Large-size high-strength 2195 aluminum-lithium alloy forged ring and preparation method thereof

Abstract

The invention discloses a large-size high-strength 2195 aluminum-lithium alloy forged ring and a preparation method thereof. The preparation method comprises the following steps: selecting a cast ingot with the size ratio of height to diameter of 3.5-4.2 as a forged ring raw material; a forging ring raw material is heated and subjected to heat preservation, upsetting and drawing-out are conducted on the forging ring raw material once in three directions on pressure equipment, double-drum rounding is conducted after each time of upsetting, four-direction pressing and eight-direction reversing are conducted after drawing-out, finally one time of axial upsetting is conducted, and punching is conducted after the last time of axial upsetting; broaching the forged ring raw material after punching, and performing radial ring rolling to obtain a ring blank; heating the ring blank, and immediately immersing the ring blank in water after heating; after solution treatment, axial cold pressing and radial cold bulging are carried out, the radial cold bulging is divided into three stages, the ring blank is rotated by a certain angle along a ring mandrel after radial cold bulging in each stage, and uniform deformation is guaranteed; the method has the advantages that anisotropy is reduced, the residual stress of the forged ring is small, and the percent of pass is high.

Description

Technical Field

[0001] The present invention relates to the field of aerospace hot forming technology, and in particular to a large-size high-strength 2195 aluminum-lithium alloy forging ring and a preparation method thereof. Background Art

[0002] As a lightweight and high-strength aluminum alloy material, 2195 aluminum-lithium alloy has developed to the fourth generation. As the fourth-generation aluminum-lithium alloy, 2195 aluminum-lithium alloy material has the characteristics of high strength, low density and good welding performance. Using 2195 aluminum-lithium alloy as the structural material of the launch vehicle tank can increase the strength by 30%, reduce the density by 5%, and increase the thrust-to-weight ratio by more than 15%. In particular, the transition ring connecting the tank and the bottom of the tank needs to use a material with high strength and good welding performance, thereby replacing the traditional 2219 aluminum alloy material to further improve the rocket's carrying efficiency.

[0003] In the related art, large-sized forging rings produced using 2195 aluminum-lithium alloy have problems such as severe anisotropy, large residual stress in the forging rings, and serious internal defects in the forging rings.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0005] The technical task of the present invention is to provide a large-size high-strength 2195 aluminum-lithium alloy forging ring and a preparation method thereof in view of the above shortcomings. By selecting ingots of specific specifications, adjusting and controlling the forging rate and setting a double-drum rolling operation, the forging ring raw material can be made without cracking, instability, or folding defects; by controlling the deformation of upsetting, drawing, hole expansion and ring rolling, the anisotropy of the forging ring can be reduced and the comprehensive mechanical properties of the forging ring can be improved; through axial-diameter bidirectional cold deformation, the residual stress of the forging ring can be significantly reduced, thereby solving the above problems.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] According to one aspect of the present application, a method for preparing a large-size high-strength 2195 aluminum-lithium alloy forging ring is provided, comprising the following steps: S100, selection of forging ring raw material: selecting an ingot with a height-to-diameter ratio of 3.5 to 4.2 as the forging ring raw material; S200, multi-directional forging and punching: heating and heat-insulating the forging ring raw material, and upsetting and stretching the forging ring raw material in three directions on a pressure device once, performing double-drum rounding after each upsetting, pressing four squares and inverting eight squares after stretching, and finally performing an axial upsetting again, and punching after the last axial upsetting; S300, hole expansion and radial ring rolling : Expand the forging ring raw material after punching, and perform radial ring rolling in a way that the axial height remains unchanged, and the full circle after the ring rolling is not less than 2 turns to obtain a ring blank; S400, solid solution: heat the ring blank, and immediately immerse the heated ring blank in water after heating; S500, axial-diameter bidirectional cold deformation: perform axial cold pressing and radial cold expansion on a pressure equipment within 4 hours after solid solution, and the radial cold expansion is divided into three stages. After each stage of radial cold expansion, the ring blank is rotated along the ring core axis by a certain angle to ensure uniform deformation; S600, aging treatment; S700, flaw detection and physical and chemical testing.

