Method for preparing high-strength aluminum alloy using recycled aluminum

Abstract

The invention discloses a method for preparing a high-strength aluminum alloy by utilizing recycled aluminum, and relates to the technical field of aluminum alloy processing. The method comprises the following steps: firstly, the recycled aluminum is heated and melted, and then a Sn-Bi alloy is pressed into the melt and rapidly stirred. Then, the aluminum alloy liquid is degassed and decontaminated by using an inert gas and a refining agent. After slagging, the liquid is allowed to stand, and then removed from the furnace for casting. The invention improves the morphology of the iron-rich phase, reduces the needle-shaped β-Fe phase, and transforms the β-Fe phase into a Chinese character-shaped or skeleton-shaped α-Fe phase by adding a certain amount of Sn-Bi alloy to the recycled aluminum melt, thereby improving the mechanical properties of the aluminum alloy.

Description

Technical field:

[0001] The present invention relates to the technical field of aluminum alloy processing, and in particular to a method for preparing a high-strength aluminum alloy by utilizing recycled aluminum. Background technology:

[0002] Aluminum alloy is an alloy based on aluminum with a certain amount of other alloying elements added. It is a type of light metal material. In addition to the general properties of aluminum, aluminum alloys also have some specific characteristics due to the different types and amounts of alloying elements added. The density of aluminum alloy is 2.63~2.85g / cm 3 , has a higher strength (σ b 110~650MPa), its specific strength is close to that of high alloy steel, and its specific stiffness exceeds that of steel. It has good castability, electrical conductivity, thermal conductivity, corrosion resistance and weldability. It can be used as a structural material and is widely used in aerospace, aviation, transportation, construction, electromechanical, light chemical and daily necessities.

[0003] Recycled aluminum, also known as "secondary aluminum," is aluminum obtained by smelting scrap aluminum parts and scrap aluminum materials. Aluminum is a recyclable resource, and recycled aluminum currently accounts for over one-third of the world's annual primary aluminum production. Recycled aluminum has the same properties as primary aluminum and is currently used primarily to produce cast aluminum alloys and ferroalloys. Cast aluminum alloys are used in automotive manufacturing, aerospace, electronics, and construction, while ferroalloys are used as deoxidizers and desulfurizers in steelmaking. The production of recycled aluminum not only reduces demand on limited resources, but also reduces energy consumption and environmental pollution. However, in the process of using recycled aluminum to produce high-performance aluminum alloys, the recycled aluminum is limited by the complex composition of the scrap aluminum raw material, resulting in insufficient hardness, strength, and toughness of the processed aluminum alloy. It is prone to deformation and even fracture during use, which seriously reduces its service life. Summary of the invention:

[0004] α-Fe and β-Fe are the two most common iron phases in aluminum alloys. Research has found that the α-Fe phase exists in the shape of Chinese characters, skeletons, or other forms, and its harmful effects on the aluminum matrix are not very obvious; however, the β-Fe phase, due to its coarse needle-like shape and uneven deformation, leads to relatively high stress concentration at the junction of the iron phase and the aluminum matrix, which significantly reduces the mechanical properties of the aluminum alloy. In addition, the presence of iron impurities will also destroy the continuity of the aluminum oxide film on the aluminum surface, forming a small anode and a large cathode on the aluminum alloy surface, reducing the corrosion resistance of the aluminum alloy and deteriorating the surface quality of the aluminum alloy after anodization.

[0005] In order to solve the above problems, the technical problem to be solved by the present invention is to provide a method for preparing high-strength aluminum alloy using recycled aluminum, which can not only promote the recycling and reuse of waste aluminum, but also the obtained aluminum alloy has excellent application effect.

[0006] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0007] The first object of the present invention is to provide a method for preparing high-strength aluminum alloy using recycled aluminum. The recycled aluminum is first heated and melted, and then Sn-Bi alloy is pressed into the melt and rapidly stirred. Then, the aluminum alloy liquid is degassed and decontaminated with inert gas and refining agent. After slagging, the liquid is allowed to stand and then taken out of the furnace for casting.

