A method for regenerating die-cast aluminum alloy waste for automobile parts

Abstract

The invention discloses a method for regenerating die-cast aluminum alloy waste for automobile parts, which belongs to the technical field of circular economy. The method comprises the following steps in sequence: sorting and pre-treating die-cast aluminum alloy waste, heating and melting die-cast aluminum alloy waste into aluminum alloy liquid, online detecting and adjusting the components of aluminum alloy liquid, performing powder spraying and mixed gas spraying refining on the aluminum alloy liquid, and finally casting the aluminum alloy liquid into aluminum alloy. The invention obtains die-cast aluminum alloy whose components and properties meet the requirements of automobile parts by sorting and pre-treating die-cast aluminum alloy waste and performing refining, purification and refinement and metamorphism treatment on the aluminum alloy liquid, thereby realizing the regeneration of die-cast aluminum alloy waste, improving the utilization value of die-cast aluminum alloy waste, reducing the production cost of automobile parts, and realizing low-carbon production of automobile parts.

Description

Technical Field

[0001] The invention belongs to the technical field of circular economy, and in particular relates to a method for regenerating die-cast aluminum alloy waste of automobile parts with guaranteed grade. Background Art

[0002] Aluminum alloy die casting is the process of injecting aluminum alloy hydraulically into a metal mold under high pressure to cool and solidify it into aluminum alloy parts. The high production efficiency of aluminum alloy die casting makes aluminum alloy die casting widely used in the production of automotive parts, such as automobile engine blocks, cylinder heads, brackets, crankcase shells, cylinder heads, intake pipes, chain covers, gearbox shells, suspension brackets, etc. Automobiles have become the largest application market for aluminum alloy die castings. According to statistics from the China Foundry Industry Association, the output of automotive aluminum alloy die castings in my country will reach more than 6 million tons in 2023. Every year, when a large number of automotive aluminum alloy die castings are produced, a large amount of die-casting aluminum alloy waste is also continuously generated, including the material handles and flash cut from the die casting blanks, aluminum chips produced by machining, unqualified die castings, and scrapped automotive parts.

[0003] The patent document with publication number CN111378841A discloses a die-cast aluminum alloy scrap recovery process, the process flow includes collecting the aluminum alloy scraps, ultrasonic cleaning, heating to above 710-730°C, transferring to a vacuum sealed container, cooling by passing a liquid inert cold medium below -150°C, breaking the aluminum alloy scraps into pieces, drying in a rotary drying kiln, soaking in a sulfuric acid solution, cleaning with clean water, ultrasonic washing, drying, medium frequency induction aluminum melting, removing slag, injecting into a die casting mold to cast into a flat ingot blank, and completing the recovery of the aluminum alloy scraps.

[0004] Patent document with publication number CN113385473A discloses a method for recycling die-cast aluminum alloy scraps, which classifies die-cast aluminum alloy scraps according to different alloy contents, and puts the same kind of die-cast aluminum alloy scraps into a drum of a recovery device through a hopper. The die-cast aluminum alloy scraps are stirred and cleaned in a cleaning liquid as the drum of the recovery device rotates, and an ultrasonic transducer located at the bottom of the recovery device generates ultrasonic waves to ultrasonically clean the die-cast aluminum alloy scraps. After cleaning, the die-cast aluminum alloy scraps are dried, and then the die-cast aluminum alloy scraps are melted and reacted, and then cast into aluminum blocks.

[0005] Patent document with publication number CN108165750A discloses a method for recycling and treating aluminum and aluminum alloy waste, which recycles and classifies aluminum and aluminum alloy waste and packages them; melts the packaged aluminum and aluminum alloy waste using a medium-frequency induction aluminum melting method to obtain a melt; introduces the melt into a smelting furnace for alloy proportioning, degassing, deslagging, and casting into a flat ingot blank, thereby completing the recycling and treatment of aluminum and aluminum alloy waste.

[0006] From the results of literature retrieval and production practice experience, it can be seen that since there are many types of die-cast aluminum alloy waste for automobile parts and their sources are wide, the surface is inevitably covered or adhered with paint, coatings, oil stains, and they carry or are inlaid with steel, rubber, plastic, wood, stones, mud, etc., which makes it difficult to recycle die-cast aluminum alloy waste. The composition of the recycled aluminum alloy is complex, the gas slag content is high, and the performance and quality are not up to standard or unstable, which cannot meet the die-casting requirements of automobile parts. The existing technology usually downgrades die-cast aluminum alloy waste for the production of non-automotive parts with low requirements for composition and performance, resulting in a huge waste of die-cast aluminum alloy for automobile parts. Therefore, the existing regeneration method of die-cast aluminum alloy waste for automobile parts still needs to be improved and developed. Summary of the invention

[0007] In view of the problems and shortcomings mentioned in the background technology, the present invention provides a method for retaining the grade of die-cast aluminum alloy waste for automobile parts. By sorting and pretreating the die-cast aluminum alloy waste and refining, removing slag and hydrogen, and refining and modifying the aluminum alloy liquid, a die-cast aluminum alloy having a composition and performance that meet the requirements of automobile parts is obtained, the grade-retaining regeneration of the die-cast aluminum alloy waste is achieved, the utilization value of the die-cast aluminum alloy waste is improved, the production cost of automobile parts is reduced, and the low-carbon production of die-cast aluminum alloy automobile parts is achieved.

