Method for driving impurity iron to enrich and purify aluminum alloy return scrap and product

Abstract

The invention relates to a method for driving impurity iron to enrich and purify aluminum alloy return scrap and a product, the aluminum alloy return scrap is placed in a crucible, is heated in a resistance furnace and is subjected to heat preservation for a period of time, so that the return scrap is fully molten, and a melt is obtained; continuously preserving the heat of the melt, connecting two parallel electrodes with a pulse power supply, vertically inserting the two parallel electrodes into the melt, and preheating for a period of time; setting a first pulse voltage, a first pulse current and a first pulse frequency according to the impurity iron content of the aluminum alloy return scrap; second pulse voltage, second pulse current and second pulse frequency are set according to different heat preservation temperatures during melt electric pulse treatment, and electric pulse treatment is applied to the melt for a period of time in the heat preservation stage; and closing the resistance furnace and the pulse power supply after treatment, and cooling the melt along with the furnace to obtain a sample. The method effectively solves the problem of malignant accumulation of impurity iron elements in the aluminum alloy resource recycling process. The method is short in treatment time and high in iron removal efficiency, and the production cost can be greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of melt purification in a remelting process of aluminum return materials, and in particular relates to a method and a product for driving impure iron to enrich and purify aluminum alloy return materials. Background Art

[0002] In recent years, aluminum products will gradually enter a scrap period, and a large amount of scrap aluminum resources can be recycled. The recycling of scrap aluminum can effectively reduce energy consumption and waste emissions, and is conducive to green and sustainable development. However, the reuse of scrap aluminum will be accompanied by the continuous accumulation of impurity elements. Most scrap aluminum products are downgraded to casting alloys, and only a small part is returned for secondary processing for subsequent production of deformed aluminum alloys. Among them, the excessive content of impurity iron elements seriously limits the grade-keeping utilization of recycled aluminum alloys. Moreover, the solid solubility of iron in aluminum is very low, and it is very easy to form a narrow needle-shaped iron-rich phase, which will split the matrix and hinder the flow of liquid metal in the shrinkage channel, seriously affecting the mechanical properties, casting properties and corrosion resistance of the alloy. Therefore, reducing the iron content in the return material of aluminum is a problem that needs to be solved urgently.

[0003] At present, the excessive content of impurity iron seriously limits the grade-keeping utilization of recycled aluminum alloys. There are measures such as diluting the original aluminum, adding alloy elements, gravity separation and adding iron removal flux, but this problem cannot be effectively solved. The first two treatment methods essentially still have impurity iron in the alloy, and with the increase of the number of cycles, the impurity elements will continue to accumulate, eventually leading to the degradation of the alloy. The latter two methods both use the density of iron-containing substances greater than that of aluminum melts, and rely on gravity sedimentation to separate impurity iron, but the required processing time is long and the efficiency is low. In recent years, pulse current melt purification technology has been continuously developed, and good progress has been made in the impurity removal of many types of metal melts. Prior art (CN111549237A) discloses a method for separating iron elements in a recycled aluminum melt, by applying a pulse current in the melt solidification stage, iron atoms can be migrated to the negative electrode to realize Al-Fe separation in the melt. However, the processing time of this technology is long, and the enrichment of impurity iron in the negative electrode is not conducive to the promotion and use of this technology in industry.

[0004] According to research, the melting points of α-Fe and β-Fe are about 860℃ and 870℃ respectively. Therefore, if the iron-rich phase is remelted at a lower temperature, it will not be completely dissolved, and the newly precipitated iron phase will take the unmelted iron phase as the nucleation substrate. Therefore, a new treatment method is urgently needed. Summary of the invention

[0005] In order to overcome the problems existing in the prior art, the present invention provides a method and product for driving impure iron to enrich and purify aluminum alloy return material.

