A heating method and a hot working method for 7xxx aluminum alloy

Abstract

The present invention provides a heating method for a 7xxx aluminum alloy, comprising the following steps: (S1) induction heating a 7xxx aluminum alloy ingot to a temperature of 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 it to a temperature of 450-480°C, and then maintaining the temperature, wherein the induction heating power is 450-800 kW, and the ultrasonic vibration frequency is 10-15 kHz; (S3) adjusting the ultrasonic vibration frequency of the aluminum alloy ingot obtained in step (S2) to 25-30 kHz, and maintaining this vibration frequency for 0.5-2 hours, wherein the holding time is 0.5-2 hours. This application also provides a heat treatment method for a 7xxx aluminum alloy. The heating method provided in this application not only ensures uniform heating of the aluminum alloy, but also improves heating efficiency and maintains mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to a heating method and a thermal processing method for a 7xxx aluminum alloy. Background Art

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

[0003] 7xxx series aluminum alloys have a high alloying element content and are prone to containing coarse phases. If not heated sufficiently, subsequent deformation will easily lead to cracking and uneven performance. Therefore, resistance furnace heating is generally used. However, this heating method will cause the cost of 7xxx series aluminum alloys to be higher than other series aluminum alloys.

[0004] To increase the heating rate and reduce costs of 7xxx series aluminum alloys, industry technicians have optimized parameters and adopted induction heating in the heating process of some aluminum alloys with relatively low alloy content and subsequent extrusion forming. However, this method is not universal and has a narrow application range. Therefore, it is necessary to develop new heating methods 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 alloy, which can achieve heating uniformity, improve mechanical properties, and improve heating efficiency.

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

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

[0008] (S2) ultrasonically vibrating the aluminum alloy ingot obtained in step (S1), induction heating the ingot to 450-480° C., and then maintaining the temperature, wherein the power of the induction heating is 450-800 kW, and the frequency of the ultrasonic vibration is 10-15 kHz;

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

[0010] In some specific embodiments, the heating method is performed in an induction-ultrasonic composite heating device, wherein the end of the induction-ultrasonic composite heating device near the aluminum alloy ingot is provided with an electromagnetic induction heating layer, and the end far from the aluminum alloy ingot is provided with an ultrasonic generator.

[0011] In some specific embodiments, in step (S1), the induction heating is performed to a temperature of 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 500-750kW.

[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 to 1.5 hours, and the insulation time is 1 to 1.5 hours.

[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] The present application also provides a method for hot working of a 7xxx aluminum alloy, comprising the following steps:

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

[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 heating method for a 7xxx aluminum alloy, which first involves rapidly induction heating a 7xxx aluminum alloy ingot to 350-430°C at a high power of 1100-1200kW, performing low-frequency ultrasonic vibration at 10-15kHz when the ingot temperature reaches 350-430°C, adjusting the induction heating power to 450-800kW, and heating to 450-480°C before entering a holding stage, adjusting the ultrasonic vibration frequency to 25-30kHz, and maintaining and holding the temperature at this vibration frequency for 0.5-2h, thereby completing the heating of the 7xxx aluminum alloy. The heating method for a 7xxx aluminum alloy provided in the present application is based on induction heating, and reduces the unevenness of induction heating by combining rapid heating at low temperature with slow heating at high temperature. At the same time, ultrasonic vibration assistance is introduced, and a low-frequency method in the heating stage and a high-frequency method in the holding stage are adopted, which is beneficial to promoting the rapid dissolution of the crystalline phase and promoting heat diffusion, thereby improving 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 structural diagram of the induction-ultrasonic composite heating device provided by the present invention;

[0024] Figure 2 This is a SEM photograph 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 alloys in the prior art cannot be simultaneously taken into account, the present application provides a heating method for 7xxx aluminum alloys, 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 heating uniformity, and promotes the dissolution of the crystalline phase, ultimately ensuring the mechanical properties of the aluminum alloy and improving the heating efficiency. Specifically, the embodiments of the present invention disclose a heating method for 7xxx aluminum alloys, comprising the following steps:

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

[0029] (S2) ultrasonically vibrating the aluminum alloy ingot obtained in step (S1), induction heating the ingot to 450-480° C., and then maintaining the temperature, wherein the power of the induction heating is 450-800 kW, and the frequency of the ultrasonic vibration is 10-15 kHz;

[0030] (S3) The ultrasonic vibration frequency of the aluminum alloy ingot obtained in step (S2) is adjusted to 25-30 kHz, and maintained at this vibration frequency for 0.5-2 hours, and the insulation time is 0.5-2 hours.

