Titanium alloy seamless pipe extrusion forming method and product thereof

Abstract

The present invention belongs to the field of metal material processing, and discloses a titanium alloy seamless pipe extrusion forming method and its product. The titanium alloy seamless pipe is produced by adopting a process route of primary hole expansion and secondary hole expansion, which solves the existing problem that the use of a large hole expansion ratio once will lead to cracking or the use of drilling a large diameter inner hole will lead to material waste, and realizes the production of products with a total hole expansion ratio greater than 1.30; by first wrapping a steel sleeve on the tube blank and then wrapping a copper sleeve, it can effectively avoid copper contamination of the titanium alloy blank by the copper sleeve, and improve the surface quality of the product; the use of double cone die extrusion can improve the metal flow stability, reduce the extrusion force, reduce extrusion defects, and deform smoothly and evenly, which can avoid cracks in the tube and improve the surface quality of the tube; at the same time, the double cone die can reduce the friction between the titanium alloy and the die and protect the copper sleeve. It is suitable for the metal material processing industry.

Description

Technical Field

[0001] The invention belongs to the field of metal material processing, in particular to a titanium alloy seamless pipe extrusion forming method and a product thereof. Background Art

[0002] Titanium alloys have excellent corrosion resistance and heat resistance, as well as low density, high specific strength, non-magneticity, good toughness and weldability. They are widely used in aerospace, weapons, petrochemicals, shipbuilding, automobiles, and medicine.

[0003] Traditional titanium alloy pipe blanking generally adopts production processes such as bar punching, plate coil welding, hot perforation, forging and hot extrusion. However, the material utilization rate of the bar punching process is low, the weld seam of the plate coil welding makes the overall performance inconsistent, the high heating temperature of the perforation process leads to poor organizational stability, which is easy to cause cracks, and the forging process is slow and has poor precision. For this reason, a hot extrusion process is proposed, which puts the blank in a three-dimensional compressive stress state, which is more conducive to improving the plastic deformation ability of the material, and the deformation is large, which is suitable for hot processing of titanium alloys.

[0004] At present, the hot extrusion process of titanium alloy tube blanking is: blank preparation + primary hole expansion + copper skin lubrication + extrusion of rough tube, but this process has the following problems:

[0005] 1. When extruding large-diameter pipes, the hole expansion deformation is relatively large. When the primary deformation hole expansion ratio is greater than 1.30, cracking often occurs. If a large-diameter inner hole is drilled to reduce the hole expansion deformation, it will lead to material waste;

[0006] Second, the heating temperature during titanium alloy extrusion exceeds 850°C, at which time a brittle Ti-Cu eutectic structure will form at the titanium-copper interface, causing copper contamination of the titanium alloy tube by the copper sheath;

[0007] 3. At present, flat dies are usually used in extruders. When extruding with flat dies, the metal deforms violently and the extrusion pressure is high. In addition, the copper sleeve is easily damaged by the flat die, resulting in cracks in the pipe. Summary of the invention

[0008] The present invention aims to provide a titanium alloy seamless tube extrusion forming method and its product, so as to solve the problems existing in the existing hot extrusion process, such as tube cracking when the primary deformation hole expansion is relatively large, copper pollution to the titanium alloy tube, damage to the copper sleeve and cracks in the tube.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0010] The present invention provides a titanium alloy seamless pipe extrusion forming method, the method comprising the following steps:

[0011] S1. Alloy smelting: using electrode pressing combined with three vacuum consumable smelting technology to melt ingots;

[0012] S2. Ingot forging: heating the ingot to 850°C to 1000°C, with a forging ratio of 3 to 10, and forging it into a cylindrical billet;

[0013] S3. The blank is processed for the first time; the blank is sawn and cut into pieces, and the inner hole is processed. The inner hole of the head is processed into a bell mouth with an angle of 46.5°, and the surface roughness Ra≤3.2μm;

[0014] S4. The blank is heated for the first time; the blank is preheated at 150°C for 40 minutes, an anti-oxidation coating is applied on the surface of the blank, and the temperature is raised with the furnace. When the temperature of the electric furnace is 850-950°C, the temperature is kept for 3.5h-6.5h;

[0015] S5. One reaming; the billet heated to temperature in step S4 is placed in the reaming tube of the vertical reaming machine for reaming;

[0016] S6. Secondary processing of the blank; swap the head and tail of the blank after the expansion in step S5, turn the outer circle, flatten the ends, and machine the bell mouth at an angle of 46° to 46.5° at the inner hole of the head, and clean the inner and outer surface defects; the grinding depth-width-length ratio is greater than 1:5:10, and the corners are smoothly transitioned, and the surface roughness after cleaning is Ra≤3.2μm;

