Preparation method of aluminum alloy cast rod

Abstract

The invention discloses a preparation method of an aluminum alloy cast rod. The preparation method comprises the following steps: mixing and melting an intermediate alloy containing an aluminum element, an intermediate alloy containing a Mn element and an intermediate alloy containing a Fe element; an online refiner is added; carrying out refining treatment on the molten liquid, and carrying out slagging-off operation to remove impurities; an intermediate alloy containing the Ce element is added into the molten liquid obtained after refining and slagging-off, and the final adding amount of the Ce element in the aluminum alloy casting rod is 0.3-1 wt% by mass; and the melt added with the Ce element is filtered, the treated melt is cast, and the aluminum alloy cast rod is obtained. The strength, the tensile strength and the yield strength of the aluminum alloy modified through the method are all remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy materials, and in particular to a method for preparing an aluminum alloy cast rod. Background Art

[0002] The rapid development of the new energy vehicle industry has put forward higher requirements on the performance of power batteries, especially stability and safety in extreme environments. During the charging and discharging process of power batteries, the thermal expansion and contraction of battery components will cause the shell to deform. This deformation is particularly significant in harsh environments such as high temperature and humidity, high altitude and high cold, which seriously affects the performance and service life of the battery. Therefore, improving the heat resistance and structural strength of the power battery shell has become the key to the current technological development.

[0003] Aluminum alloys are widely used in power battery housings due to their light weight, corrosion resistance and excellent mechanical properties. However, the protection effect of existing aluminum alloys in special operating environments, such as charge and discharge cycles and extreme climatic conditions, needs to be improved. In particular, the performance of existing materials still has room for improvement in terms of improving structural stiffness, bending limit, pressure resistance limit and thermal attenuation gradient. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is: to provide a method for preparing aluminum alloy cast rods, which significantly improves the elastic modulus and fatigue resistance of the aluminum alloy cast rods, and enhances the structural rigidity and bending limit.

[0005] In order to solve the above technical problems, a technical solution adopted by the present invention is: a method for preparing an aluminum alloy cast rod, comprising the following steps:

[0006] 1) Mixing a master alloy containing aluminum, a master alloy containing Mn and a master alloy containing Fe, and melting them in a furnace;

[0007] 2) adding an online refiner to the melt obtained in step 1) and stirring the melt simultaneously;

[0008] 3) After step 2) is completed, the melt is refined and slag is removed to remove impurities;

[0009] 4) adding a Ce-containing master alloy to the molten metal after refining and slagging in step 3) and continuing the heating treatment; wherein the Ce-containing master alloy is added so that the Ce element is finally added to the aluminum alloy casting rod in an amount of 0.3 to 1 wt% by mass;

[0010] 5) filtering the melt after the treatment in step 4), and casting the treated melt to obtain the aluminum alloy cast rod.

[0011] As an implementable manner, the master alloy containing aluminum element in step 1) is AlT i6 alloy or AlT i4 alloy, the master alloy containing Mn element is AlMn10, and the master alloy containing Fe element is AlFe10.

[0012] As an implementable manner, the online refiner in step 2) is Al T i5 or Al T i5B1.

[0013] As an achievable manner, in the step 1), the addition amounts of the master alloy containing the Mn element and the master alloy containing the Fe element are controlled so that the total mass percentage of Fe and Mn in the obtained ingot is 1.75-1.95wt%, wherein the mass percentage of Fe is 0.45-0.55wt%.

[0014] As an achievable manner, in the melt after mixing in step 4), the mass content of each element is as follows: the total mass percentage of Fe and Mn is 1.75-1.95wt%, wherein the mass percentage of Fe is 0.45-0.55wt%; the mass percentage of Cu is 0.08-0.20wt%; the mass percentage of Si is 0.18-0.70wt%; the mass percentage of Ti is 0.01-0.02wt%; the mass percentage of Ni is <0.02wt%; the mass percentage of Zn is <0.10wt%; and the balance is Al.

[0015] As an achievable manner, in the melt after mixing in step 4), the mass content of each element is as follows: Mn 1.25wt%, Si 0.48wt%, Cu 0.10wt%, Fe 0.55wt%, Mg<0.02wt%, Cr<0.001wt%, Ni 0.004wt%, Ti 0.013wt%, Zn 0.03wt%, Ce 0.38wt%, and the balance is Al.

[0016] As an achievable manner, the addition amount of the online refiner is 1.6 kg / t.

[0017] As an achievable method, in step 1), the melting temperature is 760°C, the capacity is expanded for 20-25 minutes, the furnace temperature is controlled at 750-760°C, and after the furnace is finished, it is allowed to stand at 750-760°C for 30-35 minutes.

