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WO2022022047A1 - 一种低温环境下使用的低屈强比粒状贝氏体高强钢板及其制造方法 - Google Patents

一种低温环境下使用的低屈强比粒状贝氏体高强钢板及其制造方法 Download PDF

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WO2022022047A1
WO2022022047A1 PCT/CN2021/097027 CN2021097027W WO2022022047A1 WO 2022022047 A1 WO2022022047 A1 WO 2022022047A1 CN 2021097027 W CN2021097027 W CN 2021097027W WO 2022022047 A1 WO2022022047 A1 WO 2022022047A1
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low
strength
steel plate
rolling
continuous casting
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PCT/CN2021/097027
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English (en)
French (fr)
Inventor
孙宪进
李国忠
许晓红
白云
苗丕峰
林涛
诸建阳
许峰
石艾来
周海燕
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江阴兴澄特种钢铁有限公司
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Publication of WO2022022047A1 publication Critical patent/WO2022022047A1/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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing 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
    • 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
    • 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
    • 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
    • C22C38/06—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
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite

Definitions

  • the invention belongs to the technical field of metallurgy, and relates to a granular bainite high-strength steel sheet used in a low temperature environment and a manufacturing method thereof.
  • yield-strength ratio is an indispensable requirement for high-performance steels.
  • Many pipelines, high-rise buildings, and bridge steels have requirements for yield-strength ratio in order to improve the safety factor of materials.
  • the yield-to-strength ratio is getting higher and higher, and the materials with low yield-to-strength ratio generally have lower strength. How to solve the contradiction between the yield-to-strength ratio and the material strength is the exploration of modern high-performance steel a point.
  • the problem of yield-strength ratio of high-strength steel is mainly ensured by generating a two-phase structure.
  • the soft-phase structure can ensure that the yield strength of the steel plate is low, and the hard-phase structure can improve the tensile strength of the steel plate, so that the steel plate has high strength. can still maintain a low yield ratio.
  • Patent Notice No. CN107099750A describes a manufacturing method of Q630GJ high-strength steel plate, the structure is tempered ferrite + martensite + bainite, and the yield ratio is less than or equal to 0.83 through the multiphase structure; Patent Notice No.
  • CN102433507A provides a low-yield
  • the strength ratio is easy to weld high-strength steel plates, the structure is ferrite + bainite, and the yield ratio is less than or equal to 0.7. From the production process point of view, it is divided into two categories, one is TMCP controlled rolling and controlled cooling to obtain a two-phase structure, and the other is a two-phase structure obtained by sub-temperature quenching + tempering.
  • the technical problem to be solved by the present invention is to provide a granular bainitic high-strength steel sheet for use in a low-temperature environment and a manufacturing method thereof for the above-mentioned prior art, which can be used under the condition of -60° C. At the same time, the yield-strength ratio is less than or equal to 0.70.
  • the technical scheme adopted by the present invention to solve the above problems is: a granular bainite high-strength steel sheet used in a low temperature environment, the chemical composition (wt.%) is C 0.05-0.11, Si 0.20-0.50, Mn 1.00-1.40, Al 0.02-0.04, Nb 0.01-0.03, Ti 0.01-0.03, Ni 0.80-1.30, Mo 0.30-0.60, Cr 0.30-0.60, B 0.0008-0.0020, S ⁇ 0.003, P ⁇ 0.015, the balance is Fe and unavoidable impurities.
  • C The key elements in the steel that affect the phase transformation curve and microstructure type have a significant impact on the key phase transition points and microstructure transition temperature of the material, and at the same time contribute significantly to the strength. Too high content will cause the continuous casting slab to appear at the center of the thickness direction. Serious segregation zone, thus affecting the microstructure transformation and uniformity of microstructure and properties of the steel plate. In quenched and tempered steel, carbon can improve the hardenability of the steel sheet, but for bainitic steel, too high hardenability is not desired, so comprehensively considered, the C content is in the range of 0.05-0.11%.
  • Si the main reducing agent and deoxidizer, if too high, it will adversely affect the surface quality, toughness and welding performance.
  • the selection range of Si content in the present invention is 0.20-0.50%.
