Heat treatment method suitable for Ti2AlNb alloy electron beam welding

Abstract

The invention relates to the technical field of welding, in particular to a heat treatment method suitable for Ti2AlNb alloy electron beam welding. A heat treatment method suitable for Ti2AlNb alloy electron beam welding comprises the following steps that (a) solid solution heat treatment is conducted on a Ti2AlNb alloy forge piece, PAG cooling liquid is adopted for cooling, then heat preservation stress relief annealing treatment is conducted, and a pretreated forge piece is obtained; (b) the pretreated forge piece is subjected to electron beam welding, gas quenching is adopted after electron beam welding, and a welding piece is obtained; and (c) carrying out aging treatment on the welding piece, and carrying out gas quenching after the aging treatment to obtain the Ti2AlNb alloy welding piece. According to the heat treatment method suitable for Ti2AlNb alloy electron beam welding, through cooperation of all the steps, a double-batten structure with excellent comprehensive performance is obtained, and the room-temperature and high-temperature tensile performance of a Ti2AlNb alloy weldment can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of welding, and in particular to a heat treatment method suitable for electron beam welding of Ti2AlNb alloy. Background Art

[0002] As a typical intermetallic compound, Ti2AlNb alloy has the intrinsic characteristics of high strength and poor plasticity. One of the important factors restricting its engineering application is welding. The properties of Ti2AlNb alloy are different in different heat treatment states. The methods adopted in the existing technology have poor room temperature plasticity and poor weldability of Ti2AlNb alloy.

[0003] Therefore, it is very important to perform effective heat treatment during the welding process of Ti2AlNb alloy forgings to ensure that they have excellent welding performance.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] An object of the present invention is to provide a heat treatment method suitable for electron beam welding of Ti2AlNb alloy to solve the above technical problems. This method can obtain a double-lath structure with excellent comprehensive performance, so as to improve the comprehensive mechanical properties of Ti2AlNb alloy weldments.

[0006] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0007] A heat treatment method suitable for electron beam welding of Ti2AlNb alloy, comprising the following steps:

[0008] (a) performing a solution heat treatment on a Ti2AlNb alloy forging, cooling the forging with a PAG coolant, and then performing a heat preservation stress relief annealing treatment to obtain a pretreated forging;

[0009] (b) performing electron beam welding on the pretreated forging, and gas quenching after the electron beam welding to obtain a welded part;

[0010] (c) performing aging treatment on the weldment, and then gas quenching to obtain a Ti2AlNb alloy weldment.

[0011] In some embodiments, the temperature of the solution heat treatment is 900-1000° C., and the time of the solution heat treatment is 1-4 hours.

[0012] In some embodiments, the temperature of the solution heat treatment is 930-980° C., and the time of the solution heat treatment is 1.5-3 hours.

[0013] In some implementations, the concentration of the PAG coolant is 18% to 22%.

[0014] In some implementations, the temperature of the thermal insulation stress relief annealing treatment is 350-500° C., and the time of the thermal insulation stress relief annealing treatment is 2-6 hours.

[0015] In some implementations, the temperature of the thermal insulation stress relief annealing treatment is 400-460° C., and the time of the thermal insulation stress relief annealing treatment is 2-5 hours.

[0016] In some embodiments, the microstructure of the pretreated forging includes a B2 phase, an O phase and an α2 phase, the volume fraction of the B2 phase is 65% to 90%, and the total volume fraction of the O phase and the α2 phase is 10% to 35%.

[0017] In some implementations, the room temperature plasticity of the pretreated forging is 16% to 20%.

[0018] In some embodiments, the welding surface of the pretreated forging comprises a rectangular ring with an outer diameter of 200 to 300 mm.

[0019] In some embodiments, the pretreated forging is also rough-machined before the electron beam welding, and the rough-machined includes: reducing the wall thickness of the to-be-welded portion of the pretreated forging to 5-8 mm.

[0020] In some implementations, the acceleration voltage of the electron beam welding is 130-160 kV, the electron beam current is 7-12 mA, and the welding speed is 10-15 m / s.

[0021] In some embodiments, in the step (b), the gas pressure of the gas quenching is 0.7 to 1 bar.

[0022] In some embodiments, the temperature of the aging treatment is 750-900° C., and the time of the aging treatment is 6-24 hours.

[0023] In some embodiments, the temperature of the aging treatment is 800-870° C., and the time of the aging treatment is 8-16 hours.

