The effect of single roll soft reduction (6~20mm) and reduction position (1

#

〜6

#

roll) on central carbon segregation and macrostructure of 180mmx180mm casting billet of high carbon steel SWRH92B (/%: 0.71C

0.22Si

0.64Mn

0.010P

0.006S) has been tested and studied. Results show that as solid fraction fs is 0.45~0.63 the soft reduction is available to decrease central carbon segregation of casting billet

and as the solid fraction fs is more than 0.82 the shrinkage cavity of billet can not be eliminated and the central carbon segregation can not be decreased； in condition of soft reduction 6~20mm

with increasing reduction the central carbon segregation decreases from 1.15 to 1.04

and the cracks occu

r easily in billet as the soft reduction is more than 15mm；compared with weak secondary cooling ( water ratio 0.65L/kg) and the ultra weak secondary cooling ( water ratio 0.40L/kg) is more favorable to control central carbon segregation；by comprehensive analysis it is obtained that with casting speed 1.3 m/min

mold stirring 300A and 5Hz

and secondary cooling water ratio 0.40 L/kg

the central carbon segregation and macrostructure of steel SWRH72B 180mmx180mm casting billet are better by single roll soft reduction 15mm at 5

#

roll.