[0031] In the heating method provided herein, a 7xxx aluminum alloy ingot is first subjected to induction heating at a power of 1100-1200 kW. In some embodiments, the induction heating power is 1150 kW or 1200 kW. The induction heating is performed at the above power to a temperature of 350-430°C, more specifically, 355-425°C, and more specifically, 360-410°C. In some embodiments, the induction heating is performed 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, or 426°C.

[0032] When the temperature of the aluminum alloy ingot reaches 400~430℃, ultrasonic vibration is turned on with a vibration frequency of 10~15kHz, and the power of induction heating is adjusted to 450~800kW. The aluminum alloy ingot is continued to be heated with the above induction heating power and ultrasonic vibration frequency; the above vibration frequency is specifically 10kHz, 11kHz, 12kHz, 13kHz, 14kHz, and 15kHz; specifically, the power of the induction heating is 500~750kW, specifically, the power of the induction heating is 580~720kW, more specifically, the power of the induction heating is 600~700kW; in a specific embodiment, the power of the induction heating is 510kW, 530kW, 550kW, 560kW, 590kW, 610kW, 620kW, 640kW, 650kW, 670kW, 690kW, 710kW, 730kW, and 740kW.

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

[0034] In a specific embodiment of the present application, the above heating method is carried out in an induction-ultrasound composite heating device. Specifically, the induction-ultrasound composite heating device is as follows: Figure 1 As shown, Figure 1 1 is an ultrasonic generator, 2 is an electromagnetic induction heating layer, and 3 is an aluminum alloy ingot. That is, the end of the induction-ultrasonic composite heating device near the aluminum alloy ingot is provided with an electromagnetic induction heating layer, and the end far from the aluminum alloy ingot is provided with an ultrasonic generator; the electromagnetic induction heating layer and the ultrasonic generator are components well known to those skilled in the art, and this application does not impose any special restrictions on this.

[0035] The heating method provided in this application is applicable to 7xxx aluminum alloys. Specifically, the 7xxx aluminum alloys include 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 method for hot working of a 7xxx aluminum alloy, comprising the following steps:

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

[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 in the present application, the 7xxx aluminum alloy ingot is first heated. The heating method is the heating method described in the above scheme. The heating method has been described in detail above and will not be repeated here.

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

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

[0043] Compared with the traditional thermal processing technology of 7xxx aluminum alloy, the heating method provided in this application is highly efficient and low-cost, and the performance of the aluminum alloy can also be improved; the heating method provided in this application is applicable to all 7xxx aluminum alloys, has wide applicability, and is convenient for industrial application.

[0044] In order to further understand the present invention, the heating method and hot working method of the 7xxx aluminum alloy provided by the present invention are described in detail below in conjunction with the embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0045] Example 1

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

[0047] Step 1: Place the 7055 aluminum alloy ingot into an induction-ultrasonic composite heating device, start induction heating with a heating power of 1200kW, and heat the ingot to 410°C;

[0048] Step 2: When the temperature of the aluminum alloy ingot reaches 410°C, start ultrasonic vibration with a vibration frequency of 12kHz, and adjust the induction heating power to 600kW to continue heating. After the heating temperature of the aluminum alloy ingot reaches 460°C, it enters the insulation stage;

[0049] Step 3: During the heat preservation stage, adjust the ultrasonic vibration frequency to 25kHz and maintain it at this temperature and frequency for 1 hour;

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

[0051] Step 5: After forging, solution quenching is performed. The process is as follows: heating to 475°C and holding for 6 hours. After the holding is completed, the aluminum alloy is transferred to a water tank for quenching. The transfer time does not exceed 15 seconds.

[0052] Step 6: After solution quenching, aging is carried out. The process is: heating to 120℃ and keeping warm for 24 hours.

[0053] Example 2

[0054] A processing method for 7050 aluminum alloy comprises 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 1100kW, and heat the ingot to 400°C;

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

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

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

[0059] Step 5: After forging, solution quenching is performed. The process is as follows: heating to 475°C and holding for 6 hours. After the holding is completed, the aluminum alloy is transferred to a water tank for quenching. The transfer time does not exceed 15 seconds.

[0060] Step 6: After solution quenching, aging is carried out. The process is: heating to 120℃ and keeping warm for 24 hours.

[0061] Comparative Example 1

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

[0063] Step 1: Place the 7055 aluminum alloy ingot into the resistance furnace and start heating. The heating temperature is 460℃ and the holding time is 20h.

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

[0065] Step 3: After forging, solution quenching is performed. The process is as follows: heating to 475°C and holding for 6 hours. After the holding is completed, the aluminum alloy is transferred to a water tank for quenching. The transfer time does not exceed 15 seconds.

[0066] Step 4: After solution quenching, aging is carried out. The process is: heating to 120℃ and keeping warm for 24 hours.

