JPH10158764A - Aluminum base composite material excellent in coagulation resistance and strength and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an Al base composite material excellent in coagulation resistance and strength by impregnating molten Al in a porous pellet formed of respective power materials of Ti, graphite and al and heating, and then dipping the impregnated pellets in molten Al to produce a TiC-containing molten metal and impregnating this molten metal in the separately produced Al-Fe base porous body. SOLUTION: The respective powder materials of Ti, graphite and Al are mixed to form the porous pellet. After impregnating the molten Al or a molten Al base alloy in this pellet, this pellet is heated to 1000-1800 deg.C, and TiC fine grains having <=0.5μm grain diameters are developed in the Al matrix. This pellet is dipped into molten Al to produce the molten Al dispersed with TiC fine grains. On the other hand, the porous body composed of Al or Al alloy powder and Fe alloy powder is formed, and the molten metal containing TiC is impregnated in the formed body to obtain an Al base composite material. This composite material contains coarse grain of ceramic, etc., in a content of 25-73vol%, and the TiC fine grains are contained in a content of 0.15-14wt.% to a pore filling part of the porous body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an Al-based composite material having excellent adhesion resistance and strength and a method for producing the same. INDUSTRIAL APPLICABILITY The present invention is useful for an Al-based member having at least a part of a reinforcing portion formed of an Al-based composite material, particularly an Al-based sliding member, and is typically used for a piston of an internal combustion engine, particularly for sliding conditions. It is extremely advantageous to apply to a wear-resistant ring portion provided with a piston ring groove which is a severe part.

[0002]

2. Description of the Related Art In recent years, the performance of automobile engines has been improved, and accordingly, it is inevitable that the piston temperature rises. For this reason, Al-based composite materials have been developed as piston materials having both heat resistance and light weight. Especially in the wear ring part of the piston, the piston ring groove provided there engages with the piston ring and slides repeatedly at high temperature at high speed, so it is possible to improve the wear resistance at this high temperature, especially the adhesion resistance. is important.

For example, “Iron and Steel” (published by the Iron and Steel Institute of Japan,
September 998, p. 376) discloses that the anti-adhesion property is enhanced by forming the piston ring bearing portion from an Al-based composite material. This Al-based composite material uses whisker titanate, carbon fiber, alumina fiber, alumina-silica fiber (saphir), and NiAl ₃ particles as a reinforcing material. ) Is impregnated.

[0004] The wear-resistant ring portion made of this Al-based composite material is
It was lighter in weight and higher in anti-adhesion property than the wear-resistant ring portion made of niresist cast iron used before that. However, in order to cope with higher performance of the engine, it was necessary to further improve the adhesion resistance.

Accordingly, the present applicant has filed Japanese Patent Application No. 7-13974.
As disclosed in No. 0, an Al-based composite material in which pores of a powder compact formed of an aggregate of Al-based powder particles including Si particles and the like are impregnated with an Al-based molten metal by high-pressure casting has been developed. This Al-based composite material reduces the continuity of the Al-based matrix by finely dividing the Al-based matrix by Si particles or the like as a reinforcing material, and effectively suppresses the transfer of the Al component to the partner material. This significantly improves adhesion resistance.

However, although this Al-based composite material has improved adhesion resistance, there is still room for further improvement in tensile strength.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an Al-based composite material having excellent adhesion resistance and strength, and a method for producing the same.

[0008]

In order to achieve the above object, an Al-based composite material according to the present invention comprises a matrix of Al or an Al-based alloy in which coarse particles made of a material other than TiC are dispersed as a reinforcing phase. An Al-based composite material comprising: a porous structure part formed as described above; and a hole filling part in which pores of the porous structure part are filled and TiC fine particles are dispersed as a reinforcing phase in a matrix made of Al or an Al-based alloy. The coarse particles have a larger particle size than the TiC fine particles and are present in an amount of 25 to 73% by volume with respect to the composite material. The TiC fine particles have a particle size of 0.5 μm or less and have an empty space. It is characterized by being present in an amount of 0.15 to 14% by weight with respect to the hole filling portion.

