Preparation method of low-cost thin-wall titanium steel composite pipe

Abstract

The invention provides a preparation method of a thin-wall titanium-steel composite pipe, which comprises the following steps: firstly, carrying out pipe bending forming on a titanium-steel composite plate by adopting a JCO process, and then carrying out titanium-titanium and steel-steel welding to obtain a titanium-steel composite welded pipe; and then the titanium steel composite welded pipe obtained in the previous step is subjected to continuous annealing, and then the thin-wall titanium steel composite pipe is obtained after cold machining and continuous annealing again. The cold processing comprises cold rolling and / or cold drawing. By means of the method, the high-precision titanium steel composite pipe with the wall thickness smaller than 4 mm can be obtained, the bonding strength can be guaranteed while the wall thickness is reduced, the economical efficiency of the composite pipe is exerted to the maximum extent, the cost is low, and the average economic benefit can reach 50 thousand yuan / ton. And the preparation method is simple in process, mild in condition and good in controllability, can be popularized and applied in titanium steel composite pipe production, can be used for producing the high-precision thin-wall titanium steel composite pipe, and has a good popularization and application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of thin-wall titanium-steel composite pipe preparation, relates to a thin-wall titanium-steel composite pipe preparation method and application thereof, and in particular to a low-cost thin-wall titanium-steel composite pipe preparation method. Background Art

[0002] Titanium-steel composite pipes have both the excellent corrosion resistance of titanium and the high strength of steel itself. They have great prospects in the field of corrosive medium transportation, such as chemical media, seawater transportation pipelines, etc., so the market demand is becoming more and more extensive.

[0003] At present, there are two main types of titanium-steel composite pipes: seamless composite pipes and seamed (welded) composite pipes. Seamless composite pipes are mostly produced by explosive composite methods, but the explosion method has shortcomings such as poor pipe shape control, environmental pollution, and low production efficiency. There are also mechanical composite methods, such as putting titanium and steel seamless pipes together in the form of inner titanium and outer steel for pressure expansion, plastic deformation occurs through expansion, and after pressure relief, the two are tightly fitted due to different rebound amounts. However, the titanium-steel composite pipes prepared in this way mainly rely on interference fit, and the interface does not achieve metallurgical bonding. After being subjected to a certain external force, the titanium steel is easy to delaminate, and the service life is limited. In addition, there are also titanium-steel composite pipes prepared by casting, hot rolling or hot extrusion, but the brittle compound phase at the titanium-steel interface is difficult to control, the process is complex, the technology is difficult and difficult to control, and thin-walled pipes cannot be prepared.

[0004] Welded composite pipes are made by welding the already composited titanium steel composite plates. Since the raw materials themselves have good metallurgical bonding effects, the product has high bonding strength and lower cost. However, the raw materials are titanium steel composite plates that are exploded or rolled, and the minimum thickness is limited. The minimum thickness of titanium steel composite plates prepared by the most advanced rolling method is also 3+1mm, and it is impossible to prepare titanium steel composite pipes with a wall thickness of less than 4mm.

[0005] Therefore, how to develop a method for preparing thin-walled titanium-steel composite pipes and solve the above-mentioned technical problems existing in existing titanium-steel composite pipes has become one of the urgent problems to be solved by many front-line researchers in the industry. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a method for preparing a thin-walled titanium-steel composite pipe and its application, in particular, a method for preparing a low-cost thin-walled titanium-steel composite pipe. The present invention can reduce the wall thickness while ensuring the bonding strength, and can obtain a high-precision titanium-steel composite pipe with a wall thickness of less than 4mm, and the cost is low, maximizing the economic efficiency of the composite pipe. Moreover, the preparation method has a simple process, mild conditions, good controllability, and is more suitable for the promotion and application of industrial production.

[0007] The present invention provides a method for preparing a thin-wall titanium-steel composite pipe, comprising the following steps:

[0008] 1) The titanium-steel composite plate is formed by bending the tube by JCO process, and then titanium-titanium and steel-steel welding is performed to obtain a titanium-steel composite welded pipe;

[0009] 2) The titanium-steel composite welded pipe obtained in the above steps is continuously annealed, and then cold worked and continuously annealed again to obtain a thin-walled titanium-steel composite pipe;

[0010] The cold working includes cold rolling and / or cold drawing.

