T884 heat treatment method for solid-phase additive pressure-resistant shell

Abstract

The embodiment of the invention discloses a T884 heat treatment method for a solid-phase additive pressure-resistant shell, which comprises the following steps: carrying out solid-phase additive shell forming on raw materials according to preset process parameters to obtain a to-be-treated shell; the shell to be treated is subjected to machining and polishing treatment, edge notches are removed, the wall thickness is controlled within a first preset range, and a machined shell is obtained; and the machined shell is sequentially subjected to solution treatment, quenching treatment, spinning treatment, pre-aging treatment and artificial aging treatment, and the formed shell is obtained. And circumferential cracking of the shell in the heat treatment process is completely eradicated, and the mechanical performance and the comprehensive performance of the shell are guaranteed.

Description

Technical Field

[0001] The present invention relates to the field of alloy heat treatment, and in particular to a T884 heat treatment method for a solid phase additive pressure hull. Background Art

[0002] The existing 6061 aluminum alloy is widely used in the pressure hull of underwater equipment due to its excellent mechanical properties and corrosion resistance. Friction stir solid phase deposition (AFSD) is an emerging solid-phase additive technology that is extremely suitable for the efficient forming of aluminum alloy pressure hulls. However, the performance of 6061 aluminum alloy after AFSD is between the O state and the T4 state, which cannot meet the requirements for the use of pressure hulls. Due to the special interlayer bonding process of AFSD and the specific surface "B-shaped notch" problem, the use of traditional T6 heat treatment process is very likely to cause circumferential cracking of the shell and a decrease in Z-direction elongation.

[0003] There is currently no effective solution to the above problems in the prior art. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a T884 heat treatment method for a solid phase additive pressure hull, by removing the "B-shaped notch" by edge processing of the hull, and improving the mechanical properties of the hull through a series of treatment processes, and avoiding the occurrence of shell cracking, so as to solve the problem of easy cracking of the hull and insufficient performance in the prior art.

[0005] To achieve the above-mentioned purpose, the present invention provides a T884 heat treatment method for a solid phase additive pressure-resistant shell, comprising: performing solid phase additive shell molding on the raw material according to preset process parameters to obtain a shell to be processed; performing machining and light treatment on the shell to be processed to remove edge notches, and controlling the wall thickness within a first predetermined range to obtain a processed shell; performing solid solution treatment, quenching treatment, spinning treatment, pre-aging treatment and artificial aging treatment on the processed shell in sequence to obtain a molded shell.

[0006] Further optionally, the solution treatment includes: freely heating up to 530° C.-535° C. and keeping the temperature for 1.5-2 hours.

[0007] Further optionally, the heating rate of the free heating is 75-80°C / h.

[0008] Further optionally, the quenching treatment includes: water-cooling quenching the processed shell after the solution treatment; the water temperature of the water-cooling quenching is 43-47° C., and the quenching transfer time does not exceed 20 seconds.

[0009] Further optionally, the spinning process includes: performing 4 spinning passes on the shell to be processed within 8 hours; the wall thickness thinning rate of a single spinning pass is 8%-10%, so as to control the wall thickness within a second predetermined range.

[0010] Further optionally, the pre-aging treatment includes: freely heating the processed shell to 145° C.-155° C., keeping the temperature for 3-4 hours, and then air cooling.

[0011] Further optionally, the artificial aging treatment includes: freely heating the processed shell to 160° C.-170° C., keeping the temperature for 6-8 hours, and then air cooling.

[0012] Further optionally, the preset process parameters include: spindle rotation speed 300-500r / min, spindle travel speed 100-300mm / min, bar feed speed 40-60mm / min.

[0013] Further optionally, after obtaining the molded shell, the step includes: machining the inner and outer walls of the molded shell again to obtain a finished workpiece of a finished size.

