JP5433916B2 - Cylinder sleeve alloy and cylinder sleeve using the same - Google Patents

Description

  The present invention relates to a cylinder sleeve alloy used for a cylinder sleeve, which is a metal cylinder that is cast into an engine cylinder block, and the cylinder sleeve.

  Al materials are used for cylinder blocks and cylinder sleeves in order to reduce the weight of automobile parts and motorcycle parts. For example, Patent Document 1 discloses that as a cylinder sleeve material, focusing on an Al—Cu—Mg-based alloy and containing a hard substance and a solid lubricant, it is excellent in wear resistance and lubricity. . Patent Document 2 discloses that as a cylinder sleeve material, focusing on an Al—Mg—Si alloy, adjusting the content of an additive element to obtain good extrudability is disclosed.

Japanese Patent Laid-Open No. 2-122043 JP 2002-361398 A

  When extruding a cylinder sleeve material, it is desired to perform thin-wall and high-speed extrusion in order to improve productivity and facilitate post-processing such as reducing the finishing allowance. However, in the conventional cylinder sleeve material, there is a limit in improving the strength by reducing the occurrence of cracks and surface defects during extrusion when performing thin-walled and high-speed extrusion.

  Since the cylinder sleeve material of Patent Document 1 contains a relatively large amount of Cu, thin-walled and high-speed extrusion cannot be performed. Processing heat increases when thin-walled and high-speed extrusion is performed. However, Cu-containing materials have a high flow stress at high temperatures and a relatively low solidus temperature (melting start temperature), so they are prone to cracking and surface defects during hot extrusion and can increase the extrusion speed. Therefore, it was a big restriction on productivity improvement. Furthermore, there is a demand not only for improving the productivity of the cylinder sleeve disclosed in Patent Document 1, but also for further improving the sliding characteristics (seizure resistance).

  On the other hand, the cylinder sleeve material of Patent Document 2 has excellent extrudability, but the strength is inferior to that of an Al-Cu-Mg alloy, and there is a possibility that sag may occur during casting when the structure is thin. . In addition, there is a problem that improvement in wear resistance and seizure resistance cannot be expected during operation.

  The present invention has been made in view of the above circumstances, and one of its purposes is that the cylinder sleeve material can be thin-walled and extruded at high speed, and has high strength, sag resistance, wear resistance, and seizure resistance. An object of the present invention is to provide an alloy for a cylinder sleeve which is excellent in the above.

  Another object of the present invention is to provide a cylinder sleeve using the cylinder sleeve alloy of the present invention.

  As a result of diligent research, the present inventors have determined that the cylinder sleeve alloy has a specific alloy composition, and in particular, achieves the above object by making the Cu content substantially zero and increasing the Fe content. Obtained knowledge.

  Conventionally, an alloy for a cylinder sleeve has not been made to have a Cu content of substantially zero as described above. This is because the cylinder sleeve alloy is considered to contain Cu to some extent in order to maintain sufficient strength. However, in order to enable thin and high speed extrusion of the cylinder sleeve alloy, it is necessary to increase the solidus temperature, and for that purpose, it is most effective to make the Cu content substantially zero. It is believed that there is. Therefore, by specifying the content of Fe as a high-strength element that replaces Cu, thin-wall and high-speed extrusion is possible, and even a thin-wall structure has high strength and sufficient sag resistance desired during casting Thus, a cylinder sleeve alloy having wear resistance and seizure resistance desired during operation can be obtained. The present invention is based on the above findings.

The cylinder sleeve alloy of the present invention is composed of 16-18% by mass of Si, 5.5-9% by mass of Fe, 0.5-2% by mass of Mg, 3-5% by mass of Al ₂ O ₃ and 0.5-3% by mass of graphite. %, And the balance consists of Al and inevitable impurities.

