A manufacturing method of large-size marine TC4ELI titanium alloy ring piece

Abstract

The application provides a manufacturing method of large-size marine TC4ELI titanium alloy ring pieces, which comprises the following steps: (1) sawing to the required size according to the requirement, and grinding the surface defects and sharp edges of the ingot; (2) coating the surface of the ingot with high-temperature antioxidant and heating to the process temperature for uniform heat preservation, and adopting the fast forging machine to perform two upsetting and two drawing, and the total deformation is controlled to be between 85% and 90%; (3) heating the blank to T β The temperature is kept at 70-100 DEG C, the three-upsetting and three-drawing is completed, and the single deformation is 40-50%; (4) heating the blank to T β The temperature is kept at 20-30 DEG C, the four-upsetting and four-drawing is completed, the upsetting and drawing are adopted in the deformation process, and the single deformation is not less than 40%; (5) the blank is upset and shaped and punched; (6) the blank is prepared by adopting the mandrel expanding, and the expanding size inner diameter is controlled to be 40-60% of the outer diameter; (7) the ring is formed by adopting the ring rolling machine; and (8) the annealing heat treatment is performed by adopting the electric heating furnace, the annealing temperature is 700-800 DEG C, and the heat preservation time is 1.5-2.5 h.

Description

Technical Field

[0001] This invention relates to a method for manufacturing titanium alloy forgings, and particularly to a forging method for marine TC4ELI titanium alloy ring forgings. Background Technology

[0002] Ships are the most important equipment of the navy, serving as platforms for maritime transport and combat. The materials used in shipbuilding must be resistant to corrosion from seawater and the marine atmosphere, possess high specific strength, good ductility and toughness, and adaptability to processing techniques. Ships have complex overall structures, employing a wide variety of materials in various specifications and with significant weight. TC4ELI titanium alloy has low density, light weight, high specific strength, and resistance to seawater and marine atmospheric corrosion, exhibiting excellent mechanical properties. Large-size ring forgings have large machining allowances, resulting in large ring blank sizes and a tendency for uneven microstructure during forging. Furthermore, due to the low [O] content of TC4ELI titanium alloy, the microstructure of the forged product must be a uniform equiaxed α+β two-phase structure; otherwise, the mechanical properties of the product will be unstable or even fail to meet the requirements for marine structural components. Therefore, it is necessary to invent a forging method for large-size marine TC4ELI titanium alloy rings to ensure that the forgings have a uniform equiaxed structure and good mechanical properties, while simultaneously improving the industry's technical level for marine TC4ELI titanium alloy forgings. Summary of the Invention

[0003] The main technical problem solved by this invention is to address the issues of uneven microstructure and low mechanical properties in large-size marine TC4ELI titanium alloy rings. This invention provides a forging method for large-size marine TC4ELI titanium alloy rings, achieving high-performance TC4ELI titanium alloy ring forging and forming. The method includes the following steps: Step 1: According to the material requirements of the titanium alloy ring, determine the length to be sawn from the TC4ELI titanium alloy ingot, mark the sawing dimensions and positions, and cut the ingot into blanks. Also, grind the surface of the ingot to remove defects such as cracks, shrinkage cavities and sharp edges. The purpose of this step is to reduce the tendency of cracking during the forging process of the ingot.

[0004] Step 2: Uniformly coat the surface of the TC4ELI titanium alloy ingot treated in Step 1 with a high-temperature antioxidant to prevent oxygen absorption and surface contamination. Heat the TC4ELI titanium alloy ingot coated with the high-temperature antioxidant in a furnace to a preheating temperature of 750℃~820℃ and hold for 2~2.5 hours to eliminate temperature stress caused by low-temperature heating. Then heat to 1140~1150℃ and hold for a time equal to the minimum size of the TC4ELI titanium alloy ingot (in mm) multiplied by a holding coefficient of 0.45~0.6 min / mm to ensure uniform heat penetration. Then, use a high-speed forging machine to complete two upsetting and drawing processes to obtain the TC4ELI titanium alloy billet. The total deformation of the two upsetting and drawing processes should be controlled between 85% and 90%. During forging, the initial forging temperature should not be less than 1000℃, and the final forging temperature should not be less than 800℃.

