Forging method of Ti-Al intermetallic compound for aero-engine

Abstract

The invention relates to the technical field of non-ferrous metal hot working, and discloses a forging method of a Ti-Al intermetallic compound for an aero-engine, which comprises the following steps: S1, preparing special heat insulation cotton; s2, the blank is heated through a heating process; s3, the blank is taken out of the furnace, wrapped with heat insulation cotton and returned to the furnace for continuous heating; s4, upsetting and drawing forging is conducted, and heat insulation cotton is supplemented; s5, heat insulation cotton on the surface of the blank is removed, and uniform cooling is conducted; s6, surface cracks of the blank are polished while the blank is hot; and S7, heating continues, heat insulation and heat preservation cotton is wrapped, and drawing-out and forming forging are completed. The forging method mainly solves a series of problems of serious cracking, poor process execution degree, low production efficiency, low product yield, poor quality stability and the like in the deformation process from ingot casting to bar forging of a Ti-Al intermetallic compound with poor plasticity for an aero-engine.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal hot working technology, specifically to a forging method for Ti-Al intermetallic compounds used in aero-engines. Background Technology

[0002] Intermetallic compounds are compounds composed of two or more metallic elements in a certain proportion, possessing a long-range ordered crystal structure and basic metallic properties that differ from their constituent elements. Ti and Al have low densities and excellent mechanical properties; therefore, Ti-Al compounds are attracting increasing attention, and their research and applications are becoming more widespread.

[0003] Ti-Al intermetallic compounds such as Ti3Al and Ti2AlNb used in aero-engines are lightweight structural materials that can be used for extended periods at temperatures ranging from 650 to 750°C, with a density of 3.7 to 5.3 g / cm³. 3 Ti-Al intermetallic compounds, with a specific strength of 50-60% that of traditional nickel-based superalloys, possess excellent room-temperature / high-temperature strength, elastic modulus, creep resistance, and oxidation resistance. In contrast, traditional high-temperature titanium alloys such as TC4, TC11, and TA19 have operating temperatures that rarely exceed 600℃. Within the 600-800℃ range, Ti-Al intermetallic compounds exhibit higher specific strength than both titanium alloys and nickel-based superalloys, and the price of its main raw material, sponge titanium, is approximately 50% of that of metallic nickel, the main raw material for nickel-based superalloys. Furthermore, Ti-Al intermetallic compounds also possess good specific stiffness and flame retardancy, making them increasingly widely used in the field of new high thrust-to-weight ratio aero-engines, particularly in engine components operating within the 650-750℃ temperature range. They hold promise as a replacement for nickel-based superalloys, which have complex manufacturing processes and low technological maturity.

[0004] One of the biggest problems with Ti-Al intermetallic compounds is their poor deformability. They are prone to severe brittle fracture during forging, and the cracks continue to extend during grinding, making them difficult to remove completely. In particular, the forging process from ingot blanking to bar upsetting is especially prone to multi-stage continuous cracking, resulting in an overall average yield of only 60-70% for Ti-Al intermetallic compound ingots to bars.

[0005] Forging cracking in Ti-Al intermetallic compounds significantly impacts forging process execution, production efficiency, yield, and product quality. Severe cracking can even lead to product scrap, causing substantial damage and losses. Therefore, the long production cycle, low yield, poor quality stability, and high manufacturing cost of Ti-Al intermetallic compound forging processes limit their further application in aero-engines.

[0006] The main reasons why Ti-Al intermetallic compounds are prone to cracking during forging are: (1) the high alloying of the material itself. The alloy usually contains more than 13% Al, more than 25% Nb, and a small amount of other alloying elements. When the mass fraction of Al exceeds 6%, a hard and brittle intermediate phase α2 (Ti3Al) will be generated; (2) the surface of the billet will inevitably experience temperature drop and oxidation during the forging process; (3) the forging window of this alloy material is narrow, ranging from 100 to 200°C, and the final forging temperature requirement is high, which needs to be greater than 900°C.

[0007] At present, Ti-Al intermetallic compounds are directly forged in air atmosphere, resulting in severe cracking. The main methods to prevent cracking of such alloy materials are: (1) Apply a layer of anti-oxidant to the billet before heating, and minimize the transfer time after exiting the furnace to reduce the surface temperature drop; (2) Use a high-tonnage, high-frequency forging machine with advanced performance to offset the surface temperature drop of the material with deformation heat, and fully preheat the hammer, anvil, manipulator jaws and other tools; (3) Improve the operating level of the high-speed forging machine operators and the coordination skills of the production workers to reduce the forging time and ensure the final forging temperature of the material; (4) Use hard-sleeve forging, that is, weld a stainless steel jacket to fix the insulation material on the surface of the billet and deform it together with the billet; (5) Use a soft sleeve to wrap the billet with ordinary aluminum silicate insulation cotton with glass fiber anti-oxidant evenly sprinkled on it, and continuously replenish it during the forging process to reduce the temperature drop of the billet, etc.

[0008] However, based on on-site production conditions, while measures 1-3 can reduce forging cracks in this Ti-Al intermetallic compound to some extent, the effect is not ideal and fails to fundamentally solve the temperature drop problem. In particular, severe cracking still occurs during ingot blanking and bar reforging processes. The fourth measure, using a hard-sleeve operation, is complex and cannot withstand significant external forces and deformations at high temperatures, making it unsuitable for ingot blanking and upsetting processes. The fifth measure, using ordinary thermal insulation cotton, is prone to falling off during forging, requiring constant replenishment, resulting in high consumption and poor environmental performance. Summary of the Invention

[0009] (a) Technical problems to be solved

[0010] To address the shortcomings of existing technologies, this invention provides a forging method for Ti-Al intermetallic compounds used in aero-engines. This method mainly solves a series of problems associated with Ti-Al intermetallic compounds for aero-engines, which have poor plasticity, such as severe cracking, poor process execution, low production efficiency, low product yield, and poor quality stability during the forging and deformation process from ingots to bars.

