Super-critical carbon dioxide corrosion resistant super-strength longitudinal submerged arc welded pipe and manufacturing method thereof

Abstract

A manufacturing method of a supercritical carbon dioxide corrosion resistant ultra-high strength longitudinal submerged arc welded pipe comprises the steps that S1, molten iron containing high Mn and high Cr is continuously cast into a plate blank, and the plate blank is heated at 1140-1270 DEG C to be manufactured into a steel plate; s2, gradually pressing the steel plate into a J shape for multiple times, then pressing the steel plate into a C shape for multiple times, and finally pressing the middle of the steel plate into a tubular part with an O-shaped opening; s3, the tubular part is subjected to internal and external automatic submerged arc welding, and a longitudinal submerged arc welding pipe is obtained; s4, quenching and tempering heat treatment is conducted on the longitudinal submerged arc welded pipe; and S5, the longitudinal submerged arc welded pipe is subjected to thermal diameter expansion, and the supercritical carbon dioxide corrosion resistant ultra-high-strength longitudinal submerged arc welded pipe is obtained. According to the manufacturing method, 2-3% of Mn and 3-9% of Cr are added to be rolled into a steel plate, then JCO forming is carried out, internal and external welding is completed through a welding wire containing Cr and Ni, thermal expanding is carried out after quenching and tempering heat treatment, and the ultrahigh-strength carbon dioxide conveying welded pipe which is high in corrosion resistance and excellent in low-temperature toughness is manufactured.

Description

Technical Field

[0001] The present invention relates to a longitudinally submerged arc welded pipe, and particularly to an ultra-high strength longitudinally submerged arc welded pipe resistant to supercritical carbon dioxide corrosion and a manufacturing method thereof.

Background Art

[0002] Supercritical or dense-phase carbon dioxide pipelines are used for the transportation of large-scale long-distance carbon dioxide. Generally, dry and pure carbon dioxide has no corrosiveness to carbon steel pipelines, and the purity of carbon dioxide depends on the carbon dioxide source and capture technology.

[0003] Nowadays, there will be some impurities such as H 2 O, N 2 , O 2 , H 2 S and CO in carbon dioxide. Therefore, the supercritical carbon dioxide transported through the pipeline will inevitably be corroded. Especially the free water phase in the pipeline will cause carbon dioxide to dissolve in water to form H 2 CO 3 , which causes the corrosion of carbon steel pipelines. Coupled with the coupling reaction with other impurities, the pipeline corrosion will be aggravated. To solve this problem, the purity of carbon dioxide can be improved, but this method will increase the cost of removing impurities; or pipes with stronger resistance to supercritical carbon dioxide corrosion can be selected. In addition, once the transported supercritical or dense-phase carbon dioxide leaks or is vented, due to the Joule-Thomson effect of carbon dioxide, the pressure of carbon dioxide will be reduced to varying degrees, and the pipe material may be exposed to low-temperature carbon dioxide of -20°C to -80°C. To prevent the pipe material from fracturing at low temperature and long-range expansion at low temperature, ordinary pipe materials do not have high toughness at low temperature, so it is necessary to develop carbon dioxide transportation pipe materials with excellent low-temperature toughness.

[0004] The patent with the publication number CN103320705A discloses a carbon dioxide corrosion-resistant pipeline steel for surface gathering and transportation and a preparation method thereof, and the patent with the publication number CN107502823A discloses a 415MPa-class pipeline steel for service in an environment with a high carbon dioxide partial pressure. Both of them disclose a steel plate containing Cr, but the Cr content of both is ≤3%, resulting in limited carbon dioxide corrosion resistance.

[0005] In view of this, the present invention provides an ultra-high strength longitudinally submerged arc welded pipe resistant to supercritical carbon dioxide corrosion and a manufacturing method thereof.

Summary of the Invention

[0006] To solve the above problems, the present invention provides a method for manufacturing an ultra-high strength straight seam submerged arc welded pipe resistant to supercritical carbon dioxide corrosion. On the basis of the composition of conventional low-carbon pipeline steel, the Mn element is increased to 2% - 3%, and 3% - 9% of Cr element is added and rolled into a steel plate. Then it is formed by JCO process, and the internal and external welding is completed by using submerged arc welding wire containing 1.8 - 3.0% Cr or 0.9 - 1.5% Ni. After the whole pipe (pipe body and weld) is quenched and tempered, the whole pipe is hot-expanded, and finally an ultra-high strength straight seam submerged arc welded pipe resistant to supercritical carbon dioxide corrosion is made.

[0007] The present invention is realized through the following technical solutions. A method for manufacturing an ultra-high strength straight seam submerged arc welded pipe resistant to supercritical carbon dioxide corrosion is provided, including the following steps:

[0008] S1 The hot metal containing high Mn and high Cr is pretreated, smelted in an electric furnace, refined in an RH furnace, and vacuum-treated in a VD, and then continuously cast into a slab. The slab is heated at 1140°C - 1270°C and then processed by the TMCP process to make a steel plate with high dimensional accuracy under large-tonnage rolling deformation.

