2.25Cr1Mo钢中磷的平衡晶界偏聚及其对钢的韧脆转变温度的影响
|
摘要
2.25Cr1Mo钢是一种以Cr、Mo为主要合金元素的低碳低合金结构钢,在高温下具有较高强度和抗氧化性,并具有良好的焊接性,因此广泛应用于电力、核能以及石油化学工业高温承压设备中,特别是电厂主蒸汽管道及热蒸汽管道的主要用材。然而,如果其长期在高温(350~600℃)和高压(0~28Mp)条件下工作,其中的某些微量合金元素或杂质元素会偏聚到晶界处,从而导致钢铁材料变脆,即会出现所谓的回火脆性现象。
大量的试验研究表明,产生回火脆化的根本原因是合金钢在一定温度回火及回火后冷却或时效过程中P、Sn、Sb和As等有害元素在原奥氏体晶界处偏聚,降低了铁原子在晶界处的结合力,使其晶界成为薄弱之处。而其中磷元素是引起回火脆性的主要原因。
发生回火脆性的材料,由于韧性降低,可以用一定冲击功下的转变温度或断口转变温度的上升量来定量评价回火脆化程度。由于断裂韧度的测定比较困难,通常用V型缺口Charpy试样的冲击功Ak讨论转变温度或50%断口纤维率FATT作为回火脆化的判据。
本研究利用俄歇能谱仪(AES)检测了经980℃淬火后的2. 25Cr1Mo钢在650℃回火2h后,又分别在560℃时效100h、300h、500h,520℃时效300h、500h、800h及480℃时效500h、800h、1200h的钢样品中磷元素在晶界上的偏聚情况,并将得到的结果同相关资料中给出的数值进行了比较和讨论。通过计算机VB程序,用动力学模拟讨论了磷在钢中的扩散系数,验证了俄歇试验结果的合理性。最后通过系列冲击试验及其分析得到材料的韧脆转变温度,并分析了磷的偏聚对韧脆转变温度的影响。
根据平衡晶界偏聚理论和偏聚动力学理论估算出试样中磷在560℃、520℃和480℃的平衡晶界偏聚量分别是18.86at.%、23.20at.%和28.75at.%,试样在560℃、520℃和480℃偏聚自由能都约为-38KJ/mol。随着时效温度的升高,磷的偏聚量逐渐减少,而在同一个时效温度下,随着时间的增加,偏聚量逐渐增加。通过夏比V型系列冲击试验可以看出,磷的晶界偏聚可以明显提高材料的韧脆转变温度,且偏聚量越大,韧脆转变温度的越高。
2.25Cr1Mo steel is an important low-alloy structural steel which mainly contains the elements of Cr and Mo. This steel has high strength and oxidation-resistance in the high temperature, and can be well welded. So it is widely used for pressure vessels in the power, nuclear energy and petrochemical inductries, especially used in main steam and heat steam pipes in the power industry. Unfortunately, when subjected to extended exposure to intermediate service temperature(350℃~600℃) and high pressure(0~28Mpa), the steels become embrittled because of segregation of some impurity elements to grain boundaries.
It is well known that temper embrittlement in 2.25Cr1Mo steel is caused by grain boundary segregation of impurity elements like P, Sn, Sb, and As, which decrease the grain boundary cohesion. Studies indicate that temper embrittlement is mainly caused by grain bondary segregation of P.
Temper embrittlement results in a loss of material toughness. This phenomenon is best represented by a shift of the ductile-to-brittle transition temperature(DBTT) to higher temperatures. The DBTT is usually defined as the temperature corresponding to the mean value of the upper-shelf and lower-shelf energies or the temperature at which the fracture surface contains 50% shear fracture characteristics(the fracture appearance transiton temperature(FATT)).
In the present work, we examined the equilibrium grain boundary segregation behavior of phosphorus in a 2.25Cr1Mo steel. The steel was quenched from 980℃and tempered at 650℃for 2h, followed by ageing at 560℃, 520℃, 480℃for different times. By means of Auger Electron Spectroscopy(AES), the equilibrium grain boundary segregation of phosporus was examined. By the computer software VB with the equilibrium segregation kinetic equation, we simulate the kinetic curve of the specimens aged at 480℃, which accord with the experimental results well if consider the standard deviation. In the end, the DBTTs are tested by Charpy V-notch impact test.