[0011] (II) Technical Solution

[0012] To address the severe cracking problem during the forging process of Ti-Al intermetallic compounds, this invention provides a solution through the following technical approach. The main equipment used includes a high-precision electric heating furnace, a 2000-ton high-speed forging mill, loading and unloading trolleys, and various sizes of forging fixtures. The main steps of the technical solution are as follows:

[0013] A forging method for Ti-Al intermetallic compounds used in aero-engines includes the following steps:

[0014] S1. Prepare special heat insulation cotton;

[0015] S2, Heating process for heating billet;

[0016] S3. The billet is removed from the furnace, wrapped with heat-insulating cotton, and returned to the furnace for further heating.

[0017] S4, upsetting and forging, supplemented with heat insulation cotton;

[0018] S5. Remove the heat insulation cotton from the surface of the billet and cool it evenly.

[0019] S6. Polish the surface of the blank while it is still hot to remove cracks;

[0020] S7. Continue heating, wrap with heat-insulating cotton, and complete the elongation and shaping forging.

[0021] Further, in step S1, the side and end areas of the billet are calculated according to the quantity and specifications of the Ti-Al intermetallic compound. Special heat insulation cotton is prepared in advance and placed on the ground in front of the high-precision electric heating furnace door. The Ti-Al intermetallic compound special glass fiber anti-oxidant with a working temperature range of 1000~1200℃ is evenly sprinkled onto the heat insulation cotton.

[0022] Furthermore, in step S2, heating is carried out in a high-precision electric heating furnace with a furnace temperature uniformity of ±5℃ according to the established billet heating process curve, with the β transformation temperature T β The above single-phase heating: ≤500℃ low-temperature loading, T β The following two-phase region is preheated at a suitable temperature of 800~900℃, and then the temperature is increased to T. β The β-transformation temperature T of the Ti-Al intermetallic compound was determined by metallographic method after heating the single-phase region to 1080~1200℃. β Temperature range 1020~1070℃; β transition temperature T β The following two-phase region heating: at T βHeating is carried out at 30~50℃. During preheating and single-phase heating, the heating time t = heating coefficient δ × billet cross-sectional size D, where the heating time t is in min, the heating coefficient δ is in min / mm, and the cross-sectional size D is in mm. The heating coefficient δ is 0.3~0.5 in the two-phase preheating and single-phase heating temperature range, and 0.7~1.0 in the two-phase heating temperature range. Heating is stopped 20~60 min before the furnace exit time.

[0023] Further, step S3 is as follows:

[0024] A1. The high-precision electric heating furnace door is lifted, and the alloy billet is quickly clamped and taken out of the furnace within 30 seconds to reduce the temperature drop on the surface of the billet. After the billet is taken out of the furnace, the alloy billet is quickly transferred to the pre-prepared heat insulation cotton within 15 seconds.

[0025] A2. Within 20 seconds, quickly wrap the special heat insulation cotton around the sides and ends of the alloy billet, remove the overlapping parts of the heat insulation cotton, and the special glass fiber anti-oxidation agent melts at high temperature, which can bond the heat insulation cotton and the alloy billet together to prevent the heat insulation cotton from falling off. Clamp the center of the alloy billet and lift it to the height of the bottom of the heating furnace to wait for it to be returned to the furnace.

[0026] A3. Lift the furnace door, quickly return the wrapped alloy billet to the designated position inside the high-precision electric heating furnace, and make a unique mark. Close and tighten the furnace door. The number of billets loaded into the furnace should not exceed 2 pieces. If more than 2 pieces are loaded, first take out 2 pieces, wrap them with heat insulation cotton, heat the electric heating furnace to the heating temperature, and maintain it for a certain period of time. After the surface temperature of the billet returns to the heating temperature, wrap it with heat insulation cotton according to the operation requirements of steps A1~A2.

[0027] A4. After the Ti-Al intermetallic compound billet is returned to the furnace and heated for another 30-60 minutes, the holding time can be extended within the allowable range of the heating process, depending on the billet size and the cooling during the process of wrapping the insulation cotton, to ensure that the alloy billet is thoroughly heated and the temperature is uniform.

[0028] Further, step S4 is as follows:

[0029] B1. Lift the furnace door of the high-precision electric heating furnace, load the billet onto the loading trolley, quickly transfer it from the furnace to the jaws of the 20-ton manipulator, clamp it, and then feed it to the lower anvil of the 2000-ton fast forging unit. The entire transfer process should be controlled within 45 seconds. During the transfer, prevent the special heat insulation cotton on the surface of the billet from falling off. If localized falling off is found, replenish the heat insulation cotton in time to reduce material temperature loss during the transfer process and ensure the uniformity of the billet temperature.

[0030] B2. Based on the Ti-Al intermetallic compound billet, the forging process is carried out in the 2000-ton fast forging unit for ingot opening, upsetting and drawing forging. The 20-ton manipulator is controlled to stand the billet upright along the streamline direction and perpendicular to the lower anvil. The billet is covered with heat insulation cotton on the top and bottom in time. The 2000-ton fast forging press is pressed down, and the upsetting is controlled in 3 to 4 passes to the specified dimensions. The billet is laid down on the lower anvil. The pressing amount, pressing rate and feed amount are controlled in each pass. The square, chamfer or square and octagonal deformation methods are continued to be used to draw the billet to the specified dimensions.

