Heat treatment process for high-strength aluminum alloy

Abstract

The invention provides a high-strength aluminum alloy heat treatment process which comprises the following steps: firstly, performing two-stage homogenization treatment: firstly, heating an aluminum bar to 400-420 DEG C, preserving heat for 4-10 hours, then transferring to 420-480 DEG C, and preserving heat for 10-20 hours; then, the aluminum bar is subjected to solution treatment, specifically, the aluminum bar is subjected to heat preservation for 1-4 h at the temperature of 360-420 DEG C; then, in the extrusion process, an extrusion die is preheated, the temperature is kept at 360-380 DEG C, the extrusion speed is 2-5 m / min, and the temperature of an extrusion outlet is 380-420 DEG C; then, on-line solution treatment and on-line quenching are conducted, specifically, after extrusion forming is conducted, the formed material is heated to 450-480 DEG C on line, heat preservation is conducted for 0.5-4 h, and then on-line water spraying quenching is conducted immediately to the room temperature; then, multi-stage aging is conducted, specifically, in the first-stage aging, heat preservation is conducted for 12-18 h at the temperature of 110-130 DEG In the second-stage aging, the temperature of-80 DEG C to-180 DEG C is kept for 2 And in the third-stage aging, the temperature of 160-220 DEG C is kept for 6- By means of the high-strength aluminum alloy heat treatment process, the alloy structure homogenization of the forming material can be effectively improved, and the strength, hardness and elongation of the forming material are improved.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy production, and in particular provides a high-strength aluminum alloy heat treatment process. Background Art

[0002] As a super-hard aluminum alloy material that can be strengthened by heat treatment, high-strength aluminum alloy has high specific strength and hardness, good corrosion resistance, high toughness and excellent processing performance. It has been widely used in aerospace industry, extrusion die processing, mechanical equipment and other fields. However, during the extrusion process, ultra-high-strength aluminum alloy has large deformation resistance and poor extrusion performance. When the extrusion speed is too high, the surface is prone to cracking. When the extrusion speed is too low, the solid solution temperature of the material cannot meet the requirements, which ultimately leads to insufficient strength of the obtained aluminum alloy. At present, when producing ultra-high-strength aluminum alloys in China, hot extrusion forming is mostly adopted. After cutting, it is offline quenched in a vertical quenching furnace and then artificially aged. This process has many process steps and low production efficiency. In addition, the equipment investment is large and the production cost is high. Only small-sized products can be prepared, and the production efficiency is low; the product quality stability is poor; it is not environmentally friendly. The existing technical problems include: (1) High-strength aluminum alloy has poor extrusion performance. When the extrusion speed is too high, the surface is prone to cracking. When the extrusion speed is too low, the solid solution temperature of the material cannot meet the requirements, which will make the aluminum alloy insufficient in strength. Appropriate processes are required to obtain high-quality and high-strength alloys. (2) Ultra-high strength aluminum alloy extrusion products often have the problem of uneven alloy structure and properties, resulting in low comprehensive performance of the finished alloy; (3) Currently, the production of ultra-high strength aluminum alloys mostly adopts offline quenching, which has a relatively high production cost. Summary of the invention

[0003] Based on this, the present invention provides a high-strength aluminum alloy heat treatment process to improve the alloy structure homogenization of the molding material and enhance the strength, hardness and elongation of the molding material.

[0004] In order to achieve the above object, the present invention provides a high-strength aluminum alloy heat treatment process, comprising: S100. Two-stage homogenization treatment: firstly heat the aluminum bar to 400-420℃ and keep it for 4-10h, then transfer it to 420-480℃ and keep it for 10-20h; S200. Aluminum bar solid solution treatment: Aluminum bar is kept at 360-420℃ for 1-4h; S300. Extrusion process: preheat the extrusion die and maintain it at 360-380°C, the extrusion speed is 2-5m / min, and the extrusion outlet temperature is 380-420°C; S400. Online solution treatment and online quenching: After extrusion molding, the molding material is heated online to 450℃~480℃, kept warm for 0.5~4h, and then immediately sprayed with water to quench to room temperature online; S500. Multi-stage aging: The first stage is 110-130℃ for 12-18h; the second stage is -80--180℃ for 2-10h; the third stage is 160-220℃ for 6-24h.

