连续冷却过程中低碳微合金化钢的组织转变特征  

Characteristic of microstructure transformation of low-carbon microalloyed steel during continuous cooling

作　　者：李拔[1] 刘清友[1] 贾书君[1] 陈健[1] Li Ba;Liu Qingyou;Jia Shujun;Chen Jian(Institute of Engineering Steels,Central Iron and Steel Research Institute,Beijing 100081,China)

机构地区：[1]钢铁研究总院工程用钢所

出　　处：《金属热处理》2018年第12期18-24,共7页Heat Treatment of Metals

基　　金：国家重点研发计划(2017YFB0304901)

摘　　要：通过连续冷却试验研究了一种商业用低碳微合金化钢在未变形和压缩变形条件下,显微组织随冷却速度的变化,并结合光学显微镜、扫描电镜、透射电镜和背散射电子衍射系统对不同冷速下的组织特征进行了表征与分析。结果表明,形变在细化整体组织的同时,可以显著抑制贝氏体铁素体和珠光体,并且促进针状铁素体(acicular ferrite,AF)和粒状贝氏体(granular bainite,GB)的形成。两阶段变形后,在快冷速(70~40℃/s),中等冷速(20~10℃/s)和相对较慢冷速(2~0. 5℃/s)下,组织分别以AF、GB和准多边形铁素体为主。AF组织具有不规则的板条形貌,板条内含有高密度的位错。随着冷速降低,板条内形成亚结构包括取向差接近5°的胞状结构和取向差接近10°的亚晶。此外,AF组织中还存在板条束和板条簇结构。GB组织在较快冷速时由等轴的铁素体基体和分布在晶内和晶界的粒状马奥组元构成,而在中等冷速时,基体转变成无规则形状的、随机分布的铁素体。Microstructure transformation with the cooling rate was studied through the continuous cooling test on low-carbon microalloyed steel under the condition with and without compressive deformation.The microstructure feature under different cooling rate was characterized and analyzed by synthetically using OM,SEM,TEM,and EBSD.The results show that the deformation can refine the whole microstructure, whilst restrain the formation of bainite ferrite or pearlite and promote the transformation of AF (acicular ferrite)and GB (granular bainite). After two-stage deformation,the microstructure is dominated by AF,GB,and quasi-polygonal ferrite corresponding to the fast cooling rate (70-40℃/s),middle cooling rate (20-10℃/s)and relatively slow cooling rate (2-0.5℃/s),respectively.AF microstructure with the irregular plate-type has high dislocation density inside.With the decrease of cooling rate,the substructures are formed in the ferrite plate, which consists of the cell structures with misorientation about 5^.and subgrains with misorientation about 10%In addition,both the "packet" and the "colony"structures are observed in the AF plates.GB microstructure consists of the granular M/A constitutes and equiaxed ferrite matrix under the relatively fast cooling rate.While,in the middle cooling rate,the ferrite matrix is turned into the irregular shape with random distribution.

关 键 词：组织转变 微合金化钢 连续冷却 针状铁素体 粒状贝氏体 

分 类 号：TG406[金属学及工艺—焊接]