WO2021058003A1 - 一种管线钢及其制造方法 - Google Patents

一种管线钢及其制造方法 Download PDF

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WO2021058003A1
WO2021058003A1 PCT/CN2020/118447 CN2020118447W WO2021058003A1 WO 2021058003 A1 WO2021058003 A1 WO 2021058003A1 CN 2020118447 W CN2020118447 W CN 2020118447W WO 2021058003 A1 WO2021058003 A1 WO 2021058003A1
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temperature
pipeline steel
steel
rolling
cooling
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French (fr)
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章传国
王波
孙磊磊
郑磊
吴扣根
沈燕
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宝山钢铁股份有限公司
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Priority to JP2022519416A priority Critical patent/JP2022550119A/ja
Priority to KR1020227012885A priority patent/KR20220065020A/ko
Priority to DE112020004648.6T priority patent/DE112020004648T5/de
Publication of WO2021058003A1 publication Critical patent/WO2021058003A1/zh

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    • 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
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • 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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • 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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/32—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for gear wheels, worm wheels, or the like
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • 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
    • 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
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • 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 relates to pipeline steel, in particular to a pipeline steel and a manufacturing method thereof.
  • Japan's JFE company uses online heat treatment equipment and applies the HOP process to improve the uniformity of the structure in the thickness direction of the steel plate, which is conducive to improving the toughness of thick-gauge pipeline steel and obtaining uniform mechanical properties, while also improving the ovality of the steel pipe.
  • the steel used for submarine pipelines at home and abroad mainly focuses on high-strength and high-toughness research, but there are few studies on high plasticity.
  • the requirements of high uniform elongation are proposed for the strain-designed land pipelines.
  • the design mainly adopts dual-phase structure control, and the vault-type stress-strain curve is obtained through the combination of soft and hard phases. Better work hardening rate, thereby improving the uniform deformation ability of steel.
  • the representative process directions include the ferrite + lower bainite dual phase structure obtained by the relaxation + controlled cooling process adopted by Chinese companies, and the MA component + bainite dual phase structure obtained by the online heat treatment HOP process adopted by JFE in Japan Both of these two types of microstructures can obtain high uniform elongation, but due to the existence of the dual-phase interface, the low-temperature impact toughness of steel is significantly reduced, which is not conducive to the safety of steel crack arrest.
  • European Patent No. EP2105513B1 discloses a method for manufacturing thick gauge and high toughness pipeline steel with a yield strength of 450MPa.
  • a low-C, low-Mn, and low-Nb microalloying design method By adopting a low-C, low-Mn, and low-Nb microalloying design method, combining low-temperature heating technology and controlled rolling and controlled cooling technology, A microstructure dominated by refined polygonal ferrite is obtained, the volume ratio of ferrite is 40-90%, and the ferrite grain size is less than or equal to 10 ⁇ m.
  • the pipeline steel prepared by the invention has excellent toughness.
  • Chinese patent CN101611163A discloses a kind of anti-aging dual-phase pipeline steel with yield strength ⁇ 400MPa, tensile strength ⁇ 500MPa, and yield ratio ⁇ 0.90. It adopts C-Mn basic composition and alloyed composition design. Two-stage cooling rate control obtains that the first phase is ferrite, and the second phase is one or more of pearlite, upper bainite, lower bainite, granular bainite or martensite, which can make the steel The uniform elongation rate reaches 8% and above.
  • the US patent US20120247606A1 discloses the composition and process plan of a X80 grade 6-16mm thin gauge pipeline steel. It adopts a low C high Nb and Mo alloying design without adding other alloying elements. The process adopts 675 ⁇ 715°C low temperature finishing rolling. And the air cooling process of 1 ⁇ 2°C/s, the pipeline steel with the strength level of 80Ksi can be obtained, and it has good weldability.
  • Australian patent AU2006305841A1 discloses a manufacturing method of dual-phase steel with a tensile strength of 900 MPa and a longitudinal yield ratio ⁇ 0.85. It adopts a low C, high Mn and Nb, Mo alloying composition design, and obtains 10-60 through process control. % Of refined ferrite with a grain size of ⁇ 5 ⁇ m, and the remaining structure is one or more mixed structures such as refined martensite, lower bainite, degraded upper bainite, and granular bainite.
  • Chinese patent CN109023068A discloses a manufacturing method of NbC nanoprecipitation strengthened X80 high-plasticity pipeline steel plate. It adopts a microalloyed composition design of medium C, low Mn and high Nb, through controlled rolling, controlled cooling process, and Subsequent solution treatment at 1180 to 1220°C and isothermal treatment at 670 to 710°C to control the precipitation of NbC to 0.05 to 0.20% to obtain X80 pipeline steel with a yield strength of 470Mpa, high plasticity and high toughness.
  • Chinese patent CN101343715B discloses a method for manufacturing large-strain pipeline steel pipes with a yield strength of 650MPa.
  • the composition adopts a medium-C, low-Mn, and high-alloy B-containing design method.
  • ferrite is obtained + Acicular ferrite + MA and other complex structure, can produce steel pipes with a yield strength of 650-680MPa and a uniform elongation of 12-15%.
  • the purpose of the present invention is to design a high-plasticity thick gauge pipeline steel and its manufacturing method, the yield strength R t0.5 is 450-635MPa, the tensile strength R m is 520-780MPa, especially the full-size Charpy at -20°C
  • the impact energy AKv is higher than 275J
  • the -20°C full wall thickness DWTT shear fracture area percentage SA is greater than 85%
  • its longitudinal uniform elongation Uel ⁇ 8% and it is manufacturable. It can be used for submarine pipelines, crossing pipelines and polar regions.
  • Pipeline construction is mainly used for long-distance transportation of natural gas.
