JPH06264170A - Aluminum alloy having high strength and wear resistance - Google Patents

Abstract

PURPOSE:To produce an aluminum alloy having high strength and wear resistance by specifying the density and tensile strength of an alloy and the maximum grain size of Si, respectively, in a sintered Al alloy prepared by blending specific percentages of Si, Cu, Mg, Ni, Fe, and Mn with Al. CONSTITUTION:A powder of an alloy having a composition consisting of, by weight, 8-30% Si, 0.1-10% of at least one or more elements among Cu, Mg, Ni, Fe, and Mn (where Ni+Fe+Mn<1.6%), and the balance Al is sintered, by which a sintered Al alloy is prepared. At this time, sintering is carried out by means of solid phase sintering and also plastic deformation is applied by means of extrusion or forging to make the compact dense, by which, in this alloy, a density of 95% based on true density is provided and tensile strength is regulated to >=30kg/mm<2> and, further, the maximum grain size of Si is regulated to <=10mum. By this method, the alloy having superior mechanical strength and excellent in wear resistance of the material itself, damage resistance of a mating material of sliding, wear resistance of dies used at the time of manufacture as well as in machinability can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum-silicon excellent in wear resistance of a material itself, wear resistance of a sliding mating material, wear resistance of a mold used in manufacturing, and machinability of a material. It relates to a sintered alloy material.

[0002]

2. Description of the Related Art In recent years, cast aluminum-silicon alloys having excellent wear resistance have been used among various aluminum alloys for reasons such as weight reduction of sliding parts, thermal conductivity, corrosion resistance, non-magnetism and cost. ing. In hypoeutectic or eutectic aluminum-silicon alloys with low silicon content, the primary and eutectic α of aluminum are precipitated, and the poor dispersion state of silicon results in insufficient wear resistance and severe sliding. It has drawbacks that are not available for parts under conditions. On the other hand, a hypereutectic aluminum-silicon alloy having a high silicon content deposits silicon having a high hardness as a primary crystal and has excellent wear resistance. Friction and sliding wear on the mating material significantly, and depending on the sliding conditions, the coarse silicon particles that have fallen from the matrix increase the wear of the material itself due to the abrasive action of the abrasive grain, and the machinability is poor and precise. It has drawbacks such as difficulty in processing. For this reason, various attempts have been made to reduce the size of primary crystal silicon crystal particles, but a satisfactory material has not yet been obtained in a cast alloy.

On the other hand, powder metallurgy is well known as an effective means for finely and uniformly dispersing various dispersed particles.
It is difficult to manufacture the material of the present invention by a usual powder metallurgy method. That is, both aluminum and silicon are very easily oxidized, and the surface of the powder is covered with a strong oxide film, which markedly impairs the sinterability, so that the oxide film of the aluminum-silicon alloy is required to be sintered. Cause destruction. It is necessary to select at least a sintering temperature that accompanies the formation of a liquid phase, and under such liquid phase formation temperature conditions, silicon particles are being sintered regardless of the aluminum-silicon mixed powder or alloy powder. It tends to grow and grow. This tendency is more remarkable in those containing finer silicon particles, and it is difficult to prepare a material within the scope of the present invention.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks, wear resistance of the material itself, wear resistance of the sliding mating material, and wear resistance of the mold used during manufacturing or abrasion. It is intended to provide an aluminum-silicon sintered alloy having excellent characteristics such as workability.

[0005]

The basic characteristics of the aluminum alloy of the present invention are: silicon 8 to 30% by weight, at least one or more of copper, magnesium, nickel, iron and manganese 0.1 to 10% by weight. (Although Ni + Fe + Mn <1.6% by weight) Aluminum Sintered alloy made by sintering alloy powder consisting of the balance, in which the alloy is sintered in the solid phase and plastically deformed by extrusion or forging. By densifying the alloy, the alloy has a density of 95% or more with respect to the true density,
In addition, the high-strength wear-resistant aluminum alloy is characterized by having a tensile strength of 30 kg / mm ² or more and a maximum particle size of silicon of 10 μm or less.