[0006] A method for driving impure iron to enrich and purify aluminum alloy return material, comprising the following steps:

[0007] S1. The aluminum alloy return material is placed in a crucible and heated to a certain temperature in a resistance furnace and kept warm for a period of time so that the return material is fully melted to obtain a melt;

[0008] S2. The melt is kept warm, two parallel electrodes are connected to a pulse power supply and vertically inserted into the melt, and preheated for a period of time;

[0009] S3. According to the impurity iron content of the aluminum alloy return material, setting the first pulse voltage, the first pulse current and the first pulse frequency;

[0010] S4. According to the different holding temperatures of the melt during the electric pulse treatment, the second pulse voltage, the second pulse current and the second pulse frequency are set, and the electric pulse treatment is applied to the melt for a period of time during the holding stage, so as to drive the impurity iron to be enriched at the bottom of the melt;

[0011] S5. After the treatment is completed, the resistance furnace and the pulse power supply are turned off, and the melt is cooled in the furnace to obtain a sample.

[0012] According to the above aspects and any possible implementation, an implementation is further provided, wherein the certain temperature in S1 is 660-800°C, and the insulation period is 30-120 minutes, and the melt is stirred for 5-10 minutes to make its composition and temperature uniform.

[0013] According to the above aspects and any possible implementation, an implementation is further provided, wherein the period of time in S2 is 5 to 10 minutes; and the period of time in S4 is 15 minutes.

[0014] According to the above aspects and any possible implementation, an implementation is further provided, in step S2, the two parallel electrodes are made of graphite and are inserted to a depth of 1 / 4 of the melt.

[0015] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the impurity iron content of the S3 aluminum alloy return material is 0.1 to 3.0 wt.%.

[0016] According to the above aspects and any possible implementation, there is further provided an implementation, wherein the first pulse voltage is 10 to 100 V, the first pulse current is 10 to 300 A, and the first pulse frequency is 10 to 1000 Hz.

[0017] According to the above aspects and any possible implementation, an implementation is further provided, wherein S3 specifically includes:

[0018] When the iron content in the aluminum alloy return material is [0.1, 1.0] wt.%, the first pulse voltage is 10 to 30 V, the first pulse current is 10 to 100 A, and the pulse frequency is 10 to 300 Hz;

[0019] When the iron content in the aluminum alloy return material is (1.0, 2.0) wt.%, the first pulse voltage is 31-60 V, the first pulse current is 101-200 A and the first pulse frequency is 301-600 Hz;

[0020] When the iron content in the aluminum alloy return material is [2.0, 3.0] wt.%, the first pulse voltage is 61-100 V, the first pulse current is 201-300 A, and the first pulse frequency is 601-1000 Hz.

[0021] According to the above aspects and any possible implementation, an implementation is further provided, in the step S4, according to the different holding temperatures during the electric pulse treatment of the melt, the second pulse voltage, the second pulse current and the second pulse frequency are further set, specifically:

[0022] When the heat preservation electric pulse treatment is carried out in the range of 660-700° C., the second pulse voltage, the second pulse current and the second pulse frequency are respectively increased by 10-20% on the basis of the first pulse voltage, the first pulse current and the first pulse frequency;

[0023] When the heat preservation electric pulse treatment is performed in the range of 701-750° C., the second pulse voltage, the second pulse current and the second pulse frequency are respectively the same as the first pulse voltage, the first pulse current and the first pulse frequency;

[0024] When the heat preservation electric pulse treatment is carried out in the range of 751-800° C., the second pulse voltage, the second pulse current and the second pulse frequency are respectively reduced by 10-20% based on the first pulse voltage, the first pulse current and the first pulse frequency.

[0025] According to the above aspects and any possible implementation, an implementation is further provided, wherein the iron content is 0.136 wt.%, 1.224 wt.%, or 2.241 wt.%.

