Preparation method for improving straightness of small-specification thin-wall titanium alloy pipe

Abstract

The invention discloses a preparation method for improving straightness of a small-specification thin-wall titanium alloy pipe. The method comprises the steps that firstly, after the titanium alloy thin-wall pipe is subjected to acid pickling and oil removal, the two ends of the titanium alloy thin-wall pipe are punched; 2, loading on a material lifting frame of a vacuum well type annealing furnace; 3, calculating the mass of a heavy object needing to be hung according to the cross sectional area and the yield strength of the titanium alloy thin-wall pipe, and then hanging a high-temperature-resistant heavy object at the lower end of the loaded titanium alloy thin-wall pipe; 4, cooling along with the furnace after annealing; and 5, taking out to obtain the titanium alloy thin-wall pipe. In the annealing heat treatment process of the small-specification thin-wall titanium alloy pipe, the heavy object is hung according to the cross sectional area and the yield strength of the pipe, so that the strength of the titanium alloy thin-wall pipe is reduced, and meanwhile, the titanium alloy thin-wall pipe is subjected to a pulling force caused by vertically assembling the heavy object below, and residual stress is effectively prevented from being generated in the cold straightening process; the thin-wall titanium alloy pipe with good surface quality, stable performance and up-to-standard straightness is obtained, and the application requirement of an aviation hydraulic system for hydraulic pipes is met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of non-ferrous metal material processing, and particularly relates to a preparation method for improving straightness of small-size thin-wall titanium alloy pipe. BACKGROUND

[0002] Thin-wall titanium alloy pipes have a wide range of applications in the fields of aerospace, medical devices, chemical industry and sports products due to their excellent properties such as high strength, low density and good corrosion resistance. At present, small-size thin-wall titanium alloy pipes are prepared by means of cross piercing or hot extrusion pipe blanking followed by cold rolling. When the titanium alloy pipe is prepared by cold rolling, the wall thickness and outer diameter of the pipe are gradually reduced through multiple passes of rolling, and the deformation amount in the whole deformation process is large, and the length of the finally prepared finished pipe is long, so it is difficult to guarantee the straightness of the pipe.

[0003] The commonly used straightening methods include mechanical straightening and hot straightening. In the straightening process, a large friction force and pressure are generated at the contact part between the pipe and the straightening equipment. The surface of the thin-wall titanium alloy pipe is relatively soft, and surface damage such as scratches and indentations is likely to occur, which affects the appearance quality and surface properties of the pipe. In some application scenarios with extremely high requirements for surface quality, such as aerospace and high-end medical devices, such damage may cause the pipe to be scrapped. In addition, mechanical straightening relies on external force to cause plastic deformation of the pipe to achieve straightening. For thin-wall titanium alloy pipes, this may change the grain structure inside the pipe, causing defects such as lattice distortion and dislocation, and thus affecting the mechanical properties of the pipe such as strength, toughness and fatigue performance, and reducing the overall quality and reliability of the pipe.

[0004] The temperature range of the hot straightening process is relatively narrow. If the temperature is too low, it is difficult to achieve straightening effect, and if the temperature is too high, it may cause grain growth and deterioration of the microstructure of the titanium alloy pipe, affecting the mechanical properties such as strength and toughness of the pipe. In a high-temperature environment, the surface of the titanium alloy pipe is prone to react with oxygen in the air to form an oxide layer, affecting the surface quality and corrosion resistance of the pipe, and additional surface treatment process may be required to remove the oxide layer. In addition, if hydrogen exists in the environment during the hot straightening process, the titanium alloy pipe may absorb hydrogen atoms, causing hydrogen embrittlement, reducing the toughness and fatigue resistance of the pipe, and increasing the risk of pipe rupture during use. SUMMARY