[0005] Furthermore, the aluminum bar is first placed in a 400-420℃ high temperature furnace for 4-10 hours of heat preservation for the first stage of homogenization treatment; after the first stage of homogenization treatment, it is quickly moved to a 420-480℃ high temperature furnace for 10-20 hours of second stage of homogenization treatment. The bipolar homogenization process is added before the solid solution to eliminate microsegregation and increase the uniformity of the alloy structure.

[0006] Furthermore, after the bipolar homogenization treatment is completed, the aluminum bar is quickly transferred and solution treated at 360-380°C for 1h-4h.

[0007] Furthermore, before the extrusion process, the extrusion die is preheated in advance, and the extrusion die is heated to 360-380°C and maintained. After the aluminum bar material is solution treated, the extrusion process is quickly carried out, the extrusion speed is controlled at 2-5m / min, the overall extrusion speed is kept uniform, and the extrusion outlet temperature is 380-420°C.

[0008] Furthermore, during the online solution treatment and online quenching process, an induction furnace is used to heat the molding material online to 450°C to 480°C, keep it warm for 0.5 to 4 hours for solution treatment, and then quench it online to room temperature. An induction device is set at the extrusion outlet to control the induction furnace to perform solution treatment on the molding material, and after the solution treatment, the online water spray mechanism is controlled to quickly quench the molding material to room temperature. A temperature sensing device is set at the extrusion outlet, and after the extrusion is completed, it is directly transferred to a high-temperature furnace for re-solution treatment to achieve the purpose of improving the performance of the alloy.

[0009] Furthermore, the molded material cooled to room temperature is placed in an aging furnace at a temperature of 110 to 130°C for a first-stage aging treatment of 12 to 18 hours; after the first-stage aging treatment is completed, the molded material is quickly water-cooled to room temperature, and then placed in a coolant for a second-stage aging treatment of 2 to 10 hours, and the coolant temperature is -80 to -180°C; after the second-stage aging is completed, the molded material is further placed in an aging furnace at a temperature of 160 to 220°C for a third-stage aging treatment of 6 to 24 hours. Liquid gas is usually used to cool the material, and the heat is kept in a deep cold environment for a period of time. Combined with the combination of lower temperature and higher temperature aging treatment, the comprehensive properties of the alloy can be better improved.

[0010] Furthermore, after the multi-stage aging treatment, the molded material is cooled to room temperature by strong wind.

[0011] Compared with the prior art, the present invention has the following advantages and effects: 1. A double-stage homogenization treatment was carried out before the solution treatment. At a higher temperature, the alloy was given enough time to fully dissolve and fuse the elements, eliminating microsegregation and laying the foundation for subsequent heat treatment; 2. Preheat and maintain a reasonable extrusion die temperature and a reasonable extrusion speed to reduce deformation during the entire extrusion process and ensure the quality and strength of the extruded material. A temperature sensing device is set at the extrusion outlet to measure the material temperature, and then the material is directly placed in the furnace for further solution treatment to improve the alloy performance. After the solution treatment, water cooling is immediately performed, and the online quenching mode is adopted to further reduce costs. 3. The three-stage aging technology of low temperature, ultra-low temperature and high temperature has greatly improved the strength, hardness and elongation of the alloy. Ultra-low temperature aging is a revolutionary technology, which usually uses liquid gas to cool the material and keep it warm in a deep cold environment for a period of time. Combined with the low temperature and high temperature aging treatment, the comprehensive performance of the alloy can be better improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings, which constitute a part of the specification, describe embodiments of the present disclosure and, together with the specification, are used to explain the principles of the present disclosure. With reference to the accompanying drawings, the present disclosure can be more clearly understood according to the following detailed description, in which: Figure 1 It is a process flow chart of a high-strength aluminum alloy heat treatment process provided; Figure 2 It is a process flow chart of a high-strength aluminum alloy heat treatment process embodiment 1 provided; Figure 3 is a process flow chart of a high-strength aluminum alloy heat treatment process embodiment 2 provided; Figure 4 is a process flow chart of a high-strength aluminum alloy heat treatment process embodiment 3 provided; Figure 5 This is a process flow chart of heat treatment of high-strength aluminum alloy in Comparative Example 1; Figure 6 This is a process flow chart of the high-strength aluminum alloy heat treatment process of Example 2. DETAILED DESCRIPTION

