The electroslag-remelting (ESR) test on steel Cr13Mn4Mo by 70CaF

2

-30Al

2

O

3

slag series has been carried out. The total oxygen content

sulfur content and amount

size and morphology of inclusions in Ф55mm electrode and Ф120mm (36kg) ESR ingot are analyzed and measured by SEM/EDS

oxygen-nitrogen determinator and carbon-sulfur analyzer

and the thermodynamic analysis on MnS inclusions precipitation process in steel is carried out. Results show that by ESR the total oxygen content in steel decreases from 0.0121% to 0.0044%

sulfur content in steel decreases from 0.010% to 0.002%

as compared with electrode the number per mm

2

of inclusions in ESR ingot decr

eases from 855 to 257 and the size of inclusions in ESR ingot decreases obviously which are about 1μmAl

2

O

3

and compound inclusions with Al

2

O

3

core surrounded by MnS at outside. Thermodynamic calculated results show that in test conditions there is no single MnS formation that agrees with SEM/EDS analysis results.