大量的试验研究表明,产生回火脆化的根本原因是合金钢在一定温度回火及回火后冷却或时效过程中P、Sn、Sb和As等有害元素在原奥氏体晶界处偏聚,降低了铁原子在晶界处的结合力,使其晶界成为薄弱之处。而其中磷元素是引起回火脆性的主要原因。
发生回火脆性的材料,由于韧性降低,可以用一定冲击功下的转变温度或断口转变温度的上升量来定量评价回火脆化程度。由于断裂韧度的测定比较困难,通常用V型缺口Charpy试样的冲击功Ak讨论转变温度或50%断口纤维率FATT作为回火脆化的判据。
本研究利用俄歇能谱仪(AES)检测了经980℃淬火后的2. 25Cr1Mo钢在650℃回火2h后,又分别在560℃时效100h、300h、500h,520℃时效300h、500h、800h及480℃时效500h、800h、1200h的钢样品中磷元素在晶界上的偏聚情况,并将得到的结果同相关资料中给出的数值进行了比较和讨论。通过计算机VB程序,用动力学模拟讨论了磷在钢中的扩散系数,验证了俄歇试验结果的合理性。最后通过系列冲击试验及其分析得到材料的韧脆转变温度,并分析了磷的偏聚对韧脆转变温度的影响。
根据平衡晶界偏聚理论和偏聚动力学理论估算出试样中磷在560℃、520℃和480℃的平衡晶界偏聚量分别是18.86at.%、23.20at.%和28.75at.%,试样在560℃、520℃和480℃偏聚自由能都约为-38KJ/mol。随着时效温度的升高,磷的偏聚量逐渐减少,而在同一个时效温度下,随着时间的增加,偏聚量逐渐增加。通过夏比V型系列冲击试验可以看出,磷的晶界偏聚可以明显提高材料的韧脆转变温度,且偏聚量越大,韧脆转变温度的越高。
2.25Cr1Mo steel is an important low-alloy structural steel which mainly contains the elements of Cr and Mo. This steel has high strength and oxidation-resistance in the high temperature, and can be well welded. So it is widely used for pressure vessels in the power, nuclear energy and petrochemical inductries, especially used in main steam and heat steam pipes in the power industry. Unfortunately, when subjected to extended exposure to intermediate service temperature(350℃~600℃) and high pressure(0~28Mpa), the steels become embrittled because of segregation of some impurity elements to grain boundaries.
It is well known that temper embrittlement in 2.25Cr1Mo steel is caused by grain boundary segregation of impurity elements like P, Sn, Sb, and As, which decrease the grain boundary cohesion. Studies indicate that temper embrittlement is mainly caused by grain bondary segregation of P.
Temper embrittlement results in a loss of material toughness. This phenomenon is best represented by a shift of the ductile-to-brittle transition temperature(DBTT) to higher temperatures. The DBTT is usually defined as the temperature corresponding to the mean value of the upper-shelf and lower-shelf energies or the temperature at which the fracture surface contains 50% shear fracture characteristics(the fracture appearance transiton temperature(FATT)).
In the present work, we examined the equilibrium grain boundary segregation behavior of phosphorus in a 2.25Cr1Mo steel. The steel was quenched from 980℃and tempered at 650℃for 2h, followed by ageing at 560℃, 520℃, 480℃for different times. By means of Auger Electron Spectroscopy(AES), the equilibrium grain boundary segregation of phosporus was examined. By the computer software VB with the equilibrium segregation kinetic equation, we simulate the kinetic curve of the specimens aged at 480℃, which accord with the experimental results well if consider the standard deviation. In the end, the DBTTs are tested by Charpy V-notch impact test.
