Aluminum alloy for die casting having excellent thermal conductivity and like, and method for producing die casting material using same

Abstract

The purpose of the present invention is to provide an aluminum alloy for die casting, which has excellent thermal conductivity and is suitable for die casting, and to provide an aluminum alloy for die casting, which has excellent electrical conductivity, corrosion resistance and strength and is also suitable for die casting. The purpose of the present invention is also to provide a method for producing a die casting material in which a recycled material can also be used as a starting material. The aluminum alloy material is characterized by containing, in mass%, 0.4 to 2.0% of Fe, 0.1 to 0.8% of Si, and 0.1 to 1.0% of Mg, with the remainder being Al and unavoidable impurities.

Description

Technical Field

[0001] The present invention relates to an aluminum alloy suitable for housing frames of electronic components used in vehicles, electronic equipment, etc., heat sinks for heat dissipation, etc., and more particularly to a die-casting material using the aluminum alloy and a manufacturing method. Background Art

[0002] In recent years, in the field of the automotive industry, structural changes called "CASE" such as Connected, Autonomous (Automated), Shared, and Electric have continued to develop.

[0003] Conventionally, as electronic devices have become more advanced in performance, the amount of heat generated by the electronic devices has tended to increase, and thus there has been a demand for improved cooling performance.

[0004] As one of the countermeasures, the use of aluminum materials for materials used in housings, heat sinks, etc. of electronic devices is being studied.

[0005] For example, Patent Document 1 discloses an aluminum alloy material, which comprises, by mass%, 0.0002 to 0.08% B, 0.05 to 2.5% Fe, and 0.05 to 2.5% Ni, wherein the ratio of B to the amount of Fe and Ni is 0.4 to 6.5%, and the remainder is composed of Al and unavoidable impurities.

[0006] Although the strength is improved by adding Fe and Ni, and the thermal conductivity is improved by adding B, a decrease in thermal conductivity compared to pure aluminum materials is inevitable.

[0007] Patent Document 2 discloses a heat sink formed by die casting, which contains Si: 4 to 13%, Mg: 0.22 to 2.0%, Fe: 0.2 to 1.0%, Cu or Ni: 0.5 to 5.0%, and the remainder is Al.

[0008] However, the thermal conductivity of such aluminum alloys is still insufficient.

[0009] Patent Document 3 discloses an aluminum alloy for die casting, which contains Cu: 2.30% or less, Si: 1.50% or less, Fe: 1.20 to 2.60%, and the remainder is composed of Al and inevitable impurities.

[0010] However, although this alloy has strength, its thermal conductivity and die casting properties are insufficient.

[0011] From the viewpoint of thermal conductivity, pure aluminum is known to be good, but since it is poor in die casting properties and has low strength, Al—Fe alloys have been studied.

[0012] However, the existing Al-Fe alloys for die casting have high purity, and it is difficult to use recycled materials as raw materials, which is one of the reasons for the high price.

[0013] Furthermore, when Al—Fe alloys are used as assembled structural members, thermal conductivity and strength are also required.

[0014] Furthermore, when used in housings, heat sinks, and the like of electronic devices, electromagnetic sealing properties, grounding properties, and corrosion resistance are required, and the material is required to have excellent electrical conductivity and corrosion resistance.

[0015] Prior art literature

[0016] Patent Literature

[0017] Patent Document 1: Japanese Patent No. 4328927

[0018] Patent Document 2: Japanese Patent No. 5387342

[0019] Patent Document 3: Japanese Patent No. 5301750 Summary of the invention

[0020] Technical problem to be solved by the invention

[0021] An object of the present invention is to provide an aluminum alloy for die casting which is excellent in thermal conductivity and suitable for die casting, and also to provide an aluminum alloy for die casting which is excellent in electrical conductivity, corrosion resistance and strength and suitable for die casting.

[0022] Another object of the present invention is to provide a method for producing a die-casting material in which a recycled material can also be used as a raw material.