[0013] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. The description of the exemplary embodiments is merely illustrative and is in no way intended to limit the present disclosure and its application or use. The present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to make the present disclosure thorough and complete and to fully express the scope of the present disclosure to those skilled in the art. It should be noted that unless otherwise specifically stated, the relative arrangement of the components and steps, the composition of the materials, the numerical expressions and the numerical values ​​set forth in these embodiments should be interpreted as being merely exemplary and not as limiting.

[0014] In view of the current development of high-strength aluminum alloys, the present invention creates a new heat treatment process to solve various problems in alloy production. The appropriate heat treatment process is selected while reducing the cost as much as possible to obtain an ultra-high-strength aluminum alloy with high comprehensive performance.

[0015] like Figure 1 As shown, the present invention provides a high-strength aluminum alloy heat treatment process, comprising the steps of: S100. Double-stage homogenization treatment: First, heat the aluminum bar to 400-420℃ and keep it for 4-10h, then transfer it to 420-480℃ and keep it for 10-20h; during the implementation process, first put the aluminum bar into a 400-420℃ high-temperature furnace for 4-10h first-stage homogenization treatment; after the first-stage homogenization treatment, quickly move it to a 420-480℃ high-temperature furnace for 10-20h second-stage homogenization treatment. Double-stage homogenization treatment is carried out before solution treatment. At a higher temperature, the alloy is given enough time to fully dissolve and fuse the elements, eliminating microsegregation and laying the foundation for subsequent heat treatment.

[0016] S200. Solution treatment of aluminum bars: The aluminum bars are kept at 360-420°C for 1-4 hours. In some implementations, the aluminum bars are quickly transferred after the bipolar homogenization treatment is completed and solution treated at 360-380°C for 1h-4h.

[0017] S300. Extrusion process: preheat the extrusion die and maintain it at 360-380℃, the extrusion speed is 2-5m / min, and the extrusion outlet temperature is 380-420℃; in the implementation process, the extrusion die is preheated in advance before the extrusion process, and the extrusion die is heated to 360-380℃ and maintained. By preheating and maintaining a reasonable extrusion die temperature and maintaining a reasonable extrusion speed, the deformation of the entire extrusion process is reduced to ensure the quality and strength of the extruded material.

[0018] After the aluminum bar material completes the solid solution treatment, the extrusion treatment is carried out quickly. The extrusion speed is controlled at 2-5m / min. The overall extrusion speed is kept uniform. The extrusion outlet temperature is 380-420℃.

[0019] S400. Online solution treatment and online quenching: After extrusion molding, the molding material is heated online to 450℃~480℃, kept warm for 0.5~4h, and then immediately quenched online to room temperature by spraying water; during the implementation process, during the online solution treatment and online quenching process, an induction furnace is used to heat the molding material online to 450℃~480℃, kept warm for 0.5~4h for solution treatment, and then quenched online to room temperature.

[0020] An induction device is set at the extrusion outlet to control the induction furnace to perform solution treatment on the molding material, and after the solution treatment, the online water spray mechanism is controlled to quickly quench the molding material to room temperature. The temperature sensing device is set at the extrusion outlet to measure the material temperature, and then directly put it into the furnace for further solution treatment to improve the alloy performance. After the solution treatment, water cooling is immediately performed, and the online quenching mode is adopted to further reduce costs.

[0021] S500. Multi-stage aging: The first stage aging is 110-130℃ for 12-18h; the second stage aging is -80--180℃ for 2-10h; the third stage aging is 160-220℃ for 6-24h. During the implementation process, the molding material cooled to room temperature is placed in an aging furnace at a temperature of 110-130℃ for 12-18h of first stage aging treatment; after the first stage aging treatment is completed, the molding material is quickly water-cooled to room temperature, and then placed in a coolant for 2-10h of second stage aging treatment, and the coolant temperature is -80--180℃; after the second stage aging is completed, the molding material is continued to be placed in an aging furnace at a temperature of 160-220℃ for 6-24h of third stage aging treatment. After the multi-stage aging treatment, the molding material is cooled to room temperature by strong wind.

