Preparation process of thick-wall super dual-phase steel capillary tube

Abstract

The invention provides a preparation process of a thick-wall super dual-phase steel capillary tube, and relates to the technical field of thick-wall super dual-phase steel. The preparation process of the thick-wall super dual-phase steel capillary tube comprises the following steps that a steel strip is welded, straightened and then formed, then a tube is manufactured through composite laser welding, the obtained tube is annealed and drawn, and the thick-wall super dual-phase steel capillary tube is obtained. The composite laser welding is carried out by adopting composite laser, that is, the optical fiber laser is used as main wave band laser, the semiconductor laser is used as sub-wave band laser, and the two kinds of laser are combined together through a laser emitting head for welding. According to the invention, the super dual-phase steel is taken as a raw material and is combined with a composite laser welding process, so that the super dual-phase steel can be normally used in the underground high-temperature environment containing oxygen, hydrogen sulfide and various corrosive media, and the service life of the super dual-phase steel is remarkably prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of thick-walled super duplex stainless steel, and particularly to a preparation process for a thick-walled super duplex stainless steel capillary tube. Background Art

[0002] Super Duplex Stainless Steel (SDSS) is a high-performance stainless steel alloy with a microstructure of austenite and ferrite phases. This material combines the advantages of both, possessing excellent mechanical properties and corrosion resistance, and is widely used in harsh industrial environments. The yield strength of super duplex stainless steel is more than twice that of ordinary stainless steel, usually reaching above 750 MPa, and it has extremely strong resistance to stress corrosion cracking (SCC) caused by chlorides, and is especially suitable for use in marine environments and the chemical industry. Through appropriate welding processes, super duplex stainless steel can maintain the duplex microstructure in the weld area, ensuring the mechanical properties and corrosion resistance of the welded joint. Compared with conventional stainless steel, super duplex stainless steel has a lower coefficient of thermal expansion, reducing stress accumulation during thermal cycling.

[0003] A thick-walled super duplex stainless steel capillary tube is a type of tubing that combines the excellent properties of super duplex stainless steel with the characteristics of a small diameter and high precision of a capillary tube, and has unique advantages in industrial applications. However, due to the characteristics of the capillary tube, the processing of thick-walled super duplex stainless steel capillary tubes is difficult, and their service life is significantly reduced in high-temperature environments underground containing oxygen, hydrogen sulfide, and various corrosive media, restricting the application of thick-walled super duplex stainless steel capillary tubes. Summary of the Invention

[0004] In view of this, the present invention provides a preparation process for a thick-walled super duplex stainless steel capillary tube. By selecting super duplex stainless steel and using the butt welding method for steel strips, and forming the longitudinal weld of the tube by composite laser welding for tube manufacturing, the super duplex stainless steel can be used normally in high-temperature environments underground containing oxygen, hydrogen sulfide, and various corrosive media, significantly improving the service life of super duplex stainless steel.

[0005] The preparation process for the thick-walled super duplex stainless steel capillary tube of the present invention includes the following steps:

[0006] Weld and straighten the steel strip and then form it, and then obtain a thick-walled super duplex stainless steel capillary tube through annealing and drawing of the obtained tube by composite laser welding for tube manufacturing;

[0007] The composite laser welding is carried out using composite lasers, that is, using fiber laser as the main band laser and semiconductor laser as the secondary band laser, and combining the two lasers through a laser output head for welding.

[0008] Preferably, the steel strip is a super duplex stainless steel strip, and the chemical composition of the steel strip is as follows in mass percentage: C 0.03%, Mn 1.2%, P 0.035%, S 0.02%, Si 0.8%, Ni 6.0 - 8.0%, Cr 24.0 - 26.0%, Mo 3.0 - 5.0%, N 0.24 - 0.32%, Cu 0.5%, and the balance is Fe.