[0005] Step 3: Heat the TC4ELI titanium alloy billet obtained in Step 2 to a preheating temperature of 750℃~820℃ and hold for 2~2.5h. Then heat it to 1040℃~1050℃. The holding time is the minimum size of the C4ELI titanium alloy billet (in mm) multiplied by the holding coefficient, which is 0.4~0.6min / mm. This ensures that the billet is heated evenly and thoroughly. Then, use a high-speed forging machine to complete three reverse upsetting and drawing processes to avoid the formation of Widmanstätten structure. The deformation amount of each upsetting and drawing process is 40%~50%. The initial forging temperature during forging is not lower than 950℃ and the final forging temperature is not lower than 800℃.

[0006] Step 4: Heat the TC4ELI titanium alloy billet obtained in Step 3 to a preheating temperature of 750℃~820℃, hold for 2h~2.5h, then heat to 20℃~30℃ below the phase transformation temperature, hold at 940℃~950℃, and the holding time is the minimum size of the TC4ELI titanium alloy billet (in mm) multiplied by the holding coefficient, which is 0.3~0.5min / mm. Ensure that the TC4ELI titanium alloy billet is uniformly and thoroughly heated, and then use rapid forging. The machine completes four upsetting and drawing processes. The first three upsetting and drawing processes are carried out by reversing the direction of upsetting and drawing. The fourth upsetting and drawing process is carried out by axial upsetting and drawing to eliminate the deformation dead zone. The deformation amount of each upsetting and drawing process is not less than 40%. After completing two upsetting and two drawing processes during the forging process, the machine is returned to the furnace for reheating. After reaching the temperature, the holding time is 2h to 2.5h. After reheating, the remaining two upsetting and drawing deformation processes are completed. The initial forging temperature is not lower than 800℃ and the final forging temperature is not lower than 700℃. The resulting microstructure is an equiaxed α phase + transformed β phase microstructure.

[0007] Step 5: Heat the TC4ELI titanium alloy billet obtained in Step 4 according to the heating method in Step 4 (heat to a preheating temperature of 750℃~820℃, hold for 2h~2.5h, then heat to 20℃~30℃ below the phase transformation temperature, hold at 940℃~950℃, and hold for a time equal to the minimum size of the TC4ELI titanium alloy billet (in mm) multiplied by the holding coefficient, which is 0.3~0.5min / mm) and hold at that temperature. Then perform upsetting and punching to obtain a punched billet with a punched inner diameter d=(0.2~0.35)×D, where D is the outer diameter of the billet.

[0008] Step 6: Heat the punched billet obtained in Step 5 to the heating temperature described in Step 4 and hold it at that temperature (heat to a preheating temperature of 750℃~820℃, hold for 2h~2.5h, then heat to 20℃~30℃ below the phase transformation temperature, hold at 940℃~950℃, and hold for a time equal to the minimum size of the TC4ELI titanium alloy billet (in mm) multiplied by the holding coefficient, which is 0.3~0.5min / mm). Use a frame to expand the hole to obtain an expanded billet. The inner diameter of the expanded hole should be controlled at 40%~60% of the outer diameter. The final forging temperature should not be lower than 700℃. Recycle the billet 1~2 times, and hold it in the furnace for 1.5h~2h.

[0009] Step 7: Heat the expanded blank obtained in Step 6 to the heating temperature described in Step 4 (preheating temperature 750℃~820℃, holding for 2h~2.5h, then heating to 20℃~30℃ below the phase transformation temperature, holding for 940℃~950℃). The holding time is the wall thickness of the expanded blank (in mm) multiplied by the holding coefficient, which is 0.8~1.0min / mm. The ring is formed using a ring rolling mill. The ring forging dimensions range from outer diameter φ2100mm~φ3840mm, wall thickness 80mm~429mm, and height 114mm~435mm.

[0010] Step 8: The formed ring obtained in Step 7 is subjected to annealing heat treatment process using a bell-type electric heating furnace. The annealing temperature is 700℃~800℃ and the holding time is 1.5h~2.5h.

