Manufacturing method of TC4 titanium alloy ultra-thin-wall cylindrical forge piece

Abstract

The invention discloses a manufacturing method of a TC4 titanium alloy ultra-thin-wall thick cylindrical forge piece, which comprises the steps of blanking, material changing, blank making, ring rolling, heat treatment and machining, specifically, during material changing, a heated original blank is placed on a ten-thousand-ton press for upsetting and drawing-out procedures, during blank making, the upset and drawn-out blank is heated to 950 + / -10 DEG C, the blank is heated to 950 + / -10 DEG C, and the blank is rolled into a ring; the method comprises the following steps: sequentially carrying out upsetting, punching, pre-chambering, mandrel drawing and chambering procedures, carrying out multi-heating-number ring rolling forming in a ring rolling process, and finally carrying out heat treatment and machining on the forge piece. According to the titanium alloy cylinder forge piece, a plate rolling and welding manufacturing process is replaced by a forging and ring rolling mode, so that near-net forming of the TC4 titanium alloy ultra-thin-wall cylinder forge piece is realized; welding seams are greatly reduced, the forging quality of forgings is improved, the welding workload is reduced, the manufacturing speed is high, and economical efficiency is controllable.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of titanium alloy tube forgings, and in particular to a method for manufacturing TC4 titanium alloy ultra-thin-wall thick tube forgings. Background Art

[0002] TC4 titanium alloy has the outstanding characteristics of high strength and low density, and performs extremely well in the application scenarios that pursue lightweight and high strength. Therefore, it is widely used in important fields such as shipbuilding and marine engineering, aerospace, etc., especially in recent years, with the upgrading of national defense equipment, hull structural parts, offshore platform lifting devices, deep-sea pressure tanks, large pressure-bearing equipment, casings, petrochemical, natural gas and other industries pressure vessels are increasingly developing in large-scale and high-performance specifications, and their importance is becoming more and more prominent.

[0003] At present, most of the large titanium alloy ultra-thin wall thick tube parts manufactured by existing technology are formed by rolling titanium alloy plates. However, the use of this process inevitably causes titanium alloy tube parts to have one or more highly penetrating longitudinal welds, which become the weak link in the entire forging structure. When subjected to complex loads such as pressure and vibration, stress concentration is prone to occur at the weld. Moreover, the quality of the weld is affected by many factors such as welding process, welding materials, and the skill level of the operator. Once the weld has tiny defects, such as pores, slag inclusions, or incomplete penetration, these defects may gradually expand during long-term use, eventually leading to the failure of the forging, seriously affecting the safety and reliability of the equipment. This is an existing problem. Summary of the invention

[0004] In order to make up for the above-mentioned shortcomings, the present invention provides a method for manufacturing TC4 titanium alloy ultra-thin-wall thick tube forgings. Through the ring rolling process, the traditional plate rolling-coiling-welding process is replaced, the longitudinal weld is eliminated, the quality of the forgings is improved, the ovality of the forgings is controlled, and the safety of equipment operation is improved.

[0005] The present invention is achieved through the following technical solutions:

[0006] A manufacturing method for TC4 titanium alloy ultra-thin wall thickness cylindrical forgings, characterized by the following steps: a. Blanking: Use an ingot made of TC4 material to manufacture the original blank, select the blanking specification of the original blank according to the specifications of the cylindrical forgings, ensure that the original blank is a cylinder, and the height-diameter ratio ≤ 2.5; b. Material transformation: Load the TC4 titanium alloy original blank into an electric furnace for heating, heat it to 1100 ± 10 °C, place the heated original blank on a ten-thousand-ton press, and perform upsetting and drawing processes. The number of upsetting and drawing times is 8 - 10 times to obtain a blank; c. Blank making: Heat the blank after upsetting and drawing to 950 ± 10 °C, and successively perform upsetting, punching, pre-expanding, mandrel drawing, and expanding processes to obtain a preform; d. Ring rolling: Heat the preform to 950 ± 10 °C, place it on the working platform of a ring rolling machine, insert the moving core roll of the ring rolling machine into the inner hole of the preform, and push the preform close to the main roll. Apply axial pressure through the upper and lower tapered rolls and radial pressure through the core roll to perform ring rolling to obtain a forging; e. Heat treatment: Air-cool the cylindrical forging after ring rolling to below 200 °C, load it into a heat treatment furnace for annealing heat treatment, and after the heat preservation ends, the titanium alloy forging is taken out of the furnace and air-cooled; f. Machining: Inspect the rough forging after heat treatment, perform turning machining on the forgings within the size range. First, polish the rough forging, and then machine it to the specified size.