  According to the above configuration, by making the Cu content substantially zero, the solidus temperature of the cylinder sleeve alloy can be increased, and even if hot extrusion is performed at a higher extrusion speed, cracking can occur. And surface defects are less likely to occur. Therefore, productivity can be improved by performing high speed extrusion. And the intensity | strength and abrasion resistance in both low temperature and high temperature can be improved by making content of Fe larger than before. Therefore, even if the molded product has a thin structure, the occurrence of sag during casting can be reduced, and the wear resistance and seizure resistance during operation can be improved. Furthermore, if the Al—Si—Fe—Mg quaternary alloy is within the composition ratio of the present invention, the structure becomes finer and the sliding properties (seizure resistance and resistance to attack against the opponent) are improved.

  Hereinafter, the cylinder sleeve alloy of the present invention will be described in detail. In the following description, the contents of “composition” are all “mass%”.

[composition]
(Fe: 5.5-9%)
In the cylinder sleeve alloy of the present invention, Fe is an important element for maintaining high strength. When Fe is contained in a large amount, the strength increases, but at the same time, the toughness tends to decrease. For this reason, conventionally, the alloy for cylinder sleeves has not been made to have the Fe content defined in the present invention. However, in the present invention, by specifying this content, it is possible to obtain high strength, sag resistance, wear resistance, and seizure resistance while having sufficient toughness. In particular, high temperature strength can be improved by sufficiently adding Fe. When the Fe content is 5.5% or more, high strength can improve sag resistance, wear resistance, and seizure resistance, and when it is 9% or less, high toughness can be maintained.

  At least a part of the Fe content may be substituted with one or more elements selected from Cr, Mn, Co, and Ni. In addition to Fe, Cr, Mn, Co, and Ni can also have appropriate strength and hardness by containing a predetermined amount. In particular, Ni and Mn can improve the high-temperature strength.

(Si: 16-18%)
Si is contained to adjust the thermal expansion coefficient of the cylinder sleeve alloy and to improve the wear resistance. By causing crystallization as an Si crystal in the Al matrix, the wear resistance and seizure resistance can be improved. The above effect can be sufficiently achieved when the Si content is 16% or more. On the other hand, if a large amount of Si is present, the material becomes brittle, and if high-speed extrusion is performed, cracks are likely to occur. When the Si content is 18% or less, high-speed extrusion can be achieved. The average grain size of the Si crystals is preferably 1 to 2 μm.

(Mg: 0.5-2%)
Mg is contained to improve strength and hardness. When the Mg content is 0.5% or more, the above effect can be sufficiently achieved, and when it is 2% or less, high toughness and workability can be maintained.

(Al ₂ O ₃ : 3 to 5%)
Al ₂ O ₃ is a hard particle that is contained to improve wear resistance and seizure resistance. When the Al ₂ O ₃ content is 3% or more, the wear resistance can be improved, and when it is 5% or less, high toughness can be maintained. The Al ₂ O ₃ preferably has a maximum particle size of 30 μm or less and an average particle size of 10 μm or less. Furthermore, it is preferable that there is no sharp edge, that is, a substantially spherical shape.

Note that at least a part of the content of Al ₂ O ₃ may be replaced with one or more materials selected from SiC, Si ₃ N ₄ , SiO ₂ , ZrO ₂ , MgO and AlN. . As hard particles, in addition to Al ₂ O ₃ , all of the above materials have high hardness, relatively high toughness, and are easily available. By containing a predetermined amount of these hard particles, appropriate toughness, wear resistance and seizure resistance can be obtained.

(Graphite: 0.5-3%)
Graphite is a solid lubricant that is contained for lubricity with a counterpart (here, a piston). When the graphite content is 0.5% or more, the attacking ability of the opponent can be lowered, and when it is 3% or less, brittleness and self-wear can be maintained. This graphite preferably has a cross-sectional structure and a maximum particle size of 10 μm or less. Examples of the solid lubricant include MoS ₂ and boron nitride in addition to graphite. The content of one or more selected from these solid lubricants may be 0.5 to 3%.

  As one form of this invention, it is mentioned that content of the said Fe is 7-9 mass%.

  When the Fe content is 7 to 9% by mass, high temperature strength and wear resistance can be further improved while maintaining high toughness.

