终锻温度对Nb-V-Ti微合金非调质钢显微组织和冲击韧性的影响

Influence of Final Forging Temperature on the Microstructure and Impact Toughness of Nb-V-Ti Microalloyed Non-Quenched and Tempered Steel

对比研究了经控锻-控冷处理的V—Ti和Nb—V-Ti微合金非调质钢的显微组织和力学性能。结果表明，Nb-V-Ti复合微合金化和控锻一控冷处理能有效细化组织，改善珠光体形态，促进V（C，N）相析出，提高非调质钢的冲击韧性。添加Nb显著提高抗奥氏体晶粒粗化温度，使细小碳氮化物弥散分布。与传统控锻一控冷工艺相比，850～900℃再结晶-未再结晶控锻-控冷工艺，使珠光体片碎化及部分球化，是导致V-Nb-Ti非调质钢冲击韧性提高的主要原因。

The microstructure and mechanical properties of V-Ti and Nb-V-Ti microalloyed non-quenched and tempered （NQT） steels with controlled forging and cooling process were investigated. The results showed that the ferrite grain size and pearlite colony size of the Nb-V-Ti NQT steel was refined significantly, together with promoting V （C, N） precipitation in the ferritic grain interior. Addition of Nb increased the full reerystallization temperature and expanded the non- recrystallization region of the NQT steel, and hence refining the microstructure of pearlite and ferrite and improving the distribution of the fine precipitates. Compared with the conventional V-Ti NQT steel, the impact toughness of Nb-V-Ti NQT steel was enhanced by the controlled forging and cooling process with the lowering final forging temperature. The high impact toughness of the forged Nb-V-Ti NQT steel was mainly attributed to the fragmentation and refinement of pearlitic lamellae during the controlled forging process.