[0007] Further optimized, in step b, the upsetting deformation amount of the original blank is 51%, the drawing deformation amount is 50%, and the external temperature during upsetting and drawing is controlled at 870 °C - 930 °C.

[0008] Further optimized, the blank making step c includes the following processes: S1. Upsetting: After the blank is heated to 950 ± 10 °C and held for a period of time, perform the upsetting process again on a ten-thousand-ton press, and the upsetting deformation amount is 55%; S2. Punching and pre-expanding: Select a punch with a suitable specification to punch and pre-expand the blank; S3. Mandrel drawing: Select a mandrel suitable for the inner diameter of the blank, pass the blank through the mandrel and place it on a V-shaped anvil, align the central axis of the blank with the center line of the V-shaped anvil, and apply axial pressure to the titanium alloy blank through a forging device to perform drawing; S4. Expanding process: Pass the drawn blank through a bar and place it on a horse rack to perform expanding. Expand the inner diameter size of the blank to be larger than the diameter of the core roll of the ring rolling machine to obtain a preform.

[0009] Further optimized, in the punching and pre-expanding step s2, check whether there are fractures on the inner diameter surface of the blank after punching. If there are fractures, immediately stop forging, wait for the blank to air-cool to room temperature, then perform defect cleaning, and after defect cleaning, heat it for subsequent steps.

[0010] Further optimized, in the mandrel drawing step s3, gradually and evenly apply axial pressure to control the gradual attenuation of the blank temperature and avoid cracks in the blank.

[0011] Further optimized, in step d, an infrared thermometer is used to monitor the surface temperature of the preform, strictly control the temperature during the ring rolling process, and the ring rolling process is formed in multiple heating passes.

[0012] Further optimized, in step e, the heat preservation temperature is 765 ± 10 °C, and the heat preservation time is 1 - 3 h. The beneficial effects of the present invention are as follows:

[0013] Compared with the prior art, in the present invention, the titanium alloy cylindrical forgings use the forging + ring rolling method to replace the manufacturing process of rolling plate + welding, realizing the near-net forming of TC4 titanium alloy ultra-thin wall thickness cylindrical forgings, greatly reducing the welds, improving the quality of forging of the forgings, reducing the welding workload, with fast manufacturing speed and controllable economy.

[0014] By adopting the ring rolling process, the present invention realizes the integrated forming of the forgings, without the process of rolling plate, without the Bauschinger effect, ensuring that the material properties will not be attenuated due to processing, and the properties of the finished forgings are controllable.

[0015] Finally, the cylindrical forgings in the present invention are machined, which can improve the accuracy of the finished product size, greatly reduce the residual stress, ensure that the forgings are not prone to misalignment during subsequent assembly, have low residual stress during closed welding, and the cylindrical forgings shrink uniformly during welding, ensuring high accuracy of the finally assembled equipment. Brief Description of the Drawings

[0016] Figure 1 It is a schematic flow chart of the present invention from blanking to ring rolling.

[0017] Figure 2 It is a schematic diagram of the TC4 titanium alloy ultra-thin wall thickness cylindrical forging in Embodiment 1.