[0008] Preferably, the recycled aluminum is a recycled aluminum-silicon alloy with a silicon content of 5 to 15 wt%.

[0009] Preferably, the heating and melting temperature of the recycled aluminum is 750-850° C. The heating can be carried out in stages or all at once.

[0010] Preferably, the amount of Sn-Bi alloy added is 0.05-0.5wt% of the recycled aluminum. If the amount of Sn-Bi alloy added is less than 0.05wt%, no significant effect can be achieved; if the amount of Sn-Bi alloy added is greater than 0.5wt%, the processing cost will increase significantly.

[0011] Preferably, the content of Bi in the Sn-Bi alloy is 5-10 wt %. The effect of adding Sn-Bi alloy to recycled aluminum is far better than adding only the same amount of Sn or Bi.

[0012] Preferably, the inert gas is argon, nitrogen, or a mixture of the two. Argon or nitrogen, or a mixture of argon and nitrogen can be used.

[0013] Preferably, the refining agent is composed of KCl, MgCl, K3AlF6 and CaF2, and the mass ratio of KCl, MgCl, K3AlF6 and CaF2 is (40-50):(25-35):(5-15):(5-15).

[0014] Preferably, the refining agent is composed of KCl, MgCl, K3AlF6 and Zn3N2, and the mass ratio of KCl, MgCl, K3AlF6 and Zn3N2 is (40-50):(25-35):(5-15):(5-15).

[0015] The present invention adopts the above two refining agents. The addition of Zn3N2 in the second refining agent can achieve unexpected technical effects, which are the synergistic effect with the aforementioned Sn-Bi alloy.

[0016] Preferably, the amount of the refining agent added is 0.2-0.5 wt % of the amount of recycled aluminum used. The amount of the refining agent used is controlled according to the impurity content of the raw recycled aluminum, that is, the amount of the refining agent used is not limited to this range.

[0017] Preferably, the standing time is not less than 30 minutes. The gas in the aluminum alloy liquid and the slag not removed by the standing time are allowed to float up, and the slag is removed by filtering during the casting process.

[0018] A second object of the present invention is to provide a high-strength aluminum alloy obtained by the aforementioned method.

[0019] The beneficial effects of the present invention are:

[0020] (1) The present invention improves the morphology of the iron-rich phase, reduces the needle-shaped β-Fe phase, and transforms the β-Fe phase into a Chinese character-shaped or skeleton-shaped α-Fe phase by adding a certain amount of Sn-Bi alloy to the recycled aluminum melt, thereby improving the mechanical properties of the aluminum alloy.

[0021] (2) The refining agent used in the present invention can not only remove hydrogen and floating oxide inclusions inside the aluminum alloy liquid to make the aluminum alloy liquid purer, but also reduce the amount of β-Fe phase in the aluminum alloy and reduce its size by adding an appropriate amount of Zn3N2 in the refining agent, thereby further reducing the harmful effects of impurity iron in the aluminum alloy. Specific implementation method:

[0022] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific embodiments.

[0023] The raw material recycled aluminum in the following examples and control examples is processed from the same batch of waste aluminum materials through the same recycling process.

[0024] Example 1

[0025] First, the recycled aluminum is heated to 800℃ to melt, and then Sn-Bi alloy is pressed into the melt. The amount of Sn-Bi alloy added is 0.3wt% of the recycled aluminum used, and the Bi content in the Sn-Bi alloy is 8wt%. Stir at 300r / min for 15min, and then use argon and refining agent to degas and remove impurities from the aluminum alloy liquid. The amount of refining agent is 0.35wt% of the recycled aluminum used. After skimming, let it stand for 30min and then take it out of the furnace for casting.

[0026] The refining agent is composed of KCl, MgCl, K3AlF6 and CaF2, and the mass ratio of KCl, MgCl, K3AlF6 and CaF2 is 40:30:10:5.

