【摘要】 用Gleeble-1500热模拟机测定了C-Si-Mn-Cr-Mo和C-Si-Mn-Cr-Mo-Nb两种试验钢连续冷却转变(CCT)曲线,分析了微合金元素Nb对试验钢相变规律和组织演变的影响。结果表明,Nb可显著抑制试验钢铁素体转变,随着冷却速度增加,Nb的抑制作用逐渐增强,铁素体晶粒尺寸明显细化,显微硬度明显增加。铁素体转变充分时,Nb可提高亚稳奥氏体稳定性和淬透性,但对马氏体和贝氏体产物的显微硬度影响不大。在铁素体转变量很少或未转变的情况下,Nb使得粒状贝氏体产物中马氏体-残余奥氏体(MA)岛数量明显增多,贝氏体显微硬度增加,但其增幅随着冷却速度增加逐渐减小。更多还原

【Abstract】 CCT curves of C-Si-Mn-Cr-Mo and C-Si-Mn-Cr-Mo-Nb steels were tested on Gleeble-1500 thermal-mechanical simulator,and effect of Nb on transformation rule and microstructure evolution was analyzed.It is shown that Nb restrains ferrite transformation of tested steel and its effect enhances with increasing cooling rate,meanwhile,ferrite grain size refines and ferrite microhardness increases obviously.Nb enhances stability and hardenability of metastable austenite after enough ferrite transformation,but has few effects on microhardness of its transformation product.When there are few ferrite transformations,micro-alloying of Nb increases amount of martensite-austenite(MA) islands of granular bainite and enhances microhardness of bainite,but amplitude of microhardness decreases gradually.更多还原