[0018] Figure 3 It is a schematic diagram of the TC4 titanium alloy ultra-thin wall thickness cylindrical forging after finish machining in Embodiment 1. Detailed Description of the Invention

[0019] To clearly illustrate the technical features of the present solution, the present invention will be described in detail below through specific embodiments and in conjunction with its drawings. In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "left", "right", "front", "rear", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0020] As Figures 1-3 shown, the present invention provides a manufacturing method for TC4 titanium alloy ultra-thin wall thickness cylindrical forgings, which is characterized by including the following steps:

[0021] a. Blanking: Use an ingot made of TC4 material or other methods as the raw material to manufacture the original blank. Select the blanking specification of the original blank according to the specifications of the tubular forging, ensuring that the original blank is a cylinder with a height-diameter ratio ≤ 2.5.

[0022] b. Material transformation: Load the TC4 titanium alloy original blank into an electric furnace and heat it according to the corresponding heating specifications to 1100 ± 10 °C. Within this temperature range, the plastic deformation of TC4 titanium alloy is easier, and forging operations can be effectively carried out. Place the heated original blank on a ten-thousand-ton press and perform upsetting and drawing-out processes. The number of upsetting and drawing-out times is 8 - 10 times, with an upsetting deformation of 51% and a drawing-out deformation of 50%. Ensure that each upsetting and drawing-out has sufficient deformation. Control the external temperature during upsetting and drawing-out at 870 °C - 930 °C. The purpose is to further refine the billet grains and optimize the internal organizational structure to finally obtain the blank. It should be noted that if cracks appear during forging, it needs to be cooled and the wounds cleaned, and then continue forging after heating.

[0023] c. Blank making: Heat the upset and drawn blank to 950 ± 10 °C and successively perform upsetting, punching, pre-expanding, mandrel drawing-out, and expanding processes to obtain the preform.

[0024] d. Ring rolling: Heat the preform to 950 ± 10 °C and place it on the working platform of the ring rolling machine. The moving core roll of the ring rolling machine is inserted into the inner hole of the preform and pushes the preform close to the main roll. Apply axial pressure through the upper and lower tapered rolls and radial pressure through the core roll to perform ring rolling to obtain the forging. Use an infrared thermometer to monitor the surface temperature of the preform and strictly control the temperature during the ring rolling process. The ring rolling process is formed in multiple heating passes.

[0025] e. Heat treatment: Air-cool the tubular forging after ring rolling to below 200 °C, load it into a heat treatment furnace for annealing heat treatment. Before loading, pay attention to leveling the padding iron in the furnace. If necessary, appropriately increase the number of padding irons. After loading, heat up to 765 ± 10 °C and hold for 1 - 3 h. After the holding time, the titanium alloy forging is taken out of the furnace and air-cooled to room temperature. The purpose is to eliminate the internal stress generated during the processing, improve the microstructure, enhance the plasticity and toughness of the material, and facilitate subsequent machining.

[0026] f. Machining: Inspect the blank forging after heat treatment, and turn the forging within the size range for machining. First, polish the blank forging, and then turn it to the specified size.

[0027] As a preferred implementation method, the blank making step d includes the following processes:

[0028] S1. Upsetting: After heating the blank to 950 ± 10 °C, hold it for a period of time to make the internal and external temperatures of the blank uniform. First, perform the upsetting process again on a ten-thousand-ton press, with an upsetting deformation of 55%.

[0029] S2. Punching and pre-expanding the hole. Select a punch with a suitable specification and punch and pre-expand the blank through the punch. After punching, check whether there are fractures on the inner diameter surface of the blank. If there are fractures, immediately stop forging, wait for the blank to air-cool to room temperature, then clean the fractures, and after cleaning, heat it up for subsequent steps.

[0030] S3. Mandrel drawing out. Select a mandrel suitable for the blank hole diameter, pass the blank through the mandrel and place it on the V-shaped anvil. Align the central axis of the blank with the center line of the V-shaped anvil, and apply axial pressure to the titanium alloy blank through the forging equipment to perform drawing out. It should be noted that apply axial pressure gradually and evenly, control the temperature of the blank to decay gradually, and avoid cracks in the blank.

