Forging method for improving structure performance of TB18 titanium alloy

Abstract

The invention provides a forging method for improving the structure property of TB18 titanium alloy so as to improve the mechanical property of a forge piece. The forging method for improving the structure performance of the TB18 titanium alloy comprises the steps that a bar blank is heated to 830-880 DEG C and then subjected to heat preservation, the heat preservation time is T1, T1 is equal to B, B is the minimum section size of the bar blank, then the bar blank is subjected to primary forging forming and then subjected to air cooling to the room temperature, a forging stock is obtained, and the deformation amount of each heating number of primary forging ranges from 40% to 70%; the forging stock is heated to 740-770 DEG C and then subjected to heat preservation, the heat preservation time is T2, T2 is equal to (0.5-0.7) C, C is the minimum section size of the forging stock, then the forging stock is subjected to finish forging forming and then air cooling to the room temperature, a forge piece is obtained, and the deformation of each heating number of finish forging ranges from 10% to 50%; the forging is subjected to heat treatment, the forging is heated to 730-790 DEG C and then subjected to heat preservation for 0.5-1 h, then the forging is heated to 830-880 DEG C and then subjected to heat preservation for 1-4 h, then the forging is air-cooled to 520 DEG C and then subjected to heat preservation for 6-10 h, and finally the forging is air-cooled to the room temperature.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy forging, in particular to a forging method for improving the microstructure and properties of a TB18 titanium alloy. Background Art

[0002] The advanced performance design of aviation equipment has put forward new demands on high-strength and toughness titanium alloys, requiring alloy strength to be greater than or equal to 1280MPa, and fracture toughness to be no less than 65MPa·m1 / 2 and other good comprehensive mechanical properties.

[0003] The Chinese patent application publication number CN116689674A discloses a forming method of a variable-section die forging of an ultra-high-strength and tough TB18 titanium alloy, comprising: S1, using differential scanning calorimetry to test the ω phase precipitation temperature point T of the TB18 titanium alloy. ω and β phase transition point T β ; S2, heat the bar in the furnace to (T β -30)~(T β -15)℃, then keep warm, and then use the free forging method to make a blank, and after the blank is made, cool the blank to room temperature; the deformation of a single pass is controlled at 30% to 50%; S3, heat the blank in the furnace to (T β -30)~(T β -15)℃ and then keep warm, then move the blank out of the furnace and complete the heat wrapping in the first time, and then return to the furnace for insulation; S4, transfer the blank wrapped in step S2 to the die forging machine for die forging in the second time; wherein, the pressing rate is 5.5-7mm / s, and the die forging deformation is distributed as 30% to 60%. This method can make the tensile strength of the forging reach about 1330MPa and the yield strength reach about 1190Mpa, which meets the basic performance requirements of aviation equipment, but in some special occasions, the forging is required to have higher tensile strength and yield strength, and also have good fracture toughness indicators. Therefore, it is necessary to further improve the existing method to make the mechanical properties of the forging better. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a forging method for improving the microstructure and properties of TB18 titanium alloy, so as to improve the mechanical properties of forgings.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a forging method for improving the microstructure and properties of TB18 titanium alloy, comprising the following steps:

[0006] The rod blank is heated to a surface temperature of 830-880°C and then kept warm for a holding time of T1, T1=B, B being the minimum cross-sectional dimension of the rod blank, and then the rod blank is initially forged and air-cooled to room temperature to obtain a forged blank, wherein the deformation amount of each initial forging is 40%-70%;

[0007] The forging blank is heated to a surface temperature of 740-770°C and then kept warm for a holding time of T2, where T2=(0.5-0.7)°C, and C is the minimum cross-sectional dimension of the forging blank. The forging blank is then final forged and air-cooled to room temperature to obtain a forging, wherein the deformation amount of each final forging is 10%-50%;

[0008] The forging is heat treated by first heating the forging to a surface temperature of 730-790°C and then keeping it warm for 0.5-1h, then heating it to 830-880°C and keeping it warm for 1-4 hours to perform a solid solution treatment on the forging, then air cooling the forging to 520°C and keeping it warm for 6-10 hours to perform an aging treatment on the forging, and finally air cooling the forging to room temperature.

