JPH0120218B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aluminum alloy hollow member suitable as a cylinder liner for use in internal combustion engines, swash plate compressors, etc., and more specifically, it relates to a heat-resistant, wear-resistant, high-strength aluminum alloy inner layer with particularly improved thermal stability, and the inner layer. The present invention relates to a composite structure hollow member formed by an extrusion method with a softer aluminum alloy outer layer. Recently, it has become necessary to reduce the weight of automobiles and to adopt front engine/front drive (FF) systems, and the cylinder block has changed from cast iron to Al alloy. In order to improve the wear resistance of the cylinder block's sliding surface, a cast iron cylinder liner is usually cast into the cylinder block. If this cylinder liner could be made of aluminum alloy, it would not only be lightweight, but also have a higher thermal conductivity and coefficient of thermal expansion than cast iron, which would improve the adhesion between the liner and the block even when the temperature rises, which would result in an engine with good heat dissipation. is obtained. As a result, the temperature of the liner becomes lower, which prolongs the life of the lubricating oil or allows the use of lubricating oil with a lower viscosity.Also, the coefficient of thermal expansion is similar to that of the aluminum alloy of the piston material, which reduces the Since the clearance can be set small, lubricating oil consumption and blow-by gas generation can be kept to a small amount, which is expected to improve fuel efficiency and efficiency. Furthermore, the cylinder liner made of Al alloy with high Si content has a small coefficient of friction, so it is expected to improve fuel efficiency and output by reducing friction loss between it and the piston ring. However, conventionally known aluminum alloys are insufficient as cylinder liners for castings as described above. For example, A390.0 alloy (Si16-18%, Cu4
~5%, Mg0.5~0.65%, Fe0.5%, Ti0.2%,
Casting alloys such as 0.1% Zn, residual Al) (all alloy compositions in this specification are expressed in weight percent) have a wide solid-liquid coexistence temperature range, so they require a large feeder, resulting in poor yields. Even with refinement treatment and mold casting, primary Si crystals still crystallize in a large size, resulting in poor machinability. Furthermore, a fatal drawback is that the material is softened by the heat of the molten metal when it is cast into the cylinder block, which significantly reduces wear resistance and tends to cause chatter and peeling on the machined surface, and it is difficult to honing. There are drawbacks such as making it difficult. On the other hand, in recent years powder metallurgy has been used to
A technique has been proposed in which an alloy having a similar composition to the A390.0 alloy is powdered and then hot extruded to form a hollow body (Japanese Patent Application Laid-open No. 109415/1983). According to this 12
A molten hypereutectic Al-Si alloy containing ~30% Si, 1-5% Cu, 0.5-1.5% Mg, and residual Al is granulated by atomization or atomization using centrifugal force, and then extruded. Therefore, it is a method to obtain a hollow body, and the material obtained by this method can have primary Si crystals of 20 μm or less, so it has excellent ductility and machinability, has a small coefficient of friction, and has excellent wear resistance. have Furthermore, 0.5 to 1.5% Ni is added to the Al-Si alloy with the above composition.
It has also been proposed to mix SiC, Sn, graphite, etc. with the added powder and extrude a hollow body. The present inventor conducted a tracing experiment of the above invention, and found that 20%Si-4%Cu-0.8%Mg-0.5%Ni-Al
The remaining extruded alloy powder with standard composition was used as a cylinder liner (outer diameter 73 mm, inner diameter 65 mm, height 105 mm).
According to the results of a test in which a cylinder block (weight 3.4 kg) of ADC12 alloy (JIS H5302) was die-cast at a molten metal temperature of 675℃, T6
It was discovered that a material with a hardness of about H _R B80 during processing softens to about H _R B40 after casting.