[0009] Preferably, the welding method of the steel strip is as follows: Clamp the protective plate with a clamp, wipe the welding bead and the affected area clean with alcohol, set the welding machine current, the electrode spacing is 2 mm, the motor speed is 15 m / min, align the stainless steel welding wire with the weld seam, and align the welding needle with the weld seam using the welding torch regulating valve; After welding, release the argon arc welding switch, then return to the starting point, release the clamp, check whether both sides are qualified, and repair and grind the weld with a hand grinder after qualification to ensure that the weld thickness tolerance < 0.06 mm and there is no negative tolerance.

[0010] Preferably, the forming method is as follows: Pass the steel strip through a rolling device to produce preliminary deformation to facilitate the formation of the shape of the control tube, and then pass the steel strip through a tube forming device for forming.

[0011] Preferably, the composite laser welding method is as follows: Adjust the water temperature of the chiller to 22°C - 28°C, the fixed beam axis angle of the laser welding machine is 90°, the inclination angle < 16°, the distance from the lower edge of the lens to the welding surface is 195 mm, and composite laser welding is carried out in a protective atmosphere. After welding, turn on the grinding machine to grind the longitudinal weld to ensure the formation of the longitudinal weld of the super duplex stainless steel and avoid defects.

[0012] Preferably, the annealing is bright annealing, which is carried out in a protective gas atmosphere. The temperature of the bright annealing is 1100°C, the running speed is 2.5 m / min, the holding time is 7.2 min, the cooling method is rapid cooling, the cooling speed is 3.6 m / min, and the temperature after cooling is room temperature.

[0013] Preferably, the temperature of the hot drawing treatment is 1100°C, the running speed is 2.5 m / min, the drawing process is 14 - 12 - solution treatment - 9.53 - solution treatment, and the pipe passes through the annealing furnace twice.

[0014] Compared with the prior art, the beneficial technical effects of the present invention are:

[0015] By selecting super duplex stainless steel and optimizing the preparation process, the present invention enables the thick - wall super duplex stainless steel capillary tube to be used normally for a long time in the high - temperature environment with oxygen, hydrogen sulfide and various corrosive media underground, effectively improving the corrosion resistance and structural stability.

[0016] The present invention adopts a composite laser welding method, which makes the forming quality of longitudinal welds higher. This process not only improves the welding efficiency, but also reduces welding defects, and improves the weld strength and corrosion resistance.

[0017] The present invention ensures the consistency of welding quality and the stability of the process by strictly controlling welding process parameters (such as current, welding speed, shielding gas flow rate, etc.) and the weld grinding thickness tolerance (≤0.06 mm and no negative tolerance).

[0018] The present invention adopts a method of preliminary deformation by a rolling device combined with further forming by a tube forming device, which makes the shape control of the steel strip more precise. Bright annealing and hot drawing are used to improve the surface finish and mechanical properties of the material.

[0019] The present invention adopts efficient welding and heat treatment processes to eliminate work hardening, reduce the stress of the pipe, obtain a satisfactory metallographic structure, ensure that compared with normal, it reduces material waste and energy consumption, improves production efficiency, reduces manufacturing costs. The prepared thick-walled super duplex stainless steel capillary has characteristics such as high strength, high corrosion resistance, and high temperature stability, and can be widely used in harsh downhole environments, greatly reducing maintenance costs and extending the equipment life. Description of the Drawings

[0020] Figure 1 It is the weld metallographic diagram of the thick-walled super duplex stainless steel capillary for Example 1;

[0021] Figure 2 It is the heat affected zone metallographic diagram of the thick-walled super duplex stainless steel capillary for Example 1;

[0022] Figure 3 It is the base metal metallographic diagram of the thick-walled super duplex stainless steel capillary for Example 1;

[0023] Figure 4 It is the weld macro diagram of the thick-walled super duplex stainless steel capillary for Example 1;

[0024] Figure 5 It is the weld macro diagram of the capillary for Comparative Example 1. Detailed Embodiments

