JPH029099B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is an aluminum-silicon material that is excellent in wear resistance of the material itself, wear resistance of sliding mating materials, wear resistance of molds used during manufacturing, and machinability of the material. Regarding sintered alloy materials. [Conventional technology] In recent years, the weight of sliding parts, thermal conductivity, corrosion resistance,
Among various aluminum alloys, cast aluminum-silicon alloys, which have excellent wear resistance, are used for reasons such as non-magnetism and cost. Hypoeutectic or eutectic aluminum-silicon alloys with low silicon content precipitate primary aluminum and eutectic α, and the dispersion state of silicon is poor, resulting in insufficient wear resistance and severe sliding resistance. It has drawbacks that make it unusable for parts under certain conditions. On the other hand, hypereutectic aluminum-silicon alloys with a high silicon content precipitate silicon with high hardness as primary crystals and have excellent wear resistance. Friction can cause significant wear and tear on the sliding mating material, and depending on the sliding conditions, coarse silicon particles that fall off from the matrix can increase the wear and tear of the material itself due to the abrasive abrasive action. It has disadvantages such as poor flexibility and difficulty in precise processing. For this reason, various attempts have been made to make the primary silicon crystal grains finer, but a satisfactory cast alloy material has not yet been obtained. On the other hand, although powder metallurgy is well known as an effective means for finely and uniformly dispersing various types of dispersed particles, it is difficult to produce the material of the present invention by ordinary powder metallurgy. i.e. aluminum,
Silicon is also very easily oxidized, and the surface of its powder is covered with a strong oxide film, which significantly inhibits sinterability, so the oxide film must be destroyed in order to sinter the aluminum-silicon alloy. It is necessary to select a sintering temperature that produces at least a partial liquid phase, and under such liquid phase forming temperature conditions, silicon particles, regardless of the aluminum-silicon mixed powder or alloy powder, are sintered. It has a tendency to grow and become coarser. This tendency is more pronounced as the material contains finer silicon particles, making it difficult to produce a material within the scope of the present invention. [Problems to be Solved by the Invention] The present invention improves the above-mentioned drawbacks and improves the abrasion resistance of the material itself, the abrasion resistance of the sliding partner material, and the abrasion resistance of the mold used during manufacturing. The object of the present invention is to provide an aluminum-silicon sintered alloy that has excellent characteristics such as machinability. [Means for solving the problems] The basic characteristics of the aluminum alloy of the present invention are:
Aluminum alloy powder containing 8 to 30% by weight of silicon and the balance being aluminum, or 8 to 30% by weight of silicon, at least one of copper, magnesium, nickel, iron, and manganese 0.1 to 10% by weight of aluminum, the balance In an aluminum sintered alloy made by sintering an alloy powder, the alloy is sintered in a solid phase, and the alloy is densified by plastic deformation by extrusion or forging.
It has a density of 95% or more and a tensile strength of 22Kg/mm ²
The above provides a high-strength, wear-resistant aluminum alloy characterized in that the maximum particle size of silicon is 10 μm or less. The alloy of the present invention is generally produced as follows. Part or all of various components such as copper, magnesium, nickel, manganese, and iron that usually contain aluminum and silicon as main components, containing 8 to 30% by weight (the same applies hereinafter) of silicon with a maximum particle size of 10μ or less. Contains or does not contain
Preferably, it is a compacted body obtained by press-molding an atomized alloy powder of -30 mesh + 350 mesh, or the compacted body is heated within the solid phase sintering temperature range of the alloy powder, that is, above 300°C and below the liquid phase formation temperature. It is obtained by sintering a sintered body in a non-oxidizing atmosphere and densifying it by applying external stress accompanied by plastic deformation, such as by extrusion forging, within the solid phase sintering temperature range. Although this material has excellent wear resistance as it is, it is further added with 5 to 30% by weight of graphite, WS 2 or WS ₂ , which has lubricating properties.
5 to 30% by weight of one or more types of sulfides such as MoS ₂
Contains one or more fluorides such as CaF ₂ or BaF ₂ in a total amount of 5 to 30% by weight, or contains two or more of graphite, sulfide, and fluoride,
By containing the total amount of 5 to 30% by weight or less to impart lubricity, it is possible to avoid sliding conditions where the formation of a lubricating oil film is insufficient or where lubricating oil cannot be used.
It has excellent sliding performance under so-called dry sliding conditions and also improves machinability. The reasons for selecting the composition range of the present invention will be described below. If silicon content is less than 8%, the effect of improving wear resistance is small, and even if it is contained more than 30%, the effect of improving sliding performance will hardly increase, but the strength will decrease and the temperature of the molten metal will have to be high to obtain atomized powder. Due to reasons such as the need to do so, the preferable range is set to 8 to 30%. The metal structure of the alloy of the present invention is characterized in that silicon having hardness is finely and uniformly dispersed in a matrix mainly composed of aluminum. This is the main reason why the alloy of the present invention exhibits excellent properties, and it is necessary that the maximum particle size of silicon is at least 10 μm or less, preferably 5 μm or less. (Figure 1) In order to obtain the microstructure of the alloy of the present invention, an atomized alloy powder mainly composed of aluminum and silicon containing a predetermined amount of silicon with a maximum silicon particle size of 10 μm or less, preferably 5 μm or less is used as a raw material powder. Therefore, it is necessary to maintain the heating temperature in the subsequent sintering step or densification step within a solid phase sintering temperature range that does not involve the formation of a liquid phase. The silicon particle size in the atomized alloy powder is influenced by various factors such as alloy composition, molten metal temperature, and powder particle size, but it mainly depends on the cooling solidification rate of the atomized powder, and the silicon particle size as desired in the present invention is achieved. To obtain atomized powder, the cooling solidification rate is at least 10°C/sec or more, preferably 50°C/sec.
It must be greater than or equal to sec. These conditions can be selected relatively easily using a normal atomization method. The particle size of the atomized alloy powder containing fine silicon particles is optimally in the range of -30 mesh + 350 mesh. Powder particle size is 30
