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WO2021218933A1 - Acier à haute résistance et à faible rendement économique et procédé de fabrication associé - Google Patents

Acier à haute résistance et à faible rendement économique et procédé de fabrication associé Download PDF

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Publication number
WO2021218933A1
WO2021218933A1 PCT/CN2021/090025 CN2021090025W WO2021218933A1 WO 2021218933 A1 WO2021218933 A1 WO 2021218933A1 CN 2021090025 W CN2021090025 W CN 2021090025W WO 2021218933 A1 WO2021218933 A1 WO 2021218933A1
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yield
strength steel
economical low
strength
ratio high
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Chinese (zh)
Inventor
孙磊磊
朱春生
吴扣根
郑磊
章传国
沈燕
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Baoshan Iron and Steel Co Ltd
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Baoshan Iron and Steel Co Ltd
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Priority to CA3181338A priority Critical patent/CA3181338A1/fr
Priority to DE112021001697.0T priority patent/DE112021001697T5/de
Publication of WO2021218933A1 publication Critical patent/WO2021218933A1/fr
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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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • C21D11/005—Process control or regulation for heat treatments for cooling
    • 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
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment 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
    • C21D8/0205—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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold 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
    • 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
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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
    • C22C38/04—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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/28—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
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C21D2211/001—Austenite
    • 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
    • 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
    • C21D2211/008—Martensite

Definitions

  • the invention relates to a metal material and a manufacturing method thereof, in particular to a steel grade and a manufacturing method thereof.
  • the publication number is CN102676937A, the publication date is September 19, 2012, the Chinese patent document titled "A low-cost high-strength X80 pipeline steel plate production process", a low-cost high-strength X80 pipeline steel plate production process
  • This production process achieves high strength through low final cooling temperature ( ⁇ 400°C), and does not contain Mo in chemical composition.
  • ⁇ 400°C final cooling temperature
  • Low cost is achieved, it is difficult to resist the heat impact caused by high-strength pipeline steel welding through solid solution strengthening The zone softens, which in turn affects engineering applications.
  • the publication number is CN101768703A
  • the publication date is July 7, 2010, and the Chinese patent document entitled "A low yield ratio X80 pipeline steel and its manufacturing method” discloses a low yield ratio X80 pipeline steel And its manufacturing method, its yield ratio is in the range of 0.748 to 0.845.
  • the content of the expensive alloying elements Cu, Ni, V, and Nb in the steel is higher, and a higher slab heating temperature (1180 ⁇ 1220°C) to ensure the solid solution of the alloy, so the production cost is higher.
  • the publication number is CN101962733A, the publication date is February 2, 2011, and the Chinese patent document entitled "A low-cost, high-strength X80 anti-large deformation pipeline steel and its production method" discloses a low-cost, high-toughness resistant Large-deformation X80 pipeline steel and its production method adopt a two-stage controlled cooling process of air cooling + water cooling after rolling to obtain a ferrite + bainite dual-phase structure to achieve a yield ratio of pipeline steel ⁇ 0.80, but due to ferrite
  • the content of the pipeline steel is relatively high, and the yield strength of the pipeline steel is only in the range of 530-600MPa, which does not meet the yield strength requirement of X80 ( ⁇ 555MPa).
  • the content of the expensive alloying elements Cu and Ni in the patent embodiment is above 0.15%, which is relatively high. , The production cost is relatively high.
  • One of the objectives of the present invention is to provide an economical low-yield ratio high-strength steel, which is designed with Mn, Cr, Mo, and Nb alloyed components, and does not contain Cu, Ni, The V element has good economic efficiency and effectively controls the alloy cost.
  • the present invention provides an economical low-yield ratio high-strength steel, which contains the following chemical elements in the following mass percentages:
  • the mass percentage of each chemical element is:
  • C In the economical low-yield-ratio high-strength steel of the present invention, carbon is the most basic strengthening element and has the functions of solid solution strengthening and carbide precipitation strengthening. A proper amount of C element can effectively ensure the strength of steel, but it should be noted that too high C content will increase the size and content of carbides in the structure, thereby affecting the low-temperature toughness and welding performance of steel. Therefore, in the economical low-yield ratio high-strength steel of the present invention, the mass percentage of C is controlled to be between 0.045 and 0.080%.
  • the mass percentage of C can be controlled between 0.050 and 0.075%, which helps to obtain better matching of strength and toughness.
  • Si is a solid solution strengthening element and also a deoxidizing element in the steel, but an excessively high mass percentage of Si in the steel will deteriorate the welding performance of the steel. Therefore, in the economical low-yield ratio high-strength steel of the present invention, the mass percentage of Si is controlled to be between 0.10% and 0.30%.