[0025] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] The present invention provides a preparation process for a thick-walled super duplex stainless steel capillary, including the following steps:

[0027] The steel strip is welded, straightened and formed, and then made into a pipe by composite laser welding. The obtained pipe is annealed and drawn to obtain a thick-walled super duplex stainless steel capillary tube;

[0028] The composite laser welding is carried out by using composite laser, that is, the fiber laser is used as the main band laser, the semiconductor laser is used as the secondary band laser, and the two lasers are combined together through the laser output head for welding. In the present invention, the axes of the two lasers are made to coincide or be juxtaposed in space through laser coupling. The main band fiber laser is used for deep penetration welding to ensure full and high-quality forming inside and outside. The secondary band semiconductor laser has the function of preheating and slow cooling, and moderately conducts heat conduction welding through the composite laser to improve the weld stability, enhance the weld toughness, improve the weld forming state, and reduce the generation of internal spatter.

[0029] The steel strip in the present invention is a super duplex stainless steel strip, and the chemical composition of the steel strip is as follows in mass percentage: C 0.03%, Mn 1.2%, P 0.035%, S 0.02%, Si 0.8%, Ni 6.0 - 8.0%, Cr 24.0 - 26.0%, Mo 3.0 - 5.0%, N 0.24 - 0.32%, Cu 0.5%, and the balance is Fe.

[0030] The super duplex stainless steel strip used in the present invention has excellent corrosion resistance, especially shows good corrosion resistance in an environment containing chloride ions or other corrosive media, and has strong tensile strength, fatigue resistance and stability, and is not prone to cracking or deformation. Therefore, the present invention selects super duplex stainless steel to prepare the capillary tube, so that it can operate stably for a long time in a relatively harsh environment and extend the service life of the product. At the same time, the super duplex stainless steel strip has good weldability, is suitable for the composite laser process adopted in the present invention, can realize high-quality weld forming, reduce the occurrence of welding defects, and improve the uniformity and strength of the weld. The excellent processing performance of the super duplex stainless steel strip also enables the pipe to show good stability in the processes of forming, welding, annealing and drawing, reduces the processing difficulty and material loss, and improves the production efficiency and product qualification rate. It can be seen that by selecting the super duplex stainless steel strip as the raw material to prepare the thick-walled super duplex stainless steel capillary tube, the present invention can ensure that the thick-walled super duplex stainless steel capillary tube has high performance and high reliability on the basis of taking into account the corrosion resistance, mechanical properties, processability and welding quality of the product, so as to meet the strict requirements of various application scenarios.

[0031] In some specific embodiments of the present invention, before the steel strip is welded, it further includes strip feeding and steel strip butt joint; the strip feeding refers to storing and transporting the steel strip through a strip feeding reel; the steel strip butt joint refers to cutting the steel strip evenly with a hook knife (using a foot switch) and aligning it.

[0032] The steel strip welding method of the present invention is as follows: Clamp the protective plate with a clamp, wipe the welding bead and the affected area clean with alcohol, set the welding machine current, the electrode spacing is 2 mm, the motor speed is 15 m / min, align the stainless steel welding wire with the weld, and align the welding needle with the weld using the welding torch regulating valve; After welding is completed, release the argon arc welding switch, then return to the starting point, release the clamp, check whether both sides are qualified, and repair and grind the weld with a hand grinding wheel after qualification to ensure that the weld thickness tolerance is <0.06 mm and there is no negative tolerance.

[0033] Gas tungsten arc welding (TIG welding) is a non-consumable electrode inert gas shielded arc welding technology. TIG welding uses a tungsten electrode to form a high-temperature arc through current discharge. The arc does not contact the material to be welded, but is protected by an inert gas, usually argon, to prevent oxygen, nitrogen, etc. from reacting with the arc.