[0031] B3. For the first pass of forging Ti-Al intermetallic compound billets, since they are wrapped with heat-insulating cotton and do not directly contact the anvil and jaws, special heat-insulating cotton with a thickness of 10~15 mm is prepared in advance during the upsetting and drawing forging process. During the gap between the hammer and anvil being lifted on the 2000-ton high-speed forging machine, it is replenished to the exposed parts of the billet in time.

[0032] B4. For upsetting and drawing of Ti-Al intermetallic compounds, the billet ends cool down quickly, requiring a dedicated person to wrap and cover them with heat-insulating cotton. During the forging process, the final forging temperature of the billet must be measured in a timely manner, and the surface cracking of the billet must be carefully observed. If the final forging temperature is lower than the process requirement or if serious cracking is found, forging must be stopped immediately.

[0033] Further, step S5 is as follows:

[0034] C1. After forging is completed, promptly remove any residual heat insulation cotton from the surface of the Ti-Al intermetallic compound billet.

[0035] C2. The material handling vehicle transfers the billet and gently places it on a special cooling rack to cool it evenly to a material temperature of 200~300℃.

[0036] Further, step S6 is as follows:

[0037] D1. Transfer the Ti-Al intermetallic compound billet to the grinding process and repair surface cracks while it is hot.

[0038] D2. Remove the counterweight from the grinding wheel, first grind the entire surface, then focus on grinding larger cracks. Avoid overheating during grinding. Once the cracks have shrunk, switch to a small hand grinder and gently grind until the tiny cracks are completely removed.

[0039] Further, step S7 is as follows:

[0040] E1. Continue heating according to the established Ti-Al intermetallic compound heating process. Wrap the insulation cotton according to the requirements of steps A1 to A3. For the billet elongation forging, the billet is clamped by a 30-ton manipulator and the feed amount is controlled. On the 2000-ton fast forging machine, the square, chamfer or square and octagonal deformation methods are adopted. The amount and rate of reduction of each pass are reasonably controlled. If exposed parts of the billet are found during the elongation forging process, insulation cotton is added in time.

[0041] E2. Continue heating according to the established heating process. Wrap the insulation cotton according to the requirements of steps A1 to A3. Preheat the tooling that meets the size requirements of the black bar in advance. The 30-ton manipulator clamps the billet and completes the billet rolling process. Take measures to prevent the insulation cotton from falling off during the spinning process. Replenish the insulation cotton at the end of the billet in time. If the billet is long and the exposed part is not rolled in the spinning machine, a longer insulation cotton can be temporarily covered and moved with the alloy billet to further prevent the billet temperature from dropping.

[0042] E3. After forging is completed, promptly remove the heat insulation cotton from the surface of the billet, transfer it, and gently place it on a special cooling rack to cool evenly to room temperature.

[0043] (iii) Beneficial technical effects

[0044] The forging cracking of Ti-Al intermetallic compounds was significantly reduced. The amount of billet grinding loss per firing cycle was reduced from 10-15 kg to 3-5 kg ​​before and after the improvement of the 650 kg ingot, and the overall forging yield was increased by 15-20%.

[0045] Cracking is significantly reduced, process execution is good, no additional forging cycles are required, production costs are lowered, and forging efficiency and product quality stability are improved. Reduced cracking also significantly reduces grinding work, lowers labor intensity, reduces the incidence of accidents, and significantly reduces grinding dust emissions, resulting in significant environmental benefits.

[0046] The process of wrapping the insulation cotton is simple. The antioxidant is evenly sprinkled onto the insulation cotton, and the billet is quickly wrapped around it. The specialized insulation cotton and antioxidant have good ductility and adhesion, making them less prone to falling off. This significantly reduces the amount of material needed during forging, lowers auxiliary material costs, and further reduces harmful substances and harm to on-site operators. Attached Figure Description

[0047] Figure 1 This is a diagram showing the forging cracking of the Ti3Al alloy billet before the improvement.

[0048] Figure 2 This is a diagram showing obvious forging cracks in the improved Ti3Al alloy billet.

[0049] Figure 3This is a diagram showing the uniform and refined equiaxed microstructure of the edge of a Ti3Al alloy forged bar.

[0050] Figure 4 This is a diagram showing the uniformly refined equiaxed microstructure at 0.5R of a Ti3Al alloy forged bar.

[0051] Figure 5 This is a diagram showing the uniform and refined equiaxed microstructure of the core of a Ti3Al alloy forged bar. Detailed Implementation

[0052] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0053] refer to Figures 1 to 5 As shown, in order to enable those skilled in the art to better understand the technical solution of the present invention, a further detailed description is given below in conjunction with the forging of Ti3Al bars.

[0054] Product grade: Ti3Al; Name: Bar; Specifications: Φ200 (0, +10) mm × 1000~2000 mm; Quantity: 2 pieces.

[0055] A forging method for Ti-Al intermetallic compounds used in aero-engines includes the following steps:

[0056] S1. Prepare special heat insulation cotton;

[0057] S2, Heating process for heating billet;

[0058] S3. The billet is removed from the furnace, wrapped with heat-insulating cotton, and returned to the furnace for further heating.

[0059] S4, upsetting and forging, supplemented with heat insulation cotton;

[0060] S5. Remove the heat insulation cotton from the surface of the billet and cool it evenly.

