WO2024002220A1 - 一种高频电阻焊钢管及其制备方法 - Google Patents

一种高频电阻焊钢管及其制备方法 Download PDF

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WO2024002220A1
WO2024002220A1 PCT/CN2023/103716 CN2023103716W WO2024002220A1 WO 2024002220 A1 WO2024002220 A1 WO 2024002220A1 CN 2023103716 W CN2023103716 W CN 2023103716W WO 2024002220 A1 WO2024002220 A1 WO 2024002220A1
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resistance welded
welded steel
frequency resistance
steel pipe
frequency
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PCT/CN2023/103716
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English (en)
French (fr)
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孙磊磊
屈献永
朱德锋
章传国
张豪臻
杨晓臻
华骏山
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宝山钢铁股份有限公司
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Publication of WO2024002220A1 publication Critical patent/WO2024002220A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P17/00—Metal-working operations, not covered by a single other subclass or another group in this subclass
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite

Definitions

  • the invention belongs to the field of welded pipe production, and in particular relates to a high-frequency resistance welded steel pipe with excellent low-temperature crack arresting performance and a preparation method thereof.
  • High-frequency resistance welded steel pipe is a steel pipe made from hot-rolled coils as raw materials through roller forming and high-frequency resistance welding. It has high production efficiency and dimensional accuracy. Compared with other pipe types, it also has good Economical. At present, high-frequency resistance welded steel pipes have been widely used in submarine pipeline projects.
  • high-frequency resistance welded steel pipes for submarine pipelines must also comply with the submarine pipeline standard DNVGL-ST-F101.
  • Conventional submarine pipelines only need to meet the general requirements of the standard, while some high-voltage transmission lines with higher requirements
  • the gas submarine pipeline project will also add the crack arrest performance clause in the supplementary requirements of DNVGL-ST-F101, which requires steel pipes with an outer diameter >400mm to meet the requirements of the low temperature drop weight tear test (DWTT). This is true for small-diameter thick-walled steel pipes. There is a certain degree of difficulty.
  • HFW welded pipes used for submarine pipelines usually have a large thickness-to-diameter ratio (thickness/outer diameter).
  • Hot-rolled coils will undergo large plastic deformation during cold forming of pipe making, and their toughness will decrease, especially for outer diameters.
  • the DWTT performance will be significantly reduced.
  • the toughness will be further reduced.
  • the publication number is CN110904391A
  • the Chinese patent document titled "A thick-sized ERW submarine pipeline welded pipe with excellent weld quality and its manufacturing method” discloses a thick-sized ERW submarine pipeline welded pipe.
  • Mo and V elements are added, without Cr, it has high weld impact toughness at 0°C, and the pipe body is designed with an acicular ferrite structure.
  • the publication number is CN101701315A
  • the Chinese patent document titled "Manufacturing Method of Submarine Pipeline Steel Pipe” discloses an ERW steel pipe for submarine pipelines.
  • the chemical composition is low carbon, low manganese and micro-alloyed, and the product has high strength, corrosion resistance and high pressure resistance.
  • the publication number is CN102284780B, and the Chinese patent document titled "Welding Production Process of Low-Temperature-Resistant HFW Steel Pipes for Stations" discloses a low-temperature-resistant HFW steel pipe.
  • the welding power used is 350 to 500KW to provide a low-temperature resistant station HFW steel pipe welding production process that ensures the normal operation of oil and gas transmission pipelines at low temperatures.
  • the publication number is CN103966505B
  • the Chinese patent document titled "Manufacturing Process of Large-Wall Thickness X70M Steel Grade HFW Line Pipe” discloses an X70M steel grade high-frequency resistance welded steel pipe.
  • low-carbon, micro-alloyed component design is used to produce high-frequency welded pipes that meet the requirements of tensile properties, impact toughness properties and microstructure, and can be used for coal slurry, mineral slurry, oil, gas, etc. delivery.
  • the publication number is CN103526108B, and the Chinese patent document titled "An X70MS ERW welded pipe with excellent resistance to SSCC stress corrosion and its manufacturing method" discloses an X70MS corrosion-resistant high-frequency resistance welded steel pipe.
  • the content of Mn and Cr elements is low, the base metal and weld structure of the produced welded pipe are basically the same, and it has excellent H2S corrosion resistance.
  • the publication number is JP2015190026A, and the Japanese patent document titled "Thick High Strength Electroseamed Steel Pipe for Linepipe and Manufacturing Method” discloses a high-strength high-frequency resistance welded steel pipe.
  • the technical solution disclosed in the patent document Cu, Ni, Mo, Nb, and V elements are added, and the ferrite plus pearlite structure design is adopted.
  • the produced welded pipe has high strength, high toughness, and excellent acid resistance and resistance to Hydrogen cracking.
  • a high-frequency resistance welded steel pipe with excellent low-temperature crack arrest performance is provided, which can perform at low temperatures, especially at low temperatures. -20°C, has good DWTT crack arrest performance and weld impact toughness, and can be used in low-temperature service high-end submarine pipelines with crack arrest requirements.
  • the invention provides a high-frequency resistance welded steel pipe.
  • the high-frequency resistance welded steel pipe is composed of the following mass percentages of chemical elements:
  • the mass percentage of C+(Cr+Mo)/5 is controlled in the range of 0.07 to 0.12%.
  • the mass percentage range of C+(Cr+Mo)/5 is controlled so that when a certain strength is met, the desired DWTT crack arresting performance can be achieved at the same time.
  • P, S, and B are controlled at the following mass percentages: P ⁇ 0.013%, S ⁇ 0.003%, B ⁇ 0.0005%.
  • the above scheme is adopted to strictly control the content of harmful impurity elements and reduce the impact of harmful impurity elements on the quality of high-frequency resistance welded steel pipes.
  • the microstructure of the steel pipe is polygonal ferrite + granular bainite; wherein the grain size of the polygonal ferrite is ⁇ 10 ⁇ m; and the polygonal iron
  • the volume percentage of the body is in the range of 10 to 40%.
  • the tensile properties of the high-frequency resistance welded steel pipe are: pipe body yield strength ⁇ 459MPa, pipe body tensile strength ⁇ 545MPa, weld tensile strength ⁇ 549MPa; high frequency
  • the DWTT fracture shear area ratio of resistance welded steel pipe at -20°C is above 91%.
  • the high-frequency resistance welded steel pipe provided by the present invention also meets the following requirements: the Charpy impact energy of the pipe body at -20°C is ⁇ 200J, and the Charpy impact energy of the weld seam at -20°C is ⁇ 100J.
  • S2 Cut off the head and tail of each coil. The incision is at an angle of 2 to 5° with the horizontal plane of the coil. Weld the heads and tails of two adjacent coils through carbon dioxide gas shielded welding. Together, they form a continuous strip of steel;
  • S3 Mill the steel strip.
  • the width of the steel strip after milling is determined according to the outer diameter specification of the high-frequency resistance welded steel pipe;
  • the high-frequency welding process uses high frequency to enhance the skin effect to ensure that the edge of the steel strip is in good welding condition; medium-frequency induction heating is used to heat treat the weld seam of the welded pipe, and excellent strength and toughness is obtained through the heat treatment of the weld seam.
