Q235碳素钢应变强化相变过程中的动力学问题

DYNAMIC ASPECTS OF STRAIN ENHANCED TRANSFORMATION IN Q235 PLAIN CARBON STEEL

利用热模拟单向压缩实验，分析了Ｑ２３５碳素钢应变强化相变过程中应变对铁素体晶粒数目及铁素体长大速度的影响，同时考察了铁素体转变动力学与应变速率、形变温度、奥氏体晶粒尺寸、纯净度的关系，并与无应变时进行比较．结果表明，应变使铁素体转变动力学发生一定的变化，应变作用下奥氏体晶界的形核率明显增加，但未观察到应变明显提高铁素体长大速度的现象应变作用下铁素体的长大速度被周围铁素体快速形成或铁素体的动态再结晶所抑制或掩盖应变速率的提高主要使铁素体转变时间提前；形变温度越高，应变对铁素体转变的促进作用越明显；原始奥氏体晶粒尺寸不同。转变动力学曲线的斜率稍有不同，这主要由转变初期的形核位置的多少引起．

Ferrite grain number and ferrite growth rate were measured during strain enhanced transformation in Q235 plain carbon steel by thermal simulating tests and compared with those in the absence of strain. The influences of processing parameters and the purity of materials on transformation dynamics were evaluated. Results illustrate that the nucleation rate at austenite grain boundaries was clearly increased by strain whereas a higher ferrite growth rate during straining was not detected. Strain changed ferrite transformation dynamics to some extent. A higher strain rate shortened transformation time, and the accelerating effect of strain on transformation was more pronounced at high deforming temperature. The influence of initial austenite grain size was reflected at the early stage of transformation which is related to the scarce of nucleation sites.