[0005] The technical problems to be solved by the present application are to provide a preparation method for improving the straightness of small-size thin-wall titanium alloy pipes to solve the problems of the prior art.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a preparation method for improving the straightness of small-size thin-wall titanium alloy pipes, characterized in that the method comprises the following steps: Step one: pipe punching: after the titanium alloy thin-wall pipe prepared by cold rolling or cold spinning is pickled to remove oil, holes are punched at both ends for hoisting; Step two: pipe hoisting: the titanium alloy thin-wall pipe with holes punched in step one is loaded onto a material hoisting frame of a vacuum pit-type annealing furnace; Step three: hanging heavy objects: according to the cross-sectional area and yield strength of the titanium alloy thin-wall pipe loaded in step two, the mass of the heavy objects to be hung is calculated, and then high-temperature-resistant heavy objects are hung at the lower end of the loaded titanium alloy thin-wall pipe according to the calculation result; Step four: pipe vacuum annealing: the titanium alloy thin-wall pipe with high-temperature-resistant heavy objects hung in step three is annealed in a vacuum annealing furnace, and after the annealing holding time ends, the pipe is cooled in the furnace; Step five: pipe discharge: the titanium alloy thin-wall pipe cooled in step four is taken out, the high-temperature-resistant heavy objects are removed, and a titanium alloy thin-wall pipe with straightness meeting the national standard requirements is obtained.

[0007] The preparation method for improving the straightness of small-size thin-wall titanium alloy pipes, characterized in that the outer diameter of the titanium alloy thin-wall pipe in step one is 20-30 mm, and the wall thickness is 1-2 mm.

[0008] The preparation method for improving the straightness of small-size thin-wall titanium alloy pipes, characterized in that the hole diameter of the holes punched at both ends of the titanium alloy thin-wall pipe in step one is 4-6 mm, and the distance between the punching position and the two end heads of the titanium alloy thin-wall pipe is 40 mm.

[0009] The preparation method for improving the straightness of small-size thin-wall titanium alloy pipes, characterized in that the formula for calculating the mass of the heavy objects to be hung in step three is: wherein M is the mass of the heavy objects to be hung, in kg; S is the cross-sectional area of the titanium alloy thin-wall pipe, in mm2; Y is the yield strength of the titanium alloy thin-wall pipe at room temperature, in MPa; and K is a calculation coefficient, and K=1.5×10-4. wherein M is the mass of the heavy objects to be hung, in kg; S is the cross-sectional area of the titanium alloy thin-wall pipe, in mm2; Y is the yield strength of the titanium alloy thin-wall pipe at room temperature, in MPa; and K is a calculation coefficient, and K=1.5×10-4.-4 2.0 x 10 -4 ; is the weight of the annealed pipe, in kg.

[0010] The preparation method for improving the straightness of small-size thin-walled titanium alloy pipe has the characteristics that the high-temperature-resistant heavy object in step three is a metal block with a density greater than that of the thin-walled titanium alloy pipe, and is not easy to evaporate in the annealing process in step four.

[0011] The preparation method for improving the straightness of small-size thin-walled titanium alloy pipe has the characteristics that the annealing temperature in step four is 550 DEG C to 650 DEG C, and the annealing holding time is 2h to 5h. Generally, the annealing temperature is controlled in the stress relieving annealing temperature range of the thin-walled titanium alloy pipe.

[0012] The preparation method for improving the straightness of small-size thin-walled titanium alloy pipe has the characteristics that the annealing in step four adopts a vacuum annealing process, and the vacuum degree in the annealing process is better than 5 x 10 -3 Pa.

[0013] The preparation method for improving the straightness of small-size thin-walled titanium alloy pipe has the characteristics that the straightness of the thin-walled titanium alloy pipe obtained after the high-temperature-resistant heavy object is removed in step five is not more than 2.3mm / m.

[0014] Compared with the prior art, the present application has the following advantages: 1. According to the cross-sectional area and yield strength of the pipe, the present application assembles a heavy object on the thin-walled titanium alloy pipe before annealing, so that the strength of the thin-walled titanium alloy pipe is reduced during the annealing heat treatment process, and the pipe is subjected to a pulling force caused by the vertically assembled heavy object, thereby exerting a uniform and stable force on the thin-walled titanium alloy pipe, effectively avoiding residual stress generated in the cold straightening process, significantly improving the straightness of the thin-walled titanium alloy pipe, and obtaining a thin-walled titanium alloy pipe with good surface quality, stable performance and up-to-standard straightness, which meets the application requirements of the hydraulic system for hydraulic pipes.

