CN113909805B - TC4 titanium alloy high-precision curved thin-wall part machining method - Google Patents
TC4 titanium alloy high-precision curved thin-wall part machining method Download PDFInfo
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Abstract
The invention discloses a TC4 titanium alloy high-precision curved thin-wall part machining method which comprises the following steps: forging a blank, punching, reaming, solution treatment, cryogenic treatment, annealing treatment, rough machining and semi-finishing, cold-hot circulating treatment, finishing and stepped cryogenic treatment. According to the processing method of the TC4 titanium alloy high-precision curved thin-wall part, a large number of metastable beta phases exist in a matrix of a TC4 blank which is freely forged in a two-phase region, and the transformation of the metastable beta phases to alpha phases is promoted through cryogenic treatment, and meanwhile, structure grains are refined, and the material performance is improved. According to the characteristics of a large amount of residual stress generated in the rough machining and semi-finishing processes, the residual stress generated in the machining process is released through cold and hot circulation treatment. And step cryogenic treatment is carried out, so that uniform cooling is facilitated, new stress is avoided, and the TC4 titanium alloy curved surface thin-wall part with high precision, minimized residual stress and stable structure and size is obtained.
Description
Technical Field
The invention relates to the field of processing of non-ferrous metal materials, in particular to a method for processing a TC4 titanium alloy high-precision curved thin-wall part.
Background
The TC4 titanium alloy (namely Ti-6 Al-4V) has a series of advantages of excellent corrosion resistance, low density, extremely high specific strength, better comprehensive performance, processing performance, low-temperature toughness and the like, is widely applied in the fields of aerospace, petrochemical industry, pressure vessels, automobiles, medicines and the like, and is a titanium alloy material with the largest use amount at present. With the rapid development of aerospace and other industries, the usage amount of the TC4 titanium alloy is increasing, and the heat treatment and machining process thereof is becoming mature, but still faces the following problems: the problems of easy knife sticking, large resilience amount, residual stress and the like are solved, so that the mechanical processing of high-precision parts made of TC4 titanium alloy materials, especially curved surface thin-wall parts, is generally concerned.
The TC4 titanium alloy belongs to alpha + beta type titanium alloy, and is one of typical difficult-to-machine materials, mainly because: 1) The thermal conductivity of TC4 titanium alloy is very low, a large amount of cutting heat generated in the machining process cannot be dissipated in time, so that the cutting temperature is increased, and the cutter is quickly worn;
2) The cutting stress is large, so that the cutting edge is easy to wear; 3) The cutting friction coefficient is large, more heat is generated by the friction between the cutting chips and the front cutter face, and the temperature is higher; 4) At high temperature, the TC4 titanium alloy and nitrogen, hydrogen and oxygen in the air react chemically to form a hardened layer; 5) The TC4 titanium alloy has low elastic modulus and high yield strength, so that a machined surface generates large rebound and deformation during cutting, the rear angle of a cutter is abraded, and the friction with a part is aggravated. The TC4 titanium alloy has high processing temperature and large cutting force, and the processing precision of a workpiece can be seriously influenced by the resilience and deformation in the processing process, and meanwhile, the workpiece generates large residual stress, and the residual stress can cause the deformation of the workpiece to influence the use of the workpiece when the workpiece is in service at the later stage.
There are various methods for removing residual stress generated during the machining of a workpiece. The stress relief annealing is to anneal the metal workpiece at a lower temperature under the condition of not changing the structure state, remove the residual stress of the workpiece, reduce the deformation of the workpiece and eliminate most of the residual stress. Further annealing to relieve residual stress requires heating the workpiece to higher temperatures, which can introduce texture changes that affect material properties. The cryogenic treatment is a new technology developed in the 60's of the 20 th century, and generally refers to the treatment of workpieces at a temperature below-130 ℃ by using liquid nitrogen as a refrigerant. The cryogenic treatment can reduce the residual stress without reducing the hardness and the strength of the workpiece, and can obviously improve the toughness of the workpiece and stabilize the material structure under some conditions. The cryogenic treatment can effectively improve the mechanical properties and the service lives of steel materials, nonferrous metals and composite materials, stabilize the size, improve the uniformity, reduce the deformation, has simple and convenient operation, no damage to workpieces, no pollution and low cost, and has positive application prospect and development space. The cryogenic treatment can improve the structure of the titanium alloy under certain conditions, but the influence of the cryogenic treatment on the titanium alloy is related to the state of the titanium alloy, and the structural state of the titanium alloy is difficult to control.