[0017] S7. Secondary heating of the billet; preheat the billet at 150°C for 40 minutes, apply an anti-oxidation coating on the surface of the billet, heat up with the furnace, and keep the temperature for 3.5h to 6.5h when the electric furnace temperature is 850 to 950°C;

[0018] S8. Secondary reaming; the billet heated to temperature in step S7 is placed in the reaming tube of the vertical reaming machine for reaming;

[0019] S9. The blank is processed three times; the outer circle of the blank after the second hole expansion in step S8 is turned, the ends are flattened, the inner and outer surface defects are cleaned, the depth-width-length ratio is greater than 1:5:10, and the edges and corners are smoothly transitioned, and the surface roughness after cleaning is Ra≤3.2μm;

[0020] S10. Blanket sheathing; The blank obtained in step S9 is first wrapped with a low-carbon steel sleeve, the thickness of the low-carbon steel sleeve is 0.5 to 1 mm; and then wrapped with a copper sleeve, the thickness of the copper sleeve is 1 to 1.8 mm;

[0021] S11. The billet is heated three times; it is heated by an electric furnace, put into the furnace at room temperature, and the temperature rises with the furnace. When the furnace temperature is 850-950°C, it is kept warm for 3.0h-5.0h;

[0022] S12 rough pipe extrusion; the billet after heating in step S11 is extruded into a rough pipe using a horizontal extruder with a double cone die;

[0023] S13. Straightening: straightening with temperature at 100℃~400℃;

[0024] S14. Pickling;

[0025] S15. Grinding: removing surface defects and residual copper and steel skin to form finished pipes;

[0026] S16. Finishing treatment: cutting of finished tubes, physical and chemical testing, size testing, non-destructive testing, and packaging.

[0027] As a limitation of the present invention, in the first processing of the blank, the sawing length is 600-900mm, the end face cutting slope is ≤3mm, the inner hole deviation of the blank is ±0.5mm, the concentricity of the inner and outer circles is ≤1mm, there is no turning tool mark on the inner and outer surfaces and the scratched surface, the outer diameter deviation is ±1mm, and the end face verticality is ≤1mm;

[0028] During the secondary processing and tertiary processing of the blank, the outer diameter deviation is ±1mm and the end face verticality is ≤1mm.

[0029] As a further limitation of the present invention, the hole enlarging in step S5 comprises the following steps:

[0030] a. The outer diameter of the blank before expansion is 5mm to 12mm smaller than the inner diameter of the expansion tube, and the inner wall of the expansion tube is preheated to a temperature greater than 350°C;

[0031] b. Apply glass powder lubricant evenly on the inner and outer surfaces of the high-temperature blank, and apply graphite lubricant on the inner wall of the expansion tube;

[0032] c. Place the blank into the reaming tube, place the reaming head into the bell mouth of the blank head, the reaming speed is 60mm / s~160mm / s, the reaming ratio is 1.10~1.27, and air-cool to room temperature after reaming.

[0033] As a further limitation of the present invention, the hole enlarging in step S8 comprises the following steps:

[0034] d. The outer diameter of the blank before expansion is 5mm to 12mm smaller than the inner diameter of the expansion tube, and the inner wall of the expansion tube is preheated to a temperature greater than 350°C;

[0035] e. Apply glass powder lubricant evenly on the inner and outer surfaces of the high-temperature blank, and apply graphite lubricant on the inner wall of the expansion tube;

[0036] f. Place the blank into the reaming tube, place the reaming head into the bell mouth of the blank head, the reaming speed is 100mm / s~200mm / s, the reaming ratio is 1.10~1.27, and air-cool to room temperature after reaming.

[0037] As another limitation of the present invention, the extrusion forming in step S12 specifically includes the following steps:

[0038] g. The inner wall temperature of the extrusion barrel is heated to 355℃~600℃, and the double cone die and core rod are heated to 280℃~480℃;

[0039] h. Apply graphite lubricant evenly on the surfaces of the extrusion cylinder, core rod and double cone die;

[0040] i. The billet is transferred to the extrusion barrel within 90 seconds after it comes out of the furnace. The inner diameter of the extrusion barrel is 5mm to 10mm larger than the outer diameter of the billet;

[0041] j. Heat the tail pad to 850℃~950℃, and then stick it to the tail of the billet. The tail pad is extruded together with the billet;

[0042] k. The forward speed of the extrusion rod is 40mm / s~90mm / s, the extrusion ratio of the rough pipe is 2.5~10.5, the pressure surplus is set to 30mm, and the extruded rough pipe is naturally air-cooled on the cooling bed.

