【摘要】 本文用含Nb、V、Ti等元素的42CrMo钢研究了未溶碳氮化物的r/f与奥氏体晶粒大小之间的关系,用车轴钢研究了加热速度对奥氏体晶粒长大倾向的影响以及用GCr15钢研究了不平衡组织加热对奥氏体晶粒的异常长大现象。所得结果均难以用Zener及Gladman所提出的有关奥氏体晶粒半径与r/f之间的关系式进行解释。为解释所观察到的现象,对Zener及Gladman公式进行了讨论。指出Zener公式之所以与实验情况不符是因为式中的R不是奥氏体晶粒半径而是界面曲率半径。Gladman公式之所以与实际情况不符是因为推导驱动力时的假设有误。本文导出了界面曲率半径R与界面两侧晶粒半径ρ及ρ′之间的关系为: R=ρ/2cos(60°+90°/πZ)式中Z=ρ′/ρ°由界面能提供的推动晶界迁移的驱动力P力: P=4σcos(60°+90°/πZ)/ρ奥氏体晶粒长大终止时晶粒半径ρ与r/f之间的关系为: ρ=8r/3f 2cos(60°+90°/πZ) 用导出的公式讨论了所观察到的奥氏体晶粒长大的种种异常现象并核算了Koul所得的数据,所得结果与实测值符合得较好。更多还原

【Abstract】 The abnormal growth of austenite grain during heating of non-equilibrium structure of steel GCr 15 was studied. The influence of heating rate on the growth of the austenite grain of mediuum carbon axle steel was examined and the relation between the austenite grain size and the ratio r/f of undissolved carbonitride in steel 42CrMo, containing a few Nb, V or Ti addition was also described. It has been found that the results was not in agreement with the Zener’s and Gladman’s formula. After discussing the obtained results according to the Zener’s formula, authors of this paper believe that this is due to the fact that the R in the Zener’s formula is not the radius of austenite grain, but the radius of curvaure of grain boundary. Here in this paper, the relation between the radius oef curvature of grain boundary and the radii of two grains on both side of grain boundary is obtained and represented by: where R is the curvature of grain boundary; ρ, the radius of small austenite grain and ρ’, the radius of large austenite grain, Z =ρ’/ρ. In addition, the driving force P from grain boundary energy for grain growth can be obtained and represented by: The relation between the critical radius ρ_? of austenite grain and r/f is; The observed phenomenon of austenite grain growth was discussed by the derived formula. The data of Koul are also checked by the derived formula, and the calculated results are in agreement well with Kout’s measurement value.更多还原