Low-copper high-strength aluminum alloy material and preparation method and application thereof

Abstract

The invention relates to the technical field of aluminum alloy materials, and discloses a low-copper high-strength aluminum alloy material and a preparation method and application thereof. The low-copper high-strength aluminum alloy material comprises the following components in percentage by mass: 7.3 to 8.3 percent of Zn, 2.2 to 3.2 percent of Mg, 0.2 to 0.8 percent of Cu, 0.05 to 0.3 percent of Zr, 0.05 to 0.3 percent of RE, 0 to 0.13 percent of Ti, less than 0.13 percent of Fe, less than 0.12 percent of Si and the balance of aluminum. The preparation method comprises the steps that metal raw materials are put into a smelting furnace to be smelted, then slagging-off and impurity removal, refining, casting, homogenization treatment, extrusion forming and aging treatment are conducted in sequence, and the low-copper high-strength aluminum alloy material is obtained. The low-copper high-strength aluminum alloy material has good performance and can be applied to manufacturing of a thin-wall hollow structure with the thickness of about 2 mm, manufacturing of aerospace profiles, manufacturing of new energy battery trays or manufacturing of anti-collision beams through divergent die extrusion.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy materials, and in particular to a low-copper high-strength aluminum alloy material and a preparation method and application thereof. Background Art

[0002] As the lightweighting of automobiles and the technical requirements for new equipment and products in the aerospace and military industries continue to increase, current high-strength aluminum alloys, such as 7075 or the newer 7050 and 7085, all have the problem of poor workability after the strength is increased and cannot meet the requirements of split die extrusion and welding, which greatly limits their application scenarios in aluminum alloy profiles. At the same time, due to the poor forging performance of these materials, thick aluminum alloy plates are often used as supply conditions. In actual use, CNC processing is required to achieve the required shape, which wastes most of the material and drives up the cost of parts. Therefore, while improving strength, aluminum alloys still maintain high elongation and corrosion resistance, improve stress fatigue performance, and can achieve split die extrusion. At the same time, they must have good forgeability and quenching stability. Most importantly, they can achieve weldability, especially supporting arc welding and laser welding. This material will find important uses in the automotive industry, especially in new energy battery trays and anti-collision beams, as well as various aerospace profiles. However, achieving the above effects is currently difficult.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The object of the present invention is to provide a low-copper, high-strength aluminum alloy material and a preparation method and application thereof, in order to improve at least one of the problems mentioned in the background art.

[0005] The present invention is achieved in that:

[0006] In a first aspect, the present invention provides a low-copper, high-strength aluminum alloy material comprising the following components by mass:

[0007] Zn 7.3-8.3%, Mg 2.2-3.2%, Cu 0.2-0.8%, Zr 0.05-0.3%, RE 0.05-0.3%, Ti 0-0.13%, Fe <0.13%, Si <0.12%, impurity elements <0.15%, and the balance is aluminum.

[0008] In an optional embodiment, the Ti content is 0.01-0.13%.

[0009] In an optional embodiment, RE is a rare earth mixture mainly composed of Sc, and the mass proportion of Sc in RE is not less than 82%.

[0010] In a second aspect, an embodiment of the present invention provides a method for preparing the aforementioned low-copper, high-strength aluminum alloy material, comprising:

[0011] The metal raw materials are put into the smelting furnace for smelting, and then slag removal, refining, casting, homogenization, extrusion molding and aging treatment are carried out in sequence to obtain low-copper and high-strength aluminum alloy materials.

[0012] In an optional embodiment, the method specifically includes:

[0013] Providing metal raw materials, including high-purity industrial aluminum ingots and alloys or pure metals used to meet the composition formula of low-copper high-strength aluminum alloy materials;

[0014] Adding metal raw materials into a smelting furnace, melting all the metal raw materials and making the temperature reach 760-800° C. to obtain a first melt;

[0015] Adding a slag-forming agent to the first melt, mixing well and letting it stand, then skimming off the slag to obtain a second melt;

[0016] The temperature of the second melt is controlled at 740-800° C. and refined by adding a refining agent to the second melt under an inert atmosphere, then introducing an inert gas for two refining and degassing steps, each followed by standing for 30-60 minutes and then skimming the slag; and obtaining a third melt after refining.

[0017] Casting the third melt to obtain a primary ingot;

[0018] homogenizing the initial ingot to obtain a finished ingot;

[0019] The finished ingots are subjected to extrusion molding and aging treatment in sequence.

[0020] In an optional embodiment, the method of casting the third melt includes:

[0021] Before casting, heat the crystallizer to above 220℃, set the heating casting converter runner to above 280℃, the casting temperature is 710-730℃, the ingot temperature is 690-740℃, and Al-3Ti-0.1C wire is added simultaneously during casting. The amount of wire used is 1.8-2.2kg per ton of molten aluminum.