[0011] In step 3 above, the billet is subjected to reverse upsetting deformation. The purpose is to fully break the grains, eliminate the deformation dead zone, avoid the formation of Widmanstätten structure, and obtain a uniform microstructure, based on the fact that the deformation resistance of the material is relatively small above the α+β / β phase transformation temperature.

[0012] In step 5 above, a punch with a diameter d = (0.2~0.35)×D is used to ensure the deformation of the material from the reamer hole to the size of the ring blank, and further refine the grains.

[0013] In step 7 above, the linear speed of the main roller of the ring rolling mill is no more than 700 mm / s, and the feed rate is 0.7 mm / s to 1.2 mm / s, which ensures further uniform refinement of the microstructure of the titanium alloy ring and the dimensional accuracy of the forming.

[0014] The preferred annealing heat treatment temperature for the formed ring in step 8 above is 760℃, and the holding time is 2h.

[0015] Compared with the prior art, the present invention has the following advantages: 1. The present invention employs a reversing upsetting and drawing deformation method at a temperature 70°C to 100°C above the phase transformation temperature of the billet. The deformation amount of a single upsetting and drawing reaches 40% to 50%, which can effectively eliminate the deformation dead zone and make the grains uniformly broken, thus helping to avoid the formation of Widmanstätten structure.

[0016] 2. In this invention, a large deformation process involving four upsetting and four drawing is performed at 20°C to 30°C below the α+β / β phase transformation temperature of the billet to obtain uniform and fine α equiaxed crystals on the transformed β matrix, thus ensuring the mechanical properties of the ring.

[0017] 3. In this invention, the inner diameter of the rolled ring blank obtained in the ring expansion process is 40% to 60% of the outer diameter, which ensures the flatness of the formed ring.

[0018] 4. This invention determines the main roller linear speed and feed rate in the ring rolling process, ensuring that the ring is rolled through while improving the dimensional accuracy of the ring, increasing material utilization, saving materials, and reducing costs. Attached Figure Description

[0019] Figure 1 This is a micrograph of sample 1 of a large-size marine TC4ELI titanium alloy ring according to an embodiment of the present invention. Figure 2 A micrograph of sample 2 of a large-size marine TC4ELI titanium alloy ring according to an embodiment of the present invention. Figure 3 This is a microstructure photograph of sample 3, a large-size marine TC4ELI titanium alloy ring, according to an embodiment of the present invention. Detailed Implementation

[0020] The forging of TC4ELI titanium alloy rings using this invention requires equipment including a high-temperature electric heating furnace, a high-speed forging mill, a ring rolling mill, a manipulator, a loading and unloading machine, and a grinding wheel. The specific implementation steps of this invention are detailed below using a forging method for large-size marine TC4ELI titanium alloy rings as an example: Example 1 The chemical composition (mass fraction, %) of the TC4ELI titanium alloy in this embodiment is: 6.25Al, 4.14V, 0.138Fe, 0.009C, 0.087O, 0.005N, 0.001H, balance Ti. The β / α+β phase transformation temperature of the TC4ELI alloy is calculated to be 973℃.

[0021] The specific implementation process steps are as follows: Step 1: The forming dimensions of the titanium alloy ring are φ2206mm×φ1974mm×255mm. Considering the amount of grinding after forging of the billet and the machining allowance of the ring, the material requirement is determined to be 1480kg. The blanking specifications of the TC4ELI titanium alloy ingot are φ714mm×820mm.

[0022] Step 2: Coat the surface of the TC4ELI titanium alloy ingot from Step 1 with a high-temperature antioxidant, heat it to 800℃ and hold it for 2 hours, then raise the temperature to 1150℃ and hold it for 385 minutes, with a holding coefficient of 0.6 min / mm; complete two upsetting and two drawing operations using a high-speed forging machine, with a deformation of 45% for each upsetting and drawing operation, and a total deformation of 90% for the two operations. The size of the forged billet is octagonal 567mm×1180mm, with a height-to-diameter ratio of 2.0, and the final forging temperature is 865℃.

[0023] Step 3: Coat the surface of the TC4ELI titanium alloy billet from Step 2 with a high-temperature antioxidant, heat to 800℃, hold for 2 hours, then raise the temperature to 1050℃ and hold for 385 minutes, with a holding coefficient of 0.6 min / mm; use a high-speed forging machine to complete the reverse three-upsetting and three-drawing deformation, with each upsetting and drawing deformation amounting to 45%, and the billet size after forging is octagonal 569mm×1144mm, with a height-to-diameter ratio of 2.0, and the final forging temperature is 815℃.

