Titanium alloy isothermal thermal forming process based on analogue simulation

Abstract

The invention provides a titanium alloy isothermal thermal forming process based on analogue simulation. The titanium alloy isothermal thermal forming process comprises the steps that S1, a material performance database capable of being recognized by Autoform software is established according to input variables and output variables of a material performance test; s2, determining an isothermal hot forming process route according to the characteristics of the titanium alloy part, wherein the isothermal hot forming process route comprises an isothermal hot deep drawing process and an isothermal hot sizing process; s3, theoretical analysis is conducted according to the material performance database and the isothermal thermal forming process route, and thermal forming parameters needing to be simulated in the isothermal thermal deep drawing procedure and the isothermal thermal sizing procedure are determined; s4, performing analogue simulation of an isothermal hot deep drawing process and an isothermal hot sizing process on the titanium alloy plate by using Autoform software; and S5, trial-manufacturing of the part is conducted according to the forming parameters obtained through analogue simulation, and the forming parameters of the isothermal hot deep drawing procedure and the isothermal hot sizing procedure of the part are adjusted according to the forming quality of the trial-manufactured part so that the part can meet the technical requirements of the part.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy forming, and in particular to an isothermal hot forming process of titanium alloy based on simulation. Background Art

[0002] In the application of titanium alloy materials, sheet forming, especially thin sheet forming, has always been a difficult point in the forming field. Because the forming performance of titanium alloy at room temperature is poor, in order to improve the forming performance of the material, the titanium alloy sheet is often heated before forming, which brings many uncertain factors to the forming of titanium alloy sheet and increases the complexity of the forming process.

[0003] There are generally two ways of hot forming: local hot forming and isothermal hot forming.

[0004] Local hot forming means that during the forming process, the mold is not heated, and the titanium alloy sheet is immediately transferred to the mold for forming after being heated. During the forming process, heat conduction will occur between the titanium alloy sheet and the mold, the titanium alloy sheet will cool down, and the mold will heat up. Isothermal hot forming means that during the forming process, the mold and the titanium alloy sheet are heated at the same time before forming, and the forming conditions are different.

[0005] In view of the high sensitivity of titanium alloy's forming performance to temperature, titanium alloy parts are suitable for isothermal hot forming. At the same time, the cost of isothermal hot forming experiments for titanium alloy parts is high and the cycle is long. Therefore, the isothermal hot stamping process on a single-action hot press is widely used in engineering, and the isothermal hot drawing process on a double-action hot press is only used for titanium alloy parts with relatively low process difficulty, such as rotating bodies and shallow box-shaped parts.

[0006] For parts with relatively high process difficulty (such as box-shaped parts with large depth), they need to be split into multiple parts with simple structure and easy to form according to the shape of the parts to be formed. The forming of each part is mostly done by isothermal hot forming process. After forming, the parts of each part are welded together to form the whole part. The process is complicated, the precision is difficult to control, the consistency of the welding joint is poor, and the overall precision of the multi-section welded parts is poor due to welding deformation, which leads to poor overall forming precision after the parts are formed. A single-action hot press means that only the punch or die moves, and a double-action hydraulic press means that in addition to the movement of the punch or die, it can also drive the blank holder to move. For thin-walled sheet metal parts, isothermal hot deep drawing generally requires the use of a blank holder, so double-action hot press equipment is mostly used.

[0007] To solve the above problems, the forming parameters of isothermal hot forming can be obtained through reliable simulation, and then the simulation results can be verified through isothermal hot forming test molds, thereby reducing the test cost and shortening the test cycle. However, the commonly used finite element simulation software is not very suitable for isothermal hot forming simulation. Because the calculation cycle of finite element analysis software with thermal field simulation modules such as Abaqus, Deform, MARC, and Pam-Stamp is too long, generally taking several hours to several days, and the convergence of the calculation is relatively poor, and the calculation is prone to failure. Moreover, there are few settings and optimizations for sheet metal forming, and the interaction is not friendly.

[0008] Autoform software is a dedicated sheet metal finite element analysis software with a short calculation cycle, high calculation success rate and high simulation accuracy. It is widely used in the field of automotive high-strength steel hot forming, but it is designed to simulate local hot forming processes.

[0009] Therefore, there is an urgent need for an isothermal hot forming process for titanium alloys based on simulation to solve the above technical problems. Summary of the invention

[0010] The purpose of the present invention is to propose a titanium alloy isothermal hot forming process based on simulation to solve at least one of the above problems.

[0011] The isothermal hot forming process of titanium alloy based on simulation includes: S1. Performing a material property test on a titanium alloy material, wherein the input variables of the material property test include temperature, average strain rate and sample direction, and the output variables of the material property test include elastic modulus, Poisson's ratio, flow stress-strain curve and plate thickness directivity coefficient r value; establishing a material property database identifiable by Autoform software according to the input variables and output variables of the material property test; S2. Determine an isothermal hot forming process route according to the characteristics of the titanium alloy part, wherein the isothermal hot forming process route includes an isothermal hot drawing process and an isothermal hot shaping process; S3. Perform theoretical analysis based on the material property database and the isothermal hot forming process route to determine the hot forming parameters that need to be simulated for the isothermal hot drawing process and the isothermal hot shaping process, wherein the hot forming parameters of the isothermal hot forming process include temperature, average strain rate and sheet placement direction; S4, using Autoform software to simulate the isothermal hot drawing process and the isothermal hot shaping process on the titanium alloy sheet; According to the simulation results of Autoform software, forming parameters of the isothermal hot drawing process and the isothermal hot shaping process are obtained; S5: trial-produce the parts according to the forming parameters obtained from the simulation, and adjust the forming parameters of the isothermal hot drawing process and the isothermal hot shaping process of the parts according to the forming quality of the trial-produced parts to meet the technical requirements of the parts.

[0012] Preferably, in step S3, The temperature of the titanium alloy part simulation is linearly sampled, with a simulated temperature value taken at every 50°C interval; The average strain rate adopts proportional sampling, and the value range of the average strain rate is 10 -3 s -1 -10 -1 s -1 ; The sheet placement direction is the angle between the sheet length direction and the rolling direction, which are 0°, 45° and 90° respectively.

[0013] Preferably, in step S3, the average strain rate of the titanium alloy part in the simulation of the isothermal hot drawing process and the isothermal hot shaping process is calculated respectively. ; The calculation formula is: ; is the maximum deformation of the corresponding process of titanium alloy parts; s is the stroke of the corresponding process; It is the load clamping speed of the thermoforming equipment used in the corresponding process.

