The production process of tested non-oriented electrical steel 50W350 (/%: 0.002C

2.66Si

0.25Mn

0.012P

0.002S

0.760Als

0.762Alt) is hot-metal pretreatment

adding 300kg lime in tapping of an 100t BOF

controlling end [C

]

≤0.05% and tapping liquid temperature 1640〜1650℃

CAS treating for 5min

RH blowing oxygen to decarburize

adding 99.0% Al-Fe alloy 6.69kg/t and 70% Si-Fe alloy 15.7kg/t in RH refining process

in whole process shielding-atmosphere casting 230mm slab

and using special carbon-free basic shielding agent. Analysis results show that at end CAS treatment the number of inclusions

in steel is 306.26 piece/mm

2

in cast slab that decreases to 145.12 piece/mm

2

and the ≤3μm inclusions make up more than 90 percent of the total amount of inclusions; in steelmaking process the main inclusions are high-aluminum inclusions

some single Al

2

O

3

inclusions exist in liquid at end argon blowing and in ladle

in tundish and cast slab the Al

2

O

3

combines with other inclusions to form complex inclusions in steel；besides the AIN inclusions are found in liquid in ladle and in cast slab； the total amount of large scale inclusions in cast slab is 6.20mg/10kg

the 140〜300μm inclusions make up about 60 percent of total large scale inclusions

and a small amount of large scale inclusions containing Na and K exists in slab.