氮合金化细化新型高导热性奥氏体锰钢晶粒度的作用机理

研究了氮细化新型高导热性奥氏体锰钢晶粒度的作用机理. 结果表明，铸态奥氏体锰钢中氮在固液界面形成吸附层，阻碍铁、锰、碳等原子的扩散，提高了形核过冷度和形核自由能差，提高均质形核率，降低晶体长大速度，使晶粒细化；氮在晶界固溶，与晶界处铁、锰等原子形成较强的共价键，牵制了铁、锰原子的扩散，使晶粒在热处理过程长大受阻，限制了奥氏体锰钢晶粒度长大，细化晶粒. 细化效果还与氮浓度有关. 新型试验钢种锰含量降至不高于8%，碳含量约1%，氮含量约0.07%，晶粒度达到4级，机械性能达到甚至超过标准高锰钢Mn13.

Effect of Solid Solution of Nitrogen Element on Crystal Grain Formation of Austenitic Manganese Steel with High Thermal Conductivity

The effect of solid solution of nitrogen element on crystal grain of developed austenitic manganese steel with high thermal conductivity is studied. The results indicate that the crystal grain of manganese steel in casting is affected by the nitrogen in the interface between crystal and liquid steel as surfactant, and the diffusion of relevant atoms are hindered by nitrogen, so that free energy of critical nucleation will be increased, homogeneous nucleation rate of crystal raised and growing velocity of crystal lowered, and crystal grain will be refined finally in steel casting. The effect degree of nitrogen on crystal grain of steel is affected by nitrogen content. During heat treatment, because of covalent bond between nitrogen and iron and manganese atoms, the diffusion of iron and manganese atoms will be hindered due to the existence of nitrogen at boundary of crystal or the attachment of nitrogen on the face of crystal, so that growing velocity of crystal will be lowered and the crystal grain of steel can be controlled. The new kind of austenitic manganese steel decreases the content of manganese below 8%, the content of carbon to about 1%, and the content of nitrogen about 0.07%, the crystal grain grade of developed steel reaches the class 4, and its mechanical properties meet those required by standard manganese steel Mn13.