后热温度对1000MPa级高强钢焊缝组织与性能的影响
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摘要
采用GHS90高强焊丝为填充材料对1 000 MPa级工程机械用高强钢进行熔化极活性气体保护(Metal active gas,MAG)焊,并对接头进行250℃、480℃、600℃保温2 h的焊后热处理。通过拉伸试验、显微硬度测试、光学显微镜(Optical microscope,OM)、扫面电镜(Scanning electron microscope,SEM)、透射电镜(Transmission electron microscopy,TEM)及电子背散射衍射(Electron back-scattered diffraction,EBSD)观察不同热处理温度后的焊缝微观组织及力学性能进行对比研究。结果表明,随后热温度从250℃升高到600℃,接头抗拉强度从1 014.5 MPa降低到934.5 MPa;焊缝平均冲击吸收能量从66 J降低到24 J;随后热温度升高,焊缝板条组织粗化,碳化物析出长大且连续分布是导致焊缝韧性降低的原因之一;同时焊缝有效晶粒尺寸变大和大角度晶界密度降低也是导致其韧性降低的原因。
1 000 MPa high-strength steel plates for construction machinery are welded by metal active gas(MAG) welding method with GHS90 welding wire as filler material and the weld joints are treated at 250 ℃, 480 ℃, 600 ℃ for 2 h, respectively. Microstructure and mechanical properties of welded joints with different post weld heat treatment(PWHT) is analyzed by tensile test, microhardness measurement, optical microscope(OM), scanning electron microscope(SEM), transmission electron microscopy(TEM) and electron back-scattered diffraction(EBSD). The results show that with the increase of PWHT temperature from 250 ℃ to 600 ℃, the average strength of welded joint reduces from 1 014.5 MPa to 934.5 MPa and the average –20 ℃ impact absorbing energy of weld metals decreases from 66 J to 24 J. With higher PWHT temperature, larger bainitic lath and coarser carbide precipitates result in lower toughness of weld metal. Meanwhile, the size of effective grains becomes larger and the density of high-angle grain boundary is decreased, which led to the degradation of impact property of weld metal.
1 000 MPa high-strength steel plates for construction machinery are welded by metal active gas(MAG) welding method with GHS90 welding wire as filler material and the weld joints are treated at 250 ℃, 480 ℃, 600 ℃ for 2 h, respectively. Microstructure and mechanical properties of welded joints with different post weld heat treatment(PWHT) is analyzed by tensile test, microhardness measurement, optical microscope(OM), scanning electron microscope(SEM), transmission electron microscopy(TEM) and electron back-scattered diffraction(EBSD). The results show that with the increase of PWHT temperature from 250 ℃ to 600 ℃, the average strength of welded joint reduces from 1 014.5 MPa to 934.5 MPa and the average –20 ℃ impact absorbing energy of weld metals decreases from 66 J to 24 J. With higher PWHT temperature, larger bainitic lath and coarser carbide precipitates result in lower toughness of weld metal. Meanwhile, the size of effective grains becomes larger and the density of high-angle grain boundary is decreased, which led to the degradation of impact property of weld metal.
引文
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[2]邹增大,李亚江,尹士科.低合金调质高强钢焊接及工程应用[M].北京:化学工业出版社,2000.ZOU Zengda,LI Yajiang,YIN Shike.Welding and engineering application of high strength low alloy quenched/tempered steel[M].Beijing:Chemical Industry Press,2000.
[3]陈伯蠡,周运鸿.高强钢埋弧焊焊缝的强韧化研究[J].焊接学报,1987,8(3):153-162.CHEN Boli,ZHOU Yunhong.Improvement of toughness and strength of high strength steel submerged arc weld metal[J].Transactions of the China Welding Institution,1987,8(3):153-162.
[4]尹士科,王移山,陈佩兰.热处理对低合金高强度钢及焊缝组织与性能的影响[J].钢铁研究总院学报,1987,8(3):43-49.YIN Shike,WANG Yishang,CHEN Peilan.Influence of heat treatment on the microstructure and properties of a HSLA steel and its weld metal[J].Central Iron and Steel Research Institute Technical Bulletin,1987,8(3):43-49.
[5]赵琳,张旭东,陈武柱.800MPa级低合金钢焊接热影响区韧性的研究[J].金属学报,2005,41(4):89-93.ZHAO Lin,ZHANG Xudong,CHEN Wuzhu.Toughness of heat affected zone of 800 MPa grade low alloy steel[J].Acta Metallurgica Sinica,2005,41(4):89-93.
[6]史耀武,韩准祥.工程机械用800MPa低合金高强度钢焊接热影响区断裂韧性评价[J].热加工工艺,2006,35(15):1-7.SHI Yaowu,HAN Zhunxiang.Evaluation of HAZ fracture toughness for 800 MPa grade HSLA used for construction machinery[J].Hot Working Technology,2006,35(15):1-7.
[7]魏金山,齐彦昌,彭云,等.热输入对800MPa级超厚板窄间隙焊缝金属组织和性能的影响[J].焊接学报,2012,33(6):31-34.WEI Jinshan,QI Yanchang,PENG Yun,et al.Effect of heat inputs on microstructure and properties of weld metal welding in a 800MPa grade heavy steel plate with narrow gap groove[J].Transactions of the China Welding Institution,2012,33(6):31-34.
[8]程饴萱,郦剑,陈理淳.钢的相变显微组织[M].杭州:浙江大学出版社,1989.CHENG Yixuan,LI Jian,CHEN Lichun.The microstructure of the steel phase transformation[M].Hangzhou:Zhejiang University Press,1989.
[9]陈泳,张京海,李晓泉.800 MPa级别钢熔敷金属热处理脆化机理研究[J].材料开发与应用,2008,23(6):33-37.CHEN Yong,ZHANG Jinghai,LI Xiaoquan.Embrittlement mechanism of the welding deposit metal of800 MPa grade steel[J].Development and Application of Materials,2008,23(6):33-37.
[10]兰亮云,邱春林,赵德文,等.低碳贝氏体钢焊接热影响区中不同亚区的组织特征与韧性[J].金属学报,2011,47(8):1046-1054.LAN Liangyun,QIU Chunlin,ZHAO Denwen,et al.Microstructure characters and toughness of different sub-regions in the welding heat affected zone of low carbon bainite steel[J].Acta Metallurgica Sinica,2011,47(8):1046-1054.
[11]高慧临,董玉华,余大涛.管线钢焊接局部脆化区断裂行为研究[J].机械工程材料,2001,25(7):26-29.GAO Huilin,DONG Yuhua,YU Datao.Fracture behaviors of lacal brittle zone in pipeline steel[J].Material for Mechanical Engineering,2001,25(7):26-29.
[12]ABSON D J.Non-metallic inclusion in ferritic steel weld metals-a review[J].Welding in the World,1989,27(3):31-57.
[13]韩顺昌.低碳低合金钢焊缝金属显微组织[M].北京:机械工业出版社,2004.HAN Shunchang.Microstructure of weld metal of low-carbon and low alloy steels[M].Beijing:China Machine Press,2004.
[14]廖成亮,尚成嘉,王学敏,等.高Nb X80管线钢焊接热影响区显微组织与韧性[J].金属学报,2010,46(5):541-546.LIAO Chengliang,SHANG Chengjia,WANG Xuemin,et al.Microstructure and toughness of HAZ X80 pipeline steel with high Nb content[J].Acta Metallurgica Sinica,2010,46(5):541-546.
[15]余永宁.金属学原理[M].北京:冶金工业出版社,2010.YU Yongning.Principles of metallography[M].Beijing:Metallurgical Inductry Press,2010.