Effect of rare earth Ce addition on inclusions in offshore engineering steel containing arsenic

Abstract

The present study investigates the impact of rare earth Ce addition and holding time on inclusions in offshore engineering steel containing arsenic. The analysis was conducted using scanning electron microscopy and energy spectrum (SEM-EDS), automatic statistics of inclusions, and thermodynamic analysis. The results indicate that prior to the addition of rare earth Ce, the typical inclusions in the steel were Al _2 O _3 , MnS and Al _2 O _3 -MnS, with an average size of approximately 2.51 μ m and an irregular or stripe morphology. Upon the addition of rare earth Ce, the inclusions in the steel were transformed into Ce-S(-O), Ce-As(-O) and Ce-S-As(-O), with a smaller average size and a spherical or ellipsoidal morphology. The smallest average size of inclusions in the steel was observed when rare earth Ce was added and held for 5 min; this size was 33% smaller than that prior to the addition of Ce. The thermodynamic calculation revealed that the Ce-S(-O) inclusion is formed in molten steel, while the Ce-As(-O) inclusion is formed during the solidification stage. As element replaced parts of the S and O elements in the Ce-S(-O) inclusion and formed the Ce-S-As(-O) complex inclusion, characterized by a double-layered structure.

Keywords

• offshore engineering steel
• rare earth Ce
• inclusions
• arsenic