  The cylinder sleeve of the present invention is made of the above-mentioned alloy for cylinder sleeve.

  Since the cylinder sleeve of the present invention is made of an alloy for cylinder sleeve that has good strength and wear resistance at both low and high temperatures, a thin-walled cylinder sleeve can be formed. Moreover, since the cylinder sleeve of the present invention has high strength, even if it has a thin structure, it is possible to reduce the occurrence of sag during casting, and to improve wear resistance and seizure resistance during operation.

  As an embodiment of the present invention, the cylinder sleeve has a tensile strength at room temperature of 400 MPa or more and a tensile strength at 500 ° C. of 20 MPa or more.

  When the tensile strength at room temperature is 400 MPa or more, the wear resistance and seizure resistance can be further improved. Further, when the tensile strength at 500 ° C. is 20 MPa or more, the sag resistance can be improved, and the occurrence of sag during casting can be further reduced.

  The cylinder sleeve of the present invention is preferably manufactured by extruding the cylinder sleeve alloy of the present invention at an extrusion temperature of 460 to 530 ° C., an extrusion speed of 1 to 5 mm / s, and an extrusion ratio of 15 to 30. In the extrusion process, it is preferable to form the cylinder sleeve of the present invention having a thickness of 4 to 6 mm. The extrusion speed referred to here is the ram speed of the extruder, and the extrusion speed of the product is represented by the product of the ram speed and the extrusion ratio.

  The cylinder sleeve alloy of the present invention can reduce the occurrence of cracks and surface defects even when extrusion is performed at an extrusion temperature, extrusion speed, and extrusion ratio within the above ranges, and an improvement in productivity can be expected. And by setting it as the thickness of the said range, post-processings, such as making finishing processing cost small, can be made easy. In particular, the thin-walled / high-speed extrusion in the present invention refers to extrusion at an extrusion speed of 3 to 5 mm / s and a thickness of 4 to 5 mm.

  The alloy for a cylinder sleeve of the present invention can perform thin-walled / high-speed extrusion by making the Cu content substantially zero, and can improve productivity. And even if it is a molded product of a thin structure by making content of Fe larger than before, high strength can improve sag resistance, abrasion resistance, and seizure resistance.

  Since the cylinder sleeve of the present invention is made of the cylinder sleeve alloy of the present invention, a thin-walled cylinder sleeve can be formed. Moreover, since the cylinder sleeve of the present invention has high strength, even if it has a thin structure, it is possible to reduce the occurrence of sag during casting, and to improve wear resistance and seizure resistance during operation.

It is a stereomicroscope photograph which shows the cylinder sleeve surface, (A) is sample No. 3 and (B) is sample No. 8. 4 is a scanning electron micrograph showing an alloy structure for a cylinder sleeve, where (A) is sample No. 3, (B) is sample No. 6, and (C) is sample No. 8. FIG. It is a graph which shows a TG / DTA curve, (A) is sample No. 3, (B) is sample No. 6, and (C) is sample No. 8. Sample No. 3 shows the specimen and disc after the chip-on-disk friction test, (A) is a stereomicrograph of the surface of the specimen (chip), and (B) is a stereomicrograph of the surface of the disc. . Sample No. 6 shows the test piece and disc after the chip-on-disk friction test, (A) is a stereomicrograph of the surface of the test piece (chip), (B) is a stereomicrograph of the surface of the disc. .

  A plurality of cylinder sleeve alloys were manufactured, and a plurality of cylinder sleeves made of these alloys were produced, and “thin-wall / high-speed extrudability”, “castability”, and “sliding characteristics” were examined.

