Green smelting process for aviation aluminum alloy

Abstract

The invention relates to the technical field of aviation aluminum alloy material smelting, and discloses a green smelting process for aviation aluminum alloy. Comprising the following steps of material preparation, smelting furnace feeding, stirring, alloying, smelting furnace refining, stirring, slagging-off, sampling, component adjustment, converter treatment, holding furnace refining, slagging-off, holding furnace sampling confirmation, standing, online grain refinement, online degassing, sampling component confirmation, filtering and casting. In the smelting furnace refining stage, the holding furnace refining stage and the online degassing stage, argon is introduced to remove gas slag in melt, and the argon is fine and dispersed bubbles when being introduced. According to the scheme, flux and chlorine-containing gas are not used for refining in the whole process, generated tail gas, reaction products and aluminum slag do not contain fluorine or chlorine, environmental burden is avoided, the produced aviation aluminum alloy meets the quality control requirement of aviation aluminum alloy melt, green refining of the novel aviation aluminum alloy is achieved, and unification of economic benefits and environmental benefits is met.

Description

Technical Field

[0001] The present invention relates to the technical field of aviation aluminum alloy material smelting, and in particular to a green smelting process for aviation aluminum alloy. Background Art

[0002] High-performance aviation aluminum alloys have strict requirements on the purity of the melt to ensure the quality and performance of the final product. During the smelting process, it is necessary to effectively remove the gas slag in the melt, reduce the occurrence of shrinkage, hydrogen embrittlement, pores and other phenomena, and ensure that the hydrogen content and slag content of the ingot are qualified. This step is crucial to ensure the final performance of aviation aluminum alloys.

[0003] At present, enterprises usually use flux purification to remove gas slag from the melt. These fluxes usually contain chloride salts, fluoride salts or oxidizing salts, such as CaF2, Na3AlF6, NaCl, MgCl2, etc. After the flux enters the aluminum melt, it can effectively capture the slag and free hydrogen in the melt. After a period of time, the gas slag will float to the surface of the aluminum liquid and then be removed by slag removal. However, the existing method of flux purification still has the following technical problems: (1) Limited purification effect and flux residue: No matter how much flux is used, it is impossible to completely remove impurities in the melt, and the smelting purification effect is limited; and the residual flux may cause secondary pollution to the aluminum melt, resulting in an increase in the slag content of the melt. (2) New phase formation, reducing alloy properties: Alkali metals (such as Na, Ca, etc.) in the flux remain in the aluminum melt to form new phases, resulting in a reduction in the strengthening phase in the aluminum alloy, affecting product performance. (3) Aggravated environmental pollution: The use of chlorine- and fluorine-containing fluxes leads to the emission of fluorine- and chlorine-containing pollutants. The greater the amount of flux used, the more slag is produced, which has a negative impact on the environment. (4) Not applicable to aviation aluminum alloys: The existing technology has not conducted systematic research on the purification process of high-performance aviation aluminum alloy melts, especially the lack of systematic research on the purification of melts inside and outside the furnace.

[0004] Prior art CN 110819837 A proposes a green smelting method for recycled aluminum alloys, which removes impurities in the melt by introducing argon. However, the prior art mainly smelts recycled aluminum melts, and the flow rate and gas pressure process parameters of the introduced argon are not suitable for the aviation aluminum alloy smelting process; secondly, this method only uses one argon refining and degassing, and the inclusion content and hydrogen content of the obtained recycled aluminum melt are relatively high, which does not meet the high-quality melt control requirements of the aviation aluminum alloy final product; at the same time, since aviation aluminum alloys have high requirements for alkali metal content levels, this method is difficult to ensure the alkali metal content level of the final product, which is not explained in the method. Therefore, if this method is only transferred to aviation aluminum alloy smelting and purification, it is impossible to meet the green smelting and product quality requirements of aviation aluminum alloys.

[0005] In view of this, developing a green smelting process for aviation aluminum alloys without using flux to ensure that the purity of the melt and the alkali metal content meet the quality requirements not only effectively makes up for the shortcomings of the existing technology, but also has very important significance for improving the casting quality of aviation aluminum alloys. Summary of the invention

[0006] The present invention aims to provide a green smelting process for aviation aluminum alloys to solve the technical problem of environmental pollution caused by adding smelting agents in the existing aviation aluminum alloy smelting process.

[0007] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a green smelting process of aviation aluminum alloy, comprising the following steps: material preparation - charging into smelting furnace - stirring - alloying - refining into smelting furnace - stirring - slag skimming - sampling - composition adjustment - converter - refining into holding furnace - slag skimming - sampling and confirmation into holding furnace - standing - online grain refinement - online degassing - sampling and confirmation of composition - filtering - casting; in the refining stage of smelting furnace, refining stage of holding furnace and online degassing stage, argon gas is introduced to remove gas slag in the melt, and the argon gas is introduced in the form of small, diffuse bubbles.

[0008] The principle of this scheme is:

[0009] This solution generates tiny, diffuse bubbles in the furnace, and utilizes the partial pressure difference between the hydrogen in the melt and the purifying bubbles to make the hydrogen in the melt diffuse into the bubbles and escape from the melt with the movement of the bubbles, thereby achieving the purpose of dehydrogenation. At the same time, during the floating process of the bubbles, the inclusions in the aluminum liquid will be adsorbed on the surface of the bubbles and taken out of the melt with the escape of the bubbles, playing a role in slag removal, thereby ensuring that the hydrogen content and slag content of the melt at the furnace outlet reach the level of flux refining.

[0010] The advantages of this solution are:

[0011] 1. Compared with the existing technology of adding flux to refine aviation aluminum alloys, which is easy to cause environmental pollution, this solution introduces argon gas to remove gas slag in the melt during the refining stage of the aviation aluminum alloy smelting furnace, the refining stage of the holding furnace and the online degassing stage, so as to obtain aviation aluminum alloys that meet the composition control requirements and melt quality control requirements, realize green smelting of aviation aluminum alloys, and achieve the unity of economic and environmental benefits.