The application of the cryogenic technology in the machining of high-precision parts of titanium alloys, particularly TC4 titanium alloy materials is not mature at present, the existing method for eliminating the residual stress of the titanium alloys mainly adopts annealing treatment, the process method is single, the residual stress of workpieces is difficult to be effectively reduced to the minimum, and new thermal stress can be generated in the annealing process to influence the size precision of the workpieces. And the single cryogenic process is difficult to achieve the obvious effect like the cryogenic treatment of carbon steel. Therefore, the development of a method for machining a TC4 titanium alloy curved thin-wall part with high precision, furthest reduced residual stress and stable structure and dimension is urgently needed.
Disclosure of Invention
The invention provides a method for processing a TC4 titanium alloy high-precision curved thin-wall part, and aims to solve the technical problems that the TC4 titanium alloy curved thin-wall part is difficult to reduce residual stress to the maximum extent and cannot keep stable structure and size.
The technical scheme adopted by the invention is as follows:
a TC4 titanium alloy high-precision curved thin-wall part machining method comprises the following steps:
s1, forging a blank: carrying out free forging on the TC4 blank in a two-phase region to obtain a forged blank;
s2, punching and reaming: punching and reaming the forging blank in the step S1 to obtain a forging thin-wall workpiece;
s3, solution treatment: carrying out solution heat treatment on the forged thin-wall workpiece in the step S2 to obtain a thin-wall workpiece a;
s4, cryogenic treatment: carrying out subzero treatment on the thin-wall workpiece a in the step S3 to obtain a thin-wall workpiece b;
s5, annealing treatment: annealing the thin-wall workpiece b in the step S4 to obtain a thin-wall workpiece c;
s6, rough machining and semi-finishing: performing rough machining and semi-finish machining on the thin-wall workpiece c in the step S5, and reserving machining allowance to obtain a thin-wall workpiece d;
s7, cold-hot circulation treatment: performing cold-hot cycle treatment on the thin-wall workpiece d in the step S6 to remove residual stress existing in the thin-wall workpiece d after rough machining and semi-finish machining to obtain a thin-wall workpiece e;
s8, fine machining: performing finish machining on the thin-wall workpiece e subjected to the cold and hot circulation treatment in the step S7 to obtain a thin-wall workpiece f;
s9, step cryogenic treatment: and step deep cooling treatment is carried out on the thin-wall workpiece f after finish machining in the step S8, and the TC4 titanium alloy high-precision curved thin-wall workpiece is obtained.
Further, in the step S8, a fixture matched with the structure of the thin-wall workpiece e subjected to the cooling and heating cycle processing in the step S7 is used for clamping, so that the thin-wall workpiece e is uniformly stressed and does not deform, and then the thin-wall workpiece e is subjected to finish machining.
Further, the clamp is made of TC4 titanium alloy.
Further, the step cryogenic treatment in step S9 specifically includes: cooling to minus 80 plus or minus 5 ℃, preserving heat for 2h to 6h, then continuously cooling to minus 130 plus or minus 5 ℃, preserving heat for 2h to 6h, then cooling to minus 190 plus or minus 6 ℃, preserving heat for 6h to 48h, and finally heating to room temperature.
Further, the cooling rate is 0.5-3 ℃/min; the rate of temperature rise is 0.5-3 ℃/min.
Further, the cycle frequency of the cold-hot cycle treatment in the step S7 is 2-4 times, the cold-hot cycle treatment comprises a subzero treatment and a heat treatment, the temperature of the subzero treatment is-180 ℃ to-196 ℃, the heat preservation time is 3h to 24h, the temperature of the heat treatment is 160 ℃ to 200 ℃, and the heat preservation time is 4h to 24h.
Further, the cold-hot circulation treatment adopts the steps of firstly carrying out heat treatment and then carrying out subzero treatment to finish one cold-hot circulation treatment, and so on until all cold-hot circulation treatments are finished.
Further, the deep cooling process in step S4 includes: liquid nitrogen is used as a cooling medium, and the thin-wall workpiece a in the step S3 is subjected to subzero treatment in a subzero box; the temperature of the cryogenic treatment is-180 ℃ to-196 ℃, the cooling rate is 0.5 ℃/min to 3 ℃/min, and the heat preservation time is 6 to 48 hours.
Further, the free forging temperature in the step S1 is 820-920 ℃; and/or the temperature of the solution heat treatment in the step S3 is 900-960 ℃, and the heat preservation time is 90-300 min.
Further, the annealing treatment in the step S5 is carried out at the temperature of 550-700 ℃ for 2-12 h; and/or the machining allowance in the step S6 is 0.2 mm-0.8 mm.
