中文摘要：

采用Gleeble-3500型热模拟试验机,测定一种高Nb微合金钢的变形前后及变形弛豫后的CCT曲线,并测定了奥氏体化、变形弛豫前后钢中固溶Nb的含量,分析了变形及弛豫对CCT曲线及组织的影响,结果表明：变形促进相变,使CCT曲线向左上方移动,并细化室温组织。变形后弛豫过程中,由于回复、再结晶的发生,降低了奥氏体的形变储能,降低了变形对组织的细化作用,使室温组织粗化。此外,Nb的析出降低了奥氏体中固溶Nb、C的含量,从而减弱了对相变的抑制作用,使相变温度升高。

英文摘要：

The effects of hot deformation and relaxation process on the continue cooling transformation（CCT） diagrams of a high-Nb microalloyed steel are determined by the means of the thermal simulation on a Gleeble-3500 thermal mechanical simulator.The results show that the hot deformation shifts the CCT curves to up and left,promoting the phase transformation with the refinement of the microstructure.The recovery and recrystallization involved in the relaxation process after hot deformation decreases the deformation energy and,consequently,the refinement effect of the deformaton decreases,leading to coarse microstructures at room temperature.Moreover,the amount of dissovled Nb and C in austenite decreases due to the precipitation of Nb,which weakens the restraining effect of Nb and C on phase transforntion and results the increase of the phase transformation temperature.