The alloy of the present invention is generally manufactured as follows. A part or all of various components such as aluminum containing 8 to 30% by weight (the same applies below) of silicon having a maximum particle diameter of 10 μ or less and copper, magnesium, nickel, manganese and iron usually containing silicon as a main component. And preferably, -30 mesh + 350 mesh (44-580 µm, average 100-200 µm) atomized alloy powder is press-molded, or the powder compact is solid-phase sintered with the alloy powder. In the temperature range, that is, in the solid-phase sintering temperature range, an external stress accompanied by plastic deformation such as extrusion forging of a sintered body obtained by sintering in a non-oxidizing atmosphere at 300 ° C. or higher and a liquid phase generation temperature or lower is applied. In addition, it is obtained by densification. In the present invention, since a coarse powder having a relatively small amount of adsorbed gas is used and the powder is compacted through a green compact having a specific density (65 to 85% of the true density as described later), blister and minute voids are generated. Can be suppressed. This material has excellent wear resistance up to this point, but it has 5 to 30% by weight of graphite, which has lubricity, and one or more sulfides such as WS ₂ or MoS _{2 in} total of 5 to 5% by weight. 30 wt% CaF ₂ or B
One containing one or more fluorides such as aF ₂ alone in a total of 5 to 30% by weight, or containing two or more species of graphite, sulfide and fluoride, and the total amount is 5 to 30% by weight or less It has excellent sliding performance under the so-called dry sliding condition where the lubricating oil film is not sufficiently formed or the lubricating oil cannot be used due to the added lubricity. Improve.

The reasons for selecting the composition range of the present invention will be described below. When the content of silicon is 8% or less, the effect of improving wear resistance is small, and the effect of improving sliding performance is hardly increased even if it is contained in an amount of 30% or more. On the contrary, the strength is lowered and the molten metal temperature is increased to obtain atomized powder. The preferable range is set to 8 to 30% for reasons such as necessity.

The metal structure of the alloy of the present invention is characterized in that silicon having a hard hardness is finely and uniformly dispersed in a matrix containing aluminum as a main component. This is the main reason for the excellent properties of the alloy of the present invention to be exhibited, and it is necessary that the maximum particle size of silicon is at least 10 μ or less, preferably 5 μ or less (see FIGS. 1 and 2). .

In order to obtain the fine structure of the alloy of the present invention, the atomized alloy powder containing aluminum and silicon as the main components, which contains a predetermined amount of silicon having a maximum particle size of 10 μm or less, preferably 5 μm or less, is used as a raw material powder. It is necessary to maintain the heating temperature in the subsequent sintering step or densification step within the solid-phase sintering temperature range in which liquid phase is not generated.

The silicon particle size in the atomized alloy powder is affected by various factors such as alloy composition, melt temperature, and powder particle size, but is mainly dependent on the cooling and solidification rate of the atomized powder. In order to obtain atomized powder having a diameter, the cooling solidification rate is at least 10 ° C /
It is necessary to be at least sec, preferably at least 50 ° C./sec. This condition is a usual atomizing method and can be selected relatively easily. The atomized alloy powder containing fine silicon particles has a particle size of -30 mesh +
The one having a particle size range of 350 mesh is most suitable. If the powder particle size is 30 mesh or more, it is not preferable because the silicon particles contained therein tend to be coarsened and the strength of the press-molded compact is reduced. Oxides that are necessarily present on the surface of the atomized alloy powder, in the case of the alloy of the present invention, have the effect of finely dispersing in the alloy at high temperature strength, as well as improving wear resistance,
In the case of fine powder having a particle size of 350 mesh or less, the content of oxides increases dramatically, causing wear of the press mold and the mold and die used in the densification step, and poor plastic deformation morphology, which inhibits densification. However, alumina and silica are very hard oxides and have performance problems such as increasing wear of the friction sliding material and impeding machinability. Further, it is possible to produce fine powder having a relatively small oxide content of 350 mesh or less, but handling in the air is not practical due to the risk of ignition, so the preferred range is -30 + 350 mesh. It is necessary to perform sintering or densification treatment at a heating temperature in the sintering step or the densification step of the powder compact, which is 300 ° C. or higher, preferably the recrystallization temperature or higher, and the liquid phase formation temperature or lower. is there. At a heating temperature of 300 ° C. or less, the workability required for densification cannot be obtained, and at a heating temperature accompanied by the formation of a liquid phase, the intended purpose cannot be achieved because the growth of silicon particles is obstructed. The sintering step in the present invention is performed when intermediate processing is required before the densification step or when the final product shape is complicated and material strength is required,
Usually, the compacting process of the green compact can be carried out. In the densification step, a porous green compact having a density of 65 to 85% of the true density or a porous solid obtained by solid-phase sintering of the green compact is provided in order to suppress oxidation and improve gas release. It is necessary to extrude the sintered body and apply external stress accompanied by plastic deformation such as forging to densify it to a density of at least 95% or more of the theoretical density ratio. Not surprisingly, there is a close relationship between external stress and the theoretical density ratio and strength. For example, in the case of extrusion, between the extrusion ratio and strength,
There is a relationship as shown in FIG. 3 shows the relationship between the extrusion tensile strength at various extrusion ratios after sintering the sintered aluminum alloy of the component shown in A of Example 1. When the densification is 95% or less, the residual porosity is high and the oxide film between particles is not sufficiently broken, so that the bonding property between particles is weak, and the intended purpose cannot be achieved. The alloy of the present invention has a high tensile strength of 30 kg / mm ² or more.