The invention has the following beneficial effects:
the invention discloses a processing method of a TC4 titanium alloy high-precision curved thin-wall part, which comprises the following steps of: forging a blank, punching, reaming, solution treatment, cryogenic treatment, annealing treatment, rough machining and semi-finishing, cold-hot circulating treatment, finishing and stepped cryogenic treatment to obtain the TC4 titanium alloy high-precision curved thin-wall part. The TC4 blank is subjected to free forging, punching and hole expanding to obtain a forged thin-wall workpiece, so that the cutting amount in the machining process is reduced, the material is saved, the machining time is reduced, and the overall performance of the TC4 titanium alloy high-precision curved thin-wall workpiece is improved. Moreover, a large amount of metastable beta-phase exists in the matrix of the TC4 blank which is freely forged in the two-phase region, and the transformation from the metastable beta-phase to the alpha-phase is promoted through the cryogenic treatment, and meanwhile, the structure crystal grains are refined, and the material performance is improved. According to the characteristics of a large amount of residual stress generated in the rough machining and semi-finish machining processes, the thin-wall workpiece d is subjected to cold and hot circulating treatment, so that the residual stress generated in the machining process is released, and the residual stress of the thin-wall workpiece d is eliminated to the maximum extent. And step cryogenic treatment is carried out on the thin-wall workpiece f after finish machining, so that uniform cooling of the thin-wall workpiece f is facilitated, new stress generated in the cooling process of the thin-wall workpiece f is avoided, and the TC4 titanium alloy curved surface thin-wall part with high precision, minimized residual stress and stable structure and size is obtained.
In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be described in further detail below with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a flow chart of the TC4 titanium alloy high-precision curved thin-wall part processing method of the invention;
FIG. 2 is a metallographic structure diagram of a TC4 titanium alloy obtained after solution treatment and annealing treatment,
FIG. 3 is a metallographic structure diagram of a TC4 titanium alloy obtained after solution treatment, cryogenic treatment and annealing treatment; and
FIG. 4 is a graph showing the change in microhardness of a TC4 titanium alloy during a cold-hot cycle treatment.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.
FIG. 1 is a flow chart of the TC4 titanium alloy high-precision curved thin-wall part processing method of the invention; FIG. 2 is a metallographic structure diagram of a TC4 titanium alloy obtained after solution treatment and annealing treatment, and FIG. 3 is a metallographic structure diagram of a TC4 titanium alloy obtained after solution treatment, cryogenic treatment and annealing treatment; FIG. 4 is a graph showing the change in microhardness of a TC4 titanium alloy during cold and heat cycle treatment.
As shown in fig. 1, the method for processing a TC4 titanium alloy high-precision curved thin-wall part in this embodiment includes the following steps:
s1, forging a blank: carrying out two-phase region free forging on the TC4 blank to obtain a forged blank;
s2, punching and reaming: punching and reaming the forging blank in the step S1 to obtain a forging thin-wall workpiece;
s3, solution treatment: carrying out solution heat treatment on the forged thin-wall workpiece in the step S2 to obtain a thin-wall workpiece a;
s4, cryogenic treatment: carrying out subzero treatment on the thin-wall workpiece a in the step S3 to obtain a thin-wall workpiece b;
s5, annealing treatment: annealing the thin-wall workpiece b in the step S4 to obtain a thin-wall workpiece c;
s6, rough machining and semi-finishing: performing rough machining and semi-finish machining on the thin-wall workpiece c in the step S5, and reserving machining allowance to obtain a thin-wall workpiece d;
s7, cold-hot circulation treatment: performing cold-hot circulation treatment on the thin-wall workpiece d obtained in the step S6 to remove residual stress of the thin-wall workpiece d after rough machining and semi-finish machining to obtain a thin-wall workpiece e;
s8, fine machining: performing finish machining on the thin-wall workpiece e subjected to the cold and hot circulation treatment in the step S7 to obtain a thin-wall workpiece f;
s9, step cryogenic treatment: and (5) performing stepped cryogenic treatment on the thin-wall workpiece f subjected to finish machining in the step S8 to obtain the TC4 titanium alloy high-precision curved thin-wall workpiece.