[0043] As a further limitation of the present invention, the outer diameter of the tail pad is equal to the outer diameter of the blank, the inner diameter of the tail pad is 4 mm to 6 mm larger than the inner diameter of the blank, and the length of the tail pad is 95 mm.

[0044] As a further limitation of the present invention, the vertical reaming machine adopts a 2500-ton vertical reaming machine, wherein the diameter of the reaming needle is 10 mm smaller than the diameter of the working section of the reaming head, the inner diameter of the shear ring is 0.5 to 1 mm larger than the diameter of the working section of the reaming head, the reaming needle deviates from the center line of the reaming barrel by ≤0.5 mm, the lining of the reaming cylinder has a taper of 1.1 mm to 1.5 mm in the direction of the inner circle length, the height of the reaming cylinder is 1650 mm to 1760 mm, and the thickness of the lining of the reaming cylinder is less than the thickness of the outer shell of the reaming cylinder.

[0045] As a further limitation of the present invention, the horizontal extruder adopts a 6300-ton horizontal extruder, wherein the outer cone angle γ' of the double-cone die is 24°, the inner inlet of the double-cone die has two die angles, the die angle β is 110°, and the die angle β' is 45°; the length of the sizing belt is 12.5mm~15mm, the fillet radius of the transition area between the die angle β section and the die angle β' section is 10mm, and the fillet radius of the transition area between the die angle β' section and the sizing belt is 10mm.

[0046] The present invention also provides a titanium alloy seamless pipe, which is a TB17 titanium alloy seamless pipe. The TB17 titanium alloy seamless pipe has an outer diameter ranging from 114 to 380 mm, a wall thickness ranging from 10 to 45 mm, and an inner diameter greater than 60 mm.

[0047] Due to the adoption of the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0048] The present invention adopts a process route of primary hole expansion and secondary hole expansion to produce titanium alloy seamless pipes, which solves the existing problem that a large hole expansion ratio is used once, which may lead to cracking, or that drilling a large diameter inner hole may lead to material waste, and realizes the production of products with a total hole expansion ratio greater than 1.30;

[0049] In step S10 of the present invention, the steel sleeve is first wrapped on the tube blank, and then the copper sleeve is wrapped, which can effectively prevent the copper sleeve from causing copper contamination to the titanium alloy blank, thereby improving the surface quality of the product;

[0050] The present invention adopts double-cone die extrusion, which can improve the smoothness of metal flow, reduce extrusion force, reduce extrusion defects, deform smoothly and evenly, avoid cracks in the pipe, and improve the surface quality of the pipe; at the same time, the double-cone die can reduce the friction between the titanium alloy and the die, and protect the copper sheath.

[0051] In summary, the present invention can not only prevent the tube from being cracked or the material from being wasted under a large hole expansion ratio, but also avoid copper contamination of the titanium alloy blank by the copper sheath, and can also improve the forming quality of the tube without damaging the copper sheath; it is suitable for the metal material processing industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0053] Figure 1 This is a schematic diagram of the structure of a 2500-ton vertical hole reamer;

[0054] Figure 2 It is a schematic diagram of the structure of a 6300-ton horizontal extruder;

[0055] Figure 3 It is a schematic diagram of the structure of the blank in an embodiment of the present invention;

[0056] Figure 4 It is a structural schematic diagram of a double cone mold;

[0057] Figure 5 for Figure 4 Sectional view along AA direction;

[0058] Figure 6 It is a schematic diagram of the longitudinal section of the mold base;

[0059] Figure 7 Schematic diagram of the three-dimensional structure of the mold base;

[0060] Figure 8 The figure is a schematic diagram of the production process flow of an embodiment of the present invention.

[0061] In the figure: 1-die tailstock, 2-die middle seat, 3-die seat, 4-double cone die, 5-die support, 6-extrusion cylinder, 7-core rod, 8-tail pad, 9-extrusion pad, 10-extrusion rod, 11-core rod force transmission rod, 12-blank, 13-raw pipe;

[0062] 14- ejection mechanism, 15- expansion tube base, 16- shear ring support, 17- shear ring, 18- expansion tube, 181- expansion tube lining, 182- expansion tube shell, 183- high-strength bolt, 19- expansion head, 20- expansion needle, 21- force transmission rod, 22- restraint ring. DETAILED DESCRIPTION

[0063] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the titanium alloy seamless tube extrusion forming method and the product described herein are preferred embodiments, which are only used to illustrate and explain the present invention and do not constitute a limitation to the present invention.