[0008] In some embodiments, in step S100, the flaw detection requirements of the forging ring material meet the requirements of Class A in standard YS / T1188, and the forging ring material is not allowed to have continuous point defects larger than φ0.8 and a structure with a grain size larger than Grade 4.

[0009] In some embodiments, in step S200, the heating temperature of the forging ring raw material is 480-500°C, the holding time is 2.5-3.5 min / mm×the diameter of the ingot raw material, the forging temperature during the upsetting and drawing process is 350-500°C, the upsetting rate is ≤5 mm / s, the height-to-diameter ratio of the ingot after each upsetting is 1.5, the drawing rate is 15-25 mm / s, and the ratio of the cross-sectional side length to the length of the ingot after three drawing processes is 2.4-2.8.

[0010] In some embodiments, in step 300, the ratio of the outer diameter after hole expansion to the outer diameter after ring rolling is 0.70-0.74, the ring rolling makes the growth rate of the outer diameter ≤10 mm / s, the temperature of the ring rolling is 260°C-300°C, and the material temperature is monitored in real time during the ring rolling process. If the material temperature exceeds 290°C, the growth rate of the ring rolling is reduced in time.

[0011] In some embodiments, in step S400, the final temperature of the heating is 528-535°C, and the water temperature is >35°C.

[0012] In some embodiments, in step 500, the total deformation of the axial cold pressing is less than 3%, and the total deformation of the radial cold bulging is not less than 2.2% of the outer diameter; the ratio of the bulging amounts in the three stages of the radial cold bulging is 5:3:2.

[0013] In some embodiments, in step 500, the rotation angle is 22.5°.

[0014] In some embodiments, in step S600, the aging temperature is 150-160° C., and the aging holding time is 25-40 hours.

[0015] In some embodiments, in step S700, the requirements of the flaw detection meet the A-level requirements of the GJB 1580A standard, and the physical and chemical testing of the forged ring is performed after the flaw detection is qualified, and the indicators of the physical and chemical testing are tensile strength, yield strength and elongation.

[0016] According to another aspect of the present application, a large-size high-strength 2195 aluminum-lithium alloy forging ring is provided, which is prepared by the above method. The forging ring is Φ3000mm grade and T852 state; the circumferential physical and chemical properties of the forging ring at room temperature are tensile strength ≥540MPa, yield strength ≥480MPa, and elongation ≥6%. After radial cold expansion, the roundness of the forging ring is ≤6mm and the flatness is <2mm.

[0017] Compared with the prior art, the advantages and positive effects of the present invention are:

[0018] 1. This application can ensure that the forging ring raw material does not crack, lose stability, or have folding defects by selecting ingots of specific specifications, adjusting and controlling the forging rate, and setting up a double-drum rounding operation;

[0019] 2. This application controls the deformation amount of upsetting, drawing, hole expansion and ring rolling, while ensuring sufficient deformation in three directions, further controlling the deformation uniformity, thereby reducing the anisotropy of the forging ring and improving the comprehensive mechanical properties of the forging ring;

[0020] 3. This application adopts the radial ring rolling method of low temperature, slow speed and constant axial height to prevent the grains from growing due to temperature rise, and at the same time, the internal structure of the forging ring further accumulates deformation energy storage to ensure the subsequent solid solution recrystallization grain refinement;

[0021] 4. The present application can significantly reduce the residual stress of the forging ring through axial-diameter bidirectional cold deformation. Among them, radial cold expansion can improve the dimensional accuracy of the forging ring after solid solution, which solves the current problems of severe anisotropy of forging ring performance, inability of internal structure flaw detection to meet Class A requirements, and poor dimensional accuracy of forging ring, and has the advantage of improved pass rate.

