一种Fe-Cr-Ni-Mo高强高韧合金钢焊接接头的组织和力学性能
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摘要
采用熔化极活性气体保护焊(MAG焊)对一种Fe-Cr-Ni-Mo高强高韧合金钢板进行多道次焊接,利用SEM、EPMA、TEM以及拉伸、冲击等实验研究了焊接接头的组织和力学性能。结果表明,焊缝金属由柱状晶和等轴晶组成,其中上部焊缝以柱状晶为主,而下部焊缝的等轴晶含量增加。焊缝上部因冷速较快形成回火马氏体组织;下部因合金元素含量较高,淬硬倾向较强,形成了粒状贝氏体组织。靠近焊缝的热影响区为较粗大的马氏体组织,其硬度最大(621 HV),明显高于母材(410 HV)。上部焊缝金属的硬度为365 HV,低于母材,而下部焊缝的硬度高于焊缝上部和母材,为450 HV。因此,焊接接头上部拉伸试样在焊缝处发生断裂,断裂强度为1109 MPa,而焊缝的下部拉伸试样在母材处发生断裂,断裂强度为1183 MPa。本实验用Fe-Cr-Ni-Mo合金钢的焊接接头强度较高,焊接强度系数不小于0.93,焊缝金属的冲击功为53 J。
High-strength steel has the advantages of high strength, low cost and good hot and cold workability, etc., which is widely used in various fields of national economy as engineering steel, such as bridge, vehicle, ship, pressure vessel and so on. As increasing strength, the plasticity and toughness of high strength steel have not meet the demand in some industrial areas, especially the low temperature impact toughness. Recently, a Fe-Cr-Ni-Mo steel with high-strength and high-toughness has been developed and has been successfully used to prepare high pressure vessels. In this work, metal active gas(MAG) welding with multi-pass welding was used to join a Fe-Cr-Ni-Mo high-strength and high-toughness steel. The microstructure and fracture morphologies of welded joint are investigated by SEM, EPMA and TEM and the micro-hardness, tensile strength and Charpy impact energy are tested as well. The results show that the morphologies of welded metal(WM) consist of columnar crystal(CC) and equiaxed crystal(EC), where the upper WM is predominantly CC and the proportion of EC increases in the lower WM.The microstructure of upper WM is tempered martensite for the faster cooling rate. Because the higher content of alloying elements in lower WM improves the hardening tendencies, the lower WM is granular bainite. The heat affected zone near WM is coarsen martensite and has the highest hardness(621 HV),which is significantly higher than that of the base metal(BM)(410 HV). The hardness of the upper WM is365 HV, which is lower than that of BM and the lower WM has higher hardness(450 HV). Therefore, the upper tensile sample of welded joint was broken in the WM and the fracture strength is 1109 MPa and lower than that of BM(1190 MPa). While the fracture position of lower tensile sample is in the BM and the strength is about 1183 MPa. The welded joint of experimental Fe-Cr-Ni-Mo steel has higher strength and the welding factor is not lower than 0.93. Moreover, the impact energy of WM is 53 J.
High-strength steel has the advantages of high strength, low cost and good hot and cold workability, etc., which is widely used in various fields of national economy as engineering steel, such as bridge, vehicle, ship, pressure vessel and so on. As increasing strength, the plasticity and toughness of high strength steel have not meet the demand in some industrial areas, especially the low temperature impact toughness. Recently, a Fe-Cr-Ni-Mo steel with high-strength and high-toughness has been developed and has been successfully used to prepare high pressure vessels. In this work, metal active gas(MAG) welding with multi-pass welding was used to join a Fe-Cr-Ni-Mo high-strength and high-toughness steel. The microstructure and fracture morphologies of welded joint are investigated by SEM, EPMA and TEM and the micro-hardness, tensile strength and Charpy impact energy are tested as well. The results show that the morphologies of welded metal(WM) consist of columnar crystal(CC) and equiaxed crystal(EC), where the upper WM is predominantly CC and the proportion of EC increases in the lower WM.The microstructure of upper WM is tempered martensite for the faster cooling rate. Because the higher content of alloying elements in lower WM improves the hardening tendencies, the lower WM is granular bainite. The heat affected zone near WM is coarsen martensite and has the highest hardness(621 HV),which is significantly higher than that of the base metal(BM)(410 HV). The hardness of the upper WM is365 HV, which is lower than that of BM and the lower WM has higher hardness(450 HV). Therefore, the upper tensile sample of welded joint was broken in the WM and the fracture strength is 1109 MPa and lower than that of BM(1190 MPa). While the fracture position of lower tensile sample is in the BM and the strength is about 1183 MPa. The welded joint of experimental Fe-Cr-Ni-Mo steel has higher strength and the welding factor is not lower than 0.93. Moreover, the impact energy of WM is 53 J.
