High-strength corrosion-resistant alloy coiled tubing and preparation method thereof

Abstract

The invention provides a high-strength corrosion-resistant alloy coiled tubing and a preparation method thereof. The high-strength corrosion-resistant alloy coiled tubing comprises the following elements in percentage by mass: 0.03-0.05% of C; si: less than or equal to 1.0%; mn: 3 to 25%; p: < = 0.009%; s: < = 0.003%; 13%-30% of Cr; 1 to 10 percent of Ni; 0.05 to 1.0 percent of N; 0.1% to 2.0% of Mo; cu: less than or equal to 3.5%; and the balance of Fe and inevitable impurities. The components are the basis for ensuring that the high-strength corrosion-resistant alloy coiled tubing has ultrahigh plasticity, the ultrahigh plasticity ensures that the coiled tubing has good cold drawing performance, manufacturing of the high-strength corrosion-resistant alloy coiled tubing is achieved, nitride Cr2N and the like which are distributed in a dispersed mode are beneficial for further improving the strength of the aging-state coiled tubing, and the service life of the high-strength corrosion-resistant alloy coiled tubing is prolonged. Therefore, the final high-strength corrosion-resistant alloy coiled tubing has excellent mechanical strength and corrosion resistance.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas development and deep well carbon dioxide injection and production, and in particular to a high-strength corrosion-resistant alloy continuous pipe and a preparation method thereof. Background Art

[0002] At present, the development of oil and gas fields is moving towards deep wells (≥3500) and ultra-deep wells (6000-8000). The carbon steel coiled pipe grade has also developed from the initial CT80 and CT90 to the current CT150 to meet the on-site demand for ultra-high strength coiled pipes in deep and ultra-deep wells; for the development of acidic oil and gas (hydrogen sulfide, carbon dioxide oil and gas fields) in deep wells (≥3500) and ultra-deep wells (6000-8000), deep wells (≥3500) and ultra-deep wells (6000-8000), 00) Due to the use conditions such as carbon dioxide injection and production, oil and gas fields have put forward huge demands for ultra-high strength corrosion-resistant alloy continuous pipe products, but conventional austenitic, ferritic stainless steel, and duplex stainless steel products are difficult to achieve high strength due to their own organizational characteristics. Although martensitic stainless steel has high strength, it is difficult to perform continuous pipe forming processing due to its organizational characteristics. It is difficult to produce high-strength corrosion-resistant alloy continuous pipes for acidic oil and gas fields that meet the requirements of deep wells, ultra-deep wells, and shale gas wells through conventional continuous pipe production and manufacturing methods.

[0003] In addition, the surface roughness of the coiled tube is closely related to the corrosion resistance of the tube surface. The smaller the surface roughness of the stainless steel test block, the better the resistance to salt spray corrosion and pitting corrosion. The greater the surface roughness of the test block, the worse the corrosion resistance. The reason is: when the surface roughness of the part is greater, the surface is more likely to form corrosive liquid accumulation, resulting in surface corrosion. Moreover, the greater the surface roughness, the larger the actual surface area of ​​the part surface, and the more corrosive liquid it contacts, so it is easier to corrode. At present, the surface roughness of the corrosion-resistant alloy coiled tube mainly depends on the rolling of the plate. The surface roughness of the coiled tube cannot be changed after welding. The general surface roughness Ra is 6.3~12.5. During the application of the underground well, the corrosion rate will increase due to the high surface roughness, and the better corrosion resistance of the corrosion-resistant alloy coiled tube cannot be fully exerted.

[0004] At present, the highest steel grade of domestic corrosion-resistant alloy continuous pipe is 2507 continuous pipe, with a maximum yield strength of 90,000 ksi, a tensile strength of 116,000 ksi, and a specification of Φ50.8mm*4mm. The maximum immersion depth of the continuous pipe during injection is 2,800 meters. The immersion depth of 3,500 meters requires the continuous pipe to have a minimum yield strength of 100,000 ksi steel grade. At present, no ultra-high-strength corrosion-resistant alloy continuous oil pipe with a size of Φ50.8mm*4mm suitable for wells of 3,500m and above has been developed at home and abroad. Summary of the invention

[0005] The main purpose of the present invention is to provide a high-strength corrosion-resistant alloy continuous pipe and a preparation method thereof, so as to solve the problem that the preparation method of continuous pipe in the prior art is difficult to meet the requirements of high-strength corrosion-resistant alloy continuous pipe for acidic oil and gas fields such as deep wells, ultra-deep wells and shale gas wells.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a high-strength corrosion-resistant alloy continuous tube is provided. The element composition of the high-strength corrosion-resistant alloy continuous tube comprises, by mass percentage: C: 0.03-0.05%; Si: ≤1.0%; Mn: 3-25%; P: ≤0.009%; S: ≤0.003%; Cr: 13-30%; Ni: 1-10%; N: 0.05-1.0%; Mo: 0.1-2.0%; Cu: ≤3.5%; the rest is Fe and unavoidable impurities.

[0007] Furthermore, the texture components in the above-mentioned high-strength corrosion-resistant alloy continuous tube include: austenite with an area fraction of 30-50%, ferrite with an area fraction of 40-65%, and deformation-induced martensite with an area fraction of 5-10%.

