Homogenizing heat treatment method for 7050 aluminum alloy cast ingot

Abstract

The invention provides a homogenizing heat treatment method for a 7050 aluminum alloy cast ingot. The homogenizing heat treatment method comprises the steps that S1, the 7050 aluminum alloy cast ingot is subjected to first heating, and after the cold end of the 7050 aluminum alloy cast ingot is heated to 395-400 DEG C, first heating is ended; s2, the 7050 aluminum alloy cast ingot continues to be subjected to second heating, and after the cold end is heated to 465-470 DEG C, second heating is ended; and S3, the 7050 aluminum alloy cast ingot is continuously subjected to third temperature rising, after the cold end is heated to 475-480 DEG C, heat preservation and cooling treatment are sequentially conducted, the 7050 aluminum alloy cast ingot subjected to homogenizing heat treatment is obtained, and the heat preservation time is 8-20 h. Heat preservation is not carried out in the step S1 and the step S2, the soaking treatment time of the 7050 aluminum alloy cast ingot is greatly shortened, and the phenomenon of overburning of the 7050 aluminum alloy cast ingot does not occur.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloys, and in particular to a homogenization heat treatment method for a 7050 aluminum alloy ingot. Background Art

[0002] As the main material of aviation, 7050 alloy is widely used in defense and military fields such as aerospace. Due to the high content of elements in 7050 alloy, it is easy to produce component segregation, resulting in uneven chemical composition and structure, thus forming a large number of coarse second phase compounds with different melting points, such as η (MgZn2), T (AlZnMgCu), S (Al2CuMg) and θ (Al2Cu), which seriously reduce the processing performance of the alloy. Therefore, it is necessary to perform reasonable and effective soaking treatment on 7050 alloy ingots to improve the uniformity of alloy structure and composition. Usually, soaking treatment of 7XXX series aluminum alloy ingots needs to achieve two effects: one is to eliminate the segregation of organizational components and non-equilibrium eutectic phase in the cast alloy and improve the structure; the other is to promote the precipitation of trace elements Cr, Mn, Zr, etc. with the optimal dispersed phase characteristics. At present, there are many types of soaking processes for 7050 and other 7XXX series aluminum alloy ingots, including single-stage, double-stage and multi-stage soaking processes, but most of them are based on laboratory research results, with many technical defects, and are difficult to be applied in actual industrial large-scale production.

[0003] The Chinese patent application with patent application number 201210287347.X proposes a three-stage homogenization heat treatment method suitable for 7XXX series aluminum alloys, wherein the first stage temperature is 465-473°C, the holding time is 23-25h, the second stage temperature is 480-485°C, the holding time is 11-13h, the third stage temperature is 495-500°C, and the holding time is 15-25min. The second and third stage homogenization temperatures of the process are high, especially the third stage temperature is above 495°C, which is significantly higher than the overburning temperature (~487°C) of the soluble high-temperature phase Al2CuMg of the 7XXX series aluminum alloy. Although the holding time is short, it is very easy to cause the risk of overburning of the alloy structure. In addition, the third stage high temperature short-time holding treatment of 15-25min is inconvenient to operate and difficult to achieve in actual large-scale industrial production. The Chinese patent application with patent application number 201610152790.4 proposes a homogenization treatment process for Al-Zn-Mg-Cu-Zr alloy, wherein the first stage temperature is 300-450°C, the holding time is 3-15h, the second stage temperature is 460-475°C, the holding time is 0.5-10h, and the third stage temperature is 475-485°C, the holding time is 24-48h. The Chinese patent application with patent application number 201911301751.6 proposes a homogenization treatment process for Al-Zn-Mg-Cu-Zr alloy, wherein the first stage temperature is 375-425°C, the holding time is 5-15h, the second stage temperature is 465-475°C, the holding time is 1-4h, and the third stage temperature is 480-490°C, the holding time is 16-36h. Both patent applications set a rate of heating and adopt a three-stage equalizing method. The process is basically similar. The purpose is to promote the precipitation of Al3Zr dispersed phase by adopting the first stage insulation stage, and to increase the overburning temperature of residual phase and eliminate residual phase by the second and third stages. However, in actual industrial equalizing production, the large-tonnage equalizing furnace has a large ingot loading capacity, and the temperature in the furnace cannot be heated at the set rate (the industrial equalizing furnace production temperature is heated by furnace gas, with a high-power heating output at the beginning, and the heating power is automatically reduced as it approaches the set temperature); in addition, the third stage temperature is set high, which may cause the ingot structure to overheat or overburn, resulting in the risk of product scrapping; in addition, the cumulative time of heating and insulation in the entire equalizing process is long, which will form a narrow mouth of the equalizing production process in industrial production, affecting production efficiency; therefore, the above processes have major deficiencies and technical defects, and it is difficult to meet the actual industrial equalizing production needs of current aluminum processing enterprises. Summary of the invention

