Security recovery method for 7-series aluminum alloy processing aluminum skimmings, regenerated 7-series aluminum alloy cast ingot and application of regenerated 7-series aluminum alloy cast ingot

Abstract

The invention provides a grade-preserving recovery method for 7-series aluminum alloy processing aluminum skimmings, a regenerated 7-series aluminum alloy cast ingot and application of the regenerated 7-series aluminum alloy cast ingot. The grading recovery method comprises the following steps: S1, a smelting stage; step S2, a refining stage: step S2-1, carrying out first refining on the first melt to obtain a second melt; step S2-2, proportioning the second melt according to the components of the regenerated melt to be prepared to obtain a third melt; step S2-3, carrying out second refining on the third melt in a protective atmosphere to obtain a fourth melt; s3, a purification stage; and S4, a casting stage. The side well furnace and the smelting furnace cooperate to serve as a continuous aluminum skimming melting system, the aluminum skimming burning loss rate in the recycling and smelting process can be remarkably reduced, the content of slag, hydrogen and alkali metal in the obtained regenerated melt can be effectively reduced through in-furnace two-stage refining, out-of-furnace degassing and filtering means purification, and the purity of the regenerated melt is guaranteed.

Description

Technical Field

[0001] The invention relates to the field of aluminum alloy processing, and in particular to a grade-preserving recovery method for aluminum chips processed from 7-series aluminum alloys to regenerate 7-series aluminum alloy ingots and applications thereof. Background Art

[0002] 7 series (Al-Zn-Mg-Cu series) aluminum alloy is a heat-treatable and strengthened aluminum alloy with comprehensive properties such as high strength, high toughness, and corrosion resistance. It is widely used in the aerospace field and is a key material for important structural parts such as aircraft fuselage frames, tail wings, and wing beams. However, since one of the raw materials for manufacturing 7 series aluminum alloys, namely electrolytic aluminum, consumes a lot of energy in its production process and has expensive environmental protection treatment costs, the development of the electrolytic aluminum industry has been sluggish and the supply has been insufficient. At the same time, the low yield rate in the actual production process of 7 series aluminum alloys has led to an increasing amount of waste accumulation in aluminum processing companies. In addition, during the machining of back-end products, the utilization rate of aluminum alloys is only about 5%, and almost all of the remaining materials are processed into waste aluminum chips, resulting in an increasing amount of aluminum chips stockpiled. If these aluminum chips are not recycled and reused at an accelerated rate, it will not only cause a waste of resources, but may also pollute the environment, bringing greater stockpiling pressure to companies.

[0003] However, there are the following technical problems in the recycling of 7 series aluminum alloy scraps: (1) The remelting of aluminum scraps causes large oxidation and burning losses: Aluminum scraps are small in size and large in specific surface area. If loose aluminum scraps are directly remelted, they will float on the surface of the molten pool, resulting in severe oxidation and burning losses and a low recovery rate. (2) The melt quality of remelted aluminum scraps is unstable: Aluminum scraps are easily burned during the smelting process, resulting in extremely unstable melt chemical composition and melt quality, and a high level of slag inclusions. It is difficult to meet the high-quality control requirements of slag inclusions and hydrogen content for high-performance aviation aluminum alloys, resulting in low yields. (3) Some aluminum scraps contaminated by oil and water are difficult to remelt directly: Since cutting fluid is used in the ingot casting process, most of the aluminum scraps are affected by the residence time in the factory and the storage environment, resulting in serious oil and water contamination on the surface and unable to evaporate effectively. A large amount of smoke will be generated during the smelting process, seriously polluting the environment, and easily causing a sharp increase in the gas and slag content of the melt, seriously affecting its recyclability.

[0004] Prior art CN 115341110 A proposes a method for recycling aluminum chips from aviation aluminum alloy processing, including pretreatment, pressing and oxygen-controlled smelting and refining. However, the prior art mainly first uses a pyrometallurgical high-temperature roasting of aluminum chips, then presses the aluminum chips into blocks by pressing, then controls oxygen smelting of the blocky aluminum chips in a smelting furnace to form an aluminum alloy melt, and finally casts it into an aluminum alloy ingot. First, due to the high-temperature roasting process and the oxygen-controlled smelting process, this method consumes a lot of energy and oxygen, and the cost is relatively high; secondly, the oxygen-controlled smelting process is difficult to improve on the existing smelting furnace, and is only suitable for small-batch production tests. The size of the cast aluminum alloy ingot is small, and it is difficult to mass-produce on a large scale; thirdly, because the method has no online purification link, it is difficult to ensure that the final melt quality meets the high quality control requirements of aviation aluminum alloys. Therefore, there is a large technical route difference between this method and the 100% grade-preserving recovery smelting process of aluminum chips proposed in the present invention.

[0005] Prior art CN 116287905 A proposes a method for recycling and regenerating 7-series aviation thick plates from machining waste, in which machining aluminum chips and primary waste are added to a waste smelting furnace in a ratio of 1:4 for smelting. However, in this method, the aluminum chips are severely oxidized and burned, and the purity of the melt is low. It is necessary to strictly control the heat treatment and rolling parameters in the subsequent process to ensure its performance, and the universality is poor.

[0006] Numerous studies have shown that the remelting of aluminum chips to obtain high-quality recycled ingots requires the coordinated coordination of multiple process parameters. Especially for the recycling of aluminum chips for high-performance 7-series aviation aluminum alloys, the optimization and screening of various parameter conditions in the recycling, melting and recasting process is more important. However, from the perspective of production practice and literature review, the existing technology has not yet conducted in-depth research on aluminum chip melting furnace types, melting methods, purification processes, etc., which has seriously restricted the development of grade-preserving recycling technology for 7-series aluminum alloy processing aluminum chips.

[0007] Therefore, how to develop a grade-preserving recycling and smelting method for aluminum chips processed from 7 series aluminum alloys to improve the recovery rate of aluminum chips from 7 series aluminum alloys, improve the melt purity of the recycled 7 series aluminum alloys, and break through the existing technical bottleneck of aluminum chip recycling is one of the important technical problems that need to be solved in this field. Summary of the invention

[0008] The main purpose of the present invention is to provide a method for grade-preserving recovery of aluminum chips from 7 series aluminum alloy processing to regenerate 7 series aluminum alloy ingots and applications thereof, so as to solve the problem in the prior art that it is difficult to grade-preserving recovery and smelting of aluminum chips from 7 series aluminum alloy processing and prepare a 7 series aluminum alloy melt with high purity.

[0009] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a method for grade-preserving and recycling aluminum chips processed by 7-series aluminum alloys, wherein the aluminum chips processed by 7-series aluminum alloys are 7-series aviation aluminum alloy processing aluminum chips produced in the aerospace field, and the method for grade-preserving and recycling aluminum chips processed by 7-series aluminum alloys comprises: step S1, smelting stage: step S1-1, in a smelting furnace, the first-level waste of the 7-series aluminum alloy is melted for the first time to obtain a bottoming aluminum liquid; through a circulating pump, the bottoming aluminum liquid is flowed from the smelting furnace into a side well furnace; step S1-2, in the side well furnace, the 7-series aluminum alloy processing aluminum chips are mixed with the bottoming aluminum liquid, and a first melt is obtained after a second melting; during the second melting process, the circulating pump is kept on and the circulation direction is changed to allow the first melt to circulate in the side well furnace and the smelting furnace; the thickness of the aluminum chips processed by the 7-series aluminum alloy is 0.1mm~5.0mm, and the sheet diameter is 10mm~60mm; step S2, fine Refining stage: step S2-1, subjecting the first melt to a first refining for 15min~60min to obtain a second melt; step S2-2, proportioning the second melt according to the composition of the regenerated melt to be prepared to obtain a third melt; step S2-3, subjecting the third melt to a second refining in a protective atmosphere to obtain a fourth melt; the second refining includes a refining process and a standing process, and the refining process takes 15min~60min, and the standing process takes 30min~120min; step S3, purification stage: step S3-1, subjecting the fourth melt to three-rotor degassing to obtain a fifth melt; step S3-2, subjecting the fifth melt to online filtration to obtain a regenerated melt; the filter plate accuracy of the filter used for online filtration is ≥30PPI; step S4, casting stage: the regenerated melt is cast to obtain a regenerated 7 series aluminum alloy ingot.