In the present invention, since a porous powder compact is used, the molding pressure in the press form may be 1 to ² t / cm ² , the die is less worn, and the porous body is densified to make it compact. Since the deformation resistance at the time of is small, the tool life for densification is very long.

By adding 0.1 to 10% by weight of at least one of copper, magnesium, manganese, iron and nickel as a normal alloy component to the above atomized alloy powder, strength and heat resistance can be improved. . When it is 10% by weight or more, it becomes rather brittle and it becomes difficult to densify during manufacturing. Further, if it is 0.1% by weight or more, the effect is not obtained. Among them, nickel, manganese, and iron form coarse segregates in ordinary cast aluminum alloys, and significantly reduce the strength. Therefore, addition thereof was limited to a very small amount. However, according to the present invention, segregation does not occur in the aluminum sintered alloy,
It can be added positively in order to produce fine and uniform dispersion-strengthening particles and to contribute to the improvement of strength. However, it is important that the range satisfies the relationship of Ni + Fe + Mn <1.6% by weight, so that strength and heat resistance can be maintained in a good balance.

In order to improve the sliding characteristics of the material of the present invention, 5 to 30% of graphite, 5 to 30% in total of one or more sulfides such as WS ₂ or MoS ₂ , and fluorides such as CaF ₂ or BaF ₂ are added. It is possible to contain one or more solid lubricant components of 5 to 30% in total, or two or more graphite sulfides and fluorides, the total amount of which is 5 to 30%.

Addition of these solid lubricating components has the effect of reducing the frictional resistance, improving the wear resistance of the material itself and the wear of the mating material, and especially lubrication under sliding conditions where the formation of a lubricating oil film is insufficient. It exhibits excellent sliding performance under dry sliding conditions where oil cannot be used. However, if the added content is less than each specified amount, the effect of the addition is small, and even if added more than each specified amount, the performance improving effect hardly increases and the material strength decreases, which is not preferable. Note that those that contain these solid lubricating components have slightly different sliding characteristics such as seizure resistance and wear resistance depending on the lubricating components that they contain.For example, those that are used under severe sliding conditions in lubricating oil , Such as graphite, which has self-lubricating property and oil retaining property, is suitable, and when used under the condition of large temperature change from low temperature to high temperature, it has excellent high temperature characteristics with graphite or sulfides such as WS _2. CaF ₂
It was confirmed that those containing two kinds of fluorides, etc. exhibit particularly excellent effects.

[0015]

EXAMPLES Examples of the present invention will be described below in order to specifically illustrate the constitutions and effects of the present invention as described above. Example 1 Atomized alloy powder produced by melting each alloy having the composition shown in Table 1 under the condition that the cooling solidification rate is 50 ° C./sec or more is −30 mesh + 350 mesh and −.
Use powder whose particle size has been adjusted to 350 mesh, 1.5-2
The compacted body at a pressure of ton / cm ² and the sintered compact obtained by sintering the compacted body in a hydrogen atmosphere at 500 ° C. for 30 minutes were heated at 450 ° C. in a nitrogen atmosphere to obtain an extrusion ratio of 1 Extrusion using a die of: 13 or forging at a pressure of 8 ton / cm ² was performed to obtain alloys shown in Table 2. Further, in order to obtain a comparative material, an alloy having the composition shown in Table 1 was melted and die-cast, and a casting material having a maximum silicon particle size of 40 to 50 μm (Sample No.
0) and the composition shown in Table 1 -60 mesh Al powder-250 mesh Si powder-350 mesh or less C
Table 2 (Sample No. 9) shows the characteristics of the alloy obtained by subjecting the powder obtained by uniformly mixing the powders of u, Mg and Ni to compression molding, sintering and extrusion under the same conditions as above.

[Table 1]

[Table 2]

The samples shown in Table 2 were subjected to the friction and wear tests shown in Tables 4 and 5 and the machining test shown in Table 6, and the results are shown in Tables 8 and 9, respectively. In addition, No.
1 and No. The powder of No. 7 was used to examine the degree of wear of the mold used during compacting. This method is only a model test, but according to the result, as shown in Table 10, the sample No. It is estimated that No. 1 has less wear of the mold.

