Method for improving conductivity of Al-Fe-La alloy round rod

Abstract

The invention relates to the field of aluminum alloy production, in particular to a method for improving the conductivity of an Al-Fe-La alloy round rod. According to the preparation method, the Al-Fe-La alloy cast ingot or cast rod is subjected to homogenization treatment, then the aluminum alloy round rod is prepared through hot extrusion or rolling, then the aluminum rod is subjected to annealing treatment at the proper temperature, and the Al-Fe-La alloy round rod with the high conductivity can be obtained. The Al-Fe-La alloy round rod applicable to the method comprises the following components in percentage by weight: 0.4 to 0.6 percent of Fe, 0.04 to 0.10 percent of La and the balance of Al. According to the invention, the conductivity of the aluminum round bar is greatly improved, and the yield of the aluminum round bar is obviously improved on the basis of ensuring stable performance.

Description

Technical Field

[0001] The invention relates to the field of aluminum alloy production, in particular to a method for improving the electrical conductivity of an Al-Fe-La alloy round rod. Background Art

[0002] With the introduction of various national policies on energy conservation and emission reduction, the demand for lightweight vehicles has gradually increased. Wire harnesses are the bridge connecting electrical and electronic equipment in vehicles, and the nerves of energy and information transmission of industrial products. Due to the good electrical conductivity and mechanical properties of aluminum, the application of aluminum wire harnesses has a very broad prospect.

[0003] Al-Fe-La alloy is a high-conductivity aluminum alloy used to prepare aluminum wires. Generally, for alloys with the same composition, different preparation processes have a significant effect on the conductivity of the final aluminum alloy wires. For Al-Fe-La alloys, the Fe and La elements dissolved in the matrix will cause the lattice to distort, increase the scattering of electrons, and thus reduce the conductivity of the alloy. Therefore, the alloy needs to be heat treated to precipitate the dissolved atoms. Different types of precipitated phases often correspond to different thermal stabilities. Inappropriate heat treatment temperatures will cause part of the second phase in the matrix to dissolve and re-dissolve into the matrix. In the subsequent drawing annealing process, the annealing temperature is often low and cannot reach the dissolution temperature of the Fe-rich and La-rich phases. Therefore, it is necessary to promote the dissolution of Fe and La elements as much as possible during the preparation of aluminum round rods to ensure that the alloy can obtain higher conductivity. Therefore, it is very necessary to design a suitable heat treatment system for Al-Fe-La alloys. Summary of the invention

[0004] The object of the present invention is to provide a method for improving the electrical conductivity of an Al-Fe-La alloy round rod, by adopting an appropriate coupled two-stage annealing treatment to promote the dissolution of solid solution Fe and La as much as possible, reduce the electron scattering factor, and thus improve the electrical conductivity of the Al-Fe-La alloy.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] A method for improving the electrical conductivity of an Al-Fe-La alloy round rod comprises the following process steps:

[0007] 1) Perform homogenization annealing treatment on Al-Fe-La alloy ingots or cast rods at 480℃~540℃, and the annealing time shall be not less than 12h;

[0008] 2) hot extruding the Al-Fe-La alloy ingot into an aluminum round rod, or rolling the Al-Fe-La alloy cast rod into an aluminum round rod;

[0009] 3) Annealing the aluminum round rod at 300°C to 480°C for 2 to 5 hours, followed by air cooling.

[0010] In the method for improving the electrical conductivity of the Al-Fe-La alloy round rod, in step 1), the homogenization annealing temperature is 480° C. to 520° C., and the homogenization annealing time is 16 to 24 hours.

[0011] In the method for improving the electrical conductivity of the Al-Fe-La alloy round rod, in step 3), the annealing temperature is 360° C. to 480° C., and the annealing time is 2 to 5 hours.

[0012] In the method for improving the electrical conductivity of the Al-Fe-La alloy round rod, the secondary annealing temperature is lower than the homogenization annealing temperature and higher than the subsequent drawing annealing temperature.

[0013] The method for improving the conductivity of the Al-Fe-La alloy round rod is applicable to the Al-Fe-La alloy composition range of, in terms of element mass percentage: Fe 0.4-0.6%, La 0.04-0.10%, and the balance Al.

[0014] The method for improving the conductivity of the Al-Fe-La alloy round rod is used as a blank rod for preparing ultra-fine aluminum alloy electronic wires or transmission and distribution cables.