[0024] In some embodiments, in step (c), the gas pressure of the gas quenching is 0.7-1 bar.

[0025] In some embodiments, the microstructure of the Ti2AlNb alloy weldment includes B2 phase, O phase and α2 phase, and the volume fraction of the B2 phase is 5% to 30%; the O phase and α2 phase include large slats and small slats, the length of the large slats is 1 to 5 μm, and the total volume fraction of the O phase and α2 phase of the large slats is 10% to 35%, the length of the small slats is less than 1 μm, and the total volume fraction of the O phase and α2 phase of the small slats is 35% to 60%.

[0026] In some embodiments, the Ti2AlNb alloy weldment has a tensile strength of 1020-1100 MPa at 25°C, a yield strength of 960-1050 MPa, an elongation of 6%-10%, and a cross-sectional reduction of 8%-15%.

[0027] In some embodiments, the Ti2AlNb alloy weldment has a tensile strength of 840-900 MPa at 650°C, a yield strength of 700-800 MPa, an elongation of 11%-25%, and a cross-sectional reduction of 26%-80%.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The heat treatment method suitable for electron beam welding of Ti2AlNb alloy of the present invention performs solution heat treatment, PAG coolant cooling and heat preservation stress relief annealing treatment on Ti2AlNb alloy forgings, so that the microstructure of the obtained pre-treated forgings has a suitable volume percentage of B2 phase, O phase and α2 phase, and has excellent room temperature plasticity, thereby ensuring the smooth progress of subsequent electron beam welding and improving the welding effect of electron beam welding; further, the welded parts are subjected to aging treatment to obtain a double-slat structure with excellent comprehensive performance, so as to improve the room temperature and high temperature tensile properties of the Ti2AlNb alloy welded parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 is a microstructure diagram of the pretreated forging in Example 1 of the present invention;

[0032] Figure 2 This is the microstructure diagram of the Ti2AlNb alloy weldment in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0034] A heat treatment method suitable for electron beam welding of Ti2AlNb alloy, comprising the following steps:

[0035] (a) The Ti2AlNb alloy forging is subjected to solution heat treatment, cooled with PAG coolant, and then subjected to insulation stress relief annealing to obtain a pretreated forging.

[0036] (b) Electron beam welding is performed on the pretreated forging, and gas quenching is performed after the electron beam welding to obtain a welded part.

[0037] (c) performing aging treatment on the weldment, and then gas quenching to obtain a Ti2AlNb alloy weldment.

[0038] The heat treatment method suitable for electron beam welding of Ti2AlNb alloy of the present invention performs solution heat treatment, PAG coolant cooling and heat preservation stress relief annealing treatment on Ti2AlNb alloy forgings, so that the microstructure of the obtained pre-treated forgings has a suitable volume percentage of B2 phase, O phase and α2 phase, and has excellent room temperature plasticity, thereby ensuring the smooth progress of subsequent electron beam welding and improving the welding effect of electron beam welding; further, the welded parts are subjected to aging treatment to obtain a double-slat structure with excellent comprehensive performance, so as to improve the room temperature and high temperature tensile properties of the Ti2AlNb alloy welded parts, and the comprehensive mechanical properties are good.

[0039] In some embodiments, the Ti2AlNb alloy forging is a Ti2AlNb ring forging prepared by ring rolling. In some embodiments, the Ti2AlNb alloy in each specific embodiment and comparative example is Ti-22Al-25Nb. In some embodiments, the Ti2AlNb alloy can be obtained by conventional smelting, forging, and hot rolling processes. The method of the present invention is also applicable to Ti2AlNb alloys having one or more of the alloying elements of Mo, Si, Cr, V, Fe, and Ta.

[0040] In some embodiments, the Ti2AlNb alloy forging is heated to the furnace. The temperature of the solution heat treatment is 900-1000°C, including but not limited to 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990 or 1000°C, etc., or any range between the two. The time of the solution heat treatment is 1-4h, such as 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h, etc., or any range between the two. Preferably, the temperature of the solution heat treatment is 930-980°C, and the time of the solution heat treatment is 1.5-3h. The present invention adopts suitable solution heat treatment conditions to fully dissolve various phases in the alloy, strengthen the solid solution, and improve the weldability of the Ti2AlNb alloy forging.