Here, coarse particles include Si particles and F particles.
It may include one or more types of particles selected from the group consisting of e-alloy particles and ceramic particles. In the present invention, the Al-based matrix that fills the pores of the porous structure portion in which coarse particles as a reinforcing phase corresponding to Si particles and the like in the Al-based composite material of the prior application are dispersed is reinforced by the dispersion of TiC fine particles. By doing so, it is possible to improve the tensile strength while securing the adhesion resistance obtained in the prior application.

The coarse particles must be present in an amount of at least 25% by volume based on the composite material in order to secure the strengthening action as the strengthening phase and to secure high adhesion resistance due to the matrix breaking effect. If it is present in excess, the composite material is embrittled. The TiC fine particles are used in an amount of 0.1% with respect to the pore-filled matrix in order to strengthen the pore-filled matrix and exhibit the effect of improving the tensile strength of the composite material.
It must be present in an amount of 5% by weight or more, but if present in excess, the elongation is reduced and the tensile strength is also reduced.

Since the Al-based composite material of the present invention is produced by impregnating a molten metal containing TiC fine particles into a porous compact as described below, the particle size of the TiC fine particles is assured to ensure good impregnation. It needs to be 0.5 μm or less. Also,
The smaller the particle size, the more advantageous the dispersion enhancing action is. The method for producing the Al-based composite material of the present invention includes:
The following steps: a step of mixing Ti powder, graphite powder and Al powder, a step of forming the obtained mixed powder into porous pellets, a step of impregnating the porous pellets with a molten metal of Al or an Al-based alloy, 1000 pellets after impregnation
By heating to a temperature of １1800 ° C., TiC having a particle size of 0.5 μm or less
The step of generating fine particles, and placing the pellets after heating in a molten metal of Al or an Al-based alloy,
A step of preparing a molten metal containing TiC fine particles in which C fine particles are dispersed, a step of separately forming a mixed powder of Al or an Al-based alloy powder and an Fe alloy powder to form a porous molded body, and Impregnating the TiC-containing molten metal into the hot compact.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the method of the present invention, a method for forming pellets in which TiC fine particles are generated and a method for preparing a molten metal containing TiC fine particles by placing the pellets in a molten Al or an Al-based alloy are described below. The method already disclosed in JP-A-6-17165 by the present applicant is used. At that time, the pellets after impregnation are heated at 1000 ° C. to 180
Heating to 0 ° C. produces TiC fine particles in the Al or Al-based alloy matrix. When the heating temperature is lower than 1000 ° C., substantially no TiC is generated,
If the temperature is higher than 1800 ° C., the generated TiC becomes coarse.

TiC generated in pellets by heating
The reason why the particle size of the fine particles is limited to 0.5 μm or less is to secure good impregnation as described above. The TiC fine particle-dispersed pellets thus formed can be easily dissolved in a molten metal of Al or an Al-based alloy, and a molten metal in which TiC fine particles are dispersed can be obtained. The TiC fine particles are very stable in the molten metal. For example, if the particles are kept for about one hour, neither coarsening nor reaction with the molten metal occurs, so that the TiC fine particles are very excellent for impregnating a porous compact.

In the present invention, the pores of the porous molded body are impregnated with the molten metal containing fine TiC particles. In order to sufficiently infiltrate the molten metal into the fine pores, high-pressure casting is generally performed. However, if the impregnation can be performed by ordinary gravity casting instead of high-pressure casting, it is more advantageous in terms of productivity and manufacturing cost. In a desirable mode of the present invention, in the step of producing the porous molded body, Al
Alternatively, in addition to the Al-based alloy powder and the Fe alloy powder, a Ti powder is further added. Oxygen and nitrogen in the pores are removed by the deoxidizing action and denitrifying action of Ti contained in the obtained molded body, the internal pressure in the pores is greatly reduced, and the pressure is close to a vacuum, and the suction action on the molten metal is performed. Occurs.
As a result, the molten metal can sufficiently penetrate into the pores even by ordinary gravity casting, not by high-pressure casting. Usually, when performing impregnation, the compact is preheated to, for example, about 100 ° C., and a molten metal at, for example, about 800 ° C. is cast.