[0009] Preferably, the initial forging process is performed 1 to 3 times, and the final forging process is performed 1 to 3 times.

[0010] Preferably, the room temperature is 10-35°C.

[0011] Preferably, the deformation temperature of the bar blank during initial forging is ≥750°C, and the deformation temperature of the forging blank during final forging is ≥650°C.

[0012] Preferably, in the step of heat treating the forging, the temperature is raised to 830-880° C. at the center of the forging and then kept at that temperature for 1-4 hours to perform a solid solution treatment on the forging.

[0013] Preferably, during the aging treatment, the temperature control accuracy of the aging treatment device is within the range of ±5°C.

[0014] The beneficial effects of the present invention are as follows: the forging method of the present invention first performs preliminary forging on the rod blank, the forging temperature of the rod blank is 830-880°C and is kept at T1, T1=B, B is the minimum cross-sectional size of the rod blank, so that the grain boundaries of the rod blank structure can be completely melted, and then the rod blank structure is subjected to large deformation with a deformation amount of 40%-70% per fire, so that the grains of the rod blank structure can be refined, and then the temperature and deformation amount of the forging blank are strictly controlled through final forging to obtain a forging, and finally the forging is heat treated, so that the mechanical properties of the final product (forging) are greatly improved and meet the new performance requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a flow chart of the present invention;

[0016] Figure 2 This is a macrostructure diagram of a forging sample of Example 1;

[0017] Figure 3 This is a macrostructure diagram of a forging sample of Example 2;

[0018] Figure 4 This is a macrostructure diagram of a forging sample of Example 3;

[0019] Figure 5 is a microstructure diagram of a forging sample of Example 1;

[0020] Figure 6 is a microstructure diagram of a forging sample of Example 2;

[0021] Figure 7 This is the microstructure diagram of the forging sample of Example 3. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0023] The forging method for improving the microstructure and properties of TB18 titanium alloy of the present invention comprises the following steps:

[0024] Step 1, heating the bar blank to a surface temperature of 830-880°C and then keeping the temperature for a holding time of T1 (min), T1=B, B is the minimum cross-sectional size (mm) of the bar blank, and then air-cooling the bar blank to room temperature to obtain a forged blank, wherein the deformation amount of each initial forging is 40%-70%;

[0025] Step 2, heating the forging blank to a surface temperature of 740-770°C and then keeping the temperature for a holding time of T2 (min), T2=(0.5-0.7)°C, C is the minimum cross-sectional dimension (mm) of the forging blank, and then performing final forging and air cooling to room temperature to obtain a forging, wherein the deformation amount of each final forging is 10%-50%;

[0026] Step 3, heat-treating the forging, first heating the forging to a surface temperature of 730-790°C and then keeping it warm for 0.5-1h, then heating it to 830-880°C and keeping it warm for 1-4 hours to perform solid solution treatment on the forging, then air-cooling the forging to a surface temperature of 520°C and keeping it warm for 6-10 hours to perform aging treatment on the forging, and finally air-cooling the forging to room temperature.

[0027] In the present invention, the room temperature is 10-35°C.

[0028] In order to ensure the quality of forgings, preferably, the deformation temperature of the bar billet during initial forging is ≥750°C, and the deformation temperature of the forging billet during final forging is ≥650°C.

[0029] Wherein, in the step of heat treating the forging, the temperature is raised to 830-880°C and then kept at this temperature for 1-4 hours to perform solid solution treatment on the forging, and the temperature can be based on the surface temperature of the forging or the center temperature of the forging. In the present invention, optimally, the solid solution treatment temperature is based on the center temperature of the forging, that is, the temperature is raised to 830-880°C and then kept at this temperature for 1-4 hours to perform solid solution treatment on the forging. The center temperature of the forging can be specifically measured by a thermocouple.

