TC4-DT titanium alloy frame beam forging method

Abstract

The invention provides a TC4-DT titanium alloy frame beam forging method, and relates to the field of aircraft part forging, the method comprises the following steps: obtaining a TC4-DT titanium alloy bar; the TC4-DT titanium alloy bar is made into an intermediate blank; the intermediate blank is subjected to die forging in the alpha + beta two-phase region temperature interval, and a TC4-DT titanium alloy frame beam forge piece is obtained; and quasi-beta annealing is conducted on the TC4-DT titanium alloy frame beam forged piece. The method is suitable for the forging process of TC4-DT titanium alloy frame beams and is used for providing a forging process capable of forging TC4-DT forgings meeting the requirements.

Description

Technical Field

[0001] The present application relates to the field of forging, specifically to the field of aircraft parts forging, and in particular to a TC4-DT titanium alloy frame beam forging method. Background Art

[0002] TC4-DT titanium alloy is widely used in the manufacture of aircraft load-bearing structural parts due to its high specific strength and good heat resistance and corrosion resistance.

[0003] The microstructure and properties of TC4-DT alloy are extremely sensitive to process parameters. Therefore, a forging process that can forge TC4-DT forgings that meet the requirements has become our need. Summary of the invention

[0004] The present application provides a TC4-DT titanium alloy frame beam forging method, which is used to provide a forging process capable of forging TC4-DT forgings that meet the requirements.

[0005] In a first aspect, the present application provides a TC4-DT titanium alloy frame beam forging method, the method comprising: obtaining a TC4-DT titanium alloy bar; making the TC4-DT titanium alloy bar into an intermediate billet; die forging the intermediate billet in an α+β two-phase temperature range to obtain a TC4-DT titanium alloy frame beam forging; and performing quasi-β annealing on the TC4-DT titanium alloy frame beam forging.

[0006] Optionally, the TC4-DT titanium alloy frame beam forgings are subjected to quasi-β annealing, including: β zone annealing, air cooling, then 730°C annealing, and air cooling; wherein the β zone annealing includes: after keeping warm for a preset time in the α+β two-phase temperature range, raising the temperature to the β zone for heating and keeping warm, the β zone is a temperature range of 15°C to 30°C above the phase transformation temperature point where the α phase transforms into the β phase.

[0007] Optionally, the intermediate billet is die forged in the temperature range of the α+β two-phase region, including: the intermediate billet is die forged in multiple fires in the temperature range of the α+β two-phase region, and the deformation amount of each die forging fire is 35%-40%.

[0008] Optionally, the TC4-DT titanium alloy frame beam forging is a rectangular forging; a plurality of positioning pits are provided on the upper and lower surfaces of the rectangular forging; a plurality of positioning protrusions are protruding from the side of the rectangular forging; the intermediate billet is a rectangular billet; the intermediate billet is subjected to multi-fire die forging in the α+β two-phase temperature range, including: subjecting the rectangular billet to a first fire die forging to press out a plurality of positioning pits on the upper and lower surfaces of the rectangular billet; returning the hot material to a second fire die forging to protrude a plurality of protruding blocks from the side of the rectangular billet; and subjecting the third fire die forging to remove burrs and flattening the plurality of protruding blocks to obtain a TC4-DT titanium alloy frame beam forging.

[0009] Optionally, making the TC4-DT titanium alloy bar into an intermediate billet includes: forging the TC4-DT titanium alloy bar into an intermediate billet in a temperature range of an α+β two-phase region.

[0010] Optionally, in the process of making the TC4-DT titanium alloy bar into an intermediate billet, the deformation amount under a single hammer blow is less than or equal to 8%.

[0011] Optionally, in the process of making the TC4-DT titanium alloy bar into an intermediate billet, the pressing speed of the equipment is 2mm / s-5mm / s.

[0012] Optionally, during the process of die forging the intermediate billet in the α+β two-phase temperature range, the pressing speed of the equipment is 2 mm / s.