[0061] S6. Polish the surface of the blank while it is still hot to remove cracks;

[0062] S7. Continue heating, wrap with heat-insulating cotton, and complete the elongation and shaping forging.

[0063] In step S1, the side and end areas of the billet are calculated according to the quantity and specifications of the Ti-Al intermetallic compound. Special heat insulation cotton is prepared in advance and placed on the ground in front of the high-precision electric heating furnace door. The Ti-Al intermetallic compound special glass fiber anti-oxidant with a working temperature range of 1000~1200℃ is evenly sprinkled on the heat insulation cotton.

[0064] In step S2, the billet is heated in a high-precision electric heating furnace with a furnace temperature uniformity of ±5℃ according to the established billet heating process curve, and the β transformation temperature T β The above single-phase heating: ≤500℃ low-temperature loading, T β The following two-phase region is preheated at a suitable temperature of 800~900℃, and then the temperature is increased to T. β The β-transformation temperature T of the Ti-Al intermetallic compound was determined by metallographic method after heating the single-phase region to 1080~1200℃. β Temperature range 1020~1070℃; β transition temperature T β The following two-phase region heating: at T β Heating is carried out at 30~50℃. During preheating and single-phase heating, the heating time t = heating coefficient δ × billet cross-sectional size D, where the heating time t is in min, the heating coefficient δ is in min / mm, and the cross-sectional size D is in mm. The heating coefficient δ is 0.3~0.5 in the two-phase preheating and single-phase heating temperature range, and 0.7~1.0 in the two-phase heating temperature range. Heating is stopped 20~60 min before the furnace exit time.

[0065] Step S3 is as follows:

[0066] A1. The high-precision electric heating furnace door is lifted, and the alloy billet is quickly clamped and taken out of the furnace within 30 seconds to reduce the temperature drop on the surface of the billet. After the billet is taken out of the furnace, the alloy billet is quickly transferred to the pre-prepared heat insulation cotton within 15 seconds.

[0067] A2. Within 20 seconds, quickly wrap the special heat insulation cotton around the sides and ends of the alloy billet, remove the overlapping parts of the heat insulation cotton, and the special glass fiber anti-oxidation agent melts at high temperature, which can bond the heat insulation cotton and the alloy billet together to prevent the heat insulation cotton from falling off. Clamp the center of the alloy billet and lift it to the height of the bottom of the heating furnace to wait for it to be returned to the furnace.

[0068] A3. Lift the furnace door, quickly return the wrapped alloy billet to the designated position inside the high-precision electric heating furnace, and make a unique mark. Close and tighten the furnace door. The number of billets loaded into the furnace should not exceed 2 pieces. If more than 2 pieces are loaded, first take out 2 pieces, wrap them with heat insulation cotton, heat the electric heating furnace to the heating temperature, and maintain it for a certain period of time. After the surface temperature of the billet returns to the heating temperature, wrap it with heat insulation cotton according to the operation requirements of steps A1~A2.

[0069] A4. After the Ti-Al intermetallic compound billet is returned to the furnace and heated for another 30-60 minutes, the holding time can be extended within the allowable range of the heating process, depending on the billet size and the cooling during the process of wrapping the insulation cotton, to ensure that the alloy billet is thoroughly heated and the temperature is uniform.

[0070] Step S4 is as follows:

[0071] B1. Lift the furnace door of the high-precision electric heating furnace, load the billet onto the loading trolley, quickly transfer it from the furnace to the jaws of the 20-ton manipulator, clamp it, and then feed it to the lower anvil of the 2000-ton fast forging unit. The entire transfer process should be controlled within 45 seconds. During the transfer, prevent the special heat insulation cotton on the surface of the billet from falling off. If localized falling off is found, replenish the heat insulation cotton in time to reduce material temperature loss during the transfer process and ensure the uniformity of the billet temperature.

[0072] B2. Based on the Ti-Al intermetallic compound billet, the forging process is carried out in the 2000-ton fast forging unit for ingot opening, upsetting and drawing forging. The 20-ton manipulator is controlled to stand the billet upright along the streamline direction and perpendicular to the lower anvil. The billet is covered with heat insulation cotton on the top and bottom in time. The 2000-ton fast forging press is pressed down, and the upsetting is controlled in 3 to 4 passes to the specified dimensions. The billet is laid down on the lower anvil. The pressing amount, pressing rate and feed amount are controlled in each pass. The square, chamfer or square and octagonal deformation methods are continued to be used to draw the billet to the specified dimensions.

[0073] B3. For the first pass of forging Ti-Al intermetallic compound billets, since they are wrapped with heat-insulating cotton and do not directly contact the anvil and jaws, special heat-insulating cotton with a thickness of 10~15 mm is prepared in advance during the upsetting and drawing forging process. During the gap between the hammer and anvil being lifted on the 2000-ton high-speed forging machine, it is replenished to the exposed parts of the billet in time.

[0074] B4. For upsetting and drawing of Ti-Al intermetallic compounds, the billet ends cool down quickly, requiring a dedicated person to wrap and cover them with heat-insulating cotton. During the forging process, the final forging temperature of the billet must be measured in a timely manner, and the surface cracking of the billet must be carefully observed. If the final forging temperature is lower than the process requirement or if serious cracking is found, forging must be stopped immediately.

[0075] Step S5 is as follows:

[0076] C1. After forging is completed, promptly remove any residual heat insulation cotton from the surface of the Ti-Al intermetallic compound billet.

