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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.
The effects of V on the microstructure refinement of 700 MPa high-strength automobile girder steel were studied by using Gleeble-3500 thermal simulator, scanning electron microscope, transmission electron microscopy and electron backscattering diffraction technique. At the cooling rate of 2 ~ 7 ℃ · s-1 , The microstructure was acicular ferrite + granular bainite, V addition increased the volume fraction of granular bainite, refined granular granular bainite and significantly reduced the size of M / A island in granular bainite Compared with the non-V steel, the V-containing steels with large angle grain boundaries increased by 18.2%, which is beneficial to improve the toughness of steel.Due to the low C content, no separate VC precipitation was observed in the experimental steels, The main solid solution in the matrix, alloying to promote the bainite transformation of steel, the organization effectively refined.