Therefore, a hollow body made of this type of alloy cannot be cast into a cylinder block and used as a cylinder liner. Castings are made by die-casting or low-pressure casting, but it is preferable to make the liner as thin as possible from a cost perspective, so it is easy to deform due to mechanical stress applied during the liner transportation process and positioning during casting. In order to prevent this, it is necessary to have high rigidity (high hardness). The inventor of the present invention has solved these drawbacks, and has created a material that does not soften under the heat load during casting, does not soften even in the temperature range that is applied during use, and has excellent wear resistance and seizure resistance. As a high-strength aluminum alloy material, high-strength aluminum alloy containing 10 to 30% Si by weight
Furthermore, a large amount of alloying elements such as Mn, Fe, and Ni are added to the Si-Al alloy to form an intermetallic compound containing Si crystal grains of 15 μm or less and one or more of Mn, Fe, and Ni of 20 μm or less. We have previously proposed a heat-resistant, abrasion-resistant, high-strength aluminum alloy powder compact in which aluminum is finely dispersed, and a method for manufacturing the same (Japanese Patent Application No. 119901/1983,
Publication No. 59-13040, Japanese Patent Application No. 57-119902, Japanese Unexamined Patent Publication No. Sho
59-13041). These heat-resistant, wear-resistant, high-strength aluminum alloy powder compacts have the above-mentioned metal structure,
It has excellent wear resistance and seizure resistance, and has excellent heat resistance, with very little loss of hardness even under the action of heat loads. Therefore, it can be cast into aluminum alloy cylinder blocks as a cylinder liner material. It is sufficient for use. However, the above-mentioned heat-resistant, wear-resistant, high-strength aluminum alloy powder compact is obtained by hot extrusion molding of powder obtained by rapidly cooling and solidifying the molten alloy, but the alloy powder contains Mn, Fe, Ni, etc. Since it contains a large amount of intermetallic compounds produced by the addition of metals such as The extrusion speed has to be low, the life of the extrusion die is shortened, and it is difficult to form uneven portions, that is, serrations, on the outer periphery of the cylinder liner to ensure tight connection to the cylinder block. There is a problem with this. The purpose of this invention is to provide a hollow member that solves the above problems, and the first invention is an aluminum alloy hollow member with a weight ratio of Si10 to
30%, one or more of Mn, Fe, Ni3
~15%, the remainder consists essentially of Al, and the size
A heat-resistant, wear-resistant, high-strength metal structure with a finely dispersed Si crystal grain of 15 μm or less and an intermetallic compound of 20 μm or less containing one or more of the above-mentioned Mn, Fe, and Ni. A hollow member made of an aluminum alloy, characterized in that it has a multilayer structure formed by an extrusion method, comprising an inner layer made of an aluminum alloy and an outer layer made of an aluminum alloy that is softer than the inner layer, and a second invention thereof is a first invention. According to the invention, 0.5 to 5% of Cu and 0.2 to 3% of Mg are added to the chemical composition of the inner layer. The inner layer of the multilayer hollow member of the present invention is made of a heat-resistant, wear-resistant, high-strength aluminum alloy that does not soften even under the action of heat loads and exhibits excellent wear resistance and seizure resistance in sliding conditions. Since it has an outer layer of aluminum alloy for casting, die casting, or drawing that is softer than the inner layer, extrusion processing is easy, and the hollow body can be ironed for the purpose of increasing the dimensional accuracy of the hollow body. It is easy to form serrations on the outer peripheral surface, and the outer layer material has less alloying elements and higher thermal conductivity and thermal expansion coefficient than the inner layer material, so the temperature of the sliding surface of the inner layer can be further reduced. It has advantages such as making it possible to maintain the temperature at a low temperature and also ensuring that the outer layer adheres to the casting material more reliably. Next, the present invention will be described with reference to an embodiment of a cylinder liner for a casting shown in the accompanying drawings. A cylinder liner 1 shown in FIG. 1 has a multilayer structure including an inner layer 2 and an outer layer 3. Inner layer 2 is Si10-30%, Mn, Fe,
3 to 15% of one or more types of Ni, further containing 0.5 to 5% of Cu and 0.2 to 3% of Mg as necessary,