[0014] Preferably, in step S4, the simulation using the Autoform software includes: S41, importing the material properties database of the titanium alloy obtained in the material properties test in step S1; S42, constructing simulation models of the isothermal hot drawing process and the isothermal hot shaping process of the titanium alloy sheet, and setting boundary conditions for the simulation models of the isothermal hot drawing process and the isothermal hot shaping process respectively; S43, simulating the hot forming parameters determined in step S3, obtaining the optimal thinning rate distribution cloud map corresponding to different hot forming parameters, and obtaining the forming parameters of the isothermal hot drawing process and the isothermal hot shaping process according to the simulation results.

[0015] Preferably, in step S42, in the isothermal hot drawing process, the simulation model of the titanium alloy part includes a first punch, a first die and a blank holder, the first punch is arranged above the first die, the titanium alloy sheet is arranged between the first punch and the first die, and the blank holder is arranged between the first punch and the titanium alloy sheet; In the isothermal hot shaping process, the simulation model of the titanium alloy part includes a second convex die and a second concave die, the second convex die is arranged above the second concave die, and the preformed part formed in the isothermal hot drawing process is placed between the second convex die and the second concave die; The boundary conditions in the isothermal hot drawing process in step S42 include: Using the hot forming module in the Autoform software, the first male die, the first female die and the titanium alloy sheet are simultaneously loaded with a thermal force field, and heat radiation and heat conduction are set to 0; applying a fixed constraint to the first concave die; Applying a first displacement to the blank holder ring to ensure a blank holder gap; Applying a second displacement to the first convex mold to ensure a mold-closing position of the first convex mold and the first concave mold; The friction coefficient of the first concave die is 0.1-0.15; the friction coefficient of the first convex die is 0.4-0.45; The boundary conditions in the isothermal heat correction process in step S42 include: A fixed constraint is applied to the second concave mold.

[0016] A third displacement is applied to the second punch to ensure the second punch and the second die are in a clamping position.

[0017] The friction coefficient of the second concave mold is 0.4-0.45; the friction coefficient of the second convex mold is 0.4-0.45.

[0018] Preferably, in step S5, trial production of parts is performed according to the forming parameters obtained by simulation, including: The forming parameters of the isothermal hot drawing process include: The forming parameters of the isothermal hot drawing process obtained in step S43 include temperature, hot forming equipment load clamping speed, sheet material placement direction, blank holder gap, blank holder force, and clamping force; Water-based graphite is used to lubricate titanium alloy sheets; boron nitride is used to prevent oxidation of titanium alloy sheets; The forming parameters of the isothermal heat correction process include: The forming parameters of the isothermal heat correction process obtained in step S43 are used, including temperature, hot forming equipment load clamping speed, sheet material placement direction, and clamping force; Boron nitride is used to prevent oxidation of titanium alloy parts formed by the isothermal hot drawing process.

[0019] Preferably, in step S5, trial production of parts is performed according to the forming parameters obtained by simulation, and further includes: The isothermal heat correction process selects an intermediate temperature to calculate thermal expansion compensation and determine the size of the mold surface according to the forming temperature range obtained in step S43.

[0020] Preferably, the trial production of the parts according to the forming parameters obtained by the simulation in step S5 also includes forming by a double-action hot forming hydraulic press; The working parameters of the double-action hot forming hydraulic press include: the forming pressure of the double-action hot forming hydraulic press controls the clamping force of the molds used in the isothermal hot drawing process and the isothermal hot shaping process; the ejector pin of the double-action hot forming hydraulic press is connected to the blank holder, and the ejector pin pressure controls the blank holder force of the blank holder used in the isothermal hot drawing process; The pressure control accuracy range of the forming pressure of the double-action hot forming hydraulic press is not greater than ±1%; An upper workbench is connected to the first punch or the second punch, and the upper workbench is used to control the forming speed of the titanium alloy part; The first concave die or the second concave die is fixedly mounted on the lower workbench; The maximum heating temperature of the working chamber of the double-action hot forming hydraulic press does not exceed 900°C.

[0021] Compared with the prior art, the present invention has the following beneficial effects: Titanium alloy parts are manufactured by isothermal hot forming. Compared with the segmented isothermal hot stamping and welding processes, the formation of welds is avoided, and the precision and consistency of the parts are better. The welding and shaping processes are eliminated, and the forming efficiency is higher. There is no manual intervention such as shaping and welding, and the surface quality of the parts is better.

[0022] By establishing a material properties database, the accuracy of subsequent simulations can be effectively improved.

[0023] The hot forming module of Autoform software combines the characteristics of accuracy, efficiency and interactive friendliness. Through the secondary development of its thermal field loading method, it can more accurately simulate the hot forming conditions and solve the finite element simulation problem of the isothermal hot forming process of titanium alloy.

[0024] Through Autoform finite element simulation, the forming parameters of the titanium alloy parts trial production are obtained, and the modification of the forming parameters during the manufacturing process is guided according to the influence of the forming parameters on the forming quality. While avoiding forming failure conditions such as cracks and wrinkles, the forming thinning is optimized to meet the technical requirements of the parts. This can effectively reduce the development cost of the parts, shorten the development cycle of the parts, and facilitate the rapid determination of the development process of the parts.

[0025] By controlling the forming temperature and affecting the expansion of parts and molds, the deviation of forming dimensions can be compensated within a certain range, so that the forming dimensions meet the technical requirements of the parts, avoiding a significant increase in development costs and development cycles caused by mold repair. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic structural diagram of a titanium alloy box-shaped member provided in an embodiment of the present invention; Figure 2 It is a schematic diagram of the forming process route of an embodiment of the present invention; Figure 3 It is a simulation model of the isothermal hot drawing process of the embodiment OP20 of the present invention; Figure 4 It is a simulation model of the isothermal heat correction process of the embodiment OP30 of the present invention; Figure 5 It is a flow chart of a titanium alloy isothermal hot forming process based on simulation in an embodiment of the present invention; Figure 6 In the embodiment of the present invention, when the sheet material is placed in the direction of 0° and the average strain rate is 10 -1 s -1 Flow stress-strain curve of Ti6Al4V material at simulation temperature; Figure 7 In the embodiment of the present invention, when the sheet material is placed in the direction of 0° and the average strain rate is 10 -2 s -1 Flow stress-strain curve of Ti6Al4V material at simulation temperature; Figure 8 In the embodiment of the present invention, when the sheet material is placed in the direction of 0° and the average strain rate is 10 -3 s -1 Flow stress-strain curve of Ti6Al4V material at simulation temperature; Fig. 9 The average strain rate of the embodiment of the present invention is 10 -3 s -1 The thickness directivity coefficient r value-temperature curve of Ti6Al4V material; Fig.10 is a curve diagram of the plate thickness directivity coefficient r value-average strain rate of the Ti6Al4V material at a temperature of 600° C. in an embodiment of the present invention; Fig.11 It is a simulation cloud diagram of working condition 1 in Table 2 of the embodiment of the present invention; Fig.12 It is a simulation cloud diagram of working condition 2 in Table 2 of the embodiment of the present invention; Fig.13It is a simulation cloud diagram of working condition 3 in Table 2 of the embodiment of the present invention; Fig.14 It is a simulation cloud diagram of working condition 4 in Table 2 of the embodiment of the present invention; Fig.15 It is a simulation cloud diagram of working condition 5 in Table 2 of the embodiment of the present invention; Fig.16 It is a simulation cloud diagram of working condition 6 in Table 2 of the embodiment of the present invention; Fig.17 It is a simulation cloud diagram of working condition 7 in Table 2 of the embodiment of the present invention; Fig.18 It is a simulation cloud diagram of working condition 8 in Table 2 of the embodiment of the present invention.