[0009] S2 After the steel plate prepared in S1 is inspected by ultrasonic wave, milled at the edges, and pre-bent at the edges, the JCO forming machine is used to first press one side of the pre-bent steel plate multiple times, gradually pressing it into a J shape, then press the other side of the steel plate multiple times to press it into a C shape, and finally press the steel plate once in the middle to press the steel plate into a tubular part with an opening in the shape of O.

[0010] S3 First pre-weld and then submerged arc weld

[0011] S31 The tubular part pressed in S2 is pre-welded and protected by a mixed gas. Among them, for pre-welding, a BHG-2M welding wire with a diameter of 4.0 mm is selected, and the protective gas is a mixed gas of carbon dioxide (55% - 65%) + Ar (35% - 45%). The gas flow rate of the protective gas is 60 - 75 L / min, and the welding speed V = 3.5 - 4.5 m / min;

[0012] S32 After pre-welding, a welding wire containing Cr and Ni is used, and it is combined with CaF with an alkalinity of 1.85 2 -SiO 2 -MgO-Al 2 O 3 -MnO-TiO 2 -B 2 O 3For the slag system sintered flux, first perform submerged arc automatic internal welding, and then synchronously perform submerged arc automatic external welding. The welding speed V = 1.4 m / min to 1.6 m / min. To improve welding accuracy, here, according to the actual wall thickness of the straight seam submerged arc welded pipe, choose double wire or triple wire. Among them, the 1# wire uses DC reverse connection, and the 2# (3#) wire uses AC; in this step, select a high-alkalinity flux of 1.85 to assist the welding wire for submerged arc welding, which can ensure that the weld has low-temperature high toughness.

[0013] S4 Perform tempering heat treatment on the welded straight seam submerged arc welded pipe

[0014] S41 Transport the straight seam submerged arc welded pipe to a small box-type step furnace for full-pipe quenching. The maximum temperature in the furnace is set at 940 °C, and the heating speed in the furnace is 30 °C / S to 50 °C / S. When the welded pipe is heated to 900 °C to 930 °C, it is taken out of the furnace, and the advancing welded pipe is quickly spray-quenched online within 10 S after being taken out of the furnace, so that the straight seam submerged arc welded pipe taken out of the furnace is cooled to room temperature;

[0015] S42 Send the cooled straight seam submerged arc welded pipe into the small box-type step furnace for the second time, and use the waste heat of the furnace temperature of 500 °C to 625 °C to perform full-pipe tempering heat treatment again. During the heat preservation period, heat can be supplemented to the small box-type step furnace to ensure that the heat preservation temperature of the entire welded pipe is controlled within ±5 °C. After being placed in the furnace for 20 to 40 minutes for heat preservation, it is taken out.

[0016] S5 Perform hot expansion (RE) on the welded pipe

[0017] Take out the straight seam submerged arc welded pipe from the small box-type step furnace, and use the waste heat of the straight seam submerged arc welded pipe itself when it just comes out of the furnace to perform hot expansion on the welded pipe at about 300 °C. In the present invention, to save processing man-hours, two expanding machines can be set on the production line. During expansion, align the weld of the straight seam submerged arc welded pipe with the groove of the sector block on the expanding head, insert the steel pipe into the expanding head, and perform segmented expansion. Every 500 mm to 800 mm of expansion, the trolley will send the straight seam submerged arc welded pipe forward for a section, and the two expanding machines will expand successively. The expansion rate is 0.6% to 1.0%. In the present invention, the expansion force value required for hot expansion is small, which can effectively eliminate the deformation caused by the thermal effect after quenching of the straight seam submerged arc welded pipe, reduce or even eliminate the residual stress in the pipe body and weld area after welding, and achieve the high dimensional accuracy of high-strength welded pipes that cannot be satisfied by the normal-temperature cold expansion process.

[0018] S6 Complete the quality inspection and physical and chemical corrosion performance test inspection of the production line

[0019] The SAW pipes obtained in S5 are successively subjected to weld X-ray inspection, hydrostatic test, weld ultrasonic inspection, pipe end X-ray inspection, chamfering, pipe end magnetic particle inspection, and appearance quality inspection, and finally made into ultra-high-strength SAW pipes for transporting supercritical carbon dioxide. Finally, chemical composition analysis, bending test, tensile test, Charpy impact, corrosion test, etc. are carried out according to the inspection batches to ensure that the physical and chemical properties of the ultra-high-strength SAW pipes for transporting supercritical carbon dioxide meet the requirements of API SPEC 5L PSL2 standard and low-temperature toughness requirements, and have excellent corrosion resistance to supercritical carbon dioxide.