  • Mn In the economical low-yield ratio high-strength steel of the present invention, Mn can increase the strength of the steel through solid solution strengthening, and it is the most effective and economical strengthening element in steel. Mn element in high-strength steel also has the effect of promoting the formation of MA (Mao element), which is beneficial to increase the tensile strength of steel, thereby reducing the yield ratio, but the size and content of MA should not be too large, otherwise it will reduce the steel Of resilience. On the other hand, an excessively high content of Mn will increase the difficulty of central segregation control, which will result in a decrease in the toughness of the steel. Therefore, in the economical low-yield-ratio high-strength steel of the present invention, the mass percentage of Mn is controlled to be between 1.60 and 1.85%.
  • the mass percentage of Mn can be controlled between 1.65% and 1.80%, which helps to control the content and size of the Mayo component in the microstructure.
  • Cr In the economical low-yield ratio high-strength steel of the present invention, Cr can effectively improve the hardenability of the steel, ensure the uniformity of the structure and performance in the thickness direction of the thick gauge steel plate, and increase the strength of the steel. However, it should be noted that if the Cr content in the steel is too high, the steel plate is likely to form a hard phase structure during the rapid cooling process, which is not conducive to low temperature toughness and welding performance. Therefore, in the economical low-yield-ratio high-strength steel of the present invention, the mass percentage of Cr is controlled to be between 0.15 and 0.30%.
  • Mo in the economical low-yield ratio high-strength steel of the present invention, Mo can effectively increase the strength of the steel, have the effect of expanding the ⁇ phase region, and reduce the ⁇ transformation temperature of the steel. It can refine the transformation structure and inhibit the formation of low-toughness structures such as quasi-polygonal ferrite and pearlite. In addition, Mo can also effectively suppress the softening of the heat-affected zone during pipeline welding. However, it should be noted that the Mo element is expensive and should not be added in excess. Therefore, in the economical low-yield ratio high-strength steel of the present invention, the mass percentage of Mo is controlled to be between 0.06 and 0.24%.
  • the mass percentage of Mo can be controlled between 0.06 and 0.18%, which helps to improve the stability of the microstructure of the inventive steel.
  • Nb is an important element for grain refinement, and solid solution Nb can pin deformed austenite grain boundaries through solute drag and hinder austenite Bulk crystal grains grow up. In addition, it also has the effect of increasing the recrystallization temperature, which can increase the strain accumulation in the unrecrystallized region during the finishing rolling process. As the temperature of the hot rolling process decreases, Nb nitrides and carbides precipitate, which can inhibit the growth of ferrite grains by pinning the grain boundaries during the ⁇ phase transition. At the same time, it also has a precipitation strengthening effect.
  • the mass percentage of Nb is controlled to be between 0.040 and 0.075%.
  • the mass percentage of Nb can be controlled between 0.045 and 0.065%, which helps to refine the ferrite grain size in the microstructure and improve the strength and toughness.
  • Ti has a strong bonding force with N and is a strong carbonitride forming element.
  • TiN formed by Ti element has higher heat Stability can prevent the growth of austenite grains during slab heating and rough rolling recrystallization.
  • TiN can also inhibit the growth of heat-affected zone grains during welding and improve welding performance.
  • the mass percentage of Ti is controlled to be between 0.005 and 0.020%.
  • Al is a deoxidizing element.
  • the quality of Al is controlled in the economical low-yield ratio high-strength steel of the present invention The percentage is between 0.01 and 0.05%.
  • the form of sulfides can be controlled by micro-Ca treatment, thereby suppressing the formation of MnS inclusions.
  • the mass percentage of Ca is controlled to be between 0.001 and 0.004%.
  • N element can form TiN particles with a high melting point with Ti, which can inhibit the coarsening of austenite grains during reheating.
  • the mass percentage of N is controlled to be between 0.001 and 0.005%.
  • the mass percentage content of each chemical element simultaneously satisfies: 0.34% ⁇ C+Mn/6 ⁇ 0.38%, 0.30% ⁇ Cr+Mo ⁇ 0.40%, 2.5 ⁇ Ti/N ⁇ 5.0, where C, Mo, Cr, N, Ti and Mn all represent the mass percentages of the corresponding elements.
  • the economical low-yield ratio high-strength steel of the present invention also contains 0 ⁇ B ⁇ 0.0005%.
  • the economical low-yield ratio high-strength steel of the present invention may also contain a small amount of B, which is used as a strong hardenability element, and a proper amount of B can improve the hardenability of the steel. .
