The production flowsheet of 20 Cr steel is 120 t BOF-LF-200 mm x200 mm bloom CC-rolling. The composition detection

metallographic analysis and SEM energy dispersive analysis on the scarring and warping of forged small mechenical crankshaft of Φ35mm 20Cr round steel are carried out. The results show that during the continuous casting process

the mold liquid level fluctuation exceeded ±5 mm

led to mold powder to enter the meniscus

causing slag inclusion and carburization on the surface of the bloom

finally forming scarring and warping defects during rolling. By increasing the depth of the submerged nozzle form 80 ~ 120 mm to 90 - 130 mm

strengthening the control of the tundish nozzle and stop¬per

and optimizing the operation and performance of mold powder

the liquid level fluctuation in mold is stable within ± 3 mm

to avoid entrapped slag and forgings warping.