[0011] Preferably, the thickness of the steel layer of the titanium steel composite plate is 1 to 5.5 mm;

[0012] The thickness of the titanium layer of the titanium-steel composite plate is 0.5 to 2 mm;

[0013] The total thickness of the titanium-steel composite plate is less than or equal to 6 mm.

[0014] Preferably, the titanium-steel composite welded pipe includes a titanium-steel composite welded pipe with steel outside and titanium inside or a titanium-steel composite welded pipe with titanium outside and steel inside;

[0015] The outer diameter of the titanium-steel composite welded pipe is 200-500 mm.

[0016] Preferably, the interface temperature of the welding is less than or equal to 800°C;

[0017] The welding process also includes steps of welding seam processing and rounding.

[0018] Preferably, the temperature of the continuous annealing is 650-950°C;

[0019] The continuous annealing time is 3 to 10 minutes;

[0020] The continuous annealing atmosphere includes a protective atmosphere and / or air.

[0021] Preferably, the cold working comprises single or multiple cold working;

[0022] When the cold working is performed in multiple passes, continuous annealing is performed after each pass of cold working.

[0023] Preferably, the cumulative deformation of the cold working is ≤75%;

[0024] The deformation of each cold working process is ≤50%;

[0025] The elongation coefficient of the cold working is 1.4 to 2.5.

[0026] Preferably, the temperature of the second continuous annealing is 550-1000°C;

[0027] The time of the second continuous annealing is 3 to 10 minutes;

[0028] The atmosphere of the re-continuous annealing includes a protective atmosphere and / or air;

[0029] The atmosphere during the last continuous annealing is a protective atmosphere.

[0030] Preferably, the wall thickness of the thin-walled titanium-steel composite tube is 0.5 to 4 mm;

[0031] The outer diameter of the thin-wall titanium-steel composite pipe is ≤300 mm.

[0032] The present invention also provides the use of the preparation method described in any one of the above technical solutions in the preparation of thin-walled titanium-steel composite pipes;

[0033] The wall thickness of the thin-walled titanium-steel composite tube is less than or equal to 4 mm.

[0034] The present invention provides a method for preparing a thin-walled titanium-steel composite pipe, comprising the following steps: first, a titanium-steel composite plate is formed by bending a pipe using a JCO process, and then titanium-titanium and steel-steel welding is performed to obtain a titanium-steel composite welded pipe; then the titanium-steel composite welded pipe obtained by the above steps is continuously annealed, and then cold-processed and continuously annealed again to obtain a thin-walled titanium-steel composite pipe; the cold processing includes cold rolling and / or cold drawing. Compared with the prior art, the present invention creatively designs a method for preparing a thin-walled titanium-steel composite pipe with specific steps, first preparing a titanium-steel composite welded pipe, and then using the titanium-steel composite welded pipe as a raw material to achieve wall thinning by cold rolling or cold drawing, and finally obtaining a high-precision thin-walled titanium-steel composite pipe. The entire process reduces the technical difficulty of direct compounding, and at the same time, the appearance accuracy of the product after cold processing is higher and the cost is lower.

[0035] The novel thin-wall titanium-steel composite pipe preparation method provided by the present invention can obtain a high-precision titanium-steel composite pipe with a wall thickness of less than 4 mm, while reducing the wall thickness and ensuring the bonding strength, maximizing the economic efficiency of the composite pipe, and the cost is low, and the average economic benefit can reach 5,000 yuan / ton. Moreover, the preparation method has a simple process, mild conditions, good controllability, and can be promoted and applied in the production of titanium-steel composite pipes to produce high-precision thin-wall titanium-steel composite pipes, which has a good prospect for promotion and application. DETAILED DESCRIPTION

[0036] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention.

[0037] All raw materials of the present invention have no particular limitation on their sources, and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0038] There is no particular restriction on the purity of all raw materials in the present invention. The present invention preferably uses industrial pure materials or materials with conventional purity requirements in the field of titanium-steel composite pipe preparation.

[0039] The brands and abbreviations of all raw materials of the present invention are conventional brands and abbreviations in the art. Each brand and abbreviation is clear and definite in the field of its related use. Those skilled in the art can purchase them from the market or prepare them by conventional methods according to the brands, abbreviations and corresponding uses.

[0040] The abbreviations of the processes used in the present invention are all conventional abbreviations in the field. The specific steps and conventional parameters of each abbreviation are clear and definite in its relevant field. Those skilled in the art can implement them in a conventional manner based on the abbreviations.