[0008] The present invention achieves the above-mentioned purpose by adopting the following technical solutions:

[0009] A method for regenerating die-cast aluminum alloy waste of automobile parts with guaranteed grade, characterized in that it comprises the following steps in sequence:

[0010] Step 1: sorting and pre-treating the die-casting aluminum alloy waste to obtain die-casting aluminum alloy waste that can be recycled;

[0011] Step 2: heating and melting the die-casting aluminum alloy waste after sorting and pretreatment into aluminum alloy liquid;

[0012] Step 3: Online detection and adjustment of the chemical composition of the aluminum alloy liquid;

[0013] Step 4: using argon gas and refining agent to spray and refine the aluminum alloy liquid;

[0014] Step 5: Using mixed gas to spray and refine the aluminum alloy liquid;

[0015] Step 6: Cast the aluminum alloy liquid into aluminum alloy to obtain die-cast aluminum alloy for automotive parts.

[0016] Furthermore, the separation and pretreatment of the die-cast aluminum alloy waste described in step one is to separate and remove the iron, rubber, plastic, wood, stone, mud and other inclusions carried or embedded in the die-cast aluminum alloy waste, so as to obtain die-cast aluminum alloy waste that can be recycled. The iron includes iron wire, iron nails, iron blocks, etc. The separation and pretreatment method can be manually picked and removed, or mechanically. The mechanical method usually first crushes the die-cast aluminum alloy waste with a crusher, and then removes the inclusions in the die-cast aluminum alloy waste by magnetic separation, air separation or water separation. For die-cast aluminum alloy waste without inclusions, it can be directly recycled without separation, but die-cast aluminum alloy waste containing inclusions must be sorted and pretreated. The cost of manual separation and pretreatment is low, but the disadvantage is that the labor intensity is relatively large. The mechanical method is suitable for mass production, but the disadvantage is that the investment is large and the cost is high. Manual and mechanical methods each have their own advantages and disadvantages. Whether to use manual sorting or mechanical sorting can be decided based on the die-cast aluminum alloy waste and the specific situation of the enterprise.

[0017] Furthermore, in step 2, heating and melting the die-casting aluminum alloy waste into aluminum alloy liquid is to put the die-casting aluminum alloy waste into an aluminum melting furnace and heat and melt it into aluminum alloy liquid at 720-760°C. The heating temperature should not be lower than 720°C, otherwise the melting speed of the die-casting aluminum alloy waste is too slow. The heating temperature should not be higher than 760°C, as too high a temperature will aggravate the oxidation and burning of the die-casting aluminum alloy waste. The aluminum melting furnace can be a regenerative gas-fired aluminum melting furnace or a medium-frequency induction furnace, among which the regenerative gas-fired aluminum melting furnace has high thermal utilization efficiency, is conducive to reducing energy consumption and production costs, and is an aluminum melting furnace widely used by die-casting aluminum alloy enterprises. The heating and melting speed of the medium-frequency induction furnace is fast and the production efficiency is high, but the power consumption is large, which is not conducive to reducing energy consumption and production costs. Therefore, a regenerative gas-fired aluminum melting furnace is preferably used to heat and melt the die-casting aluminum alloy waste.

[0018] Furthermore, the online detection of the chemical composition of the aluminum alloy liquid described in step three is to cast the aluminum alloy liquid into an aluminum alloy sample, and after turning and flattening, use a desktop direct-reading spectrometer or a handheld spectrometer to detect the chemical composition of the aluminum alloy sample on site. The online adjustment of the chemical composition of the aluminum alloy liquid is to compare the chemical composition of the aluminum alloy sample with the chemical composition requirements of the target die-casting aluminum alloy. If the content of a chemical element is lower than the chemical composition requirements of the target die-casting aluminum alloy, the content of the chemical element in the aluminum alloy liquid is increased by adding pure metal or alloy of the chemical element. If the content of a chemical element exceeds the chemical composition requirements of the target die-casting aluminum alloy, the content of the element in the aluminum alloy liquid is diluted by adding aluminum ingots, so that the chemical composition of the aluminum alloy liquid meets the chemical composition of the target die-casting aluminum alloy.

