Non-equilibrium forming and heat treatment combined manufacturing method for titanium alloy thin-walled component

Abstract

The non-equilibrium forming and heat treatment composite manufacturing method of the titanium alloy thin-walled component of the application relates to the precise and efficient forming technology of the titanium alloy complex plate component, and aims to solve the problems of long manufacturing period, high energy consumption, high operation and maintenance cost of the mold equipment, easy deformation in the cooling process and weakened mechanical properties of the existing technology of the titanium alloy plate component; it comprises the following steps: step one, designing the upper mold and the lower mold used for forming according to the numerical model after adding the process section; step two, obtaining the upper mold pressing amount in the multi-pass pre-forming by pre-forming simulation; step three, pre-forming multiple times according to step two; step four, after the self-resistance heating of the pre-formed component, the component is rapidly transferred to the mold for final forming and quenching; step five, taking out the component when the mold is opened, and then aging treatment and cutting off the process section to obtain the target component with high strength and high dimensional accuracy. The application realizes the efficient, low-energy and low-cost manufacturing of the titanium alloy complex plate component, and can guarantee high strength and dimensional accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of titanium alloy thin-walled component forming, in particular to a non-equilibrium state forming and heat treatment combined manufacturing method for titanium alloy thin-walled components. BACKGROUND

[0002] New generation aircrafts develop towards lightweight, stealth, high reliability, long life, and high speed, and a new type of complex thin-walled curved surface parts appears, which has three main performances: overall structure, complex variable cross-section thin-walled structure, lightweight, heat resistance and high-precision surface. Titanium alloy can play an important role in reducing the weight of the overall structure of the aircraft, improving the service life of the aircraft body, meeting the requirements of high temperature and high load, and corrosion environment, and is gradually applied in aerospace aircraft structural parts. Large complex thin-walled titanium alloy overall components are typical structures.

[0003] The traditional forming method is to adopt block stamping and then welding, and to perform heat correction. The problems are stamping springback, welding deformation, and many welds, poor overall dimensional accuracy of the parts, and poor reliability. With the development of technology, titanium alloy hot forming and superplastic forming are gradually applied. Titanium alloy hot forming and superplastic forming are both to heat the mold and the blank to a certain temperature, such as 750℃-950℃, and to form a complex overall component under the action of high temperature and other loads by using the high elongation of titanium alloy at high temperature. This type of forming belongs to balanced state forming, and the whole forming process needs to be heated and kept for a certain time before forming, and then cooled after forming. The whole forming process lasts for dozens of hours, the efficiency is low, the grains are easy to abnormally grow, and the dimensional accuracy of the parts decreases due to thermal expansion and thermal distortion after forming, and the mechanical properties after forming are lower than those of the base material. This process puts high requirements on the mold and equipment, and the operation and maintenance cost is high, and the energy consumption is large. With the increasing demand for titanium alloy thin-walled components, the production efficiency of the existing technology cannot meet the demand.

[0004] In order to solve the problems of long manufacturing cycle, high energy consumption, high operation and maintenance cost of mold equipment, easy deformation in cooling process, and weakening of mechanical properties of the existing forming technology for titanium alloy overall thin-walled components, a method for efficiently and lowly energy-consuming forming titanium alloy complex components and ensuring high strength and dimensional accuracy is needed. SUMMARY

[0005] The present application proposes a non-equilibrium state forming and heat treatment combined manufacturing method for titanium alloy thin-walled components to solve the problems of long manufacturing cycle, high energy consumption, easy deformation in cooling process, and weakening of mechanical properties of the existing forming technology for titanium alloy overall thin-walled components, which can realize the beneficial effects of high forming efficiency, low energy consumption, low cost, high mechanical properties and dimensional accuracy.