[0030] The forging method of the present invention first performs preliminary forging on the rod blank, the forging temperature of the rod blank is 830-880°C and is kept at T1, T1=B, B is the minimum cross-sectional size of the rod blank, so that the grain boundary of the rod blank structure can be completely melted, and then a large deformation (the deformation amount of each fire is 40%-70%) can be performed to refine the grains of the rod blank structure, and then the temperature and deformation amount of the forging blank are strictly controlled through final forging to obtain a forging, and finally the forging is heat treated, so that the mechanical properties of the final product (forging) are greatly improved and meet the new performance requirements.

[0031] In the embodiment of the present invention, both the forging and the forging blank are formed by free forging. The forging can be of various shapes. In the implementation of the present invention, the forging is square.

[0032] The number of initial forging and final forging is generally 1 to 3 times. In the present invention, the optimal number of initial forging is two times.

[0033] Solution treatment and aging treatment are generally carried out in a heating furnace. In order to ensure the aging treatment effect and the uniform temperature of the forgings, the temperature control accuracy of the aging treatment device (heating furnace) is within the range of ±5°C during aging treatment.

[0034] Embodiment 1:

[0035] The forging is square, the size of the forging is 920×670×230mm, the bar blank is TB18 titanium alloy bar with a diameter of Φ400mm, and the forging method is as follows:

[0036] Step 1, heating the bar blank to a surface temperature of 830°C and then keeping the temperature for 400 minutes, then performing initial forging to form the bar blank and air cooling to obtain a forged blank, wherein the deformation amount of each initial forging is 40%, the initial forging number of fires is two, and the initial forging adopts free forging;

[0037] Step 2, heating the forging blank to a surface temperature of 740°C and then keeping the temperature for a holding time of T2, T2=(0.5-0.7)°C, C being the minimum cross-sectional dimension of the forging blank, and then performing final forging and air cooling on the forging blank to obtain a forging, wherein the deformation amount of each final forging is 10%;

[0038] Step 3: heat-treat the forgings, first heat the forgings to a surface temperature of 730°C and then keep it warm for 0.5h, then heat it to a center temperature of 830°C and keep it warm for 1 hour to perform solid solution treatment on the forgings, then air-cool the forgings to a surface temperature of 520°C and then keep it warm for 6 hours to perform aging treatment on the forgings, and finally air-cool the forgings.

[0039] Embodiment 2:

[0040] The forging is square, the size of the forging is 920×670×230mm, the bar blank is TB18 titanium alloy bar with a diameter of Φ400mm, and the forging method is as follows:

[0041] Step 1, heating the bar blank to a surface temperature of 850°C and then keeping the temperature for 400 minutes, then performing initial forging to form the bar blank and air cooling to obtain a forged blank, wherein the deformation amount of each initial forging is 55%, the initial forging number of fires is two, and the initial forging adopts free forging;

[0042] Step 2, heating the forging blank to a surface temperature of 760°C and then keeping the temperature for a holding time of T2, T2=(0.5-0.7)°C, C being the minimum cross-sectional dimension of the forging blank, and then performing final forging and air cooling on the forging blank to obtain a forging, wherein the deformation amount of each final forging is 30%;

[0043] Step 3: heat-treat the forgings by first heating the forgings to a surface temperature of 760°C and then keeping it warm for 0.8h, then heating the forgings to a center temperature of 850°C and then keeping it warm for 2 hours to perform a solid solution treatment on the forgings, then air-cooling the forgings to a surface temperature of 520°C and then keeping it warm for 8 hours to perform an aging treatment on the forgings, and finally air-cooling the forgings.

[0044] Embodiment 3:

[0045] The forging is square, the size of the forging is 920×670×230mm, the bar blank is TB18 titanium alloy bar with a diameter of Φ400mm, and the forging method is as follows:

[0046] Step 1, heating the bar billet to a surface temperature of 880°C and then keeping the temperature for 400 minutes, then performing initial forging to form the bar billet and air cooling to obtain a forged billet, wherein the deformation amount of each initial forging is 70%, the initial forging number of fires is two, and the initial forging adopts free forging;

[0047] Step 2, heating the forging blank to a surface temperature of 770°C and then keeping the temperature for a holding time of T2, T2=(0.5-0.7)°C, C being the minimum cross-sectional dimension of the forging blank, and then performing final forging and air cooling on the forging blank to obtain a forging, wherein the deformation amount of each final forging is 50%;

[0048] Step 3: heat-treat the forgings by first heating the forgings to a surface temperature of 790°C and then keeping it warm for 1 hour, then heating the forgings to a center temperature of 880°C and then keeping it warm for 4 hours to perform a solid solution treatment on the forgings, then air-cooling the forgings to a surface temperature of 520°C and then keeping it warm for 6 hours to perform an aging treatment on the forgings, and finally air-cooling the forgings.