[0026] The present invention also provides an aluminum alloy return material, and the aluminum alloy return material is obtained by using the method described.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The method of the present invention sets the corresponding first pulse voltage, pulse current and pulse frequency according to the different impurity iron content in the aluminum alloy return material within the temperature range where the iron-rich phase has not been completely melted; at the same time, according to the different insulation temperatures during the electric pulse treatment, the second pulse parameters are further set, and the directional migration of the impurity iron phase can be achieved under a relatively short treatment time, and the deep purification of the aluminum alloy return material can be achieved. The method of the present invention can effectively solve the vicious accumulation of impurity iron elements in the recycling process of aluminum alloy resources. The method has a short processing time and high iron removal efficiency, which can greatly reduce production costs. The melting points of the α-Fe phase and the β-Fe phase are approximately 860°C and 870°C, respectively. Therefore, when remelting at a lower temperature (660-800°C), the iron-rich phase is not completely melted. Based on this, the present invention uses electric pulses to drive the enrichment of impurity iron to achieve the purification of the aluminum alloy melt at the stage where the iron-rich phase is not completely melted. The technology is simple to build, has a short processing time, high iron removal efficiency and is green and pollution-free, and is expected to be used as an emerging purification method in industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0030] In order to better understand the technical solution of the present invention, the content of the present invention includes but is not limited to the specific implementation methods described below, and similar technologies and methods should be considered to be within the scope of protection of the present invention. In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

[0031] It should be clear that the embodiments described in the present invention are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0033] A method for the use of recycled aluminum alloys to maintain grade due to the excessive content of impurity iron, which seriously limits the use of recycled aluminum alloys. Existing technical measures such as dilution of primary aluminum, addition of alloying elements, gravity separation and addition of iron removal flux are limited by their cost and efficiency and are therefore limited in their application in industrial production. The present invention proposes a method for enriching and purifying aluminum alloy return materials using electric pulses to drive impurity iron.

[0034] like Figure 1As shown, the present invention provides a method for enriching and purifying aluminum alloy return material by using electric pulse to drive impure iron, comprising the following steps:

[0035] S1: Place the aluminum alloy return material in a crucible and heat it to 660-800°C in a resistance furnace. Keep the temperature for 30-120 minutes to fully melt the return material to obtain a melt. At this time, the iron-rich phase in the melt is not completely melted. Then stir the melt for 5-10 minutes to make its composition and temperature uniform;

[0036] S2: The melt continues to be kept warm, and two parallel electrodes are connected to a pulse power supply and vertically inserted into the melt, and preheated for 5 to 10 minutes to keep the temperature of the electrodes and the melt stable;

[0037] S3: According to the impurity iron content of the aluminum alloy return material, in order to ensure the treatment effect of the electric pulse, the initial pulse voltage, pulse current and pulse frequency, that is, the first pulse parameters, are first set, including the first pulse voltage, the first pulse current and the first pulse frequency, which correspond to the initial pulse voltage, pulse current and pulse frequency respectively;

[0038] S4: According to the different holding temperatures during the electric pulse treatment of the melt, in order to achieve a certain purification effect on the melt, the initial pulse voltage, pulse current and pulse frequency are further adjusted, that is, the second pulse parameters, i.e., the second pulse voltage, the second pulse current and the second pulse frequency, are set on the basis of the first pulse parameters, and the second pulse parameters are used to apply the electric pulse treatment to the melt for 15 minutes during the holding stage, so as to drive the impurity iron to be enriched at the bottom of the melt;

[0039] S5: After the treatment is completed, turn off the resistance furnace, turn off the pulse power supply, and let the sample cool down with the furnace.

[0040] Preferably, in step S2, the electrode is shallowly inserted into the melt to a depth of 1 / 4 to create a non-uniform electric field, and the material is graphite.

[0041] Preferably, in step S3, the method can process aluminum alloy return material with an iron content ranging from 0.1 to 3.0 wt.%.

[0042] Preferably, in step S3, the first pulse voltage is 10-100V, the first pulse current is 10-300A, and the first pulse frequency is 10-1000Hz. The electric pulse treatment effect is best within this parameter range.