[0020] Particularly, the slab in S1, calculated by mass percentage, includes the following components:

[0021] C 0.04 - 0.07%, Si 0.15 - 0.30%, Mn 2 - 3%, Cr 3 - 9%, Ni 0.15 - 0.30%, Nb 0.05 - 0.08%, P ≤ 0.010%, S ≤ 0.003%, and the rest is iron and a small amount of impurities on the surface that cannot be removed; the above components are rolled into a hot-rolled steel plate with low carbon and high Mn and high Cr. The steel grade of the steel plate is X52 - X60, and the structure of the steel plate is polygonal ferrite + pearlite + granular bainite; in the present invention, the use of low carbon in the steel plate raw material ensures high low-temperature impact toughness of the pipe body on the one hand, and ensures the weldability of the SAW pipe during pipe manufacturing and the circumferential weld of on-site pipes on the other hand. High Mn can significantly improve the low-temperature toughness and wear resistance of the steel pipe. High Cr can improve the corrosion resistance of the welded pipe to supercritical carbon dioxide on the one hand, and improve the hardenability during the quenching and tempering process of the welded pipe, increasing the strength of the pipe body on the other hand. Adding Ni element also mainly improves the low-temperature impact toughness of the pipe body. Adding a certain amount of Nb element can refine the grains in the heat-affected zone of the submerged arc weld, improving the low-temperature impact toughness of the heat-affected zone of the weld. The low contents of S and P elements represent the purity of steel smelting, improving the low-temperature impact toughness and corrosion resistance to supercritical carbon dioxide of the pipe body and weld of the SAW pipe.

[0022] In the present invention, since the SAW pipe is made of a hot-rolled steel plate with high Mn and high Cr, in order to cope with submerged arc welding, a Cr- and Ni-containing welding wire needs to be selected. The Cr- and Ni-containing welding wire, calculated by mass percentage, includes the following components: C 0.08%, Mn 2.5%, Si 0.19%, Cr 1.8 - 3.0%, Ni 0.9 - 1.5%, Mo 0.35%, V 0.1%, P ≤ 0.015%, S ≤ 0.008%, and the rest is Fe, and Cr / Ni ≈ 2 is controlled; when preparing this welding wire, first melt the above components into circles, and draw them into a diameter For the submerged arc welding wire, in practical applications, the contents of Cr and Ni in the wire are appropriately increased or decreased according to the composition and strength of the straight seam submerged arc welded pipe. By adding Cr and Ni to the wire, on the one hand, the hardenability during the quenching and tempering heat treatment of the weld can be improved. Especially after adding Ni, the low-temperature toughness of the weld is significantly increased. On the other hand, the electrode potential of the weld is increased, thereby improving the corrosion resistance of the weld to carbon dioxide; adding a small amount of V is beneficial to avoiding embrittlement of the fusion line and heat affected zone of the submerged arc weld, thus improving the low-temperature impact toughness of the fusion line and heat affected zone of the weld; low S and P elements can ensure the purity of the weld.

[0023] Particularly, in order to cool the inside and outside of the straight seam submerged arc welded pipe synchronously after quenching, the quenching devices selected in the online water spray quenching in S41 are an inner ring water spray device and an outer ring water spraying device respectively. Among them, the inner water spraying speed is 800 - 3000 cubic meters per hour, the outer wall water spraying speed is 2000 - 4000 cubic meters per hour, and the inner spraying and outer spraying time is 15 - 25s.

[0024] The present invention also provides a straight seam submerged arc welded pipe manufactured by the above method. The microstructure of the pipe mother of the straight seam submerged arc welded pipe is bainite + martensite, the microstructure of the submerged arc weld is bainite + acicular ferrite + a small amount of retained austenite. The pipe diameter of the welded pipe is DN323mm - DN610mm, the wall thickness ≤ 25.4mm (in actual production, the pipe diameter and wall thickness of the welded pipe can be changed according to the heat treatment equipment and the pipe expanding equipment), the steel grade is X90 - X120, the yield strength of the base metal of the welded pipe is 628MPa - 953MPa, the tensile strength of the base metal is 700MPa - 1202MPa, the elongation of the base metal: A ≥ 20%, the transverse impact energy of the full-size base metal at - 60°C is 158J - 347J, the impact energy of the full-size weld and heat affected zone at - 60°C: 123J - 219J. The high toughness of the base metal, weld and heat affected zone at such a low temperature can ensure that the pipe has a certain low-temperature crack arrest and prevention of long-range propagation ability when transporting supercritical carbon dioxide. At the same time, the crack tip opening displacement CTOD characteristic value δm of the pipe body and the welded joint at - 60°C ≥ 0.254mm.

