Processing method of TA24 titanium alloy thin-wall large-diameter super-long seamless pipe

Abstract

The invention discloses a processing method of a TA24 titanium alloy thin-wall large-diameter super-long seamless pipe, which comprises the following steps: step 1, carrying out one-heating cogging forging on a TA24 titanium alloy cast ingot to obtain a bar blank; secondly, the bar blank is sequentially and continuously subjected to cross piercing, hot continuous rolling and sizing rolling, and a pipe is obtained; and thirdly, the pipe is sequentially subjected to annealing and machining, and the TA24 titanium alloy thin-wall large-diameter super-long seamless pipe is obtained. According to the machining method, a rod blank is prepared through one-heating-number cogging forging, a thick and large cast structure is crushed to a certain degree, the structure is improved, the plasticity is improved, then the TA24 titanium alloy thin-wall large-diameter super-long seamless pipe is obtained through cross piercing, hot continuous rolling, sizing rolling, annealing and machining, the machining period can be effectively shortened, and the machining cost is reduced. The method is suitable for the technical field of titanium alloy seamless tube machining.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy seamless pipe processing, and in particular relates to a processing method for a TA24 titanium alloy thin-wall large-diameter ultra-long seamless pipe. Background Art

[0002] TA24 titanium alloy is a near-α marine titanium alloy independently developed by my country. It has the characteristics of high specific strength, good welding performance, seawater corrosion resistance and easy hot and cold processing. It has obvious advantages, especially in the sea-going pipeline system with high pressure, fast flow rate and strong medium corrosion, and can significantly improve the reliability of the pipeline system. At present, the development of marine resources has been incorporated into the national development strategy. TA24 titanium alloy has a huge market and development potential in the fields of equipment manufacturing such as military ships, large civilian ships, and offshore drilling platforms. With its significant performance advantages, the application of TA24 titanium alloy in the new generation of ships and seawater pipeline systems has become inevitable, especially as the main specifications of the sea-going system Φ200mm ~ Φ325mm, the diameter-to-thickness ratio D / t is not less than 20, the demand is huge. The production of ultra-long pipes (length ≥ 10000mm) can effectively improve the efficiency of pipe use and reduce manufacturing costs. Based on the current huge market demand, the development prospects of thin-walled large-diameter ultra-long titanium pipes are broad.

[0003] At present, the main production methods of titanium tubes in China include spinning, machining, oblique rolling and perforation, extrusion, hot rolling, cold rolling, etc. The above processes cannot achieve low-cost industrial production of thin-walled, large-diameter, ultra-long titanium alloy seamless tubes due to maturity or process feasibility issues, which seriously restricts its application in the field of marine equipment and ships. The traditional pipe processing method usually prepares the tube blank first, and then processes the tube blank into a tube. Due to the complex process and cumbersome procedures, the final tube yield is only 10% to 30%. For large-diameter thin-walled tubes, the spinning method is usually used. The tube blank is first ring-rolled to thin the tube wall and expand the tube diameter. Then, the spinning process is used to increase the length of the tube and further thin the tube wall, and finally a large-diameter thin-walled titanium tube is obtained. However, the cost of spinning to prepare thin-walled seamless tubes is too high, and the spinning method can generally only be used to manufacture ultra-thin titanium alloy seamless tubes with a short length and a very large diameter-to-thickness ratio. In addition, the machining process has a low yield rate and high cost for pipe production. The oblique-rolled perforated pipes have poor microstructure and performance, the hot-extruded pipes have low dimensional accuracy, the cold-rolled pipes have many rolling passes and a long production cycle. These methods are not suitable for the production of thin-walled, large-diameter, and ultra-long seamless pipes.

