摘要
对热轧马氏体双相钢和贝氏体双相钢进行扩孔试验,利用金相显微镜和扫描电镜对2种双相钢扩孔裂纹和断面组织进行分析,研究2种双相钢的扩孔开裂机理,并分析预制孔为冲孔时的扩孔率小于预制孔为钻孔时的原因。研究结果表明:热轧贝氏体双相钢断口微观形态的主要特征是韧窝,开裂类型属于穿晶延性断裂。热轧马氏体双相钢断口微观形态的主要特征是舌状花样,开裂类型属于沿晶脆性断裂。预制孔为冲孔时扩孔率较低的主要原因是扩孔过程在圆孔边部产生加工硬化层和毛刺,且加工硬化层起着主导作用,如在扩孔前用砂纸或锉刀去除2 mm厚加工硬化层和毛刺,或采用钻孔等方法加工中心孔,其扩孔率将大幅提高。
Hole expansion tests were conducted for hot-rolled ferrite＋martensite dual phase steel and ferrite＋bainite dual phase steel. Metallographic microscope and scanning electron microscope were used to observe the expansion crack and sectional microstructure to analyze the cracking mechanism. The causes of lower hole expansion property of the preformed hole produced by piercing than that of drilled hole for hot-rolled dual phase steels were also studied. The results show that the ferrite＋bainite dual phase steel exhibits transgranular ductile fracture with dimples. The ferrite＋martensite dual phase steel displays fracture features of tongue pattern and intergranular brittle fracture. Lower hole expansion value for pierced hole samples is caused by work hardening layer and burr. The work hardening layer plays a dominant role. If the burr and work hardening layer about 2 mm away from the hole edge are removed by sandpaper or file, or the hole is preformed by drilling, the hole expansion performance will be improved greatly.
出处
《中南大学学报（自然科学版）》
EI
CAS
CSCD
北大核心
2014年第2期395-400,共6页
Journal of Central South University:Science and Technology
基金
"十一五"国家科技支撑计划项目(2006BAE03A13)
关键词
热轧双相钢
扩孔
加工硬化
扩孔机理
hot-rolled dual phase steel
hole expansion
work hardening
cracking mechanism
