WO2022199079A1 - 一种高均匀伸长率2000MPa级超高强度钢及其制备方法 - Google Patents

一种高均匀伸长率2000MPa级超高强度钢及其制备方法 Download PDF

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WO2022199079A1
WO2022199079A1 PCT/CN2021/131842 CN2021131842W WO2022199079A1 WO 2022199079 A1 WO2022199079 A1 WO 2022199079A1 CN 2021131842 W CN2021131842 W CN 2021131842W WO 2022199079 A1 WO2022199079 A1 WO 2022199079A1
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ultra
uniform elongation
strength steel
treatment
temperature
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French (fr)
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曹文全
黄崇湘
何琼
杨渤
王昌
王存宇
刘正东
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钢铁研究总院
四川大学
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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
    • C22C38/18—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
    • 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
    • C21D1/26—Methods of annealing
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • 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
    • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of 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
    • C22C38/18—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
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • 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
    • C22C38/58—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
    • C21D2211/001—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
    • C21D2211/008—Martensite

Definitions

  • the invention relates to the technical field of advanced high-strength steel, in particular to an ultra-high-strength steel with a high uniform elongation rate of 2000 MPa and a preparation method thereof.
  • the steel has excellent strength and plasticity.
  • the tensile strength of traditional advanced high-strength steel is 1500-2000MPa, but the plasticity is often less than 10%.
  • the Chinese Patent Publication No.: CN105568151A "A kind of aluminum reinforced maraging steel and its preparation method"
  • the maraging steel disclosed in To 5% the total elongation is less than 10%, which is difficult to meet the forming needs of complex parts in the automobile and other industries.
  • the invention provides a high-uniform elongation 2000MPa grade ultra-high-strength steel and a preparation method thereof.
  • the invention provides an ultra-high-strength steel with a high uniform elongation of 2000 MPa, and the chemical composition of the ultra-high-strength steel in terms of weight percentage is:
  • C is 0.3% to 0.4%
  • Ni is 8% to 9%
  • Cr is 6.5% to 10.0%
  • Mo is 3.0% to 6.0%
  • Mn is 0% to 2%
  • Si is 0% to 2%
  • Cu is 0% to 2%
  • V is 0.05% to 0.15%
  • Nb is 0.05% to 0.15%
  • the balance is Fe.
  • the preferred high-uniform elongation 2000MPa grade ultra-high-strength steel of the present invention the chemical composition of the ultra-high-strength steel is:
  • C is 0.4%, Ni is 8.0%, Cr is 8.0%, Mo is 4.0%, Mn is 1.0%, Si is 1.0%, Cu is 2%, V is 0.1%, Nb is 0.1%, and the balance is Fe.
  • the thickness of the ultra-fine lamella in the ultra-high-strength steel is 10 nm to 200 nm, and the microstructure of the steel plate is martensite and austenite.
  • the volume content (ie, volume fraction) of the martensitic structure is 60% to 90%, and the volume content (ie, volume fraction) of the austenite structure is 10% to 40%.
  • the thickness of the ultra-fine lamella is 20nm-50nm
  • the volume fraction of the martensitic structure is 70%-80%
  • the austenite structure is 70%-80%.
  • the volume content is 20% to 30%.
  • the precipitation phase of the ultra-high strength steel with high uniform elongation of 2000 MPa in the present invention is M 6 C carbide, and the size of the precipitation phase is 200 nm to 600 nm.
  • the invention obtains a dual-phase structure of martensite and austenite through composition improvement, and contains ultra-fine lamellar structure, wherein, martensite is beneficial to improve the strength of steel, and austenite is the
  • martensite is beneficial to improve the strength of steel
  • austenite is the
  • the high uniform elongation contributes, and the thickness of the ultra-fine lamellar structure is small, which is beneficial to further increase the strength.
