Effect of Heat Treatment on Delta-ferrite and Impact Toughness of P91 Heat-resistant Steel
ZHANG Jianbin1, LIU Fan1, XUE Fei2
1 State Key Laboratory of Advanced Processing and Recyling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou 730050; 2 Suzhou Nuclear Power Research Institute, Suzhou 215004
Abstract: Delta-ferrite, whose morphology, content and distribution depended on hot processing temperature, readily generated in P91 heat-resistant steel during hot processing, such as hot rolling, welding and heat treatment. The mixed microstructure, including martensite and delta-ferrite, was obtained by normalizing at different temperatures (1 150 ℃,1 250 ℃,1 300 ℃) in accor-dance with the designed heat treatment processing, and the normalizing microstructure (1 300 ℃) undertook oil cooling (at 1 050 ℃)+air cooling (at 760 ℃). The content, morphology and distribution of delta-ferrite were observed by OM (optical microscope), SEM (scanning electron microscope) with EDS (energy-dispersive spectrometry), and the microhardness, impact toughness and fracture failure mode of that were tested. The results demonstrated that delta-ferrite content of P91 steel increased along with the increase of normalizing temperature, and its morphology presented thin strip, strip and bulk, and bulk polygon. The delta-ferrite generated due normalizing at 1 300 ℃ could not be eliminated by normalizing at 1 050 ℃ and tempering at 760 ℃, while the content decreased, morphology and distribution of delta-ferrite altered. The impact energy reduced with increase in delta-ferrite content, and the impact fracture failure mode converted to brittle fracture from ductile-brittle fracture. In contrast with strip morphology, the bulk polygon of delta-ferrite at boundaries was not conducive to impact toughness.
1 Lverde D, Gomez-Acebo T, Castro F. Continuous and cyclic oxidation of T91 ferritic steel under steam[J].Corrosion Science,2004,46(3):613. 2 Zhang Lifang, Zhou Yan, Qiao Zhixia,et al. Kinetics of martensite phase transformation of T91 steels during continuous cooling[J].Mater Review,2015(s2):489(in Chinese). 张丽芳,周严,乔志霞,等.T91钢连续冷却过程中马氏体相变动力学的研究[J].材料导报,2015(s2):489. 3 Yan Chaopeng, Sun Feng, Shan Aidang, et al. Research progress of ferritic heat-resistant steels used for ultra-super critical steam turbine units[J].Materials for Mechanical Engineering,2008,32(12):1(in Chinese). 闫超鹏,孙锋,单爱党,等.超超临界火电机组用铁素体耐热钢的研究现状[J].机械工程材料,2008,32(12):1. 4 Ning Baoqun, Liu Yongchang, Yin Hongqi,et al. Developement and investigation of ferritic heat resistant steels for boiler tube of the advanced power plants[J].Materials Review,2006,20(12):83(in Chinese). 宁保群,刘永长,殷红旗,等.超高临界压发电厂锅炉管用铁素体耐热钢的发展现状与研究前景[J].材料导报,2006,20(12):83. 5 Shu Guogang, Ding Hui, Liu Shutao,et al. Fracture morphology microstructure and sbu-microstructure analyses of 9Cr-1Mo-V-Nb-N steel pipe made in china[J].Electric Power,2004(7):58(in Chinese). 束国刚,丁辉,刘树涛,等.国产9Cr-1Mo-V-Nb-N钢管的断口、组织及亚结构分析[J].中国电力,2004(7):58. 6 Guo Yuanrong, Chen Yu, Zhan Yong,et al. Research on δ ferrite contained in P91 hot-rolled seamless steel tube[J].Steel Pipe,2011,40(5):17(in Chinese). 郭元荣,陈雨,詹勇,等.P91热轧无缝钢管中δ铁素体的研究[J].钢管,2011,40(5):17. 7 Zhao Lei,Yang Chao, Qiao Hanwen,et al. Effect of welding process on δ ferrite in T92/S30432 dissimilar welded joint[J].Transaction of Materials and Heat Treatment,2014,35(11):111(in Chinese). 赵雷,杨超,乔汉文,等.焊接工艺对T92/S30432异种钢接头δ铁素体的影响[J].材料热处理学报,2014,35(11):111. 8 Zhang Jianbin, Liu Fan, Fan Ding,et al. Influence of delta-ferrite content on impact toughness of joint P91 heat-resistant steel[J].Transaction of Materials and Heat Treatment,2017(3):108(in Chinese). 张建斌,刘帆,樊丁,等.δ-铁素体对P91耐热钢接头冲击性能的影响[J].材料热处理学报,2017(3):108. 9 Liu Jiangnan, Shu Guogang, Wang Zhengpin,et al. Effect of heat treatment on microstructures and properties of 12Cr-2W-Mo-V-N-B steel[J].Heat Treatment of Metals,2004(2):7(in Chinese). 刘江南,束国刚,王正品,等.12Cr-2W-Mo-V-Nb-N-B钢的热处理与组织和性能[J].金属热处理,2004(2):7. 10 Shi Ruxing,Liu Zhengdong,Zhang Caiming.Thermodynamic calculation and experimental measurement of δ ferrite amount in P92 heat resistant steel[J].Iron and Steel,2011,46(11):89(in Chinese). 石如星,刘正东,张才明.P92耐热钢δ-铁素体含量的热力学计算与试验分析[J].钢铁,2011,46(11):89. 11 Zhao Yihan, Zhao Chengzhi, Wang Jiannan, et al. Forming mechanism of δ-ferrite and its effect on martensite heat-resitant steel impact energy[J].Iron and Steel 2013,48(4):70(in Chinese). 赵义瀚,赵成志,王健楠,等.δ-铁素体形成机制以及对马氏体耐热钢冲击功的影响[J].钢铁,2013,48(4):70. 12 Anderko K, Schafer L, Materna-Morris E. Effect of the δ-ferrite phase on the impact properties of martensitic chromium steels[J].Journal of Nuclear Materials,1991,179-181:492. 13 Alkan G, Chae D, Kims J. Effect of δ-ferrite onimpact property of hot-rolled 12Cr-Ni steel[J].Materials Science & Engineering A,2013,585:39. 14 Yan W, Wang W, Shan Y, et al. 9-12Cr heat-resistant steels[M].Berlin:Springer International Publishing,2015. 15 Voort G F V, Lucas G M, Manilova E P. Metallography and microstructures of stainless steels and maraging steels[M].Ohio:The Materials Information Company,2004.
渝公网安备50019002502923号 版权所有：《材料导报》编辑部
2018, Vol. 32 
