高强韧钻杆用低碳高铌钢的动态CCT曲线测定与分析

Determination and Analysis on Dynamic CCT(Continuous Cooling Transformation)Curve of Low Carbon High Niobium Steel for High Strength and Toughness Drill Pipe

利用MMS-200热力模拟实验机对高强韧钻杆用低碳高铌钢进行模拟轧制压缩试验,测定绘制低碳高铌钢动态连续冷却转变(CCT)曲线,并研究了冷却速率对显微组织的影响。结果表明,冷速为0.5℃/s时,组织主要由多边形铁素体(PF)和少量珠光体(P)组成,同时观察到极少量的针状铁素体(AF);冷速为1℃/s时,组织以针状铁素体(AF)为主,珠光体消失,但仍可见一定比例的多边形铁素体(PF);冷速升高到2℃/s时,转变组织完全为粒状贝氏体(GB);冷速升高到5℃/s时,转变组织以粒状贝氏体(GB)为主,同时出现少量的铁素体贝氏体(FB);冷速升高到30℃/s时,转变组织以铁素体贝氏体(FB)为主,同时出现少量的马氏体(M)。

The dynamic CCT curve of low carbon high niobium steel is determined and drawn as well as the effects of cooling rate on microstructure are studied through static simulating rolling compression test of low carbon high niobium steel with MMS-200 thermomechanical simulator.The results showed that the microstructure was mainly composed of polygonal ferrite(PF),a little pearlite(P)and small quantity of acicular ferrite(AF)observed when cooling rate was 0.5℃/s;the microstructure was mainly composed of acicular ferrite(AF)and pearlite disappeared,but certain proportion of polygonal ferrite(PF)was still visible when cooling rate was 1.0℃/s;the transformation structure was completely granular bainite(GB)when cooling rate was increased to 2℃/s;the transformation structure was mainly composed of granular bainite(GB)and a small amount of ferrite bainite(FB)when cooling rate was increased to 5℃/s;the transformation structure was mainly composed of ferrite bainite(FB)and a small amount of martensite(M)when cooling rate was increased to 30℃/s.