A profile manufacturing method for improving the performance consistency of 7 series aluminum alloy profiles for civil aircraft

Abstract

A profile manufacturing method for improving the performance consistency of a 7 series aluminum alloy profile for civil aircraft. In the field of aluminum alloy profile manufacturing for civil aircraft, the mass percentage of each substance in the alloy profile is as follows: Si content is less than 0.10%, Fe content is less than 0.15%, Zn content is 5.6%-6.0%, Cu content is 1.6%-1.8%, Mg content is 2.5%-2.7%, Mn content is less than 0.1%, Cr content is 0.23%-0.28%, Ti content is 0.02%-0.06%, other impurity element contents are all less than 0.05%, the remainder is Al, and Zn / Mg is controlled between 2.2 and 2.3. A 7 series aluminum alloy profile for civil aircraft with extremely high profile performance consistency is manufactured by adopting a high-composition uniformity rapid casting process, step-by-step heating homogenization treatment of ingots, an isothermal reverse extrusion process, precise heat treatment of section sections, and precise control of sampling positions.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy profile manufacturing, and specifically relates to a profile manufacturing method for improving the performance consistency of 7 series aluminum alloy profiles for civil aircraft. Background Art

[0002] Compared with military aircraft, civil aircraft spend most of their life cycle flying except for short stops and regular maintenance. Most aircraft fly more than 60,000 hours before being scrapped, and take off and land more than 40,000 times, which places higher demands on the reliability of the fuselage structure. Civil aircraft have very high requirements for the economy of materials. Generally, aviation aluminum alloys with very high technical maturity are used to manufacture different structural parts of different models to increase the use of a single alloy and reduce procurement costs. Therefore, although some general civil aircraft aluminum alloy profiles have no special requirements for damage tolerance, fatigue performance, etc., they have very high requirements for the consistency of mechanical properties to ensure the reliability of the aircraft structure.

[0003] 7075 aluminum alloy is a very mature heat-treatable aluminum alloy. With appropriate forming and heat treatment processes, it can obtain very high strength and is widely used in the manufacture of civil aircraft structural parts. As the first generation of aviation aluminum alloy, 7075 alloy has certain shortcomings in damage tolerance, fatigue performance, etc., but with its very large price advantage, it is still widely used in non-critical parts of various civil aircraft. Due to the lack of composition design experience in the development of the first generation of aviation aluminum alloys, and the low requirements for aluminum alloy performance for aircraft at that time, 7075 is very sensitive to alloy composition fluctuations. Moreover, the quenching sensitivity of 7075 is significantly higher than that of the third and fourth generation aviation aluminum alloys such as 7050 and 7085. Therefore, the composition differences between different batches in the production process, the thickness differences between different profiles, and the sampling position differences of different profiles will lead to poor consistency in profile performance. There are many ways to evaluate performance consistency. Among them, the simplest method is to calculate the coefficient of variation of various mechanical performance indicators. The coefficient of variation is the ratio of the standard deviation of the original data to the average of the original data. The smaller the coefficient of variation of the mechanical performance data of a batch of materials, the better the consistency of the mechanical properties. The coefficient of variation of aviation aluminum alloy products for civil aircraft generally cannot exceed 3%.

[0004] CN 101760679A discloses a method for preparing a 7B04 aluminum alloy profile, which solves the problem that large-size ingots of 7B04 aluminum alloy are difficult to form and that mechanical properties and electrical conductivity cannot simultaneously meet index requirements. The prepared profile has a tensile strength of up to 520MPa and a yield strength of up to 470MPa under single-stage aging, and can reach 540MPa and a yield strength of up to 515MPa under double-stage aging. All performances meet index requirements, and the yield rate is as high as more than 80%.

[0005] CN 109554560A discloses a method for producing ultra-high strength 7-series aluminum alloy profiles for aerospace use. The aluminum alloy profiles with ultra-high strength are obtained by optimizing the alloy composition and the heat treatment process.

[0006] CN 108465713A discloses a processing technology for 7075 aluminum alloy profiles, which adopts an online quenching process to avoid the high energy consumption caused by offline quenching of profiles. The produced profiles have a tensile strength of 600MPa and a yield strength of 530MPa, which can meet the technical indicators specified in relevant standards.

[0007] The existing technology of domestic aluminum alloy profiles mainly focuses on improving the strength and corrosion resistance of aluminum alloy profiles. Through technological innovations in alloy composition design, extrusion process, heat treatment process and other stages, the use requirements of aluminum alloy profiles in terms of strength and corrosion resistance are met. The user of the material does not pay attention to the impact of profile section differences and production batches on the mechanical properties of the material. As long as the mechanical properties of the material are higher than the minimum value specified in the standard, it is deemed qualified. The existing technology does not pay attention to the performance consistency of the material, mainly because the domestic civil aircraft aluminum alloy market has not yet matured, and the demand for special application fields such as aerospace is generally multi-variety and small batches. In terms of performance, it only pursues high strength and high corrosion resistance of the material, and does not pay attention to the performance consistency of the material. Application fields such as lightweight automobiles and building profiles tend to lower the entry threshold to reduce material costs, and will not make requirements for the performance consistency of the material. Only in the field of civil aircraft, in order to ensure the safety of long-term service of aircraft, there are requirements for the performance consistency of materials. Summary of the invention

[0008] In order to solve the deficiencies mentioned in the above-mentioned prior art, the present invention provides a profile manufacturing method for improving the performance consistency of 7 series aluminum alloy profiles for civil aircraft.