[0008] Furthermore, the surface roughness Ra of the high-strength corrosion-resistant alloy continuous pipe is 0.4 to 1.6.

[0009] Furthermore, the yield strength of the high-strength corrosion-resistant alloy continuous pipe is ≥758MPa, the tensile strength is ≥793MPa, the hardness is ≥30HRC, and the elongation is ≥20%.

[0010] According to another aspect of the present invention, a method for preparing the above-mentioned high-strength corrosion-resistant alloy continuous tube is provided, and the preparation method comprises: step S1, preparing a coil: subjecting the raw materials including scrap steel and pig iron to initial melting, decarburization and desulfurization treatment, refining, hot rolling, first solid solution treatment, pickling, and phosphating treatment in sequence to obtain a coil; step S2, longitudinal shearing of the coil, steel strip extension, and second solid solution treatment: longitudinal shearing of the coil is performed in sequence according to the specification requirements of the continuous tube to obtain a longitudinally sheared steel strip, and the longitudinally sheared steel strip is subjected to butt welding, the second solid solution treatment, and the second solid solution treatment. Second solid solution treatment to obtain the extended steel strip; step S3, forming, welding, and third solid solution treatment: the butt-joined long steel strip is formed to obtain a formed steel strip, and the formed steel strip is longitudinally welded and then subjected to the third solid solution treatment to obtain a continuous tube billet; step S4, cold drawing treatment, annealing heat treatment: the continuous tube billet is sequentially cold drawn and annealed, and multiple cold drawing, annealing (the number of cold drawing, cold drawing speed, and cold drawing reduction are determined according to the original wall thickness and final wall thickness of the tube) heat treatment are performed to obtain a high-strength corrosion-resistant alloy continuous tube.

[0011] Furthermore, in the above step S4, the cold drawing process includes rough cold drawing and fine cold drawing performed in sequence; the temperature of the rough cold drawing is preferably 550-650°C, the rate of the rough cold drawing is preferably 2-5 m / min, and the reduction amount of the rough cold drawing should be kept within the plastic range of the material, generally ≤3 mm on one side; the temperature of the fine cold drawing is preferably 550-650°C, the rate of the fine cold drawing is preferably 0.5-1 m / min, and the reduction amount of the fine cold drawing on one side is preferably ≤1 mm; the temperature of the annealing heat treatment is preferably 600°C, and the time of the annealing heat treatment is preferably 30-70s.

[0012] Furthermore, in the above step S2, the process of longitudinal shearing of the coil, extension of the steel strip, and the second solid solution treatment includes: cutting the coil into longitudinally cut steel strips with a width of 50 to 300 mm by a longitudinal shearing unit according to the specification requirements of the high-strength corrosion-resistant alloy continuous pipe, processing the ends of the front and rear two longitudinally cut steel strips to 40 to 50°, and then butt welding the welds between the front and rear two longitudinally cut steel strips in an inert gas, and then performing a second solid solution treatment to obtain a lengthened steel strip; the temperature of the second solid solution treatment is preferably 950 to 1050°C, and the time of the second solid solution treatment is preferably 30 to 70s; and the butt welding is preferably performed by any one or more of laser welding, resistance spot welding, stir friction welding, and plasma wire welding.

[0013] Furthermore, in the above step S3, the process of forming, welding, and the third solid solution treatment includes: milling the edges of the butt-jointed long steel strip and then forming it by roller bending; preferably welding in an inert atmosphere to obtain a welded steel strip; performing a third solid solution treatment on the welded steel strip in a hydrogen atmosphere to obtain a continuous tube blank; preferably, the temperature of the third solid solution treatment is 950-1050°C, and the time of the third solid solution treatment is preferably ≤60s; preferably, laser welding, carbon dioxide gas shielded welding, plasma welding, or any one or more methods are used for welding; preferably, the inert atmosphere includes 99.7wt% argon and 2wt% nitrogen.

[0014] Furthermore, in the above step S1, the temperature of the first solution treatment is 950-1050°C, and the time of the first solution treatment is preferably ≥30 min.

[0015] Furthermore, the preparation method further comprises: performing aging heat treatment on the high-strength corrosion-resistant alloy continuous tube; preferably, the aging heat treatment temperature is 700 to 850° C., and preferably, the aging heat treatment time is 10 to 60 seconds.

[0016] Applying the technical solution of the present application, the present invention provides an element composition of a high-strength corrosion-resistant alloy continuous tube, which is characterized by low C, high Cr, low Ni, high Mn, and nitrogen. This chemical composition is the basis for ensuring that the high-strength corrosion-resistant alloy continuous tube has ultra-high plasticity. The ultra-high plasticity ensures that the continuous tube has good cold drawing performance, thereby promoting the deformation-induced phase transformation of the continuous tube and realizing the manufacture of the high-strength corrosion-resistant alloy continuous tube. The dispersed nitride Cr formed by the N element and the Cr element 2 The dispersed CrMo formed by N, Mo and Cr elements, and the dispersed FeMo formed by Mo and Fe elements, both help to ensure that the strength of the aged continuous pipe is further improved, so that the final high-strength corrosion-resistant alloy continuous pipe has excellent mechanical strength and corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0018] Figure 1 The metallographic structure diagram of a high-strength corrosion-resistant alloy coiled tube provided in Example 1 of the present invention is shown;

[0019] Figure 2 A structural schematic diagram of a cold drawing unit provided according to the specification of the present invention is shown.

