WO2021179443A1 - 一种心部低温冲击韧性优良的特厚容器钢板及其制造方法 - Google Patents

一种心部低温冲击韧性优良的特厚容器钢板及其制造方法 Download PDF

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WO2021179443A1
WO2021179443A1 PCT/CN2020/092872 CN2020092872W WO2021179443A1 WO 2021179443 A1 WO2021179443 A1 WO 2021179443A1 CN 2020092872 W CN2020092872 W CN 2020092872W WO 2021179443 A1 WO2021179443 A1 WO 2021179443A1
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steel plate
temperature
cooling
impact toughness
rolling
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French (fr)
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杨宏伟
许晓红
白云
苗丕峰
叶建军
张建
张军
方寿玉
徐君
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江阴兴澄特种钢铁有限公司
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Priority to CA3157674A priority Critical patent/CA3157674A1/en
Publication of WO2021179443A1 publication Critical patent/WO2021179443A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/072—Treatment with gases
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • 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
    • 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
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper

Definitions

  • the invention belongs to the technical field of iron-based alloys.
  • the patent (CN106350644A) applied for a method of using online quenching process to produce steel for storage tanks. It uses UFC+ACC two-stage cooling method to achieve online quenching.
  • the steel plate produced has stable performance and good strength and toughness matching, but it does not mention Low-temperature impact toughness of the core of the steel plate.
  • the 15-50mm thick steel plate produced by the online quenching + offline tempering process has the characteristics of high strength and excellent weldability, but the impact test temperature is only It is -20°C, and at the same time, more Nb and Cr alloys are added, and the cost is higher.
  • the present invention provides an on-line quenching method to produce extra-thick steel plates with excellent low-temperature impact toughness of a thick core of 60-100 mm.
  • the steel plate has the characteristics of stable structure, high strength, excellent low-temperature toughness of the core, easy welding and the like.
  • the manufacturing method has the advantages of short process flow, relatively low cost, and strong operability.
  • the technical solution adopted by the present invention to solve the above-mentioned problems is: an extra-thick container steel plate with excellent low-temperature impact toughness at the core, and the production thickness of the steel plate reaches 60-100 mm.
  • the chemical composition of the steel plate is calculated as mass percentage: C: 0.13 ⁇ 0.20%, Si: ⁇ 0.40%, Mn: 1.00 ⁇ 1.60%, P ⁇ 0.015%, S ⁇ 0.005%, Als: 0.01 ⁇ 0.05%, Nb +V+Ti ⁇ 0.080%, Ni: 0.20-0.50%, Cu ⁇ 0.30%, H ⁇ 2ppm, the remainder is Fe and inevitable impurity elements, while satisfying:
  • the structure near the surface of the steel plate is tempered sorbite, and the structure at 1/4 and 1/2 of the thickness of the steel plate is bainite.
  • the yield strength of the steel plate is ⁇ 400MPa, the tensile strength Rm ⁇ 550MPa, the elongation rate A ⁇ 22%, the transverse impact energy at 1/4 of the plate thickness is -50°CKV 2 ⁇ 150J; the transverse impact energy at 1/2 of the plate thickness is -50°C KV 2 ⁇ 80J.
  • C is the most economical element to increase the strength of the steel plate, but too high content will lead to a decrease in plasticity and impact toughness, and at the same time, the sensitivity of welding cracks will increase, and cracks will easily occur during the welding process.
  • the content of C in the steel of the present invention is 0.13 to 0.20%.
  • Si can increase the strength of the steel plate and welded joints.
  • the Si content is greater than 0.45%, the toughness of the steel plate and welded joints will be significantly reduced.
  • the formed hard silicate inclusions are likely to cause surface defects of the steel plate.
  • the Si content is 0.10 to 0.40% .
  • Mn is a commonly used element to increase the strength of steel plates, and an appropriate amount of Mn can replace the C element to increase the strength of steel plates and welded joints and improve toughness.
  • Mn content With the increase of Mn content, the stability of austenite in the steel can be improved, the critical cooling rate can be reduced, the ferrite can be strengthened, and the hardenability can be significantly improved.