[0077] C2. The material handling vehicle transfers the billet and gently places it on a special cooling rack to cool it evenly to a material temperature of 200~300℃.

[0078] Step S6 is as follows:

[0079] D1. Transfer the Ti-Al intermetallic compound billet to the grinding process and repair surface cracks while it is hot.

[0080] D2. Remove the counterweight from the grinding wheel, first grind the entire surface, then focus on grinding larger cracks. Avoid overheating during grinding. Once the cracks have shrunk, switch to a small hand grinder and gently grind until the tiny cracks are completely removed.

[0081] Step S7 is as follows:

[0082] E1. Continue heating according to the established Ti-Al intermetallic compound heating process. Wrap the insulation cotton according to the requirements of steps A1 to A3. For the billet elongation forging, the billet is clamped by a 30-ton manipulator and the feed amount is controlled. On the 2000-ton fast forging machine, the square, chamfer or square and octagonal deformation methods are adopted. The amount and rate of reduction of each pass are reasonably controlled. If exposed parts of the billet are found during the elongation forging process, insulation cotton is added in time.

[0083] E2. Continue heating according to the established heating process. Wrap the insulation cotton according to the requirements of steps A1 to A3. Preheat the tooling that meets the size requirements of the black bar in advance. The 30-ton manipulator clamps the billet and completes the billet rolling process. Take measures to prevent the insulation cotton from falling off during the spinning process. Replenish the insulation cotton at the end of the billet in time. If the billet is long and the exposed part is not rolled in the spinning machine, a longer insulation cotton can be temporarily covered and moved with the alloy billet to further prevent the billet temperature from dropping.

[0084] E3. After forging is completed, promptly remove the heat insulation cotton from the surface of the billet, transfer it, and gently place it on a special cooling rack to cool evenly to room temperature.

[0085] Example 1

[0086] Raw materials and production equipment: After the ingots, which have undergone three vacuum self-consumable melting processes, are machined, sampled, and tested to ensure they pass inspection, they are then fed into the forging process. The ingots weigh 500-600 kg, with dimensions of Φ350-370 mm × 1000-1200 mm, and a quantity of 2 ingots. The billet dimensions during the upsetting and drawing process are Φ400±10 mm × 800±40 mm. The main equipment used includes a high-precision electric heating furnace, a loading and unloading trolley; a 2000-ton high-speed forging press, a 20-ton manipulator, a 30-ton manipulator, and forging tools with diameters of Φ300-Φ400 mm, Φ230-Φ300 mm, and Φ150-Φ250 mm, etc.

[0087] Step 1: Prepare Ti3Al billet-specific thermal insulation cotton. Based on the specifications of two Ti3Al billets, prepare Ti3Al-specific thermal insulation cotton with high SiO2 content, fine fiber diameter, low impurity content, and a length of 1500 mm × width of 1400 mm × thickness of 15~20 mm, large enough to wrap the entire billet. Place it on the ground near the furnace door of the high-precision electric heating furnace. Evenly sprinkle a Ti3Al-specific anti-oxidant (with an operating temperature of 1000~1200℃) onto the thermal insulation cotton. Also prepare 3~4 pieces of 500×500 mm thermal insulation cotton for later use.

[0088] Step 2: Heating Ti3Al alloy billet according to the established heating process. (1) Ti3Al material is heated in a high-precision electric heating furnace with furnace temperature uniformity of ±5℃ and metering every 6 months according to the established heating process curve. Billet heating ≤500℃ is loaded into the furnace, and the temperature is raised to 850±5℃ with the furnace. After holding for 120 min, the temperature is raised to 1180±5℃ and held for 150 min. Special heat insulation cotton is prepared 60 min in advance. After being taken out of the furnace, the special heat insulation cotton is wrapped. After returning to the furnace, the temperature is held for 30 min. Single phase zone heating: 3 heating cycles in total. ≤500℃ is loaded into the furnace, and the temperature is raised to 850±5℃ with the furnace. After holding for 120 min, the temperature is raised to 1150±5℃, 1130±5℃, and 1080±5℃. The heating temperature is gradually reduced. After holding for 150 min, the billet is taken out of the furnace and wrapped with special heat insulation cotton. After returning to the furnace, the temperature is held for 30 min.

[0089] (2) β-transformation temperature T of Ti3Al material β After four firing cycles, a sample was taken to measure the phase transformation point. The T value was determined according to the metallographic method specified in GB / T 23605. β =1060℃.

[0090] (3) The two-phase region of the Ti3Al alloy material was heated a total of 7 times. Among them, the upsetting and drawing heating was carried out in 4 times: the furnace was loaded at 850±5℃ and the temperature was raised to T with the furnace. β -30℃ = 1030±5℃, hold for 300 min. Prepare special heat insulation cotton 60 min in advance. Wrap the product with special heat insulation cotton after removing it from the furnace. After returning to the furnace and reaching the desired temperature, continue holding for 30 min. The lengthening and heating process involves two heating cycles: T β -40℃ to 1020±5℃, hold for 300 min and 240 min respectively, remove from the oven, wrap with special heat-insulating cotton, return to the oven and hold for another 30 min after reaching the desired temperature. Rounding and heating in one cycle: hold at 1020±5℃ for 190 min, remove from the oven, wrap with special heat-insulating cotton, return to the oven and hold for another 30 min after reaching the desired temperature.

