A method and die assembly for forming a high-precision seamless pipe of a zirconium alloy

Abstract

This invention discloses a forming method and mold device for high-precision seamless zirconium alloy tubes. The forming mold device, relating to the field of industrial equipment manufacturing technology, includes a vertical expanding mill. The vertical expanding mill includes an expanding barrel, which consists of an expanding barrel liner and an expanding barrel shell. A base is fixed to the bottom of the expanding barrel by high-strength bolts. An ejection mechanism is provided through the center of the bottom of the expanding barrel, and a shear ring support is provided at the top of the base. The integral conical die of this invention facilitates smooth metal flow during extrusion, changing concentrated deformation to gradual deformation, reducing extrusion pressure. Low-speed extrusion reduces the severity of metal deformation, improves the uniformity of metal flow, and solves the problem of tube cracking when using a flat die. The cold rolling process improves the surface quality, internal structure, and performance quality of the zirconium tube. The zirconium alloy tubes produced using this invention have high dimensional accuracy, good surface quality, and high yield.

Description

Technical Field

[0001] This invention relates to the field of industrial equipment manufacturing technology, specifically to a forming method and mold device for high-precision seamless zirconium alloy tubes. Background Technology

[0002] Zirconium is a rare metal with remarkable corrosion resistance, an extremely high melting point, and exceptional hardness and strength, making it widely used in aerospace, military, nuclear reactors, and atomic energy. Zirconium and its alloys have good plasticity and can be manufactured into tubes, plates, bars, and wires, with tubes being the primary product. The processing technology for zirconium and its alloys depends on the fundamental properties of zirconium and the specific requirements of nuclear reactors for zirconium components. Zirconium is easily contaminated by oxygen, nitrogen, and hydrogen, tends to stick to molds, and undergoes allotropic transformation. Nuclear reactors require zirconium components with high dimensional accuracy, strict microstructure requirements, and stable performance. Therefore, the fabrication of these alloy tubes presents challenges such as easy oxidation and hydrogen absorption, and traditional manufacturing methods result in low yields and metal waste.

[0003] Currently, the welding method used to process pipes results in weld seams, which cannot meet the requirements for seamless pipes used in nuclear power plants. Therefore, cold rolling is required for further processing. High-precision pipe processing presents challenges such as difficulty in matching the dimensions of the extruded billet with subsequent deformation, the potential for excessive extrusion pressure to cause stalling during the extrusion process, the difficulty in treating the inner and outer surfaces of the extruded tube, the difficulty in controlling the wall thickness deviation of the extruded tube, ensuring rolling dimensional accuracy, effectively controlling dimensional deformation during the finishing stage, and mastering the straightness of the finished pipe – all critical technical aspects to consider. Summary of the Invention

[0004] The purpose of this invention is to provide a method and mold device for forming high-precision seamless zirconium alloy tubes, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for forming high-precision seamless zirconium alloy tubes, comprising the following steps:

[0006] S1. First, zirconium alloy billet smelting and forging is required: sponge zirconium and alloying elements are pressed together into rod-shaped electrodes, and ingots are obtained by two melting processes using vacuum self-consumption process. Before forging, the ingots are heated in a box-type resistance furnace. In order to reduce high-temperature oxidation, the ingots can be protected with a glass coating. Cylindrical billets are forged, and the forging pressure ratio is greater than 3.5.

[0007] S2. Next, the blank needs to be processed: The forged blank is cut according to the finished product dimensions. 3mm to 10mm is machined off one side of the outer diameter, and a through hole with a diameter of 45mm to 80mm is machined in the center. Processing is done according to the blank drawing: the flared end γ angle of the blank head is 46.0°, M is the diameter of the working section of the reaming head, and L is calculated using trigonometric functions based on the γ angle. The inner and outer diameters are machined, ground, and polished to remove scratches, tool marks, and other defects. The surface roughness Ra ≤ 6.3μm, diameter deviation ±1.0mm, length deviation ±10mm, and perpendicularity at both ends ≤ 1mm.

