铌钒微合金化对22MnB5热成形钢显微组织与性能的影响

复合添加质量分数均为0.04%的铌和钒对22MnB5热成形钢进行微合金化,对比研究了微合金化前后试验钢的显微组织、拉伸性能、淬透性和极限尖冷弯性能,分析了铌钒微合金化对性能的影响机制。结果表明:微合金化前后试验钢的显微组织均为全马氏体且均存在明显的马氏体板条束,微合金化后的组织更为细小,马氏体板条束长度更短,拉伸性能略有提升;铌钒复合微合金化能有效提高试验钢的淬透性,其淬硬层深度由未微合金化的3～5mm提高到13～14mm;铌钒微合金化后试验钢的极限尖冷弯角为65°～70°,显著高于未微合金化的;NbC细化晶粒与VC沉淀强化的协同作用是微合金化后试验钢具有更优性能的根本原因。

Effect of Niobium and Vanadium Micro-alloying on Microstructure and Property of 22MnB5 Hot Press Forming Steel

22MnB5 hot press forming steel was micro-alloyed by composite addition of 0.04 wt% niobium and 0.04 wt% vanadium.The microstructure,tensile properties,hardenability and extreme tip cold bending performance of the tested steel before and after micro-alloying were studied and compared.The effect mechanism of niobium and vanadium micro-alloying on the properties was analyzed.The results show that the microstructures of the tested steel before and after micro-alloying consisted of whole martensite and had obvious martensite strip.The microstructure after micro-alloying was finer,the length of the martensite strip was shorter,and the tensile properties were improved slightly.The niobium and vanadium micro-alloying improved the hardenability of the tested steel effectively,whose hardened layer depth was improved from 3-5 mm before micro-alloying to 13-14 mm.After the niobium and vanadium micro-alloying,the extreme tip cold bending angle of the tested steel was between 65°-70°,which was higher than that before micro-alloying.The synergistic effect of grain refinement of NbC and precipitation strengthening of VC was the fundamental reason for the better performance of the microalloyed tested steel.