奥氏体化温度对铸态18CrNiMo7-6钢组织性能的影响

Effect of Austenitizing Temperature on Microstructure and Properties of As-Cast 18CrNiMo7-6 Steel

详细研究了奥氏体化温度对18CrNiMo7-6钢回火后组织和力学性能的影响。结果显示,当奥氏体化温度为750℃时,组织中仍有部分未溶解的铁素体存在,使得淬火+回火后样品的硬度和强度都较低,而且基体组织的不连续性使得塑性较差。奥氏体化温度达到840℃时,已经属于完全淬火,回火后样品具有更高的强度,而且材料的断裂机制发生明显变化,为典型韧性断裂特征,断口均为韧窝组成。随着奥氏体化温度的升高,淬火水冷至室温过程中的过冷度增大,导致不平衡转变产生的马氏体板条束更致密,力学性能进一步提高。

Effect of austenitizing temperature on microstructure and performance of 18CrNiMo7-6 Steel after tempering was studied.Results shown that when at 750℃,some undissolved ferrite was still present in the structure,which made the hardness and strength of the quenched and tempered specimens lower,and the discontinuity of the matrix structure made the plasticity poorer.At840℃,already belonging to the complete quenching,tempered specimens had the higher strength,and the fracture mechanism of the material was significantly changed with typical ductile tensile fracture characteristic composed of tough nests.With the increase of austenitizing temperature,the subcooling degree of the quenched specimen water-cooled to room temperature was increased,resulting in denser martensitic slat bundles from the unbalanced transformation and further improvement in mechanical properties.