Aluminum alloy for forged products

Abstract

To provide an aluminum alloy having heat-resistant strength.SOLUTION: An aluminum alloy contains Si of 9.0-13.5 wt.%, Fe of 0.2-0.5 wt.%, Cu of 4.5-6.5 wt.%, Ti of 0.01-0.05 wt.%, Mn of 0.01-0.2 wt.%, Mg of 0.6-1.15 wt.%, Cr of 0.05 wt.% or less, Zn of 0.8 wt.% or less, Zr of 0.01-0.1 wt.%, Ni of 1.0-2.0 wt.%, Sr of 0.005-0.025 wt.%, with the balance being Al and impurities.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an aluminum alloy having excellent heat resistance strength. For forged products

Background Art

[0002] Conventionally, for components that rotate or reciprocate at high speed while rubbing against other components at high temperatures, such as impellers, rotors, and compressor components such as pistons, forged products of Al-Si series aluminum alloys such as A4032 alloy have been frequently used. The A4032 alloy has excellent wear resistance and good forgeability, but has a problem of poor heat resistance.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In view of the above-described circumstances, the present invention aims to provide an aluminum alloy having excellent heat resistance strength. For forged products

Means for Solving the Problems

[0004] In order to achieve the above object, the aluminum alloy according to the invention described in claim 1 For forged products contains Si in an amount of 9.0 to 13.5 wt%, Fe in an amount of 0.2 to 0.5 wt%, Cu in an amount of 4.5 to 6.5 wt%, Ti in an amount of 0.01 to 0.05 wt%, Mn in an amount of 0.01 to 0.2 wt%, Mg in an amount of 0.6 to 1.15 wt%, Cr in an amount of 0.05 wt% or less, Zn in an amount of 0.8 wt% or less, Zr in an amount of 0.01 to 0.1 wt%, Ni in an amount of 1.0 to 2.0 wt%, and Sr in an amount of 0.005 to 0.025 wt%, with the balance being Al and impurities.

Effects of the Invention

[0005] According to the invention described in claim 1 For forged products ​​The aluminum alloy contains 9.0 - 13.5 wt% of Si, 0.2 - 0.5 wt% of Fe, 4.5 - 6.5 wt% of Cu, 0.01 - 0.05 wt% of Ti, 0.01 - 0.2 wt% of Mn, 0.6 - 1.15 wt% of Mg, 0.05 wt% or less of Cr, 0.8 wt% or less of Zn, 0.01 - 0.1 wt% of Zr, 1.0 - 2.0 wt% of Ni, and 0.005 - 0.025 wt% of Sr (in particular, containing 4.5 - 6.5 wt% of Cu and 1.0 - 2.0 wt% of Ni), thereby becoming excellent in heat resistance. Also, formability and wear resistance equivalent to those of the A4032 alloy can be obtained.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0007] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The For forged products aluminum alloy contains 9.0 - 13.5 wt% of Si, 0.2 - 0.5 wt% of Fe, 4.5 - 6.5 wt% of Cu, 0.01 - 0.05 wt% of Ti, 0.01 - 0.2 wt% of Mn, 0.6 - 1.15 wt% of Mg, 0.05 wt% or less of Cr, 0.8 wt% or less of Zn, 0.01 - 0.1 wt% of Zr, 1.0 - 2.0 wt% of Ni, and 0.005 - 0.025 wt% of Sr, and has a composition consisting of the balance Al and impurities. Hereinafter, each alloy element will be described.

[0008] Si: 9.0 - 13.5 wt% Si is an element that contributes to the improvement of low thermal expansion and wear resistance. If the Si content is less than 9.0 wt%, the wear resistance is poor. If the Si content is more than 13.5 wt%, the primary Si coarsens, leading to deterioration of forging formability and a decrease in fatigue strength. Therefore, the Si content should be 9.0 - 13.5 wt%. If the upper limit of Si is set to 11.1 wt%, the generation of primary Si can be suppressed, and accordingly, forging of complex shapes becomes possible, which is more preferable.