[0020] Among them, the above drawings include the following reference numerals:

[0021] 1. First reel; 2. First straightener; 3. First water cooling device; 4. First online heat treatment furnace; 5. Cold drawing unit; 6. Second online heat treatment furnace; 7. Second water cooling device; 8. Second straightener; 9. Second reel. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] As analyzed in the background technology of this application, the preparation method of the continuous pipe in the prior art is difficult to meet the problem of high-strength corrosion-resistant alloy continuous pipe for acidic oil and gas fields such as deep wells, ultra-deep wells, and shale gas wells. In order to solve this problem, the present application provides a high-strength corrosion-resistant alloy continuous pipe and a preparation method thereof.

[0024] In a typical embodiment of the present application, a high-strength corrosion-resistant alloy continuous tube is provided. The element composition of the high-strength corrosion-resistant alloy continuous tube, measured in mass percentage, includes: C: 0.03-0.05%; Si: ≤1.0%; Mn: 3-25%; P: ≤0.009%; S: ≤0.003%; Cr: 13-30%; Ni: 1-10%; N: 0.05-1.0%; Mo: 0.1-2.0%; Cu: ≤3.5%; the rest is Fe and unavoidable impurities.

[0025] The present invention provides an element composition of a high-strength corrosion-resistant alloy continuous tube, which is characterized by low C, high Cr, low Ni, high Mn, and nitrogen. This chemical composition is the basis for ensuring that the high-strength corrosion-resistant alloy continuous tube has ultra-high plasticity. The ultra-high plasticity ensures that the continuous tube has good cold drawing performance, thereby promoting the deformation-induced phase change of the continuous tube and realizing the manufacture of the high-strength corrosion-resistant alloy continuous tube. The dispersed nitride Cr formed by the N element and the Cr element 2 The dispersed CrMo formed by N, Mo and Cr elements, and the dispersed FeMo formed by Mo and Fe elements, both help to ensure that the strength of the aged continuous pipe is further improved, so that the final high-strength corrosion-resistant alloy continuous pipe has excellent mechanical strength and corrosion resistance.

[0026] In addition, the wall thickness of the high-strength corrosion-resistant alloy continuous tube is preferably 1.0-6.0 mm, and the length of the high-strength corrosion-resistant alloy continuous tube is preferably in the range of 100-8000 m, which can be wound onto a reel with a suitable core diameter for transportation and use.

[0027] In one embodiment of the present application, the texture components in the high-strength corrosion-resistant alloy continuous tube include: 30-50% austenite with an area fraction; 40-65% ferrite with an area fraction; and 5-10% deformation-induced martensite with an area fraction.

[0028] The texture directly affects the performance of the pipe. The preferred texture components mentioned above are conducive to a better balance between the various textures, so that the high-strength corrosion-resistant alloy continuous pipe has excellent mechanical strength and corrosion resistance.

[0029] In some embodiments of the present application, the surface roughness Ra of the above-mentioned high-strength corrosion-resistant alloy continuous tube is preferably 0.4-1.6, preferably 0.4-0.8, which helps to further improve the smoothness of the surface of the high-strength corrosion-resistant alloy continuous tube, and thus improve the corrosion resistance of the high-strength corrosion-resistant alloy continuous tube such as salt spray and pitting corrosion.

[0030] In some embodiments of the present application, the yield strength of the above-mentioned high-strength corrosion-resistant alloy continuous pipe is preferably ≥758MPa, the tensile strength is ≥793MPa, the hardness is ≥30HRC, and the elongation is ≥20%, so that the high-strength corrosion-resistant alloy continuous pipe of the present application can better meet the requirements of corrosion-resistant oil and gas well development such as deep wells (≥3500), ultra-deep wells (6000-8000), and carbon dioxide injection for the mechanical properties of continuous pipes.

[0031] In another typical embodiment of the present application, a method for preparing the above-mentioned high-strength corrosion-resistant alloy continuous tube is provided, and the preparation method comprises: step S1, preparing coils: subjecting raw materials including scrap steel and pig iron to initial melting, decarburization and desulfurization treatment, refining, hot rolling, first solid solution treatment, pickling, and phosphating treatment in sequence to obtain coils; step S2, longitudinal shearing of coils, extension of steel strips, and second solid solution treatment: according to the specifications of the continuous tubes, longitudinal shearing of coils is performed in sequence to obtain longitudinally cut steel strips, and the longitudinally cut steel strips are sequentially butt-welded and second solid solution treatment are performed on them to obtain extended steel strips; step S3, forming, welding, and third solid solution treatment: forming the butt-cut steel strips to obtain formed steel strips, and longitudinally welding the formed steel strips and then performing third solid solution treatment to obtain continuous tube blanks; step S4, cold drawing treatment and annealing heat treatment: the continuous tube blanks are sequentially cold drawn and annealed to obtain high-strength corrosion-resistant alloy continuous tubes.

