Ti-V-Mo复合微合金化高强钢中纳米相调控及其热稳定性研究

Ti complex microalloyed has been focused by metallurgists due to improving the volume fraction of complex precipitates and refining the size of precipitates of α-Fe and thus signifcantly increasing of the increment of precipitation hardening. However, the control of size and the thermal stability for the precipitates within the α-Fe restricted the improvement of increment of precipitation hardening. The amounts of MC carbides precipitated from austenite and ferrite in Ti-V、Ti-Mo and Ti-V-Mo microalloyed steels have been made a contrastive study by applicant, it is found that the Ti-V-Mo microalloyed steel has the greatest potential of increment of precipitation hardening. In this study, the Ti-V-Mo microalloyed steel will be selected as the research object. The kinetics of complex precipitates in ferrite will be clarified through theoretical calculation. Combining with the results from thermal simulation experiments, the intrinsic factors that affect the thermal stability of the complex precipitates will be explored. Then, the interaction of Ti、V and Mo in α-Fe matrix will be examined. In addition, the control strategy for nano-sized precipitates precipitated from ferrite will be proposed. The present work will not only provide theoretical and experimental understanding for the research and development of Ti complex microalloyed high strength steel, but also provide the foundation for further study of complex precipitates.

Ti复合微合金化因其能提高复合析出相在铁素体中的体积分数并细化其粒子尺寸、显著提高钢材的沉淀强化增量，成为国内外学者研究的焦点。然而，复合析出相在铁素体中沉淀析出的纳米相尺寸调控及其热稳定性强弱是制约沉淀强化增量提高的瓶颈。申请人曾对Ti-V、Ti-Mo和Ti-V-Mo复合微合金钢中MC相在奥氏体和铁素体中的析出量进行了对比研究，发现Ti-V-Mo复合微合金化具有最大的沉淀强化潜力。本项目拟以Ti-V-Mo复合微合金钢为研究对象，通过理论计算，获得复合析出相在铁素体中沉淀析出的动力学规律，结合热模拟实验结果，揭示影响复合析出相热稳定性的内在因素，阐明Ti、V和Mo在铁素体中沉淀析出的相互作用机理，提出实现纳米级析出相在铁素体中沉淀析出的调控策略。项目研究成果不仅可为Ti复合微合金化高强钢的研究和开发提供理论指导和实验依据，而且也可为多元复合析出相的深入研究奠定前期基础。

复合Ti微合金化技术因其能提高复合析出相在铁素体中的体积分数并细化其粒子尺寸、显著提高钢材的沉淀强化增量，成为国内外学者研究的焦点。然而，复合析出相在铁素体中沉淀析出的纳米相尺寸调控及其热稳定性强弱是制约沉淀强化增量提高的瓶颈。本项目以Ti-V-Mo复合微合金钢为研究对象，理论计算复合析出相在铁素体中沉淀析出的动力学规律，揭示影响复合析出相热稳定性的内在因素，阐明Ti、V和Mo在铁素体中沉淀析出的相互作用机理，研究纳米级析出相在铁素体中沉淀析出的调控机理。.项目研究获得以下重要结果：.（1）(Ti,V,Mo)C在铁素体中沉淀析出的NrT曲线为反“C”形状，而沉淀析出的PTT曲线为“C”形状，适当增加奥氏体中沉淀析出的形变诱导析出量，使(Ti,V,Mo)C在铁素体中沉淀析出的NrT曲线(<700℃)向短时间-低温度-大形核率方向移动，有利于获得更大析出量的纳米级粒子；.（2）Ti-V-Mo钢的最佳卷取温度为600-625℃，保温时间为1h，铁素体中沉淀析出的大量的尺寸在10nm以下的(Ti,V,Mo)C粒子，可获得最大的沉淀强化增量。.（3）在800-980℃范围，降低终轧温度，(Ti,V,Mo)C在奥氏体中的形核率不断减小，使得其在铁素体中析出的10nm以下的(Ti,V,Mo)C粒子不断增多，促进了硬度的提高。.（4）在630℃保温600s时，奥氏体向铁素体的转变和复合(Ti,V,Mo)C粒子的析出均基本完成，硬度达到峰值415HV。.（5）卷曲温度和保温时间是影响热稳定性的主要因素，卷取温度影响显著，保温时间次之；较高温度600和650℃卷取时，析出相为富V的(Ti,V,Mo)C粒子，热稳定较强，较低温度500和550℃卷取时，析出相为富Ti的(Ti,V,Mo)C粒子，热稳定性较强。Ti是(Ti,V,Mo)C粗化过程的控制性元素。.项目研究成果不仅可为纳米强化高强钢的研究和开发提供理论基础和实验依据，而且也可为多元复合析出相的深入研究奠定前期基础。