[0018] As an implementable manner, the casting parameters in step 5) are as follows: casting temperature 710-720°C, casting speed 130-140 mm / min, water flow 300-320 m3 / h·root.

[0019] As an achievable method, it also includes a homogenization step after casting, and the parameters of the homogenization step are as follows: the homogenization temperature is raised to 610-620°C, the homogenization is kept warm for 8-9 hours, and when cooling, it is first air-cooled to 280°C and then water-mist-cooled.

[0020] This application starts from the purpose of improving the strength of aluminum alloys, and adds a specific amount of Ce as a raw material into aluminum alloys for modification. On the one hand, because Ce is a rare earth element with a large atomic radius, which is much larger than the atomic radius of Al, it can bear the nucleation point in the melt, increase the nucleation concentration during solidification, and has a strong ability to refine grains. It can refine grains, improve mechanical strength and microhardness of the organization, and increase the elastic modulus, thereby improving the structural rigidity of the battery shell and ensuring the life of lithium batteries at 100 degrees Celsius. 2500-3000 breathing cycles. Compared with low-multiple organizations without adding Ce elements, it can reduce aluminum grains by one-half to one-third, which can refine grains and effectively hinder the movement of dislocations, thereby improving the strength and hardness of aluminum alloy materials; on the other hand, Ce is highly active and easy to react chemically with most metals to form a variety of refractory and hard intermetallic compounds that are very small. In aluminum alloy modification, extremely trace elements that have no strengthening effect can be converted into strengthening phases, increasing the concentration of strengthening phases and contributing to the purification of the melt.

[0021] Moreover, the Ce intermetallic compound formed is dissolved in the aluminum particles, which will cause a large lattice distortion and form high-density dislocations, hindering deformation and further ensuring strength. In the metallographic field of view, the Ce intermetallic compound generally appears as tiny white flakes, part of which is dissolved in the aluminum particles, and part of which exists in the grain boundary to form a broken chain ring, which greatly enhances the metal bond, ionic bond and van der Waals force between metals and improves the resistance to deformation.

[0022] It is precisely because the strength of the aluminum alloy cast rod obtained after the modification of the present application is increased, so when a battery casing with certain explosion-proof requirements is subsequently prepared, the aluminum alloy cast rod of the present application can be drawn due to its high strength, so thinner cast rods than other aluminum alloys can be selected for drawing, and the process is simpler and easier to operate, and it is also relatively more cost-effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the metallographic diagram of conventional 3003 aluminum alloy without modification.

[0024] Figure 2 This is the metallographic diagram of the aluminum alloy of Example 1 after modification of the present application.

[0025] Figure 3a -e is the metallographic diagram of the aluminum alloy of Example 2 and Comparative Examples 1-4. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0027] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0029] The present embodiment provides a method for preparing an aluminum alloy cast rod, comprising the following steps:

[0030] 1) Mixing a master alloy containing aluminum, a master alloy containing Mn and a master alloy containing Fe, and melting them in a furnace;

[0031] 2) adding an online refiner to the melt obtained in step 1) and stirring the melt simultaneously;

[0032] 3) After step 2) is completed, the melt is refined and slag is removed to remove impurities;

[0033] 4) adding a Ce-containing master alloy to the molten metal after refining and slagging in step 3) and continuing the heating treatment; wherein the Ce-containing master alloy is added so that the Ce element is finally added to the aluminum alloy casting rod in an amount of 0.3 to 1 wt% by mass;

[0034] 5) filtering the melt after the treatment in step 4), and casting the treated melt to obtain the aluminum alloy cast rod.

[0035] The master alloy containing aluminum element in step 1) is Al Ti 6 alloy or Al Ti 4 alloy.

[0036] In step 1), the intermediate alloy containing the Mn element is AlMn10, and the intermediate alloy containing the Fe element is AlFe10.

[0037] The online refiner in step 2) is Al Ti5 or Al Ti5B1.

[0038] In the step 1), the addition amount of the master alloy containing the Mn element and the master alloy containing the Fe element is controlled so that the total mass percentage of Fe and Mn in the obtained ingot is 1.75-1.95wt%, wherein the mass percentage of Fe is 0.45-0.55wt%.

[0039] In step 5), a ceramic filter device is used for filtering with a filtering accuracy of 40-60 PPI.

[0040] Step 4) In the mixed melt, the mass content of each element is as follows: the total mass percentage of Fe and Mn is 1.75-1.95wt%, wherein the mass percentage of Fe is 0.45-0.55wt%; the mass percentage of Cu is 0.08-0.20wt%; the mass percentage of Si is 0.18-0.70wt%; the mass percentage of Ti is 0.01-0.02wt%; the mass percentage of Ni is <0.02wt%; the mass percentage of Zn is <0.10wt%; and the balance is Al.