[0004] The main purpose of the present invention is to provide a homogenization heat treatment method for 7050 aluminum alloy ingots, so as to solve the problem that the homogenization heat treatment of 7050 aluminum alloy ingots in the prior art takes a long time and is prone to overburning.

[0005] In order to achieve the above-mentioned object, according to one aspect of the present invention, a homogenization heat treatment method for a 7050 aluminum alloy ingot is provided, and the homogenization heat treatment method comprises: step S1, heating the 7050 aluminum alloy ingot for the first time, wherein the average rate of the first heating is 44.0-57.8°C / h, and the temperature is maintained after the hot end of the 7050 aluminum alloy ingot is heated to 395-400°C, and the first heating is terminated after the cold end of the 7050 aluminum alloy ingot is heated to 395-400°C; step S2, heating the 7050 aluminum alloy ingot for the second time, and the second heating is continued. The average heating rate is 3.8-4.9°C / h, and the temperature of the hot end is maintained after the temperature is heated to 465-470°C, and the second heating is ended after the temperature of the cold end is heated to 465-470°C; step S3, the 7050 aluminum alloy ingot is further heated for the third time, and the average heating rate of the third heating is 1.3-6.7°C / h, and the temperature of the hot end is maintained after the temperature is heated to 475-480°C, and the temperature of the cold end is sequentially kept and cooled after the temperature is heated to 475-480°C to obtain the 7050 aluminum alloy ingot after homogenization heat treatment, wherein the insulation time is 8-20h.

[0006] Furthermore, in the above step S1, the average rate of the first heating is 46.8-53.6°C / h.

[0007] Furthermore, in the above step S2, the average rate of the second heating is 4.1-4.6°C / h.

[0008] Furthermore, in the above step S3, the average rate of the third heating is 1.5-4.0°C / h; and / or the insulation time is 10-15h.

[0009] Furthermore, the first heating, the second heating and the third heating are carried out in the same pusher-type heating furnace, and the 7050 aluminum alloy ingot is heated by introducing furnace gas into the pusher-type heating furnace; preferably, in step S1, the temperature of the furnace gas is set to 420-430°C to perform the first heating of the 7050 aluminum alloy ingot, and when the hot end is heated to 395-400°C, the temperature of the furnace gas is adjusted to 395-400°C to maintain the temperature of the hot end, and the cold end is heated to 395-400°C.

[0010] Furthermore, in the above step S2, the temperature of the furnace gas is set to 475°C to perform a second heating of the 7050 aluminum alloy ingot. When the hot end is heated to 465-470°C, the temperature of the furnace gas is adjusted to 465-470°C to maintain the temperature of the hot end, and the cold end is heated to 465-470°C.

[0011] Furthermore, in the above step S3, the temperature of the furnace gas is set to 482-485°C to perform a third heating of the 7050 aluminum alloy ingot. When the hot end is heated to 475-480°C, the temperature of the furnace gas is adjusted to 475-480°C to maintain the temperature of the hot end, and the cold end is heated to 475-480°C and then kept warm.

[0012] Furthermore, the furnace gas is selected from any one or more of air, nitrogen and argon.

[0013] Furthermore, the cooling treatment is air cooling or atomization cooling.

[0014] Furthermore, the total duration from the first heating in step S1 to the end of the heat preservation in step S3 does not exceed 55 hours.