  • the present invention provides the preparation method of the high-uniform elongation 2000MPa grade ultra-high-strength steel described in the technical solution, comprising the following steps:
  • Step 1 pretreating the steel plate, the pretreatment step includes solution treatment to obtain a solution state steel plate;
  • Step 2 carry out room temperature rolling treatment on the solid solution steel plate pretreated in step 1;
  • Step 3 perform dual-phase zone warm rolling treatment on the steel plate after the room temperature rolling treatment in step 2;
  • Step 4 perform high temperature and short-time annealing treatment on the steel plate after the warm rolling treatment in step 3;
  • Step 5 Perform medium-temperature and long-time aging treatment on the steel sheet after the high-temperature and short-time annealing treatment in step 4.
  • the solution temperature ranges from 900°C to 1200°C
  • the solution time ranges from 1h to 6h
  • the cooling is water cooling.
  • the temperature of the room temperature rolling treatment in the step 2 is room temperature
  • the rolling amount is 55% to 70%
  • the rolling amount of each pass is ⁇ 5%.
  • the temperature of the dual-phase zone warm rolling treatment in the step 3 is 500°C to 700°C
  • the cooling method is air cooling
  • the rolling amount is 50°C. % ⁇ 70%
  • the rolling amount of each pass is less than 5%.
  • the high temperature and short time annealing temperature in step 4 is 600°C to 800°C
  • the holding time is 10s to 600s
  • the cooling method is air cooling.
  • the temperature of the medium-temperature long-aging treatment in the step 5 is 300°C-500°C
  • the holding time is 2h-5h
  • the cooling method is air cooling .
  • the high-uniform elongation 2000MPa grade ultra-high strength steel prepared by the invention is mechanically characterized in that the tensile yield strength ranges from 1800MPa to 2000MPa, the ultimate tensile strength ranges from 2000MPa to 2200MPa, and the tensile uniform elongation ranges from 10%. ⁇ 16%.
  • the reason for the ultra-high strength and excellent uniform elongation of the preparation method of the high uniform elongation 2000MPa grade ultra-high strength steel is: compared with the solution treated steel, the high uniform elongation 2000MPa grade ultra-high Preparation method of strength steel: After rolling in step 2 at room temperature, a large number of lamellar martensitic structures are obtained, and then an ultra-fine lamellar dual-phase structure is obtained by warm rolling in the dual-phase zone, so that the steel plate can obtain high strength.
  • the ultra-fine lamella structure is ensured, and at the same time, part of the martensite after the rolling treatment is restored to an austenite structure, thereby improving the plasticity of the steel sheet.
  • the medium temperature and long-time aging treatment is carried out to obtain a precipitate phase which is M 6 C carbide, and the size of the precipitate phase is 200 nm to 600 nm, which further improves the strength of the steel sheet.
  • the steel sheet finally obtained by the multi-stage rolling and multi-stage heat treatment has both high strength and excellent uniform elongation.
  • the invention effectively solves the engineering application bottleneck of the existing 2000MPa grade ultra-high strength steel with uniform elongation rate of less than 10%, and obtains 2000MPa grade ultrahigh strength steel with high uniform elongation through a simple and effective preparation method.
  • the present invention has the following advantages:
  • the present invention prepares 2000MPa grade ultra-high strength steel with uniform elongation >10% through the improvement of the composition improvement and the improvement of the blending process.
  • the preparation process of the present invention is simple and efficient, and only requires two-step rolling to realize ultra-high-strength steel with high strength and high uniform elongation.
  • Fig. 1 is the tensile engineering stress-strain curve diagram of the ultra-high strength steel prepared in Examples 1-2;
  • Fig. 2 is the transmission electron microscope (TEM) bright field photograph of the ultra-high strength steel prepared in Example 2;
  • Example 4 is a transmission electron microscope (TEM) bright field photograph of the ultra-high strength steel prepared in Example 4;
  • FIG. 5 is a transmission electron microscope (TEM) bright-field photograph of the ultra-high strength steel containing precipitates prepared in Example 5.