If it is more than a mesh size, it is not preferable because the silicon particles contained therein tend to become coarser and the strength of the press-molded compact is reduced. In the case of the present alloy, the oxides that naturally exist on the surface of the atomized alloy powder are finely dispersed within the alloy and have the effect of improving high-temperature strength and wear resistance. In powder, the content of oxides increases dramatically, causing manufacturing problems such as wear and tear on press molds and molds and dies used in the densification process, as well as poor plastic deformation and inhibiting densification. Alumina and silica are extremely hard oxides, and have performance problems such as increasing wear and tear on the friction-sliding mating material and impairing machinability. Although it is possible to produce a fine powder with a relatively low oxide content of 350 mesh or less, handling in air is not very practical due to the risk of ignition, so the preferred range is -30+350 mesh. The heating temperature in the sintering or densification process of the compacted compact is 300°C or higher, preferably at least the recrystallization temperature, and it is necessary to perform the sintering or densification treatment at a temperature below the liquid phase formation temperature. be. A heating temperature of 300° C. or lower does not provide the workability necessary for densification, and a heating temperature that involves the formation of a liquid phase impairs the growth of silicon particles, making it impossible to achieve the intended purpose. The sintering process in the present invention is carried out when intermediate processing is required before the densification process, or when the final product shape is complex and material strength is required.
Normally, the densification process can be carried out while the compact is still in use. The densification process involves forming a porous powder compact with a density of 65 to 85% of the true density in order to suppress oxidation and improve gas release, or a porous compact formed by solid-phase sintering of the compact. It is necessary to extrude a quality sintered body and apply external stress that causes plastic deformation, such as by forging, to densify it to a density that is at least 95% of the theoretical density ratio. Naturally, there is a close relationship between external stress, theoretical density ratio and strength. For example, in the case of extrusion, there is a relationship between extrusion ratio and strength as shown in FIG. The graph shows the relationship between extrusion tensile strength and extrusion strength at various extrusion ratios after sintering the sintered aluminum alloy having the components shown in B of Example 1. If the densification is less than 95%, the desired purpose cannot be achieved because there is a large residual porosity and the oxide film between the particles is insufficiently broken, resulting in weak bonding between the particles. The alloy of the present invention has a tensile strength of
It has high strength of over 22Kg/mm ² . In the present invention, since a porous powder compact is used, the molding pressure during press molding may be 1 to 2 t/cm ² , so there is little wear and tear on the mold, and since the porous body is densified, Since the deformation resistance is low, the tool life for densification is also very long. By containing 0.1 to 10% by weight of at least one of copper, magnesium, manganese, iron, and nickel as a common alloying component in the above-mentioned atomized alloy powder, strength and heat resistance can be improved. If it exceeds 10% by weight, it may become brittle,
Difficult to densify during manufacturing. Further, if it is less than 0.1% by weight, it has no effect. Among these, nickel, manganese, and iron have been limited to addition in very small amounts because they form coarse segregated substances in ordinary cast aluminum alloys, significantly reducing strength. However, according to the present invention, since segregation does not occur in the aluminum sintered alloy, fine and uniform dispersion-strengthening particles are produced, and the strength is improved, it is possible to actively add it. Graphite 5~
30%, one or more sulfides such as WS ₂ or MoS ₂ in a total of 5 to 30%, and one or more fluorides such as CaF ₂ or BaF ₂ in a total of 5 to 30% of each solid lubricant component. Contains two or more types of graphite sulfide or fluoride, the total amount of which is 5 to 5.
It can be made to contain 30%. The addition of these solid lubricating components reduces frictional resistance and has the effect of improving the wear resistance of the material itself and the wear and tear of the mating material, especially when the lubricating oil is used or under sliding conditions where the lubricating oil film is insufficiently formed. It exhibits excellent sliding performance under dry sliding conditions. However, if the added content is less than the respective specified amount, the effect of addition is small, and even if the added content is greater than the respective specified amount, the performance improvement effect will hardly increase and the material strength will decrease, which is not preferable. Products containing these solid lubricating components have slightly different sliding properties such as seizure resistance and wear resistance depending on the lubricating component contained. For example, products that are used under harsh sliding conditions in lubricating oil , materials with self-lubricating and oil-retaining properties such as graphite are suitable, and when used under conditions with large temperature changes from low to high temperatures, materials with excellent high-temperature properties such as graphite or sulfides such as WS ₂ are suitable. It was found that a compound containing two types of fluorides such as CaF ₂ exhibited particularly excellent effects. [Examples] Examples of the present invention will be described below in order to specifically illustrate the configuration and effects of the present invention as described above. Example 1 Atomized alloy powders were prepared by melting alloys having the compositions shown in Table 1 under conditions where the cooling solidification rate was 50°C/sec or higher, and the particle size was adjusted to -30 mesh + 350 mesh and -350 mesh. The ^compacted compact was sintered at 500°C for 30 minutes in a hydrogen atmosphere, heated to 450°C in a nitrogen atmosphere, and then extruded. Extrusion was carried out using a die with a ratio of 1:3.5 to obtain the alloys shown in Table 2. In addition, in order to obtain comparative materials, an alloy having the composition shown in Table 1 was melted and cast in a mold to obtain a cast material (sample No. 12) having a silicon maximum particle size of 40 to 50μ and a -60% alloy having the composition shown in Table 1. The properties of the alloy obtained by compressing, sintering, and extruding a powder consisting of a mesh of Al powder, a Si powder of 250 mesh, and a powder of Cu, Mg, and Ni of less than 350 mesh under the same conditions as described above are shown in the second table. It is shown in the table (sample No. 11).

