700 MPa级汽车大梁钢冲压开裂原因分析及措施  

Cause analysis and measures for stamping cracking of 700 MPa grade plate for automobile frame

作　　者：刘洪银 亓伟伟 孙建卫 李雪峰 雷洲 LIU Hongyin;QI Weiwei;SUN Jianwei;LI Xuefeng;LEI Zhou(Shandong Iron and Steel Co.,Ltd.,Laiwu 271104,China)

机构地区：[1]山东钢铁股份有限公司,山东莱芜271104

出　　处：《轧钢》2023年第4期113-118,共6页Steel Rolling

摘　　要：针对700 MPa级汽车大梁钢板冲压开裂问题,对其化学成分、组织、力学性能进行了检测分析,发现其冲击韧性值低、拉伸断口分层、有严重的混晶现象并存在粗大的带状铁素体区。分析认为由于连铸工序缺乏打碎柱状晶和均匀铸坯成分的设备导致铸坯的中心偏析、树枝晶偏析严重,Ti元素在钢材中的不均匀分布导致混晶现象和冲击韧性降低,铸坯中S元素的偏析导致拉伸断口分层。根据分析结果,对700 MPa级汽车大梁钢化学成分和生产工艺进行了优化调整,适当提高了C、Nb含量,降低了Ti、S含量,并制定与铸坯厚度、w(Ti)×w(C)浓度积、Ti含量相适应的铸坯加热工艺参数,使铸坯中的大尺寸TiC粒子完全溶解并使溶解后的Ti元素充分扩散,解决了偏析和混晶问题。钢板冲击功提高约70 J,拉伸断口无分层现象,金相组织无混晶现象,冲压成形开裂率小于0.5%。In view of stamping cracking problem of 700 MPa grade plate for automotive frame,the chemical composition,microstructure and mechanical properties were tested and analyzed.It found out that the plate impact toughness value was low,the tensile fracture surface was delaminated,and there were serious mixed grain phenomenon and coarse banded ferrite areas.The analysis shows that due to the lack of equipment in the continuous casting process to break columnar grains and unify composition of the billet,the center segregation and dendrite grain segregation of the billet are severe.The uneven distribution of Ti element in the steel leads to mixed grain phenomenon and decrease in impact toughness,and the segregation of S element in the slab leads to tensile fracture delamination.Based on the analysis results,the chemical composition and production process of 700 MPa grade plate for automotive frame have been optimized and adjusted,the content of C and Nb are appropriately increase,the content of Ti and S are,and reduced the heating process parameters suitable for the thickness of the slab,w(Ti)×w(C) concentration product and Ti content,so that the large-sized TiC particles in the slab are completely dissolved and the dissolved Ti element is fully diffused,which resolve the segregation and mixed grain problems.The impact energy of the plate is increased by about 70 J,there is no tensile fracture delamination,and there is no mixed grain phenomenon in the metallographic structure.The cracking rate during stamping forming is less than 0.5%.

关 键 词：汽车大梁钢 断口分层 混晶组织 偏析 冲击韧性 化学成分 加热工艺 优化调整 

分 类 号：TG142.1[一般工业技术—材料科学与工程]