[0067] Figure 2 This is a SEM photo of the 7055 aluminum alloy prepared in Example 1 of the present invention. Figure 3 This is a SEM photo of the 7055 aluminum alloy prepared in Comparative Example 1 of the present invention. Figure 2 and Figure 3 It can be seen that by adopting the heating method of the present application, the crystalline phase in the aluminum alloy structure is dissolved more fully.

[0068] Comparative Example 2

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

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

[0071] Step 2: When the temperature of the aluminum alloy ingot reaches 410°C, start ultrasonic vibration with a vibration frequency of 12kHz and continue heating at a power of 1200kW. After the heating temperature of the aluminum alloy ingot reaches 460°C, it enters the holding stage;

[0072] Step 3: During the heat preservation stage, adjust the ultrasonic vibration frequency to 25kHz and maintain it at this temperature and frequency for 1 hour;

[0073] Step 4: After heating is completed, free forging is performed using a four-upsetting and three-drawing process;

[0074] Step 5: After forging, solution quenching is performed. The process is as follows: heating to 475°C and holding for 6 hours. After the holding is completed, the aluminum alloy is transferred to a water tank for quenching. The transfer time does not exceed 15 seconds.

[0075] Step 6: After solution quenching, aging is carried out. The process is: heating to 120℃ and keeping warm for 24 hours.

[0076] Comparative Example 3

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

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

[0079] Step 2: When the temperature of the aluminum alloy ingot reaches 410°C, start ultrasonic vibration with a vibration frequency of 12kHz, and adjust the induction heating power to 600kW to continue heating. After the heating temperature of the aluminum alloy ingot reaches 460°C, it enters the insulation stage;

[0080] Step 3: During the heat preservation stage, the ultrasonic vibration frequency is maintained at 12 kHz and maintained at this temperature and frequency for 1 hour;

[0081] Step 4: After heating is completed, free forging is performed using a four-upsetting and three-drawing process;

[0082] Step 5: After forging, solution quenching is performed. The process is as follows: heating to 475°C and holding for 6 hours. After the holding is completed, the aluminum alloy is transferred to a water tank for quenching. The transfer time does not exceed 15 seconds.

[0083] Step 6: After solution quenching, aging is carried out. The process is: heating to 120℃ and keeping warm for 24 hours.

[0084] Comparative Example 4

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

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

[0087] Step 2: When the temperature of the aluminum alloy ingot reaches 410°C, start ultrasonic vibration with a vibration frequency of 30kHz, and adjust the induction heating power to 600kW to continue heating. After the heating temperature of the aluminum alloy ingot reaches 460°C, it enters the insulation stage;

[0088] Step 3: During the heat preservation stage, the ultrasonic vibration frequency is maintained at 30kHz and maintained at this temperature and frequency for 1 hour;

[0089] Step 4: After heating is completed, free forging is performed using a four-upsetting and three-drawing process;

[0090] Step 5: After forging, solution quenching is performed. The process is: heating to 475°C and holding for 6 hours. After the holding is completed, the aluminum alloy is transferred to a water pool for quenching. The transfer time does not exceed 15 seconds.

[0091] Step 6: After solution quenching, aging is carried out. The process is: heating to 120℃ and keeping warm for 24 hours.

[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 of aluminum alloys prepared in Examples and Comparative Examples

[0094]

[0095] As shown in Table 1, the mechanical properties of the aluminum alloy prepared in Example 1, such as tensile strength, yield strength and elongation, are all higher than those in the comparative example. This is because the heating method of the present application makes the crystalline phase in the aluminum alloy dissolve more fully, thereby making the mechanical properties higher. At the same time, the heating time of the present invention is shortened from 20h of the conventional heating method to 1h, which greatly improves production efficiency and reduces costs. In the heating method provided in Comparative Example 2, high-power heating is used throughout the entire process. Even if ultrasonic vibration is introduced, the heating rate is still too fast, the microstructure will be overheated, and the elongation of the obtained aluminum alloy is reduced. In the heating method provided in Comparative Example 3, although high-power and low-power heating methods are used, low-frequency ultrasonic vibration is always used, which makes the crystalline phase dissolve insufficiently and the strength of the obtained aluminum alloy is reduced. In the heating method provided in 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, thereby reducing the performance of the aluminum alloy.

[0096] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0097] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform 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 a temperature of 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 maintaining 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 maintained at this vibration frequency 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. The end of the induction-ultrasonic composite heating device near the aluminum alloy ingot is provided with an electromagnetic induction heating layer, and the end far from the aluminum alloy ingot is provided with an ultrasonic generator.

3. The heating method according to claim 1, wherein In step (S1), the induction heating is performed to a temperature of 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 500-750kW.

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 thermally processing a 7xxx aluminum alloy, comprising the following steps: (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) heat treating the processed aluminum alloy material.

10. The thermal processing 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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