[0034] The present invention uses TIG welding to weld the steel strip. The heat input is controllable, avoiding overheating or burn-through problems of thin-walled steel strips, which is beneficial to the uniformity and stability of the steel strip in subsequent forming and welding processes, ensuring the dimensional tolerance and weld uniformity of the steel strip butt joint. TIG welding reduces weld defects and stress concentration phenomena, laying a good process foundation for subsequent pipe forming, composite laser welding and drawing processes, and reducing the finished product rejection rate. After welding, by grinding the weld, the flatness of the butt joint and the weld thickness tolerance can be maintained, ensuring a smooth transition between the weld and the base material without negative tolerance. Generally speaking, in the preparation process of the thick-walled super duplex stainless steel capillary tube of the present invention, the steel strip butt joint is a key process, and the butt joint quality directly affects subsequent composite laser welding and pipe performance. TIG welding, with its characteristics of high quality, high precision and low defect rate, has become the key process to ensure the efficient operation of the entire production chain of the present invention and the performance of the final product meeting the standards.

[0035] In some specific embodiments of the present invention, after the steel strip is welded, the steel strip is inspected, and the inspection method is as follows: The weld seam is inspected by X-ray flaw detection, and the appearance of the steel strip is inspected to ensure that there are no defects such as burrs, dents, delamination, cracks, etc. on the surface of the steel strip. If there are repairable defects such as burrs and dents on the surface of the steel strip, the surface of the steel strip can be made flat by grinding. The weld quality of the present invention directly affects the strength and integrity of the butt joint of the steel strip, and further affects the processing of subsequent pipes. Therefore, it is necessary to ensure that there are no defects such as cracks, lack of fusion, porosity, slag inclusions, etc. during the welding process in the present invention, so as to avoid fractures, deformations or other failure phenomena in subsequent processing, which seriously affect the quality and safety of the finished product. Surface defects will cause stress concentration during the pipe processing, and even affect the mechanical properties, airtightness and appearance quality of the pipe. In addition, burrs and impurities will also damage the equipment and tools, affecting production efficiency and cost. Therefore, it is necessary to check whether there are defects such as burrs, dents, delamination or cracks on the surface of the steel strip in the present invention to ensure that the surface is flat and smooth, providing a qualified material basis for subsequent forming, welding and drawing processes. The X-ray flaw detection of the weld seam and the appearance inspection of the steel strip can detect and repair salvageable defects at an early stage, prevent unqualified steel strips from entering subsequent processes such as welding, forming and drawing, reduce resource waste and subsequent rework costs, and ensure that the welding and steel strip quality meet relevant standards (such as ASTM A789). It can be seen that the inspection after the steel strip is welded is an important link to ensure the quality of the thick-walled super duplex stainless steel capillary of the present invention. Through the inspection, some welding defects can be detected and repaired in time, ensuring the surface quality, and thus directly affecting the comprehensive quality of the product.

[0036] In some specific embodiments of the present invention, the steel strip is cleaned before the forming process, specifically: the straightened steel strip is supplied by a tape feeding device and cleaned by an ultrasonic cleaning instrument to remove impurities on the surface.

[0037] The forming method of the present invention is as follows: The steel strip is passed through a roll pressing device to generate preliminary deformation to facilitate the formation of the shape of the control tube, and then the steel strip is passed through a tube forming device for forming. The extrusion pressure value of the roll pressing device is 105 Mpa.

[0038] The composite laser welding method of the present invention is as follows: adjust the water temperature of the chiller to 22°C to 28°C, fix the beam axis angle of the laser welder at 90°, the tilt angle <16°, the distance from the lower edge of the lens to the welding surface is 195 mm, and perform welding using composite laser in a protective atmosphere. After welding is completed, turn on the grinding machine to grind the longitudinal weld until the weld bead surface is smooth and free of welding defects, ensuring the formation of the longitudinal weld of super duplex stainless steel and avoiding the occurrence of defects. In some specific embodiments of the present invention, the protective gas is argon with a purity of 99.99%. Among them, the flow rate of the protective gas in the protective sleeve is 5 - 10 L / min, the flow rate of the inner protective gas is 2.5 - 8 L / min, and the flow rate of the outer protective gas is 5 - 10 L / min. In other specific embodiments of the present invention, during the composite laser welding process, the power of the fiber laser is 1300 - 1400 W, the power of the semiconductor laser is 800 - 900 W, and the welding speed is 2.3 - 3.3 m / min.