  • step S5 of the method for preparing high-frequency resistance welded steel pipes provided by the present invention the welding power is controlled to be ⁇ 700kW.
  • high welding power is used to ensure that the edge of the steel strip is fully melted to avoid cold welding. It also facilitates the outward flow of molten metal under the action of electromagnetic force and effectively discharges oxides.
  • the extrusion amount of the extrusion roller is controlled to be in the range of 10 to 25 mm.
  • the extrusion roller uses a large amount of extrusion to further squeeze out inclusions such as oxides formed in the molten state to obtain a high-purity weld; by using a high-frequency, high-power, and large-extrusion welding process , effectively remove defects such as welding oxides and obtain good weld quality.
  • step S5 in the method for preparing high-frequency resistance welded steel pipes provided by the present invention, in step S5, the opening V angle at the welding meeting point is controlled to be in the range of 3 to 6°.
  • step S1 in the preparation method of high-frequency resistance welded steel pipe provided by the present invention, includes:
  • the high-frequency resistance welded steel pipe provided by the present invention is designed with low carbon and low alloy composition, and cooperates with the optimized TMCP (Thermo Mechanical Control Process) to achieve grain refinement and effectively control the phase change structure to obtain high-frequency
  • the microstructure of the resistance welded steel pipe is fine polygonal ferrite + granular bainite.
  • the grain size of the polygonal ferrite is ⁇ 10 ⁇ m and the volume fraction is in the range of 10 to 40%.
  • the high-frequency resistance welded steel pipe produced has relatively high High strength and excellent low-temperature crack arrest performance; can be used in high-end submarine pipelines with crack arrest requirements for low-temperature service.
  • the tensile properties of the high-frequency resistance welded steel pipe of the present invention can reach: pipe body yield strength ⁇ 459MPa, pipe body tensile strength ⁇ 545MPa, weld tensile strength ⁇ 549MPa; DWTT fracture of the high-frequency resistance welded steel pipe at -20°C
  • the shear area ratio is above 91%, and it also meets the following requirements: -20°C Charpy impact energy of the pipe body ⁇ 200J, and -20°C Charpy impact energy of the weld ⁇ 100J.
  • the high-frequency resistance welded steel pipe of the present invention satisfies the low-temperature DWTT crack arresting performance while meeting other general technical requirements.
  • the invention provides a high-frequency resistance welded steel pipe.
  • the high-frequency resistance welded steel pipe is composed of the following mass percentages of chemical elements:
  • the high-frequency resistance welded steel pipe is composed of the following mass percentages of chemical elements:
  • C carbon: In the high-frequency resistance welded steel pipe of the present invention, C is the most effective strengthening element. However, it should be noted that when the C element content is too high, it is easy to form more carbides or Maho Island, and Easily forms a band in the center of thickness Hard phase structure, which has a negative impact on the material's crack arrest performance. Based on this, in the high-frequency resistance welded steel pipe of the present invention, the mass percentage content of the C element is controlled between 0.025% and 0.054%, preferably between 0.031% and 0.053%.
  • Mn manganese: In the high-frequency resistance welded steel pipe of the present invention, Mn improves the strength through solid solution strengthening and has the effect of refining the grains. However, when the Mn element content is too high, the hot-rolled coil TMCP will be quickly cooled. During the low-temperature coiling process, lath bainite structure is easily formed, which has a negative impact on the low-temperature crack arrest performance. Based on this, in the high-frequency resistance welded steel pipe of the present invention, the mass percentage content of the Mn element is controlled between 1.21% and 1.45%, preferably between 1.22% and 1.44%.
  • Ni nickel: In the high-frequency resistance welded steel pipe of the present invention, Ni is an important element for improving low-temperature crack arrest performance. Ni can reduce dislocation slip resistance at low temperatures and alleviate low-temperature embrittlement. Ni can also increase Stacking fault energy promotes the cross-slip of screw dislocations at low temperatures, increases the work consumed by crack expansion, and improves the local crack arresting ability. However, Ni is expensive and the added amount should not be too much. Therefore, in the present invention, the mass percentage of Ni element is controlled between 0.05% and 0.20%, preferably between 0.08% and 0.19%.
  • Mo mobdenum
  • Mo plays a role in controlling phase transformation and improving strength. Mo can reduce the ⁇ phase transformation temperature of steel and play a role in refining the structure. Low carbon pipeline steel can effectively promote the formation of high-toughness granular bainite and suppress pearlite. However, when the Mo content is too high, it is easy to form harder structures such as lath bainite, which is detrimental to low-temperature crack arrest performance. Therefore, in the present invention, the mass percentage of Mo element is controlled between 0.01% and 0.15%, preferably between 0.02% and 0.14%.
  • P, S, and B are controlled at the following mass percentages: P ⁇ 0.013wt%, S ⁇ 0.003wt%, and B ⁇ 0.0005%.
  • P, S, and B elements are inevitable harmful impurity elements in welded pipes. S can easily form long MnS inclusions. P is an element that reduces the low-temperature toughness of welded pipes. B is a strong hardenability element that can easily lead to The plasticity and toughness of the material decrease. Therefore, the high-frequency resistance welded steel pipe of the present invention controls P ⁇ 0.013%, S ⁇ 0.003%, and B ⁇ 0.0005%.
  • a fine granular bainite structure is obtained to achieve the desired DWTT crack arresting performance.
  • the microstructure of the steel pipe is polygonal ferrite + granular bainite; the grain size of the polygonal ferrite is ⁇ 10 ⁇ m; and the volume percentage of the polygonal ferrite is in the range of 10 to 40%.
  • the high-frequency resistance welded steel pipe provided by the present invention has a yield strength ⁇ 459MPa, a tensile strength ⁇ 545Mpa, an elongation A50 ⁇ 28%, a -20°C pipe body Charpy impact energy ⁇ 200J, and a -20°C pipe body DWTT fracture shear area ratio ⁇ 91%; preferably, the yield strength is 459 ⁇ 562MPa, the tensile strength is 545-641MPa, the elongation A50 is 28-34%, -20°C pipe body Charpy impact energy ⁇ 242J, - The DWTT fracture shear area ratio of the pipe body at 20°C is 95 to 100%.
  • the balance is Fe and inevitable impurities. Furthermore, among the inevitable impurities, P, S, and B are controlled in the following mass percentages: P ⁇ 0.013%, S ⁇ 0.003%, and B ⁇ 0.0005%.
  • the heating temperature of the slab needs to reach a certain temperature to ensure that the alloy elements are fully dissolved, but too high a heating temperature will cause the original austenite grain size to be too large; the present invention controls the heating temperature range to 1160 ⁇ 1210°C to ensure that the slab Apply heat.
  • the rough rolling process refines the austenite grains through recrystallization, so it should be carried out within the recrystallization temperature range.
  • the present invention controls the rough rolling final pass temperature to be ⁇ 960°C, such as 960-1000°C or 965-992°C.
  • the present invention controls the finishing rolling opening temperature to ⁇ 930°C. , such as 910 ⁇ 930°C or 910 ⁇ 925°C; at the same time, control the lower finishing rolling and final rolling temperature to reduce the recovery of strain storage energy, increase the phase deformation nucleation rate, and achieve the effect of refining the structure. Therefore, the present invention controls the finishing rolling temperature to be 790 to 840°C.