[0022] The three-stage aging technology of low temperature, ultra-low temperature and high temperature has greatly improved the strength, hardness and elongation of the alloy. Ultra-low temperature aging is a revolutionary technology, which usually uses liquid gas to cool the material and keep it warm in a deep cold environment for a period of time. Combined with the low temperature and high temperature aging treatment, the comprehensive performance of the alloy can be better improved.

[0023] Based on the above embodiments, the present invention provides a high-strength aluminum alloy heat treatment process to improve the alloy structure homogenization of the molding material, enhance the strength, hardness and elongation of the molding material, is suitable for the preparation of large-size products, improves production efficiency and product quality stability, and can achieve environmentally friendly and efficient production.

[0024] In the following embodiments, a 7075 aluminum alloy plate is used, the main components of the alloy are Al-5.8Zn-2.7Mg-1.8Cu-0.27Cr, the width is 200mm, the thickness is 10mm, and the length is 600mm: Example 1 like Figure 2 As shown, Example 1 of a high-strength aluminum alloy heat treatment process provided by the present invention includes the following steps: S110. Two-stage homogenization treatment of aluminum alloy ingots. First stage: holding temperature 400℃, holding time 6h, second stage: holding temperature 460℃, holding time 12h.

[0025] S210. After homogenization, the aluminum rod is quickly heated at a holding temperature of 400°C for 2 hours.

[0026] S310. Preheat the extrusion die to 360°C, and quickly extrude after completing the solution treatment. Keep the temperature unchanged during the extrusion process, keep the extrusion rate at 4m / min, and the extrusion outlet temperature at 390°C.

[0027] S410. After extrusion, directly enter the furnace for solution heating treatment again. The solution temperature is 450℃ and the time is 1h. After the solution is completed, immediately cool to room temperature with water.

[0028] S510. Multi-stage aging treatment. First stage: insulation temperature 120℃, insulation time 12h. Second stage: insulation temperature -170℃, insulation time 6h. Third stage: insulation temperature 160℃, insulation time 14h.

[0029] Example 2 like Figure 3 As shown, Example 2 of a high-strength aluminum alloy heat treatment process provided by the present invention includes the following steps: S120. Two-stage homogenization treatment of aluminum alloy ingots. First stage: holding temperature 400℃, holding time 6h, second stage: holding temperature 460℃, holding time 12h.

[0030] S220. After homogenization, the aluminum rod is quickly heated at a holding temperature of 400°C for 2 hours.

[0031] S320. Preheat the extrusion die to 360°C, and quickly extrude after completing the solution treatment. Keep the temperature unchanged during the extrusion process, the extrusion rate is maintained at 4m / min, and the extrusion outlet temperature is 390°C.

[0032] S420. After extrusion, directly enter the furnace for solution heating treatment again. The solution temperature is 470℃ and the time is 1h. After the solution is completed, immediately cool to room temperature with water.

[0033] S520. Multi-stage aging treatment. First stage: insulation temperature 120℃, insulation time 12h. Second stage: insulation temperature -170℃, insulation time 6h. Third stage: insulation temperature 160℃, insulation time 14h.

[0034] Example 3 like Figure 4 As shown, Example 3 of a high-strength aluminum alloy heat treatment process provided by the present invention includes the following steps: S130. Two-stage homogenization treatment of aluminum alloy ingots. First stage: holding temperature 400℃, holding time 6h, second stage: holding temperature 460℃, holding time 12h.

[0035] S230. After homogenization, the aluminum rod is quickly heated at a holding temperature of 400°C for 2 hours.

[0036] S330. Preheat the extrusion die to 360°C, and quickly extrude after completing the solution treatment. Keep the temperature unchanged during the extrusion process, the extrusion rate is maintained at 4m / min, and the extrusion outlet temperature is 390°C.

[0037] S430. After extrusion, directly enter the furnace for solution heating treatment again. The solution temperature is 480℃ and the time is 1h. After the solution is completed, immediately cool to room temperature with water.