[0012] 2. Compared with the prior art, in which a mixed gas of argon and chlorine is introduced during the online degassing stage to ensure that the alkali metal content in the aviation aluminum alloy meets the control requirements, and the use of chlorine is prone to cause environmental pollution, this solution introduces argon during the smelting furnace refining stage, the holding furnace refining stage and the online degassing stage to degas and remove slag from the aviation aluminum alloy melt, thereby producing aviation aluminum alloys that meet the composition control requirements and melt quality control requirements, and effectively avoiding the environmental pollution problems caused by the use of chlorine.

[0013] 3. This solution removes and purifies the gas slag in the melt by introducing argon gas in all three stages of the aviation aluminum alloy smelting process, effectively reducing the content of hydrogen, inclusions (i.e., slag) and alkali metals in the melt, and obtaining aviation aluminum alloys that meet the melt quality control requirements of the aviation aluminum alloy ingot standard YS / T 1619-2023. The applicant has found through long-term experiments that if argon gas is introduced only in the refining stage of the smelting furnace and the online degassing stage, or only in the refining stage of the holding furnace and the online degassing stage, even if the ventilation time is increased, the content of hydrogen, inclusions (i.e., slag) and alkali metals in the aviation aluminum alloy melt produced is difficult to meet the melt quality control requirements of the standard YS / T 1619-2023.

[0014] Preferably, as an improvement, argon refining is adopted in both the refining stage of the smelting furnace and the refining stage of the holding furnace, and the argon is introduced through air plugs evenly distributed on the bottom of the furnace, the air plugs are spaced 300 to 600 mm apart, the air holes in the air plugs have a diameter of 0.001 to 1.0 mm, and the average size of bubbles when the argon is introduced is 0.05 to 10.0 mm.

[0015] Beneficial effects: This solution precisely controls the spacing of the gas plugs and the aperture of the gas holes, so that when argon is introduced, small, diffuse bubbles are generated in the furnace. The hydrogen in the melt is continuously diffused into the bubbles and escapes from the melt with the movement of the bubbles by using the partial pressure difference between the purified bubbles and the melt, thereby achieving the purpose of dehydrogenation. At the same time, during the floating process of the bubbles, the inclusions in the aluminum liquid will be adsorbed on the surface of the bubbles and taken out of the melt with the escape of the bubbles, playing a role in slag removal, thereby ensuring that the hydrogen content and slag content of the melt at the furnace outlet reach the level of flux refining.

[0016] Preferably, as an improvement, during the refining stage of the smelting furnace, when the temperature of the melt in the smelting furnace reaches 720-770°C, argon gas is introduced, and the pressure of argon gas is 0.2-0.8Mpa and the gas flow rate is 2.0-5.0m 3 / h, the ventilation and refining time of the melt in the smelting furnace is 30 to 60 minutes.

[0017] Beneficial effects: This solution effectively reduces the inclusion content in the aviation aluminum alloy melt obtained by smelting by combining the control of the melt temperature, argon gas introduction pressure, gas flow rate and ventilation refining time during the smelting furnace. The applicant has found through long-term experiments that if the smelting temperature is too low, the melt is very easy to cool in the launder during the converter process, resulting in the inability to achieve continuous smelting, thereby reducing the production efficiency of aviation aluminum alloys; if the smelting temperature is too high, it will lead to increased burnout of the aviation aluminum alloy melt and increase energy consumption. If the pressure is too high when the argon gas is introduced, the slag on the surface of the melt will roll into the inside of the melt due to the large amplitude of the melt stirring, and it will be difficult to remove it by manual slagging; if the argon gas pressure is too low, the hydrogen and inclusions in the melt will be difficult to move with the bubbles to the melt surface and escape from the melt, making it difficult to meet the quality control requirements of aviation aluminum alloy melts. When the gas flow rate is too small, the amount of bubbles generated is insufficient, which will affect the hydrogen mass transfer and diffusion between the melt and the purification bubbles, resulting in low purification efficiency; if the gas flow rate is too large, the melt will also increase the degree of melt tumbling, and the slag on the melt surface will enter the melt and cause secondary pollution. If the ventilation melting time is less than 30 minutes, the purification effect will be insufficient because the gas slag inside the melt has not completely diffused to the melt surface with the bubbles; in order to prevent the slag on the melt surface from being brought into the melt again by the movement of bubbles, the slag diffused to the surface with the bubbles should be cleaned in time, and at the same time, the refining time should be avoided from being too long from the perspective of energy saving.

[0018] Preferably, as an improvement, during the refining stage in the holding furnace, when the melt temperature in the holding furnace reaches 720°C to 760°C, argon gas is introduced, and the pressure of argon gas is 0.3 to 0.9 MPa and the gas flow rate is 2.0 to 4.0 m 3 / h, and the melt refining time in the holding furnace is not less than 30min.

[0019] Beneficial effects: This solution effectively further reduces the inclusion content in the aviation aluminum alloy melt obtained by smelting by combining the control of the melt temperature, argon gas introduction pressure, gas flow rate and ventilation refining time in the holding furnace.

[0020] Preferably, as an improvement, the argon gas is introduced for online degassing outside the furnace by high-speed rotation of the rotor, and the average bubble size during the introduction of the argon gas is 0.05 to 10.0 mm.

[0021] Beneficial effects: This solution uses high-speed rotation of the rotor to pour in argon, effectively ensuring the purification effect of online degassing on the melt, further reducing the content of cyanide, inclusions and alkali metals in the melt, and improving the quality of the produced aviation aluminum alloy.

[0022] Preferably, as an improvement, in the online degassing stage, the high-purity argon gas is introduced at a pressure of 0.2-0.5 MPa and a gas flow rate of 2.0-5.0 m 3 / h, the rotor speed is 400~520r / min.

[0023] Preferably, as an improvement, in the online degassing stage, the online degassing equipment outside the furnace adopts a three-rotor degasser.