引文
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[16]Wen T,Hu X F,Song Y Y,et al.Effect of tempering temperature on carbide and mechanical properties in a Fe-Cr-Ni-Mo highstrength steel[J].Acta Metall.Sin.,2014,50:447(温涛,胡小锋,宋元元等.回火温度对一种Fe-Cr-Ni-Mo高强钢碳化物及其力学性能的影响[J].金属学报,2014,50:447)
[17]Wen T,Hu X F,Yan D S,et al.Effect of V contents on microstructure and mechanical properties in a Fe-Cr-Ni-Mo high-strength steel[J].Mater.Sci.Forum,2014,788:304
[18]Wen T,Hu X F,Song Y Y,et al.Carbides and mechanical properties in a Fe-Cr-Ni-Mo high-strength steel with different V contents[J].Mater.Sci.Eng.,2013,A588:201
[19]Zhang M,Wang Q,Li J H,et al.Microstructure numerical simulation of weld pool in rapid solidification[J].Trans.China Weld.Inst.,2013,34(7):1(张敏,汪强,李继红等.焊接熔池快速凝固过程的微观组织演化数值模拟[J].焊接学报,2013,34(7):1)
[20]Keehan E,Karlsson L,Andrén H O,et al.New developments with C-Mn-Ni high-strength steel weld metals,Part A-Microstructure[J].Weld.J.,2006,85:200-s
[21]Janovec J,VyrostkováA,Svoboda M,et al.Evolution of secondary phases in Cr-V low-alloy steels during aging[J].Metall.Mater.Trans.,2004,35A:751
[22]Shi Y W,Han Z X.Effect of weld thermal cycle on microstructure and fracture toughness of simulated heat-affected zone for a800 MPa grade high strength low alloy steel[J].J.Mater.Process.Technol.,2008,207:30
[23]AléR M,Rebello J M A,Charlier J.A metallographic technique for detecting martensite-austenite constituents in the weld heataffected zone of a micro-alloyed steel[J].Mater.Charact.,1996,37:89
[24]Li X D,Shang C J,Han C C,et al.Influence of necklace-type MA constituent on impact toughness and fracture mechanism in the heat affected zone of X100 pipeline steel[J].Acta Metall.Sin.,2016,52:1025(李学达,尚成嘉,韩昌柴等.X100管线钢焊接热影响区中链状M-A组元对冲击韧性和断裂机制的影响[J].金属学报,2016,52:1025)
[2]Mulholland M D,Seidman D N.Nanoscale co-precipitation and mechanical properties of a high-strength low-carbon steel[J].Acta Mater.,2011,59:1881
[3]Wang L J,Cai Q W,Yu W,et al.Microstructure and mechanical properties of 1500 MPa grade ultra-high strength low alloy steel[J].Acta Metall.Sin.,2010,46:687(王立军,蔡庆伍,余伟等.1500 MPa级低合金超高强钢的微观组织与力学性能[J].金属学报,2010,46:687)
[4]Tian Y Q,Zhang H J,Chen L S,et al.Effect of alloy elements partitioning behavior on retained austenite and mechanical property in low carbon high strength steel[J].Acta Metall.Sin.,2014,50:531(田亚强,张宏军,陈连生等.低碳高强钢合金元素配分行为对残余奥氏体和力学性能的影响[J].金属学报,2014,50:531)
[5]Han S Y,Shin S Y,Seo C H,et al.Effects of Mo,Cr,and V additions on tensile and charpy impact properties of API X80 pipeline steels[J].Metall.Mater.Trans.,2009,40A:1851
[6]He X L,Yang X Q,Zhang G D,et al.Quenching microstructure and properties of 300M ultra-high strength steel electron beam welded joints[J].Mater.Des.,2012,40:386
[7]Malakondaiah G,Srinivas M,Rao P R.Ultrahigh-strength lowalloy steels with enhanced fracture toughness[J].Prog.Mater.Sci.,1997,42:209
