A high-conductivity high-strength aluminum alloy material, a heat treatment method, a preparation method and an application thereof

Abstract

The application belongs to the technical field of aluminum alloy, and particularly discloses a high-conductivity and high-strength aluminum alloy material, a heat treatment method, a preparation method and application thereof. The heat treatment method comprises solid solution quenching treatment, high-temperature short-time aging treatment, pre-aging treatment and aging treatment. The preparation method comprises smelting, casting and heat treatment, and the heat treatment comprises the heat treatment method. The high-conductivity and high-strength aluminum alloy material is prepared by the preparation method. The high-conductivity and high-strength aluminum alloy material is applied to the preparation of wire and cable conductors. The aluminum alloy material with high conductivity and tensile strength can be prepared by process improvement.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aluminum alloy, and particularly relates to a high-conductivity and high-strength aluminum alloy material and a heat treatment method, a preparation method and application thereof. BACKGROUND

[0002] Although the current mainstream steel-cored aluminum stranded wire can meet the basic requirements, its line loss rate (about 6% to 8%) and mechanical performance are insufficient in the scene of extra-high voltage and super-long distance power transmission. A new generation of aluminum alloy conductor material needs to break through key technical indicators such as conductivity (greater than or equal to 62% IACS), tensile strength (greater than or equal to 110 MPa) and elongation (greater than or equal to 10%), so as to not only realize a line loss reduction of 15% to 20% compared with traditional materials, but also meet the mechanical requirements of large span (such as a span of the Yangtze River and the Yellow River exceeding 2000 meters) and extreme weather (wind pressure reaching 1.5 kN / m2 in coastal typhoon areas) in complex terrains.

[0003] At present, the industry has formed a series of products such as medium-strength (58% IACS / 160 MPa), high-strength (60% IACS / 230 MPa) and heat-resistant (strength retention rate greater than 90% at 150 DEG C), but the conductivity is low, which brings a lot of energy loss in the use process, and there is an urgent need for aluminum alloy conductors with high conductivity and high strength in the industry.

[0004] Chinese patent CN120425282A discloses a heat treatment method of a high-strength and high-conductivity magnesium-aluminum alloy, which includes the steps of surface cleaning treatment, preheating treatment, rapid heating to solid solution temperature, solid solution heat preservation treatment, quenching cooling, cold treatment after quenching, double-stage aging treatment and slow cooling treatment after aging. The first-stage aging temperature of the double-stage aging treatment is 150 DEG C to 180 DEG C, and the heat preservation time is 3 to 5 hours. The second-stage aging temperature is 200 DEG C to 230 DEG C, and the heat preservation time is 8 to 12 hours. The patent has the following defects: 1. The solid solution time is too long, and the industrial cost is high; 2. The double-stage aging operation is difficult, and the second-stage aging time is long, and the total aging time is 11 to 17 hours; 3. The chemical cleaning agent may cause potential industrial pollution. SUMMARY

[0005] The purpose of the present application is to provide a heat treatment method of a high-conductivity and high-strength aluminum alloy material, which solves the technical problem of lacking a process for preparing an aluminum alloy material with high conductivity and tensile strength in the prior art through process improvement. The aging process of the present application is simple, the energy consumption is low, and the final product is a conductor, which meets the actual production and industrial needs.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A heat treatment method of a high-conductivity and high-strength aluminum alloy material, comprising:

[0008] (a) solution treatment;

[0009] (b) high-temperature short-time aging treatment: heat preservation at 450-600℃ for 5-10 min;

[0010] (c) pre-aging treatment: heat preservation at 200-400℃ for 6-12 h;

[0011] (d) aging treatment.

[0012] Preferably, in step (a), the solution treatment comprises heat preservation at 540-560℃ for 2-6 h.

[0013] Preferably, in step (c), the pre-aging treatment is followed by cold working treatment.

[0014] Preferably, the cold working treatment comprises cold rolling and cold drawing, and the finished product is a wire with a diameter of 2-3 mm and a total deformation of 93.75%-97.22%.

[0015] Preferably, in step (d), the aging treatment comprises heat preservation at 240-280℃ for 8-12 h.

[0016] A second object of the present application is to provide a preparation method of high-conductivity high-strength aluminum alloy material, comprising the following steps:

[0017] S1: melting;

[0018] S2: casting;

[0019] S3: heat treatment: using the heat treatment method described above.