Example 2 17.1% Si, 3.1% Cu, 0.30% Mg, 0.
10% Ni melts an alloy whose balance consists essentially of Al,
Atomized alloy powder of -30 + 350 mesh, graphite powder having an average particle size of 10 μm, and W having a maximum particle size of 10 μm or less, which were produced under the condition that the cooling solidification rate was 50 ° C./sec or more.
A powder obtained by uniformly mixing the powders of S ₂ and CaF _{2 in} the composition shown in Table 3 was press-molded at a pressure of ² ton / cm ² and heated at 520 ° C. for 10 minutes to obtain a theoretical density ratio of 95% or more. Die forging to the density of Table 3
The alloy shown in was obtained. These samples were subjected to the friction and wear tests shown in Tables 4 and 5 and the machining test shown in Table 6 as in Example 1, and the results are summarized in Tables 8 and 9.

[Table 3]

[Table 4]

[Table 5]

[Table 6]

[Table 7]

[Table 8]

[Table 9]

[Table 10]

[0018]

The alloy of the present invention has excellent mechanical strength and is excellent in the wear resistance of the material itself, the wear resistance of the sliding mating material, the wear resistance of the die used during manufacturing, and the machinability. It has the characteristics described above. It is needless to say that the alloy of the present invention can be subjected to heat treatment which is usually carried out on an aluminum alloy for the purpose of improving mechanical strength. Especially, the tensile strength is 25 kg / mm ² or more and the wear amount is 8 × 10 ^-7
If the alloy is less than mm ³ / kg, it can be used in fields such as compressor vanes, connecting rods, pistons, and cylinders that could not be used before. In such fields, efforts have been made to reduce the weight of parts, and the alloy according to the present invention can be used in the fields as described above.

[Brief description of drawings]

FIG. 1 is a micrograph showing the structure of the material of the present invention (Sample No. 2), and FIG. 2 is a die casting material for comparison (Sample No. 10).
2 is a micrograph showing the structure of FIG. 3 is an explanatory view showing the outline of the apparatus used for the mold wear test shown in Table 7, and FIG. 4 is a graph showing the relationship between the amount of plastic working and strength.

[Explanation of symbols]

 1 ... Counterpart material 2 ... Stirring hand (both sides) 3 ... Alloy powder slurry 4 ... Test piece (SKD steel) 5 ... Weight

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[Procedure amendment]

[Submission date] January 25, 1993

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

[1] is a photomicrograph showing the metal structure of the present invention material (sample No.2).

2 is a cast metal material for comparison (Sample No. 10)
3 is a micrograph showing the metal structure of the above .

FIG. 3 is an explanatory diagram showing an outline of an apparatus used for the mold wear test shown in Table 7.

FIG. 4 is a graph showing the relationship between the amount of plastic working and strength.

[Explanation of symbols] 1 ... Counterpart material 2 ... Stirring hand (both sides) 3 ... Alloy powder slurry 4 ... Test piece (SKD) 5 ... Weight

Claims (3)

[Claims] 1. Silicon 8 to 30% by weight At least one or more of copper, magnesium, nickel, iron and manganese 0.1 to 10% by weight (That is Ni + Fe + Mn <1.6% by weight) Aluminum balance In the aluminum sintered alloy obtained by sintering the alloy powder, the alloy is sintered at a solid phase, and the alloy is densified by applying plastic deformation by extrusion or forging so that the alloy has a true density of 95% or more. It has a density and a tensile strength of 3
0kg / mm ² or more, maximum particle size of silicon is 10μ
A high-strength, wear-resistant aluminum alloy characterized by being m or less. 2. Silicon 8 to 30% by weight At least one or more of copper, magnesium, nickel, iron and manganese 0.1 to 10% by weight (but Ni + Fe + Mn <1.6% by weight) Aluminum balance Alloy powder and solid lubricant component of 5 to 30% by weight,
In an aluminum alloy obtained by mixing and sintering, 95% of the true density is obtained by performing sintering in a solid phase and densifying by applying plastic deformation by extrusion or forging.
A high-strength wear-resistant aluminum alloy having the above density, a tensile strength of 22 kg / mm ² or more, and a maximum particle size of silicon of 10 μm or less. 3. The solid lubricating component is graphite, WS ₂ , MoS
The high-strength wear-resistant aluminum sintered alloy according to claim 2, wherein the high-strength wear-resistant aluminum sintered alloy is made of one or more of ₂ , CaF ₂ , and BaF ₂ .