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CN-117867410-B - 785 MPa-grade steel plate with ultralow-temperature toughness and preparation method thereof

CN117867410BCN 117867410 BCN117867410 BCN 117867410BCN-117867410-B

Abstract

The invention discloses a 785 MPa-grade steel plate with ultralow temperature toughness and a preparation method thereof, belongs to the technical field of steel materials, and solves the contradiction problem that the toughness level of ultrahigh-strength steel is insufficient and the nickel content is excessively matched in the prior art. The 785 MPa-grade steel plate with the ultralow-temperature toughness comprises the following components in percentage by mass: c:0.08 to 0.15 percent, si:0.02% -0.18%, mn:0.60% -1.63%, P: less than or equal to 0.010 percent, S: less than or equal to 0.004 percent, cr:0.35 to 0.95 percent, mo:0.32 to 0.60 percent of Ni:3.15 to 4.35 percent, cu:0.75 to 1.85 percent, V:0.04 to 0.12 percent, nb:0.008 to 0.035 percent, al:0.017 to 0.036 percent, ti:0.008 to 0.022 percent, and the balance of Fe and other unavoidable impurities. The 785 MPa-grade steel plate with ultralow temperature toughness is excellent in strength and low temperature toughness.

Inventors

  • PAN TAO
  • LIANG FENGRUI
  • ZHOU NAIPENG
  • CHEN JIAN
  • XUE DONGMEI
  • YANG CAIFU
  • LI JIAN
  • SHI ZHONGRAN
  • CHAI XIYANG
  • WANG TIANQI
  • LI LI
  • LUO XIAOBING
  • CHAI FENG
  • CHEN XUEHUI

Assignees

  • 钢铁研究总院有限公司
  • 中联先进钢铁材料技术有限责任公司

Dates

Publication Date
20260512
Application Date
20240129

Claims (10)