[0009] Fe: 0.20 - 0.50 wt% Fe contributes to the improvement of heat resistance. If the Fe content is less than 0.20 wt%, this effect is weak. If the Fe content is more than 0.50 wt%, coarse precipitates of the Al-Fe-Mn system occur, adversely affecting the fatigue properties. Therefore, the Fe content should be 0.20 - 0.50 wt%.

[0010] Cu: 4.5 - 6.5 wt% Cu contributes to the improvement of heat resistance through the precipitation of Al2Cu. If the Cu content is less than 4.5 wt%, this effect is small. If the Cu content is more than 6.5 wt%, coarse precipitates occur, adversely affecting the fatigue properties. Therefore, the Cu content should be 4.5 - 6.5 wt%.

[0011] Ti: 0.01 - 0.05 wt% Ti contributes to the improvement of heat resistance through the precipitation of Al-Ti compounds. If the Ti content is less than 0.01 wt%, this effect is weak. If the Ti content is more than 0.05 wt%, coarse precipitates occur, leading to a decrease in fatigue strength. Therefore, the Ti content should be 0.01 - 0.05 wt%.

[0012] Mn: 0.01 - 0.2 wt% Mn contributes to the improvement of heat resistance. However, if the Mn content is more than 0.20 wt%, coarse precipitates of the Al-Fe-Mn system occur, adversely affecting the fatigue properties. Therefore, the Mn content should be 0.01 - 0.2 wt%. If the Mn content is 0.01 wt% - 0.05 wt%, the generation of precipitates of the Al-Fe-Mn system can be suppressed, which is more preferable.

[0013] Cr: Below 0.05 wt% Cr contributes to improving the heat resistance strength. However, if the Cr content exceeds 0.05 wt%, coarse Al-Cr-Fe-based precipitates will form, which will have an adverse effect on the fatigue properties. Therefore, the Cr content should be 0.05 wt% or less.

[0014] Zn: Below 0.8 wt% If the allowable range of Zn is wide, inexpensive raw materials can be used, which is advantageous in terms of cost. However, if Zn is contained excessively, it will conversely become difficult to recycle. Therefore, the Zn content is set to 0.8 wt% or less.

[0015] Mg: 0.6 - 1.15 wt% Mg contributes to improving the heat resistance strength by the precipitation of Mg2Si or AlSiCuMg-based intermetallic compounds. If the Mg content is less than 0.6 wt%, this effect will be small. If it exceeds 1.15 wt%, the forging formability will deteriorate. Therefore, the Mg content is 0.6 - 1.15 wt%.

[0016] Zr: 0.01 - 0.10 wt% Zr contributes to refining the microstructure, improving the heat resistance strength, and enhancing the strength after forging. However, if the Zr content exceeds 0.10 wt%, the AlZr-based precipitates will coarsen, which will have an adverse effect on the fatigue properties. Therefore, the Zr content is 0.01 - 0.1 wt%.

[0017] Ni: 1.0 - 2.0 wt% Ni contributes to improving the heat resistance strength by the precipitation of Al-(Fe)-Cu-Ni-based intermetallic compounds. If the Ni content is less than 1.0 wt%, this effect will be small. If it exceeds 2.0 wt%, the compounds will coarsen, and the forging formability will deteriorate. Therefore, the Ni content is 1.0 wt% - 2.0 wt%.

[0018] Sr: 0.005 - 0.025 wt% Sr refines eutectic Si and improves forging formability. If the Sr content is less than 0.005 wt%, this effect cannot be obtained, and if it is more than 0.025 wt%, there is a risk of porosity. Therefore, the Sr content was set to 0.005 - 0.025 wt%.

[0019] Next, the manufacturing method for a product using the aluminum alloy of the present invention will be described. The aluminum alloy melt adjusted to the above-described component range is continuously cast through a mold to produce a cylindrical billet. The continuous casting is preferably performed by the heat-insulating mold method (see, for example, Japanese Patent No. 4468267). By casting by this method, eutectic Si is finely and uniformly dispersed, improving forging formability. For forged products The cast billet is subjected to a homogenization treatment at 450°C to 500°C for 5 to 10 hours, and then forged to form the shape of the product. Thereafter, heat treatment such as T6 treatment is performed to increase the strength. The T6 treatment consists of solution treatment, quenching, and aging treatment. The solution treatment is preferably performed at 460°C to 510°C for 3 to 4 hours, and the aging treatment is preferably performed at 160°C to 200°C for 2 to 3 hours. By performing such heat treatment, fine intermetallic compounds precipitate, improving the heat-resistant strength.