  • the laminar cooling and coiling process is a process of deformed austenite phase transformation.
  • a higher cooling rate helps to refine the grains and improve strength and toughness. Therefore, the present invention controls the cooling rate to 25 ⁇ 35°C/s.
  • the coiling temperature is The stopping temperature of hot rolled coil cooling.
  • the present invention hopes to obtain a microstructure of fine polygonal ferrite + granular bainite. Therefore, it is necessary to suppress quasi-polygonal ferrite and pearlite, and the coiling temperature should not be too high.
  • the coiling temperature should not be too low. Therefore, under the composition system of the present invention, in order to obtain the target microstructure, the coiling temperature range is controlled to be 450 to 520°C.
  • S5 Use high-frequency welding and weld the edges of the raw pipe together under the action of the squeeze roller to form a welded pipe; the high-frequency welding frequency is controlled to be ⁇ 200kHz, such as 200 ⁇ 230kHz or 220 ⁇ 230kHz.
  • the use of high frequency can enhance the skin effect and ensure that the edges of the steel strip are in a good welding state.
  • the edges of the steel strip are melted under the skin effect of high-frequency current, and at the same time welded together under the action of the extrusion roller, and then scraped and extruded.
  • the internal and external burrs are made into welded pipes.
  • the high-frequency welding power is controlled to be ⁇ 700KW.
  • the welding power is 700-1020kW or 720-1020kW.
  • the extrusion roller adopts a large extrusion volume, which can further squeeze out inclusions such as oxides formed in the molten state to obtain a high-purity weld. Therefore, according to one of the specific embodiments of the present invention, the extrusion amount of the extrusion roller is controlled to be between 10 and 25 mm. Preferably, the extrusion amount is between 11 and 23 mm.
  • the specific extrusion amount the circumference of the raw pipe - the extrusion The circumference of the back.
  • the present invention adopts a high-frequency, high-power, large-extrusion welding process to effectively discharge defects such as welding oxides and obtain good weld quality.
  • the opening V angle at the welding meeting point is controlled to be in the range of 3 to 6°.
  • the opening V angle is in the range of 3.2 to 5.5°.
  • the present invention controls the heat treatment temperature to be 950-1010°C, and the holding time is ⁇ 15s; after medium-frequency induction heat treatment, spray cooling water is cooled to the range of 550-650°C, and then air-cooled; preferably, the weld heat treatment temperature is 950-1000°C, and the heat preservation time is The time is 15 to 18 seconds, spray cooling water to cool to 560 to 640°C, and then air cool. Excellent strength and toughness are obtained through weld heat treatment.
  • the high-frequency resistance welded steel pipe obtained by the above method has a -20°C Charpy impact energy of the weld ⁇ 100J.
  • the tensile strength of the weld is ⁇ 549MPa
  • the Charpy impact energy at -20°C is ⁇ 130J
  • the tensile strength of the weld is 549-635MPa
  • the Charpy impact energy at -20°C is ⁇ 170J.
  • This invention adopts low-carbon and low-alloy composition design, cooperates with the optimized TMCP process to achieve grain refinement, and effectively controls the phase change structure, obtaining a high-frequency resistance welded steel pipe with a microstructure of fine polygonal ferrite + granular bainite.
  • the grain size of polygonal ferrite is ⁇ 10 ⁇ m, and the volume fraction is in the range of 10 to 40%.
  • the high-frequency resistance welded steel pipe produced has high strength and excellent low-temperature crack arrest performance.
  • the high-frequency resistance welded steel pipes of Examples 1-6 are all produced using the following steps:
  • Table 1 Chemical composition content of Examples 1-6 (wt%, the balance is Fe and other unavoidable impurities except P, S and B)
  • Table 2-1 Specific process parameters of the step of rolling into coils in Example 1-6
  • S3 Milling the steel strip.
  • the width of the steel strip after milling is determined according to the outer diameter specification of the high-frequency resistance welded steel pipe.
  • the high-frequency resistance welded steel pipes obtained in Examples 1-6 were respectively sampled and subjected to performance testing tests.
  • the test items include tensile test, impact test, and drop weight tear test (DWTT). It should be noted that the tensile test and impact test were conducted in accordance with the ASTM A370 standard “Methods and Definitions for Mechanical Property Testing of Steel Products", and the drop weight tear test (DWTT) was conducted in accordance with the API RP 5L3 specification "Drop Weight Tear Test Method for Pipeline Steel" "conduct.
  • Example 1-6 The performance test results of Examples 1-6 are as shown in Table 3 and Table 4 respectively; Table 3 lists the tensile property test results of the high-frequency resistance welded steel pipes of Examples 1-6, and Table 4 lists the tensile property test results of Examples 1-6. DWTT and impact toughness test results of high frequency resistance welded steel pipes for 6.
  • Table 4 DWTT and impact toughness test results of high-frequency resistance welded steel pipes of Examples 1-6
  • the high-frequency resistance welded steel pipes of Examples 1-6 of the present invention have excellent comprehensive properties. It not only has high strength, but also has excellent DWTT crack arresting performance and impact toughness.
  • the pipe body yield strength of the high-frequency resistance welded steel pipes in Examples 1-6 is ⁇ 459MPa
  • the pipe body tensile strength is ⁇ 545MPa
  • the weld tensile strength is ⁇ 549MPa.
  • the DWTT fracture shear area ratio of the high-frequency resistance welded steel pipes of Examples 1-6 at -20°C is above 91%, and at the same time, it also satisfies: the pipe body -
  • the Charpy impact energy at 20°C is ⁇ 200J
  • the Charpy impact energy of the weld at -20°C is ⁇ 100J.
  • the high-frequency resistance welded steel pipe of the present invention through reasonable chemical composition design and combined with optimized technology, can obtain higher strength and impact toughness, especially has excellent low-temperature crack arrest performance, and can be used in The field of low-temperature service high-end submarine pipelines with crack arrest requirements has very broad application prospects.
  • Figure 1 is a microstructure diagram of the pipe body of the high-frequency resistance welded steel pipe obtained in Example 1.
  • the microstructure of the high-frequency resistance welded steel pipe in Example 1 is fine polygonal ferrite + granular bainite.
  • the polygons in the microstructure are measured using the GB/T 15749 standard and the GB/T 6394 standard. Ferrite content and grain size are shown in Table 5. After analysis, the volume fraction of polygonal ferrite is in the range of 10 to 40%, and the grain size is ⁇ 10 ⁇ m.