[0025] Compared with the prior art, the present invention provides a supercritical carbon dioxide corrosion-resistant ultra-high-strength longitudinally submerged arc welded pipe. Through large-tonnage rolling deformation and controlled cooling of low-C, high-Mn, and high-Cr raw material thick slabs, the steel plate has high dimensional accuracy, and the steel grains are effectively elongated and refined, with an effect far superior to that of seamless pipes. Because the C content of seamless pipes is generally about 5 times that of the raw materials for supercritical carbon dioxide-transporting ultra-high-strength longitudinally submerged arc welded pipes, this raw material composition ensures excellent low-temperature toughness and carbon dioxide corrosion resistance of the steel plates used for this welded pipe. At the same time, the present invention also provides a method for manufacturing a supercritical carbon dioxide corrosion-resistant ultra-high-strength longitudinally submerged arc welded pipe. By adding Cr elements with carbon dioxide corrosion resistance and Mn elements with excellent low-temperature toughness to low-carbon steel, steel plates of X52 / X60 steel grades are processed into JCO longitudinally submerged arc welded pipes. After completing internal and external automatic submerged arc welding with Cr- and Ni-containing submerged arc welding wires, the whole longitudinally submerged arc welded pipe is subjected to quenching and tempering heat treatment (quenching + tempering), so that the steel grade of the JCO longitudinally submerged arc welded pipe is greatly increased from X52 - X60 steel grades to X90 - X120 steel grades at one time. Through a new hot expansion process (RE), a longitudinally submerged arc welded pipe with a wall thickness non-uniformity ≤ 3%, an ovality ≤ 0.3%, a straightness ≤ 0.15%, and a residual stress ≤ 80 MPa is obtained. At the same time, a corrosion test is carried out under typical supercritical carbon dioxide transportation conditions containing impurities. It is found that when the longitudinally submerged arc welded pipe provided by the present invention is compared with the welded pipes in the prior art, the average corrosion rate is only 1 / 2 - 1 / 10 of that of the existing welded pipes, thereby greatly improving the service life and service years of the pipe material, ensuring that the developed supercritical carbon dioxide-transporting ultra-high-strength longitudinally submerged arc welded pipe can serve more safely; and this welded pipe has high geometric dimensional accuracy and low residual stress, can fully meet the supercritical carbon dioxide transportation under conditions with higher water content and other impurities, and ensure the safe long-distance transportation of millions of tons of supercritical carbon dioxide per year.

[0026]

Explanation of the Drawings

[0027] Figure 1 Microstructure of the weld of an X100 steel grade supercritical carbon dioxide Φ355×13 mm longitudinally submerged arc welded pipe prepared by the method of the present invention.

Specific Embodiments

[0028] In order to make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the following further elaborates on the present invention in detail in combination with specific embodiments.

[0029] The following takes the manufacture of an X100 steel grade Φ355×13 mm supercritical carbon dioxide corrosion-resistant longitudinally submerged arc welded pipe and an X120 steel grade Φ610×22 mm supercritical carbon dioxide corrosion-resistant longitudinally submerged arc welded pipe as examples.

[0030] A method for manufacturing a supercritical carbon dioxide corrosion-resistant ultra-high-strength longitudinally submerged arc welded pipe includes the following steps:

[0031] Step 1

[0032] Two kinds of high-Mn high-Cr steel plates with 1# having a wall thickness of 13 mm and a plate width of 1075 mm and 2# having a wall thickness of 22 mm and a plate width of 1835 mm are rolled respectively using the chemical components in Table 1 through low-temperature heavy-tonnage rolling. Their chemical components are shown in Table 1 (wt%).

[0033] Table 1 Chemical Composition Analysis of Steel Plates (wt%)

[0034]

[0035] Step 2

[0036] Before loading, 100% ultrasonic testing is carried out on the steel plates. After loading, milling of the edges starts. The groove dimensions are an uphill groove angle of 70°, a downhill groove angle of 70°, and a downhill groove depth of 4 mm. The root face of 1# steel plate is 8.0 mm, and the root face of 2# steel plate is 10 mm. Then, a plate edge pre-bending is carried out using a pre-bending machine to make the plate edge curvature meet the requirements of their respective pipe diameters. Subsequently, JCO forming is about to start. On the forming machine, first, one side of the pre-bent steel plate is pressed into a J shape, then the other side of the steel plate is pressed into a C shape again in the same method and passes, and finally, one pressing is carried out in the middle of the steel plate to press it into an O-shaped opening. The 1# steel pipe with a wall thickness of 13 mm is pressed 25 passes in total, and the 2# steel pipe with a wall thickness of 22 mm is pressed 27 passes in total.

[0037] Step 3

[0038] The steel pipes after JCO forming are sent into a pre-welding machine. The position of the pre-welding machine pressure rollers is adjusted, and welding is carried out using a mixed gas shielded welding method. The BHG-2M welding wire with a diameter of 4.0 mm is selected for pre-welding. Among them, the gas category is 60% carbon dioxide + 40% Ar, the gas flow rate is 65 L / min, and the welding speed V = 4 m / min to form a continuous and reliable pre-weld seam. For the 1# welded pipe with a wall thickness of 13 mm, both the internal and external welding are carried out using double-wire submerged arc automatic welding. For the 2# welded pipe with a wall thickness of 22 mm, both the internal and external welding are carried out using three-wire submerged arc automatic welding. The welding wires used are For the 1# welded pipe with a wall thickness of 13 mm, the special Cr, Ni-containing welding wire with a mass percentage of 0.08% C, 1.2% Mn, 0.19% Si, 2.2% Cr, 1.1% Ni, 0.35% Mo, 0.1% V, 0.014% P, 0.008% S invented is selected. For the 2# welded pipe with a wall thickness of 22 mm, the special Cr, Ni-containing welding wire with a mass percentage of 0.08% C, 1.2% Mn, 0.19% Si, 2.7% Cr, 1.35% Ni, 0.35% Mo, 0.1% V, 0.014% P, 0.008% S invented is selected. All special welding wires are combined with CaF with an alkalinity of 1.85 2 -SiO 2 -MgO-Al2 O 3 -MnO-TiO 2 -B 2 O 3 The submerged arc welding is completed with the slag system sintered flux. During automatic submerged arc welding, the DC reverse connection is adopted for both the inner and outer 1# welding wires, and the AC is adopted for the 2# (including 3#) welding wires. The welding process parameters for the inner welding of the 1# 13-mm wall thickness welded pipe are as follows: for the 1# wire, the current I = 1100 A and the voltage U = 34 V; for the 2# wire, the current I = 900 A and the voltage U = 36 V, and the welding speed V = 1.5 m / min. The welding process parameters for the outer welding of the 1# 13-mm wall thickness welded pipe are as follows: for the 1# wire, the current I = 1300 A and the voltage U = 32 V; for the 2# wire, the current I = 850 A and the voltage U = 36 V, and the welding speed V = 1.5 m / min. The welding process parameters for the inner welding of the 2# 22-mm wall thickness welded pipe are as follows: for the 1# wire, the current I = 1100 A and the voltage U = 34 V; for the 2# wire, the current I = 850 A and the voltage U = 36 V, for the 3# wire, the current I = 700 A and the voltage U = 38 V, and the welding speed V = 1.4 m / min. The welding process parameters for the outer welding of the 2# 22-mm wall thickness welded pipe are as follows: for the 1# wire, the current I = 1350 A and the voltage U = 32 V; for the 2# wire, the current I = 1100 A and the voltage U = 34 V, for the 3# wire, the current I = 650 A and the voltage U = 38 V, and the welding speed V = 1.4 m / min. Finally, the Φ355×13 mm JCO submerged arc welded pipe and the Φ610×22 mm JCO submerged arc welded pipe are welded respectively.