[0043] Further preferably, in step S3, the initial pulse voltage, pulse current and pulse frequency are set according to the impurity iron content of the aluminum alloy return material, specifically:

[0044] When the iron content in the aluminum alloy return material is [0.1,1.0]wt.%, the lower electric pulse treatment parameters can drive the impurity iron to be enriched at the bottom of the melt. The pulse voltage is 10-30V, the pulse current is 10-100A, and the pulse frequency is 10-300Hz;

[0045] When the iron content in the aluminum alloy return material is (1.0, 2.0) wt.%, as the iron content increases, the electric pulse treatment parameters need to be appropriately increased to ensure a good purification effect. The pulse voltage is 31-60V, the pulse current is 101-200A, and the pulse frequency is 301-600Hz;

[0046] When the iron content in the aluminum alloy return material is [2.0,3.0]wt.%, higher electric pulse treatment parameters can drive the impurity iron to be enriched at the bottom of the melt. The pulse voltage is 61~100V, the pulse current is 201~300A, and the pulse frequency is 601~1000Hz.

[0047] Preferably, in step S4, the initial pulse voltage, pulse current and pulse frequency are further adjusted according to the different holding temperatures during the electric pulse treatment of the melt, specifically: when the electric pulse treatment is carried out in the range of 660-700°C, the melt temperature is low, the viscosity is large, and the fluidity is poor, and the electric pulse treatment parameters need to be appropriately increased, so the second pulse voltage, the second pulse current and the second pulse frequency are all increased by 10-20% on the basis of the first pulse parameters;

[0048] When the heat preservation electric pulse treatment is carried out in the range of 701-750°C, the melt temperature is suitable and there is no need to change the electric pulse treatment parameters, so the second pulse voltage, the second pulse current and the second pulse frequency are the same as the corresponding first pulse voltage, the first pulse current and the first pulse frequency of the first pulse parameters, that is, they are unchanged on the basis of the first pulse parameters;

[0049] When the heat-insulating electric pulse treatment is carried out in the range of 751-800°C, the melt temperature is relatively high, the viscosity is low, and the fluidity is good, and very high electric pulse treatment parameters are not required. Therefore, the second pulse voltage, the second pulse current, and the second pulse frequency are all reduced by 10-20% based on the first pulse parameters, that is, the first pulse voltage, the first pulse current, and the first pulse frequency are each reduced by 10-20% as the second pulse voltage, the second pulse current, and the second pulse frequency.

[0050] As an embodiment disclosed in the present invention, the present invention also provides an aluminum alloy return material. By utilizing the method of the present invention, electric pulses are used to purify low iron to high iron content, so that the impurity iron is enriched in the lower 2 / 5 region of the obtained aluminum alloy ingot to a certain extent, and the upper 3 / 5 region is purified.

[0051] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0052] Example 1

[0053] This embodiment performs pulse current treatment on aluminum alloy return material with an iron content of 0.136wt.% in the crucible. The process includes the following steps:

[0054] S1: The aluminum alloy return material is placed in a crucible and heated to 780°C in a resistance furnace. The temperature is kept for 50 minutes to fully melt the raw material, and then the melt is stirred for 5 minutes to make its composition and temperature uniform;

[0055] S2: The melt is kept warm at 780°C, two parallel electrodes are connected to a pulse power supply and vertically inserted into the melt to a depth of 1 / 4, and preheated for 5 minutes;

[0056] S3: According to the impurity iron content of the aluminum alloy return material, the initial pulse voltage, pulse current and pulse frequency are set; the pulse voltage is 20V, the pulse current is 100A, and the pulse frequency is 150Hz.

