Methods for preparing titanium-steel composite pipes using red-clad technology

Abstract

This invention discloses a method for preparing titanium-steel composite pipes using a hot-dip annealing technique, specifically including the following steps: Step 1, treating the outer diameter surface of the titanium pipe and the inner diameter surface of the steel pipe; Step 2, determining the interference fit between the outer diameter of the titanium pipe and the inner diameter of the steel pipe based on Step 1; Step 3, calculating the hot-dip annealing temperature based on Step 2, and heating the steel pipe according to the calculated temperature; Step 4, nesting the titanium pipe inside the steel pipe heated in Step 3 to obtain a titanium-steel composite pipe; Step 5, subjecting the titanium-steel composite pipe obtained in Step 4 to a heat preservation treatment to obtain the finished titanium-steel composite pipe. This method solves the problems of low production efficiency and low bonding quality of the titanium-steel interface in existing titanium-steel composite pipe preparation methods.

Description

Technical Field

[0001] This invention belongs to the field of preparation technology of heterogeneous metal composite pipes, and relates to a method for preparing titanium-steel composite pipes using a red-coating technique. Background Technology

[0002] Currently, with the development of industries such as aerospace, nuclear industry, petrochemicals, and marine transportation, existing steel pipes are no longer sufficient to meet increasingly harsh working environments. Developing new fluid transport pipes is imperative, leading to the emergence of titanium-steel composite pipes. Titanium-steel composite pipes are bimetallic composite pipes formed through mechanical or metallurgical bonding. They combine the excellent corrosion resistance and high strength of titanium with the high toughness of steel, solving the problems of high cost of titanium pipes and insufficient performance of steel pipes. Therefore, they have broad application prospects and are gradually becoming a new favorite in the pipe market.

[0003] Currently, most titanium-steel composite pipes are manufactured by first producing titanium-steel composite plates, which are then rolled and welded into pipes. However, the welding processes for titanium and steel differ significantly, leading to welding difficulties or localized cracking or corrosion. Of course, there are also other processes for producing titanium-steel composite pipes, including explosive bonding, explosive-rolling bonding, diffusion bonding, and hot-rolling bonding. Explosive bonding utilizes the impact force generated by an explosive explosion to cause violent collisions, plastic deformation, melting, and interatomic diffusion between two or more layers of metal plates, thereby forming a strong bond at the interface of the metal plates. CN112620915A discloses a method for preparing thick-walled titanium-steel composite pipes using an explosive method, employing four explosive bonding processes to produce titanium-clad steel composite pipes with a diameter of 2220mm, a wall thickness of 100mm (20mm titanium pipe, 80mm steel pipe), and an interface bonding strength ≥140MPa. The principle of the explosion-rolling composite method is to heat-treat the composite plate after explosion, and then form a composite of two plates through hot rolling and cold rolling. Wang Jingzhong et al. used the explosion-rolling composite method to first obtain Ti / DT4 billets through explosion composite, and then hot-rolled Ti / DT4 and Q235 steel plates at a temperature of 830-880℃. Finally, after annealing at 550-650℃, a Ti / DT4 / Q235 composite plate with an interfacial bonding strength of up to 250MPa was prepared. The diffusion composite method involves stacking clean metal plates together and then applying a certain temperature and pressure to achieve interfacial bonding through interatomic interdiffusion. Kundu et al. used the diffusion composite method to prepare a titanium-steel composite material with an interfacial bonding strength of 405MPa under process parameters of 4MPa pressure, 900℃ holding time, and 2.7ks holding time. After adding a nickel transition film, the interfacial bonding strength of the material reached as high as 479MPa. The hot-rolled composite method involves welding the weld seams of the assembled titanium-steel pipe and then using hot rolling and heat treatment processes to achieve interlayer mechanical interlocking and atomic bonding of the titanium-steel composite material. Patent CN111940503A discloses a method for preparing titanium-steel composite pipes using a vacuum-free hot-rolled composite method. By using gallium to polish the surface of the Ti plate, the rolling temperature is increased from below 850℃ to 900-1100℃, and the interfacial bonding strength of the titanium-steel composite material is increased from 140MPa-220MPa to 300MPa.

