Determination and Analysis on Dynamic CCT (Continuous Cooling Transformation) Curve of Low Carbon High Niobium Steel for High Strength and Toughness Drill Pipe
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.
drill pipelow carbon high niobium steeldynamic CCT curvecooling ratemicrostructure
万方数据
维普
