Hot deformation behavior for a kind of low carbon micro-alloy pipeline steel

The hot deformation behavior and flow stress of a low carbon microalloyed pipeline steel were investigated on MMS-200 thermal-mechanical simulating tester. The experimental deformation temperatures varied from 800 ℃ to 1 150 ℃,and deformation rates were from 0.1 s-1 to 5.0 s-1. The microstructures of specimens obtained through high-temperature compressive deformation were observed by transmitted electron microscope and optical microscope. Zener-Hollomon parameters of the hyperbolic sine function were used to describe the high temperature deformation behavior of the flow stress. The results show that the flow stress decreases with the increase of temperature,while increases with the increase of strain rate. There are two kinds of softening mechanisms in thermal deformation process-dynamic recovery and dynamic recrystallization. Dynamic recrystallization occurs under the condition of high temperature and low strain rate. According to the obtained equation of flow stress,parameters A,α and n are 2.6×1018 s-1,0.012 MPa-1 and 5.73,respectively,and the hot deformation activation energy is 518.73 kJ/mol.