铌对低碳钢形变强化相变的影响

利用热模拟压缩变形实验研究了含铌钢和相应成分的低碳钢过冷奥氏体形变强化相变的组织演变规律,探讨了铌在析出状态时对形变强化相变的影响,进行了转变动力学曲线的分析.结果表明:形变强化相变之前有Nb(CN)析出可以显著促进铁素体形核.含铌钢的过冷奥氏体在A₃~A_r³之间变形,可以得到平均晶粒尺寸为1.9μm的形变强化相变铁素体.其转变动力学与低碳钢相类似,以形变强化相变为主;在铁素体转变基本完成时,含铌钢的铁素体晶粒较细小.

Effect of Nb on deformation-enhanced ferrite transformation in low carbon steel

The microstructure evolutions during deformation-enhanced transformation of undercooled austenite of Nb-microalloyed steel and low carbon steel with the similar contents of C and Mn were investigated by hot compression simulation experiment. The effect of Nb on the deformation-enhanced ferrite transformation was studied, and the transformation kinetics was analyzed. The results show that Nb(CN) precipitation promotes ferrite nucleation significantly before deformation-enhanced ferrite transformation. Ultra-fine ferrite with a grain size of about 1.9 μm is formed in Nb-microalloyed steel during deformation of undercooled austenite between A₃-A_r³. Deformation-enhanced transformation is the dominated process in the early stage of deformation; as ferrite transformation accomplished, the ferrite grain size of Nb-microalloyed steel is smaller than that of low carbon steel.