[0015] 2. The method for assembling a heavy object during the annealing process of the thin-walled titanium alloy pipe can obtain the required mass of the assembled heavy object according to the cross-sectional area and yield strength of the thin-walled titanium alloy pipe, effectively improves the straightness of the thin-walled titanium alloy pipe, and can adjust the straightness by reasonably selecting the mass of the assembled heavy object for pipes with different strength and toughness characteristics, and is suitable for thin-walled titanium alloy pipes of different grades.

[0016] 3、The weight straightening method adopted by the present application slowly corrects the straightness of the titanium alloy thin-walled pipe through gravity, avoids damage such as pipe surface scratch and deformation caused by forced correction through mechanical external force, has low damage risk to the surface and internal structure of the titanium alloy thin-walled pipe, and effectively maintains the integrity and original performance of the titanium alloy thin-walled pipe.

[0017] 4、Compared with the prior art method which needs to use advanced correction equipment or complex process, the weight straightening method provided by the present application only needs to make and install the hanging weight, and anneal using a conventional annealing furnace, without the need to purchase expensive professional equipment, consume a large amount of energy and special materials, greatly reducing the production cost, improving the production efficiency, and being simple to operate and easy to implement.

[0018] The technical solutions of the present application are further described in detail below through examples. DETAILED DESCRIPTION

[0019] The TA18, TC16 and TB2 titanium alloy thin-walled pipes used in the embodiments 1-5 are all prepared by cold rolling process and have poor straightness, all greater than 5 mm / m.

[0020] Embodiment 1 This embodiment includes the following steps: Step one, pipe punching: after the TA18 titanium alloy thin-walled pipe prepared by cold rolling and having a specification of outer diameter x wall thickness x length Φ30mm x 2.0mm x 3600mm is degreased by pickling, holes with a diameter of 6mm are punched at a distance of 40mm from both ends of the TA18 titanium alloy thin-walled pipe for hoisting; the straightness of the TA18 titanium alloy thin-walled pipe is 6.5mm / m; Step two, pipe hoisting: the TA18 titanium alloy thin-walled pipe punched in step one is loaded onto a material hoisting frame of a vacuum pit-type annealing furnace and fixed with iron wire; Step three, hanging weight: according to the cross-sectional area and yield strength of the TA18 titanium alloy thin-walled pipe loaded and fixed in step two, the mass of the hanging weight required is calculated to be 16kg, and the calculation formula is: , wherein S is the cross-sectional area of the TA18 titanium alloy thin-walled pipe 175.8mm 2 ; is the yield strength of the TA18 titanium alloy thin-walled pipe at room temperature 815MPa; K is a calculation coefficient, and K=1.5x10 -4 ; is the weight of the TA18 titanium alloy thin-walled pipe 2.85kg; the mass M of the hanging weight is calculated to be about 16kg; and then a 16kg iron block is hung under the loaded TA18 titanium alloy thin-walled pipe; Step four, pipe vacuum annealing: the TA18 titanium alloy thin-walled pipe in step three is hung after the TA18 titanium alloy thin-walled pipe in step three is hung in the vacuum annealing furnace for stress relief annealing, the annealing temperature is 550℃, the annealing holding time is 2h, and the vacuum degree in the annealing process is better than 5*10 -3 Pa, after the annealing holding time ends, the furnace is cooled; Step five, pipe out of the furnace: the TA18 titanium alloy thin-walled pipe cooled in step four is taken out, the 16kg iron block is removed, and the TA18 titanium alloy thin-walled pipe whose straightness reaches the requirement of GB / T3624-2010 "Titanium and Titanium Alloy Seamless Pipe" is obtained.

[0021] After detection, the straightness of the TA18 titanium alloy thin-walled pipe finally obtained in the embodiment is 1.35mm / m.

