A control method for improving the performance consistency of conformally machined titanium alloy blisk forgings

Abstract

The present invention belongs to the field of titanium-based alloys, and specifically relates to a control and processing method for improving the performance consistency of conformally processed titanium alloy integral blade disk forgings, including components such as applicable alloy types, characteristic structural forms of blade disks, and processing parameters. The heat treatment process of the present invention is used to treat integral blade disk forgings of alloys such as TA33, TA37, and TA38, which can improve the consistency of mechanical properties, especially tensile strength, at different positions of the forgings while maximizing the strength. This patented technology can be used for heat treatment of integral blade disk forgings of aircraft engines with integrated disk-drum design to meet the application requirements of advanced aircraft engines for large-sized integral blade disk forgings.

Description

Technical Field

[0001] The invention belongs to the field of thermal processing of titanium-based materials, and in particular relates to a control processing method for improving the performance consistency of a conformally processed titanium alloy integral blade disk forging. Background Art

[0002] Titanium alloys have the advantages of high specific strength, corrosion resistance, and heat resistance, so they are widely used in aviation, aerospace, petroleum, chemical industry, energy, automobile, medical, sports and leisure, etc. With the development of aviation and aerospace technology, the demand for titanium alloys, especially high-temperature titanium alloys, has gradually expanded, and the technical requirements have also gradually increased, such as improved temperature resistance and suitability for structural integration design.

[0003] Structural integration design is a new design concept proposed in recent years, the main purpose of which is to reduce the number of parts and improve structural efficiency. Structural integration design means that the size of parts increases and the complexity of the structure increases, which leads to an increase in the difficulty of manufacturing technology. Therefore, the idea of ​​structural integration design needs to be supported by advanced materials and process technologies.

[0004] In recent years, advanced aero-engines have put forward a strong demand for high-temperature large-size integral blade disk forgings. At the same time, from the perspective of weight reduction and reducing the number of parts types, it is necessary to adopt a disk-drum integral structure as much as possible. The characteristic of the disk-drum integral structure is that the disk and the drum are formed into one body by non-mechanical connection. There are two main preparation processes, one is welding, and the other is integral forging. The latter can be directly formed into a forging blank by die forging, and the process flow is relatively simple. However, because the disk and the drum are manufactured together, the size of the forging, especially the size in the thickness direction, is significantly increased, and the quality requirements for raw materials are increased. Subsequent performance control faces huge challenges. For example, there are obvious performance differences from the surface to the core of thick-section high-temperature titanium alloy forgings, see attached. Figure 1 , under service conditions, stress or strain concentration will form in local parts of the parts, causing premature failure of the parts. It can be seen that if the overall forging method is used to prepare the disc-drum integrated structure, it is necessary to solve the problem of large difference in mechanical properties from the surface to the core, that is, the technical problem of performance consistency control. Summary of the invention

[0005] The object of the present invention is to provide a control method for improving the performance consistency of a conformally processed titanium alloy blisk forging. The specific scheme is as follows:

[0006] A control and processing method for improving the performance consistency of conformally processed titanium alloy integral blade disk forgings, applicable high-temperature titanium alloy materials are TA32, TA33, TA37, and TA38, and the common feature of these materials is that they are cooled by quenching after high-temperature heat treatment.

[0007] A control and treatment method for improving the performance consistency of a conformally processed titanium alloy blisk forging, the process steps of which are as follows:

[0008] Step 1: Design of conformal machining blank: Based on the high-temperature titanium alloy integral blisk die forging with a thickness of ≥100mm, design the conformal machining blank drawing according to the part drawing;

[0009] Step 2: High temperature quenching treatment of the conformal processed blank: The conformal processed blank is heated in an electric furnace to a temperature within the range of 50°C to 10°C below the α+β / β phase transition point, and is kept warm for 1h to 5h after being heated through, and is taken out of the furnace after the end of the heat preservation;

[0010] Step 3: Control and treatment of the performance consistency of the conformal forging blank: The conformal forging blank is heated in an electric furnace to a temperature within the range of 800℃~850℃. It is required to be loaded into the furnace when the temperature reaches or is 10℃ below the set temperature. The timing starts after the furnace temperature returns to the set temperature. The holding time τ is required to be between 10min~0.5δ min +20min, the heat penetration time is estimated as 0.5 times the thickness of the thinnest part of the forging.

[0011] Step 4: Strengthening treatment of the forging blank for conformal processing: The forging blank for conformal processing is heated to a temperature in the range of 650°C to 750°C in an electric furnace, and is kept warm for 2h to 50h after being heated through.

[0012] The control and processing method for improving the performance consistency of conformally processed titanium alloy integral blade disk forgings, the preferred scheme is that in step one, it is required that the size of at least one direction at any position of the conformally processed blank diagram is between 30mm and 100mm, and this direction is the direction with the smallest size.