[0039] The present invention performs keyhole welding through fiber laser to ensure full formation of the internal reinforcement height. Utilize the preheating and slow cooling effect of semiconductor laser combined with moderate heat conduction welding to improve the weld stability, enhance the weld toughness, improve the weld formation state, and reduce the generation of internal spatter. The present invention makes the properties of the weld area match those of the super duplex stainless steel strip through specific welding techniques, ensuring that the weld meets the performance requirements of high strength and high corrosion resistance, and avoiding structural failure caused by welding defects.

[0040] The annealing of the present invention is bright annealing, which is carried out in a protective gas atmosphere. The temperature of the bright annealing is 1100°C, the running speed is 2.5 m / min, the holding time is 7.2 min, the cooling method is rapid cooling, the cooling speed is 3.6 m / min, and the temperature after cooling is room temperature. In some specific embodiments of the present invention, the protective atmosphere is an argon atmosphere and ammonia decomposition gas. The present invention eliminates the internal stress generated during processes such as welding and forming by heating the material to a specific temperature and then cooling it during bright annealing, improves the grain structure of the material, adjusts the grain size, enables it to have better corrosion resistance and mechanical properties, and avoids deformation or cracking of the material during subsequent processing, which is beneficial for subsequent hot drawing treatment and ensures the weld quality. Ammonia in the furnace cavity decomposes into hydrogen and nitrogen, and these gases can be used as protective gases to prevent oxidation and decarburization of the steel during heating and cooling.

[0041] The temperature of the hot drawing treatment of the present invention is 1100°C, the running speed is 2.5 m / min, and the drawing process is 14 - 12 - solution treatment - 9.53 - solution treatment, and the pipe passes through the annealing furnace twice. Hot drawing can ensure that the shape, size, and wall thickness of each pipe are consistent, meet different technical and application requirements, and improve the overall mechanical properties of the pipe through plastic deformation. The multiple solution treatments and annealing during hot drawing can further improve the comprehensive performance of the pipe.

[0042] The annealing and drawing of the present invention are carried out simultaneously, so the solution parameters are the bright annealing parameters.

[0043] In some specific embodiments of the present invention, before annealing and after hot drawing, an ET eddy current flaw detection device is used to detect whether there are unacceptable defects to ensure that there are no pores in the pipe after welding and forming operations. Defects with a maximum depth and width of ≥ 0.004 inches (0.100 mm) are unacceptable defects. Eddy current flaw detection is used to detect defects such as pores, cracks, and inclusions inside and on the surface of the pipe to ensure that these defects are discovered and repaired in a timely manner, guarantee the structural integrity of the pipe, and affect the service life and performance of the pipe. Moreover, eddy current flaw detection before annealing and after hot drawing can detect defects in the pipe at an early stage and reduce rework and scrapping caused by pipe quality problems.

[0044] In some preferred embodiments of the present invention, after the pipe is drawn, it also includes steps of marking, length counting, coiling, and inspection. Among them, marking refers to laser marking the outer surface of the pipe through a marking machine; length counting refers to supervising and controlling the production length and speed through a length counter; coiling refers to adjusting the wire arranging device to make the pipeline evenly arranged, and guiding the pipe to wind around the finished pipe through a tractor; inspection refers to detecting the performance indicators of the pipe to determine whether they meet the product requirements. The purpose of the present invention to meet the standards is to clarify the batch numbers and necessary basic parameters of different batches of products, including but not limited to: manufacturer, production order number, material, specification, product standard, manufacturing process, detection method, production date, batch code, etc. For example: (2507 material) φ3 / 8in * 0.065in: SHINDA + production order number + material + specification (φ3 / 8in * 0.065in) + product standard (ASTM A789) + WELDED + NDE + production date + BCG1904. The product detection standard of the present invention generally adopts ASTM A789.