[0041] In some embodiments, the concentration (mass content) of the PAG coolant is 18% to 22%, such as 18%, 19%, 20% or 22%. The PAG coolant includes PAG and water. The organic polymer in the PAG coolant is completely soluble in water to form a clear, homogeneous solution. During the quenching process of the Ti2AlNb alloy forging, once the liquid temperature around the workpiece rises above the turbidity point of the solution, the PAG polymer will be desolvated from the solution and suspended in the quenching liquid in the form of fine liquid droplets. Once the suspended PAG liquid droplets come into contact with the red-hot workpiece, they adhere to the surface of the workpiece by virtue of their excellent wettability, forming a water-rich membrane to wrap the workpiece. This membrane is used to adjust the cooling rate of the water to prevent the workpiece from quenching cracking; the PAG solution can overcome the shortcomings of water cooling fast, easy to cause the workpiece to crack, slow cooling rate of oil products, poor quenching effect and flammability. Specifically, the concentration of the PAG coolant in each embodiment is 20%.

[0042] In some embodiments, the temperature of the heat-insulating stress relief annealing treatment is 350-500°C, including but not limited to 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, etc., or any range between the two. The time of the heat-insulating stress relief annealing treatment is 2-6h, for example, 2h, 3h, 4h, 5h, 6h, etc. Preferably, the temperature of the heat-insulating stress relief annealing treatment is 400-460°C, and the time of the heat-insulating stress relief annealing treatment is 2-5h. The present invention obtains a pre-treated forging with suitable mechanical properties by heat-insulating stress relief annealing treatment under suitable conditions to ensure the stress relief effect before welding.

[0043] In some embodiments, the microstructure of the pretreated forging includes B2 phase, O phase and α2 phase, and the volume fraction of the B2 phase is 65% to 90%, including but not limited to 65%, 70%, 75%, 80%, 85%, 90%, etc., or any range between the two. The total volume fraction of the O phase and the α2 phase is 10% to 35%, including but not limited to 10%, 15%, 20%, 25%, 30%, 35%, etc., or any range between the two. The present invention controls the appropriate volume fraction of the B2 phase, thereby making the pretreated forging have excellent plasticity, and the room temperature plasticity of the pretreated forging is 16% to 20%, which is conducive to electron beam welding and improves welding performance.

[0044] In some embodiments, the welding surface of the pretreated forging comprises a rectangular ring with an outer diameter of 200 to 300 mm, such as 200 mm, 220 mm, 250 mm, 300 mm, etc.

[0045] In some embodiments, the pretreated forging is also rough-machined before the electron beam welding to facilitate subsequent electron beam welding, and the rough-machined includes: thinning the wall thickness of the pretreated forging to be welded to 5-8 mm, such as 5 mm, 6 mm, 7 mm, 8 mm, etc.

[0046] In some embodiments, the acceleration voltage of the electron beam welding is 130 to 160 kV, such as 130 kV, 140 kV, 150 kV, 160 kV, etc. The electron beam current is 7 to 12 mA, such as 7 mA, 8 mA, 10 mA or 12 mA, etc. The welding speed is 10 to 15 m / s, such as 10 m / s, 12 m / s, 15 m / s, etc. In step (b), gas quenching is performed after electron beam welding to ensure the microstructural characteristics and performance of the welded part, and the gas pressure of gas quenching is 0.7 to 1 bar, such as 0.7 bar, 0.75 bar, 0.8 bar, 0.85 bar, 0.9 bar, 1 bar, etc. The gas used for gas quenching includes argon and / or helium. Gas quenching is performed by gas of suitable pressure to ensure the organizational characteristics and mechanical properties of the welded part.

[0047] In some embodiments, the temperature of the aging treatment is 750-900°C, including but not limited to 750°C, 780°C, 800°C, 810°C, 830°C, 850°C, 880°C or 900°C, or any range between the two. The time of the aging treatment is 6-24h, such as 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, etc. Preferably, the temperature of the aging treatment is 800-870°C, and the time of the aging treatment is 8-16h. In the step (c), the gas pressure of the gas quenching is 0.7-1bar, such as 0.7bar, 0.8bar, 0.9bar, 1bar, etc., or any range between the two. The present invention adopts appropriate aging treatment and gas quenching after the above-mentioned solution heat treatment, cooling, insulation, electron beam welding and gas quenching, so that the microstructure of the Ti2AlNb alloy forging has appropriate volume fractions of B2 phase, O phase and α2 phase to provide excellent strength.

