新型高Cr铁素体耐热钢焊接热影响区的物理模拟研究
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摘要
随着全球用电消耗量的持续增长,为解决日益突出的能源短缺和环境污染问题,世界各国火力发电机组参数正由亚临界参数向超(超)临界参数的方向发展。9%~12%Cr系铁素体耐热钢因具有良好的强韧性、抗氧化性、耐腐蚀性和较高的蠕变强度已逐渐成为热电厂中主要设备用材和更新换代材料的主选用钢。
本文利用焊接热模拟和定量金相结合的方法对改进的新型高Cr铁素体耐热钢的连续冷却转变曲线(SHCCT图)进行了测定,并研究试验用钢在不同冷却速度下的组织构成、组织形态和沉淀物形貌。利用正交试验方法考察热输入和预热温度对试验用钢热影响区(包括粗晶区-CGHAZ、细晶区-FGHAZ、临界区-ICHAZ和二次热循环的过临界粗晶区-SRCGHAZ、临界粗晶区-IRCGHAZ)组织和性能的影响规律。
试验结果表明,试验用高Cr铁素体耐热钢CGHAZ的组织为板条马氏体加δ铁素体,不同冷速下组织中马氏体与δ铁素体界面之间均存在脆化的碳化物薄层,而且随着冷速的增加,碳化物薄层的厚度逐渐下降。不同工艺下CGHAZ的室温冲击功均较低,而ICHAZ的室温冲击功均较高。组织中过饱和的马氏体和存在脆性相δ铁素体是造成CGHAZ室温韧性很低的主要原因,δ铁素体的含量越高,韧性越差。ICHAZ马氏体板条上细小的分布均匀的沉淀物能够有效地稳定马氏体基体,提高其韧性。CGHAZ的硬度最高,ICHAZ的硬度最低,IRCGHAZ与CGHAZ相比,硬度下降较多。
As global electric power consumption increases fast in recent years, in order to solve the increasingly prominent problem of inadequate energy and environmental pollution, thermal power generating units around the world are transforming from sub-critical parameters to the super (super-) critical parameters. 9~12% ferritic heat-resistant steel has gradually become the primary election material used for main power plant equipment and timber replacement materials for its excellent strength and toughness, oxidation resistance, corrosion resistance, and high creep strength.
In this paper, the SHCCT curve of new high Cr ferritic heat-resistant steel was made by thermal simulation and quantitative metallographic method, and studied the organization structure and morphology of precipitation at different cooling rates for testing steel. Orthogonal test was used to investigate the influences of heat input and preheat temperature on the microstructure and mechanical properties of heat affected zone (HAZ) of testing steel. Moreover, the HAZ includes coarse grain heat affected zone (CGHAZ), fine grain heat affected zone (FGHAZ), critical heat affected zone (ICHAZ), super-critically reheated coarse-grained HAZ (SRCGHAZ) and inter-critically reheated coarse-grained HAZ (IRCGHAZ).
Test results showed that testing steel CGHAZ was constructed of lath martensite and delta ferrite. The brittle dioxide layer could also be observed in the interface between lath martensite and delta ferrite under different cooling rates, and the thickness of carbon layer decreased with the cooling rate increasing. The CGHAZ impact energy at room temperature was low under the different welding process, but the ICHAZ had high impact energy at room temperature. Saturated martensite and brittleδferrite existed in the CGHAZ microstructure was the main reason for its low impact energy at room temperature, andδferrite content was higher, the worse the toughness. For ICHAZ, some fine precipitation which distributed uniformly in the martensite lath was able to stabilize the martensitic matrix, and the ICHAZ toughness was improved attributed to these fine precipitation. CGHAZ showed the highest hardness, and the ICHAZ hardness was the minimum, compared with CGHAZ, the IRCGHAZ hardness decreased a lot.
