A heat treatment strengthening method for Al-Zn-Mg-Cu aluminum alloy plate

Abstract

A heat treatment strengthening method for Al-Zn-Mg-Cu aluminum alloy plate, the present invention relates to the field of heat treatment strengthening methods for aluminum alloy plate. The present invention is to solve the technical problem that the current industrial production is very time-consuming and it is difficult to ensure the hardness of the Al-Zn-Mg-Cu aluminum alloy plate after aging. Method: 1. Heat and keep the Al-Zn-Mg-Cu aluminum alloy ingot warm; 2. Rolling; 3. Solid solution; 4. Quenching; 5. Pre-stretching; 6. Aging treatment, the aging system is double-stage aging; 7. Sawing to obtain a finished plate. The heat treatment strengthening method of the present invention, due to the strengthening effect of low-temperature aging, and the time of the first-stage aging in the double-stage aging has a greater influence on the final peak hardness, so the first-stage aging time is reasonably controlled, and the internal particles can be rapidly coarsened by the second-stage aging, and the final Al-Zn-Mg-Cu aluminum alloy plate hardness can be close to the highest strength of single-stage peak aging. The present invention is used to prepare Al-Zn-Mg-Cu aluminum alloy plate.

Description

Technical Field

[0001] The present invention relates to the field of heat treatment strengthening method for aluminum alloy plate Background Art

[0002] Al-Zn-Mg-Cu aluminum alloy is a deformable aluminum alloy that can be heat-treated and strengthened. It relies on solid solution and precipitation strengthening. Zn and Mg play the main strengthening role. After the alloy forms a saturated solid solution, these two elements will gradually dissolve and precipitate to form second-phase strengthening particles. Due to its high strength-to-weight ratio, Al-Zn-Mg-Cu aluminum alloy is widely used in aircraft structural parts. It is used for high-stress structural parts in the automotive and machinery industries. Its high strength characteristics are also used for civilian sports equipment, military chariots and firearms that withstand high stress. The Al-Zn-Mg-Cu aluminum alloy heat treatment strengthening T6 state is carried out in the form of peak aging, but the current peak aging heat treatment strengthening method requires the plate to be aged at about 120°C for more than 20 hours after solid solution quenching to achieve the maximum hardness. Under industrial production conditions, it is also necessary to use a heat treatment furnace to heat the plate to about 120°C. The overall production process will take more than 24 hours. Therefore, industrial production is very time-consuming and it is difficult to ensure the hardness of the Al-Zn-Mg-Cu aluminum alloy plate after aging. Summary of the invention

[0003] The present invention provides a heat treatment strengthening method for Al-Zn-Mg-Cu aluminum alloy plate in order to solve the technical problem that the current industrial production is very time-consuming and it is difficult to ensure the hardness of the Al-Zn-Mg-Cu aluminum alloy plate after aging.

[0004] A heat treatment strengthening method for an Al-Zn-Mg-Cu aluminum alloy plate is specifically carried out in the following steps:

[0005] 1. Heat the Al-Zn-Mg-Cu aluminum alloy ingot to 420°C to 440°C and keep it warm for 8h to 10h;

[0006] 2. Rolling the ingot processed in step 1, controlling the rolling speed to be 1 m / s to 3 m / s, and the number of rolling passes to be ≤ 25, to obtain a rolled plate;

[0007] 3. Put the rolled plate obtained in step 2 into a roller hearth quenching furnace for solid solution, the solid solution temperature is 466°C to 482°C, after the plate metal temperature reaches the temperature, solid solution is kept for 30min to 60min;

[0008] Fourth, the plate heated by solid solution in step 3 is quenched using a roller hearth quenching furnace, and the temperature of the plate is cooled to 150°C to 200°C using the nozzle of the strong cooling part of the quenching zone, and the temperature of the plate is cooled to 60°C to 90°C using the nozzle of the weak cooling part of the quenching zone;

[0009] 5. Pre-stretch the plate processed in step 4, and control the stretching amount to 2.0% to 2.8%;

[0010] 6. Load the pre-stretched plate in step 5 into the aging heat treatment furnace for aging treatment. The aging system is a two-stage aging: in the first stage, the heat treatment furnace is set at a temperature of 120°C to 123°C for heating, and the actual temperature of the plate is monitored. When the actual temperature of the plate reaches 117°C to 126°C, it is maintained for 1h to 5h; in the second stage, the heat treatment furnace is set at a temperature of 135°C to 150°C, and when the actual temperature of the plate reaches 132°C to 153°C, it is maintained for 1h to 5h;

[0011] 7. Saw the plate after aging in step 6 to obtain a finished plate, i.e., an Al-Zn-Mg-Cu aluminum alloy plate.