[0015]

【Example】

[Example 1] [1] Preparation of porous molded body Al-38 wt% Si alloy powder (atomized powder, manufactured by Toyo Aluminum, average particle size 50 µm, average primary crystal Si particle size 10 µm), Fe-63 wt% Cr -7 wt% C alloy powder (crushed powder, manufactured by Fukuda Metals, average particle size 60 μm) was mixed and molded to obtain a porous molded body. The porosity of this porous formed body was 20% by volume.

[2] Preparation of molten metal containing TiC fine powder Ti powder (average particle diameter 50 μm), Al powder (average particle diameter 1
00 μm) and graphite powder (average particle size 10 μm) in a weight ratio of 8: 5: 2, and mixed with a V-type mixer for 1 hour. The obtained mixed powder was formed into a cylindrical pellet (30
φ × 10 mm). The pellet is heated at a temperature of 100
It was immersed in a 3K pure aluminum melt for 30 seconds to impregnate the pores of the pellet with pure Al. The impregnated pellets were heated to 1327K in an Ar atmosphere at a rate of 0.083K / sec, and then water-quenched.

Observation of the structure after this heat treatment revealed that only TiC fine particles having an average particle size of 0.1 μm (maximum particle size 0.5 μm or less) were dispersed in the Al matrix. It is considered that the following reaction-has progressed in the pellets being heated.
[] Indicates the reaction temperature. Ti (s) + Al (s) → Al ₃ Ti (s) ..... [890K] Al (s) → Al (l). .................... [930K] Ti (s) + Al (l) → Al ₃ Ti (s). ............ [940K] 3Al ₃ Ti (s) + Al ₄ C ₃ (s) → 3TiC (s) + 13Al (s). ....... [1150K] Al ₃ Ti (s) + C (s) → TiC (s) + Al (l) ......... [1155K ～ 1260K] The above TiC fine particles Was added to a molten aluminum-based alloy (JISAC8A), and the mixture was stirred to form a molten metal containing TiC fine particles. The amount of addition to the molten metal was varied as shown in Table 1 as the amount of TiC added. Although the pellets were easily dissolved in the molten metal, the molten metal was stirred with a stirring rod for about 15 minutes from the addition to the following casting so that the TiC fine particles did not agglomerate in the molten metal. In addition, JIS AC8A has a chemical composition of 11 to 11.
13 wt% Si, 0.8-1.3 wt% Cu, 0.7-1.
It is in the range of 3 wt% Mg, and precipitates and hardens by aging. The Si content of the molten metal used in this example was 12% by weight.

[3] Impregnation The above-mentioned molten metal was impregnated into the compact prepared in the above [1] by high-pressure casting. In the high-pressure casting, after a compact is placed in a mold for high-pressure casting and preheated at 500 ° C. × 1 hour, a casting temperature of 800 ° C., a mold temperature of 280 ° C., and a pressing condition of 130 MPa
Performed in a × 30 seconds. Immediately after casting, it was quenched in warm water at 70 ° C.

[4] Test After the obtained casting was subjected to T6 treatment at 220 ° C. for 6 hours, a test piece was sampled and subjected to an adhesion resistance test and a tensile test. As shown in FIG.
Was carried out by a test machine having built-in tables 11 and 12 facing each other. Test piece W (φ90 x thickness 10mm)
1 and a 17 wt% Cr stainless steel nitride ring 13 was attached to the base 12 assuming an engine piston ring as a mating material. In this state, the table 12 is reciprocated in the arrow Y1 direction to strike the ring 13 against the surface of the test piece W. This beating is performed at a temperature of 280 ° C. and a surface pressure of 0.1 MPa.
For 10 minutes. Thereafter, the adhesion area on the surface of the test piece W was measured to evaluate the adhesion resistance.