  • a high-plasticity thick-gauge pipeline steel whose composition weight percentages are: C: 0.03 ⁇ 0.10%, Si: 0.1 ⁇ 0.5%, Mn: 1.51 ⁇ 1.85%, P ⁇ 0.015%, S ⁇ 0.002%, Cr: 0.05 ⁇ 0.3%, Mo: 0.05 to 0.20%, Cu: 0.06 to 0.3%, Ni: 0.17 to 0.50%, Nb: 0.05 to 0.10%, Ti: 0.005 to 0.02%, Ca: 0.001 to 0.005%, Al: 0.02 to 0.045 %, N ⁇ 0.006%, B ⁇ 0.0002%, O ⁇ 0.005%, the balance is Fe and unavoidable impurities; and, at the same time, meet:
  • the microstructure of the pipeline steel of the present invention is refined polygonal ferrite + acicular ferrite, and the proportion of the refined polygonal ferrite is 15-39%.
  • the yield strength R t0.5 of the pipeline steel of the present invention is 450-635 MPa, the tensile strength R m is 520-780 MPa, especially the full-scale Charpy impact energy AKv at -20°C is higher than 275J and the full wall thickness at -20°C DWTT shear fracture area percentage SA is greater than 85%, longitudinal uniform elongation Uel ⁇ 8%.
  • Carbon C The most basic strengthening element. Carbon dissolves in steel to form interstitial solid solution, which plays a role of solid solution strengthening, and forms carbides with strong carbide forming elements to precipitate, which plays a role of precipitation strengthening. But too high C is detrimental to the toughness and welding performance of steel, and at the same time reduces the plasticity of the steel; too low C reduces the strength of the steel. Therefore, C is controlled at 0.03 to 0.10%.
  • Silicon Si a solid solution strengthening element and also a deoxidizing element in steel, but too high content will deteriorate the welding performance of the steel, reduce the plasticity, and is not conducive to the removal of hot-rolled iron scale during the rolling process, so the content is controlled at 0.1-0.5 %.
  • Manganese Mn Improve the strength of steel through solid solution strengthening. It is the most important and economical strengthening element in steel to compensate for the strength loss caused by the decrease in C content. Mn is also an element that expands the ⁇ phase region, which can reduce the ⁇ transformation temperature of steel, help obtain fine phase transformation products, and improve the toughness of steel; but Mn is an element that is easy to segregate. When the content of Mn is high, During the casting process, Mn is easy to segregate in the center of the plate thickness, and the hard phase martensite structure is formed after the rolling is completed, which reduces the plasticity and low temperature toughness of the material. Therefore, the Mn content in the present invention is limited to 1.51 to 1.85%.
  • the carbon manganese product parameter J C ⁇ Mn C*Mn*10 4 needs to meet the requirements of 0.06 ⁇ J C ⁇ Mn ⁇ 0.14, J C When ⁇ Mn is less than 0.6, due to insufficient C and Mn content, the solid solution strengthening effect is not significant and the strength is low; when J C ⁇ Mn is greater than 0.14, the range of ⁇ austenite is reduced, which is not conducive to the diffusion and distribution of C and Mn elements. , Increase the tendency of segregation.
  • Chromium Cr an important element to improve the hardenability of steel, to ensure the uniformity of the structure and performance of the thickness of the thick steel plate, and can effectively improve the corrosion resistance of the steel; but too high chromium is added to the steel to increase the strength and Hardness, reduce elongation and reduction of area; when added at the same time with higher Mn, it is easy to generate compound to produce cracks, and severely deteriorate welding performance.
  • the Cr content should be limited to 0.05-0.3%.
  • Molybdenum Mo an element that expands the ⁇ phase region, can reduce the ⁇ transformation temperature of steel, can obtain a finer transformation structure, and improve the toughness of the steel; at the same time, a small amount of Mo can improve the hardenability of the steel and improve the thickness direction The uniformity of the organization.
  • Mo content is controlled by 0.05 to 0.20%.
  • Copper Cu It can increase the strength of steel through solid solution strengthening, and improve the resistance to atmospheric corrosion; too high Cu is prone to copper brittleness, which has a negative impact on hot workability.
  • the Cu content is controlled to be 0.06-0.3%.
  • Nickel Ni can increase the strength of steel through solid solution strengthening.
  • the addition of Ni can improve the hot brittleness caused by Cu in steel; it can expand the austenite zone and increase the stability of austenite, which is beneficial to plasticity and toughness.
  • the control range of Ni content is all 0.17 to 0.50%.
  • Niobium Nb It is one of the important elements of low-carbon microalloyed steel.
  • the Nb dissolved in the hot rolling process induces precipitation to form Nb(N, C) particles, which pin the grain boundaries to inhibit the growth of deformed austenite and inhibit renewal.
  • the solid solution Nb is dispersed and precipitated in the matrix as the second phase particles NbC after coiling, which plays a role of precipitation strengthening.
  • the dispersion and precipitation effect of too low Nb content is not obvious, and it does not play the role of refining grains and strengthening the matrix; too high Nb content inhibits the occurrence of recrystallization of the steel plate core, which is not conducive to Grain Refinement.
  • the solid solution of Nb is related to the content of C. If the content of C is too high, the amount of solid solution of Nb is small, and the effect of precipitation strengthening and grain refinement cannot be achieved; if the content of C is too low, the grain boundary will be weakened, while the content of Nb is too low for precipitation strengthening Not obvious.
  • the Nb content should be limited to 0.05 to 0.10%.
  • Titanium Ti is a strong carbonitride forming element. Undissolved carbonitrides of Ti can prevent the growth of austenite grains when steel is heated. TiN precipitated during rough rolling in the high-temperature austenite zone can be Effectively inhibit the growth of austenite grains. In addition, during the welding process, the TiN particles in the steel can significantly prevent the grain growth in the heat-affected zone, thereby improving the welding performance of the steel plate and at the same time have a significant effect on improving the impact toughness of the welding heat-affected zone. In the present invention, the Ti content is controlled at 0.005 to 0.02%.