[0014] The above technical scheme has the following beneficial effects: before heat treatment, the "B-shaped notch" on the shell surface is completely removed to prevent the surface defects from causing annular cracking due to the change in notch size caused by thermal expansion effect, stress concentration, phase change and precipitation, as well as the influence of factors such as temperature gradient and stress gradient; after solution treatment, extrusion thinning is carried out to significantly refine the material grains, which has a great improvement in its mechanical properties, eliminates possible microscopic defects during the extrusion process, and improves material utilization and yield rate; pre-aging treatment can effectively control the morphology, quantity and distribution of the precipitated phase, reduce the negative effects that may be produced during the natural aging process, refine the precipitated phase, reduce internal stress, and improve material properties. Artificial aging causes the previously formed solution to precipitate into a stable metastable phase, effectively improving the material's tensile strength, yield strength and other mechanical properties, and can significantly improve the material's corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 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 or the description of the prior art 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.

[0016] Figure 1 The invention provides a T884 heat treatment method for a solid phase additive pressure hull.

[0017] Figure 2is a comparison diagram of the microstructure of the material before and after heat treatment provided by an embodiment of the present invention;

[0018] Figure 3 It is a comparison chart of test data of mechanical properties before and after heat treatment provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] In order to solve the problem of poor performance of the shell after heat treatment in the prior art, an embodiment of the present invention provides a T884 heat treatment method for a solid phase additive pressure shell. Figure 1 The T884 heat treatment method of the solid phase additive pressure hull provided in the embodiment of the present invention is as follows: Figure 1 As shown, the method includes:

[0021] S1. Performing solid phase additive shell forming on the raw material according to preset process parameters to obtain a shell to be processed;

[0022] Friction stir solid phase additive technology (AFSD) is to deposit raw materials layer by layer through mechanical stirring and local heating to form a functional shell. This process is particularly suitable for aluminum alloy materials and can avoid problems such as thermal stress and material deformation that may be caused by high-temperature melting.

[0023] As an optional implementation, the raw material in the present application is 6061 aluminum alloy bar.

[0024] The preset process parameters are specially designed for different raw materials and shell requirements to achieve the best deposition effect.

[0025] According to the preset process parameters, the raw material is subjected to friction stir solid phase additive manufacturing to obtain a shell to be processed, and a certain processing margin should be left for the shell to be processed for subsequent machining. Preferably, the thickness of the shell to be processed is 35 mm.

[0026] S2, machining and polishing the shell to be processed, removing edge notches, and controlling the wall thickness within a first predetermined range to obtain a processed shell;

[0027] Machining refers to the removal of defects on the shell surface by mechanical processing (such as turning, milling, etc.), especially surface defects such as "B-type notches". In the solid phase additive process, due to uneven material accumulation or uneven cooling, notches will appear on the edge of the shell after deposition. The cross-section of these notches is "B-type", so these edge notches are also called "B-type notches". It will become a stress concentration point in the subsequent heat treatment, increasing the risk of cracks. Therefore, these notches must be removed in this step.

[0028] In addition to machining to remove edge notches, the wall thickness is also processed to control the wall thickness within a first predetermined range, preferably 25-26 mm. This control can ensure the stability of the shell and leave enough processing allowance for subsequent heat treatment and spinning processes.

[0029] After machining, the surface of the processed shell is smooth, the edge notches are removed, and the wall thickness of the shell has been adjusted to an ideal value suitable for subsequent heat treatment, spinning and aging.

[0030] S3, performing solution treatment, quenching treatment, spinning treatment, pre-aging treatment and artificial aging treatment on the processed shell in sequence to obtain a formed shell.

[0031] The machined shell is solution treated to maximize the solubility of the aluminum alloy material and reach a certain solubility, thereby improving its plasticity and preparing for subsequent heat treatment and spinning operations.

[0032] The processed shell is then quenched. Quenching helps lock the solid solution structure, optimize the mechanical properties and grain structure of the aluminum alloy, and thus increase the strength of the material.

[0033] After that, the processed shell is subjected to spinning treatment, which can reduce the wall thickness of the shell and improve its mechanical properties. In each spinning, the wall thickness is reduced by a certain size, and the target shell is obtained after multiple spinning treatments. Spinning is to fix a flat plate or hollow blank on the mold of the spinning machine. While the blank rotates with the spindle of the machine tool, a spinning wheel or a driving rod is used to pressurize the blank to produce local plastic deformation. Through spinning, the grain structure of the material can be improved, its strength and toughness can be further enhanced, and the wall thickness can be controlled.

[0034] Afterwards, the processed shell is subjected to a pre-aging treatment, which helps to control the morphology and distribution of the precipitated phase in the material, reduce possible negative effects during the natural aging process, and optimize the performance of the material.