[0004] Analysis of the above processes reveals that the explosion and explosion-composite methods require stringent production conditions, typically making continuous, batch production impossible; the diffusion composite method has low production efficiency and is unsuitable for practical production; and the hot rolling composite method requires vacuuming and electron beam welding, resulting in high costs. Furthermore, due to the high temperatures and prolonged heat treatment, Ti-Fe intermetallic compounds often form at the titanium-steel composite interface, reducing the interfacial bonding quality and the overall plasticity and strength of the pipe. Therefore, finding a simple, rapid, and high-quality manufacturing technology for titanium-steel pipes is an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing titanium-steel composite pipes using red-coating technology, which solves the problems of low production efficiency and low bonding quality of titanium-steel interface in existing titanium-steel composite pipe preparation methods.

[0006] The technical solution adopted in this invention is a method for preparing titanium-steel composite pipes using red-coating technology, which specifically includes the following steps:

[0007] Step 1: Treat the outer diameter surface of the titanium pipe and the inner diameter surface of the steel pipe;

[0008] Step 2: Based on Step 1, determine the interference fit between the outer diameter of the titanium tube and the inner diameter of the steel tube;

[0009] Step 3: Calculate the red-heating temperature based on Step 2, and heat the steel pipe according to the calculated temperature;

[0010] Step 4: Insert the titanium pipe into the steel pipe that has been heated in Step 3 to obtain a titanium-steel composite pipe;

[0011] Step 5: Heat and insulate the steel-titanium composite pipe obtained in Step 4 to obtain the finished titanium-steel composite pipe.

[0012] The invention is further characterized by:

[0013] Step 1 involves processing the outer diameter surface of the titanium pipe and the inner diameter surface of the steel pipe, including: removing the adhering substances from the outer diameter surface of the titanium pipe and the inner diameter surface of the steel pipe, straightening the inner diameter of the steel pipe, and correcting the roundness of the titanium pipe.

[0014] In step 1, when straightening the inner diameter of the steel pipe, three grinding wheels of the same size are assembled on the chuck of the centerless mold to form a centerless rotating circle. The diameter of the centerless rotating circle is the inner diameter of the steel pipe.

[0015] In step 2, when the outer diameter of the titanium tube is less than 30mm, the total interference is between 0.02mm and 0.05mm, meaning the inner diameter of the steel tube is 0.05mm larger than the outer diameter of the titanium tube; when the outer diameter of the titanium tube is greater than 30mm but less than 150mm, the total interference is between 0.1mm and 0.2mm, meaning the inner diameter of the steel tube is 0.2mm larger than the outer diameter of the titanium tube; when the outer diameter of the titanium tube is greater than 150mm but less than 300mm, ... The total interference is between 0.2mm and 0.4mm, meaning the inner diameter of the steel pipe is 0.4mm larger than the outer diameter of the titanium pipe; when the outer diameter of the titanium pipe is greater than 300mm, the total interference is between 0.5mm and 0.8mm, meaning the inner diameter of the steel pipe is 0.8mm larger than the outer diameter of the titanium pipe; when the outer diameter of the titanium pipe is greater than 500mm, the total interference is between 1.0mm and 2.0mm, meaning the inner diameter of the steel pipe is 2mm larger than the outer diameter of the titanium pipe.

[0016] In step 3, the red packaging temperature is calculated according to the following formula (1):

[0017]

[0018] In the formula:

[0019] Δ represents the interference fit between the inner diameter of the steel pipe and the outer diameter of the titanium pipe on one side, in mm;

[0020] α represents the coefficient of linear expansion of steel;

[0021] r 内 This indicates the inner diameter of the steel pipe, in mm.

[0022] In step 3, before heating the steel pipe, support balls are placed inside the steel pipe. When the temperature in the bogie furnace rises to T℃, the steel pipe with support balls is placed into the bogie furnace for heating treatment. The temperature zone is set and held for 10 to 15 minutes without a protective atmosphere.

[0023] The specific process of step 4 is as follows: First, place the titanium tube on the ball bearings, then adjust the screw lifting platform to the required red-fitting position for the titanium tube and steel tube; then, quickly transfer the steel tube heated in step 3 from the trolley furnace to the refractory insulating brick platform; then, use multiple fixed robotic arms to clamp and fix the steel tube in the red-fitting position along the central axis of the steel tube; finally, the transmission robotic arm pushes the titanium tube into the inner diameter of the steel tube to complete the red-fitting composite.

[0024] The specific process of step 5 is as follows: the titanium-steel composite pipe blank obtained in step 4 is transferred to the heating furnace again, heated to 120℃~240℃ and held for 12h~24h to obtain the finished titanium-steel composite pipe.