  • TEM transmission electron microscope
  • Example 1 0.3 8 8 4 2 1 0 0.1 0.1 Example 2 0.3 9 8 4 1 2 0 0.1 0.1 Example 3 0.4 8 8 4 1 1 1 0.1 0.1 Example 4 0.4 9 8 4 2 2 0.1 0.1 Example 5 0.4 9 8 4 0 0 2 0.1 0.1
  • Step 1 carry out solution treatment to the steel plate
  • the initial steel plate with a thickness of 10mm is selected for solution treatment, the solution temperature is 1100°C, the holding time is 2h, and the cooling method is water cooling.
  • Step 2 carry out room temperature rolling treatment on the solution-treated steel sheet obtained in step 1;
  • the steel sheet obtained in step 1 is subjected to room temperature rolling treatment to obtain a steel sheet with a thickness of 3 mm, the lower rolling amount of each pass is less than 5%, and the total cumulative lower rolling amount is about 70%.
  • Step 3 perform secondary warm rolling on the room temperature rolled steel sheet obtained in step 2;
  • the room temperature rolled steel sheet obtained in step 2 is then warmly rolled, the warm rolling temperature is 600 ° C, and the cooling method is air cooling, to obtain a steel sheet with a thickness of 1 mm, the rolling amount of each pass is less than 5%, and the total cumulative rolling amount is about 67%.
  • Step 4 perform high temperature short-time annealing treatment on the steel sheet obtained in step 3;
  • the steel sheet with a thickness of 1 mm obtained in step 3 is annealed at a high temperature for a short time in a box furnace, the annealing temperature is 650° C., the annealing time is 300 s, and then air-cooled to room temperature.
  • the dotted line in Fig. 1 is the engineering stress-strain curve of Example 1 in the rolling direction, and its mechanical characteristics are: the yield strength is 1800 MPa, the tensile strength is 2030 MPa, and the uniform elongation is 10.5%.
  • the solid line in Figure 1 is the engineering stress-strain curve of Example 2 in the rolling direction, and its mechanical characteristics are: the yield strength is 1788 MPa, the tensile strength is 2120 MPa, and the uniform elongation is 12.1%.
  • Figure 2 is a TEM bright-field image of the side surface of the sheet obtained after step 4 high-temperature short-time annealing in Example 2. Obvious austenite and martensite structures are observed, and the existence of austenite provides ductility of the material. At the same time, a large number of ultra-fine lamellar structures can be found, and the thickness of the lamellae is about 23 nm.
  • Step 1 carry out solution treatment to the steel plate
  • the initial steel plate with a thickness of 5mm is selected for solution treatment, the solution temperature is 1100°C, the holding time is 2h, and the cooling method is water cooling.
  • Step 2 carry out room temperature rolling treatment on the solution-treated steel sheet obtained in step 1;
  • the steel sheet obtained in step 1 is subjected to room temperature rolling treatment to obtain a steel sheet with a thickness of 2 mm.
  • Step 3 carry out secondary warm rolling on the room temperature rolled steel sheet obtained in step 2;
  • the room temperature rolled steel sheet obtained in step 2 is then warmly rolled, the warm rolling temperature is 650 ° C, and the cooling method is air cooling, to obtain a steel sheet with a thickness of 1 mm, the rolling amount of each pass is less than 5%, and the total cumulative rolling amount is about 50%.
  • Step 4 perform high temperature short-time annealing treatment on the steel sheet obtained in step 3;
  • the steel sheet with a thickness of 1 mm obtained in step 3 is annealed at a high temperature for a short time in a box furnace, the annealing temperature is 600° C., the annealing time is 300 s, and then air-cooled to room temperature.
  • the dotted line in Fig. 3 is the engineering stress-strain curve of Example 3 in the rolling direction, and its mechanical characteristics are: the yield strength is 1814 MPa, the tensile strength is 2017 MPa, and the uniform elongation is 12.1%.
