Effects of Carbon on the CG HAZ Toughness and Transformation of X80 Pipeline Steel

• 作 者: Xiaohuai XUE Luhai WU Bainian
• 机 构: School of Materials Science and Engineering,Institute of Metal Research
• 出 处: 材料科学技术学报（英文版）
• 发表日期: 2004年期
• 关键词: X80 pipeline steel Weld simulation CG HAZ Ultralow carbon Fe3C carbide
• 基金项目: 科技部科研项目

X80 pipeline steel produced by TMCP has high strength and high toughness with ultrafine grain microstructure. The microstructure coarsens and the toughness worsens at the coarse grained (CG) HAZ apparently after weld simulation. The experimental results indicated that the bainitic ferrite and the second phases formed at cooling are differently as the variation of carbon in base metal. In low carbon steels, the bainitic ferrite laths are long and narrow, the second phases are complex including residual austenite, martensite, the M-A constituent and the Fe3C carbide. The formation of Fe3C carbide is the main reason of the poor toughness in CG HAZ. The ultralow carbon in base metal, however, can improve the CG HAZ toughness through restraining the formation of carbides, decreasing the M-A constituent, increasing the residual austenite content, which are beneficial to the CG HAZ toughness.