Nb微合金化对Cr-Ni-Mo-V系高强钢组织及力学性能的影响

对含Nb与不含Nb的Cr-Ni-Mo-V系高强钢进行880℃×1 h淬火+300℃×3 h回火处理，并采用SEM、EBSD、TEM和物理化学相分析等技术分别对其微观组织和析出相进行观察分析。结果表明，添加了0.035%Nb的试验钢组织得到细化，马氏体板条块尺寸从3.1μm下降至2.9μm,且Nb的添加使得MC型析出相的含量增加，析出相尺寸分布得到优化，尺寸在18～200 nm的析出相含量明显增加。由于析出相含量的增加，固溶C含量有所下降，加之含Nb试验钢中的原始C含量稍低，导致含Nb钢的强度稍有下降，但仍达到2000 MPa水平。而马氏体组织的细化及析出相尺寸分布的优化使含Nb试验钢韧性明显提升，室温和-40℃低温冲击吸收能量(KU₂)均提高至44 J。

Effect of Nb microalloying on microstructure and mechanical properties of Cr-Ni-Mo-V high-strength steels

After quenching at 880 ℃ for 1 h and tempering at 300 ℃ for 3 h, the microstructure and precipitated phases of the tested Cr-Ni-Mo-V high-strength steels with and without Nb were observed and analyzed by means of SEM, EBSD, TEM and physicochemical phase analysis. The results show that with the addition of 0.035%Nb, the microstructure of the tested steel is refined, the martensite lath block size decreases from 3.1 μm to 2.9 μm, and the content of MC-type precipitated phase increases, the size distribution of the precipitated phases is optimized, and the content of the precipitated phases with the size ranging from 18 to 200 nm is significantly increased. Due to the increase in precipitated phase content, the decrease of C content in solid solution, and the slightly lower total C content in the Nb-containing steel, so that the strength of the steel decreases slightly, but still reaching the level of 2000 MPa. The toughness of the Nb-containing tested steels is improved by the refinement of the martensite microstructure and the optimization of the size distribution of the precipitated phases, the room temperature and -40 ℃ low temperature impact absorbed energy (KU₂) are both increased to 44 J.