高Cr铁素体耐热钢高温热循环过程的组织演化规律
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摘要
为探究高Cr铁素体耐热钢高温热循环过程的组织演化规律,通过采用光镜与透射电镜显微组织分析方法,对高Cr铁素体耐热钢单次和二次高温热循环加热后基体组织和沉淀相的演变规律展开研究,从而为第4类裂纹萌生微观机制的研究提供试验依据.结果表明:高温热循环加热后,奥氏体相分数都随着峰值温度的增高呈现先增加后降低的趋势,在峰值温度1,100,℃处达到最大;M_(23)C_6碳化物在峰值温度达1,100,℃后全部溶解,而MX碳化物在峰值温度达1,300,℃后才全部溶解,且MX的尺寸在不同热循环过程中基本保持不变;马氏体板条宽度随着峰值温度的升高而增加;沉淀相的溶解和δ-铁素体的形成对基体的硬度有明显影响.
To explore the microstructure evolution of high Cr ferritic heat-resistant steel in high temperature thermal cycle,high temperature thermal cycle test was carried out. By using optical microscopy and transmission electron microscopy(TEM),the evolution of matrix and precipitate of high Cr ferritic heat-resistant steel in single high temperature thermal cycle test and double high temperature thermal cycle test was systematically studied,which provides the experimental basis for the study of initiation micro mechanism of the fourth welding crack. The results show that during high temperature thermal cycle test,the fraction of the austenite phase increases first and then decreases with the increase of thermal cycle temperature,reaching the maximum at the peak temperature 1 100 ℃.The M_(23)C_6 carbonitrides all resolve at the peak temperature 1 100 ℃,while the MX carbonitrides all resolve at the peak temperature 1 300 ℃,and their sizes in different high temperature thermal cycle tests have remained unchanged.The widths of martensite increase with the increase of thermal cycle temperature.The dissolution of precipitate and the formation of δ-ferrite have an important effect on the hardness.
To explore the microstructure evolution of high Cr ferritic heat-resistant steel in high temperature thermal cycle,high temperature thermal cycle test was carried out. By using optical microscopy and transmission electron microscopy(TEM),the evolution of matrix and precipitate of high Cr ferritic heat-resistant steel in single high temperature thermal cycle test and double high temperature thermal cycle test was systematically studied,which provides the experimental basis for the study of initiation micro mechanism of the fourth welding crack. The results show that during high temperature thermal cycle test,the fraction of the austenite phase increases first and then decreases with the increase of thermal cycle temperature,reaching the maximum at the peak temperature 1 100 ℃.The M_(23)C_6 carbonitrides all resolve at the peak temperature 1 100 ℃,while the MX carbonitrides all resolve at the peak temperature 1 300 ℃,and their sizes in different high temperature thermal cycle tests have remained unchanged.The widths of martensite increase with the increase of thermal cycle temperature.The dissolution of precipitate and the formation of δ-ferrite have an important effect on the hardness.
引文
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[3]宁保群,刘永长,乔志霞,等.T91铁素体耐热钢过冷奥氏体转变过程中临界冷却速度的研究[J].材料工程,2007(9):9-13.Ning Baoqun,Liu Yongchang,Qiao Zhixia,et al.Determination of critical cooling rates in undercooled austenite transformation process of T91 ferritic heat-resistant steel[J].Journal of Materials Engineering,2007(9):9-13(in Chinese).
[4]Liu C X,Liu Y C,Zhang D T,et al.Kinetics of isochronal austenization in modified high Cr ferritic heatresistant steel[J].Applied Physics A,2011,105(4):949-957.
[5]乔亚霞,武英利,徐联勇.9%~12%Cr高等级耐热钢的Ⅳ型开裂研究进展[J].中国电力,2008,41(5):33-36.Qiao Yaxia,Wu Yingli,Xu Lianyong.Analysis of the typeⅣcracking in advanced 9%—12%,Cr heat-resisting steel[J].Electric Power,2008,41(5):33-36(in Chinese).
[6]Fujibayashi S,Eedo T.Creep behavior at the intercritical HAZ of a 1.25Cr-0.5Mo steel[J].ISIJ International,2002,42(11):1309-1317.
[7]Francis J A,Mazur W,Bhadeshia H,et al.Review typeⅣcracking in ferritic power plant steels[J].Materials Science and Technology,2006,22(12):1387-1395.
[8]Albert S K,Matsui M,Watanabe T,et al.Microstructural investigations on typeⅣcracking in a high Cr steel[J].ISIJ International,2002,42(12):1497-1504.
[9]Watanabe T,Tabuchi M,Yamazaki M,et al.Creep damage evaluation of 9Cr-1Mo-V-Nb steel welded joints showing TypeⅣfracture[J].International Journal of Pressure Vessels and Piping,2006,83(1):63-71.
[10]Tabuchi M,Ha J,Hongo H,et al.Experimental and numerical study on the relationship between creep crack growth properties and fracture mechanisms[J].Metallurgical and Materials Transactions A,2004,35(6):1757-1764.
[11]Hald J.Microstructure and long-term creep properties of9%—12%,Cr steels[J].International Journal of Pressure Vessels and Piping,2008,85(1):30-37.
[12]Maruyama K,Sawada K,Koike J.Strengthening mechanisms of creep resistant tempered martensitic steel[J].ISIJ International,2001,41(6):641-653.
[13]Abe F.Precipitate design for creep strengthening of 9%,Cr tempered martensitic steel for ultra-supercritical power plants[J].Science and Technology of Advanced Materials,2008,9(1):013002.
[14]Hald J,Korcakova L.Precipitate stability in creep resistant ferritic steels-experimental investigations and modelling[J].ISIJ International,2003,43(3):420-427.
[15]Strang A,Vodarek V.Z phase formation in martensitic12CrMoVNb steel[J].Materials Science Journal,1996,12(7):552-556.
[16]高惠临,董玉华,Hendricks R W.超低碳QT钢焊接二次热循环的组织转变与局部脆化[J].金属学报,2001,37(1):34-38.Gao Huilin,Dong Yuhua,Hendricks R W.Microstructure transformation and brittlement of a ultra-low carbon QT steel during double welding thermal cycle[J].Acta Metallurgica Sinica,2001,37(1):34-38(in Chinese).
[17]Latha S,Laha K,Rao K B S,et al.Comparative study of tensile flow parameters in forged and rolled 9Cr-1Mo steel[J].International Journal of Pressure Vessels and Piping,1996,67(2):155-160.
[18]Gao Q Z,Liu Y C,Di X J,et al.Influence of austenitization temperature on phase transformation features of modified high Cr ferritic heat-resistant steel[J].Nuclear Engineering and Design,2013,256(3):148-152.
[19]Morito S,Saito H,Ogawa T,et al.Effect of austenite grain size on the morphology and crystallography of lath martensite in low carbon steels[J].ISIJ International,2005,45(1):91-94.
[20]Morito S,Yoshida H,Maki T,et al.Effect of block size on the strength of lath martensite in low carbon steels[J].Materials Science and Engineering A,2006,438(1):237-240.
[21]Yan B Y,Liu Y C,Wang Z J,et al.The effect of precipitate evolution on austenite grain growth in RAFM steel[J].Materials,2017,10(9):1017-1027.
[22]Schino A D,Kenny J M.Grain refinement strengthening of a micro-crystalline high nitrogen austenitic stainless steel[J].Materials Letters,2003,57(12):1830-1834.