微合金化控轧控冷钢筋纵向金相组织研究

 对微合金化控轧控冷钢筋的纵向金相组织进行了研究，并分析了不同成分试验钢纵向“条带”组织的差异及形成原因。研究结果表明：偏析元素（P、Si、Mn等）在轧制过程中沿轧制方向呈条状分布，是20MnSi、20MnSiV钢产生带状组织的原因。铌及其碳氮化物的溶质拖曳和“钉扎”作用，使20MnSiNb钢的奥氏体未再结晶轧制温度提高到1050℃，在冷却过程中，先共析铁素体在形变奥氏体晶界和内部变形带均匀析出，随后沿形变奥氏体晶界（在先共析铁素体与奥氏体的界面上）生成珠光体带，最后在形变奥氏体晶粒内部形成贝氏体条。研究条件下优势形核点的排序为：形变奥氏体晶界和形变奥氏体晶内变形带、偏析元素和夹杂、再结晶奥氏体晶界。

Investigation of Cross Section Microstructure of the Steel Bar With Micro Alloying Controlled Rolling and Controlled Cooling Technique

The cross section microstructure of the steel bar with micro alloying controlled rolling and controlled cooling technique as well as the reasons of different compositions to the microstructures were investigated. It is found that the segregation of elements (P,Si and Mn et al.) distributes like stripping which results in the such stripping microstructure for steel 20MnSi and 20MnSiV during rolling. The 20MnSiNb steel can not be recrystallized below 1050℃ for the pinning by Nb and its compound containing C and N elements. The proeutectoid ferrite is formed homogemously in grain boundaries of deformation austenite and interior of deformation zone, then, the pearlite belt is separated out in grain boundaries of deformation austenite (between the grain boundaries proeutectoid ferrite and austenite). The bainite strip is generated in the grain of deformation austenite during last cooling stage. The proper order precipitation of the microstructure of the samples shows as follow: grain boundaries of deformed austenite and deformed band of deformed austenite, segregation of elements, grain boundaries of recrystallization austenite.