[0022] 5. The forging ring with a diameter of 3000 mm or above and in T852 state prepared by the method of the present application has the following physical and chemical properties: tensile strength ≥540 MPa, yield strength ≥480 MPa, elongation ≥6%, and the roundness of the forging ring after radial cold expansion is ≤6 mm and the flatness is <2 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A schematic diagram of a method flow of an embodiment of the present application;

[0025] Figure 2 Schematic diagram of upsetting to produce double drums and rolling to eliminate double drums in the embodiment of the present application, wherein a is a schematic diagram of upsetting to produce double drums, and b is a schematic diagram of rolling to eliminate double drums;

[0026] Figure 3 It is a schematic top view of a radial cold expansion device in an embodiment of the present application;

[0027] Figure 4 This is a grain optical structure photo of the forging ring in the embodiment of the present application;

[0028] In the figure: 100, upper anvil surface; 200, lower anvil surface; 300, ingot; 400, driving device of cold bulging equipment; 500, radial cold bulging die; 600, forging ring. DETAILED DESCRIPTION

[0029] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0030] like Figure 1 As shown, a method for preparing a large-size high-strength 2195 aluminum-lithium alloy forging ring comprises the following steps:

[0031] S100. Selection of forging ring raw materials: Ingots with a height-to-diameter ratio of 3.5 to 4.2 are selected as forging ring raw materials. The flaw detection requirements of forging ring raw materials shall comply with the A-level requirements of standard YS / T 1188, and the forging ring raw materials are not allowed to have continuous point defects larger than φ0.8 and a grain size of 4 or above.

[0032] S200, multi-directional forging and punching: heat the forging ring raw material to 480-500℃ and keep it warm for 2.5-3.5min / mm×D (D is the diameter of the ingot raw material, in mm), upset and stretch the forging ring raw material in three directions (i.e., X-axis, Y-axis and Z-axis) on the pressure equipment, perform double drum rounding after each upsetting, press the square and invert the eight after stretching, and finally perform axial upsetting again, and punch after the last axial upsetting. Among them, the forging temperature during upsetting and stretching is 350℃~500℃, the upsetting rate is ≤5mm / s, the height-to-diameter ratio after each upsetting is 1.5, the stretching rate is 15-25mm / s, and the ratio of the side length to the length of the ingot section after three stretchings is 2.4-2.8.

[0033] It can be understood that there are four upsetting and three drawing in multi-directional forging; double-drum rounding is when the ingot is axially upset to form a double-drum state (such as Figure 2 a), and double drum rounding operation is performed in each direction (as shown in Figure 2 b) and adjusting and controlling the forging rate can ensure that the forging ring raw material does not crack, become unstable, or have folding defects.

[0034] Specifically, the upsetting is to press down the upper anvil surface 100, and the axial height of the ingot is reduced by moving the upper anvil surface 100 toward the lower anvil surface 200. During the upsetting process, the ingot 300 will form a double-drum state. After upsetting in each direction, the ingot is rotated 90° to make the double-drum surface contact the upper anvil surface 100 and the lower anvil surface 200, and then the upper anvil surface 100 is pressed down multiple times, and at the same time, the ingot 300 is rotated with the center axis of the ingot 300 as the rotation axis to achieve the effect of rounding the double drum.

[0035] S300, hole expansion and radial ring rolling: the forging ring raw material after punching is expanded, and radial ring rolling is performed at low temperature, slow speed and constant axial height, the ratio of the outer diameter after hole expansion to the outer diameter after ring rolling is 0.70-0.74, the ring rolling makes the outer diameter growth rate ≤10mm / s, the ring rolling temperature is 260℃-300℃, and the ring rolling is completed for not less than 2 turns to obtain a ring blank; wherein, the material temperature is monitored in real time during the ring rolling process, and if the material temperature exceeds 290℃, the ring rolling rate is reduced in time.

[0036] It can be understood that the radial ring rolling method with low temperature, slow speed and constant axial height can prevent the grains from growing due to temperature rise, and at the same time, the internal structure of the forging ring can further accumulate deformation energy storage, ensuring the subsequent solid solution recrystallization grain refinement, and the roundness after radial ring rolling is ≤1.5‰.