[0038] S530. Multi-stage aging treatment. First stage: insulation temperature 120℃, insulation time 12h. Second stage: insulation temperature -170℃, insulation time 6h. Third stage: insulation temperature 160℃, insulation time 14h.

[0039] Based on the provided process, a bipolar homogenization process is added before solution to eliminate microsegregation and increase the uniformity of the aluminum bar alloy structure. Select a suitable solution temperature and preheat the extrusion die at the same time to ensure that the temperature remains unchanged during the entire extrusion process. During the extrusion process, a reasonable extrusion rate is selected and the extrusion rate is kept constant to reduce the occurrence of extrusion deformation. A temperature sensing device is set at the extrusion outlet, and after the extrusion is completed, it is directly transferred to a high-temperature furnace for re-solidification to achieve the purpose of improving the performance of the alloy. After solution, water cooling is used to quickly cool to room temperature. The present invention adopts a three-stage aging method to perform insulation treatment on the alloy in three aging stages of lower temperature, ultra-low temperature and higher temperature, respectively, to reduce the formation of precipitation phases, increase the uniformity of microstructure, and improve the performance of the alloy.

[0040] Comparative Example 1 like Figure 5 As shown, the high-strength aluminum alloy heat treatment process of Comparative Example 1 includes the following steps: S180. Two-stage homogenization treatment of aluminum alloy ingots. First stage: holding temperature 400℃, holding time 6h, second stage: holding temperature 460℃, holding time 12h.

[0041] S280. After homogenization, the aluminum rod is quickly heated at a holding temperature of 420°C for 2 hours.

[0042] S380. Preheat the extrusion die to 360°C, and quickly extrude after completing the solution treatment. Keep the temperature unchanged during the extrusion process, the extrusion rate is maintained at 4m / min, and the extrusion outlet temperature is 410°C.

[0043] S480. Multi-stage aging treatment. First stage: insulation temperature 120℃, insulation time 12h. Second stage: insulation temperature -170℃, insulation time 6h. Third stage: insulation temperature 160℃, insulation time 14h.

[0044] Comparative Example 2 like Figure 6 As shown, the high-strength aluminum alloy heat treatment process of Comparative Example 2 includes the following steps: S190. Two-stage homogenization treatment of aluminum alloy ingots. First stage: holding temperature 400℃, holding time 6h, second stage: holding temperature 460℃, holding time 12h.

[0045] S290. After homogenization, the aluminum rod is quickly heated at a holding temperature of 400°C for 2 hours.

[0046] S390. Preheat the extrusion die to 360°C, and quickly extrude after completing the solution treatment. Keep the temperature unchanged during the extrusion process, the extrusion rate is maintained at 4m / min, and the extrusion outlet temperature is 390°C.

[0047] S490. After extrusion, the steel is directly put into the furnace for solution heating treatment again, with the solution temperature of 470℃ and the time of 1h. After the solution treatment, it is immediately cooled to room temperature.

[0048] S590. Single-stage aging treatment. Holding temperature 120℃, holding time 24h.

[0049] Table 1 Performance results of aluminum alloy materials produced by the provided process and comparative examples

[0050] It should be noted that the above-mentioned mechanical properties testing standard adopts "GB / T 228 Room Temperature Tensile Test Method for Metal Materials".

[0051] It can be seen from the test results in Table 1 that the high-strength aluminum alloy extrusion molding process provided by the present invention has significantly improved strength, hardness and elongation compared with conventional aluminum alloy plates. Specifically, in terms of tensile strength, the tensile strength of the aluminum alloy produced by the process of the present invention is 577-598MPa, and the tensile strength of the aluminum alloy produced by the comparative process is 452-546MPa. Compared with the comparative process, the tensile strength of the aluminum alloy produced by the present invention is significantly enhanced and more stable; the yield strength of the aluminum alloy produced by the process of the present invention is 537-548MPa, and the yield strength of the aluminum alloy produced by the comparative process is 407-492MPa. Compared with the comparative example, the yield strength of the aluminum alloy produced by the process of the present invention is significantly enhanced and stable. Moreover, the elongation of the aluminum alloy produced by the process of the present invention is 12-15%, while the elongation of the aluminum alloy produced by the comparative process is 9-10%. In terms of hardness, the hardness of the aluminum alloy produced by the process of the present invention is 171-178, and the hardness of the aluminum alloy produced by the comparative process is 125-156HV.