[0010] Further, in step S1, when the temperature of the base aluminum liquid is 720°C~760°C, the base aluminum liquid is flowed from the smelting furnace into the side well furnace through a circulation pump; the circulation pump is kept on, and the 7 series aluminum alloy processing aluminum chips are mixed with the base aluminum liquid and a second melting is performed.

[0011] Further, step S2-1 is performed in a smelting furnace, and step S2-1 also includes adding a refining agent in an amount of 0.8 kg / ton of melt to 1.2 kg / ton of melt to the first melt, and then performing the first refining.

[0012] Furthermore, in step S2-2, when the temperature of the second melt is 730°C~750°C, the second melt is batched; preferably, step S2-2 also includes: when the temperature of the third melt is 740°C~760°C, the third melt is transferred to a holding furnace, and the second refining in step S2-3 is performed.

[0013] Furthermore, in step S2-3, the refining process takes 15 min to 45 min, and the standing process takes 30 min to 90 min.

[0014] Furthermore, in step S2-3, the flow rate of the protective atmosphere is 2.0 m 3 / h~4.0m 3 / h; preferably, the protective atmosphere is nitrogen and / or argon.

[0015] Furthermore, in step S3-2, the filter is a double-stage plate filter, and the accuracy of the filter plate used for the first-stage filtration is 30PPI~40PPI, and the accuracy of the filter plate used for the second-stage filtration is 50PPI~60PPI.

[0016] Furthermore, in the regenerated melt, the slag content is 0.005 mm 2 / kgAl~0.030mm 2 / kgAl, the hydrogen content is 0.01mL / 100g Al~0.10mL / 100g Al, and the alkali metal content is 2ppm~6ppm.

[0017] The second aspect of the present invention provides a recycled 7 series aluminum alloy ingot, which is prepared by the above-mentioned 7 series aluminum alloy processing aluminum chips grade preservation recovery method, and the components of the recycled 7 series aluminum alloy ingot include, by weight percentage: 0.020wt.%~0.040wt.% Si, 0.05wt.%~0.09wt.% Fe, 2.0wt.%~2.4wt.% Cu, 0.0005wt.%~0.0040wt.% Mn, 1.90wt.%~2.30wt.% Mg, 0.004wt.%~0.007wt.% Cr, 6.0wt.%~6.6wt.% Zn, 0.02wt.%~0.04wt.% Ti, 0.09wt.%~0.12wt.% Zr, and the rest is Al.

[0018] A third aspect of the present invention provides an application of the above-mentioned recycled 7 series aluminum alloy ingot as a structural material in the aerospace field.

[0019] By applying the technical solution of the present invention, a grade-preserving recovery and smelting method for aluminum chips processed in 7 series aluminum alloys is provided. By using a smelting furnace and a side shaft furnace in coordination, and simultaneously undergoing two-stage refining in the furnace and degassing and purification by filtering means outside the furnace, the burning rate of aluminum chips in the recovery and smelting process can be significantly reduced, and at the same time, the slag, hydrogen and alkali metal contents in the obtained regenerated melt can be effectively reduced to ensure its purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 This is a metallographic photograph of the regenerated melt obtained in Comparative Example 2, wherein Al2O3 inclusions are shown;

[0022] Figure 2 This is a metallographic photograph of the regenerated melt obtained in Comparative Example 2, wherein MgO inclusions are shown;

[0023] Figure 3 is a metallographic photograph of the regenerated melt obtained in Comparative Example 2, wherein MgO and spinel inclusions are shown;

[0024] Figure 4 The metallographic photograph of the regenerated melt obtained in Comparative Example 2 shows Ti particle inclusions and Al2O3 inclusions;

[0025] Figure 5 This is a metallographic photograph of the recycled 7 series aluminum alloy ingot obtained in Comparative Example 6;

[0026] Figure 6 This is a scanning electron microscope photograph of the recycled 7 series aluminum alloy ingot obtained in Comparative Example 6. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0028] As described in the background art, the prior art has the problem that it is difficult to recycle and smelt aluminum chips from 7 series aluminum alloy processing in a grade-preserving manner and to prepare a 7 series aluminum alloy melt with high purity. In order to solve the above technical problems, the first aspect of the present invention provides a method for grade-preserving and recycling aluminum chips processed by 7 series aluminum alloys, wherein the aluminum chips processed by 7 series aluminum alloys are 7 series aviation aluminum alloy processing aluminum chips produced in the aerospace field, and the method for grade-preserving and recycling aluminum chips processed by 7 series aluminum alloys comprises: step S1, smelting stage: step S1-1, in a smelting furnace, the first-level waste of the 7 series aluminum alloy is first melted to obtain a bottoming aluminum liquid; through a circulating pump, the bottoming aluminum liquid is flowed from the smelting furnace to the side well furnace; step S1-2, in the side well furnace, the 7 series aluminum alloy processing aluminum chips are mixed with the bottoming aluminum liquid, and a first melt is obtained after a second melting; during the second melting process, the circulating pump is kept on and the circulation direction is changed to allow the first melt to circulate in the side well furnace and the smelting furnace; the thickness of the aluminum chips processed by the 7 series aluminum alloys is 0.1mm~5.0mm, and the sheet diameter is 10mm~60mm; step S2, Refining stage: step S2-1, performing a first refining of the first melt for 15min~60min to obtain a second melt; step S2-2, batching the second melt according to the composition of the regenerated melt to be prepared to obtain a third melt; step S2-3, performing a second refining of the third melt in a protective atmosphere to obtain a fourth melt; the second refining includes a refining process and a standing process, and the refining process takes 15min~60min, and the standing process takes 30min~120min; step S3, purification stage: step S3-1, performing three-rotor degassing on the fourth melt to obtain a fifth melt; step S3-2, performing online filtration on the fifth melt to obtain a regenerated melt; the filter plate accuracy of the filter used for online filtration is ≥30PPI; step S4, casting stage: the regenerated melt is cast to obtain a regenerated 7 series aluminum alloy ingot.

[0029] The above-mentioned grade-preserving recovery method for aluminum chips (hereinafter referred to as aluminum chips) processed by 7 series aluminum alloys provided by the present invention includes the following steps: (i) continuous melting stage: a side shaft furnace and a smelting furnace are used in combination as a continuous melting system for aluminum chips; (ii) refining stage: a first refining before batching and a second refining under a protective atmosphere after batching are designed, and the time parameters of the two refining processes are precisely controlled to achieve deep and effective impurity removal of the melt; (iii) purification stage: a three-rotor degassing system is used, and the accuracy of the filter plate in the filter used in the filtering step is strictly controlled to finally purify, degas, filter and remove impurities from the melt, and finally obtain a high-purity regenerated melt, which is cast into an aluminum alloy ingot with excellent performance.

[0030] In particular, during the first refining process, the time of the first refining is strictly controlled to be 15min~60min, so as to more effectively remove the gas and inclusions in the first melt in advance, and ensure the purity and performance stability of the obtained regenerated melt. In the second refining process including the refining process and the static process, the time of the refining process is limited to 15min~60min, and the time of the static process is limited to 30min~120min, so as to further purify the melt under the condition of the presence of a protective atmosphere, minimize the internal defects that may exist in the subsequent process, and ensure the high purity of the regenerated melt and the comprehensive performance of the final aluminum alloy ingot. And, in the purification stage, the accuracy of the filter plate used in the online filtration is ≥30PPI. Based on the high-purity melt obtained after two refining processes, this high-precision filter plate is used to thoroughly remove the tiny impurities in the regenerated melt and improve its internal purity.