[0025] The beneficial effects of this invention are that, based on the dimensions of the manufactured titanium-steel composite pipe, this invention selects titanium and steel pipes of suitable sizes, utilizes the thermal expansion and contraction characteristics of steel, heats the steel pipe to a certain temperature, and when it expands to the designed size, quickly inserts the titanium pipe into it and rapidly cools it. As a result, the titanium pipe is tightly bound by the cold-shrinking steel pipe. Then, it is kept at a low-temperature furnace for a long time. On the one hand, this can remove hydrogen (because titanium and steel are prone to hydrogen embrittlement), and on the other hand, it forces the titanium and iron atoms to diffuse into each other, which is beneficial to improving the bonding strength between them. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the large-diameter long steel pipe inner diameter straightening device used in the method for preparing titanium-steel composite pipes using the red-coating technology of the present invention.

[0027] Figure 2 This is a schematic diagram of the red-coating composite device for large-diameter long steel pipes and titanium pipes in the method for preparing titanium-steel composite pipes using the red-coating technology of the present invention.

[0028] Figure 3 This is a microstructure diagram of the titanium-steel composite pipe prepared in Example 1 of the method for preparing titanium-steel composite pipe using the red-coating technology of the present invention.

[0029] Among them, 1. Transmission robot, 2. Titanium pipe, 3. Fixed robot, 4. Steel pipe, 5. Support ball, 6. Refractory insulating brick platform, 7. Screw lifting platform, 8. Ball, 9. Steel pipe, 10. Grinding wheel, 11. Centerless mold, 12. Hose. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0031] The preparation method of the present invention has a high yield, and the titanium-steel composite plate prepared has no fine and dispersed TiC, FeTi and Fe2Ti intermediate brittle phases at the interface, and the interface bonding performance is good.

[0032] The method for preparing titanium-steel composite pipes using the red-coating technique of the present invention specifically includes the following steps:

[0033] Step 1: Select suitable steel pipes and titanium pipes;

[0034] The choice between steel and titanium pipes depends on the corrosion resistance and mechanical performance requirements of the user application. For steel pipes, options include ordinary steel pipes (such as Q235, Q345, Q357, etc.), stainless steel pipes (such as 1Cr13, etc.), or cast iron pipes. For titanium pipes, pure titanium (such as TA1, TA2) or titanium alloys (such as TC4) can be selected. To reduce costs, the wall thickness of the titanium pipe can be kept to no more than 2 mm. The outer diameter of the steel pipe can be any larger than the outer diameter of the titanium pipe (but the outer diameter of the titanium pipe must be at least larger than the inner diameter of the steel pipe).

[0035] Step 2, surface pretreatment;

[0036] The outer diameter of the titanium pipe and the inner diameter of the steel pipe selected in step 1 are subjected to surface pretreatment (including removing rust, oil and other attachments from the surface, straightening the pipe, and correcting the roundness of the inner and outer circles, etc.) to remove the surface attachments of the two to ensure the bonding quality of the interface between the two after the red-coated composite molding.

[0037] Titanium tubes are usually made by bending and welding sheet metal, resulting in poor roundness. The larger the diameter, the worse the roundness, sometimes exceeding the tolerance by up to 2 millimeters. Therefore, it is necessary to correct the roundness, which can generally be done using a commercially available roller straightening machine.

[0038] Most steel pipes are drawn, resulting in good roundness. Here, it's only necessary to straighten the inner diameter of the steel pipe. This ensures a good interference fit between the steel pipe and the titanium pipe, preventing gaps due to roundness issues. Furthermore, removing some deposits from the inner wall of the steel pipe facilitates the bonding of the titanium and steel. Specifically, the inner diameter straightening device of this invention is used. Figure 1 As shown, it consists of three grinding wheels 10, which are assembled on the chuck of the centerless mold 11 to form a centerless rotating circle. The diameter of this circle is the inner diameter of the steel pipe 9. It can be adjusted arbitrarily by replacing grinding wheels of different sizes. During operation, its rotational power is provided by high-pressure air 12 introduced through the hose 12 to drive the grinding wheels. The axial thrust is pushed by the operator, thereby completing the straightening of the inner wall of the tube. This device can not only make the steel pipe have a uniform inner hole, but also quickly remove rust and other deposits on the inner wall surface of the steel pipe, ensuring the subsequent red-coating process.

