Heating method and hot working method of 7xxx aluminum alloy

Abstract

The invention provides a 7xxx aluminum alloy heating method which comprises the following steps: (S1) a 7xxx aluminum alloy ingot is subjected to induction heating to 350-430 DEG C, and the induction heating power is 1100-1200 kW; (S2) ultrasonic vibration is started for the aluminum alloy cast ingot obtained in the step (S1), heat preservation is conducted after induction heating is conducted to 450-480 DEG C, the power of induction heating is 450-800 kW, and the frequency of ultrasonic vibration is 10-15 kHz; and (S3) the ultrasonic vibration frequency of the aluminum alloy cast ingot obtained in the step (S2) is adjusted to be 25-30 kHz, the vibration frequency is kept for 0.5-2 h, and the heat preservation time is 0.5-2 h. The invention further provides a hot working method of the 7xxx aluminum alloy. According to the heating method, the heating efficiency can be improved while the heating uniformity of the aluminum alloy is guaranteed, and the mechanical property is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and particularly relates to a heating method and a hot working method for 7xxx aluminum alloys. Background Art

[0002] Heating is one of the important links in hot working such as forging and extrusion of aluminum alloys. Existing conventional methods mainly include induction furnace heating, gas furnace heating, and resistance furnace heating. Among them, induction heating has high efficiency, and the heating time is usually 10 - 30 minutes, but the heating uniformity is poor. Gas furnace and resistance furnace heating have good uniformity, but low efficiency and high energy consumption, usually requiring 10 - 30 hours.

[0003] The alloying element content of 7xxx series aluminum alloys is high and it is easy to contain coarse phases. If the heating is insufficient, it will lead to problems such as easy cracking and uneven properties during subsequent deformation. Therefore, currently, the resistance furnace heating method is generally adopted, but this heating method will cause the cost of 7xxx series aluminum alloys to be higher than that of other series of aluminum alloys.

[0004] In order to improve the heating rate and reduce the cost of 7xxx series aluminum alloys, technicians in the industry have adopted induction heating in the heating process of some aluminum alloys with relatively low alloy content and subsequent extrusion forming processing technology through parameter optimization. However, this method is not universal and has a narrow application range. Therefore, it is necessary to develop a new heating method to improve the heating efficiency of 7xxx series aluminum alloys. Summary of the Invention

[0005] The technical problem solved by the present invention is to provide a heating method for 7xxx aluminum alloys, which can achieve heating uniformity, improve mechanical properties, and improve heating efficiency.

[0006] In view of this, the present application provides a heating method for 7xxx aluminum alloys, including the following steps:

[0007] (S1) Induction heat the 7xxx aluminum alloy ingot to 350 - 430 °C, and the power of the induction heating is 1100 - 1200 kW;

[0008] (S2) Start ultrasonic vibration for the aluminum alloy ingot obtained in step (S1), and keep the induction heating until 450 - 480 °C and then hold for heat preservation. The power of the induction heating is 450 - 800 kW, and the frequency of the ultrasonic vibration is 10 - 15 kHz;

[0009] (S3) Adjust the ultrasonic vibration frequency of the aluminum alloy ingot obtained in step (S2) to 25 - 30 kHz, and keep this vibration frequency for 0.5 - 2 hours. The heat preservation time is 0.5 - 2 hours.

[0010] In some specific embodiments, the heating method is carried out in an induction-ultrasonic composite heating device. An electromagnetic induction heating layer is provided at the end of the induction-ultrasonic composite heating device close to the aluminum alloy ingot, and an ultrasonic generator is provided at the end far from the aluminum alloy ingot.

[0011] In some specific embodiments, in step (S1), the induction heating is carried out to 400 - 430 °C.

[0012] In some specific embodiments, in step (S2), the temperature of the induction heating is 460 - 470 °C, and the power of the induction heating is 500 - 750 kW.

[0013] In some specific embodiments, in step (S2), the frequency of the ultrasonic vibration is 12 - 14 kHz.

[0014] In some specific embodiments, in step (S3), the frequency of the ultrasonic vibration is 27 - 29 kHz.

