钒微合金化600MPa级高强钢筋的组织与性能

Microstructure and properties of 600 MPa grade vanadium-microalloyed high strength steel rebar

结合Gleeble3500热力模拟与工业试验,通过显微组织观察、硬度测试、拉伸试验与TEM研究了形变与冷却工艺对钒微合金化600 MPa级钢筋组织、力学性能及析出相的影响。结果表明:试验钢的铁素体转变范围广,无变形且冷速大于5℃/s时,组织中开始形成贝氏体与马氏体。相变前粗大的原奥氏体晶粒将促进贝氏体与板条马氏体形成;原奥氏体晶粒细小与低温形变有利于铁素体与岛状马氏体的形成。冷速较小时,试验钢经形变后的硬度值大于无形变后的硬度值。冷速较大时,试验钢无形变的硬度值大于形变后的硬度值。为了获得细小铁素体与珠光体以及细小弥散的氮化钒,最佳生产工艺为:终轧温度大于1000℃,冷速为3℃/s;或终轧温度为900℃,冷速为5℃/s。

Based on Gleeble3500 thermal-mechanical simulation and industrial experiment,effects of deformation and cooling process on microstructure,mechanical properties and precipitation of 600 MPa grade steel rebar were studied by using metallographic observation,hardness test,tensile test and TEM. The results show that ferrite transformation range of tested steel is wide. No deformation and cooling rate is greater than 5 ℃ / s,the bainite and martensite are first produced. Coarse austenite grain before phase transformation will promote the formation of bainite and martensite. However,the fine prior austenite grain and low temperature deformation are beneficial to the formation of the ferrite and the island martensite. At the low cooling rate,the hardness value with deformation is greater than that without deformation. At the high cooling rate,the hardness value with deformation is smaller than that without deformation. In order to obtain the fine ferrite and pearlite as well as the fine dispersion vanadium nitride,either the finish rolling temperature is greater than 1000 ℃ and the cooling rate is 3 ℃ / s,or the finish rolling temperature is 900 ℃ and the cooling rate is 5 ℃ / s.