The invention discloses a processing method of a TC4 titanium alloy high-precision curved thin-wall part, which comprises the following steps of: forging a blank, punching, reaming, solution treatment, cryogenic treatment, annealing treatment, rough machining and semi-finishing, cold-hot circulating treatment, finishing and stepped cryogenic treatment to obtain the TC4 titanium alloy high-precision curved thin-wall part. The TC4 blank is subjected to free forging, punching and hole expanding to obtain a forged thin-wall workpiece, so that the cutting amount in the machining process is reduced, the material is saved, the machining time is reduced, and the overall performance of the TC4 titanium alloy high-precision curved thin-wall workpiece is improved. Moreover, a large amount of metastable beta-phase exists in the matrix of the TC4 blank which is freely forged in the two-phase region, and the transformation from the metastable beta-phase to the alpha-phase is promoted through the cryogenic treatment, and meanwhile, the structure crystal grains are refined, and the material performance is improved. According to the characteristics of a large amount of residual stress generated in the rough machining and semi-finishing processes, the thin-wall workpiece d is subjected to cold-hot circulating treatment, so that the residual stress generated in the machining process is released, and the residual stress of the thin-wall workpiece d is eliminated to the maximum extent. And step cryogenic treatment is carried out on the thin-wall workpiece f after finish machining, so that the thin-wall workpiece f is uniformly cooled, new stress generated in the cooling process of the thin-wall workpiece f is avoided, and the TC4 titanium alloy curved surface thin-wall part with high precision, minimized residual stress and stable structure and size is obtained.
According to the TC4 titanium alloy high-precision curved thin-wall part machining method, different treatment modes are adopted according to the characteristics of the TC4 titanium alloy in different states, and the problems of the TC4 titanium alloy in different periods are treated in stages, so that the conversion of beta opposite alpha phases is promoted to the maximum extent, the structure crystal grains are refined, and the residual stress is reduced. Aiming at the characteristic that a large amount of metastable beta-phase exists in TC4 titanium alloy after free forging (namely thermal deformation) in a two-phase region, a forging workpiece is subjected to a combination mode of solid solution treatment, cryogenic treatment and annealing treatment, so that the transformation of the metastable beta-phase is promoted to be full, the structure is more stable, crystal grains can be refined, and the material performance is improved. For the thin-wall workpiece d after rough machining and semi-finish machining, because the TC4 titanium alloy has large cutting force, large resilience and high cutting temperature, the machined thin-wall workpiece d has large residual stress, and the residual stress in the thin-wall workpiece d is relaxed by adopting cold-hot cyclic treatment, namely multiple cold-hot alternate cyclic treatment, so that the aim of eliminating the residual stress is fulfilled.
In this embodiment, in step S8, a fixture matched with the thin-walled workpiece e subjected to the cooling and heating cycle processing in step S7 is used for clamping, so as to ensure that the thin-walled workpiece e is uniformly stressed and does not deform, and then the thin-walled workpiece e is subjected to finish machining. And (3) during the finish machining of the workpiece, clamping by using a clamp matched with the structure of the thin-wall workpiece e after the cold-hot circulation treatment in the step (S7), attaching the clamp to the curved surface of the structure of the thin-wall workpiece e, and performing finish machining to reduce the deformation of the thin-wall workpiece e in the finish machining process. After finish machining is finished, the thin-wall workpiece f and the clamp are integrally placed in a deep cooling box to carry out stepped deep cooling treatment, the size of the thin-wall workpiece f is stabilized, and deformation of the thin-wall workpiece f in the unloading and stepped deep cooling treatment processes is avoided.
In this embodiment, the jig is made of TC4 titanium alloy. So as to avoid the difference between the expansion coefficients of the material of the clamp and the TC4 titanium alloy, which causes the generation of additional stress.
In this embodiment, the step cryogenic treatment in step S9 specifically includes: cooling to minus 80 plus or minus 5 ℃, preserving heat for 2h to 6h, then continuously cooling to minus 130 plus or minus 5 ℃, preserving heat for 2h to 6h, then cooling to minus 190 plus or minus 6 ℃, preserving heat for 6h to 48h, and finally heating to room temperature. And integrally placing the thin-wall workpiece f and the clamp into a deep cooling box to carry out stepped deep cooling treatment. The stepped cryogenic treatment is beneficial to uniform cooling of the thin-wall workpiece f, and new stress generated in the cooling process of the thin-wall workpiece f is avoided. The thin-wall workpiece f is stable in size by utilizing the stepped cryogenic treatment, and the precision is improved. The temperature reduction is carried out at three stages of-80 +/-5 ℃, 80 +/-5 ℃ and 190 +/-6 ℃ respectively, so that the thin-wall workpiece f is in stable transition in the temperature reduction process.
In this embodiment, the cooling rate is 0.5 ℃/min to 3 ℃/min. The rate of temperature rise is 0.5-3 ℃/min. The cooling rate is 0.5-3 ℃/min, namely, the temperature is slowly reduced, so that the thin-wall workpiece f is uniformly cooled, and the phenomenon that the temperature difference exists locally to generate new stress is avoided.
