采用热机械轧制工艺可使中碳钢(0.36% C左右)具有球化渗碳体的细晶显微组织，研究发现随变形温度的降低及变形量的增加其铁素体晶粒尺寸变小。由于形变诱发铁素体相变(DIFT)，中碳钢在略高于Ar3温度时形变就可获得尺寸约2~3μm的超细铁素体晶粒。DIF体积分数随变形温度的降低以及变形应变的增加而增加，特别是当变形温度低于750℃时DIF体积分数显著增加，远远超过平衡铁素体体积分数值的54%。在低温及高应变条件下对钢进行形变，经过控制冷却后可获得合适的球化或退化显微组织。

Medium carbon steel (0.36% C) was thermo-mechanically deformed and subsequent controlled cooled (TMCP) to obtain refined microstructure with spheroidized cementite. It was found that ferrite grain size reduced with decreasing deformation temperature or increasing deformation strain. Owing to deformation induced ferrite transformation (DIFT), ultra-fine ferrite grain size of about 2~3μm could be obtained for the steel deformed just above Ar3 temperature. The volume fraction of DIF enhanced with decreasing deformation temperature or increasing deformation strain, especially when deformed temperature lowered than 750℃ the volume fraction of DIF increased significantly, which is far beyond the equilibrium ferrite fraction of 54%. The results indicated that a fairly spheroidized microstructure could be gained for steel deformed at low temperature and high strain and then controlled cooling.