[0020] Hereinafter, examples of the present invention will be described in comparison with comparative examples. The aluminum alloys shown in Table 1 below were ingoted to a diameter of 95 mm by the heat-insulating mold method and subjected to a homogenization treatment at 460°C to 510°C for 6 to 8 hours. Examples 1 to 13 are within the range of the alloy components of Claim 1, and among them, Examples 10 and 11 are within a narrower range than Claim 1, in which Si and Mn are limited to a more preferable range (Si: 9.0 - 11.1 wt%, Mn: 0.01 - 0.05 wt%). Comparative Examples 1 to 8 are those in which the components marked with * in the table are outside the range of Claim 1, and among them, Comparative Example 1 is an A4032 alloy.

[0021]

Table 1

[0022] For each example and comparative example, measurement of heat resistance strength, evaluation of wear resistance, evaluation of forging formability, and observation of internal structure were performed. Generally, the heat resistance strength ensures strength by the intermetallic compounds crystallized during casting forming a network structure. When forging is performed, this network structure is destroyed, so the strength after forging decreases. Therefore, for the measurement of heat resistance strength, forgings with low and high forging ratios were assumed, and ingots subjected to homogenization treatment were upset forged at forging ratios of 22.5%, 80%, and 85% (see Figure 2). Thereafter, the T6 treatment shown above was performed, and a high-temperature tensile test was conducted at test temperatures of 150°C and 250°C to measure the heat resistance strength of each example and comparative example. In the case of compressor parts, a heat resistance strength of 150°C is sufficient, but assuming use in the pistons of internal combustion engines, the heat resistance strength at 250°C was also measured. For the high-temperature tensile test, thermal exposure at the test temperature × 100 hours was performed to produce a notched test piece shown in Figure 3, and in accordance with JIS G 0567, a tensile test was conducted at a strain rate of 0.3% / min up to the 0.2% proof stress and 7.5% / min after the 0.2% proof stress. The tensile strength was taken as the stress value at the maximum test force. The evaluation of wear resistance was performed by the pin-on-disk method. For the test, a sample upset forged at a forging ratio of 85% and subjected to thermal exposure at 250°C × 100 hours was used. SUS420J2 tempered material was used for the disk, and the test material was used for the pin (spherical tip). The test method was as follows: in a wet environment (medium liquid: oil, oil temperature 120°C), as shown in Figure 4, the pin and the disk were brought into contact, the disk was rotated for 2 hours while applying a constant load of 30 N to the pin, and the weight of the pin before and after the test was measured to calculate the wear amount. The evaluation of forging formability was performed by upset forging at a forging ratio of 80% and checking whether cracks occurred during that process. The observation of the internal structure was confirmed for those with a forging ratio of 0%. The results of each test are shown in Table 2. The evaluation criteria of ◎, 〇, and × in the table for each evaluation item are as described outside the columns of Table 2. As described above, since the heat resistance strength decreases as the forging ratio increases, reference values were set at forging ratios of 22.5% and 85% respectively. Also, since the material strength decreases as the temperature increases, reference values were provided at 150°C and 250°C respectively. Microstructure photographs of Example 10, Comparative Example 4, and Comparative Example 7 are shown in Fig. 1.

[0023]