In this embodiment, the cycle number of the cold-heat cycle treatment in step S7 is 2 to 4, the cold-heat cycle treatment includes a cryogenic treatment and a heat treatment, the temperature of the cryogenic treatment is-180 ℃ to-196 ℃, the heat preservation time is 3h to 24h, the temperature of the heat treatment is 160 ℃ to 200 ℃, and the heat preservation time is 4h to 24h. In the step S7, the thin-wall workpiece d is subjected to a cooling-heating cycle to relax the residual stress in the thin-wall workpiece d, so as to eliminate the residual stress in the machining process.
Preferably, the cold-hot circulation treatment is carried out by firstly carrying out heat treatment and then carrying out cryogenic treatment to finish one cold-hot circulation treatment, and so on until all cold-hot circulation treatments are finished. More preferably, the number of cycles of the cold-hot cycle treatment is 3.
See table 1 for the effect of heat treatment and cryogenic treatment on residual stress, wherein the samples were not subjected to the cold-hot cycle treatment, the heat treatment was the samples subjected to the heat treatment only, the cryogenic treatment of 12h + the heat treatment was carried out 12h after the cryogenic treatment, and the heat treatment + the cryogenic treatment of 12h was carried out 12h after the thermal treatment. As can be seen from table 1, the residual stress of the surface machining of the thin-wall workpiece d can be removed by more than 90% through the heat treatment and the cryogenic treatment, and the combined sequence of the cryogenic treatment and the heat treatment has a large influence on the effect of removing the residual stress, and the effect of removing the residual stress is the best in a manner of performing the cryogenic treatment after the heat treatment.
TABLE 1 influence of Heat treatment and cryogenic treatment on surface residual stress
The cooling-heating cycle processing of the above step S7 is actually a combination of cryogenic treatment and heat treatment, and the TC4 titanium alloy structure can be stabilized by the cooling-heating cycle processing while removing the residual stress. In the cold and hot circulation process, the hardness of the thin-wall workpiece d after heat treatment is reduced, the hardness of the thin-wall workpiece d after subzero treatment is increased, but the hardness of the thin-wall workpiece d is gradually reduced along with the fluctuation range of the cold and hot circulation treatment along with the increase of the circulation times, which shows that the TC4 titanium alloy structure gradually tends to be stable in the cold and hot circulation process, is beneficial to the size stability of the TC4 titanium alloy high-precision curved surface thin-wall part in the processing and service processes, and improves the precision and the stability. Referring specifically to fig. 4, in fig. 4, the sample originally not subjected to the heat and cold cycle processing, H1C0, H1C1, H2C 3, H4C4, H1C1, H2C2, H3C, and H4C4 are samples subjected to the heat and cold cycles of the heat and cold processing, respectively, and the change in the microhardness is observed.
In this embodiment, the deep cooling process in step S4 includes: liquid nitrogen is used as a cooling medium, and the thin-wall workpiece a in the step S3 is subjected to subzero treatment in a subzero box; the temperature of the deep cooling treatment is-180 ℃ to-196 ℃, the cooling rate is 0.5 ℃/min to 3 ℃/min, and the heat preservation time is 6 to 48 hours. Liquid nitrogen is adopted as a cooling medium to carry out cryogenic treatment in a cryogenic box, the temperature is reduced to minus 180 ℃ to minus 196 ℃ at the temperature reduction rate of 0.5 ℃/min to 3 ℃/min, the heat preservation time is 6 to 48 hours at the temperature, so as to refine the grain size of the internal structure of the thin-wall workpiece a and improve the performance of the TC4 titanium alloy. The preliminary experiments in the early period find that the microstructure can be regulated and controlled to obtain better performance through three combined treatment modes of solution treatment, cryogenic treatment and annealing treatment, compared with the traditional treatment mode (solution treatment and annealing treatment, lack of cryogenic treatment), the microstructure of the solution treatment and the annealing treatment is analyzed through a scanning electron microscope, as shown in figures 2 and 3, the thickness of the precipitated lamellar structure (as shown in figure 3) is larger than that of the lamellar structure (as shown in figure 2) obtained through the traditional treatment, and the fatigue performance of the titanium alloy is favorably improved.
In this embodiment, the free forging temperature in step S1 is 820 to 920 ℃. And/or the temperature of the solution heat treatment in the step S3 is 900-960 ℃, and the heat preservation time is 90-300 min.