【table】

[Table] Shows the results of extrusion and densification after solidification.
*2. Hardness and tensile strength indicate values at room temperature.
The samples listed in Table 2 were subjected to the friction and wear tests shown in Tables 4 and 5, and the machining tests shown in Table 6.
The results are shown in Tables 8 and 9, respectively. Furthermore, using the powders No. 3 and No. 9 listed in Table 2, the degree of wear of the mold used during compression molding was investigated. Although this method is just a model test, it is estimated that sample No. 3 has less wear on the mold, as shown in Table 10, according to the results. Example 2 -30 produced by melting an alloy consisting of 17.1% Si, 3.1% Cu, 0.30% Mg, and 0.10% Ni, the remainder of which was essentially Al, and under conditions where the cooling solidification rate was 50°C/sec or higher.
+350 mesh atomized alloy powder and average particle size
A compression-molded body obtained by press-molding a powder of 10μ graphite powder, WS ₂ with a maximum particle size of 10μ or less, and CaF ₂ powder with the composition shown in Table 3 at a pressure of 2t/cm ³ was heated at 520℃×10 The alloys shown in Table 3 were obtained by die forging to a density of 95% or more based on the theoretical density ratio. These samples were prepared in Example 1.
Similarly, the friction and wear tests shown in Tables 4 and 5 and the machinability test shown in Table 6 were conducted, and the results are summarized in Tables 8 and 9.