[0027] Example 2

[0028] First, the recycled aluminum is heated to 850℃ to melt, and then Sn-Bi alloy is pressed into the melt. The amount of Sn-Bi alloy added is 0.2wt% of the recycled aluminum used, and the Bi content in the Sn-Bi alloy is 10wt%. It is stirred at 300r / min for 15min, and then the aluminum alloy liquid is degassed and deimpurified with nitrogen and refining agent. The amount of refining agent is 0.4wt% of the recycled aluminum used. After slagging, it is allowed to stand for 60min and then taken out of the furnace for casting.

[0029] The refining agent is composed of KCl, MgCl, K3AlF6 and CaF2, and the mass ratio of KCl, MgCl, K3AlF6 and CaF2 is 45:25:10:5.

[0030] Example 3

[0031] First, heat the recycled aluminum to 750℃ and melt it. Then, press Sn-Bi alloy into the melt. The amount of Sn-Bi alloy added is 0.25wt% of the recycled aluminum. The Bi content in the Sn-Bi alloy is 5wt%. Stir at 300r / min for 15min. Then, use nitrogen and refining agent to degas and remove impurities from the aluminum alloy liquid. The amount of refining agent is 0.5wt% of the recycled aluminum. After slagging, let it stand for 30min and then take it out of the furnace for casting.

[0032] The refining agent is composed of KCl, MgCl, K3AlF6 and CaF2, and the mass ratio of KCl, MgCl, K3AlF6 and CaF2 is 45:35:12:10.

[0033] Example 4

[0034] First, the recycled aluminum is heated to 750℃ to melt, and then Sn-Bi alloy is pressed into the melt. The amount of Sn-Bi alloy added is 0.15wt% of the recycled aluminum used, and the Bi content in the Sn-Bi alloy is 10wt%. Stir at 300r / min for 15min, and then use argon and refining agent to degas and remove impurities from the aluminum alloy liquid. The amount of refining agent is 0.5wt% of the recycled aluminum used. After slagging, let it stand for 45min and then take it out of the furnace for casting.

[0035] The refining agent is composed of KCl, MgCl, K3AlF6 and CaF2, and the mass ratio of KCl, MgCl, K3AlF6 and CaF2 is 50:25:10:10.

[0036] Example 5

[0037] First, the recycled aluminum is heated to 800℃ to melt, and then Sn-Bi alloy is pressed into the melt. The amount of Sn-Bi alloy added is 0.3wt% of the recycled aluminum used. The Bi content in the Sn-Bi alloy is 8wt%. It is stirred at 300r / min for 15min, and then the aluminum alloy liquid is degassed and deimpurified with inert gas (argon and nitrogen with a volume ratio of 9:1) and refining agent. The amount of refining agent is 0.3wt% of the recycled aluminum used. After slagging, it is allowed to stand for 60min and then taken out of the furnace for casting.

[0038] The refining agent is composed of KCl, MgCl, K3AlF6 and CaF2, and the mass ratio of KCl, MgCl, K3AlF6 and CaF2 is 50:30:10:8.

[0039] Example 6

[0040] Example 6 was obtained by replacing the CaF2 in the refining agent used in Example 1 with the same mass of Zn3N2.

[0041] First, the recycled aluminum is heated to 800℃ to melt, and then Sn-Bi alloy is pressed into the melt. The amount of Sn-Bi alloy added is 0.3wt% of the recycled aluminum used, and the Bi content in the Sn-Bi alloy is 8wt%. Stir at 300r / min for 15min, and then use argon and refining agent to degas and remove impurities from the aluminum alloy liquid. The amount of refining agent is 0.35wt% of the recycled aluminum used. After skimming, let it stand for 30min and then take it out of the furnace for casting.

[0042] The refining agent is composed of KCl, MgCl, K3AlF6 and Zn3N2, and the mass ratio of KCl, MgCl, K3AlF6 and Zn3N2 is 40:30:10:5.

[0043] Example 7

[0044] Example 7 was obtained by replacing the CaF2 in the refining agent used in Example 5 with the same mass of Zn3N2.