[0023] Technical solutions for solving technical problems

[0024] The aluminum alloy for die casting having excellent thermal conductivity according to the present invention is characterized by containing, by mass%, 0.4 to 2.0% Fe, 0.1 to 0.8% Si, 0.1 to 1.0% Mg, and the remainder being Al and inevitable impurities.

[0025] Here, in consideration of the balance between thermal conductivity and strength, Fe: 0.4-2.0%, Si: 0.4-1.2%, Mg: 0.1-0.9%, and the remainder may be Al and inevitable impurities.

[0026] The reasons for selecting the components are as follows.

[0027] All the following information is in mass %.

[0028] <Fe component>

[0029] The content of the Fe component is in the range of 0.4 to 2.0%, preferably 0.5 to 1.8%.

[0030] When it is less than 0.4%, the castability during die casting decreases, and when it exceeds 2.0%, the thermal conductivity decreases.

[0031] On the other hand, when the content exceeds 2.0%, the electrical conductivity and corrosion resistance will be reduced.

[0032] <Si component>

[0033] The content of the Si component is in the range of 0.1 to 0.8%, preferably 0.2 to 0.6%.

[0034] When the content is less than 0.1%, the castability during die casting and the strength are reduced.

[0035] Here, in order to improve the strength, it is preferable to contain 0.4% or more of Si, and in order to suppress the decrease in thermal conductivity, it is preferably 1.2% or less.

[0036] <Mg component>

[0037] The content of the Mg component is in the range of 0.1 to 1.0%, preferably 0.1 to 0.9%.

[0038] More preferably, it is in the range of 0.2 to 0.7%.

[0039] When it is less than 0.1%, the strength decreases, and when it exceeds 1.0%, the thermal conductivity decreases.

[0040] <Zn component>

[0041] In the present invention, a recycled material containing a Zn component may be used as a raw material.

[0042] In this case, Zn is 0.7% or less, preferably 0.5% or less. When Zn exceeds 0.7%, the corrosion resistance decreases.

[0043] <Other ingredients>

[0044] In the present invention, components other than Fe, Si and Mg are treated as inevitable impurities, and are allowed to be mixed within a range that does not affect reduction in strength, reduction in castability, reduction in thermal conductivity, reduction in electrical conductivity and reduction in corrosion resistance.

[0045] From the viewpoint that recycled materials can be used as raw materials, the aluminum alloy for die casting according to the present invention allows impurities to be mixed therein within the above-mentioned range.

[0046] In terms of mass%, any one or more of Ti: 0.005 to 0.3%, B: 0.0001 to 0.06%, and Zn: 0.001 to 0.7% may be contained.

[0047] <Ti component>

[0048] The content of the Ti component is in the range of 0.005 to 0.3%, preferably 0.02 to 0.2%.

[0049] When the content is less than 0.005%, the effect of grain refinement is low, and the effects of improving strength and suppressing casting cracks are low.

[0050] When it exceeds 0.3%, thermal conductivity decreases.

[0051] <Ingredient B>

[0052] The content of the component B is in the range of 0.0001 to 0.06%, preferably 0.0005 to 0.04%.

[0053] When it is less than 0.0001%, the effect of grain refinement is low, and the effects of improving strength and suppressing casting cracks are low.

[0054] When it exceeds 0.06%, the hard phase which reduces the tool life increases.

[0055] In the present invention, the above-mentioned aluminum alloy for die casting may be used for die casting, and then maintained at 300 to 410° C. for 1 to 6 hours and naturally cooled in the atmosphere.

[0056] It should be noted that the furnace may be cooled by turning off the heater of the furnace while the furnace is kept in the heating furnace.

[0057] When die casting is performed using the aluminum alloy for die casting according to the present invention, the thermal conductivity is 170 W / m·K or more even without heat treatment. However, when heat treatment is performed, the thermal conductivity is 185 W / m·K or more.

[0058] Here, if the heat treatment temperature exceeds 410° C., there is a possibility that blistering may occur on the die-casting material.