  • the decomposition and transformation speed of the structure during the tempering process after quenching can be slowed down. Improve the stability of tempered structure, but too high content will coarsen steel grains at high temperature and reduce the toughness and weldability of steel plates and welded joints. Therefore, the content of Mn in the steel of the present invention is 1.00% to 1.60%.
  • P and S are unavoidable in steel as impurity elements, but they are harmful to the workability of the steel plate, especially the low-temperature impact toughness.
  • the content is less than or equal to 0.005%.
  • Ni can significantly reduce the ductile-brittle transition temperature of steel, improve low-temperature impact toughness, and can also reduce the tendency of surface cracks caused by the addition of Cu.
  • Ni is expensive, and excessive addition will significantly increase the production cost of steel. Therefore, the content of Ni in the steel of the present invention is 0.20 to 0.50%.
  • Nb and V can introduce a large number of high-density dislocations and distortion zones during rolling in the non-recrystallization zone, promote the formation of more phase transformation cores, and refine the austenite structure.
  • carbonitrides are formed and precipitated in the ferrite at the austenite grain boundary, which can inhibit the recrystallization of austenite and prevent the growth of grains during the rolling process, thereby refining the ferrite grains The effect of improving the strength and toughness of steel.
  • Ti can form high-temperature oxides, which act as nucleating particles of acicular ferrite in welded joints, promote the formation of acicular ferrite, and significantly improve the low-temperature impact toughness of the welding heat-affected zone.
  • Nb, V, and Ti can combine with C and N to produce carbonitride precipitation, which has the effect of grain refinement. Due to the center segregation during the solidification process of the cast slab, TiN mostly gathers near the core of the cast slab after precipitation, and the irregular shape of TiN inclusions is detrimental to the low-temperature impact toughness of the core of the steel plate. On the other hand, at the same temperature, the binding ability of Ti and N is stronger than that of Nb and V. Therefore, this application controls 3 ⁇ w(Nb+V+Als)/w(Ti) to reduce the formation of TiN. At the same time, considering the expensive prices of Nb and V, w(Nb+V+Als)/w(Ti) ⁇ 8.
  • H hydrogen atoms are easy to diffuse in the cast slab. Under the action of hydrogen pressure, adjacent hydrogen bubbling cracks on different levels are connected to each other, thereby forming a stepped core crack. Therefore, in order to ensure the low-temperature toughness of the steel plate, the steel of the present invention has H ⁇ 2ppm, and the continuous casting slab is subjected to hydrogen expansion treatment.
  • Another object of the present invention is to provide a method for manufacturing the above-mentioned container steel plate.
  • the method includes the following steps: hot metal pretreatment ⁇ converter smelting ⁇ ladle furnace refining ⁇ vacuum treatment ⁇ continuous casting ⁇ casting billet cooling ⁇ casting billet heating ⁇ control Rolling ⁇ controlled cooling ⁇ stack slow cooling ⁇ tempering ⁇ flaw detection ⁇ performance inspection, the specific steps are as follows:
  • the molten iron is pretreated and desulfurized by the KR method and smelted in a converter, it is refined in a ladle furnace and vacuum treated, and then smelted into high-purity molten steel after soft blowing for more than 15 minutes.
  • the cast slab is slowly cooled with a cover.
  • the continuous casting slab is heated to 1150 ⁇ 1200°C, the total time in the furnace is not less than 300min, and the soaking time is not less than 90min. After being discharged from the furnace, it is descaled by high-pressure water to remove the surface oxide scale of the casting slab.
  • the austenitized continuous casting billet is rolled in two stages (controlled rolling, the temperature of opening rolling and finishing rolling must be limited), the blooming rolling adopts a small number of passes and a large reduction, and the opening temperature is controlled to 1020 ⁇ 1100 °C, the final rolling temperature is controlled at 1000 ⁇ 1060°C, to ensure the reduction rate of the last two passes ⁇ 15%; the finishing rolling temperature is controlled at 880 ⁇ 920°C; after rolling, the two-stage cooling of DQ+ACC is adopted to achieve online quenching the goal of. Control the steel inlet water temperature at 840 ⁇ 880°C, and the cooling rate at 5 ⁇ 15°C/s. After ACC, the surface temperature of the steel plate is 100 ⁇ 200°C. After the steel plate is rolled off the line, the stack is slowly cooled, and then 600 ⁇ 680°C tempering treatment is carried out. , Leaving the factory after passing the flaw detection and performance inspection.