[0031] In particular, the above-mentioned steps in the grade-preserving recovery smelting method provided by the present invention cooperate with each other as an overall technical solution, that is, forming a complete technical route of "melting the base aluminum liquid in the smelting furnace → melting aluminum chips in the side well furnace → first refining → component detection and ingredient adjustment → second refining (including refining and standing) → online three-rotor degassing → online filtration → casting". For the grade-preserving recovery of aluminum chips processed by 7 series aluminum alloys, compared with the conventional methods including refining and degassing filtration processes commonly used in the field, there are fewer impurities, bubbles and other inclusions that may be left in the melt, and the purity of the regenerated melt obtained in the end is also higher. In other words, the above-mentioned steps in the grade-preserving recovery method provided by the present invention, in addition to the advantages of recovery and impurity removal themselves, are more importantly able to cooperate with each other, that is, as an overall solution, to achieve grade-preserving recovery of aluminum chips processed by 7 series aluminum alloys with low burn-out rate and high recovery rate.

[0032] In practical applications, it should be noted that, during the smelting stage, except for the first smelting (i.e., the first furnace), the first-level scrap must be added to the furnace and melted into the bottoming aluminum liquid. For the remaining furnaces, the remaining aluminum liquid in the smelting furnace can be used as the bottoming aluminum liquid, and it is pumped into the side well furnace for subsequent melting steps. Also, in step S1-1, the amount of bottoming aluminum liquid in the smelting furnace should be no less than 1 / 3 of the smelting furnace, so that the aluminum liquid in the smelting furnace can reach the liquid level height for the circulation pump to be normally opened. Also, in step S1-2, the 7 series aluminum alloy processing aluminum chips are transported to the side well furnace by a conveyor belt to mix with the bottoming aluminum liquid, and the aluminum chips conveying speed is preferably less than the melting speed of the aluminum chips therein.

[0033] The above-mentioned recycling smelting method can prepare a high-purity recycled melt with a high recovery rate, and in particular can achieve excellent grade preservation of aluminum alloys, so it is particularly suitable for the aerospace field that has extremely high requirements for the purity of aluminum alloy melts. Therefore, it is preferred that the 7-series aluminum alloy processing aluminum chips are 7-series aviation aluminum alloy processing aluminum chips generated in the aerospace field. At the same time, during the smelting process, it is preferred that the 7-series aluminum alloy primary waste is 7-series aviation aluminum alloy ingot cutting head and / or tail cutting waste. And, by weight percentage, the 7 series aluminum alloy primary scrap used includes 0.030wt.%~0.035wt.% Si, 0.06wt.%~0.080wt.% Fe, 2.2wt.%~2.4wt.% Cu, 0.004wt.%~0.006wt.% Mn, 2.00wt.%~2.30wt.% Mg, 0.001wt.%~0.003wt.% Cr, 6.1wt.%~6.5wt.% Zn, 0.02wt.%~0.05wt.% Ti, 0.1wt.%~0.15wt.% Zr, and the rest is Al.

[0034] In particular, by strictly controlling the size of the aluminum chips processed by the 7 series aluminum alloy, the thickness is 0.1mm~5.0mm and the diameter is 10mm~60mm, so as to better adapt to the above-mentioned smelting process, so that the aluminum chips are melted more completely, and the fusion with the base aluminum liquid is more thorough, and finally the purity of the obtained regenerated melt is improved. Specifically, if the diameter of the sheet is too large, it will cause the aluminum chips to be difficult to be quickly and effectively stirred after being added to the side well furnace, and at the same time, the melting time will be too long, which will greatly reduce the smelting efficiency of the continuous melting system constructed by the side well furnace and the smelting furnace, which is not conducive to industrial continuous production; if the diameter of the sheet is too small, the aluminum chips will be added to the side well furnace. The high temperature of the melt in the furnace will cause the aluminum chips to be instantly oxidized, causing the slag content of the melt to increase sharply, blocking the circulation channel between the side well furnace and the smelting furnace.

[0035] As for the composition of the processed 7 series aluminum alloy processing aluminum chips, by weight percentage, the 7 series aluminum alloy processing aluminum chips include 0.020wt.%~0.025wt.% Si, 0.04wt.%~0.07wt.% Fe, 2.0wt.%~2.3wt.% Cu, 0.002wt.%~0.004wt.% Mn, 2.00wt.%~2.40wt.% Mg, 0.002wt.%~0.008wt.% Cr, 6.0wt.%~6.6wt.% Zn, 0.01wt.%~0.03wt.% Ti, 0.04wt.%~0.12wt.% Zr, and the rest is Al.

[0036] During the second melting process, the circulation pump remains on and changes the circulation direction so that the first melt circulates in the side well furnace and the smelting furnace, so as to better achieve continuous and complete melting of aluminum chips, reduce its burn-out rate, and improve the purity of the resulting regenerated melt.

[0037] In summary, the above-mentioned recovery and smelting method provided by the present invention can achieve nearly 100% recycling of aluminum chips from 7-series aluminum alloy processing, and the aluminum chip smelting recovery rate is significantly improved (i.e., the aluminum chip burnout rate is extremely low), and effectively solves the technical problems such as the difficulty in controlling the inclusions in the obtained aluminum melt, unstable melt performance, and environmental pollution caused by the easy oxidation and burning of the existing 7-series aluminum alloy aluminum chips, and greatly improves the level of melt purification during the remelting of processing debris, and finally obtains aluminum alloy ingot products that meet the composition requirements of 7-series aluminum alloys. At the same time, the above-mentioned grade-preserving recycling method proposed in the present invention can realize the continuous melting and recycling of aluminum chips, especially for large-scale batch production enterprises, which can greatly improve production efficiency. Through the above-mentioned method, it can be very helpful for related enterprises to greatly absorb the 7-series aluminum alloy processing aluminum chips that are difficult to recycle, reduce the pressure of hoarding of their processing aluminum chips waste, and expand to the grade-preserving utilization of other high-performance aluminum alloy wastes, helping to save energy and reduce carbon, reduce costs and increase efficiency.

[0038] Furthermore, in order to enable the bottoming aluminum liquid to realize effective flow between the smelting furnace and the side well furnace in advance, so as to enable the aluminum chips added later to be melted more efficiently therein, reduce its burning loss and impurities that may be introduced during the addition of aluminum chips, and thus more effectively purify the obtained regenerated melt, preferably in step S1, when the temperature of the bottoming aluminum liquid is 720°C~760°C, the bottoming aluminum liquid is flowed from the smelting furnace into the side well furnace through a circulation pump. At the same time, in this process, the circulation pump is kept turned on, and the 7 series aluminum alloy processing aluminum chips are mixed with the bottoming aluminum liquid and melted for the second time. As a result, the unmelted aluminum chips in the first melt can be quickly drawn into the melt that maintains a downward vortex state, thereby effectively avoiding direct contact between the aluminum chips and the open flame, or exposure to high-temperature air, thereby suppressing the oxidation and burning of the aluminum chips to a greater extent, effectively improving its recovery rate and reducing its burning rate. The above temperature range and related operations contribute to the rapid melting and uniform distribution of aluminum chips, reducing energy consumption during the smelting process, while also improving melting efficiency, reducing local overheating, improving the uniformity and stability of the final recycled melt, and improving the production flexibility of the recycling method.

[0039] In several typical implementations, in order to more effectively remove non-metallic inclusions and gases in the first melt in advance, the first refining is preferably carried out in the presence of a refining agent and in an appropriate amount, so as to lay a good foundation for the subsequent batching and second refining process, thereby improving the purity of the recycled aluminum alloy ingot. That is, step S2-1 is preferably carried out in a smelting furnace, and step S2-1 also includes adding a refining agent to the first melt at an addition amount of 0.8 kg / ton of melt to 1.2 kg / ton of melt, and then performing the first refining.

[0040] Furthermore, in step S2-2, when the temperature of the second melt is 730° C. to 750° C., the second melt is batched. Batching within this temperature range can make the added alloy elements more evenly distributed in the melt, thereby improving the composition consistency and purity of the regenerated melt.

