DP600双相钢高温塑性失效研究

Research on Hot Ductiliy Failure Behavior of DP600 Duplex Steel

采用热模拟拉伸试验研究了DP600双相钢的高温塑性。分析在700~1200℃下DP600钢热拉伸后的微观组织。结果表明：900~1200℃钢中奥氏体的动态再结晶能有效提高其高温塑性,断口为延性断裂。在900~1200℃以下组织显示奥氏体晶界处析出薄膜状先共析铁素体造成应力集中,导致在晶界处发生断裂,在800℃时塑性降低至谷底。在700~750℃由于块状铁素体大量析出,导致形变均匀塑性得到快速回升。断口附近金相组织中发现孔洞和裂纹,并且均沿着铁素体晶界存在。由于铁素体强度较低,当铁素体量较少时,应变集中在铁素体内部,微孔的形成以及晶界的分离首先从铁素体内部开始。

The hot ductility of DP600 steel was researched by thermal simulation tensile test. The microstructure of DP600 specimens after tensile test was analyzed at 700-1200℃. The results show that the dynamic recrystallization effectively promotes the hot ductility at 900-1200℃ ,and the fracture mode is ductile failure. When the temperature is under at 900-1200℃ ,the film proeutectoid ferrite forms along the austenite grain boundary leading to the local stress concentration, then, the fracture appears at grain boundadry. The plasticity decreases to valley bottom at 800 ~C. When the temperature reduces to 700-750~C ,the substantial formation of massive ferrite makes deformation uniform ductility increase rapidly. The fracture microstructure shows that the voids and cracks exist along the ferrite grain boundary near the fracture. Due to the low strength of ferrite, the strain concentrates along the grain boundary when the volume fraction of ferrite is low, meanwhile, the formation of voids and the separation of cracks start form the interior of ferrite.