[0031] S4. Hole expanding process. Pass the drawn blank through the bar and place it on the horse frame to perform hole expanding. Expand the inner diameter size of the blank hole to be larger than the diameter of the core roll of the ring rolling machine to obtain a preform.

[0032] Example:

[0033] The blank size of the TC4 cylinder forging (outer diameter / inner diameter / height, unit: mm): φ4025 / φ3880 / 2000

[0034] The implementation includes the following steps

[0035] (1) Blanking: Use an electroslag ingot blanked by a 10-ton vacuum consumable arc furnace made of TC4 material as the original blank.

[0036] (2) Stock changing: Perform upsetting and drawing out on the original blank heated to 1100 °C on a 10,000-ton press. The number of upsetting and drawing out is 9 times, the upsetting deformation is 51%, and the drawing out deformation is 50%. Further refine the grain of the blank, optimize the internal organizational structure, ensure sufficient deformation for each upsetting and drawing out, and control the external temperature between 870 °C and 930 °C.

[0037] (3) Preform making: Heat the titanium alloy blank to 950 ± 10 °C to make the temperature inside and outside the blank uniform. First, perform the upsetting process again on a 10,000-ton press. The upsetting deformation is 55%, and the final height of the blank is 900 mm. Select a punch with a diameter of φ550 mm for punching and pre-expanding the hole. The inner diameter of the final hole after pre-expanding is φ850 mm. Monitor whether there are fractures on the inner diameter surface of the hole. If there are fractures, immediately stop forging and perform fracture cleaning after cooling to room temperature.

[0038] Then use a mandrel with a diameter of φ800 mm to perform drawing out on the V-shaped anvil. Finally, the blank is drawn out to a height of 2050 mm, and then hole expanding is performed on the horse frame to obtain a preform. The final preform size is controlled at φ2530 / φ2300 / 2050 (unit: mm, tolerance ±10 mm)

[0039] During forging, an infrared thermometer is used to monitor the surface temperature of the blank to ensure that it meets the deformation temperature requirements. If it is found that the blank drops below the temperature requirement during forging, it should be reheated in the furnace in a timely manner.

[0040] (4) Ring rolling: Heat the preform to 950 ± 10 °C, place it on the working platform of the ring rolling equipment, insert the moving core roll into the inner hole of the blank, and push the blank close to the main roll. Apply axial pressure through the upper conical roll and radial pressure through the core roll to perform ring rolling on the ring rolling machine. The ring rolling is formed in 4 passes. Finally, the wall thickness of the TC4 titanium alloy cylindrical forging after ring rolling is 71 mm, the ellipse is 22 mm, and the outer contour is good. The forging blank drawing after ring rolling is as Figure 2 shown.

[0041] (5) Air-cool the titanium alloy cylindrical forging after ring rolling to below 200 °C, load it into the heat treatment furnace for annealing heat treatment. After loading the furnace, heat it up to 765 °C, hold for 1.5 h. After the holding is completed, the titanium alloy forging is taken out of the furnace and air-cooled to room temperature.

[0042] (6) Machining: First, perform dimensional inspection on the titanium alloy cylindrical forging after heat treatment. For those that meet the blank size requirements, transfer them to a turning machine for overall polishing to remove all the surface scale. Then, perform turning. When performing turning, use soft jaws for clamping to avoid deformation of the cylinder wall, and control the cutting amount and cutting speed to ensure that the dimensions of each part after processing meet the requirements of the drawing.