[0006] The main principle of the present application is: firstly, annealing treatment is performed on the titanium alloy sheet or annealed sheet is selected, preforming is performed according to the shape of the target part, the maximum deformation of each preforming is not more than the fracture strain of the titanium alloy sheet, annealing treatment is performed between each preforming to restore the plastic deformation capacity, after the preforming is completed, the preformed blank is rapidly heated to 850-950 DEG C in a short time, the non-equilibrium state is reached (through rapid heating, the material heating time is significantly shortened, element diffusion and phase change are reduced, and the material organization is in a non-equilibrium state), then the preformed blank is rapidly transferred to the final forming die at room temperature, rapid die closing is realized to realize the final forming of the part and quenching, the die is opened to take out the part when the temperature of the part is reduced to below 400 DEG C, and aging treatment is performed, and the titanium alloy complex integral thin-walled component with high mechanical properties and size precision is obtained by cutting off the process section.

[0007] The non-equilibrium state forming and heat treatment combined manufacturing method of the titanium alloy thin-walled component of the present application comprises the following steps:

[0008] 1. Forming die design

[0009] 1.1. According to the characteristics of the target part 1-1, a part model containing a process section is obtained by adding a process section;

[0010] 1.2. The upper die and the lower die used for forming are designed according to the part model containing the process section.

[0011] 2. Part room temperature preforming simulation

[0012] 2.1. Selecting annealed titanium alloy sheet or annealing treatment of other state titanium alloy sheet;

[0013] 2.2. Sampling from the annealed titanium alloy sheet, using an electronic universal testing machine to perform room temperature uniaxial tensile test, obtaining the engineering stress-strain relationship and the fracture strain ε f of the annealed sheet;

[0014] 2.3. The engineering stress-strain relationship obtained in step 2.2 is converted into the true stress-strain relationship, which is input into the finite element software, the finite element simulation model is established according to the upper die and the lower die of the final forming die designed in step 1.2, the preforming simulation is performed by using the final forming die, and when the maximum equivalent plastic strain ε max of the sheet blank is close to 80% of the fracture strain ε f , the annealing simulation process is applied, and then the preforming simulation is continued, and the simulation is repeated until the gap between the preformed sheet and the final forming die is not greater than 2 times the wall thickness, and the simulation is terminated, and the total travel and the maximum equivalent plastic strain relationship curve of the sheet blank during preforming are recorded.

[0015] 3. Part room temperature preforming

[0016] 3.1. After the upper die and the lower die are closed, they are placed on the working platform of the press, the lower die is fixedly connected with the lower working platform, and the upper die is fixedly connected with the upper working platform, and opening and closing test is conducted to ensure normal work;

[0017] 3.2. The plate blank is preformed according to the relationship curve between the total stroke S and the maximum plastic equivalent plastic strain ε max of the plate blank obtained in step 2.3, and annealing treatment is conducted between each preforming.

[0018] 4. Part final forming heat treatment composite manufacturing

[0019] 4.1. The opposite ends of the preformed plate in step 3 are clamped on the upper electrode, and the preformed plate is heated to 850-950 DEG C by a direct current power supply at an average heating rate of not less than 10 DEG C / S;

[0020] In this step, the surface of the preformed plate can be sprayed with a heat-conducting coating, and the heat-conducting coating can be graphite. In this way, better heat transfer between the blank and the die in step 4.2 can be achieved, the cooling speed of the part is improved, and good quenching effect is achieved.

[0021] 4.2. The preformed plate after heating is quickly transferred to the lower die at room temperature and positioned, the transfer time is within 2 seconds, and then the die is quickly closed, the closing time is within 5 seconds, the preformed plate is attached to the die under the action of the upper die and the lower die and quickly cools down, and the purpose of quenching is achieved.

[0022] 5. Post-processing

[0023] 5.1. The die is opened, the final formed blank is taken out, and artificial aging treatment is conducted;

[0024] 5.2. The process section of the final formed blank is cut off to obtain the target part.