  • Nitrogen N In microalloyed steel, an appropriate nitrogen content can inhibit the coarsening of slab grains during reheating by forming high melting point TiN particles and improve the strength and toughness of the steel. However, when the N content is too high, the high concentration of free N atoms pin dislocations after aging, which significantly increases the yield strength, and significantly decreases the plasticity and toughness. Therefore, in the present invention, N ⁇ 0.006% is controlled.
  • Oxygen O For low-alloy pure steel smelting, deoxidation treatment is required at the end of the smelting process to reduce bubbles and oxide inclusions generated during the casting process, improve the internal quality of the steel, and improve the low-temperature impact toughness and dynamic tear resistance of the finished steel plate performance.
  • the oxygen content is higher than 50 ppm, internal defects such as inclusions and pores increase significantly, which reduces the plasticity and toughness of the steel. Therefore, in the present invention, O ⁇ 0.005% is controlled.
  • Sulfur and phosphorus are the unavoidable impurity elements in steel, hope the lower the better.
  • Ultra-low sulfur (less than 20ppm) and Ca treatment are used to control the form of sulfide inclusions, while controlling the P content below 150ppm, which can ensure that the invention steel has good low-temperature impact toughness.
  • Ca treatment can control the form of sulfide, improve the anisotropy of the steel sheet, and improve the low temperature toughness. To ensure the best effect, the control range of Ca is 0.0010 to 0.0050%.
  • Aluminum (A1) It is an element added to steel for deoxidation. Adding a proper amount of Al is beneficial to refine grains and improve the toughness of steel.
  • the control range of Al content in the present invention is 0.02-0.045%.
  • B Boron
  • a lower C content and higher Nb microstructure are adopted. Alloying composition design; combined with low-temperature rough rolling and finishing rolling processes to give full play to the deformation-induced phase transformation mechanism to promote ferrite phase transformation; through appropriate cooling rate and cooling stop temperature control, refined polygonal ferrite +
  • the acicular ferrite microstructure has the comprehensive mechanical properties of high strength, high toughness and high plasticity, and has good deformability.
  • the method for manufacturing high-plasticity thick-gauge pipeline steel according to the present invention includes the following steps:
  • Intermediate billet thickness 3t ⁇ 5t, t is the thickness of pipeline steel, unit mm;
  • Finish rolling start-rolling temperature 750 ⁇ 810°C
  • finishing rolling temperature 740 ⁇ 800°C
  • Water cooling temperature T start 620 ⁇ 720°C
  • water cooling stop temperature T stop 150 ⁇ 530°C
  • the heating temperature for reheating the slab in step 2) is 1110-1150°C.
  • step 3 the rough rolling opening temperature is 960-990°C, the single-pass reduction rate of the final rough rolling pass is ⁇ 14%; the intermediate billet thickness is 4 ⁇ 4.5t; the finishing rolling opening temperature is 770-800°C, The finishing temperature of rolling is 750 ⁇ 780°C.
  • step 4 the cooling is controlled, the water-cooling opening and cooling temperature T start is 660-700°C, and the water-cooling stop temperature T stop is 200-350°C.
  • the 28-40mm thick high-plasticity pipeline steel is finally obtained.
  • Cooling after rolling is a key process that determines the phase transformation structure.
  • the target refined polygonal ferrite + acicular ferrite phase transformation structure can be controlled by controlling the water-cooling opening temperature T start , the water-cooling stop temperature T stop and the water-cooling cooling speed V c Obtained, each cooling parameter must conform to the above relationship.
  • the water-cooled opening and cooling temperature T start is higher than 720°C, the precipitation power of the soft-phase polygonal ferrite is small, which will lead to high strength of the steel, and if the soft-phase polygonal ferrite is lower than 620°C, the soft-phase polygonal ferrite is coarse and the proportion is too high, which will lead to the strength.
  • the water cooling stop temperature T stop mainly determines the hardness of the hard phase acicular ferrite. When it is higher than 530°C, the dislocation density is low, the hardness is low, and the strength is low. When it is below 150°C, it is easy to form horses.
  • the microstructure causes the dislocation density to be too high, the hardness is high, and the plasticity decreases;
  • the water-cooling cooling rate V c is mainly used to match the water-cooling opening and stopping temperature to control the phase change structure type and the key parameter of the phase ratio, and the water cooling stopping temperature T stop is positively correlated and negatively correlated with the water-cooled opening and cooling temperature T start.
  • the present invention is mainly aimed at high-plasticity pipeline steel products with a yield strength of 450MPa.
  • the composition is designed with low C, high Mn and Nb microalloying, combined with low temperature controlled rolling in the recrystallization rolling stage.
  • the process suppresses the grain size of the original austenite, and through a relatively low water cooling rate control, a refined polygonal ferrite + acicular ferrite phase transformation grain size is obtained, and the proportion of polygonal ferrite is controlled at 40% Below, it has better plasticity and toughness.
  • the present invention adopts a relatively high Nb and low B design to give full play to the grain refinement and suppress the low-temperature transformation structure. Combining the low-temperature rolling process and the low cooling rate process, a refined polygonal shape is finally obtained.
  • the ferrite + acicular ferrite structure not only has a lower yield ratio, higher uniform deformation ability, but also has better low temperature toughness.
  • the present invention is mainly aimed at pipeline steel products of 28mm and above with a yield strength R t0.5 of 450-635MPa and a tensile strength R m of 520-780MPa.