[0022] Alternatively, the casting is performed using the wet well casting method, where after casting, the ingot is completely immersed in water until it is completely cooled.

[0023] In an optional embodiment, the method of homogenizing the primary ingot to obtain the finished ingot includes:

[0024] The temperature of the initial ingot is raised to 330-355°C and kept warm for 5-12 hours, then raised to 438-488°C and kept warm for 8-16 hours, taken out of the furnace and air-cooled, and the opposite ends are sawed to obtain the finished ingot.

[0025] In an optional embodiment, the extrusion molding method includes:

[0026] The finished ingots of suitable size and temperature of 420-480℃ are sent to the extruder, extruded into the shaped material through the die, the discharge temperature is controlled to be not less than 460℃, and online quenching is performed.

[0027] In an optional embodiment, the aging treatment temperature is 115 to 145° C. and the time is 20 to 26 hours;

[0028] Alternatively, the aging treatment is a two-stage aging treatment, which also includes a two-stage solution treatment between the two-stage aging treatment and the extrusion molding;

[0029] The double-stage solution treatment method includes: 420-460℃, treatment for 30-180min, heating to 440-470℃, treatment for 30-120min;

[0030] The double-stage aging treatment method includes: 100-125°C, treatment for 12-20 hours, heating to 145-175°C, and treatment for 2-3 hours.

[0031] In a third aspect, the present invention provides an application of a low-copper, high-strength aluminum alloy material as described in any of the aforementioned embodiments in manufacturing thin-walled hollow structures of 1.8 to 2.2 mm through diverter die extrusion, manufacturing aerospace profiles, manufacturing new energy battery trays, or manufacturing anti-collision beams.

[0032] The present invention has the following beneficial effects:

[0033] The low-copper, high-strength aluminum alloy material provided by the present invention achieves improved elongation and machinability of ultra-high-strength aluminum alloys by increasing the zinc and magnesium content, adding rare earth elements, and reducing the copper content based on 7-series aluminum alloys, while also improving strength and corrosion resistance. Furthermore, it can be extruded through a manifold die while also possessing a certain degree of weldability. Therefore, the low-copper, high-strength aluminum alloy material provided by the present invention can be used in the manufacture of thin-walled hollow structures less than 2 mm through manifold die extrusion, aerospace profiles, new energy battery trays, or anti-collision beams. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0035] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0036] The core problem that needs to be solved by the present invention is to improve the elongation and machinability of ultra-high-strength aluminum alloys, and to improve the strength and corrosion resistance at the same time, and to achieve diverter die extrusion, while also having a certain degree of weldability. The related properties are contradictory development goals in traditional aluminum alloy materials. For example, ultra-high strength, diverter die extrusion and weldability are contradictory goals. The basic principle is that in order to achieve high strength, it is necessary to increase the content of certain elements (such as copper). However, the increase in the content of certain elements that increase strength will lead to a decrease in elongation and difficulty in extrusion. In particular, the addition of copper elements will greatly affect the welding and corrosion resistance. Excessive magnesium content can also easily cause welding pores, thereby affecting the final welding performance. Based on the above considerations, this application is proposed:

[0037] An embodiment of the present invention provides a low-copper, high-strength aluminum alloy material, which comprises the following components by mass fraction:

[0038] Zn 7.3~8.3%, Mg 2.2~3.2%, Cu 0.2~0.8%, Zr 0.05~0.3%, RE 0.05~0.3%, Ti 0~0.13%, Fe<0.13%, Si≤0.12%, impurity elements<0.15%, and the balance is aluminum.

[0039] The low-copper, high-strength aluminum alloy material provided by the present invention increases the zinc content to about 8% on the basis of the 7 series aluminum alloy, which can maximize the contribution of zinc precipitation strengthening and solid solution strengthening. However, since a zinc content of more than 8% will cause cracking and embrittlement problems, the magnesium content is simultaneously increased to form a fine and dispersed MgZn2 phase to avoid the generation of coarse and brittle phases; and due to the increase in magnesium content, especially when magnesium is increased to about 3%, the plasticity and forming ability will decrease, and it is easy to crack during forging and extrusion. In order to avoid cracking during forging and extrusion, rare earth elements are added to the alloy composition to refine the grains and inhibit the precipitation phase at the grain boundaries, thereby improving the toughness and corrosion resistance; in addition, in order to save alloy costs, zirconium is added to the alloy components for synergistic strengthening to form Al3Zr and Al3Re dispersed phases to delay recrystallization. In this solution, the copper content is strictly controlled below 0.8%. Since copper can cause thermal cracking and generate pores during welding, and also generate brittle intermetallic compounds such as CuAl2, reducing the copper content as much as possible while meeting the mechanical properties can minimize the impact on welding. In addition, low copper content can also maintain good plasticity, so that the diverter die extrusion can achieve thin-walled complex structure extrusion of about 2mm. Good plasticity combined with improved weldability makes it a good material for manufacturing new energy battery tray structural parts. Therefore, this low-copper, high-strength aluminum alloy material can be used in the manufacture of thin-walled hollow structures of about 2mm through diverter die extrusion, the manufacture of aerospace profiles, the manufacture of new energy battery trays, or the manufacture of anti-collision beams.