[0009] This application proposes a profile manufacturing method for improving the performance consistency of 7 series aluminum alloy profiles for civil aircraft, which is achieved through the following technical solutions:

[0010] Step 1: Taking full account of factors such as alloy element burnout during alloy smelting and alloy content in waste materials, the ingredients are prepared according to the following alloy composition control requirements: Si content is less than 0.10%, Fe content is less than 0.15%, Zn content is 5.6%~6.0%, Cu content is 1.6%~1.8%, Mg content is 2.5%~2.7%, Mn content is less than 0.1%, Cr content is 0.23%~0.28%, Ti content is 0.02%~0.06%, and the content of other impurity elements is less than 0.05%, the balance is Al, and Zn / Mg is controlled between 2.2~2.3. Among them, the added aluminum ingots are customized aluminum ingots with a purity of 99.85%;

[0011] Step 2: Put fully dried scrap and aluminum ingots into the smelting furnace. After the aluminum ingots are completely melted, turn on the electromagnetic stirring equipment for stirring. After the melt temperature reaches 740°C, alloying begins. Add copper plates, magnesium ingots and various intermediate alloys in batches. The interval between adding each batch of alloys is 20 minutes, and the weight added each time does not exceed 500 kg.

[0012] Step 3: After all raw materials are completely melted, the melt is transferred from the smelting furnace to the static furnace. The temperature of the static furnace melt is controlled at 725~745℃. A rotary ventilation device is used to introduce a mixed gas of argon and chlorine for refining. During the refining process, the slag floating out of the melt is cleaned in time. The chemical composition analysis is carried out by sampling at a fixed position. If the test result is unqualified, the alloy composition of the charge is adjusted to meet the requirements.

[0013] Step 4: Raise the temperature of the degassing box to 740℃, adjust the temperature of the melt in the standing furnace to 730℃, and use flames to fully preheat the filter plate and the entire set of flow channels. After all the preparations are completed, tilt the standing furnace to start casting. The melt flows through the two-stage degassing box and the filter box and then enters the casting flow plate. In the flow channel between the two-stage degassing boxes, use the wire feeder to add Al-Ti-B refiner. During the casting process, the temperature of the two-stage double-rotor degassing box is always controlled at 735~745℃ to supplement the heat loss of the melt in the flow channel. After the melt on the casting flow plate reaches 693℃, stop the standing furnace heating and slowly reduce the melt temperature in the furnace. When the casting machine flow plate temperature is lower than 687℃, start the standing furnace heating to increase the melt temperature. By controlling the standing furnace melt temperature, the melt temperature on the casting machine flow plate is controlled between 685℃~695℃;

[0014] Step 5: immediately send the ingot cast by the casting machine into a homogenizing furnace for homogenization treatment;

[0015] Step 6: Before extrusion, the extrusion die, extrusion barrel and ingot are heated, the die temperature is set to 385~415℃, the extrusion barrel temperature is set to 360~400℃, the head end temperature of the ingot is set to 340~380℃, the temperature of the ingot from the head end to the tail end shows a gradient downward trend, and the temperature gradient downward trend is 20℃ / m. The ingot is loaded into the extrusion barrel with the tail end inside and the head end outside. The extrusion die is loaded into the extrusion barrel close to the head end of the ingot, and the hollow shaft is slowly inserted for reverse extrusion. The extrusion shaft speed of the reverse extrusion is 0.3~0.6 mm / s. After the extrusion is completed, pre-stretching and straightening with a deformation of 0.3%~1.2% is performed to obtain the initial aluminum alloy profile;

[0016] Step 7: Use offline heat treatment process to carry out solid solution treatment on the primary aluminum alloy profile. The solid solution treatment temperature is 471℃ and the holding time of solid solution treatment is 360min to ensure sufficient solid solution. After the holding is completed, spray step quenching is carried out and the quenched profile is immediately stretched and straightened with the tensile deformation controlled at 1%~3% to eliminate the quenching residual stress.

[0017] Step 8: Use an aging furnace to artificially age the profile at a temperature of 120°C. Calculate the average thickness of the profile at different locations and select the appropriate aging time in the table below.

[0018]

[0019] Specifically, the homogenization process in step five as described above is: raise the temperature to 460°C at a heating rate of 40°C / h, keep warm for 8 hours, then raise the temperature to 475°C at a heating rate of 40°C / h, keep warm for 24 hours, and the homogenized ingot is the raw material for profile extrusion.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention aims to improve the performance consistency of 7-series aluminum alloy profiles. Through precise alloy composition design and control, application of low-cost 99.85% aluminum ingots, low-temperature casting to reduce composition segregation, isothermal reverse extrusion process, precise aging control of cross-sections, and precise control of sampling positions, the coefficient of variation of mechanical properties of multi-thickness and multi-batch 7-series profiles is successfully controlled within 3%, meeting the use needs of civil aircraft equipment and filling the domestic gap.

[0022] 2. The present invention replaces the aluminum ingots with a purity of 99.99% commonly used in the production of aluminum alloys for civil aircraft with customized aluminum ingots with a purity of 99.85%, which greatly reduces the manufacturing cost of 7 series profiles for civil aircraft. The purity of conventional remelted aluminum ingots is 99.7%, which has more impurities and Fe and Si content, and is easy to form defects or coarse compounds in the material, resulting in unstable material properties. Therefore, the production of aviation aluminum alloys for civil aircraft generally adds a large amount of aluminum ingots with a purity of 99.99% on the basis of aluminum ingots with a purity of 99.7% to improve the purity of the melt. However, aluminum ingots with a purity of 99.99% need to be further purified on the basis of electrolytic aluminum water and then cast, which has high production costs and does not conform to the general trend of global energy conservation and emission reduction. Nanshan Aluminum has the advantage of a short-distance full industrial chain. It only needs to use electrolytic aluminum water with better quality for casting to produce customized 99.85% aluminum ingots, which hardly increases production costs and ensures the purity of the aluminum alloy melt.

[0023] 3. Unlike the aluminum alloys for military products, which can be optimized for performance by adding special alloy components, aviation aluminum alloys for civil aircraft generally use specified mature alloys and can only be regulated within the standard alloy composition range. Therefore, in terms of alloy composition design, the present invention has carried out a series of composition optimizations through experiments on the basis of the mature 7075 alloy. First, without adding 99.99% refined aluminum ingots, the Fe and Si content are strictly controlled to avoid the formation of coarse crystalline phases by Fe and Si elements, reduce the difficulty of controlling PSN effect recrystallization, and improve the performance consistency of the profile. Then, narrow the control range of Zn, Mg, and Cu elements, especially strictly control the Zn / Mg ratio, carefully manage the precipitation strengthening effect of the profile, and increase the performance consistency of the profile.