[0059] In the present invention, a step (T5 treatment) of performing die casting using the above-mentioned aluminum alloy for die casting, maintaining the alloy at 160 to 210° C. for 1 to 6 hours, and naturally cooling the alloy in the atmosphere may be adopted.

[0060] When the heat treatment is performed in this manner, the thermal conductivity of 170 W / m·K or more is maintained, and the 0.2% proof stress is 80 MPa or more.

[0061] It should be noted that, here, when the heat treatment temperature is lower than 160° C., the improvement in strength and thermal conductivity is small.

[0062] Effects of the Invention

[0063] By using the die-casting aluminum alloy according to the present invention, recycled materials can be used as raw materials, and a high-strength die-casting material having excellent die-casting properties and high thermal conductivity can be obtained. Therefore, the aluminum alloy can be widely used in housings for housing electronic components and heat dissipation materials.

[0064] Furthermore, even when recycled materials are used, reduction in electrical conductivity and corrosion resistance can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 Shows the evaluation results of die castings that were not subjected to heat treatment.

[0066] Figure 2 Indicates the evaluation results after heat treatment. DETAILED DESCRIPTION

[0067] In this embodiment and comparative example, raw materials containing aluminum and alloy elements are melted and used Figure 1 Aluminum alloy melts having the chemical components shown in Table 1 were used to produce die castings, and the die castings were evaluated.

[0068] Regarding the present examples and comparative examples, the thermal conductivity, electrical conductivity, and mechanical properties were measured in a cast state without heat treatment, and the corrosion resistance in a salt water spray test was evaluated.

[0069] The results are as follows Figure 1 As shown in Table 1.

[0070] In addition, the present example and the comparative example were die-cast at an injection speed of 2.2 m / sec and a casting pressure of 60 MPa, and the castability was confirmed based on the appearance and the presence or absence of internal defects.

[0071] The castables with no problems were indicated by "○", and the castables with problems were indicated by "×".

[0072] The results of castability are also shown in Figure 1 Table 1.

[0073] The casting material using the aluminum alloy of this embodiment as the heat dissipating member preferably has a thermal conductivity of 170 W / m·K or more and has no problem with die casting performance.

[0074] Here, the thermal conductivity (W / m·K) is calculated by thermal conductivity=thermal diffusivity×specific heat×density.

[0075] The thermal diffusivity was measured at a measurement temperature of 60° C. using LFA467 manufactured by NETZSCH, by cutting a sample from the die casting.

[0076] The specific heat was measured at a measurement temperature of 60° C. using DSC500 manufactured by NETZSCH.

[0077] The density used was the bulk density at room temperature obtained from the size and mass of the sample.

[0078] A sample was cut out from the die casting, and the electrical conductivity was measured at a measurement temperature of 24° C. using an eddy current conductivity meter.

[0079] The salt spray test was conducted by cutting samples from the die castings and conducting the test for 168 hours in accordance with JIS. The weight loss due to corrosion was calculated from the weight of the samples before and after the test.

[0080] Mechanical properties were measured by cutting samples from die castings using a tensile testing machine based on JIS.

[0081] In Examples 1 to 9, the ranges of Fe: 0.4 to 2.0%, Si: 0.1 to 0.8%, and Mg: 0.1 to 1.0% have a thermal conductivity of 170 W / m·K or more even if only cast without heat treatment, and the castability is also excellent.

[0082] In Examples 10 to 12, the Si content is 0.8% or more but is suppressed to 1.2% or less, and the Mg content is selected to be in the range of 0.1 to 0.9%. Therefore, although the thermal conductivity is slightly reduced, the target 170 W / m·K or more can be ensured, while the strength is relatively improved.

[0083] In addition, it was confirmed that the castability was excellent.

[0084] In addition, the conductivity is above 45% IACS and the corrosion weight loss is 1 mg / cm 2 the following.

[0085] On the other hand, in Comparative Example 1, since Fe: 0.18% is less than 0.4%, the castability is poor.

[0086] Although the castability was ensured in Comparative Examples 2 and 3, the Mg component was large and the thermal conductivity did not reach the target.

