Method for preparing high-strength and high-thermal-conductivity aluminum alloy by adopting melt purification and die-casting process

Abstract

The invention relates to the technical field of metallurgy, and discloses a method for preparing a high-strength and high-thermal-conductivity aluminum alloy by adopting a melt purification and die-casting process. The preparation method comprises the following steps: feeding according to the proportion of A356 cast aluminum alloy, and smelting to obtain a raw material solution; after smelting treatment, argon is introduced into a refining tank, a refining flux is injected into the melt through blowing, and the refined melt is obtained through degassing; the melt is injected into a die-casting die, the mold filling pressure is controlled, and then demolding treatment is conducted; and after demolding treatment, the die-casting aluminum alloy is placed in a heat treatment furnace for heat treatment, and after heat treatment is finished, the die-casting aluminum alloy is taken out and air-cooled to obtain the aluminum alloy. According to the method provided by the invention, the harmful effects of elements such as potassium, sodium, strontium and hydrogen on the heat-conducting property can be limited to the maximum extent by adopting melt purification treatment, the structure of the die-casting alloy is regulated and controlled by controlling process parameters in the die-casting process, and the die-casting defects such as air holes and shrinkage porosity are reduced, so that the alloy has relatively high strength and heat-conducting property.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a method for preparing a high-strength and high-thermal-conductivity aluminum alloy by using melt purification and die-casting processes. Background Art

[0002] Aluminum alloys are widely used in aerospace, transportation, machinery, electronics, construction and other fields. They are the most important basic materials for lightweight structures and occupy an important position in the national economy.

[0003] The cleanliness of aluminum alloy melt has a great influence on the performance of the material, especially fracture toughness, fatigue strength and corrosion resistance. Reducing the gas content and non-metallic inclusion content in the melt and achieving melt purification are the key to ensuring the metallurgical quality of aluminum alloy materials.

[0004] During the aluminum alloy smelting process, the gases, various inclusions and other metal impurities present in the melt often cause defects such as bubbles, pores, looseness, cracks, white spots, etc. in the ingot, which have a significant impact on the processing performance of the ingot and the strength, plasticity, corrosion resistance and appearance quality of the product.

[0005] During the die casting process, due to the fast cooling rate, local segregation of solute elements may occur, which not only affects the uniformity of the microstructure, but also reduces the overall performance of the material. At the same time, during the die casting process, if the melt purity is not enough or the mold conditions are not properly controlled, defects such as cold shut and flow marks may appear on the casting surface, affecting the appearance quality and subsequent processing procedures. Summary of the invention

[0006] Technical problems solved by the present invention:

[0007] Used to provide a high-strength and high-thermal-conductivity aluminum alloy.

[0008] The technical solution adopted by the present invention is:

[0009] In view of the above technical problems, the object of the present invention is to provide a method for preparing a high-strength and high-thermal-conductivity aluminum alloy by melt purification and die-casting process.

[0010] Based on this, the specific implementation plan is:

[0011] A method for preparing a high-strength and high-thermal-conductivity aluminum alloy by melt purification and die-casting process comprises the following steps:

[0012] (1) The materials are charged according to the proportion of A356 cast aluminum alloy, and the aluminum ingot is smelted to obtain pure aluminum liquid; the pure aluminum liquid is mixed with silicon source, iron source, copper source, magnesium source, titanium source and zirconium source, and then smelted to obtain raw material liquid. The smelting temperature is 650-750°C.

[0013] The chemical composition of A356 cast aluminum alloy is calculated by mass percentage: Si 7.2-7.3%, Fe0.8-0.9%, Cu4.4-4.8%, Mn≤0.002%, Mg 0.30-0.32%, Cr≤0.007%, Ni≤0.009%, Zn≤0.018%, Ti0.05-0.30%, Be≤0.0001%, Ga≤0.01%, Sr≤0.003%, Zr 0.10-0.25%, and the balance is aluminum.

[0014] (2) After smelting, argon is introduced into the refining tank. At this time, the temperature of the melt in the refining tank is 700-750°C. Refining flux is injected into the melt by spraying. The injection rate of refining flux is 420-480g / min. The introduction rate of argon is maintained at 20L / min. After adding the refining flux, argon is continued to be introduced for 50 minutes. The amount of refining flux added accounts for 0.2% of the raw material liquid. After the end, it is degassed for 8-15 minutes, and then left to stand and slag to obtain the refined melt.