[0024] Beneficial effect: This scheme effectively meets the gas flow requirements by limiting the argon gas introduction parameters in the online degassing stage, thereby achieving further purification of the melt. The applicant has found through long-term experiments that appropriate argon gas introduction pressure and flow should be selected. If the pressure and flow are too large when the argon gas is introduced, it is easy to cause the bubble size to be too large, the melt to tumble severely, and the surface scum is easy to be brought into the melt, which is not conducive to degassing and slag removal; if the pressure and flow are too small when the argon gas is introduced, it is difficult to ensure the hydrogen mass transfer and diffusion behavior between the purification bubbles and the melt, reducing the purification effect and the stability of continuous production. The rotor speed should also be controlled within a reasonable range. If the rotor speed is too large, it is easy to cause the purification bubble radius to decrease instantly after reaching the maximum value, affecting the hydrogen mass transfer and diffusion between the melt and the purification bubble, which is not conducive to improving the purification efficiency; if the rotor speed is too small, it will cause the bubble size to be too large, the surface area of ​​the purification bubble will be reduced, and the ability to adsorb inclusions will be reduced, and the final melt quality will be difficult to meet the control requirements.

[0025] Preferably, as an improvement, in the filtration stage, a two-stage plate filter is used to perform primary filtration and secondary filtration on the alloy aluminum liquid, the filter plate accuracy of the primary filtration is not less than 30PPI, and the filter plate accuracy of the secondary filtration is 60PPI.

[0026] Beneficial effects: This solution further reduces the inclusion content in the melt and improves the quality of aviation aluminum alloy by adopting two-stage filtration. The applicant has found through long-term experiments that if only one-stage filtration or two-stage filtration accuracy is lower than 60PPI, small-sized inclusions such as TiB2 and MgO are difficult to be effectively removed, which will cause serious damage to the quality of the final product.

[0027] Preferably, as an improvement, the aviation aluminum alloy melt after argon refining in the holding furnace is tested by metallographic grid method technology, and the slag content is ≤0.20mm 2 / kg, hydrogen content is ≤0.25ml / 100gAl; after three-rotor degassing and two-stage plate filtration, the slag content of aviation aluminum alloy melt is ≤0.02mm 2 / kgAl, hydrogen content ≤0.10ml / 100gAl, alkali metal content not higher than 5ppm.

[0028] Preferably, as an improvement, the purity of the introduced argon gas is not less than 99.99%.

[0029] The principles and advantages of this solution are:

[0030] 1. Compared with the prior art, the present invention innovatively proposes a green smelting process for aviation aluminum alloys. In order to achieve green smelting of aviation aluminum alloys, the key to this process is to use high-purity argon gas to purify the melt in the furnace (including the smelting furnace and the holding furnace) and outside the furnace during the smelting process of aviation aluminum alloys. Specifically, this solution accurately controls the flow rate and working pressure of the introduced argon gas to produce small, diffuse bubbles in the furnace, and utilizes the partial pressure difference between the purified bubbles and the melt in the melt to make the hydrogen in the melt continuously diffuse into the bubbles and escape from the melt with the movement of the bubbles, thereby achieving the purpose of dehydrogenation. At the same time, during the floating process of the bubbles, the inclusions in the aluminum liquid will be adsorbed on the surface of the bubbles and taken out of the melt as the bubbles escape, playing a role in slag removal, thereby ensuring that the hydrogen content and slag content of the melt at the furnace outlet reach the flux refining level.

[0031] 2. This solution uses three-rotor degassing equipment and two-stage plate filtration devices to ensure that the hydrogen content and slag content after online degassing and filtration can also meet the quality control requirements of aviation aluminum alloy melts. Importantly, since no flux or chlorine-containing gas refining is used in the entire smelting process, no additional alkali metal components will be added to the melt, ensuring that the alkali metal content in aviation aluminum alloy products meets the composition control requirements; at the same time, the products and aluminum slag produced during the entire smelting process have no fluorine or chlorine emissions, avoiding the environmental pollution caused by the use of fluorine and chlorine-containing refining agents by most companies in the production of aviation aluminum alloy products.

[0032] 3. The slag content of the aviation aluminum alloy melt after argon refining in the furnace is ≤0.20mm 2 / kg, hydrogen content is ≤0.25ml / 100gAl, achieving the flux refining effect; the slag content of aviation aluminum alloy melt after three-rotor degassing and two-stage plate filtration is ≤0.02mm 2 / kgAl, hydrogen content ≤0.10ml / 100gAl, alkali metal content not higher than 5ppm, meeting the quality control requirements of aviation aluminum alloy melt.

[0033] 4. This scheme does not use flux and chlorine-containing gas refining throughout the process. The exhaust gas, reaction products and aluminum slag produced do not contain fluorine and chlorine, and will not cause environmental burden. It realizes the green refining of new aviation aluminum alloys and meets the unity of economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a process flow chart of the green smelting process of aviation aluminum alloy of the present invention.

[0035] Figure 2 This is the SEM spectrum of the 2××× series aviation aluminum alloy ingot prepared by the green smelting process of aviation aluminum alloy in Example 1 of the present invention.

[0036] Figure 3This is the SEM spectrum of the 2××× series aviation aluminum alloy ingot prepared by the green smelting process of aviation aluminum alloy in Example 2 of the present invention.

[0037] Figure 4 This is the SEM spectrum of the 7××× series aviation aluminum alloy ingot prepared by the green smelting process of aviation aluminum alloy in Example 3 of the present invention.

[0038] Figure 5 This is the SEM spectrum of the 7××× series aviation aluminum alloy ingot prepared by the green smelting process of aviation aluminum alloy in Example 4 of the present invention.

[0039] Figure 6 These are the SEM spectra and EDS analysis results of the 7××× series aviation aluminum alloy ingots prepared by the green smelting process of aviation aluminum alloy in Comparative Example 2 of the present invention.

[0040] Figure 7 These are the SEM spectra and EDS analysis results of the 7××× series aviation aluminum alloy ingots prepared by the green smelting process of aviation aluminum alloy in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following examples and experimental examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used can be obtained from commercial sources.