[0004] In recent years, many new methods for processing titanium seamless pipes have emerged due to the needs of practical applications. However, most of them are a combination of one or more processes in the traditional seamless pipe processing methods, which cannot specifically solve the problem of low mass production efficiency and yield rate of the above-mentioned thin-walled, large-diameter and ultra-long seamless pipes. For example, the Chinese invention patent "Production Method of Large Diameter Titanium Seamless Pipe" (Announcement No. CN107199243B) adopts ingot Tβ The tube blank is prepared by directly perforating at a temperature of 5°C to 50°C, and then the tube blank is ground and hot-rolled; however, the tube blank structure prepared by this method cannot be completely broken, and the performance of the hot-rolled tube is difficult to guarantee. The Chinese invention patent "A method for producing titanium alloy oil well pipes" (Announcement No. CN103128102B) obtains titanium alloy seamless pipes through a continuous processing method of perforation + continuous rolling, but the specifications and diameter-thickness ratio of the processed oil well pipes are small, and the diameter reduction in the production process is large, which will cause the circumferential instability and folding of the pipe. At the same time, the perforation temperature of this method is too high, and the structure and performance of the pipe after perforation cannot be guaranteed. The Chinese invention patent "A method for efficiently and low-cost preparation of high-strength TC18 titanium alloy seamless pipes" (Announcement No. CN114101372B) strictly controls the processing temperature of the pipe, and the oblique rolling perforation process is at T β The above temperature is 120℃~180℃. Before entering the continuous rolling process, the tube billet needs to be quickly air-cooled to T β ±20℃, before sizing rolling, the tube billet temperature needs to be heated again to compensate to T β ±10℃, this precise temperature control in the continuous processing process undoubtedly greatly increases the difficulty of actual production and reduces the yield of pipes; at the same time, the processing temperature of this method is too high, which is not conducive to the improvement of titanium alloy structure and performance. The high-alloyed TC18 alloy can still improve its performance through subsequent heat treatment, but the low-alloyed TA24 titanium alloy cannot be effectively strengthened by heat treatment.

[0005] In summary, there is currently no short-process, low-cost process for preparing TA24 titanium alloy thin-walled, large-diameter, ultra-long seamless pipes in China. Therefore, actively developing new methods for the production of TA24 titanium alloy thin-walled, large-diameter, ultra-long seamless pipes, shortening the pipe processing process, improving the pipe processing yield, and reducing production costs while ensuring the excellent performance of TA24 thin-walled pipes, and solving the problem of short-process, low-cost, and mass production of titanium alloy thin-walled, large-diameter, ultra-long seamless pipes is of great significance to improving the modernization level of my country's marine equipment. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art and provide a processing method for TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipes. The processing method adopts a single-fire blanking forging to prepare a rod billet, so that the coarse casting structure is broken to a certain extent, the structure is improved and the plasticity is enhanced, and then the TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipes are obtained by continuous and uninterrupted oblique rolling piercing + hot rolling + sizing rolling, and annealing and machining. It can effectively shorten the processing cycle and reduce the production cost, and solves the problem that TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipes cannot be produced in a short process, low cost, and batch.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a method for processing TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe, characterized in that the method comprises the following steps:

[0008] Step 1: Forging the TA24 titanium alloy ingot into a single batch to obtain a rod blank;

[0009] Step 2: The bar blank obtained in step 1 is subjected to continuous and uninterrupted oblique rolling, piercing, hot rolling and sizing rolling in sequence to obtain a pipe;

[0010] Step 3: annealing and machining the tube obtained in step 2 in sequence to obtain a TA24 titanium alloy thin-walled large-diameter ultra-long seamless tube.

[0011] The above-mentioned method for processing a TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe is characterized in that the TA24 titanium alloy ingot in step one is an ingot prepared by VAR smelting or EB smelting.

[0012] The VAR smelting in the present invention is smelting in a consumable electrode smelting furnace, and the EB smelting is smelting in an electron beam cold hearth furnace.

[0013] The above-mentioned method for processing a TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe is characterized in that the temperature of the blank forging in step 1 is (T β +150℃)~(T β +250℃), the T β is the β phase transition temperature of TA24 titanium alloy, in °C.

[0014] The above-mentioned method for processing TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe is characterized in that the deformation amount of the blank forging in step one is greater than 60%.

[0015] The present invention can effectively break up the casting structure and improve the plasticity of the bar material by controlling the deformation amount of the blank forging to be greater than 60%, which is beneficial to the subsequent process.

[0016] The above-mentioned method for processing TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe is characterized in that the temperature of the bar billet during the oblique rolling and perforation in step 2 is (T β -50℃)~T β .

[0017] The above-mentioned method for processing TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipes is characterized in that no supplementary heat treatment is performed during the oblique rolling piercing, hot rolling and sizing rolling processes in step 2.

[0018] The present invention adopts continuous and uninterrupted oblique rolling and piercing, hot rolling and sizing rolling processes, and controls the temperature of the rod billet during oblique rolling and piercing, and can be successfully completed without supplementary heating of the pipe, thereby effectively reducing the number of times of precise temperature control during the processing, reducing the actual production difficulty, and shortening the production preparation cycle.

