NbC对HRB500钢筋凝固过程中异质形核与晶粒细化的影响

Effect of NbC on Heterogeneous Nucleation and Grain Refinement of HRB500 Reinforcement during Solidification

基于二维错配度理论,针对以NbC为基底的相对形核相γ-Fe、α-Fe进行错配度计算.利用扫描电镜(SEM)、透射电镜(TEM)、金相显微镜(OM)、动态热模拟相变仪,以及力学性能测试,研究了含Nb微合金钢的析出强化、细晶强化、控冷效果、显微组织及力学性能.结果表明:α-Fe与NbC异质形核的效果较好,γ-Fe与NbC异质形核的效果不理想;在连续冷却过程中,珠光体的临界冷却速率为1.5℃/s,贝氏体的临界冷却速率为5.0℃/s;含Nb的HRB500钢筋通过合适的控冷工艺可以有效细化晶粒尺寸,提高微合金钢的力学性能.

Based on the two-dimensional mismatch theory,the relative nucleation phasesγ-Fe andα-Fe on NbC were calculated.The precipitation strengthening,fine grain strengthening,cooling control effect,microstructure and mechanical properties of microalloyed steel containing niobium were studied by means of scanning electron microscope(SEM),transmission electron microscope(TEM),optical microscope(OM),dynamic thermal simulation transformation instrument and mechanical properties test.The results show that the effect ofα-Fe and NbC heterogeneous nucleation is better,but the effect ofγ-Fe and NbC heterogeneous nucleation is not ideal;in the continuous cooling process,the critical temperature of pearlite transformation is 1.5℃/s,and the critical temperature of bainite transformation is 5.0℃/s;the Nb containing HRB500 can effectively refine the grain size and improve the mechanical properties of microalloyed steel through appropriate controlled cooling process.