[0015] In some specific embodiments, in step (S3), the vibration frequency is maintained for 1 - 1.5 h, and the heat preservation time is 1 - 1.5 h.

[0016] In some specific embodiments, the 7xxx aluminum alloy includes 7055 aluminum alloy, 7050 aluminum alloy, 7075 aluminum alloy, 7085 aluminum alloy, 7A09 aluminum alloy or 7A04 aluminum alloy.

[0017] This application also provides a hot working method for 7xxx aluminum alloy, including the following steps:

[0018] (S1) Heating the 7xxx aluminum alloy ingot; the heating is the heating method described in the above solution;

[0019] (S2) Processing the heated 7xxx aluminum alloy ingot;

[0020] (S3) Heat-treating the processed aluminum alloy material.

[0021] In some specific embodiments, the processing method includes one or both of forging and extrusion, and the heat treatment includes one or both of solution quenching and aging.

[0022] The present application provides a method for heating a 7xxx aluminum alloy, which firstly heats a 7xxx aluminum alloy ingot to 350-430°C by rapid induction heating at a high power of 1100-1200kW, performs low-frequency ultrasonic vibration at 10-15kHz when the ingot temperature reaches 350-430°C, and adjusts the induction heating power to 450-800kW to heat to 450-480°C before entering a heat preservation stage, adjusts the ultrasonic vibration frequency to 25-30kHz, and maintains and preserves the temperature at this vibration frequency for 0.5-2h, thereby completing the heating of the 7xxx aluminum alloy; the method for heating a 7xxx aluminum alloy provided in the present application is based on induction heating, combines low-temperature rapid heating with high-temperature slow heating, reduces the non-uniformity of induction heating, and introduces ultrasonic vibration assistance, adopts a low-frequency heating stage and a high-frequency heat preservation stage, which is beneficial to promote the rapid dissolution of the crystalline phase and promotes heat diffusion, thereby facilitating the uniformity of heating the 7xxx aluminum alloy, improving the mechanical properties of the aluminum alloy, and effectively improving the heating efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the structure of the induction-ultrasound composite heating device provided by the present invention;

[0024] Figure 2 This is a SEM photo of the 7055 aluminum alloy prepared in Example 1 of the present invention;

[0025] Figure 3 This is a SEM photograph of the 7055 aluminum alloy prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0026] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0027] In view of the problem that the heating uniformity and heating efficiency of 7xxx aluminum alloy cannot be taken into account at the same time in the prior art, the present application provides a heating method for 7xxx aluminum alloy, which adopts a heating method of rapid induction heating-low-frequency ultrasonic vibration heating-slow induction heating-high-frequency ultrasonic vibration insulation, promotes heat diffusion, thereby ensuring the uniformity of heating, and promotes the dissolution of the crystalline phase, and finally ensures the mechanical properties of the aluminum alloy and improves the heating efficiency; specifically, the embodiment of the present invention discloses a heating method for 7xxx aluminum alloy, comprising the following steps:

[0028] (S1) induction heating a 7xxx aluminum alloy ingot to 350-430° C., wherein the induction heating power is 1100-1200 kW;

[0029] (S2) Start ultrasonic vibration of the aluminum alloy ingot obtained in step (S1), and keep it warm after induction heating to 450 - 480 °C. The power of the induction heating is 450 - 800 kW, and the frequency of the ultrasonic vibration is 10 - 15 kHz;

[0030] (S3) Adjust the ultrasonic vibration frequency of the aluminum alloy ingot obtained in step (S2) to 25 - 30 kHz, and maintain this vibration frequency for 0.5 - 2 h. The holding time is 0.5 - 2 h.

[0031] In the heating method provided by this application, first perform induction heating on the 7xxx aluminum alloy ingot. The power of the induction heating is 1100 - 1200 kW; in some specific embodiments, the power of the induction heating is 1150 kW, 1200 kW. Induction heat to 350 - 430 °C at the above power. Specifically, induction heat to 355 - 425 °C, and more specifically, induction heat to 360 - 410 °C; in some specific embodiments, induction heat to 365 °C, 368 °C, 370 °C, 373 °C, 378 °C, 380 °C, 386 °C, 389 °C, 390 °C, 397 °C, 400 °C, 405 °C, 412 °C, 415 °C, 418 °C, 420 °C, 426 °C.