[0087] Comparative Example 12 has a high Zn content of 0.71% and a high Cu component. Therefore, even if the castability can be ensured by the Si component, the conductivity and corrosion resistance are poor.

[0088] In addition, although the castability was ensured in Comparative Examples 10 and 11, the Si content was high and the thermal conductivity did not reach the target.

[0089] Comparative Examples 4 to 9 had poor castability.

[0090] The raw materials containing aluminum and alloy elements are dissolved and used Figure 2 Aluminum alloys with chemical compositions shown in Table 2 were die-casted.

[0091] Using these die castings, Examples 13 to 15 and Comparative Examples 13 and 14 were subjected to annealing by holding at 350° C. for 3 hours and then cooling in the atmosphere.

[0092] Examples 16 and 17 were subjected to heat treatment of T5 treatment at 190° C. for 3 hours.

[0093] The thermal conductivity, electrical conductivity and mechanical properties of these materials were measured in the same manner as above. The results are shown in Figure 2 Table 2.

[0094] exist Figure 2 In the table, Example 13 is an example of Example 2 without heat treatment, and then cooling annealing in the atmosphere after being kept at 350°C for 3 hours. Similarly, Example 14 is an example of Example 7 being heat treated, and Example 15 is an example of Example 9 being heat treated.

[0095] The thermal conductivity is increased to above 185W / m·K.

[0096] Comparative Examples 13 and 14 were heat-treated in the same manner as Comparative Examples 2 and 3, but the rate of improvement in thermal conductivity was smaller than that of Examples 13 to 15.

[0097] Examples 16 and 17 are examples in which the materials of Examples 10 and 12 were subjected to T5 treatment at 190° C. for 3 hours.

[0098] Although the rate of improvement in thermal conductivity was smaller than that in Examples 13 to 15, a tensile strength of 130 MPa or more and a yield strength of 90 MPa or more were ensured.

[0099] The microstructure of the die-cast material involved in the present invention was observed to be a eutectic structure of Al and Fe, and uniformly dispersed spherical primary crystals α and Al-Fe-based crystals in the gaps between the primary crystals α were confirmed. Therefore, it is estimated that in the Al-Fe-based crystals, the thermal conductivity is improved due to the continuity of the primary crystals α.

[0100] Industrial Applicability

[0101] The aluminum alloy for die casting according to the present invention has excellent thermal conductivity, and when combined with heat treatment, the thermal conductivity and strength can be further improved. If the composition is within this range, recycled materials can be used as raw materials.

Claims

1. A die-casting aluminum alloy, characterized in that: It contains, by mass%, 0.4 to 2.0% Fe, 0.1 to 0.8% Si, 0.1 to 1.0% Mg, and the remainder is Al and inevitable impurities, and has excellent thermal conductivity.

2. A die-casting aluminum alloy, characterized in that: It contains, by mass%, 0.4 to 2.0% Fe, 0.4 to 1.2% Si, 0.1 to 0.9% Mg, and the remainder is Al and inevitable impurities, and has excellent thermal conductivity and strength.

3. The die-casting aluminum alloy according to claim 1 or 2, characterized in that: In terms of mass%, at least one of 0.005% to 0.3% Ti, 0.0001% to 0.06% B, and 0.001% to 0.7% Zn is further contained.

4. A method for manufacturing a die-casting material, characterized in that: Die casting is performed using the die casting aluminum alloy according to any one of claims 1 to 3.

5. The method for manufacturing a die-casting material according to claim 4, characterized in that: After the die casting, the steel sheet is held at 160 to 210° C. for 1 to 6 hours and then naturally cooled in the atmosphere.

6. The method for manufacturing a die-casting material according to claim 4, characterized in that: After the die casting, the steel sheet is held at 300 to 410° C. for 1 to 6 hours and then naturally cooled in the atmosphere.

7. The method for manufacturing a die-casting material according to claim 4, characterized in that: The die-casting aluminum alloy uses recycled materials as raw materials.

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