[0040] Furthermore, in the aluminum alloy material, the total amount of impurity elements is less than 0.15%, and the amount of a single impurity element is less than 0.05%.

[0041] Optionally, the Ti content is 0.01-0.13%. The addition of titanium to the composition can further improve the balance between elongation and strength, further enhance strength and toughness, and further refine grains. The combined effects of titanium and zirconium, along with rare earth elements such as scandium, lanthanum, and cerium, can further reduce the tendency toward coarsening, enhance certain high-temperature resistance, and optimize performance after aging heat treatment.

[0042] Preferably, RE is a rare earth mixture mainly composed of Sc, with Sc accounting for no less than 82% by weight in RE. Rare earth elements mainly composed of scandium can further refine grains and inhibit the precipitation of phases at grain boundaries.

[0043] The method for preparing a low-copper, high-strength aluminum alloy material provided by an embodiment of the present invention comprises:

[0044] The metal raw materials are put into the smelting furnace for smelting, and then slag removal, refining, casting, homogenization, extrusion molding and aging treatment are carried out in sequence to obtain low-copper and high-strength aluminum alloy materials.

[0045] Specifically, the preparation method is:

[0046] S1. Melting

[0047] Providing metal raw materials, including high-purity industrial aluminum ingots and alloys or pure metals used to meet the composition formula of low-copper high-strength aluminum alloy materials;

[0048] The metal raw materials are added into a medium frequency melting furnace, and the metal raw materials are completely melted and the temperature reaches 760-800° C. (eg, 760° C., 780° C., or 800° C.) to obtain a first melt.

[0049] S2, slag removal

[0050] Add slag-forming agent to the first melt, perform mechanical stirring for about 20 minutes, then start bidirectional electromagnetic stirring in the medium frequency furnace for 20 to 40 minutes, let it stand for about 30 minutes, and then skim off slag and remove impurities to obtain the second melt.

[0051] The slag forming agent is also called slagging agent or slag removing agent. In this step, a conventional slag forming agent that can be applied to aluminum alloy refining can be selected, such as at least one of CeO2 modified cryolite, Na3AlF6-CaF2-NaCl composite, CNPC Rare-3 (composition of CeO2 15% wt, La2O3 10% wt, NaCl 40% wt and KCl 35% wt), LZ-1 (composition of NaCl 48-52% wt, KCl 28-32% wt and borax 18-22% wt), fluorite, glauber salt, sodium nitrate and sodium fluorosilicate, etc. The ratio of the added amount of the slag forming agent to the mass of the first melt is 0.1-0.3:100.

[0052] S3, Refining

[0053] Heat the converter flow channel to ensure that the flow channel temperature reaches 260-300℃ (for example, 260℃, 280℃ or 300℃), and then transfer the alloyed second melt in the medium frequency furnace into the holding furnace, and control the holding furnace temperature between 760-850℃ (for example, 760℃, 780℃, 800℃, 830℃ or 850℃).

[0054] The temperature of the second melt is controlled at 740-800° C. in the insulation furnace for refining. The refining method is as follows: under an inert atmosphere, a refining agent is added to the second melt, and then an inert gas is introduced for two refining and degassing operations. After each refining and degassing operation with the inert gas, the melt is allowed to stand for 30-60 minutes, and then slag is removed. After refining, a third melt is obtained.

[0055] Preferably, in order to improve the purity of the finished aluminum alloy material, the refining times are twice, that is, adding refining agent, standing, and slag removal, and then adding refining agent again, standing, and slag removal.

[0056] Optionally, the standing time is 30 to 60 min (eg, 30 min, 40 min, or 60 min).

[0057] Optionally, the refining agent can be a conventional refining agent for refining aluminum alloys, such as the commercially available product GFLUX-J100, or a mixture of one or more conventional refining agents such as potassium chloride, sodium chloride, fluorite, calcium fluoride, potassium feldspar, aluminum fluoride, sodium nitrate and potassium carbonate.

[0058] S4, Casting

[0059] Before casting, the crystallizer is heated to above 220°C, and the flow channel of the casting converter is set to heat to above 280°C. The casting temperature is 710-730°C, and the ingot temperature is 690-740°C. Al-3Ti-0.1C wire is added simultaneously during casting, with the amount of wire feeding 1.8-2.2 kg per ton of aluminum liquid melted; the filter plate is replaced after each furnace, and all flow channel heating plates cannot be opened to maintain the inert gas atmosphere of the flow.

[0060] The casting adopts the wet well casting method. After casting is completed, ensure that the ingot is completely immersed in water until it is completely cooled.