本文利用焊接热模拟和定量金相结合的方法对改进的新型高Cr铁素体耐热钢的连续冷却转变曲线(SHCCT图)进行了测定,并研究试验用钢在不同冷却速度下的组织构成、组织形态和沉淀物形貌。利用正交试验方法考察热输入和预热温度对试验用钢热影响区(包括粗晶区-CGHAZ、细晶区-FGHAZ、临界区-ICHAZ和二次热循环的过临界粗晶区-SRCGHAZ、临界粗晶区-IRCGHAZ)组织和性能的影响规律。
试验结果表明,试验用高Cr铁素体耐热钢CGHAZ的组织为板条马氏体加δ铁素体,不同冷速下组织中马氏体与δ铁素体界面之间均存在脆化的碳化物薄层,而且随着冷速的增加,碳化物薄层的厚度逐渐下降。不同工艺下CGHAZ的室温冲击功均较低,而ICHAZ的室温冲击功均较高。组织中过饱和的马氏体和存在脆性相δ铁素体是造成CGHAZ室温韧性很低的主要原因,δ铁素体的含量越高,韧性越差。ICHAZ马氏体板条上细小的分布均匀的沉淀物能够有效地稳定马氏体基体,提高其韧性。CGHAZ的硬度最高,ICHAZ的硬度最低,IRCGHAZ与CGHAZ相比,硬度下降较多。
As global electric power consumption increases fast in recent years, in order to solve the increasingly prominent problem of inadequate energy and environmental pollution, thermal power generating units around the world are transforming from sub-critical parameters to the super (super-) critical parameters. 9~12% ferritic heat-resistant steel has gradually become the primary election material used for main power plant equipment and timber replacement materials for its excellent strength and toughness, oxidation resistance, corrosion resistance, and high creep strength.
In this paper, the SHCCT curve of new high Cr ferritic heat-resistant steel was made by thermal simulation and quantitative metallographic method, and studied the organization structure and morphology of precipitation at different cooling rates for testing steel. Orthogonal test was used to investigate the influences of heat input and preheat temperature on the microstructure and mechanical properties of heat affected zone (HAZ) of testing steel. Moreover, the HAZ includes coarse grain heat affected zone (CGHAZ), fine grain heat affected zone (FGHAZ), critical heat affected zone (ICHAZ), super-critically reheated coarse-grained HAZ (SRCGHAZ) and inter-critically reheated coarse-grained HAZ (IRCGHAZ).
Test results showed that testing steel CGHAZ was constructed of lath martensite and delta ferrite. The brittle dioxide layer could also be observed in the interface between lath martensite and delta ferrite under different cooling rates, and the thickness of carbon layer decreased with the cooling rate increasing. The CGHAZ impact energy at room temperature was low under the different welding process, but the ICHAZ had high impact energy at room temperature. Saturated martensite and brittleδferrite existed in the CGHAZ microstructure was the main reason for its low impact energy at room temperature, andδferrite content was higher, the worse the toughness. For ICHAZ, some fine precipitation which distributed uniformly in the martensite lath was able to stabilize the martensitic matrix, and the ICHAZ toughness was improved attributed to these fine precipitation. CGHAZ showed the highest hardness, and the ICHAZ hardness was the minimum, compared with CGHAZ, the IRCGHAZ hardness decreased a lot.
引文
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[2]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
[3]肖凌,朱平,史春元,等.P92新型耐热钢焊接粗晶区回火参数选择[J].焊接,2006, 11:52-55
[4]于启湛,史春元.耐热金属的焊接[M].北京:机械工业出版社,2009
[5] M. Yoshizawa, M. Igarashia, K. Moriguchi, et al. Effect of precipitates on long-term creep deformation properties of P92 and P122 type advanced ferritic steels for USC power plants[J].Materials Science and Engineering A, 2009, 510-511:162-168
[6] MASUYAMAE. History of power plants and progress in heat resistant steels [J]. ISIJ, 2001, 41: 612-625
[7] WANG Xue, SHI Zhuan, PAN Qian-gang, et al. High-temperature creep properties of fine grained heat-affected zone in P92 weldment[J]. Transactions of Nonferrous Metals Society of China, 2009, 19:s772-s775
[8] Mats Hattestand, Hans-Olof Andren. Evaluation of particle size distributions of precipitates in a 9% chromium steel using energy filtered transmission electron microscopy[J]. Micron, 2001, 32:789-797
[9] F.Abe , T. Horiuchi,M. Taneike,et al. Stabilization of martensitic microstructure in advanced 9Cr steel during creep at high temperature[J]. Materials Science and Engineering A, 2004, A378:299-303
[10]M. Gold and R.I. Jaffee.Materials for advanced steam cycles[J].ASMJ.of Materials for Energy Systems, 1984, 6(2):130-145
[11]R. Viswanathan and W.T. Bakker. Materials for ultra supercritical fossil power plants[J]. Report TR-114750,EPRI,Palo Alto,2000
[12]吴军.T92钢管焊接接头组织和性能研究[D].济南:山东大学,2008.