  • Mn The main alloying element that affects strength, hardenability and weldability, improves the strength of steel in the form of solid solution strengthening, and makes up for the deficiency caused by the reduction of C; when the Mn content is less than 0.8%, it cannot play the role of solid solution strengthening. If it is too high, it will increase the carbon equivalent and the crack sensitivity coefficient of the steel, which will adversely affect the weldability of the steel.
  • the patent of the present invention focuses on balancing the role of Mn in hardenability and strengthening, and at the same time considering the impact on low temperature toughness, from the perspective of being beneficial to obtaining granular bainite, the selection range of Mn content in the present invention is 1.00-1.40%;
  • Al The main deoxidizing element, which has a certain effect of grain refinement.
  • the selected range of the Al content in the present invention is 0.02-0.04%.
  • Nb The main grain refining element, which can significantly refine austenite grains through pinning and precipitation strengthening during rolling, increase the temperature in the unrecrystallized zone, and is conducive to grain refinement, strength and toughness. improve. Taking comprehensive consideration, the selection range of the Nb content in the present invention is 0.02-0.04%.
  • Ti strengthens and refines grains by precipitation, and is added together with Nb-containing steel to improve the thermoplasticity of steel at high temperature and reduce microcracks. Therefore, the selected range of Ti content in the present invention is 0.01-0.03%.
  • Ni It can increase the strength and hardness of the steel, improve the toughness, and at the same time, it can suppress the precipitation of carbides in the bainite, and reduce the driving force of bainite transformation.
  • the Ni content is too high, iron oxide scale with high viscosity will be produced during the heating process of the continuous casting slab, which will affect the surface quality of the steel plate.
  • the strength of granular bainite structure is relatively low, and at the same time, in order to meet the requirement of toughness under low temperature conditions, the selection range of Ni content is 0.80-1.30%.
  • Cr It can improve the hardenability and strength of steel, but excessive addition will adversely affect the low-temperature impact toughness and weldability of steel.
  • the present invention focuses on balancing the effect of Cr on bainite transformation, hardenability improvement and strength contribution. Considering comprehensively, the selection range of Cr content is 0.30-0.60%.
  • Mo It can significantly improve the hardenability and thermal strength of the steel. Adding an appropriate amount of Mo during the quenching and tempering treatment can overcome the temper brittleness of the steel, improve the tempering stability of the steel, and thus improve the impact toughness of the steel. At the same time, Mo can delay the transformation of ferrite to pearlite and expand the bainite transformation range.
  • the selection range of Mo content in the present invention is 0.30-0.60%.
  • B The most significant element for improving hardenability, and if it is too high, weldability and low-temperature toughness are adversely affected.
  • the selection range of the B content in the present invention is 0.0008-0.0020%.
  • S element the main impurity element, which has a bad influence on the low temperature toughness, comprehensively considered, S ⁇ 0.003%; P ⁇ 0.015%.
  • the present invention also provides a method for manufacturing a granular bainite high-strength steel sheet used in a low temperature environment, comprising the following process steps:
  • the smelting raw materials are sequentially processed by KR molten iron desulfurization pretreatment, converter top and bottom blowing, LF refining, RH refining and continuous casting to form a continuous casting billet with a thickness of 150-450mm, and the continuous casting billet is covered and slowly cooled , the slow cooling time is 96 hours.
  • the first stage is rough rolling stage, the rolling temperature is 1050-1180 °C, and the average reduction rate of a single pass is ⁇ 15%; the second stage is finishing rolling stage, and the rolling temperature is 900 -930°C, cumulative pass reduction rate ⁇ 40%; hot straightening after rolling.
  • Quenching + high temperature tempering treatment is carried out on the slow-cooled steel plate. Both quenching and tempering are carried out in a continuous furnace.
  • the quenching temperature is 920-930°C, and the furnace time is 1.8-2.2min/mm; 730-740°C, the furnace time is 3.0-4.0min/mm, and it is air-cooled after being released from the furnace.
  • the invention can obtain stable granular bainite structure under high temperature and isothermal conditions through reasonable composition design and process matching.
  • the formation temperature range of this structure is higher than the upper bainite transformation temperature but lower than the pearlite transformation temperature.
  • the austenite is transformed into the bulk ferrite structure, and then on the bulk ferrite matrix, the carbon-rich residual Austenite transforms into granular bainite structure, and the grain size is above 10.