[0052] From the above comparative experiments, it can be seen that the new heat treatment process ensures high tensile strength, high yield strength and high hardness while also having good elongation, and the quality is more stable and reliable. Therefore, the high-strength aluminum alloy heat treatment process provided is suitable for the preparation of large-size products, improves production efficiency and product quality stability, and can achieve environmentally friendly and efficient production.

[0053] Although some specific embodiments of the present disclosure have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration and are not intended to limit the scope of the present disclosure. Those skilled in the art should understand that the above embodiments may be modified or some technical features may be replaced by equivalents without departing from the scope and spirit of the present disclosure.

Claims

1. A high-strength aluminum alloy heat treatment process, characterized in that: include: S100. Two-stage homogenization treatment: firstly heat the aluminum bar to 400-420℃ and keep it at this temperature for 4-10h, then transfer it to 420-480℃ and keep it at this temperature for 10-20h; S200. Aluminum bar solid solution treatment: Aluminum bar is kept at 360-420℃ for 1-4h; S300. Extrusion process: preheat the extrusion die and maintain it at 360-380°C, the extrusion speed is 2-5m / min, and the extrusion outlet temperature is 380-420°C; S400. Online solution treatment and online quenching: After extrusion molding, the molding material is heated online to 450℃~480℃, kept warm for 0.5~4h, and then immediately sprayed with water to quench to room temperature online; S500. Multi-stage aging: The first stage is 110-130℃ for 12-18h; the second stage is -80--180℃ for 2-10h; the third stage is 160-220℃ for 6-24h.

2. The high-strength aluminum alloy heat treatment process according to claim 1, characterized in that: First, the aluminum bar material is placed in a 400-420°C high-temperature furnace for a first-stage homogenization treatment of 4-10 hours of insulation; after the first-stage homogenization treatment, it is quickly moved to a 420-480°C high-temperature furnace for a second-stage homogenization treatment of 10-20 hours.

3. The high-strength aluminum alloy heat treatment process according to claim 1 or 2, characterized in that: After the bipolar homogenization treatment is completed, the aluminum bar is quickly transferred and solution treated at 360-380°C for 1h-4h.

4. The high-strength aluminum alloy heat treatment process according to claim 1, characterized in that: Before the extrusion process is carried out, the extrusion die is preheated in advance, and the extrusion die is heated to 360-380°C and maintained.

5. The high-strength aluminum alloy heat treatment process according to claim 4, characterized in that: After the aluminum bar material completes the solid solution treatment, the extrusion treatment is carried out quickly. The extrusion speed is controlled at 2-5m / min. The overall extrusion speed is kept uniform. The extrusion outlet temperature is 380-420℃.

6. The high-strength aluminum alloy heat treatment process according to claim 1, characterized in that: During the online solution treatment and online quenching process, the molding material is heated online to 450°C ~ 480°C using an induction furnace, kept warm for 0.5 ~ 4h for solution treatment, and then quenched online to room temperature.

7. The high-strength aluminum alloy heat treatment process according to claim 6, characterized in that: An induction device is arranged at the extrusion outlet to control the induction furnace to perform a solution treatment on the molding material, and after the solution treatment, the online water spraying mechanism is controlled to quickly quench the molding material to room temperature.

8. The high-strength aluminum alloy heat treatment process according to claim 1, characterized in that: The molding material cooled to room temperature is placed in an aging furnace at a temperature of 110-130°C for a first-stage aging treatment of 12-18 hours; then placed in a coolant for a second-stage aging treatment of 2-10 hours, and the coolant temperature is -80--180°C; after the second-stage aging is completed, the molding material is further placed in an aging furnace at a temperature of 160-220°C for a third-stage aging treatment of 6-24 hours.

9. The high-strength aluminum alloy heat treatment process according to claim 8, characterized in that: After the first stage aging treatment is completed, the molded material is quickly water-cooled to room temperature and then subjected to the second stage aging treatment.

10. The high-strength aluminum alloy heat treatment process according to claim 1, characterized in that: After multi-stage aging treatment, the molded material is cooled to room temperature by strong wind.

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