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, 2024, 46(11): 2017-2025. 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, 2024, 46(11): 2017-2025. DOI: 10.13374/j.issn2095-9389.2023.08.17.002
GAO Qing, LI Qian, BAI Liqin, XIAO Daheng, ZHOU Wenhao, YU Qing, XIE Zhenjia, SHANG Chengjia. Multiphase microstructure regulation and its influence on the mechanical properties of EH500-grade ultraheavy plate steel for marine engineering[J]. Chinese Journal of Engineering, 2024, 46(11): 2017-2025. DOI: 10.13374/j.issn2095-9389.2023.08.17.002
Citation: GAO Qing, LI Qian, BAI Liqin, XIAO Daheng, ZHOU Wenhao, YU Qing, XIE Zhenjia, SHANG Chengjia. Multiphase microstructure regulation and its influence on the mechanical properties of EH500-grade ultraheavy plate steel for marine engineering[J]. Chinese Journal of Engineering, 2024, 46(11): 2017-2025. 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

Multiphase microstructure regulation and its influence on the mechanical properties of EH500-grade ultraheavy plate steel for marine engineering

  • 摘要: 特厚钢板心部轧制压缩比低和中心偏析的存在,导致其心部低温韧性差,这大大限制了高强度特厚钢板的应用. 针对具有严重中心偏析的100 mm厚 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,其屈服强度和抗拉强度分别为540 MPa和869 MPa,其延伸率和‒40 ℃低温韧性很低,分别仅为5.1%和14 J. 再经过600、660和680 ℃回火后,实验钢强度相差不大,屈服强度介于528~551 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 ℃两相区退火后显微组织为临界铁素体和马氏体组织,再经过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明显恶化.

     

    Abstract: With the increasing demand for large-scale, lightweight, and highly safe ocean transportation vessels and drilling equipment, as well as the growing need for environmentally friendly steels, the demand for high-strength, high-toughness, and weldable thick steel plates for ships and ocean engineering is becoming increasingly significant. However, as the strength and thickness of steel plates increase, the low-temperature toughness of the center of high-strength and extra-thick steel plates has become a significant challenge. Owing to low rolling reduction and central segregation in ultra-heavy plate steel, the poor low-temperature toughness of the central region poses a major challenge that limits the application of high-strength ultra-heavy steels. This work systematically investigated the effects of a two-step intercritical heat treatment on regulating the 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 experimental steel exhibited a yield strength of 540 MPa and a tensile strength of 869 MPa. However, the elongation and low-temperature toughness at −40 ℃ were relatively low, at only 5.1% and 14 J, respectively. Subsequent tempering at 600 ℃, 660 ℃, and 680 ℃ did not significantly alter the yield strength of the experimental steel, which remained within the range of 528 MPa to 551 MPa, while the tensile strength decreased to between 687 MPa and 730 MPa. The elongation and low-temperature toughness of the experimental steel initially increased and then decreased with the tempering temperature. At a tempering temperature of 660 ℃, the plasticity and toughness were optimized, with an elongation of 30.6% and a Charpy impact energy of 163 J at −40 ℃. Microstructure characterization results indicated that the experimental steel annealed at 740 ℃ consisted of intercritical ferrite (IF) and martensite (M). After further tempering at 600 ℃, a multi-phase microstructure comprising IF and tempered martensite (TM) with fine carbides was obtained. At a tempering temperature of 660℃, the microstructure of the experimental steel consisted of IF, TM, and fine retained austenite (RA). The RA content in the central segregation region was significantly higher than that in the matrix, resulting in a significant improvement in the plastic toughness of the experimental steel. With the further increase in the tempering temperature to 680 ℃, the experimental steel realized an IF and TM structure, with a small proportion of RA and a significant fraction of martensite/austenite (M/A) constituents in the central segregation zone. The large fraction of M/A constituents could substantially deteriorate the plasticity and toughness of the experimental steel.

     

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