[0041] And, in the above-mentioned batching process, a chemical analysis spectrometer is used to analyze the composition, and the composition is adjusted in real time according to the composition detection results and the composition control requirements of the regenerated melt. If minor metals and intermediate alloys are added again according to the batching requirements, it is necessary to take samples again to confirm the composition until the composition meets the control requirements. The batching is considered to be completed, and the subsequent converter and refining steps can be carried out. On this basis, in order to further remove gases and inclusions in the melt, and to better enhance the removal effect of inclusions in the melt in the second refining process, improve the purity and performance stability of the regenerated melt, and promote the regenerated melt to be stably transferred to the insulation furnace under more suitable temperature conditions, it is preferred that when the temperature of the third melt is 740°C~760°C, the third melt is transferred to the insulation furnace, and the second refining in step S2-3 is carried out.

[0042] In practical applications, it should be noted that the operation of transferring the third melt to the holding furnace should ensure that the volume of the third melt transferred to the holding furnace is no more than 2 / 3 of the tonnage of the smelting furnace, so that the remaining melt in the molten aluminum can meet the requirement of turning on the circulating pump when the next batch of aluminum chips is melted in the side well furnace.

[0043] In the second refining process, if the refining time is too long and the standing time is too short, the inclusions accumulated in the melt due to the adsorption of argon will not have time to completely float to the surface of the aluminum liquid, while if the refining time is too short and the standing time is too long, the adsorption and aggregation effect of the inclusions will be poor. Therefore, after a large number of experiments, the inventor strictly optimizes the time of the refining stage and the standing stage in the second refining process, that is, in several typical embodiments, it is preferred that in step S2-3, the time of the refining process is 15min~45min, and the time of the standing process is 30min~90min. Under this condition, various inclusions are better adsorbed and taken out of the melt, ensuring that the amount of inclusions in the melt after the second refining is significantly reduced, promoting the full purification of the obtained melt, and reducing the internal defects that may occur in the subsequent casting process.

[0044] In several typical embodiments, in order to more effectively prevent the melt from being oxidized during the second refining process, thereby maintaining the purity of the melt, the inventors have optimized the flow rate of the protective atmosphere in step S2-3 to be 2.0 m / s after a large number of experiments. 3 / h~4.0m 3 In some more typical embodiments, the protective atmosphere is nitrogen and / or argon.

[0045] In order to more effectively remove impurities in the melt, the filter in step S3-2 is preferably a double-stage plate filter. More preferably, the precision of the filter plate used for the primary filtration is 30PPI~40PPI, and the precision of the filter plate used for the secondary filtration is 50PPI~60PPI, so that the two-stage filter plates with different precisions can better adapt to the aluminum alloy melt obtained after two refining treatments, thereby more effectively filtering out impurities therein, and making the obtained regenerated melt have a higher purity.

[0046] In several typical embodiments, the slag content in the regenerated melt prepared by the above-mentioned grade-preserving recovery method is 0.005 mm 2 / kgAl~0.030mm 2 / kgAl, hydrogen content is 0.01mL / 100g Al~0.10mL / 100g Al, and alkali metal content is 2ppm~6ppm. In other words, the grade-preserving recovery method provided by the present invention can obtain a regenerated melt with low slag content, hydrogen content and alkali metal content. At the same time, because the obtained regenerated melt has extremely high purity, when the ingot is subsequently cast, the corresponding 7 series aluminum alloy ingot has a more uniform internal structure, less impurities, and better comprehensive performance.

[0047] The second aspect of the present invention provides a recycled 7-series aluminum alloy ingot, which is prepared by the above-mentioned 7-series aluminum alloy processing aluminum scrap grade-preserving recycling method. The recycled 7-series aluminum alloy ingot prepared by the above-mentioned recycling method not only has mechanical properties and corrosion resistance similar to those of the original 7-series aluminum alloy material, but also has a lower production cost.

[0048] In several preferred embodiments, the composition of the recycled 7 series aluminum alloy ingot includes, by weight percentage: 0.020wt.%~0.040wt.% Si, 0.05wt.%~0.09wt.% Fe, 2.0wt.%~2.4wt.% Cu, 0.0005wt.%~0.0040wt.% Mn, 1.90wt.%~2.30wt.% Mg, 0.004wt.%~0.007wt.% Cr, 6.0wt.%~6.6wt.% Zn, 0.02wt.%~0.04wt.% Ti, 0.09wt.%~0.12wt.% Zr, and the rest is Al. That is to say, the composition of the recycled 7 series aluminum alloy ingot can fully meet the national standard requirements for 7 series aluminum alloys, and also show excellent comprehensive performance.

[0049] The third aspect of the present invention provides an application of the above-mentioned recycled 7-series aluminum alloy ingot as a structural material in the aerospace field. The recycled 7-series aluminum alloy ingot obtained by the present invention has a composition that meets the national standard and has excellent performance, and can meet the specific requirements of different industrial products for material properties. It is suitable for manufacturing industrial products that require precise control of alloy composition, especially suitable for the aerospace field, such as aircraft fuselage structural parts, aircraft engine structural parts, and high-performance automobile engine cylinder blocks.

[0050] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0051] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0052] Example 1

[0053] A method for recycling aluminum chips from 7050 aluminum alloy:

[0054] In this embodiment, a side well furnace, a smelting furnace, and a pump room are used as a system for recovering aluminum chips.

[0055] (1) Melting stage:

[0056] (1-1) 7 series aluminum alloy primary scrap is used as the base aluminum alloy, and its composition is shown in Table 1 (wherein Al is not shown, which is the balance). It is first melted in a smelting furnace. When the temperature of the base aluminum liquid in the smelting furnace reaches 725°C, the circulation pump is turned on to allow the base aluminum liquid to flow from the smelting furnace through the pump chamber into the side well furnace.

[0057] (1-2) The prepared 7 series aviation aluminum alloy processing aluminum chips (with a thickness of 0.1mm~3.0mm, a sheet diameter of 10mm~40mm, and specific components are shown in Table 2, and the residual Al is not shown in Table 2) are transported to the side well furnace by a conveyor belt, mixed with the bottom aluminum liquid therein, and then melted for the second time. During the second melting process, the circulating pump can cause the aluminum liquid to produce a downward eddy motion. The aluminum liquid in the side well furnace is kept in a downward eddy state due to the continuous operation of the circulating pump. The transported aluminum chips are quickly drawn into the eddy state of the aluminum liquid and melted below the liquid surface. At the same time, during the second melting process, the circulating pump in the pump chamber changes the circulation direction and pumps it into the smelting furnace through the bottom opening. This cycle is repeated to achieve continuous melting of the aluminum chips, and finally the first melt obtained by the second melting is pumped into the smelting furnace.

[0058] (2) Refining stage:

[0059] (2-1) The first refining is carried out in the smelting furnace. Specifically, the refining agent powder spray refining is adopted, the dosage of the refining agent is 0.8kg / ton of melt, the refining time is 30 minutes, and the refining tube is inserted into the bottom of the furnace during refining, and then slowly, evenly and steadily passes through various parts of the bottom of the furnace to make the refining reaction complete. After the first refining is completed, the slag is removed.

[0060] (2-2) When the temperature of the second melt is 735°C, a sample is taken from it and the third melt is prepared according to the composition of the regenerated melt to be prepared (the specific composition is shown in Table 3). When the temperature of the third melt is 750°C, a portion of it is transferred to the holding furnace to prepare for the second refining. The volume of the portion of the third melt transferred to the holding furnace should not be greater than 2 / 3 of the tonnage of the smelting furnace to ensure that the remaining melt in the smelting aluminum can meet the requirements of the circulation pump being turned on when the next batch of aluminum chips is melted in the side well furnace.

[0061] (2-3) After the converter is finished, the holding furnace starts the argon refining mode, and the argon flow rate is 2.5 m 3 / h, the refining time is 30min, and the standing time is 30min. Under these conditions, the third melt is subjected to a second refining to obtain a fourth melt.

[0062] (3) Purification stage:

[0063] (3-1) Online degassing: The fourth melt is degassed online using a three-rotor degassing device;

[0064] (3-2) Online filtration: The degassed fourth melt is filtered online using a two-stage plate filter, wherein the filter plate precision of the first-stage filtration is 30 PPI, and the filter plate precision of the second-stage filtration is 50 PPI. Finally, a regenerated melt is obtained.

[0065] (4) The obtained recycled melt is cast to obtain a recycled 7 series aluminum alloy ingot.