  • the mass percentage of B is controlled to be 0 ⁇ B ⁇ 0.0005%. Further, the mass percentage of B is between 0.0001 and 0.0005%.
  • both P and S are unavoidable impurity elements in the steel.
  • S is easy to form MnS inclusions, which are elongated after rolling.
  • P is an element that is easy to segregate. If the content of P and S impurity elements in steel is too high, it will greatly affect the performance of steel. Therefore, in the economical low-yield-ratio high-strength steel of the present invention, the mass percentage of P is controlled to be P ⁇ 0.015%, and the mass percentage of S to be controlled is S ⁇ 0.002%.
  • the mass percentage of each chemical element satisfies at least one of the following items:
  • Nb 0.045 to 0.065%.
  • the microstructure is polygonal ferrite+Mao element+granular bainite.
  • the phase ratio of the polygonal ferrite is 5-25%, and the phase ratio of the Ma-Ao component is 2-10%.
  • the average grain size of the polygonal ferrite is less than 10 ⁇ m; and/or the average size of the Mah-O component is less than 2 ⁇ m.
  • ferrite is the soft phase
  • the Maroon element and granular bainite are the hard phases.
  • the soft and hard phases deform synergistically, showing continuous yielding, and lower yield strength can be obtained.
  • controlling the size of the crystal grains and the Ma-Ao component can ensure that the invention steel has good impact toughness and DWTT (drop weight tear test) performance.
  • the economical low-yield ratio high-strength steel of the present invention its performance satisfies at least one of the following items: the yield strength Rt 0.5 is 560-680 MPa, and the tensile strength Rm is 640-760 MPa. , Yield ratio Rt 0.5 /Rm ⁇ 0.89, elongation A 50.8 ⁇ 22%; V-notch Charpy impact energy AKV ⁇ 230J at -20°C; DWTT fracture shear area ratio at -15°CSA% ⁇ 85 %. Among them, the V-notch Charpy impact energy of 230J and above and the fracture shear area rate of 85% and above are the average values of the steel of the present invention.
  • another object of the present invention is to provide an economical low-yield ratio high-strength steel manufacturing method, the manufacturing method has a lower production process cost, and the economical low-yield ratio high-strength steel produced by the manufacturing method
  • the yield strength of steel Rt 0.5 is 560 ⁇ 680MPa
  • the tensile strength Rm is 640 ⁇ 760MPa
  • the yield ratio Rt 0.5 /Rm ⁇ 0.89 the elongation rate A 50.8 ⁇ 22%
  • the Charpy impact energy at -20°C is AKV ⁇ 230J
  • the shear area ratio of the DWTT fracture at -15°C is SA% ⁇ 85%, which has excellent strength and toughness and low yield ratio characteristics.
  • the present invention proposes the above-mentioned economical low-yield-ratio high-strength steel manufacturing method, which includes the following steps:
  • Cooling adopt DQ (namely on-line direct quenching) + ACC (namely accelerated cooling) two-stage cooling process, in which the cooling temperature is 700 ⁇ 750°C, and the cooling rate in the DQ section is 30 ⁇ 40°C/s, DQ The cooling stop temperature is 550 ⁇ 620°C, the cooling speed of ACC section is 10 ⁇ 25°C/s, and the cooling stop temperature of ACC is 430 ⁇ 530°C.
  • the economical low-yield-ratio high-strength steel manufacturing method of the present invention by controlling the process conditions, especially the cooling process parameters, the grain refinement, precipitation strengthening, and phase transformation control of the low-carbon niobium-containing steel are used. And other theories, make full use of controlled rolling and controlled cooling technology, so that the economical low-yield-ratio high-strength steel produced by the manufacturing method of the present invention has granular bainite, fine polygonal ferrite, and fine mao
  • the microstructure of the component has excellent strength and toughness and low yield ratio characteristics.
  • the temperature of water-in and boiling-cooling is controlled to 700-750°C, which can ensure a small amount of polygonal ferrite precipitation and obtain a low yield ratio.
  • the DQ cooling section controls rapid cooling with a cooling rate of 30-40°C/s, which not only prevents ferrite from growing, but also suppresses the quasi-polygonal ferrite and pearlite structure to ensure the strength of the steel.
  • the ACC cooling section controls a relatively low cooling rate of 10-25°C/s, which can promote the formation of a small amount of fine Ma-Ao components, improve the tensile strength of the steel without reducing the toughness.
  • the ACC cooling-off temperature will affect the bainite morphology.
  • the ACC cooling-off temperature is controlled at 430-530°C to obtain fine granular bainite.
  • step (1) the continuous casting drawing speed fluctuation is controlled within ⁇ 0.3m/min, and dynamic soft reduction is used to control the continuous casting Center segregation of billet.
