Effects of Nb on microstructure and continuous cooling transformation of coarse grain heat-affected zone in 610MPa class HSLA structural steels
Coarse grain heat-affected zone continuous cooling transformation (CGHAZ-CCT) diagrams and continuous cooled microstructures were investigated for 610MPa class HSLA structural steels with and without niobium. The corresponding nonlinear cooling profiles and related transformation start and finish temperatures for various cooling rates conditions have been taken into account. For the steel without Nb, grain boundary ferrite, degenerate pearlite and acicular ferrite are produced at slower cooling rates. Bainite phase is formed at faster cooling rates. However, for the steel with Nb, granular bainite is dominant at a large range of cooling rates. At the cooling rates (<32℃/s), transformation start temperatures is decreased by 20℃ approximately in the steel with Nb compared to without Nb. Ferrite nucleation at prior austenite grain boundaries is suppressed and the cooling rate region for granular bainite transformation is broadened. At the cooling rates (>32℃/s), Nb addition has no obvious influence on transformation start temperature, but influences microstructure transformation significantly. Martensite is observed in steel with Nb at faster cooling rates, but not produced in steel without Nb.
continuous cooling transformation CCT diagram Coarse grain heat-affected zone HSLA steel Niobium
Yingqiao ZHANG Hanqian ZHANG Weiming LIU Hong HOU
Department of Materials Science and Engineering, Shanghai Jiaotong University,Shanghai 200030, China Department of Materials Science and Engineering, Shanghai Jiaotong University,Shanghai 200030, China Research Institute for Advanced Structural Steel, R&D Center, Baoshan Iron and Steel Limited Company
国际会议
郑州
英文
2007-10-23（万方平台首次上网日期，不代表论文的发表时间）