引文
1 徐 庭 栋 . 关 于 研 究 开 发 材 料 强 韧 化 创 新 技 术 的 设 想 . 材 料 导 报 . 2001,15(2):62~63
2 谈金祝. Auger 电子能谱分析方法及其在 2.25Cr-1Mo 钢回火脆性中的应用. 南京工业大学学报. 2003,25(1):73~76
3 冯端. 结构与缺陷. 科学出版社. 1998: 995
4 沈冬冬. P 的晶界偏聚对 2.25Cr-1.0Mo 钢热塑性及回火脆性的影响. 武汉科技大学硕士论文. 2002.3
5 J.R.Cowan. PH.D thesis. School of Metallurgy and Materials University of Birmingham. 1997
6 Mclean.D. Grain Boundaries in Metals. London: Oxford University Press. 1957:118
7 M .P.Seah and E.D.Hondros. R.Soc. Lond. 1973,335 A:191~212
8 E.D.Hondros and M.P.Seah. Theory of Grain Boundary Segregation in Terms of Surface Adosorption Analogues. Metallurgical Transactions A.1977,8A:1363~1371
9 R.H.Fowler and E.A.Guggen heim. Statistical Thermodymamic. pp:421~451
10 G.Rowlands and P.P.Woodruff. Kinetics of Surface and Grain Boundary Segregation in Binary and Ternary Systems. Philosophical Magazine A: Physics of Condensed Matter, Defects and Mechanical Properties. 1979,40( 4):459-476
11 M.P.Seah.Grain Boundary Segregation and the T-t Dependence of Temper Brittleness. Acta Metallurgica. 1977,25(3):345-357
12 W.R.Tyson. Acta Met. 1978,26:1471
13 M.Militzer, J.Wieting. Theory of Segregation Kinetics in Ternary Systems. Acta Metallurgica. 1986,34(7):1229-1236
14 Guttmann M. Surf. Sci. 1975,53:213
15 金国, 郑卫, 张涛. 12Cr2Mo 和 12Cr1MoV 钢的回火脆性研究. 研究探讨. 2003.5
16 Karelsson.L. Ph.D.Thesis. Chalmers University of Technology, Gateborg, Sweden. 1986
17 Xu Tingdong. A kinetic Model of Non-equilibrium Segregation.Mater.Sci. 1987, 22:337
18 Balluffi R.W. Grain-Boundary Structure and Kinetics. Metals Park. Chio: AsM. 1980:297
19 T.R.Authony, W.Thompson. Comments on “grain size effects on fatigue of constantan”. Materials Science and Engineering. 1976,26:289
20 S.J.Bercovic etal. Mater. Science. 1970,51:326
21 P.Doig and P.E.J.Flewitt. Segregation of Chromium to Prior Austenite Boundaries during Qquenching of a 2.25Cr1Mo Steel. Acta Metallurgica. 1981,29:1831~1841
22 Faulkner R.G. Non-equilibrium Grain-boundary Segregation in Austenitic Alloys. Mater Science. 1981,16:373
23 Xu Tingdong and Song shenhua. A Kinetic Model of Non-equilibrium Grain Boundary Segregation. Acta Metall. 1989,37:2499
24 宋申华, 徐庭栋, 袁泽喜等. 硼的晶界非平衡偏聚临界时间和临界冷却速度的确定. 武汉钢铁学院报. 1991, 14(3):258
25 Shinoda.T, Nakamura.T. The Effects of Applied Stress on the Intergranular Phosphorus Segregation in a Chromium Steel. Acta Metall. 1981, 29:1631~1636
26 Xu Tingdong. A Model for Intergranular Segregation/Dilution Induced by Applied Stress. J Mater Science. 2000,35:5621~5628
27 P.Sevc, J.Janovec, P.Lejcek, et al. Scripta Materialia. 2002,46:7~12
28 P.Sevc, J.Janovec, M.Koutnik, et al. Acta.Metal.Mater. 1994,43(1):251~258
29 D.D.Shen, S.H.Song, Z.X.Yuan, et al. Effect of Solute Grain Boundary Ssegregation and Hardness on the Ductile-to-brittle Transition for a Cr-Mo Low Alloy Steel. Materials Science and Engineering A. 2005,394:53~59
30 R.G.Ding, T.S.Rong and J.F.Knott. Mater.Sci.Technol. 2005,15
31 J.Janovec, A.Vyrostkova, P.Sevc, et al. Phosphorus Segregation in CrMoV Low-alloy Steels. Surface Science. 2000,30:642~646