[0024] Step 4: Heat the TC4ELI titanium alloy billet obtained in Step 3 to a preheating temperature of 800℃ and hold for 2 hours. Then heat it to 950℃ and hold for 285 minutes. The holding time is the minimum size of the billet multiplied by the holding coefficient, which is 0.5 min / mm. Then use a high-speed forging machine to complete four upsetting and drawing processes. After two upsetting and two drawing processes, the billet is returned to the furnace and heated to 950℃. After holding for 2 hours, the subsequent two upsetting and two drawing processes are completed. The deformation amount of each upsetting and drawing process is 45%. The size of the forged billet is octagonal 556mm×1140mm with a height-to-diameter ratio of 2.05. The final forging temperature is 710℃.

[0025] Step 5: Heat the TC4ELI titanium alloy billet obtained in Step 4 to a preheating temperature of 800℃, hold for 2 hours, then heat to 950℃ and hold for 250 minutes. The holding coefficient is 0.45 min / mm. Upset and shape to φ1020mm×330mm. The punch used for punching has a diameter of φ320mm and D / d=3.19. The dimensions of the titanium alloy billet after punching are φ1020mm×φ320mm×330mm.

[0026] Step 6: Heat the punched billet obtained in Step 5 to a preheating temperature of 800℃ and hold for 2 hours. Then heat it to 950℃ and hold for 165 minutes. Use a frame to expand the hole. Stop forging and return to the furnace for reheating when the hole expansion temperature reaches 710℃. When the temperature is raised to 950℃, the holding time is 2 hours. The final expanded hole billet size is φ1190mm×φ650mm×330mm.

[0027] Step 7: Heat the billet obtained in Step 6 to the preheating temperature of 800℃, hold for 2 hours, then heat to 950℃ and hold for 270 minutes. The holding time is the wall thickness of the expanded hole billet multiplied by the holding coefficient, which is 1.0 min / mm. The ring is formed by rolling the ring using a ring rolling mill. The ring forming size is φ2230mm×φ1950mm×279mm.

[0028] Step 8: The formed ring obtained in Step 7 is subjected to annealing heat treatment process using a bell-type electric heating furnace. The annealing temperature is 760℃ and the holding time is 2h.

[0029] The room temperature mechanical properties of the TC4ELI titanium alloy rings prepared by the above forging method after annealing are shown in Table 1.

[0030] Table 1. Room temperature mechanical properties of the TC4ELI titanium alloy ring in this embodiment. The large-size TC4ELI titanium alloy ring for marine applications prepared in this embodiment has high strength and good plasticity, fully meeting the application requirements of large-size TC4ELI titanium alloy rings for marine applications (the room temperature mechanical properties are higher than the technical specifications of GJB 943A-2018 "Specifications for Titanium Alloy Forgings for Ships").

[0031] The high-magnification microstructure of the large-size TC4ELLI titanium alloy ring prepared in this embodiment is a uniform equiaxed α-phase + transformed β-phase microstructure, with no original β-phase microstructure.

