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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 test of DP600 dual-phase steel was carried out to study the high temperature plasticity. The microstructure of DP600 steel after hot drawing at 700-1200 ℃ was analyzed. The results show that the dynamic recrystallization of austenite in steel from 900 ℃ to 1200 ℃ can effectively improve the high temperature plasticity and the fracture is ductile fracture. In the temperature range of 900-1200 ℃, the microstructure of the pro-eutectoid ferrite precipitated in the austenite grain boundary resulted in stress concentration, which led to the rupture at the grain boundary. The plasticity decreased to valley bottom at 800 ℃. At 700-750 ℃ due to massive precipitation of massive ferrite, resulting in uniform plastic deformation quickly rebounded. Holes and cracks were found in the microstructure near the fracture and all along the ferrite grain boundaries. Due to the lower strength of ferrite, when the amount of ferrite is small, the strain is concentrated in the ferrite. The formation of micropores and the separation of the grain boundaries start from the inside of the ferrite.