[0008] S3. Furthermore, the billet requires anti-oxidation treatment and reaming: The processed billet is heated to 80℃~95℃ in a resistance furnace, coated with boron nitride anti-oxidation paint, and then placed in the reaming barrel of a 2500-ton vertical reamer for one or two reaming operations. This includes: ① preheating the reaming barrel to 100℃~300℃ and coating the inner wall of the barrel with graphite emulsion; ② heating the billet to 780℃~1100℃; ③ applying glass powder lubricant to the inner and outer surfaces of the billet. The outer diameter of the billet is 7mm~15mm smaller than the inner diameter of the reaming barrel, with the flared end of the billet facing upwards. The reaming head is placed at the flared end of the billet for reaming at a speed of 120mm / s~180mm / s. The ratio of the cross-sectional area before reaming to the cross-sectional area after reaming is 1.01~1.30. After reaming, the billet is air-cooled.

[0009] S4. Next, the billet needs to be processed and extruded after reaming: Remove the oxide scale and defects from the inner and outer surfaces of the reamed billet using machining or grinding. Then, wrap the inner and outer surfaces with a copper sheet of 0.5mm to 1mm thickness. Place the heated billet into the extrusion barrel of a 6300-ton horizontal extrusion press for extrusion, including: ① Preheating the extrusion barrel to 250℃ to 350℃, preheating the extrusion die and mandrel to 300℃ to 400℃, and applying graphite lubricant to the inner wall of the extrusion barrel, the extrusion die, and the mandrel surface; ② Heating the copper-coated billet to 730℃ to 850℃ in an electric resistance furnace; ③ Pre-extrusion preparation... Prepare a tail gasket made of ordinary carbon steel. The outer diameter of the tail gasket is 1mm to 4mm smaller than the outer diameter of the billet, and the inner diameter of the tail gasket is 2mm to 5mm larger than the inner diameter of the billet. The length of the tail gasket is 60mm to 100mm. The heating temperature of the tail gasket is 900℃ to 1000℃. Before extrusion, it is attached to the back of the billet and extruded together. After extrusion, it automatically separates from the tube body, saving the hot cutting process and reducing the consumption of hot cutting sheets. The extrusion speed is 30mm / s to 80mm / s. The ratio of the cross-sectional area before extrusion to the cross-sectional area after extrusion is 4 to 10. Low-speed extrusion helps to reduce the degree of metal deformation and improve the stability of metal flow. After extrusion, air cool to room temperature.

[0010] S5. Subsequently, pickling to remove copper plating and finishing of extruded pipes are required: copper plating of extruded pipes is removed in acid solution. The acid solution ratio is 20% to 35% nitric acid, with the remainder being water. No other acid solution is added. The band saw is flattened, and the inner and outer surfaces are polished to remove surface defects.

[0011] S6. Finally, cold rolling, annealing, and finished product inspection, marking, and bundling are required. A two-roll cold rolling mill is used for one or more passes of cold rolling deformation, with a feed rate of 2.5-3.5 mm / pass and a rolling speed of 30-50 passes / minute. The cold rolling deformation per pass is 30%-45%. After each pass of cold rolling, annealing and degreasing are performed. Annealing is carried out in a vacuum furnace or atmosphere furnace at a temperature of 500℃-590℃. The zirconium alloy tubes are straightened, flattened, hydropressurized, and polished on both the inner and outer surfaces. Then, the dimensions and microstructure are tested. Finally, the tubes are marked, bundled, and put into storage.

[0012] Preferably, the outer diameter of the zirconium alloy tube is set to φ19mm~φ245mm, and the wall thickness of the zirconium alloy tube is set to 1.5mm~20mm.

[0013] Preferably, the graphite lubricant used in the extrusion stage is composed of calcium-based grease, graphite, and cylinder oil, and the components are in the following mass ratio: calcium-based grease: graphite: cylinder oil = 2:1:0.5. They need to be mixed evenly before use.