[0039] Step Four

[0040] The straight seam submerged arc welded pipe completed by internal and external submerged arc welding is sent into a small box-type walking beam furnace for full-pipe quenching. The temperature inside the furnace is set at 940 °C, and the heating rate is about 40 °C / S. When the welded pipe is heated to 930 °C, it is taken out of the furnace. After being taken out of the furnace, the moving welded pipe is quickly quenched by on-line water spraying. According to the pipe diameter and wall thickness of the 1# Φ355×13mm JCO submerged arc welded pipe, the distance between the cantilever water spraying device for inner ring water spraying and the inner wall of the pipe is adjusted to about 10 mm - 15 mm. The inner water spraying speed is 1200 cubic meters per hour, and the outer water spraying speed is 2200 cubic meters per hour. According to the pipe diameter and wall thickness of the 2# Φ610×22mm JCO submerged arc welded pipe, the distance between the cantilever water spraying device for inner ring water spraying and the inner wall of the pipe is adjusted to about 8 mm - 13 mm. The inner water spraying speed is 2800 cubic meters per hour, and the outer water spraying speed is 3800 cubic meters per hour. The inner spraying and outer spraying time is about 15 - 25 s, and finally the welded pipe is cooled to room temperature. The cooled straight seam submerged arc welded pipe is rolled back to the small walking beam box-type furnace for the second time, and the remaining temperature of the small walking beam box-type furnace that was used to heat the welded pipe before quenching is utilized to carry out full-pipe tempering heat treatment again. When the temperature inside the furnace drops to about 625 °C, the straight seam submerged arc welded pipe is sent into the small walking beam furnace again for full-pipe tempering heat treatment, and heat is supplemented to the small walking beam box-type furnace. The entire pipe body of the 1# Φ355×13mm JCO submerged arc welded pipe is heated to 550 °C and kept warm in the furnace for 20 minutes. The entire pipe body of the 2# 610×22mm JCO submerged arc welded pipe is heated to 525 °C and kept warm in the furnace for 30 minutes.

[0041] Step Five

[0042] The 1# Φ355×13mm JCO submerged arc welded pipe and the 2# Φ610×22mm JCO submerged arc welded pipe are respectively taken out from the small walking beam furnace. Two expanding machines are set at both ends of the production line. Align the weld seam with the groove of the segmental block on the expanding head, insert the steel pipe into the expanding head, and utilize the self-heat of about 350 °C of the Φ355×13mm JCO submerged arc welded pipe when it comes out of the furnace to carry out hot expansion (RE). For every 650 mm of expansion, the trolley will send the steel pipe forward for a certain distance, and the two expanding machines will expand successively. The expansion rate is 0.7%, which improves the dimensional accuracy of the welded pipe, improves the stress distribution state of the welded pipe. The perimeter difference between the two pipe ends is only 1.2 mm, the wall thickness non-uniformity of the pipe body is 2%, the ovality is 0.2%, the straightness is 0.05%, and the residual stress of the welded pipe measured by the blind hole method is ≤48 MPa, and the residual stress is smaller and more uniform. Utilize the self-heat of about 340 °C of the Φ610×22mm JCO submerged arc welded pipe when it comes out of the furnace to carry out hot expansion (RE). For every 700 mm of expansion, the trolley will send the steel pipe forward for a certain distance, and the two expanding machines will carry out hot expansion successively. The expansion rate is 0.8%, which improves the dimensional accuracy of the welded pipe, improves the stress distribution state of the welded pipe. The perimeter difference between the two pipe ends is only 1.3 mm, the wall thickness non-uniformity of the pipe body is 2.1%, the ovality is 0.22%, the straightness is 0.07%, and the residual stress of the welded pipe measured by the blind hole method is ≤70 MPa, and the residual stress is small and more uniform.