[0015] By applying the technical solution of the present invention, the present application completes two important second phase evolution processes of the soaking treatment of the 7050 aluminum alloy ingot by controlling the average heating rate and temperature of step S1 and step S2, namely, completing the full precipitation of the nano-dispersed phase Al3Zr particles and completing the complete transformation of the low-melting-point non-equilibrium eutectic phase T phase (AlZnMgCu phase) into the high-melting-point S phase (Al2CuMg phase), and no insulation is performed in step S1 and step S2 of the present application, which greatly reduces the soaking treatment time of the 7050 aluminum alloy ingot; step S3 can effectively eliminate the high-melting-point S phase by controlling the average heating rate, temperature and insulation time, complete the complete dissolution of the soluble coarse compounds in the entire 7050 aluminum alloy ingot, and the 7050 aluminum alloy ingot does not suffer from overburning. The homogenization heat treatment method of the present application is highly compatible with 7050 aluminum alloy ingots. The method can not only promote the precipitation of Al3Zr dispersed phase of 7050 alloy and regulate the content of recrystallized structure of final alloy plate, but also effectively eliminate the casting structure of 7050 aluminum alloy ingots and improve the comprehensive performance of aluminum materials. In addition, the method has simple process operation, short time consumption, low energy consumption and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0017] Figure 1 The SEM residual phase image of the 7050 aluminum alloy ingot after homogenization heat treatment in Example 1 of the present application is shown;

[0018] Figure 2 The figure shows the grain distribution diagram of the 7050 aluminum alloy ingot after homogenization heat treatment in Example 1 of the present application;

[0019] Figure 3The Al3Zr dispersion phase diagram of the 7050 aluminum alloy ingot after homogenization heat treatment in Example 1 of the present application is shown;

[0020] Figure 4 The SEM image of the 7050 aluminum alloy ingot after homogenization heat treatment in Comparative Example 4 of the present application is shown;

[0021] Figure 5 The OM diagram of the 7050 aluminum alloy ingot after homogenization heat treatment in Comparative Example 4 of the present application is shown. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] As analyzed in the background technology of this application, the homogenization heat treatment of 7050 aluminum alloy ingots in the prior art has the problem of long time and easy overburning. In order to solve the above problems, this application provides a homogenization heat treatment method for 7050 aluminum alloy ingots.

[0024] It should be noted that the hot end refers to the end of the 7050 aluminum alloy ingot that is close to the heating source, and the cold end refers to the end of the 7050 aluminum alloy ingot that is far from the heating source. For example, when the 7050 aluminum alloy ingot is placed in a pusher heating furnace, the 7050 aluminum alloy ingot is heated by introducing furnace gas into the pusher heating furnace, and the furnace gas is introduced from the air inlet of the pusher heating furnace and discharged from the air outlet of the pusher heating furnace. The end of the 7050 aluminum alloy ingot close to the air inlet is the hot end, and the end of the 7050 aluminum alloy ingot close to the air outlet is the cold end.

[0025] The average rate refers to the average heating rate of the cold end of the 7050 aluminum alloy ingot.

[0026] In a typical embodiment of the present application, a homogenization heat treatment method for a 7050 aluminum alloy ingot is provided, and the homogenization heat treatment method comprises: step S1, heating the 7050 aluminum alloy ingot for the first time, the average rate of the first heating is 44.0-57.8°C / h, and the temperature of the hot end of the 7050 aluminum alloy ingot is maintained after the temperature is raised to 395-400°C, and the first heating is terminated after the cold end of the 7050 aluminum alloy ingot is raised to 395-400°C; step S2, heating the 7050 aluminum alloy ingot for the second time, and the second heating is continued The average rate of the third heating is 3.8-4.9°C / h, and the temperature of the hot end is maintained after the temperature is raised to 465-470°C, and the temperature of the cold end is ended after the temperature is raised to 465-470°C; step S3, the 7050 aluminum alloy ingot is further heated for the third time, and the average rate of the third heating is 1.3-6.7°C / h, and the temperature of the hot end is maintained after the temperature is raised to 475-480°C, and the temperature of the cold end is successively kept and cooled after the temperature is raised to 475-480°C to obtain the 7050 aluminum alloy ingot after the homogenization heat treatment, wherein the heat preservation time is 8-20h.