[0035] The processed shell is then subjected to artificial aging treatment. Through this process, the dissolved substances in the solid solution will precipitate to form a stable precipitation phase, thereby increasing the yield strength and tensile strength of the material and improving the corrosion resistance of the material.

[0036] Through the above heat treatment steps, a molded shell with high yield strength, high elongation and high corrosion resistance can be obtained, which meets the technical requirements for pressure-resistant shells.

[0037] As an optional embodiment, the solution treatment includes: freely heating to 530° C.-535° C. and keeping the temperature for 1.5-2 hours.

[0038] Solution treatment is an important step in the heat treatment of aluminum alloys. Its main purpose is to make the dissolved elements in the alloy reach a uniform dissolved state, thereby improving the strength, plasticity and uniformity of the alloy.

[0039] Free heating means that the heating rate is not forcibly controlled, allowing the furnace temperature to gradually rise within a certain range and then keep warm after reaching the required temperature.

[0040] The temperature range of 530℃-535℃ is suitable for the solution treatment of 6061 aluminum alloy. This temperature can fully dissolve the alloying elements such as silicon and magnesium in the aluminum alloy.

[0041] The holding time is 1.5-2 hours to ensure that the aluminum alloy is fully and evenly dissolved and to avoid precipitates affecting the mechanical properties of the material.

[0042] As an optional implementation manner, the heating rate of free heating is 75-80° C. / h.

[0043] Heating rate is an important parameter in solution treatment. Heating too fast may cause thermal stress in the material, while heating too slowly may result in too long a treatment time and affect efficiency.

[0044] At a heating rate of 75-80℃ / h, thermal stress caused by too fast heating can be effectively avoided, while also ensuring that the elements in the alloy are fully diffused during the heating process to ensure the solid solution effect.

[0045] This rate is suitable for 6061 aluminum alloy, which can maintain uniform temperature distribution and avoid cracks or uneven solid solution.

[0046] As an optional implementation, the quenching treatment includes: water-cooling quenching the processed shell after the solution treatment; the water temperature of the water-cooling quenching is 43-47° C., and the quenching transfer time does not exceed 20 seconds.

[0047] Quenching is part of the heat treatment process, the purpose of which is to lock the structure of the solid solution through rapid cooling, thereby improving the strength of the material.

[0048] Water cooling quenching is done by immersing the high-temperature solution-treated shell into water to quickly lower the temperature and inhibit the precipitation phase in the alloy.

[0049] The water temperature of 43-47°C is the ideal water cooling temperature range, which can ensure good quenching effect and avoid material cracks caused by water cooling. Preferably, the water temperature is 45°C.

[0050] The quenching transfer time does not exceed 20 seconds to ensure that the high-temperature surface of the shell can be quickly and evenly cooled when it is quickly transferred to water, avoiding cracks or deformation caused by excessive temperature differences.

[0051] As an optional implementation, the spinning process includes: performing 4 spinning passes on the shell to be processed within 8 hours; the wall thickness thinning rate of a single spinning pass is 8%-10% to control the wall thickness within a second predetermined range.

[0052] Spinning is a process that applies rotation and pressure to metal materials to reduce their thickness and plastically deform them. It is usually used to improve the material's mechanical properties such as tensile strength and hardness.

[0053] Through 4 spinning passes, the wall thickness is reduced by 8%-10% each time, so that the material is gradually accurately formed and possible micro defects are eliminated.

[0054] Completing 4 spinning passes within 8 hours is a reasonable processing time, which can ensure accurate forming in a short time and maintain the dimensional stability of the shell. If the excess of ingredients is sufficient, the inner ring rib can be formed in one piece during the spinning process.

[0055] The final wall thickness is controlled within a second predetermined range, and the wall thickness of the shell is controlled by spinning. Usually, this range is thinner than the wall thickness during initial molding to optimize performance. The preferred second predetermined range is 18-18.5 mm.

[0056] As an optional implementation, the pre-aging treatment includes: freely heating the processed shell to 145° C.-155° C., keeping the temperature for 3-4 hours, and then air cooling.

[0057] Pre-aging treatment is a process in the heat treatment of aluminum alloys. Its purpose is to precipitate some phases in the alloy and lay the foundation for subsequent artificial aging.