32 J.Janovec, D.Grman, J.Perhacova, et al. Thermodynamics of Phosphorus Grain Boundary Segregation in 17Cr12Ni Austenitic Steel. Surf. Interface Anal. 2000,30:354~358
33 刘二宝. Cr-Mo 钢中 P 与合金元素的晶界共偏聚的研究. 哈尔滨工程大学硕士论文. 2005.1
34 林文松. 微量溶质元素在金属晶界的偏聚. 热处理. 2004,19(2):18~21
35 J.Perhacova, D.Grman, M.Svoboda, et al. Microstructure Aspects of Phosphorus Grain Boundary Segregation in Low Alloy Steels. Materials Letters. 2001,47:44~49
36 F.Christien, R.Le Gall, G.Saindrenan. Phosphorus Grain Boundary Segregation in Steel 17-4PH. Scripta Materialia. 2003,48:11~16
37 R.P.Messmer and C.L.Briant. An Electronic Model for the Effect of Alloying Elements on the Phosphorus Induced Grain Boundary Embrittlement of Steel. Acta Metallurgica. 1982,30:1811~1818
38 沈冬冬, 袁泽喜, 宋申华. 武汉科技大学学报(自然科学版). 2004.6,27(2): 124~126
39 S.H.Song, Z.X.Yuan, D.D.Shen, et al. Grain Boundary Segregation of Phosphorus and Molybdenum in a Cr-Mo Low Alloy Steel. Mater.Sci.Technol. 2004,20:117~120
40 M.Mackenbrock and H.J.Grabke Mater. Sci. Technol. 1992,8: 541~545
41 P.Lejcek and S.Hofmann. Prediction of Enthalpy and Entropy of Grain Boundary Segregation. Surface and interface analysis. 2002,33:203~210
42 D.D.Shen, Z.X.Yuan, J.Liu, et al. Phosphorus Grain Boundary Segregation in a P-doped 2.25Cr1Mo Steel. Acta Metallurgica Sinica. (English Letters). 2004.10,17(5):639~644
43 S.Takyama, T.Ogura, Shin-Cheng.FU, et al. The Calculation of Transition Temperature Changes in Steels Due to Temper Embrittlement. Metallurgical Transations A. 1980, 11A :1513~1530
44 M.Menyhard, C.J.Mcmahon. Acta metal. 1989,37 (8):2287 ~2295
45 J.Z.Tan, Kinetics of Temper Embrittlement in 2.25Cr-1Mo Steel Used for Hot-Wall Hydrofining Reactors. Acta Metallurgica Sinica. (English Letters). 2004,17(2 ):139-146
46 张灶利. 多组元溶质晶界偏聚动力学, 北京科技大学博士论文. 1997.9
47 金国. 2.25Cr1Mo 钢中 P 的晶界偏聚恒温动力学研究. 哈尔滨工程大学硕士论文. 2004,2
48 Davis LE, McDonald MC, Palmberg PW, et al. Handbook of Auger Electron Spectroscopy, 2nd ed. Physical Electronics Division, Perkin-Elmer Corporation, Minnesota, 1976
49 E.Feldman, V.Streltsov, T.Melnik. phys. stat. sol.(a). 1999,176: 911~918
50 A.V.Krajnikov, V.M.Yurchenko, E.P.Feldman, et al. Surface Science. 2002,515:36~44
51 Zaoli Zhang, Qingying Lin, Zongsen Yu. Grain Boundary Segregation in Ultra-low Carbon Steel. Materials Science and Engineering A. 2000,291: 22~26
52 R.A.Mulford, C.J.McMahon Jr., D.P.Pope, H.C.Feng, Temper Embrittlement of Ni-Cr Steels by Phosphorus. Metallurgical Transactions A. 1976,7 A (8):1183
53 A.H.Ucisik, C.J.McMahon Jr., H.C.Feng. Influence of Intercritical Heat Treatment on the Temper Emrittlement Susceptibility of a P-doped Ni-Cr Steel. Metallurgical Transactions A. 1978,9A(3):321-329
54 M.Menyhard, C.J.McMahon Jr. On the Effect of Molybdenum in the Embrittlement of Phosphorus-doped Iiron. Acta Metall. 1989,37 (8):2287
55 Ph.Dumoulin, M.Guttmann, Ph.Maynier, et al. Influence of seregregated transition metals on intergranular brittleness of tempered martensitic steels. Metal Science. 1983,17:70~74