[0022] Embodiment 2 The embodiment includes the following steps: Step one, pipe punching: the TA18 titanium alloy thin-walled pipe with the specification of outer diameter*wall thickness*length Φ20mm*1.0mm*3500mm prepared by cold rolling is punched at a distance of 40mm from the two ends of the TA18 titanium alloy thin-walled pipe after acid pickling to remove oil, and the hole diameter is 4mm; the straightness of the TA18 titanium alloy thin-walled pipe is 7.8mm / m; Step two, pipe hoisting: the TA18 titanium alloy thin-walled pipe punched in step one is loaded on the hoisting rack of the vacuum pit type annealing furnace and fixed with iron wire; Step three, hanging weight: according to the cross-sectional area and yield strength of the TA18 titanium alloy thin-walled pipe loaded and fixed in step two, the mass of the required hanging weight is calculated to be 8kg, and the calculation formula is: , wherein, S is the cross-sectional area of the TA18 titanium alloy thin-walled pipe 59.66mm 2 ; is the yield strength of the TA18 titanium alloy thin-walled pipe at room temperature 830MPa; K is the calculation coefficient, and K=2.0*10 -4 ; is the weight of the TA18 titanium alloy thin-walled pipe 0.94kg; the mass of M, i.e. the hanging weight, is calculated to be about 8kg; then 8kg iron block is hung under the loaded TA18 titanium alloy thin-walled pipe; Step four, pipe vacuum annealing: the TA18 titanium alloy thin-walled pipe hung after the TA18 titanium alloy thin-walled pipe in step three is hung in the vacuum annealing furnace for stress relief annealing, the annealing temperature is 650℃, the annealing holding time is 2h, and the furnace is cooled after the annealing holding time ends; Step five, pipe out of the furnace: take out the TA18 titanium alloy thin-walled pipe after cooling in step four, remove 8 kg of iron block, and obtain the TA18 titanium alloy thin-walled pipe with straightness reaching the requirements of national standard GB / T3624-2010 "Titanium and Titanium Alloy Seamless Pipe".

[0023] After detection, the straightness of the TA18 titanium alloy thin-walled pipe finally obtained in the embodiment is 2.3 mm / m.

[0024] Example 3 The embodiment includes the following steps: Step one, pipe punching: after acid pickling to remove oil, the TC16 titanium alloy thin-walled pipe with a specification of outer diameter x wall thickness x length Φ25 mm x 1.0 mm x 3600 mm prepared by cold rolling is punched at two ends each 40 mm away from the two end heads of the TC16 titanium alloy thin-walled pipe for hoisting, and the hole diameter is 6 mm; the straightness of the TC16 titanium alloy thin-walled pipe is 6.3 mm / m; Step two, pipe hoisting: the TC16 titanium alloy thin-walled pipe after punching in step one is loaded onto the material hoisting frame of the vacuum pit type annealing furnace and fixed with iron wire; Step three, hanging weight: according to the cross-sectional area and yield strength of the TC16 titanium alloy thin-walled pipe loaded and fixed in step two, the mass of the required hanging weight is calculated to be 16 kg, and the calculation formula is: , wherein S is the cross-sectional area of the TC16 titanium alloy thin-walled pipe 75.36 mm 2 ; is the yield strength of the TC16 titanium alloy thin-walled pipe at room temperature 903 MPa; K is the calculation coefficient, and K = 1.7 x 10 -4 ; is the weight of the TC16 titanium alloy thin-walled pipe 1.22 kg; the mass of M, i.e. the hanging weight, is calculated to be about 9.1 kg; then 9.1 kg of iron block is hung under the loaded TC16 titanium alloy thin-walled pipe; Step four, pipe vacuum annealing: the TC16 titanium alloy thin-walled pipe after hanging in step three is subjected to stress relief annealing in a vacuum annealing furnace, the annealing temperature is 570 ℃, the annealing holding time is 3 h, and after the annealing holding time ends, the furnace is cooled; Step five, pipe out of the furnace: take out the TC16 titanium alloy thin-walled pipe after cooling in step four, remove 9.1 kg of iron block, and obtain the TC16 titanium alloy thin-walled pipe with straightness reaching the requirements of national standard GB / T3624-2010 "Titanium and Titanium Alloy Seamless Pipe".