[0058] The temperature is freely raised to 145°C-155°C. By controlling the temperature, the distribution, shape and size of the precipitated phase can be controlled, thereby improving the strength and toughness of the aluminum alloy. Preferably, the temperature is freely raised to 150°C.

[0059] Keeping the temperature for 3-4 hours can ensure that the precipitates inside the alloy material are fully reacted and stabilized at this temperature.

[0060] It is then air-cooled to ensure that no stress is generated in the material during the cooling process, thereby avoiding deformation or cracking.

[0061] As an optional implementation, the artificial aging treatment includes: freely heating the processed shell to 160° C.-170° C., keeping the temperature for 6-8 hours, and then air cooling.

[0062] Artificial aging is the process of heating the aluminum alloy material that has undergone solution treatment and spinning to a certain temperature, and then maintaining it for a certain period of time to promote the stabilization of the precipitated phase, thereby improving the mechanical properties of the material.

[0063] The temperature can be freely raised to 160℃-170℃. This temperature range is suitable for aging treatment of 6061 aluminum alloy, which can effectively promote the stability of the precipitation phase and enhance the strength of the aluminum alloy.

[0064] Keeping the alloy warm for 6-8 hours ensures that the precipitated phase is evenly distributed in the alloy and enables the material to achieve optimal strength and hardness.

[0065] After that, it is air-cooled to ensure that the precipitates do not undergo adverse phase changes during the cooling process, thereby ensuring the final material properties.

[0066] As an optional implementation, the raw material is subjected to solid phase additive shell molding according to preset process parameters, including: spindle rotation speed 300-500r / min, spindle travel speed 100-300mm / min, and bar feed speed 40-60mm / min.

[0067] Spindle rotation speed: controlled at 300-500r / min to ensure sufficient stirring and heating so that the aluminum alloy material reaches appropriate fluidity for effective molding.

[0068] Spindle travel speed: controlled at 100-300mm / min, which can ensure the precise shape of the material during layer-by-layer accumulation and avoid excessive flow of the material.

[0069] Bar feed speed: between 40-60mm / min, ensuring continuous supply of raw materials without material accumulation or shortage.

[0070] As an optional implementation, after obtaining the molded shell, the method includes: machining the inner and outer walls of the molded shell again to obtain a finished workpiece of a finished size.

[0071] After the molded shell is completed, secondary machining is usually required to meet the final product requirements. Secondary machining refers to further fine processing of the inner and outer walls to remove possible minor defects and machining allowances to ensure that the size and surface quality meet the requirements of the finished workpiece. Through this step, the finished workpiece that meets the design requirements is finally obtained and can be directly used in practical applications, such as pressure-resistant shells.

[0072] The following is a specific embodiment:

[0073] 1. Solid phase additive: Use friction stir solid phase additive equipment to form the 6061 aluminum alloy shell, the spindle rotation speed is 400r / min, the spindle travel speed is 200mm / min, the bar feed speed is 50mm / min, and the shell wall thickness is controlled to be 35mm;

[0074] 2. Surface polishing: The inner and outer walls of the additively processed blank shell are polished to remove the "B-shaped notch" on the surface and the wall thickness is controlled to 25mm;

[0075] 4. Solution treatment: free heating to 532℃, keeping temperature for 2h, water cooling quenching, water temperature 45℃, quenching transfer time ≤20s;

[0076] 4. Spinning: The shell after solution treatment is spun, with a single wall thickness reduction of 8% to 10%, a total of 4 spinning passes, a total processing time of ≤8h, and the final wall thickness is controlled at 18.0 to 18.5mm;

[0077] 5. Pre-aging treatment: pre-aging treatment is performed on the shell after spinning, heating freely to 150°C, keeping warm for 4 hours, and air cooling;

[0078] 6. Artificial aging treatment: The shell after pre-aging treatment is subjected to artificial aging treatment by freely heating to 165°C, keeping warm for 7 hours, and air cooling;

[0079] 7. If necessary, the shell after artificial aging treatment is machined to reach the finished size.

[0080] The above steps can effectively prevent the circumferential cracking of the AFSD aluminum alloy shell during heat treatment, and ensure that the shell's Z-axis yield strength is ≥210MPa and the Z-axis elongation is ≥15%. m =315MPa, R p0.2 =264MPa, A (elongation) = 17.5%.