Claims

1. A method for manufacturing a large-size marine TC4ELI titanium alloy ring, characterized in that, This method includes the following steps: Step 1: According to the material requirements of titanium alloy rings, determine the length to be sawn from the TC4ELI titanium alloy ingot, mark the sawing dimensions and positions, saw and cut the material, and grind the cracks, shrinkage cavities and sharp edges on the surface of the ingot. Step 2: Uniformly coat the surface of the TC4ELI titanium alloy ingot treated in Step 1 with a high-temperature antioxidant; heat the TC4ELI titanium alloy ingot coated with the high-temperature antioxidant in a furnace to a preheating temperature of 750℃~820℃, hold for 2~2.5h, then heat to 1140~1150℃, the holding time is the minimum size of the TC4ELI titanium alloy ingot multiplied by the holding coefficient, the holding coefficient is 0.45~0.6min / mm, so that the TC4ELI titanium alloy ingot is uniformly heated through, and then use a high-speed forging machine to complete two upsetting and drawing to obtain the TC4ELI titanium alloy billet. The total deformation of the two upsetting and drawing is controlled between 85% and 90%. During the forging process, the initial forging temperature is not less than 1000℃ and the final forging temperature is not less than 800℃. Step 3: Heat the TC4ELI titanium alloy billet obtained in Step 2 to a preheating temperature of 750℃~820℃ and hold for 2~2.5h. Then heat it to 1040℃~1050℃ and hold for a time equal to the minimum size of the TC4ELI titanium alloy billet multiplied by the holding coefficient, which is 0.4~0.6min / mm. This ensures that the TC4ELI titanium alloy billet is heated evenly and thoroughly. Then, use a high-speed forging machine to complete three reverse upsetting and drawing processes to obtain the TC4ELI titanium alloy billet. The deformation amount of each upsetting and drawing process is 40%~50%. During the forging process, the initial forging temperature is not lower than 950℃ and the final forging temperature is not lower than 800℃. Step 4: Heat the TC4ELI titanium alloy billet obtained in Step 3 to a preheating temperature of 750℃~820℃, hold for 2h~2.5h, then heat to 20℃~30℃ below the phase transformation temperature, hold at 940℃~950℃, and the holding time is the minimum size of the TC4ELI titanium alloy billet multiplied by the holding coefficient, which is 0.3~0.5min / mm, to ensure uniform and thorough heating of the TC4ELI titanium alloy billet. Then, use a high-speed forging machine to complete four upsetting and drawing processes. The three upsetting and drawing processes are completed using a reversing upsetting and drawing method, and the fourth upsetting and drawing process is carried out using an axial upsetting and drawing method to eliminate the deformation dead zone. The deformation amount of each upsetting and drawing process is not less than 40%. After completing two upsetting and two drawing processes during forging, the material is returned to the furnace for reheating. After reaching the temperature, the material is held for 2 to 2.5 hours. After reheating, the material is removed to complete the remaining upsetting and drawing process, resulting in TC4ELI titanium alloy billet. The initial forging temperature during forging is not lower than 800℃, and the final forging temperature is not lower than 700℃. The resulting microstructure is an equiaxed α phase + transformed β phase microstructure. Step 5: Heat and hold the TC4ELI titanium alloy billet obtained in Step 4 according to the heating method in Step 4, perform upsetting and punching to obtain a punched billet. The inner diameter of the punch is d = (0.2~0.35) × D, where D is the outer diameter of the billet. Step 6: Heat the punched billet obtained in Step 5 to the heating temperature described in Step 4 and hold it at that temperature. Use a frame to expand the hole to obtain an expanded billet. The inner diameter of the expanded hole is controlled to be 40% to 60% of the outer diameter. The final forging temperature is not lower than 700℃. Recycle the billet 1 to 2 times and hold it in the furnace for 1.5 to 2 hours. Step 7: Heat the expanded blank obtained in Step 6 to the heating temperature described in Step 4. The holding time is the wall thickness of the expanded blank multiplied by the holding coefficient, which is 0.8 to 1.0 min / mm. The blank is formed by rolling it into a ring using a ring rolling mill. The ring forming size range is outer diameter φ2100mm to φ3840mm, wall thickness 80mm to 429mm, and height 114mm to 435mm. Step 8: The formed ring obtained in Step 7 is subjected to annealing heat treatment process using a bell-type electric heating furnace. The annealing temperature is 700℃~800℃ and the holding time is 1.5h~2.5h.

2. The manufacturing method of a large-size marine TC4ELI titanium alloy ring according to claim 1, characterized in that, In step 5, a punch with a diameter d = (0.2~0.35)×D is used.

3. The manufacturing method of a large-size marine TC4ELI titanium alloy ring according to claim 1, characterized in that, In step 7, the linear speed of the main roller of the ring rolling mill is no more than 700 mm / s, and the feed rate is 0.7 mm / s to 1.2 mm / s.

4. The manufacturing method of a large-size marine TC4ELI titanium alloy ring according to claim 1, characterized in that, Step 8: The annealing heat treatment temperature for the formed ring is 760℃, and the holding time is 2h.

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