[0048] In some embodiments, the microstructure of the Ti2AlNb alloy weldment includes a B2 phase, an O phase and an α2 phase, and the volume fraction of the B2 phase is 5% to 30%, for example, 5%, 10%, 15%, 20%, 25%, 30%, etc., or any range value between the two; the O phase and the α2 phase include the O phase and the α2 phase of the large lath and the O phase and the α2 phase of the small lath, and the length of the O phase and the α2 phase of the large lath is 1 to 5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, or any range value between the two; the total volume fraction of the O phase and the α2 phase of the large lath is 10% to 35%, for example, 10%, 1 5%, 20%, 25%, 30% or 35%, etc., or any range between two values; the length of the small lath O phase and the α2 phase is less than 1 μm, for example 0.01 μm, 0.02 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.9 μm, 0.95 μm, etc., or any range between two values; the total volume fraction of the small lath O phase and the α2 phase is 35% to 60%, for example 35%, 40%, 45%, 50%, 55%, 60%, etc., or any range between two values. The microstructure of the weldment of the present invention has suitable volume fractions of B2 phase, O phase and α2 phase, and the O phase and α2 phase have suitable volume fractions and sizes of large plate O phase and α2 phase and small plate O phase and α2 phase, which cooperate with each other, thereby ensuring that the weldment has excellent mechanical properties.

[0049] In some embodiments, the tensile strength of the Ti2AlNb alloy weldment at 25°C is 1020-1100 MPa, such as 1020 MPa, 1040 MPa, 1050 MPa, 1070 MPa, 1080 MPa, 1100 MPa, etc., or any range between the two. The yield strength is 960-1050 MPa, such as 960 MPa, 1000 MPa, 1050 MPa, the elongation is 6%-10%, such as 6%, 7.5%, 8%, 8.5%, 9%, 10%, etc., or any range between the two; the cross-sectional shrinkage is 8%-15%, such as 8%, 10%, 11%, 12%, 13%, 14%, 15%, etc., or any range between the two.

[0050] In some embodiments, the tensile strength of the Ti2AlNb alloy weldment at 650°C is 840-900 MPa, such as 840 MPa, 850 MPa, 860 MPa, 870 MPa, 880 MPa, 890 MPa, 900 MPa, etc., or any range between the two; the yield strength is 700-800 MPa, and the yield strength is 700 MPa, 710 MPa, 730 MPa, 750 MPa, etc. Pa, 770MPa, 780MPa, 800MPa, etc., or any range between them; the elongation is 11% to 25%, such as 11%, 15%, 20%, 21%, 22%, 23%, 24%, 25%, etc., or any range between them; the cross-sectional shrinkage is 26% to 80%, such as 26%, 55%, 60%, 65%, 70%, 75%, 80%, etc., or any range between them. The Ti2AlNb alloy weldment obtained by the method of the present invention has excellent mechanical properties at room temperature and high temperature.

[0051] The following is further explained in conjunction with specific embodiments and comparative examples.

[0052] Example 1

[0053] A heat treatment method suitable for electron beam welding of Ti2AlNb alloy, comprising the following steps:

[0054] (1) Preparation of Ti2AlNb ring forgings by ring rolling.

[0055] (2) The Ti2AlNb alloy forgings were subjected to solution heat treatment at a temperature of 970°C for 2.5 hours. After the solution heat treatment, they were cooled with PAG coolant and then subjected to stress relief annealing at a temperature of 455°C for 3 hours to obtain pretreated forgings. The microstructure of the pretreated forgings is shown in Figure 2. Figure 1 shown.

[0056] (3) The pre-treated forgings are rough-machined before welding, and the wall thickness of the electron beam welding is uniformly thinned to 6 mm. The welding surface is a rectangular ring with an outer diameter of

[0057] (4) Electron beam welding is performed on the pre-treated forging after rough machining, and the acceleration voltage of the electron beam welding is 150 kV, the electron beam current is 10 mA, and the welding speed is 13 m / s. After the electron beam welding, gas quenching is performed, and the gas for gas quenching is argon gas with a gas pressure of 0.85 bar to obtain a welded part.

[0058] (5) The welded parts were subjected to aging treatment at a temperature of 840°C for 12 h. After the aging treatment, gas quenching was performed using argon gas at a gas pressure of 0.85 bar to obtain a Ti2AlNb alloy weldment. The microstructure of the Ti2AlNb alloy weldment is shown in FIG. Figure 2 shown.