  • the composition is low in C,
  • the present invention is mainly aimed at high plastic pipeline steel products with a yield strength of 450MPa and a longitudinal uniform elongation Uel ⁇ 8%.
  • the composition has a low C and low Nb design, combined with recrystallization rolling.
  • the low-temperature controlled rolling process in the production stage suppresses the grain size of the original austenite, and through the relatively low water cooling rate control, a refined polygonal ferrite + acicular ferrite phase transformation grain size is obtained. Good deformability.
  • the present invention mainly adopts the Nb microalloying design with low C and high Mn, through lower recrystallization rolling temperature and low temperature non-recrystallization rolling, combined with reasonable cooling rate control, to obtain fine The microstructure of modified polygonal ferrite + acicular ferrite to ensure the high strength, high plasticity and toughness of the steel, without solid solution and isothermal heat treatment, and low cost.
  • the difference from Chinese patent CN101343715B is that the present invention mainly adopts the Nb microalloying design with low C and high Mn, through lower recrystallization rolling temperature and low temperature non-recrystallization rolling, combined with reasonable cooling rate control, to obtain fine The microstructure of modified polygonal ferrite + acicular ferrite to ensure the high strength, high plasticity and toughness of the steel.
  • the amount of alloy addition is small, and online heat treatment is not required, and the cost is low.
  • the present invention adopts a low-temperature heating process to inhibit the growth of reheated austenite grains and control the grain size from the source.
  • the heating temperature is too high, the high-temperature precipitation phase of the microalloying element Ti will undergo solid solution, which weakens the grain boundary pinning effect, the grain boundary migrates and merges, and the grains are significantly coarsened, which is not conducive to low-temperature toughness;
  • the present invention adopts a low-temperature rolling process at the recrystallization stage to inhibit the growth of recrystallized grains.
  • the recrystallization temperature is higher, the Gibbs free energy of the grain boundary is higher, and the driving force for the migration of the recrystallized grains is greater, which promotes the merger of the grains to reduce the Gibbs free energy of the grain boundary, thereby making the recrystallized crystal Grain coarsening.
  • the present invention adopts an appropriate amount of Nb alloy design promotion, combined with recrystallization low temperature rolling, and refines the recrystallization grain size.
  • Higher Nb will increase the recrystallization temperature, which is not conducive to the occurrence of recrystallization; while lower Nb will reduce the recrystallization temperature, increase the deformation resistance of recrystallization low-temperature rolling, and place high requirements on equipment capabilities;
  • the invention adopts a refined polygonal ferrite + acicular ferrite microstructure design, and improves the plastic deformation ability of the pipeline steel through the soft-phase polygonal ferrite structure design, so that the longitudinal uniform elongation of the pipeline steel Uel ⁇ 8%; and use high-density and large-angle grain boundaries to improve crack propagation resistance, thereby effectively improving the dynamic tear resistance of steel.
  • Fig. 1 is the microstructure of the steel of the embodiment of the present invention (the plate thickness is 1/2 position).
  • Fig. 2 is the microstructure of the steel of the embodiment of the present invention (the position of plate thickness 1/4).
  • the chemical composition of the design examples is shown in Table 1, and the manufacturing process of the examples is shown in Table 2.
  • the mechanical properties obtained in each example are shown in Table 3.
  • the tensile performance test of the invention adopts the Zwick Z330 tensile testing machine, the test standard is ASTM A370, the impact toughness test adopts the Zwick PSW750 impact tester, the test standard is ASTM A370, the full wall thickness of -20°C DWTT shear fracture area percentage SA adopts The 40,000-joule impact tester ZBC2404 was tested, and the test standard was API RP 5L3.
  • the components and processes designed according to the present invention can meet the target performance requirements, have good comprehensive mechanical properties, and have a low carbon equivalent, which is beneficial to improve the performance of steel pipe forming welding and field girth welding.
  • the composition of the invention is simple, the process window is wide, and the manufacturability is strong.
  • the high plastic thick gauge pipeline steel of the present invention is mainly used for subsea pipelines, pipelines passing through seismic belts and other special demand and harsh environment areas.
  • the plastic deformation capacity of the pipeline is improved through organizational control, and the pipeline's bearing weight is improved. Resist sports ability to ensure the safety and security of service.
  • high-plastic thick-gauge pipeline steel With the exploitation of oil and gas resources from inland to ocean, polar frozen soil, frequent geological movement and other areas, high-plastic thick-gauge pipeline steel will have good application prospects.