  • the steel plate produced by the above method has a yield strength ⁇ 500MPa, a tensile strength ⁇ 700MPa, a yield-strength ratio ⁇ 0.70, and the Charpy impact energy at 1/4 thickness and 1/2 thickness of the steel plate at -60°C is both ⁇ 100J. Use in a low temperature environment of -60°C.
  • composition system that can obtain stable granular bainite through heat treatment process is designed to meet the requirements of process control and final performance.
  • the steel has the characteristics of good strength, toughness and low yield ratio, and can be used under the condition of -60°C.
  • the biggest advantage of the invention is high stability. Since the dual-phase structure needs to control the ratio between different structures, the yield-strength ratio is often in a fluctuating state, and the uniformity of the structure is poor. , the single-phase granular bainite structure has high stability, which greatly improves the performance stability.
  • FIG. 1 is a photo of the microstructure of the steel sheet of Example 1 of the present invention.
  • Fig. 2 is a microstructure photograph of the steel sheet of Example 2 of the present invention.
  • KR molten iron pretreatment converter smelting—LF refining—RH/VD vacuum degassing—370mm continuous casting—continuous casting billet slow cooling for ⁇ 96 hours—cast billet heating—high pressure water Descale - rolling - slow cooling of steel plate stack - quenching treatment - tempering treatment and other process steps to manufacture granular bainite high-strength steel plates.
  • the concrete process of the above-mentioned stage is: obtain molten steel that meets the composition design requirements through KR molten iron pretreatment, converter smelting, LF and RH refining, then obtain 370mm thick continuous casting slab steel plate through slab continuous casting, slow cooling for 96 hours (Example 1 and 2).
  • the 370mm thick continuous casting billet is heated to 1170-1250 °C, and the temperature is kept for 185-190 minutes (cases 1 and 2).
  • Example 2 After the continuous casting billet is released, high-pressure water is used for descaling; then two-stage rolling is performed, and the first stage rolling temperature is 1080 °C (Example 1) and 1120°C (Example 2), the thickness of the intermediate blank is 170mm (Example 1) and 180mm (Example 2), and the average reduction rate of a single pass is 18% (Example 1) and 17% (Example 2).
  • the rolling temperature of the second stage is 900°C (Example 1) and 930°C (Example 2)
  • the cumulative pass reduction rate is 58.8% (Example 1) and 44% (Example 2)
  • rolling Steel sheets with thicknesses of 70 mm (Example 1) and 100 mm (Example 2) were hot-straightened after rolling, and the slow cooling time of the steel sheet stack was ⁇ 48 hours (Examples 1 and 2).
  • Example 1 The heating temperature was 920° C., the furnace time was 1.8 min/mm, and the quenching machine was used for water quenching.
  • Example 2 The heating temperature was 930° C., the furnace time was 1.8 min/mm, and the quenching machine was used for water quenching.
  • the quenched steel sheet is tempered in a continuous furnace.
  • Example 1 heating temperature 740°C, furnace time 3.5min/mm
  • Example 2 heating temperature 740°C, furnace time 4.0min/mm.
  • the present invention also includes other embodiments, and all technical solutions formed by equivalent transformation or equivalent replacement shall fall within the protection scope of the claims of the present invention.