[0043] Step Six

[0044] Perform X-ray detection on the welds of the Φ355×13mm JCOE hot-expanded submerged arc welded pipe for transporting supercritical carbon dioxide of X100 steel grade and the Φ610×22mm JCOE hot-expanded submerged arc welded pipe for transporting supercritical carbon dioxide of X120 steel grade in sequence. Conduct a hydrostatic test on the welded pipes. The test pressure for the Φ355×13mm JCOE hot-expanded submerged arc welded pipe is 45.8 MPa, and for the Φ610×22mm JCOE hot-expanded submerged arc welded pipe is 25 MPa. The pressure holding time is 15 s for both, and there is no leakage. Conduct 100% inspection on the welds and the heat-affected zones on both sides of the welded pipes after welding. Perform X-ray detection on the pipe ends, and take radiographs of the pipe ends of the welded pipes after sizing and hydrostatic testing to prevent defects that may be generated by sizing and hydrostatic testing. Chamfer, perform pipe end groove machining, with the groove angle of 22°-25° and the root face of 0.8-2.4 mm. Conduct magnetic particle inspection on the pipe ends of the welded pipes to further eliminate possible defects, and finally manufacture the ultra-high strength straight seam submerged arc welded pipe resistant to supercritical carbon dioxide corrosion.

[0045] In order to verify the physical and chemical properties of the straight seam submerged arc welded pipe manufactured in this embodiment, it is inspected through experiments:

[0046] The microstructure of the pipe body of the Φ355×13mm submerged arc welded pipe for transporting supercritical carbon dioxide of X100 steel grade is bainite + martensite, and the microstructure of the weld is bainite + acicular ferrite + a small amount of retained austenite, as Figure 1 . The microstructure of the pipe body of the Φ610×22mm submerged arc welded pipe for transporting supercritical carbon dioxide of X120 steel grade is also bainite + martensite, and the microstructure of the weld is bainite + a small amount of acicular ferrite + a small amount of retained austenite. The yield strength R P0.2 of the pipe body of the Φ355×13mm submerged arc welded pipe for transporting supercritical carbon dioxide of X100 steel grade: 691-835 MPa, the tensile strength R b of the pipe body: 765-930 MPa, the yield ratio of the pipe body: 0.78-0.92, the elongation of the pipe body: 20-24%, the tensile strength R m of the weld ≥765 MPa, the AkV of the pipe mother at -60°C: 180-320 J, the impact energy of the weld and the heat-affected zone at -60°C: 145 J-219 J. The reverse and forward bending tests of the welded pipes show that there are no cracks and cracking phenomena in all welds, and the crack tip opening displacement CTOD characteristic value δm of the pipe body and the welded joint at -60°C ≥0.50 mm. The yield strength R P0.2 of the pipe body of the Φ610×22mm submerged arc welded pipe for transporting supercritical carbon dioxide of X120 steel grade: 851-995 MPa, the tensile strength R b of the pipe body: 925-1030 MPa, the yield ratio of the pipe body: 0.88-0.94, the elongation of the pipe body: 20-23%, the tensile strength R of the weldm ≥915 MPa, AkV of the pipe mother at -60°C: 238 - 330 J, impact energy of the weld and heat affected zone at -60°C: 128 J - 211 J. The reverse and forward bending tests of the welded pipe show that no cracks or cracking occur in all welds. The crack tip opening displacement CTOD characteristic value δm of the pipe body and the welded joint at -60°C ≥ 0.45 mm. Referring to the API 5L PSL2 standard, the mechanical property tests of the two ultra-high strength straight seam submerged arc welded pipes resistant to supercritical carbon dioxide corrosion provided in the embodiments of the present invention all meet the standard requirements. Moreover, the high toughness of the base metal, weld and heat affected zone at -60°C can ensure that the pipe has a certain low-temperature crack arrest and prevention of long-range propagation ability when transporting supercritical carbon dioxide.

[0047] Corrosion comparison test: A supercritical carbon dioxide corrosion comparison test under typical working conditions was carried out on the submerged arc welded pipe of X100 steel grade for supercritical carbon dioxide with Φ355×13 mm and the submerged arc welded pipe of X120 steel grade for supercritical carbon dioxide with Φ610×22 mm J and the ordinary X52 / X60 steel grade straight seam submerged arc welded pipe. The carbon dioxide pressure was 10 MPa, the temperature was 35°C, containing H 2 O: 200 ppmv, containing H 2 S: 200 ppmv, SO 2 : 200 ppmv, NO 2 : 200 ppmv. As can be seen from Table 2, under typical supercritical carbon dioxide transportation working conditions, for the submerged arc welded pipe of X100 steel grade for supercritical carbon dioxide with Φ355×13 mm and the submerged arc welded pipe of X120 steel grade for supercritical carbon dioxide with Φ610×22 mm, the average corrosion rate is 1 / 2 - 1 / 10 of that of the ordinary X52 / X60 steel grade straight seam submerged arc welded pipe for comparison. Thus, the service life of the pipe is greatly improved, and at the same time, it is ensured that the pipe can serve more safely. This shows that the pipe mother and welded joint of the ultra-high strength straight seam submerged arc welded pipe resistant to supercritical carbon dioxide corrosion manufactured by the present invention have excellent anti-supercritical carbon dioxide corrosion ability.