[0066] Table 1

[0067]

[0068] Table 2

[0069]

[0070] Example 2

[0071] A method for recycling aluminum chips from 7050 aluminum alloy:

[0072] In this embodiment, a side well furnace, a smelting furnace, and a pump room are used as a system for recovering aluminum chips.

[0073] (1) Melting stage:

[0074] (1-1) The 7-series aluminum alloy primary scrap in Example 1 is used as the base aluminum alloy. It is first melted in a smelting furnace. When the temperature of the base aluminum liquid in the smelting furnace reaches 730°C, a circulation pump is turned on to allow the base aluminum liquid to flow from the smelting furnace through the pump chamber into the side well furnace.

[0075] (1-2) The prepared 7 series aviation aluminum alloy processing aluminum chips (with a thickness of 0.1mm~4.0mm, a sheet diameter of 20mm~60mm, and specific components as shown in Table 2) are transported to the side well furnace by a conveyor belt, mixed with the bottom aluminum liquid therein, and melted for the second time. During the second melting process, the circulating pump can cause the aluminum liquid to produce a downward eddy motion. The aluminum liquid in the side well furnace is kept in a downward eddy state due to the continuous operation of the circulating pump. The transported aluminum chips are quickly drawn into the eddy state of the aluminum liquid and melted below the liquid surface. At the same time, during the second melting process, the circulating pump in the pump chamber changes the circulation direction and pumps it into the melting furnace through the bottom opening. This cycle is repeated to achieve continuous melting of the aluminum chips, and finally the first melt obtained by the second melting is pumped into the melting furnace.

[0076] (2) Refining stage:

[0077] (2-1) The first refining is carried out in the smelting furnace. Specifically, the refining agent powder spray refining is adopted, the dosage of the refining agent is 0.8kg / ton of melt, the refining time is 30 minutes, and the refining tube is inserted into the bottom of the furnace during refining, and then slowly, evenly and steadily passes through various parts of the bottom of the furnace to make the refining reaction complete. After the first refining is completed, the slag is removed.

[0078] (2-2) When the temperature of the second melt is 750°C, a sample is taken from it and the third melt is prepared according to the composition of the regenerated melt to be prepared (the specific composition is shown in Table 3). When the temperature of the third melt is 760°C, a portion of it is transferred to the holding furnace to prepare for the second refining. The volume of the portion of the third melt transferred to the holding furnace should not be greater than 2 / 3 of the tonnage of the smelting furnace to ensure that the remaining melt in the smelting aluminum can meet the requirements of the circulation pump being turned on when the next batch of aluminum chips is melted in the side shaft furnace.

[0079] (2-3) After the converter is finished, the holding furnace starts the argon refining mode, and the argon flow rate is 2 m 3 / h, the refining time is 40min, the standing time is 30min, and under these conditions, the third melt is subjected to a second refining to obtain a fourth melt.

[0080] (3) Purification stage:

[0081] (3-1) Online degassing: The fourth melt is degassed online using a three-rotor degassing device;

[0082] (3-2) Online filtration: The fourth melt after degassing is filtered online using a two-stage plate filter, wherein the filter plate precision of the first-stage filtration is 40 PPI, and the filter plate precision of the second-stage filtration is 50 PPI. Finally, a regenerated melt is obtained.

[0083] (4) The obtained recycled melt is cast to obtain a recycled 7 series aluminum alloy ingot.

[0084] Example 3

[0085] A method for recycling aluminum chips from 7050 aluminum alloy:

[0086] In this embodiment, a side well furnace, a smelting furnace, and a pump room are used as a system for recovering aluminum chips.

[0087] (1) Melting stage:

[0088] (1-1) The 7-series aluminum alloy primary scrap in Example 1 is used as the base aluminum alloy. It is first melted in a smelting furnace. When the temperature of the base aluminum liquid in the smelting furnace reaches 740°C, a circulation pump is turned on to allow the base aluminum liquid to flow from the smelting furnace through the pump chamber into the side well furnace.

[0089] (1-2) The prepared 7 series aviation aluminum alloy processing aluminum chips (with a thickness of 0.1mm~5.0mm, a sheet diameter of 20mm~60mm, and specific components are shown in Table 2) are transported to the side well furnace by a conveyor belt, mixed with the bottom aluminum liquid therein, and melted for the second time. During the second melting process, the circulating pump can cause the aluminum liquid to produce a downward eddy motion. The aluminum liquid in the side well furnace is kept in a downward eddy state due to the continuous operation of the circulating pump. The transported aluminum chips are quickly drawn into the liquid surface and melted under the eddy state of the aluminum liquid. At the same time, during the second melting process, the circulating pump in the pump chamber changes the circulation direction and pumps it into the melting furnace through the bottom opening again. This cycle is repeated to achieve continuous melting of the aluminum chips, and finally the first melt obtained by the second melting is pumped into the melting furnace.

[0090] (2) Refining stage:

[0091] (2-1) The first refining is carried out in the smelting furnace. Specifically, the refining agent is sprayed with powder for refining. The dosage of the refining agent is 1.0 kg / ton of melt. The refining time is 15 min. During refining, the refining tube is inserted into the bottom of the furnace, and then slowly, evenly and steadily passes through various parts of the bottom of the furnace to complete the refining reaction. After the first refining is completed, the slag is removed.

[0092] (2-2) When the temperature of the second melt is 745°C, a sample is taken from it and the third melt is prepared according to the composition of the regenerated melt to be prepared (the specific composition is shown in Table 3). When the temperature of the third melt is 755°C, a portion of it is transferred to the holding furnace to prepare for the second refining. The volume of the portion of the third melt transferred to the holding furnace should not be greater than 2 / 3 of the tonnage of the smelting furnace to ensure that the remaining melt in the smelting aluminum can meet the requirements of the circulation pump being turned on when the next batch of aluminum chips is melted in the side well furnace.

[0093] (2-3) After the converter is finished, the holding furnace starts the argon refining mode, and the argon flow rate is 3m 3 / h, the refining time is 20min, the standing time is 60min, and under these conditions, the third melt is subjected to a second refining to obtain a fourth melt.

[0094] (3) Purification stage:

[0095] (3-1) Online degassing: The fourth melt is degassed online using a three-rotor degassing device;

[0096] (3-2) Online filtration: The fourth melt after degassing is filtered online using a two-stage plate filter, wherein the filter plate precision of the first-stage filtration is 30 PPI, and the filter plate precision of the second-stage filtration is 60 PPI. Finally, a regenerated melt is obtained.

[0097] (4) The obtained recycled melt is cast to obtain a recycled 7 series aluminum alloy ingot.

[0098] Example 4

[0099] A method for recycling aluminum chips from 7050 aluminum alloy:

[0100] In this embodiment, a side well furnace, a smelting furnace, and a pump room are used as a system for recovering aluminum chips.

[0101] (1) Melting stage:

[0102] (1-1) The 7-series aluminum alloy primary scrap in Example 1 is used as the base aluminum alloy. It is first melted in a smelting furnace. When the temperature of the base aluminum liquid in the smelting furnace reaches 760°C, a circulation pump is turned on to allow the base aluminum liquid to flow from the smelting furnace through the pump chamber into the side well furnace.

[0103] (1-2) The prepared 7 series aviation aluminum alloy processing aluminum chips (with a thickness of 0.1mm~2.0mm, a sheet diameter of 15mm~55mm, and specific components are shown in Table 2) are transported to the side well furnace by a conveyor belt, mixed with the bottom aluminum liquid therein, and then melted for the second time. During the second melting process, the circulating pump can cause the aluminum liquid to produce a downward eddy motion. The aluminum liquid in the side well furnace is kept in a downward eddy state due to the continuous operation of the circulating pump. The transported aluminum chips are quickly drawn into the eddy state of the aluminum liquid and melted below the liquid surface. At the same time, during the second melting process, the circulating pump in the pump chamber changes the circulation direction and pumps it into the smelting furnace through the bottom opening. This cycle is repeated to achieve continuous melting of the aluminum chips, and finally the first melt obtained by the second melting is pumped into the smelting furnace.