[0024] 4. In terms of casting process optimization, on the one hand, by degassing and deslagging in multiple links of smelting and casting, the metallurgical quality of the ingot is improved, the accidental impact of metallurgical slag inclusions on mechanical property testing is reduced, and the consistency of the mechanical properties of the profile is improved. On the other hand, through the temperature management of the casting process, the temperature difference between the holding furnace and the casting flow plate is reduced, the casting flow plate temperature is lowered to control between 685℃ and 695℃, the solidification undercooling of the ingot is increased, the grain size difference and composition segregation between the core and the edge of the ingot are reduced, and the performance consistency of the profile is improved.

[0025] 5. In terms of extrusion process optimization, the reverse extrusion process parameters adopted by the present invention first systematically simulate the stress field and temperature field of the extrusion process through numerical simulation software, select the optimal extrusion temperature, extrusion speed and gradient temperature, and conduct tests and corrections on the production line, basically realizing isothermal extrusion, greatly improving the performance consistency of the head and tail ends of the profile. By finely controlling the extrusion temperature and speed, dynamic recrystallization in the extrusion process is avoided, and dynamic recovery is promoted to avoid static recrystallization during the solution process, reducing the fluctuation of mechanical properties caused by recrystallization softening.

[0026] 6. During the aging heat treatment process, the profiles are divided into different intervals according to their thickness differences, and the aging process is refined through experiments. The aging time of thicker profiles is appropriately shortened to avoid significant performance degradation caused by excessive aging due to the long time for the load thermocouple to reach temperature, and the performance consistency of profiles of different thicknesses is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0028] Figure 1 Schematic diagram of the cross section of profile 1; Figure 2 Schematic diagram of the cross section of profile 2; Figure 3 Schematic diagram of the cross section of profile 3; Figure 4 Schematic diagram of the cross section of profile 4; Figure 5 Example 1 Profile longitudinal section second phase; Figure 6 The second phase of the longitudinal section of the profile of comparative example 1; Figure 7 Strength comparison between Example 2 and Comparative Example 2; Figure 8 Strength comparison between Example 3 and Comparative Example 3; Fig. 9 Comparison of coefficients of variation of different embodiments and comparative examples. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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.

[0030] Example 1

[0031] Step 1: Fully consider the alloy element burnout during alloy smelting and the alloy content in the scrap, and prepare the ingredients according to the alloy composition control requirements. Among them, the added aluminum ingots are customized with a purity of 99.85%.

[0032] Step 2: Put fully dried scrap and aluminum ingots into the smelting furnace. After the aluminum ingots are completely melted, turn on the electromagnetic stirring equipment for stirring. After the melt temperature reaches 740°C, alloying begins. Copper plates, magnesium ingots and various intermediate alloys are added in batches. The interval between adding each batch of alloys is 20 minutes, and the weight added each time does not exceed 500 kg.

[0033] Step 3: After all raw materials are completely melted, the melt is transferred from the smelting furnace to the static furnace. The temperature of the static furnace melt is controlled at 725~745℃. A rotary ventilation device is used to introduce a mixed gas of argon and chlorine for refining. During the refining process, the slag floating out of the melt is cleaned in time. Chemical composition analysis is carried out by taking samples at a fixed position. If the test results are unqualified, the alloy composition of the charge is adjusted to qualified. The measured alloy composition is: Si content 0.08%, Fe content less than 0.10%, Zn content 5.8%, Cu content 1.6%, Mg content 2.6%, Mn content 0.07%, Cr content 0.25%, Ti content 0.04%, Zn / Mg ratio is 2.23.

[0034] Step 4: Raise the temperature of the degassing box to 740°C, adjust the temperature of the melt in the standing furnace to 730°C, and use flames to fully preheat the filter plate and the entire set of flow channels. After all the preparations are completed, tilt the standing furnace to start casting, and the melt flows through the two-stage degassing box and the filter box and enters the casting flow plate. In the flow channel between the two-stage degassing boxes, use the wire feeder to add Al-Ti-B refiner. During the casting process, the temperature of the two-stage double-rotor degassing box is always controlled at 735~745°C to supplement the heat loss of the melt in the flow channel. After the melt on the casting flow plate reaches 693°C, stop the standing furnace heating and slowly reduce the melt temperature in the furnace. When the casting machine flow plate temperature is lower than 687°C, start the standing furnace heating to increase the melt temperature. By controlling the standing furnace melt temperature, the melt temperature on the casting machine flow plate is controlled between 685°C and 695°C.

[0035] Step 5: Send the ingot cast by the casting machine to the homogenization furnace for homogenization treatment immediately. The homogenization process is: use a heating rate of 40℃ / h to raise the temperature to 460℃, keep it warm for 8 hours, and then raise the temperature to 475℃ at a heating rate of 40℃ / h, and keep it warm for 24 hours. The homogenized ingot is the raw material for profile extrusion.

[0036] Step 6: Before extrusion, the extrusion die, extrusion barrel and ingot are heated, the die temperature is set to 410℃, and the extrusion barrel temperature is set to 400℃. The temperature of the head end of the ingot is set to 380℃, and the temperature of the ingot decreases gradually from the head end to the tail end, and the temperature gradient decreases by 20℃ / m. The ingot is loaded into the extrusion barrel with the tail end inside and the head end outside, and the extrusion die is loaded into the extrusion barrel close to the head end of the ingot, and the hollow shaft is slowly inserted for reverse extrusion. The extrusion shaft speed of the reverse extrusion is 0.4mm / s. After the extrusion is completed, pre-stretching and straightening with a deformation of 0.8% is performed to obtain the initial aluminum alloy profile.