[0019] Furthermore, the purity of the argon gas in step 4 is ≥99.99%, the amount of the refining agent is 0.1-0.2% of the weight of the aluminum alloy liquid, the temperature of the aluminum alloy liquid during spray refining is 700-720°C, and the spray refining time is 15-20 minutes.

[0020] Since the surface of die-cast aluminum alloy waste is inevitably covered or adhered with paint, coating, oil and water vapor, these coverings and water vapor enter the aluminum melting furnace with the die-cast aluminum alloy waste, and after heating and melting, the aluminum alloy liquid is involved in the inclusions, and the water vapor decomposes and causes the aluminum alloy liquid to absorb hydrogen, so that the aluminum alloy contains a large amount of slag and hydrogen. If the slag and hydrogen removal treatment is not carried out, the slag hydrogen will remain in the aluminum alloy to form defects such as pores, inclusions and looseness, reduce the quality of the aluminum alloy, and deteriorate the mechanical properties and corrosion resistance of the aluminum alloy. Therefore, in order to obtain die-cast aluminum alloy that meets the requirements of automotive parts, the aluminum alloy liquid must be refined, deslaged and dehydrogenated.

[0021] The spray refining adopts a powder spraying tank and a stainless steel pipe, and uses argon as a carrier to spray a solid powdered refining agent into the aluminum alloy liquid, so that the refining agent contacts and reacts with the aluminum alloy liquid, and then the inclusions and hydrogen in the aluminum alloy liquid are taken out of the aluminum alloy liquid. The deslagging and degassing effect of spray refining is related to the purity of argon, the amount of refining agent, the quality of refining agent, the temperature of the aluminum alloy liquid and the spray refining time. The higher the purity of argon, the greater the amount of refining agent, the longer the spray refining time, the better the deslagging and dehydrogenation effect, but the production cost will also increase accordingly. If the temperature of the aluminum alloy liquid is too high or the spray refining time is too long, the oxidation and burning of the aluminum alloy liquid will also increase. After the spray refining is completed, after removing the scum on the surface of the aluminum alloy liquid, a covering agent should be sprinkled on the surface of the aluminum alloy liquid in time to avoid oxidation and burning of the aluminum alloy liquid and re-absorption of hydrogen. After sprinkling the covering agent, the aluminum alloy liquid needs to be left standing for a period of time so that inclusions and bubbles in the aluminum alloy liquid have sufficient time to escape. The standing time of the aluminum alloy liquid is not less than 30 minutes, and preferably the standing time of the aluminum alloy liquid is 30-40 minutes.

[0022] Furthermore, the refining agent in step 4 is composed of the following components in mass percentage: NaCl 35.12%, NaF 19.84%, TiCl3 16.51%, SrSO4 10.06%, KPO3 11.45%, and Na2B4O 77.02%.

[0023] The deslagging and dehydrogenation effect of powder spray refining is closely related to the composition of the refining agent. The existing refining agent is mainly obtained by crushing and mixing fluoride salts and chloride salts, which leads to low deslagging and dehydrogenation efficiency of the refining agent, large emission of irritating smoke and single function, which makes it difficult to meet the needs of die-cast aluminum alloys for automotive parts. In order to improve the deslagging and dehydrogenation effect of powder spray refining, the present invention has developed a highly efficient and environmentally friendly multifunctional powder refining agent, in which NaCl reacts with aluminum liquid to generate AlCl3 with a boiling point of only 180°C. AlCl3 bubbles adsorb and capture inclusions and hydrogen in the aluminum alloy liquid during the floating process, and then escape from the aluminum alloy liquid together, playing a role in deslagging and dehydrogenation. The main function of NaF is to destroy the aluminum oxide film by forming molten salt, dissolve inclusions such as aluminum oxide in the molten salt, increase the surface tension between the inclusions and the aluminum alloy liquid, promote the separation of inclusions such as aluminum oxide from the aluminum alloy liquid, and enhance the deslagging function of the refining agent. TiCl3 reacts with aluminum alloy liquid to generate AlCl3 bubbles, which absorb and capture inclusions and hydrogen in the aluminum alloy liquid during the floating process, enhancing the slag and hydrogen removal capabilities of the refining agent. The Ti element obtained by the reaction can refine the grains of the aluminum alloy and improve the strength and plasticity of the aluminum alloy. SrSO4 reacts with aluminum alloy liquid to generate SO2 bubbles, which absorb and capture inclusions and hydrogen in the aluminum alloy liquid during the floating process, enhancing the slag and hydrogen removal capabilities of the refining agent. The Sr element obtained by the reaction can refine the eutectic Si phase of the modified aluminum alloy and improve the strength and plasticity of the aluminum alloy. KPO3 reacts with aluminum alloy liquid to generate P element, which can refine the primary Si phase of the modified aluminum alloy and improve the strength, plasticity and wear resistance of the aluminum alloy. Na2B4O7 reacts with aluminum liquid to generate B element, which can refine the coarse Fe-rich phase of the modified aluminum alloy, eliminate the harm of the coarse Fe-rich phase to the strength and plasticity of the aluminum alloy, and improve the strength and plasticity of the aluminum alloy.