[0027] In the figure: 1. titanium alloy sheet; 2. first punch; 3. first die; 4. pressure ring; 5. second punch; 6. second die. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below by referring to the accompanying drawings and by specific implementation methods. It is to be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. It should also be noted that, for the convenience of description, only the parts related to the present invention are shown in the accompanying drawings, but not all.

[0029] Some directional words are defined in the present invention. Unless otherwise specified, the directional words used, such as "up", "down", "left", "right", "inside" and "outside", are used to facilitate understanding and therefore do not constitute a limitation on the scope of protection of the present invention.

[0030] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0031] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] The parts formed by the titanium alloy isothermal hot forming process based on simulation provided in this embodiment are as follows Figure 1 The rectangular box-shaped part shown. The titanium alloy box-shaped part is made of Ti6Al4V, which contains 6% of the α-stabilizing element Al and 4% of the β-stabilizing element V. Of course, it can also be made of other titanium alloy materials, which is not limited to this. The material thickness is 1.2mm, the outer dimensions are approximately 380mm×160mm×91mm, the fillet radius at the transition between the side wall and the flange is 10mm, the side wall transition fillet radius is 20mm, the bottom fillet radius is 8mm, and the bottom fillet transition is smoothed. The maximum thinning rate of the formed Ti6Al4V titanium alloy box-shaped part does not exceed 25%.

[0033] It can be understood that the titanium alloy isothermal hot forming process based on simulation is not limited to rectangular box-shaped parts, but is also applicable to titanium alloy parts of other shapes.

[0034] In particular, the titanium alloy isothermal hot forming process based on simulation is also applicable to other isothermal hot forming processes, including but not limited to double-action hot drawing process, single-action hot stamping process, hot bending process, hot shaping process, etc.

[0035] This embodiment does not limit this and can be set according to actual needs.

[0036] like Figure 1-Figure 5 As shown in the figure, the isothermal hot forming process of titanium alloy based on simulation includes the following: S1. Conduct material property tests on titanium alloy materials. The input variables of the material property test include temperature, average strain rate and specimen direction. The output variables of the material property test include elastic modulus, Poisson's ratio, flow stress-strain curve and plate thickness directivity coefficient r value. Establish a material property database that can be recognized by Autoform software based on the input variables and output variables of the material property test. S2. Determine the isothermal hot forming process route according to the characteristics of the titanium alloy parts. The isothermal hot forming process route includes an isothermal hot drawing process and an isothermal hot shaping process; S3. According to the material property database and the isothermal hot forming process route, a theoretical analysis is performed to determine the hot forming parameters that need to be simulated for the isothermal hot drawing process and the isothermal hot shaping process. The parameters of the isothermal hot forming process include temperature, average strain rate and sheet placement direction. S4, using Autoform software to simulate the isothermal hot drawing process and the isothermal hot shaping process of the titanium alloy sheet 1; The forming parameters of the isothermal hot drawing process and the isothermal hot shaping process are obtained according to the simulation results of the Autoform software; S5: Trial-produce parts according to the forming parameters obtained from the simulation, and adjust the forming parameters of the isothermal hot drawing process and the isothermal hot shaping process of the parts according to the forming quality of the trial-produced parts to meet the technical requirements of the parts.

[0037] In step S1, a plurality of data-fitted function curves are obtained through material property tests of titanium alloy materials, and the Autoform software can identify the function of the function curve, or can identify a predetermined number of data points selected from the data.

[0038] Preferably, in step S3, the temperature of the titanium alloy part simulation is sampled linearly, and a simulated temperature value is taken every 50°C. The average strain rate is sampled proportionally, and the range of the average strain rate is 10 -3 s -1 -10 -1 s -1 The sheet placement directions are 0°, 45° and 90°.

[0039] The elastic modulus of titanium alloy materials is related to temperature. Different titanium alloy materials have different relationships with temperature, which can be obtained by querying existing data. The relationship between the elastic modulus and temperature of the Ti6Al4V titanium alloy in this embodiment can be queried based on existing technology. The Poisson's ratio of the above Ti6Al4V titanium alloy is 0.33.

[0040] The material properties test of the titanium alloy material mentioned above includes three input variables. When the values ​​of temperature, average strain rate and sheet placement direction are different, multiple groups of different simulation conditions will be formed.

[0041] Preferably, the material property test on the Ti6Al4V titanium alloy material in step S1 in this embodiment is a unidirectional deep drawing high temperature mechanical property test on the plate of the Ti6Al4V titanium alloy material, and the test standard complies with GB / T228.2-2015.

[0042] Through the material performance test of Ti6Al4V titanium alloy, a material performance database suitable for Autoform software is established. That is, the relationship between the input variables and output variables of the material performance test of Ti6Al4V titanium alloy is input into the Autoform software after data processing to build a material model for titanium alloy sheet simulation.

[0043] The input variables of the material performance test of titanium alloy materials are temperature, average strain rate and specimen direction. The specimen direction refers to the angle between the length direction of the specimen and the rolling direction of the sheet. The performance indicators in the material performance database include elastic modulus, Poisson's ratio, flow stress-strain curve and r value. The r value is the thickness directional coefficient.

[0044] In step S1, the temperature sampling point is determined by linear sampling for the variable temperature of the material performance test of the titanium alloy material. In the range of 20°C to 300°C, the forming performance of the titanium alloy material is little affected by temperature. Therefore, the titanium alloy material cannot meet the process requirements in the temperature range of 20°C to 300°C. In the range of 300°C to 500°C, as the temperature increases, the forming performance of the titanium alloy material gradually improves, but the overall change is not significant.

[0045] The lower limit of the temperature range of isothermal hot forming is the minimum temperature corresponding to the forming of the titanium alloy material part in accordance with the predetermined requirements of the forming limit of the isothermal hot forming process of the titanium alloy material. The upper limit of the temperature range of isothermal hot forming is the superplastic forming temperature of the titanium alloy material. And because the performance of the titanium alloy material changes greatly at the recrystallization temperature, the value of the forming temperature of the titanium alloy part must include the recrystallization temperature. In this embodiment, the recrystallization temperature of the Ti6Al4V titanium alloy material is 700°C, and the superplastic forming temperature is 850°C.