[0091] Step 3: Ti3Al alloy billet is removed from the furnace, wrapped with special heat-insulating cotton, and returned to the furnace for further heating: (1) The furnace door of the high-precision electric heating furnace is lifted, and the Ti3Al alloy billet is quickly clamped and removed from the furnace within 30 seconds to prevent excessive cooling of the billet surface. After the billet is removed from the furnace, under the command of the on-site operator, the Ti3Al alloy billet is quickly transferred to the special heat-insulating cotton that has been evenly sprinkled with a layer of Ti3Al glass fiber anti-oxidant to meet the size requirements of the billet within 15 seconds.

[0092] (2) Within 20 seconds, the operator should quickly wrap the sides and ends of the first Ti3Al alloy billet with special heat-insulating cotton, remove any overlapping parts, and carefully inspect for any exposed areas on the sides and ends of the billet. The special anti-oxidant melts at high temperatures, which can bond the special heat-insulating cotton and the Ti3Al alloy billet together, preventing the heat-insulating cotton from falling off. The second billet should be wrapped with special heat-insulating cotton in the same way. The center of the Ti3Al alloy billet should be clamped and raised to the height of the furnace bottom to await return to the furnace, preventing repeated adjustments to the clamping position from causing the heat-insulating cotton to fall off.

[0093] (3) Lift the furnace door and, under the command of the on-site operator, the loading and unloading worker quickly returns the two Ti3Al alloy billets wrapped with special heat insulation cotton to the designated position inside the furnace, records the loading position, closes and tightens the furnace door.

[0094] (4) Continue heating the Ti3Al alloy billet for 30 minutes after it reaches the specified holding time. Depending on the billet size and the cooling during the cotton wrapping process, extend the holding time by 10 to 30 minutes to ensure that the Ti3Al alloy billet is thoroughly heated and the material temperature is uniform.

[0095] Step 4: Forging Ti3Al alloy billet in multiple upsetting processes, and then covering it with special heat insulation cotton. (1) Lift the furnace door of the high-precision electric heating furnace, load the Ti3Al alloy billet onto the loading cart, quickly transfer it from the furnace to the jaws of the 20-ton manipulator and clamp it. The manipulator continues to feed the Ti3Al alloy billet onto the lower anvil. The entire transfer process is controlled within 45 seconds. During the transfer process, prevent the special heat insulation cotton on the surface of the billet from falling off. If local detachment is found, replenish the heat insulation cotton in time to ensure the uniformity of the billet temperature.

[0096] (2) The forging process was formulated according to the Ti3Al alloy billet, and the ingot blanking, upsetting and drawing forging processes were carried out in a 2000-ton fast forging unit. Under the control of the operator of the 2000-ton fast forging machine, the 20-ton manipulator erected the Ti3Al alloy billet along the streamline direction and perpendicular to the lower flat anvil. The billet was covered with special heat insulation cotton in time. The upper flat anvil of the 2000-ton fast forging machine pressed down, and the pressing rate was controlled at 20~30 mm / s. The billet was upset to a height H=500±10 mm. The billet was laid down on the lower flat anvil, and the pressing amount, pressing rate, and feed amount were controlled at 30~40 mm, 20~30 mm / s, and 100~150 mm per pass. The billet was squared, octagonaled, and rolled to Φ400±10 mm×800±40 mm.

[0097] (3) During the first forging pass, the Ti3Al alloy billet is wrapped with special heat-insulating cotton, which does not directly contact the anvil, jaws, and other tooling, thus significantly reducing the heat loss. During the upsetting and drawing forging process, the on-site personnel prepare special heat-insulating cotton with a thickness of 10-15 mm in advance. During the gap when the anvil is lifted on the 2000-ton high-speed forging machine, special heat-insulating cotton is promptly added to the surface of the Ti3Al alloy billet using a self-made simple clamp that prevents scalding and hand pressure, in order to ensure the billet temperature.

[0098] (4) The Ti3Al alloy billet is upset and drawn forged. The end cools down quickly, so a dedicated person is required to wrap and cover it with heat-insulating cotton. During the forging process, the final forging temperature of the Ti3Al alloy billet must be measured in time, and the surface cracking of the billet must be carefully observed. If the final forging temperature is lower than the process requirement of 900℃ or serious cracking is found, forging must be stopped in time.

[0099] Step 5 Remove the heat insulation cotton from the surface of the Ti3Al billet and cool it evenly. (1) After each forging, use an iron shovel to remove the small amount of special heat insulation cotton that is locally residual on the surface of the Ti3Al alloy billet.

[0100] (2) Use a material handling vehicle to transfer the Ti3Al alloy billet and gently place it on a special cooling rack to cool it evenly to a material temperature of 200~300℃.

[0101] Step 6: Polish the surface cracks of Ti3Al alloy billet while it is hot. (1) Transfer the Ti3Al alloy billet with a material temperature of 200~300℃ to the polishing process and polish the cracks while it is hot.

[0102] (2) Remove the counterweight of the large grinding wheel, first grind the whole body, then focus on grinding the larger cracks. Avoid obvious temperature rise that causes local red color of the billet. After the cracks become smaller, switch to a small hand grinding wheel and gently grind until the small cracks are completely removed. If necessary, perform a color penetration test on the cracks.