[0041] The present invention provides a method for preparing a thin-wall titanium-steel composite pipe, comprising the following steps:

[0042] 1) The titanium-steel composite plate is formed by bending the tube by JCO process, and then titanium-titanium and steel-steel welding is performed to obtain a titanium-steel composite welded pipe;

[0043] 2) The titanium-steel composite welded pipe obtained in the above steps is continuously annealed, and then cold worked and continuously annealed again to obtain a thin-walled titanium-steel composite pipe;

[0044] The cold working includes cold rolling and / or cold drawing.

[0045] The present invention firstly forms a titanium-steel composite plate through pipe bending by adopting a JCO process, and then performs titanium-titanium and steel-steel welding to obtain a titanium-steel composite welded pipe.

[0046] In the present invention, the thickness of the steel layer of the titanium-steel composite plate is preferably 1 to 5.5 mm, more preferably 1.5 to 5 mm, more preferably 2 to 4.5 mm, and more preferably 2.5 to 4 mm.

[0047] In the present invention, the thickness of the titanium layer of the titanium-steel composite plate is preferably 0.5 to 2 mm, more preferably 0.7 to 1.8 mm, and more preferably 1.0 to 1.5 mm.

[0048] In the present invention, the total thickness of the titanium steel composite plate is preferably less than or equal to 6 mm, more preferably less than or equal to 5 mm, less than or equal to 4 mm.

[0049] Specifically, in the present invention, the total thickness of the raw material of the titanium steel composite plate is ≤6mm, wherein the thickness of the titanium layer and the steel layer is selected according to the target thickness and designed according to the principle of equal proportion deformation. For example, if a titanium steel composite tube with a titanium layer: steel layer thickness of 1:3 is required, a titanium steel composite plate with a raw material thickness of 1mm titanium layer, 3mm steel layer, and a total thickness of 4mm can be selected, or a titanium steel composite plate with a 1.5mm titanium layer, 4.5mm steel layer, and a total thickness of 6mm can be selected.

[0050] In the present invention, the titanium-steel composite welded pipe preferably includes a titanium-steel composite welded pipe with steel outside and titanium inside or a titanium-steel composite welded pipe with titanium outside and steel inside.

[0051] In the present invention, the outer diameter of the titanium-steel composite welded pipe is preferably 200-500 mm, more preferably 250-450 mm, and more preferably 300-400 mm.

[0052] In the present invention, the interface temperature of the welding is preferably less than or equal to 800°C, more preferably less than or equal to 750°C, and more preferably less than or equal to 700°C.

[0053] In the present invention, the welding preferably further includes steps of weld seam processing and rounding.

[0054] The present invention further performs continuous annealing on the titanium-steel composite welded pipe obtained in the above steps, and then performs cold working and continuous annealing again to obtain a thin-walled titanium-steel composite pipe;

[0055] In the present invention, the cold working includes cold rolling and / or cold drawing, and can be cold rolling or cold drawing.

[0056] In the present invention, the temperature of the continuous annealing is preferably 650-950°C, more preferably 700-900°C, and even more preferably 750-850°C.

[0057] In the present invention, the continuous annealing time is preferably 3 to 10 minutes, more preferably 4 to 9 minutes, more preferably 5 to 8 minutes, and more preferably 6 to 7 minutes.

[0058] In the present invention, the continuous annealing atmosphere preferably includes a protective atmosphere and / or air, and more preferably includes a protective atmosphere or air.

[0059] In the present invention, the cold working preferably includes single or multiple cold working;

[0060] In the present invention, the cold working is preferably performed in multiple passes, and continuous annealing is performed after each pass of cold working.

[0061] In the present invention, the cumulative deformation amount of the cold working is preferably ≤75%, more preferably ≤70%, and more preferably ≤65%.

[0062] In the present invention, the deformation amount of each cold working pass is preferably ≤50%, more preferably ≤45%, and more preferably ≤40%.

[0063] In the present invention, the elongation coefficient of the cold working is preferably 1.4 to 2.5, more preferably 1.6 to 2.3, and even more preferably 1.8 to 2.1.

[0064] In the present invention, the temperature of the second continuous annealing is preferably 550 to 1000°C, more preferably 650 to 900°C, and even more preferably 750 to 800°C.

[0065] In the present invention, the time of the second continuous annealing is preferably 3 to 10 minutes, more preferably 4 to 9 minutes, more preferably 5 to 8 minutes, and more preferably 6 to 7 minutes.