<Manufacture of cylinder sleeve alloys>
[Example (Sample No. 1 to Sample No. 4)]
As the cylinder sleeve alloy of the present invention, as shown in Table 1, Sample No. 1 to Sample No. 4 were prepared. The cylinder sleeve alloy of the present invention can be manufactured according to a conventional method for manufacturing a cylinder sleeve alloy. The cylinder sleeve alloy of the present invention was manufactured by mixing the alloy powder, hard particles, and solid lubricant described later with the mass of the cylinder sleeve alloy being 100%. First, an alloy powder containing 17% by mass of Si, 6-9% by mass of Fe and 1% by mass of Mg, with the balance being Al and inevitable impurities, was rapidly solidified by air atomization. In this example, the alloy powder was formed by changing the Fe content. As shown in Table 1, in Sample No. 1 to Sample No. 4, the Fe content is 6% by mass, 7.5% by mass, 8% by mass, and 9% by mass in this order. The average particle size of these alloy powders was 50 μm. Then, 3% by mass of Al ₂ O ₃ with an average particle diameter of 3 μm as hard particles and 0.5% by mass of graphite with an average particle diameter of 1 μm as a solid lubricant are uniformly mixed in each alloy powder with a V-type mixer. A cylinder sleeve alloy was produced.

[Comparative Example (Sample No. 5 to Sample No. 11)]
As comparative examples, as shown in Table 1, cylinder sleeve alloys of Sample No. 5 to Sample No. 11 were prepared. These comparative examples differ in composition from the examples. Only the differences will be described below. Sample No. 5 is an alloy for cylinder sleeve of Al-17Si-11Fe-1Mg-3Al ₂ O ₃ -0.5Gr (graphite), and is different from the example in that the content of Fe is large. Sample No. 6 is an alloy for cylinder sleeve of Al-17Si-1Mg-3Al ₂ O ₃ -0.5Gr, which is different from the example in that it does not contain Fe. Sample No. 7 is an alloy for cylinder sleeve of Al-17Si-4.5Fe-1Mg-3Al ₂ O ₃ -0.5Gr, and is different from the examples in that the Fe content is small. Sample No. 8 is an alloy for cylinder sleeve of Al-17Si-5Fe-3.5Cu-1Mg-3Al ₂ O ₃ -0.5Gr, which has a low Fe content and contains Cu. Different. Sample No. 9 is an alloy for cylinder sleeve of Al-20Si-5Fe-1Mg-3Al ₂ O ₃ -0.5Gr, which differs from the examples in that it has a high Si content and a low Fe content. Sample No. 10 is an alloy for cylinder sleeve of Al-25Si-5Fe-1Mg-3Al ₂ O ₃ -0.5Gr, which differs from the examples in that it has a high Si content and a low Fe content. Sample No. 11 is an Al-26Si-0.2Cr-0.2Cu-0.7Mg alloy powder, containing a large amount of Si, containing Cr and Cu, Fe and hard particles of Al ₂ O ₃ and The point which does not contain Gr which is a solid lubricant differs from an Example.

<Production of cylinder sleeve>
Cylinder sleeves were prepared using the cylinder sleeve alloys (Sample No. 1 to Sample No. 11). As a specific method for producing the cylinder sleeve, first, a hollow cylindrical billet was formed from the above alloy for cylinder sleeve by CIP (cold isostatic pressing). The billet is heated in an atmospheric furnace and then loaded into a container of a hot extrusion molding apparatus. With the mandrel inserted into the center hole of the hollow cylindrical billet in the container, extrusion was performed by pressing the rear end of the billet with a ram and passing the die. By performing such extrusion, a cylinder sleeve having an inner diameter corresponding to the outer diameter of the mandrel and an outer diameter corresponding to the inner diameter of the die can be obtained.

<Evaluation>
[Thin wall / High-speed extrudability]
For each sample, the cylinder sleeve with a thickness of 4.5 mm was prepared by extruding at a extrusion rate of 4 mm / s with an extrusion ratio (ratio of container cross-sectional area to product cross-sectional area) of 23 by the above-described cylinder sleeve manufacturing method. Then, the degree of peeling such as cracks and surface defects during extrusion was examined. In addition, for each sample, the temperature change at the time of extrusion was measured by simultaneous differential heat and thermogravimetric measurement (TG / DTA), and the peak (endothermic peak) associated with melting was examined, and the temperature at that peak (solidus line) Temperature). These results are shown in Table 2. In addition, the alloy of sample No. 5 was too high in strength at high temperature, resulting in clogging, and could not be extruded and could not be evaluated.