[0013] Optionally, before die forging the intermediate blank in the α+β two-phase temperature range, the method further comprises: preheating the die forging die.

[0014] It should be understood that when titanium alloy is heated at the phase transition point, the grain size will increase with the increase in temperature and the extension of the holding time, thereby effectively improving the fracture toughness of the product and reducing the crack growth rate of the product. Therefore, it is particularly important to choose the appropriate annealing temperature and holding time.

[0015] The TC4-DT titanium alloy frame beam forging method provided in the present application can die forge the intermediate billet in the α+β two-phase temperature range to obtain a TC4-DT titanium alloy frame beam forging, and perform quasi-β annealing on the TC4-DT titanium alloy frame beam forging. It has been verified that high-performance TC4-DT titanium alloy frame beam forgings with high fracture toughness and low crack extension can be obtained through such a forging process.

[0016] In a second aspect, the present application provides a TC4-DT titanium alloy frame beam, which is forged using the TC4-DT titanium alloy frame beam forging method described in the first aspect above.

[0017] The beneficial effects of the second aspect above can be referred to those described in the first aspect above and will not be elaborated on again. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A shape diagram of the TC4-DT titanium alloy frame beam forging provided in an embodiment of the present application; Figure 2 A schematic diagram of multi-fire die forging provided in an embodiment of the present application; Figure 3 This is a cross-sectional view of the equivalent strain distribution of the third die forging fire provided in the embodiment of the present application; Figure 4 This is a cross-sectional diagram of the equivalent strain rate distribution of the third die forging fire provided in the embodiment of the present application; Figure 5 Schematic diagram of macrostructure and macrostructure of forgings provided in the embodiments of the present application; Figure 6 A schematic flow chart of the TC4-DT titanium alloy frame beam forging method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] It should be noted that, in the embodiments of the present application, words such as "exemplarily" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplarily" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplarily" or "for example" is intended to present related concepts in a specific way.

[0022] In order to facilitate the clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, the words "first", "second", etc. are used to distinguish the same items or similar items with basically the same functions and effects. Those skilled in the art can understand that the words "first", "second", etc. are not limiting the quantity and execution order.

[0023] TC4-DT titanium alloy is widely used in the manufacture of aircraft load-bearing structural parts due to its high specific strength and good heat resistance and corrosion resistance.

[0024] Compared with other medium-strength titanium alloys, TC4-DT titanium alloy has a relatively high fracture toughness (K Ⅰ C ≥ 93MPa•m 1 / 2 ) and fatigue crack growth resistance, it has the advantages of high toughness, high damage tolerance and long fatigue life in the use of large aviation components. In addition, it also has excellent electron beam welding performance, which is particularly suitable for the manufacture of large, integrated frames, beams and joints of aviation structures.

[0025] However, the microstructure and properties of TC4-DT alloy are extremely sensitive to process parameters.

[0026] Therefore, a forging process that can forge TC4-DT forgings that meet the requirements has become our need.

[0027] First, the material composition, forging production and development, and physical and chemical results are introduced.

[0028] (1) Material composition.

[0029] TC4-DT titanium alloy is developed and improved based on TC4 titanium alloy. Its main characteristics are: the allowable fluctuation range of the alloying element Al is narrow, and the maximum allowable content of interstitial elements C, O, N and impurity element Fe is reduced. This improvement greatly improves the fracture toughness of the material while maintaining or slightly reducing the strength.

[0030] The raw material composition of the test is TC4-DT titanium alloy bar with a diameter of 210 mm, and the smelting method is vacuum consumable arc furnace smelting, and the smelting times are three times. The chemical composition of the TC4-DT titanium alloy bar selected in the embodiment of the present application is shown in the following Table 1: Table 1 As shown in Table 1, the TC4-DT titanium alloy bar selected in the embodiment of the present application includes 0.015% carbon element (C), 0.03% silicon element (Si), 4.04% vanadium element (V), 6.185% aluminum element (Al), 0.05% iron element (Fe), 0.0024% yttrium element, 0.00413% hydrogen element, 0.1% oxygen element, and 0.0072% nitrogen element.

