Preparation method of bimetal composite seamless tube

Abstract

The invention discloses a preparation method of a bimetal composite seamless pipe. The preparation method comprises the following steps: S1, selecting material sizes of a base pipe and a covering pipe for preparing a composite pipe; s2, preparing a low-detonation-velocity explosive for explosive welding of the composite pipe; s3, the base pipe and the covering pipe obtained in the step S1 and the low-detonation-velocity explosive obtained in the step S2 are installed and fixed, explosive welding is conducted, and the composite pipe is obtained; and S4, the composite pipe obtained in the step S3 is cleaned, subjected to flaw inspection and corrected, then the composite pipe is machined through rolling, and the finished bimetal composite seamless pipe is obtained. And S5, diffusion annealing treatment is conducted on the finished bimetal composite seamless pipe obtained in the step S4, then damage inspection, correction and surface polishing are conducted, and the bimetal composite seamless pipe is obtained. The method disclosed by the invention solves the problems that the interface connection strength of the composite pipe compounded by other methods is not high or the manufacturing process is complicated, and the composite pipe with a relatively long size (2m and above) cannot be compounded at one time through explosive cladding.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of heterogeneous metal composite pipes, and particularly relates to a method for preparing a bimetallic composite seamless pipe. Background Art

[0002] Bimetallic composite pipes are widely applicable to the oil and gas transportation in acidic oil and gas fields with strong corrosion, the sewage reinjection of injection wells, and the pipeline engineering for offshore oil and gas development. They are also widely used in various industries such as purification condensers and high-temperature condensers for petroleum refining. They are urgently needed products for the extraction and transportation of shale gas and high-sulfur natural gas in China, and have great market potential. A bimetallic composite pipe consists of an outer base pipe and an inner lining pipe. The outer base pipe usually adopts carbon steel or alloy steel to bear the working pressure of the pipeline system; the inner lining pipe selects different corrosion-resistant alloys according to the chemical composition of the transported medium; this structural design not only improves the corrosion resistance of the pipeline but also effectively extends the service life. The corrosion-resistant alloy layer is generally coated on the inner wall of the carbon steel pipe in the form of mechanical or metallurgical bonding.

[0003] At present, bimetallic composite pipes are compounded by mechanical or metallurgical methods. Among them, mechanical rolling method, drawing composite method, and hydraulic composite method are the most commonly used composite pipe processing methods at home and abroad; in mechanical composite methods, for composite pipes prepared by methods such as mechanical drawing and mechanical spinning, there are problems such as low bonding strength between the base pipe and the lining, and it is easy to cause mechanical damage or local thinning to the lining or base pipe material during the processing; among the failure problems of current bimetallic composite pipes, the more common failures of mechanical composite pipes include welding failure and lining collapse failure, and the number of accidents in recent years has reached more than 70% of the total number of accidents.

[0004] The metallurgical composite methods include centrifugal casting method, surfacing method, hot extrusion method, brazing method, explosion welding method, centrifugal thermite method, composite plate (coil) forming welding method, etc.; it is worth mentioning that for the composite pipes made by the composite plate (coil) forming welding method, there are problems such as relatively thick cladding thickness, poor economy, and long weld length of the composite material, which is easy to generate defects; for metallurgical bonding methods such as hot processing, such as the hot extrusion method, nodular cracks are likely to occur in the inner lining layer. If the surfacing method is adopted, the material combination is limited to materials that are compatible under fusion welding, with high bonding strength but low efficiency and high cost.

[0005] Explosion welding composite uses explosives as the energy source. Under the detonation and impact of the explosives, a thin welding transition zone with characteristics of plastic deformation, melting, diffusion, and waveform is formed on the surface of the welded metals within a very short process, thereby achieving the composite process. Preparing composite pipes by explosion composite has the advantages of one-time instant molding, basically the same pressure at each point, relatively high bonding strength, a wide range of material selection, and little impact on the corrosion resistance of corrosion-resistant alloys. However, due to the limitations of explosion, the composite length of explosion composite pipes is limited, which restricts the cost reduction of their industrial applications. Therefore, there is an urgent need for a bimetallic composite pipe that can solve the disadvantages such as cladding damage or low interfacial bonding strength caused by other composite methods, and can also solve the problem that explosion composite pipes cannot composite longer size specifications. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method of a bimetallic composite seamless pipe, which can solve the disadvantages such as cladding damage or low interfacial bonding strength caused by other composite methods, and can also solve the problem that explosion composite pipes cannot composite longer size specifications.