  Regarding the solidus temperature, Cu is not contained (Sample No. 1 to Sample No. 4, Sample No. 6 to Sample No. 7, Sample No. 9 to Sample No. 10), or the Cu content is In the case of a trace amount (sample No. 11), the solidus temperature is 545 ° C. or higher. On the other hand, Sample No. 8 containing 3.5% by mass of Cu has a solidus temperature of 508 ° C., which is lower by about 40 ° C. or more than the above sample. Therefore, the solidus temperature can be increased by suppressing the Cu content. In particular, the Cu content should be substantially zero.

  As shown in Table 2, for the degree of peeling, the results of visual judgment of the degree of peeling on the outer peripheral surface of the cylinder sleeve after extrusion are shown by ◎, ○, Δ, × in order from the best. Sample No. 1 to Sample No. 7 (excluding Sample No. 5), which did not contain Cu and had a Si content of 17% by mass, had a small gap. In particular, sample No.1, sample No.6, and sample No.7 in which the Fe content was 6% by mass or less were hardly observed. FIG. 1 shows stereoscopic microscope photographs of the cylinder sleeve surfaces of Sample No. 3 and Sample No. 8, respectively. FIG. 1 (A) is Sample No. 3, and almost no flaking is observed. FIG. 1 (B) is Sample No. 8, and it can be seen that a large whip occurs.

FIG. 2 shows scanning electron micrographs (3000 times) of the alloy structures for cylinder sleeves of Sample No. 3, Sample No. 6 and Sample No. 8. Fig. 2 (A) shows Sample No.3, and the fine gray particles that exist multiple times throughout are Si crystals, and the average grain size of the Si crystals is 1-2 μm and the structure is very fine. Recognize. Further, it can be seen that white particles larger than the gray particles are Al ₂ O ₃ , and the Al ₂ O ₃ has a maximum particle size of 30 μm or less and an average particle size of 10 μm or less. FIGS. 2 (B) and 2 (C) show Sample No. 6 and Sample No. 8, respectively, and the average grain size of the Si crystals is 3 μm, and it can be seen that the structure is coarse compared to Sample No. 3. FIG. 3 shows TG / DTA curves obtained when simultaneous differential heat / thermal mass measurement (TG / DTA) is performed on samples No. 3, No. 6 and No. 8. The results obtained from FIGS. 2 and 3 are shown in Table 3.

  The higher the solidus temperature, the less likely the liquid phase will appear even if the temperature rises due to processing heat generated by high-speed extrusion. When the Si content is the same, the smaller the Si crystal grain size and the finer the structure, the greater the number of Si crystal grains, and the spacing between the Si crystal grains, that is, the Al of the matrix is almost surrounded by multiple Si crystal grains. Since the area where the ground is exposed (mean free path) is narrowed, the sliding characteristics (seizure resistance) are improved. Furthermore, if the Si crystal grain size is small, the possibility of the surface being peeled during extrusion is reduced. In order to make the structure finer, it is necessary to quickly cool the Al alloy powder when it is manufactured by the atomization method, but the smaller the alloy solid-liquid coexistence temperature range (solidus temperature-liquidus temperature), the more It becomes close to the eutectic point and the structure becomes fine.

  As shown in Table 3, sample No. 3 has a high solidus temperature and a low liquidus temperature, so the solid-liquid coexistence temperature range is as narrow as 60 ° C. In this case, as shown in FIG. 2 (A), it is considered that the average grain size of the Si crystal is 1 to 2 μm and the structure is very fine. In sample No. 6, since the solidus temperature is high but the liquidus temperature is also high, the solid-liquid coexistence temperature range is 85 ° C., which is slightly wider than that of sample No. 3. In this case, as shown in FIG. 2 (B), it is considered that the average grain size of the Si crystal is 3 μm, and the structure is coarser than that of Sample No. 3. In sample No. 8, since the solidus temperature is low, the solid-liquid coexistence temperature range is as wide as about 110 ° C. In this case, as shown in FIG. 2C, it is considered that the average grain size of the Si crystal is 3 μm and the structure is rough. From the above results, the cylinder sleeve alloy of the present invention is excellent in thinness and high-speed extrudability and has a good degree of peeling. Further, it is considered that the high solidus temperature and the narrow solid-liquid coexistence temperature range are excellent in the sliding characteristics (seizure resistance and resistance to attack against opponents) described later.

