低碳钢中以氧化物为核心针状铁素体的形成

通过高温热扩散结合法系统地研究了在含CaO,CeO₂的低碳钢中晶内针状铁素体形核现象.实验结果表明：钢中针状铁素体的形核是由稳定的氧化物CaO,CeO₂质点非均匀形核引起的.在CaO,CeO₂氧化物周围存在明显应变区,它是晶内针状铁素体非均匀形核起支配作用的驱动力,可以在一个夹杂氧化物上多处形核,同时形成大量新的奥氏体/铁素体高能内界面,提供发生激发形核的表面效应.氧化物尺寸在0.1～0.6μm范围内对形成晶内针状铁素体效果最好.

Nucleation of intragranular ferrite at oxide particles in low carbon steel

The intragranular nucleation phenomena of ferrite in low carbon steels with oxides of CaO and CeO₂ were studied using a method of hot diffusion bonding. The experimental results showed that the fine intragranular acicular ferrite structure in low carbon steels with oxides of CaO and CeO₂ was induced by heterogeneous nucleation of ferrite plates at fine dispersed CaO and CeO₂ particles. There were large thermally induced strain regions in the neighbourhood of CaO and CeO₂. The presence of these regions provided dominant driving force for the nucleation of acicular ferrite, which led to multiple nucleations on the inclusion. Meanwhile a large quantity of new austenite/ferrite high energy interfaces formed, which provided the surface effect of the sympathetical nucleation. The optimum size of oxides for adequate nucleation of acicular ferrite was 0.1 to 0.6μm.