[0019] The above-mentioned processing method of TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe is characterized in that the size specifications of the TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe in step three are: the outer diameter D is 200mm~325mm, the diameter-to-thickness ratio D / t is not less than 20, and the length is not less than 10000mm; the t is the wall thickness, the unit is mm.

[0020] The above-mentioned method for processing TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipes is characterized in that the yield of the TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipes in step three is not less than 70%.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. The present invention adopts one-time forging to prepare rod blanks, so that the coarse casting structure is broken to a certain extent, which can improve the structure and enhance the plasticity, and provide conditions for subsequent oblique rolling and piercing; compared with the prior art that adopts multiple-time forging to prepare blanks, it can effectively shorten the processing cycle and reduce production costs; compared with the prior art method that adopts direct piercing and rolling of ingots to prepare tube blanks, it can make the rod blank structure initially broken and enhance the plasticity, which is conducive to the smooth progress of subsequent oblique rolling and piercing, hot rolling and further improvement of the performance of TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipes.

[0023] 2. The present invention adopts rod billets instead of tube billets as raw materials to produce and prepare TA24 titanium alloy thin-walled large-diameter ultra-long tubes. By completing the oblique rolling piercing + hot rolling + sizing rolling steps at one time, it is equivalent to completing the two steps of tube billet preparation and tube preparation at one time. Under the premise of ensuring performance, the production process is effectively shortened and the production cost is reduced. Compared with the conventional seamless tube production process with a yield rate of less than 30%, the processing method of the present invention significantly improves the yield rate.

[0024] 3. The present invention adopts the process of large deformation oblique rolling piercing, hot continuous rolling and sizing rolling to strongly crush the grains, replace upsetting and forging to improve the structure and performance of the tube blank; at the same time, by controlling the temperature during oblique rolling piercing to (T β -50℃)~T β , below T β Large deformation at a temperature of is conducive to the formation of equiaxed primary α phase, which can effectively improve the comprehensive mechanical properties of the pipe.

[0025] The technical solution of the present invention is further described in detail below through embodiments. DETAILED DESCRIPTION

[0026] Example 1

[0027] The processing method of this embodiment comprises the following steps:

[0028] Step 1: Cast 1080 kg of TA24 titanium alloy ingot (TA24 titanium alloy nominal composition is Ti-3.4Al-2Mo-2.2Zr-0.04O, T β =943°C) is subjected to a first heat forging and drawing at 1190°C to obtain a bar blank with a diameter of 320 mm, and after cooling, it is machined to obtain a 1005 kg bare bar blank with a diameter of 310 mm; the TA24 titanium alloy ingot is an ingot prepared by VAR smelting, and the deformation amount of the forging is 70%;

[0029] Step 2: The 310 mm diameter bare bar blank obtained in step 1 is heated at 940° C. for 2 h, and then subjected to continuous and uninterrupted oblique rolling, hot rolling and sizing rolling in sequence. The whole process is carried out continuously without supplementary heating, and a 328 mm×18 mm (diameter×wall thickness) pipe is obtained;

[0030] Step 3: Anneal and machine the 328mm×18mm (diameter×wall thickness) pipe obtained in step 2 in sequence to obtain 790kg of TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe with a specification of 325mm×15mm×12000mm (diameter×wall thickness×length).

[0031] After testing, the room temperature mechanical properties of the TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe prepared in this embodiment are as follows: tensile strength R m The yield strength is 713MPa and R p0.2 The tensile strength is 621 MPa, the elongation A is 18.0%, and the pipe yield is 73.1%, which shows that the processing method of this embodiment not only shortens the production cycle of TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipes, improves the raw material utilization rate, but also the prepared TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipes have excellent comprehensive mechanical properties.

[0032] Example 2

[0033] The processing method of this embodiment comprises the following steps:

[0034] Step 1: Cast 460 kg of TA24 titanium alloy ingot (TA24 titanium alloy nominal composition is Ti-3.5Al-2.1Mo-2.4Zr-0.13O, T β=969°C) is subjected to a first heat forging and drawing at 1120°C to obtain a bar blank with a diameter of 238 mm, and after cooling, it is machined to obtain a 430 kg bare bar blank with a diameter of 230 mm; the TA24 titanium alloy ingot is an ingot prepared by EB smelting, and the deformation amount of the forging is 65%;

[0035] Step 2: The 230 mm diameter bare bar obtained in step 1 is heated at 920° C. for 2 h, and then subjected to continuous and uninterrupted oblique rolling, hot rolling and sizing rolling in sequence. The whole process is carried out continuously without supplementary heating, and a 202 mm×10 mm (diameter×wall thickness) pipe is obtained;

[0036] Step 3: Anneal and machine the 202mm×10mm (diameter×wall thickness) pipe obtained in step 2 in sequence to obtain 328kg of TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe with a specification of 200mm×8mm×15000mm (diameter×wall thickness×length).

