Forging and heat treatment process of a 7050 aluminum alloy large ring

Abstract

A forging and heat treatment process for large 7050 aluminum alloy rings, the steps of which are: S1. ingot size design; S2. ingot heating; S3. tool and die preheating; S4. ingot reforging; S5. re-furnace insulation; S6. punching; S7. re-furnace insulation; S8. rack hole expansion; S9. re-furnace insulation; S10. ring rolling; S11. machining; S12. solution treatment; S13. cold deformation; S14 aging treatment; S15 re-machining. The present invention provides a full-process forming and heat treatment process scheme for large 7050 aluminum alloy rings, fully re-forges the ingot through a multi-directional forging process, breaks up the residual crystalline phase in the cast structure, and gradually increases the solution temperature and prolongs the solution time to reduce the undissolved crystalline phase and improve the degree of solution through multi-stage intensive solution. The morphology and distribution of the intracrystalline and grain boundary precipitation phases are regulated by double-stage aging, so that the product has both high strength and high stress corrosion resistance.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy plastic forming and heat treatment, and in particular to a forging and heat treatment process of a 7050 aluminum alloy large ring. Background Art

[0002] Large rings are widely used in heavy machinery, aerospace, energy and other fields. In the aerospace field, large rings are mainly made of 2A14 and 2219 aluminum alloys, but the strength of 2XXX aluminum alloys is lower than that of 7XXX aluminum alloys, which can no longer meet the service requirements of special products. Therefore, 7XXX aluminum alloys are the focus of current aerospace research. As super-hard aluminum, 7XXX series aluminum alloys have the advantages of high specific strength, high yield strength ratio, and good stress corrosion resistance. Among them, 7050 aluminum alloy has higher comprehensive performance and is mainly used to manufacture components that bear high loads.

[0003] Large rings are the main load-bearing components in the tank structure of aerospace vehicle. They are subjected to multiple forces such as radial pressure, axial pressure and bending moment during service. The stress state is complex and the comprehensive performance requirements are very high. The manufacture of large 7050 aluminum alloy rings is the key technology in the development of aerospace vehicle tanks. However, there is currently little research and manufacturing of large 7050 aluminum alloy rings in China, and there is no mature and stable deformation and heat treatment process for reference. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a forging and heat treatment process for a large 7050 aluminum alloy ring. The product manufactured by the process has uniform structure and high comprehensive performance.

[0005] The technical solution adopted by the present invention is:

[0006] A forging and heat treatment process for a large 7050 aluminum alloy ring, comprising the following steps:

[0007] S1. Ingot size design: The raw material is 7050 aluminum alloy semi-continuous ingot, and the ingot size is designed according to the part size, requiring the height-to-diameter ratio L / D = 2 to 2.5;

[0008] S2. Ingot heating: The 7050 aluminum alloy ingot is heated by an electric furnace, loaded into the furnace at room temperature, and heated to 430±5℃ with the furnace, with a thermal insulation coefficient of 2.2~3min / mm;

[0009] S3. Preheating of tools and molds: Heat the upper and lower hammer anvils in a heating furnace and keep them at 250°C for 6 to 10 hours. Apply lubricant after installation.

[0010] S4. Ingot forging: The ingot is forged by three-upsetting and three-drawing multi-directional forging, that is, upsetting deformation is performed once in three directions perpendicular to each other, and then the last upsetting deformation is performed along the axial direction of the ingot. After upsetting, a cake blank is obtained, and the blank height is 120 to 500 mm;

[0011] S5. Return to the furnace for heat preservation: keep the dough at 430±5℃ for 4-6h;

[0012] S6. Punching: Preheat and lubricate the punch and place it in the middle of the dough. Press down slowly in multiple times. Apply lubricant after pulling out the punch and before pressing down each time. The final thickness of the dough is 100-150mm before final punching.

[0013] S7. Return to the furnace for heat preservation again: keep the dough at 430±5℃ for 4 to 6h;

[0014] S8. Hole expansion: Hole expansion and flattening of the punched blank to prepare a ring blank;

[0015] S9. Return to the furnace for heat preservation again: keep the cake-shaped blank at 430±5℃ for 4 to 6 hours;

[0016] S10. Ring rolling: preheat the rolls before rolling, keep them at 250℃ for 3-5h, rotate the main rolls of the ring rolling mill at 0.5-0.6m / s, grow at a diameter growth rate of 2-3mm / s, monitor the material temperature during the ring rolling process to ensure that the final forging temperature is not less than 380℃;

[0017] S11. Machining: Surface processing of the ring after ring rolling, especially the upper and lower end faces, to ensure that there is no folding damage on the end face and the inner and outer circular surfaces.