[0027] The present application completes two important second phase evolution processes of the soaking treatment of the 7050 aluminum alloy ingot by controlling the average heating rate and temperature of step S1 and step S2, namely, completing the full precipitation of nano-dispersed phase Al3Zr particles and completing the complete transformation of the low-melting point non-equilibrium eutectic phase T phase (AlZnMgCu phase) into a high-melting point S phase (Al2CuMg phase), and no insulation is performed in step S1 and step S2 of the present application, which greatly reduces the soaking treatment time of the 7050 aluminum alloy ingot; step S3 can effectively eliminate the high-melting point S phase by controlling the average heating rate, temperature and insulation time, complete the complete dissolution of soluble coarse compounds in the entire 7050 aluminum alloy ingot, and the 7050 aluminum alloy ingot does not suffer from overburning. The homogenization heat treatment method of the present application is highly compatible with 7050 aluminum alloy ingots. The method can not only promote the precipitation of Al3Zr dispersed phase of 7050 alloy and regulate the content of recrystallized structure of final alloy plate, but also effectively eliminate the casting structure of 7050 aluminum alloy ingots and improve the comprehensive performance of aluminum materials. In addition, the method has simple process operation, short time consumption, low energy consumption and high efficiency.

[0028] In order to improve the precipitation efficiency of nano-dispersed phase Al3Zr particles, in one embodiment of the present application, preferably, in the above step S1, the average rate of the first heating is 46.8-53.6°C / h.

[0029] In order to improve the transformation efficiency of the low melting point non-equilibrium eutectic phase T phase (AlZnMgCu phase) to the high melting point S phase (Al2CuMg phase), in one embodiment of the present application, it is preferred that in the above step S2, the average rate of the second heating is 4.1-4.6°C / h.

[0030] In one embodiment of the present application, in the above step S3, the average rate of the third heating is 1.5-4.0°C / h; and / or the insulation time is 10-15h.

[0031] It is preferred to control the average rate of the third heating within the above range, which helps to improve the elimination efficiency of the high-melting-point S phase. Too short a holding time is not conducive to the elimination of the high-melting-point S phase, and too long a holding time is not conducive to reducing energy loss. It is preferred to control the holding time within the above range, which can not only control the S phase to a level that can be eliminated by subsequent heat processing, but also shorten the homogenization time, which helps to improve the efficiency of homogenization heat treatment.

[0032] In one embodiment of the present application, the first heating, the second heating and the third heating are carried out in the same pusher-type heating furnace, and the 7050 aluminum alloy ingot is heated by introducing furnace gas into the pusher-type heating furnace; preferably, in step S1, the temperature of the furnace gas is set to 420-430°C to perform the first heating of the 7050 aluminum alloy ingot, and when the hot end is heated to 395-400°C, the temperature of the furnace gas is adjusted to 395-400°C to maintain the temperature of the hot end, and the cold end is heated to 395-400°C; further preferably, when the hot end is heated to 400°C, the temperature of the furnace gas is adjusted to 400°C to maintain the temperature of the hot end, and the cold end is heated to 395°C.

[0033] Setting the temperature of the furnace gas within the above range helps to control the average rate of the first heating, thereby helping to improve the precipitation efficiency of the nano-dispersed phase Al3Zr particles. When the hot end is heated to 400°C, setting the temperature of the furnace gas to 400°C and waiting for the cold end to be heated to 395°C helps to control the temperature of the hot end at 400°C and help avoid the hot end temperature being too high.

[0034] In one embodiment of the present application, a 7050 aluminum alloy ingot is placed in a pusher-type heating furnace, and the 7050 aluminum alloy ingot is subjected to a first temperature increase, a second temperature increase, and a third temperature increase in sequence by introducing furnace gas into the pusher-type heating furnace. The furnace gas is introduced from an air inlet of the pusher-type heating furnace and discharged from an air outlet of the pusher-type heating furnace. The hot end of the 7050 aluminum alloy ingot is close to the air inlet, and the cold end of the 7050 aluminum alloy ingot is close to the air outlet.

