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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。
The continuous cooling transformation (CCT) curves of C-Si-Mn-Cr-Mo and C-Si-Mn-Cr-Mo-Nb test steels were measured by Gleeble-1500 thermal simulator. Influence of Steel Transformation and Microstructure Evolution. The results show that Nb can significantly inhibit the ferrite transformation of the test steel. With the increase of the cooling rate, the inhibition of Nb gradually increases, the grain size of the ferrite is obviously refined, and the microhardness obviously increases. When ferrite changes sufficiently, Nb can improve the stability and hardenability of metastable austenite, but has little effect on the microhardness of martensite and bainite products. With little or no change in ferrite, Nb results in a marked increase in the number of martensite-retained austenite (MA) islands in the granular bainite product and an increase in the microhardness of the bainite, but the increase As the cooling rate increases, it gradually decreases.