[0012] According to the composition characteristics of Al-Zn-Mg-Cu aluminum alloy, the present invention proposes a special heat treatment strengthening method to improve actual production efficiency and reduce energy costs.

[0013] Beneficial effects of the present invention:

[0014] The present invention ensures the uniformity of the final rolling temperature and performance of the plate by controlling the rolling temperature, rolling speed and deformation permeability coefficient.

[0015] The solution quenching and aging process of the present invention adjusts the cooling rates of the strong cooling zone and the weak cooling zone after the plate is solutionized to ensure hardenability and realize the residual temperature to accelerate low-temperature aging.

[0016] The present invention uses pre-stretching to eliminate quenching residual stress, and simultaneously performs plastic deformation to further generate deformation heat to promote temperature increase and achieve low-temperature aging of the plate.

[0017] The double-stage aging of the present invention is different from the commonly used single-stage aging. Since the quenching residual temperature and the stretching deformation heat reduce the heating time of the plate, and the low-temperature aging accelerates the formation density of the GP zone, the GP zone can be completely precipitated by heating for 1h to 5h under the first-stage aging temperature condition, and then the high temperature is used to accelerate the precipitation of the η' phase and part of the η phase. The dual effects of shortening the heating time and shortening the double-stage aging time can shorten the total time of the aging process by more than half to less than 10 hours compared to the common single-stage aging of more than 20 hours, which greatly improves the production efficiency under industrial conditions and significantly reduces the energy consumption of equipment.

[0018] The heat treatment strengthening method of the present invention has a strengthening effect of low-temperature aging, and the time of the first-stage aging in the two-stage aging has a greater influence on the final peak hardness. Therefore, by reasonably controlling the first-stage aging time, the internal particles can be rapidly coarsened through the second-stage aging, and the final Al-Zn-Mg-Cu aluminum alloy plate hardness can be close to the maximum strength of the single-stage peak aging.

[0019] The invention is used for preparing Al-Zn-Mg-Cu aluminum alloy plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a process comparison diagram between the present invention and the conventional heat treatment strengthening method;

[0021] Figure 2 This is a comparison chart of the hardness between the present invention and the conventional heat treatment strengthening method. DETAILED DESCRIPTION

[0022] Specific implementation method 1: This implementation method is a heat treatment strengthening method of an Al-Zn-Mg-Cu aluminum alloy plate, which is specifically carried out in the following steps:

[0023] 1. Heat the Al-Zn-Mg-Cu aluminum alloy ingot to 420°C to 440°C and keep it warm for 8h to 10h;

[0024] 2. Rolling the ingot processed in step 1, controlling the rolling speed to be 1 m / s to 3 m / s, and the number of rolling passes to be ≤ 25, to obtain a rolled plate;

[0025] 3. Put the rolled plate obtained in step 2 into a roller hearth quenching furnace for solid solution, the solid solution temperature is 466°C to 482°C, after the plate metal temperature reaches the temperature, solid solution is kept for 30min to 60min;

[0026] Fourth, the plate heated by solid solution in step 3 is quenched using a roller hearth quenching furnace, and the temperature of the plate is cooled to 150°C to 200°C using the nozzle of the strong cooling part of the quenching zone, and the temperature of the plate is cooled to 60°C to 90°C using the nozzle of the weak cooling part of the quenching zone;

[0027] 5. Pre-stretch the plate processed in step 4, and control the stretching amount to 2.0% to 2.8%;

[0028] 6. Load the pre-stretched plate in step 5 into the aging heat treatment furnace for aging treatment. The aging system is a two-stage aging: in the first stage, the heat treatment furnace is set at a temperature of 120°C to 123°C for heating, and the actual temperature of the plate is monitored. When the actual temperature of the plate reaches 117°C to 126°C, it is maintained for 1h to 5h; in the second stage, the heat treatment furnace is set at a temperature of 135°C to 150°C, and when the actual temperature of the plate reaches 132°C to 153°C, it is maintained for 1h to 5h;

[0029] 7. Saw the plate after aging in step 6 to obtain a finished plate, i.e., an Al-Zn-Mg-Cu aluminum alloy plate.