[0024] Furthermore, the preparation method of the refining agent in step 4 comprises the following steps in sequence:

[0025] (1) According to the composition and mass percentage of the refining agent, NaCl, NaF, TiCl3, SrSO4, KPO3, and Na2B4O7 with a purity of ≥99.8% are selected as raw materials for batching; (2) the ingredients are added into water at a temperature of 70° C. and stirred to dissolve into an aqueous solution, wherein the mass ratio of water to the ingredients is 1.2, and then the aqueous solution is heated to 100° C. to evaporate and obtain solid crystals; (3) the solid crystals are crushed into powders with a particle size of less than 2 mm, and the powders are dried and dehydrated at 160° C. for 4 hours to obtain the refining agent.

[0026] The deslagging and dehydrogenation effects of the refining agent are closely related to its preparation method. Existing refining agents are usually obtained by directly mixing chloride salts and fluoride salts after mechanical crushing. The components of this refining agent exist independently of each other, the melting point of the refining agent is high, and there is a lack of synergy between the components, resulting in low deslagging and dehydrogenation efficiency of the refining agent. The present invention breaks through the traditional preparation method and adopts a solution evaporation method to prepare the refining agent. Through solution evaporation, the components are re-solidified and recrystallized to form a eutectic with a lower melting point. For example, the melting point of NaCl is usually 801°C, and the melting point of NaF is usually 993°C. When the two form a NaCl·NaF eutectic, the melting point drops to 698°C, thereby greatly reducing the melting point of the refining agent, making the refining agent easier to dissolve in the aluminum alloy liquid, and playing a synergistic role during refining, which can significantly enhance the deslagging and dehydrogenation capabilities of the refining agent.

[0027] Furthermore, the mixed gas in step five is composed of argon gas with a purity of ≥99.99%, sulfur hexafluoride and carbon monoxide, the volume percentage of sulfur hexafluoride in the mixed gas is 9-11%, and the volume percentage of carbon monoxide is 3-5%.

[0028] In the existing gas injection refining technology, inert gas nitrogen or argon, or a mixture of inert gas and chlorine, is usually injected into the aluminum alloy liquid. The relative molecular mass of nitrogen is 28.01 and the density is 1.25kg / m 3 The relative molecular mass of argon is 39.94 and the density is 1.78 kg / m 3 The relative molecular mass of chlorine is 70.91 and the density is 3.21kg / m 3 . Due to the small relative molecular mass and low density of nitrogen, argon and chlorine, the bubbles rise faster in the aluminum alloy liquid, and the contact time between the bubbles and the aluminum alloy liquid is shorter, which limits the time for the bubbles to capture and adsorb hydrogen and inclusions, greatly affecting the dehydrogenation and deslagging effect of gas injection refining. In addition, although the relative density of chlorine is relatively large, chlorine is a toxic gas with a strong pungent odor, which will not only corrode the smelting furnace and smelting tools, but also cause serious environmental pollution.

[0029] Aiming at the problems and shortcomings of the existing gas injection refining technology, in order to obtain a highly clean aluminum alloy liquid, the present invention injects a mixed gas consisting of argon with a purity of ≥99.99%, sulfur hexafluoride with a purity of ≥99.99% and carbon monoxide with a purity of ≥99.99% into the aluminum alloy liquid, wherein sulfur hexafluoride is a high-density, high-stability gas with a relative molecular mass of 146.05 and a density of 6.5kg / m 3, and sulfur hexafluoride is non-toxic, non-flammable and non-corrosive. Adding 9-11% by volume of sulfur hexafluoride to the mixed gas can significantly slow down the floating speed of bubbles in the aluminum alloy liquid, increase the contact time between the bubbles and the aluminum alloy liquid, and enable the bubbles to capture and absorb more hydrogen and inclusions, thereby improving the dehydrogenation and deslagging effect of gas injection refining. Adding 3-5% by volume of carbon monoxide to the mixed gas is to use carbon monoxide to capture oxygen in the aluminum alloy liquid to form carbon dioxide, avoid oxygen and aluminum forming an aluminum oxide film on the bubble surface, enhance the ability of the bubbles to capture and absorb hydrogen and inclusions, and improve the deslagging and dehydrogenation effect of gas injection refining.

[0030] Furthermore, the amount of the mixed gas in step 5 is 2-3 cubic meters per ton of aluminum alloy liquid, and the pressure of the mixed gas is 0.3-0.5×10 5 Pa, the temperature of the aluminum alloy liquid during spray refining is 700-720℃, and the spray refining time is 10-15 minutes.

