Research on Impact Toughness in Microzones of 12Cr/30Cr2Ni4MoV Dissimilar Rotor Steel Welded Joint

doi:10.3901/JME.2021.02.053

Abstract

Abstract: The dissimilar rotor steel welded joint (12Cr/30Cr2Ni4MoV) with buttering layer is fabricated by using the combined welding technology of narrow-gap tungsten inert gas (NG-TIG) and narrow-gap submerged arc welding (NG-SAW). The shear strength of joint microzone is obtained by microshear test, and the ductile-brittle transition temperature FATT50 of microzones is obtained by partition test. The influence of microstructure on hardness, strength and toughness of microzones is investigated. The results indicate that the distribution characteristics of hardness and shear strength in welded joint are basically the same. The mechanical properties of HAZs exhibit gradient distribution, and interface mechanical properties mismatch on both sides of the fusion line. There is a local weakening area in buttering layer, and the micro-hardness value is 227 HV, which is the weakest area of the whole welded joint. From base metal 12Cr to 30Cr2Ni4MoV, the ductile-brittle transition temperature FATT50 of joint microzones gradually decreases. At 20℃, the impact toughness of 30Cr2Ni4MoV and its heat affected zone is excellent, with generation of cracks at the interface between matrix and second phase, ductile fracture occurs through the aggregation of micropores. Quasi-cleavage fracture occurs in all the other microrzones, and the impact toughness of welded metal is the weakest.

Key words: dissimilar rotor steel, welded joint, microstructure, mechanical properties

CLC Number:

TG407

ZHU Bo, WANG Wenke, GUO Yang, XIONG Jiankun, ZHANG Jianxun. Research on Impact Toughness in Microzones of 12Cr/30Cr2Ni4MoV Dissimilar Rotor Steel Welded Joint[J]. Journal of Mechanical Engineering, 2021, 57(2): 53-61.

