Zong Yun, Liu Chun-Ming
Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, Shenyang 110819, China.
School of Mechanical and Automobile Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China.
Materials (Basel). 2021 Jan 9;14(2):311. doi: 10.3390/ma14020311.
Four types of ultra-low carbon bainite (ULCB) steels were obtained using unified production methods to investigate solely the effect of niobium content on the performance of ULCB steels. Tensile testing, low-temperature impact toughness testing, corrosion weight-loss method, polarization curves, electrochemical impedance spectroscopy (EIS), and the corresponding organizational observations were realized. The results indicate that the microstructure of the four steels comprise granular bainite and quite a few martensite/austenite (M/A) elements. The niobium content affects bainite morphology and the size, quantity, and distribution of M/A elements. The elongation, yield strength, and tensile strength of the four types of ULCB steels are above 20%, 500 MPa, and 650 MPa, respectively. The impact toughness of the four types of ULCB steels at -40 °C is lower than 10 J. Steel with Nb content of 0.0692% has better comprehensive property, and maximum charge transfer resistance in 3.5 wt.% NaCl solution at the initial corrosion stage. The corrosion products on the surface of steel with higher niobium content are much smoother and denser than those steel with lower niobium content after 240 h of corrosion. The degree of corrosion decreases gradually with the increase of niobium content at the later stage of corrosion.
采用统一的生产方法获得了四种类型的超低碳贝氏体（ULCB）钢，以单独研究铌含量对ULCB钢性能的影响。进行了拉伸试验、低温冲击韧性试验、腐蚀失重法、极化曲线、电化学阻抗谱（EIS）以及相应的组织观察。结果表明，四种钢的显微组织均由粒状贝氏体和相当数量的马氏体/奥氏体（M/A）组元组成。铌含量影响贝氏体形态以及M/A组元的尺寸、数量和分布。四种类型的ULCB钢的伸长率、屈服强度和抗拉强度分别高于20%、500MPa和650MPa。四种类型的ULCB钢在-40℃时的冲击韧性低于10J。铌含量为0.0692%的钢具有较好的综合性能，在初始腐蚀阶段，在3.5wt.%NaCl溶液中的电荷转移电阻最大。腐蚀240h后，铌含量较高的钢表面的腐蚀产物比铌含量较低的钢表面的腐蚀产物更光滑、更致密。在腐蚀后期，腐蚀程度随着铌含量的增加而逐渐降低。
