Preparation method of high-conductivity cast aluminum alloy casting for high-voltage switch

Abstract

The invention relates to the technical field of power transmission and transformation engineering, in particular to a preparation method of a high-conductivity cast aluminum alloy casting for a high-voltage switch. The preparation method of the high-conductivity cast aluminum alloy casting for the high-voltage switch comprises the following steps of material selection, smelting, adding of a refining agent 1 and a modifier, adding of a refining agent 2, adding of a refining agent 3, pouring and surface processing. The high-conductivity cast aluminum alloy casting for the high-voltage switch has high conductivity and strength, a conductor part for the high-voltage switch can be formed through a casting process, and the preparation method is simple in process and easy to control.

Description

Technical Field

[0001] The invention relates to the technical field of power transmission and transformation engineering, and in particular to a method for preparing a high-conductivity cast aluminum alloy casting for a high-voltage switch. Background Art

[0002] In high-voltage switch products, a large number of aluminum alloy conductive or electrical connection parts with complex structures are often formed by low-cost and low-conductivity ZL101A aluminum alloy low-pressure casting. This casting alloy has good casting performance, low cost, small elastic coefficient, isotropic structure, medium-strength mechanical properties, and is suitable for mass production. However, the conductivity of ZL101A aluminum alloy has not been significantly improved, and it is difficult to meet the development needs of high-voltage switch capacity increase, miniaturization, and high conductivity. The existing conductive aluminum alloy castings used for such switches are ZL101A materials in GB1173, and the conductivity in the T6 state is not less than 36% IACS. ABB and Siemens abroad can achieve 45% IACS. They determine the composition of the alloy based on the comprehensive performance requirements and the role of each element in the alloy, and adjust the heat treatment of the cast aluminum alloy ZL101A-T6 to T7 (called solution treatment + stabilization treatment in the national standard). As a result, the conductivity of the casting ZL101A alloy conductor can reach 45% IACS.

[0003] Existing high-voltage switch conductor castings are basically made of ZL101 aluminum alloy, which needs to be heat treated with T6 or T7 to meet the use requirements. As for the internal parts of high-voltage switches, their structures are generally complex, thin-walled, and hollow castings. During heat treatment, they are prone to deformation and bubbles on the surface. In addition, the ZL101 aluminum alloy castings that have undergone T6 heat treatment have high mechanical properties but low electrical conductivity. Although T7 heat treatment improves electrical conductivity, the mechanical properties are significantly reduced compared to T6.

[0004] Patent technical document CN202210414222.2 discloses a high-strength and high-conductivity Al-Zr-Si aluminum alloy. Although the Al-Zr-Si aluminum alloy has good conductivity, its mechanical properties still need to be improved.

[0005] In response to this situation, a new type of high-conductivity aluminum alloy material was developed, the properties of the high-conductivity aluminum alloy itself and the role of each alloy element were fully considered, and the composition of the aluminum alloy was overall controlled, so that the aluminum alloy has both excellent electrical conductivity and mechanical properties after heat treatment. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a high conductivity cast aluminum alloy casting for high voltage switch to solve the problem that traditional high conductivity cast aluminum alloy casting for high voltage switch cannot have excellent mechanical properties and conductive properties at the same time.

[0007] Based on the above purpose, the present invention provides a method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch, comprising the following steps:

[0008] S11: industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, Al-Mn master alloy are taken as raw materials, wherein the mass percentage of each element is as follows: Si: 4wt%-6wt%, Mg: 0.4wt%-0.6wt%, B: 0.06wt%-0.1wt%, Sr: 0.02wt%-0.04wt%, Ti: 0.05wt%-0.1wt%, the sum of other inevitable impurities is not more than 0.1wt%, and the rest is aluminum;

[0009] S12: In a nitrogen atmosphere, industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, and Al-Mn master alloy are melted at 700-750° C. to obtain a preliminary aluminum alloy liquid;

[0010] S13: adding refining agent 1 and modifier to the preliminary aluminum alloy liquid at 720-730° C., reacting for 20-30 minutes, adding refining agent 2, reacting for 10-20 minutes, then adding refining agent 3, reacting for 10-20 minutes, and keeping the temperature to obtain aluminum alloy liquid to be cast;

[0011] S14: pouring the aluminum alloy liquid to be cast into a mold at 720-740° C., cooling to room temperature, and then performing heat treatment to obtain a crude product;