[0007] The present invention provides a preparation method of a bimetallic composite seamless pipe, including the following steps:

[0008] S1. Select the material sizes of the base pipe and the cladding pipe for preparing the composite pipe;

[0009] S2. Configure low-detonation-velocity explosives for explosion welding of the composite pipe;

[0010] S3. Install and fix the base pipe and the cladding pipe obtained in step S1 and the low-detonation-velocity explosives obtained in step S2, and perform explosion welding to obtain a composite pipe;

[0011] S4. Clean, inspect for damage, and straighten the composite pipe obtained in S3, and then process the composite pipe through rolling to obtain a finished bimetallic composite seamless pipe;

[0012] S5. Perform diffusion annealing treatment on the finished bimetallic composite seamless pipe obtained in step S4, and then perform inspection for damage, correction, and surface grinding to obtain the bimetallic composite seamless pipe.

[0013] Further, in step S1, the sizes of the base pipe and the cladding pipe are selected using an empirical formula:

[0014] S = Kεr

[0015] Wherein, S is the radial clearance between the cladding pipe and the base pipe; K is a correction coefficient, taking a value of 0.9 when the wall thickness of the cladding pipe is greater than 2 mm, taking a value of 0.7 - 0.9 when the wall thickness of the cladding pipe is 0.5 mm - 2 mm, and in order to resist corrosion erosion, the wall thickness of the cladding layer is greater than 0.5 mm; εis the radial strain of the composite pipe, and its value range is 0.05 - 0.1; r is the outer diameter of the clad pipe.

[0016] Preferably, the base pipe material is steel, and the clad pipe material includes titanium, nickel and stainless steel; the thickness of the clad pipe is 0 - 3 mm.

[0017] Furthermore, the configuration formula of the low detonation velocity explosive in step S2 includes antimony-free rock ammonium nitrate explosive, calcium carbonate powder, silicon carbide powder and water; by mass fraction, 60 - 70 parts of antimony-free rock ammonium nitrate explosive, 15 - 20 parts of calcium carbonate powder, 5 - 15 parts of silicon carbide powder, and 5 - 10 parts of water; the low detonation velocity explosive needs to be uniformly mixed and configured on-site before use.

[0018] Furthermore, the configuration formula of the antimony-free rock ammonium nitrate explosive is: by mass fraction, 70 - 85 parts of ammonium nitrate, 3 - 6 parts of wood powder, 10 - 20 parts of modified urea nitrate, and 1.5 - 4 parts of composite modifier.

[0019] Furthermore, step S3 specifically includes the following steps:

[0020] S31. Clean the surfaces of the base pipe and the clad pipe to remove oil, impurities and oxide films;

[0021] S32. Fix the cleaned base pipe and clad pipe with a clamping die, place them in a pre-dug hole, insert a mandrel into the clad pipe, and fill the low detonation velocity explosive obtained in step S2 in a loose filling manner;

[0022] S33. Install a detonator in the middle of the pipe length, and perform explosive welding by the method of detonating in the middle of the pipe body.

[0023] Preferably, in step S31, for the base pipe, use alcohol or organic solvent to remove surface oil and impurities, and then use acid or alkali or grinding to remove the oxide film on the surface of the base pipe;

[0024] For the clad pipe, use alcohol or organic solvent to remove surface oil and impurities, and then use a solution prepared from 45% nitric acid, 5% hydrofluoric acid and 50% water to clean the oxide film on the surface of the clad pipe.

