. 7. The fine powder for improving machinability, wherein the mixed powder further comprises one or more selected from MnS, CaF ₂ , BN and enstatite having a particle size of 150 μm or less, The method for producing a porous metal sintered body for reinforcing a light alloy member according to claim 6, wherein the content of the mixed powder is 0.1 to 5% by mass. 8. An alloy powder is mixed with graphite powder and lubricant powder to form a mixed powder, and the mixed powder is molded into a green compact having a predetermined shape, and then the green compact is baked. In a method for manufacturing a light alloy composite member, which is obtained by binding a porous metal sintered body of a predetermined shape, and then impregnating a light alloy to form a composite member,
The alloy powder is an alloy powder having a particle size distribution of −60 mesh to +350 mesh, and the sintering conditions for the sintering are adjusted so that the porosity of the porous metal sintered body is 15 to 50%. A method for manufacturing a light alloy composite member, which has a strength of 200 MPa or more. 9. The fine powder for improving machinability, wherein the mixed powder further comprises one or more selected from MnS, CaF ₂ , BN and enstatite having a particle size of 150 μm or less, 9. The method for producing a light alloy composite member according to claim 8, wherein the content of the mixed powder is 0.1 to 5 mass%. 10. The production of a light alloy composite member according to claim 8, wherein the alloy powder is ferritic stainless steel powder, martensitic stainless steel powder or austenitic stainless steel powder. Method. 11. The method for producing a light alloy composite member according to claim 10, wherein the mixed powder contains the graphite powder in an amount of 1.0 mass% or less based on the total amount of the mixed powder. 12. The method for manufacturing a light alloy composite member according to claim 8, wherein the alloy powder is iron powder and Cu powder, or Fe—Cu alloy powder. 13. The light alloy composite according to claim 12, wherein the Cu powder or the Fe—Cu alloy powder is blended so that the Cu content in the mixed powder is 2 to 6 mass%. Method for manufacturing a plasticizing member. 14. The method for producing a light alloy composite member according to claim 12, wherein the mixed powder contains the graphite powder in an amount of 0.8 to 1.5 mass% with respect to the total amount of the mixed powder.