The remainder is substantially made of Al, and the outer layer 3 is made of an aluminum alloy for JIS H5202 casting, JIS H5302 die casting, or JIS H4100 drawing, which is softer than the inner layer material, or a similar alloy. The boundary between the inner layer 2 and the outer layer 3 is metallurgically bonded by mutual diffusion of component elements during casting. In the present invention, the chemical composition of the inner layer material is as follows. First, Si is fine Si particles, Mg ₂ Si, Al
-When dispersed in the matrix as an intermetallic compound such as Fe-Si, it exhibits excellent effects on high-temperature strength, wear resistance, and seizure resistance, but if its content is less than 10%, the amount of dispersed crystallization is small. On the other hand, if it exceeds 30%, not only will the melting temperature become high, but even if it is rapidly cooled, it will precipitate as primary Si crystals with a large diameter in the powder, which will significantly deteriorate the compressibility of the powder. This not only makes it difficult to produce a green compact, but also increases the deformation resistance during hot extrusion, reduces the ductility and impact value of the resulting extruded material, or impairs machinability. When used as a cylinder liner, the coefficient of thermal expansion decreases as the amount of Si added increases, resulting in poor adhesion to the outer layer material. Therefore, the Si content is 10 to 30
%, but the preferred range is 14 to 25%. Fe, Ni, and Mn have low solid solubility in Al;
Moreover, it is added for the purpose of increasing high-temperature strength by dispersing it as a fine compound by taking advantage of the slow diffusion rate in Al, and the amount thereof is 3 to 15% in total, either alone or in combination of two or more. When the molten metal is rapidly cooled to form powder, these elements are supersaturated in solid solution in Al, and the portion that cannot be dissolved in solid solution is dissolved in Al-Fe-Si.
It crystallizes as a rod-shaped phase in powder as a ternary compound or an intermetallic compound such as Al ₃ Ni, Mn ₁₂ Si ₇ Al ₅ . This compound is separated by hot extrusion,
Finely dispersed in the material structure. Furthermore, the above-mentioned compounds are precipitated from the supersaturated fraction in the base by high temperature heating. These compounds are fine and have high hardness, and have a slow diffusion rate in Al, so coarsening is difficult to occur, so they increase the high-temperature strength of the material. Together with the Si crystal grains in the material, it increases the hardness of the material and contributes to wear resistance and seizure resistance. If the amount added is less than 3%, the effect will not be significant, while if it exceeds 15%, high temperatures will be required during melting, and the deformation resistance will increase when compressing or extruding the powder, making extrusion processing difficult. , lowers the ductility and impact value of the resulting extruded material, and impairs machinability. Within the above range of 3 to 15%, when Ni is added alone at 5 to 15%, Fe3 to 15% and Mn5
Particularly good heat resistance and wear resistance properties when containing one or two types of ~15%, or when containing one or two types of Fe3~12% and Mn5~12% and Ni3~10%. is obtained. Cu or Mg is generally known as an element added to Si-Al alloys to impart age hardenability.
In the present invention, Cu is added at 0.5 to 5% for this purpose.
Mg may be added in an amount of 0.2 to 3%. Cu less than 0.5%,
If Mg is less than 0.2%, the above effects will not be sufficiently exhibited, and even if Cu is added in excess of 5% and Mg is added in excess of 3%, no significant increase in the above effects will be observed. Next, the manufacturing method will be described with reference to examples. The molten aluminum alloy adjusted to have a predetermined target chemical composition is atomized using the gas atomization method.
An alloy powder having the chemical composition shown in the table was prepared.

[Table] The structure of the obtained alloy powder particles is composed of fine Si.
It shows a structure in which a large amount of rod-shaped intermetallic compounds have crystallized in a matrix in which crystal grains are dispersed. Second
The figure is a micrograph (740x magnification) illustrating the metal structure of sample material 3. This alloy powder was sieved and -48 mesh powder was used. It has been found from many experimental results that by doing so, the size of the Si crystal grains in the extruded product can be reduced to 15 μm or less. Next, -48 mesh powder was preheated to 300℃ and placed in a divisible mold heated to the same temperature.
Compressed with upper and lower punches, outer diameter 175.4mm, inner diameter 66.5mm,
The compact was made into a compact with a height of 100 mm and a true density ratio of 70%. Next, it was obtained by billet hot extrusion method.