[0037] Step 7: Use offline heat treatment process to carry out solid solution treatment on the initial aluminum alloy profile. The solid solution treatment temperature is 471 ° C, and the holding time of the solid solution treatment is 360 minutes to ensure sufficient solid solution. After the insulation is completed, spray step quenching is carried out, and the quenched profile is immediately stretched and straightened with the tensile deformation controlled at 1.8% to eliminate the quenching residual stress.

[0038] Step 8: Use an aging furnace to artificially age the profile. The aging temperature is 120°C. The aging time is selected according to the thickness of the profile. The cross-sectional diagram of profile 1 is shown in Figure 1 , the average thickness is 28.58mm, the aging time is 1440min; the cross-sectional schematic diagram of profile 2 is shown in Figure 2 The average thickness is 40.983 mm and the aging time is 1410 mm; the cross-sectional diagram of profile 3 is shown in Figure 3, the average thickness is 47.625mm, the aging time is 1380mm; the schematic diagram of the cross section of profile 4 is shown in Figure 4 , the average thickness is 58mm, and the aging time is 1350mm. After multiple batches of verification, the average tensile strength is 538MPa, the coefficient of variation is 0.6%, and the average yield strength is 462MPa, the coefficient of variation is 0.79%.

[0039] Comparative Example 1

[0040] Step 1: Fully consider the alloy element burnout during alloy smelting and the alloy content in the scrap, and prepare the ingredients according to the alloy composition control requirements. The added aluminum ingots are all ordinary remelted aluminum ingots with a purity of 99.7%.

[0041] Step 2: Put fully dried scrap and aluminum ingots into the smelting furnace. After the aluminum ingots are completely melted, turn on the electromagnetic stirring equipment for stirring. After the melt temperature reaches 740°C, alloying begins. Copper plates, magnesium ingots and various intermediate alloys are added in batches. The interval between adding each batch of alloys is 20 minutes, and the weight added each time does not exceed 500 kg.

[0042] Step 3: After all the raw materials are completely melted, the melt is transferred from the smelting furnace to the static furnace. The temperature of the static furnace melt is controlled at 725~745℃. A rotary ventilation device is used to introduce a mixed gas of argon and chlorine for refining. The slag floating out of the melt is cleaned in time during the refining process. Chemical composition analysis is carried out by taking samples at a fixed position. If the test results are unqualified, the alloy composition of the charge is adjusted to qualified. The measured alloy composition is: Si content 0.23%, Fe content 0.29%, Zn content 6.0%, Cu content 1.7%, Mg content 2.5%, Mn content less than 0.08%, Cr content 0.25%, Ti content 0.06%, and Zn / Mg ratio is 2.4. Among them, the added aluminum ingots are all customized aluminum ingots with a purity of 99.85%.

[0043] Step 4: Raise the temperature of the degassing box to 740°C, adjust the temperature of the melt in the standing furnace to 730°C, and use flames to fully preheat the filter plate and the entire set of flow channels. After all the preparations are completed, tilt the standing furnace to start casting, and the melt flows through the two-stage degassing box and the filter box and enters the casting flow plate. In the flow channel between the two-stage degassing boxes, use the wire feeder to add Al-Ti-B refiner. During the casting process, the temperature of the two-stage double-rotor degassing box is always controlled at 735~745°C to supplement the heat loss of the melt in the flow channel. After the melt on the casting flow plate reaches 693°C, stop the standing furnace heating and slowly reduce the melt temperature in the furnace. When the casting machine flow plate temperature is lower than 687°C, start the standing furnace heating to increase the melt temperature. By controlling the standing furnace melt temperature, the melt temperature on the casting machine flow plate is controlled between 685°C and 695°C.

[0044] Step 5: Send the ingot cast by the casting machine to the homogenization furnace for homogenization treatment immediately. The homogenization process is: use a heating rate of 40℃ / h to raise the temperature to 460℃, keep it warm for 8 hours, and then raise the temperature to 475℃ at a heating rate of 40℃ / h, and keep it warm for 24 hours. The homogenized ingot is the raw material for profile extrusion.

[0045] Step 6: Before extrusion, the extrusion die, extrusion barrel and ingot are heated, the die temperature is set to 410℃, and the extrusion barrel temperature is set to 400℃. The temperature of the head end of the ingot is set to 380℃, and the temperature of the ingot decreases gradually from the head end to the tail end, and the temperature gradient decreases by 20℃ / m. The ingot is loaded into the extrusion barrel with the tail end inside and the head end outside, and the extrusion die is loaded into the extrusion barrel close to the head end of the ingot, and the hollow shaft is slowly inserted for reverse extrusion. The extrusion shaft speed of the reverse extrusion is 0.4mm / s. After the extrusion is completed, pre-stretching and straightening with a deformation of 0.8% is performed to obtain the initial aluminum alloy profile.

[0046] Step 7: Use offline heat treatment process to carry out solid solution treatment on the initial aluminum alloy profile. The solid solution treatment temperature is 471 ° C, and the holding time of the solid solution treatment is 360 minutes to ensure sufficient solid solution. After the insulation is completed, spray step quenching is carried out, and the quenched profile is immediately stretched and straightened with the tensile deformation controlled at 1.8% to eliminate the quenching residual stress.

[0047] Step 8: Use an aging furnace to artificially age the profile. The aging temperature is 120°C. The aging time is selected according to the thickness of the profile. The cross-sectional diagram of profile 1 is shown in Figure 1 , the average thickness is 28.58mm, the aging time is 1440min; the cross-sectional schematic diagram of profile 2 is shown in Figure 2 The average thickness is 40.983 mm and the aging time is 1410 mm; the cross-sectional diagram of profile 3 is shown in Figure 3 , the average thickness is 47.625mm, the aging time is 1380mm; the schematic diagram of the cross section of profile 4 is shown in Figure 4 , the average thickness is 58mm, and the aging time is 1350mm. After multiple batches of verification, the average tensile strength is 530MPa, the coefficient of variation is 3.4%, and the average yield strength is 450MPa, the coefficient of variation is 5%.

[0048] Example 2

[0049] Step 1: Fully consider the alloy element burnout during alloy smelting and the alloy content in the scrap, and prepare the ingredients according to the alloy composition control requirements. Among them, the added aluminum ingots are customized with a purity of 99.85%.