[0042] Program Overview

[0043] This solution provides a green smelting process for aviation aluminum alloys. The process flow chart is as follows Figure 1 As shown, the process includes the following steps: material preparation - charging into smelting furnace - stirring - alloying - refining in smelting furnace - stirring - slag removal - sampling - composition adjustment - converter - refining in holding furnace - slag removal - sampling and confirmation in holding furnace - standing - online grain refinement - online degassing - sampling and confirmation of composition - filtration - casting.

[0044] During the refining stage in the smelting furnace, the refining stage in the holding furnace and the online degassing stage, argon is introduced to remove gas slag in the melt. The purity of the introduced argon is not less than 99.99%. The bubble size is controlled by adjusting the argon working pressure, flow rate and ventilation time, so that the argon is introduced in the form of small, diffuse bubbles.

[0045] As a reference, during the refining stage of the smelting furnace and the refining stage of the holding furnace, the argon is introduced through the gas plugs evenly distributed on the bottom of the furnace. The interval between the gas plugs is 300-600mm, and the diameter of the gas holes is 0.001-1.0mm. The bubble size is controlled by adjusting the argon working pressure, flow rate and ventilation time, so that the bubble size when the argon is introduced is 0.05-10.0mm. As a reference, during the refining stage of the smelting furnace, the pressure of argon is 0.2-0.8Mpa, and the gas flow rate is 2.0-5.0m 3 / h, the ventilation refining time of the melt in the smelting furnace is 30 to 60 minutes. In the refining stage of the holding furnace, when the temperature of the melt in the holding furnace reaches 720℃ to 760℃, argon gas is introduced. The pressure of argon gas is 0.3 to 0.9Mpa and the gas flow rate is 2.0 to 4.0m 3 / h, and the refining time of the melt in the holding furnace is not less than 30min. In the refining stage of the smelting furnace and the refining stage of the holding furnace, this scheme controls the above-mentioned argon pressure, ventilation flow rate and ventilation time, and on the basis of the aperture of the ventilation holes in the ventilation plug being 0.001-1.0mm and the interval being 300-600mm, forms small and diffuse bubbles (the size of the bubbles is 0.05-10.0mm) when the argon is introduced, so that the small and diffuse bubbles can more easily carry away the hydrogen and inclusions in the melt when they rise, thereby realizing the removal of hydrogen from the melt. Moreover, the melt temperature, argon pressure, argon flow rate, pore diameter and spacing specified in this scheme are not only the above-mentioned ranges, but also include the range defined by any two point values ​​within the above-mentioned ranges. On the basis of pore diameters of 0.001 to 1.0 mm and spacings of 300 to 600 mm, small, diffuse bubbles of 0.05 to 10.0 mm in size can be formed, thereby improving the efficiency and effect of dehydrogenation and slag removal.

[0046] During the holding furnace sampling confirmation stage, the applicant found that the slag content of the aviation aluminum alloy melt after argon refining in the holding furnace was ≤0.20mm 2 / kg, hydrogen content is ≤0.25ml / 100gAl, achieving the flux refining effect.

[0047] As a reference, the argon gas introduction method for online degassing outside the furnace is to introduce the argon gas by high-speed rotation of the rotor. As a reference, the online degassing equipment outside the furnace adopts a three-rotor degasser. In the online degassing stage, the high-purity argon gas introduction pressure is 0.2-0.5Mpa, and the gas flow rate is 2.0-5.0m 3 / h, and the rotor speed is 400-520r / min, so that in the online degassing stage, the average bubble size when argon gas is introduced is 0.05-10.0mm.

[0048] As a reference, during the filtration stage, a two-stage plate filter is used to perform primary and secondary filtration on the alloy aluminum liquid. The filter plate accuracy of the primary filtration is not less than 30PPI, and the filter plate accuracy of the secondary filtration is 60PPI.

[0049] The applicant took samples for testing after filtration and found that the slag content of the aviation aluminum alloy melt after three-rotor degassing and two-stage plate filtration in this scheme was ≤0.02mm after metallographic grid method testing. 2 / kgAl, hydrogen content ≤0.10ml / 100gAl, alkali metal content not higher than 5ppm, meeting the melt quality control requirements of aviation aluminum alloy ingot standard YS / T 1619-2023.

[0050] The process and effect of this solution are specifically explained by taking the production of a 16-ton melting and casting unit as an example.

[0051] Example 1

[0052] The present embodiment provides a green smelting process for 2××× series aviation aluminum alloys, comprising the following steps: material preparation - charging into the smelting furnace - stirring - alloying - refining - stirring - slag skimming - sampling - composition adjustment - converter - refining in a holding furnace - slag skimming - sampling and confirmation in a holding furnace - standing - online grain refinement - online degassing - sampling and confirmation of composition - filtration - casting.

[0053] First, the materials are prepared and loaded into the furnace according to the composition control requirements of a certain 2××× series aviation aluminum alloy. After the addition is completed, the molten metal in the furnace is stirred in time to prevent local overheating of the melt; then, the intermediate alloy and small metal are added and stirred immediately after addition for alloying; when the melt temperature reaches 720°C, the refining mode of the furnace bottom air plug is turned on to introduce argon gas, the purity of the argon gas is 99.999%, the argon gas pressure is set to 0.5Mpa, and the argon gas flow rate is set to 3.0m 3 / h, refining time is set to 30min; after refining, stirring, slag removal, sampling, composition adjustment and converter are carried out; after converter, when the melt temperature reaches 740℃, the refining mode of the bottom air plug of the insulation furnace is turned on to introduce argon gas, the purity of argon gas is 99.999%, the argon gas pressure is set to 0.4Mpa, and the argon gas flow rate is set to 2.5m 3 / h, the refining time is set to 30min; after the refining is completed, slag removal, sampling and standing are carried out; after the composition of the holding furnace is confirmed, online purification is prepared, and the online degassing adopts a double-rotor degassing equipment and argon is introduced. The purity of argon is 99.999%, the argon pressure is set to 0.3Mpa, and the argon flow rate is set to 3.0m 3 / h, the rotor speed is set to 450r / min; the online filtration adopts a two-stage plate filtration method, the first-stage filter plate accuracy is 30PPI, the second-stage filter plate accuracy is 60PPI, and finally the casting is completed.