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Abstract

一种管线钢及其制造方法，其成分重量百分比为：C：0.03～0.10％、Si：0.1～0.5％、Mn：1.51～1.85％、P≤0.015％、S≤0.002％、Cr：0.05～0.3％、Mo：0.05～0.20％、Cu：0.06～0.3％、Ni：0.17～0.50％、Nb：0.05～0.10％、Ti：0.005～0.02％、Ca：0.001～0.005％，Al：0.02～0.045％，N≤0.006％，B≤0.0002％，O≤0.005％，余量为Fe及不可避免的杂质；且，0.06≤J c × Mn≤0.14，碳锰积参数J C × Mn＝C*Mn*10 4。该管线钢屈服强度450～635MPa，抗拉强度520～780MPa，-20℃全尺寸夏比冲击功AKv高于275J、-20℃全壁厚DWTT剪切断口面积百分数SA大于85％，纵向均匀延伸率Uel≥8％，可用于海底管道、穿越管道及极地管道建设，主要用于天然气的长距离输送。

Description

一种管线钢及其制造方法 技术领域
本发明涉及管线钢，特别涉及一种管线钢及其制造方法。
背景技术
随之全球消费市场对石油天然气等能源的需求加剧，石油天然气的管道输送趋于由陆地走向海洋、由小输量向大输量的方向发展，由此对管道的安全提出了高的要求。海底管道施工通常采用J型或S型方式进行铺设，服役过程中需跨越沟壑、克服流体运动等苛刻环境，因此对海底管道而言要求具有高强度、高韧性的同时，还需采用厚壁管道以提升结构稳定性，同时要求具有高的塑性变形能力，以确保服役安全。
从现有的文献调研来看，欧洲钢管、俄罗斯VSW、日本JFE等企业已有多年的海底管线钢及管线管产品开发历史。其开发研究除了在成分设计、轧制工艺控制以及显微组织控制等方面进行优化设计外，关键是通过装备能力来提升钢的强度和韧性，如迪林根拥有500mm以上的特厚连铸坯，从而为厚规格管线钢板的制造奠定了高内质、大压下比的基础，其中，高内质指管线钢板的内部质量较高，即控制偏析、夹杂物的含量，从而提高纯净度，能有效提升钢的强度和韧性，并向欧洲钢管、VSK等企业提供原材料钢板，制造的焊管厚至41mm。日本JFE公司采用在线热处理装置，应用HOP工艺改善钢板厚度方向上的组织均匀性，有利于改善厚规格管线钢的韧性并获得均匀的力学性能，同时还可以改善钢管的椭圆度。目前国内外海底管道用钢主要侧重于高强度、高韧性研究，而关于高塑性的研究较少。
就提高管线钢的塑性而言，目前主要针对应变设计的陆地管线提出了高均匀延伸率的要求，其设计主要采用双相组织控制，通过软硬相的结合得到拱顶型应力应变曲线，具有较好的加工硬化率，从而提升钢的均匀变形能力。代表的工艺方向有中国企业采用的驰豫+控冷工艺得到的铁素体 +下贝氏体双相组织，和日本JFE采用的在线热处理HOP工艺得到的MA组元+贝氏体双相组织，这两种组织类型均能够得到高的均匀延伸率，但由于双相界面的存在，显著降低钢的低温冲击韧性，不利于钢的止裂安全。
欧洲专利号EP2105513B1公开了一种屈服强度450MPa级厚规格高韧性管线钢的制造方法，通过采用低C、低Mn及较低Nb微合金化设计方法，结合低温加热工艺和控轧控冷工艺，得到以细化的多边形铁素体为主的微观组织，铁素体所占的体积比40～90％，铁素体晶粒尺寸≤10μm，该发明制备的管线钢具有优异的韧性。
中国专利CN101611163A公开了一种屈服强度≥400MPa、抗拉强度≥500MPa、屈强比≤0.90的抗时效双相管线钢，采用C-Mn基础成分及合金化的成分设计，通过控制轧制后的两阶段冷却速率控制得到第一相为铁素体，第二相为珠光体、上贝氏体、下贝氏体、粒状贝氏体或马氏体中的一种或多种，可使钢的均匀延伸率达到8％及以上。
美国专利US20120247606A1公开了一种X80级6～16mm薄规格管线钢的成分及工艺方案，采用低C高Nb及Mo合金化设计，未添加其它合金元素，工艺上采用675～715℃的低温终轧及1～2℃/s的空冷工艺，得到强度级别达到80Ksi的管线钢，并且具有较好的可焊性。
澳大利亚专利AU2006305841A1公开了一种抗拉强度900MPa级、纵向屈强比≤0.85的双相钢制造技术方法，采用低C、高Mn及Nb、Mo合金化的成分设计，通过工艺控制得到10～60％的晶粒尺寸≤5μm的细化的铁素体，余下组织为细化的马氏体、下贝氏体、退化的上贝氏体、粒状贝氏体等一种或多种混合组织。
中国专利CN109023068A公开了一种NbC纳米析出强化的X80高塑性管线钢板的制造方法，采用中C、较低Mn及高Nb的微合金化的成分设计，通过控制轧制、控制冷却工艺，并经随后的1180～1220℃的固溶处理和670～710℃的等温处理，控制NbC析出量为0.05～0.20％，可以得到屈服强度470Mpa级、具有高塑性、高韧性的X80管线钢。
中国专利CN101343715B公开了一种屈服强度650MPa级大应变管线钢管制造方法，成分上采用中C、低Mn、高合金含B设计的方法，通过控轧控冷和在线回火工艺，得到铁素体+针状铁素体+MA等复相组织，可 以制造满足屈服强度650～680MPa、均匀延伸率达到12～15％的钢管。
发明内容
本发明的目的在于设计一种高塑性厚规格管线钢及其制造方法，其屈服强度R t0.5为450～635MPa，抗拉强度R m为520～780MPa，尤其是-20℃全尺寸夏比冲击功AKv高于275J、-20℃全壁厚DWTT剪切断口面积百分数SA大于85％，同时其纵向均匀延伸率Uel≥8％，并具有可制造性，可用于海底管道、穿越管道以及极地管道建设，主要用于天然气的长距离输送。