[0031] Although the slag hydrogen content of aluminum alloy liquid is greatly reduced by powder spray refining, the aluminum alloy liquid still contains slag hydrogen because the refining agent spray refining can only remove part of the slag. In addition, although powder spray refining also has a dehydrogenation effect, the dehydrogenation effect is limited because the refining agent inevitably contains moisture, which will be brought into the powder spray refining, causing the aluminum alloy liquid to absorb hydrogen again, making the dehydrogenation always in a dynamic equilibrium process. It is difficult for powder spray refining to reduce the hydrogen content of aluminum alloy liquid to below 0.2ml / 100gAl. Therefore, in order to obtain highly clean aluminum alloy liquid, air blowing refining dehydrogenation and slag removal treatment is also required.

[0032] The mixed gas spray refining adopts a stainless steel pipe or a degasser to spray the mixed gas into the aluminum alloy liquid, so that the mixed gas forms fine bubbles to contact and react with the aluminum alloy liquid, and the hydrogen and inclusions in the aluminum alloy liquid are brought out of the liquid surface by the floating of the bubbles. The dehydrogenation and slag removal effect of the mixed gas spray refining is also related to the amount of the mixed gas, the temperature of the aluminum alloy liquid and the spray refining time. The greater the amount of the mixed gas, the longer the spray refining time, the better the deslag and hydrogen removal effect of the spray refining, but the production cost will also increase accordingly. If the temperature of the aluminum alloy liquid is too high or the spray refining time is too long, the oxidation and burning of the aluminum alloy liquid will also increase. After the spray refining is completed, after removing the scum on the surface of the aluminum alloy liquid, a covering agent should be sprinkled on the surface of the aluminum alloy liquid in time to avoid oxidation and burning of the aluminum alloy liquid and hydrogen absorption. After the coating agent is applied, the aluminum alloy liquid needs to be left to stand for a period of time so that the bubbles in the aluminum alloy liquid have sufficient time to escape. The standing time of the aluminum alloy liquid cannot be less than 20 minutes. As a preferred embodiment, the standing time of the aluminum alloy liquid is 20-30 minutes. Through mixed gas spray refining, the hydrogen content of the aluminum alloy liquid can be reduced to less than 0.15ml / 100gAl, and the inclusion content can be reduced to 0.1mm 2 / kgAl or less, thus greatly improving the cleanliness of aluminum alloy liquid

[0033] Furthermore, in step six, casting the aluminum alloy liquid into an aluminum alloy is to pour the aluminum alloy liquid at 680-700°C into a metal mold and cool and solidify it into an aluminum alloy ingot. The pouring temperature of the aluminum alloy liquid cannot be lower than 680°C, otherwise it is easy to cause incomplete filling of the aluminum alloy ingot or produce cold shut defects, affecting the appearance quality of the aluminum alloy ingot. The pouring temperature of the aluminum alloy liquid should not be too high, otherwise the cooling and solidification time of the aluminum alloy liquid is too long, reducing the casting production efficiency. The preferred pouring temperature of the aluminum alloy liquid is 680-700°C.

[0034] Compared with the prior art, the present invention has the following beneficial effects: the present invention obtains die-cast aluminum alloys whose composition and performance meet the requirements of automobile parts by sorting and pre-treating die-cast aluminum alloy waste and refining, degassing, deslagging and refining and metamorphism, realizes the grade-preserving regeneration of die-cast aluminum alloy waste for automobile parts, improves the utilization value of die-cast aluminum alloy waste, reduces the production cost of automobile parts, and realizes the low-carbon production of die-cast aluminum alloy automobile parts. In addition, the high-efficiency, environmentally friendly and multifunctional powder refining agent developed by the present invention overcomes the problems of low degassing and deslagging efficiency and single function existing in traditional refining agents, and can not only greatly improve the cleanliness of aluminum alloy liquid, but also refine and metamorphize aluminum alloy, improve the mechanical properties of aluminum alloy, without adding additional refining and metamorphism materials, which is conducive to reducing the production cost of die-cast aluminum alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a process flow chart of grade-preserving regeneration of die-cast aluminum alloy waste for automobile parts. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of 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.