[0046] The titanium alloy material will have a certain impact on the parts formed by the isothermal hot forming process under the condition of a temperature change value of 50°C, but it does not reach the level of determining whether the parts formed by the isothermal hot forming process can be formed. In addition, considering the test cost, the material property test of the titanium alloy material in this embodiment selects linear sampling at intervals of 50°C within the temperature range of 500°C to 850°C, that is, eight temperature sampling points of 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, and 850°C are selected.

[0047] The sampling range of the average strain rate of titanium alloy materials is limited by the forming speed of the hot forming equipment, that is, the load clamping speed of the hot forming equipment.

[0048] Generally, the average strain rate range for isothermal hot forming of titanium alloy materials on conventional hot forming equipment is 10 -3 s -1~ 10 -1 s -1 Specifically, considering the difficulty and cost of the experiment, this embodiment selects a proportional sampling method with an interval of 10 times, and selects 10 -3 s -1 , 10 -2 s -1 and 10 -1 s -1 Three sampling points of average strain rate.

[0049] In other embodiments, for different hot forming equipment and different forming process requirements, the sampling range of the average strain rate of the titanium alloy material may be different, and the sampling points of the average strain rate adopt proportional sampling, and the proportion can be adjusted according to actual needs.

[0050] According to the measurement specification of r value (plate thickness directional coefficient) of material performance test of titanium alloy material, the plate placement directions are selected as 0°, 45° and 90°.

[0051] In step S2, a forming process route is designed according to the characteristics of the titanium alloy part. Specifically, the part forming route is as follows: Figure 2 As shown: The part forming process is completed in two steps: OP20 isothermal hot drawing process and OP30 isothermal hot shaping process. In the OP20 isothermal hot drawing process, the features in the original mold surface that are not suitable for drawing are modified to facilitate the flow of flange material. In the OP30 isothermal hot shaping process, the unformed features or unformed features of the previous sequence are shaped. In this embodiment, Figure 3 As shown, the fillet on the flange (I) and the fillet on the flange and side wall (II) of the Ti6Al4V titanium alloy material are used to ensure the forming quality of the part and the dimensional accuracy of the part.

[0052] In this embodiment, the temperature range, average strain rate range and sheet placement direction of the Ti6Al4V titanium alloy part simulated in the Autoform software are determined.

[0053] In step S3, the temperature range of the Ti6Al4V titanium alloy part simulation is determined according to the material property database and the requirements of the isothermal hot forming process. The lower limit of the temperature range is the minimum temperature corresponding to the forming of the Ti6Al4V titanium alloy part in accordance with the predetermined requirements of the forming limit of the isothermal hot forming process of the Ti6Al4V titanium alloy material. The upper limit of the temperature range is the superplastic forming temperature of the Ti6Al4V titanium alloy material.

[0054] Specifically, according to the technical requirements of the parts of the embodiment, the maximum deformation allowed by the parts is 25%, and the forming limit of the Ti6Al4V titanium alloy material is required to be more than 25% to ensure sufficient forming threshold. Generally speaking, the higher the temperature of the Ti6Al4V titanium alloy material, the greater the forming limit of the Ti6Al4V titanium alloy parts. Therefore, according to the material performance database and the technical requirements of the parts, the lower limit of the temperature range of hot forming is the temperature corresponding to the forming limit of 25%. In this embodiment, the temperature is 600°C. The forming limit of the box-shaped part in this embodiment is required to reach 25%. The hot forming temperature of the part is related to the forming limit of the part. For example, when the hot forming temperature of the part is 600°C, the forming limit that the part can reach is 10%. After exceeding 10%, the part may continue to be drawn and cracked. In other embodiments, the lower limit of the temperature range of hot forming needs to be set according to the requirements of the hot forming process, and the forming limit is not limited to 25%.

[0055] In this embodiment, the variable temperature of the material performance test of the above-mentioned Ti6Al4V titanium alloy material is determined by linear sampling to determine the sampling point of the temperature. In the range of 20°C to 300°C, the forming performance of the Ti6Al4V titanium alloy material is little affected by temperature. Therefore, the Ti6Al4V titanium alloy material cannot meet the process requirements in the temperature range of 20°C to 300°C. In the range of 300°C to 500°C, as the temperature increases, the forming performance of the Ti6Al4V titanium alloy material gradually improves, but the overall change is not large. Above 850°C, the Ti6Al4V titanium alloy material exhibits superplasticity, the performance of the material changes greatly, and the material tends to thin rather than deform during the forming process.

[0056] In summary, in this embodiment, the temperature range of the titanium alloy part simulated in the Autoform software is 600°C~850°C.

[0057] In step S3, the average strain rate of the titanium alloy part in the simulation of the isothermal hot drawing process and the isothermal hot shaping process is calculated respectively. , and its calculation formula is

[0058] in, is the maximum deformation of the corresponding process of titanium alloy parts; that is, in the isothermal hot drawing process, It is the maximum deformation of titanium alloy parts in the isothermal hot drawing process; in the isothermal hot shaping process, It is the maximum deformation of titanium alloy parts in the isothermal heat correction process; s is the stroke in the corresponding process; that is, in the isothermal hot drawing process, s is the stroke of the isothermal hot drawing process; in the isothermal hot shaping process, s is the stroke of the isothermal hot shaping process; is the load clamping speed of the hot forming equipment used in the corresponding process; that is, in the isothermal hot drawing process, is the load clamping speed of the hot forming equipment used in the isothermal hot drawing process; in the isothermal hot shaping process, It is the load clamping speed of the hot forming equipment used in the isothermal heat shaping process.

[0059] The above calculation formula can be used to calculate the average strain rate of the isothermal hot drawing process and the isothermal hot shaping process respectively: .

[0060] Specifically, in this embodiment, the stroke of the OP20 isothermal hot drawing process of the Ti6Al4V titanium alloy part is 100mm, maximum deformation About 20%, thermoforming equipment load clamping speed The range is 0.5mm / s~5mm / s, depending on the average strain rate The calculation formula

[0061] The hot forming equipment can meet the requirements of 10 parts in this process -3 s -1 ~10 -2 s -1 The average strain rate requirement.

[0062] Specifically, in this embodiment, the stroke s of the OP30 isothermal heat correction process of the Ti6Al4V titanium alloy part is about 10 mm, and the maximum deformation About 20%, thermoforming equipment load clamping speed The range is 0.5mm / s~5mm / s, depending on the average strain rate The calculation formula

[0063] The hot forming equipment can meet the requirements of 10 parts in this process -2 s -1 ~10 -1 s -1 The average strain rate requirement.