[0061] After the casting is completed, the initial ingot is obtained.

[0062] S5. Homogenization

[0063] The primary ingot is homogenized to obtain a finished ingot.

[0064] Optionally, the homogenization process is:

[0065] The temperature of the initial ingot is raised to 330-355°C (e.g., 330°C, 340°C or 355°C) and kept warm for 10-14h (e.g., 10h, 12h or 14h), then raised to 438-488°C (e.g., 438°C, 450°C or 488°C) and kept warm for 8-16h (e.g., 8h, 10h, 13h or 16h), taken out of the furnace and air-cooled, and the opposite ends are sawed to obtain the finished ingot.

[0066] The low-temperature range (330-355°C) is mainly aimed at the dissolution of low-melting-point eutectic phases (such as Al-Si eutectic phase or Al-Cu-Mg eutectic phase). This temperature range can promote the diffusion of segregated elements between dendrites, alleviate local compositional inhomogeneities, and migrate solute elements (such as Cu and Mg) from high-concentration areas to low-concentration areas through long-term diffusion. This reduces the diffusion energy barrier for subsequent high-temperature treatment, avoids abnormal grain growth caused by excessively fast diffusion rate during direct high-temperature treatment, and thus refines the grains. At the same time, it avoids local overburning caused by rapid melting of low-melting-point phases due to direct high-temperature heating.

[0067] The high-temperature section (438-488°C) is used to dissolve high-melting-point intermetallic compounds (such as Al-Fe-Si phase and Al-Mn-Si phase) and residual refractory phases (such as AlCu and AlMg). The high-temperature section can significantly increase the diffusion coefficient of solute elements and shorten the time required to reach a homogenized equilibrium state (compared to a single-stage high-temperature process, the total time is better). At high temperatures, it promotes grain boundary migration and dislocation climb, reduces residual stress, and improves the plastic deformation capacity of subsequent hot or cold rolling. At high temperatures, the atomic diffusion rate is significantly increased (following the Arrhenius equation), which can more thoroughly eliminate intragranular segregation and improve the overall uniformity of the ingot.

[0068] Therefore, the two-stage homogenization treatment can reduce subsequent processing defects: it can eliminate more than 90% of dendrite segregation and reduce defects such as cracks and delamination caused by uneven structure during hot rolling or extrusion; it can also improve mechanical properties: the yield strength fluctuation of the ingot after homogenization is reduced by about 20%, and the elongation is increased by 15% to 30%, providing a more stable material foundation for subsequent deep processing.

[0069] Optionally, the length of the sawing at each end is, for example, 150 mm.

[0070] S6, extrusion molding

[0071] The rod-shaped ingot product is heated to 420-480°C (e.g., 420°C, 450°C, or 480°C) using a long rod furnace and kept at this temperature for a certain period of time;

[0072] When preparing for extrusion, the finished ingot obtained by homogenization is sawn to the required length according to the profile cross-section and extrusion ratio and peeled to obtain cast bars of appropriate size;

[0073] The cast rod is sent to the extruder and extruded through the die to form the profile. The discharge temperature is controlled to be no less than 420℃ and the profile is quenched online. The cooling method of water penetration, water spray, water mist and air cooling is determined by the cross section of the profile.

[0074] S7, aging treatment

[0075] The aging treatment temperature is 115-145° C. (eg, 115° C., 120° C., 130° C., or 145° C.), and the aging treatment time is 20-26 h (eg, 20 h, 22 h, 24 h, or 26 h).

[0076] Alternatively, preferably, when manufacturing products requiring high fatigue resistance, a two-stage solid solution treatment and a two-stage aging treatment are used. Specifically, the aging treatment is a two-stage aging treatment, and a two-stage solid solution treatment is also included between the two-stage aging treatment and the extrusion molding.

[0077] Specifically, the double-stage solution treatment includes: 420-460°C (for example, 420°C, 440°C or 460°C), treatment for 30-180 min (for example, 30 min, 60 min, 90 min or 180 min), heating to 440-470°C (for example, 440°C, 460°C or 470°C), treatment for 30-120 min (for example, 30 min, 60 min, 90 min or 180 min); the double-stage aging treatment includes: 100-125°C (for example, 100°C, 110°C or 125°C), treatment for 12-20 h (for example, 12 h, 15 h, 18 h or 20 h), heating to 145-175°C (for example, 145°C, 160°C or 175°C), treatment for 2-3 h (for example, 2 h, 2.5 h or 3 h).

