低碳钢低温变形γ→α相变行为的预测模型

MATHEMATICAL MODELLING OF FERRITE TRANS- FORMATION OF LOW CARBON STEEL THROUGH LOW TEMPERATURE HEAVY DEFORMATION

从变形使孕育期缩短的角度,讨论了形变诱导相变的发生条件,计算了不同变形条件下几种成分的低碳钢变形过程析出铁素体的开始温度Ar3d,发现同样变形条件下,碳含量越低的钢种,其Ar3d越高;同一成分钢种,随着变形量增加或变形速率减小,Ar3d提高.基于相变动力学理论,在形核速率计算中充分考虑变形和过冷的双重作用,探索了低温变形诱导铁素体相变的动力学模型.用该模型进行的计算机模拟结果和实验结果吻合良好,表明这种理论处理方法可用来模拟这种相变过程.

The influence of hot deformation on the incubation period of ferrite transformation was calculated to determine the conditions under which deformation induced transformation occurs. Furthermore, the austenite-ferrite transformation start temperature during deformation(Ar3d) was predicted in three grades of low-carbon steels under different processing parameters. Results indicate that Ar3d temperature decreases as carbon content increases for the same processing parameters; whereas Ar3d temperature increases as strain rate decreases or strain increases for the same steel grade. On the basis of transformation kinetics and thermodynamics, the nucleation and growth of spherical ferrite grain on austenite grain boundary have been investigated. In view of enhancement of deformation on transformation, the basic kinetics model was established to simulate deformation induced transformation behavior, in which the influence of the deformation stored energy and effective deformation ledge on the nucleation and growth was considered. The simulated results are in good agreement with experimental results. Therefore, all of these indicate that this model can be used to simulate this kind of transformation.