Strength And Plasticity Of Rare Earth (RE) Weathering Steel

Rare earth (RE) weathering steel is an important type of structural steel which has been used widely in railway vehicle, container plate and bridge steel. There are strict requirements for weathering resistance and high strength-plasticity. In this paper, RE weathering steel B450NbRE was regarded as the research subject and the mechanism of effects of alloying elements, such as RE, Nb, V, Cr, Cu and Mn, on its strength and plasticity was studied by tensile tests and metallographic analysis. The following conclusions were drawn:(1) Trace of RE could improve the strength of weathering steel. With RE content increasing, tensile strength and yield strength increased firstly and then decreased. In this study, when RE content was 0.0035%, the maximum tensile strength and yield strength were gained and they were 515MPa and 720MPa respectively.(2) With RE content increasing, the reduction of cross-sectional area and the rate of elongation increased firstly and then decreased. In this study, when RE content was 0.0035%, the minimum values were gained and they were 60.57% and 21.62% respectively, however they could satisfy the technology order.(3) With RE content increasing, the volume fraction of ferrite increased firstly and then decreased. The strength and plasticity of weathering steel were affected by RE via changing the volume fraction of ferrite.(4) The strength of weathering steel were improved by Nb remarkably. With Nb content increasing, tensile strength and yield strength increased gradually, and it affected the plasticity rarely.(5) The ferrite grain could be refined by Nb, V or Mn. With the content of Nb, V or Mn increasing, the size of ferrite grain decreased gradually.(6) The strength of weathering steel were improved by Cr, Cu, or Mn, but the adverse influence on the plasticity by Cr, Cu, or Mn was found. With the content of Nb, V or Mn increasing, the tensile strength and yield strength increased gradually and the reduction of cross-sectional area and the rate of elongation decreased gradually.