[0078] Unlike conventional solution-aging schemes, the two-stage solution-aging scheme adopts low-temperature solution in the early stage to ensure that the grain size does not exceed the control requirements, improve the corrosion resistance of the alloy, and thus help to increase the crack propagation rate. In the later stage, high-temperature solution is adopted for a certain period of time to ensure better precipitation strengthening phase and maintain the higher strength of the aluminum alloy. In the bipolar aging treatment, low-temperature aging is adopted in the early stage to promote the formation of fine precipitates after the addition of rare earths, and the distribution is more uniform, so the time will be longer. In the later stage, a short high-temperature aging is adopted to promote the formation of better stable strengthening phases of Cu and Mn, further maintain the strength of the alloy, and at the same time, a shorter time can further improve the stress corrosion resistance, thereby obtaining a higher fatigue limit.

[0079] Example 1

[0080] The low-copper, high-strength aluminum alloy material provided in this embodiment has the following elemental composition:

[0081]

[0082] The Re includes Sc in an amount of not less than 82% by mass, and the remaining rare earth element in the Re is La.

[0083] The preparation method of the low-copper, high-strength aluminum alloy material provided in this embodiment is specifically as follows:

[0084] High-purity industrial aluminum ingots, pure metal zinc, pure metal magnesium, pure metal copper, Al-Zr master alloy, Al-Cr master alloy, and aluminum-scandium alloy are added as raw materials into a medium frequency melting furnace according to the above target composition, and the metal raw materials are completely melted and the temperature reaches 780°C to obtain a first melt;

[0085] 0.2 kg of slagging agent (components by weight are 15% SrCl2, 18% LaCl3 and 30% sodium fluorosilicate, and the balance is fluorite) is added to every 100 kg of the first melt, and mechanical stirring is performed for about 20 minutes. Then, a medium-frequency furnace is turned on for two-way electromagnetic stirring for 30 minutes, and the mixture is allowed to stand for about 30 minutes. Then, slag removal is performed to obtain a second melt.

[0086] Heat the converter runner to ensure that the runner temperature reaches 280°C, then transfer the alloyed second melt in the medium frequency furnace to a holding furnace, and control the holding furnace temperature to 800°C. In the holding furnace, control the temperature of the second melt to 800°C. Under an argon atmosphere, add a refining agent (composition by weight is 50% GFLUX-J100, 20% SrCl2, 22% LaCl3, and the balance is CaF2) to every 100 kg of the melt, then pass argon for two refinings. After each argon refining, let it stand for 40 minutes before skimming the slag.

[0087] After refining, a third melt is obtained;

[0088] Heat the crystallizer to 250°C, set the heated casting converter flow channel to 300°C, the casting temperature to 700°C, the ingot plate temperature to 700°C, and transfer the third melt to the casting furnace for casting. The filter plate is replaced with each furnace, and all the flow channel heating plates cannot be opened to maintain the inert gas atmosphere. Al-3Ti-0.1C wire is added simultaneously during casting, with the amount of wire feeding 2kg per ton of aluminum liquid melted. Use the wet well casting method. After casting, ensure that the ingot is completely immersed in water until it is completely cooled to obtain the initial ingot.

[0089] The temperature of the initial ingot was raised to 340°C and kept for 12 hours, then raised to 450°C and kept for 8 hours, then taken out of the furnace and air-cooled, and the ingot was sawed off 150 mm at each end to obtain the finished ingot;

[0090] Use a long rod furnace to heat the rod-shaped ingot product to 450℃ and keep it warm for 30 minutes;

[0091] The homogenized ingots were sawn to the required length and peeled to obtain cast bars of appropriate size (120 mm). The cast bars were fed into an extruder and extruded through a split die into hollow profiles with a wall thickness of 1.8 mm. The discharge temperature was controlled to be no less than 480°C, and the bars were quenched online.

[0092] After quenching, the material was placed at 440°C for solution treatment for 60 minutes, heated to 460°C and treated for 60 minutes; then cooled to 110°C and aged for 16 hours, and then heated to 160°C and treated for 2.5 hours.

[0093] Example 2

[0094] The low-copper, high-strength aluminum alloy material provided in this embodiment has the following elemental composition:

[0095]

[0096] Here, Re includes Sc which accounts for 82% by mass, and the remaining rare earth elements in Re are La.

[0097] The preparation method of the low-copper, high-strength aluminum alloy material provided in this embodiment is specifically as follows:

[0098] High-purity industrial aluminum ingots, pure metal zinc, pure metal magnesium, pure metal copper, Al-Zr master alloy, Al-Cr master alloy, and aluminum-scandium alloy are added as raw materials into a medium frequency melting furnace according to the above target composition, and the metal raw materials are completely melted and the temperature reaches 760°C to obtain a first melt;

[0099] 0.1 kg of slagging agent (same as in Example 1) was added to every 100 kg of the first melt, and mechanical stirring was performed for about 20 minutes. Then, the medium frequency furnace was turned on for two-way electromagnetic stirring for 20 minutes, and the mixture was allowed to stand for about 30 minutes. Then, slag removal was performed to obtain a second melt.

