稀土La+Ce对含Nb结构钢强度及冲击韧性的影响

Effect of rare earth La+Ce on strength and impact toughness of Nb structural steel

摘要:

为了探索稀土元素在钢中的作用机理，分别研究混合稀土加入量La+Ce：36ppm、La+Ce：44ppm、La+Ce：51ppm与空白试样（La+Ce：0ppm）对含Nb结构钢强度及韧性的影响规律。通过拉伸试验、低温冲击试验以及SEM和EDS对材料性能和显微结构进行分析。结果表明：在Fe-0.07%C-0.025%Nb-x%(La+Ce)成分体系下，降Nb而添加适量混合La+Ce稀土化合物，随着La+Ce含量增加，断裂过程韧窝增大且逐渐加深，含Nb结构钢的屈服强度和抗拉强度呈增大趋势，且延伸率随着稀土含量和强度的增加未呈现大幅度下降趋势。说明混合La+Ce稀土化合物可以替代贵金属Nb元素来提升产品的强度指标。对于低温冲击试验，由断口形貌和四种成分系钢带试样吸收冲击能量对比得出，在含Nb结构钢中，混合La+Ce稀土加入量为36ppm时，变质钢中的夹杂物形成有效的LaCeO2S析出粒子阻碍断裂过程裂纹扩展，-40℃和-60℃的低温冲击韧性最优。

Abstract:

In order to explore the effect of rare earth (RE) element on the strength and toughness of steel, mixed La+Ce elements have been incorporated into Nb-alloyed steel at the content of La+Ce: 36ppm, La+Ce: 44ppm, La+Ce: 51ppm and reference sample (no RE). The mechical properties and microstructure of the materials were analyzed by using tensile test, low temperature impact test and SEM observation coupled with EDS. The results indicated that the reduction of Nb and the increase of the La+Ce influenced the mechanical performance of Fe-0.07%C-0.025%Nb-x%(La+Ce) component system, with the?increase of RE, dimples were enlarged and deepened, and the yield strength and tensile strength of Nb-alloyed structural steels tended to increase. meanwhile the elongation did not show a significant reduction with the increase of RE content. These results demonstrates that the mixed La+Ce rare earth compound is promising to replace the Nb element to improve the mechanical performance of the product. The comparison of fracture morphology and absorbed impact energy of different kinds of hot rolled steel belt show that the low-temperature impact toughness maximized at -40℃ and -60℃ when the content of La+Ce rare earth compounds was 36ppm, due to the fact that inclusions were modified to form precipitated LaCeO2S particles which delayed the crack growth.