[0032] When the temperature of the aluminum alloy ingot reaches 400 - 430 °C, start ultrasonic vibration with a vibration frequency of 10 - 15 kHz, and at the same time adjust the power of the induction heating to 450 - 800 kW. Continue to heat the aluminum alloy ingot with the above induction heating power and ultrasonic vibration frequency; the above vibration frequency is specifically 10 kHz, 11 kHz, 12 kHz, 13 kHz, 14 kHz, 15 kHz; specifically, the power of the induction heating is 500 - 750 kW, and more specifically, the power of the induction heating is 580 - 720 kW, and even more specifically, the power of the induction heating is 600 - 700 kW; in specific embodiments, the power of the induction heating is 510 kW, 530 kW, 550 kW, 560 kW, 590 kW, 610 kW, 620 kW, 640 kW, 650 kW, 670 kW, 690 kW, 710 kW, 730 kW, 740 kW.

[0033] After the temperature of the aluminum alloy ingot reaches 450 - 480 °C, heat preservation is carried out, and the ultrasonic vibration frequency is adjusted to 25 - 30 kHz. Under this ultrasonic vibration frequency, heat preservation is carried out for 0.5 - 2 h. In the above process, specifically, the temperature for heat preservation is 450 - 470 °C, and specifically, the temperature for heat preservation is 452 - 465 °C; in specific embodiments, the temperature for heat preservation is 455 °C, 458 °C, 459 °C, 460 °C, 463 °C, 466 °C, 468 °C. In some specific embodiments, the vibration frequency is 27 kHz, 29 kHz, 30 kHz. Specifically, the time for heat preservation is 0.8 - 1.8 h, and more specifically, the time for heat preservation is 1.0 - 1.5 h; in some specific embodiments, the time for heat preservation is 0.6 h, 0.7 h, 0.9 h, 1.1 h, 1.3 h, 1.6 h, 1.7 h, 1.9 h.

[0034] In a specific embodiment of the present application, the above heating method is carried out in an induction - ultrasonic composite heating device. Specifically, the induction - ultrasonic composite heating device is as Figure 1 shown, Figure 1 in which 1 is an ultrasonic generator, 2 is an electromagnetic induction heating layer, and 3 is an aluminum alloy ingot. That is, an electromagnetic induction heating layer is provided at the end of the induction - ultrasonic composite heating device close to the aluminum alloy ingot, and an ultrasonic generator is provided at the end far from the aluminum alloy ingot; the electromagnetic induction heating layer and the ultrasonic generator are components well - known to those skilled in the art, and no special limitation is imposed on them in this application.

[0035] The heating method provided by the present application is applicable to 7xxx aluminum alloy. Specifically, the 7xxx aluminum alloy includes 7055 aluminum alloy, 7050 aluminum alloy, 7075 aluminum alloy, 7085 aluminum alloy, 7A09 aluminum alloy or 7A04 aluminum alloy.

[0036] Furthermore, the present application also provides a hot - working method for 7xxx aluminum alloy, including the following steps:

[0037] (S1) Heating the 7xxx aluminum alloy ingot; the heating is the heating method described in the above solution;

[0038] (S2) Processing the heated 7xxx aluminum alloy ingot;

[0039] (S3) Heat - treating the processed aluminum alloy material.

[0040] In the heating method of 7xxx aluminum alloy provided by the present application, first, the 7xxx aluminum alloy ingot is heated. The heating is the heating method described in the above solution, and the heating method has been described in detail above and will not be elaborated here.

[0041] This application then processes the heated 7xxx aluminum alloy ingot. The processing methods are well-known to those skilled in the art, which can be forging, extrusion, or extrusion after forging. The specific means of processing are selected according to the type of 7xxx aluminum alloy ingot, and this application does not impose special restrictions on this. In some specific embodiments, the processing is free forging. More specifically, the free forging is carried out by the process of four upsetting and three drawing.