[0035] In one embodiment of the present application, in the above step S2, the temperature of the furnace gas is set to 475°C to perform a second heating of the 7050 aluminum alloy ingot. When the hot end is heated to 465-470°C, the temperature of the furnace gas is adjusted to 465-470°C to maintain the temperature of the hot end, and the cold end is heated to 465-470°C; preferably, when the hot end is heated to 470°C, the temperature of the furnace gas is adjusted to 470°C to maintain the temperature of the hot end, and the cold end is heated to 465°C.

[0036] Setting the temperature of the furnace gas within the above range helps to control the average rate of the second heating, thereby helping to improve the transformation efficiency of the low melting point non-equilibrium eutectic phase T phase (AlZnMgCu phase) to the high melting point S phase (Al2CuMg phase). When the hot end is heated to 470°C, setting the temperature of the furnace gas to 470°C and waiting for the cold end to heat up to 465°C helps to avoid the hot end temperature being too high.

[0037] In one embodiment of the present application, in the above step S3, the temperature of the furnace gas is set to 482-485°C to perform a third heating of the 7050 aluminum alloy ingot. When the hot end is heated to 475-480°C, the temperature of the furnace gas is adjusted to 475-480°C to maintain the temperature of the hot end, and the cold end is heated to 475-480°C and then kept warm; preferably, when the hot end is heated to 480°C, the temperature of the furnace gas is adjusted to 480°C to maintain the temperature of the hot end, and the cold end is heated to 475°C and then kept warm.

[0038] Setting the temperature of the furnace gas within the above range is helpful to control the average rate of the third heating, thereby helping to improve the elimination efficiency of the high-melting-point S phase. When the hot end is heated to 480°C, the temperature of the furnace gas is set to 480°C to wait for the cold end to be heated to 475°C and then be kept warm, which helps to avoid the hot end temperature exceeding 480°C and causing overburning of the 7050 aluminum alloy ingot.

[0039] In one embodiment of the present application, the furnace gas is selected from any one or more of air, nitrogen and argon.

[0040] It is preferred to control the type of furnace gas within the above range, which helps to reduce the adverse effects of the furnace gas on the 7050 aluminum alloy ingot.

[0041] In order to improve the efficiency of the cooling process, in one embodiment of the present application, the cooling process is preferably air cooling or atomization cooling.

[0042] In one embodiment of the present application, the total duration from the first heating in step S1 to the end of the heat preservation in step S3 does not exceed 55 hours.

[0043] Since there is no heat preservation in step S1 and step S2 of the present application, the time of the homogenization heat treatment is greatly shortened. Therefore, the homogenization heat treatment method of the present application has the advantage of being less time-consuming.

[0044] The beneficial effects of the present application will be further illustrated below in conjunction with embodiments.

[0045] Example 1

[0046] Step S1, loading a 7050 aluminum alloy ingot at 25°C into a pusher heating furnace (furnace temperature is 25°C) in the form of full furnace charge, setting the furnace gas constant temperature to 420°C, heating the ingot for the first time by furnace gas, the average rate of the first heating is 46.8°C / h, heating the hot end of the ingot to the target temperature of 400°C by differential heat, then setting the furnace gas temperature to 400°C, and when the cold end of the ingot is heated to 395°C, no insulation is performed; Step S2, setting the furnace gas temperature to 475°C to heat the ingot for the second time, the average rate of the second heating is 4.1°C / h, The hot end of the ingot is heated to a target temperature of 470°C by differential thermal heating, and then the furnace gas temperature is set to 470°C. When the cold end of the ingot is heated to 465°C, no insulation is performed; step S3, finally the furnace gas temperature is set to 482°C, and the ingot is heated for the third time by furnace gas. The average rate of the third heating is 1.5°C / h, and the hot end of the ingot is heated to a target temperature of 480°C by differential thermal heating, and then the furnace gas temperature is set to 480°C. When the thermocouple at the cold end of the ingot is heated to 475°C, the insulation timer starts, and the insulation time is set to 20h. After the equalization is completed, the 7050 aluminum alloy ingot is air-cooled to 25°C after being taken out of the furnace.