[13]D.Rojas, J.Garcia, O.Prat. 9%Cr heat resistant steels: Alloy design, microstructure evolution and creep response at 650℃[J]. Materials Science and Engineering A, 2011, 528:5164-5176
[14]Feng-shi Yin, Woo-sang Jung, Soon-hyo Chung. Microstructure and creep rupture characteristics of an ultra-low carbon ferritic/martensitic heat-resistant steel[J]. Scripta Materialia, 2007, 57:469-472
[15]P.F.Giroux, F.Dallea, M.Sauzay. Mechanical and microstructural stability of P92 steel under uniaxial tension at high temperature[J]. Materials Science and Engineering A, 2010, 527:3984-3993
[16]Allen T R,Tan L,Gan J,et al. Microstructural development in advanced ferritic-martensitic steel HCM12A[J].Journal of Nuclear Materials, 2006, 351(1-3):174-186
[17]刘正东,程世长.钒对T122铁素体耐热钢组织和性能的影响[J].特殊钢,2006, 7(1):7-11
[18]Dobrzanski J. The classification method and the technical condition evaluation of the critical elements’material of power boilers in creep service made from the 12Cr -1-Mo-V[J]. Journal of Material Processing Technology, 2005, 164:785-794
[19]Auerkari P, Holstrom S, Veivo J, et al. Creep damage and expected creep life for welded 9-11% Cr steels[J]. International Journal of Pressure Vessels and Piping, 2007, 84(1-2):69-74
[20]包汉生,傅万堂,程世长等.T122耐热钢中氮化硼(BN)化合物的探讨[J].钢铁,2005, 40(10):68-71
[21]Brozda J, Zeman M. Wrong heat treatment of martensitic steel welded tubes caused major cracking assembly of resuperheaters in a fossil fuel power plant[J]. Engineering Failure Analysis, 2003, 10(5):569-579
[22]Klueh R L. Reduced-activation bainitic and martensitic steels for nuclear fusion applications[J]. Current Opinion in Solid State and Materials Science, 2004, 8(3-4):239-250
[23]徐德录,郭军,陈玉成.T91钢的性能及在我国电站锅炉中的应用[J].电力建设,1999, 3(2):12-16
[24]Yaghi A H, Hyde T H, Becker A A. Residual stress simulation in welded sections of P91 pipes [J]. Journal of Materials Processing Technology, 2005,167(2-3):480-487
[25]王同芬.9CrlMoV钢焊接性试验及其应用[J].焊接,1995, 1:8-12
[26]王效杰,胡兰芬,亓安芳等.国产T91钢管焊接性试验及其应用[J].焊接生产与研究,1996, 9(5):31-34
[27]崔凤友.USC电站锅炉用耐热钢SA312-T92的焊接研究[D].济南:山东大学,2009
[28]卢征然,王炯祥,亓安芳等.超超临界锅炉用钢SA-335P92焊接性试验研究[J].2006, 37(1):38-55
[29]R.K. Shiue , K.C. Lan, C. Chen. Toughness and austenite stability of modified 9Cr–1Mo welds after tempering[J]. Materials Science and Engineering A, 2000, 287:10-16
[30] A. Moitra, P. Parameswaran, P.R. Sreenivasana, et al. A toughness study of the weld heat-affected zone of a 9Cr-1Mo steel[J]. Materials Characterization, 2002, 48:55-61
[31]V. Thomas Paul, S. Saroja , M. Vijayalakshmi. Microstructural stability of modified 9Cr-1Mo steel during long term exposures at elevated temperature[J]. Journal of Nuclear Materials, 2008, 378:273-281
[32]孙咸,王红鸿.新型耐热钢P91焊缝中的马氏体[J].焊接,2010, 4:7-12
[33]李晓泉,腾亚兰,初雅杰等.焊接热循环对T92钢组织脆化的影响[J].焊接学报,2010, 31(3):9-12
[34]李宜男,杨松,丁冶.超超临界锅炉用SA335-P92钢的焊接工艺性能研究[J].焊接生产应用,2007, 6:44-46
[35]Li Yajiang, Zhou Bing, Feng Tao, et al. Microstructure and fracture morphology in the welding zone of T91 heat-resistant steel used in power station[J]. Journal of Materials Science and Technology, 2002, 18(5): 427-430
[36] P. Chellapandi, S.C. Chetal . Influence of mis-match of weld and base material creep properties on elevated temperature design of pressure vessels and piping[J]. Nuclear Engineering and Design, 2000, 195:189-196
[37]王淦刚,赵军,赵建仓.P92新型耐热钢焊接接头的力学性能研究及工程应用[J].电力设备,2007, 5:1-5
[38]李全忠.P91钢焊接工艺实验[J].青海电力,2003, 2:42-46
[39]马汝坡.A335P91管道材料的焊接[J].热机技术,2002, 12(2):24-26
[40]李文彬.SA335-P92钢焊接工艺研究[D].保定:华北电力大学,2008
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