Effect of Cr content on deposited metal toughness of weathering steel

The effect of Cr content on microstructure and toughness in deposited metals of weathering steel were investigated by the tensile test,impact test,optical microscope(OM), transmission electron microscopy(TEM),scanning electron microscope(SEM) and electron back-scattered diffraction(EBSD), respectively. The results show that the microstructure consists of granular bainite,acicular ferrite and a few lath bainite for both deposited metals. Good impact toughness is obtained for both deposited metals. Comparing with 1.0% Cr containing deposited metal,the content of granular bainite increases while acicular ferrite decreases of 1.41% Cr containing deposited metal. And the yield strength,tensile strength have improved by 6%,9%, respectively,but the impact toughness has dropped by 56%. The increasing of the content of M-A constituents and mean grain size,and the decreasing of the number of the large angle boundary of 1.41% Cr containing deposited metal,which cause the rising of the probability of the crack initiation and reducing the resistance to crack propagate,result in its worse toughness.