[0037] S400, solid solution: heat the ring blank to 528-535℃, and immediately immerse the heated ring blank in water after reaching the temperature. The water temperature is >35℃, and the roundness after solid solution is <7‰.

[0038] S500, axial-diameter bidirectional cold deformation: Axial cold pressing and radial cold bulging are carried out on the pressure equipment within 4 hours after solutionizing. The total deformation of axial cold pressing is less than 3% (the percentage of the height of the forged ring after solutionizing), and the total deformation of radial cold bulging is not less than 2.2% of the outer diameter (the total deformation here refers to the radial cold deformation); radial cold bulging is divided into three stages, and the deformation ratio of the three stages is 5:3:2. After each stage of radial cold bulging, the ring blank after radial cold bulging in the previous stage is rotated 22.5° along the ring core axis to ensure uniform deformation; the roundness of the axial-diameter bidirectional cold deformation forging ring is ≤2‰.

[0039] That is to say, 3% refers to the percentage of the height of the forging ring after axial cold pressing compared to the height of the forging ring after solutionizing and before cold pressing), and 2.2% refers to the change in the outer contour diameter of the forging ring after radial cold expansion compared to the outer contour diameter of the forging ring after axial cold pressing and before cold expansion.

[0040] It can be understood that the residual stress of the forging ring can be significantly reduced through axial-diameter bidirectional cold deformation. Among them, radial cold expansion can improve the dimensional accuracy of the forging ring after solid solution, which solves the current problems of severe anisotropy of forging ring performance, inability of internal structure flaw detection to meet Class A requirements, and poor dimensional accuracy of forging rings, and has the advantage of improved pass rate.

[0041] Specifically, Figure 3 As shown, the radial cold bulging is that the radial cold bulging die 500 applies pressure to the outside of the forging ring 600 under the drive of the driving device 400 of the cold deformation equipment, thereby achieving the effect of radial cold bulging.

[0042] S600, aging treatment: The aging temperature is 150-160°C, and the aging insulation time is 25-40h.

[0043] S700, flaw detection and physical and chemical testing: The requirements for flaw detection meet the A-level requirements of GJB 1580A standard. After the flaw detection is qualified, the forging ring is subjected to physical and chemical testing, among which the physical and chemical testing indicators are tensile strength (Rm), yield strength (R p0.2 ) and elongation (A).

[0044] Specifically, the physical and chemical properties of forged rings (Ø3000mm and above, T852 state) at room temperature are R m ≥540MPa, R p0.2 ≥480MPa, A≥6%, the roundness of the forged ring after radial cold expansion is ≤6mm, and the flatness is <2mm.

[0045] Embodiment 1:

[0046] The following takes the Φ3m grade forging ring of 2195 forging ring with the specification size of Φ3410×Φ3290×255mm as an example.

[0047] S100, use Ф480×2010mm ingot, polish the surface of the ingot and then perform Class A flaw detection in accordance with YS / T 1188 standard, and it is required that no continuous point defects larger than φ0.8 and no organization with grain size larger than Class 4 are allowed.

[0048] S200, heat the ingot to 480-500℃ and keep it warm for 25h, upset it on a press, forging temperature 350℃-500℃; upsetting is divided into 4 times, upsetting rate ≤5mm / s, upsetting height of each time is 600±10mm, double drum rolling is performed for each upsetting, drawing rate 15-20mm / s, drawing, pressing four squares and then inverting eight squares, the cross-sectional size of the drawn and pressed four squares is 520±10×520±10mm, reverse upsetting and upsetting 3 times and then upsetting and punching again axially.

[0049] S300, use a horse frame to expand the hole to a size of Ф2625±10×Φ2325±10×290±5mm, to ensure that at least 35% to 40% deformation is left in the subsequent ring rolling; after expanding the hole, use a 630t axial-radial ring rolling mill to form the ring. The use of a highly constant rolling method can ensure that the equivalent strain distribution inside the ring is relatively uniform. The ring rolling temperature is 285℃~295℃, the ring growth rate is 5~10mm / s, and the contact thermocouple measures the material temperature. If the temperature of the ring billet surges, it is necessary to slow down the rolling to cool it down or use liquid spray cooling measures to achieve the cooling effect. The final stage of ring rolling requires 2 to 3 full circles to ensure that the roundness of the forged ring is within 4mm after the rolling. After ring rolling, the ring billet is obtained with a size of Ф3355±5×Φ3125±5×290±3mm.