[0064] Figure 1 It is an existing 2500-ton vertical reaming machine, including an ejection mechanism 14, a reaming tube base 15, a shear ring support 16, a shear ring 17, a reaming tube 18, a reaming head 19, a reaming needle 20, a force transmission rod 21 and a restraining ring 22. The reaming tube includes a reaming tube liner 181 and a reaming tube shell 182. The reaming tube base 15 and the reaming tube 18 are fixedly connected by four high-strength bolts 183. The reaming needle 20 is connected to the force transmission rod 21 through a threaded connector. The reaming tube base 15 supports the shear ring support 16, and the shear ring support 16 supports the shear ring 17 and the blank 12. The shear ring 17 supports the blank and cuts off the excess of the blank. The force transmission rod 21 applies a reaming force to the reaming head 19 through the reaming needle 20 to achieve reaming. The above content is the prior art and will not be described in detail in this embodiment.

[0065] The improvements on the 2500-ton vertical reaming machine in this embodiment are that the diameter of the reaming needle 20 is 10 mm smaller than the diameter of the working section of the reaming head 19, the inner diameter of the shear ring 17 is 0.5 to 1 mm larger than the diameter of the working section of the reaming head 19, the deviation of the reaming needle 20 from the center line of the reaming tube 18 is ≤0.5 mm, the reaming tube lining 181 has a taper of 1.1 mm to 1.5 mm in the direction of the inner circle length, the height of the reaming tube 18 is 1650 mm to 1760 mm, and the thickness of the reaming tube lining 181 is less than the thickness of the reaming tube outer shell 182.

[0066] Figure 2The invention is an existing 6300-ton horizontal extruder, which includes a die tail seat 1, a die center seat 2, a die base 3, a double cone die 4, a die support 5, an extrusion barrel 6, a core rod 7, a tail pad 8, an extrusion pad 9, an extrusion rod 10 and a core rod force transmission rod 11. The double cone die 4 and the die support 5 are installed inside the die base 3, the die center seat 2 and the die tail seat 1 are arranged on the left side of the die support 5, and the die support 5, the die center seat 2 and the die tail seat 1 jointly support and fix the double cone die 4. The extrusion barrel 6 is located on the right side of the die base 3, the inside of the extrusion barrel 6 is a blank 12, the inside of the blank 12 is a core rod 7, the right side of the blank 12 is sequentially provided with a tail pad 8 and an extrusion pad 9, and the right side of the extrusion pad 9 is an extrusion rod 10, the extrusion rod 10 provides extrusion force under the action of the oil pressure system, and the extrusion pad 9 is used to prevent the extrusion rod 10 from directly contacting the blank 12 and can transmit the extrusion force. A mandrel dowel rod 11 is arranged inside the extrusion rod 10, and the mandrel dowel rod 11 is connected to the mandrel 7 through a thread, and the blank 12 is extruded by the cavity formed by the mandrel 7 and the double cone die 4 to form a rough pipe 13. This part of the content is the prior art and will not be described in detail in this embodiment.

[0067] The improvement of the 6300 ton horizontal extruder in this embodiment is that Figure 4 , 5 As shown, the angle γ' of the outer cone surface of the double cone die 4 is 24°, the inner entrance of the double cone die 4 has two die angles, die angle β is 110°, and die angle β' is 45°; the length of the sizing belt is 12.5mm-15mm, the fillet radius of the transition area between the die angle β section and the die angle β' section is 10mm, and the fillet radius of the transition area between the die angle β' section and the sizing belt is 10mm. Correspondingly, as Figure 6 , 7 As shown, the cone angle γ at the position inside the mold base 3 for installing the double cone mold 4 is 24°, which is equal to the included angle γ′ of the outer cone surface of the double cone mold 4, which is convenient for matching installation.

[0068] Example 1 Titanium alloy seamless pipe extrusion forming method

[0069] In this embodiment, the material of the extruded titanium alloy tube is TB17 as an example for description.

[0070] like Figure 8 As shown, the titanium alloy seamless tube extrusion forming method of this embodiment includes the following steps:

[0071] S1. Alloy smelting: The ingot is smelted by electrode pressing combined with three vacuum consumable smelting technology to reduce macro segregation and micro segregation between the dendrite interior and the dendrite trunk, and purify the metal; the ingot specification is φ920mm in diameter × 1000mm in length.