Table 2

[0024] As is clear from Table 2, in Examples 1 to 13 of the present invention, when the forging ratio is 22.5%, the tensile strength at 150°C is 350 MPa or more, the tensile strength at 250°C is 130 MPa or more, when the forging ratio is 85%, the tensile strength at 150°C is 330 MPa or more, and the tensile strength at 250°C is 120 MPa or more, showing high values, and the heat resistance strength is improved compared with Comparative Example 1 (A4032 alloy). Also, in Examples 1 to 13 of the present invention, the forging formability and wear resistance are equal to or better than those of Comparative Example 1 in all cases. In the internal structures of Examples 1 to 13, there were no coarse crystal precipitates. It is generally known that the fatigue strength decreases when there are coarse crystal precipitates. Since there are no coarse crystal precipitates in Examples 1 to 13, it is expected that the fatigue strength is high. Examples 10 and 11, in which Si and Mn are limited to more preferable ranges, in addition to having no coarse crystal precipitates, also had no fine Al-Fe-Mn-based crystal precipitates. Although the fatigue strength may decrease when fine Al-Fe-Mn-based crystal precipitates aggregate, it is expected that Examples 10 and 11 have even better fatigue strength because they also have no fine Al-Fe-Mn-based crystal precipitates. As shown in Fig. 1(a), the structure of Example 10 had no primary Si and was fine and uniform.

[0025] On the other hand, Comparative Example 2 with an Si content of less than 9.0 wt% has poor wear resistance. In Comparative Example 3 where the Si content is more than 13.5 wt%, coarse primary Si is generated, resulting in poor forging formability and a decrease in fatigue strength. Comparative Example 4 with an Fe content of more than 0.50 wt% has coarse precipitates (see Fig. 1(b)), so there is a concern that the fatigue characteristics will deteriorate. Comparative Example 5 with a Cu content of less than 4.5 wt% has inferior tensile strength at 250°C. Comparative Example 6 with a Cu content of less than 4.5 wt% and an Mg content of less than 0.6 wt% has inferior heat resistance at both 150°C and 250°C. Comparative Example 7 with an Mn content of more than 0.2 wt% has coarse precipitates (see Fig. 1(c)), so there is a concern that the fatigue characteristics will deteriorate. Comparative Example 8 with a Ni content of more than 2.0 wt% has poor forging formability.

[0026] As described above, according to the invention of claim 1 For forged products The aluminum alloy contains Si at 9.0 - 13.5 wt%, Fe at 0.2 - 0.5 wt%, Cu at 4.5 - 6.5 wt%, Ti at 0.01 - 0.05 wt%, Mn at 0.01 - 0.2 wt%, Mg at 0.6 - 1.15 wt%, Cr at 0.05 wt% or less, Zn at 0.8 wt% or less, Zr at 0.01 - 0.1 wt%, Ni at 1.0 - 2.0 wt%, and Sr at 0.005 - 0.025 wt% (in particular, containing Cu at 4.5 - 6.5 wt% and Ni at 1.0 - 2.0 wt%), thereby becoming excellent in heat resistance. Also, formability and wear resistance equivalent to those of A4032 alloy can be obtained. If it contains Si at 9.0 - 11.1 wt% and Mn at 0.01 - 0.05 wt%, no coarse precipitates will occur regardless of the combination of the contents of each element within the range, and the generation of Al - Fe - Mn - based precipitates can also be suppressed, so a decrease in fatigue strength can be reliably prevented. The For forged products aluminum alloy of the present invention is excellent in heat resistance and wear resistance and has good formability, so it is suitable as a forging material for compressor parts. Also, since it has excellent heat resistance at 250°C, it is also suitable as a material for forged pistons of internal combustion engines.

[0027] The present invention is not limited to the embodiments described above. The alloy components can be appropriately changed within the scope described in the claims. Further, it may contain components not described in the claims. The casting method and the diameter of the continuous casting rod are not particularly limited. The specific shape and use of the forged product are arbitrary, and the method of forging is not particularly limited. Further, the aluminum alloy of the present invention can be made into various products by performing various processes such as extrusion and rolling in addition to forging, or by performing cutting on the ingot as it is.

Claims

【Claim 1】 An aluminum alloy for forged products, comprising 9.0 to 13.5 wt% of Si, 0.2 to 0.5 wt% of Fe, 4.5 to 6.5 wt% of Cu, 0.01 to 0.05 wt% of Ti, 0.01 to 0.2 wt% of Mn, 0.6 to 1.15 wt% of Mg, 0.05 wt% or less of Cr, 0.8 wt% or less of Zn, 0.01 to 0.1 wt% of Zr, 1.0 to 2.0 wt% of Ni, 0.005 to 0.025 wt% of Sr, with the balance being Al and impurities.

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