[0025] Preferably, in step S32, the clamping die includes concentric circular grooves of different sizes and a protective outer mold; the diameter of the circular groove corresponds to the diameters of the base pipe and the clad pipe; the protective outer mold is on the outer layer of the base pipe and is made of carbon steel;

[0026] When fixing the base tube and the cladding tube, the base tube and the cladding tube are fixed using corresponding circular grooves, a buffer is filled between the base tube and the protective outer mold, and a welding filler metal is placed in the welding gap; the thickness of the welding filler metal is 0.1 - 0.5 mm, the welding filler metal is rolled from a foil into a cylindrical shape, the outer diameter of the rolled welding filler metal cylinder is the same as the inner diameter of the base tube, and it is fixed to the end of the base tube with glue to prevent the welding filler metal from moving.

[0027] According to different metal combinations between the base tube material and the cladding tube material, different welding filler metals are selected, specifically:

[0028] When the base tube material is steel and the cladding tube material is titanium, a silver-based filler metal is selected for welding; the silver-based filler metal has an Ag-Cu eutectic structure as the matrix and alloying elements such as Ti, Zn, Li, Ni, Al are added to obtain filler metals with different properties;

[0029] When the base tube material is steel and the cladding tube material is stainless steel, pure copper is used as the welding filler metal.

[0030] Preferably, the mandrel is hollow to ensure the coaxiality of the assembly between the tubes; in the loose loading method, low detonation velocity explosives are filled between the mandrel and the cladding tube, and a buffer layer is filled between the low detonation velocity explosives and the cladding tube.

[0031] Preferably, a honeycomb aluminum or other porous structure devices with a preset thickness are placed under the clamping die to provide space for exhaust during explosive welding.

[0032] Further, in step S4, the surface soil of the composite tube obtained in step S3 is cleaned with a high-pressure water gun, and then the composite tube is detected for damage. The composite tubes that meet the damage detection requirements are placed in a round tube straightening machine for straightening;

[0033] Ultrasonic flaw detection is used for damage detection to determine the bonding area of the composite tube, the area with a bonding rate of less than 100% at the end is cut off, and the remaining composite tubes with a bonding rate of 100% are placed in a three-roll round tube straightening machine for straightening;

[0034] Both ends of the composite tube are welded and sealed, and then sent into a furnace for heating and rolling. A finished bimetallic composite tube with a preset size is obtained by reducing the diameter, sizing, and cutting the head;

[0035] The specific process of the heating and rolling is as follows: first, the composite tube is kept in a heating furnace for 15 min - 60 min at a temperature of 850 - 1150 °C, and then passed through pass rolling, ensuring that the single-pass reduction rate is within 20%, the area reduction rate is within 10%, and the diameter reduction rate is within 5% to elongate the composite tube to obtain a finished bimetallic composite tube with a preset size.

[0036] Further, in step S5, the finished bimetallic composite pipe obtained in step S4 is subjected to diffusion annealing treatment, and then the annealed and cooled composite pipe is inspected for defects. The composite pipe with qualified defect inspection is placed in a round pipe straightening machine for straightening, and then surface polishing is carried out to obtain the bimetallic composite seamless pipe;

[0037] The diffusion annealing treatment is specifically annealing for 1 - 3 h in a constant temperature environment at a temperature of 550 - 950 °C. After annealing, it can be cooled with the furnace or air - cooled, and ultrasonic flaw detection is carried out after cooling to room temperature.

[0038] Ultrasonic flaw detection is used to detect the bonding area of the composite pipe. The area with a bonding rate less than 100% at the end is cut off, and the composite pipe with the remaining bonding rate of 100% is placed in a three - roll round pipe straightening machine for straightening.

[0039] Principle of the present invention:

[0040] Since there are two metals combined in the bimetallic composite pipe, the bimetallic bonding interface is one of the important factors affecting the strength of the composite pipe. By adding welding filler metal in explosive cladding, the present invention solves the problem that interface delamination may occur in the rolling of bimetallic pipes due to inconsistent metal fluidity. At the same time, rolling solves the defect that the explosive cladding process cannot produce composite pipes with longer scales.