[0030] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that: step 1 uses a heat treatment furnace to heat the Al-Zn-Mg-Cu aluminum alloy ingot. The rest is the same as specific embodiment 1.

[0031] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that: in step 2, the rolling deformation permeability coefficient increases with the increase of the number of passes; when the number of passes is ≥ 5, the rolling deformation permeability coefficient is > 0.5. Other aspects are the same as specific implementation method 1 or 2.

[0032] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that the temperature of the rolled plate obtained in step 2 is ≥ 390° C. The rest is the same as specific embodiments 1 to 3.

[0033] Specific implementation method 5: This implementation method is different from specific implementation methods 1 to 4 in that: Step 3 controls the solid solution temperature to 470°C to 480°C, and after the plate metal temperature reaches the temperature, the solid solution is kept warm for 40min to 50min. The rest is the same as specific implementation methods 1 to 4.

[0034] Specific implementation example 6: This implementation example is different from specific implementation examples 1 to 5 in that: in step 4, the temperature of the plate is cooled to 150° C. to 200° C. within 10 seconds using the nozzle of the strong cooling part of the quenching zone. The rest is the same as specific implementation examples 1 to 5.

[0035] Specific implementation method 7: This implementation method is different from specific implementation methods 1 to 6 in that: the plate after solid solution quenching in step 5 is pre-stretched within 1 hour. The rest is the same as specific implementation methods 1 to 6.

[0036] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the stretching amount in step 5 is controlled to be 2.2% to 2.5%. The rest is the same as specific embodiments 1 to 7.

[0037] Specific implementation method 9: This implementation method is different from specific implementation methods 1 to 8 in that: in step 6, a load thermocouple is used to monitor the actual temperature of the plate. The rest is the same as specific implementation methods 1 to 8.

[0038] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that in step 6, the pre-stretched sheet is loaded into an aging heat treatment furnace within 2 hours. The rest is the same as specific embodiments 1 to 9.

[0039] The content of the present invention is not limited to the content of the above-mentioned embodiments. The combination of one or several specific embodiments can also achieve the purpose of the invention.

[0040] Example:

[0041] This embodiment provides a heat treatment strengthening method for an Al-Zn-Mg-Cu aluminum alloy plate, which is specifically carried out in the following steps:

[0042] 1. Heat the Al-Zn-Mg-Cu aluminum alloy ingot to (425±5)℃ in a heat treatment furnace and keep it warm for 10h;

[0043] 2. Roll the ingot treated in step 1, control the rolling speed to be (1.2±0.2) m / s, the number of rolling passes to be 15, the number of rolling passes with a rolling deformation permeability coefficient greater than 0.5 to obtain a rolled plate; the temperature of the rolled plate is ≥390°C;

[0044] 3. Put the rolled plate obtained in step 2 into a roller hearth quenching furnace for solid solution, the solid solution temperature is (472±3)℃, after the plate metal temperature reaches the temperature, solid solution is kept for 40min;

[0045] 4. Use a roller-bottom quenching furnace to quench the plate heated by solid solution in step 3. Use the nozzle of the strong cooling part of the quenching zone to cool the plate temperature to (180±5)°C within 10s, and use the nozzle of the weak cooling part of the quenching zone to cool the plate temperature to (70±5)°C;

[0046] 5. Pre-stretch the plate treated in step 4 within 1 hour, and control the stretching amount to (2.4±0.2)%;

[0047] 6. Load the pre-stretched plate in step 5 into the aging heat treatment furnace within 2 hours for aging treatment. The aging system is a two-stage aging: in the first stage, the heat treatment furnace is set at a temperature of 121°C for heating, and a load thermocouple is used to monitor the actual temperature of the plate. When the actual temperature of the plate reaches 119°C, it is maintained for 3 hours; in the second stage, the heat treatment furnace is set at a temperature of 150°C, and when the actual temperature of the plate reaches 148°C, it is maintained for 4 hours;

[0048] 7. Saw the plate after aging in step 6 to obtain a finished plate, i.e., an Al-Zn-Mg-Cu aluminum alloy plate.

[0049] The heat treatment strengthening method of the present invention has a strengthening effect of low-temperature aging, and the time of the first-stage aging in the two-stage aging has a greater influence on the final peak hardness. Therefore, by reasonably controlling the first-stage aging time, the internal particles can be rapidly coarsened through the second-stage aging, and the final Al-Zn-Mg-Cu aluminum alloy plate hardness can be close to the maximum strength of the single-stage peak aging.