[Castability]
For the cylinder sleeve, a test piece for a tensile test was prepared, and the tensile strength at 500 ° C. (500 ° C. UTS) was measured. This temperature assumes the temperature of the cylinder sleeve when the cylinder sleeve is cast into the cylinder block. Then, the sagability of the test piece was evaluated by the 500 ° C. UTS. These results are also shown in Table 2. As shown in Table 2, the results of determining the sagability of the test piece at 500 ° C. are indicated by ◎, ○, Δ, × in order from the better. When the Si content is 17% by mass, without containing Cu, the Fe content is 6-9% by mass, so that the 500 ° C UTS can be over 15MPa, and cast sagability. Was small. In particular, when the Fe content was 7% by mass or more, the 500 ° C. UTS could be 20 MPa or more, and almost no casting sag was observed.

[Sliding characteristics]
For the above cylinder sleeve, specimens for sliding test were prepared, HRB (Rockwell hardness) at room temperature, tensile strength at room temperature (room temperature UTS), and tensile strength at actual machine temperature (250 ° C) (250 ° C UTS ) Was measured. These results are also shown in Table 2.

  The HRB at room temperature is almost determined by the Fe and Cu contents. The alloy for a cylinder sleeve of the present invention has an Fe content of 6 to 9% by mass (sample No. 8) containing Cu to some extent (here 3.5% by mass) even if it does not contain Cu. Similarly, sufficient hardness can be obtained. In particular, when the Fe content is 7% by mass or more, an HRB of 70 or more can be obtained, and a hardness equal to or higher than that of Sample No. 8 can be obtained. Regarding the tensile strength at room temperature (room temperature UTS), the cylinder sleeve alloy of the present invention does not contain Cu, but the Fe content is set to 6 to 9% by mass or more in the same manner as Sample No. 8. Sufficient room temperature UTS can be obtained. In particular, when the Fe content is 7% by mass or more, the room temperature UTS can be 400 MPa or more, and a room temperature UTS larger than Sample No. 8 can be obtained. For tensile strength at 250 ° C. (250 ° C. UTS), even if the content of Si is less than 20% by mass without containing Cu, it is sufficient that the content of Fe is 6 to 9% by mass. 250 ℃ UTS can be obtained. In particular, by setting the Fe content to 7% by mass or more, the 250 ° C. UTS can be set to 220 MPa or more, and a 250 ° C. UTS larger than the case of sufficiently containing Cu or Si can be obtained.

  Further, as a wear test, a chip-on-disk wear test was performed to examine the seizure property, self-wear and counterpart wear. These results are also shown in Table 2. The chip-on-disk wear test will be described in detail below. Two test pieces of cylinder sleeve material (5 × 7 × 10mm thickness, self-made material) are used on the tip side, and a disk of piston skirt material (JIS standard A4032) (φ60 × thickness 10mm, mating material) on the disk side ) Is used. The chip is slid between the chip and the disk by pressing the chip against the disk and rotating the disk. The engine oil was thinly applied to the surface of the disk, and the test was performed at room temperature in the atmosphere with the disk rotating at 120 rpm. The chip pressing load starts at 0 and increases by 1 kg per minute. When it reaches 5 kg, hold for 3 minutes to complete the test. If the dynamic friction coefficient μ increases during the test and seizure occurs, the test ends immediately. When the test is completed without causing image sticking, the sliding surfaces of the chip and the disk are visually determined. The above test was performed three times for each sample, and the results are indicated by ◎, ○, Δ, × in order from the best. Specifically, ◎ if no seizure occurred 3 times, ○ if seized once, △ if seized twice, and x if seized 3 times.