References

[1] 谢永慧,邓实,张荻,等. 汽轮机转子焊接的三维有限元数值模型研究[J]. 热力透平,2010,39(1):12-18. XIE Yonghui,DENG Shi,ZHANG Di,et al. Study on numerical model for welding process of steam turbine rotor based on three-dimensional finite element method[J]. Thermal Turbine,2010,39(1):12-18.
[2] SHIGE T,MAGOSHI R,ITOU S,et al. Development of large-capacity,highly efficient welded rotor for steam turbines[J]. Mitsubishi Heavy Industries,2001,38(1):6-11.
[3] 蔡雄军,冷进明,熊建坤. 28CrMoNiV与25Cr2Ni4MoV异种转子钢焊接接头性能研究[J]. 电焊机,2018,48(8):114-120. CAI Xiongjun,LENG Jinming,XIONG Jiankun. Research on properties of welded joints of 28CrMoNiV and 25Cr2Ni4MoV dissimilar rotor steel[J]. Electric Welding Machine,2018,48(8):114-120.
[4] WANG W K,ZHANG J X,ZHANG L J,et al. Microstructure and local mechanical properties of a dissimilar metal welded joint with buttering layer in steam turbine rotor[J]. Materials Science & Engineering A,2019,747(18):244-254.
[5] WANG W K,ZHANG J X,XU Z Z,et al. High cycle fatigue behavior of a dissimilar metal welded joint in ultra-supercritical steam turbine rotor[J]. Materials Research Express,2020(7):1-11.
[6] 谭龙,张从平,张建勋. 焊接转子窄间隙焊接接头冲击韧性数值研究[J]. 焊管,2013,36(9):5-10. TAN Long,ZHANG Congping,ZHANG Jianxun. Numerical simulation study on welded joints impact toughness for welded rotor narrow gap[J]. Welded Pipe and Tube,2013,36(9):5-10.
[7] 林腾昌,王慧,王成杰,等. 超临界高中压转子用12%Cr钢的研究现状[J]. 铸造技术,2012,33(11):1267-1269. LIN Tengchang,WANG Hui,WANG Chengjie,et al. Research status of 12%Cr HP-IP supercritical rotor steel[J]. Foundry Technology,2012,33(11):1267-1269.
[8] 赵双群,林富生. 长期服役后低压转子30Cr2Ni4MoV钢的性能研究[J]. 动力工程学报,2013,33(2):153-159. ZHAO Shuangqun,LIN Fusheng. Investigation on mechanical properties of 30Cr2Ni4MoV LP rotor steel after long-term service[J]. Journal of Chinese Society of Power Engineering,2013,33(2):153-159.
[9] JAMES E,WITTIG,ROBERT S. Carbide evolution in temper embrittled NiCrMoV bainitic steel[J]. Steel Research International,2004,75(1):47-54.
[10] 宋思远,刘中华,黄淑秋,等. 浅析工业汽轮机转子材料的FATT[J]. 工业汽轮机,2009(2):1-8. SONG Siyuan,LIU Zhonghua,HUANG Shuqiu,et al. Analysis on FATT of industrial steam turbine rotor materials[J]. Industrial Steam Turbine,2009(2):1-8.
[11] 刘中华,何成,刘京伟,等. 工业汽轮机转子用钢28CrMoNiV脆性转变温度的研究[J]. 机电工程,2015,32(12):1564-1568. LIU Zhonghua,HE Cheng,LIU Jingwei,et al. Research on the fracture appearance transition temperature of industrial steam turbine rotor steel 28CrMoNiV[J]. Journal of Mechanical & Electrical Engineering,2015,32(12):1564-1568.
[12] 陈睿恺. 30Cr2Ni4MoV钢低压转子热处理工艺的研究[D]. 上海:上海交通大学,2012. CHEN Ruikai. Research on heat treatment technology of low pressure rotor steel 30Cr2Ni4MoV[D]. Shanghai:Shanghai Jiao Tong University,2012.
[13] 高玉芬,王绍智,唐元生. 单丝窄间隙埋弧焊焊接缺陷分析及预防[J]. 金属加工(热加工),2010(8):54-56. GAO Yufen,WANG Shaozhi,TANG Yuansheng. Analysis and prevention of welding defects in single wire narrow gap submerged arc welding[J]. MW Metal Forming,2010(8):54-56.
[14] 俞学节. 回火结构钢的断裂行为和显微组织的关系[J]. 上海钢研,1985,132(5):37-43. YU Xuejie. Relationship between fracture behavior and microstructure of tempered structural steel[J]. Journal of Shanghai Iron & Steel Research,1985,132(5):37-43.
[15] 李杰,王丽,李志,等. 热处理对高Co-Ni超高强度钢冲击断口的影响[J]. 航空材料学报,2008,28(1):35-39. LI Jie,WANG Li,LI Zhi,et al. Effect of heat treatment on impact fracture of ultra-high strength Co-Ni steel[J]. Journal of Aerospace Materials,2008,28(1):35-39.
[16] HAN Y C,CHEN X D,FAN Z C,et al. Influence of second thermal cycle on reheat cracking susceptibility of welding CGHAZ in vanadium-modified 2.25Cr1Mo steel[J]. Procedia Engineering,2015,130:487-496.
[17] 沈林,陈辉,徐力栋,等. 不锈钢激光-MAG复合焊接头微区性能研究[J]. 材料科学与工艺,2018,26(5):40-46. SHEN Lin,CHEN Hui,XU Lidong,et al. Research on micro-zone properties of laser-MAG hybrid welded stainless steel joint[J]. Materials Science and Technology,2018,26(5):40-46.
[18] 张建勋,孙茜,毕宗岳,等. X100螺旋埋弧焊管焊接HAZ微区组织与性能研究[J]. 焊管,2012,35(12):5-10. ZHANG Jianxun,SUN Xi,BI Zongyue,et al. Research on microstructure and performance in welding HAZ of X100 SAWH pipe[J]. Welded Pipe and Tube,2012,35(12):5-10.