[0100] Heat the converter flow channel to ensure that the flow channel temperature reaches 260°C, then transfer the alloyed second melt in the medium frequency furnace to the holding furnace, and control the holding furnace temperature to 760°C. Control the temperature of the second melt in the holding furnace to 760°C. Under an argon atmosphere, add 0.2 kg of refining agent (same as Example 1) to every 100 kg of melt, and then pass argon to perform two refinings. After each argon refining, let it stand for 30 minutes, and then skim off the slag. After refining, the third melt is obtained;

[0101] Heat the crystallizer to 220°C, set the heated casting converter flow channel to 280°C, the casting temperature to 680°C, the ingot plate temperature to 690°C, and transfer the third melt to the casting furnace for casting. The filter plate is replaced after each furnace, and all the flow channel heating plates cannot be opened to maintain the inert gas atmosphere. Al-3Ti-0.1C wire is added simultaneously during casting, with the amount of wire feeding 2kg per ton of aluminum liquid melted. Use the wet well casting method. After casting, ensure that the ingot is completely immersed in water until it is completely cooled to obtain the initial ingot.

[0102] The temperature of the initial ingot was raised to 330°C and kept for 14 hours, then raised to 438°C and kept for 10 hours, then taken out of the furnace and air-cooled, and the ingot was sawed off 150 mm at each end to obtain the finished ingot;

[0103] Use a long rod furnace to heat the rod-shaped ingot product to 420℃ and keep it warm for 30 minutes;

[0104] The homogenized ingot was sawn to the required length and peeled to obtain a cast rod of appropriate size (152 mm). The cast rod was sent to an extruder and extruded into a hollow profile with a wall thickness of 1.8 mm through a diverter die. The discharge temperature was controlled to be no less than 480°C and the rod was quenched online.

[0105] After quenching, the material was placed at 420°C for solution treatment for 180 minutes, heated to 440°C and treated for 180 minutes; then cooled to 100°C and aged for 20 hours, and then heated to 145°C and treated for 2 hours.

[0106] Example 3

[0107] The low-copper, high-strength aluminum alloy material provided in this embodiment has the following elemental composition:

[0108]

[0109] Here, Re includes Sc which accounts for 82% by mass, and the remaining rare earth elements in Re are La.

[0110] The preparation method of the low-copper, high-strength aluminum alloy material provided in this embodiment is specifically as follows:

[0111] High-purity industrial aluminum ingots, pure metal zinc, pure metal magnesium, pure metal copper, Al-Zr master alloy, Al-Cr master alloy, and aluminum-scandium alloy are added as raw materials into a medium frequency melting furnace according to the above target composition, and the metal raw materials are completely melted and the temperature reaches 800° C. to obtain a first melt;

[0112] 0.15 kg of slagging agent (same as in Example 1) was added to every 100 kg of the first melt, and mechanical stirring was performed for about 20 minutes. Then, the medium frequency furnace was turned on for bidirectional electromagnetic stirring for 40 minutes, and the mixture was allowed to stand for about 30 minutes. Then, slag removal was performed to obtain a second melt.

[0113] The converter flow channel was heated to ensure that the flow channel temperature reached 300°C, and then the second melt alloyed in the medium frequency furnace was transferred to a holding furnace, and the holding furnace temperature was controlled at 850°C. The temperature of the second melt was controlled at 850°C in the holding furnace. Under an argon atmosphere, 0.25 kg of refining agent (same as in Example 1) was added to every 100 kg of the melt, and then argon was introduced for two refining operations. After each argon refining operation, the melt was allowed to stand for 30 minutes.

[0114] After refining, a third melt is obtained;

[0115] Heat the crystallizer to 260°C, set the heated casting converter flow channel to 320°C, the casting temperature to 720°C, the ingot plate temperature to 720°C, and transfer the third melt to the casting furnace for casting. The filter plate is replaced after each furnace, and all the flow channel heating plates cannot be opened to maintain the inert gas atmosphere. Al-3Ti-0.1C wire is added simultaneously during casting, with the amount of wire feeding 2kg per ton of aluminum liquid melted. Use the wet well casting method. After casting, ensure that the ingot is completely immersed in water until it is completely cooled to obtain the initial ingot.

[0116] The temperature of the initial ingot was raised to 355°C and kept for 10 hours, then raised to 488°C and kept for 7 hours, then taken out of the furnace and air-cooled, and the ingot was sawed 150 mm at each end to obtain the finished ingot;

[0117] Use a long rod furnace to heat the rod-shaped ingot product to 480℃ and keep it warm for 30 minutes;

[0118] The homogenized ingots were sawn to the required length and peeled to obtain cast bars of appropriate size (178 mm). The cast bars were fed into an extruder and extruded through a split die into hollow profiles with a wall thickness of 1.8 mm. The discharge temperature was controlled to be no less than 480°C, and the bars were quenched online.

[0119] After quenching, the material was placed at 460°C for solution treatment for 30 minutes, then heated to 470°C for treatment for 30 minutes; then cooled to 125°C for aging treatment for 12 hours, and then heated to 175°C for treatment for 3 hours.