  Regarding the seizure property, when the Si content was 17% by mass, the occurrence of seizure could be reduced by making the Fe content 6-9% by mass without containing Cu. In particular, the occurrence of seizure could be prevented by setting the Fe content to 7% by mass or more. For self-wear and mating wear, the Cu content is not included, the Si content is less than 20% by mass, and the Fe content is 6 to 9% by mass. It was. In particular, when the Fe content was 7% by mass or more, almost no wear marks were observed on the self material and the counterpart material. FIG. 4 and FIG. 5 show the test pieces and discs after the chip-on-disc test of Sample No. 3 and Sample No. 6, respectively. In both figures, (A) is an example of a stereoscopic microscope photograph of the surface of the test piece (chip), and (B) is an example of a stereoscopic microscope photograph of the surface of the disk. As shown in FIG. 4, in the case of sample No. 3, it can be seen that both the test piece and the disk have substantially less wear marks. On the other hand, FIG. 5 shows sample No. 6 where seizure occurred and the test piece was greatly seized. This is considered to be due to the low strength because Fe is not contained.

  From sample No. 1 to sample No. 4 and sample No. 7 that differ only in the Fe content, the Al alloy powder with the Fe content of 5.5% by mass is the same as the Al alloy powder with the Fe content of 6.0% by mass. It can be expected that equivalent sliding characteristics can be obtained. Also, with regard to castability, it can be expected that a 500 ° C tensile strength exceeding 15 MPa can be obtained. And since Cu is not contained, even if thin-walled and high-speed extrusion is performed, it is thought that a good peeling degree can be obtained.

  From the above test results, it can be seen that the cylinder sleeve alloy of the present invention is excellent in all of “thin-wall / high-speed extrudability”, “cast castability”, and “sliding characteristics”. By limiting the alloy for a cylinder sleeve of the present invention to a specific composition, the occurrence of flaking can be reduced even when the cylinder sleeve is subjected to thin wall and high speed extrusion. This is presumably because the specific composition is a composition close to the eutectic point, and the range of the solid-liquid coexistence temperature can be narrowed. Further, the cylinder sleeve alloy of the present invention is excellent in strength at both low and high temperatures, and can have high sag resistance, wear resistance and seizure resistance. The cylinder sleeve using the cylinder sleeve alloy of the present invention has a thin-walled structure, is excellent in strength at both low and high temperatures, and has high wear resistance and seizure resistance during operation.

  The above-described embodiment can be appropriately changed without departing from the gist of the present invention, and is not limited to the above-described configuration.

  The cylinder sleeve alloy of the present invention can be suitably used for a cylinder sleeve of an internal combustion engine. The cylinder sleeve of the present invention can be suitably used as a sliding member of an engine cylinder block.

Claims (7)

Containing 16-18% by mass of Si, 5.5-9% by mass of Fe, 0.5-2% by mass of Mg, 3-5% by mass of Al ₂ O ₃ and 0.5-3% by mass of graphite, the balance being Al and inevitable Cylinder sleeve alloy characterized by consisting of mechanical impurities.   2. The cylinder sleeve alloy according to claim 1, wherein the Fe content is 7 to 9% by mass.   3. The cylinder sleeve alloy according to claim 1, wherein an average grain size of the Si crystal is 1 to 2 μm. 4. The cylinder sleeve alloy according to claim 1, wherein the maximum particle size of the Al ₂ O ₃ is 30 μm or less and the average particle size is 10 μm or less.   5. The cylinder sleeve alloy according to claim 1, wherein the maximum particle size of the graphite is 10 μm or less in cross-sectional structure.   A cylinder sleeve comprising the cylinder sleeve alloy according to any one of claims 1 to 5.   7. The cylinder sleeve according to claim 6, wherein the tensile strength at room temperature is 400 MPa or more and the tensile strength at 500 ° C. is 20 MPa or more.