为达到上述目的，本发明的技术方案是：
一种高塑性厚规格管线钢，其成分重量百分比为：C：0.03～0.10％、Si：0.1～0.5％、Mn：1.51～1.85％、P≤0.015％、S≤0.002％、Cr：0.05～0.3％、Mo：0.05～0.20％、Cu：0.06～0.3％、Ni：0.17～0.50％、Nb：0.05～0.10％、Ti：0.005～0.02％、Ca：0.001～0.005％，Al：0.02～0.045％，N≤0.006％，B≤0.0002％，O≤0.005％，余量为Fe及不可避免的杂质；且，同时满足：
0.06≤J C×Mn≤0.14，碳锰积参数J C×Mn＝C*Mn*10 4。
本发明所述管线钢的显微组织为细化的多边形铁素体+针状铁素体，其中细化的多边形铁素体相比例：15～39％。
本发明所述管线钢的屈服强度R t0.5为450～635MPa，抗拉强度R m为520～780MPa，尤其是-20℃全尺寸夏比冲击功AKv高于275J、-20℃全壁厚DWTT剪切断口面积百分数SA大于85％，纵向均匀延伸率Uel≥8％。
在本发明所述管线钢的成分体系设计中：
碳C：最基本的强化元素。碳溶解在钢中形成间隙固溶体，起固溶强化的作用，与强碳化物形成元素形成碳化物析出，则起到沉淀强化的作用。但太高的C对钢的韧性和焊接性能不利，同时降低钢的塑性；C太低降低钢的强度。所以C控制在0.03～0.10％。
硅Si：固溶强化元素，同时也是钢中的脱氧元素，但含量过高会恶化钢材的焊接性能、降低塑性，同时不利于轧制过程中热轧氧化铁皮去除，因此含量控制在0.1～0.5％。
锰Mn：通过固溶强化提高钢的强度，是钢中补偿因C含量降低而引起强度损失的最主要、经济的强化元素。Mn还是扩大γ相区的元素，可 降低钢的γ→α相变温度，有助于获得细小的相变产物，可提高钢的韧性；但Mn是易偏析元素，当Mn含量较高时，在浇铸过程中Mn易在板厚中心偏析，轧制完成后生成硬相的马氏体组织，降低材料的塑性及低温韧性。因此带本发明中Mn含量限定为1.51～1.85％。同时由于C、Mn均存为固溶强化元素且具有较大的偏析倾向，因此碳锰积参数J C×Mn＝C*Mn*10 4需符合0.06≤J C×Mn≤0.14要求，J C×Mn小于0.6时，由于C、Mn含量不足，固溶强化效果不显著，强度偏低；J C×Mn大于0.14时，缩小δ奥氏体的区间范围，不利于C、Mn元素的扩散分布，增大偏析倾向。
铬Cr：提高钢的淬透性的重要元素，确保厚规格钢板全厚度的组织及性能均匀性，而且能有效改善钢的耐腐蚀性能；但太高的铬加入钢中，提高钢的强度和硬度，降低伸长率和断面收缩率；与较高的Mn同时加入时，易生成化合物产生裂纹，并严重恶化焊接性能。本发明中Cr含量应限定在0.05～0.3％。
钼Mo：扩大γ相区的元素，可降低钢的γ→α相变温度，能够得到更加细小的相变组织，改善钢的韧性；同时少量的Mo可提高钢的淬透性，改善厚度方向的组织均匀性。但随Mo含量的上升，低温相变产物的比例增加，对钢的低温韧性不利，且有损钢的塑性。本发明中Mo含量控制0.05～0.20％。
铜Cu：可通过固溶强化作用提高钢的强度，并改善抗大气腐蚀性能；过高的Cu易出现铜脆现象，对热加工性能影响不利。本发明中Cu含量控制为0.06～0.3％。
镍Ni：可通过固溶强化作用提高钢的强度，Ni的加入即可改善Cu在钢中引起的热脆性；可扩大奥氏体区，增加奥氏体的稳定性，对塑性、韧性有益。本发明中Ni含量控制范围均为0.17～0.50％。
铌Nb：是低碳微合金钢的重要元素之一，热轧过程中固溶的Nb应变诱导析出形成Nb(N，C)粒子，钉扎晶界抑制形变奥氏体的长大并抑制再结晶的发生，经控制轧制和控制冷却使形变奥氏体相变为具有高位错密度的细小的产物。固溶的Nb在卷取后，以第二相粒子NbC在基体内弥散析出，起到析出强化作用。对于厚规格管线钢而言，太低的Nb含量弥散析出效果不明显，起不到细化晶粒、强化基体作用；太高的Nb含量， 由于抑制了钢板芯部再结晶的发生，不利于晶粒细化。且Nb的固溶与C含量有关，C含量太高Nb固溶量少，无法起到析出强化及晶粒细化效果；C含量过低会导致晶界弱化，Nb含量过低则析出强化效果不明显。本发明中Nb含量应限定在0.05～0.10％。
钛Ti：是一种强烈的碳氮化物形成元素，Ti的未溶的碳氮化物在钢加热时可以阻止奥氏体晶粒的长大，在高温奥氏体区粗轧时析出的TiN可有效抑制奥氏体晶粒长大。另外在焊接过程中，钢中的TiN粒子能显著阻止热影响区晶粒长大，从而改善钢板的焊接性能同时对改善焊接热影响区的冲击韧性有明显作用。本发明中Ti含量控制在0.005～0.02％。
氮N：在微合金化钢中，适当的氮含量可以通过形成高熔点的TiN粒子，起到抑制再加热过程中板坯晶粒粗化的作用，改善钢的强韧性。但当N含量过高时，时效后高浓度的自由N原子钉扎位错，使屈服强度明显提高，塑性及韧性显著下降。因此本发明中控制N≤0.006％。
氧O：对于低合金纯净钢冶炼，在冶炼终点均需要进行脱氧处理，以减少浇铸过程中产生的气泡以及氧化物夹杂，改善钢的内质、提高成品钢板的低温冲击韧性和抗动态撕裂性能。当氧含量高于50ppm时，夹杂物、气孔等内质缺陷显著增多，使钢的塑性、韧性降低，所以本发明中控制O≤0.005％。
硫、磷(S、P)：是钢中不可避免的杂质元素，希望越低越好。通过超低硫(小于20ppm)及Ca处理对硫化物进行夹杂物形态控制，同时控制P含量在150ppm以下，可保证发明钢具有良好的低温冲击韧性。