In this embodiment, the annealing temperature in step S5 is 550 ℃ to 700 ℃, and the annealing time is 2h to 12h. And/or the machining allowance in the step S6 is 0.2 mm-0.8 mm. The temperature of the annealing treatment in the step S5 is 550 to 700 ℃, so as to further promote the transformation from the beta phase to the alpha phase and stabilize the internal structure of the thin-walled workpiece. The machining allowance in the step S6 is 0.2 mm-0.8 mm, and when the machining allowance is too large, large deformation is caused due to large cutting force during finish machining; when the machining allowance is too small, the cutting layer is mainly a hardened layer during finish machining, which affects the machining quality.
Examples
Example 1
S1, forging a blank: performing two-phase region free forging on the TC4 blank at the initial forging temperature of 920 ℃ and the final forging temperature of 850 ℃ to obtain a forged blank;
s2, punching and reaming: punching and reaming the forging blank in the step S1 to obtain a forging thin-wall workpiece;
s3, solution treatment: carrying out solution heat treatment on the forged thin-wall workpiece in the step S2, wherein the temperature of the solution heat treatment is 960 ℃, and the heat preservation time is 90min to obtain a thin-wall workpiece a;
s4, cryogenic treatment: adopting liquid nitrogen as a cooling medium, and carrying out cryogenic treatment on the thin-wall workpiece a in the step S3 in a cryogenic box, wherein the temperature of the cryogenic treatment is-190 +/-6 ℃, the cooling rate is 0.5 ℃/min, and the heat preservation time is 6h, so as to obtain a thin-wall workpiece b;
s5, annealing treatment: annealing the thin-wall workpiece b obtained in the step S4 at the temperature of 550 ℃ for 2h to obtain a thin-wall workpiece c;
s6, rough machining and semi-finishing: performing rough machining and semi-finish machining on the thin-wall workpiece c in the step S5, and keeping the machining allowance to be 0.8mm to obtain a thin-wall workpiece d;
s7, cold-hot circulation treatment: carrying out cold and hot circulation treatment on the thin-wall workpiece d obtained in the step S6, wherein the circulation frequency of the cold and hot circulation treatment is 2 times, the cold and hot circulation treatment comprises subzero treatment and heat treatment, the temperature of the subzero treatment is-190 +/-6 ℃, the cooling rate is 0.5 ℃/min, the heat preservation time is 3h, the temperature of the heat treatment is 160 ℃, the heating rate is 0.5 ℃/min, and the heat preservation time is 4h, so as to remove residual stress existing in the thin-wall workpiece d after rough machining and semi-finish machining and obtain a thin-wall workpiece e;
s8, finish machining: firstly, clamping by using a clamp matched with the structure of the thin-wall workpiece e subjected to the cold and hot circulation treatment in the step S7 so as to ensure that the thin-wall workpiece e is uniformly stressed and does not deform, wherein the clamp is made of TC4 titanium alloy, and then finish machining is performed on the thin-wall workpiece e to obtain a thin-wall workpiece f;
s9, step cryogenic treatment: and (3) integrally placing the thin-wall workpiece f and the clamp into a deep cooling box for step deep cooling treatment, cooling to-80 +/-5 ℃, preserving heat for 2 hours, then continuously cooling to-130 ℃, preserving heat for 2 hours, then cooling to-190 +/-6 ℃, preserving heat for 6 hours, wherein the cooling rate is 0.5 ℃/min, finally heating to room temperature, and the heating rate is 0.5 ℃/min, so as to obtain the TC4 titanium alloy high-precision curved thin-wall part.