[0054] Example 2

[0055] The present embodiment provides a green smelting process for 2××× series aviation aluminum alloys, comprising the following steps: material preparation - charging into the smelting furnace - stirring - alloying - refining - stirring - slag skimming - sampling - composition adjustment - converter - refining in a holding furnace - slag skimming - sampling and confirmation in a holding furnace - standing - online grain refinement - online degassing - sampling and confirmation of composition - filtration - casting.

[0056] First, the materials are prepared and the furnace is loaded according to the composition control requirements of a certain 2××× series aviation aluminum alloy. After the addition is completed, the metal melt in the furnace is stirred in time to prevent local overheating of the melt; then, the intermediate alloy and small metal are added and stirred immediately after addition for alloying; when the melt temperature reaches 760°C, the refining mode of the furnace bottom air plug is turned on to introduce argon gas, the purity of the argon gas is 99.999%, the argon gas pressure is set to 0.4Mpa, and the argon gas flow rate is set to 5m 3 / h, refining time is set to 30min; after refining, stirring, slag removal, sampling, composition adjustment and converter are carried out; after converter, when the melt temperature reaches 720℃, the refining mode of the bottom air plug of the insulation furnace is turned on to introduce argon gas, the purity of argon gas is 99.999%, the argon gas pressure is set to 0.3Mpa, and the argon gas flow rate is set to 3.5m 3 / h, the refining time is set to 60min; after the refining is completed, slag removal, sampling and standing are carried out; after the composition of the holding furnace is confirmed, online purification is prepared, and the online degassing adopts a double-rotor degassing equipment and argon is introduced. The purity of argon is 99.999%, the argon pressure is set to 0.3Mpa, and the argon flow rate is set to 3.5m 3 / h, the rotor speed is set to 420r / min; the online filtration adopts a two-stage plate filtration method, the first-stage filter plate accuracy is 40PPI, and the second-stage filter plate accuracy is 60PPI; finally the casting is completed.

[0057] Example 3

[0058] The present embodiment provides a green smelting process for 7××× series aviation aluminum alloys, comprising the following steps: material preparation - charging into smelting furnace - stirring - alloying - refining - stirring - slag skimming - sampling - composition adjustment - converter - refining in holding furnace - slag skimming - sampling and confirmation in holding furnace - standing - online grain refinement - online degassing - sampling and confirmation of composition - filtration - casting.

[0059] First, the materials are prepared and loaded into the furnace according to the composition control requirements of a certain 7××× series aviation aluminum alloy. After the addition is completed, the metal melt in the furnace is stirred in time to prevent local overheating of the melt. Then, the intermediate alloy and small metal are added and stirred immediately after addition for alloying. When the melt temperature reaches 750°C, the refining mode of the furnace bottom air plug is turned on to introduce argon gas. The purity of the argon gas is 99.999%, the argon gas pressure is set to 0.5Mpa, and the argon gas flow rate is set to 4.0m 3 / h, refining time is set to 30min; after refining, stirring, slag removal, sampling, composition adjustment and converter are carried out; after converter, when the melt temperature reaches 760℃, the refining mode of the bottom air plug of the insulation furnace is turned on to introduce argon gas, the purity of argon gas is 99.999%, the argon gas pressure is set to 0.5Mpa, and the argon gas flow rate is set to 4.0m 3 / h, refining time is set to 30min; after refining, slag removal, sampling and standing are carried out; after the composition of the holding furnace is confirmed, online processing and casting are prepared, and online degassing uses double-rotor degassing equipment and argon is introduced. The purity of argon is 99.999%, the argon pressure is set to 0.25Mpa, and the argon flow rate is set to 4.0m 3 / h, the rotor speed is set to 450r / min; the online filtration adopts a two-stage plate filtration method, the first-stage filter plate accuracy is 40PPI, and the second-stage filter plate accuracy is 60PPI; finally the casting is completed.

[0060] Example 4

[0061] The present embodiment provides a green smelting process for 7××× series aviation aluminum alloys, comprising the following steps: material preparation - charging into smelting furnace - stirring - alloying - refining - stirring - slag skimming - sampling - composition adjustment - converter - refining in holding furnace - slag skimming - sampling and confirmation in holding furnace - standing - online grain refinement - online degassing - sampling and confirmation of composition - filtration - casting.

[0062] First, the materials are prepared and loaded into the furnace according to the composition control requirements of a certain 7××× series aviation aluminum alloy. After the materials are added, the molten metal in the furnace is stirred in time to prevent local overheating of the melt. Then, the intermediate alloy and small metals are added and stirred immediately for alloying. When the melt temperature reaches 770°C, the refining mode of the furnace bottom air plug is turned on to introduce argon gas. The purity of the argon gas is 99.999%, the argon gas pressure is set to 0.4Mpa, and the argon gas flow rate is set to 2m 3 / h, refining time is set to 30min; after refining, stirring, slag removal, sampling, composition adjustment and converter are carried out; after converter, when the melt temperature reaches 750℃, the refining mode of the bottom air plug of the insulation furnace is turned on to introduce argon gas, the purity of argon gas is 99.999%, the argon gas pressure is set to 0.3Mpa, and the argon gas flow rate is set to 3.5m 3 / h, refining time is set to 45min; after refining, slag removal, sampling and standing are carried out; after the composition of the holding furnace is confirmed, online processing and casting are prepared, and online degassing uses double-rotor degassing equipment and argon is introduced. The purity of argon is 99.999%, the argon pressure is set to 0.4Mpa, and the argon flow rate is set to 3.0m 3 / h, the rotor speed is set to 500r / min; the online filtration adopts a two-stage plate filtration method, the first-stage filter plate accuracy is 40PPI, and the second-stage filter plate accuracy is 60PPI; finally the casting is completed.