[0072] S2. Ingot forging; the ingot is heated to 850°C to 1000°C, in this embodiment, it is heated to 890°C, the forging ratio is 3 to 10, and the forging specification is a cylindrical billet with a diameter of φ430mm.

[0073] S3. The first processing of the blank; the blank is sawn and cut, the sawing length is 600 to 900 mm, and the sawing length is 500 mm in this embodiment; the end face sawing slope, the end face cutting slope ≤3 mm, the end face verticality ≤1 mm; processing the inner hole, the blank drill hole deviation ±0.5 mm, the concentricity of the inner and outer circles ≤1 mm, the outer diameter deviation ±1 mm, the inner and outer surfaces and the surface of the scratching road are free of turning tool marks; the inner hole of the blank 12 head is processed at an angle α of 46.5 ° to the bell mouth, see Figure 3 , surface roughness Ra≤3.2μm. The specifications of the processed blank are diameter φ421mm×inner diameter φ45mm×length 500mm.

[0074] S4. The blank is heated for the first time; the blank is preheated at 150°C for 40 minutes, an anti-oxidation coating is applied on the surface of the blank, and the temperature is raised with the furnace. When the temperature of the electric furnace is 850-950°C, it is kept warm for 3.5h-6.5h. Here, the temperature of the electric furnace is 890°C and it is kept warm for 6h.

[0075] S5. Primary expansion: placing the billet heated to temperature in step S4 into the expansion barrel of a 2500-ton vertical expansion machine for expansion. Specifically, this step includes the following contents:

[0076] a. The outer diameter of the blank before expansion is 5mm to 12mm smaller than the inner diameter of the expansion tube 18, and the inner wall of the expansion tube 18 is preheated to a temperature greater than 350°C; here the inner diameter of the expansion tube 18 is 428mm, and the inner wall of the expansion tube 18 is preheated to 360°C.

[0077] b. Apply glass powder lubricant evenly on the inner and outer surfaces of the high-temperature blank, and apply graphite lubricant on the inner wall of the expansion tube;

[0078] c. Place the blank into the reaming tube 18, place the reaming head 19 into the bell mouth of the blank head, the reaming speed is 60mm / s~160mm / s, the reaming ratio is 1.10~1.27, and air cool to room temperature after reaming. In this step, the diameter of the reaming head 19 is 168mm, and the reaming ratio is the ratio of the area of ​​the cross section of the blank before reaming to the area of ​​the cross section after reaming. The specific calculation of the primary reaming ratio is:

[0079] Cross-sectional area before expansion: π×(421 / 2) 2 -π×(45 / 2) 2 =137544.56mm 2 ;

[0080] Cross-sectional area after expansion: π×(428 / 2) 2 -π×(168 / 2)2 =121643.6mm 2 .

[0081] The primary hole expansion ratio is 1.13.

[0082] S6. Secondary processing of the blank: swap the head and tail of the blank after the hole expansion in step S5, turn the outer circle, the outer diameter deviation is ±1mm, and the outer diameter size in this embodiment is 421±1mm; flatten the ends, and the end surface verticality is ≤1mm; process the bell mouth at the inner hole of the head with an angle of 46° to 46.5°; clean the cracks, folds, scars, deep pits and other defects on the inner and outer surfaces; grind the depth, width and length ratio to greater than 1:5:10, and the corners are smooth, and the roughness of all surfaces after cleaning is Ra≤3.2μm. The specifications after processing are diameter φ421mm×inner diameter φ168mm×length 560mm.

[0083] S7. Reheating of the blank: preheat the blank at 150°C for 40 minutes, apply anti-oxidation coating on the surface of the blank, and heat up with the furnace. When the temperature of the electric furnace is 850-950°C, keep it warm for 3.5h-6.5h; here, when the temperature of the electric furnace is 890°C, keep it warm for 5h.

[0084] S8. Secondary hole expansion: Place the billet heated to temperature in step S7 into the expansion cylinder 18 of the 2500-ton vertical hole expansion machine for hole expansion. Specifically, this step includes the following contents:

[0085] d. The outer diameter of the blank before expansion is 5 mm to 12 mm smaller than the inner diameter of the expansion tube 18, and the inner wall of the expansion tube 18 is preheated to a temperature greater than 350°C; the inner diameter of the expansion tube 18 is 428 mm; the inner wall of the expansion tube 18 is preheated to a temperature of 360°C.

[0086] e. Apply glass powder lubricant evenly on the inner and outer surfaces of the high-temperature blank, and apply graphite lubricant on the inner wall of the expansion tube 18.