[0012] S15: machining and surface polishing the rough product to obtain a high conductivity cast aluminum alloy casting for a high voltage switch;

[0013] Further, the refining agent 1 comprises the following components in weight percentage: 45% zinc chloride, 20% cryolite powder, 10% CaF2, 5% graphene, 10% industrial salt, and 10% grain refiner;

[0014] Further, the refining agent 2 includes the following components in weight percentage: 48% zinc chloride, 20% cryolite powder, 10% CaF2, 3% graphene, 10% industrial salt, and 10% grain refiner;

[0015] Furthermore, the refining agent 3 includes the following components in weight percentage: 49.5% zinc chloride, 20% cryolite powder, 10% CaF2, 0.5% graphene, 10% industrial salt, and 10% grain refiner.

[0016] Furthermore, the particle size of the graphene is 0.5-5 μm.

[0017] Furthermore, the modifier in step S13 is Al-Sr10 master alloy.

[0018] Furthermore, the insulation time in step S13 is 15-35 minutes.

[0019] Furthermore, in step S14, the mold is preheated to 275-285° C. before pouring, and a release agent is sprayed.

[0020] Furthermore, the heat treatment in step S14 is T6 heat treatment or T7 heat treatment.

[0021] Furthermore, the addition amount of the refining agents 1, 2 and 3 is 0.2%-0.4% of the weight of the raw material.

[0022] Furthermore, refining agents 1, 2 and 3 are all obtained by mixing.

[0023] Furthermore, the grain refiner is a mixture of aluminum-titanium slag and aluminum alloy masterbatch powder in a mass ratio of 1:2.

[0024] Furthermore, the elements in the aluminum alloy masterbatch powder are calculated according to the following mass percentages: Si: 4wt%, Mg: 0.5wt%, B: 0.08wt%, Sr: 0.03wt%, Ti: 0.7wt%, the total of other inevitable impurities is not more than 0.1wt%, and the rest is aluminum.

[0025] Beneficial effects of the present invention:

[0026] The low-pressure cast aluminum alloy obtained by the present invention has high electrical conductivity and strength. After T6 heat treatment, the electrical conductivity can reach more than 42% IACS, the tensile strength is ≥230MPa, the yield strength is ≥120MPa, and the elongation is ≥3%.

[0027] The present invention further improves the mechanical properties and electrical conductivity of the aluminum alloy and reduces the usage of graphene and the refining agent by adding the refining agent containing graphene in batches and gradually reducing the addition amount of graphene in the refining agent.

[0028] The preparation method of the present invention can obtain a high-conductivity cast aluminum alloy, and the obtained aluminum alloy has process characteristics such as good thermal cracking resistance and good fluidity. It can be formed into conductor parts for high-voltage switches through a casting process, and the forming effect is no different from that of traditional ZL101A (T7 heat treatment). Compared with ZL101A, it has higher conductivity; in addition, the preparation method is simple and easy to control. The present invention also reduces production cycle and cost through heat treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art description:

[0030] Figure 1 This is a metallographic image of the cast aluminum alloy conductor obtained in Example 2 of the present invention. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0032] The particle size of the graphene used in the examples and comparative examples of the present invention is 3 μm;

[0033] The refining agent 1 used in the embodiment of the present invention is directly mixed with 45% zinc chloride, 20% cryolite powder, 10% CaF2, 5% graphene, 10% industrial salt, and 10% grain refiner according to weight percentage, and the added amount is 0.3% of the weight of the raw materials;

[0034] Refining agent 2 is directly mixed with 48% zinc chloride, 20% cryolite powder, 10% CaF2, 3% graphene, 10% industrial salt and 10% grain refiner according to weight percentage, and the added amount is 0.3% of the weight of the raw materials;

[0035] Refining agent 3 is directly mixed with 49.5% zinc chloride, 20% cryolite powder, 10% CaF2, 0.5% graphene, 10% industrial salt and 10% grain refiner according to weight percentage, and the added amount is 0.3% of the weight of the raw materials.