[0014] Preferably, a forming mold device for high-precision seamless zirconium alloy tubes includes a vertical reamer. The vertical reamer includes a reamer barrel, which is composed of a reamer barrel liner and a reamer barrel shell. A base is fixedly installed at the bottom of the reamer barrel by high-strength bolts. An ejection mechanism is provided through the center of the bottom of the reamer barrel. A shear ring support is provided at the top of the base, and a shear ring is provided at the top of the shear ring support. A force transmission rod is provided on one side of the reamer barrel. A reamer pin is provided at one end of the force transmission rod through a threaded connector, and a reamer head is provided at one end of the reamer pin.

[0015] Preferably, a forming die device for high-precision seamless zirconium alloy tubes includes a horizontal extruder. The horizontal extruder includes an extrusion barrel, which is composed of an extrusion barrel liner, an extrusion barrel middle liner, and an extrusion barrel outer shell. A mandrel is provided on the inner side of the extrusion barrel outer shell. An extrusion pad is fitted on one end of the mandrel. A mandrel connector is provided on one side of the extrusion pad. A mandrel support is provided on one end of the mandrel connector. An extrusion rod is fitted on the outer side of the mandrel support. A die base is provided on the other end of the mandrel. An integral conical extrusion die and a die support are provided inside the die base. A die middle pad and a die tail pad are sequentially provided on the rear side of the die support.

[0016] Preferably, the diameter of the reaming needle is 5mm to 10mm smaller than the diameter of the working section of the reaming head, the inner diameter of the shearing ring is 1mm to 2mm larger than the diameter of the working section of the reaming head, the deviation of the reaming needle from the center line of the reaming barrel is not greater than 1mm, the inner lining of the reaming barrel has a taper of 0.4mm to 1mm in the inner circle length direction, and the thickness of the inner lining of the reaming barrel is less than the thickness of the outer shell of the reaming barrel.

[0017] Preferably, the inner liner and the middle liner of the extrusion barrel are assembled with an interference fit. The shape of the front end of the extrusion barrel is designed to correspond to the shape of the mold base. The deviation of the extrusion rod from the center line of the extrusion barrel shall not exceed 0.5mm. The mandrel is connected to the mandrel support by a threaded connection through the mandrel connector. The gap between the extrusion rod and the inner liner of the extrusion barrel is 4mm to 5mm. The gap between the maximum outer diameter of the mandrel support and the inner hole of the extrusion rod is 0.1mm to 0.5mm.

[0018] Preferably, the cavity size of the die support is 10mm to 15mm larger than the cavity size of the integrated conical extrusion die, the cavity size of the die pad is 15mm to 20mm larger than the cavity size of the die support, and the cavity size of the die tail pad is 20mm to 25mm larger than the cavity size of the die pad. The cavities of the integrated conical extrusion die, die support, die pad, and die tail pad are all circular, and the centerline deviation is no more than 0.6mm. A lifting hole is designed at the top, and a slot is used for fixing at the bottom.