[0087] f. Place the blank into the reaming tube 18, place the reaming head 19 into the bell mouth of the blank head, the reaming speed is 100mm / s~200mm / s, the reaming ratio is 1.10~1.27, and air-cool to room temperature after reaming. In this step, the diameter of the secondary reaming head 19 is 238mm, and the specific calculation of the secondary reaming ratio is:

[0088] Cross-sectional area before expansion: π×(421 / 2) 2 -π×(168 / 2) 2 =116978.345mm 2 ;

[0089] Cross-sectional area after expansion: π×(428 / 2) 2 -π×(238 / 2) 2 =99333.9mm 2 .

[0090] The secondary hole expansion ratio is 1.18.

[0091] In this embodiment, the first hole expansion ratio is 1.13, the second hole expansion ratio is 1.18, and each hole expansion ratio is less than 1.3 to avoid expansion cracking; and the product of the two is 1.33, achieving the production of products with a total hole expansion ratio greater than 1.30.

[0092] S9. Process the blank three times; turn the outer circle of the blank after the second hole expansion in step S8, with an outer diameter deviation of ±1mm; flatten the ends, and the verticality of the end faces ≤1mm; clean the cracks, folds, scars, deep pits and other defects on the inner and outer surfaces; grind the depth-width-length ratio to be greater than 1:5:10, and the edges and corners have a smooth transition, and the surface roughness after cleaning is Ra≤3.2μm; the specifications after processing are outer diameter φ420mm×inner diameter φ235mm×length 650mm.

[0093] S10. Blanket sheathing: The blank obtained in step S9 is firstly sheathed with a low-carbon steel sheath, which is 0.5-1 mm thick, close to its inner and outer surfaces; and then sheathed with a copper sheath, which is 1-1.8 mm thick. The purpose of sheathing with the low-carbon steel sheath is to prevent the copper sheath from contacting with the titanium alloy to form a brittle substance; the purpose of sheathing with the copper sheath is to serve as a lubricating material during hot extrusion. The specifications after sheathing are φ425mm (outer diameter) × φ230mm (inner diameter).

[0094] S11. The billet is heated three times; it is heated in an electric furnace, put into the furnace at room temperature, and heated up with the furnace. When the furnace temperature is 850-950℃, it is kept warm for 3.0h-5.0h; here, when the furnace temperature is 885℃, the keeping time is 4.5h.

[0095] S12. Extrusion of rough pipe: The rough pipe 13 is extruded from the billet heated in step S11 using a 6300 ton horizontal extruder with a double cone die 4. Specifically, the process comprises the following steps:

[0096] g. The inner wall temperature of the extrusion barrel 6 is heated to 355℃~600℃, and the double cone die 4 and the core rod 7 are heated to 280℃~480℃; since too high extrusion temperature is prone to coarse grains or structural alienation, too low extrusion temperature is prone to blockage due to excessive extrusion pressure, the temperature in this step can avoid this problem.

[0097] h. Extrusion cylinder 6, mandrel 7 and double cone die surface 4 are evenly coated with graphite lubricant;

[0098] i. The billet is transported to the extrusion barrel 6 within 90 seconds after it comes out of the furnace. The inner diameter of the extrusion barrel 6 is 5mm to 10mm larger than the outer diameter of the billet; the inner diameter of the extrusion barrel 6 is 435mm;

[0099] j. The tail pad 8 prepared in advance is heated to 850°C to 950°C, and then attached to the tail of the billet. The tail pad 8 is extruded together with the billet to improve the yield rate. In this embodiment, the outer diameter of the tail pad 8 is equal to the outer diameter of the billet, the inner diameter of the tail pad 8 is 4mm to 6mm larger than the inner diameter of the billet, and the length of the tail pad 8 is 95mm. Here, the specifications of the tail pad 8 are outer diameter φ425mm×inner diameter φ235mm×length 95mm, and the material of the tail pad 8 is 20 steel;

[0100] k. The power system of the extruder makes the extrusion rod 10 push the blank to move in the extrusion direction. The extrusion rod 10 advances at a speed of 40 mm / s to 90 mm / s. The inner diameter of the double cone die 4 at the sizing zone is 305.5 mm. The diameter of the core rod 7 is 218.2 mm. The pressure surplus is set to 30 mm. The extruded rough pipe 13 is naturally air-cooled on the cooling bed. Here, the extrusion ratio of the rough pipe 13 is 2.5 to 10.5.

[0101] The specific calculation of extrusion ratio is:

[0102] Cross-sectional area before extrusion: π×(435 / 2) 2 -π×(230 / 2) 2 =107015.125mm 2 ;

[0103] Cross-sectional area after extrusion: π×(305.5 / 2) 2 -π×(230 / 2) 2 =31737.74625mm 2 .