[0041] Advantages of the present invention:

[0042] The present invention adopts the method of explosion + brazing + rolling, using explosive cladding to form the tube blank, reducing the cumbersome procedures of brazing and taking advantage of the simple and efficient re - combination rolling for extended forming. It solves two problems. One is the problem that the interface connection strength of composite pipes formed by other methods is not high or the manufacturing process is complex. On the other hand, it solves the technical disadvantage that explosive cladding cannot produce composite pipes with longer sizes (2 m and above) in a single time. Description of the drawings

[0043] Figure 1 It is a schematic diagram of the overall installation of the device before explosion welding in the embodiment;

[0044] Figure 2 It is a schematic cross - sectional view of the bimetallic composite seamless pipe obtained in the embodiment. Detailed implementation manners

[0045] Example 1

[0046] A clad pipe with an outer diameter of 100 mm, a wall thickness of 3 mm, and a length of 1.6 m is selected. The material of the clad pipe is TA1; according to the empirical formula calculation, the gap value is taken as 5 mm, and thus the outer diameter size of the base pipe is determined to be 140 mm, the wall thickness is 15 mm, and the length is 1.6 m. The material of the base pipe is 40Cr;

[0047] The low detonation velocity explosive is prepared by uniformly mixing on-site according to the ratio of 65% antimony-free rock ammonium nitrate explosive (composed of 75% ammonium nitrate, 5% wood powder, 17.5% modified urea nitrate, and 2.5% composite modifier), 17.5% calcium carbonate powder, 10% silicon carbide powder, and 7.5% water.

[0048] Use organic solvents to remove oil stains and impurities on the surfaces of the base tube and the clad tube; use a solution prepared from 45% nitric acid, 5% hydrofluoric acid, and 50% water by mass fraction to clean the oxide film, oil stains, and impurities on the surface of the clad tube.

[0049] Apply a layer of 0.15 mm Ag-27Cu-4.5Ti solder inside the base tube. The overall shape is cylindrical, and the overall length is slightly longer than the base tube, about 1601 - 1603 mm. The ends are bonded with quick-drying glue to prevent the solder from moving.

[0050] Place the processed base tube and clad tube into the clamping die at the corresponding positions. The clamping die consists of a concentric circular groove made of PVC and a protective outer mold. The diameter of the circular groove corresponds to the diameters of the base and clad tubes.

[0051] The protective outer mold is on the outer layer of the base tube, made of Q235, with an inner diameter of 200 mm, a thickness of 20 mm, and a length of 1.6 m. A buffer is filled between the base tube and the protective outer mold.

[0052] Insert a PVC tube with an outer diameter of 70 mm, a wall thickness of 1 mm, and a length of 1.6 m at the corresponding concave groove in the center of the clad tube. The space between the PVC tube and the clad tube is filled with explosive in a loose-packed manner. Sodium silicate is filled as a buffer layer between the explosive and the clad tube to ensure the explosive is arranged at a ratio of 150 g / 100 mm.

[0053] After installation, the overall schematic diagram of the device is as Figure 1 shown.

[0054] Place the clamping die in a pre-dug pit. The size of the pit is slightly larger than the protective outer mold. To ensure the exhaust effect during explosive welding, a 50 mm thick honeycomb aluminum or grid-shaped PVC can be placed under the clamping die to provide space for exhaust during explosive welding.

[0055] Place the detonator ignition point at the center of the pipe. The personnel evacuate to a safe place, and after detonation, the welding is completed.

[0056] After welding, use a high-pressure water gun to clean the composite pipe, and then use ultrasonic flaw detection to determine the bonding area of the composite pipe. Cut off the unbonded area at the end. After cutting, the length of the composite pipe is 1.5 m, ensuring that the bonding rate of the remaining part reaches 100%.

[0057] After the inspection of the carbon steel composite pipe meets the requirements, the composite pipe is placed in a three-roll round pipe straightening machine for straightening, and the two ends of the pipe are welded and sealed by argon arc welding. Then, it is kept at 850 °C for 1 h in a heating furnace, and then rolled through a pass to ensure that the maximum single-pass deformation is 15%, the area reduction rate is 8%, and the diameter reduction rate is 4%. The composite pipe is rolled and extended to 2.67 m.