  • the composition design controls the content of Nb, V, Ti and Als in the steel to reduce the formation of TiN which is unfavorable to the low-temperature impact of the core.
  • the formed carbonitrides of Nb, V and Al play a role in pinning and refining the casting.
  • the role of the slab grain 2.
  • the thickest continuous casting slab in China is used, which greatly increases the deformation of the rolling process, and combines with the differential temperature rolling process to further refine the structure of the core of the steel plate and further improve the low-temperature impact toughness Lay the foundation; 3.
  • Use on-line quenching to control the water inlet temperature, avoiding the abnormality of the organization caused by the water inlet temperature being too low or too high.
  • the molten steel is made purer and the uniformity of subsequent steel plate performance is ensured, especially the low-temperature impact of the core toughness.
  • the online quenching process is used to ensure that the steel plate has excellent strength and toughness matching, while significantly reducing production costs, shortening the delivery cycle, and strong operability.
  • Fig. 1 is a schematic diagram of tempered sorbite in the metallographic structure at the surface of a 90mm thick steel plate in the embodiment of the present invention
  • FIG. 2 is a schematic diagram of bainite in the metallographic structure at 1/4 of the 90mm thick steel plate in the embodiment of the present invention
  • Fig. 3 is a schematic diagram of bainite in the metallographic structure at 1/2 of the 90mm thick steel plate in the embodiment of the present invention.
  • the smelting chemical composition of this example and comparative example is shown in Table 1 (wt%), and the remainder is Fe and unavoidable impurity elements.
  • Example 1 0.13 0.20 1.50 0.005 0.001 0.084 0.015 0.35 0.0001 0.42 5.6
  • Example 2 0.14 0.21 1.52 0.006 0.002 0.061 0.014 0.32 0.0001 0.42 4.4 Comparison 0.16 0.25 1.40 0.012 0.006 0.030 0.018 0.45 0.0003 0.44 1.7
  • the above examples and comparative examples are all smelted in a converter, and then subjected to deep desulfurization and refining in a ladle furnace, and finally to a vacuum furnace for degassing, soft blowing for more than 15 minutes, so that large particles are fully floated and removed, and the composition and temperature are uniform. , And then lightly reduced and protected and poured into continuous casting slabs in the whole process. Choose two continuous casting billets of comparative proportions for finished product production.
  • the continuous casting slab is heated to 1150 ⁇ 1200°C, the total time in the furnace is ⁇ 300min, and the soaking time is ⁇ 90min. After being discharged from the furnace, it is descaled by high-pressure water to remove the oxide scale on the surface of the cast slab; then it is controlled rolling and blooming is opened.
  • the rolling temperature is 1020 ⁇ 1100°C, the final rolling temperature is controlled at 1000 ⁇ 1060°C, and the reduction rate of the last two passes is ⁇ 15%; the finishing rolling temperature is controlled at 880 ⁇ 920°C; after rolling, two-stage cooling of DQ+ACC is adopted , In order to achieve the purpose of online quenching.
  • Table 2 shows the main rolling, controlled cooling and tempering process parameters of each embodiment and comparative example.
  • the invention not only ensures that the steel has good strength and toughness, but also has stable core low-temperature impact toughness.
  • the invention can be implemented in medium and heavy plate plants of metallurgical enterprises, has simple process flow, strong operability and low cost, and can be applied to the construction of large pressure vessels in petroleum, chemical and other industries.