  • Table 5 Microstructural analysis of high-frequency resistance welded steel pipes of Examples 1-6

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Abstract

本发明提供一种高频电阻焊钢管，包含：C：0.025～0.054％、Si：0.10～0.30％、Mn：1.21～1.45％、Ni：0.05～0.20％、Cr：0.11～0.25％、Mo：0.01～0.15％、Nb：0.030～0.055％、Ti：0.005～0.020％、Al：0.020～0.050％、Ca：0.001～0.004％。高频电阻焊钢管在低温下具有良好的DWTT止裂性能和焊缝冲击韧性，可应用于低温服役高端海底管线领域。

Description

一种高频电阻焊钢管及其制备方法 技术领域
本发明属于焊管生产领域，尤其涉及一种具有优良低温止裂性能的高频电阻焊钢管及其制备方法。
背景技术
高频电阻焊钢管(HFW焊管)是以热轧板卷为原材料，通过排辊成型和高频电阻焊制成的钢管，具有较高的生产效率和尺寸精度，相对其他管型，还有着良好的经济型，目前，高频电阻焊钢管已广泛应用于海底管线工程中。
海底管线用高频电阻焊钢管在满足管线钢管规范API Spec 5L基础上，还要遵循海底管道标准DNVGL-ST-F101，常规海底管线只需满足标准的通用要求，而一些要求较高的高压输气海底管线工程还会附加DNVGL-ST-F101补充要求中的止裂性能条款，即要求外径＞400mm的钢管满足低温落锤撕裂试验(DWTT)要求，这对于小口径厚壁钢管，是有一定难度的。
需要说明的是，海底管线用HFW焊管通常具有较大的厚径比(厚度/外径)，热轧板卷在制管冷成型中会发生较大的塑性变形，韧性下降，特别对于外径≤508mm，壁厚≥14.3mm的小口径厚壁规格，DWTT性能会显著下降，进一步地，在DWTT试样压平过程中，韧性还会进一步下降。因此，从制管原材料和制管工艺进行优化设计，确保HFW焊管具备优良的低温DWTT止裂性能，并同时满足其他通用技术要求，特别是焊缝冲击韧性，是本领域技术人员需要解决的技术难题，而且，服役温度越低，技术难度越大。
公开号为CN110904391A，名称为“一种焊缝质量优良的厚规格ERW海底管线焊管及其制造方法”的中国专利文献公开了一种厚规格ERW海底管线焊管。在该专利文献公开的技术方案中，添加Mo、V元素，不含Cr，在0℃具有较高的焊缝冲击韧性，管体采用针状铁素体组织设计。
公开号为CN101701315A，名称为“海底管线钢管的制造方法”的中国专利文献公开了一种海底管线用ERW钢管。在该专利文献公开的技术方案中，化学成分为低碳、低锰和微合金化，产品具有高强度，耐腐蚀和抗高压的性能。
公开号为CN102284780B，名称为“耐低温站场用HFW钢管焊接生产工艺”的中国专利文献公开了一种耐低温HFW钢管。在该专利文献公开的技术方案中，所用焊接功率为350～500KW，以提供保证油气输送管线低温情况下能正常运行的耐低温站场用HFW钢管焊接生产工艺。
公开号为CN103966505B，名称为“一种大壁厚X70M钢级HFW管线管的制造工艺”的中国专利文献公开了一种X70M钢级高频电阻焊钢管。在该专利文献公开的技术方案中，采用低碳、微合金化成分设计，生产满足拉伸性能、冲击韧性性能和微观组织要求的高频焊管，可用于煤浆、矿浆、油、气等的输送。
公开号为CN103526108B，名称为“一种抗SSCC应力腐蚀优良的X70MS的ERW焊管及其制造方法”的中国专利文献公开了一种X70MS抗腐蚀高频电阻焊钢管。在该专利文献公开的技术方案中，Mn、Cr元素含量较低，生产的焊管母材和焊缝组织基本一致，且具有优良的耐H2S腐蚀性。
公开号为JP2015190026A，名称为“Thick High Strength Electroseamed Steel Pipe for Linepipe and Manufacturing Method”的日本专利文献公开了一种高强度高频电阻焊钢管。在该专利文献公开的技术方案中，添加了Cu、Ni、Mo、Nb、V元素，采用铁素体加珠光体组织设计，生产的焊管具有高强度、高韧性，以及优良的耐酸性及抗氢致开裂性。
但是上述专利改善焊管的主要目的是为了强度、韧性、耐腐蚀性、焊管生产工艺等，并未改善焊管的低温DWTT止裂性能。
发明内容
为解决现有技术的HFW焊管存在在满足其他通用技术要求时，难以同时满足低温DWTT止裂性能的问题，提供一种具有优良低温止裂性能的高频电阻焊钢管，在低温下特别是在-20℃，具有良好的DWTT止裂性能和焊缝冲击韧性，可应用于有止裂要求的低温服役高端海底管线领域。
本发明提供一种高频电阻焊钢管，高频电阻焊钢管由以下质量百分比的化学元素组成：
C：0.025～0.054％、Si：0.10～0.30％、Mn：1.21～1.45％、Ni：0.05～0.20％、Cr：0.11～0.25％、Mo：0.01～0.15％、Nb：0.030～0.055％、Ti：0.005～0.020％、Al：0.020～0.050％、Ca：0.001～0.004％；余量为Fe及不可避免的杂质。
采用上述方案，采用低碳、低合金成分设计，其中采用Mo+Cr强化，并添加Ni元素，能够获得较好的低温止裂性能。
根据本发明的另一具体实施方式，本发明提供的高频电阻焊钢管，其中C+(Cr+Mo)/5的质量百分比控制在0.07～0.12％范围。
采用上述方案，控制C+(Cr+Mo)/5的质量百分比范围，以使在满足一定强度时，同时达到期望的DWTT止裂性能。
根据本发明的另一具体实施方式，本发明提供的高频电阻焊钢管，其中不可避免的杂质中，P、S、B控制在以下质量百分比：P≤0.013％、S≤0.003％、B≤0.0005％。
采用上述方案，严格控制有害杂质元素含量，降低有害杂质元素高频电阻焊钢管品质的影响。
根据本发明的另一具体实施方式，本发明提供的高频电阻焊钢管，钢管的微观组织为多边形铁素体+粒状贝氏体；其中多边形铁素体的晶粒尺寸≤10μm；且多边形铁素体的体积百分比在10～40％范围。
根据本发明的另一具体实施方式，本发明提供的高频电阻焊钢管的拉伸性能为：管体屈服强度≥459MPa，管体抗拉强度≥545MPa，焊缝抗拉强度≥549MPa；高频电阻焊钢管在-20℃的DWTT断口剪切面积率在91％以上。
根据本发明的另一具体实施方式，本发明提供的高频电阻焊钢管还满足：管体-20℃夏比冲击功≥200J，焊缝-20℃夏比冲击功≥100J。
本发明还提供高频电阻焊钢管的制备方法，包括如下步骤：
S1：将板坯轧制成板卷；
