The steel SWRH82B is mainly applied to high strength

low relaxation pre-stressed steel wire and strand for concrete structure

required better plasticity. The abnormal fracture of Φ12. 5mm coil of steel SWRH82B (/%: 0.79~0.86C

0.15~0.35Si

0.60~0.90Mn

≤0.030P

≤0.030S

0.17~0.50Cr) produced at Xingtai steel occurs in cold-drawn process. By metallographic analysis on abnormal fracture of coil it is found that there is obvious network of cementite in center of coil

and the center carbon segregation index of corresponding casting bloom is 1.16. With optimizing 280mmx325mm bloom casting process including increasing casting speed from original 0.5m/min to 0.7m/min and adding soft reduction process ( No1~No5 roll

2mm

3.5mm

3.5 mm

4mm and 2mm)

the center carbon segregation index of casting bloom decreases from 1.16 to 1.08

the V-shaped segregation improves obviously

the reduction of area of steel coil increases from original 35% to 39%

and nonqualified rate of steel decreases markedly.