[0032] By cold drawing and annealing heat treatment of the continuous tube billet (austenitic stainless steel tube billet / duplex stainless steel tube billet), the tube billet structure is transformed from the traditional austenite, austenite + ferrite structure to the austenite + ferrite + deformation induced martensite structure, and at the same time, the tube billet structure and weld structure are refined and uniform. The cold drawing and annealing heat treatment process achieves a huge leap in the comprehensive mechanical properties of the stainless steel pipe, so that the high-strength corrosion-resistant alloy continuous tube of the present application can better meet the requirements of the mechanical properties of the continuous tube for corrosion-resistant oil and gas well development such as deep wells (≥3500), ultra-deep wells (6000-8000), and carbon dioxide injection.

[0033] Preferably, the above heat treatment realizes the deformation induced transformation of austenite to martensite through multiple cold drawing processes. Low temperature annealing after the cold drawing process can remove the residual stress of the single-pass cold-drawn tube and stabilize the deformation induced martensite structure. The cold drawing and annealing heat treatment not only realizes the uniformity of the welds of the oblique welds and the longitudinal welds, but also realizes the fine grain strengthening of the entire tube. Since the tube undergoes multiple axial cold drawing, the tube structure is fiberized along the rolling direction, thereby enabling the continuous tube to achieve the best comprehensive mechanical properties.

[0034] It is preferred that the above step S1 be equipped with full-process ultra-clean AOD furnace smelting technology + LF refining process, which helps to achieve deep degassing, decarbonization, desulfurization and dephosphorization.

[0035] In one embodiment of the present application, in the above-mentioned step S4, the cold drawing process includes rough cold drawing and fine cold drawing performed in sequence; the temperature of the rough cold drawing is preferably 550-650°C, the rate of the rough cold drawing is preferably 2-5m / min, and the reduction amount of the rough cold drawing should be kept within the plastic range of the material, generally ≤3mm on one side; the temperature of the fine cold drawing is preferably 550-650°C, the rate of the fine cold drawing is preferably 0.5-1m / min, and the reduction amount of the fine cold drawing on one side is preferably ≤1mm; the temperature of the annealing heat treatment is preferably 450-600°C, and the time of the annealing heat treatment is preferably 30-70s.

[0036] A dedicated continuous tube cold drawing process production line is used to cold draw and anneal the entire tube of the continuous tube billet, such as Figure 2 As shown, the cold drawing die is installed on the cold drawing unit, the head of the continuous tube is processed into a conical head, the heat treatment furnace is heated, the heat treatment time is guaranteed by the cold drawing speed (the heat treatment holding time is guaranteed to be ≥1min), and the tube head can pass through the cold drawing die. The tube is manually placed in the first straightening machine 2, and the tube passes through the first water cooling device 3, the first online heat treatment furnace 4, the cold drawing unit, the second straightening machine 8, the second online heat treatment furnace 6, and the second water cooling device 7. After the continuous tube enters the corresponding coiling plate, the coiling plate drives the continuous tube to be cold drawn. In this forward rough cold drawing process, the first straightening machine 2 and the second online heat treatment furnace 6 are connected to the cold drawing unit. The treatment furnace 6 and the second water cooling device 7 are in the open state; after the coiled tube is fixed to the large plate, the large plate is driven by the self-rotation of the large plate to perform cold drawing, and the large plate needs to be adaptively adjusted according to the coiling process to ensure that the cold drawing process is carried out in a straight line; after one cold drawing is completed, the directions of the two coils are reversed, the heads are reprocessed, the current water cooling and induction devices are turned off, the second straightening machine 8, the first online heat treatment furnace 4, the second water cooling device 7 are turned on, and the cold drawing dies of the corresponding passes are replaced to perform reverse secondary rough cold drawing on the coiled tube; after the reverse secondary rough cold drawing, the rough cold drawing process is repeated, and the secondary rough cold drawing, the third rough cold drawing and the subsequent fine cold drawing are performed.

[0037] In addition, by changing the size of the cold drawing die of the cold drawing unit, the rough cold drawing and fine cold drawing of the pipe can be realized, and the cold drawing of continuous pipes of different sizes can be realized. The force of cold drawing comes from the driving force of the hydraulic unit on the reel. After cold drawing, the direction is changed and the cold drawing die is replaced to realize the next pass of cold drawing of the pipe. Two sets of induction heat treatment furnaces are set on the left and right of the cold drawing unit to realize the annealing heat treatment of the pipe. Among them, the required cold drawing passes and cold drawing die sizes are calculated according to the requirements of the pipe blank specifications and the influence of rough cold drawing and fine cold drawing on the pipe.

[0038] The outer surface roughness of the pipe, the cold drawing reduction of the precision cold drawing is very small, and with the increase of the cold drawing pass, the surface roughness gradually decreases, that is, from the relatively rough 3.2 (the roughness of the general pipe processing is 3.2) to 0.4-0.8 through cold drawing. Multi-pass precision cold drawing greatly reduces the surface roughness of the pipe, making the roughness of the continuous pipe reach the mirror level. After being lowered into the bottom of the well, due to the high surface accuracy, the corrosion resistance of the corrosion-resistant alloy is better than that of the rough surface.