[0039] If there is corrosion or other deposits on the surface of the titanium pipe and the steel pipe, the outer diameter of the titanium pipe and the inner diameter of the steel pipe need to be sandblasted. The sandblasting parameters for the titanium pipe and the steel pipe are: sand particle size of 80-100 mesh (150-180μm) and impact force of 2-5m / s.

[0040] Step 3, determine the interference.

[0041] The fit between the outer diameter of the titanium tube and the inner diameter of the steel tube uses a large interference fit. Specifically, for titanium tubes with an outer diameter less than 30mm, the total interference fit is 0.02–0.05mm, meaning the inner diameter of the steel tube is 0.05mm larger than the outer diameter of the titanium tube. For titanium tubes with an outer diameter greater than 30mm but less than 150mm, the total interference fit is 0.1–0.2mm, meaning the inner diameter of the steel tube is 0.2mm larger than the outer diameter of the titanium tube. For diameters less than 150mm and 300mm, the total interference is 0.2-0.4mm, meaning the inner diameter of the steel pipe is 0.4mm larger than the outer diameter of the titanium pipe. For outer diameters greater than 300mm, the total interference is 0.5-0.8mm, meaning the inner diameter of the steel pipe is 0.8mm larger than the outer diameter of the titanium pipe. For outer diameters greater than 500mm, the total interference is 1.0-2.0mm, meaning the inner diameter of the steel pipe is 2mm larger than the outer diameter of the titanium pipe.

[0042] Step 4, calculate the red dress temperature

[0043] The calculation of the red-fitting temperature is to select an appropriate expansion amount based on a certain interference fit between the titanium tube and the steel tube, so as to avoid problems such as reduced interfacial bonding quality due to excessive fit clearance or cracking due to insufficient fit clearance. The red-fitting temperature is obtained by equation (1).

[0044]

[0045] In the formula:

[0046] Δ represents the single-sided interference (mm) between the inner diameter of the steel pipe and the outer diameter of the titanium pipe (obtained by design or measurement);

[0047] α represents the coefficient of linear expansion of steel, with a value of 12.5 to 13.5 × 10⁻⁶. -6 / ℃;

[0048] r 内 This indicates the inner diameter (mm) of the steel pipe.

[0049] Step 5, heat treatment

[0050] The steel pipes processed in step 2 are heated in a conventional box furnace at the temperature calculated in step 4. For long pipes with large diameters, support balls 5 need to be placed inside before heating (see...). Figure 2 To prevent heating or compressive deformation caused by excessively large steel pipe diameter (balls with the same diameter as the inner diameter of the steel pipe roll into the steel pipe, and the two are heated together, providing support to prevent deformation of the thin-walled pipe during heating, which would affect subsequent assembly; in addition, the presence of these steel balls also helps to prevent deformation of the steel pipe during clamping). When the temperature in the bogie furnace rises to T℃, the steel pipe is placed into the bogie furnace for heating treatment, and then the temperature zone is set and held for 10-15 minutes (i.e., the steel pipe is heated until it is red-hot and produces the desired amount of thermal expansion), no protective atmosphere is required.

[0051] Step 6, Red Dressing Reconciliation;

[0052] The heated steel pipe from step 5 is quickly transferred and placed on a ceramic tile-faced platform. Then, a titanium pipe is rapidly inserted into the hot steel pipe, followed by air cooling of the outer wall of the steel pipe. Once cooled to room temperature, the thermal expansion and contraction of the steel pipe causes the titanium pipe to be encased within the inner surface of the steel pipe, completing the fit and yielding a titanium-steel composite pipe blank. (Details follow...) Figure 2 As shown. First, place the titanium pipe 2 on the ball bearing 8, then adjust the screw lifting platform 7 to the required red-fitting position for the titanium pipe and steel pipe; then, quickly transfer the steel pipe 4, heated in step 5, from the trolley furnace to the refractory insulating brick platform 6. Immediately, multiple fixed robotic arms 3 clamp and fix it along the central axis of the steel pipe at its red-fitting position. Finally, the transmission robotic arm 1 quickly pushes the titanium pipe into the inner diameter of the steel pipe, completing the red-fitting composite. To prevent excessive deformation of the steel pipe that would prevent red-fitting, the pressure applied by the robotic arms to clamp and fix the steel pipe should not be too high. P1, P2, ..., Pn represent multiple robotic arms used to clamp the steel pipe. Because the steel pipe is heated to a certain temperature and has low strength, multiple clamping robotic arms are used, each applying relatively small force to avoid deformation of the steel pipe under the clamping force, which would lead to assembly failure.