[0103] Step 7: Continue heating to complete the elongation forging of the Ti3Al alloy billet. (1) The Ti3Al alloy billet is heated in T βHeating was performed at -40℃ = 1020±5℃, and the temperature was maintained for 300 min and 240 min respectively. After being taken out of the furnace, the special heat insulation cotton was wrapped around the material. After being returned to the furnace and heated to the desired temperature, the material was kept at the desired temperature for another 30 min. The process of wrapping the heat insulation cotton was carried out in accordance with the requirements of step three (1)~(3). Ti3Al alloy billet was drawn and forged. The billet was held by a 30-ton manipulator and the feed amount was controlled at 150~200mm. Φ300mm~Φ400mm and Φ230mm~Φ300mm slings were used to roll and draw the billet to Φ320±10mm and Φ260±10mm. The 2000-ton fast forging press controlled the reduction amount of 20~30mm and the reduction rate of 15~20mm / s per pass. The heat insulation cotton was replenished in time during the drawing and forging process. Cooling was carried out in accordance with step five (1)~(2), and hot grinding was carried out in accordance with step six (1)~(2).

[0104] Continue heating to complete the rounding and forging of the Ti3Al alloy billet. (2) The Ti3Al alloy billet is heated at T β Heating is performed at -40℃ = 1020±5℃, and the temperature is maintained for 190 min. The billet is removed from the furnace according to the requirements of step three (1)~(3), wrapped with special heat insulation cotton, and then returned to the furnace to the required temperature and kept warm for another 30 min. Prepare Φ150 mm~Φ250 mm shovels in advance. The 30-ton manipulator clamps the billet and rolls it into a bar to Φ220±5 mm. During the process of entering the shovel, measures are taken to prevent the heat insulation cotton from falling off. The end of the bar is promptly covered with heat insulation cotton. The Ti3Al alloy billet is relatively long. The exposed parts that are not rolled in the shovel can be temporarily covered with a longer heat insulation cotton and moved with the alloy billet to further prevent the billet temperature from dropping.

[0105] (3) After forging is completed, use an iron shovel to remove the small amount of special heat insulation cotton remaining on the surface of Ti3Al material in time, transfer it and gently place it on the cooling rack to cool it evenly to room temperature.

[0106] Ti3Al alloy bars are machined and peeled on a lathe. The finished product has dimensions of Φ200 (0, +10) mm, length × 2000 mm, and roughness Ra≤3.2μm.

[0107] Final inspection of Ti3Al alloy bars. Surface quality, microstructure, and ultrasonic testing were performed on the Ti3Al alloy bars in accordance with the requirements of GB / T 32185, GB / T 5168, and GB / T 5193.

[0108] The improved Ti3Al alloy achieved a yield of 80-85% from ingot casting to black-skinned bar forging, an overall average increase of 15-20% compared to the previous method. The Ti3Al alloy bars exhibited no surface defects such as peeling, wrinkles, or cracks, and possessed a refined and uniform microstructure. Ultrasonic testing of a 2000 mm long bar showed an overall Ф2.0| -18dBThe inspection results of the Ti3Al alloy Φ200 mm bars all met the quality control requirements.

[0109] The surface is peeled off to the specified dimensions on a lathe, the surface roughness Ra meets the process requirements, and surface defects are removed.

[0110] Final inspection of Ti-Al intermetallic compound rods involves surface quality, microstructure, and ultrasonic testing as required.

[0111] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A forging method for Ti-Al intermetallic compounds used in aero-engines, characterized in that, Includes the following steps: S1. Prepare special heat insulation cotton; S2, Heating process for heating billet; S3. The billet is removed from the furnace, wrapped with heat-insulating cotton, and returned to the furnace for further heating. S4, upsetting and forging, supplemented with heat insulation cotton; S5. Remove the heat insulation cotton from the surface of the billet and cool it evenly. S6. Polish the surface of the blank while it is still hot to remove cracks; S7. Continue heating, wrap with heat-insulating cotton, and complete the elongation and shaping forging.

2. The forging method of a Ti-Al intermetallic compound for aero-engines according to claim 1, characterized in that, In step S1, the side and end areas of the billet are calculated according to the quantity and specifications of the Ti-Al intermetallic compound. Special heat insulation cotton is prepared in advance and placed on the ground in front of the high-precision electric heating furnace door. The Ti-Al intermetallic compound special glass fiber anti-oxidant with a working temperature range of 1000~1200℃ is evenly sprinkled on the heat insulation cotton.

3. The forging method of a Ti-Al intermetallic compound for aero-engines according to claim 1, characterized in that, In step S2, the billet is heated in a high-precision electric heating furnace with a furnace temperature uniformity of ±5℃ according to the established billet heating process curve, and the β transformation temperature T β The above single-phase heating: ≤500℃ low-temperature loading, T β The following two-phase region is preheated at a suitable temperature of 800~900℃, and then the temperature is increased to T. β The β-transformation temperature T of the Ti-Al intermetallic compound was determined by metallographic method after heating the single-phase region to 1080~1200℃. β Temperature range 1020~1070℃; β transition temperature T β The following two-phase region heating: at T β Heating at 30~50℃; during preheating and single-phase heating, the heating time t = heating coefficient δ × billet cross-sectional dimension D, where the heating time t is in min, the heating coefficient δ is in min / mm, and the cross-sectional dimension D is in mm; The heating coefficient δ is set at 0.3~0.5 in the two-phase preheating and single-phase heating temperature range, and at 0.7~1.0 in the two-phase heating temperature range. Heating is stopped 20~60 minutes before the furnace tapping time.