[0045] First, the recycled aluminum is heated to 800℃ to melt, and then Sn-Bi alloy is pressed into the melt. The amount of Sn-Bi alloy added is 0.3wt% of the recycled aluminum used. The Bi content in the Sn-Bi alloy is 8wt%. It is stirred at 300r / min for 15min, and then the aluminum alloy liquid is degassed and deimpurified with inert gas (argon and nitrogen with a volume ratio of 9:1) and refining agent. The amount of refining agent is 0.3wt% of the recycled aluminum used. After slagging, it is allowed to stand for 60min and then taken out of the furnace for casting.

[0046] The refining agent is composed of KCl, MgCl, K3AlF6 and Zn3N2, and the mass ratio of KCl, MgCl, K3AlF6 and Zn3N2 is 50:30:10:8.

[0047] Comparative Example 1

[0048] The Sn-Bi alloy used in Example 1 was replaced with an Al-Bi alloy to obtain Comparative Example 1.

[0049] First, the recycled aluminum is heated to 800℃ to melt, and then Al-Bi alloy is pressed into the melt. The amount of Al-Bi alloy added is 0.3wt% of the recycled aluminum used, and the Bi content in the Al-Bi alloy is 8wt%. It is stirred at 300r / min for 15min, and then the aluminum alloy liquid is degassed and deimpurified with argon and refining agent. The amount of refining agent is 0.35wt% of the recycled aluminum used. After slagging, it is allowed to stand for 30min and then taken out of the furnace for casting.

[0050] The refining agent is composed of KCl, MgCl, K3AlF6 and CaF2, and the mass ratio of KCl, MgCl, K3AlF6 and CaF2 is 40:30:10:5.

[0051] Comparative Example 2

[0052] Comparative Example 2 was obtained by replacing the Sn-Bi alloy used in Example 1 with an Al-Sn alloy.

[0053] First, the recycled aluminum is heated to 800℃ to melt, and then Al-Sn alloy is pressed into the melt. The amount of Al-Sn alloy added is 0.3wt% of the recycled aluminum. The Sn content in the Al-Sn alloy is 92wt%. It is stirred at 300r / min for 15min, and then the aluminum alloy liquid is degassed and deimpurified with argon and refining agent. The amount of refining agent is 0.35wt% of the recycled aluminum. After slagging, it is allowed to stand for 30min and then taken out of the furnace for casting.

[0054] The refining agent is composed of KCl, MgCl, K3AlF6 and CaF2, and the mass ratio of KCl, MgCl, K3AlF6 and CaF2 is 40:30:10:5.

[0055] Comparative Example 3

[0056] The Sn-Bi alloy used in Example 1 was replaced with Sn powder to obtain Comparative Example 3.

[0057] First, heat the recycled aluminum to 800℃ and melt it. Then press Sn powder into the melt. The amount of Sn powder added is 0.3wt% of the recycled aluminum. Stir at 300r / min for 15min. Then, use argon and refining agent to degas and remove impurities from the aluminum alloy liquid. The amount of refining agent is 0.35wt% of the recycled aluminum. After slagging, let it stand for 30min and then take it out of the furnace for casting.

[0058] The refining agent is composed of KCl, MgCl, K3AlF6 and CaF2, and the mass ratio of KCl, MgCl, K3AlF6 and CaF2 is 40:30:10:5.

[0059] Comparative Example 4

[0060] Comparative Example 4 was obtained by replacing the Sn-Bi alloy used in Example 1 with Bi powder.

[0061] First, heat the recycled aluminum to 800℃ and melt it. Then, press Bi powder into the melt. The amount of Bi powder added is 0.3wt% of the recycled aluminum. Stir at 300r / min for 15min. Then, use argon and refining agent to degas and remove impurities from the aluminum alloy liquid. The amount of refining agent is 0.35wt% of the recycled aluminum. After slagging, let it stand for 30min and then take it out of the furnace for casting.

[0062] The refining agent is composed of KCl, MgCl, K3AlF6 and CaF2, and the mass ratio of KCl, MgCl, K3AlF6 and CaF2 is 40:30:10:5.