[0104] (2) Refining stage:

[0105] (2-1) The first refining is carried out in the smelting furnace. Specifically, the refining agent is sprayed with powder for refining. The dosage of the refining agent is 1.0 kg / ton of melt. The refining time is 15 minutes. During refining, the refining tube is inserted into the bottom of the furnace, and then slowly, evenly and steadily passes through various parts of the bottom of the furnace to complete the refining reaction. After the first refining is completed, the slag is removed.

[0106] (2-2) When the temperature of the second melt is 740°C, a sample is taken from it and the third melt is prepared according to the composition of the regenerated melt to be prepared (the specific composition is shown in Table 3). When the temperature of the third melt is 750°C, a portion of it is transferred to the holding furnace to prepare for the second refining. The volume of the portion of the third melt transferred to the holding furnace should not be greater than 2 / 3 of the tonnage of the smelting furnace to ensure that the remaining melt in the smelting aluminum can meet the requirements of the circulation pump being turned on when the next batch of aluminum chips is melted in the side shaft furnace.

[0107] (2-3) After the converter is finished, the holding furnace starts the argon refining mode, and the argon flow rate is 3.5m 3 / h, the refining time is 15min, the standing time is 60min, and under these conditions, the third melt is subjected to a second refining to obtain a fourth melt.

[0108] (3) Purification stage:

[0109] (3-1) Online degassing: The fourth melt is degassed online using a three-rotor degassing device;

[0110] (3-2) Online filtration: The degassed fourth melt is filtered online using a two-stage plate filter, wherein the filter plate precision of the first-stage filtration is 40 PPI, and the filter plate precision of the second-stage filtration is 60 PPI. Finally, a regenerated melt is obtained.

[0111] (4) The obtained recycled melt is cast to obtain a recycled 7 series aluminum alloy ingot.

[0112] Example 5

[0113] A method for recycling aluminum chips from 7050 aluminum alloy:

[0114] In this embodiment, a side well furnace, a smelting furnace, and a pump room are used as a system for recovering aluminum chips.

[0115] (1) Melting stage:

[0116] (1-1) The 7-series aluminum alloy primary scrap in Example 1 is used as the base aluminum alloy. It is first melted in a smelting furnace. When the temperature of the base aluminum liquid in the smelting furnace reaches 750°C, a circulation pump is turned on to allow the base aluminum liquid to flow from the smelting furnace through the pump chamber into the side well furnace.

[0117] (1-2) The prepared 7 series aviation aluminum alloy processing aluminum chips (with a thickness of 0.1mm~4.0mm, a sheet diameter of 15mm~60mm, and specific components are shown in Table 2) are transported to the side well furnace by a conveyor belt, mixed with the bottom aluminum liquid therein, and melted for the second time. During the second melting process, the circulating pump can cause the aluminum liquid to produce a downward vortex motion. The aluminum liquid in the side well furnace is kept in a downward vortex state due to the continuous operation of the circulating pump. The transported aluminum chips are quickly drawn into the vortex state of the aluminum liquid and melted below the liquid surface. At the same time, during the second melting process, the circulating pump in the pump chamber changes the circulation direction and pumps it into the melting furnace through the bottom opening again. This cycle is repeated to achieve continuous melting of the aluminum chips, and finally the first melt obtained by the second melting is pumped into the melting furnace.

[0118] (2) Refining stage:

[0119] (2-1) The first refining is carried out in the smelting furnace. Specifically, the refining agent powder spray refining is adopted, the refining agent dosage is 1.2kg / ton melt, the refining time is 45 minutes, and the refining tube is inserted into the bottom of the furnace during refining, and then slowly, evenly and steadily passes through various parts of the bottom of the furnace to complete the refining reaction. After the first refining is completed, the slag is removed.

[0120] (2-2) When the temperature of the second melt is 735°C, a sample is taken from it and the third melt is prepared according to the composition of the regenerated melt to be prepared (the specific composition is shown in Table 3). When the temperature of the third melt is 745°C, a portion of it is transferred to the holding furnace to prepare for the second refining. The volume of the portion of the third melt transferred to the holding furnace should not be greater than 2 / 3 of the tonnage of the smelting furnace to ensure that the remaining melt in the smelting aluminum can meet the requirements of the circulation pump being turned on when the next batch of aluminum chips is melted in the side shaft furnace.

[0121] (2-3) After the converter is finished, the holding furnace starts the argon refining mode, and the argon flow rate is 4m 3 / h, the refining time is 35min, the standing time is 90min, and under these conditions, the third melt is subjected to a second refining to obtain a fourth melt.

[0122] (3) Purification stage:

[0123] (3-1) Online degassing: The fourth melt is degassed online using a three-rotor degassing device;

[0124] (3-2) Online filtration: The fourth melt after degassing is filtered online using a two-stage plate filter, wherein the filter plate precision of the first-stage filtration is 40 PPI, and the filter plate precision of the second-stage filtration is 50 PPI. Finally, a regenerated melt is obtained.

[0125] (4) The obtained recycled melt is cast to obtain a recycled 7 series aluminum alloy ingot.

[0126] Example 6

[0127] A method for recycling aluminum chips from 7050 aluminum alloy:

[0128] In this embodiment, a side well furnace, a smelting furnace, and a pump room are used as a system for recovering aluminum chips.

[0129] (1) Melting stage:

[0130] (1-1) The 7-series aluminum alloy primary scrap in Example 1 is used as the base aluminum alloy. It is first melted in a smelting furnace. When the temperature of the base aluminum liquid in the smelting furnace reaches 755°C, a circulation pump is turned on to allow the base aluminum liquid to flow from the smelting furnace through the pump chamber into the side well furnace.

[0131] (1-2) The prepared 7 series aviation aluminum alloy processing aluminum chips (with a thickness of 0.1mm~5.0mm, a sheet diameter of 10mm~60mm, and specific components are shown in Table 2) are transported to the side well furnace by a conveyor belt, mixed with the bottom aluminum liquid therein, and then melted for the second time. During the second melting process, the circulating pump can cause the aluminum liquid to produce a downward eddy motion. The aluminum liquid in the side well furnace is kept in a downward eddy state due to the continuous operation of the circulating pump. The transported aluminum chips are quickly drawn into the eddy state of the aluminum liquid and melted below the liquid surface. At the same time, during the second melting process, the circulating pump in the pump chamber changes the circulation direction and pumps it into the smelting furnace through the bottom opening. This cycle is repeated to achieve continuous melting of the aluminum chips, and finally the first melt obtained by the second melting is pumped into the smelting furnace.

[0132] (2) Refining stage:

[0133] (2-1) The first refining is carried out in the smelting furnace. Specifically, the refining agent powder spray refining is adopted, the dosage of the refining agent is 1.2kg / ton of melt, the refining time is 45min, and the refining tube is inserted into the bottom of the furnace during refining, and then slowly, evenly and steadily passes through various parts of the bottom of the furnace to complete the refining reaction. After the first refining is completed, the slag is removed.

[0134] (2-2) When the temperature of the second melt is 735°C, a sample is taken from it and the third melt is prepared according to the composition of the regenerated melt to be prepared (the specific composition is shown in Table 3). When the temperature of the third melt is 745°C, a portion of it is transferred to the holding furnace to prepare for the second refining. The volume of the portion of the third melt transferred to the holding furnace should not be greater than 2 / 3 of the tonnage of the smelting furnace to ensure that the remaining melt in the smelting aluminum can meet the requirements of the circulation pump being turned on when the next batch of aluminum chips is melted in the side shaft furnace.

[0135] (2-3) After the converter is finished, the holding furnace starts the argon refining mode, and the argon flow rate is 2.5m 3 / h, the refining time is 45min, the standing time is 90min, and under these conditions, the third melt is subjected to a second refining to obtain a fourth melt.

[0136] (3) Purification stage:

[0137] (3-1) Online degassing: The fourth melt is degassed online using a three-rotor degassing device;

[0138] (3-2) Online filtration: The fourth melt after degassing is filtered online using a two-stage plate filter, wherein the filter plate precision of the first-stage filtration is 30 PPI, and the filter plate precision of the second-stage filtration is 60 PPI. Finally, a regenerated melt is obtained.

