Fe-C-Mn系冷轧双相钢两相区奥氏体化过程模拟

Simulation of austenization during intercritical annealing for Fe-C-Mn cold rolling dual phase steel

在对双相钢两相区奥氏体化过程进行热力学与动力学分析的基础上,建立了两相区奥氏体化过程的扩散模型,并采用显式有限体积法对740℃与780℃下的奥氏体化过程进行了数值求解.模拟结果表明:奥氏体长大初期受C元素在奥氏体中的扩散控制并很快达到亚平衡.该阶段奥氏体长大速度较快.奥氏体长大后期受Mn元素在铁素体中的扩散控制.该过程由于Mn元素的扩散速率比C元素的扩散速率低几个数量级而持续数千秒.当Mn元素在两相中的扩散通量相等时,奥氏体停止长大,Mn元素继续从铁素体向奥氏体中转移以完成其在两相中的均化.

Based on the analysis of thermodynamics and dynamics for austenization during intercritical annealing of a dual phase steel; an austenization model was established and solved by using the explicit finite volume method at two austenite temperatures of 740 ℃ and 780 ℃. The simulated results show that the initial stage of austenite growth is controlled by carbon diffusion in austenite and reaches paraequilibrium quickly, and the austenization rate in this stage is very fast. The late stage of austenite growth is controlled by manganese diffusion in ferrite. As the diffusion rate of manganese is several orders of magnitude slower than that of carbon, this stage lasts for thousands of seconds. When the diffusion flux of manganese in each phase is equal, austenite stops growing. But manganese continues its transfer from ferrite to austenite in order to achieve its homogenization in each phase.