[0018] S12. Solution treatment: The rings are solution treated by graded solution treatment. The parts are put into the furnace at the required temperature. When the furnace temperature reaches 465°C, the timing starts. The holding time is the effective size × (1.6-1.8) min. The furnace temperature is then raised to 475°C and kept at this temperature for 0.6-0.7 min. Finally, the furnace temperature is raised to 480°C and kept at this temperature for 0.6-0.7 min. The parts should be cooled in water for no less than 20 min after being taken out of the furnace and quenched.

[0019] S13. Cold deformation: After the parts are taken out of the quenching tank, they are cold forged in time, and cold pressed and deformed in the height direction of the ring. The deformation is controlled within 2-3%;

[0020] S14 aging treatment: The parts are aged in time after cold forging. The rings are aged by double-stage aging. The temperature rises with the furnace. The rings are kept at 121℃ for 4 to 6 hours, and then kept at 176℃ for 4 to 6 hours. The rings are air-cooled after being taken out of the furnace.

[0021] S15 Re-machining: Machining the aged ring to the target delivery size.

[0022] In the step S4, after three upsetting and three drawing, the length direction after the last drawing is ensured to be the height direction of the original ingot, and the upsetting deformation amount in the process is ensured to be 55-65%, and the drawing deformation amount is ensured to be 40-50%.

[0023] During the ingot casting and forging process in step S4, the material temperature is monitored in real time to ensure that the final forging temperature is not lower than 380°C.

[0024] The temperature of the blank after the punching step in step S6 is not less than 380°C.

[0025] During the hole expansion process of the rack in step S8, the material temperature is monitored in real time to ensure that the final forging temperature is not lower than 380°C.

[0026] In the step S10, when the temperature during the ring rolling process is close to 400° C., the diameter growth rate is increased, and when the temperature during the rolling process is close to 440° C., the diameter growth rate is reduced.

[0027] The S13 cold deformation process is followed by timely aging, and the interval between the cold deformation and aging processes is within 30 minutes.

[0028] Beneficial effects of the invention: The invention provides a full-process forming and heat treatment process for large 7050 aluminum alloy rings with a diameter of 5m. The ingot is fully forged through a multi-directional forging process to break the residual crystalline phase in the cast structure. Through multi-stage strengthening solid solution, the solid solution temperature is gradually increased, the solid solution time is extended to reduce the undissolved crystalline phase and improve the degree of solid solution. The morphology and distribution of the precipitation phases in the grains and grain boundaries are regulated by double-stage aging, so that the product has both high strength and high stress corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a metallographic photograph of the 7050 aluminum alloy large ring of the present invention magnified 100 times.

[0030] Figure 2 This is a metallographic photograph of the 7050 aluminum alloy large ring of the present invention magnified 500 times. DETAILED DESCRIPTION

[0031] The invention relates to a forging and heat treatment process of a 7050 aluminum alloy large ring, and manufactures a 5-meter-class 7050 aluminum alloy large ring with uniform structure and high comprehensive performance by multi-directional forging, multi-stage solid solution, double-stage aging and the like.

[0032] Example 1

[0033] For a 7050 aluminum alloy 5-meter ring in a certain space vehicle, the part size is Φ5030×Φ4984×80mm. Considering factors such as process consumption, machining allowance, and sampling ring, the forging size is designed to be Φ5070×Φ4885×105mm.

[0034] S1. Ingot size design: The raw material is 7050 aluminum alloy semi-continuous ingot, and the ingot size is designed to be Φ580×1230 according to the part size;

[0035] S2. Ingot heating: The 7050 aluminum alloy ingot is heated by an electric furnace, loaded into the furnace at room temperature, and heated to 430±5°C with the furnace, and the holding time is 580×2.5min / mm=1450min;

[0036] S3. Preheating of tools and molds: Heat the upper and lower hammer anvils in a heating furnace, keep them at 250°C for 8 hours, and apply lubricant after installation;

[0037] S4. Ingot reforging: The ingot is reforged by three-upsetting and three-drawing multi-directional forging. First, the ingot is upset to H=500mm along the Z direction, then drawn to 540×540×1115mm along the X direction, then upset to H=500mm along the X direction, then drawn to 540×540×1115mm along the Y direction, then upset to H=500mm along the Y direction, then drawn to 540×540×1115mm along the Z direction. After three upsetting and three drawing, the billet axially returns to the Z direction of the original ingot, and then upset to H=200mm along the Z direction. During the reforging process, the material temperature is monitored in real time to ensure that the final forging temperature is not lower than 380°C.