[0019] Preferably, the gap between the outer circle of the extrusion pad and the inner hole of the extrusion barrel is 1.0mm to 2.5mm, which is increased appropriately as the outer circle increases. The gap between the inner hole of the extrusion pad and the mandrel is 1.5mm to 2.5mm. The length of the extrusion pad is 200mm to 210mm. The part of the mandrel connector that connects to the mandrel is machined with an internal thread, and the part of the mandrel connector that connects to the mandrel support is machined with an external thread. The integrated conical extrusion die consists of an inlet transition zone, an intermediate sizing zone, and an outlet reverse cone, and has a thickness of 100mm. The included angle α corresponding to the assembly with the extrusion barrel is 60°. The included angle β at the inlet of the integrated conical extrusion die is 58° to 62°. The included angle δ at the outlet of the integrated conical extrusion die is 8° to 10°, and the length L of the intermediate sizing zone is 10mm to 15mm.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention discloses a forming method and die apparatus for high-precision seamless zirconium alloy tubes. Through research on smelting processes, reaming process parameters, reaming die design, extrusion process parameters, extrusion die design, and cold rolling process parameters, it provides a forming method and die apparatus for high-precision seamless zirconium alloy tubes. The integral conical die facilitates smooth metal flow during extrusion, transforming concentrated deformation into gradual deformation, reducing extrusion pressure. Low-speed extrusion reduces the severity of metal deformation and improves the uniformity of metal flow, solving the problem of tube cracking when using flat dies for extrusion. The cold rolling process improves the surface quality, internal structure, and performance quality of the zirconium tube. Zirconium alloy tubes produced using this invention have high dimensional accuracy, good surface quality, and high yield, meeting the material requirements of high-end applications. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of the zirconium alloy tube forming method of the present invention;

[0023] Figure 2 This is a schematic diagram of the mold structure of the hole reamer of the present invention;

[0024] Figure 3 This is a schematic diagram of the die structure of the extruder of the present invention;

[0025] Figure 4 This is a schematic and perspective view of the extrusion barrel of the present invention;

[0026] Figure 5 These are schematic diagrams and perspective views of the module assembly of the present invention;

[0027] Figure 6 These are schematic diagrams and perspective views of the mold base of the present invention;

[0028] Figure 7 This is a schematic diagram of the integral conical extrusion die of the present invention;

[0029] Figure 8 This is a schematic diagram of the mold support of the present invention;

[0030] Figure 9 This is a schematic diagram of the mandrel connector of the present invention.

[0031] In the diagram: 1. Ejection mechanism; 11. Mandrel support; 12. Extrusion rod; 13. Mandrel connector; 14. Extrusion pad; 15. Mandrel; 2. Base; 21. Extrusion barrel liner; 22. Extrusion barrel inner liner; 23. Extrusion barrel outer shell; 24. Extrusion barrel; 3. Shear ring support; 31. Integrated conical extrusion die; 32. Die support; 33. Die base; 34. Die inner pad; 35. Die tail pad; 4. Shear ring; 5. Expanding barrel; 51. Expanding barrel liner; 52. Expanding barrel outer shell; 6. Expanding head; 7. Expanding pin; 8. Force transmission rod. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] like Figures 1-9As shown, the present invention provides a technical solution: a forming mold device for high-precision seamless zirconium alloy tubes, including a vertical reamer. The vertical reamer includes a reamer barrel 5, which is composed of a reamer barrel liner 51 and a reamer barrel shell 52, facilitating subsequent disassembly and maintenance while increasing the overall structural strength. A base 2 is fixedly installed at the bottom of the reamer barrel 5 by high-strength bolts, which supports the reamer barrel and increases the overall stability of the reaming process. An ejection mechanism 1 is provided through the center of the bottom of the reamer barrel 5, which can eject the processed blank in real time, making the discharge efficiency higher and the effect better, avoiding damage to the blank caused by forced discharge. A shearing ring support 3 is provided at the top of the base 2. A shearing ring 4 is provided on the top of the support 3. The base 2 supports the shearing ring support 3, and the shearing ring support 3 supports the shearing ring 4 and the billet, effectively increasing the overall stability of its use. A force transmission rod 8 is provided on one side of the expansion barrel 5. One end of the force transmission rod 8 is provided with an expansion pin 7 through a threaded connection. One end of the expansion pin 7 is provided with an expansion head 6. The force transmission rod 8 applies expansion force to the expansion head 6 through the expansion pin 7, and the expansion head 6 performs the expansion operation. The thickness of the inner lining 51 of the expansion barrel is less than the thickness of the outer shell 52 of the expansion barrel. The horizontal extrusion press includes an extrusion barrel 24, which is composed of an inner lining 21, a middle lining 22, and an outer shell 23, which can effectively increase the strength of the extrusion barrel. To enhance the overall structural strength and prevent damage during use, a mandrel 15 is installed inside the outer shell 23 of the extrusion barrel. An extrusion pad 14 is fitted onto one end of the mandrel 15, increasing in size as the outer diameter increases. A mandrel connector 13 is installed on one side of the extrusion pad 14, serving as a connection limiter and fixation element, improving stability during use and preventing displacement. A mandrel support 11 is installed at one end of the mandrel connector 13, with an extrusion rod 12 fitted onto the outside of the mandrel support 11. A mold base 33 is installed at the other end of the mandrel 15. Inside the mold base 33 are an integral conical extrusion mold 31 and a mold support 32. A mold in-mold pad 34 and a mold tail pad 35 are sequentially installed on the rear side of the mold support 32. The middle pad 34 and the die tail pad 35 together fix and support the integrated conical extrusion die 31 and bear the extrusion force. The extrusion barrel liner 21 and the extrusion barrel middle liner 22 are assembled with an interference fit. The front end structure of the extrusion barrel 24 is designed to correspond to the structure of the die base 33. The mandrel 15 is connected to the mandrel support 11 by the mandrel connector 13 by a thread. The extrusion pad 14 applies force to the blank to deform it. The cavity shape of the integrated conical extrusion die 31, the die support 32, the middle pad 34 and the die tail pad 35 are all circular. The upper part is designed with a lifting hole and the bottom is fixed with a slot. The front end of the extrusion pad 14 is the blank and the rear end is the extrusion rod 12. The extrusion pad 14 plays the role of transmitting the thrust of the extrusion rod 12.