The tensile test uses an Instron type testing machine,
1 mm crosshead speed at room temperature and 250 ° C
/ Min. At the time of the test at 250 ° C., the test piece was previously subjected to a heat treatment at 250 ° C. × 100 hours. Table 1 shows the test results. In the same table, Samples 1 to 5 are those in which the amount of TiC added in the pellet addition to the molten metal of the above [2] is within the range of the present invention. The amount of TiC added is less than the range of the present invention, and the amount of TiC added is more than the range of the present invention.

The adhesion resistance was good for all the samples tested, with and without TiC addition. The tensile properties of Samples 1 to 5 to which TiC was added within the scope of the present invention were lower than those of Comparative Sample C1 to which TiC was not added.
It can be seen that in both of the cases, the tensile strength and the elongation are greatly improved. Within the scope of the present invention,
The room temperature tensile strength increases with an increase in the amount of TiC added,
Elongation tends to decrease.

In the present invention, the addition amount of TiC is at most 3% by volume with respect to the whole composite material, and although it is relatively small, a clear improvement in tensile properties is recognized. The reason is that TiC contains Al in the pores (20% by volume with respect to the composite material) of the porous structure portion of the powder compact.
Alternatively, since TiC is introduced through a molten metal of an Al-based alloy, TiC is selectively dispersed in a matrix filling the pores having the lowest strength in the structure of the composite material. It is considered that the effect is exhibited.

The reason why the elongation (ductility) is increased by the addition of TiC is that T is also used as a heterogeneous solidification nucleus of an Al alloy.
This is considered to be the result of iC acting as a refiner for the Al-based matrix. It should be noted that the comparative sample C2 to which 0.1 wt% of TiC was added, which is less than the range of the present invention, showed only a small effect compared to the comparative sample C1 to which no TiC was added. It is considered that this is because the addition amount is usually small when TiC is used as a refining agent, so that not only the dispersion strengthening but also the refining effect is not substantially obtained.

Conversely, if the amount of TiC added is too large, as in Comparative Sample C3, the dispersion strengthening or composite strengthening becomes too large and ductility decreases, resulting in a decrease in tensile strength. It has been conventionally known that the anti-adhesion property is improved as the exposed surface area of the Al-based matrix is smaller, without reducing the amount of the coarse particles as the reinforcing phase in the porous structure of the powder compact. Since the TiC fine particles can be added to the pores of the porous structure, the TiC
It is considered that the larger the amount of addition, the higher the adhesion resistance.

[0025]

[Table 1]

Example 2 The same Al-38 wt% Si alloy powder and Fe-63 wt% Cr as used in Example 1
In addition to the −7 wt% C alloy powder, pure Ti powder (Sumitomo Citix, −325 mesh) was weighed so that the volume ratio in the final composite material was 55%, 20%, and 5%.
It was mixed and molded to obtain a porous molded body. That is, the volume ratio of the molded body in the composite material is 80%, and the porosity is 20% by volume as in Example 1.

The above compact was impregnated with a TiC fine particle-containing molten metal prepared in the same manner as in Example 1 by ordinary gravity casting. This gravity casting was performed under the same preheating and casting conditions as in the high-pressure casting of Example 1 except that no pressure was applied. The obtained casting was subjected to T6 treatment under the same conditions as in Example 1. When the structure of the cross section was observed, a good structure having no micropores or the like was observed. In addition, when an anti-adhesion test and a tensile test were performed, good results almost equivalent to those of the high-pressure cast material of Example 1 were obtained.