[0020] Preferably, in step S1, the melting comprises: after heating the aluminum ingot to complete melting, sequentially adding Al-Mg, Al-Si, Al-B intermediate alloy and rare earth RE for melting to obtain an aluminum alloy liquid.

[0021] Preferably, in step S1, the melting temperature is 720-750℃.

[0022] Preferably, in step S1, after adding each intermediate alloy, stirring for 5-10 min and standing for 5-10 min.

[0023] Preferably, it further comprises refining, and the refining comprises: adding a refining agent to the aluminum alloy liquid obtained by melting, stirring for 5-10 min, and then discharging slag to obtain a high-purity aluminum alloy liquid.

[0024] Preferably, the refining agent is hexachloroethane.

[0025] Preferably, the addition amount of the refining agent is 0.5%-1% of the weight of the melt.

[0026] Preferably, the obtained high-purity aluminum alloy liquid continues to be kept at 720-750 DEG C for 20-60 min.

[0027] Preferably, in step S2, the casting comprises: pouring the high-purity aluminum alloy liquid into a mold preheated to 200-300 DEG C, and then naturally cooling to room temperature to form the aluminum alloy electrical round rod.

[0028] A third object of the present application is to provide a high-conductivity high-strength aluminum alloy material, which comprises, in percentage by weight: Mg 0.6-0.8wt%, Si 0.4-0.6wt%, B 0.1-0.2wt%, rare earth RE 0.1-0.2wt%, the sum of Cr, Mn, V and Ti being 0-0.0005wt%, and the balance being Al and other inevitable impurities; wherein the rare earth RE comprises at least one of La, Ce, Y, Sm and Er.

[0029] A fourth object of the present application is to provide the use of the high-conductivity high-strength aluminum alloy material in the preparation of wire and cable conductors.

[0030] The synergistic promotion effect of the cluster and the primary phase on the electrical and mechanical properties of the aluminum alloy wire is realized through the following double-mechanism linkage effect.

[0031] Firstly, the secondary phase refinement and interface strengthening effect. During the high-temperature short-time aging + pre-aging process, Mg and Si atoms in the supersaturated solid solution gather by diffusion and preferentially precipitate nanoscale β" phase (Mg5Si6) and a small amount of Mg2Si primary phase. The lattice distortion is caused between these secondary phases and the α-Al matrix due to the lattice mismatch, forming a significant shear strain gradient; the precipitation strengthening effect induced by the high-temperature short-time aging + pre-aging further drives the relative shear strain between the secondary phase and the matrix to increase, promoting the secondary phase to refine through mechanisms such as dislocation movement or grain boundary migration, and increasing the density of phase boundaries. The refined secondary phase not only improves the uniformity of the distribution of precipitates, but also strengthens the matrix through the hindering effect of the phase boundary on dislocations, forming a composite strengthening mechanism of "fine-grain strengthening + phase boundary strengthening".

[0032] Secondly, the matrix structure regulation and work hardening enhancement effect. The high-temperature short-time aging + pre-aging treatment realizes the significant refinement of the matrix grain size by inhibiting the initial recrystallization and promoting the competitive growth of grains, while retaining a high-density dislocation structure. The refined matrix grains limit the space for dislocation climbing, while the high-density dislocations are difficult to eliminate through dynamic recovery mechanism in subsequent rolling processing, but rather provide more dislocation slip channels due to the refinement of the matrix grains, which are more easily activated and involved in dislocation multiplication and interaction, significantly enhancing the work hardening effect.

[0033] Under the synergistic effect of high-temperature short-time aging and pre-aging, the alloy strength is significantly broken through while the high conductivity is maintained, by hindering dislocation movement through refined secondary phase (precipitation strengthening) and by improving deformation resistance through high-density dislocation structure (work hardening).

[0034] Compared with the prior art, the present application has the following beneficial effects:

[0035] In the prior art, after solid solution water quenching, high-temperature short-time aging is not performed, and direct pre-aging is performed, and the clusters and GP zones are relatively less during the pre-aging process, the precipitation effect is weak, the stable phase β (Mg2Si) is less, the interaction with dislocations during the subsequent processing process is reduced, the work hardening effect is weakened, and the conductivity is also low.