[0034] 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 method for forming high-precision seamless zirconium alloy tubing, characterized in that: Includes the following steps: S1. First, zirconium alloy billet smelting and forging is required: sponge zirconium and alloying elements are pressed together into rod-shaped electrodes, and the ingot is obtained by two melting processes using vacuum self-consumption process. Before forging, the ingot is heated in a box-type resistance furnace. In order to reduce high-temperature oxidation, the ingot can be protected with a glass coating. The cylindrical billet is forged, and the forging pressure ratio is greater than 3.

5. S2. Next, the blank needs to be processed: the forged blank is cut according to the finished product size, 3mm to 10mm is machined off one side of the outer circle, and a through hole with a diameter of 45mm to 80mm is machined in the center; the blank is processed according to the blank drawing: the γ angle of the flared mouth of the blank head is 46.0°, the M value is the diameter of the working section of the reaming head, and the L value is calculated according to the γ angle using trigonometric function relationship. The inner and outer circles are machined, ground and polished to remove scratches, tool marks and other defects. The surface roughness Ra≤6.3μm, the diameter deviation ±1.0mm, the length deviation ±10mm, and the perpendicularity of both ends ≤1mm; S3. Furthermore, the billet needs to undergo anti-oxidation treatment and reaming: The processed billet is heated to 80℃~95℃ in an electric resistance furnace, coated with boron nitride anti-oxidation paint, and then placed in the reaming barrel of a 2500-ton vertical reamer for one or two reaming operations, including ① preheating the reaming barrel to 100℃~300℃ and coating the inner wall of the reaming barrel with graphite emulsion; ② heating the billet to 780℃~1100℃; ③ applying glass powder lubricant to the inner and outer surfaces of the billet; the outer diameter of the billet is 7mm~15mm smaller than the inner diameter of the reaming barrel, with the flared end of the billet facing upwards, and the reaming head is placed at the flared end of the billet for reaming, with a reaming speed of 120mm / s~180mm / s, and the ratio of the cross-sectional area before reaming to the cross-sectional area after reaming is 1.01~1.30, followed by air cooling; S4. Next, the billet needs to be processed and extruded after reaming: Remove the oxide scale and defects from the inner and outer surfaces of the reamed billet using machining or grinding. Then, wrap the inner and outer surfaces with a copper sheet of 0.5mm to 1mm thickness. Place the heated billet into the extrusion barrel of a 6300-ton horizontal extrusion press for extrusion, including: ① Preheating the extrusion barrel to 250℃ to 350℃, preheating the extrusion die and mandrel to 300℃ to 400℃, and applying graphite lubricant to the inner wall of the extrusion barrel, the extrusion die, and the mandrel surface; ② Heating the copper-coated billet to 730℃ to 850℃ in an electric resistance furnace; ③ Pre-extrusion preparation... Prepare a tail gasket made of ordinary carbon steel. The outer diameter of the tail gasket is 1mm to 4mm smaller than the outer diameter of the billet, and the inner diameter of the tail gasket is 2mm to 5mm larger than the inner diameter of the billet. The length of the tail gasket is 60mm to 100mm. The heating temperature of the tail gasket is 900℃ to 1000℃. Before extrusion, it is attached to the back of the billet and extruded together. After extrusion, it automatically separates from the tube body, saving the hot cutting process and reducing the consumption of hot cutting sheets. The extrusion speed is 30mm / s to 80mm / s. The ratio of the cross-sectional area before extrusion to the cross-sectional area after extrusion is 4 to 10. Low-speed extrusion helps to reduce the degree of metal deformation and improve the stability of metal flow. After extrusion, air cool to room temperature. S5. Subsequently, pickling to remove copper plating and finishing of extruded pipes are required: copper plating of extruded pipes is removed in acid solution. The acid solution ratio is: 20% to 35% nitric acid, the rest is water, and no other acid solution is added. The band saw is flattened, and the inner and outer surfaces are polished to remove surface defects. S6. Finally, cold rolling, annealing, and finished product inspection, marking, and bundling are required. A two-roll cold rolling mill is used for one or more passes of cold rolling deformation, with a feed rate of 2.5-3.5 mm / pass and a rolling speed of 30-50 passes / minute. The cold rolling deformation per pass is 30%-45%. After each pass of cold rolling, annealing and degreasing are performed. Annealing is carried out in a vacuum furnace or atmosphere furnace at a temperature of 500℃-590℃. The zirconium alloy tubes are straightened, flattened, hydropressurized, and polished on both the inner and outer surfaces. Then, the dimensions and microstructure are tested. Finally, the tubes are marked, bundled, and put into storage.

2. The forming method of a high-precision seamless zirconium alloy tube according to claim 1, characterized in that: The outer diameter of the zirconium alloy tube is set to φ19mm~φ245mm, and the wall thickness of the zirconium alloy tube is set to 1.5mm~20mm.

3. The forming method of a high-precision seamless zirconium alloy tube according to claim 1, characterized in that: The graphite lubricant used in the extrusion stage consists of calcium-based grease, graphite, and cylinder oil, with the components in a mass ratio of calcium-based grease: graphite: cylinder oil = 2:1:0.

5. They need to be mixed evenly before use.

4. A forming die device for high-precision seamless zirconium alloy tubes, based on the forming method for high-precision seamless zirconium alloy tubes according to claim 1, comprising a vertical reamer, characterized in that: The vertical reaming machine includes a reaming barrel (5), which is composed of a reaming barrel liner (51) and a reaming barrel shell (52). A base (2) is fixedly installed at the bottom of the reaming barrel (5) by high-strength bolts. An ejection mechanism (1) is provided through the center of the bottom of the reaming barrel (5). A shear ring support (3) is provided at the top of the base (2). A shear ring (4) is provided at the top of the shear ring support (3). A force transmission rod (8) is provided on one side of the reaming barrel (5). A reaming needle (7) is provided at one end of the force transmission rod (8) through a threaded connector. A reaming head (6) is provided at one end of the reaming needle (7).