[0057] S4: According to the different holding temperatures during the electric pulse treatment of the melt, the initial pulse voltage is further adjusted to 18V, the pulse current is 90A, and the pulse frequency is 130Hz, and the electric pulse treatment is applied to the melt for 15min during the holding stage;

[0058] S5: After the treatment, turn off the resistance furnace, turn off the pulse power supply, and let the sample cool down with the furnace;

[0059] S6: The solidified aluminum alloy return material ingot obtained after pulse treatment was cut longitudinally along the center line of the two electrodes. After grinding and polishing, the overall distribution of the iron-rich phase can be clearly observed in the backscattering mode of the scanning electron microscope. It was observed that the impure iron phase was mainly enriched in the position below 2 / 5 of the height of the bottom of the ingot, and the upper 3 / 5 area was purified, achieving the purpose of impure iron driven enrichment. The impure iron content at different positions was detected, and the iron content dropped from the original 0.136wt.% to a minimum of 0.058wt.%, and the maximum iron removal rate was 57.4%, indicating that the aluminum alloy return material ingot was purified.

[0060] Example 2

[0061] This embodiment performs pulse current treatment on aluminum alloy return material with an iron content of 1.224wt.% in a crucible. The process includes the following steps:

[0062] S1: The aluminum alloy return material is placed in a crucible and heated to 720°C in a resistance furnace. The temperature is kept for 60 minutes to fully melt the raw material, and then the melt is stirred for 5 minutes to make its composition and temperature uniform;

[0063] S2: The melt is kept warm at 720℃, two parallel electrodes are connected to a pulse power supply and vertically inserted into the melt to a depth of 1 / 4, and preheated for 5 minutes;

[0064] S3: According to the impurity iron content of the aluminum alloy return material, the initial pulse voltage, pulse current and pulse frequency are set; the pulse voltage is 50V, the pulse current is 150A, and the pulse frequency is 500Hz.

[0065] S4: further adjusting the initial pulse voltage, pulse current and pulse frequency according to the different holding temperatures during the electric pulse treatment of the melt, and applying electric pulse treatment to the melt for 15 minutes during the holding stage;

[0066] S5: After the treatment, turn off the resistance furnace, turn off the pulse power supply, and let the sample cool down with the furnace;

[0067] S6: The solidified ingot obtained after pulse treatment was cut longitudinally along the center line of the two electrodes. After grinding and polishing, the overall distribution of the iron-rich phase can be clearly observed in the backscattering mode of the scanning electron microscope. It was observed that the impure iron phase was mainly enriched in the position below 2 / 5 of the height of the bottom of the ingot, and the upper 3 / 5 area was purified, achieving the purpose of impure iron driven enrichment. The impure iron content at different positions was detected, and the iron content dropped from the original 1.224wt.% to a minimum of 0.289wt.%, and the maximum iron removal rate was 76.4%, indicating that the aluminum alloy ingot was purified.

[0068] Example 3

[0069] This embodiment performs pulse current treatment on aluminum alloy return material with an iron content of 2.241wt.% in the crucible. The process includes the following steps:

[0070] S1: The aluminum alloy return material is placed in a crucible and heated to 670°C in a resistance furnace. The temperature is kept for 120 minutes to fully melt the raw material, and then the melt is stirred for 10 minutes to make its composition and temperature uniform;

[0071] S2: The melt is kept warm at 670℃, two parallel electrodes are connected to a pulse power supply and vertically inserted into the melt to a depth of 1 / 4, and preheated for 10 minutes;

[0072] S3: According to the impurity iron content of the aluminum alloy return material, the initial pulse voltage, pulse current and pulse frequency are set; the pulse voltage is 80V, the pulse current is 250A, and the pulse frequency is 800Hz.

[0073] S4: According to the different holding temperatures during the electric pulse treatment of the melt, the initial pulse voltage is further adjusted to 90V, the pulse current is 280A, and the pulse frequency is 900Hz, and the electric pulse treatment is applied to the melt for 15min during the holding stage;

[0074] S5: After the treatment, turn off the resistance furnace, turn off the pulse power supply, and let the sample cool down with the furnace;

[0075] S6: The solidified ingot obtained after pulse treatment was cut longitudinally along the center line of the two electrodes. After grinding and polishing, the overall distribution of the iron-rich phase can be clearly observed in the backscattering mode of the scanning electron microscope. It was observed that the impure iron phase was mainly enriched in the position below 2 / 5 of the height of the bottom of the ingot, and the upper 3 / 5 area was purified, achieving the purpose of impure iron driven enrichment. The impure iron content at different positions was detected, and the iron content dropped from the original 2.241wt.% to a minimum of 0.307wt.%, and the maximum iron removal rate was 86.3%, indicating that the aluminum alloy ingot was purified.