[0063] Comparative Example 1

[0064] The difference between this comparative example and Examples 1 and 2 is that the smelting furnace in this comparative example adopts flux refining method, and the refining agent is evenly added to various positions of the aluminum liquid in the furnace by a powder spray refining machine. The refining agent used contains NaCl, CaCl2, MgCl2, CaF2 and other components, and the refining agent addition amount is 0.8kg / t.

[0065] In this comparative example, due to the flux refining adopted, although the addition of the refining agent can purify the melt, at the same time, the refining agent itself is introduced into the aluminum melt as a new pollutant, resulting in an increase in the slag content level.

[0066] Comparative Example 2

[0067] The difference between this comparative example and Examples 3 and 4 is that the smelting furnace in this comparative example adopts flux refining method, and the refining agent is evenly added to various positions of the aluminum liquid in the furnace by a powder spray refining machine. The refining agent used contains NaCl, CaCl2, MgCl2, CaF2 and other components, and the refining agent addition amount is 0.8kg / t.

[0068] In this comparative example, due to the flux refining adopted, although the addition of the refining agent can purify the melt, at the same time, the refining agent itself is introduced into the aluminum melt as a new pollutant, resulting in an increase in the slag content level.

[0069] Comparative Example 3

[0070] The difference between this comparative example and Examples 3 and 4 is that the melting furnace refining in this comparative example adopts flux refining, and the powder spraying refining machine is used to evenly add the refining agent to each position of the aluminum liquid in the furnace. The refining agent used contains NaCl, CaCl2, MgCl2, CaF2 and other components, and the amount of refining agent added is 0.8kg / t. The holding furnace refining adopts Ar+Cl2 mixed gas refining, the refining time is 30min, and the standing time is 30min.

[0071] In this comparative example, the flux refining used can only achieve the refining effect by stirring, and the flux itself will also bring additional inclusion pollution. In addition, the Ar+Cl2 mixed gas refining used in the holding furnace will bring the risk of chlorine inclusions to the melt and easily cause environmental pollution.

[0072] Comparative Example 4

[0073] The difference between this comparative example and Examples 1 and 2 is that in this comparative example, the online filtration adopts a two-stage plate filtration method, the precision of the first-stage filter plate is 30PPI, and the precision of the second-stage filter plate is 50PPI.

[0074] In this comparative example, a 50PPI secondary filter plate was used. This is because the pore size of the 50PPI filter plate is too large to effectively filter out fine slag inclusions (such as TiB2, etc.) in the melt, resulting in a slag content level of 0.055mm. 2 / kgAl, which cannot meet the slag content control requirements of aviation aluminum alloy melt.

[0075] Comparative Example 5

[0076] The difference between this comparative example and Examples 1 and 2 is that in this comparative example, the dual-rotor degassing equipment is fed with Ar+Cl2 mixed gas, and the argon gas flow rate is set to 3.0m 3 / h, Cl2 flow rate 0.02m 3 / h, the rotor speed is set to 420r / min. The online filtration adopts a two-stage plate filtration method, the first-stage filter plate precision is 30PPI, and the second-stage filter plate precision is 60PPI.

[0077] In this comparative example, since the use of chlorine in the online degassing process can cause TiB2 particles to aggregate, a liquid chloride phase is formed in the molten aluminum to form droplets with a very small density difference with the liquid aluminum. After the droplets collide with the Ti-containing particles, aggregation occurs due to capillary force, resulting in a poor slag content level in Comparative Example 5.

[0078] Comparative Example 6

[0079] The difference between this comparative example and Examples 3 and 4 is that in this comparative example, the dual-rotor degassing equipment is fed with Ar+Cl2 mixed gas, and the argon flow rate is set to 3.5m 3 / h, Cl2 flow rate 0.02m 3 / h, and the rotor speed is set to 450r / min.

[0080] In this comparative example, since the dual-rotor degassing equipment also introduced Ar+Cl2 mixed gas, compared with Examples 4 and 5, the slag content level after online purification reached 0.040mm 2 / kgAl, which is worse than the purification effect of Examples 4 and 5.

[0081] Comparative Example 7

[0082] The difference between this comparative example and Examples 3 and 4 is that in this comparative example, the online filtration adopts a two-stage plate filtration method, the accuracy of the first-stage filter plate is 40PPI, and the accuracy of the second-stage filter plate is 50PPI.

[0083] In this comparative example, since the online filtration adopts a 40+50PPI double-stage plate filtration method, compared with Examples 4 and 5, the residue content after filtration is 0.046mm 2 / kgAl, which is significantly worse than the bipolar plate filtration effect of 40+60PPI in Examples 4 and 5, indicating that the secondary filter plate accuracy produced by the 7XXX series aviation aluminum alloy should be maintained at 60PPI.

[0084] Comparative Example 8

[0085] The difference between this comparative example and Examples 1 and 2 is that in this comparative example, when the melt temperature in the holding furnace reaches 750°C, argon gas is introduced, and the pressure of argon gas is 0.3-0.9Mpa and the gas flow rate is 1m 3 / h, and the refining time is set to 30min.

[0086] In this comparative example, since the gas flow rate is set low and the amount of bubbles generated is insufficient, it is difficult for the gas slag in the melt to completely escape from the melt through the mass transfer and diffusion of the bubbles, resulting in insufficient purification effect.

[0087] Comparative Example 9

[0088] The difference between this comparative example and Examples 1 and 2 is that in this comparative example, when the melt temperature in the holding furnace reaches 750°C, argon gas is introduced, and the pressure of argon gas is 0.3-0.9Mpa and the gas flow rate is 5.0m 3 / h, and the refining time is set to 30min.

[0089] In this comparative example, because the gas flow rate is set too high, a large amount of bubbles are generated, the degree of melt tumbling is increased, and the gas slag in the melt is easily caused to form bubbles during the rising process due to the mass transfer and diffusion of the bubbles. At the same time, it is easy to cause the surface slag to be re-involved in the melt, reducing the melt purification effect.