[0036] Embodiment 1: A method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch, the specific preparation steps are as follows:

[0037] (1) According to the element ratio of Si: 4wt%, Mg: 0.4wt%, B: 0.06wt%, Sr: 0.02wt%, Ti: 0.05wt%, and the rest is aluminum, industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, Al-Mn master alloy are taken for use;

[0038] (2) In a nitrogen atmosphere, industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, and Al-Mn master alloy are smelted at 700° C. to obtain a preliminary aluminum alloy liquid;

[0039] (3) at 720° C., refining agent 1 and Al-Sr10 master alloy were added to the preliminary aluminum alloy liquid, reacted for 20 minutes, and then refining agent 2 was added. After reacting for 10 minutes, refining agent 3 was added. After reacting for 10 minutes, the mixture was kept warm for 15 minutes to obtain the aluminum alloy liquid to be cast;

[0040] (4) preheating the mold to 275° C. and spraying a mold release agent, then pouring the aluminum alloy liquid to be cast into the mold at 720° C., cooling to room temperature, and performing T6 heat treatment to obtain a crude product;

[0041] (5) The rough product is machined and surface polished to obtain a high conductivity cast aluminum alloy casting for a high voltage switch.

[0042] Embodiment 2: A method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch, the specific preparation steps are as follows:

[0043] (1) According to the element ratio of Si: 5wt%, Mg: 0.5wt%, B: 0.08wt%, Sr: 0.03wt%, Ti: 0.08wt%, and the rest is aluminum, industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, Al-Mn master alloy are taken for use;

[0044] (2) In a nitrogen atmosphere, industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, and Al-Mn master alloy are melted at 730° C. to obtain a preliminary aluminum alloy liquid;

[0045] (3) at 725° C., refining agent 1 and Al-Sr10 master alloy were added to the preliminary aluminum alloy liquid, reacted for 25 minutes, and then refining agent 2 was added. After reacting for 15 minutes, refining agent 3 was added. After reacting for 15 minutes, the temperature was kept at 400 ° C. for 25 minutes to obtain the aluminum alloy liquid to be cast;

[0046] (4) preheating the mold to 280° C. and spraying a mold release agent, then pouring the aluminum alloy liquid to be cast into the mold at 730° C., cooling to room temperature, and performing T6 heat treatment to obtain a crude product;

[0047] (5) The rough product is machined and surface polished to obtain a high conductivity cast aluminum alloy casting for a high voltage switch.

[0048] Embodiment 3: A method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch, the specific preparation steps are as follows:

[0049] (1) According to the element ratio of Si: 6wt%, Mg: 0.6wt%, B: 0.1wt%, Sr: 0.04wt%, Ti: 0.1wt%, and the rest is aluminum, industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, Al-Mn master alloy are taken for use;

[0050] (2) In a nitrogen atmosphere, industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, and Al-Mn master alloy are melted at 750° C. to obtain a preliminary aluminum alloy liquid;

[0051] (3) at 730° C., refining agent 1 and Al-Sr10 master alloy were added to the preliminary aluminum alloy liquid, reacted for 30 minutes, and then refining agent 2 was added. After reacting for 20 minutes, refining agent 3 was added. After reacting for 20 minutes, the mixture was kept warm for 5 minutes to obtain the aluminum alloy liquid to be cast;

[0052] (4) preheating the mold to 285° C. and spraying a mold release agent, then pouring the aluminum alloy liquid to be cast into the mold at 740° C., cooling to room temperature, and performing T6 heat treatment to obtain a crude product;

[0053] (5) The rough product is machined and surface polished to obtain a high conductivity cast aluminum alloy casting for a high voltage switch.

[0054] Embodiment 4: A method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch, the specific preparation steps are as follows:

[0055] (1) According to the element ratio of Si: 4wt%, Mg: 0.4wt%, B: 0.06wt%, Sr: 0.02wt%, Ti: 0.05wt%, and the rest is aluminum, industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, Al-Mn master alloy are taken for use;

[0056] (2) In a nitrogen atmosphere, industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, and Al-Mn master alloy are smelted at 700° C. to obtain a preliminary aluminum alloy liquid;

[0057] (3) at 720° C., refining agent 1 and Al-Sr10 master alloy were added to the preliminary aluminum alloy liquid, reacted for 20 minutes, and then refining agent 2 was added. After reacting for 10 minutes, refining agent 3 was added. After reacting for 10 minutes, the mixture was kept warm for 15 minutes to obtain the aluminum alloy liquid to be cast;

[0058] (4) preheating the mold to 275° C. and spraying a mold release agent, then pouring the aluminum alloy liquid to be cast into the mold at 720° C., cooling to room temperature, and performing T7 heat treatment to obtain a crude product;

[0059] (5) The rough product is machined and surface polished to obtain a high conductivity cast aluminum alloy casting for a high voltage switch.