2 谈金祝. Auger 电子能谱分析方法及其在 2.25Cr-1Mo 钢回火脆性中的应用. 南京工业大学学报. 2003,25(1):73~76
3 冯端. 结构与缺陷. 科学出版社. 1998: 995
4 沈冬冬. P 的晶界偏聚对 2.25Cr-1.0Mo 钢热塑性及回火脆性的影响. 武汉科技大学硕士论文. 2002.3
5 J.R.Cowan. PH.D thesis. School of Metallurgy and Materials University of Birmingham. 1997
6 Mclean.D. Grain Boundaries in Metals. London: Oxford University Press. 1957:118
7 M .P.Seah and E.D.Hondros. R.Soc. Lond. 1973,335 A:191~212
8 E.D.Hondros and M.P.Seah. Theory of Grain Boundary Segregation in Terms of Surface Adosorption Analogues. Metallurgical Transactions A.1977,8A:1363~1371
9 R.H.Fowler and E.A.Guggen heim. Statistical Thermodymamic. pp:421~451
10 G.Rowlands and P.P.Woodruff. Kinetics of Surface and Grain Boundary Segregation in Binary and Ternary Systems. Philosophical Magazine A: Physics of Condensed Matter, Defects and Mechanical Properties. 1979,40( 4):459-476
11 M.P.Seah.Grain Boundary Segregation and the T-t Dependence of Temper Brittleness. Acta Metallurgica. 1977,25(3):345-357
12 W.R.Tyson. Acta Met. 1978,26:1471
13 M.Militzer, J.Wieting. Theory of Segregation Kinetics in Ternary Systems. Acta Metallurgica. 1986,34(7):1229-1236
14 Guttmann M. Surf. Sci. 1975,53:213
15 金国, 郑卫, 张涛. 12Cr2Mo 和 12Cr1MoV 钢的回火脆性研究. 研究探讨. 2003.5
16 Karelsson.L. Ph.D.Thesis. Chalmers University of Technology, Gateborg, Sweden. 1986
17 Xu Tingdong. A kinetic Model of Non-equilibrium Segregation.Mater.Sci. 1987, 22:337
18 Balluffi R.W. Grain-Boundary Structure and Kinetics. Metals Park. Chio: AsM. 1980:297
19 T.R.Authony, W.Thompson. Comments on “grain size effects on fatigue of constantan”. Materials Science and Engineering. 1976,26:289
20 S.J.Bercovic etal. Mater. Science. 1970,51:326
21 P.Doig and P.E.J.Flewitt. Segregation of Chromium to Prior Austenite Boundaries during Qquenching of a 2.25Cr1Mo Steel. Acta Metallurgica. 1981,29:1831~1841
22 Faulkner R.G. Non-equilibrium Grain-boundary Segregation in Austenitic Alloys. Mater Science. 1981,16:373
23 Xu Tingdong and Song shenhua. A Kinetic Model of Non-equilibrium Grain Boundary Segregation. Acta Metall. 1989,37:2499
24 宋申华, 徐庭栋, 袁泽喜等. 硼的晶界非平衡偏聚临界时间和临界冷却速度的确定. 武汉钢铁学院报. 1991, 14(3):258
25 Shinoda.T, Nakamura.T. The Effects of Applied Stress on the Intergranular Phosphorus Segregation in a Chromium Steel. Acta Metall. 1981, 29:1631~1636
26 Xu Tingdong. A Model for Intergranular Segregation/Dilution Induced by Applied Stress. J Mater Science. 2000,35:5621~5628
27 P.Sevc, J.Janovec, P.Lejcek, et al. Scripta Materialia. 2002,46:7~12
28 P.Sevc, J.Janovec, M.Koutnik, et al. Acta.Metal.Mater. 1994,43(1):251~258
29 D.D.Shen, S.H.Song, Z.X.Yuan, et al. Effect of Solute Grain Boundary Ssegregation and Hardness on the Ductile-to-brittle Transition for a Cr-Mo Low Alloy Steel. Materials Science and Engineering A. 2005,394:53~59
30 R.G.Ding, T.S.Rong and J.F.Knott. Mater.Sci.Technol. 2005,15
31 J.Janovec, A.Vyrostkova, P.Sevc, et al. Phosphorus Segregation in CrMoV Low-alloy Steels. Surface Science. 2000,30:642~646