[0139] (4) The obtained recycled melt is cast to obtain a recycled 7 series aluminum alloy ingot.

[0140] Example 7

[0141] A method for recycling aluminum chips from 7050 aluminum alloy:

[0142] The only difference between this embodiment and embodiment 1 is that in step (1-1), the circulation pump is turned on and the temperature of the bottom aluminum liquid converter is changed to 700°C.

[0143] Example 8

[0144] A method for recycling aluminum chips from 7050 aluminum alloy:

[0145] The only difference between this embodiment and embodiment 1 is that in the first refining process of step (2-1), the dosage of the refining agent is changed to 0.5 kg / ton of melt.

[0146] Example 9

[0147] A method for recycling aluminum chips from 7050 aluminum alloy:

[0148] The only difference between this embodiment and embodiment 1 is that in the first refining process of step (2-1), the dosage of the refining agent is changed to 1.5 kg / ton of melt.

[0149] Example 10

[0150] A method for recycling aluminum chips from 7050 aluminum alloy:

[0151] The only difference between this embodiment and embodiment 1 is that in step (2-2), the second melt temperature at the start of sampling and batching is changed to 720°C; and the third melt temperature at the start of the converter is changed to 760°C.

[0152] Embodiment 11

[0153] A method for recycling aluminum chips from 7050 aluminum alloy:

[0154] The only difference between this embodiment and embodiment 1 is that in step (2-2), the second melt temperature at the start of sampling and batching is changed to 760°C; and the third melt temperature at the start of the converter is changed to 770°C.

[0155] Example 12

[0156] A method for recycling aluminum chips from 7050 aluminum alloy:

[0157] The difference between this embodiment and embodiment 1 is that the argon gas flow rate in the second refining process in step (2-3) is changed to 1.5 m 3 / h, the refining time of the second refining was changed to 50min, and the standing time was changed to 100min.

[0158] Embodiment 13

[0159] A method for recycling aluminum chips from 7050 aluminum alloy:

[0160] The only difference between this embodiment and embodiment 1 is that the online filtration in step (3-2) adopts a double-stage plate filter, and the filter plate accuracy of the secondary filtration is changed to 40 PPI.

[0161] Comparative Example 1

[0162] A method for recycling aluminum chips from 7050 aluminum alloy:

[0163] The difference between this comparative example and Example 1 is only in step (1), specifically:

[0164] Add clean 7 series aluminum alloy used in Example 1 as the base aluminum alloy into the melting furnace, ignite and melt it through the burner installed in the melting furnace, and the amount of the base aluminum liquid molten in the melting furnace can be 1 / 3 of the melting furnace.

[0165] When the temperature of the aluminum liquid in the smelting furnace is 725℃, 7 series aluminum alloy processing aluminum chips are added in batches from the furnace door of the smelting furnace. After each batch of aluminum chips is added, they are manually stirred evenly until the smelting furnace is full and completely melted to finally obtain the first melt.

[0166] That is, the only difference between this comparative example and Example 1 is that no side shaft furnace and circulating pump are involved, and only a smelting furnace is used to complete the smelting stage of step (1).

[0167] Comparative Example 2

[0168] A method for recycling aluminum chips from 7050 aluminum alloy:

[0169] The only difference between this comparative example and Example 1 is that the first refining in step (2-1) is not performed, but the first melt is only uniformly stirred with a slag scraper, the slag is turned to the surface and scraped out, and then the subsequent steps are directly performed.

[0170] In this comparative example, the first refining was not performed, so the small-sized inclusions generated in the melt were difficult to remove by physical interception alone. The obtained regenerated melt was tested and analyzed to contain Al2O3, MgO, spinel and Ti-containing particle inclusions. The specific morphology of each type of inclusion is presented through the metallographic diagram, see Figure 1~Figure 4 .in, Figure 1 The Al2O3 inclusions in the regenerated melt are shown; Figure 2 MgO inclusions in the regenerated melt are shown; Figure 3MgO and spinel inclusions in the regenerated melt are shown; Figure 4 It shows Ti particle inclusions and Al2O3 inclusions in the regenerated melt.

[0171] Comparative Example 3

[0172] A method for recycling aluminum chips from 7050 aluminum alloy:

[0173] The only difference between this comparative example and Example 1 is that the time of the first refining in step (2-1) is changed to 10 min.

[0174] Comparative Example 4

[0175] A method for recycling aluminum chips from 7050 aluminum alloy:

[0176] The only difference between this comparative example and Example 1 is that the refining time of the second refining in step (2-3) is changed to 80 min, and the standing time is changed to 5 min.

[0177] Comparative Example 5

[0178] A method for recycling aluminum chips from 7050 aluminum alloy:

[0179] The only difference between this comparative example and Example 1 is that the refining time of the second refining in step (2-3) is changed to 10 min, and the standing time is changed to 150 min.

[0180] Comparative Example 6

[0181] A method for recycling aluminum chips from 7050 aluminum alloy:

[0182] The only difference between this comparative example and Example 1 is that in step (3-1), two-rotor degassing is used instead of three-rotor degassing.

[0183] The metallographic photograph of the obtained ingot is shown in Figure 5 , SEM photos show Figure 6 .

[0184] The composition contents of the regenerated melts obtained in the above-mentioned embodiments and comparative examples are shown in Table 3. Specifically, samples were taken from the flow channel section between the degassing device and the filter, and the chemical composition of the samples was analyzed using a chemical analysis spectrometer.

[0185] Table 3

[0186]

[0187] In the above embodiments and comparative examples, samples were taken from the flow channel section between the degassing device and the filter to test the hydrogen content. The unit of hydrogen content is mL / 100g Al, which means milliliters per hundred grams of aluminum melt. The slag content was obtained by using the off-line slag measurement method in the flow channel after the filter and the metallographic grid method was used to analyze the slag content. The unit of slag content is mm 2 / kgAl, which means square millimeter per kilogram of aluminum melt. The alkali metal content in the regenerated melt finally obtained in each embodiment and comparative example was tested by chemical element analysis method.

[0188] Among them, the degassed melt has a relatively stable quality due to no further degassing operation and no human factors interfering in the subsequent filtration and casting processes, and the hydrogen content will basically not change; and the filtered melt has a slag content that basically does not change during the casting stage due to no further slag removal operation. Therefore, the hydrogen content and slag content tested by the above method are the hydrogen content and slag content in the regenerated melt.

[0189] The above test results are shown in Table 4. In the recycling methods provided in the embodiments and comparative examples, the burning rate of aluminum scraps is shown in Table 4.

[0190] Table 4

[0191]

[0192] From the above description, it can be seen that the above-mentioned embodiment of the present invention realizes the grade-preserving recycling of aluminum chips from 7-series aluminum alloy processing, recovers and smelts with a high recovery rate to obtain a 7-series aluminum alloy melt with high purity, and then casts a recycled 7-series aluminum alloy ingot that can meet the application in the aerospace field.

[0193] Specifically, it can be seen from Examples 1 to 6 that by designing an overall recovery and smelting scheme and optimizing the conditions and parameters involved in the smelting, first refining, second refining, degassing and filtration processes, a high-standard regenerated melt is obtained by recycling and smelting with an extremely low aluminum scrap burnout rate. The chemical composition, aluminum liquid hydrogen content, slag content, and alkali metal content of each melt obtained meet the quality control requirements of 7 series aviation aluminum alloys.

[0194] By comparing Examples 1 to 6 with Example 7, it can be seen that the temperature of the bottom aluminum liquid converter is preferably selected so that the aluminum chips can be melted quickly and evenly distributed, while reducing the introduction of impurities, thereby improving the uniformity and stability of the final regenerated melt.

[0195] Comparing Examples 1 to 6 with Examples 8 and 9, it can be seen that the amount of the refining agent used in the first refining is preferably increased, which can further reduce the slag content in the obtained regenerated melt.

[0196] By comparing Examples 1 to 6 with Examples 10 and 11, it can be seen that the temperature of the second melt during the preferred formulation is 730°C~750°C, which can allow the added alloy elements to be more evenly distributed in the melt, thereby reducing impurities in the regenerated melt and making its composition more in line with the requirements of 7 series aluminum alloys.