[0025] The beneficial effects of the present application are:

[0026] Firstly, the present application preliminarily forms the blank into a shape close to the final part shape through preforming, and simultaneously performs die quenching treatment during warm forming, so that the part has high dimensional accuracy and does not have the problem of part distortion;

[0027] Secondly, the present application quickly heats the preformed blank through self-resistance heating, avoids abnormal grain growth, insufficient element diffusion, and forms a non-equilibrium state to improve the forming performance under hot state;

[0028] Thirdly, die quenching treatment is simultaneously performed during warm forming, the structure at high temperature is retained, and the part with higher strength than the base material can be obtained by combining aging treatment;

[0029] Fourthly, the blank is quickly heated at a high speed, and the oxidation problem of the blank can be greatly reduced without heat preservation treatment;

[0030] Five, in the present application, the blank is gradually cooled from hot state under the pressing state of the upper and lower molds in the final forming, the cooling of each part is relatively uniform, and the residual stress of the part is small;

[0031] Six, the scheme of the present application can avoid the problems of wrinkling, local thinning and surface scratches that are prone to occur when the blank is deformed greatly in hot state during direct hot forming, and the wall thickness uniformity of the formed part is good, and the surface quality is good;

[0032] Seven, the heating and forming time of the final forming of the present application is relatively short, the pre-forming and the final forming are carried out separately, and the efficiency is high;

[0033] Eight, the present application shares a set of molds for pre-forming and final forming, which saves cost;

[0034] Nine, the present application does not need to configure a heating furnace on the press, and the operation and maintenance cost is low, and the energy consumption is small. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a schematic diagram of a target part;

[0036] Figure 2 It is a schematic diagram of a part containing a process section;

[0037] Figure 3 It is a schematic diagram of a complex sheet metal part before pre-forming of the present application;

[0038] Figure 4 It is a schematic diagram of a complex sheet metal part after pre-forming of the present application;

[0039] Figure 5 It is a schematic diagram of the blank after pre-forming by current heating of the present application;

[0040] Figure 6 It is an axonometric view of the final forming of a complex sheet metal part of the present application;

[0041] Figure 7 It is an engineering stress-strain curve obtained by one-way stretching of TC4 titanium alloy sheet in Example 1;

[0042] Figure 8 It is a curve of the total stroke and the maximum equivalent plastic strain relationship of the TC4 titanium alloy sheet during pre-forming in Example 1;

[0043] Figure 9 It is an equivalent strain distribution diagram of the TC4 titanium alloy sheet after the first pass pre-forming in Example 1;

[0044] Figure 10 It is an equivalent strain distribution diagram of the TC4 titanium alloy sheet after the second pass pre-forming in Example 1.

[0045] Wherein 1-1 is the target part, 1-2 is the part containing process section, 2 is the slab, 2-1 is the preformed blank, 2-2 is the final formed blank, 3 is the upper die, 4 is the lower die, 5 is the electrode, and 6 is the direct current power supply. DETAILED DESCRIPTION

[0046] In order to make the above-mentioned objectives, features and advantages of the present application more apparent and easy to understand, the specific embodiments of the present application are described below in conjunction with the accompanying drawings.

[0047] Example 1

[0048] In conjunction with Figures 1-10 It is explained that the TC4 titanium alloy plate with a wall thickness of 1.5 mm is formed Figure 1 The target part 1-1 is shown.

[0049] 1. Forming die design

[0050] 1.1. According to the characteristics of the target part 1-1, a process section is added to obtain a part containing a process section 1-2, as shown in Figure 2

[0051] 1.2. According to the numerical model of the part containing the process section 1-2, the upper die 3 and the lower die 4 used for forming are designed, as shown in Figure 3

[0052] 2. Part cold preforming simulation

[0053] 2.1. Select annealed TC4 titanium alloy plate or anneal other state TC4 titanium alloy plate, annealing temperature is 750-800℃, holding for 1-2 hours, furnace cooling to 550℃ and then air cooling;

[0054] 2.2. Sample from the annealed TC4 titanium alloy plate and use an electronic universal testing machine to perform a cold unidirectional tensile test, to obtain the engineering stress-strain relationship of the annealed TC4 titanium alloy plate, as shown in Figure 7 , and to obtain the fracture strain ε f = 0.102;