[0047] Example 2

[0048] The difference from Example 1 is that the average rate of the first heating is 53.6° C. / h, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0049] Example 3

[0050] The difference from Example 1 is that the average rate of the first heating is 44.0° C. / h, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0051] Example 4

[0052] The difference from Example 1 is that the average rate of the first heating is 57.8° C. / h, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0053] Example 5

[0054] The difference from Example 1 is that the average rate of the second heating is 4.6° C. / h, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0055] Example 6

[0056] The difference from Example 1 is that the average rate of the second heating is 3.8° C. / h, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0057] Example 7

[0058] The difference from Example 1 is that the average rate of the second heating is 4.9° C. / h, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0059] Example 8

[0060] The difference from Example 1 is that the average rate of the third heating is 4.0° C. / h, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0061] Example 9

[0062] The difference from Example 1 is that the average rate of the third heating is 1.3° C. / h, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0063] Example 10

[0064] The difference from Example 1 is that the average rate of the third heating is 6.7° C. / h, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0065] Embodiment 11

[0066] Step S1, loading a 7050 aluminum alloy ingot at 25°C into a cold furnace (furnace temperature is 25°C) in the form of a full furnace charge, setting the furnace gas constant temperature to 430°C, heating the ingot for the first time by the furnace gas, the average rate of the first heating is 52.3°C / h, heating the hot end of the ingot to a target temperature of 400°C by differential heat, then setting the furnace gas temperature to 400°C, and when the cold end of the ingot is heated to 395°C, no insulation is performed; Step S2, setting the furnace gas temperature to 475°C to heat the ingot for the second time, the average rate of the second heating is 4.1°C / h, The end differential heat is heated to the target temperature of 470℃, and then the furnace gas temperature is set to 470℃, and the cold end of the ingot is heated to 465℃ without insulation; step S3, finally the furnace gas temperature is set to 485℃, and the ingot is heated for the third time by furnace gas, and the average rate of the third heating is 1.7℃ / h, and the hot end of the ingot is differentially heated to the target temperature of 480℃, and then the furnace gas temperature is set to 480℃, and when the thermocouple at the cold end of the ingot is heated to 475℃, the insulation timer starts, and the insulation time is set to 20h. After the equalization is completed, the 7050 aluminum alloy ingot is air-cooled to 25℃ after being taken out of the furnace.

[0067] Example 12

[0068] The difference from Example 1 is that the holding time in step S3 is 8 hours, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0069] Example 13

[0070] The difference from Example 1 is that the holding time in step S3 is 10 hours, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0071] Embodiment 14

[0072] The difference from Example 1 is that the holding time in step S3 is 15 hours, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0073] Comparative Example 1

[0074] The difference from Example 1 is that in step S1, when the cold end of the ingot to be cast is heated to 395° C., it is kept warm for 6 hours, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0075] Comparative Example 2

[0076] The difference from Example 1 is that in step S2, the cold end of the ingot to be cast is heated to 465° C. and kept warm for 6 hours, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0077] Comparative Example 3

[0078] The difference from Example 1 is that the holding time in step S3 is 7 hours, and finally a 7050 aluminum alloy ingot after homogenization heat treatment is obtained.

[0079] Comparative Example 4

[0080] The difference from Example 1 is that in step S3, the furnace gas temperature is set to 490°C, the ingot is heated for the third time by furnace gas, the average rate of the third heating is 1.5°C / h, the hot end of the ingot is differentially heated to the target temperature of 490°C, and then the furnace gas temperature is set to 490°C. When the thermocouple at the cold end of the ingot is heated to 485°C, the insulation time starts, and the insulation time is set to 4h, finally obtaining a 7050 aluminum alloy ingot after homogenization heat treatment.

[0081] Comparative Example 5

[0082] The difference from Example 1 is that 7055 aluminum alloy ingot is used to replace 7050 aluminum alloy ingot, and finally 7055 aluminum alloy ingot after homogenization heat treatment is obtained, and the homogenized 7055 alloy ingot is severely overburned.