[0042] According to the present invention, heat treatment is carried out after processing. The heat treatment method can be solution quenching, aging treatment, or solution quenching followed by aging treatment, which is selected according to the composition and specific performance requirements of the aluminum alloy. In some specific embodiments, the temperature of the solution quenching is 450 - 480 °C, and after holding for 5 - 8 h, it is transferred to a water tank for quenching, and the transfer time does not exceed 15 s. More specifically, the temperature of the solution quenching is 460 - 475 °C, and after holding for 6 - 7 h, it is quenched. The temperature of the aging is 100 - 150 °C, and after holding for 12 - 24 h. Specifically, the temperature of the aging is 120 - 140 °C, and after holding for 24 h.

[0043] Compared with the traditional hot processing technology of 7xxx aluminum alloy, the heating method provided by this application has high efficiency and low cost, and at the same time, the performance of the aluminum alloy can also be improved. The heating method provided by this application is applicable to all 7xxx aluminum alloys, has wide applicability, and is convenient for industrial application.

[0044] To further understand the present invention, the following examples are used to illustrate in detail the heating method and hot processing method of 7xxx aluminum alloy provided by the present invention. The protection scope of the present invention is not limited by the following examples.

[0045] Example 1

[0046] A processing method for 7055 aluminum alloy includes the following steps:

[0047] Step 1: Put the 7055 aluminum alloy ingot into the induction-ultrasonic composite heating device, start the induction heating, the heating power is 1200 kW, and heat the ingot to 410 °C.

[0048] Step 2: When the temperature of the aluminum alloy ingot reaches 410 °C, turn on the ultrasonic vibration, the vibration frequency is 12 kHz, and at the same time adjust the induction heating power to 600 kW to continue heating. After the heating temperature of the aluminum alloy ingot reaches 460 °C, it enters the holding stage.

[0049] Step 3: In the holding stage, adjust the ultrasonic vibration frequency to 25 kHz and maintain it at this temperature and frequency for 1 h.

[0050] Step 4: After heating is completed, free forging is carried out using the four-upsetting and three-drawing process;

[0051] Step 5: After forging is completed, solution quenching is carried out. The process is as follows: heat to 475 °C and hold for 6 h; after the holding is completed, transfer the aluminum alloy to a water tank for quenching, and the transfer time does not exceed 15 s;

[0052] Step 6: After solution quenching is completed, aging is carried out. The process is as follows: heat to 120 °C and hold for 24 h.

[0053] Example 2

[0054] A processing method for 7050 aluminum alloy includes the following steps:

[0055] Step 1: Place the 7050 aluminum alloy ingot into an induction-ultrasonic composite heating device, start induction heating, with a heating power of 1100 kW, and heat the ingot to 400 °C;

[0056] Step 2: When the temperature of the aluminum alloy ingot reaches 400 °C, turn on the ultrasonic vibration with a vibration frequency of 14 kHz, and at the same time adjust the induction heating power to 550 kW and continue heating. After the heating temperature of the aluminum alloy ingot reaches 460 °C, enter the holding stage;

[0057] Step 3: During the holding stage, adjust the ultrasonic vibration frequency to 30 kHz and maintain it at this temperature and frequency for 1 h;

[0058] Step 4: After heating is completed, free forging is carried out using the four-upsetting and three-drawing process;

[0059] Step 5: After forging is completed, solution quenching is carried out. The process is as follows: heat to 475 °C and hold for 6 h; after the holding is completed, transfer the aluminum alloy to a water tank for quenching, and the transfer time does not exceed 15 s;

[0060] Step 6: After solution quenching is completed, aging is carried out. The process is as follows: heat to 120 °C and hold for 24 h.

[0061] Comparative Example 1

[0062] A conventional processing method for 7055 aluminum alloy includes the following steps

[0063] Step 1: Place the 7055 aluminum alloy ingot into an electric resistance furnace, start heating, with a heating temperature of 460 °C and a holding time of 20 h;

[0064] Step 2: After heating is completed, free forging is carried out using the four-upsetting and three-drawing process;

[0065] Step 3: After forging, solution quenching is carried out. The process is as follows: heat to 475°C and hold for 6 h; after the holding is completed, transfer the aluminum alloy to a water tank for quenching, and the transfer time does not exceed 15 s;

[0066] Step 4: Aging is carried out after solution quenching. The process is as follows: heat to 120°C and hold for 24 h.