The casting temperature was set to 750 ° C. and 850 ° C. in contrast to 800 ° C., and the composition excluding TiC of the molten metal containing fine TiC particles was changed to Al-4 wt% Cu—
Similar results were obtained for samples prepared under the same conditions as above, except that 1.5 wt% Mg-0.6 wt% Mn. In addition, the volume fraction for the final composite is
e-63wt% Cr-7wt% C alloy powder is 10%, the whole compact is constant at 80% (that is, porosity is 20%), and the Ti powder is varied in a range of 0.5-30%. And the Fe-63 wt% Cr-7 wt% C alloy powder is 10%, the whole compact is constant at 75% (that is, the porosity is 25%), and the Ti powder is 0.5 to 3%.
Samples were prepared in the same manner as described above under other conditions when various changes were made within the range of 0%. As a result, except for the case where the volume ratio of the Ti powder was set to 0.5%, a good composite material having no defects such as micropores was obtained.

The porous compact formed in the same manner as described above was subjected to gravity casting under the same molten metal composition and conditions as in Example 1 except that the mold preheating temperature was about 300 ° C. and the casting temperature was 850 ° C. Was impregnated. Also in this case, an Al-based composite material having a good structure without any micropores was obtained. From the results of this example, it was found that T
It can be seen that by using a porous compact to which i-powder is added, a good Al-based composite material can be produced by ordinary gravity casting without necessarily using high-pressure casting as in Example 1.

In the examples 1 and 2, the case where the porosity of the porous compact was 20% and 25% was explained, but the impregnation of the molten metal containing TiC fine particles into the porous compact was ensured. This is because such a porosity is most suitable from the viewpoint of maintaining the structure of the porous molded body and securing the adhesion resistance of the composite material. However, the porosity need not be particularly limited, and may be any range as long as it is acceptable from the above viewpoint. As a guide, it is recommended that the porosity be in the range of 10% to 40%. That is, the porosity is 1
If it is less than 0%, the resistance to impregnation increases, and it may be difficult to impregnate the porous compact with the molten metal containing TiC fine particles. Conversely, if the porosity is greater than 40%, it may be difficult to maintain the structure of the molded body itself, and the Al portion forming the vacancy filling portion in the composite material is necessarily inevitable. Due to the increase, the adhesion resistance may decrease.

[0031]

As described above, according to the present invention,
An Al-based composite material having both excellent adhesion resistance and strength and a method for producing the same are provided.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an adhesion resistance tester.

[Explanation of symbols]

 W: test piece (disk) 13: partner material (ring)

Claims (4)

[Claims] 1. A porous structure in which coarse particles made of a material other than TiC are dispersed as a reinforcing phase in a matrix made of Al or an Al-based alloy; And a pore-filled part in which TiC fine particles are dispersed as a reinforcing phase in a matrix made of an alloy, wherein the coarse particles have a particle size larger than the TiC fine particles and are larger than the TiC fine particles. 25-73
% By volume, and the TiC fine particles have a particle size of 0.5
μm or less and 0.15 to 14
An Al-based composite material having excellent adhesion resistance and strength, characterized by being present in an amount of% by weight. 2. The adhesion resistance and strength according to claim 1, wherein the coarse particles are one or more particles selected from the group consisting of Si particles, Fe alloy particles, and ceramic particles. Excellent Al-based composite material. 3. The following steps: a step of mixing Ti powder, graphite powder and Al powder; a step of forming the obtained mixed powder into porous pellets; and a step of melting Al or an Al-based alloy into the porous pellets. By heating the impregnated pellets to a temperature of 1000 to 1800 ° C. to generate TiC fine particles having a particle size of 0.5 μm or less in the Al or Al-based alloy matrix. The TiC fine particles are dispersed in TiC by placing it in a molten Al or Al-based alloy.
A step of forming a fine particle-containing molten metal; separately, a step of forming a mixed powder of Al or an Al-based alloy powder and an Fe alloy powder to form a porous formed body; A method for producing an Al-based composite material having excellent adhesion resistance and strength, comprising a step of impregnating a molten metal. 4. The method according to claim 3, wherein in the step of forming the porous compact, a mixed powder of Al or an Al-based alloy powder, a Fe alloy powder, and a Ti powder is formed.