[0050] Step 2: Put fully dried scrap and aluminum ingots into the smelting furnace. After the aluminum ingots are completely melted, turn on the electromagnetic stirring equipment for stirring. After the melt temperature reaches 740°C, alloying begins. Copper plates, magnesium ingots and various intermediate alloys are added in batches. The interval between adding each batch of alloys is 20 minutes, and the weight added each time does not exceed 500 kg.

[0051] Step 3: After all raw materials are completely melted, the melt is transferred from the smelting furnace to the static furnace. The temperature of the static furnace melt is controlled at 725~745℃. A rotary ventilation device is used to introduce a mixed gas of argon and chlorine for refining. During the refining process, the slag floating out of the melt is cleaned in time. Chemical composition analysis is carried out by taking samples at a fixed position. If the test results are unqualified, the alloy composition of the charge is adjusted to qualified. The measured alloy composition is: Si content 0.08%, Fe content less than 0.10%, Zn content 5.8%, Cu content 1.6%, Mg content 2.6%, Mn content 0.07%, Cr content 0.25%, Ti content 0.04%, Zn / Mg ratio is 2.23.

[0052] Step 4: Raise the temperature of the degassing box to 740°C, adjust the temperature of the melt in the standing furnace to 730°C, and use flames to fully preheat the filter plate and the entire set of flow channels. After all the preparations are completed, tilt the standing furnace to start casting, and the melt flows through the two-stage degassing box and the filter box and enters the casting flow plate. In the flow channel between the two-stage degassing boxes, use the wire feeder to add Al-Ti-B refiner. During the casting process, the temperature of the two-stage double-rotor degassing box is always controlled at 735~745°C to supplement the heat loss of the melt in the flow channel. After the melt on the casting flow plate reaches 693°C, stop the standing furnace heating and slowly reduce the melt temperature in the furnace. When the casting machine flow plate temperature is lower than 687°C, start the standing furnace heating to increase the melt temperature. By controlling the standing furnace melt temperature, the melt temperature on the casting machine flow plate is controlled between 685°C and 695°C.

[0053] Step 5: Send the ingot cast by the casting machine to the homogenization furnace for homogenization treatment immediately. The homogenization process is: use a heating rate of 40℃ / h to raise the temperature to 460℃, keep it warm for 8 hours, and then raise the temperature to 475℃ at a heating rate of 40℃ / h, and keep it warm for 24 hours. The homogenized ingot is the raw material for profile extrusion.

[0054] Step 6: Before extrusion, the extrusion die, extrusion barrel and ingot are heated, the die temperature is set to 390℃, and the extrusion barrel temperature is set to 370℃. The temperature of the head end of the ingot is set to 360℃, and the temperature of the ingot decreases gradually from the head end to the tail end, and the temperature gradient decreases by 20℃ / m. The ingot is loaded into the extrusion barrel with the tail end inside and the head end outside, and the extrusion die is loaded into the extrusion barrel close to the head end of the ingot, and the hollow shaft is slowly inserted for reverse extrusion. The extrusion shaft speed of the reverse extrusion is 0.6mm / s. After the extrusion is completed, pre-stretching and straightening with a deformation of 1.1% is performed to obtain the initial aluminum alloy profile.

[0055] Step 7: Use offline heat treatment process to carry out solid solution treatment on the initial aluminum alloy profile. The solid solution treatment temperature is 471 ° C, and the holding time of the solid solution treatment is 360 minutes to ensure sufficient solid solution. After the insulation is completed, spray step quenching is carried out, and the quenched profile is immediately stretched and straightened with the tensile deformation controlled at 2.1% to eliminate the quenching residual stress.

[0056] Step 8: Use an aging furnace to artificially age the profile. The aging temperature is 120°C. The aging time is selected according to the thickness of the profile. The cross-sectional diagram of profile 1 is shown in Figure 1 , the average thickness is 28.58mm, the aging time is 1440min; the cross-sectional schematic diagram of profile 2 is shown in Figure 2 The average thickness is 40.983 mm and the aging time is 1410 mm; the cross-sectional diagram of profile 3 is shown in Figure 3 , the average thickness is 47.625mm, the aging time is 1380mm; the schematic diagram of the cross section of profile 4 is shown in Figure 4 , the average thickness is 58mm, and the aging time is 1350mm. After multiple batches of verification, the average tensile strength is 537MPa, the coefficient of variation is 0.72%, and the average yield strength is 463MPa, the coefficient of variation is 0.83%.

[0057] Comparative Example 2

[0058] Step 1: Fully consider the alloy element burnout during alloy smelting and the alloy content in the scrap, and prepare the ingredients according to the alloy composition control requirements. Among them, the added aluminum ingots are customized with a purity of 99.85%.

[0059] Step 2: Put fully dried scrap and aluminum ingots into the smelting furnace. After the aluminum ingots are completely melted, turn on the electromagnetic stirring equipment for stirring. After the melt temperature reaches 740°C, alloying begins. Copper plates, magnesium ingots and various intermediate alloys are added in batches. The interval between adding each batch of alloys is 20 minutes, and the weight added each time does not exceed 500 kg.

[0060] Step 3: After all raw materials are completely melted, the melt is transferred from the smelting furnace to the static furnace. The temperature of the static furnace melt is controlled at 725~745℃. A rotary ventilation device is used to introduce a mixed gas of argon and chlorine for refining. During the refining process, the slag floating out of the melt is cleaned in time. Chemical composition analysis is carried out by taking samples at a fixed position. If the test results are unqualified, the alloy composition of the charge is adjusted to qualified. The measured alloy composition is: Si content 0.08%, Fe content less than 0.10%, Zn content 5.8%, Cu content 1.6%, Mg content 2.6%, Mn content 0.07%, Cr content 0.25%, Ti content 0.04%, Zn / Mg ratio is 2.23.

