显微组织对460 MPa级特厚海工钢强韧性的影响

doi:10.13251/j.issn.0254-6051.2025.10.007

摘要/Abstract

摘要： 以TMCP工艺制备的460 MPa级100 mm特厚高强韧海工钢为研究对象,通过扫描电镜(SEM)、电子背散射衍射(EBSD)、电子探针显微分析(EPMA)和力学性能测试,揭示了钢板全厚度方向微观组织与力学性能的对应关系。结果表明,钢板沿厚度方向的强度呈梯度分布,即表层抗拉强度最高(731 MPa),心部次之(659 MPa),1/4厚度处最低(623 MPa),而断后伸长率呈相反的变化趋势,即1/4厚度处最高(25%),心部次之(21%),表面最低(15%)。微观强化机制分析表明,表层主要依赖位错强化(235.7 MPa)和织构强化(50 MPa),而心部析出强化贡献提升显著,为68 MPa。低温冲击试验结果表明,1/4厚度处-80 ℃冲击吸收能量高于160 J,表现出优异的低温韧性,而心部韧性下降与粒状贝氏体间弥散分布的M/A岛密切相关。微区表征和计算可知,M/A岛的存在提升了相邻贝氏体基体几何必须位错密度,会在贝氏体/铁素体相界面产生局部应力集中,成为微裂纹优先形核位点。

关键词: 海工钢, 特厚板, M/A岛, 几何必须位错密度, 屈服强度, 冲击性能

Abstract: A 460 MPa grade 100 mm super-thick high-strength and tough marine steel prepared by TMCP process was taken as the research object, the corresponding relationship between microstructure and mechanical properties in full thickness direction of the steel was revealed by means of scanning electron microscope (SEM), electron back scattering diffraction (EBSD), electron probe microanalysis (EPMA) and mechanical properties test. The results show that the strength shows a gradient along the thickness direction, that is, the tensile strength of surface layer is the highest (731 MPa), followed by the center (659 MPa), and the lowest at 1/4 thickness (623 MPa), while the elongation after fracture shows an opposite trend, that is, the highest at 1/4 thickness (25%), followed by the center (21%), and the lowest of surface layer (15%). The micro-strengthening mechanism analysis shows that the surface layer mainly dependent on dislocation strengthening (235.7 MPa) and texture strengthening (50 MPa), while the contribution of precipitation strengthening in the center is increased significantly, which is 68 MPa. The low temperature impact test results show that the -80 ℃ impact absorbed energy at 1/4 thickness is higher than 160 J, showing excellent low temperature toughness, and the decrease of toughness in the center is closely related to the M/A islands dispersed among granular bainite. Through the micro-area characterization and calculation, it can be seen that the presence of M/A islands increases the geometric dislocation density of the adjacent bainite matrix, resulting in local stress concentration at the bainite/ferrite interface, and becoming the preferred nucleation site for microcracks.

Key words: marine steel, super-thick plate, M/A island, geometrically necessary dislocation density, yield strength, impact property

中图分类号:

TG142.41

史术华, 脱臣德, 梁文洲, 金东浩, 高擎, 周文浩, 冯赞, 于新攀. 显微组织对460 MPa级特厚海工钢强韧性的影响[J]. 金属热处理, 2025, 50(10): 45-53.

Shi Shuhua, Tuo Chende, Liang Wenzhou, Jin Donghao, Gao Qing, Zhou Wenhao, Feng Zan, Yu Xinpan. Influence of microstructure on strength and toughness of 460 MPa super-thick marine steel[J]. Heat Treatment of Metals, 2025, 50(10): 45-53.

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