[0058] The rolled composite pipe is annealed under appropriate process conditions and placed in a constant temperature environment of 550 - 650 °C for 2 hours.

[0059] Ultrasonic flaw detection is used to determine that the bonding of the composite pipe is good, ensuring that the bonding rate reaches 100%.

[0060] After the inspection of the carbon steel composite pipe meets the requirements, the composite pipe is placed in a three-roll round pipe straightening machine for straightening, and then surface grinding and polishing are carried out.

[0061] Take a shear sample for testing, and the interfacial bonding strength of the titanium steel composite pipe is 176 Mpa.

[0062] Example 2

[0063] Select a cladding pipe with an outer diameter of 90 mm, a wall thickness of 3 mm, and a length of 1.6 m. The material of the cladding pipe is SUS304; according to the empirical formula calculation, the gap value is taken as 5 mm, and thus the inner diameter size of the base pipe is determined to be 100 mm, the wall thickness is 16 mm, and the length is 1.6 m. The material of the base pipe is 20 steel;

[0064] The low detonation velocity explosive is prepared by uniformly mixing on-site in the ratio of 65% antimony-free rock ammonium nitrate explosive (mixed by 75% ammonium nitrate, 5% wood powder, 17.5% modified urea nitrate, and 2.5% composite modifier), 17.5% calcium carbonate powder, 10% silicon carbide powder, and 7.5% water.

[0065] Use an 80 °C 10% NaOH solution to remove the oil and impurities on the surfaces of the base pipe and the cladding pipe; use a 10% HCl solution to remove the oxide film on the surface of the cladding pipe, and then use a wire brush to remove the residual oxide film.

[0066] Use a layer of 0.1 mm pure copper foil (brazing filler metal) to be pasted inside the base pipe, with a total cylindrical shape, and the total length is slightly longer than the base pipe, about 1601 - 1603 mm. The ends are bonded with quick-drying glue to prevent the brazing filler metal from moving.

[0067] Place the processed base pipe and cladding pipe into the clamping die according to the corresponding positions. The clamping die consists of a concentric circular ring groove made of PVC material and a protective outer die. The diameter of the circular ring groove corresponds to the diameters of the base and cladding pipes.

[0068] The protective outer mold is on the outer layer of the base pipe, made of Q235, with an inner diameter of 180, a thickness of 20 mm, and a length of 1.6 m. Wet fine sand is filled between the base pipe and the protective outer mold as a buffer during explosion, ensuring that all the fine sand is soaked and the gap is filled up.

[0069] Insert a PVC pipe with an outer diameter of 60 mm, a wall thickness of 1 mm, and a length of 1.6 m at the corresponding concave groove in the center of the clad pipe. The explosive is arranged in the form of cartridge charging between the PVC pipe and the clad pipe, ensuring a ratio of 150 g / 100 mm.

[0070] Place the clamping mold in a pre-dug pit. The size of the pit is slightly larger than the protective outer mold. To ensure the exhaust effect during explosive welding, a 50-mm-thick honeycomb aluminum or grid-shaped PVC can be placed under the clamping mold to provide space for exhaust during explosive welding.

[0071] Place the detonating point of the detonator at the center of the pipe, and the personnel evacuate to a safe place. After detonation, the welding is completed.

[0072] After cleaning the welded composite pipe with a high-pressure water gun, use ultrasonic flaw detection to determine the bonding area of the composite pipe, cut off the unbonded area at the end. After cutting, the length of the composite pipe is 1.5 m, ensuring that the bonding rate of the remaining part reaches 100%.

[0073] After the carbon steel composite pipe passes the detection and flaw detection requirements, place the composite pipe in a three-roll round pipe straightening machine for straightening. Use argon arc welding to weld and seal both ends of the pipe, then keep it at 1150 °C in a heating furnace for 30 min. Ensure the temperature is above 900 °C before rolling, and then through pass rolling, ensure a single-pass reduction rate of 15%, an area reduction rate of 8%, and a diameter reduction rate of 4%. Roll the composite pipe to extend it to 2 m.