[0120] Example 4

[0121] The preparation method of this embodiment is basically the same as that of Example 3, except that the low-copper, high-strength aluminum alloy material provided in this embodiment has the following elemental composition:

[0122]

[0123] Example 5

[0124] The preparation method of this embodiment is basically the same as that of Example 3, except that the low-copper, high-strength aluminum alloy material provided in this embodiment has the following elemental composition:

[0125]

[0126] Example 6

[0127] The preparation method of this embodiment is basically the same as that of Example 3, except that the low-copper, high-strength aluminum alloy material provided in this embodiment has the following elemental composition:

[0128]

[0129] Example 7

[0130] This embodiment is basically the same as embodiment 1, except that the components do not contain titanium.

[0131] Example 8

[0132] This embodiment is basically the same as embodiment 1, except that aging treatment is performed directly after quenching, and the aging treatment conditions are 120° C. and the time is 24 hours.

[0133] Example 9

[0134] This embodiment is basically the same as embodiment 1, except that after quenching, the material is placed at 470°C for solution treatment for 60 minutes; then the temperature is lowered to 125°C for aging treatment for 12 hours, and then the temperature is raised to 175°C for 3 hours.

[0135] Example 10

[0136] This embodiment is basically the same as embodiment 1, except that after quenching, the material is placed at 460°C for solution treatment for 30 minutes, then heated to 470°C for treatment for 30 minutes; then cooled to 125°C and aged for 15 hours.

[0137] Comparative Example 1

[0138] This comparative example is substantially the same as Example 1, except that the Zn content is reduced to 7.0%, the magnesium content is reduced to 1.5%, and the copper content is increased to 1.5%.

[0139]

[0140] Comparative Example 2

[0141] This comparative example is substantially the same as Example 1, except that the Zn content is reduced to 7.0%.

[0142] Comparative Example 3

[0143] This comparative example is substantially the same as Example 1, except that the Mg content is reduced to 1.5%.

[0144] Comparative Example 4

[0145] This comparative example is basically the same as Example 1, except that no rare earth element is added.

[0146] Comparative Example 5

[0147] This comparative example is basically the same as Example 1, except that it does not contain copper element.

[0148] Comparative Example 6

[0149] This comparative example is basically the same as Example 1, except that the copper content is 1.8.

[0150] Experimental Example 1

[0151] The tensile strength, yield strength, elongation of the aluminum alloy materials prepared in various embodiments and comparative examples, as well as the weldability of some embodiments, were tested.

[0152] The test methods for tensile strength, yield strength and elongation refer to GB / T16865.

[0153] The test method for weldability is: manually weld the aluminum alloy material, and then test the strength of the weld. If the weld strength reaches 55% of the parent material performance, the weldability is considered good.

[0154] Record the test results in Table 1.

[0155] Table 1 Mechanical properties of various embodiments and comparative examples

[0156]

[0157] It can be seen from Table 1 that the aluminum alloy materials provided by various embodiments of the present invention have relatively high tensile strength, yield strength, elongation and weldability.

[0158] Comparing Example 7 with Example 1, the strength and elongation of Example 7 are relatively poor, indicating that adding titanium to the components can improve the strength and elongation of the aluminum alloy;

[0159] Comparing Example 8 with Example 1, the strength and elongation of Example 8 are relatively poor, indicating that the method of two-step solution treatment followed by two-step aging treatment after press forming can better improve the mechanical properties of the aluminum alloy compared with direct aging treatment after extrusion;

[0160] Comparing Example 9 and Example 1, Example 8 is a single-stage solid solution treatment, and Example 10 is a single-stage aging treatment. The strength and elongation of the materials of Example 9 and Example 10 are worse than those of Example 1, indicating that the double-stage solid solution plus double-stage aging treatment can better improve the strength and elongation of the aluminum alloy;

[0161] Comparing Comparative Example 1 with Example 1, Comparative Example 1 is a 7-series aluminum alloy material currently added with rare earth elements. The strength and elongation of Comparative Example 1 are significantly worse, indicating that the present invention can improve the strength and elongation of the aluminum alloy by increasing the zinc content and the magnesium content and reducing the copper content;

[0162] Comparing Comparative Example 2 with Example 1, the strength of Comparative Example 2 is significantly worse, indicating that reducing the zinc content will reduce the strength of the aluminum alloy;

[0163] Comparing Comparative Example 3 with Example 1, the strength of Comparative Example 3 is significantly worse, indicating that although the zinc content of the aluminum alloy is high, under the condition of low magnesium content, sufficient fine dispersed MgZn2 phase cannot be formed, and it is difficult to significantly improve the strength of the aluminum alloy;

[0164] Comparing Comparative Example 4 with Example 1, the strength and elongation of Comparative Example 4 are significantly worse, indicating that it is difficult to improve the strength and elongation of the aluminum alloy by simply increasing the content of zinc and magnesium without adding rare earth elements.