[0067] Figure 2 SEM photograph of the 7055 aluminum alloy prepared in Example 1 of the present invention Figure 3 SEM photograph of the 7055 aluminum alloy prepared in Comparative Example 1 of the present invention. It can be seen from Figure 2 and Figure 3 that by using the heating method of the present application, the crystallization phase in the aluminum alloy structure dissolves back more fully.

[0068] Comparative Example 2

[0069] A processing method for 7055 aluminum alloy includes the following steps:

[0070] Step 1: Place the 7055 aluminum alloy ingot into an induction-ultrasonic composite heating device, start induction heating, the heating power is 1200 kW, and heat the ingot to 410°C;

[0071] Step 2: When the temperature of the aluminum alloy ingot reaches 410°C, turn on the ultrasonic vibration, the vibration frequency is 12 kHz, and continue to heat at a power of 1200 kW. After the heating temperature of the aluminum alloy ingot reaches 460°C, enter the holding stage;

[0072] Step 3: In the holding stage, adjust the ultrasonic vibration frequency to 25 kHz and maintain it at this temperature and frequency for 1 h;

[0073] Step 4: After heating is completed, free forging is carried out by the four-upsetting and three-drawing process;

[0074] Step 5: After forging, solution quenching is carried out. The process is as follows: heat to 475°C and hold for 6 h; after the holding is completed, transfer the aluminum alloy to a water tank for quenching, and the transfer time does not exceed 15 s;

[0075] Step 6: Aging is carried out after solution quenching. The process is as follows: heat to 120°C and hold for 24 h.

[0076] Comparative Example 3

[0077] A processing method for 7055 aluminum alloy includes the following steps:

[0078] Step 1: Place the 7055 aluminum alloy ingot into an induction-ultrasonic composite heating device, start induction heating, the heating power is 1200 kW, and heat the ingot to 410°C;

[0079] Step 2: When the temperature of the aluminum alloy ingot reaches 410°C, turn on the ultrasonic vibration with a vibration frequency of 12 kHz. At the same time, adjust the induction heating power to 600 kW and continue heating. After the heating temperature of the aluminum alloy ingot reaches 460°C, enter the heat preservation stage;

[0080] Step 3: During the heat preservation stage, keep the ultrasonic vibration frequency at 12 kHz and maintain it at this temperature and frequency for 1 h;

[0081] Step 4: After the heating is completed, perform open-die forging using the four-upsetting and three-drawing process;

[0082] Step 5: After forging, perform solution quenching. The process is as follows: heat to 475°C and keep it warm for 6 h; after the heat preservation is completed, transfer the aluminum alloy to the water tank for quenching, and the transfer time does not exceed 15 s;

[0083] Step 6: After solution quenching, perform aging. The process is as follows: heat to 120°C and keep it warm for 24 h.

[0084] Comparative Example 4

[0085] A processing method for 7055 aluminum alloy includes the following steps:

[0086] Step 1: Put the 7055 aluminum alloy ingot into the induction-ultrasonic composite heating device, start the induction heating with a heating power of 1200 kW, and heat the ingot to 410°C;

[0087] Step 2: When the temperature of the aluminum alloy ingot reaches 410°C, turn on the ultrasonic vibration with a vibration frequency of 30 kHz. At the same time, adjust the induction heating power to 600 kW and continue heating. After the heating temperature of the aluminum alloy ingot reaches 460°C, enter the heat preservation stage;

[0088] Step 3: During the heat preservation stage, keep the ultrasonic vibration frequency at 30 kHz and maintain it at this temperature and frequency for 1 h;

[0089] Step 4: After the heating is completed, perform open-die forging using the four-upsetting and three-drawing process;

[0090] Step 5: After forging, perform solution quenching. The process is as follows: heat to 475°C and keep it warm for 6 h; after the heat preservation is completed, transfer the aluminum alloy to the water tank for quenching, and the transfer time does not exceed 15 s

[0091] Step 6: After solution quenching, perform aging. The process is as follows: heat to 120°C and keep it warm for 24 h.