[0036] In the present application, after solid solution quenching treatment, high-temperature short-time aging is adopted, most of the excess vacancies after quenching are positioned by a large number of clusters formed in the high-temperature short-time aging process within a few seconds, the point defects are weakened, and the clusters are helped to rapidly nucleate. The β" phase can effectively hinder the dislocation movement while the scattering degree of free electrons is low, and it is the key to the comprehensive improvement of material performance; after high-temperature short-time aging treatment, fine and dense nanometer clusters rich in Mg elements can be formed in the subsequent pre-aging stage, and these clusters are more likely to be converted into β" phase due to the similarity of chemical composition, and after subsequent pre-aging, mechanical processing and aging treatment, fine and dispersed β" phase is formed in the matrix, so as to comprehensively improve the material performance, and an aluminum alloy material with high conductivity and tensile strength is prepared. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The flowchart of the preparation method of the aluminum alloy conductor wire with high conductivity and tensile strength provided by the present application is shown.

[0038] Figure 2 The processing process diagram of the aluminum alloy conductor wire of the present application is shown.

[0039] Figure 3 The scanning electron microscope graph of Example 1-3 of the present application is shown.

[0040] Figure 4 The scanning electron microscope graph of Comparative Example 1 of the present application is shown. DETAILED DESCRIPTION

[0041] The present application will be further described in detail below in combination with specific examples. It should be understood that the following examples are used to illustrate the present application, but not to limit the scope of the present application.

[0042] In the following examples / comparative examples of the present application, the raw materials used are commercially available.

[0043] Example 1

[0044] A high-conductivity, high-strength aluminum alloy material, by weight percentage, comprises: Mg 0.6–0.8 wt%, Si 0.4–0.6 wt%, B 0.1–0.2 wt%, rare earth RE 0.1–0.2 wt%, Cr, Mn, V and Ti totaling 0–0.0005 wt%, with the balance being Al and other unavoidable impurities; wherein the rare earth RE contains at least one of La, Ce, Y, Sm and Er.

[0045] A heat treatment method for a high-conductivity, high-strength aluminum alloy material includes the following steps:

[0046] (a) Solution treatment: Keep at 540-560℃ for 2-6 hours;

[0047] (b) High-temperature short-time aging treatment: hold at 450-600℃ for 5-10 minutes;

[0048] (c) Pre-aging treatment: keep at 200-400℃ for 6-12 hours;

[0049] (d) Cold working: cold rolling and cold drawing, the finished product is a wire with a diameter of 2-3 mm, and the total deformation is 93.75%-97.22%;

[0050] (e) Aging treatment: Keep warm at 240-280℃ for 8-12 hours.

[0051] A method for preparing a high-conductivity, high-strength aluminum alloy material includes the following steps:

[0052] S1: Ingredients: Prepare the ingredients according to the above formula;

[0053] S2: Smelting: The aluminum ingot is heated to complete melting, and Al-Mg, Al-Si, Al-B master alloys and rare earth RE are added sequentially for smelting. Each time a master alloy is added, the mixture is stirred for 5-10 minutes and then allowed to stand for 5-10 minutes to obtain an aluminum alloy liquid. The smelting temperature is 720-750℃.

[0054] S3: Refining: Add hexachloroethane refining agent to the molten aluminum alloy obtained by smelting, stir for 5-10 minutes, and then remove slag to obtain high-purity aluminum alloy liquid. The high-purity aluminum alloy liquid is then kept at 720-750℃ for 20-60 minutes. The amount of refining agent added is 0.5%-1% of the weight of the molten alloy.

[0055] S4: Casting: High-purity aluminum alloy liquid is poured into a mold that has been preheated to 200-300°C, and then allowed to cool naturally to room temperature to form an aluminum alloy electrical rod.

[0056] S5: Heat treatment: The aluminum alloy electrical round rod is heat treated using the heat treatment method described above.

[0057] Application of high-conductivity and high-strength aluminum alloy material in preparation of wire and cable conductor.

[0058] Referring to the heat treatment method, preparation method and raw material formula provided above, different treatment groups are set with high-temperature short-time aging and pre-aging as a variable, as shown in Table 1, and the influence of the variable on the performance of the prepared high-conductivity and high-strength aluminum alloy material is investigated.

[0059] Table 1

[0060]

[0061] Example 2

[0062] Referring to the raw material formula, heat treatment method and preparation method provided in Example 1 and the settings of treatments 1-3, different treatment groups are set with the addition of B and La as a variable, as shown in Table 2, and the influence of the variable on the performance of the prepared high-conductivity and high-strength aluminum alloy material is investigated.

