多道次轧制过程中超细晶粒控制

在高强度水平的基础上获得较高的韧性，控制热加工工艺实现晶粒尺寸超细化是最佳的途径之一。低碳管线钢的超细铁索体晶粒可以从相变前的超细奥氏体晶粒获得。通过优化轧制工艺使得奥氏体的动态再结晶发生在Z（Zeller-Hollomon）参数较大的工艺条件下，获得超细的奥氏体动态再结晶晶粒尺寸。然而，大的Z参数往往具有较大的动态再结晶临界应变。为了获得足够的应变积累来克服动态再结晶的临界应变，低温大变形量的变形是基本条件。提出了在多道次轧制过程中积累应变的条件以及避免混晶的技术路线，利用提出的模型对工业轧制工艺进行优化，模拟实验的结果得到了最终产品晶粒尺寸为1.5μm。

Control of Ultra-fine Grain Size in Multi-pass Rolling

In order to obtain high toughness at the high strength level, the refinement of grain size though control of hot deformation processing is the best solution. The ultra- fine ferrite grain size can be achieved from the ultra- fine austenite grain size prior to phase transformation in low carbon line pipe steels. The ultra- fine austenite rain size can be obtained by dynamic recrystallization at a large Z (Zeller- Hollomon parameter) condition. However, the large Z is associated to a large critical strain for dynamic recrystallization. Lowering temperature window of rolling and large strain accumulation is basic condition for exceeding of critical strain for dynamic recrystallization to refine austenite grain size. The condition and technology for strain accumulation in multi- pass processing to refine austenite grain size through dynamic recrystallization are presented. The experimental schedule optimized by the modeling and software based on industrial rolling schedule is simulated in laboratory, in which the final average ferrite grain size is about 1.5 micron.