摘要
采用拉伸、冲击、无塑性转变(NDT)温度落锤等力学性能测试方法和光学显微镜、扫描电镜、电子背散射衍射等显微组织分析手段,研究了EH47钢轧后弛豫60、180和360 s对特厚钢组织性能的影响。结果表明,弛豫时间为60 s和180 s的试验钢1/4厚度(t/4)处屈服和抗拉强度相差不大,分别为518、538 MPa和641、655 MPa,而弛豫时间为360 s时,试验钢t/4屈服和抗拉强度明显降低,分别为474 MPa和553 MPa。试验钢t/4低温韧性和表面P-2型NDT落锤性能随弛豫时间从60 s增加至360 s呈先降低后增加趋势。弛豫60、180和360 s的试验钢t/4处-40℃冲击功分别为248、78和340 J,钢板表面-50℃P-2型NDT落锤性能分别为无开裂、开裂和无开裂。显微组织表征结果表明,弛豫时间对试验钢表面至t/4位置的显微组织具有显著影响。弛豫时间为60 s时,试验钢表面为板条贝氏体,t/4位置为针状铁素体加贝氏体;弛豫180 s时表面为贝氏体和呈网状分布铁素体,t/4位置为少量准多边形铁素体加贝氏体;弛豫360 s时表面为多边形铁素体加少量贝氏体,t/4为准多边形铁素体加针状铁素体。进一步研究表明,弛豫时间为180 s的试验钢,由于沿晶界分布的网状铁素体的存在,在低温落锤冲击时,应变主要集中在晶界铁素体中,从而形成孔洞,这种网状分布铁素体中的孔洞很容易串联形成裂纹而开裂。
The effects of relaxation times of 60-360 s after rolling on the microstructure and properties of ultra-thick EH47 steel were studied using tensile testing,Charpy impact testing,nil-ducility transition(NDT)temperature dropweight testing,combined with optical microscopy,scanning electron microscopy,and electron back scattering diffraction.The results showed that there was no significant difference in yield and tensile strength at 1/4 thickness(t/4)of the experimental steel with a relaxation time of 60 s and 180 s,yield strength and tensile strength were 518,538 MPa and 641,655 MPa,respectively.However,at a relaxation time of 360 s,the yield and tensile strength of t/4 of the experimental steel decreased significantly to 474 MPa and 553 MPa,respectively.The low-temperature toughness of t/4 position and surface P-2 type NDT drop-weight performance of experimental steel first decreased and then increased with the relaxation time increasing from 60 s to 360 s.The impact energies at-40℃for t/4 of the experimental steel relaxed for 60 s,180 s,and 360 s were 248 J,78 J,and 340 J,respectively.The P-2 type NDT drop-weight for surface of the steel plate at-50℃were no cracking,cracking,and no cracking,respectively.The microstructure characterization results indicated that the relaxation time has a significant impact on the microstructure of the experimental steel from surface to t/4 position.When the relaxation time is 60 s,the surface of the experimental steel is lath bainite,and the t/4 position is acicular ferrite plus bainite;at a relaxation time of 180 s,the surface had bainite and a network distribution of ferrite,and t/4 position consisted of a small amount of quasi-polygonal ferrite and bainite;at a relaxation time of 360 s,the surface was polygonal ferrite with a small amount of bainite,and t/4 was quasi-polygonal ferrite with acicular ferrite.Further investigation revealed that the strain during low-temperature drop-weight was mainly concentrated in the grain boundary distributed ferrite for the experimental steel with a relaxation time of 180 s,resulting in the formation of micro-voids within the network of ferrite.These network microvoids were easily connected to form cracks,leading to poor drop-weight property at low temperature.
作者
肖大恒
李骞
高擎
周文浩
谢振家
尚成嘉
XIAO Daheng;LI Qian;GAO Qing;ZHOU Wenhao;XIE Zhenjia;SHANG Chengjia(Technical Quality Department,Hunan Valin Xiangtan Iron and Steel Co.,Ltd.,Xiangtan 411101,Hunan,China;Collaborative Innovation Center of Steel Technology,University of Science and Technology Beijing,Beijing 100083,China;State Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing,Beijing 100083,China)
出处
《钢铁》
CAS
CSCD
北大核心
2024年第5期153-160,133,共9页
Iron and Steel
基金
湖南省青年科技人才资助项目(2022RC1068)
国家自然科学基金资助项目(51701012)。
关键词
止裂钢
EH47特厚板
弛豫
无塑性转变
多相组织
crack arrest steel
EH47 heavy plate steel
relaxation
NDT
multi-phase microstructure