[0039] In one embodiment of the present application, in the above-mentioned step S2, the process of longitudinal shearing of the coil, extension of the steel strip, and the second solid solution treatment includes: cutting the coil into longitudinally cut steel strips with a width of 50 to 300 mm by a longitudinal shearing unit according to the specification requirements of the high-strength corrosion-resistant alloy continuous tube, processing the ends of the front and rear two longitudinally cut steel strips to 40 to 50°, and then butt welding the weld between the front and rear two longitudinally cut steel strips in an inert gas, and then performing a second solid solution treatment to obtain a lengthened steel strip; the temperature of the second solid solution treatment is preferably 950 to 1050°C, and the time of the second solid solution treatment is preferably 30 to 70s; and the butt welding is preferably performed by any one or more of laser welding, resistance spot welding, stir friction welding, and plasma wire welding.

[0040] Since the cold drawing process will reduce and thin the outer diameter and wall thickness of the tube, it is necessary to select the coil thickness and coil longitudinal shear width according to the final high-strength corrosion-resistant alloy continuous tube diameter, wall thickness and length, and design the outer diameter of the continuous tube blank; design the process parameters such as cold drawing reduction, cold drawing passes, and tempering temperature according to the outer diameter and inner diameter of the continuous tube blank and finished tube. The design principle is: the main function of rough cold drawing is to deform the tube, and there must be a certain amount of deformation. The main purpose of fine cold drawing is to increase the surface accuracy of the tube. The main characteristics are slow speed and small cold drawing pass reduction; the prepared coil is cut into a specified width steel strip through a longitudinal shearing unit according to the tube blank specification requirements; at the same time, the cold drawing passes and cold drawing die size are calculated accordingly.

[0041] Inert gas is beneficial for protecting the weld area between the front and rear two steel strips. Multiple steel strips are beveled and the weld area is ground and non-destructively tested, and the steel strip is further ground to the target length after the second solution heat treatment.

[0042] In one embodiment of the present application, in the above-mentioned step S3, the process of forming, welding, and the third solid solution treatment includes: milling the edges of the butt-jointed long steel strip and then forming it by roller bending; preferably welding in an inert atmosphere to obtain a welded steel strip; in an argon atmosphere, performing a third solid solution treatment on the welded steel strip to obtain a continuous tube blank; preferably, the temperature of the third solid solution treatment is 950-1050°C, and the time of the third solid solution treatment is preferably ≤60s; preferably, welding is performed by any one or more of laser welding, carbon dioxide gas shielded welding, and plasma welding; preferably, the inert atmosphere includes 99.7wt% argon and 2wt% nitrogen.

[0043] Since the continuous tube welding forming unit generally adopts row roller forming, it is very difficult to form a small diameter continuous tube such as 25.4mm outer diameter, and the laser welding has good penetration, which may cause burn damage to the corresponding area of ​​the laser weld, resulting in poor tube performance. The production of smaller-sized continuous tubes is more difficult or even impossible. The cold drawing process can be used to form small outer diameter continuous tubes, which can produce corrosion-resistant alloy continuous tubes with thinner wall thickness and higher strength. It is preferred that the longitudinal seam welding of the above welding is butt-jointed with an I-type rupture.

[0044] In some embodiments of the present application, in the above step S1, the temperature of the first solution treatment is preferably 950-1050°C, and the time of the first solution treatment is preferably ≥30 minutes, which helps to release the stress of the hot-rolled plate and improve the toughness and processability of the hot-rolled plate.

[0045] In some embodiments of the present application, the above-mentioned preparation method preferably also includes: performing aging heat treatment on the high-strength corrosion-resistant alloy continuous tube; the aging heat treatment temperature is preferably 700-850°C, and the aging heat treatment time is preferably 10-60s, thereby helping to further improve the strength and hardness of the high-strength corrosion-resistant alloy continuous tube.

[0046] The beneficial effects of the present application will be further illustrated below in conjunction with embodiments.

[0047] Example 1

[0048] The chemical composition mass percentages of the plate are as follows: C: 0.015%; Si: 0.35%; Mn: 4.85%; P: 0.003%; S: 0.0001%; ​​Cu: 1.35%; Cr: 21.5%; Ni: 1.57%; Mo: 0.14%; N: 0.23%; the rest are Fe and unavoidable impurities.

[0049] 1. After the scrap steel and low-nickel pig iron are melted in an electric furnace, they are directly poured into a 110t AOD furnace (argon oxygen refining equipment) for smelting. Decarburization and desulfurization are carried out in the AOD converter, and then the molten steel is transferred to a 110t LF furnace (refining furnace) for refining. When the composition and temperature meet the requirements, the molten steel is transported to the continuous casting platform for casting. After the ingot is smelted, the oxide scale on the surface of the ingot is polished; after polishing, it is placed in a continuous rolling unit for multiple hot rolling. The coil is subjected to the first solid solution treatment by online heat treatment. The temperature of the first solid solution treatment is 1050℃ and the time of the first solid solution treatment is 30min. After rolling, the coil is pickled and phosphated, and the rolled product is coiled.

[0050] 2. Coil slitting and strip splicing, second solution treatment:

[0051] It is necessary to prepare 4500 meters of high-strength corrosion-resistant alloy continuous pipe with an outer diameter of 63mm and a wall thickness of 4.0mm. The minimum yield strength of the pipe is calculated to be 698MPa. Therefore, the minimum steel grade of the corrosion-resistant alloy continuous pipe needs to reach CT100 steel grade. The continuous pipe with an outer diameter of 72mm and a wall thickness of 6mm is used for cold drawing. Since the length of the pipe after cold drawing is required to be 4500 meters, according to the principle of volume conservation, 2373 meters of 73mm*6mm wall thickness continuous oil pipe are required. According to calculations, the 73mm outer diameter continuous pipe requires a coil longitudinal shear size of 232mm wide, and the steel coil is longitudinally sheared into a 232mm wide steel strip.

