Morphology

size and number density of MnS inclusions of F45MnVS non-quenched and tempered steel produced by 120 t LD-LF-RH-240 mm x 240 mm CC process before improvement are analyzed. By adopting improvement measures including ： (1) the aluminum ingots for deoxidation are intermittently added into the molten steel in batches surrounding the impact zone during LD tapping； (2) low carbon and low sulfur ferromanganese without MnS inclusions being employed as alloy materials； and (3) added sulfur wire into the furnace ladle in batches during LF refining. Tlie experimental results show that based on the optimized production processes

the MnS inclusion sizes in steel during the production of LF

RH

Tundish

continuous casting bloom and the rolled products are all effectively reduced. Co

mpared with the routine production processes before improvement

the number density of large scale inclusions (＞5μm) in the position of edge

1/4 and center of the casting bloom decreases from original 35

83 and 51 per mm

2

to 24

57 and 39 per mm

2

after the optimization

respectively. The decrease amplitude reaches 31.43%

31.33% and 23.53%

respectively. The ratings for the thin and thick inclusions in the steel products after rolling have been improved. The ratio of the inclusions with the length-width ratio in the range of 0-3 to the total inclusions increases from 63.07% before improvement to 71.23% after improvement.