[0013] The preferred embodiment of the control and treatment method for improving the performance consistency of conformally processed titanium alloy integral blisk forgings is that, in step 2, water quenching or oil quenching is performed after the forging is taken out of the furnace.

[0014] The preferred embodiment of the control method for improving the performance consistency of conformally processed titanium alloy blisk forgings is as follows: in step 3, δ min In order to obtain the minimum size of the forging blank at different positions and directions according to the shape, it is air-cooled to room temperature or a temperature below 600°C after the insulation is completed.

[0015] The preferred embodiment of the control and treatment method for improving the performance consistency of conformally processed titanium alloy integral blisk forgings is that, in step 4, after the insulation is completed, air cooling, furnace cooling or temperature-controlled cooling is performed to room temperature.

[0016] The described control and processing method for improving the performance consistency of conformally processed titanium alloy integral blade disk forgings has a preferred solution of conformally processing the forgings according to the shape of the finished parts, removing part of the material and then performing heat treatment, and the preparation process is forging → conformally processing → heat treatment → finishing.

[0017] The advantages and beneficial effects of the present invention are:

[0018] This application is aimed at the design requirements of large-size high-temperature titanium alloy blades and structural integration for advanced aircraft engines. The basic idea is to firstly Figure 2 ) for conformal processing (with Figure 3 ), remove excess material, and then use quenching process to achieve an overall improvement in the hardness or strength of the forgings. However, due to the low thermal conductivity, there are still obvious microstructure and performance differences between the surface and the core of the forgings. For this reason, a medium-temperature heat treatment control process is introduced to strictly control the treatment temperature and time, so that the surface strength and hardness of the forgings are significantly reduced, and the core strength and hardness are slightly reduced or not reduced, thereby achieving an effective improvement in the consistency of the main or key performance. The use of this control treatment method can effectively reduce the obvious microstructure and mechanical property differences in the thickness direction of large-sized complex structure integral blade forgings, especially conformal processing forgings after quenching treatment, and improve the consistency of mechanical properties. See attached Figure 4 and 5 , avoiding stress or strain concentration problems caused by large differences in organizational properties in different parts of the parts.

[0019] After applying the regulation and treatment method of the present invention:

[0020] 1. After the forgings are processed according to the shape, they are subjected to high temperature quenching treatment to improve the strength reserve of the forgings;

[0021] 2. Apply a control treatment within the range of 800℃~850℃ to the quenched forgings, strictly control the holding time, reduce the difference in microstructure between the surface and the core, and improve the consistency of mechanical properties from the surface to the core of the forgings;

[0022] 3. The process is simple, and no tooling is required during the control process, which is convenient for on-site operation;

[0023] 4. The uniformity of mechanical properties of conformal forgings from the surface to the core is significantly improved, avoiding the inconsistency of mechanical properties caused by the gradient change structure formed by quenching and reducing the risk of part use. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Attached Figure 1 This is the HRC change from the quenched surface to the core of the TA38 alloy forging after quenching treatment. It can be seen that the HRC from the surface to the core has a trend from rapid decrease to flattening;

[0025] Attached Figure 2 It is a schematic diagram of a conventional blisk forging blank;

[0026] Attached Figure 3 This is a schematic diagram of the forgings processed in accordance with the present application;

[0027] Attached Figure 4 The room temperature strength curve of quenched TA38 alloy changes with homogenization temperature and time;

[0028] Attached Figure 5 This is the curve of the tensile strength of TA38 alloy at 650℃ in the quenched state changing with the homogenization treatment temperature and time. DETAILED DESCRIPTION

[0029] The present invention provides a control and processing method for improving the performance consistency of conformally processed titanium alloy blisk forgings, including components such as applicable materials, forging shape and size, and processing parameters. Specifically, the method comprises the following steps:

[0030] 1) According to the shape and size of the target part, leave a 15mm to 50mm margin on one side and design a conformal processing drawing. The size of at least one direction at any position of the conformal processing drawing should be between 30mm and 100mm;

[0031] 2) Use hot die forging or isothermal die forging to complete the forging blank, and then complete the conformal processing according to the conformal processing drawing;

[0032] 3) Perform high temperature treatment + water quenching on the conformal forgings. The high temperature treatment temperature is 50℃~10℃ below the α+β / β phase transformation point. The holding time is 1h~5h after heat penetration. After leaving the furnace, water quench or oil quench;

[0033] 4) The uniformity of the organizational properties of the quenched forgings is regulated and controlled at a temperature of 800°C to 850°C. The forgings are loaded into the furnace at the target temperature or 10°C below the target temperature. The timing starts after the temperature is reached. The holding time is strictly controlled within the range of 10min to the heat-through time + 20min. The heat-through time is estimated as 0.5 times the smallest size of the forging;

[0034] 5) The forgings after the microstructure uniformity control treatment are subjected to medium and low temperature strengthening control treatment, and the control treatment temperature is 650℃~750℃. The forgings are loaded into the furnace below the target temperature or at the temperature, and are kept warm for 2~50h after being heated through. After the heat preservation is completed, the power is turned off, and then cooled to room temperature by air cooling, furnace cooling or temperature-controlled cooling.