[0048] Table 2 Test results of corrosion performance

[0049]

[0050] From the main performance test results of the embodiments, it can be seen that the ultra-high strength straight seam submerged arc welded pipe resistant to supercritical carbon dioxide corrosion manufactured by the method described in the present invention has ultra-high strength, no defects in the weld, excellent low-temperature mechanical properties of the pipe mother and weld, strong anti-corrosion ability, and the transportation ability of the ultra-high strength straight seam submerged arc welded pipe resistant to supercritical carbon dioxide corrosion.

[0051] In summary, the present invention adopts the JCO process and selects rolled steel plates to manufacture welded pipes. After the JCO process, the yield strength of the welded pipes can only reach the steel grades of X52 to X60. The microstructure of the steel plates is polygonal ferrite + pearlite + a small amount of granular bainite. After subjecting it to the quenching + tempering heat treatment process of the whole pipe, the microstructure of the tube blank of the ultra-high strength longitudinal submerged arc welded pipe for transporting supercritical carbon dioxide is transformed into bainite + martensite, and the microstructure of the weld seam is transformed into bainite + acicular ferrite + a small amount of retained austenite. By controlling the tempering temperature and the hot expansion diameter, the adjustment of the yield ratio is achieved and the residual stress is reduced; in addition, after the quenching and tempering heat treatment process, the yield strength and tensile strength of the welded pipe body are greatly improved, and at the same time, the strength of the welded joint is greatly improved, so that the steel grade of the welded pipe is increased from X52 to X60 to X90 to X120. The yield strength of the pipe body reaches 628 MPa to 953 MPa, the tensile strength of the pipe body reaches 700 MPa to 1202 MPa, the elongation A≥20%, and the tensile strength of the weld seam reaches 710 MPa to 1250 MPa. After experiments, it is found that the longitudinal submerged arc welded pipe of steel grades X90 to X120 manufactured by the present invention can transport supercritical carbon dioxide at a pressure of 8 MPa to 20 MPa. Compared with the conventional longitudinal submerged arc welded pipe of steel grades X52 to X60 with the same pipe diameter and the same throughput, the wall thickness of the steel pipe is reduced by about half, thus reducing the consumption of pipe materials; compared with the original cold expansion, the size accuracy of the JCOE pipe body after the new hot expansion process is higher, the residual stress is greatly eliminated, the wall thickness non-uniformity after the hot expansion process ≤3%, the ovality ≤0.3%, the straightness ≤0.15%, and the residual stress of the welded pipe ≤80 MPa, and the residual stress is smaller and more uniform. Under typical supercritical carbon dioxide transportation conditions, the longitudinal submerged arc welded pipe for resisting supercritical carbon dioxide corrosion of steel grades X90 to X120 is compared with the conventional longitudinal submerged arc welded pipe of steel grades X52 to X60 in terms of corrosion rate. The average corrosion rate is 1 / 2 to 1 / 10 of that of the comparison pipe, thus greatly improving the service life and service years of the pipe materials, and ensuring that the ultra-high strength longitudinal submerged arc welded pipe for transporting supercritical carbon dioxide developed can serve more safely.

Claims

1. A manufacturing method for an ultra-high strength longitudinally submerged arc welded pipe resistant to supercritical carbon dioxide corrosion, characterized in that, it includes the following steps: S1 Molten iron containing high Mn and high Cr is continuously cast into a slab after pretreatment, electric furnace smelting, RH furnace refining, and VD vacuum treatment, and the slab is heated at 1140°C - 1270°C and then processed by the TMCP process to make a steel plate with high dimensional accuracy under large-tonnage rolling deformation; S2 After the steel plate prepared in S1 is subjected to ultrasonic inspection, edge milling, and pre-bending, the JCO forming machine is used to first press one side of the pre-bent steel plate multiple times to gradually press it into a J shape, then press the other side of the steel plate multiple times to press it into a C shape, and finally press the steel plate once in the middle to press the steel plate into a tubular part with an opening in the shape of O; S3 The tubular part pressed in S2 is subjected to internal and external automatic submerged arc welding to obtain a longitudinally submerged arc welded pipe; S4 The entire longitudinally submerged arc welded pipe is subjected to quenching and tempering heat treatment; S5 The entire longitudinally submerged arc welded pipe is subjected to full-pipe body hot expansion to obtain an ultra-high strength longitudinally submerged arc welded pipe resistant to supercritical carbon dioxide corrosion.

2. The manufacturing method for an ultra-high strength longitudinally submerged arc welded pipe resistant to supercritical carbon dioxide corrosion according to claim 1, characterized in that, in S1, the slab, calculated by mass percentage, includes the following components: C 0.04 - 0.07%, Si 0.15 - 0.30%, Mn 2 - 3%, Cr 3 - 9%, Ni 0.15 - 0.30%, Nb 0.05 - 0.08%, P ≤ 0.010%, S ≤ 0.003%, and the rest is iron; The steel grade of the steel plate hot-rolled with this composition is X52 - X60, and the structure of the steel plate is polygonal ferrite + pearlite + granular bainite.