S2：将每卷板卷的卷头和卷尾切除，切口与板卷横向所在的平面呈2～5°夹角，通过二氧化碳气体保护焊将相邻两个板卷的卷头和卷尾焊接在一起，形成连续的钢带；
S3：对钢带铣边，铣边后的钢带的宽度根据高频电阻焊钢管的外径规格确定；
S4：采用排辊成型方法，钢带经线成型和精成型形成荒管；
S5：采用高频焊接并在挤压辊作用下将荒管的边缘焊接在一起，形成焊管；其中控制高频焊接频率≥200kHz；
S6：采用中频感应加热对焊管的焊缝进行热处理，其中热处理温度为950～1010℃，保温时间≥15s；热处理后喷淋冷却水冷至550～650℃范围，然后空冷；
S7：通过定径机架对热处理后的焊管进行径向压缩，以达到规定的尺寸。
采用上述方案，高频焊接过程采用高频率增强集肤效应，保证钢带边缘处于良好的焊接状态；采用中频感应加热对焊管的焊缝进行热处理，通过焊缝热处理，获得优良的强韧性。
根据本发明的另一具体实施方式，本发明提供的高频电阻焊钢管的制备方法步骤S5中，控制焊接功率≥700kW。
采用上述方案，采用高的焊接功率确保钢带边缘充分熔化，避免发生冷焊，同时也有利于熔融金属在电磁力的作用下向外流动，有效排出氧化物。
根据本发明的另一具体实施方式，本发明提供的高频电阻焊钢管的制备方法，步骤S5中，控制挤压辊的挤压量在10～25mm范围。
采用上述方案，挤压辊采用大的挤压量，进一步挤出熔融状态下形成的氧化物等夹杂物，获得高纯净度的焊缝；通过采用高频率、高功率、大挤压的焊接工艺，有效排出焊接氧化物等缺欠，获得良好的焊缝质量。
根据本发明的另一具体实施方式，本发明提供的高频电阻焊钢管的制备方法，在步骤S5中，控制焊接会合点处的开口V角在3～6°范围内。
采用上述方案，通过控制开口V角，使焊接过程排出夹杂物，且保证焊接温度不降低。
根据本发明的另一具体实施方式，本发明提供的高频电阻焊钢管的制备方法，步骤S1包括：
S11：以加热温度为1160～1210℃对板坯进行加热；
S12：以末道次温度≥960℃对板坯进行粗轧；
S13：以开轧温度≤930℃、终轧温度为790～840℃进行精轧；
S14：以冷却速度为25～35℃/s进行层流冷却；以温度为450～520℃进行卷取。
采用上述方案，通过控制板坯轧制成板卷的工艺参数，实现晶粒细化，并有效控制相变组织，以获得微观组织为细小多边形铁素体+粒状贝氏体的高频电阻焊钢管。
本发明的有益效果：
本发明提供的高频电阻焊钢管采用低碳、低合金成分设计，配合优化的TMCP(热机械控制工艺，Thermo Mechanical Control Process)实现晶粒细化，并有效控制相变组织，获得的高频电阻焊钢管微观组织为细小多边形铁素体+粒状贝氏体，其中，多边形铁素体的晶粒尺寸≤10μm，体积分数在10～40％范围，所制得的高频电阻焊钢管具有较高的强度和优良的低温止裂性能；可应用于有止裂要求的低温服役高端海底管线领域。
本发明的高频电阻焊钢管的拉伸性能可以达到：管体屈服强度≥459MPa，管体抗拉强度≥545MPa，焊缝抗拉强度≥549MPa；高频电阻焊钢管在-20℃的DWTT断口剪切面积率均在91％以上，同时还满足：管体-20℃夏比冲击功≥200J，焊缝-20℃夏比冲击功≥100J。本发明的高频电阻焊钢管在满足其他通用技术要求时，同时满足低温DWTT止裂性能。
附图说明
图1为本发明实施例1获得的高频电阻焊钢管的管体微观组织图。
具体实施方式
为了下面的详细描述的目的，应当理解，除了在任何操作实例中，或者以其他方式指出的情况下，表示例如说明书和权利要求中使用的成分的量的所有数字应被理解为在所有情况下被术语“约”修饰。因此，除非相反指出，否则在以下说明书和所附权利要求中阐述的数值参数是根据本申请所要获得的期望性能而变化的近似值。至少并不是试图将等同原则的适用限制在权利要求的范围内，每个数值参数至少应该根据报告的有效数字的个数并通过应用普通舍入技术来解释。
本申请中使用的术语仅用于描述具体实施方式的目的并且不理解为限制性的。如本 文中使用的，单数形式“一个(种)”和“该()”也意图包括复数形式，除非上下文清楚地另外指明。表述例如“......的至少一个(种)”当在要素列表之前或之后时修饰整个要素列表，而不修饰该列表的单独要素。
进一步，本申请中使用的术语“包括”或“包含”当用在本说明书中时，表明存在所陈述的特征、区域、整体、步骤、操作、元件、和/或组分，但不排除存在或增加一种或多种另外的特征、区域、整体、步骤、操作、元件、组分、和/或其集合。
如本申请中使用的“约”或“大约”包括所描述的值并且意味着例如本领域普通技术人员考虑到所讨论的测量和与具体量的测量有关的误差(即，测量系统的限制)而确定的对于具体值的可接受的偏差范围内。除非另外指明，所公开的所有参数范围包括端点值及其间的所有值。
在本发明的描述中，如无特殊说明，术语的含义与本领域技术人员一般理解的含义相同，但如有不同，以本发明的定义为准；如无特殊说明，试验方法均为常规方法；如无特殊说明，本发明中的所用的原料及试验材料均为可常规购买得到的。
为使本发明的目的、技术方案和优点更加清楚，下面将对本发明的实施方式作详细描述。
本发明提供一种高频电阻焊钢管，高频电阻焊钢管由以下质量百分比的化学元素组成：
C：0.025～0.054％、Si：0.10～0.30％、Mn：1.21～1.45％、Ni：0.05～0.20％、Cr：0.11～0.25％、Mo：0.01～0.15％、Nb：0.030～0.055％、Ti：0.005～0.020％、Al：0.020～0.050％、Ca：0.001～0.004％；余量为Fe及不可避免的杂质。
进一步优选地，所述高频电阻焊钢管由以下质量百分比的化学元素组成：
C：0.031～0.053％、Si：0.12～0.28％、Mn：1.22～1.44％、Ni：0.08～0.19％、Cr：0.12～0.24％、Mo：0.02～0.14％、Nb：0.032～0.054％、Ti：0.01～0.018％、Al：0.022～0.047％、Ca：0.0013～0.0039％；余量为Fe及不可避免的杂质。
在本发明提供的高频电阻焊钢管中，各化学元素的设计原理具体如下：
C(碳)：在本发明的高频电阻焊钢管中，C是最有效的强化元素，但需要注意的是，当C元素含量过高时，容易形成较多碳化物或马奥岛，也容易在厚度中心形成带状 硬相组织，这对材料止裂性能有不利影响。基于此，在本发明的高频电阻焊钢管中，将C元素的质量百分含量控制在0.025～0.054％之间，优选地控制在0.031～0.053％。
Mn(锰)：在本发明的高频电阻焊钢管中，Mn通过固溶强化提高强度，并有细化晶粒的效果，但当Mn元素含量过高时，在热轧板卷TMCP快冷和低温卷取过程中，容易形成板条贝氏体组织，对低温止裂性能有不利影响。基于此，在本发明的高频电阻焊钢管中，将Mn元素的质量百分含量控制在1.21～1.45％之间，优选地控制在1.22～1.44％。
