钒氮微合金化对ULCB钢组织性能和析出行为的影响

Effect of V-N microalloying on precipitation behaviors,microstructure and properties of ultra-low carbon bainitic steel

借助光学显微镜(OM)、电子背散射衍射技术(EBSD)、透射电子显微镜(TEM)和能谱仪(EDS)研究了两种不同V、N含量的超低碳贝氏体钢(ULCB)在控轧控冷过程中的微观组织、力学性能及碳氮化物的析出行为。结果表明:两种试验钢的组织都为粒状贝氏体,但高V、N含量的试验钢具有更高的强度和硬度。低V、N钢中V(C,N)数量较少,且以沿位错线析出为主。随着钢中V、N含量的增加,贝氏体组织明显细化,大角晶界所占的比例也相应提高;同时,在贝氏体铁素体基体中5～10 nm之间的V(C,N)体积分数显著增加,且存在沿位错线析出和基体中弥散析出两种形式。细晶强化和沉淀强化是高V、N钢强度提高的主要因素。

The precipitation behavior of vanadium carbonitrides and its effect on the microstructure and mechanical property during the thermomechanical control processes（TMCP） in ultra-low carbon bainitic steel with two different vanadium and nitrogen content were studied by means of optical microscope（OM）,electron backscatter diffraction technique（EBSD）,transmission electron microscope（TEM） and energy disperse spectroscopy（EDS）.The results show that the microstructure of the two tested steels are granular bainite,but high vanadium and nitrogen content steels have higher strength and hardness.A very few number of V（C,N） particles mainly precipitate from the solid solution along the dislocation line in the low vanadium and nitrogen steels.The bainitic microstructure are obviously refined and the percent of the high-angle grain boundaries increase as the increasing of vanadium and nitrogen content in steel.Simultaneously,the volume fraction of V（C,N） particles between 5-10 nm significantly increases in bainitic ferrite matrix,and two precipitation modes that precipitating along the dislocation line and disperse in the interior of grains are observed in the tested steel.The high V-N content steels obtain the high strength mainly due to refined crystalline and precipitation strengthening.