[0059] Example 2

[0060] A heat treatment method suitable for electron beam welding of Ti2AlNb alloy, comprising the following steps:

[0061] (1) Preparation of Ti2AlNb ring forgings by ring rolling.

[0062] (2) The Ti2AlNb alloy forgings are subjected to solution heat treatment at a temperature of 930°C for 3 h. After the solution heat treatment, they are cooled with PAG coolant and then subjected to stress relief annealing at a temperature of 430°C for 2 h to obtain pretreated forgings.

[0063] (3) The pre-treated forgings are rough-machined before welding, and the wall thickness of the electron beam welding is uniformly thinned to 6 mm. The welding surface is a rectangular ring with an outer diameter of

[0064] (4) Electron beam welding is performed on the pre-treated forging after rough machining, and the acceleration voltage of the electron beam welding is 150 kV, the electron beam current is 10 mA, and the welding speed is 13 m / s. After the electron beam welding, gas quenching is performed, and the gas for gas quenching is argon gas with a gas pressure of 0.9 bar to obtain a welded part.

[0065] (5) The welded parts are subjected to aging treatment at a temperature of 800° C. for 13 h. After the aging treatment, gas quenching is performed, the gas used for the gas quenching is argon, and the gas pressure of the gas quenching is 0.9 bar, thereby obtaining a Ti2AlNb alloy welded part.

[0066] Example 3

[0067] A heat treatment method suitable for electron beam welding of Ti2AlNb alloy, comprising the following steps:

[0068] (1) Preparation of Ti2AlNb ring forgings by ring rolling.

[0069] (2) The Ti2AlNb alloy forgings are subjected to solution heat treatment at a temperature of 980°C for 1.5 h. After the solution heat treatment, they are cooled with PAG coolant and then subjected to stress relief annealing at a temperature of 400°C for 6 h to obtain pretreated forgings.

[0070] (3) The pre-treated forgings are rough-machined before welding, and the wall thickness of the electron beam welding is uniformly thinned to 6 mm. The welding surface is a rectangular ring with an outer diameter of

[0071] (4) Electron beam welding is performed on the pre-treated forging after rough machining, the acceleration voltage of the electron beam welding is 150 kV, the electron beam current is 10 mA, and the welding speed is 13 m / s. After the electron beam welding, gas quenching is performed, the gas for gas quenching is argon gas, and the gas pressure is 0.8 bar to obtain a welded part.

[0072] (5) The welded parts are subjected to aging treatment at a temperature of 870°C and a time of 13 h. After the aging treatment, gas quenching is performed, the gas used for the gas quenching is argon, and the gas pressure of the gas quenching is 0.8 bar, thereby obtaining a Ti2AlNb alloy welded part.

[0073] Example 4

[0074] A heat treatment method suitable for electron beam welding of Ti2AlNb alloy, comprising the following steps:

[0075] (1) Preparation of Ti2AlNb ring forgings by ring rolling.

[0076] (2) The Ti2AlNb alloy forgings are subjected to solution heat treatment at a temperature of 900°C for 3 h. After the solution heat treatment, they are cooled with PAG coolant and then subjected to stress relief annealing at a temperature of 400°C for 1 h to obtain pretreated forgings.

[0077] (3) The pre-treated forgings are rough-machined before welding, and the wall thickness of the electron beam welding is uniformly thinned to 6 mm. The welding surface is a rectangular ring with an outer diameter of

[0078] (4) Electron beam welding is performed on the pre-treated forging after rough machining, the acceleration voltage of the electron beam welding is 150 kV, the electron beam current is 10 mA, and the welding speed is 13 m / s. After the electron beam welding, gas quenching is performed, the gas for gas quenching is argon gas, and the gas pressure is 0.7 bar to obtain a welded part.

[0079] (5) The welded parts are subjected to aging treatment at a temperature of 750° C. for 20 h. After the aging treatment, gas quenching is performed, the gas used for the gas quenching is argon, and the gas pressure of the gas quenching is 0.7 bar, thereby obtaining a Ti2AlNb alloy welded part.

[0080] Example 5

[0081] A heat treatment method suitable for electron beam welding of Ti2AlNb alloy, comprising the following steps:

[0082] (1) Preparation of Ti2AlNb ring forgings by ring rolling.