[0053] Step 7, Low-temperature treatment

[0054] The titanium-steel composite pipe billet obtained in step 6 is transferred back to the heating furnace and heated to 120–240°C, then held at that temperature for 12–24 hours to obtain the finished titanium-steel composite pipe. This low-temperature treatment process eliminates hydrogen embrittlement that may occur during the titanium-steel composite process; on the other hand, it allows atoms at the interface between the titanium and steel pipes to diffuse sufficiently, forming a quasi-metallurgical bond and further improving the quality of the interface bonding.

[0055] Step 8, Non-destructive testing

[0056] For the titanium-steel composite pipe processed in step 7, according to the national standard SY / T 7464-2020 "Technical Standard for Welding and Non-destructive Testing of Corrosion-resistant Alloy Bimetallic Composite Pipes", non-destructive testing methods such as electromagnetic induction or ultrasonic testing are used to detect the bonding state at the interface between the two. If no loose joints or cracks are found within a unit square centimeter, it indicates that the bonding quality between the titanium pipe and the steel pipe can meet the working conditions and can be packaged and shipped.

[0057] Example 1

[0058] Prepare titanium-steel composite pipes (outer diameter 35mm, inner diameter 20mm, length unlimited), wherein the titanium pipe has an inner diameter of 20mm and an outer diameter of 25mm.

[0059] (1) Selecting suitable steel pipes and titanium pipes

[0060] Q235 steel pipe and TA2 titanium pipe are selected, with the inner diameter of the steel pipe being 25 mm. -0.1 mm, outer diameter is 35mm, titanium tube inner diameter is 20mm, outer diameter is 25mm. +0.1 mm.

[0061] (2) Surface pretreatment

[0062] The outer diameter of the titanium pipe and the inner diameter of the steel pipe selected in step 1 are subjected to surface pretreatment (including removing rust, oil and other attachments from the surface, straightening the pipe, and correcting the roundness of the inner and outer circles, etc.) to remove the surface attachments of the two to ensure the bonding quality of the interface between the two after the red-coated composite molding.

[0063] The roundness of the outer diameter of the titanium tube was straightened using a commercially available roller straightening machine.

[0064] The inner diameter of the steel pipe is straightened using the inner diameter straightening device of this invention, specifically as follows: Figure 1 As shown, the grinding wheel is powered by high-pressure air, and the operator pushes it to provide axial thrust, thereby straightening the inner wall of the tube.

[0065] The outer diameter of the titanium pipe and the inner diameter of the steel pipe were sandblasted. The sandblasting parameters were as follows: the sand particle size was 80 mesh (150μm) and the impact force was 5m / s.

[0066] (3) Determine the interference amount

[0067] The fit between the outer diameter of the titanium tube and the inner diameter of the steel tube is achieved using a large interference fit. Specifically, the interference fit is selected as follows: if the outer diameter of the titanium tube is less than 30mm, the total interference fit is 0.1mm, meaning that the inner diameter of the steel tube is 0.1mm larger than the outer diameter of the titanium tube.

[0068] (4) Calculate the temperature of red dress

[0069] The calculation of the red-fitting temperature is to select an appropriate expansion amount based on a certain interference fit between the titanium tube and the steel tube, so as to avoid problems such as reduced interface bonding quality due to excessive fit clearance or cracking due to insufficient fit clearance. The red-fitting temperature is calculated by formula (1) and ranges from 355 to 740℃, with 700℃ selected.

[0070] (5) Heat treatment

[0071] The steel pipes processed in step 2 are heated in a conventional box furnace at the temperature calculated in step 4. The steel pipes are placed in the furnace after it reaches the required temperature and then left in the set temperature zone for 15 minutes without a protective atmosphere.

[0072] (6) Red Dress Combination

[0073] The heated steel pipe from step 5 is quickly transferred and placed on a refractory insulating brick platform. Then, the titanium pipe is quickly nested inside the high-temperature steel pipe, followed by air cooling of the outer wall of the steel pipe. After cooling to room temperature, the thermal expansion and contraction of the steel pipe causes the titanium pipe to be encased within the inner surface of the steel pipe, completing the fit and thus obtaining a titanium-steel composite pipe blank. (Details follow...) Figure 2 As shown. The heated steel pipe from step 5 is quickly removed and placed on the refractory insulating brick platform 6. According to the pre-adjusted assembly position, the titanium pipe is quickly squeezed into the steel pipe under the action of the transmission manipulator 1. Then, it is rapidly cooled by air cooling to obtain a composite pipe in which the titanium pipe and the steel pipe are tightly bonded.