Si(硅)：在本发明的高频电阻焊钢管中，Si是固溶强化元素，同时也是钢中的脱氧元素，但Si元素含量过高时，容易在高频焊接中形成氧化物夹杂，不利于焊缝质量。基于此，在本发明的高频电阻焊钢管中，将Si元素的质量百分含量控制在0.10～0.30％之间，优选地控制在0.12～0.28％。
Ni(镍)：在本发明的高频电阻焊钢管中，Ni是改善低温止裂性能的重要元素，Ni能够减小低温时的位错滑移阻力，缓解低温脆化，Ni还可以通过增加层错能，促进低温时螺型位错交滑移，增加裂纹扩展的消耗功，提高局部止裂能力。但Ni价格昂贵，添加量不宜过多，因此，在本发明中，将Ni元素的质量百分含量控制在0.05～0.20％之间，优选地控制在0.08～0.19％。
Cr(铬)：在本发明的高频电阻焊钢管中，Cr可以提高材料的淬透性，提高强度，且特别有助于提高HFW焊缝的强度，但Cr元素含量过高时，会提高贝氏体的硬度，降低其韧性。因此，在本发明中，将Cr元素的质量百分含量控制在0.11～0.25％之间，优选地控制在0.12～0.24％。
Mo(钼)：在本发明的高频电阻焊钢管中，Mo起到控制相变和提高强度的作用，Mo可降低钢的γ→α相变温度，起到细化组织的作用，而且在低碳管线钢中能有效促进高韧性的粒状贝氏体的形成，并抑制珠光体，但Mo含量过高时，容易形成板条贝氏体等较硬的组织，对低温止裂性能不利。因此，在本发明中，将Mo元素的质量百分含量控制在0.01～0.15％之间，优选地控制在0.02～0.14％。
Nb(铌)：在本发明的高频电阻焊钢管中，Nb是细化晶粒最重要的微合金化元素，可有效提高焊钢管的强韧性，而Nb含量超过一定添加量以后，细化晶粒的效果不再随着Nb含量的增加而提高。因此，在本发明中，将Nb元素的质量百分含量控制在0.030～0.055％ 之间，优选地控制在0.032～0.054％。
Ti(钛)：在本发明的高频电阻焊钢管中，添加微量的Ti元素即可形成TiN，在板坯加热过程中，TiN能够阻止奥氏体晶粒长大，起到细化原始奥氏体晶粒的作用。因此，在本发明中，将Ti元素的质量百分含量控制在0.005～0.020％之间，优选地控制在0.01～0.018％。
Al(铝)：在本发明的高频电阻焊钢管中，Al是脱氧元素，有利于提高钢质纯净度，但添加量过多时容易形成氧化铝等夹杂物。因此，在本发明中，将Al元素的质量百分含量控制在0.020～0.050％之间，优选地控制在0.022～0.047％。
Ca(钙)：在本发明的高频电阻焊钢管中，采用微量Ca元素处理，可以避免长条状MnS夹杂物的形成，而Ca添加量过多亦容易形成CaO、CaS等夹杂物团聚。因此，在本发明的高频电阻焊钢管中，将Ca元素的质量百分含量控制在0.001～0.004％之间，优选地控制在0.0013～0.0039％。
本发明高频电阻焊钢管采用低碳、低合金成分设计，其中采用Mo+Cr强化，并添加Ni元素，能够获得较好的低温止裂性能。
本发明中，由于C、Cr、Mo是保证强度的重要合金元素，总含量过低不能保证强度，含量过高则对韧性不利。因此，根据本发明的另一具体实施方式，其中C+(Cr+Mo)/5的质量百分比控制在0.07～0.12％范围。
根据本发明的另一具体实施方式，其中不可避免的杂质中，P、S、B控制在以下质量百分比：P≤0.013wt％、S≤0.003wt％、B≤0.0005％。
需要说明的是，P、S、B元素是焊管中不可避免的有害杂质元素，S易形成长条形MnS夹杂物，P是降低焊管低温韧性的元素，B是强淬透性元素，容易导致材料的塑性和韧性下降。因此，本发明的高频电阻焊钢管控制P≤0.013％，S≤0.003％，B≤0.0005％。
根据本发明的另一具体实施方式，根据本发明的化学成分设计，并配合优化的制备工艺，获得细小的粒状贝氏体组织，以达到期望的DWTT止裂性能。具体地，钢管的微观组织为多边形铁素体+粒状贝氏体；其中多边形铁素体的晶粒尺寸≤10μm；且多边形铁素体的体积百分比在10～40％范围。
进一步地，本发明所提供的高频电阻焊钢管的外径为≤508mm，壁厚≥12.5；优选 地，外径≥400mm，壁厚为14.3mm～17.5mm。
进一步地，本发明所提供的高频电阻焊钢管，其屈服强度≥459MPa，抗拉强度≥545Mpa，延伸率A50≥28％，-20℃管体夏比冲击功≥200J，-20℃管体DWTT断口剪切面积率≥91％；优选地，屈服强度为459～562MPa，抗拉强度为545-641MPa，延伸率A50为28-34％，-20℃管体夏比冲击功≥242J，-20℃管体DWTT断口剪切面积率为95～100％。
本发明还提供本发明高频电阻焊钢管的制备方法，包括如下步骤：
S1：按照本发明高频电阻焊钢管的成分设计，通过冶炼和连铸获得特定成分的板坯；将板坯轧制成板卷。
其中板坯包含以下质量百分比的化学元素：
C：0.025～0.054％、Si：0.10～0.30％、Mn：1.21～1.45％、Ni：0.05～0.20％、Cr：0.11～0.25％、Mo：0.01～0.15％、Nb：0.030～0.055％、Ti：0.005～0.020％、Al：0.020～0.050％、Ca：0.001～0.004％。
进一步地，除上述成分，余量为Fe及不可避免的杂质。更进一步地，不可避免的杂质中，P、S、B控制在以下质量百分比：P≤0.013％、S≤0.003％、B≤0.0005％。
将板坯轧制成板卷的步骤包括板坯加热、粗轧、精轧、冷却和卷取。进一步地，根据本发明的其中一种具体实施方式，将板坯轧制成板卷具体步骤包括：
S11：板坯加热需达到一定温度才能保证合金元素充分固溶，但过高的加热温度会导致原始奥氏体晶粒尺寸过大；本发明控制加热温度范围为1160～1210℃以对板坯进行加热。
S12：粗轧过程通过再结晶细化奥氏体晶粒，因此应在再结晶温度范围内进行，本发明控制粗轧末道次温度≥960℃，如960～1000℃或965～992℃。
S13：精轧过程形变奥氏体积累应变储能和变形带，同时伴有回复，因此应在未再结晶区进行，为避开部分再结晶区，本发明控制精轧开轧温度≤930℃，如910～930℃或910～925℃；同时控制较低的精轧终轧温度，以减少应变储能的回复，增加相变形核率，达到细化组织的效果。因此，本发明控制精轧终轧温度为790～840℃。
S14：层流冷却和卷取过程是形变奥氏体相变的过程，较高的冷却速度有助于细化晶粒，提高强度和韧性，因此本发明控制冷却速度为25～35℃/s进行层流冷却。卷取温度是 热轧板卷冷却的停止温度，本发明期望获得微观组织为细小的多边形铁素体+粒状贝氏体，因此需要抑制准多边形铁素体和珠光体，卷取温度不宜过高，另一方面，为避免板条贝氏体组织，卷取温度又不宜过低。因此，在本发明的成分体系下，为获得目标显微组织，控制卷取温度范围为450～520℃。