[0064] In summary, the average strain rate of the titanium alloy part in the isothermal hot drawing process in this embodiment ranges from 10 -3 s -1 ~10 -2 s -1 The average strain rate in the isothermal heat correction process ranges from 10 -2 s -1 ~10 -2 s -1 .

[0065] In this embodiment, when hot forming the Ti6Al4V titanium alloy material, a proportional sampling method with an interval of 10 times is selected. -3 s -1 , 10 -2 s -1 and 10 -1 s -1 Three sampling points of average strain rate.

[0066] In step S3, the sheet placement direction is determined, that is, the sheet rolling direction and a certain angle of 0°, 45° and 90° are placed in three states with the die. The die in this embodiment is a cuboid, and the length direction of the sheet when it is cut is at a certain angle to the sheet rolling direction, that is, the sheet rolling direction and the length direction of the die are at a certain angle.

[0067] In summary, in this embodiment, the sheet material placement direction is selected, that is, the sheet material rolling direction and the mold length direction are placed in three positions of 0°, 45° and 90°.

[0068] By analyzing the material properties within the above value range, the simulated hot forming parameters of the part are further determined.

[0069] Figure 6 The average strain rate of Ti6Al4V titanium alloy is 10 -1 s -1 Flow stress-strain curves at different temperatures under the conditions of . Figure 7 The average strain rate of Ti6Al4V titanium alloy is 10 -2 s -1 Flow stress-strain curves at different temperatures under the conditions of . Figure 8 The average strain rate of Ti6Al4V titanium alloy is 10 -3 s -1 Flow stress-strain curves at different temperatures under the conditions of . Flow stress is the stress state of Ti6Al4V titanium alloy material under different temperatures, average strain rates and strain conditions. It is an important data reflecting the forming performance of Ti6Al4V titanium alloy material, and it is also a comprehensive reflection of the evolution of the metal's internal microstructure and performance changes during the deformation process.

[0070] go through Figure 6-Figure 8 The comparison and analysis show that: under the condition of constant average strain rate, in the temperature range of 600℃-850℃, the flow stress of Ti6Al4V titanium alloy decreases significantly with the increase of temperature, and the forming limit increases significantly. -3 s -1 ~10 -1 s-1 Within this range, the flow stress of Ti6Al4V titanium alloy decreases significantly with the decrease of the average strain rate, and the forming limit increases significantly.

[0071] Fig. 9 The average strain rate of Ti6Al4V titanium alloy is 10 -3 s -1 The thickness directional coefficient r value-temperature curve at different angles between the length direction and the rolling direction of the sheet. The thickness directional coefficient r value characterizes the difference between the deformation performance in the thickness direction and the plate plane direction of the sheet under the same stress conditions. The larger the r value, the more difficult it is to deform in the thickness direction, and the parts are less likely to be thinned, which is conducive to deep drawing. Comparison and analysis Fig. 9 It can be seen that the r value decreases significantly with the increase of temperature. The higher the temperature, the less significant the directional difference of the r value is, and it tends to be uniform above 800°C. The r value of the sample at 45° to the rolling direction is the largest. Therefore, the lower the temperature, the larger the r value, and the increase in the r value in the 0° and 90° directions is much lower than that in the 45° direction.

[0072] Fig.10 This is the variation curve of the plate thickness directional coefficient r value-average strain rate at different angles to the rolling direction when the forming temperature of Ti6Al4V titanium alloy material is 600℃. Fig.10 It can be seen that the greater the average strain rate, the greater the r value; the increase in the r value in the 0° and 90° directions is much lower than that in the 45° direction. In summary, the r value increases with the decrease in temperature and the increase in the average strain rate, and the increase in the r value in the 0° and 90° directions is much lower than that in the 45° direction.

[0073] comprehensive Fig. 9 and Fig.10 It can be seen that when the temperature remains constant, the average strain rate is 10 -3 s -1 to 10 -1 s -1 When the r value and the average strain rate change within a certain range, the r value and the average strain rate increase in a positive linear curve.

[0074] Specifically, based on the characteristics of titanium alloy materials themselves and according to the above material performance experimental data, the influence of titanium alloy material properties on part forming is as follows: 1. Effect of temperature on part formability ① As the forming temperature increases, the forming limit of the material increases and the deformation resistance decreases, which is conducive to deep drawing.

[0075] ② With the increase of forming temperature, material friction increases, work hardening phenomenon weakens, the bearing capacity of the deep drawing force transmission area, which is the area of ​​the side wall of the box-shaped part, weakens, and stress concentration phenomenon is obvious. The r value decreases, and the part tends to be thinner. It is not conducive to deep drawing.

[0076] ③ With the increase of forming temperature, the oxidation of parts becomes serious. There is basically no oxidation at 600℃, but there is serious oxidation above 750℃.

[0077] ④Around 700℃ is the recrystallization temperature of TC4 material. Above 700℃, the material properties change significantly, the springback of parts forming is significantly reduced, and the correction effect is significant.

[0078] 2. The average strain rate has the following effects on the formability of parts: The smaller the average strain rate, the more favorable it is for forming.

[0079] 3. The direction of sheet placement has the following effects on part formability: The higher the temperature, the smaller the effect of sheet metal placement direction on part formability. Above 700°C, the effect of sheet metal placement direction on part formability can be ignored.

[0080] For the OP20 isothermal hot drawing process, the stress in each direction of the box-shaped part is uneven, and the stress concentration phenomenon is obvious. The above factor ② has a significant effect. Combining the above four factors, especially the existence of the above factor ②, it is difficult to directly determine the optimal hot forming parameters of the part. It must be determined through simulation analysis. Therefore, the simulation temperature range is 600℃~850℃, and the sampling interval is 50℃. Figure 6-Figure 10 The curve shows that the average strain rate in this embodiment can be selected as 10 -3 s -1 If the forming temperature is lower than 700°C, it is necessary to determine the effect of the sheet placement direction on the part forming.

[0081] For the OP30 isothermal heat correction process, the deformation of the part is mainly local bulging, and the influence of the above factor ② on the forming can be ignored. Therefore, in the OP30 isothermal heat correction process, only the above factors ①③④ need to be considered comprehensively. Figure 6-Figure 10 From the curve, it can be seen that the design forming temperature is 700℃~800℃, and the sampling interval is 50℃. The average strain rate can be selected as 10 -2 s -1 ; The influence of sheet metal placement direction on part forming can be ignored.

[0082] In step S4, the isothermal hot forming simulation is performed on the titanium alloy sheet 1 using the Autoform software.