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Abstract

一种心部低温冲击韧性优良的特厚容器钢板，生产厚度为60-100mm，化学成分：C:0.13～0.20％、Si：≤0.40％、Mn：1.00～1.60％、P≤0.015％、S≤0.005％、Als：0.01～0.05％、Nb+V+Ti≤0.080％、Ni:0.20-0.50％、Cu≤0.30％、H≤2ppm，余量为Fe及不可避免的杂质元素，同时满足：CEV≤0.43％，3≤w(Nb+V+Als)/w(Ti)≤8。钢板的近表面处组织为回火索氏体，钢板板厚1/4处和1/2处组织为贝氏体。板厚1/4处横向冲击功-50℃KV 2≥150J；板厚1/2处横向冲击功-50℃KV 2≥80J。制造工艺：铁水预处理→转炉冶炼→钢包炉精炼→真空脱气处理→连铸→铸坯加罩冷却→铸坯加热→控制轧制→控制冷却→堆缓冷→回火。采用在线淬火工艺，保证钢板具有优良的强韧性，同时在线淬火能够显著缩短交货周期。

Description

一种心部低温冲击韧性优良的特厚容器钢板及其制造方法 技术领域
本发明属于铁基合金技术领域。
背景技术
近年来，国内外各种石化、天然气项目相继实施，大型反应容器或存储罐需求显著上升，调质钢板因具有良好的强韧性匹配越来越受到青睐，尤其是随着设备不断朝着大型化、高参数化发展，同时保证设备安全、稳定运行，良好的心部低温冲击韧性和焊接性显得尤为关键。综上所述，开发能够批量稳定生产的满足大型能源设备制造的易焊接心部低温韧性优良的容器钢板具有广阔的市场前景。
专利(CN107267857A)申请了一种07MnNiMoDR钢板及其在线淬火生产方法，其抗拉强度在630MPa以上，-50℃低温冲击韧性优良，但最大厚度仅为50mm。
专利(CN106350644A)申请了一种利用在线淬火工艺生产储罐用钢的方法，其利用UFC+ACC两阶段冷却方式实现在线淬火，生产的钢板性能稳定、具有良好的强韧性匹配，但未提及钢板的心部低温冲击韧性。
专利(CN106319376B)申请了一种新型低焊接裂纹敏感性高强度钢板，其利用在线淬火+离线回火工艺生产的15-50mm厚钢板，具有强度高、焊接性优良的特点，但冲击试验温度仅为-20℃，同时Nb、Cr合金添加较多，成本较高。
综上所述，现有调质高强韧钢板大都采用传统的离线淬火工艺生产，即使使用在线淬火工艺生产，所生产的钢板厚度也都在60mm以内，且心部低温冲击韧性不稳定，无法满足化工能源设备向大型化、高参数化发展的需求
发明内容
本发明提供一种在线淬火方法生产60-100mm厚心部低温冲击韧性优良的特厚钢板，该钢板具有组织稳定、强度高、心部低温韧性优良、易焊接等特性。其制造方法具有流程短、成本相对低、可操作性强的优点。
本发明解决上述问题所采用的技术方案为：一种心部低温冲击韧性优良的特厚容器 钢板，该钢板的生产厚度达到60-100mm。得该钢板的化学成分按质量百分比计为：C:0.13～0.20％、Si：≤0.40％、Mn：1.00～1.60％、P≤0.015％、S≤0.005％、Als：0.01～0.05％、Nb+V+Ti≤0.080％、Ni:0.20-0.50％、Cu≤0.30％、H≤2ppm，余量为Fe及不可避免的杂质元素，同时满足：
CEV＝C+Mn/6+(Mo+V+Cr)/5+(Ni+Cu)/15≤0.43％，
3≤w(Nb+V+Als)/w(Ti)≤8。
钢板的近表面处组织为回火索氏体，钢板板厚1/4处和1/2处组织为贝氏体。钢板的屈服强度≥400MPa，抗拉强度Rm≥550MPa，延伸率A≥22％，板厚1/4处横向冲击功-50℃KV 2≥150J；板厚1/2处横向冲击功-50℃KV 2≥80J。