[0037] Example 1

[0038] This embodiment uses die-cast aluminum alloy waste to regenerate YL101 die-cast aluminum alloy for automobile parts. According to the national standard GB / T15114-2023 "Aluminum Alloy Die Castings", YL101 die-cast aluminum alloy is composed of the following components in mass percentage: Si 9-10%, Mg 0.4-0.6%, Cu≤0.6%, Mn≤0.35%, Fe≤1.3%, Ni≤0.5%, Zn≤0.5%, Pb≤0.1%, Sn≤0.15%, other impurities single content ≤0.05%, other impurities total amount ≤0.15%, the rest is Al, the method comprises the following steps in sequence: step 1: sorting and pre-treating the die-casting aluminum alloy waste, removing iron, rubber, plastic, wood, stone, mud and other inclusions carried or embedded in the die-casting aluminum alloy waste, and obtaining die-casting aluminum alloy waste that can be recycled; step 2: putting the die-casting aluminum alloy waste after sorting and pre-treatment into a regenerative gas-fired aluminum melting furnace to heat and melt it into aluminum alloy liquid at 740°C; step 3 :Use direct reading spectrometer to detect and adjust the chemical composition of aluminum alloy liquid online; Step 4: Use argon with a purity of 99.99% and a refining agent of 0.15% of the weight of aluminum alloy liquid to spray and refine the aluminum alloy liquid at 710°C for 18 minutes, sprinkle a covering agent after slagging, and then let it stand for 35 minutes; Step 5: Use a mixed gas composed of argon, sulfur hexafluoride and carbon monoxide to spray and refine the aluminum alloy liquid at 710°C for 12 minutes, the purity of argon, sulfur hexafluoride and carbon monoxide is 99.99%, the volume percentage of sulfur hexafluoride in the mixed gas is 10%, the volume percentage of carbon monoxide is 4%, the amount of the mixed gas is 2.5 cubic meters / ton of aluminum alloy liquid, and the pressure of the mixed gas is 0.4×10 5 Pa, sprinkle covering agent after slag removal, and then let it stand for 25 minutes; Step six: cast the aluminum alloy liquid into aluminum alloy at 690°C to obtain YL101 die-casting aluminum alloy for automotive parts.

[0039] Example 2

[0040] This embodiment uses YL119 die-cast aluminum alloy for automobile parts recycled from die-cast aluminum alloy waste. According to the national standard GB / T15114-2023 "Aluminum Alloy Die Castings", YL119 die-cast aluminum alloy is composed of the following components in mass percentage: Si 9.5-11.5%, Mg 0.1-0.6%, Cu ≤ 0.05%, Mn 0.4-08%, Fe ≤ 0.25%, Zn ≤ 0.07%, Ti ≤ 0.2%, Sr 0.01-0.025%, the single content of other impurities ≤0.05%, the total amount of other impurities ≤0.15%, and the rest is Al. The method comprises the following steps in sequence: step 1: sorting and pre-treating the die-casting aluminum alloy waste, removing the iron, rubber, plastic, wood, stone, mud and other inclusions carried or embedded in the die-casting aluminum alloy waste, and obtaining the die-casting aluminum alloy waste that can be recycled; step 2: putting the die-casting aluminum alloy waste after sorting and pre-treatment into a regenerative gas-fired aluminum melting furnace to heat and melt it at 760°C into aluminum alloy liquid; step 3: using a direct reading spectrometer to conduct online detection and Adjustment; Step 4: Use argon with a purity of 99.99% and a refining agent of 0.2% by weight of the aluminum alloy liquid to spray and refine the aluminum alloy liquid at 700°C for 20 minutes, sprinkle a covering agent after slagging, and then let it stand for 30 minutes; Step 5: Use a mixed gas composed of argon, sulfur hexafluoride and carbon monoxide to spray and refine the aluminum alloy liquid at 700°C for 15 minutes, the purity of argon, sulfur hexafluoride and carbon monoxide is 99.99%, the volume percentage of sulfur hexafluoride in the mixed gas is 9%, the volume percentage of carbon monoxide is 5%, the amount of the mixed gas is 2 cubic meters / ton of aluminum alloy liquid, and the pressure of the mixed gas is 0.5×10 5 Pa, sprinkle covering agent after slag removal, and then let it stand for 20 minutes; Step six: cast the aluminum alloy liquid into aluminum alloy at 700°C to obtain YL119 die-casting aluminum alloy for automotive parts.