A5056TE, A6061TE (JIS H4080) aluminum alloy pipe (outer diameter 204mm, inner diameter 175.5mm, length
500mm), stacking and inserting 5 of the green compacts,
Both ends were caulked to form a hollow composite billet. Next, this hollow composite billet was preheated to 450℃ in _N2 gas, and then placed in a container (inner diameter
208 mm), a floating mandrel with a diameter of 66 mm is inserted into the hole of the hollow composite billet, and hot extrusion is performed using the indirect extrusion method to form an outer diameter of 73 mm consisting of the inner layer 2 and outer layer 3 as shown in Figure 1. , inner diameter 66mm
A multilayer structure hollow member 1 was obtained. In the process of hot extrusion, the aluminum alloy powder is compressed and bonded by pressure diffusion accompanied by plastic flow, but the intermetallic compounds that exist in the form of rods in the powder are fragmented and form granules in the structure. to disperse finely. Therefore, the inner layer of the obtained multilayer hollow member contains primary Si crystal grains and one or more types of Mn, Fe, and Ni in the Al--Si eutectic matrix, as illustrated in Fig. 3. This results in a structure in which intermetallic compounds are finely and uniformly dispersed. In the case of the above method, by setting the hot extrusion ratio to 10 or more, the elongated rod-shaped intermetallic compound in the alloy powder is divided into pieces of 20 μm or less in size and dispersed in the extruded material. Next, the extruded multilayer hollow member was heated to 300°C.
After heat treatment for 10 hours, a mandrel with a diameter of 66 mm was inserted into the hollow member cut to a predetermined length, a die was placed on the outer circumference, and serrations were applied at the same time as ironing, as shown in Figures 4 and 5. A hollow body 1' having serrations 4 on the outer surface as shown in the figure was prepared. The boundary between the inner and outer layers of this hollow body is located at a position of approximately 70.5 mm in diameter, and the boundary is metallurgically bonded by diffusion bonding. Multilayer structure hollow member 1′ obtained in this way
was die-cast into a cylinder block made of ADC12 alloy. The temperature of the ADC12 alloy molten metal at this time was 675°C. The liner of the multi-layer structure hollow member according to the present invention, which is cast into an aluminum alloy cylinder block, shows very little decrease in hardness of the inner layer due to heat load during casting, and still maintains sufficient hardness to prevent internal combustion. Shows sufficient wear resistance for use in engines. Table 2 shows a liner made of a multi-layer hollow material with an inner layer made of the sample powder in Table 1 and an extruded aluminum alloy outer layer as described above, which is cast into a cylinder block body made of ADC12 material by a die-casting method. After finishing the liner to an inner diameter of 68 mm, it was assembled into an engine, and durability tests were conducted to investigate the amount of wear. The results are shown in comparison to the amount of wear of a conventional flake graphite cast iron liner. Table 2 also shows the hardness of the inner layer after casting.

[Table] The durability test was conducted at a rotation speed of 5500r.pm, an oil temperature of 95℃, and a water temperature of 100℃.
The outer circumferential surfaces of the pressure ring and oil ring were each plated with iron in which SiC was dispersed in an iron matrix with an area ratio of 15 to 20%. Note that a cast iron ring without surface treatment was used as the second pressure ring. In addition, in engines using comparative cast iron liners, the first liner with chrome plating on the outer circumferential surface
Used pressure ring and oil ring. As is clear from Table 2, the cylinder liner made of the multilayer hollow member of the present invention shows wear resistance comparable to that of the conventional liner made of flaky graphite cast iron, even if it does not contain Cu or Mg. , Mg-containing and age-hardened materials have rather less wear and are sufficiently durable for practical use. As explained above, since the molten aluminum alloy having the chemical composition according to the present invention contains a large amount of Mn, Fe, or Ni, it does not grow into a rod shape even if it is atomized by the atomization method and rapidly cooled.