[0060] Embodiment 5: A method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch, the specific preparation steps are as follows:

[0061] (1) According to the element ratio of Si: 5wt%, Mg: 0.5wt%, B: 0.08wt%, Sr: 0.03wt%, Ti: 0.08wt%, and the rest is aluminum, industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, Al-Mn master alloy are taken for use;

[0062] (2) In a nitrogen atmosphere, industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, and Al-Mn master alloy are melted at 730° C. to obtain a preliminary aluminum alloy liquid;

[0063] (3) at 725° C., refining agent 1 and Al-Sr10 master alloy were added to the preliminary aluminum alloy liquid, reacted for 25 minutes, and then refining agent 2 was added. After reacting for 15 minutes, refining agent 3 was added. After reacting for 15 minutes, the temperature was kept at 400 ° C. for 25 minutes to obtain the aluminum alloy liquid to be cast;

[0064] (4) preheating the mold to 280° C. and spraying a mold release agent, then pouring the aluminum alloy liquid to be cast into the mold at 730° C., cooling to room temperature, and performing T7 heat treatment to obtain a crude product;

[0065] (5) The rough product is machined and surface polished to obtain a high conductivity cast aluminum alloy casting for a high voltage switch.

[0066] Embodiment 6: A method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch, wherein the specific preparation steps are as follows:

[0067] (1) According to the element ratio of Si: 6wt%, Mg: 0.6wt%, B: 0.1wt%, Sr: 0.04wt%, Ti: 0.1wt%, and the rest is aluminum, industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, Al-Mn master alloy are taken for use;

[0068] (2) In a nitrogen atmosphere, industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, and Al-Mn master alloy are melted at 750° C. to obtain a preliminary aluminum alloy liquid;

[0069] (3) at 730° C., refining agent 1 and Al-Sr10 master alloy were added to the preliminary aluminum alloy liquid, reacted for 30 minutes, and then refining agent 2 was added. After reacting for 20 minutes, refining agent 3 was added. After reacting for 20 minutes, the mixture was kept warm for 5 minutes to obtain the aluminum alloy liquid to be cast;

[0070] (4) preheating the mold to 285° C. and spraying a mold release agent, then pouring the aluminum alloy liquid to be cast into the mold at 740° C., cooling to room temperature, and performing T7 heat treatment to obtain a crude product;

[0071] (5) The rough product is machined and surface polished to obtain a high conductivity cast aluminum alloy casting for a high voltage switch.

[0072] Comparative Example 1: A method for preparing a cast aluminum alloy casting, the specific preparation steps are as follows:

[0073] The difference from Example 2 is that the weight percentages of the raw material components of refining agents 1, 2, and 3 are all 45% zinc chloride, 20% cryolite powder, 10% CaF2, 5% graphene, 10% industrial salt, and 10% grain refiner, and the added amount is 0.3% of the raw materials. The remaining steps are the same as Example 2.

[0074] Comparative Example 2: A method for preparing a cast aluminum alloy casting, the specific preparation steps are as follows:

[0075] The difference from Example 2 is that the weight percentage of the refining agent raw material components is 40% zinc chloride, 20% cryolite powder, 10% CaF2, 10% graphene, 10% industrial salt, and 10% grain refiner, and the added amount is 0.3% of the raw materials. The remaining steps are the same as Example 2.

[0076] Performance Testing

[0077] Conductivity: The test was performed using a First FD-101 eddy current conductivity meter. Ten points were randomly selected from the samples obtained in the embodiments and comparative examples to measure the conductivity. The highest and lowest values ​​were removed and the average value was taken as the average conductivity of the sample. The test results are shown in Table 1.

[0078] Mechanical properties: The samples obtained in the embodiments and comparative examples were tested according to GB-T 1173-2013 Casting Aluminum Alloys - National Standard. The test results are shown in Table 1.

[0079] Hardness: The samples obtained in the embodiments and comparative examples were tested according to ASTM E10. The test results are shown in Table 1.