  1. 1. The 785 MPa-grade steel plate with the ultralow temperature toughness is characterized by comprising the following components in percentage by mass of ：C：0.08%~0.15%,Si：0.06%~0.12%,Mn：0.60%~1.63%,P：≤0.010%,S：≤0.004%,Cr：0.35%~0.95%,Mo：0.32%~0.60%,Ni：3.15%~4.35%,Cu：0.75%~1.85%,V：0.04~0.11%,Nb：0.008%~0.035%,Al：0.017%~0.036%,Ti：0.008%~0.012%, balance Fe and other unavoidable impurities; The content of Ni, mn and Cu in the 785 MPa-level steel plate with ultralow temperature toughness and the thickness t of the steel plate also meet the requirements that 100Ni+67Cu+50Mn is more than or equal to 3.55+0.12t 1/2 , wherein the Ni, mn and Cu refer to the mass percent of elements, and t is calculated in mm; Ni+Cu >4.2%, wherein Ni and Cu refer to mass percent of elements; The matrix structure of the full section of the 785MPa grade steel plate with ultralow temperature toughness comprises a tempered martensite and lath bainite structure, the effective grain size is 1.75-2.35 mu m, the structure contains a small amount of reverse transformation austenite, the volume percentage of the reverse transformation austenite is 4-15%, the reverse transformation austenite is enriched with high-concentration Ni, mn and Cu, the Ni average content of an element enrichment region is 1.6-2.5 times of the matrix content, the Mn content is 1.5-2.8 times of the matrix content, the Cu content is 2.0-3.0 times of the matrix content, the structure comprises a dispersed precipitation phase, the precipitation phase comprises TiN, nb (CN) and AlN, the TiN particle distribution is 12-100 nm, the Nb (CN) particle distribution is 5-50 nm, the AlN particle distribution is 3-15 nm, the TiN precipitate content is 0.020%, the AlN precipitate content is 0.011-0.016%, and the Nb (CN) precipitate content is 0.032-0.045%; the low-temperature impact energy of-120 ℃ of 785MPa grade steel plate with ultralow temperature toughness is more than 150J, and the toughness and brittleness conversion temperature of 50% of the fiber rate of the impact section of the steel plate is less than-120 ℃.
  2. 2. The 785 MPa-level steel sheet with ultra-low temperature toughness according to claim 1, wherein the content of Mn, cr, mo in the 785 MPa-level steel sheet with ultra-low temperature toughness and the thickness t of the steel sheet satisfy 333mn+216cr+300mo >4.45+1.0 (t/50) +0.2 (t/50) 2 , wherein Mn, cr, mo refer to mass percentage of elements, and t is in mm.
  3. 3. The 785 MPa-level steel sheet with ultra-low temperature toughness according to claim 1, wherein the components of the 785 MPa-level steel sheet with ultra-low temperature toughness comprise ：C：0.09%~0.12%,Si：0.06%~0.12%,Mn：0.9%~1.5%,P：≤0.006%,S：≤0.002%,Cr：0.4%~0.9%,Mo：0.40%~0.55%,Ni：3.3%~4.05%,Cu：0.9%~1.8%,V：0.04~0.11%,Nb：0.02%~0.03%,Al：0.017%~0.03%,Ti：0.008%~0.012%, balance Fe and other unavoidable impurities in mass percent.
  4. 4. The 785 MPa-level steel sheet with ultra-low temperature toughness according to claim 1, wherein the components of the 785 MPa-level steel sheet with ultra-low temperature toughness comprise ：C：0.09%,Si：0.06%,Mn：0.95%,P：≤0.006%,S：≤0.002%,Cr：0.45%,Mo：0.42%,Ni：3.37%,Cu：0.91%,V：0.043%,Nb：0.024%,Al：0.027%,Ti：0.011%, balance Fe and other unavoidable impurities in mass percent.
  5. 5. The 785 MPa-level steel sheet with ultra-low temperature toughness according to claim 1, wherein the components of the 785 MPa-level steel sheet with ultra-low temperature toughness comprise ：C：0.10%,Si：0.10%,Mn：1.17%,P：≤0.006%,S：≤0.002%,Cr：0.56%,Mo：0.49%,Ni：3.57%,Cu：1.26%,V：0.082%,Nb：0.029%,Al：0.022%,Ti：0.009%, balance Fe and other unavoidable impurities in mass percent.
  6. 6. The 785 MPa-level steel sheet with ultra-low temperature toughness according to claim 1, wherein the components of the 785 MPa-level steel sheet with ultra-low temperature toughness comprise ：C：0.12%,Si：0.12%,Mn：1.48%,P：≤0.006%,S：≤0.002%,Cr：0.85%,Mo：0.55%,Ni：4.03%,Cu：1.68%,V：0.11%,Nb：0.021%,Al：0.017%,Ti：0.012%, balance Fe and other unavoidable impurities in mass percent.
  7. 7. The 785 MPa-level steel sheet with ultra-low temperature toughness according to claim 1, wherein the effective grain size is 1.85-2.35 μm.
  8. 8. The 785 MPa-grade steel sheet with ultra-low temperature toughness according to claim 1, wherein the volume percentage of the reverse transformed austenite is 4.5% -15%.
  9. 9. A method for producing 785 MPa-grade steel sheet having ultra-low temperature toughness according to any one of claims 1 to 8, comprising the steps of: Step 1, homogenizing a steel billet; Step 2, adopting two-stage control rolling; step 3, the rolled steel plate is put into water to be cooled in an accelerated way; And 4, carrying out heat treatment on the steel plate, wherein the heat treatment comprises quenching and tempering.
  10. 10. The preparation method according to claim 9, wherein in the step 4, the quenching comprises one-time quenching or one-time quenching plus two-phase zone quenching, and the one-time quenching temperature is 50-150 ℃ higher than Ac 3.

