钒对高强度汽车大梁钢组织细化的影响

利用Gleeble-3500热模拟试验机、扫描电镜、透射电镜、电子背散射衍射技术等手段研究V对700 MPa级高强度汽车大梁钢组织细化的影响.在冷却速度2~7℃·s-1时，显微组织为针状铁素体+粒状贝氏体组织.V添加提高粒状贝氏体体积分数，细化粒状贝氏体组织，并明显降低粒状贝氏体中M/A岛的尺寸.与无V钢相比，含V钢中大角度晶界比例提高18.2%，对提高钢的韧性有利.由于C含量过低，在实验钢中未观察到单独的VC析出，由此推测V主要固溶在基体中，以合金化方式促进钢的贝氏体相变，使组织得到有效细化.

Influence of vanadium on the microstructure refinement of high strength automobile beam steel

The effects of vanadium on the microstructure refinement of automobile beam steel with a yield strength of 700 MPa were investigated by Gleeble-3500 Thermo Simulator, scanning electron microscopy, transmission electron microscopy and electron back-scattered diffraction. The results show that a mixture structure of acicular ferrite and granular bainite can be obtained in a cooling rate range of 2 to 7℃·s-1 . It is recognized that the volume fraction of granular bainite increases and the microstructure can be refined by adding vanadium. After the addition of vanadium, the size of M/A islands decreases obviously. Compared to the V-free steel, high angle grain boundaries in the V-bearing steel increases by 18. 2%, indicating a potential improvement in toughness. No VC precipita-tion is observed in the tested steel due to low carbon content, so it can be deduced that V in the solid solution can promote the bainite transformation and refine the microstructure.