  • the solid line in FIG. 3 is the engineering stress-strain curve of Example 4 in the rolling direction, and its mechanical characteristics are: the yield strength is 1710 MPa, the tensile strength is 2023 MPa, and the uniform elongation is 15.2%.
  • Figure 4 is a TEM bright-field image of the side of the obtained sheet after step 4 high-temperature and short-time annealing in Example 4. Also, obvious ultra-fine lamellar austenite and martensite structures can be observed, and the thickness of the lamella is about 20 nm. .
  • Example 4 The difference between this example and Example 4 is that the aging treatment is performed on the basis of the completion of Example 4 to obtain an aging phase.
  • Example 4 was subjected to aging treatment in a box furnace, the aging temperature was 450 °C, the aging time was 2.5 h, and then air-cooled to room temperature.
  • the dashed line in Fig. 3 is the engineering stress-strain curve in the rolling direction after aging in this example. Its mechanical characteristics are: the yield strength is 1812MPa, the tensile strength is 2169MPa, and the average elongation is 11.6%.
  • Figure 5 is a TEM bright field image of the side of the obtained plate after aging in this example. Compared with Figure 4 before aging, it is observed that the microstructure of martensite, austenite and ultra-fine lamella is well preserved, and there are obvious first Two-phase M 6 C carbides.
  • Example 1 1800 030 10.5
  • Example 2 1788 2120 12.1
  • Example 3 1814 2017 12.1
  • Example 4 1710 2023 15.2
  • Example 5 1812 2167 11.6

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Abstract