[0074] (7) Low temperature treatment

[0075] The titanium-steel composite pipe blank obtained in step 6 is transferred to the heating furnace again, heated to 240°C and held for 12 hours to obtain the finished titanium-steel composite pipe.

[0076] (8) Non-destructive testing

[0077] For the titanium-steel composite pipe processed in step 7, ultrasonic testing was used to detect the bonding state at the interface between the titanium and steel pipes according to the national standard SY / T 7464-2020 "Technical Standard for Welding and Non-destructive Testing of Corrosion-resistant Alloy Bimetallic Composite Pipes". No loose joints or cracks were found within a unit square centimeter, indicating that the interface bonding quality between the titanium and steel pipes meets the working requirements and is ready for packaging and shipment. Figure 3It is evident that the interface between titanium and steel is of good quality, with no defects such as incomplete joints or cracks.

[0078] Example 2

[0079] Prepare titanium-steel composite pipes (outer diameter 120mm, inner diameter 100mm, length unlimited), wherein the titanium pipe has an inner diameter of 100mm and an outer diameter of 107mm.

[0080] (1) Selecting suitable steel pipes and titanium pipes

[0081] Q235 steel pipe and TA2 titanium pipe were selected, with the inner diameter of the steel pipe being 107 mm. -0.3 The outer diameter is 120mm, the inner diameter of the titanium tube is 100mm, and the outer diameter is 107mm. +0.3 mm.

[0082] (2) Surface pretreatment

[0083] The outer diameter of the titanium pipe and the inner diameter of the steel pipe selected in step 1 are subjected to surface pretreatment (including removing rust, oil and other attachments from the surface, straightening the pipe, and correcting the roundness of the inner and outer circles, etc.) to remove the surface attachments of the two to ensure the bonding quality of the interface between the two after the red-coated composite molding.

[0084] The roundness of the outer diameter of the titanium tube was straightened using a commercially available roller straightening machine.

[0085] The inner diameter of the steel pipe is straightened using the inner diameter straightening device of this invention, specifically as follows: Figure 1 As shown, the grinding wheel is powered by high-pressure air, and the operator pushes it to provide axial thrust, thereby straightening the inner wall of the tube.

[0086] The outer diameter of the titanium pipe and the inner diameter of the steel pipe were sandblasted. The sandblasting parameters were as follows: the sand particle size was 80 mesh (150μm) and the impact force was 5m / s.

[0087] (3) Determine the interference amount

[0088] The fit between the outer diameter of the titanium tube and the inner diameter of the steel tube is achieved using a large interference fit. Specifically, the interference fit is selected as follows: for titanium tube outer diameters greater than 30mm and less than 150mm, the total interference fit is 0.8mm, meaning the inner diameter of the steel tube is 0.8mm larger than the outer diameter of the titanium tube.

[0089] (4) Calculate the temperature of red dress

[0090] The calculation of the red-fitting temperature is to select an appropriate expansion amount based on a certain interference fit between the titanium tube and the steel tube, so as to avoid problems such as reduced interface bonding quality due to excessive fit clearance or cracking due to insufficient fit clearance. The red-fitting temperature is calculated by formula (1) and is 613~710℃, with 710℃ selected.

[0091] (5) Heat treatment

[0092] The steel pipes processed in step 2 are heated in a conventional box furnace at the temperature calculated in step 4. The steel pipes are placed in the furnace after it reaches the required temperature and then left in the set temperature zone for 15 minutes without a protective atmosphere.

[0093] (6) Red Dress Combination

[0094] The heated steel pipe from step 5 is quickly transferred and placed on a refractory insulating brick platform. Then, the titanium pipe is quickly nested inside the high-temperature steel pipe, followed by air cooling of the outer wall of the steel pipe. After cooling to room temperature, the thermal expansion and contraction of the steel pipe causes the titanium pipe to be encased within the inner surface of the steel pipe, completing the fit and thus obtaining a titanium-steel composite pipe blank. (Details follow...) Figure 2 As shown. The heated steel pipe from step 5 is quickly removed and placed on the refractory insulating brick platform 6. According to the pre-adjusted assembly position, the titanium pipe is quickly squeezed into the steel pipe by the action of the titanium pipe drive manipulator 1. Then, it is rapidly cooled by air cooling to obtain a composite pipe in which the titanium pipe and the steel pipe are tightly bonded.