[0074] Anneal the rolled composite pipe under appropriate process conditions, and anneal it in a constant temperature environment of 920 ± 20 °C for 1 hour.

[0075] Use ultrasonic flaw detection to determine that the bonding of the composite pipe is good, ensuring that the bonding rate reaches 100%.

[0076] After the carbon steel composite pipe passes the detection and flaw detection requirements, place the composite pipe in a three-roll round pipe

[0077] straightening machine for straightening, and then perform surface grinding and polishing.

[0078] Take a shear sample for testing, and the interfacial bonding strength of the stainless steel composite pipe is 159 Mpa.

Claims

1. 一 A method for preparing a bimetallic composite seamless pipe, characterized in that: The following steps are involved: S1. Select the material size of the base pipe and the covering pipe for preparing the composite pipe; S2. Low detonation velocity explosives for composite pipe explosion welding; S3. The base tube and the covering tube obtained in step S1 and the low detonation velocity explosive obtained in step S2 are installed and fixed, and explosion welding is performed to obtain a composite tube; S4. The composite tube obtained in S3 is cleaned, inspected, and corrected, and then the composite tube is processed by rolling to obtain a finished bimetallic composite seamless tube; S5. The finished bimetallic composite seamless pipe obtained in step S4 is subjected to diffusion annealing treatment, and then subjected to flaw inspection, correction and surface polishing to obtain the bimetallic composite seamless pipe.

2. The method for preparing a bimetallic composite seamless pipe according to claim 1, characterized in that: In step S1, the sizes of the base tube and the cover tube are selected using an empirical formula: S=Kεr Wherein, S is the radial clearance between the cladding pipe and the base pipe; K is the correction coefficient, which is 0.9 when the cladding pipe wall thickness is greater than 2 mm, and 0.7 to 0.9 when the cladding pipe wall thickness is 0.5 mm to 2 mm, and the cladding pipe wall thickness range is greater than or equal to 0.5 mm; ε is the radial strain of the composite pipe, which ranges from 0.05 to 0.1; r is the outer diameter of the cladding pipe; The base pipe material is steel, and the covering pipe materials include titanium, nickel and stainless steel; the covering pipe thickness is 0 to 3 mm.

3. The method for preparing a bimetallic composite seamless pipe according to claim 1, characterized in that: The configuration formula of the low detonation velocity explosive described in step S2 includes antimony-free rock ammonium nitrate explosive, calcium carbonate powder, silicon carbide powder and water; calculated by mass fraction, the antimony-free rock ammonium nitrate explosive is 60-70 parts, the calcium carbonate powder is 15-20 parts, the silicon carbide powder is 5-15 parts, and the water is 5-10 parts; the low detonation velocity explosive needs to be evenly mixed and configured on site before use.

4. The method for preparing a bimetallic composite seamless pipe according to claim 3, characterized in that: The antimony-free rock ammonium nitrate explosive is formulated as follows: by mass fraction, 70 to 85 parts of ammonium nitrate, 3 to 6 parts of wood flour, 10 to 20 parts of modified urea nitrate, and 1.5 to 4 parts of a composite modifier.

5. The method for preparing a bimetallic composite seamless pipe according to claim 1, characterized in that: Step S3 specifically includes the following steps: S31. Clean the surface of the base tube and the covering tube to remove oil, impurities and oxide film; S32. The cleaned base tube and the covering tube are fixed by a clamping mold, placed in a pre-dug hole, a mandrel is inserted into the covering tube, and the low detonation velocity explosive obtained in step S2 is filled in a loose manner; S33. Install detonators in the middle of the tube length and use the method of detonating in the middle of the tube to perform explosive welding.

6. The method for preparing a bimetallic composite seamless pipe according to claim 5, characterized in that: In step S31, alcohol or an organic solvent is used to remove oil and impurities on the surface of the substrate tube, and then an acid, an alkali or a polishing method is used to remove the oxide film on the surface of the substrate tube; For the covered pipe, use alcohol or organic solvent to remove surface oil and impurities, and then use a solution prepared with a mass fraction of 45% nitric acid, 5% hydrofluoric acid and 50% water to clean the oxide film on the surface of the covered pipe.