[0061] Step 4: Raise the temperature of the degassing box to 740°C, adjust the temperature of the melt in the standing furnace to 730°C, and use flames to fully preheat the filter plate and the entire set of flow channels. After all the preparations are completed, tilt the standing furnace to start casting, and the melt flows through the two-stage degassing box and the filter box and enters the casting flow plate. In the flow channel between the two-stage degassing boxes, use the wire feeder to add Al-Ti-B refiner. During the casting process, the temperature of the two-stage double-rotor degassing box is always controlled at 735~745°C to supplement the heat loss of the melt in the flow channel. After the melt on the casting flow plate reaches 693°C, stop the standing furnace heating and slowly reduce the melt temperature in the furnace. When the casting machine flow plate temperature is lower than 687°C, start the standing furnace heating to increase the melt temperature. By controlling the standing furnace melt temperature, the melt temperature on the casting machine flow plate is controlled between 685°C and 695°C.

[0062] Step 5: Send the ingot cast by the casting machine to the homogenization furnace for homogenization treatment immediately. The homogenization process is: use a heating rate of 40℃ / h to raise the temperature to 460℃, keep it warm for 8 hours, and then raise the temperature to 475℃ at a heating rate of 40℃ / h, and keep it warm for 24 hours. The homogenized ingot is the raw material for profile extrusion.

[0063] Step 6: Before extrusion, the extrusion die, extrusion barrel and ingot are heated, the die temperature is set to 420℃, and the extrusion barrel temperature is set to 410℃. The ingot temperature is set to 400℃. The ingot is loaded into the extrusion barrel with the tail end inside and the head end outside. The extrusion die is loaded into the extrusion barrel close to the head end of the ingot, and the hollow shaft is slowly inserted for reverse extrusion. The extrusion shaft speed of reverse extrusion is 0.7 mm / s. After the extrusion is completed, pre-stretching and straightening with a deformation of 0.8% is performed to obtain the initial aluminum alloy profile.

[0064] Step 7: Use offline heat treatment process to carry out solid solution treatment on the initial aluminum alloy profile. The solid solution treatment temperature is 471 ° C, and the holding time of the solid solution treatment is 360 minutes to ensure sufficient solid solution. After the insulation is completed, spray step quenching is carried out, and the quenched profile is immediately stretched and straightened with the tensile deformation controlled at 1.5% to eliminate the quenching residual stress.

[0065] Step 8: Use an aging furnace to artificially age the profile. The aging temperature is 120°C. The aging time is selected according to the thickness of the profile. The cross-sectional diagram of profile 1 is shown in Figure 1 , the average thickness is 28.58mm, the aging time is 1440min; the cross-sectional schematic diagram of profile 2 is shown in Figure 2 The average thickness is 40.983 mm and the aging time is 1410 mm; the cross-sectional diagram of profile 3 is shown in Figure 3 , the average thickness is 47.625mm, the aging time is 1380mm; the schematic diagram of the cross section of profile 4 is shown in Figure 4 , the average thickness is 58mm, and the aging time is 1350mm. After multiple batches of verification, the average tensile strength is 528MPa, the coefficient of variation is 3.4%, and the average yield strength is 454MPa, the coefficient of variation is 4.1%.

[0066] Example 3

[0067] Step 1: Fully consider the alloy element burnout during alloy smelting and the alloy content in the scrap, and prepare the ingredients according to the alloy composition control requirements. Among them, the added aluminum ingots are customized with a purity of 99.85%.

[0068] Step 2: Put fully dried scrap and aluminum ingots into the smelting furnace. After the aluminum ingots are completely melted, turn on the electromagnetic stirring equipment for stirring. After the melt temperature reaches 740°C, alloying begins. Copper plates, magnesium ingots and various intermediate alloys are added in batches. The interval between adding each batch of alloys is 20 minutes, and the weight added each time does not exceed 500 kg.

[0069] Step 3: After all raw materials are completely melted, the melt is transferred from the smelting furnace to the static furnace. The temperature of the static furnace melt is controlled at 725~745℃. A rotary ventilation device is used to introduce a mixed gas of argon and chlorine for refining. During the refining process, the slag floating out of the melt is cleaned in time. Chemical composition analysis is carried out by taking samples at a fixed position. If the test results are unqualified, the alloy composition of the charge is adjusted to qualified. The measured alloy composition is: Si content 0.07%, Fe content less than 0.09%, Zn content 5.9%, Cu content 1.7%, Mg content 2.7%, Mn content 0.07%, Cr content 0.24%, Ti content 0.04%, Zn / Mg ratio is 2.19.

[0070] Step 4: Raise the temperature of the degassing box to 740°C, adjust the temperature of the melt in the standing furnace to 730°C, and use flames to fully preheat the filter plate and the entire set of flow channels. After all the preparations are completed, tilt the standing furnace to start casting, and the melt flows through the two-stage degassing box and the filter box and enters the casting flow plate. In the flow channel between the two-stage degassing boxes, use the wire feeder to add Al-Ti-B refiner. During the casting process, the temperature of the two-stage double-rotor degassing box is always controlled at 735~745°C to supplement the heat loss of the melt in the flow channel. After the melt on the casting flow plate reaches 693°C, stop the standing furnace heating and slowly reduce the melt temperature in the furnace. When the casting machine flow plate temperature is lower than 687°C, start the standing furnace heating to increase the melt temperature. By controlling the standing furnace melt temperature, the melt temperature on the casting machine flow plate is controlled between 685°C and 695°C.

[0071] Step 5: Send the ingot cast by the casting machine to the homogenization furnace for homogenization treatment immediately. The homogenization process is: use a heating rate of 40℃ / h to raise the temperature to 460℃, keep it warm for 8 hours, and then raise the temperature to 475℃ at a heating rate of 40℃ / h, and keep it warm for 24 hours. The homogenized ingot is the raw material for profile extrusion.