Description

785 MPa-grade steel plate with ultralow-temperature toughness and preparation method thereof Technical Field The invention relates to the technical field of steel materials, in particular to a 785 MPa-grade steel plate with ultralow-temperature toughness and a preparation method thereof. Background The requirement of energy gas promotes the rapid development of low-temperature engineering, and more steel materials for service in low-temperature and ultralow-temperature environments are required. The low-temperature toughness is one of key technical indexes of low-temperature steel. Nickel-containing low-temperature steel is the most commonly used low-temperature steel, the service temperature of the steel is obviously reduced along with the increase of Ni content, and how to enable the steel to have more excellent ultralow-temperature toughness and higher strength under the condition of using equivalent or lower nickel content in consideration of the precious nickel resource, so that the steel has better cost performance and structural weight reduction effect under the low-temperature service environment and becomes the problem to be solved urgently. Disclosure of Invention In view of the above, the invention aims to provide a 785 MPa-grade steel plate with ultralow temperature toughness and a preparation method thereof, which are used for solving the contradiction problem that the toughness level of the existing ultrahigh-strength steel is insufficient and the nickel content is excessively matched. The aim of the invention is mainly realized by the following technical scheme: On one hand, the invention provides a 785 MPa-grade steel plate with ultralow temperature toughness, and the 785 MPa-grade steel plate with ultralow temperature toughness comprises ：C：0.08％～0.15％,Si：0.02％～0.18％,Mn：0.60％～1.63％,P：≤0.010％,S：≤0.004％,Cr：0.35％～0.95％,Mo：0.32％～0.60％,Ni：3.15％～4.35％,Cu：0.75％～1.85％,V：0.04～0.12％,Nb：0.008％～0.035％,Al：0.017％～0.036％,Ti：0.008％～0.022％, parts by mass of Fe and other unavoidable impurities as the rest. Furthermore, the contents of Ni, mn and Cu in the 785 MPa-level steel plate with ultralow temperature toughness and the thickness t of the steel plate also meet the conditions that 100Ni+67Cu+50Mn is more than or equal to 3.55+0.12t 1/2, wherein the Ni, mn and Cu refer to the mass percent of elements, and t is calculated in mm. Further, in the 785 MPa-grade steel plate with ultralow temperature toughness, ni+Cu is more than 4.2%, wherein Ni and Cu refer to the mass percentage of elements. Further, the thickness t of Mn, cr and Mo in the 785 MPa-grade steel plate with ultralow temperature toughness and the steel plate meet the conditions that 333Mn+216Cr+300Mo >4.45+1.0 (t/50) +0.2 (t/50) 2, wherein Mn, cr and Mo refer to the mass percent of elements, and t is expressed in mm. Further, the 785 MPa-grade steel plate with ultralow temperature toughness comprises the following components in percentage by mass, and the balance of ：C：0.09％～0.12％,Si：0.03％～0.15％,Mn：0.9％～1.5％,P：≤0.006％,S：≤0.002％,Cr：0.4％～0.9％,Mo：0.40％～0.55％,Ni：3.3％～4.05％,Cu：0.9％～1.8％,V：0.04～0.12％,Nb：0.02％～0.03％,Al：0.017％～0.03％,Ti：0.008％～0.02％, is Fe and other unavoidable impurities. Further, the matrix structure of the full section of the 785MPa grade steel plate with ultralow temperature toughness comprises tempered martensite and lath bainite, and the effective grain size is 1.75-2.35 mu m. Furthermore, the microstructure of the 785 MPa-grade steel plate with ultralow temperature toughness contains a small amount of reverse transformation austenite. Further, the volume percentage of the reverse transformation austenite is 4% -15%. The invention also provides a preparation method of the 785 MPa-grade steel plate with ultralow-temperature toughness, which comprises the following steps: Step 1, homogenizing a steel billet; Step 2, adopting two-stage control rolling; step 3, the rolled steel plate is put into water to be cooled in an accelerated way; And 4, carrying out heat treatment on the steel plate, wherein the heat treatment comprises quenching and tempering. In the step 4, the quenching comprises one-time quenching or one-time quenching and two-phase zone quenching, wherein the one-time quenching temperature is 50-150 ℃ higher than Ac 3. Compared with the prior art, the invention has the following beneficial effects: a) The 785MPa grade steel plate with ultralow temperature toughness provided by the invention adopts the austenitic elements such as Ni, mn, cu and the like to be matched with the content of C on the basis of taking nickel as a main toughening element, provides austenitizing stability chemical factors, lays a raw material foundation for obtaining reverse transformation austenite with beneficial quantity and distribution, discovers the element equivalent relation of Ni, mn and Cu, plays an important role in maintaining the austenite stabilization in different thickness ranges, and the minimum inequality of the Ni, mn and Cu is an im