中碳硅-锰钢热轧板断裂原因分析  

Analysis on Fracture Cause of Hot-rolled Medium-carbon Silicon-manganese Steel Plate

作　　者：孙中渠 刘俊亮[1,2] 刘仕龙 SUN Zhongqu;LIU Junliang;LIU Shilong(Research Institute, Baoshan Iron & Steel Co., Ltd., Shanghai 201900, China;State Key Laboratory of Development and Application Technology of Automotive Steels (Baosteel), Shanghai 201900, China;Institute of Phase Transformation and Structure, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China)

机构地区：[1]宝山钢铁股份有限公司研究院,上海201900 [2]汽车用钢开发与应用技术国家重点实验室(宝钢),上海201900 [3]上海交通大学材料科学与工程学院相变与结构研究所,上海200240

出　　处：《上海金属》2020年第2期8-13,20,共7页Shanghai Metals

基　　金：宝山钢铁股份有限公司-上海交通大学“未来钢铁联合研究中心”新一代高强钢回火脆性机理与控制方法。

摘　　要：含硅量较高是第三代汽车用高强钢的成分特点,会导致钢产生回火脆性。宝钢热轧中碳硅-锰钢板回火后断裂。采用扫描电镜研究了钢板断裂的原因。研究发现:该钢板断口有“冰糖状”和“河流花样状”特征,主要是沿晶断裂。热轧钢板中的原奥氏体晶界是微裂纹萌生和扩展的主要部位,形成“冰糖状”断口,同时产生少量的穿晶裂纹,导致钢板断裂。断裂钢板含1.7%Si影响了回火过程中的组织演变,也即使碳化物集中在板条界面和原奥氏体晶界析出,而板条内析出物很少,位错密度很低。碳化物和磷的偏聚,奥氏体晶界的位错塞积和应力集中降低了原奥氏体晶界的断裂强度,导致原奥氏体晶界成为裂纹萌生和扩展的通道。Composition of the 3rd generation automobile high-strength steels is characterized by higher silicon content,which would cause the steel to offer temper brittleness.The hot-rolled medium-carbon silicon-manganese steel plate broke after tempering in Baoshan Iron&Steel Co.,Ltd.The reason why the plate broke was investigated by scanning electron microscope.From the investigation it was discovered that the fracture of the steel plate was in the form of“crystal sugar”and“rivers”,being predominantly intercrystalline cracking.The grain boundary of prior austenite was a main position where fine crack started and propagated in the hot-rolled plate so that the fracture in the form of“crystal sugar”formed and a small amount of transcrystalline cracks produced,resulting in the plate fracture.The silicon content of 1.7%in the broken plate exerted an influence on microstructure transition during tempering,which caused carbides to precipitate predominantly in lath interface and grain boundary of prior austenite.However,precipitates were quite small,and dislocation density was quite low in lath interior.Anti-fracture strength of the grain boundary of prior austenite decreased due to segregation of carbides and phosphorus,dislocations piling-up and stress concentration in the grain boundary,which made the grain boundary become the position where crack started and propagated.

关 键 词：第三代汽车用钢 回火脆性 沿晶断裂 原奥氏体晶界 碳化物 

分 类 号：TG1[金属学及工艺—金属学]