[0165] Comparing Comparative Example 5 with Example 1, the strength of Comparative Example 5 is significantly worse, indicating that if copper is not added to the composition, the strength will be reduced. Therefore, although the copper content is reduced on the basis of the 7 series aluminum alloy in this application, the lower the copper content, the better it is not.

[0166] Comparing Comparative Example 6 with Example 1, the elongation of Comparative Example 6 is significantly worse, indicating that a higher copper content will reduce the strength of the aluminum alloy.

[0167] In summary, the low-copper, high-strength aluminum alloy material provided by the embodiment of the present invention has a better composition ratio, so it can achieve material mechanical properties with a yield strength of more than 600 MPa, while maintaining sufficient elongation and the ability to extrude thin-walled hollow profiles within 2 mm through a split die.

[0168] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A low-copper, high-strength aluminum alloy material, characterized in that: Calculated by mass fraction, it includes the following ingredients: Zn 7.3-8.3%, Mg 2.2-3.2%, Cu 0.2-0.8%, Zr 0.05-0.3%, RE 0.05-0.3%, Ti 0-0.13%, Fe <0.13%, Si <0.12%, impurity elements <0.15%, and the balance is aluminum.

2. The low-copper, high-strength aluminum alloy material according to claim 1, characterized in that: The Ti content is 0.01 to 0.13%.

3. The low-copper, high-strength aluminum alloy material according to claim 1, characterized in that: RE is a rare earth mixture mainly composed of Sc, and the mass proportion of Sc in RE is not less than 82%.

4. A method for preparing a low-copper, high-strength aluminum alloy material according to any one of claims 1 to 3, characterized in that: include: The metal raw materials are put into a smelting furnace for smelting, and then slag removal, refining, casting, homogenization, extrusion molding and aging treatment are carried out in sequence to obtain the low-copper high-strength aluminum alloy material.

5. The preparation method according to claim 4, characterized in that Specifically include: Providing the metal raw material, which includes high-purity industrial aluminum ingots and alloys or pure metals that meet the composition formula of the low-copper high-strength aluminum alloy material; Adding the metal raw material into a smelting furnace, melting the metal raw material until the temperature reaches 760-800° C., and obtaining a first melt; adding a slag-forming agent to the first melt, mixing the mixture evenly and allowing the mixture to stand, and then skimming the slag to obtain a second melt; The temperature of the second melt is controlled to be 740-800° C. and refined by adding a refining agent to the second melt under an inert atmosphere, then passing an inert gas through the second melt for two refining and degassing operations, each of which is followed by standing for 30-60 minutes and then skimming the slag; and obtaining a third melt after refining. Casting the third melt to obtain a primary ingot; homogenizing the primary ingot to obtain a finished ingot; The finished ingot is subjected to extrusion molding and aging treatment in sequence.

6. The preparation method according to claim 5, characterized in that The method of casting the third melt includes: Before casting, heat the crystallizer to above 220℃, set the heating casting converter runner to above 280℃, the casting temperature is 710-730℃, the ingot temperature is 690-740℃, and Al-3Ti-0.1C wire is added simultaneously during casting. The amount of wire used is 1.8-2.2kg per ton of molten aluminum. Alternatively, the casting is performed using the wet well casting method, where after casting, the ingot is completely immersed in water until it is completely cooled.

7. The preparation method according to claim 5, characterized in that The method of homogenizing the primary ingot to obtain a finished ingot includes: The temperature of the primary ingot is raised to 330-355° C. and kept warm for 5-12 hours, then raised to 438-488° C. and kept warm for 8-16 hours, taken out of the furnace and air-cooled, and the opposite ends are sawed to obtain the finished ingot.

8. The preparation method according to claim 5, characterized in that Extrusion molding methods include: The finished ingot with suitable size and temperature of 420-480° C. is sent to an extruder, extruded into a shaped material through a die, the discharge temperature is controlled to be not less than 460° C., and online quenching is performed.

9. The preparation method according to claim 5, characterized in that The aging treatment temperature is 115-145°C and the time is 20-26 hours; Alternatively, the aging treatment is a two-stage aging treatment, which also includes a two-stage solution treatment between the two-stage aging treatment and the extrusion molding; The double-stage solution treatment method includes: 420-460℃, treatment for 30-180min, heating to 440-470℃, treatment for 30-120min; The double-stage aging treatment method includes: 100-125°C, treatment for 12-20 hours, heating to 145-175°C, and treatment for 2-3 hours.

10. Use of the low-copper, high-strength aluminum alloy material according to any one of claims 1 to 3 in manufacturing thin-walled hollow structures of 1.8 to 2.2 mm through diverter die extrusion, manufacturing aerospace profiles, manufacturing new energy battery trays, or manufacturing anti-collision beams.

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