[0052] The plate is beveled at 45°, and the beveled plate is placed in a vacuum laser welding heat treatment device for laser butt-jointing the beveled plate. The butted plate is subjected to a second solid solution treatment. The temperature of the second solid solution treatment is 1050°C, and the preferred time for the second solid solution treatment is 30s. Argon gas is used for rapid cooling.

[0053] 3. Preparation of continuous tube billets

[0054] After the steel strip is extended, the edge of the steel strip is milled and then bent into shape by rollers. The steel strip is welded into a continuous tube billet by laser welding. A mixture of argon with a purity of 99.7wt% and nitrogen with a purity of 2wt% is used for gas protection in the straight seam welding process of the pipe to obtain a welded steel strip. The welded steel strip is subjected to a third solid solution treatment at a temperature of 1050°C and a time of 60s to obtain a continuous tube billet.

[0055] 4. Cold drawing process of tube blank

[0056] The above process is used to prepare Φ73×6.4mm tube blanks, and the size of the finished tube is expected to be Φ63×4mm. The continuous tube is transferred to the cold drawing unit by the overhead crane for cold drawing. The 73mm×6.4mm continuous tube is cold drawn using a cold drawing die with an outer diameter of 66mm and an inner diameter of 56mm. After cold drawing, the tube is annealed at 500℃ in an annealing furnace. After the first cold drawing is completed, the part of the tail that does not enter the reel becomes the head of the secondary cold drawing. The new head of the continuous tube is used for secondary cold drawing. The rotation direction of the straightening machine is reversed to perform secondary cold drawing on the continuous tube. The cold drawing of the outer diameter of 64.5mm and the inner diameter of 55mm is selected. The mold performs secondary rough cold drawing on the continuous tube, and the secondary rough cold drawing is carried out in conjunction with a secondary annealing furnace and a water cooling device. After the cold drawing is completed, the new tail of the tube is processed and three rough cold drawing are carried out. The rough cold drawing requires that each cold drawing must have a large pass reduction; the temperature of each rough cold drawing is 550℃, the rate of each rough cold drawing is 2m / min, and the reduction of the rough cold drawing should be kept within the plastic range of the material, 3mm on one side; after the three rough cold drawing are completed, the cold drawing mold is replaced for fine cold drawing. The difference between fine cold drawing and rough cold drawing is that the reduction of fine cold drawing is 0.8mm, and its main function is to ensure that the surface of the cold drawn tube has a high degree of smoothness. A combination die with an inner diameter of 63.5 mm and an outer diameter of 54.5 mm is used for fine cold drawing, and the cold drawing is combined with an annealing process. After cold drawing, the direction is turned to carry out a secondary fine cold drawing with a cold drawing die with an inner diameter of 63.2 mm and an outer diameter of 55.2 mm. The secondary fine cold drawing uses a cold drawing die with an inner diameter of 63 mm and an outer diameter of 55 mm for three fine cold drawing. The temperature of each fine cold drawing is 550°C, and the speed of each fine cold drawing is 0.5 m / min. After cold drawing, annealing treatment is performed. The temperature of the annealing heat treatment is 450°C, and the time of the annealing heat treatment is 70s.

[0057] 5. Aging heat treatment of tube body

[0058] After three precision cold drawing, the precision cold drawing die is removed, the annealing induction heat treatment furnace is heated to 700℃, the straightening unit direction is turned again, and the pipe is subjected to aging heat treatment for 60s. The pipe is water-cooled to room temperature and the supersaturated solid solution is subjected to aging stabilization treatment to improve the strength and toughness of the pipe. The pipe surface is coated with an anti-corrosion agent and rolled into a coil to obtain a high-strength corrosion-resistant alloy continuous pipe product of the required length.

[0059] 6. Main performance

[0060] The cold-drawn high-strength continuous tube prepared by the above method has a yield strength of more than 780MPa and a steel grade of CT110. The actual performance test results are shown in Table 1. The metallographic structure is shown in Figure 1 As shown in Table 1, it can be seen that the performance of the high-performance seamless continuous pipe produced by this method meets the requirements of API standards. Figure 1It can be seen that the weld structure of the pipe of the present invention is significantly optimized and is consistent with the parent material structure, which can increase the service life and operation safety of the coiled pipe.

[0061] Example 2

[0062] The difference from Example 1 is that the chemical composition mass percentages of the plate are as follows: C: 0.02%; Si: 0.2%; Mn: 10%; P: 0.002%; S: 0.0005%; Cu: 2.0%; Cr: 25%; Ni: 3%; Mo: 0.3%; N: 0.27%; the rest are Fe and unavoidable impurities, and finally a high-strength corrosion-resistant alloy continuous tube product is obtained.

[0063] Example 3

[0064] The difference from Example 1 is that the temperature of each rough cold drawing is 650° C., and a high-strength corrosion-resistant alloy continuous tube product is finally obtained.