[0045] To further illustrate the present invention, the following examples are used for detailed description below. The raw materials used in the following examples of the present invention are all commercially available.

[0046] Example 1 A preparation process for a thick-walled super duplex stainless steel capillary tube, the steps are as follows:

[0047] S1. Store and transport the super duplex stainless steel strip through a tape reel, cut the strip neatly with a hook knife (using a foot switch), and align it. Alignment is required.

[0048] The chemical composition of the steel strip is as follows in mass percentage: C 0.03%, Mn 1.2%, P 0.035%, S 0.02%, Si 0.8%, Ni 6.6%, Cr 24.8%, Mo 4.2%, N 0.28%, Cu 0.5%, and the balance is Fe;

[0049] S2. Clamp the protective plate with a clamp, wipe the weld bead and the affected area clean with alcohol, set the welding machine current, the electrode spacing is 2 mm, the motor speed is 15 m / min, align the stainless steel welding wire with the weld, and align the welding needle with the weld using the welding torch regulating valve; after welding is completed, release the argon arc welding switch, then return to the starting point, release the clamp, check whether both sides are qualified, and after passing, repair and grind the weld with a hand grinder to ensure that the weld thickness tolerance is below 0.06 mm and there is no negative tolerance;

[0050] S3. After welding is completed and meets the welding requirements, perform X-ray flaw detection on the weld, and conduct an appearance inspection on the steel strip to ensure that there should be no defects such as burrs, dents, delamination, cracks, etc. on the surface of the steel strip;

[0051] S4. Uncoil and straighten the steel strip through a straightening machine and a conveying mechanism, and supply the steel strip using a tape feeding device; the supplied steel strip is cleaned by an ultrasonic cleaning instrument to remove surface impurities; the steel strip passes through a rolling device to produce preliminary deformation to facilitate the formation of the shape of the control tube, and the extrusion pressure value of the rolling device is 105 Mpa; then the steel strip passes through a tube forming device to form the shape of the pipe;

[0052] S5. Adjust the water temperature of the chiller to 22 - 28 °C, fix the laser beam axis angle of the laser welder at 90°, the tilt angle < 16°, the distance from the lower edge of the lens to the welding surface is 195 mm, control the flow rate of the shielding gas, debug to the appropriate welding power and welding speed, use a high-penetration ultra-narrow gap fiber laser to weld the backing, and perform composite laser welding to make the pipe using a combined welding method with heat conduction semiconductor welding for capping, turn on the grinding machine to grind the longitudinal weld to ensure the formation of the longitudinal weld of the super duplex stainless steel and avoid the occurrence of defects;

[0053] The shielding gas is argon with a purity of 99.99%. Among them, the flow rate of the shielding gas in the protective sleeve is 6 L / min, the flow rate of the inner shielding gas is 5 L / min, and the flow rate of the outer shielding gas is 6 L / min; during the composite laser welding process, the power of the fiber laser is 1350 W, the power of the semiconductor laser is 840 W, and the welding speed is 2.3 m / min;

[0054] S6. Use an ET eddy current flaw detection device to detect whether there are defects in the pipe. If there are defects, the maximum depth and width of the defect size should be less than 0.004 inches;

[0055] S7. The tube is heat-treated by bright annealing in an argon atmosphere at a treatment temperature of 1100 °C, a running speed of 2.5 m / min, and a holding time of 7.2 min, and then cooled to room temperature at a speed of 3.6 m / min;

[0056] S8. Use an ET eddy current flaw detection device to detect whether there are defects in the tube. If there are defects, the maximum depth and width of the defect size should be less than 0.004 inches;

[0057] S9. Laser mark the outer surface of the tube with a marking machine. Use a counter to facilitate the supervision and control of the production length and speed. Adjust the wire arranging device to make the pipeline evenly arranged, and lead the tube around the finished tube with a tractor.

