变形和硼对低碳Mn-Nb钢连续冷却转变的影响

Effects of Deformation and Boron on Continuous Cooling Transformation of Low Carbon Mn-Nb Steels

通过热模拟实验对不含硼和含硼低碳Mn-Nb钢在连续冷却过程中的相变进行研究,分别绘制了两种钢的连续冷却转变(CCT)曲线,并对不同冷却速度的试样进行组织观察和显微硬度分析.结果表明:变形使低碳Mn-Nb钢CCT曲线左移,提高开始转变温度,促进了多边形铁素体和珠光体的转变;微量硼的加入使低碳Mn-Nb钢CCT曲线右移,显著降低开始转变温度,明显抑制铁素体和珠光体转变,减小铁素体和珠光体存在的冷却速度范围,显著提高了低碳Mn-Nb钢的显微硬度.

The continuous cooling transformation（CCT） of low carbon Mn-Nb steels with/without boron was investigated by thermal-mechanical simulator.The CCT curves of two kinds of steel were obtained and the microstructures and microhardness of the samples with different cooling rate were measured.The results showed that deformation moves the CCT curves to the left,increases the transformation start temperature,and promotes the formation of polygonal ferrite and pearlite.A trace boron addition moves the CCT curves to the right,decreases remarkably the transformation start temperature,suppresses obviously the formation of polygonal ferrite and pearlite,decreases the cooling rate range of polygonal ferrite and pearlite,and increases effectively the microhardness of low carbon Mn-Nb steel.