[0043] Details not described in this invention are all well-known technologies to those skilled in the art. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A manufacturing method for TC4 titanium alloy ultra-thin wall thickness cylindrical forgings, characterized in that, It includes the following steps: a. Blanking: Use an ingot made of TC4 material to manufacture the original blank. Select the blanking specification of the original blank according to the specifications of the cylindrical forgings, ensuring that the original blank is a cylinder with a height-to-diameter ratio ≤ 2.5; b. Material transformation: Load the TC4 titanium alloy original blank into an electric furnace for heating to 1100 ± 10 °C. Then, perform upsetting and drawing operations on the heated original blank on a ten-thousand-ton press. The number of upsetting and drawing operations is 8 - 10 times to obtain a billet; c. Billet making: Heat the billet after upsetting and drawing to 950 ± 10 °C, and successively perform upsetting, punching, pre-expanding, mandrel drawing, and expanding operations to obtain a preform; d. Ring rolling: Heat the preform to 950 ± 10 °C and place it on the working platform of a ring rolling machine. The moving core roll of the ring rolling machine is inserted into the inner hole of the preform and pushes the preform close to the main roll. Axial pressure is applied by the upper and lower tapered rolls, and radial pressure is applied by the core roll to perform ring rolling to obtain a forging; e. Heat treatment: Air-cool the ring-rolled cylindrical forging to below 200 °C, load it into a heat treatment furnace for annealing heat treatment, and after the heat preservation ends, the titanium alloy forging is taken out of the furnace and air-cooled; f. Machining: Measure the dimensions of the rough forging after heat treatment, and perform machining on the forgings within the size range. First, polish the rough forging, and then turn it to the specified size.

2. The manufacturing method of the TC4 titanium alloy ultra-thin wall thickness tubular forging according to claim 1, characterized in that: In step b, the upsetting deformation amount of the original blank is 51%, and the drawing deformation amount is 50%. The external temperature during upsetting and drawing is controlled at 870 °C - 930 °C.

3. The manufacturing method of the TC4 titanium alloy ultra-thin wall thickness cylindrical forging according to claim 1, characterized in that, The billet making step c includes the following operations: S1. Upsetting: After heating the billet to 950 ± 10 °C and holding it for a period of time, perform the upsetting operation again on a ten-thousand-ton press, and the upsetting deformation amount is 55%; S2. Punching and pre-expanding: Select a punch with a suitable specification to punch and pre-expand the billet; S3. Mandrel drawing: Select a mandrel suitable for the inner diameter of the billet, pass the billet through the mandrel and place it on a V-shaped anvil. Align the central axis of the billet with the center line of the V-shaped anvil, and apply axial pressure to the titanium alloy billet through forging equipment to perform drawing; S4. Expanding operation: Pass the drawn billet through a bar and place it on a horse rack to perform expanding. Expand the inner diameter of the billet to be larger than the diameter of the core roll of the ring rolling machine to obtain a preform.

4. The manufacturing method of the TC4 titanium alloy ultra-thin wall thickness cylindrical forging according to claim 3, characterized in that: In the punching and pre-expanding step S2, check whether there is a fracture on the inner diameter surface of the billet after punching. If there is a fracture, immediately stop forging, wait for the billet to air-cool to room temperature, then perform defect cleaning, and after defect cleaning, heat it again for subsequent steps.

5. The manufacturing method of the TC4 titanium alloy ultra-thin wall thickness cylindrical forging according to claim 3, characterized in that: In the mandrel drawing step S3, gradually and evenly apply axial pressure to control the gradual attenuation of the billet temperature and avoid cracks in the billet.

6. The manufacturing method of the TC4 titanium alloy ultra-thin wall thickness cylindrical forging according to claim 1, wherein: In step d, use an infrared thermometer to monitor the surface temperature of the preform, strictly control the temperature during the ring rolling process, and the ring rolling process is formed in multiple heating passes.

7. The manufacturing method of the TC4 titanium alloy ultra-thin wall thickness cylindrical forging according to claim 1, characterized in that: In step e, the heat preservation temperature is 765 ± 10 °C, and the heat preservation time is 1 - 3 h.

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