[0058] After testing, the tensile strength of the thick-walled super duplex stainless steel capillary tube in this example is 875 MPa, the yield strength is 640 MPa, the elongation is 34%, and the hardness is 265 HV.

[0059] The mechanical properties of the thick-walled super duplex stainless steel capillary tube in this example were tested, and the results are shown in Table 1.

[0060] Table 1 Test results of the mechanical properties of the thick-walled super duplex stainless steel capillary tube in Example 1

[0061] Tensile strength RM (MPa) Yield strength RP0.2 (MPa) Elongation (%) 879 639 34 877 624 37 875 647 34 Standard value: ≥800 Mpa Standard value: ≥500 Mpa Standard value: ≥15%

[0062] As can be seen from Table 1, the mechanical properties of the thick-walled super duplex stainless steel capillary tube prepared in this example meet the ASTM A789 standard.

[0063] The comparison and harmful phase detection of the product are shown in Figures 1 - 3 as follows. Among them, the phase ratio rating values of each part are: weld - 54.8, base metal - 54.3, heat affected zone - 53.6.

[0064] The hardness of the product was tested, and the results are shown in Table 2.

[0065] Table 2 Test results of the hardness of the thick-walled super duplex stainless steel capillary tube in Example 1

[0066]

[0067] The corrosion resistance of the product was tested. The test process is as follows:

[0068] (1) Prepare specimens;

[0069] (2) Place them in the test container;

[0070] (3) Prepare the solution;

[0071] (4) Measure the pH of the initial solution;

[0072] Deaerate with nitrogen at a rate of 100 mL / min / L for two hours;

[0073] (6) Introduce H 2 S at a rate of 200 mL / min / L for at least 1 hour until the solution is saturated;

[0074] (7) Measure the pH value of the saturated H 2 S solution and the content of H 2 S;

[0075] (8) Maintain a positive pressure of H 2 S until the test is completed;

[0076] (9) Measure the pH value of the solution at the end of the test;

[0077] (10) Check the test results.

[0078] The test method is as follows:

[0079] Test temperature: 25 ± 3 °C; Test time: 96 h; Test solution: Distilled water solution of 5% NaCl and 0.50% glacial acetic acid by mass fraction; Initial solution pH is 2.76, pH of saturated H 2 S solution is 3.07, pH of the solution at the end of the test is 3.85; H in saturated H 2 S content of the S solution is 2316 mg / mL, H in the H 2 S solution after the test is 2503 mg / mL, and the degreasing method is acetone. 2 S content of the S solution is 2 2503 mg / mL, and the degreasing method is acetone.

[0080] The test results are shown in Table 3, where 194433-21, 194433-22, and 194433-23 are different samples obtained from three parallel tests of Example 1.

[0081] Table 3 Corrosion resistance test results of thick-walled super duplex stainless steel capillary tubes in Example 1

[0082]

[0083]

[0084] No cracks appeared on the detected surfaces of the specimens.

[0085] Conduct an anti-HIC cracking test on the sample. No HIC occurred in the corrosion rate comparison test of 95% N 2 +5% O 2 It showed extremely high corrosion resistance.

[0086] Conduct a pitting corrosion test on the sample. The method is as follows:

[0087] (1) The surface of the specimen was polished.

[0088] (2) Method for cleaning corrosion products: rinsing with clear water → wiping with a brush → rinsing with clear water → ultrasonic cleaning → cleaning and drying with alcohol.

[0089] The test conditions and test results are shown in Table 4, where 194537-1 and 194537-2 are different samples obtained from two other parallel tests of Example 1.

[0090] Table 4 Detection Results of Pitting Corrosion Test

[0091]

[0092] Test Results

[0093]

[0094] Comparative Example 1

[0095] Same as Example 1, except that: only fiber laser welding was used, and the power of the fiber laser was 1350 W.