5. The forming die device for high-precision seamless zirconium alloy tubes according to claim 4, characterized in that: The diameter of the expanding needle (7) is 5mm to 10mm smaller than the working section diameter of the expanding head (6), the inner diameter of the shearing ring (4) is 1mm to 2mm larger than the working section diameter of the expanding head (6), the expansion needle (7) deviates from the center line of the expanding barrel (5) by more than 1mm, the inner lining (51) of the expanding barrel has a taper of 0.4mm to 1mm in the inner circle length direction, and the thickness of the inner lining (51) of the expanding barrel is less than the thickness of the outer shell (52) of the expanding barrel.

6. A forming die device for high-precision seamless zirconium alloy tubes, based on the forming method for high-precision seamless zirconium alloy tubes according to claim 1, comprising a horizontal extrusion press, characterized in that: The horizontal extrusion press includes an extrusion barrel (24), which is composed of an extrusion barrel liner (21), an extrusion barrel middle liner (22), and an extrusion barrel shell (23). A mandrel (15) is provided on the inner side of the extrusion barrel shell (23). An extrusion pad (14) is fitted on one end of the mandrel (15). A mandrel connector (13) is provided on one side of the extrusion pad (14). A mandrel support (11) is provided on one end of the mandrel connector (13). An extrusion rod (12) is fitted on the outer side of the mandrel support (11). A die holder (33) is provided on the other end of the mandrel (15). An integral conical extrusion die (31) and a die support (32) are provided inside the die holder (33). A die middle pad (34) and a die tail pad (35) are sequentially provided on the rear side of the die support (32).

7. The forming die device for high-precision seamless zirconium alloy tubes according to claim 6, characterized in that: The inner liner (21) and the middle liner (22) of the extrusion barrel are assembled with an interference fit. The front end structure of the extrusion barrel (24) is designed to correspond to the structure of the mold base (33). The deviation of the extrusion rod (12) from the center line of the extrusion barrel (24) shall not exceed 0.5mm. The mandrel (15) is connected to the mandrel support (11) by means of a thread through the mandrel connector (13). The gap between the extrusion rod (12) and the inner liner (21) of the extrusion barrel is 4mm to 5mm. The gap between the maximum outer diameter of the mandrel support (11) and the inner hole of the extrusion rod (12) is 0.1mm to 0.5mm.

8. The forming mold device for high-precision seamless zirconium alloy tubes according to claim 6, characterized in that: The cavity size of the mold support (32) is 10mm to 15mm larger than that of the integrated conical extrusion mold (31). The cavity size of the mold pad (34) is 15mm to 20mm larger than that of the mold support (32). The cavity size of the mold tail pad (35) is 20mm to 25mm larger than that of the mold pad (34). The cavities of the integrated conical extrusion mold (31), mold support (32), mold pad (34) and mold tail pad (35) are all circular, and the center line deviation is no more than 0.6mm. The upper part is designed with a lifting hole, and the bottom is fixed with a slot.

9. The forming die device for high-precision seamless zirconium alloy tubes according to claim 6, characterized in that: The gap between the outer circle of the extrusion pad (14) and the inner hole of the extrusion barrel (24) is 1.0 mm to 2.5 mm, which increases appropriately as the outer circle increases. The gap between the inner hole of the extrusion pad (14) and the mandrel (15) is 1.5 mm to 2.5 mm. The length of the extrusion pad (14) is 200 mm to 210 mm. The part where the mandrel connector (13) connects to the mandrel (15) is machined with an internal thread. The part where the mandrel connector (13) connects to the mandrel support (11) is machined with an external thread. The integrated conical extrusion die (31) consists of an inlet transition zone, an intermediate sizing zone and an outlet reverse cone, and has a thickness of 100 mm. The included angle α corresponding to the assembly with the extrusion barrel (24) is 60°. The included angle β at the inlet of the integrated conical extrusion die (31) is 58° to 62°. The included angle δ at the outlet of the integrated conical extrusion die (31) is 8° to 10°, and the length of the intermediate sizing zone L is 10 mm to 15 mm.

Images