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  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
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Abstract

本发明涉及一种低温环境下使用的粒状贝氏体高强钢板及制造方法，化学成分(wt.％)为C 0.05-0.11，Si 0.20-0.50，Mn 1.00-1.40，Al 0.02-0.04，Nb 0.01-0.03，Ti 0.01-0.03，Ni 0.80-1.30，Mo 0.30-0.60，Cr 0.30-0.60，B 0.0008-0.0020，S≤0.003，P≤0.015，余量为Fe及不可避免的杂质。制造方法包括依次进行的转炉冶炼、LF+RH(VD)冶炼、板坯连铸、板坯加热、轧制及热处理等工序。本发明提供一种-60℃条件下使用的粒状贝氏体高强钢板，屈服强度≥500MPa，抗拉强度≥700MPa，屈强比≤0.70，-60℃冲击功≥100J。

Description

一种低温环境下使用的低屈强比粒状贝氏体高强钢板及其制造方法 技术领域
本发明属于冶金技术领域，涉及一种低温环境下使用的粒状贝氏体高强钢板及其制造方法。
背景技术
近年来，装备工程大型化发展越来越快，500米以上的高层建筑、几十公里长的跨海大桥等越来越多。工程大型化对材料的要求也随之提高。屈强比是目前高性能钢中必不可少的一个要求，很多管线、高建、桥梁钢中均有对屈强比的要求，目的是为了提高材料的安全系数。但是，随着钢板强度的增加，屈强比越来越高，而屈强比低的材料，强度普遍较低，如何解决屈强比和材料强度之间的矛盾，是近代高性能钢探索的一个重点。
目前解决高强钢屈强比的问题主要通过生成两相组织来保证，软相组织可以保证钢板的屈服强度较低，而硬相组织可以提高钢板的抗拉强度，从而使得钢板在具备高强度的时候仍能保持较低的屈强比。专利公告号CN107099750A说明一种Q630GJ高强钢板的制造方法，组织为回火铁素体+马氏体+贝氏体，通过多相组织得到屈强比≤0.83；专利公告号CN102433507A提供一种低屈强比易焊接高强钢板，组织得到铁素体+贝氏体，屈强比≤0.7。从生产工艺上看，分为两类，一类是TMCP控轧控冷得到两相组织，一类是通过亚温淬火+回火得到两相组织。
目前还未见到通过粒状贝氏体组织得到超低屈强比高强钢的应用案例。
发明内容
本发明所要解决的技术问题是针对上述现有技术提供一种低温环境下使用的粒状贝氏体高强钢板及其制造方法，可满足在-60℃条件下使用，在保证抗拉强度≥700MPa的同时，满足屈强比≤0.70。
本发明解决上述问题所采用的技术方案为：一种低温环境下使用的粒状贝氏体高强 钢板，化学成分(wt.％)为C 0.05-0.11，Si 0.20-0.50，Mn 1.00-1.40，Al 0.02-0.04，Nb 0.01-0.03，Ti 0.01-0.03，Ni 0.80-1.30，Mo 0.30-0.60，Cr 0.30-0.60，B 0.0008-0.0020，S≤0.003，P≤0.015，余量为Fe及不可避免的杂质。
本发明中所含有所有关键组分的作用及其含量选择理由具体说明如下：
C：钢材中影响相变曲线和组织类型的关键元素，对材料的各关键相变点和组织转变温度有显著影响，同时对强度贡献明显，含量过高会导致连铸坯厚度方向中心位置出现严重偏析带，从而影响到钢板组织转变和组织性能均匀性。在调质钢中，碳能够提高钢板的淬透性，但是对于贝氏体钢来讲，不希望过高的淬透性，因此综合考虑，C含量的范围在0.05-0.11％。
Si：主要还原剂和脱氧剂，过高会对表面质量、韧性及焊接性能产生不利影响，综合考虑，本发明Si含量选择范围为0.20-0.50％。
Mn：影响强度、淬透性和焊接性的主要合金元素，以固溶强化形式提高钢的强度，弥补C降低而导致的不足；Mn含量在低于0.8％时则无法起到固溶强化的作用，过高会提高钢的碳当量和裂纹敏感系数，对钢的焊接性产生不利影响；同时，Mn容易在钢板心部产生偏析，对钢板心部的低温冲击韧性产生不利影响。本发明专利重点平衡Mn在淬透性和强化作用方面的作用，同时考虑对低温韧性的影响，从有利于获得粒状贝氏体的角度，本发明Mn含量的选择范围为1.00-1.40％；