[0050] The hardness of the Al-Zn-Mg-Cu aluminum alloy plate obtained in this embodiment is tested to be 186.9 HV, and the hardness of the Al-Zn-Mg-Cu aluminum alloy plate obtained by the conventional heat treatment strengthening method is 187.2 HV.

Claims

1. A heat treatment strengthening method for Al-Zn-Mg-Cu aluminum alloy plate, characterized in that The method is specifically carried out in the following steps:

1. Heat the Al-Zn-Mg-Cu aluminum alloy ingot to 420°C to 440°C and keep it warm for 8h to 10h; 2. Rolling the ingot processed in step 1, controlling the rolling speed to be 1 m / s to 3 m / s, and the number of rolling passes to be ≤ 25, to obtain a rolled plate; 3. Put the rolled plate obtained in step 2 into a roller hearth quenching furnace for solid solution, the solid solution temperature is 466°C to 482°C, after the plate metal temperature reaches the temperature, solid solution is kept for 30min to 60min; Fourth, the plate heated by solid solution in step 3 is quenched using a roller hearth quenching furnace, and the temperature of the plate is cooled to 150°C to 200°C using the nozzle of the strong cooling part of the quenching zone, and the temperature of the plate is cooled to 60°C to 90°C using the nozzle of the weak cooling part of the quenching zone; 5. Pre-stretch the plate processed in step 4, and control the stretching amount to 2.0% to 2.8%; 6. Load the pre-stretched plate in step 5 into the aging heat treatment furnace for aging treatment. The aging system is a two-stage aging: in the first stage, the heat treatment furnace is set at a temperature of 120°C to 123°C for heating, and the actual temperature of the plate is monitored. When the actual temperature of the plate reaches 117°C to 126°C, it is maintained for 1h to 5h; in the second stage, the heat treatment furnace is set at a temperature of 135°C to 150°C, and when the actual temperature of the plate reaches 132°C to 153°C, it is maintained for 1h to 5h; 7. Saw the plate after aging in step 6 to obtain a finished plate, i.e., an Al-Zn-Mg-Cu aluminum alloy plate.

2. The heat treatment strengthening method of the Al-Zn-Mg-Cu aluminum alloy sheet according to claim 1, characterized in that Step 1: Heat the Al-Zn-Mg-Cu aluminum alloy ingot in a heat treatment furnace.

3. The heat treatment strengthening method of the Al-Zn-Mg-Cu aluminum alloy sheet according to claim 1, characterized in that Step 2: The rolling deformation permeability coefficient increases with the number of passes; when the number of passes is ≥5, the rolling deformation permeability coefficient is >0.

5.

4. The heat treatment strengthening method of the Al-Zn-Mg-Cu aluminum alloy sheet according to claim 1, characterized in that The temperature of the rolled plate obtained in step 2 is ≥390°C.

5. The heat treatment strengthening method of the Al-Zn-Mg-Cu aluminum alloy sheet according to claim 1, characterized in that Step three: Control the solution temperature to 470°C to 480°C. After the metal temperature of the plate reaches the temperature, the solution is kept warm for 40min to 50min.

6. The heat treatment strengthening method of the Al-Zn-Mg-Cu aluminum alloy sheet according to claim 1, characterized in that Step 4: Use the nozzle of the strong cooling part of the quenching zone to cool the plate temperature to 150℃~200℃ within 10s.

7. The heat treatment strengthening method of the Al-Zn-Mg-Cu aluminum alloy sheet according to claim 1, characterized in that Step 5: The plate after solution quenching is pre-stretched within 1 hour.

8. The heat treatment strengthening method of the Al-Zn-Mg-Cu aluminum alloy sheet according to claim 1, characterized in that Step 5: Control the stretching amount to 2.2% to 2.5%.

9. The heat treatment strengthening method of the Al-Zn-Mg-Cu aluminum alloy sheet according to claim 1, characterized in that Step 6: Use a load thermocouple to monitor the actual temperature of the plate.

10. The heat treatment strengthening method of the Al-Zn-Mg-Cu aluminum alloy sheet according to claim 1, characterized in that Step 6: Load the pre-stretched sheet into the aging heat treatment furnace within 2 hours.

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