[0015] The raw material components of the refining flux include, by weight, 40-60 parts of aluminum fluoride, 1-5 parts of calcium fluoride, 1-3 parts of cerium fluoride, 1-3 parts of lanthanum fluoride, 10-20 parts of sodium chloride, 10-20 parts of potassium chloride, 5-10 parts of sodium carbonate, and 5-10 parts of sodium borate.

[0016] In the above, the raw material components of the refining flux are preferably 40-50 parts of aluminum fluoride, 1-3 parts of calcium fluoride, 1-3 parts of cerium fluoride, 1-3 parts of lanthanum fluoride, 10-15 parts of sodium chloride, 10-15 parts of potassium chloride, 5-8 parts of sodium carbonate, and 5-8 parts of sodium borate.

[0017] The preparation method of the refined flux is to weigh the aforementioned raw material components in proportion, dry them at the same time, blend the raw material components, and then bake them at 230-260° C. to obtain the refined flux.

[0018] (3) The melt is injected into the die casting mold, and the filling pressure is controlled to be maintained at 200-300 mbar. After injection, the temperature is raised to 850-950°C, and the temperature is kept for 50-100 seconds, and then the temperature is cooled to 500-600°C and kept for 10-30 seconds. After the insulation is completed, the melt is cooled to 350-400°C and demolded.

[0019] (5) After demolding, the die-cast aluminum alloy is placed in a heat treatment furnace, heated from room temperature to 150-170°C and maintained for 90-120 min, and then further heated to 200-230°C and maintained for 150-180 min. After the temperature is removed, the aluminum alloy is air-cooled to obtain an aluminum alloy.

[0020] The technical mechanism and beneficial effects adopted by the present invention are as follows:

[0021] (1) The refining flux provided by the present application uses a combination of fluoride and rare earth elements, which can effectively combine with oxygen in the aluminum alloy to form a stable compound, thereby reducing the inclusion of oxides. The combination of chloride and fluoride can significantly reduce the melting point of the flux and provide good fluidity, thereby ensuring that the flux can be evenly distributed on the surface of the melt.

[0022] (2) The refining flux provided by the present invention can enhance the ability of the flux to capture and release gas by using this combination, thereby avoiding the occurrence of internal pore defects to a certain extent.

[0023] (3) The die-casting process provided by the present invention controls the filling pressure to avoid curling or disorder caused by excessive speed, thereby reducing the appearance of pores or inclusions inside. Multi-stage cooling and demolding are used to reduce the large temperature difference caused by rapid cooling and avoid thermal cracks. By controlling the cooling rate, the shrinkage of the product is controlled, the surface quality is improved, and phase transformation and refinement are promoted, thereby improving the strength and mechanical properties. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0025] Example 1

[0026] Weigh 52 parts of aluminum fluoride, 3 parts of calcium fluoride, 2 parts of cerium fluoride, 2 parts of lanthanum fluoride, 12 parts of sodium chloride, 15 parts of potassium chloride, 7 parts of sodium carbonate, and 7 parts of sodium borate in proportion, dry the mixture, blend it, and bake it at 240°C to obtain a refined flux.

[0027] Example 2

[0028] This embodiment adopts a method for preparing A356 cast aluminum alloy, and the specific steps are as follows:

[0029] The aluminum ingot is melted at 720°C to obtain pure aluminum liquid. Silicon source, iron source, copper source, magnesium source, titanium source and zirconium source are added to the pure aluminum liquid and mixed, and then melted at 700°C to obtain a raw material liquid.

[0030] After the smelting is completed, the refining flux prepared in Example 1 is added, the temperature of the raw material liquid melt in the refining tank is maintained at 750°C, the amount of the refining flux added accounts for 0.2% of the mass of the raw material liquid, the refining flux is injected into the melt by blowing, the injection rate of the refining flux is 450g / min, the argon gas introduction rate is maintained at 20L / min, and the refining flux is continued to be introduced for 50min after the refining flux is added. After the end, the refining flux is degassed for 10min, and then left to stand and slag is removed to obtain the refined melt.

[0031] The melt is injected into the die casting mold, and the filling pressure is controlled to be maintained at 240 mbar. After injection, the temperature is raised to 900°C and kept for 100 seconds, and then cooled to 550°C and kept for 20 seconds. After the end of the insulation, it is cooled to 380°C and demolded.

[0032] After demolding, the die-cast aluminum alloy was placed in a heat treatment furnace, heated from room temperature to 160°C and maintained for 100 minutes, and then continued to heat to 220°C and maintained for 180 minutes. After the end, it was taken out and air-cooled to obtain an aluminum alloy.