本发明公开一种高均匀伸长率2000MPa级超高强度钢及其制备方法，解决了现有2000MPa级钢均匀伸长率难达到10％的瓶颈，且制备过程复杂，效率低下的技术问题。所述高均匀伸长率2000MPa级超高强度钢中化学成分重量百分比为：C为0.3％～0.4％，Ni为8％～9％，Cr为6.5％～10.0％，Mo为3.0％～6.0％，Mn为0％～2％，Si为0％～2％，Cu为0％～2％，V为0.05％～0.15％，Nb为0.05％～0.15％，余量为Fe。本发明的高均匀伸长率2000MPa级超高强度钢制备方法，包括：对钢板进行预处理，所述预处理包括固溶处理；对步骤1处理的固溶态钢板进行室温轧制处理；对步骤2处理后的钢板进行温轧处理；对步骤3温轧处理后的钢板进行高温短时退火处理；对步骤4高温短时退火处理后的钢板进行中温长时时效处理。本发明具有抗拉强度＞2000MPa，均匀伸长率＞10％且制备效率高等优点。

Description

一种高均匀伸长率2000MPa级超高强度钢及其制备方法
本申请要求于2021年03月24日提交中国专利局、申请号为CN202110316837.7、发明名称为“一种高均匀伸长率2000MPa级超高强度钢及其制备方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及先进高强钢技术领域，具体涉及一种高均匀伸长率2000MPa级超高强度钢及其制备方法，该钢种具有优异的强度和塑性。
背景技术
获得高强度高塑性一体化的先进高强钢是钢铁研究始终追求的目标。具有高强度和高塑性的高性能钢的发展由它们在汽车、航空、航天和运输中的广泛结构应用驱动。例如，具有高强度的钢在汽车工业中可提供在碰撞保护方面的高乘客安全性、高重量减轻和节能潜力。但是，高强度钢也需要具有良好延性。例如，在汽车工业中用于制造复杂汽车部件的冷冲压技术需要具有良好延性的钢。
传统的先进高强钢的抗拉强度在1500～2000MPa，但是塑性往往达不到10％。例如中国专利公开号为：CN105568151A《一种铝增强马氏体时效钢及其制备方法》中公开的马氏体时效钢具有2000MPa的优异抗拉强度，但是高强度水平下的均匀伸长率不到5％，总伸长率不足10％，难以满足汽车等行业复杂零件的成型需要。
除了强塑性一体化的要求以外，高效率的制备工艺也是先进高强钢研究中至关重要的一环，例如中国专利公开号：CN109790611A《双相钢及其制造方法》公开了一种具有高强度同时也具有良好延性的先进高强钢，该专利中的双相钢的极限拉伸强度为2300MPa，且对应的总伸长率为16％，满足工业应用需要的强塑性要求，但是其制备过程复杂，需要轧制和退火交替进行，增加了制备该过程所需时间，制备工艺效率较低。
截至目前，先进高强钢研究的瓶颈仍在于：开发具有高强度和高塑性一体化的钢种以及相应的高效率制备工艺。
基于先进高强度钢的现状，有必要对其进行改进，以一种更高效的方式获得高强度且具有良好伸长率的钢。
发明内容
本发明针对钢在工程广泛应用中的制约因素，以及现有制备工艺的复杂性，提供一种高均匀伸长率2000MPa级超高强度钢及其制备方法。
本发明实现的技术方案如下所示：
本发明提供了一种高均匀伸长率2000MPa级超高强度钢，以重量百分比计，超高强度钢的化学成分为：
C为0.3％～0.4％，Ni为8％～9％，Cr为6.5％～10.0％，Mo为3.0％～6.0％，Mn为0％～2％，Si为0％～2％，Cu为0％～2％，V为0.05％～0.15％，Nb为0.05％～0.15％，余量为Fe。
本发明优选的高均匀伸长率2000MPa级超高强度钢，所述超高强度钢的化学成分为：
C为0.4％，Ni为8.0％，Cr为8.0％，Mo为4.0％，Mn为1.0％，Si为1.0％，Cu为2％，V为0.1％，Nb为0.1％，余量为Fe。
本发明优选的高均匀伸长率2000MPa级超高强度钢，所述超高强度钢中的超细片层厚度为10nm～200nm，所述钢板组织结构为马氏体和奥氏体组织，所述马氏体组织的体积含量(即体积分数)为60％～90％，所述奥氏体组织的体积含量(即体积分数)为10％～40％。
本发明优选的高均匀伸长率2000MPa级超高强度钢，所述超细片层厚度为20nm～50nm，所述马氏体组织的体积分数占比为70％～80％，奥氏体组织的体积含量为20％～30％。
本发明优选的所述高均匀伸长率2000MPa级超高强度钢的析出相为M 6C碳化物，所述析出相尺寸为200nm～600nm。