[0050] S400, machine the surface of the ring blank, then carry out solid solution, heat the solution to 530℃, keep it warm for 4-5h, put it into water immediately after solid solution, the water temperature is 30℃, and the roundness after quenching is 21mm.

[0051] S500, after solution treatment, use hydraulic press to perform axial cold pressing (axial cold deformation) to remove residual stress of forging ring. The dimensions before axial cold pressing are: Ф3335±15×Φ3145±15×270±1mm, the pressing amount is 7±1mm, the axial cold pressing is 0%~2.6%, and the residual tensile stress of forging ring core changes: radial, 64.3MPa→18.5MPa; circumferential, 225.5MPa→52.9MPa; axial, 169.8MPa→11.9MPa; radial cold expansion (radial cold deformation) is performed after axial cold pressing, as shown in the attached Figure 3As shown, the driving device 400 of the cold bulging equipment drives 12 radial cold bulging dies 500 to move radially, forcing the forging ring 600 to grow radially in outer diameter under the action of the bulging force. The bulging is carried out in three stages, with a bulging amount distribution ratio of 5:3:2. After each stage, it is necessary to rotate a certain 22.5° to ensure uniform deformation. The dimensions after cold bulging are: Ф3410±2×Φ3220±2×260±1mm (the roundness after axial cold pressing is 5mm, and the roundness dimensional accuracy reaches 2mm after radial cold bulging).

[0052] S600, after the cold bulging is completed, the aging treatment is carried out, the aging temperature is: 160 ~ 160 ℃, the insulation time is: 35 ~ 40h.

[0053] S700, ultrasonic flaw detection after aging treatment is required to meet the A-level requirements of GJB 1508A standard. Physical and chemical tests are performed after the flaw detection to ensure that the forged ring meets the acceptance index requirements.

[0054] In this embodiment, the physical and chemical testing method is to divide the circumference of the forged ring into three sections, cut a group of unidirectional tensile test bars (one each in the circumferential direction, axial direction and radial direction) at the starting point of each section, and test the tensile strength R m (MPa), yield strength R p0.2 (MPa) and elongation index A (%).

[0055] In this embodiment, the measured values ​​are shown in Table 1 below. The anisotropy of the forging ring in all directions is significantly reduced compared with the traditional method.

[0056] Table 1 Acceptance requirements and measured data of forged rings prepared in Example 1

[0057]

[0058] In this embodiment, the large-size 2195 aluminum-lithium alloy forging products produced by the above method can meet the acceptance requirements of low anisotropy and high dimensional accuracy, and solve the current problems of severe anisotropy of forged ring performance, inability of internal structure flaw detection to meet Class A requirements, poor dimensional accuracy of forged rings, and severe subsequent machining deformation. Compared with the traditional manufacturing method, the dimensional accuracy and performance qualification rate of the forged rings are further improved, and the degree of grain refinement is better than that of the traditional method. Figure 4 As shown in the figure, the radial, axial and circumferential grain sizes are all below 20um, and the batch quality stability of 2195 aluminum-lithium alloy forging ring products is steadily improving.

[0059] Through the above specific implementations, those skilled in the art can easily implement the present invention. However, it should be understood that the present invention is not limited to the above specific implementations. On the basis of the disclosed implementations, those skilled in the art can arbitrarily combine different technical features to achieve different technical solutions.