It has a structure in which a large amount of intermetallic compounds containing Mn, Fe, and Ni are precipitated, and hot extrusion requires large extrusion equipment and shortens the life of the extrusion die. However, in the present invention, this alloy powder is To create a composite billet by holding it in a cylindrical body made of aluminum alloy for casting or drawing, which has low hardness and therefore good formability, and to easily form it into a hollow body by hot extrusion. Can be done. In addition, it is easy to perform the necessary machining on the outer periphery of the outer layer material,
In addition, the outer layer material has a low content of alloying elements and has a higher thermal conductivity and coefficient of thermal expansion than the inner layer, so it has good heat absorption efficiency from the inner layer and maintains the temperature of the inner wall sliding surface of the inner layer at a low temperature. This makes it possible to use viscous lubricating oil and also improves the close connection with the cylinder block body, which is a cast material. In addition, since the outer layer material is a soft material, vertical grooves (serrations) 4 as shown in Figures 4 and 5 are formed on the outer periphery of the hollow member at the same time as the hot extrusion process of the multilayer structure hollow body or after the hot extrusion process. It is easy to do so, and can be used as a means for improving adhesion or preventing rotation when used as a cast-in cylinder liner in a cylinder block body. The multilayer structure hollow member of the present invention has an inner layer made of a heat-resistant, wear-resistant, high-strength aluminum alloy with particularly improved heat resistance by finely dispersing Si primary crystal particles and intermetallic compound particles in the matrix, and an outer layer made of a high-strength aluminum alloy with particularly improved heat resistance. The inner layer is coated with a cast or wrought aluminum alloy that is softer than the inner layer and extruded through a die to increase thermal conductivity, so a heat load acts on it.
Moreover, it is suitable for applications requiring high levels of wear resistance and seizure resistance. In addition, in the manufacturing process of the hollow member, the inner layer is formed by mixing 0.2 to 20% of solid lubricant powder such as graphite, molybdenum disulfide, boron nitride, calcium fluoride, etc. to the aluminum alloy powder. It is also possible to further improve the lubrication properties.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an example of the extruded multilayer hollow member material (intermediate process) of the present invention, and Fig. 2 is a photograph showing an example of the microscopic structure of aluminum alloy powder particles used to form the inner layer. (740x), Figure 3 is a photograph (740x) showing an example of the microscopic structure of the inner layer of the extruded hollow member, Figure 4 is a vertical cross-sectional view showing an example of the present invention, and Figure 5 is a cross-sectional view. It is a diagram. 1...Extruded material (intermediate process), 1'...Multilayer structure hollow member, 2...Inner layer, 3...Outer layer, 4...Serration.

Claims (1)

[Claims] 1. A hollow member made of aluminum alloy, in terms of weight ratio, Si is 10 to 30%, one or more of Mn, Fe, and Ni is 3 to 15%, and the remainder is substantially Al,
Si crystal grains with a size of 15 μm or less and the above-mentioned Mn, Fe,
Size 20μm containing one or more types of Ni
A composite material formed by an extrusion method consisting of an inner layer made of a heat-resistant, wear-resistant, high-strength aluminum alloy having a metal structure in which the following intermetallic compounds are finely dispersed, and an outer layer made of an aluminum alloy that is softer than the inner layer. An aluminum alloy hollow member characterized by having a layered structure. 2. The aluminum alloy structural hollow member according to claim 1, wherein the inner layer contains 5 to 15% of Ni among Mn, Fe, and Ni. 3 The inner layer is Fe3~15% and Mn5 among Mn, Fe, and Ni.
The aluminum alloy hollow member according to claim 1, which contains 3 to 15% of one or both of the following. 4 Inner layer contains Fe3~12% and Mn5 among Mn, Fe, and Ni
~12% of one or two types and Ni3~10% for a total of 3
The aluminum alloy hollow member according to claim 1, containing ~15%. 5 In a hollow member made of aluminum alloy, the weight ratio is 10 to 30% Si, 3 to 15% of one or more of Mn, Fe, and Ni, 0.5 to 5% Cu, and 0.2 to 3 Mg.
%, the remainder essentially consists of Al, and Si crystal grains with a size of 15 μm or less and intermetallic compounds with a size of 20 μm or less containing one or more of Mn, Fe, and Ni are finely dispersed. An aluminum alloy characterized by having a multilayer structure formed by an extrusion method, consisting of an inner layer made of a heat-resistant, wear-resistant, high-strength aluminum alloy having a metal structure that is soft, and an outer layer made of an aluminum alloy that is softer than the inner layer. Made of hollow parts.