[0083] The SEM residual phase fraction, average grain size and Al3Zr number density were calculated by SEM, and the DSC peak area of ​​the residual S phase was calculated using Image-Pro-Plus software.

[0084] The 7050 aluminum alloy ingots after homogenization heat treatment prepared in the embodiment and the comparative example were statistically analyzed for the SEM residual phase fraction, the residual S phase DSC peak area, the average grain size and the Al3Zr number density, and the statistical results are shown in Table 1. The total time of homogenization heat treatment of the 7050 aluminum alloy ingot in the embodiment and the comparative example from the start of heating in step S1 to the end of heat preservation in step S3 was recorded, and the results are shown in Table 1.

[0085] Table 1

[0086]

[0087]

[0088] Figure 1 The SEM residual phase image of the 7050 aluminum alloy ingot after homogenization heat treatment in Example 1 of the present application is shown in FIG. Figure 1 It can be seen that the 7050 aluminum alloy ingot has a good heat-isolating effect and no overheating or overburning occurs.

[0089] Figure 2 The grain distribution diagram of the 7050 aluminum alloy ingot after homogenization heat treatment in Example 1 of the present application is shown in FIG. Figure 2 It can be seen that the grain size distribution of 7050 aluminum alloy ingot is relatively uniform after equalization.

[0090] Figure 3 The Al3Zr dispersion phase diagram of the 7050 aluminum alloy ingot after homogenization heat treatment in Example 1 of the present application is shown in FIG. Figure 3 It can be seen that the Al3Zr dispersion is relatively uniform.

[0091] Figure 4 This is a SEM image of the 7050 aluminum alloy ingot after homogenization heat treatment in Comparative Example 4 of the present application. Figure 4 It can be seen that the 7050 aluminum alloy ingot is severely overheated after being heated.

[0092] Figure 5 OM diagram of the 7050 aluminum alloy ingot after homogenization heat treatment in Comparative Example 4 of the present application, Figure 5 It can be seen that cracks appear on the grain boundaries of the 7050 aluminum alloy ingot after equalization.

[0093] As can be seen from Table 1, although the retention time of Example 12 is 12 hours shorter than that of Example 1, the SEM residual phase fraction, residual S phase DSC peak area and average grain size of Example 12 are all larger than those of Example 1, but the Al3Zr number density is less than that of Example 1. It can be seen that too short a retention time is not conducive to the elimination of the S phase. The SEM residual phase fraction, residual S phase DSC peak area, average grain size and average grain size of Example 1, Example 13 and Example 14 are all similar, indicating that appropriately shortening the holding time is helpful to improve the efficiency of homogenization heat treatment. The holding time of step S1 in Comparative Example 1 is 6 hours, and the holding time of step S2 in Comparative Example 2 is 6 hours, but the SEM residual phase fraction, residual S phase DSC peak area, average grain size and average grain size of Example 1, Comparative Example 1 and Comparative Example 2 are all similar, indicating that step S1 and step S2 do not need to be kept warm and can reach the same level as the warming. Although the homogenization heat treatment conditions of Comparative Example 5 are the same as those of Example 1, Comparative Example 5 uses a 7055 aluminum alloy ingot. The SEM residual phase fraction and the residual S phase DSC peak area of ​​Comparative Example 5 are much higher than those of Example 1. It can be seen that the homogenization heat treatment method of the present application has good adaptability to the 7050 aluminum alloy ingot.

[0094] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0095] The present application completes two important second phase evolution processes of the soaking treatment of the 7050 aluminum alloy ingot by controlling the average heating rate and temperature of step S1 and step S2, namely, completing the full precipitation of nano-dispersed phase Al3Zr particles and completing the complete transformation of the low-melting point non-equilibrium eutectic phase T phase (AlZnMgCu phase) into a high-melting point S phase (Al2CuMg phase), and no insulation is performed in step S1 and step S2 of the present application, which greatly reduces the soaking treatment time of the 7050 aluminum alloy ingot; step S3 can effectively eliminate the high-melting point S phase by controlling the average heating rate, temperature and insulation time, complete the complete dissolution of soluble coarse compounds in the entire 7050 aluminum alloy ingot, and the 7050 aluminum alloy ingot does not suffer from overburning. The homogenization heat treatment method of the present application is highly compatible with 7050 aluminum alloy ingots. The method can not only promote the precipitation of Al3Zr dispersed phase of 7050 alloy and regulate the content of recrystallized structure of final alloy plate, but also effectively eliminate the casting structure of 7050 aluminum alloy ingots and improve the comprehensive performance of aluminum materials. In addition, the method has simple process operation, short time consumption, low energy consumption and high efficiency.