S2：板卷对焊，将每卷板卷的卷头和卷尾切除，切口与板卷横向所在的平面呈2～5°夹角，通过二氧化碳气体保护焊将相邻两个板卷的卷头和卷尾焊接在一起，形成连续的钢带。
S3：对钢带铣边，根据设计的高频电阻焊钢管的外径规格，精确控制铣边后的钢带的宽度。
S4：采用排辊成型方法，钢带经线成型和精成型形成荒管；
S5：采用高频焊接并在挤压辊作用下将荒管的边缘焊接在一起形成焊管；其中控制高频焊接频率≥200kHz，如200～230kHz或220～230kHz。采用高频率可以增强集肤效应，保证钢带边缘处于良好的焊接状态，钢带边缘在高频电流的集肤效应作用下熔化，同时在挤压辊作用下焊接在一起，随后刮除挤出的内外毛刺，制成焊管。
进一步地，高的焊接功率可确保钢带边缘充分熔化，避免发生冷焊，同时也有利于熔融金属在电磁力的作用下向外流动，有效排出氧化物。因此，根据本发明的其中一种具体实施方式，控制高频焊接功率≥700KW，优选地，焊接功率为700～1020kW或720～1020kW。
进一步地，挤压辊采用大的挤压量，可以进一步挤出熔融状态下形成的氧化物等夹杂物，获得高纯净度的焊缝。因此，根据本发明的其中一种具体实施方式，控制挤压辊的挤压量在10～25mm，优选地，挤压量为11～23mm，具体的挤压量＝荒管周长-挤压后的周长。
本发明通过采用高频率、高功率、大挤压的焊接工艺，有效排出焊接氧化物等缺欠，获得良好的焊缝质量。
更进一步地，焊接会合点处的开口V角过小，夹杂物不易排出，开口V角过大会导致焊接温度降低。因此，根据本发明的其中一种具体实施方式，控制焊接会合点处的开口V角在3～6°范围，优选地，开口V角在3.2～5.5°。
S6：采用中频感应加热对焊管的焊缝进行热处理，由于感应加热的内外壁有一定温差，为确保焊缝组织完全奥氏体化，热处理温度不宜过低，但热处理温度过高，也会导致焊缝组织粗化，降低焊缝冲击韧性。因此，本发明控制热处理温度为950～1010℃，保温时间≥15s；中频感应热处理后喷淋冷却水冷至550～650℃范围，然后空冷；优选地，焊缝热处理温度为950～1000℃，保温时间为15～18s，喷淋冷却水冷却至560～640℃，然后空冷。通过焊缝热处理，获得优良的强韧性。
S7：通过定径机架对热处理后的焊管进行径向压缩，以达到规定的尺寸。
进一步地，通过上述方法获得的高频电阻焊钢管，焊缝-20℃夏比冲击功≥100J。优选地，焊缝的抗拉强度≥549MPa，-20℃夏比冲击功≥130J；优选地，焊缝的抗拉强度为549～635MPa，-20℃夏比冲击功≥170J。
本发明采用低碳、低合金成分设计，配合优化的TMCP工艺实现晶粒细化，并有效控制相变组织，获得微观组织为细小多边形铁素体+粒状贝氏体的高频电阻焊钢管，其中，多边形铁素体的晶粒尺寸≤10μm，体积分数在10～40％范围，所制得的高频电阻焊钢管具有较高的强度和优良的低温止裂性能。
下面将结合具体的实施例和说明书附图对本发明低温高强韧性管件用钢板的制备方法做进一步的说明。
实施例1-6
实施例1-6的高频电阻焊钢管均采用以下步骤制得：
S1：(1)按照表1所示的化学成分进行冶炼和连铸获得板坯。
表1：实施例1-6的化学成分含量(wt％，余量为Fe和除了P、S和B以外的其他不可避免的杂质)
(2)将板坯轧制成板卷：包括板坯加热、粗轧、精轧、层流冷却和卷取，得到热轧 板卷。其中，控制板坯加热温度为1160～1210℃，控制粗轧末道次温度≥960℃，精轧开轧温度≤930℃，精轧终轧温度为790～840℃；控制层流冷却速度为25～35℃/s，控制卷取温度为450～520℃。实施例1-6的高频电阻焊钢管在轧制成板卷的工艺步骤中的具体工艺参数如表2-1。
表2-1：实施例1-6轧制成板卷步骤的具体工艺参数
S2：板卷对焊，将每卷板卷的卷头和卷尾切除，切口与板卷横向所在的平面呈2～5°夹角，通过二氧化碳气体保护焊将相邻两个板卷的卷头和卷尾焊接在一起，形成连续的钢带。
S3：对钢带铣边，铣边后的钢带的宽度根据高频电阻焊钢管的外径规格确定。
S4：采用排辊成型方法，经线成型和精成型将钢带制成荒管。
S5：采用高频焊接并在挤压辊作用下将荒管的边缘焊接在一起，随后刮除挤出的内外毛刺，形成焊管；其中控制高频焊接频率≥200kHz、焊接功率≥700KW，控制挤压辊的挤压量在10～25mm范围，控制焊接会合点处的开口V角在3～6°范围内。
S6：采用中频感应加热对焊管的焊缝进行热处理，其中热处理温度为950～1010℃，保温时间≥15s；热处理后喷淋冷却水冷至550～650℃范围，然后空冷。
S7：通过定径机架对热处理后的焊管进行径向压缩，以达到规定的尺寸。
上述步骤S5-S7的具体工艺参数如表2-2。
表2-2：实施例1-6步骤S5-S7的具体工艺参数

性能测试：
将实施例1-6得到的高频电阻焊钢管分别取样进行性能检测试验，试验项目有拉伸试验、冲击试验、落锤撕裂试验(DWTT)。需要说明的是，拉伸试验和冲击试验按照ASTM A370标准《钢产品机械性能测试的方法和定义》进行，落锤撕裂试验(DWTT)按照API RP 5L3规范《管线钢落锤撕裂试验方法》进行。
实施例1-6的性能测试结果分别如表3和表4；其中表3列出了实施例1-6的高频电阻焊钢管的拉伸性能测试结果，表4列出了实施例1-6的高频电阻焊钢管的DWTT和冲击韧性测试结果。
表3：实施例1-6的高频电阻焊钢管的拉伸性能测试结果
表4：实施例1-6的高频电阻焊钢管的DWTT和冲击韧性测试结果
从表3和表4可以看出，本发明实施例1-6的高频电阻焊钢管具有综合性能优异， 不仅具有较高的强度，还具有优良的DWTT止裂性能和冲击韧性。
其中，从表3可以看出，在本发明中，实施例1-6的高频电阻焊钢管的管体屈服强度≥459MPa，管体抗拉强度≥545MPa，焊缝抗拉强度≥549MPa。
进一步地，从表4可以看出，在本发明中，实施例1-6的高频电阻焊钢管在-20℃的DWTT断口剪切面积率均在91％以上，同时还满足：管体-20℃夏比冲击功≥200J，焊缝-20℃夏比冲击功≥100J。
其中，根据表1可知，实施例5的高频电阻焊钢管的成分中，C+(Cr+Mo)/5控制为0.123(6个实施例中最高)，进一步根据表4可以看出，实施例5的管体-20℃夏比冲击功＝267J，为6个实施例中最低，证明C+(Cr+Mo)/5含量过高对韧性不利。根据表1可知，实施例6的高频电阻焊钢管的成分中，C+(Cr+Mo)/5控制为0.073(6个实施例中最低)，进一步根据表3可以看出，实施例6的管体屈服强度＝459MPa，管体抗拉强度＝545MPa，为6个实施例中最低，证明C+(Cr+Mo)/5含量过低不能保证强度。