  • step (2) the reheating temperature is controlled to be 1100-1160°C.
  • the reheating temperature is controlled to be 1100-1160°C. This is because in order to prevent the austenite grains of the slab from growing, the present invention adopts a lower reheating temperature as much as possible, and in order to ensure that Nb is fully dissolved, the reheating temperature should not be too low. Therefore, in order to ensure the overall performance of the steel, the reheating temperature is controlled to be 1100 to 1160°C.
  • step (3) in the rough rolling stage, the rough rolling temperature is controlled to be 950 ⁇ 1080°C, and the single pass reduction ratio of the last two passes of rough rolling is ⁇ 15 %, that is, the reduction ratio of each pass in the last two passes of rough rolling is ⁇ 15%; the rolling temperature of the last pass of rough rolling is in the range of 950 ⁇ 990°C, that is, the rolling temperature range control of the last pass of rough rolling In the range of 950 ⁇ 990°C.
  • the main function of rough rolling is to refine grains through recrystallization, which should be performed above the recrystallization temperature, so the rough rolling temperature is controlled to be 950-1080°C.
  • the single-pass reduction rate of the last two passes of rough rolling is ⁇ 15%, which can ensure that the deformation penetrates into the core of the slab.
  • step (3) in the finishing rolling stage, the finishing rolling temperature is controlled to be 770-860°C, the total finishing rolling reduction ratio is ⁇ 70%, and the finishing rolling temperature is It is 770 ⁇ 820°C.
  • the finishing rolling is carried out in the non-recrystallized area, and increasing the finishing rolling reduction ratio can increase the strain storage and deformation bands inside the deformed austenite grains, and promote the phase Deformed nucleus.
  • the lower the rolling temperature the less the recovery of strain storage energy. Therefore, the present invention adopts a lower finishing rolling temperature, controls the finishing temperature to 770-860°C, and controls the final finishing in the finishing rolling process.
  • the rolling temperature is 770 ⁇ 820°C, and the total rolling reduction ratio of finishing rolling is ⁇ 70%.
  • the economical low-yield-ratio high-strength steel and the manufacturing method thereof according to the present invention have the following advantages and beneficial effects:
  • the economical low-yield-ratio high-strength steel of the present invention adopts the chemical composition design of Mn, Cr, Mo, Nb alloying, does not contain Cu, Ni, and V elements, has good economy, and effectively controls the alloy cost.
  • the economical low-yield ratio high-strength steel has a yield strength Rt 0.5 of 560 ⁇ 680MPa, a tensile strength Rm of 640 ⁇ 760MPa, a yield ratio Rt 0.5 /Rm ⁇ 0.89, and an elongation rate A 50.8 ⁇ 22%; -20°C Charpy impact energy AKV ⁇ 230J; DWTT fracture shear area ratio SA% ⁇ 85% at -15°C, which realizes the characteristics of low yield ratio and high strength while having good economy.
  • the manufacturing method of the present invention controls the process conditions, especially the cooling process parameters, so that the microstructure of the economical low-yield ratio high-strength steel obtained by the manufacturing method of the present invention is polygonal ferrite.
  • +Mao element + granular bainite complex structure in which the volume percentage content of polygonal ferrite is 5-25%, the average grain size is less than 10 ⁇ m, the content of Maro element is 2-10%, the average size Less than 2 ⁇ m.
  • Fig. 1 is a metallographic structure diagram of the economical low-yield-ratio high-strength steel of Example 1 under a 500-fold microscope.
  • Example 2 is a microstructure diagram of the economical low-yield-ratio high-strength steel of Example 1 under a microscope at 1000 times.
  • Table 1 lists the mass percentages of various chemical elements in the economical low-yield ratio high-strength steels of Examples 1-6.
  • the rough rolling temperature is controlled to be 950 ⁇ 1080°C, the single pass reduction rate of the last two passes of rough rolling is ⁇ 15%, and the rolling temperature of the last pass of rough rolling is 950 ⁇ 990°C range.
  • the finishing temperature is controlled to be 770 ⁇ 860°C, the total reduction ratio of finishing rolling is ⁇ 70%, and the finishing temperature of finishing rolling is 770 ⁇ 820°C;
  • Cooling adopts DQ+ACC two-stage cooling process, in which the opening cooling temperature is 700 ⁇ 750°C, the cooling rate in the DQ section is 30 ⁇ 40°C/s, the DQ cooling stop temperature is 550 ⁇ 620°C, and the ACC section The cooling rate is 10 ⁇ 25°C/s, and the ACC cooling stop temperature is 430 ⁇ 530°C.