[0092] The properties of the aluminum alloy prepared in the embodiment of the present invention and the aluminum alloy prepared in the comparative example are shown in Table 1;

[0093] Table 1 Performance data sheet of aluminum alloys prepared in examples and comparative examples

[0094]

[0095] As can be seen from Table 1, the mechanical properties of the aluminum alloy prepared in Example 1, such as tensile strength, yield strength, and elongation, are higher than those of the comparative examples. This is because the heating method of this application enables more sufficient re-dissolution of the crystal phase in the aluminum alloy, resulting in higher mechanical properties. At the same time, the heating time of the present invention is shortened from 20 h in the conventional heating method to 1 h, greatly improving the production efficiency and reducing the cost. In the heating method provided by Comparative Example 2, high-power heating is used throughout the process. Even though ultrasonic vibration is introduced, the heating rate is still too fast, and overheating will occur in the microstructure, resulting in a decrease in the elongation of the obtained aluminum alloy. In the heating method provided by Comparative Example 3, although high-power and low-power heating methods are used, low-frequency ultrasonic vibration is always used, making the re-dissolution of the crystal phase insufficient and reducing the strength of the obtained aluminum alloy. In the heating method provided by Comparative Example 4, although high-power and low-power heating methods are used, high-frequency ultrasonic vibration is always used, which will cause damage at low temperature stages and reduce the properties of the aluminum alloy.

[0096] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0097] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for heating a 7xxx aluminum alloy, comprising the following steps: (S1) induction heating a 7xxx aluminum alloy ingot to 350-430° C., wherein the induction heating power is 1100-1200 kW; (S2) ultrasonically vibrating the aluminum alloy ingot obtained in step (S1), induction heating the ingot to 450-480° C., and then keeping the temperature, wherein the power of the induction heating is 450-800 kW, and the frequency of the ultrasonic vibration is 10-15 kHz; (S3) The ultrasonic vibration frequency of the aluminum alloy ingot obtained in step (S2) is adjusted to 25-30 kHz, and the vibration frequency is maintained for 0.5-2 hours, and the insulation time is 0.5-2 hours.

2. The heating method according to claim 1, characterized in that: The heating method is carried out in an induction-ultrasonic composite heating device, wherein an electromagnetic induction heating layer is arranged at the end near the aluminum alloy ingot, and an ultrasonic generator is arranged at the end far from the aluminum alloy ingot.

3. The heating method according to claim 1, characterized in that: In step (S1), the induction heating is performed to 400-430°C.

4. The heating method according to claim 1, characterized in that: In step (S2), the temperature of the induction heating is 460-470° C., and the power of the induction heating is 500-750 kW.

5. The heating method according to claim 1 or 4, characterized in that: In step (S2), the frequency of the ultrasonic vibration is 12-14 kHz.

6. The heating method according to claim 1, characterized in that: In step (S3), the frequency of the ultrasonic vibration is 27-29 kHz.

7. The heating method according to claim 1 or 6, characterized in that: In step (S3), the vibration frequency is maintained for 1 to 1.5 hours, and the insulation time is 1 to 1.5 hours.

8. The heating method according to any one of claims 1 to 7, characterized in that: The 7xxx aluminum alloy includes 7055 aluminum alloy, 7050 aluminum alloy, 7075 aluminum alloy, 7085 aluminum alloy, 7A09 aluminum alloy or 7A04 aluminum alloy.

9. A method for hot working a 7xxx aluminum alloy, comprising the steps of: (S1) heating a 7xxx aluminum alloy ingot; the heating is the heating method according to any one of claims 1 to 8; (S2) processing the heated 7xxx aluminum alloy ingot; (S3) The processed aluminum alloy material is heat treated.

10. The hot working method according to claim 9, characterized in that: The processing method includes one or both of forging and extrusion, and the heat treatment includes one or both of solution quenching and aging.

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