本发明中C、Si、Mn、P、S、Nb、Ni、V、Ti、H等元素的限定理由阐述如下：
C是提高钢板强度最经济的元素，但含量过高会导致塑性、冲击韧性的降低，同时焊接裂纹敏感性增大，焊接过程中容易产生裂纹。为了保证母材具有良好的强韧性匹配及可焊性等，因此本发明钢C的含量为0.13～0.20％。
Si可提高钢板及焊接接头的强度，当Si含量大于0.45％时，钢板和焊接接头韧性会显著降低，同时形成的坚硬硅酸盐夹杂物容易造成钢板表面缺陷，Si的含量为0.10～0.40％。
Mn是提高钢板强度的常用元素，适量的Mn可替代C元素来提高钢板及焊接接头的强度和改善韧性。随着Mn含量的增加，可提高钢中奥氏体的稳定性，降低临界冷却速度，强化铁素体，显著提高淬透性，同时可使淬火后回火过程中组织分解转变速度减慢，提高回火组织稳定性，但含量过高将使钢在高温下晶粒粗化，降低钢板及焊接接头的韧性和可焊性，因此本发明钢Mn的含量为1.00％～1.60％。
P、S作为杂质元素在钢中是不可避免的，但其对钢板的加工性、尤其是低温冲击韧性是有害的，其含量越低越好，因此本发明钢P的含量≤0.015％，S的含量≤0.005％。
Ni能显著降低钢材的韧脆转变温度，提升低温冲击韧性，也可减轻因Cu的添加而引起的铸坯表面裂纹倾向。但Ni价格昂贵，加入量过多会显著提高钢的生产成本，因此本发明钢Ni的含量为0.20～0.50％。
Nb、V能在非再结晶区轧制时引入大量高密度位错和畸变区，促进形成更多的相变核心，从而细化奥氏体组织。同时形成碳氮化物，在奥氏体晶界的铁素体中沉淀析出，在轧制过程中能抑制奥氏体的再结晶并阻止晶粒长大，从而起到细化铁素体晶粒的作用，提高钢的强度和韧性。Ti能形成高温氧化物，在焊接接头中作为针状铁素体的形核质点， 促进针状铁素体形成，显著改善焊接热影响区低温冲击韧性。若加入过多，不仅增加成本，而且析出物数量和尺寸增大，会导致钢的韧性尤其是心部韧性降低。因此，本发明钢Nb+V+Ti≤0.08％，Nb、V的添加量不为零。
Nb、V、Ti均可与C、N结合生产碳氮化物析出，从而起到细化晶粒的效果。由于铸坯凝固过程的中心偏析，TiN析出后多聚集在铸坯心部附近，而TiN夹杂不规则的形态对钢板的心部低温冲击韧性是不利的。另一方面，相同温度下，Ti与N的结合能力比Nb、V强，因此，本申请控制3≤w(Nb+V+Als)/w(Ti)，从而减少TiN的形成。同时，考虑到Nb、V昂贵的价格，w(Nb+V+Als)/w(Ti)≤8。
H氢原子容易在铸坯中扩散，在氢气压力的作用下，不同层面上的相邻氢鼓泡裂纹相互连接，从而形成阶梯状特征的心部裂纹。因此，为了保证钢板的心部低温韧性，本发明钢H≤2ppm，并对连铸坯进行扩氢处理。
本发明的另一目的是提供上述一种容器钢板的制造方法，该方法包括如下工序：铁水预处理→转炉冶炼→钢包炉精炼→真空处理→连铸→铸坯罩冷→铸坯加热→控制轧制→控制冷却→堆缓冷→回火→探伤→性能检验，具体步骤如下：
铁水经KR法预处理脱硫、转炉冶炼后，采用钢包炉精炼和真空处理，进行软吹15分钟以上后冶炼成高纯净钢水，采用全过程保护浇注、轻压下技术在连铸机上浇注成连铸板坯，铸坯加罩缓冷。
将连铸坯加热至1150～1200℃，总的在炉时间不少于300min，均热时间不少于90min，出炉后经高压水除鳞，除尽铸坯表面氧化铁皮。
奥氏体化后的连铸坯进行两阶段轧制(控制轧制，开轧和终轧温度均要进行限定)，初轧采用少道次大压下量，控制开轧温度为1020～1100℃，终轧温度控制在1000～1060℃，保证后2道次压下率≥15％；精轧开轧温度控制在880～920℃；轧后采用DQ+ACC两阶段冷却，以达到在线淬火的目的。控制钢板入水温度在840～880℃，冷却速度控制为5～15℃/s，经ACC后钢板表面温度在100～200℃，钢板下线后堆缓冷，再进行600～680℃回火处理，探伤及性能检验合格后出厂。