[0072] Step 6: Before extrusion, the extrusion die, extrusion barrel and ingot are heated, the die temperature is set to 400℃, and the extrusion barrel temperature is set to 380℃. The temperature of the head end of the ingot is set to 370℃, and the temperature of the ingot decreases gradually from the head end to the tail end, and the temperature gradient decreases by 20℃ / m. The ingot is loaded into the extrusion barrel with the tail end inside and the head end outside, and the extrusion die is loaded into the extrusion barrel close to the head end of the ingot, and the hollow shaft is slowly inserted for reverse extrusion. The extrusion shaft speed of the reverse extrusion is 0.5mm / s. After the extrusion is completed, pre-stretching and straightening with a deformation of 1.0% is performed to obtain the initial aluminum alloy profile.

[0073] Step 7: Use offline heat treatment process to carry out solid solution treatment on the initial aluminum alloy profile. The solid solution treatment temperature is 471 ° C, and the holding time of the solid solution treatment is 360 minutes to ensure sufficient solid solution. After the insulation is completed, spray step quenching is carried out, and the quenched profile is immediately stretched and straightened with the tensile deformation controlled at 1.5% to eliminate the quenching residual stress.

[0074] Step 8: Use an aging furnace to artificially age the profile. The aging temperature is 120°C. The aging time is selected according to the thickness of the profile. The cross-sectional diagram of profile 1 is shown in Figure 1 , the average thickness is 28.58mm, the aging time is 1440min; the cross-sectional schematic diagram of profile 2 is shown in Figure 2 The average thickness is 40.983 mm and the aging time is 1410 mm; the cross-sectional diagram of profile 3 is shown in Figure 3, the average thickness is 47.625mm, the aging time is 1380mm; the schematic diagram of the cross section of profile 4 is shown in Figure 4 , the average thickness is 58mm, and the aging time is 1350mm. After multiple batches of verification, the average tensile strength is 538MPa, the coefficient of variation is 0.59%, and the average yield strength is 462MPa, the coefficient of variation is 0.75%.

[0075] Comparative Example 3

[0076] Step 1: Fully consider the alloy element burnout during alloy smelting and the alloy content in the scrap, and prepare the ingredients according to the alloy composition control requirements. Among them, the added aluminum ingots are customized with a purity of 99.85%.

[0077] Step 2: Put fully dried scrap and aluminum ingots into the smelting furnace. After the aluminum ingots are completely melted, turn on the electromagnetic stirring equipment for stirring. After the melt temperature reaches 740°C, alloying begins. Copper plates, magnesium ingots and various intermediate alloys are added in batches. The interval between adding each batch of alloys is 20 minutes, and the weight added each time does not exceed 500 kg.

[0078] Step 3: After all raw materials are completely melted, the melt is transferred from the smelting furnace to the static furnace. The temperature of the static furnace melt is controlled at 725~745℃. A rotary ventilation device is used to introduce a mixed gas of argon and chlorine for refining. During the refining process, the slag floating out of the melt is cleaned in time. Chemical composition analysis is carried out by taking samples at a fixed position. If the test results are unqualified, the alloy composition of the charge is adjusted to qualified. The measured alloy composition is: Si content 0.07%, Fe content less than 0.09%, Zn content 5.9%, Cu content 1.7%, Mg content 2.7%, Mn content 0.07%, Cr content 0.24%, Ti content 0.04%, Zn / Mg ratio is 2.19.

[0079] Step 4: Raise the temperature of the degassing box to 740°C, adjust the temperature of the melt in the standing furnace to 730°C, and use flames to fully preheat the filter plate and the entire set of flow channels. After all the preparations are completed, tilt the standing furnace to start casting, and the melt flows through the two-stage degassing box and the filter box and enters the casting flow plate. In the flow channel between the two-stage degassing boxes, use the wire feeder to add Al-Ti-B refiner. During the casting process, the temperature of the two-stage double-rotor degassing box is always controlled at 735~745°C to supplement the heat loss of the melt in the flow channel. After the melt on the casting flow plate reaches 693°C, stop the standing furnace heating and slowly reduce the melt temperature in the furnace. When the casting machine flow plate temperature is lower than 687°C, start the standing furnace heating to increase the melt temperature. By controlling the standing furnace melt temperature, the melt temperature on the casting machine flow plate is controlled between 685°C and 695°C.

[0080] Step 5: Send the ingot cast by the casting machine to the homogenization furnace for homogenization treatment immediately. The homogenization process is: use a heating rate of 40℃ / h to raise the temperature to 460℃, keep it warm for 8 hours, and then raise the temperature to 475℃ at a heating rate of 40℃ / h, and keep it warm for 24 hours. The homogenized ingot is the raw material for profile extrusion.

[0081] Step 6: Before extrusion, the extrusion die, extrusion barrel and ingot are heated, the die temperature is set to 400℃, and the extrusion barrel temperature is set to 380℃. The temperature of the head end of the ingot is set to 370℃, and the temperature of the ingot decreases gradually from the head end to the tail end, and the temperature gradient decreases by 20℃ / m. The ingot is loaded into the extrusion barrel with the tail end inside and the head end outside, and the extrusion die is loaded into the extrusion barrel close to the head end of the ingot, and the hollow shaft is slowly inserted for reverse extrusion. The extrusion shaft speed of the reverse extrusion is 0.5mm / s. After the extrusion is completed, pre-stretching and straightening with a deformation of 1.0% is performed to obtain the initial aluminum alloy profile.

[0082] Step 7: Use offline heat treatment process to carry out solid solution treatment on the initial aluminum alloy profile. The solid solution treatment temperature is 471 ° C, and the holding time of the solid solution treatment is 360 minutes to ensure sufficient solid solution. After the insulation is completed, spray step quenching is carried out, and the quenched profile is immediately stretched and straightened with the tensile deformation controlled at 1.5% to eliminate the quenching residual stress.

[0083] Step 8: Use an aging furnace to artificially age the profiles, the aging temperature is 120°C, and the aging time is 1440min. After multiple batches of verification, the average tensile strength is 533MPa, the coefficient of variation is, and the average yield strength is 456MPa, the coefficient of variation.