[0015] The design concept of the present invention is:

[0016] First, a homogenization annealing treatment is performed at a relatively high temperature to dissolve the dissolved Fe and La elements as much as possible and eliminate micro-segregation. Eliminating or reducing micro-segregation helps to improve the subsequent uniform plastic deformation ability of the alloy, enhance the crushing effect of deformation on the second phase particles, and improve the uniformity of the organization. In addition, during hot extrusion or rolling, there is the possibility of strain-induced second phase dissolution or strain-induced localization of solid solution atoms. Therefore, it is necessary to perform a secondary annealing treatment at a relatively low temperature to promote the precipitation of the second phase and reduce the solid solubility of the alloy. The secondary annealing temperature is lower than the homogenization annealing temperature, but higher than the subsequent drawing annealing temperature to prevent the second phase particles precipitated in the primary annealing treatment (i.e., the homogenization annealing treatment) from redissolving into the matrix and reducing the electrical conductivity of the alloy.

[0017] The advantages and beneficial effects of the present invention are:

[0018] 1. The present invention significantly improves the crushing effect of the second phase particles during plastic deformation, reduces the matrix solid solubility, improves the uniformity of the Al-Fe-La alloy round rod structure, and simultaneously improves the mechanical properties and electrical conductivity of the alloy without changing the alloy composition, only through a simple and feasible two-stage annealing coupling treatment. In addition, the present invention greatly reduces the wire breakage rate in the subsequent preparation of ultra-fine electronic wires (diameter <0.3mm) through the drawing process, and significantly improves production efficiency.

[0019] 2. The present invention greatly improves the electrical conductivity of the aluminum round rod, and on the basis of ensuring stable performance, significantly improves the yield rate of the aluminum round rod. Its performance indicators are as follows: the electrical conductivity range is 62.0% IACS to 63.5% IACS, the alloy tensile strength is 80 to 100 MPa, and the elongation after fracture is 35% to 45%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the SEM structure of the aluminum alloy round rod in Example 1.

[0021] Figure 2 This is the SEM structure of the aluminum alloy round rod in Comparative Example 1.

[0022] Figure 3 This is the curve showing the influence of secondary annealing temperature on the electrical conductivity of Al-Fe-La alloy. DETAILED DESCRIPTION

[0023] In the specific implementation process, the present invention prepares an aluminum alloy round rod by hot extrusion or rolling after homogenizing an Al-Fe-La alloy ingot or cast rod, and then anneals the aluminum rod at an appropriate temperature to obtain an Al-Fe-La alloy round rod with high electrical conductivity. The composition range of the Al-Fe-La alloy round rod applicable to the present invention is: Fe content is 0.4-0.6wt.%, La content is 0.04-0.10wt.%, and the balance is Al.

[0024] The process is further described below in conjunction with examples of implementation, but the present invention is not limited to these examples.

[0025] Example 1

[0026] In this embodiment, a method for improving the electrical conductivity of an Al-Fe-La alloy round rod comprises the following steps:

[0027] 1) The Al-Fe-La alloy raw material is melted in a resistance furnace. The designed Al-Fe-La alloy composition is, by element mass percentage, iron: 0.59%, lanthanum: 0.079%, and the balance is aluminum.

[0028] The smelting process is as follows: first, industrial pure aluminum with a purity of 99.9wt% and Al-Fe master alloy are put into a resistance furnace, and the temperature is raised to 830°C along with the furnace. After they are fully melted, the temperature is lowered to 740°C, and Al-La master alloy is added. After the Al-La master alloy is melted, degassing treatment is performed, and then the temperature is lowered to 720°C for casting. The obtained Al-Fe-La alloy ingot is air-cooled to room temperature.

[0029] 2) The prepared Al-Fe-La alloy ingot was heated to 490° C. in a box-type resistance furnace for homogenization annealing, kept at this temperature for 24 h, and air-cooled to room temperature.

[0030] 3) Preheat the Al-Fe-La alloy ingot at 380℃ for 1.5h and then hot extrude it into For round rods, the extrusion die temperature is 400-420°C, the extrusion rod displacement speed is 7.2 mm / s, the extrusion ratio is about 169:1, and then air-cooled to room temperature.

[0031] 4) The extruded aluminum alloy round rod is heated to 420° C. for secondary annealing, and kept at this temperature for 3 h, and then air-cooled to room temperature.

[0032] The technical indicators of this embodiment are as follows: the electrical conductivity ranges from 62.3% IACS to 62.6% IACS, the alloy tensile strength is 88 to 95 MPa, and the elongation after fracture is ≥38%.

[0033] Example 2

[0034] The difference from Example 1 is that:

[0035] 1) The designed Al-Fe-La alloy composition is, by element mass percentage, iron: 0.49%, lanthanum: 0.081%, and the balance is aluminum.

[0036] 2) The prepared Al-Fe-La alloy ingot was heated to 520° C. in a box-type resistance furnace for homogenization annealing, kept at this temperature for 16 h, and air-cooled to room temperature.

[0037] 3) The extruded aluminum alloy round rod is heated to 380°C for secondary annealing, kept at this temperature for 4 hours, and then air-cooled to room temperature.

