高擎, 李骞, 白丽琴, 肖大恒, 周文浩, 于青, 谢振家, 尚成嘉. EH500特厚海洋工程用钢多相组织调控及对性能的影响[J]. 工程科学学报. DOI: 10.13374/j.issn2095-9389.2023.08.17.002
引用本文: 高擎, 李骞, 白丽琴, 肖大恒, 周文浩, 于青, 谢振家, 尚成嘉. EH500特厚海洋工程用钢多相组织调控及对性能的影响[J]. 工程科学学报. DOI: 10.13374/j.issn2095-9389.2023.08.17.002
Multi-phase microstructure regulation and the influence on mechanical properties of EH500 grade ultra-heavy plate steel for marine engineering[J]. Chinese Journal of Engineering. DOI: 10.13374/j.issn2095-9389.2023.08.17.002
Citation: Multi-phase microstructure regulation and the influence on mechanical properties of EH500 grade ultra-heavy plate steel for marine engineering[J]. Chinese Journal of Engineering. DOI: 10.13374/j.issn2095-9389.2023.08.17.002

EH500特厚海洋工程用钢多相组织调控及对性能的影响

Multi-phase microstructure regulation and the influence on mechanical properties of EH500 grade ultra-heavy plate steel for marine engineering

  • 摘要: 特厚钢板由于心部轧制压缩比低和中心偏析的存在导致的心部低温韧性差是限制高强度钢板应用的重大难题。本文针对具有严重中心偏析的100 mm EH500海洋工程用钢,系统研究了两步临界热处理对多相组织调控及性能的影响。结果表明,实验钢经过740 ℃两相区临界退火,实验钢屈服强度和抗拉强度分别为540 MPa和869 MPa,延伸率和-40 ℃低温韧性很低,分别仅5.1%和14 J。再经600、660和680 ℃回火后,实验钢强度相差不大,屈服强度介于528 MPa~551 MPa,抗拉强度介于687 MPa~730 MPa。而实验钢的延伸率和低温韧性随着回火温度的升高先提高后下降,660 ℃回火时塑韧性最佳,延伸率达30.6%,-40 ℃夏比冲击功为163 J。显微组织表征结果表明,实验钢740 ℃两相区退火为临界铁素体和马氏体组织,再经600 ℃回火获得了临界铁素体、回火马氏体和细小碳化物的多相组织。回火温度为660 ℃时,实验钢为临界铁素体、回火马氏体以及细小残余奥氏体,且中心偏析区残余奥氏体含量明显高于非偏析区,进而显著改善了实验钢的塑韧性。而回火温度进一步升高到680 ℃时,实验钢在中心偏析区获得了临界铁素体、回火马氏体/贝氏体、少量残余奥氏体和大量马奥岛组织,马奥岛的存在使实验钢的塑韧性又明显恶化。

     

    Abstract: Because of low rolling reduction and central segregation of ultra-heavy plate steel, the poor low-temperature toughness of the center region is a major challenge that limits the application of high-strength ultra-heavy steels. This work systematically investigates the effects of two-step intercritical heat treatment on the regulation of multiphase microstructure and properties of 100 mm EH500 marine engineering steel with severe central segregation. The results showed that after intercritical annealing in the 740 ℃ two-phase region, the yield strength and tensile strength of the experimental steel were 540 MPa and 869 MPa, respectively. The elongation and low-temperature toughness at -40 ℃ were relatively low, only 5.1% and 14 J, respectively. After further tempering at 600, 660, and 680 ℃, the yield strength of the experimental steel did not change significantly, ranging from 528 MPa to 551 MPa, and the tensile strength decreased to 687~730 MPa. The elongation and low-temperature toughness of the experimental steel firstly increased and then decreased with the increase of tempering temperature. When tempered at 660 ℃, the plasticity and toughness were the best, with an elongation of 30.6% and a Charpy impact energy of 163 J at -40 ℃. The microstructure characterization results show that the experimental steel annealed at 740 ℃ is intercritical ferrite (IF) and martensite (M). After further tempering at 600 ℃, multi-phase microstructure of IF, tempered martensite (TM) with fine carbides were obtained. When the tempering temperature is 660 ℃, microstructure of the experimental steel consisted of IF, TM and fine retained austenite (RA), and the content of RA in the central segregation region was significantly higher than that in the matrix, resulting in significantly improvement of the plastic toughness of the experimental steel. When the tempering temperature further rised to 680 ℃, the experimental steel obtained IF, TM, a small amount of retained austenite and high fraction of martensite/austenite (M/A) constituents in the central segregation zone. The large fraction of M/A constituents could worsen the plasticity and toughness of the experimental steel significantly.

     

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