[0197] By comparing Examples 1 to 6 with Example 12, it can be seen that in the preferred step S2-3, the refining process time is 15min~45min, and the standing process time is 30min~90min, which can more effectively promote the full purification of the obtained melt, thereby reducing various impurities in the obtained regenerated melt.

[0198] By comparing Examples 1 to 6 with Example 13, it can be seen that the filtration is preferably double-stage filtration, and the accuracy of the filter plate used in the latter stage of filtration is set to 50PPI~60PPI, which can more effectively filter out impurities in the melt and obtain a regenerated melt with higher purity.

[0199] Comparing Examples 1 to 6 with Comparative Example 1, it can be seen that in Comparative Example 1, only a melting furnace is used to melt aluminum chips, and the burnout rate of aluminum chips reaches 8.8%, which is much higher than the burnout level of aluminum chips in Examples 1 to 6. At the same time, due to the large burnout of aluminum chips, the melt slag is serious, and even if the same in-furnace refining and out-of-furnace purification process is used, the final aluminum liquid slag content and hydrogen content are high, which cannot meet the quality control requirements of high-performance 7 series aviation aluminum alloy melts.

[0200] Comparing Examples 1 to 6 with Comparative Example 2, it can be seen that Comparative Example 2 did not perform the first refining, but only performed the second refining in the holding furnace. Because the refining agent impurity removal in the first refining can utilize the refining agent to decompose in the melt to form liquid droplets, various inclusions (such as Al2O3, oxide film, etc.) in the first melt of the present invention are wetted and adsorbed, and then the flux that wraps the inclusions floats to the surface of the melt, thereby achieving a good impurity removal purpose. In Comparative Example 2, no refining agent was used, and the small-sized inclusions generated in the first melt were therefore difficult to remove only by physical interception. After detection and analysis, various inclusions, such as Al2O3, MgO, spinel and Ti-containing particle inclusions (see for details) were present. Figures 1 to 4 ), resulting in a significant increase in the final slag content.

[0201] By comparing Examples 1 to 6 with Comparative Example 3, it can be seen that the time of the first refining is preferably not less than 15 minutes, which can improve the refining effect, reduce various inclusions in the final melt, and improve its purity.

[0202] By comparing Examples 1 to 6 with Comparative Examples 4 and 5, it can be further known that for the second refining, it is particularly important to optimize the time of the refining process and the standing process. If the refining time is too long and the standing time is too short, the inclusions gathered in the melt due to the adsorption of argon will not have time to completely float to the surface of the aluminum liquid. If the refining time is too short and the standing time is too long, the adsorption and aggregation effect of the inclusions will be poor. Therefore, in the second refining process, the time of the refining stage and the standing stage is strictly optimized, so that various inclusions can be better adsorbed and taken out of the melt, ensuring that the amount of inclusions in the melt after the second refining is significantly reduced.

[0203] By comparing Examples 1 to 6 with Comparative Example 6, it can be seen that the online degassing using two rotors will lead to a significant increase in the hydrogen content in the final regenerated melt, and too high a hydrogen content is likely to cause defects such as looseness in the final ingot, such as Figure 5 , Figure 6 As shown, in subsequent applications, such as plate rolling, cracking is likely to occur at loose locations, reducing the product yield.

[0204] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0205] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for recycling aluminum chips from 7 series aluminum alloys, characterized in that: The 7 series aluminum alloy processing aluminum chips are 7 series aviation aluminum alloy processing aluminum chips produced in the aerospace field. The grade-preserving recycling method of the 7 series aluminum alloy processing aluminum chips includes: Step S1, smelting stage: Step S1-1, in a smelting furnace, the 7 series aluminum alloy primary scrap is first melted to obtain a bottoming aluminum liquid; the bottoming aluminum liquid is flowed from the smelting furnace into a side well furnace through a circulation pump; Step S1-2, in the side well furnace, mixing the 7 series aluminum alloy processing aluminum chips with the base aluminum liquid, and obtaining a first melt after a second melting; during the second melting process, the circulation pump is kept turned on and the circulation direction is changed so that the first melt circulates in the side well furnace and the smelting furnace; The thickness of the aluminum chips processed by the 7 series aluminum alloy is 0.1mm~5.0mm, and the diameter of the chips is 10mm~60mm; Step S2, refining stage: Step S2-1, performing a first refining of the first melt for 15 min to 60 min to obtain a second melt; Step S2-2, batching the second melt according to the composition of the regenerated melt to be prepared to obtain a third melt; Step S2-3, in a protective atmosphere, performing a second refining on the third melt to obtain a fourth melt; the second refining includes a refining process and a standing process, and the refining process lasts for 15 min to 60 min, and the standing process lasts for 30 min to 120 min; Step S3, purification stage: Step S3-1, performing three-rotor degassing on the fourth melt to obtain a fifth melt; Step S3-2, filtering the fifth melt online to obtain the regenerated melt; the filter plate accuracy of the filter used for the online filtration is ≥30PPI; Step S4, casting stage: the regenerated melt is cast to obtain a regenerated 7 series aluminum alloy ingot.

2. The method for recycling aluminum chips from 7 series aluminum alloy processing according to claim 1, characterized in that: In step S1, when the temperature of the primer aluminum liquid is 720°C~760°C, the primer aluminum liquid is flowed from the smelting furnace into the side well furnace through the circulation pump; the circulation pump is kept turned on, the 7 series aluminum alloy processing aluminum chips are mixed with the primer aluminum liquid and the second melting is performed.

3. The method for recycling aluminum chips from 7 series aluminum alloy processing according to claim 2, characterized in that: Step S2-1 is performed in the smelting furnace, and step S2-1 also includes adding a refining agent in an amount of 0.8 kg / ton of melt to 1.2 kg / ton of melt to the first melt, and then performing the first refining.

4. The method for recycling aluminum chips from 7-series aluminum alloy processing according to any one of claims 1 to 3, characterized in that: In step S2-2, when the temperature of the second melt is 730°C-750°C, the second melt is batched.

5. The method for recycling aluminum chips from 7 series aluminum alloy processing according to claim 4, characterized in that: In step S2-3, the refining process takes 15 minutes to 45 minutes, and the standing process takes 30 minutes to 90 minutes.

6. The method for recycling aluminum chips from 7 series aluminum alloy processing according to claim 5, characterized in that: In step S2-3, the flow rate of the protective atmosphere is 2.0 m 3 / h~4.0m 3 / h; Preferably, the protective atmosphere is nitrogen and / or argon.

7. The method for recycling aluminum chips from 7 series aluminum alloy processing according to claim 6, characterized in that: In step S3-2, the filter is a double-stage plate filter, and the accuracy of the filter plate used for the first-stage filtration is 30PPI~40PPI, and the accuracy of the filter plate used for the second-stage filtration is 50PPI~60PPI.

8. The method for recycling aluminum chips from 7 series aluminum alloy processing according to claim 7, characterized in that: The slag content in the regenerated melt is 0.005 mm 2 / kgAl~0.030mm 2 / kgAl, the hydrogen content is 0.01mL / 100g Al~0.10mL / 100gAl, and the alkali metal content is 2ppm~6ppm.

9. A recycled 7 series aluminum alloy ingot, characterized in that: The recycled 7 series aluminum alloy ingot is prepared by the grade-preserving recovery method of 7 series aluminum alloy processing aluminum chips according to any one of claims 1 to 8, and the components of the recycled 7 series aluminum alloy ingot include, by weight percentage: 0.020wt.%~0.040wt.% Si, 0.05wt.%~0.09wt.% Fe, 2.0wt.%~2.4wt.% Cu, 0.0005wt.%~0.0040wt.% Mn, 1.90wt.%~2.30wt.% Mg, 0.004wt.%~0.007wt.% Cr, 6.0wt.%~6.6wt.% Zn, 0.02wt.%~0.04wt.% Ti, 0.09wt.%~0.12wt.% Zr, and the rest is Al.

10. Use of the recycled 7 series aluminum alloy ingot according to claim 9 as a structural material in the aerospace field.

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