[0041] The addition amount of the online refiner is 1.6 kg / t.

[0042] The melting temperature is 760℃, the expansion time is 20-25min, the furnace temperature is controlled at 750-760℃, and after the furnace is finished, it is allowed to stand at 750-760℃ for 30-35min.

[0043] The casting parameters are as follows: casting temperature 710-720° C., casting speed 130-140 mm / min, water flow 300-320 m 3 / h·root.

[0044] It also includes a homogenization step after casting, and the parameters of the homogenization step are as follows: the homogenization temperature is raised to 610-620°C, the homogenization is kept warm for 8-9 hours, and when cooling, it is first air-cooled to 280°C and then water-mist-cooled.

[0045] The specific parameter conditions of each embodiment are as follows:

[0046]

[0047]

[0048]

[0049] The modified 3003B aluminum alloy cast rod and the unmodified 3003B aluminum alloy cast rod prepared in Example 1 were taken to take metallographic images. The results are ( Figure 1-Figure 2) shows that the unmodified 3003B aluminum alloy has uneven grain size, large grains, and uneven precipitation phases, which easily lead to problems such as reduced mechanical properties and brittleness, and have an adverse effect on the strength of the aluminum alloy. The modified 3003B aluminum alloy of Example 1 has uniform grain size and uniform precipitation phase distribution, which can improve the strength and hardness of the material and promote the plastic deformation of the material.

[0050] The modified 3003B aluminum alloy obtained above and the unmodified 3003B aluminum alloy were tested for tensile strength, yield strength and cross-sectional shrinkage / elongation respectively. The specific test methods can refer to GB / T228.1-2021 Tensile Test of Metal Materials. The results are as follows:

[0051]

[0052] It can be seen from the above experimental results that the modified 3003B aluminum alloy in the embodiment of the present application has significantly improved tensile strength and yield strength, especially the tensile strength of the 3003B aluminum alloy is increased from an average of 113 MPa to a maximum of 142 MPa, an increase of 25.7%, and the yield strength is increased from an average of 75 MPa to a maximum of 98 MPa, an increase of 30.7%. It can be seen that the embodiment of the present application has obtained an aluminum alloy with better strength.

[0053] It can be seen from the test results of cross-sectional shrinkage and elongation that the elastic modulus and toughness of the aluminum alloy in this embodiment are increased.

[0054] In addition, comparative examples 1-4 are provided, and the parameter conditions of comparative examples 1-4 are as follows:

[0055] Comparative Example 1

[0056] The difference from Example 2 is that the addition of the Ce element is eliminated and the content is adjusted to be the balance Al.

[0057] Comparative Example 2

[0058] The difference from Example 2 is that the mass percentage of Ce element is adjusted to 0.15%.

[0059] Comparative Example 3

[0060] The difference from Example 2 is that the mass percentage of Ce element is adjusted to 0.25%.

[0061] Comparative Example 4

[0062] The difference from Example 2 is that the mass percentage of Ce element is adjusted to 1.15%.

[0063] The metallographic images of the aluminum alloy cast bars of Example 2 and Comparative Examples 1 to 4 were taken respectively. Figure 3a -e as shown.

[0064] Figure 3 (a) In the aluminum alloy without Ce addition, sharp and coarse rod-shaped Al6(Mn,Fe) phases are distributed in the aluminum matrix.

[0065] In the aluminum alloys with 0.15% Ce and 0.25% Ce added in Figure 3(b) and Figure 3(c), the microstructure is still parallel thick rod-shaped Al6(Mn,Fe).

[0066] FIG3( d ) is an aluminum alloy in Example 2 with 0.45% Ce added, wherein a coarse lamellar structure is distributed on the matrix, and there are some dendrites at the edge of the structure. The overall grain size is uniform and the precipitated phase is evenly distributed.

[0067] Figure 3(e) shows that excessive addition of Ce element will cause the dendrites at the edge of the lamellar structure to grow, and the picture shows that some small white flaky structures containing cerium compounds are dispersed on the matrix.

[0068] The characteristics of the aluminum-manganese-iron phase in the 3003 aluminum alloy with excellent performance are: distributed in the aluminum alloy matrix in block or needle-shaped form, the strengthening phase should be fine-grained and evenly dispersed, and coarse phases including rod-shaped and other shapes should be avoided. Specifically, the uniformly distributed block or needle-shaped aluminum-manganese-iron phase has a relatively high hardness. Its existence contributes to the strength and hardness of the aluminum alloy, and has a relatively small effect on plasticity, reducing cracks and deformation during processing. It has high thermal stability and is not easy to decompose at high temperatures. However, if the aluminum-manganese-iron phase is too large or unevenly distributed, it may cause local stress concentration and reduce the plasticity and toughness of the alloy.