[0090] Comparative Example 10

[0091] The difference between this comparative example and Examples 1 and 2 is that in this comparative example, argon is introduced only in the smelting stage and the online degassing stage of the smelting furnace. When the melt temperature in the smelting furnace reaches 750°C, argon is introduced. The pressure of argon when introduced is 0.2-0.8Mpa and the gas flow rate is 3.5m 3 / h, and the refining time is set to 60min.

[0092] In this comparative example, due to the lack of argon refining in the holding furnace, the slag content in the melt at the outlet of the holding furnace is relatively high, and the quality level of the melt after online purification treatment cannot meet the control requirements.

[0093] Experimental Example 1: Differences in aviation aluminum alloy melts obtained by different refining methods

[0094] During the smelting of aviation aluminum alloys in Examples 1 to 3 and Comparative Examples 1 to 10, the hydrogen content was tested in the flow channel at the outlet of the holding furnace and the flow channel at the outlet of the degassing device; the slag content was tested in the flow channel at the outlet of the holding furnace and the flow channel after filtration using an offline slag measuring device, and the slag content was counted using a metallographic grid method. The ingot composition sampling position was in the flow channel section between the degassing device and the filtration device, and the alkali metal content of the ingot sample was tested using a direct reading spectrometer.

[0095] The results of each example are shown in Table 1; the SEM results of the example ingots are shown in Figure 2 to Figure 5 At the same time, the aviation aluminum alloy castings obtained in Comparative Example 2 and Comparative Example 3 with unqualified melt quality were subjected to SEM and EDS composition analysis. The results are shown in Figure 2 and Figure 3 .

[0096] Table 1 Melt quality and alkali metal content test results of each embodiment

[0097]

[0098] Experimental data show that this scheme can effectively remove gas slag in the melt by introducing argon gas during the refining stage in the smelting furnace, the refining stage in the holding furnace and the online degassing stage without using flux and chlorine-containing gas refining, thereby achieving green smelting of aviation aluminum alloy and obtaining aviation aluminum alloy that meets the quality control requirements of aviation aluminum alloy melt.

[0099] Specifically, Examples 1 and 2 are green smelting processes used by enterprises to actually produce a certain 2××× series aviation aluminum alloy. The hydrogen content, slag content and alkali metal content under the two sets of process conditions all meet the melt quality and alkali metal content control requirements of a certain 2××× series aviation aluminum alloy. Compared with the ordinary smelting process used in Comparative Example 1, the hydrogen content level at the furnace outlet of Examples 1 and 2 is better than that of Comparative Example 1, and the slag content level at the furnace outlet of Examples 1 and 2 is significantly better than that of Comparative Example 1. This is because the flux refining used in Comparative Example 1, although the addition of refining agent can purify the melt, the refining agent itself is introduced into the aluminum melt as a new pollutant, resulting in an increase in the slag content level. At the same time, the slag content level of Examples 1 and 2 after online purification treatment is also better than that of Comparative Example 1. In addition, the alkali metal content of the ingots in Examples 1 and 2 is also better than that in Comparative Example 1, because the alkali metal components (Na, Ca, etc.) in the added refining agent will bring additional alkali metal components to the melt, resulting in an increase in the alkali metal content, and the ordinary online purification process cannot effectively remove alkali metals. It is shown that the production of 2××× series aviation aluminum alloys by adopting the green smelting process in Examples 1 and 2 can effectively avoid the problem of increased slag content and alkali metal content caused by the addition of refining agents.

[0100] Examples 3 and 4 are green smelting processes used by enterprises to actually produce a certain 7××× series aviation aluminum alloy. The hydrogen content, slag content and alkali metal content under the two sets of process conditions all meet the quality and alkali metal content control requirements of a certain 7××× series aviation aluminum alloy melt. Compared with the flux refining process used in the smelting furnace of Comparative Example 2, the flux refining process used in the smelting furnace of Comparative Example 3, and the Ar+Cl2 mixed gas refining process used in the insulation furnace, the hydrogen content and slag content levels at the furnace outlet of Examples 3 and 4 are significantly better than those of Comparative Examples 2 and 3. This is because the fine dispersed bubbles generated by the bubble bed in Examples 3 and 4 continue to float up under the action of the partial pressure difference, and the hydrogen in the melt will continue to diffuse into the bubbles and escape from the melt with the movement of the bubbles. At the same time, when the bubbles float up, they will absorb the inclusions in the aluminum liquid and be taken out of the melt together. The flux refining used in Comparative Example 2 can only rely on stirring to achieve the refining effect, and the flux itself will also bring additional inclusion pollution. The Ar+Cl2 mixed gas refining used in the insulation furnace of Comparative Example 3 will bring the risk of chlorine inclusions to the melt. After online purification, the hydrogen content of Examples 3 and 4 is the same as that of Comparative Examples 2 and 3, but the slag content and alkali metal level are significantly better than those of Comparative Examples 2 and 3. In addition, the ingots were characterized by SEM. Figure 2 to Figure 5 ) were not found to be impure. Figure 6 In the ingot of Comparative Example 2, inclusions were found, and the EDS composition confirmed that they were Cl, Ca and other inclusion components. Figure 7 Inclusions were also found at the fracture of the ingot in Comparative Example 3, which were confirmed by EDS composition to be Cl, K, Ca and other inclusions. This shows that the use of refining agents and chlorine-containing gases can easily cause secondary pollution to the ingot, especially increase the risk of Cl inclusions in the ingot, and the ingot is prone to quality risks.

[0101] More importantly, compared with Examples 1 to 4, Comparative Examples 1 to 3 use refining agents and chlorine-containing gases, which will produce chlorine- and fluorine-containing solid pollutants that do not meet the requirements of the green smelting process for aluminum alloys.