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

[Table] Example 3 -30 mesh atomized alloy powder was prepared by melting the alloys having the compositions shown in Table 11 under conditions such that the cooling solidification rate was 50°C/sec or higher.
Hydrostatic pressing was carried out at a pressure of 2 t/cm ² , and the resulting compression molded product was hot extruded at an extrusion ratio of 10:1450°C. The true density (theoretical density ratio) of the obtained extruded material is as shown in Table 1, and it was subjected to T6 treatment (490℃, water quenching for 2 hours,
Table 12 shows the properties after aging heating at 190℃ for 6 hours.
Furthermore, Table 13 shows the results of the friction and wear test under the test conditions shown in Table 4.

【table】

[Table] Cast parts having the composition of the present invention cannot be produced with significant segregation. Therefore, as a comparison material, the cast product No. B in Table 1, which had been subjected to the same T6 treatment, was used.

【table】

【table】

[Table] As is clear from the data of the above examples, Fe,
When the total amount or individual amount of Mn and Ni is 3% or more, the wear resistance and strength, that is, transverse rupture strength and tensile strength are increased. Example 4 Atomized alloy powder obtained in the same manner as in Example 1 by melting an alloy consisting of 12% Si, 5% Fe, 4% Cu, 1% Mg, and the remainder substantially Al, is shown in Table 14 below. The results of measuring the tensile strength and elongation of molded products using the various methods shown are also shown:

[Table] Therefore, the alloy of the present invention has excellent mechanical strength, and has excellent wear resistance of the material itself, wear resistance of sliding mating materials, wear resistance of the mold used during manufacturing, and machinability. It has outstanding characteristics.
It goes without saying that the alloy of the present invention can be subjected to the heat treatment normally applied to aluminum alloys for the purpose of improving mechanical strength. In particular, the tensile strength
Previously, alloys with a weight of 25Kg/mm ² or more and a wear amount of 8×10 ^-7 mm ² /Kg or less could not be used.
Complex survanes, connecting rods, pistons,
It can also be used in fields such as cylinders. In these fields, efforts are being made to reduce the weight of parts, and the alloy according to the present invention can now be used in the above fields.

[Brief explanation of drawings]

FIG. 1A is a photomicrograph showing the structure of the material of the present invention (sample No. 4), and FIG. 1B is a photomicrograph showing the structure of the metal mold casting material (sample No. 12) for comparison. Figure 2 is an explanatory diagram showing the outline of the apparatus used for the mold friction test shown in Table 7, in which 1 is the mating material, 2 is the stirring hand (on both sides), 3 is the alloy powder slurry, and 4 is the test piece ( SKD Steel), 5 is a weight. FIG. 3 is a graph showing the relationship between the amount of plastic working and strength.

Claims (1)

[Scope of Claims] 1 Aluminum alloy powder containing 8 to 30% by weight of silicon and the balance being aluminum, or 8 to 30% by weight of silicon, at least one of copper, magnesium, nickel, iron, and manganese 0.1 ~10% by weight Aluminum In an aluminum sintered alloy made by sintering an alloy powder consisting of the balance, the alloy has a true density by performing sintering in a solid phase and densifying it by adding plastic deformation by extrusion or forging. A high-strength, wear-resistant aluminum alloy having a density of 95% or more, a tensile strength of 22 Kg/mm ² or more, and a maximum silicon particle size of 10 μm or less. 2 Aluminum alloy powder containing 8 to 30% by weight of silicon and the balance being aluminum, or 8 to 30% by weight of silicon, at least one of copper, magnesium, nickel, iron, and manganese 0.1 to 10% by weight, balance of aluminum In an aluminum alloy made by mixing and sintering an alloy powder consisting of the following and 5 to 30% by weight of a solid lubricant component, sintering is performed in a solid phase, and the aluminum alloy is densified by plastic deformation by extrusion or forging. High-strength wear-resistant aluminum, characterized in that the alloy has a density of 95% or more of the true density, a tensile strength of 22 Kg/mm ² or more, and a maximum silicon particle size of 10 μm or less alloy. 3 The solid lubricant components are graphite, WS ₂ , MoS ₂ ,
The high-strength, wear-resistant aluminum sintered alloy according to claim 2, characterized in that it is made of one or more of CaF ₂ and BaF ₂ .