[0038] S5. Return to the furnace and keep warm: keep the cake-shaped blank at 430±5℃ for 5h;

[0039] S6. Punching: Preheat and lubricate the punch and place it in the middle of the billet. Press down slowly in multiple times. Apply lubricant after pulling out the punch and before pressing down each time. The final thickness of the skin is 120mm. Perform the final punching to ensure that the billet temperature after punching is not lower than 380℃.

[0040] S7. Return to the furnace and keep warm: keep the cake-shaped blank at 430±5℃ for 5h;

[0041] S8. Hole expansion: Hole expansion and flattening of the punched blank to prepare a ring blank with a size of Φ2200×Φ1740×205mm. During the expansion process, the material temperature is monitored in real time to ensure that the final forging temperature is not less than 380℃;

[0042] S9. Return to the furnace for heat preservation again: keep the cake-shaped blank at 430±5℃ for 5h;

[0043] S10. Ring rolling: preheat the rollers before rolling and keep them at 250℃ for 5h. The main roller speed of the ring rolling mill is 0.6m / s, the diameter growth rate is 2.5mm / s, and the ring is rolled to Φ5090×Φ4840×150mm. During the ring rolling process, the material temperature is monitored to ensure that the final forging temperature is not lower than 380℃. When the temperature approaches 400℃ during the rolling process, the diameter growth rate is increased to 3mm / s. When the temperature approaches 440℃ during the rolling process, the diameter growth rate is reduced to 2mm / s.

[0044] S11. Machining: Surface processing is performed on the rings after ring rolling, especially on the upper and lower end faces, to ensure that there are no folding damage on the end faces and the inner and outer circular surfaces, and the rings are processed to Φ5090×Φ4840×130mm.

[0045] S12. Solution treatment: The rings are treated by graded solution treatment. The parts are put into the furnace at the right temperature. When the furnace temperature reaches 465℃, the timing starts and the temperature is kept for 220 minutes. Then the furnace temperature is raised to 475℃ and kept for 80 minutes. Finally, the furnace temperature is raised to 480℃ and kept for 80 minutes. The cooling time in water after the parts are taken out of the furnace for quenching is not less than 20 minutes.

[0046] S13. Cold deformation: After the parts are taken out of the quenching tank, they are cold forged in time (the process interval is controlled within 30 minutes), and cold pressed in the height direction of the ring, and the deformation is controlled within 3 to 4.5 mm.

[0047] S14. Aging treatment: The parts are aged in time after cold forging, and the process interval is controlled within 30 minutes. The rings are aged by double-stage aging, and the temperature rises with the furnace. The rings are kept at 121℃ for 6 hours, and then kept at 176℃ for 4 hours. The rings are air-cooled after leaving the furnace.

[0048] S15. Machining: The ring is machined to the target delivery size of Φ5070×Φ4885×105mm.

[0049] After testing, the microstructure of a 5m ring made by forging and heat treatment of a 7050 aluminum alloy large ring is as follows Figure 1 The mechanical properties are shown in Table 1.

[0050] Table 1

[0051]

[0052]

[0053] Depend on Figure 1 and Figure 2It can be seen that the 7050 aluminum alloy large ring treated by this process has uniform structure, fine grains, and a grain size of about 10 to 20 μm. From Table 1, it can be seen that the mechanical properties of the parts are relatively high, with a tangential strength of 600 MPa and an elongation of 13%; a tangential strength of 546 MPa and an elongation of 7.8%; a tangential strength of 580 MPa and an elongation of 6%, and there is no low performance point in each direction.