Al：主要脱氧元素，有一定细化晶粒作用。本发明Al含量的选择范围为0.02-0.04％。
Nb：主要细化晶粒元素，能够在轧制过程中通过钉扎作用和沉淀强化作用显著细化奥氏体晶粒，提高未再结晶区温度，有利于晶粒细化，强度和韧性的提高。综合考虑，本发明Nb含量的选择范围为0.02-0.04％。
Ti：通过析出强化细化晶粒，同时与含Nb钢一起加入可提高钢的高温段热塑性，减少微裂纹。因此，本发明Ti含量的选择范围为0.01-0.03％。
Ni：能够提高钢的强度和硬度，改善韧性，同时能够抑制贝氏体中的碳化物析出，降低贝氏体相变驱动力。Ni含量过高时，在连铸坯加热过程中会产生黏度较高的氧化铁皮，影响钢板表面质量。本发明中考虑粒状贝氏体组织强度偏低，同时为满足低温条件下韧性的需要，Ni含量的选择范围为0.80-1.30％。
Cr：能够提高钢的淬透性和强度，添加过量，则会对钢的低温冲击韧性和焊接性产生不利影响。本发明重点平衡Cr在对贝氏体转变、淬透性提升和强度贡献方面的作用， 综合考虑，Cr含量的选择范围为0.30-0.60％。
Mo：能够显著提高钢的淬透性和热强性，在调质处理时加入适量的Mo可以克服钢的回火脆性，提高钢的回火稳定性，从而提高钢的冲击韧性。同时，Mo能推迟铁素体珠光体的转变，扩大贝氏体转变区间，本发明Mo含量的选择范围为0.30-0.60％。
B：提高淬透性的最显著的元素，过高则会对焊接性和低温韧性产生不利影响。本发明B含量的选择范围为0.0008-0.0020％。
S元素：主要杂质元素，对低温韧性有坏的影响，综合考虑，S≤0.003％；P≤0.015％。
本发明还提供了一种低温环境下使用的粒状贝氏体高强钢板的制造方法，包含以下工艺步骤：
(1)冶炼原料依次经KR铁水脱硫预处理、转炉顶底吹炼、LF精炼、RH精炼和连铸工艺处理，形成厚度在150-450mm的连铸坯，对连铸坯实施加罩缓冷，缓冷时间为96小时。
(2)将连铸坯加热至1170～1250℃，保温段时间为(0.5*连铸坯厚度)min，连铸坯出炉后使用高压水除鳞。
(3)进行两阶段轧制，第一阶段为粗轧阶段，开轧温度在1050-1180℃，单道次平均压下率≥15％；第二阶段为精轧阶段，开轧温度为900-930℃，累计道次压下率≥40％；轧后热矫直。
(4)钢板轧制后进行加罩堆垛缓冷，堆垛时间≥48小时。
(5)对缓冷后的钢板进行淬火+高温回火处理，淬火和回火均在连续炉中进行，淬火温度为920-930℃，在炉时间1.8-2.2min/mm；回火温度为730-740℃，在炉时间3.0-4.0min/mm，出炉后空冷。
本发明通过合理的成分设计和工艺匹配，在高温等温条件下能够得到稳定的粒状贝氏体组织。该组织的形成温度区间高于上贝氏体转变温度但低于珠光体转变温度，先由奥氏体转变成块状铁素体组织，然后再块状铁素体基体上，富碳的残余奥氏体转变为粒状贝氏体组织，晶粒度在10级以上。
通过上述方法生产的钢板，屈服强度≥500MPa，抗拉强度≥700MPa，屈强比≤0.70，-60℃下钢板的1/4厚度和1/2厚度处夏比冲击功均≥100J，可在-60℃低温环境下使用。
与现有技术相比，本发明的优点在于：
(1)通过合理的成分匹配，设计一种能够通过热处理工艺得到稳定粒状贝氏体的 成分体系，满足过程工艺控制和最终性能要求。
(2)提供一种单相粒状贝氏体组织的低屈强比高强钢，该钢种具有良好的强韧性和低屈强比的特征，能够满足-60℃条件下使用。
(3)与双相组织钢相比，该发明最大优点在于稳定性高，由于双相组织需要控制不同组织之间的比例，因此屈强比往往处于一种波动状态，而且组织均匀性较差，单相粒状贝氏体组织稳定性高，从而使得性能稳定性大幅提升。
附图说明
图1为本发明实例1钢板的显微组织照片。
图2为本发明实例2钢板的显微组织照片。
具体实施方式
以下结合实施例对本发明作进一步详细描述。
实施例1-2：