[0063] Comparative Example 5

[0064] The Zn3N2 in the refining agent used in Example 7 was replaced by ZnCl2 to obtain Comparative Example 5.

[0065] First, the recycled aluminum is heated to 800℃ to melt, and then Sn-Bi alloy is pressed into the melt. The amount of Sn-Bi alloy added is 0.3wt% of the recycled aluminum used. The Bi content in the Sn-Bi alloy is 8wt%. It is stirred at 300r / min for 15min, and then the aluminum alloy liquid is degassed and deimpurified with inert gas (argon and nitrogen with a volume ratio of 9:1) and refining agent. The amount of refining agent is 0.3wt% of the recycled aluminum used. After slagging, it is allowed to stand for 60min and then taken out of the furnace for casting.

[0066] The refining agent is composed of KCl, MgCl, K3AlF6 and ZnCl2, and the mass ratio of KCl, MgCl, K3AlF6 and ZnCl2 is 50:30:10:8.

[0067] The aluminum alloy liquids prepared in Examples 1-7 and Comparative Examples 1-5 were cast after being taken out of the furnace to obtain aluminum alloy castings. The aluminum alloy castings were placed in a hot air circulation solution furnace and solution treated at 550°C for 8 hours. They were then quickly placed in 75°C water for quenching for 10 minutes. The aluminum alloy castings were then placed in a hot air circulation aging furnace and aged at 180°C for 5 hours. The aluminum alloy castings were then air-cooled to room temperature to obtain aluminum alloy materials. The aluminum alloy materials were cut into specimens of the same shape and size. The tensile strength and yield strength of the specimens were tested using a CMT5105 electronic universal testing machine in accordance with the standard GB / T 228.1-2021 "Tensile Tests on Metallic Materials - Part 1: Room Temperature Test Methods". The test results are shown in Table 1.

[0068] The larger the tensile strength value, the stronger the aluminum alloy's ability to resist fracture.

[0069] The larger the yield strength value, the stronger the aluminum alloy's ability to resist plastic deformation.

[0070] Table 1 Tensile strength and yield strength of aluminum alloy materials

[0071] Tensile strength / MPa Yield strength / MPa Example 1 348 240 Example 2 334 229 Example 3 320 218 Example 4 329 223 Example 5 342 238 Example 6 357 252 Example 7 351 245 Comparative Example 1 320 213 Comparative Example 2 330 226 Comparative Example 3 309 197 Comparative Example 4 294 182 Comparative Example 5 340 235

[0072] It can be seen from the data in Table 1 that the addition of Sn-Bi alloy in the recycled aluminum smelting process and the addition of Zn3N2 in the refining agent can substantially improve the tensile strength and yield strength of the produced aluminum alloy material.

[0073] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-strength aluminum alloy using recycled aluminum, characterized by: First, heat and melt the recycled aluminum, then press Sn-Bi alloy into the melt and stir it rapidly. Then, use inert gas and refining agent to degas and remove impurities from the aluminum alloy liquid. After slagging, let it stand and then take it out of the furnace for casting. The amount of Sn-Bi alloy added is 0.05-0.5wt% of the amount of recycled aluminum; The content of Bi in the Sn-Bi alloy is 5-10 wt%; The recycled aluminum is a recycled aluminum-silicon alloy with a silicon content of 5-10wt%; The refining agent is composed of KCl, MgCl, K3AlF6 and Zn3N2, and the mass ratio of KCl, MgCl, K3AlF6 and Zn3N2 is (40~50): (25~35): (5~15): (5~15).

2. The method according to claim 1, wherein: The heating and melting temperature of the recycled aluminum is 750-850°C.

3. The method according to claim 1, wherein: The inert gas is argon, nitrogen or a mixture of the two.

4. The method according to claim 1, wherein: The amount of the refining agent added is 0.2-0.5wt% of the amount of recycled aluminum used.

5. The method according to claim 1, wherein: The standing time is not less than 30 minutes.

6. A high-strength aluminum alloy obtained by the method according to any one of claims 1 to 5.