[0095] (7) Low temperature treatment

[0096] The titanium-steel composite pipe blank obtained in step 6 is transferred to the heating furnace again, heated to 120°C and held for 24 hours to obtain the finished titanium-steel composite pipe.

[0097] (8) Non-destructive testing

[0098] For the titanium-steel composite pipe processed in step 7, in accordance with the national standard SY / T 7464-2020 "Technical Standard for Welding and Non-destructive Testing of Corrosion-resistant Alloy Bimetallic Composite Pipes", ultrasonic testing was used to detect the bonding state at the interface between the two. No loose joints or cracks were found within a unit square centimeter, indicating that the bonding quality between the titanium pipe and the steel pipe can meet the working conditions and can be packaged and shipped.

[0099] Example 3

[0100] Prepare titanium-steel composite pipes (outer diameter 500mm, inner diameter 450mm, length unlimited), wherein the titanium pipe has an inner diameter of 450mm and an outer diameter of 470mm.

[0101] (1) Selecting suitable steel pipes and titanium pipes

[0102] Q235 steel pipe and TA2 titanium pipe were selected, with the inner diameter of the steel pipe being 470 mm. -1 The outer diameter is 500 mm, the inner diameter of the titanium tube is 450 mm, and the outer diameter is 470 mm. +1 mm.

[0103] (2) Surface pretreatment

[0104] The outer diameter of the titanium pipe and the inner diameter of the steel pipe selected in step 1 are subjected to surface pretreatment (including removing rust, oil and other attachments from the surface, straightening the pipe, and correcting the roundness of the inner and outer circles, etc.) to remove the surface attachments of the two to ensure the bonding quality of the interface between the two after the red-coated composite molding.

[0105] The roundness of the outer diameter of the titanium tube was straightened using a commercially available roller straightening machine.

[0106] The inner diameter of the steel pipe is straightened using the inner diameter straightening device of this invention, specifically as follows: Figure 1 As shown, the grinding wheel is powered by high-pressure air, and the operator pushes it to provide axial thrust, thereby straightening the inner wall of the tube.

[0107] The outer diameter of the titanium pipe and the inner diameter of the steel pipe were sandblasted. The sandblasting parameters were as follows: the sand particle size was 80 mesh (150μm) and the impact force was 5m / s.

[0108] (3) Determine the interference amount

[0109] The fit between the outer diameter of the titanium tube and the inner diameter of the steel tube is achieved using a large interference fit. Specifically, the interference fit is selected as follows: for titanium tube outer diameters greater than 300mm and less than 500mm, the total interference fit is 4mm, meaning the inner diameter of the steel tube is 4mm larger than the outer diameter of the titanium tube.

[0110] (4) Calculate the temperature of red dress

[0111] The calculation of the red-fitting temperature is to select an appropriate expansion amount based on a certain interference fit between the titanium tube and the steel tube, so as to avoid problems such as reduced interfacial bonding quality due to excessive fit clearance or cracking due to insufficient fit clearance. The red-fitting temperature is calculated by formula (1) and is 684~706℃, with 700℃ selected.

[0112] (5) Heat treatment

[0113] The steel pipes processed in step 2 are heated in a conventional box furnace at the temperature calculated in step 4. The steel pipes are placed in the furnace after it reaches the required temperature and then left in the set temperature zone for 15 minutes without a protective atmosphere.

[0114] (6) Red Dress Combination

[0115] The heated steel pipe from step 5 is quickly transferred and placed on a refractory insulating brick platform. Then, the titanium pipe is quickly nested inside the high-temperature steel pipe, followed by air cooling of the outer wall of the steel pipe. After cooling to room temperature, the thermal expansion and contraction of the steel pipe causes the titanium pipe to be encased within the inner surface of the steel pipe, completing the fit and thus obtaining a titanium-steel composite pipe blank. (Details follow...) Figure 2As shown. The heated steel pipe from step 5 is quickly removed and placed on the refractory insulating brick platform 6. According to the pre-adjusted assembly position, the titanium pipe is quickly squeezed into the steel pipe under the action of the transmission manipulator 1. Then, it is rapidly cooled by air cooling to obtain a composite pipe in which the titanium pipe and the steel pipe are tightly bonded.