Example 2
S1, forging a blank: performing two-phase region free forging on the TC4 blank at the initial forging temperature of 880 ℃ and the final forging temperature of 820 ℃ to obtain a forged blank;
s2, punching and reaming: punching and reaming the forging blank in the step S1 to obtain a forging thin-wall workpiece;
s3, solution treatment: carrying out solution heat treatment on the forged thin-wall workpiece in the step S2, wherein the temperature of the solution heat treatment is 930 ℃, and the heat preservation time is 180min, so as to obtain a thin-wall workpiece a;
s4, cryogenic treatment: adopting liquid nitrogen as a cooling medium, and carrying out cryogenic treatment on the thin-wall workpiece a in the step S3 in a cryogenic box, wherein the temperature of the cryogenic treatment is-190 +/-6 ℃, the cooling rate is 2 ℃/min, and the heat preservation time is 12h to obtain a thin-wall workpiece b;
s5, annealing treatment: annealing the thin-wall workpiece b obtained in the step S4 at the temperature of 600 ℃ for 6h to obtain a thin-wall workpiece c;
s6, rough machining and semi-finishing: performing rough machining and semi-finish machining on the thin-wall workpiece c obtained in the step S5, and keeping the machining allowance to be 0.5mm to obtain a thin-wall workpiece d;
s7, cold-hot circulation treatment: carrying out cold and hot circulation treatment on the thin-wall workpiece d obtained in the step S6, wherein the circulation frequency of the cold and hot circulation treatment is 3 times, the cold and hot circulation treatment comprises subzero treatment and heat treatment, the temperature of the subzero treatment is-190 +/-6 ℃, the cooling rate is 2 ℃/min, the heat preservation time is 12h, the temperature of the heat treatment is 180 ℃, the heating rate is 2 ℃/min, and the heat preservation time is 12h, so as to remove residual stress existing in the thin-wall workpiece d after rough machining and semi-finish machining and obtain a thin-wall workpiece e;
s8, fine machining: firstly, clamping by using a clamp matched with the structure of the thin-wall workpiece e subjected to the cold and hot circulation treatment in the step S7 so as to ensure that the thin-wall workpiece e is uniformly stressed and does not deform, wherein the clamp is made of TC4 titanium alloy, and then finish machining is performed on the thin-wall workpiece e to obtain a thin-wall workpiece f;
s9, step cryogenic treatment: and (3) integrally placing the thin-wall workpiece f and the clamp into a deep cooling box for step deep cooling treatment, cooling to minus 80 +/-5 ℃, preserving heat for 4 hours, then continuously cooling to minus 130 +/-5 ℃, preserving heat for 4 hours, then cooling to minus 190 +/-6 ℃, preserving heat for 24 hours, wherein the cooling rate is 2 ℃/min, and finally heating to room temperature, wherein the heating rate is 2 ℃/min, so as to obtain the TC4 titanium alloy high-precision curved surface thin-wall part.
Example 3
S1, forging a blank: carrying out two-phase region free forging on the TC4 blank at the initial forging temperature of 900 ℃ and the final forging temperature of 850 ℃ to obtain a forged blank;
s2, punching and reaming: punching and reaming the forging blank in the step S1 to obtain a forging thin-wall workpiece;
s3, solution treatment: carrying out solution heat treatment on the forged thin-wall workpiece in the step S2, wherein the temperature of the solution heat treatment is 900 ℃, and the heat preservation time is 300min, so as to obtain a thin-wall workpiece a;
s4, cryogenic treatment: adopting liquid nitrogen as a cooling medium, and carrying out cryogenic treatment on the thin-wall workpiece a in the step S3 in a cryogenic box, wherein the temperature of the cryogenic treatment is-180 ℃, the cooling rate is 3 ℃/min, and the heat preservation time is 48h, so as to obtain a thin-wall workpiece b;
s5, annealing treatment: annealing the thin-wall workpiece b obtained in the step S4, wherein the annealing temperature is 700 ℃, and the annealing time is 12 hours, so as to obtain a thin-wall workpiece c;
s6, rough machining and semi-finishing: performing rough machining and semi-finish machining on the thin-wall workpiece c in the step S5, and keeping the machining allowance to be 0.2mm to obtain a thin-wall workpiece d;
s7, cold-hot circulation treatment: carrying out cold and hot circulating treatment on the thin-wall workpiece d obtained in the step S6, wherein the circulating frequency of the cold and hot circulating treatment is 4 times, the cold and hot circulating treatment comprises subzero treatment and heat treatment, the temperature of the subzero treatment is-180 ℃, the temperature reduction rate is 4 ℃/min, the heat preservation time is 24h, the temperature of the heat treatment is 200 ℃, the temperature rise rate is 4 ℃/min, and the heat preservation time is 24h, so as to remove residual stress existing in the thin-wall workpiece d after rough machining and semi-finish machining and obtain a thin-wall workpiece e;