[0083] In step S4, the simulation using the Autoform software includes: S41, importing the material properties database of the titanium alloy obtained in the material properties test in step S1; S42, constructing simulation models of the isothermal hot drawing process and the isothermal hot shaping process of the titanium alloy sheet, and setting boundary conditions for the simulation models of the isothermal hot drawing process and the isothermal hot shaping process respectively; S43, simulating the hot forming parameters determined in step S3, obtaining the optimal thinning rate distribution cloud map corresponding to different hot forming parameters, and obtaining the forming parameters of the isothermal hot drawing process and the isothermal hot shaping process according to the simulation results.

[0084] Specifically, for the OP20 isothermal hot drawing process of the embodiment, in step S42, in the isothermal hot drawing process, as Figure 3 As shown, the simulation model of the titanium alloy part includes a first punch 2, a first die 3 and a blank holder 4, the first punch 2 is arranged above the first die 3, the titanium alloy sheet 1 is arranged between the first punch 2 and the first die 3, and the blank holder 4 is arranged between the first punch 2 and the titanium alloy sheet 1.

[0085] The boundary conditions in the isothermal hot drawing process in step S42 include: using the hot forming module in the Autoform software, the first punch 2, the first die 3 and the titanium alloy sheet 1 are simultaneously loaded with a thermal field, and the thermal radiation and heat conduction are set to 0. A fixed constraint is applied to the first die 3; a first displacement is applied to the blank holder 4 to ensure that the blank holder gap is 1.26mm~1.32mm; a second displacement is applied to the first punch 2 to ensure the clamping position of the first punch 2 and the first die 3; the friction coefficient of the first die 3 is 0.1-0.15. The friction coefficient of the first punch 2 is 0.4-0.45.

[0086] According to step S3, 8 groups of hot forming parameter combinations are selected for the simulation of the OP20 isothermal hot drawing process in step S4, as shown in Table 1.

[0087]

[0088] In step S43, without forming failure, the best maximum thinning rate results are summarized as shown in Table 2.

[0089]

[0090] like Figure 11-Figure 18 The simulation cloud diagram of the Ti6Al4V titanium alloy parts in the above-mentioned OP20 isothermal hot drawing process under the above-mentioned working conditions 1-8.

[0091] In step S43, the OP20 isothermal hot drawing process obtains the forming parameters and the influence trend of the change of the forming parameters on the forming effect according to the simulation as follows: The average strain rate in Table 2 is 10 -3 s -1 , the sheet placement direction is 0°, 45° and 90°, and the forming temperature is 600℃, 650℃, 700℃, 750℃, 800℃, 850℃ respectively. It can be seen that the influence trend of the change of forming temperature on the forming effect is as follows: the maximum thinning rate of Ti6Al4V titanium alloy parts shows a significant upward trend with the increase of temperature. Above 750℃, the stress concentration phenomenon is serious, and severe thinning occurs locally, which cannot meet the forming requirements of Ti6Al4V titanium alloy parts. Therefore, the forming temperature range of the OP20 isothermal hot drawing process of the part in this embodiment is 600℃~700℃.

[0092] Compare the forming temperature of 600℃ and the average strain rate of 10 in Table 2. -3 s -1 , three groups of hot forming parameters of 0°, 45° and 90° were selected for the sheet placement direction, and the finite element simulation of the drawing process of Ti6Al4V titanium alloy parts was carried out. It can be seen that the influence trend of the change of sheet placement direction on the forming effect is as follows: the sheet placement direction has a significant effect on the maximum thinning rate of Ti6Al4V titanium alloy parts, and the maximum thinning rate of parts formed by 0° sheet is the lowest, that is, the optimal sheet placement direction is 0°.

[0093] In summary, the forming parameters of the OP20 isothermal hot drawing process obtained by simulation are shown in Table 3:

[0094] Among them, the blank holder gap and blank holder force are the parameters that have the greatest impact on the forming quality in isothermal hot deep drawing simulation. The size of the blank holder gap affects the flow of the sheet to a great extent, thus leading to the occurrence of part forming failure (cracks, wrinkles, etc.). The blank holder force must not only meet the needs of ensuring the blank holder gap, but also avoid being too large to cause deformation in the thickness direction of the mold. According to the simulation results, the blank holder gap of 1.25mm and the blank holder force of 10t are the best forming parameters.

[0095] For the isothermal heat correction process of Example OP30, Figure 4 As shown, in the OP30 isothermal hot forming process in this embodiment, the simulation model of the titanium alloy part includes a second punch 5 and a second die 6. The second punch 5 is arranged above the second die 6, and the preformed part formed in the isothermal hot forming process is placed between the second punch 5 and the second die 6.

[0096] The boundary conditions in the medium temperature heat correction process in step S42 include: A fixed constraint is applied to the second concave die, and a third displacement is applied to the second convex die to ensure the final mold closing position.

[0097] The friction coefficient of the second concave die is 0.4-0.45; the friction coefficient of the second convex die is 0.4-0.45.

[0098] The process action is: the second die 6 does not move, the second punch 5 moves downward to close the die, and the preformed parts in the OP20 isothermal hot drawing process are calibrated.

[0099] According to step S3, three groups of parameter combinations for simulation of the OP30 isothermal heat correction process are selected, as shown in Table 4.

[0100]

[0101] In step S43, the maximum thinning rates of the isothermal heat shaping process are summarized as shown in Table 5.

[0102]

[0103] The forming parameters obtained from the simulation and the influence trend of the change of forming parameters on the forming effect are as follows: The average strain rate in Table 5 is selected as 0.01 s -1 , the sheet placement direction is selected as 0°, and the forming temperature is selected as 700℃, 750℃, and 800℃ respectively. It can be seen that the influence trend of the change of forming temperature on the forming effect is: the maximum thinning rate of the part increases with the increase of temperature, but the difference is not significant. Therefore, it can be determined that the forming temperature range of the isothermal heat correction process of the part is 700℃~800℃.

[0104] Due to the temperature range of 700℃~800℃ and 10 -2 s -1 Under the forming condition of average strain rate, the directional difference of r value tends to be consistent, so there is no requirement for the direction of sheet placement. In summary, the forming parameters of OP30 isothermal heat correction process obtained by simulation are shown in Table 6:

[0105] Among them, the clamping force has the greatest impact on the forming quality among the shaping simulation forming parameters. It should not only meet the shaping force requirements of the parts, but also avoid excessive force that causes cracks and deformation of the mold in the thickness direction. According to the simulation results, a clamping force of 30t is the best forming parameter.

[0106] In step S5, the part is trial-produced according to the forming parameters obtained by the simulation; and the part forming parameters are adjusted according to the forming quality of the trial-produced part to meet the technical requirements of the part.

[0107] Specifically, in step S5, the titanium alloy part is trial-produced by forming by a double-action hot forming hydraulic press, and some parameters of the double-action hot forming hydraulic press are shown in Table 7.