[8]Tomita Y,Okawa T.Effect of modified heat-treatment on mechanical properties of 300M steel[J].Mater.Sci.Technol.,1995,11:245
[9]Lee W S,Su T T.Mechanical properties and microstructural features of AISI 4340 high-strength alloy steel under quenched and tempered conditions[J].J.Mater.Process.Technol.,1999,87:198
[10]Youngblood J L,Raghavan M.Correlation of microstructure with mechanical properties of 300M steel[J].Metall.Trans.,1977,8A:1439
[11]Ritchie R O,Francis B,Server W L.Evaluation of toughness in AISI 4340 alloy steel austenitized at low and high temperatures[J].Metall.Trans.,1976,7A:831
[12]Chang T L,Tsay L W,Chen C.Influence of gaseous hydrogen on the notched tensile strength of D6ac steel[J].Mater.Sci.Eng.,2001,A316:153
[13]Caballero F G,Bhadeshia H K D H,Mawella K J A,et al.Design of novel high strength bainitic steels:Part 1[J].Mater.Sci.Technol.,2001,17:512
[14]Caballero F G,Bhadeshia H K D H,Mawella K J A,et al.Design of novel high strength bainitic steels:Part 2[J].Mater.Sci.Technol.,2001,17:517
[15]Li Y J.Welding of High Strength Steel[M].Beijing:Metallurgical Industry Press,2010:89(李亚江.高强钢的焊接[M].北京:冶金工业出版社,2010:89)
[16]Wen T,Hu X F,Song Y Y,et al.Effect of tempering temperature on carbide and mechanical properties in a Fe-Cr-Ni-Mo highstrength steel[J].Acta Metall.Sin.,2014,50:447(温涛,胡小锋,宋元元等.回火温度对一种Fe-Cr-Ni-Mo高强钢碳化物及其力学性能的影响[J].金属学报,2014,50:447)
[17]Wen T,Hu X F,Yan D S,et al.Effect of V contents on microstructure and mechanical properties in a Fe-Cr-Ni-Mo high-strength steel[J].Mater.Sci.Forum,2014,788:304
[18]Wen T,Hu X F,Song Y Y,et al.Carbides and mechanical properties in a Fe-Cr-Ni-Mo high-strength steel with different V contents[J].Mater.Sci.Eng.,2013,A588:201
[19]Zhang M,Wang Q,Li J H,et al.Microstructure numerical simulation of weld pool in rapid solidification[J].Trans.China Weld.Inst.,2013,34(7):1(张敏,汪强,李继红等.焊接熔池快速凝固过程的微观组织演化数值模拟[J].焊接学报,2013,34(7):1)
[20]Keehan E,Karlsson L,Andrén H O,et al.New developments with C-Mn-Ni high-strength steel weld metals,Part A-Microstructure[J].Weld.J.,2006,85:200-s
[21]Janovec J,VyrostkováA,Svoboda M,et al.Evolution of secondary phases in Cr-V low-alloy steels during aging[J].Metall.Mater.Trans.,2004,35A:751
[22]Shi Y W,Han Z X.Effect of weld thermal cycle on microstructure and fracture toughness of simulated heat-affected zone for a800 MPa grade high strength low alloy steel[J].J.Mater.Process.Technol.,2008,207:30
[23]AléR M,Rebello J M A,Charlier J.A metallographic technique for detecting martensite-austenite constituents in the weld heataffected zone of a micro-alloyed steel[J].Mater.Charact.,1996,37:89
[24]Li X D,Shang C J,Han C C,et al.Influence of necklace-type MA constituent on impact toughness and fracture mechanism in the heat affected zone of X100 pipeline steel[J].Acta Metall.Sin.,2016,52:1025(李学达,尚成嘉,韩昌柴等.X100管线钢焊接热影响区中链状M-A组元对冲击韧性和断裂机制的影响[J].金属学报,2016,52:1025)