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魏慧慧，等：稀土元素镧对Q355B低合金高强度钢组织和性能的影响

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Effect of Rare Earth Element La on Microstructure and Properties of
Q355B Low Alloy High Strength Steel

WEI Huihui , HUANG Li , YUAN Xiaoming , GAO Xueyun , WANG Haiyan 1
1, 2
2
1
2
(1. School of Materials and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010, China;
2. Technical Center of Inner Mongolia Baotou Steel Union Co., Ltd., Baotou 014010, China)
Abstract: Q355B low alloy high strength steel containing rare earth element La with mass fraction of 0.002 1%
was prepared by vacuum melting method. The microstructure, impact and tensile properties and the corrosion resistance
in NaHSO 3 solution of the test steel were studied, and were compared with those of the test steel without rare earth
element La. The results show that the microstructure of Q355B steel without and with La was ferrite and pearlite, and
the addition of La decreased the element segregation degree of the structure, reduced the band structure, and improved
the uniformity of grain size. The test steel without La had angular string Al 2 O 3 inclusions with the size of about 267 µm;
after adding La the inclusions were spherical rare earth complex sulfur oxides, and the size significantly decreased to
about 10 µm. The addition of La had no significant influence on the tensile properties of the test steel, but could improve
the impact properties. Compared with that of the test steel without La, the impact absorption energy after adding La
increased by 5.2%. Compared with those of the test steel without La, the corrosion mass loss rate of the test steel with
La was reduced by 5.5%, the corrosion product layer was denser and the corrosion resistance was better.
Key words: rare earth element La; low alloy high strength steel; microstructure; corrosion resistance

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