[0108]

[0109] The working parameters of the double-action hot forming hydraulic press include: the forming pressure of the double-action hot forming hydraulic press, which controls the clamping force of the mold used in the isothermal hot drawing process and the isothermal hot shaping process; the ejector pin of the double-action hot forming hydraulic press is connected to the blank holder 4, and the ejector pin pressure is used to control the blank holder force of the blank holder 4; The pressure control accuracy range of the forming pressure of the double-acting hot forming hydraulic press is not greater than ±1%. The control accuracy of the double-acting hot forming hydraulic press is mainly controlled by the valve on the pipeline.

[0110] The upper workbench is connected to the first punch 2 or the second punch 5, and is used to control the forming speed of the titanium alloy part.

[0111] The first die 3 or the second die 6 is fixedly mounted on the lower workbench; The effective table surface range of the lower workbench and the upper workbench in the above Table 7 refers to the size of the molds that can be installed on the upper workbench and the lower workbench.

[0112] The maximum heating temperature of the working chamber of the double-action hot forming hydraulic press does not exceed 900°C.

[0113] In step S5, trial production of parts is performed according to the forming parameters obtained by simulation, including: The forming parameters of the isothermal hot drawing process include: The forming parameters of the isothermal hot drawing process obtained in step S43 are used, including temperature, hot forming equipment load clamping speed, sheet material placement direction, blank holder gap, blank holder force, and clamping force; Water-based graphite is used to lubricate titanium alloy sheets; boron nitride is used to prevent oxidation of titanium alloy sheets; The forming parameters of the isothermal heat shaping process include: The forming parameters of the isothermal heat correction process obtained in step S43 are used, including temperature, hot forming equipment load clamping speed, sheet material placement direction, blank holding force, and clamping force; Boron nitride is used to protect titanium alloy parts formed by isothermal hot drawing process from oxidation.

[0114] Specifically, the forming pressure of the double-action hot forming hydraulic press used in this embodiment is 3150KN. The ejector rod is connected to the blank holder 4, and the ejector force of the ejector rod is 500KN. The pressure control accuracy range of the forming pressure of the double-action hot forming hydraulic press is not greater than ±1%. The lifting speed range of the upper workbench is 0.5mm / s~10mm / s. The effective table range of the workbench is 1600mm*1200mm. The maximum heating temperature of the forming mold does not exceed 900℃.

[0115] In the isothermal hot shaping process, the blank holder 4 is no longer used, the forming pressure of the double-action hot forming hydraulic press is 3150KN, and the pressure control accuracy range of the forming pressure of the double-action hot forming hydraulic press is not greater than ±1%. The speed range of the upper workbench is 0.5mm / s~10mm / s.

[0116] In this embodiment, after the first trial production of the part in the OP20 isothermal hot drawing process according to the forming parameters, the part showed forming failures such as forming wrinkles and cracks. According to the deep drawing forming experience, the adjustment effect of the blank holder force is the best, indicating that the blank holder force set in the isothermal hot drawing process is 10t, which is too small.

[0117] The second part trial was conducted with a blank holding force of 30t. The deep drawing effect of the formed part was good, with no forming failures such as cracks or wrinkles.

[0118] In this embodiment, after the first trial production of the OP30 isothermal heat correction process according to the forming parameters, the correction effect of the part is good, and there is no forming failure such as cracks and wrinkles. The part is tested for its outer dimensions. The test results show that the overall size of the part is off by about 0.16%. The key dimension of the outer shape of the cavity position of the box-shaped part is 370±0.5mm. The dimension of the cavity position is fixed after forming and can no longer be fine-machined. The actual measured dimension is about 370.6mm, which does not meet the part size tolerance requirements.

[0119] In step S5, the part is trial-produced according to the forming parameters obtained by the simulation, and the isothermal heat correction process is also included. According to the forming temperature range obtained in step S43, the intermediate temperature is selected to calculate the thermal expansion compensation and determine the mold surface size. In the trial production, within the forming temperature range, a forming temperature higher than the intermediate temperature is selected to obtain a part larger than the theoretical size; a forming temperature lower than the intermediate temperature is selected to obtain a part smaller than the theoretical size; this can be used to compensate for part size deviations caused by expansion calculation, mold processing errors, etc.

[0120] Specifically, because both the mold and the parts will produce thermal expansion during the thermoforming process, the linear expansion coefficient of the material is that for every 1° increase in the material, the size of the material will increase by a certain value. When the linear expansion coefficients of the mold and the part are the same, the two will increase year-on-year during thermoforming, and there is no need to set a compensation amount. When the linear expansion coefficients of the two are different, it is necessary to compensate for the thermal expansion of the two. At the same time, due to mold manufacturing errors, errors generated during the parts manufacturing process, and the parts will rebound after thermoforming, the rebound amount cannot be calculated accurately, and the above factors will cause the overall size of the parts to change. In this embodiment, the dimensional changes of the mold and parts during the thermoforming process are calculated according to the temperature. Therefore, the linear expansion coefficient of the mold is calculated under the condition that the thermoforming temperature is 750°C. In actual thermoforming production, at a temperature of 700°C, the size of the parts after forming will be smaller than the theoretical value, thereby overcoming the deformation caused by the rebound.

[0121] After the above-mentioned mold is processed, it is difficult to adjust the size of the mold, and the mold's blanking force needs to be adjusted. If the part is wrinkled or cracked after forming, the mold's blanking force can be adjusted, but the effect on the external dimensions of the part after forming is small. As for the size of the titanium alloy sheet 1, because the titanium alloy sheet 1 of the part is special-shaped, after multiple forming adjustments, the titanium alloy sheet 1 is finalized, and the size and shape will not be adjusted. As for the factors affecting the hot forming of parts, temperature and average strain rate, the lower the average strain rate, the better the part forming effect, but the hot forming cycle and production cost of the part need to be considered.

[0122] Specifically, according to theoretical calculations, when the forming temperature is adjusted from 750°C to 700°C, the size of the formed part will be reduced by 0.05% due to the difference in expansion between the mold and the part. The forming temperature was changed to 700°C. After the parts in this embodiment completed the second trial production of the OP30 isothermal heat correction process, the correction effect of the trial parts was good, and there was no forming failure such as cracks and wrinkles. The parts were tested for their outer dimensions. For the key outer dimension of 370±0.5mm, the actual measured dimension was reduced to 370.4mm, which met the part tolerance.