[0049] Comparative Example 1:

[0050] The forging is square, and the size of the forging is 920×670×230 mm. The rod blank is a TB18 titanium alloy rod with a diameter of 400 mm. The forging forming method adopts the forming method disclosed in CN116689674A.

[0051] The final forgings obtained in the embodiment and the comparative example were sampled and tested. The sampling points were the same and all were sampled in the middle of the thickness direction of the forging. Figures 2 to 4 And microstructure see Figures 5 to 7 The specific sampling test results are shown in Table 1.

[0052] Table 1: Mechanical properties test results of forgings

[0053] Example tensile strength Yield Strength Elongation Area reduction Shock Fracture toughness Example 1 1380 1285 6 13 26 70 Example 2 1367 1275 7.5 14 28 73 Example 3 1357 1280 7 15 29 73 Comparative Example 1 1320 1230 8 15 29 80 Standard value ≥1280 ≥1180 ≥5 ≥10 ≥25 ≥65

[0054] It can be seen from Table 1 that the mechanical properties of the forging blank: tensile strength, yield strength and fracture toughness are all greater than the standard requirements, and the tensile strength and yield strength of the forging have been significantly improved compared with the existing forging forming method, and the fracture toughness of the forging is also greater than the standard value. The forging has good fracture toughness indicators.

Claims

1. A forging method for improving the microstructure and properties of TB18 titanium alloy, characterized in that: The following steps are involved: The rod blank is heated to a surface temperature of 830-880°C and then kept warm for a holding time of T1, T1=B, B being the minimum cross-sectional dimension of the rod blank, and then the rod blank is initially forged and air-cooled to room temperature to obtain a forged blank, wherein the deformation amount of each initial forging is 40%-70%; The forging blank is heated to a surface temperature of 740-770°C and then kept warm for a holding time of T2, where T2=(0.5-0.7)°C, and C is the minimum cross-sectional dimension of the forging blank. The forging blank is then final forged and air-cooled to room temperature to obtain a forging, wherein the deformation amount of each final forging is 10%-50%; The forging is heat treated by first heating the forging to a surface temperature of 730-790°C and then keeping it warm for 0.5-1h, then heating it to 830-880°C and keeping it warm for 1-4 hours to perform a solid solution treatment on the forging, then air cooling the forging to a surface temperature of 520°C and then keeping it warm for 6-10 hours to perform an aging treatment on the forging, and finally air cooling the forging to room temperature.

2. The forging method for improving the microstructure and properties of TB18 titanium alloy according to claim 1, characterized in that: The first forging heat is 1 to 3 times, and the final forging heat is 1 to 3 times.

3. The forging method for improving the microstructure and properties of TB18 titanium alloy according to claim 1, characterized in that: The room temperature is 10-35°C.

4. The forging method for improving the microstructure and properties of TB18 titanium alloy according to claim 1, characterized in that: The deformation temperature of the rod blank during initial forging is ≥750°C, and the deformation temperature of the forging blank during final forging is ≥650°C.

5. The forging method for improving the microstructure and properties of TB18 titanium alloy according to claim 1, characterized in that: In the step of heat treating the forging, the temperature is raised to 830-880° C. at the center of the forging and then kept at that temperature for 1-4 hours to perform a solid solution treatment on the forging.

6. The forging method for improving the microstructure and properties of TB18 titanium alloy according to claim 1, characterized in that: During the aging treatment, the temperature control accuracy of the aging treatment device is within the range of ±5°C.

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