4. The forging method of a Ti-Al intermetallic compound for aero-engines according to claim 1, characterized in that, Step S3 is as follows: A1. The high-precision electric heating furnace door is lifted, and the alloy billet is quickly clamped and taken out of the furnace within 30 seconds to reduce the temperature drop on the surface of the billet. After the billet is taken out of the furnace, the alloy billet is quickly transferred to the pre-prepared heat insulation cotton within 15 seconds. A2. Within 20 seconds, quickly wrap the special heat insulation cotton around the sides and ends of the alloy billet, remove the overlapping parts of the heat insulation cotton, and the special glass fiber anti-oxidation agent melts at high temperature, which can bond the heat insulation cotton and the alloy billet together to prevent the heat insulation cotton from falling off. Clamp the center of the alloy billet and lift it to the height of the bottom of the heating furnace to wait for it to be returned to the furnace. A3. Lift the furnace door, quickly return the wrapped alloy billet to the designated position inside the high-precision electric heating furnace, and make a unique mark. Close and tighten the furnace door. The number of billets loaded into the furnace should not exceed 2 pieces. If more than 2 pieces are loaded, first take out 2 pieces, wrap them with heat insulation cotton, heat the electric heating furnace to the heating temperature, and maintain it for a certain period of time. After the surface temperature of the billet returns to the heating temperature, wrap it with heat insulation cotton according to the operation requirements of steps A1~A2. A4. After the Ti-Al intermetallic compound billet is returned to the furnace and heated for another 30-60 minutes, the holding time can be extended within the allowable range of the heating process, depending on the billet size and the cooling during the process of wrapping the insulation cotton, to ensure that the alloy billet is thoroughly heated and the temperature is uniform.

5. A forging method for a Ti-Al intermetallic compound for aero-engines according to claim 1, characterized in that, Step S4 is as follows: B1. Lift the furnace door of the high-precision electric heating furnace, load the billet onto the loading trolley, quickly transfer it from the furnace to the jaws of the 20-ton manipulator, clamp it, and then feed it to the lower anvil of the 2000-ton fast forging unit. The entire transfer process should be controlled within 45 seconds. During the transfer, prevent the special heat insulation cotton on the surface of the billet from falling off. If localized falling off is found, replenish the heat insulation cotton in time to reduce material temperature loss during the transfer process and ensure the uniformity of the billet temperature. B2. Based on the Ti-Al intermetallic compound billet, the forging process is carried out in the 2000-ton fast forging unit for ingot opening, upsetting and drawing forging. The 20-ton manipulator is controlled to stand the billet upright along the streamline direction and perpendicular to the lower anvil. The billet is covered with heat insulation cotton on the top and bottom in time. The 2000-ton fast forging press is pressed down, and the upsetting is controlled in 3 to 4 passes to the specified dimensions. The billet is laid down on the lower anvil. The pressing amount, pressing rate and feed amount are controlled in each pass. The square, chamfer or square and octagonal deformation methods are continued to be used to draw the billet to the specified dimensions. B3. For the first pass of forging Ti-Al intermetallic compound billets, since they are wrapped with heat-insulating cotton and do not directly contact the anvil and jaws, special heat-insulating cotton with a thickness of 10~15 mm is prepared in advance during the upsetting and drawing forging process. During the gap between the hammer and anvil being lifted on the 2000-ton high-speed forging machine, it is replenished to the exposed parts of the billet in time. B4. For upsetting and drawing of Ti-Al intermetallic compounds, the billet ends cool down quickly, requiring a dedicated person to wrap and cover them with heat-insulating cotton. During the forging process, the final forging temperature of the billet must be measured in a timely manner, and the surface cracking of the billet must be carefully observed. If the final forging temperature is lower than the process requirement or if serious cracking is found, forging must be stopped immediately.

6. The forging method of a Ti-Al intermetallic compound for aero-engines according to claim 1, characterized in that, Step S5 is as follows: C1. After forging is completed, promptly remove any residual heat insulation cotton from the surface of the Ti-Al intermetallic compound billet. C2. The material handling vehicle transfers the billet and gently places it on a special cooling rack to cool it evenly to a material temperature of 200~300℃.

7. The forging method of a Ti-Al intermetallic compound for aero-engines according to claim 1, characterized in that, Step S6 is as follows: D1. Transfer the Ti-Al intermetallic compound billet to the grinding process and repair surface cracks while it is hot. D2. Remove the counterweight from the grinding wheel, first grind the entire surface, then focus on grinding larger cracks. Avoid overheating during grinding. Once the cracks have shrunk, switch to a small hand grinder and gently grind until the tiny cracks are completely removed.

8. The forging method of a Ti-Al intermetallic compound for aero-engines according to claim 1, characterized in that, Step S7 is as follows: E1. Continue heating according to the established Ti-Al intermetallic compound heating process. Wrap the insulation cotton according to the requirements of steps A1 to A3. For the billet elongation forging, the billet is clamped by a 30-ton manipulator and the feed amount is controlled. On the 2000-ton fast forging machine, the square, chamfer or square and octagonal deformation methods are adopted. The amount and rate of reduction of each pass are reasonably controlled. If exposed parts of the billet are found during the elongation forging process, insulation cotton is added in time. E2. Continue heating according to the established heating process. Wrap the insulation cotton according to the requirements of steps A1 to A3. Preheat the tooling that meets the size requirements of the black bar in advance. The 30-ton manipulator clamps the billet and completes the billet rolling process. Take measures to prevent the insulation cotton from falling off during the spinning process. Replenish the insulation cotton at the end of the billet in time. If the billet is long and the exposed part is not rolled in the spinning machine, a longer insulation cotton can be temporarily covered and moved with the alloy billet to further prevent the billet temperature from dropping. E3. After forging is completed, promptly remove the heat insulation cotton from the surface of the billet, transfer it, and gently place it on a special cooling rack to cool evenly to room temperature.

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