中文摘要：

通过对低碳Mo-Cu-Nb-B系微合金钢进行连续冷却和等温实验,发现低碳Mo-Cu-Nb-B系微合金钢在过冷奥氏体亚稳定区等温,能发生针状铁素体转变。非再结晶区变形奥氏体连续冷却时虽然能得到各类低碳贝氏体组织,但各类组织特别是针状铁素体的份额却不能有效控制。通过分阶段冷却,可以控制得到针状铁素体和板条贝氏复相组织。利用针状组织分割原奥氏体晶粒能细化组织,达到优化高强度低碳微合金钢的力学性能目的。

英文摘要：

The continuous cooling and isothermal transformation microstructure evolution in a low carbon Mo-Cu-Nb-B microalloying steel were investigated. It was found that acicular ferrite could be transformed independently in the intermediate temperature range of metastable austenite. Although multi intermediate transformation phases can be transformed during the continuous cooling, the fraction of phases, especially acicular ferrite, cannot be controlled. However, the fraction of acicular ferrite could be controlled by the step cooling process. The optimum amount of acicular ferrite divides the prior-austenite grains, resulting in multi-phase mierostrueture ultrafine.