[0084] The three embodiments and three comparative examples were sampled at different positions for mechanical property testing, and the coefficient of variation of the mechanical properties of the profiles was calculated. Comparative Example 1 is produced with 99.7% aluminum ingots compared to Example 1, and the Fe and Si contents are relatively high, and the Zn / Mg content is also out of the control range. Figure 5 and Figure 6 As shown, the profile produced in Comparative Example 1 has higher Fe and Si contents, so the number and size of the coarse crystalline phase in the longitudinal section are much higher than those in Example 1, affecting the consistency of the mechanical properties of Comparative Example 1, and the statistical coefficient of variation is higher than 3%. Compared with Example 2, Comparative Example 2 does not use an isothermal extrusion process, which will cause the temperature of the tail end of the profile to be higher than that of the head end during the extrusion process, and the mechanical properties of the tail end of the profile are higher than those of the head end of the profile, affecting the performance consistency of the profile, and the statistical coefficient of variation is higher than 3%. The comparison results of the average strength of the head and tail ends of the profile are shown in Figure 7Comparative Example 3 Compared with Example 3, no special aging process was formulated according to the thickness of the profile. Instead, all profiles of different thicknesses were subjected to an aging time of 1410 min, resulting in a longer actual insulation time for profiles with thicker thicknesses, and lower profile strength, which affected the performance consistency of the profiles. The statistical coefficient of variation was higher than 3%, and the comparison results of the average strength of different sections were shown in Figure 8 .

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for manufacturing a 7 series aluminum alloy profile for civil aircraft to improve its performance consistency, characterized by: This is achieved through the following technical solutions: Step 1: Taking full account of factors such as alloy element burnout during alloy smelting and alloy content in waste materials, the ingredients are prepared according to the following alloy composition control requirements: Si content is less than 0.10%, Fe content is less than 0.15%, Zn content is 5.6%~6.0%, Cu content is 1.6%~1.8%, Mg content is 2.5%~2.7%, Mn content is less than 0.1%, Cr content is 0.23%~0.28%, Ti content is 0.02%~0.06%, and the content of other impurity elements is less than 0.05%, the balance is Al, and Zn / Mg is controlled between 2.2~2.

3. Among them, the added aluminum ingots are customized aluminum ingots with a purity of 99.85%; Step 2: Put fully dried scrap and aluminum ingots into the smelting furnace. After the aluminum ingots are completely melted, turn on the electromagnetic stirring equipment for stirring. After the melt temperature reaches 740°C, alloying begins. Add copper plates, magnesium ingots and various intermediate alloys in batches. The interval between adding each batch of alloys is 20 minutes, and the weight added each time does not exceed 500 kg. Step 3: After all raw materials are completely melted, the melt is transferred from the smelting furnace to the static furnace. The temperature of the static furnace melt is controlled at 725~745℃. A rotary ventilation device is used to introduce a mixed gas of argon and chlorine for refining. During the refining process, the slag floating out of the melt is cleaned in time. The chemical composition analysis is carried out by sampling at a fixed position. If the test result is unqualified, the alloy composition of the charge is adjusted to meet the requirements. Step 4: Raise the temperature of the degassing box to 740℃, adjust the temperature of the melt in the standing furnace to 730℃, and use flames to fully preheat the filter plate and the entire set of flow channels. After all the preparations are completed, tilt the standing furnace to start casting. The melt flows through the two-stage degassing box and the filter box and then enters the casting flow plate. In the flow channel between the two-stage degassing boxes, use the wire feeder to add Al-Ti-B refiner. During the casting process, the temperature of the two-stage double-rotor degassing box is always controlled at 735~745℃ to supplement the heat loss of the melt in the flow channel. After the melt on the casting flow plate reaches 693℃, stop the standing furnace heating and slowly reduce the melt temperature in the furnace. When the casting machine flow plate temperature is lower than 687℃, start the standing furnace heating to increase the melt temperature. By controlling the standing furnace melt temperature, the melt temperature on the casting machine flow plate is controlled between 685℃~695℃; Step 5: immediately send the ingot cast by the casting machine into a homogenizing furnace for homogenization treatment; Step 6: Before extrusion, the extrusion die, extrusion barrel and ingot are heated, the die temperature is set to 385~415℃, the extrusion barrel temperature is set to 360~400℃, the head end temperature of the ingot is set to 340~380℃, the temperature of the ingot from the head end to the tail end shows a gradient downward trend, and the temperature gradient downward trend is 20℃ / m. The ingot is loaded into the extrusion barrel with the tail end inside and the head end outside. The extrusion die is loaded into the extrusion barrel close to the head end of the ingot, and the hollow shaft is slowly inserted for reverse extrusion. The extrusion shaft speed of the reverse extrusion is 0.3~0.6 mm / s. After the extrusion is completed, pre-stretching and straightening with a deformation of 0.3%~1.2% is performed to obtain the initial aluminum alloy profile; Step 7: Use offline heat treatment process to carry out solid solution treatment on the primary aluminum alloy profile. The solid solution treatment temperature is 471℃ and the holding time of solid solution treatment is 360min to ensure sufficient solid solution. After the holding is completed, spray step quenching is carried out and the quenched profile is immediately stretched and straightened with the tensile deformation controlled at 1%~3% to eliminate the quenching residual stress. Step 8: Use an aging furnace to artificially age the profile at an aging temperature of 120°C. Calculate the average thickness of the profile at different positions. For profiles with a thickness of 15-30mm, the aging time is 1440min; for profiles with a thickness of 30-45mm, the aging time is 1410 min; for profiles with a thickness of 45-60mm, the aging time is 1380 min; for profiles with a thickness of 60-75mm, the aging time is 1350 min.

2. A method for manufacturing a profile for improving the performance consistency of a 7 series aluminum alloy profile for civil aircraft according to claim 1, characterized in that: The step 5 homogenization process is: the temperature is raised to 460°C at a heating rate of 40°C / h, kept warm for 8 hours, and then the temperature is raised to 475°C at a heating rate of 40°C / h, kept warm for 24 hours. The homogenized ingot is the raw material for profile extrusion.

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