钙(Ca)：通过Ca处理可以控制硫化物的形态，改善钢板的各向异性，提高低温韧性，为确保最佳效果Ca的控制范围为0.0010～0.0050％。
铝(A1)：是为了脱氧而加入钢中的元素，添加适量的Al有利于细化晶粒，改善钢材的强韧性能，本发明中Al的含量控制范围为0.02～0.045％。
硼(B)：强淬透性元素，且易在晶界析出导致材料的塑性、韧性下降，因此本发明控制B≤0.0002％。
因此，针对28～40mm厚规格屈服强度R t0.5为450～635MPa级的管线钢，以晶粒细化、相变控制等材料理论为基础，采用了较低的C含量、较高Nb微合金化的成分设计；并结合低温粗轧、精轧工艺，充分发挥形 变诱导相变机制促进铁素体相变；通过合适的冷却速率和停冷温度控制，得到细化的多边形铁素体+针状铁素体显微组织，得到高强度、高韧性及高塑性综合力学性能特征，具有良好的变形能力。
本发明所述的高塑性厚规格管线钢的制造方法，其包括如下步骤：
1)冶炼、铸造
按上述成分冶炼，并连铸成板坯；
2)板坯再加热，加热温度：1100～1200℃；
3)热轧
粗轧开轧温度：940～1000℃；粗轧末道次单道次压下率：≥12％；
中间坯厚度：3t～5t，t为管线钢厚度，单位mm；
精轧开轧温度：750～810℃；精轧终轧温度：740～800℃；
4)控制冷却
水冷开冷温度T start：620～720℃；水冷停冷温度T stop：150～530℃；
水冷冷却速度V c＝72-T start/10+T stop/20，单位℃/s；
5)空冷，水冷后自然空冷冷却。
优选的，步骤2)板坯再加热的加热温度为1110～1150℃。
优选的，步骤3)粗轧开轧温度960～990℃、粗轧末道次单道次压下率≥14％；中间坯厚度4～4.5t；精轧开轧温度770～800℃、精轧终轧温度750～780℃。
优选的，步骤4)控制冷却，水冷开冷温度T start为660～700℃、水冷停冷温度T stop为200～350℃。
按照上述技术方案，最终获得28～40mm厚规格高塑性管线钢。
在本发明制造方法设计中：
控制冷却步骤中：水冷开冷温度T start范围：620～720℃；水冷停冷温度T stop范围：150～530℃；水冷冷却速度V c＝72-T start/10+T stop/20，单位℃/s。
轧后冷却是决定相变组织的关键工序，目标细化的多边形铁素体+针状铁素体相变组织可以通过控制水冷开冷温度T start、水冷停冷温度T stop及水冷冷却速度V c获得，各冷却参数需符合上述关系。其中，水冷开冷 温度T start高于720℃时，软相多边形铁素体的析出动力小会导致钢的强度高，低于620℃则软相多边形铁素体粗大且比例过高会导致强度显著偏低；水冷停冷温度T stop主要是决定硬相针状铁素体的硬度，高于530℃时则位错密度小、硬度低、强度偏低，低于150℃时则易生成马氏体组织导致位错密度过高、硬度高、塑性下降；而水冷冷却速度V c主要是匹配水冷开冷、停冷温度进行相变组织类型和相比例控制的关键参数，与水冷停冷温度T stop正相关、与水冷开冷温度T start负相关。
本发明与现有技术相比：
与欧洲专利号EP2105513B1不同的是：本发明主要是针对屈服强度450MPa级高塑性管线钢产品，成分上低C、高Mn及Nb微合金化的设计，结合再结晶轧制阶段的低温控轧工艺抑制原始奥氏体的晶粒大小，并通过相对低的水冷冷却速度控制，得到细化的多边形铁素体+针状铁素体相变晶粒尺寸，多边形铁素体比例控制在40％以下，具有较好的塑性和韧性。
与中国专利CN101611163A不同的是，本发明采用相对较高Nb及低B的设计，充分发挥晶粒细化并抑制低温转变组织，结合低温轧制工艺和低冷却速度工艺，最终得到细化的多边形铁素体+针状铁素体组织，既具有较低的屈强比、较高的均匀变形能力，同时还具有较佳的低温韧性。
与美国专利US20120247606A1对比专利不同的是，本发明主要是针对屈服强度R t0.5为450～635MPa、抗拉强度R m为520～780MPa的28mm及以上规格的管线钢产品，成分上低C、高Mn及Nb微合金化的设计，结合再结晶轧制阶段的低温控轧工艺抑制原始奥氏体的晶粒大小，并通过相对低的水冷冷却速度控制，得到细化的多边形铁素体+针状铁素体相变晶粒尺寸，具有较好的塑性和韧性。
与澳大利亚专利AU2006305841A1对比专利不同的是，本发明主要是针对屈服强度450MPa级别的纵向均匀延伸率Uel≥8％的高塑性管线钢产品，成分上低C、较低Nb的设计，结合再结晶轧制阶段的低温控轧工艺抑制原始奥氏体的晶粒大小，并通过相对低的水冷冷却速度控制，得到细化的多边形铁素体+针状铁素体的相变晶粒尺寸，具有较好的变形能力。
与中国专利CN109023068A同的是：本发明主要采用低C较高Mn的Nb微合金化设计，通过较低的再结晶轧制温度和低温非再结晶轧制，结合合理的冷却速度控制，得到细化的多边形铁素体+针状铁素体的显微组织，以保证钢的高强度、高塑性及韧性，无需进行固溶和等温热处理，成本较低。
与中国专利CN101343715B不同的是：本发明主要采用低C较高Mn的Nb微合金化设计，通过较低的再结晶轧制温度和低温非再结晶轧制，结合合理的冷却速度控制，得到细化的多边形铁素体+针状铁素体的显微组织，以保证钢的高强度、高塑性及韧性。合金添加量少，且不需要进行在线热处理，成本较低。
本发明的优点在于；
1.本发明采用低温加热工艺，抑制再加热奥氏体晶粒长大，从源头控制晶粒尺寸大小。加热温度过高时，微合金元素Ti的高温析出相发生固溶，弱化了晶界钉扎效应，晶界发生迁移和合并，晶粒显著粗化，不利于低温韧性；