[0035] The characteristics of the above preparation method are: 1) making full use of the high-strength characteristics of the quenched structure of high-temperature titanium alloy; 2) making full use of the structural characteristics of forgings, changing from integral forgings to conformal forgings, significantly improving the cooling effect after quenching; 3) adopting short-time treatment measures in the range of 800°C to 850°C, and utilizing the actual effect of long surface insulation time and short core insulation time caused by the low thermal conductivity of titanium alloy, so that the surface strength is quickly reduced and the core strength is maintained as much as possible, thereby achieving the purpose of reducing the surface-core performance difference and improving performance consistency.

[0036] Below, through embodiment and attached Figure 1-5 The present invention is further described in detail.

[0037] Examples 1-6

[0038] The experimental material is TA38 alloy forgings, with a phase transition point of 1052℃. The forging dimensions are 110mm thick, 360mm long, and 140mm high. The forging is split in the middle along the length direction, one of which is directly subjected to a 1032℃ / 2h water quenching + 700℃ / 5h air cooling heat treatment, and then a tensile specimen is taken along the length direction at the center of the thickness to test the 650℃ tensile properties. The test results are shown in Table 1 Comparative Example 1; the other is taken along the length direction at the center of the thickness. The test bar is stretched and then water quenched at 1032℃ / 2h; the test bar after water quenching is heat treated according to the systems of Table 1 Comparative Examples 2 to 8 and Examples 1 to 6, and then the tensile specimens are processed to test the tensile properties. Table 1 Comparative Example 1 represents the tensile results of the center of the thick section forging, while Comparative Examples 2 to 8 and Examples 1 to 6 represent a variety of possible tensile results on the surface of the forging. It can be seen that from the perspective of reducing the performance difference between the surface and the core, Examples 1 to 6 are obviously the best; and although Comparative Examples 3 to 7 reduce the tensile strength to a level close to that of the core, the yield strength is reduced too much, and the disadvantages outweigh the advantages, so they are not optional options.

[0039] Table 1 650℃ tensile properties corresponding to Comparative Examples 1 to 8 and Examples 1 to 6

[0040]

[0041]

[0042] Note: ΔR m and ΔR p0.2 They are the differences between the tensile strength and yield strength of comparative examples 2-8 and embodiments 1-6 and comparative example 1, respectively.

[0043] Embodiment 7-9

[0044] The experimental material is TA38 alloy forgings with a phase transformation point of 1052°C. The dimensions of the forgings are 120mm thick and 250mm in diameter. The forgings are first subjected to a 1032°C / 2h insulation treatment and then water quenching. Then, four test blocks with a length of 66mm and a width of 23mm are taken along the chord direction at 1 / 2R. The height of the test blocks is the same as the thickness direction of the forging, i.e., 120mm. Three of the four test pieces were treated according to the systems of Examples 7 to 9 in Table 2, and the other one was used as a comparative example, corresponding to Comparative Example 9 in Table 2. Finally, the four test pieces were treated in the same furnace with an air cooling system of 700°C / 5h. Afterwards, the four test pieces were taken from the surface to the inside in the height direction. Tensile test bars were sampled symmetrically in 10 layers, with two samples taken from each layer; the 5 layers of samples taken from the top surface to the inside were stretched at room temperature, and the 5 layers of samples taken from the bottom surface to the inside were stretched at 650℃. The room temperature and high temperature stretching results are shown in Tables 2 and 3, respectively. As can be seen from Table 2, the room temperature tensile strength R m and yield strength R p0.2 The corresponding ranges of Example 7 and Example 8 are 80MPa and 79MPa respectively, the corresponding ranges of Example 7 and Example 8 are 46MPa and 75MPa respectively; the corresponding ranges of Example 9 are 75MPa and 60MPa respectively; it can be seen that Examples 7 to 9 reduce the strength difference between the surface and the core to varying degrees, and the effect is most obvious after 800℃ / 40min treatment.

[0045] Table 2 Room temperature tensile properties corresponding to Examples 7 to 9 and Comparative Example 9

[0046]

[0047]

[0048] Note: * corresponds to the surface of the forging; ** corresponds to the core of the forging

[0049] As shown in Table 3, the tensile strength R m and yield strength R p0.2 The ranges of are 66MPa and 36MPa respectively, the corresponding ranges of Example 7 are 38MPa and 12MPa respectively, the corresponding ranges of Example 8 are 45MPa and 26MPa respectively; the corresponding ranges of Example 9 are 76MPa and 55MPa respectively; it can be seen that Examples 7 to 8 reduce the strength difference between the surface and the core to varying degrees, the effect of Example 7 is the most obvious, and the effect of Example 9 is not obvious.