[0065] Example 4

[0066] The difference from Example 1 is that the temperature of each rough cold drawing is 500° C., and a high-strength corrosion-resistant alloy continuous tube product is finally obtained.

[0067] Example 5

[0068] The difference from Example 1 is that the rate of each rough cold drawing is 5 m / min, and a high-strength corrosion-resistant alloy continuous tube product is finally obtained.

[0069] Example 6

[0070] The difference from Example 1 is that the rate of each rough cold drawing is 1.5 m / min, and a high-strength corrosion-resistant alloy continuous tube product is finally obtained.

[0071] Example 7

[0072] The difference from Example 1 is that the temperature of each fine cold drawing is 650° C., and a high-strength corrosion-resistant alloy continuous tube product is finally obtained.

[0073] Example 8

[0074] The difference from Example 1 is that the temperature of each fine cold drawing is 500° C., and a high-strength corrosion-resistant alloy continuous tube product is finally obtained.

[0075] Example 9

[0076] The difference from Example 1 is that the speed of each fine cold drawing is 1 m / min, and a high-strength corrosion-resistant alloy continuous tube product is finally obtained.

[0077] Example 10

[0078] The difference from Example 1 is that the speed of each fine cold drawing is 1.5 m / min, and a high-strength corrosion-resistant alloy continuous tube product is finally obtained.

[0079] Embodiment 11

[0080] The difference from Example 1 is that the temperature of the annealing heat treatment is 600° C., and a high-strength corrosion-resistant alloy continuous tube product is finally obtained.

[0081] Example 12

[0082] The difference from Example 1 is that the temperature of the annealing heat treatment is 400° C., and a high-strength corrosion-resistant alloy continuous tube product is finally obtained.

[0083] Embodiment 13

[0084] The difference from Example 1 is that the annealing heat treatment time is 70 seconds, and a high-strength corrosion-resistant alloy continuous tube product is finally obtained.

[0085] Embodiment 14

[0086] The difference from Example 1 is that the annealing heat treatment time is 20 seconds, and a high-strength corrosion-resistant alloy continuous tube product is finally obtained.

[0087] Embodiment 15

[0088] The difference from Example 1 is that the temperature of the aging heat treatment is 850° C., the time of the aging heat treatment is 10 seconds, and finally a high-strength corrosion-resistant alloy continuous tube product is obtained.

[0089] Example 16

[0090] The difference from Example 1 is that the temperature of the first solid solution treatment, the temperature of the second solid solution treatment and the temperature of the third solid solution treatment are 950° C. respectively, and finally a high-strength corrosion-resistant alloy continuous tube product is obtained.

[0091] Comparative Example 1

[0092] The difference from Example 1 is that the chemical composition mass percentages of the plate are as follows: C: 0.1%; Si: 1.2%; Mn: 2%; P: 0.01%; S: 0.01%; Cu: 4%; Cr: 10%; Ni: 12%; Mo: 3%; N: 2%; the rest are Fe and unavoidable impurities, and a continuous tube product is finally obtained.

[0093] Comparative Example 2

[0094] The difference from Example 1 is that the tube blank is not subjected to the cold drawing process, and a continuous tube product is finally obtained.

[0095] The parameters such as yield strength, tensile strength, hardness, elongation and surface roughness of the coiled tubes in the above Examples 1 to 16, Comparative Example 1 and Comparative Example 2 are listed in Table 1.

[0096] Table 1

[0097]

[0098] The main principle of forming a super-strong continuous tube by cold drawing of a corrosion-resistant alloy continuous tube is that, during the rough cold drawing process, due to the large amount of reduction, the austenite contained in the material itself will produce deformation-induced martensite during the deformation process and at a certain temperature, and the strength of the deformation-induced martensite is relatively high, which can sharply increase the strength of the tube. For the tubes in the above embodiments, each rough cold drawing of the tube, that is, the reduction is 3mm to 5mm, 3% to 5% of the deformation-induced martensite is produced, and the tensile strength is increased by 60 to 80MPa; the reduction of the rough cold drawing decreases with the increase of the number of cold drawing passes; during the precision cold drawing process, the reduction of the cold drawing is less than 0.5mm, and the strength will continue to increase after cold drawing. The main principle is to achieve the simultaneous increase of the plasticity and strength of the material by crushing the grains and refining the grains. The increase in strength is slightly lower than that of the rough cold drawing, and the strength is increased by 30 to 50MPa.

[0099] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0100] The present invention provides an element composition of a high-strength corrosion-resistant alloy continuous tube, which is characterized by low C, high Cr, low Ni, high Mn, and nitrogen. This chemical composition is the basis for ensuring that the high-strength corrosion-resistant alloy continuous tube has ultra-high plasticity. The ultra-high plasticity ensures that the continuous tube has good cold drawing performance, thereby promoting the deformation-induced phase change of the continuous tube and realizing the manufacture of the high-strength corrosion-resistant alloy continuous tube. The dispersed nitride Cr formed by the N element and the Cr element 2 The dispersed CrMo formed by N, Mo and Cr elements, and the dispersed FeMo formed by Mo and Fe elements, both help to ensure that the strength of the aged continuous pipe is further improved, so that the final high-strength corrosion-resistant alloy continuous pipe has excellent mechanical strength and corrosion resistance.