[0038] The technical indicators of this embodiment are as follows: the electrical conductivity ranges from 62.5% IACS to 63.2% IACS, the alloy tensile strength is 80 to 90 MPa, and the elongation after fracture is ≥40%.

[0039] Comparative Example 1

[0040] This comparative example is different from Example 1 in that step 2) of Example 1 is not performed, that is, no homogenization annealing treatment is performed.

[0041] The technical indicators of this comparative example are as follows: electrical conductivity is 61.8% IACS, alloy tensile strength is 88.5 MPa, and elongation after fracture ranges from 35% to 40%.

[0042] Comparative Example 2

[0043] This comparative example is different from Example 1 in that in step 4) of Example 1, the secondary annealing temperature is 540°C.

[0044] The technical indicators of this comparative example are as follows: electrical conductivity ≤ 61.8% IACS, alloy tensile strength ≤ 90 MPa, and elongation after fracture ranging from 35% to 45%.

[0045] Comparative Example 3

[0046] In this comparative example, the difference from Example 1 is that:

[0047] 1) In step 2) of Example 1, the homogenization annealing temperature is 440°C.

[0048] 2) In step 4) of Example 1, the extruded aluminum alloy round rod is heated to 320° C. for secondary annealing, and kept at this temperature for 3 hours, followed by air cooling.

[0049] The technical indicators of this comparative example are as follows: electrical conductivity is 61.9% IACS, alloy tensile strength is 85 MPa, and elongation after fracture ranges from 35%.

[0050] like Figure 1 and Figure 2 As shown, the SEM photos of the second phase structure of the Al-Fe-La alloy in the above-mentioned Example 1 and Comparative Example 1. It can be seen from the figure that the crushing effect of the second phase particles during the alloy extrusion process can be improved by appropriate homogenization treatment, so that the second phase particles in the extruded alloy are finer and the distribution is more dispersed. In Comparative Example 1, the second phase particles are localized and aggregated, and the size of the second phase particles (average equal circle diameter: ~0.95 microns) is significantly larger than the size of the second phase in Example 1 (average equal circle diameter: ~0.68 microns). The reduction in the size of the second phase in Example 1 helps to improve the uniformity of the alloy structure and reduce the strain localization caused by the coarse second phase, thereby improving the electrical conductivity of the alloy.

[0051] like Figure 3 As shown in the figure, the conductivity curve of Al-Fe-La alloy annealed at different temperatures for 3h. As can be seen from the figure, the conductivity of the alloy increases first and then decreases with the increase of annealing temperature. Homogenization annealing (480℃~520℃) and secondary annealing (360℃~480℃) in the temperature range of 360℃~520℃ can ensure that the alloy obtains good conductivity performance.

[0052] The results of the embodiments and comparative examples show that the present invention improves the crushing effect of plastic deformation on the second phase particles by reasonably coupling the two-stage annealing process, the second phase particles are more evenly distributed, and the organizational uniformity and electrical conductivity of the alloy are greatly improved.

Claims

1. A method for improving the electrical conductivity of an Al-Fe-La alloy round rod, characterized in that: The process steps include: 1) Perform homogenization annealing treatment on Al-Fe-La alloy ingots or cast rods at 480℃~540℃, and the annealing time shall be not less than 12h; 2) hot extruding the Al-Fe-La alloy ingot into an aluminum round rod, or rolling the Al-Fe-La alloy cast rod into an aluminum round rod; 3) Annealing the aluminum round rod at 300°C to 480°C for 2 to 5 hours, followed by air cooling.

2. The method for improving the electrical conductivity of an Al-Fe-La alloy round rod according to claim 1, characterized in that: In step 1), the homogenization annealing treatment temperature is 480° C. to 520° C., and the homogenization annealing time is 16 to 24 hours.

3. The method for improving the electrical conductivity of an Al-Fe-La alloy round rod according to claim 1, characterized in that: In step 3), the annealing temperature is 360° C. to 480° C., and the annealing time is 2 to 5 hours.

4. The method for improving the electrical conductivity of an Al-Fe-La alloy round rod according to any one of claims 1 to 3, characterized in that: The secondary annealing treatment temperature is lower than the homogenization annealing temperature and higher than the subsequent drawing annealing temperature.

5. The method for improving the electrical conductivity of an Al-Fe-La alloy round rod according to claim 1, characterized in that: The applicable Al-Fe-La alloy composition range is, by element mass percentage: Fe 0.4-0.6%, La 0.04-0.10%, and the balance is Al.

6. The method for improving the electrical conductivity of an Al-Fe-La alloy round rod according to claim 1, characterized in that: Al-Fe-La alloy round rods are used as blank rods for preparing ultra-fine aluminum alloy electronic wires or transmission and distribution cables.

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