3. The manufacturing method for an ultra-high strength longitudinally submerged arc welded pipe resistant to supercritical carbon dioxide corrosion according to claim 1, characterized in that, S3 is specifically implemented according to the following scheme: S31 Pre-weld the tubular part. For pre-welding, select a BHG-2M welding wire with a diameter of 4.0 mm, and a mixed gas of carbon dioxide + Ar as the shielding gas, where the carbon dioxide content is 55% - 65%, and the rest is 35% - 45%. The gas flow rate of the shielding gas is 60 - 75 L / min, and the welding speed V = 3.5 - 4.5 m / min; After pre-welding at S32, use a Cr- and Ni-containing welding wire and cooperate with a CaF-based sintered welding flux with an alkalinity of 1.85 2 -SiO 2 -MgO-Al 2 O 3 -MnO-TiO 2 -B 2 O 3 Perform submerged arc automatic internal welding first with this flux system, and then synchronously perform submerged arc automatic external welding at a welding speed V = 1.4 m / min to 1.6 m / min.

4. The manufacturing method for an ultra-high strength longitudinally submerged arc welded pipe resistant to supercritical carbon dioxide corrosion according to claim 3, characterized in that, the Cr, Ni-containing welding wire, calculated by mass percentage, includes the following components: C 0.08%, Mn 2.5%, Si 0.19%, Cr 1.8 - 3.0%, Ni 0.9 - 1.5%, Mo 0.35%, V 0.1%, P ≤ 0.015%, S ≤ 0.008%, and the rest is Fe; The diameter of the Cr, Ni-containing welding wire is 4 mm.

5. The manufacturing method for an ultra-high strength longitudinally submerged arc welded pipe resistant to supercritical carbon dioxide corrosion according to claim 3, characterized in that, in S32, double-wire or three-wire is selected according to the wall thickness of the longitudinally submerged arc welded pipe, where the 1# wire uses direct current reverse connection, and the rest use alternating current.

6. A manufacturing method of an ultra-high strength straight seam submerged arc welded pipe resistant to supercritical carbon dioxide corrosion according to claim 1, characterized in that, the S4 is specifically implemented according to the following scheme: S41: Transport the straight seam submerged arc welded pipe to a small box-type step furnace for integral pipe quenching. The maximum temperature in the furnace is set at 940 °C, and the heating rate in the furnace is 30 °C / S to 50 °C / S. When the welded pipe is heated to 900 °C to 930 °C, it is taken out of the furnace, and online water spraying quenching is quickly carried out on the moving welded pipe within 10S after taking out of the furnace to cool the straight seam submerged arc welded pipe taken out of the furnace to room temperature; S42: Send the cooled straight seam submerged arc welded pipe into the small box-type step furnace for the second time, and use the waste heat of the furnace temperature of 500 °C to 625 °C to carry out integral pipe tempering heat preservation treatment again. During the heat preservation period, heat can be supplemented to the small box-type step furnace to ensure that the heat preservation temperature of the whole welded pipe is controlled within ±5 °C, and it is taken out after being placed in the furnace for 20 to 40 minutes of heat preservation.

7. A manufacturing method of an ultra-high strength straight seam submerged arc welded pipe resistant to supercritical carbon dioxide corrosion according to claim 6, characterized in that, the quenching devices selected in the online water spraying quenching in S41 are an inner ring water spraying device and an outer ring water spraying device respectively, wherein the inner water spraying speed is 800 to 3000 cubic meters per hour, the outer wall water spraying speed is 2000 to 4000 cubic meters per hour, and the inner spraying and outer spraying time is 15 to 25s.

8. A manufacturing method of an ultra-high strength straight seam submerged arc welded pipe resistant to supercritical carbon dioxide corrosion according to claim 1, characterized in that, the S5 utilizes the waste heat of the straight seam submerged arc welded pipe itself when it is taken out of the small box-type step furnace, and carries out segmented hot expansion of the straight seam submerged arc welded pipe at 300 °C, with each segment expanded by 500 mm to 800 mm, and the expansion rate is 0.6% to 1.0%.

9. A straight seam submerged arc welded pipe manufactured by using the manufacturing method of an ultra-high strength straight seam submerged arc welded pipe resistant to supercritical carbon dioxide corrosion according to any one of claims 1-8, characterized in that, the pipe mother microstructure of the straight seam submerged arc welded pipe is bainite + martensite, the submerged arc weld microstructure is bainite + acicular ferrite + a small amount of retained austenite, the pipe diameter of the welded pipe is DN323mm to DN610mm, the wall thickness ≤25.4mm, the steel grade is X90 to X120, the yield strength of the welded pipe base material is 628MPa to 953MPa, the tensile strength of the base material is 700MPa to 1202MPa, the elongation of the base material: A≥20%, the full-size base material transverse impact energy at -60 °C is 158J to 347J, and the impact energy of the full-size weld and heat affected zone at -60 °C is: 123J to 219J.

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