[0096] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A homogenization heat treatment method for 7050 aluminum alloy ingots, characterized in that: The homogenization heat treatment method comprises: Step S1, performing a first heating of the 7050 aluminum alloy ingot, wherein the average rate of the first heating is 44.0-57.8° C. / h, and the temperature of the hot end of the 7050 aluminum alloy ingot is maintained after the temperature is raised to 395-400° C., and the first heating is terminated after the temperature of the cold end of the 7050 aluminum alloy ingot is raised to 395-400° C.; Step S2, continuing to heat the 7050 aluminum alloy ingot for a second time, wherein the average rate of the second heating is 3.8-4.9° C. / h, and maintaining the temperature of the hot end after the temperature is heated to 465-470° C., and ending the second heating after the temperature of the cold end is heated to 465-470° C.; Step S3, continuing to heat the 7050 aluminum alloy ingot for the third time, the average rate of the third heating is 1.3-6.7°C / h, maintaining the temperature of the hot end after the temperature is heated to 475-480°C, and sequentially performing insulation and cooling treatment after the cold end is heated to 475-480°C to obtain a 7050 aluminum alloy ingot after homogenization heat treatment, wherein the insulation time is 8-20h.

2. The homogenization heat treatment method according to claim 1, characterized in that: In the step S1, the average rate of the first heating is 46.8-53.6°C / h.

3. The homogenization heat treatment method according to claim 1 or 2, characterized in that: In the step S2, the average rate of the second heating is 4.1-4.6°C / h.

4. The homogenization heat treatment method according to any one of claims 1 to 3, characterized in that: In the step S3, the average rate of the third heating is 1.5-4.0°C / h; and / or the insulation time is 10-15h.

5. The homogenization heat treatment method according to any one of claims 1 to 4, characterized in that: The first heating, the second heating and the third heating are carried out in the same pusher-type heating furnace, and the 7050 aluminum alloy ingot is heated by introducing furnace gas into the pusher-type heating furnace; preferably, in step S1, the temperature of the furnace gas is set to 420-430°C to perform the first heating on the 7050 aluminum alloy ingot, and when the hot end is heated to 395-400°C, the temperature of the furnace gas is adjusted to 395-400°C to maintain the temperature of the hot end, and the cold end is heated to 395-400°C.

6. The homogenization heat treatment method according to claim 5, characterized in that: In the step S2, the temperature of the furnace gas is set to 475°C to perform the second heating of the 7050 aluminum alloy ingot. When the hot end is heated to 465-470°C, the temperature of the furnace gas is adjusted to 465-470°C to maintain the temperature of the hot end, and the cold end is heated to 465-470°C.

7. The homogenization heat treatment method according to claim 5 or 6, characterized in that: In the step S3, the temperature of the furnace gas is set to 482-485°C to perform the third heating of the 7050 aluminum alloy ingot, and when the hot end is heated to 475-480°C, the temperature of the furnace gas is adjusted to 475-480°C to maintain the temperature of the hot end, and the cold end is heated to 475-480°C before the insulation is performed.

8. The homogenization heat treatment method according to any one of claims 5 to 7, characterized in that: The furnace gas is selected from any one or more of air, nitrogen and argon.

9. The homogenization heat treatment method according to any one of claims 1 to 8, characterized in that: The cooling process is air cooling or atomization cooling.

10. The homogenization heat treatment method according to any one of claims 1 to 9, characterized in that: The total duration from the first heating in step S1 to the end of the heat preservation in step S3 does not exceed 55 hours.

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