[0031] (2) Production and research of forgings.

[0032] (2.1) Process analysis.

[0033] In order to match the material's requirements for high crack growth resistance, high fracture toughness and low crack growth rate, the heat treatment system selected is quasi-β annealing.

[0034] A TC4-DT titanium alloy frame beam is taken as an example for further analysis.

[0035] For example, Figure 1 The shape diagram of the TC4-DT titanium alloy frame beam forging provided in the embodiment of the present application. Figure 1 As shown in the figure, the TC4-DT titanium alloy frame beam is a rectangular forging as a whole, the length of the rectangular forging is about 1.1m (1130mm), and the parting projection area is about 0.139 square meters (m2 ). A plurality of positioning pits are provided on the upper and lower surfaces of the rectangular forging, and a plurality of positioning protrusions are provided on the side surfaces of the rectangular forging.

[0036] according to Figure 1 The shape of the TC4-DT titanium alloy frame beam forging shown in the figure indicates that the intermediate billet is a rectangular billet with specific dimensions of 1060 mm in length, 100 mm in width and 105 mm in height.

[0037] (2.2) Numerical simulation.

[0038] The embodiment of this application uses Deform-3D software to perform a full-process numerical simulation of the die forging of TC4-DT titanium alloy forgings. The initial conditions of the simulation are: heating temperature 940°C, die preheating temperature 350°C, press speed 2mm / s, and friction factor of the contact surface between the workpiece and the die is 0.3.

[0039] In order to control the deformation of the forging, multi-fire die forging can be used for forging.

[0040] For example, Figure 2 This is a schematic diagram of multi-fire die forging provided in the embodiment of the present application. Figure 2 As shown in (a), because the forging belly is thinner, in order to control the deformation of the forging belly and facilitate the positioning of the forging, when the rectangular blank is subjected to the first fire die forging, multiple positioning pits can be pressed on the upper and lower surfaces of the rectangular blank, and then the hot material is returned to the furnace for the second fire die forging. Figure 2 As shown in (b) in the figure, the second fire die forging can protrude multiple protruding blocks (thicker than the positioning protruding blocks) on the side of the rectangular blank. Then the burrs can be removed for the third fire die forging. As shown in (c) in Figure (2), the third fire die forging can flatten the multiple protruding blocks to obtain the final TC4-DT titanium alloy frame beam forging.

[0041] For example, Figure 3 This is a cross-sectional view of the equivalent strain distribution of the third die forging fire provided in the embodiment of the present application. Figure 3 As shown in the figure, the deformation of the main body of the forging is within 40%, and the deformation of the die forging is larger only at the burrs and process bosses.

[0042] For example, Figure 4 This is a cross-sectional diagram of the equivalent strain rate distribution of the third die forging fire provided in the embodiment of the present application. Figure 4As shown in the figure, the strain rate of the forging body is less than 0.1 / s, and the strain rate of the forging is mainly between 0.02 / s and 0.06 / s. Only the strain rate at the burr is high. The large local deformation and high strain rate at the burr and process boss are due to the shape characteristics of high ribs and thin walls of frame beam structural parts and the process characteristics of die forging, which have no effect on the forging body. By analyzing the results of forging numerical simulation, the forging deformation and strain rate are within the required range, indicating that the forging scheme design is reasonable and feasible.

[0043] (2.3) Process route.

[0044] The main process flow is: blanking, billet making, die forging, heat treatment, physical and chemical testing. During production, the control points required by the following process documents are strictly followed: 1. The maximum deformation of the body for each fire is controlled at about 35% to 40%, and the relative deformation of a single hammer blow during the billet making process is controlled at ≤8%.

[0045] 2. In order to control the strain rate to a smaller level and prevent the temperature rise caused by the thermal effect of the forging, the pressing speed of the equipment in the billet making process is controlled at 2-5 mm / s, and the die forging is controlled at ≤2 mm / s.