[0033] Example 3

[0034] This embodiment adopts a method for preparing A356 cast aluminum alloy, and the specific steps are as follows:

[0035] The aluminum ingot is melted at 740°C to obtain pure aluminum liquid. Silicon source, iron source, copper source, magnesium source, titanium source and zirconium source are added to the pure aluminum liquid and mixed, and then melted at 720°C to obtain a raw material liquid.

[0036] After the smelting is completed, the refining flux prepared in Example 1 is added, the temperature of the raw material liquid melt in the refining tank is maintained at 750°C, the amount of the refining flux added accounts for 0.2% of the mass of the raw material liquid, the refining flux is injected into the melt by blowing, the injection rate of the refining flux is 450g / min, the argon gas introduction rate is maintained at 20L / min, and the refining flux is continued to be introduced for 50min after the refining flux is added. After the end, the refining flux is degassed for 10min, and then left to stand and slag is removed to obtain the refined melt.

[0037] The melt is injected into the die-casting mold, and the filling pressure is controlled to be maintained at 270mbar. After injection, the temperature is raised to 920℃ and kept for 80s, and then cooled to 560℃ and kept for 20s. After the insulation, it is cooled to 380℃ and demolded.

[0038] After demolding, the die-cast aluminum alloy was placed in a heat treatment furnace, heated from room temperature to 160°C and maintained for 100 minutes, and then continued to heat to 230°C and maintained for 180 minutes. After the end, it was taken out and air-cooled to obtain an aluminum alloy.

[0039] Example 4

[0040] This embodiment adopts a method for preparing A356 cast aluminum alloy, and the specific steps are as follows:

[0041] The aluminum ingot is melted at 730°C to obtain pure aluminum liquid. Silicon source, iron source, copper source, magnesium source, titanium source and zirconium source are added to the pure aluminum liquid and mixed, and then melted at 710°C to obtain a raw material liquid.

[0042] After the smelting is completed, the refining flux prepared in Example 1 is added, the temperature of the raw material liquid melt in the refining tank is maintained at 750°C, the amount of the refining flux added accounts for 0.2% of the mass of the raw material liquid, the refining flux is injected into the melt by blowing, the injection rate of the refining flux is 450g / min, the argon gas introduction rate is maintained at 20L / min, and the refining flux is continued to be introduced for 50min after the refining flux is added. After the end, the refining flux is degassed for 10min, and then left to stand and slag is removed to obtain the refined melt.

[0043] The melt is injected into the die-casting mold, and the filling pressure is controlled to be maintained at 250mbar. After injection, the temperature is raised to 890℃ and kept for 100s, and then cooled to 580℃ and kept for 15s. After the insulation is completed, it is cooled to 370℃ and demolded.

[0044] After demoulding, the die-cast aluminum alloy was placed in a heat treatment furnace, heated from room temperature to 160°C and maintained for 12 minutes, and then continued to heat to 220°C and maintained for 160 minutes. After the temperature was removed, it was air-cooled to obtain an aluminum alloy.

[0045] Comparative Example 1

[0046] The difference between this comparative example and Example 1 is that no fluoride is added.

[0047] Comparative Example 2

[0048] The difference between this comparative example and Example 1 is that after the heat preservation and filling, the mold is cooled and demoulded.

[0049] Comparative Example 3

[0050] The difference between this comparative example and Example 1 is that no treatment is performed after demoulding.

[0051] Test example

[0052] The chemical composition of the aluminum alloy prepared in Example 2-4 is shown in Table 1.

[0053] Table 1

[0054] chemical composition Example 2 Example 3 Example 4 Si 7.31195 7.27356 7.29275 Fe 0.08612 0.08889 0.08751 Cu 4.78261 4.45015 4.61638 Mn 0.00172 0.00175 0.00173 Mg 0.31492 0.30123 0.30808 Cr 0.0006 0.00057 0.00059 Ni 0.00847 0.00706 0.00777 Zn 0.01572 0.01602 0.01587 Ti 0.28097 0.1975 0.23924 Be 0.00004 0.00004 0.00004 Ga 0.01004 0.00984 0.00994 Sr 0.00262 0.00259 0.00260 Zr 0.18894 0.11826 0.1536

[0055] The aluminum alloy prepared in Example 2-4 was used as raw material to measure the mechanical properties of the aluminum alloy. The results are shown in Table 2.