[0063] Table 2

[0064]

[0065] Note: When B and / or La are missing in the raw materials, the preparation process is adjusted accordingly.

[0066] Comparative Example 1

[0067] The "solid solution water quenching-machining-aging" heat treatment process is as follows: 560℃ for 2h, immediately water quenching, machining Φ2mm conductor, deformation of 97.22%, then isothermal aging at 260℃ for 12h.

[0068] Comparative Example 2

[0069] Commercially available industrial pure aluminum conductor, purchased from Chenghang Cable Co., Ltd., model BLV.

[0070] Comparative Example 3

[0071] Commercially available 8-series aluminum alloy conductor, purchased from Jiangsu Shangshang Cable Group Co., Ltd., model ZC-TC90.

[0072] Comparative Example 4

[0073] Commercially available 6-series aluminum alloy conductor, purchased from Hebei Hualun Cable Co., Ltd., model LHA2.

[0074] Performance test experiment

[0075] 1. The test items and detection standards are shown in Table 3:

[0076] Table 3

[0077]

[0078] 2. The test results are shown in Table 4.

[0079] Table 4

[0080]

[0081] In Example 1, the high-temperature short-time aging treatment and pre-aging treatment temperature and time of processes 1-1 to 1-5 are within the range defined in the application, and the indicators of the materials prepared meet the standard requirements, even higher than the standard requirements.

[0082] With the increase of high-temperature short-time aging temperature, the size of the second phase increases, and the strengthening effect decreases. At 500°C, it has good strength and conductivity, and at the same time, it has acceptable elongation. With the increase of pre-aging temperature, the strength of the wire shows a typical peak aging alloy, that is, it first increases and then decreases. The reason is that during the pre-aging process, the temperature increases, the degree of grain recrystallization is large, the grains and the second phase are coarsened, and the precipitation strengthening mechanism changes from dislocation around the second phase particles to dislocation cutting through the second phase particles, resulting in weakening of the strengthening effect. EC is higher than 62 IACS% except process 1-1, which belongs to the high conductivity category. After the pre-aging temperature is higher than 250°C, the conductivity slowly increases with the increase of temperature, indicating that there is an upper limit to the degree of lattice distortion caused by the precipitation of solid solution elements to reduce the scattering of electrons to improve the conductivity.

[0083] Process 1-6 reduces the high-temperature short-time aging temperature based on process 1-1. The temperature of high-temperature short-time aging is too low, which leads to a decrease in the number of solute clusters and GP zones, and a decrease in the strengthening phase during the pre-aging process, ultimately resulting in a decrease in mechanical properties;

[0084] Process 1-7 increases the high-temperature short-time aging temperature based on process 1-5. The temperature of high-temperature short-time aging is too high, which leads to coarsening of precipitates and weakening of the strengthening effect;

[0085] Process 1-8 shortens the high-temperature short-time aging time based on process 1-5. The high-temperature short-time aging time is insufficient, which leads to insufficient diffusion and precipitation of solute atoms, a decrease in the number of GP zones and clusters, and ultimately a decrease in the strengthening effect;

[0086] Process 1-9 extends the high-temperature short-time aging time based on process 1-1. The high-temperature short-time aging time is too long, which will have the same effect as the temperature being too high, that is, a decrease in mechanical properties, which is also related to the coarsening of precipitates;

[0087] Process 1-10 reduces the pre-aging temperature based on process 1-1. The reduction of the pre-aging temperature leads to insufficient precipitation of solute atoms in the matrix, and a large number of atoms are still solid-solved in the matrix. The interaction with dislocations in the mechanical processing process is weakened, the work hardening effect is lowered, and the mechanical properties are reduced.

[0088] Process 1-11 increases the pre-aging temperature based on process 1-5. The excessively high pre-aging temperature leads to serious coarsening of the precipitated phase in the matrix, the Orowan strengthening effect disappears, and the mechanical properties are severely reduced.

[0089] Process 1-12 shortens the pre-aging time based on process 1-5. The insufficient pre-aging time, similar to the principle of the lower pre-aging temperature, leads to the failure of solute atoms to precipitate in time, the weakening of the work hardening effect, and the reduction of the mechanical properties. It is worth noting that the tensile strength of process 1-12 is better than that of process 1-10, indicating that the reduction of time is less than that of excessively low temperature.