[0025] After detection, the straightness of the TC16 titanium alloy thin-walled pipe finally obtained in the embodiment is 2.0 mm / m.

[0026] Example 4 The embodiment comprises the following steps: Step one, pipe punching: after the cold-rolled TC16 titanium alloy thin-walled pipe with the specification of outer diameter x wall thickness x length Φ25mm x 1.8mm x 3100mm is pickled to remove oil, holes with a diameter of 5mm are punched at two ends of the TC16 titanium alloy thin-walled pipe, each 40mm away from the two ends of the TC16 titanium alloy thin-walled pipe for hoisting; the straightness of the TC16 titanium alloy thin-walled pipe is 5.9mm / m; Step two, pipe hoisting: the TC16 titanium alloy thin-walled pipe punched in step one is loaded onto the material hoisting frame of the vacuum pit-type annealing furnace and fixed with iron wire; Step three, hanging weight: according to the cross-sectional area and yield strength of the TC16 titanium alloy thin-walled pipe loaded and fixed in step two, the mass of the required hanging weight is calculated to be 17kg, and the calculation formula is: , wherein S is the cross-sectional area of the TC16 titanium alloy thin-walled pipe 131.1mm 2 ; is the yield strength of the TC16 titanium alloy thin-walled pipe at room temperature 915MPa; K is the calculation coefficient, and K = 1.8 x 10 -4 ; is the self-weight of the TC16 titanium alloy thin-walled pipe 2.12kg; the mass of the M, i.e. the hanging weight, is calculated to be about 17kg; then a 17kg iron block is hung at the lower end of the loaded TC16 titanium alloy thin-walled pipe; Step four, pipe vacuum annealing: the TC16 titanium alloy thin-walled pipe hung in step three is subjected to stress relief annealing in the vacuum annealing furnace, the annealing temperature is 600℃, the annealing holding time is 3h, and the vacuum degree during the annealing process is better than 5x10 -3 Pa, and the furnace is cooled after the annealing holding time ends; Step five, pipe discharge: the TC16 titanium alloy thin-walled pipe cooled in step four is taken out, and the 17kg iron block is removed, to obtain the TC16 titanium alloy thin-walled pipe with a straightness reaching the requirements of the national standard GB / T3624-2010 “Titanium and Titanium Alloy Seamless Pipe”.

[0027] After detection, the straightness of the TC16 titanium alloy thin-walled pipe finally obtained in the embodiment is 1.3mm / m.

[0028] Embodiment 5 The embodiment comprises the following steps: Step one, pipe punching: after the cold-rolled TB2 titanium alloy thin-walled pipe with the specification of outer diameter x wall thickness x length Φ30mm x 1.8mm x 2100mm is pickled to remove oil, holes with a diameter of 6mm are punched at two ends of the TB2 titanium alloy thin-walled pipe, each 40mm away from the two ends of the TB2 titanium alloy thin-walled pipe for hoisting; the straightness of the TB2 titanium alloy thin-walled pipe is 6.5mm / m; Step two, pipe hoisting: the TB2 titanium alloy thin-walled pipe after punching in step one is loaded on the material hanging frame of the vacuum pit annealing furnace, and is fixed with iron wire; Step three, hanging weight: according to the cross-sectional area and yield strength of the TB2 titanium alloy thin-walled pipe loaded and fixed in step two, the mass of the required hanging weight is calculated to be 16 kg, and the calculation formula is: , wherein S is the cross-sectional area of the TB2 titanium alloy thin-walled pipe 159.4mm 2 ; is the yield strength of the TB2 titanium alloy thin-walled pipe at room temperature 935MPa; K is a calculation coefficient, and K=1.6×10 -4 ; is the weight of the TB2 titanium alloy thin-walled pipe 1.5kg; the mass M of the hanging weight is calculated to be about 20 kg; then 20 kg of iron block is hung under the loaded TB2 titanium alloy thin-walled pipe; Step four, pipe vacuum annealing: the TB2 titanium alloy thin-walled pipe hung in step three is subjected to stress relief annealing in a vacuum annealing furnace, the annealing temperature is 650℃, the annealing holding time is 5h, and after the annealing holding time ends, the furnace is cooled; Step five, pipe discharge: the TB2 titanium alloy thin-walled pipe cooled in step four is taken out, and the 20 kg iron block is removed, to obtain a TB2 titanium alloy thin-walled pipe with straightness reaching the requirements of GB / T3624-2010 “Titanium and Titanium Alloy Seamless Pipe”.