[0076] Comparative Example 1

[0077] This comparative example performs pulse current treatment on aluminum alloy return material with an iron content of 1.224wt.% in a crucible. The process comprises the following steps:

[0078] S1: The aluminum alloy return material is placed in a crucible and heated to 900°C in a resistance furnace. The temperature is kept for 30 minutes to fully melt the raw material, and then the melt is stirred for 5 minutes to make its composition and temperature uniform;

[0079] S2: The melt is kept at 900°C, two parallel electrodes are connected to a pulse power supply and vertically inserted into the melt to a depth of 1 / 4, and preheated for 5 minutes;

[0080] S3: According to the impurity iron content of the aluminum alloy return material, the initial pulse voltage, pulse current and pulse frequency are set, and the melt is subjected to electric pulse treatment for 15 minutes during the insulation stage; the pulse voltage is 50V, the pulse current is 150A, and the pulse frequency is 500Hz.

[0081] S4: After the treatment, turn off the resistance furnace, turn off the pulse power supply, and let the sample cool down with the furnace;

[0082] S5: The solidified ingot obtained after pulse treatment was cut longitudinally along the center line of the two electrodes, and after grinding and polishing, the overall distribution of the iron-rich phase can be clearly observed in the backscattering mode of the scanning electron microscope;

[0083] S6: The holding pulse temperature of this comparative example exceeds the melting temperature of the iron-rich phase. It is observed that the impure iron phase is randomly distributed throughout the height of the ingot, without enrichment. The impure iron content at different positions was detected, and the iron content dropped from the original 1.224wt.% to a minimum of 1.174wt.%, and the maximum iron removal rate was 4.1%. The aluminum alloy ingot failed to be purified.

[0084] Comparative Example 2

[0085] This comparative example performs pulse current treatment on aluminum alloy return material with an iron content of 1.224wt.% in a crucible. The process comprises the following steps:

[0086] S1: The aluminum alloy return material is placed in a crucible and heated to 720°C in a resistance furnace. The temperature is kept for 60 minutes to fully melt the raw material, and then the melt is stirred for 5 minutes to make its composition and temperature uniform;

[0087] S2: The melt is kept warm at 720℃, two parallel electrodes are connected to a pulse power supply and vertically inserted into the melt to a depth of 1 / 4, and preheated for 5 minutes;

[0088] S3: Set the pulse voltage to 10V, the pulse current to 10A, the pulse frequency to 10Hz, and apply electric pulse treatment to the melt for 15min during the insulation stage;

[0089] S4: further adjusting the initial pulse voltage, pulse current and pulse frequency according to the different holding temperatures during the electric pulse treatment of the melt, and applying electric pulse treatment to the melt for 15 minutes during the holding stage;

[0090] S5: After the treatment, turn off the resistance furnace, turn off the pulse power supply, and let the sample cool down with the furnace;

[0091] S6: The solidified ingot obtained after the pulse treatment was cut longitudinally along the center line of the two electrodes, and after grinding and polishing, the overall distribution of the iron-rich phase can be clearly observed in the backscattering mode of the scanning electron microscope;

[0092] S7: This comparative example does not set the initial pulse voltage, pulse current and pulse frequency according to the iron content of the aluminum alloy return material. It is observed that the impure iron phase is randomly distributed throughout the height of the ingot, without enrichment. The impure iron content at different positions was detected, and the iron content dropped from the original 1.224wt.% to a minimum of 1.064wt.%, and the maximum iron removal rate was 13.1%. The aluminum alloy ingot failed to be purified.

