增氮对钒微合金钢组织和性能的影响

 通过对不同钒、氮质量分数的试验钢进行热模拟压缩试验和实验室轧制试验，用OM、SEM和TEM分析试验钢的显微组织，研究增氮对钒微合金钢组织和性能的影响。结果表明，普通钒微合金钢为板条贝氏体＋粒状贝氏体组织，增加氮质量分数，可促进晶内铁素体相变，得到针状铁素体组织，使M/A组织细化且弥散分布，改善韧性；而增加钒质量分数，可以增加析出强化作用，提高强度，但组织形态无明显变化，不能提高韧性。增氮钢中的钒在奥氏体内以VN析出，低氮钢内的钒在铁素体内以VC的形式析出，奥氏体-铁素体、VC-铁素体和VN-铁素体的平面点阵错配度分别为6.72%、3.89% 和 1.55%，在奥氏体内析出的VN可以作为铁素体的优先形核位置，促进晶内铁素体相变。

Influence of nitrogen addition on the microstructure and properties of vanadium microalloyed steel

The influence of nitrogen addition on the microstructure and mechanical properties of vanadium microalloyed steel was studied. Experiment steels with different vanadium and nitrogen content were processed by thermal deforming simulation and rolled by laboratory roller respectively. OM， SEM and TEM were used to investigate the microstructure. Test results show that bainite laths and granular bainite are dominant in base vanadium microalloying steel. Intragranular ferrite trasnformation is promoted by nitrogen addition， which leads to acicular ferrite microstructure and refines the martensite-austeniete component. The toughness is improved as well. However， addition of vanadium increases precipitation strengthening， but has little effect on the morphology. The toughness is not improved. Vanadium precipitates in austenite as VN for nitrogen-rich steel. While for the nitrogen-low steels， it precipitates in ferrite as VC even if the content of vanadium is increased. The lattice misfit degree of austenite-ferrite， VC-ferrite and VN-ferrite are 6.72%， 3.89% and 1.55% respectively. It indicates that VN precipitated in austenite acts as preferential nucleation sites and promotes the intragranular ferrite transformation.