[0046] 3. Billet making and die forging are carried out in the two-phase zone, and air cooling is performed after forging.

[0047] 4. During the forging process, measures such as preheating the mold and wrapping the forgings with asbestos are used to prevent temperature drop.

[0048] 5. Strictly control the final forging temperature and pay attention to controlling the transfer time.

[0049] The heat treatment system is a quasi-β annealing system: β zone annealing, air cooling + 730℃ annealing, air cooling. β zone annealing is first kept in the two-phase zone for a certain period of time, and then the temperature is raised to the β zone for heating and insulation. The β zone heating and insulation is 15℃~30℃ above the phase change point, and the heating time is selected from 20min to 65min. The actual selection system for the forgings developed this time is Tβ+15℃, and the insulation time is set according to the minimum heat penetration time. A heating coefficient of 0.3min / mm is selected within the specified time range, and the furnace is air-cooled after the insulation time is up.

[0050] (3) Physical and chemical results

[0051] After production is completed, the forgings are dissected for physical and chemical testing, the room temperature tensile strength, fracture toughness, and crack propagation properties of the forgings are measured, and the high and low magnification metallographic structures are observed and determined. For example, Figure 5 This is a schematic diagram of the macrostructure and macrostructure of the forging provided in the embodiment of the present application. Figure 5 , Figure 5The high-magnification and low-magnification microstructure diagrams of different positions of the forging are shown in FIG.

[0052] The test results of room temperature tensile strength, fracture toughness and crack growth performance of forgings can be specifically shown in Tables 2 and 3 below: Table 2: Room temperature tensile test results As shown in Table 2, the TC4-DT titanium alloy frame beam forgings forged according to the above process steps were sampled in the transverse and longitudinal directions to obtain multiple specimens, and the tensile strength (Rm, unit megapascal (MPa)), stress value when 0.2% non-proportional elongation is produced (Rp0.2, unit MPa), elongation after fracture (A, unit %), and section shrinkage (Z, unit %) of each specimen all met the index requirements.

[0053] Table 3: Fracture toughness test results As shown in Table 3, the crack length (a, in mm), the ratio of crack length to specimen width (or ligament width) (a / w), and the fracture toughness (K Q , unit: MPa·m 1 / 2 ) and so on all meet the index requirements.

[0054] Table 4: Crack extension test results As shown in Table 4, under specific test conditions, the stress intensity factor amplitude at the crack tip is 11 MPa·m 1 / 2 At this time, the corresponding da / dN values ​​found in the da / dN-ΔK relationship diagram all meet the index requirements.

[0055] Based on the understanding of the above embodiments, the present application embodiment provides a TC4-DT titanium alloy frame beam forging method. Figure 6 The schematic diagram of the process of forging a TC4-DT titanium alloy frame beam provided in the embodiment of the present application is shown in FIG. Figure 6 As shown, the method includes the following steps: S101. Obtain TC4-DT titanium alloy bar.

[0056] The chemical composition of the TC4-DT titanium alloy bar can be referred to in Table 1 above, which will not be repeated here.

[0057] S102, making the TC4-DT titanium alloy bar into an intermediate billet.

[0058] For example, as mentioned above, the intermediate blank is a rectangular blank, and the specific dimensions are 1060 mm in length, 100 mm in width, and 105 mm in height.

[0059] Optionally, as described in 3 of the above process document requirements, the billet making process may also be carried out in the two-phase region. In this case, the above S102 may specifically include: forging the TC4-DT titanium alloy bar into the intermediate billet in the α+β two-phase temperature range.

[0060] Optionally, as described in 1 of the above-mentioned process document requirements, in the process of making TC4-DT titanium alloy bar into intermediate billet, the deformation amount under single hammering is less than or equal to 8%.

