中文摘要：

在Gleeble-3500热模拟机上测定了Nb-V微合化金中碳非调质钢在不同冷却速率下的膨胀曲线,并联合金相-硬度法,绘制出了Nb-V试验钢的动态CCT曲线。依据所绘试验钢动态CCT曲线,对试验钢在不同冷却速率下组织的转变转变情况进行了分析。结果表明：冷却速率低于2℃/s时,Nb-V钢的显微组织为铁素体和珠光体,冷却速率超过2℃/s时,钢中组织可以观察到贝氏体,随着冷却速率的增加贝氏体含量也明显增加;冷却速率超过10℃/s时,组织中开始出现马氏体;冷却速率超过15℃/s后Nb-V钢显微组织全部为马氏体。贝氏体转变的临界冷却速率为7-10℃/s,马氏体转变的临界冷却速率为10-15℃/s。

英文摘要：

Expansion curves of continuous cooling transformation at different cooling rates of Nb-V alloyed medium carbon non-quenched and tempered steel were measured by Gleeble-3500 thermal mechanical simulator. Based on expansion curves and microscopic test and hardness measurement,the dynamic continuous cooling transformation（ CCT） diagram was obtained. According to the CCT diagram, the transformation products of austenite at different cooling rates were analyzed. The results show that when cooling rate is less than 2 ℃/s,the microstructure of ferrite and pearlite can be obtained,when the cooling rate exceeds 2 ℃/s bainite transformation occurs,more bainite can be obtained with the increase of cooling rate; When the cooling rate is greater than 10 ℃/s,martensite is observed in the steel; When the cooling rate exceeds 15 ℃/s,the microstructure of martensite is obtained. In a word,for this steel,the bainite transformation critical cooling rate is 1-2 ℃/s,the martensitic transformation critical cooling rate is 5-7 ℃/s.