2.本发明采用再结晶阶段低温轧制工艺，抑制再结晶晶粒长大。再结晶温度较高时，晶界吉布斯自由能较高，再结晶晶粒晶界迁移驱动力较大，促进晶粒通过合并的方式降低晶界吉布斯自由能，从而使得再结晶晶粒粗化。
3.本发明采用适量Nb合金设计促进，结合再结晶低温轧制，细化再结晶晶粒尺寸。较高的Nb会提高再结晶温度，不利于再结晶的发生；而较低的Nb会降低再结晶温度，增加再结晶低温轧制的变形抗力，对装备能力提出高的要求；
4.本发明采用细化的多边形铁素体+针状铁素体的显微组织设计，通过软相多边形铁素体组织设计提升管线钢的塑性变形能力，使得管线钢的纵向均匀延伸率Uel≥8％；并利用高密度大角度晶界提升裂纹扩展阻力，从而有效提升钢的抗动态撕裂性能。
附图说明
图1为本发明实施例钢的显微组织(板厚1/2位置)。
图2为本发明实施例钢的显微组织(板厚1/4位置)。
具体实施方式
下面结合实施例和附图对本发明做进一步说明。
按照本发明钢化学成份要求，设计实施例的化学成分，如表1所示，实施例制造工艺参见表2，按上述成份和工艺设计，各实施例得到的力学性能如表3所示，本发明的拉伸性能测试采用Zwick Z330拉伸试验机，测试标准为ASTM A370，冲击韧性测试采用Zwick PSW750冲击试验机，测试标准为ASTM A370，-20℃全壁厚DWTT剪切断口面积百分数SA采用4万焦冲击试验机ZBC2404进行测试，测试标准为API RP 5L3。
可见，按照本发明设计的成分和工艺，都可达到目标性能要求，具有良好的综合力学性能，且碳当量较低，有利于改善钢管成型焊接及现场环焊焊接性能。另外本发明成分简单，工艺窗口较宽，具有较强的可制造性。
本发明高塑性厚规格管线钢主要用于海底管线、穿越地震带管道等特殊需求及恶劣环境区域，在保证钢的强度、韧性的基础上通过组织控制提升管道塑性变形能力，提升管道承载自重、抵抗运动能力，保障服役安全安全性。随着油气资源开采由内陆走向海洋、极地冻土、地质运动频繁等地带，高塑性厚规格管线钢将具有良好的应用前景。
Figure PCTCN2020118447-appb-000001
Figure PCTCN2020118447-appb-000002
Figure PCTCN2020118447-appb-000003

Claims (9)

  1. 一种管线钢，其特征在于，其成分重量百分比为：C：0.03～0.10％、Si：0.1～0.5％、Mn：1.51～1.85％、P≤0.015％、S≤0.002％、Cr：0.05～0.3％、Mo：0.05～0.20％、Cu：0.06～0.3％、Ni：0.17～0.50％、Nb：0.05～0.10％、Ti：0.005～0.02％、Ca：0.001～0.005％，Al：0.02～0.045％，N≤0.006％，B≤0.0002％，O≤0.005％，余量为Fe及不可避免的杂质；且，同时满足：
    0.06≤J C×Mn≤0.14，碳锰积参数J C×Mn＝C*Mn*10 4。
  2. 如权利要求1所述的管线钢，其特征在于，所述管线钢的显微组织为多边形铁素体+针状铁素体，所述多边形铁素体相比例：15～39％。
  3. 如权利要求1或2所述的管线钢，其特征在于，所述管线钢的屈服强度R t0.5为450～635MPa，抗拉强度R m为520～780MPa，-20℃全尺寸夏比冲击功AKv高于275J、-20℃全壁厚DWTT剪切断口面积百分数SA大于85％，纵向均匀延伸率Uel≥8％。
  4. 如权利要求1或2所述的管线钢，其特征是，所述管线钢的厚度为28～40mm。
  5. 一种管线钢的制造方法，其特征是，包括如下步骤：
    1)冶炼、铸造
    按权利要求1-4中任一项所述成分冶炼，并连铸成板坯；
    2)板坯再加热，加热温度：1100～1200℃；
    3)热轧
    粗轧开轧温度：940～1000℃；粗轧末道次单道次压下率：≥12％；
    中间坯厚度：3t～5t，t为管线钢厚度，单位mm；
    精轧开轧温度：750～810℃；精轧终轧温度：740～800℃；
    4)控制冷却
    水冷开冷温度T start：620～720℃；水冷停冷温度T stop：150～530℃；
    水冷冷却速度V c＝72-T start/10+T stop/20，单位℃/s；
    5)空冷，水冷后自然空冷冷却。
  6. 如权利要求5所述的管线钢的制造方法，其特征是，步骤2)所述板坯再加热的加热温度为1110～1150℃。
  7. 如权利要求5所述的管线钢的制造方法，其特征是，步骤3)所述粗轧开轧温度为960～990℃、所述粗轧末道次单道次压下率≥14％；所述中间坯厚度4～4.5t；所述精轧开轧温度为770～800℃、所述精轧终轧温度为750～780℃。
  8. 如权利要求5所述的管线钢的制造方法，其特征是，步骤4)控制冷却，所述水冷开冷温度T start为660～700℃、所述水冷停冷温度T stop为200～350℃。
  9. 如权利要求5-8中任一项所述的管线钢的制造方法，其特征是，所述管线钢的厚度为28～40mm。
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CN112575158B (zh) 2022-07-29

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