[0123] In this embodiment, the forming parameters of the parts are adjusted according to the forming quality of the trial-produced parts, especially the adjustment of the blank holding force and temperature, so that the parts meet the technical requirements. The final forming parameters are shown in Table 8:

[0124] Although the present invention has been described in detail above by means of general description, specific implementation methods and tests, it is obvious to those skilled in the art that some modifications or improvements may be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. The isothermal hot forming process of titanium alloy based on simulation is characterized by: include: S1. Performing a material property test on a titanium alloy material, wherein the input variables of the material property test include temperature, average strain rate and sample direction, and the output variables of the material property test include elastic modulus, Poisson's ratio, flow stress-strain curve and plate thickness directivity coefficient r value; establishing a material property database identifiable by Autoform software according to the input variables and output variables of the material property test; S2. Determine an isothermal hot forming process route according to the characteristics of the titanium alloy part, wherein the isothermal hot forming process route includes an isothermal hot drawing process and an isothermal hot shaping process; S3. Perform theoretical analysis based on the material property database and the isothermal hot forming process route to determine the hot forming parameters that need to be simulated for the isothermal hot drawing process and the isothermal hot shaping process, wherein the hot forming parameters of the isothermal hot forming process include temperature, average strain rate and sheet placement direction; S4, using Autoform software to simulate the isothermal hot drawing process and the isothermal hot shaping process on the titanium alloy sheet; According to the simulation results of Autoform software, forming parameters of the isothermal hot drawing process and the isothermal hot shaping process are obtained; S5: trial-produce the parts according to the forming parameters obtained from the simulation, and adjust the forming parameters of the isothermal hot drawing process and the isothermal hot shaping process of the parts according to the forming quality of the trial-produced parts to meet the technical requirements of the parts.

2. The isothermal hot forming process of titanium alloy based on simulation according to claim 1 is characterized in that: In step S3, The temperature of the titanium alloy part simulation is linearly sampled, with a simulated temperature value taken at every 50°C interval; The average strain rate adopts proportional sampling, and the value range of the average strain rate is 10 -3 s -1 -10 -1 s -1 ; The sheet placement direction is the angle between the sheet length direction and the rolling direction, which are 0°, 45° and 90° respectively.

3. The isothermal hot forming process of titanium alloy based on simulation according to claim 1 is characterized in that: In step S3, the average strain rate of the titanium alloy part in the simulation of the isothermal hot drawing process and the isothermal hot shaping process is calculated respectively. ; The calculation formula is: ; is the maximum deformation of the corresponding process of titanium alloy parts; s is the stroke of the corresponding process; It is the load clamping speed of the thermoforming equipment used in the corresponding process.

4. The titanium alloy isothermal hot forming process based on simulation according to claim 1 is characterized in that: In step S4, the simulation using the Autoform software includes: S41, importing the material properties database of the titanium alloy obtained in the material properties test in step S1; S42, constructing simulation models of the isothermal hot drawing process and the isothermal hot shaping process of the titanium alloy sheet, and setting boundary conditions for the simulation models of the isothermal hot drawing process and the isothermal hot shaping process respectively; S43, simulating the hot forming parameters determined in step S3, obtaining the optimal thinning rate distribution cloud map corresponding to different hot forming parameters, and obtaining the forming parameters of the isothermal hot drawing process and the isothermal hot shaping process according to the simulation results.

5. The titanium alloy isothermal hot forming process based on simulation according to claim 4 is characterized in that: In step S42, in the isothermal hot drawing process, the simulation model of the titanium alloy part includes a first punch, a first die and a blank holder, the first punch is arranged above the first die, the titanium alloy sheet is arranged between the first punch and the first die, and the blank holder is arranged between the first punch and the titanium alloy sheet; In the isothermal hot shaping process, the simulation model of the titanium alloy part includes a second convex die and a second concave die, the second convex die is arranged above the second concave die, and the preformed part formed in the isothermal hot drawing process is placed between the second convex die and the second concave die; The boundary conditions in the isothermal hot drawing process in step S42 include: Using the hot forming module in the Autoform software, the first male die, the first female die and the titanium alloy sheet are simultaneously loaded with a thermal force field, and heat radiation and heat conduction are set to 0; applying a fixed constraint to the first concave die; Applying a first displacement to the blank holder ring to ensure a blank holder gap; Applying a second displacement to the first convex mold to ensure a mold-closing position of the first convex mold and the first concave mold; The friction coefficient of the first concave die is 0.1-0.15; the friction coefficient of the first convex die is 0.4-0.45; The boundary conditions in the isothermal heat correction process in step S42 include: applying a fixed constraint to the second concave die; Applying a third displacement to the second convex mold to ensure the second convex mold and the second concave mold are in a clamping position; The friction coefficient of the second concave mold is 0.4-0.45; the friction coefficient of the second convex mold is 0.4-0.

45.

6. The titanium alloy isothermal hot forming process based on simulation according to claim 4, characterized in that: In step S5, trial production of parts is performed according to the forming parameters obtained by simulation, including: The forming parameters of the isothermal hot drawing process include: The forming parameters of the isothermal hot drawing process obtained in step S43 include temperature, hot forming equipment load clamping speed, sheet material placement direction, blank holder gap, blank holder force, and clamping force; Water-based graphite is used to lubricate titanium alloy sheets; boron nitride is used to prevent oxidation of titanium alloy sheets; The forming parameters of the isothermal heat correction process include: The forming parameters of the isothermal heat correction process obtained in step S43 are used, including temperature, hot forming equipment load clamping speed, sheet material placement direction, and clamping force; Boron nitride is used to prevent oxidation of titanium alloy parts formed by the isothermal hot drawing process.

7. The titanium alloy isothermal hot forming process based on simulation according to claim 4, characterized in that: In step S5, trial production of parts is performed according to the forming parameters obtained by simulation, and the process also includes: The isothermal heat correction process selects an intermediate temperature to calculate thermal expansion compensation and determine the size of the mold surface according to the forming temperature range obtained in step S43.

8. The titanium alloy isothermal hot forming process based on simulation according to claim 5, characterized in that: In step S5, trial production of the parts is performed according to the forming parameters obtained by the simulation, and forming is also performed using a double-action hot forming hydraulic press; The working parameters of the double-action hot forming hydraulic press include: the forming pressure of the double-action hot forming hydraulic press controls the clamping force of the molds used in the isothermal hot drawing process and the isothermal hot shaping process; the ejector pin of the double-action hot forming hydraulic press is connected to the blank holder, and the ejector pin pressure controls the blank holder force of the blank holder used in the isothermal hot drawing process; The pressure control accuracy range of the forming pressure of the double-action hot forming hydraulic press is not greater than ±1%; An upper workbench is connected to the first punch or the second punch, and the upper workbench is used to control the forming speed of the titanium alloy part; The first concave die or the second concave die is fixedly mounted on the lower workbench; The maximum heating temperature of the working chamber of the double-action hot forming hydraulic press does not exceed 900°C.

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