[0104] The extrusion ratio was about 3.37.

[0105] S13. Straightening: hot straightening is carried out at a temperature of 100°C to 400°C.

[0106] S14. Pickling; removal of copper and steel scale.

[0107] S15. Grinding: removing surface defects and residual copper and steel skin to form finished pipes;

[0108] S16. Finishing treatment: cutting of finished tubes, physical and chemical testing, size testing, non-destructive testing, and packaging.

[0109] Example 2 Titanium alloy seamless pipe

[0110] The titanium alloy seamless tube in this embodiment is manufactured by the titanium alloy seamless tube extrusion forming method in Embodiment 1, and has an outer diameter ranging from 114 to 380 mm, a wall thickness ranging from 10 to 45 mm, and an inner diameter greater than 60 mm.

[0111] This embodiment is a TB17 titanium alloy seamless pipe, and the specification of the TB17 titanium alloy seamless pipe is a titanium alloy pipe with an outer diameter of φ300 mm and an inner diameter of φ218 mm.

[0112] It should be noted that the method in Example 1 can also be used to produce titanium alloy seamless tubes such as TA10, TA18, TA22, TC4, TA15, TC11, TC18, TB17 or TC27.

[0113] It should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the above embodiment, those skilled in the art can still modify the technical solutions described in the above embodiment or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A titanium alloy seamless tube extrusion forming method, characterized in that: The method comprises the following steps: S1. Alloy smelting: using electrode pressing combined with three vacuum consumable smelting technology to melt ingots; S2. Ingot forging: heating the ingot to 850°C to 1000°C, with a forging ratio of 3 to 10, and forging it into a cylindrical billet; S3. The blank is processed for the first time; the blank is sawn and cut into pieces, and the inner hole is processed. The inner hole of the head is processed into a bell mouth with an angle of 46.5°, and the surface roughness Ra≤3.2μm; S4. The blank is heated for the first time; the blank is preheated at 150°C for 40 minutes, an anti-oxidation coating is applied on the surface of the blank, and the temperature is raised with the furnace. When the temperature of the electric furnace is 850-950°C, the temperature is kept for 3.5h-6.5h; S5. One reaming; the billet heated to temperature in step S4 is placed in the reaming tube of the vertical reaming machine for reaming; S6. Secondary processing of the blank; swap the head and tail of the blank after the expansion in step S5, turn the outer circle, flatten the ends, and machine the bell mouth at an angle of 46° to 46.5° at the inner hole of the head, and clean the inner and outer surface defects; the grinding depth-width-length ratio is greater than 1:5:10, and the corners are smoothly transitioned, and the surface roughness after cleaning is Ra≤3.2μm; S7. Secondary heating of the billet; preheat the billet at 150°C for 40 minutes, apply an anti-oxidation coating on the surface of the billet, heat up with the furnace, and keep the temperature for 3.5h to 6.5h when the electric furnace temperature is 850 to 950°C; S8. Secondary reaming; the billet heated to temperature in step S7 is placed in the reaming tube of the vertical reaming machine for reaming; S9. The blank is processed three times; the outer circle of the blank after the second hole expansion in step S8 is turned, the ends are flattened, the inner and outer surface defects are cleaned, the depth-width-length ratio is greater than 1:5:10, and the edges and corners are smoothly transitioned, and the surface roughness after cleaning is Ra≤3.2μm; S10. Blanket sheathing; The blank obtained in step S9 is first wrapped with a low-carbon steel sleeve, the thickness of the low-carbon steel sleeve is 0.5 to 1 mm; and then wrapped with a copper sleeve, the thickness of the copper sleeve is 1 to 1.8 mm; S11. The billet is heated three times; it is heated by an electric furnace, put into the furnace at room temperature, and the temperature rises with the furnace. When the furnace temperature is 850-950°C, it is kept warm for 3.0h-5.0h; S12 rough pipe extrusion; the billet after heating in step S11 is extruded into a rough pipe using a horizontal extruder with a double cone die; S13. Straightening: straightening with temperature at 100℃~400℃; S14. Pickling; S15. Grinding: removing surface defects and residual copper and steel skin to form finished pipes; S16. Finishing treatment: cutting of finished tubes, physical and chemical testing, size testing, non-destructive testing, and packaging; In steps S5 and S8, a 2500-ton vertical reaming machine is used, wherein the diameter of the reaming needle is 10 mm smaller than the diameter of the reaming head working section, the inner diameter of the shear ring is 0.5-1 mm larger than the diameter of the reaming head working section, the reaming needle deviates from the center line of the reaming barrel by ≤0.5 mm, the reaming cylinder lining has a taper of 1.1 mm to 1.5 mm in the inner circle length direction, the height of the reaming cylinder is 1650 mm to 1760 mm, and the thickness of the reaming cylinder lining is less than the thickness of the reaming cylinder shell; In step S12, the horizontal extruder uses a 6300-ton horizontal extruder, wherein the outer cone angle γ' of the double-cone die is 24°, the inner inlet of the double-cone die has two die angles, the die angle β is 110°, and the die angle β' is 45°; the length of the sizing belt is 12.5mm~15mm, the fillet radius of the transition area between the die angle β section and the die angle β' section is 10mm, and the fillet radius of the transition area between the die angle β' section and the sizing belt is 10mm.