[0093] Comparative Example 3

[0094] This comparative example performs pulse current treatment on aluminum alloy return material with an iron content of 0.136wt.% in a crucible. The process comprises the following steps:

[0095] S1: The aluminum alloy return material is placed in a crucible and heated to 780°C in a resistance furnace. The temperature is kept for 50 minutes to fully melt the raw material, and then the melt is stirred for 5 minutes to make its composition and temperature uniform;

[0096] S2: The melt is kept warm at 780°C, two parallel electrodes are connected to a pulse power supply and vertically inserted into the melt to a depth of 1 / 4, and preheated for 5 minutes;

[0097] S3: According to the impurity iron content of the aluminum alloy return material, the initial pulse voltage, pulse current and pulse frequency are set, and the melt is subjected to electric pulse treatment for 15 minutes during the insulation stage; the pulse voltage is 20V, the pulse current is 100A, and the pulse frequency is 150Hz.

[0098] S4: After the treatment, turn off the resistance furnace, turn off the pulse power supply, and let the sample cool down with the furnace;

[0099] S5: The solidified ingot obtained after pulse treatment was cut longitudinally along the center line of the two electrodes, and after grinding and polishing, the overall distribution of the iron-rich phase can be clearly observed in the backscattering mode of the scanning electron microscope;

[0100] S6: This comparative example sets the initial pulse parameters according to the iron content of the aluminum alloy return material, but does not adjust the pulse parameters according to the different holding temperatures during the melt electric pulse treatment. It is observed that the impure iron phase is mainly enriched in the position below 3 / 5 of the height of the bottom of the ingot. The impure iron content at different positions was detected, and the iron content dropped from the original 0.136wt.% to 0.096wt.%, and the maximum iron removal rate was 29.4%. The purification effect of the aluminum alloy ingot was not good.

[0101] Comparative Example 4

[0102] This comparative example performs pulse current treatment on aluminum alloy return material with an iron content of 0.136wt.% in a crucible. The process comprises the following steps:

[0103] S1: The aluminum alloy return material is placed in a crucible and heated to 780°C in a resistance furnace. The temperature is kept for 50 minutes to fully melt the raw material, and then the melt is stirred for 5 minutes to make its composition and temperature uniform;

[0104] S2: The melt is kept warm at 780°C, two parallel electrodes are connected to a pulse power supply and vertically inserted into the melt, and preheated for 5 minutes;

[0105] S3: According to the impurity iron content of the aluminum alloy return material, the initial pulse voltage, pulse current and pulse frequency are set; the pulse voltage is 20V, the pulse current is 100A, and the pulse frequency is 150Hz.

[0106] S4: According to the different holding temperatures during the electric pulse treatment of the melt, the initial pulse voltage is further adjusted to 18V, the pulse current is 90A, and the pulse frequency is 130Hz, and the electric pulse treatment is applied to the melt for 15min during the holding stage;

[0107] S5: After the treatment, turn off the resistance furnace, turn off the pulse power supply, and let the sample cool down with the furnace;

[0108] S6: The solidified ingot obtained after the pulse treatment was cut longitudinally along the center line of the two electrodes, and after grinding and polishing, the overall distribution of the iron-rich phase can be clearly observed in the backscattering mode of the scanning electron microscope;

[0109] S7: This comparative example sets the initial pulse parameters according to the iron content of the aluminum alloy return material, and also adjusts the pulse parameters according to the different holding temperatures during the melt electric pulse treatment, but the electrode is completely inserted into the melt. It is observed that the impure iron phase is randomly distributed throughout the height of the ingot, without enrichment. The impure iron content at different positions was detected, and the iron content dropped from the original 0.136wt.% to a minimum of 0.125wt.%, and the maximum iron removal rate was 8.1%. The aluminum alloy ingot failed to be purified.

[0110] It can be seen from the above embodiments and comparative examples that the present invention needs to set the corresponding initial pulse voltage, pulse current and pulse frequency according to the different impurity iron content in the aluminum alloy return material within the temperature range (660-800°C) where the iron-rich phase has not been completely melted; at the same time, according to the different insulation temperatures during the electric pulse treatment, the initial pulse parameters are further adjusted, and the directional migration of the impurity iron phase can be achieved under a relatively short treatment time, and the deep purification of the aluminum alloy return material can be achieved. The method of the present invention can effectively solve the vicious accumulation of impurity iron elements in the process of recycling aluminum alloy resources and reduce production costs.