32 J.Janovec, D.Grman, J.Perhacova, et al. Thermodynamics of Phosphorus Grain Boundary Segregation in 17Cr12Ni Austenitic Steel. Surf. Interface Anal. 2000,30:354~358
33 刘二宝. Cr-Mo 钢中 P 与合金元素的晶界共偏聚的研究. 哈尔滨工程大学硕士论文. 2005.1
34 林文松. 微量溶质元素在金属晶界的偏聚. 热处理. 2004,19(2):18~21
35 J.Perhacova, D.Grman, M.Svoboda, et al. Microstructure Aspects of Phosphorus Grain Boundary Segregation in Low Alloy Steels. Materials Letters. 2001,47:44~49
36 F.Christien, R.Le Gall, G.Saindrenan. Phosphorus Grain Boundary Segregation in Steel 17-4PH. Scripta Materialia. 2003,48:11~16
37 R.P.Messmer and C.L.Briant. An Electronic Model for the Effect of Alloying Elements on the Phosphorus Induced Grain Boundary Embrittlement of Steel. Acta Metallurgica. 1982,30:1811~1818
38 沈冬冬, 袁泽喜, 宋申华. 武汉科技大学学报(自然科学版). 2004.6,27(2): 124~126
39 S.H.Song, Z.X.Yuan, D.D.Shen, et al. Grain Boundary Segregation of Phosphorus and Molybdenum in a Cr-Mo Low Alloy Steel. Mater.Sci.Technol. 2004,20:117~120
40 M.Mackenbrock and H.J.Grabke Mater. Sci. Technol. 1992,8: 541~545
41 P.Lejcek and S.Hofmann. Prediction of Enthalpy and Entropy of Grain Boundary Segregation. Surface and interface analysis. 2002,33:203~210
42 D.D.Shen, Z.X.Yuan, J.Liu, et al. Phosphorus Grain Boundary Segregation in a P-doped 2.25Cr1Mo Steel. Acta Metallurgica Sinica. (English Letters). 2004.10,17(5):639~644
43 S.Takyama, T.Ogura, Shin-Cheng.FU, et al. The Calculation of Transition Temperature Changes in Steels Due to Temper Embrittlement. Metallurgical Transations A. 1980, 11A :1513~1530
44 M.Menyhard, C.J.Mcmahon. Acta metal. 1989,37 (8):2287 ~2295
45 J.Z.Tan, Kinetics of Temper Embrittlement in 2.25Cr-1Mo Steel Used for Hot-Wall Hydrofining Reactors. Acta Metallurgica Sinica. (English Letters). 2004,17(2 ):139-146
46 张灶利. 多组元溶质晶界偏聚动力学, 北京科技大学博士论文. 1997.9
47 金国. 2.25Cr1Mo 钢中 P 的晶界偏聚恒温动力学研究. 哈尔滨工程大学硕士论文. 2004,2
48 Davis LE, McDonald MC, Palmberg PW, et al. Handbook of Auger Electron Spectroscopy, 2nd ed. Physical Electronics Division, Perkin-Elmer Corporation, Minnesota, 1976
49 E.Feldman, V.Streltsov, T.Melnik. phys. stat. sol.(a). 1999,176: 911~918
50 A.V.Krajnikov, V.M.Yurchenko, E.P.Feldman, et al. Surface Science. 2002,515:36~44
51 Zaoli Zhang, Qingying Lin, Zongsen Yu. Grain Boundary Segregation in Ultra-low Carbon Steel. Materials Science and Engineering A. 2000,291: 22~26
52 R.A.Mulford, C.J.McMahon Jr., D.P.Pope, H.C.Feng, Temper Embrittlement of Ni-Cr Steels by Phosphorus. Metallurgical Transactions A. 1976,7 A (8):1183
53 A.H.Ucisik, C.J.McMahon Jr., H.C.Feng. Influence of Intercritical Heat Treatment on the Temper Emrittlement Susceptibility of a P-doped Ni-Cr Steel. Metallurgical Transactions A. 1978,9A(3):321-329
54 M.Menyhard, C.J.McMahon Jr. On the Effect of Molybdenum in the Embrittlement of Phosphorus-doped Iiron. Acta Metall. 1989,37 (8):2287
55 Ph.Dumoulin, M.Guttmann, Ph.Maynier, et al. Influence of seregregated transition metals on intergranular brittleness of tempered martensitic steels. Metal Science. 1983,17:70~74