[0041] Example 3

[0042] This embodiment uses YL120 die-cast aluminum alloy for automobile parts recycled from die-cast aluminum alloy waste. According to the national standard GB / T15114-2023 "Aluminum Alloy Die Castings", YL120 die-cast aluminum alloy is composed of the following components in mass percentage: Si 6-7.5%, Mg 0.1-0.45%, Cu≤0.05%, Mn 0.35-0.75%, Fe≤0.25%, Ti≤0.2%, Zn≤0.03%, other impurities single content ≤0.05%, other impurities total ≤0.15%, the rest is Al, the method comprises the following steps in sequence: step 1: sorting and pre-treating the die-casting aluminum alloy waste, removing iron, rubber, plastic, wood, stone, mud and other inclusions carried or embedded in the die-casting aluminum alloy waste, and obtaining die-casting aluminum alloy waste that can be recycled; step 2: putting the die-casting aluminum alloy waste after sorting and pre-treatment into a regenerative gas-fired aluminum melting furnace to heat and melt it into aluminum alloy liquid at 720°C; step 3: using a direct reading spectrometer to analyze the aluminum alloy liquid The chemical composition is detected and adjusted online; Step 4: Use argon with a purity of 99.99% and a refining agent of 0.1% by weight of the aluminum alloy liquid to spray and refine the aluminum alloy liquid at 720°C for 15 minutes, sprinkle a covering agent after slagging, and then let it stand for 40 minutes; Step 5: Use a mixed gas composed of argon, sulfur hexafluoride and carbon monoxide to spray and refine the aluminum alloy liquid at 720°C for 10 minutes, the purity of argon, sulfur hexafluoride and carbon monoxide is 99.99%, the volume percentage of sulfur hexafluoride in the mixed gas is 11%, the volume percentage of carbon monoxide is 3%, the amount of the mixed gas is 3 cubic meters / ton of aluminum alloy liquid, and the pressure of the mixed gas is 0.3×10 5 Pa, sprinkle covering agent after slag removal, and then let it stand for 30 minutes; Step six: cast the aluminum alloy liquid into aluminum alloy at 680°C to obtain YL120 die-casting aluminum alloy for automotive parts.

[0043] Example 4

[0044] This embodiment prepares the refining agent described in Examples 1-3. The refining agent is composed of the following components in mass percentage: NaCl 35.12%, NaF 19.84%, TiCl3 16.51%, SrSO4 10.06%, KPO3 11.45%, Na2B4O 77.02%. The preparation method of the refining agent includes the following steps in sequence:

[0045] (1) According to the composition and mass percentage of the refining agent, NaCl, NaF, TiCl3, SrSO4, KPO3, and Na2B4O7 with a purity of ≥99.8% are selected as raw materials for batching; (2) the ingredients are added into water at a temperature of 70° C. and stirred to dissolve into an aqueous solution, wherein the mass ratio of water to the ingredients is 1.2, and then the aqueous solution is heated to 100° C. to evaporate and obtain solid crystals; (3) the solid crystals are crushed into powders with a particle size of less than 2 mm, and the powders are dried and dehydrated at 160° C. for 4 hours to obtain the refining agent.

[0046] Example 5

[0047] This embodiment uses die-cast aluminum alloy waste to regenerate YL101 die-cast aluminum alloy for automobile parts. The method is the same as that of Example 1, except that the refining agent used is an existing conventional refining agent, which is composed of the following components in mass percentage: NaCl 36.13%, KCl 15.42%, CaF2 16.84%, NaF 19.24%, C2Cl6 12.37%. The refining agent is obtained by directly crushing and mixing the raw materials after drying and dehydration.

[0048] Example 6

[0049] This embodiment uses die-cast aluminum alloy waste to regenerate YL101 die-cast aluminum alloy for automobile parts. The method is the same as that of Example 1, except that in step five, a mixed gas composed of argon, sulfur hexafluoride and carbon monoxide is not used, but argon with a purity of 99.99% is used to spray and refine the aluminum alloy.

[0050] Verification Example

[0051] The hydrogen content and slag content of the aluminum alloy liquid before casting of Examples 1-3 and Examples 5-6 were detected by using a HDA-V hydrogen meter and an Analyze PoDFA slag meter. The results are shown in Table 1. As can be seen from Table 1, the hydrogen content of the aluminum alloy liquid before casting of Examples 1-3 is less than 0.14 ml / 100 gAl, and the slag content is less than 0.08 mm 2 / kgAl. Since Example 5 adopts the conventional refining agent spraying refining, and Example 6 does not adopt the mixed gas spraying refining, the gas slag content of the aluminum alloy liquid is relatively high. By comparison, it can be seen that the technical solution of the present invention can significantly reduce the gas slag content of the aluminum alloy liquid and improve the cleanliness of the die-casting aluminum alloy liquid.

[0052] Table 1 Hydrogen content and slag content of aluminum alloy liquid

[0053] Hydrogen content / (ml / 100gAl) <![CDATA[Sludge content / (mm 2 / kgAl)]]> Example 1 0.124 0.058 Example 2 0.127 0.072 Example 3 0.131 0.069 Example 5 0.188 0.157 Example 6 0.213 0.182

[0054] The chemical composition of the die-cast aluminum alloys obtained in Examples 1-3 and 5-6 was detected by a WDN-1460 photoelectric direct reading spectrometer, and the results are shown in Table 2. As can be seen from Table 2, the chemical composition of the die-cast aluminum alloys obtained in Examples 1-3 and 5-6 meets the chemical composition requirements of the national standard GB / T15114-2023 for the corresponding grades of die-cast aluminum alloys.

