显微组织特征对20万立方米LNG储罐用9Ni钢屈强比的影响  

Effect of microstructure characteristics on yield ratio of 9Ni steel used in LNG storage tanks with a capacity of 200000 cubic meters

作　　者：杜林 王堤鹤 庞启航 钟莉莉 于佳瑶 张宏亮 赵立冬 Du Lin;Wang Dihe;Pang Qihang;Zhong Lili;Yu Jiayao;Zhang Hongliang;Zhao Lidong(State Key Laboratory of Metal Materials for Marine Equipment and Their Applications,Anshan Liaoning 114009,China;School of Materials and Metallurgy,University of Science and Technology Liaoning,Anshan Liaoning 114051,China)

机构地区：[1]海洋装备用金属材料及其应用国家重点实验室,辽宁鞍山114009 [2]辽宁科技大学材料与冶金学院,辽宁鞍山114051

出　　处：《金属热处理》2024年第12期198-205,共8页Heat Treatment of Metals

基　　金：国家自然科学基金(52004122)。

摘　　要：液化天然气是重要新型清洁能源,20万立方米级的LNG储罐建造目前引领着LNG储罐发展。而9Ni钢凭借良好的综合力学性能逐步成为液化天然气储罐建造主流产品。使用X射线衍射、电子探针、透射电镜等先进表征手段,分析了显微组织对9Ni钢力学性能的影响作用,以揭示试验钢“高强度+低屈强比”的强化机制。试验结果表明,试验钢回火索氏体的晶粒尺寸和逆转变奥氏体的体积分数是影响其屈强比的关键显微组织参数。经淬火+临界淬火(Critical quenching)+回火(QLT)工艺处理后,与淬火+高温回火(QT)工艺相比,试验钢中回火索氏体晶粒尺寸由8.1μm粗化为13.1μm,而逆转变奥氏体的体积分数由5%提升为10.2%,从而其屈服强度提升至622 MPa,抗拉强度保持稳定,屈强比降到0.87。这主要因为试验钢Ni元素局部偏聚形成多尺寸级别的回火索氏体和逆转变奥氏体参数变化,从而间接影响了其力学性能。Liquefied natural gas is an important new clean energy,and the construction of 200000 cubic meters of LNG storage tanks is currently leading the development of LNG storage tanks.Meanwhile,9Ni steel has gradually become the mainstream product of LNG storage tank construction by virtue of its excellent comprehensive mechanical properties.The effect of microstructure on the mechanical properties of the tested steel was investigated by means of X-ray diffraction,electron probe and transmission electron microscopy to unravel the underlying mechanisms behind the‘high strength and low yield ratio'reinforcement exhibited by the tested steel.The tested results show that the grain size of tempered sorbite and the volume fraction of reversed austenite are crucial microstructural parameters influencing the yield ratio of the tested steel.Following treatment with QLT process,compared with the QT process,the grain size of tempered martensite in the tested steel is coarsened from 8.1μm to 13.1μm,while the volume fraction of reverse transformation austenite is increased from 5%to 10.2%.Consequently,its yield strength is improved to 622 MPa,while maintaining a stable tensile strength and reducing the yield ratio to 0.87.These changes primarily stem from localized enrichment of nickel elements within the tested steel,leading to variations in parameters associated with multi-scale levels of tempered sorbite and reversed austenite.As a result,these alterations indirectly effect its mechanical properties.

关 键 词：9NI钢 回火索氏体 逆转变奥氏体 屈强比 Ni元素局部偏聚 

分 类 号：TG142.1[一般工业技术—材料科学与工程]