[0037] After testing, the room temperature mechanical properties of the TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe prepared in this embodiment are as follows: tensile strength R m The yield strength is 747MPa and R p0.2 The tensile strength is 656MPa, the elongation A is 20.5%, and the pipe yield is 71.3%, which shows that the processing method of this embodiment not only shortens the production cycle of TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipes, improves the raw material utilization rate, but also the prepared TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipes have excellent comprehensive mechanical properties.

[0038] Example 3

[0039] The processing method of this embodiment comprises the following steps:

[0040] Step 1: Cast 720 kg of TA24 titanium alloy ingot (TA24 titanium alloy nominal composition is Ti-3.4Al-2.1Mo-2.3Zr-0.12O, T β =963°C) is subjected to a first heat forging at 1150°C and stretched to obtain a rod blank with a diameter of 278 mm, and after cooling, it is machined to obtain a 668 kg bare rod blank with a diameter of 270 mm; the TA24 titanium alloy ingot is an ingot prepared by EB smelting, and the deformation amount of the forging is 65%;

[0041] Step 2: The 270 mm diameter bare bar blank obtained in step 1 is heated at 930° C. for 2 h, and then subjected to continuous and uninterrupted oblique rolling, hot rolling and sizing rolling in sequence. The whole process is carried out continuously without supplementary heating, and a 277 mm×14 mm (diameter×wall thickness) pipe is obtained;

[0042] Step 3: Anneal and machine the 277mm×14mm (diameter×wall thickness) pipe obtained in step 2 in sequence to obtain 540kg of TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe with a specification of 275mm×12mm×12000mm (diameter×wall thickness×length).

[0043] After testing, the room temperature mechanical properties of the TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe prepared in this embodiment are as follows: tensile strength Rm is 727MPa, yield strength Rp0.2 is 632MPa, elongation A is 21.0%, and the pipe finished product rate is 75.0%; this shows that the processing method of this embodiment not only shortens the production cycle of the TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe, improves the raw material utilization rate, but also the prepared TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe has excellent comprehensive mechanical properties.

[0044] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for processing TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe, characterized in that: The method comprises the following steps: Step 1: Forging the TA24 titanium alloy ingot into a single batch to obtain a rod blank; Step 2: The bar blank obtained in step 1 is subjected to continuous and uninterrupted oblique rolling, piercing, hot rolling and sizing rolling in sequence to obtain a pipe; Step 3: annealing and machining the tube obtained in step 2 in sequence to obtain a TA24 titanium alloy thin-walled large-diameter ultra-long seamless tube.

2. The method for processing a TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe according to claim 1, characterized in that: The TA24 titanium alloy ingot in step 1 is an ingot prepared by VAR smelting or EB smelting.

3. The method for processing a TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe according to claim 1, characterized in that: The temperature of the blank forging in step 1 is (T β +150℃)~(T β +250℃), the T β is the β phase transition temperature of TA24 titanium alloy, in °C.

4. The method for processing a TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe according to claim 1, characterized in that: The deformation amount of the blank forging in step 1 is greater than 60%.

5. The method for processing a TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe according to claim 1, characterized in that: The temperature of the bar billet during the oblique rolling and piercing in step 2 is (T β -50℃)~T β .

6. The method for processing a TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe according to claim 1, characterized in that: No additional heat treatment is performed during the oblique rolling piercing, hot continuous rolling and sizing rolling processes described in step 2.

7. The method for processing a TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe according to claim 1, characterized in that: The size specifications of the TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe described in step three are: outer diameter D is 200mm~325mm, diameter-to-thickness ratio D / t is not less than 20, and length is not less than 10000mm; t is the wall thickness, in mm.

8. The method for processing a TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe according to claim 1, characterized in that: The yield rate of the TA24 titanium alloy thin-walled large-diameter ultra-long seamless pipe described in step 3 is not less than 70%.