s8, fine machining: firstly, clamping by using a clamp matched with the structure of the thin-wall workpiece e subjected to the cold and hot circulation treatment in the step S7 so as to ensure that the thin-wall workpiece e is uniformly stressed and does not deform, wherein the clamp is made of TC4 titanium alloy, and then finish machining is performed on the thin-wall workpiece e to obtain a thin-wall workpiece f;
s9, step cryogenic treatment: and (3) integrally placing the thin-wall workpiece f and the clamp into a deep cooling box for step deep cooling treatment, cooling to minus 80 +/-5 ℃, preserving heat for 6 hours, then continuously cooling to minus 130 +/-5 ℃, preserving heat for 6 hours, then cooling to minus 190 +/-6 ℃, preserving heat for 48 hours, wherein the cooling rate is 3 ℃/min, and finally heating to room temperature, wherein the heating rate is 3 ℃/min, so as to obtain the TC4 titanium alloy high-precision curved surface thin-wall part.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. The processing method of the TC4 titanium alloy high-precision curved thin-wall part is characterized by comprising the following steps of:
s1, forging a blank: carrying out free forging on the TC4 blank in a two-phase region to obtain a forged blank;
s2, punching and reaming: punching and reaming the forging blank in the step S1 to obtain a forging thin-wall workpiece;
s3, solution treatment: carrying out solution heat treatment on the forged thin-wall workpiece in the step S2 to obtain a thin-wall workpiece a;
s4, cryogenic treatment: performing subzero treatment on the thin-wall workpiece a in the step S3 to obtain a thin-wall workpiece b, wherein the subzero treatment adopts liquid nitrogen as a cooling medium and comprises the step of performing subzero treatment on the thin-wall workpiece a in the step S3 in a subzero box; the temperature of the cryogenic treatment is-180 ℃ to-196 ℃, the cooling rate is 0.5 ℃/min to 3 ℃/min, and the heat preservation time is 6 to 48 hours;
s5, annealing treatment: annealing the thin-wall workpiece b obtained in the step S4 to obtain a thin-wall workpiece c;
s6, rough machining and semi-finishing: performing rough machining and semi-finish machining on the thin-wall workpiece c in the step S5, and reserving machining allowance to obtain a thin-wall workpiece d;
s7, cold-hot circulation treatment: performing cold-hot circulation treatment on the thin-wall workpiece d obtained in the step S6 to remove residual stress existing in the thin-wall workpiece d after rough machining and semi-finish machining to obtain a thin-wall workpiece e, wherein the cycle number of the cold-hot circulation treatment is 2-4, the cold-hot circulation treatment comprises cryogenic treatment and heat treatment, the temperature of the cryogenic treatment is-180 ℃ to-196 ℃, the heat preservation time is 3h to 24h, the temperature of the heat treatment is 160 ℃ to 200 ℃, and the heat preservation time is 4h to 24h;
s8, fine machining: performing finish machining on the thin-wall workpiece e subjected to the cold-hot circulating treatment in the step S7 to obtain a thin-wall workpiece f;
s9, step cryogenic treatment: and step cryogenic treatment is carried out on the thin-wall workpiece f in the step S8 to obtain the TC4 titanium alloy high-precision curved thin-wall part, wherein the step cryogenic treatment comprises the steps of cooling to minus 80 +/-5 ℃, preserving heat for 2 h-6 h, then continuously cooling to minus 130 +/-5 ℃, preserving heat for 2 h-6 h, cooling to minus 190 +/-6 ℃, preserving heat for 6 h-48 h, and finally heating to room temperature.
2. The method for manufacturing a TC4 titanium alloy high-precision curved thin-walled workpiece according to claim 1,
and step S8, clamping by using a clamp matched with the structure of the thin-wall workpiece e subjected to the cold-hot circulation treatment in the step S7 so as to ensure that the thin-wall workpiece e is uniformly stressed and does not deform, and then performing finish machining on the thin-wall workpiece e.
3. The method for manufacturing a TC4 titanium alloy high-precision curved thin-walled workpiece according to claim 2,
the fixture is made of TC4 titanium alloy.
4. The method for manufacturing a TC4 titanium alloy high-precision curved thin-walled workpiece according to claim 1,
the cooling rate is 0.5-3 ℃/min;
the rate of temperature rise is 0.5-3 ℃/min.
5. The method for manufacturing a TC4 titanium alloy high-precision curved thin-walled workpiece according to claim 1,
the cold and hot circulation treatment adopts the steps of firstly carrying out heat treatment and then carrying out subzero treatment to finish one cold and hot circulation treatment, and the like until all cold and hot circulation treatments are finished.
6. The method for manufacturing a TC4 titanium alloy high-precision curved thin-walled workpiece according to claim 1,
the free forging temperature in the step S1 is 820-920 ℃; and/or
The temperature of the solution heat treatment in the step S3 is 900-960 ℃, and the heat preservation time is 90-300 min.
7. The method for manufacturing a TC4 titanium alloy high-precision curved thin-walled workpiece according to claim 1,
the temperature of the annealing treatment in the step S5 is 550-700 ℃, and the annealing time is 2-12 h; and/or
The machining allowance in the step S6 is 0.2 mm-0.8 mm.
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