[0069] In Figure 3(a)-(c), Al6(Mn,Fe) is a coarse, sharp, rod-shaped Al6(Mn,Fe) phase, and the phase is also unevenly distributed, which will reduce the overall performance of the alloy. In Figure 3(e), the aluminum-manganese-iron phase is too large and unevenly distributed, which is also not conducive to the overall performance of the alloy. In Figure 3(d), the aluminum-manganese-iron phase is evenly distributed and is a coarse phase, and the resulting alloy has excellent performance.

[0070] In general, adding too little or too much Ce element will be detrimental to improving the strength of the aluminum alloy. Only within the content range of Ce element added specifically in this application can the effect of improving the strength of the aluminum alloy cast rod be achieved.

[0071] The above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing an aluminum alloy cast rod, characterized in that: The steps include: 1) Mixing a master alloy containing aluminum, a master alloy containing Mn and a master alloy containing Fe, and melting them in a furnace; 2) adding an online refiner to the melt obtained in step 1) and stirring the melt simultaneously; 3) After step 2) is completed, the melt is refined and slag is removed to remove impurities; 4) adding a Ce-containing master alloy to the molten metal after refining and slagging in step 3) and continuing the heating treatment; wherein the Ce-containing master alloy is added so that the Ce element is finally added to the aluminum alloy casting rod in an amount of 0.3 to 1 wt% by mass; 5) filtering the melt after the treatment in step 4), and casting the treated melt to obtain the aluminum alloy cast rod.

2. The method for preparing the aluminum alloy cast rod according to claim 1, characterized in that: In step 1), the master alloy containing aluminum element is AlTi6 alloy or AlTi4 alloy, the master alloy containing Mn element is AlMn10, and the master alloy containing Fe element is AlFe10.

3. The method for preparing the aluminum alloy cast rod according to claim 1, characterized in that: The online refiner in step 2) is AlTi5 or AlTi5B1.

4. The method for preparing the aluminum alloy cast rod according to claim 1, characterized in that: In the step 1), the addition amount of the master alloy containing the Mn element and the master alloy containing the Fe element is controlled so that the total mass percentage of Fe and Mn in the obtained aluminum alloy cast rod is 1.75-1.95wt%, wherein the mass percentage of Fe is 0.45-0.55wt%.

5. The method for preparing the aluminum alloy cast rod according to claim 1, characterized in that: Step 4) In the mixed melt, the mass content of each element is as follows: the total mass percentage of Fe and Mn is 1.75-1.95wt%, wherein the mass percentage of Fe is 0.45-0.55wt%; the mass percentage of Cu is 0.08-0.20wt%; the mass percentage of Si is 0.18-0.70wt%; the mass percentage of Ti is 0.01-0.02wt%; the mass percentage of Ni is <0.02wt%; the mass percentage of Zn is <0.10wt%; and the balance is Al.

6. The method for preparing the aluminum alloy cast rod according to claim 1, characterized in that: Step 4) In the mixed melt, the mass content of each element is as follows: Mn 1.25wt%, Si 0.48wt%, Cu 0.10wt%, Fe 0.55wt%, Mg<0.02wt%, Cr<0.001wt%, Ni 0.004wt%, Ti 0.013wt%, Zn0.03wt%, Ce 0.38wt%, and the balance is Al.

7. The method for preparing the aluminum alloy cast rod according to claim 1, characterized in that: The addition amount of the online refiner is 1.6 kg / t.

8. The method for preparing the aluminum alloy cast rod according to claim 1, characterized in that: In step 1), the melting temperature is 760°C, the expansion time is 20-25min, the furnace temperature is controlled at 750-760°C, and after the furnace is finished, it is allowed to stand at 750-760°C for 30-35min.

9. The method for preparing the aluminum alloy cast rod according to claim 1, characterized in that: In step 5), the casting parameters are as follows: casting temperature 710-720° C., casting speed 130-140 mm / min, and water flow rate 300-320 m3 / h·root.

10. The method for preparing the aluminum alloy cast rod according to claim 1, characterized in that: It also includes a homogenization step after casting, and the parameters of the homogenization step are as follows: the homogenization temperature is raised to 610-620°C, the homogenization is kept warm for 8-9 hours, and when cooling, it is first air-cooled to 280°C and then water-mist-cooled.

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