本发明通过成分改进，获得了一种马氏体和奥氏体双相的结构组织，且含有超细片层结构，其中，马氏体有利于提高钢的强度，而奥氏体为钢的高均匀伸长率提供贡献，而该超细片层结构的厚度较小，利于进一步提高强度。
本发明提供了上述技术方案所述高均匀伸长率2000MPa级超高强度 钢的制备方法，包括如下步骤：
步骤1：对钢板进行预处理，所述预处理步骤包括固溶处理得到固溶态钢板；
步骤2：对步骤1预处理的固溶态钢板进行室温轧制处理；
步骤3：对步骤2室温轧制处理后的钢板进行双相区温轧处理；
步骤4：对步骤3温轧处理后的钢板进行高温短时退火处理；
步骤5：对步骤4高温短时退火处理后的钢板进行中温长时时效处理。
本发明优选的高均匀伸长率2000MPa级超高强度钢的制备方法，所述步骤1中的固溶处理，固溶温度范围为900℃～1200℃，固溶时间范围为1h～6h，冷却方式为水冷。
本发明优选的高均匀伸长率2000MPa级超高强度钢的制备方法，所述步骤2中的室温轧制处理的温度为室温，轧制量为55％～70％，每道次下轧量＜5％。
本发明优选的高均匀伸长率2000MPa级超高强度钢的制备方法，所述步骤3中的双相区温轧处理的温度为500℃～700℃，冷却方式为空冷，轧制量为50％～70％，每道次下轧量＜5％。
本发明优选的高均匀伸长率2000MPa级超高强度钢的制备方法，所述步骤4中的高温短时退火温度为600℃～800℃，保温时间为10s～600s，冷却方式为空冷。
本发明优选的高均匀伸长率2000MPa级超高强度钢的制备方法，所述步骤5中的中温长时时效处理的温度为300℃～500℃，保温时间为2h～5h，冷却方式为空冷。
本发明制备的高均匀伸长率2000MPa级超高强度钢，力学特征在于其拉伸屈服强度范围为1800MPa～2000MPa，极限拉伸强度范围为2000MPa～2200MPa，拉伸均匀伸长率范围为10％～16％。
所述高均匀伸长率2000MPa级超高强度钢的制备方法的超高强度和极优均匀伸长率的原因在于：与固溶处理钢相比，所述高均匀伸长率2000MPa级超高强度钢的制备方法轧制经步骤2室温轧制后获得大量片层马氏体组织，之后通过双相区温轧处理得到超细片层双相组织结构，进而使得所述钢板获得高强度。进一步通过高温短时退火处理，保证超细片 层结构的同时使得轧制处理后的部分马氏体回复成奥氏体结构，提升所述钢板的塑性。再进行中温长时时效处理，获得析出相为M 6C碳化物，所述析出相尺寸为200nm～600nm，进一步提升所述钢板的强度。所述多级轧制和多级热处理最终得到的钢板既具有高强度，又具备极优均匀伸长率。本发明有效解决了现有2000MPa级超高强钢均匀伸长率＜10％的工程应用瓶颈，通过简单有效的制备方式获得高均匀伸长率2000MPa级超高强度钢。
与现有技术相比，本发明具有如下优点：
1、本发明通过成分改进配合工艺的改进，制备出了均匀伸长率＞10％的2000MPa级超高强度钢。
2、本发明的制备工艺简单高效，仅需要两步轧制就可以实现高强高均匀延长率的超高强度钢。
附图说明
此处所说明的附图用来提供对本发明实施例的进一步理解，构成本申请的一部分，并不构成对本发明实施例的限定。在附图中：
图1是实施例1～2所制备的超高强度钢的拉伸工程应力-应变曲线图；
图2是实施例2所制备的超高强度钢的透射电子显微镜(TEM)明场照片；
图3是实施例3～5所制备的超高强度钢的拉伸工程应力-应变曲线图；
图4是实施例4所制备的超高强度钢的透射电子显微镜(TEM)明场照片；
图5是实施例5所制备的含有析出相超高强度钢的透射电子显微镜(TEM)明场照片。
具体实施方式
下面通过实施例和附图，对本发明做出进一步详细说明。这些实施例仅是对本发明的目的、技术方案和有益效果进行解释，对本发明的范围没有任何限制。
本发明实施例的化学元素成分及重量占比如表1所示：
表1 实施例钢的化学成分
编号 C Ni Cr Mo Mn Si Cu V Nb
实施例1 0.3 8 8 4 2 1 0 0.1 0.1
实施例2 0.3 9 8 4 1 2 0 0.1 0.1