[0055] 2.3. The engineering stress-strain relationship obtained in step 2.2 is converted into the true stress-strain relationship, which is input into the finite element software, and a finite element simulation model is established according to the upper die 3 and the lower die 4 of the final forming die designed in step 1.2, preforming simulation is performed using the final forming die, the maximum equivalent plastic strain ε max of the slab 2 reaches 0.075 (which does not exceed 0.8*ε f ), the first pass preforming is completed, the equivalent plastic strain distribution is shown in Figure 8 , the annealing simulation process is applied, and then the preforming simulation is continued, the maximum equivalent plastic strain ε​​max 0.077 (not more than 0.8*ε f ) when the preformed sheet 2-1 and the final forming die gap is not more than 3mm, the simulation is terminated, the equivalent plastic strain distribution is shown in Figure 9 , and the total stroke S and the maximum plastic equivalent plastic strain ε max relationship curve of the sheet 2 preforming is recorded, as shown in Figure 10 .

[0056] 3. Preforming of the part at room temperature

[0057] 3.1. After the upper die 3 and the lower die 4 are closed, they are placed on the working platform of the press, the lower die 4 is fixedly connected with the lower working platform, and the upper die 3 is fixedly connected with the upper working platform. The opening and closing test is carried out to ensure normal operation.

[0058] 3.2. According to the total stroke S and the maximum plastic equivalent plastic strain ε max relationship curve obtained in step 2.3, the first pass preforming is completed by the upper die 3 with a stroke of 171.4mm, and then the preformed sheet 2-1 is taken out for annealing treatment. The annealing temperature is 750-800℃, the holding time is 1-2 hours, the furnace is cooled to 550℃, and then air cooling is carried out. Then the upper die 3 is pressed down by 8.1mm to a total stroke of 179.5mm to complete the second pass preforming.

[0059] 4. Final forming and heat treatment composite manufacturing of the part

[0060] 4.1. The opposite ends of the preformed sheet 2-1 in step 3 are clamped on the upper electrode 5, and the preformed sheet 2-1 is heated to 900℃ by the direct current power supply 6 at an average heating rate of not less than 10℃ / S.

[0061] 4.2. The heated preformed sheet 2-1 is quickly transferred to the lower die 4 at room temperature and positioned within 2 seconds, and then the die is quickly closed within 5 seconds. The preformed sheet 2-1 is pressed against the die under the action of the upper die 3 and the lower die 4 and quickly cools down to achieve the purpose of quenching.

[0062] 5. Post-processing

[0063] 5.1. After the final forming of the blank 2-2, the temperature is reduced to 400℃, the die is opened, the final formed blank 2-2 is taken out and subjected to artificial aging treatment, the aging temperature is 480-560℃, and the aging time is 4-8 hours.

[0064] 5.2. The process section of the final formed blank 2-2 is cut off to obtain the target part 1-1.

[0065] The tensile strength of the target part obtained in this embodiment is 1183MPa, and the tire adhesion degree reaches 0.36mm.

[0066] Embodiment 2

[0067] The embodiment is characterized in that the surface of the preformed sheet 2-1 in step 3.2 can be sprayed with a heat-conducting coating, which can be graphite. The other steps are the same as in Embodiment 1. In this way, better heat transfer between the part and the mold can be achieved, the cooling rate of the part can be increased, and good quenching effect can be achieved.

[0068] Embodiment 3

[0069] The embodiment is characterized in that an atmosphere protection furnace or a vacuum furnace can be used for annealing in steps 2.1 and 3.2. The other steps are the same as in Embodiment 1. In this way, the oxidation of the outer surface of the sheet can be reduced.

[0070] Embodiment 4

[0071] The embodiment is characterized in that a plurality of slabs 2 can be annealed after the first pass preforming in step 3, and then the second pass preforming is performed. The other steps are the same as in Embodiment 1. In this way, the utilization rate of the heat treatment furnace can be improved, the production efficiency can be improved, and energy can be saved.

[0072] Embodiment 5

[0073] The embodiment is characterized in that TA31, TA18, Ti55, Ti60, etc. titanium alloy sheets can be used. The other steps are the same as in Embodiment 1.