[0029] After detection, the straightness of the TB2 titanium alloy thin-walled pipe finally obtained in the embodiment is 1.7mm / m.

[0030] The above is only a preferred embodiment of the present application, and does not limit the present application. Any simple modification, change and equivalent change of the above embodiment according to the technical essence of the present application are still within the protection scope of the technical solution of the present application.

Claims

1. A method for improving the straightness of small-diameter thin-walled titanium alloy tubing, characterized in that, The method includes the following steps: Step 1, Pipe Drilling: After pickling and degreasing, the thin-walled titanium alloy pipes prepared by cold rolling or cold forging are drilled at both ends for hoisting. Step 2, Pipe hoisting: Load the titanium alloy thin-walled pipes that have been drilled in Step 1 onto the hoisting rack of the vacuum well annealing furnace; Step 3: Attaching weights: Based on the cross-sectional area and yield strength of the titanium alloy thin-walled tube loaded in Step 2, calculate the required weight mass, and then attach high-temperature resistant weights to the lower end of the loaded titanium alloy thin-walled tube according to the calculation results. Step 4, Vacuum Annealing of Pipes: The thin-walled titanium alloy pipes with high-temperature resistant weights attached in Step 3 are annealed in a vacuum annealing furnace. After the annealing holding time is over, they are cooled with the furnace. Step 5: Tube unloading: Take out the cooled titanium alloy thin-walled tube from Step 4, remove the high-temperature resistant weights, and obtain titanium alloy thin-walled tubes with straightness meeting the requirements of the national standard GB / T3624-2010 "Titanium and Titanium Alloy Seamless Tubes".

2. The method for improving the straightness of small-diameter thin-walled titanium alloy tubing according to claim 1, characterized in that, The outer diameter of the titanium alloy thin-walled tube mentioned in step one is 20mm~30mm, and the wall thickness is 1mm~2mm.

3. The method for improving the straightness of small-diameter thin-walled titanium alloy tubing according to claim 1, characterized in that, In step one, the diameter of the holes drilled at both ends of the titanium alloy thin-walled tube is 4mm to 6mm, and the drilling position is 40mm away from each of the two ends of the titanium alloy thin-walled tube.

4. The method for improving the straightness of small-diameter thin-walled titanium alloy tubing according to claim 1, characterized in that, The formula for calculating the required mass of the hanging weight in step three is as follows: Where M is the mass of the suspended weight, in kg; and S is the cross-sectional area of ​​the titanium alloy thin-walled tube, in mm. 2 ; This represents the yield strength of thin-walled titanium alloy tubing at room temperature, expressed in MPa; K is a calculation coefficient, and K = 1.5 × 10⁻⁶. -4 ~2.0×10 -4 ; This is the weight of the annealed tubing, expressed in kg.

5. The method for improving the straightness of small-diameter thin-walled titanium alloy tubing according to claim 1, characterized in that, The high-temperature resistant weight mentioned in step three is a metal block with a density greater than that of the titanium alloy thin-walled tube, and it is not easily volatilized during the annealing process in step four.

6. The method for improving the straightness of small-diameter thin-walled titanium alloy tubing according to claim 1, characterized in that, The annealing temperature in step four is 550℃~650℃, and the annealing holding time is 2h~5h.

7. The method for improving the straightness of small-diameter thin-walled titanium alloy tubing according to claim 1, characterized in that, The annealing process described in step four employs a vacuum annealing process, and the vacuum level during the annealing process is better than 5×10⁻⁶. -3 Pa.

8. The method for improving the straightness of small-diameter thin-walled titanium alloy tubing according to claim 1, characterized in that, Its features are, The straightness of the titanium alloy thin-walled tube obtained after removing and removing the high-temperature resistant heavy object in step five shall not exceed 2.3 mm / m.

Images