  • Table 2-1 and Table 2-2 list the specific process parameters of the manufacturing method of the economical low-yield ratio high-strength steel of Example 1-6.
  • the temperature control fluctuates during actual operation and is not stable at a fixed value. Therefore, the rough rolling temperature and the finishing temperature in step (3) in Table 2-1 are in each embodiment.
  • the middle is presented as an end range value instead of a point value.
  • the economical low-yield-ratio high-strength steels of Examples 1-6 were tested for mechanical properties.
  • the tensile test was carried out on the Zwick Z2000 tensile testing machine in accordance with ASTM A370 standard using plate-shaped tensile specimens.
  • the test was conducted in accordance with ASTM A370 standard, using full-size Charpy impact specimens (10 ⁇ 10 ⁇ 55mm), and tested on the Zwick PSW750 impact testing machine.
  • the DWTT test was conducted in accordance with API RP 5L3 specifications, using full-wall thickness V-shaped compressed notch specimens.
  • the test was carried out on the SANS ZBC2404 testing machine.
  • the test results obtained are listed in Table 3.
  • Table 3 lists the mechanical performance test results of the economical low-yield ratio high-strength steels of Examples 1-6.
  • the yield strength Rt 0.5 of each embodiment of the present invention is in the range of 560 to 680 MPa
  • the tensile strength Rm is in the range of 640 to 760 MPa
  • the yield ratio Rt 0.5 / Rm ⁇ 0.89 the yield ratio Rt 0.5 / Rm ⁇ 0.89
  • the economical low-yield ratio high-strength steel of each embodiment has excellent properties, has excellent strength and toughness and low-yield ratio, and can be effectively used as a pipeline steel in the field of natural gas transportation.
  • the content of C and Cr is too high, and the content of Mo is too low.
  • the final rolling temperature and the opening cooling temperature are too high, and the DQ cooling stop temperature and ACC cooling stop temperature are too low, and the desired polygonal iron cannot be obtained.
  • the microstructure of the element body leads to too high yield strength and yield ratio, and poor impact toughness and DWTT performance.
  • the content of Mn and Cr strengthening elements is too low, the total reduction of finishing rolling is too low, the DQ cooling rate is too low, and the ACC cooling stop temperature is too high, resulting in too low strength and poor DWTT performance.
  • Fig. 1 is a metallographic structure diagram of the economical low-yield-ratio high-strength steel of Example 1 under a 500-fold microscope.
  • Example 2 is a microstructure diagram of the economical low-yield-ratio high-strength steel of Example 1 under a microscope at 1000 times.
  • the microstructure is a complex structure of polygonal ferrite + Mahau element + granular bainite.
  • the economical low-yield-ratio high-strength steel polygonal ferrite of Example 1 has a phase ratio of 5-25%, and the average grain size of the polygonal ferrite is smaller than 10 ⁇ m, the phase ratio of the Mayo component is 2-10%, and the average grain size of the Mayo component is less than 2 ⁇ m.

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Abstract

L'invention concerne un acier à haute résistance et à faible rendement économique, contenant les éléments chimiques suivants en pourcentage en masse : 0,045 à 0,080 % de C, 0,10 à 0,30 % de Si, 1,60 à 1,85 % de Mn, 0,15 à 0,30 % de Cr, 0,06 à 0,24 % de Mo, 0,040 à 0,075 % de Nb, 0,005 à 0,020 % de Ti, 0,01 à 0,05 % de Al, 0,001 à 0,004 % de Ca, and 0,001 à 0,005 % de N. En outre, l'invention concerne également un procédé de fabrication de l'acier à haute résistance et à faible rendement économique, comprenant les étapes suivantes : (1) fusion et coulée continue ; (2) réchauffage ; (3) laminage ; et (4) refroidissement : à l'aide d'un procédé de refroidissement en deux étapes DQ + ACC, la température de refroidissement initiale étant de 700 à 750 °C, la vitesse de refroidissement à l'étape DQ est de 30 à 40 °C/s, la température de refroidissement d'arrêt à l'étape DQ est de 550 °C à 620 °C, la vitesse de refroidissement à l'étape ACC est de 10 à 25 °C/s, et la température de refroidissement d'arrêt à l'étape ACC est de 430 à 530 °C. L'acier à haute résistance et à faible rendement économique de la présente invention utilise une composition chimique raisonnable et une conception de procédé, et non seulement une excellente économie, mais a également les caractéristiques d'une résistance élevée et d'un faible rendement.
PCT/CN2021/090025 2020-04-27 2021-04-26 Acier à haute résistance et à faible rendement économique et procédé de fabrication associé Ceased WO2021218933A1 (fr)

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