[0101] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-strength corrosion-resistant alloy continuous pipe, characterized in that: The element composition of the high-strength corrosion-resistant alloy continuous tube includes, in percentage by mass: C: 0.03-0.05%; Si: ≤1.0%; Mn: 3-25%; P: ≤0.009%; S: ≤0.003%; Cr: 13-30%; Ni: 1-10%; N: 0.05-1.0%; Mo: 0.1-2.0%; Cu: ≤3.5%; the rest is Fe and unavoidable impurities.

2. The high-strength corrosion-resistant alloy coiled tube according to claim 1, characterized in that: The texture components in the high-strength corrosion-resistant alloy continuous tube include: Austenite with an area fraction of 30 to 50%; Ferrite with an area fraction of 40 to 65%; The area fraction of deformation-induced martensite is 5 to 10%.

3. The high-strength corrosion-resistant alloy coiled tube according to claim 1 or 2, characterized in that: The surface roughness Ra of the high-strength corrosion-resistant alloy continuous pipe is 0.4-1.

6.

4. The high-strength corrosion-resistant alloy coiled tube according to any one of claims 1 to 3, characterized in that: The high-strength corrosion-resistant alloy continuous pipe has a yield strength of ≥758MPa, a tensile strength of ≥793MPa, a hardness of ≥30HRC, and an elongation of ≥20%.

5. A method for preparing the high-strength corrosion-resistant alloy coiled tube according to any one of claims 1 to 4, characterized in that: The preparation method comprises: Step S1, preparing a coil: subjecting the raw materials including scrap steel and pig iron to initial melting, decarburization and desulfurization treatment, refining, hot rolling, first solution treatment, pickling, and phosphating treatment in sequence to obtain a coil; Step S2, slitting of coiled plates, extension of steel strips, and second solid solution treatment: according to the specification requirements of the coiled tube, the coiled plates are sequentially slitting to obtain slitting steel strips, and the slitting steel strips are sequentially butt-welded and subjected to second solid solution treatment to obtain extended steel strips; Step S3, forming, welding, and third solid solution treatment: forming the extended steel strip to obtain a formed steel strip, longitudinally welding the formed steel strip, and then performing a third solid solution treatment to obtain a continuous tube blank; Step S4, cold drawing and annealing heat treatment: the continuous tube billet is subjected to cold drawing and annealing heat treatment in sequence, and multiple cold drawing and annealing heat treatments are performed (the number of cold drawing, the cold drawing speed, and the cold drawing reduction are determined according to the original wall thickness and the final wall thickness of the tube) to obtain the high-strength corrosion-resistant alloy continuous tube.

6. The preparation method according to claim 5, characterized in that: In step S4, the cold drawing process includes rough cold drawing and fine cold drawing performed sequentially; Preferably, the temperature of the rough cold drawing is 550-650°C, the rate of the rough cold drawing is 2-5 m / min, and the reduction amount of the rough cold drawing should be kept within the plastic range of the material, generally ≤3 mm on one side; Preferably, the temperature of the fine cold drawing is 550-650°C, the speed of the fine cold drawing is 0.5-1 m / min, and the single-side reduction of the fine cold drawing is ≤1 mm; Preferably, the temperature of the annealing heat treatment is 450-600° C., and the time of the annealing heat treatment is 30-70 seconds.

7. The preparation method according to claim 5 or 6, characterized in that: In the step S2, the process of the coiling and slitting, the steel strip extension, and the second solution treatment includes: The coiled plate is cut into 50-300 mm wide slitting steel strips by a slitting unit according to the specification requirements of the high-strength corrosion-resistant alloy continuous pipe, the ends of the front and rear slitting steel strips are processed to 40-50°, and then the weld between the front and rear slitting steel strips is butt-welded in an inert gas and then the second solid solution treatment is performed to obtain the extended steel strip; Preferably, the temperature of the second solution treatment is 950-1050°C, and the time of the second solution treatment is 30-70s; The butt welding is preferably performed by any one or more of laser welding, resistance spot welding, friction stir welding, and plasma wire welding.

8. The preparation method according to any one of claims 5 to 7, characterized in that: In step S3, the processes of forming, welding and the third solid solution treatment include: After the edge of the extended steel strip is milled, the forming is performed by means of roller bending; The welding is preferably performed in an inert atmosphere to obtain a welded steel strip; In a hydrogen atmosphere, performing the third solid solution treatment on the welded steel strip to obtain the continuous tube blank; Preferably, the temperature of the third solution treatment is 950-1050°C, and the time of the third solution treatment is preferably ≤60s; The welding is preferably performed by any one or more of laser welding, carbon dioxide gas shielded welding, and plasma welding; preferably, the inert atmosphere comprises 99.7 wt % of argon and 2 wt % of nitrogen.

9. The preparation method according to any one of claims 5 to 8, characterized in that: In the step S1, the temperature of the first solution treatment is 950-1050°C, and the time of the first solution treatment is preferably ≥30 min.

10. The preparation method according to any one of claims 5 to 9, characterized in that: The preparation method further comprises: Performing aging heat treatment on the high-strength corrosion-resistant alloy continuous tube; Preferably, the temperature of the aging heat treatment is 700 to 850° C., and preferably, the time of the aging heat treatment is 10 to 60 seconds.

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