[0055] Table 2 Chemical composition of die-cast aluminum alloy (%, mass percentage)

[0056]

[0057]

[0058] Samples were taken from the die-cast aluminum alloys obtained in Examples 1-3 and 5-6, and the tensile mechanical properties and Brinell hardness of the aluminum alloy samples in the F state were tested. The results are shown in Table 3. It can be seen from Table 3 that the tensile mechanical properties and Brinell hardness of the die-cast aluminum alloys obtained in Examples 1-3 both meet the requirements of the national standard GB / T15114-2023 for the mechanical properties of the corresponding grades of die-cast aluminum alloys. Since Example 5 adopts the commercially available conventional refining agent spray refining, and Example 6 does not adopt the mixed gas spray refining, the gas slag content of the aluminum alloy liquid is relatively high, and the tensile mechanical properties and Brinell hardness of the die-cast aluminum alloy do not meet the requirements of the national standard GB / T15114-2023 for the mechanical properties of the corresponding grades of die-cast aluminum alloys. By comparison, it can be seen that the technical solution of the present invention can achieve the grade-preserving regeneration of die-cast aluminum alloys, and obtain die-cast aluminum alloys whose chemical composition and mechanical properties meet the requirements.

[0059] Table 3 Tensile mechanical properties and Brinell hardness of die-cast aluminum alloys

[0060]

Claims

1. A method for regenerating die-cast aluminum alloy waste for automobile parts, characterized in that: The following steps are included in sequence: Step 1: sorting and pre-treating the die-casting aluminum alloy waste to obtain die-casting aluminum alloy waste that can be recycled; Step 2: heating and melting the die-casting aluminum alloy waste after sorting and pretreatment into aluminum alloy liquid; Step 3: Online detection and adjustment of the chemical composition of the aluminum alloy liquid; Step 4: using argon gas and refining agent to spray and refine the aluminum alloy liquid; Step 5: Using mixed gas to spray and refine the aluminum alloy liquid; Step 6: Casting the aluminum alloy liquid into aluminum alloy to obtain die-cast aluminum alloy for automobile parts; The refining agent in step 4 is composed of the following components in mass percentage: NaCl 35.12%, NaF 19.84%, TiCl 3 16.51%, SrSO 4 10.06%, KPO 3 11.45%, and Na 2 B 4 O 7 7.02%. The preparation method of the refining agent comprises the following steps in sequence: (1) according to the composition and mass percentage of the refining agent, NaCl, NaF, TiCl 3, SrSO 4, KPO 3, and Na 2 B 4 O 7 with a purity of ≥ 99.8% are selected as raw materials for batching; (2) the ingredients are added into water at a temperature of 70° C. and stirred to dissolve into an aqueous solution, the mass ratio of water to ingredients being 1.2, and then the aqueous solution is evaporated at 100° C. to obtain a solid crystal; (3) the solid crystal is crushed into a powder with a particle size of less than 2 mm, and the powder is dried and dehydrated at 160° C. for 4 hours to obtain the refining agent; The mixed gas in step 5 is composed of argon with a purity of ≥99.99%, sulfur hexafluoride and carbon monoxide, the volume percentage of sulfur hexafluoride in the mixed gas is 9-11%, and the volume percentage of carbon monoxide is 3-5%; the amount of the mixed gas is 2-3 cubic meters / ton of aluminum alloy liquid, and the pressure of the mixed gas is 0.3-0.5×10 5 Pa, the temperature of the aluminum alloy liquid during spray refining is 700-720℃, and the spray refining time is 10-15 minutes.

2. The method for regenerating die-cast aluminum alloy waste of automobile parts according to claim 1, characterized in that: The pretreatment of the die-casting aluminum alloy waste by sorting in step 1 is to sort out and remove the iron, rubber, plastic, wood, stone, mud and other inclusions carried or embedded in the die-casting aluminum alloy waste.

3. The method for regenerating die-cast aluminum alloy waste of automobile parts according to claim 1, characterized in that: The heating melting temperature of the die-casting aluminum alloy scrap in step 2 is 720-760°C.

4. The method for regenerating die-cast aluminum alloy waste of automobile parts according to claim 1, characterized in that: The online adjustment of the chemical composition of the aluminum alloy liquid described in step three includes adding pure metal or alloy to increase the content of elements in the aluminum alloy liquid or adding aluminum ingots to dilute the content of elements in the aluminum alloy liquid.

5. The method for regenerating die-cast aluminum alloy waste of automobile parts according to claim 1, characterized in that: The purity of the argon gas in step 4 is ≥99.99%, the amount of the refining agent used is 0.1-0.2% of the weight of the aluminum alloy liquid, the temperature of the aluminum alloy liquid during spray refining is 700-720°C, and the spray refining time is 15-20 minutes.

6. The method for regenerating die-cast aluminum alloy waste for automobile parts according to claim 1, characterized in that: The pouring temperature of the aluminum alloy liquid during casting in step six is ​​680-700°C.

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