[0081] Figure 2 is a comparison diagram of the microstructure of the material before and after heat treatment provided by the embodiment of the present invention, Figure 2 In the figure, (a) is the additive state before heat treatment, and (b) is the T884 state after heat treatment. Figure 2 It can be seen that the material after heat treatment is more uniform and ordered, with higher stability, and the precipitated phase changes into evenly distributed fine particles. Figure 3 is a comparison chart of test data of mechanical properties before and after heat treatment provided by an embodiment of the present invention, Figure 3 In the figure, AFSD-6061 is the additive state before heat treatment, and AFSD-T884-6061 is the state after heat treatment. Figure 3 It can be seen that the elongation after heat treatment remains above 15%, and the tensile strength and yield strength are improved.

[0082] The above technical scheme has the following beneficial effects: before heat treatment, the "B-shaped notch" on the shell surface is completely removed to prevent the surface defects from causing annular cracking due to the change in notch size caused by thermal expansion effect, stress concentration, phase change and precipitation, as well as the influence of factors such as temperature gradient and stress gradient; after solution treatment, extrusion thinning is carried out to significantly refine the material grains, which has a great improvement in its mechanical properties, eliminates possible microscopic defects during the extrusion process, and improves material utilization and yield rate; pre-aging treatment can effectively control the morphology, quantity and distribution of the precipitated phase, reduce the negative effects that may be produced during the natural aging process, refine the precipitated phase, reduce internal stress, and improve material properties. Artificial aging causes the previously formed solution to precipitate into a stable metastable phase, effectively improving the material's tensile strength, yield strength and other mechanical properties, and can significantly improve the material's corrosion resistance.

[0083] The specific implementation methods of the above invention further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above content is only the specific implementation methods of the present invention and is not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A T884 heat treatment method for a solid phase additive pressure hull, characterized in that: include: Performing solid phase additive shell forming on the raw material according to preset process parameters to obtain a shell to be processed; The shell to be processed is subjected to machining and light treatment to remove edge notches and control the wall thickness within a first predetermined range to obtain a processed shell; The processed shell is subjected to solution treatment, quenching treatment, spinning treatment, pre-aging treatment and artificial aging treatment in sequence to obtain a formed shell.

2. The T884 heat treatment method for a solid phase additive pressure hull according to claim 1, characterized in that: The solution treatment comprises: Heat freely to 530℃-535℃ and keep warm for 1.5-2 hours.

3. The T884 heat treatment method for the solid phase additive pressure hull according to claim 2, characterized in that: The heating rate of the free heating is 75-80°C / h.

4. The T884 heat treatment method for a solid phase additive pressure hull according to claim 1, characterized in that: The quenching treatment comprises: Water-cooling quenching is performed on the processed shell after the solution treatment; The water temperature of water-cooled quenching is 43-47°C, and the quenching transfer time does not exceed 20s.

5. The T884 heat treatment method for a solid phase additive pressure hull according to claim 1, characterized in that: The spinning process comprises: Performing 4 passes of spinning on the shell to be processed within 8 hours; The wall thickness reduction rate of a single spinning operation is 8%-10% to control the wall thickness within a second predetermined range.

6. The T884 heat treatment method for a solid phase additive pressure hull according to claim 1, characterized in that: The pre-aging treatment comprises: The processing shell is freely heated to 145° C.-155° C., kept at this temperature for 3-4 hours, and then air-cooled.

7. The T884 heat treatment method for a solid phase additive pressure hull according to claim 1, characterized in that: The artificial aging treatment includes: The processing shell is freely heated to 160° C.-170° C., kept warm for 6-8 hours, and then air-cooled.

8. The T884 heat treatment method for a solid phase additive pressure hull according to claim 1, characterized in that: The preset process parameters include: The spindle rotation speed is 300-500r / min, the spindle travel speed is 100-300mm / min, and the bar feed speed is 40-60mm / min.

9. The T884 heat treatment method for a solid phase additive pressure hull according to claim 1, characterized in that: The step of obtaining the molded shell includes: The inner and outer walls of the molded shell are machined again to obtain a finished workpiece of finished size.

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