[0066] In the present invention, the atmosphere of the re-continuous annealing preferably includes a protective atmosphere and / or air, and more preferably includes a protective atmosphere or air.

[0067] In the present invention, the atmosphere of the last re-continuous annealing is preferably a protective atmosphere.

[0068] In the present invention, the wall thickness of the thin-walled titanium-steel composite tube is preferably less than or equal to 4 mm, more preferably less than or equal to 3 mm, and more preferably less than or equal to 2 mm. Specifically, it can be 0.5 to 4 mm, or 1 to 3.5 mm, or 2 to 3 mm.

[0069] In the present invention, the outer diameter of the thin-walled titanium-steel composite pipe is preferably ≤300 mm, or ≤250 mm, or ≤200 mm.

[0070] The present invention provides application of the preparation method described in any one of the above technical solutions in the preparation of thin-walled titanium-steel composite pipes.

[0071] The wall thickness of the thin-walled titanium-steel composite tube is less than or equal to 4 mm.

[0072] The present invention is to complete and refine the overall technical solution, better guarantee the parameters and structure of the thin-walled titanium-steel composite pipe, and further improve the performance of the thin-walled titanium-steel composite pipe. The preparation method of the low-cost thin-walled titanium-steel composite pipe may specifically include the following contents:

[0073] The process scheme adopted by the present invention is: titanium steel composite plate raw material → bending tube forming → titanium and steel welding → weld seam treatment → rounding → annealing → pickling → cold processing (cold rolling or cold drawing) → annealing → straightening → flaw detection → offline. That is, first prepare the titanium steel composite welded pipe, then use it as raw material, achieve wall thickness thinning through cold rolling or cold drawing, and finally obtain a high-precision thin-wall titanium steel composite pipe.

[0074] In the above process, specifically:

[0075] 1. Titanium steel composite plates produced by rolling method are preferred. Compared with the explosion method, the rolling method can produce thinner raw materials and has higher thickness control accuracy for each layer.

[0076] 2. The JCO process is preferred as the bending process for titanium steel composite plates. JCO is a progressive pressure forming process, which makes the deformation of the composite plate more uniform during the forming process, reduces the residual stress, and avoids shearing and rubbing at the interface.

[0077] 3. After the tube is bent, the open "O" tube blank is welded from the titanium and steel sides, respectively, by titanium-titanium and steel-steel welding. When welding, titanium and steel must not be mutually dissolved, and the heat input must not be too high. The interface temperature should be controlled below 800°C, otherwise titanium and steel will diffuse to form brittle compounds, reducing the interface bonding strength.

[0078] 4. Grind the weld to remove the pile and burrs.

[0079] 5. Make the titanium steel composite welded pipe into a perfect round shape.

[0080] 6. Anneal the obtained titanium steel composite welded pipe by continuous annealing, with an annealing temperature of 650-950°C and an annealing time of 3-10 minutes. Annealing can be performed under argon protection or in an atmospheric environment.

[0081] 7. After annealing, the surface is pickled to remove the oxide scale.

[0082] 8. Cold processing of welded pipes on cold rolling or cold drawing equipment. Cold processing needs to be carried out after applying lubricant. According to the size requirements of the finished product, single or multiple cold rolling can be carried out and the composite pipe after each cold rolling can be continuously annealed. Among them, the deformation of each pass is controlled to be ≤50%, the cumulative deformation is ≤75%, and the elongation coefficient is 1.4-2.5; both intermediate annealing and finished product annealing are carried out by continuous annealing, and the finished product annealing needs to be carried out under argon protection, while the intermediate annealing can be carried out under protective atmosphere or in atmospheric environment. If continuous annealing is carried out in atmosphere, pickling is required after annealing, and the oxide scale is removed before cold rolling. The continuous annealing temperature is 550-1000℃, and the annealing time is 3-10min.

[0083] 9. Perform ultrasonic flaw detection on the finished pipe.

[0084] The above content of the present invention provides a method for preparing a thin-walled titanium-steel composite pipe and its application, and in particular relates to a method for preparing a low-cost thin-walled titanium-steel composite pipe. The method for preparing a thin-walled titanium-steel composite pipe with specific steps designed by the present invention first prepares a titanium-steel composite welded pipe, and then uses it as a raw material to achieve wall thickness thinning through cold rolling or cold drawing, and finally obtains a high-precision thin-walled titanium-steel composite pipe. The entire process reduces the technical difficulty of direct compounding, and at the same time, the appearance accuracy of the product after cold processing is higher and the cost is lower.

