Analysis of Inclusions with Unqualified Z-direction Performance of Heavy Bridge Plates

Abstract

Abstract-By using the analysis tools of scanning electron microscope (SEM) and energy dispersive X-ray (EDX), the reason for the disqualified Z-direction performance of a 60mm Q370qEZ35 heavy steel plate was investigated. The results showed that the disqualified Z-direction performance of Q370qEZ35 was due to the presence of a large number of inclusions, the types of which were mainly massive and striplike (Nb, Ti)C and metal Nb inclusions as well as spherical oxide (MgO, Al 2 O 3 , etc.) and sulfide inclusions (CaS, MnS). The cause of various types of inclusions and the impact on the Z-direction property was analyzed, and the corresponding improvement measures were put forward from smelting, casting and rolling and cooling process, such as controlling the amount and adding time of Nb and Ti, extending the refining time, controlling the superheat temperature, optimizing the process of heating, rolling and cooling, etc., and finally, we achieved good results.