[0083] (2) The Ti2AlNb alloy forgings are subjected to solution heat treatment at a temperature of 1000°C for 3 h. After the solution heat treatment, they are cooled with PAG coolant and then subjected to stress relief annealing at a temperature of 500°C for 1 h to obtain pretreated forgings.

[0084] (3) The pre-treated forgings are rough-machined before welding, and the wall thickness of the electron beam welding is uniformly thinned to 6 mm. The welding surface is a rectangular ring with an outer diameter of

[0085] (4) Electron beam welding is performed on the pre-treated forging after rough machining, and the acceleration voltage of the electron beam welding is 150 kV, the electron beam current is 10 mA, and the welding speed is 13 m / s. After the electron beam welding, gas quenching is performed, and the gas for gas quenching is argon gas with a gas pressure of 1 bar to obtain a welded part.

[0086] (5) The weldment is subjected to aging treatment at a temperature of 900° C. for 10 h. After the aging treatment, gas quenching is performed, the gas used for the gas quenching is argon, and the gas pressure of the gas quenching is 1 bar, thereby obtaining a Ti2AlNb alloy weldment.

[0087] Comparative Example 1

[0088] A heat treatment method for electron beam welding of Ti2AlNb alloy comprises the following steps:

[0089] (1) Preparation of Ti2AlNb ring forgings by ring rolling.

[0090] (2) The Ti2AlNb alloy forgings are subjected to solution heat treatment at a temperature of 1000°C for 3 hours, air-cooled, and then subjected to aging treatment at a temperature of 900°C for 10 hours; and pretreated forgings are obtained.

[0091] (3) The pre-treated forgings are rough-machined before welding, and the wall thickness of the electron beam welding is uniformly thinned to 6 mm. The welding surface is a rectangular ring with an outer diameter of

[0092] (4) Electron beam welding is performed on the pre-treated forging after rough machining, and the acceleration voltage of the electron beam welding is 150 kV, the electron beam current is 10 mA, and the welding speed is 13 m / s. Air cooling is used after electron beam welding to obtain a Ti2AlNb alloy weldment.

[0093] Comparative Example 2

[0094] A heat treatment method for electron beam welding of Ti2AlNb alloy, which differs from Example 1 in that:

[0095] In step (2), air cooling is used after solution heat treatment.

[0096] Experimental example

[0097] 1. Microstructure and room temperature plasticity of pretreated forgings

[0098] The volume fractions of the B2 phase, the O phase and the α2 phase in the microstructure of the pretreated forgings of each embodiment and comparative example, and the room temperature plasticity of the pretreated forgings are shown in Table 1.

[0099] Table 1 Microstructure and room temperature plasticity of pretreated forgings

[0100] Group B2 phase (%) O phase and α2 phase (%) Room temperature plasticity (%) Example 1 88 12 20 Example 2 65 35 17 Example 3 85 15 18 Example 4 55 45 16 Example 5 92 8 16 Comparative Example 1 32 68 8 Comparative Example 2 30 70 7

[0101] As can be seen from Table 1, the present invention combines solution heat treatment under appropriate conditions, PAG coolant cooling, and insulation stress relief annealing treatment, so that the microstructure of the pretreated forging obtained has appropriate volume fractions of B2 phase, O phase and α2 phase, which can ensure the plasticity of the pretreated forging, facilitate subsequent electron beam welding, and improve welding performance.

[0102] 2. Microstructure and room temperature plasticity of Ti2AlNb alloy weldments

[0103] The total volume fractions of B2 phase, O phase and α2 phase in the microstructure of the Ti2AlNb alloy weldments of various embodiments and comparative examples, and the room temperature plasticity of the pretreated forgings are shown in Table 2.

[0104] Table 2 Microstructure and room temperature plasticity of Ti2AlNb alloy weldments

[0105]

[0106]

[0107] 3. Mechanical properties of Ti2AlNb alloy weldments

[0108] The mechanical properties of the Ti2AlNb alloy weldments of the embodiments and comparative examples were tested. The room temperature tensile test standard was GB228.1. The high temperature tensile test standard was GB228.2.

[0109] The mechanical properties test results of Ti2AlNb alloy weldments are shown in Table 3.