[0085] The novel thin-wall titanium-steel composite pipe preparation method provided by the present invention can obtain a high-precision titanium-steel composite pipe with a wall thickness of less than 4 mm, while reducing the wall thickness and ensuring the bonding strength, maximizing the economic efficiency of the composite pipe, and the cost is low, and the average economic benefit can reach 5,000 yuan / ton. Moreover, the preparation method has a simple process, mild conditions, good controllability, and can be promoted and applied in the production of titanium-steel composite pipes to produce high-precision thin-wall titanium-steel composite pipes, which has a good prospect for promotion and application.

[0086] In order to further illustrate the present invention, a preparation method of a thin-walled titanium-steel composite pipe provided by the present invention and its application are described in detail below in combination with embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating processes are given only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention, and the protection scope of the present invention is not limited to the following embodiments.

[0087] Example 1

[0088] In this embodiment, a titanium steel composite plate with a thickness of (3+1) mm (i.e., a steel plate with a thickness of 3 mm and a titanium plate with a thickness of 1 mm) is used to prepare a titanium steel composite pipe with a specification of Φ150×2 mm (i.e., an outer diameter of 150 mm and a wall thickness of 2 mm). The titanium steel composite plate with a thickness of (3+1) mm produced by the rolling method is bent into a Φ300 mm pipe (steel outside and titanium inside) using the JCO pipe making process, and welding is completed from the steel side and the titanium side respectively. The weld is polished and piled up to make it round, then annealed at 800℃×8min, pickled to remove the oxide scale and then cold rolled, first rolled from Ф300×4 to Ф250×3mm, elongation coefficient 1.60, annealed at 900℃ argon protection for 5min, then rolled to Ф190×2.5mm, elongation coefficient 1.58, annealed at 900℃ argon protection for 5min, and finally rolled to Ф150×2mm, elongation coefficient 1.58, annealed at 800℃ argon protection for 3min. The finished product is obtained after straightening and flaw detection.

[0089] The interface shear strength of the titanium-steel composite pipe with a specification of Φ150×2mm prepared in this embodiment can reach 213MPa.

[0090] Example 2

[0091] In this embodiment, a titanium steel composite plate with a thickness of (3+1) mm (i.e., a steel plate with a thickness of 3 mm and a titanium plate with a thickness of 1 mm) is used to prepare a titanium steel composite pipe with a specification of Φ200×2 mm (i.e., an outer diameter of 200 mm and a wall thickness of 2 mm). The titanium steel composite plate with a thickness of (3+1) mm produced by the rolling method is bent into a Φ320 mm pipe (steel outside and titanium inside) using the JCO pipe making process, and welding is completed from the steel side and the titanium side respectively. The weld is polished and piled up to be round, then annealed at 850℃×5min, pickled to remove the oxide scale and then cold rolled, one pass from Ф320×4 to Ф280×3mm, elongation coefficient 1.52, annealed at 950℃ for 4min, pickled and then rolled to Ф230×2.5mm, elongation coefficient 1.46, annealed at 950℃ for 4min, finally rolled to Ф200×2mm after pickling, elongation coefficient 1.43, annealed at 900℃ for 3min in argon protection. The finished product is obtained after straightening and flaw detection.

[0092] The interface shear strength of the titanium-steel composite pipe with a specification of Φ200×2mm prepared in this embodiment can reach 196MPa.

[0093] Comparative Example 1

[0094] In this embodiment, a titanium steel composite plate with a thickness of (3+1) mm (i.e., a steel plate with a thickness of 3 mm and a titanium plate with a thickness of 1 mm) is used to prepare a titanium steel composite pipe with a specification of Φ150×2 mm (i.e., an outer diameter of 150 mm and a wall thickness of 2 mm). The titanium steel composite plate with a thickness of (3+1) mm produced by the rolling method is bent into a Φ300 mm pipe (steel outside and titanium inside) using the JCO pipe making process, and welding is completed from the steel side and the titanium side respectively. The weld was polished and piled up to make it a perfect circle, then annealed at 850℃×5min, pickled to remove the oxide scale and then cold rolled. It was first rolled from Ф300×4 to Ф250×3mm, with an elongation coefficient of 1.60, annealed at 900℃ with argon protection for 15min, then rolled to Ф190×2.5mm, with an elongation coefficient of 1.58, annealed at 900℃ with argon protection for 15min, and finally rolled to Ф150×2mm, with an elongation coefficient of 1.58. During the rolling process, the titanium steel was layered and the finished product could not be obtained.

