帘线钢渗碳体溶解与饱和磁化强度变化

依据固体与分子经验电子理论(EET),计算了渗碳体的价电子结构,确定了含V、Mn渗碳体的稳定结构分别为θ-(Fe_(2.75)Mn_(0.25))C、θ-(Fe_(2.5)V_(0.5))C。计算θ-Fe_3C、θ-(Fe2.5V_(0.5))C和θ-(Fe_(2.75)Mn_(0.25))C的比饱和磁化强度MS分别为167.19、111.20和146.32A·m~2/kg。制备的不同V含量的未冷拉70和80级帘线钢的MS计算误差在0.18%~6.22%,与振动样品磁强计(VSM)的实测值符合较好。建立了渗碳体溶解的4阶段模型,得出了渗碳体溶解对未冷拉帘线钢MS的影响规律。帘线钢冷拉后MS的巨变表明:铁素体中Fe原子的平均原子磁矩和原子状态发生重大改变;计算发现其原子状态根据钢的成分与应变量,会从甲种(A)变成乙种(B)甚至丙种(C)杂化状态。

Cementite dissolusion and variation of saturation magnetization for tire cord steel

Based on the empirical electron theory of solids and molecules (EET),the valence electron structure of cementite was calculated and the stable structures of cementite containing Mn and V were determined to beθ-(Fe2.75 Mn0.25 )C andθ-(Fe2.5 V0.5 )C,respectively.The calculated saturation magnetizations (MS )ofθ-Fe3 C,θ-(Fe2.5V0.5)C andθ-(Fe2.75Mn0.25)C were 167.19,111.20 and 146.32 A·m2/kg,respectively.The calculated MS,whose error limit is 0.18%-6.22%,for the prepared 70-grade and 80-grade tire cord steels with different contents of V and without cold drawing,are in good agreement with the measured values by vibrating sample mag-netometer (VSM).The dissolution model with four stages of cementite was built and the influence of cementite dissolution on MS of tire cord steel without cold drawing was attained.The dramatic changes of MS of tire cord steel after cold drawing indicate that the average magnetic moments and the atomic states of Fe in ferrite have changed significantly.The calculation results show that the states of Fe atoms in ferrite would change from hybrid state of A to B or even to C according to the steel′s composition and strain.