[0110] Table 3 Mechanical properties test results of Ti2AlNb alloy weldments

[0111]

[0112]

[0113] It can be seen from Tables 2 and 3 that the microstructure of the weldment of the present invention has suitable volume fractions of B2 phase, O phase and α2 phase, and the O phase and α2 phase have suitable overall volume fractions and sizes of large lath O phase and α2 phase and small lath O phase and α2 phase, which cooperate with each other, thereby ensuring that the weldment has excellent room temperature and high temperature tensile properties.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A heat treatment method suitable for electron beam welding of Ti2AlNb alloy, characterized in that: The following steps are involved: (a) performing a solution heat treatment on a Ti2AlNb alloy forging, cooling it with a PAG coolant, and then performing a heat preservation stress relief annealing treatment to obtain a pretreated forging; (b) performing electron beam welding on the pretreated forging, and gas quenching after the electron beam welding to obtain a welded part; (c) performing aging treatment on the weldment, and then gas quenching to obtain a Ti2AlNb alloy weldment.

2. The heat treatment method suitable for electron beam welding of Ti2AlNb alloy according to claim 1, characterized in that: The temperature of the solution heat treatment is 900-1000°C, and the time of the solution heat treatment is 1-4h; Preferably, the temperature of the solution heat treatment is 930-980°C, and the time of the solution heat treatment is 1.5-3h; Preferably, the concentration of the PAG coolant is 18% to 22%.

3. The heat treatment method suitable for electron beam welding of Ti2AlNb alloy according to claim 1, characterized in that: The temperature of the heat preservation stress relief annealing treatment is 350-500° C., and the time of the heat preservation stress relief annealing treatment is 2-6 hours; Preferably, the temperature of the thermal insulation stress relief annealing treatment is 400-460° C., and the time of the thermal insulation stress relief annealing treatment is 2-5 hours.

4. The heat treatment method suitable for electron beam welding of Ti2AlNb alloy according to claim 1, characterized in that: The microstructure of the pretreated forging includes B2 phase, O phase and α2 phase, the volume fraction of the B2 phase is 55% to 90%, and the total volume fraction of the O phase and the α2 phase is 10% to 45%; And / or, the room temperature plasticity of the pretreated forging is 16% to 20%.

5. The heat treatment method suitable for Ti2AlNb alloy electron beam welding according to claim 1, characterized in that: The welding surface of the pre-treated forging comprises a rectangular ring with an outer diameter of 200 to 300 mm; And / or, the pretreated forging is also rough-machined before the electron beam welding, and the rough-machined includes: thinning the wall thickness of the to-be-welded portion of the pretreated forging to 5-8 mm.

6. The heat treatment method suitable for electron beam welding of Ti2AlNb alloy according to claim 1, characterized in that: The acceleration voltage of the electron beam welding is 130-160 kV, the electron beam current is 7-12 mA, and the welding speed is 10-15 m / s; Preferably, in step (b), the gas pressure of the gas quenching is 0.7-1 bar.

7. The heat treatment method suitable for electron beam welding of Ti2AlNb alloy according to claim 1, characterized in that: The temperature of the aging treatment is 750-900°C, and the time of the aging treatment is 6-24h; Preferably, the temperature of the aging treatment is 800-870°C, and the time of the aging treatment is 8-16h; Preferably, in step (c), the gas pressure of the gas quenching is 0.7-1 bar.

8. The heat treatment method suitable for electron beam welding of Ti2AlNb alloy according to claim 1, characterized in that: The microstructure of the Ti2AlNb alloy weldment includes B2 phase, O phase and α2 phase, and the volume fraction of the B2 phase is 5% to 30%; the O phase and α2 phase include large slats and small slats, the length of the large slats is 1 to 5 μm, and the total volume fraction of the O phase and α2 phase of the large slats is 10% to 35%, the length of the small slats is less than 1 μm, and the total volume fraction of the O phase and α2 phase of the small slats is 35% to 60%.

9. The heat treatment method suitable for electron beam welding of Ti2AlNb alloy according to claim 1, characterized in that: The tensile strength of the Ti2AlNb alloy weldment at 25°C is 1020-1100 MPa, the yield strength is 960-1050 MPa, the elongation is 6%-10%, and the cross-sectional shrinkage is 8%-15%.

10. The heat treatment method suitable for electron beam welding of Ti2AlNb alloy according to claim 1, characterized in that: The tensile strength of the Ti2AlNb alloy weldment at 650°C is 840-900MPa, the yield strength is 700-800MPa, the elongation is 11%-25%, and the cross-sectional shrinkage is 26%-80%.

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