[0116] (7) Low temperature treatment

[0117] The titanium-steel composite pipe blank obtained in step 6 is transferred to the heating furnace again, heated to 180°C and held for 18 hours to obtain the finished titanium-steel composite pipe.

[0118] (8) Non-destructive testing

[0119] For the titanium-steel composite pipe processed in step 7, according to the national standard SY / T 7464-2020 "Technical Standard for Welding and Non-destructive Testing of Corrosion-resistant Alloy Bimetallic Composite Pipes", X-ray detection was used to detect the bonding state at the interface between the two. No loose joints or cracks were found within a unit square centimeter, indicating that the bonding quality between the titanium pipe and the steel pipe can meet the working conditions and can be packaged and shipped.

Claims

1. A method for preparing titanium-steel composite pipes using red-coating technology, characterized in that: Specifically, the steps include the following: Step 1: Treat the outer diameter surface of the titanium pipe and the inner diameter surface of the steel pipe; In step 1, the treatment of the outer diameter surface of the titanium pipe and the inner diameter surface of the steel pipe includes: removing the adhering substances on the outer diameter surface of the titanium pipe and the inner diameter surface of the steel pipe, straightening the steel pipe, and correcting the roundness of the titanium pipe. In step 1, when straightening the steel pipe, three grinding wheels (10) of the same size are assembled on the chuck of the centerless mold (11) to form a centerless rotating circle. The diameter of the centerless rotating circle is the inner diameter of the steel pipe. Step 2: Based on Step 1, determine the interference fit between the outer diameter of the titanium tube and the inner diameter of the steel tube. In Step 2, when the outer diameter of the titanium tube is less than 30mm, the total interference fit is 0.02mm~0.05mm, meaning the inner diameter of the steel tube is 0.05mm smaller than the outer diameter of the titanium tube. When the outer diameter of the titanium tube is greater than 30mm but less than 150mm, the total interference fit is 0.1mm~0.2mm, meaning the inner diameter of the steel tube is 0.2mm smaller than the outer diameter of the titanium tube. When the diameter is greater than 150mm but less than 300mm, the total interference is 0.2mm~0.4mm, meaning the inner diameter of the steel pipe is 0.4mm smaller than the outer diameter of the titanium pipe; when the outer diameter of the titanium pipe is greater than 300mm, the total interference is 0.5mm~0.8mm, meaning the inner diameter of the steel pipe is 0.8mm smaller than the outer diameter of the titanium pipe; when the outer diameter of the titanium pipe is greater than 500mm, the total interference is 1.0mm~2.0mm, meaning the inner diameter of the steel pipe is 2mm smaller than the outer diameter of the titanium pipe. Step 3: Calculate the red-coating temperature based on Step 2, and heat the steel pipe according to the calculated temperature; in Step 3, the red-coating temperature is calculated according to the following formula (1): （1）； In the formula: Δ represents the interference fit between the inner diameter of the steel pipe and the outer diameter of the titanium pipe on one side, in mm; α represents the coefficient of linear expansion of steel; r 内 Indicates the inner diameter of the steel pipe, in mm; In step 3, before heating the steel pipe, support balls are placed inside the steel pipe. When the temperature in the bogie furnace rises to T℃, the steel pipe with support balls is placed into the bogie furnace for heating treatment. The temperature zone is set and held for 10 to 15 minutes without a protective atmosphere. Step 4: The titanium pipe is nested inside the steel pipe heated in Step 3 to obtain a titanium-steel composite pipe. The specific process of Step 4 is as follows: First, the titanium pipe is placed on the ball bearing (8), and then the screw lifting platform (7) is adjusted to the red-fitting position required for the titanium pipe and the steel pipe. Then, the steel pipe heated in Step 3 is quickly transferred from the trolley furnace to the refractory insulating brick platform (6). Subsequently, multiple fixed manipulators (3) are used to clamp and fix the steel pipe in the red-fitting position along the central axis of the steel pipe. Finally, the transmission manipulator (1) pushes the titanium pipe into the inner diameter of the steel pipe to complete the red-fitting composite. Step 5: The steel-titanium composite pipe obtained in Step 4 is subjected to heat preservation treatment to obtain the finished titanium-steel composite pipe. The specific process of Step 5 is as follows: the titanium-steel composite pipe blank obtained in Step 4 is transferred to the heating furnace again, heated to 120℃~240℃ and then kept at the temperature for 12h~24h to obtain the finished titanium-steel composite pipe.

Images