Claims

1. A method for preparing a large-size high-strength 2195 aluminum-lithium alloy forging ring, characterized in that: The following steps are involved: S100, selection of forging ring raw materials: select ingots with a height-to-diameter ratio of 3.5-4.2 as forging ring raw materials; S200, multi-directional forging and punching: heating and keeping the forging ring raw material warm, upsetting and stretching the forging ring raw material in three directions on a pressure device, performing double-drum rounding after each upsetting, pressing four-square and eight-square after stretching, and finally performing axial upsetting again, and punching after the last axial upsetting; S300, hole expansion and radial ring rolling: expanding the hole of the forging ring raw material after punching, and performing radial ring rolling in a manner of keeping the axial height unchanged, and the ring rolling completes a full circle of not less than 2 turns to obtain a ring blank; S400, solid solution: heating the ring blank, and immediately immersing the heated ring blank in water; S500, axial-radial bidirectional cold deformation: axial cold pressing and radial cold expansion are performed on a pressure device within 4 hours after solutionizing. The radial cold expansion is divided into three stages. After each stage of radial cold expansion, the ring blank is rotated along the ring mandrel by a certain angle to ensure uniform deformation; S600, aging treatment; S700, NDT and physical and chemical testing.

2. The method for preparing a large-size high-strength 2195 aluminum-lithium alloy forging ring according to claim 1, characterized in that: In step S100, the flaw detection requirements of the forging ring raw material meet the requirements of Class A in standard YS / T 1188, and the forging ring raw material is not allowed to have The above continuous point defects and the structure of grain size above level 4.

3. The method for preparing a large-size high-strength 2195 aluminum-lithium alloy forging ring according to claim 1, characterized in that: In step S200, the heating temperature of the forging ring raw material is 480-500°C, the holding time is 2.5-3.5 min / mm×the diameter of the ingot raw material, the forging temperature during the upsetting and drawing process is 350-500°C, the upsetting rate is ≤5 mm / s, the height-to-diameter ratio of the ingot after each upsetting is 1.5, the drawing rate is 15-25 mm / s, and the ratio of the cross-sectional side length to the length of the ingot after three drawing is 2.4-2.

8.

4. The method for preparing a large-size high-strength 2195 aluminum-lithium alloy forging ring according to claim 1, characterized in that: In step 300, the ratio of the outer diameter after hole expansion to the outer diameter after ring rolling is 0.70-0.74, the ring rolling makes the growth rate of the outer diameter ≤10mm / s, the temperature of the ring rolling is 260℃-300℃, and the material temperature is monitored in real time during the ring rolling process. If the material temperature exceeds 290℃, the growth rate of the ring rolling is reduced in time.

5. The method for preparing a large-size high-strength 2195 aluminum-lithium alloy forging ring according to claim 1, characterized in that: In step S400, the final temperature of the heating is 528-535°C, and the water temperature is >35°C.

6. The method for preparing a large-size high-strength 2195 aluminum-lithium alloy forging ring according to claim 1, characterized in that: In step 500, the total deformation of the axial cold pressing is less than 3%, and the total deformation of the radial cold bulging is not less than 2.2% of the outer diameter; the ratio of the bulging amounts in the three stages of the radial cold bulging is 5:3:

2.

7. The method for preparing a large-size high-strength 2195 aluminum-lithium alloy forging ring according to claim 1, characterized in that: In step 500, the rotation angle is 22.5°.

8. The method for preparing a large-size high-strength 2195 aluminum-lithium alloy forging ring according to claim 1, characterized in that: In step S600, the aging temperature is 150-160°C, and the aging insulation time is 25-40 hours.

9. The method for preparing a large-size high-strength 2195 aluminum-lithium alloy forging ring according to claim 1, characterized in that: In step S700, the requirements of the flaw detection meet the requirements of Class A in the GJB 1580A standard. After the flaw detection is qualified, the forged ring is subjected to physical and chemical testing, and the indicators of the physical and chemical testing are tensile strength, yield strength and elongation.

10. A large-size high-strength 2195 aluminum-lithium alloy forging ring, prepared by the method described in any one of claims 1 to 9, characterized in that: The forging ring is of Ф3000mm or above and T852 state; the room temperature circumferential physical and chemical properties of the forging ring are tensile strength ≥540MPa, yield strength ≥480MPa, elongation ≥6%, and the roundness of the forging ring after radial cold expansion is ≤6mm and the flatness is <2mm.

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