2. The titanium alloy seamless tube extrusion forming method according to claim 1, characterized in that: In the first processing of the blank, the sawing length is 600-900mm, the end face cutting slope is ≤3mm, the inner hole deviation of the blank is ±0.5mm, the concentricity of the inner and outer circles is ≤1mm, there is no turning tool mark on the inner and outer surfaces and the scratched surface, the outer diameter deviation is ±1mm, and the end face verticality is ≤1mm; During the secondary processing and tertiary processing of the blank, the outer diameter deviation is ±1mm and the end face verticality is ≤1mm.

3. The titanium alloy seamless tube extrusion forming method according to claim 2, characterized in that: The hole enlarging in step S5 comprises the following steps: a. The outer diameter of the blank before expansion is 5mm to 12mm smaller than the inner diameter of the expansion tube, and the inner wall of the expansion tube is preheated to a temperature greater than 350°C; b. Apply glass powder lubricant evenly on the inner and outer surfaces of the high-temperature blank, and apply graphite lubricant on the inner wall of the expansion tube; c. Place the blank into the reaming tube, place the reaming head into the bell mouth of the blank head, the reaming speed is 60mm / s~160mm / s, the reaming ratio is 1.10~1.27, and air-cool to room temperature after reaming.

4. The titanium alloy seamless tube extrusion forming method according to claim 3, characterized in that: The hole enlarging in step S8 comprises the following steps: d. The outer diameter of the blank before expansion is 5mm to 12mm smaller than the inner diameter of the expansion tube, and the inner wall of the expansion tube is preheated to a temperature greater than 350°C; e. Apply glass powder lubricant evenly on the inner and outer surfaces of the high-temperature blank, and apply graphite lubricant on the inner wall of the expansion tube; f. Place the blank into the reaming tube, place the reaming head into the bell mouth of the blank head, the reaming speed is 100mm / s~200mm / s, the reaming ratio is 1.10~1.27, and air-cool to room temperature after reaming.

5. The titanium alloy seamless tube extrusion forming method according to any one of claims 1 to 4, characterized in that: The extrusion forming in step S12 specifically includes the following steps: g. The inner wall temperature of the extrusion barrel is heated to 355℃~600℃, and the double cone die and core rod are heated to 280℃~480℃; h. Apply graphite lubricant evenly on the surfaces of the extrusion cylinder, core rod and double cone die; i. The billet is transferred to the extrusion barrel within 90 seconds after it comes out of the furnace. The inner diameter of the extrusion barrel is 5mm to 10mm larger than the outer diameter of the billet; j. Heat the tail pad to 850℃~950℃, and then stick it to the tail of the billet. The tail pad is extruded together with the billet; k. The forward speed of the extrusion rod is 40mm / s~90mm / s, the extrusion ratio of the rough pipe is 2.5~10.5, the pressure surplus is set to 30mm, and the extruded rough pipe is naturally air-cooled on the cooling bed.

6. The titanium alloy seamless tube extrusion forming method according to claim 5, characterized in that: The outer diameter of the tail pad is equal to the outer diameter of the blank, the inner diameter of the tail pad is 4mm to 6mm larger than the inner diameter of the blank, and the length of the tail pad is 95mm.

7. A titanium alloy seamless pipe, characterized in that: The titanium alloy seamless tube is made by the titanium alloy seamless tube extrusion forming method described in any one of claims 1 to 6, wherein the titanium alloy seamless tube is a TB17 titanium alloy seamless tube, the outer diameter of the TB17 titanium alloy seamless tube ranges from 114 to 380 mm, the wall thickness ranges from 10 to 45 mm, and the inner diameter is greater than 60 mm.

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