[0080] Table 1 Performance test results

[0081]

[0082] Data analysis: It can be seen from Examples 1-6 in Table 1 that the castings finally obtained by the method for preparing high conductivity cast aluminum alloy castings for high-voltage switches of the present invention have excellent mechanical properties and hardness after T6 heat treatment, and their conductivity can reach 43.3% IACS; after T7 heat treatment, while maintaining excellent conductivity, the mechanical properties and hardness also maintain a relatively excellent level.

[0083] Table 2 Performance test results of embodiments and comparative examples

[0084]

[0085]

[0086] It can be seen from Example 2 and Comparative Examples 1 and 2 in Table 2 that when the refining agent containing graphene is added in batches and the amount of graphene added in the refining agent is gradually reduced, on the one hand, it promotes a more uniform distribution in the molten aluminum alloy, reduces the agglomeration of graphene, helps to control the growth of grains, and promotes the formation of fine grains; on the other hand, as a part of the refining agent, its addition in batches can continuously exert the refining effect, reduce inclusions, and improve the purity of the alloy; and it can form a metal-based composite material, which further improves the mechanical properties and electrical conductivity of the aluminum alloy, so that the aluminum alloy ingot has excellent performance after T6 heat treatment.

[0087] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0088] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch, characterized in that: The following steps are involved: S11: industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, Al-Mn master alloy are taken as raw materials, wherein the mass percentage of each element is as follows: Si: 4wt%-6wt%, Mg: 0.4wt%-0.6wt%, B: 0.06wt%-0.1wt%, Sr: 0.02wt%-0.04wt%, Ti: 0.05wt%-0.1wt%, the sum of other inevitable impurities is not more than 0.1wt%, and the rest is aluminum; S12: In a nitrogen atmosphere, industrial pure aluminum, Al-Si50 master alloy, pure magnesium, Al-Ti master alloy, Al-B master alloy, and Al-Mn master alloy are melted at 700-750° C. to obtain a preliminary aluminum alloy liquid; S13: adding refining agent 1 and modifier to the preliminary aluminum alloy liquid at 720-730° C., reacting for 20-30 minutes, adding refining agent 2, reacting for 10-20 minutes, then adding refining agent 3, reacting for 10-20 minutes, and keeping the temperature to obtain aluminum alloy liquid to be cast; S14: pouring the aluminum alloy liquid to be cast into a mold at 720-740° C., cooling to room temperature, and then performing heat treatment to obtain a crude product; S15: machining and surface polishing the rough product to obtain a high conductivity cast aluminum alloy casting for a high voltage switch; The refining agent 1 comprises the following components in weight percentage: 45% zinc chloride, 20% cryolite powder, 10% CaF2, 5% graphene, 10% industrial salt, and 10% grain refiner; Refining agent 2 includes the following components in weight percentage: 48% zinc chloride, 20% cryolite powder, 10% CaF2, 3% graphene, 10% industrial salt, and 10% grain refiner; Refining agent 3 includes the following components in weight percentage: 49.5% zinc chloride, 20% cryolite powder, 10% CaF2, 0.5% graphene, 10% industrial salt, and 10% grain refiner.

2. The method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch according to claim 1, characterized in that: The particle size of the graphene is 0.5-5 μm.

3. The method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch according to claim 1, characterized in that: The modifier in step S13 is Al-Sr10 master alloy.

4. The method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch according to claim 1, characterized in that: The insulation time in step S13 is 15-35 minutes.

5. The method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch according to claim 1, characterized in that: In step S14, the mold is preheated to 275-285° C. before pouring and sprayed with a release agent.

6. The method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch according to claim 1, characterized in that: The heat treatment in step S14 is T6 heat treatment or T7 heat treatment.

7. The method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch according to claim 1, characterized in that: The addition amount of the refining agents 1, 2 and 3 is 0.2%-0.4% of the weight of the raw material.

8. The method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch according to claim 1, characterized in that: The grain refiner is a mixture of aluminum-titanium slag and aluminum alloy masterbatch powder in a mass ratio of 1:

2.

9. The method for preparing a high conductivity cast aluminum alloy casting for a high voltage switch according to claim 1, characterized in that: The elements in the aluminum alloy masterbatch powder are calculated by mass percentage as follows: Si: 4wt%, Mg: 0.5wt%, B: 0.08wt%, Sr: 0.03wt%, Ti: 0.7wt%, the total of other inevitable impurities is not more than 0.1wt%, and the rest is aluminum.

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