实施例3 0.4 8 8 4 1 1 1 0.1 0.1
实施例4 0.4 9 8 4 2 2 2 0.1 0.1
实施例5 0.4 9 8 4 0 0 2 0.1 0.1
实施例1和实施例2
高均匀伸长率2000MPa级超高强度钢的制备方法，具体制备步骤流程如下：
步骤1：对所述钢板进行固溶处理；
选用厚度为10mm的初始钢板进行固溶处理，固溶温度为1100℃，保温时间为2h，冷却方式为水冷。
步骤2：对步骤1所得的固溶处理钢板进行室温轧制处理；
将步骤1所得钢板进行室温轧制处理得到厚度为3mm的钢板，每道次下轧量＜5％，总累积下轧量约为70％。
步骤3：对步骤2所得室温轧制钢板进行二次温轧；
对步骤2所得的室温轧制钢板再进行温轧，温轧温度为600℃，冷却方式为空冷，得到厚度为1mm的钢板，每道次下轧量＜5％，总累积下轧量约为67％。
步骤4：对步骤3所得钢板进行高温短时退火处理；
将步骤3所得厚度1mm的钢板在箱式炉中进行高温短时退火，退火温度为650℃，退火时间为300s，后空冷至室温。
图1中的虚线为实施例1在轧制方向上的工程应力应变曲线，其力学特征为：屈服强度为1800MPa，抗拉强度为2030MPa，均匀伸长率为10.5％。
图1中的实线为实施例2在轧制方向上的工程应力应变曲线，其力学特征为：屈服强度为1788MPa，抗拉强度为2120MPa，均匀伸长率为12.1％。
图2是实施例2完成步骤4高温短时退火之后所得板材侧面的TEM明场像照片，观察到明显的奥氏体和马氏体组织，奥氏体的存在，为材料的延展性提供了保障，同时还可以发现大量的超细片层组织结构，片层厚度约为23nm。
实施例3、实施例4
步骤1：对所述钢板进行固溶处理；
选用厚度为5mm的初始钢板进行固溶处理，固溶温度为1100℃，保温时间为2h，冷却方式为水冷。
步骤2：对步骤1所得的固溶处理钢板进行室温轧制处理；
将步骤1所得钢板进行室温轧制处理得到厚度为2mm的钢板，每道次下轧量＜5％，总累积下轧量约为60％。
步骤3：对步骤2所得室温轧制钢板进行二次温轧；
对步骤2所得的室温轧制钢板再进行温轧，温轧温度为650℃，冷却方式为空冷，得到厚度为1mm的钢板，每道次下轧量＜5％，总累积下轧量约为50％。
步骤4：对步骤3所得钢板进行高温短时退火处理；
将步骤3所得厚度为1mm的钢板在箱式炉中进行高温短时退火，退火温度为600℃，退火时间为300s，后空冷至室温。
图3中的点虚线为实施例3在轧制方向上的工程应力应变曲线，其力学特征为：屈服强度为1814MPa，抗拉强度为2017MPa，均匀伸长率为12.1％。
图3中的实线为实施例4在轧制方向上的工程应力应变曲线，其力学特征为：屈服强度为1710MPa，抗拉强度为2023MPa，均匀伸长率为15.2％。
图4是实施例4完成步骤4高温短时退火之后所得板材侧面的TEM明场像照片，同样可以观察到明显的超细片层奥氏体和马氏体组织，其片层厚度约为20nm。
实施例5
本实施例与实施例4的区别在于，在实施例4完成的基础上进行时效处理获得时效相。将实施例4在箱式炉中进行时效处理，时效温度为 450℃，时效时间为2.5h，后空冷至室温。
图3中的虚线是本实施案例完成时效之后在轧制方向上的工程应力应变曲线，其力学特征为：屈服强度为1812MPa，抗拉强度为2169MPa，均匀伸长率为11.6％。
图5是本实施案例完成时效之后所得板材侧面的TEM明场像照片，观察与图4时效前相比，马氏体和奥氏体以及超细片层组织结构保留完好，同时存在明显的第二相M 6C碳化物。
将上述实施例的性能检测结果汇总于下表2中。
表2 不同实施例的力学性能检测结果
编号 屈服强度(MPa) 抗拉强度(MPa) 均匀伸长率(％)
实施例1 1800 030 10.5
实施例2 1788 2120 12.1
实施例3 1814 2017 12.1
实施例4 1710 2023 15.2
实施例5 1812 2167 11.6
通过观察图2和图4的微观组织结构发现，本发明通过二次轧制后高温短时退火处理，材料内部马氏体与奥氏体并存，同时整体呈现明显的超细片层组织结构，从而使得本发明能在保证高强度的同时，还具有优异的塑性。而对比图4和图5，明显发现时效处理后存在析出相，进一步改善材料的强度。