与现有技术相比，本发明的优点在于：
1、成分设计上控制钢中的Nb、V、Ti和Als含量，减少对心部低温冲击不利的TiN形成，同时，形成的Nb、V和Al的碳氮化物起到钉扎和细化铸坯晶粒的作用；2、采用国内最厚的连铸板坯，大幅增加了轧制过程的变形量，并结合差温轧制工艺，进一步细化钢板心部的组织，进一步为低温冲击韧性打下基础；3、采用在线淬火，控制入水 温度，避免了入水温度过低或过高带来的组织异常。
采用C-Mn-Ni系加Nb、V等微合金化成分设计，经二次精炼及连铸坯轻压下，使钢水更纯净，保证了后续钢板性能的均匀性，尤其是心部低温冲击韧性。采用在线淬火工艺，保证钢板具有优良的强韧性匹配的同时，显著降低生产成本，缩短交货周期，操作性强。
附图说明
图1为本发明实施例90mm厚钢板的表层处金相组织中回火索氏体的示意图；
图2为本发明实施例90mm厚钢板的1/4处金相组织中贝氏体的示意图；
图3为本发明实施例90mm厚钢板的1/2处金相组织中贝氏体的示意图。
具体实施方式
以下结合附图实施例对本发明作进一步详细描述，下面描述的实施例是示例性的，旨在用于解释本发明，而不能理解为对本发明的限制。此外，列举了对比例以突出实施例。
本实施例和对比例的熔炼化学成分见表1(wt％)，剩余为Fe及不可避免的杂质元素。
表1
元素 C Si Mn P S Nb+V+Als Ti Ni H CEV (V+Nb+Als)/[Ti]
实施例1 0.13 0.20 1.50 0.005 0.001 0.084 0.015 0.35 0.0001 0.42 5.6
实施例2 0.14 0.21 1.52 0.006 0.002 0.061 0.014 0.32 0.0001 0.42 4.4
对比例 0.16 0.25 1.40 0.012 0.006 0.030 0.018 0.45 0.0003 0.44 1.7
上述实施例和对比例均在转炉冶炼，再经钢包炉深脱硫和精炼处理，最后至真空炉进行脱气，软吹15分钟以上，使大颗粒夹杂物充分上浮去除，并保证成分、温度均匀，然后经轻压下和全过程保护浇注成连铸板坯。选择两块对比例的连铸坯进行成品生产。
将连铸板坯加热至1150～1200℃，总在炉时间≥300min，均热时间≥90min，出炉后经高压水除鳞，除尽铸坯表面氧化铁皮；然后进行控制轧制，初轧开轧温度为1020～1100℃，终轧温度控制在1000～1060℃，后2道次压下率≥15％；精轧开轧温度控制在880～920℃；轧后采用DQ+ACC两阶段冷却，以达到在线淬火的目的。控制钢板入水温度在840～880℃，冷却速度控制为5～15℃/s，经ACC后钢板表面温度在100～200℃，钢板下线后堆缓冷，最后进行600～680℃回火处理。
表2为各实施例和对比例主要轧制、控冷和回火工艺参数。
表2
Figure PCTCN2020092872-appb-000001
Figure PCTCN2020092872-appb-000002
热处理后的钢板，在板厚1/4、1/2处取横向样加工成拉伸试样、冲击试样，并进行力学性能测试，检测结果见表3。
表3
Figure PCTCN2020092872-appb-000003
由表3可见，本发明实施例试验钢板强度、延伸率、冲击韧性富裕量均较大，尤其是板厚1/2处冲击功都在100J以上，而对比例板厚1/2处冲击功不稳定，单值最低仅为18J。
该发明不仅保证了钢具有较好的强韧性，还具有稳定的心部低温冲击韧性。本发明均可在冶金企业中厚板厂实施，工艺流程简单，可操作性强且成本较低，可应用于石油、化工等行业建造大型压力容器。