[0102] In addition, by comparing Comparative Examples 4 to 7 with Examples 1 to 4, it was found that the online degassing process and the two-stage plate filtration process have a very critical impact on the final melt quality. Compared with Comparative Example 4, the secondary filter plate accuracy used in Examples 1 and 2 in the production process of a certain 2××× series aviation aluminum alloy is 60PPI, and the slag content level after online purification is significantly better than the secondary filter plate using 50PPI in Comparative Example 4. This is because the pore size of the filter plate with a precision of 50PPI is relatively large, and it is unable to effectively filter the fine slag inclusions (such as TiB2, etc.) in the melt, resulting in a slag content level of 0.055mm 2 / kgAl, which cannot meet the slag content control requirements of aviation aluminum alloy melt. Compared with Example 5, Example 1 and 2 use Ar+Cl2 mixed gas to purify the melt online. Since Cl2 is a harmful gas, it does not meet the green smelting requirements. Secondly, the slag content level in Example 5 is worse than that in Examples 1 and 2. This is because the use of chlorine in the online degassing process can cause TiB2 particles to aggregate, and the liquid chloride phase is formed in the molten aluminum to form droplets with a very small density difference with the liquid aluminum. After the droplets collide with the Ti-containing particles, the aggregation phenomenon occurs due to capillary force. Comparative Example 6 In the production process of a certain 7××× series aviation aluminum alloy, the dual-rotor degassing equipment also introduced Ar+Cl2 mixed gas. Compared with Examples 4 and 5, the slag content level after online purification reached 0.040mm 2 / kgAl, which is inferior to the purification effect of Examples 4 and 5. Comparative Example 7 adopts a 40+50PPI two-stage plate filtration method for online filtration. Compared with Examples 4 and 5, the residue content after filtration is 0.046mm 2 / kgAl, which is significantly worse than the bipolar plate filtration effect of 40+60PPI in Examples 4 and 5, indicating that the accuracy of the secondary filter plate produced by 7××× series aviation aluminum alloy should be maintained at 60PPI.

[0103] In Comparative Example 8, the gas flow rate was set too low, the amount of bubbles generated was insufficient, and the gas slag in the melt was difficult to completely escape from the melt through the mass transfer and diffusion of the bubbles, resulting in insufficient purification effect. In Comparative Example 9, the gas flow rate was set too high, the amount of bubbles generated was large, the melt tumbling degree increased, and the gas slag in the melt was prone to bubble formation during the rising process due to the mass transfer and diffusion of the bubbles, and the surface slag was easily re-involved in the melt, reducing the melt purification effect. Comparative Example 10 lacked the argon refining link of the insulation furnace, resulting in a high level of slag content in the melt at the outlet of the insulation furnace, and the quality level of the melt after online purification treatment could not meet the control requirements.

[0104] In summary, the green smelting process proposed in the present invention can effectively ensure the quality of the aviation aluminum alloy melt represented by the 2××× / 7××× series and the control requirements of the alkali metal content. The products and aluminum slag produced during the entire smelting process have no fluorine or chlorine emissions, and the process is green and environmentally friendly.

[0105] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A green smelting process for aviation aluminum alloy, characterized by: The following steps are involved: Material preparation - charging into smelting furnace - stirring - alloying - refining in smelting furnace - stirring - slag removal - sampling - composition adjustment - converter - refining in holding furnace - slag removal - sampling and confirmation in holding furnace - standing - online grain refinement - online degassing - sampling and confirmation of composition - filtration - casting. During the refining stage in smelting furnace, refining stage in holding furnace and online degassing stage, argon gas is introduced to remove gas slag in the melt. The argon gas is introduced in the form of small, diffuse bubbles.

2. The green smelting process of aviation aluminum alloy according to claim 1, characterized in that: During the refining stage of the smelting furnace and the refining stage of the holding furnace, argon is introduced through the air plugs evenly distributed on the bottom of the furnace. The interval between the air plugs is 300-600 mm, the diameter of the air holes in the air plugs is 0.001-1.0 mm, and the average size of the bubbles when argon is introduced is 0.05-10.0 mm.

3. The green smelting process of aviation aluminum alloy according to claim 2, characterized in that: During the refining stage of the smelting furnace, when the temperature of the melt in the smelting furnace reaches 720-770°C, argon gas is introduced. The pressure of argon gas is 0.2-0.8Mpa and the gas flow rate is 2.0-5.0m 3 / h, the ventilation and refining time of the melt in the smelting furnace is 30 to 60 minutes.

4. The green smelting process of aviation aluminum alloy according to claim 2, characterized in that: During the refining stage of the holding furnace, when the melt temperature in the holding furnace reaches 720℃~760℃, argon gas is introduced. The pressure of argon gas is 0.3~0.9Mpa and the gas flow rate is 2.0~4.0m 3 / h, and the melt refining time in the holding furnace is not less than 30min.

5. The green smelting process of aviation aluminum alloy according to claim 1, characterized in that: The argon gas introduction method for online degassing outside the furnace is high-speed rotation of the rotor, and the average bubble size during the argon gas introduction is 0.05-10.0mm.

6. The green smelting process of aviation aluminum alloy according to claim 5, characterized in that: During the online degassing stage, the high-purity argon gas inlet pressure is 0.2-0.5Mpa, and the gas flow rate is 2.0-5.0m 3 / h, the rotor speed is 400~520r / min.

7. The green smelting process of aviation aluminum alloy according to claim 6, characterized in that: During the online degassing stage, the online degassing equipment outside the furnace adopts a three-rotor degasser.

8. The green smelting process of aviation aluminum alloy according to claim 1, characterized in that: During the filtration stage, a two-stage plate filter is used to perform primary and secondary filtration on the alloy aluminum liquid. The filter plate accuracy of the primary filtration is not less than 30PPI, and the filter plate accuracy of the secondary filtration is 60PPI.

9. The green smelting process of aviation aluminum alloy according to claim 8, characterized in that: The aviation aluminum alloy melt after argon refining in the holding furnace is tested by metallographic grid method, and the slag content is ≤0.20mm 2 / kg, hydrogen content is ≤0.25ml / 100gAl; aviation aluminum alloy melt slag content after double-stage plate filtration is ≤0.02mm 2 / kgAl, hydrogen content ≤0.10ml / 100gAl, alkali metal content not higher than 5ppm.

10. The green smelting process of aviation aluminum alloy according to claim 1, characterized in that: The purity of the introduced argon gas is not less than 99.99%.

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