[0090] Process 1-13 prolongs the pre-aging time based on process 1-1. The excessively long pre-aging time leads to the coarsening of the precipitated phase and the increase of the cost, which is not conducive to the performance improvement and actual production.

[0091] Process 1-14 cancels the high-temperature short-time aging based on process 1-3. The excess vacancies after quenching help the rapid nucleation of clusters during the high-temperature short-time aging process. The alloy after the high-temperature short-time aging process can form fine and dense nanometer clusters rich in Mg elements during the subsequent pre-aging stage. After mechanical processing, these clusters are more likely to transform into β" phase due to their chemical composition similarity, which is due to the integration of vacancies into atomic-scale clusters and the initiation of crystal structure pre-amplitude by GP zones. These small and dispersed β" phases are believed to be the reason for the comprehensive improvement of the aluminum alloy wire, because they reduce the scattering effect of lattice distortion on electrons to improve the electrical conductivity, greatly increase the proliferation of dislocations during mechanical processing to increase the work hardening effect, and effectively hinder the movement of dislocations during the final aging process to improve the mechanical properties.

[0092] Process 1-15 cancels the pre-aging based on process 1-3. The GP zones and solute clusters cannot be transformed into β" phase, and the ability to proliferate dislocations is weak, leading to a reduction in mechanical properties.

[0093] Comparative example 1 is a traditional process with the best composition: "solid solution water quenching-mechanical processing-aging", which aims to highlight the new process combination proposed by the present application compared with the traditional process, which has a certain improvement effect on the performance of the product. Comparative examples 2-4 show that the aluminum alloy wire provided by the present application has the characteristics of high strength and high conductivity compared with the commercially available products.

[0094] The specific embodiments of the present application are described above. It needs to be understood that the present application is not limited to the specific embodiments described above, and various changes or modifications can be made by those skilled in the art within the scope of the claims, which do not affect the essential content of the present application.

Claims

1. A heat treatment method of a high-conductivity high-strength aluminum alloy material, characterized by, Comprising: (a) a solid solution quenching treatment; The solid solution quenching treatment comprises: heat preservation at 540-560℃ for 2-6h; (b) a high-temperature short-time aging treatment: heat preservation at 450-600℃ for 5-10min; (c) a pre-aging treatment: heat preservation at 200-400℃ for 6-12h; (d) an aging treatment; the aging treatment comprises: heat preservation at 240-280℃ for 8-12h; The high-conductivity high-strength aluminum alloy material, in terms of weight percentage, comprises: Mg 0.6-0.8wt%, Si 0.4-0.6wt%, B 0.1-0.2wt%, rare earth RE 0.1-0.2wt%, the sum of Cr, Mn, V and Ti being 0-0.0005wt%, the balance being Al and other unavoidable impurities; wherein the rare earth RE comprises at least one of La, Ce, Y, Sm and Er.

2. The method of heat treating a high conductivity high strength aluminum alloy material of claim 1, wherein: In step (c), the pre-aging treatment is followed by a cold working treatment.

3. A method for preparing a high-conductivity, high-strength aluminum alloy material, characterized in that, Comprising the following steps: S1: melting; S2: casting; S3: heat treatment: using the heat treatment method according to claim 1 or 2.

4. The method of producing a high-conductivity high-strength aluminum alloy material according to claim 3, characterized by: In step S1, the melting comprises: after the aluminum ingot is heated to complete melting, Al-Mg, Al-Si, Al-B intermediate alloy and rare earth RE are sequentially added for melting, to obtain an aluminum alloy liquid.

5. The method of producing a high-conductivity high-strength aluminum alloy material according to claim 3, characterized by: Further comprising refining, the refining comprises: adding a refining agent to the aluminum alloy liquid obtained by melting, stirring and then discharging slag to obtain a high-purity aluminum alloy liquid.

6. The method of producing a high-conductivity high-strength aluminum alloy material according to claim 3, characterized by: In step S2, the casting comprises: pouring the aluminum alloy liquid into a mold preheated to 200-300℃, and then naturally cooling to room temperature.

7. The application of the aluminum alloy material prepared by the preparation method of the high-conductivity high-strength aluminum alloy material according to any one of claims 3-6 in the preparation of wire and cable conductors.

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