[0061] Optionally, as described in 1 of the above-mentioned process document requirements, in the process of making TC4-DT titanium alloy bar into intermediate billet, the pressing speed of the equipment is 2mm / s-5mm / s.

[0062] S103, die forging the intermediate billet in the α+β two-phase temperature range to obtain a TC4-DT titanium alloy frame beam forging.

[0063] Optionally, as described in 2 of the above-mentioned process document requirements, during the process of die forging the intermediate billet in the α+β two-phase temperature range, the pressing speed of the equipment is 2 mm / s.

[0064] In some embodiments, the intermediate billet may be subjected to multi-fire die forging in the temperature range of the α+β two-phase region, and the deformation amount of each die forging is 35%-40%.

[0065] Optionally, as described above, the TC4-DT titanium alloy frame beam forging is a rectangular forging, the upper and lower surfaces of the rectangular forging are provided with a plurality of positioning pits, the side surfaces of the rectangular forging are provided with a plurality of positioning protrusions, and the intermediate blank is a rectangular blank. In this case, the above S103 may specifically include the following steps: Step 1a: subjecting the rectangular blank to a first fire die forging to press out a plurality of positioning pits on the upper and lower surfaces of the rectangular blank.

[0066] Step 2a, the hot material is returned to the furnace for a second fire die forging, and a plurality of protruding blocks are protruded from the side of the rectangular blank.

[0067] Step 3a: After removing the burrs, the third fire die forging is performed to flatten the multiple protruding block blanks to obtain the TC4-DT titanium alloy frame beam forgings.

[0068] Steps 1a to 3a can refer to the above Figure 2 It has been described in detail and will not be repeated here.

[0069] In some possible embodiments, as described in 4 of the above-mentioned process document requirements, before the intermediate billet is die-forged in the α+β two-phase temperature range, the die forging die may be preheated.

[0070] For example, the mold may be preheated to a temperature between 200° C. and 400° C., or a temperature close to the forging temperature of the forging. This embodiment of the present application does not limit this.

[0071] S104. Perform quasi-β annealing on TC4-DT titanium alloy frame beam forgings.

[0072] In some possible embodiments, as described in the process route (2.3) above, the quasi-β annealing of the TC4-DT titanium alloy frame beam forging in S104 may specifically include the following steps: Step 1b: β zone annealing, air cooling, then 730°C annealing, air cooling.

[0073] Among them, β zone annealing includes: after keeping warm for a preset time in the temperature range of the α+β two-phase zone, raising the temperature to the β zone for heating and keeping warm, the β zone is a temperature range of 15°C to 30°C above the phase change temperature point where the α phase changes to the β phase.

[0074] It should be understood that when titanium alloy is heated at the phase transition point, the grain size will increase with the increase in temperature and the extension of the holding time, thereby effectively improving the fracture toughness of the product and reducing the crack growth rate of the product. Therefore, it is particularly important to choose the appropriate annealing temperature and holding time.

[0075] The TC4-DT titanium alloy frame beam forging method provided in the embodiment of the present application can die forge the intermediate billet in the α+β two-phase temperature range to obtain a TC4-DT titanium alloy frame beam forging, and perform quasi-β annealing on the TC4-DT titanium alloy frame beam forging. It has been verified that high-performance TC4-DT titanium alloy frame beam forgings with high fracture toughness and low crack extension can be obtained through such a forging process.

[0076] The above is an introduction to the technical solution provided by the embodiment of the present application from the perspective of the method. In an exemplary embodiment, the embodiment of the present application also provides a TC4-DT titanium alloy frame beam, which can be forged by the TC4-DT titanium alloy frame beam forging method provided in the above embodiment.

[0077] As a key part of an aircraft, frame beam forgings are subjected to complex and severe fatigue stress. In order to ensure the safety and reliability of frame beam forgings during the service of the aircraft, the present embodiment of the application has drawn the following conclusions by conducting a practical element analysis on the forming process of a frame beam forging and conducting production verification: 1. Virtual testing (numerical simulation analysis) can shorten the product development cycle, reduce the mold trial manufacturing process, and improve the quality of die forging. It is a powerful design, analysis and optimization tool for die forging process.