7. The method for preparing a bimetallic composite seamless pipe according to claim 5, characterized in that: In step S32, the clamping mold includes concentric circular grooves of different sizes and a protective outer mold; the diameter of the circular groove corresponds to the diameter of the base tube and the covering tube; the protective outer mold is on the outer layer of the base tube and is made of carbon steel; When fixing the base tube and the covering tube, the base tube and the covering tube are fixed by using corresponding annular grooves, a buffer is filled between the base tube and the protective outer mold, and a welding brazing material is placed in the welding gap; the thickness of the welding brazing material is 0.1-0.5 mm, and the welding brazing material is rolled into a tube from a foil shape, and the outer diameter of the rolled welding brazing material tube is consistent with the inner diameter of the base tube, and is fixed to the end of the base tube with glue to prevent the welding brazing material from moving. The core rod is hollow to ensure the coaxiality of the assembly between the tubes; in the loose installation method, low-detonation-velocity explosives are filled between the core rod and the covering tube, and a buffer layer is filled between the low-detonation-velocity explosives and the covering tube; A honeycomb aluminum or other supporting porous structure with a preset thickness is placed under the clamping mold to provide space for exhaust during explosion welding.

8. The method for preparing a bimetallic composite seamless pipe according to claim 7, characterized in that: Different welding filler metals are selected according to the different metal combinations between the base tube material and the cladding tube material, specifically: When the base tube material is steel and the covering tube material is titanium, the welding brazing filler metal is a silver-based brazing filler metal; the silver-based brazing filler metal is a brazing filler metal having different properties by using Ag-Cu eutectic structure as a matrix and adding Ti, Zn, Li, Ni, and Al alloy elements; When the base pipe material is steel and the covering pipe material is stainless steel, pure copper is used as the solder.

9. The method for preparing a bimetallic composite seamless pipe according to claim 1, characterized in that: In step S4, the soil on the surface of the composite pipe obtained in step S3 is cleaned with a high-pressure water gun, and then the composite pipe is inspected for defects, and the composite pipe that meets the inspection requirements is placed in a round pipe correction machine for correction; Ultrasonic flaw detection is used to determine the bonding area of ​​the composite pipe, and the area with a bonding rate of less than 100% at the end is cut off. The composite pipe with a remaining bonding rate of 100% is placed in a three-roller round pipe straightening machine for correction; The two ends of the composite pipe are welded and sealed, and then sent into a furnace for heating and rolling, and the finished bimetallic composite pipe of a preset size is obtained by reducing the diameter, sizing, and cutting the head; The specific process of the hot rolling is: first, the composite pipe is kept in a heating furnace for 15min to 60min at a temperature of 850 to 1150°C, and then rolled through a groove to ensure that the single-pass reduction rate is within 20%, the area reduction rate is within 10%, and the diameter reduction rate is within 5%, and the composite pipe is extended to obtain a finished bimetallic composite pipe of a preset size.

10. The method for preparing a bimetallic composite seamless pipe according to claim 1, characterized in that: In step S5, the finished bimetallic composite pipe obtained in step S4 is subjected to diffusion annealing treatment under a suitable process, and then the composite pipe after annealing and cooling is subjected to detection and flaw inspection, and the composite pipe that passes the flaw inspection is placed in a round pipe straightening machine for correction, and then surface polishing is performed to obtain the bimetallic composite seamless pipe; The diffusion annealing treatment is specifically annealing in a constant temperature environment of 550-950°C for 1-3h, furnace cooling or air cooling is possible, air cooling is more efficient, and the test is performed after cooling to room temperature; Ultrasonic flaw detection is used to determine the bonding area of ​​the composite pipe, and the area with a bonding rate of less than 100% at the end is cut off. The composite pipe with a remaining bonding rate of 100% is placed in a three-roller round pipe straightening machine for correction.

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