[0096] It can be seen from Figures 4 - 5 that in Comparative Example 1, the weld formation was not full, the reinforcement was 0.05 mm, and the weld width was 0.66 mm. While in Example 1, the double-laser composite laser welding had a better formation compared to single-laser welding, the weld reinforcement was 0.14 mm, the weld width was 1.20 mm, and there were no welding defects.

[0097] Comparative Example 2

[0098] Same as Example 1, except that: a thick-walled nickel-based alloy capillary was prepared using a nickel-based alloy steel strip, and the chemical composition of the steel strip in mass percentage was: C 0.02%, Si 0.4%, Mn 0.9%, S 0.02%, Ni 42%, Cr 20.5%, Mo 2.7%, Fe 26%, Al 0.1%, Ti 0.8%, Cu 2.2%, and the balance was Fe.

[0099] After testing, the tensile strength of the product prepared in this comparative example was 620 MPa, the yield strength was 305 MPa, the elongation was 50%, the hardness was 155 HV, and cracking occurred in the HIC test.

[0100] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A process for preparing a thick-walled super duplex steel capillary, characterized in that: The following steps are involved: The steel strip is welded and straightened to form, and then the tube is made by composite laser welding. The obtained tube is annealed and drawn to obtain a thick-walled super duplex steel capillary tube; The composite laser welding is performed by using a composite laser, that is, the fiber laser is used as a main-band laser, and the semiconductor laser is used as a sub-band laser, and the two lasers are combined together through a laser output head for welding.

2. The preparation process according to claim 1, characterized in that: The steel strip is a super dual-phase steel strip, and the chemical composition of the steel strip is, by mass percentage, C 0.03%, Mn 1.2%, P 0.035%, S0.02%, Si 0.8%, Ni6.0-8.0%, Cr 24.0-26.0%, Mo 3.0-5.0%, N 0.24-0.32%, Cu0.5%, and the balance is Fe.

3. The preparation process according to claim 1, characterized in that: The steel strip welding method is as follows: use a clamp to clamp the protective plate, wipe the weld and the affected area with alcohol, set the welding machine current, the electrode spacing is 2mm, the motor speed is 15m / min, align the stainless steel welding wire with the weld, and align the welding needle with the weld using the welding gun regulating valve; After welding is completed, release the argon arc welding switch, return to the starting point, loosen the clamp, and check whether both sides are qualified. If qualified, use a hand grinding wheel to repair and grind the weld to ensure that the weld thickness tolerance is less than 0.06mm and there is no negative tolerance.

4. The preparation process according to claim 1, characterized in that: The forming method is as follows: the steel strip is passed through a rolling device to produce a preliminary deformation so as to form the shape of the control tube, and then the steel strip is passed through a tube forming device for forming.

5. The preparation process according to claim 1, characterized in that: The composite laser welding method is as follows: The composite laser welding method of the present invention is as follows: adjust the water temperature of the chiller to 22°C ~ 28°C, fix the beam axis angle of the laser welder to 90°, the inclination angle is <16°, the distance from the bottom edge of the lens to the welding surface is 195mm, and use a composite laser to weld in a protective atmosphere. After welding is completed, start a grinder to grind the longitudinal weld.

6. The preparation process according to claim 1, characterized in that: The annealing is bright annealing, which is carried out in a protective gas atmosphere. The temperature of the bright annealing is 1100° C., the running speed is 2.5 m / min, the holding time is 7.2 min, the cooling method is fast cooling, the cooling speed is 3.6 m / min, and the temperature after cooling is room temperature.

7. The preparation process according to claim 1, characterized in that: The temperature of the hot drawing treatment is 1100° C., the running speed is 2.5 m / min, the drawing process is 14-12-solid solution-9.53-solid solution, and the pipe passes through the annealing furnace twice.

Images