[0111] The above description shows and describes several preferred embodiments of the present invention, but as mentioned above, it should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not depart from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for driving impure iron to enrich and purify aluminum alloy return material, characterized in that: The steps include: S1. The aluminum alloy return material is placed in a crucible and heated to a certain temperature in a resistance furnace and kept warm for a period of time so that the return material is fully melted to obtain a melt; S2. The melt is kept warm, two parallel electrodes are connected to a pulse power supply and vertically inserted into the melt, and preheated for a period of time; S3. According to the impurity iron content of the aluminum alloy return material, setting the first pulse voltage, the first pulse current and the first pulse frequency; S4. According to the different holding temperatures of the melt during the electric pulse treatment, the second pulse voltage, the second pulse current and the second pulse frequency are set, and the electric pulse treatment is applied to the melt for a period of time during the holding stage, so as to drive the impurity iron to be enriched at the bottom of the melt; S5. After the treatment is completed, the resistance furnace and the pulse power supply are turned off, and the melt is cooled in the furnace to obtain a sample.

2. The method according to claim 1, characterized in that The certain temperature in S1 is 660-800° C., and the heat preservation period is 30-120 minutes. The melt is also stirred for 5-10 minutes to make its composition and temperature uniform.

3. The method according to claim 1, characterized in that The period of time in S2 is 5 to 10 minutes; the period of time in S4 is 15 minutes.

4. The method according to claim 1, characterized in that: In step S2, the two parallel electrodes are made of graphite and inserted to a depth of 1 / 4 of the melt.

5. The method according to claim 1, characterized in that The impurity iron content of the S3 aluminum alloy return material is 0.1-3.0wt.%.

6. The method according to claim 5, characterized in that The first pulse voltage is 10-100V, the first pulse current is 10-300A and the first pulse frequency is 10-1000Hz.

7. The method according to claim 6, characterized in that The S3 specifically includes: When the iron content in the aluminum alloy return material is [0.1, 1.0] wt.%, the first pulse voltage is 10 to 30 V, the first pulse current is 10 to 100 A, and the pulse frequency is 10 to 300 Hz; When the iron content in the aluminum alloy return material is (1.0, 2.0) wt.%, the first pulse voltage is 31-60 V, the first pulse current is 101-200 A and the first pulse frequency is 301-600 Hz; When the iron content in the aluminum alloy return material is [2.0, 3.0] wt.%, the first pulse voltage is 61-100 V, the first pulse current is 201-300 A, and the first pulse frequency is 601-1000 Hz.

8. The method according to claim 1, characterized in that In the step S4, according to the different holding temperatures during the melt electric pulse treatment, the second pulse voltage, the second pulse current and the second pulse frequency are further set, specifically: When the heat preservation electric pulse treatment is carried out in the range of 660-700° C., the second pulse voltage, the second pulse current and the second pulse frequency are respectively increased by 10-20% on the basis of the first pulse voltage, the first pulse current and the first pulse frequency; When the heat preservation electric pulse treatment is performed in the range of 701-750° C., the second pulse voltage, the second pulse current and the second pulse frequency are respectively the same as the first pulse voltage, the first pulse current and the first pulse frequency; When the heat preservation electric pulse treatment is carried out in the range of 751-800° C., the second pulse voltage, the second pulse current and the second pulse frequency are respectively reduced by 10-20% based on the first pulse voltage, the first pulse current and the first pulse frequency.

9. The method according to claim 5, characterized in that The iron content is 0.136wt.%, 1.224wt.%, and 2.241wt.%.

10. An aluminum alloy return material, characterized in that: The aluminum alloy return material is obtained by the method described in any one of claims 1-9.

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