[0095] Comparative Example 2

[0096] This embodiment uses a titanium steel composite plate with a thickness of (3+1) mm (i.e., a steel plate with a thickness of 3 mm and a titanium plate with a thickness of 1 mm) to prepare a titanium steel composite pipe with a specification of Φ150×2 mm (i.e., an outer diameter of 150 mm and a wall thickness of 2 mm). The titanium steel composite plate with a thickness of (3+1) mm produced by the rolling method is bent into a Φ300 mm pipe (steel outside and titanium inside) by the JCO pipe making process, and welding is completed from the steel side and the titanium side respectively. The weld is polished and piled up to be round, and then annealed at 850℃×5min, and then cold rolled after pickling to remove the oxide scale. First, it is rolled from Φ300×4 to Φ250×3mm, with an elongation coefficient of 1.60, and annealed at 500℃ for 15min under argon protection, and then rolled to Φ190×2.5mm, with an elongation coefficient of 1.58, and annealed at 1050℃ for 10min under argon protection. After annealing, it is found that the titanium steel is layered and the finished product cannot be obtained.

[0097] The above is a detailed introduction to a method for preparing a low-cost thin-walled titanium steel composite pipe provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and its core ideas of the present invention, including the best mode, and also enables any technician in the field to practice the present invention, including the manufacture and use of any device or system, and the implementation of any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements that are not different from the text of the claims, or if they include equivalent structural elements that are not substantially different from the text of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for preparing a thin-walled titanium-steel composite pipe, characterized in that: The following steps are involved: 1) The titanium steel composite plate is formed by bending the plate by JCO process, and then titanium-titanium and steel-steel welding is performed to obtain a titanium steel composite welded pipe; 2) The titanium-steel composite welded pipe obtained in the above steps is continuously annealed, and then cold worked and continuously annealed again to obtain a thin-walled titanium-steel composite pipe; The cold working includes cold rolling and / or cold drawing.

2. The preparation method according to claim 1, characterized in that: The thickness of the steel layer of the titanium steel composite plate is 1 to 5.5 mm; The thickness of the titanium layer of the titanium-steel composite plate is 0.5 to 2 mm; The total thickness of the titanium-steel composite plate is less than or equal to 6 mm.

3. The preparation method according to claim 1, characterized in that: The titanium-steel composite welded pipe includes a titanium-steel composite welded pipe with steel outside and titanium inside or a titanium-steel composite welded pipe with titanium outside and steel inside; The outer diameter of the titanium-steel composite welded pipe is 200-500 mm.

4. The preparation method according to claim 1, characterized in that: The interface temperature of the welding is less than or equal to 800°C; The welding process also includes steps of welding seam processing and rounding.

5. The preparation method according to claim 1, characterized in that: The continuous annealing temperature is 650-950°C; The continuous annealing time is 3 to 10 minutes; The continuous annealing atmosphere includes a protective atmosphere and / or air.

6. The preparation method according to claim 1, characterized in that: The cold working includes single or multiple cold working; When the cold working is performed in multiple passes, continuous annealing is performed after each pass of cold working.

7. The preparation method according to claim 6, characterized in that: The cumulative deformation of the cold working is ≤75%; The deformation of each cold working process is ≤50%; The elongation coefficient of the cold working is 1.4 to 2.

5.

8. The preparation method according to claim 1, characterized in that: The temperature of the second continuous annealing is 550-1000°C; The time of the second continuous annealing is 3 to 10 minutes; The atmosphere of the re-continuous annealing includes a protective atmosphere and / or air; The atmosphere during the last continuous annealing is a protective atmosphere.

9. The preparation method according to claim 1, characterized in that: The wall thickness of the thin-walled titanium-steel composite tube is 0.5 to 4 mm; The outer diameter of the thin-wall titanium-steel composite pipe is ≤300 mm.

10. Application of the preparation method according to any one of claims 1 to 9 in the preparation of thin-walled titanium-steel composite pipes; The wall thickness of the thin-wall titanium-steel composite tube is less than or equal to 4 mm.