[0078] 2. The forging structure of TC4-DT titanium alloy can be controlled by multiple firings, small deformation and slow deformation to make its structure uniform and prepare the structure for subsequent quasi-β heat treatment.

[0079] 3. The process of two-phase forging + quasi-β annealing can obtain high-performance TC4-DT titanium alloy forgings with high fracture toughness and low crack extension.

[0080] Although the present application has been described in conjunction with specific features and embodiments thereof, it is obvious that various modifications and combinations may be made thereto without departing from the spirit and scope of the present application. Accordingly, this specification and the drawings are merely exemplary illustrations of the present application as defined by the appended claims, and are deemed to have covered any and all modifications, variations, combinations or equivalents within the scope of the present application. Obviously, those skilled in the art may make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

[0081] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A TC4-DT titanium alloy frame beam forging method, characterized in that: The method comprises: Get TC4-DT titanium alloy bar stock; The TC4-DT titanium alloy bar is made into an intermediate billet; The intermediate billet is die forged in the temperature range of the α+β two-phase region to obtain a TC4-DT titanium alloy frame beam forging; The TC4-DT titanium alloy frame beam forging is subjected to quasi-β annealing.

2. The method according to claim 1, characterized in that The quasi-β annealing of the TC4-DT titanium alloy frame beam forging comprises: Annealing in the β zone, air cooling, then annealing at 730°C, air cooling; Among them, β zone annealing includes: keeping the temperature in the α+β two-phase temperature range for a preset time and then raising the temperature to the β zone for heating and keeping, wherein the β zone is a temperature range of 15°C to 30°C above the phase change temperature point where the α phase changes to the β phase.

3. The method according to claim 1, characterized in that The die forging of the intermediate billet in the temperature range of the α+β two-phase region comprises: The intermediate billet is subjected to multi-fire die forging in the temperature range of the α+β two-phase region, and the deformation amount of each fire die forging is 35%-40%.

4. The method according to claim 3, characterized in that The TC4-DT titanium alloy frame beam forging is a rectangular forging; the upper and lower surfaces of the rectangular forging are provided with a plurality of positioning pits; the side surfaces of the rectangular forging are provided with a plurality of positioning protrusions; The intermediate billet is a rectangular billet; The method of performing multi-fire die forging on the intermediate billet in the temperature range of the α+β two-phase region comprises: Performing a first fire die forging on the rectangular blank to press out the plurality of positioning pits on the upper and lower surfaces of the rectangular blank; The hot material is returned to the furnace for a second fire die forging, and a plurality of convex blocks are protruded from the side of the rectangular blank; After removing the burrs, the third fire die forging is performed to flatten the plurality of raised block blanks to obtain the TC4-DT titanium alloy frame beam forging.

5. The method according to claim 1, characterized in that: The method of making the TC4-DT titanium alloy bar into an intermediate blank comprises: The TC4-DT titanium alloy bar is forged into the intermediate billet in the temperature range of the α+β two-phase region.

6. The method according to claim 1, characterized in that In the process of making the TC4-DT titanium alloy bar into an intermediate blank, the deformation amount under a single hammering is less than or equal to 8%.

7. The method according to claim 1, characterized in that In the process of making the TC4-DT titanium alloy bar into an intermediate billet, the pressing speed of the equipment is 2mm / s-5mm / s.

8. The method according to claim 1, characterized in that During the process of die forging the intermediate billet in the temperature range of the α+β two-phase region, the pressing speed of the equipment is 2 mm / s.

9. The method according to claim 1, characterized in that: Before forging the intermediate blank in the α+β two-phase temperature range, the method further comprises: Preheat the die forging.

10. A TC4-DT titanium alloy frame beam, characterized in that: The TC4-DT titanium alloy frame beam is forged by using the forging method described in any one of claims 1 to 9.

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