热处理工艺对15CrMoR钢带状组织和冲击性能的影响

利用光学显微镜、扫描电镜和冲击试验机等仪器研究了15CrMoR钢中带状组织在热处理过程中的演变及其对冲击性能的影响。结果表明:奥氏体化后缓冷会出现铁素体-珠光体带状组织, 快冷则可以抑制带状组织的出现,但快冷会导致粒状贝氏体等非平衡组织形成。粒状贝氏体组织中的贝氏体铁素体基体和马氏体-奥氏体岛在回火过程中逐渐沿Cr、Mo等碳化物形成元素偏聚的区域分解出碳化物,形成富碳化物带,降低钢的横向冲击性能。15CrMoR钢加热到1100 ℃并保温7 h后可消除带状组织,改善钢的横向冲击性能。

Effect of heat treatment process on banded structure and impact properties of 15CrMoR steel

Evolution of banded structure during heat treatment and its effect on impact properties of the 15CrMoR steel were analyzed by means of optical microscope, scanning electron microscope and impact testing machine. The results show that ferrite-pearlite banded structure appears when cooling slowly after austenitization, and can be inhibited by increasing cooling rate, but fast cooling may result in non-equilibrium structures such as granular bainite.During tempering, the martensite-austenite islands and bainitic ferrite in the granular bainite decompose gradually to form carbides in the segregation area of carbide-forming elements such as Cr and Mo, leading to the emergence of carbide-rich band and deteriorating the transverse impact properties of the 15CrMoR steel. Homogenized at 1100 ℃ for 7 h could eliminate the banded structure, and improve the transverse impact properties of the steel.