Q235碳素钢超细铁素体组织的退火过程研究

Investigation of Annealed Ultra-fine Ferrite Microstructures in a Plain Low Carbon Steel Q235

在热模拟单向压缩条件下研究了Q2 35碳素钢形变强化相变产生的超细铁素体退火时的组织及取向 (差 )演变过程及其应变量和先共析铁素体的影响。结果表明 ,形变强化相变后细晶铁素体内形变储存能有限 ,加上渗碳体的钉扎 ,一般不发生明显的静态再结晶过程。当应变量足够大时 ,形变后在6 5 0℃下保温铁素体发生正常长大。先共析铁素体存在时 ,形变后在 6 5 0℃退火时 ,形变长条铁素体发生明显的 (亚 )晶粒回复式长大。形变改变了未转变奥氏体的分解方式 ,表现为奥氏体向离异珠光体的加速转变。讨论了低碳钢形变后铁素体难以再结晶的原因。

The microstructure and(mis) orientation evolution during annealing of ultra-fine ferrite microstructure produced by deformation-enhanced transformation are investigated in a Q235 low carbon steel using single-axial compression simulating test.The results show that no apparent static recrystallization of ferrite is detected during annealing at 550～650℃,which is ascribed to the low stored energy in ferrite and the effective pinning by the second/minor phases.As strain is further increased a heterogeneous grain growth of ultra-fine ferrite occurs at 650℃.In the presence of deformed pre-eutectoid ferrite,the annealing at 650℃ leads to the strong growth of elongated deformed ferrite subgrains in the way of recovery.Deformation of austenite alters its decomposition mode to pearlite in an accelerated and divorced ways.The reasons for the difficulty of static ferrite recrystallization in low carbon steel are discussed.