以上实施例的说明只是用于帮助理解本发明的方法及其核心思想。应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以对本发明进行若干改进和修饰，这些改进和修饰也落入本发明权利要求的保护范围内。对这些实施例的多种修改对本领域的专业技术人员来说是显而易见的，本文中所定义的一般原理可以在不脱离本发明的精神或范围的情况下在其它实施例中实现。因此，本发明将不会被限制于本文所示的这些实施例，而是要符合与本文所公开的原理和新颖特点相一致的最宽的范围。

Claims (12)

  1. 一种高均匀伸长率2000MPa级超高强度钢，以重量百分比计，超高强度钢的化学成分为：
    C为0.3％～0.4％，Ni为8％～9％，Cr为6.5％～10.0％，Mo为3.0％～6.0％，Mn为0％～2％，Si为0％～2％，Cu为0％～2％，V为0.05％～0.15％，Nb为0.05％～0.15％，余量为Fe。
  2. 根据权利要求1所述的高均匀伸长率2000MPa级超高强度钢，其特征在于，所述超高强度钢的化学成分为：
    C为0.4％，Ni为8.0％，Cr为8.0％，Mo为4.0％，Mn为1.0％，Si为1.0％，Cu为2％，V为0.1％，Nb为0.1％，余量为Fe。
  3. 根据权利要求1或2所述的高均匀伸长率2000MPa级超高强度钢，其特征在于，所述超高强度钢中的超细片层厚度为10nm～200nm，所述钢板组织结构为马氏体和奥氏体组织，所述马氏体组织的体积分数为60％～90％，所述奥氏体组织的体积分数为10％～40％。
  4. 根据权利要求3所述的高均匀伸长率2000MPa级超高强度钢，其特征在于，所述超细片层的厚度为20nm～50nm，所述马氏体组织的体积分数占比为70％～80％，奥氏体组织的体积含量为20％～30％。
  5. 一种如权利要求1～4任一项所述的高均匀伸长率2000MPa级超高强度钢，其特征在于，所述高均匀伸长率2000MPa级超高强度钢的析出相为M 6C碳化物，所述析出相尺寸为200nm～600nm。
  6. 一种如权利要求1～4任一项所述的高均匀伸长率2000MPa级超高强度钢，其特征在于，所述高均匀伸长率2000MPa级超高强度钢的拉伸屈服强度为1800MPa～2000MPa，极限拉伸强度为2000MPa～2200MPa，拉伸均匀伸长率为10％～16％。
  7. 一种如权利要求1～6任一项所述的高均匀伸长率2000MPa级超高强度钢的制备方法，其特征在于，包括如下步骤：
    步骤1：对钢板进行预处理，所述预处理步骤包括固溶处理得到固溶态钢板；
    步骤2：对步骤1预处理的固溶态钢板进行室温轧制处理；
    步骤3：对步骤2室温轧制处理后的钢板进行双相区温轧处理；
    步骤4：对步骤3温轧处理后的钢板进行高温短时退火处理；
    步骤5：对步骤4高温短时退火处理后的钢板进行中温长时时效处理。
  8. 根据权利要求7所述的制备方法，其特征在于，所述步骤1中的固溶处理，固溶处理的温度为900℃～1200℃，固溶处理的时间为1h～6h，冷却方式为水冷。
  9. 根据权利要求7所述的高均匀伸长率2000MPa级超高强度钢的制备方法，其特征在于，所述步骤2中的室温轧制处理的温度为室温，轧制量为55％～70％，每道次下轧量＜5％。
  10. 根据权利要求7所述的制备方法，其特征在于，所述步骤3中的双相区温轧处理的温度为500℃～700℃，冷却方式为空冷，轧制量为50％～70％，每道次下轧量＜5％。
  11. 根据权利要求7所述的制备方法，其特征在于，所述步骤4中的高温短时退火处理的温度为600℃～800℃，保温时间为10s～600s，冷却方式为空冷。
  12. 根据权利要求7所述的制备方法，其特征在于，所述步骤5中的中温长时时效处理的温度为300℃～500℃，保温时间为2h～5h，冷却方式为空冷。
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