根据表2-2，实施例1-3的高频电阻焊钢管具有同样的外径，其中实施例2具有最小的厚径比，实施例3具有最大的厚径比；进一步根据表4，在三个实施例中实施例3的管体-20℃夏比冲击功(272J)和-20℃管体DWTT剪切面积率(93％)低于实施例1-2，表明厚径比影响冲击韧性和DWTT性能，厚径比增加，韧性下降。
综上，可以看出，本发明的高频电阻焊钢管，通过合理的化学成分设计并结合优化工艺，可以获得较高的强度和冲击韧性，特别是具有优良的低温止裂性能，可应用于有止裂要求的低温服役高端海底管线领域，具有十分广阔的应用前景。
图1为实施例1获得的高频电阻焊钢管的管体微观组织图。
如图1所示，实施例1的高频电阻焊钢管的微观组织为细小的多边形铁素体+粒状贝氏体，采用GB/T 15749标准和GB/T 6394标准分别测算微观组织中的多边形铁素体含量和晶粒尺寸，如表5所示，经分析，多边形铁素体体积分数在10～40％范围，晶粒尺寸≤10μm。
表5：实施例1-6的高频电阻焊钢管显微组织分析

以上内容是结合具体的实施方式对本发明所作的进一步详细说明，不能认定本发明的具体实施只局限于这些说明。对于本发明所属技术领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干简单推演或替换，都应当视为属于本发明的保护范围。

Claims (15)

  1. 一种高频电阻焊钢管，其特征在于，所述高频电阻焊钢管由以下质量百分比的化学元素组成：
    C：0.025～0.054％、Si：0.10～0.30％、Mn：1.21～1.45％、Ni：0.05～0.20％、Cr：0.11～0.25％、Mo：0.01～0.15％、Nb：0.030～0.055％、Ti：0.005～0.020％、Al：0.020～0.050％、Ca：0.001～0.004％；余量为Fe及不可避免的杂质。
  2. 如权利要求1所述的高频电阻焊钢管，其特征在于，所述高频电阻焊钢管由以下质量百分比的化学元素组成：
    C：0.031～0.053％、Si：0.12～0.28％、Mn：1.22～1.44％、Ni：0.08～0.19％、Cr：0.12～0.24％、Mo：0.02～0.14％、Nb：0.032～0.054％、Ti：0.01～0.018％、Al：0.022～0.047％、Ca：0.0013～0.0039％；余量为Fe及不可避免的杂质。
  3. 如权利要求1所述的高频电阻焊钢管，其特征在于，其中C+(Cr+Mo)/5的质量百分比控制在0.07～0.12％范围。
  4. 如权利要求1所述的高频电阻焊钢管，其特征在于，其中所述不可避免的杂质中，P、S、B控制在以下质量百分比：P≤0.013％、S≤0.003％、B≤0.0005％。
  5. 如权利要求1-4任一项所述的高频电阻焊钢管，其特征在于，所述高频电阻焊钢管的微观组织为多边形铁素体+粒状贝氏体；其中所述多边形铁素体的晶粒尺寸≤10μm；且所述多边形铁素体的体积百分比在10～40％范围。
  6. 如权利要求1所述的高频电阻焊钢管，其特征在于，所述高频电阻焊钢管的外径为≤508mm，壁厚≥12.5mm；优选地，外径≥400mm，壁厚为14.3mm～17.5mm。
  7. 如权利要求1所述的高频电阻焊钢管，其特征在于，所述高频电阻焊钢管屈服强度≥459MPa，抗拉强度≥545Mpa，延伸率A50≥28％，-20℃管体夏比冲击功≥200J，-20℃管体DWTT断口剪切面积率≥91％；优选地，屈服强度为459～562MPa，抗拉强度为545-641MPa，延伸率A50为28-34％，-20℃管体夏比冲击功≥242J，-20℃管体DWTT断口剪切面积率为95～100％。
  8. 如权利要求1所述的高频电阻焊钢管，其特征在于，所述高频电阻焊钢管的焊缝-20℃夏比冲击功≥100；优选的抗拉强度≥549MPa；优选地，焊缝的抗拉强度为549～635MPa，-20℃夏比冲击功≥170J。
  9. 一种如权利要求1-8任一项所述的高频电阻焊钢管的制备方法，其特征在于，所述方法包括如下步骤：
    S1：将板坯轧制成板卷；
    S2：将每卷所述板卷的卷头和卷尾切除，切口与所述板卷横向所在的平面呈2～5°夹角，通过二氧化碳气体保护焊将相邻两个所述板卷的卷头和卷尾焊接在一起，形成连续的钢带；
    S3：对所述钢带铣边，铣边后的所述钢带的宽度根据所述高频电阻焊钢管的外径规格确定；
    S4：采用排辊成型方法，所述钢带经线成型和精成型形成荒管；
    S5：采用高频焊接并在挤压辊作用下将所述荒管的边缘焊接在一起，形成焊管；其中控制高频焊接频率≥200kHz；
    S6：采用中频感应加热对所述焊管的焊缝进行热处理，其中热处理温度为950～1010℃，保温时间≥15s；热处理后喷淋冷却水冷至550～650℃范围，然后空冷；
    S7：通过定径机架对热处理后的所述焊管进行径向压缩，以达到规定的尺寸。
  10. 如权利要求9所述的高频电阻焊钢管的制备方法，其特征在于，所述步骤S5中，控制焊接功率≥700kW，优选地，焊接功率为700～1020kW。
  11. 如权利要求10所述的高频电阻焊钢管的制备方法，其特征在于，所述步骤S5中，控制所述挤压辊的挤压量在10～25mm范围，优选地，挤压量为11～23mm。
  12. 如权利要求11所述的高频电阻焊钢管的制备方法，其特征在于，在所述步骤S5中，控制焊接会合点处的开口V角在3～6°范围内，优选地，开口V角在3.2～5.5°。
  13. 如权利要求9所述的高频电阻焊钢管的制备方法，其特征在于，步骤S5中，控制高频焊接频率为200～230kHz或220～230kHz。
  14. 如权利要求9-13任一项所述的高频电阻焊钢管的制备方法，其特征在于，所述步骤S1包括：
    S11：以加热温度为1160～1210℃对所述板坯进行加热；
    S12：以末道次温度≥960℃对所述板坯进行粗轧；
    S13：以开轧温度≤930℃、终轧温度为790～840℃进行精轧；
    S14：以冷却速度为25～35℃/s进行层流冷却；以温度为450～520℃进行卷取。
  15. 如权利要求9所述的高频电阻焊钢管的制备方法，其特征在于，所述步骤S6中，焊缝热处理温度为950～1000℃，保温时间为15～18s，喷淋冷却水冷却至560～640℃，然 后空冷。
PCT/CN2023/103716 2022-06-29 2023-06-29 一种高频电阻焊钢管及其制备方法 WO2024002220A1 (zh)

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