[0056] Table 2

[0057]

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a high-strength and high-thermal-conductivity aluminum alloy by melt purification and die-casting process, characterized in that: The steps include: (1) feeding materials according to the proportion of A356 cast aluminum alloy and subjecting to smelting treatment; smelting the aluminum ingot to obtain pure aluminum liquid; mixing the pure aluminum liquid with a silicon source, an iron source, a copper source, a magnesium source, a titanium source, and a zirconium source, and further smelting to obtain a raw material liquid; (2) After the smelting treatment, argon gas is introduced into the refining tank, and the refining flux is injected into the melt by spraying. After the smelting treatment, the melt is degassed and then left to stand and slag is removed to obtain the refined melt; (3) injecting the melt into the die casting mold, controlling the filling pressure, heating the mold after injection, and keeping the temperature for filling, then cooling and keeping the temperature, cooling after the insulation, and then demolding; (4) After demolding, the die-cast aluminum alloy is placed in a heat treatment furnace, heated from room temperature to the first stage, and then continued to be heated to the second stage. After the end, it is taken out and air-cooled to obtain an aluminum alloy.

2. The method for preparing a high-strength and high-thermal-conductivity aluminum alloy by melt purification and die-casting process according to claim 1, characterized in that: In (1), the chemical composition of the A356 cast aluminum alloy is, by mass percentage, Si 7.2-7.3%, Fe 0.8-0.9%, Cu 4.4-4.8%, Mn≤0.002%, Mg0.30-0.32%, Cr≤0.007%, Ni≤0.009%, Zn≤0.018%, Ti 0.05-0.30%, Be≤0.0001%, Ga≤0.01%, Sr≤0.003%, Zr 0.10-0.25%, and the balance is aluminum.

3. The method for preparing a high-strength and high-thermal-conductivity aluminum alloy by melt purification and die-casting process according to claim 1, characterized in that: (1) The melting temperature is 650-750°C.

4. The method for preparing a high-strength and high-thermal-conductivity aluminum alloy by melt purification and die-casting process according to claim 1, characterized in that: (2), the melt temperature in the refining tank is 700-750°C, the injection rate of the refining flux is 420-480 g / min, the introduction rate of argon is maintained at 20 L / min, and the argon is continued to be introduced for 50 minutes after the refining flux is added.

5. The method for preparing high-strength and high-thermal-conductivity aluminum alloy by melt purification and die-casting process according to claim 1, characterized in that: (3), the melt is injected into the die casting mold, the filling pressure is controlled to be maintained at 200-300 mbar, the temperature is raised to 850-950°C after injection, and the temperature is kept for 50-100 seconds, and then the temperature is cooled to 500-600°C and kept for 10-30 seconds. After the insulation is completed, the melt is cooled to 350-400°C and demolded.

6. The method for preparing high-strength and high-thermal-conductivity aluminum alloy by melt purification and die-casting process according to claim 1, characterized in that: (4), the temperature is raised from room temperature to 150-170°C and maintained for 90-120 min, and then further raised to 200-230°C and maintained for 150-180 min.

7. The method for preparing a high-strength and high-thermal-conductivity aluminum alloy by melt purification and die-casting process according to any one of claims 1 to 6, characterized in that: (3), the raw materials of the refining flux include, by weight, 40-60 parts of aluminum fluoride, 1-5 parts of calcium fluoride, 1-3 parts of cerium fluoride, 1-3 parts of lanthanum fluoride, 10-20 parts of sodium chloride, 10-20 parts of potassium chloride, 5-10 parts of sodium carbonate, and 5-10 parts of sodium borate.

8. The method for preparing a high-strength and high-thermal-conductivity aluminum alloy by melt purification and die-casting process according to claim 7, characterized in that: The raw material components of the refining flux are preferably 40-50 parts of aluminum fluoride, 1-3 parts of calcium fluoride, 1-3 parts of cerium fluoride, 1-3 parts of lanthanum fluoride, 10-15 parts of sodium chloride, 10-15 parts of potassium chloride, 5-8 parts of sodium carbonate, and 5-8 parts of sodium borate.

9. The method for preparing a high-strength and high-thermal-conductivity aluminum alloy by melt purification and die-casting process according to claim 7, characterized in that: The preparation method of the refined flux is to weigh the aforementioned raw material components in proportion, dry them at the same time, blend the raw material components, and then bake them at 230-260° C. to obtain the refined flux.

10. An aluminum alloy obtained by the preparation method according to any one of claims 1 to 9.

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