[0074] The present application has been disclosed above with reference to the preferred embodiments, but is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed structure and technical content without departing from the scope of the present application, and equivalent embodiments can be obtained. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application still fall within the scope of the present application.

Claims

1. A method for manufacturing thin-walled titanium alloy components by a combination of non-equilibrium processing and heat treatment, characterized in that The method comprises the following steps: (1) forming die design 1.1) add process section according to the characteristics of the target part (1-1) to obtain a part (1-2) numerical model containing a process section; 1.2) design the upper die (3) and the lower die (4) used for forming according to the part (1-2) numerical model containing the process section; (2) part room temperature preforming simulation 2.1) select annealed titanium alloy sheet or anneal other state titanium alloy sheet; 2.2) The engineering stress-strain relationship and fracture strain of the annealed sheet were obtained by uniaxial tensile test at room temperature using an electronic universal testing machine ε f ; 2.3) Transform the engineering stress-strain relationship obtained in step 2.2 into true stress-strain relationship, input into the finite element software, establish the finite element simulation model according to the upper die (3) and the lower die (4) of the final forming die designed in step 1.2, carry out preforming simulation by using the final forming die, and record the maximum equivalent plastic strain of the blank (2) ε max near the fracture strain ε f The annealing simulation process is applied when the equivalent plastic strain is 80% of the fracture strain, and then the preforming simulation is continued, and the process is repeated until the gap between the preformed sheet (2-1) and the final forming die is not greater than 2 times the wall thickness, and the simulation is terminated. The total stroke and maximum equivalent plastic strain relationship curve of the blank (2) during preforming is recorded. (3) part room temperature preforming 3.1) place the upper die (3) and the lower die (4) in the closed state on the working platform of the press, the lower die (4) is fixedly connected with the lower working platform, and the upper die (3) is fixedly connected with the upper working platform, and the opening and closing test is carried out to ensure normal work; 3.2) Total stroke S and maximum plastic equivalent plastic strain of preforming according to the slab (2) obtained in step 2.3 ε max Each pass preforming is performed according to the relationship curve, and annealing is performed between each pass preforming. (4) part final forming heat treatment composite manufacturing 4.1) clamp the opposite ends of the preformed sheet (2-1) on the electrode (5) through the direct current power supply (6), heat the preformed sheet (2-1) to 850-950 DEG C at an average heating rate of not less than 10 DEG C / S; The preformed sheet (2-1) is sprayed with a heat-conducting coating on the surface, and the heat-conducting coating is graphite; 4.2) quickly transfer the heated preformed sheet (2-1) to the lower die (4) at room temperature and position it, the transfer time is within 2 seconds, then quickly close the die, the closing time is within 5 seconds, the preformed sheet (2-1) is attached to the die under the action of the upper die (3) and the lower die (4) and quickly cools down to achieve the purpose of quenching; (5) post-processing 5.1) open the die when the temperature of the final formed blank (2-2) drops to 400 DEG C, take out the final formed blank (2-2) and perform artificial aging treatment; 5.2) cut off the process section of the final formed blank (2-2) to obtain the target part (1-1).

2. The titanium alloy thin-walled component non-equilibrium processing and heat treatment hybrid manufacturing method of claim 1, wherein: In steps 2.1 and 3.2, the annealing is carried out in an atmosphere protection furnace or a vacuum furnace.

3. The non-equilibrium processing and heat treatment hybrid manufacturing method of a titanium alloy thin-walled component of claim 1 or 2, wherein: In step 3, after the first pass preforming of the multiple sheet blanks (2) is completed, annealing is carried out, and then the second pass preforming is carried out respectively.

4. The non-equilibrium processing and heat treatment hybrid manufacturing method of a titanium alloy thin-walled component of claim 1 or 2, wherein: The titanium alloy sheet is TA31, TA18, Ti55 or Ti60 titanium alloy sheet.

5. The titanium alloy thin-walled component non-equilibrium processing and heat treatment hybrid manufacturing method of claim 3, wherein: The titanium alloy sheet is TA31, TA18, Ti55 or Ti60 titanium alloy sheet.

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