根据本发明的化学成分范围及制造方法，经KR铁水预处理—转炉冶炼—LF精炼—RH/VD真空脱气—370mm连铸—连铸坯堆缓冷≥96小时—铸坯加热—高压水除鳞—轧制—钢板堆缓冷—淬火处理—回火处理等工艺步骤，制造粒状贝氏体高强钢板。
上述阶段的具体工艺为：通过KR铁水预处理、转炉冶炼、LF和RH精炼得到符合成分设计要求的钢水，然后通过板坯连铸得到370mm厚度连铸坯钢板，缓冷96小时(实施例1和2)。将370mm厚度连铸坯加热至1170-1250℃，保温185-190min(实施案例1和2)，连铸坯出炉后使用高压水除鳞；然后进行两阶段轧制，第一阶段开轧温度1080℃(实施例1)和1120℃(实施例2)，中间坯厚度170mm(实施例1)180mm(实施2)，单道次平均压下率18％(实施例1)和17％(实施例2)；第二阶段开轧温度为900℃(实施例1)和930℃(实施例2)，累计道次压下率58.8％(实施例1)和44％(实施例2)，轧制钢板厚度为70mm(实施例1)和100mm(实施例2)轧后进行热矫直，钢板堆缓冷时间≥48小时(实施例1和2)。
缓冷完成后的钢板进入连续炉进行淬火处理。实施例1：加热温度920℃，在炉时间1.8min/mm，使用淬火机水淬。实施例2：加热温度930℃，在炉时间1.8min/mm，使用淬火机水淬。对完成淬火处理的钢板在连续炉中进行回火处理。实施例1:加热温度740 ℃，在炉时间3.5min/mm，实施例2：加热温度740℃，在炉时间4.0min/mm。
实施例制得的钢板化学成分见表1，钢板的力学性能见表2，钢板的显微组织如图1和图2所示。
表1实施例钢板的化学成分(wt.％)
实例 C Si Mn P S Al Nb Ti Cr+Ni+Mo B
1 0.08 0.30 1.18 0.010 0.001 0.023 0.017 0.018 1.89 0.0012
2 0.08 0.28 1.30 0.011 0.001 0.025 0.018 0.016 2.11 0.0013
表2实施例的力学性能
Figure PCTCN2021097027-appb-000001
除上述实施例外，本发明还包括有其他实施方式，凡采用等同变换或者等效替换方式形成的技术方案，均应落入本发明权利要求的保护范围之内。

Claims (3)

  1. 一种低温环境下使用的低屈强比粒状贝氏体高强钢板，其特征在于：所述钢板的化学成分按质量百分比为C 0.05-0.11，Si 0.20-0.50，Mn 1.00-1.40，Al 0.02-0.04，Nb 0.01-0.03，Ti 0.01-0.03，Ni 0.80-1.30，Mo 0.30-0.60，Cr 0.30-0.60，B 0.0008-0.0020，S≤0.003，P≤0.015，余量为Fe及不可避免的杂质。
  2. 根据权利要求1所述的一种低温环境下使用的低屈强比粒状贝氏体高强钢板，其特征在于：所述钢板的屈服强度≥500MPa，抗拉强度≥700MPa，屈强比≤0.70，-60℃下钢板的1/4厚度和1/2厚度处夏比冲击功均≥100J，可在-60℃低温环境下使用。
  3. 一种如权利要求2所述的低温环境下使用的低屈强比粒状贝氏体高强钢板的制造方法，其特征在于：所述方法包括以下步骤：
    ①冶炼原料依次经KR铁水脱硫预处理、转炉顶底吹炼、LF精炼、RH精炼和连铸工艺处理，形成厚度在150-450mm的连铸坯，对连铸坯实施加罩缓冷，缓冷时间为96小时；
    ②将连铸坯加热至1170～1250℃，保温段时间为(0.5×连铸坯厚度)min，连铸坯出炉后使用高压水除鳞；
    ③进行两阶段轧制，第一阶段为粗轧阶段，开轧温度在1130-1180℃，单道次平均压下率≥15％；第二阶段为精轧阶段，开轧温度为900-930℃，累计道次压下率≥40％；轧后热矫直；
    ④钢板轧制后进行加罩堆垛缓冷，堆垛时间≥48小时；
    ⑤对缓冷后的钢板进行淬火+高温回火处理，淬火和回火均在连续炉中进行，淬火温度为920-930℃，在炉时间1.8-2.2min/mm；回火温度为730-740℃，在炉时间3.0-4.0min/mm，出炉后空冷。
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