[0050] Table 3 650℃ tensile properties corresponding to Examples 7 to 9 and Comparative Example 9

[0051]

[0052] Note: * corresponds to the surface of the forging; ** corresponds to the core of the forging

[0053] Embodiment 10-11

[0054] The experimental material is TA38 alloy forging, with a phase transition point of 1052°C. The forging dimensions are 110 mm thick, 180 mm long, and 140 mm high. The tensile test bar was then subjected to 1032°C / 2h+water quenching treatment; the test bar after water quenching was treated according to the systems of Examples 10 and 11 in Table 4, and then the tensile specimens were processed to test the tensile properties at room temperature and 650°C. It can be seen from the table that under the two treatment conditions of Examples 10 and 11, the difference between the 650°C tensile and yield strengths is about 26MPa, which is within the dispersion band of the material tensile data and can be considered to be at a similar level.

[0055] Table 4 650℃ tensile properties corresponding to Comparative Example 1 and Examples 10 and 11

[0056] Heat treatment status <![CDATA[R m ,MPa]]> <![CDATA[R p0.2 ,MPa]]> Comparative Example 1 1032℃ / 2h air cooling+700℃ / 5h air cooling 652 510 Example 10 800℃ / 60min air cooling+650℃ / 50h furnace cooling 642 514 Embodiment 11 800℃ / 60min air cooling+750℃ / 2h furnace cooling 616 489

[0057] In summary, structural integration design is one of the directions for optimizing the design of aircraft and engine parts in the future, and heat treatment after conformal processing is a necessary means to solve the problem of using low thermal conductivity materials for thick-section forgings. From the perspective of the design and application of large-size integral blade disk forgings of high-temperature titanium alloys, the present invention proposes a control and processing method for improving the performance consistency of conformal titanium alloy integral blade disk forgings. By adopting this method, the performance difference in the thickness direction of the conformal forgings can be reduced to varying degrees, the performance consistency can be improved, and potential hidden dangers can be eliminated for the safe use of subsequent parts. The technical means of this application will effectively promote the technological development of large-size thick-section parts, further promote the expanded application of high-temperature titanium alloy materials such as TA33, TA37, and TA38 in aircraft engines, and the prospects for promotion and application in other models and structures are also very broad.

Claims

1. A control method for improving the performance consistency of a conformally processed titanium alloy blisk forging, characterized in that: Applicable high-temperature titanium alloy materials are TA32, TA33, TA37, and TA38. The common feature of these materials is that they are cooled by quenching after high-temperature heat treatment; The process steps are as follows: Step 1: Design of conformal machining blank: Based on the high-temperature titanium alloy integral blisk die forging with a thickness of ≥100mm, design the conformal machining blank drawing according to the part drawing; Step 2: High-temperature quenching treatment of the conformal blank: The conformal blank is heated in an electric furnace to a temperature within the range of 50°C to 10°C below the α+β / β phase transition point, and is kept warm for 1 h to 5 h after being heated through. After the heat preservation is completed, it is taken out of the furnace; after being taken out of the furnace, water quenching or oil quenching is performed; Step 3: Control and treatment of the performance consistency of the conformal forging blank: The conformal forging blank is heated in an electric furnace to a temperature within the range of 800℃~850℃, and the furnace is loaded 10℃ below the set temperature. The timing starts after the furnace temperature returns to the set temperature. The holding time τ is required to be between 10min~0.5δ min +20min, the heat penetration time is estimated as 0.5 times the thickness of the thinnest part of the forging; δ min In order to follow the minimum size of the forging blank at different positions and directions, it is air-cooled to a temperature below 600°C after the insulation is completed; Step 4: Strengthening treatment of forging blanks for conformal processing: The forging blanks for conformal processing are heated to a temperature in the range of 650℃ to 750℃ in an electric furnace, and kept warm for 2 h to 50 h after being heated through; after the end of the heat preservation, they are air-cooled or temperature-controlled cooled to room temperature.

2. A control and treatment method for improving the performance consistency of a conformally processed titanium alloy blisk forging according to claim 1, characterized in that: In step one, it is required that the dimension of at least one direction of any position of the conformal machining blank is between 30 mm and 100 mm, and this direction is the direction with the smallest dimension.

3. A control and treatment method for improving the performance consistency of a conformally processed titanium alloy blisk forging according to claim 1, characterized in that: The forgings are processed according to the shape of the finished parts, and heat treatment is performed after removing part of the material. The preparation process is forging → processing → heat treatment → finishing.

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