尽管以上详细地描述了本发明的优选实施例，但是应该清楚地理解，对于本领域的技术人员来说，本发明可以有各种更改和变化。凡在本发明的精神和原则之内所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (6)

  1. 一种心部低温冲击韧性优良的特厚容器钢板，其特征在于：该钢板的化学成分按质量百分比计为：C:0.13～0.20％、Si：≤0.40％、Mn：1.00～1.60％、P≤0.015％、S≤0.005％、Als：0.01～0.05％、Nb+V+Ti≤0.080％、Ni:0.20-0.50％、Cu≤0.30％、H≤2ppm，余量为Fe及不可避免的杂质元素，同时满足：
    CEV＝C+Mn/6+(Mo+V+Cr)/5+(Ni+Cu)/15≤0.43％，
    3≤w(Nb+V+Als)/w(Ti)≤8。
  2. 根据权利要求1所述的心部低温冲击韧性优良的特厚容器钢板，其特征在于：钢板的厚度为60-100mm。
  3. 根据权利要求1所述的心部低温冲击韧性优良的特厚容器钢板，其特征在于：钢板的近表面处组织为回火索氏体，钢板板厚1/4处和1/2处组织为贝氏体。
  4. 根据权利要求1所述的心部低温冲击韧性优良的特厚容器钢板，其特征在于：所述钢板的屈服强度≥400MPa，抗拉强度Rm≥550MPa，延伸率A≥22％，板厚1/4处横向冲击功-50℃KV 2≥150J；板厚1/2处横向冲击功-50℃KV 2≥80J。
  5. 一种制造权利要求1-4中任一权项所述的心部低温冲击韧性优良的特厚容器钢板的方法，其特征在于，工艺流程：铁水预处理→转炉冶炼→钢包炉精炼→真空脱气处理→连铸→铸坯加罩冷却→铸坯加热→控制轧制→控制冷却→堆缓冷→回火，
    具体的操作：
    铁水经KR预处理脱硫、转炉冶炼后，采用钢包炉精炼和真空处理，进行软吹15分钟以上后冶炼成高纯净钢水，采用全过程惰性气体保护浇注、轻压下技术在连铸机上浇注成连铸板坯，铸坯加罩缓冷；
    将连铸板坯加热至1150～1200℃，在炉保温时间不少于300min，均热时间不少于90min，出炉后经高压水除鳞，除尽铸坯表面氧化铁皮；然后进行两阶段控制轧制，初轧开轧温度为1020～1100℃，终轧温度为1000～1060℃，初轧的后两道次压下率≥15％；精轧开轧温度为880～920℃；轧后采用DQ+ACC两阶段冷却以达到在线淬火的目的。
  6. 根据权利要求5所述的心部低温冲击韧性优良的特厚容器钢板的制造方法，其特征在于：轧后冷却时，控制钢板入水温度在840～880℃，冷却速度控制为5～15℃/s，经ACC冷却后钢板出水表面温度在100～200℃，钢板下线后堆缓冷，然后进行回火处 理，回火温度：600～680℃，回火保温时间180min～300min。
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CN115094331A (zh) * 2022-07-18 2022-09-23 柳州钢铁股份有限公司 一种低成本的q690钢板及其生产方法
CN115505848A (zh) * 2022-09-28 2022-12-23 马鞍山钢铁股份有限公司 一种V-Nb-Ti复合微合金化500MPa级-165℃低温抗震钢筋及其生产方法
CN115505848B (zh) * 2022-09-28 2023-08-11 马鞍山钢铁股份有限公司 一种V-Nb-Ti复合微合金化500MPa级-165℃低温抗震钢筋及其生产方法

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