[0054] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A forging and heat treatment process for a large 7050 aluminum alloy ring, characterized in that the steps are: S1. Ingot size design: The raw material is 7050 aluminum alloy semi-continuous ingot, and the ingot size is designed according to the part size, requiring the height-to-diameter ratio L / D = 2 to 2.5; S2. Ingot heating: The 7050 aluminum alloy ingot is heated by an electric furnace, loaded into the furnace at room temperature, and heated to 430±5℃ with the furnace, with a thermal insulation coefficient of 2.2~3min / mm; S3. Preheating of tools and molds: Heat the upper and lower hammer anvils in a heating furnace and keep them at 250°C for 6 to 10 hours. Apply lubricant after installation. S4. Ingot forging: The ingot is forged by three-upsetting and three-drawing multi-directional forging, that is, upsetting deformation is performed once in three directions perpendicular to each other, and then the last upsetting deformation is performed along the axial direction of the ingot. After upsetting, a cake blank is obtained, and the blank height is 120 to 500 mm; S5. Return to the furnace for heat preservation: keep the dough at 430±5℃ for 4-6h; S6. Punching: Preheat and lubricate the punch and place it in the middle of the dough. Press down slowly in multiple times. Apply lubricant after pulling out the punch and before pressing down each time. The final thickness of the dough is 100-150mm before final punching. S7. Return to the furnace for heat preservation again: keep the dough at 430±5℃ for 4 to 6h; S8. Hole expansion: Hole expansion and flattening of the punched blank to prepare a ring blank; S9. Return to the furnace for heat preservation again: keep the cake-shaped blank at 430±5℃ for 4 to 6 hours; S10. Ring rolling: preheat the rolls before rolling, keep them at 250℃ for 3-5h, rotate the main rolls of the ring rolling mill at 0.5-0.6m / s, grow at a diameter growth rate of 2-3mm / s, monitor the material temperature during the ring rolling process to ensure that the final forging temperature is not less than 380℃; S11. Machining: Surface processing of the ring after ring rolling, especially the upper and lower end faces, to ensure that there is no folding damage on the end face and the inner and outer circular surfaces; S12. Solution treatment: The rings are subjected to solution treatment by graded solution treatment. The rings are put into the furnace at the required temperature. When the furnace temperature reaches 465°C, the timing starts. The holding time is the effective size × (1.6-1.8) min. The furnace temperature is then raised to 475°C and held for 0.6-0.7 min. Finally, the furnace temperature is raised to 480°C and held for 0.6-0.7 min. The cooling time in water after the parts are taken out of the furnace and quenched is not less than 20 min. S13. Cold deformation: After the parts are taken out of the quenching tank, they are cold forged in time, and cold pressed and deformed in the height direction of the ring. The deformation is controlled within 2-3%; S14 aging treatment: The parts are aged in time after cold forging. The rings are aged by double-stage aging. The temperature rises with the furnace. The rings are kept at 121℃ for 4 to 6 hours, and then kept at 176℃ for 4 to 6 hours. The rings are air-cooled after being taken out of the furnace. S15 Re-machining: Machining the aged ring to the target delivery size.

2. The forging and heat treatment process of 7050 aluminum alloy large ring according to claim 1 is characterized in that: In the step S4, after three upsetting and three drawing, the length direction after the last drawing is ensured to be the height direction of the original ingot, and the upsetting deformation amount in the process is ensured to be 55-65%, and the drawing deformation amount is ensured to be 40-50%.

3. The forging and heat treatment process of 7050 aluminum alloy large ring according to claim 2 is characterized in that: During the ingot casting and forging process in step S4, the material temperature is monitored in real time to ensure that the final forging temperature is not lower than 380°C.

4. The forging and heat treatment process of 7050 aluminum alloy large ring according to claim 1, characterized in that: The temperature of the blank after the punching step in step S6 is not less than 380°C.

5. The forging and heat treatment process of 7050 aluminum alloy large ring according to claim 1, characterized in that: During the horse frame hole expansion process in step S8, the material temperature is monitored in real time to ensure that the final forging temperature is not lower than 380°C.

6. The forging and heat treatment process of 7050 aluminum alloy large ring according to claim 1, characterized in that: In the step S10, when the temperature during the ring rolling process is close to 400° C., the diameter growth rate is increased, and when the temperature during the rolling process is close to 440° C., the diameter growth rate is reduced.

7. The forging and heat treatment process of 7050 aluminum alloy large ring according to claim 1, characterized in that: The S13 cold deformation process is followed by timely aging, and the interval between the cold deformation and aging processes is within 30 minutes.

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